Isaac,

Thanks for reply.
I did clean chamber and I also tried to etch dummy a-Si on Quartz wafer for
prelimiarly study. That is, there was no polymer mask when I varied plasma
power(20,40,60,80 and 100W). Result were only 100W gave me noticible
thickness change (visually and UV absorption, yelloish to light yelloish).
However, 60W etched a-Si a lot sometimes. I am confusing why sometimes 60W
etched a-Si film and sometimes didn't.

I will try one more time but it seems like that PECVD grown a-Si plasma
etching rate with low power CF4 is vary a lot every batch.

Do you have any idea??


Thanks,

Young

>From: Isaac Chan 
>Reply-To: General MEMS discussion 
>To: General MEMS discussion 
>Subject: Re: [mems-talk] amorphous Si ethcing
>Date: Fri, 13 Oct 2006 11:00:37 -0400 (EDT)
>
>Young,
>
>CF4 do create some polymerization and the polymer will accumulate on
>chamber wall over time after several runs. Do you clean your chamber with
>O2 plasma? a-Si:H at that thickness is yellowish brown color. Sometimes it
>can be confused with the polymer layer deposited on the etched area. When
>you say it doesn't etch, do you mean it looks the same by eye, by SEM, or
>has the same thickness measured by a profiler?