U.S. patent application number 12/878043 was filed with the patent office on 2012-03-15 for method and system for providing a reliable light emitting diode semiconductor device.
Invention is credited to Andreas EDER, Henrik EWE, Stefan LANDAU, Joachim MAHLER.
Application Number | 20120061700 12/878043 |
Document ID | / |
Family ID | 45756226 |
Filed Date | 2012-03-15 |
United States Patent
Application |
20120061700 |
Kind Code |
A1 |
EDER; Andreas ; et
al. |
March 15, 2012 |
METHOD AND SYSTEM FOR PROVIDING A RELIABLE LIGHT EMITTING DIODE
SEMICONDUCTOR DEVICE
Abstract
A method and a system for a reliable LED semiconductor device
are provided. In one embodiment, the device comprises a carrier, a
light emitting diode disposed on the carrier, an encapsulating
material disposed over the light emitting diode and the carrier, at
least one through connection formed in the encapsulating material,
and a metallization layer disposed and structured over the at least
one through connection.
Inventors: |
EDER; Andreas;
(Weissenstein, AT) ; EWE; Henrik; (Burglengenfeld,
DE) ; LANDAU; Stefan; (Wehrheim, DE) ; MAHLER;
Joachim; (Regensburg, DE) |
Family ID: |
45756226 |
Appl. No.: |
12/878043 |
Filed: |
September 9, 2010 |
Current U.S.
Class: |
257/98 ; 257/99;
257/E33.059; 257/E33.066; 257/E33.068; 438/23 |
Current CPC
Class: |
H01L 2933/0066 20130101;
H01L 2924/12042 20130101; H01L 24/24 20130101; H01L 2924/12042
20130101; H01L 2224/97 20130101; H01L 2924/1461 20130101; H01L
2924/1305 20130101; H01L 2224/97 20130101; H01L 2924/12041
20130101; H01L 24/97 20130101; H01L 2924/1305 20130101; H01L
2924/14 20130101; H01L 24/82 20130101; H01L 2224/32225 20130101;
H01L 2224/73267 20130101; H01L 2924/13055 20130101; H01L 2924/1461
20130101; H01L 2924/00 20130101; H01L 2224/82 20130101; H01L
2224/32245 20130101; H01L 2924/14 20130101; H01L 2924/12041
20130101; H01L 33/54 20130101; H01L 2924/13055 20130101; H01L
2924/00 20130101; H01L 2924/00 20130101; H01L 2924/00 20130101;
H01L 2924/00 20130101; H01L 2924/00 20130101; H01L 33/62 20130101;
H01L 33/56 20130101 |
Class at
Publication: |
257/98 ; 257/99;
438/23; 257/E33.068; 257/E33.066; 257/E33.059 |
International
Class: |
H01L 33/50 20100101
H01L033/50; H01L 33/52 20100101 H01L033/52; H01L 33/62 20100101
H01L033/62 |
Claims
1. A semiconductor device comprising: a carrier; a light emitting
diode disposed on the carrier; an encapsulating material disposed
over the light emitting diode; at least one through connection
formed in the encapsulating material; and a metallization layer
disposed and structured over the at least one through
connection.
2. The device of claim 1, further comprising: a metal layer
disposed over the encapsulating material.
3. The device of claim 1, wherein the encapsulating material is a
polymer material.
4. The device of claim 3, wherein the polymer material is acrylic
resin, ormocers, silicon epoxy copolymer or epoxy-acrylate
copolymer.
5. The device of claim 3, wherein the polymer material is epoxy
resin.
6. The device of claim 1, wherein the encapsulating material is a
low light absorbing material absorbing light in a full wavelength
range.
7. The device of claim 6, wherein the encapsulating material is a
low light absorbing material absorbing light in a short wavelength
range of a full wavelength range.
8. The device of claim 1, wherein the encapsulating material is
highly transparent, and has a low coefficient of thermal
expansion.
9. The device of claim 1, wherein the at least one through
connection is at least one via opening to at least one contact of
the light emitting diode.
10. The device of claim 1, further comprising: an organic
protective layer disposed over the light emitting diode.
