TWM644163U - Semiconductor epitaxy substrate and chemical vapor deposition device - Google Patents

Abstract

The invention provides a semiconductor epitaxy substrate and a chemical vapor deposition device. The substrate includes a central area and an edge area, the edge area includes a transition area disposed on one side close to the central area, the transition area surrounds the edge of the central area, and the transition area is an arc surface or a slope. For the substrate provided by the present invention, a thin film with a polycrystalline structure with poor crystal quality and disordered crystal orientation can be obtained by epitaxy in the edge region, and a thin film with a single crystal structure cannot be formed. The inside of the film with the polycrystalline structure can absorb stress, so that the cracks are concentrated in the edge area without extending to the central area, thereby improving the finished product yield and the usable area of the epitaxial wafer.

Description

Substrate and Chemical Vapor Deposition Device for Semiconductor Epitaxy

The invention relates to the technical field of semiconductor processing, in particular to a semiconductor epitaxy (Epitaxy) substrate and a chemical vapor deposition device.

Group III nitride materials have superior physical properties and are often used to make light-emitting diodes (LEDs), electronic devices (such as: HEMTs), etc. The epitaxy of devices mostly uses chemical vapor deposition processes, such as MOCVD processes. The MOCVD process is usually carried out in a reaction chamber through thermal processing. The gas containing multiple reaction sources is introduced into the reaction chamber through the gas inlet device, and a chemical reaction occurs on the heated substrate to form a thin film. These substrates can be the same material as the epitaxial film, or a material with a crystal structure similar to the epitaxial film. The crystal structure of the substrate, the facet index of the substrate surface, and the surface temperature when the reaction occurs will all affect the quality of the epitaxial film.

Due to the high price of homogeneous substrates, heterogeneous substrates are mainly used for epitaxy at present. Common substrates include sapphire, silicon, and silicon carbide. However, due to the large lattice mismatch and thermal mismatch between the heterogeneous substrate and the formed film, there will be a large stress inside the film. When the film thickness reaches a certain critical thickness, cracks will appear at the edge of the film. As the thickness of the film increases, the cracks at the edge will spread to the center, thereby affecting the available area of the epitaxial wafer.

The purpose of this model is to provide a semiconductor epitaxial substrate and a chemical vapor deposition device to solve the problem in the prior art that cracks are easy to occur when growing a thin film on a heterogeneous substrate, which affects the available area of the epitaxial wafer.

In order to achieve the above purpose, the present invention is realized through the following technical solutions:

A substrate for semiconductor epitaxy, the substrate includes a central area and an edge area surrounding the central area, the edge area includes a transition area disposed close to the central area, and the transition area surrounds the central area The edge is connected to the central area, the transition area is an arc and/or an inclined plane, the edge area is ring-shaped, and the width of the ring is 0.5mm-4mm.

Optionally, the thickness of each position of the central region is equal.

Optionally, the edge region is made by cutting, grinding or etching.

Optionally, the crystal plane index of the upper surface of the edge region is different from the crystal plane index of the upper surface of the central region.

Optionally, along a direction away from the central region, the thickness of the edge region decreases gradually.

Optionally, along a direction away from the central region, the thickness of the edge region first decreases and then increases.

Optionally, the curvature radii of the arc surfaces are the same or the curvature radii gradually change.

Optionally, the included angle between the slope and the diameter direction of the substrate is less than arctan (T/L), and the included angle is greater than 4 degrees, where T represents the thickness of the central region of the substrate, and L represents the edge The width of the region.

Optionally, the edge region is formed by arc-shaped grooves.

Optionally, the edge area is formed by V-shaped grooves.

Optionally, the edge region is connected to the central region through a first upwardly arched arc, and the edge region is connected to the side wall of the substrate through a second upwardly arched arc.

A chemical vapor deposition device, the chemical vapor deposition device includes a substrate tray, a heater is arranged below the substrate tray, and a reaction gas inlet device is provided above the substrate tray to feed a variety of reaction gases downward. The semiconductor epitaxial substrate is arranged on the substrate tray, and the reaction gas forms a thin film on the surface of the substrate, wherein the thin film grown in the central region of the substrate has a single crystal structure, and the thin film grown in the edge region of the substrate It is a polycrystalline structure or a crystal structure that does not have exactly the same crystal orientation as the thin film grown in the central region.

