Further to Xianling's comments,

If you want to eliminate the effect of surface roughness (say you have a
range of substrates with different, unknown surface qualities) you could
immerse them in concentrated HF for a few minutes. Depending on your etch
time, all substrates would then have similar surface conditions.

Michael


>
>Another thing from my experience. The adhesion between SU-8 and glass
>substrate seems fairly much depending on the surface conditions
>(maybe roughness) of the substrate. There are a couple of times I ran
>borofloat wafers using exactly the same process (pirahna cleaning,
>dehydtration, spinning, soft bake, exposure and PEB) but SU-8 patterns
>show up nicely on some wafers without any peel off after development
>for a few mins, while nothing is left on other wafers with the same
>develop time. Because the wafers used are mixed from different vendors, I
>could not trace down the difference between their surface quality.
>However, besides surface conditions, I could not think of any other
>factors contributing to this huge difference in adhesion. So, try some
>other glass substrates if nothing else helps.
>
>Xianling Chen
>

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