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Dr. Keiichiro Urabe, Assistant Professor

Development of laser interferometry methods for high-speed and precise plasma electron-density diagnostics

Dr. Keiichiro Urabe, Assistant Professor
Department of Aeronautics and Astronautics, Graduate School of Engineering, Kyoto University

*The organization and the title are those when awarded

DOWNLORD

Research summary

Plasmas(*1) are ionized(*2) gases composed of electrons, ions and neutral particles. Plasmas generated in low-pressure gases with a thermal non-equilibrium feature have been widely utilized in semiconductor fabrication processes. Among various parameters and particles in the plasmas, electron density is crucial to understand their physical and chemical characteristics.

Laser interferometry(*3) is a method to measure the electron density inside the plasmas. However, considering its application to advanced plasma processes, conventional interferometry arrangement has difficulties in spatiotemporal resolution and sensitivity of the electron density.

Dr. Urabe has proposed and experimentally verified his idea of interferometry techniques, such as combination with millimeter wave transmission(*4) and near-infrared diode laser interferometry, in order to overcome the difficulties of the existing laser interferometry.

In near future, it is expected that the developed laser interferometry will be integrated with semiconductor process equipment for continuous electron-density monitoring and fault detection. That can contribute to precise process optimization and yield improvement in the semiconductor fabrication processes.

*1 The artificial state of gas where molecules are ionized by electronic power injection.
*2 The transition of atom or molecule from electrically neutral mode to positively or negatively charged mode, which is called positive or negative “ion”.
*3 The apparatus for material examination by analyzing interference pattern generated by two or more laser beams originating from the same source where reference beam and object beam are interfering.
*4 A method of optical absorption spectroscopy irradiating a millimeter wave to plasma and measuring the absorption.