Hi,

We have had success in using ECR-PECVD deposited SixNy with low stress
that withstands KOH etching.

Please contact us if you want more info.

Dr. Roberto R. Panepucci
UNICAMP                                 |  UNICAMP-IFGW - DFA/LPD
Instituto de Fisica Gleb Wataghin       |  Caixa Postal 6165 - Campinas - SP
Departamento de Fisica Aplicada         |  CEP 13083-970
Laboratorio de Pesquisa em Dispositivos |  Fone (019) 788 2341
roberto@ifi.unicamp.br                  |  Fax (019) 788 2376

> Dear MEMS researchers,
>
> I'm now working on wet etching of silicon using KOH solution, I meet one
> problem in my study, I wonder if anyone could help me.
>
> I use KOH to etch 200um thick of (100) silicon, I propose to use 2000A
> thick of Si3N4 as a mask, but before this etching step, a metal electrode
> has been deposied on the wafer. The material of the electrode to be chosen
> is TiW/Au, Al or Pt. By using TiW/Au I could use LPCVD to get good quality
> Si3N4 which would satisfy my need of protecting the desired part on my
> wafer through wet etching. But unfortunately, the process center don't
> allow me to put a wafer whith Au into their LPCVD machine used mainly for
> IC processing which would bring heavy pollition to the machine. Then other
> alternatives of electrode material would be Al or Pt which can't withstand
> the high temperature of LPCVD and other Si3N4 deposition process except for
> PECVD. As you know, however, I can't get good quality Si3N4 mask that is
> enough to protect sturcture on wafer by using KOH to etch 200um thick of
> silicon in at least 3hrs.
>
> Could anyone who have experiences in this field can give me any advice on
> how to make my Si3N4 mask and how thick is the Si3N4 layer and the SiO2
> layer under it, and how thick would be prefered if I have to use only SiO2
> as a mask though my wet etching as a tradeoff.
>
> Any help from you would be greatly appreciated!
>
> Please return to Liujing@cenpok.net.
>
> Sincerely yours,
>
> Jing Liu
>
>
>
>