U.S. patent application number 11/964397 was filed with the patent office on 2009-07-02 for semiconductor device and method of forming the device using sacrificial carrier.
This patent application is currently assigned to STATS CHIPPAC, LTD.. Invention is credited to Seng Guan Chow, Yaojian Lin, Il Kwon Shim.
Application Number | 20090170241 11/964397 |
Document ID | / |
Family ID | 40798955 |
Filed Date | 2009-07-02 |
United States Patent
Application |
20090170241 |
Kind Code |
A1 |
Shim; Il Kwon ; et
al. |
July 2, 2009 |
Semiconductor Device and Method of Forming the Device Using
Sacrificial Carrier
Abstract
A semiconductor device is made by forming contact pads on a
sacrificial carrier. The contact pads may be formed on a pillar. A
semiconductor die is mounted to electrically connect to the contact
pads with solder bumps or wire bonds. The semiconductor die is
encapsulated with molding compound. The sacrificial carrier is
removed. A backside interconnect structure has a first conductive
layer formed over the molding compound to electrically connect to
the contact pads. A first insulating layer is formed over the first
conductive layer. A portion of the first insulating layer is
removed to expose the first conductive layer. Solder material is
deposited in electrical contact with the first conductive layer.
The solder material is reflowed to form a solder bump. A wire bond
electrically connects to a contact pad. A front-side interconnect
structure can be formed through the molding compound to the contact
pads.
Inventors: |
Shim; Il Kwon; (Singapore,
SG) ; Lin; Yaojian; (Singapore, SG) ; Chow;
Seng Guan; (Singapore, SG) |
Correspondence
Address: |
Robert D. Atkins
605 W. Knox Road, Suite 104
Tempe
AZ
85284
US
|
Assignee: |
STATS CHIPPAC, LTD.
Singapore
SG
|
Family ID: |
40798955 |
Appl. No.: |
11/964397 |
Filed: |
December 26, 2007 |
Current U.S.
Class: |
438/107 ;
257/E21.502; 438/118 |
Current CPC
Class: |
H01L 24/96 20130101;
H01L 2924/351 20130101; H01L 24/16 20130101; H01L 2924/00014
20130101; H01L 21/568 20130101; H01L 2224/24137 20130101; H01L
2924/01006 20130101; H01L 2224/04042 20130101; H01L 2224/16225
20130101; H01L 24/48 20130101; H01L 24/73 20130101; H01L 2224/73204
20130101; H01L 2924/181 20130101; H01L 2924/01013 20130101; H01L
2224/73265 20130101; H01L 2924/30105 20130101; H05K 3/4644
20130101; H01L 2224/82039 20130101; H01L 2924/19107 20130101; H01L
2924/01029 20130101; H05K 1/187 20130101; H01L 23/3128 20130101;
H01L 24/19 20130101; H01L 2924/01079 20130101; H01L 2924/014
20130101; H01L 2924/01005 20130101; H01L 2924/15311 20130101; H05K
1/185 20130101; H01L 2924/15192 20130101; H01L 2924/19043 20130101;
H01L 2924/3025 20130101; H01L 2224/48091 20130101; H01L 2924/01033
20130101; H05K 2201/10674 20130101; H01L 2224/32225 20130101; H01L
2224/48227 20130101; H01L 21/6835 20130101; H01L 2924/01082
20130101; H01L 2924/19041 20130101; H05K 3/205 20130101; H01L
2924/14 20130101; H01L 2924/01047 20130101; H01L 2924/01078
20130101; H01L 2924/19042 20130101; H01L 2224/0401 20130101; H01L
2224/04105 20130101; H01L 2224/12105 20130101; H01L 2224/48091
20130101; H01L 2924/00014 20130101; H01L 2924/15311 20130101; H01L
2224/73204 20130101; H01L 2224/16225 20130101; H01L 2224/32225
20130101; H01L 2924/00 20130101; H01L 2224/73265 20130101; H01L
2224/32225 20130101; H01L 2224/48227 20130101; H01L 2924/00012
20130101; H01L 2224/73204 20130101; H01L 2224/16225 20130101; H01L
2224/32225 20130101; H01L 2924/00012 20130101; H01L 2924/15311
20130101; H01L 2224/73265 20130101; H01L 2224/32225 20130101; H01L
2224/48227 20130101; H01L 2924/00 20130101; H01L 2924/351 20130101;
H01L 2924/00 20130101; H01L 2924/181 20130101; H01L 2924/00012
20130101; H01L 2924/00014 20130101; H01L 2224/45099 20130101; H01L
2924/00014 20130101; H01L 2224/45015 20130101; H01L 2924/207
20130101 |
Class at
Publication: |
438/107 ;
438/118; 257/E21.502 |
International
Class: |
H01L 21/56 20060101
H01L021/56 |
Claims
1. A method of making a semiconductor device, comprising: providing
a first sacrificial metal carrier; forming a photoresist layer over
the first sacrificial metal carrier; forming openings in the
photoresist layer extending to the first sacrificial metal carrier;
forming conductive pillars in the openings of the photoresist
layer; forming a plurality of contact pads over the conductive
pillars, the contact pads being selectively electroplated through
the openings in the photoresist layer onto the conductive pillars
