ORCID
https://orcid.org/0009-0008-1493-4361
Date of Award
Fall 2024
Language
English
Embargo Period
11-30-2024
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
College/School/Department
Department of Nanoscale Science and Engineering
Program
Nanoscale Engineering
First Advisor
Dr. Alain Diebold
Committee Members
Dr. Andrew Antonelli, Dr. Markus Kuhn, Dr. Vincent Labella, Dr. Carl Ventrice
Keywords
Semiconductor metrology, mueller matrix spectroscopic ellipsometry (MMSE), x-ray diffraction (XRD), Gate all around nanowire test structure (GAA NWTS), selective cavity etch, Si/SiGe superlattices
Subject Categories
Nanoscience and Nanotechnology
Abstract
Advanced semiconductor devices are moving toward 3D geometries due to scaling demands and performance requirements. Nondestructive metrology necessary for process control of 3D structures must be advanced to facilitate their transition from technology development to high volume manufacturing. Thin film metrology using Mueller Matrix Spectroscopic Ellipsometry (MMSE) and X-ray Diffraction (XRD) film metrology, as well as patterned structure metrology using Optical Critical Dimension (OCD) and X-ray Fluorescence (XRF) techniques have proved capable of measuring the Si/ Si(1-x)Ge(x) superlattices and gate-all-around (GAA) transistor test structures. Because these techniques are indirect, their limitations associated with superlattice device structures need to be further understood. To understand these limitations, a four superlattice layer Si/ Si(1-x)Ge(x)structure was measured at four process steps: as an un-patterned film stack, after anisotropic column etch, and at low and high levels of cavity etch. Cavity etch is the selective etching of exposed parts of the Si(1-x)Ge(x)layers. Thin film samples were analyzed with XRD and MMSE and patterned samples were analyzed using OCD, as well as XRF. An OCD model was developed describing primary and secondary process effects on the structure. This was evaluated for consistency on datasets collected at different measurement azimuth angles. Square error-based methods were evaluated to quantify OCD model detectability of fit variable step deviations, as well as sensitivity relative to the model to measurement error. OCD and XRF results were compared to reference scanning transmission electron microscopy (STEM) images of Nanowire Test Structures (NWTS) lamellae. Dual azimuth OCD results were achieved showing low spectral mean square error (MSE) and mean matching within 0.3 nm of the STEM cavity etch reference. Results indicate that accurate non-destructive metrology of buried dimensions 3D nanowire test structures can be achieved, making MMSE based OCD metrology a potential candidate for in-line cavity etch process control.
The results of the four-layer superlattice point to the need for hybrid metrology in stacks composed of higher number of superlattice layers. An eight layer superlattice NWTS sample set was analyzed, and a hybrid approach was evaluated where XRD film thickness results were used to define the superlattice structure for OCD measurements. OCD dimensions were then used to model the cavity etch structure for XRF determination of cavity etch . Preliminary results for combined metrology are also presented for eight-layer superlattice structures on intact 300 mm wafers using cleanroom compatible measurement systems.
License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Recommended Citation
Pasikatan, Ezra Mel Beltran, "Characterization and measurement limitations using non-destructive mueller matrix scatterometry (MMSE) and x-ray diffraction (xXRD) techniques for gate all around (GAA) transistor test structures: Limitations and superlattice effects in advanced Si/Si(1-x)Ge(x) superlattice nanowire test structures and measurability of simulated horizontal GAA test structures" (2024). Electronic Theses & Dissertations (2024 - present). 109.
https://scholarsarchive.library.albany.edu/etd/109
