Photodiode Current Calibration Across ADC Dynamic Range
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Solution Overview
Problem
Contactless temperature measurement systems in semiconductor manufacturing, such as pyrometers and emissometers, face challenges due to the limited sensitivity of analog to digital converters (ADCs) across their entire dynamic range, leading to inaccuracies in temperature readings.
Innovation Solution
The integration of a calibration module within the pyrometer or emissometer that uses a calibrated current source to determine transfer functions for different modes, allowing for improved sensitivity by segmenting the dynamic range and applying specific coefficients to calculate accurate electrical currents, including adjustments for dark current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single ADC is used to cover the entire dynamic range of photocurrent, then the device complexity is reduced, but the measurement precision deteriorates due to limited sensitivity across the full range
Solution Approach 1:
The dynamic range of the ADC is divided into multiple segments or modes (first mode and second mode). Each mode covers a specific range of the dynamic range with optimized sensitivity. The system selects the appropriate mode based on the signal level, thereby maintaining high measurement precision across the entire range while using a single ADC.
2Adaptability or versatility
If the ADC operates across the entire dynamic range, then the adaptability is improved, but the measurement precision deteriorates in specific regions due to uniform sensitivity limitations
Solution Approach 1:
The system dynamically switches between different ADC modes based on the signal level. The first mode is used for lower signal levels where higher sensitivity is needed, while the second mode is used for higher signal levels. This dynamic adaptation allows the system to maintain optimal sensitivity across the entire dynamic range.
3Measurement precision
If multiple ADCs are used to improve sensitivity across different ranges, then the measurement precision is improved, but the device complexity increases
Solution Approach 1:
A single ADC is designed to perform multiple functions by operating in different modes. The ADC can be configured to handle both low-level and high-level signals through mode switching, eliminating the need for multiple dedicated ADCs while maintaining high measurement precision across the entire dynamic range.
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 approach enhances the accuracy and sensitivity of temperature measurements across the entire dynamic range of the ADC, reducing noise and improving process uniformity in semiconductor processing.
Implementation Method 1
the temperature measurement tools include photodiodes that receive an optical signal from the surface of the substrate being measured. For example, an infrared signal may be received by the photodiodes.
Data Source
AI summary
Embodiments disclosed herein include a method of calibrating a tool for converting photonic signals to electrical signals. In an embodiment, the method comprises connecting a calibration module to a calibrated current source, finding a transfer function for a plurality of modes with the calibration module, and storing the transfer functions in a lookup table.