EUV Laser Pulse Timing for Dose Regulation
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Solution Overview
Problem
EUV lithography systems face challenges in achieving consistent EUV light output due to random energy variations from droplet irradiation, leading to non-uniform wafer processing and quality control issues.
Innovation Solution
A method and system that regulate EUV energy dose by adjusting the timing of laser beam pulses to irradiate droplets, using a controller to set dose servo values, sense EUV energy, accumulate energy, and mistime pulses to maintain a stable energy output, ensuring that only necessary pulses generate EUV energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If laser beam pulses are fired at every droplet to maximize EUV output, then EUV light energy is maximized, but energy output becomes variable and unreliable
Solution Approach 1:
The laser pulses are fired in periodic packets rather than continuously at every droplet. By controlling the timing and frequency of pulse packets, the system achieves consistent average EUV energy output while maintaining the ability to generate high energy when needed. The periodic structure allows for predictable energy delivery patterns.
Solution Approach 2:
The system monitors the actual EUV energy output and uses this feedback to adjust the laser pulse timing and frequency. By comparing measured energy output with target values, the control system can compensate for variations in droplet properties and laser performance, ensuring consistent energy delivery.
2Reliability
If laser pulses are mistimed to reduce EUV energy generation, then energy consistency is improved, but total EUV output decreases
Solution Approach 1:
The system dynamically adjusts the laser pulse timing and frequency based on real-time conditions. Rather than using a fixed mistimed schedule, the control system modifies pulse parameters on-the-fly to maintain target energy levels while ensuring consistency. This dynamic adaptation allows the system to optimize both energy output and reliability simultaneously.
Solution Approach 2:
The system changes multiple parameters including pulse timing, pulse frequency, and packet structure to achieve the desired balance between energy output and consistency. By adjusting these parameters in combination rather than relying on a single parameter change, the system can maintain high energy output while ensuring reliable delivery.
3Power
If all laser pulses are timed to hit droplets, then maximum EUV energy is produced, but downstream processing suffers from non-uniformity
Solution Approach 1:
By structuring laser pulses in periodic packets with controlled timing, the system delivers energy in a pattern that ensures uniform exposure across the wafer surface. The periodic structure prevents hotspots and ensures even distribution of EUV energy, maintaining manufacturing precision while preserving total energy power.
Solution Approach 2:
The system uses feedback from energy sensors to adjust pulse timing and distribution, ensuring uniform energy delivery across the processing area. This feedback control prevents localized over-exposure while maintaining overall high energy output, thereby preserving both power and manufacturing precision.
4Reliability
If laser pulses are mistimed to skip droplet irradiation, then EUV energy consistency is maintained, but productivity decreases
Solution Approach 1:
The system uses periodic pulse packets optimized to maintain consistent energy delivery without excessive skipping of droplets. By carefully designing the packet structure and timing, the system achieves reliable dose control while minimizing the number of missed pulses, thereby preserving productivity.
Solution Approach 2:
The system adjusts multiple parameters including packet frequency, pulse density within packets, and timing offsets to optimize the balance between dose control reliability and processing throughput. By coordinating changes across multiple parameters rather than relying on single parameter adjustments, the system maintains both reliability and productivity.
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 maintains EUV energy output at a consistent level, reducing variability and improving downstream processing quality by fine-tuning dose targets based on accumulated errors, thereby enhancing the reliability of EUV light generation.
Implementation Method 1
converting a material into a plasma state that has one or more elements (e.g., xenon, lithium, tin, indium, antimony, tellurium, aluminum, etc.) with one or more emission line(s) 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, such as a droplet, stream or cluster of material having the desired line-emitting element, with a laser beam at an irradiation site.
Implementation Method 2
irradiating a target material, such as a droplet, stream or cluster of material having the desired line-emitting element, with a laser beam at an irradiation site
Data Source
AI summary
Described herein are embodiments of a method to control energy dose output from a laser-produced plasma extreme ultraviolet light system by adjusting timing of fired laser beam pulses. During stroboscopic firing, pulses are timed to lase droplets until a dose target of EUV has been achieved. Once accumulated EUV reaches the dose target, pulses are timed so as to not lase droplets during the remainder of the packet, and thereby prevent additional EUV light generation during those portions of the packet. In a continuous burst mode, pulses are timed to irradiate droplets until accumulated burst error meets or exceeds a threshold burst error. If accumulated burst error meets or exceeds the threshold burst error, a next pulse is timed to not irradiate a next droplet. Thus, the embodiments described herein manipulate pulse timing to obtain a constant desired dose target that can more precisely match downstream dosing requirements.