EUV Fly's-Eye Mirror Correction Mirrors Illumination Uniformity
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Solution Overview
Problem
Projection-exposure systems using extreme ultraviolet (EUV) light face challenges in achieving uniform illumination, leading to exposure irregularities due to slight irregularities in the illumination distribution, which affect the quality of microdevice manufacturing.
Innovation Solution
The implementation of an illumination-optical system comprising a light source emitting EUV light, a collimator, a fly's-eye mirror with correction mirrors or filters, and a condenser, where the correction elements are designed to correct illumination irregularities by adjusting the reflectivity or transmissivity distribution to match the illumination area, ensuring minimal exposure irregularities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional illumination-optical systems are used with EUV light sources, then the system can achieve short wavelength exposure capability, but illumination irregularities and exposure non-uniformity occur
Solution Approach 1:
The patent applies local quality by creating correction mirrors with spatially varying reflectivity properties. Specifically, the correction mirrors have reflectivity irregularities that are non-uniformly distributed across their surfaces, with different regions having different reflectivity characteristics to compensate for local illumination defects in the EUV optical system
Solution Approach 2:
The patent implements parameter changes by modifying the reflectivity parameter of the correction mirrors. The reflectivity is intentionally made non-uniform across the mirror surface, with specific reflectivity values at different positions calculated to counterbalance the illumination irregularities, thereby transforming a uniform parameter into a controlled non-uniform parameter
2Manufacturing precision
If correction mirrors with reflectivity irregularities are introduced, then illumination irregularities are corrected, but device complexity increases
Solution Approach 1:
The patent applies merging by integrating the correction mirrors into the existing fly's-eye mirror structure. The correction mirrors are combined with the beam-splitting mirrors in a unified optical component, allowing the correction function to be embedded within the existing system architecture rather than adding separate correction devices
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 significantly reduces illumination and exposure irregularities, resulting in high-performance microdevice manufacturing with improved uniformity and precision in projection-exposure systems.
Implementation Method 1
each unit mirror and correction mirror comprises a respective multilayer film that facilitates the respective reflectivity of the unit mirror
Implementation Method 2
The multiple unit mirrors and the correction mirrors can be oriented in the fly's-eye mirror such that their respective angles of incidence to incident light are respective angles of total reflection
Implementation Method 3
The fly's-eye mirror comprises multiple unit mirrors. At least one of the unit mirrors of the fly's-eye mirror is a correction mirror that has one or more 'reflectivity irregularities' that correct a portion of, or all of, corresponding 'illumination irregularities' in the illumination area
Data Source
AI summary
An object of this invention is to reduce even slight irregularities in illumination that occur after assembly of an optical system. To this end, in an exemplary illumination-optical system, a light source that emits extreme ultraviolet (EUV) light, a collimator, a fly's-eye mirror, and a condenser are positioned, in this stated order. A prescribed illumination area on the emission side of the condenser is irradiated with Köhler illumination. At least one unit mirror, among multiple unit mirrors of the fly's-eye mirror, is a correction mirror that has reflectivity irregularities. The reflectivity irregularities correct a portion of, or all, the illumination irregularities in the illumination area.