U.S. patent application number 14/936442 was filed with the patent office on 2016-03-03 for electronic devices and method of fabricating the same.
This patent application is currently assigned to ELECTRONICS AND TELECOMMUNICATIONS RESEARCH INSTITUTE. The applicant listed for this patent is ELECTRONICS AND TELECOMMUNICATIONS RESEARCH INSTITUTE. Invention is credited to Yoo Jeong LEE, JungWook LIM, Chang Bong YEON, Sun Jin YUN.
Application Number | 20160064503 14/936442 |
Document ID | / |
Family ID | 49993690 |
Filed Date | 2016-03-03 |
United States Patent
Application |
20160064503 |
Kind Code |
A1 |
YUN; Sun Jin ; et
al. |
March 3, 2016 |
ELECTRONIC DEVICES AND METHOD OF FABRICATING THE SAME
Abstract
An electronic device includes a substrate. A lower electrode is
disposed on the substrate and has a flat portion and protrusions.
An intermediate layer is on the lower electrode. An upper electrode
is on the intermediate layer. The lower electrode includes an alloy
of a first metal and a second metal. The protrusions have a content
ratio of the second metal higher than that of the flat portion.
Inventors: |
YUN; Sun Jin; (Daejeon,
KR) ; YEON; Chang Bong; (Namyangju-si, KR) ;
LEE; Yoo Jeong; (Seoul, KR) ; LIM; JungWook;
(Daejeon, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ELECTRONICS AND TELECOMMUNICATIONS RESEARCH INSTITUTE |
Daejeon |
|
KR |
|
|
Assignee: |
ELECTRONICS AND TELECOMMUNICATIONS
RESEARCH INSTITUTE
Daejeon
KR
|
Family ID: |
49993690 |
Appl. No.: |
14/936442 |
Filed: |
November 9, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13952904 |
Jul 29, 2013 |
|
|
|
14936442 |
|
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|
Current U.S.
Class: |
257/40 ; 257/101;
257/431; 257/618 |
Current CPC
Class: |
H01L 33/40 20130101;
H01L 51/5203 20130101; Y02E 10/52 20130101; H01L 51/5209 20130101;
H01L 2933/0016 20130101; H01L 29/43 20130101; H01L 31/056 20141201;
H01L 29/423 20130101; H01L 31/0224 20130101; H01L 31/02366
20130101; H01L 33/405 20130101; H01L 31/022425 20130101 |
International
Class: |
H01L 29/43 20060101
H01L029/43; H01L 29/423 20060101 H01L029/423; H01L 31/0224 20060101
H01L031/0224; H01L 51/52 20060101 H01L051/52; H01L 33/40 20060101
H01L033/40 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 30, 2012 |
KR |
10-2012-0083394 |
May 10, 2013 |
KR |
10-2013-0053136 |
Claims
1. An electronic device comprising: a substrate; a lower electrode
disposed on the substrate and having a flat portion and
protrusions; an intermediate layer on the lower electrode; and an
upper electrode on the intermediate layer, wherein the lower
electrode comprises an alloy of a first metal and a second metal,
and the protrusions have a content ratio of the second metal higher
than that of the flat portion.
2. The electronic device of claim 1, further comprising a
conductive film disposed between the substrate and the lower
electrode, wherein the conductive film comprises the first
metal.
3. The electronic device of claim 1, wherein the first metal
comprises copper, and the second metal comprises silver.
4. The electronic device of claim 1, wherein the intermediate layer
comprises at least one of silicon (Si), silicon germanium (SiGe),
silicon carbide (SiC), silicon oxide (SiO), silicon nitride (SiN),
silicon oxynitride (SiON), silicon carbonitride (SiCN), silicon
germanium oxide (SiGeO), silicon germanium oxynitride (SiGeON),
silicon germanium carbide (SiGeC), a chalcopyrite-based compound
semiconductor, and a Group II-IV compound semiconductor.
5. The electronic device of claim 1, wherein the intermediate layer
comprises a light absorbing layer generating electrical power from
light.
6. The electronic device of claim 1, wherein the intermediate layer
comprises an organic light-emitting material.
7. The electronic device of claim 1, wherein the intermediate layer
comprises an inorganic light-emitting material.
