CN103866380B - A kind ofly use graphical annealing loose structure to carry out the method for GaN crystal growth - Google Patents

Abstract

Use graphical annealing loose structure to carry out a method for GaN crystal growth, comprise the following steps: (1) prepares SiO on GaN epitaxial wafer₂Graphic mask; (2) will be with SiO₂GaN epitaxial wafer high annealing in vacuum drying oven of graphic mask; (3) by annealing after with SiO₂The GaN epitaxial wafer of graphic mask forms porous GaN substrate; (4) by porous GaN substrate HVPE epitaxial growth, obtain GaN monocrystalline. The method is by the preparation of GaN epitaxial wafer graphic mask, high annealing, cleaning-drying and the growth of HVPE method, finally obtain high-quality GaN monocrystalline, and be conducive to epitaxially grown GaN monocrystalline from peeling off formation self-supported substrate, this method is made simple, technical maturity, can improve the quality of epitaxial growth GaN monocrystalline, be conducive to realize certainly peeling off of GaN monocrystalline and foreign substrate, be applicable to batch production.

Description

A kind ofly use graphical annealing loose structure to carry out the method for GaN crystal growth

Technical field

The present invention relates to one and prepare graphical loose structure GaN growth substrates by annealing process, then utilize HVPE(hydrogenCompound vapour phase epitaxy) method of method growing GaN monocrystalline, belong to GaN Crystal Growth Technique field.

Background technology

Along with the develop rapidly of electronic information industry, modern electronic technology is in the situations such as semi-conducting material high temperature, high frequency, high pressurePerformance new requirement has been proposed, the third generation semi-conducting material taking GaN as representative has that energy gap is large, breakdown electric field is high,The character such as the chemical stability that thermal conductivity is large, saturated electron drift velocity is high, dielectric constant is little, capability of resistance to radiation is strong, good,Have a wide range of applications in fields such as light emitting diode (LED), laser diodes (LD).

Owing to lacking GaN body monocrystalline, current business-like GaN base device is substantially all to adopt hetero-epitaxy, but due to differentMatter substrate exists larger thermal coefficient of expansion and the mismatch of lattice paprmeter, causes epitaxially grown device to exist higher dislocation closeDegree, thus the raising of device performance seriously restricted. The GaN substrate of preparation self-supporting is then prepared GaN in homo-substrateBase device becomes a kind of method of generally acknowledged raising device performance. The main method using is first to obtain good body piece or standard at presentBody piece crystal, then further processing obtains the good crystal cut of quality (self-supported substrate) to carry out the homogenous growth of device.

Hydride gas-phase epitaxy (HydrideVapor-PhaseEpitaxy, HVPE) method is considered to the most potential and obtains from propping upOne of method of support substrate, this method can be traced back to about 1970 the earliest, and its process is mainly to deposit in foreign substrateThe GaN epitaxial layer that thickness is larger, employing laser lift-off or the technology of certainly peeling off obtain block crystal. This method exists lifeFast, the lower-cost advantage of long speed, due to the foreign substrate extension using, exists lattice mismatch between substrate and grown layerAnd thermal mismatching, so can produce various defects in growth course and temperature-fall period, dislocation density can be larger.

The method of the crystal mass of HVPE raising is at present to use cushion and insert layer, reduces GaN layer and substrate because lattice losesJoin the stress producing with thermal mismatching. The most successfully one of research is that Hitachi company is used the auxiliary isolation technics in room(void-assistedseparation, VAS) [referring to Y.Oshima, etal, phys.stat.sol. (a), 194 (2002) 554-558],Obtain the thick pure GaN layer in 2-3 inch diameter 600 μ m left and right. This method is on the substrate obtaining in MOCVD methodCover the nanometer network of one deck Ti, form TiN insert layer through high annealing and ammonification, form the loose structure with room,On this substrate, grow, both can reach and reduce mismatch stress effect, can realize again certainly peeling off of substrate. Loose structureIn peeling GaN monocrystalline, play vital effect in preparation, carry thereby foreign study person has adopted several different methods to introduce roomHigh-crystal quality [Y.Fu, etal, AppliedPhysicsLetters86 (4), 043108 (2005), C.Hennig, JournalofCrystalGrowth310 (5), 911-915 (2008)]. But the complex process of these methods, exigence is a kind of autonomous nowSimple new method prepare porous-substrates, thereby improve the quality of HVPE growing GaN.

Summary of the invention

The present invention is directed to important function and the existing GaN Crystal Growth Technique of loose structure substrate to GaN crystal growth existsDeficiency, provide a kind of simple method that uses efficiently graphical annealing loose structure to carry out GaN crystal growth, the method energyEnough improve the quality of epitaxial growth GaN monocrystalline, be conducive to realize certainly peeling off of GaN monocrystalline and foreign substrate.

The use of the present invention method that loose structure carries out GaN crystal growth of graphically annealing, comprises the following steps:

(1) on GaN epitaxial wafer, prepare SiO₂Graphic mask, the thickness of GaN epitaxial wafer is 2 μ m-5 μ m, SiO₂Mask isThe perforate of Square array or the perforate of Hexagonal array, SiO₂Mask thicknesses is 50nm-100nm, and the perforate cycle is 60 μ m-150 μ m, opening diameter is 10 μ m-15 μ m;

(2) will be with SiO₂The GaN epitaxial wafer of graphic mask in vacuum drying oven, high annealing 60 minutes at 1200-1300 DEG C-90 minutes;

(3) by annealing after with SiO₂The GaN epitaxial wafer of graphic mask cleans 5 minutes in deionized water for ultrasonic, thenRinsing 1 minute-5 minutes in SPA (more than 80% phosphoric acid of mass ratio), rinses well by deionized water; Then existIn 25 DEG C of-53 DEG C of acetone and 25 DEG C of-73 DEG C of ethanolic solutions, clean respectively 1 minute-5 minutes, rinse well by deionized water, then useSiO is removed in hydrofluoric acid (mass ratio 40%) rinsing for 20 seconds-5 minutes₂Layer, rinses well by deionized water, and nitrogen is dried, shapeBecome porous GaN substrate;

(4) porous GaN substrate is passed through to HVPE epitaxial growth, obtain GaN monocrystalline.

The present invention, by the preparation of GaN epitaxial wafer graphic mask, high annealing, cleaning-drying and the growth of HVPE method, finally obtainsArrive high-quality GaN monocrystalline, and be conducive to epitaxially grown GaN monocrystalline from peeling off formation self-supported substrate, this methodMake simple, technical maturity, can improve the quality of epitaxial growth GaN monocrystalline, be conducive to realize GaN monocrystalline and heterogeneous liningCertainly peeling off of the end, is applicable to batch production.

Brief description of the drawings

Fig. 1 is that the present invention uses graphical annealing acquisition loose structure to carry out the flow chart of GaN method for monocrystal growth.

Fig. 2 is the section SEM(SEM of the loose structure substrate prepared in Sapphire Substrate) figure.

Fig. 3 uses loose structure substrate to carry out the section SEM(SEM of the GaN monocrystalline of HVPE growth)Figure.

Fig. 4 is that the present invention uses figure annealing loose structure GaN substrate and the GaN substrate institute that uses the growth of MOCVD methodThe PL(luminescence generated by light of the sample of preparation) spectrum.

Fig. 5 is the back side microphoto (× 200) at the bottom of peeling liner prepared by the present invention.

Detailed description of the invention

Embodiment 1

Fig. 1 has provided the present invention and has used graphical annealing loose structure to carry out the flow process of GaN crystal growth, and growth course comprises:SiO₂Graphic mask preparation, high annealing and cleaning and HVPE growing GaN monocrystalline three phases. Concrete steps are as follows:

(1) at MOCVD(metallo-organic compound chemical gaseous phase deposition) on the GaN epitaxial wafer prepared of method, utilize photoetchingThe method of technique and wet etching is prepared SiO₂Graphic mask, SiO₂Figure is the perforate of Square array, the thickness of GaN epitaxial waferBe 2 μ m, SiO₂Mask thicknesses is 50nm, and the perforate cycle is 60 μ m, and opening diameter is 10 μ m;

(2) will be with SiO₂The GaN epitaxial wafer of graphic mask in vacuum drying oven, high annealing 90min at 1200 DEG C;

(3) by annealing after with SiO₂The GaN epitaxial wafer of graphic mask is at deionized water for ultrasonic 5min, then at dense phosphorusRinsing 5min in acid (more than 80% phosphoric acid of mass ratio), deionized water rinsing is clean, then at 50 DEG C of acetone and 50 DEG C of ethanolIn solution, clean respectively 2min, deionized water rinsing is clean, then uses hydrofluoric acid (hydrofluoric acid of commercially available mass ratio 40%) rinsingWithin 1 minute, remove SiO₂Layer, deionized water rinsing is clean, and nitrogen is dried, and forms porous GaN substrate;

(4) the porous GaN substrate after cleaning is put into HVPE(hydride gas-phase epitaxy) growing system epitaxial growth,Obtain GaN monocrystalline.

Fig. 2 is the section SEM(SEM of the loose structure substrate prepared in Sapphire Substrate) figure. Fig. 3 makesCarry out the section SEM(SEM of the GaN monocrystalline that HVPE grows prepared with loose structure substrate) figure. FromIn figure, can find out in the interface of growth and have so-called room (void), these rooms have effectively stoped the upwards extension of dislocation,Improved crystal mass, the stress release that is simultaneously conducive to cause due to thermal mismatching produces from peeling off.

