U.S. patent application number 14/861550 was filed with the patent office on 2017-03-23 for mems sensor with side port and method of fabricating same.
The applicant listed for this patent is FREESCALE SEMICONDUCTOR, INC.. Invention is credited to CHAD S. DAWSON, STEPHEN R. HOOPER, FENGYUAN LI, ARVIND S. SALIAN.
Application Number | 20170081179 14/861550 |
Document ID | / |
Family ID | 56958810 |
Filed Date | 2017-03-23 |
United States Patent
Application |
20170081179 |
Kind Code |
A1 |
DAWSON; CHAD S. ; et
al. |
March 23, 2017 |
MEMS SENSOR WITH SIDE PORT AND METHOD OF FABRICATING SAME
Abstract
A MEMS sensor package comprises a MEMS die that includes a
substrate having a sensor formed thereon and a cap layer coupled to
the substrate. The cap layer has a cavity overlying a substrate
region at which the sensor resides. A port extends between the
cavity and a side wall of the MEMS die and enables admittance of
fluid into the cavity. Fabrication methodology entails providing a
substrate structure having sensors formed thereon, providing a cap
layer structure having inwardly extending cavities, and forming a
channel between pairs of the cavities. The cap layer structure is
coupled with the substrate structure and each channel is interposed
between a pair of cavities. A singulation process produces a pair
of sensor packages, each having a port formed by splitting the
channel, where the port is exposed during singulation and extends
between its respective cavity and side wall of the sensor
package.
Inventors: |
DAWSON; CHAD S.; (QUEEN
CREEK, AZ) ; HOOPER; STEPHEN R.; (MESA, AZ) ;
LI; FENGYUAN; (CHANDLER, AZ) ; SALIAN; ARVIND S.;
(GILBERT, AZ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FREESCALE SEMICONDUCTOR, INC. |
AUSTIN |
TX |
US |
|
|
Family ID: |
56958810 |
Appl. No.: |
14/861550 |
Filed: |
September 22, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B81B 2203/0315 20130101;
H01L 2924/00012 20130101; H01L 2924/00012 20130101; B81B 2207/097
20130101; B81C 1/00865 20130101; H01L 2224/48145 20130101; B81B
2201/0264 20130101; B81B 2203/0118 20130101; B81B 2203/0127
20130101; B81B 7/0061 20130101; H01L 2224/48145 20130101; B81C
1/00309 20130101; H01L 2924/181 20130101; B81B 2207/012 20130101;
B81C 2203/0109 20130101; B81B 2203/0392 20130101; H01L 2924/181
20130101 |
International
Class: |
B81B 7/00 20060101
B81B007/00; B81C 1/00 20060101 B81C001/00 |
Claims
1. A microelectromechanical systems (MEMS) sensor package
comprising: a MEMS die, said MEMS die comprising: a substrate
having a first inner surface and a first outer surface; a MEMS
sensor formed on said first inner surface; and a cap layer having a
second inner surface and a second outer surface, wherein said
second inner surface of said cap layer is coupled to said first
inner surface of said substrate, said cap layer includes a cavity
extending inwardly from said second inner surface and overlying a
region of said first inner surface of said substrate, said MEMS
sensor resides in said cavity at said region of said first inner
surface of said substrate, and a port extends between said cavity
and a side wall of said MEMS die, said side wall extending between
said first outer surface of said substrate and said second outer
surface of said cap layer; and an encapsulant covering said MEMS
die, wherein said encapsulant is absent from said side wall and
said encapsulant does not obstruct said port.
2. The MEMS sensor package of claim 1 wherein said port is
configured to admit a fluid external to said cavity into said
cavity.
3. (canceled)
4. The MEMS sensor package of claim 1 wherein said substrate has a
recess formed therein, and said MEMS die further comprises a
cantilevered platform structure having a platform and an arm
extending from said platform, wherein said platform and said arm
are suspended over said recess, said arm is fixed to said
substrate, and said platform includes said region at which said
MEMS sensor resides.
5. The MEMS sensor package of claim 4 wherein said arm is a sole
attachment point of said platform to said substrate.
6. The MEMS sensor package of claim 1 further comprising a
semiconductor die coupled to one of said first outer surface of
said substrate and said second outer surface of said cap layer.
7. The MEMS sensor package of claim 6 further comprising conductive
interconnects electrically coupling said MEMS sensor with said
semiconductor die.
