Patent Publication Number: US-11643325-B2

Title: Micro-electromechanical system package having movable platform

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation application of U.S. application Ser. No. 17/091,062, filed on Nov. 6, 2020, which is a continuation application of U.S. application Ser. No. 16/783,627, filed on Feb. 6, 2020, which is a continuation application of U.S. application Ser. No. 16/448,612, filed on Jun. 21, 2019, which is a divisional application of U.S. application Ser. No. 15/891,975, filed on Feb. 8, 2018, the full disclosures of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Field of the Disclosure 
     This disclosure generally relates to a sensor package, more particularly, to an encapsulation with a movable sensor that arranges a sensor on a movable platform of a MEMS actuator and a manufacturing method thereof. 
     2. Description of the Related Art 
     The micro-electromechanical system (MEMS) is a micro-mechanical structure formed by etching a silicon wafer, and can be used as a MEMS actuator which converts electrical signals to mechanical motion for controlling tiny movement. 
     In the image acquiring device having an auto-focus (AF) function or optical image stabilization (OIS) function, the MEMS actuator can be used to implement the exact adjustment of the focus length and sampling position. 
     SUMMARY 
     The present disclosure provides an encapsulation having a movable sensor and a manufacturing method thereof that have a sensor chip arranged on the elastic structure which has functions of restoring position and transmitting electrical signals. 
     The present disclosure provides a MEMS package including a fixed frame, a moveable platform and multiple elastic restoring members. The moveable platform is configured to be moved with respect to the fixed frame along at least one direction and having a rectangular shape, wherein the moveable platform comprises a plurality of comb electrodes at two opposite edges of the rectangular shape of the moveable platform. The multiple elastic restoring members are formed between the fixed frame and another two opposite edges, different from the two opposite edges, of the rectangular shape of the moveable platform, and configured to restore a position of the moved moveable platform. 
     The present disclosure further provides a MEMS package including a fixed frame, a moveable platform and four elastic restoring members. The fixed frame has a rectangular inner edge. The moveable platform is configured to be moved with respect to the fixed frame along two directions. The four elastic restoring members are straightly connected between the fixed frame and the moveable platform, and configured to restore a position of the moved moveable platform, wherein one end of each of the four elastic restoring members is arranged at one of four corners of the rectangular inner edge of the fixed frame. 
     The present disclosure further provides a MEMS package including a fixed frame, a moveable platform and at least one elastic restoring member. The moveable platform is configured to be moved with respect to the fixed frame along at least one direction. Each elastic restoring member is formed as a straight line between the fixed frame and the moveable platform, and configured to restore a position of the moved moveable platform. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other objects, advantages, and novel features of the present disclosure will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
         FIG.  1    is a top view of a sensor package according to one embodiment of the present disclosure. 
         FIG.  2    is a top view of a sensor package according to another embodiment of the present disclosure. 
         FIG.  3    is a top view of a sensor package according to an alternative embodiment of the present disclosure. 
         FIG.  4    is a side view of a sensor package according to an alternative embodiment of the present disclosure. 
         FIGS.  5   a - 5   f    are schematic diagrams of the manufacturing of a sensor package according to a first embodiment of the present disclosure. 
         FIGS.  6   a - 6   h    are schematic diagrams of the manufacturing of a sensor package according to a second embodiment of the present disclosure. 
         FIG.  7    is a flow chart of a manufacturing method of a sensor package according to a first embodiment of the present disclosure. 
         FIG.  8    is a flow chart of a manufacturing method of a sensor package according to a second embodiment of the present disclosure. 
         FIG.  9    is a top view of a sensor package according to an alternative embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENT 
     It should be noted that, wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
     Referring to  FIG.  1   , it is a top view of a sensor package  10  according to one embodiment of the present disclosure. The sensor package  10  is, for example, an image sensor package. The sensor package  10  includes a micro-electromechanical system (MEMS) actuator used to change the one-dimensional or two-dimensional position of a carried optoelectronic component. The optoelectronic component is a component independent from the MEMS actuator, and is arranged on the MEMS actuator via elastic restoring members after the MEMS actuator is manufactured. The optoelectronic component transmits detected data via the elastic restoring members. 
