Abstract:
Quartz-crystal vibrating devices are disclosed, including vibrating and frame portions separated by a through-slot. An edge surface of the slot has a protrusion preventing unwanted formation of artifact “electrodes.” The vibrating portion and frame are made of AT-cut quartz as a unit. A joining portion couples the frame and vibrating portion together across the through-slot. A package base has two external electrodes. A third frame region has first and second plane surfaces. The protrusion projects toward the vibrating portion and has first and/or second sloped surfaces. First and second extraction electrodes extend from respective excitation electrodes via respective joining portions to respective external electrodes. The extraction electrodes pass across the first plane surface and first sloped surface or across the second plane surface and second slanted surface.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to and the benefit of Japan Patent Application No. 2011-003801, filed on Jan. 12, 2011, in the Japan Patent Office, the disclosure of which is incorporated herein by reference in its entirety. 
       FIELD 
       [0002]    The present disclosure relates to, inter alia, AT-cut quartz-crystal devices having a quartz-crystal vibrating portion separated, at least in part, from a surrounding quart-crystal frame portion by a through-slot. 
       DESCRIPTION OF THE RELATED ART 
       [0003]    Conventional quartz-crystal devices include a vibrating portion that vibrates when electrically energized and a frame portion surrounding the vibrating portion. The combination of a vibrating portion and its frame portion is termed a “quartz-crystal frame.” By forming multiple quartz-crystal frames on a wafer, quartz-crystal devices can be mass-produced on a wafer scale. 
         [0004]    Regarding a quartz-crystal frame, the vibrating portion and the frame portion are formed on a wafer and defined in part by a through-slot extending through the thickness dimension of the wafer around at least three edges of the vibrating portion. The vibrating portion includes excitation electrodes for causing the vibrating portion to vibrate. Each excitation electrode is connected to a corresponding extraction electrode situated on the frame portion. (Usually there are two excitation electrodes and two corresponding extension electrodes.) These electrodes are usually formed by sputtering according to a pattern defined by a mask. However, a mask that is misaligned during sputtering causes the particles of sputtered metal to spread undesirably via the through-slots, which forms “electrodes” at undesired positions. 
         [0005]    A conventional way in which to prevent misalignment of the sputtering mask is to form a blockade on the through-slot that prevents the sputtered metal particles from spreading there. An example of such a blockade is disclosed in Japan Unexamined Patent Application No. 2010-147627, in which protruding portions are formed on edge surfaces of the through-slots on the frame portion. Unfortunately, the extraction electrodes are formed only on protruding portions of the frame portion, which tends to make the surface area of the extraction electrodes small. Smaller extraction electrodes have greater electrical impedance, which can degrade the vibrating characteristics of the vibrating portion. 
         [0006]    In view of the foregoing, the present invention provides, inter alia, quartz-crystal devices of which the electrical impedance is reduced by forming respective protruding portions on the edge surfaces of each through-slot of each frame portion. The protruding portions suppress the formation of unnecessary electrodes in unnecessary regions, and suppress formation of extraction electrodes on the front surfaces of the frame portion. 
       SUMMARY 
       [0007]    Among various aspects of the invention, according to one aspect, quartz-crystal devices are provided. An exemplary embodiment of such a device comprises an AT-cut quartz-crystal frame including a rectangular quartz-crystal vibrating portion, a rectangular frame portion surrounding the vibrating portion, and at least one joining portion. The vibrating portion has first, second, third, and fourth edges and first and second principal surfaces. The principal surfaces each include a respective excitation electrode. The frame portion comprises first, second, third, and fourth frame regions that are coupled together to form the rectangular frame, wherein the first frame region is coupled at a right angle to the third frame region, the third frame region is coupled at a right angle to the second frame region, the second frame region is coupled at a right angle to the fourth frame region, and the fourth frame region is coupled at a right angle to the first frame region. Thus, the first, second, third, and fourth frame regions are adjacent respective edges of the rectangular frame portion. The at least one joining portion couples the vibrating portion to the frame portion at or near the first frame region. This embodiment also includes a package base bonded to the frame portion. The package base includes first and second external electrodes situated at respective sites on an external principal surface of the package base. The first and second external electrodes are electrically connected via respective extraction electrodes to respective excitation electrodes on the vibrating portion. The third frame region near its coupling with the first frame region includes a depth dimension and first and second plane surfaces that are parallel to respective principal surfaces of the vibrating portion. The third frame region also has an edge surface that extends into the depth dimension and faces a corresponding edge surface of the vibrating portion. The edge surface of the third frame region includes one or both of first and second sloped surfaces extending into the depth dimension from the first plane surface and second plane surface, respectively, to form a protrusion that projects toward the corresponding edge surface of the vibrating portion. The frame portion comprises a first extraction electrode extending a joining portion from a respective excitation electrode to a respective external electrode. A second extraction electrode extends from a respective excitation electrode to a respective external electrode via a joining portion, the first plane surface and the protrusion, or the second plane surface and the protrusion. 
         [0008]    The AT-cut quartz-crystal frame includes a thickness dimension and desirably defines a through-slot extending through the thickness dimension along at least three edges of the vibrating portion between the vibrating portion and corresponding regions of the frame portion. In these embodiments the second extraction electrode extends from the first principal surface to the second principal surface, or from the second principal surface to the first principal surface, via the through-slot. 
