Specific Process Knowledge/Etch/IBE⁄IBSD Ionfab 300/IBE Au etch

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This page is written by Berit Herstrøm @ DTU Nanolab (BGHE) if nothing else is stated

Results from the acceptance test in February 2011

Acceptance test for Au etch:

.	Acceptance Criteria	Acceptance Results
Substrate information	50 mm SSP Si wafer 525 µm thick Supplied by Nanolab	.
Material to be etched	E-beam deposited Au	.
Mask information	E-beam resist mask: 400 nm of spin coated ZEP520A e-beam resist Patterned by E-beam lithography	.
Features to be etched	300 nm - 3µm dots and lines + a square of 200µmx200µm	.
Etch depth	300nm	~272 nm
Etch rate	>80nm/min	54.5nm/min +- 0.6nm/min (one standard deviation)
Etch rate uniformity	<+-2%	+-(0.2% +-0.2%)
Reproducibility	<+-2%	+-0.9%
Selectivity (Au etch rate/ZEP etch rate)	At least 1:1	1.2:1
Etch profile	70-90 dg.	75 dg

Process parameters for the acceptance test

Parameter	Au etch acceptance
Neutralizer current [mA]	550
RF Power [W]	1300
Beam current [mA]	500
Beam voltage [V]	600
Beam accelerator voltage	400
Ar flow to neutralizer [sccm]	5.0
Ar flow to beam [sccm]	10.0
Rotation speed [rpm]	20
Stage angle [degrees]	30

Some SEM profile images of the etched Au

s18-Au-ZEP3

s18-Au-ZEP5

IBE Au etch with Ti mask

by bghe@nanolab

Work has been started to find a good process for etching gold with a Titanium mask with high selectivity.

	Ti etch test with Zep520A as mask - To etch the Ti mask	Au etch test with high selectivity to Ti
General description	This recipe has a good selectivity between ZEP520A resist and Ti, which makes it good for patterning the Ti that should be used as masking layer for the Au etch. It can also be used to etch Au if the selectivity to the mask is good enough.	This recipe has especially good selectivity between Ti and Au which makes it good for gold etching using a thin Ti mask as masking layer. The selectivity to resist is very bad so do not use it with a resist mask.
Recipe name	Ti acceptance 20111129	Au_acceptance_with_O2
IBE parameters	Rotation speed = 20 rpm Sample angle = 20 degrees Ar flow to neutralizer = 6 sccm Ar flow to beam = 6 sccm Neutralizer current = 300 mA Power = 1200 W Beam current = 250 mA Beam voltage = 800 V Beam accelerator voltage = 300 V	Rotation speed = 20 rpm Sample angle = 30 degrees Ar flow to neutralizer = 5 sccm Ar flow to beam = 10 sccm O2 flow to beam = 4sccm Neutralizer current = 550 mA Power = 1300 W Beam current = 500 mA Beam voltage = 600 V Beam accelerator voltage = 400 V
Results
Etch rate in resist	12.8 nm/min (15-12-2011)	72 nm/min (13-12-2011)
Etch rate in Au	32.7nm/min (15-12-2011)	42.6nm/min (13-12-2011)
Etch rate in Ti	8.3nm/min (15-12-2011)	4.3nm/min (13-12-2011)
Selectivity Ti/Zep	0.65 (15-12-2011)	0.06 (13-12-2011)
Selectivity Au/Ti	3.9 (15-12-2011)	9.9 (13-12-2011)
SEM images of the etch profile (click to view a larger image)	600nm lines etched for 14 min (15-12-2011) Several line profiles through Ti and Au. Line profile through Ti and Au. Several line profiles in Au after Ti has been removed. Line profile in Au after Ti has been removed. Line in Au after Ti has been removed. Sample is tilted	Ti mask etched for 6min30sec with recipe test Ti acceptance 20111129. The Au was etched for 7min with recipe Au_acceptance_with_O2. The result was less fenching because a thinner mask was used (Ti instead off resist) Tilted line in Au after Ti has been removed. Profile in Au after Ti has been removed. Tilted line in Au after Ti has been removed.