Hemisphere Target for EUV Light Uniformity
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Solution Overview
Problem
Current extreme ultraviolet (EUV) light sources for photolithography processes face challenges in achieving high conversion efficiency and uniform EUV light emission, as existing targets often result in non-uniform energy absorption and limited directional emission due to their shape and density distribution.
Innovation Solution
A hemisphere-shaped target system is introduced, where a target material is initially transformed into a collection of pieces using a pre-pulse, and then converted to plasma with a main pulse, allowing for increased energy absorption and isotropic EUV light emission by distributing target material pieces in a hemisphere-shaped volume with a density gradient that maximizes energy interaction and minimizes backside reflections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional target shape is used, then the structure is simple, but the EUV light emission is non-uniform and limited in directionality
Solution Approach 1:
The target material is divided into multiple discrete pieces distributed throughout a hemisphere-shaped volume rather than using a single conventional shape. This segmentation allows each piece to contribute to uniform EUV emission while maintaining overall structural simplicity through the hemispherical arrangement.
Solution Approach 2:
The target transitions from conventional 2D or simple 3D shapes to a hemisphere-shaped volume with pieces distributed in three-dimensional space. This dimensional change enables isotropic EUV emission in all directions while maintaining manufacturing feasibility through the regular hemispherical geometry.
2Illumination intensity
If target material is concentrated in a single location, then the energy absorption is high, but the EUV light emission is directional and non-uniform
Solution Approach 1:
The concentrated target material is segmented into multiple pieces distributed throughout the hemisphere volume. This distribution maintains high total energy absorption while enabling uniform EUV emission in all directions, resolving the contradiction between energy concentration and emission isotropy.
Solution Approach 2:
The hemisphere-shaped volume acts as an intermediary spatial framework that distributes target material pieces throughout the volume. This intermediary structure enables both high energy absorption (through sufficient material quantity) and uniform isotropic emission (through spatial distribution).
3Illumination intensity
If the target material density is uniform, then the manufacturing is simple, but the energy absorption and EUV emission are non-uniform
Solution Approach 1:
The target employs non-uniform density distribution with higher density regions positioned to optimize energy absorption and EUV emission uniformity. This local variation in density is achieved within the simple hemispherical framework, balancing manufacturing ease with performance optimization.
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
The hemisphere-shaped target system enhances EUV light generation efficiency and emission uniformity, increasing the conversion efficiency of the EUV light source and allowing for radially isotropic light emission, which improves performance in photolithography tools by reducing calibration needs and minimizing intensity variations.
Implementation Method 1
directing a first amplified light beam toward the initial target material, the first amplified light beam having an energy sufficient to form a collection of pieces of target material from the initial target material
Implementation Method 2
directing a second amplified light beam toward the collection of pieces to convert the pieces of target material to plasma that emits EUV light
Implementation Method 3
converting a material that has an element, for example, xenon, lithium, or tin, with an emission line in the EUV range into a plasma state
Data Source
AI summary
Techniques for forming a target and for producing extreme ultraviolet light include releasing an initial target material toward a target location, the target material including a material that emits extreme ultraviolet (EUV) light when converted to plasma; directing a first amplified light beam toward the initial target material, the first amplified light beam having an energy sufficient to form a collection of pieces of target material from the initial target material, each of the pieces being smaller than the initial target material and being spatially distributed throughout a hemisphere shaped volume; and directing a second amplified light beam toward the collection of pieces to convert the pieces of target material to plasma that emits EUV light.