TW201621979A - Wafer tray for MOCVD reaction system - Google Patents

Abstract

The present invention provides a wafer tray for a MOCVD reaction system. An upper surface of said wafer tray includes a first sub-surface and a second sub-surface. A first structure on which wafers are placed is arranged on the first sub-surface. A second structure is installed on the second sub-surface. Said second structure enlarges the area of the second sub-surface such that a reaction rate constant between the reaction gas and the second sub-surface of the wafer tray is equal to the reaction rate constant between the reaction gas and the wafer surface. As such, with the wafer tray provided by this invention, the gas concentration above the wafer perimeter close to a front end of the gas rotation direction is ensured to be equal to the gas concentrations above other areas. Thus, the reaction rates on the entire wafer surface can be ensured to be identical, which in turn assures that the crystal materials grown on the entire surface of the wafer have the same thickness.

Description

Wafer carrier for MOCVD reaction system

The present invention relates to the field of semiconductor processing equipment, and more particularly to a wafer carrier for an MOCVD reaction system.

For the growth of thin layer crystalline materials, important indicators are the uniformity of the thickness and the uniformity of the composition ratio. In order to ensure that the growing crystalline material meets these specifications, in MOCVD technology, it is necessary to have a uniform growth rate of the crystalline material over the entire wafer surface.

Since the growth rate of the crystalline material on the surface of the wafer is proportional to the concentration of the reactive gas above the wafer. In order to ensure a uniform growth rate of the crystal material over the entire wafer surface, it is required that the concentration of the reactive gas over the entire wafer surface be uniform at the respective wafer surface locations.

It should be noted that when the crystal material is grown on the surface of the wafer by MOCVD technology, the wafer is placed in a groove on the wafer carrier for placing the wafer. Since the material of the wafer carrier is different from the material of the wafer, the reaction constant of the reaction gas on the wafer carrier surface is smaller than the reaction constant of the reaction gas on the wafer surface, because the gas concentration above the wafer carrier and the wafer surface is the same. Therefore, the reaction rate between the surface of the wafer carrier and the gas is smaller than the reaction rate between the surface of the wafer and the gas, so that the amount of gas consumed on the surface of the wafer carrier is smaller than the amount of gas consumed on the surface of the wafer, thereby causing the surface of the wafer carrier after the reaction. The concentration of the reaction gas above is greater than the concentration of the reactant gas above the surface of the wafer.

In the actual MOCVD technology process, the wafer carrier is rotated, which is equivalent to the flow of gas above the wafer carrier is a rotating gas flow. Thus, the flow of gas to the surface of the wafer can be equivalent to a gas flow in two directions, one being a vertical direct flow of gas from the top, which is ejected by a gas showerhead; the other is flowing from the wafer carrier to the crystal. The horizontal flow of gas at the edge of the circle. Since the gas concentration above the wafer carrier surface is greater than the gas concentration above the wafer surface, the gas concentration at the edge of the wafer near the front end of the gas rotation direction is greater than the gas concentration in other regions of the wafer, and because the growth rate and gas concentration are In a proportional relationship, the growth rate of the edge of the wafer near the front end of the gas rotation direction is greater than the growth rate of other areas of the wafer. Fig. 1 is a simplified diagram showing the cause of uneven growth rate.

In order to solve the above technical problems, the present invention adopts the following technical solutions:

A wafer carrier for an MOCVD reaction system, the upper surface of the wafer carrier including a first sub-surface and a second sub-surface, on which the first structure for placing a wafer is disposed, The second sub-surface is provided with a second structure capable of increasing the area of the second sub-surface such that the reaction rate constant of the reaction gas and the second sub-surface of the wafer carrier is equal to the reaction gas and The reaction rate constant of the wafer surface.

Preferably, the ratio of the area of the second sub-surface provided with the second structure to the area of the second sub-surface not provided with the second structure ranges between 1.05 and 1.15.

Preferably, the second structure is a recessed structure and/or a raised structure.

