JPH10270438A - Combustion apparatus for producing high-purity steam and method for producing high-purity steam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a combustion apparatus for producing high-purity steam by burning hydrogen, in particular, exhibiting stable durability by preventing peeling, melting and the like of a gas ejection nozzle thereof, and a semiconductor manufacturing process. Provided is a combustion apparatus for producing water vapor having a significantly reduced content of impurities such as alkali metals suitable for oxidation treatment of water. SOLUTION: In a combustion apparatus for producing high-purity steam having a combustion chamber, a gas supply pipe comprising a hydrogen gas supply pipe and an oxygen gas supply pipe, a erosion prevention mechanism at a tip of a gas ejection nozzle of the gas supply pipe is provided. A combustion device for producing steam. A erosion prevention mechanism is provided between the hydrogen gas and the oxygen gas at the gas ejection nozzle introduction part of the gas supply pipe, and circulates the cooling medium by heat radiation means disposed at the gas ejection nozzle introduction part of the gas supply pipe. It is preferable that the cooling unit is made of quartz glass and formed as possible. Further, the erosion prevention mechanism is formed such that the gas supply pipe is formed in a triple pipe or a quadruple pipe, and at least hydrogen gas and oxygen gas are supplied to the combustion chamber via an inert gas in the middle. The gas supply pipe is preferably used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion apparatus for producing high-purity steam and a method for producing high-purity steam, and more particularly to a combustion apparatus for producing high-purity steam gas used in an oxidation step of a semiconductor production process. The present invention relates to a combustion apparatus for producing high-purity steam and a method for producing high-purity steam, which prevents erosion of a gas ejection nozzle, reduces impurities in generated steam gas, and has excellent durability.

[0002]

2. Description of the Related Art In an oxide film forming step of a semiconductor manufacturing process, there is a method of contacting a wafer with a high-temperature steam gas as one of the oxide film forming methods. It is desired that the steam gas used for forming the oxide film has a high purity in which impurities such as alkali metals contaminating the semiconductor wafer are reduced as much as possible. Generally, a high-purity hydrogen gas and an oxygen gas are brought into contact with each other to form a hydrogen gas. It is manufactured by burning gas. As a method of burning hydrogen gas, for example, as disclosed in JP-A-56-62326, a wafer to be oxidized is set in a heating furnace, and hydrogen gas and oxygen gas are directly introduced into the heating furnace. There is a method of generating steam by burning. But,
This method has a problem that the temperature in the heating furnace is affected by the flame and it is difficult to keep the oxidation treatment conditions constant.

In order to solve the above problem, for example, Japanese Patent Application Laid-Open
As disclosed in Japanese Patent Application Laid-Open No. 7-18328, a method is provided in which a combustion device is provided outside the wafer oxidation furnace to burn hydrogen gas to generate steam, and the obtained steam gas is introduced into the furnace. was suggested. In the case of producing steam gas by this external combustion method, since the oxidation treatment conditions in the semiconductor manufacturing process are stable, this method is widely used at present. This external combustion type hydrogen gas combustion device is usually
For example, as shown schematically in FIG. 7 and an enlarged cross-sectional view taken along the line DD in FIG. 8, the high-purity steam generated in the combustion chamber 72 and the combustion chamber 72 is supplied to an external wafer heat treatment furnace or the like. It has a water supply pipe 73 for supplying water and a gas supply pipe 74 for supplying hydrogen and oxygen gas, and is mainly made of quartz glass. A cooling device 79 such as a water-cooled cylinder is provided on the outer periphery of the combustion chamber 72, and an ignition device for heating the hydrogen and oxygen gas supplied at the time of start to spontaneously ignite is provided on the outer periphery of the gas supply pipe 74. Preheating heater 8
0 is provided. The gas supply pipe 74 is composed of a double circular pipe, a hydrogen gas supply pipe 75 is arranged in the center, an oxygen gas supply pipe 76 is annularly arranged on the outer periphery thereof, and a hydrogen gas supply pipe 7 is formed.
The hydrogen gas supply pipe 77 and the oxygen gas supply pipe 78 are connected to the fifth gas supply pipe and the oxygen gas supply pipe 76, respectively. Further, a gas ejection nozzle is provided continuously at the distal end of the gas supply pipe 74, and a heat insulating material 81 is generally provided on the outer peripheral portion of the distal end of the gas supply pipe 74. The hydrogen gas and the oxygen gas are heated by the heater 80 for preheating, are jetted from the gas jet nozzle into the combustion chamber, come into contact in the combustion chamber, spontaneously ignite, and then oxidize and burn the hydrogen gas to produce steam.

[0004] The combustion device configured as described above is generally formed of quartz glass material as described above. In this case, in particular, there is a problem that the tip of the gas ejection nozzle is melted and consumed due to the high temperature during combustion, and the tip of the gas ejection nozzle and the inner wall of the combustion chamber are crystallized, separated, dropped, and damaged. These are not only the durability problem that the life of the combustion device that generates steam is short, but also the particles generated by the above-mentioned melting and the like and impurities in the quartz glass material are mixed in the generated steam gas. The semiconductor silicon wafer to be oxidized may be contaminated. For this reason, it eventually causes a reduction in the yield of semiconductor device manufacturing in a semiconductor manufacturing process using these water vapors. In addition, with the recent increase in the diameter of semiconductor wafers, it is desired to increase the amount of steam production. For this reason, increasing the supply gas amount requires increasing the temperature of the tip of the gas ejection nozzle and the combustion chamber. Therefore, it is difficult to implement the method because the erosion at the nozzle tip is further increased.

As a method for solving the above-mentioned problem of the external combustion system, for example, in Japanese Patent Application Laid-Open No. Hei 6-267932, an oxygen gas ejection nozzle is made to protrude inward in a combustion chamber (vessel) from a hydrogen gas ejection nozzle tip, and A dispersive oxygen gas ejection nozzle having a plurality of ejection holes for dispersing and ejecting oxygen gas in a wide range has been proposed. This method has a double circular pipe structure (a hydrogen gas is supplied to the center pipe and an oxygen gas is supplied to the outer pipe) which is generally used in the conventional external combustion type gas supply pipe described in Japanese Patent Publication No. Sho 63-60528. A) farther away from the hydrogen gas jet nozzle,
In addition, by blowing oxygen gas over a wide range, a thick flame is formed at the oxygen gas ejection nozzle portion. As a result, as compared with the conventional gas ejection nozzle, the tip of the hydrogen gas ejection nozzle is not heated, and the temperature in the combustion chamber can be prevented from becoming high. Therefore, a larger amount of high-purity steam gas can be produced by increasing the supply amounts of hydrogen and oxygen gas than before, and the amount of steam gas produced for the oxidation treatment of a semiconductor wafer having a large diameter is increased.

[0006]

According to the combustion apparatus in which the gas ejection nozzle proposed above is improved, a large amount of high-purity steam gas required for stabilizing an oxidation process in a semiconductor manufacturing process and processing a large-diameter wafer is provided. Thus, problems such as durability of the combustion device are solved. However, according to the inventors,
It has been found that, despite the lowering of the combustion chamber temperature, the impurity content level in the steam gas does not decrease to a sufficiently satisfactory level. That is, as shown in a comparative example described later, even in the above-described proposed combustion apparatus, compared with the above-described conventional gas ejection nozzle composed of a double pipe gas supply pipe, impurities in the produced steam gas are different. It was confirmed that the contents were almost the same.

In the combustion apparatus proposed in Japanese Patent Application Laid-Open No. 6-267932, the reason why the content of impurities in the steam gas does not decrease as expected is that the temperature near the hydrogen gas ejection nozzle drops and the combustion chamber (vessel) Although the temperatures of the upper part and the outer periphery also decrease, the flame having the highest temperature in the combustion chamber is formed near the oxygen gas ejection nozzle as described above. It is presumed that the quartz glass material is melted and damaged at the tip of the gas ejection nozzle as in the past, and particles and impurities in the quartz glass member are mixed into the steam gas. That is, in the conventional gas ejection nozzle in which a hydrogen gas and an oxygen gas are ejected from substantially the same position to form a flame, the tip of the entire gas ejection nozzle of the supply gas is melted, compared with the conventional gas ejection nozzle. Although it is possible to prevent the erosion and the like at the tip of the hydrogen gas ejection nozzle, it is estimated that the same phenomenon occurs at the tip of the oxygen gas ejection nozzle. Further, in the above-described proposed combustion device, the continuous outer peripheral portion of the gas ejection nozzle is covered with the heat insulating material at the tip of the gas supply pipe in the same manner as in the conventional combustion device shown in FIGS. It is difficult for heat from the flame to be released, and the temperature in the vicinity of the gas jet nozzle and the gas supply pipe near the gas jet nozzle is likely to be high. It is presumed that erosion at the tip or the like occurs. Furthermore,
As the heat insulating material, alumina-based or silica-based refractories are generally used, and these heat-insulating materials may be exposed to unexpectedly high temperatures, and impurities in the heat-insulating materials may diffuse to the adjacent nozzle members. It is presumed that this may also cause an increase in impurities.

