CN103137793A

CN103137793A - Vertical-structure LED (light emitting diode) production method utilizing multi-layer dielectric film reflection

Info

Publication number: CN103137793A
Application number: CN 201110379687
Authority: CN
Inventors: 郭德博
Original assignee: TONGFANG OPTO-ELECTRONIC Co Ltd
Current assignee: TONGFANG OPTO-ELECTRONIC Co Ltd
Priority date: 2011-11-25
Filing date: 2011-11-25
Publication date: 2013-06-05

Abstract

A vertical-structure LED production method utilizing multi-layer dielectric film reflection relates to semiconductor photoelectric devices. The method comprises the steps of firstly epitaxially growing a GaN-based (gallium nitride-based) epitaxial layer on a sapphire substrate; secondly, depositing multilayer dielectric films on the surface of a p-type GaN-based semiconductor layer, and removing the multilayer dielectric films on the partial region to reveal the surface of a p-type GaN semiconductor layer; thirdly, depositing an ohmic contact metal layer on the multilayer dielectric films and the upper surface of the revealed p-type GaN-based semiconductor layer; fourthly, depositing an electroplating seed layer on the upper surface of the ohmic contact metal layer; fifthly, forming a metal substrate on the upper surface of the electroplating seed player; sixthly, removing the sapphire substrate and reverting the device; seventhly, depositing a p-type electrode on an n-type GaN-based semiconductor layer; and eighthly, depositing an n-type electrode on the lower surface of the metal substrate. By utilizing the multilayer dielectric films to further improve the reflectivity of the p-type GaN ohmic contact layer of the vertical-structure LED, the light extraction efficiency of the GaN-based vertical-structure LED is effectively improved.

Description

A kind of method for preparing vertical structure LED that adopts the multilayer dielectric film reflection

Technical field

The present invention relates to semiconductor photoelectric device, particularly adopt the method for preparing vertical structure LED of multilayer dielectric film reflection.

Background technology

Light-emitting diode is due to the advantage such as have low energy consumption, long-life, lightweight, volume is little, its application is more and more wide, present light-emitting diode light, display backlight, outdoor Landscape Lighting inside and outside automobile, portable system photoflash lamp, projector light source, advertising lamp box, torch, traffic lights etc. all are widely used.Low and technology is relatively ripe due to the Sapphire Substrate price, and GaN base epitaxial growth at present is most or take Sapphire Substrate as growth substrates.Yet because sapphire is non-conductive, so the most electrodes that adopt of GaN based light-emitting diode are at the transversary of the same side.The shortcoming that the following aspects is arranged for this transversary, at first due to p, n electrode in the same side of light-emitting diode, electric current lateral flow in the n-GaN layer is not equidistant, has the electric current jam, cause the local pyrexia amount high, thereby reliability is affected; Secondly, transversary needs the etching table top, has sacrificed the area of active area; The 3rd, the poor thermal conductivity (35W/ (mK)) due to Sapphire Substrate has also limited the heat radiation of GaN base luminescent device.In order to overcome above problem, the GaN based light emitting diode with vertical structure becomes the focus of Recent study.

In prior art, at first light emitting diode with vertical structure is bonded together translate substrate (high heat conductance, high heat conductivity substrate) and GaN base epitaxial wafer by bonding or electric plating method, then the method for peeling off by excimer laser is removed original Sapphire Substrate, forms light emitting diode with vertical structure finally by crossing cutting and separating.For light emitting diode with vertical structure, the ohmic contact layer that has high reflectance, low specific contact resistivity rate in p-type GaN surface making is the important step that affects its light extraction efficiency.Current, make the GaN based light emitting diode with vertical structure, the p-type ohmic contact metals with high reflectance that adopt such as Ag more, but the adhesiveness of well-known Ag is relatively poor, so must preplating one deck adhesion layer before plating Ag, yet due to the introducing of adhesion layer, will certainly reduce reflectivity, on the other hand, rising metal diffusion aggravation along with temperature certainly will also can affect reflectivity after the metal diffusion, thereby affect the light extraction efficiency of light-emitting diode.

