Optical properties of ion-implanted silicon and separation by implantation of oxygen silicon-on-insulator substrates in the infrared: Study of B + and P 2 + implantation doping C.C. Katsidis a, ⁎, D.I. Siapkas b a Department of Materials Science and Technology, University of Crete, P.O. Box 2208, 71003 Heraklion, Crete, Greece b Solid State Section, Department of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece abstract article info Article history: Received 2 June 2008 Received in revised form 26 November 2008 Accepted 26 November 2008 Available online 3 December 2008 Keywords: FTIR Ion implantation Profiles Refractive index Mobility Activation The optical properties of ion implanted silicon and silicon-on-insulator substrates have been studied by Fourier transform infrared spectroscopy. The influence of the implanted-ion mass in changing the refractive index of a silicon target has been examined by implanting 80 keV 11 B + and 62 P 2 + ions respectively. A refractive index rise not exceeding 2% and total amorphization were observed respectively in the vicinity of the Si surface after boron and phosphorous implantations. Free carrier profiles generated after thermal annealing at 950 °C/30 min and 1150 °C/120 min were modeled by Pearson and half-Gaussian distributions respectively. The phosphorous implantation was also performed in silicon-on-insulator substrates, yielding after annealing nearly homogeneous free-carrier profiles in the top-Si layer and optical mobility values comparable to those of bulk-Si. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Phosphorous and boron are recognized as classical dopants for the formation of regions with n- and p-type conductivity respectively in Si, either by diffusion or by ion implantation [1,2]. Although classical, they still attract scientific interest since new trends and applications push microelectronic devices to shrink and therefore new questions emerge regarding the redistribution, the electrical activation and, generally, the profile engineering of the ion implanted dopants [2–9]. Recently, ion implantation amorphization and annealing kinetic effects on the dielectric functions of silicon [9–11] and polycrystalline silicon [12] samples have been extensively reported. The development of silicon-on-insulator (SOI) structures has created another pole of scientific interest [13–23] due to the ad- vantages of SOI substrates in complementary metal-oxide semicon- ductor device fabrication and performance. The performance advantages include: low power consumption, increased speed, reduced short channel effects, latchup (parasitic thyristor action) eli- mination and radiation hardness. The improved speeds and improved radiation tolerances of devices built on SOI substrates are achieved by limiting the working device space in the thin silicon layer that resides above the insulating layer. It is the limited volume of active Si that leads to reduced paracitic capacitances and hence to higher switching speeds and reduced dynamic power consumption. A well established procedure to form a SOI substrate involves implantation of reactive oxygen ions into Si and subsequent high temperature furnace annealing (typically 1300 °C for few hours). A buried insulating oxide layer is thus created leading to the so called SIMOX (separation by implanted oxygen)–SOI structure [13]. The behavior of dopants in the top silicon layer (Si-overlayer) can be affected by the presence of the two interfaces (the interface between the native oxide and the Si-overlayer and the interface between the Si- overlayer and the buried oxide) yielding anomalous doping profiles [15,16]. Furthermore, dopant interstitial clustering as well as dopant segregation to the buried oxide (BOX) can result in low activation efficiencies [19]. Besides the implantation of atomic ion species, molecular dopant ions, such as As 2 + and P 2 + dimer ions, can be implanted as an alternative [24–26]. The implantation of multi-atomic molecular ions such as As n + and P n + can be performed at energies n-times larger than the energy of atomic-ion implantation while the ion dose can be reduced by a factor of n. Molecular ion implantation thus exhibits appreciable throughput advantages compared with monomer ion implantation. This is found to be very useful for shallow junction formation by ultra-low energy (below 1 keV) ion implantation as device dimensions continue to shrink [25]. The experimental work of this paper involves monomer boron ( 11 B + ) ion implantation into bulk-Si and dimer phosphorous ( 62 P 2 + ) ion Thin Solid Films 517 (2009) 4307–4317 ⁎ Corresponding author. E-mail address: katsidis@materials.uoc.gr (C.C. Katsidis). 0040-6090/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.tsf.2008.11.144 Contents lists available at ScienceDirect Thin Solid Films journal homepage: www.elsevier.com/locate/tsf