Minority lifetime degradation of silicon wafers after electric zone melting

The degradation of minority lifetime of mono- and multi-crystalline silicon wafers after electric zone melting, a simple and contamination-free process, was investigated. The thermal-stress induced dislocations were responsible to the degradation; however, the grain size also played a crucial role. It was believed that the grain boundaries helped the relaxation of thermal stress, so that the degradation was reduced as the grain size decreased. In addition to lifetime mapping and etch pit density, photoluminescence mapping was also used to examine the electrically active defects after zone melting.