Patent Publication Number: US-2010109103-A1

Title: Mems package

Description:
CLAIM OF PRIORITY 
     This application claims priority to Taiwanese Application 97142652, which was filed on Nov. 5, 2008, and which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a MEMS package, particularly to a cavity based MEMS sensor package. 
     2. Description of Related Art 
     A MEMS package or a cavity based MEMS sensor package contains a MEMS chip or a cavity based MEMS sensor chip in the packaging system similar to that of integrated chips or microelectronics.  FIG. 1A  is a schematic cross-sectional view of a conventional MEMS chip  100  having a sensing device  110  and a resonant chamber  120 . The sensing device  110 , for example, can include a vibration diaphragm  111 , a fixed plate  112 , and a piezoresistor  113 . The basic operation of the MEMS chip  100  is that when an external signal transmits via the through-holes of the fixed plate  112  to reach the vibration diaphragm  111 , the signal is amplified by the resonant chamber  120  to cause the vibration diaphragm  111  to produce mechanical vibration, and the piezoresistor  113  then converts the mechanical vibration into an electronic signal, thereby detecting the external signal. For the package of this type of MEMS chip, a resonant chamber is needed for the effective detection of an external signal, and therefore the package structure has to include a variety of chambers and channels to allow the sensing device of the MEMS chip to communicate with the external environment. Under the circumstances, the package is required to install additional components or carve out internal space in the original structure to form chambers and channels, for example, forming a front chamber and a back chamber each disposed at one side of the sensing device, the front chamber being the first chamber to receive the external signal and the back chamber facilitating or indirectly receiving the external signal. As shown in  FIG. 1B , it is well known that an additional chamber  131  is provided in a conventional MEMS package. The chamber  131  is formed by covering a carved-out wafer material  140  on a MEMS chip  160 , and a sealing member  150  is provided to seal the chamber  131 . The chamber  132  in the MEMS chip and the additional chamber  131  form a front chamber and a back chamber respectively. However, since a MEMS device is often exposed to electromagnetic radiation in the operation environment, the converted signal may be subject to the electromagnetic interference. To guard against the radiation, as shown in  FIG. 1C , a general method is to dispose a metallic cover  190  on the substrate  180 , the metallic cover  190  being above and spaced apart from the MEMS chip  170 . A space between the substrate  180  and the metallic cover  190  is formed as a resonant chamber (front chamber)  191 , and a back chamber  192  is formed in the MEMS chip  170 . By grounding the metallic cover  190 , the aforementioned structure can exclude the interference caused by the electromagnetic radiation, as explained in U.S. Pat. No. 3,781,231. There are many techniques which provide improvements on the structure of a metallic cover, for example, the extra-ordinary protection within a metallic cover disclosed in Taiwan Patent No. 29961, and the integrally formed substrate/cover structure disclosed in U.S. Pat. No. 7,202,552. However, each of the structures uses a cover having a chamber, which not only increases package volume but also results in insufficient mechanical strength and compactness despite using more metal materials, and the packaging process is complicated and expensive. 
     In view of the above problems, the invention provides a MEMS package, specifically a cavity based MEMS sensor package that can overcome the aforementioned disadvantages. 
