He Ming Zhang

Highly Strained Silicon Nitride Thin Film Deposited by PECVD with Double Frequencies in Strained Silicon Technologies

The mechanism of high stress in silicon nitride thin film is studied systematically in this paper. The effects of the various process parameters on the stress in silicon nitride thin film deposited by PECVD are analyzed and discussed. The silicon nitride thin film with high compressive and tensile stress has been deposited on the optimized process parameters and the compressive and tensile stress are up to-1.38GPa and 866MPa, respectively. Finally, the method of further improving the stress in silicon nitride thin film is presented.

Electron Mobility Model for Strained-Si/(001) Si1-XGex

There has been much interest in the Si-based strained technology lately. The improvement of strained-Si device performance is due to the enhancement of the mobility, so the further study on mobility is essential in both theory and practice aspects. In this paper, an analytical model of the electron mobility of strained-Si material, such as biaxial tensile strained-Si material grown on relaxed Si1-xGex (0≤x≤0.6) substrates, as a function of strain and different orientations is obtained. The results show that the electron mobilities for [100] and [010] orientations increase rapidly with increasing Ge fraction x, and there is no electron mobility enhancement for [001] orientation in comparison to relaxed Si material.

Effect of High-K Material on Gate Threshold Voltage for Double-Gate Tunnel FET

The effect of high-k material on gate threshold voltage for double gate tunnel field-effect transistor (DG-TFET) is studied in this paper. By physically derived the model of threshold voltage for DG-TFET, the quantitative relationship between threshold voltage and gate length is also discussed. It is shown that the proposed model is consistent with the simulation results, and can also easily predict the improved performance on the gate threshold voltage when using high-κ dielectrics and the limited effect on gate threshold voltage when changing the gate length.

Model of Closed-Loop Detection System for Capacitive MEMS Accelerometer and its IC Realization

A type of closed-loop system model for capacitive MEMS accelerometer, with simple working clock , is presented in this paper. After establishing the force-feedback model and disgussing the magnitude of the feedback voltage, the readout interface IC for closed-loop detection is designed and the layout area of the ciruit is only 1435×2543 um2. Post simulation results indicated that the circuit has large detection range, high accuracy and linearity, giving evidence for the validity of our model.

Intrinsic Carrier Concentration in Strained Si1-XGex/(101)Si

The intrinsic carrier concentration is the important parameter for researching strained Si1-xGex materials properties and evaluating Si-based strained devices parameters. In this paper, at the beginning of analyzing the band structure of strained Si1-xGex/(101)Si, the dependence of its effective densities of states for the conduction and valence bands (Nc, Nv) and its intrinsic carrier concentration (ni) on Ge fraction (x) and temperature were obtained. The results show that ni increases significantly due to the effect of strain in strained Si1-xGex/(101)Si. Furthermore, Nc and Nv decrease with increasing Ge fraction (x). In addition, it is also found that as the temperature becomes higher, the increase in Nc and Nv occurs. The results can provide valuable references to the understanding on the Si-based strained device physics and its design.

Research on Accumulation PMOS Capacitors Based on Strained-Si/SiGe Material

This paper presents a physical-based model for accumulation PMOS capacitor based on strained-Si/SiGe material. With this model, the physical mechanism of the “plateau”, observed in accumulation region of the C-V characteristics of the strained-Si(SSi)/SiGe PMOS capacitor, is studied. The results from the model show excellent agreement with the experimental data. The proposed model can provide valuable reference to the strained-Si device design and has been implemented in the software for extracting the parameter of strained-Si MOSFET.

Research on Electron Mobility Model for Tensile Strained-Si(101) with Properties of Semiconducting Materials

Abstract. Mobility is one of the most important properties of semiconductor material, and it has a great impact on the property of MOS devices.In this paper, the influence of ionizing impurity scattering, acoustic phonon scattering and intervalley scattering to strained-Si(101) material is discussed.In addition, a calculation of the electron mobility in Strained-Si(101) material is made using the average momentum relaxation time method described in Ref[1]. The results show that the electron mobility increases gradually for both [001] and [100] orientations while for [010] orientation increases rapidly with the increasing Ge fraction x.

Electron Mobility Model of Strained Si1-xGex(001)

Solving the Schrödinger equation with strain Hamiltonian and combining with KP theory, we obtained the conductivity effective mass and density of states effective mass of strained Si1-xGex(001) in this paper. On the basis of conductivity effective mass and density of states effective mass, considered of Fermi golden rule and Boltzman collision term approximation theory, scattering rate model was established in strained Si1-xGex(001). Based on the conductivity effective mass and scattering rate models we discussed the dependence of electron mobility on stress and doping concentration in strained Si1-xGex(001), it shows that electron mobility decrease with the increasing of stress and doping concentration. This result can provide valuable references to the research of electron mobility of strained Si1-xGex materials and the design of devices.

Effect of Alloy Disorder Scattering on Electron Mobility Model for Strained-Si1-xGex/Si (101)

Si-based strained technology is currently an important topic of concern in the microelectronics field. The stress-induced enhancement of electron mobility contributes to the improved performance of Si-based strained devices. In this paper, Based on both the electron effective mass and the scattering rate models for strained-Si1-xGex/Si (101), an analytical electron mobility model for biaxial compressive strained-Si1-xGex /Si (101) is presented. The results show that the stress doesn’t make the electron mobility increased, but the electron mobility for [100] and [001] orientations decrease with increasing Ge fraction x, especially for [010] orientation expresses a sharp decrease. This physical phenomenon can be explained as: Although the applied stress (the higher the Ge fraction, the greater the applied stress) can enhance the electron mobility, alloy disorder scattering rate markedly increase. Overall the electron mobility decreases instead. The above result suggests that not all the mobilities for Si-based strained materials enhance with the stress applied. For the biaxial strained-SiGe material represented by Ge fraction, the effect of alloy disorder scattering on the enhancement of mobility must be concerned. The result can provide theoretical basis for the understanding of the improved physical characterizations and the enhanced mobility for Si-based strained materials.

Anisotropic Hole Mobility in Strained Si1-xGex/(001)Si

Applying KP theory combined with deformation potential we obtained the valence band structure, and based on this result we calculated the orientation-dependent effective mass which is also called conductivity effective mass in strained Si1-xGex/(001)Si in this research, and furthermore ,we established the scattering rate model by using the density-of-states effective mass. On the basis of conductivity effective mass and scattering rate model, utilizing analytical method and relaxation time approximation we obtained the dependence of the value of hole mobility on stress and doping concentration in strained Si1-xGex/(001)Si along different crystal orientations. Compare to the unstrained Si, the anisotropy of hole mobility is more obvious in strained Si1-xGex/(001)Si, for example, It shows that under the same stress and doping concentration (Ni=1x1014cm-3, x=0.4), the value of hole mobility along [010] crystal orientation is visibly higher than other crystal orientations. This result can provide valuable references to the research of hole mobility of strained Si1-xGex materials and the design of devices.