Note: Descriptions are shown in the official language in which they were submitted.
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INFRARED CAMERA ARCHITECTURE SYSTEMS AND METHODS
RELATED APPLICATIONS
This patent application is a PCT patent application that claims priority to
and
incorporates by reference in their entirety U.S. Patent Application No.
12/844,124, filed
July 27, 2010, and U.S. Provisional Patent Application No. 61/469,651, filed
March 30,
2011.
TECHNICAL FIELD
One or more embodiments of the invention relate generally to infrared cameras
and,
more particularly, to infrared detectors and other types of infrared camera
architectures and
systems and methods for manufacturing infrared camera architectures.
BACKGROUND
Thermal infrared cameras are well known and used in a wide variety of
applications. A typical thermal infrared camera, often referred to simply as
an infrared
camera or IR camera, uses an infrared detector to detect infrared energy that
is provided to
the infrared detector through an infrared camera lens - a lens capable of
transmitting
infrared energy. The infrared camera may also include a display for a user to
view images
generated by the infrared camera based on the infrared energy, or the images
may be stored
by the infrared camera or transmitted (e.g., via a wireless or wired network)
for remote
viewing and/or storage.
A conventional infrared camera typically includes a large number of
individual,
non-integrated electronic components that require various printed circuit
boards and power
supply voltages to support these electrical components. The conventional
infrared camera
may also require an external heat sink or other type of external thermal
management device
to control temperature conditions associated with the infrared detector and
other sensitive
components of the infrared camera.
Furthermore, the conventional infrared camera may have cumbersome optical
alignment procedures and/or complex calibration processes that may need to be
performed
by a user integrating the infrared camera into a desired system. Consequently,
the
conventional infrared camera may represent a device that is relatively
expensive to
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manufacture and complex to integrate into a desired system. As a result, there
is a need for
an improved infrared camera architecture.
SUMMARY
Infrared camera architecture systems and methods are disclosed in accordance
with
one or more embodiments of the invention. For example, in accordance with one
or more
embodiments of the invention, an infrared camera architecture is disclosed
that integrates
various elements of an infrared camera, such as electronics, thermal
management, and/or
optical alignment, into a single package that may be manufactured using high
volume
manufacturing processes. This infrared camera architecture, for one or more
embodiments
of the invention, may offer an elegant solution (e.g., relative to
conventional, complex
infrared camera alternatives) that may be easily designed into various
products by system
engineers without the usual complexity and without the need for in-depth,
infrared domain
knowledge.
More specifically, in accordance with one embodiment of the invention, an
infrared
camera includes an infrared detector; a substrate; a plurality of electrical
components
coupled to the substrate; a pedestal made of a thermally conductive material
and having a
leg coupled to the substrate, wherein the infrared detector is supported by
and thermally
coupled to the pedestal, the pedestal thermally isolating the infrared
detector from the
plurality of electrical components; and a core housing coupled to the infrared
detector, the
substrate, the pedestal, and the plurality of electrical components to form an
infrared
camera core.
In accordance with another embodiment of the invention, an infrared camera
includes an infrared detector adapted to capture infrared images; a pedestal
coupled to the
infrared detector and having an infrared detector alignment feature; a
substrate coupled to
the pedestal; a die stack coupled to the substrate, wherein the pedestal is
configured to
thermally protect the infrared detector from the die stack; an infrared camera
core housing
configured to at least partially house the infrared detector, the pedestal,
the substrate, and
the die stack to form an infrared camera core; a camera housing having an
optical
alignment feature within the camera housing and at least partially enclosing
the infrared
camera core; and a lens within the camera housing; wherein the optical
alignment feature
and the infrared detector alignment feature are coupled to provide optical
alignment of the
infrared detector with the lens.
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In accordance with another embodiment of the invention, a method of assembling
an infrared camera includes mounting a die stack to a substrate; securing a
pedestal to the
substrate and above the die stack, the pedestal made of a thermally conductive
material;
adhering an infrared detector to the pedestal, wherein the pedestal is
configured to
thermally isolate the infrared detector from the die stack; and encapsulating
at least
partially the substrate, the die stack, the pedestal, and the infrared
detector in a core
housing to form an infrared camera core.
In accordance with another embodiment of the invention, infrared detectors for
infrared camera architecture systems and methods are provided, together with
methods for
producing them reliably and efficiently in volume quantities using wafer level
packaging
(WLP) techniques. More specifically, in accordance with one embodiment of the
invention, an infrared detector includes a substrate having an array of
infrared detectors
(e.g., microbolometers) and a readout integrated circuit interconnected with
the array
disposed on an upper surface thereof. A generally planar window is spaced
above the array,
the window being substantially transparent to infrared light. A mesa is bonded
to the
window. The mesa has closed marginal side walls disposed between an outer
periphery of a
lower surface of the window and an outer periphery of the upper surface of the
substrate
and defines a closed cavity between the window and the substrate that encloses
the array.
The mesa is bonded to the substrate (e.g., by way of a solder seal) so as to
seal the cavity.
In accordance with another embodiment of the invention, a method for making an
infrared detector includes providing a window wafer having a layer of oxide
sandwiched
between two layers of a semiconductor. An array of cavities is formed in a
surface of the
window wafer. In various embodiments, the cavity depth is defined by the
positioning of
the oxide layer. Each cavity defines a window substantially transparent to
infrared light and
surrounded by a mesa having closed marginal side walls bonded to the wafer by
the layer
of oxide. Adjacent rows and columns of the array are separated from each other
by dicing
lanes. A detector (e.g., bolometer) wafer is also provided. The detector wafer
has an upper
surface with an array of infrared detector arrays corresponding in size and
location to the
array of cavities in the window wafer and a corresponding array of readout
integrated
circuits respectively interconnected with associated ones of the infrared
detector arrays
disposed thereon. Adjacent rows and columns of the infrared detector array are
separated
from each other by dicing lanes. The window wafer is aligned over the
bolometer wafer
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such that the cavities of the window wafer are respectively disposed over
corresponding
ones of the infrared detector arrays. Lower surfaces of the side walls of the
mesa are
bonded with the upper surface of the detector wafer such that each of the
cavities is sealed
and a plurality of infrared detectors is defined between the two wafers.
