Microphone package with integrated substrate

MEMS microphone packages are described that include an ASIC integrated in the base substrate of the package housing. Methods of manufacturing the same and methods for separating individual microphone packages from wafer form assembly arrays are also described.

BACKGROUND

The present invention relates to microphone system packages and singulation methods for extracting and separating individual packages from an array of packages in wafer form.

SUMMARY

Some existing microphone packages include a package housing configured to form a cavity within. A MEMS microphone component can be coupled to an interior surface of the base layer of the package housing. An application specific integrated circuit (ASIC) or other control circuit is also mounted to the interior surface of the base layer. The ASIC is configured to communicate electric signals from the MEMS microphone component and to provide some control functionality of the microphone component. The ASIC is formed on a chip that includes mounting hardware and bond pads to provide for electrical and physical interconnect between the ASIC chip and the microphone package housing.

When microphone packages of this type are manufactured in array form (i.e., a plurality of microphone packages formed as a single original wafer and cleaved/separated into individual packages), the base layer of the package (and the ASIC chip itself) must be of a minimum thickness to provide for secure physical support of the MEMS device and the ASIC chip during assembly and separation from wafer form. Furthermore, the package must be designed to provide a sufficient saw street width between the microphone packages.

In some embodiments, the invention provides a MEMS microphone package with an ASIC integrated as part of the silicon substrate base layer. As a result, a separate ASIC chip does not need to be mounted inside the package cavity during manufacture. Furthermore, because the bond pad and other interconnect mechanisms are not required between the substrate base of the microphone and a separate ASIC chip, layout density and overall size of the microphone package are reduced. Substrate thickness is also reduced as compared to die-in-substrate solutions that use a separate ASIC chip as there is no minimum thickness requirement for ASIC handling during lamination into a secondary substrate assembly.

In one embodiment, the invention provides a MEMS microphone package that includes a base substrate layer, a lid, and a MEMS microphone component positioned within a package cavity. The base substrate layer includes an acoustic port opening configured to allow acoustic pressures to reach the MEMS microphone component inside the package cavity. An application specific integrated circuit is formed as an integrated part of the base substrate layer. The MEMS microphone component is electrically coupled to the application specific integrated circuit of the base substrate layer.

In another embodiment, the invention provides a method of forming a plurality of MEMS microphone packages. A silicon substrate base layer is provided and a silicon substrate spacer layer is coupled to the base layer. A silicon substrate lid layer is coupled to the spacer layer opposite the base layer. The spacer layer has been etched to form an array of microphone package cavities. A stealth dice is performed to define laser scribe lines through the spacer layer between each of the MEMS microphone packages. The MEMS microphone component is coupled to the base layer and electrical interconnects are made after the spacer layer has been bonded to the substrate base and may be done either before or after the stealth dice is performed on the spacer layer. An application specific integrated circuit is formed as an integrated part of the base layer. A first partial saw cut of the base layer and a second partial saw cut of the lid layer are performed after coupling the MEMS microphone component to the base layer. The partial saw cut completely separates the base layer and the lid layer, respectively, along the laser scribe lines in the spacer layer, but does not fully separate the spacer layer. After the partial saw cuts are performed, the MEMS microphone devices are separated by performing a tape expansion to fracture the silicon substrate base layer along the laser scribe lines.

In still another embodiment, the invention provides a method of separating a plurality of MEMS microphone packages from an array of MEMS microphone packages. The array includes a silicon substrate top lid layer, a silicon substrate base layer, and a silicon substrate spacer layer etched to define a plurality of microphone package cavities. An application specific integrated circuit is formed in the base layer in each of the plurality of the microphone package cavities and an acoustic port opening is formed through the base layer in each of the microphone package cavities. A MEMS microphone component is also coupled to the base layer in each of the microphone package cavities. The method of separating the MEMS microphone packages includes performing a stealth dice of the spacer layer to define laser scribe lines. The stealth dice is performed before the MEMS microphone component is coupled to the base layer in each microphone package cavity. After the MEMS microphone components are coupled to the base layer, a first partial saw cut of the base layer and a second partial saw cut of the lid layer are performed. The partial saw cuts completely separate the base layer and the lid layer, respectively, along the laser scribe lines, but do not fully separate the spacer layer. After the partial saw etches are performed, the MEMS microphone devices are separated by performing a tape expansion to fracture the silicon substrate base layer along the laser scribe lines.

