Attenuation Optical System for Regenerative Ring Resonator Pulse Energy Control
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Solution Overview
Problem
High power deep ultraviolet light sources used in photolithography require precise control over pulse energy and bandwidth, but existing designs struggle to efficiently adjust these parameters without altering the operating voltage or modifying the gain medium, which can lead to instability and reduced performance.
Innovation Solution
A regenerative ring resonator with an attenuation optical system that includes a partially reflective surface with adjustable attenuation states, allowing for precise control of light beam energy by reflecting a portion of the flux, maintaining the operating voltage within acceptable limits and adjusting pulse energy without altering the gain medium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the operating voltage is altered to adjust pulse energy, then pulse energy can be controlled, but the stability and performance of the light source deteriorates
Solution Approach 1:
The invention separates the pulse energy control function from the voltage control system by introducing a separate attenuation optical system. This segmentation allows voltage to remain constant for stability while energy is adjusted independently through optical attenuation, resolving the contradiction between ease of operation and reliability.
Solution Approach 2:
An attenuation optical system acts as an intermediary between the light source and output, providing a mechanism to control pulse energy without directly affecting the electrical operating conditions. This mediator enables energy adjustment while preserving the stability of the gain medium and electrical system.
2Ease of operation
If the gain medium is modified to adjust pulse energy, then pulse energy can be controlled, but the complexity of the system increases
Solution Approach 1:
The invention extracts the energy control function from the gain medium itself and places it in a separate attenuation optical system. This extraction allows the gain medium to remain simple and stable while providing flexible energy control through an add-on optical component, resolving the contradiction between ease of operation and device complexity.
3Manufacturing precision
If the bandwidth is narrowed to improve resolution, then spectral bandwidth is reduced, but the pulse energy decreases
Solution Approach 1:
The invention changes the control parameter for energy from voltage or gain medium properties to optical attenuation. This parameter change allows independent optimization of bandwidth (for resolution) and energy (through attenuation settings) without the direct trade-off that previously existed, as attenuation does not affect spectral bandwidth.
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
Enables flexible adjustment of pulse energy and bandwidth in high power deep ultraviolet light sources, maintaining stability and performance by applying distinct attenuation factors to the light beam within the resonator, thereby optimizing output for photolithography applications.
Implementation Method 1
an attenuation optical system having a surface that is at least partly reflective to the light beam and is placed in the path of the light beam within the resonator
Implementation Method 2
an optical coupler that is partially reflective so that at least a portion of a light beam impinging on the optical coupler from the discharge chamber is reflected back through the discharge chamber and at least a portion of the light beam impinging on the optical coupler from the discharge chamber is transmitted through the optical coupler
Data Source
AI summary
An attenuation optical system is in a beam path of a light beam traveling through a regenerative ring resonator. The attenuation optical system includes an actuator configured to receive an electromagnetic signal; and a plate mounted to the actuator to be moveable between a plurality of positions, with each position placing an attenuation region in the beam path such that the beam profile is covered by the attenuation region and each attenuation region representing an attenuation factor applied to the light beam as determined by a geometry of the attenuation region. At least one attenuation region includes a plurality of evenly-spaced elongated openings between solid energy-reflecting surfaces and at least one attenuation region includes an open area that is larger than the beam profile of the light beam.