Summary of the invention

The deficiency that exists in order to overcome above-mentioned prior art the purpose of this invention is to provide a kind of method for preparing vertical structure LED that adopts the multilayer dielectric film reflection.It adopts multilayer dielectric film further to improve the reflectivity of light emitting diode with vertical structure p-type GaN ohmic contact layer, thereby effectively improves the light extraction efficiency of GaN based light emitting diode with vertical structure.

In order to reach the foregoing invention purpose, technical scheme of the present invention realizes as follows:

A kind of method for preparing vertical structure LED that adopts the multilayer dielectric film reflection, it comprises step:

1. epitaxial growth GaN base epitaxial loayer on Sapphire Substrate, GaN base epitaxial loayer comprises N-shaped GaN based semiconductor, active layer and p-type GaN semiconductor layer from bottom to up successively;

2. deposit multilayer deielectric-coating on p-type GaN based semiconductor, remove the multilayer dielectric film of subregion, exposes p-type GaN semiconductor layer surface;

3. has the ohmic contact metal layer of high reflectance in the p-type GaN of multilayer dielectric film and exposure semiconductor layer upper surface deposition;

4. at ohmic contact metal layer upper surface deposition plating seed layer;

5. form metal substrate at the plating seed layer upper surface by the mode of electroplating;

6. Sapphire Substrate is removed, and device is inverted;

7. at N-shaped GaN based semiconductor upper surface deposition p-type electrode;

8. at metal substrate lower surface deposition N-shaped electrode.

In above-mentioned method for preparing vertical structure LED, described epitaxial growth GaN base epitaxial loayer is to form by the organic chemical vapor deposition MOCVD of metal method.

In above-mentioned method for preparing vertical structure LED, described deposit multilayer deielectric-coating adopts the method for evaporation, sputter or chemical deposition to form; The preparation material of multilayer dielectric film is selected from SiO2, TiO2, ZnS, ZrO2, Ta2O5, PbF2, MgF2 or Al2O3; The multilayer dielectric film of removing the subregion adopts the method for wet method or dry etching.

In above-mentioned method for preparing vertical structure LED, after described deposition has the ohmic contact metal layer of high reflectance, ohmic contact metal layer is carried out annealing in process, annealing temperature 300-550 ℃, annealing time 3-20min; The material of ohmic contact metal layer comprises NiAgTiAu, NiAgPtAu, NiAgNiAu, NiAgWAu metal system.

In above-mentioned method for preparing vertical structure LED, the preparation material of described plating seed layer adopts Au, Ni, Cu, Ta, Ti and alloy thereof.

In above-mentioned method for preparing vertical structure LED, the mode of described removal Sapphire Substrate adopts laser lift-off, grinding or wet etching; The depositional mode of described p-type electrode, N-shaped electrode adopts the method for evaporation or sputter.

The present invention is owing to having adopted above-mentioned manufacture method, utilize the multilayer dielectricity highly reflecting films to merge the metal highly reflecting films as the high reflective ohmic contact layer of light emitting diode with vertical structure, can effectively reduce Ag pre-metal-coated membrane before to the impact of reflectivity, simultaneously, also the impact of metal diffusion couple reflectivity can be effectively reduced, thereby the light extraction efficiency of light emitting diode with vertical structure can be effectively increased.

The invention will be further described below in conjunction with the drawings and specific embodiments.

Description of drawings

Fig. 1 to Fig. 7 is the schematic flow sheet of manufacture method of the present invention.

Embodiment

The making step of the inventive method is as follows:

1. at first, as shown in Figure 1, heteroepitaxial growth GaN base epitaxial loayer 101 on Sapphire Substrate 100, GaN base epitaxial loayer 101 comprises N-shaped GaN based semiconductor, active layer and p-type GaN based semiconductor from bottom to up successively.

2. as shown in Figure 2, adopt electron beam evaporation method deposit multilayer deielectric-coating 102 on GaN base epitaxial loayer 101, multilayer dielectric film 102 is selected SiO2 and TiO2 material, thickness is respectively 75nm and 40nm, one 10 pairs of codepositions, and by traditional chemical wet etching technique, expose part p-type GaN semiconductor layer surface with as conductive channel.

