Two-Dimensional Marks for Focus Exposure Matrix Calibration
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Solution Overview
Problem
In semiconductor fabrication, controlling critical dimensions of features on wafers is challenging due to drifts in photolithography tool settings over time, requiring effective methods to model and monitor relationships between measured characteristics and focus and exposure settings to ensure consistent feature formation.
Innovation Solution
A Focus-Exposure Matrix (FEM) model is created using two-dimensional test marks formed under varying exposure and focus conditions, measured by optical tools like scatterometers, to determine optimal settings and adjust for drifts in photolithography equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If photolithography tool settings are used over time, then production efficiency is maintained, but focus and exposure settings drift causing feature characteristic variations
Solution Approach 1:
The patent applies preliminary action by pre-forming two-dimensional marks with varying densities under different focus and exposure conditions before production. These marks serve as reference standards that are measured to determine the actual focus and exposure settings used during feature formation, enabling drift detection and correction without interrupting production flow
Solution Approach 2:
The patent implements feedback by measuring the characteristics of formed features and comparing them against the pre-formed two-dimensional marks to determine actual focus and exposure settings. This feedback loop allows for continuous monitoring and adjustment of photolithography tool settings to maintain feature characteristic consistency despite drift over time
2Measurement precision
If traditional measurement methods are used, then feature characteristics can be monitored, but the complexity of modeling relationships between measurements and tool settings increases
Solution Approach 1:
The patent applies parameter changes by varying the density of the two-dimensional marks (different pitch values) to create a set of reference structures. By measuring features with different densities and comparing them against the pre-formed marks, the system can determine focus and exposure settings without requiring complex multi-parameter models, simplifying the relationship between measurements and tool settings
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
The FEM model allows for precise determination and adjustment of focus and exposure settings, ensuring consistent feature formation and maintaining desired characteristics in semiconductor components, thereby improving the control and efficiency of semiconductor fabrication processes.
Implementation Method 1
Methods for measuring features formed into a semiconductor substrate include optical tools that utilize scatterometry. Scatterometry refers to the process of measuring light spectra to determine the size of periodic structures.
Implementation Method 2
The intensity of light used to expose a photoresist layer affects the characteristics of the feature. The photolithography tool can be set to focus at varying depths into a photoresist layer.
Data Source
AI summary
A method for controlling semiconductor production through use of a Focus Exposure Matrix (FEM) model includes taking measurements of characteristics of a two-dimensional mark formed onto a substrate, the two-dimensional mark including two different patterns along two different cut-lines, and comparing the measurements with a FEM model to determine focus and exposure conditions used to form the two-dimensional mark. The FEM model was created using measurements taken of corresponding two-dimensional marks formed onto a substrate under varying focus and exposure conditions.