U.S. patent application number 14/985165 was filed with the patent office on 2017-07-06 for light emitting device.
The applicant listed for this patent is EPISTAR CORPORATION. Invention is credited to CHIEN CHENG HUANG, YU-WEI KUO, PEI-HSIANG TSENG, YAO-WEI YANG, KUO-WEI YEN.
Application Number | 20170194531 14/985165 |
Document ID | / |
Family ID | 59226987 |
Filed Date | 2017-07-06 |
United States Patent
Application |
20170194531 |
Kind Code |
A1 |
HUANG; CHIEN CHENG ; et
al. |
July 6, 2017 |
LIGHT EMITTING DEVICE
Abstract
A light emitting device, includes a substrate; a plurality of
light emitting stacked layers, comprising a first surface and a
second surface; a mesa structure; a current blocking (CB) layer; a
transparent conductive layer; a first pad electrode and a second
pad electrode; and a passivation layer, wherein the second surface
is electrically opposite to the first surface, the transparent
conductive layer is disposed on or above the first surface, the
first pad electrode is disposed on the transparent conductive layer
and on the first surface, and the second pad electrode is disposed
on the second surface and on the mesa structure, the CB layer is
disposed on the first surface, surrounded by the transparent
conductive layer, and at a lower region of the first pad electrode,
a portion of the first pad electrode is filling a first opening of
the transparent conductive layer and the CB layer.
Inventors: |
HUANG; CHIEN CHENG;
(Hsinchu, TW) ; YEN; KUO-WEI; (Hsinchu, TW)
; KUO; YU-WEI; (Hsinchu, TW) ; YANG; YAO-WEI;
(Hsinchu, TW) ; TSENG; PEI-HSIANG; (Hsinchu,
TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
EPISTAR CORPORATION |
Hsinchu |
|
TW |
|
|
Family ID: |
59226987 |
Appl. No.: |
14/985165 |
Filed: |
December 30, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 33/38 20130101;
H01L 33/32 20130101; H01L 33/24 20130101; H01L 2933/0025 20130101;
H01L 33/44 20130101; H01L 33/0075 20130101; H01L 33/42 20130101;
H01L 2933/0016 20130101; H01L 33/145 20130101 |
International
Class: |
H01L 33/14 20060101
H01L033/14; H01L 33/24 20060101 H01L033/24; H01L 27/15 20060101
H01L027/15; H01L 33/42 20060101 H01L033/42; H01L 33/44 20060101
H01L033/44; H01L 33/38 20060101 H01L033/38; H01L 33/00 20060101
H01L033/00; H01L 33/32 20060101 H01L033/32 |
Claims
1. A light emitting device, comprising: a substrate; a plurality of
light emitting stacked layers, comprising a first surface and a
second surface; a mesa structure; a current blocking (CB) layer; a
transparent conductive layer; a first pad electrode and a second
pad electrode; and a passivation layer, wherein the second surface
is electrically opposite to the first surface, the transparent
conductive layer is disposed on or above the first surface, the
first pad electrode is disposed on the transparent conductive layer
and on the first surface, and the second pad electrode is disposed
on the second surface and on the mesa structure, the CB layer is
disposed on the first surface, surrounded by the transparent
conductive layer, and at a lower region of the first pad electrode,
a portion of the first pad electrode is filling a first opening of
the transparent conductive layer and the CB layer.
2. The light emitting device as claimed in claim 1, wherein a
sidewall of the CB layer comprises a first surface section and a
second surface section having different slopes, the first surface
section has a slope of between 10 degrees to 50 degrees and the
second surface section has a slope of 50 degrees to 70 degrees, the
first surface section is disposed closer than the second surface
section to the first surface of the light emitting stacked
layers.
3. The light emitting device as claimed in claim 1, wherein a
sidewall of the transparent conductive layer and a sidewall of the
light emitting stacked layers are substantially flush located
adjacent to one end of the second surface of the light emitting
stacked layers and the mesa structure, and adjacent to one end of
the first surface of the light emitting stacked layers.
4. The light emitting device as claimed in claim 1, wherein a
retract distance of the transparent conductive layer with respect
to an edge of the mesa structure is less than 3 .mu.m.
