Illumination Optical System Uniformizing Laser Intensity
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Solution Overview
Problem
The degradation of glass material performance in optical members due to local concentration of optical energy from short-wavelength laser sources, such as excimer lasers, used in exposure apparatuses, particularly when quartz glass is employed, as it leads to increased costs when fluorite is used instead.
Innovation Solution
An illumination optical system that includes an optical lens with distinct first and second regions, where the light beam from the laser source is transmitted through these regions to overlap and uniformize the light intensity distribution on the incident surface of a diffraction optical element, reducing local energy concentration and extending the glass material's performance degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fluorite is used as the glass material of the optical member, then the degradation of glass material performance is reduced, but the cost of the exposure apparatus increases
Solution Approach 1:
The patent applies local quality by creating different regions within the optical member with different light transmission characteristics. The first region transmits light beams from the center of the light source, while the second region transmits light beams from the peripheral portion, allowing different parts of the optical member to handle different light intensities appropriately
Solution Approach 2:
The optical member is segmented into multiple regions (first region and second region) with different optical properties. This segmentation allows the system to distribute light energy more evenly across the optical member, preventing local concentration of optical energy that would otherwise require expensive fluorite material
2Ease of manufacture
If quartz glass is used as the glass material of the optical member, then the cost is reduced, but the degradation of glass material performance occurs more quickly
Solution Approach 1:
The patent changes the optical parameters of the system by introducing an optical member with specific transmission characteristics that modify the light intensity distribution. This allows quartz glass to be used while preventing the light intensity conditions that would cause rapid degradation
Solution Approach 2:
The patent converts the potentially harmful concentrated light energy into a beneficial distributed energy pattern. By using the optical member to redistribute light from the high-intensity center region to include peripheral regions, the system transforms what would be a damaging concentration of energy into a useful uniform distribution
3Productivity
If the output of the light source is increased to improve throughput, then the productivity increases, but the local concentration of optical energy accelerates glass material degradation
Solution Approach 1:
The patent introduces a dynamic solution where the optical member actively manages light distribution regardless of the light source output level. The first and second regions work together to maintain proper light intensity distribution even when the overall light output is increased for higher productivity
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 effectively reduces the local concentration of optical energy on the glass material, thereby delaying its degradation and maintaining performance without the need for more expensive fluorite, thus reducing overall exposure apparatus costs.
Implementation Method 1
an optical element configured to transmit the light beam from the light source... the optical element is formed so as to overlap a part of a light beam which is transmitted through the first region and a part of the light beam which is transmitted through the second region
Data Source
AI summary
The present invention provides an illumination optical system that illuminates a surface to be illuminated by using a light beam from a light source, comprising: an optical element configured to transmit the light beam from the light source; and a member that has an incident surface on which the light beam transmitted through the optical element is incident, wherein the optical element has a first region including a central portion of the optical element, and a second region outside the first region, and wherein the optical element is formed so as to overlap a part of a light beam which is transmitted through the first region and a part of the light beam which is transmitted through the second region, on the incident surface.