I n s i t u ellipsometry as a diagnostic of thin-film growth: Studies of amorphous carbon

Abstract

Amorphous carbon (a-C:H) thin-film growth, surface modification, and etching have been studied using in situ ellipsometry. Accurate values of the film thickness, deposition or etch rate, and bulk optical functions, the latter providing information on bonding configurations, can all be deduced from real time measurements during film growth or etching. Substrate modification and film–substrate reactions that occur in the initial stages of film growth upon igniting the deposition plasma or ion beam can be detected and characterized at the monolayer level. Such information is not easily accessible to ex situ measurements. In addition, ellipsometry provides monolayer-level detection of changes in the near-surface bonding. Transitions between polymer- or diamondlike and graphitic bonding caused by inert and reactive gas plasma exposure can be observed. Finally, the applicability of in situ ellipsometry is demonstrated for mapping preparation parameter space according to specific deposition regimes or film properties.