U.S. patent application number 14/564725 was filed with the patent office on 2016-06-09 for mems cavity substrate.
The applicant listed for this patent is InvenSense, Inc.. Invention is credited to Ilya Gurin.
Application Number | 20160159640 14/564725 |
Document ID | / |
Family ID | 55920010 |
Filed Date | 2016-06-09 |
United States Patent
Application |
20160159640 |
Kind Code |
A1 |
Gurin; Ilya |
June 9, 2016 |
MEMS CAVITY SUBSTRATE
Abstract
In accordance with an example embodiment of this disclosure, a
micro-electromechanical system (MEMS) device comprises a substrate,
a CMOS die, and a MEMS die, each of which comprises a top side and
a bottom side. The bottom side of the CMOS die is coupled to the
top side of the substrate, and the MEMS die is coupled to the top
side of the CMOS die, and there is a cavity positioned between the
CMOS die and the substrate. The cavity may be sealed by a sealing
substance, and may be filled with a filler substance (e.g., an
adhesive) that is different than the sealing substance (e.g., a
gaseous or non-gaseous substance). The cavity may be fully or
partially surrounded by one or more downward-protruding portions of
the CMOS die and/or one or more upward-protruding portions of the
substrate.
Inventors: |
Gurin; Ilya; (Mountain View,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
InvenSense, Inc. |
San Jose |
CA |
US |
|
|
Family ID: |
55920010 |
Appl. No.: |
14/564725 |
Filed: |
December 9, 2014 |
Current U.S.
Class: |
257/415 |
Current CPC
Class: |
B81B 2203/0315 20130101;
B81B 7/0048 20130101; B81B 2207/012 20130101; B81C 1/00674
20130101; B81B 7/0058 20130101 |
International
Class: |
B81B 7/00 20060101
B81B007/00 |
Claims
1. A micro-electro-mechanical system (MEMS) device comprising: a
substrate comprising a top side and a bottom side; an integrated
circuit (IC) die comprising a top side and a bottom side, where the
bottom side of the IC die is coupled to the top side of the
substrate; and a MEMS die coupled to the top side of the IC die,
wherein there is a cavity positioned between the IC die and the
substrate.
2. The MEMS device of claim 1, wherein: the cavity is sealed by a
sealing substance; and the cavity is filled with a filler
substance.
3. The MEMS device of claim 2, wherein the sealing substance is an
adhesive and the filler substance is a gas.
4. The MEMS device of claim 2, wherein the sealing substance is an
adhesive and the filler substance is non-gaseous.
5. The MEMS device of claim 1, wherein the cavity is fully or
partially surrounded by one or more downward-protruding portions of
the IC die and/or one or more upward-protruding portions of the
substrate.
6. The MEMS device of claim 1, wherein the cavity is formed, at
least in part, by one or more standoffs inserted between the IC die
and the substrate.
7. The MEMS device of claim 1, wherein the cavity is formed, at
least in part, by removing material from one or both of the bottom
side of the IC die and the top side of the substrate.
8. The MEMS device of claim 1, wherein the cavity is formed, at
least in part, by one or more upward-protruding portions of the
substrate and/or downward-protruding portions of the IC die.
9. The MEMS device of claim 1, wherein a height of the cavity is
formed by a single upward-protruding pedestal of the substrate
and/or a single downward-protruding portion of the IC die.
10. The MEMS device of claim 1, wherein the IC die comprises a
complementary metal-oxide semiconductor (CMOS) die.
11. A micro-electro-mechanical system (MEMS) device comprising: an
interposer comprising a top side and a bottom side; an integrated
circuit (IC) die comprising a top side and a bottom side, where the
bottom side of the IC die is coupled to the top side of the
interposer; and a MEMS die coupled to the top side of the IC die,
wherein there is a cavity positioned between the IC die and the
interposer.
12. The MEMS device of claim 11, wherein: the cavity is sealed by a
sealing substance; and the cavity is filled with a filler substance
that is different from the sealing substance.
13. The MEMS device of claim 12, wherein the sealing substance is
an adhesive and the filler substance is a gas.
14. The MEMS device of claim 12, wherein the sealing substance is
an adhesive and the filler substance is non-gaseous.
15. The MEMS device of claim 11, wherein the cavity is fully or
partially surrounded by one or more downward-protruding portions of
the IC die and/or one or more upward-protruding portions of the
interposer.
16. The MEMS device of claim 11, wherein the cavity is formed, at
least in part, by one or more standoffs inserted between the IC die
and the interposer.
17. The MEMS device of claim 11, wherein the cavity is formed, at
least in part, by removing material from one or both of the bottom
side of the IC die and the top side of the interposer.
18. The MEMS device of claim 11, wherein the cavity is formed, at
least in part, by one or more upward-protruding portions of the
interposer and/or downward-protruding portions of the IC die.
19. The MEMS device of claim 11, wherein a height of the cavity is
formed by a single upward-protruding pedestal of the substrate
and/or a single downward-protruding portion of the IC die.
20. A micro-electro-mechanical system (MEMS) device comprising: a
packaging substrate comprising a top side and a bottom side; an
interposer comprising a top side and a bottom side, where the
bottom side of the interposer is coupled to the top side of the
packaging substrate; an integrated circuit (IC) die comprising a
top side and a bottom side, where the bottom side of the IC die is
coupled to the top side of the interposer; and a MEMS die coupled
to the top side of the IC die, wherein there is a cavity positioned
between the IC die and the interposer.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS/INCORPORATION BY
REFERENCE
[0001] [Not Applicable]
FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] [Not Applicable]
SEQUENCE LISTING
[0003] [Not Applicable]
MICROFICHE/COPYRIGHT REFERENCE
[0004] [Not Applicable]
BACKGROUND
[0005] Various devices, for example MEMS devices, are susceptible
to failure or performance change due to substrate flexing. For
example, a flexing motherboard and/or package substrate may damage
or change the performance parameters of a MEMS structure mounted
thereon.
BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS
[0006] FIG. 1 shows an example electromechanical circuit structure
comprising a stress isolation gap formed in a CMOS die, in
accordance with various aspects of the present disclosure.
[0007] FIG. 2 shows an example electromechanical circuit structure
comprising a stress isolation gap formed in a substrate, in
accordance with various aspects of the present disclosure.
[0008] FIG. 3 shows an example electromechanical circuit structure
comprising a stress isolation gap formed in a CMOS die and in a
substrate, in accordance with various aspects of the present
disclosure.
[0009] FIG. 4 shows an example electromechanical circuit structure
comprising a stress isolation gap formed in a substrate, in
accordance with various aspects of the present disclosure.
[0010] FIG. 5 shows an example electromechanical circuit structure
comprising a stress isolation gap formed in a CMOS die and in a
substrate, in accordance with various aspects of the present
disclosure.
