U.S. patent application number 10/790724 was filed with the patent office on 2005-04-14 for wavelength converted light emitting apparatus using phosphor and manufacturing method thereof.
Invention is credited to Kim, Hyun Kyung.
Application Number | 20050077531 10/790724 |
Document ID | / |
Family ID | 36385328 |
Filed Date | 2005-04-14 |
United States Patent
Application |
20050077531 |
Kind Code |
A1 |
Kim, Hyun Kyung |
April 14, 2005 |
Wavelength converted light emitting apparatus using phosphor and
manufacturing method thereof
Abstract
Disclosed herein is a wavelength converted light emitting
apparatus comprising a substrate, a light emitting diode, and a
phosphor layer. The substrate is formed at its upper surface with
first and second conductive patterns. At a partial region of the
first conductive pattern and at the second conductive pattern are
formed first and second connection bumps, respectively. The light
emitting diode has first and second surfaces opposite to each
other, and a side surface. The first surface of the light emitting
diode is formed with first and second electrodes. The light
emitting diode is disposed at the upper surface of the substrate so
that the first and second electrodes are connected to the first and
second connection bumps, respectively. The phosphor layer is formed
along the second surface and side surface of the light emitting
diode by a certain thickness, thereby serving to convert a
wavelength of light emitted from the light emitting diode.
Inventors: |
Kim, Hyun Kyung; (Suwon,
KR) |
Correspondence
Address: |
LOWE HAUPTMAN GILMAN & BERNER, LLP
1700 Diagonal Road, Suite 310
Alexandria
VA
22314
US
|
Family ID: |
36385328 |
Appl. No.: |
10/790724 |
Filed: |
March 3, 2004 |
Current U.S.
Class: |
257/98 ; 257/100;
438/25; 438/29 |
Current CPC
Class: |
H01L 33/505 20130101;
H01L 33/62 20130101; H01L 2224/49107 20130101; H01L 2924/00014
20130101; H01L 2924/00 20130101; H01L 2924/00 20130101; H01L
2933/0041 20130101; H01L 2924/10253 20130101; H01L 2924/01322
20130101; H01L 2224/48091 20130101; H01L 2924/01322 20130101; H01L
2924/10253 20130101 |
Class at
Publication: |
257/098 ;
438/025; 257/100; 438/029 |
International
Class: |
H01L 021/00; H01L
033/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 10, 2003 |
KR |
2003-70716 |
Claims
What is claimed is:
1. A wavelength converted light emitting apparatus comprising: a
substrate having an upper surface formed with first and second
conductive patterns, at a partial region of the first conductive
pattern and at the second conductive pattern being formed first and
second connection bumps, respectively; a light emitting diode
having first and second surfaces opposite to each other, and a side
surface connected between the first and second surfaces, the first
surface being formed with first and second electrodes, the light
emitting diode being disposed at the upper surface of the substrate
so that the first and second electrodes are connected to the first
and second connection bumps, respectively; and a phosphor layer
formed along the second surface and side surface of the light
emitting diode by a certain thickness, the phosphor layer serving
to convert a wavelength of light emitted from the light emitting
diode.
2. The apparatus as set forth in claim 1, wherein: the light
emitting diode emits ultraviolet or blue light; and the phosphor
layer is a material for converting the light emitted from the light
emitting diode into white light.
3. The apparatus as set forth in claim 1, wherein the phosphor
layer extends from the side surface of the light emitting diode so
as to reach to the upper surface of the substrate.
4. The apparatus as set forth in claim 1, wherein the phosphor
layer is formed by a physical vapor deposition, chemical vapor
deposition, or spin coating method.
5. The apparatus as set forth in claim 1, wherein the phosphor
layer is formed by a sputtering method.
6. The apparatus as set forth in claim 1, wherein: the light
emitting diode further has a transparent substrate, first and
second conductive semiconductor layers and an active layer, which
are successively stacked on the transparent substrate in multiple
layers; the first and second electrodes are formed on the first and
second conductive semiconductor layers, respectively; and one
surface of the transparent substrate opposite to the surface formed
with the first conductive semiconductor layer is provided as the
second surface of the light emitting diode.
7. The apparatus as set forth in claim 6, wherein the phosphor
layer is formed along one surface of the transparent substrate
provided as the second surface of the light emitting diode, and
along the side surfaces of the transparent substrate, the first and
second conductive semiconductor layers and active layer, by a
certain thickness.
