Patent Publication Number: US-2021179423-A1

Title: Capless semiconductor package with a micro-electromechanical system (mems)

Description:
BACKGROUND 
     Technical Field 
     The present disclosure relates to a micro-electromechanical system (MEMS) sensor that is exposed to the external environment. 
     Description of the Related Art 
     Many semiconductor packages having a micro-electromechanical system (MEMS) die include a cavity that exposes a sensor component of the MEMS die to an external environment. The sensor component monitors a physical quantity or quality of the external environment outside of the package. Such semiconductor packages are typically formed using a rigid cap that is glued to a substrate on which the MEMS die is positioned. The cap is shaped to form the cavity between the MEMS die and the cap and includes an opening or hole that exposes the cavity to the external environment. This opening and cavity expose the sensor component of the MEMS die to the external environment. For example, the sensor component may monitor pressure, temperature, sound, light, or some other quantity, quality, or combination of quantities and qualities of the external environment to which the sensor component is exposed. 
     There is a large and expanding market for semiconductor packages having a MEMS sensor to monitor a greater number of physical quantities and qualities of the external environment, an environment of an electronic device, an input from a user, or any other physical quantity or quality desired to be monitored. However, there are significant challenges in reducing the manufacturing cost, size, footprint, and thickness of the semiconductor packages; and providing semiconductor packages that perform increasingly complex functions. Examples of electronic devices include laptops, displays, televisions, smart phones, tablets, computers, bendable electronic devices, or any other electronic device that may benefit from monitoring of physical quantities or qualities of the external environment. 
     One significant challenge is producing a semiconductor package with a MEMS die that is decreased in size, decreased in footprint and profile, and decreased in thickness, while maintaining the MEMS die&#39;s capability of monitoring physical quantities and qualities of the external environment. As a semiconductor package with a MEMS die is reduced in size, footprint, profile, and thickness, it becomes more difficult to provide a cap with sufficient clearance to avoid failure in the sensor component of the MEMS die while exposing the sensor component of the MEMS die to the external environment for monitoring. 
     Another significant challenge is reducing the cost of producing a semiconductor package with a MEMS die. As the number of components and materials used in the semiconductor package increases, the cost of manufacturing the semiconductor package with the MEMS die increases and the number of manufacturing steps increases. For example, forming a semiconductor package with a cap to protect the MEMS die includes manufacturing the cap, placing the cap in the correct position using a high-accuracy cap attach machine, and attaching the cap to the substrate using an adhesive. Also, making such semiconductor packages smaller by making a smaller cap would be expensive because it would include manufacturing a new high-accuracy cap attach machine to handle the smaller cap and place the cap in the correct position due to small offsets and clearances and low levels of allowed tolerance in the positioning of the cap. 
     BRIEF SUMMARY 
     In view of the list of significant challenges above, which is not a complete list, it is desirable to provide a semiconductor package with a micro-electromechanical system (MEMS) die that does not require a cap to protect the MEMS die or expose the MEMS die to an external environment, has a smaller thickness and a smaller size, does not require as many manufacturing steps, and allows greater tolerances for variation when manufacturing the semiconductor package, thereby increasing the yield of usable semiconductor packages formed. 
     The present disclosure is directed to various embodiments of a semiconductor package that contains a MEMS die and that does not require the use of a cap glued to a substrate. In other words, the semiconductor package is a capless semiconductor package. 
     According to one embodiment of a semiconductor package containing a MEMS die, a molding compound covers sidewalls and surfaces of the MEMS die and is directly in contact with the sidewalls and surface of the MEMS die such that the MEMS die is held in place within the semiconductor package. The MEMS die is exposed to an external environment through an opening formed in a substrate and an air cavity that is positioned between the substrate and a sensor component of the MEMS die. This semiconductor package may be referred to as a capless semiconductor package. The MEMS die is electrically coupled to a substrate of the semiconductor package by a bonding wire. 
     In this embodiment, the molding compound acts in a similar fashion that a cap would normally act if a cap were utilized to protect and expose a sensor component of a MEMS die to an external environment. However, by removing the necessity to include a cap, the manufacturing cost of producing a semiconductor package with a MEMS die is reduced, the yield of the number of usable and functioning semiconductor packages with MEMS die is increased, and the overall thickness of semiconductor packages with MEMS die is reduced. The cost is reduced and the yield is increased because a high-accuracy cap attach machine is not required to place the cap, the cap does not have to be manufactured, and standard strip molding processes and materials can be utilized to form the semiconductor package to protect the MEMS die. 
     According to an alternative embodiment of a semiconductor package containing a MEMS die, a molding compound covers sidewalls of the MEMS die and a surface of the MEMS die is flush and co-planar with a surface of the molding compound. The surface of the MEMS die flush and co-planar with the surface of the molding compound is exposed to an external environment. The MEMS die is electrically coupled to the substrate by solder balls that are positioned within an air cavity separating the MEMS die from the substrate. 
     According to another alternative embodiment of a semiconductor package containing a MEMS die, a molding compound covers sidewalls and a surface of the MEMS die that is facing away from the substrate. The MEMS die is electrically coupled to the substrate by solder balls that are positioned within an air cavity separating the MEMS die from the substrate. 
     According to a method of manufacturing of the above embodiment and alternative embodiments of a semiconductor package containing a MEMS die, the MEMS die is coupled to a substrate by a sacrificial material. The sacrificial material is a thermally decomposable die attach that is removed by exposing the thermally decomposable die attach to heat. The method of manufacturing also includes forming an opening in the substrate that is aligned with both a sensor component of the MEMS die and the air cavity separating the MEMS die from the substrate. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       In the drawings, identical reference numbers identify similar elements or acts unless the context indicates otherwise. The sizes and relative portions of the elements in the drawings are not necessarily drawn to scale. 
         FIG. 1A  is directed to a cross-sectional view of an embodiment of a semiconductor package containing a micro-electromechanical system (MEMS) die and an applied specific integrated circuit (ASIC) die; 
         FIG. 1B  is a cross-sectional view of an alternative embodiment of a semiconductor package containing a MEMS die and an ASIC die; 
         FIG. 1C  is a cross-sectional view of an alternative embodiment of a semiconductor package containing a MEMS die and an ASIC die; 
         FIG. 2A  is directed to a cross-sectional view of an alternative embodiment of a semiconductor package containing a MEMS die and an ASIC die; 
         FIG. 2B  is directed to a cross-sectional view of an alternative embodiment of a semiconductor package containing a MEMS die and an ASIC die; 
         FIG. 3  is directed to a cross-sectional view of an alternative embodiment of a semiconductor package containing a MEMS die and an ASIC die; 
         FIGS. 4A-4E  are directed to an embodiment of a method of manufacturing an embodiment of a semiconductor package containing a MEMS die and an ASIC die; 
         FIG. 5  is directed to a method of manufacturing an alternative embodiment of a semiconductor package containing a MEMS die and an ASIC die; and 
         FIG. 6  is directed to an embodiment of an electronic device that contains an embodiment of a semiconductor package containing a MEMS die and an ASIC die. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, certain specific details are set forth in order to provide a thorough understanding of various embodiments of the disclosure. However, one skilled in the art will understand that the disclosure may be practiced without these specific details. In other instances, well-known structures associated with electronic components and semiconductor fabrication techniques have not been described in detail to avoid unnecessarily obscuring the descriptions of the embodiments of the present disclosure. 
