Micromirror Array Stitching for Large Illumination Area
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Solution Overview
Problem
Scanning exposure apparatus using a micromirror array as a variable shaped mask faces challenges in increasing the illumination area, leading to prolonged exposure times, temperature variations affecting measurement accuracy, and inefficiencies in screen stitching due to small pattern formation areas.
Innovation Solution
A method and apparatus for high-precision exposure using a pattern forming apparatus that detects positional variations between the energy beam and object during exposure, employing a measurement pattern to adjust and refine the exposure process, and a pattern forming method that controls modulation elements of a variable shaped mask to stitch light patterns for precise pattern formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the micromirror array size is increased to enlarge the illumination area, then the exposure time can be reduced, but it is relatively difficult to increase the size of the micromirror array
Solution Approach 1:
The patent divides the large illumination area into multiple smaller regions by using multiple projection optical systems arranged in a matrix configuration. Each projection optical system handles a specific region, allowing the system to achieve a large total illumination area without requiring a single large micromirror array. This segmentation approach resolves the contradiction by achieving area expansion through spatial distribution rather than increasing individual component size.
Solution Approach 2:
The patent transitions from a single-dimensional scanning exposure approach to a two-dimensional matrix arrangement of multiple projection optical systems. By organizing the projection systems in rows and columns, the system achieves expanded illumination area in both scanning and non-scanning directions simultaneously, effectively resolving the area limitation without requiring excessive enlargement of individual micromirror arrays.
2Device complexity
If the illumination area is kept small, then the micromirror array size can be reduced, but the exposure time becomes prolonged
Solution Approach 1:
The patent segments the exposure task across multiple projection optical systems that operate simultaneously. While each individual system maintains a manageable micromirror array size, the combined system covers a large total area, thereby reducing the overall exposure time compared to sequential exposure of the same area with a single small system.
Solution Approach 2:
The patent merges the capabilities of multiple projection optical systems with smaller micromirror arrays to achieve the functional equivalent of a single system with a much larger illumination area. This combination allows the system to maintain simplicity of individual components while achieving high productivity through parallel operation.
3Device complexity
If the illumination area is small, then the micromirror array can be smaller, but temperature variation affects measurement accuracy during prolonged exposure
Solution Approach 1:
The patent segments the total exposure time into shorter intervals by using multiple projection optical systems that expose different regions simultaneously. This reduces the duration of continuous operation in any single location, thereby minimizing temperature variations and their impact on measurement accuracy while maintaining a manageable micromirror array size.
4Area of moving object
If multiple projection optical systems are arranged in a zigzag shape for screen stitching, then the illumination area can be expanded, but some micromirrors are not used efficiently
Solution Approach 1:
The patent employs an asymmetric matrix arrangement of projection optical systems where the number of systems in the scanning direction differs from the number in the non-scanning direction. This asymmetric configuration, combined with appropriate field stop settings, enables efficient utilization of micromirrors across all systems while achieving the desired screen stitching and illumination area expansion, avoiding the inefficiencies of symmetric zigzag arrangements.
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
The solution enables high-precision exposure and pattern formation across larger areas, reducing exposure time and improving accuracy by continuously monitoring and adjusting for positional variations, and optimizing the use of micromirror arrays for efficient pattern stitching.
Implementation Method 1
a photodetector 38 to receive the light 110 having passed through the slit 34y
Implementation Method 2
a condenser lens 36 and a photodetector 38... the condenser lens 36 to focus the light 110
Implementation Method 3
a scanning exposure apparatus that uses a micromirror array which is a type of a reflective spatial light modulator, as a variable shaped mask
Implementation Method 4
the measurement values of a measurement device (such as a laser interferometer) used for position measurement of the substrate stage
Data Source
AI summary
During a period after starting exposure to a plurality of shot areas subject to exposure on a wafer until completing the exposure, a light via a slit pair arranged on a stage that holds the wafer, of illumination light via a pattern generating device, is received, and information on a positional relation between an illumination light and the stage (and hence a positional relation between the illumination light and the wafer) is detected. With this operation, even if the information on the positional relation between the illumination light and the wafer varies due to some reason, information on the variation can be detected while performing the exposure to the plurality of shot areas. Accordingly, high-precision exposure can be achieved in an exposure operation, by considering this detection results.