11. The device of claim 9, further comprising: an optical
conversion layer disposed between the at least one contact and an
organic sacrificial layer of the light emitting diode.
12. A semiconductor device comprising: a carrier; a light emitting
diode and at least one semiconductor chip disposed on the carrier;
a first type of encapsulating material disposed over the light
emitting diode; a second type of encapsulating material disposed
over at least one of the at least one semiconductor chip and the
carrier; at least one through connection formed in the
encapsulating material; and a metallization layer disposed and
structured over the at least one through connection.
13. The device of claim 12, wherein the first type of encapsulating
material is a polymer material.
14. The device of claim 12, wherein the first type of encapsulating
material and the second type of encapsulating material is a same
material.
15. The device of claim 12, wherein the second type of
encapsulating material is an epoxy.
16. The device of claim 12, wherein the first type of encapsulating
material is a low light absorbing material absorbing light in a
full wavelength range.
17. The device of claim 16, wherein the first type of encapsulating
material is a low light absorbing material absorbing light in a
short wavelength range of the full wavelength range.
18. The device of claim 12, wherein the first type of encapsulating
material is highly transparent and has a low coefficient of thermal
expansion.
19. The device of claim 12, wherein the at least one semiconductor
chip comprises a power semiconductor chip and an integrated
circuit.
20. The device of claim 12, wherein the at least one through
connection is at least one via opening to at least one contact of
the light emitting diode and at least one of the at least one
semiconductor chip.
21. A method for forming a semiconductor device comprising:
providing a carrier; disposing at least one light emitting diode on
the carrier; encapsulating the at least one light emitting diode
with an encapsulating material; forming at least one through
connection in the encapsulating material; and forming a
metallization layer over the at least one through connection.
22. The method of claim 21, wherein encapsulating the at least one
light emitting diode and the carrier with an encapsulating material
comprises: encapsulating the at least one light emitting diode and
the carrier with an encapsulating material having a low coefficient
of thermal expansion.
23. The method of claim 21, wherein encapsulating the at least one
light emitting diode with an encapsulating material comprises:
encapsulating the at least one light emitting diode with a low
light absorbing material absorbing light in a full wavelength
range.
24. The method of claim 23, wherein encapsulating the at least one
light emitting diode with an encapsulating material comprises:
encapsulating the at least one light emitting diode with a low
light absorbing material absorbing light in a short wavelength
range of the full wavelength range.
25. The method of claim 21, wherein encapsulating the at least one
light emitting diode with an encapsulating material comprises:
encapsulating the at least one light emitting diode with an
encapsulating material that is highly transparent.
26. The method of claim 21, further comprising: forming a metal
layer over the encapsulating material.
27. The method of claim 26, wherein forming at least one through
connection in the encapsulating material comprises: forming at
least one via opening in the encapsulating material and the metal
layer.
28. The method of claim 21, wherein forming a metallization layer
over the at least one through connection comprises: filling the at
least one through connection with a metal; and removing portions of
the metal to expose the encapsulating material.
29. The method of claim 21, further comprising: encapsulating at
least one semiconductor chip and the carrier with the encapsulating
material
30. The method of claim 21, further comprising: encapsulating at
least one semiconductor chip and the carrier with an encapsulating
material different from the encapsulating material for
encapsulating the at least one light emitting diode.
Description
TECHNICAL FIELD
[0001] The present invention relates generally to a reliable light
emitting diode (LED) semiconductor device. In particular, the
present disclosure relates to a method and system for encapsulating
and embedding LEDs to provide a reliable LED semiconductor
device.
BACKGROUND
[0002] LEDs have been used widely in many applications due to its
light sensing capability. In many current semiconductor
applications, LEDs are mounted directly on a printed circuit board
as individual components and electrically connected to other
components, such as power and logic components, on the board. In
other applications, LEDs are placed into semiconductor devices
using silicone or silicon-based materials. These materials,
however, has poor performances due to its high coefficient of
thermal expansion (CTE), poor adhesive to metal and high moisture
permeability. Therefore, a need exists for a method and system to
provide a reliable LED semiconductor device that provides a better
performance.
