Abstract:
An electronic device includes: a housing having a concave portion in the first surface of the housing; a lid made of a semiconductor material containing an impurity material; a first metal film formed in a metal film formation region on the first surface of the housing, wherein the metal film formation region is defined as a region surrounding the concave portion on the first surface of the housing; a second metal film formed on the first surface of the lid to overlap with the metal film formation region in a top view of the electronic device; a third metal film formed on the second surface of the lid to overlap with the metal film formation region in the top view; and an electronic component disposed in the concave portion. The lid is bonded onto the housing via the first and second metal films to cover the electronic component.

Description:
This application claims priority from Japanese Patent Application No. 2012-133235, filed on Jun. 12, 2012, the entire contents of which are herein incorporated by reference. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to an electronic device. 
     2. Related Art 
     In the related art, there is a semiconductor package which includes a base substrate in which a cavity having an opening portion on an upper surface is provided and an electronic component which is mounted into the cavity, wherein a lid is welded to an upper surface of the base substrate so as to seal the cavity. In the semiconductor package, each of convex portions having the same height is formed in a rectangular frame shape and formed on the upper surface of the lid to face the peripheral wall portions of the cavities formed in the base substrate (see e.g., JP-A-2012-039022). 
     However, since the lid which is welded to the base substrate of the related-art semiconductor package is formed of a metal such as Kovar, current or heat is diffused at the time of welding, and power required for the welding is increased. 
     In the related art, since the power required for the welding is increased, there is a problem that a hollow housing in which the lid is welded to the base substrate cannot be effectively manufactured. 
     SUMMARY OF THE INVENTION 
     According to one or more aspects of the present embodiment, there is provided an electronic device comprising: a housing comprising a first surface and a second surface opposite to the first surface, wherein a concave portion is formed in the first surface of the housing; a lid made of a semiconductor material containing an impurity material and comprising a first surface and a second surface opposite to the first surface, wherein the first surface of the lid faces the first surface of the housing; a first metal film formed in a metal film formation region on the first surface of the housing, wherein the metal film formation region is defined as a region surrounding the concave portion on the first surface of the housing; a second metal film formed on the first surface of the lid to overlap with the metal film formation region in a top view of the electronic device; a third metal film formed on the second surface of the lid to overlap with the metal film formation region in the top view; and an electronic component disposed in the concave portion, wherein the lid is bonded onto the housing via the first and second metal films to cover the electronic component disposed in the concave portion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A to 1C  are views showing a hollow housing and an electronic device of a Comparative Example; 
         FIGS. 2A and 2B  are views showing a process of mounting a lid  30  onto a housing  20  in a manufacturing process of an electronic device  1  of the Comparative Example; 
         FIGS. 3A to 3E  are views showing a hollow housing and an electronic device of an embodiment of the present invention; 
         FIGS. 4A and 4B  are views showing a process of mounting a lid  130  onto a housing  120  in a manufacturing process of an electronic device  100  of the embodiment; 
         FIGS. 5A to 5C  are cross-section views showing transmission paths of current and heat in a hollow housing  110  of the embodiment and hollow housings  10  and  10 A of the Comparative Example, respectively; 
         FIGS. 6A to 6D  are plan views showing transmission paths of current in the hollow housing  110  of the embodiment and the hollow housings  10  and  10 A of the Comparative Example, respectively; 
         FIG. 7  is a view showing specific resistance, current density, and loss of the lid  30  of the Comparative Example, the lid  130  of the embodiment, and a lid  30 A of a modification of the Comparative Example; 
         FIGS. 8A and 8B  are views showing distribution of current density in the lid  130  made of silicon and the lid  130  made of Kovar, respectively; and 
         FIG. 9  is a view showing a cross-sectional structure of an electronic device  100 A of a modification of the embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, an electronic device of the present embodiment will be now described with reference to the drawings. First, a hollow housing of a Comparative Example will be now described with reference to  FIGS. 1A to 2B . 
     Comparative Example 
       FIGS. 1A to 1C  are views showing the hollow housing and the electronic device of a Comparative Example,  FIG. 1A  is a perspective view thereof,  FIG. 1B  is an exploded cross-sectional view in a cross-section taken along a line A-A, and  FIG. 1C  is a plan view of a housing. 
     An electronic device  1  of the Comparative Example shown in  FIGS. 1A and 1B  includes a Micro Electronic Mechanical System (MEMS) chip  40  provided in a hollow housing  10 . That is, the electronic device  1  includes the hollow housing  10  and the MEMS chip  40 . The hollow housing  10  is a housing in which the MEMS chip  40  is eliminated from the electronic device  1 . 
     As shown in  FIGS. 1A and 1B , the hollow housing  10  of the Comparative Example includes a housing  20  and a lid  30 .  FIG. 1C  is a plan view showing the housing  20  in a state before the lid  30  is bonded to the housing  20 . 
     The housing  20  is formed in a rectangular parallelepiped-shape and includes a concave portion  21  and is made by processing a ceramic substrate. The concave portion  21  is concaved in a rectangular parallelepiped shape from an upper surface side of the housing  20 . As shown in  FIG. 1C , the concave portion  21  is exposed to an opening portion  22  in the state before the lid  30  is bonded to the housing  20 . 
     The MEMS chip  40  is disposed on a lower surface of the concave portion  21 . The MEMS chip  40  is connected to a pad (not shown), which is disposed on the bottom surface of the concave portion  21 , by a bonding wire  41 . For example, the MEMS chip  40  is an actuator of an acceleration sensor. 
     The concave portion  21  of the housing  20  is continuously surrounded by a wall portion  23 , and the opening portion  22  is a rectangular opening portion which is surrounded by the wall portion  23 . Moreover, the wall portion  23  is formed in a rectangular annular shape in a plan view. 
     A plating layer  24  is formed on an upper surface of the wall portion  23  along the periphery of the opening portion  22 . The plating layer  24  is formed on a rectangular annular shaped region of the upper surface of the wall portion  23  in a plan view. That is, the plating layer  24  is formed in a rectangular shape so as to surround the opening portion  22 . 
     For example, the plating layer  24  is a two-layered plating layer having a nickel plating layer formed on the upper surface of the wall portion  23  and a gold plating layer formed on the nickel plating layer. 
     The lid  30  is a plate-shaped member made of Kovar. The size of the lid  30  in a plan view is the same as the size of the housing  20  in a plan view. 
