KR101457208B1

KR101457208B1 - Group ⅲ nitride compound semiconductor device

Info

Publication number: KR101457208B1
Application number: KR1020080091879A
Authority: KR
Inventors: 최재빈; 유홍재
Original assignee: 서울바이오시스 주식회사
Priority date: 2007-09-21
Filing date: 2008-09-19
Publication date: 2014-10-31
Also published as: KR20090031272A; JP2009076914A; JP5097661B2

Abstract

A Group III nitride compound semiconductor device comprising a substrate, buffer layers on the substrate, and a Group III nitride compound semiconductor layer on top of the buffer layers. The buffer layers include a first buffer layer formed on the substrate and a second buffer layer formed on the first buffer layer. The first buffer layer is made of a transition metal nitride, and the second buffer layer is made of a nitride of gallium and a transition metal.

Substrate, buffer layer, transition metal, TiN, gallium, nitride

Description

III-NITRIDE COMPOUND SEMICONDUCTOR DEVICE [0001]

The present invention relates to a semiconductor field, and more particularly, to a Group III nitride compound semiconductor device suitable for a light emitting optoelectronic device.

Group-III nitrides provide a significant advantage of strong chemical bonding, so that they are very stable and prevent degradation under light conditions of large current and strong light present in the active area of the optoelectronic device. Further, the group III nitride is prevented from dislocation formation once it is grown.

Due to the high growth temperature of the Group III nitride, the type of known substrate suitable for supporting nitride film growth is currently limited. The most commonly used substrate materials are sapphire and silicon carbide. These materials have significantly different lattice constants and thermal expansion coefficients than the Group III nitride. Thus, the interface formed between the substrate and the nitride lacks coherence, increasing interface strain and interfacial energy, and reducing film wetting. These factors have a great influence on the nitride film growth process and the resulting nitride film. For example, a process of three-dimensionally growing Group III nitride on sapphire is known. By forming a discrete three-dimensional nitride island on the substrate, Group III nitride film growth first occurs. These islands grow and coalesce together. The lattice matching is poor in regions of the film where the island is incorporated. High dislocation densities occur in these regions. The dislocation arrangement in the nitride film adversely affects the optoelectronic properties of optoelectronic devices fabricated on the nitride by affecting the carrier recombination action in the active area of the optoelectronic device and ultimately reduces the emission intensity and efficiency of the device.

In recent years, many developers have sought new nitride platforms without adjacent bulk GaN for commercial reasons, and some engineers have started to look at composites and metals beyond silicon and SiC as platforms for nitride growth. Among the many composites and metals, there is a growing interest in TiN materials as candidates for new nitride platforms. In general, TiN thin films have many uses for covering electronic to biomaterials from mechanical hard coatings, including military applications, aerospace industry, due to their excellent chemical, mechanical and thermal stability. Though less visible, thin-film TiN is also used in the semiconductor industry. In a copper-based chip, in order to operate it, the TiN film has the use of a conductive barrier between a silicon device and a metal contact. The thin film is conductive enough to block diffusion of the metal into the silicon, while allowing enough good electrical connection (30-70 μΩ-cm).

However, few attempts have been made to introduce transition metal nitrides such as TiN for use in the production of Group III nitride semiconductor devices. To date, no growth method has been established to form (Ti, Ga) N deposited TiN or co-deposited on a sapphire substrate with or without a pattern for optoelectronic applications.

Two-dimensional growth of Group III nitride films on a substrate is desirable to reduce the dislocation density of the films. However, in a known process, two-dimensional growth is inhibited by high interfacial energy between the substrate and the film. After the Irish coalesce and become dislocated, two-dimensional growth begins.

GaN and its associated compounds have successfully penetrated the light emitting device market. Less than that, but also in the photodetector market. However, in addition to bringing high-performance electronics to the market, the momentum for device improvement has come from GaN technology, which improves the electronic or optical properties that are greatly affected by the non-native substrate on which GaN is heteroepitaxially grown It is driving. As such, heteroepithelium GaN has a high density of penetration dislocations (TDs) and associated point defects, all of which contribute to carrier scattering, degradation of radiative recombination efficiency, or instability, It is harmful. For penetration dislocation (TD) problems, ELO (epitaxial lateral overgrowth) techniques have been developed and widely used to obtain device-quality GaN epilayers. However, the ELO process requires an x-situ (off-site) photolithographic step (s), which are frequent, cumbersome, and costly as the process repeats itself in a given structure.