BRIEF DESCRIPTION OF DRAWINGS
[0003] FIGS. 1A to 1E are diagrams illustrating an exemplary
process for forming a reliable LED semiconductor device accordance
with one embodiment of the present disclosure.
[0004] FIG. 2 is a flowchart of an exemplary process for forming a
reliable LED semiconductor in accordance with one embodiment of the
present disclosure.
[0005] FIGS. 3A to 3E are diagrams illustrating a reliable LED
semiconductor package in accordance with one embodiment of the
present disclosure.
[0006] FIG. 4 is a flowchart of an exemplary process for forming a
reliable LED semiconductor package in accordance with one
embodiment of the present disclosure.
SUMMARY OF INVENTION
[0007] The present disclosure provides a reliable LED semiconductor
device. In one embodiment, the device comprises a carrier, a light
emitting diode disposed on the carrier, an encapsulating material
disposed over the light emitting diode and the carrier, at least
one through connection formed in the encapsulating material, and a
metallization layer disposed and structured over the at least one
through connection.
[0008] In another embodiment, the device comprises a carrier, a
light emitting diode and at least one semiconductor chip disposed
on the carrier, an encapsulating material disposed over the light
emitting diode, the at least one semiconductor device and the
carrier, at least one through connection formed in the
encapsulating material, and a metallization layer disposed and
structured over the at least one through connection.
[0009] In yet another embodiment, a method for forming a reliable
LED semiconductor device is provided. The method comprises
providing a carrier, disposing at least one light emitting diode on
the carrier, encapsulating the at least one light emitting diode
and the carrier with an encapsulating material, forming at least
one through connection in the encapsulating material, and forming a
metallization layer over the at least one through connection.
DETAILED DESCRIPTION
[0010] In the following Detailed Description, reference is made to
the accompanying drawings, which form a part hereof, and in which
is shown by way of illustration specific embodiments in which the
invention may be practiced. In this regard, directional
terminology, such as "top," "bottom," "front," "back," "leading,"
"trailing," etc., is used with reference to the orientation of the
Figure(s) being described. Because components of embodiments can be
positioned in a number of different orientations, the directional
terminology is used for purposes of illustration and is in no way
limiting. It is to be understood that other embodiments may be
utilized and structural or logical changes may be made without
departing from the scope of the present invention. The following
detailed description, therefore, is not to be taken in a limiting
sense, and the scope of the present invention is defined by the
appended claims.
[0011] It is to be understood that the features of the various
exemplary embodiments described herein may be combined with each
other, unless specifically noted otherwise.
[0012] Devices with semiconductor chips are described below. The
semiconductor chips may be of extremely different types, may be
manufactured by different technologies and may include for example,
integrated electrical or electro-optical circuits or passives or
MEMS etc. Semiconductor chips may be configured, for example, as
power transistors, power diodes, IGBTs (Isolated Gate Bipolar
Transistors). Semiconductor chips may have a vertical structure and
may be fabricated in such a way that electrical currents can flow
in a direction perpendicular to the main surfaces of the
semiconductor chips. These semiconductor chips may have contact
elements disposed on its main surfaces, which includes a top
surface and a bottom surface. Examples of semiconductor chips
having a vertical structure include power transistors and power
diodes. In case of power transistors, the source electrode and the
gate electrode may be disposed on a first main surface while the
drain electrode may be disposed on a second main surface. In case
of a power diode, the anode electrode may be disposed on a first
main surface while the cathode electrode may be disposed on a
second main surface.
[0013] The integrated circuits may, for example, be designed as
logic integrated circuits, analog integrated circuits, mixed signal
integrated circuits, power integrated circuits, memory circuits or
integrated passives. Furthermore, the semiconductor chips may be
configured as MEMS (micro-electro mechanical systems) and may
include micro-mechanical structures, such as bridges, membranes or
tongue structures. The semiconductor chips may be configured as
sensors or actuators, for example, pressure sensors, acceleration
sensors, rotation sensors, microphones etc. The semiconductor chips
may be configured as antennas and/or discrete passives. The
semiconductor chips may also include antennas and/or discrete
passives. Semiconductor chips, in which such functional elements
are embedded, generally contain electronic circuits which serve for
driving the functional elements or further process signals
generated by the functional elements. The semiconductor chips need
not be manufactured from specific semiconductor material and,
furthermore, may contain inorganic and/or organic materials that
are not semiconductors, such as for example, discrete passives,
antennas, insulators, plastics or metals. Moreover, the
semiconductor chips may be packaged or unpackaged.
