Piezoelectric transducer, piezoelectric transducer manufacturing method, oscillator, electronic device, and radio clock

A piezoelectric transducer, comprising:

• a tuning-fork type piezoelectric oscillation piece which has a pair of oscillation arms;
• a package which contains the piezoelectric oscillation piece;
• and
• a first mass control film formed on the oscillation arms,
• wherein
• the frequency of the piezoelectric oscillation piece can be increased by removing a part of the first mass control film,
• a second mass control film is formed inside the package in the vicinity of the first mass control film, and
• at least a part of the second mass control film is removed in an area in the vicinity of the first mass control film.

A piezoelectric transducer manufacturing method for manufacturing a piezoelectric transducer which includes a piezoelectric oscillation piece having a pair of oscillation arms disposed in parallel with each other with base ends of the oscillation arms fixed to a base of the piezoelectric oscillation piece and with weight metal films formed at the tips of the oscillation arms, a base substrate on the upper surface of which the piezoelectric oscillation piece is mounted, a lid substrate joined with the base substrate such that the mounted piezoelectric oscillation piece can be accommodated in a cavity, and a control film disposed in the vicinity of the pair of the oscillation arms as viewed in the plan view and formed at least on either of the substrates in such a manner as to extend from the base end side to the tip side in the longitudinal direction of the oscillation arms for increasing the degree of vacuum inside the cavity by heating, the method comprising:

• a control film forming step which forms the control film at least on either the base substrate or the lid substrate;
• a joining step which joins the base substrate and the lid substrate after mounting the piezoelectric oscillation piece on the upper surface of the base substrate to seal the piezoelectric oscillation piece into the cavity;
• a gettering step which locally heats and evaporates the control film while measuring series resonance resistance and a frequency after oscillating the piezoelectric oscillation piece sealed in the cavity to adjust the degree of vacuum inside the cavity to a certain level or higher and also adjust the frequency to a value lying within an approximate range around a target value;
• and
• a fine control step which performs fine control of the frequency within the approximate range by heating the weight metal films while continuously measuring the frequency to adjust the frequency to a value close to the target value,
• wherein
• in the gettering step, the heating position of the control film is determined according to the difference between the approximate range and the measured frequency, and
• oscillation characteristics are changed by locally depositing the heated control film on the side surfaces of the oscillation arms positioned in the vicinity of the heating position.