CN115799044A - AlN substrate manufacturing method, composite substrate and AlN substrate - Google Patents

Abstract

The application provides an AlN substrate manufacturing method, a composite substrate and an AlN substrate, and relates to the technical field of semiconductors. Firstly, providing a matrix substrate, depositing a first AlN layer on the basis of the surface of the matrix substrate, depositing a second AlN layer on the basis of the surface of the first AlN layer, and obtaining a wafer; and finally, stripping the host substrate from the first AlN layer to obtain the AlN substrate. The AlN substrate manufacturing method, the composite substrate and the AlN substrate have the advantages of improving the substrate peeling yield and reducing the preparation cost.

Description

AlN substrate manufacturing method, composite substrate and AlN substrate

Technical Field

The application relates to the technical field of semiconductors, in particular to an AlN substrate manufacturing method, a composite substrate and an AlN substrate.

Background

The AlN material (aluminum nitride material) has the advantages of direct band gap, high temperature and high pressure resistance, good chemical stability, high electron mobility, good thermal conductivity, high piezoelectric coefficient, strong polarization effect and the like, and has wide application prospect in new-generation photoelectric and electronic devices. Meanwhile, due to good ultraviolet transmittance and good lattice matching degree and chemical compatibility with other III-group nitrides, alN is also used as an important template substrate for preparing III-group nitride semiconductor materials. AlN substrates are one of the ideal template substrates, whether homoepitaxy of AlN material or heteroepitaxy of other group III nitrides.

However, due to the lack of commercially available low-cost large-size AlN substrates, alN materials are currently commonly grown on sapphire, silicon carbide, or silicon substrates for use as composite template substrates. However, since the composite substrate has two different materials, the lattice constant and the thermal expansion coefficient of the composite substrate have large differences, new dislocations, thermal stress and warpage are additionally introduced in the growth process, and the subsequent device preparation is seriously influenced.

Therefore, after an AlN material is grown on a sapphire, silicon carbide, or silicon substrate, the substrate and the AlN material need to be separated, but the conventional separation method has problems of low yield and high cost.

In summary, the prior art has the problems of low yield and high cost when the substrate and the AlN material are peeled off.

Disclosure of Invention

The invention aims to provide an AlN substrate manufacturing method, a composite substrate and an AlN substrate, and aims to solve the problems of low yield and high cost in the prior art when the substrate is stripped from an AlN material.

In order to achieve the above purpose, the embodiments of the present application employ the following technical solutions:

in a first aspect, an embodiment of the present application provides an AlN substrate manufacturing method, where the method includes:

providing a host substrate;

depositing a first AlN layer based on a surface of the host substrate;

depositing a second AlN layer on the basis of the surface of the first AlN layer, and obtaining a wafer; wherein the first AlN layer has a lower density than the second AlN layer;

annealing the wafer to form air holes at the interface of the host substrate and the first AlN layer;

and stripping the host substrate from the first AlN layer to obtain the AlN substrate.

Optionally, the step of depositing a first AlN layer based on the surface of the host substrate includes:

depositing a first AlN layer at a first temperature by utilizing a magnetron sputtering process;

the step of depositing a second AlN layer based on the surface of the first AlN layer includes:

depositing a second AlN layer at a second temperature using a MOCVD, HVPE, MBE, PVT, or CVT process; wherein the second temperature is higher than the first temperature.

Optionally, the step of depositing the first AlN layer at the first temperature using a magnetron sputtering process includes:

depositing a first AlN layer at a temperature of less than 900 ℃ by utilizing a magnetron sputtering process;

the step of depositing a second AlN layer at a second temperature using a MOCVD, HVPE, MBE, PVT, or CVT process comprises:

the second AlN layer is deposited using MOCVD, HVPE, MBE, PVT, or CVT processes at temperatures greater than 1000 ℃.

