Sommaire
- 1. Fabrication of new wafer BPC9 High Z design
- 1.1. Litho 1st step
- 1.1.1. mercredi 09/03
- 1.1. Litho 1st step
- 2. Fabrication of new wafer BPCT9
- 2.1. Litho 1st step
- 2.1.1. mercredi 09/03
- 2.2. Litho 2nd step
- 2.2.1. vendredi 11/03
- 2.2.2. lundi 14/03
- 2.3. Litho 3rd step
- 2.4. Litho 4th step
- 2.1. Litho 1st step
started 2016-03-09
Fabrication of new wafer BPC9
High Z design
lift-off process on 1st step
Batch 3481, Si <100>, intrinsic, rho > 20kohm.cm, 300µm
Litho 1st step
mercredi 09/03
- spin
spun with cleaned pipette. Tiny spots but not so much.
bake wafer >10' @ 110°C (solvent evaporation) spin AZ5214E (Aurelie bottle, per 12/2014) 60" @ 4krpm bake 1' @ 110°C Expo 20mJ/cm2 @ 365nm, Vacuum contact -> 2" @ 10mW bake 2'40 @ 120°C Flood expo 40" Dev MIF726 1'15 @ 21.2°C, rinse ODI 60" beaker + 30" water tap
- Residue removal
2' ozone plasma @ 100W, 200µb
TODO
- multilayer evaporation (old plassys)
P_init = 1.4e-7mb, N2 trap -> 1.1e-7mb - Al 150nm @ 1nm/s, P_ev ~ 2.5e-7mb, 100nm @ +7° / 51nm @ 0° - Ti 10nm @ 0.5nm/s -> P_ev = 3.0e-7mb (hot) -> 3.5e-8mb (cold) - Pd 4nm @ 0.2nm/s -> P_ev = 6e-8mb /!\ Loadlock pressure always very high!!!
- Lift-off
remover PG 70°C, 30'
Fabrication of new wafer BPCT9
In parallel with BPC9, to do the exact same steps in advance
Take wafer lot 2451, DSP
Litho 1st step
mercredi 09/03
bake wafer 5' @ 110°C (solvent evaporation) spin AZ5214E (Aurelie bottle, per 12/2014) 60" @ 4krpm bake 1' @ 110°C Expo 20mJ/cm2 @ 365nm, Vacuum contact -> 2" @ 10mW bake 2'40 @ 120°C Flood expo 40" Dev MIF726 1'15 @ 21.2°C, rinse ODI 60" beaker + 30" water tap
- Residue removal
2' ozone plasma @ 100W, 200µb
- multilayer evaporation (old plassys)
P_init = e-7mb, N2 trap -> e-7mb, Ti pump -> - Al 130nm @ 1nm/s, P_ev ~ e-7mb, 100nm @ +7° / 51nm @ -3° - Ti 20nm @ 0.5nm/s -> P_ev = e-7mb (hot), 15nm @ +7° / 5nm @ -3° - Au 10nm @ 0.5nm/s -> P_ev = e-8mb, all at 0° /!\ Loadlock pressure always very high!!! Maybe the gauge doesn't work anymore It could be that there is a H2O leak on the crucible of Ti, to be confirmed
- Lift-off
remover PG 70°C, 30'
Litho 2nd step
BCB bottle refilled on 07/03
thickness was 4640nm on center, 4600nm on the edge.
Now is 4580nm
- BCB spin
bake wafer >10' @ 110°C spin AP3000 - 5" @ 500rpm acc 200rpm/s; 60" @ 6000rpm ; bake 1' @ 110°C spin BCB4024-40 - 5" @ 500rpm acc 250rpm/s; 60" @ 5000rpm acc 1500rpm ; bake 3'30 @90°C
- expose
Expo 70mJ/cm2 @ 365nm, Vacuum contact -> 7" @ 10mW/cm2
- develop
pre-dev bake 30" @ 65°C
dev DS3000 at 31-32°C (very important) for 8 min
rinse DS3000 1' @ 20°C
rinse ODI 1' water tap
NB: made a unexposed test wafer for the development time: 4' when interferences finish (instead of 2'30 when out of the fridge)
Still, the patterns are much wider than they should, we see residues at the bottom, and yet it is clearly overdevelopped!!! (because patterns at 7min or BPCT8 that was made at the same time are better shaped than those of BPCT9)
WE SHOULD NOT KEEP ON USING BCB THAT WAS NOT HELD IN THE FRIDGE ... Goddam
vendredi 11/03
- BCB hardening bake
Hot plate 1h @200ºC
Obs: patterns went much smoother
- BCB RIE cleaning
SF6:O2 5:45, 250µb, 25W -> 70V, 35"
Overal OK, but there are also very tiny spots, like the layer was attacked from place to place
Does SF6 etches Al ??? (unprotected by Al2O3)
lundi 14/03
Litho 3rd step
- spin PMGI SF15 +AZ5214
NB: there are still a lot of tiny spots on the spun resist!!! I try to clean the pipette the best I can.
