Movable Body System Position Measurement for Lithography
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Solution Overview
Problem
In lithography processes for semiconductor device manufacturing, existing exposure apparatuses face challenges in maintaining precise position measurement and drive control of movable bodies, particularly when encoder heads are installed on substrate tables, leading to potential degradation in measurement accuracy due to changes in their setting position and attitude during movement.
Innovation Solution
A movable body system equipped with a measurement device featuring multiple encoder heads that measure positional information based on a grating section outside the body, allowing for precise drive control by accounting for the relative position between the encoder heads and the movable body, ensuring accurate positioning even when the encoder head moves with respect to the body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If an encoder head is installed on a substrate table, then the position measurement system can be integrated with the movable body, but the movement of the substrate table changes the setting position and attitude of the encoder head, degrading measurement accuracy
Solution Approach 1:
The system divides the measurement function into multiple encoder heads (first and second encoder heads) positioned at different locations on the substrate table. Each encoder head measures position in different directions, and the control unit synthesizes these measurements while compensating for the movement and attitude changes of the substrate table, thereby maintaining measurement accuracy despite the integrated configuration.
2Measurement precision
If multiple encoder heads are provided on the movable body to improve measurement accuracy, then the system complexity increases
Solution Approach 1:
The control unit serves multiple functions: it receives signals from multiple encoder heads, calculates the position of the substrate table in the scanning direction, determines the relative position between encoder heads and substrate table, and performs correction calculations. This multi-functional approach consolidates what could be separate devices into a single control unit, reducing overall system complexity while maintaining high measurement precision.
3Measurement precision
If the encoder head position is corrected based on relative position information, then measurement accuracy is maintained during movement, but the drive control system becomes more complex
Solution Approach 1:
The control unit continuously receives position information from the encoder heads, calculates the relative position between the encoder heads and the substrate table, and uses this feedback to correct the measured position. This closed-loop feedback mechanism maintains measurement accuracy during substrate table movement and scanning operations, with the control unit integrating the correction logic into the existing drive control system.
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 solution enables highly precise measurement and drive control of the movable body, maintaining accuracy during scanning exposure and pattern formation, thereby improving the precision of pattern transfer onto semiconductor wafers.
Implementation Method 1
measures positional information of the movable body, based on an output of at least one encoder head which faces a grating section placed parallel with the predetermined plane outside the movable body
Data Source
AI summary
An exposure apparatus exposes a substrate with an exposure beam via a projection system supported by a frame. A substrate stage having a table that mounts the substrate is placed on a base under the projection system. A measurement device has a plurality of heads provided at the table and each irradiate a measurement beam on a grating section supported by the frame, and measures positional information of the table by a head of the plural heads, that faces the grating section. A drive device drives the substrate stage to move the substrate. A controller controls a drive of the substrate stage based on displacement information of a head used in measurement of the positional information or correction information to compensate a measurement error of the measurement device that occurs due to a displacement of the head, and based on the positional information measured by the measurement device.