[0008] First, the present inventors consider the problem of the content of impurities in the high-purity steam gas produced in the above-described combustion apparatus for producing high-purity steam and introduced into the oxidation treatment step of the semiconductor production process. The reduction of impurity content in steam gas was studied. For example, there is a method of purifying a member in which a nozzle constituent member is made of high-purity synthetic quartz glass from quartz glass, but there is a possibility that impurities may be diffused from the outside due to an increase in the temperature near the nozzle. Even when synthetic quartz glass is used, the fact that the quartz glass dissolves in the gas at the tip of the high-temperature gas ejection nozzle and reprecipitates in the low-temperature portion to generate particles is the same as a conventional quartz glass member. For this reason, the present inventors have intensively studied the gas supply pipe and the gas ejection nozzle of the combustion device in order to achieve a more fundamental solution in order to sufficiently reduce the content of impurities in the obtained steam gas. As a result, it has been found that the prevention of the gas supply pipe and the gas ejection nozzle from increasing the temperature significantly reduces the content of impurities, thereby completing the present invention.

[0009]

According to the present invention, there is provided a combustion apparatus for producing high-purity steam having a combustion chamber and a gas supply pipe comprising a hydrogen gas supply pipe and an oxygen gas supply pipe. There is provided a combustion apparatus for producing steam, comprising a erosion prevention mechanism at a nozzle tip.

In the combustion apparatus for producing high-purity steam of the present invention, the erosion prevention mechanism is a heat radiating means disposed at a gas ejection nozzle introduction portion of the gas supply pipe, and the heat radiating means is a gas supply pipe. It is preferable that the cooling unit is a quartz glass cooling unit that is formed between the hydrogen gas supply pipe and the oxygen gas supply pipe of the gas ejection nozzle introduction unit and that allows a cooling medium to flow therethrough. In addition to the above, it is preferable that a cooling section made of quartz glass, which is formed so as to allow a cooling medium to flow, is provided on the outer peripheral portion of the oxygen gas supply pipe. Further, at least the tip of the gas ejection nozzle of the gas supply pipe is made of quartz glass, and the temperature of the tip is 900 ° C.
It is preferable to provide a heat radiating means described below. Also,
The erosion prevention mechanism is such that the gas supply pipe is a triple pipe, and a supply pipe of hydrogen gas, an inert gas and an oxygen gas is formed from a central pipe, and a hydrogen gas supply pipe and an oxygen gas supply pipe are adjacent to each other. It is preferable that the flame is formed at a predetermined distance from the tip of the gas ejection nozzle without disposing the gas through an inert gas supply pipe. Furthermore, the erosion protection mechanism is characterized in that the gas supply pipe is a quadruple pipe, and an inert gas is provided from a central pipe;
A supply pipe for hydrogen gas, an inert gas and an oxygen gas, and a hydrogen gas supply pipe and an oxygen gas supply pipe arranged via an inert gas supply pipe without being adjacent to each other, and a predetermined distance from the tip of the gas ejection nozzle; It is preferable to form a flame with

According to the present invention, the gas supply pipe is heated by using the combustion apparatus for the high-purity steam production apparatus to preheat the flowing hydrogen gas and oxygen gas. And igniting the gas supply pipe to stop the heating of the gas supply pipe, and at the same time, radiates heat by the radiating means to burn hydrogen to generate steam. .

The apparatus for producing high-purity steam of the present invention is configured as described above, and supplies hydrogen and oxygen to the combustion chamber and causes the supplied gases to contact and burn.
(1) Since a heat radiating means such as a cooling chamber is provided at the gas ejection nozzle introduction portion of the gas supply pipe, the gas ejection nozzle introduction portion that ejects hydrogen and oxygen gas into the combustion chamber can be cooled and heated by the hydrogen combustion flame. The heat at the tip of the gas ejection nozzle can be dissipated in the cooling section, and the entire area of the gas ejection nozzle, particularly the tip, can be prevented from becoming hot, and melting damage can be suppressed. Also,
(2) Since the gas supply pipe is formed as a triple pipe or a quadruple pipe, and the supply pipes for the hydrogen gas and the oxygen gas are not adjacent to each other and the inert gas supply pipe is arranged between them, the hydrogen gas and the oxygen gas are used. Do not come into contact with each other immediately after being ejected from the gas ejection nozzle, and a hydrogen combustion flame is formed in the combustion chamber farther from the tip of the gas ejection nozzle. Is suppressed.

Further, the method for producing high-purity steam of the present invention comprises:
In the operation of the combustion apparatus for producing high-purity steam configured as described above, the gas supply pipe is heated at the start of the operation, and after the hydrogen and oxygen gases are preheated and ignited, the heating of the gas supply pipe is stopped. And, even if the tip of the gas ejection nozzle is heated by the combustion flame, the heat is radiated by the action of the cooling section provided at the tip of the gas ejection nozzle, the formation of the isolation of the flame, and the erosion prevention mechanism such as the use of no heat insulating material. Therefore, the temperature is not excessively increased. For this reason, in the present invention, excessive high-temperature heating of these gas ejection nozzles is prevented, and erosion of the quartz glass material as a constituent material can be suppressed. Can significantly reduce the content of impurities in the steam gas,
It is suitable as a high-purity steam gas required in a wafer oxidation process in a semiconductor manufacturing process.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. However, the present invention is not limited by the following examples. First, a first embodiment will be described. FIG. 1 is an explanatory view showing an outline of the structure of a combustion apparatus according to a first embodiment of the high-purity steam generator of the present invention, and FIG. 2 is an enlarged view of a portion A in FIG. 1 and 2, a main part of a combustion apparatus 1 includes a combustion chamber 2, a steam supply pipe 3 for supplying high-purity steam generated in the combustion chamber 2 to a wafer heat treatment furnace, and a combustion chamber 2.
And a gas supply pipe 4 for supplying a raw material gas to the fuel cell, and these main parts are formed of a quartz glass material as in the prior art. The gas supply pipe 4 is configured such that a hydrogen gas supply pipe 5 is disposed at a central portion, and an oxygen gas supply pipe 6 is disposed annularly on the outer periphery thereof. A hydrogen gas supply pipe 7 and an oxygen gas supply pipe 8 are connected to the hydrogen gas supply pipe 5 and the oxygen gas supply pipe 6, respectively. Further, a cooling device 9 such as a water-cooled cylinder is disposed on the outer peripheral portion of the combustion chamber 2, and the outer peripheral portion of the gas supply pipe 4 is used for heating the supplied hydrogen and oxygen gas to spontaneously ignite at the time of ignition. A preheating heater 10 is provided. These configurations are almost the same as those of the above-described conventional combustion device. After ignition, each gas supply amount is appropriately selected and controlled in accordance with combustion conditions such as a combustion apparatus and a nozzle size, and combustion by oxidation of hydrogen can generate high-purity steam. Supply to silicon wafer heat treatment process.

In the combustion apparatus 1 of the present invention, as shown in an enlarged view in FIG. 2, each gas ejection nozzle at the tip of the hydrogen gas supply pipe 5 and the oxygen gas supply pipe 6 of the gas supply pipe 4 made of quartz glass. Are cooling units 11 and 1 made of quartz glass, respectively.
2 are deployed. Cooling medium supply pipes 13 and 14 and cooling medium discharge pipes 15 and 16 are provided in the cooling sections 11 and 12, respectively, and a cooling medium such as water, N2, and Ar is supplied to each cooling section to cool the nozzle tip. It is configured so that it can be cooled by a medium. The cooling section 11 provided in an annular shape at the inner peripheral portion at the tip of the hydrogen gas supply pipe 5 has a tip portion of the hydrogen gas supply pipe 5 having a small diameter, and a supply pipe 13 and a discharge pipe 14 for a cooling medium provided at the thinned outer ring. Deployed and formed. Further, the cooling part 12 at the tip of the nozzle of the oxygen gas supply pipe 6 is formed by arranging an annular pipe at the outer periphery of the tip of the supply pipe 6. In FIG. 2, the cooling units are respectively provided on the outer circumferences of the hydrogen and oxygen gas supply pipes, but between the hydrogen gas supply pipe 5 and the oxygen gas supply pipe 6, that is, the hydrogen gas supply pipe 5 It is also possible to dispose only the cooling unit 11 formed by the outer peripheral wall and the inner peripheral wall of the oxygen gas supply pipe 6 to share the cooling unit, and to cool both hydrogen and oxygen gas through each peripheral wall. By cooling the nozzle tip of each gas supply pipe in this way, it is possible to directly radiate the heat at the nozzle tip which tends to be heated to a high temperature when hydrogen gas and oxygen gas are burned. Further, the diameter of the end portion of the hydrogen gas supply pipe 5 is reduced, and the flow rate of the hydrogen gas can be increased. On the other hand, the oxygen gas supply pipe is formed straight, and the oxygen gas can be ejected linearly. The nozzle tip is not excessively heated. Therefore, devitrification at the nozzle tip and overheating in the combustion chamber can be prevented, a large amount of high-purity water vapor can be generated by hydrogen gas combustion, and an oxide film can be formed on a large-diameter semiconductor silicon wafer substrate. Can be fully supported. The method of disposing each cooling chamber is not particularly limited to the above, and it is sufficient that the distal end of each gas supply pipe can be cooled in a predetermined manner.

