Dear MEMS, I am trying to create stripe lasers.i am evaporating Ti(300A)/Au(1200A) broad area using e-beam on my sample. then, using S1813 to create the steps. The purpose of the photoresist is to cover the areas where i don't want the etch to etch the metal. my sample is p-GaAs/pAlGaAS/n-AlGaAs/n-GaAs. i have been using 2 types of etch processing. 1) 3HCL:1HNO3:2H2O(DI) to etch the Au and then using HF to etch the Ti. My photoresist holds to both etches for at least 3 min. On the surface of the sample, i can see that the the etch creates black dots. I have noticed this every time i use the Aqua Regia diluted etch. It seems that the etch bubbles and creates these black dots on the sample surface. 2) using KI/I2 etch for gold and then using the HF to etch Ti. The etch rate on this one is very slow, 8A/min. and as a result, my photoresist can't hold against the etch because it will take me at least 15min to etch through the gold. Can someone suggest another etch that can be used with my process. the etch should be ok with S1813 photoresist and that it should be ok with p-GaAs layer. Because i don't want to etch trought the p-GaAs. Need your help Ali