JPH10149988A - Method and device for forming doped semiconductor film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the gaseous start material of a dopant adsorbed by a dopant supply tube from being vaporized and incorporated into a reaction tube which occurs when the gaseous start material is supplied to the reaction tube from the dopant supply tube whenever a doped semiconductor film is formed, because the vaporized material gives an adverse influence to the characteristics of the film and no good doped semiconductor film can be formed. SOLUTION: The flow passage of the gaseous starting material of a dopant is formed from a reaction tube 1 to a dopant discharge tube 12 through a dopant supply tube 11 by connecting the discharge tube 12 to the middle of the supply tube 11. When the supply tube 11 is evacuated from the discharge tube 12, a vaporized dopant in the supply tube 11 is drawn out together with the gas in the reaction tube 1 and discharged to the outside through the discharge tube 12. The vacuum evacuation is continuously performed while no semiconductor film is formed. Therefore, the adverse influence of a residual dopant on a doped semiconductor film can be prevented at the time of forming the semiconductor film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a method and an apparatus for forming a doped semiconductor film, and more particularly to a method for removing a residual dopant in a dopant supply tube.

[0002]

2. Description of the Related Art A doped semiconductor film forming apparatus heats a wafer by a heater provided outside an outer tube, and supplies and circulates a semiconductor raw material gas and a dopant raw material gas through a supply pipe into an inner tube. By evacuating from the exhaust port through between the inner tube and the inner tube, a doped semiconductor film is formed on the wafer.

A conventional doped semiconductor film forming apparatus independently includes a dopant supply pipe having an injector for replenishing a dopant source gas, in addition to a reaction gas supply pipe for supplying a semiconductor source gas and a doping source gas. , The uniformity of the doping amount is improved.

[0004]

However, in the above-mentioned prior art in which a dopant supply pipe is provided independently, the dopant raw material is decomposed and adsorbed in the injector, and the dopant accumulated in the injector after the formation of the doped semiconductor film is removed. In some cases, it adheres to the inside or on a processed substrate on which a film is formed, and forms an unintended high-concentration layer on the substrate surface, which may adversely affect the film characteristics. In addition, the dopant is gradually vaporized from the injector even after taking out the substrate, and the vaporization amount also changes with time, thereby affecting the doping concentration in the next film forming process and deteriorating the dope reproducibility between batches. There was also a problem.

An object of the present invention is to provide a method and apparatus for forming a doped semiconductor film capable of solving the above-mentioned problems of the prior art and forming a semiconductor film having a dopant distribution as intended with good reproducibility. Is to do.

[0006]

A method of forming a doped semiconductor film according to the present invention is a method of forming a doped semiconductor film on a substrate by supplying a dopant source gas from a dopant supply tube into a reaction tube. At other times, the dopant in the dopant supply tube is excluded. Here, the dopant in the dopant supply pipe includes a residual dopant source gas, a dopant gas adsorbed from the dopant adsorbed in the dopant supply pipe, and a solidified dopant separated from the dopant supply pipe.

[0007] As the dopant source gas is supplied into the reaction chamber, the dopant remains on the inner wall of the dopant supply pipe. The dopant remaining in the dopant supply pipe is removed to the outside during a period other than the time when the semiconductor film is formed. Thus, at the time of the next formation of the doped semiconductor film, unintended residual dopant does not flow into the reaction tube, and does not adversely affect the film formation reaction.

Further, the doped semiconductor film forming apparatus of the present invention comprises a dopant supply pipe for supplying a dopant source gas into a reaction chamber for forming a doped semiconductor film on a substrate, and a dopant supply pipe connected to the dopant supply pipe. And a dopant exhaust pipe for exhausting the dopant in the pipe.

By connecting the dopant exhaust pipe to the dopant supply pipe, even if the dopant accumulates in the dopant supply pipe, this can be eliminated, so that the doped semiconductor film can be formed with good reproducibility.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a schematic sectional view of a vertical CVD apparatus as a doped semiconductor film forming apparatus. In FIG.
The reaction tube 1 includes an outer tube 2 and an inner tube 3. A boat 6 having wafers 5 mounted in multiple stages on a boat mounting table 4 is inserted into the inner tube 3 of the reaction tube 1, and the bottom of the reaction tube 1 is sealed with the cap 7.
A rotation mechanism 8 is attached to the cap 7 so that the boat 6 can rotate in the reaction tube 1. A heater 9 is arranged on the outer periphery of the reaction tube 1 to heat the wafer 5 to a predetermined temperature.

A reaction gas supply pipe 10 is inserted into a lower portion of the reaction tube 1 to supply a semiconductor source gas and a dopant source gas into the inner tube 3 of the reaction tube 1. Further, the dopant supply pipe 11 is
And the dopant source gas is supplied independently of the reaction tube 1.
Can be refilled into the inner tube 3.
The dopant supply pipe 11 extends from the lower part to the upper part in the reaction tube 1, and the extension part constitutes an injector 13 for uniformly injecting the dopant source gas into the reaction tube 1.

