JPH07183233A - 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 arranging multiple gas introducing tubes along the peripheral surface of a furnace tube and fixing each gas introducing tube to its adjacent tubes. CONSTITUTION:A reaction space 5 surrounded by introducing tubes 2 is formed by arranging the tubes 2 along the peripheral surface of a furnace tube and fixing each tube 2 to its adjacent tubes. A furnace tube for vapor growth is constituted of gas introducing tubes 2 and a cap, all of which are made of quartz glass. The cross-sectional shape of each tube 2 is defined by dividing the annular shape by the number of the tubes 2 in the circumferential direction. The tubes 2 are arranged on a prescribed peripheral surface 4, with their surfaces 2a constituting the internal surface of the furnace inside, and welded to each other at their welding parts 2c.

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. 7, the 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 21
A tubular flow path 23 is formed between the outer tube 22 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, there is a problem that the thickness and concentration of the diffused impurity layer vary among a plurality of semiconductor wafers, and 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 present invention arranges a plurality of hollow tube-shaped gas introduction pipes side by side along the peripheral surface of a furnace core pipe and adjoins each other. A furnace core tube for vapor phase growth is characterized in that a gas introduction tube is fixed and a space for reaction surrounded by the gas introduction tubes is formed.

[0011]

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

This vapor-phase growth furnace core tube is provided in a vertical furnace. The vertical furnace is, for example, a heat treatment furnace for semiconductors, and has the same configuration as the conventional one except for a vapor-phase growth furnace core tube.

Referring to FIGS. 1 to 4, the vapor-phase growth furnace core tube 1 is composed of a plurality of (for example, at least four) gas introduction tubes 2 and a cap 3. In the illustrated example, the number of gas introduction pipes 2 is eight. The material of the gas introduction tube 2 and the cap 3 is quartz glass.

1 to 4, the dimensions of the gas introduction pipe 2 and the like are exaggerated and different from the actual dimensions. Further, in order to show the shape of the gas introduction pipe 2 in an easy-to-understand manner, one gas introduction pipe 2 is shown as being extracted in FIG. 1 and the others are omitted, and the cap 3 is omitted in FIG. .

Each gas introduction pipe 2 is a hollow pipe and has a shape along a straight line in the vertical direction. A preferable example of the cross-sectional shape is a shape in which an annular shape is equally divided in the circumferential direction by the number of gas introduction pipes 2. In the illustrated example, each gas introduction pipe 2
The cross-sectional shape of is a shape obtained by dividing the annular shape into eight equal parts in the circumferential direction. Each gas introduction pipe 2 is composed of a furnace inner surface portion 2a, a furnace outer surface portion 2b and two welded portions 2c.

The gas introduction pipes 2 are provided on the inner surface portions 2 of the respective furnaces.
They are arranged side by side along the predetermined peripheral surface 4 with a facing the inside of the predetermined peripheral surface 4. The predetermined peripheral surface 4 is a cylindrical peripheral surface whose center axis is the vertical axis 4a. The welded portions 2c of the gas introduction pipes 2 adjacent to each other are in contact with each other over the entire surface, and are welded and fixed by a laser.

The furnace inner surface portion 2a of the gas introduction pipe 2 thus laser-welded has a shape along a predetermined peripheral surface 4. The furnace outer surface portion 2b of the gas introduction pipe 2 has a shape larger than the predetermined peripheral surface 4 and along a concentric peripheral surface 4b.

The cap 3 is a member having a shape along a part of a spherical surface, and has a concave circular furnace inner surface 3a, a convex circular furnace outer surface 3b, and a flat annular end surface 3c. The end surface 3c has a shape corresponding to the end surface of the upper end of the furnace outer surface portion 2b of the gas introduction pipe 2.

The cap 3 includes a furnace inner surface 3a and an end surface 3c.
Is arranged downward, and the end surface of the upper end of the furnace outer surface portion 2b of the gas introduction pipe 2 and the end surface 3c of the cap 3 are welded to each other by laser welding.

A reaction space 5 is formed by being surrounded by the furnace inner surface portion 2a of the gas introduction pipe 2, and a wafer boat (not shown) having a large number of semiconductor wafers mounted therein is accommodated therein. Has become.