Optionally, the step of depositing a first AlN layer based on the surface of the host substrate includes:

depositing a first AlN layer having a thickness of 50nm or less on the basis of a surface of the host substrate;

depositing a second AlN layer on the basis of the surface of the first AlN layer, and obtaining the wafer comprises the following steps of:

depositing a second AlN layer of less than or equal to 2 μm on the basis of the surface of the first AlN layer.

Optionally, the step of annealing the wafer to form air holes at the interface of the host substrate and the first AlN layer comprises:

and (3) putting the wafer into a high-temperature annealing furnace at 1500-1900 ℃ for annealing for 30 min-12 h, wherein the protective atmosphere is at least one of nitrogen, hydrogen and carbon monoxide.

Optionally, the step of peeling the host substrate from the first AlN layer to obtain an AlN substrate includes:

depositing a third AlN layer based on a surface of the second AlN layer, such that the first AlN layer and the host substrate are self-dissociated; wherein a thickness of the third AlN layer is larger than a thickness of the second AlN layer.

Optionally, the step of peeling the host substrate from the first AlN layer to obtain an AlN substrate includes:

depositing a third AlN layer on the basis of the surface of the second AlN layer, wherein the thickness of the third AlN layer is greater than that of the second AlN layer;

the host substrate is peeled off from the first AlN layer using a laser lift-off process.

Optionally, the second AlN layer has a thickness of less than or equal to 2 μm, and the step of depositing a third AlN layer based on the surface of the second AlN layer includes:

and depositing a third AlN layer of 10-1000 mu m on the surface of the second AlN layer.

In a second aspect, embodiments of the present application further provide a composite substrate, where the composite substrate includes:

a host substrate;

a first AlN layer on a surface of the host substrate; wherein an air hole is formed at an interface of the host substrate and the first AlN layer;

and a second AlN layer on a surface of the first AlN layer, wherein the first Al layer has a lower compactness than the second AlN layer.

In a third aspect, an embodiment of the present application further provides an AlN substrate manufactured by the AlN substrate manufacturing method described above, where the AlN substrate includes:

a first AlN layer;

a second AlN layer on a surface of the AlN layer; wherein the first AlN layer has a lower density than the second AlN layer.

Compared with the prior art, the method has the following beneficial effects:

the application provides an AlN substrate manufacturing method, a composite substrate and an AlN substrate, wherein a matrix substrate is firstly provided, a first AlN layer is deposited on the basis of the surface of the matrix substrate, a second AlN layer is deposited on the basis of the surface of the first AlN layer, and a wafer is obtained; and finally, stripping the host substrate from the first AlN layer to obtain the AlN substrate. Because the air holes are formed at the interface of the matrix substrate and the first AlN layer, the contact area of the matrix substrate and the first AlN layer is reduced, and then when the matrix substrate and the first AlN layer are stripped, the stripping difficulty is reduced, the stripping yield is improved, and meanwhile, the cost is reduced.

In order to make the aforementioned objects, features and advantages of the present application comprehensible, preferred embodiments accompanied with figures are described in detail below.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and it will be apparent to those skilled in the art that other related drawings can be obtained from the drawings without inventive effort.

Fig. 1 is a schematic cross-sectional view of a prior art composite substrate.

Fig. 2 is an exemplary flowchart of an AlN substrate fabrication method provided in an embodiment of the present application.

Fig. 3 is a schematic diagram of a tem test result of the AlN substrate provided in this embodiment of the present invention after high-temperature thermal annealing to form air holes.

Fig. 4 is a schematic cross-sectional view of a composite substrate provided in an embodiment of the present application.

Fig. 5 is a schematic cross-sectional view of an AlN substrate provided in an embodiment of the present application.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. The components of the embodiments of the present application, generally described and illustrated in the figures herein, can be arranged and designed in a wide variety of different configurations.

Thus, the following detailed description of the embodiments of the present application, presented in the accompanying drawings, is not intended to limit the scope of the claimed application, but is merely representative of selected embodiments of the application. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments in the present application without making any creative effort belong to the protection scope of the present application.

