Dear all,

Sample: AlGaN/GaN (2um) on Silicon substrate (500um)
Size: 1.4cmx1.4cm pieces

At some point of my process line I have Ti/Al/Ti/Au contact on the top side.
After that, I had to deposit PECVD 12um oxide on the back side to have pockets
for Si etch (SiO2 acts as masking layer for anisotrpic Si etch- Bosch process).
After I dip it in BOE soltion, the top contacts wash away :( .

Any solution or suggestion?

Muhammad Qazi
Dept of EE
University of South Carolina