TWI792550B - Method of manufacturing a composite substrate - Google Patents

Abstract

A method of manufacturing a composite substrate is provided in some embodiments of the present disclosure, including: forming a barrier layer on a gallium nitride epitaxial structure of an epitaxial substrate, in which the epitaxial substrate includes a base material and the gallium nitride epitaxial structure, and the gallium nitride epitaxial structure is disposed on a first surface of the base material; forming a diamond layer below a second surface opposite to the first surface of the base material; and removing the barrier layer, obtaining the composite substrate, in which the composite substrate includes the diamond layer, the base material and the epitaxial substrate from bottom to top.

Description

Method of manufacturing composite substrate

The present disclosure relates to methods of making composite substrates.

Recently, there has been an increasing demand for downsizing GaN microwave power components and increasing output power. However, with the increase in the density of power components (such as high-frequency components containing gallium nitride epitaxial structures), the heat accumulation of the components increases rapidly, reducing the performance of the components, which seriously challenges the reliability and stability of the components. It becomes the limit to increase the power of power components.

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

An object of an embodiment of the present disclosure is to provide a method for manufacturing a composite substrate, comprising: forming a barrier layer on the GaN epitaxial structure of the epitaxial substrate, wherein the epitaxial substrate includes a substrate and a GaN epitaxial structure. crystal structure, the gallium nitride epitaxial structure is disposed on the first surface of the substrate; forming a diamond layer under the second surface of the substrate opposite to the first surface; and removing the barrier layer to obtain a composite substrate, wherein the composite substrate The diamond layer, substrate and GaN epitaxial structure are sequentially included from bottom to top.

In some embodiments, the substrate includes a silicon substrate, a silicon-on-insulator substrate, a sapphire substrate, or a silicon carbide substrate.

In some embodiments, before the step of forming the barrier layer on the GaN epitaxial structure of the epitaxial substrate, the step of thinning the substrate is further included.

In some embodiments, the step of thinning the substrate comprises: using a Taiko lapping technique to thin the substrate.

In some embodiments, the step of forming a barrier layer on the GaN epitaxial structure of the epitaxial substrate includes: coating a glass photoresist material on the GaN epitaxial structure; and heating the glass photoresist material, so that The glass photoresist material is sintered and hardened to form a barrier layer on the GaN epitaxial structure.

In some embodiments, the step of forming the diamond layer under the second surface of the substrate relative to the first surface comprises: providing a plurality of diamond particles in an organic solution; placing the epitaxial substrate formed with the barrier layer into the organic solution ; In an organic solution, ultrasonic treatment is performed on the epitaxial substrate, so that diamond particles are embedded under the second surface of the substrate to form a nucleation layer under the second surface of the substrate; and performing on the second surface of the substrate The diamond growth process is used to form a diamond layer under the second surface of the substrate, wherein the diamond layer includes a nucleation layer.

In some embodiments, the step of performing a diamond growth process on the second surface of the substrate includes: injecting a reactive gas to grow the diamond layer to form the diamond layer under the second surface of the substrate, wherein the reactive gas includes methane and hydrogen.

In some embodiments, the reaction gas further comprises chlorine, methyl chloride and a combination of the aforementioned materials.

In some embodiments, the weight percentage of methane ranges from 1% to 16% based on 100% weight percentage of the sum of the reaction gases.

In some embodiments, the step of growing the diamond layer by introducing the reaction gas includes the step of growing the diamond layer at a temperature lower than 850°C.

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 represent 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.

As used herein, "about" generally means within about 20 percent, preferably within about 10 percent, and more preferably within about 5 percent of the error or range of the value of the index . If there is no explicit statement in the text, the values mentioned are regarded as approximate values, that is, the error or range indicated by "approximately".

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

First, as shown in FIG. 1A , an epitaxial substrate 110 is provided. The epitaxial substrate 110 includes a substrate 112 and a GaN epitaxial structure 114 is disposed on the first surface 112A of the substrate 112 .

