U.S. patent application number 14/209325 was filed with the patent office on 2014-07-10 for light emitting semiconductor structure.
This patent application is currently assigned to SemiLEDs Optoelectronics Co., Ltd.. The applicant listed for this patent is SemiLEDs Optoelectronics Co., Ltd., VisEra Technologies Company Limited. Invention is credited to Wu-Cheng KUO.
Application Number | 20140191260 14/209325 |
Document ID | / |
Family ID | 46926048 |
Filed Date | 2014-07-10 |
United States Patent
Application |
20140191260 |
Kind Code |
A1 |
KUO; Wu-Cheng |
July 10, 2014 |
LIGHT EMITTING SEMICONDUCTOR STRUCTURE
Abstract
The invention provides a light emitting semiconductor structure,
which includes a substrate; a first LED chip formed on the
substrate; an adhesion layer formed on the first LED chip; and a
second light emitting diode chip formed on the adhesion layer,
wherein the second LED chip has a first conductive wire which is
electrically connected to the substrate.
Inventors: |
KUO; Wu-Cheng; (Hsinchu
City, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SemiLEDs Optoelectronics Co., Ltd.
VisEra Technologies Company Limited |
Miao-Li County
Hsin-Chu City |
|
TW
TW |
|
|
Assignee: |
SemiLEDs Optoelectronics Co.,
Ltd.
Miao-Li County
TW
VisEra Technologies Company Limited
Hsin-Chu City
TW
|
Family ID: |
46926048 |
Appl. No.: |
14/209325 |
Filed: |
March 13, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13078541 |
Apr 1, 2011 |
8735913 |
|
|
14209325 |
|
|
|
|
Current U.S.
Class: |
257/89 |
Current CPC
Class: |
H01L 2224/48091
20130101; H01L 33/62 20130101; H01L 25/0756 20130101; H01L
2924/00014 20130101; H01L 2224/73265 20130101 |
Class at
Publication: |
257/89 |
International
Class: |
H01L 33/62 20060101
H01L033/62 |
Claims
1-5. (canceled)
6. A light emitting semiconductor structure light emitting
semiconductor structure, comprising: a substrate; a first LED chip
formed on the substrate; an adhesion layer formed on the first LED
chip; a second LED chip formed on the adhesion layer, wherein the
second LED chip has a first conductive wire which is electrically
connected to the substrate; a second adhesion layer formed on the
second LED chip; and a third LED chip formed on the second adhesion
layer.
7. The light emitting semiconductor structure as claimed in claim
6, wherein the second LED chip has a third surface contacting the
second adhesion layer, the third LED chip has a fourth surface
contacting the second adhesion layer, and the third surface is
insulated from the fourth surface.
8. The light emitting semiconductor structure as claimed in claim
6, wherein the third LED chip has a third conductive wire which is
electrically connected to the substrate.
9. The light emitting semiconductor structure as claimed in claim
6, wherein the first LED chip, the second LED chip and the third
LED chip emit three different colors of light.
10. The light emitting semiconductor structure as claimed in claim
9, wherein the three different colors of light comprises blue
light, green light and red light.
11. The light emitting semiconductor structure as claimed in claim
9, wherein the three different colors of light comprises blue
light, yellow light and red light.
12. The light emitting semiconductor structure as claimed in claim
6, further comprising a phosphor coated on the first LED chip, the
second LED chip and the third LED chip.
13. The light emitting semiconductor structure as claimed in claim
6, further comprising a third LED chip formed on the adhesion
layer.
14. The light emitting semiconductor structure as claimed in claim
13, wherein the first LED chip has a first surface contacting the
adhesion layer, the third LED chip has a fifth surface contacting
the contacting the adhesion layer, and the first surface is
insulated from the fifth surface.
15. The light emitting semiconductor structure as claimed in claim
13, wherein the third LED chip has a third conductive wire which is
electrically connected to the substrate.
16. The light emitting semiconductor structure as claimed in claim
13, wherein the first LED chip, the second LED chip and the third
LED chip emit three different colors of light.
17. The light emitting semiconductor structure as claimed in claim
16, wherein the three different colors of light comprises blue
light, green light and red light.
