Ion Implantation and Synthesis of Materials - Studium

140 10 Crystallization and Regrowth of Amorphous Siand ν (E) is the energy deposited into displacement production at the α–c interface.The data indicates an activation energy of 0.32 eV for IBIEC, which isapproximately an order of magnitude smaller that the activation energy of 2.7 eVfor the pure thermal process.10.4 Laser Annealing of SiDirected laser beams provide another method of supplying the thermal energyrequired for the annealing of defects in Si and the regrowth of amorphous layers.(Poate and Mayer 1982). Laser annealing not only presents a new annealingtechnique but also has the additional advantage of selective area energydeposition. That is, one deposits the energy (heat) not only in a small area but alsoin a near surface layer that contains the region damaged by the ion beam.The laser annealing concept is demonstrated by the channeling spectra of thearsenic-implanted and pulsed ruby laser annealed Si sample in Fig. 10.13. On thebasis of channeling, the reduction in Si disorder is as complete for the laser as forthermal annealing. The interesting differences lie in the impurity behavior, thebroadening of the depth distribution of the impurity, and the very high substitutionalconcentration. From an analysis of Fig. 10.13, with a peak concentrationnear 10 21 As cm −3 , the ratio of random and aligned spectra indicates ~98%substitutional arsenic.Si DEPTH ( µ m) 75 As DEPTH ( µ m)0.4 0.3 0.2 0.1 0 0.2 0.1 020001600RANDOMALIGNED BEFORE ANNEALALIGNED X3ALIGNED X3 AFTER ANNEALALIGNED X3 VIRGINYIELD (counts)120080040000.81.0 1.2 1.41.6 1.8 2.0 2.2ENERGY (MeV)Fig. 10.13. Random and channeling backscattering spectra of as-implanted Si (100)showing the annealing results from pulsed laser irradiation (Q-switched ruby laser1.6 J cm −2 , 75 As 100 keV, 1.4 × 10 16 in 〈100〉 Si, [110] aligned spectrum) (after White et al.1979)