Germanium CMOS potential from material and process perspectives: Be more positive about germanium

Hall-effect measurements of n-channel MOS devices were used to determine the main scattering mechanisms limiting mobility in SiC MOSFETs. MOS-gated Hall characterization, which was performed as a function of gate bias and body bias, indicates that surface-roughness scattering and Coulomb scattering are the main scattering mechanisms limiting electron mobility in SiC MOSFETs at room temperature. A charge-sheet model, including incomplete ionization and Fermi-Dirac statistics, is used to calculate the surface electric fields in order to develop an expression for surface-roughness scattering. In the samples used for this paper, at electron sheet densities less than 1.8times1012 cm-2, Coulomb scattering dominates, while surface roughness is dominant at higher sheet densities.

Electron-Scattering Mechanisms in Heavily Doped Silicon Carbide MOSFET Inversion Layers

Computations of scattering rates from strain variations in high‐mobility n‐channel Si/SiGe heterostructures are presented, and the results compared with experiment. Two sources of strain variation are considered—interface roughness and misfit dislocations—both of which form to relieve strain in the Si channel layer which is under tension. Strain variations induced by interface roughness are demonstrated to provide a source of scattering which, for highly strained systems of the type considered here, is significantly larger than conventional geometrical roughness scattering. Misfit dislocations provide a source of localized scattering centers, and an appropriate formalism is developed to describe this case. For both types of scattering, reasonable agreement with measured mobilities is found for various values of channel thickness.

Scattering from strain variations in high‐mobility Si/SiGe heterostructures

The roughness at the metal/gate oxide interface of metal‐oxide‐semiconductor field‐effect transistor (MOSFET) has been modeled. The mobility of electrons inside the channel of the MOSFET, limited by the scattering resulting from this roughness, has been calculated. The magnitude of this scattering mechanism is a strong function of the oxide thickness. For a MOSFET with very thin gate oxide (<100 A), this limiting mobility may become comparable to the total mobility, and the scattering of electrons by the remote interface roughness can no longer be ignored.

Kazushige Matsumoto

Papers

Effect of Thin Oxide Film on Breakdown Voltage of Silicon N+P Junction