| Summary: | 博士 === 國立清華大學 === 工程與系統科學系 === 88 === ABSTRACT
The goal of this research is to develop high density microwave electron cyclotron resonance (ECR) plasma sources. The research focused on improving the impedance matching between the microwave and the plasma, and the effects of the microwave modes and the magnetic field configurations on the plasma characteristics. The ECR plasma source designed in this study can achieve high plasma density (> 1011 cm-3 ) at low gas pressures (< 5 mTorr) with large area ( up to 10 cm ) and good uniformity (< 5 % ) in the down stream area. In order to improve the impedance matching, the microwave is transmitted into a height tunable cavity, then through a quarter-wave length thick quartz window before entering the plasma chamber. Very low power reflection and very easy impedance tuning can be achieved by such designs. For TM01 mode microwave with permanent magnet ring system, the low power reflection points occurred at cavity heights roughly equal to . For TE11 mode microwave with solenoid magnetic field, the low power reflection points occurred at cavity heights roughly equal to . It was found that the TE11 mode microwave ECR can generate higher plasma density and with better uniformity than the TM01 mode microwave, and also can achieve lower power reflection at best tuned conditions. In comparing the effects of the magnetic filed configurations, it was found that solenoid design can have higher plasma density, the permanent magnetic ring system is the second and the multi-cusp permanent magnet system is the lowest. In terms of plasma uniformity in the downstream, the solenoid design is the best, the multi-cusp design is the second and the permanent magnet ring system ranks the third. The solenoid system also has lower power reflection than the permanent magnet systems at best tuned conditions. The microwave plasma source was successfully modified into a neutralized ion beam system. By this technique the plasma ions can be accelerated to higher energy and transported to the downstream substrate with small divergent angles.
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