EUV Light Source Using Dispersed Tin Particles in Resin
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Solution Overview
Problem
Conventional EUV light sources using solid tin targets face challenges such as high plasma density, debris generation, and low conversion efficiency due to the absorption of laser energy and EUV light, as well as difficulties in supplying solid materials to discharge plasma sources, limiting the effectiveness of tin as a target substance.
Innovation Solution
A plasma EUV light source is developed where fine particles of a solid target, such as tin, are dispersed in a medium, preferably a heated and melted thermoplastic resin, to prevent excessive plasma density and debris, allowing for stable and efficient EUV light generation by converting the target into a plasma within a vacuum chamber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If solid Sn target is used as is, then high conversion efficiency is expected, but plasma density becomes too high causing laser absorption and EUV light absorption
Solution Approach 1:
The solid Sn target is segmented into fine particles with a diameter of 1 μm or less, which are then dispersed in a liquid carrier. This segmentation reduces the local plasma density when particles are irradiated, preventing excessive absorption of the exciting laser and generated EUV light, while maintaining high conversion efficiency through controlled particle distribution.
Solution Approach 2:
A liquid carrier serves as an intermediary medium to disperse and transport the fine Sn particles. The liquid carrier allows controlled delivery of particles to the irradiation region, managing plasma density by spacing particles apart while enabling efficient energy transfer from the laser to the target material.
2Power
If solid Sn target is irradiated with laser, then EUV light is generated, but large amount of debris is generated
Solution Approach 1:
By segmenting the Sn target into fine particles (1 μm or less in diameter), the surface area to volume ratio increases, enabling more complete and uniform ablation. This reduces the generation of large debris fragments while maintaining high EUV light output through efficient plasma formation from numerous small particles.
Solution Approach 2:
The invention uses fine particles that can be continuously supplied and replaced, creating a renewable target system. Each particle serves as a mini-target that is completely ablated, generating EUV light without leaving behind large debris structures that would occur with bulk solid targets.
3Object-generated harmful factors
If Sn is heated and converted into vapor to avoid debris, then density is reduced, but sufficiently high conversion efficiency cannot be obtained
Solution Approach 1:
The invention utilizes phase transition by heating and vaporizing fine Sn particles contained in a liquid carrier. The particles are heated from solid → liquid → vapor phases during laser irradiation. This controlled phase transition of fine particles achieves complete ablation without debris while maintaining high conversion efficiency through the confined vaporization of small particle volumes.
4Loss of energy
If Xe gas or liquefied Xe is used as target, then high conversion efficiency is obtained and debris problem is avoided, but limits are reached for higher output EUV light source
Solution Approach 1:
The invention changes the physical state parameter of the target material from gaseous Xe to solid/fine-particle Sn. By using fine Sn particles with optimized size distribution and dispersion, the system achieves both high conversion efficiency (comparable to or exceeding Xe) and high EUV light output, overcoming the output limits of gas-based systems.
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 approach enhances EUV light conversion efficiency and reduces debris, enabling higher intensity EUV light production and improved stability in EUV exposure apparatuses, thereby increasing semiconductor device manufacturing throughput.
Implementation Method 1
pulzed laser light is focused on a target material inside a vacuum vessel so that this target material is converted into a plasma, and the EUV light that is radiated from this plasma is utilized
Implementation Method 2
X-rays are generated from the target S by the plasma phenomenon
Implementation Method 3
the EUV light that is radiated from this plasma is utilized
Implementation Method 4
These X-rays are reflected by reflective mirrors C and D, and are incident on the illumination optical system as parallel X-rays. Then, the X-rays are successively reflected by the reflective mirrors IR1 through IR4 of the illumination optical system
Implementation Method 5
The X-rays reflected by the pattern formed on the mask M are successively reflected by the reflective mirrors PR1 through PR4 of the projection optical system, so that an image of the pattern is focused on the surface of the wafer W
Data Source
AI summary
A liquid in which fine solid Sn particles are dispersed in a resin is accommodated inside the heated tank 4. The resin pressurized by a pressurizing pump is conducted to a nozzle 1, so that a liquid-form resin is caused to jet from the tip end of the nozzle 1 that is disposed inside a vacuum chamber 7. The liquid-form resin which is caused to jet from the nozzle 1 assumes a spherical shape as a result of surface tension, and is solidified by being cooled in a vacuum, so that a solid-form target 2 is formed. A laser introduction window 10 used for the introduction of laser light is formed in the vacuum chamber 7, and laser light generated from a laser light source 8 disposed on the outside of the vacuum chamber 7 is focused by a lens 9 and conducted into the vacuum chamber 7, so that the target is converted into a plasma, thus generating EUV light.