KR101890750B1 - Method for growing nitride semiconductor - Google Patents

Abstract

A method for growing a nitride semiconductor layer is disclosed. A method for growing a nitride semiconductor layer includes the steps of preparing a substrate, nitriding the substrate with a gas containing nitrogen, surface-treating the nitrided substrate to produce growth nuclei, And a step of laminating a nitride semiconductor on the buffer layer.

Description

[0001] The present invention relates to a method for growing a nitride semiconductor layer,

And a method of growing a nitride semiconductor layer.

The electronics industry using nitride semiconductors is expected to meet the development and growth of the green industry. Particularly, GaN, which is one of nitride semiconductors, is widely used for manufacturing blue light emitting diodes among red, green and blue light emitting diodes which are core elements of high output electronic component devices including light emitting diodes (LEDs). This is because blue light emitting diodes using GaN are superior to zinc selenide (ZnSe), which is a semiconductor material of light emitting devices that emit light in the blue region, because of their superior physical and chemical properties, to be. In addition, since GaN has a direct band gap bandgap structure and the band gap can be controlled from 1.9 to 6.2 eV through an alloy of In or Al, it is very useful as an optical device. In addition, it is useful in various fields such as high output devices and high temperature electronic devices which can not be realized by conventional materials since the breakdown voltage is high and stable at high temperature. For example, a large electric signboard using a full color display, a light source of a signal lamp, an optical recording medium, a high output transistor of an automobile engine, and the like. GaN substrates are indispensable for the fabrication of high output LEDs because of fewer defects, the same refractive index of substrate and element layer, and larger thermal conductivity than sapphire.

There is provided a nitride semiconductor layer growth method capable of improving a crack generation and a melt back problem due to a difference in lattice constant and a difference in thermal expansion coefficient when a nitride semiconductor layer is grown on a substrate.

A method of growing a nitride semiconductor layer according to an embodiment of the present invention includes: preparing a substrate; Nitriding the substrate using a gas containing nitrogen; Subjecting the nitrided substrate to surface treatment to produce growth nuclei; Low temperature growth of the buffer layer on the growth nuclei; And stacking the nitride semiconductor on the buffer layer.

The substrate may be nitrided using ammonia gas.

Nitriding of the substrate may be performed at a temperature of 800 to 1100 degrees.

The nitridation of the substrate can proceed within 0.1 minute to 100 minutes.

When the substrate is nitrided, the partial pressure of the nitrogen-containing gas may be 1 to 30%.

HCl may be used for the surface treatment.

HCl and NH ₃ may be used for the surface treatment.

The surface treatment of the substrate may be performed in a temperature range of 800 to 1100 degrees.

The HCl and NH ₃ may have a flow rate of 1 to 20000 sccm or a partial pressure of 1 to 30%.

The substrate is a silicon substrate, and? -Si ₃ N ₄ can be produced by nitriding the substrate.

The substrate may be nitrided to produce beta -Si ₃ N ₄ having an HCP structure.

The buffer layer may be grown in a temperature range of 800 to 900 degrees.

The growth temperature of the nitride semiconductor may be higher than the growth temperature of the buffer layer.

The growth temperature of the nitride semiconductor may be in the range of 800 to 1100 degrees.

The nitride semiconductor may be GaN.

The nitride semiconductor may be grown to a thickness of 100 nm to 400 탆.

According to the method of growing a nitride semiconductor layer according to an embodiment of the present invention, it is possible to improve a crack generation and a melt back problem due to a difference in lattice constant and a difference in thermal expansion coefficient when a nitride semiconductor layer is grown on a substrate.

