JP5609755B2 - Epitaxial wafer manufacturing method - Google Patents

Description

  The present invention relates to a method for cleaning a reaction vessel of an epitaxial growth apparatus and a method for manufacturing an epitaxial wafer.

In the production of a silicon epitaxial wafer using an epitaxial growth apparatus, Si is epitaxially grown on the wafer by using H ₂ and a silane gas such as SiHCl ₃ , SiH ₂ Cl ₂ , and SiCl ₄ that are Si source gases. By-products are also deposited in the reaction vessel during the epitaxial growth, which may reduce the quality of the wafer, and the by-products deposited on the components of this apparatus must be periodically removed. In addition, cleaning with hydrogen chloride gas is performed.

  In the conventional cleaning method, first, a region in which a wafer is placed in a reaction vessel is heated to a high temperature, and a deposit is etched by circulating hydrogen chloride gas. Then, silane gas is circulated in the reaction vessel, and the surface of the susceptor is covered with a polysilicon layer to prevent contamination by the susceptor or the like.

  Here, when the hydrogen chloride gas is transported into the reaction vessel from the outside, it is easy to take in contaminants from metal members such as SUS and stainless steel used in the epitaxial growth apparatus, and these contaminants enter the susceptor during cleaning. May adhere.

  The contamination level in the epi process is monitored by SPV (Surface Photo Voltage) or WLT (Wafer Life Time), and is managed at a certain level. In particular, after the reaction container is released by regular maintenance, the contamination level deteriorates, and a process of repeating deposition and cleaning with a dummy wafer or the like is necessary to recover the control level. For this reason, the recovery process takes time, and the productivity of the silicon epitaxial wafer is greatly reduced.

For example, in Patent Document 1, a silicon film is deposited on a holding surface of a susceptor that holds a semiconductor wafer, contaminants of the susceptor are taken into the silicon film, and the silicon film that has taken in the contaminants is removed. It is described that this process is further repeated once or more, and after that, after the silicon coating is applied to the holding surface of the susceptor, the semiconductor wafer is placed and epitaxial growth is performed.
Further, in Patent Document 2, by forming a 0.05 to 1 μm silicon film on the inner surface of the concave portion of the susceptor, the wafer placed on the susceptor slips, whereby the peripheral edge of the wafer comes into contact with the susceptor and cracks. In addition, it is described that it is possible to prevent the occurrence of back surface deposition due to transfer of silicon on the back surface of the wafer by making the average thickness of the silicon film too thick.
Furthermore, Patent Document 3 describes that the growth of the rear surface deposition of the wafer can be suppressed by forming a polysilicon film having a grain size of 0.3 to 0.7 μm on the susceptor surface.

JP-A-10-125603 JP 2010-27880 A JP 2011-14771 A

  However, with the miniaturization of devices, the influence of the polysilicon film formed on the susceptor surface on the wafer has become a problem. If a polysilicon film is formed on the susceptor, the wafer and the polysilicon film are fused during the epitaxial growth, and the fused polysilicon film is peeled off from the wafer when the wafer is moved from the susceptor, and this causes the wafer back surface to be peeled off. Deep flaws occurred, and some slipped.

In addition, the high purity of the susceptor material has progressed, and the influence of contaminants on the surface of the susceptor has been reduced, but the influence of contaminants from hydrogen chloride gas used for cleaning the reaction vessel by vapor phase etching has not been solved. Absent. Here, after the distribution of hydrogen chloride gas, instead of performing the polysilicon film formation process, a method of reducing contaminants adhering to the susceptor by performing H ₂ purge or H ₂ bake was also studied. A sufficient effect could not be obtained.

  Accordingly, in view of the above circumstances, the present invention can prevent deep scratches from occurring on the back surface of the wafer due to fusion of the wafer and the polysilicon film formed on the susceptor surface, and further cleaning by vapor phase etching. It is an object of the present invention to provide a method for cleaning a reaction vessel of an epitaxial growth apparatus and a method for manufacturing an epitaxial wafer, which can reduce the influence of contaminants taken into hydrogen chloride gas used in the process.

  That is, in the present invention, after the inside of the reaction vessel of the epitaxial growth apparatus is cleaned by gas phase etching with a gas containing hydrogen chloride, the temperature of the susceptor in the reaction vessel is further set to 400 ° C. or more and 800 ° C. or less to contain the silane-containing gas. Is provided in the reaction vessel. A method of cleaning the reaction vessel of the epitaxial growth apparatus is provided.

