CN115985762A

CN115985762A - GaN epitaxial layer stripping structure, preparation method and stripping method

Info

Publication number: CN115985762A
Application number: CN202310158889.5A
Authority: CN
Inventors: 李京波; 钱昊; 汪禹; 王小周
Original assignee: Zhejiang Xinke Semiconductor Co Ltd
Current assignee: Zhejiang Xinke Semiconductor Co Ltd
Priority date: 2023-02-17
Filing date: 2023-02-17
Publication date: 2023-04-18

Abstract

The application discloses a GaN epitaxial layer stripping structure, a preparation method and a stripping method, wherein the GaN epitaxial layer stripping structure comprises a substrate, an etching layer set and a GaN stripping layer which are sequentially arranged from bottom to top, the etching layer set comprises an AlGaN buffer layer, an n-GaN layer, a u-GaN layer and a GaN sacrificial layer which are sequentially arranged from bottom to top, and the etching layer set is provided with a groove set penetrating through the etching layer set. This application sculpture bed course exists and runs through the slot group of whole sculpture bed course, when carrying out electrochemistry at follow-up and peeling off, solution gets into behind the empty slot group, fully contacts with the sculpture bed course, and the sculpture can be gone on to the centre along the cavity region, and the required distance of sculpture significantly reduces, has promoted the chemical reaction efficiency when peeling off by a wide margin.

Description

GaN epitaxial layer stripping structure, preparation method and stripping method

Technical Field

The invention relates to the field of semiconductors, in particular to a GaN epitaxial layer stripping structure, a preparation method and a stripping method.

Background

Because gallium nitride (GaN) has the characteristics of wide band gap, high temperature resistance, radiation resistance, high critical breakdown field and the like, the gallium nitride (GaN) is very beneficial to power electronic devices such as Light Emitting Diodes (LEDs), field Effect Transistors (FETs), schottky diodes (SBDs) and the like, and gallium nitride (GaN) and related semiconductor alloys (such as AlGaN, inGaN and the like) thereof become promising materials suitable for high-power high-frequency electronic devices. However, due to the lack of a native substrate, group iii nitrides are typically grown on foreign substrates such as sapphire, silicon carbide, and the like. However, due to lattice mismatch and thermal expansion mismatch between the substrate and the epitaxial layer, the dislocation density of devices on foreign substrates is much higher than devices fabricated on native substrates. Therefore, the self-supporting GaN substrate is an effective way to improve the quality of the epitaxial layer and the device performance.

Currently, a separate GaN substrate can be prepared by separating a sapphire substrate using a laser lift-off method. The method utilizes high-power ultraviolet laser to separate the GaN at the interface of the sapphire and the GaN, the cost is very high, the GaN is cracked due to high temperature, and the method is not suitable for separation on SiC and Si;

electrochemical lift-off is a technique that utilizes lateral etching and can be used to separate the GaN epitaxial layer from the substrate regardless of the type of substrate. At present, most methods for separating a substrate from an epitaxial layer by an electrochemical technology are sacrificial layers with micron-level thickness etched from bottom to top by positive electrodes, the completely hollowed area is extremely small, the surface appearance of etched GaN is poor, and the separated substrate has no practical value; in addition, the mismatch stress of the heterogeneous substrate and the GaN can be utilized to realize large-area self-separation in the annealing process, but the method is only suitable for the heterogeneous substrate, the process is complex, the uncontrollable factors are more, and the GaN is easy to crack due to the stress mismatch in the annealing process.

The existing electrochemical wet stripping only stops on the separation of small-sized GaN, and Ga + generated by reaction in an etching channel, unreacted GaN fragments and nitrogen gas can block the reaction and even stop the etching when the GaN is etched. The current solution is mainly to increase the thickness of the sacrificial layer (about 100 μm or more) to increase the etching channel, however, the thick sacrificial layer greatly increases the industrial cost and is not suitable for commercialization. How to realize the separation of large-area GaN epitaxial layers of 2 inches and more is still a technical problem to be solved urgently in the industry.

Disclosure of Invention

The invention provides a GaN epitaxial layer stripping structure, a preparation method and a stripping method aiming at the problems.

The technical scheme adopted by the invention is as follows:

a GaN epitaxial layer stripping structure comprises a substrate, an etching layer group and a GaN stripping layer which are sequentially arranged from bottom to top, wherein the etching layer group comprises an AlGaN buffer layer, an n-GaN layer, a u-GaN layer and a GaN sacrificial layer which are sequentially arranged from bottom to top, and the etching layer group is provided with a groove group which penetrates through the etching layer group.

