CN103839777A - Large area continuous lossless laser stripping method for gallium nitride film - Google Patents

Abstract

The invention discloses a large-area continuous non-destructive laser lift-off method for gallium nitride films. The method comprises: taking an epitaxial wafer on which a gallium nitride film is grown on a sapphire substrate; depositing a transition layer on the surface of the gallium nitride film; Fabricating a transfer substrate on the surface of the transition layer; and scanning and irradiating the back of the entire polished sapphire substrate with a long strip laser spot in a step-scanning manner, so as to realize the overall separation of the sapphire substrate and the gallium nitride thin film. The invention adopts the strip-shaped flat-top laser spot to scan, which can not only ensure that the stripped large-area gallium nitride thin film sample has no cracks, but also can obtain acceptable processing speed. The invention has a very important effect especially on the progress of the manufacturing technology of gallium nitride-based vertical structure light-emitting diodes and gallium nitride single crystal.

Description

A large-area continuous non-destructive laser lift-off method for GaN thin films

technical field

The invention belongs to the technical field of semiconductor device manufacturing technology, in particular to a large-area continuous non-destructive laser lift-off method for gallium nitride thin films.

Background technique

At present, growing gallium nitride thin films on sapphire substrates is the most widely used growth technology for gallium nitride materials. Since the sapphire substrate is insulating and has poor thermal conductivity, the performance of GaN-based optoelectronic devices made of GaN thin films grown on the sapphire substrate is restricted, so the technology of replacing the sapphire substrate with a new substrate has been widely used. Research. Among them, the laser lift-off technology can separate the gallium nitride film from the sapphire substrate, which provides a good solution for solving the technical problem of replacing the sapphire substrate. However, nitrogen gas is generated when the GaN film at the interface is decomposed by laser peeling, forming a large shock wave, which causes cracks around the GaN film receiving the laser spot, so it is impossible to obtain a large-area continuous and non-destructive GaN film.

In order to solve this problem, it is necessary to use laser spot scanning with a particularly small area to reduce the shock wave generated by a single irradiation. However, this greatly increases the burden on the moving platform of the equipment and greatly reduces the processing speed.

Contents of the invention

(1) Technical problems to be solved

In view of this, the main purpose of the present invention is to provide a large-area continuous non-destructive laser lift-off method for gallium nitride thin films, so as to eliminate and reduce the impact of shock waves generated during laser lift-off of gallium nitride and increase the processing speed.

(2) Technical solutions

In order to achieve the above object, the present invention provides a large-area continuous non-destructive laser lift-off method for gallium nitride films, the method comprising: taking an epitaxial wafer with gallium nitride films grown on a sapphire substrate; Deposit a transition layer on the surface; fabricate a transfer substrate on the surface of the transition layer; and scan and irradiate the back of the entire polished sapphire substrate with a long strip laser spot in a step-and-scan mode to achieve the overall separation of the sapphire substrate and the gallium nitride film .

In the above solution, depositing the transition layer on the surface of the gallium nitride thin film is to deposit a multi-layer metal layer on the surface of the gallium nitride thin film by electron beam evaporation technology, and the multi-layer metal layer is used as the transition layer. The multilayer metal layer is a combination of Ni, Ag, Pt, Au and AuSn alloy.

In the above scheme, the preparation of the transfer substrate on the surface of the transition layer includes: taking a gold-plated tungsten-copper alloy or molybdenum-copper alloy disc as the transfer substrate, and the tungsten-copper alloy or molybdenum-copper alloy disc contains 5% - 25% copper by weight; and connecting the transfer substrate to the transition layer by thermocompression bonding. The transfer substrate is connected on the transition layer by thermocompression bonding, the bonding temperature is between 270-330 degrees Celsius, the pressure is 1-500 kg, and the constant temperature and pressure time is 10-60 seconds.

In the above scheme, the scanning and irradiation of the entire polished back of the sapphire substrate with the long-strip laser spot in the step-and-scan mode includes: adjusting the laser spot generated by the laser stripping equipment into a long strip, and adopting the step-scan method The long-strip laser spot scans and irradiates the entire polished back of the sapphire, so that the front, rear, left, and right laser spots are just docked, so as to realize the overall separation of sapphire and GaN thin film. The length of the strip-shaped laser spot ranges from 100 microns to 10000 microns, and the width ranges from 0.1 microns to 50 microns.

(3) Beneficial effects

The present invention adopts the strip-shaped flat-top laser spot for scanning. Under the condition of the same laser spot area, compared with the traditional square laser spot, the impact torque generated on both sides of the peeling interface is much smaller, which can ensure the peeling of a large area. GaN thin film samples were free of cracks and acceptable processing rates were obtained. If the traditional square laser spot is used for laser lift-off, in order to ensure that the gallium nitride film does not produce cracks, the spot area must be set very small, which greatly prolongs the processing time and processing cost, making this square laser lift-off method unusable. The actual production of the large-area continuous gallium nitride thin film is removed, but the large-area continuous gallium nitride thin film without cracks can be prepared quickly and effectively by using the invention. The invention has a very important effect especially on the progress of the manufacturing process of the gallium nitride-based vertical structure light-emitting diode and the gallium nitride single crystal.

Description of drawings

FIG. 1 is a schematic cross-sectional structure diagram of an epitaxial wafer grown on a sapphire substrate with a gallium nitride thin film.

Fig. 2 is a schematic cross-sectional structure diagram of an epitaxial wafer on which a transfer substrate has been fabricated.

Fig. 3 is a schematic top view of the path of the strip-shaped laser spot scanning the wafer. The cross-sectional structure of the wafer is the structure shown in Fig. 2, with the sapphire surface facing upwards, and the dotted line in the figure is the scanning path.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be described in further detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

In the drawings, for convenience and clarity of explanation, the thickness or size of each layer may be exaggerated, reduced or schematically shown, and the size of each constituent part does not necessarily or may not necessarily reflect its actual size.

The large-area continuous non-destructive laser lift-off method of the gallium nitride thin film provided by the present invention comprises the following steps:

Step 1: Take the epitaxial wafer with gallium nitride film grown on the sapphire substrate;

Step 2: Depositing a transition layer on the surface of the gallium nitride film;

In this step, depositing a transition layer on the surface of the gallium nitride film is to deposit a multi-layer metal layer on the surface of the gallium nitride film by electron beam evaporation technology. The multi-layer metal layer is used as a transition layer, and the multi-layer metal layer is Ni , Ag, Pt, Au and AuSn alloy combination.

Step 3: making a transfer substrate on the surface of the transition layer;

In this step, making the transfer substrate on the surface of the transition layer includes: taking a gold-plated tungsten-copper alloy or molybdenum-copper alloy disc as the transfer substrate, and the tungsten-copper alloy or molybdenum-copper alloy disc contains 5%-25 weight percent copper; and the transfer substrate is connected on the transition layer by thermocompression bonding. The transfer substrate is connected on the transition layer by thermocompression bonding, the bonding temperature is between 270-330 degrees Celsius, the pressure is 1-500kg, and the constant temperature and pressure time is 10-60 seconds. Preferably, the bonding The temperature is 300 degrees Celsius, the pressure is 500kg, and the constant temperature and pressure time is 30 seconds.

Step 4: Scan and irradiate the back of the entire polished sapphire substrate with a long-strip laser spot in a step-and-scan manner to realize the overall separation of the sapphire substrate and the gallium nitride film;

In this step, scanning and irradiating the entire backside of the polished sapphire substrate with a long-strip laser spot in a step-scanning manner includes: adjusting the laser spot generated by the laser lift-off The bar-shaped laser spot scans and irradiates the entire polished back of the sapphire, so that the front, rear, left, and right laser spots are just docked, so as to realize the overall separation of the sapphire and the gallium nitride film. Wherein, the length of the strip-shaped laser spot ranges from 100 microns to 10000 microns, and the width ranges from 0.1 microns to 50 microns.

Hereinafter, a large-area continuous non-destructive laser lift-off method for a gallium nitride thin film according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. The method includes the following steps:

First take an epitaxial wafer 100 on which a gallium nitride thin film 102 is grown on a sapphire substrate 101 , as shown in FIG. 1 .

A transition layer 200 is deposited on the surface of the GaN thin film 102 .

A transfer substrate 300 is fabricated on the transition layer 200, and the transition layer 200 is used to connect the gallium nitride thin film 102 and the transfer substrate 300, as shown in FIG. 2 .

The laser spot generated by the laser lift-off equipment is adjusted into a strip shape, and the length of the strip-shaped laser spot ranges from 100 microns to 10,000 microns, and the width ranges from 0.1 microns to 50 microns. The elongated laser spot in the step-and-scan mode is used to scan and irradiate the entire polished back of the sapphire 101, as shown in FIG.

Example

Firstly, take an epitaxial wafer 100 grown on a sapphire substrate 101 with a gallium nitride thin film 102. The epitaxial wafer 100 is a wafer with a diameter of 2 inches and a thickness of 450 microns. The cross-sectional structure of the epitaxial wafer 100 is shown in FIG. 1 .

Electron beam evaporation technology is used to deposit multi-layer metal layers on the surface of gallium nitride film 102 - Ni, Ag, Pt and AuSn alloys, the thickness of each layer is 10, 3000, 500, 40000 angstroms respectively, and the multi-layer metal layer is used as a transition layer 200.

Take a tungsten-copper alloy disc with a diameter of 2 inches, a thickness of 200 microns, and a gold-plated (85% tungsten, 15% copper) tungsten-copper alloy disc. The tungsten-copper alloy disc is used as the transfer substrate 300, and the transfer substrate 300 is connected to the transition layer 200 by thermocompression bonding. The bonding temperature is 300 degrees Celsius, the pressure is 500 kg, and the constant temperature and pressure time is 30 seconds. The cross-section of the wafer after thermocompression bonding is shown in FIG. 2 .

Adjust the laser spot generated by the laser lift-off equipment into a strip shape, the length of the strip-shaped laser spot is 1000 microns, and the width is 10 microns. The elongated laser spot of the step-and-scan method is used to scan and irradiate the entire polished back of the sapphire 101. The vertical step length of the stepping movement is 1000 microns, and the horizontal step length is 10 microns. Just docked. The scanning range of the laser is slightly larger than the area of the wafer, so as to realize the overall separation of the sapphire 101 and the gallium nitride film 102 .

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (7)

1. the large area of a gallium nitride film harmless laser-stripping method continuously, is characterized in that, the method comprises:

The epitaxial wafer of gallium nitride film that has been taken at Grown on Sapphire Substrates;

At the surface deposition transition zone of gallium nitride film;

Make translate substrate on transition zone surface; And

Adopt the strip laser facula scanning of step-scan mode to irradiate the back side of the Sapphire Substrate of whole polishing, realize the overall separation of Sapphire Substrate and gallium nitride film.

2. the large area of gallium nitride film according to claim 1 harmless laser-stripping method continuously, it is characterized in that, the described surface deposition transition zone at gallium nitride film, is to adopt electron beam evaporation technique at gallium nitride film surface deposition multiple layer metal layer, and this multiple layer metal layer is as transition zone.

3. the large area of gallium nitride film according to claim 2 harmless laser-stripping method continuously, is characterized in that, described multiple layer metal layer is the combination of Ni, Ag, Pt, Au and AuSn alloy.

4. the large area of gallium nitride film according to claim 1 harmless laser-stripping method continuously, is characterized in that, described in transition zone surface making translate substrate, comprising:

Get the tungsten-copper alloy of surface gold-plating or molybdenum-copper disk as translate substrate, the copper that contains 5%-25% weight in this tungsten-copper alloy or molybdenum-copper disk; And

This translate substrate is connected on transition zone by the mode of thermocompression bonding.

5. the large area of gallium nitride film according to claim 4 harmless laser-stripping method continuously, it is characterized in that, described this translate substrate is connected on transition zone by the mode of thermocompression bonding, bonding temperature is between 270-330 degree Celsius, pressure is got 1-500kg, constant temperature and pressure time 10-60 second.

6. the large area of gallium nitride film according to claim 1 harmless laser-stripping method continuously, is characterized in that, the back side of the Sapphire Substrate of whole polishing is irradiated in the strip laser facula scanning of described employing step-scan mode, comprising:

The laser facula that laser lift-off equipment is produced is adjusted into strip, adopt the strip laser facula scanning of step-scan mode to irradiate the sapphire back side of whole polishing, laser facula all around is just in time docked, thereby realize the overall separation of sapphire and gallium nitride film.

7. the large area of gallium nitride film according to claim 6 harmless laser-stripping method continuously, is characterized in that, the length range of described strip laser facula is 100 microns to 10000 microns, and width range is 0.1 micron to 50 microns.

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