U.S. patent application number 09/943802 was filed with the patent office on 2003-03-06 for stacked microelectronic devices and methods of fabricating same.
Invention is credited to Connell, Michael, Jiang, Tongbi.
Application Number | 20030042615 09/943802 |
Document ID | / |
Family ID | 25480287 |
Filed Date | 2003-03-06 |
United States Patent
Application |
20030042615 |
Kind Code |
A1 |
Jiang, Tongbi ; et
al. |
March 6, 2003 |
STACKED MICROELECTRONIC DEVICES AND METHODS OF FABRICATING SAME
Abstract
Certain methods of the invention permit spacerless manufacture
of stacked microelectronic devices by mechanically supporting a
second microelectronic component with a wire coating. This wire
coating may be sufficiently adhesive to also mechanically bond the
second microelectronic component to a first microelectronic
component. Other embodiments of the invention provide spacerless
stacked microelectronic devices wherein a second microelectronic
component is mechanically supported by a wire coating.
Inventors: |
Jiang, Tongbi; (Boise,
ID) ; Connell, Michael; (Boise, ID) |
Correspondence
Address: |
PERKINS COIE LLP
PATENT-SEA
P.O. BOX 1247
SEATTLE
WA
98111-1247
US
|
Family ID: |
25480287 |
Appl. No.: |
09/943802 |
Filed: |
August 30, 2001 |
Current U.S.
Class: |
257/777 ;
257/781; 257/784; 257/E21.705; 257/E25.013 |
Current CPC
Class: |
H01L 2924/01087
20130101; H01L 2924/01005 20130101; H01L 2224/48091 20130101; H01L
2924/10253 20130101; H01L 2225/06575 20130101; H01L 2224/48227
20130101; H01L 2924/181 20130101; H01L 25/50 20130101; H01L
2224/2612 20130101; H01L 2924/09701 20130101; H01L 2224/8592
20130101; H01L 2224/32145 20130101; H01L 2224/73265 20130101; H01L
24/32 20130101; H01L 2924/01082 20130101; H01L 2224/32225 20130101;
H01L 24/33 20130101; H01L 25/0657 20130101; H01L 2225/0651
20130101; H01L 2224/48472 20130101; H01L 2225/06582 20130101; H01L
2924/14 20130101; H01L 2924/01033 20130101; H01L 2224/48091
20130101; H01L 2924/00014 20130101; H01L 2224/73265 20130101; H01L
2224/32145 20130101; H01L 2224/48227 20130101; H01L 2224/73265
20130101; H01L 2224/32225 20130101; H01L 2224/48227 20130101; H01L
2924/00 20130101; H01L 2224/48472 20130101; H01L 2224/48227
20130101; H01L 2924/00 20130101; H01L 2224/48472 20130101; H01L
2224/48091 20130101; H01L 2924/00 20130101; H01L 2924/10253
20130101; H01L 2924/00 20130101; H01L 2924/14 20130101; H01L
2924/00 20130101; H01L 2924/181 20130101; H01L 2924/00012
20130101 |
Class at
Publication: |
257/777 ;
257/781; 257/784 |
International
Class: |
H01L 023/48 |
Claims
What is claimed is:
1. A method of assembling a stacked microelectronic device
assembly, comprising: attaching a first microelectronic component
to a support, an active surface of the first microelectronic
component facing away from a contact surface of the support, the
support including a plurality of first electrical contacts and the
first microelectronic component including a plurality of second
electrical contacts; electrically connecting a first wire to a
first one of the first electrical contacts and to a first one of
the second electrical contacts, and electrically connecting a
second wire to a second one of the first electrical contacts and to
a second one of the second electrical contacts, the first wire
being spaced from the second wire; disposing a wire coating on at
least a portion of the first wire and at least a portion of the
second wire; placing at least a portion of a second microelectronic
component proximate to the active surface of the first
microelectronic component such that the wire coating mechanically
supports the second microelectronic component and defines an
intercomponent gap between a facing surface of the second
microelectronic component and the active surface of the first
microelectronic component.
2. The method of claim 1 wherein the facing surface of the second
microelectronic component has a peripheral portion and a central
portion bounded by the peripheral portion; the peripheral portion
of the facing surface contacting the coating when the facing
surface of the second microelectronic component is placed proximate
to the active surface of the first microelectronic component; the
central portion overlying the intercomponent gap and remaining
exposed prior to further processing.
3. The method of claim 2 further comprising encapsulating the first
and second microelectronic components in an encapsulant.
4. The method of claim 3 wherein the encapsulant is permitted to
flow into the intercomponent gap.
5. The method of claim 1 further comprising encapsulating the first
and second microelectronic components in an encapsulant.
6. The method of claim 5 wherein the encapsulant is permitted to
flow into the intercomponent gap.
7. The method of claim 1 further comprising electrically connecting
a third wire to a first one of the third electrical contacts and to
a third one of the first electrical contacts
8. The method of claim 1 wherein the wire coating comprises a
thixotropic material.
9. The method of claim 1 wherein the wire coating is initially
applied in an uncured state and is partially cured to yield an
adhesive, mechanically stable wire coating prior to juxtaposing the
facing surface of the second microelectronic component with the
active surface of the first microelectronic component.
10. The method of claim 9 further comprising further curing the
partially cured wire coating after the wire coating mechanically
supports the second microelectronic component.
11. A method of assembling a stacked microelectronic device
assembly, comprising: attaching a first microelectronic component
to a support, the support including a plurality of first electrical
contacts and the first microelectronic component including a
plurality of second electrical contacts; electrically connecting a
first one of the first electrical contacts to a first one of the
second electrical contacts via a first bonding wire; electrically
connecting a second one of the first electrical contacts to a
second one of the second electrical contacts via a second bonding
wire, the first one of the second electrical contacts being spaced
from the second one of the second electrical contacts; coating at
least a portion of the first bonding wire and at least a portion of
the second bonding wire with a wire coating; partially curing the
wire coating; contacting at least a portion of a second
microelectronic component with the wire coating, thereby
mechanically supporting the second microelectronic component with
respect to the first microelectronic component and defining an
intercomponent gap between the first and second microelectronic
components; and electrically connecting a first one of a plurality
of third electrical contacts carried by the second microelectronic
component to a third one of the first electrical contacts.
