A Study of Structural Damage & Recovery of Si, Ge and Ga FIB implants in Silicon
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A Study of Structural Damage & Recovery of Si, Ge and Ga FIB implants in Silicon Prabhu Balasubramanian1,a), Jeremy F. Graham2 and Robert Hull1 1 2
Rensselaer Polytechnic Institute, Troy, NY 12180-3590, USA. FEI, Hillsboro, OR, 97124, USA
ABSTRACT The focused ion beam (FIB) has the necessary precision, spatial resolution and control over ion delivery for potential nano-scale doping of nanostructures such as semiconductor quantum dots (QDs). The ion current density in a FIB is 0.1-10 A/cm2, which is at least three orders of magnitude higher than that in a commercial broad beam ion implanter. Therefore an understanding of FIB implantation damage and recovery is of substantial interest. In this work we employ Raman probes of wavelengths 514 nm and 405 nm for quantifying ion implantation damage—both before and after annealing—in 30 kV Si2+, Ge2+ and Ga+ implants (fluences: 1x1012-5x1015 ions/cm2) into Si(100), for the purpose of understanding the effect of ion species on damage recovery. INTRODUCTION Focused ion beam (FIB) instruments employ a nano-scale ion beam for controlled delivery of ions for locally modifying specimen surfaces. For example, it has been shown that 2D arrays of spots created on Si(100) surfaces using FIB can template, upon subsequent epitaxial growth of SixGe(1-x), the positions of strain relieving quantum dot structures1. Also, it has been shown that FIB has the necessary precision and spatial resolution for delivering ions (at fluences down to a single ion) with nano-scale precision, thus making nano-scale doping possible2. While only a handful of ion species are available in a conventional FIB, a mass-selecting FIB (MSFIB), that is a FIB incorporating a Wien filter with orthogonal electric and magnetic fields for massseparation can be used to produce ion beams of many of the elements in the periodic table from suitable alloy sources. While the ion implantation damage and recovery of Si substrate caused by broad ion beams in commercial ion implanters has been extensively studied, ion implantation damage & recovery of Si by the FIB is not as well understood, although there are reports in the literature that show that the damage and recovery in FIB implants is different from that in the corresponding broad beam implants (e.g.3). In this work we study the effect of FIB ion species (Ge, Si, Ga) on structural damage recovery of FIB-ion implanted Si using Raman spectroscopy. MATERIALS & METHODS FIB implantation damage and post-annealing recovery of Si(100) substrates was studied by performing implantation (ion fluences: 1x1012-5x1015 ions/cm2) of Si2+, Ge2+ and Ga+ accelerated to 30 kV into Si(100), such that the ion energy of the Si and Ge species is 60 keV and that of the Ga species is 30 keV. The ion range and the associated straggle for the Si2+, Ge2+ and Ga+ are 88±33 nm, 48±17 nm and 28±11 nm respectively, determined by performing a)
Email address of the corresponding author: [email protected]
simulations in SRIM 2013 (www.srim.org) that simulates ion-solid interactions. The FIB imp
