A plasma etching method is performed by plasma etching an SiN layer through a mask layer to form a first wiring portion and a second wiring portion, the first and the second wiring portions having different wiring densities in the etched SiN layer, the mask having two pattern portions respectively corresponding to the first and the second wiring portions. The signal generation unit 107 or the signal generation unit 207 performs prescribed signal processing based on a set value. The portable power module includes an air flow switch configured to regulate air flow within the portable power module and a turbine generator configured to generate a voltage from the air flow.