12. The method of claim 11 wherein the second microelectronic
component has a facing surface including a peripheral portion and a
central portion bounded by the peripheral portion; the peripheral
portion of the facing surface contacting the coating; the central
portion overlying the intercomponent gap and remaining exposed when
electrically connecting a first one of the third electrical
contacts to a third one of the first electrical contacts.
13. The method of claim 12 further comprising encapsulating the
first and second microelectronic components in an encapsulant and
permitting the encapsulant to flow into the intercomponent gap and
into contact with the central portion of the facing surface of the
second microelectronic component.
14. The method of claim 11 further comprising encapsulating the
first and second microelectronic components in an encapsulant.
15. The method of claim 14 wherein the encapsulant is permitted to
flow into the intercomponent gap.
16. The method of claim 11 wherein the wire coating comprises a
thixotropic material.
17. The method of claim 11 wherein the wire coating is initially
applied in an uncured state and is partially cured to yield an
adhesive, mechanically stable wire coating prior to bringing the
second microelectronic component into contact with the wire
coating.
18. The method of claim 17 further comprising further curing the
partially cured wire coating after bringing the second
microelectronic component into contact with the wire coating.
19. A method of assembling a stacked microelectronic device
assembly, comprising: attaching a first microelectronic component
to a support; wire bonding a first electrical contact carried by
the support to a second electrical contact carried by the first
microelectronic component using a first bonding wire; covering at
least a portion of the first bonding wire with a wire coating, the
wire coating having an exposed upper surface; contacting the upper
surface of the wire coating with a second microelectronic
component, the wire coating mechanically bonding the second
microelectronic component to the first microelectronic component;
and electrically connecting a third electrical contact carried by
the second microelectronic component to a fourth electrical contact
carried by the substrate.
20. The method of claim 19 wherein the support includes a plurality
of first electrical contacts and the first microelectronic
component carries a plurality of second electrical contacts, the
first bonding wire being electrically connected to a first one of
the first electrical contacts and to a first one of the second
electrical contacts.
21. The method of claim 20 further comprising wire bonding a second
one of the first electrical contacts to a second one of the second
electrical contacts using a second bonding wire, the first bonding
wire being spaced from the second bonding wire.
22. The method of claim 21 further comprising covering at least a
portion of the second bonding wire with the wire coating.
23. The method of claim 22 wherein the wire coating is applied as a
plurality of discrete coatings, a first of the discrete coatings
covering the portion of the first bonding wire and a second of the
discrete coatings covering the portion of the second bonding
wire.
24. The method of claim 19 further comprising partially curing the
wire coating before contacting the wire coating with the second
microelectronic component.
25. The method of claim 24 wherein partially curing the wire
coating yields an adhesive, mechanically stable coating.
26. The method of claim 24 further comprising further curing the
partially cured wire coating after contacting the wire coating with
the second microelectronic component.
27. The method of claim 19 wherein the wire coating contacts a
peripheral portion of a facing surface of the second component, a
central portion of the facing surface being exposed to an
intercomponent gap between the first and second microelectronic
components.
28. The method of claim 27 further comprising introducing a second
material into the intercomponent gap.
29. The method of claim 27 wherein the second material comprises an
encapsulant having a composition which differs from a composition
of the wire coating.
30. The method of claim 19 further comprising encapsulating the
first and second components in an encapsulant.
31. The method of claim 30 wherein the encapsulant has a
composition which differs from a composition of the wire
coating.
32. The method of claim 19 wherein the first and second components
define an intercomponent gap therebetween when the upper surface of
the wire coating is contacted with the second microelectronic
component.
33. The method of claim 32 further comprising encapsulating the
first and second components in an encapsulant, the encapsulant
being introduced into the intercomponent gap.
34. The method of claim 19 wherein the wire coating is initially
applied as a curable thixotropic coating, the method further
comprising at least partially curing the thixotropic coating.
35. A method of assembling a stacked microelectronic device
assembly including a support, a first microelectronic component,
and a second microelectronic component; the support carrying a
plurality of first electrical contacts, the first microelectronic
component carrying a plurality of second electrical contacts, and
the second microelectronic component carrying a plurality of third
electrical contacts, the method comprising: attaching the first
microelectronic component to the substrate and electrically
connecting one of the first electrical contacts to one of the
second electrical contacts via a first bonding wire; coating at
least a portion of the first bonding wire with a first curable
coating; partially curing the first curable coating, yielding an
adhesive, mechanically stable coating; contacting at least a
portion of the second microelectronic component with the adhesive,
mechanically stable coating, thereby mechanically supporting the
second microelectronic component with respect to the first
microelectronic component; and electrically connecting one of the
third electrical contacts to one of the first electrical
contacts.
36. The method of claim 35 further comprising further curing the
adhesive, mechanically stable coating after the second
microelectronic component is mechanically supported.
37. The method of claim 35 wherein the second microelectronic
component has a facing surface including a peripheral portion and a
central portion bounded by the peripheral portion; the peripheral
portion of the facing surface contacting the coating; the central
portion remaining exposed when electrically connecting a first one
of the third electrical contacts to a third one of the first
electrical contacts.
38. The method of claim 37 further comprising encapsulating the
first and second microelectronic components in an encapsulant and
permitting the encapsulant to flow into contact with the central
portion of the facing surface of the second microelectronic
component.
39. The method of claim 35 further comprising encapsulating the
first and second microelectronic components in an encapsulant.
40. The method of claim 39 wherein the encapsulant is permitted to
flow into an intercomponent gap between the first and second
microelectronic components.
41. The method of claim 35 wherein the wire coating comprises a
thixotropic material.