Optionally, the thin film formed on the surface of the substrate is selected from at least one of AlN, GaN, Ga2O3, AlGaN or SiC.

Compared with the prior art, the present invention has the following advantages:

In the semiconductor epitaxial substrate provided by the present invention, a transition area is provided near the central area in the edge area, the transition area is arranged around the edge of the central area, and is connected to the central area, and the transition area is a An arc surface or an inclined surface causes the temperature of the upper surface of the edge region to be different from the temperature of the upper surface of the central region, and the surface temperature of at least part of the edge region deviates from a specific temperature window for optimum growth; meanwhile, due to the edge region The crystal plane index of the upper surface is different from the crystal plane index of the upper surface of the central region, and unfavorable factors such as the shielding of the reaction source in the edge region by the substrate tray make the distribution of the reaction gas uneven in the edge region, so the epitaxy obtained in the edge region It is a thin film with a polycrystalline structure with poor crystal quality and disordered crystal orientation, and cannot form a thin film with a single crystal structure. The inside of the polycrystalline film can absorb stress, so that the cracks are concentrated in the edge area instead of extending to the central area, thereby improving the finished product yield and the usable area of the epitaxial wafer.

The scheme proposed by the present invention will be further described in detail below in conjunction with the drawings and specific embodiments. According to the description below, the advantages and features of the present invention will be more clear. It should be noted that the diagrams are in a very simplified form and all use imprecise scales, which are only used to facilitate and clearly illustrate the purpose of the implementation of the present invention. In order to make the purpose, features and advantages of the present invention more obvious and understandable, please refer to the drawings. It should be noted that the structures, proportions, sizes, etc. shown in the diagrams in this manual are only used to match the content disclosed in the manual, for those who are familiar with this technology to understand and read, and are not used to limit the implementation of the new model. Conditions, so it has no technical substantive meaning, any modification of structure, change of proportional relationship or adjustment of size shall still fall within the scope of the present invention without affecting the effect and purpose of the present invention. within the scope covered by the disclosed technical content.

The chemical vapor deposition process is widely used in the manufacture of semiconductor devices such as LED wafers and power devices. The structural diagram of the chemical vapor deposition apparatus is shown in FIG. 1 , which includes a reaction chamber 100 , and the bottom of the chamber includes a substrate tray 110 on which one or more substrates 10 to be processed are placed. The bottom of the substrate tray 110 is driven to rotate by a driving device such as a rotating shaft 112 , and a heater 114 is arranged under the substrate tray 110 to heat the substrate tray 110 to a required temperature (for example, 600 to 1400 degrees). The heater 114 and the rotating shaft 112 are surrounded by a heat insulating sleeve 113 to reduce heat radiation to the surroundings and prevent reaction gas from entering the substrate tray 110 . The top of the reaction chamber 100 includes a top cover 200, and the top cover 200 includes a reaction gas inlet device for supplying various reaction gases downward. The reaction gas inlet device includes a plurality of gas diffusion chambers 201, 202 gas-isolated from each other, and different reaction gases, such as metal Organic gas (TMAl) and nitrogen-containing gas (NH 3 ), etc. finally form desired compounds on the substrate 10 , such as aluminum nitride AlN. The reaction gas inlet device further includes a cooling liquid pipeline 205 connected to a cooling liquid source to cool the reaction gas inlet device.

At present, the substrate used for epitaxy is usually a single crystal substrate, and the materials include but are not limited to sapphire, silicon, silicon carbide, gallium nitride, aluminum nitride, etc. Under certain growth window conditions, there is a strict correspondence between the group III nitrides obtained by epitaxy and the crystal plane index of the substrate surface. , the AlN epitaxially obtained on a silicon substrate with a plane index (111) is a (001) plane. However, due to the large lattice mismatch and thermal mismatch between the heterogeneous substrate and the epitaxial material, there will be a large stress inside the material obtained by epitaxial growth, and the prepared epitaxial wafer will first have cracks at the edge. The increase of the crack extends towards the center.