8. The apparatus as set forth in claim 1, wherein: the substrate is
a conductive substrate provided with a rear surface electrode; and
the first conductive pattern is formed on an insulation layer
provided at the conductive substrate, and the second conductive
pattern is formed in a region where the insulation layer is removed
so as to be connected with the conductive substrate, thereby being
connected to the rear surface electrode.
9. A method of manufacturing a wavelength converted light emitting
apparatus comprising the steps of: a) preparing a light emitting
diode having first and second surfaces opposite to each other, and
a side surface connected between the first and second surfaces, the
first surface being formed with first and second electrodes; b)
preparing a substrate having an upper surface formed with first and
second conductive patterns, and forming first and second connection
bumps at a partial region of the first conductive pattern and at
the second conductive pattern, respectively; c) disposing the light
emitting diode at the upper surface of the substrate, and
connecting the first and second electrodes of the light emitting
diode to the first and second connection bumps, respectively; and
d) forming a phosphor layer along the second surface and side
surface of the light emitting diode by a certain thickness, the
phosphor layer serving to convert a wavelength of light emitted
from the light emitting diode.
10. The method as set forth in claim 9, wherein: the light emitting
diode emits ultraviolet or blue light: and the phosphor layer is a
material for converting the light emitted from the light emitting
diode into white light.
11. The method as set forth in claim 9, wherein the step d) is the
step of forming the phosphor layer so that the phosphor layer
extends along the second surface and side surface of the light
emitting diode, and reaches the upper surface of the substrate
extending from the side surface of the light emitting diode.
12. The method as set forth in claim 9, wherein the step d)
includes the steps of: d-1) forming a photoresist at a terminal
connection region provided on an upper surface of at least one of
the first and second conductive patterns, the terminal connection
region being connected to an external terminal; d-2) forming the
phosphor layer on the substrate on which the light emitting diode
is disposed; and d-3) removing the photoresist.
13. The method as set forth in claim 12, wherein the step d-2) is
performed by using one process selected from among a group
consisting of physical vapor deposition, chemical vapor deposition,
and spin coating methods.
14. The method as set forth in claim 12, wherein the step d-2) is
performed by a sputtering method.
15. The method as set forth in claim 9, wherein: the light emitting
diode is formed by successively stacking a first conductive
semiconductor layer, an active layer, and a second conductive
semiconductor layer on a transparent substrate in multiple layers;
the first and second electrodes are formed on the first and second
conductive semiconductor layers, respectively; and one surface of
the transparent substrate opposite to the surface formed with the
first conductive semiconductor layer is provided as the second
surface of the light emitting diode.
16. The method as set forth in claim 15, wherein the step d) is the
step of forming the phosphor layer along one surface of the
transparent substrate provided as the second surface of the light
emitting diode, and along the side surfaces of the transparent
substrate, the first and second conductive semiconductor layers and
active layer, by a certain thickness.
17. The method as set forth in claim 9, wherein the step b)
includes the steps of: b-1) preparing the conductive substrate;
b-2) forming an insulation layer on the upper surface of the
conductive substrate; b-3) forming the first and second conductive
patterns; b-4) forming a rear surface electrode at a lower surface
of the conductive substrate; and b-5) forming the first and second
connection bumps at the partial region of the first conductive
pattern and at the second conductive pattern, respectively, wherein
the step b-3) includes the steps of: b-3-1) forming the first
conductive pattern on the insulation layer: and b-3-2) forming the
second conductive pattern at a region of the upper surface of the
conductive substrate, the region being exposed to the outside by
removing a corresponding partial region of the insulation layer.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a wavelength converted
light emitting apparatus, and more particularly to a light emitting
apparatus and manufacturing method thereof for producing specific
colors of light, such as white light, by converting the wavelength
of a portion of the light to be emitted, by making use of
phosphors.
[0003] 2. Description of the Related Art
[0004] Semiconductor light emitting diodes are devices having a
great potential for miniaturization and good light emission
efficiency, and thus they have been utilized as optical sources of
various display apparatuses and optical communication equipment.
Further, as semiconductor light emitting diodes, which produce blue
or ultraviolet light of a short wavelength, have been
commercialized in recent years, the semiconductor light emitting
diodes can serve to produce white light through the combination of
blue, red and green light.