This application etching layer group exists and runs through whole etching layer group's slot group, when follow-up carrying out the electrochemistry and peeling off, solution gets into behind the hollow slot group, fully contacts with etching layer group, and the sculpture can be gone on to the centre along the cavity region, and the required distance of sculpture significantly reduces, has promoted the chemical reaction efficiency when peeling off by a wide margin.

In practical application, the sacrificial layer with the thickness of several micrometers can be used for peeling off the whole GaN epitaxial wafer with the size of 2 inches, so that the sacrificial layer with the thickness of hundreds of micrometers is prevented from being epitaxial, and the peeling efficiency is improved.

In the present application, the GaN sacrificial layer is an n + -GaN layer. In practice, the substrate is preferably Al ₂ O ₃ (sapphire), gaN, siC, si, or the like may be used.

In one embodiment of the present invention, the groove set includes a plurality of first grooves distributed in parallel and at intervals.

In one embodiment of the present invention, the width of the first trench is 1.5 μm to 3.5 μm, and the distance between two adjacent first trenches is 5 μm to 12 μm.

The design of the groove group can greatly reduce the etching distance.

In an embodiment of the invention, the groove set includes a plurality of first grooves distributed in parallel and at intervals and a plurality of second grooves distributed in parallel and at intervals, and the first grooves are perpendicular to the second grooves.

In one embodiment of the present invention, the width of the first trench is 1.5 μm to 3.5 μm, and the distance between two adjacent first trenches is 5 μm to 12 μm; the width of the second grooves is 1.5-3.5 μm, and the distance between two adjacent second grooves is 5-12 μm.

In one embodiment of the present invention, the AlGaN buffer layer has a thickness of 20 to 30nm; the thickness of the n-GaN layer is 1-2 mu m; the thickness of the u-GaN layer is 0.3-0.7 mu m; the thickness of the GaN sacrificial layer is 1-4 mu m.

The application also discloses a preparation method of the GaN epitaxial layer stripping structure, which comprises the following steps:

s1, growing an AlGaN buffer layer on a substrate;

the method specifically comprises the following steps: firstly, introducing hydrogen into an MOCVD reaction chamber, and carrying out heat treatment on the substrate at the temperature of 1000-1150 ℃ for 5-8 min; then reducing the temperature to 550-650 ℃, growing AlGaN buffer layers with the thickness of 20-30 nm at the growth pressure of 50-200mbar, wherein the Al source, the Ga source and the N source are respectively TMAl, TMGa and NH ₃ 。

S2, sequentially extending an n-GaN layer, a u-GaN layer and a GaN sacrificial layer on the AlGaN buffer layer in an epitaxial manner, and forming an etching layer group on the AlGaN buffer layer, the n-GaN layer, the u-GaN layer and the GaN sacrificial layer;

the method comprises the following specific steps: heating to 1050-1150 ℃, sequentially extending an n-GaN layer, a u-GaN layer and a sacrificial layer (n < + > -GaN layer) on the AlGaN buffer layer, wherein the thickness of the n-GaN layer is 1.5um, the thickness of the u-GaN layer is 0.5um, the thickness of the sacrificial layer is 1-4 mu m, and SiH is used ₄ As a doping source.

S3, preparing a patterned substrate through photoetching and ICP etching, and etching a groove group on the etching layer group, wherein the grooves of the groove group extend to the surface of the substrate;

and S4, growing a GaN stripping layer on the etching layer group in a secondary epitaxial mode, wherein the GaN stripping layer covers the groove group.

The characteristic that the bonding energy of the etched pattern region is different from that of the surface of the sacrificial layer is utilized, the set epitaxial condition is used, so that the epitaxy only occurs in the GaN region, then the lateral growth of the GaN is utilized to completely cover the pattern etching region, and a pattern-free complete high-quality GaN stripping layer is obtained. Epitaxial back slot group continues to exist, and when follow-up electrochemistry was peeled off, solution got into among the cavity, fully contacted with the sculpture region, and the sculpture can go on to the figure middle along the cavity region, and the required distance of sculpture significantly reduces, has promoted the chemical reaction efficiency when peeling off by a wide margin, only needs epitaxial sacrificial layer about 2um to be used for the whole piece of 2 cun's of size to peel off, has avoided epitaxial hundreds of microns sacrificial layer, has promoted peeling efficiency.

