Method for controlling wafer bow and substrate tray

Abstract

The application is suitable for the field of semiconductor technology, and provides a control method for wafer warpage and a substrate tray. The method comprises the following steps: placing a substrate with non-zero warpage on a substrate tray containing an air cavity; performing epitaxial layer growth on an epitaxial growth surface of the substrate by using an epitaxial process; and performing cooling treatment on the substrate and the epitaxial layer to obtain an epitaxial wafer with small warpage, wherein the air cavity of the substrate tray is shaped such that the temperature difference between the edge and the middle of the substrate tray is kept within a preset range. The application can reduce the warpage of the generated epitaxial wafer, improve the uniformity of the epitaxial wafer, and further improve the uniformity and yield of the semiconductor device prepared by using the epitaxial wafer.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor technology, in particular to a control method of wafer bow and a substrate tray. BACKGROUND

[0002] In the field of semiconductor, as an important primary product, wafer is used to manufacture various types of semiconductor devices. In the epitaxial growth process of semiconductor substrate, when there is a difference between the thermal expansion coefficients of the substrate and the epitaxial layer, the shrinkage of the epitaxial layer and the substrate is different after the high-temperature growth process is completed, resulting in that the obtained wafer is convex or concave, and the wafer bow is large.

[0003] At present, the method for controlling wafer bow is usually optimization and improvement from the epitaxial process. However, due to the difference between the thermal expansion coefficients of the substrate and the epitaxial layer, the improvement effect of the epitaxial process is limited, that is, the existing wafer growth method still has the problems of large wafer bow and low uniformity, which further leads to poor uniformity and low yield of semiconductor devices prepared by using the above wafer. SUMMARY

[0004] Therefore, the embodiments of the present application provide a control method of wafer bow and a substrate tray to solve the technical problems of large wafer bow and low uniformity of the wafer generated by the existing wafer growth method, which further leads to poor uniformity and low yield of semiconductor devices prepared by using the above wafer.

[0005] In a first aspect, the embodiments of the present application provide a control method of wafer bow, comprising:

[0006] placing a substrate with a non-zero wafer bow on a substrate tray containing an air cavity inside;

[0007] adopting an epitaxial process to grow an epitaxial layer on an epitaxial growth surface of the substrate, and performing a cooling treatment on the substrate and the epitaxial layer to obtain a wafer with a small wafer bow.

[0008] In a possible implementation of the first aspect, before the substrate with a non-zero wafer bow is placed on the substrate tray containing an air cavity inside, the method further comprises:

[0009] obtaining a first thermal expansion coefficient of the substrate and a second thermal expansion coefficient of the epitaxial layer to be grown;

[0010] if the first thermal expansion coefficient is less than the second thermal expansion coefficient, a first substrate tray is selected as the substrate tray, and a substrate with a positive wafer bow is selected as the substrate; wherein the shape of the air cavity in the first substrate tray is such that the temperature difference between the edge and the middle of the first substrate tray is maintained within a preset range.

[0011] If the first thermal expansion coefficient is greater than the second thermal expansion coefficient, a second substrate tray is selected as the substrate tray, and a substrate with a negative warpage value is selected as the substrate; wherein the shape of the air cavity in the second substrate tray keeps the temperature difference between the edge and the middle of the second substrate tray within a preset range.

[0012] In a possible implementation of the first aspect, for the first substrate tray, the first thickness of the air cavity is greater than the second thickness of the air cavity;

[0013] For the second substrate tray, the first thickness of the air cavity is less than the second thickness of the air cavity;

[0014] wherein the first thickness is the thickness of the air cavity at the edge of the substrate tray, the second thickness is the thickness of the air cavity at the middle of the substrate tray, and the first thickness and the second thickness are the distances between the upper and lower edges of the air cavity in the thickness direction of the substrate tray.

[0015] In a possible implementation of the first aspect, the thickness of the air cavity decreases linearly or non-linearly from the edge to the middle of the first substrate tray;

[0016] The thickness of the air cavity increases linearly or non-linearly from the edge to the middle of the second substrate tray.

[0017] In a possible implementation of the first aspect, the air cavity of the substrate tray is a vacuum or filled with gas;

[0018] For the case that the air cavity is filled with gas, the gas includes at least one of the following: hydrogen, nitrogen, oxygen, vacuum, argon, helium, nitric oxide, nitrogen dioxide.

