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;
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;
Automatic acquisition PC;