Patrick,

Based on our experience and on the advice of the resist manufacturer (AZ
P4620), the preferred method to softbake multiple layers of resist is to
reduce the time of the bake for the first layer(s). This helps to avoid over
baking the first layers of resist. Also, for each layer of resist, it is
best to ramp up the bake temperature in a few steps. This is easily done on
a hotplate with programmable proximity pins, but can also be done by using
several hotplates at different temperatures.

Cory

Cory Wajda
Electronic Visions, Inc.
e-mail  info@elvisions.com 
web     http://www.elvisions.com 
Ph.     602 437 9492


                -----Original Message-----
                From:   P.Leech@mst.csiro.au [mailto:P.Leech@mst.csiro.au]
                Sent:   Monday, October 25, 1999 9:04 PM
                To:     MEMS@ISI.EDU
                Subject:        4620 resist

                Dear Colleagues,
                in the use of multiple layers of 4620 and 4903 resists, is
there a
                preferred method of  softbake? We are talking of total of 30
microns thick
                built up in 5 layers. I have both vacuum oven bake and
hotplate available.

                Yours sincerely,

                Patrick Leech,
                CSIRO CMST,
                Private Bag 33, Clayton South MDC,
                Victoria , Australia.