ABSTRACT
Total Reflection X-ray Fluorescence (TXRF) spectrometry has proven to be a powerful tool for the elemental analysis of contamination on silicon wafer surfaces down to concentration levels of 1010 atoms/square centimeters. This chapter describes a simple procedure which distinguishes between contaminants, whose distances from the surface are less than approximately 10 ran (film type) and those which rise more than 100 ran above the surface (particle type), if only two classes are present. The general case with a continuous size distribution is also discussed. The chapter demonstrates certain capabilities of TXRF to provide information, in addition to the elemental composition, about geometrical properties of contaminants. This may be helpful for tracking down the sources of contamination. TXRF enables the distinction between the two contamination types on wafers quite well, if one contamination type outweighs the other or if the particulate type consists entirely or predominantly of particles which exceed 100 nanometers or so.
