Using an Insulator-Metal Transition to Overcome the Fundamental Limits of Non-Volatile Memory Based on Ferroelectric Field Effect Transistors

University Of Virginia Main Campus, Charlottesville VA

Investigators

Abstract

Nontechnical: The era of Big Data is creating enormous challenges to computing systems and networks. As the computing infrastructure evolves to meet these challenges, memory technology plays an increasingly important role. Over one hundred Zeta Bytes of data is expected to be generated annually by the year 2025. Future generations of computers will therefore need high performance memory that is fast, energy efficient, reliable, and compact. While existing technologies have some of the desired properties, they crucially lack others. For example, ferroelectric field effect transistors (FETs) based on hafnium oxide, a recently discovered material, exhibit very promising properties. They are persistent, retaining information even when turned off, have nanosecond switching speeds, and a small footprint. However, practical realization of this technology is impeded by fundamental issues which compromise reliability and constrain the operation of devices at low voltages. The proposed research aims at addressing this challenge by integrating a new functional material into ferroelectric FETs. Vanadium dioxide exhibits an insulator-to-metal phase transition, allowing it to be switched back and forth between an insulating and conductive states. This property will used to overcome the fundamental barriers associated with existing materials and enable a memory technology that significantly exceeds the performance of the current state-of-the-art. The project provides a natural platform for participating students to be involved in cross-disciplinary research at the intersection of electrical engineering and materials science. Outreach efforts will expose undergraduates and high school students to modern electronics, and broaden their experience and understanding of the opportunities in the area. Technical: This research project aims to overcome the fundamental design trade off involved in writing to, and reading from doped hafnium oxide ferroelectric field effect transistor-based non-volatile memory by replacing the conventional silicon channel of the transistor with an insulator-metal phase transition oxide, VO2. The ferroelectric state dependent abrupt resistance switching across the phase transition in VO2 that will be engineered in this device, will help de-convolute the read and write constraints, and enable the memory cell to be written at low voltages without adversely affecting the read margin, as well as also improve the reliability. A fundamental aspect of this research will focus on stabilizing the ferroelectric phase of doped hafnium oxide on the VO2 under a constrained thermal budget. Furthermore, through a materials-device co-design approach, the project will seek to experimentally demonstrate a ferroelectric transistor-based memory that can operate at a low write voltage and energy, provide large read distinguishability, and exhibit large endurance and reliability. Physics based models and simulations that capture the operation of the device as well as account for its compatibility with array level operation will be developed to support and guide the experimental effort. The results of the proposed research stand to have immense implications towards realizing a universal memory to support and accelerate the data revolution. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.