Study on Narrow Tube Inner Coating Method by Harmonic ECR Plasma

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For the inner surface coating of narrow tubes, we have investigated pulsed coaxial sputtering process with the micro plasmas in a magnetic field, especially, the 2nd harmonic electron cyclotron resonance (ECR) plasmas. Resonant confinement of electrons at the 2nd harmonic ECR leads to interesting micro plasma characteristics: the higher electron density, the lower plasma potential, the lower electron temperature and the effective power absorption compared with ECR condition.As a result of detailed investigation of temporal evolutions of the target ion current and voltage, we found that the selection rule of pulse bias voltage and gap length. The target ion current was measured at uniform type, and the ion current is decreased with increasing the target bias voltage. Expansion of a sheath width can be considered as this reason. When the uniform type and the mirror type are compared, it is understood that the tendency to the ion current density was the same. However, the ion current density was higher than that of uniform type one. It is considered that the increase of ion current density in mirror-type is caused by decreased axial electron loss by mirror effect. From this result, it is understood that plasma density was higher than that of uniform type one.As a result, we have succeeded in sputter coating of Au films onto the inner surface of insulated narrow tube with 1mm inner diameter by using Xe gas. And it was performed that inner coating of narrow tube with 40mm length by using scanning-mirror-type magnetic field.