Hello,

I am trying to make silver polarization gratings for optical spectrum, i.e.
I am making thin silver wires about 100nm high and with a period of about
250nm. My method is as follows,

I evaporate 100nm Ag onto a silica (or glass) substrate. Spin 150nm
thickness of photoresist on top of this. Then I over expose and develop
(using NaOH) the photoresist into a diffraction grating so that part of the
silver is exposed. I think I have got this far sorted ok (though I am not
sure if I am actually revealing the silver underneath the photoresist
properly.

My problem is in the next stage, I am then trying to etch the revealed
silver using nitric acid. When I try to do this the silver that is exposed
changes to a milky colour (and becomes transparent) and then stops
dissolving no matter how long I attempt to etch for. The photoresist mask
seems unaffected, but when I remove in it do not see any diffraction or
polarization effects as expected.

What am I doing wrong?! Or is there a easier way to do this e.g. better etch
solution?

Thanks

Martyn Gadsdon