Fiber Bragg Grating Temperature Sensing for Lithographic Optics
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Solution Overview
Problem
Conventional temperature sensors in lithographic apparatuses face challenges such as structural implementation difficulty, limited scalability, and electrical noise, leading to inaccurate temperature correction and increased error tolerances in thermally sensitive components like projection optics.
Innovation Solution
A temperature sensor system comprising a waveguide device with scattering features and a detector is used to measure temperature variations, allowing for precise temperature correction by correlating reflected spectra with temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional temperature sensors (e.g., thermistors) are used, then temperature measurement can be performed, but structural implementation difficulty and electrical noise increase
Solution Approach 1:
The patent replaces conventional electrical temperature sensors (thermistors) with an optical temperature sensing system. The optical sensor uses optical fibers and spectral analysis to measure temperature, eliminating electrical noise and complex electrical connections. The system analyzes temperature-induced spectral shifts in optical signals rather than relying on electrical resistance changes, thereby simplifying the structural implementation while maintaining measurement precision.
2Measurement precision
If conventional temperature sensors are used, then temperature measurement can be performed, but electrical noise increases leading to inaccurate temperature correction
Solution Approach 1:
The patent substitutes electrical sensing with optical sensing to eliminate electrical noise. The optical sensor measures temperature through spectral analysis of light interactions with the target object, completely avoiding electrical noise that plagues conventional thermistor-based systems. This substitution enables more accurate temperature correction by providing clean, noise-free temperature data.
3Measurement precision
If conventional temperature sensors are used, then temperature measurement can be performed, but scalability is limited
Solution Approach 1:
The patent creates a universal optical sensing platform that can be applied to various temperature measurement scenarios. The optical fiber-based system with spectral analysis capability can sense temperature at different locations and under different conditions by simply changing the optical path or target characteristics, without requiring different sensor types. This multi-functionality enables easy scalability across diverse applications.
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 system provides accurate temperature sensing and correction, reducing errors and improving the performance of thermally sensitive objects in lithographic apparatuses.
Implementation Method 1
The waveguide device comprises an input end, a downstream end opposite the input end, and first and second scattering features
Implementation Method 2
The first scattering feature is configured to reflect a first spectrum based on a temperature at the first scattering feature
Implementation Method 3
the first scattering feature is configured to reflect a first spectrum based on a temperature at the first scattering feature
Implementation Method 4
The detector is disposed to receive radiation comprising the reflected first and second spectra from the input end and to generate a measurement signal based on the received radiation
Data Source
AI summary
A lithographic apparatus includes an illumination system, a projection system, a temperature-sensitive object, and a temperature sensor that includes a detector and waveguide device that is thermally coupled to the temperature-sensitive object and includes an input end, a downstream end, and first and second scattering features. The illumination system illuminates a pattern of a patterning device. The projection system projects an image of the pattern onto a substrate. Based on temperature, the first scattering feature reflects a first spectrum. Radiation not reflected by the first scattering feature is allowed downstream. Based on temperature, the second scattering feature reflects a second spectrum different from the first spectrum. Radiation not reflected by the second scattering feature is allowed downstream. The detector is disposed to receive radiation including the reflected first and second spectra from the input end and generates a measurement signal based on the received radiation.