Flat Panel Display Mask Reduction via Gray Scale Photolithography
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Solution Overview
Problem
The conventional method for manufacturing liquid crystal displays requires five masks, leading to high manufacturing costs due to the increased number of masks needed as the size of the liquid crystal device grows, making it economically inefficient.
Innovation Solution
A method utilizing a single gray scale or halftone mask to simultaneously form contact holes and pixel electrodes, reducing the number of masks required and incorporating different transparency regions to define patterns through controlled light exposure and etching processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If five masks are used to form gate metal layer, semiconductor layer, source/drain metal layer, contact holes and pixel electrodes separately, then the manufacturing precision and reliability are improved, but the manufacturing cost and device complexity increase significantly
Solution Approach 1:
The patent combines multiple mask functions into a single mask by forming a multi-layer metal structure (first metal layer with first pattern, second metal layer with second pattern, third metal layer with third pattern) that simultaneously defines contact holes, pixel electrodes, and other display elements. This merging approach reduces the total number of masks from five to one while maintaining the precision of individual pattern formations through the selective etching of each metal layer.
Solution Approach 2:
The single mask is segmented into multiple functional layers, where each metal layer (first, second, and third metal layers) carries a specific pattern that will become a different functional element in the final display device. The segmentation allows each layer to be independently patterned and etched, preserving the manufacturing precision of individual features while reducing overall process complexity.
2Reliability
If five masks are used for manufacturing, then the quality of each layer is maintained, but the manufacturing time and cost increase
Solution Approach 1:
Multiple patterning operations that would normally require five separate masks are merged into a single mask process. The multi-layer metal structure allows simultaneous definition of contact holes, pixel electrodes, and other elements in one exposure and etching cycle, significantly reducing manufacturing cycle time while maintaining layer quality through controlled sequential etching of each metal layer.
Solution Approach 2:
The metal layers are pre-formed with their respective patterns before the final etching step. The first metal layer is formed with a first pattern, the second metal layer with a second pattern, and the third metal layer with a third pattern, allowing subsequent etching processes to quickly convert these pre-patterned layers into the final functional structures without requiring multiple separate mask applications.
3Ease of manufacture
If the number of masks is reduced to one, then the manufacturing cost and time are reduced, but the process complexity in forming multiple patterns increases
Solution Approach 1:
Each metal layer in the single mask structure is assigned a specific local function: the first metal layer forms contact holes, the second metal layer forms pixel electrodes, and the third metal layer forms other display elements. This local quality assignment allows each layer to be optimized for its specific purpose while being integrated into a unified mask structure, reducing overall manufacturing cost without sacrificing functional performance.
Solution Approach 2:
The single mask employs dynamic pattern formation through selective etching. The mask structure allows different regions and layers to be etched at different times and with different etching conditions, enabling the formation of diverse patterns (contact holes, pixel electrodes, etc.) from a single static mask structure. This dynamic approach reduces the need for multiple static masks while maintaining pattern precision.
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 approach reduces the manufacturing cost and time by minimizing the number of masks used, while maintaining the quality of the display substrate by effectively forming contact holes and pixel electrodes with fewer steps and lower material costs.
Implementation Method 1
The photoresist layer 16 is a positive photoresist that can be removed by a developer after the absorption of light energy
Implementation Method 2
The photoresist layer 16 is a positive photoresist that can be removed by a developer after the absorption of light energy
Implementation Method 3
The region not covered by the chromium film 22 defines the patterns of the contact holes. When the light source 3 is shone on the fourth mask 2, part of available light cannot pass through the region covered by the chromium film 22
Implementation Method 4
a soaking process is carried out in a developer (not shown in FIG. 1B). As shown in FIG. 1B, the developer removes only the B region of the photoresist layer 16 and the A region of the photoresist layer 16 is retained
Implementation Method 5
a soaking process is carried out in an etching liquid (not shown in FIG. 1C) for a period of time to form contact holes 151 and 152. The part of the dielectric layer 15 covered by the photoresist layer 16 (i.e. the A region of the dielectric layer 15) is protected from being etched
Data Source
AI summary
The present invention relates to a method for manufacturing a flat panel display. Herein, the same mask is used to form contact holes and pixel electrodes in the display substrate. Hence, the number of masks needed for manufacturing the flat panel display can be reduced to decrease the manufacturing cost.