Optical Metrology Error Tracking with Standard Wafer Feedback
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Solution Overview
Problem
Existing optical metrology tools lack universal criteria for tool maintenance, leading to inefficient and time-consuming calibration processes that do not guarantee the correctness of calibration mechanisms, affecting measurement accuracy and stability.
Innovation Solution
An instrumental error tracking and identification system that uses a real-time monitoring method to collect and analyze spectroscopic ellipsometry and reflectometry spectrums, evaluating performance indices like fitting residue and area under curve to continuously track and identify errors in optical metrology tools, providing universal criteria for maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If internal calibration control unit is used to calibrate the commercial spectrometer, then calibration can be performed, but the process is time consuming and cannot prove the correctness of calibration mechanism
Solution Approach 1:
The system uses a standard wafer with known properties to enable the optical metrology tool to self-diagnose and self-calibrate. The control unit automatically compares measured spectrums against reference data and identifies instrumental errors without requiring external intervention or manual calibration procedures.
Solution Approach 2:
The system implements continuous feedback by measuring the standard wafer, comparing results with reference data, identifying deviations, and triggering recalibration when instrumental errors are detected. This closed-loop feedback mechanism ensures calibration correctness while minimizing time loss through automated error tracking.
2Ease of manufacture
If traditional calibration procedures are used, then calibration can be completed, but there are no universal criteria for tool maintenance
Solution Approach 1:
The system establishes universal maintenance criteria that can be applied across different optical metrology tools by using a standard wafer with known properties. The same reference data and evaluation methods can be used for all tools of the same type, providing consistent and reliable maintenance standards throughout the semiconductor fabrication facility.
Solution Approach 2:
The patent replaces manual, mechanical calibration procedures with an automated electronic system that uses spectral analysis and computer-controlled calibration. The control unit automatically processes measured spectrums, compares them with reference data, and performs calibration adjustments without manual intervention, improving both reliability and ease of maintenance.
3Measurement precision
If continuous monitoring is implemented, then error detection sensitivity is improved, but system complexity increases
Solution Approach 1:
The system uses a standard wafer with known properties as an intermediary reference object. This standard wafer serves as a mediator between the optical metrology tool and the calibration process, enabling continuous monitoring without requiring complex additional sensors or measurement systems. The standard wafer translates instrumental errors into measurable spectral deviations.
Data Source
AI summary
An instrumental error tracking and identification method, an instrumental error tracking and identification system and an optical metrology tool are provided. The instrumental error tracking and identification method is for an optical metrology tool in semiconductor fabrication facility. The instrumental error tracking and identification method includes: collecting a plurality of measured spectrums including a spectroscopic ellipsometry (SE) Mueller spectrum matrix or two spectroscopic reflectometry (SR) spectrums from a standard wafer measured by the optical metrology tool; evaluating a performance index of the optical metrology tool, wherein the performance index is a fitting residue for a single wavelength or an area under curve (AUC) for a wavelength interval; and continuously tracking and identifying an instrumental error according to the performance index.