Guangqing,

As I mentioned before, this was over 20 years ago.  I do not remember the
concentration or makeup of the EDTA etch. Maybe someone else has an idea.  I
think the best answer is to etch the Ti:W with H2O2 in a Stainless-Steel
container.

Good Luck,
Charles.....

----- Original Message -----
From: "Guangqing Meng" 
To: 
Sent: Monday, May 20, 2002 4:48 PM
Subject: Re: [mems-talk] Wet etching TiW


> Dear Charles,
>
> Do you know if EDTA will attack photoresist or not? When you dip the
wafers
> into EDTA etchant, is the etchant  commercially available or is it needed
to
> mix?
>
> Your reply will be highly appreciated.
>
> Guangqing
>
>   -----Original Message-----
>   From: Charles Ellis 
>   To: mems-talk@memsnet.org 
>   Date: Thursday, April 25, 2002 7:58 AM
>   Subject: Re: [mems-talk] Wet etching TiW
>
>
>   Hello Anke,
>
>   I seem to remember having this problem 22 years ago. After etching the
> Ti:W
>   (in 30% H2O2 - stock solution), there would be a very slight residue.
> Many
>   times we could only see it after passivation, but if you looked close
> enough
>   you could detect it.  If my memory serves me correctly, we dipped the
> wafers
>   in an EDTA etchant (after the H2O2), the other thing that worked was to
> etch
>   the Ti:W in 30% H2O2 in a Stainless-Steel tank.  I know it sounds
strange,
>   but we fond that just using the SS tank made a great difference. I
> remember
>   we tried adding various Fe products in the Ti:W without much success.  I
>   hope this helps.
>
>   Charles Ellis
>   Auburn University...
>
>   ----- Original Message -----
>   From: "Anke Stock" 
>   To: 
>   Sent: Thursday, April 25, 2002 2:17 AM
>   Subject: [mems-talk] Wet etching TiW
>
>
>   > Hello to everybody,
>   > is there someone who has experience in wet etching of TiW? I use a
>   > mixture of HCl and H2O2, but it seems that there are small amounts of
>   > TiW on the wafer after etching. Has someone experiences with
parameters
>   > like temperature, time, other mixtures or something else? Many thanks
>   > for your help
>   > Anke
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