Gettering of Cu by microcavities in bonded/ion-cut silicon-on-insulator and separation by implantation of oxygen

Abstract

Microcavities formed by H+ and He+ implantation and subsequent annealing are effective gettering sites for transition metal impurities in silicon. However, gettering in silicon-on-insulator (SOI) materials is quite different from that in silicon. In this work, we investigate the gettering of Cu to these microcavities in silicon, separation by implantation of oxygen (SIMOX) and bonded/ion-cut SOI wafers. Our data indicate that He+ implantation in the high dose regime (0.2–1×1017 cm−2) creates a wide band of microcavities near the projected range without causing blistering on the sample surface. On the other hand, the implantation dose of H+ needed for stable microcavity formation is relatively narrow (3–4×1016 cm−2), and this value is related to the projected range. The different behavior of H and He in silicon is discussed and He implantation is more desirable with regard to impurity gettering. Cu is implanted into the surface region of the Si and SOI samples, followed by annealing at 700 and 1000 °C. Our results indicate that the microcavities can effectively getter a high dose of Cu (2.5×1015 cm−2) at 700 °C in bulk Si wafer, but higher temperature annealing is needed for the effective gettering in SIMOX. Gettering of Cu by the intrinsic defects at or beneath the buried oxide interface of the SIMOX is observed at 700 °C, but no trapped impurities are observed after 1000 °C annealing in the samples in the presence of microcavities. Almost all of the 1×1014 cm−2 Cu implanted into the Si overlayer of the bonded/ion-cut SOI diffuse through the thermally grown oxide layer and are captured by the cavities in the substrate after annealing at 1000 °C.