Mask Blank Resist Film Sensitivity Control
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Solution Overview
Problem
The challenge in mask blank manufacturing is the occurrence of CD failures due to changes in resist film sensitivity over time, which existing methods struggle to prevent, especially with chemically amplified resists, leading to inefficiencies in semiconductor manufacturing.
Innovation Solution
A method involving the storage and correlation of resist film forming information, including the date of formation, to identify and strip resist films with sensitivity changes exceeding allowable ranges, followed by re-coating, allowing for the efficient reuse of mask blanks and preventing CD failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If mask blanks are stored for extended periods to meet production scheduling demands, then production flexibility is improved, but resist film sensitivity changes cause CD failures
Solution Approach 1:
The patent applies preliminary action by measuring and recording resist film sensitivity immediately after coating, and establishing an allowable range in advance. This allows the system to proactively identify mask blanks that will later exhibit sensitivity changes, preventing CD failures before they occur during production scheduling.
Solution Approach 2:
The patent implements feedback by continuously monitoring resist film sensitivity through measurements taken after coating and before use. The system compares measured sensitivity values against the pre-established allowable range and provides feedback information to control the usage timing and scheduling of mask blanks, thereby maintaining CD precision despite storage duration variations.
2Reliability
If mask blanks with out-of-range sensitivity are discarded, then CD failure prevention is improved, but manufacturing efficiency and resource utilization deteriorate
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the sensitivity threshold criteria based on actual production conditions and resist film characteristics. Instead of using fixed discard criteria, the system measures actual sensitivity values and compares them against an allowable range, allowing mask blanks to be used if their sensitivity falls within acceptable parameters, thereby reducing unnecessary discards while maintaining CD quality.
Solution Approach 2:
The system uses feedback to distinguish between mask blanks with sensitivity changes that cause CD failures versus those that do not. By measuring sensitivity and comparing against the allowable range, the system provides feedback that enables selective usage rather than blanket discarding, improving manufacturing efficiency while preventing CD failures.
3Manufacturing precision
If experimental rules and exposure amount correction are used to compensate for sensitivity changes, then some CD degradation is suppressed, but the method is insufficient when sensitivity changes exceed allowable ranges
Solution Approach 1:
The patent applies preliminary action by establishing the allowable sensitivity range in advance based on pre-experimental data and CD requirements. This preliminary establishment of criteria enables the system to proactively identify and prevent usage of mask blanks that would exceed correction capabilities, rather than relying solely on post-coating correction methods.
Solution Approach 2:
The system enhances experimental rules by adding a feedback mechanism that measures actual sensitivity values and compares them against the pre-established allowable range. When sensitivity changes exceed this range, the system provides feedback to prevent usage, supplementing exposure amount correction with a proactive prevention approach that addresses the insufficiency of correction alone.
Data Source
AI summary
A method of manufacturing a mask blank includes a thin film forming step of forming a thin film, which becomes a mask pattern, on a mask blank substrate and a resist film forming step of forming a resist film on the thin film. The method further includes a step of storing resist film forming information including information about a date of formation of the resist film on the thin film, a step of correlating the resist film forming information with the mask blank, a step of identifying, based on the resist film forming information, the mask blank having the resist film whose sensitivity change exceeds an allowable range, a step of stripping the resist film formed in the identified mask blank, and a step of forming again a resist film on the thin film stripped of the resist film.