Published online by Cambridge University Press: 25 February 2011
Recent studies have shown that surface metals, introduced by scraping metals either on the silicon wafer front or back surface, can contribute to surface crystalline defects during rapid thermal processing (RTP). These studies have been qualitative in the sense that the quantitative amount of surface metallic contamination was unknown. The work involved here uses Total reflection X-Ray Fluorescence (TXRF) analysis to quantitate the surface metallic contamination on silicon wafers from cleaning (rather than scraping) both before and after RTP. In this study there was no correlation found between surface copper (ranging from 2 to 200 ×1012 atoms/cm2) and surface defects after a RTP of 600°C for 30 seconds in argon, nor was there a correlation between temperature (ranging from 600°C to 1150°C) of the RTP (120 seconds in argon) and surface defects for constant surface copper of about 30×1012 atoms/cm2. The data also revealed the introduction of cross contamination of tungsten to the frontside surface of silicon wafers when air was used as the ambient with an activation energy of 0.8 eV for RTP of 120 seconds in air with temperatures ranging from 500°C to 1000°C. This cross contamination is presumed to come from prior tungsten silicide RTP, even though the quartz tube was etched before this study. Furthermore, the cross contamination of Ga and As occurred to the wafer backsides with no apparent activation energy, and this contamination is presumed to come from prior GaAs annealing several months before.