Abstract:
A method is provided for making packaged micro-devices each including a micro movable element, a first packaging member formed with a recess, and a second packaging member formed with another recess. The micro movable element has a movable part. In accordance with the method, a device wafer is prepared for forming a plurality of micromovable elements. A first packaging wafer, formed with a plurality of recesses corresponding in position to the movable parts of the respective movable elements, is bonded to one surface of the device wafer. A second packaging wafer, formed with a plurality of recesses, is bonded to the other surface of the device wafer. The resulting laminate assembly is cut into separate products.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to packaged micro movable devices such as acceleration sensors and angular velocity sensors. The present invention also relates to methods for making such micro movable devices. 
         [0003]    2. Description of the Related Art 
         [0004]    In recent years, very small devices produced by micromachining technology have been finding wide application in various technical fields. Those devices, having tiny movable or swingable parts, serve as sensing devices such as angular velocity sensors and acceleration sensors. These sensing devices are used in fields of camera shake control technology for video cameras or mobile telephones equipped with cameras, for example. In addition, the sensing devices can be used for car navigation systems, airbag release timing control systems, and attitude control systems in automobiles and robots. 
         [0005]    Miniaturized sensing devices include, for example, a swingable or movable part, a stationary part, a connecting part for connecting the movable part and the stationary part, a driver-electrode pair for driving the movable part, and a detection-electrode pair for detecting the operation or the amount of displacement of the movable part. Such a sensing device has a problem of deteriorated operation performance due to electrode contamination by foreign matters or dirt, or damage caused to the electrode. In order to avoid such electrode contamination or damage, packaging is often performed at a wafer level in manufacturing process of the sensing device. Techniques covering such a packaging process are disclosed in the following patent documents 1 and 2 for example.
       Patent Document 1: JP-A-2001-196484   Patent Document 2: JP-A-2006-46995       
 
         [0008]      FIG. 17  shows part of a conventional process through which a packaged sensing device  300  is manufactured. 
         [0009]      FIG. 17(   a ) shows a device wafer  300 ′, in which a plurality of sensing devices  300  are already formed after a predetermined process. Each sensing device  300  includes a movable part  301  which is swingable, a stationary part  302 , a connecting part (not illustrated) for connecting the movable part  301  and the stationary part  302 , a driver-electrode pair (not illustrated) for driving the movable part  301 , and a detection-electrode pair (not illustrated) for detecting the operation or the amount of displacement of the movable part  301 . The movable part  301  is thinner than the stationary part  302 . To the device wafer  300 ′, packaging wafers  303 ′,  304 ′ are bonded. In other words, the device wafer  300 ′ or each of the sensing devices  300  is packaged at a wafer level. The device wafer  300 ′ which is packaged at a wafer level is then separated as shown in  FIG. 17(   b ) into individual pieces in a dicing step. Through this process, packaged sensing devices  300  each packaged by packaging members  303 ,  304  are obtained. 
         [0010]    In the sensing device  300 , a sufficient amount of gaps G, G′ are provided between the movable part  301  and the packaging members  302 ,  304  so that the movable part  301 , which makes a swinging movement when the device is driven will not make contact with the packaging members  303 ,  304 . Each of the parts in each sensing device  300 , e.g. the movable part  301  and the stationary part  302 , is formed within the device wafer  300 ′ through etching and other predetermined processes performed to the device wafer  300 ′ which has a uniform thickness originally. In order to create the gaps G, G′, the device wafer  300 ′ is etched so as to make the movable part  301  thinner than the stationary part  302  which is bonded to the packaging members  303 ,  304 . 
         [0011]    However, according to such a conventional method as the above, relatively large nonuniformity is unavoidable in the thickness of a plurality of movable parts  301  formed in the device wafer  300 ′. As a result, relatively large nonuniformity is unavoidable among those movable parts  301  obtained from the same single devicewafer  300 ′, in terms of the inertia of those movable parts  301  in their swinging movement when the devices are in operation. Inertial nonuniformity in the movable part  301  of the sensing device  300  or micro movable device can be a cause of nonuniformity in operational characteristic of the movable part  301 , and therefore should be as small as possible. Likewise, inertial nonuniformity in the movable part  301  in the sensing device  300  can be a cause of nonuniformity in the detecting characteristic regarding detection of movement or the amount of displacement of the movable part  301 , and therefore should be as small as possible. 
       SUMMARY OF THE INVENTION 
       [0012]    The present invention has been proposed under the above-described circumstances, and it is therefore an object of the present invention to provide a packaged micro-device that is suitable for reducing operational characteristic nonuniformity of the movable part in the micro movable device. 
