We report on the development of unique, high-density helicon plasma sources and describe their applications. Characterization of one of the largest helicon plasma sources yet constructed is made. Scalings of the particle production efficiency are derived from various plasma production devices in open literature and our own data from long and short cylinder devices, i.e., high and low values of the aspect ratio $A$ (the ratio of the axial length to the diameter), considering the power balance in the framework of a simple diffusion model. A high plasma production efficiency is demonstrated, and we clarify the structures of the excited waves in the low $A$ region down to 0.075 (the large device diameter of 73.8 cm with the axial length as short as 5.5 cm). We describe the application to plasma propulsion using a new concept that employs no electrodes. A very small diameter (2.5 cm) helicon plasma with ${10}^{13}{\text{cm}}^{-3}$ density is produced, and the preliminary results of electromagnetic plasma acceleration are briefly described.

Corrosion of ceramic chamber parts in mass-production plasma etching equipment causes the decrease in the production yield of LSI and overall equipment effectiveness. For the development of chamber parts with high resistance and long useful life under plasma etching environment, the investigation of detailed corrosion mechanism is required. In this study, we investigate the relationship between plasma etching characteristics and microstructures of alumina ceramics, which is the most typical ceramic material for chamber parts, under mass-production plasma etching condition using CF ₄ gas. The results of this study indicate that the microstructures have little influence on the etching amount, whereas the surface roughness depends on the microstructures such as grain size and microstructural defect.

A low-aspect ratio, high-density helicon plasma source with a large-diameter of ∼74 cm that utilizes an end-launch flat-spiral antenna has been characterized under three different axial boundary conditions. Whereas one end of the device is a quartz-glass window through which an excitation rf wave is injected, the other end is a movable plasma terminating plate of three different kinds: (1) metal with small holes, (2) solid metal, and (3) solid insulator. Using this movable plate, the device aspect ratio A (device axial length/device diameter) can be reduced to ∼0.075 corresponding to the device axial length of 5.5 cm. The plasma production efficiency (PPE, defined as the ratio of the total number of electrons in the plasma to the input rf power) and helicon wave structures are examined for plasmas with various aspect ratios and boundary conditions to characterize our helicon device. Even for the lowest aspect ratio case (A ∼0.075), a plasma with the electron density of 7.5 × 10¹¹ cm⁻³ can be produced. The PPE of our device is higher than that of other helicon devices that utilize winding-type antennas. Discrete axial wave modes, which can be explained by a simple model, have been identified for helicon waves excited in our low-aspect ratio helicon plasmas. A comparison between the experimental results and helicon wave theory suggests that second order radial modes must have been excited when the electron density is sufficiently high.

To investigate the mechanism of instantaneous generation of many flaked particles in plasma etching chambers, we study the relationship between particle generation from deposited films and electric field stress acting on the films under mass-production conditions. The particles are formed by stress working as an impulsive force due to rapid changes in floating potential on the chamber walls. The results indicate that Maxwell’s stress and electrostriction stress both affect particle generation in terms of the impulsive force of electric field stress. Although Maxwell’s stress mainly influences the outbreak of particles, the electrostriction stress also acts with considerable intensity.