OPT application lab:
5 µm deep, anisotropic etch

OPT application lab:
10 µm deep etch with profile control

Plasmalab 80 Plus

15 µm deep, anisotropic etch
(1,8 µm uniform undercut
under the SiO2 mask)

1,6 µm deep, anisotropic etch
(SiO2 mask still in place)

etch rate > 0.5 µm/min with SF6/ O2
                > 0.05 µm/min with CF4/ O2
uniformity < ± 5% (100 mm wafer)
selectivity to positive photoresist up to 10:1
selectivity to silicon dioxide > 30:1
undercut typically 10% of depth

The undercut is very dependent on silicon load
(wafer size, pattern density) and the total gas flow.
The selectivity to resist or oxide can be increased
by reducing the DC bias.

The process strategy to achieve the anisotropy in
F based Si RIE is best explained by the
"black Si method" described by TU Twente.

Plasmalab System 100

RIE technology

10 µm deep etch by Uni Kassel