[0011] FIG. 6 shows an example electromechanical circuit structure
comprising a stress isolation gap formed between a CMOS die and a
substrate, in accordance with various aspects of the present
disclosure.
[0012] FIG. 7 shows an example electromechanical circuit structure
comprising a stress isolation gap formed in a CMOS die, in
accordance with various aspects of the present disclosure.
[0013] FIG. 8 shows an example electromechanical circuit structure
comprising a stress isolation gap formed in an interposer, in
accordance with various aspects of the present disclosure.
[0014] FIG. 9 shows an example electromechanical circuit structure
comprising a stress isolation gap formed in a CMOS die and in an
interposer, in accordance with various aspects of the present
disclosure.
[0015] FIG. 10 shows an example electromechanical circuit structure
comprising a stress isolation gap formed in a CMOS die, in
accordance with various aspects of the present disclosure.
[0016] FIG. 11 shows an example electromechanical circuit structure
comprising a stress isolation gap formed in a substrate, in
accordance with various aspects of the present disclosure.
[0017] FIG. 12 shows an example electromechanical circuit structure
comprising a stress isolation gap formed in a CMOS die and in a
substrate, in accordance with various aspects of the present
disclosure.
[0018] FIG. 13 shows an example electromechanical circuit structure
comprising a stress isolation gap formed in a CMOS die, in
accordance with various aspects of the present disclosure.
[0019] FIG. 14 shows an example circuit structure comprising a
stress isolation gap formed in a CMOS die, in accordance with
various aspects of the present disclosure.
SUMMARY
[0020] Various aspects of this disclosure provide a device
structure and method for forming a device structure that is robust
with regard to substrate flexing. In a non-limiting example, an
electromechanical device comprising MEMS and CMOS elements is
formed that comprises a stress isolation gap positioned between the
MEMS/CMOS structure and a substrate.
DETAILED DESCRIPTION OF VARIOUS ASPECTS OF THE DISCLOSURE
[0021] FIG. 1 shows an example electromechanical circuit structure
100 comprising a stress isolation gap formed in a CMOS die, in
accordance with various aspects of the present disclosure.
[0022] The circuit structure 100 may, for example, comprise a
micro-electro-mechanical system (MEMS) die 110. The MEMS die 110
may, for example, comprise at least one of any of a variety of MEMS
structures (e.g., MEMS sensor structures). For example, the MEMS
die 110 may comprise one or more of a gyroscope, a compass, a
magnetometer, an accelerometer, a microphone, a pressure sensor, a
proximity sensor, a moisture sensor, a temperature sensor, a
biometric sensor, and/or an ambient light sensor, among others
known in the art. The MEMS die 110 may, for example, comprise a top
side, a bottom side, and side edges. The top side may, for example,
comprise MEMS sensors and/or other MEMS structures. The bottom side
may, for example, comprise a MEMS substrate. The top and bottom
sides may alternatively be inverted. Though the discussion will
generally refer to a MEMS die 110, it should be understood that the
MEMS die 110 may also be in wafer form (e.g., prior to singulating
the wafer into individual die and/or sets of die).
[0023] The circuit structure 100 may, for example, comprise a CMOS
die 120. The CMOS die 120 may, for example, comprise sensor
processing circuitry (e.g., a motion processing unit, audio signal
processor, biometric signal processor, environmental processor,
etc.). The CMOS die 120 may, for example comprise a top side, a
bottom side, and side edges. The top side may for example comprise
an active semiconductor surface, and the bottom side may for
example comprise an inactive surface. The top and bottom sides may
alternatively be inverted. As with the MEMS die 110, it should be
understood that the CMOS die 120 may also be in wafer form (e.g.,
prior to singulating the wafer into individual die and/or sets of
die). Additionally, though only one CMOS die 120 is illustrated, it
should be understood that a plurality of CMOS die may be stacked at
item 120. Additionally, though a CMOS die is utilized as an
example, in FIG. 1 and in all figures herein, the scope of this
disclosure is by no means limited to a CMOS die. For example, any
of a variety of different types of integrated circuit (or
semiconductor) dies may be utilized without departing from the
spirit and scope of this disclosure.
[0024] The MEMS die 110 may, for example, be coupled to the CMOS
die 120. For example, the bottom side of the MEMS die 110 may be
directly and/or indirectly (e.g., with intervening layers) coupled
to the top side of the CMOS die 120. Such mechanical and/or
electrical coupling may be performed in any of a variety of
manners. In an example embodiment, the first substrate is attached
to the second substrate through wafer bonding, as described in
commonly owned U.S. Pat. No. 7,104,129, which is hereby
incorporated herein by reference in its entirety, to simultaneously
provide electrical connections and hermetically seal the MEMS
devices. The MEMS die 110 and CMOS die 120 may, for example, be
coupled to the CMOS die 130 using solder bonding, adhesive bonding,
etc. The MEMS die 110 and CMOS die 120 may, for example, be
electrically coupled using wire-bonding, TSV technology (e.g., with
backside bumping technology, etc.).
[0025] The circuit structure 100 may, for example, comprise a
substrate 130. The substrate 130 may comprise characteristics of
any of a variety of different substrates. For example, the
substrate 130 may comprise a printed circuit board (PCB), lead
frame paddle, silicon die or wafer, glass, etc. As will be
discussed in greater detail herein, the substrate 130 may comprise
an interposer between the CMOS die 120 and/or another substrate
(e.g., a packaging substrate). Also for example, the substrate 130
may comprise a package substrate, such as may be used to provide
electrical connectivity between circuitry in an electronic package
and an external print circuit board (e.g., a product mother board).
Further for example, the substrate 130 may comprise a mother board
substrate (e.g., a circuit board to which device packages are
typically coupled).
[0026] The CMOS die 120 may, for example, be coupled to the
substrate 130. For example, the bottom side of the CMOS die 120 may
be directly and/or indirectly (e.g., with intervening layers)
coupled to the top side of the substrate 130. The CMOS die 120 may
be coupled to the substrate 130 in any of a variety of manners. For
example, the CMOS die 120 may be mechanically coupled to the
substrate 130 using a die-attach film and/or adhesive, and
electrically coupled to the substrate 130 using wire-bonds 125. In
an example implementation in which die-attach film is utilized to
couple the CMOS die 120 and the substrate 130, the die-attach film
may be formed to coincide with the downward-protruding portions 128
of the CMOS die 120 discussed herein, or alternatively formed to
cover the entire substrate, at least beneath the CMOS die 120. Also
for example, the CMOS die 120 may be mechanically coupled to the
substrate 130 using solder and/or conductive adhesive, and
electrically coupled to the substrate 130 via the solder and
through-silicon vias (TSVs) 127 extending between the top and
bottom sides of the CMOS die 120.
