CN114045470B - Cleaning method for normal-pressure epitaxial reaction chamber and epitaxial silicon wafer - Google Patents

Abstract

The embodiment of the invention discloses a cleaning method for a normal-pressure epitaxial reaction chamber and an epitaxial silicon wafer; the cleaning method comprises the following steps: in the heating stage and the baking stage of the etching reaction, carrier gas is introduced into the reaction chamber at a first gas flow rate; in the etching stage of the etching reaction, the carrier gas and the etching gas are introduced into the reaction chamber at a second gas flow rate; wherein the first gas flow rate is less than the second gas flow rate.

Description

A cleaning method for atmospheric pressure epitaxy reaction chamber and epitaxial silicon wafer

technical field

Embodiments of the present invention relate to the technical field of semiconductor manufacturing, and in particular, to a method for cleaning an atmospheric pressure epitaxy reaction chamber and an epitaxial silicon wafer.

Background technique

As an important part of today's semiconductor material field, epitaxial silicon wafers can be prepared by depositing a single crystal silicon epitaxial layer on a polished silicon wafer substrate by vacuum epitaxial deposition, reduced pressure epitaxial deposition and atmospheric pressure epitaxial deposition. Atmospheric pressure epitaxial deposition is the most widely used epitaxial layer growth method.

During the atmospheric pressure epitaxy deposition reaction process, after the silicon source reaction gas enters the reaction chamber, not only a single crystal silicon epitaxial layer will be grown on the polished silicon wafer substrate, but also a polycrystalline silicon layer will be grown on the inner wall of the reaction chamber. Therefore, the reaction chamber usually needs to perform an etching reaction after the growth of the epitaxial silicon wafer is completed, so that the polysilicon on the inner wall of the reaction chamber is sufficiently etched to ensure stable quality of the epitaxial silicon wafer.

SUMMARY OF THE INVENTION

In view of this, the embodiments of the present invention are expected to provide a method for cleaning an epitaxial reaction chamber at atmospheric pressure and an epitaxial silicon wafer, which can fully etch the polysilicon deposited on the inner wall of the reaction chamber, thereby ensuring the flatness of the epitaxial silicon wafer and reducing the epitaxial silicon wafer. level of particle contamination on the wafer surface.

The technical solution of the embodiment of the present invention is realized as follows:

In a first aspect, an embodiment of the present invention provides a method for cleaning an atmospheric pressure epitaxy reaction chamber, the cleaning method comprising:

In the heating stage and the baking stage of the etching reaction, the carrier gas is introduced into the reaction chamber at the first gas flow rate;

In the etching stage of the etching reaction, the carrier gas is introduced into the reaction chamber with the etching gas at a second gas flow rate;

Wherein, the first gas flow rate is smaller than the second gas flow rate.

In a second aspect, an embodiment of the present invention provides an epitaxial silicon wafer, the epitaxial silicon wafer is prepared in an atmospheric pressure epitaxy reaction chamber cleaned according to the cleaning method described in the first aspect.

The embodiments of the present invention provide a method for cleaning a normal pressure epitaxy reaction chamber and an epitaxial silicon wafer; in the heating stage and the baking stage of the etching reaction, only a carrier gas is introduced into the reaction chamber, and the carrier gas is reduced The injection speed is so that the temperature of the carrier gas in the high temperature reaction chamber rises to a higher temperature and the heat is transferred to the upper quartz dome by thermal conduction. During the etching stage, the etching gas enters the reaction chamber together with the carrier gas. In addition, in order to ensure that there is sufficient etching gas in the reaction chamber, it is necessary to increase the gas injection rate in this etching stage.

