Functional 2D-enabled microchips become a reality
(Nanowerk News) The first demonstration of a functional microchip integrating atomically thin two-dimensional materials with exotic properties heralds a new era of microelectronics.
The world’s first fully integrated and functional microchip based on exotic two-dimensional materials has been created at KAUST. This breakthrough demonstrates the potential of 2D materials to extend the functionality and performance of microchip-based technologies.
Since the manufacture of the first layers of atomically very thin graphite – called graphene – in 2004, there has been strong interest in such a material for advanced and novel applications because of its exotic and promising physical properties. However, despite two decades of research, these functional micro-devices based on 2D materials have proved elusive due to challenges in manufacturing and handling fragile thin films.
Inspired by recent achievements at the Lanza lab on functional 2D film, the collaboration has now produced and demonstrated a 2D-based microchip prototype.
These findings have been published in Natural (“2D–CMOS microchip for memristive applications”).
“Our motivation is to increase the technological readiness of 2D material-based electronic circuits and devices by using conventional silicon-based CMOS microcircuits as the basis and standard semiconductor fabrication techniques,” said Lanza. “However, the challenge is that synthetic 2D materials can contain local defects such as atomic impurities that can lead to small device failure. In addition, it is very difficult to integrate 2D materials into microchips without damaging them.”
The research team optimized the chip design to make it easier to manufacture and minimize the effects of defects. They did this by fabricating a standard complementary metal oxide semiconductor (CMOS) transistor on one side of the chip and feeding the interconnect to the bottom, where 2D materials can be reliably transferred in tiny pads less than 0.25 micrometers.
“We manufacture the 2D material — hexagonal boron nitride, or h-BN, on copper foil — and transfer it to a microchip using a low-temperature wet process, and we then shape the electrodes on top of it by conventional vacuum evaporation and photolithography, which are processes we own. ,” Lanza said. “In this way we generate a 5×5 array of one transistor/one memristor cells connected in a cross matrix.”
The exotic nature of 2D h-BN, here only 18 atoms or 6 nanometers thick, makes it an ideal memristor — a resistive component whose resistance can be regulated by an applied voltage. In this 5×5 arrangement, each micro-scale memristor pad is connected to one dedicated transistor. This provides the smooth voltage control required to operate the memristor as a functional device with high performance and reliability for thousands of cycles, in this case as a low-power neural network element.
