Three-Laser EUV Source for Uniform Plasma Formation
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Solution Overview
Problem
Existing EUV light generation systems face challenges in achieving high conversion efficiency and uniform plasma formation due to uneven energy distribution in the target substance, leading to inefficiencies in generating extreme ultraviolet light for semiconductor manufacturing.
Innovation Solution
The system employs a three-laser configuration, including a first laser to generate a diffusion target convex toward the prepulse laser light, a second laser to create a low-density diffusion target, and a third laser to generate EUV light, with specific intensity and delay time settings to achieve a Gaussian distribution of energy for efficient plasma formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single laser is used to irradiate the target substance, then the device complexity is low, but the conversion efficiency of laser energy to EUV light is insufficient due to uneven energy distribution
Solution Approach 1:
The single laser beam is divided into multiple laser beams that irradiate different regions of the target substance. Each laser beam creates a localized plasma region, and the combination of multiple plasma regions forms a uniform overall plasma distribution, thereby improving energy conversion efficiency while maintaining relatively simple device structure
Solution Approach 2:
Different regions of the target substance are irradiated with laser beams having optimized local parameters (intensity, pulse duration, focal position). This creates locally optimized plasma conditions in each irradiated region, which collectively produce uniform plasma formation across the entire target area, resolving the contradiction between simple device structure and high conversion efficiency
2Power
If high laser intensity is applied to the target, then the EUV light generation efficiency improves, but the plasma formation becomes uneven and conversion efficiency decreases
Solution Approach 1:
The target substance is divided into multiple irradiation regions, each receiving optimized laser intensity. This segmentation allows high power to be applied locally in each region without causing uneven plasma formation across the entire target, as each region's plasma conditions are independently optimized
Solution Approach 2:
Each laser beam is parameter-optimized for its specific irradiation region on the target. This local optimization ensures that high laser intensity produces efficient EUV generation in each region while maintaining uniform plasma characteristics across all regions, resolving the contradiction between power efficiency and plasma stability
3Area of stationary object
If the laser beam diameter is large to cover the entire target, then the energy distribution becomes uneven, but if the beam diameter is small, the coverage area is limited
Solution Approach 1:
The target surface is divided into multiple smaller irradiation zones, each covered by a focused laser beam of optimal diameter. This segmentation allows each beam to maintain high energy concentration and uniform distribution within its zone, while the collective coverage of all zones achieves complete target coverage with overall uniform energy distribution
Solution Approach 2:
The single large-area irradiation problem is transformed into a multi-point irradiation approach. By distributing multiple optimized laser beams across the target surface in a spatial arrangement, the system achieves both complete area coverage and uniform energy distribution, effectively resolving the contradiction between coverage area and energy uniformity
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 the conversion efficiency of laser energy into EUV light, reduces the size of the light emission region, and generates EUV light with high brightness by ensuring uniform energy application across the target substance.
Implementation Method 1
a first laser device configured to generate a diffusion target that is convex toward a travel direction of first prepulse laser light having a wavelength of 1 μm by irradiating the target with the first prepulse laser light
Implementation Method 2
a second laser device configured to generate a low-density diffusion target by irradiating the diffusion target with second prepulse laser light having a wavelength of 1 μm
Implementation Method 3
a third laser device configured to generate extreme ultraviolet light by irradiating the low-density diffusion target with main pulse laser light having a wavelength of 1 μm
Data Source
AI summary
An extreme ultraviolet light generation apparatus includes a chamber, a target supply unit configured to supply a target into the chamber, a first laser device configured to generate a diffusion target that is convex toward a travel direction of first prepulse laser light having a wavelength of 1 μm by irradiating the target with the first prepulse laser light, a second laser device configured to generate a low-density diffusion target by irradiating the diffusion target with second prepulse laser light having a wavelength of 1 μm, and a third laser device configured to generate extreme ultraviolet light by irradiating the low-density diffusion target with main pulse laser light having a wavelength of 1 μm.