A nitride semiconductor layer can be grown by an in situ process without an ex situ process for forming a separate buffer layer. For example, a high quality GaN thick film is grown on a low-cost silicon substrate Can

FIGS. 1 to 5 are views for explaining a process of growing a nitride semiconductor layer according to an embodiment of the present invention.
6a to 6c are graphs showing the morphology changes of the GaN buffer layer according to the nitridation time when the buffer GaN was grown to a thickness of about 10 mu m by the HVPE method at a temperature of about 870 degrees on the silicon substrate. SEM: scanning electron microscope).
Figure 7a by appropriate nitride time, silicon nitride (Si ₃ N ₄₎ determining the structure is formed on the silicon nitride (Si ₃ N ₄₎ distribution and silicon nitride and the silicon substrate when the appropriate HCP structure of the GaN epitaxial growth GaN growth nuclei.
FIG. 7B shows the resulting amorphous silicon nitride (SiNx) distribution and the amorphous silicon nitride and the GaN growth nuclei formed on the silicon substrate when the nitridation time increases.
FIGS. 8A and 8B show morphology photographs of buffer GaN according to the HCl flow rate in the surface treatment step using HCl + NH _{3 in} growing HVPE buffer GaN on a silicon substrate. FIG.
FIGS. 9A and 9B are photographs showing GaN growth of about 30 .mu.m thick on a silicon substrate on which buffer GaN is grown to a thickness of about 10 .mu.m when the buffer GaN growth temperature is about 890 and about 1030, respectively.
10A to 10C show the morphology change of GaN thick film according to the buffer layer growth temperature when HVPE GaN is grown on the silicon substrate. The nitridation time is about 0.1 min and the thick film thickness is about 100 μm .

Gallium nitride (GaN) in a nitride semiconductor has a bandgap energy of about 3.39 eV and is a wide bandgap semiconductor material which is a direct transition type and is useful for manufacturing a light emitting device in a short wavelength region.

Since the GaN single crystal has a high nitrogen vapor pressure at the melting point, the liquid crystal growth requires a high temperature of about 1500 ° C or higher and a nitrogen atmosphere of about 20000 atmospheres, which is not only difficult to mass-produce, but also has a crystal size of about 100 mm 2 It is difficult to use in production.

Therefore, the GaN thin film is grown on a heterogeneous substrate by a vapor phase growth method such as MOCVD (Metal Organic Chemical Vapor Deposition) or HVPE (Hydride Vapor Phase Epitaxy).

However, when GaN is grown on a silicon substrate, for example, when silicon and GaN directly contact each other, silicon diffuses into GaN and the surface of the silicon substrate is etched to cause melt back, And the difference in the thermal expansion coefficient and the lattice constant of GaN, a crack may be generated during GaN growth on the silicon substrate. In order to solve this problem, although a method of growing GaN on a silicon substrate by using a graded buffer layer or the like is used, a thin GaN thin film can be grown by this method. However, There is still a problem. In addition, when GaN is grown on a silicon substrate by a HVPE (Hydride Vapor Phase Epitaxy) method, the buffer layer can not be grown in situ, and most of it is grown by MOCVD (Metal Organic Chemical Vapor Deposition) sputtering or the like is used. Therefore, it takes much time and cost to grow GaN on the buffer layer.

According to the method of growing a nitride semiconductor layer according to an embodiment of the present invention, a high-quality nitride semiconductor, for example, GaN is grown on a substrate with a meltback preventing effect and a stress-complete effect depending on the density of nuclei And can be in situ, which is a great advantage in terms of time and cost.

For example, GaN can be grown from a low temperature using Si ₃ N ₄ nuclei generated by the reaction of NH ₃ with a silicon substrate during GaN growth on a silicon substrate in an HVPE reactor, It is possible to grow high-quality GaN on the silicon substrate by an in-situ process due to the meltback prevention effect and the stress relaxation effect due to the density of the Si ₃ N ₄ nuclei.

The structure including the nitride semiconductor layer, for example, a GaN layer, grown on a different substrate such as a silicon substrate can substantially serve as a GaN substrate. In a subsequent step, when a heterogeneous substrate such as a silicon substrate is removed, the grown nitride semiconductor layer, for example, a GaN layer, may be used as a freestanding nitride semiconductor substrate, for example, a GaN substrate.

Hereinafter, a method of growing a nitride semiconductor layer according to an embodiment of the present invention will be described in more detail with reference to the accompanying drawings. The thickness of the layers in the drawings may be exaggerated for convenience of explanation.

FIGS. 1 to 5 are views for explaining a process of growing a nitride semiconductor layer according to an embodiment of the present invention.

Referring to FIG. 1, first, a substrate 1 is prepared. As the substrate 1, for example, a silicon substrate can be used.

