The present work investigates the technology development of state-of-the-art SiGe and SiGeC Heterojunction Bipolar Transistors (HBT) by means of technology computer aided design (TCAD). The objective of this work is to obtain an advanced HBT very close to the real device not only in its process fabrication steps, but also in its physical behavior, geometric architecture, and electrical results. This investigation may lead to achieve the best electrical performances for the devices studied, in particular a maximum operating frequency of 500 GHz. The results of this work should help to obtain more physical and realistic simulations, a better understanding of charge transport, and to facilitate the development and optimization of SiGe and SiGeC HBT devices.The TCAD simulation kits for SiGe/SiGeC HBTs developed during our work have been carried out in the framework of the STMicroelectronics bipolar technology evolution. In order to achieve accurate simulations we have used, developed, calibrated and implemented adequate process models, physical models and extraction methodologies. To our knowledge, this work is the first approach developed for SiGe/SiGeC HBTs which takes into account the impact of the strain, and of the germanium and carbon content in the base, for both: process and electrical simulations.In this work we will work with the successive evolutions of B3T, B4T and B5T technologies. For each new device fMAX improves of 100 GHz, thus the technology B3T matches to 300 GHz, B4T and B5T to 400 and 500 GHz, respectively.Chapter one introduces the SiGe SiGeC heterojunction bipolar technologies and their operating principles. This chapter deals also with the high frequency AC transistor operation, the extraction methods for fMAX and the carrier transport in extremely scaled HBTs.Chapter two analyzes the physical models adapted to SiGeC strained alloys used in this work and the electrical simulation of HBT devices. This is also an important work of synthesis leading to the selection, implementation and development of dedicated models for SiGeC HBT simulation.Chapter three describes the B3T TCAD simulation platform developed to obtain an advanced HBT very close to the real device. In this chapter the process fabrication of the B3T technology is described together with the methodology developed to simulate advanced HBT SiGeC devices by means of realistic TCAD simulations.Chapter four describes the HBT architectures developed during this work. We will propose low-cost structures with less demanding performance requirements and highly performing structures but with a higher cost of production. The B4T architecture which has been manufactured in clean-room is deeply studied in this chapter. The impact of the main fabrication steps is analyzed in order to find the keys process parameters to increase fMAX without degrading other important electrical characteristics. At the end of this chapter the results obtained is used to elaborate a TCAD simulation platform taking into account the best trade-off of the different key process parameters to obtain a SiGeC HBT working at 500 GHz of fMAX.

Heteroepitaxial SiGeC layers have attracted immenseattention as a material for high frequency devices duringrecent years. The unique properties of integrating carbon inSiGe are the additional freedom for strain and bandgapengineering as well as allowing more aggressive device designdue to the potential for increased thermal budget duringprocessing. This work presents different issues on epitaxialgrowth, defect density, dopant incorporation and electricalproperties of SiGeC epitaxial layers, intended for variousdevice applications. Non-selective and selective epitaxial growth of Si1-x-yGexCy(0≤x≤30, ≤y≤0.02) layershave been optimized by using high-resolution x-ray reciprocallattice mapping. The incorporation of carbon into the SiGematrix was shown to be strongly sensitive to the growthparameters. As a consequence, a much smaller epitaxial processwindow compared to SiGe epitaxy was obtained. Differentsolutions to decrease the substrate pattern dependency (loadingeffect) of SiGeC growth have also been proposed. The key pointin these methods is based on reduction of surface migration ofthe adsorbed species on the oxide. In non-selective epitaxy,this was achieved by introducing a thin silicon polycrystallineseed layer on the oxide. The thickness of this seed layer had acrucial role on both the global and local loading effect, andon the epitaxial quality. Meanwhile, in selective epitaxy,polycrystalline stripes introduced around the oxide openingsact as migration barriers and reduce the loading effecteffectively. Chemical mechanical polishing (CMP) was performedto remove the polycrystalline stripes on the oxide. Incorporation and electrical properties of boron-doped Si1-x-yGexCylayers (x=0.23 and 0.28 with y=0 and 0.005) with aboron concentration in the range of 3x1018-1x1021atoms/cm3 have also been investigated. In SiGeClayers, the active boron concentration was obtained from thestrain compensation. It was also found that the boron atomshave a tendency to locate at substitutional sites morepreferentially compared to carbon. These findings led to anestimation of the Hall scattering factor of the SiGeC layers,which showed good agreement with theoretical calculations. Keywords:Silicon germanium carbon (SiGeC), Epitaxy,Chemical vapor deposition (CVD), Loading effect, Highresolution x-ray diffraction (HRXRD), Hall measurements, Atomicforce microscopy (AFM).

