Method for growing diamond layer and microwave plasma CVD device

Abstract

The present invention is a method for growing a diamond layer according to a microwave plasma CVD method, the method being characterized by comprising the steps of: arranging a substrate (2) in a reaction vessel (1) of a microwave plasma CVD device (10); introducing a starting material gas (reaction gas) (6) into the reaction vessel (1); and irradiating the surface of the substrate (2) with microwave plasma to grow a diamond layer on the surface of the substrate (2), in the step of growing the diamond layer, the substrate (2) is moved in a direction parallel to the surface of the substrate (2), and / or the irradiation position of the microwave plasma is moved in a direction parallel to the surface of the substrate (2). As a result, a large-diameter diamond substrate is provided.

Description

Technical Field

[0001] The present invention relates to a diamond layer growth method and a microwave plasma CVD device. In particular, the present invention relates to a technology for artificially growing diamond on a semiconductor substrate, and more specifically, to a diamond growth method and a device when growing diamond on a silicon substrate by CVD (chemical vapor deposition). Background Art

[0002] Diamond is expected to be used in various semiconductor elements and electronic devices because of its excellent physical properties such as high hardness, good thermal conductivity, high carrier mobility, and wide band gap. Artificially synthesized diamond is being used for the semiconductor elements and electronic devices. There are two methods for synthesizing diamond: growing diamond using ultra-high pressure and growing diamond by vapor phase. In semiconductor applications, vapor phase growth (CVD growth) has attracted attention because it can produce large diameters (Patent Documents 1 to 3).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2001-354491

[0006] Patent Document 2: Japanese Patent Application Publication No. 2004-176132

[0007] Patent Document 3: Japanese Patent Application Publication No. 2006-143561 Summary of the invention

[0008] 1. Technical issues to be resolved

[0009] CVD growth is a method in which a substrate is placed inside a reaction tube, a raw material gas (reaction gas) and a carrier gas are circulated under normal pressure or reduced pressure, and the raw material gas (reaction gas) is decomposed and activated by thermal decomposition or plasma to grow on the substrate.

[0010] For diamond, there are hot filament methods (Japanese: ホッフィメント method) using microwave plasma, DC (direct current) plasma or tungsten filament (Japanese: フィメント) or the like, but microwave plasma method has attracted attention in single crystal growth. Microwave plasma growth is a method that irradiates microwaves to the substrate, decomposes and activates the raw material gas (reaction gas) and grows a single crystal diamond.

[0011] Figure 5 This is an explanatory diagram of a conventional microwave plasma CVD device.

[0012] like Figure 5As shown, a conventional microwave plasma CVD apparatus 110 includes a reaction vessel 101, and a silicon substrate (film formation substrate) 102 can be placed inside the reaction vessel 101. The reaction vessel 101 can reduce the pressure inside.

[0013] A reaction gas introduction pipe 109 is installed on the wall to introduce the reaction gas 106 into the interior. The reaction gas 106 is, for example, a mixed gas of hydrogen and methane.

[0014] A microwave introduction pipe 104 connected to a microwave generator 105 (2.45 GHz) is installed on the top plate so as to irradiate microwave plasma in a downward direction.

[0015] A plate-shaped stage (substrate heating) 103 is disposed on the bottom surface side. The surface of the stage 103 is arranged parallel to a direction perpendicular to the directly downward direction. In addition, the surface of the stage 103 is arranged so that the silicon substrate 102 can be disposed.

[0016] A silicon substrate 102 is disposed on the surface of the stage 103 .

[0017] Depend on Figure 5 It is understood that, since there is a limit to the area that can be irradiated with microwaves in principle, there is a limit to the diameter of the substrate.

[0018] Diamond substrates have attracted attention due to their heat dissipation characteristics and other aspects. The growth method corresponding to single crystal substrates is microwave plasma growth, but due to the limitation of the area that can be irradiated with plasma, it is impossible to achieve a large diameter such as 300mmφ.

[0019] Therefore, the formation of a large-diameter diamond substrate becomes a technical problem.

[0020] The present invention has been made to solve the above-mentioned problems, and its object is to provide a growth method and a microwave plasma CVD device that can realize a diamond layer with a larger diameter.