Next, the prepared substrate 1 is nitrided by using a gas containing nitrogen. Nitriding is a step of forming a nitrogen compound 5 through ammonia treatment. When the silicon substrate 1 is used as the substrate 1, a silicon nitride (Si ₃ N ₄ ) may be generated.

The nitridation of the substrate 1 can be performed at a temperature of about 800 to about 1100 degrees in about 0.1 minute to about 100 minutes. Further, when nitriding the substrate 1, the partial pressure of the nitrogen-containing gas such as ammonia gas (NH ₃ ) may be in the range of about 1 to about 30%.

For example, the silicon substrate 1 may be nitrided at a temperature in the range of about 800 to about 1100 degrees with NH ₃ in an HVPE reactor, at which time the silicon substrate 1 has a hexagonal close-packed lattice (HCP) structure suitable for epitaxial growth of a nitride semiconductor such as GaN. That is, when the nitriding time is appropriate, β-Si ₃ N ₄ having the HCP structure can be produced. Also, the area ratio of β-Si ₃ N ₄ on the silicon substrate 1 may vary depending on the nitridation time and the flow rate.

Next, as shown in FIG. 3, the nitrided substrate 1 is surface-treated to form nuclei 7. Here, the growth nuclei 7 refers to a state in which the surface of a part of the nitrogen compound 5 (for example, silicon nitride) generated at the time of surface nitrification is activated surface by surface treatment). The adsorption of the nitride semiconductor, for example, GaN, on the surface of the activated nitrogen compound 5 can be facilitated.

For the surface treatment of the nitrided substrate 1, HCl may be used. That is, HCl and NH ₃ can be used for the surface treatment. At this time, the surface treatment of the substrate 1 may be performed in a temperature range of about 800 to about 1100 degrees. In addition, the HCl and NH ₃ may have a flow rate of about 1 to about 20000 sccm, and the partial pressure may range from about 1% to about 30%.

For example, the silicon substrate 1 can be surface-treated with HCl and NH ₃ at a temperature of about 800 to about 1100 degrees on the silicon substrate 1 on which β-Si ₃ N ₄ has been formed. The silicon substrate 1 and the β-Si ₃ N ₄ surface-treated with HCl and NH ₃ can easily adsorb and nucleate the nitride semiconductor such as GaN. At this time, crystallinity and nuclei density of GaN produced according to surface treatment temperature, HCl, NH ₃ flow rate and surface treatment time can be determined.

Next, a buffer nitride semiconductor, for example, buffer GaN is grown on the surface-treated substrate 1 to form a buffer layer 10 as shown in FIG. At this time, the buffer nitride semiconductor can be low temperature grown at a temperature at which no melt back occurs, for example, in a temperature range of about 800 to about 900 degrees.

The growth of the buffer nitride semiconductor, for example, buffer GaN, has a region directly grown on the nitrogen compound 5 produced through the surface nitridation and a region grown on the substrate 1 material, Can vary. During the growth of the buffer nitride semiconductor, the lateral growth rate is increased to grow the nitride semiconductor grown on the nitrogen compound to coalesce.

For example, when a GaN layer is to be grown on the substrate 1, the buffer nitride semiconductor becomes a buffer GaN. When a GaN layer is to be grown on the silicon substrate 1, buffer GaN is grown at a temperature at which melt back does not occur, for example, in the range of about 800 to about 900 degrees. At this time, the growth of the buffer GaN has a region directly grown on the β-Si ₃ N ₄ phase and a region grown on the silicon, and the ratio varies depending on the degree of nitriding. When the lateral growth rate of the buffer layer 10 is increased, the GaN grown on the β-Si ₃ N ₄ phase grows to coalesce and form the buffer layer 10.

Next, a nitride semiconductor such as GaN is stacked on the buffer layer 10 to obtain a structure in which a thick nitride semiconductor layer 30, that is, a GaN layer, is stacked on the substrate 1 without cracks . The nitride semiconductor layer 30 may be grown to a thickness of about 100 nm to about 400 탆. At this time, the nitride semiconductor layer 30 can be grown at a temperature higher than the growth temperature of the buffer layer 10, for example, within a range of about 800 to about 1100 degrees.