42. A stacked microelectronic device, comprising: a support having
a plurality of first contacts; a first microelectronic component
carried by the support, the first microelectronic component
comprising an active surface having a plurality of second contacts;
a first bonding wire electrically connecting a first one of the
first contacts to a first one of the second contacts; a wire
coating covering at least a portion of the first bonding wire; a
second microelectronic component comprising a facing surface and an
outer surface, the outer surface having a plurality of third
contacts, the facing surface being juxtaposed with the active
surface of the first microelectronic component, the wire coating
mechanically supporting the second microelectronic component to
define an intercomponent gap between the facing surface of the
second microelectronic component and the active surface of the
first microelectronic component.
43. The stacked microelectronic device of claim 42 further
comprising a second material within the intercomponent gap, the
second material having a different composition from the wire
coating.
44. The stacked microelectronic device of claim 42 wherein the
facing surface of the second microelectronic component has a
peripheral portion in supportive contact with the wire coating and
an exposed central portion bounded by the peripheral portion.
45. The stacked microelectronic device of claim 42 further
comprising a second wire electrically connecting a second one of
the first electrical contacts to a second one of the second
electrical contacts, the second wire being spaced from the first
wire.
46. The stacked microelectronic device of claim 44 wherein the wire
coating also covers at least a portion of the second bonding wire
and at least a portion of the active surface of the first
microelectronic component, the wire coating contacting both a
peripheral portion and a central portion of the facing surface of
the second microelectronic component.
47. The stacked microelectronic device of claim 42 wherein the wire
coating also covers the first one of the first electrical
contacts.
48. A stacked microelectronic device, comprising: a support
carrying a plurality of first contacts; a first microelectronic
component carried by the support, the first microelectronic
component comprising an active surface bearing a plurality of
second contacts; a first bonding wire electrically connecting a
first one of the first contacts to a first one of the second
contacts; a wire coating covering at least a portion of the first
bonding wire; a second microelectronic component comprising a
facing surface and an outer surface, the outer surface bearing a
plurality of third contacts, the facing surface being juxtaposed
with the active surface of the first microelectronic component, the
wire coating mechanically supporting the second microelectronic
component to define an intercomponent gap between the facing
surface of the second microelectronic component and the active
surface of the first microelectronic component; and a deformable
adhesive carried in the intercomponent space and adhering the
facing surface of the second microelectronic component to the
active surface of the first microelectronic component.
Description
TECHNICAL FIELD
[0001] The present invention relates to an apparatus and method for
increasing microelectronic device density. The invention has
particular utility in connection with producing vertically
superimposed, multi-component microelectronic devices in which at
least one of the devices is wire-bonded to a substrate.
BACKGROUND
[0002] Higher performance, lower cost, increased miniaturization of
components, and greater packing density of integrated circuits are
ongoing goals of the computer industry. Greater integrated circuit
density is primarily limited by the space or "real estate"
available for mounting microelectronic components on a substrate
such as a printed circuit board. The microelectronic component may
be electrically connected to circuitry on the circuit board via
flip chip attachments, wirebonding, tape automated bonding (TAB),
or a variety of other techniques.
[0003] Increasingly, microelectronic components are being
vertically stacked atop one another to conserve valuable substrate
real estate. In such a vertically stacked assembly, a first
microelectronic component is attached directly to the substrate and
a second microelectronic component may be physically attached to
the first microelectronic component (e.g., stacked on the first
microelectronic component). If the first microelectronic component
is electrically connected to the substrate via flip chip
attachments or TAB, the active surface of the microelectronic
component (i.e., the surface bearing the electrical contacts for
connection to the circuitry of the microelectronic component) faces
toward the substrate. Commonly, the bare backside surface of the
first microelectronic component is exposed and faces away from the
substrate, and the second microelectronic component is attached
directly to the backside surface.
[0004] If the first microelectronic component is electrically
connected to the substrate by wire bonding, however, attachment of
the second microelectronic component to the first microelectronic
component can be more problematic. In wire-bonding techniques, the
backside of the first microelectronic component is mounted to the
substrate and the active surface of a wire-bonded microelectronic
component defines the outer surface which faces away from the
substrate. The contacts on the active surface are then electrically
coupled to the contacts on the substrate by very small conductive
wires that extend from the active surface to the substrate. The
wires that electrically connect the active surface of the
microelectronic component to the substrate accordingly interfere
with attaching the second microelectronic component directly on the
active surface. FIGS. 1 and 2 schematically illustrate two
techniques currently used to bond a second microelectronic device
to a first microelectronic device which is wire-bonded to the
substrate.
[0005] FIG. 1 illustrates a substrate 20 carrying a pair of
microelectronic devices 30, 40. The substrate 20, which may be a
circuit board or the like, has a contact surface 24 bearing a
plurality of electrical contacts 26a-26d. A first microelectronic
component 30 is attached to the component surface 24 of the
substrate 20 by means of an adhesive 35. The adhesive 35 may cover
the entire mounting face 32 of the first microelectronic component
30. The active surface 34 to the first microelectronic component 30
includes a plurality of electrical contacts 36a-36b. A first
bonding wire 38a electrically connects the first electrical contact
36a of the first microelectronic component 30 to the first
electrical contact 26a of the substrate 20, and a second bonding
wire 38b electrically connects a second electrical contact 36b of
the first microelectronic component 30 to a second electrical
contact 26b of the substrate 20.
[0006] The second microelectronic component 40 is carried by the
first microelectronic component 30. In some conventional stacked
microelectronic devices, a facing surface 42 of the second
microelectronic component is attached to the active surface 34 of
the first microelectronic component 30 via a single, thick adhesive
layer (not shown). This adhesive layer conventionally has a
thickness which is greater than the height to which the bonding
wires 38 extend above the active surface 34 so the second
microelectronic device 40 does not directly contact or rest against
the bonding wires 38. Such a structure is shown in U.S. Pat. No.
