Exposure Apparatus Encoder System for Lithography Positioning
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Solution Overview
Problem
In the lithography process for producing micro-devices like liquid crystal display devices, existing exposure apparatuses face challenges in accurately positioning substrates due to the influence of air fluctuations, especially as substrate sizes increase, making it difficult to maintain precise positioning across the entire moving range.
Innovation Solution
An exposure apparatus with a measurement system using a grating member and multiple heads that move in orthogonal directions to measure position information, allowing for precise control of the movable body's movement in three degrees of freedom within a predetermined plane, and a control system that adjusts movement based on measured data from multiple heads to correct for air fluctuation effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an optical interferometer system with bar mirrors is used to obtain position information, then positioning accuracy can be maintained, but the system becomes complex and air fluctuation influence cannot be ignored
Solution Approach 1:
The patent replaces the optical interferometer system (optical measurement method) with an encoder system (mechanical measurement method). The encoder uses a scale attached to the movable body and read heads that mechanically read position information, eliminating the need for complex optical paths with bar mirrors while achieving comparable positioning accuracy.
Solution Approach 2:
The patent extracts the measurement function from the optical system by separating the scale (attached to movable body) from the read heads (fixed to stationary body). This allows the measurement system to be simplified while maintaining positioning accuracy through direct mechanical coupling rather than optical paths susceptible to air fluctuations.
2Reliability
If encoder system is used to reduce air fluctuation influence, then measurement stability improves, but large substrates require scales that cover entire moving range making the system larger
Solution Approach 1:
The patent divides the scale into multiple segments or sections along the scanning direction. Each segment can be independently manufactured and positioned, allowing the encoder to cover large substrate areas without requiring a single continuous long scale. The read heads read position information from their respective segments, maintaining measurement stability across the entire moving range.
3Area of moving object
If substrate size increases, then manufacturing capability improves, but positioning accuracy across entire moving range becomes difficult to maintain
Solution Approach 1:
The patent implements segmentation of the encoding system where the scale is divided into multiple sections that can accommodate large substrate dimensions. Each section maintains high positioning accuracy through precise mechanical coupling, allowing the system to handle larger substrates while preserving manufacturing precision across the entire area.
Solution Approach 2:
The patent introduces an intermediary mechanical coupling system between the movable body and the scale that maintains precise positional relationships even over large distances. This intermediary mechanism ensures that positioning accuracy is maintained across the entire substrate area regardless of size increases.
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 enhances positioning accuracy for both the mask and substrate, reduces the impact of air fluctuations, and allows for more compact and cost-effective systems by eliminating the need for large bar mirrors, improving maintainability and reducing costs.
Implementation Method 1
a measurement system, having a grating member with a plurality of grating areas arranged mutually apart in the first direction
Implementation Method 2
the measurement beam of each of the plurality of heads moves off of one of the plurality of grating areas, and moves to irradiate another grating area adjacent to the one grating area
Data Source
AI summary
A liquid crystal exposure apparatus has a measurement system having scales arranged apart from each other in the X-axis direction provided at a substrate stage holding a substrate and heads each irradiating the scales with a measurement beam; and a measurement device that measures positions of head units in the Y-axis direction. The measurement system measures a position of the substrate holder in directions of three degrees of freedom within a plane, based on measurement information of at least three heads. Each of the heads move off of one scale while the substrate holder is moved in the X-axis direction and moves to irradiate another scale adjacent to the one scale, and correction information to control movement of the substrate holder using the head moving to irradiate another scale is acquired, based on measurements of at least three heads.