U.S. patent number RE46,671 [Application Number 14/069,136] was granted by the patent office on 2018-01-16 for substrate-level assembly for an integrated device, manufacturing process thereof and related integrated device.
This patent grant is currently assigned to STMicroelectronics S.r.l.. The grantee listed for this patent is STMicroelectronics S.r.l.. Invention is credited to Lorenzo Baldo, Chantal Combi, Ernesto Lasalandra, Manuela Magugliani, Caterina Riva, Benedetto Vigna, Federico Giovanni Ziglioli.
United States Patent |
RE46,671 |
Combi , et al. |
January 16, 2018 |
Substrate-level assembly for an integrated device, manufacturing
process thereof and related integrated device
Abstract
A substrate-level assembly having a device substrate of
semiconductor material with a top face and housing a first
integrated device, including a buried cavity formed within the
device substrate, and with a membrane suspended over the buried
cavity in the proximity of the top face. A capping substrate is
coupled to the device substrate above the top face so as to cover
the first integrated device in such a manner that a first empty
space is provided above the membrane. Electrical-contact elements
electrically connect the integrated device with the outside of the
substrate-level assembly. In one embodiment, the device substrate
integrates at least a further integrated device provided with a
respective membrane, and a further empty space, fluidly isolated
from the first empty space, is provided over the respective
membrane of the further integrated device.
Inventors: |
Combi; Chantal (Oggiono Lecco,
IT), Vigna; Benedetto (Potenza, IT),
Ziglioli; Federico Giovanni (Pozzo d'adda, IT),
Baldo; Lorenzo (Bareggio, IT), Magugliani;
Manuela (Cornaredo, IT), Lasalandra; Ernesto (San
Donato Milanese, IT), Riva; Caterina (Cusago,
IT) |
Applicant: |
Name |
City |
State |
Country |
Type |
STMicroelectronics S.r.l. |
Agrate Brianza |
N/A |
IT |
|
|
Assignee: |
STMicroelectronics S.r.l.
(Agrate Brianza, IT)
|
Family
ID: |
37459387 |
Appl.
No.: |
14/069,136 |
Filed: |
October 31, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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PCT/EP2006/064298 |
Jul 14, 2006 |
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Reissue of: |
12102709 |
Apr 14, 2008 |
8049287 |
Nov 1, 2011 |
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Foreign Application Priority Data
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Oct 14, 2005 [EP] |
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0542719 |
Apr 28, 2006 [WO] |
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PCT/EP2006/061940 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B81C
1/0023 (20130101); B81B 7/02 (20130101); B81B
7/0061 (20130101); B81C 1/0023 (20130101); B81B
2201/0264 (20130101); B81B 2201/0235 (20130101); H04R
19/005 (20130101); H04R 1/04 (20130101); H01L
2924/1461 (20130101); B81B 2201/0235 (20130101); H01L
2224/48091 (20130101); H01L 2924/1461 (20130101); H01L
2924/3025 (20130101); H01L 2224/73265 (20130101); H01L
2224/48091 (20130101); H01L 2924/00014 (20130101); H01L
2924/3025 (20130101); H01L 2924/00 (20130101); H01L
2924/1461 (20130101); H01L 2924/00 (20130101) |
Current International
Class: |
H01L
29/84 (20060101); B81C 1/00 (20060101) |
Field of
Search: |
;257/416 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1577656 |
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Mar 2004 |
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EP |
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1 577 656 |
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Sep 2005 |
|
EP |
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1 684 079 |
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Jul 2006 |
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EP |
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7-225240 |
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Aug 1995 |
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JP |
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9-304211 |
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Nov 1997 |
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JP |
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11111878 |
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Apr 1999 |
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JP |
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2003-163998 |
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Jun 2003 |
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JP |
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2005-180930 |
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Jul 2005 |
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JP |
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5043297 |
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Oct 2012 |
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JP |
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2004/068094 |
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Aug 2004 |
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WO |
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2007/112743 |
|
Oct 2007 |
|
WO |
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2007/112743 |
|
Oct 2007 |
|
WO |
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Other References
Sebastiano, Conti et al., "Assembly of a Capacitive Acoustic
Transducer of the Microelectromechanical Type and Package Thereof,"
U.S. Appl. No. 12/777,058, filed May 10, 2010, 48 pages. cited by
applicant.
|
Primary Examiner: Andujar; Leonardo
Attorney, Agent or Firm: Seed Intellectual Property Law
Group LLP
Claims
The invention claimed is:
1. .[.A substrate-level.]. .Iadd.An .Iaddend.assembly, comprising:
a device substrate of semiconductor material.[.,.]. having a top
face .[.and housing a first integrated device provided with an
active area adjacent to the top face.]. .Iadd.that includes a first
buried cavity in the device substrate and a first membrane
suspended above the first buried cavity, the device substrate
further including a second membrane.Iaddend.; a .[.capping
substrate.]. .Iadd.cap .Iaddend.coupled to the device substrate
above the top face .[.so as to cover the first integrated device in
such a manner that.]. .Iadd.and covering an upper portion of the
device substrate and forming .Iaddend.a first empty space .[.is
provided in a position corresponding to the active area.].
.Iadd.between an inner surface of the cap and the first membrane of
the device substrate and forming a second empty space between an
inner surface of the cap and a surface of the second membrane, the
first and second empty spaces being isolated from each other; and
an access duct in the cap that provides fluid connectivity between
the first empty space and an environment outside of the
assembly.Iaddend.; and electrical-contact elements for electrical
connection of the .[.first integrated device.]. .Iadd.device
substrate to a location .Iaddend.outside of the
.[.substrate-level.]. assembly.
2. The assembly of claim 1, wherein .[.the first integrated device
is provided with a buried cavity formed within the device substrate
and a membrane suspended over the buried cavity at the active area;
the first empty space being provided in a position corresponding to
the membrane.]. .Iadd.electrical-contact elements include at least
one of contact pads located on the top surface of the device
substrate or on a bottom surface of the device
substrate.Iaddend..
3. The assembly of claim .[.1, wherein an access duct is provided
within the capping substrate, the access duct being fluidly
connected to the first empty space and to the outside of the
substrate-level assembly.]. .Iadd.2 wherein the electrical-contact
elements include through vias that are coupled to a respective
contact pad on the bottom surface of the device
substrate.Iaddend..
4. The assembly of claim 1, wherein .[.the capping substrate has a
first sensor cavity above the active area of the first integrated
device, the first sensor cavity forming at least in part the first
empty space; in particular,.]. the first .[.sensor cavity having.].
.Iadd.empty space has .Iaddend.a depth in the range of 10 .mu.m and
400 .mu.m.
5. The assembly of claim 1, further comprising .Iadd.a surface of
the cap bonded to a surface of the device substrate at .Iaddend.a
bonding region .[.arranged between the device substrate and the
capping substrate to ensure joining thereof, and placed in contact
with the top face in such a manner as to surround, without being
superimposed thereon, the active area of the first integrated
device; the first empty space being delimited, at least in part, by
the bonding region.]..
6. The assembly of claim 5, wherein .[.the capping substrate is
flat and not patterned and.]. the bonding region has a thickness
between 6 .mu.m and 100 .mu.m .[.to entirely define a thickness of
the first empty space.]..
7. The assembly of claim 5, wherein the .[.capping substrate
includes one between.]. .Iadd.cap is formed from at least one of
the following materials.Iaddend.: semiconductor material, glass,
ceramic, and polymeric material.[.; and wherein the bonding region
includes glass frit or a metal or polymeric material.]..
8. The assembly of claim 5, wherein .[.at least one of.]. the
.[.capping substrate.]. .Iadd.cap .Iaddend.and bonding region is
made of a conductive material configured to provide an
electrostatic shield for the first integrated device.[.; the first
integrated device comprising.]..Iadd., and wherein the first
membrane is part of .Iaddend.a microphone.
9. The assembly of claim .[.2, wherein the electrical-contact
elements comprise at least one of through vias made through the
device substrate and electrical-connection pads formed on a portion
of the top face of the device substrate not covered by the capping
substrate; and.]. .Iadd.1 .Iaddend.wherein the .[.first integrated
device further comprises a buried cavity formed within the device
substrate, a membrane suspended over the buried cavity, and.].
.Iadd.device substrate includes .Iaddend.transduction elements
configured to transform a deformation of the .Iadd.first
.Iaddend.membrane into electrical signals, the electrical-contact
elements being .[.connected.]. .Iadd.coupled .Iaddend.to the
transduction elements.
