KR20080062651A - Method for producing single crystal gallium nitride substrate - Google Patents

Abstract

The present invention provides a first growth step of growing a separation boundary film on a base substrate by supplying a nitrogen source and a gallium source in a V / III ratio of 2: 1 to 7: 1, and growing a gallium nitride thick film on the separation boundary film. And a second growth step, and a separation step of separating the base substrate by irradiating a laser to the interface between the base substrate and the separation boundary layer. According to the method, it is easy to separate the gallium nitride substrate and the base substrate, and cracks do not occur in the gallium nitride substrate when the substrate is separated.

Description

Method of manufacturing single crystal gallium nitride substrate

1A to 1D are cross-sectional views conceptually illustrating a method of manufacturing a single crystal gallium nitride substrate according to an embodiment of the present invention.

Figure 2 is a perspective view of one embodiment of a growth reactor used to grow gallium nitride in accordance with one embodiment of the present invention.

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

110: base substrate 120: separation boundary film

130: gallium nitride thick film 132: crack prevention film

134: gallium nitride growth film

The present invention relates to a method for manufacturing a single crystal gallium nitride substrate, and more particularly, to a method for manufacturing a single crystal gallium nitride substrate that can easily separate the substrate, and can effectively suppress the occurrence of cracks during substrate separation.

Recently, as the demand for high-efficiency short-wavelength light emitting devices increases, research on nitride-based semiconductors that are known to be suitable for such applications is being actively conducted. In particular, gallium nitride (GaN) is a wide bandgap semiconductor having a band gap energy of 3.39 eV, which is a direct transition type of nitride-based material, and thus, gallium nitride is widely used for manufacturing such a short wavelength light emitting device.

In general, sapphire (Al ₂ O ₃ ), 6HSiC, LiGaO ₂ , MgAl ₂ O _4, or the like is used as a growth substrate for growing the gallium nitride film. In addition, the growth of the gallium nitride film may be performed by metalorganic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), high temperature and high pressure, sublimation method, and the like. However, the high temperature and high pressure method and the sublimation method are not used in reality because of the low production efficiency and economic efficiency of gallium nitride. Recently, a method of growing a single crystal gallium nitride film on a sapphire substrate by halide vapor phase epitaxy (HVPE) has been used.

The gallium nitride film thus grown may be used as a freestanding substrate by being separated from the base substrate. In order to separate the gallium nitride film grown from the base substrate, a laser having a predetermined wavelength range is generally used.

In general, when the gallium nitride film is separated using a laser, the gallium nitride film is not properly separated, or even when separated, cracks are generated during the separation process, thereby causing a problem of propagation through the entire gallium nitride film. In addition, only part of the gallium nitride film may be separated.

Accordingly, an object of the present invention is to provide a method for manufacturing a single crystal gallium nitride substrate, which is easy to separate the base substrate and the grown gallium nitride film and does not generate cracks during the separation process. .

In order to manufacture a single crystal gallium nitride substrate according to an aspect of the present invention, a separation boundary film is first formed on a base substrate by supplying a nitrogen source and a gallium source in a V / III ratio of 2: 1 to 7: 1. The gallium nitride thick film is grown on the separation boundary film. The single crystal gallium nitride substrate may be obtained by separating the base substrate by irradiating a laser to the interface between the base substrate and the separation boundary layer.

The separation boundary membrane is preferably grown to have a thickness of 10 μm to 30 μm.

In the second growth step, cracks are formed to supply a nitrogen source and a gallium source to form a crack prevention film while decreasing the Group V / III ratio sequentially within the Group V / III ratio range of 8: 1 to 18: 1. And a growth film forming step of supplying a nitrogen source and a gallium source at a V / III ratio of 2: 1 to 10: 1 to form a gallium nitride growth film.

The crack prevention film is preferably adjusted to a thickness of 10㎛ to 30㎛.

Ammonia (NH ₃ ) gas may be used as the nitrogen source, and gallium chloride (GaCl) gas may be used as the gallium source.

