Exposure Apparatus Focus Control via Optical Conjugate Detection
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Solution Overview
Problem
Existing exposure apparatuses face challenges in achieving high-speed and accurate focus control, particularly in maskless exposure systems, where the intensity distribution of spot light on the substrate affects pattern resolution performance, and traditional focus control methods are slow and inaccurate.
Innovation Solution
An exposure apparatus with a projection optical system, a light shielding member, and a control unit that adjusts the defocus amount based on light received by a light receiving element, where the light shielding member is positioned optically conjugate to the substrate, allowing for high-speed and accurate focus control by detecting and correcting defocus through the amount of light received.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional focus control methods using image processing sensors are used, then focus control can be performed on substrate defocus, but the control speed is slow and accuracy is insufficient
Solution Approach 1:
The patent replaces the mechanical/image-processing-based focus control system with an optical detection system. By using a light receiving element to detect light flux intensity variations caused by defocus, the system achieves faster and more accurate focus control without the delays inherent in image capture and processing methods.
Solution Approach 2:
The patent implements a feedback mechanism where the light receiving element continuously monitors the light flux intensity, and the control unit adjusts the condensing lens position based on this feedback to minimize defocus. This closed-loop control enables high-speed and accurate focus adjustment by responding immediately to detected focus deviations.
2Manufacturing precision
If the condensed position of spot light deviates from the substrate, then pattern resolution performance degrades, but adjusting focus takes time
Solution Approach 1:
The patent performs preliminary focus detection and adjustment before exposure using the light receiving element to detect defocus conditions. By detecting and correcting focus deviations in advance through optical measurement rather than image processing, the system ensures optimal pattern resolution is achieved without time-consuming post-exposure adjustments.
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-speed and accurate focus control, improving pattern resolution performance and reducing the time required for focus adjustments, thereby enhancing the overall efficiency of the exposure process.
Implementation Method 1
a light shielding member having an opening for allowing light reflected by the substrate to pass therethrough; a light receiving element configured to receive a light flux passing through the opening after being reflected by the substrate
Implementation Method 2
a projection optical system configured to project, onto a substrate, exposure light for forming a pattern on the substrate
Data Source
AI summary
An exposure apparatus includes a projection optical system configured to project, onto a substrate, exposure light for forming a pattern on the substrate; a light shielding member having an opening for allowing light reflected by the substrate to pass therethrough and a light receiving element configured to receive a light flux passing through the opening after being reflected by the substrate; and a control unit configured to perform focus control for changing a defocus amount representing a positional deviation between a condensed position of the exposure light and the substrate in accordance with the amount of light received by the light receiving element. The light shielding member is disposed at a position that is optically conjugate to the substrate in an in-focus state where the defocus is smaller than a predetermined amount.