Characterizing optical properties of red, green, and blue color filters for automated film-thickness measurement

In order to utilize the non-destructiveness and quickness of spectroscopic reflectometry based technique for red, green, and blue (RGB) color filter thickness measurement, the refractive indices (n's) and the extinction coefficients (k's) of the RGB color filter coatings need to be precisely determined. This work demonstrates the use of variable angle spectroscopic ellipsometry (VASE) for measuring n and k values of RGB color filter coatings. The thickness of each color filter thin film is determined in its respective transparent band. The optical constants are calculated directly from Fresnel equations at each wavelength. Fitting data acquired at multiple angles of incidence helps to reduce measurement noise, and multi-sample analysis reduces correlation between thickness and optical constants in the regression calculation. Using the determined n and k values, high repeatability and high throughput are demonstrated for the thickness measurement of the RGB color filter films on an automated thin film measurement tool.