GaN基LED制程概论

5.
GaN-
LED
An Introduction to the fabrication of GaN-based LEDs
[
- Sep 2006]
GaN-based LEDs Fabrication
1

Complexity of LED production
[Dr. Volker Harle, Opto Semiconductor, OSRAM, Sep. 2005]
3
LED production flow
[Dr. Wei-Kai Wang, Recently Progress on Nitride Light Emitting Diode Technology, Dept. of Institute Precision Engineering, National Chung Hsing University, 2008]
Wafer
Chip
Lamp
4
2

Chip Designs for GaN-based LEDs
[Dr. Wei-Kai Wang, Recently Progress on Nitride Light Emitting Diode Technology, Dept. of Institute Precision Engineering, National Chung Hsing University, 2008]
5
GaN chip processing flow
[Dr. Wei-Kai Wang, Recently Progress on Nitride Light Emitting Diode Technology, Dept. of Institute Precision Engineering, National Chung Hsing University, 2008]
1. Mesa etching 2. Electrode metallization 3. Lapping and polishing 4. Laser scribing 5. Chip sorting
6
3

Mesa etching
[Dr. Wei-Kai Wang, Recently Progress on Nitride Light Emitting Diode Technology, Dept. of Institute Precision Engineering, National Chung Hsing University, 2008]
7
Electrode metallization
[Dr. Wei-Kai Wang, Recently Progress on Nitride Light Emitting Diode Technology, Dept. of Institute Precision Engineering, National Chung Hsing University, 2008]
8
4

Process flow of electrode metallization
[氮化鎵發光二極體製程技術之研究-中央電研所碩論-陳銘勝-基振瀛-2004]
10
Electrode metallization
[Dr. Wei-Kai Wang, Recently Progress on Nitride Light Emitting Diode Technology, Dept. of Institute Precision Engineering, National Chung Hsing University, 2008]
11
5

Process for LEDs with surface roughness and TCL
[氮化鎵發光二極體製程技術之研究-中央電研所碩論-陳銘勝-基振瀛-2004]
12
Surface roughness design for GaN-LED
[氮化鎵發光二極體製程技術之研究-中央電研所碩論-陳銘勝-基振瀛-2004]
13
6

SEM images of roughened surface
[氮化鎵發光二極體製程技術之研究-中央電研所碩論-陳銘勝-基振瀛-2004]
14
Process flow for flip-chip LEDS fabrication
[覆晶式藍光發光二極體製程技術之研究-中央電研所碩論-蔣國軍-辛裕明-2005]
15
7

Key fabrication Processes of flip-chip LEDS
[覆晶式藍光發光二極體製程技術之研究-中央電研所碩論-蔣國軍-辛裕明-2005]
16
Structure and top view of fabricated FC-LEDs
[覆晶式藍光發光二極體製程技術之研究-中央電研所碩論-蔣國軍-辛裕明-2005]
17
8

Typical I-V characteristics of FC-LEDs
[氮化鎵發光二極體製程技術之研究-中央電研所碩論-陳銘勝-基振瀛-2004]
18
Lapping and polishing
[Dr. Wei-Kai Wang, Recently Progress on Nitride Light Emitting Diode Technology, Dept. of Institute Precision Engineering, National Chung Hsing University, 2008]
19
9

Lapping and polishing
[Dr. Wei-Kai Wang, Recently Progress on Nitride Light Emitting Diode Technology, Dept. of Institute Precision Engineering, National Chung Hsing University, 2008]
20
Laser Scribing
[Dr. Wei-Kai Wang, Recently Progress on Nitride Light Emitting Diode Technology, Dept. of Institute Precision Engineering, National Chung Hsing University, 2008]
21
10

Chip sorting
[Dr. Wei-Kai Wang, Recently Progress on Nitride Light Emitting Diode Technology, Dept. of Institute Precision Engineering, National Chung Hsing University, 2008]
22
Process flowchart for regular GaN-based LEDs
(Ni/Au TCL wafer)
11

Sample preparation
? Activation of Mg-doped PGaN layer – At 750°C furnace for 15 min in N2 ambient. Surface cleaning – Rinsed in H2SO4:H2O2 (3:1) solution (> 70°C) for 2 min – [ or aqua regia solution for 5min]. Hotplate – 120°C for 2 min Deposition of SiO2 layer (served as a mask for ICP) – A Thickness of about 4.8 k? deposited by PECVD.
SiO2 layer
p-GaN p-AlGaN
Active region
?
n-GaN u-GaN
Sapphire
? ?
24
Photolithography
? ?
Photolithography
PR
SiO2 layer
p-GaN p-AlGaN
Active region
(1)
? ? ? ?
n-GaN u-GaN
Sapphire
? ?
Coating HMDS – 600 rpm/6000 rpm for 8s/15s Hotplate – At 90°C for 90s Coating photoresist (S-3020) – 600/6000 rpm for 8s/15s Hotplate – At 90°C for 90s Exposure (Mask-MESA) – For 2s Development – Rinsed in TMAH developer for 20s/20s – DI water for 1 min – Drying by N2 blow Checking in OM Hotplate – At 120°C for 90s
25
12