         [0013]    A first aspect of the present invention provides a method for making a packaged micro-device which includes a micro movable device having a movable part, a first packaging member having a first recess located correspondingly to the movable part, and a second packaging member having a second recess located correspondingly to the movable part. The method includes a first bonding step, a second bonding step and a dicing step. In the first bonding step, a first packaging wafer is bonded to a first surface side of a device wafer from which a plurality of the micro movable elements each having the movable part are to be formed. The device wafer has the first surface and a second surface which faces away from the first surface. The first packaging wafer is provided with a plurality of the first recesses. In the second bonding step, a second packaging wafer is bonded to the second surface side of the device wafer. The second packaging wafer is provided with a plurality of the second recesses. In the dicing step, a laminate assembly which includes the device wafer, the first packaging wafer and the second packaging wafer is cut. 
         [0014]    In the first bonding step of the present method described above, the device wafer and the first packaging wafer are bonded together in such a way that each of the first recesses faces or will face the movable part in one of the micro movable devices which are already formed or to be formed in the device wafer. In the second bonding step, the device wafer and the second packaging wafer are bonded together in such a way that each of the second recesses faces the movable part in one of the micro movable devices which are already formed in the device wafer. Through such a first and a second bonding steps as described above, packaging at a wafer level is accomplished. Thereafter, the dicing step is performed to obtain individual pieces, i.e. individual micro movable elements each being in a packaged state. 
         [0015]    In the present method, the first packaging wafer which is already formed with the first recesses each providing operation space for the movable part is bonded to the device wafer in the first bonding step, and further, the second packaging wafer which is already formed with the second recesses each providing operation space for the movable part is bonded to the device wafer in the second bonding step. Therefore, there is no need for etching the movable part thereby making the movable part thinner than the stationary part in order to provide a sufficient gap between the movable part and the two packaging members to prevent the movable part from contacting the first or the second packaging members as it makes swinging movement when the device is in operation. If the movable part is made thinner than the stationary part by etching, relatively large nonuniformity is unavoidable in the thickness of the movable part in a plurality of micro movable devices as has been described earlier in relation with a conventional method. The nonuniformity causes inertial nonuniformity in the movable parts, and the inertial nonuniformity can cause undesirable operational characteristic nonuniformity of the movable part. The present method which requires no thinning of the movable part is suitable for reducing inertial nonuniformity in the movable part. The present method which is suitable for reducing inertial nonuniformity in the movable part that swings when the device is in operation is suitable for reducing operational characteristic nonuniformity of the movable part. 
         [0016]    Further, the present method does not require any step of thinning the movable part that is formed within a device wafer having a uniform thickness. Thus, the present method is suitable for manufacturing packaged micro-devices at a high yield rate. 
         [0017]    In addition, the present method enables packaging at a wafer level during manufacturing process of the micro-device, and therefore is suitable to reduce operation performance deterioration of the movable part caused by dirt attached to the micro-device, or by damage incurred thereto. 
         [0018]    The micro movable element of the present invention preferably includes, in addition to the movable part, a stationary part and a connecting part for connecting the stationary part and the movable part. The movable part is swingable. The micro movable element (and hence the micro-device) serves as a sensing device such as an angular velocity sensor or an acceleration sensor. Inertial nonuniformity in the movable part as a part of the sensing device is a cause for detection characteristic nonuniformity which affects detection of movement or the amount of displacement of the movable part. The present method which is suitable for reducing inertial nonuniformity in the movable part is suitable for reducing operational characteristic nonuniformity of the movable part, and in addition, suitable for reducing detection characteristic nonuniformity regarding detection of movement or the amount of displacement of the movable part. 
         [0019]    In the method according to the first aspect of the present invention, preferably, the device wafer has a laminate structure including: a first layer having the first surface; a second layer having the second surface; and an intermediate layer between the first and the second layers. With this arrangement, a step of etching the first layer using a predetermined mask pattern as a mask may be performed before the first bonding step. In this case, the etching of the second layer using a predetermined mask pattern as a mask may be performed after the first bonding step and before the second bonding step. 
         [0020]    Preferably, the stationary part of the micro movable device includes a terminal portion for external connection. The first packaging member includes an electroconductive portion extending through the first packaging member to be connected with the terminal portion. Such an arrangement as the above allows for electric wires which are electrically connected with the micro movable device and extended out of the package appropriately. With this arrangement, the electroconductive portion penetrating the first packaging member may be formed before the first bonding step. Alternatively, it is possible to make the electroconductive portion after the first bonding step. 
         [0021]    Preferably, the first bonding step or the second bonding step or the both may be performed by one of methods such as an anodic bonding method, a direct bonding method, a room-temperature bonding method or an eutectic bonding method. 
         [0022]    Preferably, the border between the device wafer and the first packaging wafer and the border between the device wafer and the second packaging wafer may be provided by an insulation film. Such an arrangement as described above prevents undue electric connection between the device wafer or each micro movable device and the first packaging wafer, or between the device wafer or each micro movable device and the second packaging wafer. 