10. The assembly of claim 1, .[.wherein the first integrated device
further comprises a buried cavity formed within the device
substrate and a membrane suspended over the buried cavity; and a
first access duct is provided within the capping substrate and
fluidly connected to the first empty space and to the outside of
the substrate-level assembly; and.]. .Iadd.further comprising
.Iaddend.a second access duct is provided within the device
substrate in fluid communication with the .Iadd.first
.Iaddend.buried cavity .[.of the integrated device.]. and with the
.Iadd.environment .Iaddend.outside of the .[.substrate-level.].
assembly.
11. The assembly of claim 1, wherein .[.a first access duct and a
plurality of further access ducts are provided within the capping
substrate, and fluidly connected to.]. .Iadd.the cap includes a
plurality of access ducts that provide fluid connectivity between
.Iaddend.the first empty space and to the .Iadd.environment
.Iaddend.outside of the .[.substrate-level.]. assembly.[.; the
first and further access ducts being at least one of: different
size and separated by a different inter-spacing.]..
.[.12. The assembly of claim 1, wherein the device substrate houses
at least a further integrated device provided with a respective
active area; and wherein a further empty space is provided in a
position corresponding to the respective active area of the further
integrated device; the further empty space being fluidly isolated
with respect to the first empty space..].
13. The assembly of claim .[.12.]. .Iadd.1.Iaddend., wherein .[.the
capping substrate has at least one further sensor cavity set above
the respective active area of the further integrated device, and
forming, at least in part, the further empty space; the first empty
space and further empty space separated in a fluid-tight manner, at
least in part, by a separation portion of the capping substrate
placed between the first empty space and the further empty space.].
.Iadd.the second empty space is not in fluid communication with the
environment outside the assembly.Iaddend..
14. The assembly of claim .[.12.]. .Iadd.1.Iaddend., .[.further
comprising a bonding region placed between the device substrate and
the capping substrate, and in contact with the top face of the
device substrate in such a manner as to surround, without being
superimposed thereon, the active area of the first integrated
device and the respective active area of the further integrated
device; the first empty space and the further empty space being
delimited, at least in part, by the bonding region.]. .Iadd.wherein
the device substrate includes a second buried cavity and the second
membrane is suspended above the second buried cavity.Iaddend..
15. The assembly of claim .[.12.]. .Iadd.1.Iaddend., wherein .[.the
first integrated device further comprises a buried cavity formed
within the device substrate and a membrane suspended over the
buried cavity, and the further integrated device comprising a
respective buried cavity formed within the device substrate and a
respective membrane suspended over the respective buried cavity;
and wherein the first integrated device is a pressure sensor, and
the further integrated device is an inertial sensor, the inertial
sensor comprising an inertial mass arranged on the respective
membrane within the further empty space.]. .Iadd.the second
membrane is an inertial sensor.Iaddend..
16. The assembly of claim 15, wherein the inertial .Iadd.sensor
includes an inertial .Iaddend.mass .Iadd.arranged on the second
membrane and the inertial mass .Iaddend.includes metal
material.[.,.]. deposited directly on top of the .[.respective.].
membrane.[.; the metal material chosen from the group comprising
silver, tin, copper, lead, and gold, and having a density greater
than 7000 kg/m.sup.3.]..
17. The assembly of claim .[.12.]. .Iadd.1.Iaddend., wherein the
first .[.integrated device comprises.]. .Iadd.membrane, the first
empty space, and the first buried cavity are part of .Iaddend.a
pressure sensor, and the .[.further integrated device comprises.].
.Iadd.second membrane, second empty space, and a second buried
cavity are part of .Iaddend.a reference pressure sensor for the
pressure sensor.
18. The assembly of claim 1, wherein the first .[.integrated device
further comprises a buried cavity formed within the device
substrate and a membrane suspended over the buried cavity; the
first integrated device comprising.]. .Iadd.membrane, the first
empty space, and the first buried cavity are part of .Iaddend.a
microphone sensor having a back-chamber separated from the
.Iadd.first .Iaddend.buried cavity by a sensing diaphragm
configured to move as a result of the pressure exerted thereon by
sound waves reaching the .Iadd.first .Iaddend.buried cavity.
19. The assembly of claim .[.18.]. .Iadd.1.Iaddend., wherein the
first .[.integrated device further comprises a buried cavity formed
within the device substrate and a membrane suspended over the
buried cavity; the first integrated device comprising.].
.Iadd.membrane, the first empty space, and the first buried cavity
form .Iaddend.a gas sensor and the .Iadd.first .Iaddend.membrane
.[.including.]. .Iadd.includes .Iaddend.a detection material
configured to allow detecting the presence of a gaseous
material.[.; the membrane being thermally decoupled from the device
substrate.]..
20. The assembly of claim .[.1.]. .Iadd.12.Iaddend., wherein the
.[.capping substrate includes a layer grown on the device
substrate, in particular by electroplating or epitaxial steps; the
capping substrate being integral to the device substrate.].
.Iadd.second membrane includes an accelerometer.Iaddend..
21. An electronic device, comprising: .[.a substrate-level.].
.Iadd.an .Iaddend.assembly that includes: a device substrate of
semiconductor material.[.,.]. having a top face and .[.housing a.].
.Iadd.including .Iaddend.first .[.integrated device provided with
an active area adjacent to the top face.]. .Iadd.and second sensor
regions.Iaddend.; a .[.capping substrate.]. .Iadd.cap
.Iaddend.coupled to the device substrate above the top face so as
to cover the first .[.integrated device.]. .Iadd.and second sensor
regions .Iaddend.in such a manner that a first .[.empty space.].
.Iadd.cavity .Iaddend.is provided .[.in a position corresponding to
the active area.]. .Iadd.above the first sensor region and a second
cavity is provided above the second sensor region, the first cavity
being separate from the second cavity.Iaddend.; and
electrical-contact elements for electrical connection .[.of.].
.Iadd.to .Iaddend.the first .[.integrated device.]. .Iadd.and
second sensor regions extending .Iaddend.outside of the
.[.substrate-level assembly.]. .Iadd.first and second
cavities.Iaddend.; and a package .[.encasing and mechanically
protecting the substrate-level assembly; wherein the package
comprises.]. .Iadd.that includes.Iaddend.: a base body mechanically
supporting the .[.substrate-level.]. assembly, and .[.a.]. .Iadd.an
insulative .Iaddend.coating .[.region configured to coat
laterally.]. .Iadd.material that is located on lateral sides of
.Iaddend.the .[.substrate-level.]. assembly.
22. The device of claim 21, wherein an access duct is provided
within the .[.capping substrate.]. .Iadd.cap.Iaddend., the access
duct being fluidly connected to the first empty space and to
.[.the.]. .Iadd.an environment .Iaddend.outside of
.[.substrate-level.]. .Iadd.the .Iaddend.assembly, wherein the
coating .[.region.]. leaves .Iadd.the access duct
.Iaddend.uncovered and accessible from the outside: a top surface
of the .[.capping substrate.]. .Iadd.cap .Iaddend.defining part of
a first outer face of the package, and the access duct.
23. The device of claim 21, wherein the package is of an LGA, SO,
QFN or BGA type, and has contact pads carried by a surface of the
base body.[., which is not in contact with the substrate-level
assembly and.]. .Iadd.that .Iaddend.defines a second outer face of
the package.
24. The device of claim 21, .[.further comprising a circuit die
electrically coupled to the substrate-level assembly and encased by
the package: wherein the device substrate and circuit die are
mechanically coupled to the base body through a respective adhesion
layer, and arranged side by side.]. .Iadd.wherein the first sensor
region includes a buried cavity formed in the device substrate and
a membrane suspended above the buried cavity.Iaddend..
25. The device of claim .[.21.]. .Iadd.24.Iaddend., .[.further
comprising a circuit die electrically coupled to the
substrate-level assembly and encased by the package; the circuit
die being mechanically coupled to the base body, and the device
substrate being mechanically coupled to the circuit die in a
stacked manner.]. .Iadd.wherein the cap includes an access duct
that places the first cavity is fluid communication with an
environment outside of the assembly.Iaddend..
26. The device of claim 21, further comprising an access duct
extending through the base body and reaching the
.[.substrate-level.]. assembly at a surface thereof, opposite to
the top face.
27. The device of claim 21, wherein the electronic device comprises
one of: a tire-pressure monitoring system, a blood-pressure
monitoring system, an ink-ejection system, and a mobile phone.
