Hello Bill and all,

one question in regards to HMDS I was wondering about - does HMDS actually
increase the adhesion in mechanical sense or only due to higher
hydrophobicty prevents water and developer penetration between photo resist
and substrate and prevents the delamination that way.

In other words, if I would do a dry cross-cutter peel test, would I measure
higher adhesion on HMDS primed wafers than on untreated?

Thanks.

With best regards,

Daniel



Daniel Figura

smartfabgroupT Company

process consulting . data processing . fab software

Phone: +421 944 45 26 86

E-mail: daniel.figura@smartfabgroup.com, Web: www.smartfabgroup.com



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-----Original Message-----
From: mems-talk-bounces+daniel.figura=smartfabgroup.com@memsnet.org
[mailto:mems-talk-bounces+daniel.figura=smartfabgroup.com@memsnet.org] On
Behalf Of Bill Moffat
Sent: Monday, December 16, 2013 18:18
To: General MEMS discussion
Subject: Re: [mems-talk] Questions regarding HMDS (Hexamethyldisilazane)

Practical input from the developer of vacuum vapor prime and Silylation in
the 80's.  HMDS has very active NH ending to the molecule which is looking
for hydrogen, given hydrogen it quickly forms ammonia NH3, usually from
water or hydroxyl ions. When reacting with a totally dry silicon dioxide
surface it reacts with the hydroxyl ions and leaves a mono layer.  In This
mono layer the molecule is now Silicon with 3 methyl atoms. A
inorganic/organic molecule, a perfect adhesion for  an organic photoresist
to adhere to an inorganic substrate Silicon. Bill Moffat

Sent from my iPad

On Dec 16, 2013, at 5:44 AM, "Gianmario Scotti" 
wrote:

> Hello Sk,
>
>
> I am no HMDS expert, and am talking from memory, so don't take my word for
> any of this:
>
>
> 1: Yes, I believe HMDS is polar, just by looking at the molecule.
> 2. and 3: HMDS forms a monolayer on SiO2, glass and hopefully (some)
> metals, making the surface hydrophobic. Since we're talking of monolayers,
> the thickness is probably below 1 nm. During sylilation by HMDS, some
> ammonia may be produced.
>
> You will find more info in this reference: F. Deyhimi, J. A. Coles, Helv.
> Chim. Acta 65, 1752 (1982)
> Rapid Silylation of a Glass Surface: Choice of Reagent and Effect of
> Experimental Parameters on Hydrophobicity
> http://onlinelibrary.wiley.com/doi/10.1002/hlca.19820650610/abstract
>
>
>
>
>
>
>
> On Thu, Nov 21, 2013 at 8:17 PM, Sk Fahad Chowdhury <
> sk.chowdhury.fahad@gmail.com> wrote:
>
>> Hi
>>
>> I have a few questions about hexamethyldisilazane or HMDS
>> (CH3-Si-NH2-Si-CH3)
>>
>> 1.       1. Is HMDS a polar molecule? Is there any dipole present?
>> electronegativity values of constituents are : H 2.2, C 2.55, Si 1.9, N
>> 3.04. Carbon (2.55) - flourine (4) bonds are polar because of their
>> electronegativity difference.
>>
>> 2.       2. How thick can HMDS on top of SiO2-Si be when it is dried in
air
>> from a liquid state? Can the thickness of HMDS be determined when it is
air
>> dried?
>> 3. If HMDS is air dried and some molecules are left in sample, is it
going
>> to be HMDS molecule or it will be something else? Will it release
ammonia?
>> Also will it be a continuous layer or there will be clustering?
>>
>> Thanks a lot :)
>>
>> regards
>>
>> Sk
>> _______________________________________________
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>
>
>
> --
> Gianmario Scotti
>
> Researcher
> Aalto University, Dept. of Materials Science and Engineering
> http://materials.aalto.fi/en/
>
> Micronova, Tietotie 3
> 02150 Espoo
> Finland
> _______________________________________________
> Hosted by the MEMS and Nanotechnology Exchange, the country's leading
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_______________________________________________
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_______________________________________________
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