KR101094409B1 - Preparation of single crystalline gallium nitride thick film - Google Patents

Abstract

The present invention relates to a method for producing a gallium nitride single crystal thick film using a hydride vapor deposition method (HVPE), GaN is supplied by first supplying a nitrogen source of Group 5 and a gallium source of Group 3 in a volume ratio of 8: 1 to 20: 1 According to the present invention for lateral growth of GaN by vertically growing and then changing the volume ratio from 1: 1 to 5: 1 and supplying secondly, a nitride having sufficient growth thickness and good crystallinity due to reduction of dislocation defect density and crack occurrence A gallium single crystal thick film can be produced, and such a gallium nitride thick film can be very usefully used as a substrate for semiconductor devices.

Description

Manufacturing method of gallium nitride single crystal thick film {PREPARATION OF SINGLE CRYSTALLINE GALLIUM NITRIDE THICK FILM}             

1 is a view schematically showing a manufacturing process of a gallium nitride single crystal thick film according to the present invention.

<Description of Main Parts of Drawings>

1: sapphire substrate 2: nitrided layer (AlN layer)

3: GaN vertical growth pillar 4: GaN single crystal

The present invention relates to a method for producing a gallium nitride single crystal thick film, and more particularly, to a method for producing a high quality gallium nitride single crystal thick film by controlling and supplying a supply ratio of a gallium nitride forming material.

Group III-V nitride semiconductors, such as GaN, GaInN mixed crystals, AlGaInN mixed crystals, and AlGaN mixed crystals, have a large energy band gap and are directly transition type semiconductor materials, which are useful for manufacturing light emitting devices in a short wavelength region and light emitting devices in a broad wavelength region. It is used. When using heterogeneous substrates such as sapphire as a substrate for growing GaN-based semiconductors, the same substrate of GaN single crystal has been used due to problems such as high dislocation density and cracks. There is a situation in which a free standing GaN single crystal substrate that satisfies the available thickness, size, and other characteristics has not been manufactured.

The single crystal gallium nitride (GaN) film is a vapor-growth method such as metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy, and hydride vapor phase epitaxy (HVPE). The HVPE growth method is advantageous for thick film growth of several to several hundred μm. In addition, according to the HVPE growth method, bulk growth of several mm is possible depending on growth conditions, substrate use conditions, and the like.

Sapphire (Al ₂ O ₃ ) substrates are most commonly used because of their hexagonal structure, such as gallium nitride, inexpensive, and stable at high temperatures. However, sapphire is advantageous for thin film growth of GaN, but in thick film growth, the difference in sapphire and gallium nitride and lattice constant (about 16%) and the coefficient of thermal expansion (about 36%) are large, making it difficult to grow a thick film of a certain thickness. It is difficult and has a high potential defect density of 10 ⁸ / cm 2, which may shorten the life of the final light emitting device.

In order to solve the dislocation defect problem of the sapphire / gallium nitride single crystal laminate, epitaxial lateral overgrowth (ELOG) technology [US Pat. No. 6,051,849] and similar PENDEO epitaxy technology [selective overlateral growth method] [US Patent 6,265, 289], a facet-initiated epitaxial lateral overgrowth (FIELO) technique for growing gallium nitride laterally [ Jpn, J. Appl. Phys. Vol. 36 (1997) L899-902] and similar void-assisted separation (VAS) techniques [ Jpn, J. Appl. Phys. Vol. 42 (2003) L1-L3] and the like. The above methods grow GaN thin films by sapphire using MOCVD, pattern them using a mask material such as SiO ₂ , Sn, W, and then secondly grow GaN using HVPE through an exposure and etching process. Therefore, the GaN growth process is not only complicated by using two different equipments, but also the potential defect density of the sapphire substrate and the GaN growth layer is not lowered to 6 × 10 ⁶ / cm 2 or less, and an artificial mask is used. Because of the stress caused by the application of the growth thickness of 330㎛ or more cracks occur and there is a problem that the growth film is shattered.