One object of the present invention is to provide a Group III nitride semiconductor device which avoids the above-mentioned disadvantages.

Another object of the present invention is to provide a method for manufacturing a Group III nitride compound semiconductor which overcomes the above-mentioned disadvantages.

The above objects are achieved by using nitride of a transition metal nitride and Ga and a nitride of a transition metal as buffer layers between the substrate and the Group III nitride compound semiconductor layer.

One aspect of the present invention provides a Group III nitride compound semiconductor device comprising a substrate, buffer layers on the substrate, and a Group III nitride compound semiconductor layer on top of the buffer layers. The buffer layers include a first buffer layer formed on the substrate and a second buffer layer formed on the first buffer layer. The first buffer layer is made of a transition metal nitride, and the second buffer layer is made of a nitride of gallium and a transition metal.

Preferably, the transition metal comprises at least one element selected from the group consisting of titanium (Ti), zirconium (Zr), hafnium (Hf) and tantalum (Ta).

Preferably, the buffer layers further comprise a third buffer layer interposed between the second buffer layer and the Group III nitride compound semiconductor layer, and the third buffer layer is made of GaN.

Preferably, the substrate is made of a material selected from sapphire, silicon carbide, gallium nitride, gallium phosphide, gallium arsenide.

Preferably, the first buffer layer has a thickness of 20-100 A, the second buffer layer has a thickness of 50-100 A, and the third buffer layer has a thickness of 200-300 A.

Preferably, the first buffer layer is made of TiN, and the second buffer layer is made of (Ti, Ga) N. More preferably, the (Ti, Ga) N comprises a Ti ₂ GaN phase.

Another aspect of the present invention provides a method of manufacturing a Group III nitride compound semiconductor device including a substrate, a buffer layer on the substrate, and a Group III nitride compound semiconductor layer on a top layer of the buffer layers. The method includes forming a first buffer layer made of a transition metal nitride on the substrate, and forming a second buffer layer made of gallium and a transition metal nitride on the first buffer layer.

Preferably, the method further comprises forming a third buffer layer on the second buffer layer, and interposing the third buffer layer between the second buffer layer and the Group III nitride compound semiconductor layer. The third buffer layer is made of GaN.

Preferably, the first buffer layer, a transition metal nitride layer, a TiN layer may be formed using a metal selected from the organic source of titanium and more preferably, TDEAT, TDMAT, TTIP and TiCl _4.

Preferably, the second buffer layer can be a layer (Ti, Ga) formed using a metal organic source of titanium selected from the TDEAT, TDMAT, TTIP and TiCl ₄ N.

Unlike the conventional method of forming a single buffer layer on a substrate at low temperature, one embodiment of the present invention is a method of forming an interface layer between a sapphire substrate and a Group III nitride (GaN layer) in a reactor having a high growth temperature a new method of in-situ growth of a TiN layer, which is a transition metal nitride, and a TiN compound layer (more specifically, a (Ti, GaN) layer), which is a nitride of a transition metal and Ga, to provide.

Generally, according to the conventional method, it is known that forming the buffer layer on the sapphire substrate enhances the formation of the two-dimensional nuclei on the GaN film on the buffer layer. This has improved the electrical performance and the light emitting performance, but if the atomic crystallinity is further increased on the interface between the substrate and the GaN film, the quality of the GaN films may be further increased.

Therefore, it is desirable to grow an improved Group III nitride film on the substrate. In particular, improved Group III nitride films are desirable, which have reduced dislocation densities, improved electrical performance, and are used in optoelectronic devices to provide improved device performance.

On the substrate and between the substrate and the Group III nitride, a TiN buffer layer and a buffer layer containing the Ti compound with it can play an important role in controlling the photoelectron performance of material quality such as TD (penetration potential) problems. Moreover, with the present invention, optical performance can be further enhanced due to the excellent infrared reflection characteristics of TiN that reflects light in a spectrum similar to gold (Au) elements.

The present invention provides Group-III nitride films having reduced dislocation density and grown on a substrate. The present invention also provides a method of forming an improved Group III nitride film on a substrate. The Group III nitride film may be used in a light emitting device including LEDs and a diode laser for improving the performance.

