We have to create a cavity inside wafer.
Here is the link for detail of the etchant : https://www.microchemicals.com/technical_information/wet_etching_metals_al_au_cu_cr_ni_ti_ag.pdf
It contains H3PO4 * : HNO3 * : CH3COOH* : H2O = 80 %: 5 % : 5 % : 10%
The same composition I have used for Aluminium electrode etching in my phd days but I am wondering if it's also good for Al2O3.
Or otherwise can someone suggest or recommend me some other etchant for Al2O3?
Thanks in advance!