JPH082911A - Method for cleaning silicon dioxide and method for treating its exhausted gas - Google Patents

Abstract

PURPOSE:To prevent the corrosion of the metal, quartz, etc., of material and enable to clean even the outside of a plasma region by reacting silicon dioxide deposited on the reactor and jigs of a silicon dioxide production device with BrF3. CONSTITUTION:The method for cleaning the silicon dioxide comprises reacting the deposited silicon dioxide with BrF3 at 250-900 deg.C, or at 600-900 deg.C under a BrF3 partial pressure which satisfies an inequality I: 0.1<=P<=-0.6T+560 [P is the partial pressure (Torr) of the BrF3; T is a temperature ( deg.C)], or at 250-600 deg.C under a pressure which satisfies an inequality II: 0.1<=P (P is the BrF3 partial pressure), or reacting the silicon dioxide with BrF5 at 0-40 deg.C or at 600-900 deg.C under a pressure which satisfies an inequality: 0.1<=P-9.3T+857 [P is a BrF5 partial pressure (Torr); T is a temperature ( deg.C)] or at 180-600 deg.C under a pressure which satisfies an inequality: 0.1<=P [P is the partial pressure (Torr)]. The exhausted gas is removed with water having a pH of 7-14, an alkali aqueous solution, or soda lime and active carbon.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is a process for forming films such as CVD, vacuum deposition, sputtering, thermal spraying, epitaxy, spin coating, and dipping, whiskers, and particle forming processes. The present invention relates to a method for easily removing and cleaning and a method for treating exhaust gas thereof.

[0002]

2. Description of the Related Art Silicon oxide is widely used as an impurity diffusion preventing film in a glass substrate, an insulating film for thin film application devices such as LSI, and a passivation film. Known methods for forming this silicon oxide film include a sol-gel method using TEOS and fluorotheos, and a CVD method using a silicon-containing gas such as TEOS, fluorotheos and SiH ₄ . However, when forming these films, an unnecessary film is formed not only on the substrate such as glass or silicon wafer but also on the inner wall of the device. The silicon oxide deposited on such a place is generally washed with a buffered hydrofluoric acid aqueous solution, but this method has the following problems. It significantly corrodes metal such as stainless steel, which is a reactor material, and quartz. It requires a lot of work such as dismantling, cleaning, drying and assembling of the reactor. Therefore, a gas cleaning method (gas cleaning) that does not have these problems is desired. Regarding the gas cleaning method, plasma cleaning using NF ₃ or C ₂ F ₆ is partially performed. However, since NF ₃ and C ₂ F ₆ themselves are inactive with respect to silicon oxide, they cannot remove silicon oxide deposited outside the plasma region in the reactor, and have a mechanism for generating plasma. Naturally, this cannot be done with a device that does not have it.

[0003]

As a result of intensive studies, the present inventors have found that a bromine fluoride-based gas is effective as a cleaning material for silicon oxide, and further, BrF ₃ ,
The present invention has been completed by finding out that the use conditions and methods effective for cleaning are different when BrF ₅ is the main component.

Regarding BrF ₃ and BrF ₅ , a removing agent for impurities on the inner surface of a resin container (Japanese Patent Laid-Open No. 3-112632).
No.), a reactor having a gas inlet for exclusive use of bromine fluoride gas (JP-A-2-185977), and contaminants remaining in the reactor cleaned with bromine fluoride as SiH ₄
The method described in Japanese Patent Laid-Open No. 2-190472 describes the method. However, etching of silicon oxide with BrF ₃ or BrF ₅ is described in JP-B-60-12779 in a method of manufacturing a semiconductor device characterized by plasma etching or sputter etching.
There is no known method for cleaning the inside of the reactor without plasma and a method for removing silicon oxide deposited outside the plasma atmosphere even in an apparatus capable of generating plasma, and conditions and methods that can be specifically used are also known. Absent. In addition, plasmaless dry etching (J. App
l. Phys. , 56 (10) (1984) 2939).
However, there is only a description that etching of silicon oxide cannot be performed without plasma.

Since each bromine fluoride has greatly different physical and chemical properties, BrF, BrF ₃ , BrF ₅ and BrF ₇
The supply conditions and silicon oxide cleaning conditions differ depending on which of these is contained as the main component.

Particularly, the supply conditions of BrF ₃ and BrF ₅ are as follows:
Since rF ₃ is a liquefied gas with a boiling point of 127 ° C. and BrF ₅ is 41 ° C., theoretically it would be possible to supply it without problems if the cylinder and pipe filled with it were heated above this temperature. Is the temperature of the cylinder, the pipe connecting the cylinder to the gas flow controller, the gas flow controller, and the pipe connecting the gas flow controller to the reactor have a temperature difference. It is preferable to have a temperature gradient of. In addition, stainless steel and Hastelloy are used as materials for the gas contact part of the cylinder, piping, flow rate controller, and gas contact part of the valve. When the corrosion resistance of BrF ₃ and BrF ₅ with these metals was examined, each was 215 ° C. 260 ° C
It has been found that it is necessary to keep the gas at the following temperature and to circulate the gas. That is, when the pipe is heated to a temperature higher than these temperatures and the gas is circulated, stainless steel and Hastelloy are corroded, and serious damage is caused to the device system.

Next, the cleaning conditions will be described. T
The etching rates of BrF ₃ and BrF _{5 with} respect to the silicon oxide film manufactured by using EOS and oxygen were measured. Br
Regarding the case of F ₃ , it was found that there are two inflection points in the relationship between the etching rate and the temperature as shown in FIG. That is, the etching rate is 150 ° C
It has been found that the etching rate becomes the minimum in the range from 1 to 250 ° C., and the etching rate rapidly increases at a temperature of 150 ° C. or lower or a temperature of 250 ° C. or higher. Therefore, cleaning is 1
It is necessary to carry out at a temperature of 50 ° C or lower, or 250 ° C or higher, a temperature range of 0 to 150 ° C, or 250 to 90 ° C.
It is preferably carried out in the temperature range of 0 ° C.

Further, as shown in FIG. 2, the etching rate of BrF ₅ shows a remarkable increase tendency from 180 ° C. as in the case of BrF ₃ , and the etching rate shows an increasing tendency even at 40 ° C. or lower. Therefore, cleaning is 40
It is necessary to carry out the treatment at a temperature of not higher than 0 ° C, or at a temperature of not lower than 180 ° C, and it is preferable to carry out at a temperature range of 0 to 40 ° C or a temperature range of 180 to 900 ° C. Further, in consideration of damage to the material of the device, the faster the etching rate of silicon oxide is, the better for cleaning. However, the etching rate for silicon oxide is high, and at the same time, the damage to the device material is large. In addition, the content of —OH groups and the like contained in silicon oxide varies depending on the manufacturing method. Therefore, it is necessary to properly select the cleaning conditions depending on the manufacturing method and the reaction device used.

Silicon oxide produced by thermal CVD is more difficult to clean than those produced by other methods,
Moreover, it is common to use quartz as a reactor material. In this case, the cleaning temperature is 600 ℃
Under the above conditions, it is necessary to optimize the conditions for removing silicon oxide and maximize the reaction selectivity with quartz.
As a result of diligent studies, the inventors of the present invention used B for cleaning.
It was found that the quartz can be cleaned without damaging the quartz by controlling the gas partial pressures of rF ₃ and BrF ₅ .

That is, in the temperature range of 900 to 600 (° C.), it is preferable to perform cleaning in the regions of formula (II) and formula (IV) in the formula (I), formula (III) and 600 ° C. or less. Further, if the gas partial pressure is less than 0.1 Torr, it takes a long time for cleaning, which is not preferable. Regarding the temperature, if it is higher than 900 (° C.), even if the partial pressure of BrF ₃ or BrF ₅ is smaller than 0.1 Torr, the quartz is severely damaged (devitrification), which is not suitable.

When alumina or aluminum nitride is used as a material for the apparatus, it is not necessary to specify pressure conditions. When stainless steel or Hastelloy is used, the place where they are used is BrF as in the case of supply conditions. ₃ is 215
It is necessary to keep the temperature below ℃ and BrF ₅ below 260 ℃. Since the film and particles produced by plasma CVD or the sol-gel method are easier to gasify and remove than those produced by thermal CVD, they can be cleaned even at low temperature.
In the case of F _3, the inside of the reactor may be kept at 150 ° C. or lower and in the case of BrF ₅ the temperature may be kept at 40 ° C. or lower, and the liquid may be introduced into the reactor as a liquid for cleaning.

