Positive Photoresist Copolymer for High-Resolution Resist Patterns
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Solution Overview
Problem
Conventional polyhydroxystyrene-based resins fail to provide adequate resolution and rectangularity in resist patterns, especially in thermal flow processes, leading to poor verticality and rounding of resist pattern side walls, and are prone to developing defects such as residues.
Innovation Solution
A positive resist composition comprising a copolymer with structural units derived from hydroxystyrene and (meth)acrylate esters, protected with acid dissociable dissolution inhibiting groups, combined with a diazomethane-based and onium salt-based acid generator, which improves resolution and rectangularity while reducing developing defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional polyhydroxystyrene-based resins are used, then the resist material can be manufactured with standard processes, but the resolution and rectangularity of the resist pattern are insufficient
Solution Approach 1:
The patent changes the chemical parameters of the base resin by introducing copolymer structures with specific functional groups (carboxyl, hydroxyl, and their protected forms) and controlling the protection ratio of hydroxyl groups. This modifies the resin's solubility characteristics and acid-base properties, enabling better pattern definition and rectangularity while maintaining manufacturing feasibility
Solution Approach 2:
The patent uses composite resin structures combining polyhydroxystyrene with copolymer units containing carboxyl groups and protected hydroxyl groups. This composite approach creates a material that exhibits both the desired high resolution and rectangularity, while the carboxyl groups provide additional functionality for pattern formation and stability
2Manufacturing precision
If the protection ratio of hydroxyl groups is increased to improve resolution, then the resolution improves, but developing defects such as residues increase
Solution Approach 1:
The patent optimizes the protection ratio parameter to a specific range (5-50 mol%) rather than maximizing it. This balanced parameter setting achieves sufficient resolution while preventing excessive protection that would cause developing defects. The carboxyl group content is also controlled to maintain proper solubility and development characteristics
Solution Approach 2:
The patent introduces local functional groups (carboxyl groups) at specific locations in the polymer chain to provide localized solubility control and acid-base reactions. This local quality enhancement allows the resin to maintain proper development characteristics while achieving high resolution through the protected hydroxyl groups
3Length of moving object
If thermal flow process is used to reduce pattern size, then the pattern size is reduced, but the rectangularity deteriorates with poor verticality and rounded shapes
Solution Approach 1:
The patent modifies the thermal and rheological parameters of the resist material through the copolymer structure and protected group ratio. This enables the material to maintain its shape and rectangularity during thermal flow processing, achieving both pattern size reduction and shape preservation
Solution Approach 2:
Instead of relying on thermal flow to create the final pattern shape, the patent inverts the approach by first forming a pattern with excellent rectangularity through the specialized resin composition, then using thermal flow only for controlled size reduction. The resin's inherent shape stability prevents rounding and maintains verticality
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 resist composition achieves excellent resolution and rectangularity with reduced developing defects, enabling the formation of high-quality resist patterns suitable for semiconductor and liquid crystal display element production.
Implementation Method 1
an acid generator that generates acid on exposure
Implementation Method 2
the resist pattern is heated and softened, causing the pattern to flow towards the gaps in the pattern
Data Source
AI summary
A positive resist composition that includes a resin component (A), which contains acid dissociable, dissolution inhibiting groups and exhibits increased alkali solubility under the action of acid, and an acid generator component (B) that generates acid on exposure, wherein the resin component (A) is a copolymer (A1) containing a first structural unit (a1) derived from hydroxystyrene and a second structural unit (a2) derived from a (meth)acrylate ester having an alcoholic hydroxyl group, in which a portion of the hydroxyl groups of the structural units (a1) and the alcoholic hydroxyl groups of the structural units (a2) have been protected with the acid dissociable, dissolution inhibiting groups; and either the acid generator component (B) includes a diazomethane-based acid generator and an onium salt-based acid generator; or the composition further contains a compound, which contains at least one acid dissociable, dissolution inhibiting group, and generates an organic carboxylic acid under the action of acid generated from the component (B).