5,323,060, the entirety of which is incorporated herein by
reference. In the embodiment shown in FIG. 1, a separate spacer 50
is positioned between the first and second microelectronic
components 30 and 40. This spacer 50 is attached to the active
surface 34 of the first microelectronic component 30 via one
adhesive layer 52 and is attached to the facing surface 42 of the
second microelectronic component 40 by another adhesive layer 54.
The spacer 50 is commonly either a polymeric tape or a thin silicon
wafer. Once the second microelectronic device 40 is in place, a
first electrical contact 46a on the outer surface 44 of the second
microelectronic component 40 can be electrically connected to a
third electrical contact 26c carried by the substrate 20.
Similarly, a second electrical contact 46b on the outer surface 44
can be electrically connected to a fourth electrical contact 26d
carried by the substrate 20.
[0007] A stacked microelectronic device such as that shown in FIG.
1 can present some manufacturing difficulties. For example, rapidly
and precisely positioning the spacer 50 and adhesive layers 52, 54
can be a challenge. Even if the stacked microelectronic device is
properly assembled initially, the multiple layers of different
materials can lead to product defects. If the second
microelectronic component 40 is attached to the first
microelectronic component 30 by a single, thick adhesive layer (not
shown), any difference in the coefficient of thermal expansion
between the adhesive layer and the microelectronic components 30
and 40 can cause deleterious warping of the microelectronic
components 30 and 40. If a polymeric tape is used as the spacer 50
shown in FIG. 1, differences in the coefficients of thermal
expansion can still lead to warping of the microelectronic
components 30 and 40 during subsequent thermal processing. If the
microelectronic components 30 and 40 are silicon-based dies, the
use of a silicon spacer 50 can reduce the problems associated with
differences in coefficients of thermal expansion. However, the
different coefficient of thermal expansion of the adhesive layers
52 and 54 can still induce some stress in the microelectronic
components 30 and 40. In addition, the structure shown in FIG. 1
has four separate interfaces between the first and second
microelectronic components 30 and 40, namely the interface between
the active surface 34 of the first microelectronic component 30 and
the adhesive layer 52; the interface between the adhesive layer 52
and the spacer 50; the interface between the spacer 50 and the
adhesive layer 54; and the interface between the adhesive layer 54
and the facing surface 42 of the second microelectronic component
40. Each additional interface increases the number of manufacturing
steps, necessitating more manufacturing time and/or equipment, and
heightens the risk of producing an unacceptable stacked
microelectronic device. Spacers also increase the size of the final
stacked microelectronic device, with both silicon and polymer
spacers having typical thicknesses on the order of 6 mils.
[0008] FIG. 2 schematically illustrates another conventional
stacked microelectronic device. Instead of having a thick adhesive
layer or a spacer 50 between the first and second microelectronic
components 30 and 40, the second microelectronic component 40 may
be attached to the active surface 34 of the first microelectronic
component 30 is using a relatively thin adhesive layer 55. To avoid
interference with the bonding wires 38, however, the second
microelectronic component 40 is significantly smaller than the
first microelectronic component 30. While this avoids direct
physical contact between the second microelectronic component 40
and the bonding wires 38, it significantly limits the size of the
second microelectronic component 40. Although the stacked
microelectronic device of FIG. 2 can be made shorter than the
stacked device of FIG. 1, the smaller size of the second
microelectronic component 40 reduces the number of integrated
circuits which can be incorporated in the second microelectronic
component 40 and, hence, the stacked microelectronic device.
SUMMARY OF THE INVENTION
[0009] Embodiments of the present invention provide stacked
microelectronic devices and method for manufacturing stacked
microelectronic devices. In certain embodiments, a second
microelectronic component is mechanically supported with respect to
the first microelectronic component without requiring a thick
spacer layer therebetween or necessitating that the second
microelectronic component be materially smaller than the first
microelectronic component.
[0010] In one embodiment, the invention provides a method of
assembling a stacked microelectronic device assembly. In accordance
with this embodiment, a first microelectronic component is attached
to a support. A first electrical contact carried by the support is
wirebonded to a second electrical contact carried by the first
microelectronic component using a first bonding wire. At least a
portion of the first bonding wire is covered with a wire coating
which has an exposed upper surface. The upper surface of the wire
coating may contact a second microelectronic component, with the
wire coating mechanically bonding the second microelectronic
component to the first microelectronic component. A third
electrical contact carried by the second microelectronic component
may be electrically connected to a fourth electrical contact
carried by the substrate. If so desired, the fourth electrical
contact may be the same as the first electrical contact, i.e., the
second and third electrical contacts may be electrically connected
to the same electrical contact on the substrate.
[0011] In accordance with a further embodiment of the invention, a
method of assembling a stacked microelectronic device assembly may
include attaching a first microelectronic component to a support
with an active surface of the first microelectronic component
facing away from a contact surface of the support. The support may
include a plurality of first electrical contacts and the first
microelectronic component may include a plurality of second
electrical contacts. A first wire may be electrically connected to
a first one of the first electrical contacts and to a first one of
the second electrical contacts. A second wire may be electrically
connected to a second one of the first electrical contacts and to a
second one of the second electrical contacts, with the first wire
being spaced from the second wire. A wire coating may be disposed
on at least a portion of the first wire and at least a portion of
the second wire. At least a portion of a second microelectronic
component may be placed proximate to the active surface of the
first microelectronic component such that the wire coating
mechanically supports the second microelectronic component and
defines an intercomponent gap between a facing surface of the
second microelectronic component and the active surface of the
first microelectronic component. In one further aspect of this
embodiment, the first and second microelectronic components may be
encapsulated in an encapsulant. This encapsulant may be permitted
to flow into the intercomponent gap.
[0012] In certain embodiments of the invention, the wire coating
may be applied in an initial uncured state and may be partially
cured to yield an adhesive, mechanically stable wire coating.
Thereafter, the second microelectronic component may be brought
into contact with the adhesive, mechanically stable wire coating
whereby the wire coating can both mechanically support the second
microelectronic component and bond the second microelectronic
component to the first microelectronic component. If so desired,
the partially cured wire coating may then be further cured.
