Model-free methodology for thin film thickness analysis by spectroscopic reflectometry

Spectroscopic reflectometry-based thin film measurement plays an important role in modern semiconductor, hard disk drive, and display industry because of its non-destructive nature and high throughput. In spectroscopic reflectometry, conventional model-based iterative algorithms often face challenges such as high computational costs, risk of converging to local minima, and limitations imposed by predefined library boundaries. We propose a technique to determine the thin film thickness in a direct fashion from the reflectance spectrum. The technique achieves a 92.6% improvement in computational throughput by avoiding iterative processes. The repeatability of the new technique is statistically validated by conducting a 280-sampling gage repeatability and reproducibility test (GR&R), demonstrating a 76.9% improvement in repeatability (equipment variation), a 61.6% improvement in reproducibility (appraiser variation), and a 60.9% improvement in GR&R%.