Description of drawings

FIG. 1 is a schematic structural diagram of an atmospheric pressure epitaxy reaction device provided by an embodiment of the present invention;

FIG. 2 is a schematic diagram of the variation trend of the temperature of the quartz dome over time at each stage of the existing etching reaction provided by the embodiment of the present invention;

FIG. 3 is a schematic flowchart of a method for cleaning an atmospheric pressure epitaxy reaction chamber according to an embodiment of the present invention;

FIG. 4 is a schematic diagram showing the variation trend of the temperature of the quartz dome at each stage of the etching reaction with time according to an embodiment of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

Referring to FIG. 1, it shows an atmospheric pressure epitaxy reaction device 1 capable of implementing an embodiment of the present invention. The atmospheric pressure epitaxy reaction device 1 may include: a pedestal 10, the pedestal 10 is used for carrying a polished silicon wafer W; a pedestal A support frame 20, the base support frame 20 is used to support the base 10 and drive the base 10 to rotate around the central axis X at a certain speed during the epitaxial growth, wherein during the rotation of the base 10, the polished silicon wafer W follows the base The seat 10 rotates together around the central axis X, that is to say, the polished silicon wafer W is kept stationary relative to the susceptor 10. Therefore, the radial edge of the susceptor 10 and the adjacent part 10A (usually the preheat ring) are required to be in contact with each other. There is a small gap G between them; an upper quartz dome 30A and a lower quartz dome 30B, which together enclose the reaction chamber in which the susceptor 10 and the susceptor support 20 are accommodated RC, wherein the base 10 divides the reaction chamber RC into an upper reaction chamber RC1 and a lower reaction chamber RC2, and the polished silicon wafer W is placed in the upper reaction chamber RC1; The gas pressure in the upper reaction chamber RC1 is greater than that in the lower reaction chamber RC2, so that the gas in the upper reaction chamber RC1 will enter the lower reaction chamber RC2 through the gap G; 30A and the lower quartz dome 30B are composed; the gas inlet 40 is used to transport the reaction gas in the upper reaction chamber RC1, including silicon source gas, hydrogen gas, and dopant gas, so as to react with the hydrogen gas through the silicon source gas Silicon atoms are generated and deposited on the polished silicon wafer W to grow an epitaxial layer on the polished silicon wafer W, and the epitaxial layer is doped with a dopant gas to obtain the desired resistivity; the exhaust port 50, the The exhaust port 50 is used to discharge the reaction exhaust gas from the reaction chamber RC; a plurality of heating bulbs 60 are arranged on the periphery of the upper quartz dome 30A and the lower quartz dome 30B and are used to pass through the upper quartz dome 30A and the lower quartz dome 30A. The quartz dome 30B provides a high temperature environment for the vapor phase epitaxy deposition reaction in the reaction chamber RC, which is why the material of the upper quartz dome 30A and the lower quartz dome 30B is a transparent quartz material; Part 70 is installed.

During the continuous production of epitaxial silicon wafers based on the reaction chamber RC in the above-mentioned atmospheric pressure epitaxy reaction device 1, the reaction chamber RC needs to be etched (also called epitaxial silicon wafer growth one or more times) in the reaction chamber RC. It is called "self-cleaning"), in this process, the deposition reaction of the epitaxial silicon wafer and the etching reaction of the reaction chamber RC alternately occur in the reaction chamber RC.

In addition, in the process of mass production, it was found that after replacing the quartz dome, the longer the quartz dome was used, the worse the flatness of the epitaxial silicon wafer prepared by the reaction chamber RC, and the greater the level of particle contamination on the surface of the epitaxial silicon wafer. At the same time, this also shows that the etching reaction of the inner wall of the reaction chamber RC is not sufficient, which causes the residual polysilicon on the upper quartz dome 30A to deteriorate the flatness of the epitaxial silicon wafer; and the upper quartz dome 30A is located directly above the epitaxial silicon wafer. During the epitaxial growth reaction, the residual polysilicon on the upper quartz dome 30A may fall off and fall to the surface of the epitaxial silicon wafer, so that the particle contamination level on the surface of the epitaxial silicon wafer increases. It is found through research that the insufficient polysilicon etching on the upper quartz dome 30A is mainly due to the fact that during the etching reaction, when the temperature inside the reaction chamber RC rises to the highest point, the temperature of the upper quartz dome 30A does not rise to the point of etching. optimum temperature for the reaction. Referring to FIG. 2 , it shows a schematic diagram of the variation trend of the temperature of the upper quartz dome with time in each stage of the existing etching reaction, wherein the abscissa represents the time used for the etching reaction, and the ordinate represents the temperature of the upper quartz dome 30A in the etching reaction. It can be seen from FIG. 2 that the etching reaction includes a heating stage, a baking stage, an etching stage and a cooling stage. In order to facilitate the identification of the time spent in each stage, a black vertical dashed line is used to distinguish each stage in FIG. 2 . It can be seen from FIG. 2 that in the existing etching reaction, the total time spent in the heating stage and the baking stage is about 145s; after the baking is over, in the initial stage of the etching, the temperature of the upper quartz dome 30A is 577°C. The temperature is not the optimum temperature for the etching reaction, so the upper quartz dome 30A cannot be sufficiently etched at this temperature. It should be noted that the optimum temperature for the etching reaction is 590°C or higher. Therefore, in order to etch and remove the polysilicon deposited on the upper quartz dome 30A as much as possible, the etching reaction time can only be extended. As shown in FIG. 2, in the entire etching reaction stage, the carrier gas and the etching Etching gas, the time used in the etching stage is about 105s.

