Three-Photomask Array Substrate Fabrication for Reduced Light Leakage
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Solution Overview
Problem
In the three-photomask manufacturing process of amorphous silicon semiconductor thin film transistor (TFT) displays, the active layer protrudes on both sides below the second metal layer, leading to light leakage and reduced panel resolution.
Innovation Solution
A method involving three photomask processes is employed, including first, second, and third depositions, where the first photomask forms a gate and channel, the second photomask forms a source-drain metal layer, and the third photomask forms a passivation layer and pixel electrode, with specific etching and deposition techniques to prevent active layer protrusion and improve resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a three-photomask manufacturing process is used to reduce costs and improve production efficiency, then production efficiency is improved, but the active layer protrudes on both sides below the second metal layer causing light leakage and reduced resolution
Solution Approach 1:
The patent applies preliminary action by depositing the second metal layer before completing the photomask patterning process. Specifically, the second metal layer is deposited over the active layer before the active layer is fully etched back, ensuring that the metal layer is already in place to prevent protrusion issues before they occur during subsequent processing steps.
Solution Approach 2:
The patent segments the photomask patterning into multiple distinct steps with different photoresist applications. The first photoresist defines the active layer pattern, then after etching, a second photoresist is applied to define the source and drain regions. This segmentation allows precise control over the active layer boundaries while maintaining the benefits of the three-photomask process.
2Object-affected harmful factors
If the active layer is etched back to prevent protrusion, then light leakage is reduced, but the process complexity increases
Solution Approach 1:
The patent merges the etching of the active layer with the formation of source and drain regions into a coordinated multi-step process. Rather than separate etching operations, the process combines photoresist patterning, etching, and metal layer deposition in an integrated sequence that achieves both protrusion prevention and source/drain formation simultaneously, reducing overall process complexity.
Solution Approach 2:
The patent uses the second metal layer as an intermediary element that mediates between the active layer and the final device structure. The metal layer is deposited early and serves as a reference boundary that guides subsequent etching steps, ensuring the active layer is etched back to the correct position without requiring complex direct etching control.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method reduces light leakage and enhances panel resolution while shortening the process flow and improving production efficiency.
Implementation Method 1
The first deposition includes depositing a first metal layer, an insulating layer, an active layer and a doping layer on a substrate in sequence
Implementation Method 2
an etching method of the first metal layer is wet etching
Implementation Method 3
an etching processing method of the doping layer, the active layer and the insulating layer is dry etching
Implementation Method 4
exposing and developing the photoresist
Data Source
AI summary
A method for preparing an array substrate and an array substrate. The method for preparing an array substrate includes: depositing a first metal layer, an insulating layer, an active layer and a doping layer on the substrate; forming a photoresist on doping layer by using a first photomask process, and etching the photoresist to form a gate and a channel; depositing a second metal layer on the substrate; using the second photomask process to form the source-drain metal layer; depositing a passivation layer on the substrate; using the third photomask process to form a pixel electrode layer.