This paper describes film deposition rates for rf planar magnetron sputtering when the magnetic field parallel to the target surface is varied. Magnetic-field strength is a key parameter to control deposition rate in rf magnetron sputtering but applying a high magnetic field does not increase the deposition rate. Self-bias voltage also decreases as the target magnetic field increases and plasma impedance involving the ion sheath region and glow discharge region is inductive. Plasma impedance measurements lead to the conclusion that a deteriorated deposition rate in the high magnetic field occurs due to decreased self-bias voltage resulting from an increased sheath capacitance.

This article describes the effect of the target magnetic field on the plasma process and the physical properties of films deposited by magnetically controlled rf and dc planar magnetron sputtering techniques. The target magnetic field, which is parallel to the target surface, is controlled and its’ strength is a key parameter in controlling the deposition rate in both rf and dc magnetron sputtering. Based on this technique, we propose a way of suppressing variations in a magnetic film’s deposition rate and suppressing changes in its structural characteristics during rf magnetron sputtering. For dc magnetron sputtering, we clarified the mechanism that automatically stabilizes the deposition rate even if the target magnetic field is changed. We also clarified that controlling the target magnetic field (controlling the self-bias voltage) is very important for controlling the physical properties of sputter-deposited films in both rf and dc magnetron sputtering.

To find a way to control the compositional change in Bi-substituted garnet during sputtering, we studied the effects of controlling the cathode magnetic field. The magnetic-field-controlled rf magnetron sputtering method that we developed can create a garnet film whose composition is the same as that of the sputtering target. When we deposited a film of Bi-substituted Dy iron garnet–ferrite (Bi2DyFe4GaO12) by this method, there was no compositional change between the target and the film even after a long sputtering process. Therefore, this sputtering method is effective at suppressing compositional change during the film formation process.

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We developed a compact and low-cost electro-optic (EO) sensor module for intra-body communication using optical pickup technology. An EO crystal of zinc telluride (ZnTe) mainly contributes to use of the cost-effective optical pickup technology. ZnTe has the shortest wavelength for optical transmission, about 570 nm; therefore it can use a low-cost 790-nm wavelength laser diode widely used in compact disc players. The measured modulation depth of the new EO sensor module was about 1.56 times deeper than our old one. The measured value agreed with the calculated value; therefore, there is no performance deterioration by downsizing the sensor module. The sensor module was successfully applied to 10-Mbps half-duplex intra-body communication.