Optical Wafer Temperature Measurement Using Interference Phase Analysis
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Solution Overview
Problem
Existing methods for measuring wafer temperature during semiconductor manufacturing processes are inadequate, particularly when the wafer temperature deviates from the temperature of the wafer stage, leading to instability in the processing conditions.
Innovation Solution
A measuring apparatus using optical interference to directly measure wafer temperature by emitting measurement light, capturing interference light, performing Fourier transform on the spectroscopic spectrum, extracting phase angles, and calculating temperature changes based on these angles, thereby providing accurate and direct wafer temperature measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If indirect temperature measurement methods are used, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent replaces indirect mechanical/thermal measurement methods with optical measurement. A light source emits light that passes through the wafer, and a photodetector detects the transmitted light intensity. The temperature is calculated based on the absorption coefficient that varies with temperature, eliminating the need for direct thermal contact or complex thermal modeling.
Solution Approach 2:
The patent introduces light as an intermediary medium to measure wafer temperature. Instead of directly measuring thermal properties, the system uses light absorption characteristics as an intermediate indicator that correlates with temperature, providing a non-contact measurement approach.
2Measurement precision
If direct optical measurement is implemented, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent exploits changes in the optical absorption parameter of the wafer material with temperature. The absorption coefficient at a specific wavelength varies predictably with temperature, allowing temperature determination through optical intensity measurement without requiring complex optical setups.
Solution Approach 2:
The optical measurement system serves multiple functions: it measures wafer temperature, monitors wafer properties, and can be integrated into existing semiconductor processing equipment. The same optical path can potentially measure different parameters by adjusting the wavelength or detection method.
3Reliability
If conventional temperature measurement methods are used, then device complexity is low, but reliability deteriorates when wafer temperature deviates from wafer stage temperature
Solution Approach 1:
The wafer itself serves as the measurement medium. The wafer's optical absorption properties directly indicate its own temperature, eliminating the need for separate temperature sensors or indirect inference from wafer stage temperature. The measurement is self-referential and directly tied to the actual wafer state.
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 precise and stable management of wafer temperature during processing, reducing variations and improving the consistency of semiconductor manufacturing processes.
Implementation Method 1
A method of measuring a wafer temperature using optical interference is known
Implementation Method 2
perform Fourier transform of the spectroscopic spectrum waveform
Data Source
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AI summary
A measuring apparatus according to one embodiment includes a light source, a spectrometer, and a calculator. The light source emits measurement light. The spectrometer measures a spectroscopic spectrum waveform of light. The calculator executes measurement processing. In the measurement processing, the calculator is configured to: perform Fourier transform of the spectroscopic spectrum waveform; extract a waveform; calculate a phase angle at an amplitude peak position of the extracted waveform; calculate a temperature or thickness change amount based on the change amount of the phase angle; and calculate a temperature by adding the temperature change amount to a reference temperature, or calculate a thickness of the measurement target object by adding the thickness change amount to a reference thickness.