Rapid and accurate measurements of photoresist refractive index dispersion using the prism coupling method

A commercially available instrument (Metricon ^TM 2010) was used to perform refractive index measurements at wavelengths of 543 nm, 632.8 nm and 780 nm on AZ ^R photoresist and antireflection (AR) coating products. This instrument is computer-controlled and performs all analyses required to determine film indices and thicknesses. The samples were various i-line and g-line photoresists and AR coatings, spun onto silicon at thicknesses of approximately 1 - 2 microns. The reproducibility of the refractive index measurements at different spots on a given sample was found to be very high (usually less than 0.0002) and the time to measure one sample at all the wavelengths was about 15 minutes. The data were fit to a Cauchy function and low error fits were obtained. Most photoresists measured exhibited similar values for the Cauchy coefficients, while BARLi ^TM had much different coefficients, owing to its large absorption in the visible.