Next, a second embodiment will be described. FIG. 3 is an explanatory diagram showing an outline of the structure of a combustion apparatus according to a second embodiment of the high-purity steam generator of the present invention,
FIG. 4 is an enlarged view of an end portion taken along a line BB in FIG. In FIG. 3, the combustion device 31 has a gas supply pipe 34
It is the same as the combustion device of FIG. 1 except that it is formed in a heavy circular tube. 3, the same members as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. Gas supply pipe 34 different from FIG.
Is provided with a hydrogen gas supply pipe 35 in the center, a double annular pipe provided on the outer periphery thereof, and an oxygen gas supply pipe 36 on the outside.
An inert gas gas supply pipe 39 is disposed inside. The hydrogen gas supply pipe 35, the oxygen gas supply pipe 36, and the inert gas supply pipe 39 have a hydrogen gas introduction pipe 37,
The oxygen gas introduction pipe 38 and the inert gas introduction pipe 40 are respectively connected. As shown in an enlarged cross-sectional end in FIG. 4, the triple circular pipe of the gas supply pipe 34 is formed concentrically. As described above, as a triple circular tube, the supply of hydrogen gas and oxygen gas is burned through an inert gas such as nitrogen gas, helium, or argon gas, so that the hydrogen gas and oxygen gas are generated immediately after the nozzle tip. The combustion flame is formed by contact at a remote position without contact. Therefore, it is possible to prevent the end of the nozzle from becoming hot and devitrifying, thereby shortening the durability. As the inert gas, nitrogen gas, helium, argon gas and the like are generally used. Among them, argon gas is suitable because high-purity gas can be obtained relatively inexpensively and has good thermal conductivity.

FIG. 5 is an explanatory view showing an outline of the structure of a combustion apparatus according to a second other embodiment of the present invention, and FIG. 6 is an enlarged view of an end portion taken along the line CC in FIG. It is. 5 and 6, the combustion apparatus 51 is the same as the combustion apparatus of FIG. 3 except that the gas supply pipe 54 is formed as a concentric quadruple pipe. 5, the same members as those in FIG. 3 are denoted by the same reference numerals, and description thereof will be omitted. In the quadruple gas supply pipe 54, an inert gas supply pipe 59 is disposed at the center, and an oxygen gas supply pipe 56, an inert gas supply pipe 60, and a hydrogen gas supply A tube 55 is arranged. The inert gas supply pipe 59, the hydrogen gas supply pipe 55, the inert gas supply pipe 60, and the oxygen gas supply pipe 56 have an inert gas introduction pipe 61, a hydrogen gas introduction pipe 57, an oxygen gas introduction pipe 58, and an inert gas supply pipe, respectively. The gas introduction pipes 62 are respectively connected. When the gas supply pipe 54 is a quadruple pipe, a flame can be formed at a position away from the nozzle tip similarly to the above-mentioned triple pipe nozzle, and the dissolution due to devitrification at the nozzle tip can be prevented. In addition to improving the durability, the temperature of the flame formed by combustion can be controlled by appropriately selecting the amount of the outflow of the inert gas from the center and flowing out, thereby further preventing overheating of the combustion chamber. be able to.

In any of the above-described second embodiments, when the hydrogen and oxygen gas supplied by the preheater 10 provided on the outer peripheral portion of the gas supply pipe 34 or 54 are heated and spontaneously ignited, during the ignition sequence, Then, the supply of the inert gas to the inert gas supply pipes 39, 59, and 60 is ignited by decreasing or stopping the flow rate, and after the ignition, according to the combustion conditions such as the capacity of the combustion device used and the size of the nozzle. It is preferable that the flow rates of the inert gas and the flow rates of the hydrogen gas and the oxygen gas are appropriately selected and supplied to predetermined amounts, and then flow out from the nozzles.
Further, it is preferable that the flame state is detected by a flame sensor, and the amount of each supplied gas is controlled so as to always maintain a stable flame state. In addition, by detecting the flame sensor, when the flame is extinguished, the supply of the hydrogen gas and the oxygen gas is stopped, and only the inert gas is supplied to stop the combustion. Further, in the present invention, a cooling unit is provided in a predetermined manner at the tip of each gas supply pipe of the gas supply pipe of the multi-circular pipe of the second embodiment, similarly to the first embodiment of the present invention. Each supply gas is cooled and discharged from the nozzle, so that overheating of the combustion chamber can be further prevented. In this case, the arrangement of the cooling unit is not limited. For example, as in the system of FIG. The cooling unit can be provided by a method in which the tip of the hydrogen gas supply pipe 5 is made thinner.

When the tip of the gas ejection nozzle of the gas supply pipe is made of quartz glass, a cooling unit may be provided in a predetermined manner so that the temperature of the tip is 900 ° C. or less, and cooling is performed. preferable. Preferably, the cooling is performed at 700 ° C. or lower, more preferably at 500 ° C. or lower.

Further, in the combustion apparatus for producing high-purity steam of the present invention, the surface of the quartz glass material mainly forming the apparatus is treated with hydrofluoric acid, treated with high-temperature hydrogen chloride gas, or a combination thereof. By doing so, metal impurities such as sodium, iron, copper, and aluminum near the surface at a depth of about 100 μm from the surface are reduced to 10 ng /
g or less, or a synthetic quartz glass material having a high bulk purity of 10 ng / g or less in metal impurities is used in consideration of the possibility of erosion due to hydrogen gas supplied to the combustion device or generated steam. Is more preferable. Since the content of the above metal impurities in steam produced by a combustion apparatus for producing high-purity steam using these high-purity quartz glass materials is 10 ng / m 3 or less,
It can be used when higher purity steam is required.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to embodiments. However, the present invention is not limited by the following examples. Example 1 Using a combustion apparatus configured in the same manner as in FIG. 1 described above, a hydrogen gas was supplied to the hydrogen gas supply pipe 5 at a flow rate of 6 L / min, and an oxygen gas was supplied to the oxygen gas supply pipe 6 at a flow rate of 5 L / min. The gas was discharged from the front end, and the gas supply pipe 4 was heated to 950 ° C. by the preheater 10 and ignited in the combustion chamber 2 and burned for 1 hour. In this case, the cooling units 11, 1
2 from the cooling medium supply pipes 13 and 14 respectively.
° C water is flowed at a flow rate of 1 liter / min and discharged from the cooling medium discharge pipes 15 and 16, and the ends of the hydrogen gas supply pipe 5 and the oxygen gas supply pipe 6 are cooled to about 50 ° C. 9 was circulated with the same water. Thus, in the combustion chamber 2, steam gas was generated by the oxidation reaction (combustion) of hydrogen. The amount of impurities in the steam gas flowing out of the steam supply pipe 3 was measured. The results are shown in Table 1.

Example 2 Using the same combustion apparatus as in Example 1, hydrogen combustion was performed in exactly the same manner as above except that heating of the preheating heater 10 was stopped after ignition and the cooling effect was further enhanced. The amount of impurities in the steam gas was measured. The results are shown in Table 1.

Embodiment 3 Using the same combustion apparatus as in Embodiment 1, using a cooling medium of argon, a cooling unit 11 for hydrogen gas and a cooling unit 1 for oxygen gas
2, hydrogen combustion was carried out in exactly the same manner, except that the preheating heater was continued, except that the gas flowed at a flow rate of 3 liters / minute through the cooling medium supply pipes 13 and 14, respectively.
The amount of impurities in the generated steam gas was measured. The results are shown in Table 1.

[0024]

[Table 1]

Example 4 Hydrogen combustion was performed in exactly the same manner as in Example 3 except that the heating of the preheating heater 10 was stopped and the cooling effect was further enhanced, and the amount of impurities in the generated steam gas was measured. The results are shown in Table 1.

Comparative Example 1 The same apparatus as in Example 1 was used, except that a heat insulating material was provided at the tip of the gas supply pipe 4 in the same manner as in the above-described conventional method without flowing a cooling medium through the cooling units 11 and 12. , Hydrogen combustion was performed in the same manner as in Example 1, and the content of impurities in the generated steam gas was measured. The results are shown in Table 1.

COMPARATIVE EXAMPLE 2 The combustion apparatus is substantially the same as the combustion apparatus shown in FIGS. 8 and 9 except that the oxygen gas ejection nozzle protrudes from the tip of the hydrogen gas ejection nozzle toward the combustion chamber, and a plurality of gas dispersion holes are formed. Using the dispersed oxygen gas ejection nozzle, hydrogen combustion was performed in the same manner as in Example 1, and the content of impurities in the generated steam gas was measured. The results are shown in Table 1.

