JP2012171811A - Method for producing silicon carbide single crystal epitaxial wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a silicon carbide single crystal epitaxial wafer, with which occurrence of a defect of an epitaxial film originating from a work-affected layer is suppressed while reducing time periods required for removal treatment of the work-affected layer.SOLUTION: In producing a silicon carbide single crystal epitaxial wafer, a silicon carbide single crystal substrate 100 is heated to be 1600°C or more, a raw material gas is supplied so that a C/Si ratio is made to be 1.0 or less, and a growth rate of the epitaxial film is controlled to be 2.0 μm/h or less. At this time, the growth rate of the epitaxial film is controlled to be 2.0 μm/h or less by adjusting the flow rate of a carrier gas to be 50 slm or more, adjusting the flow rate of monosilane as the raw material gas to be 20 sccm or less, and adjusting the pressure of the space, where the silicon carbide single crystal substrate 100 of the growth apparatus is arranged, to be 100 mbar or more.

Description

  The present invention relates to a method for manufacturing a silicon carbide single crystal epitaxial wafer in which an epitaxial film is grown on a silicon carbide single crystal substrate.

  On the surface of a silicon carbide single crystal substrate (hereinafter abbreviated as “substrate” as appropriate) on which an epitaxial film is grown, a work-affected layer is present due to processing at the time of forming the substrate. When an epitaxial film is grown on the substrate while the work-affected layer exists, defects are likely to occur in the epitaxial film due to the work-affected layer.

  For this reason, the removal process was performed on the surface of the substrate by a polishing process, a chemical mechanical polishing process (CMP), an etching process, or the like (see, for example, Patent Document 1). As a result, the work-affected layer is removed, and the occurrence of defects in the epitaxial film is suppressed.

JP 2011-9661 A

  The thickness of the work-affected layer varies from substrate to substrate, and also varies from place to place even on the same substrate. For this reason, if the removal treatment considering the maximum thickness of the work-affected layer existing in all the substrates is not performed, an epitaxial film may be grown on the substrate from which the work-affected layer has not been completely removed. Therefore, even when the removal process is performed, when the removal amount is small, there is a problem in that the occurrence of defects in the epitaxial film cannot be sufficiently suppressed.

  If the removal amount is increased in consideration of the maximum thickness of the work-affected layer, all work-affected layers are removed, so that any substrate can be sufficiently suppressed from causing defects in the epitaxial film. Can do. However, in this case, a portion that is not a work-affected layer is also removed, and there is a problem that a lot of time is spent on the removal process.

  Accordingly, the present invention has been made in view of such a situation, and carbonization that can suppress the occurrence of defects in the epitaxial film derived from the work-affected layer while reducing the time required for the removal process of the work-affected layer. It aims at providing the manufacturing method of a silicon single crystal epitaxial wafer.

  In order to solve the above-described problems, the present invention has the following features. A feature of the present invention is that a silicon carbide single crystal substrate (substrate 100) is prepared, a preparation step (preparation step S1) in which the silicon carbide single crystal substrate is disposed in a growth apparatus (growth apparatus 1), and a raw material in the growth apparatus. A method of manufacturing a silicon carbide single crystal epitaxial wafer, comprising: a growth step (growth step S2) of supplying a gas and growing an epitaxial film on the silicon carbide single crystal substrate, wherein the silicon carbide includes The single crystal substrate is heated to 1600 ° C. or higher, and the source gas is supplied so that the C / Si ratio, which is the ratio of carbon to silicon, is 1.0 or less, and the growth rate of the epitaxial film is set to 2.0 μm. The summary is as follows.

  Further, in the growth step, a carrier gas is supplied, the flow rate of the carrier gas is 50 slm or more, the source gas contains monosilane, the flow rate of the monosilane is 20 sccm or less, and the silicon carbide of the growth apparatus The pressure in the space (reaction chamber 10) in which the single crystal substrate is disposed may be 100 mbar or more.

  According to the present invention, it is possible to provide a method for manufacturing a silicon carbide single crystal epitaxial wafer capable of suppressing the occurrence of defects in an epitaxial film derived from a work-affected layer while reducing the time taken to remove the work-affected layer. it can.

FIG. 1 is a schematic view showing a configuration of an epitaxial film growth apparatus 1 according to the present embodiment. FIG. 2 is a flowchart for explaining the method for manufacturing the silicon carbide single crystal epitaxial wafer according to the present embodiment. FIG. 3 is a view for explaining the manufacturing conditions of the method for manufacturing the silicon carbide single crystal epitaxial wafer according to the present embodiment. FIG. 4 is a diagram showing the defect density of the silicon carbide single crystal epitaxial wafer according to the example and the comparative example.

  One example of a method for producing a silicon carbide single crystal epitaxial wafer according to the present invention will be described with reference to the drawings. Specifically, (1) schematic configuration of epitaxial film growth apparatus 1, (2) silicon carbide single crystal epitaxial wafer manufacturing method, (3) operational effects, (4) comparative evaluation, (5) other embodiments explain.

  In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. It should be noted that the drawings are schematic and ratios of dimensions and the like are different from actual ones. Accordingly, specific dimensions and the like should be determined in consideration of the following description. Moreover, the part from which the relationship and ratio of a mutual dimension differ also in between drawings may be contained.

(1) Schematic Configuration of Epitaxial Film Growth Apparatus 1 A schematic configuration of the epitaxial film growth apparatus 1 according to the present embodiment will be described with reference to FIG. FIG. 1 is a schematic view showing a configuration of an epitaxial film growth apparatus 1 according to the present embodiment.

  As shown in FIG. 1, an epitaxial film growth apparatus 1 (hereinafter abbreviated as “growth apparatus 1”) includes a reaction chamber 10, a mass flow controller 20 (MFC 20), a susceptor 40, a heat insulating material 50, an induction heating coil 60, an open / close valve. 70 and a pump 80.

  Reaction chamber 10 is a place where an epitaxial film is grown on silicon carbide single crystal substrate 100 (substrate 100).

The MFC 20 controls the flow rates of the source gas and the carrier gas. A source gas and a carrier gas are supplied to the reaction chamber 10 through the MFC 20. The MFC 20 includes an MFC 20a, an MFC 20b, and an MFC 20c. The MFC 20a controls the flow rate of monosilane (SiH ₄ ) that is a source gas. MFC20b controls the flow rate of the propane as a raw material gas _(C 3 _{H 8).} The MFC 20c controls the flow rate of the carrier gas. The carrier gas may be any gas that does not react during the formation of the epitaxial film, and generally hydrogen is used as the carrier gas.

  The susceptor 40 is located inside the reaction chamber 10. In susceptor 40, silicon carbide single crystal substrate 100 (substrate 100) is arranged. A heat insulating material 50 is located between the susceptor 40 and the induction heating coil 60. The induction heating coil 60 is located outside the reaction chamber 10. The induction heating coil 60 generates an induced current in the susceptor 40 and heats the susceptor 40.

  The gas in the reaction chamber 10 is sucked into the pump 80 through the open / close valve 70. Thereby, the pressure of the reaction chamber 10 is adjusted appropriately.

(2) Method for Manufacturing Silicon Carbide Single Crystal Epitaxial Wafer A method for manufacturing a silicon carbide single crystal epitaxial wafer according to the present embodiment will be described with reference to FIGS. 1 to 3. FIG. 2 is a flowchart for explaining the method for manufacturing the silicon carbide single crystal epitaxial wafer according to the present embodiment. FIG. 3 is a view for explaining the manufacturing conditions of the method for manufacturing the silicon carbide single crystal epitaxial wafer according to the present embodiment. As shown in FIG. 2, the method for manufacturing a silicon carbide single crystal epitaxial wafer according to this embodiment includes a preparation step S1 and a growth step S2.

(2.1) Preparation step S1
The preparation step S1 is a step of preparing the substrate 100 and placing the substrate 100 on the growth apparatus 1. The preparation step S1 includes a substrate preparation step S11 and a substrate arrangement step S12.

(2.1.1) Substrate preparation step S11
In substrate preparing step S11, substrate 100 made of silicon carbide single crystal is prepared. Substrate 100 is prepared by slicing a bulk of silicon carbide single crystal into a predetermined shape. A process for removing the work-affected layer from the surface 100a of the substrate 100 is performed. However, as will be described later, since it is possible to suppress the occurrence of defects in the epitaxial film even if a work-affected layer is present, the work-affected layer may not be completely removed. The time spent on can be shortened.

(2.1.2) Substrate placement step S12
In the substrate placement step S12, the prepared substrate 100 is placed in the reaction chamber 10 of the growth apparatus 1. As shown in FIG. 1, the substrate 100 is disposed on the susceptor 40.

(2.2) Growth process S2
The growth step S <b> 2 is a step in which a source gas is supplied to the growth apparatus 1 and an epitaxial film is grown on the substrate 100.

  As shown in FIG. 1, the source gas and the carrier gas are supplied to the reaction chamber 10 of the growth apparatus 1 through the MFC 20. Specifically, as shown in FIG. 3, first, a carrier gas is supplied. The flow rate of the carrier gas is preferably 50 slm or more. While supplying the carrier gas, the susceptor 40 is heated.

When the elapsed time t _c from the start of heating, supply the propane. When t ₁ hour elapses from the start of heating and the temperature of the susceptor 40 reaches T ° C., the temperature T ° C. is kept constant. The temperature T ° C. is 1600 ° C. or higher. Thereby, the substrate 100 is heated to 1600 ° C. or higher.

Once you have elapsed t _s time from the start of heating, supply the monosilane. The flow rate of monosilane is preferably 20 sccm or less. Monosilane and propane are supplied so that the C / Si ratio, which is the ratio of carbon to silicon, is 1.0 or less.

  The pressure inside the reaction chamber 10, which is a space in which the substrate 100 of the growth apparatus 1 is disposed, is preferably 100 mbar or more.

  By starting the supply of monosilane, monosilane and propane start to react. Thereby, an epitaxial film is formed on the surface 100a of the substrate 100, and the epitaxial film grows. The growth rate of the epitaxial film is 2.0 μm / h or less.

When t ₂ hours have elapsed from the start of heating and the epitaxial film has grown to a desired thickness, heating of the susceptor 40 is stopped. As a result, the temperature of the susceptor 40 decreases.

  Thus, the silicon carbide single crystal epitaxial wafer according to this embodiment is manufactured.

(3) Effects According to the method for manufacturing a silicon carbide single crystal epitaxial wafer according to the present embodiment, in the growth step S2, the substrate 100 is heated to 1600 ° C. or higher so that the C / Si ratio is 1.0 or lower. In addition, monosilane and propane which are raw material gases are supplied, and the growth rate of the epitaxial film is set to 2.0 μm / h or less. Thereby, even if the work-affected layer remains on the surface 100a, the generation of defects in the epitaxial film derived from the work-affected layer can be suppressed. For this reason, it is possible to reduce the time required for the processing-affected layer removal processing.

  According to the method for manufacturing a silicon carbide single crystal epitaxial wafer according to the present embodiment, the flow rate of the carrier gas is set to 50 slm or more, the flow rate of monosilane is set to 20 sccm or less, and the pressure inside the reaction chamber 10 is set to 100 mbar or more. Thereby, the growth rate of the epitaxial film can be reduced to 2.0 μm / h or less.

(4) Comparative evaluation In order to confirm the effect of the present invention, the following measurements were performed. The present invention is not limited to the following examples.

  Except for the following conditions, silicon carbide single crystal epitaxial wafers (hereinafter abbreviated as wafers) according to Examples and Comparative Examples were manufactured by the above-described manufacturing method.

  In both Examples and Comparative Examples, a substrate subjected to a removal process for removing the work-affected layer was prepared using two methods. Specifically, in the removal process A, the CMP process was performed 10 μm or more after the opportunity polishing. In the removal process B, only mechanical polishing was performed.

  In the examples, monosilane and propane were used as the source gas. Monosilane was supplied at 14 sccm and propane was supplied at 3.2 sccm. The C / Si ratio is 0.7. Carrier gas was supplied at 70 slm. The pressure inside the reaction chamber 10 during the formation of the epitaxial film was adjusted to 200 mbar. Thereby, the growth rate was adjusted to 2.0 μm / h or less.

  In the comparative example, monosilane and propane were used as in the example. Monosilane was supplied at 34 sccm and propane at 7.9 sccm. The C / Si ratio is 0.7. Carrier gas was supplied at 50 slm. The pressure inside the reaction chamber 10 during the formation of the epitaxial film was adjusted to 130 mbar. Thereby, the growth rate was adjusted to 6.0 μm / h.

  The defect density of the wafer according to the example and the comparative example was measured. The results are shown in FIG. FIG. 4 is a diagram showing the defect density of the silicon carbide single crystal epitaxial wafer according to the example and the comparative example. In FIG. 4, “reduction rate%” is a numerical value indicating how much the defect density of the example is reduced as compared with the comparative example. The “preceding process influence degree” is obtained by subtracting the defect density of the removal process A from the defect density of the removal process B.

  As shown in FIG. 4, it can be seen that the defect density is small in the embodiment even when the removal process is hardly performed. When the removal process is sufficiently performed, it can be seen that the defect density is smaller in the example than in the comparative example. From this, it has been confirmed that according to the present invention, it is possible to suppress the occurrence of defects in the epitaxial film derived from the work-affected layer while reducing the time required for the process-affected layer removal treatment.

(5) Other Embodiments Although the contents of the present invention have been disclosed through the embodiments of the present invention, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. The present invention includes various embodiments not described herein.

  For example, the supply order and supply time of the source gas are not limited to the above-described embodiments.

  As described above, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

  DESCRIPTION OF SYMBOLS 1 ... Epitaxial film growth apparatus (growth apparatus), 10 ... Reaction chamber, 20, 20a, 20b, 20c ... Mass flow controller (MFC), 40 ... Susceptor, 50 ... Thermal insulation material, 60 ... Induction heating coil, 70 ... Open / close valve, 80 ... Pump, 100 ... Silicon carbide single crystal substrate (substrate), 100a ... Surface

Claims (2)

Preparing a silicon carbide single crystal substrate and arranging the silicon carbide single crystal substrate in a growth apparatus;
A method for producing a silicon carbide single crystal epitaxial wafer, comprising: a source gas supplied to the growth apparatus; and a growth step of growing an epitaxial film on the silicon carbide single crystal substrate,
In the growth process,
Heating the silicon carbide single crystal substrate to 1600 ° C. or higher;
Supplying the source gas so that the C / Si ratio, which is the ratio of carbon to silicon, is 1.0 or less;
A method for producing a silicon carbide single crystal epitaxial wafer, wherein the growth rate of the epitaxial film is 2.0 μm or less. In the growth process,
A carrier gas is supplied, and the flow rate of the carrier gas is set to 50 slm or more;
The source gas contains monosilane, the monosilane flow rate is 20 sccm or less,
2. The method for producing a silicon carbide single crystal epitaxial wafer according to claim 1, wherein a pressure of a space in which the silicon carbide single crystal substrate of the growth apparatus is disposed is set to 100 mbar or more.

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