CN1381870A

CN1381870A - Technology for obtaining large-area high-quality GaN self-supporting substrate

Info

Publication number: CN1381870A
Application number: CN 02113080
Authority: CN
Inventors: 张�荣; 修向前; 徐剑; 顾书林; 卢佃清; 毕朝霞; 沈波; 刘治国; 江若琏; 施毅; 朱顺明; 韩平; 胡立群
Original assignee: Nanjing University
Current assignee: Nanjing University
Priority date: 2002-05-31
Filing date: 2002-05-31
Publication date: 2002-11-27
Anticipated expiration: 2022-05-31
Also published as: CN1140915C

Abstract

A process for preparing large-area high-quality self-supporting GaN substrate includes such steps as firstly transversely expitaxying on a sapphire substrate to obtain low-dislocation-density GaN film, then gas-phase epitaxying of hybride on ELO GaN film to obtain low-dislocation-density large-area thick GaN film, stripping the thick GaN film without damage by laser scan and radiation, and polishing the surface.

Description

Obtain the method for large-area high-quality GaN self-supporting substrate

One, technical field

The present invention relates to the method that horizontal extension technology, hydride gas-phase epitaxy (HVPE) thick film technology and laser lift-off technique prepare large tracts of land self-standing gan (GaN) substrate.

Two, technical background

III-V group nitride material (claiming the GaN sill again) based on GaN and InGaN, AlGaN alloy material is the novel semiconductor material of extremely paying attention in the world in recent years, is the most preferably material of short wavelength's semiconductor photoelectronic device and high frequency, high pressure, the preparation of high temperature microelectronic component.

Because the restriction of the physical property of GaN own, the growth of GaN body monocrystalline has very big difficulty, as yet practicability not.Owing to lack the body monocrystalline, the acquisition of GaN film is mainly by heteroepitaxy.The most frequently used backing material is sapphire (α-Al2O3).Huge lattice mismatch and thermal mismatching have caused the dislocation of GaN epitaxial loayer middle-high density, typically can reach 10 ¹⁰/ cm ², had a strong impact on the performance and the life-span of device.The key technology that reduces dislocation density at present is that (Epitaxial-Lateral-Overgrown, method ELO), dislocation density can reduce by 4～5 more than the magnitude to the employing horizontal extension.Horizontal extension is exactly deposit masking material on the GaN planar materials that has obtained (as SiO2, Si3N4, W etc.) and carves specific graphical window, carries out the secondary epitaxy of GaN more thereon." accurate free " growth conditions owing to meet, and the direction of growth is perpendicular to the direction of climbing of former GaN dislocation, thereby very high quality is arranged.

Large tracts of land GaN substrate all is to go up vapor phase growth GaN thick film in foreign substrate (as sapphire, SiC, Si etc.) usually, obtains after then former foreign substrate being separated.Wherein growing GaN is the most general on Sapphire Substrate, and quality is also the highest.In order to obtain self-supporting GaN substrate, must remove Sapphire Substrate.Because sapphire is extremely stable, is difficult to adopt chemical corrosion method.General method is a mechanical grinding, but because of sapphire is very hard, not only will consume a large amount of diamond abrasives, and cost is very high and speed is extremely slow.Adopt the method for laser irradiation, utilize laser that the boundary zone heating of GaN thick film and substrate is made it fusing, thereby obtain the GaN substrate of self-supporting.Carefully control laser energy density and scan mode, can obtain the GaN substrate of large area, non-gap.Compare with additive method, the advantage of laser-stripping method is that the time is fast, and Sapphire Substrate is recyclable.

The GaN growth for Thin Film mainly contains gas phase epitaxy of metal organic compound (MOCVD), molecular beam epitaxy (MBE), hydride gas-phase epitaxy (HVPE) etc.Compare with MOCVD, MBE, the HVPE technology has lot of advantages: growth rate is very high, per hour can reach tens even the hundreds of micron; High horizontal-longitudinal growth rate ratio; There are not hole and yellowish leukorrhea; Can the growing large-area film etc.In conjunction with the ELO technology, GaN film that can growing high-quality.

Three, summary of the invention

The present invention seeks to: adopt the horizontal extension method in conjunction with HVPE thick film growing technology and laser lift-off technique, obtain large tracts of land low-dislocation-density high-quality GaN self-supporting substrate.

Technical solution of the present invention is: deposition, etching mask layer pattern (SiO on MOCVD, MBE or additive method growing GaN inculating crystal layer ₂, Si ₃N ₄, W etc.); Carry out transversal epitaxial growth with the HVPE method then, obtain the thick film of GaN/ sapphire structures.With the laser scanning irradiation technique Sapphire Substrate is separated with the GaN thick film, obtain high-quality GaN self-supporting substrate.