8. The MEMS sensor package of claim 1 wherein said MEMS sensor
comprises a pressure sensor, said pressure sensor including a
pressure deformable diaphragm disposed at said region of said first
inner surface of said substrate.
9-17. (canceled)
18. A structure comprising: a substrate having a first inner
surface and a first outer surface; a MEMS pressure sensor formed on
said first inner surface; a cap layer having a second inner surface
and a second outer surface; and an encapsulant covering said
substrate and said cap layer, wherein: said second inner surface of
said cap layer is coupled to said first inner surface of said
substrate; said cap layer includes a cavity extending inwardly from
said second inner surface and overlying a region of said first
inner surface of said substrate; said MEMS pressure sensor resides
in said cavity and includes a pressure deformable diaphragm
disposed at said region of said first inner surface of said
substrate; a port extends between said cavity and a side wall of
said cap layer, said side wall extending between said first outer
surface of said substrate and said second outer surface of said cap
layer; said encapsulant is absent from said side wall; and said
encapsulant does not obstruct said port.
19. The structure of claim 18 wherein said port is configured to
admit a fluid external to said cavity into said cavity.
20. The structure of claim 18 wherein said MEMS pressure sensor is
a first MEMS pressure sensor, said region is a first region, said
cavity is a first cavity, said port is a first port, said side wall
is a first side wall, said first MEMS pressure sensor residing in
said first cavity is a first intermediate sensor structure and:
said structure comprises a second MEMS pressure sensor at a second
region of said first inner surface, said second region being
laterally displaced from said first region; and said cap layer
includes a second cavity laterally displaced from said first
cavity, wherein: said second cavity extends inwardly from said
second inner surface and overlies a second region of said first
inner surface; said second MEMS pressure sensor resides in said
second cavity at said second region of said first inner surface of
said substrate to form a second intermediate sensor structure; a
channel extends inwardly from said second inner surface of said cap
layer, said channel being interposed between said first and second
cavities; said first intermediate sensor structure is configured to
be separated from said second intermediate sensor structure to
produce a first MEMS pressure sensor package that includes said
first MEMS pressure sensor having said first port and to produce a
second MEMS pressure sensor that includes said second MEMS pressure
sensor having a second port, said first port being a first portion
of said channel, said second port being a second portion of said
channel; and said second port extends between said second cavity
and a second side wall of said second MEMS sensor package, said
second side wall extending between said first outer surface of said
substrate and said second outer surface of said cap layer.
Description
TECHNICAL FIELD OF THE INVENTION
[0001] The present invention relates generally to
microelectromechanical systems (MEMS) sensor packages. More
specifically, the present invention relates to a MEMS sensor with a
side wall port to provide a path for passage of an external fluid
medium.
BACKGROUND OF THE INVENTION
[0002] Microelectromechanical systems (MEMS) devices are
semiconductor devices with embedded mechanical components. MEMS
devices include, for example, pressure sensors, accelerometers,
gyroscopes, microphones, digital mirror displays, micro fluidic
devices, and so forth. MEMS devices are used in a variety of
products such as automobile airbag systems, control applications in
automobiles, navigation, display systems, inkjet cartridges, and so
forth.
[0003] There are significant challenges to be surmounted in the
packaging of MEMS devices due at least in part to the necessity for
the MEMS devices to interact with the outside environment, the
fragility of many types of MEMS devices, and severe cost
constraints. Indeed, many MEMS device applications require smaller
size and low cost packaging to meet aggressive cost targets.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] The accompanying figures in which like reference numerals
refer to identical or functionally similar elements throughout the
separate views, the figures are not necessarily drawn to scale, and
which together with the detailed description below are incorporated
in and form part of the specification, serve to further illustrate
various embodiments and to explain various principles and
advantages all in accordance with the present invention.
[0005] FIG. 1 shows a side sectional view of a
microelectromechanical systems (MEMS) sensor package in accordance
with an embodiment;
[0006] FIG. 2 shows a side sectional view of a structure that
includes a first intermediate sensor structure and a second
intermediate sensor structure prior to singulation;
[0007] FIG. 3 shows a side sectional view of the structure of FIG.
