Immersion Lithography Stage Drive Method for Liquid Handling
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Solution Overview
Problem
The immersion method for exposure apparatuses in lithography processes faces challenges with liquid recovery and supply times, leading to decreased throughput and potential water stains on optical components, which affect image-forming performance and require frequent lens replacements.
Innovation Solution
A stage drive method where two stages are independently driven within a two-dimensional plane with a locally supplied liquid, allowing simultaneous transition between states without full liquid recovery and supply, maintaining a close state to prevent leakage and maintain immersion conditions, thereby reducing transition time and preventing water stains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If liquid is recovered and supplied each time the wafer is exchanged, then the immersion method can maintain high resolution and depth of focus, but the time required for liquid recovery and supply decreases throughput
Solution Approach 1:
The liquid is supplied in advance to the first stage before the wafer is exchanged, so that when the stage transitions to the second area, the liquid is already in position. This eliminates the need for liquid recovery and re-supply during wafer exchange, maintaining immersion conditions continuously and improving throughput while preserving resolution and depth of focus benefits
Solution Approach 2:
The liquid supply system maintains continuous immersion conditions by supplying liquid to the first stage in advance and maintaining it there during wafer exchange. This ensures that when the stage moves to the second area, immersion is already established, eliminating interruptions and maintaining continuous useful action without throughput penalties
2Reliability
If liquid is recovered and supplied frequently, then immersion conditions are maintained, but water stains are generated on optical components requiring frequent lens replacements
Solution Approach 1:
By supplying liquid to the first stage in advance and maintaining it there during wafer exchange, the system eliminates the liquid recovery and re-supply cycle that causes water stains on optical components. The preliminary action ensures immersion is established before the stage moves, preventing harmful condensation and staining
Solution Approach 2:
The invention converts the potential harm of liquid handling operations into a benefit by eliminating the recovery and re-supply cycle. By maintaining liquid on the first stage during transitions, the system prevents water stains that would otherwise form during frequent liquid handling, turning a potentially harmful process into a protective measure
3Manufacturing precision
If the space between projection optical system and wafer is locally filled with liquid, then resolution and depth of focus are improved, but liquid leakage may occur during stage transitions
Solution Approach 1:
The liquid is supplied to the first stage in advance before the stage transitions to the second area. This preliminary action ensures that when the stage moves, the liquid is already contained and secured on the first stage, minimizing the risk of leakage during the transition while maintaining immersion benefits
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 method enables faster transitions between exposure states, improves throughput by reducing liquid handling time, and minimizes water stains on optical components, maintaining image quality and extending the lifespan of optical members.
Implementation Method 1
the wavelength of the exposure light in the liquid becomes 1/n of the wavelength in the air (n is the refractive index of the liquid which is normally around 1.2 to 1.6)
Implementation Method 2
the exposure apparatus that uses the immersion method is recently gathering attention... the apparatus that performs exposure in a state where the space between the lower surface of the projection optical system and the wafer surface is locally filled with liquid
Implementation Method 3
the depth of focus can be also substantially increased n times when compared with the case where the same resolution is obtained by a projection optical system (supposing that such a projection optical system can be made) that does not employ the immersion method
Data Source
AI summary
A lithographic projection apparatus includes a substrate table to hold a substrate, a projection system to project a patterned beam of radiation onto the substrate and a liquid confinement structure to confine a liquid in a space between the projection system and the substrate, the substrate, the substrate table, or both, to form a part of a boundary of the space. In addition, a closing plate forms a part of a boundary of the space in place of the substrate, the substrate table, or both, when moved without substantially disturbing the liquid, the liquid confinement structure, or both.