     The MEMS actuator includes a fixed frame  11  and a moveable platform  13  that are micro-electromechanical structures formed by processing a silicon wafer (illustrated by an example below) using the photolithography or etching process. In the processed silicon wafer, the moveable platform  13  is separated from the fixed frame  11  (only connected by elastic restoring members as mentioned below) such that the moveable platform  13  can move with respect to the fixed frame  11 . 
     The fixed frame  11  has a plurality of first comb electrodes  111  (only a few being shown), and the moveable platform  13  has a plurality of second comb electrodes  131  (only a few being shown). As shown in  FIG.  1   , the first comb electrodes  111  are arranged at two opposite inner sides of the fixed frame  11 , and the second comb electrodes  131  are arranged at two opposite edges of the moveable platform  13 . The first comb electrodes  111  and the second comb electrodes  131  are used to generate electrostatic force to cause the moveable platform  13  to have movement along at least one direction with respect to the fixed frame  11 . As shown in  FIG.  1   , each of the first comb electrodes  111  is arranged between two second comb electrodes  131 , and each of the second comb electrodes  131  (in addition to the most outside second comb electrodes) is arranged between two first comb electrodes  111 . By applying voltages on the first comb electrodes  111  and the second comb electrodes  131 , attractive force or repulsive force is generated (depending on the voltage polarity being applied) to move the moveable platform  13 . 
     The elastic restoring members  15  are formed by a patterned conductive metal layer such as Aluminum, Nickel, Gold or a combination thereof. The elastic restoring members  15  are the structure additionally formed on a silicon wafer (e.g., using deposition technology), but not formed by etching the silicon wafer. The elastic restoring members  15  are connected between the fixed frame  11  and the moveable platform  13 , and used to restore the moved moveable platform  13  to an original position. 
     For example in  FIG.  1   , the moveable platform  13  is shown to have a rectangular shape, and the elastic restoring members  15  are formed between two opposite edges (shown as left and right edges) of the rectangular shape and the fixed frame  11 . For example, one end of the elastic restoring members  15  is arranged on a surface of the fixed frame  11 , and the other end thereof is arranged on a surface of the moveable platform  13 . When the first comb electrodes  111  and the second comb electrodes  131  form electrostatic force along an up-down direction, the moveable platform  13  is moved along the up direction or down direction. The elastic restoring members  15  generate restoring force opposite to the electrostatic force. 
     The sensor chip  17  is, for example, a CMOS image sensor chip or CCD image sensor chip, and is disposed on the moveable platform  13 . The sensor chip  17  transmits detected data, e.g., image data or data detected by other optoelectronic components, via the elastic restoring members  15 . For the electrical connection, the sensor chip  17  includes solder balls or contact pads, e.g., multiple solder balls or contact pads under a bottom surface of the sensor chip  17  as electrical connection points. The sensor chip  17  is electrically connected to the elastic restoring members  15  via the solder balls or contact pads. 
       FIGS.  2  and  3    are top views of a sensor package according to other embodiments of the present disclosure. The sensor packages  10 ′ and  10 ″ also include a fixed frame  11 , a moveable platform  13 , elastic restoring members  15  and a sensor chip  17 . The difference from  FIG.  1    is that the fixed frame  11  and the moveable platform  13  in  FIGS.  2  and  3    are connected by elastic restoring members  15  arranged in a different way to allow the moveable platform  13  to move in the one-dimensional direction or two-dimensional directions with respect to the fixed frame  11 . 
     For example in  FIG.  2   , more elastic restoring members  15  are arranged at left and right edges of the rectangular moveable platform  13  to generate larger restoring force. It is appreciated that the amount of restoring force is determined not only according to a number of the elastic restoring members  15 , but also according to a size and thickness of the elastic restoring members  15 . The size, thickness and/or number of the elastic restoring members  15  are arranged during manufacturing according to the electrostatic force generated by the first comb electrodes  111  and the second comb electrodes  131 . The amount of electrostatic force is determined, for example, according to a number, size, pitch and applied voltages of the first comb electrodes  111  and the second comb electrodes  131 . 
