Damage-free Pattern Transfer by Low Energy Electron Enhanced Etching (LE4): Mechanisms and Applications

Abstract

The conventional ion-enhanced dry etch methods inflict 2 nm or more of "etch process damage" through surface ion bombardment, and this inherent surface damage creates a potentially limiting condition for IC manufacturing at feature sizes below 45 nm. As an alternative we describe the LE4 dry etch method, in which electrons with energies below about 200 eV stimulate anisotropic etching for high-resolution feature definition. Features as small as 20 nm have been etched with no damage. Line edge roughness (LER) in poly-silicon etching with LE4 is substantially less than with ion-enhanced etching. LE4 avoids trenching, bowing, and notching effects in etched profiles. In addition to control of critical dimensions, LE4 gives atomically smooth etched surfaces and maintains stoichiometry of compound materials. The absence of ion bombardment damage and the ability to tune the process to specific material energy thresholds, enable very high selectivity in LE4.