EUV Light Source Debris Control via Ionized Tin Supply
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Solution Overview
Problem
Existing extreme ultraviolet light source devices face challenges in efficiently generating high-output EUV radiation due to debris damage to the EUV collector mirror, which reduces the operation rate and requires frequent mirror replacements, as most debris is electrically neutral and difficult to control.
Innovation Solution
An extreme ultraviolet light source device that ionizes the target material outside the plasma generation chamber and supplies the ionized material at high speed, using a combination of laser beams and magnetic fields to control and converge the ionized target material, preventing debris from reaching the collector mirror.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a conventional LPP type light source uses solid or liquid tin as a target material, then the target density is high (4×10^22/cm³), but the EUV radiation emission efficiency is low because the density is much higher than the optimal density (10^17 to 10^18/cm³)
Solution Approach 1:
The patent divides the laser irradiation process into two separate stages: a heating pulse that diffuses the tin target to reduce its density, followed by a main pulse that generates EUV radiation. This segmentation allows the target density to be dynamically adjusted from an initially high state to an optimal state for EUV emission, resolving the contradiction between maintaining high target quantity and achieving high emission efficiency.
Solution Approach 2:
The heating pulse is applied as a preliminary action before the main EUV-generating pulse. This preliminary heating action diffuses the tin atoms, reducing the target density from 4×10^22/cm³ to the optimal range of 10^17 to 10^18/cm³, thereby preparing the target for efficient EUV radiation emission in the subsequent main pulse.
2Productivity
If laser beam is irradiated on tin target to generate plasma, then EUV radiation is emitted, but debris is generated and damages the EUV collector mirror, reducing operation rate
Solution Approach 1:
The patent extracts and removes debris from the system by introducing a gas flow that carries the debris away from the EUV collector mirror path. This separation removes the harmful debris component while preserving the useful EUV radiation, thereby protecting the mirror and maintaining high operation rates.
Solution Approach 2:
The patent converts the harmful debris byproducts of plasma generation into a beneficial controlled flow. By using gas flow to carry the debris in a predetermined direction away from critical components, the harmful debris generation is transformed into a manageable process that does not compromise mirror lifespan or operation rate.
3Productivity
If heating pulsed laser beam is irradiated to diffuse tin target and reduce density, then EUV emission efficiency improves, but additional laser system and process complexity is required
Solution Approach 1:
The patent merges the heating function and the EUV generation function into a single laser system by using two pulses from the same laser source. This combining approach achieves the complex goal of density reduction and EUV generation without requiring entirely separate heating and generation systems, thereby limiting the increase in device complexity.
Solution Approach 2:
The patent employs periodic pulsed laser irradiation with two distinct phases: a first pulse for heating and diffusion, followed by a second pulse for EUV generation. This periodic action sequence achieves the desired target density modification and high-efficiency EUV emission using a single laser system operating in pulsed mode, avoiding the need for continuously complex multi-system arrangements.
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 effectively reduces debris damage to the EUV collector mirror, enhancing the device's operation rate and extending its lifespan by ensuring the ionized target material is efficiently converted into EUV radiation without unnecessary material loss.
Implementation Method 1
irradiating laser beam on a target material for turning into a plasma
Implementation Method 2
a heating pulsed laser beam is irradiated on a tin target to diffuse the tin target
Implementation Method 3
using a combination of laser beams and magnetic fields to control and converge the ionized target material
Implementation Method 4
a main pulsed laser beam is irradiated on the tin target to turn into plasma the target, thereby efficiently generating EUV radiation
Data Source
AI summary
An EUV (Extreme Ultra Violet) light source device ionizes a target material in an ionizer, and supplies the ionized target material to a point of generating a plasma. This reduces the generation of debris. The ionizer simultaneously irradiates laser beams of plural wavelengths corresponding to the excited level of tin on a target material to ionize the target material. The ionized target material is extracted from the ionizer with a high voltage applied from an ion beam extractor, and accelerated and supplied to a plasma generation chamber. When driver laser beam is irradiated on the ionized target material, a plasma is generated, thereby emitting EUV radiation.