5. The light emitting device as claimed in claim 1, wherein a
retract distance of the transparent conductive layer with respect
to an edge of the mesa structure is 1 to 2 .mu.m.
6. The light emitting device as claimed in claim 1, wherein the
first pad electrode on the first surface is filling the first
opening of the transparent conductive layer and in contact with a
thinner portion of the CB layer between the first pad electrode and
the first surface.
7. The light emitting device as claimed in claim 1, wherein the
first pad electrode on the first surface is filling the first
opening of the transparent conductive layer and in contact with the
first surface.
8. The light emitting device as claimed in claim 1, wherein the CB
layer has a ring-shape in a top view of the light emitting
device.
9. The light emitting device as claimed in claim 1, wherein the
plurality of light emitting stacked layers comprises a first
semiconductor layer, a second semiconductor layer, and an active
layer interposed between the first semiconductor layer and the
second semiconductor layer.
10. The light emitting device as claimed in claim 9, wherein the
mesa structure comprises a second opening exposing the second
layer, and the second pad electrode is formed in the second opening
of the mesa structure and in contact with the second layer.
11. (canceled)
12. (canceled)
13. (canceled)
14. (canceled)
15. (canceled)
16. (canceled)
17. (canceled)
18. (canceled)
19. (canceled)
20. (canceled)
Description
BACKGROUND OF THE APPLICATION
[0001] (a) Technical Field
[0002] The present application is related to a light emitting
device and method of fabricating the same, and more particularly,
to a light emitting device fabricated by chip on wafer processes
with photolithography adopting a technique using a current blocking
(CB) layer serving as a hard mask.
[0003] (b) Description of Background Art
[0004] The typical chip on wafer processes for fabricating a
horizontal III-nitride based LED chip includes the following steps:
first, the light emitting stacked layers (which typically includes
p-type layers, n-type layers, and an active layer made from an
inorganic semiconductor material sandwiched between one of the
p-type layers and one of the n-type layers) are etched to form a
mesa structure (requiring a first photolithography process).
Second, a current blocking (CB) layer is formed on one of the upper
LED stacked layer, and located underneath a p-side electrode, by
wet etching (second photolithography process). Third, an ITO layer
is formed to be covering the light emitting stacked layers, and
exposing a reserved region for a p-side pad electrode of the p-side
electrode and the mesa structure (third photolithography process).
Fourth, p, n-side pad electrodes/finger electrodes are formed
(fourth photolithography process). Fifth, a passivation layer is
deposited over the entire top surface of the horizontal nitride LED
chip except p, n-side pad electrodes (fifth photolithography
process). Thus, conventional technique for fabricating the
horizontal III-nitride based LED chip typically includes at least
five separate photolithography processes, in which each time, the
photolithography process requires the following individual
sub-steps: cleaning and preparation of a photoresist-coated
surface, applying and coating a photoresist layer onto a material
layer such as by spin coating, performing exposure and developing
after prebaking to form a patterned photoresist mask, performing
wet or dry etching using the patterned photoresist mask, and
removing the remaining patterned photoresist layer. In the
above-described first step, the mesa structure etching process can
be performed using inductively coupled plasma (ICP) etching to
expose the n-type layer, such as a n-GaN layer (forming the n-mesa)
upon etching a portion of the p-type layer, such as a p-GaN layer
and the active layer (or can be also referred to as multiple
quantum wells, MQW). Meanwhile, for the sake of preventing ITO
layer pattern shift issues, for example leakage current issues
between residue ITO and light emitting stacked layers sidewalls,
the subsequent four photolithography processes are required to use
the resulting mesa pattern obtained at the completion of the first
photolithography process, as alignment reference. As a result, the
conventional fabrication method for LED chip can be more time
consuming (higher cycle time) and requires relatively high process
costs.
SUMMARY OF THE APPLICATION
[0005] One purpose of the present application is to provide a light
emitting device, such as an LED chip, or a laser diode (LD) that is
fabricated by chip on wafer processes with photolithography
adopting a technique using a current blocking (CB) layer serving as
a hard mask.
