Hybrid 2D–CMOS microchips for memristive applications

Abstract

Exploiting the excellent electronic properties of two-dimensional (2D) materials to fabricate advanced electronic circuits is a major goal for the semiconductor industry1,2. However, most studies in this field have been limited to the fabrication and characterization of isolated large (more than 1 µm2) devices on unfunctional SiO2–Si substrates. Some studies have integrated monolayer graphene on silicon microchips as a large-area (more than 500 µm2) interconnection3 and as a channel of large transistors (roughly 16.5 µm2) (refs. 4,5), but in all cases the integration density was low, no computation was demonstrated and manipulating monolayer 2D materials was challenging because native pinholes and cracks during transfer increase variability and reduce yield. Here, we present the fabrication of high-integration-density 2D–CMOS hybrid microchips for memristive applications—CMOS stands for complementary metal–oxide–semiconductor. We transfer a sheet of multilayer hexagonal boron nitride onto the back-end-of-line interconnections of silicon microchips containing CMOS transistors of the 180 nm node, and finalize the circuits by patterning the top electrodes and interconnections. The CMOS transistors provide outstanding control over the currents across the hexagonal boron nitride memristors, which allows us to achieve endurances of roughly 5 million cycles in memristors as small as 0.053 µm2. We demonstrate in-memory computation by constructing logic gates, and measure spike-timing dependent plasticity signals that are suitable for the implementation of spiking neural networks. The high performance and the relatively-high technology readiness level achieved represent a notable advance towards the integration of 2D materials in microelectronic products and memristive applications.

Recent Advances and Future Prospects for Memristive Materials, Devices, and Systems

“…Two-dimensional (2D) layered materials have also been introduced as switching medium in memristors. − The best resistive switching performance for memory and neuromorphic applications has been obtained in multilayer hexagonal boron nitride (h-BN) produced using chemical vapor deposition (CVD). − The reasons are (i) h-BN is an insulator with a band gap ∼6 eV, meaning that it can block current in HRS and reduce energy consumption; and (ii) CVD provides the right amounts of native defects that enable stable RS. , A recent study reported crossbar arrays of small (<0.053 μm 2 ) h-BN memristors with high endurance (>5 × 10 6 cycles), and low energy consumption per state transition (∼1.41 pJ) . It has been studied that the switching occurs by metal penetration from the electrodes , as in ECM.…”

Inkjet-printed h-BN memristors for hardware security

“…1 Among them, the fabrication of solid-state microelectronic devices and circuits made of 2D materials has attracted much attention, as it may be a solution to produce advanced electronic devices and circuits beyond the complementary metal-oxide-semiconductor (CMOS) technology. 2,3 However, most 2D material-based electronic devices consist of prototypes fabricated using methods that are not compatible with wafer-scale circuital technologies, such as mechanical exfoliation of small crystals. 4 Chemical vapor deposition (CVD) is a scalable method to produce large-area 2D materials; however, the CVD method requires the use of high temperatures >850 °C, which impedes the direct growth of the 2D material on wafers containing CMOS circuits.…”

A Researcher’s Perspective on Unconventional Lab-to-Fab for 2D Semiconductor Devices

“…In contrast, 2D materials, such as graphene, TMDs, and other members of the Xene family, excel in the context of scaled up to chip integration and offer enhanced performance. 9 Due to their unique atomic-layer structure, 2D materials possess exceptional electrical, optical, and mechanical properties. Their ultrathin nature allows for precise control over the device dimensions and properties, enabling better performance and more meaningful applications.…”

“…Additionally, the band gap of atomically layer thick non-2D materials, such as Si or GaAs, would be far too large for most electronic applications. In contrast, 2D materials, such as graphene, TMDs, and other members of the Xene family, excel in the context of scaled up to chip integration and offer enhanced performance . Due to their unique atomic-layer structure, 2D materials possess exceptional electrical, optical, and mechanical properties.…”