Multi-Layer Film Thickness Analysis Using XPS and XRF Feed-Forward
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Solution Overview
Problem
Current X-ray photoelectron spectroscopy (XPS) and X-ray fluorescence (XRF) analysis technologies face challenges in accurately determining the thickness and composition of complex, multi-layer films, particularly in providing effective process control and feed-forward solutions for subsequent operations.
Innovation Solution
The method involves measuring XPS and XRF intensity signals for multiple layers, combining these signals with realistic film stack models to determine thickness and compositional properties, and using a database to feed-forward pre-measurement results for accurate thickness and composition determination in subsequent operations, accounting for the effective substrate model.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional XPS and XRF analysis methods are used for multi-layer films, then the analysis can be performed with standard equipment, but the measurement precision and reliability deteriorate due to inability to accurately decouple signals from multiple layers and substrate
Solution Approach 1:
The patent segments the complex multi-layer film analysis into distinct measurement stages: first measuring the substrate, then measuring each subsequent layer sequentially. By treating each layer independently and using the previous measurements as reference, the system decouples the overlapping signals from different layers, enabling precise thickness and composition determination for each individual layer without being confounded by the complexity of the entire multi-layer structure.
Solution Approach 2:
The patent performs preliminary measurements of the substrate and previously deposited layers before analyzing the current layer. These preliminary measurements establish baseline characteristics and effective substrate models that are fed forward to guide the analysis of subsequent layers. This preliminary action enables the system to account for the underlying structure's influence on the current layer's signal, improving measurement precision.
2Reliability
If feed-forward of pre-measurement results is implemented, then process control and measurement accuracy improve, but the system complexity and computational requirements increase
Solution Approach 1:
The patent implements a feedback mechanism where measurement results from previous layers and substrate are fed forward to inform the analysis of subsequent layers. The effective substrate model created from preliminary measurements is continuously updated and reused as reference data for analyzing each new layer. This feedback loop ensures that process variations are accounted for and maintains measurement reliability across multiple layers, while the systematic approach to feedback integration manages system complexity.
3Device complexity
If conventional single-technique analysis is used, then the equipment setup remains simple, but the ability to accurately characterize complex multi-layer films deteriorates
Solution Approach 1:
The patent combines XPS and XRF measurement techniques within a single integrated system. By merging these two complementary techniques, the system leverages the depth-sensitive nature of XPS and the bulk-sensitive nature of XRF to obtain complementary information about each layer's composition and thickness. This combination enables accurate characterization of complex multi-layer films while maintaining a unified equipment configuration that performs both measurement modes.
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 enables precise and stable process control by decoupling multi-operation measurements, allowing for accurate thickness and composition determination in increasingly complex film stacks, extending the capability of XPS and XRF for fab process control.
Implementation Method 1
an X-ray source for generating an X-ray beam
Implementation Method 2
an X-ray photoelectron spectroscopy (XPS) signal generated by bombarding said sample with said X-ray beam
Implementation Method 3
an X-ray fluorescence (XRF) signal generated by bombarding said sample with said X-ray beam
Data Source
AI summary
Methods and systems for feed-forward of multi-layer and multi-process information using XPS and XRF technologies are disclosed. In an example, a method of thin film characterization includes measuring first XPS and XRF intensity signals for a sample having a first layer above a substrate. The first XPS and XRF intensity signals include information for the first layer and for the substrate. The method also involves determining a thickness of the first layer based on the first XPS and XRF intensity signals. The method also involves combining the information for the first layer and for the substrate to estimate an effective substrate. The method also involves measuring second XPS and XRF intensity signals for a sample having a second layer above the first layer above the substrate. The second XPS and XRF intensity signals include information for the second layer, for the first layer and for the substrate. The method also involves determining a thickness of the second layer based on the second XPS and XRF intensity signals, the thickness accounting for the effective substrate.