TWI785763B - Composite substrate and manufacture method thereof - Google Patents

Abstract

A composite substrate is provided in some embodiments of the present disclosure, including a first substrate, an aluminum oxide layer, a second substrate and a gallium nitride epitaxial layer. The aluminum oxide layer is disposed on the first substrate. The second substrate is disposed on the aluminum oxide layer. The gallium nitride epitaxial layer is disposed on the second substrate. A method of manufacturing a composite substrate is also provided in some embodiments of the present disclosure.

Description

Composite substrate and manufacturing method thereof

The present disclosure relates to composite substrates and methods of making the same.

Recently, based on the demand for consumer electronics and automotive components, the demand for component size miniaturization and power improvement is increasing. However, as the power density of components increases (such as high-frequency components containing gallium nitride epitaxial layers), the heat accumulation effect increases rapidly, reducing the performance of component efficiency, and severely challenging the reliability and stability of components.

Therefore, how to improve the heat dissipation effect of the composite substrate carrying components is a problem to be solved.

An object of an embodiment of the present disclosure is to provide a composite substrate, including a first substrate; an aluminum oxide layer is disposed on the first substrate; a second substrate is disposed on the aluminum oxide layer; and a gallium nitride epitaxial structure is disposed on the second substrate. on the second substrate.

In some embodiments, the first substrate or the second substrate is a silicon substrate, a silicon-on-insulator substrate, a sapphire substrate, a silicon carbide substrate, a diamond substrate, any two or a combination of the foregoing materials.

In some embodiments, an aluminum layer is disposed between the first substrate and the aluminum oxide layer.

In some embodiments, the surface of the aluminum layer in contact with the aluminum oxide layer has a plurality of regular grooves, wherein the regular grooves include a diameter error of the grooves within 20%, and the grooves have Consistent hole shape.

In some embodiments, the aluminum oxide layer includes a plurality of holes distributed between the aluminum oxide.

An object of an embodiment of the present disclosure is to provide a method for manufacturing a composite substrate, comprising: providing a first substrate; depositing a first aluminum layer on the first substrate, a second aluminum layer on the first aluminum layer, and a third an aluminum layer on the second aluminum layer; performing a first anodic treatment on the third aluminum layer to oxidize the third aluminum layer to form a first aluminum oxide layer on the second aluminum layer; removing the first aluminum oxide layer; An aluminum layer and the second aluminum layer perform a second anodic treatment to oxidize the second aluminum layer, thereby forming a second aluminum oxide layer on the first aluminum layer, wherein the second aluminum oxide layer includes an aluminum oxide body and a plurality of holes distributed in the Between the alumina bodies; performing hole expansion treatment on the second alumina layer to improve the uniformity of holes in the second alumina layer; providing a second substrate; and bonding the second alumina layer and the second substrate to obtain The first composite substrate, wherein the second aluminum oxide layer is located between the first substrate and the second substrate.

In some embodiments, performing the first anodic treatment on the third aluminum layer includes: using the first acidic solution as the electrolyte, and disposing the aluminum layer on the anode, performing an anodic oxidation reaction to grow aluminum oxide on the second aluminum layer , to form the first aluminum oxide layer.

In some embodiments, the step of performing hole expansion on the second alumina layer includes soaking the second alumina layer in a second acidic solution.

In some embodiments, after the step of bonding the first substrate and the second substrate, further comprising: removing the first substrate and the first aluminum layer in the first composite substrate; providing a third substrate; and bonding the second substrate. an aluminum oxide layer and a third substrate to obtain a second composite substrate, wherein the second aluminum oxide layer is located between the second substrate and the third substrate.

In some embodiments, after the step of bonding the second aluminum oxide layer and the second substrate, further comprising forming a GaN epitaxial structure on the second substrate.

