A DEEP LEVEL TRANSIENT SPECTROSCOPY STUDY OF THE INTERNAL GETTERING OF CR IN CZOCHRALSKI-GROWN SILICON - EFFICIENCY AND REVERSIBILITY UPON LAMP PULSE ANNEALINGS

The interaction of lamp pulses with the internal gettering of chromium (Cr) in Czochralski-grown silicon (Si) has been studied by deep level transient spectroscopy profiling of the electrically active Cr concentration on beveled samples. B-doped Si wafers were submitted to various sequences of thermal treatments consisting in different combinations of Cr diffusion, gettering treatments (high-low-high or high-low), and lamp pulse annealings. An inhibition of the internal gettering mechanism was observed whenever Cr was diffused in a lamp furnace before gettering, or when a lamp pulse was applied before Cr diffusion in a quartz tube furnace. In addition, the stability of the Cr precipitates, formed inside the wafer after internal gettering, was found to depend significantly on the gettering temperature. These results were consistently explained in the framework of the "oxygen precipitation" gettering model, taking into account the two basic requirements of efficient denuded zone formation by oxygen nucleation, and further oxygen precipitate growth rate enhancement of the metal precipitation.