28. A process for manufacturing .[.a substrate-level.]. .Iadd.an
.Iaddend.assembly, comprising: providing a device substrate of
semiconductor material, having a top face; forming a first
.[.integrated device within.]. .Iadd.sensor region in a top face of
.Iaddend.the device substrate, .[.and with an active area adjacent
to the top face.]..Iadd.the first sensor region including a buried
cavity and a membrane suspended above the buried cavity.Iaddend.;
coupling a .[.capping substrate.]. .Iadd.cap .Iaddend.to the device
substrate above the top face so as to cover .[.the first integrated
device, the coupling comprising forming.]. .Iadd.and form
.Iaddend.a first empty space .[.in a position corresponding to the
active area.]. .Iadd.above the membrane, the cap including a
plurality of access ducts that places the first empty space in
fluid communication with an environment outside of the assembly,
the plurality of access ducts being of different sizes or a
different inter-spacing being provided therebetween or a
combination of different sizes and different
inter-spacing.Iaddend.; and forming electrical-contact elements
.Iadd.from the top face of the device substrate to a bottom face of
the device substrate .Iaddend.for electrical connection of the
first integrated device with the outside of the
.[.substrate-level.]. assembly.
29. The process of claim 28, .[.wherein forming a first integrated
device further comprises forming a buried cavity within the device
substrate and a membrane suspended over the buried cavity, the
first empty space formed in a position corresponding to the
membrane.]. .Iadd.further comprising forming a second sensor region
in the top face of the device substrate, wherein coupling the cap
to the device substrate further comprises forming a second empty
space above the second sensor region.Iaddend..
30. The process of claim .[.28, further comprising forming in the
capping substrate access duct fluidly connected to the first empty
space and to the outside of the substrate-level assembly.].
.Iadd.29, wherein the first empty space is fluidly isolated from
the second empty space.Iaddend..
31. The process of claim 28, wherein .[.forming a first empty space
comprises forming in the capping substrate a sensor cavity above
the active area of the first integrated device.]. .Iadd.the first
sensor region includes a pressure sensor component and the second
sensor region includes an accelerometer component or a reference
pressure sensor component.Iaddend..
32. The process of claim 28, wherein .[.the mechanically.].
coupling .Iadd.the cap to the device .Iaddend.comprises: forming a
bonding region between the device substrate and the .[.capping
substrate.]. .Iadd.cap .Iaddend.and in contact with the top face of
the device substrate in such a manner as to surround.[., without
being superimposed thereon, the active area of the first integrated
device;.]. .Iadd.an active area of the first sensor region
.Iaddend.and joining the device substrate and the .[.capping
substrate.]. .Iadd.cap .Iaddend.via the bonding region; and wherein
the first empty space is delimited, at least in part, by the
bonding region.
33. The process of claim 28, wherein .[.forming a first integrated
device further comprises forming a buried cavity within the device
substrate, and a membrane suspended over the buried cavity, and
forming.]. .Iadd.the first sensor region includes
.Iaddend.transducer elements configured to transform .[.into
electrical signals.]. a deformation of the membrane.[., and forming
electrical-contact elements comprises: forming at least one between
through vias through the device substrate, and forming
electrical-connection pads on a portion of the top face of the
device substrate not covered by the capping substrate; and
connecting the through vias or the electrical-connection pads to
the transduction elements.]. .Iadd.into electrical
signals.Iaddend..
34. The process of claim 28, .[.wherein forming a first integrated
device further comprises forming a buried cavity within the device
substrate, and a membrane suspended over the buried cavity; further
comprising forming in the capping substrate a first access duct,
fluidly connected to the first empty space and to the outside of
the substrate-level assembly, and.]. .Iadd.further comprising
.Iaddend.forming in the device substrate a second access duct in
fluid communication with the buried cavity of the .[.integrated
device.]. .Iadd.first sensor region .Iaddend.and with the
.Iadd.environment .Iaddend.outside of the .[.substrate-level.].
assembly.
.[.35. The process of claim 28, further comprising forming a first
access duct and a plurality of further access ducts within the
capping substrate and fluidly connected to the first empty space
and to the outside of the substrate-level assembly; in particular,
the first and further access ducts being of different size or a
different inter-spacing being provided therebetween or a
combination of different size and different inter-spacing..].
36. The process of claim 28, further comprising: forming in the
device substrate at least one .[.further integrated device provided
with a respective.]. .Iadd.second sensor region having an
.Iaddend.active area; .Iadd.and .Iaddend. the coupling further
comprising forming a .[.further.]. .Iadd.second .Iaddend.empty
space in a position corresponding to the respective active area of
the .[.further integrated device;.]. .Iadd.second sensor region,
.Iaddend.the .[.further.]. .Iadd.second .Iaddend.empty space being
fluidly isolated from the first empty space.
37. The process of claim 36, wherein forming a .[.further.].
.Iadd.second .Iaddend.empty space comprises forming at least .[.a
further.]. .Iadd.one second .Iaddend.sensor cavity in the
.[.capping substrate.]. .Iadd.cap.Iaddend., over the respective
active area of the .[.further integrated device.]. .Iadd.second
sensor region.Iaddend.; the forming at least .[.a further.].
.Iadd.one second .Iaddend.sensor cavity comprising separating the
first empty space and the .[.further.]. .Iadd.second .Iaddend.empty
space via a separation portion of the .[.capping substrate.].
.Iadd.cap.Iaddend..
38. The process of claim 36, wherein .[.the.]. coupling .Iadd.the
cap to the device substrate .Iaddend.comprises forming a bonding
region set between the device substrate and the .[.capping
substrate.]. .Iadd.cap .Iaddend.and in contact with the top face in
such a manner as to surround.[., without being superimposed
thereon, the active area of the first integrated device and the
respective active area of the further integrated device; the first
empty space and the further empty space being delimited, at least
in part, by the bonding region.]. .Iadd.the membrane of the first
sensor region.Iaddend..
39. The process of claim .[.36, wherein forming a first integrated
device.]. .Iadd.29 wherein forming the second sensor region
.Iaddend.comprises forming a buried cavity within the device
substrate and a membrane suspended over the buried cavity, .[.and
forming a further integrated device comprises forming a respective
buried cavity within the device substrate and a respective membrane
suspended over the respective buried cavity; and wherein forming a
first integrated device comprises forming a pressure sensor, and
forming at least one further integrated device comprises.].
.Iadd.the process further comprising .Iaddend.forming an inertial
sensor that comprises forming an inertial mass on the
.[.respective.]. membrane .[.and within the further empty space.].
.Iadd.of the second sensor region.Iaddend..
40. The process of claim 39, wherein forming .[.an.]. .Iadd.the
.Iaddend.inertial mass comprises depositing directly on top of the
respective membrane metal material chosen in the group comprising
silver, tin, copper, lead, and gold, and having a density higher
than 7000 kg/m.sup.3.
41. The process of claim .[.36.]. .Iadd.29.Iaddend., wherein
forming .[.a first integrated device.]. .Iadd.the first sensor
region .Iaddend.comprises forming .Iadd.a portion of .Iaddend.a
pressure sensor, and forming .[.at least one further integrated
device.]. .Iadd.a second sensor region .Iaddend.comprises forming
.Iadd.a portion of .Iaddend.a reference pressure sensor for the
pressure sensor.
42. The process of claim 28, wherein forming .[.a first integrated
device.]. .Iadd.the first sensor region .Iaddend.comprises forming
.Iadd.a portion of .Iaddend.a microphone sensor .[.that includes a
buried cavity within the device substrate, a membrane suspended
over the buried cavity,.]. and a back-chamber separated from the
buried cavity by a sensing diaphragm configured to move as a result
of pressure exerted thereon by sound waves reaching the buried
cavity.
43. The process of claim 28, wherein forming .[.a first integrated
device.]. .Iadd.the first sensor region .Iaddend.comprises forming
.Iadd.a portion of .Iaddend.a gas sensor, .[.and in particular a
buried cavity within the device substrate, and a membrane suspended
over the buried cavity; forming.]. the membrane .[.comprising
forming.]. .Iadd.of the gas sensor including .Iaddend.a detection
material configured to allow detecting the presence of a gaseous
material.[., the membrane being thermally decoupled from the device
substrate.]..
44. The process of claim 28, wherein coupling the .[.capping
substrate.]. .Iadd.cap .Iaddend.comprises growing a layer of
material on the device substrate by electroplating or epitaxial
steps; the .[.capping substrate.]. .Iadd.cap .Iaddend.being
integral to the device substrate.
45. A process for manufacturing an electronic device, comprising:
forming .[.a substrate-level.]. .Iadd.an .Iaddend.assembly, the
forming including: .[.providing a device substrate of semiconductor
material, having a top face;.]. forming a first .[.integrated
device within the device substrate and with an active area adjacent
to the top face.]. .Iadd.buried cavity in a device substrate of
semiconductor material, a first membrane being located above the
buried cavity.Iaddend.; .Iadd.forming a second buried cavity in the
device substrate, a second membrane being located above the second
buried cavity; .Iaddend. coupling a .[.capping substrate.].