The scope of the invention is defined by the claims, which are incorporated
into this
Summary by reference. A more complete understanding of embodiments of the
invention
will be afforded to those skilled in the art, as well as a realization of
additional advantages
thereof, by a consideration of the following detailed description of one or
more
embodiments. Reference will be made to the figures of the appended sheets of
drawings
that will first be described briefly.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. la-lc show diagrams illustrating infrared camera architectures in
accordance
with one or more embodiments of the invention;
FIG. 2 shows a diagram illustrating an example for bonding various elements
within the infrared camera architecture in accordance with an embodiment of
the invention;
FIG. 3 shows a perspective view diagram illustrating an infrared camera
architecture in accordance with an embodiment of the invention;
FIG. 4 shows a side view diagram illustrating an example of thermal paths for
an
infrared camera architecture in accordance with an embodiment of the
invention;
FIG. 5 shows a perspective, cross-sectional view diagram illustrating an
infrared
camera architecture in accordance with an embodiment of the invention;
FIGS. 6a and 6b show exploded, perspective view diagrams illustrating an
infrared
camera architecture in accordance with an embodiment of the invention;
FIGS. 7a and 7b show cross-sectional, side view diagrams illustrating infrared
camera architectures in accordance with one or more embodiments of the
invention;
FIG. 8 shows a perspective view diagram illustrating an infrared camera
architecture in accordance with an embodiment of the invention;
FIG. 9 shows a block diagram illustrating an infrared camera system in
accordance
with one or more embodiments of the invention;
FIG. 10 is a cross-sectional side elevation view of an example embodiment of
an
infrared detector in accordance with an embodiment of the invention;
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FIG. 11 is process flow diagram of an example embodiment of a wafer level
processing (WLP) method for producing an infrared detector in accordance with
an
embodiment of the invention;
FIG. 12 a top plan view of the example infrared detector of FIG. 10 in
accordance
with an embodiment of the invention;
FIG. 13 is a more detailed process flow diagram of the example WLP method of
FIG. 11 in accordance with an embodiment of the invention;
FIG. 14 is a process flow diagram of an example embodiment of a WLP method for
producing a window wafer in accordance with an embodiment of the invention;
FIG. 15 is a process flow diagram of the example window wafer WLP method of
FIG. 14, showing a target etching step of the method applied to the window
wafer in
accordance with an embodiment of the invention;
FIG. 16 is a process flow diagram of the example window wafer WLP method of
FIG. 14, showing a mesa etching step of the method applied to the window wafer
in
accordance with an embodiment of the invention;
FIG. 17 is a process flow diagram of the example window wafer WLP method of
FIG. 14, showing an antireflective (AR) coating step of the method applied to
the window
wafer in accordance with an embodiment of the invention;
FIG. 18 is a process flow diagram of the example window wafer WLP method of
FIG. 14, showing a sealing ring deposition step of the method applied to the
window wafer
in accordance with an embodiment of the invention;
FIG. 19 is a process flow diagram of the example window wafer WLP method of
FIG. 14, showing a getter deposition step of the method applied to the window
wafer in
accordance with an embodiment of the invention;
FIG. 20 is a process flow diagram of an example embodiment of a WLP method for
producing a bolometer wafer in accordance with an embodiment of the invention;
FIG. 21 is a process flow diagram of the example bolometer wafer WLP method of
FIG. 20, showing a solder seal etching step of the method applied to the
bolometer wafer in
accordance with an embodiment of the invention;
FIG. 22 is a process flow diagram of the example bolometer wafer WLP method of
FIG. 20, showing a solder seal deposition step of the method applied to the
bolometer
wafer in accordance with an embodiment of the invention;
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FIG. 23 is a process flow diagram of the example bolometer wafer WLP method of
FIG. 20, showing an etching step of the method applied to the bolometer wafer
in
accordance with an embodiment of the invention;
FIG. 24 is a process flow diagram similar to FIG. 14, showing steps involved
in the
wafer level bonding, testing and dicing of the window wafer and the bolometer
wafer in
accordance with an embodiment of the invention;
FIG. 25 is a process flow diagram of the example WLP method of FIG. 24,
showing
a wafer alignment etching step of the method applied to the window and
bolometer wafers
in accordance with an embodiment of the invention;
FIG. 26 is a process flow diagram of the example WLP method of FIG. 24,
showing
a fixtured wafer assembly insertion step of the method applied to the window
and
bolometer wafers in accordance with an embodiment of the invention;
FIG. 27 is a process flow diagram of the example WLP method of FIG. 24,
showing
a wafer bonding step of the method applied to the window and bolometer wafers
in
accordance with an embodiment of the invention;
FIG. 28 is a process flow diagram of the example WLP method of FIG. 24,
showing
a wafer slicing step of the method applied to the window wafer in accordance
with an
embodiment of the invention;
FIG. 29 is a process flow diagram of the example WLP method of FIG. 24,
showing
a wafer level bolometer testing step of the method applied to the window and
bolometer
wafers in accordance with an embodiment of the invention;
FIG. 30 is a process flow diagram of the example WLP method of FIG. 24,
showing
a wafer dicing step of the method applied to the bolometer wafer in accordance
with an
embodiment of the invention;
FIG. 31 is a schematic diagram illustrating features of an example sealing
ring and
solder capture ring of an infrared detector in accordance with an embodiment
of the
invention; and,
FIGS. 32A ¨ 32H are schematic partial cross-sectional side elevation views of
a
vacuum bonding chamber and wafer assembly, respectively showing sequential
steps
involved in an example WLP process for bonding the wafer assembly in
accordance with
an embodiment of the invention.
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Embodiments of the invention and their advantages are best understood by
referring
to the detailed description that follows. It should be appreciated that like
reference
numerals are used to identify like elements illustrated in one or more of the
figures.
DETAILED DESCRIPTION
FIGS. la-lc illustrate infrared camera architectures 100, 160, and 180,
respectively,
in accordance with one or more embodiments of the invention. Infrared (IR)
camera
architecture 100, shown in an exploded view in FIG. 1a, includes an IR
detector 102, a
pedestal 104, a die stack 106, and a substrate 110. IR camera architecture 100
may
represent, for example in accordance with one or more embodiments, an IR
camera or an
IR camera core that may be incorporated into an IR camera (e.g., an IR camera
system).
IR detector 102, for example, represents any type of IR detector or IR
detector
package (e.g., a focal plane array (FPA) or vacuum package assembly (VPA),
such as a
wafer level package (WLP) VPA type of IR camera). IR detector 102 may be wire
bonded
(e.g., reverse wire bonding, wedge bonding, or forward wire bonding) or
otherwise
electrically connected, for example, to die stack 106 and/or substrate 110. As
a specific
example, IR detector 102 may be reverse wire bonded between pads of IR
detector 102 and
substrate pads of substrate 110.
IR detector 102 may be secured to pedestal 104, in accordance with an
embodiment
of the invention, with a low stress adhesive. For example, Zymet TC-601.1
adhesive (made
by Zymet, Inc. of East Hanover, New Jersey) may be used to adhere IR detector
102 to
pedestal 104 and provide a low stress bond that may reduce thermal expansion
coefficient
(CTE) mismatch issues between IR detector 102 (e.g., silicon) and pedestal 104
(e.g.,
copper). As a specific example, the adhesive may substantially match the CTE
of pedestal
104 and IR detector 102, reduce stress on IR detector 102 (e.g., to IR window
solder joints
of IR detector 102), and reduce warping of IR detector 102 due to stresses
(e.g., which may
reduce image anomalies and other artifacts).
