U.S. patent application number 12/967613 was filed with the patent office on 2011-05-05 for method for protecting encapsulated sensor structures using stack packaging.
Invention is credited to Karsten Funk.
Application Number | 20110101474 12/967613 |
Document ID | / |
Family ID | 32850598 |
Filed Date | 2011-05-05 |
United States Patent
Application |
20110101474 |
Kind Code |
A1 |
Funk; Karsten |
May 5, 2011 |
METHOD FOR PROTECTING ENCAPSULATED SENSOR STRUCTURES USING STACK
PACKAGING
Abstract
A method of protecting a micro-mechanical sensor structure
embedded in a micro-mechanical sensor chip, in which the
micro-mechanical sensor structure is fabricated with a protective
membrane, the micro-mechanical sensor chip is arranged so that a
surface of the protective membrane faces toward a second chip, and
the micro-mechanical sensor chip is secured to the second chip.
Inventors: |
Funk; Karsten; (Mountain
View, CA) |
Family ID: |
32850598 |
Appl. No.: |
12/967613 |
Filed: |
December 14, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11903900 |
Sep 25, 2007 |
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12967613 |
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10404567 |
Mar 31, 2003 |
7335971 |
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11903900 |
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Current U.S.
Class: |
257/415 ;
257/E21.002; 257/E29.324; 438/51 |
Current CPC
Class: |
G01P 15/18 20130101;
H01L 2224/48137 20130101; H01L 2224/49171 20130101; G01P 15/125
20130101; G01P 2015/0814 20130101; H01L 2224/48465 20130101; H01L
2224/05554 20130101; H01L 2224/48465 20130101; H01L 2224/48465
20130101; H01L 2224/48465 20130101; G01P 1/023 20130101; H01L
2224/48247 20130101; H01L 2224/48091 20130101; B81C 1/00333
20130101; B81B 2207/095 20130101; H01L 2924/181 20130101; H01L
2924/181 20130101; H01L 2224/16145 20130101; B81C 2203/0136
20130101; H01L 2224/48247 20130101; H01L 2224/48091 20130101; H01L
2924/00 20130101; H01L 2224/48091 20130101; H01L 2924/00012
20130101; H01L 2924/00014 20130101; H01L 2924/00 20130101; H01L
2924/00012 20130101; H01L 2224/48247 20130101 |
Class at
Publication: |
257/415 ; 438/51;
257/E29.324; 257/E21.002 |
International
Class: |
H01L 29/84 20060101
H01L029/84; H01L 21/02 20060101 H01L021/02 |
Claims
1-20. (canceled)
21. A micro-mechanical sensor device, comprising: a first chip; and
a micro-mechanical sensor chip having an embedded micro-mechanical
sensor structure and a protective membrane arranged on a face of
the embedded micro-mechanical sensor structure, wherein the
micro-mechanical sensor chip is arranged directly onto a face of
the first chip that faces and is parallel to the face of the
embedded micro-mechanical sensor structure so that the protective
membrane is arranged between the faces.
22. The micro-mechanical sensor device of claim 21, wherein the
protective membrane is configured at a reduced thickness.
23. The micro-mechanical sensor device of claim 21, wherein a
thickness of the protective membrane is less than 10 microns.
24. The micro-mechanical sensor device of claim 21, further
comprising: a bond to secure the micro-mechanical sensor chip to
the first chip.
25. The micro-mechanical sensor device of claim 21, further
comprising: a sealing bond ring to surround the embedded
micro-mechanical structure.
26. The micro-mechanical sensor device of claim 21, wherein the
protective membrane includes an opening.
27. The micro-mechanical sensor device of claim 21, wherein the
protective membrane is at least partially absent.
28. The micro-mechanical sensor device of claim 21, wherein the
embedded micro-mechanical sensor structure is sensitive to one of a
pressure, acceleration, a rotation, and a temperature.
29. The micro-mechanical sensor device of claim 21, wherein the
first chip is at least one of an electronic integrated circuit chip
and an actuator chip.
30. A method of protecting a micro-mechanical sensor structure
embedded in a micro-mechanical sensor chip, comprising: fabricating
the micro-mechanical sensor structure with a protective membrane;
arranging the micro-mechanical sensor chip so that a surface of the
protective membrane faces toward a second chip; and securing the
micro-mechanical sensor chip to the second chip.
31. The method of claim 30, further comprising: configuring the
protective membrane at a reduced thickness.
32. The method of claim 30, wherein the protective membrane is
configured using a chemical and mechanical planarization
process.
33. The method of claim 30, wherein a thickness of the protective
membrane is less than 10 microns.
34. The method of claim 30, further comprising: configuring a
sealing bond ring to surround the micro-mechanical sensor
structure.
35. The method of claim 30, wherein the protective membrane
includes an opening.
36. The method of claim 30, wherein the protective membrane is
configured to be at least partially absent.
37. The method of claim 30, further comprising: arranging at least
one additional micro-mechanical sensor chip at least one of on,
underneath, and between the micro-mechanical sensor chip and the
second chip to provide a multi-sensor device.