[0006] Another purpose of the present application is to provide a
method for fabricating a light emitting device, such as an LED
chip, or a laser diode (LD), having more efficient and less costly
chip on wafer photolithography processes
[0007] To achieve at least one of the purposes, a method for
fabricating a light emitting device comprising the following steps
is disclosed herein in accordance with an embodiment of present
application: first, a plurality of light emitting stacked layers
(which typically includes p-type layers, n-type layers, and a
planar active layer made from an inorganic semiconductor material
sandwiched between one of the p-type layers and one of the n-type
layers) are formed above a substrate. Second, a current blocking
(CB) layer is coated and patterned on the LED stacked layers.
Third, a transparent conductive layer, such as an ITO layer is
formed covering the light emitting stacked layers and the current
blocking (CB) layer. Fourth, the transparent conductive layer is
etched and exposing a reserved region for a pad electrode and for a
mesa structure. The reserved region includes an exposed portion of
the light emitting stacked layers and an exposed portion of the
current blocking layer. Fifth, the exposed portion of the light
emitting stacked layers and the substantial portion of the current
blocking layer are dry-etched to form the mesa structure and a pad
opening for the p-pad electrode. Sixth, for an option A, the
current blocking layer is not wet-etched but dry etched under
inductively coupled plasma (ICP), and leaves behind 1000.about.2000
angstrom in thickness, and a p-pad electrode is formed by filling
the pad opening above the remaining current blocking layer having
1000.about.2000 angstrom in thickness, and another pad electrode
(n-pad) is formed on the mesa structure. Meanwhile, for an option
B, after the ICP dry etching, the current blocking layer is
wet-etched to be completely removed, and a pad electrode (p-pad
electrode) is formed by filling the pad opening and another pad
electrode (n-pad electrode) is formed on the mesa structure.
Seventh, a passivation layer is deposited over the entire or
selected surface of the light emitting device.
[0008] To achieve at least one of the purposes, a light emitting
device which includes a substrate, a plurality of light emitting
stacked layers, a mesa structure, a current blocking layer, a
transparent conductive layer, such as an ITO layer, a p-pad
electrode, a n-pad electrode, and a passivation layer is disclosed
herein for the embodiment of present application. The light
emitting stacked layers comprising a first surface and a second
surface, in which the second surface is closer to the substrate and
is electrically opposite to the first surface. The transparent
conductive layer is disposed and formed on or above the first
surface of the light emitting stacked layers. The p-pad electrode
is disposed on the transparent conductive layer and on the first
surface of the light emitting stacked layers, and the n-pad
electrode is disposed on the second surface of the light emitting
stacked layers and on the mesa structure. The CB layer is disposed
on the first surface of light emitting stacked layers, surrounded
by the transparent conductive layer, and at a lower region of the
p-pad electrode. In addition, the transparent conductive layer has
an opening in which a portion of the p-pad electrode is filling the
opening of the transparent conductive layer. The CB layer has a
pattern such as a ring shape when shown in a top view of the light
emitting device.
[0009] To achieve at least one of the purposes, a sidewall of the
CB layer includes two surface sections having different slopes
under cross-sectional view, in which one of the surface section has
a slope of 10 degrees to 50 degrees and the other one surface
section has a slope greater than that of the one and smaller than
or equal to 90 degrees. The sidewall of the transparent conductive
layer and the sidewall of the light emitting stacked layers are
substantially flush and planar to one another located adjacent to
the second surface of light emitting stacked layers and the mesa
structure, and adjacent to one end of the first surface of light
emitting stacked layers.
[0010] To achieve at least one of the purposes and to prevent
residue transparent conductive layer from causing leakage current
issues for the light emitting device, embodiments of present
application adopt a self-alignment process for performing
photolithography process, in which the transparent conductive
layer, the patterned CB layer, and the mesa structure are formed
using the same photoresist mask, and performed at the same step,
the sidewall of the transparent conductive layer and the sidewall
of the mesa structure are substantially coplanar or flush, and the
transparent conductive layer can be retracted a shorter
gap/distance as measured from edge of the mesa structure or the CB
layer, of 1 to 2 .mu.m in a preferred embodiment, or less than 3
.mu.m, for other embodiments for the transparent conductive layer.
Such retract distance for ITO-to-mesa or ITO-to-CB is much less
than the retracting gap/distance of conventional fabrication method
which typically has an ITO-to-mesa or ITO-to-CB retract distance of
5 .mu.m to 7 .mu.m.