[0005] Generally, respective semiconductor light emitting diodes
have a feature of emitting single color of light having a
predetermined wavelength. Therefore, two typical methods have been
used in order to realize emission of white light. One typical
method is for integrating two or more kinds of light emitting
diodes into a single package, and the other method is for
converting a portion of the light emitted from a blue or
ultraviolet light emitting device by making use of phosphor, so as
to produce white light. Conventionally, the latter method is widely
utilized since it is advantageous in view of miniaturization of
products.
[0006] FIG. 1a illustrates a wavelength converted light emitting
diode using phosphor. More particularly, the light emitting diode
shown in FIG. 1a may be a light emitting diode 10 adapted to mainly
emit white light.
[0007] Referring to FIG. 1a, the white light emitting diode 10
comprises a gallium nitride (GaN) based light emitting structure
including an n-type GaN clad layer 12, a single quantum well (SQW)
or multiple quantum well (MQW) active layer 13, and a p-type GaN
clad layer 14, which are successively stacked on a sapphire
substrate 11 in multiple layers. This GaN based light emitting
structure further includes a first bonding electrode 16a formed on
the upper surface of the n-type GaN clad layer 12, and a second
electrode 16b formed on the upper surface of the p-type GaN clad
layer 14. For the formation of these electrodes, the clad layers
are processed by mesa-etching. The white light emitting diode 10
further comprises a phosphor layer 20 provided at the overall upper
surface thereof. As used herein, "phosphor" refers to a wavelength
convertible material for producing white light. That is, in a state
wherein the active layer 13 of the white light emitting diode 10
emits blue or ultraviolet light, most of the emitted blue or
ultraviolet light is converted into long wavelength light while
passing through the phosphor layer 20. Then, the long wavelength
light is combined with the remaining unconverted portion or
differently converted portion of the blue or ultraviolet light,
thereby allowing desired white light to be finally produced.
[0008] Since the conventional white light emitting diode 10 shown
in FIG. 1a is manufactured in such a manner that, after the
phosphor layer 20 is formed on the overall upper surface of a
wafer, which is formed with a plurality of the light emitting
diodes, and then the wafer is cut so as to form a plurality of
individual chips, the phosphor layer 20 exists only on the upper
surface of the white light emitting diode 10.
[0009] In this case, upward light A emitted from the upper surface
of the white light emitting diode 10 passes through the phosphor
layer 20 serving to stimulate the light emitted from the active
layer 13 into white light, while lateral light B emitted from the
side surface of the white light emitting diode 10 does not pass the
phosphor layer 20, thereby being inevitably emitted as the original
blue or ultraviolet light itself. As can be well noted from this
fact, the light emitting diode 10 shown in FIG. 1a, which is formed
only on the upper surface thereof with the phosphor layer 20 due to
its manufacturing manner, has a problem in that it is very
disadvantageous for the emission of appropriate white light.
[0010] As another example of conventional light emitting diodes,
FIG. 1b illustrates the structure of a white light emitting diode
using a phosphor material in accordance with the prior art. In FIG.
1b, the phosphor material is added at a package level of the light
emitting diode.
[0011] Referring to FIG. 1b, the white light emitting diode
package, designated as reference numeral 50, comprises a cup shaped
package structure 42, which is mounted with a substrate 44 having a
first electrode formed thereon. That is, the first electrode is
formed on the substrate 44 within the cup shaped package structure
42. On the first electrode is mounted an ultraviolet or blue light
emitting diode 30. This light emitting diode 30 is connected to an
electrode pattern provided in the cup shaped package structure 42,
that is, to a second electrode formed on the substrate 44 through
wires 45.
[0012] Inside the package structure 42 mounted with the light
emitting diode 30 is formed a molded portion 40, which is made of a
luminescent material including appropriate phosphor. The phosphor
for use in the molded portion 40, for example, may be a
yttrium-aluminum-garnet-based luminescent material. Such a
luminescent material is obtained by mixing a hardener with an
unhardened epoxy resin powder as a main material, thereby producing
epoxy slurry. As the epoxy slurry is provided inside the package
structure by using a dispensing method, the phosphor molded portion
40 is constructed. Since the phosphor existing inside the molded
portion 40 takes the form of scattered phosphor particles, a
portion of the light emitted from the light emitting diode collides
with the scattered phosphor particles, thereby undergoing
wavelength conversion, while the remaining portion of the light
directly passes through the molded portion 40 without conversion of
wavelength. The combination of the wavelength converted light and
other light can appear white to the human eye. The formation method
of the phosphor as stated above is further applicable to form the
phosphor layer 20 as shown in FIG. 1a.
