JP2003332240A - Gas cleaning method for deposited-silicon film forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that, though a gas cleaning step can improve the productivity of semiconductor crystals by shortening the time required for performing the step as much as possible, the possibility of finding out a new gas composition is small and, when a chemical reaction is caused at a high temperature so as to increase the rate of the reaction, devices and members are corroded and contaminants are produced. <P>SOLUTION: In a gas cleaning method for deposited-silicon film forming device, a silicon film caused to deposit on the surface of the supporting base of a silicon semiconductor substrate is removed at the time of causing a silicon film to deposit on the substrate. At the time of removing the silicon film deposited on the surface of the supporting base, the film is etched off by using a hydrogen chloride gas at a concentration of 85-100% after the temperature of the supporting base is raised to 1,000-1,200°C. It is preferable to raise the temperature of the supporting base while the internal pressure of the reaction chamber of the film forming deice is maintained at 1 atm after the silicon semiconductor substrate having the deposited film silicon film is taken out of the reaction chamber in a state where the internal pressure of the reaction chamber is 1 atm. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a semiconductor thin film on a substrate by using a chemical reaction such as a CVD method, and more particularly to a method for forming a silicon thin film on a silicon substrate.
The present invention relates to a gas cleaning method for etching and removing a silicon thin film deposited on a region other than a substrate in a film forming apparatus when forming a thin film.

[0002]

2. Description of the Related Art In a process of forming a semiconductor silicon crystal thin film on a silicon substrate, as shown in FIG. 1, a reaction apparatus mainly composed of a reaction vessel 1, a support base 2 and a silicon substrate 3 is used. A diluent gas and a source gas are introduced from the inlet 4 of the reaction container to cause a chemical reaction on the surface of the silicon substrate 3 which is heated to a high temperature.

Hydrogen gas is used as a diluent gas for the chemical reaction, and silane gas (monosilane, disilane, dichlorosilane, trichlorosilane, silicon tetrachloride) is used as a source gas. At this time, the temperature of the silicon substrate 3 is 800 ° C. to 1200 ° C.
Since it needs to be uniformly heated to a high temperature of ° C, it is supported on a support base 2 made of a material having good thermal conductivity such as silicon carbide and having a diameter larger than that of the silicon substrate 3. Therefore, when a chemical reaction occurs using silane gas, silicon is deposited not only on the silicon substrate 3 heated to a high temperature but also on the surface of the support base 2 also heated to a high temperature to form a thin film.

Since this deposited silicon film is a thin film composed of a collection of particles, it is easily peeled off, and when peeled off, it becomes fine particles which float in the reaction vessel 1 and adhere to the surface of the silicon substrate 3 to form a semiconductor silicon crystal thin film. Of the semiconductor silicon crystal thin film having a large number of protrusion defects on the surface. In order to prevent this, usually, after forming the semiconductor silicon crystal thin film, after taking out the semiconductor crystal, only the support base 2 is heated to a desired temperature, and a mixed gas of hydrogen gas and nitrogen gas is introduced from the inlet of the reaction vessel. A cleaning gas such as a mixed gas of hydrogen gas and hydrogen chloride gas is supplied to remove the silicon film deposited on the silicon substrate and the inner wall of the reaction container.

For example, in Japanese Unexamined Patent Publication (Kokai) No. 1-61986 (Patent No. 2761913), when the reaction vessel is gas-cleaned, the inside of the reaction vessel is first purged with hydrogen gas, and then a hydrogen-supporting stream of 20 slm is treated with HCl. A high flow of a high etching gas is added for about 20 slm to etch the deposited film of the susceptor at 1200 ° C. After the susceptor is etched, the hydrogen flow is increased to 100 slm for 20 seconds to dilute the HCl gas, A method of etching away the deposited film on the walls of the reactor and finally purging the reaction vessel with a hydrogen stream of 100 slm.

[0006]

In the production of a semiconductor silicon crystal film using a reaction apparatus such as a CVD method, a hydrogen gas and a nitrogen gas are mixed to remove the silicon film deposited on the surface of the supporting table or the inner wall surface of the reaction vessel. Gas or a mixed gas of hydrogen gas and hydrogen chloride gas is usually used.

However, the above-mentioned Japanese Patent Laid-Open No. 1-61986.
As disclosed in the publication, even in the method using a mixed gas of hydrogen gas and hydrogen chloride gas, when a single crystal silicon of 10 μm is grown in 2 minutes, the susceptor etching can be performed by 4 times.
It took 0 seconds and 65 seconds to etch the tube wall of the reaction vessel.