[0019] In a possible implementation of the first aspect, the range of the positive warpage value is greater than 0 and less than or equal to 100 microns, and the range of the negative warpage value is greater than or equal to -100 microns and less than 0.

[0020] In a possible implementation of the first aspect, the epitaxial layer growth on the epitaxial growth surface of the substrate includes:

[0021] For the substrate with a positive warpage value, the epitaxial layer growth is performed on the convex surface of the substrate;

[0022] For the substrate with a negative warpage value, the epitaxial layer growth is performed on the concave surface of the substrate.

[0023] In a second aspect, the embodiments of the present application provide a substrate tray for placing a substrate with a non-zero warpage to grow an epitaxial layer on an epitaxial growth surface of the substrate; the substrate tray is internally provided with an air cavity for keeping a temperature difference between an edge and a middle part of the substrate tray within a preset range.

[0024] In a possible implementation of the second aspect, the first thickness of the air cavity is greater than the second thickness of the air cavity, or the first thickness of the air cavity is less than the second thickness of the air cavity, the first thickness being a thickness of the air cavity at the edge of the substrate tray, and the second thickness being a thickness of the air cavity at the middle part of the substrate tray, the first thickness and the second thickness being distances between upper and lower edges of the air cavity in a thickness direction of the substrate tray.

[0025] In a possible implementation of the second aspect, the thickness of the air cavity linearly or nonlinearly decreases from the edge to the middle part of the substrate tray, or the thickness of the air cavity linearly or nonlinearly increases from the edge to the middle part of the substrate tray.

[0026] In a third aspect, the embodiments of the present application provide an epitaxial wafer generated by the method for controlling warpage of an epitaxial wafer in any one of the first aspect.

[0027] The method for controlling warpage of an epitaxial wafer and the substrate tray provided by the embodiments of the present application can obtain an epitaxial wafer with small warpage and high uniformity by placing a substrate with a non-zero warpage on a substrate tray internally provided with an air cavity, growing an epitaxial layer on an epitaxial growth surface of the substrate by an epitaxial process, and performing a cooling process on the substrate and the epitaxial layer, thereby improving the uniformity and yield of a semiconductor device prepared by using the epitaxial wafer.

[0028] It should be understood that the general description above and the detailed description below are only exemplary and explanatory, and cannot limit the present specification. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative labor.

[0030] Figure 1 is a comparative diagram of growth changes of an epitaxial wafer not processed by the method of the present application;

[0031] Figure 2 is a flowchart of the method for controlling warpage of an epitaxial wafer provided by an embodiment of the present application.

[0032] Figure 3 is a flowchart of a control method of wafer warpage provided by an embodiment of the present application;

[0033] Figure 4 is a comparison chart of growth changes of a wafer provided by an embodiment of the present application;

[0034] Figure 5 is a comparison chart of growth changes of a wafer provided by an embodiment of the present application;

[0035] Figure 6 is a structural diagram of a substrate tray provided by an embodiment of the present application. DETAILED DESCRIPTION

[0036] The present application will be described in more detail with reference to specific embodiments. The following embodiments will help to further understand the role of the present application, but do not limit the present application in any form. It should be noted that for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made. These all belong to the protection scope of the present application.

[0037] It should be understood that when used in the specification and appended claims of the present application, the term "comprising" indicates the presence of the described features, whole, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, whole, steps, operations, elements, components and / or sets thereof.

[0038] It should also be understood that the term "and / or" used in the specification and appended claims of the present application means any combination of one or more of the associated listed items and all possible combinations, and includes these combinations.

[0039] In the description of the present application and the appended claims, the terms "first", "second", "third" and the like are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0040] In the present application, the reference "one embodiment" or "some embodiments" and the like means that the specific features, structures or characteristics described in connection with the embodiment are included in one or more embodiments of the present application. Therefore, the statements "in one embodiment", "in some embodiments", "in other some embodiments", "in additional some embodiments" and the like appearing in the specification are not necessarily all referring to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized. The terms "include", "contain", "have" and their variants mean "include but not limited to", unless otherwise specifically emphasized.

[0041] In addition, the "multiple" mentioned in the embodiments of the present application should be interpreted as two or more than two.

