Abstract
Title: Resolving individual impurities in statistical variability simulations
One of the problems involved in performing the device simulation of random-dopant-fluctuation (RDF) is the formation of steep and short-range electric potential around a discrete impurity atom by the Poisson solver. Extremely fine meshing around the impurity atom enhances the singular steepness of potential, which sometimes forces us to adjust the impurity-limited mobility unphysically higher than the well-known bulk values. The treatment to stabilize the singularity is to decompose an impurity potential into long- and short-range components and the latter components are eliminated in the Poisson equation, as is already proposed in Ref. [1]. Only the long-range components representing smoothly varied band-edge are dealt with in the Poisson solver, while the short-range components representing impurity scattering potential are taken into consideration in the impurity mobility model as a function of doping concentration.
Since the application examples using the above-mentioned long-/short-range separation model are not so widely known, the purpose of this talk is to present our recent results of RDF simulation by our in-house drift-diffusion simulator. The focus will be on Si devices of various situations: NAND flash memories [2], Schottky contact resistances [3], and so on. It is worthwhile to mention that the general use of density-gradient model for RDF simulation is also regarded as one of the approaches to eliminate the short-range components. Some results comparing the long/short-range separation model with the density-gradient model will also be discussed.
[1] N. Sano et al., IEDM Tech. Dig., 275 (2000). [2]. M. Mizukami et al., Jpn. J. Appl. Phys. 49, 04DD09 (2010). [3]. K. Matsuzawa et al., Proc. of SISPAD, 231 (2004).
Bios
Shuichi Toriyama received his B. S. and M. S. degrees in electronic engineering from the University of Tsukuba, Ibaraki, Japan, in 2002 and 2004, respectively. He joined the Toshiba Research and Development Center at Yokohama, Japan, in 2004, where he is currently working on the development of physical models for device simulation. In 2009, he received the Ph. D. degree in electronic engineering from the University of Tsukuba.