material request - Stycast W 19 epoxy

Peter Chen jwpchen at stanford.edu
Tue Sep 2 14:40:59 PDT 2008


Mary,

To answer your questions:

(1) Yes, my silicon wafer will have backside pockets topped by 
frontside membranes (metal/dielectric stack). After insertion, the 
chips should be flush with or recessed into the wafer backside.

(2) The epoxy need to be measured and mixed. I do not yet know how 
critical the mixing ratio is... hopefully I can get by without 
precision weighing, and just mix by volume.

(3) Regarding ASML, I will see if I can shuffle steps around, such 
that there will be no epoxy going into ASML. (e.g. litho PR for 
liftoff before insertion then epoxy)

(4) You have a good point about cured polyimide and I will need to 
look at dry etch of polyimide. I do not yet know a good etcher for 
polyimide though.

Thanks,
-Peter


Mary Tang wrote:
> 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.)
> 
> Mary
> 
> 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
> 
> 




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