CORRELATION OF SURFACE PHOTOVOLTAIC TECHNIQUE WITH DEEP LEVEL TRANSIENT SPECTROSCOPY FOR IRON CONCENTRATION MEASUREMENT IN P-TYPE SILICON-WAFERS

The room temperature transformation of iron, with time, from the interstitial form to iron-acceptor complexes was clearly observed by measuring the decrease in concentration of iron interstitials and the increase of iron-boron complexes with deep level transient spectroscopy (DLTS), and by measuring the increase of minority carrier diffusion length with the surface photovoltaic technique. It was concluded that the range of concentration of interstitial iron, which significantly reduces the minority carrier diffusion length, is about 1E11-1E12 atoms/cm3. It was also observed that surface photovoltaic technique is more practical than DLTS for surface iron concentration measurements. Finally, the correlation of surface iron concentration of wafers with minority carrier diffusion length using surface photovoltaic technique and DLTS was developed. It was observed that this correlation is insensitive to various silicon wafer properties, as long as a homogenization treatment is performed.