Hello,

I have been trying to wet etch 300 nm thick Al layer using 2um wide PR
stripe. However I have problems width adhesion of resist to aluminum. PR
stripe seems to peal of when I'm etching.

I have been using following process.

1.    Spin HDMS on wafer (no I can't use vapor prime)
2.    Spin 1um thick AZ6612 on wafer
3.    Soft bake 2 min @ 110 C on hotplate
4.    Exposure
5.    Develop
6.    Hard bake 3 minutes in oven. 120 C.
7.    Etch with wet etchant

I have tried
HCl:H20 1:2 => very non uniform etching + Resist was removed
BOE => Resist was removed
HF:H2O2:H2O 1:1:20 => Resist was removed
H3PO4:HNO3:CH3COOH:H2O 4:1:4:1 => Resist was removed

Does anyone have good solutions. I know that I can grow SiN on Al and use
that as an etch mask or use dry etching but these steps make process more
complicated and I'm designing fast test process to test epi-wafers.

-Jukka Viheriala