Hi Lu,

You can adopt two way approach. One is to avoid HF sieve in through Au
film  pin holes and attack the Cr-Si interface by protecting the pads
using shadow masking with resist for HF release and second one to
thicken up the Au film (at least 1 um)  so that you can have good wire
bonding.

Best regards,

Parshant Kumar (Ph D)
Draper Inc- Cambridge
617-258-4417