Immersion Lithography Acoustic Meniscus Stabilization
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Solution Overview
Problem
The existing lithographic apparatuses face challenges in maintaining high throughput while minimizing defects caused by droplets and bubbles in the immersion liquid, which limits the substrate's movement speed.
Innovation Solution
A lithographic apparatus is designed with a fluid handling system that includes a substrate holder, a projection system, and an excitation device generating surface acoustic waves. These surface acoustic waves propagate towards the immersion liquid, stabilizing the meniscus and preventing droplet formation, even at higher substrate movement speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the substrate movement speed is increased to improve throughput, then productivity increases, but droplet formation and bubble introduction increase causing defects
Solution Approach 1:
The patent applies mechanical vibration by generating surface acoustic waves in the substrate using a piezoelectric transducer. These vibrations propagate through the substrate to the immersion liquid, creating acoustic radiation pressure that stabilizes the meniscus and prevents droplet formation, allowing high-speed substrate movement without defects
Solution Approach 2:
The patent replaces the conventional approach of reducing substrate speed to prevent droplets with an acoustic field-based solution. The piezoelectric transducer generates surface acoustic waves that interact with the immersion liquid to stabilize the meniscus, substituting mechanical speed control with acoustic field control
2Reliability
If the substrate movement speed is reduced to prevent droplet formation, then defect rate decreases, but throughput is limited
Solution Approach 1:
The piezoelectric transducer generates surface acoustic waves that propagate through the substrate to the immersion liquid interface. These acoustic waves create radiation pressure that stabilizes the meniscus, preventing droplet formation even at high substrate movement speeds, thus maintaining both low defect rates and high throughput
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 implementation of surface acoustic waves in the lithographic apparatus effectively reduces droplet-related defects and allows for increased substrate movement speeds, thereby enhancing the throughput of the lithographic process without compromising yield.
Implementation Method 1
an excitation device configured to generate surface acoustic waves in the substrate and propagating toward the immersion liquid
Data Source
AI summary
A lithographic apparatus has a substrate holder configured to hold a substrate and a projection system configured to project a radiation beam onto the substrate held by the substrate holder. There is also a fluid handling system configured to confine immersion liquid to a space between a part of the projection system and a surface of the substrate so that the radiation beam can irradiate the surface of the substrate by passing through the immersion liquid. An excitation device is provided to generate surface acoustic waves in the substrate and propagating toward the immersion liquid.