Hi guys

I am using E-Beam lithography tool with glass substrate.
The PMMA is coated on glass  and this is not conductive material so I
deposited 5nm Al layer to make it conductive using evaporator.
When I have done EBL and I have to remove Al layer to develpe PMMA.

But problem is here.
I have used NH4OH and diluted HCl.
The Al layer is removed but still remain .
I tested with just glass substrate like Al/glass.
When I soak this into the solution, I can see the color become light within
couple of minutes, I think it means the Al layer is thinner. But it keeps
same color in 30 minutes.

Please tell me the possible solution.

Thank you guys.