[0042] In the semiconductor field, epitaxial wafer as an important primary product is used to manufacture various types of semiconductor devices, such as heterojunction field effect transistor (HFET) and light-emitting diode (LED) devices. In the epitaxial growth process of semiconductor substrate, when there is a difference in the thermal expansion coefficient between the substrate and the epitaxial layer, after the high-temperature growth process is over, the shrinkage of the epitaxial layer and the substrate is different, resulting in a convex or concave epitaxial wafer with a large warpage, which brings difficulties to the subsequent preparation of semiconductor devices.

[0043] Exemplary, Figure 1 is a comparison chart of the growth change of an epitaxial wafer not processed by the method of the present application. As Figure 1 shown, in the preparation of GaN-based heterojunction field effect transistor devices, GaN epitaxial layer is epitaxially grown on SiC substrate. Since the thermal expansion coefficient (3.78×10 -6 K -1 ) of SiC substrate is less than the thermal expansion coefficient (5.59×10 -6 K -1 ) of GaN epitaxial layer, after the high-temperature growth process of epitaxial growth is over, the shrinkage of GaN epitaxial layer is greater than that of SiC substrate, resulting in a concave GaN epitaxial wafer with a large warpage.

[0044] Currently, the method for controlling the warpage of epitaxial wafer is usually optimization and improvement from epitaxial process. However, due to the difference in the thermal expansion coefficient between the substrate and the epitaxial layer, the improvement effect of epitaxial process is limited, that is, the existing epitaxial wafer growth method still has the problems of large warpage and low uniformity of the generated epitaxial wafer, which further leads to poor uniformity and low yield of the semiconductor devices prepared using the above epitaxial wafer.

[0045] Based on the above problems, the inventors have found that, in the epitaxial growth process of semiconductor substrate, the temperature difference between the edge and the middle of the substrate tray containing special-shaped air cavity inside is small, which can produce a uniform heating temperature field, so that the epitaxial layer grows in the uniform heating temperature field. At the same time, by taking advantage of the difference in the thermal expansion coefficient between the substrate and the epitaxial layer, a substrate with a non-zero warpage can be selected to reduce the warpage of the generated epitaxial wafer.

[0046] That is, the embodiment of the present application can obtain the epitaxial wafer with small warping and high uniformity by placing the substrate with non-zero warping on the substrate tray containing air cavity inside, growing the epitaxial layer on the epitaxial growth surface of the substrate by epitaxial process, and cooling the substrate and the epitaxial layer, thereby improving the uniformity and yield of the semiconductor device prepared by using the epitaxial wafer.

[0047] Figure 2 is a flowchart of the method for controlling the warping of the epitaxial wafer provided by an embodiment of the present application. As shown in Figure 2 , the method in the embodiment of the present application can include:

[0048] Step 201, placing the substrate with non-zero warping on the substrate tray containing air cavity inside.

[0049] The substrate with non-zero warping is convex or concave, and the air cavity contained inside the substrate tray has a special shape, which can reduce the temperature difference between the edge and the middle of the substrate tray, so that the substrate tray can generate a uniform heating temperature field.

[0050] Optionally, the type of the substrate can be: semi-insulating substrate, conductive substrate, or composite substrate, which is not specifically limited here.

[0051] In a possible implementation, referring to Figure 3 , before step 201, the method can further include:

[0052] Step 301, obtaining the first thermal expansion coefficient of the substrate and the second thermal expansion coefficient of the epitaxial layer to be grown.

[0053] The first thermal expansion coefficient of the substrate and the second thermal expansion coefficient of the epitaxial layer to be grown can be obtained by obtaining the operation of the worker inputting the first thermal expansion coefficient of the substrate and the second thermal expansion coefficient of the epitaxial layer, wherein the first thermal expansion coefficient and the second thermal expansion coefficient are determined according to the substrate to be epitaxially grown and the epitaxial layer to be grown on the epitaxial growth surface thereof.

[0054] Step 302, if the first thermal expansion coefficient is less than the second thermal expansion coefficient, selecting the first substrate tray as the substrate tray and selecting the substrate with positive warping as the substrate; wherein the shape of the air cavity in the first substrate tray keeps the temperature difference between the edge and the middle of the first substrate tray within a preset range interval.

[0055] Optionally, for the first substrate tray, the first thickness of the air cavity is greater than the second thickness of the air cavity, wherein the first thickness is the thickness of the air cavity at the edge of the substrate tray, and the second thickness is the thickness of the air cavity at the middle of the substrate tray, and the first thickness and the second thickness are the distances between the upper and lower edges of the air cavity in the thickness direction of the substrate tray.

