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Simulation of Transient Enhanced Diffusion in Silicon Taking into Account Ostwald Ripening of Defects

Masashi Uematsu NTT Basic Research Laboratories, 3-1 Morinosato-Wakamiya, Atsugi, 243-0198, Japan ABSTRACT The transient enhanced diffusion (TED) of high-dose implanted P is simulated taking into account Ostwald ripening of end-of-range (EOR) defects. First, we integrated a basic diffusion model based on the simulation of in-diffusion, where no implanted damages are involved. Second, from low-dose implantation, we developed a model for TED due to {311} self-interstitial (I) clusters involving Ostwald ripening and the dissolution of {311} clusters. Third, from medium-dose implantation, we showed that P-I clusters should be taken into account, and during the diffusion, the clusters are dissolved to emit self-interstitials that also contribute to TED. Finally, from high-dose implantation, EOR defects are modeled and we derived a formula to describe the time-dependence for Ostwald ripening of EOR defects, which is more significant at higher temperatures and longer annealing times. The simulation satisfactorily predicts the TED for annealing conditions, where the calculations overestimate the diffusion without taking Ostwald ripening into account.

INTRODUCTION The transient enhanced diffusion (TED) of dopants in silicon is a central issue in silicon device processing because TED is a limiting factor in the scaling down of device size [1]. End-of-range (EOR) defects form at the amorphous/crystalline (a/c) interface following amorphizing implantation [2]. EOR defects act as both a sink for and source of self-interstitials (I), depending on temperature and annealing time, and hence affect TED. In addition, Ostwald ripening of EOR defects reduces their efficiency as a source of self-interstitials, which further complicates TED. In this study, TED of high-dose implanted P is simulated taking into account Ostwald ripening of EOR defects. Our simulation is integrated step-by-step so that the simulation is done in a unified manner with a reduced number of variables and parameters, because diffusion of high-concentration P in Si during post-implantation annealing is a complex phenomena and the simulation tends to include many variables and parameters. The present simulation is started with integrating a basic diffusion model based on in-diffusion, where no implantation damages are involved. Then, diffusion after low-dose implantation is simulated and we develop a model for {311} self-interstitial clusters with Ostwald ripening and the dissolution of the clusters. In addition, we show that electrically inactive and immobile P-I clusters should be taken into account for a consistent simulation for medium-dose implanted P. Finally, from high-dose implantation, a model for EOR defects with Ostwald ripening is developed. We show that the simulation satisfactorily predicts the diffusion of high-dose implanted P and describe the effect of Ostwald ripening of EOR defects on TED. C5.1.1

INTEGRATED DIFFUSION MODEL In order to simulate