It should be noted that there are two sources of heat for the temperature rise of the upper quartz dome 30A. One is that the heating bulb 60 transfers heat to the upper quartz dome 30A in the form of thermal radiation, and the other is that the gas in the reaction chamber RC is in the form of heat conduction. Heat is transferred to the upper quartz dome 30A.

Based on the above description, the embodiment of the present invention expects that in different stages of the etching reaction, by controlling the gas flow rate of the carrier gas flowing into the reaction chamber RC to enhance the temperature of the gas heat conduction, thereby increasing the temperature of the quartz dome 30A in the early stage of the etching stage, And in different stages of the etching reaction, the pressure in the reaction chamber RC is kept constant at normal pressure. Referring to FIG. 3 , it shows a method for cleaning an atmospheric pressure epitaxy reaction chamber provided by an embodiment of the present invention, which can be applied to the atmospheric pressure epitaxy reaction device 1 shown in FIG. 1 , and the method includes:

S301, in the heating stage and the baking stage of the etching reaction, the carrier gas is introduced into the reaction chamber at a first gas flow rate;

S302, in the etching stage of the etching reaction, the carrier gas is introduced into the reaction chamber with the second gas flow rate and the etching gas;

Wherein, the first gas flow rate is smaller than the second gas flow rate.

For the technical solution shown in FIG. 3, in the heating stage and the baking stage of the etching reaction, only the carrier gas is introduced into the reaction chamber RC, and the injection speed of the carrier gas is reduced, so that the carrier gas is in the high temperature reaction chamber. The temperature in the chamber RC rises to a higher temperature and the heat is transferred to the upper quartz dome 30A by thermal conduction. During the etching stage, the etching gas enters the reaction chamber RC together with the carrier gas, and in order to ensure the reaction chamber RC There is sufficient etching gas in it, and it is necessary to increase the gas injection rate at this stage.

。这些化学反应生成的混合 物会随着载气H₂排出反应腔室RC，且不会和载气H₂发生化学反应。 For the technical solution shown in FIG. 3 , in some possible implementations, the carrier gas is hydrogen H ₂ , and the etching gas is hydrogen chloride gas HCl. It can be understood that the etching gas is hydrogen chloride gas HCl. In the etching stage, the etching gas HCl reacts with the polysilicon deposited on the upper quartz dome 30A at high temperature to generate a mixture of SiHCl ₃ , SiCl ₄ and H ₂ , specifically. The chemical reaction equation is:

. The mixture generated by these chemical reactions will be discharged from the reaction chamber RC along with the carrier gas H ₂ , and will not chemically react with the carrier gas H ₂ .

For the technical solution shown in FIG. 3, in some possible implementations, in the heating stage and the baking stage of the etching reaction, the first gas flow rate of the carrier gas is not greater than 40 L/min; In the etching stage of the etching reaction, the second gas flow rate of the carrier gas is between 40 and 60 L/min. It can be understood that in the embodiment of the present invention, although the injection speed of the carrier gas is reduced in the heating stage and the baking stage; in the etching stage, in order to ensure the concentration of the etching gas in the reaction chamber RC, it is necessary to increase the injection rate of the carrier gas. The injection rate of the large carrier gas.

It can be understood that the entire etching reaction includes a heating stage, a baking stage, an etching stage and a cooling stage. The size of the gas flow rate, the reaction chamber RC should be maintained under normal pressure. Therefore, if the injection rate of the carrier gas is reduced, in order to keep the internal pressure of the reaction chamber RC constant, the exhaust rate of the carrier gas needs to be reduced. In this way, the carrier gas will stay longer after entering the high temperature reaction chamber RC, so that the temperature of the carrier gas inside the reaction chamber RC will rise to a higher level.