In addition, it is preferable to use the laser which can irradiate the wavelength region of 345-385nm.

The method of manufacturing the single crystal gallium nitride substrate may further include a nitriding treatment step of nitriding the surface of the base substrate before the growth of the gallium nitride film. The nitriding treatment may include a first nitriding treatment under an ammonia gas atmosphere, a heat treatment under a mixed gas atmosphere including ammonia gas and hydrogen chloride gas, and a second nitriding treatment under the ammonia gas atmosphere. .

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings and the contents described in the accompanying drawings, but the present invention is not limited or limited by the embodiments.

1A to 1D are cross-sectional views sequentially illustrating a method of manufacturing a single crystal nitride substrate according to an embodiment of the present invention.

Referring to FIG. 1A, first, a base substrate 110 is provided as a base material for growing gallium nitride. According to one embodiment of the present invention, a base substrate including sapphire (Al ₂ O ₃ ) is used as the base substrate 110. That is, a sapphire substrate made of single crystal sapphire (Al ₂ O ₃ ) or a substrate including sapphire only on the surface of the base substrate 110 may be used. Alternatively, in addition to the sapphire substrate, as the base substrate 110, LiNbO ₃ , LiTaO ₃ , or the like may be used as a trigonal substrate or SiC, GaAs, Si, or the like.

Referring to FIG. 1B, an isolation boundary layer 120 is grown on the base substrate 110. The separation boundary membrane 120 may be formed by supplying a chamber at a V / III ratio of a nitrogen source and a gallium source of 2: 1 to 7: 1. Ammonia gas (NH ₃ ) may be used as the nitrogen source, and gallium chloride (GaCl) gas may be used as the gallium source. The gallium chloride is not directly supplied into the chamber, and substantially the material supplied to the chamber is hydrogen chloride (HCl) gas. The hydrogen chloride gas reacts with gallium metal (Ga), which is disposed at a predetermined position in the chamber, to generate gallium chloride (GaCl) gas.

Therefore, in order to adjust the V / III ratio, it is necessary to substantially adjust the volume ratio of the ammonia gas and the hydrogen chloride gas supplied into the chamber. This will be described later together with the description of the reaction apparatus.

The separation boundary layer 120 formed by the above method has good crystallinity and may induce stable separation upon separation of the gallium nitride substrate grown on the base substrate 110. Separation of the gallium nitride substrate is performed at the interface between the separation boundary layer 120 and the base substrate 110.

If the thickness of the separation boundary membrane 120 is less than 10 μm, there is a problem in that the separation does not separate, whereas if the thickness of the separation boundary membrane 120 exceeds 30 μm, there is a problem that cracks are generated. Therefore, the separation boundary membrane 120 is grown to have a thickness of 10 to 30 μm. Preferably, the thickness of the separation membrane 120 is adjusted to about 20 ㎛.

Referring to FIG. 1C, a thick gallium nitride film 130 is grown on the separation boundary film 120. The growth of the gallium nitride thick film 130 is divided into two steps.

First, the crack prevention membrane 132 is supplied by supplying a nitrogen source and a gallium source while sequentially decreasing the V / III group ratio within the V / III group ratio range of 8: 1 to 18: 1 on the separation boundary membrane 120. ).

The gallium nitride growth film 134 is formed on the crack prevention film by supplying a nitrogen source and a gallium source in a V / III ratio of 2: 1 to 10: 1.

In other words, the crystallization is initially made to weaken the crystallinity, and then the crystallinity is gradually formed to form the gallium nitride growth layer 134.

The crack preventing film may reduce the stress of the gallium nitride thick film 130 to be formed, thereby minimizing the crack generation of the grown gallium nitride thick film 130.

The crack preventing layer 132 may be variably adjusted according to the thickness of the gallium nitride growth layer 134. According to the present invention, the crack prevention layer 132 may have a thickness of 4 to 10% of the thickness of the gallium nitride growth layer 134. It is desirable to grow.