6A to 6C show morphology changes of the GaN buffer layer 10 with nitridation time when buffer GaN is grown to a thickness of about 10 mu m at a temperature of about 870 degrees on the silicon substrate 1 by the HVPE method Showing scanning electron microscope (SEM) photographs. 6A to 6C show morphology changes of the GaN buffer layer at nitriding times of 0.1 minute, 1 minute, and 5 minutes, respectively. In FIG. 6A, well-oriented GaN is generated, and in FIGS. 6B and 6C, polycrystalline GaN is generated. As can be seen from Figs. 6A to 6C, as the nitridation time decreases, the density of well-aligned GaN increases and vice versa. This is because when the nitriding time is short, the crystal structure of silicon nitride (Si ₃ N ₄ ) generated in the silicon substrate 1 becomes an HCP structure suitable for GaN epitaxial growth, and when the nitriding time is increased, it becomes amorphous SiNx, The GaN grown on the nitride may not be epitaxially oriented and may be formed of polycrystalline GaN.

Figure 7a by appropriate nitride time, silicon nitride (Si ₃ N ₄₎ crystal structure of the silicon nitride when the appropriate HCP structure of the GaN epitaxial growth: on (40 Si ₃ N ₄₎ distribution and silicon nitride (40) The GaN growth nuclei 50 formed on the silicon substrate 1 and the GaN growth nuclei 50 'formed on the silicon substrate 1 are shown. 7B shows a GaN growth nucleus 50 " formed on the amorphous silicon nitride (60: SiNx) distribution and amorphous silicon nitride and a GaN growth nucleus 50 "formed on the silicon substrate 1 50 ').

FIGS. 8A and 8B show morphology photographs of buffer GaN according to the HCl flow rate in the surface treatment step using HCl + NH ₃ in the HVPE buffer GaN growth on the silicon substrate 1. FIG. FIGS. 8A and 8B show the results obtained when the buffer GaN growth temperature is 870 ° C. and the buffer GaN thickness is 10 μm, and the HCl flow rates are 50 sccm and 100 sccm, respectively. When the HCl flow rate was reduced to 50 sccm, as shown in FIG. 8A, polycrystalline GaN and single crystalline GaN were mixed, and when the HCl flow rate was increased to 100 sccm, There is only a single crystalline GaN phase, as can be seen in Fig. That is, when the surface treatment with HCl is insufficient, it is not easy to nucleate β-Si ₃ N ₄ phase GaN and polycrystalline GaN is generated. On the other hand, when surface treatment with HCl is sufficient, nucleation of GaN is easy, The density of GaN can be increased and single crystalline GaN can be produced. Of course, when the surface treatment by HCl is too much, the density of GaN becomes too high, so cracks may occur as shown in the photograph of FIG. 8B.

8A and 8B, it can be seen that a single crystal buffer GaN can be produced by appropriately adjusting the HCl flow rate in the surface treatment step using HCl + NH ₃ in the HVPE buffer GaN growth on the silicon substrate 1 .

FIGS. 9A and 9B are photographs showing GaN growth of about 30 .mu.m thick on a silicon substrate on which buffer GaN is grown to a thickness of about 10 .mu.m when the buffer GaN growth temperature is about 890 and about 1030, respectively. FIG. 9A shows a state in which a GaN layer in a mirror surface state is grown in the region of most of the substrate. FIG. 9B shows a state in which melt back occurs in the region of most of the substrate.

As can be seen from the comparison of Figs. 9A and 9B, when buffer GaN is grown at a high temperature of about 1030 deg. C, melt back occurs in most regions of the substrate, but buffer GaN grows at a temperature of about 890 deg. , It is confirmed that no melt back occurs when GaN is grown.

Therefore, it can be seen that when the buffer GaN is grown at a relatively low GaN growth temperature of about 890 degrees, that is, when the buffer layer 10 is grown at a low temperature, the meltback can be prevented.

Therefore, according to the method of growing a nitride semiconductor layer according to an embodiment of the present invention, the buffer layer 10 is grown at a low temperature in a temperature range in which no meltback occurs, so that meltback can be prevented during growth of the gan.

