Ab-Initio Pseudopotential Calculations of Boron Diffusion in Silicon

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First-principle calculations of formation and migration energies of dopant atoms and native defects in semiconductors are a very useful input to improve semiconductor process simulations One example of this is the widely accepted first-principles model for B diffusion and clustering in Si by Zhu et. al. that is used by numerous groups to predict the transient enhanced diffusion (TED) after B implantation. The recent coupling of the nudged elastic band method with first-principles metods resuls in a powerful tool which allows a more sstematic and reliable search for diffusion paths and migration barriers. Using such a method, we study the diffusion of B in Si once again and find qualitatively new diffusion mechanisms with lower barriers. Two examples for our results are new paths for the kick-out process from a B-interstitial complex to a hexagonal B site and for B diffusion from one hexagonal site to another, sown in Figs. 1 and 2. These events are part of the kick-out mechanism described in earlier work. We also find the consideration of the different charge states of B and interstitial atoms to be essential for the calculation of binding and migration energies. The implications of the new diffusion mechanisms on modeling on the macroscopic scale and the prediction of junction depths and B activation in future technologies will also be discussed.

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Journal: TechConnect Briefs
Volume: Technical Proceedings of the 1999 International Conference on Modeling and Simulation of Microsystems
Published: April 19, 1999
Pages: 369 - 372
Industry sector: Sensors, MEMS, Electronics
Topic: Modeling & Simulation of Microsystems
ISBN: 0-9666135-4-6