.Iadd.cap .Iaddend.to the device substrate above the top face so as
to cover the first .[.integrated device.]. .Iadd.and second
membranes.Iaddend., the coupling .[.comprising.]. forming a first
empty space .[.in a position corresponding to the active area.].
.Iadd.and a second empty space, the first empty space being located
over the first membrane, the second empty space being located over
the second membrane, the first empty space being fluidly isolated
from the second empty space; .Iaddend.and forming
electrical-contact elements .Iadd.in the device substrate
.Iaddend.for electrical connection of the first integrated device
with the outside of the .[.substrate-level.]. assembly; and
encasing the .[.substrate-level.]. assembly in a package, .[.for
coating and mechanically protecting the substrate-level
assembly;.]. wherein the encasing comprises providing a base body
to support the .[.substrate-level.]. assembly, and coating
.[.laterally the substrate-level.]. .Iadd.sides of the
.Iaddend.assembly with .[.a.]. .Iadd.an insulative .Iaddend.coating
.[.region.]. .Iadd.material.Iaddend..
46. The process of claim 45, further comprising providing an access
duct within the .[.capping substrate.]. .Iadd.cap.Iaddend., the
access duct being fluidly .[.connected to.]. .Iadd.connecting
.Iaddend.the first empty space and to .[.the.]. .Iadd.an
environment .Iaddend.outside of the .[.substrate-level.]. assembly,
wherein the coating .[.region.]. .Iadd.material .Iaddend.is
configured to leave .Iadd.the access duct .Iaddend.uncovered and
accessible from the outside: a top surface of the .[.capping
substrate.]. .Iadd.cap .Iaddend.defining part of a first outer face
of the package, and the access duct.
47. The process of claim 45, comprising forming contact pads at a
surface of the base body.[., which is not in contact with the
substrate-level assembly.]. and defines a second outer face of the
package.
48. The process of claim 45, further comprising .[.electrically
coupling a circuit die to the substrate-level assembly within the
package; and wherein the encasing further comprises mechanically
coupling, arranged side by side, the device substrate and circuit
die to the base body through a respective adhesion layer.].
.Iadd.an inertial sensor located on top of the second membrane, the
inertial sensor being configured to sense an
acceleration.Iaddend..
49. The process of claim 45, .[.further comprising electrically
coupling a circuit die to the substrate-level assembly within the
package; and wherein the encasing further comprises mechanically
coupling the circuit die to the base body, and said mechanically
coupling the device substrate to the circuit die in a stacked
manner.]. .Iadd.wherein the base body includes through vias that
electrically couple the electrical-contact elements of the device
substrate outside of the package.Iaddend..
50. The process of claim 45, further comprising .[.forming an
access duct extending through the base body and reaching the
substrate-level assembly at a surface thereof, opposite to the top
face.]. .Iadd.forming a third buried cavity in the device
substrate, a third membrane being located above the third buried
cavity.Iaddend..
51. An assembly comprising: .[.an article, and.]. .Iadd.a base
substrate having a first surface and a second surface; .Iaddend.
.[.a sensor assembly adapted to monitor at least one condition of
the article, the sensor assembly comprising:.]. a .Iadd.first
.Iaddend.device substrate of semiconductor material.[.,.]. having a
top face and .[.housing.]. .Iadd.including .Iaddend.a first
.[.integrated device provided with.]. .Iadd.sensor region having
.Iaddend.an active area adjacent to the top face; .Iadd.a second
device substrate of semiconductor material having a first surface
and including an integrated circuit, the first device substrate
being located on the first substrate of the second device
substrate, the integrated circuit being electrically coupled to the
first sensor region; .Iaddend. a .[.capping substrate.]. .Iadd.cap
.Iaddend.coupled to the .Iadd.first .Iaddend.device substrate above
the top face so as to cover the first .[.integrated device in such
a manner.]. .Iadd.sensor region so .Iaddend.that a first empty
space is provided in a position .[.corresponding to.]. .Iadd.above
.Iaddend.the active area; and electrical-contact elements
.Iadd.extending from the first surface to the second surface of the
base substrate .Iaddend.for electrical connection of the first
.[.integrated device.]. .Iadd.sensor region and the integrated
circuit .Iaddend.outside of the .[.substrate-level.]. assembly.
52. The assembly of claim 51, wherein the first .[.integrated
device is provided with.]. .Iadd.sensor region includes .Iaddend.a
buried cavity formed within the .Iadd.first .Iaddend.device
substrate and a membrane suspended over the buried cavity at the
active area; the first empty space being provided in a position
corresponding to the membrane.
53. The assembly of claim 51, wherein a first access duct is
provided within the .[.capping substrate.]. .Iadd.cap.Iaddend., the
first access duct being fluidly connected to the first empty space
and to .[.the.]. .Iadd.an environment .Iaddend.outside of the
.[.substrate-level.]. assembly.
54. The assembly of claim 51, wherein the .[.capping substrate.].
.Iadd.cap .Iaddend.has a first sensor cavity above the active area
of the first .[.integrated device.]. .Iadd.sensor region.Iaddend.,
the first sensor cavity forming at least in part the first empty
space; the first sensor cavity having a depth in the range of 10
.mu.m and 400 .mu.m.
55. The assembly of claim 51, further comprising a bonding region
arranged between the .Iadd.first .Iaddend.device substrate and the
.[.capping substrate.]. .Iadd.cap .Iaddend.to ensure joining
thereof.[., and placed in contact with the top face in such a
manner as to surround, without being superimposed thereon, the
active area of the first integrated device; the first empty space
being delimited, at least in part, by the bonding region.]..
56. The assembly of claim 55, wherein the .[.capping substrate.].
.Iadd.cap .Iaddend.is .Iadd.a .Iaddend.flat .[.and not patterned.].
.Iadd.substrate .Iaddend.and the bonding region has a thickness
between 6 and 100 .mu.m .[.to entirely define.]. .Iadd.that defines
.Iaddend.a thickness of the first empty space.
57. The assembly of claim 52, wherein .[.the electrical-contact
elements comprise at least one through via made through the device
substrate; and electrical-connection pads formed on a portion of
the top face of the device substrate not covered by the capping
substrate; and wherein.]. the first .[.integrated device further
comprises.]. .Iadd.sensor region includes .Iaddend.a buried cavity
formed within the device substrate and a membrane suspended over
the buried cavity, and transduction elements configured to
transform a deformation of the membrane into electrical signals,
the electrical-contact elements being connected to the transduction
elements.
58. The assembly of claim 51, wherein the first .[.integrated
device.]. .Iadd.sensor region .Iaddend.further comprises a buried
cavity formed within the .Iadd.first .Iaddend.device substrate and
a membrane suspended over the buried cavity; and .Iadd.the cap
includes .Iaddend.a first access duct .[.is provided within the
capping substrate and is fluidly connected to the.]. .Iadd.that
places the .Iaddend.first empty space .[.and to the.]. .Iadd.in
fluid communication with an environment .Iaddend.outside of the
.[.substrate-level.]. assembly .[.and a second access duct is
provided within the device substrate in fluid communication with
the buried cavity of the integrated device and with the outside of
the substrate-level assembly.]..
59. The assembly of claim 51, wherein a first access duct and a
plurality of .[.further.]. .Iadd.second .Iaddend.access ducts are
provided within the .[.capping substrate.]. .Iadd.cap.Iaddend., and
fluidly connected to the first empty space and to .[.the.].
.Iadd.an environment .Iaddend.outside of the .[.substrate-level.].
assembly.[.; the first and further access ducts being at least one
of different size and separated by a different
inter-spacing.]..
60. The assembly of claim 51, wherein .[.the device substrate
houses at least a further integrated device provided with a
respective active area; and wherein a further empty space is
provided in a position corresponding to the respective active area
of the further integrated device; the further empty space being
fluidly isolated with respect to the first empty space.]. .Iadd.the
first and second access ducts are at least one of different size
and separated by a different inter-spacing.Iaddend..
61. The assembly of claim 60, wherein .[.the capping substrate has
at least one further sensor cavity set above the respective active
area of the further integrated device, and forming, at least in
part, the further empty space; the first empty space and further
empty space being separated in a fluid-tight manner, at least in
part, by a separation portion of the capping substrate placed
between the first empty space and the further empty space.].
.Iadd.a second device substrate includes an access
duct.Iaddend..
62. The assembly of claim 60, further comprising a bonding region
placed between the .Iadd.first .Iaddend.device substrate and the
.[.capping substrate.]. .Iadd.cap.Iaddend., and in contact with the
top face of the .Iadd.first .Iaddend.device substrate in such a
manner as to surround, without being superimposed thereon, the
active area of the first .[.integrated device and the respective
active area of the further integrated device; the first empty space
and the further empty space being delimited, at least in part, by
the bonding region.]. .Iadd.sensor region.Iaddend..
