Abstract:
A MEMS device for use in some embodiments in a microphone or pressure sensor and method of making the same wherein a portion of the package surrounding the acoustic port is deformed either away from, towards, or both away from and towards the interior of the package. By providing this raised area proximate the acoustic port, external debris is less likely to enter the acoustic port and damage the fragile MEMS die. Further, internal attachment material holding the MEMS die to the inside of the package is prevented by flowing into and obscuring the acoustic port. The advantages of this design include longer operation lifetimes for the MEMS device, greater design freedom, and increases in production yield.

Description:
FIELD OF THE DISCLOSURE 
       [0001]    Disclosed is a package for housing a microelectromechanical system (MEMS) device with improved protection for the MEMS device disposed therein, and further a method of manufacture for the package, particularly for use as a MEMS microphone. 
       BACKGROUND OF THE DISCLOSURE 
       [0002]    MEMS devices have been incorporated into personal electronic devices which commonly employ at least one microphone to enable voice communication between the user and the device. In some systems, the MEMS device is an acoustic transducer, deflection by sound waves of a diaphragm within the device results in a change of capacitance which can be measured, interpreted, and translated by the device into a desired output (e.g. a voice command for controlling software on the device). The MEMS device is often enclosed within a frame or package and attached to the interior of the package near a hole or port which allows the interior of the package to communicate with the surrounding environment. Sound thus enters the package through this port and acts upon the MEMS device. 
         [0003]    Performance of the MEMS device is vital to successful operation of the system and the electronic device as a whole. With electronic devices becoming part of the day to day lives of most individuals and thus subject to the day-to-day wear and tear that does along with it, maintaining reliability of the devices has become an increasing issue. Given the fragility and sensitivity of the MEMS device, it vital to protect the device from dust, dirt, and any other material or force which could lead to mechanical damage. Further, optimal performance of the device is predicated at least in part on the device&#39;s ability to sense the acoustic environment outside (and inside) of the system. Therefore, it is important that the package be designed to prevent potential obstruction of the port and maintain and clear pathway for travel of sound waves and deflection of the diaphragm. 
         [0004]    Methods of making generic MEMS device packages are known in the art, such as in United States patent applications US 2014/0246738 and US 2014/0246739, which are incorporated herein by reference in their entireties. 
         [0005]    MEMS device packages with increased protection for the MEMS device therein are disclosed in U.S. Pat. Nos. 4,691,363 and 8,130,979, both of which are incorporated herein by reference in their entireties. 
         [0006]    U.S. Pat. No. 4,691,363 discloses a MEMS device package including a sound port that is mounted over the passage between the surrounding environment of the package and the MEMS device located within. U.S. Pat. No. 8,130,979 also discloses a MEMS device package where a cap is mounted over the port and provides communication between the surrounding environment and the MEMS device located at the other end of the port. 
         [0007]    MEMS device packages with internal structures for preventing flow of material into the acoustic port are disclosed in U.S. Pat. No. 7,537,964, which is incorporated herein by reference in its entirety. U.S. Pat. No. 7,537,964 discloses a MEMS device package that includes an internal retaining ring for preventing wicking of material into the sound port or onto the MEMS device. 
         [0008]    Demands on the package housing a MEMS device are stringent. Package designs are progressing in two directions: better performance through optimization of certain design parameters and miniaturization to comply with the spatial constraints of ever more compact electronic devices. Additionally, while the complexity of these devices continues to increase, there is a continued desire to simplify the manufacturing process to keep production costs as low as possible and improve efficiency. 
         [0009]    There is a desire, therefore, for a durable MEMS device package which allows for increased design freedom, decreased manufacturing complexity and cost, and improved manufacturing efficiency. 
       BRIEF SUMMARY 
       [0010]    Disclosed herein is a method of making a microelectromechanical system. In one embodiment, the method includes the steps of providing a package base having a first interior portion and a first perimeter, providing a lid on the package base to define a cavity, the lid having a second interior portion and a second perimeter, wherein the first interior portion and the second interior portion are substantially planar, providing a non-planar portion on one of the first interior portion and the second interior portion, extending a port through the non-planar portion to the cavity, providing an attachment portion within the cavity and proximate the port, and configuring the attachment portion to receive a MEMS device. In some embodiments, the step of providing a non-planar portion on one of the first interior portion and the second interior portion includes the step of deforming material in one of the first interior portion and the second interior portion. In some embodiments, the step of deforming material in one of the first interior portion and the second interior portion deforms at least a portion of one of the first interior portion and the second interior portion into the cavity. In some embodiments, the step of deforming material in one of the first interior portion and the second interior portion deforms at least a portion of one of the first interior portion and the second interior portion away from the cavity. In some embodiments, the step of deforming material in one of the first interior portion and the second interior portion deforms at least a portion of one of the first interior portion and the second interior portion into and away from the cavity. 
