JP4366500B2 - Substrate support for microwave plasma CVD equipment - Google Patents

Description

  The present invention relates to a substrate support of a microwave plasma CVD apparatus used for vapor phase growth of diamond.

Conventionally, a microwave plasma CVD apparatus is widely known as a diamond gas phase synthesis apparatus (for example, Patent Documents 1 and 2).
JP-A-2-188494 Japanese Patent Laid-Open No. 6-183887

  However, the microwave plasma CVD apparatus is desired to grow at a high speed in order to improve productivity. However, conventionally, a sufficient growth rate has not been obtained.

  In order to grow diamond at high speed in a microwave plasma CVD apparatus, increasing the plasma density directly on the substrate is considered as one method. Simply, increasing the microwave power increases the plasma density, so it is possible to increase the speed to some extent. However, even if the microwave power is increased unnecessarily, the plasma density in the vicinity of the microwave inlet will be increased, and the target density on the substrate will not be increased efficiently.

  Accordingly, an object of the present invention is to provide means capable of growing diamond at a high speed using a microwave plasma CVD apparatus.

The object of the present invention is a substrate support disposed in a reaction vessel of a microwave plasma CVD apparatus, and has a mounting portion for mounting a substrate at a position separated from an outer peripheral edge of the substrate support. In addition, the mounting portion has a shape that continuously protrudes from the outer peripheral edge portion of the substrate support via a smooth inclined surface with respect to the outer peripheral edge portion. This is achieved by the substrate support characterized in that the height of the surface to be worked is higher than the height of the outer peripheral edge .

The inclined surface may be a curved convex surface or a curved concave surface.

Further, the object of the present invention is a substrate support disposed in a reaction vessel of a microwave plasma CVD apparatus, and a position where a placement portion for placing a substrate is separated from an outer peripheral edge portion of the substrate support. And the mounting portion has a shape that is continuously raised with respect to the outer peripheral edge portion through the outer peripheral edge portion of the substrate support and the horizontal plane and a smooth inclined surface connected to the horizontal plane , This is achieved by the substrate support body , wherein the height of the surface on which the substrate of the placement portion is placed is higher than the height of the outer peripheral edge portion . The outer diameter of the raised portion is preferably λ / 2 or less where λ is the free space wavelength of the microwave generated by the microwave plasma CVD apparatus.

  The height of the substrate support is preferably λ / 25 to λ / 2, where λ is the free space wavelength of the microwave generated by the microwave plasma CVD apparatus.

  In a microwave plasma CVD apparatus using a metal reaction vessel, the metal substrate support can be regarded as a part of the reaction vessel wall confining the microwave, and its shape is a predetermined shape. Thus, the plasma generation shape in the reaction vessel can be controlled.

  According to the present invention, by setting the substrate support of the microwave plasma CVD apparatus to the shape and dimensions as described above, the plasma generation position in the reaction vessel is located on the substrate, so that the microwave power to be input is increased. This makes it possible to grow diamond at high speed.

  The substrate support of the microwave plasma CVD apparatus according to the present invention will be described below with reference to FIGS.

  First, an outline of a microwave plasma CVD apparatus will be described. As shown in FIG. 1, a microwave plasma CVD apparatus 1 includes a microwave power source 2, a waveguide 3 for propagating microwaves, a microwave introduction quartz window 4, A cavity resonator type reaction vessel 5, a stage 6 through which cooling water W passes, and a substrate support 7 placed on the stage 6 are provided. As a substrate supported by the substrate support 7, a known substrate such as a diamond substrate, a single crystal Si substrate, a c-BN substrate (cubic boron nitride), a Pt substrate, or an Ir substrate can be used.

  The reaction vessel 5 is provided with a source gas introduction port 5a for introducing a source gas and an exhaust port 5b for evacuating the inside of the vessel. In the case of diamond synthesis, the source gas is a mixed gas of methane gas, hydrogen gas, and nitrogen gas.

  The microwave generated by the microwave power source 2 is introduced into the reaction vessel 5 as indicated by an arrow in FIG.

  Next, the substrate support 7 will be described in detail with reference to FIG. In addition, the same code | symbol is attached | subjected through the whole figure about the same component.

  The shape of the substrate support 7 is determined on the basis that the microwave electric field in the reaction vessel 5 is concentrated near the substrate. The substrate support 7 is made of metal or alloy, and is made of molybdenum in the illustrated example.

On the other hand, in an apparatus capable of supplying a high-power microwave of several kW or more for the purpose of high-speed growth, cooling water W is placed inside the stage 6 in order to keep the substrate at a temperature of about 800 ° C. to 1300 ° C. suitable for diamond growth. The substrate support 7 is forcedly cooled exclusively by passing water.

  Therefore, the shape of the substrate support 7 needs to be a shape that can appropriately control the substrate temperature together with the concentration of the microwave electric field.

  In order to satisfy such conditions of electric field concentration and substrate temperature setting, the substrate support 7 has a mounting portion 7a for mounting the substrate at a position separated from the outer peripheral edge portion 7b of the substrate support 7, The mounting portion 7 a has a raised shape with respect to the outer peripheral edge portion 7 b of the substrate support 7.