63. The assembly of claim 58, .[.wherein the first integrated
device further comprises a buried cavity formed within the device
substrate and a membrane suspended over the buried cavity, and the
further integrated device comprising a respective buried cavity
formed within the device substrate and a respective membrane
suspended over the respective buried cavity; and wherein the first
integrated device is a pressure sensor, and the further integrated
device is an inertial sensor, the inertial sensor comprising an
inertial mass arranged on the respective membrane within the
further empty space.]. .Iadd.further comprising a coating material
that is located on a portion of the first surface of the base
substrate.Iaddend..
64. The assembly of claim 60, wherein the first .[.integrated
device comprises.]. .Iadd.sensor region is a portion of .Iaddend.a
pressure sensor.[., and the further integrated device comprises a
reference pressure sensor for the pressure sensor.]..
65. The assembly of claim 51, wherein the first .[.integrated
device.]. .Iadd.sensor region .Iaddend.further comprises a buried
cavity formed within the device substrate and a membrane suspended
over the buried cavity; the first .[.integrated device
comprising.]. .Iadd.sensor region forming part of .Iaddend.a
microphone sensor having a back-chamber separated from the buried
cavity by a sensing diaphragm configured to move as a result of the
pressure exerted thereon by sound waves reaching the buried
cavity.
66. The assembly of claim 65, wherein the first .[.integrated
device.]. .Iadd.sensor region .Iaddend.further comprises a buried
cavity formed within the device substrate and a membrane suspended
over the buried cavity; the first .[.integrated device
comprising.]. .Iadd.sensor region forming a portion of .Iaddend.a
gas sensor and the membrane including a detection material
configured to allow detecting the presence of a gaseous material;
the membrane being thermally decoupled from the device
substrate.
67. The assembly of claim 51, wherein the .[.capping substrate
includes a layer grown on the device substrate, in particular by
electroplating or epitaxial steps; the capping substrate being
integral to the device substrate.]. .Iadd.second device substrate
includes an access duct that extends from the first surface to a
second surface, the access duct placing a portion of the first
sensor region in fluid communication with an environment outside of
the assembly.Iaddend..
Description
BACKGROUND
1. Technical Field
The present disclosure relates to a substrate-level assembly
(usually known as "wafer-level package") for an integrated device
and, in particular, a sensor device, as well as to a corresponding
manufacturing process and the related integrated device.
2. Description of the Related Art
Semiconductor sensors are known (for example, pressure sensors,
inertial sensors, microphones, or gas sensors) which are made with
microfabrication techniques and whose operation is based upon the
presence of a membrane that is suspended over a cavity.
For example, EP 1 577 656, filed in the name of the present
applicant, describes a pressure sensor and a manufacturing process
thereof. In detail (FIG. 1), the pressure sensor, designated by 1,
is integrated in a substrate 2 made of semiconductor material, in
particular monocrystalline silicon, having a top surface 2a. A
buried cavity 3 is formed within the substrate 2, and is separated
from the top surface 2a by a flexible and deformable membrane 4
suspended over the buried cavity 3 (in particular, the expression
"buried cavity" denotes herein a cavity that is formed within a
single body of semiconductor material at a distance from a top
surface thereof). The buried cavity 3 is in this case also isolated
and entirely contained within the substrate 2. Transducer elements
5, namely, piezoresistors formed by diffusion or implantation of
dopant atoms, are arranged within the membrane 4, detect
deformations of the membrane 4 (due to an applied pressure), and
generate corresponding electrical signals as a function of the
pressure to be detected. In brief, the manufacturing process of the
pressure sensor 1 envisages: forming, within the substrate 2, a
plurality of deep trenches, separated from one another by
separation walls made of semiconductor material; then carrying out
an epitaxial growth in a de-oxidizing environment so as to form an
epitaxial layer, which closes the deep trenches at the top; and,
finally, carrying out a thermal annealing step so as to form the
buried cavity 3. A thin silicon layer remains above the buried
cavity 3, and is constituted partly by epitaxially grown silicon
atoms and partly by migrated silicon atoms; this silicon layer
forms the membrane 4.
European patent application EP 05425028.7, filed in the name of the
present applicant on Jan. 25, 2005, describes a piezoresistive
accelerometer and a corresponding manufacturing process. In detail
(FIG. 2), the piezoresistive accelerometer, designated by 10, has a
structure substantially similar to that of the pressure sensor 1
described above, so that parts that are similar are designated by
the same reference numbers, and moreover has an inertial mass 11,
formed on the membrane 4, in particular approximately at the
geometrical center of the membrane 4. The inertial mass 11 is
constituted by welding paste, for example of silver, tin, copper,
lead, gold, or other high-density metals, preferably having a
density higher than 7000 kg/m.sup.3. For example, the inertial mass
11 comprises a cylindrical base portion and a hemispherical top
portion, and has a radius of between 100 .mu.m and 200 .mu.m and a
thickness of between 50 .mu.m and 350 .mu.m (given a side of the
membrane 4 of approximately 500 .mu.m, the ratio between the radius
of the inertial mass 11 and the side of the membrane 4 is between
20% and 40%).
The inertial mass 11 is deposited through a metal mesh, made, for
example, of nickel or steel, having suitable openings in positions
corresponding to the areas where the welding paste is to be
deposited. Furthermore, the deposition is accompanied by a
temperature increase step, during which the inertial mass 11
adheres to the top surface of the membrane 4, assuming, after
cooling, the described shape.
The center of gravity of the inertial mass 11 is placed outside of
the membrane 4, so that, in use, an acceleration acting on the
accelerometer 10 determines a momentum on the inertial mass 11,
which causes inclination thereof in a corresponding direction. The
displacement of the inertial mass 11 causes a deformation of the
membrane 4 and a variation in the resistivity of the piezoresistive
elements 5, whence an appropriate detection circuit determines the
amount of the acceleration acting on the accelerometer 10.
The aforesaid patent application No. EP 05425028.7 further
discloses (FIG. 3) integration of the pressure sensor 1 and of the
accelerometer 10 described above in separate and distinct surface
portions of a same substrate 2 of semiconductor material, in
particular to obtain a pressure monitoring system 15, for example,
a so-called tire-pressure monitoring system (TPMS) for monitoring
the inflating pressure of a tire for a vehicle. In use, the
pressure monitoring system 15 is installed on the inside surface of
a tire, and the pressure sensor 1 measures the state of inflation
thereof, whilst the accelerometer 10 performs a wake-up function,
by supplying a start-of-measurement signal to the pressure sensor 1
and a data-collection signal to an electronic circuit coupled
thereto. In particular, the accelerometer 10 detects a centrifugal
acceleration of the tire during rotation. An acceleration of
intensity greater than a pre-set threshold is representative of a
condition of movement of the vehicle, and consequently causes the
start of pressure monitoring, so limiting monitoring to time
intervals during which the vehicle is moving.
Moreover, MEMS microphone sensors are known, an example of which is
shown in FIG. 4. The microphone sensor, designated by 16, is again
integrated in a substrate 2 made of semiconductor material, having
a top surface 2a, and comprises a buried cavity 3 formed within the
substrate 2 and separated from the top surface 2a by a membrane 4
suspended over the buried cavity 3. The membrane 4 is fixed and has
a plurality of holes (not shown) allowing the passage of air from
the external environment to the buried cavity 3. A sensor diaphragm
17, which is flexible and free to move as a result of the air
pressure, separates the buried cavity 3 from a back-chamber 18
formed at the back of the substrate 2. The membrane 4 and the
sensor diaphragm 17 form two facing plates of a sensing capacitor,
whose capacitance varies as a function of their relative distance.
In use, the sensor membrane 17 undergoes deformation as a result of
sound waves reaching the buried cavity 3, thus causing a
corresponding variation of the capacitance value of the sensing
capacitor.
The dimensions of the sensors described are particularly small,
namely, in the region of 0.8 mm.times.0.8 mm.times.0.3 mm
(length.times.width.times.thickness), or in the region of 2
mm.times.2 mm.times.0.3 mm, so that traditional packaging
techniques do not prove advantageous, and in particular packages of
a traditional type, of a molded or pre-molded type, prove to be of
excessive encumbrance and in any case not optimized for
applications, such as automotive or consumer applications, which
require size minimization. For example, existing packages for MEMS
microphones envisage the use of a rather bulky metallic casing (or
made by a combination of FR4 and a metallic material) which
protects and electrostatically shields the sensor die. Moreover,
packages of the traditional type are not optimized in terms of
manufacturing costs.