to provide precise alignment of the contact pads for electrical
interconnect, the conductive pillars and first sacrificial metal
carrier providing a plating current path for electroplating the
contact pads; removing the photoresist layer; mounting a first
semiconductor die to electrically connect to the contact pads;
encapsulating the first semiconductor die, contact pads, and
conductive pillars with molding compound; removing the first
sacrificial metal carrier; mounting a second sacrificial carrier
over a first side of the molding compound opposite the contact
pads; forming a first conductive layer over a second side of the
molding compound opposite the first side of the molding compound,
the first conductive layer being electrically connected to the
contact pads; forming a first insulating layer over the first
conductive layer and molding compound; removing a portion of the
first insulating layer to expose the first conductive layer;
forming a second conductive layer over the first conductive layer
and first insulating layer; forming a second insulating layer over
the first insulating layer and second conductive layer; removing a
portion of the second insulating layer to expose the second
conductive layer; depositing solder material in electrical contact
with the second conductive layer; reflowing the solder material to
form a solder bump; removing the second sacrificial carrier;
forming vias through the first side of the molding compound to the
contact pads, the vias having a reduced depth due to the conductive
pillars; forming a third conductive layer over the molding compound
and sidewalls of the vias to electrically connect to the contact
pads; forming a third insulating layer over the molding compound
and third conductive layer, the third insulating layer extending
into the vias to cover the third conductive layer; and removing a
portion of the third insulating layer to expose the third
conductive layer.
2. The method of claim 1, further including forming a wire bond
electrically connected to one of the plurality of contact pads.
3. The method of claim 1, wherein the first semiconductor die
electrically connects to the contact pads with solder bumps or wire
bonds.
4-5. (canceled)
6. The method of claim 1, further including: mounting a second
semiconductor die to the solder bump; and encapsulating the second
semiconductor die with molding compound.
7. (canceled)
8. A method of making a semiconductor device, comprising: providing
a sacrificial metal carrier; forming a photoresist layer over the
sacrificial metal carrier; forming openings in the photoresist
layer extending to the sacrificial metal carrier; forming a
plurality of contact pads on the sacrificial carrier, the contact
pads being selectively electroplated through the openings in the
photoresist layer onto the sacrificial metal carrier to provide
precise alignment of the contact pads for electrical interconnect,
the sacrificial metal carrier providing a plating current path for
electroplating the contact pads; removing the photoresist layer;
mounting a first semiconductor die to electrically connect to the
contact pads; encapsulating the first semiconductor die with
molding compound; removing the sacrificial metal carrier; mounting
a second sacrificial carrier over a first side of the molding
compound opposite the contact pads; forming a first conductive
layer over a second side of the molding compound opposite the first
side of the molding compound, the first conductive layer being
electrically connected to the contact pads; forming a first
insulating layer over the first conductive layer; removing the
second sacrificial carrier; forming vias through the first side of
the molding compound to the contact pads; forming a second
conductive layer over the molding compound and into the vias to
electrically connect to the contact pads; and forming a second
insulating layer over the molding compound and second conductive
layer
9. The method of claim 8, further including: depositing solder
material on the first conductive layer; and reflowing the solder
material to form a solder bump.
10. The method of claim 9, further including: mounting a second
semiconductor die to the solder bump; and encapsulating the second
semiconductor die with molding compound.
11. (canceled)
12. The method of claim 8, wherein the first semiconductor die
electrically connects to the contact pads with solder bumps or wire
bonds.
