Patent Publication Number: US-2023145942-A1

Title: Vibration element and method of manufacturing vibration element

Description:
The present application is based on, and claims priority from JP Application Serial Number 2021-183881, filed Nov. 11, 2021, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a vibration element and a method of manufacturing a vibration element. 
     2. Related Art 
     There has been known that an identification code is attached to a vibration element in order to ensure traceability of a waster and so on in a manufacturing process. In, for example, JP-A-2004-363980 (Document 1), there is disclosed forming an identification code formed of Arabic numerals on an extraction electrode of a quartz crystal element. 
     Further, in, for example, JP-A-2013-157908 (Document 2), there is disclosed forming an identification code formed of a bar-code or the like on a surface of a base of a tuning-fork vibration piece. According to Document 2, the identification code is, for example, a matrix-type two-dimensional code or a one-dimensional code, and has information unique to the piezoelectric vibration piece such as a variety of types of manufacturing information such as a manufacturing number, a manufacturing year, and a manufacturing plant, or information for identifying a state in the manufacturing process and so on. Further, in, for example,  FIG.  5    in Document 2, there is illustrated an appearance in which the identification code having a square shape is formed on the base of the tuning-fork vibration piece. 
     However, in either of the technologies in Document 1 and Document 2, there is a problem that it is difficult to dispose an identification code easy to discriminate in a given space which is made small due to reduction is size of the element. In particular, in the case of the identification code formed of numbers in Document 1, some numerals such as 6 and 8 are blurred to be difficult to discriminate. 
     Further, in Document 2, it is difficult to form the one-dimensional code or the two-dimensional code in a recognizable size in the given small space. 
     In other words, there has been demanded a vibration element provided with an identification symbol which can be formed in a small space and which is easy to discriminate. 
     SUMMARY 
     A vibration element according to the present disclosure includes a vibrating part, and a support part which is coupled to the vibrating part to support the vibrating part, wherein the vibrating part and the support part have a first surface and a second surface having a front and back relationship with the first surface, a first electrode is disposed on the first surface, the first electrode includes a first layer as a foundation layer, and a second layer as an upper layer of the first layer, when performing zoning into a first area in which the first electrode is not disposed, a second area in which the first layer and the second layer are stacked on one another, and a third area in which the first layer is formed, identification symbols formed of two or more of the first area, the second area, and the third area are disposed, and an identification code formed of a plurality of the identification symbols is provided. 
     A method of manufacturing a vibration element according to the present disclosure includes forming a first layer to be a foundation layer on a first surface in a vibrating part and a support part configured to support the vibrating part, stacking a second layer on the first layer to form a second area to be an electrode, forming a first area from which the electrode is removed, and removing the second layer from the electrode to form a third area in which the first layer is exposed, wherein an identification code in which identification symbols of two or more of the first area through the third area are arranged is formed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a transmissive plan view of a vibrator device according to Embodiment 1. 
         FIG.  2    is a cross-sectional view of the vibrator device in a b-b cross-section in  FIG.  1   . 
         FIG.  3    is a plan view of a vibration element. 
         FIG.  4    is an enlarged view of an arm portion of a support arm. 
         FIG.  5    is a manufacturing process diagram of an identification symbol in a c-c cross-section in  FIG.  4   . 
         FIG.  6    is a cross-sectional view of an aspect in the c-c cross-section in  FIG.  4   . 
         FIG.  7    is an enlarged view of the arm portion of the support arm in a different aspect. 
         FIG.  8    is a plan view of the vibration element in a different aspect. 
         FIG.  9    is a plan view of an identification code related to Embodiment 2. 
         FIG.  10    is a cross-sectional view of an aspect in a d-d cross-section in  FIG.  9   . 
         FIG.  11    is a flowchart of a method of manufacturing the identification code. 
         FIG.  12    is a manufacturing process diagram in the d-d cross-section in  FIG.  9   . 
         FIG.  13    is a manufacturing process diagram in the d-d cross-section in  FIG.  9   . 
         FIG.  14    is a cross-sectional view of an identification symbol in a modified example. 
         FIG.  15    is a cross-sectional view of the identification symbol in the modified example. 
         FIG.  16    is a plan view of an identification symbol related to Embodiment 3. 
         FIG.  17    is a plan view showing an aspect of an identification symbol. 
         FIG.  18    is a plan view showing an aspect of an identification symbol. 
         FIG.  19    is a plan view showing an aspect of an identification symbol. 
         FIG.  20    is a plan view showing an aspect of an identification symbol. 
         FIG.  21    is a plan view of a vibration element according to Embodiment 4. 
         FIG.  22    is a plan view showing an aspect of a vibration element. 
         FIG.  23    is a plan view showing an aspect of a vibration element. 
         FIG.  24    is a plan view showing an aspect of a vibration element. 
         FIG.  25    is a plan view showing an aspect of a vibration element. 
         FIG.  26    is a plan view showing an aspect of a vibration element. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Embodiment 1 
     Schematic Configuration of Vibrator Device 
       FIG.  1    is a plan view showing a configuration of a vibrator device according to the present embodiment.  FIG.  2    is a cross-sectional view in a b-b cross-section in  FIG.  1   . The b-b cross-section is a cross-section in a centerline  8  in a plan view of the vibrator device  100 . 
     The vibrator device  100  is constituted by a package  80 , a vibration element  50 , and the like housed in the package  80 . It should be noted that  FIG.  1    is a transmissive view, and illustrates an inside of the package  80  in a see-through manner. In a preferred example, the vibration element  50  is a tuning-fork quartz crystal vibration element, and the vibrator device  100  is a quartz crystal oscillator. It should be noted that it is possible to provide an oscillation circuit in the package  80 , and the oscillation circuit is provided in a bottom portion of a base  60  in the preferred example, but is not shown in the drawings. 
