Spin-On Glass: Materials and Applications in Advanced IC Technologies

This thesis deals with the study of shallow PN junction formation by dopant diffusion from Spin-On Glass (SOG) for future deep sub-micron BiCMOS technology. With the advantages of no transient enhanced diffusion and no metal contamination, diffusion from highly doped SOG (also called spin-on dopant - SOD) is a good technology for shallow junction formation. In this thesis, diffusion of impurities from SOD into Si and polysilicon on silicon structure has been studied. This shallow junction formation technique using SOD has been applied in realisation of two important devices, i.e. high frequency bipolar transistor and deep sub-micron elevated source/drain MOSFET

A Novel Method for the Bottom-Up Microstructuring of Silicon and Patterning of Polymers

The aim of this work was the development of a method for the generation of surface features on n-type silicon samples with deeply buried p-implants, in the form of heterogeneities aligned directly above the buried implants. This task was motivated by the realisation of a simpler process for the formation of superjunction transistors, which currently require the repeated creation of the same implantation structure over multiple steps of photolithography These lithography steps can be potentially replaced, if a suitable process for the self-alignment in accordance to the buried implants can be found. The work on this goal was separated into three parts: the analysis of samples for suitable surface properties, the generation of surface heterogeneities using such a property and the analysis of the mechanism for the used process of contrast generation. Within this doctoral thesis, a before unseen method of selective etching on silicon was discovered and investigated. Hence, the overall aim of this work was successfully achieved. • Samples containing buried p-implants inside a n-type silicon substrate were characterised with regard to various properties. Of these, the through-sample resistance showed a significant variation in accordance to the buried implants also through a homogeneous epitaxial layer. • Various methods aimed at the usage of the resistance variation in order to generate a surface heterogeneity through electrodeposition failed to enable a suitable process. Instead, another method was found, which enables the replication of the implant structure via selective etching. This novel process enables the lithography free patterning of the substrates through a simple alkaline etch process performed under illumination. This results in a surface heterogeneity as an alteration of the sample topography combined with a material contrast due to the formation of an in-situ SiO2 etch mask. This material variation can also be used for the selective deposition of polymers, enabling further processing of the etched samples. • For this new method, named Light Induced Selective Etching (LISE), a mechanism underlying the selectivity was proposed and through a number of experiments. In essence, the illumination during the etching process produces a flux of photogenerated electrons directed from the buried implants toward the surface, which increase the negative surface charge in the areas above these implants. The locally increased surface charge causes a local protection of the native silicon oxide layer against the alkaline etching, leading to the structuring of the substrate. In essence, this novel method allows for the previously unreported self-adjusted structuring of silicon based on deeply buried implant structures. In general, even the characterisation of such implant structures is difficult, whereas this method allows for structuring with regard to such buried structures with a very simple setup of only an etchant solution and a suitable light source. With regard to the introduction and motivation of this thesis, this process can possibly be applied for the intended purpose of creating a self-aligned resist in order to replace repeating lithography steps. This is the case in particular in combination with polymer deposition, as shown in the last part of the results. Certain limitations, such as the resolution limit and dimensional size increase exist, but can be circumvented by appropriate device design and further optimisation of the process parameters. Furthermore, the LISE process appears applicable for the manufacturing of MEMS and MOEMS devices, as the typical feature sizes in these cases fit well to the achieved resolution of the LISE process. For devices needing a certain implant structure in combination with a corresponding topography, the new method allows for the elimination of at least one lithography step, including the necessary substeps such as alignment and measurement. Accordingly, LISE has the potential of simplifying the manufacturing process, enabling better and cheaper devices