[0014] The semiconductor chips have contact elements which allow
electrical contact to be made with the semiconductor chips. The
contact elements may be composed of any desired electrically
conductive material, for example, of a metal, such as aluminum,
nickel, palladium, gold or copper, a metal alloy, a metal stack or
an electrically conductive organic material. The contact elements
may be situated on the active main surfaces of the semiconductor
chips or on other surfaces of the semiconductor chips. The active
or passive structures of the semiconductor chips are usually
arranged below the active main surfaces and can be electrically
contacted via the contact elements. In case of power transistors,
the contact elements may be drain, source or date electrodes.
[0015] The devices described in the following may include external
contact elements that are accessible from outside of the devices to
allow electrical contact to be made from outside of the devices. In
addition, the external contact elements may be thermally conductive
and serve as heat sinks for heat dissipation of the semiconductor
chips. The external contact elements may be composed of any
electrically conductive material, for example, a metal such as
copper, Pd, Ni, Au, etc.
[0016] The devices described in the following may include an
encapsulating material covering at least parts of the semiconductor
chips. The encapsulating material is an electrically insulating
material, which is at most marginally electrically conductive
relative to the electrically conductive components of the device.
Examples of an encapsulating material include a mold material and
an epoxy based material. The encapsulating material may be any
appropriate duroplastic, thermoplastic, laminate (prepreg) or
thermosetting material and may contain filler materials. Various
techniques may be employed to cover the semiconductor chips with
the mold material, for example, compression molding, lamination or
injection molding.
[0017] The present disclosure provides a method and system for a
reliable LED semiconductor device by encapsulating LEDs with a
special encapsulating material that is highly transparent, in
particular, to the blue color spectrum, and has good adhesion to
metals. In addition, the transparent encapsulating material has a
low coefficient of thermal expansion and stability under high
temperature. The resulting device is therefore easily integrated
with other semiconductor devices and processes without affecting
the performance of the LEDs.
[0018] Referring to FIGS. 1A to 1E, diagrams illustrating an
exemplary process for forming a reliable LED semiconductor device
are depicted in accordance with one embodiment of the present
disclosure. As shown in FIG. 1A, a reliable LED semiconductor
device 100 is provided which comprises a carrier 102 serving as a
lead frame. The carrier 102 may be made of metals, ceramics,
plastics or any other types of material. The carrier 102 may be a
structured or unstructured lead frame. An adhesive layer 104 is
then applied over the carrier 102 for attaching the LED 106. The
adhesive layer 104 may be made of any adhesive material, such as
metallic glue. LED 106 is placed onto the carrier 102 over the
adhesive layer 104. The LED 106 may comprise a first electrical
contact 108 disposed on the back surface 110 of LED 106 and a
second electrical contact 112 disposed on the top surface 114 of
LED 106.
[0019] Referring to FIG. 1B, a highly transparent encapsulating
material 120 is applied to encapsulate carrier 102 and LED 106. In
one embodiment, the encapsulating material may be a reliable
polymer material, such as acrylic resins, ormocers, epoxy-acrylate
copolymer, silicon epoxy copolymer, etc. Alternatively, the
encapsulating material may be made of other polymer materials such
as epoxy resins, which increases elasticity of the structure and
provides good light transmission for a given wavelength range.
[0020] These types of encapsulating material have a very low light
absorption in the full range of LED light wavelengths, but
particularly, in a short wavelength range. In one example, these
types of encapsulating material have a light absorption of less
than five percent, but preferably less than one percent, over a
full range of LED light wavelengths. The LED wavelengths may range
anywhere from infrared to ultra-violet.
