The Effect of Damage Density Profile on Moving specles in Ion-Induced Reactions
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[lIE EFFECT OF DAMAGE DENSITY PROFILE ON MOVING SI'E(CIES IN ION-INDUCED REACTIONS
K. TAO,* C.A. HEWETT,* S.S. LAU,* Ch. BUCHAL,** and D.B. POKER** *Department of Electrical Engineering and Computer Sciences, University of California San Diego, La Jolla, CA 92093 **Solid State Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831
ABSTRACT We present evidence in this study that the moving species under ion mixing conditions are affected by the implantation damage distribution in the sample. This observation holds for metal-semiconductor, metal-metal and semiconductorsemiconductor systems. The direction of thermal annealing and atomic transport appears to play a role in ion-mixing as well. When these two factors are in the same direction, only one dominant moving species is observed. When these two factors are in opposite directions, both constituents can contribute to the atomic transport in ion mixing.
INTRODUCTION It has been shown that metal-semiconductor interactions in ion mixing may differ with those of the corresponding thermally annealed cases 1-31. These differences have been attributed to the significant Si atomic motion during ion mixing 11-3j annealing mixingPt-S[5]l and thermal Investigations of the moving species under Cr Cr-SS NiS 1-IP ion -S the] both 15 1 -Si . -Si , Cr-Si 4-5 conditions have been carried out in the Ni-Si - , Pd-Si , 61 16 systems. The conclusion of these studies is that Si always an W-Si Mo-Si contributes to the net atomic motion under ion irradiation, regardless of the dominant moving species under thermal annealing. Three possible explanations have been advanced by Hung and Mayer [7ýas to why Si atomic motion is always enhanced relative to that of the metal in ion mixing . Two of the explanations, the influence of ion irradiation induced amorphous Si, and the release of Si at the metal-Si interface within the collision cascade, were ruled out by experiments 7. The presence of ion-irradiation induced defects in the samples was concluded as the third possible cause to enhance Si motion under ion mixing conditions . .. The objective of this work was to study the possible correlations between ionirradiated defects and the atomic transport in ion-induced reactions. Upon examination of existing experimental results of marker motion, we note that the instantaneous damage energy density, as calculated by the TRIM computer simulation 191,is always higher on the metal side for all metal-Si systems reported 14,51 The damage density depends basically on four material parameters; atomic density, atomic numbers, atomic mass and displacement energy, in that order. For all cases of metalSi systems reported, there is in fact a damage density difference across the metal-Si interface. When a silicide layer is induced to form by ion mixing near the interface, the damage density is graded by the presence of the reacted zone; the damage density is thus highest in the unreacted metal layer, and lowest in the unreacted Si layer and at some intermediate value in the ion-mixed layer. It was temp
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