XPS Small-Box Film Thickness Measurement Using Beam Mixing Fractions
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Solution Overview
Problem
The challenge is to accurately measure the thickness of film layers within small box regions in semiconductor structures using X-ray photoelectron spectroscopy (XPS), as conventional XPS methods struggle due to the large beam size relative to the small box dimensions, leading to signal spillage and difficulty in distinguishing signals from within and outside the box.
Innovation Solution
The proposed solution involves using multiple XPS measurements with different beam sizes to determine the mixing fraction of the X-ray beam within the small box region. By analyzing the attenuation of XPS signals and using a merit function to model the signal intensities, the technique allows for the calculation of the film layer thickness within the small box region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional XPS beam is used to measure small box regions, then the measurement process is simple, but the measurement precision deteriorates due to signal spillage from areas outside the box
Solution Approach 1:
The measurement process is segmented into multiple steps: first measuring a reference area to determine the mixing fraction, then applying this fraction to correct the measurement of the small box region. This segmentation allows the complex problem of signal spillage to be broken down into manageable correction steps, improving measurement precision without requiring a complete redesign of the XPS system
Solution Approach 2:
The method changes the parameter approach by introducing the mixing fraction as a correction parameter. Instead of trying to physically isolate the beam to the small box region, the solution mathematically adjusts the measured signal using the mixing fraction parameter derived from reference measurements, thereby improving thickness measurement accuracy while maintaining beam size
2Measurement precision
If the XPS beam size is reduced to fit within small box regions, then the signal spillage is reduced, but the beam may not cover the entire box region adequately
Solution Approach 1:
The reference area measurement serves as an intermediary that bridges the gap between the large beam size and the small box region. By measuring the reference area first and calculating the mixing fraction, the method creates a mathematical intermediary that allows the large beam to be effectively used for small box measurements without losing signal intensity or causing excessive spillage
3Measurement precision
If multiple XPS measurements with different beam sizes are performed, then the film layer thickness can be accurately determined, but the measurement time increases
Solution Approach 1:
The method performs preliminary action by first measuring a reference area to determine the mixing fraction before measuring the actual small box region. This preliminary measurement establishes a correction parameter that simplifies the subsequent measurement process, allowing accurate thickness determination while minimizing the time required for the actual sample measurement
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 method enhances the accuracy of XPS analysis for small box regions by accounting for signal spillage and allowing for precise determination of film layer thickness, thereby improving the characterization and measurement of semiconductor structures.
Implementation Method 1
XPS spectra are obtained by irradiating the substrate with a beam of X-rays, while simultaneously measuring the kinetic energy and number of electrons that escape from the top layers of the substrate
Data Source
AI summary
A system to characterize a film layer within a measurement box is disclosed. The system obtains a first mixing fraction corresponding to a first X-ray beam, the mixing fraction represents a fraction of the first X-ray beam inside a measurement box of a wafer sample, the measurement box represents a bore structure disposed over a substrate and having a film layer disposed inside the bore structure. The system obtains a contribution value for the measurement box corresponding to the first X-ray beam, the contribution value representing a species signal outside the measurement box that contributes to a same species signal inside the measurement box. The system obtains a first measurement detection signal corresponding to a measurement of the measurement box using the first X-ray beam. The system determines a measurement value of the film layer based on the first measurement detection signal, the contribution value, and the first mixing fraction.