Perspective of 2D Integrated Electronic Circuits: Scientific Pipe Dream or Disruptive Technology?

Abstract

Within the last decade, considerable efforts have been devoted to fabricating transistors utilizing 2D semiconductors. Also, small circuits consisting of a few transistors have been demonstrated, including inverters, ring oscillators, and static random access memory cells. However, for industrial applications, both time‐zero and time‐dependent variability in the performance of the transistors appear critical. While time‐zero variability is primarily related to immature processing, time‐dependent drifts are dominated by charge trapping at defects located at the channel/insulator interface and in the insulator itself, which can substantially degrade the stability of circuits. At the current state of the art, 2D transistors typically exhibit a few orders of magnitude higher trap densities than silicon devices, which considerably increases their time‐dependent variability, resulting in stability and yield issues. Here, the stability of currently available 2D electronics is carefully evaluated using circuit simulations to determine the impact of transistor‐related issues on the overall circuit performance. The results suggest that while the performance parameters of transistors based on certain material combinations are already getting close to being competitive with Si technologies, a reduction in variability and defect densities is required. Overall, the criteria for parameter variability serve as guidance for evaluating the future development of 2D technologies.

Challenges for Nanoscale CMOS Logic Based on Two-Dimensional Materials

“…The most straightforward way of testing this possibility for very-large scale integration (VLSI) is to fabricate CMOS inverters using the previously discussed doping schemes. At the same time, CMOS inverters are important benchmark circuits for the performance, variability, and electrical stability of digital logic [ 101 ]. Up to now, CMOS inverters based on 2D materials have often combined different TMDs such as MoS for the n-type FET and WSe for the p-type FET, even though this method makes the integration of n- and p-type FETs in close vicinity as well as the tuning of difficult [ 102 , 103 ].…”

Application of Two-Dimensional Materials towards CMOS-Integrated Gas Sensors

“…Over the years, many materials have attempted to replace silicon, including materials with higher charge carrier mobility, such as germanium, and various group III-IV materials. However, none have been successful in commercialization on a broad scale and have only made breakthroughs in certain niche markets [ 22 ]. However, the continued scaling of silicon appears to have reached saturation and sub-3 nm channels pose significant challenges due to increased variability and reliability issues, but also due to the limited carrier mobility at these reduced scales [ 149 , 150 ].…”

“…Research on 2D transition metal dichalcogenides (TMDs) has been dramatically increased during the last decade and, in that time, many research groups have demonstrated working transistors with these films [ 136 , 258 , 259 , 260 , 261 , 262 , 263 ]. Among TMDs, molybdenum disulfide (MoS 2 ) [ 22 , 259 , 263 ] and tungsten sulfide (WS 2 ) [ 264 ] are of particular interest for transistors, since they are naturally occurring layered crystals, are robust and relatively abundant, and present a wide band gap; nevertheless, many other TMDs are also readily being investigated [ 132 , 260 , 265 ]. One of the main issues with 2D TMD semiconductor FETs is finding a fitting insulator, whether in the top-gated or back-gated configuration, where the interface defect concentration is minimal and does not negatively impact transistor operation or its long-term reliability [ 21 , 266 , 267 ].…”

“…As can be observed, this section has primarily summarized the progress made in MoS 2 -based gas sensors. This was chosen, because MoS 2 appears to be the 2D semiconductor, which is the closest to being realized with digital transistor devices and is one which has been heavily studied for gas sensor applications [ 22 ]. Nevertheless, at the beginning of this section, we also mentioned the potential that WS 2 shows.…”

“…With a focus on chemiresistive sensors, based on semiconductor materials which demonstrate the greatest potential for future CMOS integration and miniaturization, we build on the review we presented at the 32nd International Conference on Microelectronics (MIEL) in 2021 [ 1 ] and summarize some key aspects of currently available gas sensor technologies. Our analysis results in the conclusion that the most likely materials which have the potential for both sensing applications and digital logic are two-dimensional (2D) materials, and we expect this integration in the relatively near future [ 21 , 22 ]. First, we introduce different gas sensing technologies, their integration with CMOS processes, and the current research into room-temperature gas sensing.…”