         [0023]    Preferably, the first recesses and/or the second recesses may be formed by DRIE, anisotropic wet etching or isotropic wet etching. These methods enable one to make the first recesses and the second recesses properly. 
         [0024]    According to a second aspect of the present invention, there is provided a packaged micro-device that includes: a micro movable element having a movable part; a first packaging member including a first recess corresponding in position to the movable part; and a second packaging member including a second recess corresponding in position to the movable part. The micro-device configured in this manner can be appropriately made by the method according to the present invention. The micro movable element may further include, in addition to the movable part, a stationary part, and a connecting part for connecting the movable part to the stationary part so that the movable part is swingable relative to the stationary part. The micro movable element (hence the micro-device) may serve as a sensing device such as an angular velocity sensor and an acceleration sensor. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0025]      FIG. 1  is a plan view of a packaged micro-device according to the present invention, with some portions omitted. 
           [0026]      FIG. 2  is another plan view of the packaged device according to the present invention, with some portions omitted. 
           [0027]      FIG. 3  is a sectional view taken in lines III-III in  FIG. 1 . 
           [0028]      FIG. 4  is a sectional view taken in lines IV-IV in FIG. 
           [0029]      FIG. 5  is a sectional view taken in lines V-V in  FIG. 1 . 
           [0030]      FIG. 6  is a sectional view taken in lines VI-VI in  FIG. 1 . 
           [0031]      FIG. 7  is a sectional view taken in lines VII-VII in  FIG. 1 . 
           [0032]      FIG. 8  is a sectional view taken in lines VIII-VIII in  FIG. 1 . 
           [0033]      FIG. 9  shows steps in a method for making a packaged device, according to the present invention. 
           [0034]      FIG. 10  shows steps following  FIG. 9 . 
           [0035]      FIG. 11  shows steps following  FIG. 10 . 
           [0036]      FIG. 12  shows variations of a packaging member. 
           [0037]      FIG. 13  shows variations of another packaging member. 
           [0038]      FIG. 14  is a plan view showing a case where eutectic metal pattern is formed. 
           [0039]      FIG. 15  shows a case where eutectic bonding method is used to perform a first bonding step. 
           [0040]      FIG. 16  shows a variation of the method for making a packaged device. 
           [0041]      FIG. 17  shows steps in a conventional method of making a packaged micro-device. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0042]      FIG. 1  through  FIG. 8  show a packaged micro-device X according to the present invention.  FIG. 1  is a plan view of the device X with some portions omitted, and  FIG. 2  is another plan view of the device X.  FIG. 3  through  FIG. 8  are sectional views taken in lines III-III, IV-IV, V-V, VI-VI, VII-VII, and VIII-VIII respectively in  FIG. 1 . 
         [0043]    The packaged device X includes a sensing device Y, a packaging member  81  (not illustrated in  FIG. 1 ), and a packaging member  82  (not illustrated in  FIG. 2 ). 
         [0044]    The sensing device Y includes a land  10 , an inner frame  20 , an outer frame  30 , a pair of connecting parts  40 , a pair of connecting parts  50 , and comb-teeth electrodes  61 ,  62 ,  63 ,  64 ,  71 ,  72 ,  73 ,  74 , and serves as an angular velocity sensor or an acceleration sensor. Also, the sensing device Y is made by means of bulk micromachining technology such as MEMS technology, from an SOI (Silicon On Insulator) substrate wafer. The wafer has a laminate structure including e.g. a first and a second silicon layer, and an insulation layer between the silicon layers. Each silicon layer is doped with impurity and has a predetermined level of electric conductivity. In  FIG. 1 , the hatched area represents a portion which is made from the first silicon layer and is higher than the insulation layer, projecting toward the viewer of the drawing, whereas in  FIG. 2 , the hatched area represents a portion which is made from the second silicon layer and is higher than the insulation layer, projecting toward the viewer of the drawing. 
         [0045]    As shown in  FIG. 3  and  FIG. 5 , the land  10  has a laminate structure provided by a first layer portion  11  formed from the first silicon layer, a second layer portion  12  formed from the second silicon layer, and an insulation layer  13  formed from the insulation layer. 
         [0046]    As shown in  FIG. 3  for example, the inner frame  20  has a laminate structure provided by a first layer portion  21  formed from the first silicon layer, a second layer portion  22  formed from the second silicon layer, and an insulation layer  23  between these. As shown in  FIG. 1 , the first layer portion  21  includes portions  21   a,    21   b,    21   c,    21   d,    21   e,  and  21   f.  The portions  21   a  through  21   f  are separated from each other via gaps. The inner frame  20  as described above constitutes a movable part of the sensing device Y, together with the land  10 . 
