JP6671640B2 - Manufacturing method of epitaxial wafer - Google Patents

Description

  The present invention relates to a method for manufacturing an epitaxial wafer.

  2. Description of the Related Art An epitaxial wafer in which an epitaxial layer is formed on a surface of a silicon single crystal substrate by a vapor phase growth method is widely used in electronic devices. As a source gas used for growing an epitaxial layer on a silicon single crystal substrate, for example, four types of silicon tetrachloride, trichlorosilane, dichlorosilane, and monosilane are given. Among them, the raw material gas used industrially is mainly trichlorosilane. In some cases, a raw material gas such as dichlorosilane or monosilane, which can vapor-grow an epitaxial layer at a low temperature, is used.

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

  Since dichlorosilane decomposes at a lower temperature than trichlorosilane, if dichlorosilane is used as a source gas for growing an epitaxial layer on a silicon single crystal substrate, the epitaxial layer can be grown at a low growth temperature. In an epitaxial wafer having an epitaxial layer grown at such 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, if the 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 reduced. Therefore, 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, all of them tend to promote the gas phase decomposition of the source gas, so that 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 been reduced. Accordingly, guarantee contents (contents of product guarantee) required for an epitaxial wafer as a product have become strict. For example, when assuring that there are no epi-defects and the number of epi-defects exceeding the reference value, the values of the epi-defect size and the number of epi-defects serving as the reference value tend to be small. Therefore, if the concentration of dichlorosilane is increased or the growth temperature of the epitaxial growth is increased as described above, the quality of the epitaxial wafer may be deteriorated from the current state, which is not suitable. Therefore, in a method of manufacturing an epitaxial wafer using dichlorosilane as a source gas, it is an issue to maintain the quality of the epitaxial wafer and to improve the productivity at the same time.

  For example, Patent Document 1 discloses a method for manufacturing an epitaxial wafer 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 is possible to maintain the flatness quality of a wafer by using the above-mentioned mixed gas as a source gas. The haze level can be reduced by lowering the growth temperature.

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

Japanese Patent No. 5516158 JP-T-2009-545883

  In Patent Document 2, it is possible to maintain a 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 a method for manufacturing an epitaxial wafer, which can maintain the quality of an epitaxial layer and improve the growth rate of the epitaxial layer.

Means for Solving the Problems and Effects of the Invention

The manufacturing method of the epitaxial wafer of the present invention,
The method comprises 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 step of vapor phase growth is characterized by using a raw material gas in which the mixing ratio of monosilane in the mixed gas is 3% or more and less than 50%.

  In the method of manufacturing an epitaxial wafer according to the present invention, epitaxial growth is performed using a raw material gas in which a mixture ratio of monosilane in a mixed gas of dichlorosilane and monosilane is 3% or more and less than 50%. This makes it possible to improve the growth rate of the epitaxial layer while maintaining the quality of the epitaxial layer. This is more effective when the mixing ratio of monosilane is 3% or more and 30% or less. When 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, the rate of increase in the growth rate of growing the epitaxial layer with the mixed gas of dichlorosilane and monosilane (the rate of increase (%) with respect to the growth rate when the epitaxial layer was grown only with dichlorosilane) was shown. table. 9 is a table showing the number of epi-defects (pieces / wafer) generated in epitaxial wafers manufactured in Example 2 and Comparative Example 2 by changing the mixing ratio of dichlorosilane and monosilane. 9 is a table showing the number of epi-defects (pieces / wafer) generated in epitaxial wafers manufactured in Example 3 and Comparative Example 3 by changing the amount of raw material gas (mol / min).

  Hereinafter, as an example of the method of manufacturing an epitaxial wafer of the present invention, a method of manufacturing 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 a vapor-phase growth on a substrate cut out from a silicon single crystal ingot and subjected to predetermined processing will be described.

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

  The manufactured 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 step). In the growth step, 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 obtained by mixing dichlorosilane and monosilane is used. The proportion of monosilane in the mixed gas is at least 3% and less than 50%. Specifically, assuming that the entire mixed gas is 100%, the ratio (mixing ratio) of monosilane 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 the source gas supplied to the substrate W during the growth step is 0.01 mol / min or more and 0.1 mol / min or less. Preferably, the amount of the source gas is 0.05 mol / min or more and 0.1 mol / min or less. In the growth step, a carrier gas for diluting the source gas and a dopant gas are supplied to the substrate W heated to 800 ° C. or higher and 1100 ° C. or lower together with the source gas to grow an epitaxial layer on the substrate W. Thus, an epitaxial layer is grown on the substrate W, and a silicon epitaxial wafer is manufactured.

  In the above, a series of flows for manufacturing an epitaxial wafer by growing an epitaxial layer on the substrate W has been described. In this embodiment, a gas obtained by mixing dichlorosilane and monosilane is used as a source gas for growing an epitaxial layer on the substrate W in the growth step. Specifically, a raw material gas is used in which the ratio of monosilane is 3% or more and less than 50% when the entire gas is 100%. This makes it possible to improve the growth rate of the epitaxial layer grown on the substrate W as compared with the case where only dichlorosilane is used as the source gas. Then, it becomes possible to manufacture an epitaxial wafer having the same quality as when only dichlorosilane is used as the source gas.

  The following experiment was performed to confirm the effects of the present invention. Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but these do not limit the present invention.

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

  In Example 1, the growth rate V of the epitaxial layer was calculated from the manufactured epitaxial wafer. Specifically, the film thickness of the epitaxial layer was measured from the manufactured epitaxial wafer, and the 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. Further, the growth rate (reference value) of the epitaxial layer grown in the same manner as described above except that only dichlorosilane was used as the source gas was calculated. Then, an increase rate (%) of the growth rate V was calculated with respect to the reference value. The thickness of the epitaxial layer required to calculate the growth rate V was measured by using Fourier transform infrared spectroscopy (FT-IR (Fourier Transform InfraRed)).

  In Example 1, while changing the mixing ratio of monosilane in the mixed gas (source gas) of dichlorosilane and monosilane, and changing the amount of source gas supplied during the growth step, the epitaxial layer was grown to produce an epitaxial wafer, The growth rate (%) of the growth rate V of the epitaxial layer was calculated from each epitaxial wafer. More specifically, the mixing ratio of monosilane in the raw material gas is set to 4 types of 3%, 10%, 30%, and 50%, and the amount of the raw material gas is set to 0.01 mol / min, 0.05 mol / min, 0.10 mol. / Min, and an epitaxial wafer was manufactured under a total of 12 conditions, and the increase rate (%) 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 manufactured in the same manner as in Example 1 were evaluated. Specifically, the epi-defect was evaluated in a DCO (Darkfield Composite Oblique) mode of 46 nmup of a particle counter SP2 manufactured by KLA Tencor, Inc. (Epi-defects having a size of 46 nm or more were evaluated).

  In Example 2, the amount of the source gas was fixed at 0.05 mol / min, and the mixing ratio of monosilane in the source gas was 3%, 10%, 30%, and 50%. Produced. Then, the epi-defects of each of the produced epitaxial wafers were evaluated, and the average of the number of epi-defects (pieces / wafer) at each mixing ratio was calculated.

  In Example 3, the mixing ratio of monosilane in the source gas was fixed at 10%, and the amount of the source gas was 0.01 mol / min, 0.05 mol / min, and 0.10 mol / min. An epitaxial wafer was produced. Then, the epi-defects of each of the manufactured epitaxial wafers were evaluated, and the average of the number of epi-defects (pieces / wafer) in each amount in the source gas was calculated.

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

  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 source gas was changed to 60%. Then, the epi-defects of each manufactured epitaxial wafer were evaluated, and the average of the number of epi-defects (pieces / wafer) was calculated. In the following, “(pieces / wafer)” is referred to as “(pieces)”.

  In Comparative Example 3, a plurality of epitaxial wafers were produced in the same manner as in Example 3 except that the amount of the source gas was fixed at 0.2 mol / min. Then, the epi-defects of each of the produced epitaxial wafers were evaluated, and the average of the number of epi-defects was calculated.

  FIG. 1 shows the increase rate (%) of the growth rate in Example 1 and Comparative Example 1. The increase rate (%) of the first embodiment is indicated by reference sign E1, and the increase rate (%) of the comparative example 1 is indicated by reference sign C1. In Example 1, when the amount of the source gas was fixed at 0.01 mol / min, the growth rate (%) of the growth rate was 5.1 in the order of 3%, 10%, 30%, and 50% of the monosilane mixture ratio. %, 15.0%, 45.0%, and 75.0%. Similarly, when the amount of the source gas is fixed at 0.05 mol / min, the amount becomes 5.6%, 15.7%, 47.1%, and 78.6%, and the amount of the source gas becomes 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, when the amount of the raw material gas was fixed at 0.005 mol / min, the growth rate (%) of the growth rate was 1%, 3%, 10%, 30%, 50% %, In order of 0.0%, 0.1%, 0.3%, 0.7% and 1.7%. When the mixing ratio of monosilane is fixed to 1%, the growth rate (%) of the growth rate is 1.5 mol / min, 0.05 mol / min, and 0.10 mol / min in the order of the raw material gas amount. %, 1.6% and 1.8%. Therefore, when the amount of the 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), the rate of increase (%) of the growth rate is 5%. % Or more. Therefore, by growing the epitaxial layer under such conditions, the growth rate of the epitaxial layer could be improved as compared with the case where only dichlorosilane was used as the source gas.

  FIG. 2 shows the number of epi defects (number) in Example 2 and Comparative Example 2. The number of epi-defects (pieces) of Example 2 is indicated by reference sign E2, and the number of epi-defects (pieces) of Comparative Example 2 is indicated by sign C2. In Example 2, when the amount of the source gas was fixed at 0.05 mol / min, the number of epi defects (pieces) 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). In contrast, 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 the source gas is 0.05 mol / min, the number of epi defects can be reduced to 10 (pieces) or less by adjusting the mixing ratio of monosilane to 3% or more and 50% or less (or less). Similarly, by setting the mixing ratio of monosilane to 3% or more and 30% or less, the number of epi defects can be reduced to 4 (pieces) or less. Therefore, by setting the mixing ratio of monosilane to 50% or less (or less), it is possible to maintain the quality of the epitaxial wafer.

  FIG. 3 shows the number (number) of epi defects in Example 3 and Comparative Example 3. The number (number) of epi-defects in Example 3 is indicated by reference numeral E3, and the number (number) of epi-defects in Comparative Example 3 is indicated by reference numeral C3. In Example 3, when the mixing ratio of monosilane was fixed at 10%, the number of epi-defects (pieces) was 3. mol / min of raw material gas, 0.05 mol / min, and 0.1 mol / min in this order. 0 (pieces), 2.5 (pieces), and 2.4 (pieces). On the other hand, in Comparative Example 3 in which the amount of the source 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 epi defects can be reduced to 10 or less by adjusting the amount of the source gas to 0.01 mol / min or more and 0.1 mol / min or less. It is possible to maintain the quality of the epitaxial wafer.

  As described above, the embodiments of the present invention have been described. However, the present invention is not limited to the specific description, and may be implemented by appropriately combining the exemplified configurations within a technically consistent range. In addition, some elements and processes may be replaced with a well-known mode for implementation.

  W substrate

Claims (3)

The method comprises 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,
In the vapor phase growing step, the raw material gas in which the mixing ratio of the monosilane in the mixed gas is 3% or more and 30 % or less and 0.01 mol / min or more and 0.1 mol / min or less is mixed with the silicon single crystal substrate. A method for producing an epitaxial wafer. 2. The method of claim 1, wherein the vapor-phase growing step uses the source gas having a mixing ratio of the monosilane in the mixed gas of 10 % or more and 30% or less. 3. 3. The method of manufacturing an epitaxial wafer according to claim 1, wherein, in the step of vapor-phase growing, the raw material gas of 0.05 mol / min or more and 0.1 mol / min or less is supplied to the silicon single crystal substrate. 4.

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