Manufacturing method for semiconductor device

Abstract

To provide a technique that reduces the influence of impurities present in an environment in a manufacturing step for a semiconductor device.SOLUTION: A manufacturing method for a semiconductor device includes the steps of: forming a first semiconductor layer on the surface of a substrate through epitaxial growth; cleaning the surface of the first semiconductor layer inside a cleaning device; conveying the substrate from the cleaning device into a deposition device; and forming a second semiconductor layer on the surface of the first semiconductor layer through epitaxial growth inside the deposition device. In the step of conveying the substrate, the substrate is conveyed into the deposition device from the cleaning device in a state where the surface of the first semiconductor layer is covered with a protective substrate.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The technology disclosed in this specification relates to a method for manufacturing a semiconductor device. [Background technology]

[0002] Non-Patent Document 1 discloses a MOSFET. In this MOSFET, an n-type drain region, an n-type drift region, an n-type JFET region, a p-type body region, and an n-type source region are provided inside a semiconductor substrate. The drain region is exposed on the lower surface of the semiconductor substrate and is in contact with a drain electrode. The drift region is disposed above the drain region. The body region is disposed above the drift region and is exposed on the upper surface of the semiconductor substrate. The JFET region is disposed above the drift region, is sandwiched between two body regions, and is exposed on the upper surface of the semiconductor substrate. The source region is exposed on the upper surface of the semiconductor substrate and is surrounded by the body region. At a position exposed on the upper surface of the semiconductor substrate, the body region located between the source region and the JFET region faces the gate electrode via an interlayer insulating film. The source region is in contact with a source electrode. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Katsunori Ueno, "Applied Physics Vol. 86, No. 5", 2017, pp. 376-380 Summary of the Invention [Problem to be solved by the invention]

[0004] The body region and JFET region of the MOSFET of Non-Patent Document 1 are formed, for example, by the following process. First, the body region is formed on the upper surface of the drift region by epitaxial growth. Next, a recess is formed by etching from the upper surface of the body region to the drift region. Next, the surface of the body region and the inside of the recess are cleaned by a cleaning device. After that, the JFET section is formed by epitaxial growth so as to fill the inside of the recess. In the above-mentioned manufacturing method, after the surface of the body region and the inside of the recess are cleaned, the cleaned surface is dried by blowing with nitrogen or the like. At this time, impurities (e.g., Si, etc.) present in the environment are attached to the cleaned surface. As a result, the impurities are taken in at the initial stage of growth of the JFET region, and a high concentration layer of n-type is formed locally. This causes a problem of a decrease in breakdown voltage. In this specification, a technology is provided for reducing the influence of impurities present in the environment in the manufacturing process of a semiconductor device. [Means for solving the problem]

[0005] A method for manufacturing a semiconductor device (10) disclosed in this specification includes the steps of forming a first semiconductor layer (34) by epitaxial growth on a surface (12a) of a substrate (12), cleaning the surface (34a) of the first semiconductor layer in a cleaning device (20), transporting the substrate from the cleaning device to a film forming device (22), and forming a second semiconductor layer (38) by epitaxial growth on the surface of the first semiconductor layer in the film forming device. In the step of transporting the substrate, the substrate is transported from the cleaning device to the film forming device with the surface of the first semiconductor layer covered with a protective substrate (50).

[0006] In the above manufacturing method, after cleaning the surface of the first semiconductor layer, the substrate is transported from the cleaning device to the film forming device with the surface of the first semiconductor layer covered with a protective substrate. This prevents impurities present in the environment from adhering to the surface of the first semiconductor layer during the transport of the substrate. In addition, since the inside of the film forming device is kept clean, impurities are unlikely to be introduced when the second semiconductor layer is formed on the surface of the first semiconductor layer in the film forming device. This prevents a high concentration layer from being formed in the early stage of growth of the second semiconductor layer (i.e., near the interface between the first semiconductor layer and the second semiconductor layer). [Brief description of the drawings]

[0007] [Figure 1] FIG. 4 is a diagram for explaining a substrate preparation step. [Diagram 2] 1A to 1C are diagrams for explaining a body region forming step. [Diagram 3] 5A to 5C are diagrams illustrating a recess forming step. [Figure 4] FIG. [Diagram 5] FIG. [Figure 6] 5A and 5B are diagrams for explaining the state of a substrate during transportation. [Figure 7] FIG. [Figure 8] FIG. 2 is a diagram for explaining a JFET region forming step. [Figure 9] 1 is a cross-sectional view of a semiconductor device manufactured by a manufacturing method according to an embodiment of the present invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] In one example of the manufacturing method disclosed herein, after the step of forming the first semiconductor layer and before the step of cleaning the surface of the first semiconductor layer, a step of forming a recess in the surface of the first semiconductor layer by etching may be included. In the cleaning step, the surface of the first semiconductor layer and the inside of the recess may be cleaned. In the step of forming the second semiconductor layer, the second semiconductor layer may be formed so as to fill the inside of the recess.