         [0047]    As shown in  FIG. 3  and  FIG. 4  for example, the outer frame  30  has a laminate structure provided by a first layer portion  31  formed from the first silicon layer, a second layer portion  32  formed from the second silicon layer, and an insulation layer  33  between these. As shown in  FIG. 1 , the first layer portion  31  includes portions  31   a,    31   b,    31   c,    31   d,    31   e,    31   f,    31   g  and  31   h.  The portions  31   a  through  31   h  are separated from each other via gaps, and constitute external connection terminals in the sensing device Y. The outer frame  30  as described above constitutes a stationary part of the sensing device Y. 
         [0048]    The pair of connecting parts  40  which connect the land  10  and the inner frame  20  are formed from the first silicon layer. Each connecting part  40  is provided by two torsion bars  41 . As shown in  FIG. 1 , each of the torsion bars  41  in one of the pair of connecting parts  40  is connected with the first layer portion  11  of the land  10  as well as with the portion  21   a  of the inner frame  20 , thus providing electrical connection between the first layer portion  11  and the portion  21   a.  Likewise, each of the torsion bars  41  in the other of the pair of connecting parts  40  is connected with the first layer portion  11  of the land  10  as well as with the portion  21   d  of the inner frame  20 , thus providing electrical connection between the first layer portion  11  and the portion  21   d.  Such a pair of connecting parts  40  as described define an axis Al for swinging operation of the land  10 . Each connecting part  40  which includes two torsion bars  41  each extending from the inner frame  20  to the land  10  with a gradually increasing gap between the two is suitable for reducing unnecessary displacement component in the swinging operation of the land  10 . 
         [0049]    The pair of connecting parts  50  which connect the inner frame  20  and the outer frame  30  are formed from the first silicon layer. Each connecting part  50  is provided by three torsion bars  51 ,  52 ,  53 . As shown in  FIG. 1 , in one of the pair of connecting parts  50 , the torsion bar  51  is connected with the portion  21   a  of the inner frame  20  as well as the portion  31   a  of the outer frame  30 , thus providing electrical connection between the portion  21   a  and the portion  31   a,  whereas the torsion bar  52  is connected with the portion  21   b  of the inner frame  20  as well as the portion  31   b  of the outer frame  30 , thus providing electrical connection between the portion  21   b  and the portion  31   b.  Likewise, the torsion bar  53  is connected with the portion  21   c  of the inner frame  20  as well as the portion  31   c  of the outer frame  30 , thus providing electrical connection between the portion  21   c  and the portion  31   c.  In the other of the connecting parts  50 , the torsion bar  51  is connected with the portion  21   d  of the inner frame  20  as well as the portion  31   d  of the outer frame  30 , thus providing electrical connection between the portion  21   d  and the portion  31   d,  whereas the torsion bar  52  is connected with the portion  21   e  of the inner frame  20  as well as the portion  31   e  of the outer frame  30 , thus providing electrical connection between the portion  21   e  and the portion  31   e.  Likewise, the torsion bar  53  is connected with the portion  21   f  of the inner frame  20  as well as the portion  31   f  of the outer frame  30 , thus providing electrical connection between the portion  21   f  and the portion  31   f.  Such a pair of connecting parts  50  as described define an axis A 2  for swinging operation of the inner frame  20 . Each connecting part  50  which includes two torsion bars  51 ,  53  each extending from the outer frame  30  to the inner frame  20  with a gradually increasing gap between the two is suitable for reducing unnecessary displacement component in the swinging operation of the inner frame  20 . 
         [0050]    The comb-teeth electrode  61  is formed from the first silicon layer, and is provided by a plurality of electrode teeth  61   a  extending from the first layer portion  11  of the land  10 . As shown in  FIG. 1  and  FIG. 4  for example, the electrode teeth  61   a  are parallel to each other. 
         [0051]    The comb-teeth electrode  62  is formed from the first silicon layer, and is provided by a plurality of electrode teeth  62   a  extending from the first layer portion  11  of the land  10  away from the electrode teeth  61   a  of the comb-teeth electrodes  61 . The electrode teeth  62   a  are parallel to each other. 
         [0052]    The comb-teeth electrode  63  is formed from the first silicon layer, opposed to the comb-teeth electrode  61 , and provided by a plurality of electrode teeth  63   a  which extends from the portion  21   b  of the first layer portion  21  in the inner frame  20 . As shown in  FIG. 1  and  FIG. 4 , the electrode teeth  63   a  are parallel to each other, as well as to the electrode teeth  61   a  of the comb-teeth electrode  61 . The comb-teeth electrode  63  and the comb-teeth electrode  61  as described above constitute a detection-electrode pair in the sensing device Y. 
