CN102157638A

CN102157638A - Method for preparing substrate for epitaxial growth of GaN

Info

Publication number: CN102157638A
Application number: CN2011100338512A
Authority: CN
Inventors: 张昊翔; 金豫浙; 陈立人; 李东昇; 江忠永
Original assignee: Hangzhou Silan Azure Co Ltd
Current assignee: Hangzhou Silan Azure Co Ltd
Priority date: 2011-01-31
Filing date: 2011-01-31
Publication date: 2011-08-17

Abstract

The invention relates to a method for preparing a substrate for epitaxial growth of GaN. The method comprises the following steps of: depositing a layer of thin film material with a low refractive index on the surface of a C-face sapphire; making a mask layer pattern by using a conventional photoetching technology, transferring the pattern to the thin film with the low refractive index by erosion, and performing wet-method corrosion on the substrate by using mixed solution of sulfuric acid and phosphoric acid; and finally washing the sapphire pattern substrate with the thin film of the low refractive index for future epitaxial growth. By the invention, the preparation process is low in cost; the wet-method corrosion cannot damage the substrate, and the shape of the sapphire pattern is easy to control; due to the growth on the substrate, the dislocation of an epitaxial layer is reduced, and the static electricity resistance is improved; moreover, the crystal quality is enhanced, and the luminous brightness of an instrument is improved.

Description

A kind of epitaxially grown substrate fabrication method of GaN that is used for

Technical field

The present invention relates to be used for the epitaxially grown substrate fabrication method of GaN, belong to technical field of semiconductors.

Background technology

Be extensive use of Sapphire Substrate among the GaN of blue green light base LD and the LED, but sapphire and gallium nitride lattice mismatch (reaching 13.6%) greatly.Generally adopt low-temperature epitaxy GaN/AlN resilient coating technology now, the dislocation density of the GaN epitaxial loayer that growth obtains still reaches 10 ⁹-10 ¹⁰Cm ^-2These dislocations have limited the internal quantum efficiency of device, and the linear dislocation of TDs() locate easily by the electronic breakdown active layer reduction device reliability.Gallium nitride refractive index (n=2.4) is 23 ° with air (n=1) cirtical angle of total reflection at the interface simultaneously, and substrate sapphire (n=1.8) is close with the refractive index of gallium nitride, and can there be the bright dipping of part bottom surface in substrate; Smooth substrate surface forms secondary reflection to the photon of active area, is strapped in the epitaxial loayer, finally causes junction temperature to raise reducing device useful life.

Therefore improve the luminous efficiency of GaN base LD and LED, the growth quality of palpus consideration raising GaN epitaxial loayer reduces dislocation density and improves the surperficial light extraction efficiency of device.Generally adopt the sapphire graphical substrate technology, by the laterally overgrown of GaN, end the extension of TDs dislocation to epitaxial loayer, the dislocation density that reduces epitaxial loayer improves crystal mass;

The processing procedure of sapphire graphical has two kinds of dry etching and wet etchings in addition, dry etching adopts coupling plasma etching (ICP) technology of inducing usually, this etching technology adopts apparatus expensive, the process conditions harshness, and the consistency of 3-D graphic is relatively poor after the etching that substrate is caused certain etching injury; If adopt H ₂SO ₄And H ₃PO ₄Mixed solution as corrosive liquid, because of this mixed solution has anisotropic corrosive effect to sapphire, vertically etch rate is greater than the side direction etch rate, the acid corrosion speed of the etching of (11-2 k) face is also greater than (1-10k) simultaneously, k determined the time by wet etching, thus by the control etching time can the better controlled sapphire graphical consistency.Along＜1-100〉direction has the etched surface of two symmetries, and＜11-20〉two etched surfaces of direction are asymmetric.

Summary of the invention

The object of the present invention is to provide the epitaxially grown substrate fabrication method of a kind of GaN of being used for, realize to reduce in the epitaxial growth dislocation density that causes because of GaN and sapphire crystal lattice constant mismatch, raising device luminous efficiency.

The epitaxially grown substrate fabrication method of GaN that is used for of the present invention comprises the steps:

1) utilizes electron-beam vapor deposition method, vapour deposition process, sputtering method, pulsed laser deposition, molecular beam epitaxy or sol-gal process, in C surface sapphire substrate surface deposition one deck ranges of indices of refraction between 1 to 1.8, thickness is the oxide of 0.1 um～3 um, nitride or nitride oxide film;

2) on the film of step 1), make the mask layer convex graphical by etching and photoetching;

3) substrate for preparing more than the general is put into corrosive liquid, corrodes 1min～24h in 100 ℃～600 ℃; Described corrosive liquid is H ₂SO ₄And H ₃PO ₄The mixed liquor of 1:10～10:1 by volume;

4) substrate that corrodes more than cleaning successively with acetone, alcohol, deionized water.

Among the present invention, the vertical view of described mask layer convex graphical is edge＜1-100〉or＜11-20〉striated pattern of direction, the circle of periodic arrangement, hexagon or triangle square formation; The side-looking figure of convex graphical is taper, platform shape or hemisphere.

Among the present invention, edge＜1-100〉or＜11-20〉the width 1 um-100 um that goes to the bottom of direction bar pattern, height 0.1um-3um, spacing 1um-100 um, graphic length 1um-20cm; The width 0.1 um-10 um that goes to the bottom of the circle of described periodic arrangement, hexagon or triangle square formation, height 0.1 um-3 um; The array pattern of spacing 0.1 um-10 um.

