Semiconductor device manufacturing: process – Repair or restoration
Reexamination Certificate
2002-05-30
2004-08-17
Le, Vu A. (Department: 2824)
Semiconductor device manufacturing: process
Repair or restoration
C438S022000, C438S099000, C257S040000
Reexamination Certificate
active
06777249
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of repairing a light-emitting device, and to a method of manufacturing a light-emitting device using the repairing method in an intermediate process step. More specifically, the present invention relates to a method of repairing a light-emitting device by applying a reverse bias to organic light emitting elements, and to a method of manufacturing a light-emitting device using the repairing method.
The term “light-emitting device” is a generic term referring to organic light emitting displays in which organic light emitting elements formed on a substrate are enclosed between the substrate and a covering material, and to modules in which ICs are mounted in the organic light emitting displays.
2. Description of the Related Art
Organic light emitting elements are self light emitting, and therefore have high visibility. In addition to organic light emitting elements being optimal for making devices thinner because a backlight like that used in liquid crystal display devices (LCDs) is not needed, there is no limit on the angle of view. Light-emitting devices using organic light emitting elements have therefore been in the spotlight in recent years as electro-optical devices that can replace CRTs and LCDs.
Organic light emitting elements have a layer containing an organic compound (hereafter referred to as an organic compound layer) in which luminescence (electroluminescence) is generated by the addition of an electric field, an anode layer, and a cathode layer. Two types of luminescence exist, light emission when returning to a base state from a singlet excited state (fluorescence), and light emission when returning to a base state from a triplet excited state (phosphorescence), and it is possible to apply the repairing method of the present invention to light-emitting devices using either type of light emission.
Note that, in this specification, all layers formed between an anode and a cathode are defined as the organic compound layer. Specifically, light emitting layers, hole injecting layers, electron injecting layers, hole transporting layers, electron transporting layers, and the like are included in the term organic compound layer. Organic light emitting elements basically have a structure in which an anode, a light emitting layer, and a cathode are laminated in the order. Other structures also exist in addition to this structure, such as one in which an anode, a hole injecting layer, a light emitting layer, and a cathode are laminated in the order, and one in which an anode, a hole injecting layer, a light emitting layer, an electron transporting layer, and a cathode are laminated in the order.
Further, making a light emitting element emit light is referred to as driving the light emitting element in this specification. Light emitting elements formed by an anode, an organic compound layer, and a cathode are referred to as organic light emitting elements in this specification.
Organic light emitting elements have high rectification characteristics, and electric current flows in the organic compound if the electric potential of the anode is higher than the electric potential of the cathode. Light is emitted due to recombination of the carrier. Conversely, if the anode is at a lower electric potential than the cathode, almost no electric current will flow in the organic compound layer. From this diode structure, organic light emitting elements are also referred to as organic light emitting diodes (OLEDs).
In making organic light emitting elements, generally one electrode, either the anode of the cathode, is formed, after which the organic compound layer is formed so as to contact the electrode. The remaining electrode is then formed so as to contact the organic compound layer.
The main methods of forming the organic compound layer are a film formation method by evaporation, and a film formation method by spin coating. Whichever method is used, care is taken when performing film formation. Substrates are washed before film formation so that refuse and the like does not adhere to the substrate during film formation of the electrodes and the organic compound layer, and management of the cleanliness of a clean room within which film formation takes place is performed thoroughly.
However, even if every effort is made for cleanliness, there are cases in which refuse and the like adhere to the electrodes or other films, forming holes (pinholes) in the organic compound layer.
FIG. 12A
shows a simple cross sectional diagram of an organic light emitting element
200
for a case in which there is a short circuit between two electrodes
201
and
202
. If a pinhole is opened in an organic compound layer
203
, then the two electrodes
201
and
202
are connected in the pinhole when forming the electrode
202
on the organic compound layer
203
, thus forming a short circuit in some cases. Note that portions in which two layers formed sandwiching a light emitting layer therebetween are connected through pinholes formed in the light emitting layer are hereafter referred to as defect portions
204
.
The voltage-current characteristics of an organic light emitting element that does not have a defect portion are shown in
FIG. 13A
, and the voltage-current characteristics of an organic light emitting element that has a short circuit in a defect portion are shown in FIG.
13
B.
Comparing
FIGS. 13A and 13B
, it can be seen that the electric current flowing in the organic light emitting element
200
when a reverse bias voltage is applied to the organic light emitting element
200
is larger for the case of FIG.
13
B.
This is because the two electrodes are shorted in the defect portion
204
for the case of
FIG. 13B
, and current therefore flows in the defect portion
204
, differing from FIG.
13
A.
If the two electrodes
201
and
202
are shorted in the defect portion
204
, then the brightness of light emitted from the organic compound layer drops. The electric current flowing in an organic light emitting element having a defect portion when a forward bias voltage is applied is shown schematically in FIG.
12
B.
It can be considered that the defect portion
204
has a resistance R
SC
therein, and thereby the two electrodes of the organic light emitting element
200
are connected for cases in which the two electrodes
201
and
202
are shorted in the defect portion
204
. Consequently, if the electric current flowing in the defect portion
204
is taken as I
SC
, and the electric current flowing in the organic compound layer
203
is taken as I
dio
when an electric current I
ori
flows from one electrode of the organic light emitting element, then the electric current I
ori
satisfies the equation I
ori
=I
SC
+I
dio
.
If I
ori
is taken as fixed in the aforementioned equation I
ori
=I
SC
+I
dio
, then the current I
dio
actually flowing in the organic compound layer
203
becomes smaller in organic light emitting elements having defect portions. If the resistance R
SC
in the defect portion
204
becomes smaller, then I
SC
increases, and therefore this tendency becomes more conspicuous and the rectification properties of the organic light emitting element
200
collapse.
If the current I
dio
flowing in the organic compound layer
203
becomes smaller, then the brightness of light emitted from the organic light emitting element
200
drops. That is, if there is a short circuit in the defect portion, then the brightness of light emitted from the organic light emitting element when a forward bias voltage is applied becomes lower compared to a case in which there is no short circuit.
Further, even if the organic compound layer is formed by laminating together a plurality of layers, if a pinhole is formed in the light emitting layer, then the hole injecting layer or the hole transporting layer will be connected to the electron injecting layer or the electron transporting layer through the pinhole. Portions in which the hole injecting layer or the hole transporting layer
Cook Alex McFarron Manzo Cummings & Mehler, Ltd.
Le Vu A.
Semiconductor Energy Laboratory Co,. Ltd.
Smith Brad
LandOfFree
Method of repairing a light-emitting device, and method of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of repairing a light-emitting device, and method of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of repairing a light-emitting device, and method of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3317263