Current Variability in Si Nanowire MOSFETs Due to Random Dopants in the Source/Drain Regions: A Fully 3-D NEGF Simulation Study

In this paper, we study the impact of random discrete dopants in the source/drain (S/D) leads on the current variability of a gate-all-around Si nanowire transistor. Due to the strong inhomogeneities of the self-consistent electrostatic potential, a fully 3D real-space nonequilibrium Green's function (NEGF) formalism is used. N-channel transistors with random discrete donors in the S/D regions varying in both numbers and locations have been simulated. We have studied the impact of quasi-bound (QB) states and transmission resonances associated with the attractive potential of the donors on the screening of the impurities and on the current transport. The convergence of the coupled 3D Poisson-NEGF equations for narrow wires with discrete dopants is cumbersome due to the quasi-discrete nature of QB states and resonances of the attractive impurity potential. We present a robust solution strategy dealing with the convergence challenges. Large variations in the on-current and modest variations in the subthreshold slope are observed in the I D-V G characteristics when comparing devices with microscopically different discrete dopant configurations. We have also estimated the access resistance associated with the random dopant regions in the source and the drain leads and find very good agreement with the resistance estimated from the bulk silicon mobility at the same doping concentration.

[1]  Simulation of impurities with an attractive potential in fully 3-D real-space Non-Equilibrium Green’s Function quantum transport simulations , 2008, 2008 International Conference on Simulation of Semiconductor Processes and Devices.

[2]  Ming Zhu,et al.  5 nm gate length Nanowire-FETs and planar UTB-FETs with pure germanium source/drain stressors and laser-free Melt-Enhanced Dopant (MeltED) diffusion and activation technique , 2008, 2008 Symposium on VLSI Technology.

[3]  Donggun Park,et al.  Gate-all-around single silicon nanowire MOSFET with 7 nm width for SONOS NAND flash memory , 2008, 2008 Symposium on VLSI Technology.

[4]  Boundary conditions for Density Gradient corrections in 3D Monte Carlo simulations , 2008 .

[5]  Experimental evidence of ballistic transport in cylindrical gate-all-around twin silicon nanowire metal-oxide-semiconductor field-effect transistors , 2008 .

[6]  Transport in silicon nanowires: role of radial dopant profile , 2008, 0801.1186.

[7]  M. Anantram,et al.  Multidimensional Modeling of Nanotransistors , 2007, IEEE Transactions on Electron Devices.

[8]  A. Asenov,et al.  Nanowire MOSFET variability : a 3 D density gradient versus NEGF approach , 2007 .

[9]  Erratum: “Two-dimensional quantum mechanical modeling of nanotransistors” [J. Appl. Phys. 91, 2343 (2002)] , 2006 .

[10]  A. Asenov,et al.  Simulation Study of Individual and Combined Sources of Intrinsic Parameter Fluctuations in Conventional Nano-MOSFETs , 2006, IEEE Transactions on Electron Devices.

[11]  X. Blase,et al.  Surface segregation and backscattering in doped silicon nanowires. , 2006, Physical review letters.

[12]  D. Munteanu,et al.  Influence of band-structure on electron ballistic transport in silicon nanowire MOSFET's: an atomistic study , 2005, Proceedings of 35th European Solid-State Device Research Conference, 2005. ESSDERC 2005..

[13]  Charles M. Lieber,et al.  One-dimensional hole gas in germanium/silicon nanowire heterostructures. , 2005, Proceedings of the National Academy of Sciences of the United States of America.

[14]  A. Manolescu,et al.  Coherent electronic transport in a multimode quantum channel with Gaussian-type scatterers , 2004, cond-mat/0408435.

[15]  S. Datta.  Quantum Transport: Atom to Transistor , 2004 .

[16]  S. Datta,et al.  Simulating quantum transport in nanoscale transistors: Real versus mode-space approaches , 2002 .

[17]  M. Anantram,et al.  Two-dimensional quantum mechanical modeling of nanotransistors , 2001, cond-mat/0111290.

[18]  Andrew R. Brown,et al.  Increase in the random dopant induced threshold fluctuations and lowering in sub-100 nm MOSFETs due to quantum effects: a 3-D density-gradient simulation study , 2001 .

[19]  D. Frank,et al.  Monte Carlo modeling of threshold variation due to dopant fluctuations , 1999, 1999 Symposium on VLSI Technology. Digest of Technical Papers (IEEE Cat. No.99CH36325).

[20]  R. Landauer,et al.  Conductance viewed as transmission , 1999 .

[21]  Robert Hull,et al.  Properties of Crystalline Silicon , 1999 .

[22]  Gerhard Klimeck,et al.  Single and multiband modeling of quantum electron transport through layered semiconductor devices , 1997 .

[23]  Meir,et al.  Landauer formula for the current through an interacting electron region. , 1992, Physical review letters.

[24]  M. Büttiker.  Symmetry of electrical conduction , 1988 .

[25]  J. C. Inkson.  Many-body theory of solids , 1984 .

[26]  P. Anderson,et al.  Definition and measurement of the electrical and thermal resistances , 1981 .

[27]  R. Landauer.  Electrical resistance of disordered one-dimensional lattices , 1970 .

[28]  A. B. Migdal,et al.  INTERACTION BETWEEN ELECTRONS AND THE LATTICE VIBRATIONS IN A NORMAL METAL , 1958 .