It can be understood that different implementations or examples provided in the following content can implement different features of the subject matter of the present disclosure. The examples of specific components and arrangements are used to simplify the present disclosure and not to limit the present disclosure. Of course, these are examples only and are not intended to be limiting. For example, the description below that a first feature is formed on a second feature includes that the two are in direct contact, or that there are other additional features between the two instead of direct contact. In addition, the present disclosure may repeat reference numerals and/or symbols in several embodiments. Such repetition is for simplicity and clarity and does not imply a relationship between the various embodiments and/or configurations discussed.

The terms used in this specification generally have their ordinary meanings in the art and the context in which they are used. The examples used in this specification, including examples of any term discussed herein, are illustrative only and do not limit the scope and meaning of the disclosure or any exemplified term. Likewise, the disclosure is not limited to some of the embodiments provided in this specification.

In addition, relative terms in space, such as "below" and "upper", are used to conveniently describe the relative relationship between one element or feature and other elements or features in the drawings. These spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the drawings. The device may be otherwise positioned (eg, rotated 90 degrees or at other orientations) and the spatially relative descriptions used herein interpreted accordingly.

In this article, "a" and "the" can generally refer to one or more, unless the article is specifically limited in the context. It will be further understood that the terms "comprising", "comprising", "having" and similar words used herein indicate the features, regions, integers, steps, operations, elements and/or components described therein, but do not exclude Other features, regions, integers, steps, operations, elements, components, and/or groups thereof.

It will be understood that, although the terms first, second etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present embodiments.

As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Several implementations are listed below to describe the touch device of the present invention in more detail, but they are only for illustrative purposes and are not intended to limit the present invention. The scope of protection of the present invention shall prevail as defined by the scope of the appended patent application . It should be noted that the proportional relationship among the elements in the drawings is only for illustration.

Figures 1A-1H exemplarily depict schematic diagrams of various process stages for manufacturing a composite substrate in accordance with some embodiments of the present disclosure.

First, please refer to FIG. 1A , a first substrate 110 is provided.

In some embodiments, the first substrate 110 is a silicon substrate, a silicon-on-insulator (Silicon On Insulator; SOI) substrate, a sapphire substrate, a silicon carbide substrate, a diamond substrate, any two of the foregoing materials, or a combination of more than two . In some embodiments, the thickness of the first substrate 110 ranges from 300 microns to 1000 microns, such as 300 microns, 400 microns, 500 microns, 600 microns, 700 microns, 800 microns, 900 microns, 1000 microns, or any value in the aforementioned range. In some embodiments, a silicon dioxide layer can be first formed on the upper surface of the silicon substrate and the lower surface relative to the upper surface, and then the silicon dioxide on the upper surface is removed to form an insulating layer on the silicon substrate, and the prepared A first substrate 110 is obtained, wherein the second surface 114 of the first substrate 110 is silicon dioxide, and subsequent processes are performed on the first surface 112 (silicon) of the first substrate 110 .

Next, please refer to FIG. 1B , an aluminum layer 120 is deposited on the first surface 112 of the first substrate 110 . Specifically, depositing the aluminum layer 120 includes depositing a first aluminum layer on the first substrate 110, a second aluminum layer on the first aluminum layer, and a third aluminum layer on the second aluminum layer, wherein the first aluminum layer, The second aluminum layer and the third aluminum layer are not shown.

In some embodiments, the aluminum layer 120 can be grown on the first substrate 110 by using a sputtering machine in an environment filled with argon gas. In some embodiments, the thickness of the aluminum layer 120 is 100 nm to 400 nm, such as 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm or the aforementioned Numeric values in any interval.