2 following singulation;
[0008] FIG. 4 shows a side sectional view of a portion of the
structure of FIG. 2;
[0009] FIG. 5 shows a top view of a substrate structure that may be
used to form the structure of FIG. 2;
[0010] FIG. 6 shows a bottom view of a cap layer structure that may
be used to form the structure of FIG. 2;
[0011] FIG. 7 shows a side sectional view of a structure that
includes a first intermediate sensor structure and a second
intermediate sensor structure prior to singulation in accordance
with another embodiment;
[0012] FIG. 8 shows a side sectional view of a structure that
includes a first intermediate sensor structure and a second
intermediate sensor structure prior to singulation in accordance
with another embodiment;
[0013] FIG. 9 shows a side sectional view of a structure that
includes a first intermediate sensor structure and a second
intermediate sensor structure prior to singulation in accordance
with yet another embodiment; and
[0014] FIG. 10 shows a flowchart of a sensor package fabrication
process in accordance with another embodiment.
DETAILED DESCRIPTION
[0015] As the uses for microelectromechanical systems (MEMS)
devices continue to grow and diversify, increasing emphasis is
being placed on smaller size and low cost packaging without
sacrificing part performance. Embodiments entail a MEMS sensor
package and a method of fabricating the MEMS sensor package. In
particular, the MEMS sensor package is formed, through the
execution of relatively simple methodology, to include a MEMS
sensor on a substrate that is covered by a cap layer. The MEMS
sensor resides in a cavity formed in the cap layer, and a port
extends between the cavity and a side wall of one of the substrate
and the cap layer. The pressure port formed in the side wall is
exposed during a strip singulation operation of the methodology so
that fluid, such as air, external to the cavity can be admitted
into the cavity.
[0016] The instant disclosure is provided to explain in an enabling
fashion the best modes, at the time of the application, of making
and using various embodiments in accordance with the present
invention. The disclosure is further offered to enhance an
understanding and appreciation for the inventive principles and
advantages thereof, rather than to limit in any manner the
invention. The invention is defined solely by the appended claims
including any amendments made during the pendency of this
application and all equivalents of those claims as issued.
[0017] Referring to FIG. 1, FIG. 1 shows a side sectional view of a
microelectromechanical systems (MEMS) sensor package 20 in
accordance with an embodiment. FIG. 1 and subsequent FIGS. 2-8 are
illustrated using various shading and/or hatching to distinguish
the different elements of the MEMS sensor packages, as will be
discussed below. These different elements within the structural
layers may be produced utilizing current and upcoming
micromachining techniques of depositing, patterning, etching, and
so forth. It should be further understood that the use herein of
relational terms, if any, such as first and second, top and bottom,
and the like are used solely to distinguish one from another entity
or action without necessarily requiring or implying any actual such
relationship or order between such entities or actions.
[0018] MEMS sensor package 20 generally includes MEMS die 22
coupled to an application specific integrated circuit (ASIC),
generally referred to herein as a semiconductor die 24.
Semiconductor die 24, in turn, may be coupled to a mounting pad 26
of a carrier, referred to herein as a lead frame 28. MEMS die 22
includes a substrate 30 and a cap layer 32. In an embodiment,
substrate 30 has a first inner surface 34 and a first outer surface
36. Similarly, cap layer 32 has a second inner surface 38 and a
second outer surface 40. Second inner surface 38 of cap layer 32 is
coupled to first inner surface 34 of substrate 30. A MEMS sensor 42
is formed on first inner surface 34 of substrate 30. More
particularly, cap layer 32 includes a cavity 44 extending inwardly
from second inner surface 38 and overlying a region 46 of first
inner surface 34 of substrate 30. MEMS sensor 42 resides in cavity
44 at region 46 of first inner surface 34 of substrate 30.
[0019] One or both of substrate 30 and cap layer 32 includes a port
48 extending between cavity 44 and a side wall 50 of MEMS die 22,
where side wall 50 extends between first outer surface 36 of
substrate 30 and second outer surface 40 of cap layer 32. In the
illustrated embodiment, port 48 is formed as a recess in second
inner surface 38 of cap layer 32. In other embodiments, port 48 may
be formed as a recess in first inner surface 34 of substrate 30.
MEMS sensor 42 may be a pressure sensor having a pressure
deformable diaphragm 52 disposed at region 46 of first inner
surface 34 of substrate 30. Port 48 is configured to admit a fluid,
e.g., air, from an environment external to cavity 44 into cavity
44. Since fluid can enter cavity 44 via port 48, MEMS pressure
sensor 42 having pressure deformable diaphragm 52 can detect an
ambient pressure 53, labeled P, of an environment external to MEMS
sensor package 20.
