Effects of permanent magnet arrangements and antenna locations on the generation of multicusp electron cyclotron resonance plasma

A comparative study on the generation of 2.45-GHz multicusp electron cyclotron resonance (ECR) plasma is performed. Looped cusp structures such as the ring-cusp give a low-power and low-pressure ignition, and vice versa, indicating an importance to keep the electron trajetory of gradient-B drift motion inside the chamber even in the case of ECR plasmas. The importance of the antenna location in such multicusp fields is elucidated by comparison in two cases of the axial antenna located in the weak magnetic field region, generating a hydrogen plasma of limited density (ne<7.4x1010 cm-3), and a radial antenna located in the strong magnetic field region, generating an overdense plasma (ne∼2x1011 cm-3)