[0027] Coupling the CMOS die 120 to the substrate 130 may, for
example, be performed before and/or after coupling the MEMS die 110
to the CMOS die 120. For example, the MEMS die 120 and the CMOS die
120 may be coupled (e.g., using the technique(s) described in
incorporated U.S. Pat. No. 7,104,129), prior to coupling the CMOS
die 120 (in die or wafer form) to the substrate 130. In another
example, the CMOS die 120 may be coupled to the substrate 130 prior
to coupling the MEMS die 110 to the CMOS die 120.
[0028] All couplings discussed herein may, for example, be
performed at the die and/or wafer level. For example, the MEMS die
110, CMOS die 120, and substrate 130 may all be bonded to each
other at the wafer level prior to singulation into separate circuit
packages.
[0029] The circuit structure 100 comprises a stress isolation gap
140 between the CMOS die 120 and the substrate 130. The gap 140
may, for example, be filled with any gaseous (e.g., air) or
non-gaseous (e.g., foam) substance having a suitable compliance
(inverse of spring constant) that absorbs stress such that stress
transferred from the substrate 130 to the CMOS die 120 and/or MEMS
die 110 is below a level determined likely to cause damage or
performance degradation.
[0030] The gap 140 may, for example, reduce stress on the CMOS die
120 and/or the MEMS die 110 due to flexing of the substrate 130.
For example, the substrate 130 may bow into or away from the gap
140 such that a substantially lower amount of stress is placed on
the CMOS die 120 and/or the MEMS die 110 than would have resulted
without the gap 140. For example, if instead of the gap 140, the
CMOS die 120 and the substrate 130 were tightly coupled over the
entirety of their facing sides, the substrate 130 flexing might
cause the CMOS die 120 (and thus the MEMS die 110) to also flex in
unison. Such flexing of the CMOS die 120 and MEMS die 110 might,
for example, cause the circuit structure 100 to fail, reduce
performance of the circuit structure 100, alter performance
characteristics of the circuit structure 100, etc.
[0031] As shown in FIG. 1, the stress isolation gap 140 may
comprise a cavity formed in the CMOS die 120. The cavity may, for
example, be completely or partially surrounded laterally by one or
more downward-protruding portions 128 of the CMOS die 120. For
example, the downward-protruding portion(s) 128 of the CMOS die 120
may extend fully around the entire perimeter of the CMOS die 120.
Also for example, the downward-protruding portion(s) 128 of the
CMOS die 120 may be segmented into two or more segments, each of
which only extends partially around the perimeter of the CMOS die
120. For example, the downward-protruding portion(s) 128 of the
CMOS die 120 may comprise four corner posts (or feet), each
protruding downward at a respective corner of the CMOS die 120.
Such posts may, for example, comprise a rectangular footprint
(e.g., looking up or down at the post), a circular footprint, an
elliptical footprint, etc. Also for example, as will be discussed
herein, the downward-protruding portion(s) 128 may comprise a
single solid protrusion or pedestal (e.g., extending from the
center of the bottom side of the CMOS die 120, offset from the
center of the CMOS die 120 yet still covering the center, offset
from the center of the CMOS die 120 and not covering the center of
the CMOS die 120, etc.).
[0032] In an example implementation in which wire-bonding is
utilized for electrically coupling the CMOS die 120 to the
substrate 130, the downward-protruding portion(s) 128 of the CMOS
die 120 may be positioned directly below wire-bond pads that are on
the top side of the CMOS die 120. In such a configuration, the
downward-protruding portion(s) 128 may provide structural support
during the wire-bonding process.
[0033] The cavity and/or downward-protruding portion(s) 128 of the
CMOS die 120 may be formed in any of a variety of manners. For
example, the cavity may be etched into the bottom side of the CMOS
die 120. For example, the bottom side (e.g., an inactive surface)
of the CMOS die 120 may be masked at the protruding portions and
chemically etched at the non-masked areas to form the cavity. Also
for example, in an implementation that comprises feet at the
corners of the CMOS die 120, the cavity may be ground into the CMOS
die 120. For example, while the CMOS die 120 is still in wafer
form, a matrix pattern may be ground into the bottom side of the
CMOS die 120 to form the corner feet. The corner feet may, for
example, be formed to protrude orthogonally relative to the primary
plane of the CMOS die 120, for example generally orthogonal to the
top and bottom sides of the CMOS die 120, but may also be formed at
a non-orthogonal angle. The corner feet may, for example, be formed
thin enough to have a spring-like compliance, which may further
isolate the CMOS die 120 and MEMS die 110 from stress due to a
flexing substrate 130.
[0034] Also for example, the downward-protruding portion(s) 128 may
be positively formed on the CMOS die 120 (e.g., as opposed to being
negatively formed by surrounding material being removed). For
example, the downward-protruding portion(s) 128 may be deposited on
the bottom side of the CMOS die. Such downward-protruding
portion(s) 128 may, for example, comprise dielectric material that
is deposited (e.g., printed, sprayed, vapor-deposited, grown in a
MEMS or MEMS-like process, etc.). In an example implementation, the
downward-protruding portion(s) 128 may be formed of deposited
photoresist material. In such an implementation, the deposited
photoresist material may comprise enough adhesion to provide the
mechanical coupling between the CMOS die 120 and the substrate 130
(e.g., after curing).
[0035] Also for example, such downward-protruding portion(s) 128
may be plated (e.g., electrode-based plating, electroless plating,
etc.). In an example implementation, the downward-protruding
portion(s) 128 may comprise a metal post that is plated on the
bottom surface of the CMOS die 120. In such an example
implementation, the metal post may be strictly a mechanical
feature, or may also be utilized as an electrical connection.
Additionally, in a scenario in which the downward-protruding
portion(s) 128 comprise metal posts, other metal posts (e.g., of
different dimensions than the downward-protruding portion(s) 128)
or conductive features may provide electrical connections between
the CMOS die 120 and the substrate 130. For further example, in a
scenario in which the downward-protruding portion(s) 128 comprise
metal posts, wire-bonds may be utilized to provide electrical
connections between the CMOS die 120 and the substrate 130 (e.g.,
bonded to the top side of the CMOS die 120 and the top side of the
substrate 130).
[0036] The stress isolation gap 140 may be characterized by any of
a variety of dimensions. For example, the gap 140 may be at least
10 microns thick. Also for example, the gap 140 may be at least 15
microns thick. In an example implementation, the gap 140 may
comprise a thickness between 1% and 10% of the thickness of the
CMOS die 120. In another example implementation, the gap 140 may
comprise a thickness greater than 10% of the thickness of the CMOS
die 120. The gap 140 may, for example, be at least 80% as wide as
the CMOS die 120. Also for example, the gap 140 may be at least 90%
as wide as the CMOS die 120.