     SUMMARY OF THE INVENTION 
     The invention relates to a MEMS package. According to an embodiment of the invention, a MEMS package includes: a MEMS chip having a first surface, a second surface, a first cavity, and a sensing device, the sensing device defining a first end of the first cavity; a leadframe having a second cavity and being electrically connected to the first surface of the MEMS chip, the second cavity being adjacent to the sensing device of the MEMS chip; a conductive layer disposed on the second surface of the MEMS chip to define a second end of the first cavity and grounded via the leadframe that is electrically connected to the conductive layer so as to provide electromagnetic shielding to the MEMS chip; and an encapsulant covering the MEMS chip, the leadframe, and the conductive layer so as to define the shape of the MEMS package and allowing outer surfaces of the leadframe to emerge from the MEMS package. In another embodiment, the MEMS package further includes an active component, such as a chip, or a passive component, such as a capacitor. In addition, the MEMS chip of the invention can further include a circuit component. Moreover, the MEMS package can further include an adhesive for bonding the conductive layer to the second surface of the MEMS chip. The MEMS package can also include a conductive adhesive for electrically connecting and bonding the leadframe to the first surface of the MEMS chip. Furthermore, the conductive layer can be electrically connected to the leadframe via a wire and a plurality of bonding pads, or alternatively, via a through-silicon via. In an embodiment of the invention, the aforementioned leadframe has an opening that communicates with the second cavity and that emerges from the MEMS package. Additionally, the volume of the first cavity can be changed by varying the shape of the conductive layer. Yet in another embodiment of the invention, an encapsulant covers the MEMS chip, the leadframe, and part of the conductive layer to define the shape of the MEMS package and allows outer surfaces of the leadframe and the uncovered part of the conductive layer to emerge from the MEMS package. 
     The MEMS package of the invention provides several advantages. When the MEMS package is acted on by electromagnetic radiation, the charges induced by the electromagnetic radiation in the conductive layer will be discharged to the external environment via a grounding device, and as a result the electromagnetic interference to the MEMS chip can be substantially reduced, thereby achieving the effect of electromagnetic shielding. The conductive layer is dual functional in that the conductive layer seals the first cavity of the MEMS chip by bonding itself to the MEMS chip and the conductive layer, in cooperation with a grounding device, provides electromagnetic shielding for the MEMS chip. Moreover, the volume of the first cavity can be increased by incorporating an additional space created by a protruded conductive layer, and thus the sensing device improves the damping characteristics to enhance the signal/noise ratio (SNR) by expanding the frequency response of the signals. For the MEMS package structure, the first cavity, the second cavity and the opening together form a passage for signal transmission by use of the MEMS chip, the leadframe and the conductive layer only so that the overall package remains a small volume or has a more compact structure. Furthermore, the encapsulant protects the MEMS chip, the leadframe and the conductive layer by providing shielding against external hazards such as moisture, light and particles. Besides, the encapsulant also makes the overall package easier to be grasped and improves the mechanical properties of the package. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The advantages and features of the invention will be appreciated by the various embodiments and examples set forth below in conjunction with the accompanied drawings. The drawings should be regarded as exemplary and schematic, and are shown not to scale and should not be implemented exactly as shown. 
         FIG. 1A  shows a cross-sectional view of a conventional MEMS chip. 
         FIG. 1B  shows a cross-sectional view of a conventional double-wafer MEMS structure. 
         FIG. 1C  shows a cross-sectional view of a conventional MEMS package with a cover. 
         FIG. 2A  shows a cross-sectional view of a MEMS package according to an embodiment of the invention. 
         FIG. 2B  shows a cross-sectional view of a MEMS package in which the susceptor of the leadframe has no opening according to another embodiment of the invention. 
         FIG. 3A  shows a perspective view showing the structural relationship of the MEMS chip, the leadframe and the conductive layer according to an embodiment of the invention. 
         FIG. 3B  shows a perspective view of a MEMS package according to an embodiment of the invention. 
         FIG. 4  shows a partially enlarged cross-sectional view showing the adhesive overflow between the MEMS chip and the susceptor of the leadframe according to an embodiment of the invention. 
         FIG. 5  shows a partially enlarged cross-sectional view of a MEMS package having a through-silicon via grounding device according to an embodiment of the invention, wherein an encapsulant covers part of the conductive layer. 
         FIG. 6A  shows a cross-sectional view of a MEMS package having a conductive layer different from that of  FIG. 2A , according to an embodiment of the invention. 
         FIG. 6B  shows a cross-sectional view of a MEMS package having a conductive layer different from that of  FIG. 2A  or  FIG. 6A , according to an embodiment of the invention. 
         FIG. 6C  shows a cross-sectional view of a MEMS package having a through-silicon via grounding device and a conductive layer with a cavity according to an embodiment of the invention. 
         FIG. 7A  shows a cross-sectional view of a MEMS package having a passive component according to an embodiment of the invention. 