In some embodiments, after the step of depositing the aluminum layer 120 on the first substrate 110 , planarizing the aluminum layer 120 is further included. For example, the first substrate 110 on which the aluminum layer 120 is deposited can be firstly ground with sandpaper, and after mechanical polishing, the first substrate 110 is immersed in a solution containing perchloric acid (HClO ₄ ), ethylene glycol butyl ether (CH ₃ (CH ₂ ) ₃ OCH ₂ CH ₂ OH) and ethanol (C ₂ H ₆ O), electrolytic polishing is performed to planarize the aluminum layer 120 and improve the gloss of the aluminum layer 120 . It should be noted that, as the surface roughness of the aluminum layer 120 increases, the regularity of the hole arrangement of anodic aluminum oxide (AAO) formed by the subsequent anodic oxidation treatment will decrease. Therefore, through the pre-planarization of the aluminum layer 120 , the surface roughness of the aluminum layer 120 is reduced, and the regularity of the pores of the anodized aluminum formed subsequently is improved.

Next, see FIG. 1C, the aluminum layer 120 is subjected to a first anodic treatment to form a first aluminum oxide layer 130 on the second aluminum layer (retained in FIG. 1C) with the third aluminum layer in the aluminum layer 120. The aluminum layer 120 is the second aluminum layer and the first aluminum layer (not shown) from top to bottom), the first aluminum oxide layer 130 is anodized aluminum, and has a plurality of grooves A1 in the top view Distributed between the first alumina bodies 132 (it should be noted that although the groove A1 is shown here, however, in some embodiments, the groove A1 can also be a hole).

In some embodiments, performing the first anodic treatment on the aluminum layer 120 includes: using the first acidic solution as the electrolyte, and disposing the aluminum layer 120 on the anode, and performing an anodic oxidation reaction to grow the first alumina body 132 (Al ₂ O ₃ ) on the aluminum layer 120 . In some embodiments, the first acidic solution includes sulfuric acid, oxalic acid, phosphoric acid, any two or a combination of the foregoing materials. The size, shape, thickness and regularity of the groove A1 (or hole) of anodized aluminum can be adjusted by matching the appropriate applied voltage, electrolyte type (for example, with different conductivity), concentration, temperature, and time. For example, as the applied voltage increases, the melting speed of the first alumina body 132 will increase, forming larger grooves A1 (or holes). However, at low temperature (for example, below 10° C.), the order regularity of the grooves A1 (or holes) can be improved, and the formed first alumina body 132 has better hardness and wear resistance.

In one embodiment, the aluminum layer 120 can be connected to the anode, the platinum metal can be connected to the cathode, and sulfuric acid with a concentration of 0.3M is used as the electrolyte at a temperature of 10°C, an applied voltage of 25V, and an action time of 1 hour. Under these conditions, the first aluminum oxide layer 130 is grown to have a circular groove A1 (or hole) in plan view, wherein the groove A1 (or hole) has a thickness of about 150 nm and a diameter of about 10 nm to 70 nanometers, such as 10 nanometers, 20 nanometers, 30 nanometers, 40 nanometers, 50 nanometers, 60 nanometers, 70 nanometers, or a value in any interval of the foregoing.

In another embodiment, the first aluminum oxide layer 130 can be grown by using oxalic acid with a concentration of 0.3M as the electrolyte at a temperature of 1°C, an applied voltage of 40V, and an action time of 1 hour, wherein The first aluminum oxide layer 130 has a hexagonal or nearly circular groove A1 (or hole), wherein the thickness of the groove A1 (or hole) is about 150 nm, and the diameter is about 30 nm to 100 nm , such as 30 nanometers, 40 nanometers, 50 nanometers, 60 nanometers, 70 nanometers, 80 nanometers, 90 nanometers, 100 nanometers, or a value in any range of the foregoing.

In yet another embodiment, phosphoric acid with a concentration of 0.3M can be used as the electrolyte, and the first aluminum oxide layer 130 can be grown under the conditions of a temperature of 3°C, an applied voltage of 160V, and an action time of 1 hour, wherein The first aluminum oxide layer 130 has a circular groove A1 (or hole), wherein the thickness of the groove A1 (or hole) is about 150 nm, and the diameter is about 50 nm to 130 nm, such as 50 nm, 60 nanometers, 70 nanometers, 80 nanometers, 90 nanometers, 100 nanometers, 110 nanometers, 120 nanometers, 130 nanometers or a value in any range of the foregoing.