In view of this, in order to prevent the cracks at the edge from extending to the center, the present invention provides a semiconductor epitaxial substrate, as shown in Figure 2, the substrate 10 includes a central region 11 and an edge region 12, and the edge region 12 includes a A transition area 121 is disposed on one side of the central area 11 , the transition area 121 is disposed around the edge of the central area 11 and connected to the central area 11 . The transition region 121 is an arc or an inclined surface, thus, the surface temperature of at least part of the edge region 12 will deviate from the reaction temperature window, and at the same time, due to the crystal plane index of the upper surface of the edge region 12 and the The crystal plane index on the upper surface of the central region 11 is different, and unfavorable factors such as the shielding of the reaction source in the edge region 12 by the substrate tray 110 make the distribution of the reaction gas uneven in the edge region 12, so the crystal quality obtained by epitaxy in the edge region 12 is poor, A thin film with a polycrystalline structure with disordered crystal orientation, but a thin film with a single crystal structure cannot be formed. The interior of the polycrystalline film can absorb stress, so that the cracks are concentrated in the edge region 12 instead of extending to the central region 11 .

Optionally, the width L2 of the transition region 121 is greater than 0.2 mm, and less than or equal to the width of the edge region 12 .

Optionally, other positions of the edge region 12 except the transition region 121 are an arc and/or a slope.

The edge area 12 is arranged concentrically with the central area 11 and is ring-shaped with a width L1 of 0.5mm-4mm. Existing substrates are generally circular flakes with a diameter of 2 to 8 inches, and the cracks are concentrated in this ring-shaped edge region 12 with a width of several millimeters, and the edge region 12 is discarded after the epitaxial wafer is made later, so as not to damage the entire epitaxial wafer. The usable area has a great impact, but it can greatly reduce the occurrence probability of cracks in the central region 11 , improve the finished product yield of the epitaxial wafer, and thus increase the usable area of the epitaxial wafer. Optionally, the edge region 12 can be made by cutting, grinding, etching and other processes.

FIG. 3 shows a structure diagram of a semiconductor epitaxy substrate according to the first embodiment of the present invention. This embodiment is a cross-sectional view of the substrate shown in FIG. 2 along the direction A-A'. As shown in FIG. 3 , along the direction away from the central region 11, the thickness of the edge region 12 gradually decreases. Optionally, the thickness of each position of the central region 11 is equal. Specifically, in the substrate structure shown in FIG. 3 , the edge region 12 is an arc surface, and the radius of curvature of the transition region 121 is the same as that of other positions of the edge region 12 . In other embodiments, the radius of curvature of the transition region 121 may also be different from the radius of curvature of other positions of the edge region 12 . In some other embodiments, the radius of curvature of the transition region 121 and the radius of curvature of other positions of the edge region 12 may also be gradual. The crystal plane index of the upper surface of the central region 11 is the same everywhere, and the crystal plane index of the upper surface of the edge region 12 is different from the crystal plane index of the upper surface of the central region 11 . Optionally, along the direction away from the central region 11 , the crystal plane indices of the upper surface of the edge region 12 are also different.

When the substrate shown in Figure 3 is used in a chemical vapor deposition process, the epitaxial wafer prepared under a specific process window condition is shown in Figure 4, and the central region 11 is epitaxially obtained as a continuous and dense single crystal film 21, and in the edge region 12, from the center to the outside, a polycrystalline thin film 22 with poor crystal quality and disordered crystal orientation is obtained, and the crystal quality is worse as it gets closer to the edge. The polycrystalline region at the edge can effectively prevent cracks from extending to the central region 11, thereby increasing the available area of the epitaxial wafer.

FIG. 5 shows a structure diagram of a semiconductor epitaxy substrate according to a second embodiment of the present invention. This embodiment is a cross-sectional view of the substrate shown in FIG. 2 along the direction A-A'. The difference from the substrate of the first embodiment above is that the edge region 12 is a slope. Due to the limitation of the thickness T of the substrate 10 , the inclination angle θ of the slope can be any angle less than arctan (T/L1 ) degrees and greater than 4 degrees. The inclination angle of the transition region 121 is the same as the inclination angles of other positions of the edge region 12 . In other embodiments, the inclination angle of the transition region 121 may also be different from the inclination angles of other positions of the edge region 12 . This kind of substrate structure can also obtain a different surface crystal plane index and surface temperature in the edge region 12 and the center region 11, so that a single crystal thin film can be obtained by epitaxy in the center region 11, and a single crystal thin film can be obtained by epitaxy in the edge region 12. The polycrystalline film concentrates the cracks in the edge region 12 and increases the available area of the epitaxial wafer.

