CN1300387C

CN1300387C - Process for non-mask transverse epitaxial growth of high quality gallium nitride

Info

Publication number: CN1300387C
Application number: CNB2004100656765A
Authority: CN
Inventors: 修向前; 张�荣; 陈琳; 谢自力; 顾书林; 施毅; 韩平; 沈波; 江若琏; 朱顺明; 胡立群; 郑有炓
Original assignee: Nanjing University
Current assignee: Nanjing University
Priority date: 2004-11-12
Filing date: 2004-11-12
Publication date: 2007-02-14
Anticipated expiration: 2024-11-12
Also published as: CN1632186A

Abstract

The present invention relates to a method for maskless transverse epitaxial growth of a gallium nitride film with high quality. Firstly, the thin films of SiO2, Si3N4, W, etc. is deposited on a sapphire substrate so as to form a mask area, a pattern window is etched at the mask area by using ion beam method, a photoetching method and an electron beam exposure method, the surface of a sapphire pattern is etched to roughness, or is etched to the depth of 80 nm to 2 mum, and then, a mask is removed by a corrosive method so as to obtain a pattern sapphire substrate. GaN is epitaxially grown by an MOCVD or HVPE method, until an etching area is fully paved by GaN, and a gallium nitride thin film with low dislocation density can be obtained by continuous growth.

Description

Process for non-mask transverse epitaxial growth of high quality gallium nitride

Technical field

The present invention relates to use non-mask transverse epitaxy technology and hydride gas-phase epitaxy thin film techniques such as (HVPE) method and the technology at graphical sapphire substrate growing high-quality gan (GaN) film, the low dislocation density GaN film is used to grow.

Background technology

III-V group nitride material (claiming the GaN sill again) is the novel semiconductor material of extremely paying attention in the world in recent years, the direct band gap of its 1.9-6.2eV continuous variable, excellent physics, chemical stability, high saturated electron drift velocity, high-performances such as high breaking down field strength and high heat conductance make it become the most preferably material of short wavelength's semiconductor photoelectronic device and high frequency, high pressure, the preparation of high temperature microelectronic device.

Because the restriction of the physical properties of GaN own, the growth of GaN body monocrystalline has very big difficulty, as yet practicability not.Early stage people mainly adopt hydride gas-phase epitaxy (HVPE) method direct growth GaN on Sapphire Substrate, are separated again, obtain the GaN substrate material.The outstanding shortcoming of this method is that dislocation desity is very high in the GaN epitaxial film, generally reaches 10 ⁹-10 ¹⁰Cm ^-2About.The gordian technique that reduces dislocation desity at present is to adopt horizontal extension (Epitaxial-Lateral-Overgrown, method ELO).Employing horizontal extension technology can reduce the dislocation desity in the epitaxial film significantly, and improves epitaxial layer quality.Dislocation desity can reduce by 4～5 magnitudes.

Common GaN horizontal extension technology is meant that the deposit masking material is (as SiO on the GaN planar materials that has obtained ₂, Si ₃N ₄, W etc.) and carve specific graphical window, carry out the secondary epitaxy of GaN more thereon, can significantly reduce dislocation desity.

In the present invention, we adopt is the non-mask transverse epitaxy method in conjunction with the HVPE film growth techniques low dislocation density GaN film of growing on the graphical sapphire substrate.

Summary of the invention

The present invention seeks to: adopt the non-mask transverse epitaxy method in conjunction with MOCVD or the HVPE film growth techniques low dislocation density GaN film of on the graphical sapphire substrate, growing.

Technical solution of the present invention:

At first, on Sapphire Substrate, deposit SiO ₂, Si ₃N ₄, film such as W, utilize ionic fluid, photoetching, methods such as electron beam exposure etch certain figure (as strip, hexagon etc.), also be etched certain degree of depth or only to be etched to patterned surface coarse of Sapphire Substrate; Then mask is got rid of,, obtained the GaN film with MOCVD or the epitaxy of HVPE method.Zhi Bei GaN thin film dislocation density is lower like this, is of high quality.

Mechanism of the present invention and technical characterstic are:

In common GaN horizontal extension technology, because selective epitaxy, only in the epitaxy of GaN window portion GaN ability, and SiO ₂Partly be difficult to nucleation Deng mask layer.When the GaN that goes out when extension in the GaN window region surpasses mask layer thickness, when grow with vertical direction, the generation transverse growth.After acquiring a certain degree, transverse growth just can be carried out the GaN epitaxial film of lid entirely.This growth is " accurate free " growth conditions because meet, and the direction of growth is perpendicular to the direction of climbing of former GaN dislocation, thereby very high quality is arranged, and dislocation desity is lower more than direct growth.The HVPE growth velocity is very fast, can reach tens even hundreds of μ m/ hour.Owing to can reduce away from dislocation desity at the interface, thus on the horizontal extension film HVPE thick film extension, can obtain the lower GaN film of dislocation desity.

