Laser Wavelength Control via Segmented Grating and Etalon Actuators
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Solution Overview
Problem
Semiconductor exposure apparatuses face challenges in resolving power due to chromatic aberration caused by wide spectrum line widths of KrF and ArF excimer laser apparatuses, leading to decreased performance in miniaturization and high integration of semiconductor integrated circuits.
Innovation Solution
A laser apparatus with a first and second optical element, actuators to change wavelength components, and encoders to measure actuator positions, controlled by a processor to adjust the wavelength components and intensity ratio, enabling precise control of pulse laser beams for improved resolving power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a gas laser apparatus (KrF or ArF excimer laser) is used for semiconductor exposure, then the wavelength can be shortened for miniaturization, but the spectrum line width becomes wide (350 pm to 400 pm) causing chromatic aberration and decreasing resolving power
Solution Approach 1:
The patent divides the wavelength control into two independent segments: a first optical element (grating) controlled by a first actuator for coarse wavelength adjustment, and a second optical element (etalon) controlled by a second actuator for fine wavelength adjustment. This segmentation allows the system to achieve both wide wavelength tuning range and high wavelength precision, thereby resolving the chromatic aberration issue while maintaining the short wavelength capability needed for miniaturization.
2Manufacturing precision
If a line narrowing module with a single line narrowing element (etalon or grating) is added to the laser resonator, then the spectrum line width can be narrowed, but the device complexity increases
Solution Approach 1:
Instead of using a single complex line narrowing element, the patent employs two simpler optical elements (a grating and an etalon) with independent actuators. Each element performs a specific function: the grating provides broad wavelength selection while the etalon provides precise wavelength refinement. This segmented approach narrows the spectrum line width effectively while keeping individual component complexity manageable.
Solution Approach 2:
The patent introduces an intermediary control system consisting of a processor that reads relations between actuator positions and wavelength components, and encoders that measure actuator positions. This intermediary control layer coordinates the two actuators to work together, enabling precise wavelength control without requiring a overly complex mechanical structure. The encoders provide feedback to the processor, which adjusts the actuators accordingly.
3Measurement precision
If multiple optical elements with independent actuators are used for wavelength control, then the wavelength components can be precisely adjusted, but the device complexity and control difficulty increase
Solution Approach 1:
The patent introduces an intermediary control system consisting of a processor that reads relations between actuator positions and wavelength components, and encoders that measure actuator positions. This intermediary control layer coordinates the two actuators to work together, enabling precise wavelength control without requiring an overly complex mechanical structure. The encoders provide feedback to the processor, which adjusts the actuators accordingly based on the stored wavelength-position relations.
Solution Approach 2:
The patent implements feedback control by using encoders to measure the actual positions of the first and second actuators, and feeding this information back to the processor. The processor compares the measured positions with the target positions (derived from the stored relations) and makes real-time adjustments to achieve the desired wavelength components. This feedback mechanism simplifies the control of multiple optical elements by automatically compensating for positioning errors.
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
The solution effectively narrows the spectrum line width, reducing chromatic aberration and enhancing the resolving power of semiconductor exposure apparatuses, thereby supporting the miniaturization and high integration of semiconductor integrated circuits.
Implementation Method 1
a first actuator configured to change a first wavelength component included in a pulse laser beam by changing a posture of the first optical element
Implementation Method 2
a second actuator configured to change a second wavelength component included in the pulse laser beam by changing a posture of the second optical element
Data Source
AI summary
A laser apparatus includes a first optical element, a second optical element, a first actuator configured to change a first wavelength component included in a pulse laser beam by changing a posture of the first optical element, a second actuator configured to change a second wavelength component included in the pulse laser beam by changing a posture of the second optical element, a first encoder configured to measure a position of the first actuator, a second encoder configured to measure a position of the second actuator, and a processor. The processor reads a first relation and a second relation and performs control of the first actuator based on the first relation and the position of the first actuator measured by the first encoder and control of the second actuator based on the second relation and the position of the second actuator measured by the second encoder.