Preferably, the second structure is plural. When the second structure is a recessed structure, each of the recessed structures is a recessed cavity, and the shape of the recessed cavity is a hemisphere; When the structure is a protruding structure, each of the protruding structures has a shape of a hemisphere.

Preferably, the radius of the hemisphere is the same as the depth, or the radius of the hemisphere is greater than the depth.

Preferably, when the second structure is a concave structure, the concave structure is a concave groove, and when the second structure is a protruding structure, the protruding structure is a protruding strip.

Preferably, the recessed structure is a plurality of annular grooves, each annular groove being the same as the center of the wafer carrier.

Preferably, the protruding structure is a plurality of annular protruding strips, each annular protruding strip being the same as the center of the wafer carrier.

Preferably, the recessed structure is a plurality of recessed grooves, and the protruding structure is a plurality of protruding strips, each of the protruding strips or each of the recessed grooves extending in a radial direction from a center of the wafer carrier .

Preferably, the protruding strips or the grooves extending in the radial direction are inclined in the same direction.

Preferably, the first structure is plural, and the second structure is disposed inside a part of the first structure.

A wafer carrier for an MOCVD reaction system, the upper surface of the wafer carrier includes a plurality of downwardly recessed mounting regions for mounting wafers to be processed, and an isolation region between the mounting regions So that the mounting regions are isolated from each other, the upper surface of the isolation region includes at least one recessed structure or a protruding structure, the recessed structure or the protruding structure such that the area of the upper surface of the isolation region and the isolation region The ratio of the planar area of the lower projection is between 1.05 and 1.15.

Compared with the prior art, the present invention has the following beneficial effects:

The wafer carrier for an MOCVD reaction system provided by the present invention is provided with a second structure on a second sub-surface on which the first structure for placing the wafer is not disposed, the second structure capable of increasing the second sub-surface area. Compared with the area of the second sub-surface where the second structure is not disposed, the second sub-surface of the wafer carrier provided by the present invention has a larger area, and the increased surface area can increase the reaction between the surface of the wafer carrier and the reaction gas. Rate constant. By adjusting the area of the second sub-surface, the reaction rate constant of the wafer carrier surface and the reaction gas can be made equal to the reaction rate constant of the wafer surface and the reaction gas, so that the reaction rate between the wafer carrier surface and the gas can be equal to the wafer surface. The reaction rate with the gas is such that the amount of gas consumed on the surface of the wafer carrier is equal to the amount of gas consumed on the surface of the wafer, further allowing the concentration of the reactive gas above the surface of the wafer carrier after the reaction to be equal to the concentration of the reactive gas above the surface of the wafer. Therefore, the phenomenon that the gas above the surface of the wafer carrier having a large concentration spreads above the surface of the wafer does not occur, so that the gas concentration above the edge of the wafer near the front end of the gas rotation direction is not greater than that above the other areas of the wafer. Gas concentration. Therefore, the wafer carrier provided by the present invention can ensure that the gas concentration above the edge of the wafer near the front end of the gas rotation direction is equal to the gas concentration above the other regions, thereby ensuring that the reaction rates on the entire surface of the wafer are equal, further Ensure that the thickness of the crystalline material grown on the entire surface of the wafer is the same.

As described in the background section, MOCVD is a crystal generation source material of an organic compound of a group III or a group II element and a hydride of a group V or a group VI element, and is subjected to vapor phase epitaxy and growth on a wafer by thermal decomposition reaction. A variety of III-V, II-VI compound semiconductors and their thin-layer crystalline materials of multiple solid solution.

The growth mechanism of the crystalline material GaN on the wafer will be described below by taking the growth of the gallium nitride GaN crystal material as an example in conjunction with FIGS. 2 to 3. Figure 2 is a schematic diagram of the gas flow and chemical reaction mechanism in the gas phase; Figure 3 is a schematic diagram of the reaction mechanism of GaN growth on the wafer surface. It should be noted that the MOCVD technology can realize the growth of a plurality of crystal materials on the surface of the wafer, and is not limited to the gallium nitride crystal described in the embodiments of the present invention.

