You shouldn't have a problem doing this, I've done films 30ums (using AZ40XT resist) and resolved lines smaller than 5um (Although this was on a variable NA i-line stepper using .5NA). Still what you're doing shouldn't be a problem at .6NA. You'll need to run a Focus exposure matrix to find the best focus though. Typically best focus is at about 1/2 your film thickness. I find it hard to believe for a 10um CD you only have .5um DOF. DOF does not relate to thickness, It is how far you can vary from best focus and still be within spec (spec is usually +/- 10%) Robert -----Original Message----- From: mems-talk-bounces@memsnet.org [mailto:mems-talk-bounces@memsnet.org] On Behalf Of Figura Daniel Sent: Wednesday, November 04, 2009 2:31 AM To: General MEMS discussion Subject: [mems-talk] Exposing thick resist with stepper Hello MEMS talk, Does anybody know what will happen if I try to expose relatively thick positive resist (10 um) with i-line stepper with NA 0.6 and achieve CD of 10 um? By calculation depth of focus of such projection system is +/- 0.5 um - far bellow thickness I am dealing with. Will it be possible to resolve? What kind of profile I should expect? Any concerns of using stepper for such unintended application? Thank you in advance Daniel