Optical Metrology Systematic Error Correction
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Solution Overview
Problem
Optical metrology tools face challenges in semiconductor manufacturing due to systematic errors, leading to the need for tool-specific libraries and frequent regeneration, which is time-consuming and disrupts in-situ process control in expensive semiconductor manufacturing environments.
Innovation Solution
A method using a common set of library spectra across multiple metrology tools, where a reference sample with known properties is used to derive hardware errors, allowing for correction of measurements and enabling the use of a single library across different tools, thereby reducing the need for tool-specific libraries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If tool-specific libraries are generated for each metrology tool to account for systematic errors, then measurement accuracy is improved, but the time required for library regeneration increases and tool availability decreases
Solution Approach 1:
The measurement system is segmented into two independent components: a tool-independent master library containing reference spectra, and a tool-specific correction factor that accounts for systematic errors. This segmentation allows the master library to be generated once and reused across multiple tools, while only lightweight correction factors need to be determined for each tool, dramatically reducing library regeneration time.
Solution Approach 2:
The patent transforms the problem from regenerating entire libraries for each tool to determining a small set of correction parameters (systematic error factors) for each tool. By changing the approach from full library regeneration to parameter-based correction, the time required is significantly reduced while maintaining measurement accuracy.
2Reliability
If frequent library regeneration is performed to maintain accuracy across different tools, then measurement reliability is improved, but productivity and tool availability deteriorate
Solution Approach 1:
The master library is designed to be universal and tool-independent, containing reference spectra that can be used across multiple metrology tools. This universality allows a single library to serve multiple tools simultaneously, eliminating the need for each tool to have its own separate library and enabling the library to be generated once for use by all tools.
Solution Approach 2:
Correction factors serve as intermediaries between the universal master library and individual metrology tools. These correction factors translate the tool-independent reference data into tool-specific accurate measurements without requiring full library regeneration, thus maintaining reliability while preserving productivity.
3Productivity
If a common library is used across multiple metrology tools, then productivity and tool availability are improved, but measurement precision deteriorates due to tool-specific systematic errors
Solution Approach 1:
While the master library maintains uniform, tool-independent quality, local quality is restored through tool-specific correction factors. Each correction factor is tailored to the specific systematic errors of its associated tool, ensuring that local measurement accuracy is maintained even though a common library is used across all tools.
4Measurement precision
If tool-specific libraries are generated for each metrology tool, then measurement accuracy is improved, but device complexity and the number of libraries required increase
Solution Approach 1:
The patent merges the library management approach by consolidating all tool-specific reference data into a single universal master library. This eliminates the need for multiple separate libraries and reduces system complexity, while tool-specific accuracy is maintained through correction factors rather than separate libraries.
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 allows for accurate identification of layer profiles and critical dimensions without the need for frequent library regeneration, enhancing the efficiency and reliability of optical metrology in semiconductor manufacturing by decoupling instrument errors and enabling real-time process control.
Implementation Method 1
Scatterometry is an optical measurement technology based on an analysis of one or more wavelengths of light scattered from a layer or array of layers and/or device structures
Implementation Method 2
Prediction of scatterometry spectra is provided by a numerical solution of governing Maxwell's equations
Data Source
AI summary
A method for correcting systematic errors in an optical measurement tool in which a first diffraction spectrum is measured from a standard substrate including a layer having a known refractive index and a known extinction coefficient by exposing the standard substrate to a spectrum of electromagnetic energy. A tool-perfect diffraction spectrum is calculated for the standard substrate. A hardware systematic error is calculated by comparing the measured diffraction spectrum to the calculated tool-perfect diffraction spectrum. A second diffraction spectrum from a workpiece is measured by exposing the workpiece to the spectrum of electromagnetic energy, and the measured second diffraction spectrum is corrected based on the calculated hardware systematic error to obtain a corrected diffraction spectrum.