Movable Body Drive Precision via Arm-Mounted Encoder
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Solution Overview
Problem
Existing exposure apparatuses face challenges in achieving high precision position control of fine movement stages due to temperature fluctuations and vibrations, which affect measurement accuracy, especially in liquid immersion exposure systems where the wafer stage can be deformed by heat and vibrations interfere with encoder systems.
Innovation Solution
A movable body apparatus with a measurement system that uses an arm member with a solid section allowing light to pass through, irradiating measurement beams on a plane parallel to the movement plane, enabling precise position measurement and driving of the movable body without adverse effects from stage drive vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an encoder system with a grating on the wafer stage upper surface is used for position measurement, then measurement precision is improved, but the grating is deformed by heat of vaporization and vibrations when liquid evaporates
Solution Approach 1:
A cover glass is introduced as an intermediary protective layer between the liquid immersion medium and the grating. This cover glass prevents direct contact with the liquid, protecting the grating from heat of vaporization and deformation while allowing the encoder system to function. The cover glass acts as a mediator that isolates the sensitive measurement component from harmful environmental factors.
2Measurement precision
If the encoder main body is provided at the stage surface plate supported by suspension, then position measurement is enabled, but vibration and stage drive affect measurement accuracy
Solution Approach 1:
The encoder main body is extracted from the stage surface plate support structure and relocated to the coarse movement stage support structure. This spatial separation removes the encoder from the vibration-prone environment of the fine movement stage, isolating it from stage drive vibrations while maintaining its position measurement function through the optical connection via the cover glass and grating.
3Measurement precision
If the encoder main body is placed on the surface plate, then position measurement is achieved, but it is difficult to adopt in coarse/fine movement structure where coarse movement stage comes between fine movement stage and surface plate
Solution Approach 1:
The encoder system is reconfigured to operate in a different spatial dimension by placing the encoder main body on the coarse movement stage support structure rather than the surface plate. This dimensional relocation allows the encoder to measure the position of the fine movement stage through optical transmission through the cover glass and grating, making it compatible with the coarse/fine movement structure where the coarse stage is positioned between the surface plate and fine stage.
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 allows for precise driving of the movable body, enhancing pattern transfer accuracy on objects by minimizing the impact of temperature fluctuations and vibrations, thereby improving measurement accuracy and reducing Abbe errors.
Implementation Method 1
the first measurement system irradiating at least one first measurement beam on the measurement plane from the arm member, receiving light from the measurement plane of the first measurement beam
Data Source
AI summary
A drive system drives a movable body, based on measurement results of a first measurement system which measures the position of the movable body in an XY plane by irradiating a measurement beam from an arm member on a grating placed on a surface parallel to the XY plane of the movable body. In this case, because a configuration in which the arm member irradiates a measurement beam on the grating is employed, there is no adverse effect due to the drive of the moving body, unlike the case when an encoder system is arranged on a stage surface plate. Accordingly, it becomes possible to drive the movable body with good precision.