JPH07183232A - Furnace tube for vapor growth - Google Patents

Abstract

PURPOSE:To provide a furnace tube for vapor growth which can make uniform the flow and temperature distribution of a carrier gas in the tube and the thickness and concentration of an impurity layer by providing four or more passages for introducing gases on the outside of the main body of the furnace tube and allowing one end of each passage to communicate with one end of the main body. CONSTITUTION:A furnace tube for vapor growth is constituted of a furnace tube main body 3 and at least four passages 2 for introducing gases formed along the outer peripheral surface of the main body 3 on the outside, with one end of each passage 2 communicating with one end of the main body 3. The furnace tube 1 for vapor growth is constituted of, for example, four or more quartz gas introducing tubes 2, quartz furnace tube main body 3, and quartz cap 4. The cap 4 is fixed to the upper end of the main body 3 and has circular through holes the number of which is the same as that of the tubes 2. One end of tube 2 is inserted into each through hole of the cap 4 and fixed in the hole by welding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a furnace core tube for vapor phase growth.

[0002]

2. Description of the Related Art A vapor-phase growth furnace core tube is used for diffusing impurities on the surface of a semiconductor wafer. This type of furnace core tube is equipped with one introduction tube for introducing a carrier gas containing impurities (also referred to as a diffusion gas), for example, O ₂ (oxygen) gas or N ₂ (nitrogen) gas. Or
This furnace core tube is used when forming an oxide film on the surface of a semiconductor wafer.

The carrier gas introduced by the introduction tube passes through the surface of the semiconductor wafer set in the furnace core tube to diffuse impurities into the surface.

In addition to the aforementioned furnace core tube, a double tube type furnace core tube has been proposed. Referring to FIG. 12, this double tube type furnace core tube includes an inner tube 21 and an outer tube 22.
The inner pipe 21 is coaxially inserted into the outer pipe 22, and the inner pipe 2
A tubular flow path 23 is formed between the outer tube 1 and the outer tube 22. The carrier gas flows through the tubular flow path 23 along the arrow 24 and is introduced into the inner pipe 21. The carrier gas is preheated when passing through the tubular flow path 23.

[0005]

However, in the above-described furnace core tube having one introduction tube, the carrier gas is introduced from one introduction tube, passes through the semiconductor wafer, and enters the furnace core tube. Since it flows toward the exhaust pipe provided, it is difficult to obtain a uniform carrier gas flow in the furnace core pipe. Therefore, the thickness and the concentration of the diffused impurity layer vary between the semiconductor wafers, which causes a problem that the quality of the semiconductor wafer cannot be improved.

Moreover, since the temperature of the carrier gas introduced into the furnace core tube by the introducing tube is room temperature and lower than the temperature in the furnace core tube, the temperature distribution in the furnace core tube tends to be non-uniform.
As a result, there is a problem that the yield of semiconductor wafers deteriorates.

Further, in the above-mentioned double tube type furnace core tube,
It is necessary to prepare two relatively thick quartz glass tubes that can be used as furnace core tubes. In the production of this relatively thick quartz glass tube, the problem of cracking is likely to occur, and in order to prevent it, the overall cost of the furnace core tube becomes high.

Moreover, in the tubular flow path 23, a turbulent flow easily occurs in the flow of the carrier gas. Therefore, the thickness and concentration of the impurity layer formed on the surface of the semiconductor wafer are likely to vary. Therefore, there is a problem that the quality of the semiconductor wafer cannot be improved.

The present invention has been made to solve the above-mentioned problems, and makes the carrier gas flow uniform.
Moreover, a furnace core tube for vapor phase growth, which can make the temperature distribution of the carrier gas uniform inside the furnace core tube to make the thickness and concentration of the impurity layer uniform and can be easily manufactured at low cost, is provided. The purpose is to provide.

[0010]

In order to solve the above-mentioned problems, the first invention of the present application is provided with a furnace core tube main body having a hollow tube shape, and at least four passages for introducing gas are respectively provided in the furnace. A furnace core tube for vapor phase growth is characterized in that it is formed outside the core tube body along the outer peripheral surface thereof, and one end of each passage and one end of the furnace core tube body communicate with each other.

