On Tue, 29 Oct 2002, Priyanka Aggarwal wrote:

> Well according to me, it is difficult to deposit silcion nitride directly on
> silicon , so it might be the reason for the same.
>
> ----- Original Message -----
> From: "Qintao Zhang" 
> To: 
> Sent: Monday, October 28, 2002 6:14 PM
> Subject: [mems-talk] silicon/sio2/si3n4
>
hi.....


In your struture u r using sio2 and then silicon nitride.
Actually when u deposit sio2 there will be Tensile stress in the
film.....but when u deposit silicon nitride there will be compressive
stress in the film so when u deposit silicon nitride over silicon oxide
these stresses which we dont require at all will be cancelled by some
extent. To avoid the stress developed in sio2 film it is done.





>
> >
> > Hi, all
> >
> > I am a new member on MEMS. I am trying to understand a capacitor structure
> composed of silicon/silicon dioxide/ silicon nitride sandwich. I am
> wondering why need a silicon dioxide layer in the middle? silicon nitride is
> also a good insulator, why we need two insulators for a capacitance? Are
> there big difference between silicon dioxide and silicon nitride, especially
> on electrical property?
> >
> > Thanks a lot
> >
> > Qintao Zhang
> >
> >
> >
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