Acetoxystyrene Deprotection for Stable Resist Polymers
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Solution Overview
Problem
Current methods for producing polymers with p-hydroxystyrene and acetal-protected carboxylic acid units face challenges such as low stability and difficulty in industrial-scale production due to issues like polymerization during storage and unwanted side reactions that affect sensitivity, resolution, and storage stability in resist compositions for semiconductor lithography.
Innovation Solution
A method involving deprotection of p-acetoxystyrene in an organic solvent with a base having a pKa of 12 or more at 0° C. to 50° C. to convert p-acetoxystyrene units into p-hydroxystyrene units while minimizing acetal group elimination or migration, resulting in a polymer with improved stability and performance as a chemically amplified resist.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If p-hydroxystyrene is directly polymerized with acetal-protected monomer, then polymer with desired structure is obtained, but polymerization occurs during storage reducing stability
Solution Approach 1:
The patent applies preliminary action by using p-acetoxystyrene instead of p-hydroxystyrene as the starting material. The acetyl group serves as a protecting group that prevents premature polymerization during storage, while allowing controlled deprotection later to form the desired p-hydroxystyrene units in the polymer chain.
Solution Approach 2:
The patent uses an intermediary approach by introducing a protecting group (acetyl) that mediates between the need for stability during storage and the need for reactivity during polymerization. The acetyl group acts as a temporary substitute for the hydroxyl group, enabling stable storage while maintaining the capability to form the final desired structure through controlled deprotection.
2Stability of the object's composition
If tertiary butoxystyrene or acetoxystyrene is used as starting material, then polymer production is stabilized, but acid-leaving group elimination causes solubility changes and development contrast decrease
Solution Approach 1:
The patent applies local quality by carefully selecting the protecting group (acetyl) and its removal conditions to achieve different properties in different parts of the polymer structure. The deprotection conditions are optimized to remove only the acetyl group from p-acetoxystyrene units while preserving the acetal-protected carboxylic acid groups, maintaining local structural integrity and resist performance.
Solution Approach 2:
The patent uses parameter changes by controlling the deprotection reaction conditions (base type, temperature, solvent) to selectively remove the acetyl group while maintaining the stability of other functional groups. This precise control of reaction parameters enables selective deprotection without triggering unwanted elimination reactions of the acid-leaving groups.
3Manufacturing precision
If deprotection is performed to convert protecting groups, then p-hydroxystyrene units are formed, but acetal group elimination and migration occur as side reactions
Solution Approach 1:
The patent applies preliminary anti-action by selecting deprotection conditions that preemptively prevent side reactions. The use of specific bases with controlled strength and appropriate solvents creates a reaction environment that favors selective acetyl group removal while suppressing acetal group elimination and migration before they can occur.
Solution Approach 2:
The patent uses an intermediary approach by introducing a solvent system that mediates between the deprotection reaction and the polymer structure. The solvent acts as a buffer that facilitates acetyl group removal while stabilizing the acetal groups against elimination and migration, reducing harmful side reactions.
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 approach allows for the production of polymers with high sensitivity, high resolution, and excellent storage stability, effectively addressing the limitations of existing methods by minimizing by-product formation and maintaining desired resist performance.
Implementation Method 1
a method involving deprotection of p-acetoxystyrene in an organic solvent with a base having a pKa of 12 or more at 0° C. to 50° C. to convert p-acetoxystyrene units into p-hydroxystyrene units
Data Source
AI summary
The present invention provides a polymer comprising a structural unit derived from p-hydroxystyrene and a structural unit having a structure in which a carboxylic acid is protected by an acetal group, wherein the structural unit generated by elimination of the acetal group or migration of the acetal group during the production process is extremely small; and a process for producing the same.A solution containing a polymer comprising a structural unit derived from p-acetoxystyrene and a structural unit having a structure in which a carboxylic acid is protected by an acetal group is subjected to deprotection reaction at 50° C. or lower in the presence of a base in which a pKa of a conjugated acid is 12 or more.