EUV Illumination Facet Mirror Gap Angles for Homogenization
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Solution Overview
Problem
Existing projection exposure apparatuses for EUV projection lithography face challenges in maintaining homogeneous illumination due to gaps between mirror arrays, which affect the quality of the illumination field.
Innovation Solution
The apparatus incorporates a first facet mirror with mirror arrays arranged in an array superstructure, featuring gaps between neighboring arrays that are angled between 20° and 44° relative to the displacement direction, and a second facet mirror with facets that image individual mirror groups into the illumination field, ensuring complementary imaging and effective homogenization of the illumination field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If mirror arrays are arranged with gaps between them in the illumination optical unit, then the device complexity is reduced and thermal dissipation is improved, but the homogeneity of illumination in the illumination field deteriorates
Solution Approach 1:
The first facet mirror is segmented into multiple mirror arrays with gaps between them, allowing thermal dissipation while maintaining functional illumination coverage through the second facet mirror's imaging capability
Solution Approach 2:
The second facet mirror acts as an intermediary that images the individual mirrors of the first facet mirror into the illumination field, causing their images to complement one another and form the complete illumination field, thereby compensating for the gaps in the first facet mirror
2Illumination intensity
If the gaps between mirror arrays are oriented at certain angles to the displacement direction, then scan-integrated homogenization of illumination is achieved, but the design complexity increases due to precise angular requirements
Solution Approach 1:
The orientation angle of the gaps between mirror arrays is optimized to specific ranges (20°-44° with the displacement direction) to achieve scan-integrated homogenization of illumination, transforming a potential defect into a controllable parameter
3Illumination intensity
If individual mirrors are imaged into the illumination field with complementary coverage, then illumination homogeneity is improved, but the device complexity increases due to the need for precise imaging optics
Solution Approach 1:
The second facet mirror serves multiple functions: it images the individual mirrors of the first facet mirror into the illumination field, compensates for gap effects, and enables scan-integrated homogenization, thereby achieving illumination homogeneity without requiring additional complex optical components
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 ensures scan-integrated homogenization of illumination across the object field, preventing undesired resonance effects and allowing for high thermal dissipation, resulting in improved structure resolution for microstructured or nanostructured components like semiconductor chips.
Implementation Method 1
a first facet mirror, which comprises a plurality of mirror arrays with respectively a plurality of individual mirrors which provide individual mirror illumination channels for guiding illumination light partial beams to the illumination field
Implementation Method 2
a second facet mirror, which is arranged downstream of the first facet mirror in the beam path of the illumination light and comprises a plurality of facets, which respectively contribute to imaging a group of the individual mirrors of the field facet mirror into the illumination field via a group mirror illumination channel
Data Source
AI summary
An assembly for a projection exposure apparatus for EUV projection lithography has an illumination optical unit for guiding illumination light to an illumination field, in which a lithography mask can be arranged. The illumination optical unit comprises a first facet mirror, which comprises a plurality of mirror arrays with respectively a plurality of individual mirrors. The individual mirrors provide individual mirror illumination channels for guiding illumination light partial beams to the illumination field. The mirror arrays of the first facet mirror are arranged in an array superstructure. Gaps extend along at least one main direction (HRα) between neighboring ones of the mirror arrays. Furthermore, the illumination optical unit comprises a second facet mirror, which comprises a plurality of facets, which respectively contribute to imaging a group of the individual mirrors of the field facet mirror into the illumination field via a group mirror illumination channel.