[0013] Another embodiment of the invention provides a stacked
microelectronic device which comprises a support carrying a
plurality of first contacts. A first microelectronic component may
be carried by the support, with the first microelectronic component
comprising an active surface bearing a plurality of second
contacts. A first bonding wire may electrically connect a first one
of the first contacts to a first one of the second contacts. A wire
coating may cover at least a portion of the first bonding wire. A
second microelectronic component may comprise a facing surface and
an outer surface, with the outer surface bearing a plurality of
third contacts. The facing surface is juxtaposed with the active
surface of the first microelectronic component and the wire coating
mechanically supports the second microelectronic component to
define an intercomponent gap between the facing surface and the
active surface. If so desired, the intercomponent gap may be filled
with a second material having a composition different from the
composition of the wire coating. The second material may, for
example, be an encapsulant such an epoxy resin or a silicone
material.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a schematic view of one conventional stacked
microelectronic device employing a spacer between the
microelectronic components.
[0015] FIG. 2 is a schematic view of another conventional stacked
microelectronic device wherein the second microelectronic device is
smaller than the first microelectronic device.
[0016] FIGS. 3A-3C schematically illustrate sequential stages in a
method of manufacturing a stacked microelectronic device in
accordance with one embodiment of the invention.
[0017] FIGS. 3D and 3E schematically illustrate sequential stages
in a method of manufacturing a stacked microelectronic device
including three microelectronic components in accordance with a
further embodiment of the invention.
[0018] FIGS. 4A-4C schematically illustrate sequential stages in a
method of manufacturing a stacked microelectronic device in
accordance with an alternative embodiment of the invention.
[0019] FIGS. 5A-5C schematically illustrate sequential stages in a
method of manufacturing a stacked microelectronic device in
accordance with still another embodiment of the invention.
[0020] FIGS. 6A-6C schematically illustrate sequential stages in a
method of manufacturing a stacked microelectronic device in
accordance with yet another embodiment of the invention.
DETAILED DESCRIPTION
[0021] Various embodiments of the present invention provide stacked
microelectronic devices and methods of manufacturing stacked
microelectronic devices. The following description provides
specific details of certain embodiments of the invention
illustrated in the drawings to provide a thorough understanding of
those embodiments. It should be recognized, however, that the
present invention can be reflected in additional embodiments and
the invention may be practiced without some of the details in the
following description.
[0022] Embodiments of the present invention provide stacked
microelectronic devices which include a substrate 20 and at least
first and second microelectronic components. The microelectronic
components are supported in a novel and beneficial manner, but
stacked microelectronic devices in accordance with embodiments of
the present invention may employ some of the same components used
in the conventional stacked microelectronic devices shown in FIGS.
1 and 2. Accordingly, like reference numbers have been used in
FIGS. 1-6 to indicate like components.
[0023] FIGS. 3A-3C schematically illustrate stages in the
manufacture of a stacked microelectronic device in accordance with
one embodiment of the invention. The substrate 20 shown in FIG. 3A
is provided with a plurality of first electrical contacts 26a-26d
on its contact surface 24. The substrate 20 may be flexible or
rigid and have any desired configuration. The substrate 20 may be
formed of materials commonly used in microelectronic substrates,
such as ceramic, silicon, glass, or combinations thereof. The
substrate 20 can alternatively be formed of an organic material or
other materials suitable for printed circuit boards (PCBs). In one
embodiment of the invention, the substrate 20 comprises a printed
circuit board such as an FR-4 PCB.
[0024] The first microelectronic component 30 has a mounting
surface 32 (i.e., backside) and an active surface 34 (i.e., front
side) bearing a plurality of second electrical contacts 36a-b. The
first microelectronic component 30 may be SIMM, DRAM, flash-memory,
a processor, or any of a variety of other types of microelectronic
devices. Typically, the first microelectronic component 30 is a
silicon die carrying an integrated circuit. Although the first
microelectronic component 30 is illustrated in the drawings as
being a single element, it should be understood that the first
microelectronic component 30 can comprise any number of
subcomponents.
[0025] The first microelectronic component 30 may be attached to
the substrate 20 in any desired fashion. In one embodiment, the
first microelectronic component 30 is attached to the contact
surface 24 of the substrate 20 by an adhesive 35. The adhesive 35
may be an epoxy, a thermoplastic material, a polymeric tape, a
polymeric tape coated with thermoplastic materials, or any other
conventional adhesive or cementitious material compatible with the
materials of the substrate 20 and first microelectronic component
30 and stable in the anticipated conditions of use.
[0026] After the first microelectronic component 30 is attached to
the substrate 20, the microelectronic component 30 may be
electrically connected to the substrate 20. In the illustrated
embodiment, each of the second electrical contacts 36 of the first
microelectronic component 30 is separately connected to a different
one of the first electrical contacts 26 of the substrate 20. In
particular, a first bonding wire 38a is electrically connected to
electrical contact 26a carried by the substrate 20 and to
electrical contact 36a carried by the first microelectronic
component 30. Similarly, a second bonding wire 38b electrically
connects electrical contact 26b carried by the substrate 20 to
electrical contact 36b carried by the first microelectronic
component 30. The bonding wires 38 may be applied using
conventional wire bonding equipment such as that available from
Kulicka & Soffa Industries, Inc. of Willow Grove, Pa., USA.
[0027] At least a portion of each of the bonding wires 38 may be
coated with a first wire coating 60. In the illustrated embodiment,
a wire coating segment 60a coats electrical contact 36a of the
first microelectronic component 30 and an adjacent length of the
first bonding wire 38a. The remainder of the first bonding wire 38a
and the electrical contact 26a to which the first bonding wire 38a
is attached can remain exposed, such that it is not covered by the
wire coating 60a. Similarly, wire coating segment 60b covers
electrical contact 36b and an adjacent length of the second bonding
wire 38b, but the rest of the second bonding wire 38b and the other
electrical contact 26b to which it is connected remain exposed. The
two wire coating segments 60a-b are shown as being two discrete
coatings. It should be understood, however, that the wire coating
segments 60a-b may be part of a single, continuous wire coating 60.
