Picture of XeF2 Isotropic Si etcher
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The XeF2 Isotropic Si etcher is used for isotropic etching of silicon.
XeF2 (xenon difluoride) isotropic silicon etching is particularly well suited to MEMS applications. XeF2 vapor phase etching exhibits nearly infinite selectivity of silicon to photo-resist, silicon dioxide, silicon nitride and aluminum. 
However, the etch rates and uniformity are highly dependent on the amount of exposed silicon, being in the microns/minute range.
Being  a  vapor  phase  etchant,  XeF2  avoids  many  of  the  problems  typically associated with wet processes.
The Xetch software may be run in one of three operating modes that can be used during an etch.
The  normal  mode,  utilizes  a  pulsed  etch  with  a  set  xenon  difluoride pressure and etch time. 
An  advanced  normal  etch  mode allows  for  the  user  to  set  the  expansion chamber pump-out pressure between cycles. 
The flow through mode creates a continuous flow of xenon difluoride.
The major components of the Xetch X4 are:
XeF2 source bottle containing solid XeF2;
N2 source:  supplies N2 gas for venting and purging the process chamber, and combining with XeF2 for etching;
Expansion  chambers  where
sublimated  XeF2  and  nitrogen  gas  are collect  before  entering  the  process  chamber;
Process chamber: this is where the etching occurs. When the etch cycle time is up, gas is pumped out and another etch cycle begins;
Vacuum  pump;
A needle valve for adjusting the flow rate of process N2;
A mass flow controller to control the xenon difluoride flow in continuous etch processes;
An  automatic  pressure  controller  valve;
Temperature control of the expansion chambers, gas panel, XeF2 source bottles, XeF2 source bottle valves, and the process chamber;
Control PC;
Automatic acquisition PC;
Optical microscope.
Tool name:
XeF2 Isotropic Si etcher
01.01. Cleanroom
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Micro and Nanofabrication Facility
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