[0021] In addition, these materials provide excellent adhesion to
metals, in particular, to copper surfaces, and other types of
materials, such as polymers and ceramics. These materials also have
a low coefficient of thermal expansion, for example, less than 50
ppm/K, which provides stability even in high temperature, for
example, temperature greater than 150.degree. C. The encapsulating
material 120 may be applied by molding or other encapsulation
methods.
[0022] Optionally, a thin metal layer 122 is applied over the
encapsulating material 120. The metal layer 122 may be made of
metals such as copper to provide a RCC film. The metal layer 122
may serve as a heat sink or dissipation for the structure or
electrical contacts and redistribution layer for the LED 106. The
thickness of the metal layer 122 may be a few micrometers. However,
metal layer 122 may be made of other types of metals or may have
different thickness without departing the spirit and scope of the
present disclosure.
[0023] Referring to FIG. 1C, a plurality of via openings 124, 126
are formed in the encapsulating material 120 and optionally, the
metal layer 122, to provide through connections to the electrical
contacts 108 and 112 of LED 106. For example, via opening 124 is
formed to provide a through connection to first electrical contact
108 disposed on the back surface 110 of LED 106. Via opening 126 is
formed to provide a through connection to the second electrical
contact 112 disposed on the top surface 114 of LED 106.
[0024] In one embodiment, the plurality of via openings 124, 126
may be formed using laser drilling or plasma etching. However,
other methods for forming the plurality of via openings may be used
without departing the spirit and scope of the present
disclosure.
[0025] Referring to FIG. 1D, the plurality of via openings 124, 126
may be filled with a metal, such as copper, to form a metallization
layer 128. To fill the plurality of via openings, a barrier layer
may first be deposited (e.g. sputtered) over the plurality of via
openings, in this example, via openings 124, 126 and optionally the
metal layer 122. The barrier layer may be composed of an
electrically conductive material, such as chrome or titanium or an
alloy of different metals like titanium and tungsten. Then, a seed
layer may be deposited (e.g. sputtered) onto the barrier layer. The
seed layer may be composed of an electrically conductive material,
such as copper.
[0026] After a barrier and/or seed layer is applied, another layer
of electrically conductive material, such as copper, or multiple
layers of similar or different electrically conductive materials,
such as copper, nickel, gold or palladium is galvanically
deposited. The electrically conductive material may be copper or
any other conductive metal, and may consist of a layer stack of
different metals, such as Copper, Nickel and Gold or copper, nickel
and copper or copper, nickel and palladium.
[0027] Before the electrically conductive material is applied, a
plating resist is placed over the barrier and/or seed layer. The
plating resist may be placed over the entire barrier and/or seed
layer except the plurality of via openings, such as via openings
124, 126, and the wafer edge (edge exclusion). Typically, the
plating resist is exposed and developed after application with
photolithography mask (Mask Aligner) or a reticle (Stepper).
Another possibility would be to structure the resist by laser (e.g.
laser direct imaging) or apply the electrically conductive material
already structured (e.g. printing). Dual damascene redistribution
is possible as well.
[0028] After electrically conductive material is applied into areas
not covered by the plating resist, the plating resist is stripped
and the barrier and/or seed layer are removed chemically, for
example, by wet etching. The plating resist may be removed easily
with common resist stripping technique. The barrier and/or seed
layer may be removed by wet etching. However, portions of the
barrier and/or seed layer may be removed using other methods
without departing the spirit and scope of the present
disclosure.
[0029] Referring to FIG. 1E, after the plating resist and the
barrier and/or seed layer is removed, metallization layer 128 is
formed. The metallization layer 128 is then structured to provide
electrical connection to external component, such as a print
circuit board. In this example, portions of the metallization layer
128 are removed by ablation, such as photolithography. As shown in
FIG. 1E, portion 130 of metallization layer 128 is removed by
ablation, which in turn exposes the highly transparent
encapsulating material 120. The exposed highly transparent
encapsulating material 120 allows LED 106 to absorb a full range of
LED light wavelengths 132, including the blue color spectrum.
