[mems-talk] Exposing thick resist with stepper

[Robert Black]

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 at memsnet.org [mailto:mems-talk-bounces at 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