         [0009]    In some embodiments the through-slot includes a corner thereof, having an angle less than 90°, formed at a conjunction of two or more of a joining portion, the first frame region, the second frame region, and the third frame region. A portion of the through-slot through which the second extraction electrode passes can include the corner. 
         [0010]    For convenience, the longitudinal direction of the AT-cut quartz-crystal frame is denoted the X-axis direction, the thickness direction is denoted the Y′-axis direction, and the short direction is denoted the Z′-axis direction. The frame portion is formed by wet-etching, resulting in the first frame region and second frame region extending in the Z′-axis direction, and the third frame region extending in the X-axis direction. 
         [0011]    In the various embodiments summarized above, quartz-crystal devices are provided that have the protrusion located on an edge surface of the frame portion facing the through-slot. This configuration prevents the formation of “electrodes” (unwanted metal deposits on unnecessary locations, which suppressing the electrical impedance of the extraction electrodes. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is an exploded perspective view of a first embodiment of a quartz-crystal device. 
           [0013]      FIG. 2  is a cross-sectional view along the line A-A in  FIG. 1 . 
           [0014]      FIG. 3A  is a plan view of the quartz-crystal frame of the first embodiment. 
           [0015]      FIG. 3B  is a cross-sectional view along the line B-B in  FIG. 3A . 
           [0016]      FIG. 3C  is a cross-sectional view along the line C-C in  FIG. 3A . 
           [0017]      FIG. 4  is a flow-chart of an exemplary method for manufacturing the quartz-crystal device of the first embodiment. 
           [0018]      FIG. 5  is a plan view of a quartz-crystal wafer on which multiple quartz-crystal devices according to the first embodiment are formed. 
           [0019]      FIG. 6  is a flow-chart of an exemplary method for manufacturing the quartz-crystal wafer of  FIG. 5 , wherein  FIGS. 6A-6D  depict the result of the corresponding step. 
           [0020]      FIG. 7  is a continuation of the flow-chart of  FIG. 6 , wherein  FIGS. 7A-7D  depict the result of the corresponding step. 
           [0021]      FIG. 8  is a continuation of the flow-chart of  FIG. 7 , wherein  FIGS. 8A-8C  depict the result of the corresponding step. 
           [0022]      FIG. 9  is a plan view of a lid wafer used in mass-production of quartz-crystal vibrating devices. 
           [0023]      FIG. 10  is a plan view of a base wafer used in mass-production of quartz-crystal vibrating devices. 
           [0024]      FIG. 11  is an exploded perspective view of a quartz-crystal device according to a second embodiment. 
           [0025]      FIG. 12A  is a plan view of a quartz-crystal frame of the second embodiment. 
           [0026]      FIG. 12B  is a cross-sectional view along the line D-D in  FIG. 12A . 
           [0027]      FIG. 12C  is a cross-sectional view along the line E-E in  FIG. 12A . 
           [0028]      FIG. 13A  is a plan view of a quartz-crystal frame according to a third embodiment. 
           [0029]      FIG. 13B  is a plan view of the quartz-crystal frame according to an alternative configuration of third embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0030]    Various representative embodiments are described below with reference to the respective drawings. It will be understood that the scope of the disclosure is not limited to the described embodiments, unless otherwise stated. 
       First Embodiment of Quartz-Crystal Device 
       [0031]      FIG. 1  is an exploded perspective view of a quartz-crystal device  100  according to this embodiment. The quartz-crystal device  100  is a surface-mountable quartz-crystal device that can be mounted on, for example, a “printed” substrate such as printed circuit boards. The quartz-crystal device  100  comprises a quartz-crystal frame  110 , a package lid  120 , and a package base  130 . The quartz-crystal frame  110  is fabricated from an AT-cut quartz-crystal material. An AT-cut quartz-crystal material has a principal surface (in the YZ plane) that is tilted by 35° 15′ about the Y-axis of a crystal-coordinate system (XYZ) in the direction of the Y-axis from the Z-axis around the X-axis. In the following description, new axes tilted with respect to the axial directions of the quartz-crystal material are denoted as the Y′-axis and Z′-axis, respectively. Therefore, in the quartz-crystal device  100 , the longitudinal direction of the piezoelectric device is the X-axis direction, the height direction is the Y′-axis direction, and the direction perpendicular to the X-axis and Y′-axis directions is the Z′-axis direction. 
         [0032]    The quartz-crystal frame  110  comprises a vibrating portion  111  that vibrates when electric voltage is applied to it. The quartz-crystal frame  110  also comprises a frame portion  112  surrounding the vibrating portion  111 . A pair of joining portions  117  connects the vibrating portion  111  to the frame portion  112 . Between the vibrating portion  111  and frame portion  112  is a through-slot  113  extending through the Y′-axis direction (thickness direction) of the quartz-crystal frame  110  and extending around at least three edges of the vibrating portion  111 . 
