JP2018098323A - Method for manufacturing epitaxial wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an epitaxial wafer, by which the quality of an epitaxial layer can be maintained, and the growth rate of the epitaxial layer can be increased.SOLUTION: A method for manufacturing an epitaxial wafer according to the present invention comprises a vapor phase-growing step. In the vapor phase-growing step, a silicon epitaxial layer is grown on a substrate W in vapor phase while using a gas mixture of dichlorosilane and monosilane as a material gas. The material gas is used in the vapor phase-growing step is 3% or more and less than 50% in monosilane mixing rate in the gas mixture. Preferably, the material gas in which the monosilane mixing rate is 3% or more and 30% or less is used. In addition, the material gas of 0.01 mol/min or more and 0.1 mol/min or less is supplied to the substrate W in the vapor phase-growing step.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an epitaxial wafer manufacturing method.

  An epitaxial wafer in which an epitaxial layer is formed on the surface of a silicon single crystal substrate by a vapor phase growth method is widely used for electronic devices. Examples of source gases used for growing an epitaxial layer on a silicon single crystal substrate include four types of silicon tetrachloride, trichlorosilane, dichlorosilane, and monosilane. Of these, the raw material gas used industrially is mainly trichlorosilane. In some cases, a raw material gas capable of vapor phase epitaxy growth of the epitaxial layer such as dichlorosilane or monosilane is used.

  When dichlorosilane is used as the source gas, the epitaxial layer is generally grown on a silicon single crystal substrate at a growth temperature of about 800 ° C. to 1100 ° C. When the growth temperature is lower than 800 ° C., the growth rate of the epitaxial layer becomes insufficient. Further, when the growth temperature is higher than 1100 ° C., the gas phase reaction (gas phase decomposition reaction) of the raw material gas becomes excessive and particles are generated. These particles are taken into the epitaxial layer during the epitaxial growth and cause crystal defects in the epitaxial layer. Therefore, when the growth temperature is higher than 1100 ° C., the number of crystal defects (hereinafter referred to as “epi defects”) generated in the epitaxial layer increases (hereinafter referred to as “epi defect number”). Further, when dichlorosilane is used as the source gas, if the inside of the furnace for epitaxial growth is made higher than 200 torr, the gas phase reaction of the source gas becomes excessive as described above, and the number of epi defects increases. Therefore, generally, the inside of the furnace must be in a state where the pressure is reduced to, for example, 200 torr or less.

  Since dichlorosilane decomposes at a lower temperature than trichlorosilane, it is possible to grow an epitaxial layer at a low growth temperature by using dichlorosilane as a source gas for growing an epitaxial layer on a silicon single crystal substrate. In such an epitaxial wafer having an epitaxial layer grown at a low temperature, effects such as a reduction in surface haze level, a reduction in slip, and a reduction in contamination level can be expected. On the other hand, when an epitaxial layer is grown at a low temperature using dichlorosilane as a source gas, the growth rate of the epitaxial layer is low and the productivity of the epitaxial wafer is lowered. In order to increase the growth rate, it is conceivable to increase the concentration of dichlorosilane or increase the growth temperature of epitaxial growth. However, since both tend to promote vapor phase decomposition of the source gas, the number of epi defects may increase.

  In recent years, electronic devices have been miniaturized, and the size of particles that can be measured has become minute. Along with this, the guarantee content (content of product guarantee) required for epitaxial wafers as products has become stricter. For example, when it is guaranteed that there are no epi defects and the number of epi defects exceeding the reference value, the epi defect size and the number of epi defects serving as the reference value tend to be small. Therefore, increasing the concentration of dichlorosilane or increasing the growth temperature of epitaxial growth as described above may deteriorate the quality of the epitaxial wafer from the current level and is not appropriate. Therefore, in the manufacturing method of an epitaxial wafer using dichlorosilane as a raw material gas, it is a problem to achieve both maintenance of the quality of the epitaxial wafer and improvement of productivity.

  For example, Patent Document 1 discloses an epitaxial wafer manufacturing method in which an epitaxial layer is grown at a low growth temperature using a mixed gas of trichlorosilane and dichlorosilane as a source gas. In patent document 1, it becomes possible to maintain the flatness quality of a wafer by using said mixed gas for source gas. And it becomes possible to reduce a haze level by making growth temperature low.

  For example, Patent Document 2 discloses a method of performing selective epitaxial growth using a mixed gas of monosilane and dichlorosilane.

Japanese Patent No. 5516158 Special table 2009-54584 gazette

  In Patent Document 2, it is possible to maintain the selectivity during selective epitaxial growth by using a mixed gas. However, in Patent Document 2, the reaction temperature during selective epitaxial growth is limited to less than 800 ° C. and the amount of source gas is limited to 100 sccm or less.

