> I am a student of M.Tech in IIT Kanpur and i am working in the field of
electronic materials.
> I have to etch gold and nickel, but the microetchant should not affect the
negative photoresist (SC100).The film deposited is
> Silicon (substrate) / Nickel / Gold / photoresist(during pattering). I
have used aquaregia (aquaregia:water :: 1:2 ) for 5 min.,for the
microetching of both nickel and gold but it stripped away the photoresist
only.
> What should i do now.
>
> Thanking You
> Your's Sincerely
> Hare Krishna

Use a KI + I2 chemistry, available commercially as AU-100 or AU-5 for the
gold.
    --Kirt Williams