The growth temperature and growth rate of the separation boundary layer 120 and the gallium nitride thick film 130 may be variously adjusted according to process efficiency and the use of the gallium nitride substrate to be manufactured, but preferably 10 μm under a temperature of 900 to 1100 ° C. grow at a growth rate of / h to 300 μm / h. On the other hand, it can be adjusted differently according to the membrane (120, 132, 134) respectively.

The gallium nitride substrate according to the present invention is a concept including all of the separation boundary layer 120, the crack prevention layer 132, and the gallium nitride growth layer 134. The gallium nitride substrate may be separated from the base substrate 110 and used as a freestanding substrate.

Referring to FIG. 1D, the gallium nitride substrates 120 and 130 and the base substrate 110 are irradiated with laser light having a wavelength of a predetermined region on the boundary surfaces of the separation boundary layer 120 and the base substrate 110. , Can be separated.

The wavelength of the laser light is preferably 345 to 385 nm. Since gallium nitride has a bandgap energy of 3.39 eV and its intrinsic wavelength is ultraviolet (UV) light, sapphire substrates pass through and absorption occurs in gallium nitride when UV wavelength is used. Not be allowed

The separated gallium nitride substrate may be manufactured as a finished product through an additional polishing process.

Although not shown in FIG. 1, the method of manufacturing the gallium nitride substrate may further include nitriding a surface of the base substrate 110 before the separation boundary layer 120 is formed.

When the surface of the base substrate 110 is nitrided, the surface state of the base substrate 110 may be improved, and further, macropores may be prevented from occurring in the gallium nitride film during the growth process of the gallium nitride film.

The nitriding treatment is specifically a three step process. First, the base substrate 110 is charged into a chamber, and the first nitriding treatment is performed under an ammonia gas atmosphere while supplying ammonia (NH ₃ ) gas into the chamber. When the first nitriding process is completed, the base substrate 110 is heat-treated under the mixed gas atmosphere while supplying a mixed gas composed of ammonia gas and hydrogen chloride (HCl) gas. After the heat treatment is completed, the second nitriding treatment is performed under an ammonia gas atmosphere while supplying ammonia gas into the chamber in the same manner as the first nitriding treatment.

That is, the nitriding treatment step includes three steps of primary nitriding treatment, heat treatment, and secondary nitriding treatment. The nitriding treatment step including the heat treatment is preferably performed at a temperature of 1000 ° C. or higher.

By growing gallium nitride on the nitrided base substrate 110, it is possible to effectively prevent the generation of large pores in the gallium nitride film. In addition, when performing the nitriding treatment process, an additional buffer layer may not be used at the interface between the base substrate 110 and the gallium nitride film.

Hereinafter, a method of growing gallium nitride will be described in more detail with reference to a growth reactor. Figure 2 is a perspective view of one embodiment of a growth reactor used to grow gallium nitride in accordance with one embodiment of the present invention.

The gallium nitride film may be grown from the surface of the nitrided base substrate 110 through a halide vapor phase epitaxy (HVPE) using the growth reactor of FIG. 2. Referring to FIG. 2, the growth reactor 200 includes an electric furnace 210, a chamber 220, an injection pipe 230, a sampling boat 240, A reaction pipe 250 and a susceptor 260.

The electric furnace 210 is mounted on the outer circumferential surface of the growth reactor 200 to supply a heat source to the chamber 220. The chamber 220 may be heated to a high temperature, and the chamber 220 forms a constant temperature atmosphere therein. One side of the chamber 220 is mounted to the injection tube 230 for injecting nitrogen generating gas, spaced apart from the injection tube 230 by a predetermined distance, a compound containing a group III element or group III elements, such as gallium therein The sample boat 240 accommodated in powder form and a reaction tube 250 for discharging the reactants in which the reaction gas injected from the outside and the group III elements contained in the sample boat 240 are discharged are mounted. In addition, in the chamber 220, a base material such as a sapphire substrate for growing by depositing a nitride formed by combining the nitrogen generating gas injected through the injection pipe 230 and the reactant discharged from the reaction pipe 250. And a susceptor 260 supporting iii) is disposed.