18. The light emitting semiconductor structure as claimed in claim
16, wherein the three different colors of light comprises blue
light, yellow light and red light.
19. The light emitting semiconductor structure as claimed in claim
13, further comprising a phosphor coated on the first LED chip, the
second LED chip and the third LED chip.
20. The light emitting semiconductor structure as claimed in claim
6, further comprising a phosphor coated on the first LED chip and
the second LED chip.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Divisional of co-pending application
Ser. No. 13/078,541, filed on Apr. 1, 2011, for which priority is
claimed under 35 U.S.C. .sctn.120, the entire contents of which are
hereby incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a light emitting
semiconductor structure and in particular relates to a light
emitting semiconductor structure with at least two LED chips.
[0004] 2. Description of the Related Art
[0005] Because light emitting semiconductor structure have several
advantages over conventional lamps, such as a long lifetime, a
small size, low power consumption, high response speed, etc.,
considerable research attention has been recently focused on
development thereof.
[0006] Conventionally, one way to generate a white light emitting
semicondcutor structure is to coat or fill a yellow phosphor on a
blue LED chip. The blue light emitted by the LED chip is then mixed
with the complimentary yellow light from phosphor to generate white
light.
[0007] The other way to generate a white light emitting
semiconductor structure is to mix different colors emitted from a
plurality of the LEDs to produce a white light emitting diode. U.S.
Pat. No. 7,005,667 discloses a light emitting diode, wherein a blue
LED chip is arranged parallel to a blue-complimentary LED chip
(such as yellow LED chip) to generate white light. However, two
LEDs are arranged in the same plane and thus occupy too much area.
Therefore, the package size of the light emitting semiconductor
structure can not be reduced.
[0008] Therefore, there is a need to develop a light emitting
semiconductor structure which has a small package size to simplify
the design of the secondary optical lens in the subsequent
steps.
BRIEF SUMMARY OF THE INVENTION
[0009] The present invention provides a light emitting
semiconductor structure, comprising: a substrate; a first LED chip
formed on the substrate; an adhesion layer formed on the first LED
chip; and a second light emitting diode chip formed on the adhesion
layer, wherein the second LED chip has a first conductive wire
which is electrically connected to the substrate
[0010] A detailed description is given in the following embodiments
with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The present invention can be more fully understood by
reading the subsequent detailed description and examples with
references made to the accompanying drawings, wherein:
[0012] FIG. 1A to 1B show cross-sectional schematic representations
of a light emitting semiconductor structure in accordance with
embodiments of the invention;
[0013] FIG. 2 shows a cross-sectional schematic representation of a
light emitting semiconductor structure in accordance with a second
embodiment of the invention;
[0014] FIG. 3 shows a cross-sectional schematic representation of a
light emitting semiconductor structure in accordance with a third
embodiment of the invention;
[0015] FIG. 4A to 4B show cross-sectional schematic representations
of a light emitting semiconductor structure in accordance with a
fourth embodiment of the invention; and
[0016] FIG. 5 shows a cross-sectional schematic representation of a
light emitting semiconductor structure in accordance with a fifth
embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0017] The following description is of the best-contemplated mode
of carrying out the invention. This description is made for the
purpose of illustrating the general principles of the invention and
should not be taken in a limiting sense. The scope of the invention
is best determined by reference to the appended claims.
[0018] The following descriptions of FIG. 1 to FIG. 5 are used to
describe a light emitting semiconductor structure of the invention.
The drawings are idealized representations for better illustration
of the structure of the invention, and various elements are not
necessarily shown to scale.
[0019] FIG. 1A shows a cross-sectional schematic representation of
an embodiment of a light emitting semiconductor structure 10. The
light emitting semiconductor structure 10 comprises two light
emitting diode chips which are vertically stacked and emit
different colors of light to produce a white light.
[0020] The light emitting semiconductor structure 10 comprises a
substrate 100, a first LED chip 200, an adhesion layer 300 and a
second LED chip 400, wherein the first LED chip 200 is formed on
the substrate 100, the adhesion layer 300 is formed on the first
LED chip 200, and the second LED chip 400 is formed on the adhesion
layer 300. The second LED chip 400 has a first conductive wire 450
which is electrically connected to the substrate 100.
