Modeling Atomistic Ion-Implantation and Diffusion for Simulating Intrinsic Fluctuation in MOSFETs arising from Line-Edge
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Modeling Atomistic Ion-Implantation and Diffusion for Simulating Intrinsic Fluctuation in MOSFETs arising from Line-Edge Roughness Masami Hane, Takeo Ikezawa† , and Tatsuya Ezaki System Devices Research Laboratories, NEC Corporation 1120 Shimokuzawa, Sagamihara 229-1198, Japan, E-mail: [email protected] † NEC Informatec Systems, Ltd. ABSTRACT We have developed new simulation tools to enable more precise design of sub-100nm MOSFETs. Intrinsic fluctuations in the characteristics of these devices occur as part of their statistical nature. Our three-dimensional atomistic approach to both process and device simulations enabled us to examine the coupling effects of the most significant sources of fluctuation, i.e. line-edge-roughness and random discrete dopants, considering practical fabrication processes. INTRODUCTION The use of atomistic approaches to modeling dopant diffusion and activation kinetics has been reported over the last few years [1][2] with the demand for more accurate technology/CAD tools for developing ULSI devices. Attempts were made to improve predictive capability by incorporating ab initio calculations of the energetics of key species in the model, e.g. boron clustering [3]. Simulation of even a full-CMOS process is feasible if the atomistic approach incorporates more practical aspects, such as Fermi-level effects, and more efficient computational tasks for three-dimensional simulation. In this paper, we review our recent demonstration of atomistic process simulation [4][5]. For instance, various spike-annealing experiments can be reproduced using our kinetic Monte Carlo calculation program, considering all possible charged species and Fermi-level effects and incorporating boron diffusion/activation kinetics obtained through ab-initio calculation [8]. We extended this atomistic modeling approach to simulate three-dimensional (3D) MOSFET dopant-distribution profiles. We also developed an atomistic 3D device simulator to evaluate device characteristics associated with these profiles. In the future small-size (sub-100nm) MOSFETs, atomistic positional discreteness of the dopant-distribution will be critical for assessing the intrinsic fluctuations in device characteristics in relation to ULSI applications. Figure 1 summarizes the typical sources of intrinsic fluctuation considered in this work. This paper describes a method for simulating atomistic 3D processes/devices and the results of Monte Carlo statistical simulation of device characteristics fluctuation, considering practical fabrication processes.
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(a)Random-discrete-dopants
(b)Line-edge-roughness
Fixed crystal
Figure 1: Intrinsic fluctuation sources considered in this simulation. (a)Random discrete dopant orientation, distribution. (b)Line edge roughness. Top view
mostly (110).
Halo implantation
MODELING Ion-implantation processes can be simulated using a BCA (binary-collision-approximation) Random crystal -based Monte Carlo program [6]. This program is an in-house code that can be used in simulating orientation appears the
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