     Unless the context requires otherwise, throughout the specification and claims that follow, the word “comprise” and variations thereof, such as “comprises” and “comprising,” are to be construed in an open, inclusive sense, that is, as “including, but not limited to.” 
     The use of ordinals such as first, second and third does not necessarily imply a ranked sense of order, but rather may only distinguish between multiple instances of an act or structure. 
     Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. 
     As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the content clearly dictates otherwise. It should also be noted that the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise. 
     As used in this specification and the appended claims, the terms “top” and “bottom” refer to the orientation of surfaces of semiconductor packages when viewed in the Figures. The terms “top” and “bottom” do not limit the surfaces of the semiconductor packages in the Figures to the specific orientation of the semiconductor packages as disclosed in the Figures. 
     As used in the specification and the appended claims, the terms “left” and “right” refer to the orientation of surfaces of a semiconductor package when viewed in the Figures. The terms “left” and “right” do not limit the surfaces of the semiconductor package in the Figures to the specific orientation of the semiconductor packages disclosed in the Figures. 
     The present disclosure is directed to various embodiments of a semiconductor package containing a MEMS die that includes an air cavity, which may be referred to as a space, a cavity, and an opening, that separates the MEMS die from a substrate of the semiconductor package and exposes a sensor component or MEMS element of the MEMS die to an external environment. A molding compound or encapsulant of the semiconductor package is around the MEMS die and is in direct contact with the MEMS die to hold the MEMS die within the semiconductor package and protect the MEMS die. 
       FIG. 1A  is directed to a cross-sectional view of an embodiment of a semiconductor package  100   a . The semiconductor package  100   a  includes a substrate  102  on one side of the semiconductor package  100   a.  The substrate  102  includes an insulating polymeric core and conductive connections, conductive contacts, and conductive vias that are on or in the insulating polymeric core. The conductive connections, the conductive contacts, and the conductive vias are utilized for supplying signals and power to a die  110 ,  116   a  in the semiconductor package  100   a.  For example, the die may be an applied specific integrated circuit (ASIC) die  110  or a micro-electromechanical system (MEMS) die  116   a  that are electrically coupled to the conductive connections, the conductive contacts, and the conductive vias of the substrate  102  of the semiconductor package  100   a.    
     The MEMS die  116   a  includes a sensor element  118 , which may be a pressure sensor, a temperature sensor, a sound sensor, or any other type of MEMS sensor. The sensor element  118  in  FIG. 1A  is a place holder for any structure for a sensor element  118  of the MEMS die  116   a.  For example, structures of the sensor element  118  of the MEMS die  116   a  will be discussed in greater detail with respect to possible structures of a sensor element of a MEMS die  116   b,    116   c  in  FIGS. 1B and 1C . 
     In this embodiment, the ASIC die  110  and the MEMS die  116   a  are coupled to a surface of the substrate  102 . This surface of the substrate  102  includes a first contact pad  117  coupled to the ASIC die  110  and a second contact pad  119  coupled to the MEMS die  116   a  through respective bonding wires  112 ,  124 . A bottom surface  101  of the substrate  102  faces away from the MEMS die  116   a  and the ASIC die  110 . The bottom surface  101  of the substrate  102  includes a plurality of contact pads  121  that are electrically coupled to the first contact pad  117  and the second contact pad  119  through conductive vias or other connectors in the substrate  102  as discussed above, which are not shown in the Figures for simplicity. 
     The ASIC die  110  is coupled to the substrate by an adhesive or a coupling material  108 , which may be a conductive adhesive, a non-conductive adhesive, a die attach film, or any other material utilized for attaching a die to a substrate. The adhesive or coupling material  108  is coupled to a bottom surface  151  of the ASIC die  110  and the top surface  103  of the substrate  102 . A top surface  153  of the ASIC die  110  includes a contact pad  114  coupled to active and passive components in the substrate  102  by a bonding wire  112 , and a contact pad  111  coupled to a contact pad  115  of the MEMS die  116   a  by another bonding wire  113 . The bottom surface  151  of the ASIC die  110  faces the top surface  103  of the substrate  102  and the top surface  153  of the ASIC die  110  faces away from the top surface  103  of the substrate  102 . 
     The bonding wire  112  coupling the ASIC die  110  to the substrate  102  includes an end coupled to the contact pad  114  and an end coupled to active or passive components within the substrate  102  through the contact pad  117 . The bonding wire  112  allows electrical signals and power to be supplied to the ASIC die  110  from other electrical components as discussed earlier. The bonding wire allows electrical signals to be sent by the ASIC die  110  to other electrical components. These electrical signals may be instruction signals, control signals, data signals, or any other types of electrical signals for communicating information between electrical components within an electronic device. 
     Similarly, the bonding wire  113  coupling the contact pad  111  of the ASIC die  110  to the contact pad  115  of the MEMS die  116   a  includes an end coupled to the contact pad  111  of the ASIC die  110  and an end coupled to the contact pad  115  of the MEMS die  116   a.  The bonding wire  113  allows electrical signals to be transmitted from the ASIC die  110  to the MEMS die  116   a,  and vice versa. These electrical signals may be instruction signals, control signals, data signals, or any other types of electrical signals for communicating information between electrical components. The contact pad  115  may be coupled to the sensor element  118  of the MEMS die  116   a  through a conductive connection such as a conductive via. 
     The MEMS die  116   a  includes a contact pad  122  that is coupled to a conductive via  120  and a bonding wire  124 . The conductive via  120  extends through the MEMS die  116   a  from the contact pad  122  to a sensor element  118  and couples the contact pad  122  to the sensor element  118 . 
     The contact pad  122  of the MEMS die  116   a  is coupled to an end of the bonding wire  124  and another end of the bonding wire  124  is coupled to the second contact pad  119  in the substrate  102 . The bonding wire  124  transmits electrical signals from the MEMS die  116   a  to external electrical components and transmits electrical signals from external electrical components to the MEMS die  116   a.  These electrical signals may be instruction signals, control signals, data signals, or any other types of electrical signals for communicating information between electrical components. 
     The semiconductor package  100   a  includes an air cavity  106 , which may be referred to as a space, an opening, or a cavity. The air cavity  106  is positioned between a bottom surface  105  of the MEMS die  116   a,  which includes the sensor element  118 , and a top surface  103  of the substrate  102  facing the MEMS die  116   a.  The air cavity  106  separates the bottom surface  105  of the MEMS die  116   a  and the top surface  103  of the substrate  102 . 
     The air cavity  106  is in fluid communication and is aligned with an opening  104  that extends through the substrate  102 . The opening  104  may be circular, rectangular, square, triangular, or any other shape as desired. The opening  104  in the substrate allows the air cavity  106  to be exposed to the external environment and allows the sensor element  118  to be exposed to the external environment. The sensor element  118  monitors a physical quantity or quality of the external environment such as pressure, temperature, sound, or any other quantity or quality of the external environment as desired. 