According to the above Examples 1 to 4 and Comparative Examples 1 and 2, the cooling section is provided at the tip of the gas supply pipe to cool the hydrogen gas and the oxygen gas. It is clear that the content is significantly reduced as compared with the steam gas obtained by the conventional combustion device. Also from this point, it can be seen that in the combustion apparatus in which the cooling means is provided in the gas ejection nozzle area at the tip of the gas supply pipe according to the present invention, the erosion at the tip of the gas ejection nozzle is significantly suppressed.

Embodiment 5 Using a combustion apparatus constructed in the same manner as in FIG. 3, hydrogen gas was supplied to the hydrogen gas supply pipe 35 at 2 liter / minute, and oxygen gas was supplied to the oxygen gas supply pipe 36 at 2 liter / minute. Further, argon gas is passed through the inert gas supply pipe 39 at a flow rate of 5 liters / minute to flow out from the tip of the gas ejection nozzle, and the preheater 10
The gas supply pipe 34 was heated to 950 ° C. to ignite in the combustion chamber 2 and burned for 1 hour. In this case, water at 15 ° C. was passed through the water-cooled cylinder 9. In this way,
In the combustion chamber 2, a steam gas was generated by an oxidation reaction (combustion) of hydrogen. The amount of impurities in the steam gas flowing out of the steam supply pipe 3 was measured. The results are shown in Table 2. Further, the measurement point a (in the vicinity of the nozzle) shown in FIG.
And b (the inner surface of the top plate just above the flame). The results are shown in Table 2.

[0030]

[Table 2]

Embodiment 6 Using a combustion apparatus provided with a quadruple gas supply pipe constructed in the same manner as in FIG. Oxygen gas 2
Argon was flowed at 0.5 liter / minute through the inert gas supply pipes 29 and 30 at 0.5 liter / minute, respectively, and allowed to flow out from the tip of the gas ejection nozzle. Was heated and ignited in the combustion chamber 2. Thereafter, the heating of the preheater 10 is continued as it is, and the hydrogen gas is supplied at a rate of 2 liters / minute and the oxygen gas is supplied at a rate of 2 liters / minute.
The gas was burned at a rate of 5 liters / minute at a rate of 5 liters / minute, and the flow rate was controlled at 5 liters / minute. The amount of impurities in the steam gas flowing out was measured in the same manner as in Example 5. The results are shown in Table 2. The temperature was measured at the measurement points a (near the nozzle) and b (the inner surface of the top plate immediately above the flame) shown in FIG. 5 in the combustion chamber 2. The results are shown in Table 2.

Example 7 The combustion of hydrogen gas was carried out in the same manner as in Example 6, except that the heating of the preheater 10 was stopped after ignition, and the content of impurities in the outflowing steam gas was measured in the same manner. It was shown to.
In addition, temperature measurements at the measurement points a and b shown in FIG. 5 in the combustion chamber 2 were performed in the same manner, and the results are shown in Table 2.

COMPARATIVE EXAMPLE 3 In the conventional general structure shown in FIGS. 8 and 9, a double gas supply pipe is provided, a combustion device 71 is used, and a hydrogen gas supply pipe 55 and an oxygen gas supply pipe 76 are used. The gas supply pipe was heated by the preheater 80 and ignited in the combustion chamber 2 as in Example 5.
Thereafter, the heating of the preheater 80 was continued as it was, and the hydrogen gas and the oxygen gas were controlled at a flow rate of 2 liter / min and 2 liter / min, respectively, and burned for one hour. The amount of impurities in the steam gas flowing out was measured in the same manner as in Example 5. The results are shown in Table 2. The temperature was measured at the measurement points a (near the nozzle) and b (the inner surface of the top plate immediately above the flame) shown in FIG. The results are shown in Table 2.

COMPARATIVE EXAMPLE 4 This is substantially the same as the combustion apparatus shown in FIGS. 8 and 9 except that the oxygen gas ejection nozzle projects from the tip of the hydrogen gas ejection nozzle toward the combustion chamber, and a plurality of gas dispersion holes are formed. Using the dispersed oxygen gas ejection nozzle, hydrogen combustion was performed in the same manner as in Comparative Example 3, and the content of impurities in the generated steam gas was measured. The results are shown in Table 1. The temperature was measured at a point near the nozzle (point a) in the combustion chamber 72 shown in FIG. 8 and at an inner surface of the top plate immediately above the flame (point b). The results are shown in Table 2.

As is clear from the above Examples 5 to 7 and Comparative Examples 3 and 4, the hydrogen gas supply pipe and the oxygen gas supply pipe of the gas supply pipe according to the present invention were connected via an inert gas supply pipe without being adjacent to each other. It is formed in a triple or quadruple tube and arranged in a predetermined manner. The contact between the hydrogen gas and the oxygen gas immediately after the tip of the gas ejection nozzle in the combustion chamber is suppressed, and the combustion flame is formed at a predetermined interval. It can be seen that the formation of the gas significantly reduces the content of impurities in the generated and discharged steam gas.
From this point, it can also be seen that in the combustion apparatus in which the cooling means is provided in the gas ejection nozzle area at the tip of the gas supply pipe according to the present invention, the erosion at the tip of the gas ejection nozzle is significantly suppressed. Further, it can be seen that the temperature in the combustion chamber also decreases.

Next, the degree of wear (etching) due to the temperature of the quartz glass was verified. This verification result is shown in FIG. FIG. 7 is a diagram showing the relationship between the temperature of quartz glass and the amount of consumption (etching), in which the horizontal axis represents the temperature of quartz glass,
The vertical axis shows the ratio of the amount of etching at each temperature when the amount of etching of quartz glass at 300 ° C. with hydrogen is set to 1. The temperature at the tip of the conventional gas ejection nozzle is 1000 ° C. or higher. As is apparent from this figure, quartz glass having an etching amount of 20 times or more the etching amount at 300 ° C. is etched. By setting the temperature at the tip of the gas ejection nozzle to 900 ° C. or less, the etching amount at 300 ° C. can be suppressed to 10 times or less.
5 times or less of the etching amount of
By controlling the temperature to 500 ° C. or lower, the amount of etching at 300 ° C. can be suppressed to the same amount. Therefore, in the present invention, the temperature of the tip of the gas ejection nozzle made of quartz glass is 900 ° C. or less, preferably 700 ° C. or less,
It has been found that cooling to 500 ° C. or less is more preferable.

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[Procedure amendment]

[Submission date] May 15, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction contents]

[Document Name] Statement

Patent application title: Combustion apparatus for producing high-purity steam and method for producing high-purity steam

[Claims]

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion apparatus for producing high-purity steam and a method for producing high-purity steam, and more particularly to a combustion apparatus for producing high-purity steam gas used in an oxidation step of a semiconductor production process. The present invention relates to a combustion apparatus for producing high-purity steam and a method for producing high-purity steam, which prevents erosion of a gas ejection nozzle, reduces impurities in generated steam gas, and has excellent durability.

[0002]

2. Description of the Related Art In an oxide film forming step of a semiconductor manufacturing process, there is a method of contacting a wafer with a high-temperature steam gas as one of the oxide film forming methods. It is desired that the steam gas used for forming the oxide film has a high purity in which impurities such as alkali metals contaminating the semiconductor wafer are reduced as much as possible. Generally, a high-purity hydrogen gas and an oxygen gas are brought into contact with each other to form a hydrogen gas. It is manufactured by burning gas. As a method of burning hydrogen gas, for example, as disclosed in JP-A-56-62326, a wafer to be oxidized is set in a heating furnace, and hydrogen gas and oxygen gas are directly introduced into the heating furnace. There is a method of generating steam by burning. But,
This method has a problem that the temperature in the heating furnace is affected by the flame and it is difficult to keep the oxidation treatment conditions constant.

In order to solve the above problem, for example, Japanese Patent Application Laid-Open
As disclosed in Japanese Patent Application Laid-Open No. 7-18328, a method is provided in which a combustion device is provided outside the wafer oxidation furnace to burn hydrogen gas to generate steam, and the obtained steam gas is introduced into the furnace. was suggested. In the case of producing steam gas by this external combustion method, since the oxidation treatment conditions in the semiconductor manufacturing process are stable, this method is widely used at present. This external combustion type hydrogen gas combustion device is usually
For example, as shown schematically in FIG. 8 and an enlarged cross-sectional end view taken along the line DD in FIG. 9, high-purity steam generated in the combustion chamber 72 and the combustion chamber 72 is supplied to an external wafer heat treatment furnace or the like. It has a water supply pipe 73 for supplying water and a gas supply pipe 74 for supplying hydrogen and oxygen gas, and is mainly made of quartz glass. A cooling device 79 such as a water-cooled cylinder is provided on the outer periphery of the combustion chamber 72, and an ignition device for heating the hydrogen and oxygen gas supplied at the time of start to spontaneously ignite is provided on the outer periphery of the gas supply pipe 74. Preheating heater 8
0 is provided. The gas supply pipe 74 is composed of a double circular pipe, a hydrogen gas supply pipe 75 is arranged in the center, an oxygen gas supply pipe 76 is annularly arranged on the outer periphery thereof, and a hydrogen gas supply pipe 7 is formed.
The hydrogen gas supply pipe 77 and the oxygen gas supply pipe 78 are connected to the fifth gas supply pipe and the oxygen gas supply pipe 76, respectively. Further, a gas ejection nozzle is provided continuously at the distal end of the gas supply pipe 74, and a heat insulating material 81 is generally provided on the outer peripheral portion of the distal end of the gas supply pipe 74. The hydrogen gas and the oxygen gas are heated by the heater 80 for preheating, are jetted from the gas jet nozzle into the combustion chamber, come into contact in the combustion chamber, spontaneously ignite, and then oxidize and burn the hydrogen gas to produce steam.

