Line shaped (one-dimensional) microwave plasma is generated by a sectoral horn antenna (490×5 mm in cross section) and magnetic field. The electric field strength distribution is optimized by adjusting the distance between the aperture of a sectoral horn antenna and the microwave inlet quartz window. The plasma density of 1.5×10
11 cm
-3 is obtained under the electron-cyclotron resonance (ECR) condition (87.5 mT). The spatial uniformity of the ion saturation current is ±11% within 250 mm length at 300 W for 0.067 Pa. The profile of the ion saturation current distribution becomes ununiform at more than 0.40 Pa, and then it is found that the plasma impedance discontinuously varies at the gas pressure of 0.40 Pa.
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