In der vorliegenden Arbeit wurde ausgedehntes Si_1−x Ge_x für unterschiedliche Zusammensetzungen 0 ≤ x ≤ 1 untersucht. Die Untersuchungen basierten auf der DFT, wobei das Programm QuantumATK 18.06 zum Einsatz kam. Für die Korrektur der Bandlücke wurden empirische Pseudopotential Projektor Shifts verwendet [34]. Für jede untersuchte Zusammensetzung wurden 500 zufällig generierte Konfigurationen der 64-atomigen Superzelle berechnet und statistisch ausgewertet. Nach der Optimierung der Struktur erfolgte die Auswertung der Bandlücke indem über äquivalente Pfade in der Brillouinzone gemittelt wurde. Zusätzlich wurden nach dieser Art auch kleine Anteile an C untersucht. Die Ergebnisse der Berechnungen zeigen für die Bildungsenergie der Mischstrukturen positive Werte mit einem Maximum bei mittleren Zusammensetzungen. Zur Stabilitätsuntersuchung der Legierungen wurde die Gibbs-Energie berechnet. Es ergeben sich negative Werte, was die Stabilität von SiGe bestätigt. Die berechnete Gitterkonstante der relaxierten Strukturen zeigt eine leichte Überschätzung der experimentellen Werte. Die ermittelten Bandlücken reproduzieren den Übergang von Si-artigen zu Ge-artigen Bandlücken bei x = 0.85. Die Werte der Bandlücke zeigen eine gute Übereinstimmung mit dem Experiment. Aus den statistischen Untersuchungen wird deutlich, dass sowohl Bildungsenergie als auch Bandlücke Variationen von 10 % und mehr aufweisen. Es zeigt sich dadurch ein nicht zu vernachlässigender Unterschied zwischen verschie denen Konfigurationen der Superzelle, die alle eine Legierung mit gleicher Zusammensetzung beschreiben. Wird in die Strukturen Kohlenstoff eingebracht, so vergrößern sich die Variationen mit steigendem C-Anteil. Für die betrachteten kleine C-Anteile zeigt sich eine Erhöhung der Bildungsenergie und einer Verkleinerung der Gitterkonstante und der Bandlücke. Es wird deutlich, dass bereits wenig C einen Einfluss auf die wichtigen Eigenschaften der Legierung hat und für genaue Simulationen berücksichtigt werden muss. Wie die Ergebnisse zeigen, spielt die spezielle Konfiguration von Strukturen im nm-Bereich eine wichtige Rolle. Aus diesem Grund wurde im zweiten Teil der Arbeit ein Ge-Profil nachgebildet, wie es in der Basis von HBTs vorkommt. Die Ergebnisse zeigen eine Verkleinerung der Bandlücke im SiGe-Bereich, welche im Wesentlichen durch zusätzliche Valenzzustände hervorgerufen wird. Diese Zustände sind in die z-Richtung lokalisiert. Die Leitungsbandkante bleibt von der SiGe-Region nahezu unbeeinflusst. Die Vergrößerung der SiGe-Region verkleinert die Bandlücke.:Abkürzungsverzeichnis - 5 1 Motivation - 6 2 Theoretische Grundlagen der Dichtefunktionaltheorie - 8 2.1 Quantenmechanische Vielteilchensysteme - 8 2.2 Hohenberg-Kohn-Theoreme - 9 2.3 Austausch-Korrelations-Funktional und Kohn-Sham-Gleichung - 10 3 Siliziumgermanium - 12 3.1 Kristallstruktur und Gitterkonstante - 12 3.2 Bandstruktur - 13 3.2.1 Bandstruktur von Si und Ge - 13 3.2.2 Bandlücke von SiGe - 14 3.2.3 Bandlücke von SiGe:C - 15 4 Modellierung und Methoden - 16 4.1 Modellzellen - 16 4.1.1 8-atomige konventionelle Einheitszelle - 16 4.1.2 64-atomige Superzelle - 17 4.2 Bildungsenergie und Stabilität von Legierungen - 20 4.2.1 Gibbs-Energie - 21 4.3 Faltung der Bandstruktur - 22 4.4 Korrektur und Ermittlung der Bandlücke - 24 4.4.1 Korrektur der Bandlücke - 24 4.4.2 Bestimmung der Bandlücke von ungeordneten Legierungen - 26 4.5 Berechnungsverfahren der Kristallstrukturen - 28 5 Ergebnisse und Auswertung - 29 5.1 Gitterkonstante - 29 5.2 Bildungsenergie und Änderung der Gibbs-Energie - 32 5.3 Bandlücke - 36 5.3.1 Leitungsbandminimum - 38 5.3.2 Bildungsenergie - 40 5.4 Bandstruktur - 42 6 Anwendung für die Basis von HBTs - 44 6.1 Modellierung - 45 6.2 Ergebnisse - 46 7 Zusammenfassung und Ausblick Literatur - 49 Danksagung - 53 Selbstständigkeitserklärung - 54