8. An electronic device comprising: a substrate; a conductive film
disposed on the substrate and including a first metal; a lower
electrode disposed on the substrate and including the first metal
and a second metal; an intermediate layer on the lower electrode;
and an upper electrode on the intermediate layer, wherein the lower
electrode comprises: a flat portion on the conductive film; and
protrusions extending from the flat portion.
9. The electronic device of claim 8, wherein the protrusions have a
content ratio of the second metal higher than that of the flat
portion.
10. The electronic device of claim 8, wherein the protrusions have
the same content ratio of the second metal as that of the flat
portion.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a Divisional of U.S. application Ser. No.
13/952,904, which was filed on Jul. 29, 2013, and allowed on Aug.
5, 2015. Both of these U.S. non-provisional patent applications
claim priority under 35 U.S.C. .sctn.119 of Korean Patent
Application Nos. 10-2012-0083394, filed on Jul. 30, 2012, and
10-2013-0053136, filed on May 10, 2013, the entire contents of
which are hereby incorporated by reference.
BACKGROUND
[0002] The present invention disclosed herein relates to electronic
devices, and more particularly, to electrodes for an electronic
device having protrusions.
[0003] The amount of fossil fuel energy, such as petroleum, coal,
and natural gas, commonly used today is limited and the use of
fossil fuels emits pollutants. Therefore, development of
alternative energy sources capable of replacing the fossil fuel
energy is very important. One of the techniques receiving most
attention is a photo-conversion device utilizing photoelectric
effect, such as a solar cell. An electric power generation
technique using sunlight generates power by converting photo-energy
into electrical energy. The photo-conversion device converts
unlimitedly available energy of sunlight into electrical energy.
The photo-conversion device is environmentally friendly, because
solar cells cause no pollution, such as air pollution, noise, heat,
or vibration. Since the transportation of fuel and the maintenance
of power generation facility are not required for the
photo-conversion device, the photo-conversion device may have
semi-permanent lifespan. Therefore, an improvement of the
efficiency of the photo-conversion device has been the main
direction for the development of solar cells.
SUMMARY
[0004] The present invention provides a solar cell having an
improved light absorption ratio.
[0005] The present invention provides a light-conversion device
which may increase conversion efficiency of light into electricity
by effectively utilizing the light.
[0006] The present invention also provides a light-emitting device
having improved luminous efficiency.
[0007] The present invention also provides a display and a
light-emitting device which may increase luminous efficiency, i.e.,
the conversion efficiency of electricity into light, by generating
and effectively emitting the light.
[0008] The object of the present invention is not limited to the
aforesaid, but other objects not described herein will be clearly
understood by those skilled in the art from descriptions below.
[0009] Embodiments of the present invention provide methods of
fabricating an electronic device including: forming a lower
electrode having a flat portion and protrusions on a substrate;
forming at least one intermediate layer on the lower electrode; and
forming an upper electrode on the at least one intermediate layer,
wherein the forming of the lower electrode may include: forming a
conductive film by depositing a first metal on the substrate; and
depositing a second metal on the conductive film to prepare an
alloy of the first metal and the second metal, and the flat portion
and the protrusions may include the alloy of the first metal and
the second metal.
[0010] In some embodiments, the protrusions may have a content
ratio of the second metal higher than that of the flat portion.
[0011] In other embodiments, the first metal may include copper,
and the second metal may include silver.
[0012] In still other embodiments, the flat portion may have the
same compositional ratio as that of the protrusions.
[0013] In even other embodiments, the first metal may include
aluminum, and the second metal may include silver.
[0014] In yet other embodiments, the deposition of the second metal
may be performed at a temperature ranging from about 270.degree. C.
to about 400.degree. C.
[0015] In further embodiments, the lower electrode may be formed
between the conductive film and the at least one intermediate
layer.
[0016] In still further embodiments, the lower electrode may be
formed to be in contact with the substrate.
[0017] In even further embodiments, the protrusions may extend from
the flat portion.
[0018] In other embodiments of the present invention, electronic
devices include: a substrate; a lower electrode disposed on the
substrate and having a flat portion and protrusions; an
intermediate layer on the lower electrode; and an upper electrode
on the intermediate layer, wherein the lower electrode may include
an alloy of a first metal and a second metal, and the protrusions
may have a content ratio of the second metal higher than that of
the flat portion.