While the gallium nitride is deposited and grown on the surface of the base material such as a sapphire substrate, the formation of the reactant and the nitride is continued, so that the growth material gallium nitride is continuously supplied to the surface of the base material.

In order to make it easier to understand the sequential formation reaction mechanism of the reactants and nitrides, the reaction reaction schemes of the reactants and nitrides are shown in the following reaction formula (1).

In Scheme (1), X represents a group III element such as gallium (Ga), aluminum (Al), or indium (In). Therefore, nitrides such as gallium nitride (GaN), aluminum nitride (AlN), or indium nitride (InN) may be generated by the reaction produced by the reaction formula (1). As shown in the reaction formula (1), hydrogen chloride (HCl) gas may be used as the reaction gas, and ammonia (NH ₃ ) gas may be used as the nitrogen generating gas. That is, the present invention assumes that X is gallium (Ga).

Therefore, referring back to FIG. 2 and the reaction formula (1), the gallium chloride gas injected through the reaction tube 250 and the gallium component contained in the sample boat 240 are chemically reacted to form gallium chloride (GaCl) gas. Create When the gallium chloride gas is discharged into the chamber 220, ammonia gas is injected through the injection pipe 230 connected to one side of the chamber 220. When the ammonia gas is injected, the ammonia gas and the gallium chloride gas discharged from the reaction tube 250 are combined in the chamber 220 to generate gallium nitride (GaN). The produced gallium nitride is deposited and grown on a surface of a base material such as a sapphire substrate supported by the susceptor 260. When the growth is completed, a single crystal gallium nitride film having a predetermined thickness is formed on the sapphire substrate.

As described above, according to the method for manufacturing a single crystal gallium nitride substrate according to the present invention, it is easy to separate the gallium nitride substrate and the base substrate by including a separation boundary film, and the crack propagates to the gallium nitride substrate during the separation process. It can be suppressed.

As described above, although the present invention has been described with reference to limited embodiments and drawings, the present invention is not limited to the above embodiments, and those skilled in the art to which the present invention pertains various modifications and variations from such descriptions. This is possible. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the claims below but also by the equivalents of the claims.

Claims (8)

A first growth step of growing a separation barrier on the base substrate by supplying a nitrogen source and a gallium source at a V / III ratio of 2: 1 to 7: 1; A second growth step of growing a thick gallium nitride film on the separation boundary film; And And separating the base substrate by irradiating a laser to an interface between the base substrate and the separation boundary layer. The method of claim 1, The separation boundary film is grown to have a thickness of 10 μm to 30 μm. The method of claim 1, The second growth stage, A crack prevention step of supplying a nitrogen source and a gallium source while sequentially decreasing the Group V / III ratio within a Group V / III ratio range of 8: 1 to 18: 1 to form a crack prevention film; And And a growth film forming step of supplying a nitrogen source and a gallium source in a V / III group ratio of 2: 1 to 10: 1 to form a gallium nitride growth film. The method of claim 3, The thickness of the crack preventing film is adjusted to 4 to 10% of the thickness of the gallium nitride growth film manufacturing method of a single crystal gallium nitride substrate. The method of claim 1, The nitrogen source is ammonia (NH ₃ ) gas and the gallium source is gallium chloride (GaCl) gas manufacturing method of a single crystal gallium nitride substrate. The method of claim 1, A method for producing a single crystal gallium nitride substrate, which uses a laser capable of irradiating a wavelength region of 345 to 385 nm. The method of claim 1, A method of manufacturing a single crystal gallium nitride substrate further comprising a nitriding step of nitriding the surface of the base substrate. The method of claim 7, wherein the nitriding treatment step, First nitriding under an ammonia gas atmosphere; Heat treatment under a mixed gas atmosphere containing ammonia gas and hydrogen chloride gas; And And a second nitriding process under the ammonia gas atmosphere.

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