Inversion carrier

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View with images and charts Compact Modeling Of Inversion Carrier Effective Mobility For Nano Scale Finfet CHAPTER 1

1.1

Introduction

The invention of the metal-oxide-semiconductor field-effect transistor (MOSFET) in early 1960’s broke the barrier to the large-scale integration (LSI) that the initial integrated circuits (IC) with bipolar transistors could not reach [1]. MOSFET has since then become the fundamental semiconductor component of almost all modern electronic circuits. And the steady dimensional downscaling of the MOSFET has been the main drive of the IC technology and information technology, since shrinking the size especially the distance between the source and drain of a MOSFET means increasing the circuit speed, makes more space available to bringing more transistors on the same area, and reduces the manufacturing cost. As shown in Fig.1.1 [2], the downscaling of the MOSFETs has been kept in pace with Moore’s law quite well, and the number of transistors on a chip has indeed been doubled about every two years. The key dimension that is reduced from one transistor generation to the next is the gate length (LG). However, scaling of conventional MOSFET devices is limited due to short channel effects (SCE), gate insulator tunneling and limited control of doping concentrations. An important short channel effect is the so called Drain Induced Barrier Lowering (DIBL). DIBL becomes more prominent as the length of the device is reduced. DIBL is a secondary effect in MOSFETs referring to a reduction of threshold voltage at higher drain voltages. Due to the higher drain voltage the depletion region between the drain and body increases in size and extends under the gate. Gate tunneling is reduced by using thicker gate oxides of insulators with a higher dielectric constant, the so called high-k materials, which increases the barrier width between the gate and the channel. The short channel effects can also be suppressed by developing multigate devices [3-4]. In a multigate device, the channel is surrounded by several gates on multiple surfaces, so the control over the channel is improved. Various types of multigate devices are under research such as double gate transistors, FinFETs and gate-all-around FETs.


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