IWCE10 October 24 27 2004 Indiana USA Analysis

IWCE-10 October 24 -27, 2004, Indiana USA Analysis of Strained-Si Device including Quantum Effect Fujitsu Laboratories Ltd. Ryo Tanabe Takahiro Yamasaki Yoshio Ashizawa E-mail : tanabe. ryou@jp. fujitsu. com 1 Hideki Oka

Background tensile strain ns compressive strain te y ile st ra i n z x Gate Source Strained Si Drain Strained Si is studied and used aggressively as one of “Technology Booster” Si. Ge buffer layer Si Substrate Is the merit of strain kept with scaling ? ・Quantum Effect ・Ballistic Transport The necessity of Strained-Si Monte Carlo simulation including quantum effect. 2

The Implementation of Strained Band The first principle band calculation program : PHASE ky, kz direction 2 1. 5 Energy (e. V) Full band Monte Carlo simulator : FALCON 2. 5 1 0. 5 kx direction 0 0 Full band structure of Strained Si 0. 2 0. 4 k 0. 6 0. 8 Band structure of conduction band near X point with 50% expansion of ky, kz direction. kz Monte Carlo Analysis We linked the first principle band calculation program to the FUJITSU ensemble full band Monte Carlo simulator FALCON directly 3 1 ky kx

Evaluated Structure ・We calculated below Lg=50 nm. ・We used Double Gate structure. 4 Lg=40 nm Tsoi=10 nm Tox=1 nm Phonon, Impurity and Surface Roughness scattering

Id-Vg@Vd=0. 05 V ・Drain current is saturated at Ge=20% 5

Id-Vg@Vd=0. 8 V ・Drain current is not saturated. 6

Valley Distribution 2 fold 1 Vd=0. 05 V Vd=0. 2 V Vd=0. 4 V Vd=0. 6 V Vd=0. 8 V Vd=1. 0 V 0. 9 0. 8 0. 7 0. 6 4 fold② 0. 5 4 fold① 0. 4 0. 3 0. 2 0. 1 0 2 fold 7 4 fold① 0% 4 fold② 2 fold 4 fold① 30% 4 fold②

The Introduction of Quantum Effect ・We implemented quantum effect by Bohm Potential method Scattering V(r) Eq. (1) V * (r) Eq. (2) E(r) t < tmax 8 ・・・(1) ・・・(2) V(r)：Potential V*(r)：Quantum Corrected Potential E(r)：Electric Field

The Comparison with Schrödinger-Poisson Gate Oxide 9 L=40 nm Vg=0. 8 V, Vd=0 V

Id-Vd@Vg=0. 8 V 10

The Comparison of Scattering Strain Effect Including quantum effect 11 Quantum Effect

Ballistic Rate and Ion Improvement ・Ballistic particles exceed 50% at L=10 nm. ・Both ballistic rate and Ion improvement with quantum effect are larger than with classical. 12

The Comparison of Electron Velocity Source region Vg=Vd=0. 8 V 6. 0 E+07 L=5 nm x=0. 3 x=0 Electron Velocity (cm/sec) L=10 nm 4. 0 E+07 L=20 nm L=40 nm 2. 0 E+07 0. 0 E+00 -30 13 -20 -10 0 10 Position along the channel (nm) 20 30

Summary • We linked the first principle band calculation program to full-band MC simulator directly. • We implemented Bohm Potential Quantum correction model and analyzed Strained-Si device including quantum effect. • As gate length is scaled down, Ion improvement by strain effect will decrease, but In the regime that ballistic transport is dominant (about below 10 nm), strain effect will increase again due to increasing injection velocity from source region. 14