Low-energy electron beam induced regrowth of isolated amorphous zones in Si and Ge
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Low-energy electron beam induced regrowth of isolated amorphous zones in Si and Ge I. Jenˇciˇc J. Stefan Institute, Jamova 39, 61000 Ljubljana, Slovenia
I. M. Robertson Department of Materials Science and Engineering, University of Illinois, 1304 West Green Street, Urbana, Illinois 61801 (Received 27 September 1995; accepted 31 May 1996)
Spatially isolated amorphous regions in Si and Ge have been regrown at room temperature by using an electron beam with an energy less than that required to cause displacement damage in crystalline material. The rate at which the zones regrow is a function of the energy of the electron beam. As the electron energy is increased from 25 keV (lowest energy employed), the regrowth rate decreases and reaches a minimum below the threshold displacement voltage. With further increases in the electron energy, the rate again increases. It is suggested that at the lower electron energies this room temperature regrowth process is stimulated by electronic excitation rather than by displacive-type processes. I. INTRODUCTION To realize the potential of ion implantation in the production of semiconductor devices, thermal programs have been developed to remove the implant damage and to electrically activate the dopants.1 With the trend in the microelectronics industry toward further miniaturization, and with the need to reduce transient enhanced diffusion, there is a growing demand to understand the fundamental damage state produced by ion implantation and the processes which govern its removal. Typically, the damage is removed through an annealing procedure, although ion and electron beams have been used too. For the ion and electron irradiations it has generally been found that the rate of regrowth scales with the energy deposited in the nuclear component of the damage (for a review of the work on Si, see Ref. 2). That is, some form of displacement damage is required to stimulate the regrowth process. The ion and electron irradiation induced regrowth processes tend to show the same dependencies as thermally induced regrowth, although they tend to occur at lower temperatures and are characterized by a lower activation energy.2,3 Recently, it has been shown that displacement damage mechanisms are not necessary to recrystallize spatially isolated amorphous zones.4,5 In that work an energetic electron beam was used to stimulate the room temperature regrowth of spatially isolated amorphous regions in Si, Ge and GaP. The rate of regrowth decreased as the energy of the beam decreased, but at some energy below the threshold displacement energy (145 keV for Si; 350 keV for Ge; unknown, but estimated ,200 keV for GaP6,7 ) the rate again increased. In the initial studies this trend was most apparent in Ge, although it appeared that both Si and GaP would exhibit the same behavior for electron beam energies ,50 keV. The weaker trend in Si and GaP was attributed to the small difference between the 2152
http://journals.cambridge.org
J. Mater. Res., Vol. 11, No. 9,
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