Vapor phase growth device

Abstract

To provide a vapor phase growth device that can suppress the influence of a substrate holding portion on the uniformity of film formation.SOLUTION: A vapor phase growth device 10 includes a gas passage 12 that guides a raw material gas G and a susceptor 14 that supports a substrate 13 relative to the gas passage 12, in which the raw material gas G is guided in a direction along the surface 13a of the substrate 13, and the susceptor 14 has a substrate holding portion 15 that protrudes above the surface 13a of the substrate 13 toward the gas passage 12, and the substrate holding portion 15 has a shape consisting only of a non-perpendicular surface relative to the surface 13a of the substrate 13.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a vapor phase growth apparatus. [Background technology]

[0002] In vapor phase growth equipment for forming compound semiconductor thin films, compound semiconductor thin films such as gallium nitride are formed by heating and reacting source gases on a substrate. The substrate surface on which the thin film is formed is positioned so that the source gases flow uniformly to ensure uniformity and reproducibility of the thin film grown on the substrate surface. Semiconductors obtained by vapor phase growth require electrical properties and yield control.

[0003] Since the adhesion of reaction products generated by the reaction of source gases and the inclusion of foreign matter affect the performance of thin films, structures and means are required that minimize the effects of reaction products and foreign matter. As means for suppressing the effects of reaction products and foreign matter, various substrate holding methods are used, such as positioning the substrate surface facing vertically downward (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 61-150322 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-344758 Summary of the Invention [Problem to be solved by the invention]

[0005] The area where the substrate comes into contact with the substrate holder or its surroundings is more susceptible to source gas turbulence than areas not affected by the substrate holder, which poses a problem of affecting the uniformity of film deposition.

[0006] In view of the above circumstances, an object of the present invention is to provide a vapor phase growth apparatus that can suppress the influence of a substrate holder on the uniformity of film formation. [Means for solving the problem]

[0007] One aspect of the present invention is a vapor phase growth apparatus comprising a gas passage for guiding a source gas and a susceptor for supporting a substrate relative to the gas passage, wherein the source gas is guided in a direction along the surface of the substrate, the susceptor has a substrate holding portion that protrudes above the surface of the substrate toward the gas passage, and the substrate holding portion has a shape consisting only of non-perpendicular surfaces relative to the surface of the substrate.

[0008] In one aspect of the present invention, the susceptor can rotate the substrate by rotating around a central axis of rotation perpendicular to a surface of the substrate. In one aspect of the present invention, the non-perpendicular surface is a surface parallel to the surface of the substrate or a surface inclined relative to the surface of the substrate. In one aspect of the present invention, the substrate holder is pyramidal. In one aspect of the present invention, the substrate holder is spherical. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a vapor phase growth apparatus that can suppress the influence of a substrate holder on the uniformity of film formation. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a vertical cross-sectional view showing an example of a vapor phase growth apparatus according to an embodiment of the present invention. [Figure 2] 1 is a perspective view showing an example of a vapor phase growth apparatus according to an embodiment of the present invention. [Figure 3] 10(a) to 10(c) are explanatory diagrams showing the analysis results in a plane perpendicular to the substrate surface. [Figure 4]10(a) to 10(c) are explanatory diagrams showing analysis results on a plane parallel to the substrate surface when the direction connecting the center of the substrate and the position of the substrate holder is along the gas flow direction. [Figure 5] 10(a) to 10(c) are explanatory diagrams showing analysis results on a plane parallel to the substrate surface when the direction connecting the center of the substrate and the position of the substrate holder is inclined from the gas flow direction. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0012] As one embodiment of the present invention, a vapor phase growth apparatus 10 for growing a semiconductor thin film on the surface of a substrate will be described. Fig. 1 is a vertical cross-sectional view showing an example of the vapor phase growth apparatus of this embodiment. Fig. 2 is a perspective view showing an example of the vapor phase growth apparatus of this embodiment. In Fig. 2, a substrate holder 15 is not shown.

[0013] 1 and 2, a vapor phase growth apparatus 10 of this embodiment includes a gas passage 12 that guides a source gas G, and a susceptor 14 that supports a substrate 13 relative to the gas passage 12. The source gas G is guided so as to flow in a direction along a surface 13a of the substrate 13. Here, the surface 13a of the substrate 13 refers to the surface of the outer surface of the substrate 13 on which a thin film is grown.