On the other hand, the tendency to use alternative packaging
techniques for integrated devices is known, said techniques
enabling a reduction in the overall dimensions of the resulting
electronic devices, and a simultaneous reduction in the
manufacturing costs. In particular, the so-called "wafer-level
packaging" technique is known, which envisages formation of a
protection layer directly on top of a layer of semiconductor
material housing integrated devices, to mechanically protect the
integrated devices.
BRIEF SUMMARY
The present disclosure provides a substrate-level assembly for
integrated devices that will enable minimization of the costs of
the manufacturing process and of the final dimensions of the
corresponding electronic devices.
According to the present disclosure, a substrate-level assembly and
a manufacturing process are consequently provided.
In accordance with one embodiment of the present disclosure, a
substrate-level assembly is provided that includes a device
substrate of semiconductor material having a top face and housing a
first integrated device provided with an active area in the
proximity of said top face; a capping substrate coupled to the
device substrate above said top face so as to cover the first
integrated device in such a manner that a first empty space is
provided in a position corresponding to the active area; and
electrical-contact elements for electrical connection of the first
integrated device outside of the substrate-level assembly.
In accordance with another embodiment of the present disclosure, an
electronic device is provided that includes the substrate-level
assembly described above, and a package encasing and mechanically
protecting the substrate-level assembly, the package having a base
body mechanically supporting the substrate-level assembly and a
coating region configured to coat laterally the substrate-level
assembly.
In accordance with another embodiment of the present disclosure, a
process for manufacturing a substrate-level assembly is provided,
the processing including providing a device substrate of
semiconductor material, having a top face; forming a first
integrated device within the device substrate and with an active
area in the proximity of the top face; coupling a capping substrate
to the device substrate above the top face so as to cover the first
integrated device, the coupling comprising forming a first empty
space in a position corresponding to the active area; and forming
electrical-contact elements for electrical connection of the first
integrated device with the outside of the substrate-level
assembly.
In accordance with another embodiment of the present disclosure, an
assembly is provided, the assembly including an article, and a
sensor assembly adapted to monitor at least one condition of the
article, the sensor assembly including a device substrate of
semiconductor material, having a top face and housing a first
integrated device provided with an active area in the proximity of
the top face; a capping substrate coupled to the device substrate
above the top face so as to cover the first integrated device in
such a manner that a first empty space is provided in a position
corresponding to the active area; and electrical-contact elements
for electrical connection of the first integrated device outside of
the substrate-level assembly.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
For a better understanding of the present disclosure, preferred
embodiments thereof are now described, purely by way of
non-limiting example and with reference to the attached drawings,
wherein:
FIG. 1 is a cross-sectional view of a pressure sensor of a known
type;
FIG. 2 is a cross-sectional view of an inertial sensor of a known
type;
FIG. 3 is a cross-sectional view of a pressure monitoring system of
a known type;
FIG. 4 is a cross-sectional view of a microphone sensor of a known
type;
FIG. 5 is a cross-sectional view of a substrate-level assembly for
a pressure sensor, according to an aspect of the present
disclosure;
FIG. 6 is a cross-sectional view of a substrate-level assembly for
a differential pressure sensor;
FIG. 7 is a cross-sectional view of a substrate-level assembly for
a relative pressure sensor;
FIG. 8 is a cross-sectional view of a substrate-level assembly for
a pressure monitoring device;
FIG. 9 is a cross-sectional view of a substrate-level assembly for
an integrated device comprising a plurality of semiconductor
sensors;
FIG. 10 is a cross-sectional view of an electronic device
comprising a package and a substrate-level assembly, according to
an aspect of the present disclosure;
FIG. 11 is a perspective view of the electronic device of FIG.
10;
FIG. 12 is a cross-sectional view of a further electronic device
comprising a package and a substrate-level assembly;
FIG. 13 shows a variant of the electronic device of FIG. 12;
FIGS. 14-16 show further variants of the electronic device of FIG.
13; and
FIG. 17 shows a possible variant of the substrate-level assembly of
FIG. 5.
DETAILED DESCRIPTION
FIG. 5 shows a substrate 20 of semiconductor material, for example,
monocrystalline silicon, having a top surface 20a and a bottom
surface 20b, opposite to the top surface 20a (in what follows, the
substrate 20 will be referred to as "device substrate," in so far
as it is designed to integrate one or more integrated devices, in
particular, sensor devices).
An integrated device, namely a pressure sensor 1, is formed inside
the device substrate 20, as described with reference to FIG. 1 (so
that parts that are similar are designated by the same reference
numbers). In particular, the membrane 4, suspended over the buried
cavity 3, is formed at the top surface 20a of the device substrate
20.
According to an aspect of the present disclosure, a capping
substrate 21, made of semiconductor material (for example,
silicon), glass, or other ceramic or polymeric material, is
(mechanically or electrically or a combination of mechanically and
electrically) coupled to the device substrate 20, on top of the top
surface 20a, so as to coat and protect the pressure sensor 1 and so
as to provide a substrate-level assembly 22 for the pressure sensor
1. In particular, by the expression "substrate-level assembly" is
meant herein the composite structure comprising the device
substrate 20, the capping substrate 21, and the corresponding
electrical input/output connections (made as described
hereinafter).
According to an aspect of the present disclosure, the capping
substrate 21 is joined to the device substrate 20 via a bonding
process, which exploits a bonding region 23 (advantageously a
sealing region), set in contact with, and on top of, the top
surface 20a, to ensure joining. For example, the bonding region 23
is made of glass frit or a metal or polymeric material. The bonding
region 23 has a ring conformation, and surrounds, without being
superimposed thereon, the membrane 4 of the pressure sensor 1.
Furthermore, the bonding region 23 has a main dimension of
extension of between 100 .mu.m and 300 .mu.m, in the case of
glass-frit bonding, and smaller than 100 .mu.m, in the case of
metal bonding, with a maximum thickness of approximately 10 .mu.m
in both cases.
According to an aspect of the present disclosure, a sensor cavity
24 is formed within the capping substrate 21, in a position
corresponding to, and in communication with, the membrane 4. The
sensor cavity 24 is made, for example, via an anisotropic (or
isotropic) chemical etch, starting from a first surface 21a of the
capping substrate 21 in contact with the device substrate 20, and
has a depth of between 10 .mu.m and 400 .mu.m. Consequently, after
joining between the device substrate 20 and the capping substrate
21, an empty space 25 remains over the membrane 4 so as to ensure
freedom of movement thereof and so as not to alter deformation
thereof as a function of a pressure applied. In particular, the
empty space 25 is defined partly by the thickness of the bonding
region 23 and partly by the sensor cavity 24 dug in the capping
substrate 21, and is delimited partly by the bonding region 23 and
partly by the walls of the sensor cavity 24.
Furthermore, a first access duct 26 is formed within the capping
substrate 21, starting from a second surface 21b of the capping
substrate 21, not in contact with the device substrate 20, and
reaching the sensor cavity 24, in such a manner as to be
fluidically connected to the empty space 25 and to the outside of
the capping substrate 21. For example, the first access duct 26 can
be formed via an anisotropic chemical etch or a deep silicon etch
or a combination thereof.
Electrical input/output connections are finally provided for
electrical connection of the pressure sensor 1 with the outside of
the substrate-level assembly 22, in the form of through vias 28a,
which traverse the device substrate 20 until the bottom surface 20b
is reached, or else in the form of connection pads 28b carried by a
portion of the top surface 20a placed externally of the bonding
region 23 and the capping substrate 21 so as to be accessible from
the outside and enable contact using the "wire-bonding" technique
(as illustrated schematically in FIG. 5 and in the subsequent
figures). In particular, the input/output electrical connections
28a, 28b are connected, for example, via metallizations (not
shown), to transduction elements 5 of the membrane 4. The through
vias 28a can be formed with any known technique, for example, by
means of conductive through holes, obtained by etching of the
device substrate 20, so as to form through trenches extending
throughout the thickness of the substrate, and by subsequent
filling of said through trenches with a conductive material, for
example, with a metal material. The use of the through vias 28a is
advantageous for reducing the dimensions of the resulting
assembly.
In use, a fluid at a given pressure, the value of which must be
determined, penetrates within the capping substrate 21 through the
first access duct 26, reaches the empty space 25, and acts on the
membrane 4, e.g., causing its deformation, which is detected by the
transduction elements 5.
FIG. 6 shows a substrate-level assembly 22 for a differential
pressure sensor. In this case, a second access duct 30 is formed
through the device substrate 20, starting from the bottom surface
20b as far as the buried cavity 3 and so as to be in fluid
connection with the buried cavity 3. For example, the second access
duct 30 is made via a digging from the back or bottom of the device
substrate 20 by means of an anisotropic chemical etch.
