Dynamic Laser Timing for EUV Droplet Positioning
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Solution Overview
Problem
Current EUV radiation sources for lithographic apparatuses face challenges in achieving optimal efficiency due to the interference of ion shock waves from vaporized fuel droplets, which affect the timing and shape of subsequent droplets, leading to position errors and reduced EUV generation efficiency.
Innovation Solution
A method and system where a stream of fuel droplets is supplied to a target area, with a laser emitting pulses timed based on the effects of vaporization of preceding droplets, including a pre-pulse to condition the droplets, optimizing the timing to account for the delay and shape oscillations caused by ion shock waves, ensuring precise alignment and energy emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser pulses are emitted at fixed intervals to vaporize fuel droplets, then the laser system operation is simple, but the vaporization of one droplet affects subsequent droplets causing position errors and reduced efficiency
Solution Approach 1:
The laser pulse timing is made dynamic rather than fixed. The system adjusts the interval between laser pulses based on real-time detection of droplet position and the effects of previous vaporizations on subsequent droplets. This dynamic adjustment compensates for position errors and maintains optimal droplet-laser interaction despite the disruptive effects of ion shock waves.
Solution Approach 2:
The system implements a feedback mechanism where the position of each fuel droplet is detected, and this information is used to adjust the timing of subsequent laser pulses. The feedback loop accounts for the cumulative effects of vaporization on droplet stream dynamics, allowing the system to maintain precision by continuously adapting to changing conditions.
2Reliability
If the timing of laser pulses is adjusted to account for droplet oscillations, then droplet shape optimization is improved, but the control system complexity increases
Solution Approach 1:
The system performs preliminary detection and calculation of optimal laser timing before each vaporization event. By detecting droplet position and characteristics in advance and pre-calculating the optimal pulse timing based on predicted droplet oscillations and previous vaporization effects, the system achieves reliable EUV generation without requiring complex real-time control during the actual vaporization process.
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 EUV radiation generation efficiency by minimizing position errors and optimizing droplet shape, leading to improved lithographic performance and reduced power consumption by synchronizing laser pulses with droplet oscillations and arrival times.
Implementation Method 1
configuring a laser to emit pulses of laser radiation directed at said target area timed to strike and vaporize a fuel droplet to generate EUV radiation
Implementation Method 2
EUV radiation may be produced using a plasma. A radiation system for producing EUV radiation may include a laser for exciting a fuel to provide the plasma
Implementation Method 3
the interference of ion shock waves from vaporized fuel droplets, which affect the timing and shape of subsequent droplets
Data Source
AI summary
A radiation source for generating EUV radiation includes a laser configured to fire laser pulses at a target area to which is supplied a stream of fuel droplets, which may be tin droplets that emit EUV radiation when excited by the laser beam. The EUV radiation is collected by a collector. The tin droplets may be pre-conditioned by a laser pre-pulse before the main laser pulse to change the shape of the droplets so that the droplets are in an optimum condition for receiving the main laser pulse. Embodiments of the invention take into account the effect of the vaporization of one fuel droplet on succeeding droplets and allow the timing of the main and/or pre-pulse to be adjusted to take into account any delay in arrival of the subsequent droplet or oscillations in the shape of the subsequent droplet which may be caused by vaporization of the preceding droplet.