Further, the second invention of the present application is provided with at least four hollow tube-shaped gas introduction pipes on the outside of the hollow tube-shaped furnace core pipe main body, and one end of each gas introduction pipe and the furnace core pipe main body. The gist of the furnace core tube for vapor phase growth is characterized in that one ends of the respective tubes are communicated with each other, and a predetermined portion of each gas introduction tube is arranged along the outer peripheral surface of the furnace core tube main body.

A third invention of the present application comprises a hollow tube-shaped furnace core tube main body and a hollow tube-shaped gas introducing means,
The furnace core tube main body is coaxially inserted into the gas introducing means, and at least four passages are formed between the outer peripheral surface of the furnace core tube main body and the inner peripheral surface of the gas introducing means to form an outer periphery of the furnace core tube main body. A furnace core tube for vapor phase growth, characterized in that the surface and the inner peripheral surface of the gas introduction means are brought into close contact with each other at least at four places, and one end of each passage and one end of the furnace core tube body are communicated with each other. Is the gist.

[0013]

EXAMPLES First Example A vapor-phase growth furnace core tube according to a first example of the present invention will be described.

The furnace core tube for vapor phase growth is provided in a vertical furnace. The vertical furnace is, for example, a heat treatment furnace for semiconductors.

Referring to FIG. 1, the vapor-phase growth furnace core tube 1 is composed of at least four gas introduction tubes 2, a furnace core tube body 3 and a cap 4. In the illustrated example, the number of gas introduction pipes 2 is 24. Note that, in FIG. 1, the dimensions of the gas introducing pipe 2 and the like are exaggeratedly shown, which is different from the actual dimensions.

The material of the gas introduction tube 2, the furnace core tube body 3 and the cap 4 is quartz glass.

An insertion tube (not shown) is inserted in the furnace core tube body 3. A temperature measuring instrument (not shown), for example, a rod-shaped thermocouple thermometer can be inserted into the insertion tube. The furnace core tube main body 3 is a hollow circular tube and has a shape along a straight line in the vertical direction. The dimensions of the furnace core tube body 3 can be set to the same dimensions as those of the conventional furnace core tube, for example, the inner tube of the above-mentioned double tube type furnace core tube. In the illustrated example, the outer diameter of the furnace core tube body 3 is 250 m.
m.

The cap 4 is a disk-shaped member bent along a part of a spherical surface, and is fixed to the upper end of the furnace core tube body 3.

The cap 4 is formed with circular through holes in the same number as the gas introducing pipes 2. These through holes are formed at equal intervals along a circumference concentric with the furnace core tube main body 3, and penetrate through each in the vertical direction. In the illustrated example, the number of through holes is 24, and the through holes are formed at positions close to the inner peripheral surface of the furnace core tube body 3. The position of the through hole is
It is preferably formed on the outer peripheral side of the spherical cap. As a result, a more uniform gas flow can be obtained.

Each gas introduction pipe 2 is a hollow circular pipe.

One end 2a of each gas introduction pipe 2 is provided with a cap 4
Is inserted into each through hole and is welded and fixed to the cap 4 by a laser. One end 2 a of each gas introduction pipe 2 opens downward on the concave lower surface of the cap 4.

Each of the gas introduction pipes 2 rises upward from the convex upper surface of the cap 4 and extends in a radial direction along a shape in which a substantially U-shape is turned upside down and extends in the radial direction.
b, and a predetermined portion 2c having a shape extending downward from the curved portion 2b along a straight line.

The predetermined portion 2c is arranged along the outer peripheral surface of the furnace core tube body 3. The predetermined portion 2c is in contact with the outer peripheral surface of the furnace core tube main body 3 or is spaced apart from the outer peripheral surface of the furnace core tube main body 3 outside. In the illustrated example, they are separated from the outer peripheral surface of the furnace core body 3 toward the outside by a distance of 1 mm. The space is preferably as narrow as possible. Inside the furnace core tube body 3, a wafer boat 5 on which a large number of semiconductor wafers are mounted is accommodated. Also,
The vertical furnace has a base 6 for supporting a furnace core tube for vapor phase growth.
Is equipped with. The vapor-phase growth furnace core tube 1 is fixed to a base 6. Further, a heating means (not shown) is arranged outside the vapor phase growth furnace core tube 1. The furnace core tube 1 for vapor phase growth is heated by a heating means.

The vertical furnace can have the same structure as the conventional one except for the vapor phase growth furnace core tube 1. For example, as the wafer boat 5, the base 6 and the heating means, those similar to the conventional one can be adopted.

When the semiconductor wafer is, for example, a silicon wafer, O ₂ gas or N ₂ gas, which is a carrier gas containing impurities such as phosphorus, is introduced into the other end of each gas introduction pipe 2 by a gas supply means (not shown). Then, the gas flows inside the gas introducing pipe 2 along the arrow 7, and is introduced into the cap 4 and the furnace core tube main body 3 through one end of the gas introducing pipe 2.
The gas supply means may be the same as the conventional one.

As described above, since the carrier gas is introduced into the inside of the cap 4 and the furnace core tube main body 3 in a state in which the carrier gas is substantially rectified by the at least four gas introduction pipes 2, the introduced carrier gas is in a large number. It is almost evenly distributed over the semiconductor wafer. In addition, the carrier gas evenly reaches the space between the adjacent semiconductor wafers. Therefore, a uniform and high-quality phosphorus diffusion layer is formed on the surface of each semiconductor wafer. Thereafter, the carrier gas is discharged from the furnace core tube body 3 through a discharge port (not shown).

Moreover, the carrier gas is preheated when flowing inside the gas introducing pipe 2. Therefore, the temperature distribution of the carrier gas becomes uniform inside the furnace core body 3 and the cap 4. The dimensions of the gas introduction pipe 2 are set so that the carrier gas is sufficiently preheated. In the illustrated example, the outer diameter of the gas introduction pipe 2 is 8 mm, the inner diameter thereof is 6 mm, and the length along the axis is 10 mm.
It is 00 mm.

The through hole of the cap 4 is, for example, a laser.
It is formed by processing. In the case of laser processing, chipping, burrs, etc. do not remain in the opening, and the carrier gas containing impurities is smoothly introduced into the inside of the furnace core body 3 and the cap 4.

Next, with reference to FIGS. 2 to 6, a method for manufacturing the furnace core tube 1 for vapor phase growth will be described.

First, the circular tube material 2 ', the furnace core tube body 3 and the cap 4 are separately prepared.

The circular tube material 2'is a hollow circular tube having a shape along a straight line, and is fixed to the cap 4 and then bent to form the gas introduction tube 2 as described later.
That is, the circular pipe material 2 ′ is the material of the gas introduction pipe 2, and the portions corresponding to the gas introduction pipe 2 are given the same reference numerals.

Thereafter, as shown in FIGS. 2 and 3, one end 2a of each circular pipe material 2'is inserted into each through hole of the cap 4 from above, and one end 2a of each circular pipe material 2'is cap 4
Open downward on the concave lower surface of. Then, the circular tube material 2'and the cap 3 are welded and fixed to each other by a laser.

Thereafter, as shown in FIG. 4, the cap 4 is placed on the upper end of the furnace core tube body 3, and the cap 4 and the furnace core tube body 3 are welded and fixed to each other by a laser.

Thereafter, as shown in FIGS. 5 and 6, the circular tube material 2'is bent to form a curved portion 2b and a straight portion 2c. As a result, the circular pipe material 2'constitutes the gas introduction pipe 2 described above.

In this way, the vapor-phase growth furnace core tube 1 is manufactured.

Next, referring to Table 1, in terms of manufacturing difficulty, manufacturing cost, and film uniformity of the vapor phase epitaxy furnace core tube 1, as compared with the above-mentioned conventional double tube type core tube. explain.

[0037]

[Table 1] First, the manufacturing difficulty will be described. In the vapor-phase growth furnace core tube 1 of the first embodiment, cracks are less likely to occur in the manufacturing process as compared with the conventional double-tube type furnace core tube described above. Therefore, as shown in Table 1, the production of the vapor-phase growth furnace core tube 1 of the first embodiment is easier than the production of the conventional double-tube type furnace core tube described above.

As shown in Table 1, the manufacturing difficulty of the vapor phase epitaxy furnace core tube 1 of the first embodiment differs depending on the interval between the connecting portions of the adjacent gas introduction tubes 2, and the interval is 0.
It is particularly easy when it is 1 mm or more.