[0037] The stress isolation gap 140 may be formed at various points
in the manufacturing process of the circuit structure 100. For
example, the cavity in the CMOS die 120 corresponding to the gap
140 may be formed after the MEMS die 110 and the CMOS die 120 have
been coupled. Also for example, the cavity in the CMOS die 120
corresponding to the gap 140 may be formed before the MEMS die 110
and CMOS die 120 are coupled.
[0038] Note that although the example structure 100 is illustrated
with a single CMOS layer, a plurality of such layers and/or other
types of layers may be present. In other words, there may be one or
more structural layers between the MEMS die 110 and the CMOS die
120.
[0039] Though the example circuit 100, shown in FIG. 1, shows the
cavity corresponding to the gap 140 formed in the CMOS die 120, the
cavity may alternatively be formed in the substrate 130. An example
of such a configuration will now be discussed.
[0040] FIG. 2 shows an example electromechanical circuit structure
200 comprising a stress isolation gap formed in a substrate, in
accordance with various aspects of the present disclosure. The
example circuit structure 200 may share any or all characteristics
with the example circuit structure 100 illustrated in FIG. 1 and
discussed herein, including production methods thereof.
[0041] The circuit structure 200 may, for example, comprise a
stress isolation gap 240 formed in the substrate 230. As discussed
herein with regard to the CMOS die, a cavity may be formed in the
substrate 230 and positioned below the CMOS die 220 to at least
partially isolate the CMOS die 220 from stresses caused by the
substrate 230 (e.g., by flexing). The CMOS die 220 may then, for
example, span the cavity formed in the substrate 240.
[0042] The circuit structure 200 may, for example, comprise a
substrate 230. The substrate 230 may comprise characteristics of
any of a variety of different substrates. For example, the
substrate 230 may comprise a printed circuit board (PCB), lead
frame paddle, silicon die or wafer, glass, etc. As will be
discussed in greater detail herein, the substrate 230 may comprise
an interposer between the CMOS die 220 and another substrate (e.g.,
a package substrate). Also for example, the substrate 230 may
comprise a package substrate, such as may be used to provide
electrical connectivity between circuitry in an electronic package
and an external printed circuit board (e.g., a product mother
board). Further for example, the substrate 230 may comprise a
mother board substrate (e.g., a circuit board to which device
packages are typically coupled).
[0043] The CMOS die 220 may be coupled to the substrate 230 in any
of a variety of manners. For example, the CMOS die 220 may be
mechanically coupled to the substrate 230 using a die-attach film
and/or adhesive, and electrically coupled to the substrate 230
using wire-bonds (e.g., which are not illustrated in FIG. 2, for
illustrative clarity). In an example implementation in which
die-attach film is utilized to couple the CMOS die 220 and the
substrate 230, the die-attach film may be formed to coincide with
the upward-protruding portion(s) 228 of the substrate 230 discussed
herein, or alternatively formed to cover the entire CMOS die 220,
at least above the substrate 230. Also for example, the CMOS die
220 may be mechanically coupled to the substrate 230 using solder
and/or conductive adhesive, and electrically coupled to the
substrate 230 via the solder and through-silicon vias (TSVs) (e.g.,
which are not illustrated in FIG. 2 or most other figures herein,
for illustrative clarity) extending between the top and bottom
sides of the CMOS die 220.
[0044] Coupling the CMOS die 220 to the substrate 230 may, for
example, be performed before and/or after coupling the MEMS die 210
to the CMOS die 220. For example, the MEMS die 210 and the CMOS die
220 may be coupled (e.g., using the technique(s) described in U.S.
Pat. No. 7,104,129, prior to coupling the CMOS die 220 (in die or
wafer form) to the substrate 230. In another example, the CMOS die
220 may be coupled to the substrate 230 prior to coupling the MEMS
die 210 to the CMOS die 220.
[0045] All couplings discussed herein may, for example, be
performed at the die and/or wafer level. For example, the MEMS die
210, CMOS die 220, and/or substrate 230 may all be bonded to each
other at the wafer level prior to singulation into separate circuit
packages.
[0046] The circuit structure 200 comprises a stress isolation gap
240 between the CMOS die 220 and the substrate 230. The gap 240
may, for example, be filled with any gaseous (e.g., air) or
non-gaseous (e.g., foam) substance having a suitable compliance
(inverse of spring constant) that absorbs stress such that stress
transferred from the substrate 230 to the CMOS die 220 and/or MEMS
die 210 is below a level determined likely to cause damage or
performance degradation.
[0047] The gap 240 may, for example, provide for reduced stress on
the CMOS die 220 and/or the MEMS die 210 due to flexing of the
substrate 230. For example, the substrate 230 may bow into or away
from the gap 240 while transferring a substantially lower amount of
stress to the CMOS die 220 and/or the MEMS die 210 than would have
been transferred without the gap 240. For example, if instead of
the gap 240, the CMOS die 220 and the substrate 230 were tightly
coupled over the entirety of their facing sides, the substrate 230
flexing might cause the CMOS die 220 (and thus the MEMS die 210) to
also flex in unison. Such flexing of the CMOS die 220 and MEMS die
210 might, for example, cause the circuit structure 200 to fail,
reduce performance of the circuit structure 200, alter performance
characteristics of the circuit structure 200, etc.
[0048] As shown in FIG. 2, the stress isolation gap 240 may
comprise a cavity formed in the substrate 230. The cavity may, for
example, be completely or partially surrounded laterally by one or
more upward-protruding portion(s) 228 of the substrate 230. For
example, the upward-protruding portion(s) 228 of the substrate 230
may extend toward the entire perimeter of the CMOS die 220. Also
for example, the upward-protruding portion of the substrate 230 may
be segmented into two or more segments, each of which only extends
toward part of the perimeter of the CMOS die 220. For example, the
upward-protruding portion(s) 228 of the substrate 230 may comprise
four corner posts (or feet), each protruding upward toward a
respective corner of the CMOS die 220. Such posts may, for example,
comprise a rectangular footprint (e.g., looking up or down at the
post), a circular footprint, an elliptical footprint, etc. Also for
example, as will be discussed herein, the upward-protruding
portion(s) 228 may comprise a single solid protrusion or pedestal
(e.g., extending from the center of the substrate 230 toward the
center of the bottom side of the CMOS die 220, offset from the
center of the CMOS die 220 but still covering the center, offset
from the center of the CMOS die 220 and not covering the center of
the CMOS die 220, etc.).
[0049] In an example implementation in which wire-bonding is
utilized for electrically coupling the CMOS die 220 to the
substrate 230, the upward-protruding portion(s) 228 of the
substrate 230 may be positioned directly below wire-bond pads that
are on the top side of the CMOS die 220. In such a configuration,
the upward-protruding portion(s) 228 may provide structural support
during the wire-bonding process.