     The electronic device  1  of the Comparative Example is manufactured by bonding the lid  30  to the wall portion  23  of the housing  20  via the plating layer  24  in a state where the MEMS chip  40  is mounted on the bottom surface of the concave portion  21  of the housing  20  of the hollow housing  10 . In the state where the wall portion  23  of the housing  20  and the lid  30  are bonded to each other by the plating layer  24 , the concave portion  21  of the housing  20  in which the MEMS chip  40  is disposed is sealed by the plating layer  24  and the lid  30 . 
       FIGS. 2A and 2B  are views showing a process of mounting the lid  30  onto the housing  20  in a manufacturing process of the electronic device  1  of the Comparative Example,  FIG. 2A  is a cross-sectional view corresponding to  FIG. 1B , and  FIG. 2B  is a plan view corresponding to  FIG. 1C . 
     As shown in  FIG. 2A , the plating layer  24  is melted using a welding machine  50 , and the electronic device  1  is manufactured by bonding the upper surface of the wall portion  23  of the housing  20  and the lower surface of the lid  30  through the melted plating layer  24 . 
     The welding machine  50  includes roller electrodes  51 A and  51 B. Current flows between the roller electrodes  51 A and  51 B while the roller electrodes  51 A and  51 B abut the lid  30  and moves along the periphery of the lid  30 , and the upper surface of the wall portion  23  of the housing  20  and the lower surface of the lid  30  are seam-welded by melting the plating layer  24  with resistance heat of the lid  30 . 
     In order to melt the housing  20  and the lid  30  by the plating layer  24 , as shown in  FIG. 2A , the roller electrodes  51 A and  51 B of the welding machine  50  abuts the upper surface of the lid  30 . 
     If current flows from the roller electrode  51 A to the roller electrode  51 B as shown by an arrow, the current flows from the roller electrode  51 A shown in  FIG. 2A  to the lid  30  made of Kovar, and reaches the plating layer  24 . At this time, the current reaches a point A of the plating layer  24  shown in  FIG. 2B . The point A is positioned around a corner of the plating layer  24  having a rectangular annular shape in a plan view. 
     Moreover, the current flows to the plating layer  24  having a rectangular annular shape in a plan view as shown by an arrow in  FIG. 2B , flows to the lid  30  from the plating layer  24  in the thickness direction at a point B, and flows to the roller electrode  51 B. 
     In this way, the current flows to the plating layer  24 , and thus, the plating layer  24  is melted with resistance heat, the portion of the plating layer  24 , in which the temperature is decreased according to the movement of the roller electrodes  51 A and  51 B, is solidified again, and the housing  20  and the lid  30  are bonded to each other. 
     The roller electrodes  51 A and  51 B move along sides of the lid  30 , and thus the housing  20  and the lid  30  are bonded to each other over one round of the plating layer  24  having the rectangular annular shape. Thereby, the housing  20  and the lid  30  are bonded to each other by seam welding. 
     As described above, the hollow housing  10  of the Comparative Example includes the housing  20  made of ceramic and the lid  30  made of Kovar, wherein the housing  20  and the lid  30  are seam-welded via the plating layer  24 . 
     However, in the hollow housing  10  of the Comparative Example, if the roller electrodes  51 A and  51 B abut the lid  30  made of Kovar and current flows at the time of the seam welding, the current flows to the entire lid  30  and thus current and heat are diffused to the entire lid  30 . As such, there is a problem that usage efficiency of energy is decreased. 
     Moreover, in the hollow housing  10  of the Comparative Example, since the housing  20  is made of ceramic and the lid  30  is made of Kovar, miniaturization of the device is difficult. This is mainly because miniaturization of the ceramic substrate is difficult. 
     Accordingly, an object of the embodiment described below is to provide a hollow housing and an electronic device that can solve the above-described problems. 
       FIGS. 3A to 3E  are views showing the hollow housing and the electronic device of the embodiment,  FIG. 3A  is a perspective view,  FIG. 3B  is an exploded cross-sectional view in a cross-section taken along a line C-C of  FIG. 3A ,  FIG. 3C  is a plan view of the hollow housing and the electronic device,  FIG. 3D  is a bottom view of the hollow housing, and  FIG. 3E  is a plan view of the housing. Here, as shown in  FIGS. 3A to 3E , a rectangular coordinate system (XYZ coordinate system) is defined. 
     An electronic device  100  of the embodiment shown in  FIGS. 3A and 3B  is a device which mounts a Micro Electronic Mechanical System (MEMS) chip  40  in an inner portion of a hollow housing  110 . That is, the electronic device  100  includes the hollow housing  110  and the MEMS chip  40 . The hollow housing  110  is a housing in which the MEMS chip  40  is removed from the electronic device  100 . 
     As shown in  FIGS. 3A and 3B , the hollow housing  110  of the embodiment includes a housing  120  and a lid  130 . Since the lid  130  is bonded onto the housing  120 , the plan view of the  FIG. 3C  shows an upper surface of the lid  130 . The upper surface of the lid  130  is the same as the surfaces of the electronic device  100  and the hollow housing  110 . 
       FIG. 3D  is a view showing a bottom surface of the lid  130  in a state before the lid  130  is bonded to the housing  120 .  FIG. 3E  is a plan view showing the housing  120  in a state before the lid  130  is bonded to the housing  120 . 
     The housing  120  is a rectangular parallelepiped-shaped member which includes a concave portion  121  and is formed by processing a silicon substrate. The concave portion  121  is concaved in a rectangular parallelepiped shape when viewed from an upper surface side of the housing  120 , and as shown in  FIG. 3E , is exposed to an opening portion  122  in the state before the lid  130  is bonded to the housing  120 . 
     For example, as the silicon substrate which is used for forming the housing  120 , a silicon substrate to which boron (B) or phosphorus (p) is implanted may be used. In addition, since the lid  130  described below is formed of a silicon substrate to which impurities are implanted, a case where the housing  120  is also formed of a silicon substrate is described. However, the housing  120  may be formed by a silicon substrate to which impurities are not implanted. 
     Although the details will be described below, the lid  130  is formed of a silicon substrate to which impurities are implanted since current flows to the lid  130 , but the silicon substrate which forms the housing  120  may not be implanted by impurities since current does not flow to the housing  120 . 