[0030] Referring to FIG. 2, a flowchart of an exemplary process for
forming a reliable LED semiconductor package is depicted in
accordance with one embodiment of the present disclosure. Process
200 begins at step 202 to provide a carrier as a lead frame. For
example, a metal carrier 102 is provided as a lead frame. Process
200 then continues to step 204 to place an LED on the carrier over
an adhesive layer. For example, LED 106 is placed onto carrier 102
over adhesive layer 104.
[0031] Process 200 then continues to step 206 to encapsulate the
LED and the carrier with a highly transparent encapsulating
material. For example, encapsulating material 120 is applied to
encapsulate LED 106 and carrier 102. The encapsulating material may
be a reliable polymer material, such as acrylic resins,
epoxy-acrylate copolymer, or other materials such as epoxy resins,
that provides elasticity of the structure and good light
transmission in a given wavelength range.
[0032] Process 200 then continues to step 208 to optionally apply a
metal layer over the encapsulating material. For example, a metal
layer 122, made of copper, may be applied over the encapsulating
material 120. Process 200 then continues to step 210 to form a
plurality of via openings in the encapsulating material and the
optional metal layer to provide through connections to electrical
contacts of the LED. For example, via openings 124, 126 may be
formed in metal layer 122 and encapsulating material 120 using
laser drilling or plasma etching to provide through connections to
contacts 114 and 108 of LED 106.
[0033] To protect contacts 114 and 108 from laser damage, an
organic protective layer may be applied over the LED 106, including
at least contacts 114 and 108 of the LED 106. Alternatively, a thin
organic layer, referred to as optional conversion layer may be
applied between contacts 114 and 108 of LED 106 and the organic
sacrificial layer of the LED 106 to adjust the LED emitted light
wavelength to a desired color spectrum.
[0034] Process 200 then continues to step 212 to fill the plurality
of via openings with a metal to form a metallization layer. For
example, via openings 124, 126 may be filled with copper to form
metallization layer 128. Process 200 then completes at step 214 to
structure the metallization layer. For example, portion 130 of
metallization layer 128 is removed by ablation to expose the
transparent encapsulating material 120.
[0035] In addition to an LED semiconductor device 100 as
illustrated above, the present disclosure provides a method and
system for a reliable LED semiconductor package, which embeds the
LED semiconductor device along with other semiconductor devices,
such as power and logic components. Referring to FIGS. 3A to 3E,
diagrams illustrating a reliable LED semiconductor package are
depicted in accordance with one embodiment of the present
disclosure.
[0036] As shown in FIG. 3A, a plurality of semiconductor devices
may be placed onto a carrier 302. For example, an LED 306, an
integrated circuit 308 for logic operations, and a power
semiconductor device 310 may be placed onto carrier 302. In one
embodiment, the semiconductor devices 306, 308, and 310 may be
placed onto carrier 302 over adhesive layer 304. Semiconductor
devices 306, 308, and 310 may comprise first electrical contacts
312 on top surfaces 314 and second electrical contacts 316 on back
surfaces 318 of devices 306, 308, and 310 for electrical
connections to external components.
[0037] Referring to FIG. 3B, a highly transparent encapsulating
material 320 is applied to encapsulate carrier 302, LED 306, IC
308, and power component 310. In one embodiment, the highly
transparent encapsulating material 320 may be applied to
encapsulate the LED 306, the carrier 302, the IC 308 and the power
component 310 together. In another embodiment, the highly
transparent encapsulating material may be disposed over the LED 306
alone, to provide low light absorption, low thermal coefficient and
good adhesion to metals, while a second type of encapsulating
material, or a common encapsulating material, such as epoxy, may be
disposed over the carrier 302, the IC 308 and the power component
310. In this way, the cost of encapsulation may be reduced.
[0038] In one embodiment, the encapsulating material 320 may be a
reliable polymer material, such as acrylic resins, ormocers,
silicon epoxy copolymer, epoxy-acrylate copolymer, etc.
Alternatively, the encapsulating material 320 may be made of other
materials such as epoxy resins, which increases elasticity of the
structure and provides good light transmission for a given
wavelength range.