[0013] The phosphor molded portion 40 or the phosphor layer 20,
however, results in a non-uniformity in spatial distribution of the
phosphor particles scattered therein, and especially, in case of
the structure shown in FIG. 1a, the phosphor layer 20 cannot be
formed throughout the light emitting surface of the light emitting
diode as stated above. Therefore, there is a problem in that it is
very difficult to obtain desired colors of light from the overall
light emitting surface of the light emitting diode. This problem is
a big roadblock to commercialization of the wavelength converted
light emitting diodes using phosphors.
[0014] Therefore, there has been a requirement of a wavelength
converted light emitting diode structure capable of overcoming the
above problems in the art.
SUMMARY OF THE INVENTION
[0015] Therefore, the present invention has been made in view of
the above problems, and it is an object of the present invention to
provide a white light emitting apparatus comprising a light
emitting diode, which is formed in a flip chip bonding structure so
as to allow a phosphor layer to be formed throughout the light
emitting surface thereof.
[0016] It is another object of the present invention to provide a
manufacturing method of a light emitting apparatus of the
above-mentioned type.
[0017] In accordance with one aspect of the present invention, the
above and other objects can be accomplished by the provision of a
wavelength converted light emitting apparatus comprising: a
substrate having an upper surface formed with first and second
conductive patterns, at a partial region of the first conductive
pattern and at the second conductive pattern being formed first and
second connection bumps, respectively; a light emitting diode
having first and second surfaces opposite to each other, and a side
surface connected between the first and second surfaces, the first
surface being formed with first and second electrodes, the light
emitting diode being disposed at the upper surface of the substrate
so that the first and second electrodes are connected to the first
and second connection bumps, respectively; and a phosphor layer
formed along the second surface and side surface of the light
emitting diode by a certain thickness, the phosphor layer serving
to convert a wavelength of light emitted from the light emitting
diode.
[0018] Preferably, the light emitting diode may emit ultraviolet or
blue light, and the phosphor layer may be a material for converting
the light emitted from the light emitting diode into white
light.
[0019] Preferably, the phosphor layer employed in the present
invention may be formed by a physical vapor deposition, chemical
vapor deposition, or spin coating method, so as to be precisely
formed in an uniform thickness. More preferably, the phosphor layer
may be formed by a sputtering method.
[0020] Preferably, the light emitting diode may be formed by
successively stacking a first conductive semiconductor layer, an
active layer, and a second conductive semiconductor layer, on a
transparent substrate in multiple layers, the first and second
electrodes may be formed on the first and second conductive
semiconductor layers, respectively, and a lower surface of the
transparent substrate layer may be provided as the second surface
of the light emitting diode.
[0021] Preferably, the phosphor layer may be formed along the lower
surface of the transparent substrate, and along the side surfaces
of the first and second conductive semiconductor layers and active
layer.
[0022] Preferably, the substrate may be a conductive substrate
provided with a rear surface electrode, the first conductive
pattern may be formed on an insulation layer provided at the
conductive substrate, and the second conductive pattern may be
formed in a region where the insulation layer is removed so as to
be connected with the conductive substrate, thereby being connected
to the rear surface electrode.
[0023] In accordance with another aspect of the present invention,
there is provided a method of manufacturing a wavelength converted
light emitting apparatus comprising the steps of: a) preparing a
light emitting diode having first and second surfaces opposite to
each other, and a side surface connected between the first and
second surfaces, the first surface being formed with first and
second electrodes; b) preparing a substrate having an upper surface
formed with first and second conductive patterns, and forming first
and second connection bumps at a partial region of the first
conductive pattern and at the second conductive pattern,
respectively; c) disposing the light emitting diode at the upper
surface of the substrate, and connecting the first and second
electrodes of the light emitting diode to the first and second
connection bumps, respectively; and d) forming a phosphor layer
along the second surface and side surface of the light emitting
diode by a certain thickness, the phosphor layer serving to convert
a wavelength of light emitted from the light emitting diode.