[0004] The combustion device configured as described above is generally formed of quartz glass material as described above. In this case, in particular, there is a problem that the tip of the gas ejection nozzle is melted and consumed due to the high temperature during combustion, and the tip of the gas ejection nozzle and the inner wall of the combustion chamber are crystallized, separated, dropped, and damaged. These are not only the durability problem that the life of the combustion device that generates steam is short, but also the particles generated by the above-mentioned melting and the like and impurities in the quartz glass material are mixed in the generated steam gas. The semiconductor silicon wafer to be oxidized may be contaminated. For this reason, it eventually causes a reduction in the yield of semiconductor device manufacturing in a semiconductor manufacturing process using these water vapors. In addition, with the recent increase in the diameter of semiconductor wafers, it is desired to increase the amount of steam production. For this reason, increasing the supply gas amount requires increasing the temperature of the tip of the gas ejection nozzle and the combustion chamber. Therefore, it is difficult to implement the method because the erosion at the nozzle tip is further increased.

As a method for solving the above-mentioned problem of the external combustion system, for example, in Japanese Patent Application Laid-Open No. Hei 6-267932, an oxygen gas ejection nozzle is made to protrude inward in a combustion chamber (vessel) from a hydrogen gas ejection nozzle tip, and A dispersive oxygen gas ejection nozzle having a plurality of ejection holes for dispersing and ejecting oxygen gas in a wide range has been proposed. This method has a double circular pipe structure (a hydrogen gas is supplied to the center pipe and an oxygen gas is supplied to the outer pipe) which is generally used in the conventional external combustion type gas supply pipe described in Japanese Patent Publication No. Sho 63-60528. A) farther away from the hydrogen gas jet nozzle,
In addition, by blowing oxygen gas over a wide range, a thick flame is formed at the oxygen gas ejection nozzle portion. As a result, as compared with the conventional gas ejection nozzle, the tip of the hydrogen gas ejection nozzle is not heated, and the temperature in the combustion chamber can be prevented from becoming high. Therefore, a larger amount of high-purity steam gas can be produced by increasing the supply amounts of hydrogen and oxygen gas than before, and the amount of steam gas produced for the oxidation treatment of a semiconductor wafer having a large diameter is increased.

[0006]

According to the combustion apparatus in which the gas ejection nozzle proposed above is improved, a large amount of high-purity steam gas required for stabilizing an oxidation process in a semiconductor manufacturing process and processing a large-diameter wafer is provided. Thus, problems such as durability of the combustion device are solved. However, according to the inventors,
It has been found that, despite the lowering of the combustion chamber temperature, the impurity content level in the steam gas does not decrease to a sufficiently satisfactory level. That is, as shown in a comparative example described later, even in the above-described proposed combustion apparatus, compared with the above-described conventional gas ejection nozzle composed of a double pipe gas supply pipe, impurities in the produced steam gas are different. It was confirmed that the contents were almost the same.

In the combustion apparatus proposed in Japanese Patent Application Laid-Open No. 6-267932, the reason why the content of impurities in the steam gas does not decrease as expected is that the temperature near the hydrogen gas ejection nozzle drops and the combustion chamber (vessel) Although the temperatures of the upper part and the outer periphery also decrease, the flame having the highest temperature in the combustion chamber is formed near the oxygen gas ejection nozzle as described above. It is presumed that the quartz glass material is melted and damaged at the tip of the gas ejection nozzle as in the past, and particles and impurities in the quartz glass member are mixed into the steam gas. That is, in the conventional gas ejection nozzle in which a hydrogen gas and an oxygen gas are ejected from substantially the same position to form a flame, the tip of the entire gas ejection nozzle of the supply gas is melted, compared with the conventional gas ejection nozzle. Although it is possible to prevent the erosion and the like at the tip of the hydrogen gas ejection nozzle, it is estimated that the same phenomenon occurs at the tip of the oxygen gas ejection nozzle. Further, in the above-described proposed combustion device, the continuous outer peripheral portion of the gas ejection nozzle is covered with the heat insulating material at the tip of the gas supply pipe in the same manner as the conventional combustion device shown in FIGS. It is difficult for heat from the flame to be released, and the temperature in the vicinity of the gas jet nozzle and the gas supply pipe near the gas jet nozzle is likely to be high. It is presumed that erosion at the tip or the like occurs. Furthermore,
As the heat insulating material, alumina-based or silica-based refractories are generally used, and these heat-insulating materials may be exposed to unexpectedly high temperatures, and impurities in the heat-insulating materials may diffuse to the adjacent nozzle members. It is presumed that this may also cause an increase in impurities.

[0008] First, the present inventors consider the problem of the content of impurities in the high-purity steam gas produced in the above-described combustion apparatus for producing high-purity steam and introduced into the oxidation treatment step of the semiconductor production process. The reduction of impurity content in steam gas was studied. For example, there is a method of purifying a member in which a nozzle constituent member is made of high-purity synthetic quartz glass from quartz glass, but there is a possibility that impurities may be diffused from the outside due to an increase in the temperature near the nozzle. Even when synthetic quartz glass is used, the fact that the quartz glass dissolves in the gas at the tip of the high-temperature gas ejection nozzle and reprecipitates in the low-temperature portion to generate particles is the same as a conventional quartz glass member. For this reason, the present inventors have intensively studied the gas supply pipe and the gas ejection nozzle of the combustion device in order to achieve a more fundamental solution in order to sufficiently reduce the content of impurities in the obtained steam gas. As a result, it has been found that the prevention of the gas supply pipe and the gas ejection nozzle from increasing the temperature significantly reduces the content of impurities, thereby completing the present invention.

[0009]

According to the present invention, there is provided a combustion apparatus for producing high-purity steam having a combustion chamber and a gas supply pipe comprising a hydrogen gas supply pipe and an oxygen gas supply pipe. There is provided a combustion apparatus for producing steam, comprising a erosion prevention mechanism at a nozzle tip.

In the combustion apparatus for producing high-purity steam of the present invention, the erosion prevention mechanism is a heat radiating means disposed at a gas ejection nozzle introduction portion of the gas supply pipe, and the heat radiating means is a gas supply pipe. It is preferable that the cooling unit is a quartz glass cooling unit that is formed between the hydrogen gas supply pipe and the oxygen gas supply pipe of the gas ejection nozzle introduction unit and that allows a cooling medium to flow therethrough. In addition to the above, it is preferable that a cooling section made of quartz glass, which is formed so as to allow a cooling medium to flow, is provided on the outer peripheral portion of the oxygen gas supply pipe. Further, at least the tip of the gas ejection nozzle of the gas supply pipe is made of quartz glass, and the temperature of the tip is 900 ° C.
It is preferable to provide a heat radiating means described below. Also,
The erosion prevention mechanism is such that the gas supply pipe is a triple pipe, and a supply pipe of hydrogen gas, an inert gas and an oxygen gas is formed from a central pipe, and a hydrogen gas supply pipe and an oxygen gas supply pipe are adjacent to each other. It is preferable that the flame is formed at a predetermined distance from the tip of the gas ejection nozzle without disposing the gas through an inert gas supply pipe. Furthermore, the erosion protection mechanism is characterized in that the gas supply pipe is a quadruple pipe, and an inert gas is provided from a central pipe;
A supply pipe for hydrogen gas, an inert gas and an oxygen gas, and a hydrogen gas supply pipe and an oxygen gas supply pipe arranged via an inert gas supply pipe without being adjacent to each other, and a predetermined distance from the tip of the gas ejection nozzle; It is preferable to form a flame with

According to the present invention, the gas supply pipe is heated by using the combustion apparatus for the high-purity steam production apparatus to preheat the flowing hydrogen gas and oxygen gas. And igniting the gas supply pipe to stop the heating of the gas supply pipe, and at the same time, radiates heat by the radiating means to burn hydrogen to generate steam. .