As shown in Fig. 2, the gas source trimethylgallium TMG and the gas carrier H2 or N2 are ejected from the shower head, and when the temperature reaches about 100 ° C, TMG starts to thermally decompose to form monomethyl gallium MMG. When the temperature rises to about 500 ° C, TMG begins to decompose at the chemical boundary layer CBL to form monomethyl gallium MMG. At temperatures above 500 ° C, MMG reacts with NH ₃ to form gaseous GaN. Gas GaN diffuses into a region near the surface of the wafer with a diffusion coefficient of .

As shown in Fig. 3, the gas GaN diffuses to the surface reaction interface where a portion of the gas GaN molecules are solidified and deposited on the surface of the wafer.

When the steady state is reached, the flow rate of the gas GaN ejected from the jet head is equal to the flow rate of GaN consumed on the surface of the wafer. Formulated as follows: ; ; ; among them, Is the gas diffusion coefficient; Is the gas phase molecular concentration above the chemical interface layer; For the gas concentration above the wafer surface; Is the heterogeneous reaction rate constant on the wafer surface; GaN (g): vapor phase GaN; GaN (s): solid phase GaN.

It should be noted that the growth rate of the crystal material and the gas phase molecular concentration, as well as In direct proportion.

The MOCVD reaction system includes a wafer carrier on which an upper surface is provided with a recess for placing a wafer. When a crystal material is grown on a wafer using an MOCVD reaction system, the wafer needs to be placed in a recess of the wafer carrier for placing the wafer. Since the groove only occupies a part of the wafer carrier, the upper surface of the wafer carrier in the portion where the groove is not provided is also covered by the reaction gas during the MOCVD technique. For convenience of description, a surface provided with a groove for placing a wafer is defined as a first sub-surface, and other surfaces other than an upper surface of the first sub-surface are defined as a second sub-surface. When the MOCVD technique is performed, the reactive gas is enveloped over the upper surface of the entire wafer carrier. Thus, while the crystal is grown on the surface of the wafer, the crystal also grows on the second subsurface of the wafer carrier. The schematic diagram of its anti-growth mechanism is shown in Figure 4. set up: , The flow of gas from the gas phase region of the reactive gas to the wafer carrier and the wafer, respectively; , The flow of gas consumed by the reaction on the wafer carrier surface and the wafer surface, respectively; Is the gas diffusion coefficient; Is the gas phase molecular concentration above the chemical interface layer; , The gas concentration above the wafer carrier and wafer surface; , The heterogeneous reaction rate constants on the wafer carrier and wafer surface, respectively. Above the second subsurface of the wafer carrier: (1) (2) Above the wafer surface: (3) (4) Under normal circumstances, >> or , then, (5) (6); and because in steady state, the inflowing gas flow rate is equal to the gas flow rate consumed, therefore, (7) Under normal circumstances, < ,and so, > (8).

In the actual MOCVD process, the wafer carrier is rotated, which is equivalent to the flow of gas above the wafer carrier being a rotating gas stream. Thus, the flow of gas to the surface of the wafer can be equivalent to a gas flow in two directions, one being a vertical direct flow of gas from the top, which is ejected by a gas showerhead; the other is flowing from the wafer carrier to the crystal. The horizontal flow of gas at the edge of the circle. Since the gas concentration above the wafer carrier surface is greater than the gas concentration above the wafer surface, the gas concentration at the edge of the wafer near the front end of the gas rotation direction is greater than the gas concentration in other regions of the wafer, and because the growth rate and gas concentration are In a proportional relationship, the growth rate of the edge of the wafer near the front end of the gas rotation direction is greater than the growth rate of other areas of the wafer. This phenomenon can be called "leading edge".

In order to prevent the growth rate of the wafer edge near the front end of the gas rotation direction from being greater than the growth rate of other regions of the wafer, it is necessary to suppress a large concentration of gas above the wafer carrier. This requires the wafer carrier to consume the same amount of gas as the wafer. That is, it is necessary to make the reaction rate of the reaction gas and the wafer carrier equal to the reaction rate of the reaction gas and the wafer. Since the gas concentration above the wafer carrier surface is equal to the gas concentration above the wafer surface before the reaction, so that the reaction rates of the two are equal, the rate constant for reacting the reaction gas with the wafer carrier surface is equal to the reaction gas and The rate constant of the wafer surface reaction.

