Thin-Film Characterization Using Heterodyne Phase Reflectometry
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Solution Overview
Problem
Existing spectroscopic ellipsometry processes for determining the thickness, refractive index, and extinction coefficient of thin layers in semiconductor devices face challenges due to the need for accurate modeling and environmental factors affecting polarization, leading to inaccuracies and reduced robustness, as well as limitations in measuring variations across the sample surface.
Innovation Solution
A heterodyne reflectometry and common-path interferometry process using a heterodyne light source, beam splitters, analyzers, and light sensors to measure phase differences between reference and test beams, enabling accurate determination of thickness, refractive index, and extinction coefficient without relying on layer modeling, and allowing two-dimensional scanning for surface distribution measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If spectroscopic ellipsometry is used to measure thin layer properties, then measurement capability is provided, but environmental factors affect polarization and reduce measurement robustness
Solution Approach 1:
The patent introduces a reference beam as an intermediary that does not interact with the test layer, allowing comparison between the reference beam (unaffected by environmental factors) and the test beam (affected by both environmental factors and layer properties). This mediator enables separation of environmental effects from actual measurement signals, improving robustness while maintaining precision.
Solution Approach 2:
The patent extracts the environmental factor effects from the measurement by using a reference beam that experiences the same environmental conditions but does not interact with the test layer. By taking out and measuring the environmental component separately, the system can compensate for these effects and improve measurement robustness.
2Measurement precision
If accurate modeling of layers is used to determine thickness and optical constants, then determination capability is provided, but modeling accuracy requirements increase measurement complexity
Solution Approach 1:
The reference beam serves as a mediator that provides a direct measurement reference, eliminating the need for complex layer modeling. By comparing the test beam to the reference beam, the system directly determines property changes without requiring accurate models of intermediate layers, thus reducing modeling complexity while maintaining determination accuracy.
Solution Approach 2:
The patent measures changes in optical parameters (phase difference, polarization state) rather than absolute values requiring complex modeling. By focusing on parameter changes between reference and test conditions, the system simplifies the determination process and reduces dependency on accurate layer modeling.
3Measurement precision
If point-by-point measurement is used to characterize thin layers, then measurement capability is provided, but measurement time increases for surface distribution
Solution Approach 1:
The patent transitions from one-dimensional point-by-point scanning to two-dimensional surface characterization by using an expanded beam that illuminates the entire surface simultaneously. This dimensional change allows parallel measurement across the surface, dramatically improving productivity while maintaining precision through the reference beam comparison method.
Solution Approach 2:
The patent combines multiple point measurements into a single simultaneous measurement by expanding the beam to cover the entire surface. By merging the measurement of multiple points into one operation, the system achieves rapid surface distribution characterization without sacrificing the precision enabled by the reference beam method.
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 enhances measurement accuracy and robustness by minimizing environmental impacts and allows for rapid, precise determination of these properties across the sample surface, improving characterization of thin layers in semiconductor devices.
Implementation Method 1
A first source beam of heterodyne light is generated toward a first test layer
Implementation Method 2
A first source beam of heterodyne light is generated toward a first test layer
Implementation Method 3
A first source beam of heterodyne light is generated toward a first test layer
Implementation Method 4
An intensity signal of the first reference beam is measured; An intensity signal of the first test beam is measured
Data Source
AI summary
A method includes generating a source beam of heterodyne light toward a test layer so that the source beam is incident on the test layer at a first incidence angle. The source beam is polarized, thereby forming a reference beam. A portion of the source beam that is reflected by the test layer is polarized, thereby forming a test beam. An intensity signal of the reference beam and an intensity signal of the test beam are measured. A difference between a phase of the intensity signal of the test beam and a phase of the intensity signal of the reference beam is determined. A refractive index, an extinction coefficient, and a thickness of the test layer are determined based on the difference between the phase of the intensity signal of the test beam and the phase of the intensity signal of the reference beam.