         FIG. 7B  shows a cross-sectional view of a MEMS package having a chip according to an embodiment of the invention. 
         FIG. 7C  shows a cross-sectional view of a MEMS package having a flip chip according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention is explained using several embodiments and examples having numerous details. It should be noted that the details are exemplary and do not limit the invention. 
       FIG. 2A  shows a cross-sectional view of a MEMS package  200  according to an embodiment of the invention. The MEMS package  200  includes a MEMS chip  201 , a leadframe  202 , and a conductive layer  203 . In the embodiment, the MEMS chip  201  is a silicon based chip having a Micro-Electro-Mechanical Systems (MEMS) device. As shown in  FIG. 2A , the MEMS chip  201  has a first surface  211  and a second surface  212 . The first surface  211  of the MEMS chip  201  is electrically connected to a leadframe  202 . A conductive layer  203  is provided on the second surface  212  of the MEMS chip  201 , which substantially covers the second surface  212 . Alternatively, the conductive layer  203  covers only a part of the second surface  212 . Additionally, the MEMS package  200  further includes a grounding device  230 . The grounding device  230  includes a wire  231  and a plurality of bonding pads  232 . The wire  231  electrically connects the conductive layer  203  to the leadframe  202  via the bonding pads  232 . As can be seen from the embodiment, when the MEMS package  200  is acted on by electromagnetic radiation from external environment, charges will be induced in the conductive layer  203  due to the electromagnetic effect. The charges will reach the leadframe  202  via the grounding device  230 , and eventually reach the ground plane at the outside of the MEMS package  200 . As a result, the electromagnetic interference to the MEMS chip  201  is substantially reduced, thereby achieving the effect of electromagnetic shielding. Alternatively, the grounding device  230  may include a plurality of wires  231  and a plurality of bonding pads  232 , wherein the plurality of wires  231  together lower the grounding resistance and further enhance the effect of electromagnetic shielding. 
     As also shown in  FIG. 2A , the MEMS chip  201  includes a first cavity  204 , wherein a diaphragm  206  and a fixed plate  207  are provided at the side of the first cavity  204  near the first surface  211 . The fixed plate  207  has a plurality of through-holes, and the diaphragm  206  can freely vibrate. Alternatively, the fixed plate  207  can be provided on the other side of the diaphragm  206 , namely, provided on top of the diaphragm  206  in  FIG. 2A . Furthermore, the diaphragm  206  or the fixed plate  207  can be regarded as a part of the first surface  211  depending on the arrangement of the diaphragm  206  and the fixed plate  207 . However, it is to be noted that the components defining the side of the first cavity  204  near the first surface  211  are not limited to the diaphragm  206  and the fixed plate  207  shown in  FIG. 2A . Alternatively, two components sealing the first cavity  204  are provided at the side of the first cavity  204  near the first surface  211 . Alternatively, a sensing device including at least a mechanical or electrical component is provided at the side of the first cavity  204  near the first surface  211 . 
     Moreover, as shown in  FIG. 2A , the leadframe  202  includes a susceptor  222  and a plurality of conductive segments  223 .  FIG. 3A  is a perspective view showing the structural relationship of the MEMS chip  201 , the leadframe  202  (including a susceptor  222  and a plurality of conductive segments  223 ), and the conductive layer  203  of a MEMS package  200  with the first surface  211  facing upward according to an embodiment of the invention.  FIG. 3A  shows merely four of the plurality of conductive segments  223 . Actually, the number of the conductive segments  223  is not limited to four. The plurality of conductive segments  223  are provided around the susceptor  222  that is configured to support the MEMS chip  201 . One or more conductive segments  223  allow signals to be transmitted between the package  200  and an external device (such as a printed circuit board, not shown), and the remaining one or more conductive segments  223  are connected to the grounding device  230 . Namely, the plurality of conductive segments  223  are configured as signal transmission ends or grounding ends respectively. Moreover, as shown in  FIG. 2A , a second cavity  205  is formed on the susceptor  222 . In  FIG. 2A , the side of the second cavity  205  near the first cavity  204  is walled by the diaphragm  206  that functions between the two cavities. Specifically, the second cavity  205  communicates with the diaphragm  206  via the through-holes on the fixed plate  207  so that the diaphragm  206  can vibrate between the first cavity  204  and the second cavity  205 . Preferably, the dimensions of the second cavity  205  are defined by the leadframe  202 , the diaphragm  206  and optionally, part of the first surface  211 . Preferably, a sensing device is provided between the first cavity  204  and the second cavity  205 , the sensing device defines the side of the second cavity  205  that is near the first cavity  204 . 
