Exposure Apparatus Optical Member Position Control
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Solution Overview
Problem
Current projection exposure apparatuses face challenges in achieving high overlay accuracy and minimizing detection errors due to coma aberration and optical axis shifts in alignment detection systems, especially under varying conditions such as different materials, thicknesses, and line widths, leading to asymmetrical waveforms and detection errors.
Innovation Solution
An exposure apparatus with a position detection system that includes an optical member whose position can be adjusted based on evaluation values for waveform symmetry and optical axis shift, using a control unit to optimize the optical system's alignment and reduce detection errors by adjusting the optical member's position to achieve symmetrical waveforms and satisfy defocus characteristic specifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the alignment detection system uses a projection optical system to detect alignment marks, then the detection capability is improved, but coma aberration and optical axis shifts cause asymmetrical waveforms and detection errors
Solution Approach 1:
The patent changes the parameter of the optical system by introducing a cylindrical lens to modify the wavefront shape. This parameter change compensates for coma aberration and optical axis shifts, transforming asymmetrical detection waveforms into symmetrical ones, thereby reducing detection errors while maintaining high detection accuracy
Solution Approach 2:
The patent introduces a cylindrical lens as an intermediary optical element between the projection optical system and the photoelectric converter. This intermediary component actively corrects the asymmetrical wavefront caused by coma aberration and optical axis shifts, enabling reliable detection without sacrificing measurement precision
2Shape
If the optical system is adjusted to minimize coma aberration, then waveform symmetry is improved, but detection errors may still occur due to optical axis shifts
Solution Approach 1:
The patent applies parameter changes by introducing a cylindrical lens with specific optical power to compensate for residual asymmetry caused by optical axis shifts. This additional parameter adjustment ensures waveform symmetry is maintained even when optical axis shifts occur, preventing detection errors while preserving measurement precision
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 improves detection accuracy by reducing detection errors and maintaining waveform symmetry across various conditions, enabling precise alignment and high-resolution pattern transfer in semiconductor device fabrication.
Implementation Method 1
a photoelectric conversion device configured to receive light from a mark to detect the position of the reticle and the position of the substrate via the optical system
Data Source
AI summary
The present invention provides an exposure apparatus including a position detection apparatus that detects at least one of a position of a reticle and a position of a substrate. The position detection apparatus includes an optical member whose position can be changed, a photoelectric conversion device that receives light from a mark and outputs a detection signal, and a control unit that controls the position of the optical member based on information on a first evaluation value representing a symmetry of a waveform of the detection signal at each of a plurality of positions of the optical member and information on a second evaluation value representing a position shift of the mark detected upon changing a position of the mark in an optical axis direction of an optical system at each of the plurality of positions of the optical member.