Model-Based XPS Technique for Characterization of Surface Composition on Nano-Scale SiCOH Sidewalls

The objective of this study is to develop an in-line metrology technique that employs X-ray Photoelectron Spectroscopy to measure photoelectron intensity from patterned trench surfaces of low-k dielectric film. A mathematical model uses linear regression method to separate the intensities into individual elemental compositions of the constituent surfaces. The initial segment of the model uses measured data from CD-SEM and spectroscopic Ellipsometry to determine the respective surface areas visible to the XPS electron analyzer. The second segment derives the surface composition of the line top, trench bottom, and vertical sidewalls based on a linear relationship between photoelectron intensity, emitting area, and characteristic elemental composition of each surface. The study has verified the predicted compositions from the model through physical measurements, demonstrating excellent agreement and concurrence with the physical mechanisms expected from the applied etch and ash chemistry in a commercial CCP RIE etch chamber.