<p>Recrystallisation annealing, a repeated heat treatment between different stages of cold rolling of martensitic chromium steel strip, is successful when neither high rolling forces nor wear of the working rolls occur during the subsequent cold rolling. Mechanical properties as tensile strength, yield, elongation or hardness have been, by tradition, the criteria that described the quality of the annealing process. In recent years, the development of the measurement equipment in the rolling mills and of the instruments for material investigations has accentuated more and more the role played by the microstructural properties in the evaluation of the heat treatment. Two microstructural characteristics of the degree of annealing are, firstly and most important, the recrystallisation degree, and, secondly, the secondary carbide density.</p><p>The sample manufacturing and heat treatment, modelling and microstructure investigations by light optical- (LOM) and scanning electron microscopy (SEM) described in this article were carried out at Sandvik Materials Technology’s R&D Department and Bell Furnace Line in Sandviken, Sweden, while microstructure investigations and evaluation by scanning electron microscopy with field emission gun (FEG-SEM) and electron back scatter diffraction (EBSD) were done at the Corrosion and Metals Research Institute (KIMAB) in Stockholm, Sweden.</p><p>The first part of this work shows that, in contrast to the traditional methods LOM and SEM, that use chemical etching for the preparation of the samples, EBSD can successfully characterise recrystallised structures in annealed martensitic chromium steels. Unlike conventional microscopy with LOM and SEM, EBSD is able to reveal the grain geometry, as well as to separate and identify the different phases in this kind of steels (ferrite, M23-, M6-carbides). Important parameters such as grain size, particle size and recrystallised fraction can be measured with high accuracy. This information can be used to understand, evaluate, control and even predict the recrystallisation annealing of martensitic chromium steel.</p><p>The second part of this work presents how the results from microstructure description by EBSD can be directly used in relatively simple empirical models for determination of recrystallisation degree as function of the annealing parameters and the deformation history. EBSD was applied to evaluate the degree of recrystallisation in a series of annealing tests, with the purpose to model recrystallisation temperature in two types of martensitic chromium steel strip, a traditional one and one alloyed with molybdenum, cold rolled with different amounts of reduction and annealed with different temperatures, soaking times and heating rates. The empirical quadratic models were built with Umetrics’ software for experimental design, MODDEÒ 8.0 and they defined the recrystallisation degree (limits for LAGB and HAGB were set to 1.5° and 7.5° for the first grade and 2.5° and 10° for second one) and the secondary carbides density as functions of annealing temperature, soaking time and cold reduction (the factor heating rate was removed as nonsignificant). To be observed that these empirical models were fit much better for the recrystallisation degree than for the secondary carbides density.</p><p>The modelling work described above, together with the implementation of online physical temperature models in the bell annealers may lead to an increased productivity in the production plant by shortening the annealing cycle and minimising scrap and thus to an economical gain of ca 1,5 MSEK per year at Sandvik Materials Technology.</p><p> </p>

No description available.

Isotropic and anisotropic etching have been used in silicon processing for the past few decades. However, optimization and adaptation of anisotropic etching to standard I.C. fabrication is a more recent technology. This paper describes new methods for process and material optimization in Orientation and Concentration dependent etching of the (1 0 0) plane in silicon. Furthermore, methods of oxide and nitride pinhole detection in (1 0 0) planes in silicon are presented. New mask alignment techniques to obtain an accurate etch front termination in silicon are also shown.

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Chan Siu-pang. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves 45-47). / Abstract also in Chinese. / TITLE PAGE --- p.i / THESIS COMMUTE --- p.ii / ABSTRACT (English) --- p.iii / ABSTRACT (Chinese) --- p.iv / ACKNOWLEDGMENT --- p.v / TABLE OF CONTENTS --- p.vi / LIST OF FIGURES --- p.vii / LIST OF TABLES --- p.viii / Chapter CHAPTER 1. --- Introduction --- p.1 / Chapter Section 1.1. --- General Introduction --- p.1 / Chapter Section 1.2. --- Background Information --- p.2 / Chapter 1.2.1. --- Si(100) Surface --- p.2 / Chapter 1.2.2. --- Structure of Cl/Si(100) --- p.7 / Chapter Section 1.3. --- Etching of Si(100) by Chlorine --- p.9 / Chapter Section 1.4. --- Theory --- p.14 / Chapter Section 1.5. --- Computational Model --- p.17 / Chapter CHAPTER 2. --- Desorption Mechanism of SiCl4 --- p.19 / Chapter Section 2.1. --- Desorption Mechanism --- p.19 / Chapter 2.1.1. --- Trajectory1 --- p.20 / Chapter 2.1.2. --- Trajectory2 --- p.23 / Chapter 2.1.3. --- Trajectory3 --- p.26 / Chapter 2.1.4. --- Trajectory4 --- p.29 / Chapter 2.1.5. --- Trajectory5 --- p.32 / Chapter 2.1.6. --- Trajectory6 --- p.35 / Chapter Section 2.2. --- Discussion --- p.38 / Chapter Section 2.3. --- Conclusion --- p.44 / REFERENCES: --- p.45

