Exposure Apparatus Illumination Segmentation Astigmatism Control
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Solution Overview
Problem
Conventional exposure apparatuses experience rotationally asymmetric aberration changes, particularly astigmatism, due to differing light distribution states in the x and y directions on the pupil plane of the projection optical system, which complicates apparatus arrangement and increases costs.
Innovation Solution
The exposure apparatus employs an illumination optical system that illuminates the original with a first portion entering the incident pupil and a second portion outside it, separated on the pupil plane, to maintain optical characteristics and suppress astigmatism by adjusting the position, shape, and light intensity of the second illumination light portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dipole illumination is used to illuminate the original pattern, then the optical characteristic (image formation characteristic) of the projection optical system changes due to rotationally asymmetric aberration, but using a technique to suppress such aberration change requires additional equipment to irradiate optical members with a different wavelength range, which complicates apparatus arrangement and increases cost
Solution Approach 1:
The illumination light is divided into two distinct portions: a first portion that enters the incident pupil and a second portion that enters a region outside the incident pupil. This segmentation allows differential illumination of optical members, enabling suppression of rotationally asymmetric aberration without requiring additional wavelength-range equipment. The separated portions create different temperature distributions that counterbalance the asymmetric heating effects.
Solution Approach 2:
Different regions of the illumination light are directed to different locations relative to the incident pupil. The first portion (entering the incident pupil) and second portion (outside the incident pupil) create localized temperature variations on optical members. This local quality differentiation enables targeted thermal compensation for rotationally asymmetric aberrations while maintaining a simple apparatus configuration.
2Reliability
If dipole illumination is used, then the optical member near the pupil plane is illuminated with greatly different distribution states in the X direction and the Y direction, causing rotationally asymmetric aberration change, but adding equipment to correct this increases cost
Solution Approach 1:
The illumination system segments the light into two portions with different spatial distributions. The first portion enters the incident pupil while the second portion enters outside the incident pupil, creating complementary temperature distributions that suppress rotationally asymmetric aberration. This approach achieves optical stability without requiring expensive additional correction equipment.
Solution Approach 2:
The illumination system changes the spatial distribution parameters of the illumination light by separating it into two portions with different incident positions on the projection optical system. This parameter modification creates balanced temperature distributions that compensate for asymmetric heating, maintaining optical characteristics without additional costly equipment.
3Reliability
If normal illumination is used for line-and-space patterns, then diffracted light is mainly generated in only a single direction, causing the optical member to be illuminated in greatly different states in the x direction and the y direction, generating rotationally asymmetric aberration
Solution Approach 1:
The illumination light is segmented into two portions that enter different regions relative to the incident pupil. This segmentation creates multiple illumination paths that generate diffracted light in multiple directions, preventing the single-direction diffraction problem of normal illumination while maintaining a relatively simple illumination system configuration.
Solution Approach 2:
The illumination system intentionally creates an asymmetric illumination pattern by separating the light into two portions with different incident positions. This controlled asymmetry in illumination distribution generates balanced diffraction patterns that suppress rotationally asymmetric aberration, transforming the problem of asymmetric heating into a solution.
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 effectively reduces rotational asymmetry in the temperature distribution on the optical members, maintaining the projection optical system's optical characteristics and preventing astigmatism, thereby simplifying the apparatus arrangement and reducing costs.
Implementation Method 1
an optical member near the pupil plane of a projection optical system will be illuminated by exposure light with greatly different distribution states in the X direction and the Y direction
Implementation Method 2
rotational asymmetry in the temperature distribution on the optical members
Data Source
AI summary
The present invention provides an exposure apparatus that exposes a substrate via an original, including an illumination optical system configured to illuminate the original, and a projection optical system configured to project a pattern of the original onto the substrate, wherein the illumination optical system illuminates the original by illumination light which includes a first portion that enters an incident pupil of the projection optical system and a second portion which enters a region outside the incident pupil, and the first portion and the second portion are separated from each other on an incident pupil plane of the projection optical system.