Immersion Lithography Polymer Coating for Pattern Stability
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Solution Overview
Problem
Current immersion lithography technologies face challenges with water-soluble antireflective coatings dissolving during light exposure and the need for special fluorocarbon strippers, which increases costs and complexity, while water-insoluble coatings require additional stripping units, and existing polymers have refractive indices that are not optimal for immersion lithography.
Innovation Solution
A polymer with recurring units that are insoluble in water but dissolvable in alkaline solutions, having a refractive index of approximately 1.57, is used as a resist protective coating, allowing for simultaneous stripping and development during alkaline water processing, and copolymerization with (meth)acrylic acid and cyclic structures to enhance glass transition temperature and prevent intermixing with the resist layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If water-soluble antireflective coating is used, then the coating can be easily stripped during development, but the coating dissolves during light exposure causing profile changes and pattern collapse
Solution Approach 1:
The polymer is designed with dual chemical functionality: water-insoluble segments (carboxyl-containing cyclic structures) provide pattern stability during exposure, while alkali-soluble segments enable easy stripping during development. This local differentiation of chemical properties within the same material resolves the contradiction between stability and ease of removal.
Solution Approach 2:
The polymer's solubility parameters are precisely controlled through copolymerization ratios and molecular weight selection. The material transitions from water-insoluble (maintaining pattern integrity) to alkali-soluble (enabling stripping) based on the chemical environment, allowing the same material to satisfy both contradictory requirements under different process conditions.
2Reliability
If water-insoluble coating is used, then the coating maintains pattern stability during exposure, but additional stripping units and special fluorocarbon strippers are required increasing cost and complexity
Solution Approach 1:
The polymer serves multiple functions: it acts as a protective coating during exposure, maintains pattern stability, and simultaneously serves as the antireflective coating. Its dual solubility characteristics allow it to be stripped using the existing alkaline development system already present in the lithography process, eliminating the need for separate stripping units and specialized fluorocarbon strippers.
Solution Approach 2:
The coating is designed to be self-stripping during the standard alkaline development process. The alkali-soluble carboxyl groups react with the alkaline developer, causing the coating to dissolve and be removed automatically during the development step without requiring any additional stripping equipment or chemicals.
3Manufacturing precision
If polymer with refractive index optimized for immersion lithography is used, then pattern formation precision is improved, but the polymer must also maintain water-insolubility and alkali-solubility properties
Solution Approach 1:
The polymer is a composite material combining fluorinated cyclic structures (providing optimal refractive index of 1.57 for immersion lithography) with carboxyl-containing alkali-soluble groups. This composite structure integrates optical performance with chemical functionality, achieving both precise pattern formation and appropriate solubility characteristics for the immersion lithography process.
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 polymer enables effective pattern formation in immersion lithography by maintaining a water-insoluble, alkali-soluble property, allowing for efficient stripping and development, and preventing intermixing with the resist layer, thus improving the process's precision and reducing operational complexity.
Implementation Method 1
the polymer is insoluble in water
Implementation Method 2
the polymer is insoluble in water
Implementation Method 3
the polymer is dissolvable in alkaline solutions
Implementation Method 4
the polymer is immiscible with resist films
Implementation Method 5
copolymerization with (meth)acrylic acid and cyclic structures to enhance glass transition temperature
Data Source
AI summary
In an immersion lithography process, a pattern is formed by forming a photoresist layer on a wafer, forming a protective coating on the photoresist layer from an overlay material, exposing the layer structure to light in water, and developing. A water-insoluble, alkali-soluble material is used as the overlay material.