Pedestal 104 supports IR detector 102 above substrate 110 by using legs 114
(e.g.,
any number of legs 114, such as three or four) couplable to substrate 110. For
example,
legs 114 may be secured using adhesive to corresponding portions 116 (e.g.,
holes,
depressions, or pads) of substrate 110. Pedestal 104, with legs 114, provides
adequate
space for thermal isolation (e.g., to set apart and/or shield to provide some
degree of
protection from thermal energy) of IR detector 102 from die stack 106. For
example, for
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one or more embodiments, pedestal 104 may provide thermal isolation of IR
detector 102
from die stack 106 (or other thermal energy sources within IR camera
architecture 100) by
providing sufficient spacing from the undesired thermal energy to provide some
degree of
shielding or protection for IR detector 102 from the undesired thermal energy.
Pedestal 104 may be made, for example, of copper formed by metal injection
molding (MIM) and provided with a black oxide or nickel-coated finish.
Alternatively,
pedestal 104 may be made of any desired material, such as for example zinc,
aluminum, or
magnesium, as desired for a given application and may be formed by any desired
applicable process, such as for example aluminum casting, MIM, or zinc rapid
casting, for
the given application.
Die stack 106, for example, represents various die, chip packages, or other
forms of
electrical circuits coupled to substrate 110. As a specific example, die stack
106 may
represent an application specific integrated circuit (ASIC, e.g., a mixed
signal ASIC) die
106a, a memory die 106b (e.g., a flash memory, such as a serial flash memory),
an optional
spacer 106c (e.g., a silicon spacer), a memory die 106d (e.g., a DRAM), and an
ASIC 106e
(e.g., a logic die).
Die stack 106 may be stacked (e.g., three-dimensional (3D) stack) and secured
and
electrically coupled to substrate 110, as would be understood by one skilled
in the art.
Various other electrical components (e.g., passive and/or active components),
such as, for
example, capacitors, inductors, resistors, and/or dies (e.g., a power
management IC 108)
also may be secured and/or electrically coupled to substrate 110, as needed
for a desired
application. As a specific example, power management IC (PMIC) 108 may
represent a
power die or chip that receives 3.3 volts (e.g., a power supply voltage such
as from a
battery or other external power source) and provides various voltages required
(e.g., 1.2,
1.8, and 2.5 volts) for IR camera architecture 100. Consequently, IR camera
architecture
100, in accordance with an embodiment, may receive 3.3 volts from and provide
IR
thermal image data to an IR camera system incorporating IR camera architecture
100.
As a specific example, referring briefly to FIG. 2, die stack 106, in
accordance with
an embodiment of the invention, may be wire bonded 202 to each other and/or to
substrate
110, as shown in the perspective view and magnified side view. PMIC 108 may
also be
wire bonded or otherwise electrically coupled to substrate 110, as shown in
FIG. 2.
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ASIC 106e (e.g., a logic die) may be coupled to substrate 110, as an example,
using
flip chip technology, and substrate 110 may be configured with solder balls
204 using ball
grid array (BGA) technology to form electrical connections, as shown in the
magnified
view of FIG. 2. In general, substrate 110 may represent any type of substrate
(e.g., a printed
circuit board (PCB), which may be made of, for example, a bismaleimide
triazine (BT)
substrate, a ceramic, and/or other conventional materials.
FIG. lb illustrates an IR camera architecture 160, which may represent a cross-
sectional, side elevation view of IR camera architecture 100 (FIG. 1a), in
accordance with
an embodiment of the invention. IR camera architecture 160 shows a portion of
IR detector
102, pedestal 104, and die stack 106 encapsulated within a housing 162. For
example, after
IR camera architecture 100 is completely assembled, a mold may be placed on
substrate
110 and liquid epoxy may be injected into the mold, which hardens to form
housing 162
(e.g., a hardened, liquid epoxy housing), as would be understood by one
skilled in the art.
For example for one or more embodiments, the liquid epoxy may cover substrate
110, die
stack 106, and/or fill in various recesses of IR camera architecture 160. In a
specific
implementation example, the liquid epoxy fills in and hardens to cover
substrate 110, die
stack 106, and various recesses of IR camera architecture 160.
The mold may be designed such that the liquid epoxy does not cover IR detector
102 or otherwise interfere or block IR energy from reaching IR detector 102
(e.g., through
an IR window of the VPA). For example, FIG. lc illustrates an IR camera
architecture 180,
which may represent a top, perspective view of IR camera architecture 100
(FIG. la) or IR
camera architecture 160 (FIG. lb), in accordance with an embodiment of the
invention. As
shown, a top portion of IR detector 102 is exposed and not covered by housing
162 to
allow IR energy to reach IR detector 102. Also, a portion of pedestal 104
(e.g., side rails
182) may also be exposed and not covered by housing 162.
Pedestal 104 may have one or more alignment indents 112 (e.g., alignment
features)
in accordance with one or more embodiments of the invention. For example, six
alignment
indents 112 are shown in pedestal 104 of IR camera architecture 100 (FIG. la),
while two
alignment indents 112 are shown in pedestal 104 of IR camera architecture 180
(FIG. 1c).
Pedestal 104 may also have one or more alignment tabs 302 (e.g., alignment
protrusions,
features, datums, or marks), in accordance with one or more embodiments of the
invention,
such as illustrated in FIG. 3 for an IR camera architecture 300.
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IR camera architecture 300 may represent an alternative embodiment of IR
camera
architectures 100 (FIG. la), 160 (FIG. lb), or 180 (FIG. 1c). IR camera
architecture 300
may include four legs 114, four alignment indents 112, and two alignment tabs
302.
Alignment indents 112 and/or alignment tabs 302 may be used to align IR camera
architecture 300 and properly position it into an infrared camera system. For
example,
alignment indents 112 may correspond with alignment tabs on a housing of the
infrared
camera system and/or alignment tabs 302 may correspond with alignment indents
on the
housing of the infrared camera system to align IR camera architecture 300
within the
housing of the infrared camera system.
In general, pedestal 104 may provide certain advantageous features for the IR
camera architecture (e.g., FIGS. 1a-3), in accordance with one or more
embodiments of the
invention. For example for an embodiment, pedestal 104 may provide optical
alignment of
the IR camera architecture within an infrared camera system, such as with the
use of
alignment features (e.g., indents 112 and/or alignment tabs 302). As another
example for an
embodiment, pedestal 104 may provide heat dissipation and heat spreading in a
beneficial
fashion, such as for IR detector 102. As another example for an embodiment,
pedestal 104
may provide space for heat isolation, such as for example to isolate IR
detector 102 from
unwanted heat from die stack 106 (e.g., to provide some degree of thermal
protection for
IR detector 102 from die stack 106).
As a specific example, FIG. 4 shows a side view diagram illustrating an
example of
thermal paths for an IR camera architecture 400 in accordance with an
embodiment of the
invention. IR camera architecture 400 may represent an example embodiment of
an IR
camera architecture (e.g., such as described in reference to FIGS. la-3). As
shown, thermal
paths 402 illustrate the thermal connection between die stack 106 and
substrate 110,
allowing the dissipation of heat, such as through substrate 110 and through
solder balls 204
(e.g., BGA balls or other types of electrical connections).
