Master Mold Imprint Exposure Control for Forward Taper Structures
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Solution Overview
Problem
Existing methods for manufacturing master molds for imprinting struggle to easily control the taper angle of side shapes, requiring labor-intensive and costly operations, which hinders the formation of smaller sizes and higher aspect ratios in the transferred patterns.
Innovation Solution
A method involving exposure of a resist coated on a base material through a mask, with exposure amounts set to less than twice the minimum solarization threshold, using binary or grayscale masks to achieve forward tapers with optimal taper angles, considering the target pattern's size, pitch, and aspect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the exposure amount is set high to ensure complete polymerization of the resist, then the structures achieve sufficient strength, but the side shapes become perpendicular or inverted taper which causes deformation during pressurization
Solution Approach 1:
The invention changes the exposure amount parameter to be equal to or less than twice Df (the minimum exposure amount for complete solarization), which creates a controlled gradient in polymerization degree through the resist thickness. This parameter change produces the desired forward taper shape while maintaining sufficient structural strength for the application.
2Reliability
If the side shapes of master mold structures are formed with forward taper to prevent deformation, then smooth replica mold formation is achieved, but the recess shapes in the replica mold become compromised affecting wiring and bump quality
Solution Approach 1:
By precisely controlling the exposure amount to the range of equal to or less than twice Df, the invention optimizes the forward taper angle to balance two requirements: preventing deformation during pressurization and maintaining proper recess shapes for high-quality wiring and bump formation. This parameter optimization resolves the contradiction between reliability and manufacturing precision.
3Manufacturing precision
If complicated operations are used to control the taper angle of master mold structures, then precise taper angles can be achieved, but the manufacturing process becomes labor-intensive and costly
Solution Approach 1:
The invention simplifies the manufacturing process by controlling only the exposure amount parameter during photopolymerization. This single parameter control (exposure amount ≤ 2×Df) automatically produces the desired forward taper shapes without requiring complex mechanical operations, multi-step processes, or specialized equipment, thereby achieving precise taper angles with ease of manufacture.
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
Enables the formation of master molds with structures having forward tapers at optimal angles, ensuring smooth pattern transfer and high yield, even under polymerization and pressurization, by controlling the exposure amount and using masks to manipulate light intensity distribution.
Implementation Method 1
Df: the minimum exposure amount at which the resist 3 coated on the base material 1 undergoes solarization across the entire thickness of the resist 3
Data Source
Figure 1(a)~1(b)
Figure 2
Figure 3(a)~3(g)
AI summary
Provided is a method for manufacturing a master mold for imprinting, with which structures formed in a desired forward taper can be formed on a base material. This method comprises a coating step in which a resist 3 having a predetermined film thickness is coated on a base material 1, an exposure step in which the resist 3 coated on the base material 1 is exposed through a mask 4, and a development step in which the exposed resist 3 is developed, the exposure step involving setting the exposure amount to be equal to or less than twice the minimum exposure amount (Df) at which the resist 3 coated on the base material 1 undergoes solarization across the entire thickness of the resist, and exposing predetermined portions of the resist 3, so that the side surface shape of the structures 2 constituted of the resist 3 formed by development in the development step is a forward taper.