13-15. (canceled)
16. A method of making a semiconductor package, comprising:
providing a sacrificial metal carrier; forming a photoresist layer
over the sacrificial metal carrier; forming openings in the
photoresist layer extending to the sacrificial metal carrier;
forming a plurality of contact pads on the sacrificial carrier, the
contact pads being selectively electroplated through the openings
in the photoresist layer onto the sacrificial metal carrier to
provide precise alignment of the contact pads for electrical
interconnect, the sacrificial metal carrier providing a plating
current path for electroplating the contact pads; mounting a first
semiconductor die to electrically connect to the contact pads;
encapsulating the first semiconductor die with molding compound;
and forming an interconnect structure over the molding compound and
electrically connected to the contact pads.
17. The method of claim 16, wherein forming the interconnect
structure includes: forming a first conductive layer over the
molding compound and electrically connected to the contact pads;
forming a first insulating layer over the first conductive layer;
and removing a portion of the first insulating layer to expose the
first conductive layer.
18. The method of claim 17, further including: forming a second
conductive layer over the first insulating layer and electrically
connected to the first conductive layer; forming a second
insulating layer over the second conductive layer; and removing a
portion of the second insulating layer to expose the second
conductive layer.
19. The method of claim 18, further including mounting a front-side
process carrier to the second insulating layer with an adhesive
layer.
20. The method of claim 19, further including: forming vias through
the molding compound to the contact pads; forming a second
conductive layer in the vias to electrically connect to the contact
pads; forming a second insulating layer over the second conductive
layer; and removing a portion of the second insulating layer to
expose the second conductive layer.
21. The method of claim 17, further including: depositing solder
material on the first conductive layer; and reflowing the solder
material to form a solder bump.
22. The method of claim 16, further including removing the
sacrificial carrier.
23. The method of claim 16, wherein the first semiconductor die
electrically connects to the contact pads with solder bumps or wire
bonds.
24. The method of claim 16, further including forming a pillar
under each of the plurality of contact pads.
Description
FIELD OF THE INVENTION
[0001] The present invention relates in general to semiconductor
devices and, more particularly, to a semiconductor device and
method of forming the device using a sacrificial carrier.
BACKGROUND OF THE INVENTION
[0002] Semiconductor devices are found in many products in the
fields of entertainment, communications, networks, computers, and
household markets. Semiconductor devices are also found in
military, aviation, automotive, industrial controllers, and office
equipment. The semiconductor devices perform a variety of
electrical functions necessary for each of these applications.
[0003] The manufacture of semiconductor devices involves formation
of a wafer having a plurality of die. Each semiconductor die
contains hundreds or thousands of transistors and other active and
passive devices performing a variety of electrical functions. For a
given wafer, each die from the wafer typically performs the same
electrical function. Front-end manufacturing generally refers to
formation of the semiconductor devices on the wafer. The finished
wafer has an active side containing the transistors and other
active and passive components. Back-end manufacturing refers to
cutting or singulating the finished wafer into the individual die
and then packaging the die for structural support and environmental
isolation.
[0004] One goal of semiconductor manufacturing is to produce a
package suitable for faster, reliable, smaller, and higher-density
integrated circuits (IC) at lower cost. Flip chip packages or wafer
level chip scale packages (WLCSP) are ideally suited for ICs
demanding high speed, high density, and greater pin count. Flip
chip style packaging involves mounting the active side of the die
facedown toward a chip carrier substrate or printed circuit board
(PCB). The electrical and mechanical interconnect between the
active devices on the die and conduction tracks on the carrier
substrate is achieved through a solder bump structure comprising a
large number of conductive solder bumps or balls. The solder bumps
are formed by a reflow process applied to solder material deposited
on contact pads which are disposed on the semiconductor substrate.
The solder bumps are then soldered to the carrier substrate. The
flip chip semiconductor package provides a short electrical
conduction path from the active devices on the die to the carrier
substrate in order to reduce signal propagation, lower capacitance,
and achieve overall better circuit performance.
[0005] In many applications, it is desirable to stack WLCSPs.
Appropriate electrical interconnect must be provided for complete
device integration. The interconnect typically involves formation
of redistribution layers (RDL) and other conductive lines and
tracks. These metal lines have limited pitch and line spacing due
to etching processing. The formation of the interconnect structure
requires a high degree of alignment accuracy in attaching the die
to the wafer carrier for subsequent encapsulation and further RDL
buildup processes.
[0006] A need exists to form the interconnect structures for WLCSPs
while accounting for the interconnect alignment requirements.