         [0053]    The comb-teeth electrode  64  is formed from the first silicon layer, opposed to the comb-teeth electrode  62 , and provided by a plurality of electrode teeth  64   a  which extends from the portion  21   e  of the first layer portion  21  in the inner frame  20 . The electrode teeth  64   a  are parallel to each other, as well as to the electrode teeth  62   a  of the comb-teeth electrode  62 . The comb-teeth electrode  64  and the comb-teeth electrode  61  as described above constitute a detection-electrode pair in the sensing device Y. 
         [0054]    The comb-teeth electrode  71  is formed from the first silicon layer, and provided by a plurality of electrode teeth  71   a  which extends from the portion  21   c  of the first layer portion  21  in the inner frame  20 . As shown in  FIG. 1  and  FIG. 6  for example, the electrode teeth  71   a  are parallel to each other. 
         [0055]    The comb-teeth electrode  72  is formed from the first silicon layer, and provided by a plurality of electrode teeth  72   a  which extends from the portion  21   f  of the first layer portion  21  in the inner frame  20 . The electrode teeth  72   a  are parallel to each other. 
         [0056]    The comb-teeth electrode  73  is formed from the first silicon layer, opposed to the comb-teeth electrodes  71 , and provided by a plurality of electrode teeth  73   a  which extends from the portion  31   g  of the first layer portion  31  in the outer frame  30 . As shown in  FIG. 1  and  FIG. 6  for example, the electrode teeth  73   a  are parallel to each other, as well as to the electrode teeth  71   a  of the comb-teeth electrode  71 . The comb-teeth electrode  73  and the comb-teeth electrodes  71  as described above constitute a driver-electrode pair in the sensing device Y. 
         [0057]    The comb-teeth electrode  74  is formed from the first silicon layer, opposed to the comb-teeth electrodes  72 , and provided by a plurality of electrode teeth  74   a  which extends from the portion  31   h  of the first layer portion  31  in the outer frame  30 . The electrode teeth  74   a  are parallel to each other, as well as to the electrode teeth  72   a  of the comb-teeth electrode  72 . The comb-teeth electrode  74  and the comb-teeth electrodes  72  as described above constitute a driver-electrode pair in the sensing device Y. 
         [0058]    The packaging member  81  is bonded to the first layer portion  31  side of the outer frame  30  in the sensing device Y, and has a recess  81   a  correspondingly to the movable part of the sensing device Y. As shown in  FIG. 3 ,  FIG. 7 , and  FIG. 8  for example, the packaging member  81  is formed in itself with electrically conductive plugs P 1  through P 8 . As shown in  FIG. 7 , the conductor plugs P 1  through P 3  are in contact with the portions  31   a,    31   b,    31   c  of the first layer portion  31  in the outer frame  30  respectively, while being exposed to the outside. As shown in  FIG. 8 , the conductor plugs P 4  through P 6  are in contact with the portions  31   d,    31   e,    31   f  of the first layer portion  31  in the outer frame  30  respectively, while being exposed to the outside. As shown in  FIG. 3 , the conductor plugs P 7 , P 8  are in contact with the portions  31   g,    31   h  of the first layer portion  31  in the outer frame  30  respectively, while being exposed to the outside. On the other hand, packaging member  82  is bonded to the second layer portion  32  side of the outer frame  30  in the sensing device Y, and has a recess  82   a  at a location correspondingly to the movable part of the sensing device Y. The sensing device Y is sealed by the packaging members  81 ,  82  as described above. 
         [0059]    In the packaged device X, a sufficient amount of gap is provided between the movable part and the packaging members  81 ,  82  so that the movable part (the land  10  and the inner frame  20 ) will not make contact with the packaging members  81 ,  82  during its swinging operation when the device is in operation. 
         [0060]    When the sensing device Y is in operation, the movable part (the land  10  and the inner frame  20 ) makes a swinging operation around the axis A 2  at a predetermined frequency or period. The swinging operation is accomplished by repeating a cycle of voltage application to between the comb-teeth electrodes  71 ,  73  and voltage application to between the comb-teeth electrode  72 ,  74 . The voltage application to the comb-teeth electrodes  71  can be achieved through the conductor plug P 3 , the portion  31   c  in the outer frame  30 , the torsion bar  53  of one of the connecting parts  50  and the portion  21   c  in the inner frame  20 . The voltage application to the comb-teeth electrodes  72  can be achieved through the conductor plug P 6 , the portion  31   f  in the outer frame  30 , the torsion bar  53  of the other of the connecting parts  50  and the portion  21   f  in the inner frame  20 . The voltage application to the comb-teeth electrode  73  can be achieved through the conductor plug P 7  and the portion  31   g  in the outer frame  30 . The voltage application to the comb-teeth electrode  74  can be achieved through the conductor plug P 8  and the portion  31   h  in the outer frame  30 . In the present embodiment, the swinging operation of the movable part can be accomplished by grounding the comb-teeth electrodes  71 ,  72 , and then repeating a cycle of sequential application of a predetermined electric potential to the comb-teeth electrode  73  and a predetermined electric potential to the comb-teeth electrode  74 . 
