Iron Precipitation and Dissolution in Float-Zone Silicon

Abstract

ABSTRACTA quantitative analysis of the phase changes of iron in silicon from interstitial to precipitate phase and vice-versa is presented. Temperature dependent iron precipitation and dissolution in float-zone grown silicon wafers is experimentally investigated. A quantitative analysis of iron silicide precipitate stability and dissolution with respect to time and temperature is also presented. Precipitation of iron in silicon was analyzed by a quantitative assessment of change in interstitial iron using a surface photo voltage minority carrier lifetime analysis technique. Contamination levels of iron in the range 1011 to 1013 atoms/cm3 are investigated. It is concluded that maximum iron precipitation occurs in the temperature range of 500°C to 600°C. Iron precipitation is rapid in this region where more than 90% of the interstitial iron precipitates in a period of 30 minutes. Iron silicide precipitates were found to dissolve above a temperature of 760°C restoring iron back to an interstitial phase in the silicon matrix.