[0019] In some embodiments, the electronic device may further
include a conductive film disposed between the substrate and the
lower electrode, wherein the conductive film may include the first
metal.
[0020] In other embodiments, the first metal may include copper,
and the second metal may include silver.
[0021] In still other embodiments, the at least one intermediate
layer may include at least one of silicon (Si), silicon germanium
(SiGe), silicon carbide (SiC), silicon oxide (SiO), silicon nitride
(SiN), silicon oxynitride (SiON), silicon carbonitride (SiCN),
silicon germanium oxide (SiGeO), silicon germanium oxynitride
(SiGeON), silicon germanium carbide (SiGeC), a chalcopyrite-based
compound semiconductor, and a Group II-IV compound
semiconductor.
[0022] In still other embodiments, the at least one intermediate
layer comprises a light absorbing layer generating electrical power
from light.
[0023] In even other embodiments, the at least one intermediate
layer may include an organic light-emitting material.
[0024] In yet other embodiments, the at least one intermediate
layer may include an inorganic light-emitting material.
[0025] In still other embodiments of the present invention,
electronic devices include: a substrate; a conductive film disposed
on the substrate and including a first metal; a lower electrode
disposed on the substrate and including the first metal and a
second metal; an intermediate layer on the lower electrode; and an
upper electrode on the intermediate layer, wherein the lower
electrode may include a flat portion on the conductive film and
protrusions extending from the flat portion.
[0026] In some embodiments, the protrusions may have a content
ratio of the second metal higher than that of the flat portion.
[0027] In other embodiments, the protrusions may have the same
content ratio of the second metal as that of the flat portion.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] The accompanying drawings are included to provide a further
understanding of the present invention, and are incorporated in and
constitute a part of this specification. The drawings illustrate
exemplary embodiments of the present invention and, together with
the description, serve to explain principles of the present
invention. In the drawings:
[0029] FIG. 1 is a cross-sectional view illustrating an electronic
device according to an embodiment of the present invention;
[0030] FIG. 2 is a cross-sectional view illustrating an electronic
device according to another embodiment of the present
invention;
[0031] FIGS. 3 through 5 are cross-sectional views illustrating a
method of fabricating an electronic device according to an
embodiment of the present invention;
[0032] FIGS. 6 and 7 are cross-sectional views illustrating a
method of fabricating an electronic device according to another
embodiment of the present invention; and
[0033] FIG. 8 is a graph illustrating root mean square (rms)
roughness values vs. temperature for comparative examples and
experimental examples of the present invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0034] Preferred embodiments of the present invention will be
described below in more detail with reference to the accompanying
drawings in order to fully understand the constitution and effect
of the present invention. The present invention may, however, be
embodied in different forms and should not be construed as limited
to the embodiments set forth herein. Rather, these embodiments are
provided so that this disclosure will be thorough and complete, and
will fully convey the scope of the present invention to those
skilled in the art. Those skilled in the art will understand that
the present inventive concept can be implemented in an appropriate
environment.
[0035] In the following description, the technical terms are used
only for explaining a specific exemplary embodiment while not
limiting the present invention. The terms of a singular form may
include plural forms unless referred to the contrary. The meaning
of "comprises" and/or "comprising" specifies a property, a region,
a fixed number, a step, a process, an element and/or a component
but does not exclude other properties, regions, fixed numbers,
steps, processes, elements and/or components.
[0036] In addition, it will be understood that when an element such
as a layer, film, region, or substrate is referred to as being "on"
another element, it can be directly on the other element or
intervening elements may also be present.
[0037] Also, though terms like a first, a second, and a third are
used to describe various regions and layers in various embodiments
of the present invention, the regions and the layers are not
limited to these terms. These terms are used only to distinguish
one region or layer from another region or layer. Therefore, a
layer referred to as a first layer in one embodiment can be
referred to as a second layer in another embodiment. An embodiment
described and exemplified herein includes a complementary
embodiment thereof. Like reference numerals refer to like elements
throughout.
[0038] Unless otherwise defined, all terms used herein have the
same meaning as commonly understood by one of ordinary skill in the
art to which this inventive concept belongs.
[0039] Hereinafter, an electronic device according to the present
invention will be described with reference to the accompanying
drawings.