Yanzhong outside non-mask transverse, the part that is etched on the substrate is difficult for nucleation.And at rest part, GaN also carries out transverse growth in longitudinal growth.The GaN epitaxial film has just covered whole Sapphire Substrate surfaces after transverse growth acquires a certain degree.Similar to the horizontal extension principle that mask is arranged, this no mask epitaxy meets " accurate free " growth conditions equally, and the direction of growth is perpendicular to the direction of climbing of former GaN dislocation, thereby also has very high quality.At growth conditions: 1050 ℃, [NH ₃]: the GaN film surface SEM shape appearance figure of [HCl]=60: 1 o'clock horizontal extension and HVPE technology growth.

Description of drawings

Fig. 1 non-mask transverse extension GaN synoptic diagram (figure has certain depth).From the bottom up, at first etch figure on the Sapphire Substrate, degree of depth 80nm-2 μ m; Begin extension then, horizontal extension covers substrate surface until GaN.Another kind of situation is that visuals is etched coarse, need not certain degree of depth.

The GaN film AFM surface topography map of Fig. 2 horizontal extension and HVPE technology growth.Growth conditions: 1100 ℃, [NH ₃]: [HCl]=60: 1.

Embodiment

The transversal epitaxial growth technology that the present invention adopts comprises following a few step:

1, deposit SiO on Sapphire Substrate ₂, Si ₃N ₄, film such as W makes mask layer, thickness is 80-100nm.

2, obtain certain figure with photoetching method etch mask layer, mask regions is generally all greater than window region.Graphics shape mainly contains parallel long strip and orthohexagonal.For the parallel long strip, mask regions width 2-200 μ m, window region width 0.2-20 μ m.

The Sapphire Substrate etching that 3, mask will be arranged, promptly window region (no mask regions) is located Sapphire Substrate and is etched degree of depth 80nm-2 μ m.

4, with methods such as corrosion mask is removed, can be obtained the graphical sapphire substrate that there are etching figure or striped in the surface.Caustic solution adopts the method for chemical corrosion, common methods such as acid or employing ionic fluid.

5, under different growth conditionss, MOCVD or HVPE extension GaN film on above-mentioned graphical sapphire substrate.As control V valency N atom and III valency Ga atomic ratio (20～100: 1), growth temperature (1000～1100 ℃), the selection of window and mask regions is compared etc.The time of carrying out horizontal extension and thick film growth with MOCVD is long more than HVPE.Can be earlier with conventional MOCVD growing GaN, after film covers with whole mask layer, adopt the conventional H VPE growing technology acquisition thick film of growing fast again.The method of MOCVD or HVPE is a prior art, and the MOCVD unstripped gas adopts metallorganics and ammonia, and the HVPE raw material adopts gallium, ammonia and hydrogenchloride etc.The GaN film that utilizes aforesaid method to obtain, dislocation desity can reduce greatly.

6, adopt twice or horizontal extension technology repeatedly, dislocation desity is expected to be reduced to 102-104/cm ²Magnitude.

Claims

1, the method for process for non-mask transverse epitaxial growth of high quality gallium nitride film is characterized in that depositing earlier SiO on Sapphire Substrate ₂, Si ₃N ₄Or W film is made mask regions, utilize ionic fluid, photoetching or electron beam exposure method to etch graphical window in mask regions, the sapphire graphical surface etching is to coarse or etched degree of depth 80nm2 μ m, then mask is removed with corroding method, can obtain the graphical sapphire substrate, or/and HVPE method epitaxy GaN is paved with by GaN until etching region, continued growth can obtain the low-dislocation-density gallium nitride film with MOCVD.

2, the method for process for non-mask transverse epitaxial growth of high quality gallium nitride film as claimed in claim 1, when it is characterized in that being the parallel long strip for graphical window, mask regions width 2-200 μ m, window region width 0.2-20 μ m.

3, the method for process for non-mask transverse epitaxial growth of high quality gallium nitride film as claimed in claim 1 is characterized in that this method deposit SiO on Sapphire Substrate ₂, Si ₃N ₄, the W film thickness of making mask layer is 80-100nm.

4, the method for process for non-mask transverse epitaxial growth of high quality gallium nitride film as claimed in claim 1 is characterized in that using the MOCVD growing GaN earlier, after film covers with whole mask layer, adopts the HVPE growth to obtain thick film again.