Dear colleagues

Is HMDS really hydrophobic? I've measured the contact angle of a Si-wafer
treated with HMDS as a adhesion promoter and it turned out to be around 80 deg
and that is also about the values you found in litterature (75-80 deg).
The hydrophobicity of HMDS is a topic witch has been discussed in this forum
before if I remember right. I know that the surface chemistry people use HMDSO
(hexamethyldisiloxane) to make stable real hydrophobic surfaces (contact angle >
90 deg) witch is another monomer then HMDS.

best regards
Niclas Roxhed

>Dear Jessica,

>you did not mention if the hydrophobic layer you are looking for needs to
>have a certain thickness and what your substrate material is. In case the
>substrate is a silicon wafer and the layer could be a monolayer, the easiest
>way is to use the adhesion promoter HMDS (hexamethyldisilazane) as the
>hydrophobic chemical and pattern it with a standard alkaline developer (KOH,
>NaOH).

>You may try the following recipe:
>1) prime your wafer with HMDS (e.g. heat up the wafer to 120 degC and let it
>cool down in a HMDS saturated atmosphere)
>3) coat the wafer with any type of a novolak based photoresist (AZ 1512,
>S1813, ....)
>4) pattern it with an appropriate lithography tool
>5) develop it with an alkaline developer
>6) remove the photoresist with acetone, NMP, etc.
>7) you now have a patterned hydrphobic HMDS monolayer on your wafer

>Best Regards,

>Frank.

>--------------------------------------------
>SUSS MicroTec
>Applications Center Europe
>Frank Runkel
>Schleissheimer Str. 90
>85748 Garching
>Germany
>Fon    +49 89 32007 - 302
>Fax    +49 89 32007 - 390
>email  [email protected]



>> ------------------------------
>>
>> Date: Wed, 22 Jan 2003 12:31:45 +0100
>> From: Jessica Melin 
>> To: [email protected]
>> Subject: [mems-talk] Patterning A Hydrophobic Layer
>> Message-ID: 
>> Content-Type: text/plain; charset="iso-8859-1" ; format="flowed"
>> MIME-Version: 1.0
>> Content-Transfer-Encoding: quoted-printable
>> Precedence: list
>> Reply-To: General MEMS discussion 
>> Message: 3
>>
>> Dear Colleagues,
>>
>> Am searching for practical information / experience on patterning
>> hydrophobic layers. For example, depositing a hydrophobic layer (i.e.
>> C4F8) on a silicon substrate, spinning on positive or negative
>> photoresist (achieving good coverage with or without the use of an
>> adhesive intermediate layer), achieving good lithographic results,
>> and etching the hydrophobic layer resulting in a patterned
>> hydrophobic layer while the silicon retains its surface properties.
>> Alternatively, using a successful lift-off process. Any experiences,
>> information, recipes, etc would be greatly appreciated.
>>
>> Best regards,
>>
>> Jessica Melin