MOPA EUV Laser Pre-Pulse Debris Reduction
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Solution Overview
Problem
Current laser-produced plasma (LPP) EUV light sources face challenges in minimizing plasma-generated debris and optimizing pre-pulse and main pulse interactions to enhance EUV light production efficiency and reduce source material consumption, while managing limitations in seed laser output energy and amplifier gain.
Innovation Solution
A Master Oscillator-Power Amplifier (MOPA) drive laser system with a pre-pulse seed laser and main pulse seed laser, both using CO2 gain media, are combined through an optical amplifier with distinct gain bands for the pre-pulse and main pulse wavelengths, allowing for efficient amplification and focusing of EUV light, minimizing debris generation, and optimizing energy conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single high-energy laser pulse is used to produce plasma, then EUV light generation is achieved, but plasma-generated debris increases and energy conversion efficiency decreases
Solution Approach 1:
The pre-pulse laser irradiates the target material before the main pulse to create a prepared plasma state, which improves subsequent EUV generation efficiency while reducing debris. The pre-pulse performs preliminary heating and material preparation, allowing the main pulse to interact with pre-conditioned material rather than cold solid, thereby reducing harmful debris generation.
Solution Approach 2:
The laser system is divided into separate pre-pulse and main pulse components with distinct functions. The pre-pulse seed laser and main pulse seed laser operate at different wavelengths and are amplified separately through optical amplifiers, allowing optimized interaction with the target material to maximize EUV production while minimizing debris.
2Device complexity
If pre-pulse and main pulse are combined in a single amplifier, then device complexity is reduced, but wavelength-specific gain optimization is lost
Solution Approach 1:
The amplification system is segmented into separate optical amplifiers for pre-pulse and main pulse wavelengths. Each amplifier is optimized for its specific wavelength range, allowing maximum gain and energy conversion efficiency for each pulse type without compromise from the other wavelength's requirements.
3Productivity
If larger target materials are used to increase interaction volume, then EUV light output increases, but source material consumption increases
Solution Approach 1:
The pre-pulse creates a prepared plasma state that enhances the interaction efficiency of the main pulse with smaller target materials. This preliminary preparation allows sufficient EUV generation from reduced target sizes, thereby decreasing source material consumption while maintaining or improving EUV output.
Solution Approach 2:
The system changes the physical state parameters of the target material through pre-pulse heating and ionization, transforming solid/liquid material into a pre-plasma state that is more efficient at converting main pulse energy into EUV radiation. This parameter change allows smaller target volumes to produce equivalent or superior EUV output.
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 MOPA system enhances EUV light production efficiency by optimizing pre-pulse and main pulse interactions, reducing debris, and allowing the use of smaller target materials, thereby improving the overall performance and operational efficiency of the EUV light source.
Implementation Method 1
an optical amplifier having a gain band including wavelengths λ1 and λ2, with λ1≠λ2
Implementation Method 2
a pre-pulse seed laser and main pulse seed laser, both using CO2 gain media
Implementation Method 3
laser-produced plasma (LPP) EUV light sources
Implementation Method 4
converting a material into a plasma state that has an element, e.g., xenon, lithium or tin, with an emission line in the EUV range
Data Source
AI summary
A device is described herein which may comprise an optical amplifier having a gain band including wavelengths λ1 and λ2, with λ1≠λ2; a pre-pulse seed laser having a tuning module for tuning a pre-pulse output to wavelength λ1; a main pulse seed laser generating a laser output having wavelength, λ2; and a beam combiner for directing the pre-pulse output and the main pulse output on a common path through the optical amplifier.