It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures. Meanwhile, in the description of the present application, the terms "first", "second", and the like are used only for distinguishing the description, and are not construed as indicating or implying relative importance.

It should be noted that, in this document, relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrases "comprising a," "8230," "8230," or "comprising" does not exclude the presence of additional like elements in a process, method, article, or apparatus that comprises the element.

Some embodiments of the present application will be described in detail below with reference to the accompanying drawings. The embodiments described below and the features of the embodiments can be combined with each other without conflict.

As described in the background, in the prior art, when using AlN material as a substrate, it is common practice to grow AlN material on a sapphire, silicon carbide or silicon substrate as a composite template substrate. As illustrated in fig. 1, alN material is grown on a substrate to form a composite substrate, and then additional levels of the structure are grown using the composite substrate, i.e., the additional levels of the structure continue to grow along the surface of the AlN material.

However, since the composite substrate has two different materials, and the lattice constant and the thermal expansion coefficient of the composite substrate have large differences, new dislocations, thermal stress and warpage are additionally introduced in the growth process, which seriously affects the subsequent device preparation. Therefore, the development of a self-supporting substrate of pure AlN material is of great importance.

And when the AlN self-supporting substrate needs to be realized, the AlN material needs to be stripped from the composite template substrate. That is, based on the structure of fig. 1, the substrate and the AlN material are separated, and the remaining AlN material may be used as the AlN substrate.

The current substrate lift-off technology mainly comprises laser lift-off technology for sapphire substrates and wet etching technology for SiC and Si substrates. Due to the lack of a commercially available low-cost high-power extreme ultraviolet laser, the conventional laser stripping machine generally adopts a laser with the main wavelength of 266nm for stripping, the wavelength energy of the laser is lower than the forbidden bandwidth of an AlN material, and the laser energy absorption at the interface of the AlN and a substrate is insufficient, so that the laser stripping is difficult and the yield is too low. The wet etching technique is limited by the etching rate of the material, and the cost is high.

In summary, the conventional method has problems of low yield and high cost when the substrate and the AlN material are peeled off.

In view of this, the present application provides a method for manufacturing an AlN substrate, which reduces the peeling difficulty by forming air holes at the interface between a host substrate and an AlN material, so as to achieve the purposes of increasing the peeling yield and reducing the cost.

The following is an exemplary description of the AlN substrate fabrication method provided in the present application:

as an alternative implementation, please refer to fig. 2, the method includes:

s102, providing a host substrate.

S104, depositing a first AlN layer on the basis of the surface of the host substrate;

s106, depositing a second AlN layer on the basis of the surface of the first AlN layer, and obtaining a wafer; wherein the compactness of the first AlN layer is lower than that of the second AlN layer;

s108, annealing the wafer to form air holes at the interface of the substrate and the first AlN layer;

s110, stripping the host substrate from the first AlN layer to obtain the AlN substrate.

The host substrate can be a sapphire substrate, a silicon carbide substrate, a silicon substrate, and the like. The term "a-based surface deposition B" means that a layer B is grown on the surface of a, for example, when a first AlN layer is deposited on the base substrate surface, then a first AlN layer is grown on the growth surface of the base substrate. When a second AlN layer is deposited on the surface of the first AlN layer, this means that one side of the first AlN layer is in contact with the host substrate and the other side is in contact with the second AlN layer.

Since the first AlN layer has a lower density than the second AlN layer, and AlN undergoes lattice rearrangement at a high temperature during high-temperature annealing to form an AlN crystal having a higher density and a better crystal quality, air holes are easily formed in the first AlN layer having a lower density, and since the second AlN layer has a higher density, the air holes cannot move upward and are confined in the vicinity of the host substrate, as a result of which fig. 3 shows. Due to the combination of the plurality of air holes, air holes larger in size are finally formed, so that the contact area of the first AlN layer and the substrate becomes smaller. And then when peeling the substrate and the first AlN layer, the peeling difficulty is lower, the peeling yield is improved, and the cost is reduced.