[0040] FIG. 1 is a cross-sectional view illustrating an electronic
device according to an embodiment of the present invention.
[0041] Referring to FIG. 1, an electronic device 1 may include a
lower electrode 200, an intermediate layer 300, and an upper layer
400, which are sequentially stacked on a substrate 100. The
electronic device 1 may be a display device, such as an organic
light-emitting device or an inorganic electroluminescent device, or
a solar cell. The electronic device 1 may further include a back
reflection layer 250.
[0042] The substrate 100 may be opaque. The substrate 100 may
include stainless steel, plastic, metal, or a polymer.
[0043] The lower electrode 200 may be opaque. The lower electrode
200 may be rough. For example, a top surface of the lower electrode
200 may have a root mean square (rms) roughness ranging from about
30 nm to about 500 nm. The lower electrode 200 may have a flat
portion 201 and protrusions 203. The protrusions 203 may extend
from the flat portion 201 and may have a shape of an island.
Hereinafter, the protrusions may be indicated to have an rms
roughness of about 30 nm or more. Since the lower electrode 200 has
protrusions 203, diffuse reflectance of light at an interface
between the lower electrode 200 and the intermediate layer 300 or
an interface between the lower electrode 200 and the back
reflection layer 250 may be increased. With respect to a solar
cell, when the diffuse reflectance increases, the distance traveled
by the light passing through a light absorbing layer increases, and
thus, a light absorption ratio may increase. With respect to a
light-emitting device, when the diffuse reflectance increases, in
which the outcoupling of emitted light from the device may
increase. Thus, luminous efficiency may increase. The lower
electrode 200 may include an alloy of a first metal and a second
metal. The first metal may include copper (Cu) or aluminum (Al),
and the second metal may include silver (Ag). For example, when the
first metal includes Cu, a content ratio of the second metal in the
protrusions 203 may be higher than that in the flat portion 201. As
another example, when the first metal includes Al, the content
ratio of the second metal in the protrusions 203 may be the same or
similar to that in the flat portion 201. The lower electrode 200
may have a thickness ranging from about 50 nm to about 400 nm. The
content of the second metal (e.g., Ag) of the lower electrode 200
may be decreased, but the lower electrode 200 may have identical or
similar conductivity in comparison to the case in which the first
metal is omitted.
[0044] The back reflection layer 250 may be disposed between the
lower electrode 200 and the intermediate layer 300. The back
reflection layer 250 may include transparent conductive oxide,
e.g., zinc oxide or impurity-doped zinc oxide. In the case that the
lower electrode 200 includes copper, the back reflection layer 250
may prevent the degradation of the performance of the intermediate
layer 300 caused by the diffusion of copper into the intermediate
layer 300. As another example, the back reflection layer 250 may be
omitted.
[0045] The intermediate layer 300 may have a curved section by
extending along the protrusions 203. According to an embodiment of
the present invention, the intermediate layer 300 may function as a
light absorbing layer by including a semiconductor material. The
intermediate layer comprises a photo-conversion material. In this
case, the electronic device 1 may function as a solar cell by
converting the incident sunlight to electrical energy. For example,
the intermediate layer 300 may include at least one of silicon
(Si), silicon germanium (SiGe), silicon carbide (SiC), silicon
oxide (SiO), silicon nitride (SiN), silicon oxynitride (SiON),
silicon carbonitride (SiCN), silicon germanium oxide (SiGeO),
silicon germanium oxynitride (SiGeON), and silicon germanium
carbide (SiGeC). The intermediate layer 300 may include a single
layer or multilayers. The intermediate layer 300 may have a PIN
diode structure. For example, the intermediate layer 300 may
include a p-type silicon layer, an intrinsic silicon layer, and an
n-type silicon layer, which are sequentially stacked. As another
example, the intermediate layer 300 may include an n-type silicon
layer, an intrinsic silicon layer, and a p-type silicon layer,
which are sequentially stacked. Alternatively, the intermediate
layer 300 may include a Group I-III-IV chalcopyrite-based compound
semiconductor, such as copper indium gallium selenium (CuInGaSe).
Alternatively, the intermediate layer 300 may include a Group II-VI
compound semiconductor, such as ZnO, ZnS, ZnSe, ZnOS, ZnOSe, and
ZnOSSe. As another example, the intermediate layer 300 may include
a Group II-IV compound semiconductor, such as cadmium telluride
(CdTe).
[0046] As another example, the intermediate layer 300 may include
an organic light-emitting material. In this case, the electronic
device 1 may be an organic light-emitting device. For example, the
intermediate layer 300 may include at least any one of a
polyfluorene derivative, a (poly)paraphenylenevinylene derivative,
a polyphenylene derivative, a polyvinylcarbazole derivative, a
polythiophene derivative, an anthracene derivative, a butadiene
derivative, a tetracene derivative, a distyrylarylene derivative, a
benzazole derivative, and/or carbazole. The intermediate layer 300
may further include a dopant in the organic light-emitting
material.
[0047] According to an embodiment of the present invention, the
intermediate layer 300 may include an organic photoelectric
material.
[0048] As another example, the intermediate layer 300 may include
an inorganic light-emitting material.
[0049] According to an embodiment of the present invention, the
intermediate layer 300 may be composed of a light absorbing layer,
an n-type semiconductor, and a p-type semiconductor. The light
absorbing layer may generate carriers by absorbing light. The
n-type semiconductor and the p-type semiconductor may function as a
diode. According to another embodiment of the present invention,
the intermediate layer 300 may be composed of a light-emitting
layer, an n-type semiconductor, and a p-type semiconductor. The
light-emitting layer may convert electrical energy into light
energy. The n-type semiconductor and the p-type semiconductor may
function as a diode.
[0050] The upper electrode 400 extends along the intermediate layer
300 and may have a curved section. The upper electrode 400 may
include a transparent conductive oxide. For example, the upper
electrode 400 may include zinc oxide (ZnO) doped with Al, Ga, B, or
In, tin oxide (SnO.sub.2), or tin oxide doped with fluorine, indium
tin oxide (ITO).
[0051] Photo-conversion efficiency or luminous efficiency of the
intermediate layer 300 of the electronic device 1 of the present
invention may be increased in comparison to the case in which the
protrusions 203 are omitted.
[0052] FIG. 2 is a cross-sectional view illustrating an electronic
device according to another embodiment of the present invention.
Hereinafter, descriptions overlapping with those of FIG. 1 will be
omitted.
[0053] Referring to FIG. 2, an electronic device 2 may include a
conductive film 210, a lower electrode 200, a back reflection layer
250, an intermediate layer 300, and an upper electrode 400, which
are sequentially stacked on a substrate 100.
[0054] The conductive film 210 may include a first metal, e.g., Cu
or Al.
[0055] The lower electrode 200 may have a flat portion 201 and
protrusions 203. The lower electrode 200 may have an rms roughness
ranging from about 30 nm to about 500 nm. The lower electrode 200
may include the first metal and a second metal. The second metal
may include Ag. For example, in the case that the first metal
includes Cu, a content ratio of the second metal in the protrusions
203 may be higher than that in the flat portion 201. As another
example, a content ratio of the first and second metals in the
protrusions 203 may be the same or similar to that in the flat
portion 201.
[0056] A method of fabricating an electronic device according to
the present invention will be described with reference to the
accompanying drawings. Hereinafter, descriptions overlapping with
the aforementioned descriptions will be omitted.
[0057] FIGS. 3 through 5 are cross-sectional views illustrating a
method of fabricating an electronic device according to an
embodiment of the present invention.
[0058] Referring to FIG. 3, a conductive film 210 may be formed on
a substrate 100. The substrate 100 may be opaque, and may include
stainless steel, plastic, metal, or a polymer. The conductive film
210 may be formed by depositing a first metal, e.g., Cu or Al, on
the substrate 100. The deposition of the conductive film 210 may be
performed by electron beam evaporation, thermal evaporation,
sputter deposition, solution-based coating, printing, or chemical
vapor deposition. The substrate 100 may not be heated during the
deposition of the conductive film 210, and thus, the substrate 100
may not be damaged by heat.
[0059] Referring to FIG. 4, a lower electrode 200 including a first
metal and a second metal may be formed on the substrate 100. The
lower electrode 200 may include a flat portion 201 and protrusions
203. For example, the second metal (e.g., Ag) may be deposited on
the conductive film 210 under a temperature condition ranging from
about 270.degree. C. to about 400.degree. C. The deposition of the
second metal may be performed by thermal evaporation, electron beam
evaporation, sputter deposition, or chemical vapor deposition. The
second metal may be deposited to have a thickness ranging from
about 33.3% to about 10000% of a thickness of the conductive film
210. An alloy may be prepared from the second metal and the
conductive film 210 to form the lower electrode 200. The conductive
film 210 may promote the formation of the protrusions 203. In the
case that the formation of the conductive film 210 is omitted, the
protrusions 203 may be formed at a temperature of about 500.degree.
C. or more. Since the second metal is deposited on the conductive
film 210, the protrusions 203 may be formed at a temperature
ranging from about 270.degree. C. to about 400.degree. C.
Therefore, the substrate 100 may not be damaged by heat. The lower
electrode 200 prepared from the conductive film 200 may be rougher,
in comparison to the case in which the formation of the conductive
film 210 is omitted. For example, in the case that an alloy is
prepared by sequentially depositing the first metal and the second
metal, a surface roughness of the lower electrode 200 may be
higher, in comparison to the case in which an alloy is prepared by
simultaneously depositing the first metal and the second metal.
[0060] In the case that Cu is used as the first metal, a content
ratio of the second metal in the protrusions 203 may be higher than
that in the flat portion 201. In the case in which Al is used as
the first metal, since mutual solubility between the first metal
and the second metal may be high, a content ratio of the first and
second metals in the protrusions 203 may be the same or similar to
that in the flat portion 201.
[0061] Referring to FIG. 5, a back reflection layer 250, an
intermediate layer 300, and an upper electrode 400 may be
sequentially formed on the lower electrode 200. The fabrication of
the electronic device 1 described as an example of FIG. 1 may be
completed, according to the above-described fabrication
example.
[0062] FIGS. 6 and 7 are cross-sectional views illustrating a
method of fabricating an electronic device according to another
embodiment of the present invention.
[0063] Referring to FIG. 6, a substrate 100 including a conductive
film 210 may be prepared. The conductive film 210 may be formed by
using the same material and method as those described in FIG.
3.
[0064] Referring to FIG. 7, a lower electrode 200 may be formed on
the conductive film 210 by preparing an alloy of a first metal and
a second metal. The conductive film 210 may promote the formation
of protrusions 203. For example, the second metal (e.g., Ag) may be
deposited on the conductive film 210 under a temperature condition
ranging from about 270.degree. C. to about 400.degree. C. The
conductive film 210 may have a thickness ranging from about 1% to
about 300% of a thickness of the second metal deposited. An upper
portion of the conductive film 210 (see 210a in FIG. 6) may be
combined with the second metal to form an alloy. A lower portion of
the conductive film 210 (see 210b in FIG. 6) may not form an alloy
with the second metal, and thus, may be included in the electronic
device 2. The substrate 100 may not be damaged by heat during the
formation process of the lower electrode 200. A back reflection
layer 250, an intermediate layer 300, and an upper electrode 400
may be sequentially formed on the lower electrode 200. The
fabrication of the electronic device 2 described as an example of
FIG. 2 may be completed, according to the above-described
fabrication example.
[0065] Hereinafter, the fabrication methods and evaluation results
of characteristics of the electronic devices according to the
present inventive concept will be described in more detail,
according to experimental examples of the present invention.
[0066] Fabrication of Electronic Devices
COMPARATIVE EXAMPLE 1-1
[0067] An about 125 .mu.m thick stainless steel (STS) substrate may
be prepared. A silver layer having a thickness of about 200 nm may
be deposited on the STS substrate by magnetron sputtering using
about 99.99% pure silver as a target. The deposition was performed
at a temperature of about 25.degree. C.
COMPARATIVE EXAMPLE 1-2
[0068] An electronic device was fabricated in the same manner as
Comparative Example 1-1 except that deposition was performed at a
temperature of about 400.degree. C.
EXPERIMENTAL EXAMPLE 1-1
[0069] An electronic device was fabricated in the same manner as
Comparative Example 1-1 except that an aluminum layer having a
thickness of about 100 nm was formed on a STS substrate and a
silver layer was then deposited on the aluminum layer. The
deposition was performed at a temperature of about 270.degree.
C.
EXPERIMENTAL EXAMPLE 1-2
[0070] An electronic device was fabricated in the same manner as
Experimental Example 1-1. Deposition in the present experimental
example was performed at a temperature of about 320.degree. C.
EXPERIMENTAL EXAMPLE 1-3
[0071] An electronic device was fabricated in the same manner as
Experimental Example 1-1 except that deposition in the present
experimental example was performed at a temperature of about
350.degree. C.
EXPERIMENTAL EXAMPLE 1-4
[0072] An electronic device was fabricated in the same manner as
Experimental Example 1-1 except that deposition in the present
experimental example was performed at a temperature of about
370.degree. C.
EXPERIMENTAL EXAMPLE 1-5
[0073] An electronic device was fabricated in the same manner as
Experimental Example 1-1 except that deposition in the present
experimental example was performed at a temperature of about
400.degree. C.
EXPERIMENTAL EXAMPLE 2
[0074] An electronic device was fabricated in the same manner as
Experimental Example 1-5 except that a copper layer, instead of an
aluminum layer, was formed on a STS substrate in the present
experimental example.
[0075] Evaluation of Characteristics of Electronic Devices
[0076] <Auger Electron Spectroscopy>
[0077] A flat portion and protrusions of each of Experimental
Example 1-5 and Experimental Example 2 were measured by Auger
electron spectroscopy (AES).
[0078] Table 1 presents results of AES measurements of Experimental
Example 1-5.
[0079] Referring to Table 1 with FIGS. 1 and 2, it may be confirmed
that the protrusions 203 had a content ratio of silver similar to
that of the flat portion 201. In Experimental Example 1-5, the
first metal was composed of aluminum and the second metal was
composed of silver. As a result, mutual solubility between the
first metal and the second metal were high, and thus, it may be
understood that the content ratio of the second metal in the
protrusions 203 may be the same or similar to that in the flat
portion 201.
TABLE-US-00001 TABLE 1 AES Flat portion (%) Protrusions (%) Silver
(Ag) 54.9 55.3 Aluminum (Al) 45.1 44.7
[0080] Table 2 presents results of AES measurements of Experimental
Example 2.
[0081] Referring to Table 2 with FIGS. 1 and 2, it may be confirmed
from the results of AES that a surface of the protrusions 203 had a
content ratio of silver similar to that of a surface of the flat
portion 201. In Experimental Example 2, the first metal was
composed of copper and the second metal was composed of silver. As
a result, it may be understood that mutual solubility between the
first metal and the second metal in Experimental Example 2 was
lower than that of Experimental Example 1-5.
TABLE-US-00002 TABLE 2 AES Flat portion (%) Protrusions (%) Silver
(Ag) 95.09 96.71 Copper (Cu) 4.91 3.29
[0082] FIG. 8 is a graph illustrating rms roughness values vs.
temperature for the comparative examples and Experimental Examples
1-1 to 1-5 of the present invention. Comparative Examples 1-1 and
1-2 were respectively represented as c1 and c2. Experimental
Examples 1-1 and 1-5 were respectively represented as e1 to e5.
[0083] Referring to FIG. 8, it may be observed that Experimental
Example 1-5 (e5) had an rms roughness higher than that of
Comparative Example 1-2 at the same temperature. Therefore, it may
be confirmed that higher rms roughness may be obtained in
comparison to the case in which the conductive film 210 was
omitted, according to the fact that the lower electrode 200 was
formed by the deposition of the second metal on the conductive film
210.
[0084] A lower electrode having protrusions according to the
present inventive concept may cause diffuse reflection of light at
an interface between the lower electrode and an intermediate layer
to obtain a high light utilization rate in comparison to the case
in which a lower electrode is flat with no protrusions. A method of
forming a lower electrode according to the present inventive
concept may include the formation of a conductive pattern and may
promote the formation of the protrusions. The lower electrode may
be formed of an alloy of the conductive pattern and a second metal.
Since the lower electrode may be prepared at a temperature ranging
from about 270.degree. C. to about 400.degree. C., a substrate may
not be damaged by heat.
[0085] While preferred embodiments of the present invention has
been particularly shown and described with reference to the
accompanying drawings, it will be understood by those of ordinary
skill in the art that various changes in form and details may be
made therein without departing from the spirit and scope of the
present invention as defined by the following claims.
* * * * *