Non-destructive measurement of foot/notch on etched polysilicon gates using spectroscopic ellipsometry

Precise control of the full 2-dimensional profile of polysilicon gate structures is critical to ensure optimal device performance. As the minimum dimension of the gate continues to shrink in accordance with Moore´s Law, small variations in the bottom 20% of the etch profile can have significant consequences on the electrical performance of the device. In order to control the polysilicon profile, one must first be able to measure it with a high degree of precision and accuracy. Most of the currently available metrology techniques face some sort of limitation for detection of footing/notching at the bottom of an etched polysilicon profile. In this paper we discuss the use of spectroscopic ellipsometry (SE) to provide non-destructive detection of profile variation (footing/notching) in the bottom 20% of the polysilicon profile