The apparatus for producing high-purity steam of the present invention is configured as described above, and supplies hydrogen and oxygen to the combustion chamber and causes the supplied gases to contact and burn.
(1) Since a heat radiating means such as a cooling chamber is provided at the gas ejection nozzle introduction portion of the gas supply pipe, the gas ejection nozzle introduction portion that ejects hydrogen and oxygen gas into the combustion chamber can be cooled and heated by the hydrogen combustion flame. The heat at the tip of the gas ejection nozzle can be dissipated in the cooling section, and the entire area of the gas ejection nozzle, particularly the tip, can be prevented from becoming hot, and melting damage can be suppressed. Also,
(2) Since the gas supply pipe is formed as a triple pipe or a quadruple pipe, and the supply pipes for the hydrogen gas and the oxygen gas are not adjacent to each other and the inert gas supply pipe is arranged between them, the hydrogen gas and the oxygen gas are used. Do not come into contact with each other immediately after being ejected from the gas ejection nozzle, and a hydrogen combustion flame is formed in the combustion chamber farther from the tip of the gas ejection nozzle. Is suppressed.

Further, the method for producing high-purity steam of the present invention comprises:
In the operation of the combustion apparatus for producing high-purity steam configured as described above, the gas supply pipe is heated at the start of the operation, and after the hydrogen and oxygen gases are preheated and ignited, the heating of the gas supply pipe is stopped. And, even if the tip of the gas ejection nozzle is heated by the combustion flame, the heat is radiated by the action of the cooling section provided at the tip of the gas ejection nozzle, the formation of the isolation of the flame, and the erosion prevention mechanism such as the use of no heat insulating material. Therefore, the temperature is not excessively increased. For this reason, in the present invention, excessive high-temperature heating of these gas ejection nozzles is prevented, and erosion of the quartz glass material as a constituent material can be suppressed. Can significantly reduce the content of impurities in the steam gas,
It is suitable as a high-purity steam gas required in a wafer oxidation process in a semiconductor manufacturing process.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. However, the present invention is not limited by the following examples. First, a first embodiment will be described. FIG. 1 is an explanatory view showing an outline of the structure of a combustion apparatus according to a first embodiment of the high-purity steam generator of the present invention, and FIG. 2 is an enlarged view of a portion A in FIG. 1 and 2, a main part of a combustion apparatus 1 includes a combustion chamber 2, a steam supply pipe 3 for supplying high-purity steam generated in the combustion chamber 2 to a wafer heat treatment furnace, and a combustion chamber 2.
And a gas supply pipe 4 for supplying a raw material gas to the fuel cell, and these main parts are formed of a quartz glass material as in the prior art. The gas supply pipe 4 is configured such that a hydrogen gas supply pipe 5 is disposed at a central portion, and an oxygen gas supply pipe 6 is disposed annularly on the outer periphery thereof. A hydrogen gas supply pipe 7 and an oxygen gas supply pipe 8 are connected to the hydrogen gas supply pipe 5 and the oxygen gas supply pipe 6, respectively. Further, a cooling device 9 such as a water-cooled cylinder is disposed on the outer peripheral portion of the combustion chamber 2, and the outer peripheral portion of the gas supply pipe 4 is used for heating the supplied hydrogen and oxygen gas to spontaneously ignite at the time of ignition. A preheating heater 10 is provided. These configurations are almost the same as those of the above-described conventional combustion device. After ignition, each gas supply amount is appropriately selected and controlled in accordance with combustion conditions such as a combustion apparatus and a nozzle size, and combustion by oxidation of hydrogen can generate high-purity steam. Supply to silicon wafer heat treatment process.

In the combustion apparatus 1 of the present invention, as shown in an enlarged view in FIG. 2, each gas ejection nozzle at the tip of the hydrogen gas supply pipe 5 and the oxygen gas supply pipe 6 of the gas supply pipe 4 made of quartz glass. Are cooling units 11 and 1 made of quartz glass, respectively.
2 are deployed. The cooling units 11 and 12 are provided with cooling medium supply pipes 13 and 14 and cooling medium discharge pipes 15 and 16, respectively, and supply a cooling medium such as water, N ₂ , or Ar to each cooling unit to make the nozzle tip. It is configured so that it can be cooled by a cooling medium. The cooling section 11 provided in an annular shape at the inner peripheral portion at the tip of the hydrogen gas supply pipe 5 has a tip portion of the hydrogen gas supply pipe 5 having a small diameter, and a supply pipe 13 and a discharge pipe 14 for a cooling medium provided at the thinned outer ring. Deployed and formed. Further, the cooling part 12 at the tip of the nozzle of the oxygen gas supply pipe 6 is formed by arranging an annular pipe at the outer periphery of the tip of the supply pipe 6. In FIG. 2, the cooling units are respectively provided on the outer circumferences of the hydrogen and oxygen gas supply pipes, but between the hydrogen gas supply pipe 5 and the oxygen gas supply pipe 6, that is, the hydrogen gas supply pipe 5 It is also possible to dispose only the cooling unit 11 formed by the outer peripheral wall and the inner peripheral wall of the oxygen gas supply pipe 6 to share the cooling unit, and to cool both hydrogen and oxygen gas through each peripheral wall. By cooling the nozzle tip of each gas supply pipe in this way, it is possible to directly radiate the heat at the nozzle tip which tends to be heated to a high temperature when hydrogen gas and oxygen gas are burned. Further, the diameter of the end portion of the hydrogen gas supply pipe 5 is reduced, and the flow rate of the hydrogen gas can be increased. On the other hand, the oxygen gas supply pipe is formed straight, and the oxygen gas can be ejected linearly. The nozzle tip is not excessively heated. Therefore, devitrification at the nozzle tip and overheating in the combustion chamber can be prevented, a large amount of high-purity water vapor can be generated by hydrogen gas combustion, and an oxide film can be formed on a large-diameter semiconductor silicon wafer substrate. Can be fully supported. The method of disposing each cooling chamber is not particularly limited to the above, and it is sufficient that the distal end of each gas supply pipe can be cooled in a predetermined manner.

Next, a second embodiment will be described. FIG. 3 is an explanatory diagram showing an outline of the structure of a combustion apparatus according to a second embodiment of the high-purity steam generator of the present invention,
FIG. 4 is an enlarged view of an end portion taken along a line BB in FIG. In FIG. 3, the combustion device 31 has a gas supply pipe 34
It is the same as the combustion device of FIG. 1 except that it is formed in a heavy circular tube. 3, the same members as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. Gas supply pipe 34 different from FIG.
Is provided with a hydrogen gas supply pipe 35 in the center, a double annular pipe provided on the outer periphery thereof, and an oxygen gas supply pipe 36 on the outside.
An inert gas gas supply pipe 39 is disposed inside. The hydrogen gas supply pipe 35, the oxygen gas supply pipe 36, and the inert gas supply pipe 39 have a hydrogen gas introduction pipe 37,
The oxygen gas introduction pipe 38 and the inert gas introduction pipe 40 are respectively connected. As shown in an enlarged cross-sectional end in FIG. 4, the triple circular pipe of the gas supply pipe 34 is formed concentrically. As described above, as a triple circular tube, the supply of hydrogen gas and oxygen gas is burned through an inert gas such as nitrogen gas, helium, or argon gas, so that the hydrogen gas and oxygen gas are generated immediately after the nozzle tip. The combustion flame is formed by contact at a remote position without contact. Therefore, it is possible to prevent the end of the nozzle from becoming hot and devitrifying, thereby shortening the durability. As the inert gas, nitrogen gas, helium, argon gas and the like are generally used. Among them, argon gas is suitable because high-purity gas can be obtained relatively inexpensively and has good thermal conductivity.

FIG. 5 is an explanatory view showing an outline of the structure of a combustion apparatus according to a second other embodiment of the present invention, and FIG. 6 is an enlarged view of an end portion taken along the line CC in FIG. It is. 5 and 6, the combustion apparatus 51 is the same as the combustion apparatus of FIG. 3 except that the gas supply pipe 54 is formed as a concentric quadruple pipe. 5, the same members as those in FIG. 3 are denoted by the same reference numerals, and description thereof will be omitted. In the quadruple gas supply pipe 54, an inert gas supply pipe 59 is disposed at the center, and an oxygen gas supply pipe 56, an inert gas supply pipe 60, and a hydrogen gas supply A tube 55 is arranged. The inert gas supply pipe 59, the hydrogen gas supply pipe 55, the inert gas supply pipe 60, and the oxygen gas supply pipe 56 have an inert gas introduction pipe 61, a hydrogen gas introduction pipe 57, an oxygen gas introduction pipe 58, and an inert gas supply pipe, respectively. The gas introduction pipes 62 are respectively connected. When the gas supply pipe 54 is a quadruple pipe, a flame can be formed at a position away from the nozzle tip similarly to the above-mentioned triple pipe nozzle, and the dissolution due to devitrification at the nozzle tip can be prevented. In addition to improving the durability, the temperature of the flame formed by combustion can be controlled by appropriately selecting the amount of the outflow of the inert gas from the center and flowing out, thereby further preventing overheating of the combustion chamber. be able to.

