Monolithic 3D Stacked Carbon Nanotube/Indium–Tin–Oxide Complementary Transistors for High-Frequency Logic and Sense Amplifier Integration with Memory

Abstract

Complementary field-effect transistors (CFETs) maximize 3D integration density but face two fundamental bottlenecks: the stringent thermal budget of silicon-based sequential stacking and the inherent electrical mismatches in homogeneous material systems. To overcome these challenges, we demonstrate a monolithic 3D-stacked heterogeneous CFET architecture integrating back-end-of-line (BEOL)-compatible p-type carbon nanotube (CNT) and n-type indium–tin–oxide (ITO) channels. Both materials exhibit high carrier mobility and low-temperature process, which simultaneously resolve the bipolar transport disparity and mitigate thermal degradation. Consequently, the resulting CFET inverters exhibit favorable statistical uniformity and symmetric transfer characteristics, enabling the fabrication of versatile logic gates. Besides, a 5-stage ring oscillator (RO) achieves a high frequency of 334 MHz, with a 0.3 ns stage delay, demonstrating potential applications of CFET in high-speed digital circuits. Furthermore, bridging logic and memory, a CFET-based sense amplifier (SA) is integrated with an ITO-based planar capacitorless (2T0C) dynamic random-access memory (DRAM) cell. This hybrid system achieves data write/read operations and signal amplification, providing an architectural platform for next-generation ultradense 3D logic and memory systems.