EUV Light Generation Control for Thermal Alignment Drift
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Solution Overview
Problem
Existing EUV light generation systems face challenges in maintaining stable EUV energy output due to thermal deformation of optical elements, leading to deviations in the coaxial relationship between prepulse and main pulse laser beams, which affects the accuracy and stability of EUV energy generation.
Innovation Solution
The system incorporates an EUV light generation control unit that adjusts the position of the light concentrating unit using conversion efficiency (CE) and temporal variation of EUV energy (EUV energy 3σ) as indices, along with a first actuator to control the optical path of the main pulse laser light, ensuring stable EUV energy output by compensating for thermal deformations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thermal deformation of optical elements is present, then the coaxial relationship between prepulse and main pulse laser beams deviates, but EUV energy stability deteriorates
Solution Approach 1:
The system performs preliminary alignment of the prepulse and main pulse laser beams using the alignment mark on the target substrate. By establishing the correct coaxial relationship before thermal deformation occurs, the system can compensate for subsequent thermal effects and maintain EUV energy stability throughout operation.
Solution Approach 2:
The system uses the alignment mark as a feedback reference to continuously monitor and adjust the coaxial relationship between the two laser beams. This feedback mechanism allows the system to detect deviations caused by thermal deformation and correct them in real-time, maintaining both alignment accuracy and EUV energy stability.
2Reliability
If the optical path is adjusted to compensate for thermal deformation, then EUV energy stability improves, but the system complexity increases
Solution Approach 1:
The system uses the target substrate itself as the alignment reference through the alignment mark. This self-service approach eliminates the need for external alignment systems or complex optical path control mechanisms, as the target substrate provides its own reference for maintaining coaxial alignment between the laser beams.
Solution Approach 2:
The system changes the reference frame for alignment from external optical elements to the target substrate's alignment mark. This parameter change simplifies the control mechanism by using the target substrate's position and orientation as the primary reference, reducing the complexity of optical path adjustment while maintaining EUV energy stability.
3Manufacturing precision
If the alignment mark is used for position adjustment, then the coaxial relationship accuracy improves, but the measurement and detection difficulty increases
Solution Approach 1:
The system extracts the alignment function from complex external alignment systems and embeds it directly into the target substrate through the alignment mark. This extraction simplifies the detection process by using the target substrate's own features as the reference, eliminating the need for separate measurement and detection systems.
Solution Approach 2:
The alignment mark on the target substrate serves multiple functions: it provides the reference for coaxial alignment between laser beams, serves as a position reference for the target substrate itself, and enables the feedback mechanism for maintaining alignment accuracy. This multi-functionality reduces the need for separate alignment systems and simplifies the overall measurement and detection 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 stability and accuracy of EUV energy generation by maintaining consistent EUV energy levels and reducing unnecessary debris, even in the presence of thermal deformations, thereby improving the overall performance of the EUV light generation apparatus.
Implementation Method 1
a laser produced plasma (LPP) type apparatus using plasma generated by irradiating a target substance with laser light has been developed
Implementation Method 2
a main pulse laser configured to output main pulse laser light to be radiated to the target irradiated with the prepulse laser light
Data Source
AI summary
An EUV light generation apparatus includes a chamber; a prepulse laser outputting prepulse laser light; a main pulse laser outputting main pulse laser light; a combiner combining optical paths of the prepulse laser light and the main pulse laser light; a light concentrating unit concentrating, on the target, the prepulse laser light and the main pulse laser light having the optical paths combined; a stage changing a position of the light concentrating unit; a first actuator changing a travel direction of the main pulse laser light; an EUV light sensor detecting EUV energy; a laser energy sensor detecting pulse energy of the main pulse laser light; and an EUV light generation control unit controlling the stage so that temporal variation of the EUV energy decreases and controlling the first actuator so that a ratio of the EUV energy to the pulse energy increases.