single step process:
thin sidewall deposition visible
on brocken line: Si:Cl:O

gas chopping process:
sidewall deposition gets thinner
towards the bottom
Aspect Ratio Dependent
Deposition "ARDD"

with kind permission of TU Vienna
S. Golka, W. Schrenk, G. Strasser

laser interferometer trace
time_DEPOSITION
time_SPUTTERETCH

time_SPUTTERETCH /time_DEPOSITION

for a grating etch
As the etch continues it takes less
time to sputteretch off the deposited
film (Si:Cl:O)

gas chopping process:
roughness at the top 200 nm
for the non optimised process

gas chopping process:
roughness < 20 nm
for the optimised process

Plasmalab System 100
with ICP180 source

ICP RIE
Inductive Coupled Plasma

rate > 0.5 µm/ min

selectivity to SiN mask 60 - 100 : 1

low bias process for low substrate damage

published at JVST-B 25, 839 (2007)