Next, see FIG. 1D (and also refer to FIG. 1C ), the first aluminum oxide layer 130 is removed. In some embodiments, the first aluminum oxide layer 130 can be soaked in an acidic solution to remove the first aluminum oxide layer 130, for example, using chromic acid with a weight percentage (weight percentage; wt %) of 2%, and Phosphoric acid with a percentage of 6% is used as a solute to prepare a working solution, and the first aluminum oxide layer 130 is soaked in the working solution for about 30 minutes to 60 minutes at 60° C., and the first aluminum oxide layer 130 is removed.

Next, please refer to FIG. 1E (also refer to FIG. 1C), perform a second anodic treatment on the aluminum layer 120 (ie, the first aluminum layer and the second aluminum layer (not shown)) retained in the 1D figure, Oxidize the second aluminum layer to form a second aluminum oxide layer 140 on the first aluminum layer (that is, the aluminum layer 120 retained in Figure 1E), wherein the second aluminum oxide layer 140 includes a plurality of holes A2 distributed in the first aluminum layer between the alumina bodies 142 . Specifically, in a top view, the second aluminum oxide layer 140 has a honeycomb three-dimensional structure with regular holes A2, where the regularity includes, but is not limited to, the diameters of the holes A2 are consistent or similar (for example, the error is within 20 %), or the holes have the same or similar shape (such as hexagonal or circular), or the hole diameters are the same or similar, and the hole shapes are the same or similar.

It should be noted that (please also refer to FIG. 1C to FIG. 1E ), due to the first aluminum oxide layer 130 formed by the first anodic treatment, the surface roughness of the aluminum layer 120 is prone to produce irregular concaves. Groove A1 (or hole) structure (for example, the shape of the hole is different, the diameter error of the groove A1 (or hole) is greater than 20%). In order to improve the regularity of the pores between the aluminum oxides, after the aforementioned step of removing the first aluminum oxide layer 130, then use the regular concave holes that exist on the surface 122 of the aluminum layer 120 due to the first anodic treatment. Groove B (wavy structure in plan view, such as, but not limited to, the height, distance, or both of adjacent crests to troughs in the wavy structure are consistent or similar (for example, the error is within 20%)) As the base for forming the subsequent second alumina body 142 , the second alumina layer 140 with better hole regularity is formed to improve the bending resistance of the second alumina layer 140 .

The conditions of the second anodic treatment may be basically the same or similar to those of the first anodic treatment. In other embodiments, different acidic solutions may be used as electrolytes for the first anodic treatment and the second anodic treatment. In some embodiments, the thickness of the second aluminum oxide layer 140 is 100 nm to 400 nm, such as 100 nm, 200 nm, 300 nm, 400 nm, or any value in the aforementioned range. In some embodiments, compared with the first anodic treatment, in order to obtain a higher thickness of the second aluminum oxide layer 140, the treatment time can be further increased, for example, the treatment time can be increased from 1 hour (thickness is about 40 to 100 nm ) to 3 hours to form a second aluminum oxide layer 140 with a thickness of 300 nm to 400 nm.

Next, see FIG. 1F, the second aluminum oxide layer 140 is subjected to a hole expansion process to improve the diameter and uniformity of the holes A2 in the second aluminum oxide layer 140 (for example, by corroding the second aluminum oxide layer 140 The sidewalls make the shapes and diameters of the holes A2 tend to be consistent or similar (for example, the diameter error between the holes A2 is within 20%)). In some embodiments, the step of performing hole expansion on the second alumina layer 140 includes soaking the second alumina layer 140 in an acidic solution (such as sulfuric acid, oxalic acid, phosphoric acid, or chromic acid, etc.) to corrode the second alumina layer 140. Layer 140. For example, at 25°C, the second aluminum oxide layer 140 is placed in a 5% by weight phosphoric acid solution for hole expansion, wherein the diameter of the hole A2 of the second aluminum oxide layer 140 is between 10 nm and 150 nm , such as 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 110nm, 120nm, 130 nanometers, 140 nanometers, 150 nanometers, or a value in any of the aforementioned intervals. However, those skilled in the art can choose different acidic solutions to expand the hole according to the requirements of the hole A2.

Next, please refer to FIG. 1G , providing the second substrate 150 , and then bonding the second aluminum oxide layer 140 and the second substrate 150 , wherein the second aluminum oxide layer 140 is located between the first substrate 110 and the second substrate 150 . Specifically, the composite substrate 100 includes an aluminum layer 120 (first aluminum layer) disposed on the first substrate 110, a second aluminum oxide layer 140 disposed on the aluminum layer 120 (first aluminum layer), and a second substrate 150 disposed on the first substrate 110. on the second aluminum oxide layer 140 (that is, the second aluminum oxide layer 140 is located between the first substrate 110 and the second substrate 150 ).

The material and thickness of the second substrate 150 may be the same as or similar to that of the first substrate 110 , which will not be repeated here.

In some embodiments, the first substrate 110, the second aluminum oxide layer 140, and the second substrate may be heated in a nitrogen-containing gas condition (such as hydrogen and nitrogen, hydrogen and ammonia, or nitrogen and ammonia). 150 (ie, annealing treatment), bonding the second aluminum oxide layer 140 and the second substrate 150 . In another embodiment, the first substrate 110, the second aluminum oxide layer 140, and the second substrate 150 can be preliminarily heated, and after the second aluminum oxide layer 140 and the second substrate 150 are bonded, the nitrogen-containing base Perform annealing treatment in the gas condition to improve the strength of the bond.

Next, see FIG. 1H, a GaN epitaxial structure E (belonging to a high electron mobility transistor (High electron mobility transistor; HEMT)) is formed on the second substrate 150 to obtain a high-frequency composite substrate 200. For example, it can be used Metal-organic Chemical Vapor Deposition (MOCVD) forms the GaN epitaxial structure E with a thickness of 1 to 10 micrometers.

In some embodiments, the GaN epitaxial structure E sequentially includes a nucleation layer disposed on the second substrate 150, a buffer layer disposed on the nucleation layer, a resistive layer disposed on the buffer layer, and a channel layer disposed on the resistive layer. On, the barrier layer is disposed on the channel layer, and the covering layer is disposed on the barrier layer. In some embodiments, the nucleation layer may comprise aluminum nitride and have a thickness between 30 nm and 300 nm. In some embodiments, the buffer layer may comprise AlGaN, GaN, or a combination of the foregoing, such as ladder AlGaN or superlattice AlGaN/GaN, with a thickness of 300 nm to 1000 nm. In some embodiments, the resistance layer is gallium nitride, and its thickness may be between 0.5 microns and 2.5 microns. In some embodiments, the channel layer is GaN with a thickness between 0.05 micron and 1 micron. In some embodiments, the barrier layer comprises aluminum gallium nitride and has a thickness between 10 nm and 50 nm. In some embodiments, the capping layer is GaN with a thickness of 0.5 nm to 150 nm.

In some embodiments, before the step of forming the GaN epitaxial structure E on the second substrate 150, it further includes thinning the second substrate 150 to an appropriate thickness, for example, thinning the second substrate 150 to 1 μm to 10 μm. between microns.

In some other embodiments, metal-oxide-semiconductor field-effect transistors (Metal-Oxide-Semiconductor Field-Effect Transistor; MOSFET) can be used to replace the gallium nitride epitaxial structure E, that is, to form a metal-oxide-semiconductor field-effect transistor The crystal is on the second substrate 150 (not shown).