[0024] Preferably, the step d) may include the steps of: d-1)
forming a photoresist at a terminal connection region provided on
an upper surface of at least one of the first and second conductive
patterns, the terminal connection region serving to be connected to
an external terminal; d-2) forming the phosphor layer on the
substrate on which the light emitting diode is disposed; and d-3)
removing the photoresist.
[0025] Preferably, the step d-2) may be performed by using one
process selected from among a group consisting of physical vapor
deposition, chemical vapor deposition, and spin coating method.
More preferably, the step d-2) may be performed by a sputtering
method.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] The above and other objects, features and other advant ages
of the present invention will be more clearly understood from the
following detailed description taken in conjunction with the
accompanying drawings, in which:
[0027] FIGS. 1a and 1b are side sectional views, respectively,
illustrating a wavelength converted light emitting diode and light
emitting diode package using phosphors in accordance with the prior
art;
[0028] FIG. 2 is a side sectional view illustrating a wavelength
converted light emitting apparatus having a flip chip bonding
structure in accordance with an embodiment of the present
invention;
[0029] FIGS. 3a to 3f are sectional views illustrating the
sequential steps of manufacturing the wavelength converted light
emitting apparatus having a flip chip bonding structure in
accordance with the present invention;
[0030] FIG. 4 is a schematic sectional view illustrating one
example of a sputtering apparatus, which is for use in the
formation process of a phosphor layer in accordance with the
present invention; and
[0031] FIGS. 5a and 5b are side sectional views illustrating a
package containing a wavelength converted light emitting apparatus
in accordance with the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0032] FIG. 2 is a side sectional view illustrating a light
emitting apparatus in accordance with an embodiment of the present
invention.
[0033] Referring to FIG. 2, the light emitting apparatus,
designated as reference numeral 100, comprises a substrate 110, and
a light emitting diode 120 provided on the substrate 110 in a flip
chip bonding manner. In the present embodiment, the substrate 110
is a conductive silicone substrate, and formed on the upper surface
thereof with first and second conductive patterns 112 and 114.
[0034] The first conductive pattern 112 is formed on an insulation
layer 113, which is formed at the upper surface of the conductive
substrate 110 by making use of SiO.sub.2. The second conductive
pattern 114 is directly formed on the upper surface of the
conductive substrate 110. At a partial region of the first
conductive pattern 112 and at the second conductive pattern 114 are
formed connection bumps 116 and 118, respectively, which are for
use in the formation of flip chip bonding. The remaining portion of
the first conductive pattern 112, where the connection bump 116 is
not formed, serves as a terminal connection region, which will be
connected with an external terminal (not shown). The second
conductive pattern 114 is connected to a rear surface electrode 115
provided at the lower surface of the substrate 110 through the
conductive substrate 110.
[0035] The light emitting diode 120 comprises a transparent
substrate 121 made of sapphire, and a light emitting structure 125
formed at the transparent substrate 121. The light emitting
structure 125 has first and second electrodes 126a and 126b formed
to face the same direction, and may be a blue or ultraviolet light
emitting diode illustrated in FIG. 1a. That is, the light emitting
structure 125 has a mesa type structure consisting of a first
conductive GaN-based semiconductor layer, a multiple quantum well
GaN/InGaN-based active layer, and a second conductive GaN-based
semiconductor layer. The first and second electrodes 126a and 126b
are formed on the first and second conductive semiconductor layers,
respectively, thereby enabling them to face the same direction.
[0036] The light emitting diode 120 structured as stated above is
mounted on the substrate 110 in a flip chip bonding manner. More
particularly, the light emitting diode 120 is disposed on the upper
surface of the conductive substrate 110 so that the first and
second electrodes 126a and 126b are connected to the first and
second connection bumps 116 and 118, respectively, which are in
turn formed at the first and second conductive patterns 112 and
114. The first and second connection bumps 116 and 118 are means
for connecting the first and second electrodes 126a and 126b to
desired positions of the first and second conductive patterns 112
and 114, and fixing them at the desired positions, respectively.
The connection bumps can be made of common metals well known in the
art, such as Au, Pb/Sn, Au/Sn, Au/Ge, Au/Sn/Ge, Au/Pb/Sn or
Cu/Pb/Sn.
