Fwd: Re: XR1541 ebeam resist (SOG) for bonding experiment

Mary Tang mtang at stanford.edu
Sat Aug 13 08:45:39 PDT 2011


Hi all --

I don't recall a request for SOG in the tylan oxidation furnaces from 
Jae, but it would appear he's doing this.  It's not disastrous, I 
suppose, but it brings up some questions about our policy.

We've relied for a long time on the Gold/semiclean/clean designation 
system which is awfully handy, but as we know, simplistic.  It's overly 
conservative for some processes (etchers) and sometimes not enough for 
others (furnaces, wet benches).

I wonder if we should also incorporate some aspects of the semiconductor 
fab convention distinguishing front end and back end processing.  The 
SOG is a case in point.  It's originally designed to be a back-end 
material, so is clean enough for back-end and cured to withstand backend 
temperatures.  But if it's used as a bonding material, it will be going 
into high-temp  front-end tools, like the oxidation furnaces.  It's 
normally cured at 400 C - but going into a furnace at 900 C, the film 
will continue to change.  And I really think that it should not go into 
Epi (not that this has come up, but no doubt it will.)  So, I think 
there's a case to be be made for defining different levels of "clean" -- 
without getting too convoluted.

Also, for this specific case, HSQ for ebeam resist strikes me as being 
different from SOG designed to be interlevel dielectric.  It's designed 
to be removable hard mask, so I'm not sure it's metal-free.  Also, got a 
lot of covalently-bound organics in it whereas I think that classic 
SOG's do not -- which suggests that high temperature curing will result 
in different by-products.

Maurice and I will follow up with J and Jae for more info.  But I 
thought this might be a good illustration of an area where our 
contamination policy isn't sufficient.  There's a lot of SOG work going 
on and it seems to be increasing.

Mary


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Subject: 	Re: XR1541 ebeam resist (SOG) for bonding experiment
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Hi J --

Jae's Specmat process request from April had nothing to do with SOG, 
just W from Sandia.  So, we're still trying to figure out how we got 
from W to SOG-coated innotec-deposited metal in wet benches where metal 
films/non-silicides are prohibited.  But your question brings up some 
good questions about our cleanliness policy.

Spin-on-glasses for electronics applications are certified electronics 
grade -- I'm not sure HSQ's for resist applications are.  Would you 
happen to have an elemental analysis for this stuff?  If it can be 
considered electronics grade (i.e., metal ion free), then it's 
considered clean by our current lab standards.

M

On 8/13/2011 7:12 AM, J Provine wrote:
> hi mary and maurice,
> due to some recent confusion i wanted to double check with you about a 
> procedure using the XR1541 ebeam resist (a type of SOG) for a high 
> temperature bond.  i want to spin XR1541 onto clean wafers (Si and 
> SiO2 covered) and bond with pressure from a weight in litho.  the 
> weight i'll cover in fresh foil and i'll use another clean wafer 
> between my process wafers and weight.  this will be baked with 
> pressure up to 400C for several hours on a hot plate.  then i would 
> anneal the wafers in tylan1 or tylan2 with the recipe slow900a that 
> maurice set up with jae lee.  but before going into tylan1/2 i would 
> do a diffusion clean.
>
> the question is, is it ok to diffusion clean and introduce the wafers 
> into tylan1/2 with the XR1541 after the 400C bake?
>
> thank you,
>
> j


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