It is worth emphasizing that the high-frequency composite substrate 200 uses the second alumina layer 140 to connect the first substrate 110 and the second substrate 150, and anodized aluminum (the second alumina body 142) has a high heat dissipation coefficient (the heat dissipation coefficient is that of silicon dioxide 9 to 25 times of that), compared with the conventional composite substrate (for example, silicon dioxide is used as the connection layer between the first substrate and the second substrate), the high-frequency composite substrate 200 can be endowed with better heat dissipation. Therefore, when a high-frequency component (such as a gallium nitride epitaxial structure E) is arranged on the composite substrate 100 to form the high-frequency composite substrate 200, it has better heat dissipation compared with the conventional composite substrate. , so that the problem of efficiency reduction due to heat accumulation can be avoided, so that the high-frequency components have better efficiency.

In addition, the second aluminum oxide layer 140 produced by anodic oxidation has a honeycomb three-dimensional structure (such as hexagonal or circular) with regular holes A2, and this three-dimensional structure endows the second aluminum oxide layer 140 with good bending resistance. properties, contributing to the bending resistance of the high-frequency composite substrate 200.

Figures 2A to 2C exemplarily depict schematic diagrams of various process stages of manufacturing composite substrates in other embodiments of the present disclosure, wherein Figures 2A to 2C are continuation of Figure 1G (replacing Figure 1H) Another follow-up process aims to obtain a composite substrate in which only the alumina layer (without the aluminum layer) is used as the connection layer between the substrates.

Specifically, referring to FIG. 2A (see also FIG. 1G ), the first substrate 110 and the aluminum layer 120 in the composite substrate 100 are removed (that is, the first aluminum layer remaining after the anodic oxidation treatment). In some embodiments, the first substrate 110 and the aluminum layer 120 may be removed by grinding or chemical mechanical polishing.

Next, please see FIG. 2B, providing a third substrate 310, and then bonding the second aluminum oxide layer 140 and the third substrate 310 to obtain a composite substrate 300 (that is, steps similar to those in FIG. 1F to FIG. 1G ), The second aluminum oxide layer 140 is located between the second substrate 150 and the third substrate 310 . The difference between the composite substrate 300 and the composite substrate 100 (see also FIG. 1G below) is that the composite substrate 100 includes an aluminum layer 120 disposed between the first substrate 110 and the second aluminum oxide layer 140, and the composite substrate 300 is on the second substrate 150 There is no aluminum layer 120 between (or the third substrate 310 ) and the second aluminum oxide layer 140 .

The material and thickness of the third substrate 310 can be the same or similar to that of the first substrate 110 (see also FIG. 1G ) or the second substrate 150 , as for the bonding reaction conditions. It may be the same or similar to the discussion in FIG. 1G , and will not be repeated here.

Next, please see Figure 2C, forming the gallium nitride epitaxy structure E on the third substrate 310 to obtain a high-frequency composite substrate 400, the steps here and the composition of the gallium nitride epitaxy structure E can be referred to the discussion in Figure 1H , which will not be described further here. In some embodiments, before the step of forming the GaN epitaxial structure E on the third substrate 310, thinning the third substrate 310 to an appropriate thickness is further included. In other embodiments, the gallium nitride epitaxial structure E may be replaced by a metal oxide semiconductor field effect transistor (MOSFET), that is, a metal oxide semiconductor field effect transistor is formed on the third substrate 310 (not shown in the figure). Show). In some embodiments, the GaN epitaxial structure E can also be formed on the second substrate 150 (ie, instead of being originally formed on the third substrate 310 ).

In summary, some embodiments of the present disclosure provide a composite substrate and a manufacturing method thereof, by arranging an aluminum oxide layer with high heat dissipation between the substrates (for example, between the first substrate and the second substrate, or Between the second substrate and the third substrate) to improve the heat dissipation of the composite substrate, which can avoid the efficiency reduction of high-frequency components due to heat accumulation, thereby achieving better efficiency; in addition, the aluminum oxide layer has a regular hole structure, It can endow the composite substrate with good bending resistance, prevent the composite substrate from curling due to being too thin, and improve the convenience of the manufacturing process.

