Array Substrate Protection Layer for Photodiode Etching Damage
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Solution Overview
Problem
The etching process in manufacturing array substrates for display apparatuses damages the side walls of PIN photodiodes, increasing hidden current and reducing the signal-to-noise ratio, and requires multiple etching steps for the first transparent electrode, which decreases the effective area of the photodiode.
Innovation Solution
A method for manufacturing an array substrate involving a protection layer with a through-hole, where the PN junction of the photodiode is formed within the hole, and a thin-film transistor is integrated with the photodiode, allowing for a single-layer structure and reduced etching damage, with a planarization layer connecting transparent electrodes to minimize further etching and maintain photodiode area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the etching gas is used in the typical etching process to manufacture PIN photodiode, then the photodiode can be formed, but the side wall of PIN photodiode is damaged which increases hidden current and reduces signal-to-noise ratio
Solution Approach 1:
A protection layer is introduced as an intermediary between the etching process and the photodiode structure. This protection layer covers the photodiode during etching operations, preventing direct contact between etching gas and the photodiode side walls, thereby eliminating damage while still allowing the etching process to proceed for other components
Solution Approach 2:
The protection layer is formed before the etching process to preemptively protect the photodiode. By preparing this protective structure in advance, the photodiode is shielded from harmful etching effects before they can occur, allowing subsequent etching steps to be performed safely on other parts of the substrate
2Reliability
If the first transparent electrode is etched twice to reduce hidden current, then hidden current is reduced, but the effective area of PIN photodiode decreases
Solution Approach 1:
The protection layer serves as a mediator that allows the first transparent electrode to be etched only once. During this single etching process, the protection layer prevents damage to the photodiode side walls, eliminating the need for a second etching step that would otherwise be required to reduce hidden current, thereby preserving the photodiode's effective area
Data Source
AI summary
An array substrate includes a substrate, a protection layer, and a photodiode. The protection layer is disposed over the substrate, has a single layer-structure, and is provided with a through-hole therein. The photodiode includes a lower electrode, a PN junction and an upper electrode, which are sequentially over the substrate. The PN junction is within the through-hole. The protection layer and the PN junction of the photodiode have a substantially same thickness. The array substrate further includes a thin-film transistor over the substrate. An orthographic projection of an active layer of the thin-film transistor on the substrate does not overlap with an orthographic projection of the PN junction of the photodiode on the substrate.