Electron Enhanced Atomic Layer Deposition (EE-ALD)

Electron enhanced atomic layer deposition (EE-ALD) can dramatically reduce the temperatures required for film growth. Temperature reduction is possible because of electron stimulated desorption (ESD) of surface species. The desorption process creates highly reactive "dangling bond" surface sites. Precursors can then adsorb efficiently on the dangling bonds. Our work has demonstrated the EE-ALD of GaN, BN, Si and Co at room temperature. Film growth was performed using alternating exposures of chemical precursors and low energy electrons. In situ ellipsometry measurements have monitored linear film growth versus number of reaction cycles. Additionally, we have observed the dependence ofthe EE-ALD growth rates on electron energy. Maximum growth rates have varied from 0.3 A/cycle for Si films at 100-150 eV to 3.2 A/cycle for BN films at 80-160 eV. Recent measurements have also obtained maximum growth rates of 0.5 A/cycle for Co films at 125 eV. EE-ALD is also topographically selective. This area selectivity is derived from the directionality of the electron flux. Surfaces normal to the incident electrons receive full electron flux, whereas surfaces parallel to the incident electrons receive no electron flux. EE-ALD should be useful for the bottom-up fill of high aspect ratio structures.