Crystal device and method for manufacturing crystal device

• US 8,258,676 B2
• Filed: 05/17/2010
• Issued: 09/04/2012
• Est. Priority Date: 06/21/2004
• Status: Expired due to Fees

• Current Assignee: Citizen Holdings Co., Ltd. (Citizen Electronics Company Limited)
• Original Assignee: Citizen Holdings Co., Ltd. (Citizen Electronics Company Limited)
• Inventors: Ikeda, Tomoo
• Primary Examiner(s): Deo, Duy
• Application Number:
  US12/801,020
• Publication Number:
  US 20100223769A1
• Time in Patent Office: 841 Days
• Field of Search: None
• US Class Current: 310/323.06
• CPC Class Codes: H03H 3/02 for the manufacture of piezoelectric or electrostrictive resonators or networks H03H3/08 takes precedence
• CPC Class Codes: H03H 9/21 Crystal tuning forks
• CPC Class Codes: Y10T 29/42 Piezoelectric device making

Abstract

A crystal device that has stable vibration characteristics and that offers high reliability and high accuracy. The crystal device includes a first major face, which contains a portion of a base and a portion of a vibrating prong within a single plane, formed on the crystal plate, and a second major face, which contains another portion of the base and another portion of the vibrating prong within a single plane, formed on a crystal plate, wherein the first major face and the second major face have different outer shapes. The shapes of the first and second major faces can be produced by first forming mask layer patterns on a crystal substrate by exposure through different mask patterns and then etching the crystal substrate using the thus formed mask layer patterns.

Claims

1. A method for manufacturing a crystal device having a crystal plate that includes a base and a vibrating prong including at least a first vibrating prong and a second vibrating prong protruding from said base, the method comprising the steps of:

forming a mask layer having corrosion resistance and a resist layer made of a photosensitive material on top thereof on each of two plane surfaces of a crystal substrate;

exposing the resist layer formed on a first of the two plane surfaces of said crystal substrate to radiation through a first mask on which a first mask pattern is drawn, and exposing the resist layer formed on a second of the two plane surfaces of said crystal substrate to radiation through a second mask on which a second mask pattern is drawn that differs in shape from said first mask pattern, wherein said first and second mask patterns each have a crotch portion defined by a line that originates from a tip of said first vibrating prong, passes through a root of said first vibrating prong and through a root of said second vibrating prong, and leads to a tip of said second vibrating prong, and an angle of a bend contained in the crotch portion of said first mask pattern is different from an angle of a bend contained in the crotch portion of said second mask pattern;

forming a first resist layer pattern by patterning the resist layer on the first plane surface of said crystal substrate into a shape corresponding to said first mask pattern, and forming a second resist layer pattern by patterning the resist layer on the second plane surface of said crystal substrate into a shape corresponding to said second mask pattern;

forming a first mask layer pattern by patterning the mask layer on the first plane surface of said crystal substrate into the shape corresponding to said first mask pattern, and forming a second mask layer pattern by patterning the mask layer on the second plane surface of said crystal substrate into the shape corresponding to said second mask pattern; and

forming said crystal plate having a first major face and a second major face on said crystal plate by etching said crystal substrate through said first mask layer pattern and said second mask layer pattern, wherein said first major face contains a portion of said base, a portion of said first vibrating prong and a portion of said second vibrating prong within a single plane, and said second major face contains another portion of said base, another portion of said first vibrating prong and another portion of said second vibrating prong within a single plane and wherein the crotch portion of said first major face and the crotch portion of said second major face have different outer shapes.

2. A method for manufacturing a crystal device having a crystal plate that includes a base and a vibrating prong including at least a first vibrating prong and a second vibrating prong protruding from said base, the method comprising the steps of:

forming a mask layer having corrosion resistance and a resist layer made of a photosensitive material on top thereof on each of two plane surfaces of a crystal substrate;

exposing the resist layer formed on a first of the two plane surfaces of said crystal substrate to radiation through a first mask on which a first mask pattern is drawn, and exposing the resist layer formed on a second of the two plane surfaces of said crystal substrate to radiation through a second mask on which a second mask pattern is drawn that differs in shape from said first mask pattern, wherein said first and second mask patterns each have a crotch portion defined by a line that originates from a tip of said first vibrating prong, passes through a root of said first vibrating prong and through a root of said second vibrating prong, and leads to a tip of said second vibrating prong, and a number of center points representing curved sections contained in the crotch portion of said first mask pattern is different from a number of center points representing curved sections contained in the crotch portion of said second mask pattern;

forming a first resist layer pattern by patterning the resist layer on the first plane surface of said crystal substrate into a shape corresponding to said first mask pattern, and forming a second resist layer pattern by patterning the resist layer on the second plane surface of said crystal substrate into a shape corresponding to said second mask pattern;

forming a first mask layer pattern by patterning the mask layer on the first plane surface of said crystal substrate into the shape corresponding to said first mask pattern, and forming a second mask layer pattern by patterning the mask layer on the second plane surface of said crystal substrate into the shape corresponding to said second mask pattern; and

forming said crystal plate having a first major face and a second major face on said crystal plate by etching said crystal substrate through said first mask layer pattern and said second mask layer pattern, wherein said first major face contains a portion of said base, a portion of said first vibrating prong and a portion of said second vibrating prong within a single plane, and said second major face contains another portion of said base, another portion of said first vibrating prong and another portion of said second vibrating prong within a single plane and wherein the crotch portion of said first major face and the crotch portion of said second major face have different outer shapes.

3. A method for manufacturing a crystal device having a crystal plate that includes a base and a vibrating prong including at least a first vibrating prong and a second vibrating prong protruding from said base, the method comprising the steps of:

forming a mask layer having corrosion resistance and a resist layer made of a photosensitive material on top thereof on each of two plane surfaces of a crystal substrate;

exposing the resist layer formed on a first of the two plane surfaces of said crystal substrate to radiation through a first mask on which a first mask pattern is drawn, and exposing the resist layer formed on a second of the two plane surfaces of said crystal substrate to radiation through a second mask on which a second mask pattern is drawn that differs in shape from said first mask pattern, wherein said first and second mask patterns each have a crotch portion defined by a line that originates from a tip of said first vibrating prong, passes through a root of said first vibrating prong and through a root of said second vibrating prong, and leads to a tip of said second vibrating prong, and a curvature of a curbed section contained in the crotch portion of said first mask pattern is different from a curvature of a curved section contained in the crotch portion of said second mask pattern;

forming a first resist layer pattern by patterning the resist layer on the first plane surface of said crystal substrate into a shape corresponding to said first mask pattern, and forming a second resist layer pattern by patterning the resist layer on the second plane surface of said crystal substrate into a shape corresponding to said second mask pattern;

forming a first mask layer pattern by patterning the mask layer on the first plane surface of said crystal substrate into the shape corresponding to said first mask pattern, and forming a second mask layer pattern by patterning the mask layer on the second plane surface of said crystal substrate into the shape corresponding to said second mask pattern; and

forming said crystal plate having a first major face and a second major face on said crystal plate by etching said crystal substrate through said first mask layer pattern and said second mask layer pattern, wherein said first major face contains a portion of said base, a portion of said first vibrating prong and a portion of said second vibrating prong within a single plane, and said second major face contains another portion of said base, another portion of said first vibrating prong and another portion of said second vibrating prong within a single plane and wherein the crotch portion of said first major face and the crotch portion of said second major face have different outer shapes.