7th Asia-Pacific Conference on Plasma Physics, 12-17 Nov, 2023 at Port Messe Nagoya

Booming Low-temperature Plasma Sciences for a Creation of New Value
M. Hori1
1Center for Low-temperature Plasma Sciences, Nagoya University
e-mail: hori@nuee.nagoya-u.ac.jp

Low-temperature plasma science is positioned as animportant science and technology that fundamentallysupports the creation of cutting-edge devices and systems,
the establishment of innovative environmental
improvement technologies, the challenge of the global
food crisis, and next-generation medical technologies.
It is a strategic science and technology that can make asignificant contribution to the SDGs. In other words, lowtemperature plasma science is a driving force for creating
new value by opening up the future of diverse fields,
sparking disruptive innovation, and creating social
innovation that interweaves diverse fields.
For example, logic devices for advanced large-scale
integrated circuits are being developed toward ultra-fineprocessing with 1 nm dimensions. In this process, it isnecessary to precisely control the kind and density ofradicals in the plasma and to maintain a constant substratetemperature during the process. In the nano-patterning oforganic thin films, a one-degree change in substratetemperature causes a change in dimension of 1 nm. As an
approach to this problem, nano-pattern etching of organic
thin films was performed in a dual-frequency capacitively
coupled plasma etching system using a mixture ofhydrogen and nitrogen gases. The absolute density ofhydrogen and nitrogen radicals was measured by vacuum
ultraviolet absorption spectroscopy, and the ratio ofhydrogen to nitrogen radicals was kept constant. Substratetemperature was measured in real time using an opticalinterferometer, and the temperature was kept constantduring the process by modulating the plasma on and off.

As a result, nanometer-sized patterns were successfully
formed as shown in Fig.1. [1] The significance of thisresearch is that the etching characteristics of organic
materials are not described by the parameters of theequipment (power, pressure, gas flow rate, etc.), but byinternal parameters (radical density caused by particles,substrate temperature), it is significant that processcharacteristics (etching speed and shape) can becontrolled by controlling these internal parameters withhigh precision. In order to further advance next-generation
semiconductor plasma processes, it is necessary toaccumulate a database expressed in terms of internalparameters.
Meanwhile, the development of atmospheric pressure
and low-temperature plasma has begun to build science
for new applications and mechanisms in theenvironmental and biotechnology fields. In addition toplasma chemistry, molecular biological elucidation ofplasma and biological reactions is necessary to realize thedevelopment of selective killing of cancer andregenerative medicine, physiology of growth promotion
through interaction between plasma and plants, and thescience of efficient production of methanol by converting
CO2 to other substances.
For this purpose, it is necessary to accumulate thesevarious sciences in a reliable scientific database andsystematize them with AI. In particular, the behavior ofradicals is unknown in low-temperature plasma science,and it is important to measure radicals and systematize andcontrol their behavior.[2] Low-temperature plasma scienceis extremely attractive for the creation of a future society
and can contribute significantly to the SDGs.
In this talk, the current status and future prospects oflow-temperature plasma science will be outlined.
This work is supported in part by a Grant-in-Aid forSpecially Promoted Research (no. 19H05462) from the
Ministry of Education, Culture, Sports, Science andTechnology of Japan.
References[1] Y. Fukunaga et al, Jpn. J. Appl. Phys. 58, 020906(2019)[2] M. Hori et al, Rev. mod. plasma phys. 6:36, 1 (2022)

Figure 1 The evolution of organic film etching profile.[1]