Analysis of Temperature and Stress Profiles Induced by a CW Line Scanned Electron Beam in <100> Oriented Silicon
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ANALYSIS OF TEMPERATURE AND STRESS PROFILES ELECTRON BEAM IN ORIENTED SILICON
INDUCED
BY
G. G. BENTINI AND L. CORRERA C.N.R. - ISTITUTO LAMEL, Via Castagnoli 1, 40126 Bologna,
A CW LINE
SCANNED
Italy
ABSTRACT Evaluation of thermal profiles along the scan direction of a line shaped e-beam as well as the topographic distribution of the thermally induced stresses have been performed by solving the heat diffusion equation for several incident power values. The resulting stresses have been computed in the "nearly isotropic" approximation but taking into account that the slip planes, in oriented silicon crystals, are{lll} and the slip directions in the plane are . The threshold of damage introduction has been evaluated by comparing the computed stresses with the yield stress of the material at any annealing temperature. Experimental observations based on X-Ray topography have been performed in order to study the damage introduction on silicon samples annealed in the same conditions used for stress computation. A very good agreement between computed and experimental results was found. INTRODUCTION There is a growing interest in the use of a scanning e-beam source to anneal wide areas in semiconductors [1,2,3 ] working in solid phase regime. In fact the recrystallization of thin films as well as the silicide formation or the recovery of damage consequent to Ion Implantation, can successfully be achieved. However, severe stresses can be generated in the sample, due to the thermal gradient induced by the scanning beam; if these stresses become greater than the elastic limit a severe damage is introduced. Aim of this work is to evaluate both the temperature profile and the topographic distribution of stresses in silicon samples as a function of the power dissipated by the beam in the case of a line shaped source scanned across the sample. The ratio between the computed stresses and the yield stress of the material has been evaluated in order to investigate the threshold of damage introduction and its topographic distribution as a function of the irradiation conditions. The experimental observations of defects introduction as a function of the beam power have been performed by using a linear energy source obtained by fast multiscanning an e-beam along a line; the sample was mechanically driven through the scanned area. TEMPERATURE PROFILE The temperature profile computation has been performed in the geometry shown in fig.l, and considering a line source oriented along the y direction and gaussian along the x direction. In order to match the available experimental conditions, the scan speed and the gaussian width were chosen to be 1 cm/sec and 0.8 cm respectively. Mat.
Res.
Soc.
Symp. Proc.
Vol.
13 (1983)
OElsevier Science Publishing Co.,
Inc.
242
Under these conditions the dwell time is long enough to obtain a heat diffusion length much longer than the wafer thickness, and a volume heat source uniform in y and z (shadowed area in fig.l) running along the x direction can be considered. In this case the temperat
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