ULTRAVIOLET-VISIBLE ELLIPSOMETRY FOR PROCESS-CONTROL DURING THE ETCHING OF SUBMICROMETER FEATURES

Microelectronics processing of ultralarge-scale-integration devices, w hich use increasingly thinner films and deep submicrometer design rule s, requires sensitive diagnostic techniques to achieve tight process c ontrol. Film thickness and etched profiles are commonly characterized by postprocess and/or destructive techniques such as cross-sectional s canning electron microscopy. Because of its sensitivity and compatibil ity with plasma processing environments, in situ spectroscopic ellipso metry has become an extremely useful diagnostic for plasma etching app lications, but until recently it was thought to require a sacrificial, unpatterned area on the wafer to provide film thickness information. We show that the applications of ellipsometry in microelectronics are no longer restricted to the control of uniform films or to unpatterned areas dedicated to film thickness measurement but extend also to moni toring the etching of multilayer stacks during the fabrication of subm icrometer devices or gratings with high aspect ratios. Some new interp retation models are developed and presented.