Nanoscience and Nanoengineering 3(2): 19-24, 2015 http://www.hrpub.org DOI: 10.13189/nn.2015.030202 Quantum Effects Investigation in 20 nm Gate Underlap SOI MOSFET for Millimeter Wave Applications Indra Vijay Singh 1,* , M.S. Alam 2 1 Department of Electronics & Communication Engineering, School of Engineering & Technology, ITM University Gwalior, India 2 Department of Electronics Engineering, Aligarh Muslim University, India Copyright © 2015 by authors, all rights reserved. Authors agree that this article remains permanently open access under the terms of the Creative Commons Attribution License 4.0 International License Abstract This paper presents the investigation of quantum effects of gate underlap 20nm Silicon-On-Insulator (SOI) MOSFETs at 60 GHz. At optimized spacer s = 0.8LG with doping gradient d = 5nm/decade the device DC and AC performances have been investigated with and without quantum effects. After incorporation of quantum effects, at 60 GHz the device current gain, unilateral gain (ULG) and device intrinsic gain are found 50 dB, 70 dB and 36dB respectively at power consumption 0.6 mW. All these parameters have been extracted using 2D ATLAS device simulator. The average 50% performance of device has been increased after incorporating quantum effects model. Although simulated result for current gain nearly 25% higher than measured data (gate length L G = 20nm) whereas for transit frequency f T is differ (>13%). However, these comparisons with limited measured data suggest the possibility of use of this device technology in the design of key blocks like low noise amplifier (LNA) and Mixer for mm-w applications. Keywords Quantum Effects, Underlap, Silicon-On-Insulator, Millimeter Wave 1. Introduction In the past few years, low-power low-voltage silicon-on insulator (SOI) MOSFET technology has emerged as a leading candidate for highly integrated circuits for wireless applications [1]. However, below the 20 nm technology node, upcoming CMOS technologies face many technological challenges, the most crucial being the short channel effects (SCEs) that tend to degrade sub threshold characteristics and increase leakage current because of quantum effects [2]. The influence of film-thickness reduction on the threshold voltage of single and double-gate SOI MOSFETs has been reported in the literature [3]. It is found that, due to quantum confinement of carriers in a thin silicon layer, the minimum energy for electrons in the conduction band increases when the thickness of the silicon film is reduced [4]. As a result, the threshold voltage increases as the film thickness is reduced. This effect was first predicted by Omura et al. in 1993, and has been simulated and observed experimentally by several groups since [5]. It is included in modern thin-film SOI and double-gate MOSFET simulators [6]. In this paper, we report a similar effect in n-channel single gate underlap fully depleted SOI MOSFETs. The threshold voltage increases when the cross section of the device is decreased—due to quantum-confinement effects. Furthermore, the minimum energy for the electrons in the conduction energy sub-bands increases with the electron concentration, which dynamically increases the threshold voltage as the inversion charge builds up [7-8]. This effect reduces the current drive of the device and is not predicted by classical simulators. That’s for solving such a problem we need to add a self-consistent Poisson–Schrödinger solver for more explanation about that has been given in section-2. The effects of quantum at high frequency (> 60 GHz) has been observed and discussed in section-4. 2. What is Quantum Effects? To adequately predict quantum effects due to the formation of energy sub bands, it is necessary to solve the Poisson equation and the Schrödinger equation self-consistently [9]. The Poisson equation is given by. ∇ 2 Φ (, )= −    [(, ) − (, )+   −   ] (1) in the silicon and the silicon dioxide ∇ 2 Φ(, )=0 (2) In these equations, Φ, p, n, N D , and N A are the potential (V), hole concentration (m −3 ), electron concentration (m −3 ), donor atom concentration (m −3 ), and acceptor atom concentration (m −3 ), respectively. The doping impurity concentrations, N A and N D , are considered to be constant. The Schrödinger equation is written.