Epitaxially grown SiGe(C) materials have a great importance for many device applications. In these applications, (strained or relaxed) SiGe(C) layers are grown either selectively on the active areas, or on the entire wafer. Epitaxy is a sensitive step in the device processing and choosing an appropriate thermal budget is crucial to avoid the dopant out–diffusion and strain relaxation. Strain is important for bandgap engineering in (SiGe/Si) heterostructures, and to increase the mobility of the carriers. An example for the latter application is implementing SiGe as the biaxially strained channel layer or in recessed source/drain (S/D) of pMOSFETs. For this case, SiGe is grown selectively in recessed S/D regions where the Si channel region experiences uniaxial strain.The main focus of this Ph.D. thesis is on developing the first empirical model for selective epitaxial growth of SiGe using SiH2Cl2, GeH4 and HCl precursors in a reduced pressure chemical vapor deposition (RPCVD) reactor. The model describes the growth kinetics and considers the contribution of each gas precursor in the gas–phase and surface reactions. In this way, the growth rate and Ge content of the SiGe layers grown on the patterned substrates can be calculated. The gas flow and temperature distribution were simulated in the CVD reactor and the results were exerted as input parameters for the diffusion of gas molecules through gas boundaries. Fick‟s law and the Langmuir isotherm theory (in non–equilibrium case) have been applied to estimate the real flow of impinging molecules. For a patterned substrate, the interactions between the chips were calculated using an established interaction theory. Overall, a good agreement between this model and the experimental data has been presented. This work provides, for the first time, a guideline for chip manufacturers who are implementing SiGe layers in the devices.The other focus of this thesis is to implement SiGe layers or dots as a thermistor material to detect infrared radiation. The result provides a fundamental understanding of noise sources and thermal response of SiGe/Si multilayer structures. Temperature coefficient of resistance (TCR) and noise voltage have been measured for different detector prototypes in terms of pixel size and multilayer designs. The performance of such structures was studied and optimized as a function of quantum well and Si barrier thickness (or dot size), number of periods in the SiGe/Si stack, Ge content and contact resistance. Both electrical and thermal responses of such detectors were sensitive to the quality of the epitaxial layers which was evaluated by the interfacial roughness and strain amount. The strain in SiGe material was carefully controlled in the meta–stable region by implementingivcarbon in multi quantum wells (MQWs) of SiGe(C)/Si(C). A state of the art thermistor material with TCR of 4.5 %/K for 100×100 μm2 pixel area and low noise constant (K1/f) value of 4.4×10-15 is presented. The outstanding performance of these devices is due to Ni silicide contacts, smooth interfaces, and high quality of multi quantum wells (MQWs) containing high Ge content.The novel idea of generating local strain using Ge multi quantum dots structures has also been studied. Ge dots were deposited at different growth temperatures in order to tune the intermixing of Si into Ge. The structures demonstrated a noise constant of 2×10-9 and TCR of 3.44%/K for pixel area of 70×70 μm2. These structures displayed an improvement in the TCR value compared to quantum well structures; however, strain relaxation and unevenness of the multi layer structures caused low signal–to–noise ratio. In this thesis, the physical importance of different design parameters of IR detectors has been quantified by using a statistical analysis. The factorial method has been applied to evaluate design parameters for IR detection improvements. Among design parameters, increasing the Ge content of SiGe quantum wells has the most significant effect on the measured TCR value. / QC 20110405