         [0033]    Hereinafter, the region of the frame portion  112  extending in the −X-axis direction is denoted as the first region  112   a , the region extending in the +X-axis direction is denoted the second region  112   b , the region in the +Z′-axis direction is denoted the third region  112   c , and the region in the −Z′-axis direction is denoted the fourth region  112   d . The vibrating portion  111  is connected to the first region  112   a  by the joining portions  117 . A respective excitation electrode  114  is situated on the +Y′-surface and −Y′-surfaces of the vibrating portion  111 . The quartz-crystal frame  110  also comprises a first extraction electrode  115   a , which is connected to the excitation electrode  114  on the −Y′-surface of the vibrating portion. The first extraction electrode  115   a  passes over a respective joining portion  117  to the (−Z′, −X) corner of the frame portion  112 . The quartz-crystal frame  110  also comprises a second extraction electrode  115   b , which is connected to the excitation electrode  114  on the +Y′-surface of the vibrating portion. The second extraction electrode  115   b  passes over a respective joining portion  117  and then crosses through the thickness dimension from the +Y′-surface to the −Y′-surface of the quartz-crystal frame  110  via a respective terminus of the through-slot  113 . The second extraction electrode  115   b  also extends on the −Y′-surface of the quartz-crystal frame  110  over the first region  112   a  and third region  112   c  to the +Z′, +X) corner of the frame portion  112 . 
         [0034]    The package lid  120  is a planar board without any concavity of convexity on either the +Y′-surface or −Y′-surface thereof. In  FIG. 1 , the package lid  120  is disposed in the +Y′-axis direction relative to the quartz-crystal frame  110 . A bonding surface  121  ( FIG. 2 ) is disposed on the −Y′-surface of the package lid  120  for bonding to the regions  112   a ,  112   b ,  112   c ,  112   d  of the frame portion  112 . 
         [0035]    The package base  130  is disposed in the −Y′-axis direction relative to the quartz-crystal frame  110 . The package base  130  defines a recess  131  and a bonding surface  132  on the +Y′-surface thereof. A respective conductive pad  135  is located on the +Y′-surface at each corner of the package base  130 . The conductive pads  135  (and respective electrodes  136  in respective castellations  134 ) provide respective electrical connections from the +Y-surface to the −Y-surface of the package base  130 . The conductive pads  135  on the −X-corners of the package base  130  are connected together on the −Y-surface of the package base  130  by an external electrode  133 . Similarly, the conductive pads  135  on the +X-corners of the package base  130  are connected together on the −Y-surface of the package base  130  by an external electrode  133 . Thus, the castellation electrodes  136  are electrically connected to respective conductive pads  135  on the +Y′-surface and to an external electrode  133  on the −Y′-surface of the package base  130 . 
         [0036]      FIG. 2  is a cross-sectional view of the device  100  along the line A-A in  FIG. 1 . The package lid  120  is situated on the +Y′-side of the quartz-crystal frame  110 , and the package base  130  is situated on the −Y′-side of the quartz-crystal frame. The bonding surface  121  of the package lid  120  and the bonding surface  132  of the package base  130  are bonded to respective opposing surfaces of the frame portion  112  using a sealing material  140 . Also visible in  FIG. 2  are the first and second extraction electrodes  115   a ,  115   b . These extraction electrodes, formed on the −Y′-surface of the quartz-crystal frame  110 , are connected to respective conductive pads  135  on the +Y′-surface of the package base  130 . Thus, the excitation electrodes  114  on the vibrating portion  111  are electrically connected to respective external electrodes  133 , situated on the outer (lower) principal surface of the package base  130 , by respective extraction electrodes  115   a ,  115   b , conductive pads  135 , and castellation electrodes  136 . 
         [0037]    As shown in  FIG. 2 , the vibrating portion  111  is thinner than the frame portion  112  and is displaced, in the −Y′-direction, relative to the frame portion  112  toward the recess  131  in the package base  130 . Also, the vibrating portion  111  is mesa-shaped, having central (“mesa”) regions  116  on each of the −Y′- and +Y′-surfaces thereof. Thus, the vibrating portion  111  is thicker in the Y′-axis direction in the mesa regions  116  than in the peripheral regions surrounding the mesa regions. The excitation electrodes  114  are situated on respective mesa regions  116 . 
         [0038]      FIG. 3A  is a plan view of the quartz-crystal frame  110 , which comprises a vibrating portion  111 , a frame portion  112 , and joining portions  117  that couple the vibrating portion  111  to the first region  112   a  of the frame portion  112 . Visible is the through-slot  113  situated between the vibrating portion  111  and the frame portion  112  and extending around three sides of the vibrating portion. The vibrating portion  111  is mesa-shaped on both its +Y′-surface and −Y′-surface, and a respective excitation electrode  114  is situated on each mesa surface  116 . Each excitation electrode is surrounded by a thin periphery of the vibrating portion  111 . A respective extraction electrode  115   a ,  115   b  is connected to each excitation electrode  114 . The first extraction electrode  115   a  connects to the excitation electrode  114  on the −Y′-surface of the vibrating portion  111  and extends across a respective joining portion  117  to the (−X, −Z′) corner of the frame portion  112  as shown. The second extraction electrode  115   b  connects to the excitation electrode  114  on the +Y′-surface of the vibrating portion  111  and extends across a respective joining portion  117  to the adjacent end of the through-slot  113 , through the through-slot  113  onto the −Y′-surface of the frame portion  112 , and then to the (+X, +Z′) corner of the frame portion  112 . 
         [0039]    In a vertical profile, the through-slot  113  is defined by edge walls ( FIG. 3B ). The edge wall on the frame portion  112  includes a protrusion  118  extending toward the opposing edge of the vibrating portion  111 . The opposing edge wall on the vibrating portion  111  protrudes toward the edge wall of the frame portion  112 . The second extraction electrode  115   b  in the third region  112   c  of the frame portion  112  extends partially over the protruding portion  118 . At the respective terminus of the through-slot  113  the second extraction electrode  115   b  passes from the +Y′-surface to the −Y′-surface of the quartz-crystal frame  110  ( FIG. 3C , detailing the region encircled by the dotted line  191  in  FIG. 3A ). This terminal region of the through-slot  113  includes a first edge projection  113   a  located adjacent the juncture of the first region  112   a  and third region  112   c  of the frame portion  112 , and a second edge projection  113   b  located adjacent the juncture of the joining portion  117  and the first region  112   a  of the frame portion. These edge projections  113   a ,  113   b  present angles that are less than 90° relative to the +Y′-surface or −Y′-surface of the quartz-crystal frame  110 . Also, in these edge projections  113   a ,  113   b  the protrusion  118  projects outward more than in other regions (e.g.,  FIG. 3B ). Consequently, a metal film destined to become an electrode in an edge projection  113   a ,  113   b  can be easily deposited or otherwise formed on side walls of the through-slot  113 . These electrodes, for conducting electrical energy from the +Y′-surface to the −Y′-surface for example, are located at the terminus of the through-slot  113 . 
         [0040]      FIG. 3B  is a cross-sectional view of  FIG. 3A  along the line B-B. In this figure the +Y′-surface of the frame portion  112  is denoted the first plane surface  119   a , and the −Y′-surface of the frame portion is denoted the second plane surface  119   b . The edge surface of the through-slot  113  in this area includes the inclined-surface protrusion  118 . One portion  118   b  of the protrusion  118  is joined to the second plane surface  119   b , and is called a second inclined slanted surface  118   b . The second extraction electrode  115   b  on the second plane surface  119   b  extends onto the second inclined surface  118   b.    
         [0041]      FIG. 3C  is a cross-sectional view of  FIG. 3A  along the line C-C. In this region the second extraction electrode  115   b  connects from the +Y′-surface to the −Y′-surface of the frame portion  112  via the first and second edge projections  113   a ,  113   b  in the through-slot  113 . In these edge projections  113   a ,  113   b  the protrusion  118  has relatively large width (in the X×Z′ plane) to facilitate formation of a metal film that extends completely through the through-slot  113 . 
         [0042]    Exemplary Method for Manufacturing Quartz-Crystal Device 
         [0043]    A flow-chart of this exemplary method for manufacturing the first embodiment of a quartz-crystal device  100  is shown in  FIG. 4 . In step S 101  a quartz-crystal wafer W 110  is fabricated from an AT-cut quartz-crystal material. Multiple quartz-crystal frames  110  are formed on a quartz-crystal wafer W 110  (further details of which are described below with reference to  FIG. 5 ). Further details of a method for manufacturing the quartz-crystal wafer W 110  are described later below with reference to  FIGS. 6-8 . 
         [0044]      FIG. 5  is a plan view of the +Y′-surface of the quartz-crystal wafer W 110 . Multiple quartz-crystal frames  110  have been formed on the wafer W 110 . In  FIG. 5 , the borders of adjacent quartz-crystal frames  110  are indicated by dash-dot lines. Each dash-dot line is a scribe line  170  used as a reference for separating individual devices in step S 105  of  FIG. 4 . Each quartz-crystal frame  110  comprises a respective vibrating portion  111 , frame portion  112 , through-slot  113 , and joining portions  117 . Each vibrating portion  111  includes a respective excitation electrode  114  on the +Y′-surface and −Y′-surface thereof. A respective extraction electrode  115   a ,  115   b  is connected to each excitation electrode  114 . 
         [0045]      FIGS. 6-8  are flow-charts of steps in an exemplary method for manufacturing the quartz-crystal wafer W 110 . The steps shown in  FIGS. 6-8  are particularly directed to forming the vibrating portions  111  and through-slots  113 . In  FIGS. 6-8  each step includes a respective cross-section depicting the result of the step. The cross-sections shown in  FIGS. 6-8  are of the quartz-crystal wafer W 110  along the line F-F in  FIG. 5 . 
         [0046]    In step S 201  of  FIG. 6 , an AT-cut quartz-crystal wafer W 110  is prepared.  FIG. 6A  is a cross-sectional view of the AT-cut quartz-crystal wafer W 110  as prepared. The quartz-crystal wafer W 110  has principal surfaces on its +Y′-surface and on its −Y′-surface. Both surfaces are planar, without concavities or convexities. 
         [0047]    In step S 202  a metal film  180  and a resist film  181  are sequentially formed on both principal surfaces of the quartz-crystal wafer W 110 .  FIG. 6B  is a cross-section of the quartz-crystal wafer W 110  after application of the metal film  180  and the resist film  181 . The metal film  180  comprises a foundation layer of chromium (Cr) formed on both principal surfaces of the quartz-crystal wafer W 110 . An overlying layer of gold (Au; not shown) is formed on the surface of the chromium layer. A resist film  181  is formed on the surface of the metal film  180 . The resist film  181  is, for example, a positive photoresist that acquires, when exposed, a high solubility in developing solution. 