[0039] These types of encapsulating material have a very low light
absorption in the full range of LED light wavelengths, but
particularly, in a short wavelength range. In one example, these
types of encapsulating material have a light absorption of less
than five percent, but preferably less than one percent, over a
full range of LED light wavelengths. The LED wavelengths may range
anywhere from infrared to ultra-violet.
[0040] In addition, these materials provide excellent adhesion to
metals, in particular, to copper surfaces, and other types of
materials, such as polymers and ceramics. These materials also have
a low coefficient of thermal expansion, for example, less than 50
ppm/K, which provides stability even in high temperature, for
example, temperature greater than 150.degree. C. The encapsulating
material 320 may be applied by molding or other encapsulation
methods.
[0041] Optionally, a thin metal layer 322 is applied over the
encapsulating material 320. The metal layer 322 may be made of
metals such as copper to provide a RCC film. The metal layer 322
may serve as a heat sink or dissipation for the structure or
electrical contacts and redistribution layer for devices 306, 308,
and 310. The thickness of the metal layer 322 may be a few
micronmeters. However, metal layer 322 may be made of other types
of metals or may have different thickness without departing the
spirit and scope of the present disclosure.
[0042] Referring to FIG. 3C, a plurality of via openings 324, 326
are formed in the encapsulating material 320 and optionally, the
metal layer 322, to provide through connections to the first
electrical contacts 312 on top surfaces 314 and second electrical
contacts 316 on back surfaces 318 of devices 306, 308, and 310. In
one embodiment, the plurality of via openings 324, 326 may be
formed using laser drilling or plasma etching. However, other
methods for forming the plurality of via openings may be used
without departing the spirit and scope of the present
disclosure.
[0043] Referring to FIG. 3D, the plurality of via openings 324, 326
may be filled with a metal, such as copper, to form a metallization
layer 328. To fill the plurality of via openings 324, 326, a
barrier layer may first be deposited (e.g. sputtered) over the
plurality of via openings, in this example, via openings 324, 326
and the optional metal layer 322. The barrier layer may be composed
of an electrically conductive material, such as chrome or titanium
or an alloy of different metals like titanium and tungsten. Then, a
seed layer may be deposited (e.g. sputtered) onto the barrier
layer. The seed layer may be composed of an electrically conductive
material, such as copper.
[0044] After a barrier and/or seed layer is applied, another layer
of electrically conductive material, such as copper, or multiple
layers of similar or different electrically conductive materials,
such as copper, nickel, gold or palladium is galvanically
deposited. The electrically conductive material may be copper or
any other conductive metal, and may consist of a layer stack of
different metals, such as Copper, Nickel and Gold or copper, nickel
and copper or copper, nickel and palladium.
[0045] Before the electrically conductive material is applied, a
plating resist is placed over the barrier and/or seed layer. The
plating resist may be placed over the entire barrier and/or seed
layer except the plurality of via openings, such as via openings
324, 326 and the wafer edge (edge exclusion). Typically, the
plating resist is exposed and developed after application with
photolithography mask (Mask Aligner) or a reticle (Stepper).
Another possibility would be to structure the resist by laser (e.g.
laser direct imaging) or apply the electrically conductive material
already structured (e.g. printing). Dual damascene redistribution
is possible as well.
[0046] After electrically conductive material is applied into areas
not covered by the plating resist, the plating resist is stripped
and the barrier and/or seed layer are removed chemically, for
example, by wet etching. The plating resist may be removed easily
with common resist stripping technique. The barrier and/or seed
layer may be removed by wet etching. However, portions of the
barrier and/or seed layer may be removed using other methods
without departing the spirit and scope of the present
disclosure.
[0047] Referring to FIG. 3E, after the plating resist and the
barrier and/or seed layer are removed, metallization layer 328 is
formed. The metallization layer 328 is then structured to provide
connection to external component, such as a print circuit board. In
this example, portions of the metallization layer 328 are removed
by ablation, such as photolithography. As shown in FIG. 3E,
portions 330 of metallization layer 328 are removed by ablation,
which in turn exposes the highly transparent encapsulating material
320. The exposed highly transparent encapsulating material 320
allows LED 306 to absorb a full range of LED light wavelengths 332,
including the blue color spectrum.