In use, the outer surface of the membrane 4 (opposite, i.e., to the
buried cavity 3) is set in communication with a fluid at a first
pressure through the first access duct 26 made through the capping
substrate 21. The internal surface of the membrane 3, instead, is
set in communication with a fluid at a second pressure through the
second access duct 30. In this way, the membrane 3 deforms as a
function of the difference between the first and second pressures
so as to enable a differential measurement of pressure.
FIG. 7 shows a substrate-level assembly 22 for a relative pressure
sensor. In detail, within the device substrate 20, in addition to
the pressure sensor 1, a reference pressure sensor 1' is formed, in
a surface portion of the device substrate 20, separate and distinct
from the one dedicated to integration of the pressure sensor 1. A
further sensor cavity 24' is formed in the capping substrate 21, in
a position corresponding to the reference pressure sensor 1', so as
to ensure the presence of a further empty space 25' above the
respective membrane 4' of the reference pressure sensor 1'. The
further empty space is closed and not accessible from the outside,
since no access duct is provided in fluidic communication
therewith. The bonding region 23 surrounds in this case the
membrane of both of the pressure sensors, without being
superimposed thereon, and is, for example, shaped like the figure
eight. A separation portion 32 of the capping substrate 21 is
placed between the sensor cavity 24, 24', and between the
respective empty spaces 25, 25'. In particular, the separation
portion 32, together with the underlying bonding region 23,
separates in a fluid-tight manner the two empty spaces 25, 25',
which are thus fluidically isolated.
In use, within the further sensor cavity 24' a fluid having a given
reference pressure is entrapped, whilst the sensor cavity 24 is set
in fluid communication with a fluid at a given pressure through the
first access duct 26 so as to implement a relative pressure
measurement.
FIG. 8 shows a currently preferred embodiment of the present
disclosure and, in particular, a substrate-level assembly 22 for a
pressure monitoring device 15 of the type described with reference
to FIG. 3, in particular configured to monitor the inflating
pressure of a tire of a vehicle. In detail, in distinct surface
portions of the device substrate 20, a pressure sensor 1 and an
accelerometer 10 are integrated. Also in this case, in a way
similar to what has been described above, the further sensor cavity
24' corresponding to the accelerometer 10 is provided, so as to
ensure the further empty space 25' within which the inertial mass
11 is free to move to cause a corresponding deformation of the
respective membrane 4'. In addition, further input/output
electrical connections 28a' are provided for ensuring electrical
connection of the accelerometer 10 with the outside of the
substrate-level assembly 22, also in this case in the form, for
example, of through vias. Advantageously, in a way not illustrated,
an appropriate electronic circuit (or ASIC--Application Specific
Integrated Circuit) connected to the accelerometer 10 and to the
pressure sensor 1 can also be integrated within the device
substrate 20.
In use, the accelerometer 10 detects an acceleration imparted on
the monitoring device as a function of the deformation of the
respective membrane 4', due to the displacement of the inertial
mass 11. As described above, the separation portion 32 of the
capping substrate 21, and the bonding region 23, set between the
free spaces 25, 25' do not enable the fluid under pressure to reach
the further sensor cavity 24'.
In general, the device substrate 20 can integrate an arbitrary
number of sensor devices, and in this case there is provided a
corresponding number of additional free spaces 25', fluidically
isolated from one another, and possibly of additional sensor
cavities 24', separated by additional separation portions 32' of
the capping substrate 21, and of additional access ducts
communicating with respective sensor cavities. By way of example,
in FIG. 9 four sensors 1, 1' integrated in a same device substrate
20 are shown. It is clear that each one of the sensors shown can be
a pressure sensor, possibly a differential pressure sensor or a
relative pressure sensor, or an accelerometer (or another type of
sensor device) and a corresponding number of first and second
access ducts can be provided.
According to a further aspect of the present disclosure (FIGS. 10
and 11), the substrate-level assembly 22 can further be encased in
a package 40, of a land-grid-array (LGA) type, SO, QFN or
ball-grid-array (BGA) type. In detail (FIG. 10), the
substrate-level assembly 22 (in particular, FIG. 10 shows the case
where the device substrate 20 integrates a pressure sensor 1 and an
accelerometer 10) is joined, via an adhesion layer 41, to a base
body 42, in particular, a multilayer organic substrate (for example
a BT--Bismaleimide Triazine--layer), defining the base of the
package 40. The adhesion layer 41 includes an epoxy or acrylic
glue, or bismaleimide (BMI), or else an epoxy, or acrylic, or
bismaleimide laminated layer. The base body 42 has a size greater
than that of the substrate-level assembly 22, and hence has outer
portions not covered by the assembly. Then, via a mould of
appropriate shape and size, the substrate-level assembly 22 is
covered at the sides by a coating 44, made of plastic material, for
example including resin. In particular, the coating 44 covers at
the top the outer portions of the base body 42, but does not cover
the second surface 21b of the capping substrate 21 (i.e., the
surface not in contact with the device substrate 20), which hence
constitutes part of a first outer face 40a of the package 40. In
this way, the first access duct 26 remains free and exposed on the
outside of the package 40 (as is evident from FIG. 11). In
addition, further through vias 45, formed through the base body 42,
are connected to the connection pads 28b of the substrate-level
assembly 22 (for example, via conductive paths, not shown, arranged
at the outer portions of the base body 42), and to outer contact
pads 46, made of metal material, carried by an outer surface of the
base body 42, defining a second outer face 40b of the package 40.
In the case of an LGA package, the contact pads 46 constitute the
input/output interface towards the outside of the package 40. In
the case of a BGA package, conductive bumps, for example metal
balls (not shown), are instead provided for said purpose and are in
direct contact with the outer contact pads 46. Advantageously, the
outer face 40a of the package 40 may be covered with a temporary
protection layer, in order to protect the integrated devices during
storage or assembling procedures. Also, it is clear that the second
access duct 30, if present (e.g., in the case of a differential
pressure sensor), extends also through the adhesion layer 41 and
the base body 42, in order to reach the second outer face 40b of
the package 40.
FIG. 12 shows another example of the package 40, encasing a
substrate-level assembly 22 including a device substrate 20,
integrating in this case a microphone sensor 16 (see FIG. 4, but it
is clear that the same teachings applies mutatis mutandis to all
sensor devices described therein, e.g., to a pressure sensor), and
the capping substrate 21, having the first access duct 26 allowing
passage of sound waves towards the sensor diaphragm 17 of the
microphone sensor 16. The package 40 further encases an ASIC die 50
integrating a processing circuit electrically coupled to the
microphone sensor 16. The ASIC die 50 is joined to the base body 42
via a respective adhesion layer 51, laterally with respect to the
substrate-level assembly 22, and is surrounded and completely
covered by the coating 44. First electrical connections 52 (e.g.,
electrical wires) connect (e.g., via the wire-bonding technique)
the ASIC die 50 to the connection pads 28b of the device substrate
20, while second connections 53 connect the ASIC die 50 to the
further through vias 45 made through the base body 42, and to the
outer contact pads 46.
A possible variant of the package 40 envisages, FIG. 13 (which
again refers to the microphone sensor without this however implying
any loss of generality), stacking of the substrate-level assembly
22 and the ASIC die 50 within the coating 44. In detail, the ASIC
die 50 is joined to the base body 42 with a first surface 50a
thereof, and the device substrate 20 is joined to a second surface
50b (opposite to the first surface 50a) of the ASIC die 50 via the
adhesion layer 41, thus being stacked to the ASIC die within the
package 40. Also in this case, the first access duct 26 remains
free and exposed on the outside of the package 40, and the second
surface 21b of the capping substrate 21 constitutes part of a first
outer face 40a of the package 40. Again, the first and second
connections 52, 53 are provided, for example originating from
respective connection pads on a portion of the second surface 50b
of the ASIC die 50 not covered by the adhesion layer 41.
As shown in FIG. 14, in case of the above described stacked
arrangement, the second access duct 30, if present, can extend
through the base body 42, the adhesion layers 41 and 51, and the
ASIC die 50 for an entire thickness thereof. In the case of the
microphone sensor 16, the second access duct 30 reaches the
back-chamber 18, thus increasing its size, and the diaphragm 17
from the back.
The described substrate-level assembly has the following
advantages.
In particular, the manufacturing process of the assembly is
optimized in terms of costs and duration, in so far as it is
performed directly starting from the device substrate, with process
steps that are a continuation of those used for the formation of
the integrated sensors. The resulting assemblies have extremely
contained dimensions, which are generally in the region of 1.7
mm.times.1.7 mm.times.0.8 mm but can reach 1.3 mm.times.1.3
mm.times.0.8 mm in the case of just one pressure sensor, and which
are generally in the region of 1.7 mm.times.2.5 mm.times.0.8 mm,
but can reach 1.3 mm.times.2.5 mm.times.0.8 mm in the case of the
pressure monitoring device (which integrates both the pressure
sensor and the accelerometer). In particular, in the latter case, a
single substrate-level assembly is advantageously provided for the
pressure sensor and for the accelerometer, and said assembly
enables an effective fluid isolation between the empty spaces
provided above the membrane of the two sensors.
