U.S. patent application number 12/979625 was filed with the patent office on 2012-06-28 for package with a cmos die positioned underneath a mems die.
Invention is credited to Daniel Giesecke, Peter V. Loeppert, Anthony Minervini, Jeffery Niew.
Application Number | 20120161258 12/979625 |
Document ID | / |
Family ID | 46315616 |
Filed Date | 2012-06-28 |
United States Patent
Application |
20120161258 |
Kind Code |
A1 |
Loeppert; Peter V. ; et
al. |
June 28, 2012 |
PACKAGE WITH A CMOS DIE POSITIONED UNDERNEATH A MEMS DIE
Abstract
A package is provided. The package has a substrate and a cover.
A MEMS die is provided having a diaphragm. A CMOS die is provided
wherein at least a portion of the CMOS die is positioned between
the diaphragm and the substrate.
Inventors: |
Loeppert; Peter V.; (Hoffman
Estates, IL) ; Niew; Jeffery; (Burr Ridge, IL)
; Minervini; Anthony; (Palos Hills, IL) ;
Giesecke; Daniel; (West Chicago, IL) |
Family ID: |
46315616 |
Appl. No.: |
12/979625 |
Filed: |
December 28, 2010 |
Current U.S.
Class: |
257/416 ;
257/E29.324 |
Current CPC
Class: |
H01L 2924/1461 20130101;
H01L 2224/48137 20130101; H01L 2924/00014 20130101; H01L 2224/05553
20130101; H01L 2224/16225 20130101; H04R 2499/11 20130101; H01L
2224/48265 20130101; H01L 24/16 20130101; H01L 2224/48227 20130101;
H01L 2924/00014 20130101; H01L 2924/19107 20130101; H01L 2224/48195
20130101; H01L 25/165 20130101; H04R 19/04 20130101; H01L
2924/16151 20130101; H04R 31/00 20130101; H01L 2224/48265 20130101;
H01L 2924/16251 20130101; H01L 2924/00014 20130101; H01L 2224/48471
20130101; H01L 24/48 20130101; H01L 2224/48195 20130101; H01L
2924/15151 20130101; H04R 19/005 20130101; H01L 2224/45015
20130101; H01L 2924/207 20130101; H01L 2224/45099 20130101; H01L
2924/00014 20130101; H01L 2924/00014 20130101 |
Class at
Publication: |
257/416 ;
257/E29.324 |
International
Class: |
H01L 29/84 20060101
H01L029/84 |
Claims
1. A package comprising: a substrate; a cover; a MEMS die located
on the substrate; a CMOS die located underneath the MEMS die having
a volume; an acoustic port in the package, wherein the package has
a back volume located between the MEMS die and the substrate;
wherein an effective back volume exists which is equal to the back
volume minus the volume of the CMOS die.
2. The package of claim 1 wherein the acoustic port is in the
cover.
3. The package of claim 1 wherein the acoustic port is in the
substrate.
4. The package of claim 1 further comprising: a channel created
within the MEMS die wherein the CMOS die is partially nested
underneath the MEMS die.
5. A package comprising: a substrate; a cover; a MEMS die located
on the substrate; a CMOS die located underneath the MEMS die having
a volume; an acoustic port in the package, wherein the package has
a front volume located between the MEMS die and the substrate;
wherein an effective front volume exists which is equal to the
front volume minus the volume of the CMOS die.
6. The package of claim 5 wherein the acoustic port is in the
substrate.
7. The package of claim 5 wherein the acoustic port is positioned
adjacent to the CMOS die.
8. A package comprising: a substrate; a cover; a MEMS die having
sidewalls and a diaphragm connected to the sidewalls; a CMOS die
positioned on the substrate, underneath the MEMS die and surrounded
by the sidewalls of the MEMS die.
9. The package of claim 8 further comprising: an acoustic port
within the cover.
10. The package of claim 8 further comprising: an acoustic port
within the substrate.
