Upper Layer Film Composition for Liquid Immersion Lithography
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Solution Overview
Problem
Existing methods for forming upper layer films in liquid immersion lithography fail to prevent photoresist component elution into water, leading to reduced lithographic performance and lens pollution, while also suffering from blob defects during the rinsing process.
Innovation Solution
A composition comprising a resin dissolvable in developers and a compound with a sulfonic acid residue group, forming a film with a receding contact angle of 70° or more, which is stable in water and effectively suppresses watermark, pattern, and blob defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an upper layer film is formed to block photoresist from water in liquid immersion lithography, then photoresist component elution and lens pollution are suppressed, but the film must maintain high transparency to radiation while being stable in water and dissolvable in developer
Solution Approach 1:
The upper layer film is formed as a composite material comprising a water-soluble polymer (such as polyvinyl alcohol or carboxymethyl cellulose) and a surfactant. This composite structure provides simultaneous water solubility for stability, surfactant properties for preventing blob defects, and appropriate transparency to radiation, resolving the contradiction between film stability and composition complexity.
Solution Approach 2:
The film composition parameters are optimized by controlling the molecular weight, degree of substitution, and concentration of the water-soluble polymer, as well as the type and amount of surfactant. These parameter adjustments enable the film to achieve the desired balance between water stability, radiation transparency, and developer dissolvability without requiring overly complex formulations.
2Manufacturing precision
If existing upper layer film methods are used, then watermark and pattern defects are suppressed, but blob defects occur during rinsing operation
Solution Approach 1:
A surfactant is introduced as an intermediary substance in the upper layer film composition. The surfactant acts as a mediator during the rinsing process, preventing water from aggregating into droplets that cause blob defects, while maintaining the film's protective function against watermark and pattern defects. The surfactant reduces surface tension and prevents reattachment of photoresist components.
Solution Approach 2:
The surface properties of the upper layer film are modified by incorporating surfactants with specific hydrophilic-lipophilic balance (HLB) values. This parameter change in surface chemistry enables the film to repel water effectively during rinsing, preventing blob defects while maintaining pattern integrity and suppressing watermark defects through controlled wetting properties.
3Measurement precision
If photoresist is directly exposed through water in liquid immersion lithography, then resolution is improved, but photoresist components elute into water causing reduced lithographic performance
Solution Approach 1:
The upper layer film serves as an intermediary barrier between the photoresist and the water immersion medium. It allows radiation to pass through for high-resolution exposure while blocking photoresist components from eluting into the water, thus preserving both lithographic performance and preventing substance loss.
Solution Approach 2:
A thin film structure is employed that is sufficiently transparent to the exposure radiation wavelength (such as 193 nm or 248 nm) to maintain high resolution, while being thick enough to act as an effective barrier against photoresist component elution. The film's thin geometry allows radiation penetration while its molecular structure provides selective permeability.
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 solution forms a high-resolution resist pattern by preventing photoresist component elution and lens pollution, while maintaining film stability and preventing blob defects during liquid immersion lithography.
Implementation Method 1
a compound having a sulfonic acid residue group... forming an upper layer film with a receding contact angle to water of 70° or more... suppressing elusion of photoresist components
Implementation Method 2
receding contact angle to water of 70° or more... stable in water... suppressing elusion of photoresist components into water
Implementation Method 3
a resin dissolvable in a developer for the photoresist film... easily dissolved in a developer such as an alkaline solution
Implementation Method 4
must possess sufficient transparency to radiation of a wavelength used in liquid immersion lithography... blocking the photoresist film from the medium
Data Source
AI summary
An upper layer film forming composition for forming an upper layer film on the surface of a photoresist film includes (A) a resin dissolvable in a developer for the photoresist film and (B) a compound having a sulfonic acid residue group, the composition forming an upper layer film with a receding contact angle to water of 70° or more. The upper layer film forming composition of the present invention can form an upper layer film which has a sufficient transparency and is stably maintained without eluting the components into a medium without being intermixed with a photoresist film, can form a resist pattern with high resolution while effectively suppressing a defect, and can suppress a blob defect.