     The concave portion  121  of the housing  120  is continuously surrounded by a wall portion  123 , and the opening portion  122  is a rectangular opening portion which is surrounded by the wall portion  123 . Moreover, the wall portion  123  is formed in a rectangular annular shape in a plan view. 
     In the housing  120 , an oxide film  120 A is formed on the inner surface of the concave portion  121 . The outer surface of the housing  120  includes a bottom surface of the housing  120 , a side surface (the outer surface of the wall portion  123 ), and an upper surface of the wall portion  123 . The inner surface of the concave portion  121  is a surface forming the concave portion  121 , and includes one bottom surface and four side surfaces. 
     Thereby, the oxide film  120 A is formed on the bottom surface of the housing  120 , the side surfaces (outer surface of wall portion  123 ), the upper surface of the wall portion  123 , and one bottom surface and four side surfaces which form the concave portion  121 . 
     For example, the oxide film  120 A is formed by oxidizing the surface after cutting a silicon substrate to the size of the housing  120  and forming the concave portion  121 . Since the oxide film  120 A formed by oxidizing the surface of the silicon substrate is a silicon oxide film (SiO 2  film), the oxide film is an insulating film. 
     A plating layer  124  is formed on an upper surface of the wall portion  123  along the periphery of the opening portion  122 . The plating layer  124  is formed on the oxide film  120 A. 
     The plating layer  124  is formed on a rectangular annular shaped region of the upper surface of the wall portion  123  in a plan view, and is an example of a first metal film. That is, the plating layer  124  is formed so as to surround the opening portion  122  and make one round in a rectangular shape. 
     For example, the plating layer  124  is a plating layer having a two-layer structure which includes a nickel plating layer formed on the upper surface of the wall portion  123  and a gold plating layer formed on the nickel plating layer. 
     The MEMS chip  40  is disposed on the bottom surface of the concave portion  121 , and is connected to a pad (not shown) or the like, which is disposed on the bottom surface of the concave portion  121 , by a bonding wire  41 . For example, the MEMS chip  40  is an actuator of an acceleration sensor. 
     Moreover, a penetration electrode is formed in the housing  120 , and the MEMS chip  40  and the external device are electrically connected to each other via the penetration electrode. 
     In addition, the MEMS chip  40  is described as an example of an electronic component. However, the electronic component which is accommodated in the hollow housing  110  of the embodiment is not limited to the MEMS chip  40 . The electronic component which is accommodated in the hollow housing  110  of the embodiment may be an electronic component which is accommodated in a sealed space (encapsulated space). For example, as the electronic component, a semiconductor element such as an IC (Integrated Circuit) chip may be accommodated in the hollow housing  110 . 
     The lid  130  is a plate-shaped member made of silicon. The size of the lid  130  in a plan view is the same as the size of the housing  120  in a plan view. For example, the lid  130  is formed by processing a silicon substrate. 
     For example, as the silicon substrate which is used for forming the lid  130 , a silicon substrate to which boron (B) or phosphorus (p) is implanted may be used. This is because current flows to the lid  130 . 
     A plating layer  131  is formed on the bottom surface (lower surface) of the lid  130 . The plating layer  131  is formed in a rectangular annular shaped region along the outer circumference of the rectangular lid  130  in a bottom surface view. The rectangular annular shaped region on which the plating layer  131  is formed corresponds to the plating layer  124  which is formed on the rectangular annular shaped region of the upper surface of the wall portion  123  of the housing  120 . That is, the plating layer  131  is formed at the position corresponding to the plating layer  124 . 
     The plating layer  131  is an example of a second metal film. For example, the plating layer  131  is manufactured by forming a nickel plating film on the bottom surface (lower surface) of the lid  130 . Since the lid  130  is a silicon substrate, for example, the formation of the plating layer  131  may be performed by a semi-additive process. 
     Here, in the case where the plating layer  131  is formed at the position corresponding to the plating layer  124 , when transparently viewed in a plan view, the region on which the plating layer  131  is formed and the region on which the plating layer  124  is formed are not needed to completely coincide with each other, and the overlapped region only needs to exist over one round in the rectangular annular shape. 
     The plating layer  131  is bonded to the plating layer  124  by seam-welding. Moreover, the lid  130  is formed of a silicon substrate. 
     Thereby, the plating layer  131  may be formed on the bottom surface (lower surface) of the lid  130  to be bonded to the plating layer  124  over one round in the outer circumference in the XY direction of the hollow housing  110 . Thus, the lid  130  seals the concave portion  121  of the housing  120 . 
     In addition, a plating layer  132  is formed on the upper surface of the lid  130 . When the plating layer  132  is transparently viewed in a plan view, the plating layer  132  is formed on a region which overlaps with the plating layer  131 . That is, the plating layer  132  is formed on a rectangular annular shaped region along the outer circumference of the rectangular lid  130 . 
     The plating layer  132  is an example of a third metal film. For example, the plating layer  132  may be formed by forming a copper coating film on the upper surface of the lid  130 . Since the lid  130  is a silicon substrate, for example, the formation of the plating layer  132  may be performed by a semi-additive process. Moreover, the plating layer  132  has a higher melting point than that of the plating layer  131 . 
     The plating layer  132  is formed at a position corresponding to the plating layer  131 . In the case where the plating layer  132  is formed at the position corresponding to the plating layer  131 , when transparently viewed in a plan view, the region on which the plating layer  132  is formed and the region on which the plating layer  131  is formed are not needed to completely coincide with each other, and the overlapped region only needs to exist over one round in the rectangular annular shape. 
     As shown in  FIG. 3C , the plating layer  132  includes a plurality of metal films  132 X and  132 Y separated from each other in the rectangular annual shaped region along the outer circumference of the lid  130 . The metal films  132 X and  132 Y are examples of a plurality of metal film portions which are separated from each other in a plan view and surround the center portion of the upper surface of the lid  130 . 
     The metal films  132 X are arranged along sides  130 X 1  and  130 X 2  which extend in the X axis direction in the outer circumference of the lid  130 , and are a plurality of rectangular metal films having the longitudinal direction in the Y axis direction. In the plurality of metal films  132 X, the lengths in the X axis direction and the Y axis direction are approximately the same as each other except for the metal films  132 X of the both ends in the X axis direction. Moreover, all metal films  132 X are disposed at approximately equal intervals in the X axis direction. 