[0008] Usually, even if the susceptor is heated to about 1200 ° C, the temperature of the reaction vessel does not rise sufficiently, and even if the deposit on the surface of the susceptor can be removed, the deposit on the inner wall surface of the reaction vessel cannot be completely removed. There is a problem. 1 of this solution
As an example, hydrogen chloride gas (20 to 40
%) And a chlorine trifluoride gas are separately supplied with a time lag (Japanese Patent Laid-Open No. 7-12).
No. 2493), the operation becomes complicated and the cleaning time cannot be shortened.

In such a conventional cleaning method using hydrogen chloride gas, a cleaning time of about 2/3 is required, which is about the same as the film forming time of the deposited film or at the shortest, which is required for complete removal of the deposited film. The time required was at least 1 minute at the earliest.

Although the gas cleaning step is a step in which the productivity of semiconductor crystals is improved by shortening the time as much as possible, it is unlikely that a new gas composition will be found, and the chemical reaction rate should be as fast as possible. In order to do so, the reaction must be carried out at a high temperature, but this causes the problem of corrosion and contaminants of equipment members.

[0011]

Conventionally, when a mixed gas of hydrogen gas and hydrogen chloride gas is used as a cleaning gas, the metal part of the reactor and parts made of carbon or silicon carbide are corroded and damaged by the hydrogen chloride gas. However, there is a problem that contaminants generated by corrosion are mixed in the epitaxial film, and a gas containing hydrogen chloride gas in a concentration of about 10% to 60% has been selected as a preferable condition based on experience.

However, the inventor of the present invention has found that the rate at which the silicon film deposited on the surface of the support in the semiconductor crystal manufacturing apparatus or the inner wall surface of the reaction vessel is changed to a compound that easily vaporizes is the surface temperature to be treated and the concentration of hydrogen chloride gas. Related to the above, the speed increases as the concentration of the hydrogen chloride gas increases with the surface temperature to be treated of 1000 ° C. or higher, and the cleaning time of the surface of the support table and the inner wall surface of the reaction vessel can be significantly shortened, and Even with such a high concentration, surprisingly, corrosion and damage to the metal part of the reactor and parts made of carbon or silicon carbide can be suppressed for a long period of time, and the comprehensive evaluation of the quality of the deposited wafer can be improved. Found.

That is, the present invention is a gas cleaning method for removing a silicon film deposited on a surface of a support base of a semiconductor silicon substrate when the silicon film is deposited on the semiconductor silicon substrate, and the temperature of the support base of the substrate is 1000 ° C. A gas cleaning method for a deposition apparatus for depositing a silicon film, which comprises heating the temperature to ˜1200 ° C. and then etching and removing the silicon film with a hydrogen chloride gas having a concentration of 85% to 100%.

Further, according to the present invention, a substrate having a silicon film deposited on a semiconductor silicon substrate is taken out from the reaction container in the reaction container of the film forming apparatus under a pressure of 1 atm, and then kept at 1 atm. In the above gas cleaning method, the temperature of the substrate support is raised.

Further, the present invention is the above-mentioned gas cleaning method, characterized in that the silicon film deposited on the inner wall surface of the quartz glass reaction vessel is simultaneously etched and removed.

Further, according to the present invention, the material of the substrate support is carbon or silicon carbide, and the substrate support is heated by irradiating infrared rays from outside the reaction vessel. Is the way.

According to the method of the present invention, the silicon gas deposited on the surface of the support and the inner wall surface of the reaction vessel can be rapidly etched by etching by supplying the cleaning gas to the reaction vessel without changing the composition of the cleaning gas. It can be removed, and the removal rate can be 40 μm or more per minute.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a perspective view conceptually showing a state during film formation in a silicon CVD film forming apparatus. The film forming apparatus can be applied not only to horizontal CVD, but also to vertical and various CVD apparatuses. As shown in FIG. 1, a semiconductor silicon substrate 3 having a smaller diameter is placed on a support 2 in a quartz glass reaction vessel 1, and hydrogen gas and trichlorosilane gas are flown from a gas supply pipe (not shown), A silicon film is formed on the semiconductor silicon substrate 3.

The pressure at the time of gas cleaning has a higher molar concentration per volume than that at low pressure even if the gas concentration is the same at a higher pressure, so that the removal rate of the silicon film proceeds more quickly, but the semiconductor silicon substrate is removed from the reaction vessel. It is advantageous to set the pressure at the time of taking out and charging the semiconductor silicon substrate into the reaction vessel to be the same because throughput can be increased. Since loading and unloading of the semiconductor silicon substrate are usually performed at 1 atm, it is desirable from the viewpoint of throughput that the pressure during cleaning is also kept at 1 atm.

FIG. 2 is a perspective view conceptually showing a state during gas cleaning in the silicon CVD film forming apparatus. After the film formation, the inside of the reaction vessel 1 made of quartz glass is evacuated to one side and the concentration of the cleaning gas is 85 to 10
0% hydrogen chloride gas is introduced into the reaction vessel 1 from the other side. At this time, the pressure in the reaction vessel 1 may remain at 1 atm. The silicon film deposited on the surface of the support installed in the reaction vessel and the inner wall of the reaction vessel chemically reacts with hydrogen chloride gas, and the silicon film is changed to a compound that easily vaporizes and is vaporized and removed.