[0037] In the light emitting apparatus 100 comprising the light
emitting diode 120 mounted thereto in a flip-chip bonding manner,
light emitted from the light emitting diode 120 is mainly
discharged from a second surface of the light emitting diode 120,
that is, one surface of the transparent substrate 121 opposite to a
first surface of the light emitting diode 120 formed with the first
and second electrodes 126a and 126b. Further, a great portion of
the light is discharged through the side surface of the light
emitting diode 120. Therefore, the light emitting apparatus 100 in
accordance with the present invention is formed to have a phosphor
layer 130 throughout the light emitting surface of the light
emitting diode 120 in a uniform thickness. The phosphor layer is
made of any luminescent material for converting the wavelength of
ultraviolet or blue light, thereby achieving white light.
[0038] By virtue of the fact that the phosphor layer 130 is formed
throughout the second surface, as an essential light emitting
surface, and the side surface of the light emitting diode 120 so
that substantially all light passes the phosphor layer 130, the
light emitting apparatus 100 of the present invention can improve
its conversion efficiency into white light. A conventional
dispensing process for mixing phosphor powder and epoxy resin, and
spraying and hardening the resulting mixture inevitably causes a
non-uniformity in spatial distribution of phosphor particles. In
order to solve this non-uniformity problem, the phosphor layer of
the present invention can be formed by a sputtering method.
Alternatively, the phosphor layer can be formed by one selected
from among physical vapor deposition, chemical vapor deposition,
and spin coating methods. By using these methods, it is possible to
precisely form the phosphor layer 130 with a uniform thickness.
Therefore, a conventional problem of applying the phosphor layer by
an excessive thickness can be solved, thereby preventing the
generation of sparsely applied portions, which generally appear in
the conventional dispensing method.
[0039] As can be seen from FIG. 2, the phosphor layer 130 can be
formed to reach the upper surface of the conductive substrate 110
in order to sufficiently cover the light emitting surface of the
light emitting diode 120. In this case, the second conductive
pattern 114 of the present embodiment is connected to the rear
surface electrode 115 through the conductive substrate 110, and the
rear surface electrode 115 serves as a terminal connection region,
which will be connected to the outside, while the first conductive
pattern 112 has to define a certain region on the upper surface
thereof for allowing it to serve as a terminal connection region
capable of being connected to the outside through a wire (not
shown). Therefore, the certain partial region of the first
conductive pattern 112 is not formed with the phosphor layer
130.
[0040] FIGS. 3a to 3f are sectional views illustrating the
sequential steps of manufacturing the wavelength converted light
emitting apparatus having a flip chip bonding structure in
accordance with the present invention. The present embodiment shows
a manufacturing method of the light emitting apparatus having a
flip chip bonding structure at a wafer level.
[0041] As shown in FIG. 3a, the manufacturing method of the
wavelength converted light emitting apparatus in accordance with
the present invention begins with the step of preparing a wafer
160, which is formed at the upper surface thereof with an
insulation layer 163. The wafer 160 is a conductive silicone
substrate, and is for use as a substrate for allowing flip chip
bonding of individual chip type light emitting diodes. In general,
a silicone wafer can be used as the wafer 160. In FIG. 3a, each
region sectionalized by dotted lines shows a region corresponding
to a light emitting apparatus.
[0042] At the respective regions of the wafer 160, subsequently,
are formed a wiring structure for forming a flip chip bonded light
emitting apparatus, respectively. As shown in FIG. 3b, the
insulation layer 163 provided on the upper surface of the wafer 160
is formed thereon with first conductive patterns 162. Differently
from the first conductive patterns 162, second conductive patterns
164 are directly formed on the upper surface of the wafer 160 as a
conductive substrate after etching partial regions of the
insulation layer 163. Such direct formation of the second
conductive patterns on the wafer is for allowing connection
terminals, which will be connected to the outside, to be formed at
the lower surface of the wafer 160. Then, the wafer 160 as a
conductive substrate is formed at the lower surface thereof with
rear surface electrodes 165. Further, at a partial region of each
first conductive pattern 162 and at each second conductive pattern
164 are formed connection bumps 166 and 168, respectively, which
are for use in the mounting of light emitting diodes on the
conductive patterns. The connection bumps 166 and 168, as stated
above, can be formed by using common metals well known in the art,
such as Au, Pb/Sn, Au/Sn, Au/Ge, Au/Sn/Ge, Au/Pb/Sn, or
Cu/Pb/Sn.