         [0048]    In step S 203  the resist film  181  on the upper surface of the wafer is exposed and developed, followed by removal of the metal film  180 . Specifically, in this step, the metal film  180  and resist film  181  (formed on the +Y′-surface and defining the vibrating portion  111  and the through-slot  113  in  FIG. 3A ) are removed after exposure, except from regions of the wafer corresponding to the frame portion  112 .  FIG. 6C  is a cross-sectional view of the quartz-crystal wafer W 110  after exposing and developing the resist film  181  and after removing unprotected regions of the metal film  180 . Also in this step S 203 , a first mask  161  is placed on the +Y′-surface of the quartz-crystal wafer W 110 . The first mask  161  extends over the +Y′-surface wherever frame portions  112  have been formed. After placing the first mask  161 , a UV exposure light  190  is irradiated onto the +Y′-surface of the quartz-crystal wafer W 110  to expose the resist film  181  in regions unprotected by the first mask  161 . The exposed resist film  181  is immersed in developer (not shown) to remove it from the wafer surface. 
         [0049]    In step S 204  the unprotected regions of the metal film  180  are wet-etched to produce reduced-thickness vibrating portions  111  (see  FIG. 3A ).  FIG. 6D  is a cross-sectional view of the quartz-crystal wafer W 110  after performing this thickness-reducing etching step. In step S 204  the +Y′-surface of the quartz-crystal wafer W 110  (except for frame portions  112 ) is wet-etched, which reduces the thickness of the regions in contact with the etchant. During etching of the quartz-crystal material, the etching rate varies in each of the X-axis, Y′-axis, and Z′-axis directions, which results in the wafer W 110  being etched in an anisotropic manner. In  FIG. 6D , the etched regions  171   a  and  171   b  (each encircled by a respective dotted-line in  FIG. 6D ) exhibit a sloped thickness profile due to different respective etching rates and different angles relative to the principal surfaces. 
         [0050]    Turning now to  FIG. 7 , in step S 205  a metal film  180  and a resist film  181  are formed on both surfaces of the quartz-crystal wafer W 110 . More specifically, in step S 205  the metal films  180  and resist films  181  remaining from step S 204  are removed, followed by application of new metal layers  180  and resist layers  181  for use in forming the mesa regions  116  on the vibrating portion  111 .  FIG. 7A  is a cross-sectional view of the quartz-crystal wafer W 110 , on which new films of metal  180  and resist  181  have been applied. The new metal film  180  and resist film  181  are formed on both the +Y′-surface and the −Y′-surface of the quartz-crystal wafer W 110 . 
         [0051]    In step S 206 , the resist film  181  is exposed and developed, and resulting unprotected regions of the metal film  180  and resist film  181  are removed, except from regions defining the frame portion  112  and the mesa portion  116  (see  FIG. 2 ) of the vibrating portion  111 .  FIG. 7B  is a cross-sectional view of the quartz-crystal wafer W 110 , on which the resist film  181  has been exposed and developed, and from which the metal film  180  has been removed. Specifically, the metal film  180  and resist film  181  in the vicinity of the through-slots  113  and periphery of the vibrating portion  111  (see  FIG. 3A ) are removed. Respective second masks  162  are placed relative to the +Y′-surface and −Y′-surface of the wafer W 110 . The second masks  162  are placed so as to superpose regions in which frame portions  112  and mesa regions  116  have been formed (see  FIG. 2 ). After placing the second masks  162 , UV exposure light  190  is irradiated onto the +Y′-surface and −Y′-surface of the wafer W 110  to expose the resist. Then, the resist film  181  is immersed into developer (not shown) to remove exposed resist. 
         [0052]    In step S 207 , the vibrating portion  111  is provided with a mesa-configuration. The periphery of the vibrating portion  111  (now unprotected by resist) is wet-etched to reduce the thickness of the periphery of the vibrating portion  111 .  FIG. 7C  is a cross-sectional view of the wafer W 110  showing the result of this step. Also during this step S 207 , regions destined to become the through-slot  113  ( FIG. 3A ) are wet-etched. As a result of this step, mesa regions  116  are formed on the vibrating portion  111 . 
         [0053]    In step S 208 , new metal film  180  and resist film  181  are sequentially formed on both surfaces of the quartz-crystal wafer W 110 . More specifically, after completing step S 207 , remaining metal film  180  and resist film  181  are removed, followed by application of new metal films  180  and resist films  181  ( FIG. 3A ) on both surfaces of the wafer. The new metal films and resist films are destined for use in forming the through-slots  113 .  FIG. 7D  is a cross-sectional view of the quartz-crystal wafer W 110  after formation of a new metal film  180  and new resist film  181  on the +Y′-surface and −Y′-surface of the wafer W 110 . 
         [0054]    Turning now to  FIG. 8 , in step S 209  the resist film  181  is exposed and developed, and metal film is removed. More specifically, in regions of exposed and developed resist, the metal film  180  and the resist film  181  on both surfaces of the wafer are removed. These regions are destined to be locations of the through-slot  113  ( FIG. 3A ).  FIG. 8A  is a cross-sectional view of the result of this step, showing a section of the wafer W 110  from which new metal film  180 , unprotected by developed resist, has been removed by etching from both surfaces of the wafer. Third masks  163  are placed relative to the +Y′-surface and −Y′-surface of the wafer W 110 . The third masks  163  cover the entire respective surfaces except for regions destined to become the through-slots  113  ( FIG. 3A ). After placing the third masks  163 , UV exposure light  190  is irradiated onto both surfaces of the wafer W 110  to expose the resist film  181 . Exposed resist film  181  is immersed in developer (not shown), followed by removal of developed resist. 