     The air cavity  106  extends from a first sidewall  141  of the MEMS die  116   a  to a second sidewall  143  of the MEMS die  116   a.  In other words, in this embodiment, the air cavity  106  has a width that is substantially equal to a width of the MEMS die  116   a.  The air cavity  106  has a width that is substantially equal to the width of the MEMS die  116   a  because the air cavity may be slightly larger or slightly smaller when the semiconductor package is manufactured in a manner to produce an air cavity with a width equal to a width of a MEMS die. This understanding of the use of “substantially,” will also apply to other similar uses of the word “substantially” in the present disclosure. 
     In alternative embodiments, an air cavity positioned between and separating a MEMS die from a substrate may extend past sidewalls of the MEMS die and have a width that is greater than a width of the MEMS die, or have a width that is less than the width of the MEMS die. 
     In this embodiment of the semiconductor package  100   a,  the sensor element  118  is aligned with the opening  104  in this substrate  102 . However, in alternative embodiments of a semiconductor package, a MEMS element of a MEMS die may not be aligned with an opening that extends through the substrate. Instead, in alternative embodiments of a semiconductor package, a MEMS element of a MEMS die may be offset from an opening that extends through a substrate. 
     In this embodiment, a molding compound  126  covers a top surface  107  of the MEMS die  116   a,  which includes the contact pads  115 ,  122 , and covers the sidewalls  141 ,  143  of the MEMS die  116   a.  The bottom surface  105  of the MEMS die  116   a  that the sensor element  118  is on is left exposed. The sensor element  118  is exposed to the external environment through the air cavity  106  and the opening  104  in the substrate  102  because the air cavity  106  and the opening  104  in the substrate  102  are in fluid communication. 
     The molding compound  126  may be an encapsulant material, an insulating material, or some other combination of materials. The direct contact of the molding compound  126  with the sidewalls  141 ,  143  of the MEMS die  116   a  holds the MEMS die  116   a  in position within the semiconductor package  100   a  such that the air cavity  106  separates the MEMS die  116   a  from the substrate  102 . In other words, the MEMS die  116   a  is not in physical contact with the substrate  102 . 
     In this embodiment, the air cavity  106  has a height H 1  that is less than a height H 2  of the substrate  102 . However, in alternative embodiments, an air cavity between a MEMS die and a substrate may have a height that is greater than a height of the substrate. In another alternative embodiment, an air cavity between a MEMS die and a substrate may have a height that is substantially equal to a height of the substrate. 
     In this embodiment, the molding compound  126  has a thickness T 1  that extends from the surface of the substrate  102  that faces the MEMS die  116   a  and the ASIC die  110  to the surface of the molding compound  126  that faces away from the substrate  102 . The air cavity  106  has a height H 1  that is less than a height H 2  of the opening  104  that extends through the substrate  102 . The MEMS die  116   a  has a height H 3 . The addition of the height H 1  of the air cavity  106  and the height H 3  of the MEMS die  116   a  is less than the thickness T 1  of the molding compound  126 . 
     Semiconductor packages  100   b,    100   c  according to alternate embodiments are illustrated in  FIGS. 1B and 1C . The semiconductor packages  100   b,    100   c  include similar features as discussed above with respect to the semiconductor package  100   a  in  FIG. 1A  and reference numbers may be repeated for the sake of simplicity and brevity. In addition, only different details in these alternative embodiments of semiconductor packages  100   b,    100   c  will be discussed for the sake of simplicity and brevity. However, the alternative embodiments provide possible structures that may be incorporated into the MEMS die  116   a in  FIG. 1A  as for the sensor element  118 , which is a place holder for a more complex structure of the sensor element  118 . 
       FIG. 1B  is directed to a cross-sectional view of the semiconductor package  100   b  containing a MEMS die  116   b  and an ASIC die  110 . The semiconductor package  100   b  includes several features that are similar to those in the semiconductor package  100   a  in  FIG. 1A . However, in the semiconductor package  100   b,  a sensor component  129  is shown on a surface of the MEMS die  116   b.  The sensor component  129 , which is a cantilever pressure sensor, senses pressure of the external environment. The sensor component  129  may be electrically coupled to the conductive via  120 , the contact pad  122 , and the bonding wire  124  that is coupled to the second contact pad  119  of the substrate  102 . While the sensor component  129  is shown as only being a cantilever beam pressure sensor for simplicity, the sensor component  129  may include a number of electrical contacts, a cavity in the MEMS die  116   b  that is aligned with the cantilever beam, and other active and passive components. 
     A cap  125  is coupled to a surface of the MEMS die  116   b  that faces towards the substrate  102 . The cap overlays the sensor component  129  of the MEMS die  116   b  and forms a cavity  127  that surrounds the sensor component  129  of the MEMS die  116   b.  The cap  125  further includes an opening  123  that extends through the cap  125  that exposes the sensor component  129  to the external environment. The opening  123  of the cap  125  is in fluid communication with the air cavity  106  that is positioned between the cap  125  and the substrate  102 , and the air cavity  106  is in fluid communication with the opening  104  that extends through the substrate  102 . 
     In this alternative embodiment, the molding compound  126  covers the sidewalls  141 ,  143  of the MEMS die  116   b,  a top surface  107  of the MEMS die  116   b  that faces away from the substrate  102 , and sidewalls  145 ,  147  of the cap  125 . Similar to the molding compound  126  in the semiconductor package  100   a,  the molding compound  126  in the semiconductor package  100   b  is in direct contact with the sidewalls  141 ,  143  of the MEMS die  116   b  and the sidewalls  145 ,  147  of the cap  125  such that the air cavity  106  separates the MEMS die  116   b  and the cap  125  from the substrate  102 . In other words, the cap  125  of the MEMS die  116   b  is not in physical contact with the substrate  102 . 
     In the semiconductor package  100   b,  the cap  125  is on and coupled to the bottom surface  105  of the MEMS die  116   b.  The bottom surface  105  faces the top surface  103  of the substrate  102 . The cap  125  has a bottom surface  155  that faces the top surface  103  of the substrate  102 . The bottom surface  155  of the cap  125  is spaced apart from the top surface  103  of the substrate  102  by the air cavity  106 . 
     In the semiconductor package  100   b,  the opening  123  in the cap  125  is offset from the opening  104  that extends through the substrate  102 . However, in other alternative embodiments, the opening  123  in the cap  125  may be aligned with the opening  104  in the substrate  102 . 
     The opening  123  in the cap  125  has a width W 1 that is less than a width W 2  of the opening  104  that is in the substrate  102 . However, in other alternative embodiments, the width W 1  of the opening  123  in the cap  125  may be greater than or equal to the width W 2  of the opening  104  in the substrate  102 . 
