Grating Curvature Control for Laser Bandwidth Stability
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Solution Overview
Problem
Existing high power, high repetition rate excimer and molecular fluorine gas discharge laser systems face challenges in actively controlling bandwidth due to thermal effects and wavefront changes, which affect the stability and precision required in integrated circuit manufacturing photolithography, particularly in maintaining constant wavefront pulse-to-pulse and compensating for wavefront changes in real time.
Innovation Solution
A method and apparatus that incorporate a static wavefront compensation mechanism and an active wavefront compensation mechanism, using a pneumatic drive mechanism to independently adjust the grating's curvature based on bandwidth feedback, allowing for real-time correction of wavefront and bandwidth transients without introducing heat into the laser system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a motor driven bandwidth control device is used to actively control grating shape for wavefront control, then wavefront control capability is improved, but thermal effects are introduced into the laser system causing undesirable wavefront transients
Solution Approach 1:
The patent replaces the motor driven mechanical system with a piezoelectric actuator system. The piezoelectric actuators convert electrical signals directly to mechanical displacement, enabling grating shape control without the thermal effects associated with motor operation. This substitution eliminates the harmful thermal transients while maintaining the wavefront control capability.
Solution Approach 2:
The patent employs pneumatic actuators to apply forces to the grating for wavefront control. By using compressed gas instead of electric motors, the system achieves mechanical actuation without introducing significant heat into the laser system, thereby avoiding thermal effects that would cause wavefront transients.
2Reliability
If existing bandwidth control mechanisms are used, then bandwidth control is achieved, but thermal transients and vibration affect component lifetime and system stability
Solution Approach 1:
The patent replaces traditional motor driven bandwidth control mechanisms with piezoelectric actuators. These actuators provide precise control with minimal thermal output and vibration, thereby improving system stability and reliability while extending component lifetime by minimizing thermal transients and mechanical stress.
3Productivity
If high power, high repetition rate laser operation is maintained, then productivity is improved, but wavefront changes and bandwidth instability occur pulse to pulse
Solution Approach 1:
The patent implements feedback control systems that monitor laser output characteristics pulse to pulse and adjust the piezoelectric actuators accordingly. This real-time feedback enables the system to maintain stable bandwidth and wavefront characteristics even during high power, high repetition rate operation, ensuring consistent performance across hundreds of pulses.
Solution Approach 2:
The patent employs dynamically adjustable piezoelectric actuators that can respond to pulse-to-pulse variations in laser operation. The system adapts the grating shape in real-time for each pulse, maintaining optimal bandwidth control and wavefront quality throughout the pulse sequence, thereby enabling high productivity without sacrificing stability.
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 solution enables precise control of wavefront and bandwidth, improving the stability and accuracy of laser output, reducing thermal transients, and extending the lifetime of laser components by minimizing vibration and power dissipation, while maintaining optimal performance over a large number of pulses.
Implementation Method 1
The active wavefront compensation mechanism may comprise a piezoelectric actuator
Implementation Method 2
The active wavefront compensation mechanism may comprise a pneumatic actuator
Implementation Method 3
The nominal center wavelength and bandwidth selection optic comprises a grating
Data Source
AI summary
A method and apparatus is disclosed for operating a laser output light beam pulse line narrowing mechanism that may comprise a nominal center wavelength and bandwidth selection optic; a static wavefront compensation mechanism shaping the curvature of the selection optic; an active wavefront compensation mechanism shaping the curvature of the selection optic and operating independently of the static wavefront compensation mechanism. The method and apparatus may comprise the nominal center wavelength and bandwidth selection optic comprises a grating; the static wavefront compensation mechanism applies a pre-selected bending moment to the grating; the active wavefront compensation mechanism applies a separate selected bending moment to the grating responsive to the control of a bending moment controller based on bandwidth feedback from a bandwidth monitor monitoring the bandwidth of the laser output light beam pulses. The active wavefront compensation mechanism may comprise a pneumatic drive mechanism.