The Effect of Atomic Mixing on the Depth Profiles of Metal Markers in Silicon
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THE EFFECT OF ATOMIC MIXING ON THE DEPTH PROFILES OF METAL MARKERS IN SILICON
B. V. KING, D. G. TONN, I.S.T. TSONG, Physics Department, Arizona State University, AND J.
A.
Tempe,
AZ 85287
LEAVITT
Physics Department,
University of Arizona, Tucson,
AZ 85721
ABSTRACT Atomic mixing effects of sputter depth-profiles are modeled by a diffusion theory with a depth-dependent diffusion constant D. The model is compared to SIMS depth profiles, using 5 keV Ar+ bombardment of dilute thin-film multilayers of Al, Ag, Ti and Mo in silicon. The experimental values of D can be explained by cascade mixing and radiation enhanced diffusion within the cascade for Al, Ag and Ti markers but not for the Mo marker. INTRODUCTION During sputter depth-profiling of a solid, a damaged region precedes the analyzed volume. The impurity depth profile measured by SIMS or AES is then different from the true profile. The mixing effect of the impurity profile is due to a combination of prompt processes - cascade and recoil mixing and the delayed process of radiation enhanced diffusion. Isotropic cascade mixing is the dominant material transport process for incident ion energies above about 1 keV in materials in which delayed processes are absent[l]. Isotropic cascade mixing has been modeled by a diffusion equation[2] where the diffusion constant D is related to the nuclear stopping power of the incident ion F the mean square target atom recoil range and effective displacetent energy Ed by O.07FDU S
4MIMT (MI+MT)2
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