EUV LPP Source Dose Control via Pulse Modulation and Skipping
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Solution Overview
Problem
Current EUV light source technologies face challenges in accurately controlling the dose of EUV radiation applied to semiconductor wafers due to variations in laser pulse energy, leading to inconsistent and non-uniform energy distribution, which results in inefficient use of energy and plasma instability.
Innovation Solution
A hybrid control method combining pulse modulation and pulse control mode, where a controller adjusts the energy of each laser pulse to achieve a desired average EUV energy per pulse, allowing for precise modulation within a range and skipping of pulses if the desired energy is outside the actuator's range, thereby optimizing EUV energy delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pulse control mode is used to control EUV dose by skipping pulses, then dose accuracy is improved, but plasma stability deteriorates due to irregular pulse gaps
Solution Approach 1:
The system dynamically adjusts the energy of each laser pulse in real-time based on feedback from EUV energy measurements, rather than using fixed energy pulses with skipping. This dynamic adjustment maintains regular pulse timing while achieving dose control, preserving plasma stability.
Solution Approach 2:
The invention changes the laser pulse energy parameter continuously within a range rather than using discrete on/off pulse skipping. By modulating pulse energy dynamically, the system achieves fine-grained dose control while maintaining consistent pulse timing that stabilizes the plasma.
2Stability of the object's composition
If pulse modulation is used to adjust laser pulse energy, then plasma stability is improved, but dose control precision deteriorates due to actuator range limitations
Solution Approach 1:
The system implements a feedback loop where each laser pulse's EUV energy is measured and used to determine the energy of the next pulse. This closed-loop control allows precise dose accumulation while maintaining plasma stability through regular pulsing.
Solution Approach 2:
The laser pulse energy is dynamically adjusted on a pulse-by-pulse basis based on real-time feedback, allowing the system to adapt to variations and achieve precise dose control while maintaining plasma stability.
3Power
If high laser pulse energy is used to compensate for energy variation, then EUV power is improved, but energy waste increases due to skipped pulses
Solution Approach 1:
Instead of skipping pulses to control dose, the system changes the energy parameter of each pulse dynamically. This allows full utilization of each pulse's energy contribution while maintaining precise dose control, eliminating the energy waste associated with skipped pulses.
Solution Approach 2:
The system maintains continuous useful action by ensuring every laser pulse contributes to EUV generation with optimized energy. By avoiding pulse skipping and instead modulating pulse energy, the system eliminates gaps in useful energy delivery and reduces energy waste.
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 precise control of the EUV dose, reducing energy waste, stabilizing the plasma, and achieving a more uniform energy distribution over time, allowing for a smaller dose margin and improved EUV power efficiency.
Implementation Method 1
laser produced plasma (LPP) EUV light source... converting a material into a plasma state... by irradiating a target material... with a laser pulse
Implementation Method 2
the droplet is vaporized and the reflective collector causes the resulting EUV light output to be maximized
Implementation Method 3
the reflective collector causes the resulting EUV light output to be maximized
Implementation Method 4
the irradiation site is at one focal point of a reflective collector... EUV light output to be maximized at another focal point
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 that combines pulse control mode and pulse modulation. The EUV energy created by each pulse is measured and total EUV energy created by the fired pulses determined, 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. If the desired pulse energy for the next droplet is within the range of one or more pulse modulation actuators, the pulse is modulated; otherwise, the pulse is fired to miss the droplet. This provides greater control of the accumulated dose as well as uniformity of the EUV energy over time, greater ability to compensate for pulses that generate EUV energy that is higher or lower than nominal expected values, and ability to provide an average EUV energy per pulse that is less than the nominal minimum EUV energy per pulse of the system.