EUV LPP Source Dose Control via Variable Laser Pulse Width
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Solution Overview
Problem
Current LPP EUV light sources face challenges in accurately and uniformly controlling the dose of EUV radiation applied to semiconductor wafers due to variations in laser pulse energy, leading to inefficiencies and instability in plasma temperature, which results in wasted energy and reduced effective EUV power.
Innovation Solution
A method and apparatus that extend the duration of laser pulses to ensure uniform energy extraction from the source laser, using actuators like EOMs and RF modulators to adjust pulse width and energy, allowing for precise control of EUV dose by measuring and adjusting the energy of each pulse to maintain a consistent average energy per pulse.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If laser pulse energy is increased to improve EUV power output, then EUV energy generation is improved, but dose control precision deteriorates due to pulse-to-pulse energy variations
Solution Approach 1:
The system dynamically adjusts the duration of each laser pulse based on real-time feedback from EUV energy measurements. The controller modifies pulse width parameter to compensate for pulse-to-pulse energy variations, ensuring consistent EUV dose delivery while maintaining high power output through optimized energy extraction.
Solution Approach 2:
The system implements a feedback control mechanism where EUV energy from each pulse is measured and used to determine the duration of the next pulse. This closed-loop control ensures that despite variations in laser pulse energy, the accumulated EUV dose remains precise and consistent across multiple pulses.
2Use of energy by moving object
If pulse duration is extended to extract more energy from the laser, then EUV energy extraction is improved, but plasma temperature stability deteriorates
Solution Approach 1:
The system uses dynamic pulse duration adjustment to optimize energy extraction while maintaining plasma stability. By adapting pulse width based on real-time EUV energy measurements, the system extracts maximum energy from each pulse without causing plasma temperature fluctuations that would occur with fixed long pulse durations.
Solution Approach 2:
The system changes the pulse duration parameter dynamically based on measured EUV energy output. This parameter adjustment allows the system to extract optimal energy from the laser while preventing plasma temperature instability that would result from consistently extended pulse durations.
3Manufacturing precision
If pulse modulation is used to control EUV dose, then dose precision is improved, but device complexity increases due to additional actuators and control mechanisms
Solution Approach 1:
The system implements dynamic pulse duration control using existing laser system actuators (EOMs, RF modulators) rather than adding complex new hardware. This approach achieves precise EUV dose control by dynamically adjusting pulse width based on feedback, utilizing already-present control mechanisms in the laser system.
Solution Approach 2:
The system uses the laser system's own existing actuators and control infrastructure to implement pulse modulation for dose precision. By leveraging already-available EOMs and RF modulators in the laser path, the system achieves precise EUV dose control without requiring additional external control devices or complex added hardware.
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 enables more consistent and efficient extraction of EUV energy, reducing waste and plasma instability, allowing for a broader range of dose targets with simpler implementation, and preventing self-lasing and debris issues, thereby enhancing the overall EUV power and uniformity.
Implementation Method 1
When a laser pulse hits a droplet at the irradiation site, the droplet is vaporized and the reflective collector causes the resulting EUV light output to be maximized
Implementation Method 2
A pulse width of extended duration is produced, for example, by an EOM
Implementation Method 3
MOPA systems, in which a master oscillator and power amplifier form a source laser
Data Source
AI summary
A method and apparatus for control of a dose of extreme ultraviolet (EUV) radiation generated by a laser produced plasma (LPP) EUV light source. Each laser pulse is modulated to be of a width that is determined to be sufficient to allow for extraction of a suitable uniform amount of energy in the laser source gain medium; in some embodiments the suitable uniform amount of energy to be extracted may be selected to avoid self-lasing. The EUV energy created by each pulse is measured and total EUV energy created by the fired pulses determined, and a desired energy for the next pulse is determined based upon whether the total EUV energy is greater or less than a desired average EUV energy times the number of pulses. The energy of the next pulse is modulated, either by modulating its magnitude or by modulating the amplification of the pulse by one or more amplifiers, but without decreasing the determined width of the laser pulse.