100 NM Thick Aluminum Nitrade Based Piezoelectric Nano Switches Exhibiting 1 MV Threshold Voltage via Body-Biasing

This paper reports on the first demonstration of aluminum nitride (AIN) piezoelectric logic switches that were fabricated with ultra-thin (100nm) AIN films and exhibit a 1 mV threshold voltage via the body-biasing scheme. The application of a relatively low (< 6 V) fixed potential to the body terminal of a 4-terminal switch has been cycled to > 109 cycles and, although the contact resistance was found to be high (~ 1 MΩ), the nano-films have functioned throughout to show high piezoelectric nano-film reliability. Disciplines Engineering | Mechanical Engineering Comments Suggested Citation: Chengjie Zuo, Jan Van der Spiegel, and Gianluca Piazza. "1.5-GHz CMOS Voltage-Controlled Oscillator Based On Thickness-Field-Excited Piezoelectric AlN Contour-Mode MEMS Resonators" 2010 IEEE Custom Integrated Circuits Conference (CICC 2010) (2010). ©2010 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. This conference paper is available at ScholarlyCommons: http://repository.upenn.edu/meam_papers/256 100 NM THICK ALUMINUM NITRIDE BASED PIEZOELECTRIC NANO SWITCHES EXHIBITING 1 MV THRESHOLD VOLTAGE VIA BODY-BIASING Nipun Sinha 1* , Zhijun Guo 1 , Valery V. Felmetsger 2 and Gianluca Piazza 1 1 University of Pennsylvania, Philadelphia, Pennsylvania, USA 2 Tegal Corporation, San Jose, California, USA ABSTRACT This paper reports on the first demonstration of aluminum nitride (AlN) piezoelectric logic switches that were fabricated with ultra-thin (100nm) AlN films and exhibit a 1 mV threshold voltage via the body-biasing scheme. The application of a relatively low (< 6 V) fixed potential to the body terminal of a 4-terminal switch has resulted in a repeatable threshold voltage of 1 mV. The nanoswitch has been cycled to > 10 cycles and, although the contact resistance was found to be high (~ 1 MΩ), the nano-films have functioned throughout to show high piezoelectric nano-film reliability.This paper reports on the first demonstration of aluminum nitride (AlN) piezoelectric logic switches that were fabricated with ultra-thin (100nm) AlN films and exhibit a 1 mV threshold voltage via the body-biasing scheme. The application of a relatively low (< 6 V) fixed potential to the body terminal of a 4-terminal switch has resulted in a repeatable threshold voltage of 1 mV. The nanoswitch has been cycled to > 10 cycles and, although the contact resistance was found to be high (~ 1 MΩ), the nano-films have functioned throughout to show high piezoelectric nano-film reliability. INTRODUCTION With the continuous scaling of the transistor the CMOS industry has recognized the emergence of some key problems that are proving to be serious obstacles to further miniaturization. Some of the major hurdles that need to be overcome involve the source-to-drain leakage in the standby state, the gate leakage because of ultra-thin dielectric layers, the inability to reduce operating power, the variation of threshold voltages over a wafer and the increasing effect of parasitics on the device performance. With miniaturization, transistors have become faster, but the gain in speed has come at a penalty in terms of standby power consumption. Also, with the CMOS transistors already switching in less than few nanoseconds, power is becoming a more relevant aspect to consider than speed. Keeping all these factors in mind the International Technology Roadmap for Semiconductors (ITRS) [1] has emphasized the need to develop alternate devices, like NEMS switches, that will consume less power in the standby state and will help in minimizing the transistor operating voltages. Mechanical switches have been a topic of research and investment for few decades. They have nearly zero standby leakage due to the presence of an air gap between the source and the drain terminals. In addition, they are characterized by a very sharp transition between their standby and on states. This transition is not governed, as in a semiconductor, by the modulation of carriers in the channel, but by the actual mating of contacts due to mechanical motion. Therefore, mechanical switches exhibit a subthreshold slope that is orders of magnitude lower than that of CMOS devices. Because of these characteristics they are the ideal candidate to lower power consumption in the standby state and operating voltages. Most of the mechanical switches developed to date have utilized electrostatic [2-3], magnetic [4], thermal [5] or piezoelectric [6-9] actuation mechanisms. These mechanical switches have not been commercialized on a large scale as they are not as reliable and as fast as the semiconductor transistors. Micromechanical switch reliability has been limited by the very stringent requirements on the on-resistance as dictated by radio frequency (RF) applications (i.e. few Ohm of contact resistance), which have so far been the most attractive for microswitches. When we consider the same devices for implementation of mechanical computing/logic, the main design challenge resides not in the loss due to the contact resistance but the speed of operation. According to these new guidelines a mechanical switch can operate with contact Figure 1: SEM of a nano-film based three-finger dual-beam AlN switch illustrating the source, drain, gate and body bias terminals. This nano-switch is being termed as a Mechanical Transistor. The figure above also shows its similarity with a Semiconductor Transistor shown on the right of the figure. Body Drain Gate Source