         [0011]    In a further embodiment, the method of making a microelectromechanical system includes the steps of providing a package base having a first interior portion and a first perimeter, providing a lid on the package base to define a cavity, the lid having a second interior portion and a second perimeter, deforming material in one of the first interior portion and the second interior portion into, away from, or both into and away from the cavity to provide a non-planar portion, extending a port through the non-planar portion, the port allowing acoustic communication between the cavity and an environment surrounding the microelectromechanical system, and providing an attachment portion within the cavity and substantially surrounding the non-planar portion for receiving a MEMS device. 
         [0012]    Also disclosed herein are packages produced by the methods described in the exemplary embodiments above. In some embodiments, the package includes a package base having a first interior portion and a first perimeter portion, a lid having a second interior portion and a second perimeter portion, wherein the first interior portion and the second interior portion are substantially planar, a cavity defined by the package base and the lid, a non-planar portion in at least one of the first interior portion and the second interior portion, a port extending through the non-planar portion to the cavity; and an attachment portion within the cavity and proximate the port, wherein the attachment portion is configured to receive a MEMS device. In some embodiments, the non-planar portion is configured to substantially prevent flow of an attachment material from entering the port. In some embodiments, the attachment material is selected from the group consisting of: epoxy, silicone, glue, and combinations thereof. In some embodiments, the non-planar portion extends away from the cavity. In some embodiments the non-planar portion extends both into and away from the cavity. In some embodiments, the attachment portion substantially surrounds the non-planar portion. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The subject matter that is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the invention will be apparent from the following detailed description taken in conjunction with the accompanying drawings. 
           [0014]      FIG. 1  depicts a cross-sectional view of a top port MEMS package device consistent with one embodiment of the present disclosure. 
           [0015]      FIG. 2  depicts a cross-sectional view of a further embodiment of the MEMS package device shown  FIG. 1 . 
           [0016]      FIG. 3  depicts a cross-sectional view of a further embodiment of the MEMS package devices shown in  FIGS. 1 and 2 . 
           [0017]      FIG. 4  depicts a method of making the MEMS package device shown in  FIG. 1 . 
           [0018]      FIG. 5  depicts a method of making the MEMS package device shown in  FIGS. 1-3 . 
           [0019]      FIG. 6  depicts a specific embodiment of the method step of providing a non-planar portion on one of the first interior portion and the second interior portion from  FIG. 4 . 
           [0020]      FIG. 7  depicts a specific embodiment of the method step of deforming material in one of the first interior portion and the second interior portion from  FIG. 6 . 
           [0021]      FIG. 8  depicts a specific embodiment of the method step of deforming material in one of the first interior portion and the second interior portion from  FIG. 6 . 
           [0022]      FIG. 9  depicts a specific embodiment of the method step of deforming material in one of the first interior portion and the second interior portion from  FIG. 6 . 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    The embodiments disclosed by the invention are only examples of the many possible advantageous uses and implementations of the innovative teachings presented herein. In general, statements made in the specification of the present application do not necessarily limit any of the various claimed inventions. Moreover, some statements may apply to some inventive features but not to others. In general, unless otherwise indicated, singular elements may be in plural and vice versa with no loss of generality. In the drawings, like numerals refer to like parts through several views. 
         [0024]      FIGS. 1-3  show cross-sectional views of various embodiments of a top port MEMS package device  1  of the present disclosure. In some embodiments, MEMS package device  1  includes a lid  100  and a package base  101 . Lid  100  is defined by an interior portion  110  and a perimeter portion  111 . Package base  101  is likewise defined by an interior portion  112  and a perimeter portion  113 . In some embodiments, MEMS package device  1  may also include walls. As shown in  FIG. 1 , in some embodiments perimeter portion  111  themselves form the walls. In some embodiments, the walls are formed by perimeter portion  113 . In some other embodiments, the boundaries of the package are defined by other structures found within the device into which MEMS package device  1  is integrated. In some embodiments, MEMS package device  1  is not bound by walls at all, but rather by curved lid  100  or package base  101  structures which interface at perimeter portions  111  and  113 . The general size and shape of MEMS package device  1 , including the presence or absence of wall structures, are matters of design choice well within the capabilities of those having ordinary skill in the art. 
         [0025]    In some embodiments, interior portions  110  and  112  are substantially planar. When assembled, therefore, lid  100  and package base  101  define a cavity  114 . In some embodiments, cavity  114  will house MEMS device  13  (discussed in greater detail below) and other electrical components as well (not pictured). Cavity  114  provides protection for these fragile and sensitive components and in some embodiments, is designed to approximate the conditions of the surround environment as close as possible to increase performance of MEMS package device  1 . 
         [0026]    A non-planer portion  10  is provided in one of lid  100  and package base  101 , although  FIGS. 1-3  only show exemplary embodiments with non-planar portion  10  on lid  100 . In some embodiments, such as  FIG. 1 , non-planar portion  10  rises above lid  100  in a direction generally away from cavity  114 . In some embodiments, such as that shown in  FIG. 2 , non-planar portion  10  extends into cavity  114 . In some embodiments, such as that shown in  FIG. 3 , non-planar portion  10  extends in multiple directions, such as into and away from cavity  114 . 