DETAILED DESCRIPTION

FIG. 1Ashows a first construction of a silicon microphone package100. The package housing is formed of a silicon substrate base layer101, a silicon substrate spacer layer103, and a silicon substrate lid layer105. As illustrated in further detail below, the spacer layer103is at least partially hollowed to form a cavity inside the microphone package housing. A tapered edge107is etched around an acoustic port opening109in the base layer101. The tapered edge107reduces acoustic impedance as compared to a purely cylindrical acoustic port. A series of three electrical contacts111are also positioned on the exterior surface of the base layer101. As described in further detail below, these contacts111provide for electrical signal communication with an application specific integrated circuit (ASIC) that is formed as a integrated part of the base layer101and MEMS microphone component that is mounted on an internal surface of the base layer101.

As shown inFIG. 1B, in this example, no acoustic port openings are formed in the lid layer105, nor are any electrical contacts, circuit components, or through silicon vias on the lid layer105. However, in some alternative constructions, an ASIC can be integrated into the silicon substrate of the lid layer105instead of (or in addition to) the silicon substrate of the base layer101. Furthermore, the construction illustrated inFIGS. 1A and 1Bis a bottom-ported microphone package. In other “top-ported” microphone packages, the acoustic port opening is formed through the lid layer105instead of the base layer101.

FIG. 1Cshows the microphone package100with the lid layer105removed to illustrate the arrangement and configuration of components inside the microphone package. As noted above, the spacer layer103is etched to form a hollow cavity113inside the microphone package100. A MEMS microphone component115is positioned within the cavity113and coupled to the base layer105. The MEMS microphone component115in this example includes a diaphragm117that physically moves in response to acoustic pressures that enter through the acoustic port opening109. The movement of the microphone diaphragm117causes a change in the capacitance of the microphone component115. This change in capacitance generates a voltage signal that can be electrically communicated to components outside of the microphone package through the electrical contacts111.

The ASIC119is integrated into the remaining portion of the silicon base layer101. As illustrated in the cross-sectional view ofFIG. 1D, one or more active circuit components121are formed in the portion of the base layer substrate101containing the ASIC119. Re-distribution layers (RDLs) are used on the top and bottom surface of the base layer substrate101to form the necessary interconnect structures such as wire bond/flip chip bond pads for the MEMS die, connections to the active circuitry, and land pads for the I/O interface on the exterior surface of the base layer substrate101. In the example ofFIG. 1D, a series of electrical traces123are also provided on the top (interior) surface of the base layer substrate101. These traces and electrical interconnects on the interior and exterior surfaces of the base layer substrate are tied together through the use of through-silicon electrical vias (TSVs). Additional routing layers may be added to the top and/or bottom surface of the base layer substrate101through traditional silicon processing techniques including, for example, bonded materials such as polyimide routing patches, ultra-thin silicon die, redistribution layers (RDL) or metallization layers used in the integrated circuit fabrication process. These additional routing layers are used to construct passive devices (e.g., resistors, capacitors, inductors, etc.) or for additional space for signal interconnects.

The cross-sectional view ofFIG. 1Eillustrates the mechanical operation of the MEMS microphone component115mounted to the base layer substrate101inside the cavity113of the microphone package100. Additional space in the cavity113between the MEMS microphone component115and the lid layer105allows for movement of the microphone diaphragm. Furthermore, as noted above, a tapered edge107etched around the acoustic port opening109allows for reduced acoustic impedance as acoustic pressures (i.e., sounds) reach the MEMS microphone component115through the acoustic port opening109.

Because the ASIC119is integrated directly as part of the base layer101of the microphone package, there is no need for mounting hardware between the ASIC and the microphone package housing. Nor is there a need for electrical contact pads to provide for electrical communication between the package housing and a separate ASIC chip. As such, the microphone package100illustrated inFIGS. 1A-1Dallows for reduced size and/or layout density. Furthermore, a microphone package such as described above provides for new techniques for manufacturing an array of microphone packages in wafer form and separating the individual microphone packages from the wafer array.