[0014] The illustrated vapor phase growth apparatus 10 includes a flow channel portion 11 for guiding a source gas G toward a substrate 13. The vapor phase growth apparatus 10 can grow a compound semiconductor thin film on a surface 13a of the substrate 13 by thermally reacting the source gas G in a vapor phase.

[0015] Compound semiconductors include, but are not limited to, gallium nitride (GaN) and gallium oxide (Ga2O3). The material of the substrate 13 is also not limited to, but is exemplified by sapphire and gallium oxide (Ga2O3). When synthesizing gallium compounds such as GaN and Ga2O3, source gases include, but are not limited to, organic gallium compounds such as trimethylgallium. Note that the vapor phase growth apparatus 10 of this embodiment is not limited to growing compound semiconductor thin films.

[0016] The flow channel portion 11 in the illustrated example is a portion of a reaction tube that uses heat to cause a gas-phase reaction of raw material gas G near a substrate 13. Although not particularly shown, a gas inlet portion that introduces raw material gas G into the flow channel portion 11 and a gas outlet portion that blows raw material gas G from the gas inlet portion toward the substrate may be disposed upstream of the reaction tube. The flow of raw material gas G flowing in the reaction tube portion is a uniform flow in which the velocity component in the thickness direction of the substrate 13 is suppressed compared to the velocity component in the direction along the surface 13a of the substrate 13.

[0017] A susceptor 14 is disposed in the flow channel portion 11. The susceptor 14 has a substrate holding portion 15 that protrudes above the surface 13a of the substrate 13 toward the gas passage 12. The substrate holding portion 15 is integrated with the main body of the susceptor 14 on the outside of the substrate 13. Furthermore, the tip side of the substrate holding portion 15 protrudes in a cantilevered (claw-like) manner from the susceptor 14 above the surface 13a of the substrate 13. A plurality of substrate holding portions 15 are disposed at intervals around the circumferential direction of the substrate 13. The substrate 13 is held by the portion of the substrate holding portion 15 that protrudes above the surface 13a of the substrate 13.

[0018] The planar shape of substrate 13 when viewed from a direction perpendicular to surface 13a of substrate 13 is generally circular, but may be other shapes. It may have a cutout portion such as an orientation flat (orientation flat) or a notch at one or more locations on the circumference.

[0019] The number of substrates 13 supported by the substrate holders 15 can be set appropriately taking into consideration the manufacturing cost of the substrate holders 15 and the possibility of maintaining support for the substrates 13 even if the substrate holders 15 are damaged. For example, it is preferable that the susceptor 14 has 3 to 5 substrate holders 15 for one substrate 13.

[0020] In the vapor phase growth apparatus 10 of this embodiment, the substrate holding portion 15 of the susceptor 14 has a shape consisting only of non-perpendicular surfaces relative to the surface 13a of the substrate 13. Examples of non-perpendicular surfaces include parallel surfaces and inclined surfaces. A parallel surface is a surface that is parallel to the surface 13a of the substrate 13. An inclined surface is a surface that is inclined relative to the surface 13a of the substrate 13. By having the substrate holding portion 15 consisting only of non-perpendicular surfaces, such as parallel surfaces or inclined surfaces, the substrate holding portion 15 can be designed to avoid having a shape that includes vertical surfaces.

[0021] The inclined surface may be a flat surface with a constant inclination angle, or a curved surface with a different inclination angle depending on the position. The inclination angle may be greater than 0° and less than 90°, but the maximum inclination angle may be set to, for example, 75° or less, 60° or less, 45° or less, or 30° or less. Since an inclination angle close to 0° is close to a parallel surface, a region with an inclination angle of 0° (i.e., a parallel surface) and a region with an inclination angle greater than 0° (i.e., an inclined surface) may be arranged consecutively.

[0022] If the substrate holding part 15 of the susceptor 14 includes a surface perpendicular to the surface 13a of the substrate 13, turbulence is likely to occur in the flow of the source gas G that flows in the direction along the surface 13a of the substrate 13. Therefore, if the substrate holding part 15 has a shape that does not include a surface perpendicular to the flow direction of the source gas G, it is possible to prevent turbulence in the flow of the source gas G from being caused by the substrate holding part 15.