  In this way, contamination of the wafer placed on the susceptor and the epitaxial layer formed on the wafer surface can be suppressed.

Further, since the gas containing silane is circulated with the temperature of the susceptor being set at a relatively low temperature of 400 ° C. or more and 800 ° C. or less, an extremely thin polysilicon film is formed on the susceptor surface or almost a polysilicon film. In the epitaxial growth, the wafer and the polysilicon film are fused, and when the wafer is moved from the susceptor, it is possible to prevent the polysilicon film from being peeled off from the wafer, thereby causing a scratch on the back surface of the wafer. In addition, this can also prevent the occurrence of slip.
Further, it does not take too much time to lower the susceptor temperature, and cleaning can be performed in a short time.

  At this time, it is preferable that the average thickness of the polysilicon film formed on the surface of the susceptor in the reaction container is less than 0.5 μm by flowing the gas containing the silane into the reaction container.

  In this way, it is possible to more effectively suppress the occurrence of back surface deposition due to transfer of polysilicon on the back surface of the wafer, which is caused by the thick polysilicon film formed on the susceptor surface.

  At this time, the gas containing silane may be trichlorosilane gas.

  Thus, trichlorosilane is a common source gas used during epitaxial growth, and has a very low possibility of adverse effects such as contamination on the wafer and the epitaxial layer formed on the surface of the wafer. It is preferable because hydrogen gas can be discharged out of the reaction vessel.

  Further, the present invention provides a method for cleaning the surface of the wafer by placing a wafer on a susceptor in the cleaned reaction vessel after circulating the reaction vessel of the epitaxial growth apparatus and circulating the source gas while heating with a heating device. An epitaxial wafer manufacturing method characterized by forming an epitaxial layer thereon is provided.

  In this way, in cleaning by vapor phase etching, while suppressing contamination from hydrogen chloride remaining in the reaction vessel, scratches on the back surface of the wafer due to fusion between the wafer and the polysilicon film formed on the susceptor surface are further suppressed. It is possible to manufacture a high-quality epitaxial wafer while maintaining high productivity while suppressing occurrence and occurrence of slip.

  As described above, according to the present invention, the wafer placed on the susceptor by the gas containing hydrogen chloride remaining in the reaction vessel while containing contaminants such as heavy metals by vapor phase etching, Contamination of the epitaxial layer formed on the wafer surface can be suppressed.

Further, since the gas containing silane is circulated at a relatively low temperature of 400 ° C. to 800 ° C., a very thin polysilicon film is formed on the susceptor surface, or polysilicon. A film is not formed, and it is possible to prevent the wafer and the polysilicon film from fusing at the time of epitaxial growth, and when the wafer is moved from the susceptor, the polysilicon film is peeled off from the wafer, so that the back surface of the wafer is not damaged. In addition, this can also prevent the occurrence of slip.
Further, it does not take too much time to lower the susceptor temperature, and cleaning can be performed in a short time.

It is the figure which showed an example of the schematic sectional drawing of the common epitaxial growth apparatus used in this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto.

  First, a general single wafer epitaxial growth apparatus to which the cleaning method of the present invention is applied will be described with reference to FIG. 1, but the present invention is not limited to this, and various types such as a vertical type and a barrel type are described. The present invention can be applied even when an epitaxial growth apparatus is used.

  In the reaction vessel 2 of the epitaxial growth apparatus 1 shown in FIG. 1, a susceptor 4 provided with a plurality of through holes 3 inside the outermost periphery is connected to a wafer rotation mechanism (not shown). Thus, during epitaxial growth, the susceptor 4 is rotated, and the silicon epitaxial layer is epitaxially grown uniformly on the silicon wafer W while the inside of the reaction vessel 2 is heated by the heating device 5.

In the reaction vessel 2, an epitaxial growth gas containing a raw material gas and a carrier gas (for example, hydrogen) is circulated in the reaction vessel 2 to the upper region of the susceptor 4, and the main of the silicon wafer W placed on the susceptor 4. A gas introduction pipe 6 for supplying a source gas and a carrier gas is connected on the surface. An atmosphere gas such as hydrogen is circulated in the lower region of the susceptor 4 using the gas introduction pipe 6.
A gas discharge pipe 7 for discharging gas from the reaction container 2 is connected to the side opposite to the side where the gas introduction pipe 6 of the reaction container 2 is connected.

