Laser Bandwidth Control via Differential Firing and Prism Adjustment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current photolithography systems face challenges in maintaining stable spectral bandwidth, particularly E95 bandwidth, which affects the Optical Proximity Effect (OPE), requiring advanced active control techniques to meet tighter specifications and stabilize other key performance parameters.
Innovation Solution
A multi-stage gas discharge laser system with a variable magnification line-narrowing module and differential firing time control, combined with a beam dimension adjustment system using multiple prisms and a grating, allows for simultaneous control of bandwidth and center wavelength, enabling precise adjustment of E95 bandwidth through a combination of mechanical and electro-actuated mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If passive bandwidth stabilization techniques are used, then the system is simpler to operate, but the bandwidth stability and regulation precision deteriorate, failing to meet tighter OPE specifications
Solution Approach 1:
The patent implements active feedback control by continuously measuring the laser bandwidth using on-board metrology and adjusting control parameters (such as pump power, cavity length, or dispersive elements) to maintain the desired bandwidth. This closed-loop system responds to real-time bandwidth variations, ensuring stability and regulation precision required for tighter OPE specifications.
Solution Approach 2:
The patent replaces passive mechanical stabilization mechanisms with active electronic control systems. Instead of relying on fixed mechanical adjustments, the system uses electronically controlled elements (such as piezoelectric actuators, electro-optic modulators, or software-controlled parameter adjustment) to dynamically regulate bandwidth, achieving superior precision and flexibility.
2Manufacturing precision
If the spectral bandwidth is reduced to improve OPE control, then the Optical Proximity Effect correction effectiveness improves, but the laser system complexity increases due to additional bandwidth control mechanisms
Solution Approach 1:
The patent integrates multiple functions into unified control mechanisms. The same control elements (such as dispersive optics or feedback control loops) are used both to regulate bandwidth for OPE control and to maintain other laser performance parameters. This multi-functionality reduces overall system complexity while achieving precise OPE control through bandwidth management.
Solution Approach 2:
The patent achieves OPE control by dynamically adjusting laser parameters (such as spectral bandwidth, center wavelength, or pulse duration) through controlled modifications of operating conditions. By changing parameters like pump power, cavity geometry, or dispersive element positioning, the system optimizes bandwidth to improve OPE correction effectiveness without requiring fundamentally different system architecture.
3Measurement precision
If active control techniques are implemented to regulate E95 bandwidth, then bandwidth regulation precision improves, but the device complexity and control algorithm sophistication increase
Solution Approach 1:
The patent employs feedback control where the measured bandwidth (via on-board metrology) is compared to a target value, and the error signal drives adjustments to control parameters. This feedback loop continuously corrects deviations, achieving high regulation precision through systematic error reduction rather than overly complex algorithms.
Solution Approach 2:
The patent implements self-regulating control mechanisms where the system automatically adjusts its own parameters based on real-time bandwidth measurements. The control system monitors and corrects bandwidth deviations without external intervention, using inherent system properties and simple control logic to maintain precision, thereby avoiding the need for sophisticated external control algorithms.
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 provides high-frequency disturbance rejection and large actuation range, effectively stabilizing E95 bandwidth within a narrow range, improving the stability and precision of the laser light source for photolithography, thereby enhancing the effectiveness of mask Optical Proximity Correction (OPC).
Implementation Method 1
a dispersive optical element, such as a grating, in the line narrowing module
Implementation Method 2
a beam expansion assembly including a first prism assembly and a second prism assembly
Data Source
AI summary
A method and apparatus may comprise a seed laser, along with an amplifier laser amplifying the output of the seed laser. A bandwidth metrology module may provide a bandwidth measurement and a bandwidth error signal may be provided using a bandwidth set point. A differential timing system responsive to the error signal can selectively adjust a differential firing time between the seed laser and amplifier laser. A beam dimension and center wavelength control system may adjust a beam dimension, within the cavity of the seed laser, to select bandwidth, and may adjust center wavelength at the same time, using a plurality of beam expansion prisms and at least one other prism or other optical element in the cavity to select center wavelength.