[0023] Generally, vapor phase growth apparatus 10 rotates substrate 13 during film formation using a rotation mechanism (not shown). When substrate 13 is rotated by the rotation of susceptor 14, the difference in rotation speed between substrate 13 and substrate holder 15 is substantially eliminated, and the area on substrate 13 that can be affected by substrate holder 15 can be limited.

[0024] The method for rotating the susceptor 14 is not particularly limited, and for example, the substrate 13 held by the susceptor 14 can be rotated by rotating the susceptor 14. When the susceptor 14 rotates, a mechanism for rotating the substrate 13 does not need to be mounted inside the susceptor 14. The method for rotating the susceptor 14 from outside the susceptor 14 is not particularly limited, and for example, a rotational force may be applied to the outer periphery of the susceptor 14, or a rotational force may be applied near the center of the susceptor 14.

[0025] Although not shown, when multiple substrates 13 are supported on the same susceptor 14, a mechanism for rotating or revolving the substrates 13 relative to the rotation of the susceptor 14 may be provided. For example, in a susceptor having multiple substrate mounting portions, a mechanism for rotating the substrate mounting portions relative to the susceptor body using gears or the like may be incorporated between the susceptor body excluding the substrate mounting portions and the substrate mounting portions. In this case, a substrate holder 15 can be provided for each substrate mounting portion. The shapes of the substrate holders 15 arranged on each substrate mounting portion may be different from each other depending on the positional relationship in the susceptor body, or may be the same shape common to all the substrate mounting portions.

[0026] The rotation direction of substrate 13 is preferably such that the rotation axis is a perpendicular line passing through the center or vicinity of surface 13a of substrate 13, and may be either clockwise or counterclockwise. Here, the rotation axis does not necessarily refer to a mechanical axis member such as a shaft existing on the rotation axis, but may refer to a virtual rotation axis of rotation that occurs as a result of a rotational force acting on a portion other than the center, such as the outer periphery of substrate 13. When rotation and revolution act together, the position of the rotation axis of the rotation may move in accordance with the revolution.

[0027] By rotating the susceptor 14 holding the substrate 13, the upstream and downstream positions on the substrate 13 in the flow direction of the source gas G change relative to each substrate holder 15. This makes it possible to further reduce the influence of the substrate holder 15 on the uniformity of film formation at locations on the surface 13a of the substrate 13 that are distant from the substrate holder 15.

[0028] However, the source gas G is likely to be disturbed in the region on the surface 13a of the substrate 13 where the substrate holder 15 and the substrate 13 come into contact or in the vicinity thereof. Therefore, the substrate holder 15 that holds the substrate 13 has a problem in that it affects the uniformity of the film formation.

[0029] When substrate 13 is rotated around a rotation axis perpendicular to surface 13a of substrate 13, the flow direction of source gas G remains parallel to surface 13a of substrate 13 regardless of the rotation angle of substrate 13. Therefore, to maintain a state in which substrate holding unit 15 does not include any surfaces perpendicular to the flow direction of source gas G regardless of the rotation angle of substrate 13, substrate holding unit 15 only needs to have a shape that is composed of only surfaces that are non-perpendicular to surface 13a of substrate 13. This makes it possible to prevent substrate holding unit 15 from causing turbulence in the flow of source gas G while substrate 13 is rotating. Furthermore, it is possible to reduce the influence of substrate holding unit 15 on the uniformity of film formation.

[0030] The shape of the substrate holder 15 is not particularly limited as long as it satisfies the above-mentioned requirements, but it is preferable that the cross-sectional shape parallel to the surface 13a of the substrate 13 is large at a height close to the surface 13a of the substrate 13 and that the cross-sectional shape parallel to the surface 13a of the substrate 13 becomes smaller as the distance in the height direction increases from the surface 13a of the substrate 13. Specific examples of such a shape include a cone shape, a spherical shape, etc.

[0031] The pyramidal substrate holder 15 may be pyramidal, conical, or the like, or may have a shape in which the apex of the pyramid is replaced with a flat or curved surface. When the substrate holder 15 is pyramidal, the shape of the substrate holder 15 that satisfies the requirements can be designed as a simple geometric shape consisting of only flat surfaces.