     For example in  FIG.  3   , the elastic restoring members  15  are arranged between four corners of the moveable platform  13  and the fixed frame  11  to generate restoring force along two directions (e.g., up-down direction and left-right direction). Meanwhile, to generate electrostatic force in two directions, the first comb electrodes  111  and the second comb electrodes  131  are further arranged at two opposite sides along the left-right direction. 
     In the present disclosure, a number and position of the comb electrode sets  111  and  131  are not particularly limited but determined according to actual applications as long as the restoring force generated by the elastic restoring members  15  can balance the electrostatic force generated by the comb electrode sets  111  and  131 . 
     It is appreciated that positions of the elastic restoring members  15  are arranged corresponding to electrical contacts (e.g., solder balls or contact pads) of the sensor chip  17  to allow the sensor chip  17  to be directly disposed on the moveable platform  13  and electrically combined to the elastic restoring members  15  via the electrical contacts. In addition, as the elastic restoring members  15  are further used to transmit detected data as well as the fixed frame  11  and the moveable platform  13  are applied with voltages to generate electrostatic force, an electrical insulation layer  16  is further formed between the moveable platform  13  and the elastic restoring members  15  and between the fixed frame  11  and the elastic restoring members  15 , as shown in  FIG.  4   , to prevent from degrading the signal quality. 
       FIG.  4    is a side view of a sensor package according to another embodiment of the present disclosure, wherein the sensor chip  17  transmits electrical signals (e.g., control signals and/or detected data of the sensor chip  17 ) not only via the elastic restoring members  15  but also via at least one bonding wire  19  connected between the sensor chip  17  and the fixed frame  11 . For example, the fixed frame  11  further has at least one electrical contact pad thereon, and at least one bonding wire is connected between the solder balls  18  and the at least one electrical contact pad on the fixed frame  11  using wire bonding technology. In  FIG.  4   , the fixed frame  11  includes a first silicon layer  111 , a second silicon layer  13  and an oxide insulating layer  12  between the first silicon layer  111  and the second silicon layer  13 . 
     Referring to  FIGS.  5   a - 5   f    and  7 , a manufacturing method of a sensor package according to a first embodiment of the present disclosure is illustrated below. The manufacturing method includes the steps of: providing a silicon on insulator (SOI) wafer having a first silicon layer, an oxide insulating layer and a second silicon layer (Step S 71 ); forming a patterned metal layer on the first silicon layer (Step S 72 ); etching the first silicon layer to form a platform region, a fixed frame and a groove between the platform region and the fixed frame (Step S 73 ); etching the second silicon layer to form an exposed region corresponding to the platform region and the groove (Step S 74 ); etching the oxide insulating layer within the exposed region to release the platform region to form a movable platform (Step S 75 ); and arranging a sensor chip on the patterned metal layer (Step S 76 ). 
     Step S 71 : The SOI wafer has a first silicon layer  51 , a second silicon layer  53  and an oxide insulating layer  52  sandwiched therebetween, as shown in  FIG.  5   a   . The SOI wafer is selected from commercial available SOI wafers or a self-manufactured SOI wafer without particular limitations. For example, the first silicon layer  51  is a silicon wafer used as a device layer and having a thickness of about 10-20 micrometers, and the second silicon layer  53  is a silicon wafer used as a handle layer and having a thickness of about 300-400 micrometers. The oxide insulating layer  52  is used as an etch stop layer. 
     Step S 72 : Next, a patterned metal layer  55  having a predetermined pattern is formed on the first silicon layer  51 , as shown in  FIG.  5   b   , used as elastic restoring members for the MEMS actuator. The predetermined pattern is previously arranged according to positions of the solder balls  58  or contact pads of the sensor chip  57  to be disposed later (e.g., referring to  FIG.  5   f   ). The patterned metal layer  55  is formed, for example, by photolithography. 