In order to achieve the above object, the present invention provides a wafer carrier for an MOCVD reaction system. As shown in FIG. 5, the upper surface of the wafer carrier 500 includes a first sub-surface and a second sub-surface, on the first sub-surface, a first structure 501 for placing a wafer, and a second sub-surface disposed on the second sub-surface There is a second structure 502, which can increase the area of the second sub-surface, so that the area of the second sub-surface provided with the second structure 502 in the embodiment of the present invention is larger than the second area in which the second structure 502 is not disposed. The area of the subsurface. Compared with the reaction rate constant of the second sub-surface of the conventional structure and the reaction gas, the reaction rate constant of the second sub-surface provided with the second structure and the reaction gas is increased, and the reaction rate constant can be made equal to the wafer surface and The reaction rate constant of the reaction gas. It should be noted that the second sub-surface of the conventional structure is a flat surface.

It should be noted that the upper surface of the wafer carrier according to the embodiment of the present invention refers to the surface facing the reaction gas in the MOCVD technology. In the embodiment of the present invention, the material of the wafer carrier may be graphite.

As the area of the second sub-surface of the wafer carrier increases, the reaction rate constant of the wafer carrier surface and the reactive gas is increased. By adjusting the area of the second sub-surface, the reaction rate constant of the wafer carrier surface and the reaction gas can be made equal to the reaction rate constant of the wafer surface and the reaction gas, so that the reaction rate between the wafer carrier surface and the gas can be equal to the wafer surface. The reaction rate with the gas is such that the amount of gas consumed on the surface of the wafer carrier is equal to the amount of gas consumed on the surface of the wafer, further allowing the concentration of the reactive gas above the surface of the wafer carrier after the reaction to be equal to the concentration of the reactive gas above the surface of the wafer. Therefore, the phenomenon that the gas above the surface of the wafer carrier having a large concentration spreads above the surface of the wafer does not occur, so that the gas concentration above the edge of the wafer near the front end of the gas rotation direction is not greater than that above the other areas of the wafer. Gas concentration. Therefore, the wafer carrier provided by the present invention can ensure that the gas concentration above the edge of the wafer near the front end of the gas rotation direction is equal to the gas concentration above the other regions, thereby ensuring that the reaction rates on the entire surface of the wafer are equal, further It is ensured that the thickness of the crystal material grown on the entire surface of the wafer is the same.

Furthermore, the area of the second sub-surface is not as large as possible. If the area of the second sub-surface is too large, it may occur that the reaction rate constant of the wafer carrier surface and the reaction gas is larger than the surface of the wafer and the reaction gas. The reaction rate constant, and thus the phenomenon of uneven reaction rate. Therefore, as a preferred embodiment of the present invention, the ratio of the area of the second sub-surface provided with the second structure to the area of the second sub-surface not provided with the second structure is limited to a certain range. It has been experimentally verified that the area ratio is preferably in the range of 1.05 to 1.15. Within this range, the reaction rate constant of the wafer carrier surface and the reaction gas is substantially the same as the reaction rate constant of the wafer surface and the reaction gas, thereby ensuring that the amount of gas consumed by the wafer carrier is substantially the same as the amount of gas consumed on the wafer surface. Can achieve better results.

In addition, in general, the area of the wafer carrier is significantly larger than the area of one wafer. Therefore, as shown in FIG. 5, a plurality of first structures 501 may be disposed on the wafer carrier 500 for placing a plurality of crystals. circle. The first structure 501 is generally a groove structure. In order to increase the area of the second sub-surface, a plurality of second structures 502 may be disposed on the second sub-surface.