[0011] These and other objectives of the present application will
no doubt become obvious to those of ordinary skill in the art after
reading the following detailed description of the preferred
embodiment that is illustrated in the various figures and
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The present application is illustrated by way of example and
not limited by the figures of the accompanying drawings in which
same references indicate similar elements. Many aspects of the
disclosure can be better understood with reference to the following
drawings. Moreover, in the drawings same reference numerals
designate corresponding elements throughout. Wherever possible, the
same reference numerals are used throughout the drawings to refer
to the same or similar elements of an embodiment.
[0013] FIG. 1 shows a flow chart of a method for fabricating a
light emitting device according to an embodiment of present
application.
[0014] FIG. 2(a) shows cross-sectional views of a plurality of
light emitting stacked layers formed above a substrate for the
method of fabricating the light emitting device according to the
embodiment of present application.
[0015] FIG. 2(b) shows a cross-sectional view of a current blocking
layer patterned on the light emitting stacked layers for the method
of fabricating the light emitting device according to the
embodiment.
[0016] FIG. 2(c) shows a cross-sectional view of a transparent
conductive layer formed on the light emitting stacked layers and
the current blocking layer for the method of fabricating the light
emitting device according to the embodiment.
[0017] FIG. 2(d) shows a cross-sectional view of the transparent
conductive layer etched to expose a reserved region R for the
method of fabricating the light emitting device according to the
embodiment.
[0018] FIG. 2(e) shows a cross-sectional view of a first opening
and a mesa structure being formed by dry-etching for the method of
fabricating the light emitting device according to the
embodiment.
[0019] FIG. 2(f) shows a cross-sectional view of a p-pad electrode
and a n-pad electrode formed in the pad opening and on the mesa
structure respectively for an option 1 for the method of
fabricating the light emitting device according to the
embodiment.
[0020] FIG. 2(g) shows a cross-sectional view of a passivation
layer formed for the fabricated light emitting device of the option
1 for the method of fabricating the light emitting device according
to the embodiment.
[0021] FIG. 2(h) shows a cross-sectional view of the current
blocking layer being completely removed by wet-etching to form a
pad opening for an option 2 (continuing from FIG. 2(e)) of the
method of fabricating the light emitting device according to the
embodiment.
[0022] FIG. 2(i) shows a cross-sectional view of a p-pad electrode
and a n-pad electrode formed in the pad opening and on the mesa
structure respectively for the option 2 for the method of
fabricating the light emitting device according to the
embodiment.
[0023] FIG. 2(j) shows a cross-sectional view of a passivation
layer formed for the fabricated light emitting device of the option
2 for the method of fabricating the light emitting device according
to the embodiment
[0024] FIG. 3 shows top views of each layer in steps of FIGS. 2(b),
2(h)-2(j).
[0025] FIG. 4A shows a partial top view of the light emitting
device with the CB layer exhibiting a ring-shape.
[0026] FIG. 4B shows an enlargement view of a portion of the
light-emitting device of FIG. 4A.
[0027] FIG. 5A shows a top view of the p-pad electrode.
[0028] FIG. 5B shows a magnified cross-sectional view SEM diagram
of a sidewall of the CB layer having two surface sections of
different slopes, which is taken along a dashed line C-C' shown in
FIG. 5A.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0029] The present application will now be described more
specifically with reference to the following embodiments. It is to
be noted that the following descriptions of the embodiments of this
application are presented herein for purpose of illustration and
description only. It is not intended to be exhaustive or to be
limited to the precise form disclosed.
[0030] A method for fabricating a light emitting device, such as an
LED chip or an LD chip, according to an embodiment of present
application is described as follow: FIG. 1 illustrates a flow chart
of a method for fabricating a light emitting device according to an
embodiment of present application, and FIGS. 2(a)-2(j) show a
plurality of cross-sectional views of the corresponding chip on
wafer fabrication processes for fabricating the light emitting
device according to the embodiment, which includes the following
steps: In Step S10, a plurality of light emitting stacked layers 15
(which may include p-type layers, n-type layers, and a planar
active layer made from an inorganic semiconductor material
sandwiched between one of the p-type layers and one of the n-type
layers) are formed above a substrate 10, as shown in FIG. 2(a). The
material of the light emitting stacked layers 15 includes aluminum
gallium indium phosphide (AlGalnP), or aluminum gallium indium
nitride (AlGalnN). The active layer includes single heterostructure
(SH), double heterostructure (DH), double-side double
heterostructure (DDH), or multi-quantum well (MQW) structure.
Specifically, the active layer includes i-type, p-type, or n-type
semiconductor. The active layer emits light when an electrical
current passes through the light emitting stacked layers 15. When
the active layer includes AlGaInP based material, the active layer
emits amber series light, such as red light, orange light, or
yellow light; when the active layer includes AlGalnN based
material, the active layer emits blue, green, or UV light. The
present embodiment illustrates the semiconductor light emitting
stacked layer 15 with aluminum gallium indium nitride (AlGalnN)
based material. These layers can be deposited by a variety methods,
including MOVPE (metal organic vapor phase epitaxy), MBE (molecular
beam epitaxy), or HVPE (hydride vapor phase epitaxy). The substrate
10 can be made of sapphire. In Step S15, a current blocking (CB)
layer 25 is coated and patterned on the light emitting stacked
layers 15, but without etching an opening for the CB layer 25, as
shown in FIG. 2(b). The CB layer 25 is made for example, of
SiO.sub.2, SiN.sub.x or alternate multiple layers made thereof to
form a DBR. In Step S20, a transparent conductive layer 30 (serving
as a current spreading layer) is formed covering the light emitting
stacked layers 15 and the CB layer 25, as shown in FIG. 2(c). The
transparent conductive layer 30 preferable includes an oxide
containing at least one element selected from zinc, indium, or tin,
such as ZnO, InO, SnO, ITO (indium tin oxide), IZO (indium zinc
oxide), GZO (gallium-doped zinc oxide). In the illustrated
embodiment, the transparent conductive layer 30 is an ITO layer. In
Step S25, the ITO layer 30 is etched and exposing a reserved region
R for a first pad electrode (p-pad electrode) and for a mesa
structure 20 (formed by etching a portion of the light emitting
stacked layers), as shown in FIG. 2(d). The reserved region R
includes an exposed portion of the light emitting stacked layers 15
and an exposed portion of the current blocking layer 25. In Step
S30, the exposed portion of the light emitting stacked layers 15
and a substantial portion of the CB layer 25 are dry-etched by
Inductively Coupled Plasma (ICP) to form the mesa structure 20
(n-mesa) and a first opening 12. In the illustrated embodiment, the
first opening 12 is a pad opening for a p-pad electrode 35
described latter, as shown in FIG. 2(e). In Step S35 (Option 1 as
shown in FIG. 1), the CB layer 25 is not wet-etched but dry-etched
under ICP, and leaves behind 1000.about.2000 angstrom in thickness,
and a p-pad electrode 35 is formed by filling the pad opening 12
above the remaining CB layer 25 having 1000.about.2000 angstrom in
thickness, and a second pad electrode (n-pad electrode) 40 is
formed on the mesa structure 20, as shown in FIG. 2(f).
Alternatively, instead of Step S35, Step S40 (Option 2 as shown in
FIG. 1) can be performed, in which the CB layer 25 is wet-etched to
be completely removed to form a pad opening 12' as shown in FIG.
2(h), and in Step S45, a pad (p-pad) electrode 35 is formed by
filling the pad opening 12 and a second pad electrode (n-pad
electrode) 40 is formed on the mesa structure 20, as shown in FIG.