     The metal films  132 X formed along the side  130 X 1  and metal films  132 X formed along the side  130 X 2  are disposed at positions symmetrical in the Y axis direction while interposing the center portion of the upper surface of the lid  130 , and are disposed so as to be pairs in the Y axis direction. Here, the side  130 X 1  is a side which extends in the X axis direction of a Y-axis negative direction side in the rectangular lid  130  in a plan view, and the side  130 X 2  is a side which extends in the X axis direction in a Y-axis positive direction side. 
     A distance D 1  in the Y axis direction between the metal films  132 X formed along the side  130 X 1  and the metal films  132 X formed along the side  130 X 2  is set so as to be longer than the thickness (the thickness of the silicon substrate which does not include the plating layers  131  and  132 ) of the lid  130 . That is, the interval in the Y axis direction between the metal films  132 X formed along the side  130 X 1  and the metal films  132 X formed along the side  130 X 2  is larger than the thickness of the silicon substrate of the lid  130 . 
     The metal films  132 Y are arranged along sides  130 Y 1  and  130 Y 2  which extend in the Y axis direction in the outer circumference of the lid  130 , and are a plurality of rectangular metal films having the longitudinal direction in the X axis direction. In the plurality of metal films  132 Y, the lengths in the X axis direction and the Y axis direction are approximately the same as each other except for the metal films  132 Y of the both ends in the Y axis direction. Moreover, all the metal films  132 Y are disposed at approximately equal intervals in the Y axis direction. 
     The metal films  132 Y formed along the side  130 Y 1  and metal films  132 Y formed along the side  130 Y 2  are disposed at positions symmetrical in the X axis direction while interposing the center portion of the upper surface of the lid  130 , and are disposed so as to be pairs in the X axis direction. Here, the side  130 Y 1  is a side which extends in the Y axis direction of an X-axis negative direction side in the rectangular lid  130  in a plan view, and the side  130 Y 2  is a side which extends in the Y axis direction in an X-axis positive direction side. 
     A distance D 2  in the X axis direction between the metal films  132 Y formed along the side  130 Y 1  and the metal films  132 Y formed along the side  130 Y 2  is set so as to be longer than the thickness (the thickness of the silicon substrate which does not include the plating layers  131  and  132 ) of the lid  130 . That is, the interval in the X axis direction between the metal films  132 Y formed along the side  130 Y 1  and the metal films  132 Y formed along the side  130 Y 2  is larger than the thickness of the silicon substrate of the lid  130 . 
     As described above, the plating layer  131  is formed on the lower surface of the lid  130  which is formed of a silicon substrate, and the plating layer  132  is formed on the upper surface of the lid. The lid  130  comes into ohmic contact with the plating layers  131  and  132 . 
     Next, a process of bonding the housing  120  of the hollow housing  110  and the lid  130  in the embodiment will be described with reference to  FIGS. 4A and 4B . 
       FIGS. 4A and 4B  are views showing a process of mounting the lid  130  to the housing  120  in a manufacturing process of an electronic device  100  of the embodiment,  FIG. 4A  is a cross-sectional view corresponding to the  FIG. 3B , and  FIG. 4B  is a plan view corresponding to  FIG. 3E . 
     As shown in  FIG. 4A , the plating layer  124  and the plating layer  131  are melted using the welding machine  50 , and the electronic device  100  is manufactured by bonding the upper surface of the wall portion  123  of the housing  120  and the lower surface of the lid  130  through the melted plating layers  124  and  131 . 
     In order to melt the plating layers  124  and  131 , as shown in  FIG. 4A , the roller electrodes  51 A and  51 B of the welding machine  50  abut the plating layer  132  which is formed on the upper surface of the lid  130 . The roller electrodes  51 A and  51 B abut a pair of metal films  132 Y which are positioned at the most positive direction side in the Y axis direction in the plurality of metal films  132 X and  132 Y of the plating layer  132 . 
     Here, since the lid  130  is formed of a silicon substrate to which impurities are implanted, currents can flow to the lid. 
     Thereby, as shown in  FIG. 4A , the roller electrodes  51 A and  51 B abut the metal films  132 Y of the side  130 Y 1  of the lid  130  and the metal film  132 Y of the side  130 Y 2  respectively, and if current flows in the direction from the roller electrode  51 A to the roller electrode  51 B, the current flows as follows. 
     That is, the current flows in the thickness direction of the lid  130  via the metal films  132 Y of the side  130 Y 1  from the roller electrode  51 A, and reaches the plating layers  131  and  124 . At this time, the current reaches a point A of the plating layer  124  shown in  FIG. 4B . The point A is positioned below the metal film  132 Y positioned the most positive direction side in the Y axis direction in the metal films  132 Y of the side  130 Y 1 . 
     In addition, the current flows in the thickness direction (in Z-axis positive direction) of the lid  130  from the plating layer  131  in a point B via the plating layer  124  having a rectangular annular shape in a plan view as shown in  FIG. 4B , reaches the metal films  132 Y, and flows to the roller electrode  51 B. Moreover, the point B is positioned below the metal film  132 Y positioned at the most positive direction side in the Y axis direction in the metal films  132 Y of the side  130 Y 2 . 
     In addition, for convenience of descriptions, a pathway of the current which flows to the plating layer  124  is shown in  FIG. 4B . However, since the plating layer  124  and the plating layer  131  contact each other over one round in the rectangular annular shape, when current flows to the plating layer  124 , similarly, current also flows to the plating layer  131 . 
     Here, the distance D 2  (refer to  FIG. 3C ) between the pair of metal films  132 Y which abut the roller electrodes  51 A and  51 B is longer than the thickness of the lid  130 . 
     That is, a resistance value of the lid  130  (silicon substrate) between the pair metal films  132 Y disposed with the distance D 2  in the X axis direction is larger than a resistance value of the lid  130  (silicon substrate) between the metal film  132 Y and the plating layer  131  formed on the lower surface of the lid  130  with the thickness of the lid  130 . 
     Thereby, if the roller electrodes  51 A and  51 B abut the pair of metal films  132 Y and current flows to the electrodes, the current does not directly flow between the pair of metal films  132 Y in the X axis direction in the inner portion of the lid  130 , and the current flows between the metal film  132 Y and the plating layer  131  in the Z axis direction. 