BrF ₃ has a high boiling point, and it may be difficult to introduce a large amount into a reactor having a relatively low temperature for cleaning. In such a case, BrF ₅ can be used as BrF ₃ by heating it to 150 ° C. or higher before introducing it into the reactor and dissociating part of it into BrF ₃ + F ₂ and introducing it.

Strictly speaking, the silicon oxide which is the object to be cleaned in the present invention may not have a composition of Si and O of 1: 2, and may be applied to those containing F, Cl, B and P. . As described above, by using the gas containing bromine fluoride, it is possible to easily clean the SiO ₂ film forming apparatus, which has been difficult to perform the gas cleaning conventionally.

[0014]

The details of the present invention will be described with reference to the following examples. Examples 1 to 7, Comparative Examples 1 to 5 A stainless steel cylinder filled with bromine fluoride is a (° C), and a pipe connecting the cylinder and the mass flow controller is b.
(° C), the mass flow controller is heated to c (° C), the pipe connecting the mass flow controller to the reactor is heated to d (° C), and the pressure inside the reactor is controlled to 100 Torr to observe the flow state of bromine fluoride gas. did. Table 1 shows the results of observation by cutting the inside of the pipe after distribution.

[0015]

[Table 1]

Examples 8 to 51 Comparative Examples 6 to 23 A quartz wafer (4 inch) with a quartz plate (1 mm × 1 mm) was placed in a thermal CVD apparatus made of quartz, and TEOS and the atmosphere were heated to 700 to 900 ° C. S into the reactor
An iO ₂ film was grown to about 1 μm. Then, bromine fluoride was introduced to clean the inside of the reactor and the oxide film on the wafer. Whether the cleaning was possible or not was determined by measuring the level difference between the lower portion of the quartz plate on which the oxide film thickness on the wafer was placed on the wafer and the periphery thereof with a stylus type surface profiler. The results are shown in Tables 2 and 3,
The results are shown in Tables 4 and 5. Further, the same experiment was conducted with silicon oxide containing phosphorus and boron produced by using TEOS and oxygen, trimethyl phosphate, and trimethyl borate, but the same result was obtained.

[0017]

[Table 2]

[0018]

[Table 3]

[0019]

[Table 4]

[0020]

[Table 5]

Comparative Example 24 An exhaust gas treating agent-filled tube having a diameter of 10 cm and a length of 1.3 m was filled with soda lime, the reaction tube was set to 25 ° C. with an external heater, N ₂ : 0.9SLM, BrF ₅ : 0. .1 SLM
Was supplied (10%) in the reactor SiO ₂ was deposited for 20 minutes. The gas discharged from the reactor before entering the treatment agent filling tube was analyzed by FT-IR, gas chromatography, and UV, and it was found that Br ₂ , F ₂ , BrF, BrF ₃ , SiF
₄ was detected. In addition, when a part of the outlet gas was collected and analyzed in the same manner, the concentrations of BrF ₃ , BrF, F ₂ and SiF ₄ were less than the lower limit of quantification (1 ppm), but Br ₂ could not be processed and was detected. It was

Example 52 An exhaust gas treating agent-filled tube having a diameter of 10 cm and a length of 1.3 m was filled with soda lime, and an exhaust gas treating agent-filled column having a diameter of 25 A and a length of 30 cm was filled with activated carbon and connected. Next, the reaction tube was set to 25 ° C. with an external heater and N ₂ : 0.9S
LM, BrF ₅ : 0.1 SLM (10%) for 20 minutes S
The iO ₂ was fed to the reactor where it was deposited. When the gas discharged from the reactor before entering the treatment chemical filling pipe was analyzed by FT-IR, gas chromatography, and UV, B
r _2, F _2, BrF, were detected _{BrF 3, BrF 5, SiF 4} . Moreover, when a part of the outlet gas was collected and analyzed in the same manner, BrF ₅ , BrF ₃ , BrF, F ₂ , Si
The F ₄ and Br ₂ concentrations were less than the lower limit of quantification (1 ppm).

