Crystal Device and Method for Manufacturing Crystal Device

Abstract

An object of the present invention is to provide 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.

1 . A crystal device having a crystal plate that includes a base and a vibrating prong protruding from said base, comprising: 
 a first major face, which contains a portion of said base and a portion of said vibrating prong within a single plane, and    formed on said crystal plate;    a second major face, which contains another portion of said base and another portion of said vibrating prong within a single plane, formed on said crystal plate, wherein    said first major face and said second major face have different outer shapes.    
     
     
         2 . The crystal device according to  claim 1 , wherein said crystal plate includes at least a first vibrating prong and a second vibrating prong.  
     
     
         3 . The crystal device according to  claim 2 , wherein said first and second major faces each have a crotch portion defined by a line that originates from the tip of said first vibrating prong, passes through the root of said first vibrating prong and through the root of said second vibrating prong, and leads to the tip of said second vibrating prong, and wherein the crotch portion of said first major face and the crotch portion of said second major face have different shapes.  
     
     
         4 . The crystal device according to  claim 3 , wherein the number of bends contained in the crotch portion of said first major face is different from the number of bends contained in the crotch portion of said second major face.  
     
     
         5 . The crystal device according to  claim 3 , wherein the angle of a bend contained in the crotch portion of said first major face is different from the angle of a bend contained in the crotch portion of said second major face.  
     
     
         6 . The crystal device according to  claim 3 , wherein the number of center points representing curved sections contained in the crotch portion of said first major face is different from the number of center points representing curved sections contained in the crotch portion of said second major face.  
     
     
         7 . The crystal device according to  claim 3 , wherein the curvature of a curved section contained in the crotch portion of said first major face is different from the curvature of a curved section contained in the crotch portion of said second major face.  
     
     
         8 . A method for manufacturing a crystal device having a crystal plate that includes a base and a vibrating prong protruding from said base, the method comprising the steps of: 
 forming a resist layer made of a photosensitive material and a mask layer having corrosion resistance on each of two plane surfaces of a crystal substrate;    exposing the resist layer formed on the first plane surface 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 the second plane surface 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;    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 by etching said crystal substrate through said first mask layer pattern and said second mask layer pattern.    
     
     
         9 . The method according to  claim 8 , wherein said first mask layer pattern has an outer shape that contains a portion of said base and a portion of said vibrating prong within a single plane, and said second mask layer pattern has an outer shape that contains another portion of said base and another portion of said vibrating prong within a single plane.  
     
     
         10 . The method according to  claim 8 , wherein said crystal plate includes at least a first vibrating prong and a second vibrating prong.  
     
     
         11 . The method according to  claim 10 , wherein said first and second mask layer patterns each have a crotch portion defined by a line that originates from the tip of said first vibrating prong, passes through the root of said first vibrating prong and through the root of said second vibrating prong, and leads to the tip of said second vibrating prong.  
     
     
         12 . The method according to  claim 11 , wherein the crotch portion of said first mask layer pattern and the crotch portion of said second mask layer pattern have different shapes.  
     
     
         13 . The method according to  claim 12 , wherein the number of bends contained in the crotch portion of said first mask layer pattern is different from the number of bends contained in the crotch portion of said second mask layer pattern.  
     
     
         14 . The method according to  claim 12 , wherein the angle of a bend contained in the crotch portion of said first mask layer pattern is different from the angle of a bend contained in the crotch portion of said second mask layer pattern.  
     
     
         15 . The method according to  claim 12 , wherein the number of center points representing curved sections contained in the crotch portion of said first mask layer pattern is different from the number of center points representing curved sections contained in the crotch portion of said second mask layer pattern.  
     
     
         16 . The method according to  claim 12 , wherein the curvature of a curved section contained in the crotch portion of said first mask layer pattern is different from the curvature of a curved section contained in the crotch portion of said second mask layer pattern.