On the other hand, a technique for growing GaN single crystal directly to sapphire to a thickness of about 120 μm without the aid of a mask or the like [ APL. Vol. 80 (2002) L9] was introduced, but cracks also occurred, failing to obtain commercially available thicknesses.

Therefore, the inventors have made a thorough study and found that the GaN growth film formation raw material ratio is controlled to a specific range by HVPE single process without the dependence of other processes such as mask patterning, so that the density of dislocation defects is 8.5 × 10 ⁶ / cm 2 or less. In addition, it has been found that the GaN single crystal thick film having a commercially available growth thickness without cracking and excellent crystallinity can be grown.

An object of the present invention is to provide a gallium nitride single crystal thick film having a low dislocation defect density, a sufficient growth thickness without generation of cracks, and good crystallinity.

In order to achieve the above object, in the present invention, by means of hydride vapor deposition (HVPE), a nitrogen source of Group 5 and a gallium source of Group 3 are firstly supplied on a substrate in a volume ratio of 8: 1 to 20: 1. It provides a method for producing a gallium nitride single crystal thick film characterized in that the GaN is grown vertically, and then the nitrogen source and the gallium source are supplied secondly in a volume ratio of 1: 1 to 5: 1.

Hereinafter, the present invention will be described in more detail.

According to the present invention, by a single process of hydride vapor deposition, raw material is supplied in two stages on a nitrided substrate while the temperature is kept constant so that GaN single crystal is continuously grown, thereby providing sufficient potential defect density. It is possible to produce single crystal GaN thick films which are not only low but also have commercially available growth thickness without cracks and are excellent in crystallinity.

1 schematically illustrates a growth process of a GaN single crystal according to the present invention, which is performed using an HVPE reactor maintained at a constant temperature, and this growth process will be described in detail as follows.

First, the substrate surface is nitrided by mounting a substrate 1, preferably a sapphire substrate, in a growth zone of an HVPE reactor maintained at 600 ° C. or higher, preferably 990 to 1040 ° C., and then flowing ammonia gas. .

Then, GaN is grown by supplying ammonia and nitrogen, for example NH ₃ and GaCl gas, onto the nitrided substrate 1, wherein NH ₃ is primarily in excess of GaCl, such as in an amount of 8 to 20 times. By feeding for a predetermined time, preferably 0.5 to 4 hours, GaN (single crystal) is induced to grow vertically in a columnar shape. As such, when an excessive amount of nitrogen in Group 5 is supplied compared to Group 3 Ga, GaN is formed in a columnar shape by the vertical growth mode, and dislocation defects are generated only at a portion where the substrate and GaN are in contact with a large number of pillars. The overall dislocation defect density becomes low.

Subsequently, when the columnar GaN single crystal was grown to about 20 to 300 μm, the amount of NH ₃ was decreased while the amount of GaCl was increased, for example, for 4 to 6 hours such that the volume ratio of NH ₃ and GaCl was 1: 1 to 5: 1. During the second feed. In this case, as GaCl is enriched, lateral growth of GaN occurs additionally, so that the total growth thickness of GaN becomes 400 µm or more, thereby improving crystallinity.

In addition, in the present invention, Si-precursor gases such as silane (SiH ₄ ) or dichlorosilane (SiH ₂ Cl ₂ ) or the like may be incorporated in an amount of 0.1 to 100 cc / min to make the GaN single crystal n-type. have. At this time, the Si doping concentration is preferably 1 × 10 ¹⁶ to 10 ¹⁸ (pieces / cm 3).

The GaN single crystal grown as described above can be separated from sapphire by a conventional separation method to obtain a freestanding GaN single crystal thick film.

GaN single crystal thick film prepared according to the present invention has a low dislocation defect density of 8.5 × 10 ⁶ / cm 2 or less, (002) peak reference half-value width (FWHM) is 150 arcsec, excellent in crystallinity, the thickness is 300㎛ or more Even if the crack does not occur.