In some embodiments, the substrate 112 includes a silicon substrate, a silicon-on-insulator (SOI) substrate, a sapphire substrate, or a silicon carbide substrate. In some embodiments, the thickness of the substrate 112 is in the range of 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, the lattice orientation of the substrate 112 comprises <111>, <100>, <110>, or a combination thereof. It is worth noting that if it is desired to form the GaN epitaxial structure 114 on the substrate 112, the substrate 112 adopts a suitable lattice orientation, which can achieve better lattice matching, avoid defects, and improve epitaxial growth. For example, the lattice orientation of silicon substrate and SOI substrate is <111>, the lattice orientation of silicon carbide is <11-20>, and the lattice orientation of sapphire substrate is <0001>.

In some embodiments, metal-organic chemical vapor deposition (Metal-organic Chemical Vapor Deposition; MOCVD) can be used to form a gallium nitride epitaxial structure with a thickness of 1 to 10 microns on the first surface 112A of the substrate 112 114 (High electron mobility transistor (HEMT)). In some embodiments, the gallium nitride epitaxial structure 114 sequentially includes a seed layer disposed on the substrate 112, a buffer layer disposed on the seed layer, a resistive layer disposed on the buffer layer, a channel layer disposed on the resistive layer, a barrier A layer is disposed on the channel layer and a cover layer is disposed on the barrier layer. In some embodiments, the seed 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, combinations of the foregoing, such as ladder AlGaN or superlattice AlGaN/GaN, with a thickness of 300 nm to between 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, after forming the GaN epitaxial structure 114 , the gate and the source/drain are disposed on the GaN epitaxial structure 114 subsequently.

Next, as shown in FIG. 1B , the substrate 112 is thinned to reduce the on-resistance and thermal resistance of the HEMT, and improve the efficiency of the transistor.

In some embodiments, a protective film (such as a blue film (for example, pyrolytic glue or ultraviolet glue) can be pasted on the surface 114A of the gallium nitride epitaxial structure 114 with a thickness of 100 microns to 200 microns. , not shown in the figure) to protect the GaN epitaxial structure 114 . Next, mechanical thinning is performed from the side of the second surface 112B of the substrate 112 to reduce the thickness of the substrate 112 to 65 microns to 125 microns, and then remove the protective film. For example, please refer back to FIG. 1A, the inner region R1 of the substrate 112 can be thinned by using taiko grinding technology, and the peripheral region R2 is reserved, and the second surface 112B side of the substrate 112 after thinning will form The outer thick and inner thin structure (not shown in Figure 1B) concave from the outside to the inside, this structure will be beneficial to overcome the thin substrate 112 and GaN epitaxial structure 114 caused by thinning the substrate 112, and the stress is easy The phenomenon of warping due to excessive accumulation.

Next, please refer to FIG. 1C , a barrier layer 120 is formed on the GaN epitaxial structure 114 for protecting the GaN epitaxial structure 114 in subsequent processes.

In some embodiments, the material of the barrier layer 120 is easy to install and remove, can protect the gallium nitride epitaxial structure 114 from the impact damage of the diamond particles in the ultrasonic environment, and can withstand high temperature (for example, can withstand chemical vapor phase Deposition temperature (for example, at least 400 ° C above)). For example, the barrier layer 120 can be a glass photoresist.

Specifically, the step of forming the barrier layer 120 on the GaN epitaxial structure 114 includes coating a glass photoresist material on the GaN epitaxial structure 114; and heating the glass photoresist material (for example, 500 ° C to 700°C), the glass photoresist material is sintered and hardened to form a barrier layer 120 on the GaN epitaxial structure 114 . In some embodiments, the barrier layer 120 covers only the surface 114A of the GaN epitaxial structure 114 . In some embodiments, in addition to covering the surface 114A of the GaN epitaxial structure 114 , the barrier layer 120 may also extend to cover the sidewall 114S of the GaN epitaxial structure 114 to improve the protection of the GaN epitaxial structure 114 effect (not shown). In some embodiments, the thickness of the barrier layer 120 may range from 50 microns to 100 microns (eg, 50 microns, 60 microns, 70 microns, 80 microns, 90 microns, 100 microns, or a value in any of the aforementioned intervals). It is worth noting that the barrier layer 120 is not only used for protection, but also serves as a temporary substrate to support the epitaxial substrate 110 to prevent the epitaxial substrate 110 from being too thin and warped.