Le nitrure de gallium (GaN) est un semi-conducteur à grand gap dont les propriétés en font un bon candidat pour remplacer le Si dans le domaine de l’électronique de puissance. Dans cette optique, cette thèse s’est intéressée à l’une des étapes de la conception d’une diode de puissance Schottky à base de GaN épitaxié sur Si : la gravure. L’objectif était alors de développer des procédés permettant une reprise de contact sur une couche enterrée de GaN n+. Ils devaient combiner des performances de gravure compatibles avec des processus industriels et conduire à des profils et états de surface adaptés à la réalisation d’un contact ohmique. La réalisation d’une structure pseudo-verticale, au travers de la gravure par la face supérieure d’une couche de 5 à 6 μm de GaN a été étudiée avec quatre réacteurs plasma différents. Des analyses du plasma et du matériau après gravure ont mis en évidence que le meilleur compromis était obtenu pour des plasmas inductifs en chimie chlorée avec une tension d’auto-polarisation modérée. Il a également été déterminé que l’ajout d’un gaz fluoré dans un plasma de ce type permettait de générer une passivation à même de protéger la surface du GaN. Pour répondre à la chute de vitesse de gravure qu’elle entraîne, un procédé alternant des étapes de gravure et de passivation a été développé et étudié. D’autre part, des recherches ont été menées afin de créer une structure verticale. Afin d’atteindre le GaN n+, des gravures en face arrière de vias de Si d’une profondeur de 300 μm par les procédés cryogéniques standard et STiGer anisotrope ont été effectuées. Un procédé de révélation permettant l’étude des couches composant le tampon, situé entre le Si et le GaN, a été mis au point. Leur gravure par des plasmas chlorés s’est révélée efficace au travers ou non de vias de Si. / Gallium nitride (GaN) is a wide bandgap III-V semiconductor with interesting electrical properties in order to replace Si in the field of power devices. The subject of this thesis was then to study one of the essential steps to realize a GaN based Schottky diode : the etch. The aim was to develop etching processes allowing the realization of an ohmic contact on an embedded GaN n+ layer. They must combine GaN etching performances compatible with industrial requirements and etch profiles and surface states compatible with an ohmic contact. The etching of a 5 to 6 μm GaN layer by four different reactors was studied in order to realize a pseudovertical structure. Plasma and GaN surfaces analyses were performed during and after etching by five developed and optimized processes. These analyses showed that best compromise was obtained for inductive chlorine plasmas with a moderate bias. The creation of a passivation layer which is able to protect GaN surface, thanks to fluorine addition in plasma chemistries was also established. To overcome the etch rate decreases induced by fluorine addition, a time multiplexed etching process, alternating etch and passivation steps, was developed and studied. Researches were also performed to achieve a vertical diode. Etching of 300 μm depth Si vias by standard cryogenic and anisotropic STiGer processes were carried out. A revelation process was also developed in order to study buffer layers etching. Effective buffer etching by chlorine plasma was demonstrated with or without Si vias.

Microfluidic technology is a useful tool to help answer unsolved problems in multidisciplinary fields, including molecular biology, clinical pathology and the pharmaceutical industry.Current microfluidic based devices with diverse structures have been constructed via extensively used soft lithography orphotolithography fabrication methods. A layer-by-layer stacking of 2D planar microchannel arrays can achieve limited degrees of three dimensionality. However, assembly of large-scale multi-tiered structures is tedious, and the inherently planar nature of the individual layers restricts the network’s topological complexity. In order to overcome the limitations of existing microfabrication methodswe demonstrate several novel methods that enable microvasculature networks: electrostatic discharge,global channel deformation and enzymatic sculpting to fabricate complex surface topologies. These methods enable construction of networks of branched microchannels arranged in a tree-like architecture with diameters ranging from approximately 10 μm to 1 mm. Interconnected networks with multiple fluidic access points can be straightforwardly constructed, and quantification of their branching characteristics reveals remarkable similarity to naturally occurring vasculature. In addition, by harnessing enzymatic micromachining we are able to construct nanochannels, microchannels containing embedded features templated by the substrate’s crystalline morphology, and an irregular cross section of microchannel capable of performing isolation and enrichment of cells from whole blood with throughput 1 – 2 orders of magnitude faster than currently possible. These techniques can play a key role in developing an organ-sized engineered tissue scaffolds and high-throughput continuous flow separations.

This diploma thesis deals with the investigation of the metal-assisted catalytic etching (MaCE) of Si. One of the main goals is to study fabrication of stamps for nanoimprint lithography using MaCE. Formation of nanoporous silicon (PSi), Si nanowires (SiNWs) and three-dimensional nanostructures in Si by MaCE is demonstrated. For this purpose optical lithography, electron beam lithography (EBL), shadow mask evaporation and aerosol nanoparticles deposition techniques have been utilized. The etching rate and surface morphology of Si (with Au lift-off films as a catalyst) as functions of time and concentrations of chemicals are measured in the current diploma work using optical microscope and scanning electron microscopy (SEM). In the current thesis it is shown that Si structures with sub-150 nm lateral sizes, high aspect ratio (up to 1:21), well-defined shapes, and various complexity can easily be fabricated by means of MaCE process.

The introduction of deep reactive ion etching (DRIE) technology has greatly expanded the accessible design space for microscopic systems. Structures that are hundreds of micrometers tall with aspect ratios of 40:1, heretofore impossible, can now be achieved. However, this technology is primarily a forming technology, sculpting structures from a substrate. This work seeks to complement deep reactive ion etching by developing an electrical isolation technology to enable electro-mechanical function in these new deep reactive ion etched structures. The objective of the research is twofold. The first is to develop and characterize an electrical isolation technology for DRIE, single crystal silicon (SCS) micro-electro-mechanical systems (MEMS) using temperature gradient zone melting (TGZM) of aluminum junctions for diodic isolation. The second is to demonstrate the utility of this electrical isolation technology in the design, simulation, fabrication, and testing of a MEMS device, i.e. a micro-gyroscope, in such a way that the benefits from junction isolated, deep reactive ion etched, single crystal silicon devices are preserved.