Active solid-state devices (e.g. – transistors – solid-state diode – Organic semiconductor material
Reexamination Certificate
2000-04-17
2003-09-09
Lee, Eddie (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Organic semiconductor material
C257S072000, C257S059000, C257S083000, C257S099000
Reexamination Certificate
active
06617608
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electro-luminescent display (ELD) and a method of manufacturing thereof. More specifically, the present invention relates to an active ELD including an organic luminescent layer.
2. Discussion of the Related Art
An ELD is a luminescent device that emits light when electrons and holes that are injected into a luminescent layer recombine. The emission of light by the recombination of electrons and holes eliminates the need for a back-light in the ELD. Thus, it is easy to manufacture a very thin panel using an ELD. Further, the ELD has the added advantage of low power consumption. Additionally, an organic ELD, having a light-emitting layer with an organic electro-luminescent (EL) substance, is characterized by a low driving voltage, high light-emitting efficiency, and low process temperature. However, organic EL substances are vulnerable to moisture so that the patterns are defined by a method that prevents the organic EL substance from contacting moisture directly, unlike conventional photolithography.
In an active ELD, a plurality of pixels are defined by providing a plurality of scanning lines that cross with a plurality of signal lines, and also such that a power supply line is arranged in the same direction as the signal line in each of the pixels. Each pixel includes a storage capacitor, an EL portion, and at least one switching device such as a thin film transistor (TFT).
When the pixel includes two TFTs, an excitation signal for the EL portion is distinguished from the scanning signal. The EL portion is selected by a logic TFT which is the first TFT, and the excitation signal for the EL portion is controlled by the second TFT. The storage capacitor then maintains the excitation power in the EL portion of the selected cell.
FIGS. 1A
to
FIGS. 1D
illustrate a method of manufacturing an ELD according to a related art method. Referring to
FIG. 1A
, polysilicon is deposited on an insulating substrate
11
having a switching part and a pixel part, via a chemical vapor deposition (CVD) process. Then an active layer
13
is formed by patterning the polysilicon via a photolithography process. An insulating substance such as silicon oxide, silicon nitride, or other similar substances are then deposited on the insulating substrate
11
to cover the active layer
13
. Next, an electrically-conductive substance is deposited on the insulating substance. Then, a gate insulating layer
15
and a gate electrode
17
is formed by sequentially patterning the electrically-conductive substance and the insulating substance so that they remain on the middle portion of the active layer
13
. Note that a scanning line (not shown in the drawing) that is connected to the gate electrode
17
may be provided as soon as the gate electrode
17
is formed. A source region
19
and a drain region
21
are then formed by heavily doping the exposed portions of the active layer
13
with either n type or p type impurities with the gate electrode
17
functioning as a mask. Note that the middle portion of the active layer
13
, which is not doped with impurities, becomes a channel region.
Referring to
FIG. 1B
, a first insulating interlayer
23
is then provided and covers the active layer
13
, the gate electrode
17
, and the scanning line by depositing an insulating substance such as silicon oxide, silicon nitride, or other similar substances on the insulating substrate
11
. Next, the first insulating interlayer
23
is patterned to expose the source region
19
and the drain region
21
, and a source electrode
25
and a drain electrode
27
are connected electrically with the exposed source region
19
and exposed drain region
21
, respectively, by depositing and then patterning a known conductive substance. Thus, a TFT that functions as a switching device is manufactured. Note that a signal line (not shown in the drawing) may be defined on the insulating interlayer
23
at the same time the source electrode
25
and the drain electrode
27
are provided.
Referring to
FIG. 1C
, a second insulating interlayer
29
is provided and covers the source electrode
25
and the drain electrode
27
and the signal line by depositing silicon oxide or silicon nitride on the first insulating interlayer
23
. A contact hole
30
exposes the drain electrode
27
and is provided by patterning the second insulating interlayer
29
. Next, a transparent conductive substance is deposited so as to contact the exposed portion of the drain electrode
27
through the contact hole
30
that is provided in the second insulating interlayer
29
. Then, an anode electrode
31
is formed by patterning via a photolithography process the transparent conductive substance so that the anode electrode
31
remains in the pixel portion of the second insulating interlayer
29
. Note that the anode electrode
31
is electrically connected to the drain electrode
27
, and is isolated electrically from other anode electrodes in adjacent pixel cells.
Referring to
FIG. 1D
, a passivation layer
33
covers the anode electrode
31
by the deposition of silicon oxide or silicon nitride on the second insulating interlayer
29
. Alternatively, the passivation layer
33
may be formed with an organic substance such as BCB (benzocyclobutene), SOG(spin-on glass), and other similar substances. Note that the passivation layer
33
made of an organic substance may be relatively thick in order to provide an even surface. Next, the passivation layer
33
is patterned via a photolithography process, including a dry etching process, so as to expose the anode electrode
31
. An organic EL layer
35
, which emits a predetermined color such as red, blue, or green, is provided on the passivation layer
33
by an evaporation process. Note that the organic EL layer
35
just contacts the anode electrode
31
and the exposed pixel portion. Next, a cathode electrode
37
, which functions as a common electrode, is disposed on the organic EL layer
35
.
As mentioned in the above description, the ELD of the related art carries out the switching operation by selecting a TFT that has an n-type channel in a certain pixel, which has a predetermined signal line (not shown in the drawing) crossing with a predetermined scanning line (not shown in the drawing), such that a ‘high’ signal is applied to the predetermined scanning line while a ‘high’ signal is applied to the predetermined signal line. Thus, the selected TFT turns on and transfers the signal of the predetermined signal line to the drain electrode by which holes are injected into the organic EL layer via the anode electrode and electrons are injected into the organic EL layer via the cathode electrode. Thus, the pixel achieves light-emission through the recombination of electrons and holes.
Unfortunately, in the structure and method of the related art, the exposed portion of the anode electrode is easily damaged by the collision of the ions when dry-etching the passivation layer for exposing the anode electrode. Further, contaminant particles, albeit a small amount, remain on the exposed portion of the anode electrode after the etching process. Thus, the damage to the anode electrode caused by the collision of the ions during the etching process and the remaining contaminant particles on the anode electrode after the etching process creates a barrier interface between the anode electrode and the EL layer that hinders the efficient transport of charge carriers such as holes. Therefore, the expected life span, brightness, and efficiency of the ELD suffers greatly from the structure and method of the related art.
SUMMARY OF THE INVENTION
To overcome the problems described above, preferred embodiments of the present invention provide an ELD and a method of manufacturing the ELD that improves the expected life span, brightness, and efficiency of the ELD by preventing the generation of a barrier interface between the anode electrode and the organic EL layer, which hinders the transport of charge carriers such as holes across t
Bae Sung-Joon
Park Jae-Yong
Birch & Stewart Kolasch & Birch, LLP
Lee Eddie
Lee Eugene
LG. Philips LCD Co. Ltd.
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