  Hereinafter, an example of a method for cleaning a reaction vessel and a method for manufacturing an epitaxial wafer of an epitaxial growth apparatus of the present invention will be described with reference to the drawings. However, the present invention is not limited to this.

First, the cleaning method of the present invention will be described.
In the epitaxial growth apparatus as shown in FIG. 1, the temperature of the susceptor is set to about 1100 to 1200 ° C., a gas containing hydrogen chloride is circulated into the reaction vessel 2 through the gas introduction pipe 6, and the reaction vessel 2 through the gas discharge pipe 7. By discharging the mixed gas to the outside, the mixed gas is circulated in the reaction vessel 2 for about 1 to 2 minutes, and the polysilicon deposits in the reaction vessel 2 and on the surface of the susceptor 4 are vapor-phase etched.
At this time, the gas containing hydrogen chloride is not particularly limited. For example, a gas mixture of hydrogen chloride gas and hydrogen gas can be used.

Thereafter, the temperature of the susceptor 4 is lowered to 400 to 800 ° C. while only hydrogen gas is circulated into the reaction vessel 2. Then, in a state where the temperature of the susceptor 4 is lowered to 400 to 800 ° C., a gas containing silane is circulated for about 1 to 2 minutes, and the gas containing hydrogen chloride remaining in the reaction vessel 2 by the gas phase etching is obtained. The gas is discharged from the gas discharge pipe 7 to the outside of the reaction vessel 2.
If the temperature of the susceptor is set to 400 ° C. to 800 ° C., since the temperature is relatively low, a thick polysilicon film is not formed on the surface of the susceptor, and it takes too much time to lower the susceptor temperature. The productivity of epitaxial wafers manufactured thereafter is not deteriorated.

At this time, the gas containing silane is not particularly limited, but for example, a mixed gas of trichlorosilane gas and hydrogen gas can be used. If it is trichlorosilane, there is no risk of adverse effects such as contamination on the silicon wafer W and the silicon epitaxial layer subsequently grown on the surface of the silicon wafer W, and it is more effective than H ₂ purge and H ₂ bake. It is preferable because hydrogen chloride can be discharged out of the reaction vessel 2.
Of course, other silanes may be used, and monosilane, monochlorosilane, dichlorosilane, tetrachlorosilane (silicon tetrachloride), or the like may be used.

In addition, a polysilicon film may be formed on the surface of the susceptor by flowing the gas containing silane. The average thickness of the polysilicon film formed at this time is preferably less than 0.5 μm. More preferably, it is less than 0.05 μm.
There is no particular problem unless a polysilicon film is formed on the susceptor surface, but even if it is formed, if the polysilicon film is extremely thin as described above, the silicon film and the silicon wafer It is possible to suppress the occurrence of a problem in which W is fused with W during epitaxial growth and a deep flaw is generated on the back surface of the silicon wafer W when it is peeled off, thereby causing a partial slip. it can.
Further, since the polysilicon film formed on the surface of the susceptor becomes thick, it is possible to suppress the occurrence of back surface deposition due to the transfer of polysilicon on the back surface of the wafer.

Next, the manufacturing method of the epitaxial wafer of this invention is demonstrated.
First, using the epitaxial growth apparatus 1 having the reaction vessel 2 cleaned by the method of the present invention as described above, a silicon wafer is placed on the susceptor 4 in the reaction vessel 2 with the input temperature (for example, 500 to 700 ° C.) adjusted. Place. Here, hydrogen gas is circulated in the reaction vessel 2 through the gas introduction pipe 6 from the stage before the silicon wafer W is introduced.

Next, the silicon wafer W on the susceptor 4 is heated to a hydrogen heat treatment temperature (for example, 1050 to 1200 ° C.) by the heating device 5.
Then, the temperature of the silicon wafer W is lowered to a desired growth temperature (for example, 1000 to 1180 ° C.), and a raw material gas (for example, trichlorosilane: SiHCl ₃ ) and a carrier gas are formed on the main surface of the silicon wafer W through the gas introduction pipe 6. By supplying (for example, hydrogen) substantially horizontally, a silicon epitaxial layer is formed on the main surface of the silicon wafer W, and a silicon epitaxial wafer can be manufactured.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited to these.