Similarly, thermal paths 404 illustrate the thermal connection between IR
detector
102 and pedestal 104, allowing the spreading and dissipation of heat, such as
through
pedestal 104 and via the top portion of pedestal 104 (e.g., side rails 182
having alignment
tabs 302) and possibly to other portions (e.g., optics) of an infrared camera
system
incorporating IR camera architecture 400. Pedestal 104 may provide a high
thermally
conductive structure to maintain good thermal contact with IR detector 102
(e.g., and also
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to a housing and associated optics), dissipate localized heat rapidly under IR
detector 102,
and improve thermal uniformity under IR detector 102. As noted, pedestal 104
also
provides a spacing above die stack 106 and other electrical components (e.g.,
PMIC 108)
on substrate 110 to provide thermal isolation for IR detector 102.
FIG. 5 provides a perspective, cross-sectional view illustrating an IR camera
architecture 500 in accordance with an embodiment of the invention. IR camera
architecture 500 (e.g., an IR camera or IR camera system) includes a housing
502 (e.g., an
enclosure), an optics housing 504 that contains one or more lenses 506, and a
rear cover
510. As shown, optics housing 504 may engage threads 514 or be secured within
housing
502 by other conventional techniques to be properly positioned relative to IR
detector 102,
in accordance with one or more embodiments.
Rear cover 510 is secured to housing 502 via fasteners 508 (e.g., screws,
bolts, or
other types of fasteners) and encloses an IR camera architecture (e.g., IR
camera
architecture 300) within housing 502. In accordance with one or more
embodiments, rear
cover 510 may be a camera board (e.g., a PCB) with associated electrical
components to
support and interface with substrate 110. For example, rear cover 510 may
include
electrical connections to couple with electrical connections of substrate 110
(e.g., solder
bumps to couple with solder balls 204 (FIG. 2)) and may include electrical
components
(e.g., passive and/or active components), such as for example capacitors,
inductors,
resistors, and/or dies, as needed for a desired application as would be
understood by one
skilled in the art.
Thermal paths 402 and 404 are shown and illustrate the thermal routes within
IR
camera architecture 500. For example, thermal paths 402 are shown from die
stack 106,
through substrate 110, rear cover 510, and fasteners 508, to housing 502.
Furthermore,
thermal paths 404 are shown from IR detector 102, through pedestal 104 and a
partial
divider 512, to housing 502 and on through lens 506. Therefore, pedestal 104
provides for
temperature coupling of the IR detector 102 with the optics (e.g., lens 506)
via pedestal 104
and further provides for temperature uniformity under IR detector 102 (e.g.,
along readout
circuitry of IR detector 102 due to pedestal 104 made of a high thermally
conductive
material), in accordance with one or more embodiments.
FIGS. 6a and 6b provide exploded, perspective views illustrating an IR camera
architecture 600 in accordance with an embodiment of the invention. IR camera
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architecture 600 (e.g., an IR camera system) is similar to IR camera
architecture 500 (FIG.
5), but further illustrates the use of optical X, Y, and/or Z datums (i.e.,
alignment features)
to align and properly position an IR camera architecture, such as IR camera
architecture
300, within housing 502 and relative to lens 506 within optics housing 504.
Specifically, in accordance with an embodiment, housing 502 includes alignment
indents 602 that correspond with alignment tabs 302 on pedestal 104 (i.e.,
corresponding
alignment datums). Consequently, when alignment tabs 302 are inserted into
alignment
indents 602, IR detector 102 of IR camera architecture 300 will be properly
positioned
within housing 502 to receive IR energy through lens 506 via an opening 604
within
housing 502 when optics housing 504 is properly positioned within housing 502.
As a
specific example for an embodiment, alignment tabs 302 couple with alignment
indents
602 (e.g., to at least provide proper X and Y positioning and possibly Z
positioning), and
side rails 182 couple with (e.g., abut) an inner surface 606 of IR camera
architecture 600
(e.g., to provide proper Z positioning relative to the example XYZ coordinate
system
shown), such that IR camera architecture 300 is properly positioned within
housing 502.
As shown in FIG. 6b, rear cover 510 (e.g., a PCB electrically coupled to
substrate
110) may include an interface connector 516 to provide an interface through
which power,
command and control, and/or other electrical signals may be provided to IR
camera
architecture 600 and through which IR thermal image data and/or other
electrical signals
may be received from IR camera architecture 600. Consequently, IR camera
architecture
600 may be easily incorporated into an IR camera system.
FIGS. 7a and 7b provide cross-sectional, side views illustrating IR camera
architectures 700 and 750, respectively, in accordance with one or more
embodiments of
the invention. IR camera architectures 700 and 750 are similar to IR camera
architectures
500 (FIG. 5) and 600 (FIG. 6), but illustrate certain alternative or
additional features in
accordance with one or more embodiments.
IR camera architecture 700 illustrates rear cover 510 coupled to substrate 110
of the
IR camera architecture (e.g., IR camera architecture 300) and secured to
housing 502 by
fasteners 508. A thermal pad 702 may be disposed between pedestal 104 and
partial divider
512 (e.g., a portion of the optics barrel), as shown in FIG. 7a.
IR camera architecture 750 illustrates a thermal pad 754 disposed between
substrate
110 and rear cover 510. A housing cover 752 and fasteners 508 enclose the IR
camera
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architecture (e.g., IR camera architecture 300) within housing 502, while
pedestal 104
directly contacts partial divider 512 (e.g., a portion of the optics barrel),
as shown in FIG.
7b.
In accordance with one or more embodiments, infrared camera architectures
(e.g.,
as discussed in reference to FIGS. la-4) are disclosed, which may provide
certain
advantages over conventional infrared camera architectures. For example, the
infrared
camera architecture may be viewed as and represent a single IR camera package
(e.g., a
one chip IR camera core architecture or a single IR camera core) that may
operate as an
uncooled IR camera core that requires minimal external support circuitry
(e.g., 3.3 volts in,
IR image data out).
The IR camera architecture, for example, may include a pedestal that supports
an IR
detector and provides adequate space for thermal isolation between the IR
detector and the
associated electronics below the pedestal. The associated electronics may
include a die
stack (e.g., chip stack or heat sink chip/die stack) and possibly other
electrical components
(e.g., discrete capacitors, inductors, resistors, and/or chips, such as a
power management
chip) such that the IR detector and the associated electronics are merged
within a single
core package (e.g., encapsulated within a plastic overmold with optical
alignment
tabs/indents on the pedestal and an unobstructed IR detector window).
The pedestal, for one or more embodiments, may provide optical alignment, heat
dissipation, and heat spreading to aid the IR detector's functionality. The
pedestal may also
provide sufficient space to thermally isolate the IR detector from the
associated electronics
on the substrate below the pedestal.
