How are you!

I thank that you have some ideas about Al etchant. We also try to find
Al etchant for selective etching.

Maybe the etchant what you want is KOH, NaOH or NH4OH solution.

What I want to use is the etchant that etchs Al but doesn't etch Mo and
Cr metal layers. Futhermore, it doesn't contain Na-ion or K-ion. If you
know some etchant for Al please inform me.

Best regards,

Young-Rae Cho
Email: yrcho@etri.re.kr