     In the semiconductor package  100   b,  the cap  125  and the sensor component  129  may be incorporated in the semiconductor package  100   a  in  FIG. 1A  where the sensor element  118  is positioned in  FIG. 1A . In other words, the structure of the cap  125  and the sensor component  129  may be the sensor element  118  in the semiconductor package  100   a . However, in other alternative embodiments of a semiconductor package, the sensor element  118  may have a different structure. For example, the structure of a sensor component  133  of the MEMS die  116   c  in  FIG. 1C  is different. 
       FIG. 1C  is directed to a cross-sectional view of the semiconductor package  100   c  containing the MEMS die  116   c  and the ASIC die  110 . The semiconductor package  100   c  includes several features that are similar to those in the semiconductor packages  100   a ,  100   b  in  FIGS. 1A-1B . However, in this alternative embodiment of the semiconductor package  100   c , the sensor component  133  is a thin membrane that detects sounds or vibrations. 
     The MEMS die  116   c  includes a first internal cavity  131  on a first side of the sensor component  133  and a second internal cavity  135  that is on a second side of the sensor component  133  opposite to the first side of the sensor component  133 . The sensor component  133  separates the first internal cavity  131  from the second internal cavity  135  of the MEMS die  116   c . An opening  137  extends into the MEMS die  116   c  and is in fluid communication with the first internal cavity  131 , the air cavity  106  that separates the MEMS die  116   c  from the substrate  102 , and the opening  104  that extends through the substrate  102 . Accordingly, the opening  104 , air cavity  106 , and first internal cavity  131  expose the sensor component  133  of the MEMS die  116   c  to the external environment. 
     In this alternative embodiment of the semiconductor package  100   c,  the opening  137  in the MEMS die  116   c  has a width W 3  that is less than a width W 4  of the opening  104  that is in the substrate  102 . However, in other alternative embodiments, the width W 3  of the opening  123  in the cap  125  may be greater than or equal to the width W 4  of the opening  104  in the substrate  102 . 
     In the semiconductor package  100   c,  the opening  137  is aligned with the opening  104  in the substrate  102 . However, in other alternative embodiments, the opening  137  may be offset from the opening  104 . 
     In the semiconductor package  100   c,  the molding compound  126  covers the top surface  103  and sidewalls  141 ,  143  of the MEMS die  116   c.  The direct contact of the molding compound  126  with the sidewalls  141 ,  143  of the MEMS die  116   c  holds the MEMS die  116   c  in position within the semiconductor package  100   a  such that the air cavity  106  separates the MEMS die  116   c  from the substrate  102 . In other words, the MEMS die  116   c  is not in physical contact with the substrate  102 . 
     In the semiconductor package  100   c,  the first internal cavity  131 , the sensor component  133 , and the second internal cavity  135  correspond to the sensor element  118  in the semiconductor package  100   a.  However, in other alternative embodiments of a semiconductor package, the sensor element  118  may have a different structure. Accordingly, the sensor element  118  in  FIG. 1A  can have any desired structure for monitoring a quality or physical quantity of an external environment such as pressure, temperature, sound, light, or any other quality or quantity of an external environment as desired, and is not simply limited to those structures described in  FIGS. 1B-1C . 
     In the semiconductor packages  100   a,    100   b,    100   c  in  FIGS. 1A-1C , a plurality of walls  139  of the molding compound  126  are flush with the plurality of sidewalls  141 ,  143  of the MEMS die  116   a,    116   b,    116   c.  The walls  139  of the molding compound  126  are around the air cavity  106 . However, in alternative embodiments of semiconductor packages, the walls  139  may not be flush or co-planar with the plurality of sidewalls  141 ,  143  of the MEMS die  116   a,    116   b,    116   c  of a semiconductor package. Instead or in addition, a portion of the molding compound  126  may be on the bottom surface  105  of the MEMS die  116   a,    116   b,    116   c  facing the substrate  102 , or the walls  139  may be positioned inwardly from the plurality of sidewalls  141 ,  143  of the MEMS die  116   a,    116   b,    116   c . Alternatively, the walls  139  could be spaced apart from the plurality of sidewalls  141 ,  143  of the MEMS die  116   a,    116   b,    116   c  to give the air cavity  106  a width greater than the MEMS die  116   a,    116   b,    116   c.    
       FIG. 2A  is a cross-sectional view of a semiconductor package  200   a  that contains a MEMS die  216  and an ASIC die  210 , according to an alternate embodiment. The ASIC die  210  and the MEMS die  216  are coupled to a top surface  203  of the substrate  202 . The ASIC die  210  is coupled to the top surface  203  of the substrate  202  by an adhesive or coupling material  208  on a bottom surface  251  of the ASIC die  210 , which may be a conductive adhesive, a non-conductive adhesive, a die attach film, or any other adhesive material as desired. The MEMS die  216  includes a sensor element  218 . 
     The top surface  203  of the substrate  202  includes a first contact pad  217  that is coupled to a contact  214  on a top surface  253  of the ASIC die  210  by a bonding wire  212 . Unlike the semiconductor packages  100   a,    100   b,    100   c  in  FIGS. 1A-1C , the ASIC die  210  is in electrical communication with a MEMS die  216  through conductive elements in the substrate  202 , which are not shown for simplicity. For example, the conductive elements in the substrate  202  may be conductive vias, conductive connectors, or some other conductive connection that couples. Alternatively, respective contact pads of a plurality of contact pads  221  on a bottom surface  201  of the substrate  202  that faces away from the ASIC die  210  and the MEMS die  216  are coupled to contact pads  217 ,  225  on a top surface  203  of the substrate  202  that faces the ASIC die  210  and the MEMS die  216 . Alternatively, a respective contact pad  217  of the substrate  202  coupled to the ASIC and a respective contact pad of a plurality of contact pads  225  of the substrate  202  coupled to the MEMS die  216  may be electrically coupled to each other by conductive elements within the substrate  202 , which again are not shown for simplicity. 
     The plurality of contact pads  225  on the substrate  202  are coupled to a plurality of contact pads  222  on a bottom surface  205  of the MEMS die  216 . The bottom surface  205  of the MEMS die  216  faces the top surface  203  of the substrate  202 . Each contact pad of the plurality of contact pads  222  of the MEMS die  216  is aligned with and coupled to a respective contact pad  225  of the substrate  202 . The contact pads  222  of the MEMS die  216  are coupled to the contact pads  225  of the substrate  202  by solder balls  220  that are present within an air cavity  206  that separates the substrate  202  from the MEMS die  216 . 
     In this embodiment, the solder balls  220  are spaced apart from sidewalls  227  of the molding compound  224  that are flush with sidewalls  241 ,  243  of the MEMS die  216 . The sidewalls  227  of the molding compound  224  are around the air cavity  206 . However, in alternative embodiments of the semiconductor package  200   a,  the solder balls  220  may be in contact or cover these walls of the molding compound  224 . Also, the solder balls  220  could be replaced by other known conductive connectors, such as pins and conductive adhesives. 