Improved Group III nitride films formed in accordance with the present invention may be used in optoelectronic devices for improved performance.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided by way of example so that those skilled in the art can fully understand the spirit of the present invention. Therefore, the present invention is not limited to the embodiments described below, but may be embodied in other forms. In the drawings, the width, length, thickness, and the like of the components may be exaggerated for convenience. Like reference numerals designate like elements throughout the specification.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic cross-sectional view of a substrate comprising a substrate, a first buffer layer on the substrate, a second buffer layer on the first buffer layer, a third buffer layer on the second buffer layer, and a Group III nitride layer on the third buffer layer, Fig.

Referring to FIG. 1, the substrate 17 may be sapphire, silicon carbide (SiC), Si, gallium nitride, gallium phosphide, zinc oxide (ZnO) or other types of substrates.

Layer 27 is a first buffer layer 17 made of titanium nitride wherein the titanium is selected from the group consisting of tetrakis-diethylamino-titanium, [Ti (NEt2) 4], tetrakis-dimethylamino- ], TTIP (titanium isopropoxide, Ti (OC 3 H 7) 4), or TiCl ₄ gas, and nitrogen comes from nitrogen gas or NH ₃ .

Since the transition metal nitride has metallic luster, an increase in luminescence is expected in the case of an LED using sapphire as a substrate. Light emitted from the LED is reflected by a transition metal nitride having metallic luster, such as titanium nitride, hafnium nitride, zirconium nitride, tantalum nitride, and the like.

Further, since the transition metal nitride such as TiN has a hardness lower than that of sapphire, the function of alleviating the twist (or internal stress) caused by the difference in lattice constant or thermal expansion coefficient between the sapphire substrate and each Group III nitride compound semiconductor layer have. Useful methods for growing transition metal nitride include, for example, CVD (chemical vapor deposition) such as plasma CVD, thermal CVD, optical CVD, and the like; But are not limited to, PVD (physical vapor deposition) such as sputtering, reactive sputtering, laser ablation, ion plating, evaporation, ECR, and the like.

The first buffer layer 27 is interposed between the second buffer layer 28 and the substrate 17. The first buffer layer 27 is formed on the substrate by a vapor deposition method or a sputtering method.

Layer 28 is a second buffer layer made of (Tix, Gay) N (where 0 <x <10, O <y <10).

After the growth of the first buffer layer 27, each of TMG (trimethyl gallium), Ti precursor, and ammonia (NH ₃ ) flows into the substrate or substrate assembly in the presence of an inert gas. (Ti, Ga) N layer is formed by chemical vapor deposition, more preferably MOCVD. For the growth of the second buffer layer 28 with better crystallinity, a relatively higher growth temperature is required compared to the growth temperature of the third buffer layer 29. Layer 29 is a third buffer layer having a thickness of about 200-300 angstroms. The third buffer layer 29 is typically made of GaN formed at a low temperature of 580 캜. The growth conditions of the third buffer layer 29 are the same as the growth conditions of the second buffer layer 28 except for stopping the flow of the Ti precursor and lowering the growth temperature to about 580 캜.

2 shows a structure of a light emitting diode according to a second embodiment of the present invention. The Group III nitride compound semiconductor device includes a substrate, a first buffer layer on the substrate, a second buffer layer on the first buffer layer, a third buffer layer on the second buffer layer, and a Group III nitride layer on the third buffer layer .

Referring to FIG. 2, the substrate may be a hexagonal material such as sapphire, SiC (silicon carbide), or GaN (gallium nitride), or a material such as Si (silicon), GaP (gallium phosphide), GaAs (gallium azide) And may be equiaxed crystal material. According to this embodiment, the substrate is made of sapphire (Al ₂ O ₃ ). Further, the surface shape of the substrate 47 may be flat or may be a patterned shape having a different crystal orientation.

The first buffer layer 57 made of titanium nitride can be formed on the substrate 47 at a relatively high temperature. The optimum growth temperature for obtaining a high quality titanium nitride layer can be determined by parameters such as the growth process, such as the ambient gas, the type of metal organic source, and the growth method. The first buffer layer 57 is formed when the substrate temperature is about 500 ° C to about 1000 ° C. The formation of the first buffer layer 57 may be performed in a deposition chamber having a pressure of about 0.1 torr to about 100 torr. The first buffer layer 57 has a thickness of about 20 ANGSTROM to about 100 ANGSTROM.

