CN1725445A

CN1725445A - Epitaxial growing technology of III class nitride semiconductor on silicon substrate

Info

Publication number: CN1725445A
Application number: CNA2004100548281A
Authority: CN
Inventors: 冯玉春; 郭宝平; 牛憨笨; 李忠辉
Original assignee: Shenzhen University
Current assignee: Shenzhen University
Priority date: 2004-07-23
Filing date: 2004-07-23
Publication date: 2006-01-25

Abstract

This invention relates to a new technology for growing group III nitride semiconductor mono-crystal material, which grows two buffer layer and one graded bedding before growing the semiconductor material, buffer layer 2 is SiO2 film, buffer layer 3 is AIN film and the graded bedding is a rich GaN grown under high temperature and deviating from the chemical test ratio. The two buffer layers and the graded bedding structure can reduce the crack of nitride group III semiconductor mono-crystal material due to the too large difference of the thermal expansion factor between the substrate and the material and the high defect concentration because of the mismatched lattices.

Description

III group-III nitride semiconductor growth technology on the silicon substrate

One. technical field

The present invention relates to a kind of double-buffering layer that utilizes and add the method that the graded bedding technology obtains the special-shaped extension III of high-quality group-III nitride crystalline material.

Two. technical background

The III group-III nitride semiconductor has been widely used in light-emitting diode, semiconductor laser and other high-performance electronic device with its excellent photoelectric characteristic.

Because lack gallium nitride background monocrystalline, present gallium nitrate based photoelectric device all forms by the foreign substrate extension.The foreign substrate of commercialization production usefulness mainly contains Al at present ₂O ₃And SiC, although Al ₂O ₃Ripe with epitaxial growth GaN technology on the SiC monocrystalline, released GaN based light-emitting diode and semiconductor laser; But the price of SiC is expensive high, has seriously restricted applying of corresponding device; With the comparatively ripe Al of technology ₂O ₃Compare with SiC, the Si monocrystalline is with its ripe processing technology, cheap price, extensive attention and the research that wafer size is subjected to people greatly.

Because Si monocrystalline and GaN lattice constant and thermal coefficient of expansion differ too big, cause extension GaN crystal mass too poor, defect concentration is too high, produces be full of cracks when particularly the stress of thermal expansion generation makes epitaxy layer thickness surpass 1 μ m; These problems have seriously limited the development of silica-based GaN epitaxial growth technology.

Because the interface energy height between GaN and silicon substrate, so can not direct growth go out the III group-III nitride crystal of high-quality at silicon substrate.Have only growth earlier three-dimensional (3D) to become the nucleation layer (resilient coating) of kernel normal form growth, and then realize 2 dimension (2D) layer growths on this basis, obtain high-quality epitaxial crystal material.

In the research process of silica-based III group-III nitride extension, multiple material is all attempted as resilient coating improving crystal mass, as AlN, AlAs, the Si of GaN, low temperature and the high growth temperature of low-temperature epitaxy ₃N ₄, GaAs, ZnO, LiGaO ₂Deng, but defect concentration is too high in the crystalline material, is still the major obstacle of silica-based III group nitride material of restriction and device development than the problem of thick epitaxial layer be full of cracks.

Three. summary of the invention

The present invention is directed to the problem that the epitaxial growth of III group-III nitride semiconductor exists on the silicon substrate, adopt double-buffering layer to add the method for graded bedding, reduce because of lattice mismatch, thermal coefficient of expansion differing the problem that causes high defect concentration and thick epitaxial layer be full of cracks in the epitaxial crystal too greatly.

III group-III nitride semiconductor epitaxial growth structure comprises silicon monocrystalline substrate 1, resilient coating 2, resilient coating 3, graded bedding 4 and III group-III nitride semiconductor crystal 5 on the silicon monocrystalline substrate of the present invention.

Further set forth the present invention below in conjunction with accompanying drawing.

Resilient coating 2 adopts wet-oxygen oxidation to form or the PECVD deposit forms SiO ₂Oxidation or the formed SiO of plasma gas phase deposit ₂Film is an amorphous glass shape structure, and the elementary cell of this structure is the polyhedron that the Si-O atom is formed.Silicon atom is positioned at polyhedral center, and 4 oxygen atoms are positioned on polyhedral angle, and adjacent two polyhedrons connect the three-dimensional net structure that constitutes random arrangement by a bridged bond oxygen atom.SiO ₂Film is the unordered and vitreous silica of shortrange order of a kind of long-range, and its crystal region size is about several nanometers to tens nanometers; The outer network configuration of crystal region is loosened inhomogeneous.With dried oxygen thermal oxidation mutually the specific heat wet-oxygen oxidation form or the PECVD deposit forms SiO ₂Network configuration more loose, so on silicon substrate, adopt the SiO of short texture in the epitaxial growth of III group-III nitride semiconductor ₂As ground floor resilient coating, SiO ₂Good with silicon adhesion, its loose loose structure is at this mask material as a kind of epitaxial lateral overgrowth; This SiO with the short texture porous ₂It is simple, easy to operate to have technology as mask material; And precision is guaranteed.

