PHYSICAL REVIEW B VOLUME 46, NUMBER 4 15 JULY 1992-II Hydrogen-related complexes as the stressing species in high-Suence, hydrogen-implanted, single-crystal silicon G. F. Cerofolini and L. Meda Functional Materials Laboratory, Istituto Guido Donegani, Eni Chem, 20097 San Donato MI, Italy R. Balboni, F. Corni, S. Frabboni, G. Ottaviani, and R. Tonini Dipartimento di Fisica, Universita di Modena, 41100 Modena MO, Italy M. Anderle and R. Canteri IRST — Divisione di Scienza dei Materiali, 38050 Povo TN, Italy (Received 6 May 1991; revised manuscript received 6 February 1992) This work is devoted to the characterization of the Si:H system obtained by high-fluence, low-energy, hydrogen implantation into single-crystal silicon. The implanted hydrogen profile and the ones resulting after thermal annealing in the range 100 — 800'C are detected by secondary-ion mass spectrometry and elastic-recoil detection analysis. The displacement field in the crystal, measured by channeling Rutherford-backscattering spectrometry, is found to depend on the direct radiation damage, the extend- ed defects formed after ion implantation (revealed by transmission electron microscopy), and the im- planted species. The contribution to the displacement field due to hydrogen-related defects has a charac- teristic "reverse annealing" in the range 100-400'C, essentially due to their formation kinetics. I. INTRODUCTION Though "none of the numerous hydrogen-related vi- bration bonds have yet been assigned to a specific de- fect", ' there is now a reasonable consensus on hydrogen configurations in single-crystal silicon at low concen, tra- tion. (1}The bond-centered (BC) configuration, typical of in- trinsic or p-type silicon [Fig. 1(a) and Refs. 2 and 3]. (2} The antibonding (AB} configuration, where hydro- gen is kept close to an interstitial tetrahedral (Td} posi- tion by an antibonding state of silicon [Fig. 1(b) and Ref. 4]. (3) The H2 configuration, resulting from pairing of close, ionized, AB (H ) and BC (H+) hydrogen atoms [Fig. 1(c) and Ref. 3]. (4) The silanic Si-H configuration, resulting from hy- drogen reaction with a silicon dangling bond [Fig. 1(d)]. The standard theory of shallow dopants ascribes accep- tor passivation to a positively ionized BC hydrogen in the vicinity of a negatively ionized acceptor [Fig. 2(a) and Ref. 3]; the deep-dopant description ascribes passivation to the formation of a silanic bond in the vicinity of an sp -hybridized acceptor [Fig. 2(b) and Ref. 5]. Much more complex is the situation at high concentra- tion, where unsaturated or ionized hydrogen con- figurations (AB, BC, or H2) are expected to rearrange and form saturated configurations (e.g. , molecular hydro- gen, H2), this process being counterbalanced by steric fac- tors that make the incorporation of the molecules in the lattice dificult. The existence of H2 in crystalline silicon is highly con- troversial: Quantum calculations show that H2 in an in- terstitial Td site oriented in a (100) direction is one of Si /pe (a) I f H (b) yyyyXX S i //////, I I H „yZXX S i 4j~» 1) (c) FIG. 1. Suggested hydrogen configuration in silicon: (a) bond-centered, {b) antibonding, (c) H2, and (d) silanic. the most stable compounds in silicon and is therefore ex- pected to be one preferred configuration of high concen- tration in crystalline, nondefective silicon; ' however, no direct spectroscopic evidence for H2 has yet been present- ed. On the experimental side, H2 has been advocated in 46 2061 1992 The American Physical Society