Dissertation: Manufacturing of ever smaller and more powerful chips made possible with patented new technology
In her doctoral dissertation, Zahra Rad developed cutting-edge technology that could have revolutionary impact on areas such as semiconductor manufacturing. This new type of atomic-level surface cleaning technology makes it possible to manufacture smaller, longer-lasting and more efficient electronic devices.
Semiconductors play an important role in our lives today, as they are essential to almost all electronics. They are used in satellites, industrial production systems, medical devices, computers and other smart devices, home electronics, and transportation, and our society could not operate normally without them.
Semiconductors are used in devices that form new infrastructures in our societies. For example, a local server failure can instantly affect the lives of people living on another continent. This central role of semiconductors has generated a wealth of new research in both academia and industry.
Due to the strategic importance of the industry, governments have also started to invest in it and enact related legislation, such as the European Chip Act. The semiconductor industry involves many different areas, including mining and recycling raw materials, designing chips and circuits, and building equipment for production lines that make semiconductor device components.
The size of electronic and photonic components made from semiconductors has steadily decreased, leading to faster and more efficient devices. New devices are becoming smaller, lighter, more widely available, and more affordable. This development makes surface physics research increasingly important.
“As components become smaller, the role of the surface in the performance and properties of devices becomes more effective and important. The surface area of a crystalline semiconductor naturally contains more defects than the bulk material beneath it, which causes electrical and optical losses in devices made from semiconductors,” says doctoral researcher Zahra Rad.
In her doctoral research, Rad focused on improving the defective surfaces of silicon and gallium arsenide semiconductors by using ultra-high vacuum (UHV) and chemical treatments.
The aim of the research was to find surface treatment or surface cleaning methods that are scalable and could be applied on an industrial scale. Further investigation was done by testing the effect of the above treatments on selected devices.
The study was able to demonstrate that, after the ultra-high vacuum pre- or post-treatment the defect density and leakage current of the silicon semiconductor decreased and the life-time of the semiconductor could be extended.
The study also developed a simple wet chemistry method for growing gallium oxide nanocrystals on the surface of gallium arsenide semiconductors, which can be used to reduce surface losses in optoelectronic devices made of them.
“These new surface cleaning techniques have truly significant potential in the manufacturing of semiconductors and other electronics. The technology makes it possible to clean semiconductors at the atomic level. This enables the manufacture of smaller and more efficient chips, which also have a longer service life,” Rad explains. “For example, data center chips will use less electricity and have longer working lifespan or solar panels produce more electricity from the same amount of sunlight.“
The methods developed in Rad's doctoral research have been granted several patents, and a new startup, SisuSemi Oy, has been established based on part of the research. The company has secured over one million euros in investment in the first investment round.
Dissertation defense on Friday 29 August
MSc Zahra Jahanshah Rad defends the dissertation in Physics titled “Wet chemical and ultra-high vacuum treatments of semiconductor surfaces to decrease electrical and optical losses in devices” at the University of Turku on 29 August 2025 at 12.00 (University of Turku, Main building, Tauno Nurmela Lecture Hall, Turku).
Opponent: Professor Harri Lipsanen (Aalto University)
Custos: Professor Kalevi Kokko (University of Turku)
The audience can participate in the defence by remote access
