Publisher Summary This chapter deals with atomic layer deposition (ALD), which is a chemical gas phase thin film deposition method based on alternate saturative surface reactions. As distinct from the other chemical-vapor-deposition techniques, in ALD the source vapors are pulsed into the reactor alternately—one at a time—separated by purging or evacuation periods. Each precursor exposure step saturates the surface with a monomolecular layer of that precursor. This results in a unique self-limiting film-growth mechanism with a number of advantageous features—such as excellent conformality and uniformity and simple and accurate film-thickness control. As the current interest in ALD is largely centered on non-epitaxial films, the chapter focuses on these materials and the related chemistry. ALD is a unique process based on alternate surface reactions, which are accomplished by dosing the gaseous precursors on the substrate alternately. Under ideal conditions, these reactions are saturative, ensuring many advantageous features, such as excellent conformity, large-area uniformity, accurate and simple film-thickness control, repeatability, and large-batch processing capability.

Atomic layer deposition

REVIEW The role of defects as essential entities in semiconductor materials is reviewed. Early experiments with semiconductors were hampered by the extreme sensitivity of the electronic properties to minute concentrations of impurities. Semiconductors were viewed as a family of solids with irreproducible properties. Scientific efforts overcame this idiosyncrasy and turned the art of impurity doping into today9s exceedingly useful and reproducible technology that is used to control precisely electrical conductivity, composition, and minority-carrier lifetimes over wide ranges. Native defects such as vacancies and self-interstitials control basic processes, foremost self- and dopant diffusion. The structural properties of dislocations and higher dimensional defects have been studied with atomic resolution, but a thorough theoretical understanding of their electronic properties is incomplete. Reactions between defects within the host lattices are increasingly better understood and are used for gettering and electrical passivation of unwanted impurities. Metastable defects such as DX centers and the EL2-related arsenic antisite are briefly discussed. The recent development of isotopically controlled semiconductors has created new research opportunities in this field.

http://science.sciencemag.org/content/sci/281/5379/945.full.pdf

Defects in Semiconductors: Some Fatal, Some Vital

High-resolution x-ray photoelectron spectroscopy (XPS) at 6 keV photon energy has been realized utilizing high-flux-density x rays from the third generation high-energy synchrotron radiation facility, SPring-8. The method has been applied to analysis of high-k HfO2/interlayer/Si complementary metal–oxide–semiconductor gate-dielectric structures. With the high energy resolution and high throughput of our system, chemical-state differences were observed in the Si 1s, Hf 3d, and O 1s peaks for as-deposited and annealed samples. The results revealed that a SiOxNy interlayer is more effective in controlling the interface structure than SiO2. Our results show the wide applicability of high resolution XPS with hard x rays from a synchrotron source.

https://shin.issp.u-tokyo.ac.jp/print/publication/1005.pdf

High resolution-high energy x-ray photoelectron spectroscopy using third-generation synchrotron radiation source, and its application to Si-high k insulator systems

A long-standing problem in molecular biology is the determination of a complete functional conformational landscape of proteins. This includes not only proteins’ native structures, but also all their respective functional states, including functionally important intermediates. Here, we reveal a signature of functionally important states in several protein families, using direct coupling analysis, which detects residue pair coevolution of protein sequence composition. This signature is exploited in a protein structure-based model to uncover conformational diversity, including hidden functional configurations. We uncovered, with high resolution (mean ∼1.9 A rmsd for nonapo structures), different functional structural states for medium to large proteins (200–450 aa) belonging to several distinct families. The combination of direct coupling analysis and the structure-based model also predicts several intermediates or hidden states that are of functional importance. This enhanced sampling is broadly applicable and has direct implications in protein structure determination and the design of ligands or drugs to trap intermediate states.

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Coevolutionary signals across protein lineages help capture multiple protein conformations.