[0050] The cavity and/or upward-protruding portion(s) 228 of the
substrate 230 may be formed in any of a variety of manners. For
example, the cavity may be etched into the top side of the
substrate 230. For example, the top side of the substrate 230 may
be masked at the protruding portions and chemically etched at the
non-masked areas to form the cavity. Also for example, in an
implementation that comprises feet protruding upward to the corners
of the CMOS die 220, the cavity may be ground into the substrate
230. For example, while the substrate 230 is still in wafer or
other non-singulated form, a matrix pattern may be ground into the
top side of the substrate 230 to form the corner feet. The corner
feet may, for example, be formed to protrude orthogonally relative
to the primary plane of the substrate 230, but may also be formed
at a non-orthogonal angle. The corner feet may, for example, be
formed thin enough to have a spring-like compliance, which may
further isolate the CMOS die 220 and MEMS die 210 from stress due
to a flexing substrate 230. Additionally for example, in an
implementation in which the substrate 230 comprises a lead frame
(e.g., a paddle of a lead frame), the cavity may be stamped into
the substrate 230.
[0051] Also for example, the upward-protruding portion(s) 238 may
be positively formed on the substrate 230 (e.g., as opposed to
being negatively formed by surrounding material being removed). For
example, the upward-protruding portion(s) 238 may be deposited on
the top side of the substrate 230. Such upward-protruding portions
238 may, for example, comprise dielectric material that is
deposited (e.g., printed, sprayed, vapor-deposited, grown in a MEMS
or MEMS-like process, etc.). In an example implementation, the
upward-protruding portion(s) 238 may be formed of deposited
photoresist material. In such an implementation, the deposited
photoresist material may comprise enough adhesion to provide the
mechanical coupling between the CMOS die 220 and the substrate 230
(e.g., after curing).
[0052] Also for example, such upward-protruding portion(s) 238 may
be plated (e.g., electrode-based plating, electroless plating,
etc.). In an example implementation the upward-protruding
portion(s) 238 may comprise a metal post that is plated on the top
surface of the substrate 230. In such an example implementation,
the metal post may be strictly a mechanical feature, but may also
be utilized as an electrical connection. Additionally, in a
scenario in which the upward-protruding portions 238 comprise metal
posts, other metal posts (e.g., of different dimensions than the
protruding portions) or conductive features may provide electrical
connections between the CMOS die 220 and the substrate 230. For
further example, in a scenario in which the upward-protruding
portion(s) 238 comprise metal posts, wire-bonds may be utilized to
provide electrical connections between the CMOS die 220 and the
substrate 230 (e.g., bonded to the top side of the CMOS die 220 and
top side of the substrate 230).
[0053] The stress isolation gap 240 may be characterized by any of
a variety of dimensions. For example, the gap 240 may be at least
10 microns thick. Also for example, the gap 240 may be at least 15
microns thick. In an example implementation, the gap 240 may
comprise a thickness between 1% and 10% of the thickness of the
CMOS die 220. In another example implementation, the gap 240 may
comprise a thickness greater than 10% of the thickness of the CMOS
die 220. The gap 240 may, for example, be at least 80% as wide as
the CMOS die 220. Also for example, the gap 240 may be at least 90%
as wide as the CMOS die 220.
[0054] Though the example circuit structure 200 shown in FIG. 2,
shows the cavity corresponding to the gap 240 formed in the
substrate 230, the cavity may alternatively be formed in both the
CMOS die 220 and in the substrate 230. An example of such a
configuration will now be discussed.
[0055] FIG. 3 shows an example electromechanical circuit structure
300 comprising a stress isolation gap formed in a CMOS die 320 and
in a substrate 330, in accordance with various aspects of the
present disclosure. The example circuit structure 300 may share any
or all characteristics with the example circuit structures 100-200
illustrated in FIGS. 1-2 and discussed herein, including production
methods thereof.
[0056] The example circuit structure 300 may, for example, comprise
a stress isolation gap 340 formed in both the CMOS die 320 and in
the substrate 330. For example, a cavity may be formed in the CMOS
die 320 corresponding to the gap 340. Such cavity formation may,
for example, share any or all characteristics with the cavity
formation discussed with regard to the circuit structure 100 of
FIG. 1. Also for example, a cavity may be formed in the substrate
330 corresponding to the gap 340. Such cavity formation may, for
example, share any or all characteristics with the cavity formation
discussed with regard to the circuit structure 200 of FIG. 2.
[0057] The respective cavities formed in the CMOS die 320 and in
the substrate 330 may, for example, be symmetrical with regard to
each other. Alternatively, such cavities may be asymmetrical. For
example, the cavity formed in the CMOS die 320 may be deeper (or
wider) than the cavity formed in the substrate 330. In such a
scenario, the cavity formed in the substrate 330 may be kept as
shallow as possible to reduce flexing in the substrate 330. For
example, in an example scenario, the cavity might be formed in the
substrate 330 only when the cavity formed in the CMOS die 320 does
not provide enough total depth.
[0058] As shown in FIG. 3 and discussed herein, the
upward-protruding portion(s) of the substrate 330 may extend beyond
the lateral boundaries (or the perimeter) of the CMOS die 320, for
example extending to the side edges of the substrate 330. For
example, the upward-protruding portion(s) may be wider than needed
for coupling to the CMOS die 320. In other implementations, the
upward-protruding portion may not extend laterally to the side edge
of the substrate.
[0059] FIG. 4 shows an example electromechanical circuit structure
400 comprising a stress isolation gap formed in a substrate, in
accordance with various aspects of the present disclosure. The
example circuit structure 400 may share any or all characteristics
with the example circuit structures 100-300 illustrated in FIGS.
1-3 and discussed herein, including production methods thereof.
[0060] Compared to the example circuit structure 200 illustrated in
FIG. 2, the example circuit structure 400 comprises a substrate 430
that comprises an upward-protruding portion(s) that extend(s)
upward at a position that is entirely laterally inward from the
side edge of the substrate 430. In comparison, the
upward-protruding portion(s) of the circuit structure 200
illustrated in FIG. 2 extend(s) laterally to the edges of the
substrate 230. Also for example, the upward-protruding portion(s)
may, for example, begin extending upward at a lateral location
corresponding to an edge of the CMOS die 420, as is shown in FIG.
4.
[0061] The upward-protruding portion(s) of the substrate 430 may be
formed in any of the manners discussed herein (e.g., with regard to
any other substrates and/or die discussed herein). For example, the
upward-protruding portion(s) of the substrate 430 may be formed in
a negative manner by removing portion of the substrate 430 and/or
in a positive manner by building up the upward-protruding
portion(s) on the substrate 430.
