Hi.

I've had similar problems with KOH etching and found that I had
an upstream contamination problem in my process. I'm fairly certain
that the contaminants were metal ions, but they could have been
organic as well. I'd suggest using an RCA clean immediately before
your etch to see if you get better selectivity.

小翰 wrote:

>Dear all
>I would like to ask if anyone have experiences with  etching by KOH+IPA.
>I need to use KOH with IPA to get appropriate ratio of etching rate <100> to
other higher surface, but it results in some problems.
>
><1>  The etching rate seems not stable. I try the same parameter (the
concentration of KOH I use is below 30%, temp. is aournd 75~65 centigrade)
>but often get different results. Etching rate and ratio of different surface in
first 1 hr seems different from following several hours.
>It means that I need to check etching rate and change the KOH everytime I etch.
>Could someone has the same experience or help me explain it?
><2> When I use KOH below 30% with IPA, the hillock problem become very serious,
do anyone have some ways to solve this ?
>
>Regards,
>
>Kuang H.
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