Low dislocation density GaN growth for Thin Film method such as following: on the GaN inculating crystal layer, deposit SiO ₂, Si ₃N ₄, film such as W, utilize photoetching method to etch certain figure, low dislocation density GaN film, graphics shape mainly contain parallel long strip and orthohexagonal.For the parallel long strip, mask sector width 2-20 μ m, GaN window region width 0.2-20 μ m, the opening direction of parallel long strip is orientated along GaN [1 ī 00].Orthohexagonal opening makes [1 ī 00] orientation of GaN with MOCVD or HVPE method epitaxial growth GaN, be paved with by GaN until mask layer then perpendicular to orthohexagonal limit, and continued growth obtains the low-dislocation-density gallium nitride film.

Adopt excimer laser when laser lift-off prepares the self-standing gan substrate: the pairing energy of optical maser wavelength is less than the sapphire band-gap energy, but band-gap energy greater than GaN, laser irradiation sees through Sapphire Substrate, irradiation sapphire-gallium nitride GaN at the interface, heating or weak acid corrosion then, GaN and sapphire are separated, obtain GaN self-supporting substrate.

Technical characterstic of the present invention is:

The present invention combines the advantage of three kinds of different technologies: the horizontal extension technology can obtain the GaN film of high-quality dislocation density; The hydride gas-phase epitaxy technology is the GaN thick film of tens even hundreds of micron thickness of growing large-area fast; And laser lift-off technique can undamagedly apace be separated the GaN film from Sapphire Substrate.So the employing laser lift-off technique strips down the horizontal extension GaN film of hydride gas phase epitaxial growth from Sapphire Substrate, just can obtain the self-supporting GaN substrate of large-area high-quality.

Four, embodiment

Concrete steps are as follows:

1, obtains MOCVD, MBE or additive method growing GaN inculating crystal layer on Sapphire Substrate.

On the GaN of step 1 inculating crystal layer, carry out transversal epitaxial growth, cover whole mask district, obtain ELO-GaN/ mask layer/GaN/ sapphire thin film structure until the GaN film.Mask layer adopts flexible substrate such as SiO ₂, Si ₃N ₄, film such as W.Mask pattern can adopt parallel long strip and hexagon, and graphics shape mainly contains parallel long strip and orthohexagonal.For the parallel long strip, mask sector width 2-20 μ m, GaN window region width 0.2-20 μ m, the opening direction of parallel long strip is orientated along GaN [1 ī 00].Orthohexagonal opening, [the 1 ī 00] orientation that makes GaN is perpendicular to orthohexagonal limit.Usually, masked area is all greater than the GaN window region.

2, carry out hydride gas phase epitaxial growth on the ELO GaN film in step 2, until needed thickness.

3, laser lift-off obtains the GaN self-supporting film.Select suitable laser, sapphire is passed in the laser vertical incident that will have certain energy density, and according to certain mode, scanning and irradiation sapphire/GaN interface is separated Sapphire Substrate and GaN thick film.The pairing energy of optical maser wavelength is less than the sapphire band-gap energy, but greater than the band-gap energy of GaN.Laser energy density has the scope of certain suitable use according to the difference that adopts optical maser wavelength.Present embodiment adopts KrF ultraviolet light excimer laser (wavelength 248nm, the wide 38ns of pulse).

4, the GaN self-supporting film that step 4 is obtained carries out processed such as surface finish, just can obtain large tracts of land, low-dislocation-density, self-supporting GaN substrate.

Claims

1, obtains the method for large-area high-quality GaN self-supporting substrate, it is characterized in that at first horizontal extension acquisition low dislocation density GaN film on Sapphire Substrate; On ELO GaN film, carry out hydride gas-phase epitaxy then, obtain the GaN thick film of large tracts of land, low-dislocation-density; Adopt laser scanning irradiation lift-off technology, the GaN thick film is stripped down from Sapphire Substrate, carry out surface finish again and handle, just can obtain high-quality GaN self-supporting substrate.

2, by the method for the described acquisition large-area high-quality GaN of claim 1 self-supporting substrate, it is characterized in that low dislocation density GaN growth for Thin Film method such as following: on GaN seed product layer, deposit SiO ₂, Si ₃N ₄, film such as W, utilize photoetching method to etch certain figure, low dislocation density GaN film, graphics shape mainly contain parallel long strip and orthohexagonal.For the parallel long strip, mask sector width 2-20 μ m, GaN window region width 0.2-20 μ m, the opening direction of parallel long strip is orientated along GaN [1 ī 00].Orthohexagonal opening makes [1 ī 00] orientation of GaN with MOCVD or HVPE method epitaxial growth GaN, be paved with by GaN until mask layer then perpendicular to orthohexagonal limit, and continued growth obtains the low-dislocation-density gallium nitride film.

3, by the method for the described acquisition large-area high-quality GaN of claim 1 self-supporting substrate, it is characterized in that adopting excimer laser when laser lift-off prepares the self-standing gan substrate: the pairing energy of optical maser wavelength is less than the sapphire band-gap energy, but band-gap energy greater than GaN, laser irradiation sees through Sapphire Substrate, irradiation sapphire-gallium nitride GaN at the interface, GaN and sapphire are separated in heating or weak acid corrosion then, obtain GaN self-supporting substrate.