SUMMARY OF THE INVENTION
[0007] In one embodiment, the present invention is a method of
making a semiconductor device comprising the steps of providing a
sacrificial carrier, forming a plurality of contact pads on the
sacrificial carrier, mounting a first semiconductor die to
electrically connect to the contact pads, encapsulating the first
semiconductor die with molding compound, removing the sacrificial
carrier, forming a first conductive layer over the molding compound
in electrical contact with the contact pads, forming a first
insulating layer over the first conductive layer, removing a
portion of the first insulating layer to expose the first
conductive layer, depositing solder material in electrical contact
with the first conductive layer, and reflowing the solder material
to form a solder bump.
[0008] In another embodiment, the present invention is a method of
making a semiconductor device comprising the steps of providing a
sacrificial carrier, forming a plurality of contact pads on the
sacrificial carrier, mounting a first semiconductor die to
electrically connect to the contact pads, encapsulating the first
semiconductor die with molding compound, forming a first conductive
layer over the molding compound in electrical contact with the
contact pads, forming a first insulating layer over the first
conductive layer, and removing a portion of the first insulating
layer to expose the first conductive layer.
[0009] In another embodiment, the present invention is a method of
making a semiconductor package comprising the steps of providing a
sacrificial carrier, forming a plurality of contact pads on the
sacrificial carrier, mounting a first semiconductor die to
electrically connect to the contact pads, encapsulating the first
semiconductor die with molding compound, and forming an
interconnect structure over the molding compound in electrical
contact with the contact pads.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a flip chip semiconductor device with solder bumps
providing electrical interconnect between an active area of the die
and a chip carrier substrate;
[0011] FIGS. 2a-2f illustrate formation of a semiconductor package
using a sacrificial carrier;
[0012] FIG. 3 illustrates the semiconductor package with solder
bumps and wire bonds;
[0013] FIGS. 4a-4c illustrate an alternate formation of the
semiconductor package with a sacrificial carrier;
[0014] FIG. 5 illustrates the semiconductor package with wire bond
interconnects to the semiconductor die;
[0015] FIGS. 6a-6b illustrate the semiconductor package with
front-side and backside interconnects;
[0016] FIG. 7 illustrates the semiconductor package with pillars
under the contact pads;
[0017] FIG. 8 illustrates the semiconductor package with solder
bump and wire bond interconnects to the die;
[0018] FIG. 9 illustrates the semiconductor package with underfill
material disposed under the semiconductor die;
[0019] FIG. 10 illustrates the semiconductor package with secondary
die mounted to the front-side interconnects;
[0020] FIG. 11 illustrates the semiconductor package with the
sacrificial carrier left intact for heat dissipation; and
[0021] FIG. 12 illustrates the semiconductor package with
photoresist left intact between the contact pads.
DETAILED DESCRIPTION OF THE DRAWINGS
[0022] The present invention is described in one or more
embodiments in the following description with reference to the
Figures, in which like numerals represent the same or similar
elements. While the invention is described in terms of the best
mode for achieving the invention's objectives, it will be
appreciated by those skilled in the art that it is intended to
cover alternatives, modifications, and equivalents as may be
included within the spirit and scope of the invention as defined by
the appended claims and their equivalents as supported by the
following disclosure and drawings.
[0023] The manufacture of semiconductor devices involves formation
of a wafer having a plurality of die. Each die contains hundreds or
thousands of transistors and other active and passive devices
performing one or more electrical functions. For a given wafer,
each die from the wafer typically performs the same electrical
function. Front-end manufacturing generally refers to formation of
the semiconductor devices on the wafer. The finished wafer has an
active side containing the transistors and other active and passive
components. Back-end manufacturing refers to cutting or singulating
the finished wafer into the individual die and then packaging the
die for structural support and/or environmental isolation.
[0024] A semiconductor wafer generally includes an active surface
having semiconductor devices disposed thereon, and a backside
surface formed with bulk semiconductor material, e.g., silicon. The
active side surface contains a plurality of semiconductor die. The
active surface is formed by a variety of semiconductor processes,
including layering, patterning, doping, and heat treatment. In the
layering process, semiconductor materials are grown or deposited on
the substrate by techniques involving thermal oxidation,
nitridation, chemical vapor deposition, evaporation, and
sputtering. Photolithography involves the masking of areas of the
surface and etching away undesired material to form specific
structures. The doping process injects concentrations of dopant
material by thermal diffusion or ion implantation.
