Strain Effects in p-type Devices using Full-Band Monte Carlo Simulations

Abstract

The particle-based Monte Carlo (MC) technique is acknowledged as a powerful method for accurately describing the carrier transport in semiconductor materials and devices within the semi-classical approximation, i.e. the Boltzmann transport equation (BTE) for the distribution function. It has been developed by many groups to study a wide variety of transport problems in many kinds of devices, to such a point that it is impossible to summarize here the most significant examples of its applications. The accuracy of the semiclassical transport description is then given by the models used for the band structure and the scattering mechanisms. Hole transport properties in realistic Si devices are particularly affected by the strong anisotropy of the valence band (Thomson et al., 2006), which is further increased by the presence of strain. Analytic approximations fail to describe the valence band structure of Si, and an accurate or « full » description of the energy dispersion is then needed to describe hole transport correctly. In this work, the valence band structure is calculated thanks to a stress-dependent 30-band k.p model (Rideau et al., 2006). With this accurate valence band description, « Full-Band » Monte Carlo simulation becomes an appropriate tool to study various (unstrained or strained) p-type devices. Beyond the description of the model in Section 2, we show here two typical examples of application of the full-band Monte simulator to strain effects in p-type devices. In Section 3, the influence of mechanical stress on Double Gate p-MOSFET performance is be investigated. Multiple gate structures are now recognized as promising architectures to overcome short channel effects in nanometer scaled MOSFET. Double Gate MOSFETs (DGMOS) are found to reach the best performance among SOI-based transistors (Saint Martin et al., 2006). In addition, mechanical stress is used as a technological performance booster for CMOS technology. The impact of stress on carrier transport is then of great importance and is both studied experimentally (Huet et al., 2008 ; Suthram et al., 2007) and theoretically (Huet et al., 2008a; Bufler et al., 2008; Pham et al., 2008). In this work, device performance of strained Si p-DGMOS is studied considering uniform biaxial and uniaxial stresses in the channel. The effect of strain is analyzed via some of the main usual figures of