Are you using a system that resembles a PECVD reactor?
If you use insulating o condutive samples, they behave very differently;
and their sizes, which cover more or less of the holder, can easy change the
bias.

Paolo Tassini


-----Messaggio Originale-----
Da: "xiaodong wang" 
Oggetto: [mems-talk] Questions about DC-bias in dry etching

> I have questions about DC-bias in dry etching.
>
> Conditions:
> I use the same recipe, size of carrier wafer and Therma plasma (dry
etching machine),
> only slight difference may be the size of the samples (on the carrier
wafer).
>
> Results:
> for example, the DC bias for the first sample is 90 V,  the bias for the
second sample is 10 V
> sometime it is 0. Etching results are very different.
>
> My questions:
> what are the parameters affecting the DC bias?
> why are there so much difference of the bias in my etching condictions.