material request - Stycast W 19 epoxy

Peter Chen jwpchen at stanford.edu
Wed Sep 3 23:00:38 PDT 2008


Mahnaz,

I have indicated the relevant process steps and equipment below:

(1) start -- semi-clean wafer with frontside membrane and backside 
cavities.
(2) solvent bench -- insert chiplets and fill gaps with epoxy
(3) solvent bench -- cure on hotplate, 120 degC

(4a)headway -- polyimide coat
(4b)svgcoat -- PR coat, likely SPR220-3 or -7

(5x)karlsuss/evalign -- expose with lift-off mask
(5y)asml -- expose with lift-off mask

(6a)manual develop? -- also cure polyimide
(6b)svgdev -- develop PR

(7a)gryphon -- sputter aluminum, no heat
(7b)metallica -- sputter Al or Au (still need to run tests first)

(8a) p5000etch + TBD -- dry etch back of Al, then O2 etch polyimide
(8b) solvent bench -- acetone lift-off of PR

Note that
(*a) = draft of polyimide flow
(*b) = PR flow

I can try to draw cross-sections for some of the steps if that helps 
visualization.

Thanks,
-Peter

Mahnaz Mansourpour wrote:
> 
> Hello Peter,
> 
> I need a process flow with indication of equipment use please that would 
> be very helpful to me.
> 
> mahnaz
> 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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