3D X-ray of chip interiors; two-mirror EUV; water with silk protein as non-toxic solvent.
Researchers from the Paul Scherrer Institute, EPFL Lausanne, ETH Zurich, and the University of Southern California used X-rays to take non-destructive, three-dimensional images of the inside of a microchip at 4 nanometer resolution.
To create the images, the researchers relied on a technique called ptychography, in which a computer combines many individual images to create a single, high-resolution picture.
Instead of focusing the X-ray beam on a nanometer scale, the sample is moved. “Our sample is moved such that the beam follows a precisely defined grid – like a sieve. At each point along the grid, a diffraction pattern is recorded,” said Mirko Holler, a physicist at the Swiss Light Source SLS at PSI, in a release. The distance between the individual grid points is less than the diameter of the beam, so the imaged areas overlap, producing enough information to reconstruct the sample image at a high resolution.
Initial efforts resulted in a 15nm resolution, limited by the tiny amount of wobble in the X-ray beam caused by vibrations. This was reduced through the use of shorter exposure times, a faster detector, and improved algorithms that enabled the team to take many more pictures at an individual point. “In some of the pictures, the beam is in the same position, in others it has moved. We can use these changes to track the actual position of the beam caused by the unknown vibrations,” said Tomas Aidukas, a physicist at the Swiss Light Source SLS at PSI, in a release. “Our algorithm compares the positions of the beam in the individual images. If the positions are the same, they are put in the same group and added to the sum.” This enabled reconstruction of a sharp image with a high light content using many short-exposure pictures. [1]
A researcher from the Okinawa Institute of Science and Technology proposed an EUV lithography design that is simpler and can work with smaller EUV light sources, reducing both cost and power.
The approach uses an optical projection system that consists of only two axisymmetric mirrors that are aligned with tiny center-holes in a straight line, along with a ‘dual line field’ method which irradiates a flat mirror photomask with EUV light from the front without interfering with the optical path. This enables it to use a light source of only 20W, reducing the total power consumption of the system to less than 100kW. It retains a very high contrast while also reducing mask 3D effects.
“This configuration is unimaginably simple, given that conventional projectors require at least six reflective mirrors. This was made possible by carefully rethinking the aberration correction theory of optics,” said Tsumoru Shintake, a professor at OIST, in a statement. “The performance has been verified using optical simulation software (OpTaliX) and it is guaranteed to be sufficient for the production of advanced semiconductors.”
OIST has applied for a patent and intends to undertake demonstration experiments. [2]
Researchers from Tufts University and Istituto Italiano di Tecnologia developed a chip nanomanufacturing approach that uses water as the primary solvent, reducing the amount of toxic chemicals required.
Many materials used in chip manufacturing are hydrophobic. But adding small amounts of silk fibroin, the protein found in silk, to water enhanced its ability to evenly cover almost any surface.
“This opens up a huge opportunity in device fabrication,” said Fiorenzo Omenetto, a professor of engineering at Tufts, in a press release. “Not only can one deposit water-soluble materials and metals on silicon, but on all sorts of polymers. We can even deposit and print biological molecules on virtually any surface with nanometer precision.”
In addition to silicon, the researchers found the method was compatible with indium gallium zinc oxide transistors, aluminum oxide insulators, nickel oxide films, and perovskite films. They believe the method could be easily substituted into current manufacturing processes. [3]
[1] Aidukas, T., Phillips, N.W., Diaz, A. et al. High-performance 4-nm-resolution X-ray tomography using burst ptychography. Nature 632, 81–88 (2024). https://doi.org/10.1038/s41586-024-07615-6
[2] Shintake, S. Can we improve the energy efficiency of EUV lithography? Photomask Japan symposium, Yokohama 2024 https://doi.org/10.48550/arXiv.2405.11717
[3] Kim, T., Kim, B.J., Bonacchini, G.E. et al. Silk fibroin as a surfactant for water-based nanofabrication. Nat. Nanotechnol. (2024). https://doi.org/10.1038/s41565-024-01720-3
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