Gated lateral silicon p-i-n junction photodiodes

Research in silicon photonics has recently seen a significant push to develop complete silicon-based optical components for optical communications. Silicon has shown its potential to overcome the bandwidth limitations of microprocessor interconnect, whereas, the silicon platform has already displayed the benefits of low manufacturing costs and CMOS compatibility. The work on “gated lateral silicon p-i-n junction photodiodes” has demonstrated the silicon potential, to detect optical radiations, compatibility to standard CMOS process flow and tuneable spectral response. The lateral structure of gated p-i-n junction photodiodes contributes to high responsivity to short wavelength radiations in these single and dual gate devices. The final objective of this work was to develop high responsivity, CMOS-compatible silicon photodiodes, where the spectral response can be modulated. The lateral p-i-n junction architecture led to high responsivity values, whereas, the MOS gate structure became the basis for tuneable spectral response. The MOS gate structure, made the devices appear as a transistor to the surrounding circuitry and the gate structure in dual gate devices can be used to modulate the spectral response of the device. Single gate devices showed higher responsivity values and comparatively high blue and ultraviolet (UV) response as compared to conventional photodiodes. Surface depletion region in these devices is utilized by placing a MOS gate structure and by patterning an integrated metal grating to detect polarized light. Single and dual gate devices with two variations were fabricated to characterise the device response. Novel lateral architecture of p-i-n junction photodiodes provides a surface depletion region. It is generally anticipated that photodetectors with surface depletion region might produce higher noise. In these devices the surface depletion region has a lateral continuation of gate dielectric which acts as a passivation layer and thus considerably reduced the noise. Physical device modelling studies were performed to verify the experimentally obtained results, which are provided in the relevant measurement chapters. In these devices the speed of operation is a compromise over the high responsivity, CMOS compatibility and tuneable spectral response

Through Silicon Via Field-Effect Transistor with Hafnia-based Ferroelectrics and the Doping of Silicon by Gallium Implantation Utilizing a Focused Ion Beam System

3-dimensional integration has become a standard to further increase the transistor density and to enhance the integrated functionality in microchips. Integrated circuits are stacked on top of each other and copper-filled through-silicon VIAs (TSVs) are the industry-accepted choice for their vertical electrical connection. The aim of this work is to functionalize the TSVs by implementing vertical field-effect transistors inside the via holes. The front and back sides of 200 ... 300 µm thin silicon wafers were doped to create the source/drain regions of n- and p-FETs. The TSVFETs showed very stable saturation currents and on/off current ratios of about 10^6 (n-TSVFET) and 10^3 (p-TSVFET) for a gate voltage magnitude of 4V. The use of hafnium zirconium oxide on a thin SiO_2 interface layer as gate dielectric material in a p-TSVFET, enabled the implementation of a charge trapping memory inside the TSVs, showing a memory window of about 1V. This allows the non-volatile storage of the transistor on/off state. In addition, the demonstration of the use of gallium as the source/drain dopant in planar p-FET test structures (ion implanted from a focused ion beam tool) paves the way for maskless doping and for a process flow with a low thermal budget. It was shown, that ion implanted gallium can be activated and annealed at relatively low temperatures of 500 °C ... 700 °C.:Abstract / Kurzzusammenfassung Danksagung Index I List of Figures III List of Tables X List of Symbols XI List of Abbreviations XV 1 Introduction 1 2 Fundamentals 5 2.1 Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) 5 2.1.1 Historical Development - Technological Advancements 7 2.1.2 Field-Effect Transistors in Semiconductor Memories 10 2.2 3D Integration and the Use of TSVs (Through Silicon VIAs) 16 2.3 Doping of Silicon 19 2.3.1 Doping by Thermal Diffusion 20 2.3.2 Doping by Ion Implantation 22 3 Electrical Characterization 24 3.1 Resistivity Measurements 24 3.1.1 Resistance Determination by Four-Point Probes Measurement 24 3.1.2 Contact Resistivity 27 3.1.3 Doping Concentration 32 3.2 C-V Measurements 35 3.2.1 Fundamentals of MIS C-V Measurements 35 3.2.2 Interpretation of C-V Measurements 37 3.3 Transistor Measurements 41 3.3.1 Output Characteristics (I_D-V_D) 41 3.3.2 Transfer Characteristics (I_D-V_G) 42 4 TSV Transistor 45 4.1 Idea and Motivation 45 4.2 Design and Layout of the TSV Transistor 47 4.2.1 Design of the TSV Transistor Structures 47 4.2.2 Test Structures for Planar FETs 48 5 Variations in the Integration Scheme of the TSV Transistor 51 5.1 Doping by Diffusion from Thin Films 51 5.1.1 Determination of Doping Profiles 52 5.1.2 n- and p- TSVFETs Doped Manufactures by the Use of the Diffusion Technique 59 5.2 Ferroelectric Hafnium-Zirconium-Oxide (HZO) in the Gate Stack 81 5.2.1 Planar ferroelectric p-MOSFETs Doped by Thermal Diffusion 82 5.2.2 p-TSVFETs with Hafnium-Zirconium-Oxide Metal Gate 90 5.3 Doping by Ion Implantation of Gallium with a Focused Ion Beam (FIB) Tool 96 5.3.1 Ga doped Si Diodes 97 5.3.2 Planar p-MOSFETs Doped by Ga Implantation 108 5.3.3 Proposal for a parallel integration of Cu TSVs and p-TSVFETs 117 6 Summary and Outlook 120 Bibliography XVIII A Appendix XXXVI A.1 Resistivity and Dopant Density XXXVI A.2 Mask set for the TSVFET XXXVII A.3 Mask Design of the Planar Test Structures XXXVIII Curriculum Vitae XXXIX List of Scientific Publications XL

