IBM demonstrates nanosheet transistor prototype optimized for liquid nitrogen cooling, doubling performance over room temperature

On December 25, at the IEEE International Electron Devices Meeting (IEDM) held in San Francisco in early December this year, IBM researchers demonstrated the first advanced CMOS transistor optimized for liquid nitrogen cooling.

It is understood that the boiling point of liquid nitrogen is extremely low, only -196°C, which is an ultra-low temperature that mainstream electronic devices cannot withstand. However, in such a cold environment, the resistance and leakage current of transistors will be greatly reduced, thereby improving performance and reducing power consumption.

The nanosheet transistor developed by IBM cuts the silicon channel into thin nanosheet layers and completely surrounds it with a gate to achieve more effective electric field control. This structure can not only cram 50 billion transistors into an area the size of a fingernail, but also double the performance under liquid nitrogen cooling.

The cryogenic environment brings two major advantages: lower charge carrier scattering and lower power consumption. Reduced scattering means lower resistance and smoother movement of electrons in the device; while reduced power consumption allows the device to drive higher currents at the same voltage. In addition, liquid nitrogen cooling also improves the on/off sensitivity of the transistor, requiring smaller voltage changes to switch states, further reducing power consumption.

However, low temperatures also bring new challenges: increased threshold voltage. The threshold voltage refers to the voltage required to turn on the transistor, which increases as the temperature drops, making it more difficult to switch the device. Traditional processes have difficulty reducing the threshold voltage, so IBM researchers have adopted a new dual metal gate and dual dipole technology. They add different metal impurities at the interface of n-type and p-type transistors to form dipoles, thereby reducing the energy required for electrons to cross the conduction band edge, making the transistor more efficient.