[0043] In the next step, as shown in FIG. 3c, a plurality of light
emitting diodes 170 are mounted at individual regions of the wafer
160, respectively. The light emitting diodes 170 have a first
surface formed with first and second electrodes 176a and 176b, and
a second surface opposite to the first surface. The light emitting
diodes 170 can include a transparent substrate 171 such as a
sapphire substrate, and have a PN bonded light emitting structure
175 of a mesa shape wherein a first conductive semiconductor layer,
an active layer and a second conductive semiconductor layer are
successively stacked thereon in multiple layers. The light emitting
diodes 170 are mounted on the wafer 160 in such a fashion that
their first surfaces face downward, and the first and second
electrodes 176a and 176b thereof are connected and fixed to the
first and second conductive patterns 162 and 164 by using the
previously prepared connection bumps 166 and 168, respectively,
resulting in a desired flip chip bonding structure.
[0044] After completing the mounting of the light emitting diodes
170, the overall light emitting surface of the respective light
emitting diodes 170 are formed with a phosphor layer 180 having a
uniform thickness. In the respective light emitting diodes 170 flip
chip bonded as shown in FIG. 3c, the light emitting surface thereof
includes the second surface of the light emitting diode 170 coming
into contact with the transparent substrate, and the side surface
thereof. The present embodiment utilizes a vapor deposition method
in order to precisely form the phosphor layer in a uniform
thickness. FIGS. 3a to 3e illustrate the sequential steps of
forming the phosphor layer on the light emitting surface in
accordance with the present invention. The formation process of the
phosphor layer employed in the present invention begins with the
step of forming a photoresist pattern at a partial region of the
upper surface of at least one of the first and second conductive
patterns.
[0045] In the present embodiment, as shown in FIG. 3d, the first
conductive patterns 162 are formed with photoresist patterns 179 at
partial side regions serving as a terminal connection region,
respectively. The photoresist patterns 179 function to allow the
conductive patterns 162 to be connected to external terminals
through the terminal connection regions. The second conductive
patterns 164 generally define such terminal connection regions
through the rear surface electrodes 166. In case that the second
conductive patterns 164 are formed only on the upper surface of the
wafer 160 like the first conductive patterns 162, since a partial
region of the respective first conductive patterns 162 serves as a
terminal connection region to be connected to the outside through a
wire, the photoresist patterns 179 are formed so that they are not
formed with a phosphor layer during performing a subsequent vapor
deposition method.
[0046] Subsequent to the formation of the photoresist patterns 179,
the wafer 160, on which the light emitting diodes 170 are mounted,
is formed with a phosphor layer 180 by using a sputtering, physical
vapor deposition, chemical vapor deposition, or spin coating
method, and then the photoresist patterns 179 are removed. As a
result, as shown in FIG. 3e, it is possible to form the phosphor
layer throughout the second surface and side surface, as the light
emitting surface, of the respective light emitting diodes. The
phosphor layer obtained according to the present formation process
can be formed so as to reach the upper surface of the wafer and a
partial region of the conductive patterns, in order to sufficiently
cover the side region of the light emitting diodes. The phosphor
layer can be formed at desired regions by adjusting the position of
the photoresist patterns shown in FIG. 3d. In order to precisely
form the phosphor layer having a uniform thickness, a sputtering,
physical vapor deposition, chemical vapor deposition, or spin
coating method can be utilized.
[0047] By cutting the resulting wafer depicted in FIG. 3e by
predetermined distances, finally, it is possible to achieve a
desired wavelength converted light emitting apparatus as shown in
FIG. 3f. The wavelength converted light emitting apparatus is
mainly used as a white light emitting apparatus. In this case, its
light emitting diode may be a light emitting diode producing short
wavelength ultraviolet or blue light, and the phosphor layer can be
made of an appropriate luminescent material, which can produce
white light by converting such short wavelength light. The light
emitting apparatus shown in FIG. 3f can be manufactured to have a
package form shown in FIGS. 5a and 5b. This will be explained
hereinafter.