Among the present invention, described etching is dry etching or wet etching, by etching time may command surfacial pattern pattern.Described photoetching comprises even glue, exposure, development and hot plate baking successively.

The invention has the advantages that: making the lower thin-film material (ranges of indices of refraction is between 1 to 1.8) of one deck refractive index on the substrate, and make mask with this layer film material, substrate is carried out pattern etching, etching does not relate to expensive ICP and RIE equipment, cost is low, wet etching can not bring damage to substrate, and is easier to control the sapphire graphical pattern; Behind the intact substrate of etching, do not need to remove mask layer, in epitaxial growth, utilize lower graphic films layer of refractive index and graph substrate can improve the extraction efficiency of light in device, on the sapphire graphical substrate, utilize simultaneously the epitaxial lateral overgrowth technology to reduce the dislocation density of crystal growth, improve antistatic effect, improve crystal mass, improve the luminosity of device.

Description of drawings

Fig. 1 is the profile behind the Sapphire Substrate first step; 1 is that Sapphire Substrate 2 is film;

Fig. 2 is the profile after Sapphire Substrate second step; 1 is that Sapphire Substrate 2 is film;

Fig. 3 is the profile behind the Sapphire Substrate third step; 1 is that Sapphire Substrate 2 is film.

Embodiment

Below with 2 examples to further instruction of the present invention:

Example 1:

Be used for the epitaxially grown substrate fabrication method of GaN, step is as follows:

1) film growth: use plasma-reinforced chemical vapor deposition method (PECVD) at 250 ℃, under the chamber pressure 900mtorr, reacting gas SiH ₄: N ₂O gas volume ratio=1:20 at C surface sapphire substrate superficial growth 30min, forms the SiO that a layer thickness is 1 um ₂Film; See Fig. 1

2) making the width of going to the bottom with photoetching that comprises even glue, exposure, development and hot plate baking successively and dry etching is 3 μ m, and spacing is the SiO of 2 μ m ₂Hemisphere convex mask layer patterns; See Fig. 2

3) wet etching: the substrate for preparing more than inciting somebody to action is put into 350 ℃ corrosive liquid 15min, and corrosive liquid is the H with volume ratio 3:1 preparation ₂SO ₄And H ₃PO ₄Mixed liquor; See Fig. 3

4) clean substrate: the substrate after the corrosion is cleaned and dries with acetone, alcohol, deionized water, prepare and be used for the epitaxially grown substrate of GaN, treat subsequently epitaxial growing usefulness.

Example 2:

1) film growth: use plasma-reinforced chemical vapor deposition method (PECVD) under 350 ℃, under the chamber pressure 120Pa, reacting gas mass ratio SiH ₄: NH ₃=1:10 forms the SiN film that a layer thickness is 1 um at C surface sapphire substrate superficial growth 25min;

2) make edge＜1-100 with the photoetching and the dry etching that comprise even glue, exposure, development and hot plate baking successively〉the SiN striated pattern of direction, bottom width 3 μ m under the striped, spacing 2 μ m, length is 10 cm

3) wet etching: the substrate for preparing more than inciting somebody to action is put into 350 ℃ corrosive liquid 15min, and corrosive liquid is the H with volume ratio 3:1 preparation ₂SO ₄And H ₃PO ₄Mixed liquor;

4) clean substrate: the substrate after the corrosion is cleaned and dries with acetone, alcohol, deionized water, prepare and be used for the epitaxially grown substrate of GaN, treat subsequently epitaxial growing.

The epitaxially grown substrate of GaN that is used for that the present invention makes is made the GaN based light-emitting diode, this substrate can effectively reduce in the epitaxial growth dislocation density that causes because of GaN and sapphire crystal lattice constant mismatch, owing between Sapphire Substrate and GaN crystal, insert the low refractive index film layer of one deck between 1 and 1.8, low refractive index film makes light path refraction angle increase, and can reduce the effusion of light from substrate surface.Thereby improve the internal quantum efficiency and the light extraction efficiency of epitaxial loayer, reach the purpose that improves the device luminous efficiency.

Claims

1. one kind is used for the epitaxially grown substrate fabrication method of GaN, comprises the steps:

2. the epitaxially grown substrate fabrication method of GaN that is used for according to claim 1, it is characterized in that the vertical view of described mask layer convex graphical is edge＜1-100〉or＜11-20〉striated pattern of direction, the circle of periodic arrangement, hexagon or triangle square formation; The side-looking figure of convex graphical is taper, platform shape or hemisphere.

3. the epitaxially grown substrate fabrication method of GaN that is used for according to claim 2, it is characterized in that described edge＜1-100〉or＜11-20〉the width 1 um-100 um that goes to the bottom of direction bar pattern, height 0.1um-3um, spacing 1um-100 um, graphic length 1um-20cm; The width 0.1 um-10 um that goes to the bottom of the circle of described periodic arrangement, hexagon or triangle square formation, height 0.1 um-3 um; The array pattern of spacing 0.1 um-10 um.

4. the epitaxially grown substrate fabrication method of GaN that is used for according to claim 1 is characterized in that described etching is dry etching or wet etching; Described photoetching comprises even glue, exposure, development and hot plate baking successively.

5. the epitaxially grown substrate fabrication method of GaN that is used for according to claim 1 is characterized in that,

Oxide is silica or titanium oxide, and nitride is a silicon nitride, and nitrogen oxide is a silicon oxynitride.