Dielectric Films for Advanced Microelectronics

The dielectric properties of silicon dioxide (SiO2), such as high resistivity and excellent dielectric strength, have aided the evolution of microelectronics during the past 40 years. Silica films have been successfully used over this period for both gate and interconnect applications in ultra large-scale integration (ULSI) devices. Dielectric films for gate applications need to have a higher dielectric constant, while interconnect dielectric materials need to have a lower dielectric constant, compared with SiO2. In order to maintain the high drive current and gate capacitance required of scaled MOSFETs (metal-oxide-silicon field effect transistors), SiO2 gate dielectrics have decreased in thickness to less than 2 nm today, with a continued effort to shrink to the thickness below 1 nm. However, SiO2 layers thinner than 1.2 nm do not have the insulating properties required of a gate dielectric and ultrathin SiO2 gate dielectrics give rise to a number of problems, such as high gate leakage current and reliability degradation. Therefore, alternative gate dielectric materials are required. SiO2, having been the universal dielectric material for both gate and interlayer dielectric (ILD) applications for many years, must be replaced by materials with a higher dielectric constant for the gate applications and a reduced dielectric constant for interconnect applications. Replacements for silicon dioxide, such as HfO2, ZrO2, and Al2O3, for introduction as high-k dielectrics (described in the central section of the book), have material properties that are quite different compared with those of traditional dense SiO2 and these differences create many technological challenges that are the subject of intensive research. In addition, not only the development of new gate materials but also re-engineering of many technological processes is needed. For example, in the case of low-k materials (discussed in the first section of the book), active species formed during different technological processes diffuse into the pores and create severe damage. All these problems have been stimulating the development of new technological approaches, which will be dealt with in this book. This book presents an in-depth overview of novel developments made by scientific leaders in the microelectronics community. It covers a broad range of related topics, from physical principles to design, fabrication, characterization, and application of novel dielectric films. This book is intended for postgraduate level students, PhD students and industrial researchers, to enable them to gain insight into this important area of research.