[0020] MEMS die 22 further includes bond pads 54 on first inner
surface 34 of substrate 30, but external to cap layer 32, and
conductive traces 56 (shown in FIG. 5) interconnected between MEMS
sensor 42 and bond pads 54. Conductive traces 56 suitably
electrically couple MEMS sensor 42 with bond pads 54. Bond pads 54
may be utilized to electrically connect MEMS sensor 42 to bond pads
58 of semiconductor die 24 via electrically conductive
interconnects, or bond wires 60 in this example. Semiconductor die
24 may include additional bond pads 62 that may be utilized to
electrically connect semiconductor die 24 to external connection
leads 64 of lead frame 28 via electrically conductive
interconnects, or bond wires 66 in this example. Leads 64 provide
input to and output from MEMS sensor package 20, as known to those
skilled in the art.
[0021] An encapsulant 68 covers, or encapsulates, MEMS die 22,
semiconductor die 24, bond wires 60, bond wires 66, and the top
surfaces of leads 64. Encapsulant 68 (e.g., a mold compound or
protective resin system) protects the components of MEMS sensor
package 20 from exposure to external elements (e.g., air, moisture,
and/or liquids) to provide robust mechanical and environmental
protection. It should be noted, however, that encapsulant 68 does
not obstruct port 48 in side wall 50 of MEMS sensor package 20.
Fabrication methodology presented in detail herein enables the
assembly of the components of MEMS sensor package 20 and, in some
embodiments, their encapsulation with encapsulant 68 without
obstructing port 48 in side wall 50.
[0022] Referring now to FIGS. 2 and 3, FIG. 2 shows a side
sectional view of a structure 70 that includes a first intermediate
sensor structure 72 and a second intermediate sensor structure 74
prior to singulation, and FIG. 3 shows a side sectional view of
structure 70 following singulation. First intermediate sensor
structure 72 is laterally displaced from second intermediate sensor
structure 74 within structure 70. Additionally, each of first and
second intermediate sensor structures 72, 74 includes the
structural components described in connection with FIG. 1. That is,
each of first and second intermediate sensor structures 72, 74
includes MEMS die 22, semiconductor die 24, lead frame 28, and bond
wires 60, 66 all of which are covered in encapsulant 68. Further
description of MEMS die 22, semiconductor die 24, lead frame 28,
and bond wires 60, 66 of first and second intermediate sensor
structures 72, 74 is not repeated herein for brevity.
[0023] In accordance with a particular embodiment, first and second
intermediate sensor structures 72, 74 of structure 70 are
interconnected via inactive/unused material regions 76 of each of a
cap layer structure 78, a substrate structure 80, a semiconductor
die structure 82, and a strip 84 of lead frames 28. Structure 70
further includes a channel 86 interposed between cavity 44 of first
intermediate sensor structure 72 and cavity 44 of second
intermediate sensor structure 74. Thus, cavity 44 of first
intermediate sensor structure 72 and cavity 44 of second
intermediate sensor structure 74 are in fluid communication with
one another.
[0024] First intermediate sensor structure 72 is configured to be
separated from second intermediate sensor structure 74 to produce a
first MEMS sensor package, referred to herein as a first pressure
sensor package 20A (FIG. 3), and to produce a second MEMS sensor
package, referred to herein as a second pressure sensor package 20B
(FIG. 3). That is, structure 70 may be sawn, diced, or otherwise
singulated at inactive/unused material regions 76 bounded by dashed
lines 88 in order to remove the material portion of structure 70
between dashed lines 88.
[0025] Following singulation, each of first and second pressure
sensor packages 20A, 20B includes the structural components
described in connection with FIG. 1. That is, each of first and
second sensor packages 20A, 20B includes MEMS die 22, semiconductor
die 24, lead frame 28, and bond wires 60, 66 all of which are
covered in encapsulant 68. The letter "A" is used in FIG. 3 to
denote the elements of first pressure sensor package 20A and the
letter "B" is used herein to denote the elements of second pressure
sensor package 20B for clarity of description. It should be
observed that the singulation process separates channel 86 into two
remaining portions. Thus, a first port 48A of first pressure sensor
package 20A is a first portion of channel 86 and a second port 48B
of second pressure sensor package 20B is a second portion of
channel 86.
