Patterning of electrodes in oled devices

Details Patterning of electrodes in oled devices Patterning of electrodes in oled devices

2001-11-20

2004-03-02

Fourson, George (Department: 2823)

Semiconductor device manufacturing: process

Making device or circuit emissive of nonelectrical signal

Mesa formation

C313S504000, C313S506000, C438S024000, C438S099000

Reexamination Certificate

active

06699728

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to patterning of an electrode, such as those in organic light emitting diode (OLED) devices.
BACKGROUND OF THE INVENTION
FIG. 1
shows a pixelated OLED device
100
which serve, for example, as a display in various types of consumer electronic products, including cellular phones, cellular smart phones, personal organizers, pagers, advertising panels, touch screen displays, teleconferencing and multimedia products, virtual reality products, and display kiosks.
The OLED device comprises a functional stack formed on a substrate
101
. The functional stack comprises of one or more organic functional layers
110
between two conductive layers (
115
and
105
) which serve as electrodes (cathode and anode). The conductive layers are patterned as desired. For example, the conductive layers can be patterned to form rows of cathodes in a first direction and columns of anodes in a second direction. OLED cells or pixels are located where the cathodes and anodes overlap. Charge carriers are injected through the cathodes and anodes via bond pads
150
for recombination in the functional layers. The recombination of the charge carriers causes the functional layer of the pixels to emit visible radiation. The device is encapsulated with a cap
160
, hermetically sealing cells.
The radiation from the cells can either be visible through the cap or through the substrate. To view the radiation through the cap, a transparent upper electrode and cap are used; a transparent lower electrode and substrate are used for viewing through the substrate.
As shown in
FIG. 2
, tapered or shaped pillars
170
are used to facilitate patterning of the upper electrode. Tapered or shaped pillars are described in, for example, Ext. Abstr. 44
th
Spring Meeting Japan Society of applied Physics and related Societies, 1997, and U.S. Pat. Nos. 5,962,970, 5,952,037, 5,742,129, or 5,701,055, which are all herein incorporated by reference for all purposes. The pillars are formed on the substrate after the formation of the lower electrode. Thereafter, the functional materials are deposited by, for example, spin-coating techniques. A conductive material is then deposited over the functional layer by, for example, vacuum deposition methods. Due to the profile of the pillars, the conformality of the conductive layer is disrupted, leaving segments of the conductive layer
115
a
over the functional material and segments
115
b
on top of the pillars.
As shown in
FIG. 2
, the deposition of the polymer solution causes polymers to pile up at the base of the pillars. The piling up of polymer material at the base of the pillars alter the pillar's profile and can prevent the pillars from disrupting the conformality of the conductive layer
115
, thus causing shorts between cells.
As evidenced from the foregoing discussion, it is desirable to provide shaped pillar structures which can effectively pattern electrodes in the fabrication of OLED devices.
SUMMARY OF THE INVENTION
The invention relates generally to fabrication of, for example, OLED devices. More particularly, the invention relates to patterning of a conductive layer. In one embodiment, a pillar is separated into first and second sub-pillars wherein a pillar includes an undercut and separated by a gap. The undercuts of the sub-pillars disrupt the continuity of a subsequently deposited conductive layer. The sub-pillars are formed by photolithography. In one embodiment, the sub-pillars are formed from a photosensitive material which is inert to the solvents associated with deposition of the functional organic layer.


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