U.S. patent application number 10/342825 was filed with the patent office on 2004-07-15 for piezoelectric devices mounted on integrated circuit chip.
Invention is credited to Byers, Charles L., Mandell, Lee J., Schnittgrund, Gary D., Schulman, Joseph H..
Application Number | 20040135473 10/342825 |
Document ID | / |
Family ID | 32655468 |
Filed Date | 2004-07-15 |
United States Patent
Application |
20040135473 |
Kind Code |
A1 |
Byers, Charles L. ; et
al. |
July 15, 2004 |
Piezoelectric devices mounted on integrated circuit chip
Abstract
The invention is a filter circuit that includes an
electromechanical resonator that is mounted directly to the surface
of a silicon integrated circuit, rather than being mounted as a
surface mounted or leaded filter can on a circuit board. This
filter system allows the integrated circuit electronic package to
be significantly smaller than when a conventional electromechanical
resonator package is used. The electromechanical resonator may be
protected during processing and during use with a protective cover
that is made of a material such as titanium. The protective cover
is attached to the integrated circuit chip.
Inventors: |
Byers, Charles L.; (Canyon
Country, CA) ; Schnittgrund, Gary D.; (Granada Hills,
CA) ; Schulman, Joseph H.; (Santa Clarita, CA)
; Mandell, Lee J.; (West Hills, CA) |
Correspondence
Address: |
ALFRED E. MANN FOUNDATION FOR
SCIENTIFIC RESEARCH
PO BOX 905
25134 RYE CANYON LOOP, SUITE 200
SANTA CLARITA
CA
91380
US
|
Family ID: |
32655468 |
Appl. No.: |
10/342825 |
Filed: |
January 15, 2003 |
Current U.S.
Class: |
310/348 |
Current CPC
Class: |
Y10T 29/4908 20150115;
H01L 2224/48465 20130101; Y10T 29/49005 20150115; H03H 9/1021
20130101; H03H 9/54 20130101; H01L 2924/00 20130101; H01L
2224/48227 20130101; H05K 13/04 20130101; Y10T 29/49007 20150115;
H01L 2224/48227 20130101; H01L 2224/48465 20130101 |
Class at
Publication: |
310/348 |
International
Class: |
H01L 041/053 |
Claims
What is claimed is:
1. An integrated circuit filter system comprising: an integrated
circuit chip containing an electronic circuit; and at least one
electromechanical resonator mounted to and supported by said
integrated circuit chip and electrically coupled to said electronic
circuit.
2. The integrated circuit filter system according to claim 1
wherein said electromechanical resonator is mounted to said
integrated circuit chip by at least one mounting pad.
3. The integrated circuit filter system according to claim 2
wherein said at least one mounting pad is a gold bump.
4. The integrated circuit filter system according to claim 2
wherein said at least one mounting pad is electrically
conductive.
5. The integrated circuit filter system according to claim 2
wherein said at least one mounting pad is comprised of an
electrically conductive epoxy.
6. The integrated circuit oscillator system according to claim 1
wherein said at least one electromechanical resonator is comprised
of quartz.
7. The integrated circuit filter system according to claim 1
wherein said integrated circuit chip is comprised of silicon.
8. The integrated circuit filter system according to claim 1
wherein said electronic circuit is at least partially comprised of
an oscillator circuit.
9. The integrated circuit filter system according to claim 1
wherein said integrated circuit chip has a top surface and a bottom
surface and at least one electromechanical resonator is mounted on
said top surface.
10. The integrated circuit filter system according to claim 1
wherein said integrated circuit chip has a top surface and a bottom
surface and at least one electromechanical resonator is mounted on
said top surface of said integrated circuit chip and a second
electromechanical resonator is mounted on said bottom surface of
said integrated circuit chip.
11. The integrated circuit filter system according to claim 1
wherein said integrated circuit chip is comprised of a stack of at
least two integrated circuit chips.
12. The integrated circuit filter system according to claim 11
wherein said at least two integrated circuit chips are oriented to
define a cavity therebetween and said at least one
electromechanical resonator is mounted in said cavity.
13. The integrated circuit filter system according to claim 1
wherein said at least one electromechanical resonator is under a
protective cover.
14. The integrated circuit filter system according to claim 13
wherein said protective cover is comprised of titanium.
15. A method of forming a filter circuit on an integrated circuit
chip comprising the steps of: selecting an integrated circuit chip,
selecting at least one electromechanical resonator, forming at
least one mounting pad on at least one surface of said integrated
circuit chip, and attaching at least one electromechanical
resonator to said at least one mounting pad.