[0032] The spherical substrate holder 15 may have a curved surface on one side of a plane when a sphere is cut with the plane. If the plane passes through the center of the sphere, it will be a hemisphere, but it is preferable that the curved surface be the smaller side when the sphere is cut with a plane that does not pass through the center of the sphere. Instead of a sphere, it may have a curved surface obtained by cutting a spheroid with the plane. When the substrate holder 15 is spherical, the shape of the substrate holder 15 that satisfies the requirements can be designed as a simple geometric shape consisting of a single curved surface.

[0033] 3 to 5 are explanatory diagrams showing the results of analyzing the flow of source gas when the source gas flows along the substrate surface for substrate holders of various shapes, where the substrate surface is placed facing downward in the vertical direction (face down).

[0034] Figure 3 shows the analysis results for a plane perpendicular to the substrate surface. Figure 4 shows the analysis results for a plane parallel to the substrate surface when the direction connecting the center of the substrate and the position of the substrate holder is along the gas flow direction. Figure 5 shows the analysis results for a plane parallel to the substrate surface when the direction connecting the center of the substrate and the position of the substrate holder is tilted from the gas flow direction.

[0035] The direction connecting the center of the substrate and the position of the substrate holder is the radial direction from the center of the substrate toward the substrate holder, and hereinafter may be referred to as the radial direction of the substrate holder. The position of the plane parallel to the substrate surface in Figures 4 and 5 is offset 0.1 mm below the substrate surface.

[0036] There are five substrate holders located around the periphery of the substrate. For this reason, the substrate holders in Figure 4 and Figure 5 are separated by a central angle of 72° relative to the circumference. Since a typical substrate has an orientation flat along part of its outer periphery, the number of locations at which the substrate holders support the substrate is four, excluding the orientation flat position.

[0037] The shape of the substrate holder A shown in Figures 3(a), 4(a), and 5(a) is a quadrangular pyramid. More specifically, on a plane perpendicular to the substrate surface, as shown in Figure 3(a), the center of the base of the quadrangular pyramid is located approximately on the outer periphery of the substrate, and the apex of the quadrangular pyramid is located inside the outer periphery of the substrate. On the other hand, on a plane parallel to the substrate surface, as shown in Figures 4(a) and 5(a), the base of the quadrangular pyramid is rhombic, and the radial dimension of the substrate is longer than the circumferential dimension of the substrate.

[0038] The shape of the substrate holder B shown in Figures 3(b), 4(b), and 5(b) is a rectangular parallelepiped with cutouts along some of the ridges. More specifically, the outer periphery of the susceptor has cutouts along the sides parallel to the surface of the substrate, as shown on the left side of Figure 3(b), and the inner periphery of the susceptor has cutouts along each of the two sides perpendicular to the surface of the substrate, as shown on the right side of Figure 4(b).

[0039] The shape of the substrate holder C shown in Figures 3(c), 4(c), and 5(c) is spherical. More specifically, in a plane perpendicular to the substrate surface, it has an arched cross section as shown in Figure 3(c), and in a plane parallel to the substrate surface, it has a circular bottom as shown in Figures 4(c) and 5(c).

[0040] The simulation conditions were as follows: type of gas flowing along the substrate surface: N2; gas pressure: 20 Torr; gas flow rate: 7.5 SLM (liters per minute under standard conditions); gas temperature: 600°C; no susceptor rotation; substrate holder material: quartz; component temperature: 800°C.

[0041] In Figure 3(a)-(c), the flow velocity range of 0-0.1 m / s is divided into 13 color-coded intervals. Low speeds are indicated by dark colors, and high speeds by light colors. The flow velocity values ​​on the intermediate subscale, from lowest to highest, are approximately 0.0077, approximately 0.0154, approximately 0.0231, approximately 0.0308, approximately 0.0385, approximately 0.0462, approximately 0.0538, approximately 0.0615, approximately 0.0692, approximately 0.0769, approximately 0.0846, and approximately 0.0923 (units: m / s).

[0042] The gas flow velocity is constant at approximately 0.1 m / s away from the substrate, but drops to approximately 0.01 m / s near the substrate surface. Near the substrate holder, stagnant regions are formed on both the upstream and downstream sides of the flow direction (left and right in each figure), where the flow velocity is below approximately 0.008 m / s.