[0021] The material of the substrate 100 comprises silicon
substrate, ceramic substrate or lead frame. The first LED chip 200
or the second LED chip 400 comprises a sub-substrate, an N-type
conductive layer, an active layer and a P-type conductive layer.
The adhesion layer 300, such as transparent adhesive glue, is used
to combine the first LED chip 200 and the second LED chip 400
together. The first LED chip 200 comprises a first pad 210 and a
second pad 212 which are electrically connected to the substrate
100. Additionally, a connective layout (not shown) is formed
between the substrate 100 and the firs pad 210 and second pad 212,
and the conductive layout may be a conventional adhesive or metal
bump (such as solder, gold or aluminum bumps).
[0022] FIG. 1B shows a detailed schematic representation of the
light emitting semiconductor structure 10 of FIG. 1A. A first
conductive type semiconductor layer 204, an active layer 206 and a
second conductive type semiconductor layer 208 are in sequence
formed on a sub-substrate 202. The first pad 210 is formed on the
first conductive type, semiconductor layer 204, and the second pad
212 is formed on the second conductive type semiconductor layer
208.
[0023] The first conductive type semiconductor layer 204 or the
second conductive type semiconductor layer 208 are made of a III-V
compound semiconductor. In one embodiment, the first conductive
type semiconductor layer 204 is an N-type nitride, and the second
conductive type semiconductor layer 208 is a P-type nitride. In
another embodiment, the first conductive type semiconductor layer
204 is a P-type nitride, and the second conductive type
semiconductor layer 208 is an N-type nitride. The first conductive
type semiconductor layer 204 may optionally be doped with silicon
(Si) and the second conductive type semiconductor layer 208 may
optionally be doped with zinc (Zn) or magnesium (Mg).
[0024] Likewise, a first conductive type semiconductor layer 404,
an active layer 406 and a second conductive type semiconductor
layer 408 are in sequence formed on a sub-substrate 402. The third
pad 410 is formed on the first conductive type semiconductor layer
404, and the fourth pad 412 is formed on the second conductive type
semiconductor layer 408.
[0025] In FIG. 1A, the first LED chip 200 is electrically connected
to the substrate 100 by a flip-chip method, and more specifically,
the first LED chip 200 is electrically connected to the substrate
100 by the first pad 210 and the second pad 212. The second LED
chip 400 is electrically connected to the substrate 100 by a wire
bonding method, and more specifically, the second LED chip 400 is
electrically connected to the substrate 100 by the third pad 410
and the fourth pad 414 through the first conductive wire 450.
[0026] The first LED chip 200 and the second LED chip 400 may be
electrically connected in parallel or in series with each other. In
one embodiment, the first LED chip 200 has a P-type first pad 210P
and an N-type second pad 212N, and the second LED chip 400 has a
P-type third pad 410P and an N-type fourth pad 412N, and the P-type
first pad 210P is electrically connected to the P-type third pad
410P by an electrical interconnection built on the substrate and
the N-type second pad 212N is electrically connected to the N-type
fourth pad 412N by another electrical interconnection built on the
substrate. Thus, the first LED chip 200 and the second LED chip 400
are electrically connected in parallel with each other.
[0027] In another embodiment, the first LED chip 200 has a P-type
first pad 210P and an N-type second pad 212N, and the second LED
chip 400 has an N-type third pad 410N and a P-type fourth pad 412P,
and the P type first pad 210P is electrically connected to the
N-type third pad 410N by an electrical interconnection built on the
substrate and the N-type second pad 212N is electrically connected
to the P-type fourth pad 412P by another electrical interconnection
built on the substrate. Thus, the first LED chip 200 and the second
LED chip 400 are electrically connected in series with each
other.
[0028] Note that in FIG. 1 the first LED chip 200 and the second
LED chip 400 are combined by the adhesion layer 300. Thus, the
first LED chip 200 and the second LED chip 400 are insulated from
each other by the adhesion layer 300. More specifically, the first
LED chip 200 has a first surface 200a contacting the adhesion layer
300, the second LED chip 400 has a second surface 400a contacting
the adhesion layer 300, and the first surface 200a is insulated
from the second surface 400a by the adhesion layer 300. In other
words, there is no electrical connection between the first surface
200a and the second surface 400a. Because the first surface 200a is
insulated from the second surface 400a, the electrical connection
relationship between the first LED chip 200 and the second LED chip
400 depends on the electrical interconnections built on the
substrate.