Fig. 6 shows a structure diagram of a semiconductor epitaxial substrate according to a third embodiment of the present invention, which is a cross-sectional view of the substrate shown in Fig. 2 along the direction A-A'. The difference from the substrates of the above two embodiments is that the edge region 12 is formed by an arc-shaped groove, the arc of the arc-shaped groove is greater than or equal to 90°, so that in the direction away from the central region 11 , the thickness of the edge region 12 gradually decreases, and the crystal plane index of the upper surface of the edge region 12 is different from the crystal plane index of the upper surface of the central region 11 . The radius of curvature of the transition region 121 is the same as that of other positions of the edge region 12 . In other embodiments, the radius of curvature of the transition region 121 may also be different from the radius of curvature of other positions of the edge region 12 . In some other embodiments, the radius of curvature of the transition region 121 and the radius of curvature of other positions of the edge region 12 may also be gradually changed.

In other embodiments, along the direction away from the central region 11 , the thickness of the edge region 12 may first decrease and then increase. Thus, a single crystal thin film can also be epitaxially obtained in the central region 11 , and a polycrystalline thin film can be obtained by epitaxy in the edge region 12 , so that cracks can be concentrated in the edge region 12 and the available area of the epitaxial wafer can be increased. Fig. 7 shows the substrate structure diagram of the semiconductor epitaxy of the fourth embodiment of the present invention, this embodiment is the sectional view of the substrate shown in Fig. 2 along the AA' direction, wherein, the edge region 12 adopts arc-shaped concave Grooves are formed, and the radius of curvature of the transition region 121 is different from the radius of curvature of other positions of the edge region 12 . Fig. 8 shows the structure diagram of the semiconductor epitaxy substrate of the fifth embodiment of the present invention, which is a cross-sectional view of the substrate shown in Fig. 2 along the AA' direction, wherein the edge region 12 adopts a V-shaped concave Grooves are formed, and the inclination angle of the transition region 121 is different from the inclination angle of other positions of the edge region 12 .

Optionally, in the above-mentioned second, third, fourth, and fifth embodiments, the edge area 12 and the central area 11 can also be connected by an upwardly arched arc surface, and the edge area 12 and the The sidewalls of the substrate 10 are connected by an upwardly arched arc surface, so that the edge region 12 and the central region 11 and the sidewall of the substrate 10 make a smooth transition.

It should be noted that the structure of the edge region is not limited to the structures shown in the above five embodiments, any transition region is an arc or an inclined surface, so that the edge region can grow out of the same shape as the central region. Substrate structures of thin films with different appearances or crystal orientations shall be included in this application.

To sum up, this new model utilizes the selective characteristics of the chemical vapor deposition process for the crystal plane of the substrate and the temperature of the substrate, and through simple processing of the edge area of the substrate, the crystal plane index of the upper surface of the edge area is the same as that of the central area. Different, the industry problem of suppressing cracking of epitaxial wafers can be realized, and the implementation scheme is simple and easy to operate.

It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is a relationship between these entities or operations. There is no such actual relationship or order between them. Furthermore, the terms "comprises", "comprises" or any other variation thereof are intended to cover a non-exclusive inclusion such that a process, method, article, or apparatus comprising a set of elements includes not only those elements, but also includes elements not expressly listed. other elements of or also include elements inherent in such a process, method, article, or device. Without further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article or apparatus comprising said element.

Although the content of the present invention has been described in detail through the above preferred embodiments, it should be recognized that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions of the present invention will be apparent to those skilled in the art after reading the above contents. Therefore, the protection scope of the present invention should be defined by the appended patent application scope.

