material request - Stycast W 19 epoxy

Mary Tang mtang at
Tue Sep 2 08:20:56 PDT 2008

Hi Peter --

So, if I understand correctly, you'd like to glue your chips to a 
silicon wafer with chip pockets and process through litho and lift-off?  
A few questions:

1.  Mixing and applying your epoxy.  These are all liquids, correct?  Do 
they require weighing or are they pre-measured?  We don't really have 
the appropriate balance inside the cleanroom for this.  However, we do 
have accurate balances outside the cleanroom (in the wafersaw/CMP 
room.)  Would you be applying the epoxy from a syringe?  Since the stuff 
appears to have a long working time, I'd suggest mixing outside the 
cleanroom and bringing the syringe (appropriately labeled and enclosed 
in something like a wafer box) into the cleanroom (through the service 
aisle) and applying it in a solvent bench.  You could also mix inside 
the lab in a solvent bench, but I have not yet ordered a replacement 
balance as yet (though you are welcome to nag me about this).  If you 
will be curing on a hot plate for several hours, please be careful to 
use foil (and not occupy all the hot plates at once.)  The concern is 
that the epoxy will be very difficult to remove if it gets on cassettes, 
bench tops, or hot plates, so precautions should be taken to make sure 
none gets on these.  If you want to store the unmixed chemicals in the 
lab, please get the appropriate labels from Mahnaz or me.  The chemicals 
should be stored in the personal Flammables area.  Any solid waste 
should be bagged and placed in one of the Flammables solid waste 
containers in the Litho area.

2.  Standard litho flow should be OK for contact alignment.  Hopefully, 
your desired resolution isn't better than a couple of microns.  If this 
is for ASML, please check first with Mahnaz, Ed, and the ASML engineers.

3.  PR lift-off in metalica should be OK.

4.  Polyimide lift-off for standard polyimides is not a process we're 
familiar with.  Fully cured polyimide is allowed in the gryphon, but is 
typically then very hard to remove by wet cleans.  Polyimide that is not 
fully cured is not allowed in the gryphon because off gassing of 
volatile organics could contaminate the system.  Polyimide, if I 
remember correctly, is also not typically allowed on the laurell, but 
only on the headway because it does not dissolve in acetone.  If you 
really need polyimide in the gryphon, please provide more details (and 
probably another SpecMat request.)


Peter Chen wrote:
> Hi specmat,
> Here is my request:
> Material - Stycast W 19 epoxy, Catalyst 11, Catalyst 9, from Emerson 
> and Cuming
> Where -
> (1) a litho bench (for the exhaust)
> (2) standard litho flow (after epoxy cure)
> (3) PR lift-off in Metallica
> (4) alternatively, polyimide flow at laurell then lift-off in Gryphon
> Process -
> (1) Insertion chiplets into backside of pocketed wafer. Mix, apply, 
> and cure epoxy at a wetbench (for exhaust). Epoxy only used on 
> backside of wafer.
> (2) Downstream to standard litho equipment for other (non-epoxy) litho 
> steps on frontside
> (3) PR lift-off process in Metallica
> (4) polyimide lift-off in Gryphon if that can be approved.
> Notes -
> (1) I don't need a litho bench per se, I would just like an approved 
> place that has enough exhaust and 120C hotplate for curing
> (2) Epoxy will be applied by syringe or pipette to chiplet insertion 
> sites only. Goal is to achieve a reconstituted wafer.
> (3) Cured epoxy should easily handle 155C.
> (4) The raw epoxy and catalyst can be stored at room temperature, 
> preferably in lab.
> (5) After chiplet insertion into wafer backside, my process is to have 
> metal lift-off on frontside to complete the electrical contacts. I 
> need to cover some frontside topography, hence sputtering.
> I have attached datasheet and MSDS. Please let me know if there are 
> other things I should bring to specmat.
> Thanks,
> -Peter Chen

Mary X. Tang, Ph.D.
Stanford Nanofabrication Facility
CIS Room 136, Mail Code 4070
Stanford, CA  94305
mtang at

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