[0026] Referring to FIGS. 4 and 5, FIG. 4 shows a side sectional
view of a MEMS die structure 89 that is part of structure 70 (FIG.
2), and FIG. 5 shows a top view of substrate structure 80 that may
be used to form structure 70. More particularly, MEMS die structure
89 of FIG. 4 includes cap layer structure 78 coupled with substrate
structure 80 to form a pair of MEMS dies 22. However, it should be
observed that FIG. 4 does not include semiconductor dies 24 (FIG.
2) and lead frames 28 (FIG. 2). FIG. 5 shows substrate structure 80
with cap layer structure 78 absent in order to reveal the features
of substrate structure 80.
[0027] In general, substrate structure 80 includes a bulk substrate
88 and a structural layer 90 fixed to a surface 92 of bulk
substrate 88. MEMS sensors 42 are formed on, or alternatively in,
structural layer 90. As shown, sets of bond pads 54 and conductive
traces 56 are also formed on structural layer 90. Substrate
structure 80 is shown with only two MEMS sensors 42 for simplicity
of illustration. It should be understood, however, that substrate
structure 80 can include multiple MEMS sensors 42 arranged in pairs
(as shown) in a high volume manufacturing configuration.
[0028] In accordance with an example embodiment, bulk substrate 88
has recesses 94 extending inwardly from surface 92 of bulk
substrate 88, and structural layer 90 is fixed to surface 92 of
bulk substrate 88 surrounding recesses 94. Material portions of
structural layer 90 are removed surrounding each of MEMS sensors 42
to form cantilevered platform structures 96 at which each of MEMS
sensors 42 reside. Thus, cantilevered platform structures 96 are
formed in structural layer 90 and each extends over a respective
one of recesses 94.
[0029] Each of cantilevered platform structures 96 includes a
platform 98 and an arm 100 extending from platform 98. One end of
arm 100 is fixed to platform 98 and the other end of arm 100 is
fixed to bulk substrate 88 via an attachment of arm 100 to a
portion of structural layer 90 fixed to surface 92 of bulk
substrate 88 surrounding recess 94. Thus, once the material
portions of structural layer 90 are removed, openings 102 extend
through structural layer 90 and partially surround cantilevered
platform structures 96. Accordingly, platforms 98 and arms 100 are
suspended over recesses 94, with an end of each of arms 100 being
the sole attachment point of each of cantilevered platform
structure 96 to the surrounding bulk substrate 88. Although each of
cantilevered platform structures 96 includes an arm 100 which forms
a sole attachment point to the surrounding bulk substrate 88, other
configurations may include more than one attachment point to the
surrounding bulk substrate.
[0030] The illustrated configuration yields MEMS sensors 42 each of
which is formed on a cantilevered platform structure 96 that is
suspended over a recess 94. The cantilevered platform structure can
achieve the benefits of improved package stress isolation and
improved device performance, especially for pressure sensor
configurations. However, it should be understood that alternative
embodiments need not include that cantilevered platform structures
overlying recesses. Instead, some embodiments may include MEMS
sensors that are formed on a solid substrate (i.e., do not have
recesses) and reside in cavities 44, but still require porting to
an external environment via port 48 (FIG. 1) in side wall 50 (FIG.
1).
[0031] Referring now to FIGS. 4 and 6, FIG. 6 shows a bottom view
of cap layer structure 78 that may be used to form structure 70
(FIG. 2). Cap layer 78 includes two cavities 44 and channel 86
extending inwardly from a surface 104 of cap layer structure 78.
Cap layer structure 78 is shown with only two cavities 44 formed
therein to correspond with substrate structure 80 (FIG. 5) and for
simplicity of illustration. It should be understood, however, that
cap layer structure 78 can include multiple cavities 44 arranged in
pairs with channels 86 extending between pairs of cavities 44 in a
high volume manufacturing configuration.
