Laser Annealing of Ion Implanted Silicon
We present here a detailed theoretical and experimental investigation of the dynamics of surface melting and regrowth and electrical activation of Si('+) and BF(,2)('+) ion implanted amorphized silicon annealed with a Q-switched Nd:glass laser ((lamda)= 1.06 (mu)m). In the theoretical calculations we have used the technique of finite difference equations to solve the one-dimensional heat conduction equations for the solid and liquid phases. We have taken into account the temperature dependence of all the parameters involved to give us a realistic model. The melting model is supported by time resolved reflectivity measurements using a He-Ne and an Ar laser. We use SEM to investigate the electron channelling pattern to study the quality of crystalline regrowth. For BF(,2)('+) implanted silicon, the boron and fluorine atomic profiles are measured by secondary ion mass spectrometry (SIMS) on as-implanted samples as well as laser annealed samples. The impurity redistribution is explained on the basis of the melting model. Differential resistivity and Hall effect measurements in conjunction with successive layer removal are used to obtain the electrical carrier distributions as a function of the laser fluence. For good quality crystalline regrowth and full electrical activation, the laser fluence should lie between the melting threshold and the damage threshold. Therefore, a reliable model is useful in designing experiments of laser annealing.
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign