Partial annealing of defects in boron-implanted p-type silicon by hydrogen implantation
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Partial annealing of defects in boron-implanted p-type silicon by hydrogen implantation Yutaka Tokuda1 and Hiroyuki Iwata2 1 Department of Electronics, Aichi Institute of Technology, Toyota 470-0392, Japan 2 Research Institute for Industrial Technology, Aichi Institute of Technology, Toyota 470-0392, Japan ABSTRACT Hydrogen implantation has been used to anneal defects produced in p-type silicon by boron implantation. Boron implantation is performed with an energy of 300 keV to a dose of 1x109 cm-2. Deep level transient spectroscopy measurements show the production of four hole traps (Ev + 0.21, 0.35, 0.50, 0.55 eV) by boron implantation. Subsequent hydrogen implantation is performed with energies of 60, 90, 120 and 150 keV to a dose of 2x1010 cm-2. Among four traps produced by boron implantation, the most significant effect of hydrogen implantation is observed on one trap (Ev + 0.50 eV). A 62% decrease in concentration is caused for this trap by hydrogen implantation with energies of 120 and 150 keV. This partial annealing is ascribed to the reaction of boron-implantation-induced defects with point defects produced by hydrogen implantation.
INTRODUCTION Hydrogen implantation in silicon has been applied to local control of recombination lifetime [1], gettering of metallic impurities [2,3] and fabrication of silicon-on-insulator wafers [4]. Moreover, it has been reported that implanted phosphorus ions in n-type silicon are partly activated by subsequent hydrogen implantation at a low temperature 400 and that further with a sharper carrier electrical activation has been achieved by annealing at 800 concentration profile compared with the profile of the phosphorus-implanted sample [5]. Recently, it has been shown that electron traps in n-type silicon produced by phosphorus implantation are annealed partly by subsequent hydrogen implantation at room temperature [6]. These positive effects of hydrogen implantation have been explained by the interaction of phosphorus-implantation-induced defects with defects produced by hydrogen implantation [5,6]. On the other hand, boron implantation is a common method to introduce acceptors into silicon. It is important to investigate the effect of hydrogen implantation on boron-implanted silicon, which might give a method to form the sharper carrier concentration profiles. In this work, we study the effect of hydrogen implantation on hole traps produced in p-type silicon by boron implantation with deep level transient spectroscopy (DLTS) [7,8]. It is shown that a significant decrease in concentration of one trap in the boron-implanted sample is caused by subsequent hydrogen implantation.
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EXPERIMENTAL Wafers used were prepared from boron-doped, p-type (100) Czochralski-grown silicon F8.6.1
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crystals which had a resistivity of between 6 and 8 cm. Boron implantation was performed with an energy of 300 keV to a dose of 1x109 cm-2 {B(300) sample}. Subsequent hydrogen implantation for the B(300) sample was performed with energies of 60, 90, 120 and 150 keV to a dose of 2x1010 cm-
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