If you dispense photoresist from a dropper bottle with no filter, you are
going to get a lot of contaminants.  What is happening is that you have
bubbles, particulates, and gel slugs within the resist that do not get
filtered.  You have to use a dispenser with a filter.

One of the other sources of contaminants are the nozzles you use to dispense
the resist.  You have to make sure you clean the nozzle with solvent to
insure that dried-up resist has not accumulated on the nozzle.

This is of course dependent on the environment that you are handling your
wafer.  If you are doing the coating process in a bad cleanroom environment
you are going to have particles depositing on the wafer.


The way that I know how resist is dispensed is by Resist Reduced
Consumption.  It helps in reducing the amount of resist you have to apply on
the wafer.  First, the wafer is spun on a spin chuck.  Then, pre-wet solvent
is placed on the wafer to decrease the surface tension.  Last, resist is
placed on the wafer.  I wouldn't pre-wet the wafer without an adhesion
module or else you will get fluttering of the reisit off of the wafer.


I hope this helps,

Fred Sanchez
fsanchez@alumni.utexas.net




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