  The substrate support body 7 has a shape in which the placement portion 7a is raised with respect to the outer peripheral edge portion of the substrate support body 7, thereby concentrating the microwave electric field on the raised portion, that is, the placement portion 7a of the substrate. be able to. On the other hand, since the outer peripheral edge portion of the substrate support 7 and the raised mounting portion 7a are arranged apart from each other, a heat radiation effect can be obtained by the surface area from the mounting portion 7a to the outer peripheral edge portion.

In the illustrated example, the placing portion 7a can be formed by a flat surface, but is preferably formed by the concave portion 7c. This is because if the plasma is concentrated on the corners of the substrate 8, non-uniform film growth occurs. Therefore, when the mounting portion 7a is formed by the recess 7c, the depth of the recess 7c is equal to or slightly deeper than the thickness of the substrate 8 so that the corner of the substrate is not exposed from the recess 7c. It is desirable to set the degree. Moreover, it is preferable that the mounting portion 7 a is disposed at the approximate center of the substrate support 7.

  In the example of FIG. 2A, the placement portion 7 a is raised from the horizontal plane 7 d via the horizontal plane 7 d from the outer peripheral edge portion 7 b of the substrate support 7. In this case, the board | substrate support body 7 becomes a shape which has a protrusion with respect to a flat plate as a whole shape.

  In the form shown in FIG. 2A, the outer diameter (D) of the portion raised from the horizontal plane is λ / 2 when the free space wavelength of the microwave generated by the microwave plasma CVD apparatus is λ. The following is preferable. This is because when the outer diameter (D) is larger than λ / 2, the increase in growth rate due to plasma concentration is reduced.

  As the outer diameter (D) is smaller, the growth rate tends to increase. In the illustrated example, the outer diameter (D) of the portion protruding from the horizontal surface 7d is 5 mm, because the size of the substrate in the illustrated example is 3 mm square, and the outer diameter on which the substrate can be placed. And the microwave power used in the illustrated example is a microwave plasma CVD apparatus having a power of 500 W or more, and the outer diameter (D) of the portion protruding from the horizontal plane 7d is smaller than 5 mm. This is because the plasma is too concentrated and the temperature of the substrate rises so that it becomes difficult to control. However, depending on the application, if the substrate size is made smaller than 3 mm square and the microwave power is made smaller than 500 W, the outer diameter (D) can be made smaller than 5 mm unless the high-speed diamond growth is reduced. it can.

  In the example shown in FIGS. 2B and 2C, the mounting portion 7 a has a shape protruding from the outer peripheral edge portion 7 b of the substrate support 7 through a smooth inclined surface 7 e. In this case, the substrate support 7 is an example having a truncated cone shape as an overall shape. The inclined surface 7e can be a flat surface (FIG. 2B), a curved convex surface (FIG. 2C), or a curved concave surface (not shown).

  The height dimension (H) of the substrate support 7 is preferably λ / 25 to λ / 2, where λ is the free space wavelength of the microwave generated by the microwave plasma CVD apparatus. This is because if the height dimension (H) is smaller than λ / 25, it enters the plasma sheath region, and the plasma concentration effect cannot be obtained. In general, in the microwave plasma CVD apparatus, the height dimension of the space for generating plasma in the reaction vessel 5 (the dimension from the upper surface of the stage 6 to the top surface of the reaction vessel 5) is a standing wave in the space. The plasma is designed to be slightly longer than the free space wavelength λ of the microwave, and the plasma is designed to be formed at a substantially middle height position of its height dimension. Therefore, by placing the mounting portion 7a at a position lower than the intermediate height position and distorting the microwave electric field generated in the reaction vessel 5 toward the mounting portion 7a, the plasma is concentrated on the mounting portion 7a. Let Therefore, the height dimension (H) is preferably λ / 2 or less.

  In the illustrated example, the substrate support 7 is separate from the stage 6 and is placed on the stage 6. Accordingly, the substrate support 7 has a flat bottom surface, and the peripheral edge of the bottom surface is connected to the outer peripheral edge portion 7b. The substrate support 7 is not a separate member from the stage 6, and the substrate support 7 can be an integrally molded product with the stage 6.

When the substrate support 7 shown in FIG. 2 is used, a high-density plasma P can be generated immediately above the substrate under a certain pressure condition. At this time, the conventional substrate support is used for the same microwave input power. The diamond growth rate is dramatically increased as compared with the case where it is used. The pressure condition is preferably 10 Torr to 200 Torr. The higher the pressure, the faster the growth, so it is preferable to grow it under high pressure conditions. However, if the pressure exceeds 200 Torr, the anxiety that the plasma suddenly moves not on the substrate but near the microwave-introduced quartz window 4. This is not preferable because qualitative characteristics are increased and there is a risk of vacuum leakage due to damage to the microwave-introduced quartz window 4.

