QUANTITATIVE-DETERMINATION OF DIELECTRIC THIN-FILM PROPERTIES ON PRODUCT WAFERS USING INFRARED REFLECTION-ABSORPTION SPECTROSCOPY

Process monitoring of-borophosphosilicate glass (BPSG) dielectric thin films used in the manufacture of microelectronic devices is currently performed using multivariate calibration models developed from transm ission infrared (IR) spectra of the films deposited on undoped monitor Si wafers. It would more be desirable to monitor the BPSG deposition on the actual product or device wafers. Because product wafers are opa que in the IR, reflection rather than transmission spectroscopy must b e used to monitor the BPSG films deposited on product wafers. In this article, we demonstrate, for the first time, that TR reflection spectr a of product wafers can be used to monitor the boron and phosphorus co ntents of the film and the film thickness to a precision that is compa rable to that found for IR analysis of BPSG deposited on monitor wafer s. The cross-validated standard errors of prediction of 0.11 wt %, 0.1 1 wt %, and 3 nm for B, P, and thickness, respectively, were achieved using multivariate-partial least squares (PLS) models applied to the I R reflectance spectra obtained from reference product wafers. The pred iction abilities were found to be independent of the position of the i nfrared spectrum on a given device and independent of which devices of the same structure were examined. The multivariate calibration models could be used to predict the B and P contents and film thickness of B PSG on device structures of different types and even for devices of di fferent feature sizes if the PLS models were adjusted for slope and in tercept differences. Therefore, the time and expense of generating cal ibrations for new device structures can be greatly reduced by the use of a small number of reference samples of the new devices to estimate the required slope and intercept adjustments for the models. (C) 1998 American Vacuum Society. [S0734-2101(98)03106-6].