The Journal of Microelectronic Research 2008

https://scholarworks.rit.edu/meec_archive/1016/thumbnail.jp

Report / Institute für Physik

The 2014 Report of the Physics Institutes of the Universität Leipzig presents a hopefully interesting overview of our research activities in the past year. It is also testimony of our scientific interaction with colleagues and partners worldwide. We are grateful to our guests for enriching our academic year with their contributions in the colloquium and within the work groups. The open full professorship in the Institute for Experimental Physics I has been filled with an outstanding candidate. We could attract Prof. Ralf Seidel from the University of Münster. He is an expert in molecular biophysics that complements the existing strength in cellular biophysics. Prof. Hollands could fill all positions of his ERC Starting Grant, so that the work on the project \"Quantum Fields and Curvature – Novel Constructive Approach via Operator Product Expansion\" is now running at full pace. Within the Horizon 2020 project LOMID \"Large Cost-effective OLED Microdisplays and their Applications\" (2015-2017) with eight European partners including industry the semiconductor physics group contributes with transparent oxide devices. A joint laboratory for single ion implantation was established between the Leibniz-Institute for Surface Modification (IOM) and the university under the guidance of Profs. Rauschenbach and Meijer. The EU IRSES Network DIONICOS \"Dynamics of and in Complex Systems\", a consortium of 6 European and 12 non-European partners, including sites in England, France and Germany as well as in Russia, Ukraine, India, the United States and Venezuela, started in February 2014. In the next four years the Leipzig node headed by Prof. Janke will profit from the numerous international contacts this network provides. With a joint project, Prof. Kroy and Prof. Cichos participate in the newly established priority research programme SPP 1726 \"Microswimmers\", which started with a kick-off workshop in October 2014. In 2014 the International Graduate College \"Statistical Physics of Complex Systems\" run by the computational physics group has commenced its third 3-years granting period funded by Deutsch-Französische Hochschule (DFH-UFA). Besides the main partner Université de Lorraine in Nancy, France, now also Coventry University, UK, and the Institute for Condensed Matter Physis of the National Academy of Sciences of Ukraine in Lviv, Ukraine, participate as associated partners. During the last week of September the TCO2014 conference \"Transparent Conductive Oxides – Fundamentals and Applications\" took place in honor of the 100th anniversary of the death of Prof. Dr. KarlW. Bädeker. In 1907 Karl Bädeker had discovered transparent conductive materials and oxides in Leipzig. About a hundred participants joined for many invited talks from international experts, intense discussion and new cooperations. At the end of November the by now traditional 15th nternational Workshop on Recent Developments in Computational Physics \"CompPhys14\" organized by Prof. Janke took place in Leipzig. Around 60 scientists from over 10 different countries exchanged ideas and discussed recent progress in several fields of computational physics. Work has successfully continued in the Centers of Excellence (Sonderforschungsbereiche) SFB 762 \"Functionality ofOxide Interfaces\" and SFB TRR 102 \"Polymers under Multiple Constraints: Restricted and Controlled Molecular Order and Mobility\" (just renewed for 2015-2019). Our activities and success are only possible with the generous support fromvarious funding agencies for which we are very grateful and which is individually acknowledged in the brief reports

