Hi Guangqing and Charles,

I have seen a similar experience with residue, my solution was to spike
the H2O2 with 1-2% of NH4OH. At these low concentrations the PR should
survive.

Rick


Charles Ellis wrote:

>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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