Furthermore, the pedestal may thermally link the IR detector with associated
optics,
in accordance with one or more embodiments. For example, as discussed in
reference to
FIGS. 4-7b, the IR camera architecture may be thermally coupled within an IR
camera
(e.g., IR camera architectures 500, 600, 700, or 750) to thermally link the IR
detector to the
IR camera's optics and housing and further thermally link and dissipate and
spread heat
from the associated electronics (e.g., via the substrate and/or BGA) to the IR
camera
housing and optics, which may provide a thermally uniform and stable
architecture.
FIG. 8 provides a perspective view illustrating an assembled IR camera 800 in
accordance with an embodiment of the invention. IR camera 800 may include an
IR camera
architecture, such as IR camera architecture 100, 160, 180, 300, or 400 (e.g.,
as discussed
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in reference to FIGS. 1-4) and may further represent an IR camera architecture
similar to
IR camera architectures 500, 600, 700, and 750 (e.g., as discussed in
reference to FIGS. 5-
7b). In general, IR camera 800 may be self contained and easily implemented
within a
system requiring IR imaging capability.
FIG. 9 provides a block diagram illustrating a system 900 (e.g., an IR camera
or IR
camera system), which is configured to capture and process IR images, in
accordance with
one or more embodiments of the invention. System 900 may represent an IR
camera
system, which includes one of the IR camera architectures disclosed herein.
System 900 comprises, in one implementation, a processing component 910, a
memory component 920, a control component 930, a power component 940, an image
capture component 950, and a display component 970. Optionally, system 900 may
include
a sensing component 960.
System 900 may represent, for example, an infrared imaging device, such as an
infrared camera (e.g., an infrared camera system), to capture and process
images, such as
still or video IR images of a scene 980. System 900 includes at least one of
the IR camera
architectures disclosed herein (e.g., IR camera architecture 100 or IR camera
architecture
500), with the IR camera architecture represented by various portions of
system 900.
For example, the IR camera architecture may be represented by image capture
component 950 (e.g., IR detector 102), power component 940 (e.g., ASIC 106a
and/or
PMIC 108), memory component 920 (e.g., within die stack 106, such as memory
die 106b
and 106d), and processing component 910 (e.g., within die stack 106, such as
ASIC 106a
and/or 106e of FIG. la). System 900 may, for example, include further
functionality in
addition to what is represented by IR camera architecture, for the above
example. For
example, there may be additional memory and processing functionality (e.g.,
additional
portions of memory component 920, power component 940, and processing
component
910) within system 900 that is not included within the IR camera architecture.
As a specific example, system 900 may represent a distributed network system
with
one or more IR camera architectures that are networked to a computer (e.g., a
server) to
receive the IR image data and store, display, and/or further process the IR
image data.
System 900 may also comprise, for example, a portable device and may be
incorporated,
e.g., into a vehicle (e.g., an automobile or other type of land-based vehicle,
an aircraft, a
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marine craft, or a spacecraft) or a non-mobile installation requiring infrared
images (e.g.,
IR image data) to be stored and/or displayed.
In accordance with one or more embodiments, processing component 910 may
comprise any type of a processor or a logic device (e.g., a programmable logic
device
(PLD) or ASIC configured to perform processing functions). Processing
component 910
may be adapted to interface and communicate with components 920, 930, 940,
950, and
970 to perform method and processing steps and/or operations, as would be
understood by
one skilled in the art.
Memory component 920 comprises, in accordance with an embodiment, one or
more memory devices adapted to store data and information, including for
example
infrared data and information. Memory device 920 may comprise one or more
various
types of memory devices, including volatile and non-volatile memory devices.
Processing
component 910 may be adapted to execute software or be configured by a bit
stream stored
in memory component 920 so as to perform method and process steps and/or
operations
described herein.
Image capture component 950 comprises, in accordance with an embodiment, any
type of infrared image sensor, such as for example one or more infrared
sensors (e.g., any
type of multi-pixel infrared detector, such as a focal plane array) for
capturing infrared
image data (e.g., still image data and/or video data) representative of an
image, such as
scene 980. In one example implementation, the infrared sensors of image
capture
component 950 provide for representing (e.g., converting) the captured image
data as
digital data (e.g., via an analog-to-digital converter included as part of the
infrared sensor
or separate from the infrared sensor as part of system 900).
In accordance with an embodiment, the infrared image data (e.g., infrared
video
data) may comprise non-uniform data (e.g., real image data) of an image, such
as scene
980. Processing component 910 may be adapted to process the infrared image
data (e.g., to
provide processed image data), store the infrared image data in memory
component 920,
and/or retrieve stored infrared image data from memory component 920. For
example,
processing component 910 may be adapted to process infrared image data stored
in
memory component 920 to provide processed image data and information (e.g.,
captured
and/or processed infrared image data).
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Control component 930 comprises, in accordance with an embodiment, a user
input
and/or interface device that is adapted to generate a user input control
signal. For example,
the user input and/or interface device may include a rotatable knob (e.g., a
potentiometer),
push buttons, a slide bar, a keyboard, and the like. Processing component 910
may be
adapted to sense control input signals from a user via control component 930
and respond
to any sensed control input signals received therefrom. Processing component
910 may be
adapted to interpret such a control input signal as a parameter value, as
generally
understood by one skilled in the art.
In accordance with an embodiment, control component 930 may comprise a control
unit (e.g., a wired or wireless handheld control unit) having push buttons
adapted to
interface with a user and receive user input control values. In one
implementation, the push
buttons of the control unit may be used to control various functions of the
system 900, such
as autofocus, menu enable and selection, field of view, brightness, contrast,
noise filtering,
high pass filtering, low pass filtering, and/or various other features as
understood by one
skilled in the art.
Power component 940, in accordance with an embodiment, provides various power
supply voltages (e.g., reference voltages, bias voltages, reference currents,
or other desired
bias and power signals) required by the IR camera architecture and optionally
for the entire
system 900, depending upon the specific application and requirements. As a
specific
example, power component 940 may represent PMIC 108 of FIG. la, in accordance
with
an embodiment, and system 900 may further include additional power supply
sources.
Display component 970 comprises, in accordance with an embodiment, an image
display device (e.g., a liquid crystal display (LCD) or various other types of
generally
known video displays or monitors). Processing component 910 may be adapted to
display
image data and information on display component 970. Processing component 910
may be
adapted to retrieve image data and information from memory component 920 and
display
any retrieved image data and information on display component 970. Display
component
970 may comprise display electronics, which may be utilized by processing
component 910
to display image data and information (e.g., infrared images). Display
component 970 may
be adapted to receive image data and information directly from image capture
component
950 via the processing component 910, or the image data and information may be
transferred from memory component 920 (e.g., via processing component 910).
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Optional sensing component 960 comprises, in accordance with an embodiment,
one or more sensors of various types, depending on the application or
implementation
requirements, as would be understood by one skilled in the art. The sensors of
optional
sensing component 960 provide data and/or information to at least processing
component
910. In one aspect, processing component 910 may be adapted to communicate
with
sensing component 960 (e.g., by receiving sensor information from sensing
component
960) and with image capture component 950 (e.g., by receiving data and
information from
image capture component 950 and providing and/or receiving command, control,
and/or
other information to and/or from one or more other components of system 900).
