Infrared spectroscopy is a versatile tool that is well adapted to in-situ diagnostics of many thin film properties and processes. In this paper, we will describe the application of infrared instrumentation for real-time in-situ measurements of film temperature, emissivity, thickness, free carriers, and optical constants using model based spectral analysis. We will illustrate the use of Fourier transform infrared (FT-IR) emission and reflection spectroscopy to monitor the fabrication of stacks of ferroelectric and conductive oxides on silicon substrates during pulsed laser deposition. The ability to measure the infrared optical constants of dielectrics such as silicon dioxide, including the detailed spectral dependence of the vibrational absorption bands at high temperatures, will be presented. The suitability of the technique for real-time sensing during rapid thermal processing will be illustrated using the example of carrier activation during a shallow-junction rapid thermal anneal.