[0032] In general, cap layer structure 78 may be coupled with
substrate structure 80 via a bond material 106, where bonding may
be, for example, glass frit bonding, aluminum-germanium bonding,
copper-to-copper bonding, or any other suitable bonding process and
bonding material. Bond material 106 may be suitably located between
cap layer structure 78 and substrate structure 80 outside of the
boundaries of cavities 44 and channel 86. In some embodiments, when
cap layer structure 78 is coupled with substrate structure,
material portions 108 overlie bond pads 54. Thus, a saw-to-reveal
process may be performed to expose bond pads 54 from cap layer
structure 78. That is, following coupling with substrate structure
80, cap layer structure 78 may be sawn along saw lines (represented
by dashed lines 110) shown in FIG. 6 to remove material portions
108 and thereby expose bond pads 54. As such, bond material 106 may
be limited to those regions between saw lines 110 so as not to come
in contact with bond pads 54. In other embodiments, bond material
106 may not be limited to the regions between saw lines 110. As
such, following a saw-to-reveal process, bond material 106 may be
removed from bond pads 54.
[0033] FIG. 7 shows a side sectional view of a structure 112 that
includes a first intermediate sensor structure 114 and a second
intermediate sensor structure 116 prior to singulation in
accordance with another embodiment. Structure 112 is similar to
structure 70 (FIG. 2) described above. Thus, structure 112 includes
cap layer structure 78, substrate structure 80, and strip 84 so
that each of first and second intermediate sensor structures 114,
116 includes MEMS die 22, lead frame 28, and bond wires 60, 66 all
of which are covered in encapsulant 68. However, in lieu of
semiconductor die structure 82 (FIG. 2), structure 112 is
fabricated utilizing previously singulated semiconductor dies 24
that are suitably coupled to strip 84. The resulting encapsulated
structure 112 is singulated and channel 86 is split to expose the
two ports 48A, 48B to the external environment, as discussed
above.
[0034] FIG. 8 shows a side sectional view of a structure 118 that
includes a first intermediate sensor structure 120 and a second
intermediate sensor structure 122 prior to singulation in
accordance with another embodiment. Structure 118 is similar to
structure 70 (FIG. 2). Thus, structure 118 includes cap layer
structure 78, semiconductor die structure 82, strip 84, and bond
wires 66 all of which are covered in encapsulant 68. However, in
lieu of substrate structure 80 (FIG. 2), structure 118 is
fabricated utilizing a substrate structure 124 that includes many
of the elements described above including MEMS sensors 42. However,
substrate structure 124 includes electrically conductive
interconnects in the form of electrically conductive vias 126
extending through a bulk substrate 128 of substrate structure in
lieu of bond wires 60 (FIG. 2). Conductive vias 126 can thus form
the electrical connections between MEMS sensors 42 and
semiconductor dies 24 of semiconductor die structure 82.
[0035] Such a structural configuration eliminates the need for bond
wires between the MEMS sensor and the underlying semiconductor die
which may reduce packaging size and complexity. The resulting
encapsulated structure 118 is singulated and channel 86 is split to
expose the two ports 48A, 48B to the external environment, as
discussed above.
[0036] FIG. 9 shows a side sectional view of a structure 130 that
includes a first intermediate sensor structure 132 and a second
intermediate sensor 134 structure prior to singulation in
accordance with yet another embodiment. Structure 130 includes cap
layer structure 78 and substrate structure 124 having electrically
conductive vias 126 extending through it. Structure 130 further
includes a semiconductor die structure 136 having electrically
conductive vias 138 extending through it. Electrically conductive
vias 138 are provided in lieu of bond wires 66 (FIG. 2) and lead
frame 28 (FIG. 2) and enable input to and output from the resulting
MEMS sensor packages.
[0037] Since conductive vias 126 are internal to substrate
structure 124 and conductive vias 138 are internal to semiconductor
die structure 136, the resulting package need not be encapsulated
in encapsulant 68 (FIG. 1). Furthermore, savings may be achieved in
terms of the packaging complexity and overall size of the resulting
MEMS sensor packages. The resulting structure 130 is singulated and
channel 86 is split to expose the two ports 48A, 48B to the
external environment, as discussed above.
[0038] Now referring to FIG. 10, FIG. 10 shows a flowchart of a
sensor package fabrication process 140 in accordance with another
embodiment. The methodology entails fabrication of side oriented
ports (for example, pressure ports) into the silicon that are
exposed at strip singulation. Sensor package fabrication process
140 will be described in connection with the fabrication of two
MEMS sensor packages 20A, 20B (FIG. 3) shown in detail in FIGS. 1-6
for simplicity of illustration. However it should be apparent to
those skilled in the art that the ensuing methodology may be
executed to concurrently fabricate more than two MEMS sensor
packages 20 in a high volume manufacturing environment.