Example 53 In the same manner as in Example 45, N ₂ : 0.9SLM and BrF ₅ : 0.1SLM were introduced into the interior of the reactor to which SiO ₂ was adhered to perform cleaning. Next, when the outlet gas was supplied to a scrubber having a diameter of 4 inches and a height of 1 m and filled with a lashing ring and washed with a 20% NaOH solution, the fluorine content of the exhaust gas was below the lower limit of quantification (1 ppm).

Example 54 A stainless gas decomposition tank was installed in front of a reactor for forming a silicon oxide film, and the decomposition tank was heated to 150 ° C. to deposit a silicon oxide film (400 ° C., 10 Torr).
Into r), N ₂ : 0.9SLM and BrF ₅ : 0.1SLM were introduced for 60 minutes. After replacing the atmosphere with N ₂ and observing the inside of the reactor and the gas decomposition tank, the silicon oxide film deposited inside the reactor was completely removed.
There was no corrosion inside the gas decomposition tank.

Example 55 A quartz gas decomposition tank was installed in front of a reactor for forming a silicon oxide film, and the decomposition tank was set at 250 ° C., 300 ° C., 500 ° C.
° C. was heated to the reactor (400 ° C. to SiO ₂ film is deposited,
10 Torr) with N ₂ : 0.9SLM, BrF ₅ : 0.
1 SLM was introduced for 60 minutes. After replacing the atmosphere with N ₂ and then observing the inside of the reactor and the gas decomposition tank, the SiO ₂ film deposited inside the reactor was completely removed. The gas decomposition tank was not devitrified.

Examples 56 and 57 A quartz wafer (4 inch) with a quartz plate (1 mm × 1 mm) was placed in a quartz thermal CVD apparatus, and silicon oxide was formed at 600 ° C. using SiH ₄ and N ₂ O. Filmed Next, BrF ₅ : 0.1 SLM, N ₂ : 0.9 SLM, 10T
When the inside of the reactor was cleaned under the conditions of orr, 60 minutes and 600 ° C., unnecessary SiO ₂ accumulated inside the reactor
Was completely removed. Also, change to BrF ₅ and BrF
Similar results were obtained using ₃ .

Examples 58 and 59 A SiO ₂ film of about 1 μm was deposited on an electrode substrate (400 ° C.) using a parallel plate type plasma CVD apparatus using TEOS and O ₂ . At that time, SiO is also formed around the electrodes (≤400 ° C).
₂ had accumulated. Next, the electrode substrate temperature was maintained at 400 ° C., and high frequency power of 13.56 MHz was applied to the electrodes to generate plasma, BrF ₅ was 0.1 SLM, reactor pressure was 0.1 Torr, and electrode substrate temperature was 400 ° C. , Introduced for 20 minutes. As a result, SiO ₂ of SiO ₂ is also near the on the electrode substrate was also completely removed. Also, BrF ₅
Similar results were obtained when BrF ₃ was used instead of.

Examples 60 and 61 A SiO ₂ film of about 1 μm was deposited on an electrode substrate (400 ° C.) using a parallel plate type plasma CVD apparatus using TEOS and O ₂ . At that time, SiO was also formed around the electrodes (≦ 400 ° C.).
₂ had accumulated. Next, the electrode substrate temperature was kept at 200 ° C., high frequency power of 13.56 MHz was applied to the electrodes to generate plasma, BrF ₅ was 0.1 SLM, the reactor internal pressure was 0.1 Torr, and the electrode substrate temperature was 400 ° C. , Introduced for 20 minutes. As a result, SiO ₂ of SiO ₂ is also near the on the electrode substrate was also completely removed. Also, BrF ₅
Similar results were obtained when BrF ₃ was used instead of.

Examples 62 and 63 A quartz plate (1 mm × 1 mm) was placed in a quartz thermal CVD apparatus.
Place the placed quartz wafer (4 inch), and
Introduce rotriethoxysilane and oxygen into the reactor at 120 ℃
Approximately 1000 A of silicon oxide film containing fluorine
Lengthened After that, keep the temperature in the reactor at 120 ℃
And BrF_FiveTo remove the oxide film inside the reactor and on the wafer.
I cleaned it. Whether or not cleaning is possible
The area under the quartz plate where the oxide film thickness is placed on the wafer and its periphery
The step difference between and was measured with a stylus type profilometer. That conclusion
As a result, oxidation accumulated inside the reactor, supply pipe and exhaust pipe
Fluorotheos decomposition products such as silicon can be completely removed.
I was Furthermore, the gas is BrF ₃Changed to
Got the same result.