[0025] Flip chip semiconductor packages and wafer level packages
(WLP) are commonly used with integrated circuits (ICs) demanding
high speed, high density, and greater pin count. Flip chip style
semiconductor device 10 involves mounting an active area 12 of die
14 facedown toward a chip carrier substrate or printed circuit
board (PCB) 16, as shown in FIG. 1. Active area 12 contains active
and passive devices, conductive layers, and dielectric layers
according to the electrical design of the die. Analog circuits may
be created by the combination of one or more passive device formed
within active area 12 and may be electrically interconnected. For
example, an analog circuit may include one or more inductor,
capacitor and resistor formed within active area 12. The electrical
and mechanical interconnect is achieved through a solder bump
structure 20 comprising a large number of individual conductive
solder bumps or balls 22. The solder bumps are formed on bump pads
or interconnect sites 24, which are disposed on active area 12. The
bump pads 24 connect to the active circuits by conduction tracks in
active area 12. The solder bumps 22 are electrically and
mechanically connected to contact pads or interconnect sites 26 on
carrier substrate 16 by a solder reflow process. The flip chip
semiconductor device provides a short electrical conduction path
from the active devices on die 14 to conduction tracks on carrier
substrate 16 in order to reduce signal propagation, lower
capacitance, and achieve overall better circuit performance.
[0026] Further detail of forming a semiconductor package in
accordance with semiconductor device 10 is shown in FIGS. 2a-2f. In
FIG. 2a, a dummy or sacrificial metal carrier 30 is shown. Metal
carrier 30 is made with copper (Cu), aluminum (Al), or other stiff
material. Carrier 30 can also be flexible tape. A photoresist layer
32 is deposited on metal carrier 30. A plurality of openings is
formed by a photo patterning process to define areas for selective
plating. Contact pads 34 are then selectively plated on photoresist
defined opening areas. Contact pads 34 can be made with Cu, tin
(Sn), nickel (Ni), gold (Au), or silver (Ag). Metal carrier 30
serves as a support member and plating current path for the
electroplating process to form wettable metal contact pads 34 on
the metal carrier. Part or all of photoresist 32 is removed by a
resist stripper. Alternatively, a layer of photoresist 32 may
remain between contact pads 34.
[0027] In FIG. 2b, semiconductor die 36 and 40 are mounted to
contact pads 34 on metal carrier 30 with solder bumps 38 and 42,
respectively. Alternatively, discrete components or other
semiconductor packages can be mounted to contact pads 34. An
optional underfill material can be formed below semiconductor die
36 and 40. A molding compound 44 is formed around semiconductor die
36 and 40 to encapsulate the die, interconnections, and contact
pads. The metal carrier is removed by an etching process to expose
contact pads 34 as shown in FIG. 2c.
[0028] In FIG. 2d, the semiconductor die are inverted such that
contact pads 34 face upward. An optional process carrier 50 is
mounted to a backside of the semiconductor die using adhesive layer
48 to support the package. The adhesive layer can be made with
thermally or ultraviolet (UV) light releasable temporary adhesive,
typically having a glass transition temperature (Tg) of at least
150.degree. C. A conductive layer 46 is sputtered and patterned, or
selectively plated, on a surface of molded compound 44 using an
adhesion layer, such as titanium (Ti). Conductive layer 46 is made
with Cu, Al, Au, or alloys thereof. Conductive layer 46
electrically connects to contact pads 34 according to the
electrical function and interconnect requirements of semiconductor
die 36 and 40.
[0029] In FIG. 2e, an insulating layer 51 is formed over molding
compound 44 and conductive layer 46. The insulating layer 51 can be
made with single or multiple layers of photosensitive polymer
material or other dielectric material having low cure temperature,
e.g. less than 200.degree. C. A portion of insulating layer 51 is
removed by an etching process, such as photo patterning or chemical
etching, to form openings and expose conductive layer 46. A
conductive layer 52 is formed over insulating layer 51 to
electrically contact conductive layer 46. An insulating layer 54 is
formed over conductive layer 52 and insulating layer 51. The
insulating layer 54 can be made with single or multiple layers of
photosensitive polymer material or other dielectric material having
low cure temperature, e.g. less than 200.degree. C. A portion of
insulating layer 54 is removed by an etching process, such as photo
patterning or chemical etching, to form openings and expose
conductive layer 52. Conductive layers 46 and 52 and insulating
layers 51 and 54 constitute a portion of an interconnect structure
which routes electrical signals between semiconductor die 36 and
40, as well as external to the package. Additional insulating
layers and conductive layers can be used in the interconnect
structure.
