ABSTRACT
CONTENTS 6.1 Introduction and Background.......................................................................................... 164 6.2 ESR....................................................................................................................................... 165
6.2.1 Spin-Orbit Coupling .............................................................................................. 165 6.2.2 Electron-Nuclear Hyperfine Interactions............................................................ 167 6.2.3 Quantitative Analysis (Spin Counting) ............................................................... 171 6.2.4 Spin-Dependent Recombination ........................................................................... 172
6.3 Defect Structure.................................................................................................................. 172 6.3.1 Pb Center Structure ................................................................................................. 172 6.3.2 E0 Center Structure.................................................................................................. 177
6.3.2.1 Structure of Conventional E0 Centers ..................................................... 177 6.3.2.2 Structure of Hydrogen Complexed E0 Centers ..................................... 180 6.3.2.3 Structure of E0d (or EP) Center ................................................................. 181 6.3.2.4 Structure of Other Less Well-Characterized E0
Variants Found in Thin Oxide Films...................................................... 182 6.4 Electronic Properties of Pb and E0 Centers..................................................................... 182
6.4.1 Pb0 and Pb1 Centers and the Density of States of Si=SiO2 Interface Traps...................................................................................... 182
6.4.2 Role of Pb Centers in Device Performance: The Correspondence between Pb Density and Interface Trap Density................................................ 187 6.4.2.1 Pb Centers in As-Processed Structures ................................................... 187 6.4.2.2 Pb Centers and Radiation Damage ......................................................... 187 6.4.2.3 Pb Centers Generated by High and Low Oxide Field
Electron Injection ....................................................................................... 189 6.4.2.4 Pb Centers Generated by Hot Carrier Stress
of Short-Channel MOSFETs..................................................................... 189 6.4.2.5 Pb Centers Generated in the Negative Bias
Temperature Instability ............................................................................ 190 6.4.2.6 Conclusion Regarding Pb Centers and Si=SiO2 Instabilities ............... 191
6.4.3 Roles of E0 Centers in MOS Devices .................................................................... 191 6.4.3.1 E0 Centers as Oxide Hole Traps .............................................................. 191 6.4.3.2 Neutral Paramagnetic E0 Centers ............................................................ 195 6.4.3.3 Positive but Compensated E0 Centers .................................................... 196
from Repeated Charge Cycling ............................................................... 197
6.4.3.5 Near Si=SiO2 Interface E0 Centers: Electronic Properties..................... 197 6.4.3.6 Hydrogen Complexed E0 Centers ........................................................... 199 6.4.3.7 Electronic Properties of E0d (or EP) .......................................................... 199 6.4.3.8 Role of E0 Centers in Oxide Leakage Currents ..................................... 200
6.5 Intrinsic Defects and Device Reliability: Physically Based Predictive Models and Statistical Mechanics................................................................. 202 6.5.1 Predicting Oxide Hole Trapping .......................................................................... 203 6.5.2 Predicting Interface Trap Formation.................................................................... 205
6.6 Relevance of Pb and E0 Centers to High Dielectric Constant (High-K) MOSFETs........................................................................................... 209
6.7 Summary............................................................................................................................. 209 References.................................................................................................................................... 210
Two types of silicon dangling bond centers play dominating roles in metal=oxide=silicon (MOS) device limitations. Silicon dangling bonds defects at the Si=SiO2 boundary, Pb centers dominate Si=SiO2 interface trapping. Silicon dangling bond defects called E0 centers dominate deep levels in the oxide. E0 centers can also play dominating roles in the electronic properties of the near Si=SiO2 interface dielectrics, serving as switching traps or border traps (Chapter 7). Under some circumstances, some E0 centers also act as interface traps. Analysis of a combination of electron spin resonance (ESR) and electrical measurements provides a fairly detailed understanding of the relationship between the structure and electronic properties of the Pb interface centers and E0 oxide centers. Straightforward application of the fundamental principles of statistical mechanics provides a partial explanation of the frequently noted correlation between oxide deep level defects and Si=SiO2 interface trap defects. This chapter reviews the spectroscopy, electronic properties, and device relevance of
these two families of defects. Since the understanding of the defects has come from ESR, the chapter begins with a brief introduction to this technique. It is important to note that Pb and E0 centers are not necessarily the only electrically active point defects in MOS devices. Although many studies have established the dominating roles of these two families of silicon dangling bond centers, the limited precision of ESR measurements as well as that of the relevant electrical measurements precludes concluding with certainty that either defect is entirely responsible for any device limitation. However, they are clearly responsible for the majority of the deep levels in most and perhaps all the phenomena discussed in this chapter. Furthermore, under some circumstances, it is clear that other defects are playing important roles. For example, the addition of nitrogen introduces greater complexity in plasma-nitrided gate oxides. Not surprisingly, several very different defects clearly play important roles in gate stacks based on hafnium oxide=silicon dioxide systems. Several decades of ESR [1] studies of the MOS system have established the roles of these
two families of silicon dangling bond defects in MOS device instabilities. At the Si=SiO2 boundary the Pb center family dominates interface trapping under many circumstances [2-32]. Largely due to the simplicity of the ESR spectroscopy, most earlier studies focused upon the (111) Si=SiO2 interface, where only one Pb defect, called simply Pb, appears [2-15].