         [0055]    In step S 210 , regions of the wafer W 110  unprotected by resist are wet-etched, thereby forming the through-slots  113 .  FIG. 8B  is a cross-sectional view of the quartz-crystal wafer W 110  after formation of the through-slots  113  in this step. Note that the quartz-crystal material of the wafer W 110  is etched at a slope relative to principal surfaces of the wafer. This is due to the anisotropic aspect of the AT-cut quartz-crystal material. In any event, in this step the protrusions  118  are formed on the edge surfaces of the through-slots  113 . 
         [0056]    In step S 211 , the excitation electrodes  114 , first extraction electrode  115   a  (see  FIG. 3A ) and second extraction electrode  115   b  are formed on the quartz-crystal wafer W 110 . More specifically, in this step, metal film  180  and resist film  181  remaining from step S 210  are removed. The excitation electrodes  114  and extraction electrodes  115   a ,  115   b  (see  FIG. 3A ) are formed using respective fourth masks  164   a ,  164   b . The result is shown in  FIG. 8C . The fourth mask  164   a  defines an opening shaped as an excitation electrode for the +Y′-surface of the quartz-crystal frame  110 , and the fourth mask  164   b  defines an opening shaped as an excitation electrode for the −Y′-surface of the quartz-crystal frame  110 . Similar to the metal film  180  described in step S 202 , the excitation electrodes  114  and extraction electrodes  115   a ,  115   b  are formed on the wafer W 110  as a chromium layer with overlying gold layer. 
         [0057]    Returning to  FIG. 4 , in step S 102  the lid wafer W 120  is prepared. Multiple package lids are formed simultaneously on the lid wafer W 120 . The lid wafer W 120  can be fabricated of the quartz-crystal material (used for fabricating the wafer W 110 ) or glass. An exemplary lid wafer W 120  is shown in  FIG. 9 , in which the depicted lid wafer W 120  defines multiple package lids  120 . The dot-dash lines in  FIG. 9  are scribe lines  170  that denote the borders of the adjacent package lids  120 . During assembly of a quartz-crystal device  100 , a package lid  120  is bonded to the bonding surface  121  of a frame portion  112  of a corresponding quartz-crystal frame  110 . The bonding surface  121  is the −Y′-surface of the frame portion. 
         [0058]    In step S 103 , the base wafer W 130  is prepared. Multiple package bases  130  are formed simultaneously on the base wafer W 130 . The base wafer W 130  can be fabricated of the quartz-crystal material or glass, for example. An exemplary base wafer W 130  is shown in  FIG. 10 , in which the depicted base wafer W 130  defines multiple package bases  130 . The dot-dash lines  170  In  FIG. 10  are scribe lines that denote the borders of the adjacent package bases  130 . Each package base  130  has a −Y′-surface (outer principal surface) on which external electrodes  133  are formed. Corresponding conductive pads  135  are formed on the +Y′-axis surface. Respective scribe lines extend in the X-axis and Z′-axis directions, and respective through-holes  134   a  are defined at each intersection of X- and Z′-direction scribe lines  170 . The through-holes  134   a  extend through the base wafer W 130  in the Y′-axis (thickness) direction. The through-holes  134   a  are destined to form respective castellations  134  (see  FIG. 1 ) during the device-separation step S  105 . Respective castellation electrodes  136  (see  FIG. 1 ) are formed on the inner walls of the through-holes  134   a , and respective external electrodes  133  are electrically connected to the conductive pads  135 . A respective recess  131  is formed on each package base  130  facing the +Y′-direction. The bonding surfaces  132  are peripheral to the respective recesses  131 . 
         [0059]    In step S 104  the quartz-crystal wafer W 110 , lid wafer W 120 , and base wafer W 130  are bonded together as a three-wafer sandwich. For bonding, the frame portion  112  of the quartz-crystal wafer W 110 , the bonding surface  121  of the lid wafer W 120 , and the bonding surface  132  of the base wafer W 130  are aligned with each other along the Y′-axis. These surfaces are bonded together using the sealing material  140  (see  FIG. 2 ) to form a three-wafer sandwich. 
         [0060]    In step S 105 , the three-wafer sandwich is divided into individual devices by cutting along the scribe lines  170  indicated in  FIGS. 5 ,  9 , and  10 . Thus, as shown in  FIG. 1 , multiple individual quartz-crystal devices  100  are produced. 
         [0061]    In a quartz-crystal device  100 , the protrusions  118  on the frame portion  112  block formation of the second extraction electrode  115   b  at undesired locations. For example, in  FIG. 8C , even if the fourth mask  164   b  is misaligned in the −Z′-axis direction, the protrusion  118  blocks formation of the second extraction electrode  115   b  on the edge surface of the third region  112   c . Also, the anisotropic nature of AT-cut quartz-crystal material forms the protrusion  118  during the etching step; therefore, the protrusion  118  is formed automatically without requiring an extra process step. In addition, formation of the second extraction electrode  115   b  on the second plane surface  119   b  of the third region  112   c  of the frame portion  112  keeps electric impedance low. 