2(i). Then, afterwards, in Step S50: a passivation layer 50 is
deposited over a top surface of the light emitting device 1 except
for the top surfaces of the p-pad electrode 35 and the n-pad
electrode 40 respectively, which are left exposed, as shown in
FIGS. 2(g) and 2(j). Referring to FIG. 3, the current blocking
layer (CB) 25 formed in step S15 of FIG. 2(b), the mesa structure
20 and the transparent conductive layer 30 (MESA/ITO) formed in
step s40 of FIG. 2(h), the pad electrodes 35,40 (Pad) formed in
step S45 of FIG. 2(i), and the passivation layer 50 (PSV) formed in
step S50 of FIG. 2(j) are shown from a top view perspective,
respectively. In the above fabrication method, the current blocking
layer (CB) 25 being made of for example, SiO.sub.2 or SiN.sub.x,
can be used serving as a hard mask upon inductively coupled plasma
(ICP) dry etching a portion of the light emitting stacked layers 15
to form the mesa structure 20, while at substantially the same
time, a portion of the current blocking layer (CB) 25 is removed by
ICP dry etching, and upon completion of the mesa structure 20, wet
etching, such as buffered oxide etching (BOE) can be used to remove
the remaining CB layer 25, and a P-pad electrode 35 can be filled
into the pad opening 12' for contacting a p-GaN layer of the light
emitting stacked layers 15, and the pad opening 12' is formed
through the CB/ITO layers 25, 30 beneath the p-pad electrode 35 as
shown in FIG. 3. The mesa structure 20 includes two portions. in
which one portion of the mesa structure 20 is a periphery portion
20a (as shown in FIG. 3) surrounding the light emitting stacked
layers 15 and the ITO layer 30, and an another portion of the mesa
structure 20 includes a second opening 55 as shown in FIG. 3 and
FIG. 4A. In the illustrated embodiment, the second opening 55 is a
n-pad electrode opening for the n-pad electrode. The n-pad
electrode opening 55 is in and surrounded by the light emitting
stacked layers 15 and the ITO layer 30, and a portion of a n-GaN
layer (not labeled) of the light emitting stacked layers 15 is
exposed in the n-pad electrode opening 55. A n-pad electrode 40 can
be filled into the n-pad electrode opening 55 for contacting the
n-GaN layer of the light emitting stacked layers 15. The p, n-pad
electrodes 35, 40 can respectively include a pad and/or an
extending electrode connecting to and extending from the pad. The
pad is disposed for an outer power connecting and the extending
electrode is used for current spreading when current is injected
from the outer power through the pad, current can be spread through
the extending electrode. A ratio of thickness of the CB layer 25 to
depth of the mesa structure 20 (as measured with respect to the
first surface 42 of the light emitting stacked layers 15 is between
1.3.about.3.3, so as to ensure prevention of over-etching or
excessive residue CB layer 25 being formed. Due to adoption of the
self-alignment technique in which the patterned ITO layer 30, the
patterned CB layer 25, and the mesa structure 20 are formed using
the same photoresist mask as described in above Steps S25 and S30,
the sidewall of the transparent conductive layer (ITO layer) 30 and
the sidewall of the mesa structure 20 are substantially coplanar or
flush. In the above light emitting device 1 fabrication method, the
passivation layer 50 can be made of insulating material, such as
silicon nitride, silicon oxide, silicon oxynitride, or aluminum
oxide which is deposited on the defined surface area of the light
emitting device 1 using CVD (Chemical Vapor Deposition) technology,
PECVD (Plasma Enhanced Chemical Vapor Deposition) technology,
electron cyclotron resonance chemical vapor deposition (ECR-CVD)
technology, or LPCVD (Low Pressure Chemical Vapor Deposition)
technology, whereby the passivation layer 50 is accurately formed
without covering the areas of the pad electrodes 35, 40.