Example 1
In the epitaxial growth apparatus as shown in FIG. 1, the susceptor temperature is set to 1190 ° C., and a mixed gas of hydrogen chloride and hydrogen is allowed to flow for 1 minute at a flow rate of 10 slm. The temperature of the reactor was lowered to 800 ° C., and the reaction vessel was cleaned by flowing a mixed gas of trichlorosilane and hydrogen at this temperature for 2 minutes at a flow rate of 10 slm.

Thereafter, in the reaction vessel where the cleaning was performed, a silicon single crystal wafer having a diameter of 200 mm and a resistivity of 10 Ωcm was placed on the susceptor, and at a temperature of 1100 ° C., SiHCl ₃ was supplied as a source gas from a gas introduction tube. Then, hydrogen gas was supplied as a carrier gas, and epitaxial growth of 10 μm was performed to manufacture a silicon epitaxial wafer.

The silicon epitaxial wafer thus manufactured was subjected to chemical passivation treatment, and then the wafer lifetime was measured by the μ-PCD method.
As a result, the average thickness of the polysilicon film formed on the susceptor surface was 0.4 μm, and the in-plane average lifetime was 2100 μsec. In addition, it was confirmed by the slip evaluation under the condenser lamp that no slip occurred. The results at this time are shown in Table 1 below.

(Example 2)
The reaction vessel was cleaned in the same manner as in Example 1 except that the temperature of the susceptor was lowered to 600 ° C. instead of 800 ° C., and then a silicon epitaxial wafer was manufactured in the reaction vessel in which the cleaning was performed. .

The silicon epitaxial wafer thus manufactured was subjected to chemical passivation treatment, and then the wafer lifetime was measured by the μ-PCD method.
As a result, formation of a polysilicon film was not confirmed on the susceptor surface, and the in-plane average lifetime was 2080 μsec. In addition, it was confirmed by the slip evaluation under the condenser lamp that no slip occurred. The results at this time are shown in Table 1 below.

(Example 3)
The reaction vessel was cleaned in the same manner as in Example 1 except that the temperature of the susceptor was lowered to 400 ° C. instead of 800 ° C., and then a silicon epitaxial wafer was manufactured in the reaction vessel in which the cleaning was performed. .

The silicon epitaxial wafer thus manufactured was subjected to chemical passivation treatment, and then the wafer lifetime was measured by the μ-PCD method.
As a result, the formation of a polysilicon film on the susceptor surface was not confirmed, and the in-plane average lifetime was 2130 μsec. In addition, it was confirmed by the slip evaluation under the condenser lamp that no slip occurred. The results at this time are shown in Table 1 below.

(Comparative Example 1)
The reaction vessel was cleaned in the same manner as in Example 1 except that the mixed gas of trichlorosilane and hydrogen was allowed to flow at the same temperature without lowering the temperature of the susceptor from 1190 ° C. Then, the cleaning was performed. A silicon epitaxial wafer was manufactured in the reaction vessel.

The silicon epitaxial wafer thus manufactured was subjected to chemical passivation treatment, and then the wafer lifetime was measured by the μ-PCD method.
As a result, the average thickness of the polysilicon film formed on the susceptor surface was 1 μm, and the in-plane average lifetime was 2100 μsec. However, the silicon wafer and the polysilicon film are fused, and when the silicon wafer is moved from the susceptor, the back surface of the wafer is scratched. Further, in the slip evaluation under the condenser lamp, one slip was detected from each of the two locations. The results at this time are shown in Table 1 below.

(Comparative Example 2)
The reaction vessel was cleaned in the same manner as in Example 1 except that the temperature of the susceptor was lowered to 300 ° C. instead of 800 ° C., and then a silicon epitaxial wafer was manufactured in the reaction vessel in which the cleaning was performed. .

The silicon epitaxial wafer thus manufactured was subjected to chemical passivation treatment, and then the wafer lifetime was measured by the μ-PCD method.
As a result, the formation of a polysilicon film on the surface of the susceptor was not confirmed, and it was confirmed by the slip evaluation under the condenser lamp that no slip occurred, but it took a very long time to lower the susceptor temperature. In addition, the in-plane average lifetime was 1810 μsec, which was not so good. The results at this time are shown in Table 1 below.