     It should be noted that in each of the drawings, there are shown an X axis, a Y axis, and a Z axis as three axes perpendicular to each other for the sake of convenience of explanation. Further, the arrow side of each of the axes is also referred to as a positive side, and the opposite side is also referred to as a negative side. Further, the positive side in the Z-axis direction is also referred to as an “upper side,” the negative side is also referred to as a “lower side,” but regarding an object to be stacked such as an electrode disposed on a surface crossing the Z axis, a layer more distant from the surface is referred to as an “upper layer” regardless of the positive side and the negative side. Further, a plan view viewed from the Z-axis direction is also referred to simply as a “plan view.” 
     As shown in  FIG.  2   , the package  80  is constituted by the base  60  provided with a recess  61  opening on an upper surface, a lid  70  as a lid body for closing the opening of the recess  61 , and so on. The lid  70  is bonded to the base  60  via a bonding member  66  as a seal ring disposed along an upper surface of a sidewall surrounding the recess  61 . In the preferred example, the base  60  is formed of ceramics such as alumina, and the lid  70  is formed of a metal material such as Kovar. In the preferred example, the lid  70  and the bonding member  66  are bonded to each other with seam welding. It should be noted that these materials are not a limitation, and for example, the lid  70  can be formed using a glass material. 
     In the inside of the package  80 , there is formed a space by the recess  61 , and the vibration element  50  is housed in that space. The vibration element  50  is supported by a pair of protrusions  62 ,  63  disposed in the recess  61  so as to be able to vibrate. In particular, the vibration element  50  is supported by a pair of support arms  4 ,  5  of the vibration element  50  being bonded to the protrusions  62 ,  63  with coupling pads  64 ,  65 , respectively. Thus, as shown in  FIG.  2   , the vibration element  50  is fixed in a state in which the vibrating arms  1 ,  2  of the vibration element  50  can vibrate in the space of the recess  61 . 
     The coupling pads  64 ,  65  are electrically coupled to the oscillation circuit (not shown). The oscillation circuit is electrically coupled to coupling terminals  68 ,  69  on a bottom surface of the package  80 . It should be noted that the details of the vibration element  50  will be described later. 
     The bottom portion of the base  60  is provided with a through hole  78 . The vibration element  50  and so on are housing in the recess  61 , and the lid  70  is bonded to the base  60 , and then the package  80  is put into a reduced-pressure atmosphere. Further, in the reduced-pressure environment, the through hole  78  is filled with a sealing material  67  made of a metal material or the like. Thus, the inside of the package  80  is sealed in a state of keeping the reduced-pressure atmosphere. It should be noted that the reduced-pressure environment is not a limitation, and it is possible to adopt an atmosphere obtained by encapsulating an inert gas such as nitrogen or Ar. 
     Structure of Vibration Element 
       FIG.  3    is a plan view of the vibration element  50 . 
     As shown in  FIG.  3   , the vibration element  50  is constituted by the pair of vibrating arms  1 ,  2  as vibrating parts, a base  3 , the pair of support arms  4 ,  5 , and so on. 
     The vibrating arm  1  extends from the base  3  toward the positive Y direction, and is constituted by an arm part  1   a  located at the base side and coupled to the base  3 , and a weight part  1   b  located at a terminal side. Similarly, the vibrating arm  2  also extends from the base  3  toward the positive Y direction, and is constituted by an arm part  2   a  located at the base side and coupled to the base  3 , and a weight part  2   b  located at a terminal side. In other words, the vibrating arm  2  has a configuration line symmetric with the vibrating arm  1  taking the centerline  8  as an axis of symmetry. The vibrating arms  1 ,  2  are branched into two branches by a cut-out part  6  of the base  3 , and a tuning-fork vibration piece is constituted by the vibrating arms  1 ,  2 . 
     An upper surface of the arm part  1   a  having a prismatic shape is provided with a bottomed groove. Similarly, a lower surface of the arm part  1   a  is also provided with a bottomed groove. Thus, the cross-section of the arm part  1   a  has a cross-sectional configuration having a substantially H shape. The same applies to the arm part  2   a . It should be noted that the upper surface corresponds to a first surface, and the lower surface corresponds to a second surface. The weight part  1   b  is wider in width than the arm part  1   a , and is disposed at a tip side of the arm part  1   a . The same applies to the weight part  2   b.    
     The support arm  4  is a support arm for supporting the base  3  and the vibrating arms  1 ,  2 , and is constituted by an arm part  4   a , an arm part  4   b , an arm part  4   c , and an arm part  4   d . The arm part  4   a  is branched from a cut-out part  7   a  of the base  3  to project toward the positive X direction, and is then folded at a substantially right angle to be coupled to the arm part  4   b  extending toward the positive Y direction. The arm part  4   c  is a coupling portion between the arm part  4   b  and the arm part  4   d , and is formed thinner in width than the arm part  4   d  extending toward the positive Y direction. Further, the arm part  4   c  is substantially the same in width as the arm part  4   d , but is slightly inflected in a coupling part to the arm part  4   b.    
     The support arm  5  is also a support arm for supporting the base  3  and the vibrating arms  1 ,  2 , and is constituted by an arm part  5   a , an arm part  5   b , an arm part  5   c , and an arm part  5   d . The arm part  5   a , the arm part  5   b , the arm part  5   c , and the arm part  5   d  have configurations line symmetric with the arm part  4   a , the arm part  4   b , the arm part  4   c , and the arm part  4   d , respectively, taking the centerline  8  as an axis of symmetry. 
     As described above, the vibration element  50  is provided with a configuration in which the support arms  4 ,  5  are folded at both sides of the base  3  to extend along the extending directions of the vibrating arms  1 ,  2  to thereby achieve a vibration piece small in size and compact. 
     Further, the base  3  and the pair of support arms  4 ,  5  are collectively referred to as a support part. In other words, the support part is a region which is coupled to the vibrating arms  1 ,  2  as the vibrating part to support the vibrating part. 