     Furthermore, the susceptor  222  of the leadframe  202  has an opening  208 , through which the second cavity  205  can communicate with external environment, allowing the transmission of signals through the opening  208 . Based on the structure, signals such as sonic waves or pressure variations from external environment can be transmitted into the second cavity  205  through the opening  208 . Resonance occurring in the first cavity  204  and the second cavity  205  cause the diaphragm  206  to vibrate, thereby the signals can be received by the MEMS chip  201 . Conversely, MEMS chip  201  may produce signals which cause the diaphragm  206  to vibrate. Resonance thus occurs in the first cavity  204  and the second cavity  205 , which makes the signals transmitted to the external environment via the opening  208 . The MEMS package  200  having an opening  208  in accordance with the invention is applicable to microphones, pressure meters, barometers, tire gauges, altimeters, and so on. Depending on different applications, the MEMS package is configured to have a different predetermined maximum or minimum operating frequency, hence the dimensions of the first cavity  204  and the second cavity  205 , and the area and depth (the distance from external environment to the second cavity  205 ) of the opening  208  being different, which affects the dimensions and structures of the MEMS chip  201  and the leadframe  202  (susceptor  222 ). Hence, the MEMS package in accordance with the invention, as illustrated by  FIG. 2A , has a first cavity  204  and a second cavity  205  that can be of different shapes and volumes. For example, the shape of the cavity is designed such that the package has an adequate structural strength. In addition, as can be seen from the equation for the resonant frequency of an Helmholtz resonator, the resonant frequency increases with a decreasing cavity volume, and the resonant frequency increases with an increasing area of the opening or a decreasing depth of the opening. The second cavity  205  and the opening  208  can be formed by etching or pressing the leadframe  202  and then drilling a hole through the leadframe  202 . Compared with the double-wafer bonding technique, as illustrated by  FIG. 1B , forming the second cavity  205  directly on the leadframe  202  can expedite the manufacturing process and reduce the material cost. 
     In the MEMS package  200  shown in  FIG. 2A , the conductive layer  203  is provided on the back side (the second surface  212 ) of the MEMS chip  201 , and the front side (the first surface  211 ) of the MEMS chip  201  for transmitting signals is provided as facing downward and electrically connected to the leadframe  202 . Under this configuration, the first cavity  204 , the second cavity  205  and the opening  208  together form a passage for signal transmission by use of the MEMS chip  201 , the leadframe  202  and the conductive layer  203  only so that the overall package remains a small volume or has a more compact structure. 
     Furthermore,  FIG. 2A  and  FIG. 3B  show that the MEMS package  200  in accordance with the invention further includes an encapsulant  240  covering the MEMS chip  201 , the leadframe  202 , the conductive layer  203  and the grounding device  230 . The encapsulant  240  defines the shape of the MEMS package  200  and allows the outer surfaces of the leadframe  202  to emerge from the MEMS package  200 . As shown in  FIG. 3B , the exposed surfaces of the leadframe  202  on the MEMS package  200  are part of the surfaces of the susceptor  222  and the plurality of conductive segments  223 . Apart from the exposed surfaces of the leadframe  202 , the opening  208 , the second cavity  205  communicating with the opening  208 , the diaphragm  206  and the fixed plate  207 , the encapsulant  240  prohibits the remaining part of the MEMS package  200  from contacting the external environment. As shown in  FIG. 2A  and  FIG. 3B , the MEMS chip  201 , the conductive layer  203 , the grounding device  230 , and the part of leadframe  202  excluding the exposed surfaces are all protected by the encapsulant  240 . It should be noted that the encapsulant  240  covers the portion  240 V between the susceptor  222  and the plurality of conductive segments  223 , but not the opening  208 . The encapsulant  240  can be formed from ceramics, plastic or the like, wherein the plastic material such as epoxy can be molded and cured to form the encapsulant. It should be noted that the encapsulant  240  protects the MEMS chip  201 , the leadframe  202  and the conductive layer  203  by providing shielding against external hazards such as moisture, light and particles. Besides, the encapsulant  240  also makes the overall package easier to be grasped and improves the mechanical properties of the package. 