  An object of the present invention is to provide an epitaxial wafer manufacturing method capable of maintaining the quality of an epitaxial layer and improving the growth rate of the epitaxial layer.

Means for Solving the Problems and Effects of the Invention

The method for producing an epitaxial wafer of the present invention includes:
Comprising a step of vapor-phase-growing a silicon epitaxial layer on a silicon single crystal substrate using a mixed gas of dichlorosilane and monosilane as a source gas,
The vapor phase growth step is characterized by using a source gas in which the mixing ratio of monosilane in the mixed gas is 3% or more and less than 50%.

  In the method for producing an epitaxial wafer of the present invention, epitaxial growth is performed using a raw material gas in which a mixing ratio of monosilane in a gas obtained by mixing dichlorosilane and monosilane is 3% or more and less than 50%. As a result, the growth rate of the epitaxial layer can be improved while maintaining the quality of the epitaxial layer. This becomes more effective when the mixing ratio of monosilane is 3% or more and 30% or less. If the source gas supplied to the silicon single crystal substrate is supplied at 0.01 mol / min or more and 0.1 mol / min or less, the quality of the epitaxial layer can be maintained and the growth rate of the epitaxial layer can be improved.

In Example 1 and Comparative Example 1, an increase rate of the growth rate when the epitaxial layer was grown with the mixed gas of dichlorosilane and monosilane (increase rate (%) relative to the growth rate when the epitaxial layer was grown only with dichlorosilane) was shown. table. The table | surface which shows the number of epi defects (piece / wafer) which arose in the epitaxial wafer produced by changing the mixing ratio of a dichlorosilane and monosilane in Example 2 and Comparative Example 2. FIG. The table | surface which shows the number of epi defects (piece | piece / wafer) which arose in the epitaxial wafer produced by changing the quantity (mol / min) of source gas in Example 3 and Comparative Example 3. FIG.

  Hereinafter, as an example of the method for producing an epitaxial wafer of the present invention, a method for producing a silicon epitaxial wafer by growing a silicon epitaxial layer on a silicon single crystal substrate will be described. In the following description, a method of manufacturing an epitaxial wafer using a well-known single-wafer type vapor phase growth apparatus that performs vapor phase growth on a substrate cut out from a silicon single crystal ingot and subjected to a predetermined process will be described.

  In order to manufacture a silicon epitaxial wafer using a known vapor phase growth apparatus, a silicon single crystal substrate (hereinafter referred to as “substrate W”), which is a growth substrate on which an epitaxial layer is grown, is manufactured. For example, a silicon single crystal ingot is produced by immersing and pulling a seed crystal silicon rod on the surface of a melt obtained by melting a polycrystalline crucible in a quartz crucible and a dopant in order to adjust the resistivity. Next, the produced silicon single crystal ingot is cut out, and the cut wafer is subjected to rough polishing, etching, polishing, and the like to produce a substrate W having a mirror-finished surface.

  The produced substrate W is transferred to a known vapor phase growth apparatus. An epitaxial layer is vapor-phase grown on the main surface of the substrate W by a vapor phase growth apparatus (growth process). In the growth process, a source gas is supplied onto the main surface of the substrate W to grow an epitaxial layer. As the raw material gas, a mixed gas in which dichlorosilane and monosilane are mixed is used. The proportion of monosilane in the mixed gas is 3% or more and less than 50%. Specifically, when the total mixed gas is 100%, the monosilane ratio (mixing ratio) is 3% or more and less than 50%. Preferably, the mixing ratio of monosilane is 3% or more and 30% or less. Further, the amount of source gas supplied to the substrate W during the growth process is 0.01 mol / min or more and 0.1 mol / min or less. Preferably, the amount of source gas is 0.05 mol / min or more and 0.1 mol / min or less. In the growth step, a carrier gas and a dopant gas for diluting the source gas are supplied together with the source gas to the substrate W heated to 800 ° C. to 1100 ° C. to grow an epitaxial layer on the substrate W. In this way, an epitaxial layer is grown on the substrate W, and a silicon epitaxial wafer is manufactured.

  In the foregoing, a series of processes for manufacturing an epitaxial wafer by growing an epitaxial layer on the substrate W has been described. In this embodiment, a gas in which dichlorosilane and monosilane are mixed is used as a source gas for growing an epitaxial layer on the substrate W in the growth process. Specifically, when the total gas is 100%, a raw material gas having a monosilane ratio of 3% or more and less than 50% is used. Thereby, the growth rate of the epitaxial layer grown on the substrate W can be improved as compared with the case where only dichlorosilane is used as the source gas. And it becomes possible to manufacture the epitaxial wafer which becomes the quality similar to the case where only dichlorosilane is used for source gas.