[0056] Optionally, the air cavity of the substrate tray is vacuum or filled with gas; for the case that the air cavity is filled with gas, the gas includes at least one of the following: hydrogen, nitrogen, oxygen, vacuum, argon, helium, nitric oxide, and nitrogen dioxide. The type of the gas can be determined according to the substrate and the material of the epitaxial layer to be generated, and is not specifically limited herein.

[0057] It should be noted that when the first thermal expansion coefficient is less than the second thermal expansion coefficient, it indicates that the thermal expansion coefficient of the substrate is less than the thermal expansion coefficient of the epitaxial layer. After the high-temperature growth process of the conventional epitaxial growth is completed, the epitaxial layer will shrink more than the substrate. In addition, due to the specific properties of the epitaxial growth device, when the thermal expansion coefficient of the substrate is less than the thermal expansion coefficient of the epitaxial layer, the temperature of the edge of the substrate tray is higher than the temperature of the middle, so that the substrate tray cannot generate a uniform heating temperature field, which affects the uniform growth of the epitaxial layer, and further affects the warpage of the epitaxial wafer. The above reasons will cause the obtained epitaxial wafer to be concave.

[0058] At this time, the first substrate tray is selected as the substrate tray, the thickness of the air cavity at the edge of the first substrate tray is greater than the thickness of the air cavity at the middle, and the air cavity is vacuum or filled with gas. The vacuum or gas plays a role of heat insulation, that is, the air cavity can reduce the temperature difference between the edge and the middle of the first substrate tray, so that the temperature difference between the edge and the middle of the first substrate tray is maintained within a smaller preset range interval, a uniform heating temperature field can be generated, the uniform growth of the epitaxial layer in the uniform heating temperature field is ensured, and then an epitaxial wafer with high flatness and small warpage is obtained.

[0059] For example, a substrate with a positive warpage value, i.e., a convex substrate, is selected as the substrate, and the thermal expansion coefficient of the substrate with the positive warpage value is the first thermal expansion coefficient. After the high-temperature growth process of the epitaxial growth is completed, since the epitaxial layer shrinks more than the convex substrate, an epitaxial wafer with small warpage can be generated.

[0060] In step 303, if the first thermal expansion coefficient is greater than the second thermal expansion coefficient, the second substrate tray is selected as the substrate tray, and a substrate with a negative warpage value is selected as the substrate; wherein the shape of the air cavity in the second substrate tray is such that the temperature difference between the edge and the middle of the second substrate tray is maintained within a preset range interval.

[0061] Optionally, for the second substrate tray, the first thickness of the air cavity is less than the second thickness of the air cavity, wherein the first thickness is the thickness of the air cavity at the edge of the substrate tray, and the second thickness is the thickness of the air cavity at the middle of the substrate tray, and the first thickness and the second thickness are the distances between the upper and lower edges of the air cavity in the thickness direction of the substrate tray.

[0062] In contrast to the foregoing embodiments, when the first thermal expansion coefficient is greater than the second thermal expansion coefficient, it indicates that the thermal expansion coefficient of the substrate is greater than the thermal expansion coefficient of the epitaxial layer, and after the high-temperature growth process of the conventional epitaxial growth is completed, the epitaxial layer is less contracted than the substrate, and due to the specific properties of the epitaxial growth equipment, when the thermal expansion coefficient of the substrate is greater than the thermal expansion coefficient of the epitaxial layer, the temperature of the edge of the substrate tray is lower than the temperature of the middle, so that the substrate tray cannot generate a uniform heating temperature field, which affects the uniform growth of the epitaxial layer, and further affects the warpage of the epitaxial wafer. The above reasons can cause the obtained epitaxial wafer to be convex.

[0063] At this time, the second substrate tray is selected as the substrate tray, the thickness of the air cavity at the edge of the second substrate tray is less than the thickness of the air cavity at the middle, and the air cavity is filled with a vacuum or a gas. The vacuum or the gas serves to insulate heating, that is, the air cavity can reduce the temperature difference between the edge and the middle of the second substrate tray, so that the temperature difference between the edge and the middle of the second substrate tray is maintained within a smaller preset range interval, a uniform heating temperature field can be generated, the uniform growth of the epitaxial layer in the uniform heating temperature field is ensured, and further a epitaxial wafer with high flatness and small warpage is obtained.

