Wafer Thickness Metrology Using Synchronized Shutter Temporal Segmentation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing thickness measurement techniques for wafers are prone to errors due to mechanical vibrations on the production floor, particularly when using single detectors that measure signals from both probes simultaneously, leading to interference and reduced accuracy.
Innovation Solution
A metrology system utilizing multiple probes positioned on both sides of the wafer with a single detector, synchronized to measure spectra containing interference signals, which reduces the number of spectrometers and detectors needed, and employs a method to analyze these signals using differential Fourier transforms to accurately determine wafer thickness despite vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single detector is used to measure signals from both probes simultaneously, then the number of detectors is reduced, but measurement accuracy deteriorates due to interference and vibration-induced errors
Solution Approach 1:
The patent divides the measurement process into separate temporal segments using synchronized shutters. Each probe's signal is measured in distinct time intervals (first probe during time interval T1, second probe during time interval T2), preventing signal interference while using a single detector. This temporal segmentation resolves the contradiction by maintaining measurement accuracy without requiring multiple detectors.
Solution Approach 2:
The system employs periodic switching between measuring signals from the first and second probes using synchronized shutters. The shutters open and close in a periodic sequence, allowing the single detector to alternately capture signals from each probe. This periodic action enables accurate thickness measurement by preventing signal overlap while minimizing vibration-induced errors through rapid switching.
2Measurement precision
If multiple spectrometers and detectors are used to measure signals from both probes, then measurement accuracy is maintained, but device complexity increases
Solution Approach 1:
The patent merges the functions of multiple detectors into a single detector by using temporal separation with synchronized shutters. Instead of having separate detectors for each probe, the system combines signal detection into one detector that sequentially measures each probe's signal in distinct time intervals. This merging reduces device complexity while maintaining measurement accuracy through proper signal isolation.
Solution Approach 2:
The single detector is designed to serve multiple functions by measuring signals from both the first and second probes through temporal separation. The detector universally handles both measurement tasks by switching between them using synchronized shutters, eliminating the need for dedicated detectors for each probe and reducing overall system complexity.
3Productivity
If measurements are performed in a vibrating production floor environment, then wafer thickness can be measured in real-time, but measurement accuracy deteriorates due to mechanical vibrations
Solution Approach 1:
The system performs preliminary synchronization of the shutters with the wafer transport and processing machinery before measurements begin. The shutters are pre-configured to open and close at specific times that account for the wafer's position and the vibration cycle of the production floor equipment. This preliminary action allows real-time measurement while compensating for vibration effects through advance timing coordination.
Solution Approach 2:
The measurement system dynamically adapts to the vibrating production floor environment by using rapid shutter switching that can be adjusted in real-time. The synchronized shutters dynamically control signal capture windows to coincide with periods of minimal vibration, allowing continuous real-time measurement while maintaining accuracy through adaptive timing adjustments.
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 measurement accuracy by minimizing interference and vibration-induced errors, allowing for precise thickness determination of wafers in motion, thereby improving the reliability of wafer thickness control in backend semiconductor processing.
Implementation Method 1
performing measurements of spectra containing interference signals containing distance information using a plurality of probes positioned on both sides of the measured wafer
Data Source
AI summary
The invention describes a metrology system allowing for the reduction of the errors caused by vibration of the production floor and allowing for measurements of the thickness of wafers in motion. This is accomplished by performing simultaneous measurements of spectra containing interference signals containing distance information using a plurality of probes positioned on both sides of the measured wafer on the same detector at the same time or by means of plurality of synchronized detectors. System is also able to measure thickness of the individual optically accessible layers present in the sample.