Semiconductor Metrology for Isolating Vertical Parameters in Stacks
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Solution Overview
Problem
Existing methods struggle to accurately measure vertical parameters of interest, such as recess depth and gate height, in semiconductor devices due to interference from nuisance contributors in the stack, leading to inaccurate measurements and inefficiencies in high-volume manufacturing.
Innovation Solution
A method involving training targets with varied correlated parameters, processed similarly to the device, is used to derive vertical parameters by removing nuisance contributor effects through data-driven models, utilizing scatterometry and pupil imaging to enhance measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional scatterometry is used to measure vertical parameters, then measurement speed is improved for high-volume manufacturing, but measurement precision deteriorates due to interference from nuisance contributors in the stack
Solution Approach 1:
The measurement process is segmented into two distinct phases: first measuring the stack without the layer of interest to capture nuisance contributor effects, then measuring with the layer of interest present. This segmentation allows separate characterization of interference effects and target parameters, resolving the contradiction between speed and precision.
Solution Approach 2:
The nuisance contributor effects are extracted from the total measurement signal by performing a measurement without the layer of interest. This extracted interference signature is then removed from the measurement with the layer present, isolating the vertical parameter of interest and improving measurement precision while maintaining scatterometry's inherent speed advantages.
2Measurement precision
If multiple measurements are performed to account for nuisance contributors, then measurement precision is improved, but measurement time increases reducing productivity
Solution Approach 1:
The measurement without the layer of interest is performed as a preliminary action to establish the nuisance contributor baseline. This pre-characterization of interference effects enables rapid correction of subsequent measurements, achieving high precision without requiring multiple iterative measurements and thus minimizing time loss.
Solution Approach 2:
A reference measurement of the stack without the layer of interest serves as a template or copy of the nuisance contributor signature. This reference copy is then subtracted from measurements with the layer present, enabling precise parameter extraction from a single primary measurement and avoiding time-consuming repeated measurements.
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 allows for precise determination of vertical parameters by disentangling nuisance contributors, improving measurement efficiency and accuracy in high-volume manufacturing environments.
Implementation Method 1
These devices direct a beam of radiation onto a target and measure one or more properties of the scattered radiation - e.g., intensity at a single angle of reflection as a function of wavelength; intensity at one or more wavelengths as a function of reflected angle; or polarization as a function of reflected angle - to obtain a diffraction 'spectrum' from which a property of interest of the target can be determined.
Implementation Method 2
obtain a diffraction 'spectrum' from which a property of interest of the target can be determined
Data Source
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AI summary
Disclosed is a method of determining at least one vertical parameter of interest relating to a structure of interest on a substrate comprising: obtaining first metrology data and/or data derived therefrom, the first metrology data relating to a measurement of the structure of interest when not comprising a layer of interest to which the vertical parameter of interest relates, or a representative structure being representative of the structure of interest when not comprising the layer of interest; obtaining second metrology data relating to a measurement of the structure of interest when comprising the layer of interest; removing the first metrology data and/or data derived therefrom from the second metrology data to obtain residual metrology data; obtaining at least one model to relate the residual metrology data to the vertical parameter of interest; and using the model to derive the vertical parameter of interest from the residual metrology data.