JPH08330246A - Method of growing polycrystalline silicon film - Google Patents

Abstract

PURPOSE: To grow a polycrystalline silicon film equal in thickness and surface resistance in short time by thermally diffusing the phosphorus heaving adhered to the surface compulsively into a polycrystalline silicon film after doping the polycrystalline silicon film on a semiconductor substrate with phosphorus. CONSTITUTION: A polycrystalline silicon film is deposited on the surface of a silicon substrate 42 by decompressing the inside of a reaction tube 41, and performing heating by a heater 45, and introducing polycrystalline silicon material gas by a nozzle 43. Next, phosphorus source gas is introduced into a reaction tube 41 from the nozzle 44, and the phosphorus is thermally diffused as dopant within the polycrystalline silicon film. Phosphorus reactive species remaining on the surface of the polycrystalline silicon film is thermally diffused compulsorily into this polycrystalline film. By repeating the above operation several times, a polycrystalline silicon film, where a multilayer of polycrystalline silicon film doped with phosphorus is deposited, is grown.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film forming method for forming a phosphorus-doped polycrystalline silicon film on a semiconductor substrate.

[0002]

2. Description of the Related Art A conventional method for forming a phosphorus-doped polycrystalline silicon film will be described with reference to FIGS.

FIG. 4 is a sectional view showing an example of the structure of a film forming apparatus for forming such a polycrystalline silicon film. In the figure, in the reaction tube 41, a large number of silicon substrates 4
2 are arranged in the vertical direction. The nozzle 43 is used to introduce a gas (for example, SiH ₄ gas) of a silicon forming material into the reaction tube 41 when forming a polycrystalline silicon film. The nozzle 44 is used to introduce a phosphorus source gas (for example, PH ₃ gas) into the reaction tube 41 when performing phosphorus doping. Furthermore, the heater 45
Are used to control the temperature in the reaction tube 41.

FIG. 5 is a diagram for explaining a step of forming a phosphorus-doped polycrystalline silicon film by using the film forming apparatus shown in FIG.

First, while the inside of the reaction tube 41 under reduced pressure is heated to a predetermined temperature by using the heater 45, the silicon forming material gas is introduced from the nozzle 43. As a result, a polycrystalline silicon film is formed on the surface of the silicon substrate 42.

Next, while keeping the set temperature as it is, phosphorus source gas is introduced from the nozzle 44 into the reaction tube 41.
As a result, phosphorus reactive species are attached as a dopant to the surface of the polycrystalline silicon film, and are thermally diffused in the polycrystalline silicon film.

Subsequently, a second-layer polycrystalline silicon film is deposited on the surface of the phosphorus-doped polycrystalline silicon film in the same manner as in the above step, and further, in the same manner as in the above-mentioned step, the second-layer polycrystalline silicon film is formed. Dope with phosphorus.

By repeating the above steps a plurality of times, a plurality of phosphorus-doped polycrystalline silicon films can be laminated.

[0009]

However, in the process of forming such a phosphorus-doped polycrystalline silicon film, compared with the process of forming undoped polycrystalline silicon,
There are drawbacks that the deposition rate of polycrystalline silicon is slow, and the deposited polycrystalline silicon film has poor film thickness uniformity and surface resistance uniformity.

This is because the phosphorus reactive species adhered to the surface of the polycrystalline silicon film (see the above process) does not completely diffuse into the film but remains on the film surface, and the phosphorus reactive species remaining on This is because the deposition of the polycrystalline silicon film is suppressed. That is, if the phosphorus reactive species remain on the surface of the polycrystalline silicon film, the polycrystalline silicon will not be deposited for a while after the introduction of the silicon forming material gas is started. The unevenness of the residual density of the above causes the unevenness of the film thickness and the unevenness of the surface resistance.

Here, the deterioration of the deposition rate causes an increase in the manufacturing cost, and the unevenness of the film thickness and the unevenness of the surface resistance cause the deterioration of the quality of the semiconductor element.

The present invention has been made in view of the above drawbacks of the prior art, and is capable of forming a polycrystalline silicon film having a uniform film thickness and surface resistance in a short time. It is an object of the present invention to provide a film forming method.

[0013]

A method for producing a polycrystalline silicon film according to the present invention is a method for forming a polycrystalline silicon film by laminating a plurality of phosphorus-doped polycrystalline silicon films on a semiconductor substrate. A first step of forming a polycrystalline silicon film thereon; a second step of doping the polycrystalline silicon film formed in the first step with phosphorus; and a second step of forming a polycrystalline silicon film on the surface of the polycrystalline silicon film. And a third step of forcibly thermally diffusing the attached phosphorus into the polycrystalline silicon film.

[0014]

According to the present invention, by providing the step (third step) forcibly thermally diffusing the phosphorus adhered to the surface of the polycrystalline silicon film in the second step into the polycrystalline silicon film,
The residual concentration of the phosphorus reactive species on the surface of the polycrystalline silicon film is reduced.