In any of the above-described second embodiments, when the hydrogen and oxygen gas supplied by the preheater 10 provided on the outer peripheral portion of the gas supply pipe 34 or 54 are heated and spontaneously ignited, during the ignition sequence, Then, the supply of the inert gas to the inert gas supply pipes 39, 59, and 60 is ignited by decreasing or stopping the flow rate, and after the ignition, according to the combustion conditions such as the capacity of the combustion device used and the size of the nozzle. It is preferable that the flow rates of the inert gas and the flow rates of the hydrogen gas and the oxygen gas are appropriately selected and supplied to predetermined amounts, and then flow out from the nozzles.
Further, it is preferable that the flame state is detected by a flame sensor, and the amount of each supplied gas is controlled so as to always maintain a stable flame state. In addition, by detecting the flame sensor, when the flame is extinguished, the supply of the hydrogen gas and the oxygen gas is stopped, and only the inert gas is supplied to stop the combustion. Further, in the present invention, a cooling unit is provided in a predetermined manner at the tip of each gas supply pipe of the gas supply pipe of the multi-circular pipe of the second embodiment, similarly to the first embodiment of the present invention. Each supply gas is cooled and discharged from the nozzle, so that overheating of the combustion chamber can be further prevented. In this case, the arrangement of the cooling unit is not limited. For example, as in the system of FIG. The cooling unit can be provided by a method in which the tip of the hydrogen gas supply pipe 5 is made thinner.

When the tip of the gas ejection nozzle of the gas supply pipe is made of quartz glass, a cooling unit may be provided in a predetermined manner so that the temperature of the tip is 900 ° C. or less, and cooling is performed. preferable. Preferably, the cooling is performed at 700 ° C. or lower, more preferably at 500 ° C. or lower.

Further, in the combustion apparatus for producing high-purity steam of the present invention, the surface of the quartz glass material mainly forming the apparatus is treated with hydrofluoric acid, treated with high-temperature hydrogen chloride gas, or a combination thereof. By doing so, metal impurities such as sodium, iron, copper, and aluminum near the surface at a depth of about 100 μm from the surface are reduced to 10 ng /
g or less, or a synthetic quartz glass material having a high bulk purity of 10 ng / g or less in metal impurities is used in consideration of the possibility of erosion due to hydrogen gas supplied to the combustion device or generated steam. Is more preferable. Since the content of the above-mentioned metal impurities in steam produced by the combustion apparatus for producing high-purity steam using these high-purity quartz glass materials is 10 ng / m ³ or less,
It can be used when higher purity steam is required.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to embodiments. However, the present invention is not limited by the following examples. Example 1 Using a combustion apparatus configured in the same manner as in FIG. 1 described above, a hydrogen gas was supplied to the hydrogen gas supply pipe 5 at a flow rate of 6 L / min, and an oxygen gas was supplied to the oxygen gas supply pipe 6 at a flow rate of 5 L / min. The gas was discharged from the front end, and the gas supply pipe 4 was heated to 950 ° C. by the preheater 10 and ignited in the combustion chamber 2 and burned for 1 hour. In this case, the cooling units 11, 1
2 from the cooling medium supply pipes 13 and 14 respectively.
° C water is flowed at a flow rate of 1 liter / min and discharged from the cooling medium discharge pipes 15 and 16, and the ends of the hydrogen gas supply pipe 5 and the oxygen gas supply pipe 6 are cooled to about 50 ° C. 9 was circulated with the same water. Thus, in the combustion chamber 2, steam gas was generated by the oxidation reaction (combustion) of hydrogen. The amount of impurities in the steam gas flowing out of the steam supply pipe 3 was measured. The results are shown in Table 1.

Example 2 Using the same combustion apparatus as in Example 1, hydrogen combustion was performed in exactly the same manner as above except that heating of the preheating heater 10 was stopped after ignition and the cooling effect was further enhanced. The amount of impurities in the steam gas was measured. The results are shown in Table 1.

Embodiment 3 Using the same combustion apparatus as in Embodiment 1, using a cooling medium of argon, a cooling unit 11 for hydrogen gas and a cooling unit 1 for oxygen gas
2, hydrogen combustion was carried out in exactly the same manner, except that the preheating heater was continued, except that the gas flowed at a flow rate of 3 liters / minute through the cooling medium supply pipes 13 and 14, respectively.
The amount of impurities in the generated steam gas was measured. The results are shown in Table 1.

[0024]

[Table 1]

Example 4 Hydrogen combustion was performed in exactly the same manner as in Example 3 except that the heating of the preheating heater 10 was stopped and the cooling effect was further enhanced, and the amount of impurities in the generated steam gas was measured. The results are shown in Table 1.

Comparative Example 1 The same apparatus as in Example 1 was used, except that a heat insulating material was provided at the tip of the gas supply pipe 4 in the same manner as in the above-described conventional method without flowing a cooling medium through the cooling units 11 and 12. , Hydrogen combustion was performed in the same manner as in Example 1, and the content of impurities in the generated steam gas was measured. The results are shown in Table 1.

COMPARATIVE EXAMPLE 2 This is almost the same as the combustion apparatus shown in FIGS. 8 and 9 except that the oxygen gas jetting nozzle projects from the tip of the hydrogen gas jetting nozzle toward the combustion chamber, and a plurality of gas dispersion holes are formed. Using the dispersed oxygen gas ejection nozzle, hydrogen combustion was performed in the same manner as in Example 1, and the content of impurities in the generated steam gas was measured. The results are shown in Table 1.

According to the above Examples 1 to 4 and Comparative Examples 1 and 2, the cooling section is provided at the tip of the gas supply pipe to cool the hydrogen gas and the oxygen gas. It is clear that the content is significantly reduced as compared with the steam gas obtained by the conventional combustion device. Also from this point, it can be seen that in the combustion apparatus in which the cooling means is provided in the gas ejection nozzle area at the tip of the gas supply pipe according to the present invention, the erosion at the tip of the gas ejection nozzle is significantly suppressed.

Embodiment 5 Using a combustion apparatus constructed in the same manner as in FIG. 3, hydrogen gas was supplied to the hydrogen gas supply pipe 35 at 2 liter / minute, and oxygen gas was supplied to the oxygen gas supply pipe 36 at 2 liter / minute. Further, argon gas is passed through the inert gas supply pipe 39 at a flow rate of 5 liters / minute to flow out from the tip of the gas ejection nozzle, and the preheater 10
The gas supply pipe 34 was heated to 950 ° C. to ignite in the combustion chamber 2 and burned for 1 hour. In this case, water at 15 ° C. was passed through the water-cooled cylinder 9. In this way,
In the combustion chamber 2, a steam gas was generated by an oxidation reaction (combustion) of hydrogen. The amount of impurities in the steam gas flowing out of the steam supply pipe 3 was measured. The results are shown in Table 2. Further, the measurement point a (in the vicinity of the nozzle) shown in FIG.
And b (the inner surface of the top plate just above the flame). The results are shown in Table 2.

[0030]

[Table 2]

Embodiment 6 Using a combustion apparatus provided with a quadruple gas supply pipe constructed in the same manner as in FIG. Oxygen gas 2
Argon was flowed at 0.5 liter / minute through the inert gas supply pipes 29 and 30 at 0.5 liter / minute, respectively, and allowed to flow out from the tip of the gas ejection nozzle. Was heated and ignited in the combustion chamber 2. Thereafter, the heating of the preheater 10 is continued as it is, and the hydrogen gas is supplied at a rate of 2 liters / minute and the oxygen gas is supplied at a rate of 2 liters / minute.
The gas was burned at a rate of 5 liters / minute at a rate of 5 liters / minute, and the flow rate was controlled at 5 liters / minute. The amount of impurities in the steam gas flowing out was measured in the same manner as in Example 5. The results are shown in Table 2. The temperature was measured at the measurement points a (near the nozzle) and b (the inner surface of the top plate immediately above the flame) shown in FIG. 5 in the combustion chamber 2. The results are shown in Table 2.

Example 7 The combustion of hydrogen gas was carried out in the same manner as in Example 6, except that the heating of the preheater 10 was stopped after ignition, and the content of impurities in the outflowing steam gas was measured in the same manner. It was shown to.
In addition, temperature measurements at the measurement points a and b shown in FIG. 5 in the combustion chamber 2 were performed in the same manner, and the results are shown in Table 2.

COMPARATIVE EXAMPLE 3 In the conventional general structure shown in FIGS. 8 and 9, a double gas supply pipe is provided, a combustion device 71 is used, and a hydrogen gas supply pipe 55 and an oxygen gas supply pipe 76 are used. The gas supply pipe was heated by the preheater 80 and ignited in the combustion chamber 2 as in Example 5.
Thereafter, the heating of the preheater 80 was continued as it was, and the hydrogen gas and the oxygen gas were controlled at a flow rate of 2 liter / min and 2 liter / min, respectively, and burned for one hour. The amount of impurities in the steam gas flowing out was measured in the same manner as in Example 5. The results are shown in Table 2. The temperature was measured at the measurement points a (near the nozzle) and b (the inner surface of the top plate immediately above the flame) shown in FIG. The results are shown in Table 2.

