Initial Anomalous Diffusion of Boron Atoms at Low-Temperature Annealing Tomoya Saito, Jianxin Xia, Ryangsu Kim, Takenori Aoki, Hiroyuki Kobayashi, Yoshikazu Furuta, Yoshinari Kamakura, and Kenji Taniguchi Department of Electronics and Information Systems, Faculty of Engineering, Osaka Univer sity, Suita, 565-0871 Japan SUMMARY Experiments on the transient enhanced diffusion (TED) of boron in superlattice silicon wafers, for the first time demonstrated the existence of the anomalous en- hanced diffusion of boron at the very early stage of low- temperature annealing at locations situated deeper than the implantation damage zone. It was confirmed that this phe- nomenon is caused by free self-interstitial silicon atoms present in the implantation tail region. © 2001 Scripta Technica, Electron Comm Jpn Pt 2, 84(10): 5964, 2001 Key words: Transient enhanced diffusion (TED); boron; superlattice silicon wafers; low-temperature anneal- ing. 1. Introduction Ion implantation technology is instrumental for con- trolling profile of dopant in semiconductors in the process of fabrication of fine MOS structures. In the future, for the formation of junctions with even shallower profiles, it will be necessary to employ low-energy ion implantation and low-temperature annealing techniques. However, ex- tremely shallow junctions cannot be produced without solv- ing the problem of transient enhanced diffusion (TED) [1]. TED is a phenomenon caused by temporary coupling of interstitial Si atoms produced by ion implantation with atoms of such dopants as boron, phosphorus, and the like, that manifests itself in a more than tenfold increase in the diffusivity of dopants compared to the state of thermal equilibrium. In addition, during the initial stage of the annealing, these interstitials form {311} defects [2]. Since {311} defects grow due to temporary capture of intersti- tials, distribution of dopants is controlled by {311} defects [3, 4]. Therefore, the processes of formation and dissolution of {311} defects are important factors in the phenomenon of dopant diffusion, in which interstitial Si atoms play the role of the medium. However, direct observations of inter- stitials introduced in the Si crystalline structure by ion implantation represent substantial difficulties [58]. In our experiments, we used superlattice silicon wa- fers having six boron marker layers to observe low-tem- perature TED produced in each of these layers. In this paper, we report a new phenomenon of the enhanced diffusion taking place deep in the implantation damage region, which was discovered based on these observations, and offer a qualitative model of this phenomenon [9]. 2. Experimental Methods Experiments were conducted using superlattice Si wafers having six layers of boron markers formed by the molecular beam epitaxy method (MBE). Boron-doped lay- ers having a concentration of 4 to 8 K 10 18 cm 3 were grown to a thickness of 30 nm alternating with 110-nm-thick nondoped silicon layers (Fig. 1). © 2001 Scripta Technica Electronics and Communications in Japan, Part 2, Vol. 84, No. 10, 2001 Translated from Denshi Joho Tsushin Gakkai Ronbunshi, Vol. J82-C-II, No. 8, August 1999, pp. 446450 59