(Comparative Example 3)
The reaction vessel was cleaned in the same manner as in Example 1 except that the temperature of the susceptor was not lowered from 1190 ° C. and the mixed gas of trichlorosilane and hydrogen was not circulated. A silicon epitaxial wafer was manufactured in the container.

The silicon epitaxial wafer thus manufactured was subjected to chemical passivation treatment, and then the wafer lifetime was measured by the μ-PCD method.
As a result, the formation of a polysilicon film on the surface of the susceptor was not confirmed, and it was confirmed that slip did not occur even in the slip evaluation under a condenser lamp. The remaining hydrogen chloride contaminated the wafer, and the in-plane average lifetime was 330 μsec. The results at this time are shown in Table 1 below.

(Comparative Example 4)
The reaction vessel was cleaned in the same manner as in Example 2 except that hydrogen gas was circulated (H ₂ purge) instead of the mixed gas of trichlorosilane and hydrogen, and then in the reaction vessel where the cleaning was performed. A silicon epitaxial wafer was manufactured.

The silicon epitaxial wafer thus manufactured was subjected to chemical passivation treatment, and then the wafer lifetime was measured by the μ-PCD method.
As a result, formation of a polysilicon film on the susceptor surface was not confirmed, and slip evaluation under a condenser lamp confirmed that no slip occurred. However, the hydrogen chloride used in the gas phase etching and remaining in the reaction vessel cannot be completely removed, and the silicon wafer is contaminated by the slightly remaining hydrogen chloride, and the in-plane average lifetime is 1520 μsec. It was. The results at this time are shown in Table 1 below.

(Comparative Example 5)
The reaction vessel was the same as in Example 2 except that the temperature of the susceptor was lowered to 600 ° C., the temperature of the susceptor was raised again to 1190 ° C., and hydrogen gas was circulated for 1 minute at a flow rate of 10 slm (H ₂ bake). After that, a silicon epitaxial wafer was manufactured in the reaction container in which the cleaning was performed.

The silicon epitaxial wafer thus manufactured was subjected to chemical passivation treatment, and then the wafer lifetime was measured by the μ-PCD method.
As a result, formation of a polysilicon film on the susceptor surface was not confirmed, and slip evaluation under a condenser lamp confirmed that no slip occurred. However, the hydrogen chloride used in the gas phase etching and remaining in the reaction vessel cannot be completely removed, and the silicon wafer is contaminated by the slightly remaining hydrogen chloride, and the in-plane average lifetime becomes 1350 μsec. It was. The results at this time are shown in Table 1 below.

From Examples and Comparative Examples, after performing gas phase etching using a mixed gas of hydrogen chloride and hydrogen, by circulating a mixed gas of trichlorosilane and hydrogen at a relatively low temperature of 400 to 800 ° C., It can be seen that it is possible to suppress the generation of scratches on the back surface of the wafer in a short time, thereby suppressing the occurrence of slip.
Also, by circulating a mixed gas of trichlorosilane and hydrogen in the reaction vessel, hydrogen chloride remaining in the reaction vessel can be removed more effectively than when nothing is circulated or only hydrogen gas is circulated. You can see that

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

DESCRIPTION OF SYMBOLS 1 ... Epitaxial growth apparatus, 2 ... Reaction container, 3 ... Through-hole, 4 ... Susceptor,
5 ... Heating device, 6 ... Gas introduction pipe, 7 ... Gas discharge pipe, W ... Silicon wafer.

Claims (2)

After the inside of the reaction vessel of the epitaxial growth apparatus is cleaned by vapor phase etching with a gas containing hydrogen chloride, the temperature of the susceptor in the reaction vessel is further set to 400 ° C. to 800 ° C., and the trichlorosilane gas is circulated in the reaction vessel. By cleaning the reaction vessel of the epitaxial growth apparatus, the wafer is placed on the susceptor in the cleaned reaction vessel, and the raw material gas is circulated while being heated to 1000 ° C. or higher and 1180 ° C. or lower by the heating device. A method of manufacturing an epitaxial wafer, comprising forming an epitaxial layer on the wafer surface. The average thickness of the polysilicon film formed on the surface of the susceptor in the reaction vessel by flowing the trichlorosilane gas into the reaction vessel is set to less than 0.5 μm. Epitaxial wafer manufacturing method.

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