11. A package comprising: a substrate; a cover; a MEMS die having
sidewalls and a diaphragm connected to the sidewalls; a CMOS die
positioned on the substrate, partially underneath the MEMS die and
through a channel in a sidewall of the MEMS die.
12. The package of claim 11 further comprising: a sealant enclosing
a portion of the CMOS die which is positioned exterior to the MEMS
die.
13. The package of claim 11 further comprising: an acoustic port
within the substrate.
14. The package of claim 11 further comprising: an acoustic port
within the cover.
15. A package comprising: a substrate; a cover; a MEMS die having a
diaphragm; a CMOS die wherein at least a portion of the CMOS die is
positioned between the diaphragm and the substrate.
16. The package of claim 15 wherein the CMOS die is contained
within sidewalls of the MEMS die.
17. The package of claim 15 wherein the CMOS die extends through a
channel in the MEMS die.
18. The package of claim 17 further comprising: a sealant enclosing
a portion of the CMOS die which extends exterior to the MEMS
die.
19. The package of claim 15 further comprising: an acoustic port
within the substrate.
20. The package of claim 15 further comprising: an acoustic port
within the cover.
Description
TECHNICAL FIELD
[0001] This invention relates to packages for MEMS transducers and
particularly to MEMS packages with a reduced footprint.
BACKGROUND
[0002] It has been known in the art to build packages for
containing micro-electromechanical systems ("MEMS") microphones. A
typical package includes the MEMS transducer die, along with a
separate complimentary metal-oxide-semiconductor ("CMOS") die for
amplification of the signal arising from the MEMS transducer die.
These die are mounted onto a substrate in a side-by-side formation
within a package and wire bonded to each other and the substrate.
For an example of this type of configuration, one can reference
U.S. Pat. Nos. 6,781,231 and 7,242,089, the disclosures of which
are incorporated herein by reference (including materials used to
construct such types of packages, MEMS dies, and CMOS dies;
dimension ranges for all parts/components; mechanical and/or
electrical coupling methods; and any related manufacturing
details). FIG. 1 also provides an example of this configuration. A
package 101 comprises a substrate 102 and a cover 103. The package
101 has a MEMS transducer die 104 and a CMOS die 106 attached to
the substrate 102. Because of the location of an acoustic port 108
above the transducer 104, a diaphragm 105 of the transducer 104
divides the package 101 into a back volume 107 and a front volume
109 (adjacent to the acoustic port 108). It is desirable to reduce
the footprint of packages, such as those described above, to better
fit into a variety of consumer electronic devices, such as cell
phones, music players, computing devices, etc.
[0003] To this end, attempts have been made to stack the dies of a
given package to reduce the footprint of the package. See, for
example, the package 201 of FIG. 2. In this configuration, a CMOS
die 206 is placed at least partially under a MEMS die 204 to reduce
the footprint of the package. A major drawback with placement of
the CMOS die 206 underneath the MEMS die 204 is that by doing so,
either the height of the package is increased or if the MEMS die
204 is thinned, the back volume 207 of the package is decreased,
thereby negatively impacting the microphone sensitivity and signal
to noise ratio. It is at least one objective of the present
invention to address this drawback.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] For a more complete understanding of the disclosure,
reference should be made to the following detailed description and
accompanying drawings wherein:
[0005] FIG. 1 is a cross-sectional view of a prior art package
containing a separate CMOS and MEMS die in a side by side
configuration;
[0006] FIG. 2 is a cross-sectional view of a prior art package
comprising separate CMOS and MEMS die in a stacked
configuration;
[0007] FIG. 3 is a cross-sectional view of a package having a CMOS
die located underneath a MEMS die in an embodiment of the present
invention;
[0008] FIG. 4 is a cross-sectional view of a further embodiment of
the present invention in which a package has a CMOS die located
under a MEMS die, wherein the CMOS die is flip chip mounted, and
the MEMS die is wire bonded, and wherein the acoustic port is
located in a substrate;
[0009] FIG. 5 is a cross-sectional view of a further embodiment of
a package of the present invention in which a package has a CMOS
die located under a MEMS die, and wherein the acoustic port is
located in a substrate underneath the MEMS die;
[0010] FIG. 6 is a cross-sectional view of a further embodiment of
a package of the present invention in which a package has a CMOS
die located under a MEMS die, wherein the acoustic port is located
in a substrate but offset from the CMOS die;
[0011] FIG. 7 is a bottom perspective view of a MEMS die in an
embodiment of the present invention, whereby the MEMS die contains
a partial cut through the sidewalls of a back chamber;
[0012] FIG. 8 is a perspective view of an embodiment of the present
invention in which a CMOS die is partially nested under a MEMS die
containing a partial cut through the sidewalls of the back chamber;
and
[0013] FIG. 9 is a cross-sectional view of a package in an
embodiment of the present invention in which a CMOS die is
partially nested under a MEMS die with a partial cut through the
sidewalls of the back chamber and wherein the MEMS die has channels
associated therewith.