A heating means (not shown) is arranged outside the vapor phase growth furnace core tube 1. Furnace core tube for vapor phase growth 1
Is heated by the heating means. The wafer boat and the heating means may be the same as the conventional one.

An insertion tube (not shown) is provided in the reaction space 5.
Has been inserted. A temperature measuring instrument (not shown) can be inserted into this insertion tube.

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 equalized at the lower end of each gas introduction pipe 2 by a gas supply means (not shown). Was introduced in the arrow 6
Along the inside of each gas introduction pipe 2 upward,
The gas is introduced into the reaction space 5 through the upper end of each gas introduction pipe 2 and the cap 3 in order. The gas supply means may be the same as the conventional one.

The carrier gas is preheated when flowing inside the gas introducing pipe 2. Therefore, the temperature distribution of the gas becomes uniform in the reaction space 5.

Moreover, since the carrier gas is introduced into the reaction space 5 in a state of being rectified by at least four gas introduction pipes 2, the introduced carrier gas is evenly distributed over a large number of semiconductor wafers. Go around. 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. After that, the carrier gas is discharged from the reaction space 5 through an outlet (not shown).

Next, the manufacturing difficulty, the manufacturing cost, and the film uniformity of the vapor-phase growth furnace core tube 1 will be sequentially described in comparison with the conventional double-tube type furnace core tube.

First, the degree of 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, the production of the vapor-phase growth furnace core tube 1 is easier than the production of the conventional double-tube type furnace core tube described above.

Next, the manufacturing cost will be described. Since each gas introduction pipe 2 can be made into a thin shape as compared with the inner pipe or the outer pipe of the above-mentioned conventional double-tube type furnace core tube,
It can be manufactured at low cost. Therefore, 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.
Since the carrier gas is rectified by the at least four gas introduction pipes 2 as described above, turbulent flow is less likely to occur as compared with the conventional double tube type furnace core tube. Therefore, the film uniformity of the diffusion layer formed by the vapor phase growth furnace core tube 1 is good.

The described vapor phase growth furnace core tube according to a second embodiment of the second embodiment the present invention.

This vapor phase growth furnace core tube is provided in a vertical furnace as in the first embodiment.

Referring to FIGS. 5 and 6, this furnace core tube 11 for vapor phase growth is composed of at least four gas introduction tubes 12 and a cap (not shown). In the illustrated example, the number of gas introduction pipes 12 is 12. The material of the gas introduction tube 12 and the cap is quartz glass.

In FIGS. 5 and 6, the dimensions of the gas introduction pipe 12 and the like are exaggerated and different from the actual dimensions. Further, in order to clearly show the shape of the gas introduction pipe 12, the cap is omitted in FIG.

Each gas introduction pipe 12 is a hollow circular pipe,
It has a shape along a vertical straight line.

The gas introduction pipes 12 are arranged side by side along a predetermined peripheral surface 14. The predetermined peripheral surface 14 is a cylindrical peripheral surface whose center axis is the vertical axis 14a.
The outer peripheral surfaces of the gas introduction pipes 12 adjacent to each other are in contact with each other over the entire length in the axial direction. The portion 12c in such contact is welded by laser welding.

In the reaction space 15 surrounded by the gas introduction pipe 12, a wafer box on which a large number of semiconductor wafers are placed.
A housing (not shown) is accommodated. Also,
A heating means (not shown) is arranged outside the vapor-phase growth furnace core tube 11. The furnace core tube 11 for vapor phase growth is heated by a heating means. The wafer boat and the heating means may be the same as the conventional one.

The cap is arranged at the upper end of the gas introducing pipe 12. The upper end of the gas introduction pipe 12 and the reaction space 15 communicate with each other via the cap. The gas introduction pipe 12 and the cap are welded to each other by laser welding.

An insertion tube (not shown) is inserted in the reaction space 15. A temperature measuring instrument (not shown) can be inserted into this insertion tube.