     Further, an excitation electrode  71  is disposed on an upper surface and side surfaces of the arm part  1   a  of the vibrating arm  1 . The excitation electrode  71  is electrically coupled to the coupling pad  64  on a lower surface of the support arm  4  via an extraction electrode  73   a  on an upper surface of the base  3  and an extraction electrode  74  on an upper surface of the support arm  4 . Similarly, an excitation electrode  72  is disposed on an upper surface and side surfaces of the arm part  2   a  of the vibrating arm  2 . The excitation electrode  72  is electrically coupled to the coupling pad  65  on a lower surface of the support arm  5  via an extraction electrode  73   b  on the upper surface of the base  3  and an extraction electrode  75  on an upper surface of the support arm  5 . In other words, the excitation electrodes  71 ,  72  are provided to the vibrating arms  1 ,  2  as the vibrating part, the extraction electrodes  73   a ,  73   b  are provided to the base  3  as the support part, and the extraction electrodes  74 ,  75  are provided to the support arms  4 ,  5  as the support part. It should be noted that the extraction electrodes  73   a ,  73   b ,  74 , and  75  correspond to support part electrodes. 
     According to this vibration element  50 , when a drive signal is supplied from an outside via the coupling pads  64 ,  65 , a drive voltage is applied to the excitation electrodes  71 ,  72  of the vibrating arms  1 ,  2 , and the vibrating arms  1 ,  2  make flexural vibrations at a predetermined frequency so as to repeat getting closer to each other and getting away from each other as indicated by the arrows. 
     It should be noted that the weight parts  1   b ,  2   b  of the vibrating arms  1 ,  2  are each provided with a metal film for adjusting a vibration state, but the illustration is omitted. 
     Further, the arm part  4   b  of the support arm  4  is provided with an identification code  20 . The identification code  20  is identification information unique to the vibration element  50  in the manufacturing process, and unique identification information of the vibration element  50  such as a manufacturing device which manufactures the vibration element  50 , a production lot, a manufacturing data, manufacturing time, and a manufacturing number. Thus, when a waster in the manufacturing process occurs, it becomes possible to trace a feature of the vibration element  50  back to a wafer state from the identification code. 
     Details of Identification Code 
       FIG.  4    is an enlarged view of the vicinity of the arm part  4   b  of the support arm  4 . 
     The identification code  20  in  FIG.  4    is constituted by a plurality of identification symbols  10   a ,  10   b  arranged along an extending direction of the arm part  4   b  of the support arm  4 . 
     The identification symbol  10   b  is a portion of the arm part  4   a  where the extraction electrode  74  is removed in a circle, and is formed using a photolithography technology. Similarly, the identification symbol  10   a  is formed by removing only an outline portion of a circle from the extraction electrode  74 . The identification symbol  10   a  and the identification symbol  10   b  are the same in diametrical size as each other. 
     The identification symbol  10   a  and the identification symbol  10   b  are identification symbols of patterns reversed from each other, and for example, the identification symbol  10   a  represents “0,” and the identification symbol  10   b  represents “1.” In other words, it is possible to describe a binary number with the identification symbol  10   a  and the identification symbol  10   b . It should be noted that it is possible for the identification symbol  10   a  to represent “1,” and it is possible for the identification symbol  10   b  to represent “0.” 
     In the identification code  20 , seven digits of identification symbols are arranged in a line in the order of the identification symbol  10   a , the identification symbol  10   b , the identification symbol  10   a , the identification symbol  10   a , the identification symbol  10   b , the identification symbol  10   b , and the identification symbol  10   a . In other words, the identification code  20  represents “0100110” as a binary number, which represents  38  as a decimal number. As described above, in the identification code  20 , it is possible to describe identification codes from 0 to 127. It should be noted that the seven digits are not a limitation, but it is possible to arbitrarily set the number of digits in accordance with a necessary amount of information. 
     It is possible to recognize the identification code  20  with a known image recognition technology using an imaging camera. In a preferred example, as shown in  FIG.  3   , since a position at a distance of a dimension  111  from an outer shape in a negative Y direction of the vibration element  50  is defined as a start position  30  of the identification code  20 , it is possible to perform an image recognition of the identification code  20  from the start position  30  with reference to the outer shape of the vibration element  50 . Alternatively, it is possible to take an image of the whole of the arm part  4   b  to extract the seven-digit identification symbol by the image recognition. 
     It should be noted that although in the identification code  20 , there are used the reverse patterns each having a circular shape as the identification symbols, but this is not a limitation, and it is sufficient to adopt identification symbols of patterns reversed from each other, and it is possible to use, for example, a polygonal shape such as a triangle or a quadrangle, a star shape, or a crisscross shape. 
     In the preferred example, the identification symbols  10   a ,  10   b  are arranged at a regular pitch, and a size  112  of the identification symbol  10   b  is no smaller than 1 μm and no larger than 80 μm, and a gap  113  between the identification symbols adjacent to each other is made no smaller than 1 μm and no larger than 150 μm. This is because when the size of the identification symbol is smaller than 1 μm, it is difficult to form the identification symbol, and when the size of the identification symbol is larger than 80 μm, it becomes unachievable for the identification symbol to fall within a formation space such as an arm part  4   b . Further, this is because when the size of the gap  113  is smaller than 1 μm, there is a possibility that the identification symbols adjacent to each other overlap each other, and when the gap  113  is larger than 150 μm, it becomes unachievable for the identification code to fall within the formation space such as an arm part  4   b.    
       FIG.  5    is a cross-sectional view in a c-c cross-section in  FIG.  4   , and is a diagram showing a manufacturing process of the identification symbol.  FIG.  6    is a cross-sectional view in the c-c cross-section in  FIG.  4   . 
     Then, a method of forming the identification symbol  10   b  will be described. 
     As shown in  FIG.  5   , on an upper surface  40   a  of a base member  40  to be the base of the vibration element  50 , there is formed the extraction electrode  74  as the support part electrode. In the preferred example, the base member  40  is a quartz crystal substrate. The extraction electrode  74  has a stacked structure of two layers with a foundation electrode  41  and an upper electrode  42 . In the preferred example, chromium is used as the foundation electrode  41 , and gold is used as the upper electrode  42 . It should be noted that this is not a limitation, and it is possible to use a metal material such as platinum (Pt), aluminum (Al), aluminum alloy, silver (Ag), silver alloy, chromium (Cr), chromium alloy, copper (Cu), molybdenum (Mo), niobium (Nb), tungsten (W), iron (Fe), titanium (Ti), cobalt (Co), zinc (Zn), zirconium (Zr), or nickel (Ni), or an electrically-conductive material such as indium tin oxide (ITO). It should be noted that a method of forming the extraction electrode  74  will be described later. Further, an extraction electrode  94  is formed also on a lower surface  40   b  of the base member  40  similarly to the upper surface  40   a  side. The extraction electrode  94  is also provided with the two-layer structure with a foundation electrode  43  and an upper electrode  44 , which are the same in material as the foundation electrode  41  and the upper electrode  42 . 
