METHOD OF PIEZOELECTRIC VIBRATING PIECE, WAFER, PIEZOELECTRIC VIBRATOR, OSCILLATOR, ELECTRONIC APPARATUS, AND RADIO-CONTROLLED TIMEPIECE
The present invention provides a novel method of producing piezoelectric vibration pieces in which a plurality of piezoelectric vibration pieces are formed at once from a wafer, using a plurality of photoresist processes. The wafer is marked with wafer marks each unique to a different one of photoresist masks to prevent a wrong use of the photoresist masks during the photoresist processes.
1 . A method of producing piezoelectric vibration pieces comprising:
(a) forming in a wafer a plurality of piezoelectric pieces and wafer marks which comprise pairs of marks formed at predetermined locations in the wafer, wherein each mark has a predetermine shape which is asymmetrical in any directions, and each pair presents a unique mark pattern which is asymmetrical in any directions;
(b) providing a plurality of masks each comprising a pair of marks identical in mark pattern to a different one of the pairs of marks formed in the wafer;
(c) forming layers of electrode films on the wafer in which the plurality of piezoelectric pieces and the wafer marks are formed;
(d) applying a resist film on the wafer on which the layers of electrode films are formed;
(e) placing one of the masks on the wafer so as to coincide a pair of marks of the one mark with a corresponding pair of marks formed in the wafer;
(f) partially removing the resist film according to a pattern of the mask;
(g) partially removing at least one layer of electrode film using a remnant of the resist film; and
(h) repeating steps (d), (e), (f) and (g) using a different mask.
2 . The method according to claim 1 , wherein the applying a resist film comprises covering the corresponding mark pair formed in the wafer.
3 . The method according to claim 1 , where marks of each pair is identical to each other.
4 . The method according to claim 1 , wherein the marks formed in the wafer are identical to one another.
5 . The method according to claim 1 , wherein a distance between marks is different in the respective pairs.
6 . The method according to claim 3 , wherein the mark is in a form of letter “L”.
7 . The method according to claim 1 , wherein the marks of the respective pairs are formed respectively in two opposite margins of the wafer.
8 . The method according to claim 1 , wherein the mark pairs are arranged in parallel to each other in the wafer.