Role of C and Ge in the electrical activation of In implanted in Silicon
- PDF / 5,595,263 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 81 Downloads / 214 Views
C8.7.1
Role of C and Ge in the electrical activation of In implanted in Silicon. S. Scalese1, V. Privitera1, M. Italia1, A. La Magna1, P. Alippi1, L. Renna2 CNR-IMM Sezione Catania, Stradale Primosole 50, 95121 Catania, Italy 2 ST-Microelectronics Stradale Primosole 50, 95121 Catania, Italy
1
ABSTRACT An experimental study on In implantation in Si was performed, considering some factors that affect its electrical activation. One of the critical issues concerning In is represented by its outdiffusion, during the post-implantation annealing, a limiting factor to get active In concentration suitable for applications in microelectronics. The use of different thermal processes was evaluated, aimed to achieve a reduction of the outdiffusion and an increase of the electrical activation of In in silicon. The influence of the substrate purity on the electrical activation was shown to be of great importance: in particular, it was shown that C, present in the silicon substrate as a contaminant or as a co-implanted species, has a key-role in the electrical activation and diffusion of In in silicon. Furthermore, for the first time at our knowledge, the behaviour of In implanted in Si1-xGex layers grown by CVD on Si wafers was investigated, for Ge concentration of 0.5% and 1%. An enhancement in the electrical activation was observed with increasing the Ge content in the alloy. INTRODUCTION An increasing attention has recently been devoted to the use of indium as a p-type dopant in silicon, since it could be an alternative to boron in some applications requiring very shallow and steep profiles. In fact, the heavy mass of In allows to reduce the implant depth, although poor electrical activation is achieved due to the incomplete ionization of its deep-lying acceptor level [1]. Furthermore, the severe out-diffusion taking place during thermal processes reduces the maximum amount of In atoms that can be electrically activated [2]. Recently it was shown that the C-In interaction represents a path to improve the electrical activation. Indeed, the active fraction of the In diffusion profiles can be calculated by considering an interaction between In atoms and C background, present in the CZ-grown silicon and introducing a double-level activation model [3]. The use of other co-implanted species can improve the electrical activation of In, like in this case of C, due to the formation of In-C pairs that introduce a shallower level into the Si band gap (Ev+0.111 eV), with respect to the rather deep level (Ev+0.156 eV) of In alone [2,4,5].In this work we considered and studied many possible factors that can influence the electrical activation of In in Si, with the aim to overcome some limitations in the use of this dopant. In particular, we investigated the effect of different thermal treatments, of the substrate purity and of the interaction with other species, deliberately introduced or present as contaminants in the silicon wafers, on the out-diffusion and on the electrical activation. This study also shows some preliminary results con
Data Loading...