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 equalized at the lower end of each gas introduction pipe 12 by a gas supply means (not shown). Is introduced into the gas introduction pipe 12, flows upward inside each gas introduction pipe 12, passes through the upper end of each gas introduction pipe 12 and the cap in order, and the reaction space 1 is introduced.
Introduced in 5. The gas supply means may be the same as the conventional one.

The carrier gas is preheated when flowing inside the gas introducing pipe 12. Therefore, the temperature distribution of the gas becomes uniform in the reaction space 15.

Moreover, at least four gas introduction pipes 12
Since the carrier gas is rectified and introduced into the reaction space 15, the introduced carrier gas uniformly spreads over a large number of semiconductor wafers. In addition, the carrier gas evenly reaches the space between the adjacent semiconductor wafers. Therefore, on the surface of each semiconductor wafer,
A uniform and high-quality phosphorus diffusion layer is formed. After that, the carrier gas is discharged from the reaction space 15 through a discharge port (not shown).

As in the second embodiment, when the plurality of gas introduction pipes are in the shape of a circular tube, the outer periphery of the space 15 is formed with continuous irregularities in the vertical direction. In order to control the uniform flow of the gas in the space 15, it is preferable to heat-process the outer periphery of the space 15 into a circular shape by an arbitrary method after the laser welding.

The manufacturing difficulty, the manufacturing cost, and the film uniformity of the vapor phase growth furnace core tube 11 are all improved as compared with the conventional double tube type core tube, as in the first embodiment. Can be made.

The present invention is not limited to the above-mentioned first and second embodiments.

For example, the shape of the gas introduction pipe is not limited to the above-mentioned shape, but may be other shapes. Further, the material of the gas introduction tube is not limited to quartz glass, and other materials may be used.

Further, the furnace core tube for vapor phase growth of the present invention can be used not only for the above-mentioned diffusion of impurities but also for other vapor phase growth.

[0047]

According to the present invention, at least four hollow tube-shaped gas introduction pipes are arranged side by side along the peripheral surface of the furnace core tube, and the gas introduction pipes adjacent to each other are fixed, and Since the reaction space surrounded by the introduction pipe is formed, the semiconductor wafer is accommodated in the reaction space, the carrier gas is caused to flow from the other end of each gas introduction pipe toward one end, and further through one end thereof. Can be introduced into the reaction space,
In this case, since the flow of the carrier gas is rectified by at least four gas introduction pipes, the carrier gas is evenly distributed in the space between the plurality of semiconductor wafers and the gap between the semiconductor wafers, and the impurity layers of the plurality of semiconductor wafers A high-quality diffusion layer having a uniform thickness and concentration can be obtained, and the quality of the semiconductor wafer can be improved.

Moreover, since at least four hollow tube-shaped gas introduction pipes are arranged side by side, it is easier to manufacture as compared with the above-mentioned double pipe type furnace core pipe. 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 perspective view in which one gas introduction tube of a vapor phase growth furnace core tube according to a first embodiment of the present invention is shown as being drawn out and the other parts are omitted.

FIG. 2 is a horizontal sectional view showing the vapor-phase growth furnace core tube shown in FIG.

FIG. 3 is a perspective view partially showing the vicinity of the upper end of the gas introduction pipe, omitting the cap of the vapor-phase growth furnace core pipe shown in FIG. 1.

4 is a vertical cross-sectional view showing the furnace core tube for vapor phase growth shown in FIG.

FIG. 5 is a horizontal sectional view showing a furnace core tube for vapor phase growth according to a second embodiment of the present invention.

FIG. 6 is a perspective view partially showing the vicinity of the upper end of the gas introduction pipe with the cap of the furnace core tube for vapor phase growth shown in FIG. 5 omitted.

FIG. 7 is a vertical cross-sectional view showing a conventional double tube type furnace core tube.

[Explanation of symbols]

 1 vapor phase growth furnace core tube 2,12 gas introduction tube 3,13 cap 4 predetermined axis 5,15 space for reaction

Claims (1)

[Claims] 1. A plurality of hollow tube-shaped gas introduction tubes are arranged side by side along the peripheral surface of a furnace core tube, and the gas introduction tubes adjacent to each other are fixed and surrounded by the gas introduction tubes. A furnace core tube for vapor phase growth characterized in that a space for reaction is formed.