Lithography Projection Objective Aberration Correction via Segmented Elements
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Solution Overview
Problem
Current projection objectives for lithography face challenges in effectively correcting both field-constant and field-dependent aberrations, which can lead to suboptimal imaging quality and efficiency in microlithographic processes.
Innovation Solution
The introduction of a projection objective with at least one intermediate image plane and two correction elements, one positioned near the pupil plane for field-constant aberration correction and another in an intermediate region for field-dependent aberration correction, allows for efficient measurement and correction of aberrations with minimal design changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If correction elements are added to correct both field-constant and field-dependent aberrations, then imaging quality is improved, but device complexity increases
Solution Approach 1:
The optical arrangement is segmented into multiple functional zones: object plane, intermediate image plane, image plane, pupil plane, and field plane. Correction elements are strategically placed in specific zones (one near the pupil plane for field-constant aberrations, another in an intermediate region for field-dependent aberrations) rather than uniformly distributed, allowing targeted correction while maintaining manageable system complexity.
Solution Approach 2:
Different correction elements are assigned to different spatial regions with distinct aberration characteristics. The first correction element addresses field-constant aberrations in the pupil plane region, while the second correction element handles field-dependent aberrations in the intermediate region, optimizing local correction effectiveness without requiring comprehensive correction across all regions.
2Measurement precision
If multiple correction elements are implemented for comprehensive aberration correction, then measurement precision is improved, but ease of operation deteriorates
Solution Approach 1:
The aberration correction function is segmented into two independent correction elements with distinct roles. This segmentation allows each element to be optimized for specific aberration types, improving measurement precision for different aberration categories while enabling independent adjustment and operation of each correction element, thereby maintaining operational simplicity.
3Manufacturing precision
If an intermediate image plane is introduced for aberration correction, then imaging quality is improved, but device complexity increases
Solution Approach 1:
An intermediate image plane is introduced between the object plane and the final image plane to perform preliminary aberration correction. This intermediate stage allows correction elements to act on the optical path before final image formation, enabling effective aberration compensation while maintaining a relatively simple overall optical structure through staged correction.
Data Source
AI summary
In some embodiments, a projection objective for lithography includes an optical arrangement of optical elements between an object plane and an image plane. The arrangement generally has at least one intermediate image plane, the arrangement further having at least two correction elements for correcting aberrations, of which a first correction element is arranged optically at least in the vicinity of a pupil plane and a second correction element is arranged in a region which is not optically near either a pupil plane or a field plane.