4160 SEM

Mary Tang mtang at stanford.edu
Wed Jan 23 15:31:27 PST 2008

Yeah, you're right, we should settle this and make our documentation 
consistent. My opinion: it's a "litho" tool. It was designed for in-line 
CD measurement so should be able to handle samples which outgas to a 
higher degree than what can be tolerated by the Sirion. That said, we 
should establish some sort of minimal resist treatment, though granted 
this might have to change with the type of resist. As for gold, I think 
there have been a number of discussions about it -- one conclusion being 
(if I recall correctly) that as a low voltage SEM, the likelihood of 
sputtering gold from a gold-contaminated sample onto the chamber walls 
which could sputter back onto "clean" samples was pretty low.

It seems if we categorize it as a "litho" tool, then anything that goes 
back into the fab must undergo standard cleans before any high 
temperature processing. This should avoid concerns of 
cross-contamination, at least within the framework we've established 
thus far.


Ed Myers wrote:
> All,
> I had another question today regarding the cleanliness category of the 
> 4160 SEM. It seems to me, people may be putting in gold coated samples 
> and there is a fair likelihood of gold contaminated samples are being 
> imaged. Should we categorized the 4160 as a "litho" tool?
> The following was taken from SNL's sample restriction for their Sirion 
> SEM.
> Restrictions on samples:
> The sample material must be able to withstand a high vacuum 
> environment without outgassing. It must be clean. It may be attached 
> to the sample holder using any suitable SEM vacuum-quality adhesive. 
> The sample must be electrically grounded to the sample holder to 
> minimize sample charging. If the sample is nonconductive (plastic, 
> fiber, polymer, or other substance with an electrical resistance 
> greater than 1E10 ohms), the sample may be coated with a 200 – 300 Å 
> layer of carbon or other conductor. Rough surfaced samples must be 
> evenly coated from every direction. Biological, cloth and powder 
> samples may require carbon or other conductive painting on portions of 
> the sample that are hard to coat. The workstation can accommodate up 
> to 150 mm (6") wafers.
> Ed

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

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