[0029] In one embodiment, the first LED chip 200 emits blue light
and the second LED chip 400 emits yellow light. The blue light is
mixed with the yellow light to generate white light. In another
embodiment, the first LED chip 200 emits yellow light and the
second LED chip 400 emits blue light.
[0030] FIG. 2 shows a cross-sectional schematic representation of a
second embodiment of a light emitting semiconductor structure 20,
wherein like elements are identified by the same reference numbers
as in FIG. 1A, and are thus omitted for clarity. The difference
between FIG. 2 and FIG. 1A is that a plurality of second LED chips
400 shown in FIG. 2. In FIG. 2, there are at least two second LED
chips 400 formed on the adhesion layer 300, and thus a size of
these second LED chips 400 is smaller than a size the first LED
chip 200. The advantage of the second embodiment is that these
second LED chips 400 may be arranged in any shape, such as
circular, triangular, rectangular, or irregular shapes (from a top
view of the LED 20, not shown in the Figure), depending on actual
application needs.
[0031] FIG. 3 shows a cross-sectional schematic representation of a
third embodiment of a light emitting semiconductor structure 30,
wherein like elements are identified by the same reference numbers
as in FIG. 1A, and are thus omitted for clarity. The difference
between FIG. 3 and FIG. 1A is that the first LED chips 200 is
electrically connected to the substrate 100 by a wire bonding
method in FIG. 3. As shown in FIG. 3, a silver glue 150 is formed
on the substrate 100 and the first LED chip 200 is formed on the
silver glue 150. Additionally, the first LED chip 200 has a second
conductive wire 250 which is electrically connected to the
substrate 100. Note that the first LED chip 200 has the second
conductive wire 250 which occupies some surface areas of the first
LED chip 200, and thus a size of the second LED chip 400 is smaller
than a size the first LED chip 200.
[0032] Note that in the third embodiment, the first LED chip 200
and the second LED chip 400 are combined by the adhesion layer 300.
Thus, the first LED chip 200 and the second LED chip 400 are
insulated from each other by the adhesion layer 300. More
specifically, the first LED chip 200 has a first surface 200a
contacting the adhesion layer 300, the second LED chip 400 has a
second surface 400a contacting the adhesion layer 300, and the
first surface 200a is insulated from the second surface 400a by the
adhesion layer 300. In other words, there is no electrical
connection between the first surface 200a and the second surface
400a. Because the first surface 200a is insulated from the second
surface 400a, the electrical connection relationship of the first
LED chip 200 and the second LED chip 400 depends on the electrical
interconnections built on the substrate.
[0033] FIG. 4A shows a cross-sectional schematic representation of
a fourth embodiment of a light emitting semiconductor structure 40,
wherein like elements are identified by the same reference numbers
as in FIG. 1A, and are thus omitted for clarity. The difference
between FIG. 4A and FIG. 1A is that an additional third LED chip
600 is shown in FIG. 4A. A second adhesion layer 500 is formed on
the second LED chip 400, and a third LED chip 600 is formed on the
second adhesion layer 500. Furthermore, the third LED chip 600 has
a third conductive wire 650 which is electrically connected to the
substrate 100 by a wire bonding method.
[0034] Note that the advantage of the third embodiment is that
several monochromatic colors emitted by the LED chips 200, 400, and
600 are mixed to improve the color rendering index (CRI) of the LED
40.
[0035] Additionally, in FIG. 4A the second LED chip 400 and the
third LED chip 600 are combined by the second adhesion layer 500.
Thus, the second LED chip 400 and the third LED chip 600 are
insulated from each other by the second adhesion layer 500. More
specifically, the second LED chip 400 has a third surface 400b
contacting the second adhesion layer 500, the third LED chip 600
has a fourth surface 600a contacting the second adhesion layer 500,
and the third surface 400b is insulated from the fourth surface
600a by the second adhesion layer 500. In other words, there is no
electrical connection between the third surface 400b and the fourth
surface 600a.