In order to make the compactness of the first AlN layer lower than that of the second AlN layer, as one implementation, S102 includes:

a first AlN layer is deposited at a first temperature using a magnetron sputtering process.

S104 comprises the following steps:

depositing a second AlN layer at a second temperature using a MOCVD, HVPE, MBE, PVT, or CVT process; wherein the second temperature is higher than the first temperature.

A first AlN layer with low compactness is deposited on a substrate at a lower temperature by adopting a magnetron sputtering method. The first AlN layer is low in preparation temperature, and the physical deposition method is adopted, so that the transverse migration of atoms is less, and the formed first AlN layer is low in compactness. Subsequently, a second highly dense AlN layer is deposited at a high temperature by using any one of MOCVD (Metal-organic Chemical Vapor Deposition), HVPE (Hydride Vapor Phase Epitaxy), MBE (Molecular beam Epitaxy), PVT (Physical Vapor Transport), or CVT (Chemical Vapor Transport), and then the sample is subjected to high-temperature thermal annealing.

In an alternative implementation manner, the first temperature may be less than 900 ℃, the second temperature may be greater than 1000 ℃, and in practical applications, the first temperature may be selected by a user, which is not limited herein.

Further, to ensure that the first AlN layer, which is less dense, does not affect the overall performance of the AlN substrate, in one implementation, the first AlN layer has a thickness of 50nm or less and the second AlN layer has a thickness of 2 μm or less. Through the implementation mode, the first AlN layer can be ensured to be thin, air holes are formed conveniently, and the overall performance of the AlN substrate is not affected.

Wherein the high temperature annealing process is used to form air holes at an interface of the host substrate and the first AlN layer, in one implementation, the step of S108 includes:

and (3) putting the wafer into a high-temperature annealing furnace at 1500-1900 ℃ for annealing for 30 min-12 h, wherein the protective atmosphere is at least one of nitrogen, hydrogen and carbon monoxide.

The annealing time may be set according to actual conditions, for example, the annealing time may be determined by an area ratio of the air holes in the actual annealing process, which is equal to an area of the air holes at an interface area of the first AlN layer and the host substrate. Preferably, the area of the air holes is more than 20% after the high temperature annealing process.

In peeling the host substrate from the first AlN layer, the present application provides two peeling processes, S110 including, as one implementation:

depositing a third AlN layer based on the surface of the second AlN layer, such that the first AlN layer and the host substrate are self-dissociated; wherein the thickness of the third AlN layer is greater than the thickness of the second AlN layer.

In this implementation, the first AlN layer and the host substrate may be separated by self-dissociation, and referring to fig. 4, by depositing a third AlN layer with a greater thickness on the surface of the second AlN layer, sufficient stress may be generated to cause self-dissociation of the first AlN layer and the host substrate to form a self-supporting substrate of pure AlN.

In this embodiment, the process of depositing the third AlN layer is the same as the process of depositing the second AlN layer, and the thicknesses of the third AlN layer and the second AlN layer are different. And, in one implementation, the third AlN layer has a thickness of 10 to 1000 μm.

As another implementation, S110 includes:

depositing a third AlN layer on the basis of the surface of the second AlN layer, wherein the thickness of the third AlN layer is larger than that of the second AlN layer.

The host substrate is stripped from the first AlN layer using a laser lift-off process.

That is, in embodiments, the host substrate may also be stripped from the first AlN layer in a laser process after the third AlN layer is deposited. It should be noted that, due to the existence of the air holes, the light at the interface is reflected for multiple times, so that the laser energy is gathered, the peeling difficulty is reduced, and the yield is improved.

In practical applications, the applicant fabricated AlN substrates under the following different conditions, respectively:

example 1

(1) Depositing a first AlN layer with the thickness of 30nm on the sapphire substrate at 650 ℃ by adopting a magnetron sputtering method;

(2) Continuously depositing a second AlN layer with the thickness of 400nm on the first AlN layer by MOCVD, wherein the deposition temperature is 1250 ℃;

(3) Placing the sample in a high-temperature annealing furnace, and annealing for 1 hour at 1700 ℃ in a nitrogen atmosphere to form air holes, wherein the duty ratio of the area of the air holes is 40%;

(4) And depositing a third AlN layer with the thickness of 500 mu m at 1400 ℃ by using HVPE, and performing self-dissociation between the first AlN layer and the substrate due to the action of stress to obtain the AlN self-supporting substrate.

