vcsel fab overview
TRANSCRIPT
VCSEL Fabrication Processing
The following is pictorial description of the fabrication process for oxidized VCSELs.
A detailed description of each step is contained in “VCSEL Fab Details.ppt”
This work was performed in Micro and Nanotechnology Laboratory
at the University of Illinois
by members of the Photonic Device Research Group
Photonic Device Research Group
p-DBR
n-DBR
n-GaAs substrate
VCSEL fabrication – Bare wafer
CleaveLabel substrate backsideClean
Photonic Device Research Group
p-DBR
n-DBR
n-GaAs substrate
VCSEL fabrication – Backside contact
Target: 40 nm AuGe / 20 nm Ni / 150 nm Au
Photonic Device Research Group
p-DBR
n-DBR
n-GaAs substrate
PR
VCSEL fabrication – Spin PR
Degrease /N2 dry /Dehydration bakeHMDS (can spin-on or vapor prime)Spin on photoresist (usually 4330)
Photonic Device Research Group
p-DBR
n-DBR
n-GaAs substrate
PR
VCSEL fabrication – Top contact lithography
4330 lithography
Photonic Device Research Group
p-DBR
n-DBR
n-GaAs substrate
PR
Photonic Device Research Group
VCSEL fabrication – Metal deposition
O2 Plasma (300W – 3 min)1:10 NH4OH:DI dip (15 sec)Flowing DI rinse (10 min)N2 dry, inspect, load, evaporateTarget: 15 nm Ti / 150 nm Au
Photonic Device Research Group
p-DBR
n-DBR
n-GaAs substrate
VCSEL fabrication – Liftoff
Acetone soak ~5 min / Squirt gun
Photonic Device Research Group
p-DBR
n-DBR
n-GaAs substrate
SiO2
VCSEL fabrication – SiO2 deposition
Degrease, N2 dryload, deposit dielectric> 400 nm thickness (based on color)
Photonic Device Research Group
VCSEL fabrication – SiO2 pattern
Degrease /N2 dry /Dehydration bakeHMDS vapor primeSpin on AZ5214Hardbake (110° C for 60 sec)Patern & developp-DBR
n-DBR
n-GaAs substrate
SiO2
PR
Photonic Device Research Group
p-DBR
n-DBR
n-GaAs substrate
SiO2
PR
VCSEL fabrication – CF4 RIE etch
Freon 14 (CF4) for > 400 nm (22 min)Remove PR mask with acetone
Photonic Device Research Group
p-DBR
n-DBR
n-GaAs substrate
SiO2
VCSEL – SiCl4 ICP-RIE mesa etch
Clean ICP (O2 process – 15 min)
ICP predep (SiCl4 recipe – 10 min)
Etch > 5 mirror pair into bottom DBR
To be replaced by Semigroup RIETo be replaced by Semigroup RIE
Photonic Device Research Group
p-DBR
n-DBR
n-GaAs substrate
SiO2
VCSEL fabrication – Selective oxidation
Oxidation rate from test pieceUse optical (below) or electrical probeRecord actual pinch off in log book
Photonic Device Research Group
p-DBR
n-DBR
n-GaAs substrate
VCSEL fabrication – CF4 RIE etch
Freon 14 (CF4) process (~200 Å/min)Test for conduction on probe station2 min etch, testRepeat until all SiO2 is removed
Photonic Device Research Group
VCSEL Structure and Operation
Top-view optical photograph of
fabricated VCSEL
Side-view schematic of fabricated VCSEL
Top contact
Bottom contact
Oxide layers
Active region
p-DBR
n-DBR
n-GaAs substrate
Laser Emission
Photonic Device Research Group
Test VCSELs!