I made evaporated Cr/Au patterns through lift-off process on silica on Si.
Then, I sputtered Cr on the wafer and pattered the Cr layer for SiO2 dry etch mask formation.
Cr/Au was for heater on silica waveguide, and etched trench was for thermal isolation between waveguides.
After SiO2 etch process, Cr etchant did not remove completely the Cr hard mask on Au layer.
On the other hand, Cr on SiO2 was removed without problem.
The residual Cr was confirmed by measuring the surface profile, showing ~100nm thickness.
Has anyone experienced something similar?
Hi, there are two types of chromium etchant, what you observe happens quite frequently using the mixture of perchloric acid and ceric ammonium nitrate on heterostructures which have undergone certain processes. Instead the Cr etchant based on sodium hydroxide and potassium permanganate does not have such issues. You can find different commercial solutions CR etch 100, 200, 210... tailored for different material selectivity but i do not expect particular problems for gold.
Thank you for the information, Marco.
I will buy a CR-etch and try soon.
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