The goal of any absorption spectroscopy is to measure how well a sample absorbs light at each wavelength. The most straightforward way to do this, the "dispersive spectroscopy" technique e.g. reflectometry.
Fourier transform spectroscopy is a less intuitive way to obtain the same information. This technique shines a beam containing multi-wavelength infrared light, and measures how much of that beam is absorbed by the sample. This method is very well suited to measure thick epitaxial materials which have a high absorbance in the visible wavelength range such as Si. By adding a transmission detector underneath the wafer surface, the transmitted spectrum of infrared light travelling through the material can be analyzed for presence of contaminating materials such as carbon, oxygen or hydrogen in Si substrates.
There are many applications which benefit from the FTIR technique:
Thickness of epitaxial materials
SiC epi layer & substrate thickness
B and P concentration in PSG, BSG and BPSG
CO – Substitutional carbon and interstitial oxygen in silicon substrates
SolarSiCO – Substitutional carbon and interstitial oxygen in thin silicon substrates
FSG – Fluorine content of FSG
SiN – Measures hydrogen in silicon nitride films
HSQ – Hydroxyl and hydrogen content in oxides SOG, FOX
SiON – Oxygen, nitrogen and hydrogen in SiON.
SiCN – Carbon in SiCN
SiOC – Carbon in SiOC
Oxygendose – Measurement of oxygen implant dose at SIMOX process
Oxygen Precipitate – Measurement of oxygen precipitates in Si substrates