[0062] Although the example circuit 400, shown in FIG. 4, shows the
cavity corresponding to the gap 440 formed in the substrate 430,
the cavity may alternatively be formed in both the CMOS die 420 and
in the substrate 430. An example of such a configuration will now
be discussed.
[0063] FIG. 5 shows an example electromechanical circuit structure
500 comprising a stress isolation gap formed in a CMOS die and in a
substrate, in accordance with various aspects of the present
disclosure. The example circuit structure 500 may share any or all
characteristics with the example circuit structures 100-400
illustrated in FIGS. 1-4 and discussed herein, including production
methods thereof.
[0064] The example circuit structure 500 may, for example, comprise
a stress isolation gap 540 formed in both the CMOS die 520 and in
the substrate 530. For example, a cavity may be formed in the CMOS
die 520 corresponding to the gap 540. Such cavity formation may,
for example, share any or all characteristics with the cavity
formation discussed with regard to the circuit structure 100 of
FIG. 1. Also for example, a cavity may be formed in the substrate
530 corresponding to the gap 540. Such cavity formation may, for
example, share any or all characteristics with the cavity formation
discussed with regard to the circuit structure 400 of FIG. 4.
[0065] The respective cavities formed in the CMOS die 520 and in
the substrate 530 may, for example, be symmetrical with regard to
each other. Alternatively, such cavities may be asymmetrical. For
example, the cavity formed in the CMOS die 520 may be deeper (or
wider) than the cavity formed in the substrate 530. In such a
scenario, the cavity formed in the substrate 530 may be kept as
shallow as possible to reduce flexing in the substrate 530. For
example, in an example scenario, the cavity might be formed in the
substrate 530 only when the cavity formed in the CMOS die 520 does
not provide enough total depth.
[0066] As shown in FIG. 5 and discussed herein, the
upward-protruding portion(s) of the substrate 530 may match (e.g.,
laterally) the downward-protruding portion(s) of the CMOS die 520.
Alternatively, though not illustrated, the upward-protruding
portion(s) of the substrate 530 may extend laterally beyond inner
and/or outer surfaces of the downward-protruding portion(s) of the
CMOS die 520. For example, the upward-protruding portion(s) of the
substrate 530 may be wider than the downward-protruding portion(s)
of the CMOS die 520. Also for example, though not illustrated, the
downward-protruding portion(s) of the CMOS die 520 may extend
laterally beyond inner and/or outer surfaces of the
upward-protruding portion(s) of the substrate 530. For example, the
downward-protruding portion(s) of the CMOS die 520 may be wider
than the upward-protruding portion(s) of the substrate 530.
[0067] As discussed herein, upward and/or downward protrusions (or
standoffs or feet) may be utilized to form the stress isolation
gap, where such upward and/or downward protrusions may be
integrally formed in (including on) the substrate and/or CMOS die.
The standoffs may also be formed in a layer that is independent of
the substrate and CMOS die and then inserted between the substrate
and CMOS die during production.
[0068] FIG. 6 shows an example electromechanical circuit structure
600 comprising a stress isolation gap formed between a CMOS die and
a substrate, in accordance with various aspects of the present
disclosure. The example circuit structure 600 may, for example,
comprise an intervening layer 650 that is formed independently of
the CMOS die 620 and substrate 630, and then inserted between the
CMOS die 620 and substrate 630 during production.
[0069] The intervening layer 650, which may also be referred to
herein as a gasket 650, may comprise various shapes. For example,
the gasket 650 may form a closed shape (e.g., a square, a
rectangle, a circle, an ellipse, etc.). Such a closed shape may,
for example, comprise height characteristics that cause the gap 640
to be sealed. Also, the closed shape may, for example, comprise
height characteristics that result in an unsealed gap 640, for
example with protruding standoffs and relatively thin connecting
material between the standoffs. Also for example, the intervening
layer 650 may comprise independent standoffs, for example placed
around the perimeter of the CMOS die 620 (e.g., at each of four
corners, at a single center location, etc.).
[0070] The intervening layer 650 may comprise any of a variety of
materials. For example, the intervening layer 650 may comprise
glass, silicon, PCB material (e.g., interposer material),
die-attach film, an adhesive layer, an elastomer, etc. The
intervening layer 650 may, for example, comprise a compliant
material that enhances the stress isolation provided by the gap
640.
[0071] The intervening layer 650 may, for example, be applied
between the CMOS die 620 and substrate 630 in wafer form and/or in
a form corresponding to singulated die and/or substrates. For
example, the intervening layer 650 may comprise a wafer-shaped disc
of standoff material comprising apertures corresponding to the top
and bottom of the gap 640 and/or protrusions corresponding to
standoffs.
[0072] The intervening layer 650 (e.g., apertures, standoffs, etc.)
may comprise characteristics (e.g., dimensional characteristics,
material characteristics, etc.) of any of the upward- and/or
downward-protruding portions discussed herein.
[0073] As discussed herein the substrates shown and discussed with
regard to FIGS. 1-6 may comprise an interposer-type substrate to
which a semiconductor die is bonded. FIGS. 7-9 present various
non-limiting examples of interposer-based implementations.
[0074] FIG. 7 shows an example electromechanical circuit structure
700 comprising a stress isolation gap 740 formed in a CMOS die 720,
in accordance with various aspects of the present disclosure.
[0075] The example circuit structure 700 may share any or all
characteristics with the example circuit structures 100-600
illustrated in FIGS. 1-6 and discussed herein, including production
methods thereof. The CMOS die 720 may, for example, share any or
all characteristics with the CMOS die 120, 320, and 520 illustrated
in FIGS. 1, 3, and 5, and discussed herein. The interposer 731 may,
for example, share any or all characteristics with the substrates
130 and 630 illustrated in FIGS. 1 and 6 and discussed herein.
[0076] The interposer 731 may, for example, comprise an intervening
layer between the CMOS die 720 and the package substrate 732. The
interposer 731 may, for example, be mechanically and/or
electrically coupled to the package substrate 732 in any of a
variety of manners. The CMOS die 720 may, for example, be coupled
to the interposer 731 before or after the interposer 731 is coupled
to the package substrate. For example, the CMOS die 720 and the
interposer 731 may be coupled to each other in wafer form, prior to
singulation.
[0077] FIG. 8 shows an example electromechanical circuit structure
800 comprising a stress isolation gap 840 formed in an interposer
831, in accordance with various aspects of the present
disclosure.
[0078] The example circuit structure 800 may share any or all
characteristics with the example circuit structures 100-700
illustrated in FIGS. 1-7 and discussed herein, including production
methods thereof. The CMOS die 820 may, for example, share any or
all characteristics with the CMOS die 220, 420, 620 illustrated in
FIGS. 2, 4, and 6, and discussed herein. The interposer 831 may,
for example, share any or all characteristics with the substrates
230, 330, 430, and 530 illustrated in FIGS. 2, 3, 4, and 5, and
discussed herein.