Transmission of mitochondrial DNA following assisted reproduction and nuclear transfer

Review of the articleMitochondria are the organelles responsible for producing the majority of a cell's ATP and also play an essential role in gamete maturation and embryo development. ATP production within the mitochondria is dependent on proteins encoded by both the nuclear and the mitochondrial genomes, therefore co-ordination between the two genomes is vital for cell survival. To assist with this co-ordination, cells normally contain only one type of mitochondrial DNA (mtDNA) termed homoplasmy. Occasionally, however, two or more types of mtDNA are present termed heteroplasmy. This can result from a combination of mutant and wild-type mtDNA molecules or from a combination of wild-type mtDNA variants. As heteroplasmy can result in mitochondrial disease, various mechanisms exist in the natural fertilization process to ensure the maternal-only transmission of mtDNA and the maintenance of homoplasmy in future generations. However, there is now an increasing use of invasive oocyte reconstruction protocols, which tend to bypass mechanisms for the maintenance of homoplasmy, potentially resulting in the transmission of either form of mtDNA heteroplasmy. Indeed, heteroplasmy caused by combinations of wild-type variants has been reported following cytoplasmic transfer (CT) in the human and following nuclear transfer (NT) in various animal species. Other techniques, such as germinal vesicle transfer and pronuclei transfer, have been proposed as methods of preventing transmission of mitochondrial diseases to future generations. However, resulting embryos and offspring may contain mtDNA heteroplasmy, which itself could result in mitochondrial disease. It is therefore essential that uniparental transmission of mtDNA is ensured before these techniques are used therapeutically

The Journal of Microelectronic Research 2009

https://scholarworks.rit.edu/meec_archive/1017/thumbnail.jp

Superlattice Nanowire Pattern Transfer (SNAP)

During the past 15 years or so, nanowires (NWs) have emerged as a new and distinct class of materials. Their novel structural and physical properties separate them from wires that can be prepared using the standard methods for manufacturing electronics. NW-based applications that range from traditional electronic devices (logic and memory) to novel biomolecular and chemical sensors, thermoelectric materials, and optoelectronic devices, all have appeared during the past few years. From a fundamental perspective, NWs provide a route toward the investigation of new physics in confined dimensions. Perhaps the most familiar fabrication method is the vapor−liquid−solid (VLS) growth technique, which produces semiconductor nanowires as bulk materials. However, other fabrication methods exist and have their own advantages. In this Account, I review a particular class of NWs produced by an alternative method called superlattice nanowire pattern transfer (SNAP). The SNAP method is distinct from other nanowire preparation methods in several ways. It can produce large NW arrays from virtually any thin-film material, including metals, insulators, and semiconductors. The dimensions of the NWs can be controlled with near-atomic precision, and NW widths and spacings can be as small as a few nanometers. In addition, SNAP is almost fully compatible with more traditional methods for manufacturing electronics. The motivation behind the development of SNAP was to have a general nanofabrication method for preparing electronics-grade circuitry, but one that would operate at macromolecular dimensions and with access to a broad materials set. Thus, electronics applications, including novel demultiplexing architectures; large-scale, ultrahigh-density memory circuits; and complementary symmetry nanowire logic circuits, have served as drivers for developing various aspects of the SNAP method. Some of that work is reviewed here. As the SNAP method has evolved into a robust nanofabrication method, it has become an enabling tool for the investigation of new physics. In particular, the application of SNAP toward understanding heat transport in low-dimensional systems is discussed. This work has led to the surprising discovery that Si NWs can serve as highly efficient thermoelectric materials. Finally, we turn toward the application of SNAP to the investigation of quasi-one-dimensional (quasi-1D) superconducting physics in extremely high aspect ratio Nb NWs