Silicon waveguide

Xenon Difluoride Etching System

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Homebuilt system
XeF2 etcher is a system to expose Si samples to XeF2 gas in a cyclic mode in which the etch chamber is repeatedly filled (~2 mbar) with XeF2 gas and pumped out again. Silicon will etch isotropically. Higher etching pressure gives a smoother etching surface. The etch rate does not depend on feature size when > 10 micron.

cleanroom xef2 etcher HJB4055 amsterdam nanocenter

2 XeF2 + Si => 2Xe(g) + SiF4(g)

Sample preparation
Samples must be clean, dry and free from oxide. Apply a HF dip, rinse and bake 120 ºC.

The etching is selective
Si : SiO2 => 500 : 1
Si : Si3N4 => 100: 1

Source: Marvell Nanolab

etch  no etch
Mo  Acrylic
Nb etches rapidly  Al
polySi  AlN
Si up to
10 micron/min
 Ga
SiGe  Ni
Spin-on glass
~50 nm /min
 Pt
Ti  photoresist
W very rapidly  SiC, ZnO