Fig. 4 is graphically anneal loose structure GaN substrate and the GaN that uses the growth of MOCVD method of use prepared by the present inventionThe PL(luminescence generated by light of the prepared GaN monocrystalline of substrate) spectrum. Can find out and use figure annealing porous GaN substrate and generalAll there is the glow peak of 363nm in the GaN substrate of logical MOCVD method growth, under same test condition, uses porousGaN monocrystalline prepared by substrate is luminous stronger, and simultaneously at the acomia photopeak in the gold-tinted region of 500nm-600nm, this shows use figureShape annealing loose structure can effectively improve the quality of GaN monocrystalline; Fig. 5 is that the back side at the bottom of peeling liner prepared by the present invention showsMicro-photo (× 200), there is obvious graphic structure in the back side at the bottom of peeling liner, the graphical annealing porous that the present invention uses is describedStructure is playing fine effect in stripping process.

Embodiment 2

The difference of the present embodiment and embodiment 1 is:

In step (1), the thickness of GaN epitaxial wafer is 3 μ m, SiO₂Graphic mask figure is the perforate of Hexagonal array, SiO₂CoverFilm thickness is 100nm, and the perforate cycle is 150 μ m, and opening diameter is 12 μ m;

In step (2), high temperature anneal temperature is 1300 DEG C, and annealing time is 70min;

In step (3), SPA rinsing time is 1min; In 53 DEG C of acetone and 73 DEG C of ethanolic solutions, clean respectively 1min; HydrogenFluoric acid rinsing time is 20 seconds.

Embodiment 3

The difference of the present embodiment and embodiment 1 is:

In step (1), the thickness of GaN epitaxial wafer is 5 μ m, SiO₂Graphic mask thickness is 60nm, and the perforate cycle is 120 μ m,Opening diameter is 15 μ m;

In step (2), high temperature anneal temperature is 1250 DEG C, and annealing time is 80min;

In step (3), SPA rinsing time is 4min; In 25 DEG C of acetone and 25 DEG C of ethanolic solutions, clean respectively 5min; HydrogenFluoric acid rinsing time is 5 minutes.

Embodiment 4

The difference of the present embodiment and embodiment 1 is:

In step (1), the thickness of GaN epitaxial wafer is 4 μ m, SiO₂Graphic mask figure is the perforate of Hexagonal array, SiO₂CoverFilm thickness is 85nm, and the perforate cycle is 80 μ m, and opening diameter is 13 μ m;

In step (2), high temperature anneal temperature is 1300 DEG C, and annealing time is 60min;

In step (3), SPA rinsing time is 2min; In 35 DEG C of acetone and 40 DEG C of ethanolic solutions, clean respectively 3min; HydrogenFluoric acid rinsing time is 3 minutes.

In the scope of the each parameter providing in the present invention, all can obtain different graphic annealing by the occurrence that changes each parameterThe GaN monocrystal chip of loose structure, utilizes outside HVPE method carries out the various graphical annealed structure GaN substrate obtainingEpitaxial growth, can both obtain high-quality GaN monocrystalline, and the GaN growing can and substrate between occur from peeling off.

Claims (1)

1. a method that uses graphical annealing loose structure to carry out GaN crystal growth, is characterized in that, comprises the following steps:

(1) on GaN epitaxial wafer, prepare SiO₂Graphic mask, the thickness of GaN epitaxial wafer is 2 μ m-5 μ m, SiO₂FigureMask is the perforate of Square array or the perforate of Hexagonal array, SiO₂Graphic mask thickness is 50nm-100nm, the perforate cycleBe 60 μ m-150 μ m, opening diameter is 10 μ m-15 μ m;

(2) will be with SiO₂The GaN epitaxial wafer of graphic mask in vacuum drying oven, high annealing 60 minutes at 1200-1300 DEG C-90 minutes;

(3) by annealing after with SiO₂The GaN epitaxial wafer of graphic mask cleans 5 minutes in deionized water for ultrasonic, thenRinsing 1 minute-5 minutes in SPA at mass ratio more than 80%, rinses well by deionized water; Then at 25 DEG C-53 DEG C thirdIn ketone and 25 DEG C of-73 DEG C of ethanolic solutions, clean respectively 1 minute-5 minutes, rinse well by deionized water, then use hydrofluoric acid rinsingWithin 20 seconds-5 minutes, remove SiO₂Layer, rinses well by deionized water, and nitrogen is dried, and forms porous GaN substrate;

(4) porous GaN substrate is passed through to HVPE epitaxial growth, obtain GaN monocrystalline.