  As a result, in the present invention, it becomes possible to produce a diamond single crystal thin film at a growth rate of 100 μm or more per hour, making the production of a diamond semiconductor element a reality, a high power / high frequency electronic element using diamond as a material, a high temperature Semiconductor devices and environmental electronic devices can be manufactured. In addition, it can contribute to the improvement of productivity in the production of polycrystalline diamond.

  Next, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples without departing from the gist thereof.

Example 1
In a microwave plasma CVD apparatus (FIG. 1) having a cavity resonator-type reaction vessel (FIG. 1), polishing using diamond powder, which is a general pretreatment, is performed on a substrate support as shown in FIG. The fixed single crystal Si substrate was fixed, and after evacuating the reaction vessel, CH ₄ , H ₂ , and N ₂ gases were introduced at 60, 500, and 1.8 sccm, respectively, and the pressure inside the reaction vessel was controlled by controlling the evacuation rate. Is set to 10 Torr and the plasma is ignited by applying microwave (2.45 GHz) power of 500 W, then the pressure and microwave power are gradually increased to 160 Torr and 1600 W, respectively, and the substrate to 1200 ° C. Set and move to steady diamond growth. As for the dimensions of the substrate, the thickness dimension is 0.5 mm and the vertical and horizontal dimensions are 3 mm each.

  After growing the substrate for the required time, the substrate is taken out, the weight increase measurement and the thickness of the diamond grown with a micrometer are measured, and the growth rate is divided by the growth time to obtain a maximum growth rate of 16 μm / hour. It was.

Example 2
In Example 1, the substrate was changed from a single crystal Si substrate to a single crystal diamond substrate cut and polished parallel to the (100) plane, and the same diamond growth was performed. The maximum growth rate was 124 μm. / Growth rate was obtained. The thickness of the board is 0.5m.
m and vertical and horizontal dimensions are 3 mm each.

  The CVD diamond grown on this diamond single crystal was confirmed to be a single crystal similar to the substrate by channeling measurement, X-ray diffraction, and Raman scattering (FIG. 3) in Rutherford backscattering method. Similar results were obtained even when the shape of the substrate support was changed to that shown in FIGS.

Comparative Example 1
The substrate support was shaped as in the conventional example shown in FIG. 4, and the other conditions were the same as in Example 2. As a result of growing the diamond, a growth rate of 19 to 22 μm / hour was obtained.

In the substrate support 7 ′ shown in FIG. 4, the placement portion 7a ′ is not separated from the outer peripheral edge portion 7b ′, and the height of the placement portion 7a ′ and the height of the outer peripheral edge portion 7b ′ are the same height. It has become.

  From the above example, in order to obtain high-speed growth, the shape of the substrate support is such that the placement portion 7a on which the substrate is placed is separated from the outer peripheral edge portion 7b of the substrate support 7 as shown in FIG. It can be seen that a configuration in which the mounting portion 7a is raised with respect to the outer peripheral edge portion 7b is effective.

It is a schematic block diagram which shows schematically the internal structure of a microwave plasma CVD apparatus. 3 shows examples (a), (b), and (c) of the substrate support according to the present invention, wherein the upper figure is a plan view and the lower figure is a central longitudinal front view, respectively. It is a graph which shows the Raman scattering spectrum of the diamond thin film synthesize | combined using the board | substrate support body of Fig.2 (a). The comparative example of a board | substrate support body is shown, the upper figure is a top view, and the lower figure is a center vertical front view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Microwave plasma CVD apparatus 7 Substrate support body 7a Mounting part 7b Outer peripheral edge part 7c Recessed part 7d Horizontal surface 7e Inclined surface

Claims (6)

A substrate support disposed in a reaction vessel of a microwave plasma CVD apparatus,
The mounting portion for mounting the substrate is located at a position separated from the outer peripheral edge of the substrate support, and the mounting portion is continuously connected to the outer peripheral edge of the substrate support via the smooth inclined surface. A substrate support characterized in that it has a raised shape with respect to the outer peripheral edge, and the height of the surface on which the substrate of the mounting portion is placed is higher than the height of the outer peripheral edge .   The substrate support according to claim 1, wherein the inclined surface is a curved convex surface or a curved concave surface. A substrate support disposed in a reaction vessel of a microwave plasma CVD apparatus,
The mounting portion for mounting the substrate is located at a position spaced from the outer peripheral edge of the substrate support, and the mounting portion is connected to the outer peripheral edge of the substrate support, the horizontal plane, and the horizontal plane. And the height of the surface on which the substrate of the mounting portion is placed is higher than the height of the outer peripheral edge portion. A substrate support characterized.   The substrate support according to any one of claims 1 to 3, wherein the placement portion is formed by a concave portion.   The outer diameter of the protruding portion is λ / 2 or less, where λ is a free space wavelength of the microwave generated by the microwave plasma CVD apparatus. Substrate support.   The height of the substrate support is λ / 25 to λ / 2, where λ is a free space wavelength of the microwave generated by the microwave plasma CVD apparatus. A substrate support according to any one of the above.

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