     First, as shown in  FIG.  5   , on the extraction electrode  74 , there is formed a resist  55  in which portions to be the identification symbols  10   b  are opened. 
     Then, by performing etching processing using the resist  55  as a mask, the extraction electrode  74  is removed from the portions to be the identification symbols  10   b . Subsequently, the resist  55  is removed. 
     Thus, the identification symbols  10   b  from which the surface of the base member  40  is exposed are provided to the arm part  4   b  of the support arm  4  as shown in  FIG.  6   . In the preferred example, since gold on the surface of the extraction electrode  74  and a quartz crystal surface in the identification symbols  10   b  are different in color tone, reflectance, and so on, it is possible to surely perform the image recognition on the identification symbols  10   b.    
     Further, as shown in  FIG.  6   , it is possible to provide an opening  10   c  to the extraction electrode  94  at the lower surface  40   b  side of the base member  40  at a reverse side of the identification symbol  10   b . As a method of forming the opening  10   c , it is possible to use the same formation method as that for the identification symbol  10   b . It should be noted that it is preferable to make the opening  10   c  one-size larger in diameter than the identification symbol  10   b.    
     According to the above, due to a light transmissive property of quartz crystal, when observing the identification symbol  10   b  from the upper surface  40   a  side of the base material  40 , the color tone, the reflectance, and so on become different compared to when the opening  10   c  does not exist. Therefore, since it becomes possible to use the identification symbol  10   b  without the opening  10   c  and the identification symbol  10   b  with the opening  10   c  as the identification symbols different from each other, it becomes possible to describe a ternary number. In other words, the identification code includes two or more types of identification symbols. Further, the base member  40  has the upper surface  40   a  as a first surface, and the lower surface  40   b  as a second surface opposed to the first surface, the extraction electrode  74  on the upper surface  40   a  is provided with the identification symbol  10   b , and in a portion of the lower surface  40   b  overlapping the identification symbol  10   b  on the upper surface  40   a , there is disposed the opening  10   c , but no electrode is disposed. 
     Modified Examples 
       FIG.  7    is an enlarged view of the vicinity of the arm part  4   b  of the support arm  4  in a modified example, and corresponds to  FIG.  4   . 
     In an identification code  21  shown in  FIG.  7   , an unpatterned portion of the surface of the extraction electrode  74  is used as an identification symbol  10   d  representing “0” instead of the identification symbol  10   a  ( FIG.  4   ). Further, a start line  31  is formed along the start position  30 . The start line  31  is a portion which is formed by removing the extraction electrode  74 , and in which the base member  40  is exposed similarly to the identification symbol  10   b . In these points, the identification code  21  is different from the identification code  20  shown in  FIG.  4   . 
     Since the identification symbols of the identification code  21  are arranged at regular pitch similarly to the identification code  20 , even the unpatterned identification symbol  10   d  functions as the identification symbol. In detail, when the number of digits of the identification code  21 , and the arrangement pitch of the identification symbols are known in advance, by performing the image recognition on the portion corresponding to the setting position from the start line  31 , it is possible to perform the image recognition in which the identification symbols  10   b  is recognized as “1,” and the unpatterned identification symbol  10   d  portion is recognized as “0.” 
     It should be noted that it is not required to dispose the start line  31 , and as described above, it is sufficient to recognize the start position based on the outer shape of the vibration element  50 . Further, as described with reference to  FIG.  6   , it is possible to use an identification symbol obtained by providing the opening  10   c  to the identification symbol  10   b  in addition to the identification symbol  10   b . According to the above, it becomes possible to describe a ternary number. 
       FIG.  8    is a plan view of the vibration element  50  in the modified example. 
     In the vibration element  50  shown in  FIG.  8   , the identification code  20  is provided to the base  3 . In detail, the identification code  20  is provided to the extraction electrode  73   a  as the support part electrode of the base  3 . In other words, the identification code  20  is provided to the extraction electrode  73   a  in the base  3 . 
     It should be noted that the position where the identification code is disposed is not limited thereto, but is sufficiently the position where the electrode is disposed, and can be disposed in, for example, any one of the arm part  4   a , the arm part  4   c , and the arm part  4   d , or can be disposed in any one of the arm parts of the support arm  5 . Alternatively, it is possible to dispose the identification code in the arm part  1   a , the weight part  1   b  of the vibrating arm  1  or the arm part  2   a , the weight part  2   b  of the vibrating arm  2 . It should be noted that when providing the identification code to the vibrating arms  1 ,  2 , it is preferable to adopt a design of taking a weight variation due to the identification code into consideration such as disposing a pair of identification codes at symmetric positions of the vibrating arms  1 ,  2  to thereby adopt setting so that a desired vibration can be obtained within an adjustable range by metal films in the weight parts  1   b ,  2   b.    
     Going back to  FIG.  4   , although there is presented the description assuming that the seven identification symbols are arranged in a line in the identification code  20 , it is possible for the seven identification symbols to adopt a regular zigzag arrangement. When adopting the zigzag arrangement, it is possible to shorten the length of the identification code. 
     Further, although in the above description, it is assumed that the identification symbols  10   a ,  10   b  are formed using a photolithography method, this is not a limitation, it is sufficient to adopt a method capable of removing the extraction electrode  74  to achieve patterning, and it is possible to form the identification symbols  10   a ,  10   b  using, for example, laser processing. 
     As described hereinabove, according to the vibration element  50  and the vibrator device  100  in the present embodiment, the following advantages can be obtained. 
