QUANTITATIVE-ANALYSIS OF INFRARED REFLECTION SPECTRA FROM PHOSPHOSILICATE GLASS-FILMS

Infrared (IR) external reflection spectra of phosphosilicate glass (PS G) dielectric thin films deposited on undoped silicon wafer substrates were measured at an incident angle of 15-degrees. The IR reflection s pectra of PSG thin films exhibited nonlinear or distorted spectral fea tures arising from competing optical effects, including specular refle ction and reflection-absorption. Quantitative analysis of the PSG IR r eflection spectra was achieved by partial least squares (PLS) multivar iate calibration techniques. The spectral regions used for the PLS ana lysis were selected to minimize the detrimental effects of competing o ptical effects in the IR reflection spectra. Phosphorus content and fi lm thickness were determined with a cross-validated standard error of prediction (SEP) of 0.10 weight percent (w/o) and 60 angstrom, respect ively These standard errors corresponded well to the precisions of the analytical reference methods, which were reported as 0.1 w/o for phos phorus and 30 angstrom for film thickness. The quantitative results ac hieved for these PSG thin films indicate the promise of IR external re flection spectroscopy as a method for at-line process monitoring and q uality control of dielectric thin films in the microelectronics indust ry.