DETAILED DESCRIPTION OF THE INVENTION
[0014] While the invention of the present disclosure is susceptible
to various modifications and alternative forms, certain embodiments
are shown by way of example in the drawings and these embodiments
will be described in detail herein. It will be understood, however,
that this disclosure is not intended to limit the invention to the
particular forms described, but to the contrary, the invention is
intended to cover all modifications, alternatives, and equivalents
falling within the spirit and scope of the invention defined by the
appended claims. Moreover, it is understood that like numerals will
refer to like parts.
[0015] As mentioned above, the diaphragm of a MEMS microphone
effectively divides the package into two acoustic volumes, denoted
the front volume and the back volume. The front volume is the
portion of the package which is adjacent to the acoustic port while
the back volume is that portion of the package which is on the side
of the diaphragm opposite to where the acoustic port is located,
The size of the back volume is a key acoustic parameter and
contributes to the microphone sensitivity and signal to noise
ratio. Maximization of the back volume can lead to maximization of
the acoustic performance of the microphone.
[0016] In an embodiment, a package is provided. The package has a
substrate and a cover. A MEMS die is located on the substrate. A
CMOS die is located underneath the MEMS die. The CMOS die has a
volume. An acoustic port is located in the package, wherein the
package has a back volume located between the MEMS die and the
substrate. An effective back volume exists which is equal to the
back volume minus the volume of the CMOS die.
[0017] In an embodiment, the acoustic port is in the cover,
[0018] In an embodiment, the acoustic port is in the substrate.
[0019] In an embodiment, the package has a channel created within
the MEMS die wherein the CMOS die is partially nested underneath
the MEMS die.
[0020] In another embodiment, a package is provided. The package
has a substrate and a cover. A MEMS die is located on the
substrate. A CMOS die is located underneath the MEMS die. The CMOS
die has a volume. An acoustic port is provided in the package,
wherein the package has a front volume located between the MEMS die
and the substrate. An effective front volume exists which is equal
to the front volume minus the volume of the CMOS die.
[0021] In an embodiment, the acoustic port is located in the
substrate,
[0022] In an embodiment, the acoustic port is positioned adjacent
to the CMOS die.
[0023] In another embodiment, a package is provided. The package
has a substrate and a cover. A MEMS die is provided which has
sidewalls and a diaphragm connected to the sidewalls. A CMOS die is
positioned on the substrate, underneath the MEMS die and surrounded
by the sidewalls of the MEMS die.
[0024] In an embodiment, the package has an acoustic port within
the cover.
[0025] In an embodiment, the package has an acoustic port within
the substrate.
[0026] In another embodiment, a package is provided. The package
has a substrate and a cover. A MEMS die is provided having
sidewalls and a diaphragm connected to the sidewalls. A CMOS die is
positioned on the substrate, partially underneath the MEMS die and
through a channel in a sidewall of the MEMS die.
[0027] In an embodiment, the package has a sealant enclosing a
portion of the CMOS die which is positioned exterior to the MEMS
die.
[0028] In an embodiment, the package has an acoustic port within
the substrate.
[0029] In an embodiment, the package has an acoustic port within
the cover.
