Specific Process Knowledge/Lithography/ZEP520A

This is a standard positive resist from ZEON. The resist is out of stock from the manufacturer and also very expensive; DTU Danchip will thus stop buying this resist. As of August 2016 we have around 0.5L left. Use CSAR instead.

Contact lithography@danchip.dtu.dk if you wish to use this resist.

Process Flow

Test of ZEP resist; a positive e-beam resist from ZEON.

Equipment	Process Parameters	Comments	Initials and date
Pretreatment
4" Si wafers	No Pretreatment		TIGRE, 23-04-2014
Spin Coat
Spin Coater Manual, LabSpin, A-5	ZEP520A 1:1 or ZEP520A 1:2 E-beam resist 60 sec at various spin speed. Acceleration 4000 s-2, softbake 2 min at 180 deg Celcius	Resist poured directly from bottle or by use of disposable pipette1	TIGRE, 23-04-2014, 21-05-2014
Characterization
Ellipsometer VASE B-1	9 points measured on 100 mm wafer	ZEP program used; measured at 70 deg only	TIGRE, 23-04-2014, 21-05-2014
E-beam Exposure
JEOL 9500 E-beam writer, E-1	Dosepattern 14nm - 100nm, dose 120-280 muC/cm2	Virtual chip mark height detection2	TIGRE
Development
Fumehood, D-3	60 sec in N50, 60 sec rinse in IPA, N2 Blow dry	Agitation (by hand) while developing	TIGRE, XX-04-2014
Characterization
Zeiss SEM Supra 60VP, D-3			TIGRE, ??-04-2014

1 The disposable pipettes are not cleanroom compatible and must therefore be handled with care inside the cleanroom. Each bag contain 10 pipettes; the bags must be opened inside a fumehood and each pipette must be cleaned with a N₂ gun before use.

2 The e-beam writer measures the height of the substrate and adjust the focus accordingly. This requires no actual chip marks on the wafer. See e-beam writer manual.

Spin Curves

The thickness is measured on VASE Ellipsometer using a simple Cauchy model for a transparent polymer on a Si wafer with native oxide. The measurements are performed at one incidence angle (70 degrees) only. 9 points on each 4" wafer has been measured; the standard deviation thus represents the homogeinity of the film on the 4" wafers.

ZEON ZEP520A1:1 in anisole spinning on Spin Coater: Manual LabSpin A-5, TIGRE, 23-04-2014. Resist was mixed 13-01-2014, i.e. approximatley 3 months old.
Spin Speed [rpm]	Acceleration [1/s2]	Thickness [nm]	St Dev
3000	4000	111.29	0.65
4000	4000	95.17	2.16
5000	4000	87.23	0.81

ZEON ZEP520A1:1 in anisole spinning on Spin Coater: Manual LabSpin A-5, TIGRE, 21-05-2014. Resist was mixed 15-05-2014, i.e. approximatley 6 days old.
Spin Speed [rpm]	Acceleration [1/s2]	Thickness [nm]	St Dev
2000	4000	141.03	1.02
3000	4000	115.96	0.98
4000	4000	100.56	0.80
5000	4000	91.01	0.38
6000	4000	84.85	0.37

ZEON ZEP520A1:2 in anisole spinning on Spin Coater: Manual LabSpin A-5, TIGRE, 21-05-2014. Resist was mixed 15-05-2014, i.e. approximatley 6 days old.
Spin Speed [rpm]	Acceleration [1/s2]	Thickness [nm]	St Dev
2000	4000	79.12	1.74
3000	4000	64.30	0.34
4000	4000	55.50	0.48
5000	4000	50.53	0.62
6000	4000	46.34	1.01