     This is because the resistance value of the lid  130  (silicon substrate) between the metal film  132 Y and the plating layer  131  formed on the lower surface of the lid  130  is smaller than the resistance value of the lid  130  (silicon substrate) between the pair of metal films  132 Y disposed with the distance D 2  in the X axis direction. 
     Accordingly, if the roller electrodes  51 A and  51 B abut the pair of metal films  132 Y and current flows to the electrodes, the plating layer  131 , which is disposed at the rear side (lower surface side) of the lid  130  with respect to the pair of metal films  132 Y, is heated. Moreover, since the plating layer  131  abuts the plating layer  124 , current also flows in the plating layer  124 . Thereby, the plating layer  124  is also heated by resistance heat and melted. In this way, the plating layer  131  and the plating layer  124  can be melted. 
     Moreover, if the roller electrodes  51 A and  51 B move to the Y-axis negative direction side in the state where the plating layer  131  and the plating layer  124  are melted, since the portion to which current flows moves to the Y-axis negative direction side, the plating layer  131  and the plating layer  124  are solidified and bonded to each other. 
     Thereby, if the roller electrodes  51 A and  51 B move to the Y-axis negative direction side, seam welding can be performed to the plating layer  124  and the plating layer  131  along the sides  130 Y 1  and  130 Y 2  of the lid  130 . 
     In addition, if the roller electrodes  51 A and  51 B abut the pair of metal films  132 Y and current flows to the metal film in order to melt the plating layer  131  and the plating layer  124 , since the current flows to the lid  130  made of a silicon substrate, the lid  130  is also heated. It is considered that the heating of the lid  130  also contributes to the melting of the plating layers  131  and  124 . 
     Moreover,  FIG. 4A  shows the state where the seam welding is performed in the Y axis direction by abutting the roller electrodes  51 A and  51 B to the pair of metal films  132 Y and flowing current to the metal films. However, this is also applied in the X axis direction similarly. 
     The distance D 1  (see  FIG. 3C ) between the pair of metal films  132 X is longer than the thickness of the lid  130 . 
     That is, the resistance value of the lid  130  (silicon substrate) between the pair metal films  132 X disposed with the distance D 1  in the Y axis direction is larger than the resistance value of the lid  130  (silicon substrate) between the metal film  132 X and the plating layer  131  formed on the lower surface of the lid  130  with the thickness of the lid  130 . 
     Thereby, if the roller electrodes  51 A and  51 B abut the pair of metal films  132 X and current flows to the electrodes, the current does not directly flow between the pair of metal films  132 X in the Y axis direction in the inner portion of the lid  130 , and the current flows between the metal film  132 X and the plating layer  131  in the Z axis direction. 
     Accordingly, if the roller electrodes  51 A and  51 B abut the pair of metal films  132 X and current flows to the electrodes, the plating layer  131 , which is disposed at the rear side (lower surface side) of the lid  130  with respect to the pair of metal films  132 X, is heated, and the plating layer  131  and the plating layer  124  can be effectively melted. 
     Moreover, if the roller electrodes  51 A and  51 B move in the X axis direction in the state where the plating layer  131  and the plating layer  124  are melted, since the portion to which current flows moves in the X axis direction, the plating layer  131  and the plating layer  124  are solidified and bonded to each other. 
     Thereby, if the roller electrodes  51 A and  51 B move in the X axis direction, seam welding can be performed to the plating layer  124  and the plating layer  131  along the sides  130 X 1  and  130 X 2  of the lid  130 . 
     Moreover, since the plating layer  132  which abuts the roller electrodes  51 A and  51 B has a higher melting point than the plating layer  131 , when the seam welding is performed, a current amount or the like may be adjusted to a temperature in which the plating layer  131  is melted but the plating layer  132  is not melted. 
     Next, transmission paths of current and heat in the hollow housing  110  (see  FIGS. 3A to 3E ) of the embodiment and the hollow housing  10  (see  FIG. 1 ) of the Comparative Example will be described with reference to  FIGS. 5A to 6D . 
       FIGS. 5A to 5C  are cross-section views showing transmission paths of current and heat in the hollow housing  110  of the embodiment and the hollow housings  10  and  10 A of the Comparative Example.  FIGS. 6A to 6D  are plan views showing transmission paths of current in the hollow housing  110  of the embodiment and the hollow housings  10  and  10 A of the Comparative Example. 
       FIG. 5A  is a view showing transmission paths of current and heat in the hollow housing  10  (see  FIGS. 1A to 1C ) of the Comparative Example, and  FIG. 5B  is a view showing transmission paths of current and heat in a hollow housing  10 A of the modification of the Comparative Example.  FIG. 5C  is a view showing transmission paths of current and heat in the hollow housing  110  of the embodiment. 
     In addition, the welding machine  50  (see  FIGS. 2A and 4A ) is not shown in  FIGS. 5A to 5C . However, in order to perform seam welding by roller electrodes  51 A and  51 B of the welding machine  50 , the roller electrodes  51 A and SIB abut the upper side of the lid and current is supplied to the electrodes. 
       FIG. 6A  is a view showing the transmission path of current in the lid  30  of the hollow housing  10  of the Comparative Example shown in  FIG. 5A , and  FIG. 6B  is a view showing the transmission path of current in a lid  30 A of the hollow housing  10 A of the modification of the Comparative Example shown in  FIG. 5B .  FIG. 6C  is a view showing the transmission path of current on the upper surface of the lid  130  of the hollow housing  110  of the embodiment shown in  FIG. 5C , and  FIG. 6D  is a view showing the transmission path of current on the lower surface of the lid  130  shown in  FIG. 6C . 
     As shown in  FIG. 5A , in the hollow housing  10  of the Comparative Example, since the lid  30  is made of Kovar, if current is supplied to roller electrodes (not shown), the current flows to the lid  30  as shown by an arrow of a solid line. At this time, in the inner portion of the lid  30 , current flows in the thickness direction (Z-axis negative direction), and current also flows in the transverse direction (X axis direction). This is because the lid  30  is a conductor. 
     Moreover, at this time, as shown in an arrow of a broken line, similar to the current, heat is transmitted in the thickness direction (Z-axis negative direction), and is also transmitted in the transverse direction(X axis direction). The heat is generated by resistance heat of the lid  30  since current flows to the lid  30  made of Kovar. 
