Influence of the Implanted Species on the Residual Damage After Hot Implants in Silicon
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INFLUENCE OF THE IMPLANTED SPECIES ON THE RESIDUAL DAMAGE AFTER HOT IMPLANTS IN SILICON Lacan*CSiea*
L.CaIcag , C.Spinela G.FerlaY and E.Rimini
* ,
M.Catania
*
, S.U.Campisano
*
, G.Foti*,
*Dipartimento di Fisica, Corso Italia 57 - 95129 Catania (Italy) #SGS-Thompson, Stradale Primosole 50-95100 Catania (Italy)
ABSTRACT Damage formation during hot implants of 600 keV As or Ge ions into Si was investigated by changing the target temperature (>150 °C) and the ion fluence. The defect distributions, as obtained by channeling analysis, are characterized by a gaussian shape whose maximum coincide with the peak of the energy density deposition and with a width of 200 nm. The amount of damage is a factor of two higher for Ge than for As ion implants, and a similar result was found for the damage created by Ge implants into bare Si or Si doped with a near constant As concentration of 2xl0 2 0 /cm 3 . The transition to amorphous formation is quite sharp for As (around 120 °C) and quite broad for Ge implants. The different amount and kind of extended defects is probably due to an interaction of the mobile point defects, vacancies and interstitials, with As. The interaction probably increases the defects annihilation rate. INTRODUCTION The damage created by ion implantation depends on the ballistic parameters of the colliding ion-atom couple and on the target temperature. During irradiation the generated point defects, Frenkel pairs, migrate, recombine, anneal out at the preexisting sinks, agglomerate into amorphous regions, small dislocation loops, dislocations network. The prevalence of one mechanism over the others is mainly determined by temperature. Silicon amorphous layers are formed at room temperature at a fluence of about 1014 As/cm 2 . The fluence for amorphization increases rapidly with temperature and above 200 0C the transition to the amorphous phase does not occurs [1,2]. The majority of experiments has been performed at relatively low ion energy, 25-100 keV, with the dopants confined in the near surface region. Infact the predeposition step to dope silicon is the main industrial application of ion implantation. The surface, provided the defects are mobile, may play, in this case, an important role being an active sink for defect annihilation. High energy implants are now being used for several applications in microelectronics devices and ionassisted processes, as the epitaxial regrowth of amorphous silicon layers [3]. The growth process, under ion irradiation occurs at temperatures as low as 2000C with an apparent Mat. Res. Soc. Symp. Proc. Vol. 128. (1989 Materials Research Society
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activation energy of about 0.3 eV, one order of magnitude lower than that of the pure thermal process [4]. It induces epitaxial crystallization even in chemical vapor deposited amorphous layer, or in layers heavily contaminated with argon or oxygen [5]. This process has a draw back in the generation of extended defects during the irradiation at high temperature. A suitable annealing step is necessary to remove, at lea
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