     Preferably, the MEMS package  201  includes a circuit component (not shown) on the first surface  211 , such as a MEMS SoC circuit component. The circuit component can be connected to any sensing device or electronic component (not shown) on the diaphragm  206  and be connected to the leadframe  202  as well. The circuit component is shielded from the electromagnetic radiation by the grounded conductive layer  203 . In another example, the MEMS circuit component is provided on another chip that is electrically connected to the MEMS package  200 , where only the MEMS devices within the package are protected from the electromagnetic radiation by the conductive layer  203 . 
     Preferably, the MEMS chip  201  can be electrically connected to the leadframe  202  (the susceptor  222  or the conductive segments  223 ) via a conductive adhesive  250  such as silver paste, conductive epoxy or the like. A shown in  FIG. 4 , since the second cavity  205  is designed to be wider than the diaphragm  206  and the fixed plate  207  of the MEMS chip  201 , which has the merit that when overflowing adhesive of the conductive adhesive  250  exists between the MEMS chip  201  and the susceptor  222  and the overflowing adhesive flows down along the side wall of the second cavity  205  in the susceptor  222 , the overflow will not affect the diaphragm  206  and the fixed plate  207 . Therefore, the gluing and chip bonding processes can be more tolerant in accuracy control, thus the yield of package will be enhanced. The MEMS chip  201  can be connected to the conductive layer  203  via an adhesive  251 . As shown in  FIG. 2A  and  FIG. 4 , the part of the adhesive  251  that does not contact the MEMS chip  201  will cure after being coated on the conductive layer  203 , thus it will not affect the first cavity  204 , the diaphragm  206  and the fixed plate  207 . Alternatively, the adhesive  251  is only coated on the part of the conductive layer  203  that contacts the MEMS chip  201  via the adhesive  251 . 
     Preferably, the grounding device includes a through-silicon via (TSV). According to an embodiment of the invention,  FIG. 5  shows a partially enlarged cross-sectional view of a MEMS package  200  having a grounding device  230 T that is electrically connected to the conductive layer  203  and the leadframe  202 . The grounding device  230 T includes a through-silicon via  235  and a plurality of conductive elements  236 . Similar to the grounding device  230  described above, the charges induced by the electromagnetic radiation in the conductive layer  203  will reach the leadframe  202  via the grounding device  230 T, and eventually reach the ground plane at the outside of the MEMS package  200 , thereby providing electromagnetic shielding. The grounding device  230 T consists of a plurality of through-silicon via  235  and a plurality of conductive elements  236  to reduce the grounding resistance and improve the effect of the electromagnetic shielding of the conductive layer  203 . As shown in  FIG. 5 , the encapsulant  240 ′ covers part of the conductive layer  203 . Alternatively, the encapsulant  240 ′ may cover no part of the conductive layer  203 . In other words, some part or all of the conductive layer  203  is in contact with the external environment so as to achieve certain physical characteristics of the package, such as heat dissipation through the conductive layer  203 . 
