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