[0030] In another embodiment, a package is provided. The package
has a substrate and a cover. A MEMS die is provided having a
diaphragm. A CMOS die is provided wherein at least a portion of the
CMOS die is positioned between the diaphragm and the substrate.
[0031] In an embodiment, the CMOS die is contained within sidewalls
of the MEMS die.
[0032] In an embodiment, the CMOS die extends through a channel in
the MEMS die.
[0033] In an embodiment, the package has a sealant enclosing a
portion of the CMOS die which extends exterior to the MEMS die.
[0034] In an embodiment, the package has an acoustic port within
the substrate.
[0035] In an embodiment, the package has an acoustic port within
the cover.
[0036] The present invention seeks to counter the teachings against
placing the CMOS die underneath the MEMS die and thereby reducing
the volume underneath the MEMS die. In a first embodiment of the
present invention, illustrated in FIG. 3, a package 301 contains a
CMOS die 306 underneath a MEMS transducer die 304. An acoustic port
308 is above the MEMS die 304; therefore, the package 301 has a
front volume 309 and a back volume 307 on a side of a diaphragm 305
opposite to the acoustic port 308, In order to reduce the footprint
of the package 301, it is possible to increase the dimensions of
the MEMS die 304 to accommodate the placement of the CMOS die 306
underneath the MEMS die 304 and within the back chamber or back
volume 307 of the MEMS die 304. The increased back chamber volume
307, less the volume of the CMOS die 306, will provide an overall
back volume that will exceed the back volume of the conventional
implementation that is known in the art, i.e., that of FIG. 1.
Increasing the dimensions of the MEMS die 304 may increase the
overall cost of manufacture of the MEMS die 304. However, the
increased cost is compensated by the overall reduced size and/or
cost of the package. Thus, a package having a reduced footprint is
achieved with the same or better performance acoustically, while
demonstrating a cost comparable to that of a conventional package
known in the art.
[0037] The following is an embodiment of the present invention in
which, for example, the package 301 is configured to provide an
acoustic performance similar to the package 101. Assuming the MEMS
die 104 in FIG. 1 has dimensions 1.1 mm.times.1.1 mm.times.0.4mm,
with a back chamber having dimensions that are 0.74 mm.times.0.74
mm.times.0.4 mm, the back chamber volume (otherwise understood as
the volume underneath the diaphragm 305) is 0.22 mm 3. The CMOS die
106 has dimensions of 0.5 mm.times.0.5 mm.times.0.2 mm for a volume
of 0.05 mm 3. To achieve the same level of performance in the
embodiment in FIG, 3 as that in FIG. 1, the dimensions of the MEMS
die 304 must increase to 1.2 mm.times.1.2 mm.times.0.4 mm, to
provide a back chamber having dimensions of 0.84 mm.times.0.84
mm.times.0.4 mm. This provides a back chamber volume of 0.28mm 3.
When the CMOS die 306 is placed underneath and within the back
chamber of the MEMS die 304, the effective back volume (or volume
of back chamber minus the volume of the CMOS die 306) becomes
0.23mm 3 which is slightly larger than that of the back volume 107
of the package 101 of FIG. 1. Thus, a slightly better performance
can be achieved by nesting the CMOS die under the larger-sized MEMS
die. The larger MEMS die may be, for example, 20% more expensive to
manufacture; however, the package size (and therefore, cost) can be
reduced to compensate for the increased cost of the MEMS.
[0038] Referring now to FIG. 4, an embodiment is shown in which a
package 401 (having substrate 402 and cover 403) contains a MEMS
die 404 and a CMOS die 406 located underneath the MEMS die 404. The
entire CMOS die 406 is located between sidewalls 414 of the MEMS
die 404. The CMOS die 406 is shown as flip chip bonded while the
MEMS die 404 is wire bonded. It should be understood, however, that
any type of coupling known to those skilled in the art is
contemplated, The MEMS die 404 may have dimensions such that an
overall or effective back volume 407 of the package 401 (i.e.,
volume underneath the diaphragm minus the volume of the CMOS die
406) is sufficient to produce an acoustic performance demonstrated
by conventional transducer packages. In this embodiment, an
acoustic port 408 is provided in the substrate 402 and is adjacent
to the MEMS die 404.