38. The method of claim 30, further comprising: applying a bond
between the micro-mechanical sensor chip and the second chip to
secure the micro-mechanical sensor chip to the second chip;
arranging the micro-mechanical sensor chip and the second chip on a
package frame to support the micro-mechanical sensor chip and the
second chip in a single package; and applying a plastic mold to
seal the micro-mechanical sensor chip and the second chip in the
single package.
39. The method of claim 30, further comprising: configuring a
sealing bond ring to surround the micro-mechanical sensor
structure; arranging the micro-mechanical sensor chip and the
second chip on a package frame to support the micro-mechanical
sensor chip and the second chip in a single package; and applying a
plastic mold to seal the micro-mechanical sensor chip and the
second chip in the single package.
40. A method of protecting a micro-mechanical sensor structure
embedded in a micro-mechanical sensor chip, comprising: fabricating
the micro-mechanical sensor structure with a sealing bond to
surround the micro-mechanical sensor structure; arranging the
micro-mechanical sensor chip so that a surface of the protective
membrane faces toward a second chip; and securing the
micro-mechanical sensor chip to the second chip.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application is a continuation of, and claims priority
under 35 U.S.C. .sctn.120 to, U.S. patent application Ser. No.
11/903,900 filed on Sep. 21, 2007, which is a continuation of U.S.
patent application Ser. No. 10/404,567, filed on Mar. 31, 2003, all
of which are incorporated herein by reference in their
entireties.
FIELD OF THE INVENTION
[0002] The present invention relates to a method for protecting
encapsulated micro-mechanical sensor structures.
BACKGROUND INFORMATION
[0003] Micro-mechanical sensor structures may be fragile and may be
easily damaged and/or destroyed if they come in contact with
foreign particles and/or liquids (including, for example, dirt and
condensed humidity). Therefore, it may be desired to protect such
structures early in the production process.
[0004] Micro-mechanical sensor structures may be protected by
applying an additional film or membrane layer during the production
process to encapsulate the sensor structure and to shield its
sensitive areas from undesired external contaminants, such as, for
example, dust and dirt, or potentially harmful environmental
conditions, such as, for example heat and humidity. The protective
membrane layer, however, may be too thin to withstand the high
pressures that may occur during the plastic molding of the
micro-mechanical sensor structure device. Although enhancing the
thickness of the protective membrane layer may provide greater
mechanical stability, such an enhancement may be costly and may not
always be feasible, especially if the overall package thickness of
the sensor structure device is limited by design constraints.
[0005] Micro-mechanical sensor structures may also be protected by
stacking several sensor chips or wafers on top of each other within
the package. For example, a sensor wafer with etched holes and
grooves may be bonded on top of an another sensor wafer to provide
reinforcement. In such a configuration, the grooves may be arranged
to provide access directly above the sensor structure and the holes
may be aligned to provide openings for the contacts. The process of
stacking several sensor wafers, however, may increase the material
cost (e.g., two wafers may be required instead of only one) and the
resulting multi-wafer sensor device may be undesirably thick.
SUMMARY OF THE INVENTION
[0006] An exemplary embodiment and/or exemplary method of the
present invention for protecting a micro-mechanical sensor
structure may arrange the micro-mechanical sensor structure
"face-down" onto a complementary electronic integrated circuit chip
so that the thin membrane encapsulating the sensor structure is
completely covered. By doing so, the chip carrying the electronic
circuitry may take over an additional mechanical task of supporting
the thin membrane which would otherwise be too weak to withstand
the pressures exerted on it during fabrication.
[0007] It is believed that the exemplary embodiment and/or
exemplary method may provide a higher stability for the
micro-mechanical sensor structure at reduced cost. In particular,
the exemplary embodiment and/or exemplary method may permit the
encapsulated mechanical sensor structure to withstand the high
molding pressures that may be encountered during fabrication, while
at the same time reducing the overall package size and/or a
required number of bond wires.
[0008] According to another exemplary embodiment and/or exemplary
method, an electronic integrated circuit chip may be flipped onto a
"face-up" micro-mechanical sensor chip whose thin film covering an
embedded micro-mechanical sensor structure faces the electronic
integrated circuit chip.
[0009] According to another exemplary embodiment and/or exemplary
method, several micro-mechanical sensor chips with thin protective
membranes covering their micro-mechanical sensor structures may be
stacked upon, underneath, or in conjunction with one or more
electronic integrated circuit chips to provide a variety of
combined micro-mechanical sensor/electronic integrated circuit chip
configurations for a wide variety of micro-mechanical sensor
applications. For example, such a multi-layer arrangement of
micro-mechanical sensor chips with electronic integrated circuit
chips may be used to create a multi-dimensional micro-mechanical
accelerometer, gyroscope, or other sensory device by stacking
multiple micro-mechanical sensor chips having thin protective
membranes onto, underneath, or in conjunction with one or more
electronic integrated circuit or other types of micro-chips.
[0010] In a further exemplary embodiment and/or exemplary method,
the thin protective membrane may be eliminated. In this case, a
sealing bond ring arranged to surround the micro-mechanical sensor
structure may protect the micro-mechanical element once the
electronic integrated circuit chip is bonded to the sensor
chip.