     In this embodiment, the molding compound has sidewalls  227  that are flush and co-planar with the sidewalls  241  of the MEMS die  216  similar to the walls  139  in  FIGS. 1A-1C . However, in alternative embodiments, the molding compound  224  may extend onto the bottom surface  205  of the MEMS die  216  that faces the substrate  202 , a portion of the molding compound  224  may be on the bottom surface  205  of the MEMS die  216 , or the walls  139  may be positioned inwardly from the plurality of sidewalls  241  of the MEMS die  216 . In another alternative embodiment, the sidewalls  227  may be positioned outwardly from the plurality of sidewalls  241 ,  243  of the MEMS die  216 . 
     The air cavity  206  may be referred to as a space, an opening, or a cavity. The air cavity  206  is positioned between the bottom surface  205  of the MEMS die  216  that the sensor element  218  is on and a top surface  203  of the substrate  202  that is facing the MEMS die  216 . The air cavity  206  separates the bottom surface  205  of the MEMS die  216  and the top surface  203  of the substrate  202 . 
     An opening  204  extending through the substrate  202  is in fluid communication and is aligned with the air cavity  206 . The opening  204  may be circular, rectangular, square, triangular, or any other shaped opening as desired. The opening  204  in the substrate  202  allows the air cavity  206  and the sensor element  218  to be exposed to the external environment. 
     The sensor element  218  monitors a quantity or quality of the external environment such as pressure, temperature, sound, or any other quantity or quality of the external environment as desired. The air cavity  206  extends from a first respective sidewall  241  of the MEMS die  216  to a second respective sidewall  241  of the MEMS die  216 . In this embodiment, the air cavity  206  has a width that is substantially equal to a width to the MEMS die  216 . However, in alternative embodiments, the air cavity  206  may extend past sidewalls of the MEMS die and have a width that is greater than a width of the MEMS die, or have a width that is less than the width of the MEMS die. 
     Unlike the semiconductor packages  100   a,    100   b,    100   c  in  FIGS. 1A-1C , in this embodiment to the semiconductor package  200   a  in  FIG. 2A , the MEMS die  216  has a top surface  207  that faces away from the substrate  202 . The top surface  207  is flush or co-planar with a top surface  223  of a molding compound  224  that faces away from the substrate  202 . This allows the semiconductor package  200   a  to be manufactured to be thinner than the semiconductor packages  100   a,    100   b,    100   c  in  FIGS. 1A-1C . 
     In the semiconductor package  200   a,  the molding compound  224  has a thickness T 2  that extends from the top surface  203  of the substrate  202  to the top surface  223  of the molding compound  224  that faces away from the substrate  202 . The air cavity  206  and the solder balls  220  have a height H 4  that is less than a height H 5  of the opening  204  that extends through the substrate  202 . The MEMS die  216  has a height H 6 . The height H 4  of the air cavity  206  and solder balls  220 , the height H 5  of the opening  204 , and the height H 6  of the MEMS die  216  are all less than the thickness T 2  of the molding compound  224 . The addition of the height H 4  of the air cavity  206  and the solder balls  220  and the height H 6  of the MEMS die  216  is substantially equal to the thickness T 2  of the molding compound  224 . 
       FIG. 2B  is directed to a semiconductor package  200   b  that is similar to the semiconductor package  200   a.  The features of the semiconductor package are the same, however, the molding compound  224  covers the plurality of sidewalls  241 ,  243  of the MEMS die  216 , and covers the top surface  207  of the MEMS die  216 . The molding compound  224  has a thickness T 3  that is greater than the addition of the height H 4  of the air cavity  206  and the height H 6  of the MEMS die  216 . 
       FIG. 3  is a cross-sectional view of a semiconductor package  400 . The features of the semiconductor package  400  are similar to those in the semiconductor package  100   a  in  FIG. 1A  and are provided similar reference numerals. However, in the semiconductor package  400 , the ASIC die  110  is coupled to the top surface  107  of MEMS die  116   a  that faces away from the substrate  102  by an adhesive  418 . The adhesive  418  may be a conductive adhesive, a non-conductive adhesive, or some other adhesive. For example, if the adhesive  418  is a conductive adhesive, the ASIC die  110  may be electrically coupled to the MEMS die  216  by the conductive adhesive. 
     In this embodiment, the air cavity  106  has a height H 7 , and the substrate  102  and the opening  104  have a height H 8  that is greater than the height H 7  of the air cavity  106 . In alternative embodiments, the height H 7  of the air cavity  106  may be greater than or equal to the height H 8  of the substrate  102 . 
     The MEMS die  116   a  has a height H 9  and the ASIC die  110  has a height H 10 . In this embodiment, the height H 9  of the MEMS die  116   a  is greater than the height H 10  of the ASIC die  110 . In alternative embodiments, the height H 9  of a MEMS die  116   a  may be less than or equal to the height H 10  of the ASIC die  110 . 
     The molding compound  126  has a thickness T 4  that extends from a top surface  103  of the substrate  102  that is facing the MEMS die  116   a  and the ASIC die  110 . The thickness T 4  of the molding compound  126  is greater than the addition of the height H 7  of the air cavity  106 , the height H 9  of the MEMS die  116   a,  and the height H 10  of the ASIC die  110 . The molding compound  126  covers sidewalls  141 ,  143 , which may be referred to as a right sidewall  141  and a left sidewall  143 , of the MEMS die  116   a  and covers sidewalls  141 ,  143  of the ASIC die  110 . The molding compound  126  holds the MEMS die  116   a  in a position that is spaced apart by the air cavity  106  from the substrate  102 . In other words, the MEMS die  116   a  is not in physical contact with the substrate  102 . 
     The ASIC die  110  includes the contact pad  114  that is coupled to a contact pad  117  on the top surface  103  of the substrate  102  that faces towards the MEMS die  116   a  and the ASIC die  110 . Similar to the contact pad  119  of the substrate  102  that is coupled to the MEMS die  116   a  utilizing the bonding wire  124 , the contact pad  117  of the substrate  102  is coupled to the contact pad  114  of the ASIC die  110  by a bonding wire  424 . The contact pad  117  is coupled to at least one contact pad  121  of the plurality of contact pads  121 . 
     In this embodiment of the semiconductor package  400  in  FIG. 3 , walls  139  of the molding compound  126  are flush with sidewalls  141 ,  143  of the MEMS die  116   a.  The walls  139  of the molding compound  126  are around the air cavity  106 . However, in alternative embodiments of semiconductor packages, the walls  139  may not be flush or co-planar with the plurality of sidewalls  141 ,  143  of the MEMS die  116   a  of the semiconductor package  400 . Instead, the walls  139  may be on the bottom surface  105  of the MEMS die  116   a  facing the substrate  102 , a portion of the molding compound  126  may be on the bottom surface  105  of the MEMS die  116   a,  or the walls  139  may be positioned inwardly from the sidewalls  141 ,  143  of the MEMS die  116   a.  Alternatively, the sidewalls  141 ,  143  of the MEMS die  116   a  may be positioned closer to the opening  104  in the substrate  102  than the walls  139 . In other words, the air cavity  106  may have a width greater than the MEMS die  116   a,  or the walls  139  may be positioned outwardly from the sidewalls  141 ,  143  of the MEMS die  116   a.    