As a more specific embodiment of the present invention, the second structure capable of increasing the second sub-surface area 502 of the wafer carrier may be a recessed structure, a protruding structure, or a combination of the two, and thus by a recessed structure and/or Or the raised structure can increase the area of the second sub-surface.

The structure of the wafer carrier can also be understood as follows: the upper surface of the wafer carrier 500 includes a plurality of downwardly recessed mounting regions 501 (corresponding to the first structure) for mounting the wafer to be processed. An isolation area is included between the plurality of mounting areas 501, the isolation areas separating the different mounting areas 501 from each other. The upper surface of the isolation region includes at least one recessed structure or protrusion structure 502 (corresponding to the second structure), the recessed structure or protrusion structure 502 such that the area of the upper surface of the isolation region and the planar area of the isolation region projected downward The ratio is between 1.05 and 1.15.

In the embodiment of the present invention, the second structure 502 can be implemented by using various specific structures and shapes. For details, refer to the following embodiments.

6A is a schematic structural view of a wafer carrier according to Embodiment 1 of the present invention, and FIG. 6B is a schematic structural view of a second structure on a wafer carrier according to Embodiment 1 of the present invention.

As shown in FIG. 6A, the upper surface of the wafer carrier provided in the first embodiment includes a first sub-surface and a second sub-surface, wherein 12 recesses 601 for placing the wafer are disposed on the first sub-surface. A plurality of recessed cavities 602 are disposed on the second sub-surface. The shape of the recessed cavity 602 is a hemisphere, and an enlarged schematic view of the single recessed cavity 602 is shown in FIG. 6B. It should be noted that, in the embodiment of the present invention, the division of the first sub-surface and the second sub-surface is divided according to the structure disposed thereon. In an embodiment of the invention, the wafer carrier may have a diameter of 500 mm. The groove 601 can be provided as a groove for placing a 4 inch wafer.

The hemispherical shaped cavity 602 as shown in FIG. 6B may have a radius and a depth equal to each other, or a radius slightly larger than the depth. As a more specific embodiment of the present invention, the hemispherical shaped recessed cavity 602 may have a radius of 1 mm. Assuming that the radius of the hemisphere is r and the depth is d, the surface area P of the hemisphere can be calculated by: .

According to the wafer carrier of the embodiment of the invention, the reaction rate constant of the surface of the wafer carrier and the reaction gas is equal to the reaction rate constant of the surface of the wafer and the reaction gas. Therefore, the gas concentration above the wafer carrier surface after the reaction is equal to the gas concentration above the wafer surface, thereby suppressing the occurrence of "leading edge" and ensuring equal gas concentration on the entire surface of the wafer, thereby ensuring the entire The crystal growth on the surface of the wafer has the same growth rate, so that crystals grown on the surface of the wafer have a uniform thickness.

In the embodiment of the present invention, the distribution of the plurality of concave cavities on the second sub-surface is distributed in a cubic symmetry axis, and the three concave cavities forming the third symmetry axis distribution are referred to as a second structural unit, and a second structure. The configuration of the unit on the second sub-surface is as shown in Fig. 6C. Wherein, the concave cavity is respectively located at the apex of the equilateral triangle, and if the equivalent side length of the triangle is a, the radius of the concave cavity is r, and the depth is d, the calculation formula of the area of a second structural unit is as follows: (9).

It should be noted that the equivalent side length a of the triangle determines the distance between each recessed cavity on the surface of the wafer carrier.

In the embodiment of the present invention, each parameter of the second structural unit (the equivalent side length a of the triangle, the radius r of the hemisphere and the depth d) is adjusted to obtain a plurality of area ratios, as shown in Table 1. The area ratio ratio shown in Table 1 is an area ratio of the second sub-surface provided with the second structure and the second sub-surface not provided with the second structure, that is, the second sub-surface and the second sub-surface are projected downward. The area ratio of the plane. Table 1

In addition, the Reynolds index of the gas in the recessed cavity 602 may reach 200, so turbulence may be generated in the recessed cavity, thereby further increasing the gas consumption, so that the reaction rate constant of the surface of the wafer carrier and the reaction gas is constant. Increase. The recessed cavity of the first embodiment is a hemisphere. In fact, the recessed cavity according to the embodiment of the present invention may also have other shapes, such as a cylindrical shape, an inverted conical shape, a groove or other irregular concave shape. It is within the scope of the present invention that the shape of the recessed cavity can change the path of the airflow over the surface of the carrier.