[0011] An exemplary method of protecting a micro-mechanical sensor
structure embedded in a micro-mechanical sensor chip includes
fabricating the micro-mechanical sensor structure with a protective
membrane, arranging the micro-mechanical sensor chip so that a
surface of the protective membrane faces toward a second chip, and
securing the micro-mechanical sensor chip to the second chip.
[0012] Yet another exemplary method of protecting a
micro-mechanical sensor structure embedded in a micro-mechanical
sensor chip includes configuring the protective membrane at a
reduced thickness.
[0013] Still another exemplary method is directed to protecting a
micro-mechanical sensor structure embedded in a micro-mechanical
sensor chip in which the protective membrane is configured using a
chemical and mechanical planarization process.
[0014] Yet another exemplary method is directed to protecting a
micro-mechanical sensor structure embedded in a micro-mechanical
sensor chip in which a thickness of the protective membrane is less
than 10 microns.
[0015] Still another exemplary method of protecting a
micro-mechanical sensor structure embedded in a micro-mechanical
sensor chip includes configuring a sealing bond ring to surround
the micro-mechanical sensor structure.
[0016] Yet another exemplary method is directed to protecting a
micro-mechanical sensor structure embedded in a micro-mechanical
sensor chip in which the protective membrane includes an
opening.
[0017] Still another exemplary method is directed to protecting a
micro-mechanical sensor structure embedded in a micro-mechanical
sensor chip in which the protective membrane is configured to be at
least partially absent.
[0018] Yet another exemplary method of protecting a
micro-mechanical sensor structure embedded in a micro-mechanical
sensor chip includes applying a bond between the micro-mechanical
sensor chip and the second chip to secure the micro-mechanical
sensor chip to the second chip.
[0019] Still another exemplary method of protecting a
micro-mechanical sensor structure embedded in a micro-mechanical
sensor chip includes arranging the micro-mechanical sensor chip and
the second chip on a package frame to support the micro-mechanical
sensor chip and the second chip in a single package, and applying a
plastic mold to seal the micro-mechanical sensor chip and the
second chip in the single package.
[0020] Still another exemplary method of protecting a
micro-mechanical sensor structure embedded in a micro-mechanical
sensor chip includes arranging at least one additional
micro-mechanical sensor chip at least one of on, underneath, and
between the micro-mechanical sensor chip and the second chip to
provide a multi-sensor device.
[0021] Yet another exemplary method is directed to protecting a
micro-mechanical sensor structure embedded in a micro-mechanical
sensor chip in which the multi-sensor device includes at least one
of an accelerometer, a gyroscope, a temperature sensor, and a
pressure sensor.
[0022] Still another exemplary method is directed to protecting a
micro-mechanical sensor structure embedded in a micro-mechanical
sensor chip in which the multi-sensor device includes at least one
of a multi-dimensional accelerometer and a multi-dimensional
gyroscope.
[0023] Yet another exemplary method is directed to protecting a
micro-mechanical sensor structure embedded in a micro-mechanical
sensor chip in which the embedded micro-mechanical sensor structure
is sensitive to one of a pressure, an acceleration, a rotation, and
a temperature.
[0024] Still another exemplary method of protecting a
micro-mechanical sensor structure embedded in a micro-mechanical
sensor chip in which the second chip is at least one of an
electronic integrated circuit chip and an actuator chip.
[0025] Yet another exemplary method of protecting a
micro-mechanical sensor structure embedded in a micro-mechanical
sensor chip includes applying a bond between the micro-mechanical
sensor chip and the second chip to secure the micro-mechanical
sensor chip to the second chip, arranging the micro-mechanical
sensor chip and the second chip on a package frame to support the
micro-mechanical sensor chip and the second chip in a single
package, and applying a plastic mold to seal the micro-mechanical
sensor chip and the second chip in the single package.
[0026] Yet another exemplary method is directed to protecting a
micro-mechanical sensor structure embedded in a micro-mechanical
sensor chip in which the protective membrane is configured using a
chemical and mechanical planarization process.
[0027] Still another exemplary method is directed to protecting a
micro-mechanical sensor structure embedded in a micro-mechanical
sensor chip in which a thickness of the protective membrane is less
than 10 microns
[0028] Yet another exemplary method of protecting a
micro-mechanical sensor structure embedded in a micro-mechanical
sensor chip includes configuring a sealing bond ring to surround
the micro-mechanical sensor structure, arranging the
micro-mechanical sensor chip and the second chip on a package frame
to support the micro-mechanical sensor chip and the second chip in
a single package, and applying a plastic mold to seal the
micro-mechanical sensor chip and the second chip in the single
package.
[0029] Still another exemplary method is directed to protecting a
micro-mechanical sensor structure embedded in a micro-mechanical
sensor chip in which the protective membrane includes an
opening.
[0030] Yet another exemplary method is directed to protecting a
micro-mechanical sensor structure embedded in a micro-mechanical
sensor chip in which the protective membrane is configured to be at
least partially absent.
[0031] An exemplary embodiment of a micro-mechanical sensor device
includes a first chip and a micro-mechanical sensor chip having an
embedded micro-mechanical sensor structure and a protective
membrane arranged on the embedded micro-mechanical sensor
structure, in which the micro-mechanical sensor chip is arranged
onto the first chip so that the protective membrane faces toward
the first chip.
