Dear Andreas,

I wonder if you have any integrated circuit on your wafer.

I am asking this because most of my cases a silicon/poly silicon layer under
Al or Al/Cu/Si is attacked.
According to the following paper, they succeeded in Si etching with CMOS
though they did not etch through the wafer. Even I am not sure they use Ti/W
for the contact of CMOS for this case.

 E.H.Klassen, R.J.Reay, G.T.A.Kovacs, 'Diode-based thermal r.m.s. converter
with on-chip circuitry fabrication using CMOS technology', Sensors and
Actuators A,52(1996)33-40

I want to know whether long duration of TMAH etching with CMOS (Al is only
metal)  is usually challenging or not.
Or am I the only person who has a trouble with this?

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


----- Original Message -----
From: "Andreas Jahn" 
To: "General MEMS discussion" 
Sent: Friday, March 07, 2003 9:24 AM
Subject: RE: [mems-talk] Etch through Si wafer with TMAH


> Ilseok,
>
> I etch holes all the way through a 4" Si-Wafer with TMAH. But unless the
> etchtime takes quite long, I use 240um thick wafer. but I also did it with
> 550um thick ones. The etchrate is about 1um per minute. What kind of
> information do you need?
> -Andreas
>
> -----Original Message-----
> From: il-seok Son [mailto:[email protected]]
> Sent: Thursday, March 06, 2003 4:32 PM
> To: [email protected]
> Subject: [mems-talk] Etch through Si wafer with TMAH
>
>
> Dear users.
>
> I have a question about TMAH etching.
> Dual-doped TMAH ( 5% TMAH + Silicic acid + Ammonium persulfate) is widely
> used because it is enable to etch Si without attacking Aluminum, in
addition
> to its CMOS compatibility. Many papers have been published regarding
> TMAH/dual-doped TMAH.
> However, I found that the Si was etched for a short duration (maybe less
> then 2 hours) in most papers.
>
> In order to etch through a 3" wafer with dual-doped TMAH, it needs at
least
> 8 hours.
> I wonder if there is anyone who etches a wafer through ( 3" or 4") with
> TMAH/ dual-doped TMAH, with CMOS or any integrated circuit.
>
> Any information would be very helpful.
>
> Thank you very much.
>
> __________________________________________________________
> Il-seok  Son (Sunny)
> Dept. of Electrical and Computer Engineering
> University of Wisconsin - Madison, Sonic MEMS Lab
> __________________________________________________________
>
>
>
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