Example 2

(1) Depositing a first AlN layer with the thickness of 50nm on the sapphire substrate at 500 ℃ by adopting a magnetron sputtering method;

(2) Continuously depositing a second AlN layer with the thickness of 300nm on the first AlN layer by MOCVD, wherein the deposition temperature is 1250 ℃;

(3) Placing the sample in a high-temperature annealing furnace, and annealing for 3 hours at 1700 ℃ in a nitrogen atmosphere to form air holes with the duty ratio of the area of the holes being 50%;

(4) Depositing a third AlN layer with a thickness of 10 μm at 1200 ℃ by MOCVD;

(5) Continuing to deposit a fourth AlN layer with the thickness of 300 mu m at 1450 ℃ by adopting HVPE;

(6) And stripping the substrate by adopting a laser stripping method to obtain the AlN self-supporting substrate.

Example 3

(1) Depositing a first AlN layer with the thickness of 20nm on the silicon substrate at the temperature of 600 ℃ by adopting a magnetron sputtering method;

(2) Continuously depositing an AlN layer with the thickness of 400nm on the first AlN layer by MOCVD, wherein the deposition temperature is 1250 ℃;

(3) Placing the sample in a high-temperature annealing furnace, and annealing for 1 hour at 1500 ℃ in a nitrogen atmosphere to form air holes, wherein the area duty ratio of the air holes is 30%;

(4) And depositing a third AlN layer with the thickness of 600 mu m at 1400 ℃ by using HVPE, and performing self-dissociation between the first AlN layer and the substrate due to the action of stress to obtain the AlN self-supporting substrate.

Example 4

(1) Depositing a first AlN layer with the thickness of 40nm on the silicon carbide substrate at 700 ℃ by adopting a magnetron sputtering method;

(2) Continuously depositing an AlN layer with the thickness of 200nm on the first AlN layer by adopting MBE, wherein the deposition temperature is 1000 ℃;

(3) Placing the sample in a high-temperature annealing furnace, and annealing for 1 hour at 1650 ℃ in a nitrogen atmosphere to form air holes with the duty ratio of the area of the holes being 20%;

(4) And depositing a third AlN layer with the thickness of 800 mu m at 1450 ℃ by adopting HVPE, and performing self-dissociation between the first AlN layer and the substrate under the action of stress to obtain the AlN self-supporting substrate.

Based on the foregoing implementation, the present application further provides a composite substrate, please refer to fig. 4, where the composite substrate includes:

providing a host substrate; a first AlN layer provided on a surface of the host substrate; wherein, an air hole is formed at the interface of the substrate and the first AlN layer; and a second AlN layer on a surface of the first AlN layer, wherein the first AlN layer has a lower compactness than the second AlN layer.

Referring to fig. 5, the present application further provides an AlN substrate fabricated by the method for fabricating an AlN substrate, including:

a first AlN layer; a second AlN layer on a surface of the AlN layer; wherein the first AlN layer has a lower density than the second AlN layer.

In summary, the present application provides an AlN substrate manufacturing method, a composite substrate, and an AlN substrate, wherein a host substrate is provided first, then a first AlN layer is deposited on the basis of the surface of the host substrate, and then a second AlN layer is deposited on the basis of the surface of the first AlN layer, and a wafer is obtained; and finally, stripping the matrix substrate from the first AlN layer to obtain the AlN substrate. According to the method, the air holes are formed in the interface between the host substrate and the first AlN layer, so that the contact area between the host substrate and the first AlN layer is reduced, the stripping difficulty is reduced when the host substrate is stripped from the first AlN layer, the stripping yield is improved, and the cost is reduced.

