Projection Optical System Aberration Correction via Multi-Mirror Segmentation

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing projection optical systems face challenges in achieving both small size and high performance, particularly in increasing numerical aperture (NA) while maintaining accurate aberration correction, which is essential for improving optical performance and resolving power in photolithography for large-screen FPD manufacturing.

Innovation Solution

A three-mirror, five-time-reflection optical system is designed with specific arrangements of concave and convex mirrors, along with aspherical lenses and a meniscus lens, to optimize the distance and curvature relationships between mirrors and lenses, ensuring aplanatic conditions and high NA without increasing the system's size or weight.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a concave mirror with large diameter is used as the main mirror to achieve high resolving power and large simultaneous exposure region, then the numerical aperture and exposure area are improved, but the optical system size, weight, and occupied area increase significantly

Engineering Contradiction:

Improveresolving powerVSAvoidoptical system weight

Core Design Contradiction:

Measurement precisionVSWeight of stationary object

Solution Approach 1:

The optical system is divided into multiple mirror components (first concave mirror, second concave mirror, and convex mirror) that work together to achieve the required resolving power without requiring a single large-diameter mirror. This segmentation allows the system to maintain high NA while reducing the size and weight of individual mirror components.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces a convex mirror component that adds a new dimension to the optical path configuration. By incorporating this additional mirror at a specific position and orientation, the system achieves improved resolving power and exposure area without proportionally increasing the overall system size or weight.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Measurement precision

If the optical system is enlarged to increase the simultaneous exposure region and numerical aperture, then the resolving power is improved, but the apparatus-occupied area and system complexity increase

Engineering Contradiction:

Improveresolving powerVSAvoidapparatus-occupied area

Core Design Contradiction:

Measurement precisionVSArea of stationary object

Solution Approach 1:

Multiple mirror functions are merged into a compact configuration where the first concave mirror, second concave mirror, and convex mirror are arranged to share space efficiently. This merging allows the system to achieve high resolving power and large exposure region while minimizing the apparatus-occupied area through optimal spatial arrangement.

Inventive Principle:

Principle #5Merging (Combining)

3Area of stationary object

If a multi-lens optical system with multiple equal-magnification optical systems is used to ensure large-screen area, then the exposure area is improved, but chromatic aberration increases and resolution decreases in overlapping regions

Engineering Contradiction:

Improveexposure areaVSAvoidresolution

Core Design Contradiction:

Area of stationary objectVSMeasurement precision

Solution Approach 1:

The patent replaces lens-based optical systems with a mirror-based optical system. By using mirrors (first concave mirror, second concave mirror, and convex mirror) instead of lenses, the system eliminates chromatic aberration while maintaining the ability to cover large exposure areas. This substitution preserves resolution even in overlapping regions through precise geometric control of the mirror arrangement.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

This configuration allows for a compact optical system with improved aberration correction and increased resolving power, enabling efficient exposure of large substrates with high precision and accuracy, addressing the limitations of previous systems in terms of size, weight, and performance.

Implementation Method 1

a mask pattern is reflected three times by a concave mirror and convex mirror which are almost concentrically arranged, and further reflected twice by a no-power trapezoidal mirror

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 2

along with aspherical lenses and a meniscus lens, to optimize the distance and curvature relationships between mirrors and lenses, ensuring aplanatic conditions

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS10578846B2Projection optical system, exposure apparatus, and article manufacturing method

Publication Date: 2020.03.03 CANON KK

AI summary

The present invention provides a projection optical system including a first concave reflecting surface, a first convex reflecting surface, a second concave reflecting surface, and a third concave reflecting surface, wherein the first concave reflecting surface, the first convex reflecting surface, the second concave reflecting surface, and the third concave reflecting surface are arranged such that light from an object plane forms an image on an image plane by being reflected by the first concave reflecting surface, the first convex reflecting surface, the second concave reflecting surface, the first convex reflecting surface, and the third concave reflecting surface in an order named.