  In order to confirm the effect of the present invention, the following experiment was conducted. EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated concretely, these do not limit this invention.

(Example)
In the example, as a plurality of substrates W, a silicon single crystal wafer having a diameter of 300 mm, a crystal plane orientation (100), and a conductivity type P type was prepared. Subsequently, an epitaxial layer was grown on a substrate W prepared by a well-known single-wafer vapor phase growth apparatus to produce an epitaxial wafer.

  In Example 1, the growth rate V of the epitaxial layer was calculated from the produced epitaxial wafer. Specifically, the film thickness of the epitaxial layer was measured from the produced epitaxial wafer, and a value obtained by dividing the measured film thickness by the growth (film formation) time of the epitaxial layer was calculated as the growth rate V. The growth rate (reference value) of the epitaxial layer grown in the same manner as described above was calculated except that only dichlorosilane was used as the source gas. And the increase rate (%) of said growth rate V was calculated with respect to the reference value. The film thickness of the epitaxial layer necessary for calculating the growth rate V was measured using Fourier transform infrared spectroscopy (FT-IR (Fourier Transform InfraRed) method).

  In Example 1, while changing the mixing ratio of monosilane in the mixed gas (source gas) of dichlorosilane and monosilane, the epitaxial layer is grown by changing the amount of source gas supplied during the growth process, and an epitaxial wafer is produced. The increase rate (%) of the growth rate V of the epitaxial layer was calculated from each epitaxial wafer. Specifically, the mixing ratio of monosilane in the raw material gas is set to four types of 3%, 10%, 30%, and 50%, and the amount of the raw material gas is 0.01 mol / min, 0.05 mol / min, 0.10 mol. Epitaxial wafers were produced under a total of 12 conditions, and the rate of increase (%) of the growth rate V was calculated.

  In Examples 2 and 3, crystal defects (epi defects) generated in the epitaxial layer of each epitaxial wafer produced in the same manner as in Example 1 were evaluated. Specifically, epi defects were evaluated by a DCO (Darkfield Composite Oblique) mode 46 nmup of a particle counter SP2 manufactured by KLA Tencor (evaluated as an epi defect having a size of 46 nm or more).

  In Example 2, the amount of source gas was fixed at 0.05 mol / min, and the number of monowafers mixed in the source gas was 3%, 10%, 30%, and 50%, respectively. Produced. And the epitaxial defect of each produced epitaxial wafer was evaluated, and the average of the number of epi defects (piece / wafer) in each mixing ratio was calculated.

  In Example 3, the mixing ratio of monosilane in the raw material gas was fixed to 10%, and the amount of raw material gas was 0.01 mol / min, 0.05 mol / min, and 0.10 mol / min. An epitaxial wafer was produced. And the epitaxial defect of each produced epitaxial wafer was evaluated, and the average of the number of epi defects (piece / wafer) in each quantity in source gas was computed.

(Comparative example)
Comparative Example 1 is the same as Example 1 except that the amount of raw material gas is fixed at 0.005 mol / min and the mixing ratio of monosilane in the raw material gas is 3%, 10%, 30%, and 50%. Similarly, an epitaxial wafer was produced. In the same manner as in Example 1, the growth rate increase rate (%) was calculated from each epitaxial wafer. In Comparative Example 1, the mixing ratio of monosilane is fixed at 1%, and the amount of the raw material gas is 0.005 mol / min, 0.01 mol / min, 0.05 mol / min, and 0.10 mol / min. An epitaxial wafer was prepared. In the same manner as in Example 1, the growth rate increase rate (%) was calculated from each epitaxial wafer.

  In Comparative Example 2, a plurality of epitaxial wafers were produced in the same manner as in Example 2 except that the mixing ratio of monosilane in the raw material gas was 60%. And the epitaxial defect of each produced epitaxial wafer was evaluated and the average of the number of epi defects (piece / wafer) was computed. In the following, “(piece / wafer)” is referred to as “(piece)”.

  In Comparative Example 3, a plurality of epitaxial wafers were produced in the same manner as in Example 3 except that the amount of source gas was fixed at 0.2 mol / min. And the epitaxial defect of each produced epitaxial wafer was evaluated and the average of the number of epi defects (piece) was computed.