[0032] Still another exemplary embodiment is directed to a
micro-mechanical sensor device in which the protective membrane is
configured at a reduced thickness.
[0033] Yet another exemplary embodiment is directed to a
micro-mechanical sensor device in which a thickness of the
protective membrane is less than 10 microns.
[0034] Still another exemplary embodiment is directed to a
micro-mechanical sensor device including a bond to secure the
micro-mechanical sensor chip to the first chip.
[0035] Yet another exemplary embodiment is directed to a
micro-mechanical sensor device including a sealing bond ring to
surround the embedded micro-mechanical structure.
[0036] Still another exemplary embodiment is directed to a
micro-mechanical sensor device in which the protective membrane
includes an opening.
[0037] Yet another exemplary embodiment is directed to a
micro-mechanical sensor device in which the protective membrane is
at least partially absent.
[0038] Still another exemplary embodiment is directed to a
micro-mechanical sensor device including a package frame to support
the first chip and the micro-mechanical sensor chip in a single
package, and a plastic mold to seal the first chip and the
micro-mechanical sensor chip in the single package.
[0039] Yet another exemplary embodiment is directed to a
micro-mechanical sensor device in which at least one additional
micro-mechanical sensor chip arranged at least one of on,
underneath, and between the micro-mechanical sensor chip and the
first chip to provide a multi-sensor device.
[0040] Still another exemplary embodiment is directed to a
micro-mechanical sensor device in which the multi-sensor device
includes at least one of an accelerometer, a gyroscope, a
temperature sensor, and a pressure sensor.
[0041] Yet another exemplary embodiment is directed to a
micro-mechanical sensor device in which n the multi-sensor device
includes at least one of a multi-dimensional accelerometer and a
multi-dimensional gyroscope.
[0042] Still another exemplary embodiment is directed to a
micro-mechanical sensor device in which the embedded
micro-mechanical sensor structure is sensitive to one of a
pressure, acceleration, a rotation, and a temperature.
[0043] Yet another exemplary embodiment is directed to a
micro-mechanical sensor device in which the first chip is at least
one of an electronic integrated circuit chip and an actuator
chip.
[0044] Still another exemplary embodiment is directed to a
micro-mechanical sensor device including an RF chip arranged on the
micro-mechanical sensor chip for wireless communication.
[0045] Yet another exemplary embodiment is directed to a
micro-mechanical sensor device including a substrate, wherein a
difference in dielectric coefficient for the RF chip as an upper
chip and an additional space between the upper RF chip and the
substrate provided by the use of the micro-mechanical sensor chip
as an intermediate chip provides an improved RF performance.
[0046] Still another exemplary embodiment is directed to a
micro-mechanical sensor device including a bond to secure the
micro-mechanical sensor chip to the first chip, a package frame to
support the first chip and the micro-mechanical sensor chip in a
single package, and a plastic mold to seal the first chip and the
micro-mechanical sensor chip in the single package, in which the
protective membrane is configured at a reduced thickness.
[0047] Yet another exemplary embodiment is directed to a
micro-mechanical sensor device in which a thickness of the
protective membrane is less than 10 microns.
[0048] Still another exemplary embodiment is directed to a
micro-mechanical sensor device including a sealing bond ring to
surround the embedded micro-mechanical structure, a package frame
to support the first chip and the micro-mechanical sensor chip in a
single package, and a plastic mold to seal the first chip and the
micro-mechanical sensor chip in the single package, in which the
protective membrane is at least partially absent.
[0049] An exemplary method of protecting a micro-mechanical sensor
structure embedded in a micro-mechanical sensor chip includes
fabricating the micro-mechanical sensor structure with a sealing
bond to surround the micro-mechanical sensor structure, arranging
the micro-mechanical sensor chip so that a surface of the
protective membrane faces toward a second chip, and securing the
micro-mechanical sensor chip to the second chip.
BRIEF DESCRIPTION OF THE DRAWINGS
[0050] FIG. 1A shows an exterior view of a combined
micro-mechanical sensor and electronic integrated circuit
package.
[0051] FIG. 1B shows an interior view of the combined
micro-mechanical sensor and electronic integrated circuit package
of FIG. 1A.
[0052] FIG. 2 shows an exemplary method to protect a
micro-mechanical sensor structure embedded in a micro-mechanical
sensor chip.
[0053] FIG. 2A shows a structured layer deposited onto a substrate
wafer.
[0054] FIG. 2B shows an oxide layer deposited on the structured
layer.
[0055] FIG. 2C shows a conducting layer deposited on the oxide
layer.
[0056] FIG. 2D shows an oxide layer removed and an opened
conducting layer.
[0057] FIG. 2E shows filled etch holes and a planarized smooth
surface.
[0058] FIG. 3A shows an exemplary flipping of a micro-mechanical
sensor chip onto a electronic integrated circuit chip.
[0059] FIG. 3B shows a combined arrangement of a micro-mechanical
sensor chip and an electronic integrated circuit chip.
[0060] FIG. 3C shows the combined arrangement of a micro-mechanical
sensor chip and electronic integrated circuit chip further stacked
onto a package frame and sealed with a plastic mold.
