Scan Driver Transistor Segmentation for Hot Carrier Stability
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Solution Overview
Problem
Display devices face challenges with hot carrier instability (HCl) phenomenon, leading to reduced driving current and flicker phenomena due to increased electric fields and electron penetration through insulating films, affecting the reliability of scan and light emission control drivers.
Innovation Solution
The implementation of transistors with reduced channel width and length in the scan and light emission control drivers, featuring parallel and series configurations of sub-transistors with shared gate electrodes and specific edge region designs to minimize the hot carrier instability, thereby reducing the area occupied by the bulk region and increasing the edge regions, which decreases the lateral electric field and enhances stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transistors with standard channel width and length are used in scan and light emission control drivers, then the device structure is simple and manufacturing is easier, but hot carrier instability occurs leading to reduced driving current and flicker phenomena
Solution Approach 1:
The transistor is divided into multiple sub-transistors (first, second, and third sub-transistors) with different channel widths and lengths. This segmentation allows each sub-transistor to contribute differently to the overall current, with narrower channel sub-transistors providing higher current stability against hot carrier effects while wider channel sub-transistors maintain sufficient drive current capability.
Solution Approach 2:
Different regions of the transistor structure are given different properties - specifically, sub-transistors with narrower channel widths are positioned in regions where hot carrier stability is most critical. This local differentiation of channel dimensions optimizes the balance between stability and drive current in specific areas of the driver circuit.
2Reliability
If transistors with narrower channel width are used to reduce hot carrier instability, then driving current stability improves, but the transistor area increases
Solution Approach 1:
Instead of using a single wide-channel transistor that would be area-efficient but unstable, the structure is segmented into multiple sub-transistors where narrower channels provide stability. The series-parallel combination allows area optimization while maintaining the stability benefits of narrow channels.
Solution Approach 2:
Multiple sub-transistors with different channel dimensions are merged in series and parallel configurations. This merging allows the narrow-channel sub-transistors (providing stability) and wider-channel sub-transistors (providing drive current) to work together, achieving both stability and area efficiency that neither configuration could achieve alone.
Data Source
AI summary
A display device includes: a pixel unit including a plurality of pixels; a scan driver having a plurality of stages and configured to supply a scan signal to the pixel unit; and a light emission control driver having a plurality of stages and configured to supply a light emission control signal to the pixel unit, wherein a first transistor of a plurality of transistors included in at least one of the stages of the scan driver or the stages of the light emission control driver comprises: an active layer pattern on a base layer, and including a channel region forming a channel, and first and second regions on opposite sides of the channel region; and a gate electrode spaced apart from the active layer pattern with a first insulating film therebetween, and overlapping the channel region.