There are many different films in IC processes whose thicknesses must be tightly controlled following each deposition or growth step. In the FEOL and MOL, there are isolation films, such as silicon oxide (SiO2) and silicon nitride (SiN); poly silicon; gate thin films, such as titanium nitride (TiN) and tantalum nitride (TaN); gate oxide; high-k oxide (usually involving hafnium oxide); etc. Low-k dielectric films and barrier films are deposited in the BEOL of the Cu damascene process. Furthermore, advanced transistors use compressive and tensile epitaxial films, such as SiGe (Narasimha1) and SiP, within source/drain regions to enhance the performance of advanced node devices (45-nm node and beyond technologies). All of these films require precise and accurate measurement of thicknesses and concentration to ensure tight process control of these processes. Spectroscopic ellipsometry (SE) and reflectometry are two major categories of optical systems used in the semiconductor industry to measure and monitor these films.
Online access to SPIE eBooks is limited to subscribing institutions.