Simulation and Modeling of Kinetics of Silicon Oxidation in the thin Oxide Regime
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SIMULATION AND MODELING OF KINETICS OF SILICON OXIDATION IN THE THIN OXIDE REGIME TIRTHANKAR DUTTA and N. M. RAVINDRA Microelectronics Research Center, New Jersey Institute of Technology, Newark, NJ 07102
ABSTRACT Thermal oxidation of Silicon in the thin regime is of vital importance to VLSI device engineers because thin layers of SiO 2 are exclusively used as the gate dielectric for high performance of MOS devices. There exists a number of models to explain this kinetics of oxidation. However there is a considerable variance among the reported rate constants, which are supposed to describe the oxidation process. Rather than arriving at an alternative model, the present study aims at simulation of existing models of oxidation in dry oxygen, with a recent set of experimental data and arrive at the best possible model and provide accurate rate constants for oxidation in dry oxygen. These experimental data have been obtained, earlier, using high-resolution transmission electron microscopy (HRTEM) and ellipsometry techniques to measure thicknesses of silicon oxide, grown at 8000C in dry oxygen, in the thickness range of 2-20 nm.
INTRODUCTION The oxidation of silicon is necessary during the entire process of fabricating modern integrated circuits. The production of high-quality ICs requires not only an understanding of the basic oxidation mechanism, but the ability to form in a controlled and reproducible manner a high quality oxide. Thus the growth of Si0 2 by thermal oxidation has been a critical step in semiconductor processing since the very inception of microelectronics industry. With devices approaching submicron dimensions, production and characterization of highly reliable ultrathin Si0 2 films are assuming major importance in very large-scale integration (VLSI) technology. The thermal oxidation of Si in the thin regime (< 50 nm) is of vital importance to VLSI processing and technology because thin layers of SiO2 are exclusively used as the gate oxides, requiring a low thermal budget, compatible with the rest of the processing steps involved in silicon technology [1]. The oxidation of single-crystal Si is for the most part actually characterized by Deal and Grove model [2] formalism. The major deviation of this model consists of anomalously rapid initial oxidation for the first 20-40 nm of growth in dry 02. The standard linearparabolic formulation accounts for the regime especially by the incorporation of a time constant -t in the expression for oxide growth. Moreover this model is based on arguable physical assumptions e.g steady state is possible in solid state diffusion, and linear and diffusion specific rate constants can be rate limiting at the same time. Extensive research efforts have been devoted to the study of this initial regime and number of different forms and mechanisms have been suggested. Rather than arriving at a new model, this paper aims at reviewing the current models and arrive at a relationship, which best describes the initial regime during oxidation in dry oxygen, in the light of the Ma
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