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Researchers Submit Patent Application, "Organic Light Emitting Diode Display and Method of Manufacturing the Same", for Approval

June 12, 2014



By a News Reporter-Staff News Editor at Politics & Government Week -- From Washington, D.C., VerticalNews journalists report that a patent application by the inventors PARK, Kyung-Min (Yongin-City, KR); PARK, Ji-Yong (Yongin-City, KR); KIM, Tae-Gon (Yongin-City, KR), filed on August 7, 2013, was made available online on May 29, 2014.

The patent's assignee is Samsung Display Co., Ltd.

News editors obtained the following quote from the background information supplied by the inventors: "The present invention relates generally to an organic light emitting diode display and a method of manufacturing the same, and more particularly, to an organic light emitting diode display which broadens a driving range of a gate voltage applied to a driving transistor so as to display a lot of grayscales.

"An organic light emitting diode display includes two electrodes and an organic emission layer interposed therebetween. Electrons injected from a cathode that is one electrode and holes injected from an anode that is another electrode are bonded to each other in the organic emission layer to form an exciton, and light is emitted while the exciton discharges energy.

"The organic light emitting diode display includes a plurality of pixels including an organic light emitting diode that is formed of a cathode, an anode and an organic emission layer, and a plurality of transistors and capacitors for driving the organic light emitting diode are formed in each pixel. A plurality of transistors basically includes a switching transistor and a driving transistor.

"When light emitted from the organic light emitting diode is displayed so as to have a range from a black color to a white color according to a driving current Id flowing through the organic light emitting diode, an interval between a gate voltage displaying the black color and a gate voltage displaying the white color is defined as a driving range of the gate voltage. The higher the resolution of the organic light emitting diode display is, the lower the size of one pixel is, and thus, an amount of flowing current per the pixel is reduced, such that a driving range of a gate voltage applied to a gate electrode of the switching transistor and the driving transistor becomes narrow. Accordingly, it is difficult to adjust the magnitude of the gate voltage Vgs applied to the driving transistor so as to ensure a lot of grayscales.

"The above information disclosed in this Background section is only for enhancement of an understanding of the background of the described technology and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art."

As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventors' summary information for this patent application: "The present invention has been developed in an effort to provide an organic light emitting diode display which broadens a driving range of a gate voltage applied to a driving transistor so as to display a lot of grayscales.

"An exemplary embodiment provides an organic light emitting diode display including: a substrate; a semiconductor layer formed on the substrate and including a switching semiconductor layer, a driving semiconductor layer, and a light emission control semiconductor layer spaced apart from each other; a first gate insulating layer covering the semiconductor layer; a light emission control gate electrode formed on the first gate insulating layer and overlapping the light emission control semiconductor layer; a second gate insulating layer covering the light emission control gate electrode; a switching gate electrode and a driving gate electrode formed on the second gate insulating layer and respectively overlapping the switching semiconductor layer and the driving semiconductor layer; and an interlayer insulating layer covering the switching gate electrode, the driving gate electrode, and the second gate insulating layer. A doping concentration of a channel region of the driving semiconductor layer may be higher than the doping concentration of the channel region of the light emission control semiconductor layer.

"The doping concentration of the channel region of the driving semiconductor layer may be 2.times.10.sup.11 to 5.times.10.sup.13 /cm.sup.3, and the doping concentration of the channel region of the light emission control semiconductor layer may be 9.times.10.sup.10 /cm.sup.3 or less.

"A doping impurity of the channel region of the driving semiconductor layer and the doping impurity of the channel region of the light emission control semiconductor layer may be the same type of doping impurity.

"The doping impurity of the channel region of the driving semiconductor layer and the doping impurity of the channel region of the light emission control semiconductor layer may each be any one selected from an N type impurity or a P type impurity and different types of doping impurities.

"The organic light emitting diode display may further include: a scan line formed on the substrate and transferring a scan signal, a data line and a driving voltage line crossing the scan line and transferring a data signal and a driving voltage, respectively, a switching transistor connected to the scan line and the data line and including the switching semiconductor layer and the switching gate electrode, a driving transistor connected to a switching drain electrode of the switching transistor and including the driving semiconductor layer and the driving gate electrode, and an organic light emitting diode connected to a driving drain electrode of the driving transistor, in which the doping concentration of the channel region of the switching semiconductor layer may be the same as the doping concentration of the channel region of the driving semiconductor layer.

"The first gate insulating layer and the second gate insulating layer may be formed between the driving semiconductor layer and the driving gate electrode of the driving transistor.

"The first gate insulating layer and the second gate insulating layer may be formed between a switching semiconductor layer and a switching gate electrode of a switching transistor.

"The organic light emitting diode display may further include: an operation control transistor turned-on by a light emission control signal transferred by a light emission control line spaced apart from the scan line to transfer the driving voltage to the driving transistor, and a light emission control transistor turned-on by the light emission control signal to transfer the driving voltage from the driving transistor to the organic light emitting diode, in which a first gate insulating layer may be formed between a light emission control semiconductor layer and a light emission control gate electrode of the light emission control transistor, and a doping concentration of a channel region of an operation control semiconductor layer of the operation control transistor may be the same as the doping concentration of the channel region of the light emission control semiconductor layer.

"The organic light emitting diode display may further include: a compensation transistor turned-on by a scan signal to compensate a threshold voltage of the driving transistor and connected to the driving transistor, and an initialization transistor turned-on according to a prior scan signal transferred through a prior scan line spaced apart from a scan line to transfer an initialization voltage transferred through an initialization voltage line adjacent to the prior scan line to a driving gate electrode of the driving transistor, in which the first gate insulating layer and a second gate insulating layer may be formed in the compensation transistor and the initialization transistor, and the doping concentrations of the channel regions of a compensation semiconductor layer of the compensation transistor and an initialization semiconductor layer of the initialization transistor may be the same as the doping concentration of the channel region of a driving semiconductor layer.

"The organic light emitting diode display may further include: a storage capacitor including a first storage capacitive plate formed on the first gate insulating layer and a second storage capacitive plate formed on the second gate insulating layer covering the first storage capacitive plate and overlapping the first storage capacitive plate, in which a driving voltage line may be connected to the second storage capacitive plate.

"Another exemplary embodiment provides a method of manufacturing an organic light emitting diode display, including: forming a semiconductor layer on a substrate, performing first channel doping on the semiconductor layer, forming a first gate insulating layer covering the semiconductor layer, forming a light emission control gate electrode on the first gate insulating layer, performing second channel doping on the semiconductor layer by using the light emission control gate electrode as a blocking mask, forming a second gate insulating layer covering the light emission control gate electrode and the first gate insulating layer, forming a switching gate electrode and a driving gate electrode on the second gate insulating layer, performing source and drain doping on the semiconductor layer to form a driving semiconductor layer, a switching semiconductor layer, and a light emission control semiconductor layer, and forming an interlayer insulating layer covering the switching gate electrode and the driving gate electrode on the second gate insulating layer.

"A doping concentration of a channel region of the driving semiconductor layer may be higher than the doping concentration of the channel region of the light emission control semiconductor layer.

"A doping impurity used in the first channel doping and the doping impurity used in the second channel doping may be the same type of doping impurity.

"A doping impurity used in the first channel doping and the doping impurity used in the second channel doping may be any one selected from an N type impurity or a P type impurity and different types of doping impurities.

"According to the exemplary embodiments, it is impossible to broaden a driving range of a gate voltage applied to a driving transistor to display a lot of grayscales and, at the same time, improve a charge mobility of an operation control transistor and a light emission control transistor by forming a first gate insulating layer and a second gate insulating layer between a gate electrode and a semiconductor layer of the driving transistor, and by forming only the first gate insulating layer between the gate electrode and the semiconductor layer of the operation control transistor and the light emission control transistor.

"Furthermore, a threshold voltage Vth of the driving transistor may be set to be the same as the threshold voltage Vth between the operation control transistor and the light emission control transistor by setting a doping concentration of a channel region of the semiconductor layer of the driving transistor to be higher than the doping concentration of the channel region of the semiconductor layer of the operation control transistor and the light emission control transistor.

BRIEF DESCRIPTION OF THE DRAWINGS

"A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings, in which like reference symbols indicate the same or similar components, wherein:

"FIG. 1 is an equivalent circuit view of one pixel of an organic light emitting diode display according to an exemplary embodiment of the invention.

"FIG. 2 is a view schematically illustrating a plurality of transistors and capacitors of the organic light emitting diode display according to the exemplary embodiment.

"FIG. 3 is a specific layout view of one pixel of FIG. 2.

"FIG. 4 is a cross-sectional view of the organic light emitting diode display of FIG. 3, which is taken along line IV-IV.

"FIG. 5 is a cross-sectional view of the organic light emitting diode display of FIG. 3, which is taken along line V-V' and line V'-V''.

"FIGS. 6, 8, 10 and 12 are layout views sequentially illustrating a method of manufacturing the organic light emitting diode display according to the exemplary embodiment.

"FIG. 7 is a cross-sectional view of the organic light emitting diode display of FIG. 6, which is taken along line VII-VII.

"FIG. 9 is a cross-sectional view of the organic light emitting diode display of FIG. 8, which is taken along line IX-IX.

"FIG. 11 is a cross-sectional view of the organic light emitting diode display of FIG. 10, which is taken along line XI-XI.

"FIG. 13 is a cross-sectional view of the organic light emitting diode display of FIG. 12, which is taken along line XIII-XIII."

For additional information on this patent application, see: PARK, Kyung-Min; PARK, Ji-Yong; KIM, Tae-Gon. Organic Light Emitting Diode Display and Method of Manufacturing the Same. Filed August 7, 2013 and posted May 29, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=5280&p=106&f=G&l=50&d=PG01&S1=20140522.PD.&OS=PD/20140522&RS=PD/20140522

Keywords for this news article include: Electronics, Semiconductor, Light-emitting Diode, Samsung Display Co. Ltd..

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Source: Politics & Government Week


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