[0015]

The present invention will now be described in more detail while describing one embodiment of the present invention.

First, a method of forming a polycrystalline silicon film according to this embodiment will be described with reference to FIG. FIG. 1 is a diagram for explaining a process of forming a phosphorus-doped polycrystalline silicon film by using this embodiment. The process conditions at this time are shown in Tables 1 and 2.

[0017]

[Table 1]

[0018]

[Table 2] In addition, also in this example, a film forming apparatus (see FIG. 4) similar to the conventional film forming method was used.

First, the inside of the reaction tube 41 is set to 67 Pa.
The pressure was reduced to, and the temperature was raised to 620 ° C. using the heater 45.
Then, SiH ₄ gas (polycrystalline silicon material gas) was introduced from the nozzle 43 at a flow rate of 100 sccm (corresponding to the “first step” of the present invention). As a result, a 30-nm-thick polycrystalline silicon film was deposited on the surface of the silicon substrate 42 (diameter 200 mm).

Next, with the set temperature kept at 620 ° C., PH ₃ gas (phosphorus source gas) was introduced into the reaction tube 41 from the nozzle 44 at a flow rate of 20 sccm for 3 minutes (the “second step of the present invention”). )). As a result, phosphorus was thermally diffused in the polycrystalline silicon film as a dopant.

Then, the internal temperature of the reaction tube 41 is set to 850
By heating to 10 ° C. and heating for 10 minutes, the phosphorus reactive species remaining on the surface of the polycrystalline silicon film were forcibly diffused into the polycrystalline silicon film (see “Third step of the present invention”). Equivalent to).

Subsequently, a second-layer polycrystalline silicon film is formed on the surface of the phosphorus-doped polycrystalline silicon film in the same manner as in the above step, and subsequently, the second-layer polycrystalline silicon film is formed in the same manner as in the above-mentioned step. The film was doped with phosphorus, and forced thermal diffusion of phosphorus reactive species was performed in the same manner as in the above step.

By repeating the above steps 8 times, a polycrystalline silicon film is formed by laminating 10 layers of phosphorus-doped polycrystalline silicon film.

Subsequently, for comparison, a phosphorus-doped polycrystalline silicon film was also formed by using the conventional film forming method (see FIG. 5). Table 2 shows the film forming conditions at this time.

Next, the uniformity of the film thickness and the surface resistance of the phosphorus-doped polycrystalline silicon film (in this example and the conventional example) thus manufactured was evaluated. The evaluation results are shown in FIGS. 2 and 3 and Table 2. 2 is a graph showing the evaluation results of the sample according to this example, and FIG. 3 is a graph showing the evaluation results of the sample according to the conventional example. In both figures, the horizontal axis represents the distance from the center of the silicon substrate, and the vertical axis represents the film thickness and surface resistance.

As can be seen from FIGS. 2, 3 and Table 2,
According to this example, both the film thickness uniformity and the surface resistance uniformity could be improved as compared with the sample of the conventional example.

Further, according to the present embodiment, since no phosphorus reactive species remain on the surface of the polycrystalline silicon film, the polycrystalline silicon is deposited and film-formed immediately after the introduction of the silicon forming material gas is started. It was also possible to save time.

[0028]

As described in detail above, according to the method for forming a polycrystalline silicon film according to the present invention, a polycrystalline silicon film having a uniform film thickness and surface resistance can be formed in a short time. it can.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a process of forming a phosphorus-doped polycrystalline silicon film by using an example of the present invention.

FIG. 2 is a graph showing evaluation results of samples according to an example of the present invention.

FIG. 3 is a graph showing an evaluation result of a sample according to a conventional film forming method.

FIG. 4 is a cross-sectional view showing an example of a film forming apparatus used for forming a polycrystalline silicon film.

FIG. 5 is a diagram for explaining a step of forming a phosphorus-doped polycrystalline silicon film by using a conventional film forming method.

[Explanation of symbols]

 41 Reaction Tube 42 Silicon Substrate 43 Nozzle 44 Nozzle 45 Heater

Claims (2)

[Claims] 1. A film forming method for laminating and forming a plurality of phosphorus-doped polycrystalline silicon films on a semiconductor substrate, comprising: a first step of forming a polycrystalline silicon film on the semiconductor substrate; A second step of doping phosphorus into the polycrystalline silicon film formed in the step, and forcibly diffusing the phosphorus adhering to the surface of the polycrystalline silicon film into the polycrystalline silicon film in the second step A method for producing a polycrystalline silicon film, comprising: a third step. 2. The polycrystalline silicon according to claim 1, wherein the third step is a step of heating the semiconductor substrate at a temperature higher than those of the first step and the second step. Deposition method.