[0009] In such a configuration, adhesion of impurities to the inner surface of the recess is suppressed, and the formation of a high concentration layer can be suppressed when a semiconductor layer is formed in the recess by epitaxial growth.

[0010] In one example manufacturing method disclosed in the present specification, in the step of transporting the substrate, the surface of the first semiconductor layer and the protection substrate may be transported in a state of contact with each other via a liquid.

[0011] In such a configuration, the liquid is present on the surface of the first semiconductor layer in the step of transporting the substrate, thereby making it possible to further prevent impurities from adhering to the surface of the first semiconductor layer.

[0012] In one example of the manufacturing method disclosed in this specification, after the step of transporting the substrate and before the step of forming the second semiconductor layer, a step of drying the substrate may be included.

[0013] In this configuration, the liquid present on the surface of the first semiconductor layer can be removed by a simple method.

[0014] (Example) A method for manufacturing a semiconductor device 10 according to an embodiment will be described with reference to the drawings. First, as shown in FIG. 1, a substrate 12 having an n-type drain region 30 and an n-type drift region 32 provided on the upper surface of the drain region 30 is prepared. The substrate 12 can be manufactured, for example, by epitaxially growing the drift region 32 on the drain region 30. The substrate 12 is made of, for example, GaN. The material of the substrate 12 is not particularly limited, and may be other semiconductor materials.

[0015] 2, a p-type body region 34 made of GaN is formed on the surface 12a of the substrate 12 by epitaxial growth using a film formation apparatus (not shown). Specifically, the body region 34 is formed by a metal-organic chemical vapor deposition (MOCVD) method. For ease of explanation, the drain region 30, drift region 32, and body region 34 will hereinafter be referred to as the "substrate 12" as a whole.

[0016] 3, a recess 36 is formed in the surface 34a of the body region 34 by etching. The recess 36 is formed so as to extend from the surface 34a of the body region 34 through the body region 34 to reach the drift region 32.

[0017] Next, as shown in Fig. 4, the substrate 12 is cleaned in a cleaning device 20 (see Fig. 5). More specifically, the surface 34a of the body region 34 and the inner surface of the recess 36 are cleaned. The cleaning device 20 may be a known one.

[0018] Next, as shown in FIG. 5, the substrate 12 is transferred from the cleaning apparatus 20 into the film forming apparatus 22. In this step, first, as shown in FIG. 6, the surface 34a side of the body region 34 is placed on the protective substrate 50 in the cleaning apparatus 20 (i.e., the surface 34a is covered by the protective substrate 50). More specifically, the surface 34a of the body region 34 and the protective substrate 50 are brought into contact with each other via the liquid 52. Next, the substrate 12 is transferred from the cleaning apparatus 20 into the film forming apparatus 22 in the state shown in FIG. 6. During the transfer from the cleaning apparatus 20 to the film forming apparatus 22, the surface 34a of the body region 34 and the protective substrate 50 are kept in contact with each other via the liquid 52. The material of the protective substrate 50 is not particularly limited, but for example, sapphire or the like can be used. The liquid 52 is not particularly limited, but for example, water, an organic solvent, or the like can be used.

[0019] Next, the substrate 12 is dried in the film forming apparatus 22 (see FIG. 5). In this step, for example, as shown in FIG. 7, the substrate 12 is placed on the heating plate 24 together with the protective substrate 50, and the substrate 12 is heated. As a result, the liquid 52 interposed between the surface 34a of the body region 34 and the protective substrate 50 is evaporated and removed.

[0020] 8, the recess 36 is filled by epitaxial growth in the film forming apparatus 22 to form an n-type JFET region 38 made of GaN in the recess 36. A known film forming apparatus can be used as the film forming apparatus 22.

[0021] 9, an n-type source region 40 is formed by ion implantation, and an interlayer insulating film 42, a gate electrode 44, a source electrode 46, and a drain electrode 48 are formed by a conventionally known method. In this way, the semiconductor device 10 is completed.