     As can be seen from the various embodiments and examples explained above, the MEMS package  200  of the invention not only has an improved overall mechanical strength and a smaller overall volume, but also offers a better protection for the internal components within the package, as compared with a conventional MEMS package (such as the one in  FIG. 1C ). Therefore, the MEMS package of the invention can be adapted for use in a more hostile environment, or in a smaller mobile device. Moreover, the conductive layer  203  is dual functional in that it seals the first cavity  204  of the MEMS chip  201  by bonding itself to the MEMS chip  201  and it, in cooperation with a grounding device  230  or  230 T, provides electromagnetic shielding to the MEMS chip  201 . In an application of the invention, the leadframe  202  of the MEMS package  200  is attached to a printed circuit board having a metal layer to create a double shielding for the MEMS chip. Namely, the conductive layer  203  and the printed circuit board having a metal layer shield the electromagnetic radiation from upper and lower sides of the package  200 , thereby enhancing the electromagnetic shielding for the package. Moreover, one skilled in the art will understand that the conductive layer  203  is configured to have a thickness that is determined by the necessary strength required by the conductive layer  203  to withstand the pressure occurred during the molding of the encapsulant  240 . Furthermore, for example, the conductive layer  203  can be a copper layer. The copper layer  203  can be attached to the MEMS chip  201  by first bonding a MEMS wafer to a copper plate and then after conducting circuit probe on the bonded wafer sawing the bonded wafer to form individual MEMS chips  201 , each with a conductive layer  203 . This simple manufacturing process of adhering the conductive layer  203  to the MEMS chip  201  by using the wafer-level bonding technique does not require very high accuracy for the process and therefore brings the cost down. 
     According to an embodiment of the invention, as shown in  FIG. 2B , a MEMS package  280  has most of the technical features of the MEMS package  200  in  FIG. 2A , except that, first, the diaphragm  206  and the fixed plate  207  in  FIG. 2A  are now replaced by a more general sensing device  290  in  FIG. 2B , and second, the susceptor  222  in  FIG. 2B  has no opening so that the second cavity  205 ′ forms a closed chamber. Apart from the two differences, the MEMS package  280  has all the technical characteristics of the MEMS package  200 , and can be configured to all the variations of the MEMS package  200  described above. Here, the sensing device  290  is provided on the MEMS chip  201 , and it defines one end of the first cavity  204  near the first surface  211 . The second cavity  205 ′ does not communicate with the external environment and totally protects the sensing device  290 . The second cavity  205 ′ can be a vacuum or filled with gas or a filler. As compared with the double-wafer bonding structure (as shown in  FIG. 1B ), the second cavity  205 ′ can be formed by etching or stamping the leadframe  202 . It should be noted that the invention allows the conductive adhesive  250  bonding the MEMS chip  201  and the leadframe  202  to have a relatively low hermeticity, for as long as the encapsulant  240  completely encapsulate the package elements except those exposed surfaces of the leadframe, the portion  240 V of the cured encapsulant  240  substantially seals the second cavity  205 ′ or enhance the overall hermeticity of the cavity. The MEMS package  280  without an opening in accordance with the invention is applicable to accelerometers, gyroscopes and so on. 
     In other embodiments, the conductive layer  203  in the MEMS package  200  or  280  has many variations. According to an embodiment of the invention, a MEMS package  600  in  FIG. 6A  includes all the elements that are shown in  FIG. 2A , where like reference numerals in the figures denote like elements, for example, MEMS chip  601  corresponds to MEMS chip  201 , leadframe  602  corresponds to leadframe  202 , and so on. However, the main difference is that the conductive layer  603  has a structure (shape) different from that of the conductive layer  203 . The conductive layer  603 , bonded to the second surface  612  of the MEMS chip  601  via the adhesive  651 , forms an additional cavity between the conductive layer  603 , the second surface  612 , and the extension of the second surface  612  (an imaginary surface that extends from the second surface  612  over the cavity of the chip  601 ) such that the additional cavity of the conductive layer  603  and the cavity of the MEMS chip  601  together form a first cavity  604 . That is, the conductive layer  603  has a structure protruded away from the second surface  612  of the MEMS chip  601 . In other words, the first cavity  604  can increase or vary in volume by taking in the additional cavity created by the protruded conductive layer  603 , and thus the vibration diaphragm  606  (or the sensing device in other embodiments of the invention) improves the damping characteristics to enhance the signal/noise ratio by expanding the frequency response of the signals.  