100: reaction chamber 200: top cover 110: substrate tray 10: Substrate 112: rotating shaft 113: heat insulation sleeve 114: heater 201, 202: gas diffusion chamber 211, 212: gas pipeline 205: Coolant pipe 11: Central area 12: Edge area 121: Transition area 21: Single crystal thin film 22: Polycrystalline film L1: Margin area width L2: Transition area width A-A': hatching

In order to illustrate the technical solution of the present invention more clearly, the drawings that need to be used in the description will be briefly introduced below. Obviously, the drawings in the following description are an embodiment of the present invention. For those of ordinary skill in the art In other words, on the premise of not paying progressive labor, other schemas can be obtained according to these schemas: Fig. 1 is the structural diagram of chemical vapor deposition device; Fig. 2 is the top view of a kind of semiconductor epitaxy substrate provided by the present invention; Fig. 3 is the A-A' sectional view of the substrate shown in Fig. 2 provided by the first embodiment of the present invention; Fig. 4 is the structural diagram of the epitaxial wafer made by the substrate shown in Fig. 3; Fig. 5 is the A-A' sectional view of the substrate shown in Fig. 2 provided by the second embodiment of the present invention; Fig. 6 is the A-A' sectional view of the substrate shown in Fig. 2 provided by the third embodiment of the present invention; Fig. 7 is the A-A' sectional view of the substrate shown in Fig. 2 provided by the fourth embodiment of the present invention; Fig. 8 is an A-A' sectional view of the substrate shown in Fig. 2 provided by the fifth embodiment of the present invention.

11: Central area

12: Edge area

21: Single crystal thin film

22: Polycrystalline film

Claims (13)

A substrate for semiconductor epitaxy, comprising: a central area; and an edge area surrounding the central area, the edge area including a transition area disposed adjacent to the central area, the transition area surrounding the edge of the central area and connected to the central area, the The transition area is an arc and/or an inclined surface, the edge area is ring-shaped, and the width of the ring is 0.5mm-4mm. The substrate for semiconductor epitaxy as claimed in claim 1, wherein the thicknesses of all positions of the central region are equal. The substrate for semiconductor epitaxy according to claim 1, wherein the edge region is produced by cutting, grinding or etching. The semiconductor epitaxial substrate according to claim 1, wherein the crystal plane index of the upper surface of the edge region is different from the crystal plane index of the upper surface of the central region. The semiconductor epitaxial substrate as claimed in claim 1, wherein, along the direction away from the central region, the thickness of the edge region gradually decreases. The semiconductor epitaxial substrate according to claim 1, wherein, along the direction away from the central region, the thickness of the edge region first decreases and then increases. The substrate for semiconductor epitaxy according to claim 1, wherein the curvature radius of the arc surface is the same or the curvature radius gradually changes. The substrate for semiconductor epitaxy according to claim 1, wherein the angle between the slope and the diameter of the substrate is smaller than arctan (T/L), and the angle is greater than 4 degrees, where T represents the angle of the substrate The thickness of the central region, L represents the width of the edge region. The semiconductor epitaxial substrate as claimed in claim 6, wherein the edge region is formed by arc-shaped grooves. The semiconductor epitaxial substrate as claimed in claim 6, wherein the edge region is formed by a V-shaped groove. The substrate for semiconductor epitaxy as claimed in claim 1, wherein the edge region is connected to the central region through an upwardly arched first arc surface, and the edge region is connected to the side wall of the substrate through an upwardly arched surface from the second arc surface connection. A chemical vapor deposition device, the chemical vapor deposition device includes: a substrate tray, a heater is arranged below the substrate tray, and a reaction gas inlet device is provided above the substrate tray to feed a variety of reaction gases downward, The semiconductor epitaxial substrate as described in any one of claims 1-11 is set on the substrate tray, and the reaction gas forms a thin film on the surface of the substrate, wherein the thin film grown in the central region of the substrate is a single crystal structure, the thin film grown on the edge region of the substrate has a polycrystalline structure or a crystal structure that has a different crystal orientation than the thin film grown on the central region. The chemical vapor deposition device according to claim 12, wherein the thin film formed on the surface of the substrate is selected from at least one of AlN, GaN, Ga2O3, AlGaN or SiC.