FIG. 3 shows the relationship between the hydrogen chloride gas concentration and the heating temperature of the support, which affects the removal rate of the silicon film. Figure 3
As shown in FIG. 5, it is understood that the heating temperature may be lower as the concentration of the hydrogen chloride gas is higher when the removal rate of the silicon film is constant. The heating temperature may be lowest when the hydrogen chloride gas is 100%. When the hydrogen chloride gas concentration is about 85%, there is practically no great difference from when the hydrogen chloride gas concentration is 100%. As a gas for diluting the concentration of hydrogen chloride gas to about 85%, an inert gas such as hydrogen gas, argon gas or helium gas can be used.

Even if the hydrogen chloride gas concentration is the same, the higher the reaction temperature is, the higher the reaction rate of the hydrogen chloride gas and the silicon deposited film is. Therefore, it is desirable to raise the heating temperature of the support base. When the temperature exceeds 1200 ° C., carbon or silicon carbide, which is the material of the support, and other metal parts in the reaction apparatus are easily corroded by hydrogen chloride gas, which is not desirable. The upper limit temperature is more preferably 115
Set to 0 ° C.

Members other than the support, such as the inner wall surface of the reaction vessel, have a slower rate of temperature rise than the support, and the silicon film deposited on these members reacts with hydrogen chloride gas at a temperature lower than the temperature of the support. However, the film thickness of these silicon films is usually
Under the condition that the thickness of the silicon film deposited on the surface of the support is thinner and the silicon film deposited on the surface of the support is completely removed,
The silicon film deposited on the inner wall surface of the reaction container is also removed almost at the same time.

As the heating means for the support and the inner wall of the reaction vessel, any suitable heating means such as high frequency heating, resistance heating, infrared lamp heating or the like can be used, but the heating source is installed outside the reaction vessel. The method of heating the substrate by irradiating infrared rays from the outside of the lamp with a halogen lamp does not enter the reaction container even if contaminants are generated from the heating source, and the heating / cooling speed is fast (throughput is high). There is an advantage that the temperature distribution can be finely adjusted. In other methods, carbon and silicon carbide, which are the materials of the supporting base, are directly heated, so that they are considerably outgassed and may become a source of pollution.

Directly heating the interior of the film forming apparatus and heating the cleaning gas are effective in increasing the cleaning rate of the inner wall of the reaction vessel, which is slow in temperature rise due to infrared heating.

When removing the deposited film only on the surface of the support of the film forming apparatus, instead of performing the semiconductor thin film formation and the removal of the deposited film on the surface of the support in the same reaction vessel, the support is externally provided. It is also possible to remove the deposited silicon film by using hydrogen chloride gas in a separately provided reaction container in the same manner as above.

Since the removal rate of the silicon film is determined by the heating temperature of the support and the hydrogen chloride gas concentration, the point of complete removal of the silicon film can be predicted from this removal rate of the silicon film. After the removal of the silicon film by hydrogen chloride gas etching, it is necessary to stop the supply promptly to avoid overetching. Therefore, the supply of hydrogen chloride gas is stopped immediately after the complete removal of the silicon film. As a result, it is possible to prevent corrosion and damage to the metal member of the reaction vessel due to unnecessary supply of hydrogen chloride gas.

Since the silicon deposited film of 40 μm or more per minute can be removed by the method of the present invention, if the silicon deposited film is 20 μm, the supply of hydrogen chloride gas may be stopped in 30 seconds. The time of complete removal of the silicon film can be determined from the removal rate of the silicon film based on previously obtained data determined by the heating temperature and the hydrogen chloride gas concentration. in this way,
According to the method of the present invention, the removal time of the silicon film is shortened to 70% to 30% of the conventional method.

[0029]

Example 1 A semiconductor silicon substrate 3 having a diameter of 200 mm is placed on a support base 2 having a diameter of 280 mm in a quartz glass reaction vessel 1 of the film forming apparatus shown in FIG. 1, and a gas supply pipe (not shown). Thus, the temperature of the support base 2 and the semiconductor silicon substrate 3 was raised while only hydrogen gas was allowed to flow as the diluent gas from the inlet 4 of the reaction vessel. The flow rate of hydrogen gas was 40 liters per minute. The pressure in the reaction vessel 1 was 1 atm. As the temperature raising method, a method of irradiating the semiconductor silicon substrate 3 and the support base 2 with infrared rays from the outside of the reaction vessel 1 by using a halogen lamp (not shown) was adopted.