As described above, in order to reduce defects caused by heteroepitaxial growth between the sapphire (Al ₂ O ₃ ) substrate and the nitride layer in consideration of the quality of the LED device, using titanium nitride as the interface layer (or buffer layer) Little was reported. The first buffer layer 57 is made of a titanium nitride (111) surface having a rock salt structure. The epitaxial relationship of the TiN / sapphire (Al ₂ O ₃ ) heterostructure was already confirmed from theta / 2theta scan and FWHM of the X-ray diffraction. In addition, there is a report from the XRD oscillation curve measurement that the FWHM of TiN on sapphire is narrower than GaN on sapphire (Al ₂ O ₃ ). 3 is Al ₂ O ₃ a (0001) on, and, Al ₂ O ₃ (0001), and epi-and high-resolution image of the boundary between the epitaxial TiN (111), processing by software in the "Digital micrographs (Digital Micrograph)" Fourier-filtered images are displayed. Note the extra faces specified by the arrows. These are discordant dislocations that mitigate lattice mismatch.

After the first buffer layer 57 is directly grown on the substrate 47, the second buffer layer 58 is grown on the first buffer layer 57 at a temperature of about 500 ° C. to about 1000 ° C., more preferably about 850 ° C. . The second buffer layer 58 may be composed of a (Ti, Ga) N alloy. During or immediately after the formation of the second buffer layer 58 on the first buffer layer 57, a spontaneous thermodynamic action such as diffusion between the Ti, Ga, and N (nitrogen) And therefore occurs at a predetermined interval. In fact, the basic research on the thermal stability of the Ti-Ga-N (ternary) system has been carried out by other researchers.

Fig. 4 shows a Ti-Ga-N (ternary) isotherm at room temperature. This is roughly calculated by a partial thermodynamic estimate.

The observed diffusion path in the annealed diffusion couples at 850 [deg.] C is supplemented. From Fig. 4, it can be seen that the reaction between Ti and GaN is possible at a temperature of about 850 캜 (estimated at the annealing temperature). This means that a (Ti, Ga) N ternary alloy containing a Ti ₂ GaN phase can be identified. The results of this study using Ti / GaN cells are in good agreement with the present invention.

A Ti precursor from a metal organic source such as TiCl ₄ gas, trimethyl-gallium (TMG) and ammonia (NH 3) is added to a reactor having a pressure of 100 torr to 500 torr to form a second buffer layer 58 having a thickness of 50 ANGSTROM to 100 ANGSTROM On the substrate. The third buffer layer 59 is made of GaN. This layer is typically grown at a low temperature of 530 캜 to 600 캜, most preferably 580 캜.

A process for obtaining a kind of low temperature single buffer layer is already known. Therefore, the third buffer layer 59 of the present invention is almost the same as the low temperature GaN buffer layer of the known process. The third buffer layer 59 has a thickness of 200 ANGSTROM to 300 ANGSTROM. According to this embodiment, new layers such as a second buffer layer 58 and a first buffer layer 57, which include a TiN material between the substrate 47 and the third buffer layer 59, It plays an important role in reducing potential.

Thus, the overall quality of a Ill-nitride semiconductor LED device can be improved by using a new interlayer with a TiN compound. Figures 5A and 5B show the effect of the TiN layer on GaN dislocation reduction in a cross-sectional view showing the case with TiN and the case without TiN.

The Group III nitride compound semiconductor layer 67 may be a light emitting device, a photodetector, or an optical receiver. The Group III nitride compound semiconductor layer 67 may include a p-type GaN layer, an n-type GaN layer, and an active layer interposed between the p-type GaN layer and the n-type GaN layer.

Using a method or apparatus for forming a buffer layer on a substrate, in particular a semiconductor substrate or a substrate assembly, the use of a deposition process with one or more precursor compounds comprising titanium ligands from the present invention, A Group III nitride compound semiconductor device can be obtained.

1 illustrates a structure according to an embodiment of the present invention including a substrate, a first buffer layer on the substrate, a second buffer layer on the first buffer layer, a third buffer layer on the second buffer layer, and a Group III nitride film on the third buffer layer. Fig.

Figure 2 shows a structure according to another embodiment of the present invention comprising a substrate, a first buffer layer on the substrate, a second buffer layer on the first buffer layer, a third buffer layer on the second buffer layer, and a Group III nitride film on the third buffer layer. Fig.

