Evaluation of lifetime and Hi-Q modules in surface charge analysis

摘要

Surface Charge Analysis (SCA) has been successfully used to monitor oxidation furnaces in semiconductor production fabs. Recently, surface lifetime and higher levels of induced charge (Hi-Q) options have become available to SCA instrumentation, opening an avenue for detecting heavy metals and a wider range of dielectric charges. In this paper, data on the evaluation of these new options is reviewed. It is found that lifetime measurements are affected by both oxygen content in the substrate as well as metal contaminants on the wafer surface. 30 ppms oxygen content in the wafer degrades lifetime more than 10$+11$/ - 10$+12$//cm$+2$/ metal contaminants on the wafer surface. The Hi-Q module in turn permits the evaluation of even unannealed LPCVD and PECVD dielectric films, previously out of instrumental range due to their high level of charge. Within the 2.6E12/cm$+2$/ charge limit, SCA shows that oxide charge (Qox) is inversely proportional to deposition temperature of both TEOS and nitride, and is proportional to NH$-3$//DCS ratio for nitride. SCA also shows that certain anneal ambients for PETEOS can cause field Vt changes by annihilating or generating charges in the dielectric films. In short, both the lifetime and Hi-Q enhancements of SCA are shown to offer added capabilities for evaluating metallic contamination if oxygen-free substrates are used, and for deposited dielectrics within the fab as long as the charge is below 2.6E12/cm$+2$/.