70 µm deep etch with low ARDE effect

ARDE is "Aspect ratio dependent etch (rate)"
The etch rate lowers at high aspect ratios (> 5 : 1)
due to gas transport limitations.

optimised conditions for both steps by "gas chopping"

Technology:
Reactive Ion Etching
Inductive Coupled Plasma Source ICP380
ICP Accelerator Technology ©
room temperature “Bosch” process
He backside cooling

Results
Rate : > 10 µm/min for most applications
-up to 20 µm/ min is possible under certain cirmcumstances
selectivity to SiO2 > 150 : 1
-up to 400 : 1 is possible under certain cirmcumstances
selectivity to PR > 75 : 1
anisotropic etch 90° ± 1°
aspect ratio > 30 : 1
controllable wall profile

twin spot laser interferometry
for in situ depth measurement

100 µm deep etch at 17 µm/ min

Plasmalab System 100
with ICP Souce and loadlock

etch rate vs ICP power

110 µm deep etch without ARDE effect

100 µm high aspect ratio etch

ICP layout

Sytem 100 cluster
with cassette loading,
two ICP 380 sources and
one laser interferometer