Dear Mike,

I am very interested in your experiment, and have a question about it.

I wonder if the metal came off is Pt.



I have used Ti/Pt/Au layer to cover a island. After 9 hours of TMAH etching,
the layer was peeled off.

Based on the following article, I concluded that the Pt was exposed by poor
step coverage, and the delaminating caused by the exposed Pt etching.
According to article, Pt is etched by TMAH. However, I haven't double check
it.


Yan,G., Hsing,I., Sharma,R., Sin,J. An improved TMAH Si-etching solution
without attacking exposed aluminium, Sensors-and-Actuators-A-(Physical), Vol
89:1-2, p. 135-141, March, 2001



The TMAH solution in this paper is doped with Si and ammonium persulfate.





__________________________________________________________
Il-seok  Son (Sunny)
Dept. of Electrical and Computer Engineering
University of Wisconsin - Madison
Sonic MEMS Lab
__________________________________________________________


----- Original Message -----
From: "Michael D Martin" 
To: 
Sent: Wednesday, April 10, 2002 11:03 AM
Subject: Re: [mems-talk] Etching through a silicon wafer


> I have had problems with deadhesion of Ti/Pt in TMAH. That is the Pt
> came off! I would not be surprised if Au behaves similarly, unless I had
> a sputtering problem.
>
> -Mike
>
> >>> [email protected] 04/09/02 03:09PM >>>
> Dear all,
>
> I plan to use anisotropic wet etching to etch through holes in a
> <100>silicon
> wafer, using LPCVD silicon nitride as mask layer,
> also there is a exposed Ti/Au layer(Ti act as a adhesion layer)
> on top of silicon nitride.
> My concern is:
>
> 1. Will Ti/Au layer resist the long time KOH etching?
> 2. If KOH doesn't work, will other etchants like TMAH do?
> 3. Will KOH etching damage the silicon nitride membrane?
>
> Thank you very much!
>
> Yuanfang Gao
>
> University of Missouri
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