     In addition, to improve signal quality, before the metal layer is deposited, an electrical insulation layer  16  (as shown in  FIG.  4   ) is formed on the first silicon layer  51  firstly to electrically insulate the patterned metal layer  55  from the first silicon layer  51 . 
     Step S 73 : Next, the first silicon layer  51  is etched by the vapor-phase etching or wet etching to form a platform region  513 , a fixed frame  411  and a groove  515  between the platform region  513  and the fixed frame  511  as shown in  FIG.  5   c   . The arrangement after the etching is selected from one of  FIGS.  1 - 3    according to actual applications. With the existence of the oxide insulating layer  52 , the etching  51  on the first silicon layer  51  stops while reaching the oxide insulating layer  52 . After the etching of this step, the patterned metal layer  55  crosses the groove  515  and connects between the platform region  513  and the fixed frame  511  to be used as the elastic restoring member. The platform region  513  connects to the fixed frame  511  through the oxide insulating layer  511 . 
     Step S 74 : To release the platform region  513  in the following steps, the second silicon layer  53  is etched (e.g., using dry/wet etching) to form an exposed region  531  corresponding to the platform region  513  and the groove  515  to expose a part of the oxide insulating layer  52 . The etching also stops while reaching the oxide insulating layer  52 , as shown in  FIG.  5     d.    
     It is appreciated that the protection layer is formed during the process of etching the first silicon layer  51  and the second silicon layer  53  in order to form a predetermined structure in the first silicon layer  51  and the second silicon layer  53 . The first silicon layer  51  and the second silicon layer  53  are etched using the etching technology for manufacturing the MEMS, and thus details thereof are not described herein. 
     In addition, the Step S 73  is not limited to be performed before the Step S 74 . It is possible to etch the second silicon layer  53  at first, and then the first silicon layer  51  is etched as long as the exposed oxide insulating layer  52  corresponds to the platform region  513  and the groove  515 . 
     Step S 75 : Next, the oxide insulating layer  52  within the exposed region  531  is etched to release the platform region  513  to form a moveable platform, as shown in  FIG.  5   e   . Due to different etching selection ratio, the etching performed on the oxide insulating layer  52  does not etch the first silicon layer  51  and the second silicon layer  53 , or vice versa. After this step is finished, the platform region  513  connects to the fixed frame  511  only via the patterned metal layer  55 , and the other part of the platform region  513  is totally separated from the fixed frame  511 . 
     Step S 76 : Finally, a predetermined sensor chip  57  is disposed on the patterned metal layer  55 . The sensor chip  57 , for example, has solder balls  58  previously arranged on a bottom surface thereof. After the solder balls  58  are combined to the patterned metal layer  55  using a high temperature technology, the sensor package of the present disclosure is accomplished, as shown in  FIG.  5   f   . The high temperature being used is determined according to the material of solder balls  58  and the temperature tolerance of the sensor chip  57 . 
     In addition, if bonding wires are required to be arranged in addition to the patterned metal layer  55 , the wire bonding is performed after the Step S 76  or before the moveable platform  513  is released in the Step S 75  to form at least one bonding wire between the sensor chip  57  and the fixed frame  511 , as shown in  FIG.  4   . For example, at least one electrical contact pad is further formed on the fixed frame  511  and the platform region  513  to bond with the bonding wire. Accordingly, a part of solder balls  58  of the sensor chip  57  are arranged on the patterned metal layer  55 , and the other part of solder balls  58  are arranged on the electrical contact pad of the platform region  513  to electrically connect with the bonding wire. 
     In the sensor package manufactured by  FIGS.  5   a - 5   f   , the fixed frame  11  includes a first silicon layer  511 , a second silicon layer  53  and an oxide insulating layer  52  between the first silicon layer  511  and the second silicon layer  53 . 