The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made to the present application by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

It will be evident to those skilled in the art that the application is not limited to the details of the foregoing illustrative embodiments, and that the present application may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the application being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.

Claims (10)

1. A method for manufacturing an AlN substrate, the method comprising:

providing a host substrate;

depositing a first AlN layer based on a surface of the host substrate;

depositing a second AlN layer on the basis of the surface of the first AlN layer, and obtaining a wafer; wherein the first AlN layer has a lower density than the second AlN layer;

annealing the wafer to form air holes at the interface of the host substrate and the first AlN layer;

and stripping the host substrate from the first AlN layer to obtain an AlN substrate.

2. The AlN substrate fabrication method of claim 1, wherein the step of depositing a first AlN layer based on the surface of the host substrate includes:

depositing a first AlN layer at a first temperature by utilizing a magnetron sputtering process;

the step of depositing a second AlN layer based on the surface of the first AlN layer includes:

depositing a second AlN layer at a second temperature using a MOCVD, HVPE, MBE, PVT, or CVT process; wherein the second temperature is higher than the first temperature.

3. The AlN substrate fabrication method of claim 2, wherein the step of depositing the first AlN layer at the first temperature using a magnetron sputtering process includes:

depositing a first AlN layer at a temperature of less than 900 ℃ by utilizing a magnetron sputtering process;

the step of depositing a second AlN layer at a second temperature using a MOCVD, HVPE, MBE, PVT, or CVT process comprises:

the second AlN layer is deposited using MOCVD, HVPE, MBE, PVT, or CVT processes at temperatures greater than 1000 ℃.

4. The AlN substrate fabrication method of claim 1, wherein the step of depositing a first AlN layer based on the surface of the host substrate includes:

depositing a first AlN layer having a thickness of 50nm or less on the basis of a surface of the host substrate;

depositing a second AlN layer on the basis of the surface of the first AlN layer, and obtaining the wafer comprises the following steps of:

depositing a second AlN layer of less than or equal to 2 μm on the basis of the surface of the first AlN layer.

5. The AlN substrate fabrication method of claim 1, wherein the step of annealing the wafer to form air voids at an interface of the host substrate and the first AlN layer includes:

and (3) putting the wafer into a high-temperature annealing furnace at 1500-1900 ℃ for annealing for 30 min-12 h, wherein the protective atmosphere is at least one of nitrogen, hydrogen and carbon monoxide.

6. The AlN substrate fabrication method of claim 1, wherein the step of peeling the host substrate from the first AlN layer to obtain an AlN substrate includes:

depositing a third AlN layer based on a surface of the second AlN layer, such that the first AlN layer and the host substrate are self-dissociated; wherein a thickness of the third AlN layer is greater than a thickness of the second AlN layer.

7. The AlN substrate fabrication method of claim 1, wherein the step of peeling the host substrate from the first AlN layer to obtain an AlN substrate includes:

depositing a third AlN layer on the basis of the surface of the second AlN layer, wherein the thickness of the third AlN layer is greater than that of the second AlN layer;

the host substrate is delaminated from the first AlN layer using a laser delamination process.

8. The AlN substrate manufacturing method of claim 6 or 7, wherein the second AlN layer has a thickness of 2 μm or less, and the step of depositing a third AlN layer based on the surface of the second AlN layer includes:

depositing a third AlN layer of 10 to 1000 μm on the surface of the second AlN layer.

9. A composite substrate, comprising:

a host substrate;

a first AlN layer on a surface of the host substrate; wherein an air hole is formed at an interface of the host substrate and the first AlN layer;

a second AlN layer on a surface of the first AlN layer, wherein the first AlN layer has a lower compactness than the second AlN layer.

10. An AlN substrate manufactured by the AlN substrate manufacturing method according to any one of claims 1 to 8, the AlN substrate including:

a first AlN layer;

a second AlN layer on a surface of the AlN layer; wherein the first AlN layer has a lower density than the second AlN layer.

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