Flash Bake Substrate Heating for Acid Diffusion Control
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Solution Overview
Problem
Conventional post-exposure bake processes for semiconductor and liquid crystal display substrates face challenges in minimizing acid diffusion length, leading to incomplete photoresist pattern formation and reduced dimension accuracy due to temperature uniformity issues and prolonged processing times.
Innovation Solution
A method and apparatus utilizing flashes of light for the post-exposure bake process, with a cooling plate to maintain temperature uniformity and a filter to prevent chemically amplified resist film reaction, significantly reducing processing time and acid diffusion length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the processing temperature is decreased to minimize acid diffusion length, then the diffusion length is reduced, but the temperature uniformity of the substrate deteriorates and the process becomes susceptible to environmental effects
Solution Approach 1:
The patent employs periodic flash heating cycles where the substrate is rapidly heated to the desired temperature and then quickly cooled. This periodic action allows the substrate to reach uniform temperature throughout the short processing time, minimizing acid diffusion while maintaining temperature uniformity by avoiding prolonged exposure to environmental variations.
Solution Approach 2:
The patent replaces the conventional thermal conduction-based heating system with a light-based flash heating system. This substitution enables rapid, uniform heating across the entire substrate surface simultaneously, achieving both short processing time and uniform temperature distribution without the gradual heating limitations of traditional hot plates.
2Length of moving object
If the processing time is shortened to minimize acid diffusion length, then the diffusion length is reduced, but the substrate cannot reach the intended heating temperature
Solution Approach 1:
The flash heating process uses periodic, intense light pulses that rapidly raise the substrate temperature to the required level within milliseconds. This allows the substrate to reach the intended heating temperature almost instantaneously, maintaining the temperature needed to minimize acid diffusion without requiring prolonged heating time.
Solution Approach 2:
The patent changes the heating parameter from gradual thermal conduction to intense, short-duration flash heating. This parameter change enables the substrate to reach the target temperature extremely quickly, reducing the time available for acid diffusion while still achieving the necessary temperature for effective post-exposure bake processing.
3Productivity
If the substrate is scanned with a laser to perform post-exposure bake, then the processing can be performed, but the time difference between start and end positions causes nonuniform pattern dimensions and increases processing time
Solution Approach 1:
The patent divides the heating process into discrete flash pulses that illuminate the entire substrate surface simultaneously rather than scanning sequentially. This segmentation of the heating action into simultaneous full-field pulses eliminates the positional time differences inherent in scanning methods, ensuring uniform pattern dimensions across the entire substrate while maintaining high throughput.
Solution Approach 2:
The patent transitions from a one-dimensional scanning approach to a two-dimensional simultaneous heating approach using flash lamps that illuminate the entire substrate surface at once. This dimensional change eliminates the sequential processing time differences between different positions on the substrate, achieving both uniform pattern dimensions and high productivity.
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 acid diffusion length, improves pattern dimension accuracy, and increases throughput by minimizing processing time while maintaining temperature uniformity between substrates.
Implementation Method 1
irradiating the surface of the substrate put in the chamber with flashes of light to perform a post-exposure bake process
Implementation Method 2
a cooling plate to maintain temperature uniformity
Data Source
AI summary
A substrate subjected to a pattern exposure process is transported to a flash bake unit. The flash bake unit performs a post-exposure bake process in which flashes of light are directed from flash lamps onto a surface of the substrate held on an upper surface of a cooling plate to momentarily heat the surface of the substrate, thereby causing crosslinking, deprotection or decomposition and the like of resist resin to proceed by using active species produced in a resist film by a photochemical reaction during the pattern exposure process as an acid catalyst, so that the solubility of only the exposed portion of the resist film in a developing solution is locally changed. The flash heating treatment performed by the irradiation with flashes of light requires extremely short treatment time of not greater than one second. This reduces the diffusion length of acid during the post-exposure bake process.