         [0061]    Now, assume that a certain amount of angular velocity or acceleration acts on the sensing device Y or the land  10  while the movable part is being swung as described above. This causes the land  10  to rotate about the axis A 1  to a predetermined extent, thereby making a displacement to change the electrostatic capacity between the comb-teeth electrodes  61 ,  63  and as well as between the comb-teeth electrodes  62 ,  64 . Based on the electrostatic change between the comb-teeth electrodes  61 ,  63 , and the electrostatic change between the comb-teeth electrodes  62 ,  64 , it is possible to detect the amount of rotational displacement of the land  10 . Based on the detection result, it is possible to calculate the amount of angular velocity or acceleration acting on the sensing device Y or the land  10 . 
         [0062]      FIG. 9  through  FIG. 11  show a method of manufacturing the packaged device X. The method is an example of how the packaged device X can be manufactured through micromachining technology.  FIG. 9  and  FIG. 10  show a series of views of a conceptual composite section, illustrating various portions included in a single device formation block.  FIG. 11  shows a partial section including a plurality of device formation blocks. For the sensing device Y, a formation process will be illustrated mainly through formation of those parts shown in  FIG. 10(   c ) for example, i.e. a land L, an inner frame F 1 , an outer frame F 2  and connecting parts C 1 , C 2 . The land L represents part of the land  10 . The inner frame F 1  represents part of the inner frame  20 . The outer frame F 2  represents part of the outer frame  30 . The connecting part C 1  represents the connecting part  40  as a cross section of the torsion bar  41 . The connecting part C 2  represents the connecting part  50  as a longitudinal section of the torsion bar  51 ,  52  or  53 . 
         [0063]    In the manufacture of the packaged device X, first, a device wafer  100  as shown in  FIG. 9(   a ) is prepared. The device wafer  100  is an SOI (Silicon On Insulator) wafer having a laminate structure provided by silicon layers  101 ,  102 , and an insulation layer  103  between the silicon layers  101 ,  102 , and includes a plurality of sensing device formation blocks. The silicon layer  101  is made of a silicon material doped with impurity to render electrical conductivity, and has a surface  101   a . The silicon layer  102  is made of a silicon material doped with impurity to render electrical conductivity, and has a surface  102   a.  The impurity may be a p-type impurity such as B, or an n-type impurity such as P and Sb. The insulation layer  103  is made of silicon oxide for example. The silicon layer  101  has a thickness of e.g. 10 through 100 μm, whereas the silicon layer  102  has a thickness of e.g. 100 through 500 μm, and the insulation layer  103  has a thickness of e.g. 1 through 2 μm. The silicon layers  101 ,  102  and the insulation layer  103  represent the first and the second layers and the intermediate layer respectively, according to the present invention. 
         [0064]    Next, as shown in  FIG. 9(   b ), micromachining is performed to the silicon layer  101 , to form part of the land L, part of the inner frame F 1 , part of the outer frame F 2  and connecting parts C 1 , C 2 . Specifically, a resist pattern (not illustrated) is formed on the silicon layer  101 , and thereafter the silicon layer  101  is subjected to dry etching by means of DRIE (Deep Reactive Ion Etching), using the resist pattern as a mask. In the DRIE operation, good anisotropic etching can be performed by using a Bosch process in which etching and side-wall protection are alternated with each other. The DRIE operation in this step and other steps to be described later may be performed by means of the Bosch process. 
         [0065]    Next, as shown in  FIG. 9(   c ), the silicon layer  102  is micromachined. Specifically, a predetermined mask pattern (not illustrated) is formed on the silicon layer  102 , and thereafter dry etching by means of DRIE is performed to the silicon layer  102 , using the mask pattern as a mask until a midway point of the thickness in the silicon layer  102  is reached. The mask pattern used in this step is provided by e.g. an oxide film pattern and a resist pattern thereon. 
         [0066]    Next, as shown in  FIG. 10(   a ), a packaging wafer  201  is bonded to the silicon layer  101  side of the device wafer  100  (first bonding step). The packaging wafer  201  is obtained from a predetermined silicon wafer through micromachining. The micromachined packaging wafer  201  has a plurality of recesses  81   a  each corresponding to a movable part of the sensing device Y, and a plurality of conductor plugs Px in each of the device formation blocks. The conductor plugs Px represent the conductor plugs P 1  through P 8 . The packaging wafer  201  is formed, in advance, with an insulation film (not illustrated) on a surface which is to face the device wafer  100  (excluding the conductor plug surfaces). The insulation film such as the above can be formed by thermal oxidation method for example. The present bonding step is performed by anodic bonding method, direct bonding method, or room-temperature bonding method. The insulation film which is formed in advance on the surface of packaging wafer  201  enables to prevent undesirable electric connection between different parts of the device wafer  100  via the packaging wafer  201 . 
