OVERPRESSURIZED BUBBLES VERSUS VOIDS FORMED IN HELIUM IMPLANTED AND ANNEALED SILICON

The formation of helium induced cavities in silicon is studied as a fu nction of implant energy (10 and 40 keV) and dose (1 x 10(15), 1 x 10( 16), and 5 x 10(16) cm(-2)). Specimens art: analyzed after annealing ( 800 degrees C, 10 min) by transmission electron microscopy (TEM) and e lastic recoil detection (ERD). Cavity nucleation and growth phenomena are discussed in terms of three different regimes depending on the imp lanted He content. For the low (1 x 10(15) cm(-2)) and high (5 x 10(16 ) cm(-2)) doses our results are consistent with the information in the literature. However, at the medium dose (1 x 10(16) cm(-2)), contrary to the gas release calculations which predict the formation of empty cavities, ERD analysis shows that a measurable fraction of the implant ed He is still present in the annealed samples. In this case TEM analy ses reveal that the cavities are surrounded by a strong strain field c ontrast and dislocation loops are generated. The results obtained are discussed on the basis of an alternative nucleation and growth behavio r that allows the formation of bubbles in an overpressurized state irr espective of the competition with the gas release process. (C) 1997 Am erican Institute of Physics.