Depends a bit on the thickness of your ScAlN coating is. If you have to etch a few microns of the film, I would start out with using a resist mask. Both Sc and Al have pretty high vapour pressures for the chlorines, so with a chlorine of BCl3/Cl2 plasma you should be able to etch this material with resist. If you have thicker layers, I would recommend using a metal mask or SiO2 mask.

Hi Peter Knapen , thanks for your advice. ScAlN layer is of around 750 nm in my film. We were trying to etch with Si02 mask. We used Ni/SiO2/ScAlN layer configuration. (Used Ni for protecting Si02 layer during Chlorine Etch). Unfortunately it didn't came out that much good. (considering the verticality of the walls and surface quality).

And also, we tried Ar/N2 separately with BCl3 & Cl2. What's your suggestion here?

The 750 nm should nog be a problem. How did your profile of the etch lok like, was it more vertical or did you have under etch of the mask? Normaly you only use a fraction of BCl3 (surface scavenger for oxides) in the Cl flow. What is your ratio for the gasses. Adn what was your dc-bias during etching ?

Peter Knapen , Please check your message.

Peter Knapen , Thanks for your continuous support. Well, our etching was not exact vertical. Around 70 Degree (Inside) or 110 Degree (Outside). Used Cl2 (20 sccm), BCl3 (10 sccm), N2 (30 sccm), RF Power (100 W), ICP (550 W), Pressure (5 mTorr). That's what I used. Ni-Si02-ScAlN (That's the layer configuration)