         [0067]    The packaging wafer  201  can be made as follows for example: Specifically, first, dry etching (anisotropic dry etching) by means of DRIE is performed to a silicon wafer, using a predetermined mask, to form recesses  81   a.  Next, through-holes which penetrate the silicon wafer are formed through dry etching by means of DRIE performed to the silicon wafer, using a predetermined mask. Then, the through-holes are filled with electrically conductive material to form the conductor plugs Px. 
         [0068]    Continuing with the manufacture of the packaged device X, next, as shown in  FIG. 10(   b ), micromachining is performed to the silicon layer  102 , to form part of the land L, part of the inner frame F 1  and part of the outer frame F 2 . Specifically, the silicon layer  102  is subjected to dry etching by means of DRIE, using a predetermined mask pattern. 
         [0069]    Next, exposed portions of the insulation layer  103  are removed by predetermined etching, and thereafter, as shown in  FIG. 10(   c ), a packaging wafer  202  is bonded to the silicon layer  102  side of the device wafer  100  (second bonding step). The packaging wafer  202  is obtained from a predetermined silicon wafer through micromachining. The micromachined packaging wafer  202  has a plurality of recesses  82   a  each corresponding to a movable part of the sensing device Y. The packaging wafer  202  is formed, in advance, with an insulation film (not illustrated) on its surface which is to face the device wafer  100 . The insulation film such as the above can be formed by thermal oxidation method for example. The present bonding step is performed by anodic bonding method, direct bonding method, or room-temperature bonding method. The insulation film which is formed in advance on the surface of packaging wafer  202  enables to prevent undesirable electronic connection between different parts of the device wafer  100  via the packaging wafer  202 . 
         [0070]    The packaging wafer  202  can be made as follows for example: Specifically, dry etching (anisotropic dry etching) by means of DRIE is performed to a silicon wafer, using a predetermined mask, to form recesses  82   a.  Additionally, if the sealing of the packaged device X need not be air-tight, through-holes may be formed so that inside of the recess  82   a  in the packaging wafer  202  will communicate with the outside. 
         [0071]    Next, as shown in  FIG. 11(   a ) and  FIG. 11(   b ), the laminate structure made of the device wafer  100  and the packaging wafers  201 ,  202   a  is cut into pieces (dicing step). Through these steps, it is possible to manufacture the packaged device X according to the present invention. 
         [0072]    In the first bonding step described with reference to  FIG. 10(   a ), the device wafer  100  and the packaging wafer  201  are bonded together in such a way that each of the recesses  81   a  faces the movable part (the land  10  and the inner frame  20 ) in one of the sensing devices Y to be formed in the device wafer  100 . In the second bonding step described with reference to  FIG. 10(   c ), the device wafer  100  and the packaging wafer  202  are bonded together in such a way that each of the recesses  82   a  faces the movable part (the land  10  and the inner frame  20 ) in one of the sensing devices Y which have already been formed in the device wafer  100 . Through the first and the second bonding steps, packaging at a wafer level can be achieved, and thereafter, the dicing step described with reference to  FIG. 11  is performed to obtain, individual pieces (the packaged device X) in which one of the sensing devices Y is packaged. 
         [0073]    According to the present method, the packaging wafer  201 , which is formed with recesses  81   a  each providing operation space for the movable part (the land  10  and the inner frame  20 ) in corresponding one of the sensing devices Y is bonded to the device wafer  100  in the first bonding step, and further, the packaging wafer  202 , which is formed with recesses  82   a  each providing operation space for the movable part (the land  10  and the inner frame  20 ) in corresponding one of the sensing device Y is bonded to the device wafer  100  in the second bonding step. Therefore, according to the present method, there is no need for etching the movable part thereby making the movable part thinner than the stationary part (the outer frame  30 ) in order to provide a sufficient gap between the movable part and the packaging members  81 ,  82  to prevent the movable part from contacting the packaging members  81 ,  82  when it swings during operation of the device. If the movable part is made thinner than the stationary part (the outer frame  30 ) by etching, relatively large nonuniformity is unavoidable in the thickness of the movable parts in a plurality of micro movable devices as has been described earlier in relation with a conventional method. The nonuniformity causes inertial nonuniformity in the movable parts, and the inertial nonuniformity can cause undesirable operational nonuniformity of the movable parts. The present method, which requires no thinning of the movable part, is suitable for reducing inertial nonuniformity in the movable part. The present method which is suitable for reducing inertial nonuniformity in the movable part that swings when the device is in operation, is suitable for reducing operational nonuniformity of the movable part. Also, inertial nonuniformity of the movable part as a part of the sensing device is a cause for detection characteristic nonuniformity which affects detection of movement or the amount of displacement of the movable part. The present method which is suitable for reducing inertial nonuniformity in the movable part is suitable for reducing operational nonuniformity of the movable part, and in addition, for reducing detection characteristic nonuniformity which relates to detection of movement or the amount of displacement of the movable part. 
