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Über dieses Buch

This book focuses on the experimental and theoretical aspects of the time-dependent breakdown of advanced dielectric films used in gigascale electronics. Coverage includes the most important failure mechanisms for thin low-k films, new and established experimental techniques, recent advances in the area of dielectric failure, and advanced simulations/models to resolve and predict dielectric breakdown, all of which are of considerable importance for engineers and scientists working on developing and integrating present and future chip architectures. The book is specifically designed to aid scientists in assessing the reliability and robustness of electronic systems employing low-k dielectric materials such as nano-porous films. Similarly, the models presented here will help to improve current methodologies for estimating the failure of gigascale electronics at device operating conditions from accelerated lab test conditions. Numerous graphs, tables, and illustrations are included to facilitate understanding of the topics. Readers will be able to understand dielectric breakdown in thin films along with the main failure modes and characterization techniques. In addition, they will gain expertise on conventional as well as new field acceleration test models for predicting long term dielectric degradation.

Inhaltsverzeichnis

Frontmatter

Chapter 1. Introduction

Abstract
Dielectric breakdown in a solid film is characterized as the irreversible loss of the material’s local dielectric insulation property. Failure originates when the dielectric is subjected to electrical stress beyond a critical point. In general, dielectric breakdown mechanisms in amorphous films can be categorized as either intrinsic or extrinsic in nature (He and Sun, High-k gate dielectrics for CMOS technology, 2012, p.166). Intrinsic failure corresponds to damage caused by the transport of electrons across the dielectric matrix, which eventually degrades the material and causes it to exceed its innate limit. Extrinsic failure corresponds to a breakdown accelerated by flaws stemming from the transport of foreign species across the dielectric film. Extrinsic failure occurs on a much faster timescale than intrinsic breakdown. Some of the most common causes of extrinsic failure are metal atoms, ions, and moisture. These foreign species are the result of manufacturing process steps and instabilities in metal/dielectric interfaces (He and Lu, Metal-Dielectric Interfaces in Gigascale Electronics Thermal and Electrical Stability, 2012, p.127).
Juan Pablo Borja, Toh-Ming Lu, Joel Plawsky

Chapter 2. General Theories

Abstract
In this section, we present a general survey of the theories and models that have been used to describe dielectric breakdown in amorphous thin films. The fundamental concepts for each theory are presented as initially proposed by the authors. Some of the models explained in this section include the E, 1/E, \( \sqrt{E} \), power-law, and the metal-catalyzed failure model. Commentary on the limitations for each model is provided. In the latter part of this chapter, we will discuss the most recent models for describing reliability trends in contemporary interconnect structures that employ low-κ nano-porous films. A general comparison between model predictions at low field is presented.
Juan Pablo Borja, Toh-Ming Lu, Joel Plawsky

Chapter 3. Measurement Tools and Test Structures

Abstract
This section provides a brief summary of the instruments, data acquisition processes, and test vehicles now used for studying dielectric breakdown. The range of instruments includes both bench-top and large throughput systems. Bench-top systems are conventionally used to gather information about fundamental material and device properties, while large throughput systems provide significant advantages for gathering statistically meaningful data on device properties and performance and on production capabilities. Test structures described in this section include simple planar capacitors, comb–comb, comb–serpentine, and new p-cap devices. The inherent design of each test structure will be shown to be appropriate for understanding certain fundamental aspects of dielectric failure.
Juan Pablo Borja, Toh-Ming Lu, Joel Plawsky

Chapter 4. Experimental Techniques

Abstract
Various tests to characterize dielectric properties and breakdown will be presented in this section. The fundamental concepts behind each test are explained along with potential limitations. The chapter is divided into three parts: breakdown assessment, material characterization, and interfacial/bulk composition analysis. Tests presented in this section for breakdown will include constant bias, constant current, ramped voltage, ramped current, and bipolar field. These tests provide insight into dielectric reliability and failure mode. Material and device characterization tests covered here will include capacitance–voltage spectroscopy and triangular voltage spectroscopy. These tests can help to identify important charged species inside the dielectric and their impact on failure mechanisms. Secondary ion mass spectrometry and its application to resolving interfacial/bulk dielectric properties will also be explained.
Juan Pablo Borja, Toh-Ming Lu, Joel Plawsky

