SPM-Calibrated WLI for Semiconductor Chip Topography
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Solution Overview
Problem
Existing semiconductor chip surface topography measurement techniques, such as atomic force microscopy (AFM) and electron microscopy (SEM/TEM), suffer from low throughput, long cycle times, and inaccurate measurements due to the mismatch between measurement scales, while conventional white light interferometry (WLI) lacks the precision required for advanced semiconductor manufacturing.
Innovation Solution
A system combining optical measurements with machine learning models classifies interference and spectrum signals to accurately determine surface topography, using extended light sources like Xe lamps to enhance signal-to-noise ratio and reduce fringe widths, and integrates scanning probe microscopy (SPM) for calibration, enabling high-throughput, precise measurements without damaging the sample.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional white light interferometry (WLI) is used for surface topography measurement, then measurement speed is improved, but measurement precision deteriorates
Solution Approach 1:
The patent segments the measurement process into two distinct stages: (1) a calibration stage using scanning probe microscopy (SPM) to obtain precise height information at selected calibration points, and (2) a measurement stage using white light interferometry (WLI) to capture the entire surface. The SPM provides high-precision reference data that calibrates the WLI system, enabling the WLI to achieve both high speed and high precision by correcting its measurements based on the SPM calibration data.
2Measurement precision
If atomic force microscopy (AFM) or electron microscopy (SEM/TEM) is used for surface topography measurement, then measurement precision is improved, but productivity deteriorates
Solution Approach 1:
The patent divides the measurement task between two instruments with complementary strengths: SPM/SEM/TEM is used only for calibration at specific points where high precision is critical, while WLI handles the bulk surface area measurement at high speed. This segmentation allows the system to achieve overall high precision without sacrificing throughput, as the fast WLI measurements are corrected by the high-precision but slow SPM calibration data.
Solution Approach 2:
The patent performs preliminary calibration using SPM at selected points before conducting the main WLI measurement. This preliminary action establishes reference height values that are used to correct and enhance the precision of the subsequent fast WLI measurements, allowing the system to achieve high precision without requiring the entire measurement to be performed at slow SPM speeds.
3Reliability
If extended light sources like Xe lamps are used in interferometry, then signal-to-noise ratio is improved, but device complexity increases
Solution Approach 1:
The patent changes the spectral parameters of the light source by using extended sources like Xenon lamps that emit across a broader wavelength range. This parameter change increases the signal-to-noise ratio in the interferometric measurements by providing more spectral information. The system manages the increased complexity through automated calibration and classification algorithms that process the enhanced spectral data.
Solution Approach 2:
The patent introduces classification algorithms as an intermediary between the optical measurement system and the final topography results. These algorithms automatically classify interference patterns and correct measurements, serving as a mediator that handles the complexity of processing data from extended light sources while improving measurement reliability through automated error correction.
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 efficient, high-throughput, and accurate surface topography measurements suitable for semiconductor chip mass production, maintaining precision and reducing the need for opaque film deposition and wafer consumption.
Implementation Method 1
A plurality of interference signals and a plurality of spectrum signals are received by at least one processor. Each of the interference signals and spectrum signals corresponds to a respective one of a plurality of positions on a surface of the semiconductor chip.
Implementation Method 2
The spectrometer is configured to provide a plurality of spectrum signals each corresponding to a respective one of the plurality of positions on the surface of the semiconductor chip.
Implementation Method 3
The SPM or the electron microscope is configured to provide a plurality of calibration signals.
Data Source
AI summary
Systems and methods for measuring a surface topography of a semiconductor chip are disclosed. A disclosed system comprises a light source configured to provide low coherent light to a first beam splitter, a scanner configured to use the low coherent light reflected from the first beam splitter to scan positions on a surface of a semiconductor chip, a second beam splitter configured to receive reflected signals from the positions on the surface of the semiconductor chip, a detector configured to detect interference signals from a first output of the second beam splitter, wherein each of the interference signals corresponds to a respective one of the positions, and a spectrometer configured to detect spectrum signals from a second output of the second beam splitter, wherein each of the spectrum signals corresponds to the respective one of the positions.