         [0074]    Further, the present method does not require any step of thinning the movable part (the land  10  and the inner frame  20 ) which is formed within a device wafer  100  that has a uniform thickness originally. Thus, the present method is suitable for manufacturing sensing devices Y at a high yield rate. 
         [0075]    In addition, the present method enables packaging at a wafer level, and therefore is suitable to reduce operation performance deterioration of the movable part caused by dirt attached to the micro movable device or sensing device Y, or by damage incurred thereto. 
         [0076]      FIG. 12(   a ) shows a packaging member  83  as a variation of the packaging member  81 . The packaging member  83  includes a recess  83   a.  The recess  83   a  is formed in the silicon wafer by means of anisotropic wet etching performed with the use of a predetermined mask. The etchant for this wet etching may be KOH or TMAH. In the first bonding step which was described with reference to  FIG. 10(   a ), a packaging wafer formed with a plurality of packaging members  83  may be used in place of the packaging wafer  201  formed with a plurality of packaging members  83 , for bonding onto the silicon layer  101  side of the device wafer  100 . 
         [0077]      FIG. 12(   b ) shows a packaging member  84  as a variation of the packaging member  81 . The packaging member  84  includes a recess  84   a.  The recess  84   a  is formed in the silicon wafer by means of isotropic wet etching performed with the use of a predetermined mask. The etchant for this wet etching may be a solution mix containing HF, HNO 3 , and CH 3 COOH. In the first bonding step which was described with reference to  FIG. 10(   a ), a packaging wafer formed with a plurality of packaging members  84  may be used in place of the packaging wafer  201 , for bonding onto the silicon layer  101  side of the device wafer  100 . 
         [0078]      FIG. 13(   a ) shows a packaging member  85  as a variation of the packaging member  82 . The packaging member  85  includes a recess  85   a.  The recess  85   a  is formed in the silicon wafer by means of anisotropic wet etching performed with the use of a predetermined mask. The etchant for this wet etching may be KOH or TMAH. If the sealing of the packaged device X need not be air-tight, through-holes may be formed so that inside of the recess  85   a  will communicate with the outside. In the second bonding step which was described with reference to  FIG. 10(   c ), a packaging wafer formed with a plurality of packaging members  85  may be used in place of the packaging wafer  202  which is formed with a plurality of packaging members  82 , for bonding onto the silicon layer  102  side of the device wafer  100 . 
         [0079]      FIG. 13(   b ) shows a packaging member  86  as a variation of the packaging member  82 . The packaging member  86  includes a recess  86   a.  The recess  86   a  is formed in the silicon wafer by means of isotropic wet etching performed with the use of a predetermined mask. The etchant for this wet etching may be a solution mix containing HF, HNO 3 , and CH 3 COOH. If the sealing of the packaged device X need not be air-tight, through-holes may be formed so that inside of the recess  86   a  will communicate with the outside. In the second bonding step which was described with reference to  FIG. 10(   c ), a packaging wafer formed with a plurality of packaging members  86  may be used in place of the packaging wafer  202 , for bonding onto the silicon layer  102  side of the device wafer  100 . 
         [0080]    The first bonding step in the above-described manufacturing method may be performed by eutectic bonding method. If eutectic bonding method is used in the first bonding step, a eutectic metal pattern  91  as shown in  FIG. 14  is formed in advance on the silicon layer  101  of the device wafer  100 . The eutectic metal pattern  91  is formed of Au for example. In addition, electrode pads  92  as shown in  FIG. 14  are formed in advance on the silicon layer  101  of the device wafer  100 . The electrode pads  92  are formed of Au for example and to be bonded to conductor plugs P 1  through P 8 . Then, in the first bonding step, the device wafer  100  and the packaging wafer  201  are pressed to fit together as shown in  FIG. 15 , while being heated at a predetermined temperature, thereby achieving a bond between the device wafer  100  and the packaging wafer  201  by eutectic between silicon and Au. 
         [0081]    In the first bonding step of the above-described manufacturing method, a packaging wafer  201  as shown in  FIG. 16(   a ), which has not yet formed with conductor plugs Px may be bonded to the silicon layer  101  side of the device wafer  100 . If such a step is used, the second bonding step is performed as shown in  FIG. 16(   b ), and then the conductor plugs Px are formed as shown in  FIG. 16(   c ) by filling the through-holes in the packaging wafer  201  with electrically conductive material. Thereafter, the dicing step is performed as has been described earlier with reference to  FIG. 11 . Manufacture of the packaged device X according to the present invention is also possible by such a method as described above.