Monolithic 3D integration of back-end compatible 2D material FET on Si FinFET

Abstract

The performance enhancement of integrated circuits relying on dimension scaling (i.e., following Moore’s Law) is more and more challenging owing to the physical limit of Si materials. Monolithic three-dimensional (M3D) integration has been considered as a powerful scheme to further boost up the system performance. Two-dimensional (2D) materials such as MoS2 are potential building blocks for constructing upper-tier transistors owing to their high mobility, atomic thickness, and back-end-of-line (BEOL) compatible processes. The concept to integrate 2D material-based devices with Si field-effect transistor (FET) is technologically important but the compatibility is yet to be experimentally demonstrated. Here, we successfully integrated an n-type monolayer MoS2 FET on a p-type Si fin-shaped FET with 20 nm fin width via an M3D integration technique to form a complementary inverter. The integration was enabled by deliberately adopting industrially matured techniques, such as chemical mechanical planarization and e-beam evaporation, to ensure its compatibility with the existing 3D integrated circuit process and the semiconductor industry in general. The 2D FET is fabricated using low-temperature sequential processes to avoid the degradation of lower-tier Si devices. The MoS2 n-FETs and Si p-FinFETs display symmetrical transfer characteristics and the resulting 3D complementary metal-oxide-semiconductor inverter show a voltage transfer characteristic with a maximum gain of ~38. This work clearly proves the integration compatibility of 2D materials with Si-based devices, encouraging the further development of monolithic 3D integrated circuits.

Van der Waals polarity-engineered 3D integration of 2D complementary logic

“…However, application-wise, 3D integrated circuits of 2D semiconductors have largely been restricted due to the difficulty in obtaining controllable doping of n-and p-type polarities, which is fundamental for complementary logic 34 . To date, a limited number of examples have been realized in vertical complementary field-effect transistors (CFETs) constructed using 2D semiconductors, such as mixed-dimensional heterostructures 4,5 and hetero-2D layers with different carrier polarities [6][7][8] , among which a maximum of two vertical layers of complementary logic has been demonstrated. Indeed, while n-type 2D semiconductors are advancing rapidly in terms of electrical performance 39,40 , only a handful of p-doping strategies are known for 2D semiconductors such as WSe 2 (refs.…”

Two-dimensional materials for future information technology: status and prospects

“…The integration of h-BN memristors into the BEOL interconnects of the microchip through low-temperature processes demonstrated superior electrical characteristics compared to similar devices connected to 2D material-based transistors by several orders of magnitude. Furthermore, the current BEOL hybrid integration of 2D materials with CMOS also includes scalable research achievements in logic circuits [1028,1029], memories [1030], biosensors [1031], gas sensors [1032], and microphones [1033]. The high performance and relatively advanced technological level achieved in these studies represent significant progress and enormous potential in the heterogeneous integration of 2D materials into existing silicon lines.…”

Submicron Memtransistors Made from Monocrystalline Molybdenum Disulfide

“…Two-dimensional (2D) transition-metal dichalcogenides (TMDs) such as monolayer molybdenum disulfide (MoS 2 ) possess atomically thin thicknesses, high carrier mobility, and high on/off current ratios, making them a potential alternative for channel materials in transistors. These properties also make 2D TMDs a promising avenue for extending the scaling limit and breaking through Moore’s law. , In addition to logic devices, 2D TMDs hold great promise for memory devices owing to effective electrostatic control of band structures . Extensive 2D material memory research has focused on memristors, which are two-terminal passive electronic devices possessing a nonlinear relationship between the resistance and the electrical charge passing through the device .…”

“…These properties also make 2D TMDs a promising avenue for extending the scaling limit and breaking through Moore's law. 4,5 In addition to logic devices, 2D TMDs hold great promise for memory devices owing to effective electrostatic control of band structures. 6 Extensive 2D material memory research has focused on memristors, which are two-terminal passive electronic devices possessing a nonlinear relationship between the resistance and the electrical charge passing through the device.…”