<div dir="ltr"><div class="gmail_default" style="font-family:arial,sans-serif">Hello everyone,</div><div class="gmail_default" style="font-family:arial,sans-serif"><br></div><div class="gmail_default" style="font-family:arial,sans-serif">I am having some trouble developing recipes or testing performance on our Heidelberg MLA150. Especially when testing performance, it is required for us to expose the test pattern once, develop, inspect and repeat.
We usually coat a larger sample (e.g. a 4" wafer) with resist and expose a small test design, allowing us to use the same sample many times.
The problem that I encounter is that the development time increases after each iteration, and it is not due to the developer getting weaker (I tried using a new developer to make sure). This behavior is observed on AZ 1500 and AZ 4000 series resists, with the latter presenting a more drastic change.</div><div class="gmail_default" style="font-family:arial,sans-serif"><br></div><div class="gmail_default" style="font-family:arial,sans-serif">It seems to me that the developer changes something on the unexposed resist, making it harder to develop. This is made obvious by the fact that we don't see this problem when processing multiple samples and developing them with the same developer bath. In that case the only problem we encounter is the developer getting weaker depending on the exposed area and number of samples, as expected.</div><div class="gmail_default" style="font-family:arial,sans-serif"><br></div><div class="gmail_default" style="font-family:arial,sans-serif">I thought that it could be over-hydration, since the developer is a water solution and we rinse with water as well. But high water content tends to make development faster, not slower. Does anyone have more information on the interaction between developer and unexposed resist? I'd appreciate any input you may have.</div><div class="gmail_default" style="font-family:arial,sans-serif"><br></div><div class="gmail_default" style="font-family:arial,sans-serif">Best regards,</div><div class="gmail_default" style="font-family:arial,sans-serif">--</div><div class="gmail_default" style="font-family:arial,sans-serif">Gustavo de Oliveira Luiz, PhD</div><div class="gmail_default" style="font-family:arial,sans-serif">Applications/Research Specialist</div><div class="gmail_default" style="font-family:arial,sans-serif">nanoFAB, University of Alberta</div><div class="gmail_default" style="font-family:arial,sans-serif">+1 (780) 619-1463<br></div></div>