FUNDAMENTALS OF EPITAXIAL SILICON FILM THICKNESS MEASUREMENTS USING EMISSION AND REFLECTION FOURIER-TRANSFORM INFRARED-SPECTROSCOPY

A theoretical analysis of the principles and results of film thickness measurements using a reflection and an emission Fourier transform inf rared spectrometer (FT-IR) is presented. Epitaxial film thickness meas urements by emission FT-IR (E/FT-IR) have been recently demonstrated a nd the study reported here was conducted to understand further the und erlying physical principles. The theoretical basis for spatial Fourier transformation using the Michelson interferometer is introduced. More over, a transfer function for a linear system model of the Michelson i nterferometer is derived. The transfer function and the model are subs equently used to calculate interferograms, which agree well with our e xperimentally measured interferograms. The difference in the interfero grams obtained by IR reflection and IR emission is explained theoretic ally. The limitation of the FT-IR techniques is discussed. Furthermore , a comparison of the reflection FT-IR and emission FT-IR for epitaxia l film thickness measurement will be given. Finally, an application of E/FT-IR for real-time in situ monitoring of epitaxial silicon film th ickness is demonstrated.