     These above embodiments of the semiconductor packages  100   a,    100   b,    100   c,    200   a ,  200   b,    400  are thinner than semiconductor packages that utilize a cap instead of a molding compound to protect an ASIC die and a MEMS die. The reason these semiconductor packages are thinner than a semiconductor package that utilizes a cap to protect an ASIC die and a MEMS die instead of a molding compound is because a space must be provided between the cap and dies to form bonding wires coupling the dies to a substrate. Instead, when utilizing a molding compound the molding compound can be formed more precisely such that the molding compound has an overall height that is less than the cap and still provide protection for the bonding wires because the molding compound reinforces the bonding wires. Similarly, if a MEMS die is coupled to a substrate using solder balls similar to the semiconductor packages disclosed in  FIGS. 2A-2B , the packages can be made even thinner than utilizing a cap because a surface of the MEMS die can be made flush with a surface of the molding compound, which would be extremely difficult to accomplish utilizing a cap to protect the MEMS die instead. The molding compound surrounds the dice and provides reinforcement unlike a cap as well. 
       FIGS. 4A-4E  are directed to a flowchart for a method of manufacturing the semiconductor packages discussed above. Specifically,  FIGS. 4A-4E  depict the method of manufacturing for the semiconductor package  100   a  in  FIG. 1A . 
     A first step  501  illustrated in  FIG. 4A  includes coupling a MEMS die  116   a  and an ASIC die  110  to a substrate  102 . The MEMS die  116   a  is coupled to the top surface of the substrate  102  by an adhesive or coupling material  504 . In this embodiment, the adhesive or coupling material  504  is a thermally decomposable die attach, thermally decomposable adhesive, thermally decomposable die attach material, or thermally decomposable coupling material. Alternatively the adhesive or coupling material  504  could be other known sacrificial materials. The thermally decomposable die attach  504  covers a surface of the MEMS die  116   a  including a sensor element  118 . The sensor element  118  is covered by the thermally decomposable die attach  504 . The sensor element  118  faces towards the substrate  102 . 
     The thermally decomposable die attach  504  includes sidewalls  543 . In this embodiment, the sidewalls  543  of the thermally decomposable die attach  504  are co-planar or flush with the sidewalls  141 ,  143  of the MEMS die  116   a.  However, in alternative embodiments, the sidewalls  543  of the thermally decomposable die attach  504  may extend outward from the sidewalls  141 ,  143  of the MEMS die  116   a,  may extend inwards from the sidewalls  141 ,  143  of the MEMS die  116   a,  or may extend outwardly or inwardly in any combination as desired. 
     The thermally decomposable die attach  504  may be a tetracyclododecene-based sacrificial polymer (TD) material; a polycarbonate material such as polyethylene carbonate (PEC), polypropylene carbonate (PPC), polycyclohexene carbonate (PCC), copolymer of polypropylene carbonate (PPC) and polycyclohexene carbonate (PCC); a polyoxymethylene (POM) or acetal material; a polynorbornene (PNB) material; a parylene material; or any other thermally decomposable die attach material as desired. However, these thermally decomposable materials are preferred to couple the MEMS die  116   a  to the top surface  103  of the substrate  102  facing the MEMS die  116   a  because these materials can be removed by a heat or temperature generally produced by a reflow oven, which will be discussed in greater detail with respect to  FIG. 4E . The temperature range for decomposing the thermally decomposable die attach  504  is from 240 to 300 degrees Celsius. 
     After the MEMS die  116   a  is coupled to the top surface  103  of the substrate  102  by the thermally decomposable die attach  504 , a contact pad  122  of the MEMS die  116   a  is coupled to a contact pad  119  on the top surface  103  of the substrate  102  by a bonding wire  124 . The contact pad  122  is on a top surface  107  of the MEMS die  116   a  that faces away from the substrate  102 . The bonding wire  124  may be formed utilizing a wire bonding technique such as a wire-bond loop formation technique, a ball bonding technique, a wedge bonding technique, or any other wire bonding technique desired. The bonding wire  124  is formed to have an end coupled to the contact pad  122  on the MEMS die  116   a  and an end that is coupled to a contact pad  119  of the substrate  102  on the top surface  103  of the substrate  102  facing the MEMS die  116   a.    
     The ASIC die  110  is coupled to the top surface  103  of the substrate  102  by an adhesive or coupling material  108 . The adhesive or coupling material  108  is on a bottom surface  151  of the ASIC die  110 . The adhesive or coupling material  108  may be a conductive adhesive, a non-conductive adhesive, or any other adhesive or coupling material  108  desired. However, the adhesive or coupling material  108  is generally not a thermally decomposable die attach, which is unlike the thermally decomposable die attach  504  utilized to couple the MEMS die  116   a  to the substrate  102 . 
     Similar to the MEMS die  116   a,  after the ASIC die  110  is coupled to the top surface  103  of the substrate  102  by the adhesive or the coupling material  108 , a contact pad  114  of the ASIC die  110  is coupled to a contact pad  117  on a top surface  103  of the substrate  102  facing the ASIC die  110  by a bonding wire  112 . The contact pad  114  is on a top surface  153  of the ASIC die  110  facing away from the substrate  102 . The bonding wire  112  may be formed utilizing a wire bonding technique such as a wire-bond loop formation technique, a ball bonding technique, a wedge bonding technique, or any other wire bonding technique desired. The bonding wire  112  is formed to have an end coupled to the contact pad  114  on the top surface  153  of the ASIC die  110  and an end that is coupled to a contact pad  117  on the top surface  103  of the substrate  102 . The contact pad  117  on the top surface  103  of the substrate  102  coupled to the contact pad  114  by the bonding wire  112  is coupled to at least one external contact pad  121  of a plurality of external contact pads  121  on the bottom surface  101  of the substrate  102 . The external contact pad  121  is coupled to external electrical components and is in electrical communication with external electrical components. Accordingly, the contact pad  114  of the ASIC die  110 , the bonding wire  112 , the contact pad  117  on the top surface  103  of the substrate  102 , and the at least one contact pad  121  of the plurality of contact pads  121  on the bottom surface  101  of the substrate  102  allow the ASIC die  110  to electrically communicate with external electrical components outside the semiconductor package  100   a.    
     A bonding wire  113  extends from a contact pad  111  on the top surface  153  of the ASIC die  110  to a contact pad  115  on the top surface  107  of the MEMS die  116   a.  The bonding wire  112  may be formed utilizing a wire bonding technique such as a wire-bond loop formation technique, a ball bonding technique, a wedge bonding technique, or any other wire bonding technique desired. However, in an alternative embodiment of a semiconductor package, the contact pad  111  of the ASIC die  110  and the contact pad  115  on the MEMS die  116   a  may not be present and, accordingly, the bonding wire  113  may not be present either. 