16. The method of forming a filter system according to claim 15
wherein said step of forming at least one mounting pad is forming
said pad directly on said at least one surface of said integrated
circuit chip.
17. The method of forming a filter system according to claim 15
wherein said step of attaching said electromechanical resonator is
adhesive bonding with an electrically conductive adhesive.
18. The method of forming a filter system according to claim 15
further comprising the step of attaching a protective cover over
said electromechanical resonator.
19. An integrated circuit filter system for an implantable
electronic device, that is implantable in living tissue, which may
be a microstimulator or a microsensor having an axial dimension of
less than 60 mm and a lateral dimension of less than 6 mm, wherein
said electronic device includes at least two electrodes for
delivering electrical signals between said electronic device and
living tissue, said system comprising: an integrated circuit chip
containing an electronic circuit; and at least one
electromechanical resonator mounted to and supported by said
integrated circuit chip and electrically coupled to said electronic
circuit.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is related to but in no way dependent on
commonly assigned U.S. patent application, Space Saving Packaging
of Electronic Circuits, Attorney Docket No. A285, filed on even
date herewith and incorporated herein by reference
FIELD OF THE INVENTION
[0002] This invention relates to high-density electronic modules,
which are intended to meet the desire for incorporating more
electronic capacity in a given space, or reducing the space
required for a given amount of electronic capacity by placing the
mechanical resonator directly on the integrated circuit chip. One
of the primary uses of the present invention is to provide size
reduction for synchronous integrated circuitry useful in
implantable microstimulators and microsensors for implantation in
living tissue. However, the same concepts may be applied to any
field where high-density electronic circuitry is desired.
BACKGROUND OF THE INVENTION
[0003] Most integrated circuits (ICs) and other miniature
components such as oscillators, magnetic sensors, etc. are packaged
in plastic or ceramic packages with solder pads or with extending
metal leads for soldering to a printed circuit board or for
insertion into a socket. Piezoelectric devices are common, and
include electromechanical resonators, filters, sensors, and
actuators. Electronic filters may be made with one or more
mechanical resonators. Mechanical resonators are a key element of
oscillator circuits, for example, and may be a quartz crystal, a
piezoelectric crystal, an aluminum nitride bulk acoustic resonator,
or a surface acoustic wave device. In most cases, a single package
will only contain a single circuit component, although multiple IC
chips are more commonly being manufactured within a single package.
The use of such packages results in a low circuit density as the
ceramic or plastic package consumes relatively large areas of the
mounting surface, particularly if a socket is used.
[0004] Some of the primary considerations in developing improved
high-density electronic packaging modules are:
[0005] (1) Optimizing packing density to achieve the lowest
possible volume per element, essentially the smallest module that
is production worthy.
[0006] (2) Eliminating packaging elements where possible, such as
ceramic and plastic boxes and printed circuit boards, flex circuits
and other substrates.
[0007] (3) Simplifying the fabrication procedures.
[0008] (4) Enhancing the structural strength of the elements.
[0009] (5) Improving reliability of the electronics and of the
techniques for interconnecting the electronics with the electrical
leads.
[0010] (6) Maximizing suitability for test and repair at the lowest
level of assembly and throughout assembly.
[0011] 7) Minimizing the cost per element.
[0012] A significant deterrent to reducing microcircuitry size is
the electromechanical resonator. While companies, such as Statek
Corporation, Orange, Calif., endeavor to produce small crystals,
which are one form of electromechanical resonator. The mechanical
resonator packages themselves, which may be surface mounted or
leaded, are relatively large. The electromechanical resonator
package is generally a package comprised of metal, glass and/or
ceramic that contains the crystal resonator, inverter, active
element transistors, resistors, capacitors and/or inductors.
[0013] Microstimulators, as exemplified by the devices and systems
described in U.S. Pat. Nos. 6,164,284, 6,185,452, 6,208,894,
6,472,991, and 6,315,721, which are incorporated herein by
reference in their entirety. Microstimulators are typically
elongated devices with metallic electrodes at each end that deliver
electrical current to the immediately surrounding living tissue.
One significant characteristic of these microstimulators is that
they eliminate the need for electrical lead wires. The
microelectronic circuitry and inductive coils that control the
electrical current applied to the electrodes are protected from the
body fluids by a hermetically sealed capsule. This capsule is
typically made of rigid dielectric materials, such as glass or
ceramic, that transmits magnetic fields but is impermeable to
water, as well as biocompatible materials such as titanium.