[0048] As stated above, the light emitting apparatus according to
the present invention can achieve good wavelength conversion
efficiency by forming the phosphor layer throughout the light
emitting surface, that is, the side surface and second surface of
the light emitting diode. Further, by virtue of the fact that the
phosphor layer is formed by using a vapor deposition method, it is
possible to precisely form the phosphor layer having a uniform
thickness.
[0049] In relation to the phosphor layer, the present invention can
use a vapor deposition apparatus suitable for improving step
coverage of the phosphor layer in order to achieve a more uniform
thickness. FIG. 4 is a schematic sectional view illustrating one
example of a sputtering apparatus, which is for use in the
formation process of the phosphor layer in accordance with the
present invention.
[0050] Referring to FIG. 4, the sputtering apparatus 200 can be
defined by a vacuum chamber, in which a phosphor source 207 and a
rotatable support 205 are mounted. The support 205 takes a
semi-spherical structure so as to allow a mounted wafer and the
phosphor source 207 to form a certain inclination angle. For
achieving improvement of step coverage, the sputtering apparatus
200 is constructed so that the mounted wafer as well as the support
itself are rotatable. By performing a vapor deposition method with
the sputtering apparatus constructed as stated above, it is
possible to form the phosphor layer having a substantially uniform
thickness throughout the second surface and side surface of the
light emitting diode, which is mounted on the wafer in a flip chip
bonding manner. The sputtering apparatus shown in FIG. 4 is given
only as an example, and the present invention can preferably use
other vapor deposition apparatuses or methods well known in the art
for achieving improvement of step coverage.
[0051] FIGS. 5a and 5b are side sectional views illustrating a
package containing the wavelength converted light emitting
apparatus in accordance with the present invention.
[0052] As shown in FIGS. 5a and 5b, the light emitting apparatus of
the present invention can be manufactured to have a package form
similar to that shown in FIG. 1b. Referring to FIGS. 5a and 5b, the
package, designated as reference numeral 300, employing the light
emitting apparatus of the present invention comprises a cup shaped
package structure 242. To the package structure 242 is mounted a
package substrate 244, on which first and second lead frames (not
shown) are provided at separated different regions, respectively.
At a certain region of the substrate 244 connected to the second
lead frame is mounted a light emitting apparatus 250, which is
further connected to the remaining region of the substrate 244
connected to the first lead frame through a wire 245.
[0053] In this way, a light emitting diode 230 provided in the
light emitting apparatus comprises a first electrode 236a, which
can be connected to the second lead frame (not shown) through a
first conductive pattern 222 and the wire 245, and a second
electrode 236b, which can be electrically connected to the first
lead frame (not shown) provided at the package substrate 244
through a second conductive pattern 224, conductive substrate 220,
and rear surface electrode 225. In such a connection structure,
when a certain driving voltage is applied to the first and second
lead frames, an active layer 233 of the light emitting diode 230
produces ultraviolet or blue light of a short wavelength, and the
produced light is converted through a phosphor layer 240
surrounding the overall light emitting surface of the light
emitting diode, thereby producing white light.
[0054] In the present invention, especially, the electrical
connection structure, defined on the conductive substrate for flip
chip bonding, can be variously changed, and its defining process
can be embodied differently from that shown in FIGS. 5a and 5b.
That is, instead of using the conductive substrate, the first and
second conductive patterns are formed on the upper surface of a
nonconductive substrate, and then only the second conductive
pattern is connected to the rear surface electrode through a
conductive via hole. Further, instead of previously forming the
insulation layer on the upper surface of the wafer, the insulation
layer can be formed after forming the second conductive
pattern.
[0055] As apparent from the above description, the present
invention provides a light emitting apparatus, which is configured
in such a fashion that a light emitting diode is mounted on a
substrate in a flip chip bonding manner, and a phosphor layer is
formed throughout the light emitting surface of the light emitting
diode, resulting in an improved light wavelength conversion
efficiency. Further, according to the present invention, it is
possible to precisely form the phosphor layer having a uniform
thickness by using a vapor deposition method, thereby eliminating a
non-uniformity in spatial distribution of phosphor particles caused
in a dispensing process.
[0056] Although the preferred embodiment of the present invention
have been disclosed for illustrative purposes, those skilled in the
art will appreciate that various modifications, additions and
substitutions are possible, without departing from the scope and
spirit of the invention as disclosed in the accompanying
claims.
* * * * *