Liquid Immersion Exposure Stage Position Control
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Solution Overview
Problem
Existing exposure apparatuses face challenges in maintaining high precision positional control of stages due to reaction forces from electromagnetic drive systems, which degrade measurement accuracy and position control, especially when using planar motors without adequate vibration isolation.
Innovation Solution
The exposure apparatus employs two movable bodies with measurement surfaces, a guide surface forming member, and measurement systems to obtain positional information, allowing for precise movement and liquid transfer between the bodies, utilizing noncontact guidance methods like static gas bearings or magnetic levitation to minimize vibration and enhance precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a planar motor is used to drive the stage at high speed with high acceleration, then productivity is improved, but reaction forces cause vibration of the surface plate, degrading measurement precision and position control accuracy
Solution Approach 1:
The patent divides the measurement function into two independent measurement systems: one for measuring the position of the first movable body and another for measuring the position of the second movable body. This segmentation allows each measurement system to operate independently without being affected by vibrations from the other, thereby maintaining high measurement precision even when the stage is driven at high speed by the planar motor.
Solution Approach 2:
The patent introduces a liquid transfer mechanism as an intermediary between the first and second movable bodies. The liquid is transferred from the first movable body to the second movable body, which then moves to a predetermined position. This intermediary approach allows the system to maintain high position control accuracy by using the second measurement system to precisely control the position of the liquid-containing movable body, independent of vibrations affecting the first measurement system.
2Difficulty of detecting and measuring
If a two-dimensional encoder system is fixed to the surface plate to measure positional information, then measurement capability is improved, but reaction forces from the drive system cause vibration of the surface plate, degrading measurement accuracy
Solution Approach 1:
The patent implements two separate measurement systems that independently measure the positions of the first and second movable bodies. By segmenting the measurement function, each encoder system can operate without being affected by vibrations from the planar motor, as they are not shared on a common platform. This ensures high measurement accuracy for both bodies simultaneously.
Solution Approach 2:
The patent introduces a temporal dimension to the measurement process by sequentially using the first measurement system to measure the first movable body, then transferring the liquid to the second movable body, and using the second measurement system to measure the second movable body. This dimensional approach to measurement timing and separation allows the system to overcome the limitation of shared measurement platforms subject to vibration.
3Productivity
If the first and second movable bodies are moved in proximity to transfer liquid, then productivity is improved, but position control accuracy becomes more difficult to maintain due to vibration and measurement interference
Solution Approach 1:
The patent segments the liquid transfer process into two distinct phases with dedicated measurement systems: the first measurement system controls the position of the first movable body during liquid dispensing, and the second measurement system controls the position of the second movable body during liquid reception and subsequent positioning. This segmentation ensures high position control accuracy even when bodies are moved in proximity for efficient liquid transfer.
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 configuration enables high-precision positional control and measurement, reducing the impact of reaction forces and maintaining accurate position control, thereby improving the overall precision and efficiency of the exposure process.
Implementation Method 1
a first measurement system that irradiates the measurement surface of the first or second movable body that moves within a first area, with a measurement beam from a side opposite to the optical system with respect to the guide surface forming member, and receives light from the measurement surface
Implementation Method 2
utilizing noncontact guidance methods like static gas bearings or magnetic levitation to minimize vibration and enhance precision
Implementation Method 3
utilizing noncontact guidance methods like static gas bearings or magnetic levitation to minimize vibration and enhance precision
Data Source
AI summary
When a liquid immersion area (liquid) formed on a wafer stage is moved onto another wafer stage, a fine movement stage position measuring system measures positional information of the wafer stage, interferometers of a coarse movement stage position measuring system measure positional information of the another wafer stage, and different interferometers measure positional information of the wafer stage. Based on these measurement results, the wafer stage and the another wafer stage are made to be in proximity to each other and are driven while the scrum state is maintained, and thereby the liquid immersion area (liquid) formed on the wafer stage can be moved onto the another wafer stage.