[0079] The interposer 831 may, for example, comprise an intervening
layer between the CMOS die 820 and the package substrate 832. The
interposer 831 may, for example, be mechanically and/or
electrically coupled to the package substrate 832 in any of a
variety of manners. The CMOS die 820 may, for example, be coupled
to the interposer 831 before or after the interposer 831 is coupled
to the package substrate 832. For example, the CMOS die 820 and the
interposer 831 may be coupled to each other in wafer form, prior to
singulation.
[0080] In an alternative example, the interposer 831 may be
vertically flipped, thus positioning the gap 840 between the
interposer 831 and the package substrate 832.
[0081] Though the example circuit 800 shown in FIG. 8, shows the
cavity corresponding to the gap 840 formed in the interposer 831,
the cavity may alternatively be formed in both the CMOS die 820 and
in the interposer 831. An example of such a configuration will now
be discussed.
[0082] FIG. 9 shows an example electromechanical circuit structure
900 comprising a stress isolation gap 940 formed in a CMOS die 920
and in an interposer 931, in accordance with various aspects of the
present disclosure. The example circuit structure 900 may share any
or all characteristics with the example circuit structures 100-800
illustrated in FIGS. 1-8 and discussed herein, including production
methods thereof.
[0083] The example circuit structure 900 may, for example, comprise
a stress isolation gap 940 formed in both the CMOS die 920 and in
the interposer 931. For example, a cavity may be formed in the CMOS
die 920 corresponding to the gap 940. Such cavity formation may,
for example, share any or all characteristics with the cavity
formation discussed with regard to the circuit structure 700 of
FIG. 7. Also for example, a cavity may be formed in the interposer
931 corresponding to the gap 940. Such cavity formation may, for
example, share any or all characteristics with the cavity formation
discussed with regard to the circuit structure 800 of FIG. 8.
[0084] The respective cavities formed in the CMOS die 920 and in
the interposer 931 may, for example, be symmetrical with regard to
each other. Alternatively, such cavities may be asymmetrical.
Examples of such cavity characteristics are discussed herein, for
example with regard to FIGS. 3 and 5.
[0085] As discussed herein, a stress isolation gap may be formed
using a single downward protrusion or foot. For example, a stress
isolation gap may be formed with a single downward-protruding
portion from a CMOS die and/or a single upward-protruding portion
from a substrate. Examples of implementations comprising one or
more of such protrusions are shown in FIGS. 10-12.
[0086] FIG. 10 shows an example electromechanical circuit structure
1000 comprising a stress isolation gap formed in a CMOS die, in
accordance with various aspects of the present disclosure.
[0087] The example circuit structure 1000 may share any or all
characteristics with the example circuit structures 100-900
illustrated in FIGS. 1-9 and discussed herein, including production
methods thereof. For example, the example MEMS die 1010, CMOS die
1020, and substrate 1030 may share any or all characteristics with
the MEMS die 110, CMOS die 120, and substrate 130 shown in FIG. 1
and discussed herein.
[0088] As discussed herein, for example with regard to FIG. 1, the
CMOS die 1020 may comprise a downward-protruding 1028 portion that
comprises a single solid or substantially solid protrusion (e.g.,
extending from the center of the bottom side of the CMOS die 1020,
offset from the center of the CMOS die 1020 but still covering the
center, offset from the center of the CMOS die 1020 and not
covering the center of the CMOS die 1020, etc.). The isolation gap
1040 may then, for example, extend laterally from any or all sides
of the downward-protruding portion 1028. For example, the isolation
gap 1040 may extend laterally from the downward-protruding portion
1028 to the side edges of the CMOS die 1020. The
downward-protruding portion 1028 may, for example, be formed in a
same manner as any downward-protruding portions 1028 discussed
herein.
[0089] The stress isolation gap 1040 may, for example, be filled
with any gaseous (e.g., air) or non-gaseous (e.g., foam) substance
having a suitable compliance (inverse of spring constant) that
absorbs stress such that stress transferred from the substrate 1030
to the CMOS die 1020 and/or MEMS die 1010 is below a level
determined likely to cause damage or performance degradation.
[0090] In an example implementation in which the CMOS die 1020 is
wire-bonded to the substrate 1030, the wire-bonding may be
performed in a symmetrical manner, for example balancing
wire-bonding forces around the downward-protruding portion 1028 to
reduce tipping forces. Also for example, a support material may be
temporarily placed in the gap 1040 below the wire-bonding pads on
the CMOS die 1020 to provide support during the wire-bonding
process, and then such material may be removed after wire-bonding.
In an example implementation, TSVs may extend through the
downward-protruding portion.
[0091] Though the example circuit 1000 shown in FIG. 10, shows the
cavity corresponding to the gap 1040 formed in the CMOS die 1020
(e.g., due to the downward-protruding portion of the CMOS die
1020), the cavity may alternatively be formed in the substrate
1030. An example of such a configuration will now be discussed.
[0092] FIG. 11 shows an example electromechanical circuit structure
1100 comprising a stress isolation gap formed in a substrate, in
accordance with various aspects of the present disclosure.
[0093] The example circuit structure 1100 may share any or all
characteristics with the example circuit structures 100-1000
illustrated in FIGS. 1-10 and discussed herein, including
production methods thereof. For example, the example MEMS die 1110,
CMOS die 1120, and substrate 1130 may share any or all
characteristics with the MEMS die 210 and 410, CMOS die 220 and
420, and substrate 230 and 430, shown in FIGS. 2 and 4, and
discussed herein.
[0094] As discussed herein, for example with regard to FIG. 2, the
substrate 1130 may comprise an upward-protruding portion 1128 that
comprises a single solid or substantially solid protrusion (e.g.,
extending from the center of the substrate 1130 toward the center
of the bottom side of the CMOS die 1120, offset from the center of
the CMOS die 1120 but still covering the center, offset from the
center of the CMOS die 1120 and not covering the center of the CMOS
die 1120, etc.). The isolation gap 1140 may then, for example,
extend laterally from any or all sides of the upward-protruding
portion. For example, the isolation gap 1140 may extend laterally
from the upward-protruding portion to the side edges of the CMOS
die 1120. The upward-protruding portion 1128 may, for example, be
formed in a same manner as any upward-protruding portions discussed
herein.
[0095] The gap 1140 may, for example, be filled with any gaseous
(e.g., air) or non-gaseous (e.g., foam) substance having a suitable
compliance (inverse of spring constant) that absorbs stress such
that stress transferred from the substrate 1128 to the CMOS die
1120 and/or MEMS die 1110 is below a level determined likely to
cause damage or performance degradation
[0096] In an example implementation in which the CMOS die 1120 is
wire-bonded to the substrate 1130, the wire-bonding may be
performed in a symmetrical manner, for example balancing
wire-bonding forces around the downward-protruding portion to
reduce tipping forces. Also for example, a support material may be
temporarily placed in the gap 1140 below the wire-bonding pads on
the CMOS die 1120 to provide support during the wire-bonding
process, and then such material may be removed after wire-bonding.