[0064] Optionally, the air cavity is filled with a vacuum or a gas, and the type of the gas can be determined according to the material of the substrate and the epitaxial layer to be generated, which is not specifically limited herein.

[0065] For example, a substrate with a negative warpage value, that is, a concave substrate, is selected as the substrate, and the thermal expansion coefficient of the substrate with the negative warpage value is the first thermal expansion coefficient. After the high-temperature growth process of the epitaxial growth is completed, since the epitaxial layer is less contracted than the concave substrate, an epitaxial wafer with small warpage can be generated.

[0066] Optionally, the range of the positive warpage value is greater than 0 and less than or equal to 100 microns, and the range of the negative warpage value is greater than or equal to -100 microns and less than 0.

[0067] The value of the warpage of the substrate is determined according to the thermal expansion coefficients of the substrate and the epitaxial layer to be generated.

[0068] Optionally, the thickness of the air cavity linearly or nonlinearly decreases from the edge to the middle of the first substrate tray, and the thickness of the air cavity linearly or nonlinearly increases from the edge to the middle of the second substrate tray.

[0069] The thickness of the air cavity can decrease non-linearly from the edge to the middle of the first substrate tray, for example, in a stepwise manner, in a zigzag manner, or in a wavy manner, etc. The thickness of the air cavity can increase non-linearly from the edge to the middle of the second substrate tray, for example, in a stepwise manner, in a zigzag manner, or in a wavy manner, etc. The specific manner is not limited herein.

[0070] In step 202, an epitaxial layer is grown on the epitaxial growth surface of the substrate by an epitaxial process. The substrate and the epitaxial layer are cooled to obtain an epitaxial wafer with a small warping degree.

[0071] The epitaxial process can include metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), pulsed laser deposition (PLD), magnetron sputtering deposition, electron beam evaporation deposition, chemical vapor deposition (CVD), etc.

[0072] In practical applications, the type of the epitaxial process is not limited.

[0073] The step of growing an epitaxial layer on the epitaxial growth surface of the substrate can be performed in the following manner: for a substrate with a positive warping degree, the epitaxial layer is grown on the convex surface of the substrate; for a substrate with a negative warping degree, the epitaxial layer is grown on the concave surface of the substrate.

[0074] Specifically, during the epitaxial growth, the substrate tray with the air cavity of a special shape can generate a uniform heating temperature field, so that the epitaxial layer grows uniformly in the uniform heating temperature field, and thus an epitaxial wafer with a high flatness and a small warping degree can be obtained.

[0075] After the high-temperature growth process of the epitaxial growth is completed, the substrate and the epitaxial layer are cooled. The substrate and the epitaxial layer start to shrink. Because the thermal expansion coefficients of the substrate and the epitaxial layer are different, the shrinkage degrees of the substrate and the epitaxial layer are different. Therefore, an epitaxial layer with a small warping degree can be generated on a convex or concave substrate, and an epitaxial wafer with a small warping degree can be further obtained.

[0076] Figure 4 is a comparison diagram of the growth of an epitaxial wafer provided in an embodiment of the present application. As shown in Figure 4 A substrate 10 with a positive warping degree is placed on a first substrate tray 20 with an air cavity. The thickness of the air cavity 21 of the first substrate tray decreases linearly from the edge to the middle of the first substrate tray 20. An epitaxial layer is grown on the convex surface of the substrate 10 by an epitaxial process. After the substrate 10 and the epitaxial layer 30 are cooled, an epitaxial wafer with a small warping degree is obtained.

[0077] Figure 5is a comparative diagram of the growth change of the epitaxial wafer provided by an embodiment of the present application. As shown in Figure 5 The substrate 50 with a negative warpage is placed on the second substrate tray 60 containing an air cavity inside, wherein the thickness of the air cavity 61 of the second substrate tray increases linearly from the edge to the middle of the second substrate tray. The epitaxial layer is grown on the concave surface of the substrate 50 by using the epitaxial process, and the substrate 50 and the epitaxial layer 70 are subjected to the cooling treatment, thereby obtaining the epitaxial wafer with a small warpage.

