Organic Light Emitting Display Capacitor Mask Misalignment Compensation
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Solution Overview
Problem
Existing organic light emitting display devices face challenges in maintaining constant capacitance of capacitors due to mask misalignment during photolithography and etching processes, leading to fluctuations in capacitance values.
Innovation Solution
The display device design includes a specific configuration of storage electrodes and channel shapes for transistors, where the lower storage electrode has multiple portions and the upper storage electrode overlaps these portions, ensuring consistent overlap areas even with mask misalignment, thus maintaining constant capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional photolithography and etching processes are used to form transistors and capacitors, then manufacturing efficiency is maintained, but mask misalignment causes fluctuation in capacitor capacitance
Solution Approach 1:
The lower storage electrode is segmented into multiple portions (first portion, second portion, third portion, fourth portion) positioned at different locations. This segmentation ensures that even if mask misalignment occurs, at least some portions will maintain proper overlap with the upper storage electrode, thereby maintaining stable capacitance
Solution Approach 2:
Different portions of the lower storage electrode are strategically positioned to overlap with different regions of the upper storage electrode. Each portion serves a local function in maintaining capacitance, with the first and second portions positioned at opposite sides of the gate electrode and the third and fourth portions connected to the switching transistor
2Reliability
If the upper storage electrode overlaps the channel of the driving transistor to maximize capacitance, then capacitance value increases, but mask misalignment causes overlap area variation and capacitance fluctuation
Solution Approach 1:
The lower storage electrode is divided into multiple portions positioned at different locations relative to the upper storage electrode and gate electrode. This segmentation distributes the overlap area across multiple regions, ensuring that mask misalignment affects only some portions while others maintain proper overlap, thereby stabilizing total capacitance
Solution Approach 2:
The lower storage electrode portions are positioned asymmetrically with respect to the gate electrode and upper storage electrode, with specific portions placed at opposite sides and others connected to the switching transistor. This asymmetric distribution optimizes capacitance stability while avoiding direct overlap with the channel region
Data Source
AI summary
A display device includes: a substrate; a driving voltage line and a data line that are on the substrate; a semiconductor layer that includes a first electrode, a channel, and a second electrode of a driving transistor, the driving transistor being connected to the driving voltage line; a gate electrode of the driving transistor overlapping the channel; a lower storage electrode extending from the gate electrode; and an upper storage electrode overlapping the lower storage electrode, wherein the semiconductor layer further includes a first electrode, a channel, and a second electrode of a switching transistor, the switching electrode being connected between the lower storage electrode and the data line, the upper storage electrode does not overlap the channel of the driving transistor, the lower storage electrode includes a first portion and a second portion that are at opposite sides of the gate electrode.