[0030] In FIG. 2f, an electrically conductive solder material is
deposited over conductive layer 52 through an evaporation,
electrolytic plating, electroless plating, ball drop, or screen
printing process. The solder material can be any metal or
electrically conductive material, e.g., Sn, lead (Pb), Ni, Au, Ag,
Cu, bismuthinite (Bi) and alloys thereof. The solder material is
reflowed by heating the conductive material above its melting point
to form spherical balls or bumps 56. In some applications, solder
bumps 56 are reflowed a second time to improve electrical contact
to conductive layer 52. An additional under bump metallization can
optionally be formed under solder bumps 56. The interconnections
can be solder bumps or bond wires.
[0031] Process carrier 50 and adhesive layer 48 are removed.
Alternatively, process carrier 50 and adhesive layer 48 can remain
attached to the semiconductor device and operate as a heat sink for
thermal dissipation or electromagnetic interference (EMI)
barrier.
[0032] FIG. 3 illustrates the semiconductor device from FIGS. 2a-2f
with semiconductor device 58 electrically connected to solder bumps
56. In addition, wire bonds 60 are electrically connected to
conductive layer 52. Bond wires 62 extend from wire bonds 60 to
other semiconductor devices or external electrical connections.
Solder bumps 56 and bond wires 62 provide electrical interconnect
for semiconductor die 36 and 40.
[0033] Another embodiment of the initial stages of making the
semiconductor device is shown in FIGS. 4a-4c. In FIG. 4a, a dummy
or sacrificial metal carrier 70 is shown. Metal carrier or foil 70
can be circular or rectangular and made with Cu or Al. A process
carrier 72 is mounted to carrier 70 with adhesive layer 74. A
photoresist layer 76 is deposited on metal carrier 70. A plurality
of openings is formed by a photo patterning process to define areas
for selective plating. Contact pads 78 are then selectively plated
on photoresist defined opening areas. Contact pads 78 can be made
with Cu, Sn, Ni, Au, or Ag. Metal carrier 70 serves as a support
member and plating current path for the electroplating process to
form wettable metal contact pads 78 on the metal carrier.
Photoresist 76 is removed by a resist stripper.
[0034] In FIG. 4b, semiconductor die 80 and 84 are mounted to
contact pads 78 on metal carrier 70 with solder bumps 82 and 86,
respectively. Alternatively, discrete components or other
semiconductor packages can be attached to contact pads 78. An
optional underfill material can be formed below semiconductor die
80 and 84. A molding compound 88 is formed all around semiconductor
die 80 and 84 to encapsulate the die, interconnections, and contact
pads. Process carrier 72 and adhesive 74 are released first,
followed by removal of metal carrier 70 by an etching process to
expose contact pads 78 as shown in FIG. 4c.
[0035] The interconnect structure is then formed using the steps
described in FIGS. 2d-2f. More specifically, a first conductive
layer like 46 is sputtered and patterned, or selectively plated, on
a surface of molded compound 88 using an adhesion layer, such as
Ti. The first conductive layer electrically connects to contact
pads 78 according to the electrical function and interconnect
requirements of semiconductor die 80 and 84. A first insulating
layer like 51 is formed over molding compound 88 and the first
conductive layer. The first insulating layer can be made with
single or multiple layers of photosensitive polymer material or
other dielectric material having low cure temperature, e.g. less
than 200.degree. C. A portion of the first insulating layer is
removed by an etching process to form openings and expose the first
conductive layer. A second conductive layer like 52 is formed over
the first insulating layer to electrically contact the first
conductive layer. A second insulating layer like 54 is formed over
the first conductive layer and first insulating layer. The second
insulating layer can be made with single or multiple layers of
photosensitive polymer material or other dielectric material having
low cure temperature, e.g. less than 200.degree. C. A portion of
the second insulating layer is removed by an etching process to
form openings and expose the second conductive layer. Solder bumps
like 56 can be formed on the exposed second conductive layer. The
first and second conductive layers and first and second insulating
layers constitute a portion of an interconnect structure which
routes electrical signals between semiconductor die 80 and 84, as
well as external to the package. Additional insulating layers and
conductive layers can be used in the interconnect structure.
