Dear Karin,
     If thermal contact is d main issue in etch rate variation, then you
can try Spin coat 'Photoresist' on your 3"Carrier wafer and nicely place
all your waferpieces. After that do a normal hardbake recommended for
the photoresist which you are using. You might know well how to remove
the resist, 'acetone' will do it nicely. I got good consistency in etch
rate and profile by doing this way, moreover I found this way is more
comfortable in fixing and removing the samples from the carrier wafers.

Good Luck

Mohanraj


Karin Buchholz wrote:

> Dear mems talkers,
>
> we have a RIE chamber with temperature control of the 3" carrier
> wafer. Since we are just using  waferpieces we just place these on top

> of the carrier wafer. It seems now that these small pieces
>  do not have proper thermal contact to the chuck, so the temperature
of
> the sample is not constant
>  from etch to etch and the etch rate also varies by 50per cent...
>
> Do you have any suggestions how to provide good thermal contact? The
> manufacturer suggested Fomblin vaccuum oil, but it is impossible to
> remove it from the samples after etching...
>
> I appreciate any help! Have a nice day,
>
> Karin
>
> --
> Dipl.-Ing. Karin Buchholz
> Walter Schottky Institut
> Technische Universitaet Muenchen
>
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