PATTERN-DEPENDENT CHARGING AND THE ROLE OF ELECTRON-TUNNELING

We review the prevailing causes of and remedies for profile distortion (notching) resulting from pattern-dependent charging during etching i n high density plasmas. A new mechanism for notch reduction. based on electron tunneling through thin gate oxides, is explained through deta iled modeling and simulations of charging and profile evolution in pol ysilicon gate definition. Tunneling currents from the substrate decrea se surface charging potentials-responsible for ion deflection-at the b ottom oi high aspect ratio trenches. The exponential dependence of ele ctron tunneling on the oxide electric held predicts an abrupt transiti on from severe notching to virtually no notching as the gate oxide thi ckness is decreased, which has been seen in experiments.