The second structure in the wafer carrier provided in the first embodiment is a hemispherical concave cavity. In fact, the second structure may also be a hemispherical protrusion structure. A schematic structural view of the hemispherical projection structure is shown in Fig. 6D. The radius r and the depth d of the hemispherical protrusion structure are the same as the radius r and depth d of the hemispherical recessed cavity. For the sake of brevity, it will not be described in detail here.

The second structure described in the first embodiment is a hemispherical concave cavity or a hemispherical protrusion structure. In fact, as another embodiment of the present invention, the second structure may also be a groove or a protruding strip. See the second embodiment for details. When the second structure is a groove or a protruding strip, the number, depth, and width of the groove or the protruding strip determine the area of the second sub-surface. Embodiment 2

As shown in FIG. 7A, on the first sub-surface of the upper surface of the wafer carrier 700, there are disposed 12 first structures 701 for placing wafers, and the first structures 701 may be grooves. A plurality of annular grooves or protruding strips 702 are disposed on the second sub-surface. In the embodiment of the invention, each annular groove or protruding strip 702 coincides with the center of the wafer carrier 700. That is, the wafer carrier 700 is concentric with the environmental grooves or protruding strips 702.

The groove or protruding strip 702 of the second embodiment is annular. In fact, the groove or protruding strip 702 may extend from the center of the wafer carrier to the periphery of the wafer carrier in a radial direction. As shown in Figure 7B.

In order to facilitate the flow of the gas during the rotation of the wafer carrier, the grooves or protruding strips 702 described above may also be inclined in the same direction as the impeller of the windmill.

The wafer carrier of the first embodiment and the second embodiment is provided with the second structure only on the second sub-surface. When the wafer carrier of the structure is applied to the MOCVD system, if the wafer is placed on the first structure for placing the wafer, the reaction rate constant of the surface of the wafer carrier and the gas can be ensured to be equal to the surface of the wafer and the gas. The reaction rate constant, in turn, ensures the uniformity of the thickness of the crystalline material grown on the surface of the wafer. However, if the wafer is placed only on part of the first structure, leaving part of the first structure idle, at this time, the idle first structure corresponds to the surface of the wafer carrier, and the reaction of these idle first structural surfaces with the gas The rate constant is smaller than the reaction rate constant of the wafer surface and the gas. At this time, there is a possibility that the thickness of the crystal material on the wafer surface is not uniform. In order to avoid the occurrence of such a situation, the present invention also provides the third embodiment. Embodiment 3

As shown in FIG. 8, a plurality of first structures 801 for placing wafers and a plurality of second structures 802 are disposed on the second sub-surfaces on the first sub-surface of the upper surface of the wafer carrier 800. And a second structure 802' is also disposed inside the portion of the first structure 801. Thus, when the wafer is placed on the portion of the first structure 801, the wafer is placed on the first structure 801 where the second structure is not disposed, and the first structure 801 provided with the second structure 802' is left idle. The second structure is also disposed on the surface of the first structure, so that the reaction rate constant of the surface of the idle first structure and the gas is equal to the reaction rate constant of the surface of the wafer and the gas, thereby ensuring that the first structural portion is placed The uniformity of the thickness of the crystalline material grown on the wafer surface is also ensured during the wafer.

It should be noted that, in the embodiment of the present invention, the second structure 802 may be any one of the first embodiment or the second embodiment. The form of the second structure is not limited in this embodiment.

The above description is only a preferred embodiment of the present invention, and it should be noted that those skilled in the art can make several improvements and refinements without departing from the principles of the present invention. It is considered as the scope of protection of the present invention.

