EUV Light Source Pulse Timing for Dose Regulation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
EUV lithography systems face challenges in maintaining consistent EUV light output due to random fluctuations in energy generation from droplet irradiation, leading to variability in wafer processing quality and downstream application reliability.
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, thereby controlling the EUV dose within predetermined targets.
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 variability in EUV output increases due to random energy fluctuations from droplet irradiation
Solution Approach 1:
The system performs preliminary actions by accumulating EUV energy from irradiated droplets and comparing it against a target dose before determining whether to fire the next laser pulse. This advance preparation and comparison mechanism allows the system to proactively control output consistency rather than reactively adjusting after variability occurs.
Solution Approach 2:
The system implements feedback by sensing EUV energy generated from droplet irradiation, comparing the accumulated energy against a target dose, and using this information to determine whether to fire the next laser pulse. This closed-loop feedback mechanism directly addresses the variability problem by continuously monitoring and adjusting output based on actual measured energy levels.
2Productivity
If laser pulses are timed to irradiate every droplet, then productivity is maximized, but manufacturing precision deteriorates due to non-uniform wafer processing
Solution Approach 1:
The system performs preliminary accumulation of EUV energy from multiple droplets before determining whether to proceed with the next laser pulse. This advance accumulation and comparison against target dose ensures that the total energy delivered to the wafer remains uniform, directly addressing the manufacturing precision requirement while maintaining productivity.
Solution Approach 2:
The system uses feedback from EUV energy sensing to control the timing of laser pulses, ensuring that the accumulated energy meets the target dose before proceeding. This feedback mechanism guarantees uniform wafer processing by preventing over-exposure or under-exposure, thereby maintaining manufacturing precision at high productivity levels.
3Productivity
If continuous laser firing is used to maintain high EUV output, then productivity increases, but energy consumption and heat generation increase
Solution Approach 1:
The system implements periodic action by firing laser pulses only when the accumulated EUV energy from previous droplets is insufficient to meet the target dose. This periodic, conditional firing pattern maintains high EUV output productivity while reducing overall laser energy consumption compared to continuous firing, as the laser remains inactive when the energy target is already achieved.
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 ensures a consistent and stable EUV energy output, reducing variability and improving the reliability of downstream processes such as semiconductor lithography by maintaining the EUV dose within ±0.5% of the target, enhancing the quality control of wafer processing.
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
sensing by a sensor EUV energy generated by irradiation of the droplet
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.