110 µm deep etch without ARDE effect

44 : 1 aspect ratio

novel twin spot laser interferometry/ "polarimetrie"
for in situ depth measurement

Reactive Ion Etching

Inductive Coupled Plasma Source

room temperature “Bosch” process

He backside cooling

The process can often be optimised for very high rates/ aspect ratios/ uniformities/ selectivities.
The optimisation options strongly depend on mask details !

100 µm deep etch at
400 : 1 selectivity to the SiO2 mask

100 µm deep etch at 17 µm/ min
using the ICP accelerator technology

Plasmalab System 100
with ICP Souce and loadlock

400 µm deep etch with reproducible
wall angle (91°) at 3.5 µm/ min and
75 : 1 selectivity to PR
courtesy of Acreo Kista

150 µm deep etch with
reproducible wall angle (91°)
at 6.5 µm/ min and
60 : 1 selectivity to PR
uniformity over a 6" wafer ±1.7 %

100 µm very high aspect ratio etch

ICP layout

21 µm deep anisotropic etch
stopping on SiO2
courtesy of Uni Kassel