Nanotopography Inspection Using Segmented Auto-Interferometry
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Solution Overview
Problem
Current nanotopography inspection methods for semiconductor wafers are slow and sensitive to surface movement, limiting production rates and making it impractical to incorporate them into manufacturing processes.
Innovation Solution
A device and method that rapidly acquire measurement data using localized gradient values to establish a current surface equation, minimizing deviation and enabling quick characterization of semiconductor wafer surfaces, allowing for systematic inspection without significantly impacting production rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If interferometric techniques are used for nanotopography measurement, then measurement precision is improved, but productivity deteriorates due to slow data acquisition
Solution Approach 1:
The patent divides the wafer surface into multiple discrete areas and processes each area independently through auto-interferometry. By segmenting the measurement into manageable zones with overlapping boundaries, the system can process data in parallel and reduce overall acquisition time while maintaining nanotopography precision for each local area.
Solution Approach 2:
The patent performs preliminary phase unwrapping and surface reconstruction calculations on each local area before combining results. By pre-processing the interferometric data in segmented zones and storing intermediate results, the system avoids redundant calculations and accelerates the overall measurement process while preserving measurement accuracy.
2Measurement precision
If interferometric techniques are used for nanotopography measurement, then measurement precision is improved, but the device becomes sensitive to surface movement and vibrations
Solution Approach 1:
By dividing the wafer surface into multiple small areas for measurement, the patent reduces the spatial baseline required for each interferometric measurement. This segmentation makes each local measurement less sensitive to vibrations and surface movements, as the measurement path length is shorter and the measurement time for each area is reduced.
Solution Approach 2:
The patent uses periodic scanning of the wafer surface with the measurement beam, acquiring interferometric data from multiple areas in a systematic sequence. This periodic measurement approach allows for shorter exposure times per area and enables synchronization with the wafer handling process, reducing sensitivity to vibrations.
3Productivity
If multiple inspection stations are added to manufacturing stations to maintain production rates, then productivity is maintained, but device complexity and investment costs increase
Solution Approach 1:
The patent creates a single inspection station that performs multiple functions: it measures nanotopography, detects defects, and characterizes wafer surface properties. By integrating these functions into one multi-functional device using auto-interferometry, the system maintains production rates without requiring multiple separate inspection stations, thereby reducing overall system complexity and investment costs.
4Productivity
If multiple inspection stations are added to manufacturing stations to maintain production rates, then productivity is maintained, but space occupation and investment costs increase
Solution Approach 1:
The patent integrates nanotopography measurement, defect detection, and surface characterization into a single multi-functional inspection station. This consolidation eliminates the need for multiple separate inspection stations, thereby reducing the total space required in the clean room environment while maintaining the same productivity level.
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 solution enables rapid nanotopographic measurement of semiconductor wafers, achieving production rates comparable to existing manufacturing capabilities, with high repeatability and the ability to systematically inspect wafers post-manufacturing.
Implementation Method 1
The light reflected from a reference surface is made to interfere with the light reflected from a surface undergoing inspection
Data Source
AI summary
A nanotopographic measuring device comprises an input arranged to receive sets of measurement data relating to a semiconductor wafer and memory organized into first and second working tables and a results table. A calculation function is capable of establishing a current surface equation from localized gradient values. The equation is established in such a way as to generally minimize a deviation amount between the gradient values calculated from the current surface equation and the localized gradient values. A reconstruction function calculates localized gradient values from a set of measurement data corresponding to an area of the wafer and completes the working tables with these values. It repeatedly calls the calculation function, each time with a part of the values of the first working table and the second working table corresponding to a portion of the area of the wafer to determine, each time, a current surface equation. It completes the results table with the localized height data corresponding to this area, in relation to the reference plane of the wafer, the localized height data being calculated from at least certain of the current surface equations.