[0061] FIG. 4A shows a micro-mechanical linear accelerometer sensor
chip without a thin protective membrane.
[0062] FIG. 4B shows the micro-mechanical linear accelerometer
sensor chip of FIG. 4A with a thin protective membrane.
[0063] FIG. 5A shows an exemplary arrangement for a two-dimensional
accelerometer in which two micro-mechanical linear accelerometer
sensor chips are secured and electrically connected to an
underlying electronic integrated circuit chip via bond wires.
[0064] FIG. 5B shows the exemplary arrangement of FIG. 5A with an
additional top chip, substrate wafer, and additional bond
wires.
[0065] FIG. 5C shows the arrangement of FIG. 5B in a perspective
side view without bond wires.
[0066] FIG. 6A shows an exemplary arrangement to protect a
micro-mechanical sensor structure of a micro-mechanical sensor chip
without the need for a thin membrane to cover its sensitive
area.
[0067] FIG. 6B shows the electronic integrated circuit chip lifted
away from the micro-mechanical sensor chip so that the sealing bond
ring may be fully viewed.
[0068] FIG. 7 shows an exemplary arrangement for a two-dimensional
gyroscope in which two rotationally-sensitive micro-mechanical
sensor chips are secured and electrically connected to an
underlying electronic integrated circuit chip via bond wires.
[0069] FIG. 8 shows an exemplary multi-layer micro-mechanical
sensor arrangement for stacking several micro-mechanical sensor
chips on one or more electronic integrated circuit chips to provide
a variety of micro-mechanical sensor configurations and
applications.
[0070] FIG. 9 shows an exemplary multi-layer micro-mechanical
sensor arrangement for a combined micro-mechanical sensor and
wireless communication device.
DETAILED DESCRIPTION
[0071] FIG. 1A shows an exterior view of a combined
micro-mechanical sensor and electronic integrated circuit package
100 having a plastic molding 101 and outside electrical contacts
102. The plastic molding 101 provides a protective covering and
mechanical support for the internal components of the combined
micro-mechanical sensor and electronic integrated circuit package
100. The outside electrical contacts 102 provide an electrical
connection to the internal components of the combined
micro-mechanical sensor and electronic integrated circuit package
100.
[0072] FIG. 1B shows an interior view of the combined
micro-mechanical sensor and electronic integrated circuit package
100 of FIG. 1A showing, in addition to the plastic molding 101 and
outside electrical contacts 102, a micro-mechanical sensor chip
103, an electronic integrated circuit chip 105, a first series of
bond wires 104, and a second series of bond wires 106. The
micro-mechanical sensor chip 103 includes a micro-mechanical sensor
structure that produces micro-mechanical sensor signals that may
indicate, for example, a sensed pressure, acceleration, or
temperature. The electronic integrated circuit chip 105 processes
the mechanical sensor signals and communicates with elements
outside the package 100. The first series of bond wires 104
provides an electrical connection between the micro-mechanical
sensor chip 103 and the electronic integrated circuit chip 105. The
second series of bond wires 106 provides an electrical connection
between the electronic integrated circuit chip 105 and the outside
electrical contacts 102.
[0073] As shown in FIG. 1B, the electronic integrated circuit chip
105 and the micro-mechanical sensor chip 103 are arranged next to
each other within the same plastic molding 101. Such an
arrangement, however, may limit the overall reduction in size that
may be achieved for the combined micro-mechanical sensor and
electronic integrated package 100.
[0074] FIG. 2 shows an exemplary method to protect a
micro-mechanical sensor structure embedded in a micro-mechanical
sensor chip. In step s21, the micro-mechanical sensor chip is
fabricated with a thin protective membrane to cover a sensitive
area of the embedded micro-mechanical sensor structure. In step
s22, the micro-mechanical sensor chip is arranged face-down onto an
electronic integrated circuit chip so that the thin membrane is
covered and/or supported by the underlying electronic integrated
circuit chip. In step s23, the micro-mechanical sensor chip is
secured to the electronic integrated circuit chip.
[0075] FIGS. 2A through 2E demonstrate an exemplary production
method and process to fabricate a micro-mechanical sensor chip with
an additional thin membrane layer to shield and protect an embedded
micro-mechanical sensor structure.
[0076] In FIG. 2A, a structured layer 201 is deposited on a
substrate wafer 202 so that a first oxide layer 203 made from, for
example, an electrically non-conducting material such as silicon
dioxide, is followed by a first conducting layer 204 made from, for
example, an electrically conducting material such as silicon. The
substrate wafer 202 may also be made from, for example, an
electrically conducting material such as silicon.
[0077] In FIG. 2B, a second oxide layer 205 made from, for example,
a non-conducting material such as silicon, is deposited on the
structured layer 201 to close gaps 206 within the structured layer
201 between structured micro-mechanical beams 250 which may be
supported on at least one side and grouped in pairs so that one of
each of the paired micro-mechanical beams 250 is mounted to the
substrate wafer 202 while its counterpart is suspended by
springs.
[0078] In FIG. 2C, a second conducting layer 207 made from, for
example, an electrically conducting material such as silicon, is
deposited and then structured to provide electrical contacts to the
micro-mechanical beams 250. A third oxide layer 208, made from, for
example, a non-conducting material such as silicon dioxide, is then
deposited to fill the gap(s) 209 between the electrical contact
areas and the remaining surface.
