Al2O3 with RIE O2

Al2O3 with RIE O2Edit

RIE parameters adjustments:

Power (W)	Vpol, 10µb (V)	Vpol, 50µb (V)
50	200	205
70	230	240
90	270	272
110	300	302
150	344	351
175	380	382
200	407	403
225	434	426
250	464	450
275	490	475
295	510	494

NB: the maximum voltage is achieved (~constant) in between 10µb and 20µb.

Ellipsometer measurements

recipe which seems to work: 

/!\ To modify: do not lock together... otherwise the fit can converge, but the error bar is = thickness if thicknesses are different

First measures with ellipsometer (model Al2O3 -fit param 20nm, +/-99%-, Al 30nm -fit param, +/-30%-, SiO2 100nm):
find between 2 and 9nm depending on how much one let the Al thickness be varied. Uniformity is usually more or less equivalent to thickness. GOF is around 85%.
Second batch of measures used the above model and worked with more than 0.95 GOF
The key points -or so it seems- are to
- let the lamp warm for ~ 15'
- measure often background, reference and reflectance
- set Al and Al2O3 to half the total thickness of Al (then one can let these parameters be adjusted within 100% without a change on the resulting fit)
- Si wafer thickness and backside reflection should not play a role, but...

Resistance to TMAH

sample 1:  Al 30nm + RIE on hot Al rod (oven 220°C), 10cc O2, 10µb, 260W (V = 460V) 1'
sample 2: only Al 30nm
Put both at the same time in MIF 319

From the beginning, bubbles appear on sample 2. At 2'30, all Al disappeared, leave up to 3'.
The sample 1 has nothing, no bubbles even close to corners (visually OK -> observe it in SEM)

Voltage dependence of the oxide thickness

- Take 5', 10µb, 220°C as a basis to test the effect of voltage.
- test wafers for rough adjustements on Si-B [100] 1-10ohm.cm, 280µm, 100nm th. oxide
     Al 5nm - 10nm - 15nm - 20nm - 30nm

- Samples for capacitance measurements with following design and spin parameters:
1 step

Use bilayer spun in 2013 for tests called MAPMA6
- spin MAA8.5 EL10 @ 2000rpm for 45"
- bake hot plate setpoint 180°C, 5'
- spin PMMA A6 @ 6000rpm for 45"
- bake hot plate setpoint 180°C, 15'

Expo 30keV -> dev 1' -> evap 60nm Al -> RIE -> lift remover PG (with or without US)

2nd step

- spin MAA8.5 EL10 (batch 14020103, exp. 3/1/2015) @ 2000rpm for 45"
5" 500rpm 200rpm/s + 45" 2000rpm 1000rpm/s + 10" 8000rpm 4000rpm/s (edge removal)
- bake hot plate setpoint 180°C, 5'
- spin PMMA A6 (batch 14020103, exp. 3/1/2015) @ 5000rpm for 45" (same trick)
- bake hot plate setpoint 180°C, 15'

Expo 25keV-> dev 1' -> evap 90nm Al -> lift remover PG (with or without US)
NB: alignement very hard because cannot see crosses!

Predicted capacitance in the range 40fF per pad -> 20fF between 2 pads (80Mohms at 100kHz)

sample name	Al thick (nm)	RIE (if applicable) Voltage / power (V/W)	ellipsometer				capacitance
			Al2O3 (nm)	Al (nm)	GOF	fit
wafer test 1	30	native	9.4 +/- 4.7	29.7 +/- 10	0.9503
wafer test 1	30	510 / 295	28.8 +/-	4.1 +/-	0.9803
Al2O3-RIE_1	60	400 / 180