For example, the wire coating 60 may extend around a periphery of
the first microelectronic component 30 and cover any number of
electrical contacts 36 and bonding wires 38. In other applications,
it may be desirable to apply two or more discrete wire coating
segments but some or all of the wire coating segments may cover
more than one electrical contact 36 and more than one associated
bonding wire 38. For example, the electrical contacts 36 may be
arranged in two generally parallel rows extending adjacent opposite
edges of the first microelectronic component 30, with the wire
coating segments 60a-b being applied as two discrete, elongate
beads, each of which covers one row of electrical contacts 36. If
so desired, the shape and position of the wire coating 60 may be
controlled using a mold, a dam or other structure.
[0028] For reasons explained below, the wire coating 60 should be
sufficiently mechanically stable to mechanically support the second
microelectronic component 40. The wire coating 60 need not be rigid
to provide the requisite mechanical support. Instead, a relatively
viscous wire coating 60 may be sufficiently strong to support the
second microelectronic component 40 during subsequent manufacturing
steps.
[0029] In one embodiment of the invention, the wire coating 60 is
both mechanically stable and can serve as an adhesive to bond the
second microelectronic component 40 to the first microelectronic
component 30 without need of any other adhesive. If so desired,
this combination of properties may be accomplished by applying the
wire coating 60 and subsequently treating the wire coating 60, such
as by chemically treating an exterior surface of the wire coating
60 to cause it to adhere to the second microelectronic component
40. More preferably, though, the material of the wire coating 60 is
selected to be both sufficiently mechanically stable to support the
second microelectronic component 40 and provide a sufficiently
adhesive surface to adhere the second microelectronic component 40
without any further surface treatments.
[0030] In one particular embodiment of the invention, the wire
coating 60 is a curable thixotropic material. Thixotropic materials
tend to have quite high viscosities and may behave much like a
solid in the absence of shear, but can be "liquefied" when shaken
to significantly reduce viscosity. When shaking ceases, the
thixotropic material will tend to return to its mechanically
stable, high-viscosity state.
[0031] The wire coating 60 may be a multi-component coating which
can be cured from an initial state adapted for application using
automated equipment to a final state better suited for use or
further manufacturing steps. Such a wire coating 60 may be cured in
any suitable fashion such as by heat treatment or exposure to
ultraviolet radiation. In one specific embodiment, the wire coating
60 is relatively tacky or adhesive when first applied, but may
harden and become less adhesive as it is cured. Those skilled in
the field should be able to identify or develop suitable curable,
thixotropic coatings without undue experimentation. Kulicka &
Soffa Industries, Inc. is also promoting such coatings for use in
wire bonding applications under the tradename NOSWEEP, e.g., as
product number EW707-002.
[0032] In accordance with one embodiment of the invention, the wire
coating 60 is applied as shown in FIG. 3B and is partially cured,
e.g., by heat treatment or exposure to ultraviolet radiation, but
for a time or at conditions which are insufficient to fully cure
the material of the coating. This partial curing may enhance the
mechanical stability of the wire coating 60 while leaving the wire
coating 60 sufficiently adhesive to permit the second
microelectronic component 40 to adhere thereto, at least during
further manufacture if not also during use.
[0033] The wire coating 60 may be electrically insulative and it
may have a coefficient of thermal expansion similar to that of the
first and/or second microelectronic components 30, 40. If an
encapsulant 80 (discussed below) is employed, the wire coating 60
and the encapsulant may be selected to have a similar coefficient
of thermal expansion. Conductivity and other properties may be
adjusted by fillers incorporated into the matrix of the wire
coating 60. For instance, metal fillers provide enhanced electrical
conductivity and thermal dissipation. Dielectric fillers such as
fused silica can reduce conductivity and may provide a coefficient
of thermal expansion closer to that of the microelectronic
component, e.g., a silicon die.
[0034] After the wire coating 60 is applied to the bonding wires 38
and, if so desired, partially or wholly cured, the facing surface
42 of the second microelectronic component 40 may be juxtaposed
with the active surface 34 of the first microelectronic component
30 and the facing surface 42 of the second microelectronic
component 40 is brought into contact with the wire coating 60. The
wire coating 60 is sufficiently mechanically stable to mechanically
support the second microelectronic component 40 with respect to the
first microelectronic component 30. Desirably, the exposed upper
surface of the wire coating 60 is sufficiently adhesive to cause
the second microelectronic component 40 to adhere thereto. This
mechanically bonds the second microelectronic component 40 to the
first microelectronic component 30.
[0035] As noted above, the wire coating 60 may be applied as two or
more discrete wire coatings 60a-b. In the illustrated embodiment,
the first bonding wire 38a and its associated wire coating 60a is
spaced from the second bonding wire 38b and its associated coating
60b. As shown in FIG. 3C, when discrete wire coating portions 60a
and 60b mechanically support the second microelectronic component
40, an intercomponent gap 52 may be defined between the active
surface 34 of the first microelectronic component 30 and the facing
surface 42 of the second microelectronic component 40. In the
illustrated embodiment, this intercomponent gap 52 may be exposed
to the ambient atmosphere.
[0036] In the embodiment of FIG. 3C, only a portion of the facing
surface 42 of the second microelectronic component 40 is covered by
contact with the wire coating 60. The remainder of the facing
surface 42 remains exposed to the intercomponent gap 52. Where the
first and second microelectronic components 30 and 40 are similar
in dimensions, a central portion 42c of the facing surface 42 may
be exposed to the intercomponent gap 52 while only a peripheral
portion 42p of the facing surface 42 is in direct contact with the
wire coating 60.
