Preface

Solid-state and Microelectronics technology attempts to fill the gap between a general solid-state physics book and real-life application by providing detailed explanations of the electronic, vibrational, transport and optical properties of semiconductors. The approach is physical and instinctive rather than prescribed. The enhanced application of semiconductors to the different electronic industries helped to explore various aspects of microelectronics technology which was made possible with the availability of solid-state devices known for their versatile applications.

This technological advancement also demanded the proper understanding of new device physics as the properties of materials alters significantly at this reduced dimension. These dimensions are comparable to the electron wavelength of motion, and hence the device characteristics are governed by the confinement of the electron wave function, commonly referred to as the quantum confinement effect.

For the purpose of commercialization, integration of different electronic components on the same platform is very much essential to develop an integrated device using a standard IC fabrication process. Thus, low power, low cost, highly sensitive and miniaturized electronic system on chip using silicon is possible. This book consists of thirteen chapters.

The most apparent package for PART I consists of chapter 1 to 6, and PART II consists of chapter 7 to 12. The goal was to give a brief idea about the microfabrication technology needed to fabricate solid-state devices through part II.

Chapter 1 provides an introduction to Semiconductor Physics fundamentals. Basic quantum mechanics have been introduced in order to explain the fundamental properties of semiconducting materials. In this context, Sommerfeld’s free electron theory has been considered. Although this model corroborates with a few experimental observations, but can’t differentiate between semiconductors, insulators and metal. Then Kronig – Penney, who successfully explains the deviation on the basis of the band concept, has been considered. Followed by Kronig – Penney model, Bloch’s theory has been introduced, and it well explains the origin of conduction and valence bands. From this concept, different types of semiconducting materials, e.g., direct and indirect band gap semiconductors, n- and p-type semiconductors, etc., have emerged. Here, properties of charge carriers, such as their charge, effective mass, etc., have also been discussed. Knowing these parameters, conductivity expression and related scattering phenomena influencing conductivity have been briefly elaborated.

Chapter 2 briefly discusses the fundamentals of the p – n junction, the electric field across the junction, equilibrium carrier concentration on each side, etc. Expression of built-in potential in terms of carrier density has been derived. Magnitudes of the current under zero, forward, and reverse biased conditions have been calculated. Unlike a resistor, p – n junction corresponds to static, dynamic and average ac resistance, and they have been briefly discussed here along with protocol to examine their values. These p – n junctions also exhibit capacitance, namely transition capacitance and diffusion capacitance. Herein, these parameters and their relevance in terms of current-voltage characteristics of p – n junction and applicational aspects, have been elaborated.

Chapter 3 discusses metal-semiconductor contacts. Schottky and Ohmic contact with a detailed band diagram has been presented. I-V characteristics are also given to interpret the contact behaviour.

Chapter 4 deals with JFET and its I-V characteristics expressed in a detailed manner with necessary equations. JFET parameters are another important factor to understand the characteristics of it which have been mentioned. Small signal model of JFET illustrated in a very lucid manner.

Chapter 5 discusses the fabrication of MOSFET and its principle operations based on the concept of metal-oxide-semiconductor technology. Further the discussion is focused on the details mathematical modelling of MOS capacitors, device characteristics and the process of channel length modulation and its application. The conversation is continuing on the concept of CMOS technology and its combination with the transistor – the BiCMOS technology.

Chapter 6 discusses advanced semiconductor devices where Semiconductor resistivity can be changed by the incorporation of an electric or magnetic field, by revelation to light or heat, or by mechanical distortion. The doping of silicon significantly modulates the characteristics of semiconductors to have different types of devices like LED, Tunnel diode, Solar cells and many more, which have been discussed in this section.

Chapter 7 introduces silicon as an electronic material for microelectronic device fabrication. It discusses, in-depth, the various aspects of crystalline silicon, wafer manufacturing and their identification techniques. Finally, the various steps involved in a microfabrication process are also discussed. From this chapter, the readers are expected to learn how to process a silicon wafer successfully and proceed with customized device fabrication.

Chapter 8 introduces the readers to the oxidation process focusing on silicon. It establishes the importance of oxidation in a silicon process and discusses in depth the thermal oxidation process and its growth mechanism. Towards the end, a detailed discussion of the oxide film characterization and its properties has been provided. After reading this chapter, the readers are expected to have a sound knowledge of the oxidation process as a whole and its significance in the silicon processing industry.

Chapter 9 introduces the readers to the diffusion process which is used for doping intrinsic silicon. It discusses in depth Fick’s Law of diffusion and the different types of diffusion that may be observed. Towards the later part of the chapter, the process of diffusion in semiconductors is discussed in detail, explaining the diffusion-assisted doping process commonly employed for semiconductors, especially silicon.

Chapter 10 discusses in depth the ion implantation process of silicon processing technology. The chapter gives an in-depth insight into various aspects of the ion implantation process and ion-implanted silicon systems commonly encountered in a silicon process. The readers, after reading this chapter, will have a sound understanding of the ion implantation process and its various aspects.

Chapter 11 represents the concept of MEMS technology. Fabrication technique, including bulk and surface micromachining with CMOS compatibility issues, has been elaborated. The most important etch-stop techniques have also been elaborated in this chapter.

Chapter 12 provides the idea about photo-resist, and its properties. It also narrates some advanced lithographic techniques, including the most common one, optical lithography.