500, 600, 700, 800‧‧‧ wafer carrier
501, 701, 801‧‧‧ first structure
502, 802, 802'‧‧‧ second structure
601‧‧‧ Groove
602‧‧‧ recessed cavity
702‧‧‧ Grooves or protruding strips

Figure 1 is a schematic illustration of the reason why the growth rate of the crystalline material on the surface of the wafer is not uniform.

2 to 3 are schematic views of a GaN reaction mechanism for a crystalline material.

Figure 4 is a schematic diagram showing the growth mechanism of crystalline material GaN on a wafer.

Fig. 5 is a schematic structural view of a wafer carrier according to an embodiment of the present invention.

FIG. 6A is a schematic structural view of a wafer carrier according to Embodiment 1 of the present invention.

FIG. 6B is a schematic structural view of a second structure according to Embodiment 1 of the present invention.

FIG. 6C is a schematic structural diagram of a configuration of a second structure provided on a wafer carrier according to Embodiment 1 of the present invention.

FIG. 6D is a schematic structural view of another second structure according to Embodiment 1 of the present invention.

FIG. 7A is a schematic structural view of a wafer carrier according to Embodiment 2 of the present invention.

FIG. 7B is a schematic structural view of another wafer carrier according to Embodiment 2 of the present invention.

FIG. 8 is a schematic structural view of a wafer carrier according to Embodiment 3 of the present invention.

500‧‧‧ wafer carrier

501‧‧‧ first structure

502‧‧‧Second structure

Claims (12)

A wafer carrier for an MOCVD reaction system, comprising: an upper surface of the wafer carrier comprising a first sub-surface and a second sub-surface, wherein a first surface for placing a wafer is disposed on the first sub-surface a structure having a second structure disposed on the second sub-surface, the second structure capable of increasing an area of the second sub-surface such that a reaction rate constant of the reaction gas and the second sub-surface of the wafer carrier is equal to a reactive gas The reaction rate constant with the wafer surface. The wafer carrier according to claim 1, wherein a ratio of an area of the second sub-surface provided with the second structure to an area of the second sub-surface not provided with the second structure is in the range of 1.05 to 1.15. between. The wafer carrier of claim 1 or 2, wherein the second structure is a recessed structure, a raised structure, or a combination thereof. The wafer carrier of claim 3, wherein the second structure is plural, and when the second structure is a recessed structure, each of the recessed structures is a recessed cavity, and the shape of the recessed cavity is Hemisphere; when the second structure is a protruding structure, each of the protruding structures is in the shape of a hemisphere. The wafer carrier of claim 4, wherein the hemisphere has the same radius or depth, or the hemisphere has a radius greater than the depth. The wafer carrier of claim 3, wherein when the second structure is a recessed structure, the recessed structure is a groove, and when the second structure is a protruding structure, the protruding structure is a protruding strip. The wafer carrier of claim 6, wherein the recessed structure is a plurality of annular grooves, each of the annular grooves being the same as a center of the wafer carrier. The wafer carrier of claim 6, wherein the protruding structure is a plurality of annular protruding strips, each of the annular protruding strips being the same as a center of the wafer carrier. The wafer carrier of claim 6, wherein the recessed structure is a plurality of the grooves, the protruding structure is a plurality of the protruding strips, and each of the protruding strips or each of the grooves is carried from the wafer The center of the disk extends in the radial direction. The wafer carrier of claim 9, wherein the protruding strip or the groove extending in a radial direction is inclined in the same direction. The wafer carrier of claim 1 or 2, wherein the first structure is plural, and the second structure is disposed inside a portion of the first structure. A wafer carrier for an MOCVD reaction system, wherein an upper surface of the wafer carrier includes a plurality of mounting regions that are recessed downwardly, the plurality of mounting regions for mounting a wafer to be processed, between the plurality of mounting regions An isolation region is included to isolate the plurality of mounting regions from each other, the upper surface of the isolation region including at least one recessed structure or protrusion structure, the recessed structure or the protrusion structure causing an area of an upper surface of the isolation region and the isolation region The ratio of the planar area of the lower projection is between 1.05 and 1.15.