Defect Evolution from Low Energy, Amorphizing, Germanium Implants on Silicon
- PDF / 403,977 Bytes
- 5 Pages / 612 x 792 pts (letter) Page_size
- 109 Downloads / 261 Views
Defect Evolution from Low Energy, Amorphizing, Germanium Implants on Silicon Andres F. Gutierrez1, Kevin S. Jones2 and Daniel F. Downey3 1 Intel Corporation, 5000 W. Chandler Blvd., Mailstop CH5-263, Chandler, AZ 85226, U.S.A. 2 Materials Science and Engineering, Bldg #33 Rm 538, University of Florida, Gainesville, FL 32611, U.S.A. 3 Varian Semiconductor Equipment Associates, 35 Dory Road, Gloucester, MA 01930, U.S.A. ABSTRACT Plan-view transmission electron microscopy (PTEM) was used to characterize defect evolution upon annealing of low-to-medium energy, 5-30 keV, germanium implants into silicon. The implant dose was 1 x 1015 ions/cm2, sufficient for surface amorphization. Annealing of the samples was done at 750 °C in nitrogen ambient by both rapid thermal annealing (RTA) and conventional furnace, and the time was varied from 10 seconds to 360 minutes. Results indicate that as the energy drops from 30 keV to 5 keV, an alternate path of excess interstitials evolution may exist. For higher implant energies, the interstitials evolve from clusters to {311}’s to loops as has been previously reported. However, as the energy drops to 5 keV, the interstitials evolve from clusters to small, unstable dislocation loops which dissolve and disappear within a narrow time window, with no {311}’s forming. These results imply there is an alternate evolutionary pathway for {311} dissolution during transient enhanced diffusion (TED) for these ultra-low energy implants. INTRODUCTION Preamorphization is commonly used in the formation of ultra-shallow junctions for Si-based microelectronic devices [1-3]. However, this step alone will not achieve the necessary highly doped, low resistivity structures required for next generation devices since the process itself introduces end-of-range (EOR) defects that influence diffusion and dopant activation mechanisms upon annealing [4]. Knowing that excess interstitials provide a source for TED [5], it becomes necessary to understand all sources and conditions for interstitial formation and evolution from preamorphizing implants, especially at the technologically important low-energy regimes i.e., less than 5 keV. Low to high-energy Si+ implants (~ 1-100 keV) have been previously studied [6-9], and a consensus regarding the path of interstitial evolution, as it affects TED, has emerged [10]. In essence, this path includes the formation of small precursor clusters, which coalesce into {311} type defects. With time, these EOR defects switch in function from interstitial sink to source, and dissolve, either driving dislocation loop formation or TED. At longer times, these loops either dissolve and drive TED, or become stable and trap interstitials. The objective of this work is to enhance the understanding of defect (and consequently interstitial) evolution from low energy, germanium implants on silicon, since it has not been reported in the literature. EXPERIMENTAL DETAILS Czochralski (CZ) grown (100) Si wafers were implanted with germanium ions at 5, 10 and 30 keV implant energies at a 7° tilt. The
Data Loading...