Additionally, it should be understood that sensor package
fabrication process 140 may be adapted to produce any of the MEMS
sensor package configurations alternatively described in connection
with FIGS. 7-9 above.
[0039] The ordering of process operations presented below in
connection with sensor package fabrication process 140 should not
be construed as limiting, but is instead provided as an example of
a possible fabrication method that may be implemented. Furthermore,
it will be understood by those skilled in the art that the
following process operations may be executed in a different order
than presented below.
[0040] Sensor package fabrication process 140 includes process
blocks related to the fabrication of MEMS die structure 89 (FIG. 4)
having MEMS sensors 42 formed therein. These process blocks are
delineated by a larger dashed line box and include blocks 142, 144,
and 146. At block 142 of sensor package fabrication process 140,
substrate structure 80 is provided having MEMS sensors 42 formed
thereon. At block 144, cap layer structure 78 (FIGS. 4 and 6) is
provided, with cavities 44 and channel 86 being formed in cap layer
78. At block 146, cap layer 78 is coupled to substrate structure 80
via bond material 106 to form MEMS die structure 89. As mentioned
previously, bonding may be performed using any other suitable
bonding process and material.
[0041] At a block 148, semiconductor die structure 82 containing
semiconductor dies 24 may be coupled to strip 84 (FIG. 2) of lead
frames 28 in some embodiments. Of course, in configurations that do
not include a lead frame (e.g., structure 130 of FIG. 9), block 148
need not be performed. At a block 150, MEMS die structure 89 formed
in accordance with process blocks 142, 144, 146 is coupled with
semiconductor die structure 82 using, for example, a die attach
adhesive.
[0042] At a block 152, the electrically conductive interconnects
may be formed. Referring to FIG. 2, bond wires 60 may be formed
between substrate structure 80 and semiconductor die structure 82.
Additionally, bond wires 66 may be formed between semiconductor die
structure 82 and external connection leads 64 of lead frames 28.
Referring to FIG. 8, in configurations that do not include bond
wires 60 (e.g., structure 118), the electrically conductive
interconnects in the form of conductive vias 126 will be formed
during fabrication of substrate structure 124 and the electrically
conductive interconnects in the form of bond wires 66 will be
formed after semiconductor die structure 82 is coupled to strip 84
of lead frames 28. Referring now to FIG. 9, in still other
configurations that do not include any bond wires 60, 66 (e.g.,
structure 130), the electrically conductive interconnects in the
form of conductive vias 126 will be formed during fabrication of
substrate structure 124 and the electrically conductive
interconnects in the form of vias 138 will be formed during
fabrication of semiconductor die structure 136.
[0043] At a block 154, strip 84, semiconductor die structure 82,
substrate structure 80, cap layer 78, and bond wires 60, 66 are
encapsulated (i.e., covered) in encapsulant 68. Referring to FIGS.
2, 7, and 8, the side oriented channel 86 that will become ports
48A, 48B following singulation is protected from encapsulant 68. In
configurations that do not include encapsulant 68 (e.g., structure
130 of FIG. 9), block 154 need not be performed.
[0044] Some prior art structures call for the bond wires to pass
through a gel coating. The gel coating is prone to bubble formation
and can cause flexing of the bond wires. Bubble formation and
flexing of the bond wires can cause the parasitic capacitances
between neighboring wires to change, thus adversely affecting the
sensor offset. In accordance with the embodiments described herein,
since bond wires 60 and bond wires 66 are encapsulated (FIGS. 2 and
6) in encapsulant 68 and/or through the use of conductive vias 126
(FIG. 7), the bond wires advantageously need not pass through the
gel coating.
[0045] Following encapsulation block 154, a process block 156 is
performed. At block 156, a singulation process (e.g., wet sawing,
laser cutting, or the like) may be performed to separate the over
molded structure into the individual first and second sensor
packages 20A, 20B and to expose ports 48A, 48B. In cases in which
the structure may be damaged by debris entering cavities 44 via
ports 48A, 48B by conventional singulation techniques, singulation
may be performed using a stealth dicing technique, by using a two
step dicing operation to clear out any electrically conductive
material produced by a first dicing operation prior to performing
the second dicing operation, or any other technique which largely
prevents or limits the entry of debris into cavities 44 via ports
48A, 48B.