Next, as shown in FIG. 1D, a nucleation layer 132 is formed under the second surface 112B of the substrate 112 to provide sufficient density of nucleation crystal grains in advance for the subsequent diamond layer to be grown, so as to enhance the subsequent diamond layer to be grown The continuity (that is, the degree of connection and extension between adjacent grains). In some embodiments, the step of forming the nucleation layer 132 under the second surface 112B of the substrate 112 includes: providing a plurality of diamond particles P in an organic solution (such as acetone); forming the epitaxial substrate with the barrier layer 120 110 is placed in an organic solution; in the organic solution, the epitaxial substrate 110 is subjected to ultrasonic treatment, so that diamond particles P are embedded under the second surface 112B of the substrate 112 to form a nucleation layer 132 on the second surface of the substrate 112 under surface 112B. In some embodiments, placing the epitaxial substrate 110 formed with the barrier layer 120 into the organic solution includes immersing the entire epitaxial substrate 110 formed with the barrier layer 120 into the organic solution, that is, the barrier layer 120 and the epitaxial substrate 110 The epitaxial substrates 110 are all immersed in the organic solution. Compared with only immersing the second surface 112B of the epitaxial substrate 110 in the organic solution, a better embedding effect of the diamond particles P can be achieved. In some embodiments, parameters such as the frequency of the ultrasonic wave and the density of the diamond particles P in the organic solution can be adjusted, so as to realize the desired density of the diamond particles P in the nucleation layer 132, for example, the diamond particle P density in the nucleation layer 132 When the particle P density is greater than 10 ¹⁰ per square centimeter, the continuity of the subsequently formed diamond layer can be improved.

Next, see FIG. 1E (and refer to FIG. 1D at the same time), using the nucleation layer 132 as a seed layer, a diamond growth process is performed on the second surface 112B of the substrate 112 to form a diamond layer 130 on the second surface 112B of the substrate 112. Under the two surfaces 112B, and after the diamond layer 130 is formed, the original nucleation layer 132 will exist as a part of the diamond layer 130 (not shown).

In some embodiments, the step of performing the diamond growth process on the second surface 112B of the substrate 112 includes: growing the diamond layer 130 by introducing a reactive gas comprising methane and hydrogen to form the diamond layer 130 on the second surface of the substrate 112 112B under. Specifically, chemical vapor deposition (Chemical Vapor Disposition; CVD) can be carried out under negative pressure (such as a pressure of 1x10 ^-3 Torr), 400°C to 850°C (such as 400°C, 450°C, 500° C, 550°C, 600°C, 650°C, 700°C, 800°C, 850°C, or a value in any of the preceding intervals), and a temperature range of 1% to 16% (such as 1%, 2% , 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16% or any value in the aforementioned range) The diamond layer 130 is grown within the range of the methane concentration (here the concentration unit is weight percentage, and the weight percentage of the total reaction gas is 100%).

It is worth noting that the smaller the grain size, the smaller the roughness of the surface 130B of the diamond layer 130 and the better the heat dissipation effect. In some embodiments, the grain size and growth rate of the diamond layer 130 can be controlled by adjusting parameters such as the type of reaction gas, the concentration of the reaction gas, and the temperature.

Regarding the control of the grain size, the grain size can be controlled by adjusting the concentration of the reaction gas. For example, under the condition that the working gases are methane and hydrogen, and the temperature is kept constant, as the concentration of methane increases from 8% to 16%, the grain size will decrease from about 20 nm to about 14 nm. As the methane concentration continues to increase (for example, to 20%), the grain size will still be maintained at about 14 nanometers and will not continue to decrease. Therefore, the methane concentration of 16% is the lowest methane concentration that can obtain the smallest grain size. With this concentration, the smallest grain size can be obtained at the lowest reaction cost. Therefore, the relationship between the concentration of the reaction gas and the grain size is not completely positive or negative, and an appropriate concentration can be selected through actual testing to obtain the desired grain size.

