Spectroscopic ellipsometry in optical coatings manufacturing

This paper reviews the present status of spectroscopic ellipsometry (SE) as a metrology tool in production of optical coatings. Spectroscopic ellipsometry is often used to determine optical constants and layer thickness for single or multilayered stacks. Both ex situ and in situ SE results will be discussed. Ex situ SE has been used for optical coatings for many years, and is still an important characterization tool. A greatly expanded spectral range is now available, including vacuum-ultraviolet to the far infrared. In situ SE generally covers a narrower spectral range; however data acquisition can include hundreds of wavelengths simultaneously in less than a second. This allows closed-loop feedback process control and large area mapping of material properties on a short time scale.