[0036] FIG. 5 illustrates an embodiment of the semiconductor
device. Contact pads 94 are formed using a dummy or sacrificial
metal carrier as described in FIG. 2a. Semiconductor die 90 and 98
are mounted to contact pads 94 on the metal carrier with wire bonds
96 and 100, respectively. A molding compound 101 is formed all
around semiconductor die 90 and 98 to encapsulate the die, wire
bonds, and contact pads, similar to FIG. 2b. The metal carrier is
removed by an etching process to expose contact pads 94, in the
same manner as described in FIG. 2c.
[0037] A process carrier is applied to a backside of the
semiconductor die using an adhesive layer to support the package. A
conductive layer 102 is selectively plated on a surface of molded
compound 101 using an adhesion layer, such as Ti. Conductive layer
102 electrically connects to contact pads 94 according to the
electrical function and interconnect requirements of semiconductor
die 90 and 98.
[0038] An insulating layer 103 is formed over molding compound 101
and conductive layer 102. The insulating layer 103 can be made with
material having dielectric properties. A portion of insulating
layer 103 is removed by an etching process to form openings and
expose conductive layer 102. A conductive layer 104 is formed over
insulating layer 103 to electrically contact conductive layer 102.
An insulating layer 106 is formed over conductive layer 104 and
insulating layer 103. The insulating layer 106 can be made with
material having dielectric properties. A portion of insulating
layer 106 is removed by an etching process to form openings and
expose conductive layer 104. Conductive layers 104 and 106 and
insulating layers 103 and 106 constitute a portion of an
interconnect structure to route electrical signals between
semiconductor die 90 and 98 as well as external to the package.
Additional insulating layers and conductive layers can be used in
the interconnect structure.
[0039] An electrically conductive solder material is deposited over
conductive layer 104 through an evaporation, electrolytic plating,
electroless plating, ball drop, or screen printing process. The
solder material can be any metal or electrically conductive
material, e.g., Sn, Pb, Ni, Au, Ag, Cu, Bi, and alloys thereof. The
solder material is reflowed by heating the conductive material
above its melting point to form spherical balls or bumps 108. In
some applications, solder bumps 108 are reflowed a second time to
improve electrical contact to conductive layer 104. An additional
under bump metallization can optionally be formed under solder
bumps 108. The interconnections can be solder bumps or bond
wires.
[0040] FIGS. 6a-6b illustrates an embodiment of the semiconductor
device using a front-side and backside process carrier. In FIG. 6a,
contact pads 124 are formed using a dummy or sacrificial metal
carrier, as described in FIG. 2a. Semiconductor die 120 and 126 are
mounted to contact pads 124 on the metal carrier with solder bumps
122 and 128, respectively. A molding compound 130 is formed around
semiconductor die 120 and 126 to encapsulate the die, interconnect,
and contact pads, similar to FIG. 2b. The metal carrier is removed
by an etching process to expose contact pads 124, in the same
manner as described in FIG. 2c.
[0041] A process carrier is applied to a backside of the
semiconductor die using an adhesive layer to support the package. A
conductive layer 136 is selectively plated on a surface of molded
compound 130 using an adhesion layer, such as Ti. Conductive layer
136 electrically connects to contact pads 124 according to the
electrical function and interconnect requirements of semiconductor
die 120 and 126.
[0042] An insulating layer 138 is formed over molding compound 130
and conductive layer 136. The insulating layer 138 can be made with
materials having dielectric properties. A portion of insulating
layer 138 is removed by an etching process to form openings and
expose conductive layer 136. A conductive layer 140 is formed over
insulating layer 138 to electrically contact conductive layer 136.
An insulating layer 142 is formed over conductive layer 140 and
insulating layer 138. The insulating layer 142 can be made with
material having dielectric properties. A portion of insulating
layer 142 is removed by an etching process to form openings and
expose conductive layer 140. Conductive layers 136 and 140 and
insulating layers 138 and 142 constitute a portion of a front-side
interconnect structure which routes electrical signals between
semiconductor die 120 and 126, as well as external to the package.
Additional insulating layers and conductive layers can be used in
the front-side interconnect structure.
[0043] A front-side process carrier 146 is mounted to conductive
layer 140 and insulating layer 142 using adhesive layer 144. The
adhesive layer 144 can be made with thermally or UV light
releasable temporary adhesive, typically having a Tg of at least
150.degree. C. The front-side process carrier can be flexible tape
or stiff material. The backside process carrier is removed. Vias
are formed through molding compound 130 using laser drilling or
deep reactive ion etch (DRIE). The vias expose contact pads 124.