[0014] An implantable miniature stimulator represents a typical
application for a microstimulator. U.S. patent application Ser. No.
10/280,841, incorporated herein by reference in its entirety,
presents the state of the art for crystal oscillators in these
microstimulator devices. Because the microstimulator is small and
leadless, it may be advantageously placed anywhere in the body of a
human. Typical dimensions for this device are about 5 to 60 mm in
length and about 1 to 6 mm in diameter. Obviously, the smaller the
microstimulator, the more readily it may be placed in living
tissue.
[0015] Therefore, there is a need to reduce the size of the
oscillator to enable production of smaller microcircuitry and hence
smaller devices.
SUMMARY OF THE INVENTION
[0016] The apparatus of the instant invention is the
electromechanical resonator of an integrated circuit oscillator
system comprising an integrated circuit chip containing an
electronic circuit and at least one electromechanical resonator
mounted to and supported by the integrated circuit chip, and
electrically coupled to the electronic circuit. The
electromechanical resonator is mounted to the integrated circuit
chip by at least one mounting pad. The mounting pad is an
electrically conductive epoxy. The electromechanical resonator is
mounted on a top surface of the integrated circuit chip, and a
second crystal resonator may be mounted on a bottom surface of the
integrated circuit chip. The integrated circuit chip may also be
comprised of a stack of at least two integrated circuit chips. The
electromechanical resonator may be under a protective cover, which
may be titanium, or may be within a cavity formed by a stack of
chips. The novel features of the invention are set forth with
particularity in the appended claims. The invention will be best
understood from the following description when read in conjunction
with the accompanying drawings.
OBJECTS OF THE INVENTION
[0017] It is an object of the invention to replace the
electromechanical package in an electronic circuit with a
direct-mounted electromechanical resonator and associated
electronic circuitry on the integrated circuit substrate.
[0018] It is an object of the invention to mount a
electromechanical resonator directly on a silicon chip integrated
circuit.
[0019] It is an object of the invention to mount a
electromechanical resonator directly on a silicon chip integrated
circuit by means of gold bumping, conductive epoxy, and/or
solder.
[0020] Other objects, advantages and novel features of the present
invention will become apparent from the following detailed
description of the invention when considered in conjunction with
the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 presents a perspective view of an integrated circuit
chip with electromechanical resonator mounting pads.
[0022] FIG. 2 presents a perspective view of an integrated circuit
chip with an electromechanical resonator mounted on one
surface.
[0023] FIG. 3 presents a perspective view of an integrated circuit
chip with an electromechanical resonator mounted on one surface and
a protective cover over the electromechanical resonator.
[0024] FIG. 4 is a perspective view of an integrated circuit chip
stack with a cavity mounted electromechanical resonator.
[0025] FIG. 5 is a side view of the integrated circuit chip stack
of FIG. 4.
[0026] FIG. 6 is a perspective view of the bottom chip of the
integrated circuit from FIG. 4.
[0027] FIG. 7 is a perspective view of the bottom chip of FIG. 6
showing a cut-away view of the bond pad.
[0028] FIG. 8 is a cross-sectional view of the bond pad from FIG.
7.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0029] A great amount of size reduction can be achieved by
eliminating the ceramic and glass box that the electromechanical
resonator is normally packaged in, or by combing the oscillator IC
and other appropriate circuit elements in one package. In every
such case, size reduction is facilitated by having a method for
mounting an electromechanical resonator directly on an IC chip.
[0030] FIG. 1 provides a perspective view of a preferred embodiment
of the electromechanical resonator mounting scheme. A conventional
integrated circuit chip 106, which when purchased typically has a
thickness on the order of about 0.020 inches, and which is
preferably comprised of silicon, but may be comprised of other
materials that are well know to one skilled in the art, such as
gallium, has at least one mounting pad 108 and preferably has two
mounting pads 108 securedly attached to at least one surface of the
integrated circuit chip 106. In a preferred embodiment, the two
mounting pads 108 are on a top surface 114 of the integrated
circuit chip 106. The top surface 114 preferably contains the
integrated circuits and the circuitry that forms an oscillator
circuit when combined with an electromechanical resonator 110 of
FIG. 2.