[0036] In one embodiment, the first LED chip 200, the second LED
chip 400 and the third LED chip 600 emit three different colors of
light. The three different colors of light comprise blue light,
green light and red light. Thus, there are six permutations. In one
embodiment, the first LED chip 200 emits blue light, the second LED
chip 400 emits green light and the third LED chip 600 emits red
light. In another embodiment, the first LED chip 200 emits green
light, the second LED chip 400 emits blue light and the third LED
chip 600 emits red light. In yet another embodiment, the first LED
chip 200 emits red light, the second LED chip 400 emits green light
and the third LED chip 600 emits blue light. In one embodiment, the
first LED chip 200 emits green light, the second LED chip 400 emits
red light and the third LED chip 600 emits blue light.
[0037] In another embodiment, the first LED chip 200, the second
LED chip 400 and the third LED chip 600 emit three different colors
of light. The three different colors of light comprise blue light,
yellow light and red light. Thus, there are six permutations. In
one embodiment, the first LED chip 200 emits blue light, the second
LED chip 400 emits yellow light and the third LED chip 600 emits
red light. In another embodiment, the first LED chip 200 emits
yellow light, the second LED chip 400 emits blue light and the
third LED chip 600 emits red light. In yet another embodiment, the
first LED chip 200 emits red light, the second LED chip 400 emits
yellow light and the third LED chip 600 emits blue light. In one
embodiment, the first LED chip 200 emits blue light, the second LED
chip 400 emits red light and the third LED chip 600 emits yellow
light.
[0038] FIG. 4B shows a modified fourth embodiment of the light
emitting semiconductor structure 40, wherein the third LED chip 600
is formed on the adhesion layer 300 rather than the second adhesion
layer 500. In other words, the third LED chip 600 is formed on the
first LED chip 200. Likewise, the third LED chip 600 has a third
conductive wire 650 which is electrically connected to the
substrate 100 by a wire bonding method. More specifically, the
first LED chip 200 has a first surface 200a contacting the adhesion
layer 300, the third LED chip 600 has a fifth surface 600b
contacting the adhesion layer 300, and the first surface 200a is
insulated from the fifth surface 600b by the adhesion layer
300.
[0039] FIG. 5 shows a cross-sectional schematic representation of a
fifth embodiment of a light emitting semiconductor structure 50,
wherein like elements are identified by the same reference numbers
as in FIG. 1A, and are thus omitted for clarity. The difference
between FIG. 5 and FIG. 1A is that an additional phosphor 700 is
coated on the first LED chip 200 and the second LED chip 400. A
white light is generated by mixing at least two LED chips 200, and
400 and the phosphor 700.
[0040] In one embodiment, one of the first LED chip 200 or the
second LED chip 400 emits blue light, the other emits red light,
and the phosphor 700 emits yellow light.
[0041] In another embodiment, one of the first LED chip 200 or the
second LED chip 400 emits blue light, the other emits yellow light,
and the phosphor 700 emits green light.
[0042] In yet another embodiment, the phosphor 700 is coated on
third LED chip 600 of FIG. 4A. Thus, a white light is generated by
mixing three LED chips 200, 400, and 600 and the phosphor 700. Note
that the monochromatic color lights emitted by the LED chips or the
phosphor are not limited to the above descriptions; thus, those
skilled in the art may adjust the colors of the LED chips or
phosphor according to actual application needs.
[0043] The invention provides a light emitting semiconductor
structure in which at least two LED chips are vertically stacked.
Compared with the LED chips arranged in the same plane, the
semiconductor structure of the invention has a smaller package
size. Thus, in sequential steps, a secondary optical lens may be
easily designed. Additionally, several monochromatic colors emitted
by the LED chips are mixed to generate and to improve the color
rendering index (CRI) of the semiconductor structure of the
invention.
[0044] While the invention has been described by way of example and
in terms of the preferred embodiments, it is to be understood that
the invention is not limited to the disclosed embodiments. To the
contrary, it is intended to cover various modifications and similar
arrangements (as would be apparent to those skilled in the art).
Therefore, the scope of the appended claims should be accorded the
broadest interpretation so as to encompass all such modifications
and similar arrangements.
* * * * *