10A to 10C show the morphology change of GaN thick film according to the buffer layer growth temperature when HVPE GaN is grown on the silicon substrate. The nitridation time is about 0.1 min and the thick film thickness is about 100 μm . FIGS. 10A to 10C show the results when the buffer layer growth temperature is about 870 degrees, about 890 degrees, and about 900 degrees, respectively. 10A to 10C are a photograph of a wafer of GaN after thick-film GaN growth after HVPE buffer GaN growth and an XTEM image of a buffer GaN layer, respectively.

Referring to FIGS. 10A to 10C, well-oriented GaN is generated from the growth temperature of the buffer GaN layer of about 890 degrees in the wafer photograph, so that the wafer surface shows a mirror surface, , The GaN morphology becomes finer and the crystallinity is also improved. This is because lateral growth is increased with increasing growth temperature, and well-aligned GaN production is easy, and XTEM photograph shows the same result.

As described above, according to the method of growing a nitride semiconductor layer according to an embodiment of the present invention, an in situ process can be carried out without an ex situ process for forming a separate buffer layer 10, A high-quality GaN film can be grown on the silicon substrate.

Claims (20)

Preparing a silicon substrate;
Nitriding the silicon substrate using a gas containing nitrogen to produce a silicon nitride crystal structure;
Nitriding the surface of the silicon substrate on which the silicon nitride crystal structure has been formed to produce a growth nuclei having a surface state in which a part of the surface of the silicon nitride is activated by surface treatment;
Growing a nitride semiconductor buffer layer on the growth nucleus at a low temperature;
And laminating a nitride semiconductor on the nitride semiconductor buffer layer. The method of growing a nitride semiconductor layer according to claim 1, wherein the nitridation of the silicon substrate is performed using ammonia gas. The method of growing a nitride semiconductor layer according to claim 2, wherein the nitridation of the silicon substrate is performed at a temperature of 800 to 1100 degrees. The method of growing a nitride semiconductor layer according to claim 1, wherein the nitridation of the silicon substrate proceeds within 0.1 minute to 100 minutes. The method of growing a nitride semiconductor layer according to claim 1, wherein a partial pressure of the nitrogen-containing gas during nitridation of the silicon substrate is 1 to 30%. The method of growing a nitride semiconductor layer according to claim 1, wherein HCl is used for the surface treatment. The method of growing a nitride semiconductor layer according to claim 1, wherein HCl and NH ₃ are used for the surface treatment. The method of growing a nitride semiconductor layer according to claim 7, wherein the surface treatment of the silicon substrate is performed in a temperature range of 800 to 1100 degrees. The method of growing a nitride semiconductor layer according to claim 7, wherein the HCl and NH ₃ have a flow rate of 1 to 20000 sccm or a partial pressure of 1 to 30%. The method for growing a nitride semiconductor layer according to any one of claims 1 to 9, wherein β-Si ₃ N ₄ is produced by nitriding the silicon substrate. 11. The method of claim 10, by nitriding the silicon substrate, β-Si ₃ N ₄ is produced nitride semiconductor growth method that is having a HCP structure. The method of growing a nitride semiconductor layer according to claim 10, wherein the buffer layer is grown in a temperature range of 800 to 900 degrees. 13. The method of growing a nitride semiconductor layer according to claim 12, wherein a growth temperature of the nitride semiconductor is higher than a growth temperature of the buffer layer. 14. The method of growing a nitride semiconductor layer according to claim 13, wherein the nitride semiconductor has a growth temperature of 800 to 1100 degrees. The method of growing a nitride semiconductor layer according to claim 10, wherein the nitride semiconductor is GaN. The method of growing a nitride semiconductor layer according to claim 10, wherein a growth temperature of the nitride semiconductor is higher than a growth temperature of the buffer layer. 10. The nitride semiconductor layer growth method according to any one of claims 1 to 9, wherein a growth temperature of the nitride semiconductor is higher than a growth temperature of the buffer layer. 18. The method of growing a nitride semiconductor layer according to claim 17, wherein the nitride semiconductor has a growth temperature of 800 to 1100 degrees. 10. The nitride semiconductor layer growth method according to any one of claims 1 to 9, wherein the nitride semiconductor is grown to a thickness of 100 nm to 400 占 퐉. 10. The nitride semiconductor layer growth method according to any one of claims 1 to 9, wherein the nitride semiconductor is GaN.

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