Halftone Mask Design for Precision Lithography
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Solution Overview
Problem
Conventional exposure apparatuses and masks struggle to form precise, small patterns on substrates for liquid crystal display apparatuses due to light diffraction and interference issues, resulting in insufficient exposure intensity and manufacturing precision.
Innovation Solution
A mask design incorporating a blocking portion, a halftone portion, and an opening (or transparent) portion, where the halftone portion has a light transmittance between 10% and 20% and is adjacent to the blocking portion, enabling sufficient exposure intensity and precision in forming small patterns, such as black matrices and column spacers, using proximity exposure apparatuses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional masks with only transparent and blocking portions are used, then the mask structure is simple, but light diffraction and interference cause insufficient exposure intensity and poor manufacturing precision for small patterns
Solution Approach 1:
The mask is segmented into three distinct portions: a transparent portion, a halftone portion with intermediate light transmittance, and a blocking portion. This segmentation allows independent optimization of each region's function - the transparent portion provides high light transmission, the halftone portion controls diffraction effects, and the blocking portion prevents light leakage, thereby improving overall pattern formation precision without excessive complexity
Solution Approach 2:
Different regions of the mask are assigned different light transmittance properties tailored to their specific functions. The transparent portion has high transmittance for maximum light delivery, the halftone portion has intermediate transmittance (e.g., 50% or less) to control diffraction, and the blocking portion has zero transmittance to prevent leakage. This local differentiation of properties resolves the contradiction between simplicity and precision
2Illumination intensity
If the light source is positioned to irradiate the mask perpendicularly, then the exposure is uniform, but the light cannot adequately illuminate areas wider than the opening portion due to diffraction and interference
Solution Approach 1:
The patent converts the harmful diffraction and interference effects of light into beneficial control mechanisms. By introducing the halftone portion with intermediate light transmittance, the diffraction that would normally cause blur is instead harnessed to create a controlled gradient in light intensity. This gradient allows the light to effectively illuminate areas wider than the opening portion while maintaining pattern precision through the controlled reduction in intensity
3Use of energy by moving object
If the halftone portion has high light transmittance, then more light reaches the substrate, but the diffraction and interference effects increase causing poor pattern precision
Solution Approach 1:
The patent changes the light transmittance parameter of the halftone portion to a specific range (greater than 0% and less than 100%, preferably 50% or less) to optimize the balance between light transmission and diffraction control. This parameter optimization allows sufficient light to reach the substrate for good exposure while the reduced transmittance keeps diffraction effects manageable, achieving both high energy utilization and high manufacturing 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
The mask design allows for the precise formation of small patterns with high resolution and aperture ratio in display apparatuses, overcoming the limitations of conventional technologies by ensuring adequate light exposure and manufacturing precision.
Implementation Method 1
an area corresponding to the opening portion of the mask may receive an exposure with insufficient intensity due to diffraction and interference
Implementation Method 2
an area corresponding to the opening portion of the mask may receive an exposure with insufficient intensity due to diffraction and interference
Implementation Method 3
the patterns may be formed using one or more photo resist processes
Data Source
AI summary
A mask includes a substantially transparent portion. The mask further includes a halftone portion abutting the substantially transparent portion, a light transmittance of the halftone portion being greater than 0% and less than 100%. The mask further includes a blocking portion abutting the halftone portion, a light transmittance of the blocking portion being less than the light transmittance of the halftone portion.