Lithographic Scatterometry Profile Measurement
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Solution Overview
Problem
In lithographic processes, measuring the profile of a scatterometry object on a substrate with multiple product layers is challenging due to the large number of degrees of freedom, leading to increased probability of erroneous results, as existing methods fail to account for the thickness of underlying layers effectively.
Innovation Solution
A method that involves measuring the thickness of product layers, estimating the object's position, detecting the diffraction pattern, deriving a model diffraction pattern, and comparing it with the actual pattern to determine the object's shape, while using a detector, controller, and comparator to select and adjust model profiles based on variable and non-variable parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing scatterometry methods are used to measure the profile of an object on a substrate with multiple product layers, then the measurement process can be performed, but the number of degrees of freedom in the reconstruction equation increases, leading to a higher probability of erroneous results
Solution Approach 1:
The patent segments the complex measurement problem by separating the object of interest from the underlying product layers. It focuses the scatterometry measurement specifically on the object while treating the product layers as a distinct, measured parameter rather than attempting to simultaneously reconstruct all layers together, thereby reducing the degrees of freedom in the reconstruction equation.
Solution Approach 2:
The patent applies preliminary action by measuring the thickness of product layers before performing the scatterometry reconstruction of the object profile. This pre-measurement of layer thicknesses allows these parameters to be fixed or constrained during the subsequent object profile reconstruction, reducing the number of variables and improving measurement reliability.
2Measurement precision
If the thickness of product layers is not accounted for in the scatterometry measurement, then the reconstruction process is simpler, but the shape determination of the scatterometry object becomes less accurate
Solution Approach 1:
The patent introduces an intermediary approach by using the measured thickness of product layers as a known parameter in the scatterometry reconstruction model. This intermediary measurement of layer thickness serves as a bridge that allows accurate object profile determination without requiring the complex simultaneous reconstruction of all layers, thus improving accuracy while managing complexity.
3Loss of information
If a comprehensive model including all product layers is used for scatterometry reconstruction, then complete information can be obtained, but the computational complexity and time required increase significantly
Solution Approach 1:
The patent extracts the measurement of product layer thickness as a separate, preliminary step from the object profile reconstruction process. By taking out the layer thickness measurement and using it as a known parameter, the system avoids the computationally intensive task of simultaneously reconstructing all layers and objects, thereby reducing measurement time while preserving the necessary information for accurate object characterization.
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
This approach reduces the number of degrees of freedom in the reconstruction equation, minimizing errors and providing accurate shape determination of the scatterometry object by accounting for the thickness of product layers, thus improving measurement precision.
Implementation Method 1
detecting the diffraction pattern of radiation diffracted from the object
Data Source
AI summary
Measurement of a profile of a scatterometry object on top of one or more product layers on a substrate is disclosed. To prevent an unknown parameters of one or more product layers having an effect on the measurement of the object profile, the thickness of the one or more product layers is measured prior to measuring the profile of the scatterometry object on the layer(s). In an embodiment, each of a plurality of product layers is measured as it is exposed so that only the degree of freedom of the most recently exposed product layer is unknown at each measurement step. When each of a plurality of product layers has been measured, and a scatterometry object is placed at the top of the layers, only the degrees of freedom of that scatterometry object should be unknown and only the profile of the object should need to be measured.