FIG. 6B  shows another MEMS package  600 E of the invention. The package  600 E is the same as the package  600  except that the conductive layer  603 E of the package  600 E is structurally different from the conductive layer  603  of the package  600 . Still, similar to the conductive layer  603 , the conductive layer  603 E forms an additional cavity that forms a first cavity  604 ′ together with the cavity of the chip  601 . The additional cavity formed by the conductive layer  603  or  603 E can be formed by etching or stamping the conductive layer. In related art, a long period of time must be spent to deep etch a cavity with a sufficient volume in the MEMS chip, making the etching process time-consuming and costly. The invention enables relatively fast mechanical polishing of the MEMS wafer followed by fast shallow etching on the wafer, which is then bonded to a pre-etched or pre-stamped metal plate and sawed to obtain individual chips, each of which is attached with a conductive layer having the additional cavity. In an example, the MEMS package of the invention can use a thinner MEMS wafer, which, after being shallow etched during the manufacturing process, can have a volume of the first cavity  604  or  604 ′ “restored” or increased by bonding to the conductive layer  603  or  603 E having the additional cavity. Namely, the smaller cavity volume of the thinner MEMS chip is compensated by adding the additional cavity of the conductive layer. According to another embodiment of the invention,  FIG. 6C  shows that a MEMS chip  601 T has a through-silicon via grounding device and a cavity based conductive layer (leadframe and encapsulant not shown). In  FIG. 6C , the conductive layer  603 T is attached to the MEMS chip  601 T via the adhesive  651 . The through-silicon via grounding device  630 T is electrically connected to the conductive layer  603 T via a conductive bump  690  that is in electrical contact with the conductive layer  603 T and the through-silicon via grounding device  630 T. The through-silicon via grounding device  630 T is also electrically connected to the external environment via the conductive adhesive  650  (and via the leadframe). As a result, the conductive layer  603 T is grounded to provide electromagnetic shielding, and it contributes to define part of the back chamber of the chip. 
     The MEMS package of the invention can further include other active or passive components. According to an embodiment of the invention, as shown in  FIG. 7A , a MEMS package  700 A can include all the technical features and their variations of the MEMS package  200 ,  280 ,  600 , or  600 E and further includes a passive component  710 . The passive component  710  is provided on the leadframe  702  and covered by the encapsulant  740 . The passive component  710  is electrically connected to the MEMS chip  721 , which includes all the technical features and their variations of the MEMS chip in the MEMS package  200 ,  280 ,  600 , or  600 E. For example, the passive component  710  is a capacitor provided at the signal output end of the MEMS chip to enhance the electromagnetic shielding against a certain range of frequencies, such as the radio frequencies used in the GSM or 3G standard. 
     Alternatively, the MEMS package of the invention can be configured as a multi-chip module (MCM) package, in which the MEMS chip is coplanar or stacked with another chip provided within the package. For example, a MEMS package  700 B shown in  FIG. 7B  can include all the technical features and their variations of the MEMS package  200 ,  280 ,  600 , or  600 E and further includes a chip  720  that is covered by the encapsulant  742 . The chip  720  is electrically connected to the leadframe  704  via wires. Namely, the chip  720  may then be electrically connected to the MEMS chip  721 . Moreover, as shown in  FIG. 7C , a MEMS package  700 C can include all the technical features and their variations of the MEMS package  200 ,  280 ,  600 , or  600 E and further includes a flip chip  730  that is covered by the encapsulant  744 . The flip chip  730  is electrically connected to the leadframe  706 . In either  FIG. 7B  or  7 C, the MEMS chip  721  can include all the technical features and their variations of the MEMS chip in the MEMS package  200 ,  280 ,  600 , or  600 E. 
     While the invention has been shown and described with reference to several embodiment thereof, and in terms of the illustrative drawings, it should not be considered as limited thereby. Various possible modifications, alterations, and equivalents could be conceived of by one skilled in the art to the form and the content of any particular embodiment, without departing from the scope of the invention.