Polysilicon over gate oxide thickness measurements are one of the most important thickness measurements in today's semiconductor manufacturing industry. Polysilicon thickness variations affect the film's ability to perform efficiently in controlling implant distribution. Further, polysilicon thickness variations can cause variations in electrical characteristics like IDSAT. Theory predicts that the inherent physical properties of the polysilicon will limit the effectiveness of optical thin film thickness measurement instruments, especially when measuring over very thin oxides. An experiment was performed to determine the effect of underlying oxide thickness on optical polysilicon over oxide thickness measurements.
Anne M. Kaiser,
"Optical polysilicon over oxide thickness measurement", Proc. SPIE 1464, Integrated Circuit Metrology, Inspection, and Process Control V, (1 July 1991); doi: 10.1117/12.44466; https://doi.org/10.1117/12.44466