     Referring to  FIGS.  6   a - 6   h    and  8 , a manufacturing method of a sensor package according to a second embodiment of the present disclosure is illustrated below. The manufacturing method includes the steps of: providing a first silicon layer having a first surface and a second surface (Step S 81 ); forming a patterned metal layer on the first surface of the first silicon layer (Step S 82 ); bonding a second silicon layer to the first surface of the first silicon layer (Step S 83 ); thinning the first silicon layer (Step S 84 ); etching the thinned first silicon layer to form a movable platform and a fixed frame (Step S 85 ); bonding a third silicon layer to the thinned surface of the first silicon layer (Step S 86 ); removing the second silicon layer to expose the moveable platform and the patterned metal layer (Step S 87 ); and arranging a sensor chip on the patterned metal layer (Step S 88 ). 
     Step S 81 : Instead of using an SOI wafer, a first silicon layer  61  is directly used to start the manufacturing. The first silicon layer  61  has a first surface  61 S 1  and a second surface  61 S 2  opposite to each other. 
     Step S 82 : A metal layer is deposited on the first surface  61 S 1  of the first silicon layer  61 , as shown in  FIG.  6   a   . The metal layer is formed by conductive metal such as Aluminum, Nickle, Gold or a combination thereof. Then, the patterned metal layer  65  is formed using photolithography, as shown in  FIG.  6   b   . As mentioned above, a pattern of the patterned metal layer  65  is determined previously according to the arrangement of the solder balls or contact pads of the sensor chip being used. 
     In addition, to allow the patterned metal layer  65  to have good insulation from the first silicon layer  61 , an electrical insulation layer  16 , as shown in  FIG.  4   , is firstly formed on the first surface  61 S 1  of the first silicon layer  61  before the patterned metal layer  65  is formed to electrically isolate the first silicon layer  61  and the patterned metal layer  65 . 
     Step S 83 : Next, a second silicon layer  63  having an accommodation space is used to bond with the first surface  61 S 1  (with the part whose metal layer and electrical insulation layer  16 , if there is, being removed) of the first silicon layer  61 , and the patterned metal layer  65  is accommodated in the accommodation space. For example,  FIG.  6   c    shows that the second silicon layer  63  is bonded to the first surface  61 S 1  of the first silicon layer  61  only with the fringe region thereof, but not limited thereto. The bonded region is determined according to a position of the moveable platform being arranged. For example, the second silicon layer  63  has walls extending upward from edges thereof such that the central area is lower than the fringe area. The first silicon layer  61  and the second silicon layer  63  are bonded using conventional wafer bonding technology without particular limitations. 
     Step S 84 : Next, the first silicon layer  61  is thinned to form a thinned first silicon layer  61 ′ having a thickness of about 10-20 micrometers, as shown in  FIG.  6   d   . The thinning is performed by grinding or etching the second surface  61 S 2 . In some embodiments, if the first silicon layer  61  is thin enough, the thinning step is omitted. 
     Step S 85 : Next, the thinned first silicon layer  61 ′ is etched to form a moveable platform  613  and a fixed frame  611 , as shown in  FIG.  6   e   . The arrangement of the moveable platform  613  and the fixed frame  611  by etching the first silicon layer  61  is selected from one of  FIGS.  1 - 3   . 
     After this etching step is accomplished, the patterned metal layer  65  is connected between the moveable platform  613  and the fixed frame  611  to be used as elastic restoring members. 
     Step S 86 : Next, a third silicon layer  64  having an accommodation space is bonded to the thinned surface  61 S 2 ′ of the first silicon layer  61 , wherein the accommodation space is to allow the third silicon layer  64  not to contact with the moveable platform  613  to maintain the movement freedom of the moveable platform  613 . Accordingly, as shown in  FIG.  6   f    the third silicon layer  64  is bonded to the thinned surface  61 S 2 ′ with the fringe region thereof (e.g., the region corresponding to the fixed frame  611 ). For example, the third silicon layer  64  has walls extending upward from edges thereof such that the central area is lower than the fringe area. The bonding between the thinned surface  61 S 2 ′ of the first silicon layer  61  and the third silicon layer  64  is performed using conventional wafer bonding technology. 
