Process Monitoring And Surface Characterization By XPS In A Semiconductor Fabrication Line

This paper discusses the implementation of an X-ray Photoelectron Spectrometer as a tool for process monitoring and characterizing thin film chemical composition and thickness in a manufacturing environment. Process monitoring of ultra thin nitrided gate oxides is performed on monitor wafers using XPS measurements of nitrogen dose and SiON thickness. In addition to gate oxide monitoring, XPS is used as a process characterization technique in the fabrication line. The implementation of new materials and the decrease of film thickness in advanced CMOS technologies require more sophisticated metrology. XPS is a technique that allows non-destructive chemical composition and bonding state analyses along with thickness measurements. This paper presents different applications in which XPS is utilized for 65nm and 45nm nodes. Thickness measurements of amorphous silicon on top of an amorphous carbon stack are presented. Two examples of surface characterization are studied. They included the impact of a dry cleaning plasma step on a silicon surface for the Source/Drain implantation process, and fluorine contamination of a TiN hard mask for back end applications.