In an example implementation, TSVs may extend through the CMOS die
1120 to the upward-protruding portion of the substrate 1130.
[0097] Though the example circuit 1100 shown in FIG. 11, shows the
cavity corresponding to the gap 1140 formed in the substrate 1130
(e.g., due to the upward-protruding portion of the substrate 1130),
the cavity may alternatively be formed in both the CMOS die 1120
and the substrate 1130. An example of such a configuration will now
be discussed.
[0098] FIG. 12 shows an example electromechanical circuit structure
1200 comprising a stress isolation gap formed in a CMOS die and in
a substrate, in accordance with various aspects of the present
disclosure. The example circuit structure 1200 may share any or all
characteristics with the example circuit structures 100-1100
illustrated in FIGS. 1-11 and discussed herein, including
production methods thereof.
[0099] The example circuit structure 1200 may, for example,
comprise a stress isolation gap 1240 formed in both the CMOS die
1220 and in the substrate 1230. For example, a cavity may be formed
in the CMOS die 1220 corresponding to the gap 1240. Such cavity
formation may, for example, share any or all characteristics with
the cavity formation discussed with regard to the circuit structure
1000 of FIG. 10. Also for example, a cavity may be formed in the
substrate 1230 corresponding to the gap 1240. Such cavity formation
may, for example, share any or all characteristics with the cavity
formation discussed with regard to the circuit structure 1100 of
FIG. 11.
[0100] The respective cavities formed in the CMOS die 1220 and in
the substrate 1230 may, for example, be symmetrical with regard to
each other. Alternatively, such cavities may be asymmetrical. For
example, the cavity formed in the CMOS die 1220 may be deeper (or
wider) than the cavity formed in the substrate 1230. In such a
scenario, the cavity formed in the substrate 1230 may be kept as
shallow as possible to reduce flexing in the substrate 1230. For
example, in an example scenario, the cavity might be formed in the
substrate 1230 only when the cavity formed in the CMOS die 1220
does not provide enough total depth.
[0101] The upward-protruding portion of the substrate 1230 may
match (e.g., laterally match) the downward-protruding portion of
the CMOS die 1220. The upward-protruding portion of the substrate
1230 may also extend beyond the lateral boundaries (or the
perimeter) of the downward-protruding portion of the CMOS die 1220,
for example extending laterally to a position between the side
edges of the CMOS die 1220 and the downward-protruding portion of
the CMOS die 1220. For example, the upward-protruding portion may
be wider than needed for coupling to the CMOS die 1220 (e.g., to
provide for manufacturing tolerance). Similarly, the
downward-protruding portion of the CMOS die 1220 may be wider than
needed for coupling to the substrate 1230.
[0102] The circuit structures discussed herein may, for example, be
covered by a hollow packaging lid (e.g., to further isolate the
MEMS die and/or CMOS die from stress due to a flexing substrate).
Also for example, the circuit structures may be at least partially
encapsulated in a package encapsulant.
[0103] FIG. 13 shows an example electromechanical circuit structure
1300 comprising a stress isolation gap formed in a CMOS die, in
accordance with various aspects of the present disclosure. The
example circuit structure 1300 may share any or all characteristics
with the example circuit structures 100-1200 illustrated in FIGS.
1-12 and discussed herein, including production methods
thereof.
[0104] The circuit structure 1300 may, for example, comprise an
encapsulant 1350. The gap 240 may, for example, be filled with any
gaseous (e.g., air) or non-gaseous (e.g., foam) substance having a
suitable compliance (inverse of spring constant) that absorbs
stress such that stress transferred from the substrate 1340 to the
CMOS die 1320 and/or MEMS die 1310 is below a level determined
likely to cause damage or performance degradation. The stress
isolation gap 1340 may, for example, be sealed around its edges
(e.g., with an underfill material, epoxy, adhesive, etc.) prior to
encapsulating. Also for example, the gap 1340 may be unsealed with
the encapsulant having a degree of viscosity that inhibits the
encapsulant from flowing into the gap 1340.
[0105] The general examples discussed herein are generally
presented in the context of an electromechanical circuit. Various
aspects discussed herein may also apply to non-electromechanical
structures. For example, in any of FIGS. 1-13, the MEMS die may be
replaced with a solid-state circuit die (e.g., a second CMOS die).
A non-limiting example of such a circuit structure is shown in FIG.
14, which shows an example circuit structure comprising a stress
isolation gap formed in a CMOS die, in accordance with various
aspects of the present disclosure.
[0106] In accordance with an example embodiment of this disclosure,
a micro-electro-mechanical system (MEMS) sensor circuit or device
(e.g., 100) comprises a substrate (e.g., 130), a CMOS die (120),
and a MEMS die (110), each of which comprises a top side and a
bottom side. The bottom side of the CMOS die is coupled to the top
side of the substrate, and the bottom side of the MEMS die is
coupled to the top side of the CMOS die, and there is a cavity
(e.g., 140) positioned between the CMOS die and the substrate. The
cavity may be sealed by a sealing substance, and may be filled with
a filler substance (e.g., an adhesive) that is different than the
sealing substance (e.g., a gaseous or non-gaseous substance). The
cavity may be fully or partially surrounded by one or more
downward-protruding portions (e.g., 128) of the CMOS die and/or one
or more upward-protruding portions of the substrate (e.g. 228). The
cavity may be fully or partially surrounded by one or more
standoffs (e.g., 650) inserted between the CMOS die and the
substrate. The cavity may be the result of material being removed
from one or both of the bottom side of the CMOS die and the top
side of the substrate. The cavity may be the result of one or more
upward-protruding portions of the substrate and/or
downward-protruding portions of the CMOS die. The one or more
upward-protruding portions of the substrate and/or
downward-protruding portions of the CMOS die are characterized by a
compliance value (inverse of a spring constant) suitable for
absorbing stress that would otherwise be transferred to the CMOS
die upon flexure of the substrate.
[0107] As utilized herein, "and/or" means any one or more of the
items in the list joined by "and/or". As an example, "x and/or y"
means any element of the three-element set {(x), (y), (x, y)}. In
other words, "x and/or y" means "one or both of x and y." As
another example, "x, y, and/or z" means any element of the
seven-element set {(x), (y), (z), (x, y), (x, z), (y, z), (x, y,
z)}. In other words, "x, y and/or z" means "one or more of x, y and
z." As utilized herein, the terms "e.g.," and "for example" set off
lists of one or more non-limiting examples, instances, or
illustrations.
* * * * *