     A second step  503  illustrated in  FIG. 4B  includes forming a molding compound  126  to surround the MEMS die  116   a,  the ASIC die  110 , the bonding wires  112 ,  113 ,  124 , the adhesive or the coupling material  108 , and the thermally decomposable die attach  504 . The molding compound  126  is on the top surface  103  of the substrate  102 . The molding compound  126  covers and is in direct contact with the top surface  153  of the ASIC die  110  and the top surface  107  of the MEMS die  116   a.  The molding compound  126  covers and is in direct contact with a plurality of sidewalls  141 ,  143  of the MEMS die  116   a,  and the molding compound  126  covers and is in direct contact with a plurality of sidewalls of the ASIC die  110 . The molding compound  126  may be formed utilizing injection molding, pressure and compression molding, strip molding, or any other molding compound formation technique. The molding compound  126  is formed such that the molding compound  126  will hold the MEMS die  116   a  in a stationary position within the semiconductor package allowing the air cavity  106  to separate the bottom surface  105  of the MEMS die  116   a  from the top surface  103  of the substrate  102 . However, this will be discussed in greater detail later. 
     A third step  505  illustrated in  FIG. 4C  includes forming an opening  104  in the substrate  102 . The opening  104  in the substrate  102  extends from the bottom surface  101  of the substrate  102  to the top surface  103  of the substrate  102 . The opening  104  exposes the thermally decomposable die attach  504  that couples the MEMS die  116   a  to the substrate  102 . The opening  104  is formed in the substrate  102  by removing a portion of the substrate  102  that is aligned with the sensor element  118  of the MEMS die  116   a.  The portion of the substrate  102  that is removed to form the opening  104  may be removed utilizing a laser drilling technique, a cutting technique, an etching technique, or some other type of removal technique as desired. However, in the preferred embodiment of the third step  505 , a laser drilling technique is utilized to form the opening  104 . When forming the opening  104  utilizing the laser drilling technique, a portion of the thermally decomposable die attach  504  may be removed as well, due to the heat of the laser when forming the opening  104  in the substrate  102  to expose the thermally decomposable die attach  504 . The opening  104  is formed in the substrate  102  to eventually be utilized to expose the air cavity  106 , which is aligned with the sensor element  118 , and the sensor element  118  to an external environment of the semiconductor package  100   a.  However, this will be discussed in greater detail later. 
     In an alternative embodiment, the third step  505  in  FIG. 4D  may be completed before coupling the MEMS die  116   a  to the substrate  102 . However, in that case, the MEMS die  116   a  should be thick enough such that when the molding compound  126  is later formed to cover the MEMS die  116   a,  the MEMS die  116   a  is thick enough to resist a pressure applied to the MEMS die  116   a  when the molding compound  126  is formed. Otherwise, if the MEMS die  116   a  is not thick enough in this alternative method, the MEMS die  116   a  may be cracked when the molding compound  126  is formed on the MEMS die  116   a.  Accordingly, the preferred embodiment is forming the opening  104  in the substrate  102  aligned with the MEMS die  116   a  after the MEMS die  116   a  and the molding compound  126  are formed on the substrate  102 . 
     A fourth step  507  illustrated in  FIG. 4E  includes exposing the thermally decomposable die attach  504  to heat. The opening  104  formed in the third step is utilized to expose the thermally decomposable die attach  504  to heat produced by a heat source  526 . The heat source  526  may be a light heat source, a reflow oven, or any other heat source desired. However, the preferred option in this case is to utilize a reflow oven as the heat source  526 . A reflow oven generally appropriately heats semiconductor packages present within the reflow oven without harming or damaging other active and passive components within the semiconductor package. A reflow oven is also beneficial as it may be used in the formation of reflow of a solder material to form solder connections within a semiconductor package. 
     As discussed earlier in the description of  FIG. 4A , the thermally decomposable die attach  504  may be several materials that can be decomposed with a temperature or heat produced by the heat source  526 . For example, generally, the reflow oven is used to produce a temperature between 240-260° C. to decompose the thermally decomposable die attach  504 . However, in alternative embodiments of this method, the heat source  526  may produce temperatures greater than or less than the range of temperatures between 240-260° C. The length of time that the semiconductor package and the thermally conductive adhesive  504  are exposed to the temperature provided by the reflow oven or heat source  526  will depend on the size of the overall semiconductor package, the amount of thermally decomposable die attach  504 , the type of dies that are present within the semiconductor package, as well as several other factors. 
       FIG. 4E  is directed to a completed semiconductor package  100   a  after the thermally decomposable die attach  504  is decomposed by exposure to heat. By removing the thermally decomposable die attach  504  in the fourth step  507 , the air cavity  106 , which is positioned between the MEMS die  116   a  and the substrate  102 , is formed. The air cavity  106  separates the substrate  102  from the MEMS die  116   a  such that the MEMS die  116   a  is physically separate from the substrate  102 . 
     While the following discussion is directed to the semiconductor package  100   a  in  FIG. 1A  for simplicity and brevity, the following discussion also applies to the alternative embodiments of the semiconductor package  100   b,    100   c,    200   a,    200   b,    400  in  FIGS. 1B-1C, 2A-2B, and 3 . 
     As discussed earlier, the thermally decomposable die attach  504  is utilized to form the air cavity  106 . This thermally decomposable die attach  504  allows the air cavity  106  to be formed between MEMS die  116   a  and the substrate  102  after the molding compound  126  has been formed on the MEMS die  116   a,  the ASIC die  110 , and the substrate  102 . By removing the thermally decomposable die attach  504  after the molding compound  126  is formed, no cap is required to be coupled to the substrate  102  to protect the MEMS die  116   a  and the ASIC  110  on the substrate  102 . Instead, the molding compound  116   a  protects the ASIC die  110  and the MEMS die  116   a  from external stresses and forces that may cause failure in the ASIC die  110  and the MEMS die  116   a.  By removing the necessity of a cap to protect the ASIC die  110  and the MEMS die  116   a,  the cost of manufacturing materials is decreased because no caps are needed to form a semiconductor package and no high-precision machines and tools need to be utilized to couple the cap to the substrate  102 . The yield of usable packages formed by this method is increased as well because coupling a cap to the substrate  102  to protect the ASIC die  110  and the MEMS die  116   a  requires high precision tools and high precision accuracy. Accordingly, by removing the need of this high precision process to place the cap, the tolerances to form a semiconductor package are much more lenient and tolerant than compared to high precision tolerances when positioning a cap on the semiconductor package. In other words, when a cap is utilized to protect a semiconductor die and to form a semiconductor package, alignment issues of the cap occur frequently when the cap is being coupled to a substrate to protect a die of a semiconductor package. 
     By utilizing the molding compound  126  and thermally decomposable die attach  504  to form the semiconductor package  100   a,  the semiconductor package  100   a  can be made even thinner. The semiconductor package  100   a  can be made thinner because clearance between the bonding wires  113 ,  124  and a surface of the molding compound  126  facing away from the substrate  102  is less than when a cap is utilized to protect the components of the semiconductor package. Accordingly, a semiconductor package can be manufactured thinner than a semiconductor package when utilizing a cap to protect a MEMS die and an ASIC die. 
     In an alternative embodiment, a molding compound  224  can be made flush with a surface of the MEMS die in a semiconductor package  200   a.  For example, as illustrated in  FIG. 2A , the molding compound  224  in the semiconductor package  200   a  is flush with the top surface  207  of the MEMS die  216  facing away from the substrate  202 . 