[0021] (II) Technical solution

[0022] The present invention is completed in order to achieve the above-mentioned purpose, and provides a method for growing a diamond layer, which is a method for growing a diamond layer according to a microwave plasma CVD method, characterized in that it has the following steps: disposing a substrate in a reaction vessel of a microwave plasma CVD device; introducing a raw material gas (reaction gas) into the reaction vessel; and irradiating the surface of the substrate with microwave plasma to grow a diamond layer on the surface of the substrate. In the step of growing the diamond layer, the substrate is moved in a direction parallel to the surface of the substrate, and / or the irradiation position of the microwave plasma is moved in a direction parallel to the surface of the substrate.

[0023] According to such a diamond layer growth method, a large-diameter diamond layer can be formed. More specifically, when diamond is grown on a large-diameter silicon substrate, the large-diameter silicon substrate can be placed on a stage of a microwave plasma growth device, and a raw material gas (reaction gas) can be introduced while irradiating microwaves to make it grow, and the stage can be moved at predetermined intervals while making it grow, so that even a microwave plasma CVD device can grow a large-diameter single-crystal diamond layer. Furthermore, the growth in the vertical direction (lateral) at a position with high plasma density and the growth in the horizontal direction at a position with low plasma density can also help reduce defects.

[0024] Furthermore, it is provided that the substrate is moved in a direction parallel to the surface of the substrate, and / or the irradiation position of the microwave plasma is moved in a direction parallel to the surface of the substrate. Regardless of whether the plasma irradiation position is fixed and the substrate is moved, or vice versa, the substrate is fixed and the microwave plasma irradiation position (where the microwave plasma density is higher) is moved in the X and Y directions, or both the substrate and the irradiation position are moved, single crystal diamond with a large diameter can be grown in either method.

[0025] At this time, it can be set as: in the growth method of the diamond layer as described above, it is characterized in that after the step of growing the diamond layer, the substrate on which the diamond layer is grown is moved to a reaction container of a hot filament CVD device, and diamond is further grown on the diamond layer by hot filament CVD.

[0026] Thus, the thickness of the large-diameter diamond layer can be increased. A hot filament CVD device capable of large-diameter growth can be used to further grow a substrate that has been grown by a microwave plasma CVD method, so that thicker diamond can be grown on a large-diameter substrate. In more detail, a diamond film grown by a microwave plasma CVD method can be used directly, but in order to further grow it thicker, it is not grown only by microwave plasma, but for the substrate that has been grown by microwave plasma by the above method, in a diamond growth device based on a hot filament method, methane and hydrogen are introduced as gases into a reaction vessel, and a filament such as tungsten set on the substrate is energized, and the gas is heated and decomposed to grow diamond on the substrate, thereby growing diamond on the entire large-diameter substrate.

[0027] At this time, it may be assumed that in the aforementioned method for growing a diamond layer, a silicon substrate is used as the substrate.

[0028] Therefore, when an integrated circuit is formed on a silicon substrate on which a diamond layer is formed, the diamond layer can be used as a heat dissipation layer.

[0029] In addition, the present invention provides a microwave plasma CVD device, which is a microwave plasma CVD device for a diamond layer growth method, characterized in that it has: a mechanism for moving the substrate in a direction parallel to the surface of the substrate, and / or a mechanism for moving the irradiation position of the microwave plasma.

[0030] According to such a microwave plasma CVD apparatus, a large-diameter diamond layer can be formed. More specifically, if it is an apparatus having this mechanism, even a microwave plasma CVD apparatus can grow a large-diameter single-crystal diamond.

[0031] In this case, the microwave plasma CVD apparatus as described above may be characterized by further comprising a mechanism for heating the substrate.

[0032] Thereby, the growth of a large-diameter diamond layer can be promoted.

[0033] (III) Beneficial effects

[0034] As described above, according to the diamond layer growth method of the present invention, a large-diameter diamond layer can be formed by microwave plasma CVD. In particular, in the present invention, a single-crystal large-diameter diamond layer can be grown by microwave plasma CVD.

[0035] In addition, according to the microwave plasma CVD apparatus of the present invention, a large-diameter diamond layer can be formed. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is an explanatory diagram of the microwave plasma CVD device of the present invention.

[0037] Figure 2 This is an explanatory diagram of a hot filament CVD apparatus used in the diamond layer growth method of the present invention.

[0038] Figure 3A It is the Raman peak of the diamond film grown by the diamond layer growth method (microwave plasma method only) of the present invention.