[0079] In FIG. 2D, the third oxide layer 208 is removed and the
second conducting layer 207 is opened (i.e., structured) to allow
removal of the second oxide layer 205 via an etching process, such
as, for example, chemical etching, which produces etch holes 211.
In this manner, the second oxide layer 205 may function, for
example, as a sacrificial layer.
[0080] In FIG. 2E, the etch holes 211 in the second conducting
layer 207 are filled with a conducting material, such as, for
example, silicon and the entire wafer is planarized or polished, to
obtain a smooth surface 212, which provides a thin membrane layer
protecting the underlying micro-mechanical sensor structure. The
planarization or polishing may be performed using a chemical and
mechanical polishing or planarization (CMP) process in which
mechanical particles polish the surface while a chemical acid or
base is present. It is believed the chemical component of the CMP
process should provide a smoother surface since sharp scratches may
be etched away.
[0081] The exemplary method process described in FIGS. 2A through
2E may produce a thin membrane covering a micro-mechanical sensor
structure embedded within a micro-mechanical sensor chip. However,
if left exposed without taking further measures, the thin membrane
covering the micro-mechanical sensor structure may not be strong
enough to withstand the relatively high pressures that may exist
during plastic molding, whereupon melted plastic is pressed onto a
mold containing a metal frame holding the micro-mechanical sensor
chip. The required strength of the membrane and therefore its
required thickness may depend on a number of factors, including,
for example, the length or diameter of the surface to be covered,
the particular plastic molding process utilized, and the particular
environmental conditions.
[0082] FIGS. 3A through 3C demonstrate an exemplary method to
package a micro-mechanical sensor chip 200 whose embedded
micro-mechanical sensor structure has been encapsulated with a thin
protective membrane using the exemplary method and process
described in FIGS. 2A through 2E. It is believed that the exemplary
method and process should permit the thin protective membrane to
withstand the relatively high pressures that may exist during
plastic molding without damaging to the encapsulated
micro-mechanical sensor structure.
[0083] In FIG. 3A, the micro-mechanical sensor chip 200, acting as
the upper chip, is flipped face-down onto an underlying electronic
integrated circuit chip 300 so that the contact areas 225 of the
micro-mechanical sensor chip 200 match the contact areas 301 of the
electronic integrated circuit chip 300.
[0084] FIG. 3B shows the combined stacked arrangement 302 of the
flipped micro-mechanical sensor chip 200 whose embedded
micro-mechanical sensor structure now faces the underlying
electronic integrated circuit chip 300. In this configuration, the
electronic integrated circuit chip 300 may provide additional
shielding and support to the micro-mechanical sensor chip 200 so
that the overall mechanical stability of the micro-mechanical
sensor chip 200 is enhanced, while at the same time, permitting a
reduction in the required thickness of the protective membrane
encapsulating the embedded micro-mechanical sensor structure. A
mechanical bond 303 may also be provided to further enhance the
mechanical stability.
[0085] FIG. 3C shows the combined stack arrangement 302 of the
micro-mechanical sensor chip 200 and electronic integrated circuit
chip 300 further stacked onto a package frame 305 and sealed with a
plastic mold 306. Bond wires 307 secure the combined stack
arrangement 302 to the package frame 305 and ensure electrical
connectivity to the outside of the package. Such an arrangement in
which the micro-mechanical sensor chip 200 is flipped face-down
onto the electronic integrated circuit chip 300 is intended to
reduce the overall package size by reducing and/or eliminating the
protective membrane, as well as the required number of bond wires.
In particular, it is believed that the protective membrane may be
reduced, for example, to a thickness of between about 10 microns to
0.1 microns. The protective membrane may be reduced further, for
example, to less than 0.1 microns depending on various factors,
including, for example, the length or diameter of the surface to be
protected, the particular plastic molding process utilized, and the
particular environmental conditions.
[0086] It is understood that other flipped arrangements of the
micro-mechanical sensor 200 and the electronic integrated circuit
chip 300 may be provided. For example, although it may be desirable
to flip the micro-mechanical sensor chip 200 onto of the electronic
integrated circuit chip 300, the electronic integrated circuit chip
300 may alternatively be flipped onto the micro-mechanical sensor
chip 200. The alternative flipped arrangements of the
micro-mechanical sensor chip and electronic integrated circuit chip
may be implemented in a variety of applications including, for
example, a micro-mechanical accelerometer and a micro-mechanical
gyroscope.
[0087] FIG. 4A shows a micro-mechanical linear accelerometer sensor
chip 400 having an embedded micro-mechanical sensor structure 401
and electrical contact pads 402 arranged along an outer edge of the
micro-mechanical sensor chip 400. The micro-mechanical sensor
structure 401 is sensitive to a linear movement in a direction
along sensitivity axis X. The electrical contact pads 402 provide
an electrical connection to the internal components of the
micro-mechanical linear accelerometer sensor chip 400. The
electrical contact pads 402 may also provide a convenient
attachment point for bond wires which, in addition to completing
the electrical connection, may secure the micro-mechanical linear
accelerometer chip 400 to one or more other package elements, such
as, for example, another micro-chip or a substrate wafer.
