Polysilicon–Oxide TFT Display Structure with Integrated Light Shielding
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Solution Overview
Problem
The integration of polysilicon and oxide semiconductor TFTs on a single substrate faces challenges such as process contamination, complex manufacturing processes due to multiple through holes, and instability in oxide semiconductor characteristics due to hydrofluoric acid exposure and light shading requirements.
Innovation Solution
A display device structure is devised where polysilicon and oxide semiconductor TFTs are formed on different layers with shared light shading films, reducing the need for separate through holes and eliminating the formation of protecting metals on oxide semiconductors, thereby stabilizing their characteristics and simplifying the manufacturing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If polysilicon semiconductor TFTs and oxide semiconductor TFTs are formed on the same substrate with separate through holes, then both types of TFTs can be integrated, but the manufacturing process becomes complex and the oxide semiconductor characteristics become unstable due to hydrofluoric acid exposure
Solution Approach 1:
The patent merges the light shading film and shielding film into a single integrated structure formed from the same conductive layer. This combined film serves dual functions: shading light from reaching the oxide semiconductor TFTs and shielding them from electric fields generated by the polysilicon TFTs below. By eliminating the need for separate through holes and protecting metal layers, the manufacturing process is simplified while maintaining stable oxide semiconductor characteristics.
2Reliability
If separate through holes are formed for polysilicon and oxide semiconductor TFTs, then both can be connected to their respective electrodes, but the number of through holes increases manufacturing complexity
Solution Approach 1:
The patent creates a multi-functional conductive layer that simultaneously serves as the light shading film, shielding film, and electrode connection path. This single layer performs multiple functions that previously required separate components: it shades light, shields from electric fields, and provides electrical connections to both polysilicon and oxide semiconductor TFTs through its continuous structure, thereby reducing the number of manufacturing steps.
3Reliability
If protecting metals are formed on oxide semiconductors to prevent hydrofluoric acid contamination, then oxide semiconductor characteristics are stabilized, but the manufacturing process becomes more complex
Solution Approach 1:
The patent extracts and eliminates the protecting metal layer from the manufacturing process. Instead of forming separate protecting metal layers on oxide semiconductor regions to prevent hydrofluoric acid damage, the invention uses a bottom-gate transistor structure where the gate electrode and gate insulating layer inherently protect the oxide semiconductor channel during etching processes, simplifying the overall manufacturing process.
4Adaptability or versatility
If polysilicon semiconductor TFTs are formed on the lower layer, then they can serve as driving circuits, but light from the back light influences the TFT characteristics
Solution Approach 1:
The patent combines the light shading function and electric field shielding function into a single integrated conductive layer positioned above the polysilicon TFTs and below the oxide semiconductor TFTs. This merged film structure effectively blocks light from reaching the oxide semiconductor regions while simultaneously shielding them from electric fields generated by the polysilicon driving circuits, solving both problems with one structure.
Data Source
AI summary
A display device including: a substrate; a first thin film transistor of polysilicon semiconductor, a second thin film transistor of oxide semiconductor; a first light shading film opposing to the polysilicon semiconductor, and a second light shading film opposing to the oxide semiconductor; a first insulating film, a second insulating film which is constituted from plural insulating films, and a third insulating film superposed in this order; a first through hole penetrating the second insulating film and not penetrating the first insulating film and the third insulating film; a second through hole penetrating the first insulating film and the third insulating film; the first light shading film connects with a first conductive component, a part of the first conductive component exists on the third insulating film, through the second through hole.