On Wed, 21 Feb 1996, Perry Skeath wrote:
> The edge-reflow problem is certainly reduced by lowering the hard bake
> temperature to 110 degrees C, but then come increased problems with the
> wafer sticking to the mask plate after alignment and exposure.  This is a
> situation where we'd like to try a mask aligner that makes a softer
contact
> during exposure -- unfortunately we do not have such an aligner.
>
> Has anyone had success with using a low hard bake temperature (110 degrees
> C or less, Shipley 1800 series resist) and avoiding problems with the wafer
> sticking to the mask plate after alignment and exposure?
>
> Perry Skeath
Different groups call the bakes during lithography by different names. We have
a Dehydrate bake before spinning, a Soft bake before alignment and exposure and
a Hard bake after developing. I figure your hard bake step is the same as our
soft bake, in anycase, we regularly do our softbake @ 90C, before alignment and
exposure (using Shipley's 1800 series and other resists). We use a Karl Suss
MA6 aligner having three different types of contact alignment. Even with the
highest contact force - vacuum being drawn from between the wafer and the mask
plate - we usually (95% of the time) never have any sticking problems. This is
assuming you do your bakes inside an oven and not on hotplates.

Arjun Selvakumar