LCD Pixel Structure Four Photomask Process Black Matrix
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional TFT LCD fabrication methods require five photomasks, leading to decreased yield rate and throughput as panel sizes increase, necessitating a reduction in the number of photomasks to enhance efficiency and reduce fabrication time and cost.
Innovation Solution
A method using four photomask processes to form the pixel structure of an LCD, including the formation of a black matrix pattern, which reduces the number of photolithographic processes and simplifies the fabrication of the TFT-array substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If five photomasks are used to form the pixel structure, then the black matrix pattern can be formed with respect to metal lines, but the fabrication time increases and throughput decreases
Solution Approach 1:
The patent combines the black matrix formation process with the pixel electrode pattern formation process into a single photomask step. The fourth photomask simultaneously defines both the pixel electrode pattern and the black matrix pattern, eliminating the need for a separate fifth photomask step. This merging of operations reduces the total number of photomasks from five to four, thereby increasing throughput while maintaining proper alignment of the black matrix pattern with the pixel structure.
Solution Approach 2:
The fourth photomask serves multiple functions: it defines the pixel electrode pattern, defines the black matrix pattern, and establishes the alignment between these two critical components. By making this single photomask perform multiple patterning tasks that previously required separate steps, the process achieves multi-functionality that improves productivity without sacrificing manufacturing precision.
2Manufacturing precision
If five photomasks are used to form the pixel structure, then complete pattern definition is achieved, but the fabrication cost increases
Solution Approach 1:
The patent merges the black matrix formation operation with the pixel electrode pattern formation operation into a single photomask step. This consolidation reduces the total number of photomasks required from five to four, directly lowering material costs and process complexity while maintaining complete pattern definition for both the pixel electrode and black matrix structures.
Solution Approach 2:
The patent eliminates the redundant fifth photomask step that was previously required solely for black matrix formation. By discarding this separate step and integrating its function into the fourth photomask process, the invention reduces fabrication costs without compromising the completeness of pattern definition, as both patterns are successfully formed in the combined step.
3Manufacturing precision
If five photomasks are used to form the pixel structure, then all layers are properly patterned, but the fabrication time increases
Solution Approach 1:
The patent combines two separate photomask operations (pixel electrode patterning and black matrix patterning) into a single fourth photomask step. This merging eliminates the need for a fifth photomask and its associated processing time, including photoresist coating, exposure, development, and etching operations. The layer patterning accuracy is maintained because the single photomask step simultaneously defines both patterns with proper alignment, reducing total fabrication time while preserving manufacturing precision.
Solution Approach 2:
The patent achieves continuous useful action by performing multiple patterning functions in a single uninterrupted photomask process. Instead of completing the pixel electrode pattern and then separately forming the black matrix pattern in distinct steps, both operations are executed continuously in one photomask exposure and development cycle, eliminating idle time between steps while maintaining accurate layer patterning.
Data Source
AI summary
A method of fabricating a pixel structure of liquid crystal display is described. A transparent conductive layer and a first metal layer are formed over a substrate sequentially. The first metal layer and the transparent conductive layer are patterned to form a gate pattern and a pixel electrode pattern. A gate insulating layer and a semiconductor layer are formed over the substrate sequentially. A patterning process is performed to preserve the semiconductor layer and the gate insulating layer above the gate pattern and remove the first metal layer of the pixel electrode pattern. A second metal layer is formed over the substrate. The second metal layer is patterned to form a source pattern and a drain pattern. A black material layer is formed over the substrate, and then the black material layer is patterned to form a black matrix pattern uncovering the transparent conductive layer of the pixel electrode pattern.