Polarization Control of Pulsed Light Beams in Photolithography
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Solution Overview
Problem
In photolithography, the polarization of pulsed deep ultraviolet light beams can fluctuate due to temperature gradients, stress gradients, and optical distortions, leading to degradation in the performance of optical devices and the inability to maintain ideal polarization ratios, which affects the precision of microelectronic feature patterning on silicon wafers.
Innovation Solution
A photolithography system with an optical system, actuation apparatus, and control module that actively adjusts the polarization of pulsed light beams by modifying the physical properties of optical elements, such as angle and stress, based on real-time measurements to maintain optimal polarization ratios, using components like partially-transmissive optical elements and variable optical phase retarding elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If passive optical elements are used in the beam path, then the system structure is simple, but the polarization ratio fluctuates due to temperature gradients and stress gradients
Solution Approach 1:
The patent introduces a dynamic polarization control system with adjustable optical elements (such as wave plates or polarizers) that can be actively modified during operation. The control module receives feedback about polarization state and dynamically adjusts the optical elements to compensate for temperature and stress-induced fluctuations, transforming a static system into a dynamic one that maintains stable polarization ratios despite environmental changes
Solution Approach 2:
The patent implements a feedback mechanism where the polarization state of the light beam is monitored and fed back to the control module. The control module then sends control signals to adjust the physical properties of optical elements in the beam path, creating a closed-loop system that automatically corrects polarization drift caused by temperature gradients and stress gradients
2Reliability
If active polarization control is implemented, then the polarization ratio stability is improved, but the device complexity increases
Solution Approach 1:
The patent employs optical elements that serve multiple functions: they act as both beam path components and polarization control elements. For example, a wave plate can be used for both beam shaping and polarization adjustment, reducing the need for separate dedicated control components and thereby limiting the increase in overall system complexity
3Use of energy by moving object
If optical elements with anti-reflective coatings are used, then the light transmission is optimized, but the polarization control capability is reduced
Solution Approach 1:
The patent applies different surface treatments to different faces of optical elements. One face may have an anti-reflective coating optimized for maximum light transmission at specific wavelengths, while the other face has a polarization-dependent reflective coating that enables polarization control. This local differentiation allows each surface to optimize its specific function without compromising the overall system performance
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 ensures precise control of polarization ratios, reducing degradation and maintaining high performance of optical devices, thereby enhancing the precision and consistency of microelectronic feature patterning on silicon wafers.
Implementation Method 1
The actuation apparatus is configured to adjust a physical property of the optical element based on a control signal to thereby adjust a polarization of the pulsed light beam
Data Source
AI summary
A photolithography system includes an optical system, an actuation apparatus, and a control module. The optical system includes an optical source that produces a pulsed light beam traveling along a beam path; a plurality of optical components positioned between the optical source and a photolithography exposure apparatus, at least some of the plurality of optical components configured to receive the pulsed light beam and direct the pulsed light beam to the photolithography exposure apparatus; and an optical element positioned to interact with the pulsed light beam. The actuation apparatus is coupled to the optical element. The actuation apparatus is configured to adjust a physical property of the optical element based on a control signal from the control module to thereby adjust a polarization of the pulsed light beam.