Overlay Error Measurement for Lithography Process Parameter
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Solution Overview
Problem
Measuring process parameters such as side-wall asymmetries in lithographic processes is time-consuming and can damage the substrate, limiting efficiency in process control and verification.
Innovation Solution
A method involving first and second measurements of overlay error, where the first measurement is designed to be more sensitive to perturbations in the process parameter, allowing for the efficient determination of the process parameter based on the difference in overlay error measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional measurement methods are used to measure process parameters like side-wall asymmetries, then measurement accuracy is improved, but measurement time increases and substrate damage occurs
Solution Approach 1:
The invention changes the measurement parameter from direct process parameter measurement to overlay error measurement. By measuring overlay error between two layers instead of directly measuring side-wall asymmetry, the method achieves indirect measurement of process parameters with reduced measurement time and without substrate damage. The overlay error serves as a proxy parameter that correlates with the actual process parameter of interest.
2Measurement precision
If traditional measurement methods are used to measure process parameters like side-wall asymmetries, then measurement accuracy is improved, but substrate damage occurs
Solution Approach 1:
The invention introduces overlay error measurement as an intermediary method. Instead of directly measuring the process parameter (side-wall asymmetry) which may require destructive techniques, the method uses overlay error between two lithographically formed layers as an intermediary indicator. This intermediary measurement provides information about the process parameter without directly damaging the substrate.
3Reliability
If multiple measurements are performed to determine process parameters, then measurement reliability is improved, but productivity decreases
Solution Approach 1:
The invention merges the measurement of overlay error with the measurement of process parameters. By performing a single overlay error measurement that simultaneously provides information about both overlay accuracy and process parameters (through their correlation), the method achieves reliable process parameter determination without requiring separate measurement steps, thereby maintaining productivity.
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
Enables faster and non-destructive measurement of process parameters like side-wall angle unbalance, improving process control and verification efficiency in lithographic manufacturing.
Implementation Method 1
an optical system arranged to direct radiation onto a substrate. A detector arranged to detect radiation after interaction between the radiation and the substrate
Data Source
AI summary
There is disclosed a method of measuring a process parameter for a manufacturing process involving lithography. In a disclosed arrangement the method comprises performing first and second measurements of overlay error in a region on a substrate, and obtaining a measure of the process parameter based on the first and second measurements of overlay error. The first measurement of overlay error is designed to be more sensitive to a perturbation in the process parameter than the second measurement of overlay error by a known amount.