Sampling Transistor Segmentation for Narrow Pitch Stability
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Solution Overview
Problem
In active matrix type liquid crystal display devices, the stability of the sample and hold circuit is compromised due to stress-induced cracks in the insulating film, particularly when transistors are disposed at a narrow pitch, leading to operational issues and display unevenness.
Innovation Solution
The solution involves configuring the sampling transistors with multiple transistors connected in parallel and a monitor transistor with a single transistor, along with a light shielding layer arrangement that disperses stress and prevents cracks, ensuring stable operation and reliable signal transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If transistors are disposed at a narrow pitch to increase pixel density, then high-definition display is achieved, but stress-induced cracks occur in the insulating film leading to circuit instability
Solution Approach 1:
The sampling transistor is divided into multiple sub-transistors (first, second, third, and fourth sampling transistors) connected in parallel. This segmentation reduces the channel width of each individual transistor, allowing them to be disposed at narrower pitches without causing stress concentration that would lead to insulating film cracks, thereby maintaining circuit reliability while achieving high-definition display
Solution Approach 2:
Different regions of the circuit are designed with different transistor configurations. The sampling transistor region uses multiple divided transistors to prevent cracks, while the monitoring transistor uses a single transistor design. This local differentiation optimizes each region for its specific function while maintaining overall circuit stability at high pixel densities
2Reliability
If multiple transistors are used in parallel for sampling, then circuit stability is improved, but device complexity increases
Solution Approach 1:
Multiple sampling transistors are connected in parallel to form a single functional sampling unit. This merging approach distributes the sampling function across multiple transistors, improving reliability through redundancy and reduced stress on individual components, while the parallel configuration maintains the same external interface and control logic, thus managing complexity
3Manufacturing precision
If gate electrodes are meandered to fit narrow pitch, then transistor density increases, but channel length variation occurs affecting operation stability
Solution Approach 1:
Instead of meandering a single gate electrode, the sampling transistor is segmented into multiple sub-transistors with straight, simple gate electrodes. This segmentation allows each sub-transistor to have a uniform and controlled channel length, eliminating the channel length variation that would result from meandering while still achieving narrow pitch through the parallel arrangement of multiple units
Data Source
AI summary
An electro-optical device (e.g., a liquid crystal device) includes a data line connected to a switching element provided for each pixel, a sampling transistor that has a gate supplied with a selection signal, a source supplied with an image signal, and a drain connected to the data line, and a monitoring transistor. A gate of the monitoring transistor is supplied with an input signal. A delay signal indicating a delay amount of the selection signal is sent out from a drain of the monitoring transistor. The sampling transistor includes a plurality of transistors connected in parallel to each other along the data line. The monitoring transistor includes one transistor along the data line.