The substrate-level assembly can constitute a complete device made
of semiconductor material, in so far as the integrated sensors
housed within the device substrate are automatically protected from
the back by the device substrate 20 and on the top by the capping
substrate 21. However, the use of the package 40 can be
advantageous in all the cases where it is not convenient to have a
complete integrated device made of semiconductor material (for
example, in the case where particular environmental conditions
require a further protection from the outside environment). In any
case, also the package 40 has small dimensions, in the region of 3
mm.times.3 mm.times.1 mm.
Furthermore, the package 40, as well as the substrate-level
assembly 22, can be handled and positioned easily, and in
particular can be advantageously used as surface-mount devices
(SMDs).
The described manufacturing process does not envisage the use of
protection gels, as is, instead, required in the case where molded
packages of a traditional type are used.
Finally, it is clear that modifications and variations can be made
to what is described and illustrated herein, without thereby
departing from the scope of the present disclosure, as defined in
the attached claims.
In particular, the capping substrate 21 can advantageously be doped
in order to increase its conductivity and provide an electrostatic
shielding for the sensor(s) integrated within the device substrate
20. To improve this shielding effect (which is important, for
example, in the case where the electronic device integrating the
substrate-level assembly is a mobile phone), also the bonding
region 23 could be made conductive so as to shield the
electromagnetic radiations.
The capping substrate 21 can also be realized by means of an
epitaxial or galvanic (electroplating) growth on the device
substrate 20 instead of being bonded thereto, in order to be
integral with the device substrate 20. In this case, the empty
space 25 can be provided with standard techniques, e.g., by etching
of a sacrificial layer interposed between the device substrate and
the grown layer.
Alternatively, as shown in FIG. 15, in the case of the microphone
sensor 16 (or any other type of sensor envisaging the presence of a
back chamber), the back-chamber could be made by the empty space
25, with no access duct being provided in the capping substrate 21;
in this case, the second access duct 30, extending through the base
body 42, the adhesion layer 41 and the ASIC die 50 and in
communication with the back-chamber 18 (now having the function of
the empty space 25, due to the reversal arrangement), allows the
communication with the outside of the package. Also (in a way not
shown), since no access duct is provided in the capping layer 21,
the same capping layer could even be coated on its second surface
21b by the coating 44; in this case, the same ASIC die could have a
capping function for the integrated sensors. An analogous structure
could be used for a relative pressure sensor, the first empty space
25 containing a first fluid at a reference pressure, and the second
access duct 30 allowing a second fluid to enter the buried cavity
3.
Furthermore, as shown in FIG. 16 that depicts, as an example, a
variant of the package of FIG. 13, a plurality of openings can be
provided in the capping substrate 21 to provide a plurality of
access ducts 26 to the underlying empty space 25; in particular,
different size, inter-spacing and position can be envisaged for the
various access ducts 26. For example, the presence of a plurality
of access ducts can reduce the risk of damages to the sensor
membranes due to the external environment. It is clear that such a
variant also applies to the other embodiments previously described,
e.g., to the pressure or accelerometer sensor, or to the
combination thereof; also, it is clear that in the case where the
substrate-level assembly comprises a plurality of semiconductor
sensors (as shown e.g., in FIG. 9), the capping substrate 21 can be
provided with one or more access duct 26 (even of different size,
inter-spacing and position) communicating with one or more of the
empty spaces 25, 25' associated with the various sensors.
It should be clear that the substrate-level assembly 22 could be
encased in the package 40 even with more than one die, integrating
other circuits or passive components, in a stacked or side-by-side
arrangement, as described previously.
Also, in the substrate-level assembly the device substrate could
house other types of micromechanical devices, e.g., not provided
with a membrane, having an active area at a top surface thereof
that must remain free and/or accessible from the outside of the
assembly (or package). In the sensors described, the active area
comprises the membrane suspended over the buried cavity.
Joining between the device substrate 20 and the capping substrate
21 can be made via direct or anodic bonding, so without the need to
envisage the bonding region 23 on the top surface 20a of the device
substrate 20. In this case, the empty space 25 above the membrane 4
is determined just by the sensor cavity 24, which accordingly must
be appropriately sized.
Instead, as shown in FIG. 17, in the case where the bonding region
has a sufficient thickness, the sensor cavity 24 could not be
provided within the capping substrate 21 (which remains flat and
not patterned). In this case, the empty space 25 is defined and
surrounded just by the bonding region 23. The cavity is thus
realized using the bonding material, such as glass-frit, polymer
and so on, as spacer between the device substrate 20 and (in this
case) a flat, not patterned capping substrate 21; the thickness of
this spacer can be in the range of 6-80 (or even 100) .mu.m.
Furthermore, above the membrane of the integrated sensors, a single
through cavity could be provided (not illustrated), which traverses
the entire thickness of the capping substrate 21 and is
consequently accessible from outside the substrate-level assembly
22.
The capping substrate 21 could be patterned also on the outer and
exposed side (second surface 21b), e.g., for realizing a first
access duct with a different shape (having a larger section towards
the outside).
Even though FIG. 10 illustrates the case where the substrate-level
assembly 22 is connected to the outside via wire bonding and the
connection pads 28b, it is evident that a similar structure can be
provided using the through vias 28a. In particular, in this case,
the through vias 28a traverse the adhesion layer 41 and are
connected, for example via conductive paths, to the additional
through vias 45.
In addition, further types of sensors can be integrated within the
device substrate 20. For example, a gas sensor can be integrated
therein, which also bases its operation upon the presence of a
membrane suspended over a cavity. Also for said sensor a respective
first access duct 26 must be provided to enable entry of a fluid
within the substrate-level assembly 22. In detail, the suspended
membrane 4 is covered by a layer of sensing material, depending on
the chemical(s) it is desired to detect. The membrane is important
to guarantee a thermal decoupling with the substrate device 20
during the assembling steps. The silicon cap acts as a protection
for the gas sensor, and can be covered with a sticky foil or any
other laminated film during a storage period, in order to prevent
dust and moisture from damaging the sensor. It is advantageous that
the electrical input/output connections (e.g., the connection pads
28b) are arranged outside the capping substrate 21 and covered by
the coating 44, so that any kind of damages is avoided due to the
presence of the fluid to be detected within the first empty space
25 (especially in case of a humidity sensor).
The deformation of the membrane 4 of the integrated sensors could
be detected with capacitive, instead of piezoresistive, techniques
in a known way which is not described in detail.
The inertial mass 11 could have a shape different from the one
described and illustrated; in any case, it is configured so as to
be affected by the accelerations imparted on the integrated device,
and to undergo a consequent displacement.
Finally, it is clear that the pressure monitoring device described
can be used for other applications. For example, in the automotive
field, it can be used for monitoring the pressure of the air-bag,
for checking the pressure of failure of an ABS system, or for
monitoring the pressure of the oil or the pressure of injection of
the fuel.
Other possible applications are in the medical field, where the
pressure sensor can be used for monitoring blood pressure, or in
ink-jet applications. In the latter case, an ink chamber can be
provided within the capping substrate 21; the first access duct 26
acts as a nozzle, offering a way out for the ink contained within
the empty space 25 when heated by an appositely provided circuitry,
which can be implemented in the suspended membrane. In particular,
in this application, the presence of a flared access duct to the
empty space 25 could be advantageous to facilitate ink expulsion.
Accordingly, the manufacturing process of the capping substrate 21
could envisage a first etching, of a wet type, to provide the
sensor cavity 24 having sloping lateral walls and a tapered section
towards the outside, and a second etching, of a dry type, to
provide the first access duct 26, having rectilinear walls and a
smaller section.
The various embodiments described above can be combined to provide
further embodiments. All of the U.S. patents, U.S. patent
application publications, U.S. patent applications, foreign
patents, foreign patent applications and non-patent publications
referred to in this specification and/or listed in the Application
Data Sheet are incorporated herein by reference, in their entirety.
Aspects of the embodiments can be modified, if necessary to employ
concepts of the various patents, applications and publications to
provide yet further embodiments.
These and other changes can be made to the embodiments in light of
the above-detailed description. In general, in the following
claims, the terms used should not be construed to limit the claims
to the specific embodiments disclosed in the specification and the
claims, but should be construed to include all possible embodiments
along with the full scope of equivalents to which such claims are
entitled. Accordingly, the claims are not limited by the
disclosure.
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