Cross-linked Polymer Resist with Acid-Labile Protective Groups
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Solution Overview
Problem
Conventional resist compositions for photolithography in semiconductor manufacturing face challenges in maintaining resolution and sensitivity due to film light permeability issues, especially in thick film processes, where the cross-linked polymer chains do not sufficiently dissolve in alkaline developing solutions, leading to inadequate resist pattern formation.
Innovation Solution
A cross-linked polymer for resists is developed, where phenolic hydroxyl groups are protected by specific acid-dissociable protective groups containing oxyethylene and cross-linking structures, allowing for controlled solubility in developing solutions, enhancing sensitivity and contrast by varying molecular weight based on acid exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the film thickness is increased to achieve thick film process requirements, then the aspect ratio of resist patterns is improved, but the resolution properties and sensitivity deteriorate due to film light permeability issues
Solution Approach 1:
The invention changes the chemical parameters of the resist polymer by introducing specific protective groups (formula 1 and formula 2) that modify the polymer's solubility characteristics. This allows the resist to maintain high molecular weight for strength while enabling controlled dissolution after acid exposure, resolving the contradiction between film thickness and resolution
2Strength
If cross-linked polymer chains are used to provide sufficient strength in unexposed portions, then the mechanical strength is improved, but the dissolving ability against alkaline developing solution deteriorates when cross-linked portions are not decomposed
Solution Approach 1:
The invention performs preliminary action by pre-installing acid-labile protective groups on the polymer chains before exposure. During development, the acid generated by exposure triggers decomposition of these groups, which then enables the cross-linked structure to dissolve. This preliminary preparation resolves the contradiction between maintaining strength and enabling dissolution
Solution Approach 2:
The invention changes the chemical state of the cross-linked polymer by introducing protective groups that can be decomposed by acid. This transforms the polymer from a permanently cross-linked insoluble structure to one that becomes soluble after acid exposure, resolving the contradiction between strength and dissolving ability
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 polymer exhibits improved sensitivity and developing contrast, enabling the formation of high-aspect-ratio resist patterns with better verticality and reduced unexposed portion solubility, addressing the limitations of conventional resists in thick film photolithography.
Implementation Method 1
a cross-linked polymer for a resist whose solubility against a developing solution varies by the action of an acid
Implementation Method 2
the polymers are cross-linked to each other... at least a portion of phenolic hydroxyl groups in the polymer is protected by a group represented by the following formula (1)... formula (2)
Implementation Method 3
the exposed portion will have cross-links disconnected by the acid generated by the exposure and becomes a small structural unit and dissolve by the time developing is carried out
Data Source
AI summary
A cross-linked polymer including a structure wherein at least a portion of phenolic hydroxyl groups in the polymer is protected by a group represented by the following formula (1):wherein R1 represents an alkyl group having 1 to 5 carbons and n represents an integer from 1 to 5; and * represents a bond part of the phenolic hydroxyl group to a residue other than a hydrogen atom, and a structure wherein at least a portion of phenolic hydroxyl groups in the polymer is protected by a group represented by the following formula (2):wherein R2 represents a divalent saturated hydrocarbon group having 2 to 17 carbons, containing an aromatic ring; and * represents a bond part of the phenolic hydroxyl group to a residue other than a hydrogen atom, and the polymers are cross-linked to each other.