[0046] Following block 156, sensor package fabrication process 140
ends following the production of multiple MEMS sensor packages,
each of which includes a side port extending between a cavity and a
side wall of the sensor package. The side port is configured to
admit a fluid, e.g., air, external to the cavity into the cavity.
When the MEMS sensor package includes a pressure sensor, the
pressure of the fluid entering the cavity can be suitably detected
by the pressure sensor.
[0047] An embodiment of a MEMS sensor package comprises a MEMS die,
said MEMS die comprising a substrate having a first inner surface
and a first outer surface, a MEMS sensor formed on the first inner
surface, and a cap layer having a second inner surface and a second
outer surface. The second inner surface of the cap layer is coupled
to the first inner surface of the substrate. The cap layer includes
a cavity extending inwardly from the second inner surface and
overlying a region of the first inner surface of the substrate. The
MEMS sensor resides in the cavity at the region of the first inner
surface of the substrate, and one of the substrate and the cap
layer includes a port extending between the cavity and a side wall
of the MEMS die, where the side wall extends between the first
outer surface of the substrate and the second outer surface of the
cap layer.
[0048] An embodiment of a method of making MEMS sensor packages
comprises providing a substrate having a first inner surface and a
second outer surface, the substrate including a first MEMS sensor
at a first region of the first inner surface and a second MEMS
sensor at a second region of the first inner surface, the second
region being laterally displaced from the first region, and
providing a cap layer having a second inner surface and a second
outer surface, the cap layer including a first cavity and a second
cavity laterally displaced from the first cavity, each of the first
and second cavities extending inwardly from the second inner
surface. A channel is formed extending inwardly from one of the
first inner surface of the substrate and the second inner surface
of the cap layer. The second inner surface of the cap layer is
coupled to the first inner surface of the substrate such that the
first cavity overlies the first region to form a first intermediate
sensor structure, the second cavity overlies the second region to
form a second intermediate sensor structure, and the channel is
interposed between the first and second cavities such that the
first and second cavities are in fluid communication with one
another. The first intermediate sensor structure is separated from
the second intermediate sensor structure to produce a first MEMS
sensor package and a second MEMS sensor package.
[0049] An embodiment of a structure comprises a substrate having a
first inner surface and a first outer surface, a MEMS pressure
sensor formed on the first inner surface, a cap layer having a
second inner surface and a second outer surface, and an encapsulant
covering the substrate and the cap layer, wherein the second inner
surface of the cap layer is coupled to the first inner surface of
the substrate, the cap layer includes a cavity extending inwardly
from the second inner surface and overlying a region of the first
inner surface of the substrate, the MEMS pressure sensor resides in
the cavity and includes a pressure deformable diaphragm disposed at
the region of the first inner surface of the substrate, one of the
substrate and the cap layer includes a port extending between the
cavity and a side wall of the cap layer, the side wall extending
between the first outer surface of the substrate and the second
outer surface of the cap layer, and the encapsulant does not
obstruct the port.
[0050] Thus, a MEMS sensor package is formed, through the execution
of relatively simple methodology, to include a MEMS sensor on
substrate that is covered by a cap layer. The MEMS sensor resides
in a cavity formed in the cap layer, and a port extends between the
cavity and a side wall of one of the substrate and the cap layer.
The port, formed in the side wall, is exposed during a strip
singulation operation of the methodology so that fluid, such as
air, external to the cavity can be admitted into the cavity.
Accordingly, the MEMS sensor may be a pressure sensor which is
stress isolated and can be overmolded, and the pressure sensor is
capable of sensing pressure from an environment external to the
sensor via the port.
[0051] This disclosure is intended to explain how to fashion and
use various embodiments in accordance with the invention rather
than to limit the true, intended, and fair scope and spirit
thereof. The foregoing description is not intended to be exhaustive
or to limit the invention to the precise form disclosed. A vast
number of variations or modifications are possible in light of the
above teachings. The embodiment(s) was chosen and described to
provide the best illustration of the principles of the invention
and its practical application, and to enable one of ordinary skill
in the art to utilize the invention in various embodiments and with
various modifications as are suited to the particular use
contemplated. All such modifications and variations are within the
scope of the invention as determined by the appended claims, as may
be amended during the pendency of this application for patent, and
all equivalents thereof, when interpreted in accordance with the
breadth to which they are fairly, legally, and equitably
entitled.
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