A study on photolithographic patterning for organic electronics
Date Issued
2006
Date
2006
Author(s)
Jhuo, Syue-Jhao
DOI
en-US
Abstract
Abstract
The objective of this study is to realize high-resolution patterning of organic electronic materials by photolithography, with a goal of facilitating the development of commercially viable manufacturing processes for producing organic light-emitting diode (OLED) displays. Current patterning technologies such as inkjet printing and shadow-mask deposition are inadequate for commercializing organic electronics due to their limitations on resolution, throughput, and displays size. Photolithography, well-developed for industrial patterning, is well positioned to overcome the challenge of patterning for organic electronics. We developed a photolithographic method for patterning organic electroluminescent materials for OLED displays, and demonstrated its practicality.
In the first part of our study, we determined the mechanism of a ~60% reduction in feature size, discovered with chemically amplified (CA) photo-resists, upon post-development UV irradiation. When a CA photo-resist is treated with post-development UV irradiation, it is both deprotected and cross-linked. Deprotection of the protecting groups turns them into gases to escape the photoresist, increasing the free volume of the photoresist. Crosslinking of the photoresist contracts the increased free volume, inducing a macroscopic reduction in the feature size. This technique enhances the resolution limitation for 248-nm photolithography from 90-nm feature sizes to sub-50-nm feature sizes.
In the second part of our study, we fabricated OLED displays with photolithography, using MEH-PPV as the electroluminescent materials. Before the photolithographic process, a 15-cycle ALD Al2O3 layer was overcoated onto the MEH-PPV layer to isolate the MEH-PPV surface from direct contact with the solvents used in the photolithographic process.
We observed that OLED devices, whose MEH-PPV layer was passivated with an Al2O3 film and was photolithographically patterned thereafter, showed 3-fold increase in efficiency and 10-fold increase in emissive intensity, compared to the control. This enhancement of performance may result from the Al2O3 film’s dual functions: protecting and buffering. An Al2O3 film is known to function as a buffer layer, which reduces the barrier height for the injection of electrons in OLEDs, leading to dramatic increases in current efficiency and emissive intensity.
Through our study, we have demonstrated the extendability of the 248-nm photolithography to feature sizes smaller than 50 nm. We have also demonstrated photolithographic patterning for OLEDs with a passivating ALD Al2O3 layer, achieving enhanced device performance.
Subjects
圖樣
共軛
原子層沉積
有機光電
光阻
pattern
conjugated polymer
atomic layer deposition
photoresists
Type
thesis
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