In one embodiment of the present invention, in the step S4, the temperature of the secondary epitaxial growth is 1050 to 1150 ℃, the growth pressure is 50 to 100mbar, and the v/III ratio is 1000 to 4000.

Under this condition, gaN is mainly grown in 2D (layer-by-layer growth), and hardly nucleated at the heterointerface. The material will enter the groove in a small amount, so the lateral growth rate of the groove is slow, and the experiment shows that when the upper part is closed, the transverse epitaxial length of the groove is only about 0.5 um. After the upper part of the groove is closed, gaN continues to grow epitaxially, and a GaN stripping layer to be stripped is formed.

In one embodiment of the present invention, the substrate is a sapphire substrate;

the thickness of the AlGaN buffer layer is 20-30 nm; the thickness of the n-GaN layer is 1-2 mu m; the thickness of the u-GaN layer is 0.3-0.7 mu m; the thickness of the GaN sacrificial layer is 1-4 mu m;

the groove group comprises a plurality of first grooves which are parallel and distributed at intervals, the width of each first groove is 1.5-3.5 mu m, and the distance between every two adjacent first grooves is 5-12 mu m; or the groove group comprises a plurality of first grooves which are distributed in parallel and at intervals and a plurality of second grooves which are distributed in parallel and at intervals, the first grooves are perpendicular to the second grooves, the width of each first groove is 1.5-3.5 micrometers, and the distance between every two adjacent first grooves is 5-12 micrometers; the width of the second grooves is 1.5-3.5 micrometers, and the distance between two adjacent second grooves is 5-12 micrometers.

The application also discloses a stripping method of the GaN epitaxial layer stripping structure, and the GaN stripping layer of the GaN epitaxial layer stripping structure is stripped through an electrochemical wet process.

The invention has the beneficial effects that: this application etching layer group exists and runs through whole etching layer group's slot group, when follow-up carrying out the electrochemistry and peeling off, solution gets into behind the hollow slot group, fully contacts with etching layer group, and the sculpture can be gone on to the centre along the cavity region, and the required distance of sculpture significantly reduces, has promoted the chemical reaction efficiency when peeling off by a wide margin. In practical application, the sacrificial layer with the size of several micrometers can be used for peeling the whole GaN epitaxial wafer with the size of 2 inches, so that the sacrificial layer with the size of hundreds of micrometers is prevented from being epitaxial, and the peeling efficiency is improved.

Drawings

FIG. 1 is a schematic view of a substrate;

FIG. 2 is a schematic view of a substrate and an etch layer stack;

FIG. 3 is a schematic view of a trench set machined from an etched layer set;

FIG. 4 is a schematic view of a GaN epitaxial layer lift-off structure;

FIG. 5 is a schematic view after separation of the GaN lift-off layer by an electrochemical wet process;

FIG. 6 is a top view of an etched group of layers having first trenches;

FIG. 7 is a top view of an etched layer group having a first trench and a second trench;

FIG. 8 is an optical microscope photograph after the second epitaxy;

fig. 9 is an SEM image of a GaN epitaxial layer lift-off structure.

The figures are numbered:

1. a substrate; 2. etching a layer group; 21. an AlGaN buffer layer; 22. an n-GaN layer; 23. a u-GaN layer; 24. a GaN sacrificial layer; 25. a groove group; 251. a first trench; 252. a second trench; 3. a GaN peeling layer.

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. It is to be understood that the embodiments described are only a few embodiments of the present application and 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.

In the description of the present application, it should be noted that the terms "inside", "outside", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings or orientations or positional relationships that the products of the application usually place when using, and are only used for convenience in describing the present application and simplifying the description, but do not indicate or imply that the devices or elements that are referred to must have a specific orientation, be constructed in a specific orientation, and operate, and thus, should not be construed as limiting the present application. Furthermore, the terms "first," "second," and the like are used solely to distinguish one from another, and are not to be construed as indicating or implying relative importance.

In the description of the present application, it is also to be noted that, unless otherwise explicitly specified or limited, the terms "disposed" and "connected" are to be interpreted broadly, e.g., as being either fixedly connected, detachably connected, or integrally connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present application can be understood in a specific case by those of ordinary skill in the art.

The present invention will be described in detail below with reference to the accompanying drawings.