[0037] As noted above, in accordance with one method of the
invention the wire coating 60 is partially cured before the second
microelectronic component 40 is brought into contact with the wire
coating 60. In such an embodiment, the wire coating 60 in FIG. 3C
may be further cured. This may enhance the mechanical support of
the second microelectronic component 40 and may further
mechanically bond the second microelectronic component 40 to the
first microelectronic component 30.
[0038] Like the first microelectronic component 30, the second
microelectronic component 40 can be any of a variety of
microelectronic devices, including SIMM, DRAM, flash-memory, or
processors. The second microelectronic component 40 is shown as
being a single element, but it could comprise any number of
subcomponents. The first and second microelectronic components 30
and 40 may be the same type of microelectronic components or they
may be different types of components. For example, both of the
microelectronic components 30 and 40 may comprise memory modules,
such as DRAMs.
[0039] The second microelectronic component 40 may have any
suitable size. As noted above in connection with FIG. 2, if a
relatively thin adhesive layer 55 is used to bond the second
microelectronic component 40 to the first microelectronic component
30 in conventional stacked microelectronic devices, the second
microelectronic component 40 commonly is smaller than the first
microelectronic component 30 upon which it rests. This is necessary
to ensure that the electrical contacts 36 and the bonding wires 38
remain exposed and are not damaged by contact with the second
microelectronic component 40.
[0040] If so desired, the second microelectronic component 40 in
the present invention may be smaller than the first microelectronic
component 30. The methods and devices in accordance with the
present invention are not so limited, however. In the embodiment
shown in FIG. 3C, the first and second microelectronic components
30 and 40 are approximately the same size and the second
microelectronic component 40 is superimposed over the first
microelectronic component 30. The wire coating 60 may serve to both
mechanically support the second microelectronic component 40 and to
protect the bonding wires 38. This permits the second
microelectronic component 40 to directly overlie the bonding wires
38. As a consequence, the second microelectronic component 40 may
be larger than the first microelectronic component 30 or otherwise
cover any portion of the bonding wires 38 and their associated
electrical connections 36 on the first microelectronic component
30.
[0041] The second microelectronic component 40 may be electrically
connected to the substrate 20 in any desired fashion. In one
embodiment, the second microelectronic component 40 has an outer
surface 44 carrying a plurality of third electrical contacts 46
which may be electrically connected to the first electrical
contacts 26 carried by the substrate 20. In the particular
embodiment shown, a third bonding wire 48a electrically connects an
electrical contact 46a carried by the second microelectronic
component 40 to electrical contact 26c carried by the substrate 20.
Similarly, a fourth bonding wire 48b electrically connects an
electrical contact 46b carried by the second microelectronic
component 40 to electrical contact 26d carried by the substrate 20.
Each of the bonding wires 38, 48 are shown as connecting one
electrical contact 36 or 46 carried by one of the microelectronic
components 30 or 40 to a different one of the electrical contacts
26 carried by the substrate 20. It should be understood, however,
that this need not be the case. For example, the third bonding wire
48a may connect the electrical contact 46a of the second
microelectronic component 40 to the electrical contact 26a on the
substrate 20 to which the second bonding wire 38a had already been
attached and the fourth bonding wire 48b may similarly connect
electrical contact 46b of the second microelectronic component 40
to electrical contact 26b on the substrate 20.
[0042] If so desired, the first and second microelectronic
components 30 and 40 may be encapsulated within an encapsulant 80.
The encapsulant 80 may have a composition which is the same as or
different from the composition of the wire coating 60. For example,
the encapsulant 80 may be an epoxy resin, a silicone material, or
any other material commonly used as an encapsulant or in glob top
applications. In the embodiment of FIG. 3C, the encapsulant 80 may
cover not only the first and second microelectronic components 30
and 40, but also the bonding wires 38 and 48 and a portion of the
contact surface 24 of the substrate 20 including the electrical
contacts 26a-d. In one embodiment, the encapsulant is applied as a
flowable material which is permitted to flow into and may
substantially fill the intercomponent gap 52 between the first and
second microelectronic components 30 and 40. So covering the active
surface 34 of the first microelectronic component 30 and the facing
surface 40 of the second microelectronic component 40 helps protect
those surfaces and any active features exposed thereon from
environmental damage. The layer of encapsulant 80 between the
microelectronic components 30 and 40 may also help structurally
strengthen the stacked microelectronic device so it may better
withstand the rigors of use.
[0043] FIGS. 3D and 3E illustrate a further embodiment of the
invention. Turning first to FIG. 3D, instead of encapsulating the
structure shown in FIG. 3C with an encapsulant 80, a second wire
coating 62 has been applied. In particular, a first wire coating
segment 62a is applied over electrical contact 46a and a portion of
the third bonding wire 48a. This wire coating segment 62a may also
cover the previously exposed portion of the first bonding wire 38a
and may also cover the electrical contact 26a to which the first
bonding wire 38a is connected. In this embodiment, a portion of the
third bonding wire 48a and the electrical contact 26c carried by
the substrate 20 remain exposed, but these may be covered by the
wire coating 62a if so desired. Similarly, the other wire coating
segment 62b may enclose the electrical contact 46b carried by the
microelectronic component 40 and a portion of the fourth bonding
wire 48b, leaving exposed the remainder of the fourth bonding wire
48b and the other electrical contact 26d to which it is connected.
The second wire coating 62 may be similar to the first wire coating
60 and have similar mechanical properties. In particular, the wire
coating 62 may be a curable, thixotropic material which is capable
of mechanically supporting another microelectronic component. In
one embodiment of the invention, the two wire coatings 60 and 62
are formed of the same material, but they may be formed of
different materials.
[0044] After the second wire coating 62 is applied, it may be
partially cured to give it the desired mechanical properties.
