A team of researchers from University of Wisconsin - Madison have pioneered a unique method that could allow manufacturers to easily and economically fabricate high-performance transistors with wireless capabilities on huge rolls of flexible plastic.
The team of researchers led by Zhenqiang (Jack) Ma, fabricated a transistor that operates at a record 38 GHz, though the simulations show it could be capable of operating all the way up to 110 GHz. In computing, that translates to lightning-fast processor speeds.
This research is very useful for wireless applications. This transistor can transmit data or transfer power wirelessly, a capability that could unlock advances in a whole host of applications ranging from wearable electronics to sensors.
Their nanoscale fabrication method upends conventional lithographic approaches, which use light and chemicals to pattern flexible transistors overcoming limitations such as light diffraction, imprecision that leads to short circuits of different contacts, and the need to fabricate the circuitry in multiple passes.
Using low-temperature processes, they patterned the circuitry on their flexible transistor - single-crystalline silicon ultimately placed on a polyethylene terephthalate (more commonly known as PET) substrate - drawing on a simple, low-cost process called nanoimprint lithography. They took an unconventional approach: they blanketed their single crystalline silicon with a dopant, rather than selectively doping it.
Afterwards they added a light-sensitive material, or photoresist layer, and used a technique called electron-beam lithography, which uses a focused beam of electrons to create shapes as narrow as 10 nanometers wide on the photoresist to create a reusable mold of the nanoscale patterns they desired. They also applied the mold to an ultrathin, very flexible silicon membrane to create a photoresist pattern. After finishing with a dry-etching process, a nanoscale knife is used that cut precise, nanometer-scale trenches in the silicon following the patterns in the mold, and added wide gates, which function as switches, atop the trenches.
With this unique, three-dimensional current-flow pattern, the high performance transistor consumes less energy and operates more efficiently. And this method enables them to slice much narrower trenches than conventional fabrication processes can, it also could enable semiconductor manufacturers to squeeze an even greater number of transistors onto an electronic device.
This mold can be reused and this method could easily scale for use in a technology called roll-to-roll processing (think of a giant, patterned rolling pin moving across sheets of plastic the size of a tabletop), and that would allow semiconductor manufacturers to repeat their pattern and mass-fabricate many devices on a roll of flexible plastic.