Next, the manufacturing cost will be described. In this first embodiment, each gas introduction tube 2 is connected to the furnace core tube body 3
Since it is thinner, as shown in Table 1, a large tube (core tube main body 3
No. of tubes with a thickness equal to or greater than the thickness of (core core tube body 3)
Is. On the other hand, the number of thick tubes (tubes having a thickness equal to or larger than that of the inner tube 21) of the above-mentioned conventional double-tube type furnace core tube is two (the inner tube 21 and the outer tube 22). Since the gas introduction pipe 2 can be manufactured at a lower cost than the thick pipe, the manufacturing cost can be reduced as compared with the conventional double-tube type furnace core tube.

Next, the film uniformity of the coating film will be described.
In this first embodiment, as described above, at least 4
Since the carrier gas is almost rectified by the gas introducing pipe 2 of the book, as shown in Table 1, the film uniformity of the diffusion layer is better than that of the conventional double-tube furnace core tube described above. The distance between the connecting portions of the adjacent gas introduction pipes 2 is determined by the distance between the gas introduction pipes 2
It is particularly good when the diameter is less than or equal to.

[0041] With reference to the second embodiment FIG. 7, a description is given of a second embodiment vapor phase growth furnace core tube according to an example of the present invention.

The structure of this furnace core tube for vapor phase growth is the same as the structure of the furnace core tube for vapor phase growth of the above-mentioned first embodiment except for the cap 10, and therefore its explanation is omitted. In FIG. 7, the same parts as those in the first embodiment described above are designated by the same reference numerals.

The cap 10 is arranged on the upper end of the furnace core tube body 3. The cap 10 and the furnace core tube body 3 are welded and fixed to each other by a laser. The cap 10 has a shape that closes the upper end of the furnace core tube body 3 and has a substantially disc shape.

The disk portion of the cap 10 is formed with circular through holes of the same number as the gas introducing pipes 2. These through holes are formed at equal intervals along a circumference concentric with the furnace core tube main body 3, and penetrate through each in the vertical direction. In the illustrated example, the number of through holes is 24, and the through holes are formed at positions close to the inner peripheral surface of the furnace core tube body 3.

One end 2a of each gas introduction pipe 2 is provided with a cap 1
0 is inserted into each through hole, and is welded and fixed to the cap 10 by a laser. Each gas introduction pipe 2
One end 2a of the cap 10 opens downward on the lower surface of the cap 10.

[0046] With reference to the third embodiment FIGS. 8 to 11, a description is given of a third vapor phase growth furnace core tube according to an embodiment of the present invention.

With reference to FIGS. 10 and 11, the vapor-phase growth furnace core tube 11 is composed of a furnace core tube body 12, a gas introducing means 13 and a cap 14.

The material of the furnace core tube main body 12, the gas introducing means 13 and the cap 14 is quartz glass.

The furnace core tube body 12 has the same structure as the furnace core tube body of the first embodiment.

The gas introducing means 13 has a hollow tubular shape. Its axial length is the same as that of the furnace core tube body 12. The cross-sectional shape of the gas introducing means 13 is a so-called flower shape, which is a shape in which the circumference is undulated in the radial direction to form a waveform.

The furnace core tube body 12 is coaxially inserted into the gas introducing means 13. The outer peripheral surface of the furnace core tube body 12 and the inner peripheral surface of the gas introducing means 13 are at least four contact portions 1
3a are in close contact with each other over the entire length in the axial direction. The close contact portions 13a are provided at equal intervals in the circumferential direction. In the illustrated example, the number of the close contact portions 13a is eight.

Between the adjacent close parts 13a, the inner peripheral surface of the gas introducing means 13 is separated from the outer peripheral surface of the furnace core tube body 12 in the radial direction over the entire length in the axial direction, and the gas introducing passage 15 is formed. There is. The gas introduction passages 15 are passages for introducing gas, and are formed at equal intervals along the outer peripheral surface of the furnace core tube body 12. In the illustrated example, the number of gas introduction paths 15 is eight.

The cap 14 has a hollow tubular shape, and its cross-sectional shape corresponds to that of the gas introducing means 13. The upper end of the cap 14 is closed and the lower end is open. The lower end of the cap 14 and the upper end of the gas introduction means 13 are welded and fixed to each other by a laser, and the inside of the core tube main body 12 and the gas introduction path 15 are in communication with each other via the cap 14.

The carrier gas is introduced into the lower end of each gas introduction path 15 by a gas supply means (not shown), flows upward in the gas introduction path 15, and moves along the arrow 16 through the cap 14 to the furnace core. It is introduced inside the tube body 12.