FIG. 2illustrates one method of manufacturing a plurality of microphone packages in wafer form. An ASIC is formed for each microphone package in the array on a substrate that will serve as the base layer base (step201). An acoustic port opening is also etched into base substrate for each microphone package (step203). A spacer layer substrate is then etched to form the package cavity for each microphone package (step205). The etched spacer layer substrate is then coupled to the base layer substrate (step207).

A stealth dice is then performed through the spacer layer (step209) leaving the base substrate layer intact. The depth of the laser stealth dice is controlled such that lattice disruption is confined to the spacer layer wafer. From this point in the assembly, the substrate wafer provides mechanical structure needed to maintain the packages in an arrayed format suitable for assembly. A MEMS die is then coupled to the base substrate layer in each of the microphone cavities and electrical connections are made to the corresponding ASIC previously built into the base substrate layer (step211). A lid layer substrate wafer is then placed to seal each individual microphone package cavity (step213).

After assembly of each package in the array (e.g., spacer wafer, MEMS die, wire bonds, lid wafer), a partial saw cut is performed on the top and bottom surface of the package such that the lid layer and the base layer are singulated leaving only the spacer layer intact. As shown inFIG. 3, the stealth dice (step209) defines laser scribe lines301through the spacer layer103between each microphone package in the array. A first partial saw cut (step215) cuts the lid layer105along the same pattern as the laser scribe lines301. A second partial saw cut (step217) also cuts the base layer101along the same pattern as the laser scribe lines301. As shown inFIG. 3, the first partial saw pass303cuts completely through the lid layer105and partially through the spacer layer103. Similarly, the second partial saw pass305cuts completely through the base layer101and partially through the spacer layer103. After the partial saw cuts are completed, separation of the spacer layer103is achieved through tape expansion (step219) to fracture the package along the laser scribe lines that were made earlier (i.e., during step209).

The examples described above provide a bottom-ported microphone package. However, as noted above, other configurations are possible. For example, a top-ported microphone package can be assembled by a process similar to the one illustrated inFIG. 2. However, in the top-ported construction, patterned silicon wafers are used on both the top and bottom layers of the package (i.e., the base layer101and the lid layer105). One or more through-silicon vias (TSVs) are formed through the spacer layer to make electrical connection between the lid layer and the base layer of the package. The MEMS device in some top-ported constructions is mounted on the internal surface of the lid layer while portions of the ASIC are formed in both the lid layer and the base layer as required by the specific details of the package design and the microphone functionality provided by the ASIC.

Furthermore, in the examples discussed above, the microphone packages are formed by etching silicon layers to form a cavity. However, in other constructions, discrete lid components can be mounted directly to the base substrate layer to form the cavity. One such construction is illustrated inFIG. 4. The base layer401of the microphone package400is much the same as the base layer101illustrated inFIG. 1Aabove. A tapered edge403is etched around an acoustic port opening405that is formed through the base layer401. A series of electrical contacts407provide for electrical communication with an ASIC that is integrated into the silicon substrate of the base layer401. However, instead of including an etched spacer layer and a silicon lid layer to form the cavity on the interior surface of the base layer401, a separate lid component409is coupled to the rear surface of the base substrate layer401to define a cavity.

Also like the constructions described above, the microphone package400ofFIG. 4can be formed as an array of microphone packages on a single wafer. However, because only a single layer needs to be singulated (i.e., the base layer401), stealth dicing can be performed to extract individual units from the assembly array. Because this type of dicing requires a near-zero width saw street, the overall package size and the array size can be significantly reduced by eliminating the need to maintain clearances (i.e., the saw street or dicing street) between the individual components in the array wafer.

Thus, the invention provides, among other things, a MEMS microphone device package with an ASIC integrated into the base substrate of the microphone package as well as method of manufacturing such microphone packages and separating individual microphone packages from an assembly array. Various features and advantages of the invention are set forth in the following claims.