Hi folks,

I have an adhesion issue with PMMA.

PMMA 495 C4 was spun on a thermal oxide substrate and after e-beam
lithography, 6 um x 10 um window was opened.
Instead of dry etching, I wanted to wet etch SiO2 (~50nm thick) with 1:6 BOE
(etch rate ~90 nm/min).But the problem is after wet etching and PMMA
removal, the pattern is no longer rectangle. It's close to an oval shape. I
think it's because the adhesion of PMMA layer to the substrate is not goo.
Is there any way to improve adhesion?

What if I use ZEP resist? Is there a way to improve ZEP adhesion to SiO2
substrate?

Thanks

TK