[0043] The stagnation area of ​​the gas flow is quite small at substrate holder A in Figure 3(a), quite large at substrate holder B in Figure 3(b), and somewhat smaller at substrate holder C in Figure 3(c). Furthermore, in Figure 3(b), a situation is observed in which the gas flow includes velocity components that move in the opposite direction to its original direction on the upstream and downstream sides of substrate holder B.

[0044] In Figures 4(a)-(c) and Figure 5(a)-(c), the flow velocity range of 0-0.03 m / s is divided into 13 color-coded intervals. Dark colors indicate low speeds, and light colors indicate high speeds. The flow velocity values ​​on the intermediate subscale, from lowest to highest, are approximately 0.0023, approximately 0.0046, approximately 0.0069, approximately 0.0092, approximately 0.0115, approximately 0.0138, approximately 0.0162, approximately 0.0185, approximately 0.0208, approximately 0.0231, approximately 0.0254, and approximately 0.0277 (units: m / s).

[0045] As shown in Figures 5(a) to 5(c), when the radial direction of the substrate holder is inclined from the gas flow direction, the stagnant region tends to extend somewhat wider to areas where the flow velocity is lower than approximately 0.005 m / s compared to when the radial direction of the substrate holder is aligned with the gas flow direction, as shown in Figures 4(a) to 4(c).

[0046] Among these, the stagnation area of ​​the gas flow at substrate holder A in Figures 4(a) and 5(a) is quite small, the stagnation area of ​​the gas flow at substrate holder B in Figures 4(b) and 5(b) is quite large, and the stagnation area of ​​the gas flow at substrate holder C in Figures 4(c) and 5(c) tends to be somewhat smaller. Furthermore, in Figures 4(b) and 5(b), situations are observed where the gas flow includes velocity components that are counter-directional to the original direction on the upstream and downstream sides of substrate holder B.

[0047] The above analysis results show that (1) gas flow turbulence is observed around substrate holder B, which has a shape with a surface perpendicular to the substrate surface, and (2) gas flow turbulence is not observed around square pyramidal substrate holder A and spherical substrate holder C, which have only surfaces non-perpendicular to the substrate surface, thereby suppressing the impact of the substrate holders on the uniformity of film deposition.

[0048] In the above simulation conditions, the substrate surface was set to face down in the vertical direction, but considering the effect of the shape of the substrate holder on the gas flow direction, it is expected that the same tendency will be obtained even if the substrate surface is set to face up in the vertical direction (face up). Furthermore, the substrate material, gas composition, number of substrate holders, and material of the substrate holders are not limited to the above simulation conditions and can be set as appropriate.

[0049] While the present invention has been described above based on preferred embodiments, the present invention is not limited to the above-described embodiments and various modifications are possible without departing from the spirit of the present invention. Modifications include addition, substitution, omission, and other changes to components in each embodiment. [Explanation of symbols]

[0050] G... source gas, 10... vapor phase growth apparatus, 11... flow channel portion, 11a... upstream side, 11b... downstream side, 12... gas passage, 13... substrate, 13a... surface of substrate, 14... susceptor, 15... substrate holder.

Claims

1. A vapor phase growth apparatus comprising: a gas passage for guiding a source gas; and a susceptor for supporting a substrate relative to the gas passage, the source gas is guided in a direction along the surface of the substrate; the susceptor has a substrate holding portion that protrudes above the surface of the substrate toward the gas passage; The vapor phase growth apparatus, wherein the substrate holding part has a shape consisting only of non-perpendicular surfaces relative to the surface of the substrate.

2. 2. The vapor phase growth apparatus according to claim 1, wherein the susceptor is capable of rotating the substrate by rotating about a central axis of rotation perpendicular to a surface of the substrate.

3. 3. The vapor phase growth apparatus according to claim 1, wherein the non-perpendicular surface is a surface parallel to the surface of the substrate or a surface inclined relative to the surface of the substrate.

4. 3. The vapor phase growth apparatus according to claim 1, wherein the substrate holder is pyramidal.

5. 3. The vapor phase growth apparatus according to claim 1, wherein the substrate holder is spherical.

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