As shown in fig. 4, the GaN epitaxial layer stripping structure includes a substrate 1, an etching layer group 2 and a GaN stripping layer 3, which are sequentially arranged from bottom to top, wherein the etching layer group 2 includes an AlGaN buffer layer 21, an n-GaN layer 22, a u-GaN layer 23 and a GaN sacrificial layer 24, which are sequentially arranged from bottom to top, and the etching layer group 2 has a trench group 25 penetrating through the etching layer group 2.

This application sculpture bed group 2 has the slot group 25 that runs through whole sculpture bed group 2, when in the follow-up electrochemistry is peeled off, and solution gets into behind the hollow slot group 25, and with sculpture bed group 2 abundant contact, the sculpture can be gone on to the centre along the cavity region, and the required distance of sculpture significantly reduces, has promoted the chemical reaction efficiency when peeling off by a wide margin.

In the present application, the GaN sacrificial layer 24 is an n + -GaN layer. In practical use, the substrate 1 is preferably Al ₂ O ₃ (sapphire), it may also beGaN, siC, si, or the like.

As shown in fig. 6, in the present embodiment, the trench group 25 includes a plurality of first trenches 251 distributed in parallel and at intervals. The width of the first grooves 251 is 1.5 μm to 3.5 μm, and the distance between two adjacent first grooves 251 is 5 μm to 12 μm. The design of the trench group 25 can greatly reduce the etching distance.

In other embodiments, as shown in fig. 7, the groove set 25 may be configured to: the groove set 25 includes a plurality of first grooves 251 distributed in parallel and at intervals and a plurality of second grooves 252 distributed in parallel and at intervals, wherein the first grooves 251 are perpendicular to the second grooves 252. At this time, the width of the first trench 251 is 1.5 μm to 3.5 μm, and the distance between two adjacent first trenches 251 is 5 μm to 12 μm; the width of the second trench 252 is 1.5 μm to 3.5 μm, and the distance between two adjacent second trenches 252 is 5 μm to 12 μm.

In the present embodiment, the AlGaN buffer layer 21 has a thickness of 20 to 30nm; the thickness of the n-GaN layer 22 is 1-2 μm; the thickness of the u-GaN layer 23 is 0.3-0.7 μm; the thickness of the GaN sacrificial layer 24 is 1 to 4 μm.

The embodiment also discloses a preparation method of the GaN epitaxial layer stripping structure, which comprises the following steps:

s1, as shown in figures 1 and 2, growing an AlGaN buffer layer on a substrate;

the method comprises the following specific steps: firstly, introducing hydrogen into an MOCVD reaction chamber, and carrying out heat treatment on the substrate 1 at the temperature of 1000-1150 ℃ for 5-8 min; then reducing the temperature to 550-650 ℃, growing an AlGaN buffer layer 21 with the thickness of 20-30 nm at the growth pressure of 50-200mbar, wherein the Al source, the Ga source and the N source are respectively TMAl, TMGa and NH ₃ 。

S2, as shown in figure 2, sequentially extending an n-GaN layer 22, a u-GaN layer 23 and a GaN sacrificial layer 24 on the AlGaN buffer layer 21, wherein the AlGaN buffer layer 21, the n-GaN layer 22, the u-GaN layer 23 and the GaN sacrificial layer 24 form an etching layer group 2;

the method comprises the following specific steps: heating to 1050-1150 ℃, sequentially extending an n-GaN layer, a u-GaN layer and a sacrificial layer (n < + > -GaN layer) on the AlGaN buffer layer, wherein the thickness of the n-GaN layer is 1.5um, the thickness of the u-GaN layer is 0.5um, the thickness of the sacrificial layer is 1-4 mu m, and SiH is used ₄ AsA doping source.

S3, preparing a patterned substrate through photoetching and ICP etching as shown in the figure 3, and etching a groove group 25 on the etching layer group, wherein the grooves of the groove group extend to the surface of the substrate;

and S4, as shown in figures 4, 8 and 9, secondary epitaxial growth of a GaN stripping layer is carried out on the etching layer group, and the GaN stripping layer covers the groove group. In this embodiment, in step S4, the temperature of the second epitaxial growth is 1050-1150 ℃, the growth pressure is 50-100mbar, and the V/III ratio is 1000-4000. Under the condition, gaN is mainly grown in 2D, and nucleation growth is difficult to realize at a heterogeneous interface. The material will enter the groove in a small amount, so the lateral growth rate of the groove is slow, and the experiment shows that when the upper part is closed, the transverse epitaxial length of the groove is only about 0.5 um. After the upper part of the groove is closed, gaN continues to grow epitaxially, and a GaN stripping layer to be stripped is formed.