[0039] Figure 3B This is an optical microscope image of the surface of a diamond film grown by the diamond layer growth method of the present invention (microwave plasma method only).

[0040] Figure 4A It is the Raman peak of the diamond film grown by the diamond layer growth method (microwave plasma method + hot filament method) of the present invention.

[0041] Figure 4BThis is an optical microscope image of the surface of a diamond film grown by the diamond layer growth method (microwave plasma method + hot filament method) of the present invention.

[0042] Figure 5 This is an explanatory diagram of a conventional microwave plasma CVD device. DETAILED DESCRIPTION

[0043] The present invention will be described in detail below, but the present invention is not limited to these.

[0044] As described above, a diamond layer growth method and a microwave plasma CVD device are sought, which can form a large-diameter diamond layer, especially a single-crystal diamond layer, on a large-diameter silicon substrate.

[0045] The present inventors have repeatedly conducted in-depth studies on the above-mentioned problems, and as a result, have found that a large-diameter diamond layer, in particular a single-crystal diamond layer, can be formed on a large-diameter silicon substrate by a method for growing a diamond layer according to a microwave plasma CVD method, which comprises the following steps: placing a substrate in a reaction vessel of a microwave plasma CVD device; introducing a raw material gas (reaction gas) into the reaction vessel; and irradiating a surface of the substrate with microwave plasma to grow a diamond layer on the surface of the substrate, wherein in the step of growing the diamond layer, the substrate is moved in a direction parallel to the surface of the substrate, and / or the irradiation position of the microwave plasma is moved in a direction parallel to the surface of the substrate, thereby completing the present invention.

[0046] Below, while referring to Figure 1 Next, a diamond layer growth method and a microwave plasma CVD apparatus according to a first embodiment of the present invention will be described.

[0047] (First embodiment)

[0048] (Microwave plasma CVD device)

[0049] Figure 1 An explanatory diagram showing a microwave plasma CVD apparatus according to the present invention.

[0050] like Figure 1 As shown, the microwave plasma CVD device 10 of the present invention has a reaction vessel 1, and a large-diameter silicon substrate 2 can be arranged inside the reaction vessel 1. The reaction vessel 1 is set to be roughly circular in a plan view, but the shape of the reaction vessel 1 is not limited to this, and can also be roughly quadrilateral in a plan view. The reaction vessel 1 is set to be able to reduce the pressure inside.

[0051] In addition, the left-right direction of the paper surface is set as an X direction, and the direction perpendicular to the paper surface is set as a Y direction.

[0052] A reaction gas introduction pipe 9 is installed on the wall to introduce the reaction gas 6 into the interior. The reaction gas 6 is, for example, a mixed gas of hydrogen and methane.

[0053] A microwave introduction pipe 4 connected to a microwave generator (2.45 GHz) 5 is installed on the top plate so as to irradiate microwave plasma in a downward direction.

[0054] A plate-shaped (X, Y direction movable substrate heating) stage 7 is arranged on the bottom side. The surface of the stage 7 is set to be parallel to the direction perpendicular to the downward direction. In addition, the surface of the stage 7 is set to be able to arrange the large-diameter silicon substrate 2. Furthermore, the stage 7 has a mechanism that can move in the X, Y directions, and a mechanism that can heat the large-diameter silicon substrate (film formation substrate) 2 arranged on the surface.

[0055] A large-diameter silicon substrate 2 is placed on the surface of the stage 7 .

[0056] The large-diameter silicon substrate 2 is, for example, the following substrate: a boron-doped high-resistance single-crystal silicon substrate with a diameter of 300 mm (111) is prepared, and the surface is ground with a #8000 grindstone (average particle size of the abrasive grains 2 to 4 μm) to roughen the silicon surface and introduce damage to form a nucleus for diamond growth.

[0057] (Diamond layer growth method)

[0058] Next, a method for growing a diamond layer will be described.

[0059] The diamond layer growth method of the present invention is a method for growing a diamond layer, particularly a single crystal diamond layer, by microwave plasma CVD.

[0060] The method comprises: a step of configuring a substrate in a reaction vessel of a microwave plasma CVD device (substrate configuration step), a step of introducing a raw material gas (reaction gas) into the reaction vessel (raw material gas (reaction gas) introduction step), and a step of irradiating a surface of the substrate with microwave plasma to grow a diamond layer on the surface of the substrate (diamond layer growth step).

