Eccentric Test Matrix Decouples Tool and Process Effects
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Solution Overview
Problem
Current methods for determining photolithography parameters suffer from confounding influences, making it difficult to accurately correlate input parameters with output properties of integrated circuits, especially due to unknown variables like photoresist thickness and exposure uniformity.
Innovation Solution
A method involving an eccentric test matrix where parameter values are scrambled or randomly ordered, reducing confounding effects by disrupting uniform incremental changes, allowing for a more accurate correlation between parameters and properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional orthogonal test matrix with uniform incremental shifts is used to determine photolithography parameters, then the test structure is simple and easy to implement, but confounding influences from unknown variables reduce the accuracy of correlation between parameters and properties
Solution Approach 1:
The patent applies asymmetry by transforming the conventional symmetric orthogonal test matrix into an asymmetric eccentric test matrix. The parameter values are arranged in an eccentric (non-uniform) pattern rather than uniform incremental shifts, which disrupts the symmetry that allows confounding variables to systematically correlate with parameter changes. This asymmetric arrangement reduces the confounding effects and improves measurement precision.
Solution Approach 2:
The patent inverts the conventional approach by using an eccentric test matrix instead of an orthogonal one. Rather than maintaining the traditional uniform incremental structure, the patent reverses the paradigm by deliberately using non-uniform, eccentric parameter arrangements to decouple tool effects from process effects, thereby improving correlation accuracy.
2Measurement precision
If uniform incremental shifts in parameters are applied across test matrix dimensions, then the parameter variation is systematic and easy to analyze, but confounding effects from variables like photoresist thickness and exposure uniformity reduce correlation accuracy
Solution Approach 1:
The patent replaces the symmetric uniform incremental parameter shifts with asymmetric eccentric parameter arrangements. This asymmetry disrupts the systematic confounding that occurs with uniform shifts, allowing for more accurate isolation of parameter effects from confounding variables like photoresist thickness variations and exposure uniformity issues.
Solution Approach 2:
The patent changes the parameter arrangement from uniform incremental values to eccentric non-uniform values. This parameter change in the test matrix structure fundamentally alters how confounding variables interact with parameter variations, reducing their ability to create spurious correlations and improving the accuracy of parameter-property relationships.
3Measurement precision
If an eccentric test matrix with scrambled parameter values is used, then confounding effects are reduced and correlation accuracy improves, but the test matrix becomes more complex and harder to implement
Solution Approach 1:
The patent deliberately introduces asymmetry into the test matrix structure by using eccentric parameter arrangements instead of symmetric uniform patterns. This asymmetric design, while more complex, successfully reduces confounding effects and improves correlation accuracy by preventing systematic alignment between parameter changes and confounding variables.
Solution Approach 2:
The patent inverts the conventional test matrix approach by adopting an eccentric structure rather than the traditional orthogonal design. This inversion accepts increased complexity as a necessary trade-off to achieve the goal of reduced confounding effects and improved measurement precision.
Data Source
AI summary
A method of characterizing a process by selecting the process to characterize, selecting a parameter of the process to characterize, determining values of the parameter to use in a test matrix, specifying an eccentricity for the test matrix, selecting test structures to be created in cells on a substrate, processing the substrate through the process using in each cell the value of the parameter as determined by the eccentric test matrix, measuring a property of the test structures in the cells, and developing a correlation between the parameter and the property.