21 March 2018
Rochester Institute of Technology improves nano-structure fabrication process
© Semiconductor Today Magazine / Juno PublishiPicture: Disco’s DAL7440 KABRA laser saw.
Rochester Institute of Technology (RIT) in the USA says it has found a more efficient fabricating process to produce semiconductors for electronic devices, and that the inverse metal-assisted chemical etching (I-MacEtch) method can help to meet the growing demand for more powerful and reliable nano-technologies needed for solar cells, smartphones, telecommunications grids and new applications in photonics and quantum computing (Wilhelm et al, ‘Fabrication of Suspended III-V Nanofoils by Inverse Metal-Assisted Chemical Etching of In0.49Ga0.51P/GaAs Heteroepitaxial Films’, ACS Applied Materials and Interfaces (2018) 10(2) 2058).
The I-MacEtch process combines the benefits of the two traditional methods of wet etching and reactive-ion etching (RIE). “I-MacEtch is an alternative to two conventional approaches and is a technique that has been used in the field - but the materials that have been explored are fairly limited,” says Parsian Mohseni, assistant professor of microsystems engineering in RIT’s Kate Gleason College of Engineering and director of the Epitaxially-Integrated Nanoscale Systems (EINS) Laboratory at the university. MacEtch has been used extensively for processing silicon. At the same time, assessments are underway of III-V semiconductor materials that may be conducive to this same type of fabrication with similar advantages.
Mohseni is looking at different alloys of III-V materials, namely ternary alloys such as indium gallium phosphide (InGaP). “For the first time we are looking at applying I-MacEtch processing to InGaP materials,” he says. “This is a very well-known material and has applications in the electronics and solar cell industries,” Mohseni adds. “We are establishing new protocols for treating the existing material that is more cost effective, and a more sustainable process.”
The research highlights how the nanofabrication methodology was applied to InGaP and how it can impact the processing of device applications and generation of high-aspect-ratio and nano-scale semiconductor features, says microsystems engineering doctoral student Thomas Wilhelm (first author of the paper). It is reckoned that the novel processing method can be significant in the development of ordered arrays of high-aspect-ratio structures such as nanowires.
For solar cells, the goal is to minimize the cost-to-power-produced ratio. If it is possible to lower the cost of making the cell and increase the efficiency of it, then this improves the device overall. Exploring new methods of fabricating the existing materials in a way that allows for faster, less expensive and more controlled processing by combining the benefits of wet etching and RIE has been the focus of Mohseni’s work. The improved process means avoiding expensive, bulky, hazardous processing methods.
“We are using a simple benchtop set up and we end up with very similar structures; in fact, one can argue that they are higher in quality than the structures that we can generate with RIE for a fraction of the cost and with less time, less steps throughout, without the higher-temperature conditions or expensive instrumentation,” Mohseni says.