As such, the GaN single crystal thick film according to the present invention may be usefully used as a substrate for various light emitting devices by having a commercially available thickness and characteristics. For example, when the GaN single crystal thick film of the present invention is subjected to mirror processing on both surfaces, a GaN wafer having a surface roughness of 1 to 10 microseconds can be obtained, and it is 0.5 탆 or more and several to several ten 탆 on the GaN wafer by using a MOCVD deposition apparatus. The GaN, GaInN, AlGaInN, and AlGaN thin films can be deposited well without a hillock.

In addition, the GaN single crystal thick film of the present invention may be used as a seed substrate for regrowth of the GaN single crystal to a thickness of about 2 mm, and the regrown GaN single crystal is processed through a slicing process or the like. It can be used as a GaN wafer.

Hereinafter, the present invention will be described in more detail based on the following examples. However, the following examples are not intended to limit the invention only.

Example 1

A sapphire substrate having a diameter of 2 inches and a thickness of 430 μm was mounted in an HVPE reactor maintained at 980 ° C., and ammonia gas was flowed to the substrate surface to perform nitriding. Subsequently, GaN was grown by supplying 2400 sccm of NH ₃ and 300 sccm of GaCl for 30 minutes while maintaining the initial temperature, followed by 200 sccm of NH ₃ and 200 sccm of GaCl for 6 hours to grow GaN, followed by 5 cc / By supplying min dichlorosilane, an n-GaN single crystal thick film having a final growth thickness of 450 mu m was grown. The GaN single crystal thick film thus grown was separated from sapphire to obtain a freestanding GaN single crystal thick film.

Examples 2-8 and Comparative Examples 1-4

A GaN single crystal thick film was prepared in the same manner as in Example 1, except that the temperature of the HVPE reactor, the supply amount of NH ₃ and GaCl, and the supply time were changed to those shown in Table 1 below.

Crystallinity, dislocation defect density and crack formation of the freestanding GaN single crystal thick film obtained in Examples 1 to 8 were measured by double-crystal X-ray diffraction (DXRD), photo luminecence (PL) and optical microscope, respectively. 2 is shown.

From Table 2, the GaN single crystal thick film prepared according to Examples 1 to 8 had a sufficient growth thickness of 400 µm or more, but almost no cracking, and the dislocation defect density was low, such as 8.5 × 10 ⁶ / cm 2 or less. On the other hand, while the crystallinity was excellent, the GaN single crystal according to Comparative Example 1 had cracks and a high dislocation defect density, and in Comparative Examples 2 to 4, it was confirmed that the GaN thick film of the single crystal could not be obtained.

The monocrystalline thick film of GaN according to the present invention has low potential defect density as the vertical growth of columnar shape proceeds primarily, resulting in low crack incidence even when grown above a certain thickness, and excellent crystallinity according to secondary side growth. It can be usefully used as a substrate for an element.

Claims (14)

By hydride vapor deposition (HVPE), GaN is grown by first supplying a Group 5 nitrogen source and a Group 3 gallium source on a substrate in a volume ratio of 8: 1 to 20: 1, and then the nitrogen source and gallium source are 1 A method for producing a gallium nitride single crystal thick film, characterized in that the GaN is further grown by second supply in a volume ratio of 1: 1 to 5: 1. The method of claim 1, wherein the substrate is nitrided at a high temperature of at least 600 [deg.] C. before the supply of the nitrogen source and the gallium source. The method of claim 1 wherein the substrate is sapphire. The method of claim 1 wherein the HVPE run temperature is at least 600 ° C. 3. The method of claim 4, wherein the HVPE run temperature is between 990 and 1040 ° C. The method of claim 1 wherein the nitrogen source is ammonia (NH ₃ ) and the gallium source is gallium chloride (GaCl). The method according to claim 1, wherein the primary supply time of the nitrogen source and the gallium source is 0.5 to 4 hours, and the secondary supply time is 4 to 6 hours. The method of claim 1 further comprising supplying a Si precursor gas for Si doping. The method of claim 8, wherein the Si precursor gas is silane (SiH ₄ ) or dichlorosilane (SiH ₂ Cl ₂ ). delete delete delete delete delete

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