Confocal Drum Temperature Monitoring for Cryogenic EUV Sources
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Solution Overview
Problem
Existing methods for temperature measurement in extreme ultraviolet (EUV) light sources, such as infrared pyrometry and thermocouples, face challenges due to low emissivity of copper drums and poor coupling at cryogenic temperatures, leading to inaccurate temperature readings and inefficient inspection processes.
Innovation Solution
A confocal sensor assembly integrated with a rotatable drum coated with plasma-forming material, using a pulsed laser to emit broadband light, and a controller to monitor temperature via confocal optical signals, enabling accurate temperature measurement under cryogenic conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If infrared pyrometry is used for temperature measurement, then non-contact measurement is achieved, but measurement precision deteriorates due to low emissivity of copper drum
Solution Approach 1:
The patent introduces a high-emissivity coating layer on the drum surface as an intermediary between the infrared sensor and the copper drum. This coating layer has high emissivity in the infrared range, enabling accurate non-contact temperature measurement while solving the low emissivity problem of copper. The coating acts as a mediator that transforms the measurement interface without requiring direct contact with the drum.
2Measurement precision
If thermocouples are used for temperature measurement, then direct temperature sensing is achieved, but reliability deteriorates due to poor coupling with dynamically moving drum
Solution Approach 1:
The patent replaces the mechanical contact-based thermocouple system with a non-contact infrared measurement system. This substitution eliminates the coupling problems between thermocouples and the moving drum, as the infrared sensor measures temperature remotely without physical contact. The mechanical system (thermocouple contact) is replaced by an optical field-based system.
3Device complexity
If traditional temperature monitoring methods are used, then system structure is simple, but productivity deteriorates due to inaccurate temperature readings and extended downtime
Solution Approach 1:
The patent implements a feedback mechanism where the infrared sensor continuously monitors drum temperature, and this temperature information is fed back to the control system. The control system uses this feedback to adjust operating parameters and optimize the plasma generation process, enabling real-time process optimization and reducing downtime through accurate temperature-based control decisions.
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
Provides real-time, precise temperature determination of the drum, reducing downtime and improving operational efficiency by eliminating reliance on indirect temperature sensors, facilitating quicker system recovery and optimizing process conditions.
Implementation Method 1
a confocal sensor assembly including a sensor head and a light source for measuring a surface of the rotating drum
Implementation Method 2
a laser source configured to direct pulsed illumination to a material-coated portion of the rotatable drum for exciting the plasma-forming target material
Implementation Method 3
exciting the plasma-forming target material and emitting broadband light
Data Source
AI summary
A broadband light source includes a confocal sensor assembly configured to measure a surface of a rotatable drum coated with plasma-forming target material. The broadband light source includes a laser source configured to direct pulsed illumination to the rotatable drum for exciting the plasma-forming target material and emitting broadband light as the drum is rotated in an angular direction and translated in an axial direction. The broadband light source includes a controller configured to direct the confocal sensor assembly to transmit a confocal optical signal to the rotatable drum, record a calibration measurement of a distance from the confocal sensor assembly to the rotatable drum, direct a cryogenic cooling sub-system to cryogenically cool the rotatable drum, record one or more distance measurements from a sensor head to the rotatable drum, convert the distance measurements to temperature values, and determine whether a target process condition temperature is achieved.