Experimental Demonstration of $\text{VO}_{2}$ based Lateral/Vertical Devices and Relaxation Oscillator with an Ultra-low Thermal Budget Process

Vanadium dioxide (V02) has been exploited in steep subthreshold slope switches, coupled oscillators for neuromorphic computing, and selectors for RRAM due to its intrinsic insulator to metal phase transition properties. The thin-film synthesis of V02 needs a high-temperature process or long annealing duration, which increases the thermal budget and is difficult to integrate with the back-end of line CMOS technology process. In this work, we use a low thermal budget process to fabricate and characterize both horizontal and vertical V02 devices. In both configurations, V02 devices show voltage induced reversible switching beyond a threshold voltage. The threshold voltage of devices decreases monotonically as a function of decreasing channel length of the devices. The vertical device shows the lowest threshold voltage compared to the horizontal structure due to significantly smaller channel length. Finally, we demonstrate a relaxation oscillator using the fabricated V02 devices which shows stable oscillations over half a million cycles with an oscillation frequency of 1.75 kHz. We also demonstrate voltage-controlled tuning of the oscillation frequency in the range of ~1.3-2 kHz. This demonstration of V02 devices with a low-thermal budget process will be helpful for integrating V02-based phase transition devices with CMOS technology