etching Al2O3

Dear Labmembers,

 

One of my collaborators try to etch off Al2O3 at the corners of samples (consisting of Al2O3 / InGaAs / InP substrate) for Hall measurements. He found that photo-resist used to define the corners on Al2O3 surface was peeled off during etching by BHF. Has anyone sucessfully done photolithography on Al2O3? If so, what kind of adhesion promotor was used? Also, does anyone know the etch rate of Al2O3 by BHF?

 

Thanks,

Byungha