Boron and Phosphorus Implantation Induced Electrically Active Defects in p-type Silicon Jayantha Senawiratne 1,a, Jeffery S. Cites 1, James G. Couillard 1, Johannes Moll 1, Alex Usenko 1, Carlo A. Kosik Williams 1, and Patrick G. Whiting 2 1 Corning Incorporated, Corning, NY 14831, USA, 2 Rochester Institute of Technology, Dept. of Microelectronic Eng., Rochester, NY 14623, USA a Motivation Boron and phosphorus are considered common dopants for the formation of p- and n-type regions for the ohmic contacts in Si based microelectronic devices. Degenerate doping of boron or phosphorus in Si is accommodated either by ion implantation or by diffusion. Typically, ion implantation into Si introduces both implantation related lattice defects and electrically active point defects. Most of these unstable defect complexes are either eliminated from the material or are converted into a more stable configuration upon thermal treatment. The choice of annealing temperature, however, depends on both the reaction kinetics of these defects and thermal stability of the underlying material. For example, the microelectronic devices developed on thin film Si on glass (SiOG) cannot withstand annealing temperatures in excess of 665 o C. Therefore, understanding reaction kinetics of the implantation related defects and their recovery during low temperature annealing is important. Deep Level Transient Spectroscopy (DLTS) 1  A temperature-dependent capacitive method for studying electrically active defects in MOS and pn devices  Makes use of cryogenic temperatures to “freeze out” certain traps from 77°K to room temperature and above  Identify trap species * D. V. Lang, J. Appl. Phys. 45, 3014 (1974)  C(T)= C(t 1 )-C(t 2 ) T cold < T max < T hot if T ~ T max, find max difference emission systematically measure  C(T) get T max  d  C(T)/d  e = 0 emission rate: Trap concentration: graph of ln(T 2 /e n ) vs. 1000/T slope → ∆E and intercept → σ n Temperature Dependent Capacitance Transient  Photo-current in MOS is due to direct tunneling of photo-generated minority (electron) carriers in the depletion region  Photo-current  Energy of the traps  Trap density DLTS: Boron Implanted Si DLTS: Phosphorus Implanted Si Photoconductivity: Thermal annealing and Recovery of Implant Damage T Metal Oxide Semiconductor (MOS) Structure Sample ID un-annealed (annealed) Implanted species Energy (keV) Dose (atm/cm 2 ) B11 (B11an) 11 B452x10 11 P31 (P31an) 31 P602x10 11  E V eV (σ n = 7.3x cm -2 )  Thermally unstable (dissociates > 350 o C) 3  Common in both 11 B and 31 P  C-O complexes due to 11 B irradiation 2  E V eV (σ n = 1.8x cm -2 )  Thermally unstable H-B-interstitials 4  B-implantation related electrically active defects have been strongly suppressed/recovered upon low temperature thermal annealing at 450 o C for 1/2 Hr. Summary/Conclusion  Ion implantation induced electronic defects in 11 B and 31 P implanted p-type Si and their recovery under low temperature annealing were investigated using DLTS and photoconductive spectroscopy  Common to both 11 B and 31 P implanted Si, thermally unstable deep trap states were observed prior to annealing, while they were suppressed or eliminated upon thermal annealing at 450 o C  Corroborating the DLTS results, the photocurrent measurement also revealed a strong reduction of near band edge defect states after the thermal annealing step  E V eV: C-O complexes associated with 31 P irradiation  E V eV and E V eV:  Interaction of P-centers with H  Possibly due to formation of H-P- interstitial sites in Si due to 31 P irradiation DLTS Spectra ∆E, σ n : Arrhenius Plot DLTS Spectra Photoconductivity Spectra 31 P Implanted/Un-annealed 31 P Implanted/Annealed  E V +0.25:  Fatima et al. and Feklisova et al. E V eV: H-divacancy † in p-Si 4,5  Enhances upon thermal annealing 4,5  Assignment: H-divacancy in Si  Band edge absorption:  The onset of the strongest absorption at 1.12 eV: band gap of Si  Absorption ( eV): electrically active defects-  Suppressed upon thermal annealing  Strength of the band: 31 P > 11 B  Implantation energy: 60 keV ( 31 P) > 45 keV ( 11 B)  Size: 31 P > 11 B  Lattice damage due to high energy particle bombardment References 1.D. V. Lang, J. Appl. Phys. 45, 3014 (1974) 2.M. O. Aboelfotoh et al., Phys. Rev. B 52, 2522 (1995) 3.B. G. Svensson et al. Phys. Stat. Sol. A 95, 537 (1986) 4.S. Fatima et al. J. Appl. Phys. 85, 2562 (1999) 5.O. Feklisova et al. Physica B , 235 (1999) Acknowledgments The authors would like to thank the technical staff at Corning and Rochester Institute of Technology who provided analytical services and sample preparation. Photoconductivity Spectroscopy