[mems-talk] GaAs mirror finish

[deepa sree]

Hi All,

I am trying to scribe GaAs wafers with back side up. The back side has streets and gold pads. Gold pads are obtained by a lift-off process or through gold etching, I have tried both. Due to these chemical processes the street of GaAs is getting rough and causing scribing problems. I tried etching the wafer in NH4OH:H2O2:H2O in 1:1:10 ratio to smoothen the streets. This is causing an undercut and the gold pads are getting lifted off. 

Can anyone suggest me a chemical process to smoothen the GaAs surface to a near mirror finish so that scribing can be done?

Thanks

Deepa