Multi-tone Optical Mask for Uniform TFT Photoresist Patterns
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Solution Overview
Problem
Current photolithography processes for manufacturing TFT substrates require multiple optical masks, leading to non-uniform photoresist patterns and reduced manufacturing efficiency due to the limitations of slit and half-tone optical masks.
Innovation Solution
A multi-tone optical mask with a substrate, light-blocking pattern, and multiple semi-transmitting patterns of different light-transmittance values, allowing for the formation of a multi-step photoresist pattern with various thicknesses and improved uniformity, enhancing manufacturing efficiency and yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a slit optical mask is used to form photoresist patterns, then the number of optical masks required is reduced, but the residual photoresist layer becomes non-uniform and patterns with great width cannot be formed
Solution Approach 1:
The optical mask is segmented into multiple regions with different light transmittance characteristics (first light-transmissive region, second light-transmissive region, and third light-transmissive region), allowing different portions of the photoresist layer to be exposed to different amounts of light, thereby achieving both reduced mask count and uniform pattern formation
Solution Approach 2:
Different regions of the optical mask are assigned different light transmittance properties to address local requirements: the first light-transmissive region allows full exposure for certain areas, the second region provides partial exposure for other areas, and the third region blocks light completely, enabling uniform photoresist patterns across the entire substrate while reducing the number of masks needed
2Manufacturing precision
If a half-tone optical mask is used to improve uniformity of slit portion, then light transmittance uniformity is improved, but photoresist patterns cannot have various thicknesses and line patterns become non-uniform
Solution Approach 1:
The optical mask is divided into three distinct light-transmissive regions with different transmittance characteristics, enabling the formation of photoresist patterns with various thicknesses while maintaining uniformity in each region, thereby resolving the limitation of half-tone masks that can only provide two transmittance levels
Solution Approach 2:
Each region of the optical mask is optimized with specific light transmittance properties tailored to the local pattern requirements, allowing different portions of the substrate to receive customized exposure doses, which enables both uniform local patterns and variable thickness across the entire photoresist layer
3Manufacturing precision
If multiple photolithography processes are used to manufacture TFT substrate, then manufacturing precision is maintained, but manufacturing cost and time increase
Solution Approach 1:
Multiple photolithography processes that previously required separate optical masks are merged into a single exposure process using the multi-region optical mask, allowing simultaneous formation of different photoresist pattern thicknesses and maintaining manufacturing precision while reducing process time and cost
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
The multi-tone optical mask enables the formation of uniform multi-step photoresist patterns, reducing the number of masks needed and increasing the manufacturing yield of TFT substrates by allowing multiple layers to be etched using a single mask, thereby improving the overall manufacturing efficiency.
Implementation Method 1
The first semi-transmitting pattern is formed on the substrate and has a light-transmittance of a first value. The second semi-transmitting pattern has a light-transmittance of a second different value.
Data Source
AI summary
A multi-tone optical mask includes a substrate, a light-blocking pattern, a first semi-transmitting pattern and a second semi-transmitting pattern. The light-blocking pattern is formed on the substrate. The first semi-transmitting pattern is formed on the substrate. The second semi-transmitting pattern partially overlaps the first semi-transmitting pattern. The multi-tone optical mask has at least five different light-transmittances corresponding to a plurality of areas divided on the substrate.