COMPARATIVE EXAMPLE 4 This is substantially the same as the combustion apparatus shown in FIGS. 8 and 9 except that the oxygen gas ejection nozzle projects from the tip of the hydrogen gas ejection nozzle toward the combustion chamber, and a plurality of gas dispersion holes are formed. Using the dispersed oxygen gas ejection nozzle, hydrogen combustion was performed in the same manner as in Comparative Example 3, and the content of impurities in the generated steam gas was measured. The results are shown in Table 1. The temperature was measured at a point near the nozzle (point a) in the combustion chamber 72 shown in FIG. 8 and at an inner surface of the top plate immediately above the flame (point b). The results are shown in Table 2.

As is clear from the above Examples 5 to 7 and Comparative Examples 3 and 4, the hydrogen gas supply pipe and the oxygen gas supply pipe of the gas supply pipe according to the present invention were connected via an inert gas supply pipe without being adjacent to each other. It is formed in a triple or quadruple tube and arranged in a predetermined manner. The contact between the hydrogen gas and the oxygen gas immediately after the tip of the gas ejection nozzle in the combustion chamber is suppressed, and the combustion flame is formed at a predetermined interval. It can be seen that the formation of the gas significantly reduces the content of impurities in the generated and discharged steam gas.
From this point, it can also be seen that in the combustion apparatus in which the cooling means is provided in the gas ejection nozzle area at the tip of the gas supply pipe according to the present invention, the erosion at the tip of the gas ejection nozzle is significantly suppressed. Further, it can be seen that the temperature in the combustion chamber also decreases.

Next, the degree of wear (etching) due to the temperature of the quartz glass was verified. This verification result is shown in FIG. FIG. 7 is a diagram showing the relationship between the temperature of quartz glass and the amount of consumption (etching), in which the horizontal axis represents the temperature of quartz glass,
The vertical axis shows the ratio of the amount of etching at each temperature when the amount of etching of quartz glass at 300 ° C. with hydrogen is set to 1. The temperature at the tip of the conventional gas ejection nozzle is 1000 ° C. or higher. As is apparent from this figure, quartz glass having an etching amount of 20 times or more the etching amount at 300 ° C. is etched. By setting the temperature at the tip of the gas ejection nozzle to 900 ° C. or less, the etching amount at 300 ° C. can be suppressed to 10 times or less.
5 times or less of the etching amount of
By controlling the temperature to 500 ° C. or lower, the amount of etching at 300 ° C. can be suppressed to the same amount. Therefore, in the present invention, the temperature of the tip of the gas ejection nozzle made of quartz glass is 900 ° C. or less, preferably 700 ° C. or less,
It has been found that cooling to 500 ° C. or less is more preferable.

[0037]

The combustion apparatus for producing high-purity steam according to the present invention is contained in steam gas produced by a conventional combustion apparatus, mainly by providing a mechanism for preventing erosion at the tip of the gas ejection nozzle. A steam gas in which the content of impurities such as alkali metals is significantly reduced can be produced. Melting loss at the tip of the gas ejection nozzle is suppressed, and the temperature in the combustion chamber is reduced, so that the durability of the entire combustion apparatus is improved, and high-purity steam gas can be stably produced. Therefore, it can be suitably used especially in a thermal oxidation treatment step in a semiconductor manufacturing process in which a minute amount of impurity contamination poses a problem.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a combustion apparatus for producing high-purity steam according to a first embodiment of the present invention.

FIG. 2 is an enlarged explanatory view of a portion A in FIG. 1;

FIG. 3 is a schematic configuration diagram of a combustion apparatus for producing high-purity steam according to a second embodiment of the present invention.

FIG. 4 is an enlarged end view of a section taken along line BB of FIG. 3;

FIG. 5 is a schematic structural explanatory view of a combustion apparatus for producing high-purity steam according to a third embodiment of the present invention.

FIG. 6 is an enlarged end view of a cross section taken along line CC of FIG. 5;

FIG. 7 is a diagram showing the relationship between the temperature of quartz glass and the amount of consumption (etching).

FIG. 8 is a schematic diagram illustrating the configuration of a conventional combustion apparatus for producing high-purity steam.

9 is an enlarged end view of a section taken along line DD of FIG. 8;

[Description of Signs] 1, 31, 51, 71 Steam production and combustion apparatus 2, 72 Combustion chamber 3, 73 Steam supply pipe 4, 34, 54, 74 Gas supply pipe 5, 35, 55, 75 Hydrogen gas supply pipe 6, 36, 56, 76 Oxygen gas supply pipe 7, 37, 57, 77 Hydrogen gas introduction pipe 8, 38, 58, 78 Oxygen gas introduction pipe 39, 59, 60 Inert gas supply pipe 40, 62, 61 Inert gas introduction Pipe 9, 79 Water-cooling cylinder 10, 80 Preheating heater 11 Hydrogen gas supply pipe cooling section 12 Oxygen gas supply pipe cooling section 13, 14 Cooling medium supply pipe 15, 16 Cooling medium discharge pipe 81 Insulation material

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroto Ikuno 30 Soya, Hadano-shi, Kanagawa Toshiba Ceramics Co., Ltd. (72) Inventor Yoshinobu Nagamine 30 Soya, Hadano-shi, Kanagawa Toshiba Ceramics Co., Ltd. Inside the laboratory (72) Inventor Masanori Fujimoto 1-26-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Toshiba Ceramics Co., Ltd. (72) Inventor Hiroshi Tomita 1st Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa-ken Toshiba Research Corporation Inside the Development Center (72) Inventor Yoshio Kasai 1 Toshiba, Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Inside the Toshiba R & D Center (72) Inventor Yoshiki Nagai 25-1 Ekimae Honcho, Kawasaki-ku, Kawasaki-shi, Kanagawa Shiba Microelectronics Co., Ltd.

Claims (9)

[Claims] 1. A combustion apparatus for producing high-purity steam having a combustion chamber and a gas supply pipe comprising a hydrogen gas supply pipe and an oxygen gas supply pipe, comprising a erosion prevention mechanism at a tip of a gas ejection nozzle of the gas supply pipe. A combustion device for producing steam, characterized in that the combustion device comprises: 2. The combustion apparatus for producing high-purity steam according to claim 1, wherein the erosion prevention mechanism is a heat radiating means disposed at a gas ejection nozzle introduction portion of the gas supply pipe. 3. A cooling device made of quartz glass, wherein said heat radiating means is interposed between a hydrogen gas supply tube and an oxygen gas supply tube of a gas ejection nozzle introduction portion of said gas supply tube so as to allow a cooling medium to flow therethrough. The combustion device for producing high-purity steam according to claim 2, which is a part. 4. The combustion apparatus for producing high-purity steam according to claim 3, further comprising a cooling section made of quartz glass formed so as to allow a cooling medium to flow therethrough at an outer peripheral portion of the oxygen gas supply pipe. 5. The gas supply pipe according to claim 2, wherein at least a tip of the gas ejection nozzle of the gas supply pipe is made of quartz glass, and a heat radiating means for controlling a temperature of the tip to 900 ° C. or less is provided. The combustion device for producing high-purity steam according to any one of the above. 6. The combustion apparatus for producing high-purity steam according to any one of claims 2 to 5, wherein the gas supply pipe is heated to circulate hydrogen gas and oxygen gas, and the gas supply pipe is preheated. A method for producing high-purity steam, comprising: heating the gas supply pipe after igniting by firing into a combustion chamber; and simultaneously radiating heat by the radiating means to burn hydrogen to generate steam. 7. The erosion prevention mechanism according to claim 1, wherein the gas supply pipe is a triple pipe, and a hydrogen gas, an inert gas and an oxygen gas supply pipe are provided from the center, and a hydrogen gas supply pipe and an oxygen gas supply pipe are provided. 2. The combustion device for producing high-purity steam according to claim 1, wherein the flame is formed adjacent to the gas ejection nozzle tip at a predetermined distance from the tip of the gas ejection nozzle without being adjacent to each other. 8. The erosion prevention mechanism is characterized in that the gas supply pipe is a quadruple pipe, and a supply pipe for an inert gas, a hydrogen gas, an inert gas and an oxygen gas is provided from the center, and a hydrogen gas supply pipe and an oxygen gas are provided. 2. The combustion for producing high-purity steam according to claim 1, wherein the gas supply pipe is disposed via an inert gas supply pipe without being adjacent to the gas supply pipe, and a flame is formed at a predetermined distance from the tip of the gas ejection nozzle. apparatus. 9. The combustion apparatus for producing high-purity steam according to claim 6, wherein the gas supply pipe is heated to preheat the flowing hydrogen gas and oxygen gas, and the gas supply pipe is supplied to the combustion chamber from the gas ejection nozzle. A method for producing high-purity steam, comprising: stopping the heating of the gas supply pipe after squirting and igniting, and simultaneously radiating heat by the radiating means to burn hydrogen to generate steam.