       Second Embodiment of Quartz-Crystal Device 
       [0062]    In the first embodiment of a quartz-crystal device  100 , although the second extraction electrode  115   b  extends from the first region  112   a  to the second region  112   b  via the second plane surface  119   b  of the third region  112   c  of the frame portion  112 , the electrode alternatively can extend from the first region  112   a  to the second region  112   b  via the first plane surface  119   a . The second embodiment of a quartz-crystal device  200  is now described, in which the second extraction electrode extends from the first region  112   a  to the second region  112   b  via the first plane surface  119   a . In the following description, features that are similar to corresponding features in the first embodiment have the same respective reference numerals. 
         [0063]      FIG. 11  is an exploded perspective view of the second embodiment  200  of a quartz-crystal device. The quartz-crystal device  200  is surface-mountable to a printed circuit board or the like. The quartz-crystal device  200  comprises a quartz-crystal frame  210 , a package lid  120 , and a package base  130 . 
         [0064]    The quartz-crystal frame  210  comprises a vibrating portion  111 , a frame portion  112 , and joining portions  117 . A through-slot  113  extends, through the thickness dimension (Y′-axis dimension) of the frame  210 , along at least three edges of the vibrating portion  111 . The vibrating portion  111  includes first and second excitation electrodes  114  connected to respective first and second extraction electrodes  215   a ,  215   b . The extraction electrodes  215   a ,  215   b  extend across respective joining portions  117  to respective corners of the frame portion  112 . Specifically, the first extraction electrode  215   a , connected to the excitation electrode  114  on the −Y′-surface, extends across a respective joining portion  117  to the −X, +Z′-corner of the −Y′-surface of the frame portion  112 . The second extraction electrode  215   b , connected to the excitation electrode  114  on the +Y′-surface, extends across a respective joining portion  117 , then extends in the +X-direction on the fourth region  112   d  of the frame portion  112 , passes from the +Y′-surface to the −Y′-surface at a corner  113   c  of the through-slot  113 , and then extends to the (−X, −Z′) corner of the −Y′-surface of the frame portion  112 . 
         [0065]    This embodiment of a quartz-crystal device  200  is formed by bonding together a three-wafer sandwich in which the quartz-crystal frame  210  is situated between the package lid  120  and the package base  130 . This bonding also electrically connects the first extraction electrode  215   a  and the second extraction electrode  215   b  automatically to respective electrodes on the package base  130 , which involves connecting the excitation electrodes  114  to respective external electrodes  133 . 
         [0066]      FIG. 12  is a plan view of a quartz-crystal frame  210  of this embodiment. The quartz-crystal frame  210  comprises the vibrating portion  111 , the frame portion  112 , the joining portions  117 , and a through-slot  113  separating three edges of the vibrating portion  111  from the frame portion  112 . Respective excitation electrodes  114  are formed on the +Y′-surface of one mesa region  116  and on the −Y′-surface of the other mesa region  116  of the vibrating portion  111 . The first extraction electrode  215   a , connected to the excitation electrode  114  (not shown) on the −Y′-surface of the vibrating portion  111 , extends to the first region  112   a  of the frame portion  112  via one of the joining portions  117 , and continues to the (−X, +Z′) corner of the first region  112   a . The second extraction electrode  215   b , connected to the excitation electrode  114  on the +Y′-surface of the vibrating portion  111 , extends to the first region  112   a  of the frame portion  112  via the other joining portion  117 , and continues on the fourth region  112   d . The second extraction electrode  215   b  then passes from the +Y′-surface to the −Y′-surface at the corner  113   c  of the through-slot  113  (in the region denoted by the dotted line  192 ), which is at the intersection of the second region  112   b  and the fourth region  112   d , and finally extends to the (+X, −Z′) corner of the frame portion  112 . 
         [0067]      FIG. 12B  is a cross-sectional view of  FIG. 12A  taken along the line D-D, showing the second extraction electrode  215   b  as formed on the first plane surface  119   a  on the +Y′-surface of the frame portion  112 . Also shown are the first inclined surface  118   a  (a surface connected to the first plane surface  119   a ) of the protrusion  118 . 
         [0068]      FIG. 12C  is a cross-sectional view of  FIG. 12A  along the line E-E. The second extraction electrode  215   b  is shown as it passes from the +Y′-surface to the −Y′-surface of the frame portion  112  at the corner of the through-slot  113  where the second region  112   b  and fourth region  112   d  intersect. Also, the protrusion  118  exhibits a large projection outward on this corner, which allows a metal film to be formed easily on the edge surface of the frame portion  112 . Also, the second extraction electrode  215   b  is formed on the first plane surface  119   a  of the fourth region  112   b  of the frame portion  112 , which reduces crystal impedance (CI). 
       Third Embodiment of Quartz-Crystal Device 
       [0069]    According to this embodiment, the joining portions of the quartz-crystal frame are formed in different locations than described in the first and second embodiment. In one configuration according to this third embodiment ( FIG. 13A ), a first joining portion  317  extends diagonally from the (−X, −Z′) corner of the vibrating portion  111  to an adjacent intersection of the first region  112   a  and the fourth region  112   d , and a second joining portion  317  extends diagonally from the (−X, +Z′) corner of the vibrating portion  111  to an adjacent intersection of the second region  112   b  and the third region  112   c . In another configuration according to this embodiment ( FIG. 13B ), a first joining portion  417  extends in the −Z′-direction and serves as a bridge for the extraction electrode  415   a  from the excitation electrode  114  to the fourth region  112   d , and a second joining portion  417  extends in the +Z′-direction and serves as a bridge for the extraction electrode  415   b  from the excitation electrode  114  to the third region  112   c.    
