Hi, there,

I have 2 questions when i did processing on a optical laser.

Question 1:

I made a Ti/Cu seed layer on a GaAs substrate, and then electroplated Cu
thick layer (2 um) on top with certain patter. Now i want to etched off the
unplated Cu seed layer, which is about 800A. I tried to use the commercial
Cu etch solutions, but find out it is not very good for small area etching.
Can anybody give a suggestion on the Cu etching solutions for small area? I
heard someone applied surfactant in the etching solutions, but not sure how
it will work in this case and what surfactant i can use.

Question 2:

I made ohmic contact pad Ti/Pt on the p+/GaAs. And then I use it as a metal
mask for plasma etching using Cl2/BCl3. But found out the Pt was off after
the plasma etching, i.e. the selectivity is not good. Can anyone give a
suggestion on the metals should be used, providing ohmic contact and also
can stand in good shape during the Cl2 plasma etching.

Thank you very much,

Zhiyan