In some embodiments, the grain size can also be reduced by lowering the temperature. For example, under the condition of using methane and hydrogen as the reaction gas, when the temperature is controlled at 750°C, a grain size of about 15.5 nm can be obtained, and when the temperature drops to 650°C, the grain size drops to It is about 14.5 nm, and when the temperature further drops to 550° C., the grain size drops to about 6 nm to about 7 nm.

In some embodiments, the range of grain size can be controlled between 9 nm and 50 nm, such as 9 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm Nanometer, 40nm, 45nm, 50nm, or any value in the aforementioned range.

, for the control of the growth rate, the growth rate can also be regulated by regulating the methane concentration. It should be noted that, under different concentration ranges of methane, the trend of growth rate will change. When the methane concentration is less than 3.5%, the growth rate increases as the methane concentration increases. For example, when the methane concentration is 1.5%, the growth rate is about 0.25 μm/hour, and when the methane concentration increases to 3.5%, the growth rate increases to about 2.0 μm /Hour. However, when the methane concentration is greater than 3.5%, the growth rate will decrease as the methane concentration increases. For example, when the methane concentration is 4.5%, the growth rate will decrease to about 1.5 μm/hour. In some embodiments, the range of growth rate can be controlled at 0.25 micron/hour, 0.5 micron/hour, 0.5 micron/hour, 1 micron/hour, 1.5 micron/hour, 1.8 micron/hour, 2 micron/hour, 2.5 micron/hour Hours or any value in the preceding range.

In some embodiments, in order to increase the growth rate, the reaction gas may further include methyl chloride (CH _x Cl _y , where 1≦x≦2, 2≦y≦3), chlorine (C1 ₂ ) and a combination of the aforementioned materials. The principle that the -Cl bond is weaker than the CH bond can generate a higher concentration of carbon-containing free radicals under gas-phase conditions. At the same time, chlorine atoms can also accelerate the hydrogen abstraction reaction (hydrogen abstraction), and jointly enhance the diamond layer 130 nucleation density, thereby increasing the growth rate. Thereby, the diamond layer 130 with a smaller grain size can be obtained at a lower reaction temperature (generally speaking, the lower the temperature, the slower the growth rate), while maintaining or even increasing the diamond growth rate. For example, when the reaction gas further includes methyl chloride and chlorine, the growth temperature of the diamond layer 130 only needs to be in the range of 400°C to 600°C (400°C, 450°C, 500°C, 550°C , 600°C or any combination of the foregoing), the reaction gas can be only methane and hydrogen, and when the reaction temperature is 850°C, the reaction rate achieved (for example, maintain a growth rate of 0.8 μm/hour to 1.8 μm/hour between), while obtaining a smaller grain size.

In some embodiments, the thickness of the diamond layer 130 ranges from 1 micron to 40 microns, for example 1 micron, 5 microns, 10 microns, 15 microns, 20 microns, 25 microns, 30 microns, 35 microns, 40 microns , or a value in any of the aforementioned intervals.

In some alternative implementations, the diamond layer 130 can also be formed directly under the second surface 112B of the substrate 112 by CVD, without the step of pre-forming the core layer 132 through the ultrasonic treatment referring to FIG. 1D .

Next, as shown in FIG. 1F , the barrier layer 120 is removed to obtain a composite substrate 100 , which sequentially includes a diamond layer 130 , a substrate 112 and a GaN epitaxial structure 114 from bottom to top. In some embodiments, the thickness of the composite substrate 100 ranges from 67 microns to 175 microns, for example, 67 microns, 80 microns, 90 microns, 100 microns, 125 microns, 150 microns, 175 microns or any value in the aforementioned range.

The composite substrate 100 provided in some embodiments of the present disclosure adopts a design in which the diamond layer 130 is disposed under the second surface 112B of the substrate 112, and utilizes the high thermal conductivity (2000 watts/meter·degree (W /m·K)) principle (in comparison, the thermal conductivity of silicon is only 150 W/m·degree, and the thermal conductivity of GaN is only 130 W/m·degree), as the epitaxial substrate 110 The heat dissipation substrate improves the heat dissipation efficiency of the composite substrate 100, improves the problem of heat accumulation caused by the epitaxial substrate 110 or the components (such as the source) carried on it, and can be used as a way to improve the power density and high power characteristics of the components. .