The embodiment also discloses a stripping method of the GaN epitaxial layer stripping structure, and as shown in FIG. 5, the GaN stripping layer of the GaN epitaxial layer stripping structure is stripped through an electrochemical wet process.

The method utilizes the characteristic that the bonding energy of the etched pattern region and the surface of the sacrificial layer is different, uses the set epitaxial condition to ensure that the epitaxy only occurs in the GaN region, and then utilizes the transverse growth of the GaN to completely cover the pattern etching region to obtain a pattern-free complete high-quality GaN stripping layer. Epitaxial back slot group continues to exist, and when follow-up electrochemistry was peeled off, solution got into among the cavity, fully contacted with the sculpture region, and the sculpture can go on to the figure middle along the cavity region, and the required distance of sculpture significantly reduces, has promoted the chemical reaction efficiency when peeling off by a wide margin, only needs epitaxial sacrificial layer about 2um to be used for the whole piece of 2 cun's of size to peel off, has avoided epitaxial hundreds of microns sacrificial layer, has promoted peeling efficiency.

The above description is only for the preferred embodiment of the present invention and is not intended to limit the scope of the present invention, and all equivalent structural changes made by using the contents of the present specification and the drawings can be directly or indirectly applied to other related technical fields and are included in the scope of the present invention.

Claims

1. The GaN epitaxial layer stripping structure is characterized by comprising a substrate, an etching layer group and a GaN stripping layer which are sequentially arranged from bottom to top, wherein the etching layer group comprises an AlGaN buffer layer, an n-GaN layer, a u-GaN layer and a GaN sacrificial layer which are sequentially arranged from bottom to top, and the etching layer group is provided with a groove group penetrating through the etching layer group.

2. The GaN epitaxial layer taking-off structure of claim 1, wherein the set of trenches comprises a plurality of first trenches distributed in parallel and spaced apart.

3. The GaN epitaxial layer taking-off structure of claim 2, wherein the width of the first trench is 1.5 μm to 3.5 μm, and the distance between two adjacent first trenches is 5 μm to 12 μm.

4. The GaN epitaxial layer lift-off structure of claim 1 wherein the set of trenches comprises a plurality of first trenches distributed in parallel and spaced apart and a plurality of second trenches distributed in parallel and spaced apart, the first trenches being perpendicular to the second trenches.

5. The GaN epitaxial layer taking-off structure of claim 4, wherein the width of the first trench is 1.5-3.5 μm, and the distance between two adjacent first trenches is 5-12 μm; the width of the second grooves is 1.5-3.5 micrometers, and the distance between two adjacent second grooves is 5-12 micrometers.

6. The GaN epitaxial layer taking-off structure of claim 1, wherein the AlGaN buffer layer has a thickness of 20 to 30nm; the thickness of the n-GaN layer is 1-2 mu m; the thickness of the u-GaN layer is 0.3-0.7 mu m; the thickness of the GaN sacrificial layer is 1-4 mu m.

7. A preparation method of a GaN epitaxial layer stripping structure is characterized by comprising the following steps:

s1, growing an AlGaN buffer layer on a substrate;

s3, etching a groove group on the etching layer group, wherein the grooves of the groove group extend to the surface of the substrate;

8. The method for preparing a GaN epitaxial layer taking-off structure according to claim 7, wherein in the step S4, the temperature of the secondary epitaxial growth is 1050 to 1150 ℃, the growth pressure is 50 to 100mbar, and the v/III ratio is 1000 to 4000.

9. The method for manufacturing a GaN epitaxial layer taking-off structure according to claim 7, wherein the substrate is a sapphire substrate;

the groove group comprises a plurality of first grooves which are parallel and distributed at intervals, the width of each first groove is 1.5-3.5 mu m, and the distance between every two adjacent first grooves is 5-12 mu m; or the groove group comprises a plurality of first grooves which are distributed in parallel and at intervals and a plurality of second grooves which are distributed in parallel and at intervals, the first grooves are perpendicular to the second grooves, the width of each first groove is 1.5-3.5 micrometers, and the distance between every two adjacent first grooves is 5-12 micrometers; the width of the second grooves is 1.5-3.5 μm, and the distance between two adjacent second grooves is 5-12 μm.

10. A method for peeling off a GaN epitaxial layer peeling off structure as claimed in any of claims 1 to 6, characterized in that the GaN peeling off layer of the GaN epitaxial layer peeling off structure is peeled off by an electrochemical wet process.