In situ roughness monitoring of sputtered Pt thin film under dynamic turbulence using adaptive optics

A new optical monitoring system for rapid and in situ surface roughness measurement of Pt film on silicon is developed in this study. The in-process measurement is achieved by combining an optical probe of laser-scattering phenomena and adaptive optics for aberration correction. Platinum (Pt) thin film is selected due to the extensive utilization in semiconductor industry and excellent chemical inertness. The aim of this study was to demonstrate the necessity for adaptive optics (AO) compensation in regions containing room-temperature turbulences. Measurement results of eight Pt films (roughness ranging from 58 to 83 nm) sputtered on top of P-type silicon wafer demonstrate excellent correlation between the peak power and average roughness with a correlation coefficient (R2) of 0.9962 and a trend equation for predicting the surface roughness of Pt thin films is obtained as y = 9E07x−3.783. Roughness average (Ra) of Pt thin films (x) of can be directly determined from the peak power (y) using the proposed method under dynamic disturbance. Furthermore, the proposed AO-assisted system is in good agreement with stylus method and less than 1.1% error values are obtained for the aforementioned average sample roughness.