3 is Al ₂ O ₃ and epitaxial TiN (111) interfaces with the image, the software Fourier-filtered image of the processing in "Digital micrographs" between the in-phase Al ₂ O _3.

FIG. 4 is a isotherm chart showing the Ti-Ga-N (ternary) isotherm at room temperature, approximated by partial thermodynamic estimates.

Figs. 5A and 5B are cross-sectional views showing the effect of TiN interlayers on the reduction of GaN dislocations, with and without TiN. Fig.

Claims

A Group III nitride compound semiconductor device comprising a substrate, buffer layers on the substrate, and a Group III nitride compound semiconductor layer on top of the buffer layers,

A first buffer layer formed on the substrate, the first buffer layer being made of a transition metal nitride;

And a second buffer layer formed on the first buffer layer and made of a nitride of gallium and a transition metal.

The Group III nitride compound semiconductor device according to claim 1, wherein the transition metal comprises at least one element selected from the group consisting of titanium (Ti), zirconium (Zr), hafnium (Hf) and tantalum (Ta) .

The Group III nitride compound semiconductor device according to claim 1, wherein the buffer layers further comprise a third buffer layer interposed between the second buffer layer and the Group III nitride compound semiconductor layer, and the third buffer layer is made of GaN. .

The method of claim 1, wherein the substrate is made of a material selected from sapphire, silicon carbide, gallium nitride, gallium phosphide, gallium arsenide, Lt; RTI ID = 0.0 > III-nitride < / RTI >

2. The Group-III nitride compound semiconductor device of claim 1, wherein the first buffer layer has a thickness of 20 ~ 100A.

2. The Group-III nitride compound semiconductor device of claim 1, wherein the second buffer layer has a thickness of 50-100 A.

4. The Group-III nitride compound semiconductor device of claim 3, wherein the third buffer layer has a thickness of 200 to 300 angstroms.

The Group III nitride compound semiconductor device according to claim 3, wherein the first buffer layer has a thickness of 20 to 100A, the second buffer layer has a thickness of 50 to 100A, and the third buffer layer has a thickness of 200 to 300A. .

2. The Group III nitride compound semiconductor device of claim 1, wherein the first buffer layer is made of TiN and the second buffer layer is made of (Ti, Ga) N.

10. The Group-III nitride compound semiconductor device according to claim 9, wherein the (Ti, Ga) N comprises a Ti ₂ GaN phase.

A method for fabricating a Group III nitride compound semiconductor device comprising a substrate, buffer layers on the substrate, and a Group III nitride compound semiconductor layer on top of the buffer layers,

Forming a first buffer layer made of a transition metal nitride on the substrate; And

And forming a second buffer layer made of gallium and a transition metal nitride on the first buffer layer.

12. The Group III nitride compound semiconductor device according to claim 11, wherein the transition metal comprises at least one element selected from the group consisting of titanium (Ti), zirconium (Zr), hafnium (Hf) and tantalum (Ta) Gt;

[12] The method of claim 11, further comprising forming a third buffer layer on the second buffer layer and interposing the third buffer layer between the second buffer layer and the Group III nitride compound semiconductor layer, Lt; RTI ID = 0.0 > GaN. &Lt; / RTI >

[Claim 13] The Group III nitride compound semiconductor device of claim 13, wherein the first buffer layer has a thickness of 20-100 A, the second buffer layer has a thickness of 50-100 A, and the third buffer layer has a thickness of 200-300A. Manufacturing method

12. The method of claim 11, wherein the first buffer layer is made of TiN and the second buffer layer is made of (Ti, Ga) N.

16. The Group III nitride compound semiconductor device manufacturing method according to claim 15, wherein the (Ti, Ga) N comprises a Ti ₂ GaN phase.

The method according to claim 11, wherein the first buffer layer is TDEAT, TDMAT, Ⅲ nitride compound semiconductor device A method as TiN wherein the layer formed using a metal selected from an organic titanium source TTIP and TiCl _4.

The method according to claim 11, wherein the second buffer layer using a metal organic source of titanium selected from the TDEAT, TDMAT, TTIP and TiCl ₄ is formed (Ti, Ga) Ⅲ nitride compound semiconductor device manufacturing method characterized in that the N layer.

12. The method of claim 11, wherein the substrate is made of a material selected from sapphire, silicon carbide, gallium nitride, gallium phosphide, gallium arsenide, Lt; RTI ID = 0.0 > III-nitride < / RTI >