Examples 64 to 68 In the apparatus for hydrolyzing TEOS in a stainless steel container to granulate silicon oxide, SiO ₂ particles which are not taken out as a product and remain on the inside of the apparatus and silicon oxide is deposited on the reactor wall. Liquid bromine fluoride was introduced into this container to clean the inside, and then bromine fluoride was extracted from the drain extractor attached to the bottom of the reactor and the inside was observed. Table 6 shows the results.

[0031]

[Table 6]

[0032]

According to the method of the present invention, cleaning can be easily performed by reacting silicon oxide and bromine fluoride deposited on a CVD apparatus or the like under specific conditions. Further, the exhaust gas after cleaning can be easily treated with soda lime and activated carbon or an alkaline aqueous solution.

[Brief description of drawings]

FIG. 1 shows the relationship between the temperature of BrF ₃ and the etching rate.

FIG. 2 shows the relationship between the temperature of BrF ₅ and the etching rate.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C23G 5/00 H01L 21/304 341 G // C23C 14/34 Z 8939-4K

Claims (9)

[Claims] 1. In an apparatus for producing silicon oxide,
BrF ₃ and silicon oxide deposited on the reactor and jig
A method for cleaning silicon oxide, characterized by reactively removing in a temperature range of 50 to 900 ° C. 2. In an apparatus for producing silicon oxide,
The silicon oxide and BrF ₃ deposited on the reactor and the jig were removed.
A method for cleaning silicon oxide, which comprises removing by reaction in a temperature range of 150 ° C to 150 ° C. 3. An apparatus for producing silicon oxide,
The silicon oxide and BrF ₃ deposited on the reactor and jig were
In a temperature range of from 00 to 900 ° C., the general formula (I) 0.1 ≦ P ≦ -0.6T + 560 (I) BrF 3 represented by [P:: BrF ₃ partial pressure (Torr), T Temperature (℃)] The method for cleaning silicon oxide according to claim 1, wherein the reaction is removed by partial pressure. 4. An apparatus for producing silicon oxide,
The silicon oxide and BrF ₃ deposited on the reactor and jig are 2
In the temperature range of 50 to 600 ° C., the reaction is removed by BrF ₃ partial pressure represented by the general formula (II) 0.1 ≦ P (II) [P: BrF ₃ partial pressure (Torr), T: temperature (° C.)]. The method for cleaning silicon oxide according to claim 1, wherein: 5. In an apparatus for producing silicon oxide,
BrF ₅ and silicon oxide deposited on the reactor and jig
A method for cleaning silicon oxide, characterized by reactively removing in a temperature range of 80 to 900 ° C. 6. An apparatus for producing silicon oxide,
The silicon oxide and BrF ₅ deposited on the reactor and jig were
A method for cleaning silicon oxide, which comprises removing by reaction in a temperature range of -40 ° C. 7. An apparatus for producing silicon oxide,
The silicon oxide and BrF ₅ deposited on the reactor and jig are
In a temperature range of 00-900 ° C., the general formula (III) 0.1 ≦ P ≦ -9.3T + 857 (III) BrF 5 represented by [P:: BrF ₅ min pressure (Torr), T Temperature (℃)] The method for cleaning silicon oxide according to claim 5, wherein the reaction is removed by partial pressure. 8. In an apparatus for producing silicon oxide,
BrF ₅ and silicon oxide deposited on the reactor and jig
In the temperature range of 80 to 600 ° C., the reaction removal is carried out with the partial pressure of BrF _{5 represented} by the general formula (IV) 0.1 ≦ P (IV) [P: BrF ₅ partial pressure (Torr), T: temperature (° C.)]. The method for cleaning silicon oxide according to claim 5, wherein: 9. Removal of exhaust gas containing bromine fluoride when removing silicon oxide in a reactor in an apparatus for producing silicon oxide with water adjusted to pH 7 to 14, an aqueous alkali solution, or soda lime and activated carbon. A method for treating exhaust gas, which is characterized by: