LTPO Display Panel Insulating Layer Segmentation
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Solution Overview
Problem
The existing LTPO display panel structure requires multiple layers, leading to increased via hole length, smaller aperture, and higher contact resistance between the source/drain and polysilicon layer, causing process difficulties and potential disconnections.
Innovation Solution
The display panel design includes a substrate with a first thin film transistor and a second thin film transistor, where a third gate insulating layer covers part of the oxide semiconductor layer, reducing the number of layers and via hole depth, and a second gate insulating layer is patterned to minimize contact resistance and facilitate hole digging in the bonding area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thicker insulating film is formed to prevent mutual interference between oxide semiconductor TFT and LTPS TFT, then the barrier effect is improved, but the via hole becomes deeper and smaller, increasing contact resistance and process difficulty
Solution Approach 1:
The patent segments the insulating film into two distinct parts: a first insulating film (thicker, 50-150nm) providing the barrier function, and a second insulating film (thinner, 10-50nm) that is easier to etch. This segmentation allows the via hole to penetrate fewer layers and with less resistance, reducing contact resistance while maintaining the necessary barrier effect between the oxide semiconductor TFT and LTPS TFT.
Solution Approach 2:
The patent applies different material compositions and thicknesses to different regions of the insulating structure. The first insulating film uses a material with higher barrier properties (such as AlOx or HfOx) in the region requiring strong barrier function, while the second insulating film uses a material that is easier to etch (such as SiO2 or SiN). This local differentiation optimizes both the barrier effect and the via hole etching process.
2Use of energy by moving object
If more layers are added to form the LTPO structure, then the low-power performance is improved, but the layer thickness in bonding area increases, making hole digging difficult and impacting pad bending performance
Solution Approach 1:
The patent segments the insulating film structure to reduce the total thickness in the bonding area. By using a thinner second insulating film (10-50nm) compared to conventional single-layer structures, the overall layer thickness is reduced, making hole digging easier and pad bending performance better, while the first insulating film provides the necessary barrier function.
Solution Approach 2:
The patent changes the thickness parameter of the insulating films to optimize both low-power performance and bonding area processing. The first insulating film is set at 50-150nm and the second at 10-50nm, creating a total thickness that maintains the barrier effect while reducing the difficulty of subsequent processing steps in the bonding area.
3Measurement precision
If the via hole aperture is reduced to increase pixel density, then the resolution is improved, but the via hole becomes deeper with smaller aperture, increasing contact resistance and causing abnormal connection
Solution Approach 1:
The patent segments the insulating structure to reduce the depth of via holes needed to reach the polysilicon layer. By having a thinner second insulating film (10-50nm) compared to conventional structures, the via hole depth is reduced even when the aperture is small, thereby maintaining connection reliability while achieving high pixel density.
Solution Approach 2:
The patent uses different material properties in different layers to optimize via hole formation. The second insulating film is specifically chosen to be easier to etch (such as SiO2 or SiN with lower hydrogen content), allowing for precise formation of small-aperture via holes with reduced depth, thereby maintaining connection reliability in high-resolution displays.
4Reliability
If a hydrogen-rich insulating layer is used to cover the entire surface, then the insulation performance is improved, but hydrogen ions invade the IGZO layer causing conductorization and failure
Solution Approach 1:
The patent applies different material compositions to different insulating layers. The second insulating film is specifically chosen to have low hydrogen content (such as SiO2 or SiN deposited by PECVD or sputtering), creating a hydrogen barrier that protects the IGZO layer from conductorization, while the first insulating film provides the main insulation function.
Solution Approach 2:
The second insulating film acts as an intermediary barrier between the hydrogen-rich first insulating film and the hydrogen-sensitive IGZO layer. This intermediate layer with low hydrogen content prevents hydrogen ions from reaching and damaging the IGZO layer, thereby preventing conductorization and device failure.
Data Source
AI summary
The present application proposes a display panel, which includes a substrate, and a first thin film transistor and a second thin film transistor disposed on the substrate at intervals, wherein a first metal layer is disposed on a side of the oxide semiconductor layer away from the third gate, a first interlayer insulating layer is disposed between the first metal layer and the oxide semiconductor layer, a second gate insulating layer is disposed on a side of the first metal layer away from the oxide semiconductor layer, and the first metal layer includes a second gate corresponding to the oxide semiconductor layer.