DEFECT REACTIONS IN COPPER-DIFFUSED AND QUENCHED P-TYPE SILICON

Electrical measurements carried out on copper-diffused and quenched p-type silicon indicate that a large acceptor deactivation occurs throughout the material. The passivation stability, limited to subambient temperatures, is shown to be dopant dependent, thus confirming previous results. The measurements also provide information on the generation of Cu-related defects and copper behavior. One of the observed defects, labeled an M center, exhibits metastability. It is shown that this can be understood as a pairing mechanism between the M defect and free Cu atoms, with the pair being electrically inactive. Kinetic studies reveal a correlation between the dopant-copper binding energy and the M-Cu reaction. The available mobile copper ions result from dissociation of acceptor-copper pairs leading to a dopant-dependent association frequency of the MCu(i) complex. On the basis of these results, certain recent data related to copper-defect reactions in silicon are reanalyzed. In particular, the so-called X-defect diffusion coefficient is reconsidered, taking into account the internal built-in electric field. The results support identification of the X defect as interstitial copper.