While this disclosure has described details in terms of certain implementations, other implementations are possible. Therefore, the spirit and scope of the appended claims should not be limited to the implementations described herein.

100, 300: composite substrate

110: the first substrate

112: first surface

114: second surface

120: aluminum layer

130: the first aluminum oxide layer

132: the first alumina body

140: second aluminum oxide layer

142: the second alumina body

150: second substrate

200, 400: high frequency composite substrate

310: the third substrate

A1: Groove

A2: hole

B: Groove

E: GaN epitaxial structure

A more complete understanding of the present disclosure can be obtained by reading the following detailed description of the embodiments with reference to the accompanying drawings. Figures 1A-1H exemplarily depict schematic diagrams of various process stages for manufacturing a composite substrate in accordance with some embodiments of the present disclosure. FIG. 2A to FIG. 2C exemplarily depict schematic diagrams of various process stages of manufacturing a composite substrate in other embodiments of the present disclosure, wherein FIG. 2A to FIG. 2C are another subsequent process following FIG. 1G .

100: composite substrate

110: the first substrate

120: aluminum layer

140: second aluminum oxide layer

150: second substrate

200: High frequency composite substrate

A2: hole

E: GaN epitaxial structure

Claims (9)

A composite substrate, comprising: a first substrate; an aluminum oxide layer comprising a plurality of holes distributed between aluminum oxides is disposed on the first substrate; a second substrate is disposed on the aluminum oxide layer; and a gallium nitride The epitaxial structure is disposed on the second substrate. The composite substrate as described in Claim 1, wherein the first substrate or the second substrate is a silicon substrate, a silicon-on-insulator substrate, a sapphire substrate, a silicon carbide substrate, a diamond substrate, any of the aforementioned materials A combination of two or more. The composite substrate as claimed in claim 1 further comprises an aluminum layer disposed between the first substrate and the aluminum oxide layer. The composite substrate as claimed in claim 3, wherein a surface of the aluminum layer in contact with the aluminum oxide layer has a plurality of regular grooves, wherein the regular grooves include a diameter error of 20% of the grooves Within, and the grooves have a consistent hole shape. A method of manufacturing a composite substrate, comprising: providing a first substrate; depositing a first aluminum layer on the first substrate, a second aluminum layer on the first On the aluminum layer, and a third aluminum layer on the second aluminum layer; a first anodic treatment is performed on the third aluminum layer to oxidize the third aluminum layer to form a first aluminum oxide layer on the second on the aluminum layer; removing the first aluminum oxide layer; performing a second anodic treatment on the first aluminum layer and the second aluminum layer to oxidize the second aluminum layer, thereby forming a second aluminum oxide layer on the On the first aluminum layer, wherein the second alumina layer includes an alumina body and a plurality of holes distributed between the alumina bodies; performing a hole expansion process on the second alumina layer to enhance the second alumina uniformity of the holes in the layer; providing a second substrate; and bonding the second aluminum oxide layer and the second substrate to obtain a first composite substrate, wherein the second aluminum oxide layer is located on the first substrate and the second substrate. The method according to claim 5, wherein performing the first anodic treatment on the third aluminum layer comprises: using a first acidic solution as an electrolyte, and disposing the aluminum layer on an anode, performing an anodic oxidation reaction, to growing alumina on the second aluminum layer to form the first alumina layer. The method as claimed in claim 5, wherein the step of performing the hole-enlarging treatment on the second alumina layer comprises soaking the second alumina layer in a second acidic solution. The method according to claim 5, wherein after the step of bonding the first substrate and the second substrate, further comprising: removing the first substrate and the first aluminum layer in the first composite substrate; providing a third substrate; and bonding the second aluminum oxide layer and the third substrate to obtain a second composite substrate, wherein the second aluminum oxide layer is located between the second substrate and the third substrate. The method according to claim 5, further comprising forming a GaN epitaxial structure on the second substrate after the step of bonding the second aluminum oxide layer and the second substrate.

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