Density record

New method should enable even smaller chips

Researchers in Switzerland have discovered a new method for packing microchips even more densely with circuits. With their findings, they hope to help further advance the miniaturization of computer chips.

The most modern microchips currently available have conductor paths that are twelve nanometers apart. With their new technique, the researchers at the Swiss Paul Scherrer Institute in Villigen created conductor paths that are five nanometers apart. To give you an idea: five nanometers is to the thickness of a hair as half a centimetre is to the length of a soccer pitch.

Photolithography further developed
According to the research institute, the light with which the circuits are applied to the chips is decisive for the reduction in size and ever more compact chips. So-called photolithography is used for the production of microchips: A light-sensitive layer, the photoresist, is applied to a thin slice of silicon, known as a wafer. Light can be used to burn conductive tracks onto the photoresist.

In the new process, the photoresist is not irradiated directly with extreme ultraviolet light (EUV) as is normally the case, but is instead reflected by two mirrors. In this EUV mirror interference lithography (MIL), two mutually coherent beams are reflected onto the wafer by two identical mirrors. The beams then generate an interference pattern with a pattern that depends on both the angle of the incident light and its wavelength.

The group thus achieved resolutions, i.e. distances between the conductive paths, of five nanometers - with a single exposure. According to the institute, the conductor paths revealed good contrasts with sharp edges under the electron microscope. 

"No fundamental limits"
"Our results show that EUV photon lithography can produce extremely high resolutions, suggesting that there are no fundamental limits yet," noted Dimitrios Kazazis from the Laboratory of X-ray Nanoscience and Technology. "This is really exciting because it broadens the horizon of what we think is possible and can also open up new avenues for research in the field of EUV lithography and photoresist materials."

Currently, this approach is not interesting for industrial chip production, as it is very slow compared to industrial standards and can only produce simple structures instead of a chip design, the PSI wrote. However, it offers a method for the early development of photoresists, which will be needed for future chip production.