[0078] A simple example is that, in the process of preparing a GaN heterojunction field effect transistor device, a GaN epitaxial layer is grown on a semi-insulating SiC substrate by using a metal-organic chemical vapor deposition (MOCVD) epitaxial deposition process. The steps of the method for controlling the warpage of the epitaxial wafer in the present application are as follows:

[0079] (1) The thermal expansion coefficient of the SiC substrate is 3.78 x 10 -6 K -1 , and the thermal expansion coefficient of the GaN epitaxial layer to be generated is 5.59 x 10 -6 K -1 .

[0080] (2) The thermal expansion coefficient of the SiC substrate is less than the thermal expansion coefficient of the GaN epitaxial layer to be generated, a substrate tray is selected in which the thickness of the air cavity decreases linearly from the edge to the middle of the substrate tray, and a semi-insulating SiC substrate with a warpage of +10 μm is selected.

[0081] (3) The semi-insulating SiC substrate is placed on the substrate tray.

[0082] (4) The GaN epitaxial layer is grown on the convex surface of the semi-insulating SiC substrate by using the metal-organic chemical vapor deposition (MOCVD) epitaxial deposition process, and the semi-insulating SiC substrate and the GaN epitaxial layer are subjected to the cooling treatment, thereby obtaining the GaN epitaxial wafer.

[0083] It is detected that the warpage of the GaN epitaxial wafer is -0.26 μm.

[0084] It should be noted that, in a possible implementation, the epitaxial growth of the substrate is homoepitaxy, i.e., the substrate and the epitaxial layer to be grown on the epitaxial growth surface are of the same material, for example, the SiC epitaxial layer is homoepitaxially grown on the SiC substrate. In this case, the thermal expansion coefficients of the substrate and the epitaxial layer are the same, i.e., the first thermal expansion coefficient is equal to the second thermal expansion coefficient, and in this case, the third substrate tray is selected as the substrate tray, and the substrate with a warpage of zero is selected as the substrate.

[0085] The third substrate tray does not contain an air cavity to minimize the temperature difference between its edge and center, thus enabling a uniform heating field. The substrate with zero warpage has planar upper and lower outer surfaces, and its coefficient of thermal expansion is the first coefficient of thermal expansion.

[0086] The above-mentioned method for controlling the warpage of epitaxial wafers involves placing a substrate with a non-zero warpage value on a substrate tray containing an air cavity, and using an epitaxial process to grow an epitaxial layer on the epitaxial growth surface of the substrate. Cooling the substrate and the epitaxial layer can produce an epitaxial wafer with low warpage and high uniformity, thereby improving the uniformity and yield of semiconductor devices prepared using the epitaxial wafers.

[0087] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0088] Figure 6 This is a schematic diagram of the structure of a substrate tray provided in one embodiment of this application. Figure 6 As shown, the substrate tray is used to place a substrate with a non-zero warpage value for epitaxial layer growth on the epitaxial growth surface of the substrate; an air cavity is provided inside the substrate tray to keep the temperature difference between the edge and the center of the substrate tray within a preset range.

[0089] Optionally, the first thickness of the air cavity is greater than the second thickness of the air cavity, or the first thickness of the air cavity is less than the second thickness of the air cavity. The first thickness is the thickness of the air cavity at the edge of the substrate tray, and the second thickness is the thickness of the air cavity in the middle of the substrate tray. The first thickness and the second thickness are the distance between the upper and lower edges of the air cavity in the thickness direction of the substrate tray.

[0090] Optionally, the thickness of the air cavity decreases linearly or non-linearly from the edge to the center of the substrate tray, or the thickness of the air cavity increases linearly or non-linearly.

[0091] For example, the substrate tray has a first thickness greater than the second thickness of the air cavity (see...). Figure 6 (a) in the text is used to match a substrate with a positive warpage, i.e., a convex substrate, to generate an epitaxial layer with low warpage on the epitaxial growth surface of the aforementioned convex substrate, thereby obtaining an epitaxial wafer with low warpage. The first thickness of the air cavity is less than the second thickness of the air cavity in the substrate tray (see...). Figure 6 (b) is used to match a substrate with a negative warpage value, i.e., to match a concave substrate, so as to generate an epitaxial layer with small warpage on the epitaxial growth surface of the concave substrate, thereby obtaining an epitaxial wafer with small warpage.

[0092] The substrate tray provided by the embodiment can be applied to the method embodiments, and the implementation principles and technical effects are described above, which will not be described here again.

[0093] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features can be replaced equivalently; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.

