Cu gettering to vacancies in Si studied by a positron beam

Kawasuso, Atsuo; Maekawa, Masaki; Fujinami, Masanori*; Oguma, Koichi*; Akahane, Takashi*; Watanabe, Kazuya*; Matsukawa, Kazuto*

Transition-metals are ubiquitous in Si devices to degrade their properties. Gettering has proved effective to trap contaminants and it is important to study their interaction. Extended defects such as stacking faults and precipitates have been investigated by TEM and impurity profile is analyzed by SIMS. However, such a approach cannot afford us the interaction of them. PAS is a powerful tool to analyze the defects and their coupled elements. A Cz-Si wafer was implanted with 3MeV Si ions to dose of 1E+14/cm and Cu ion implantation was done into the back side (200 keV, 1E+14/cm). Variable-energy positron beam was employed and coincidence Doppler broadening spectra were taken at 15 keV after sample annealing. Up to 500C, no differences between with and without Cu ion implantation are found and the clustering of vacancies takes place. At 600C, the profile is very similar to that for the bulk Cu. At 700C, the trapped Cu are released and oxygen atoms are coupled with vacancy clusters.