We report the effects of annealing on the morphology and crystallization kinetics for the high-κ gate dielectric replacement candidate hafnium oxide (HfO2). HfO2 films were grown by atomic layer deposition (ALD) on thermal and chemical SiO2 underlayers. High-sensitivity x-ray diffractometry shows that the as-deposited ALD HfO2 films on thermal oxide are polycrystalline, containing both monoclinic and either tetragonal or orthorhombic phases with an average grain size of ∼8.0 nm. Transmission electron microscopy shows a columnar grain structure. The monoclinic phase predominates as the annealing temperature and time increase, with the grain size reaching ∼11.0 nm after annealing at 900 °C for 24 h. The crystallized fraction of the film has a strong dependence on annealing temperature but not annealing time, indicating thermally activated grain growth. As-deposited ALD HfO2 films on chemical oxide underlayers are amorphous, but show strong signatures of ordering at a subnanometer level in Z-contrast scannin...

/pdf/morphology-and-crystallization-kinetics-in-hfo2-thin-films-2nu7j0wsaq.pdf

Morphology and crystallization kinetics in HfO2 thin films grown by atomic layer deposition

High-k dielectric materials including zirconium oxide and hafnium oxide produced by atomic layer deposition have been evaluated for thermal stability. As-deposited samples have been compared with rapid thermal annealed samples over a range of source/drain dopant activation temperatures consistent with conventional complimentary metal oxide semiconductor polysilicon gate processes. Results of this initial investigation are presented utilizing analyses derived from X-ray diffraction (XRD), X-ray reflectometry (XRR), medium energy ion spectroscopy, high resolution transmission electron microscopy (HRTEM), tunneling atomic force microscopy, scanning electron microscopy, Auger electron spectroscopy and secondary ion mass spectroscopy. Changes in interface and surface roughness, percent crystallinity and phase identification for each material as a function of anneal temperature have been determined by XRD, XRR and HRTEM. Finally, high-k wet etch issues are presented relative to subsequent titanium silicide blanket film resistivity values.

Experimental observations of the thermal stability of high-k gate dielectric materials on silicon

The interpretation of single-molecule measurements is greatly complicated by the presence of multiple fluorescent labels. However, many molecular systems of interest consist of multiple interacting components. We investigate this issue using multiply labeled dextran polymers that we intentionally photobleach to the background on a single-molecule basis. Hidden Markov models allow for unsupervised analysis of the data to determine the number of fluorescent subunits involved in the fluorescence intermittency of the 6-carboxy-tetramethylrhodamine labels by counting the discrete steps in fluorescence intensity. The Bayes information criterion allows us to distinguish between hidden Markov models that differ by the number of states, that is, the number of fluorescent molecules. We determine information-theoretical limits and show via Monte Carlo simulations that the hidden Markov model analysis approaches these theoretical limits. This technique has resolving power of one fluorescing unit up to as many as 30 f...

/pdf/hidden-markov-model-analysis-of-multichromophore-2hc8l1o5y4.pdf

Hidden Markov Model Analysis of Multichromophore Photobleaching

Wet Etch Enhancement of HfO2 Films by Implant Processing

Protein Free Energy Landscapes Remodeled by Ligand Binding

A method is described to empower students to efficiently perform general and specific literature searches using online resources. The method was tested on undergraduate and graduate students with varying backgrounds in scientific literature. Students involved in this study showed marked improvement in their awareness of how and where to find accurate scientific information. © 2009 American Association of Physics Teachers. DOI: 10.1119/1.3213525

/pdf/a-student-s-guide-to-searching-the-literature-using-online-2o9nmuhvip.pdf

Troy C. Messina

Papers

Experimental observations of the thermal stability of high-k gate dielectric materials on silicon

Hidden Markov Model Analysis of Multichromophore Photobleaching

Wet Etch Enhancement of HfO2 Films by Implant Processing

Protein Free Energy Landscapes Remodeled by Ligand Binding

A student's guide to searching the literature using online databases