In addition, using the second flow rate to inject the carrier gas and the etching gas into the reaction chamber RC in the etching stage can ensure the concentration of the etching gas in the etching stage, thereby ensuring the etching effect.

It should be noted that, in the embodiment of the present invention, preferably, the second gas flow rate is the gas flow rate set in the existing etching reaction.

For the technical solution shown in FIG. 3, in some possible implementations, in the etching reaction, the total time spent in the heating stage and the baking stage is 142 seconds; and in the etching stage Initially, the temperature of the upper quartz dome 30A was 596°C.

Referring to FIG. 4, it shows a schematic diagram of the variation trend of the temperature of the reaction chamber RC with time in different stages of the etching reaction according to the embodiment of the present invention, wherein the abscissa represents the time used in the etching reaction, and the ordinate represents the time of the upper quartz dome 30A in the etching reaction. temperature, and the black vertical dashed lines are used to distinguish between the stages in FIG. 4 . It can be seen from FIG. 4 that, in the embodiment of the present invention, the total time spent in the heating stage and the baking stage is 142s. Compared with the total time spent in the heating stage and the baking stage in the existing etching reaction in FIG. 2 , 145s, it can be seen that, The cleaning method provided by the embodiment of the present invention can reduce the time spent in the heating stage and the baking stage. Secondly, in the embodiment of the present invention, after the baking is completed, the temperature of the upper quartz dome 30A is 596° C. in the early stage of the etching stage, which reaches the optimum temperature of the etching reaction, and the time of the entire etching stage is about 48s. Compared with the 105 s used in the etching stage in the existing etching reaction in FIG. 2, the etching reaction time is greatly shortened, the polysilicon deposited on the upper quartz dome 30A is fully removed, the etching time is saved, and the etching time is improved. Etching efficiency.

Finally, the embodiment of the present invention also provides an epitaxial silicon wafer, and the epitaxial silicon wafer is prepared in a normal-pressure epitaxial reaction chamber cleaned by the cleaning method described in the foregoing technical solution.

It should be noted that the technical solutions described in the embodiments of the present invention may be combined arbitrarily unless there is a conflict.

The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention. should be included within the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims (7)

1. A cleaning method for an atmospheric pressure epitaxy reaction chamber, wherein the cleaning method comprises: In the heating stage and the baking stage of the etching reaction, the carrier gas is introduced into the reaction chamber at the first gas flow rate; In the etching stage of the etching reaction, the carrier gas is introduced into the reaction chamber with the etching gas at a second gas flow rate; Wherein, in the heating stage, the baking stage and the etching stage of the etching reaction, the reaction chamber is maintained at normal pressure, and the flow rate of the first gas is smaller than the flow rate of the second gas so as to increase the temperature during the heating stage. stage and bake stage to increase the temperature of the quartz dome at the beginning of the etch stage by increasing the residence time of the carrier gas in the reaction chamber; and, to increase the etch gas during the etch stage concentration to etch the polysilicon deposited on the quartz dome. 2 . The cleaning method according to claim 1 , wherein the carrier gas is hydrogen H ₂ , and the etching gas is hydrogen chloride gas HCl. 3 . 3 . The cleaning method according to claim 1 , wherein in the heating stage and the baking stage of the etching reaction, the first gas flow rate of the carrier gas is not greater than 40 L/min. 4 . 4 . The cleaning method according to claim 1 , wherein in the etching stage of the etching reaction, the second gas flow rate of the carrier gas is between 40 and 60 L/min. 5 . 5 . The cleaning method according to claim 1 , wherein in the etching reaction, the total duration of the heating stage and the baking stage is 142 seconds. 6 . 6 . The cleaning method according to claim 1 , wherein, at the beginning of the etching stage, the temperature of the upper quartz dome is 596° C. 7 . 7 . An epitaxial silicon wafer, characterized in that, the epitaxial silicon wafer is prepared in a normal-pressure epitaxial reaction chamber cleaned by the cleaning method according to any one of claims 1 to 6 .

Images