[0088] FIG. 4B shows the micro-mechanical linear accelerometer
sensor chip 400 of FIG. 4A having a thin film or membrane 403
covering the micro-mechanical sensor structure 401 to protect it
from undesired contaminants (such as, for example, dust or dirt) or
potentially harmful environmental conditions (such as, for example,
heat and moisture). Although dependent on many factors as explained
above, the membrane 403 may be configured, for example, to a width
of 50 .PHI.m to 200 .PHI.m, and a thickness of about 2 .PHI.m to
0.5 .PHI.m, or less.
[0089] FIG. 5A shows an exemplary arrangement 500 for a
two-dimensional accelerometer in which two micro-mechanical linear
accelerometer sensor chips 501 and 502 are secured and electrically
connected to an underlying electronic integrated circuit chip 503
via bond wires 525. The two micro-mechanical linear accelerometer
sensor chips 501 and 502 are arranged face-down so that the thin
membranes which cover the embedded micro-mechanical sensor
structures face the electronic integrated circuit chip 503. The two
micro-mechanical linear accelerometer sensor chips 501 and 502 are
further arranged so that they are sensitive to linear movements
along axises that are perpendicular to each other. In particular,
micro-mechanical linear accelerometer sensor chip 501 is arranged
to be sensitive to a linear movement in a direction along axis X,
and micro-mechanical linear accelerometer sensor chip 502 is
arranged to be sensitive to a linear movement in a direction along
axis Y which is perpendicular to axis X.
[0090] FIG. 5B shows the exemplary arrangement of FIG. 5B with an
additional top chip 504, substrate wafer 505, and additional bond
wires 525a-525e. The top chip 505 is arranged on the two
micro-mechanical linear accelerometer chips 501 and 502, the
substrate wafer 505 is arranged underneath the electronic
integrated circuit chip 503, and the additional bond wires
425a-425e are arranged on contact pads to secure and electrically
connect the entire package. In particular, bond wires 525a secure
and electrically connect the top chip 504 to an intermediate
micro-mechanical linear accelerometer chips 501 or 502, bond wires
525b secure and electrically connect an intermediate
micro-mechanical linear accelerometer sensor chip 501 or 502 to the
electronic integrated circuit chip 503, bond wires 525c secure and
electrically connect the electronic integrated circuit chip 503 to
the substrate wafer 505, bond wires 525d secure and electrically
connect the top chip 504 to the substrate wager 505, and bond wires
525e secure and electrically connect top chip 504 to the the
electronic integrated circuit chip 503. Other configurations of the
bond wires 525 may be provided, such as, for example, a
configuration of the bond wires between the two intermediate
micro-mechanical liner accelerometer sensor chips 501 or 502 and
the substrate wafer 505.
[0091] In this configuration, one or more of the two
micro-mechanical linear accelerometer sensor chips may be arranged
face-up so that the thin membrane encapsulating the embedded
micro-mechanical sensor structure faces the top chip 504 which
covers the thin membrane providing addition mechanical support and
protection from undesired contaminants and/or potentially harmful
environmental conditions.
[0092] FIG. 5C shows the arrangement of FIG. 5B in a perspective
side view without bond wires.
[0093] FIG. 6A shows an exemplary arrangement 600 to protect a
micro-mechanical sensor structure of a micro-mechanical sensor chip
without the need for a thin membrane to cover its sensitive area.
The exemplary arrangement 600 includes a micro-mechanical sensor
chip 601, an electronic integrated circuit chip 602, and a sealing
bond ring 603. The electronic integrated circuit chip 602 is
arranged on the micro-mechanical sensor chip 601 and the sealing
bond ring 603 is arranged between them. The sealing bond ring 603
provides a seal between the micro-mechanical sensor chip 601 and
the electronic integrated circuit chip 602 to prevent undesired
contaminants and/or potential harmful environmental conditions from
entering between the micro-mechanical sensor chip 601 and the
electronic integrated circuit chip 602. Additionally, the sealing
bond 603 may even out stress due to punctual bonds. In FIG. 6A, the
sealing bond ring 603 is only partially visible.
[0094] FIG. 6B shows the electronic integrated circuit chip 602
lifted away from the micro-mechanical sensor chip 601 so that the
sealing bond ring 603 may be fully viewed. The sealing bond ring
603 surrounds the micro-mechanical sensor structure 601a which is
embedded within the micro-mechanical sensor chip 601 and exposed
without a protective thin film covering it. Alternatively, if
additional protection is required, the micro-mechanical sensor
structure 601a may be both surrounded by the sealing bond ring 603
and shielded with a thin protective membrane layer.
[0095] FIG. 7 shows an exemplary arrangement 700 for a
two-dimensional gyroscope in which two rotationally-sensitive
micro-mechanical sensor chips 701 and 702 are secured and
electrically connected to an underlying electronic integrated
circuit chip 703 via bond wires 725. The rotationally-sensitive
micro-mechanical sensor chips 701 and 702 are arranged face-down so
that the thin membrane encapsulating the embedded micro-mechanical
sensor structures faces the electronic integrated circuit chip 702.