[0061] (Substrate placement process)

[0062] First, if Figure 1 As shown, the large-diameter silicon substrate 2 is placed on the surface of a plate-shaped stage 7 , and the stage 7 is placed on the bottom surface side of the reaction container 1 of the microwave plasma CVD device 10 .

[0063] (Raw material gas (reaction gas) introduction process)

[0064] Next, after the interior of the reaction container 1 is depressurized, the reaction gas 6 is introduced into the interior from the reaction gas introduction pipe 9 .

[0065] (Diamond layer growth process)

[0066] Next, microwave plasma is irradiated onto the surface of the large-diameter silicon substrate 2 , so that a diamond layer grows on the surface of the large-diameter silicon substrate 2 .

[0067] When the diamond layer is grown, the large-diameter silicon substrate 2 is moved in a direction parallel to the surface of the large-diameter silicon substrate 2, and / or the irradiation position of the microwave plasma is moved in a direction parallel to the surface of the substrate. Thus, the locally generated microwave plasma can be evenly irradiated to the surface of the large-diameter silicon substrate, and a uniform large-diameter diamond layer can be formed on the surface of the large-diameter silicon substrate.

[0068] Furthermore, the movement in a direction parallel to the surface of the substrate is not limited to the case where the substrate is moved parallel to the XY directions, and also includes rotational movement such as rotation and revolution.

[0069] The moving speed is preferably about 1 to 50 mm / min when the substrate is parallel-moved in the XY directions, and is preferably about 1 to 100 rpm when the substrate is rotationally moved, for example.

[0070] When growing the diamond layer, it is preferable to heat the large-diameter silicon substrate 2. This can promote the growth.

[0071] (About evaluation)

[0072] The diamond layer is evaluated by, for example, Raman measurement, surface optical microscope image observation, X-ray diffraction, etc. at multiple locations within the surface of the large-diameter diamond layer. The crystallinity of the large-diameter diamond layer and whether the surface is homogeneous can be determined.

[0073] (Second embodiment)

[0074] First, refer to Figure 2 Next, a hot filament CVD apparatus used for the diamond layer growth method in the second embodiment of the present invention will be described.

[0075] (Hot filament CVD device)

[0076] Figure 2 This is an explanatory diagram showing a hot filament CVD apparatus used in the diamond layer growth method of the present invention.

[0077] like Figure 2As shown, the hot filament CVD device 20 used in the diamond layer growth method of the present invention has a reaction container 1, and a large-diameter silicon substrate 2 with a thin diamond layer formed on the surface can be arranged inside the reaction container 1. The reaction container 1 is set to be able to reduce the pressure inside.

[0078] A reaction gas introduction pipe 9 is installed on the top plate, and can introduce the reaction gas 6 into the interior. The reaction gas 6 is, for example, a mixed gas of hydrogen and methane.

[0079] A linear filament 8 is attached to the bottom of the top plate, which is separated from the bottom of the top plate and directly below the reaction gas introduction pipe 9 , in parallel with the bottom surface of the top plate.

[0080] The heating temperature of the filament 8 is, for example, 2200° C. The filament 8 is, for example, tungsten, but is not limited thereto. The shape of the filament is not limited to a linear shape, and may be a mesh shape.

[0081] (Diamond layer growth method)

[0082] Next, a method for growing a diamond layer according to the second embodiment will be described.

[0083] The diamond layer growth method of the second embodiment is a method of further growing a diamond layer by a hot filament CVD device on the diamond layer formed by the diamond layer growth method of the first embodiment.

[0084] That is, the diamond layer growth method of the second embodiment includes, in addition to the substrate configuration step, the raw material gas (reaction gas) introduction step, and the diamond layer growth step of the diamond layer growth method of the first embodiment, the following further steps: a step of configuring the substrate in a reaction vessel of a hot filament CVD device (substrate configuration step), and a step of further growing a diamond layer by the hot filament CVD device (diamond layer additional growth step).

[0085] (Substrate placement process)

[0086] A large-diameter substrate 2 having a thin diamond layer, particularly a single-crystal diamond layer, formed on its surface by the diamond layer growth method of the first embodiment is placed in a reaction vessel of a hot filament CVD apparatus with the diamond layer facing the top plate.