[0048] Referring to FIG. 4, a flowchart of an exemplary process for
forming a reliable LED semiconductor package is depicted in
accordance with one embodiment of the present disclosure. Process
400 begins at step 402 to provide a carrier as a lead frame. For
example, a metal carrier 302 is provided as a lead frame. Process
200 then continues to step 404 to place an LED and at least one
semiconductor chip on the carrier over an adhesive layer. For
example, LED 306, integrated circuit 308, and power semiconductor
chip 310 are placed onto carrier 302 over adhesive layer 304.
[0049] Process 400 then continues to step 406 to encapsulate the
LED, the at least one semiconductor chip and the carrier with a
highly transparent encapsulating material. For example,
encapsulating material 120 is applied to encapsulate LED 306,
integrated circuit 308, power semiconductor chip 310 and carrier
302. The encapsulating material may be a reliable polymer material,
such as acrylic resins, epoxy-acrylate copolymer, or other epoxy
materials such as epoxy resins, that provides elasticity of the
structure and provides good light transmission in a given
wavelength range.
[0050] Process 400 then continues to step 408 to optionally apply a
metal layer over the encapsulating material. For example, a copper
layer 322 may be applied over the encapsulating material 320.
Process 400 then continues to step 410 to form a plurality of via
openings in the encapsulating material and the optional metal layer
to provide through connections to electrical contacts of the LED.
For example, via openings 324, 326 may be formed in copper layer
322 and encapsulating material 320 using laser drilling or plasma
etching to provide through connections to contacts 312 and 316 of
devices 306, 308, and 310. To protect contacts 312 and 316 from
laser damage, an organic protective layer may be applied over the
LED 306, including at least contacts 312 and 316 of the LED 306.
Alternatively, a thin organic layer, referred to as optional
conversion layer may be applied between contacts 312 and 316 of LED
306 and the organic sacrificial layer of the LED 306 to adjust the
LED emitted light wavelength to a desired color spectrum.
[0051] Process 400 then continues to step 412 to fill the plurality
of via openings with a metal to form a metallization layer. For
example, via openings 324, 326 may be filled with copper to form
metallization layer 328. Process 400 then completes at step 414 to
structure the metallization layer. For example, portions 330 of
metallization layer 328 are removed by ablation to expose the
transparent encapsulating material 320.
[0052] Thus, the present disclosure also provides a method and a
system for embedding LEDs in a semiconductor package along with
other semiconductor devices by using a transparent encapsulating
material. The method and system provide a reliable solution for
embedding LEDs without damaging the LED surface during the process
and provide desirable properties for LED light absorption.
[0053] In addition, while a particular feature or aspect of an
embodiment of the invention may have been disclosed with respect to
only one of several implementations, such feature or aspect may be
combined with one or more other features or aspects of the other
implementations as may be desired and advantageous for any given or
particular application. Furthermore, to the extent that the terms
"include", "have", "with", or other variants thereof are used in
either the detailed description or the claims, such terms are
intended to be inclusive in a manner similar to the term
"comprise". The terms "coupled" and "connected", along with
derivatives may have been used. It should be understood that these
terms may have been used to indicate that two elements co-operate
or interact with each other regardless whether they are in direct
physical or electrical contact, or they are not in direct contact
with each other. Furthermore, it should be understood that
embodiments of the invention may be implemented in discrete
circuits, partially integrated circuits or fully integrated
circuits or programming means. Also, the term "exemplary" is merely
meant as an example, rather than the best or optimal. It is also to
be appreciated that features and/or elements depicted herein are
illustrated with particular dimensions relative to one another for
purposes of simplicity and ease of understanding, and that actual
dimensions may differ substantially from that illustrated
herein.
[0054] Although specific embodiments have been illustrated and
described herein, it will be appreciated by those of ordinary skill
in the art that a variety of alternate and/or equivalent
implementations may be substituted for the specific embodiments
shown and described without departing from the scope of the present
invention. This application is intended to cover any adaptations or
variations of the specific embodiments discussed herein. Therefore,
it is intended that this invention be limited only by the claims
and the equivalents thereof.
* * * * *