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?

Regards,

Isaac Chan, Ph.D.


On Thu, 12 Oct 2006, Young Rae Hong wrote:

> I am tring to etch PECVD grown amorphous Si using CF4 with polymer mask.
> I have to etch around 40nm. (SF6 is too fast for my purpose)
> However, it seems like etching behavior is not consistent.
> In low power(20W_80mW/cm2_15mTorr_10sccm), it seems like that it did not
> etch at all.
> In medium power(60W_240mW/cm2)_15mToor_10sccm), it seems like that it etched
> sometimes and didn't the other times.
>
> What is going on? does anybody have any idea????