[0022] As described above, in the manufacturing method of this embodiment, after cleaning the inner surface of the recess 36, the substrate 12 is transported from the cleaning apparatus 20 into the film forming apparatus 22 in a state in which the surface 34a of the body region 34 is covered with the protective substrate 50. This prevents impurities present in the environment from adhering to the inner surface of the recess 36 during the transportation of the substrate 12. In addition, since the inside of the film forming apparatus 22 is kept clean, impurities are unlikely to be introduced when the JFET region 38 is formed in the recess 36 in the film forming apparatus 22. This prevents a high concentration layer from being formed in the early stage of growth of the JFET region 38 (i.e., near the interface between the body region 34 and the JFET region 38).

[0023] In addition, in this embodiment, in the process of transporting the substrate 12, the liquid 52 is present on the surface 34a of the body region 34, which further suppresses the adhesion of impurities to the surface 34a of the body region 34. In addition, the liquid 52 can be removed by a simple method of heating the substrate 12.

[0024] In the above-described embodiment, the configuration is such that the adhesion of impurities to the inside of the recess 36 is suppressed. However, the technology disclosed in this specification is a technology for suppressing the formation of a high concentration layer at the interface between two semiconductor layers when epitaxial growth is used, and is also applicable, for example, when simply forming two adjacent semiconductor layers by epitaxial growth.

[0025] In the above-described embodiment, when the substrate 12 is transported, the liquid 52 does not have to be interposed between the surface 34a of the body region 34 and the protection substrate 50. The surface 34a may be directly covered with the protection substrate 50.

[0026] The configurations disclosed in this specification are listed below. (Configuration 1) A method for manufacturing a semiconductor device, comprising: forming a first semiconductor layer on a surface of a substrate by epitaxial growth; cleaning a surface of the first semiconductor layer in a cleaning apparatus; transporting the substrate from the cleaning apparatus into a film forming apparatus; forming a second semiconductor layer on the surface of the first semiconductor layer by epitaxial growth in the film formation apparatus; In the step of transporting the substrate, the substrate is transported from the cleaning apparatus into the film forming apparatus in a state where the surface of the first semiconductor layer is covered with a protection substrate. Manufacturing method. (Configuration 2) forming a recess in the surface of the first semiconductor layer by etching after the step of forming the first semiconductor layer and before the step of cleaning the surface of the first semiconductor layer; In the cleaning step, the surface of the first semiconductor layer and the inside of the recess are cleaned, 2. The manufacturing method according to configuration 1, wherein in the step of forming the second semiconductor layer, the second semiconductor layer is formed so as to fill the recess. (Configuration 3) 3. The manufacturing method according to claim 1, wherein in the step of transporting the substrate, the surface of the first semiconductor layer and the protection substrate are transported in a state of being in contact with each other via a liquid. (Configuration 4) 4. The manufacturing method according to configuration 3, further comprising the step of drying the substrate after the step of transporting the substrate and before the step of forming the second semiconductor layer.

[0027] Although the embodiments have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or drawings achieves multiple objectives simultaneously, and achieving one of the objectives itself has technical utility. [Explanation of symbols]

[0028] 10: semiconductor device, 12: substrate, 12a: surface, 20: cleaning device, 22: film forming device, 24: heating plate, 30: drain region, 32: drift region, 34: body region, 34a: surface, 36: recess, 38: JFET region, 40: source region, 42: interlayer insulating film, 44: gate electrode, 46: source electrode, 48: drain electrode, 50: protective substrate, 52: liquid

Claims

1. A method for manufacturing a semiconductor device (10), comprising the steps of: forming a first semiconductor layer (34) by epitaxial growth on a surface (12a) of a substrate (12); cleaning the surface (34a) of the first semiconductor layer in a cleaning apparatus (20); transporting the substrate from the cleaning apparatus into a film forming apparatus (22); forming a second semiconductor layer (38) by epitaxial growth on the surface of the first semiconductor layer in the film formation apparatus; In the step of transporting the substrate, the substrate is transported from the cleaning apparatus to the film forming apparatus in a state in which the surface of the first semiconductor layer is covered with a protective substrate (50). Manufacturing method.

2. forming a recess (36) in the surface of the first semiconductor layer by etching after the step of forming the first semiconductor layer and before the step of cleaning the surface of the first semiconductor layer; In the cleaning step, the surface of the first semiconductor layer and the inside of the recess are cleaned, The manufacturing method according to claim 1 , wherein in the step of forming the second semiconductor layer, the second semiconductor layer is formed so as to fill the recess.

3. The manufacturing method according to claim 1 , wherein in the step of transporting the substrate, the surface of the first semiconductor layer and the protection substrate are transported in a state of being in contact with each other via a liquid (52).

4. The manufacturing method according to claim 3 , further comprising the step of drying the substrate after the step of transporting the substrate and before the step of forming the second semiconductor layer.

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