Harnessing starfire: plasma, the cleaner from the cosmos
It is created when a gas is energised until its atoms begin to shed electrons
Plasma is associated with stars, lightning or neon lights, but it is also quietly at work in factories here on Earth. From microchips and medical implants to aircraft engines, this ionised “fourth state of matter” has become one of industry’s most powerful cleaning tools.
A recent review by Stephen Sammut, of the Malta College of Arts, Science and Technology, as part of the project ‘PlasmaSemiCon’ on whether devices succeed or fail shows how a technology inspired by physics at the heart of stars is being tamed for precision manufacturing.
Plasma is created when a gas is energised until its atoms begin to shed electrons, forming a charged mix of particles that can be steered by electric and magnetic fields. In industry, gases such as oxygen, hydrogen or argon are pumped into low-pressure chambers and exposed to radiofrequency or microwave energy.
“Once you switch on the power, you have an environment full of radicals, ions and photons,” Sammut explains. “They bombard the surface with energy and energised particles, cleaning and activating it in ways that liquids or brushes cannot.”
The choice of gas is critical. Oxygen plasmas generate radicals that break down hydrocarbons into carbon dioxide and water vapour. Hydrogen plasmas strip away metal oxides, essential in preparing copper or aluminium surfaces. Argon, an inert gas, cleans by physical bombardment, useful for devices such as delicate optics and microelectromechanical systems. Nitrogen plasmas activate polymer surfaces, improving wettability and adhesion.
In the semiconductor field, plasma cleaning ensures that bonding pads and lead frames are atomically clean, providing reliable surfaces for wire bonding and secure adhesion during moulding. The benefits are clear, as plasma is dry, solvent-free and generates little waste. It is non-contact, making it safe for fragile microstructures, and tuneable, with gas mixtures and power levels tailored to each task.
Once you switch on the power, you have an environment full of radicals, ions and photons
The process is also striking to watch as inside the chamber the plasma often glows with colour, violet for argon, pale blue for oxygen, and pinkish purple for hydrogen. The hues are not decorative but diagnostic, revealing which species dominate inside.
In the PlasmaSemiCon project, spectroscopy was studied as a tool to develop better plasma diagnostics. By measuring the precise wavelengths of light emitted by the plasma, engineers can identify the charged atoms, ions and radicals present. This turns what looks like a simple glow into a detailed fingerprint of the processes at work inside the chamber.
A follow-up project, ‘ScienceSemiCon’, is continuing this work, and MCAST has now also procured sophisticated spectrometry equipment to conduct these studies.
The academic-industrial partnership between STMicroelectronics Malta and MCAST is vital for connecting research and real-world applications, driving innovation and nurturing talent for the future. This powerful synergy is crucial for maintaining momentum in today’s rapidly evolving technological environment, particularly by advancing cutting-edge manufacturing technologies like artificial intelligence and automation.
These collaborations between academic institutions and industry leaders accelerate the advancement of smart, efficient and sustainable production systems, effectively addressing both current and future market demands.
Stephen Sammut is an electrical engineer holding a PhD in microelectronics focused on piezoelectric micromachined ultrasonic transducers. He has worked across microelectronics, power distribution, aviation, and project management, and currently serves as deputy principal for vocational and professional education and training at MCAST while conducting research in collaboration with STMicroelectronics and CERN.
Photo of the week
Source: FreepikThe Aurora Borealis is a stunning example of plasma physics at work. The sun constantly releases streams of charged particles, which travel through space and interact with Earth’s magnetic fields. Guided toward the poles, the particles collide with our atmosphere, transferring energy that’s released as shimmering greens, reds, purples, and blues.
The characteristic green auroral emission is produced when energetic electrons excite oxygen atoms at altitudes of roughly 100–150 km. Lightning is also a plasma phenomenon, created when an electric field becomes strong enough to ionise air and form a conductive channel. Both auroras and lightning demonstrate how ionised gases respond to electromagnetic forces in Earth’s atmosphere.
