Multi-Amplifier EUV Laser Source with Pulse Shaping
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Solution Overview
Problem
Current laser systems for producing extreme ultraviolet (EUV) light, such as those used in photolithography, face challenges in optimizing laser output characteristics like pulse duration, energy, repetition rate, and conversion efficiency, while also being cost-effective and reliable.
Innovation Solution
A laser light source system comprising multiple amplifiers with specific gain media characteristics and a temporal pulse stretcher to produce EUV light, where each amplifier has distinct saturation energy and small signal gain parameters, and the stretcher modifies the pulse shape to include a pre-pulse and main pulse for efficient EUV emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single amplifier is used to amplify the laser beam, then the device complexity is reduced, but the laser output energy and conversion efficiency cannot be optimized
Solution Approach 1:
The laser amplification system is divided into multiple amplifiers (first amplifier, second amplifier, third amplifier) with different gain medium characteristics. Each amplifier contributes differently to the overall amplification process, allowing optimization of laser output energy at different stages while managing device complexity through modular design.
Solution Approach 2:
The patent employs amplifiers with varying saturation energy and small signal gain parameters. By changing these parameters across different amplifiers, the system optimizes laser output energy and conversion efficiency without requiring a single overly complex amplifier design.
2Productivity
If the laser pulse duration is shortened to increase repetition rate, then productivity is improved, but the pulse energy and EUV conversion efficiency deteriorate
Solution Approach 1:
The system uses pulsed laser operation with optimized pulse characteristics. By carefully controlling the periodic pulse delivery with specific durations and energies through the multi-amplifier system, the patent achieves both high repetition rate and sufficient pulse energy for efficient EUV conversion.
Solution Approach 2:
The patent optimizes pulse duration and energy parameters independently through the multi-amplifier configuration. This allows the system to deliver short high-repetition-rate pulses while maintaining sufficient energy content for EUV generation, resolving the trade-off between productivity and power.
3Productivity
If higher laser power is used to increase EUV output, then conversion efficiency is improved, but material consumption and by-product generation increase
Solution Approach 1:
The multi-amplifier system with varying gain characteristics enables precise control of laser power delivery. This optimized power delivery achieves high EUV conversion efficiency while minimizing excess energy that would cause unnecessary material consumption and by-product formation.
Solution Approach 2:
The system uses optimized pulse durations that deliver the necessary energy quickly and efficiently. By 'rushing through' the interaction process with precisely timed pulses, the system maximizes EUV output while minimizing the time for unwanted side reactions and material consumption.
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 configuration enhances EUV intensity and conversion efficiency, reduces material consumption, and minimizes by-products, improving the overall performance and reliability of the EUV light source.
Implementation Method 1
a first amplifier amplifying the output beam to produce a first amplified beam, and a second amplifier amplifying the first amplified beam to produce a second amplified beam. For this aspect, the first amplifier may have a gain medium characterized by a saturation energy (Es, 1) and a small signal gain (go, 1)
Implementation Method 2
the stretcher modifies the pulse shape to include a pre-pulse and main pulse for efficient EUV emission
Implementation Method 3
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. In one such method, often termed laser produced plasma (LPP) the required plasma can be produced by irradiating a target material
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 laser light source is disclosed having a laser oscillator producing an output beam; a first amplifier amplifying the output beam to produce a first amplified beam, and a second amplifier amplifying the first amplified beam to produce a second amplified beam. For the source, the first amplifier may have a gain medium characterized by a saturation energy (Es, 1) and a small signal gain (go, 1); and the second amplifier may have a gain medium characterized by a saturation energy (Es, 2) and a small signal gain (go, 2), with (go, 1)>(go, 2) and (Es, 2)>(Es, 1). In another aspect, a laser oscillator of a laser light source may be a cavity dumped laser oscillator, e.g. a mode-locked laser oscillator, q-switched laser oscillator and may further comprising a temporal pulse stretcher.