Infrared spectroscopic techniques for quantitative characterization of dielectric thin films on silicon wafers

Dielectric thin films are critical components of microelectronic devices, and for proper device function their properties must be carefully controlled. Rapid and efficient quality control techniques are needed for characterizing these films. Infrared (IR) spectroscopy in the mid-IR region (400–4000 cm⁻¹) has been widely used for qualitative characterization of solid, dielectric thin films in the microelectronics industry. The IR spectra of these films on silicon exhibit overlapping spectral bands, solid—solid molecular interactions, and nonlinear behavior of spectral bands arising from a variety of sources. Conventional univariate analysis of such spectra did not yield reliable quantitative predictions of the dielectric thin-film properties. The relatively recent appearance of quantitative IR studies of dielectric thin films has followed progress in chemistry toward multivariate analysis of IR spectral data. This article reviews some of the processing and non-IR characterization methods for dielectric thin films currently used in the production of integrated circuits, and it reviews univariate quantitative and semi-quantitative analyses that have used IR spectroscopy. It stresses recent developments in IR techniques and multivariate calibration that together permit rapid, precise, nondestructive, and quantitative determinations of various critical dielectric thin-film properties. Results from the application of quantitative IR techniques to the analysis of dielectric thin films are drawn from a review of the authors' work in the field.