[mems-talk] SiO2 cracking problem

[henson at bu.edu]

We've been evaporating 250nm thick layers of SiO2 (for antireflection 
coatings) using an ebeam evaporator on GaN and on sapphire. The samples 
appear fine when we unload them from the chamber but when we start 
unmounting the GaN sample, cracking of the oxide occurs. The sapphire 
sample remains fine. Any ideas? We tried a plasma ash before hand on 
both samples but still saw the cracking and also made sure the samples 
were in good contact (for thermal purposes) with the metal mount.
Thanks
--John, Boston University Photonics