bake the wafer 30' @ 110°C for water removal tape the wafer on blue clean room tape, cut to a ~3" square (half the width of blue tape) dispense PMGI SF15 1-1.5mL (no more!) slowly from a pipette well centered on wafer 2" @ 300rpm acc 250rpm/s 3" @ 800rpm acc 500rpm/s 60" @ 1500rpm acc 500rpm/s bake SF15 5min at 150°C spin AZ5214E (Aurelie bottle, per 12/2014) 60" @ 4krpm bake 1'30 @ 110°C Expo 50mJ/cm2 @ 365nm, Vacuum contact -> 5" @ 9.5mW bake 3' @ 120°C Flood expo 45" Dev MIF726 2' + rinse ODI 60" beaker + 30" water tap
Patterns are OK, but the PMGI unsticks from noble metal parts
Hopefully, Ti/Au is sufficiently protective and Al is not etched. I decide to continue the process and put it in evaporator
- etch + bridge evaporation (new plassys)
P_init = 4e-8mb (pumped over night) - etch 500V, 65mA, 10", 16°/s planetary - Ti 5nm @ 0.2nm/s - Al 250nm @ 1nm/s -> P_ev ~ 4e-7mb
- Lift-off
hot acteon 30' -> the whole layer peels off 5" US rinse IPA remover PG 70°C, 30'
Litho 4th step
mercredi 16/03
- spin MAA / PMMA bilayer
- spin MAA8.5 EL10 (batch 14020103, exp. 01/2015) @ 2000rpm for 60" - bake hot plate setpoint 180°C, 5' - spin PMMA A6 (batch 15121016, exp. 1/1/2017) @ 6000rpm for 60" - bake hot plate setpoint 180°C, 15' - spin UV III (Vivien bottle) @ 4000rpm 60" - bake hot plate 140°C, 90"
MAA = 530 +/- 20nm
PMMA = 240 +/- 20nm
reprocess once because spin was inhomogeneous.
- dice
Cut wafer in 2, and take 1/4 to make tests for the 4th and 5th steps, to tune the geometry, and doses of all patterns.
Isolate a chip to measure its Tc, and a possible resonance at 300mK.
Measured Tc in Marcelo's fridge: between 1.12 and 1.15K. As expected, seems higher than it should. (though the temperature is not calibrated in that range. cal exists from 300K to 1.5K and from 230mK to 500mK)
TEST n°1:
upper left 1/4 of the wafer
- e-beam exposure XL30 (18/03 et 21/03), take time to setup the right procedure on wafer with alignement on each chip
remove UV3 in IPA, 2'
BB gold
30keV, 300µC/cm2, 1200pC/cm, spot 1, I~ 22pA, WD=17mm, field x2000 : area step size 4nm (dwell time ~ 2.2µs), line step size 1nm (dwell time ~5.5µs) dose factor on all patterns: 1.2 for chips after the first one (4Q)
- development
dev: MIBK - IPA (1:3) 1'30 rinse: IPA - ethanol (1:1) 30"
- evap (old plassys), 22/03
etch : 5mA 500V, 20" Al 100nm @ 1nm/s, 0°
- lift
warm aceton (30°C): a bit longer than usual but mostly OK
Results:
The PMMA mask is too thick, the MAA was not well exposed so we have residues in the bottom or on the side of patterns. (even though dose was 1.2)
On silicon, the alignement marks have well defined edges, but still residues on the bottom
On gold, they are rounded (overdosed), but still residues on the bottom
-> should use thinner PMMA
Litho 5th step on test n°1
- spin MAA / PMMA bilayer
- spin MAA8.5 EL10 (batch 14020103, exp. 01/2015) 45" @ 2000rpm + 5" @ 8krpm acc 4k - bake hot plate setpoint 180°C, 5' - spin PMMA A6 (batch 15121016, exp. 1/1/2017) 45" @ 6000rpm + 5" @ 8krpm acc 4k - bake hot plate setpoint 180°C, 15'
MAA = 580 +/- 10nm
PMMA = 340 +/- 20nm
NB: I did no wait for the result of step 4 to spin step 5, so I found out afterwards that I should use thinner PMMA
- e-beam exposure XL30 (23/03): alignement marks
BB gold
30keV, 300µC/cm2, 1200pC/cm, spot 1, I~ 22pA, WD=17mm, field x2000 : area step size 4nm (dwell time ~ 2.2µs), line step size 1nm (dwell time ~5.5µs) dose factor on all patterns: 1.1
- development
dev: MIBK - IPA (1:3) 1' rinse: IPA 30"
- e-beam exposure XL30 (23/03): junctions
30keV, 300µC/cm2, 1200pC/cm, spot 1, I~ 22pA, WD=17mm, field x2000 : area step size 4nm (dwell time ~ 2.2µs) patterns, step size 8nm undercut boxes dose factor 1.3 main patterns, 0.9 island, 0.4 undercut boxes
Put undercut boxes on the sides of main patterns, and all around island.
- dice all chips
- process BPCT9_1: 4Q (2,2)
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