Projection Exposure Alignment Using Dual-Wavelength Mark Imaging
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Solution Overview
Problem
Existing projection exposure apparatuses face challenges in achieving high-precision alignment, particularly in small-sized exposure areas, due to potential interference between alignment marks and disturbances such as temperature changes, and require improved methods for precise alignment without irradiating the work with exposure light.
Innovation Solution
A projection exposure apparatus and method utilizing a mask mark illumination light source for exposure light and a work mark illumination light source for a different wavelength, with an imaging optical system that includes an optical path length changing system to align mask and work marks, ensuring equivalent optical positional relationships, allowing high-precision alignment even in small-sized areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If alignment is performed using the same wavelength light for both mask and work alignment marks, then alignment precision is improved, but interference between multiple alignment units occurs in small-sized exposure areas
Solution Approach 1:
The patent applies local quality by assigning different wavelengths to different alignment mark types: mask alignment marks are illuminated with first wavelength light (e.g., UV), while work alignment marks are illuminated with second wavelength light (e.g., visible light). This localized differentiation allows multiple alignment units to operate simultaneously in small exposure areas without interference, as each unit operates at its designated wavelength.
Solution Approach 2:
The patent changes the wavelength parameter of illumination light based on the alignment mark type. By using first wavelength light for mask alignment and second wavelength light for work alignment, the system enables simultaneous operation of multiple alignment units without mutual interference, thereby achieving high-precision alignment even in small-sized exposure areas.
2Measurement precision
If exposure light is used for alignment, then alignment precision is improved, but the work is irradiated with exposure light causing unwanted exposure
Solution Approach 1:
The patent applies local quality by using different wavelengths for different purposes: first wavelength light (exposure light) is used only for illuminating mask alignment marks, while second wavelength light (non-exposure light) is used for illuminating work alignment marks. This localized wavelength differentiation allows precise alignment without irradiating the work with exposure light, preventing unwanted exposure.
Solution Approach 2:
The patent introduces second wavelength light as an intermediary for work alignment. Instead of using exposure light directly on the work, the system uses non-exposure light to illuminate work alignment marks, serving as an intermediary that enables alignment without causing harmful exposure effects on the photosensitive work.
3Productivity
If multiple alignment units are used to improve alignment speed, then productivity is improved, but interference occurs in small-sized exposure areas
Solution Approach 1:
The patent changes the wavelength parameter to enable multiple alignment units to operate simultaneously without interference. By assigning first wavelength to mask alignment units and second wavelength to work alignment units, the system achieves high productivity through parallel operation while avoiding interference in small-sized exposure areas.
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
Enables high-precision alignment without interference between alignment units, even in small-sized exposure areas, by using different wavelength alignment lights and an optical path length changing system, thereby enhancing alignment accuracy and supporting miniaturization and high-resolution exposure.
Implementation Method 1
a mask mark illumination light source capable of irradiating an alignment mark of the mask with the exposure light itself or first alignment light having substantially the same wavelength as the exposure light
Implementation Method 2
an alignment unit including a work mark illumination light source capable of irradiating an alignment mark of the work with second alignment light having a wavelength different from the wavelength of the exposure light
Implementation Method 3
the imaging optical system has an optical path length changing optical system for splitting and merging the first alignment light from the first alignment light and the light from the alignment mark of the work synthesized by the synthesizing optical element such that an optical path length of the first alignment light from the synthesizing optical element to the imaging device is longer than an optical path length of the light from the alignment mark of the work from the synthesizing optical element to the imaging device
Implementation Method 4
an imaging device that obtains an image of the alignment mark of the mask by the first alignment light and the alignment mark of the work
Data Source
AI summary
A projection exposure apparatus includes a mask mark illumination light source irradiating a mask mark with exposure light itself or a first alignment light having substantially the same wavelength as the exposure light, and an alignment unit having a work mark illumination light source irradiating a work mark with second alignment light having a wavelength different from the wavelength of the exposure light, an imaging device, and an imaging optical system. The imaging optical system includes a first dichroic prism for synthesizing the first alignment light and the light from the work mark and emitting the synthesized light toward the imaging device, and an optical path length changing optical system for splitting and merging the first alignment light, in which the optical positional relationships of the work mark and the image of the mask mark with respect to the imaging device are equivalent.