By holding the semiconductor silicon substrate 3 at 1150 ° C. for 60 seconds, the silicon oxide thin film covering the surface of the semiconductor silicon substrate 3 was removed to expose the silicon surface. Next, the temperatures of the semiconductor silicon substrate 3 and the support base 2 are set to 1125.
The temperature was adjusted to ° C. 4% trichlorosilane gas in hydrogen gas
The mixture was mixed at a concentration of 1 to be introduced from the inlet 4 of the reaction vessel through a gas supply pipe (not shown), and the mixture was kept for 5 minutes to form a silicon thin film having a thickness of 20 μm on the surface of the semiconductor silicon substrate 3.

At this time, a silicon thin film having a thickness of about 20 μm was deposited on the surface of the support base 2 on the region outside the semiconductor silicon substrate 3. Next, stop the supply of trichlorosilane gas,
After setting the atmosphere of only hydrogen gas, the infrared rays irradiating the semiconductor silicon substrate 3 and the support base 2 were weakened to lower the temperature, and the semiconductor silicon substrate 3 was taken out.

Here, on the surface of the support base 2, there is no silicon deposition film in the central portion where the semiconductor silicon substrate 3 was placed,
The silicon deposition film was attached only to the outer peripheral portion. While the pressure inside the reaction vessel 1 remains at 1 atm, while supplying hydrogen gas as a dilution gas into the reaction vessel 1, the infrared rays irradiating the semiconductor silicon substrate 3 and the support base 2 are strengthened to raise the temperature. The temperature of 1 was raised to 1100 ° C. The removal rate of the silicon film is 80 μm when hydrogen chloride concentration of 100% is used at this temperature.
Since it is more than 1 minute / minute, it is sufficient to remove the deposited film of 20 μm in 15 seconds.

When the temperature of the support table 2 reaches 1100 ° C., the pressure in the reaction vessel 1 remains at 1 atm, the supply of the hydrogen gas as the diluent gas is stopped, and the flow rate of the hydrogen chloride gas is changed to 20 at the same time. It was adjusted to 1 liter / min and was supplied into the reaction vessel 1 through a gas supply pipe (not shown), and when it was allowed to flow for 15 seconds, the supply of hydrogen chloride gas was stopped, and at the same time, the hydrogen gas flow rate was set to 40 liters / min. The infrared rays irradiating the semiconductor silicon substrate 3 and the support base 2 were weakened to lower the temperature. When the surface of the support 2 and the inner wall surface of the reaction vessel were observed after the temperature was finished, no silicon deposition film was observed.

The holding time of 15 seconds in this embodiment is 50% of hydrogen chloride concentration under conventional conditions, for example, 1200 ° C.
It is equivalent to the removal rate when gas cleaning with
The same removal rate could be achieved at about 100 ° C lower temperature. In addition, the film-forming equipment will not corrode even if it is used for 1 month to 6 months.
It was visually confirmed that the damage was suppressed.

[Brief description of drawings]

FIG. 1 is a perspective view conceptually showing a state during film formation in a silicon CVD film forming apparatus.

FIG. 2 is a perspective view conceptually showing a state during gas cleaning in the silicon CVD film forming apparatus.

FIG. 3 is a graph showing the relationship between the hydrogen chloride gas concentration and the heating temperature of the support, which affects the removal rate of the silicon film.

[Explanation of symbols]

1 reaction vessel 2 support 3 Semiconductor silicon substrate 4 Reaction vessel inlet 5 Silicon deposited film

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 4K030 AA06 AA17 BA29 CA04 CA17                       DA06 FA10 GA02 JA09 JA10                       KA46                 5F045 AB02 AC01 AC03 AD12 AD13                       AD14 AD15 AD16 AE29 AF03                       BB14 DP04 DP19 DP20 EB06                       EK14 EM09

Claims (4)

[Claims] 1. A gas cleaning method for removing a silicon film deposited on a surface of a support base of a substrate when depositing a silicon film on a semiconductor silicon substrate, wherein a temperature of the support base of the substrate is set to 1
After the temperature is raised from 000 ° C to 1200 ° C, the concentration is 85% to 1
A gas cleaning method for a film deposition apparatus for depositing a silicon film, which comprises etching and removing the silicon film with a hydrogen chloride gas of 00%. 2. A substrate in which a silicon film is deposited on a semiconductor silicon substrate is taken out from the reaction container in the reaction container of the film forming apparatus under a pressure of 1 atm, and then the substrate is supported under the condition of 1 atm. The gas cleaning method according to claim 1, wherein the temperature of the table is raised. 3. The gas cleaning method according to claim 1, wherein the silicon film deposited on the inner wall surface of the quartz glass reaction vessel is simultaneously etched and removed. 4. The substrate of the substrate is made of carbon or silicon carbide, and the substrate of the substrate is heated by irradiating infrared rays from outside the reaction vessel. The gas cleaning method described in.