[0087] (Diamond layer additional growth process)

[0088] After the interior of the reaction container 1 is depressurized, the filament 8 is heated to a predetermined temperature.

[0089] Then, a reaction gas 6 composed of a mixed gas of hydrogen gas and methane gas is introduced into the interior from the reaction gas introduction pipe 9 .

[0090] By installing a linear filament 8 in a manner parallel to the lower surface of the top plate, separated from the lower portion of the top plate and directly below the reaction gas introduction pipe 9, the reaction gas 6 ejected from the reaction gas introduction pipe 9 is heated by the filament 8 and collides with the thin diamond layer formed on the surface of the large-diameter silicon substrate 2. Thus, a further diamond layer can be grown.

[0091] Example

[0092] The present invention is specifically described below with reference to examples, but the present invention is not limited by these examples.

[0093] (Example 1)

[0094] A boron-doped high-resistance single-crystal silicon substrate with a diameter of 300 mm (111) was prepared, and the surface was polished with a #8000 grindstone (average grain size of the abrasive grains 2 to 4 μm) to roughen the silicon surface and introduce damage to form nuclei for diamond growth.

[0095] The substrate was introduced into a microwave plasma growth device, and growth was carried out while moving the irradiation position at a speed of 10 mm / min under the conditions of 2.45 GHz microwaves at 1500 W, H2 flow rate of 10 SLM, CH4 concentration of 3%, substrate temperature of 850°C, and 60 Torr.

[0096] As a result, a large-diameter diamond layer can be formed.

[0097] Afterwards, Raman measurements and surface optical microscope imaging were performed on multiple locations within the surface of the large-diameter diamond layer.

[0098] Figure 3A , Figure 3B Indicates the result in any position. Figure 3A As shown in , the growth of diamond was confirmed. Figure 3B As shown, high crystallinity can be observed.

[0099] That is, the Raman peak was confirmed at any position, and the surface optical microscope image was observable.

[0100] (Example 2)

[0101] The substrate of Example 1 (substrate on which diamond is grown) was placed in a hot filament device and grown for 4 hours under the conditions of a filament temperature of 2200°C, a H2 flow rate of 10 SLM, a CH4 concentration of 3%, a substrate temperature of 850°C, and 5 Torr.

[0102] As a result, the thickness of the large-diameter diamond layer can be increased.

[0103] Afterwards, Raman measurements and surface optical microscope imaging were performed on multiple locations within the surface of the large-diameter diamond layer.

[0104] Figure 4A , Figure 4B Indicates the result in any position. Figure 4A As shown in , the growth of diamond was confirmed. Figure 4B As shown, high crystallinity can be observed.

[0105] That is, the Raman peak was confirmed at any position, and the surface optical microscope image was observable.

[0106] As described above, according to the embodiments of the present invention, a large-diameter diamond layer with high crystallinity can be formed.

[0107] The present invention is not limited to the above-described embodiments. The above-described embodiments are illustrative, and any scheme having substantially the same structure and achieving the same function and effect as the technical concept described in the claims of the present invention is included in the technical scope of the present invention.

Claims

1. A method for growing a diamond layer, which is a method for growing a diamond layer according to a microwave plasma CVD method, characterized in that: The method comprises the following steps: placing a substrate in a reaction vessel of a microwave plasma CVD device; introducing a raw material gas (reaction gas) into the reaction vessel; and irradiating the surface of the substrate with microwave plasma to grow a diamond layer on the surface of the substrate. In the step of growing the diamond layer, the substrate is moved in a direction parallel to the surface of the substrate, and / or the irradiation position of the microwave plasma is moved in a direction parallel to the surface of the substrate.

2. The method for growing a diamond layer according to claim 1, wherein: After the step of growing the diamond layer, the substrate on which the diamond layer is grown is moved into a reaction vessel of a hot filament CVD device, and diamond is further grown on the diamond layer by hot filament CVD.

3. The method for growing a diamond layer according to claim 1 or 2, characterized in that: A silicon substrate was used as the substrate.

4. A microwave plasma CVD device, which is a microwave plasma CVD device used in a method for growing a diamond layer, characterized in that: The device is provided with a mechanism for moving the substrate in a direction parallel to the surface of the substrate and / or a mechanism for moving the irradiation position of microwave plasma.

5. The microwave plasma CVD device according to claim 4, characterized in that: It also includes a mechanism for heating the substrate.

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