In addition, compared with the conventional heat dissipation technology of bonding the heat dissipation substrate and substrate through bonding technology, the present disclosure avoids performing the bonding process by directly growing the diamond layer 130 under the substrate 112, and at the same time eliminates the need for bonding on the bond. The thinning of the heat dissipation substrate and the steps of separately oxidizing the heat dissipation substrate and the base material before the bonding process can not only simplify the manufacturing process, but also avoid the problem of damage to the base material 112 due to excessive stress accumulation in the bonding-related steps. .

To sum up, some embodiments of the present disclosure provide a method for manufacturing a composite substrate, directly forming a diamond layer on the base material as a heat dissipation substrate, and utilizing the high thermal conductivity of diamond to improve the heat dissipation efficiency of the composite substrate. In addition, the design of directly forming the diamond layer on the substrate can avoid the cumbersome steps required for bonding the heat dissipation substrate and the substrate, as well as the problem that the substrate may be damaged during the bonding process, and improve the process efficiency and composite substrate. yield.

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: composite substrate 110: Epitaxy substrate 112: Substrate 114: Gallium Nitride Epitaxial Structure 120: barrier layer 130: diamond layer 132: Nucleation layer 112A: first surface 112B: second surface 114A, 130B: surface 114S: side wall P: diamond particles R1, R2: area

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

100: composite substrate

110: Epitaxy substrate

112: Substrate

114: Gallium Nitride Epitaxial Structure

130: diamond layer

112B: second surface

Claims (9)

A method for manufacturing a composite substrate, comprising: coating a glass photoresist material on a gallium nitride epitaxial structure of an epitaxial substrate, wherein the epitaxial substrate includes a substrate and the gallium nitride epitaxial structure, the The GaN epitaxial structure is disposed on a first surface of the base material; the glass photoresist material is heated to sinter and harden the glass photoresist material, and a barrier layer is formed on the GaN epitaxial structure; A diamond layer is under a second surface of the substrate relative to the first surface; and the barrier layer is removed to obtain a composite substrate, wherein the composite substrate comprises the diamond layer, the substrate in sequence from bottom to top material and the gallium nitride epitaxial structure. The method according to claim 1, wherein the substrate comprises a silicon substrate, a silicon-on-insulator substrate, a sapphire substrate, or a silicon carbide substrate. The method according to claim 1, further comprising a step of thinning the substrate before the step of forming the barrier layer on the GaN epitaxial structure of the epitaxial substrate. The method as claimed in claim 3, wherein the step of thinning the substrate comprises: using a Taiko lapping technique to thin the substrate. The method as claimed in claim 1, wherein the diamond layer is formed The steps on the second surface of the substrate opposite to the first surface include: providing a plurality of diamond particles in an organic solution; placing the epitaxial substrate formed with the barrier layer into the organic solution; In the organic solution, the epitaxial substrate is subjected to an ultrasonic treatment, so that the diamond particles are embedded under the second surface of the substrate to form a nucleation layer under the second surface of the substrate; and A diamond growth process is performed on the second surface of the substrate to form the diamond layer under the second surface of the substrate, wherein the diamond layer includes the nucleation layer. The method as claimed in item 5, wherein the step of performing the diamond growth process on the second surface of the substrate comprises: feeding a reaction gas to grow the diamond layer, so as to form the diamond layer on the first surface of the substrate Two subsurfaces, wherein the reactive gas comprises methane and hydrogen. The method as claimed in item 6, wherein the reaction gas further comprises a combination of chlorine gas and methyl chloride. The method as claimed in item 6, wherein the weight percentage of the total reaction gas is 100%, and the weight percentage of methane is 1% to 16%. The method as claimed in item 6, wherein the step of feeding the reaction gas to grow the diamond layer comprises growing at a temperature lower than 850°C The diamond layer steps.

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