[0039] FIG. 5 illustrates a package 501 in another embodiment of
the present invention. A CMOS die 506 is located underneath a MEMS
transducer die 504, An acoustic port 508 is located under the CMOS
die 506 in substrate 502. Because the acoustic port 508 is located
underneath the MEMS die 504, the back volume 507 is defined as that
portion of the package 501 that is between the cover 503 and the
MEMS die 504. The front volume 509 is that portion under the MEMS
die 504, less the volume of the CMOS die 506. In this case, the
back volume 507 is increased by having the CMOS die 506 in the
front volume 509. Accordingly, the package 501 may demonstrate
sensitivity and signal-to-noise characteristics as seen in
conventional packages while providing a smaller overall
footprint.
[0040] FIG. 6 illustrates an embodiment similar to that of FIG. 5;
however, in this embodiment, the acoustic port 608 is adjacent to
the CMOS die 606, rather than under it. However, both the CMOS die
606 and the acoustic port 608 are under the MEMS die 604. In this
embodiment, the front volume 609 is defined as the volume between
the acoustic port 608 and the diaphragm 605. It is contemplated
that, in this embodiment, the MEMS die 604 may have dimensions, at
least in length and/or width, which are greater than the MEMS die
304, 404, 504 previously described. It is also contemplated that,
in an embodiment, the MEMS die 604 is sized to partially cover the
acoustic port 608. Moreover, it is further contemplated that, in an
embodiment, the acoustic port 608 is located in the substrate 602
but only partially underneath the CMOS die 606.
[0041] Referring now to FIG. 7, a MEMS die 704 is illustrated which
has been modified by etching or cutting a channel 710 partially
through the sidewalls 714 of the back chamber 716. The preferred
method to achieve this channel 710 is by partially dicing with a
dicing saw; however, other methods are available as contemplated by
those of skill in the art. The MEMS die 704 of this embodiment may
be utilized in packages 801 and 901 described below. The channel
710 is rectangular in shape; however, other shapes may be used as
necessary for a given application.
[0042] FIG. 8 shows an isolated view of a MEMS die 804 with a
channel 810 similar to that demonstrated by the MEMS die 704,
wherein the die 804 is mounted to a substrate 802. A CMOS die 806
(shown in dotted line) is also mounted to the substrate 802 and is
partially nested under the MEMS die 806. A portion of the CMOS die
806 protrudes through the channel 810 in the MEMS die 804. The CMOS
die 806 may be connected to the substrate 802 by a variety of well
known methods, including but not limited to, wire bonding,
flip-chip bonding, and through-silicon vias. A sealant material
812, such as silicone, is applied to the sides of the MEMS die 804
to seal the channels 810 on both sides of the die and cover the
CMOS die 806. This isolates the volume under the MEMS die 804 from
the outside. FIG. 9 shows an embodiment of a package 901 that
includes a CMOS die 906 partially nested under a MEMS die 904
having a channel 910 to accommodate the CMOS die 906, i.e., similar
to the embodiment of FIG. 8. A sealant material 912 is applied to
either side of the MEMS die 904 over the channel 910 to isolate the
back volume 907 from the front volume 909. An acoustic port 908
through the cover 903 completes the assembly. In an embodiment, an
acoustic port (not shown in the figure but contemplated based on
previously described embodiments) may be located in the substrate
902 of the package 901. The port may be located underneath or
adjacent to the MEMS die 904. These embodiments may provide desired
sensitivity and signal-to-noise characteristics while still
providing a reduced overall footprint to the package 901.
[0043] Preferred embodiments of this invention are described
herein, including the best mode known to the inventors for carrying
out the invention. It should he understood that the illustrated
embodiments are exemplary only, and should not be taken as limiting
the scope of the invention.
* * * * *