Wet Etch Logbook

2021-08-16

Yinan

Remove Oxidized AlSb layer (exposed during dry etching)

B210416A Sample 6

• Add acid & water, mix @600RPM for 10min
• Dip sample in for 1min
• Take out, rinse, blow dry, wait for 30s - 1min, repeat.

Repeated for about 1h 20min, successfully removed the exposed and oxidized AlSb layer that looked brown. 

The hole patterns got half-destroyed, too (undercut the hole blocks). Just an isotropic etch doing its thing.

2021-09-02

Yinan

H2O: H3PO4: Citric: H2O2 =
120mL : 15mL : 20g : 15mL

Etch W-SL 
(10 nm GaSb +
30 nm AlAsSb +
300 nm W-SL +
30 nm AlAsSb +
100 nm GaSb buffer +
GaSb substrate)

B210701A AbsTest

• Phosphoric + Citric recipe
• Etch time = 1min 40s

2022-02-21

Yinan

Etch GaAs 

Deep-etch backfill dummy 2

• Phosphoric + Citric recipe
• Etch time = 5min
• Etch time = +4min

DEKTAK before etch: ~5 um (resist thickness)

DEKTAK @ 5min etch: ~ 7.5 um

DEKTAK @ +4min etch: ~9.45 um

Etch rate about a steady 490 nm/min for pure GaAs

2022-03

Etch B210416A 

InSb 600 nm +
AlSb 200 nm

Sac sample

• Phosphoric + Citric recipe
• Etch time = 1min
• Etch time = +2min

DEKTAK before etch: 2080 nm

DEKTAK @ 1min etch: ~2390 nm

DEKTAK @ +2 min etch: (need to check) seems about finishes AlSb

Etch rate for InSb: ~300 nm/min

Etch rate for AlSb: ~200 nm/min

H2O: H3PO4: Citric: H2O2 =
120mL : 15mL : 20g : 15mL

HCl: H2O = 
40mL: 200mL.

Etch B210416A 

InSb 600 nm +
AlSb 200 nm

Holey S2-5

• Phosphoric + Citric recipe
• Etch time = 3min
  
  
  
• HCl dips (unfortunately)

(need to check measured heights)

Stopped inside AlSb layer, gradually turned dark in air.
Did a lot of additional HCl dip to remove the oxidized Al layers
(ate a bit of holey block away due to probably undercutting)

Etch nBn T2SL with AlAsSb barrier (need to check sample number)

50 nm (n-LWIR) + 140 nm (B) +340 nm (n-LWIR) + 750 nm (n++)

• Phosphoric + Citric recipe
• Etch time = 9 min (deep etch)

DEKTAK before etch: 5.3 um (this is SPR 220 resist from Ruochen's group)
@ 9min = 9.01 um (3.7 um/9 min = 410 nm/min on average)

Etch nBn T2SL with AlAsSb barrier (need to check sample number)

50 nm (n-LWIR) + 140 nm (B) +340 nm (n-LWIR) + 750 nm (n++)

• Phosphoric + Citric recipe
• Etch time = 1.5min
• Etch time = +0.75min (45s)
• Etch time = +0.25min (15s)

DEKTAK before etch: 2.1 um
@ 1.5min = 2.37 um (first 270 nm in 1.5 min, in the absorber)
@ +0.75min = 2.76 um (660 nm, likely in n++)
@ + 0.25min = 2.9 um (800 nm, ensure to be in n++)

Etch rate for Barrier layer seems to be much slower than the 500 nm/min on average