     Moreover, as shown in  FIG. 6A , in a plan view, current flows in the direction from the roller electrode  51 A toward the roller electrode  51 B in the lid  30 . 
     Accordingly, the plating layer  24  can be melted, and thus, seam welding can be performed to the lid  30  and the housing  20  through the plating layer  24 . 
     In this way, in the hollow housing  10  of the Comparative Example, since the lid  30  made of Kovar has high electrical conductivity and high thermal conductivity, seam welding is possible. However, current and heat are also transmitted to a portion of the lid  30  (center portion of the lid  30 ) at which the seam welding is not performed. Thereby, usage efficiency of energy is decreased by the diffusion of current and heat. 
     Moreover, in the hollow housing  10 A of the modification of the Comparative Example shown in  FIGS. 5B and 6B , the lid  30 A made of ceramic is used instead of the lid  30  made of Kovar. The plating layer  31  is formed on a rectangular annular shaped region along four sides on the upper surface of the lid  30 A made of ceramic. 
     As shown in  FIG. 6B , if roller electrodes  51 A and  51 B abut the plating layer  31  of the upper surface of the lid  30 A and current flows to the electrodes, as indicated with an arrow of a solid line, the current flows to the plating layer  31  between the roller electrodes  51 A and  51 B. Since the lid  30 A is made of ceramic and is an insulator, as shown in  FIGS. 5B and 6B , current does not flow to the lid  30 A. 
     Thereby, even when the roller electrodes  51 A and  51 B abut the plating layer  31  and current flows to the plating layer as shown in  FIG. 6B , as shown in  FIG. 5B , heat does not sufficiently reach the plating layer  24  which is the lower surface of the lid  30 A, and it is difficult to melt the plating layer  24 . 
     Accordingly, like the hollow housing  10 A of the modification of Comparative Example, even when the plating layer  31  is formed on the upper surface of the lid  30 A made of ceramic, it is difficult to melt the plating layer  24 , and it is difficult to bond the housing  20  and the lid  30 A by seam welding. Moreover, large power is consumed, and thus, manufacturing efficiency is deteriorated. 
     On the other hand, as shown in  FIGS. 5C and 6C , in the hollow housing  110  of the embodiment, the plating layer  131  is formed on the lower surface of the lid  130  made of a silicon substrate to which impurities are implanted, and the plating layer  132  is formed on the upper surface of the lid  130 . The plating layer  132  includes the plurality of metal films  132 X and  132 Y (see  FIG. 3C ). 
     Thereby, if roller electrodes  51 A and  51 B abut the plating layer  132  and current flows to the electrodes as shown in  FIG. 6C , as shown in  FIGS. 5C and 6D , current flows in the thickness direction of the lid  130  from the plating layer  132  as shown in a solid line, and the current reaches the plating layers  131  and  124 . 
     As a result, the plating layers  131  and  124  are melted by resistance heat of the plating layers  131  and  124 , and the housing  120  and the lid  130  can be bonded to each other by seam welding. 
     In the hollow housing  110  of the embodiment, as shown in  FIGS. 5C and 6D , current flows in the thickness direction of the lid  130  from the plating layer  132  which includes the plurality of metal films  132 X and  132 Y, and reaches the plating layer  131 . 
     Since the plating layer  131  has a rectangular annular shape in a plan view, current does not diffuse in the center portion of the lid  130 , and current flows along the plating layer  131  having a rectangular annular shape. Moreover, at this time, current also flows to the plating layer  124  which contacts the plating layer  131 . 
     In addition, the plating layer  131  and the plating layer  124  are melted by resistance heat, and the plating layer  131  and the plating layer  124  are integrated with each other. Thereby, the housing  120  and the lid  130  are bonded to each other. 
     Accordingly, the plating layer  131  is formed on the lower surface of the lid  130  made of a silicon substrate to which impurities are implanted, the plating layer  132  is formed on the upper surface, and thus, current can flow from the plating layer  132  to the plating layer  131  via the lid  130 . Thus, the housing  120  and the lid  130  can be bonded to each other by seam welding. 
     In this way, the lid  130  is formed of a silicon substrate to which impurities are implanted, and current flows to the lid if voltage is applied to the lid. 
     In addition, the thickness of the lid  130  is set to the length which is shorter than the distances D 1  and D 2  between the pair of metal films  132 X and  132 Y of the plating layer  132  formed on the upper surface of the lid  130 . 
     Thereby, if the roller electrodes  51 A and  51 B abut the pair of metal films  132 X and  132 Y of the plating layer  132  and current flows to electrodes, current almost does not flow in the plane direction (XY direction) of the lid  130 , and the current can selectively flow in the thickness direction (Z direction). 
     Thereby, diffusion of current to the center portion of the lid  130  can be suppressed, the target place (the plating layer  131  immediately below the pair of metal films  132 X and  132 Y which abuts the roller electrodes  51 A and  51 B) of the seam welding can be selectively heated. 
     Thereby, usage efficiency of energy is improved, and the seam welding can be performed by power which is smaller than the case where the hollow housing  10  of the Comparative Example is bonded by the seam welding. 
     Moreover, since the lid  130  is made of a silicon substrate, thermal conductivity of the lid  130  is lower than that of the lid  30  made of Kovar of the Comparative Example. Thereby, heat diffusion to the center portion of the lid  130  can be also suppressed. 
     As described above, in the hollow housing  110  of the embodiment, if the roller electrodes  51 A and  51 B abut the pair of metal films  132 X and current flows to electrodes, the current flows in the thickness direction of the lid  130  which is formed of a silicon substrate to which impurities are implanted. Thereby, when seam welding is performed, current can be prevented from being diffused to the center portion of the lid  130 , and consumed power can be decreased. 
     Moreover, since the lid  130 , which is formed of a silicon substrate to which impurities are implanted, is used, heat can be suppressed from being diffused to the center of the lid  130  when seam welding is performed. Also, consumed power can be decreased. 
     Therefore, according to the embodiment, the hollow housing  110  and the electronic device  100  which are effectively manufactured can be provided. 
     Moreover, in the hollow housing  110  of the embodiment, it is possible to improve usage efficiency of energy. 
     In addition, since the hollow housing  110  of the embodiment includes the housing  120  made of a silicon substrate and the lid  30  made of a silicon substrate, it is possible to achieve the miniaturization in a semiconductor manufacturing technology. According to the embodiment, the hollow housing  110  and the electronic device  100  having improved miniaturization can be provided. 
