HI All,
We have an ICPRIE system from SEMCO. Using this system how can I get anisotropic etching of c-Si/ a-Si with HSQ as a mask? For RIE the gases available are Cl2, CF4, O2, and SF6. Thanks in advance.
The easiest way is to use relatively high pressure chlorine; the high pressure gives great mask selectivity and the chlorine is inherently directional with silicon. You just need to make sure that the Si surface is clean otherwise you will get nasty 'black Si'.
Chris Horwitz, Thanks for the answer. Using Cl we saw some loading effect i.e., etch rate significantly varies when chip size varies. However, we used 5 sccm Cl at 0.2 Pa. Did you aware of loading effect at higher pressure?
Typically one would pre-load the chamber so that your added variability will not change the situation much. So if you etch a mainly masked pattern, you would use a dummy larger platform that is mainly masked; or if you have a mostly Si surface, then use a Si wafer as a baseplate. This all assumes small substrates on a larger platen; if you are etching full wafer sizes then you must either accept the global loading effect or use something like the Electrogrip hollow cathode system which permits an opposing preloaded target to be used.
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