ABSTRACT
Nonvolatile memory chips with low power consumption and low cost have attracted increasing attention due to the booming portable electronic devices market, particularly devices such as cellular phones and digital cameras. There are mainly four types of nonvolatile memory technologies: flash memory, ferro-electric random access memory, magnetic random access memory, and phase change memory. Among these, flash memory can achieve the highest chip density and possesses multi-bit per cell storage capability [1-3]. Therefore, it has become the mainstream nonvolatile
5.1 Introduction .......................................................................................................................... 167 5.1.1 Quantum Dot Nonvolatile Flash Memory ................................................................ 168 5.1.2 Band Structure of Silicon ......................................................................................... 170 5.1.3 The Band Gap in nc-Si ............................................................................................. 170
5.2 Microstructure of nc-Si/a-SiO2 Nanocomposites ................................................................. 172 5.2.1 Types of nc-Si/a-SiO2 Nanocomposites .................................................................... 172 5.2.2 Local Atomic Structure of the Amorphous SiOx Films ........................................... 174 5.2.3 Thermal Decomposition of Si Suboxides ................................................................. 177 5.2.4 The Growth Mechanism of nc-Si in a-SiOx Matrix .................................................. 180 5.2.5 Defects in nc-Si/a-SiO2 Nanocomposites ................................................................. 186
5.2.5.1 Non-Bridging Oxygen Hole Center ........................................................... 186 5.2.5.2 E′ Center .................................................................................................... 187
5.3 Electrical Characteristics of nc-Si/a-SiO2 Nanocomposites ................................................. 187 5.3.1 Coulomb Blockade Effect in Quantum Dots ............................................................ 187 5.3.2 Charge Transport in nc-Si/a-SiO2 Nanocomposites ................................................. 188
5.3.2.1 Single-Electron Device .............................................................................. 189 5.3.2.2 Current Conduction Mechanism ................................................................ 190
5.3.3 Memory Effect of nc-Si/a-SiO2 Nanocomposites ..................................................... 192 5.3.3.1 Influence of nc-Si Density on the Memory Effect ..................................... 195 5.3.3.2 Charge Trapping in nc-Si ........................................................................... 197
5.3.4 Conduction Modulation Caused by Charging and Discharging of nc-Si ................. 199 5.4 Summary ..............................................................................................................................206 Abbreviations .................................................................................................................................206 Symbols..........................................................................................................................................207 References ......................................................................................................................................208
memory technology nowadays. Furthermore, flash memory enjoys a fabrication process compatible with the current complementary metal-oxide-semiconductor (CMOS) process, and thus has become a suitable solution for embedded memory applications.
