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Development and Characterization of a Dispersion-Encoded Method for Low-Coherence Interferometry

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About this book

This Open Access book discusses an extension to low-coherence interferometry by dispersion-encoding. The approach is theoretically designed and implemented for applications such as surface profilometry, polymeric cross-linking estimation and the determination of thin-film layer thicknesses. During a characterization, it was shown that an axial measurement range of 79.91 µm with an axial resolution of 0.1 nm is achievable. Simultaneously, profiles of up to 1.5 mm in length were obtained in a scan-free manner. This marked a significant improvement in relation to the state-of-the-art in terms of dynamic range. Also, the axial and lateral measurement range were decoupled partially while functional parameters such as surface roughness were estimated. The characterization of the degree of polymeric cross-linking was performed as a function of the refractive index. It was acquired in a spatially-resolved manner with a resolution of 3.36 x 10-5. This was achieved by the development of a novel mathematical analysis approach.

Table of Contents

Frontmatter

Open Access

Chapter 1. Introduction and Motivation
Abstract
The electronics industry with all its branches such as semiconductors, organic-electronics and the photovoltaics industry, is continuously growing in terms of its economic as well as its technological influence, [1]. This trend is fostered by the ongoing integration of various electronic functionalities in fields such as energy generation & distribution, transport & mobility as well as in consumer goods. Over three decades, electronic and semiconductor products as well as processes were driven by Moores law, [2].
Christopher Taudt

Open Access

Chapter 2. Related Works and Basic Considerations
Abstract
The characterization and measurement of surface profiles is one of the most basic metrology tasks in industrial manufacturing. What started with mechanical stylus profilometers has developed with ultrasonic transducers towards optical instruments. These are capable of appropriate resolutions to enable nanometrology, [14].
Christopher Taudt

Open Access

Chapter 3. Surface Profilometry
Abstract
As outlined in the previous chapter, existing technologies for surface profilometry show certain drawbacks in terms of resolution, dynamic measurement range, three-dimensional measurement capabilities and speed. The following chapter introduces a novel approach to surface profilometry which aims to provide solutions to the problems named. The basic setup for all experiments is centered around a two-beam interferometer of the Michelson type.
Christopher Taudt

Open Access

Chapter 4. Polymer Characterization
Abstract
As discussed in section 2.​2, the characterization of cross-linking and especially its spatial distribution is crucial for the fabrication of micro optics, MEMS, and semiconductors. Some studies have found that the measurement of the refractive index over the cross-linking process can be used as an indicator for the degree of cross-linking of a sample. According to Kudo et al., [130], the cross-linking of a polymeric material leads to a densification which can be directly related to an increase in refractive index using the Lorentz-Lorenz equation.
Christopher Taudt

Open Access

Chapter 5. Thin-film Characterization
Abstract
The third intended application for the proposed dispersion-encoded low-coherence interferometry is the evaluation of thin-film characteristics on substrate materials. Due to the usage of thin-film technologies in high-volume production in e.g. the photovoltaics and semiconductor industry, process monitoring becomes relevant in order to ensure functional parameters such as solar cell efficiency, [289]. In this context, film thickness as well as film homogeneity over large areas are important criteria for quality assurance.
Christopher Taudt

Open Access

Chapter 6. Conclusion
Abstract
The characterization of features such as geometrical dimensions or functional parameters like roughness or degree of cross-linking plays an important role during production in industries such as semiconductors, organic-electronics and the photovoltaics industry. The ability to gather measurements in a process-integrated fashion is of high interest.
Christopher Taudt
Backmatter
Metadata
Title
Development and Characterization of a Dispersion-Encoded Method for Low-Coherence Interferometry
Author
Christopher Taudt
Copyright Year
2022
Electronic ISBN
978-3-658-35926-3
Print ISBN
978-3-658-35925-6
DOI
https://doi.org/10.1007/978-3-658-35926-3