The rotationally-sensitive micro-mechanical sensor chips 701 and
702 are further arranged so that they are sensitive to rotational
movements about axises that are perpendicular to each other. In
particular, rotationally-sensitive micro-mechanical sensor chip 701
is arranged to be sensitive to a rotational movement about an axis
X and rotationally-sensitive micro-mechanical sensor chip 702 is
arranged to be sensitive to a rotational movement about axis Y,
which is perpendicular to axis X.
[0096] Several micro-mechanical sensor chips with thin protective
membranes covering their micro-mechanical sensor structures may be
stacked upon, underneath, or in conjunction with one or more
electronic integrated circuit chips to provide a variety of
combined micro-mechanical sensor/electronic integrated circuit chip
configurations for a wide variety of micro-mechanical sensor
applications. For example, such a multi-layer arrangement of
micro-mechanical sensor chips with electronic integrated circuit
chips may be used to create a multi-dimensional micro-mechanical
accelerometer, gyroscope, or other sensory device by stacking
multiple micro-mechanical sensor chips having thin protective
membranes onto, underneath, or in conjunction with one or more
electronic integrated circuit or other types of micro-chips.
[0097] FIG. 8 shows an exemplary multi-layer micro-mechanical
sensor arrangement 800 for stacking several micro-mechanical sensor
chips on one or more electronic integrated circuit chips to provide
a variety of micro-mechanical sensor configurations and
applications. The exemplary multi-layer micro-mechanical sensor
arrangement 800 includes two micro-mechanical sensor chips 801 and
802 and an electronic integrated circuit chip 803. A first
micro-mechanical sensor chip 801 is arranged face-down on a second
micro-mechanical sensor chip 802, which is arranged on the
underlying electronic integrated circuit chip 803. The exemplary
multi-layer micro-mechanical sensor arrangement 800 may be used to
create a multi-dimensional micro-mechanical accelerometer,
gyroscope, or other sensory device by stacking multiple
micro-mechanical accelerometer chips onto one or more electronic
integrated circuit chips.
[0098] FIG. 9 shows an exemplary multi-layer micro-mechanical
sensor arrangement 900 for a combined micro-mechanical sensor and
wireless communication device. The exemplary multi-layer
micro-mechanical sensor arrangement 900 includes an RF chip 901, a
micro-mechanical sensor chip 902, and an electronic integrated
circuit chip 903. The RF chip 901 includes an antennae 901a for
wireless communication. The micro-mechanical sensor chip 902
includes a micro-mechanical sensor structure that may be sensitive
to, for example, a change in pressure, movement, acceleration, or
temperature. The micro-mechanical sensor structure is encapsulated
by a thin membrane.
[0099] In the exemplary multi-layer micro-mechanical sensor
arrangement 900, the RF chip 901 is arranged on the
micro-mechanical sensor chip 902 and the electronic integrated
circuit chip 903 is arranged underneath so that the thin membrane
encapsulating the embedded micro-mechanical sensor structure may be
shielded and protected from either above or below.
[0100] Alternatively, other arrangements of the RF chip 901 and the
micro-mechanical sensor chip 902 may be provided. For example,
instead of the RF chip 901 being arranged on the micro-mechanical
sensor chip 902 and the electronic integrated circuit chip 903
being arranged underneath, the micro-mechanical sensor chip 902 may
be arranged on the RF chip 901, or the electronic integrated
circuit chip 903 may be arranged on the RF chip 901 and the
micro-mechanical sensor chip 902 is arranged underneath. However,
it is believed that the difference in dielectric coefficient for
the RF chip 901 as the upper chip and the additional space between
the upper RF chip and the substrate provided by the use of the
micro-mechanical sensor chip 902 as the intermediate chip may
provide a better RF performance.
[0101] The RF chip 902 may include high speed electronic circuitry
on a Gallium Arsenic (GaAs) substrate to provide advanced detection
techniques for microwave technologies since the thin membrane(s)
protecting the embedded micro-mechanical sensor structure(s) may
permit detection of various penetration characteristics.
[0102] The multi-layer and/or multi-sensor arrangement of
micro-mechanical sensor chips may provide a wide variety of
combined micro-mechanical sensor devices despite a diverse set of
required working environments (e.g., a micro-mechanical
accelerometer may perform best at an atmospheric pressure while a
micro-mechanical gyroscope may perform best at nearly a vacuum). In
particular, the combined micro-mechanical sensor device may
include, for example, a combination of a single or
multi-dimensional gyroscope with a single or multi-dimensional
accelerometer, an RE sensor with either or both a single or
multi-dimensional gyroscope and a single or multi-dimensional
accelerometer, a temperature sensor and/or an RF sensor with either
or both a single or multi-dimensional gyroscope and a single or
multi-dimensional accelerometer, etc., or any combination
thereof.
[0103] Although exemplary embodiments and/or exemplary methods have
been described using an electronic integrated circuit and/or sensor
chips to shield and protect the embedded micro-mechanical sensor
structure, other chips may also be used. For example, the flipped
micro-mechanical sensor chip may be combined with an actuator chip
(e.g., changing properties of a chip due to magnetic or electric
fields, temperature, mechanical pressure, etc.).
* * * * *