     Particularly, when the MEMS chip  40  is mounted on the hollow housing  110 , since the miniaturization of the MEMS chip  40  is realized and miniaturization of the hollow housing  110  is improved, a significantly small-sized electronic device  100  can be provided. Moreover, the MEMS chip  40  may be integrally formed of the same silicon substrate as the case  120 . 
     Next, specific resistance, current density, and loss of the lid  130  of the embodiment, the lid  30  of the Comparative Example, and the lid  30 A of the modification of the Comparative Example will be described with reference to  FIG. 7 . 
       FIG. 7  is a view showing specific resistance, current density, and loss of the lid  30  of the Comparative Example, the lid  130  of the embodiment, and the lid  30 A of a modification of the Comparative Example. The current density and the loss shown in  FIG. 7  are values which are obtained by electromagnetic field simulation. 
     In  FIG. 7 , as materials of the lid  30  of the Comparative Example, the lid  130  of the embodiment, and the lid  30 A of the modification of the Comparative Example, Kovar (the lid  30 ), silicon (the lid  130 ), and alumina (the lid  30 A) are shown. 
     In order to match conditions, the specific resistance, the current density, and the loss of Kovar (the lid  30 ) and the alumina (the lid  30 A) shown in  FIG. 7  are simulation values which are obtained by changing the material of the lid  130  of the hollow housing  110  of the embodiment shown in  FIGS. 3A to 3E  from silicon to Kovar and alumina. 
     That is, the specific resistance, the current density, and the loss of Kovar (lid  30 ) and the alumina (the lid  30 A) are simulation values which are obtained by changing the material of the lid  130  from silicon to Kovar and alumina in a state where the plating layer  131  and the plating layer  132  are formed on the lower surface and the upper surface of the lid  130  respectively as shown in  FIGS. 3A to 3E . 
     Thereby, in the descriptions of  FIG. 7 , expressions such as the lid  130  made of Kovar and the lid  130  made of alumina are used in addition the lid  130  made of silicon. 
     As shown in  FIG. 7 , the specific resistance of Kovar was 4.9E-5 (4.9×10 −5 ) Ω·cm, the specific resistance of silicon was 0.01 Ω·cm, and the specific resistance of alumina was 1E10 (1.0×10 10 )Ω·cm. 
     Since Kovar is a metal (alloy) and a conductor, the specific resistance is significantly low. Moreover, since the alumina is an insulator, the specific resistance is significantly high. On the other hand, in the silicon to which impurities was implanted, the specific resistance indicated a value closer to Kovar than an intermediate value of the specific resistance of Kovar and alumina. 
     Moreover, the specific resistance of the plating layer  131  made of nickel coating film was 1E-4 (1.0×10−4) Ω·=in all cases of Kovar, silicon, and alumina. 
     In addition, the current density in Kovar was 5.2E10 (5.2×10 10 ) A/m 2 , and the current density in the silicon was 1.1E11 (1.1×10 11 ) A/m 2 . Moreover, since the alumina is an insulator and current does not flow to the alumina, the value of the current density was not obtained. 
     In this way, it was shown that the current density of the silicon was higher than that of Kovar. This is because the specific resistance of the silicon is higher than that of Kovar, and thus, diffusion of current is suppressed and the current density is increased. 
     Moreover, the loss (resistance loss) in Kovar was 2.4E14 (2.4×10 14 ) W/m3, and the loss in the plating layer  131  of the lower surface of the lid  130  made of Kovar was 1.5E14 (1.5×10 14 ) W/m 3 . 
     On the other hand, the loss in the case of silicon was 7.8E14 (7.8×10 14 ) W/m 3 , and the loss in the plating layer  131  of the lower surface of the lid  130  made of silicon was 5.2E14 (5.2×10 14 ) W/m 3 . 
     That is, it was found that the loss of the lid  130  made of silicon was larger than the loss of the lid  130  made of Kovar. This is because the specific resistance and the current density of the lid  130  made of silicon are larger than those of the lid  130  made of Kovar. 
     This means that the plating layer  131  is more efficiently heated when the lid  130  made of silicon is used. 
     That is, as shown in  FIG. 7 , it can be understood that heating efficiency of the plating layer  131  is higher and seam welding is performed by less power when the seam welding is performed using the lid  130  made of silicon than when the seam welding is performed using the lid  130  made of Kovar. 
     Next, the distribution of the current density in case of using the lid  130  made of silicon and in case of using the lid  130  made of Kovar will be described with reference to  FIGS. 8A and 8B . 
     Moreover, similar to  FIG. 7 , the current density shown in  FIGS. 8A and 8B  is electromagnetic field simulation results which are obtained when the material of the lid  130  is silicon (the embodiment) and when the material of the lid  130  is Kovar in the structure of the hollow housing  110  of the embodiment. Thereby, in the descriptions of  FIGS. 8A and 8B , expression such as the lid  130  made of Kovar is used in addition to the lid  130  made of silicon. 
       FIGS. 8A and 8B  are views showing distribution of current density in case of using the lid  130  made of silicon and in case of using the lid  130  made of Kovar, respectively. 
       FIG. 8A  shows the current density in a copper layer, a nickel layer, and a gold layer of the plating layer  124  and a nickel layer of the plating layer  131 . 
     The copper (Cu) layer, the nickel (Ni) layer, and the gold (Au) layer of the plating layer  124  and the nickel (Ni) layer of the plating layer  131  are provided between the wall portion  123  of the housing  120  and the lid  130  as shown  FIG. 8B . 
     In this way,  FIGS. 8A and 8B  show simulation results when the plating layer  124  has a three-layer structure. Moreover,  FIGS. 8A and 8B  show a case where the width of the plating layer  131  is smaller than that of the plating layer  124 . This is because the current density can be increased in the plating layer  131  when current flows to the plating layer  131  by narrowing the width of the plating layer  131 . If the current density is increased, a heating value in the plating layer  131  can be increased, and thus, the plating layer  131  and the plating layer  124  can be effectively melted. 
     Cu, Ni, Au, Ni indicated in a horizontal axis direction of  FIG. 8A  correspond to the copper (Cu) layer, the nickel (Ni) layer, and the gold (Au) layer of the plating layer  124  and the nickel (Ni) layer of the plating layer  131 , respectively. 