     The vibration element  50  has the vibrating arms  1 ,  2  as the vibrating part, the base  3  and the support arms  4 ,  5  as the support part which is coupled to the vibrating arms  1 ,  2 , and supports the vibrating arms  1 ,  2 , the excitation electrodes  71 ,  72  provided to the vibrating arms  1 ,  2 , and the electrodes including the extraction electrode  74  as the support part electrode provided to the support arm  4 , and the extraction electrode  74  is provided with the identification code  20 . 
     Since the identification code  20  is an arrangement of the identification symbols  10   a ,  10   b  formed of the reverse patterns each having a simple circular shape, even when making the identification code  20  smaller, a deformation or a blur which occurs in numerals of the related-art identification code is little, and therefore, the identification code  20  can easily be discriminated. Further, it is possible to provide the identification code  20  also to the support arm  4  small in width in the resonator unit  50  small in size without requiring the square space which is required for the two-dimensional code. Further, the identification symbols are capable of performing the expression by a binary number or a ternary number, and is therefore capable of dealing with necessary amounts of information. 
     Therefore, it is possible to provide the vibration element  50  and the vibrator device  100  each provided with the identification code  20  which can be formed in a small space, and which is easy to discriminate. 
     Further, the identification code  20  includes the identification symbols  10   a ,  10   b  of patterns reversed from each other, and can also include more than two types of identification symbols. 
     According to the above, since the contrast becomes clear due to the reverse patterns, it is possible to surely discriminate even the identification symbols  10   a ,  10   b  small in size. Further, by using the more than two types of identification symbols, it is possible to describe a large amount of information even with a small number of digits. 
     Further, the size of the identification symbol  10   b  is no smaller than 1 μm and no larger than 80 μm, and the gap between the identification symbols adjacent to each other is no smaller than 1 μm and no larger than 150 μm. 
     According to the above, even in the small space, it is possible to form the identification symbols which can be discriminated, and the identification code the image recognition of which can be achieved. 
     Further, the base member  40  has the upper surface  40   a  as the first surface, and the lower surface  40   b  as the second surface opposed to the first surface, the extraction electrode  74  on the upper surface  40   a  is provided with the identification symbol  10   b , and in a portion of the lower surface  40   b  overlapping the identification symbol  10   b  on the upper surface  40   a , there is disposed the opening  10   c , but no electrode is disposed. 
     According to the above, since it becomes possible to use the identification symbol  10   b  without the opening  10   c  and the identification symbol  10   b  with the opening  10   c  as the identification symbols different from each other, it becomes possible to describe a ternary number. 
     Further, in the preferred example, the identification code  20  is provided to the extraction electrode  73   a  in the base  3 , or the extraction electrode  74  in the support arm  4 . 
     According to the above, since the identification code  20  is provided to the extraction electrode  74  in the support arm  4  instead of the vibrating arms  1 ,  2 , it is possible to decrease the frequency deviation due to the formation of the identification code  20 , and thus, it is possible to obtain the vibration element  50  high in accuracy. 
     Embodiment 2 
     Different Aspect-1 of Identification Code 
       FIG.  9    is a plan view of an identification code according to the present embodiment, and corresponds to  FIG.  7   .  FIG.  10    is a cross-sectional view along a d-d cross-section in  FIG.  9   . 
     The identification code  22  in the present embodiment is different in the point that it is possible to express ternary numbers with the stacked structure of the upper surface  41   a , and the formation method thereof from that in Embodiment 1. Hereinafter, the same constituent regions as in Embodiment 1 are denoted by the same reference numerals, and redundant descriptions will be omitted. 
     In the identification code  22  shown in  FIG.  9   , three gray levels can be expressed by an identification symbol  10   e  formed of the surface of the foundation electrode  41  in the extraction electrode  74  as shown in  FIG.  10    in addition to the identification symbol  10   d  formed of the unpatterned surface of the extraction electrode  74 , and the identification symbol  10   b  formed of the surface of the base member  40  from which the electrode is removed. For example, by the identification symbol  10   d  representing “0,” the identification symbol  10   b  representing “1,” and the identification symbol  10   e  representing “2,” it is possible to express ternary numbers. It should be noted that it is possible for the identification symbol  10   e  to represent “1,” and it is possible for the identification symbol  10   b  to represent “2,” and it is sufficient to arbitrarily set the association with the numerals. 
     Method of Forming Identification Code 
       FIG.  11    is a flowchart showing a flow of the method of forming the identification code.  FIG.  12    and  FIG.  13    are manufacturing process diagrams. 
     Then, the method of forming the identification code  22  will be described using mainly  FIG.  11    and arbitrarily  FIG.  12    and  FIG.  13   . 
     In the step S 10 , the foundation electrode  41  to be a first layer of the extraction electrode  74  is formed on the upper surface  40   a  of the base member  40 . In detail, the foundation electrode  41  is formed using an evaporation method. In the preferred example, chromium is used as a material of the foundation electrode  41 . It should be noted that chromium is not a limitation, and it is possible to use other materials described above. In other words, the foundation electrode  41  to be the foundation layer is formed on the upper surface  40   a  as the first surface of the base member  40 . 
     In the step S 11 , the upper electrode  42  to be a second layer of the extraction electrode  74  is formed on the foundation electrode  41 . In detail, the upper electrode  42  is formed using an evaporation method. Thus, as shown in  FIG.  12   , the extraction electrode  74  having a two-layer configuration is formed on the upper surface  40   a  of the base member  40 . In the preferred example, gold is used as a material of the upper electrode  42 . It should be noted that gold is not a limitation, and it is possible to use other materials described above. In other words, the upper electrode  42  as a second layer is stacked on the foundation electrode  41  as the first layer to form a second area formed of the extraction electrode  74  as the electrode. 
     In the step S 12 , as shown in  FIG.  12   , on the extraction electrode  74 , there is formed a resist  56  in which portions to be the identification symbols  10   b  are opened. Subsequently, by performing etching processing using the resist  56  as a mask, the extraction electrode  74  is removed from the portions to be the identification symbols  10   b . In other words, the extraction electrode  74  is removed to thereby form the first area where the surface of the base member  40  is exposed. 