The present invention is not limited to the first to third embodiments described above.

For example, the shapes of the furnace core tube body, the gas introduction pipe, the cap, the gas introduction means, etc. are not limited to the above-mentioned shapes,
Other shapes may be used. Further, the materials thereof are not limited to quartz glass, and other materials may be used.

Further, the furnace core tube for vapor phase growth may be manufactured not only by the manufacturing method of the first embodiment described above but also by other manufacturing methods. For example, in the manufacturing method of the first embodiment described above, the circular pipe material may be bent before being fixed to the cap, and then fixed to the cap.

[0058]

According to the present invention, at least four passages for introducing gas are formed outside the furnace core tube body along the outer peripheral surface thereof, and one end of each passage and one end of the furnace core tube body are formed. Since they are communicated with each other, it is possible to accommodate the semiconductor wafer inside the furnace core tube body, flow the carrier gas from the other end of each passage toward one end, and further introduce the carrier gas into the furnace core tube main body through that one end. In this case, since the flow of the carrier gas is rectified by at least four passages, the carrier gas is evenly distributed in the spaces between the plurality of semiconductor wafers and the gaps between the semiconductor wafers, and the impurity layers of the plurality of semiconductor wafers are formed. A high-quality diffusion layer having a uniform thickness and concentration can be obtained, and the quality of the semiconductor wafer can be improved.

Further, since at least four hollow tubular gas introduction tubes are provided outside the furnace core tube body, the furnace core tube can be manufactured more easily than the double tube type furnace core tube described above. is there. Moreover, each gas introduction tube can be made thinner than the furnace core tube body. In this case, the manufacturing cost can be reduced as compared with the above-mentioned double tube type furnace core tube.

[Brief description of drawings]

FIG. 1 is a sectional view partially showing a vertical furnace provided with a vapor-phase growth furnace core tube according to a first embodiment of the present invention.

FIG. 2 is a plan view showing a cap and a circular tube material.

[Fig. 3] AA of the cap and the circular tube material shown in Fig. 2.
Sectional view.

FIG. 4 is a sectional view showing a cap, a circular tube material, and a furnace core tube main body.

5 is a sectional view showing the furnace core tube for vapor phase growth shown in FIG.

6 is a perspective view showing the furnace core tube for vapor phase growth shown in FIG.

FIG. 7 is a cross-sectional view showing a furnace core tube for vapor phase growth according to a second embodiment of the present invention.

FIG. 8 is a sectional view showing a furnace core tube body.

FIG. 9 is a sectional view showing a gas introducing means.

FIG. 10 is a sectional view showing a furnace core tube for vapor phase growth according to a third embodiment of the present invention.

11 is a BB cross-sectional view of the furnace core tube for vapor phase growth shown in FIG.

FIG. 12 is a sectional view showing a conventional double-tube type reactor core tube.

[Explanation of symbols]

 1,11 Vapor-phase growth furnace core tube 2 Gas introduction tube 3,12 Furnace core tube main body 4,14 Cap 5 Wafer boat 13 Gas introduction means

Claims (3)

[Claims] 1. A furnace core tube main body having a hollow tube shape, wherein at least four passages for introducing gas are formed outside the furnace core tube main body along the outer peripheral surface thereof, and one end of each passage is formed. A furnace core tube for vapor phase growth, characterized in that one end of a furnace core tube main body is made to communicate with each other. 2. A hollow tube-shaped furnace core tube main body is provided with at least four hollow tube-shaped gas introduction tubes, and one end of each gas introduction tube and one end of the furnace core tube main body communicate with each other, A furnace core tube for vapor phase growth, wherein a predetermined portion of each gas introduction tube is arranged along the outer peripheral surface of the furnace core tube body. 3. A furnace core tube body having a hollow tube shape and a hollow tube-shaped gas introducing means, wherein the furnace core tube body is coaxially inserted into the gas introducing means, and an outer peripheral surface of the furnace core tube body is provided. And at least four passages are formed between the inner peripheral surface of the gas introducing means and the outer peripheral surface of the core tube main body and the inner peripheral surface of the gas introducing means at at least four places, and one end of each passage is formed. A furnace core tube for vapor phase growth, characterized in that one end of a furnace core tube main body is made to communicate with each other.