Micromechanical switch and inverter for digital logic integrated circuit

Abstract

In this work, new mechanical switching device, with which can replace MOS transistor, was proposed. As MOS technology is approaching practical scaling limits, it is projected that conventional MOS transistor cannot be scaled beyond 0.05~0.07um in its minimum feature size because of well known semiconductor phenomena, such as hot electron injection, gate oxide tunneling, short channel effects, and sub-threshold leakage. Proposed micro mechanical switching device will satisfy a need for lower power consumption, lower operating voltage, faster switching time, higher electrical reliability beyond MOS transistor’s physical limits. Proposed mechanical switch and inverter, which is the basis of digital logic integrated circuit, were fabricated through two different materials. One is Cu material as structural layer for better current characteristic and the other is poly-silicon material as structural layer for stable and CMOS compatible process. We can find that Cu structure has a little bit of stress and loss by lateral etch, while poly-silicon structure is well formed without stress and loss. Fundamental characteristics of proposed mechanical switch and inverter, which were fabricated through two different materials, were measured and compared. Micro mechanical switch made by Cu material has excellent electrical property and mechanical property. Drain voltage of 0.1V can flow 40mA current. Resonant frequency is 300kHz corresponding to the switching time of 3us. Micro mechanical switch made by poly-silicon material has also excellent ‘ON-OFF’ ratio, i.e. almost zero subthreshold swing (3mV/decade). Voltage transfer curve (VTC) of mechanical inverter was measured. We can find that mechanical inverter has the same as that of CMOS. Measured total noise margin of mechanical inverter is 14V, when $V_{DD}$ is 20V. If we know a unique pull-down voltage, then it will be expected that VTC characteristic is exactly 20V. Consequently, this work shows that mechanical switch...