Resilient coating 3 adopts the AlN of high growth temperature.High temperature can promote the nucleating growth of AlN; Adopt the low reaction cavity pressure with suitable increase cross growth speed and control grain size size simultaneously.

Behind the resilient coating 3-AlN that grown, do not change growth temperature, continue the rich Ga GaN of epitaxial growth graded bedding 4-nonstoichiometry ratio as seed crystal with the AlN in the resilient coating 3.Be gradient to 3000 at graded bedding growing period V/III from 660, V/III stabilizes to 3000 then, high-quality GaN that epitaxial growth is required or III group nitride material.At the lower V/III of early growth period employing of high temperature GaN is in order to strengthen the three dimensional growth pattern, to roll into a ball density because help the crystallization nucleation of GaN in rich gallium environment to obtain the low crystallization of large-sized crystallization group; Reduce the associating speed that isolates between the crystallization group, reduce dislocation density.Along with the associating mutually of the large-sized crystallization of the increase of V/III ratio group, surface topography transforms in graded bedding 4 growth courses, and the strain mismatch between epitaxial crystal and substrate is alleviated, and accurate two-dimensional layer growth pattern constantly strengthens.The epitaxial crystal surface is tending towards smooth, and crystal mass is improved.

Technical characterstic of the present invention:

1. the porous sio2 film of oxidation or deposit has compression on the silicon, can discharge the tensile stress in the GaN epitaxial loayer greatly, produces and does not have be full of cracks back extension GaN material; To satisfy the quality requirement of GaN base photoelectric device, improve photoelectric characteristic, increase the service life.

2. adopt double-buffering layer to add the graded bedding structure, can reduce the dislocation density in the epitaxial crystal greatly, reduce non-radiative compound.Improve the luminous efficiency of photoelectric device.

3. simple, the easy to operate may command of technology of the present invention.

Four. description of drawings

Accompanying drawing is each layer structure principle chart of the silica-based epitaxial growth GaN of the present invention.

Five. embodiment

With the silicon chip of single or double polishing with following cleaning fluid H ₂SO ₄: H ₂O ₂, NH ₄OH:H ₂O ₂: H ₂O, HCl:H ₂O ₂: H ₂O, HF:H ₂O and a large amount of hot and cold deionized water rinsing are clean; Dry.

2. the silicon chip that will clean, dries is put into PECVD reaction chamber deposit SiO ₂Or put into oxidation furnace and be oxidized to required oxidated layer thickness.

3. with the good SiO of deposit ₂Or put into the MOCVD reaction chamber immediately after the good silicon chip taking-up of oxidation.

4. the temperature with MOCVD is raised to 1000 ℃～1150 ℃ rapidly, logical simultaneously H ₂

5. grown buffer layer 3AlN, growth time 200 seconds～450 seconds, logical simultaneously NH ₃And trimethyl aluminium (TMAl).

6. growth graded bedding 4 rich Ga-GaN, about 200 seconds～800 seconds of growth time, logical NH ₃And trimethyl gallium (TMG); The flow of trimethyl gallium is constant, and NH ₃Flow constantly increase, make V/III be gradient to 3000 from 660.

7. under the constant situation of growth conditions, continue epitaxial growth GaN to required thickness.

8. as needing to make photoelectric device, required each layer structure of growth of device on above-mentioned extension GaN crystal.

Claims

1. the new method of epitaxial growth III nitride semiconductor single crystal material on the silicon monocrystalline substrate is characterized in that 1 of III hi-nitride semiconductor material 5 and silicon substrate have SiO ₂Resilient coating 2 and AlN resilient coating 3 and GaN component-gradient layer 4.

2. by the described resilient coating 2 of claim 1, it is characterized in that resilient coating is SiO ₂, the SiO2 thickness is about 20 to 200 .

3. by the described SiO of claim 2 ₂, can adopt the method for thermal oxidation to form 600 ℃～800 ℃ of oxidizing temperatures.For the thickness of controlled oxidation layer more accurately, the proper extension high-temperature oxydation time; The oxygen that adopts argon-dilution reduces the voltage ratio of oxygen as oxidizing gas, reaches the purpose that reduces oxidation rate.

4. by the described SiO of claim 2 ₂, can adopt the PECVD deposit to form.Deposit SiO ₂Underlayer temperature from room temperature to 300 ℃, process gas adopts SiH ₄, N ₂O.

5. by the described AlN resilient coating 3 of claim 1, it is characterized in that resilient coating is a high growth temperature.1000 ℃～1150 ℃ of growth temperatures, AlN layer thickness 20～30nm.

6. by the described GaN component-gradient of claim 1 layer 4, it is characterized in that the rich Ga HT-GaN of the gradual change nonstoichiometry ratio of high growth temperature, the thickness of graded bedding 4 is about 0.1～0.5 micron.