As the world pushes for smaller and faster electronic devices, scientists are searching for new materials and cleaner methods to build them.
One material that has captured attention is hafnium oxide (HfO₂), known for its strong atomic bonds, stability under heat, and ability to act as an excellent electrical insulator.
These qualities make it ideal for future semiconductors, especially as circuits shrink to just a few nanometers in size.
However, the very strength of hafnium oxide also makes it difficult to process. Engineers need to etch or carve away thin films of this material with atomic-level precision.
Traditionally, this has been done using halogen-based gases like fluorine or chlorine in plasma etching systems. While effective, these gases are highly toxic and contribute to environmental problems, including greenhouse emissions.
Now, a team of researchers from Japan’s Nagoya University and Taiwan’s Ming Chi University of Technology has developed a new way to etch hafnium oxide without relying on halogen gases.
Their results, published in the journal Small Science, show that it is possible to achieve atomic-level smoothness and uniformity while also making the process safer and more sustainable.
The researchers used a plasma-based process that alternates between nitrogen and oxygen treatments. In the first step, nitrogen ions are directed at the hafnium oxide surface with a carefully applied voltage.
This causes nitrogen atoms to temporarily bond with the material.
In the second step, the film is exposed to oxygen plasma without added voltage, which removes the nitrogen-bonded layer through a self-limiting reaction. By repeating these cycles, the team was able to remove the material layer by layer, with etch depths as small as 0.023 nanometers per cycle.
Advanced monitoring techniques confirmed that the process works through a mechanism called ligand exchange, in which nitrogen atoms briefly replace oxygen atoms on the surface before being removed. Importantly, the method also smoothed the surface significantly—after just 20 cycles, the roughness of the film decreased by 60 percent.
Lead researcher Shih-Nan Hsiao explained that this is the first successful demonstration of halogen-free atomic-layer etching of hafnium oxide at room temperature. By avoiding halogen gases, the process reduces environmental risks. Operating at room temperature also saves energy and lowers costs, while preventing the formation of sticky byproducts that often complicate conventional etching methods.
This breakthrough could pave the way for cleaner, more efficient production of semiconductors used in advanced transistors, memory devices, and other microelectronics.
As the demand for smaller, faster, and greener technology grows, innovations like this will be key to powering the next generation of electronics.