Thereafter, a third microelectronic component 70 may be brought
into contact with the second wire coating 62. The second wire
coating 62 may mechanically support the third microelectronic
component 70 and mechanically bond the third microelectronic
component 70 to the second microelectronic component 40. The third
microelectronic component may have a mounting surface 72 which is
spaced from the outer surface 44 of the second microelectronic
component 40 by the second wire coating 62. This may define an open
second intercomponent gap 54 between the second and third
microelectronic components 40 and 70. The third microelectronic
component 70 may have an outward surface 74 carrying a plurality of
electrical contacts 76. In particular, electrical contact 76a may
be electrically connected to electrical contact 26e carried by the
substrate 20 via a fifth bonding wire 78a. Similarly, electrical
contact 76b may be electrically connected to electrical contact 26d
carried by the substrate 20 via a sixth bonding wire 78b. For
purposes of illustration, this sixth bonding wire 78b is shown
connected to the same electrical contact 26d to which the
electrical contact 46b on the second microelectronic component is
attached via the fourth bonding wire 48b. If so desired, the sixth
bonding wire 78b could, instead, be attached to its own, separate
electrical contact (not shown) on the substrate 20.
[0045] As explained above in connection with FIG. 3C, the three
stacked microelectronic components 30, 40 and 70 may be
encapsulated within an encapsulant 80. This encapsulant 80 may fill
both of the intercomponent gaps 52 and 54.
[0046] FIGS. 4A-4C schematically illustrate an alternate embodiment
of the invention. The process schematically outlined in FIGS. 4A-4C
is directly analogous to the process outlined above in connection
with FIGS. 3A-3C. The primary distinction between the embodiment of
FIGS. 4A-4C and the embodiment of FIGS. 3A-3C is the structure
covered by the wire coating. In FIGS. 3B and 3C, the wire coating
60 covers the electrical contacts 36 carried by the first
microelectronic component 30 and a portion of the first and second
bonding wires 38a-b, but leaves exposed the remainder of these
bonding wires and the associated electrical contacts 26a-b carried
by the substrate 20. In the embodiment of FIGS. 4B and 4C, the wire
coating 64 covers the entire length of the bonding wires and both
of the electrical contacts to which each of the bonding wires is
attached. In particular, the wire coating portion segment 64a
covers the electrical contact 36a carried by the first
microelectronic component 30, the first bonding wire 38a, and the
electrical contact 26a carried by the substrate 20. Similarly, the
wire coating segment 64b covers electrical contact 36b, the second
bonding wire 38b, and electrical contact 26b.
[0047] The wire coating 64 may be partially cured, if so desired,
and the second microelectronic component 40 may be brought into
contact with the wire coating 64. The wire coating 64 will
mechanically support the second microelectronic component 40 and
may also mechanically bond the second microelectronic component 40
to the first microelectronic component 30. As shown in FIG. 4C, the
first and second microelectronic components 30 and 40, the
associated bonding wires 38 and 48 and the electrical contacts
26a-d may all be encapsulated within an encapsulant 80.
[0048] FIGS. 5A-5C illustrate another alternate embodiment of the
invention. Again, the structure and process steps schematically
shown in FIGS. 5A-5C are directly analogous to those shown in FIGS.
3A-3C, with the primary difference relating to the nature of the
wire coating. In FIGS. 3A-3C, the wire coating 60 is applied in
discrete wire coating portions 60a and 60b. In the embodiment of
FIGS. 5B and 5C, a monolithic wire coating 66 may cover the entire
active surface 34 of the first microelectronic component 30. This
wire coating 66 may also cover the electrical contacts 36 carried
by the active surface 34, as well as some or all of the length of
the first and second bonding wires 38a and 38b. This monolithic
wire coating 66 may be formed of the same types of materials as is
the wire coating 60 of FIGS. 3B and 3C and may be partially cured
before the second microelectronic component 40 is brought into
contact therewith. By comparing FIG. 3C to FIG. 5C, it can be seen
that there is no exposed intercomponent gap 52. Instead, the
monolithic wire coating 66 substantially fills the space between
the first microelectronic component 30 and the second
microelectronic component 40. This can enhance the mechanical
support of the second microelectronic component 40 and the
mechanical bonding of the first and second microelectronic
components 30 and 40.
[0049] FIGS. 6A-6C illustrate yet another embodiment of the
invention. This embodiment is directly analogous to the embodiment
illustrated in FIGS. 4A-4C. As a matter of fact, the intermediate
structure shown in FIG. 6B may be substantially identical to the
intermediate structure shown in FIG. 4B, but FIG. 6C illustrates a
modification of the process and structure shown in FIG. 4C. In the
embodiment illustrated in 4B, the wire coating 64 is both
mechanically stable and sufficiently tacky to adhere to the facing
surface 42 of the second microelectronic component 40. If the wire
coating 64 is deemed insufficiently adhesive to ensure adequate
adhesion of the second microelectronic component 40, a pliable
adhesive 90 may be positioned within the intercomponent gap 52. In
the embodiment of FIG. 6C, the wire coating 64 provides mechanical
support for the second microelectronic component 40 and the
adhesive 90 may be readily deformable. As the second
microelectronic component 40 is brought into mechanically
supportive contact with the wire coating 64, the adhesive 90 may be
squeezed between the active surface 34 of the first microelectronic
component 30 and the facing surface 42 of the second
microelectronic component 40. In FIG. 6C, a relatively small
quantity of adhesive 90 is generally centered within the
intercomponent gap 52. In an alternative embodiment (not shown),
the adhesive substantially fills the intercomponent gap 52. After
the second microelectronic component 40 is properly positioned, the
adhesive 90 and/or wire coating 64 may be cured, if desired. An
encapsulant 80 may also be employed to cover the first and second
microelectronic components 30 and 40. If so desired, the
encapsulant 80 may flow into the intercomponent gap 52 to fill
those portions, if any, of the intercomponent gap 52 not already
filled with the adhesive 90.
[0050] From the foregoing, it will be appreciated that specific
embodiments of the invention have been described herein for
purposes of illustration, but that various modifications may be
made without deviating from the spirit and scope of the invention.
Accordingly, the invention is not limited except as by the appended
claims.
* * * * *