Immersion Lithography Liquid Extraction Timing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The removal of immersion liquid from the gap between a substrate and a support table in lithography apparatuses using underpressure can induce significant cooling loads, leading to imaging errors due to accelerated evaporation, which are unpredictable and vary between substrates.
Innovation Solution
A method and apparatus where the underpressure for removing immersion liquid is applied before the immersion space moves onto the object and stopped at a predetermined time after it moves off, to induce a consistent thermal profile, allowing for compensation during pattern projection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If underpressure is applied continuously to remove immersion liquid from the gap, then liquid removal effectiveness is improved, but thermal stability deteriorates due to excessive evaporation cooling
Solution Approach 1:
The extraction unit is activated before the immersion space moves onto the object to preemptively remove liquid from the gap, and continues running after the immersion space moves off to complete the removal process. This timing strategy ensures thorough liquid removal while allowing controlled thermal recovery during the exposure phase, resolving the contradiction between removal effectiveness and thermal stability.
2Reliability
If underpressure is applied for extended duration to ensure complete liquid removal, then liquid removal completeness is improved, but imaging precision deteriorates due to thermal profile variations
Solution Approach 1:
The extraction unit starts before exposure begins to remove liquid proactively, and continues after exposure to complete removal. This timing ensures complete liquid removal without interfering with the exposure process, maintaining imaging precision while achieving removal completeness.
Solution Approach 2:
The extraction unit operates in periodic cycles: active before and after exposure, and inactive during exposure. This periodic operation pattern allows complete liquid removal to occur in phases that do not interfere with the critical exposure process, thereby maintaining imaging precision while ensuring removal completeness.
3Productivity
If underpressure is applied strongly to accelerate liquid removal, then removal speed is improved, but thermal control worsens due to accelerated evaporation
Solution Approach 1:
The extraction unit is activated at optimized moments before and after exposure rather than continuously at high intensity during exposure. This timing strategy achieves effective liquid removal speed while preventing excessive evaporation cooling during the critical exposure phase, thereby maintaining thermal control.
Solution Approach 2:
The extraction unit operates periodically with controlled intensity: active before and after exposure at speeds optimized for removal, and inactive during exposure to maintain thermal control. This periodic operation resolves the contradiction between removal speed and thermal control by decoupling the high-speed removal phase from the thermal-sensitive exposure phase.
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 approach results in a more predictable thermal profile, reducing imaging errors and increasing yield by ensuring consistent thermal conditions across substrates, thereby improving the reliability of the lithography process.
Implementation Method 1
A difficulty with using an underpressure source to remove immersion liquid from the gap is that this can induce a large cooling load on the substrate or object due to accelerated evaporation of the immersion liquid resulting from gas flow into the gap.
Data Source
AI summary
A device manufacturing method includes: confining a liquid to an immersion space between a projection system and an object; starting application of an underpressure to an extraction unit to remove fluid from a position proximate an edge of the object before the immersion space moves onto the object; moving the support table along a route comprising a series of motions such that a plurality of target positions on the object pass under the projection system; projecting through the immersion space a beam onto the target portions as the target portions pass under the projection system, the projecting performed to account for a certain predetermined thermal profile in the object; and stopping application of the underpressure at a predetermined time after the immersion space moves off the object for the last time during the series of motions to at least partly induce the certain predetermined thermal profile in the object.