Patent ID: 8865498

Claim:
A method for manufacturing a three-dimensionally shaped comb-tooth electret electrode, provided with an electret in which ions having positive electric charge are held, comprising: a first step of forming a three-dimensionally shaped movable comb-tooth electrode and a three-dimensionally shaped fixed comb-tooth electrode that are made from an Si substrate by a semiconductor process; a second step of, in a state in which heat is being applied to the three-dimensionally shaped movable comb-tooth electrode and to the three-dimensionally shaped fixed comb-tooth electrode, contacting a vapor including the ions thereto, and forming an oxide layer including the ions upon surfaces of the three-dimensionally shaped movable comb-tooth electrode and of the three-dimensionally shaped fixed comb-tooth electrode; and a third step of, along with applying a voltage between the three-dimensionally shaped movable comb-tooth electrode and the three-dimensionally shaped fixed comb-tooth electrode so as to make these electrodes be either a positive side and a negative side respectively or a negative side and a positive side respectively, also applying heat to the three-dimensionally shaped movable comb-tooth electrode and to the three-dimensionally shaped fixed comb-tooth electrode, and causing the ions included in the oxide layer on the three-dimensionally shaped movable comb-tooth electrode or the three-dimensionally shaped fixed comb-tooth electrode to shift to a surface of the oxide layer; wherein the third step includes: a voltage elevation step of raising the voltage between the three-dimensionally shaped movable comb-tooth electrode and the three-dimensionally shaped fixed comb-tooth electrode up to a pulling in voltage at which the three-dimensionally shaped movable comb-tooth electrode is pulled against the three-dimensionally shaped fixed comb-tooth electrode; a voltage maintenance step of maintaining the pulling in voltage for a predetermined time interval; and a voltage reduction step of reducing the voltage to a pulled-in state release voltage at which the three-dimensionally shaped movable comb-tooth electrode, that was pulled against the three-dimensionally shaped fixed comb-tooth electrode, is pulled away therefrom; and the voltage elevation step, the voltage maintenance step, and the voltage reduction step are repeatedly performed while the values of the pulling in voltage and of the pulled-in state release voltage are changed so as to be gradually increased, so that the operation of each of the comb-teeth of the three-dimensionally shaped comb-tooth electrode being alternatingly pulled in against two opposed comb-teeth of the three-dimensionally shaped fixed comb-tooth electrode is repeated.