Conductive material 148 is deposited in the vias and electrically
connects to contact pads 124. An insulating layer 150 is formed
over conductive layer 148 and molding compound 130. The insulating
layer 150 can be made with material having dielectric properties. A
portion of insulating layer 150 is removed by an etching process to
form openings and expose conductive layer 148. Conductive layer 148
and insulating layer 150 constitute a portion of a backside
interconnect structure which routes electrical signals between
semiconductor die 120 and 126, as well as external to the package.
Additional insulating layers and conductive layers can be used in
the backside interconnect structure.
[0044] In FIG. 6b, an electrically conductive solder material is
deposited over conductive layer 140 through an evaporation,
electrolytic plating, electroless plating, ball drop, or screen
printing process. The solder material can be any metal or
electrically conductive material, e.g., Sn, Pb, Ni, Au, Ag, Cu, Bi,
and alloys thereof. The solder material is reflowed by heating the
conductive material above its melting point to form spherical balls
or bumps 152. In some applications, solder bumps 152 are reflowed a
second time to improve electrical contact to conductive layer 140.
An additional under bump metallization can optionally be formed
under solder bumps 152. For the backside interconnects, solder bump
or wire bond interconnects are formed on conductive layer 148 or
the outermost layer.
[0045] The semiconductor device in FIG. 7 follows a similar
construction as described in FIGS. 6a-6b, with the exception that
metal pillars 154 are formed by selective etching, using contact
pads 124 as etching mask. Pillars 154 are made with Cu, Al, or
alloys thereof. Metal pillars 154 facilitate depositing molded
underfill material below semiconductor die 120 and 126 due to the
elevated interconnect structure. Metal pillars 154 further
facilitate the formation of vias by laser drilling or DRIE process
as the via depth can be reduced. The semiconductor device
experiences less thermal stress or thermal strain with the higher
interconnection structure.
[0046] FIG. 8 shows the semiconductor device of FIG. 7 with contact
pads 124 and semiconductor die 120 elevated by metal pillars 154.
Semiconductor die 158 is mounted to insulating layer 138 with die
attach adhesive 160 and electrically connected to contact pads 124
and metal pillars 154 with wire bonds 162. The die attach adhesive
160 can be made with epoxy based or film based adhesive.
[0047] In FIG. 9, the semiconductor device of FIG. 6b has underfill
material 164. The underfill material can be made with resin having
proper Theological and dielectric properties.
[0048] In FIG. 10, the semiconductor device of FIG. 6b has
semiconductor die 166 physically mounted to and electrically
connected through solder bumps 152. Semiconductor die 168 is
physically mounted to insulating layer 142 with die attach material
170 and electrically connected to conductive layer 140 with wire
bonds 172. A molding compound 174 is applied over semiconductor die
166 and 168 and associated interconnect structures.
[0049] FIG. 11 shows the semiconductor device of FIG. 2f with
process carrier 176 and adhesive layer 178 remaining as a heat sink
for thermal dissipation or EMI shield.
[0050] FIG. 12 shows the semiconductor device of FIG. 2f with a
layer of photoresist 180 remaining between contact pads 124.
[0051] In summary, the semiconductor device employs a copper sheet
as a dummy or sacrificial carrier. A plurality of wettable contact
pads is patterned on the sacrificial carrier. The individual
semiconductor die are mounted to the sacrificial carrier and are
electrically connected to the contact pads. The semiconductor die
and contact pads are encapsulated with a molding compound. The
sacrificial carrier is removed to expose the metal pads. An
interconnect build-up layer is formed on the contact pads. The
wettable contact pads are selectively plated on the sacrificial
metal carrier to provide a highly accurate alignment of the bonding
pad positions for the electrical interconnect according to the
electrical function of the semiconductor die. By forming contact
pads on the sacrificial carrier, a precise placement and alignment
for the later formed requisite interconnect structure can be
achieved. Accordingly, the semiconductor package has greater
interconnect density and lower line pitch for individual
traces.
[0052] While one or more embodiments of the present invention have
been illustrated in detail, the skilled artisan will appreciate
that modifications and adaptations to those embodiments may be made
without departing from the scope of the present invention as set
forth in the following claims.
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