Lithographic Drain System Ambient Pressure Gas Seal
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithographic apparatuses face challenges in efficiently managing immersion liquids, particularly in preventing liquid leakage and bubble formation between the substrate and the substrate table, which can lead to imaging errors and substrate damage.
Innovation Solution
A lithographic apparatus with a substrate table featuring a drain system that maintains ambient pressure and a chamber open to the substrate table's surface, allowing liquid to collect and remove leaks without creating underpressure, and using a flexible flap to manage liquid flow, ensuring the liquid has a contact angle greater than 45° with the gap surfaces to minimize liquid loss and bubble introduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If liquid is supplied to fill the space between the projection system and substrate, then imaging precision is improved, but liquid leakage and bubble formation occur causing harmful effects
Solution Approach 1:
A gas seal acts as an intermediary between the liquid supply system and the substrate gap. The gas seal prevents liquid from reaching the gap between substrate and substrate table, while allowing the liquid to fill the required space for imaging. This mediator eliminates the harmful liquid leakage and bubble formation while preserving the imaging precision benefits of liquid immersion.
Solution Approach 2:
The harmful liquid is extracted or removed from the gap area between substrate and substrate table through the gas seal system. The gas seal creates a barrier that extracts or prevents liquid intrusion into this specific region, eliminating bubble formation and liquid leakage hazards while maintaining liquid presence in the imaging zone.
2Loss of substance
If liquid is removed using underpressure, then liquid loss is reduced, but bubble formation is caused
Solution Approach 1:
The gas seal serves as a mediator that enables liquid removal without creating underpressure conditions. By maintaining gas pressure balance, the gas seal allows liquid to be managed and removed through alternative pathways while preventing the vacuum conditions that cause bubble formation in the immersion liquid.
Solution Approach 2:
The pressure parameter is changed from negative (underpressure) to balanced (ambient pressure maintained by gas seal). This parameter change eliminates the driving force for bubble formation while still allowing liquid loss to be controlled through the gas seal's selective permeability and pressure balance mechanism.
3Loss of substance
If gas seal is used to prevent liquid leakage, then liquid loss is reduced, but device complexity increases
Solution Approach 1:
The gas seal system operates autonomously to prevent liquid leakage. Once configured, the gas seal self-regulates liquid management without requiring external control systems or additional complex mechanisms. The gas pressure balance is self-maintaining, reducing the need for complex active control and minimizing device complexity while effectively reducing liquid loss.
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 solution effectively reduces liquid loss and prevents bubble formation in the immersion liquid, enhancing imaging accuracy and preventing substrate damage by maintaining ambient pressure and optimizing liquid removal without underpressure, thus improving the operational efficiency of the lithographic apparatus.
Implementation Method 1
A gas seal may be formed between the liquid supply system and the substrate or substrate table
Implementation Method 2
ensuring the liquid has a contact angle greater than 45° with the gap surfaces to minimize liquid loss and bubble introduction
Data Source
AI summary
Embodiments of a drain in a lithographic projection apparatus are described that have, for example, a feature which reduces inflow of gas into the drain during a period when no liquid is present in the drain. In one example, a passive liquid removal mechanism is provided such that the pressure of gas in the drain is equal to the ambient gas pressure and in another embodiment a flap is provided to close off a chamber during times when no liquid needs removing.