     In the step S 13 , as shown in  FIG.  13   , on the extraction electrode  74  and the identification symbols  10   b , there is formed a resist  57  in which portions to be the identification symbols  10   e  are opened. Subsequently, by performing etching processing using the resist  57  as a mask, the upper electrode  42  is removed from the portions to be the identification symbols  10   e . In detail, the etching rate is controlled to selectively remove only the upper electrode  42 . In other words, the upper electrode  42  as the second layer is removed from the extraction electrode  74  to form a third area where the foundation electrode  41  as the first layer is exposed. It should be noted that it is possible to use laser processing for the formation of the identification symbols  10   b  and the identification symbols  10   e . When forming the identification symbols  10   e  using the laser processing, it is preferable to control the irradiation intensity to be lower than in the formation of the identification symbols  10   b  so as to selectively remove only the upper electrode  42 . 
     Going back to  FIG.  10   , thus, there are formed the identification symbol  10   d  as the second area formed of the surface of the extraction electrode  74  obtained by stacking the upper electrode  42  as the second layer on the foundation electrode  41  as the first layer, the identification symbol  10   b  as the first area formed of the surface of the base member  40 , and the identification symbol  10   e  as the third area formed of the surface of the foundation electrode  41  as shown in  FIG.  10   . In the preferred example, the identification symbol  10   e  has a chromium surface which is different in color tone, reflectance, and so on from a gold surface of the identification symbol  10   d  and a quartz crystal material surface of the identification symbol  10   b  to create a contrast, and can therefore be clearly discriminated due to the contrast. 
     The identification code  22  shown in  FIG.  9    represents “0120120” as a ternary number, which represents  420  as a decimal number. As described above, in the identification code  22 , it is possible to describe identification codes from 0 to 2186. It should be noted that the seven digits are not a limitation, but it is possible to arbitrarily set the number of digits in accordance with a necessary amount of information. In other words, the identification code  22  is formed of an arrangement of two or more identification symbols including the identification symbol  10   b  using the first area, the identification symbol  10   d  using the second area, and the identification symbol  10   e  using the third area. 
     Different Aspect-2 of Identification Code 
       FIG.  14    is a cross-sectional view of an identification code according to the present embodiment, and corresponds to  FIG.  10   . 
     In  FIG.  14   , the three gray levels are realized by using an identification symbol  10   f  using the opening  10   c  on the lower surface  40   b . In detail, in the identification symbol  10   f , the opening  10   c  is provided to the extraction electrode  94  at the lower surface  40   b  side of the base member  40  at a reverse side of the identification symbol  10   b . In other words, on the lower surface  40   b  as the second surface of the base member  40 , there is disposed the extraction electrode  94  as a second electrode, the extraction electrode  94  includes the foundation electrode  43  as a third layer which is the foundation layer and the upper electrode  44  as a fourth layer which is an upper layer of the third layer, and when performing zoning into the opening  10   c  as a fourth area where the extraction electrode  94  is not disposed and a fifth area where the foundation electrode  43  and the upper electrode  44  are stacked on one another, the identification symbol  10   f  is formed of the identification symbol  10   b  as the first area and the opening  10   c  overlapping each other. 
     Thus, when performing a see-through observation of the identification symbol  10   f  from the upper surface  40   a  side, since no electrode exists on the lower surface  40   b  side of the base member  40  having a light transmissive property, the color tone, the reflectance, and so on are different compared to the identification symbol  10   b  in which the extraction electrode  74  is observed via the base member  40  when performing the see-through observation, and therefore, a contrast occurs to make it possible to clearly discriminate between the identification symbol  10   f  and the identification symbol  10   b . It should be noted that the identification symbol  10   f  can be formed by a combination of the formation methods described above. 
       FIG.  15    is a cross-sectional view of an identification code according to the present embodiment, and corresponds to  FIG.  10    and  FIG.  14   . 
       FIG.  15    shows the identification code of four gray levels obtained by combining the identification symbols shown in  FIG.  10    and  FIG.  14   . In detail, there are arranged the identification symbol  10   d , the identification symbol  10   b , the identification symbol  10   f , and the identification symbol  10   e  in this order from the left side. According to the above, it is possible to describe 256 types of identification codes with these four digits. Further, in the case of seven digits, it is possible to describe 16384 types of identification codes. 
     As described hereinabove, according to the vibration element  50  and the vibrator device  100  in the present embodiment, the following advantages can be obtained in addition to the advantages in Embodiment 1. 
     The vibration element  50  is provided with the vibrating arms  1 ,  2  as the vibrating part, and the base  3  as the support part which is coupled to the vibrating arms  1 ,  2  and supports the vibrating arms  1 ,  2 , the base member  40  constituting the vibrating arms  1 ,  2  and the base  3  has the upper surface  40   a  as the first surface and the lower surface  40   b  as the second surface opposed to the upper surface  40   a , on the upper surface  40   a , there is disposed the extraction electrode  74  as the first electrode, the extraction electrode  74  includes the foundation electrode  41  as the first layer which is the foundation layer, and the upper electrode  42  as the second layer which is an upper layer of the first layer, and when performing zoning into the first area where the extraction electrode  74  is not disposed, the second area where the foundation electrode  41  and the upper electrode  42  are stacked on one another, and the third area where the foundation electrode  41  is formed, there are formed the identification symbols using two or more areas out of the first through third areas, and there is provided the identification code  22  constituted by the plurality of identification symbols. 
     According to the above, in the extraction electrode  74  located at the upper surface  40   a  side, using the three areas different in gray level from each other, namely the first area where the surface of the base member  40  made of quartz crystal is exposed, the second area as the surface of the extraction electrode  74 , and the third area as the surface of the foundation electrode  41 , it is possible to separately create the identification symbol  10   b , the identification symbol  10   d , and the identification symbol  10   e . Therefore, it is possible to form the identification code  22  of three gray levels only with the upper surface  40   a  side of the base member  40 . Further, the formation method is also simple. 
     Therefore, it is possible to provide the vibration element  50  provided with the identification code which can be formed in a small space, and which is easy to discriminate. Further, it is possible to provide the manufacturing method of easily forming the identification code easy to discriminate. 
