As makers of computer microchips continue their consumer-driven pursuit of higher processor power and lower energy consumption, they are rapidly approaching the physical limits of miniaturization. The nanometer-scale transistors that comprise the latest microprocessor’s logic circuits simply cannot be made any smaller, leaving industry with little choice but to increase the number of transistors on each chip and operate the processor at higher frequency — both of which lead to increased power consumption and heat generation.
Scientists and engineers around the world are searching for new architectures that could supersede conventional silicon-based processors as the basis for the next generation of computers. Although quantum and optical computers have received much attention, devising an industrially viable platform for implementing such computing systems remains a distant target. Molecule-based computing, on the other hand, despite having a shorter history of development, is much closer to implementation compared to other possible computing technologies and could emerge as a promising next-generation technology if a commercially useful fabrication platform can be developed.
Christian Joachim from the National Center for Scientific Research (CNRS) in France and a visiting international professor at A*STAR’s Institute for Materials Research and Engineering (IMRE) is leading a collaboration between ten European Union partners and the IMRE in an ambitious four-year project starting in 2011 to develop a complete fabrication process for single-molecule-based computing. The Atomic Scale and Single Molecule Logic Gate Technologies project, dubbed AtMol, is funded to the tune of close to 10 million Euros and brings together some of the most prestigious institutes in Europe. “IMRE’s unique ‘atom tech’ research group is a key partner in AtMol because we have the technological know-how and the only atomic-scale interconnection machine in the world,” says Joachim. Two more of these cryogenic ultrahigh-vacuum fabrication instruments are under construction as part of the AtMol project.
The project has coalesced out of technology developed by Joachim’s team at the IMRE and CNRS for constructing molecular machines, and follows recent demonstrations of a process that allows single molecules to be deposited with atomic precision in arrangements that could provide computing capabilities. “We are developing a process to package a molecular chip in a way that separates the molecular logic circuits from the backside interconnects and allows the molecular circuit to be brought out from vacuum without destroying it,” says Joachim. “Using A*STAR’s patented back interconnect process, we can preserve the atomic precision of the top part of the chip.”
The development of a packaging process that effectively separates the nanoscale molecular circuits from the microscale connections that interface with conventional silicon-based circuitry is a critical step forward in demonstrating the potential and viability of molecular processing technology. “A molecular chip derives its processing power from a set of well-connected molecules, where each molecule acts like a conventional logic gate, or even better, a small processor, and the interconnections among molecules are formed by wires just one atom wide,” says Joachim. “We are aiming at 0.01-nanometer precision, placing each molecule optimally on the substrate. This would not be possible without our atomic fabrication technology and encapsulation process.”
Releasing the restrictions of microscale processing will also allow the AtMol team to investigate new ways to achieve logic functions. “In AtMol, we are optimally aiming to do away with transistors all together, instead using atomic-scale quantum effects to achieve gate logic functions.” Such an approach would allow miniaturization far beyond that achievable in conventional transistor-based nanocircuits, and according to Joachim, could mean that the circuit complexity could be raised without increasing the lateral dimensions of the circuit. “We already have the technology to connect a single molecule to four nanoscale electrodes with atomic precision. I am looking forward to seeing how far we can push our molecular chip technology by the end of this four-year project.”
The AtMol project aims to establish a comprehensive process flow for fabricating a molecular chip through the development of atomic-scale and single-molecule logic gate technologies. AtMol is the flagship project of the Molecular Scale Devices and Systems project launched by the European Commission under the Information and Communication Technologies program of Future and Emerging Technologies, which supports transformational, long-term collaborative frontier research in Europe with a view to developing scientific excellence and technological innovation. A*STAR’s Institute of Materials Research and Engineering is the only non-EU partner of the 11 participating organizations.
About the Institute of Materials Research and Engineering
The Institute of Materials Research and Engineering (IMRE) was established in 1997 with the aim of becoming a leading research institute for materials science and engineering. The IMRE has developed strong capabilities in materials analysis, characterization, materials growth, patterning, fabrication, synthesis and integration, and has established reseach and development program in collaboration with industry partners.