[0031] Electromechanical resonators are well known to one skilled
in the art and are typically comprised of a piezoelectric material,
such as quartz, that has been manufactured to have a precise and
well-defined resonance frequency. The bottom surface 116 of the
integrated circuit chip 106 may also contain electrical circuitry
and may comprise an oscillator circuit with an electromechanical
resonator 110. The electromechanical resonator is preferably a
crystal resonator, such as a piezoelectric crystal. It is also
conceived that the electromechanical resonator 110 may be located
on a surface of the integrated circuit chip 106 that is opposite to
that on which all or a portion of the electronic circuitry is
located. The electromechanical resonator circuitry includes devices
that are well know to one skilled in the art, and may include
various electronic components, including an inverter, active
element transistors, resistors, capacitors and/or inductors.
[0032] The mounting pads 108, FIG. 2, are preferably electrically
conductive and carry an electrical signal between the
electromechanical resonator circuitry and the electromechanical
resonator 110. The electrical signal is well known to one skilled
in the art and is, at least in part, responsible for the
electromechanical resonator 110 vibration. A preferred material for
the mounting pads 108 is an electrically conductive epoxy, such as
product number H20E from Epoxy Technology, Billerica, Mass. This
preferred electrically conductive epoxy material is heat cured for
one hour at about 125.degree. C. Many other conductive adhesives
are known by those skilled in the art. As illustrated in FIG. 2,
the electromechanical resonator 110 is securedly attached to the
mounting pads 108, preferably by an electrically conductive
adhesive such as H20E. Alternative mounting embodiments include
using gold bumping or thick film technology of conductive materials
such as gold, platinum, palladium, or combinations thereof. As is
well known in the art, the electromechanical resonator or crystal
is preferably cantilever mounted, although alternative mounting
schemes are well know, such as supplying additional support with a
soft, flexible mounting material, such as a low durometer
silicone.
[0033] The mounting pads 108 are preferably formed directly on the
integrated circuit chip 106. In an alternative embodiment, the
mounting pads 108 are formed, prior to attachment to the integrated
circuit chip 106, by molding and curing the electrically conductive
pads in a silicone mold prior to removing them and placing them on
the integrated circuit chip 106. The mounting pads 108 are
positioned at a location on the integrated circuit chip 106 to
establish electrical contact with the circuit on the surface of the
integrated circuit chip 106.
[0034] In order to achieve a compact microcircuit it is preferred
that the height of the mounting pads 108 be about 0.002 to 0.003
inches, although in alternative embodiments the mounting pads 108
may be taller or shorter. In a preferred embodiment, the mounting
pads 108 determine the final distance between the integrated
circuit chip 106 and the electromechanical resonator 110, which is
preferably about 0.002 inches. As is well known to one skilled in
the art, contact between the electromechanical resonator 110 and
any other surfaces is unacceptable, although contact with the
mounting pads 108 is designed to optimize performance of the
electromechanical resonator 110.
[0035] As presented in FIG. 3, a protective cover 112 is preferably
placed over the electromechanical resonator 110 to protect the
resonator 110 during processing and during use. It is preferred
that the protective cover 112 be comprised of titanium, although
any number of other materials may be used successfully. The
protective cover 112 is attached to the top surface 114 of the
integrated circuit by an adhesive.
[0036] An alternative embodiment is presented in FIGS. 4-8, wherein
an electromechanical resonator 210 is preferably mounted in a
cavity 212. FIG. 4 presents a chip stack 200 with the cavity 212
formed by a top integrated circuit chip 202, a bottom integrated
circuit chip 204, a first intermediate integrated circuit chip 207
and a second intermediate integrated circuit chip 206. As is known
to one skilled in the art, electrical signals are carried by bond
wires 214, which are connected to ball bonds 216 on the top
integrated circuit chip 202 and to recessed bond pads 218 on first
intermediate chip 207.
[0037] FIG. 5 presents a side view of the chip stack 200 wherein an
electromechanical resonator 210 is preferably secured to mounting
pads 208 in the cavity 212.
[0038] FIG. 6 presents a preferred embodiment with the bottom chip
204 having a gold ball 220 on the bond pad 218. Alternative
embodiments have gold ball 220 comprised of solder or of other
materials that are known to one skilled in the art. Gold ball 220
forms an electrically conductive connection between
electromechanical resonator 210 and bottom chip 204.
[0039] FIG. 7 presents the preferred embodiment of FIG. 6 with a
cut away section through the mounting pad 208 so that the gold ball
220 can be seen in its preferred orientation on the bond pad
218.
[0040] FIG. 8 presents a more detailed view of the gold ball 220
forming an electrical connection between the electromechanical
resonator 210 and the bond pad 218.
[0041] Obviously, many modifications and variations of the present
invention are possible in light of the above teachings. It is
therefore to be understood that, within the scope of the appended
claims, the invention may be practiced otherwise than as
specifically described.
* * * * *