Chapter 5. Breakdown Experiments

Abstract
In this section a set of dynamic applied field experiments are presented. We designed these experiments to study intrinsic and metal-catalyzed failure. Techniques such as ramped voltage sweeps and bipolar applied field tests are utilized to characterize fundamental aspects of breakdown in thin low-κ films. We studied intrinsic breakdown using inert (Au) and self-limiting electrodes (Al). Metal-catalyzed failure was investigated by employing reactive electrodes such as Cu and Ag, and we present a model for the transport of ionic species and their impact on dielectric failure. The motion of ions is correlated with field form, polarity, and magnitude. This chapter concludes with a brief discussion of the impact of plasma treatments and moisture on dielectric breakdown and its fundamental failure mechanisms.
Juan Pablo Borja, Toh-Ming Lu, Joel Plawsky

Chapter 6. Kinetics of Charge Carrier Confinement in Thin Dielectrics

Abstract
The trapping of charge carriers in thin dielectric films is discussed in the present section. Mechanisms affecting electron confinement are studied in order to gain insight into the interplay between the various charged species contributing to dielectric failure (i.e., electrons, traps, and ions). A novel detection method for identifying ion drift in interconnect devices is presented. This technique is based on the change in charge fluence as a result of ionic drift during BTS. Leakage current relaxation is described as originating from the trapping of charge carriers into defects (i.e., traps and ions). A model is proposed for describing the kinetics of charge trapping at very early stages of field and temperature stress. This section concludes with a mathematical representation of electron trapping that will serve as the premise for the theory of dielectric breakdown in nano-porous films.
Juan Pablo Borja, Toh-Ming Lu, Joel Plawsky

Chapter 7. Theory of Dielectric Breakdown in Nano-Porous Thin Films

Abstract
Dielectric breakdown and its relation to computer chip components and interconnects have been covered in the previous chapters. Multiple theories were presented to describe mechanisms that can result in failure. In addition, it was discussed how such mechanisms can be affected by material properties, fabrication steps, and type of stress. Complex concepts have been reduced to empirical expression and fitting parameters. These methodologies have been shown to replicate experimental data in high-field and high-temperature conditions. However, a great deal of uncertainty remains about whether they can accurately and cohesively describe breakdown behavior and values in device operating conditions. The present chapter will pursue a higher level of understanding about dielectric failure and the fundamental mechanisms that control it. The concepts discussed in previous chapters as well as some novel ideas have been merged to generate a comprehensive physical description of the phenomena. This physical description has been translated into mathematical terms by using transport equations for major species participating in dielectric failure. Our intent is to generate a framework for general dielectric breakdown in nano-porous thin films that can be applied to multiple systems.
Juan Pablo Borja, Toh-Ming Lu, Joel Plawsky

Chapter 8. Dielectric Breakdown in Copper Interconnects

Abstract
The theory introduced in Chap. 7 was primarily applied to scenarios involving intrinsic failure. The model was used to describe the dynamics of dielectric breakdown as caused by the transport of charge carriers and the formation of traps. In this chapter, the role of Cu and ionic species on catalyzing dielectric failure is explored and integrated into the theory. Experimental evidence demonstrating the presence and transport of ions is discussed. Ultimately, a complete depiction of dielectric breakdown as caused by the complex interplay between charged species is presented.
Juan Pablo Borja, Toh-Ming Lu, Joel Plawsky

Chapter 9. Reconsidering Conventional Field Acceleration Models

Abstract
The theory developed in the previous chapters can be useful for understanding the role of charge species in dielectric breakdown. However, a more attractive feature of the model developed in Chap. 7 rests on its ability to make predictions on dielectric breakdown at low fields from data collected at high fields without needing to use empirical field acceleration formulas. In this chapter, we discuss estimates from the model and compare these with predictions from conventional field acceleration fits. The objective is to establish which empirical expression replicates this complex phenomenon the best. In essence, fundamental concepts ought to drive the predictions, not the other way around.
Juan Pablo Borja, Toh-Ming Lu, Joel Plawsky
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