Researchers Develop Black-Phosphorus Transistors to Fight Against IP Theft
14-12-2020 | By Robin Mitchell
Recently, researchers from Purdue University have created black-phosphorus transistors with configurable properties to hide the nature of the operation. How can IP be stolen from chips, what are the new devices, and how can their concept help to fight against IP theft?
Reverse-Engineering Devices
The development of new technologies is only possible thanks to the ability to profit from development; a crucial in a market-driven society. If a new technology proves to be useful, it can be commercialised, and the profits from the commercialisation can go towards developing even more technology. While some may argue that technology can still develop without the incentive for profit, history shows that such development takes significantly longer.
However, once a piece of tech has been designed, it usually doesn’t take long for either the competition to find out how it works, or for businesses in more shady areas of the world to reverse engineer the device and then produce it themselves. Such practices can harm businesses which have invested millions into the development of new technology, and if not kept in check can potentially ruin those businesses.
In the integrated circuit world, such reverse engineering often comes in the form of “decapping” an IC whereby a genuine integrated circuit is purchased, and then the IC packaging is removed. From there, the microchip can be studied under a microscope, and many images can be combined to result in an overall image of the die. This image is then studied further with each transistor being observed, and once mapped, its function can be determined.
Of course, improving technology also means that those involved with reverse-engineering are looking towards new ways to determine how devices work. Some researchers are even looking at x-ray imaging techniques to see if they can determine transistor layouts without the use of decapping techniques.
Researchers Develop Black-Phosphorus Transistors
Recently, researchers from the University of Purdue have been able to develop transistors utilising black-phosphorus. The transistors themselves are fragile 2D structures, but unlike traditional CMOS transistors, the type of device (N or P) is defined using an electrostatic charge. Therefore, the property of the transistors can be changed in real-time, and both transistor types look identical to each other.
Not only do the new transistors have electrically alterable properties, but they also operate on lower voltages than their CMOS counterparts. These transistors also have on-off ratios of 105, have a subthreshold swing of 72mV/decade, and have been used in an inverter design with a gain of 33.3 operating at a VDD of 0.2V. The researchers also used the transistors to create a primitive security circuit containing NAND/NOR obfuscation functionality using sub 1V operation.
How can the new devices help to protect against IP theft?
One of the key features behind the new transistors is their ability to change their type dynamically. While this may provide a circuit with reconfigurable properties, its application is more geared towards security. Since an N or P transistor looks identical in this technology, anyone reverse-engineering the design would not be able to determine the difference between the two.
Of course, chip manufactures already use camouflaging techniques to protect their devices with the use of redundant logic and transistors, the use of black-phosphorus would provide a design that not only is protected against reverse engineering but also from the manufacturer themselves. Once fabricated, even the manufacturer would not be able to distinguish the type of each transistor without referring to the original designs.
It was the security benefits of black-phosphorus transistors that lead the team to develop the experimental circuits. The idea originally came from the realisation that a circuit having identical N and P transistors would be near-impossible to reverse engineer. That ultra-thin black-phosphorus can be made to exhibit both N-type and P-type properties. While the devices developed by the researchers will be unlikely used by semiconductor companies, the concept behind identical transistor design is being considered as a method to protect future designs.
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