SURFACE-BARRIER DETECTION IN PLASMA-ENHANCED CHEMICAL-VAPOR-DEPOSITION OXIDES

The performance standards of plasma-enhanced chemical vapor deposition (PECVD) oxides increase as device sizes shrink and densities increase for ULSI. Future PECVD dielectric quality may be compromised by the e ffects of contaminants and/or charged ionic species that are present i n the gaseous ambient which the wafers are exposed to. As a result of being left at the oxide/silicon interface, these gaseous ambient defec ts such as metallic ions can adversely effect reliability and performa nce. Moreover different types of PECVD oxides require different deposi tion chemistries and are grown to differing thicknesses making it diff icult to apply a single C-V test. In this article, the problem is addr essed by detecting, nondestructively, such residual interfacial charge postprocessing on product wafers rather than the traditional test waf ers. For the first time the effects of mobile ions and interface state s at the oxide/silicon interface and in the as-processed films for var ious PECVD oxides will be shown using no electrical test methods befor e and after anneal. Charge effects and approximate generation lifetime estimates are separated out from the total charge measurement using p assive high-injection surface photovoltage. Thus one can passively exa mine the induced surface barrier height and interface charge for any P ECVD oxide type at any thickness. This technique is demonstrated for s everal types of single-oxide samples. The charge effects (if any) in P ECVD oxides as-deposited with or without rapid thermal annealing treat ments are illustrated. (C) 1996 American Vacuum Society.