material approval

Mary Tang mtang at
Mon Nov 26 17:34:01 PST 2007

Hi Dien --

I believe I mentioned this in my previous note, but perhaps wasn't as 
clear as I ought to have been. I may be mistaken, but I gather these are 
positive tone resins -- meaning that these are monomers, not a polymer 
like PMMA, which is negative tone. PMMA is safe to use in the lab 
because its solvent (usually anisole) is mostly removed during the soft 
bake and as a polymer, it does not have significant vapors. If these 
materials are monomers, then I suspect they are of lower molecular 
weight and may be quite volatile. That is, after you spin coat and 
before you fully cure them, they will continue to outgas. Acrylate 
monomers are considered harmful to inhale and typically have PEL limits 
on the order of 10 ppm. I don't know if this is the case for the 
materials you have, but for SNF, chemicals with a PEL of 10 ppm must 
remain under fully ventilated benches or equipment at all times. As it 
turns out, you would have to transport your wafers from the spin coater, 
which is ventilated, to the aligner, which is not. Understand that we're 
learning about this, from our experience with positive tone, uv-curable 
nanoimprint resists.

If your materials are of low volatility, then please ask the 
manufacturer to provide this information. Or, if you have a procedure 
that includes some sort of soft bake after spin coating, yet before you 
move them to the aligner, this would be appreciated. We just want to 
make sure that no volatiles will be released into the breathing air 
zones while your processing is taking place.



Dien Nguyen wrote:
> Mary,
> I just received the MSDS for the WR material. The solvent used will be 
> acetone. Please let me know if this contains sufficient information. 
> I’d like to process the polymer as soon as possible as its lifetime is 
> limited. Thanks.
> Dien
> -----Original Message-----
> *From:* Dien Nguyen [mailto:a.d.nguyen at]
> *Sent:* Wednesday, October 31, 2007 3:15 PM
> *To:* 'mtang at'
> *Cc:* 'kj.jackson at'
> *Subject:* material approval
> Hi Mary,
> I plan to ask Kathy Jackson to process a new family of UV-cure, 
> acrylate-based material (WR-326, 346, or 388, see attached), at SNF. 
> The acrylate material and its processing steps are similar to PMMA.
> The polymer will be spin coated on Si wafers in a similar manner as 
> PMMA, UV cured by a evalign, and post baked. Drytek 2 will be used for 
> etching. Standard disposal procedure (for PMMA) will be used. We would 
> like to store the material in a 100g bottle in the yellow solvent 
> cabinet.
> Please let me know if this is OK with the special material committee. 
> Thanks.
> Dien Nguyen, PI
> Los Gatos Research, Inc.
> 67 E. Evelyn Ave., Suite 3
> Mountain View, CA 94041
> (650)965-7772 x 223 (phone)
> (650)965-7074 (fax)

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

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