Claims

1. A method for controlling the warpage of an epitaxial wafer, characterized in that, include: A substrate with a non-zero warpage is placed on a substrate tray containing an internal air cavity; An epitaxial layer is grown on the epitaxial growth surface of the substrate using an epitaxial process, and the substrate and the epitaxial layer are cooled to obtain an epitaxial wafer with low warpage. The method further includes, before placing the substrate with a non-zero warpage on a substrate tray containing an internal air cavity: Obtain the first thermal expansion coefficient of the substrate and the second thermal expansion coefficient of the epitaxial layer to be grown; If the first coefficient of thermal expansion is less than the second coefficient of thermal expansion, then the first substrate tray is selected as the substrate tray, and the substrate with a positive warpage is selected as the substrate; wherein, the shape of the air cavity in the first substrate tray ensures that the temperature difference between the edge and the center of the first substrate tray is maintained within a preset range. If the first coefficient of thermal expansion is greater than the second coefficient of thermal expansion, then the second substrate tray is selected as the substrate tray, and the substrate with a negative warpage is selected as the substrate; wherein, the shape of the air cavity in the second substrate tray ensures that the temperature difference between the edge and the middle of the second substrate tray is maintained within a preset range. For the first substrate tray, the first thickness of the air cavity is greater than the second thickness of the air cavity; for the second substrate tray, the first thickness of the air cavity is less than the second thickness of the air cavity. Wherein, the first thickness is the thickness of the air cavity at the edge of the substrate tray, the second thickness is the thickness of the air cavity in the middle of the substrate tray, and the first thickness and the second thickness are the distance between the upper and lower edges of the air cavity in the thickness direction of the substrate tray.

2. The method of controlling the wafer bow of an epitaxial wafer according to claim 1, wherein From the edge to the center of the first substrate tray, the thickness of the air cavity decreases linearly or non-linearly. From the edge to the center of the second substrate tray, the thickness of the air cavity increases linearly or non-linearly.

3. The method of controlling the warpage of an epitaxial wafer according to claim 1 or 2, wherein The air cavity of the substrate tray is either a vacuum or filled with gas; When the air cavity is filled with gas, the gas includes at least one of the following: hydrogen, nitrogen, oxygen, argon, helium, nitric oxide, and nitrogen dioxide.

4. The method for controlling the warpage of an epitaxial wafer according to claim 1, characterized in that, The positive warpage ranges from greater than 0 to less than or equal to 100 micrometers, and the negative warpage ranges from greater than or equal to -100 micrometers to less than 0.

5. The method for controlling the warpage of an epitaxial wafer according to claim 4, characterized in that, The epitaxial layer growth on the epitaxial growth surface of the substrate includes: For a substrate with a positive warpage, an epitaxial layer is grown on the convex surface of the substrate; For a substrate with a negative warpage, an epitaxial layer is grown on the concave surface of the substrate.

6. A substrate tray, characterized in that, The substrate tray is used to place a substrate with a non-zero warpage for epitaxial layer growth on the epitaxial growth surface of the substrate; an air cavity is provided inside the substrate tray to keep the temperature difference between the edge and the center of the substrate tray within a preset range. If the first thermal expansion coefficient of the substrate is less than the second thermal expansion coefficient of the epitaxial layer to be grown, then the first substrate tray is selected as the substrate tray, and the substrate with a positive warpage is selected as the substrate; wherein, the shape of the air cavity in the first substrate tray ensures that the temperature difference between the edge and the middle of the first substrate tray is maintained within a preset range. If the first coefficient of thermal expansion is greater than the second coefficient of thermal expansion, then the second substrate tray is selected as the substrate tray, and the substrate with a negative warpage is selected as the substrate; wherein, the shape of the air cavity in the second substrate tray ensures that the temperature difference between the edge and the middle of the second substrate tray is maintained within a preset range. For the first substrate tray, the first thickness of the air cavity is greater than the second thickness of the air cavity; for the second substrate tray, the first thickness of the air cavity is less than the second thickness of the air cavity. Wherein, the first thickness is the thickness of the air cavity at the edge of the substrate tray, the second thickness is the thickness of the air cavity in the middle of the substrate tray, and the first thickness and the second thickness are the distance between the upper and lower edges of the air cavity in the thickness direction of the substrate tray.

7. The substrate tray according to claim 6, characterized in that, From the edge to the center of the substrate tray, the thickness of the air cavity decreases linearly or non-linearly, or the thickness of the air cavity increases linearly or non-linearly.

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