I made that mistake before, depositing LPCVD polysilicon at 610 C on
titanium. In later inspection in a SEM, I could see that I produced what was
likely titanium silicide on titanium.

You may  be producing platinum silicide (I don't know the reaction
temperature or time) or titanium silicide.

    --Kirt Williams

----- Original Message -----
From: "Umer Izhar" 
To: "General MEMS discussion" 
Sent: Tuesday, January 27, 2009 12:34 AM
Subject: [mems-talk] LPCVD Polysilicon over metal

>
> Hi,
>
> I am depositing LPCVD polysilicon film (in NON-MOS furnace) on my SOI
> sample which has a layer of titanium and platinum exposed. After
> deposition I can see the metal surface becomes rough and formation of
> 'black spots' on it. I tried changing the dep. temperature but still get
> the same result. Moreover when I etch the deposited poly layer (RIE) the
> dots and roughness seems to stay there.
>
> I would appreciate any help in this regard.
>
> Umer