Welcome to Semiconductor and Device Research labs
A Group of young engineers looking for the next generation of memory technology
Our Research Motivation
•The emerging memory technology has shown great promise as an alternative to conventional non-volatile memory technologies, such as PCM, FeRAM, MRAM, and RRAM.
•Conventional transistors and their tendency to leak when scaled has proved problematic for RRAM arrays leading to a phenomenon known as “Sneak Path Current”. Two terminal selector devices show great potential for replacing transistors in 1T1S cell configuration due to their ultra scalability (~4F2), ease of fabrication, volatile switching and self-complaint nature.
•In this work, asymmetric selector device were developed in the device design structure of Pt (80 nm) / NbOx (5 nm) / Pt (100 nm) using E-Beam deposition.
Current Devices and fabrication
We currently have two device types fabricated. We used E-Beam Fabrication to create a NbOx-based selector device with platinum top and bottom electrodes. The device is a Pt(80 nm) / NbOx (5 nm) / Pt (100 nm) structure
Test Flow
Device Parameters and Metrics
All devices from, 50 µm, 100 µm, and 200 µm sizes (Pt and V) exhibited volatile switching behavior. This is defined by the change in resistance from high to low when applying a sweeping bias.
In our testing, we want to observe how shape, size, and electrode material affect the devices' voltage threshold and
selectivity. So that we may better understand how to improve on these parameters in future devices
Squares VS. Circles: Selectivity and Vth (Pt)
The figures above compare the selectivity and threshold voltages of the square and circular devices for the Platinum 50 µm, 100 µm, and 200 µm size. In both the square and circular devices, we see an improvement in selectivity as the device is scaled up. However, there appears to be little to no correlation between size and threshold voltage.
Platinum VS. Vanadium: Selectivity and Vth
The figure above compares the selectivity and threshold voltage of the Platinum and Vanadium circle devices from the 50 µm, 100 µm, and 200 µm sizes. It can be observed that Platinum has better selectivity than Vanadium and both improve on selectivity with an increase in size. Vanadium has a lower Vth than Platinum
across all sizes. The Vanadium Vth decreases as size increases
Conclusion and Future Work
The volatile behavior of our selector devices show good promise as transistor alternatives in crossbar arrays. Platinum devices exhibit greater selectivity, but vanadium offers a lower Vth for low-power operations. However, both may struggle slightly when scaled since both devices show a decrease in selectivity as the device size is decreased .
The Team
John Hardy
Anna Roux
Tyler Shepherd