     By utilizing the molding compound  126  and thermally decomposable die attach  504  to form the molding compound  126  to protect the MEMS die  116   a  and the ASIC die  110  less steps are required to form a completed package, and the lead time is reduced to manufacture a completed semiconductor package  100   a.  The lead time is reduced because coupling a cap to the substrate  102  in the correct position to protect the MEMS die  116   a  and the ASIC die  110  is a high precision process, and because this is a high precision process, this is a relatively time-insensitive process as well. By removing the need of the cap, several steps can be removed from a method of manufacturing when a cap is not needed to form the semiconductor package  100   a.  For example, no adhesive needs to be placed or formed to couple the cap to the substrate  102 , the cap does not need to be placed, and high precision placement tools do not need to be utilized to form the semiconductor package  100   a.  Instead, utilizing the molding compound  126  to cover the MEMS die  116   a  and the ASIC die  110 , which protects the MEMS die  116   a  and the ASIC die  110 , the lead time for producing the semiconductor package  100   a  can be reduced significantly because a cap does not need to be placed on each individual ASIC die  110  and the MEMS die  116   a.    
       FIG. 5  is directed to a step  509  in a method of forming the semiconductor packages  200   a,    200   b  in  FIGS. 2A-2B . In this method of forming the semiconductor packages  200   a,    200   b,  the method is similar to the method of forming the semiconductor package  100   a  in  FIGS. 4A-4E . However, unlike the method of forming the semiconductor package  100   a  in  FIGS. 4A-4E , no bonding wires are coupled to a MEMS die  216  in the semiconductor packages  200   a,    200   b.  While the following discussion applies to both the semiconductor package  200   a,    200   b  in  FIGS. 2A-2B , the following discussion will only reference the semiconductor package  200   a  in  FIG. 2A  for simplicity and brevity, and will only discuss differences when in view of the method of forming the semiconductor package  100   a  in  FIG. 1A  as discussed earlier. 
     The first step  509  of this method of forming the semiconductor package  200   a  is illustrated in  FIG. 5 . In this method, a plurality of solder balls  220  are coupled to a plurality of contact pads  222  that are on the bottom surface  205  of the MEMS die  216  that has a sensor element  218  and faces the substrate  202 . Each respective solder ball  220  of the plurality of solder balls  220  is aligned with a respective contact pad  225  of a plurality of contact pads  225  on the top surface  203  of the substrate  202  facing the MEMS die  216 . The plurality of solder balls  220  are surrounded by the thermally decomposable die attach or material  504  that couples the MEMS die  216  to the substrate  202 . The plurality of solder balls  220  are in contact with the plurality of contact pads  225 . However, in alternative embodiments of this method, a portion of the thermally decomposable die attach  504  may separate each respective solder ball  220  of the plurality of solder balls  220  from the plurality of contact pads  225  on the substrate  202 . The first step  501  illustrated in  FIG. 4B  may be utilized to form semiconductor packages  200   a,    200   b  as illustrated in  FIGS. 2A-2B . 
     When forming the air cavity  206  in  FIGS. 2A-2B , the thermally decomposable die attach  504  on the bottom surface  205  of the MEMS die  216  has sidewalls  543  that are flush with the sidewalls  241 ,  243  of the MEMS die  216 . In an alternative embodiment, the sidewalls  543  of the thermally decomposable die attach  504  may extend outwardly from the sidewalls  241 ,  243  of the MEMS die  216 , which means that the width of the thermally decomposable die attach  504  is greater than the width of the MEMS die  216 . Alternatively, in another alternative embodiment, the sidewalls  543  of the thermally decomposable die attach  504  may extend inwardly from the sidewalls  241 ,  243  of the MEMS die  216 , which means that the width of the thermally decomposable die attach  504  is less than the width of the MEMS die  216 . 
     Alternatively, when alternative first step  509  in  FIG. 5  is utilized in this process, the thermally decomposable die attach  504  is exposed to a heat from a heat source  526 , which may be a reflow oven, to remove the thermally decomposable die attach  504  to form the air cavity  206 . The heat from the heat source  526  causes the plurality of solder balls  220  to reflow at the same time the thermally decomposable material  504  is decomposed and removed. As the plurality of solder balls  220  are reflowed by the heat from the heat source  526 , the plurality of solder balls  220  couple the plurality of contact pads  225  on the top surface  203  of the substrate  202  to the plurality of contact pads  222  on the bottom surface  205  of the MEMS die  216 . This forms an electrical connection between the MEMS die  216  and the substrate  202 . The completion of this reflow of the plurality of solder balls  220  can be seen in  FIGS. 2A-2B  as discussed earlier. Also, the solder balls  220  could be replaced by other known conductive connectors, such as pins and conductive adhesives that may initially be present in the thermally decomposable die attach  504 . 
       FIG. 6  is directed to an electronic device  602  that includes a semiconductor package  604 . The semiconductor package  604  is based on the embodiments discussed above in  FIGS. 1A-3  or a semiconductor package within the scope of  FIGS. 1A-3  and is manufactured utilizing a manufacturing method disclosed in  FIGS. 4A-4F  or a method within the scope of  FIGS. 4A-4F . 
     In the electronic device  602 , the semiconductor package  604  is electrically coupled to a microprocessor  606  that is within the electronic device  602 . The microprocessor  606  sends electrical signals to the semiconductor package  604  and the microprocessor  606  receives electrical signals from the semiconductor package  604 . For example, the microprocessor  606  may transmit power signals, command signals, or any other signals to control or power the semiconductor package  604 . Conversely, the semiconductor package  604  may transmit data signals, information signals, or any other signals to provide feedback, data, or information to the microprocessor  606  utilized to control the electronic device  602 . The semiconductor package  604  and the microprocessor  606  may be coupled by electrical connections such as a wire, an conductive via, a PCB, or any other electrical connection as desired. For example, in relation to the semiconductor package in  FIG. 1A , the ASIC die  110  receives and transmits power and electrical signals from and to the power source  608 , the microprocessor  606 , and the memory  610  that the substrate  102  is in electrical communication. Because the ASIC die  110  is coupled to the substrate  102 , the ASIC die  110  is in electrical communication with the power source  608 , the microprocessor  606 , and the memory  610 . 
     The microprocessor  606  is coupled to a power source  608 . The microprocessor  606  directs and controls where power from the power source is supplied. For example, the microprocessor  606  controls and transmits a percentage of power from the power supply to the semiconductor package, controls and transmits another percentage of power to a touch display of the electronic device, and controls and transmits the amount of power supplied to each electrical component within the electronic device  602 . 
     The microprocessor  606  is coupled to a memory  610 . The microprocessor  606  sends data or information to the memory  610  for storage. For example, the microprocessor  606  may transmit data or information signals received from the semiconductor package  604  to the memory  610  for storage. Alternatively, the microprocessor  606  may transmit any other data or information signals from any other electronic component within the electronic device to which the microprocessor  606  is coupled. 
     The various embodiments described above can be combined to provide further embodiments. These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.