A dopant exhaust pipe 12 is connected in the middle of the dopant supply pipe 11, and the dopant gas accumulated in the dopant supply pipe 11 is evacuated from the dopant exhaust pipe 12 through the dopant supply pipe 11. . An exhaust pipe 14 is provided below the reaction tube 1 on the opposite side of the dopant supply pipe 11 and the reaction gas supply pipe 10.
Is connected, and the gas supplied into the reaction tube 1 is evacuated.

In such a vertical CVD apparatus, a doped CVD film is formed on a wafer by batch processing every time the boat 6 is inserted. When forming a doped CVD film, the wafer 5 inserted into the reaction tube 1 is heated to a predetermined temperature by the heater 9. And the valve 1 of the exhaust pipe 14
7 is opened, and the valve 16 of the dopant exhaust pipe 12 is closed as shown in FIG.
1 valve 15 is opened to supply a semiconductor source gas and a dopant source gas into the reaction tube 1 from the reaction gas supply tube 10 and the dopant supply tube 11, and to perform doped C on the wafer.
A VD film is generated. Excess gas passes through the passage 18 between the inner tube 3 and the outer tube 2 and passes through the exhaust pipe 14.
And evacuated from the reaction tube 1. At this time, in the injector 13, the dopant source gas is decomposed, and the dopant adheres and accumulates on the inner wall of the injector 13.

The general processing conditions in the reaction tube for the P-doped polysilicon film forming method using the SiH ₄ —PH ₃ source gas are as follows.

Temperature: 500 ° C. to 600 ° C. Pressure: 10 Pa to 200 Pa SiH ₄ : 200 to 2000 ccm PH ₃ : 1 to 1000 ccm (diluted to 0.1% to 4% with N _2, He, H _2, etc.) Semiconductor 1B, the supply of the semiconductor source gas and the dopant source gas from the reaction gas supply pipe 10 is stopped, and the carrier gas (N _2, He, H ₂ , or the like) is stopped as shown in FIG. The reaction tube 1 is purged by flowing only the gas. At this time, in the dopant supply pipe 11, the valve 15 of the dopant supply pipe 11 is closed, and the dopant exhaust pipe 12
Is opened. Then, by evacuating from the dopant exhaust pipe 12, the reaction pipe 1 passes through the injector 13, the dopant supply pipe 11, and the dopant exhaust pipe 1.
2, the dopant gas remaining in the injector 13 or the dopant gas generated by vaporizing the dopant adsorbed on the inner wall of the injector 13 is removed to the outside, and the dopant accumulated in the injector 13 is removed. Is prevented from flowing into the reaction tube 1.

As described above, according to the present embodiment, the dopant exhaust pipe 12 is connected to the dopant supply pipe 11, and the inside of the injector 13 is independently evacuated except for the formation of the doped semiconductor film. Therefore, the dopant accumulated in the injector 13 after the formation of the doped semiconductor film adheres to the inside of the reaction tube 1 or the processing substrate on which the film is formed, thereby forming a high-concentration layer or affecting the doping concentration in the next film-forming process. Will not give. As a result, the reproducibility of the dope amount between batches is improved.

In the above-described embodiment, the dopant supply pipe 11 is evacuated to remove the dopant gas in the dopant supply pipe 11 to the outside. However, the present invention is not limited to this. Dopant supply pipe 1
Conversely, an inert gas is blown into 1 to supply dopant supply pipe 11.
The dopant gas in the inside may be excluded. For example, an inert gas such as N ₂ gas is supplied from the dopant exhaust pipe 12 into the dopant supply pipe 11 and exhausted from the exhaust pipe 14 of the reaction pipe 1 together with the carrier gas supplied to the reaction gas supply pipe 10. Is also good.

[0019]

According to the method of the present invention, the high-concentration layer caused by the residual dopant in the dopant supply tube is eliminated, the doped semiconductor film can be formed as designed, and the reproducibility of the doping amount between batches is improved. Therefore, the stability of device characteristics and the yield can be improved.

According to the apparatus of the present invention, by connecting the dopant exhaust pipe to the dopant supply pipe, even if the dopant accumulates in the dopant supply pipe, this can be eliminated, so that the doped semiconductor film is formed with good reproducibility. be able to.

[Brief description of the drawings]

FIGS. 1A and 1B are schematic diagrams illustrating a gas flow in a reaction tube for explaining an embodiment of the present invention, in which FIG. 1A illustrates a case where a semiconductor film is formed, and FIG. FIG.

FIG. 2 is a schematic configuration diagram of a vertical CVD apparatus as a doped semiconductor film forming apparatus for describing an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reaction tube 11 Dopant supply pipe 12 Dopant exhaust pipe

Claims (2)

[Claims] 1. A method for forming a doped semiconductor film on a substrate by supplying a dopant source gas into a reaction tube from a dopant supply tube, wherein the dopant in the dopant supply tube is excluded during a time other than the time when the semiconductor film is formed. A method for forming a doped semiconductor film, characterized in that: 2. A dopant supply pipe for supplying a dopant source gas into a reaction tube for forming a doped semiconductor film on a substrate; a dopant exhaust pipe connected to the dopant supply pipe for exhausting the dopant in the dopant supply pipe; An apparatus for forming a doped semiconductor film, comprising: