KR20020004380A - Method for fabricating GaN single crystal substrate - Google Patents

Abstract

PURPOSE: A method for fabricating a GaN single crystalline substrate is provided to form a large-scaled substrate by preventing a crack phenomenon in a fabrication process. CONSTITUTION: A multitude of sapphire substrate(12) is arranged within a cylinder(10) according to a predetermined interval. Wax is filled between the sapphire substrates(12) and to an outside of the outer sapphire substrate of the sapphire substrates(12). An inside diameter of the cylinder(10) is equal to the diameter of the sapphire substrate(12). A multitude of slot is formed to arrange the sapphire substrates(12) in the interval of 5 to 10mm. The cylinder(10) is covered by covers(16,18). A predetermined gap(15) is formed when the cylinder(10) is covered by covers(16,18). The cylinder(10) is formed with a thin metal film. An interval of the gap is determined according to the diameter of the cylinder(10).

Description

Method for fabricating gallium nitride single crystal substrate {Method for fabricating GaN single crystal substrate}

The present invention relates to a method for manufacturing a gallium nitride single crystal substrate, and more particularly, to a method for manufacturing a gallium nitride single crystal substrate that can secure a large area substrate by reducing cracking during the process.

Gallium nitride is a semiconductor material having an energy bandgap of 3.39 eV and a direct transition type, and is useful for manufacturing light emitting devices in a short wavelength region.

Because of the high nitrogen vapor pressure at the melting point of gallium nitride single crystal, liquid crystal growth requires high temperature of 1500 ℃ or higher and 20000 atmosphere of nitrogen atmosphere, which makes it difficult to mass-produce it. Difficult to use

Until now, gallium nitride films have been grown on heterogeneous substrates by vapor phase growth methods such as metal organic chemical vapor deposition (MOCVD) or hydraulic vapor phase epitaxy (HVPE).

A sapphire substrate is most commonly used as a dissimilar substrate for manufacturing a gallium nitride film because the sapphire has a hexagonal structure such as gallium nitride, which is inexpensive and stable at high temperatures. However, sapphire causes strain at the interface due to the difference in lattice constant (about 16%) and the coefficient of thermal expansion (about 35%), and the strain causes lattice defects and cracks in the crystals. It is difficult to grow a high quality gallium nitride film and shorten the life of the device fabricated on the gallium nitride film.

In order to solve this problem, a free standing gallium nitride substrate is required, and a gallium nitride film must be formed on the gallium nitride substrate by homoepitaxy to manufacture the device.

The pre-standing gallium nitride substrate is manufactured by forming a gallium nitride film on a sapphire substrate, separating the gallium nitride film from the sapphire substrate, and processing the separated gallium nitride film to have a desired diameter. Of course, the gallium nitride film may be first formed on the sapphire substrate, processed into a desired diameter, and the gallium nitride film may be separated from the sapphire substrate.

The gallium nitride film is processed into a desired diameter by using a cutter such as a diamond tip to cut to a desired size or to use a circular processing machine or the like.

However, when the above method is used, the gallium nitride film has only a small impact during the machining operation due to the cleavage of gallium nitride and the thermal expansion coefficient difference between the sapphire substrate 2 and the gallium nitride film 4 as shown in FIG. Cracking easily occurs even when applied, making it difficult to obtain a large size pre-standing gallium nitride substrate. In the case where the gallium nitride film is processed using a circular processing machine without separating the substrate, and then separated from the substrate, if a crack occurs on either the gallium nitride film or the sapphire substrate, the whole crack is generated along the generated crack. There is a problem that cracks are easily generated along the cleaved surface of the gallium nitride film due to the easily cracked vulnerability. Therefore, there is a problem that it is difficult to manufacture a pre-standing gallium nitride substrate having a large size by the above method.

An object of the present invention is to provide a method for producing a gallium nitride single crystal substrate that can form a gallium nitride single crystal substrate having a desired diameter by forming a predetermined thickness of crystal wax on both surfaces of the gallium nitride film and the sapphire substrate. To provide.

1 is a view for explaining a problem that occurs during the production of gallium nitride single crystal substrate.

2 to 6 are views for explaining a method of manufacturing a gallium nitride single crystal substrate according to the present invention.

<Description of the symbols for the main parts of the drawings>

2, 12: sapphire substrate 4, 14: gallium nitride film

10: cylinder 15: gap

16: the first lid 18: the second lid

20: wax 22: sapphire substrate assembly

24: grinder 26: laser beam

28 gallium nitride substrate

Method for producing a gallium nitride single crystal substrate according to the present invention for achieving the above object comprises the steps of forming a gallium nitride (GaN) film on the entire surface of the sapphire substrate; Forming a wax having a predetermined thickness on the gallium nitride layer and on the rear surface of the sapphire substrate; Grinding edges to make the sapphire substrate the desired diameter; Removing wax on the gallium nitride layer and the sapphire substrate back surface; And

Irradiating a laser beam to a rear surface of the sapphire substrate to separate the gallium nitride film from the sapphire substrate.

The wax may be formed by melting the wax, applying the wax on the sapphire substrate and the gallium nitride film, and cooling the film to room temperature.

The step of removing the wax preferably comprises a) removing the primary by heating the sapphire substrate to the melting point of the wax and b) removing the residual amount with acetone after the primary removal.

Another method of manufacturing a gallium nitride single crystal substrate according to the present invention for achieving the above object comprises the steps of preparing a plurality of sapphire substrate on which a gallium nitride (GaN) film is formed; Bonding the sapphire substrates to each other using wax to form a predetermined distance to form a sapphire substrate assembly; Grinding an edge of the sapphire substrate assembly to make the sapphire substrates the desired diameter; Removing wax between the sapphire substrates; And separating the gallium nitride film from the sapphire substrate by irradiating a laser beam to the rear surface of each of the sapphire substrates.

The step of forming the sapphire substrate assembly preferably comprises the steps of: a) arranging the sapphire substrate to form a predetermined distance in a cylinder of metal material that can be separated from side to side; B) melting wax between the sapphire substrates; And c) cooling the entire cylinder to room temperature.

The sapphire substrate is preferably arranged so that the gallium nitride (GaN) film is formed in the same direction, and wax is also formed on the outer surface of the edge substrate when the sapphire substrates are bonded.

Hereinafter, with reference to the accompanying drawings a specific embodiment of the present invention will be described in detail.

2 to 6 are views for explaining a method of manufacturing a gallium nitride single crystal substrate according to the present invention.

First, referring to FIG. 2, the sapphire substrate 12 having the gallium nitride thin film formed in the cylinder 10 is arranged at a predetermined interval, and then the wax 20 is filled between the sapphire substrate 12 and the outer surface of the edge substrate. Put it in.

The cylinder 10 has an inner diameter equal to the diameter of the sapphire substrate 12, and slots (not shown) are arranged so that the sapphire substrate 12 can be individually arranged in a range of 5 to 10 mm along an inner surface thereof. It is. Caps 16 and 18 which can be opened to the left and right are configured at an upper portion thereof, and when the caps 16 and 18 are closed, a gap 15 of a predetermined interval L is formed.

The cylinder 10 is preferably made of a thin plate made of metal. In addition, the gap 15 may vary depending on the diameter of the cylinder 10, and 5 to 30 mm is preferable.

First, a gallium nitride film is grown on the sapphire substrate 12 by HVPE to a thickness of about 300 μm. Then, the sapphire substrate 12 is arranged in the cylinder 10 and the lids 16 and 18 are closed. Melting the crystal wax (Crystal wax) in the temperature range of ℃ and poured between the sapphire substrate 12 through the gap 15 and cooled to room temperature. In this case, the sapphire substrate 12 is arranged such that the gallium nitride film has the same direction.

3, the cylinder 10 is removed to form a sapphire substrate assembly 22 (diameter: R).

Subsequently, referring to FIG. 4, the sapphire substrate assembly 22 is ground using a grinder 24 to completely remove polycrystalline gallium nitride formed at the edge of the substrate and to have a desired diameter r. R> r)

The wax 20 bonds the sapphire substrates 12 to each other to prevent cracks in the substrates during grinding. That is, the wax 20 may process a plurality of sapphire substrate 12 at the same time.

Subsequently, referring to FIG. 5, the processed sapphire substrate assembly 22 is heated to a temperature range of 70 to 140 ° C. to first remove wax, and then a second amount of wax is completely removed in a bath containing acetone.

Therefore, the sapphire substrate 12 is separated independently.

6, the gallium nitride film 14 is separated from the sapphire substrate 12 by irradiating a laser beam 26 to the rear surface of the processed individual sapphire substrate 12 (laser lift-off method). A gallium nitride substrate 28 is formed.

Accordingly, the present invention can produce a large area gallium nitride single crystal substrate without cracks, and has the effect of improving productivity in manufacturing devices such as gallium nitride laser diodes.

Although the present invention has been described in detail only with respect to the described embodiments, it will be apparent to those skilled in the art that various modifications and variations are possible within the technical scope of the present invention, and such modifications and modifications are within the scope of the appended claims.

Claims (10)

Forming a gallium nitride (GaN) film on the entire surface of the sapphire substrate; Forming a wax having a predetermined thickness on the gallium nitride layer and on the rear surface of the sapphire substrate; Grinding an edge to make the sapphire substrate the desired diameter; Removing wax on the gallium nitride layer and the sapphire substrate back surface; And Irradiating a laser beam onto a rear surface of the sapphire substrate to separate the gallium nitride film from the sapphire substrate; Method for producing a gallium nitride single crystal substrate comprising a. The method of claim 1, The thickness of the wax is a method of producing a gallium nitride single crystal substrate, characterized in that 5 to 10mm. The method of claim 1, The wax is formed by dissolving the wax and coating the sapphire substrate and the gallium nitride film to cool to room temperature. The method of claim 1, Removing the wax is A) first removing the sapphire substrate by heating it to the melting point of the wax; And B) a second removal step of removing the residue with acetone after the first removal; Method for producing a gallium nitride single crystal substrate comprising a. Preparing a plurality of sapphire substrates on which a gallium nitride (GaN) film is formed; Bonding the sapphire substrates to each other using wax to form a predetermined distance to form a sapphire substrate assembly; Grinding an edge of the sapphire substrate assembly to make the sapphire substrates the desired diameter; Removing wax between the sapphire substrates; And Irradiating a laser beam onto a rear surface of each of the sapphire substrates to separate the gallium nitride film from the sapphire substrates; Method for producing a gallium nitride single crystal substrate comprising a. The method of claim 5, Forming the sapphire substrate assembly A) arranging a sapphire substrate to form a predetermined distance in a cylinder of metal material which can be separated from right to left; B) melting wax between the sapphire substrates; And C) cooling the entire cylinder to room temperature; Method for producing a gallium nitride single crystal substrate comprising a. The method of claim 6, Method for producing a gallium nitride single crystal substrate, characterized in that the distance between the sapphire substrate is 5 to 10 mm. The method of claim 6, The sapphire substrate is a method of manufacturing a gallium nitride single crystal substrate, characterized in that the gallium nitride (GaN) film is arranged in the same direction. The method of claim 6, The method of manufacturing a gallium nitride single crystal substrate, characterized in that the wax is formed on the outer surface of the edge substrate when the sapphire substrates are bonded. The method of claim 5, Removing the wax is A) primary removal of the sapphire substrate assembly by heating to the melting point of the wax; And B) a second removal step of removing the residue with acetone after the first removal; Method for producing a gallium nitride single crystal substrate comprising a.