In various implementations, sensing component 960 may provide information
regarding environmental conditions, such as outside temperature, lighting
conditions (e.g.,
day, night, dusk, and/or dawn), humidity level, specific weather conditions
(e.g., sun, rain,
and/or snow), distance (e.g., via a laser rangefinder), and/or whether a
tunnel or other type
of enclosure has been entered or exited. Sensing component 960 may represent
conventional sensors as generally known by one skilled in the art for
monitoring various
conditions (e.g., environmental conditions) that may have an effect (e.g., on
the image
appearance) on the data provided by image capture component 950.
In some implementations, optional sensing component 960 (e.g., one or more of
sensors) may comprise devices that relay information to processing component
910 via
wired and/or wireless communication. For example, optional sensing component
960 may
be adapted to receive information from a satellite, through a local broadcast
(e.g., radio
frequency (RF)) transmission, through a mobile or cellular network and/or
through
information beacons in an infrastructure (e.g., a transportation or highway
information
beacon infrastructure), or various other wired and/or wireless techniques.
In accordance with one or more embodiments, components of system 900 may be
combined and/or implemented or not, as desired or depending on the application
or
requirements, with system 900 representing various functional blocks of a
related system.
In one example, processing component 910 may be combined with memory component
920, image capture component 950, display component 970, and/or optional
sensing
component 960. In another example, processing component 910 may be combined
with
image capture component 950 with only certain functions of processing
component 910
performed by circuitry (e.g., a processor, a microprocessor, a logic device, a
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microcontroller, etc.) within image capture component 950. Furthermore,
various
components of system 900 may be remote from each other (e.g., image capture
component
950 may comprise a remote sensor with processing component 910, etc.,
representing a
computer that may or may not be in communication with image capture component
950).
As discussed above, for example in connection with FIGS. la ¨ lc, in some
embodiments, the infrared detector 102 may comprise a vacuum package assembly
(VPA),
such as a wafer level package (WLP) VPA. Fig. 10 is a cross-sectional side
elevation view
of an example embodiment of such an infrared detector 102 produced in
accordance with
one or more embodiments of wafer level packaging (WLP) methods, and FIG. 12 is
a top
plan view thereof.
As illustrated in FIGS. 10 and 12, the example infrared detector 102 includes
a
substrate 1002 having an array 1004 of infrared detectors (e.g.,
microbolometers) and a
readout integrated circuit 1006 interconnected with the array 1004 disposed on
an upper
surface thereof. As an example implementation, the array 1004 may be referred
to herein as
a microbolometer array for a specific type of infrared detector, but it should
be understood
that the WLP techniques disclosed herein may be applied more generally to
various types
of infrared detectors, as would be understood by one skilled in the art.
A generally planar window 1008 is spaced above the array 1004, the window 1008
being substantially transparent to infrared light. A mesa 1010 is coupled
(e.g., bonded) to
the window 1008, e.g., with a thermal oxide layer 1014 such that the window
1008 and the
mesa 1010 may form a bonded silicon on insulator (SOI) wafer pair for one or
more
embodiments. The mesa 1010 has closed marginal side walls disposed between an
outer
periphery of a lower surface of the window 1008 and an outer periphery of the
upper
surface of the substrate 1002 and defines a closed cavity 1012 between the
window 1008
and the array 1004 that encloses the infrared detector array 1004. A solder
seal ring 1016 is
shown bonding the mesa 1010 to the substrate 1002 so as to seal the cavity
1012 (e.g., to
provide a hermetic seal for an evacuated WLP VPA).
As illustrated in FIG. 10, in one example embodiment, the window 1008 may
comprise low-oxygen (02) silicon (Si) (or alternatively float zone silicon)
having a
thickness of about 625 microns (pm). In another example embodiment, the side
walls of the
mesa 1010 may comprise Si having a width of about 550 pm and a height of about
100 pm.
In another example embodiment, the mesa 1010 and the window 1008 may comprise
a
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semiconductor, e.g., low-02 Si, and the upper surface of the side walls of the
mesa 1010
may be bonded to the lower surface of the window 1008 by a layer of a thermal
oxide 1014
of the same semiconductor, e.g., silicon dioxide (5i02), having a thickness of
about 1 pm.
In yet another embodiment, the lower surface of the side walls of the mesa
1010 may be
bonded to an upper surface of the substrate 1002 by a joint of fused or
layered solder rings
1016 of, e.g., an alloy of titanium (Ti)/nickel (Ni)/gold-tin-gold (AuSnxAu),
respectively
formed, e.g., using photolithography techniques, on the lower surface of the
side walls of
the mesa 1010 and the upper surface of the substrate 1002 and having a
combined
thickness of, e.g., about 4 pm and a width of, e.g., about 450 pm.
In one embodiment, the infrared detector 102 may include at least one
antireflective
coating 1018, e.g., Zinc Sulfide (ZnS)/Germanium (Ge), formed, e.g., by a
physical vapor
deposition (PVD) method, on an upper and/or a lower surface of the window 1008
to
prevent infrared light incident upon the coated surfaces from being reflected
away from the
microbolometer array 1004. In another embodiment, a getter 1020, e.g.,
Zirconium (Zr)
alloy, may be formed, e.g., by sputtering, on a lower surface of the window
1008 in the
cavity 1012 before, during, and/or after it has been evacuated. The getter
material process
may be provided, for example, by SAES GettersTM of Colorado Springs, CO. It
should be
understood that the materials, dimensions, and processes disclosed herein are
examples for
one or more embodiments and are not limiting and that other suitable materials
and
processes, as would be understood by one skilled in the art, may be used in
accordance
with one or more embodiments.
As illustrated in FIG. 10, in another example embodiment, the infrared
detector 102
may include at least one electrical test pad 1022 disposed on the upper
surface of the
substrate 1002 adjacent to the outer periphery of the window 1008. As
discussed in more
detail below, the test pad 1022 may be coupled to the readout integrated
circuit 1006 and
used to test the infrared detector 102 electrically at the wafer level and
before it is
singulated.
Following is a description of an example embodiment of a method 1102 (FIG. 11)
by which the example infrared detector 102 of FIGS. 10 and 12, as well as
other infrared
detectors, may be manufactured reliably and efficiently in volume quantities
using wafer
level packaging (WLP) techniques. As illustrated in the top level overview of
the method
in FIG. 11, in one embodiment, the example method 1102 may begin at stage or
step 1 (51)
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with the provision of a "window" wafer and at S2 with a "bolometer" wafer as
described in
more detail below, then proceed at S3 with the WLP processes that combines the
two
wafers into an assembly and process the assembly that results in a plurality
of infrared
detectors 102.
