Lithography Measurement Characterization for Confidence and Throughput
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Solution Overview
Problem
Existing semiconductor lithography measurement systems face challenges in achieving reproducibility and confidence intervals for critical dimension (CD) and registration measurements, particularly for structures near or below the resolution limit, with conflicting objectives of throughput and precision.
Innovation Solution
A method utilizing the Allan variance to quantify the reduction of standard deviation by averaging measurement data, optimizing parameters M (number of measurement runs) and N (individual measurements) to improve confidence intervals and throughput, employing a control unit for automated high-precision measurement methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of measurement runs and individual measurements is increased to improve confidence intervals and reproducibility, then measurement precision is improved, but measurement time and throughput are reduced
Solution Approach 1:
The system performs preliminary characterization measurements to determine the optimal number of measurement runs and individual measurements needed to achieve a predefined confidence interval threshold. This preliminary action allows the system to establish measurement parameters in advance, avoiding unnecessary repeated measurements and thereby improving throughput while maintaining required precision.
Solution Approach 2:
The measurement system dynamically adjusts the number of measurement runs and individual measurements based on the measured value and its confidence interval. When the confidence interval meets the predefined threshold, the system reduces the number of measurements; when it exceeds the threshold, the system increases measurements. This dynamic adaptation resolves the contradiction by optimizing the balance between precision and throughput in real-time.
2Ease of operation
If automated control is implemented to optimize measurement parameters, then ease of operation is improved, but device complexity increases
Solution Approach 1:
The control unit automatically determines the optimal number of measurement runs and individual measurements by evaluating measured values against predefined confidence interval thresholds. The system self-adjusts measurement parameters without requiring manual intervention or complex external control systems, thereby improving ease of operation while keeping the added complexity minimal and contained within the control unit.
Data Source
AI summary
Disclosed is a method for characterizing a measurement apparatus for semiconductor lithography, comprising the following steps:performing a plurality of measurements, in particular of a marker property or die property (for example, registration values or CD values)determining a relationship between the width of a confidence interval of the measurement result from averaging and the number of elements of a subset of all the measurements carried out. Also disclosed is a measurement apparatus in which the method is applied.