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????

Thanks,

Young