Defining the area of p-Mesa
? ? ? Wet etching – BOE solution (6:1) for 150s. Check in OM Removal of photoresist – H2SO4:H2O2 (3:1) solution (>40°C) for 2 min. Measurement – Depth of SiO2 layer Hotplate – 120°C for 3 min Dry etching by Unaxis ICP – Cl(80 sccm)/CH4(2.7 sccm)/ He(10 sccm) for 190s. KOH solution – 90°C for 5 min in ultrasonic cleaner. Removal of the residual SiO2 – BOE solution for 5 min. Measurement – Etching depth Check in OM (Removal of all SiO2 layer)
Removal of ICP wet-etching BOE dry-etching Removal of SiO2 photoresist & KOH solution
PR
SiO2
? ? ?
? ? ? ?
26
NiAu TCLTCL-
photolithography
?
(2)
?
PR
? ? ? ?
Ni/Au TCL
?
BOE solution – Ultrasonic cleaner for 3 min – DI water E-beam evaporation – Ni(22 ?)/Au(35 ?) Coating photoresist (S-3020) – 600 rpm/6000 rpm for 8/15s Hotplate – 90°C for 90s Exposure (Mask-TCL) – For 2s Development – TMAH developer for 20s/20s – DI water for 1min – Drying by N2 blow Hotplate – 120°C for 90s
27
13

NiAu TCL
-
Annealing
? TCL wet-etching – Au etchant for 10s – DI water – Drying by N2 blow – Check in OM Removal of PR – In 60°C S-100 stripper for 5 min/5 min – DI water – Check in OM Annealing – At 520°C furnace in O2 ambient (5 sccm) for 15 min
Removal of Annealing wet etching Photoresist
PR
?
?
28
Passivation & Metal pad- photolithography (3)
? ? ?
PR
? ? ? ? ?
SiO2 Passivation
?
Passivation layer (SiO2) by PECVD – About 800-900 ? Coating HMDS – 600 rpm/6000 rpm for 8s/15s Hotplate – 90°C for 90s Coating photoresist (300D1) – 400 rpm/4000 rpm for 8s/15s Hotplate – 103°C for 90s Exposure (Mask-PAD) – 8s Hotplate – 103°C for 90s Development – TMAH developer for 30s/30s – DI water for 2min – Drying by N2 blow Hotplate – 120°C for 90s
29
14

Passivation and Metal pad
? ? ?
TCL
PR
BOE wet-etching
– Ultrasonic cleaner for 10s/10s
Check in OM Hotplate
– 120°C for 90s
Cr(150 ?)/Al (4 K?)/Cr(1000 ?)/Au(4K?)
? ? ?
Metal-pad deposition
–
SiO2 Passivation
Metal Lift-Off by Blue tape Removal of photoresist
– – – – 70°C NMP stripper in ultrasonic cleaner for 3 min 85°C PMR stripper in ultrasonic cleaner for 5 min DI water Drying by N2 blow
?
Check in OM
30
Masks for device fabrication
Mask-MESA Dark (with Cr metal) Clear Aligned key Mask-TCL Mask-PAD
31
15

The fabrication of VM-LEDs
The applications of high-power LEDs
34
16

Current status of SSL efficiency
(Dec. 2008)
35
Commercial white LEDs are breaking the 100 lm/W barrier
36
17

Barriers to replacement of traditional light with SSL
Cost Still 50× than that of bulb The $80B lathing industry is slow and conservative Compact fluorescent (CFL) has taken decades to penetrate Lighting fixtures of LEDs Low voltage DC Supporting technologies/infrastructure Consumer education and demand
37
Tendency of Lighting in 21 Century
38
18

How achievable is 150 lm/W?
39
Regular and VM LEDs
Ohmic Contact Active Layer p-GaN n-GaN Ohmic Contact
Ohmic Contact n-GaN p-GaN Electroplating Ni Layer Active Layer Adhesive and Mirror Layer
Sapphire
Regular-LED
(Vertical-structured Metal-substrate LED )
VM-LED
40
19

Cross-section scheme of VLEDMS
[https://www.360docs.net/doc/7411409118.html,/] 41
High Power (HP) LEDs
Power LEDs are rapidly improving and continued improvements is expected. Key issue of future improvement are IQE (especially green) The LEDs should dominate general illumination.
42
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