     Further, on the lower surface  40   b  as the second surface of the base member  40 , there is disposed the extraction electrode  94  as the second electrode, the extraction electrode  94  includes the foundation electrode  43  as the third layer which is the foundation layer and the upper electrode  44  as the fourth layer which is an upper layer of the third layer, and when performing zoning into the opening  10   c  as the fourth area where the extraction electrode  94  is not disposed and the fifth area where the foundation electrode  43  and the upper electrode  44  are stacked on one another, the identification symbol  10   f  is formed of the identification symbol  10   b  as the first area and the opening  10   c  overlapping each other. 
     According to the above, when performing the see-through observation of the identification symbol  10   f  from the upper surface  40   a  side, since no electrode exists on the lower surface  40   b  side of the base member  40  having a light transmissive property, the color tone, the reflectance, and so on are different compared to the identification symbol  10   b  in which the extraction electrode  74  is observed via the base member  40  when performing the see-through observation, and therefore, a contrast occurs to make it possible to clearly discriminate between the identification symbol  10   f  and the identification symbol  10   b.    
     Therefore, by combining the lower surface  40   b  of the base member  40 , it becomes possible to form the identification symbols of four gray levels, and thus, it is possible to increase the amount of information. 
     The method of manufacturing the vibration element  50  includes a step which includes a step of forming the foundation electrode  41  as the first layer to be the foundation layer on the upper surface  40   a  of the base member  40 , a step of stacking the upper electrode  42  as the second layer on the foundation electrode  41  to form the second area formed of the extraction electrode  74 , a step of forming the identification symbol  10   b  using the first area where the extraction electrode  74  is removed, and a step of forming the third area where the upper electrode  42  is removed from the extraction electrode  74  to expose the foundation electrode  41 , and which forms the identification code obtained by arranging the identification symbols constituted by two or more of the first through third areas. 
     According to the above, it is possible to provide the manufacturing method capable of easily forming the identification code easy to discriminate. 
     Embodiment 3 
     Different Aspect of Identification Symbol 
       FIG.  16    is a plan view of identification symbols according to the present embodiment, and corresponds to  FIG.  4   ,  FIG.  7   , and  FIG.  9   . 
     In each of the embodiments described above, the description is presented assuming that the shape of the identification symbol is a circular shape, but this is not a limitation, and it is sufficient for the identification symbol to have a shape easy to discriminate. Hereinafter, the same constituent regions as in Embodiment 1 are denoted by the same reference numerals, and redundant descriptions will be omitted. 
     As shown in  FIG.  16   , an identification symbol  11  has a triangular shape, and an identification symbol  12   a  has a quadrangular shape. It should be noted that it is also possible to use other polygonal shapes. Further, an identification symbol  13  has a star shape, and an identification symbol  14   a  has a crisscross shape. As described above, as the identification symbol, there can be used a variety of shape patterns easy to discriminate. Further, similarly to the identification symbol  10   a  ( FIG.  4   ), it is possible to use reverse patterns obtained by etching only the outlines of these identification symbols. It is possible to describe quaternary numbers in four digits with the identification symbols shown in  FIG.  16   . Further, when adding the circular pattern of the identification symbol  10   b  ( FIG.  4   ) thereto, it becomes possible to describe quinary numbers in five digits. 
       FIG.  17    through  FIG.  20    are plan views of identification symbols according to the present embodiment, and each correspond to  FIG.  16   . 
     Identification symbols  15  shown in  FIG.  17    are identification symbols including a direction pointer  9   a  indicating a direction of the identification symbol. The identification symbols  15  each form a circular shape, and a part of the circular shape is cut out to open with the direction pointer  9   a  having a rectangular shape. It should be noted that in  FIG.  17   , a suffix is attached to the reference numeral in accordance with the orientation of the direction pointer  9   a.    
     In an identification symbol  15   a , the direction pointer  9   a  is directed toward the positive X direction. In an identification symbol  15   b , the direction pointer  9   a  is directed toward the positive Y direction. In an identification symbol  15   c , the direction pointer  9   a  is directed toward the negative X direction. In an identification symbol  15   d , the direction pointer  9   a  is directed toward the negative Y direction. In other words, with reference to the identification symbol  15   a , the identification symbol  15   b  rotates clockwise as much as 90°, the identification symbol  15   c  rotates as much as 180°, and the identification symbol  15   d  is directed toward the direction rotated as much as 270°. In other words, assuming the arrangement direction of the identification symbols as the positive Y direction as a first direction, the identification code includes the identification symbol having the direction pointer  9   a  directed toward the first direction or the direction pointer  9   a  directed toward a direction different from the first direction. 
     Identification symbols  16  shown in  FIG.  18    each form a quadrangular shape, and a part of the quadrangular shape is cut out to open with the direction pointer  9   a  having a rectangular shape. In an identification symbol  16   a , the direction pointer  9   a  is directed toward the positive X direction. In an identification symbol  16   b , the direction pointer  9   a  is directed toward the positive Y direction. In an identification symbol  16   c , the direction pointer  9   a  is directed toward the negative X direction. In an identification symbol  16   d , the direction pointer  9   a  is directed toward the negative Y direction. In other words, with reference to the identification symbol  16   a , the identification symbol  16   b  rotates clockwise as much as 90°, the identification symbol  16   c  rotates as much as 180°, and the identification symbol  16   d  is directed toward the direction rotated as much as 270°. It should be noted that the shape of the direction pointer  9   a  is not limited to the rectangular shape, and is only required to be a shape opening direction of which can be identified, and can be, for example, a V shape or can also be a U shape. 
     Identification symbols  17  shown in  FIG.  19    are each a rod-like rectangular shape, and one side of the rectangular shape plays a role of a direction pointer  9   b . As described above, as long as a shape includes a line segment indicating a direction, the shape can be used as the direction pointer. In an identification symbol  17   a , the direction pointer  9   b  is directed toward the positive X direction. Further, with reference to the identification symbol  17   a , an identification symbol  17   b  rotates clockwise as much as 45°, an identification symbol  17   c  rotates as much as 90°, and an identification symbol  17   d  is directed toward the direction rotated as much as 135°. As described above, by adjusting the rotational angle in accordance with the shape pattern, it is possible to zone the four identification symbols. 
