Abstract: Microelectronics is a central area within information technology, which is still one of the most important global technologies. It will be shown that the development of integrated circuits is based on a long and fascinating history, which is unique in modern time. Yet, the fantastic growth in semiconductor electronics is due to a unique combination of basic conceptional advances, the perfection of new materials and the development of new device principles. A brief survey of the development of microelectronics is given by not only focusing on the history of microelectronics but also taking into account materials and market aspects. Since microelectronics is an extremely complex area, a few criteria and reference points for integrated circuits are given. Thereafter, some examples are presented indicating the rapidly changing state-of-the-art. It will be shown that the development of material science within the area of microelectronics is not always driven by scientific curiosity but often by arbitrary and not always obvious preferences. After a short discussion of the performance advantages and disadvantages of germanium, silicon and III-V compound semiconductors, the SiGe heterojunction bipolar transistor is taken as an example for demonstrating a few important differences in the performance of all-silicon devices with regard to silicon-based heterojunction devices in general. In conclusion, the impact of human enterprise and research policy on the development of microelectronics is briefly discussed.
Abstract: Requirements and applications for three different scenarios in material science of microelectronics are discussed. Dimension scaling continous at the same pace (More Moore) by changing to immersion lithography and later to extreme ultraviolet lithography. The functionality of system on chip solutions will be increased by heterogeneous technologies combined with a microelectronics core ( More than Moore). Material science and physical understanding of new device principles started well in advance to judge difficulties and options. The strong links to economy are illustrated by a simple model of exponential growth.
Abstract: Heterostructure device concepts promise several advantages in micro- and optoelectronics. From the material point of view, the main obstacle to be overcome is the large lattice mismatch of silicon based heterostructures. One of the best of them, silicon germanium (SiGe) is lattice mismatched to silicon by up to 4% depending on its Ge content. Basic investigations on strained layer growth, interface properties, and deviation from equilibrium are done with SiGe / Si heterostructures. Early results are discussed in context with our recent understanding. The application focus of this review is devoted to micro- and optoelectronic devices which could be fabricated after solving or understanding the basic interface problems. This includes devices already in production, and those in emerging fields for inclusion in the next generation of integrated circuits, as well as a selection of future device concepts with high merits to be proven in experiment.
Abstract: Electrical properties of thin high-k dielectric films are influenced (or even governed) by the presence of macroscopic, microscopic and atomic-size defects. For most applications, a structurally perfect dielectric material with moderate parameters would have sufficiently low leakage and sufficiently long lifetime. But defects open new paths for carrier transport, increasing the currents by orders of magnitude, causing instabilities due to charge trapping, and promoting the formation of defects responsible for electrical breakdown events and for the failure of the film. We discuss how currents flow across the gate stack and how damage is created in the material. We also illustrate the contemporary basic knowledge on hazardous defects (including certain impurities) in high-k dielectrics using the example of a family of materials based on Pr oxides. As an example of the influence of stoichiometry on the electrical pa-rameters of the dielectric, we analyze the effect of nitrogen incorporation into ultrathin Hf silicate films.
Abstract: The development of the semiconductor industry through the CMOS technology has been possible thanks to the unique properties of the silicon and silicon dioxide material. Nevertheless the continuous scaling of the device dimension and the increase of the integration level, i.e. the capability to follow for more than 20 years the so-called Moore’s law, has been enabled not only by the Si-SiO2 system, but also by the use of other materials. The introduction of new materials every generation has allowed the integration of sub-micron and now of nanometer scale devices: different types of dielectrics, like Si3N4 or doped-SiO2, to form spacer, barrier and separation layers; conductive films, like WSi2, TiSi2, CoSi2 and NiSi2, to build low resistive gates; metals, like W, Ti, TiN, to have low resistive contacts, or like Al or Cu, to have low resistive interconnects. Although the technology development has been mainly driven by the CMOS transistor downscaling, other devices and most of all Non-Volatile Memories (NVM) have been able to evolve due to the large exploitation of these materials.
NVM today represent a large portion of the overall semiconductor market and one of the most important technologies for the mobile application segment. In particular the main technology line in the NVM field is represented by the Flash Memory. Flash memory cell is based on the concept of a MOS transistor with a Floating-Gate (FG). The writing/reading operations of the cell are possible thanks again to the unique properties of the SiO2 system, being a quasi-ideal dielectric at low electric field, enabling the Flash memory to store electrons for several years, and becoming a fair conductor at higher electric field by tunnel effect, thus allowing reaching fast programming speeds. Flash have now reached the integration of many billions of bits in one monolithic component with cell dimension of 0.008um2 at 45nm technology node, always based on the FG concept. Nevertheless Flash have technological and physical constraint that will make more difficult their further scaling, even if the scaling limits are still under debate.
In this contest there is the industrial interest for alternative technologies that exploit new materials and concepts to go beyond the Flash technology, to allow better scaling, and to enlarge the memory performance. Hence other technologies, alternative to floating gate devices, have been proposed and are under investigation. These new proposals exploit different physical mechanisms and different materials to store the information: magnetism and magnetoresistive materials (e.g. Co, Ni, Fe, Mn) in magnetic memories or MRAM; ferroelectricity and perovskite materials (e.g. PbTixZr1-xO3 or SrBi2Ta2O9 or BaxSr1-xTiO3) in ferroelectric memories or FeRAM; phase change and chalcogenide materials (e.g. Ge2Sb2Te5 or AsInSbTe) in phase-change memory or PCM. Among these alternative NVM, PCM are one of the most promising candidates to become a mainstream NVM, having the potentiality to improve the performance compared to Flash - random access time, read throughput, direct write, bit granularity, endurance - as well as to be scalable beyond Flash technology.
Abstract: Organic materials have been developed to operate as the active semiconductor in a wide range of semiconductor devices, including light-emitting diodes, LEDs, field-effect transistors, FETs, and photovoltaic diodes, PVs. The ability to process these materials as thin films over large areas makes possible a range of applications, currently in displays, as LEDs and as active matrix FET arrays, and solar cells. This article reviews developments in semiconductor physics of these materials and in their application in semiconductor devices
Abstract: Solar power is seen by many as a solution to the world’s energy problems. The earth receives 1.7x1017W from the sun compared to a total electricity generation capacity of 4.6x1012W (OECD prediction for 2010). However the average power density is low with a daytime average over the earth of 680Wm-2. This makes centralised generation problematic but distributed photoelectric generation by domestic and commercial users is a rapidly developing market. However typical commercially available modules have an energy conversion efficiency of less than 12%. Silicon cells with 24% efficiency have been produced in the lab while multi-junction tandem cells using different semiconductor materials (GaInAs, GaInP and Ge) to absorb different parts of the sun’s spectrum have reached 40%. This chapter describes some of the materials and device achievements so far and looks at possible ways in which higher efficiencies might be achieved with particular emphasis on nano-materials to use more of the solar spectrum efficiently. The possibility of using quantum slicing and multiple exciton generation to make more efficient use of high energy photons is considered and impurity band generation as a possible route to use low energy photons. One of the greatest challenges is to do this cheaply using semiconductors made from non-toxic abundant elements.