As illustrated in detail in FIG. 13, the example WLP method 1102 comprises two
methods, viz., a "window wafer" production method 1302 and a "bolometer wafer"
production method 1304, that merge into yet a third "wafer assembly and
bonding" method
1306. The various stages set forth in FIG. 13 are described in detail as
follows for one or
more embodiments.
As illustrated in FIG. 14, the example window wafer production method 1302
begins at Si with the provision of a wafer 1502 (see FIG. 15), e.g., a silicon-
on-insulator
(SOI) wafer, having a layer of oxide 1014, e.g., a thermal oxide layer,
sandwiched between
two layers, i.e., a "window" layer and a "mesa" layer, each of a semiconductor
material,
e.g., Si. As illustrated in FIG. 15, at S2, an array of "targets" 1504 (e.g.,
used to define the
resulting windows for resulting infrared detectors 102 and may be useful for
the formation
of corresponding mesas 1010 and associated cavities 1012) is formed using,
e.g.,
photolithography techniques, on a surface of the window wafer 1502, e.g., on
the window
layer or the mesa layer of the wafer 1502.
As illustrated in FIG. 16, at S3 of the example method 1302, the array of mesa
1010
and cavity 1012 targets 1504 on the wafer 1502 are then etched using, e.g., a
Deep
Reactive Ion Etching (DRIE) process, in the surface of the mesa layer of the
window wafer
1502. The etching defines an array of windows 1008 in the window layer of the
wafer 1502
that are substantially transparent to infrared light, each of which is
surrounded by a mesa
1010 having closed marginal side walls bonded to the window wafer 1502 by the
oxide
layer 1014. As shown in FIG. 15, adjacent rows and columns of the array are
separated
from each other by dicing lanes 1506.
While using a single semiconductor and etch process may suffice to form a mesa
and windows, in one advantageous embodiment, a two part window wafer may be
used
which is separated by a separation or bonding layer (e.g. oxide layer). In
such an
embodiment, the etching process at S3 of the method 1302 may include etching
the surface
of the window wafer 1502 down to the oxide layer 1014 using, e.g., a DRIE
process, so as
to form the array of mesas 1010 and associated cavities 1012. The oxide layer
1014, which
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may act as a etch stop, may be selectively removed from the surface of the
window wafer
1502 in such a way that the lower surfaces of the windows 1008, which
correspond to
lower surface of the window layer of the window wafer 1502, retain their as-
formed
window-layer smoothness and planarity, while the respective marginal side
walls of the
mesas 1010 remain firmly bonded to the window wafer 1502 by the remaining
oxide layer
1014. This latter removal process may be effected, for example, using a
hydrofluoric acid
etching technique to remove the oxide layer 1014 in the region of cavities
1012. In various
embodiments, the separation layer may be a variety of other boding materials.
As illustrated in FIG. 17, the example method 1302 proceeds at S4 with the
formation of antireflective coatings 1018 on the upper and lower surfaces of
the windows
1008 in the window wafer 1502. As shown in FIG. 18, the example method 1302
continues
at 55 with the deposition of a sealing ring 1016, which may comprise liftoff
seal layers of
an adhesion layer (e.g., titanium (Ti)), a barrier material (e.g., nickel),
and a solder layer
comprising, e.g., gold (Au) and tin (Sn). As illustrated in FIG. 19, the
example method
1302 continues at S6 with the deposition of a getter material 1020 on the
lower surface of
each of the windows 1008 of the window wafer 1502, and concludes at S7 with a
solderable window wafer 1502 that is ready for assembly with a corresponding
bolometer
wafer, as discussed in more detail below.
As discussed above in connection with FIG. 13, the example WLP method 1102
comprises two methods, viz., a "window wafer" production method 1302 and a
"bolometer
wafer" production method 1304, that merge into a third "wafer assembly and
bonding"
method 1306.
FIG. 20 illustrates some more of the details of the bolometer wafer production
method 1304, which begins at 51 with the provision of wafer, e.g., of Si, and
proceeds at
S2 with conventional processing to produce an array of infrared detectors
(e.g.,
microbolometers) 1004 on a surface thereof to form a bolometer wafer 2102 (see
FIG. 21).
Up to this stage, the method 1304 for producing the bolometer wafer 2102 is
relatively
conventional. However, as illustrated in FIG. 20, after this stage or if
desired at an earlier
stage, it is desirable to form a solder sealing ring 1016 on the surface of
the bolometer
wafer 2102 around each of the microbolometer arrays 1004 thereon for effecting
a sealing
bond with the window wafer 1502, as described below.
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Accordingly, as illustrated in FIG. 21, at S3 of the example bolometer wafer
production method 1304, in one embodiment, a layer of a polymer 2104 is etched
using,
e.g., photolithography techniques, to form a trench 2106 in the layer 2104
around each of
the microbolometer arrays 1004 of the wafer 2102. Then, as illustrated in FIG.
22, at S4 of
the example method 1304, a sealing ring material is deposited (e.g., using
conventional
liftoff photolithography techniques) in the trenches 2106 of the polymer layer
2104 to form
sealing rings 1016 therein. As illustrated in FIG. 23, following the
deposition of the sealing
ring 1016 material, the polymer layer 2104 is removed from the wafer 2102,
e.g., by
etching, to conclude the method 1304 at S7 with a solderable bolometer wafer
2102 that is
ready for assembly with a corresponding window wafer 1502, as discussed in
more detail
below.
As discussed above in connection with FIG. 13, the window wafer production
method 1302 and the bolometer wafer production method 1304 merge into a third,
wafer-
assembly-and bonding method 1306. This is illustrated in FIG. 24, wherein the
method
1306 begins at Si with the provision of the window wafer 1502 produced by the
example
method 1302 and the bolometer wafer 2102 produced by the example method 1304
described above. The window wafer 1502 and the bolometer wafer 2102 may be
pretreated
with a heated vacuum bake at Si, as would be understood by one skilled in the
art.
As illustrated in FIG. 25, the example method 1306 then proceeds at S2 with a
cleaning and alignment of the two wafers 1502 and 2102 in a fixture or tool
(e.g., either
within or outside of vacuum chamber 2604) designed to hold them in alignment
such that
the window wafer 1502 is positioned above the bolometer wafer 2102, the
cavities 1012 of
the window wafer 1502 are respectively disposed over corresponding ones of the
microbolometer arrays 1004 on the bolometer wafer 2102, and the respective
solder seal
rings 1016 on the mesas 1010 and the bolometer wafer 2102 are precisely
aligned with
each other. In this regard, the two wafers 1502 and 2102 may be spaced apart
from each
other using one or more optional shims 2502.