     An identification symbol  12   b  shown in  FIG.  20    is obtained by rotating the identification symbol  12   a  ( FIG.  16   ) clockwise as much as 45°, wherein one side of the quadrangular shape plays the role of a direction pointer  9   c . Thus, as shown in  FIG.  20   , the identification symbol  12   b  can be discriminated from the identification symbol  12   a  in which the direction pointer  9   c  is directed toward the positive X direction. Similarly, an identification symbol  14   b  is obtained by rotating the identification symbol  14   a  ( FIG.  16   ) clockwise as much as 45°, wherein one side of the crisscross shape plays the role of a direction pointer  9   d . Thus, as shown in  FIG.  20   , the identification symbol  14   b  can be discriminated from the identification symbol  14   a  in which the direction pointer  9   d  is directed toward the positive X direction. 
     According to the experiment conducted by the inventors, it is confirmed that the discrimination by the image recognition can be achieved also by these identification symbol  11  through the identification symbol  17 . 
     Further, in the above description, the identification symbols similar in kind are collectively described in each drawing, but it is possible to mix these identification symbols with each other to create the identification code. According to the above, it is possible to describe the identification codes in quaternary or higher number. 
     Further, in the above description, the description is presented assuming that the base member  40  of the vibration element  50  is the quartz crystal substrate, but this is not a limitation. It is possible to use a variety of types of piezoelectric material such as lithium niobate, lithium tantalate, lead zirconium titanate, lithium tetraborate, langasite, potassium niobate, gallium phosphate, gallium arsenide, aluminum nitride, zinc oxide, barium titanate, lead titanate, sodium potassium niobate, bismuth ferrite, sodium niobate, bismuth titanate, or bismuth sodium titanate, or it is possible to use a material other than the piezoelectric material such as a silicon substrate. 
     As described hereinabove, according to the vibration element  50  and the vibrator device  100  in the present embodiment, the following advantages can be obtained in addition to the advantages in the embodiments described above. 
     Assuming the arrangement direction of the identification symbols as the positive Y direction as the first direction, the identification code includes the identification symbol having the direction pointer  9   a  directed toward the first direction or the direction pointer  9   a  directed toward a direction different from the first direction. 
     According to the above, it is possible to discriminate the plurality of identification symbols  15   a  through  15   d  from each other using a single identification symbol  15  having the direction pointer  9   a  by changing the direction of the identification symbol  15 . Even the shapes are the same as each other, it is possible to make the identification symbols easy to discriminate by making the directions different using the direction pointer  9   a.    
     Embodiment 4 
     Application Examples 
       FIG.  21    through  FIG.  26    are each a plan view of the vibration element according to the present embodiment, and correspond to  FIG.  3   . 
     The identification code described above can be applied to a variety of vibration elements. 
     For example, a vibration element  51  shown in  FIG.  21    is a tuning-fork vibration element, and has a configuration in which the base  3  is formed to be large in size, and the vibrating arms  1 ,  2  as the vibrating part are supported by the base  3 . Therefore, the support arm is not provided. 
     As shown in  FIG.  21   , in the vibration element  51 , it is possible to provide the identification code  20  to an electrode such as an extraction electrode of the base  3 . 
     A vibration element  52  shown in  FIG.  22    is a tuning-fork vibration element, the distance between the vibrating arms  1 ,  2  is set long, and a support arm  53  is disposed between the vibrating arms  1 ,  2 . The support arm  53  is coupled to the base  3  similarly to the vibrating arms  1 ,  2 . 
     As shown in  FIG.  22   , in the vibration element  52 , it is possible to provide the identification code  20  to an electrode such as an extraction electrode of the support arm  53 . It should be noted that it is possible to provide the identification code  20  to the base  3 . 
     A vibration element  81  shown in  FIG.  23    is provided with a vibrating part  54  formed of an AT-cut quartz crystal substrate having a thickness-shear vibration mode. 
     As shown in  FIG.  23   , in the vibration element  81 , it is possible to provide the identification code  20  to an electrode such as an extraction electrode of the base  3 . 
     A vibration element  82  shown in  FIG.  24    is provided with a vibrating part  58  in the thickness-shear vibration mode having an inverted-mesa structure having a recessed part  89  in substantially the central portion of the quartz crystal substrate. 
     As shown in  FIG.  24   , in the vibration element  82 , it is possible to provide the identification code  20  to an electrode such as an extraction electrode of the base  3 . 
     A vibration element  83  is a gyro sensor element for respectively detecting angular velocities around three axes (three detection axes) of an x axis, a y axis, and a z axis perpendicular to each other. 
     The base member of the vibration element  83  is formed of a Z-cut quartz crystal substrate, and has the base  3 , a pair of detection arms  852 ,  853 , a pair of coupling arms  854 ,  855 , a pair of drive arms  856 ,  857 , and a pair of drive arms  858 ,  859 , wherein the base  3  is located in a central portion, the pair of detection arms  852 ,  853  are the vibrating arms extending toward both sides in the Y-axis direction from the base  3 , the pair of coupling arms  854 ,  855  extend toward both sides in the X-axis direction from the base  3 , the pair of drive arms  856 ,  857  are the vibrating arms extending toward both sides in the Y-axis direction from a tip portion of the coupling arm  854 , and the pair of drive arms  858 ,  859  are the vibrating arms extending toward the both sides in the Y-axis direction from a tip portion of the coupling arm  855 . 
     As shown in  FIG.  25   , in the vibration element  83 , it is possible to provide the identification code  20  to an electrode such as an extraction electrode of the base  3 . 
     A vibration element  84  shown in  FIG.  26    is a vibration element using an MEMS (Micro Electro Mechanical Systems) which has three movable parts  87   a ,  87   b , and  87   c  and the base  3  to which base ends of the movable parts are coupled on an SOI (Silicon on Insulator) substrate. 
     As shown in  FIG.  26   , in the vibration element  84 , it is possible to provide the identification code  20  to an electrode such as an extraction electrode of the base  3 .