LOCAL ELECTRIC-FIELD EFFECT IN REACTIVE ION ETCHING

We present unambiguous evidence that under reactive ion etching conditions, i.e., P less-than-or-equal-to 75 mTorr, the perturbation of the local electric field by the geometric shape of the trench has very little influence on ion trajectories and hence on the etching rate. This local electric field effect is negligible even for trenches with depths as large as 50 mum, and even for incident ions with energies as small as 20 eV. These results are in sharp disagreement with the previous models in the literature.