As illustrated in FIG. 26, at S3 of the example method 1306, the cleaned and
fixtured assembly 2602 of wafers 1502 and 2102 is placed (or left in) in a
vacuum chamber
2604, and may be subjected to certain temperature cycles and evacuation for
outgassing
and evacuation for cavities 1012 to prepare the VPA, as would be understood by
one
skilled in the art. As shown in FIG. 27, at S4 of the method 1306, the chamber
2604 is
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evacuated and the two wafers 1502 and 2102 are pressed together and heated (or
heated
and then pressed together) to a temperature sufficient to join the respective
solder sealing
rings 1016 on the two wafers together, thereby sealing the evacuated cavities
1012
enclosing respective ones of the microbolometer arrays 1004 against exposure
to any
undesirable atmospheric gasses. Additionally, in some embodiments, the
application of
heat to the wafer assembly 2602 may used to "fire," i.e., activate, the
getters 1020 in the
cavities 1012 such that they function to adsorb any air molecules or other
undesired gasses
that might remain in the cavities 1012 before, during, and/or after they are
vacuum sealed.
The getters 1020 may also be activated by application of a current or other
type of trigger
to activate, as would be understood by one skilled in the art.
As illustrated in FIG. 28, the example method 1306 proceeds at S5 with slicing
through the dicing lanes 1506 so as to expose the underlying test pads 1022 on
the upper
surface of the bolometer wafer 2102, and as shown in FIG. 29, at S6, may
effect a wafer
level electrical test of some or all of the infrared detectors 102 in the
wafer assembly 2602
using, e.g., a probe card, before they are singulated from the wafer assembly
2602.
As illustrated in FIG. 30, after any wafer level electrical testing of the
wafer
assembly 2602 has been concluded, the method 1306 proceeds at S7 with the
dicing of the
individual infrared detectors 102 from the wafer assembly 2602, e.g., by
slicing through the
dicing lanes 1506 of the bolometer wafer 2102 (e.g., between test pads 1022 of
adjacent
infrared detectors 102), and concludes at S8 with a plurality of completed
infrared detectors
102.
FIG. 31 is a diagram illustrating features and example dimensional details of
an
example solder sealing ring 1016 and optional solder capture rings 3102 of an
example
infrared detector 102 in accordance with an embodiment of the invention. As
illustrated in
FIG. 31, at least one solder capture ring 3102 may be formed on the substrate
1002
adjacent to the solder sealing ring 1016 (or formed as part of solder sealing
ring 1016), and
may function during the wafer assembly 2602 bonding process described above to
prevent
excess solder from flowing away from the bonding joint effected between the
respective
sealing rings 1016 of the window wafer 1502 and the bolometer wafer 2102 and
onto the
surface of the microbolometers 1004. For example for an embodiment, solder
capture ring
3102 may be formed along solder sealing ring 1016 with solder connections to
(e.g.,
periodically) to solder sealing ring 1016.
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FIGS. 32A ¨ 32H are schematic partial cross-sectional side elevation views of
a
vacuum bonding chamber 2604 and fixtured wafer assembly 2602, respectively
showing
sequential steps involved in an example WLP process for bonding the wafer
assembly
2602, as described above in connection with FIGS. 24 ¨27, for one or more
embodiments.
As illustrated in FIG. 32A, the vacuum chamber 2604 may include a fixed press
platen
3202, a press platen 3204 that is moveable relative to the fixed press platen
3202 by means
of, e.g., a hydraulic motor 3206, a source 3208 of a neutral gas, e.g.,
nitrogen (N2), for
purging the chamber 2604 of air, a chamber door 3210 that may be closed and
sealed
against a high pressure vacuum, and a pump 3212 for forming a relatively hard
vacuum in
the chamber 2604.
As illustrated in FIG. 32A, the example bonding process may begin with venting
the chamber with N2 using the N2 source 3208, then opening the chamber door
3210 (FIG.
32B). In FIG. 32C, the fixtured wafer assembly 2602 is inserted into the
chamber 2604 and
between the two press platens 3202 and 3204. In FIG. 32D, the door 3210 of the
chamber
2604 is closed, and the chamber 2604 is pumped out using the pump 3212, purged
using
the purging source 3208, then pumped out again using the pump 3212 to form a
relatively
hard vacuum in the chamber 2604. In FIG. 32E, the press platens 3202 and 3204
are
brought in contact with the fixtured wafer assembly 2602 using the motor 3206,
and the
two press platens 3202 and 3404 are heated, e.g., with internal heating
elements, to an
elevated temperature to bake the fixtured wafer assembly 2602 in preparation
to bonding
the two wafers 1502 and 2102 together, as described above.
In FIG. 32F, a pressing force is applied to the fixtured wafer assembly 2602
by the
press platens 3202 and 3204, and the temperature of the two press platens 3202
and 3404 is
then ramped up to the melting temperature of the solder sealing rings 1016 of
the two
wafers 1502 and 2102, causing them to fuse together and seal a vacuum within
each of the
cavities 1012 of the wafer assembly 2602, as described above. In FIG. 32G, the
press
platens 3202 and 3204, together with the fixtured wafer assembly 2602, are
allowed to cool
to a temperature below the melting temperature of the solder sealing rings
1016, and in
FIG. 32H, the chamber 2604 is vented using the purging source 3208, the press
platen 3202
and 3204 are moved apart to relieve the force applied by them to the wafer
assembly 2602,
the door 3210 of the chamber 2604 is opened, and the fixtured and wafer
assembly 2602,
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PCT/US2011/045600
70052.283W0
now bonded together, is removed from the chamber 2604 for subsequent post-
bonding
processing, for example, as discussed above in connection with FIGS. 28 ¨ 30.
Systems and methods are disclosed herein to provide infrared camera
architectures
and infrared detectors in accordance with one or more embodiments of the
invention. For
example, in accordance with an embodiment of the invention, an infrared camera
architecture is disclosed that integrates the entire IR camera electronics,
thermal
management, and optical alignment functionality into a single component (e.g.,
a single
package or chip core). The infrared camera architecture, for example, may
represent an
easy to design-in electronic component for device and system applications.
Techniques are
also disclosed to manufacture the infrared detector based on WLP techniques in
accordance
with one or more embodiments.
The infrared camera architectures disclosed herein may provide certain
advantages
over conventional infrared camera architectures. For example, the techniques
disclosed
herein for one or more embodiments of the invention may provide for greater
miniaturization of the infrared camera and at reduced manufacturing costs and
allow for
higher volume production. The infrared camera architectures may reduce the
number of
external circuit boards, components, heat sinks, packages, and additional
electronic
circuitry and power supply voltages that would conventionally be required to
create and
support the infrared camera. The infrared camera architectures further may
reduce,
simplify, or eliminate complex calibration procedures, thermal management, and
optical
alignment requirements and thus, provide an infrared camera that may be easily
incorporated into and supported for a desired application.
While the invention has been described in detail in connection with only a
limited
number of embodiments of the invention, it should be readily understood that
the invention
is not limited to such disclosed embodiments. Rather, the invention may be
modified to
incorporate any number of variations, alterations, substitutions or equivalent
arrangements
not heretofore described, but which are commensurate with the spirit and scope
of the
invention. Additionally, while various embodiments of the invention have been
described,
it is to be understood that aspects of the invention may include only some of
the described
embodiments. Accordingly, the invention is not to be seen as limited by the
foregoing
description, but is only limited by the scope of the appended claims and
functional
equivalents thereof.
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