         [0027]    In some embodiments, port  11  is included in non-planar portion  10  and provides communication between cavity  114  and the environment surrounding MEMS package device  1 . The size and shape of non-planar portion  10  and port  11  is a matter of design choice, and design of port  11  will be discussed in greater detail below. In some embodiments, a MEMS device  13  is located within cavity  114  and attached to a surface within cavity  114  at an attachment portion  12 . In some embodiments, as shown in  FIGS. 1-3 , MEMS device  13  is located within cavity  114  and covers the inside of port  11  at an attachment portion  12  which surrounds port  11 . In some embodiments, MEMS device  13  does not cover all of and/or completely surround port  11 . In some embodiments, MEMS device  13  does not cover port  11  at all. In some embodiments, MEMS device  13  is attached to attachment portion  12  using at least one adhesive material  14 , such as epoxy, silicone, glue, and the like. 
         [0028]    In some embodiments, MEMS package device  1  is a microphone. In other embodiments, MEMS package device  1  is a pressure sensor. The benefits realized from non-planar portion  10  depend on whether non-planar portion  10  extends generally away from cavity  114  or into cavity  114 . When non-planar portion  10  extends above interior portion  110 , non-planar portion  10  acts as a guard, preventing material such as dust and other debris from entering port  11  via interior portion  110  and potentially damaging the fragile MEMS device  13 . In some embodiments of MEMS package device  1  in this configuration, non-planar portion  10  also acts as a reservoir to contain attachment material  14  and redirect flow of attachment material  14  away from MEMS device  13 . When non-planar portion  10  extends into cavity  114 , it again acts as a guard or dam that stops attachment material  14  from flowing into port  11 . Attachment material  14  is therefore prevented from obstructing port  11 , interfering with sound waves or pressure changes through port  11 , and causing decreased performance of MEMS package device  1 . 
         [0029]    By limiting the risk of damage or obstruction to MEMS device  13 , the design constraints for the package can be relaxed and production yield can be increased. 
         [0030]      FIGS. 4-9  show embodiments of a method for making MEMS package device  1  discussed in the above paragraphs. In some embodiments, the method of making MEMS package device  1  includes providing  400  a package base having a first interior portion and a first perimeter. A lid is provided  410  to define a cavity, the lid having a second interior portion and a second perimeter. While providing step  410  shows a package where first interior portion and second interior portion are planar,  FIG. 5  shows a providing step  510  wherein planarity of the first and second interior portions is not required. In some embodiments, the providing steps  400  and  410  are performed in successive steps in some order. In some embodiments, the providing steps  400  and  410  are performed simultaneously, for instance where the entire package is cast in a single step. 
         [0031]    The method further includes the step of providing  420  a non-planar portion on one of the first interior portion and the second interior portion. In some embodiments, providing step  420  may occur subsequent to at least one of providing step  400  and providing step  410 . In some embodiments, providing step  420  occurs simultaneously with at least one of providing step  400  and providing step  410 . In some embodiments, such as the one shown in  FIG. 6 , providing step  420  is performed by deforming  620  material in one of the first interior portion and the second interior portion. 
         [0032]    In some embodiments, such as the embodiment shown in  FIG. 4 , a port is extended  430  through the non-planar portion of the cavity. In some embodiments, such as the one shown in  FIG. 5 , an extending step  530  allows acoustic communication between the cavity and an environment surrounding MEMS package device  1 . In some embodiments, providing step  420  is performed first, and extending step  430  is performed afterwards. In other embodiments, the port is extended through at least one of the first interior portion and the second interior portion prior to the formation of the non-planar portion. In this embodiment, after the port has been provided, the area surrounding the port is deformed to provide the non-planar portion. 
         [0033]    In some embodiments where the port is extended  430  or first provided (discussed above, not pictured), material in one of the first interior portion and the second interior portion is deformed  520  into, away from, or both into and away from the cavity of MEMS package device  1 . Such a step is shown in  FIG. 5 , as well as in  FIGS. 7-9 . Deformation steps  520 ,  720 ,  820 , and/or  920  may be performed with any suitable technique using any suitable apparatus and at any suitable conditions. 
         [0034]    In some embodiments, an attachment portion is provided  440  within the cavity and proximate the port and configured  450  to receive a MEMS device. As discussed above, the MEMS device may be attached using any suitable adhesive process, like application of adhesives such as epoxy, silicone, glue, and the like. In some embodiments, such as the one shown in  FIG. 5 , an attachment portion is provided  540  within the cavity and substantially surrounding the non-planar portion. In some embodiments, the attachment portion substantially surrounds the port. 
         [0035]    One or more embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.