         [0070]    Turning now to  FIG. 13A , in the following description thereof, features that are similar to corresponding features in the first embodiment have the same reference numerals.  FIG. 13A  is a plan view of the quartz-crystal frame  310 . The quartz-crystal frame  310  comprises a vibrating portion  111 , a frame portion  112 , and a pair of joining portions  317  that couple the vibrating portion  111  to the frame portion  112 . A respective excitation electrode  114  is situated on a respective mesa  116  on the −Y′-surface and +Y-surface of the vibrating portion  111 . A through-slot  313  extends between the vibrating portion  111  and the frame portion  112  around at least three edges of the vibrating portion. An additional through-slot  313  is defined between the vibrating portion  114  and the first region  112   a . A respective extraction electrode  315   a ,  315   b  is connected to each excitation electrode  114 . 
         [0071]    More specifically, one joining portion  317  diagonally couples the (−X, −Z′) corner of the vibrating portion  114  to the intersection of the first frame region  112   a  and the fourth frame region  112   d . The extraction electrode  315   a  passes over this joining portion and continues to the (−X, −Z′) corner of the quartz-crystal frame  310 . The other joining portion  317  diagonally couples the (−X, +Z′) corner of the vibrating portion  114  to the intersection of the first frame region  112   a  and the third frame region  112   c . The second extraction electrode  315   b  passes over this joining portion (dashed-line circle  193 ) and  317  and continues to the (−X, +Z′) corner of the quartz-crystal frame  310 . 
         [0072]    On the quartz-crystal frame  310 , the angle between the joining portion  317  and respective third region  112   c  or fourth region  112   d  of the frame portion  112  is less than 90°. The respective protrusions  118  formed on edge surfaces located between the joining portion  317  and respective frame region  112  are wider (i.e., project outward more) than the respective protrusions  118  formed on edges of the frame region  112 . This favors formation of electrodes on the edge surfaces of the frame region. Also, the second extraction electrode  315   b  formed on the second plane surface  119   b  of the third region  112   c  of the frame portion  112  reduces electrical impedance. 
         [0073]      FIG. 13B  is a plan view of the alternative configuration  410  of the quartz-crystal frame. The quartz-crystal frame  410  comprises a vibrating portion  111 , a frame portion  112 , and a pair of joining portion  417  coupling the vibrating portion  111  to the frame portion  112 . A through-slot  413  extends between the vibrating portion  111  and the frame portion  112  around three edges of the vibrating portion  111 . A second through-slot  413  extends along the fourth edge of the vibrating portion. A first joining portion  417  couples the (−X, −Z′) corner of the vibrating portion to the fourth region  112   d  of the frame portion  112 . A second joining portion  417  couples the (−X, +Z′) corner of the vibrating portion  111  to the third region  112   c  of the frame portion  112 . The vibrating portion  111  has a +Y′-surface and a −Y′-surface each having a mesa configuration. Each of these surfaces of the vibrating portion has a respective excitation electrode  114 . A first extraction electrode  415   a  extends from the respective excitation electrode  114  (not shown) on the −Y′-surface of the vibrating portion  111 . The extraction electrode  415   a  extends to the third region  112   c  of the frame portion  112  via a respective joining portion  417  and proceeds to the (−X, +Z′) corner of the frame portion  112 . A second extraction electrode  415   b  extends from the respective excitation electrode  114  on the +Y′-surface of the vibrating portion  111 . The extraction electrode  415   b  extends to the fourth region  112   d  of the frame portion  112  via a respective joining portion and proceeds along the fourth region  112   d . Before reaching the (+X, −Z′) corner of the frame portion  112 , the extraction electrode  415   b  passes from the +Y′-surface to the −Y′-axis surface at the respective corner of the through-slot  413  (dashed-line circle  194 ) at which the second region  112   b  and fourth region  112   d  intersect. The extraction electrode then extends, in the thickness dimension, to the −Y′-surface and then to the (+X, −Z′) corner. 
         [0074]    In the quartz-crystal frame  410 , the angle between each joining portion  417  and the third or fourth edge regions  112   c  is a right angle. Consequently, the protrusion  118  projecting between the joining portion  417  and the respective frame portion  112  projects outward farther than the protrusion  418  formed on the edges of the regions of the frame portion  112 . This facilitates formation of electrodes on the edge surfaces of the frame portion, specifically on the protrusions  118  formed between the joining portion  417  and the frame portion  112 . Also, since the second extraction electrode  415   b  is located on the first plane surface  119   a  of the fourth region  112   d  of the frame portion  112 , electric impedance is favorably reduced. 
       Industrial Applicability 
       [0075]    Representative embodiments have been described in detail above. As evident to those skilled in the art, the present invention may be changed or modified in various ways within the technical scope of the invention. 
         [0076]    For example, in the described embodiment of a method for manufacturing the vibrating portion, although the vibrating portion and the through-slot are formed using a positive photoresist, a negative photoresist alternatively can be used. Since a negative photoresist degrades when exposed, regions thereof destined to be etched should be covered with the exposure mask during etching.