3. as shown in Figure 3, adopt electron beam evaporation method at multilayer dielectric film 102 and the part p-type GaN semiconductor layer surface deposition ohmic contact metal layer 103 that exposes, select Ni/Ag/Ni/Au, thickness is 1.5/300/200/300nm, then 400 ℃ of annealing 10min under nitrogen atmosphere make ohmic contact metal layer 103 and p-type GaN semiconductor layer form good ohmic contact and make all the other multilayer dielectric films 102 and p-type GaN semiconductor layer that part exposes has better adhesion.

4. as shown in Figure 4, adopt electron beam evaporation method on reflection-type ohmic contact metal layer 103, deposition plating seed layer 104 is selected Ti/Cu, and thickness is 200/300nm.

5. as shown in Figure 5, form the metal substrate 105 of 200um by electroplating technology on plating seed layer 104.

6. as shown in Figure 6, carry out peeling off of Sapphire Substrate 100 with the excimer laser of 248nm, remove Sapphire Substrate 100, laser energy density 980mJ/cm2 used, and device is inverted.

7. as shown in Figure 7, adopt electron beam evaporation method to deposit N-shaped electrode 106 on N-shaped GaN based semiconductor, at metal substrate 105 backside deposition p-type electrodes 107, all select Cr/Au, thickness is 100/2000nm.

Claims

1. method for preparing vertical structure LED that adopts multilayer dielectric film reflection, it comprises step:

1. at the upper epitaxial growth GaN base of Sapphire Substrate (100) epitaxial loayer (101), GaN base epitaxial loayer (101) comprises N-shaped GaN based semiconductor, active layer and p-type GaN semiconductor layer from bottom to up successively;

2. deposit multilayer deielectric-coating (102) on p-type GaN based semiconductor, remove the multilayer dielectric film (102) of subregion, exposes p-type GaN semiconductor layer surface;

3. has the ohmic contact metal layer (103) of high reflectance in the p-type GaN semiconductor layer upper surface deposition of multilayer dielectric film (102) and exposure;

4. at ohmic contact metal layer (103) upper surface deposition plating seed layer (104);

5. form metal substrate (105) at plating seed layer (104) upper surface by the mode of electroplating;

6. Sapphire Substrate (100) is removed, and device is inverted;

7. at N-shaped GaN based semiconductor upper surface deposition p-type electrode (107);

8. at metal substrate (105) lower surface deposition N-shaped electrode (106).

2. method for preparing vertical structure LED according to claim 1, is characterized in that, described epitaxial growth GaN base epitaxial loayer (101) is to form by the organic chemical vapor deposition MOCVD of metal method.

3. method for preparing vertical structure LED according to claim 1 and 2, is characterized in that, described deposit multilayer deielectric-coating (102) adopts the method for evaporation, sputter or chemical deposition to form; The preparation material of multilayer dielectric film (102) is selected from SiO2, TiO2, ZnS, ZrO2, Ta2O5, PbF2, MgF2 or Al2O3; The multilayer dielectric film (102) of removing the subregion adopts the method for wet method or dry etching.

4. method for preparing vertical structure LED according to claim 3, it is characterized in that, after described deposition has the ohmic contact metal layer (103) of high reflectance, ohmic contact metal layer (103) is carried out annealing in process, annealing temperature 300-550 ℃, annealing time 3-20min; The material of ohmic contact metal layer (103) comprises NiAgTiAu, NiAgPtAu, NiAgNiAu, NiAgWAu metal system.

5. method for preparing vertical structure LED according to claim 4, is characterized in that, the preparation material of described plating seed layer (104) adopts Au, Ni, Cu, Ta, Ti and alloy thereof.

6. method for preparing vertical structure LED according to claim 5, is characterized in that, the mode of described removal Sapphire Substrate (100) adopts laser lift-off, grinding or wet etching; The depositional mode of described p-type electrode (107), N-shaped electrode (106) adopts the method for evaporation or sputter.