[0031] Referring to FIGS. 2(g) and 2(j), an light emitting device 1
as fabricated according to the embodiment of present application is
shown in a cross-sectional view, which includes a substrate 10, a
plurality of light emitting stacked layers 15, a mesa structure 20,
a CB layer 25, a transparent conductive layer 30 in the form of an
ITO layer 30, a p-pad electrode 35, a n-pad electrode 40, and a
passivation layer 50. The light emitting stacked layers 15
comprising a first surface 42 and a second surface 44, in which the
second surface 44 is closer to the substrate 10 and is electrically
opposite to the first surface 42. The transparent conductive layer
30 is disposed and formed on or above the first surface 42 of the
light emitting stacked layers 15. The p-pad electrode 35 is
disposed on the transparent conductive layer 30 and on the first
surface 42 of the light emitting stacked layers 15, and the n-pad
electrode 40 is disposed on the second surface 44 of the light
emitting stacked layers 15 and on the mesa structure 20. Referring
to FIG. 2(g), there is a thinner portion/section of the CB layer 25
between the p-pad electrode 35 and the first surface 42, and the
p-pad electrode 35 is in contact with the thinner portion/section
of the CB layer 25. Referring to FIG. 2(i), the p-pad electrode 35
is in contact with the first surface 42. The CB layer 25 is
disposed on the first surface 42 of the light emitting stacked
layers 15, surrounded by the transparent conductive layer 30, and
at a lower region of the p-pad electrode 35. In addition, the mesa
structure 20 has a n-pad electrode opening 55 in which a portion of
the n-pad electrode 40 is filling the n-pad electrode opening 55 of
the mesa structure 20. FIG. 4A, shows a top view of the mesa
structure 20, the CB layer 25, and the transparent conductive layer
30. The CB layer 25 has a ring-shape as shown in a top view of the
light emitting device 1. FIG. 4B shows a partial enlargement view
of a (circular dashed-line) portion A of the light-emitting device
1 of FIG. 4A. The mesa structure 20 including the n-pad electrode
opening 55 has an edge, the transparent conductive layer 30 of the
illustrated embodiment is retracted by a shorter distance B with
respect to the edge of the mesa structure 20 from top view. For the
sake of preventing residue ITO from causing leakage current issues
for the light emitting device 1 and due to having a self-alignment
process in which the transparent conductive layer 30 and the mesa
structure 20 are formed using the same photoresist mask, the
transparent conductive layer 30 of the illustrated embodiment is
retracted by the shorter distance B with respect to the edge of the
mesa structure 20, of 1 to 2 .mu.m, or less than 3 .mu.m, which is
less than that of the conventional fabrication method having
ITO-to-mesa retract distance/gap of 5 .mu.m-7 .mu.m. Referring to
FIG. 5A, an enlargement top view of the p-pad electrode 35 is
shown, and the CB layer 25 under the p-pad electrode 35 is shown by
a dashed-line ring structure. In FIG. 5A, a cutting-plane location
is identified along a dashed line C-C' in the illustrated
embodiment, and a magnified cross-sectional view SEM diagram of a
sidewall of the CB layer 25 having two surface sections of
different slopes is shown in FIG. 5B. Referring to FIG. 5B, as
shown in a cross-sectional view, a sidewall of the CB layer 25
includes two surface sections 26a, 26b having different slopes, in
which the surface section 26a has a slope of 10 degrees to 50
degrees and the surface section 26b has a slope of 50 degrees to 70
degrees. In one embodiment, a slope of the surface section 26a is
between 10 degrees to 15 degrees. In the illustrated embodiment,
the surface section 26a has a slope of 41.6 degrees, and the
surface section 26b has a slope of 65 degrees. A sidewall 31 of the
transparent conductive layer 30 and a sidewall 16 of the light
emitting stacked layers 15 are substantially flush and planar
located adjacent to one end of the second surface 44 of the light
emitting stacked layers 15 and the mesa structure 20, and adjacent
to one end of the first surface 42 of the light emitting stacked
layers 15. For the sake of preventing residue ITO from causing
leakage current issues for the light emitting device 1 and due to
having a self-alignment process in which the transparent conductive
layer 30 and the mesa structure 20 are formed using the same
photoresist mask, the transparent conductive layer 30 of the
illustrated embodiment is retracted a shorter distance with respect
to the edge of the surface section 26b of the CB layer 25, of 1 to
2 .mu.m, or less than 3 .mu.m, which is less than that of the
conventional fabrication method having ITO-to-CB retract
distance/gap of 5 .mu.m-7 .mu.m. In the embodiment, the transparent
conductive layer 30 is retracted by a distance with respect to the
edge of the surface section 26b of the CB layer 25, of 1.116 .mu.m.
In one embodiment, the surface section 26b caused by ICP is also
wet-etched during the following remaining CB layer wet etching
process. The slope of the surface section 26a is equal to that of
the surface section 26b. The slope of the surface section 26a is
between 10 degrees to 15 degrees. The ITO-to CB retract distance is
between 2 .mu.m to 3 .mu.m.
[0032] It is believed that the present embodiments and their
advantages will be understood from the foregoing description, and
it will be apparent that various changes may be made thereto
without departing from the spirit and scope of the embodiments or
sacrificing all of its material advantages.
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