     Moreover, in  FIG. 8A , a solid line represents the characteristic of the current density in case of using the lid  130  made of a silicon, and a broken line represents the characteristic of the current density in case of using the lid  130  made of Kovar. 
     As can be seen from  FIG. 8A , in case of using the lid  130  made of silicon compared to the case of using the lid  130  made of Kovar, the current density was higher in all areas of the copper (Cu) layer, the nickel (Ni) layer, and the gold (Au) layer of the plating layer  124  and the nickel (Ni) layer of the plating layer  131 . 
     Here, the current density in the nickel (Ni) layer was the lowest of the copper (Cu) layer, the nickel (Ni) layer, and the gold (Au) layer of the plating layer  124 . This is because the resistance values of the copper (Cu) layer and the gold (Au) layer are lower than that of the nickel (Ni) layer. 
     Moreover, the current density of the nickel (Ni) layer of the plating layer  131  was higher than that of the gold (Au) layer of the plating layer  124 . This is because the width of the plating layer  131  is smaller than the width of the plating layer  124 . 
     In this way, since the width of the plating layer  131  is smaller than the width of the plating layer  124 , the heating value in the plating layer  131  can be increased, and the plating layer  131  and the plating layer  124  can be effectively melted. 
     As described above, the lid  130  was formed of a silicon substrate to which impurities are implanted, the plating layer  131  was formed on the lower surface of the lid  130 , the plating layer  132  was formed on the upper surface of the lid  130 . With this configuration, it was understood that the current density in the plating layers  124  and  131  could be increased in seam-welding. 
     Furthermore, it was understood that heating efficiency of the plating layers  124  and  131  could be increased and the seam welding could be effectively performed by less power. 
     Finally, a modification of the embodiment will be described with reference  FIG. 9 . 
       FIG. 9  is a cross-sectional view showing an electronic device  100 A of the modification of the embodiment. The cross-section shown in  FIG. 9  corresponds to the cross-section shown in  FIG. 3B . 
     In the electronic device  100  (refer to  FIGS. 3A to 3E ) of the embodiment, since the housing  120  is formed of a silicon substrate, before one housing  120  is formed by dicing a silicon wafer in order to form one electronic device  100 , a plurality of housings  120  before dicing may be formed on the silicon wafer. 
     The electronic device  100 A shown in  FIG. 9  includes a plurality of electronic devices  100 , which are collectively manufactured before dicing. In  FIG. 9 , the electronic device  100 A which includes four electronic devices  100  is shown as an example. However, when the plurality of housings  120  are formed on the silicon wafer before dicing, the electronic device  100 A which includes the plurality of electronic devices  100  can be collectively manufactured. 
     In this way, when the plurality of electronic devices  100  are collectively manufactured, the manufacturing cost can be reduced. 
       FIG. 9  shows the state where four lids  130  of four electronic devices  100  are separated from each other. However, four lids  130  may be integrally formed with each other, and then the lids  130  may be divided. 
     As described above, according to the embodiment, since the power required for the seam welding is decreased, power saving can be improved. 
     Moreover, when the seam welding is performed, since current and heat can be suppressed from being diffused to the center of the lid  130 , usage efficiency of energy can be improved. 
     Moreover, the hollow housing  110  and the electronic device  100  having improved miniaturization can be supplied. 
     In addition, since the housing  20  is a ceramic substrate and the lid  30  is made of Kovar in the hollow housing  10  of the Comparative Example (see  FIGS. 1A to 1C ), coefficients of linear expansion of the housing  20  and the lid  30  are largely different from each other. In this way, when the coefficients of linear expansion are largely different from each other, it may be difficult to collectively manufacture the plurality of electronic devices  1  in the heating process such as the seam welding. 
     Moreover, when a somewhat large electronic device  1  is manufactured, the manufacturing may be difficult due to the difference of coefficients of linear expansion. This is because a shrinkage rate of the lid  30  made of Kovar is larger than that of the housing  20  made of a ceramic substrate when the temperatures of the housing  20  and the lids  30  which are heated for the seam welding are lowered. 
     On the other hand, in the hollow housing  110  (see  FIGS. 3A to 3E ) of the embodiment, since the housing  120  and the lid  130  are all made of a silicon substrate, defects due to the coefficient of linear expansion do not easily occur, and the plurality of hollow housings  110  or electronic devices  100  can be collectively manufactured. In addition, an increase in the size of the hollow housing  110  or the electronic device  100  is possible. 
     Moreover, in the above, the shape is described in which the plating layer  132  is formed in a rectangular annular shape on the upper surface of the lid  130  in a plan view. However, in a case where current flows to the thickness direction of the lid  130  at the time of the seam welding and diffusion of current and heat to the center portion of the lid  130  does not cause any problem, the plating layer  132  may be formed on one surface of the upper surface of the lid  130 . In this case, the plating layer  132  may be separated into the plurality of metal films  132 X and  132 Y or may not be separated. 
     Moreover, each shape of the metal films  132 X and  132 Y shown in  FIG. 3C  is an example, and other shapes may be adopted. In addition, the disposition pattern of the metal films  132 X and  132 Y shown in  FIG. 3C  is an example, and the metal films may be disposed in other patterns. 
     Moreover, in the above, the shape is described in which the distance D 1  between the pair of metal films  132 X and the distance D 2  between the pair of metal films  132 Y are larger than the thickness of the lid  130 . However, in addition to the condition, the intervals of the metal films  132 X and  132 Y adjacent to each other in a plan view may be wider than the thickness of the lid  130 . In this case, flowing of current to adjacent metal films  132 X and  132 Y is difficult, and thus, the current density is increased, and efficiency of the seam welding is further improved. 
     Moreover, in the above description, the housing  120  and the lid  130  are made of a silicon substrate. However, the housing  120  and the lid  130  may be semiconductor substrates which are formed by materials other than silicon. 
     In addition, the housing  120  may not be a semiconductor substrate. For example, the housing  120  may be manufactured using a substrate made of ceramic such as alumina. If the housing  120  is made of ceramic and the lid  130  is made of a semiconductor substrate, problems of the coefficient of linear expansion do not occur. 
     While the preferred embodiments and their modifications and examples have been described now, the present invention is not limited to the preferred embodiments and their modifications and examples described above, and the preferred embodiments and their modifications and examples may be modified and replaced in various ways without deviating from the scope defined in the appended claims.