Low-Temperature Process at 52°C Realizes SiO₂ Thin Films Comparable to Thermal Oxide Films

What is it about?

We believe that the technology we have developed is an important step that has the potential to overcome one of the technical issues that has been preventing the practical application of flexible devices. We have successfully developed a method to form silicon dioxide (SiO₂) thin films at an ultra-low temperature of just 52°C, achieving leakage current density-electric field strength (J-E) characteristics comparable to those of thermally oxidized SiO₂ thin films formed at approximately 1000°C. This achievement holds great promise for contributing to the evolution of flexible devices, such as flexible displays and wearable sensors, as well as next-generation electronics. SiO₂ thin films can be formed on various substrates under atmospheric pressure (non-vacuum conditions) using a precursor solution of perhydropolysilazane (PHPS). However, obtaining SiO₂ thin films requires heat treatment at 450°C for over an hour. If silica conversion becomes possible at a low temperature of around 50°C, which plastic films can withstand, it would open up a wide range of applications, including next-generation flexible electronics and the creation of new electronics fields. We have successfully developed a technique to rapidly convert PHPS into high-quality SiO₂ thin films at a temperature of 52°C using a unique approach that applies atmospheric pressure plasma.

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Photo by Onur Binay on Unsplash

Photo by Onur Binay on Unsplash

Why is it important?

If it becomes possible to form high-quality thermally oxidized SiO₂ thin films, which are used as gate insulating films in semiconductor devices, at low temperatures of around 50°C, which plastic films can withstand, and at high speeds, then revolutionary progress can be expected in many of the cutting-edge fields listed below. ‣ Gate insulating films in high-performance flexible TFTs (thin-film transistors) ‣ Insulating layers in flexible ICs and LSIs ‣ Foundational layers for transparent electronics ‣ Gas barrier layers Additionally, because plastic films are lightweight and cost-effective to produce, combining them with SiO₂ thin films could lead to the development of new eco-friendly electronic products, thereby contributing to sustainable technology. We have succeeded in converting PHPS into a SiO₂ thin film with quality equivalent to the J-E characteristics of thermal oxide thin film at a low temperature of 52°C, and have elucidated the silica conversion mechanism using real-time FT-IR measurement. Understanding this mechanism is expected to lead to further technological innovations that enable even lower-temperature and faster silica conversion. Additionally, since SiO₂ thin films can be created at atmospheric pressure without a vacuum system, this technology can simplify production, reduce costs, and enhance scalability.

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