  The growth rate increase rate (%) in Example 1 and Comparative Example 1 is shown in FIG. The increase rate (%) of Example 1 is indicated by a symbol E1, and the increase rate (%) of Comparative Example 1 is indicated by a symbol C1. In Example 1, the rate of increase (%) in the growth rate when the amount of source gas was fixed at 0.01 mol / min was 5.1 in the order of the monosilane mixing ratio of 3%, 10%, 30%, and 50%. %, 15.0%, 45.0%, and 75.0%. Similarly, when the amount of source gas is fixed at 0.05 mol / min, the amounts are 5.6%, 15.7%, 47.1%, and 78.6%, and the amount of source gas is reduced to 0.10 mol / min. When fixed, they were 5.8%, 18.0%, 54.0%, and 90.0%. On the other hand, in Comparative Example 1, the growth rate increase rate (%) when the amount of the raw material gas was fixed at 0.005 mol / min was 1%, 3%, 10%, 30%, 50% of the monosilane mixing ratio. % In the order of 0.0%, 0.1%, 0.3%, 0.7%, and 1.7%. The growth rate increase rate (%) when the mixing ratio of monosilane is fixed at 1% is 1.5 in the order of the amount of the raw material gas 0.01 mol / min, 0.05 mol / min, and 0.10 mol / min. %, 1.6%, and 1.8%. Therefore, the growth rate increase rate (%) is 5 in the range where the amount of source gas is 0.01 mol / min or more and 0.1 mol / min or less and the mixing ratio of monosilane is 3% or more and 50% or less (or less). It became more than%. Therefore, by growing the epitaxial layer under such conditions, the growth rate of the epitaxial layer could be improved as compared with the case of using only dichlorosilane as the source gas.

  The number of epi defects (pieces) in Example 2 and Comparative Example 2 is shown in FIG. The number of epi defects in Example 2 (number) is indicated by symbol E2, and the number of epi defects in Comparative Example 2 is indicated by symbol C2. In Example 2, the number of epitaxial defects (pieces) when the amount of the source gas was fixed at 0.05 mol / min was 3.1 (pieces in the order of 3%, 10%, 30%, and 50% of monosilane. ), 2.5 (pieces), 2.7 (pieces), and 8.4 (pieces). On the other hand, in Comparative Example 2 in which the mixing ratio of monosilane in Example 2 was 60%, the number of epi defects (pieces) was 26.3 (pieces). Therefore, when the amount of source gas is 0.05 mol / min, the number of epi defects can be reduced to 10 (pieces) or less by setting the mixing ratio of monosilane to 3% or more and 50% or less (or less). Similarly, when the mixing ratio of monosilane is 3% or more and 30% or less, the number of epi defects can be 4 or less. Therefore, the quality of the epitaxial wafer can be maintained by setting the monosilane mixing ratio to 50% or less (or less).

  The number of epi defects (pieces) in Example 3 and Comparative Example 3 is shown in FIG. The number of epi defects (pieces) in Example 3 is indicated by symbol E3, and the number of epi defects in Comparative Example 3 (pieces) is indicated by symbol C3. In Example 3, the number of epitaxial defects (pieces) when the mixing ratio of monosilane was fixed to 10% was 3. In the order of 0.01 mol / min, 0.05 mol / min, and 0.1 mol / min of the amount of source gas. 0 (pieces), 2.5 (pieces), and 2.4 (pieces). On the other hand, in Comparative Example 3 where the amount of the raw material gas in Example 3 was 0.2 mol / min, the number of epi defects was 12.5 (pieces). Therefore, when the mixing ratio of monosilane in the source gas is 10%, the number of epitaxial defects can be reduced to 10 or less by setting the amount of source gas to 0.01 mol / min to 0.1 mol / min. It is possible to maintain the quality of the epitaxial wafer.

  The embodiments of the present invention have been described above. However, the present invention is not limited to the specific description, and the illustrated configurations and the like can be appropriately combined within a technically consistent range. In addition, certain elements and processes may be replaced with known forms.

  W substrate

Claims (3)

Comprising a step of vapor-phase-growing a silicon epitaxial layer on a silicon single crystal substrate using a mixed gas of dichlorosilane and monosilane as a source gas,
The method for producing an epitaxial wafer, wherein the vapor phase growth step uses the source gas in which the mixing ratio of the monosilane in the mixed gas is 3% or more and less than 50%.   2. The method for producing an epitaxial wafer according to claim 1, wherein the vapor phase growth step uses the source gas in which a mixing ratio of the monosilane in the mixed gas is 3% or more and 30% or less.   3. The method for producing an epitaxial wafer according to claim 1, wherein the vapor phase growth step supplies the source gas of 0.01 mol / min to 0.1 mol / min to the silicon single crystal substrate.

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