Movable Body Encoder with Arm Variance Correction
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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, particularly in liquid immersion exposure systems where the wafer stage can be deformed by heat and vibrations impact the optical axis of the encoder system.
Innovation Solution
A movable body apparatus with a measurement system that includes a first measurement system to irradiate and measure a position beam on a measurement plane and a second measurement system to measure variance information of an arm member, allowing for correction of measurement errors and precise positioning, integrated into an exposure apparatus for improved precision in pattern transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a laser interferometer is used to measure the position of the fine movement stage, then the measurement can be performed, but temperature fluctuation and temperature gradient of the atmosphere affect the beam path and cause short-term variation in measurement values
Solution Approach 1:
The patent introduces an encoder system with a grating and cover glass as an intermediary measurement mechanism. The cover glass acts as a mediator that protects the grating from direct exposure to liquid while still allowing optical measurement, thereby eliminating the harmful effects of temperature fluctuation on the measurement beam path.
Solution Approach 2:
The patent replaces the laser interferometer optical measurement system with an encoder system that uses a physical grating structure. This substitution eliminates the problem of temperature-induced beam path variation by using a mechanically stable grating-based measurement approach.
2Reliability
If the grating is covered with a cover glass to protect it from heat of vaporization, then the grating becomes immune to heat damage, but the encoder main body supported by suspension allows vibration to travel to the stage surface plate and incline the optical axis
Solution Approach 1:
The patent extracts the encoder main body from the suspended support structure and relocates it to a vibration-isolated position. This separation removes the harmful vibration transmission path from the projection optical system surface plate to the encoder, while maintaining the protective cover glass over the grating.
Solution Approach 2:
The patent introduces a vibration isolation mechanism as an intermediary between the suspended support member and the encoder main body. This intermediary blocks the transmission of vibration to the optical axis while allowing the encoder to function properly.
3Ease of operation
If the encoder main body is supported by suspension via the projection optical system surface plate, then the encoder can be positioned, but vibration during exposure travels through the support members and inclines the optical axis of the encoder head
Solution Approach 1:
The patent extracts the encoder main body from the vibration-prone suspended support structure and repositions it on a vibration-isolated platform. This extraction maintains the encoder's positioning capability while removing it from the harmful vibration environment.
Solution Approach 2:
The patent implements vibration isolation measures beforehand by providing a vibration isolation mechanism between the suspended support member and the encoder main body. This prior cushioning prevents vibration from reaching the optical axis before it can cause measurement errors.
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
Enables precise driving of the movable body within a predetermined plane, enhancing the accuracy of pattern formation on objects by correcting measurement errors caused by arm member variance, thus improving the overall precision and reliability of the exposure process.
Implementation Method 1
a first measurement system which has an arm member having at least one end section facing the measurement plane... 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
Implementation Method 2
a second measurement system which measures a variance information of the arm member
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 and measurement results of a second measurement system which measures a variance of the arm member using a laser interferometer. In this case, the drive system corrects measurement errors caused due to a variance of the arm member included in the measurement results of the first measurement system, using the measurement results of the second measurement system.