Shimul--
You need an adhesion layer under the tungsten. Pure Ti or Ti/W alloy will
work.
You might also want to lower the stress in the tungsten. See my
dissertation, section 6.2.2, on how to control the stress in sputtered films
by varying the pressure and power (I used DC sputtered tungsten in a
different machine). Link at
http://web.archive.org/web/20011125113849/www-
bsac.eecs.berkeley.edu/archive/kirt_williams_phd.zip
..
    --Kirt Williams

----- Original Message -----
From: "shimul saha" 
To: "General MEMS discussion" 
Sent: Wednesday, May 23, 2007 8:44 AM
Subject: Re: [mems-talk] Tungsten adhesion probelm


> Hello,
>
> We are DC sputtering Tungsten on SiO2. But the tungsten fells of after dry
> etching tungsten , or during nitride deposition afterwards (high temp
> process).
>
> We are using DC sputterng at 7500 watts. The stress in the film is around
> 2 GPa compressive. The thickness of the film is 0.5 um.
>
> Can anyone please give us some hint how we can improve the adhesion (to
> oxide) or have a low stress tungsten so that the metal can survive
> afterward high temp process.