Robust electrode patterning in OLED devices

Details Robust electrode patterning in OLED devices Robust electrode patterning in OLED devices

2002-09-06

2004-02-24

Fourson, George (Department: 2823)

Semiconductor device manufacturing: process

Making device or circuit emissive of nonelectrical signal

Mesa formation

C438S024000, C438S099000, C313S506000, C313S509000, C313S505000, C313S507000

Reexamination Certificate

active

06696312

ABSTRACT:

BACKGROUND OF INVENTION
FIG. 1
shows a pixelated OLED device
100
, comprising a functional stack on a substrate
102
. The functional stack comprises one or more organic functional layers
104
between two conductive functional layers (
106
and
108
) which serve as electrodes (i.e. anode and cathode). The conductive layers are patterned as desired. For example, the conductive layers can be patterned to form rows of anodes in a first direction and columns of cathodes in a second direction. OLED cells or pixels are located in an active region where the cathodes and anodes overlap. Charge carriers are injected through the cathodes and anodes via bond pads
112
for recombination in the organic layers. The recombination of the charge carriers causes the organic layer of the pixels to emit visible radiation. The device is encapsulated with a cap
110
, hermetically sealing the cells.
As shown in
FIG. 1
, pillars
114
are used to facilitate patterning of the upper conductive layer
108
. The pillars are formed on the substrate after the formation of the lower conductive layer
106
. Thereafter, the organic layer and conductive layer are deposited. Due to the profile of the pillars, the continuity of the upper conductive layer is disrupted, leaving segments of the conductive layer
108
a
over the organic layer
104
and segments
108
b
on top of the pillars.
Referring to FIG.
2
(
a
), the upper conductive layer
108
is deposited selectively onto the active region, through an aperture in a shadow mask
202
. The shadow mask is typically in contact with the substrate during deposition. Close contact between the substrate and the shadow mask may lead to the generation of shorts between adjacent electrodes, such as
108
a
(
i
) and
108
a
(
ii
). Particles
206
accumulated on the shadow mask surface may be transferred to the substrate, causing shorting between electrodes
108
a
(
i
) and
108
a
(
ii
), as shown in FIG.
2
(
b
). Shorting may also be caused by, for example, damage of the pillar structures by the shadow mask during alignment.
Known methods employed to protect the substrate from damage by the shadow mask include maintaining a gap between the shadow mask and the substrate. This gives rise to a blurring of the edges of the conductive layer and a reduction in precision. The conductive layer is deposited over an area larger than the active area to compensate for the blurring. Hence, the outer dimensions of the OLED device are increased without increasing the useful light emitting active area. Moreover, maintaining the gap between the shadow mask and substrate requires additional control complexity.
As evidenced from the foregoing discussion, it is desirable to provide a method that improves the reliability of electrode patterning in the fabrication of OLED devices.
SUMMARY OF INVENTION
The invention relates generally to the fabrication of devices such as OLED devices. The invention relates particularly to the patterning of a conductive layer to form electrodes. Pillars are provided to pattern the conductive layer, wherein portions of the pillars have at least 2 sub-rows to prevent shorting of adjacent electrodes. In one embodiment, the ends of the pillars are split into at least 2 sub-rows.


REFERENCES:
patent: 5952778 (1999-09-01), Haskal et al.
patent: 6111356 (2000-08-01), Roitman et al.
patent: 6373187 (2002-04-01), Nagayama et al.
patent: 2001/0017516 (2001-08-01), Gonther

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