     Step S 87 : Next, the second silicon layer  63  is removed to expose the moveable platform  613  and the patterned metal layer  65 , as shown in  FIG.  6   g   . For example, the second silicon layer  63  is removed by grinding or etching process to completely remove the second silicon layer  63  or leave a part of second silicon layer  63 ′ behind which is bonded with the fixed frame  611  according to the MEMS structure and etching process. 
     Step S 88 : Finally, the sensor chip  67  to be carried is arranged on the patterned metal layer  65  to accomplish the sensor package of the present disclosure. The sensor chip  67 , for example, has solder balls  68  or contact pads in the bottom surface thereof, and the solder balls  68  are combined to the patterned metal surface  65  using high temperature process to have good electrical connection. 
     In addition, if other signal transmission path in addition to the patterned metal layer  65  is required, at least one bonding wire  19 , as shown in  FIG.  4   , is formed between the sensor chip  67  and the fixed frame  611  using wire bonding technology. Similarly, before forming the bonding wire  19 , contact pads are firstly formed on the moveable platform  613  and the fixed frame  61  to electrically combine with the bonding wire  19 . 
     In the sensor package manufactured by  FIGS.  6   a - 6   h   , the fixed frame  11  includes silicon layers bonded to each other (e.g., first silicon layer  61 , second silicon layer  63  and third silicon layer  64 ) but has no oxide insulating layer therebetween. The second silicon layer  63  and the third silicon layer  64  are respectively disposed at two different sides of the first silicon layer  61 . 
     The MEMS actuator of the present disclosure is electrically connected to a circuit board (not shown) by solder so as to electrically connect to other components of the system (e.g., a portable electronic device) for transmitting signals via traces on the circuit board. 
     It should be mentioned that although the above embodiments are described with one- or two-dimensional linear movement as an example, the present disclosure is not limited thereto. In other embodiments, the MEMS actuator triggers the movement or rotation in multiple dimensions by other arrangements of the elastic restoring members. 
     It should be mentioned that although the above embodiments are described with the fixed frame  11  surrounding the moveable platform  13  continuously, the present disclosure is not limited thereto. In other embodiments, the fixed frame  11  is formed corresponding to only two or three edges of the moveable platform  13 , or formed in a discontinuous way surrounding the moveable platform  13  without particular limitations as long as the moveable platform  13  is moveable with respect to the fixed frame  11 . 
     It should be mentioned that although the above embodiments are described with a single sensor package, the present disclosure is not limited thereto. In the mass production, a plurality of sensor packages of the present disclosure are manufactured on a wafer simultaneously, and a plurality of single sensor packages is divided by wafer dicing. The dicing technology is known to the art and thus details thereof are not described herein. 
     It should be mentioned that although the above embodiments are described with the moveable platform being located in a middle position of the MEMS actuator, the present disclosure is not limited thereto. In other embodiments, the moveable platform is located at a position instead of the central position. In addition, it is possible to arrange more than one optoelectronic devices on the moveable platform according to different applications. 
     Although the above embodiments show that the sensor package  10  includes multiple elastic restoring members  15 , but the present disclosure is not limited thereto. In a non-limiting embodiment, the sensor package  10  includes one elastic restoring members  15 , e.g., as shown in  FIG.  9   . That is, in the present disclosure, the sensor package  10  includes at least one elastic restoring member  15  for providing a restoring force and a path for transmitting electrical signals. 
     As mentioned above, the conventional MEMS can be used as an actuator to adjust the exact position. Therefore, the present disclosure provides a sensor package having a movable sensor (as shown in  FIGS.  1  to  4   ) and a manufacturing method thereof (as shown in  FIGS.  7 - 8   ) that dispose a sensor chip on the elastic restoring member to allow the elastic restoring member to have functions of transmitting signals and providing restoring force at the same time. 
     Although the disclosure has been explained in relation to its preferred embodiment, it is not used to limit the disclosure. It is to be understood that many other possible modifications and variations can be made by those skilled in the art without departing from the spirit and scope of the disclosure as hereinafter claimed.