Photomask Slit Width Variation for TFT Formation
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Solution Overview
Problem
Conventional methods for manufacturing bottom gate type TFTs in LCDs face issues with improper formation due to over-exposure of photo-resist layers at bending portions of the photomask, leading to unsatisfactory yield rates in mass production.
Innovation Solution
A photomask with slits having turning regions of narrower width than other regions is used to control exposure intensity, ensuring uniformity and preventing over-exposure, thereby improving the formation of TFTs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional photomask with uniform slit width is used, then the manufacturing process is simple, but over-exposure occurs at bending portions leading to improper TFT formation
Solution Approach 1:
The photomask slit width is varied locally: narrower at turning regions and wider at other regions. This local variation compensates for the increased light transmission at bending portions, ensuring uniform exposure intensity across the entire photomask and preventing over-exposure that causes improper TFT formation.
Solution Approach 2:
The physical parameter of slit width in the photomask is changed from uniform to non-uniform. By adjusting the slit width parameter differently at turning regions versus other regions, the exposure intensity is balanced across the photomask, resolving the over-exposure issue while maintaining manufacturing feasibility.
2Reliability
If photomask slit width is reduced at turning regions, then over-exposure is prevented, but manufacturing complexity increases
Solution Approach 1:
The photomask is designed with local quality variation where only specific turning regions have narrower slit widths while other regions maintain wider widths. This targeted approach improves TFT formation reliability at critical turning portions without requiring the entire photomask to be manufactured with high precision, thus balancing reliability improvement with manufacturing ease.
3Productivity
If uniform exposure is achieved through variable slit width, then yield rate improves, but photomask design complexity increases
Solution Approach 1:
The photomask design applies local quality variation specifically at turning regions where over-exposure occurs. By narrowing slits only at these critical locations rather than uniformly across the entire photomask, the design achieves uniform exposure and improved yield rate while minimizing the overall design complexity and the number of parameters that need to be optimized.
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 enhances the yield rate of TFT arrays in mass production by maintaining consistent exposure intensity across the photo-resist layer, ensuring proper formation and functionality of TFTs.
Implementation Method 1
a photomask having at least one slit is provided; a source/drain electrode metal pattern is formed
Data Source
AI summary
An exemplary photomask (150) has a slit. The slit has at least one turning region (D1) and at least one other regions, and the slit at the at least one turning region has a narrower width than the slit at the at least one other regions. An exemplary method for manufacturing a thin film transistor (TFT) using the photomask is also provided.