Abstract
Interest in resistance switching is currently growing apace. The promise of novel high-density, low-power, high-speed nonvolatile memory devices is appealing enough, but beyond that there are exciting future possibilities for applications in hardware acceleration for machine learning and artificial intelligence, and for neuromorphic computing. A very wide range of material systems exhibit resistance switching, a number of which-primarily transition metal oxides-are currently being investigated as complementary metal-oxide-semiconductor (CMOS)-compatible technologies. Here, the case is made for silicon oxide, perhaps the most CMOS-compatible dielectric, yet one that has had comparatively little attention as a resistance-switching material. Herein, a taxonomy of switching mechanisms in silicon oxide is presented, and the current state of the art in modeling, understanding fundamental switching mechanisms, and exciting device applications is summarized. In conclusion, silicon oxide is an excellent choice for resistance-switching technologies, offering a number of compelling advantages over competing material systems.
Highlights
Silicon oxide (SiOx) has long played a vital role in semiconductor microelectronics
The dominance of silicon as the universal semiconductor has been driven in no small part by its ability to form readily a stable, wide-bandgap insulating oxide (SiO2) with a near-perfect interface with Si, which enables the fabrication of field effect transistors (FETs) monolithically integrated onto silicon substrates
Redox-based Resistive Random Access Memory (ReRAM), which we will be mostly concerned with in this review, represents a subclass of broader Resistive RAM (RRAM)[8], in which resistance switching is governed by nanoionic redox processes and by correlation between electron and ion dynamics
Summary
Silicon oxide (SiOx) has long played a vital role in semiconductor microelectronics. The dominance of silicon as the universal semiconductor has been driven in no small part by its ability to form readily a stable, wide-bandgap insulating oxide (SiO2) with a near-perfect interface with Si, which enables the fabrication of field effect transistors (FETs) monolithically integrated onto silicon substrates. With application of suitable voltage bias, it is possible to induce soft breakdown, where the cell exhibits much higher electrical conduction post voltage stimulus This process, with respect to ReRAM operation, is termed electroforming. Extrinsic resistance switching in silicon oxide, more commonly known as Electrochemical Metallization (ECM) or Conductive Bridge (CBRAM), is shown schematically in Figure 1 (upper left panel) This type of switching is governed by the electrodeposition of mobile metallic ions (typically Ag or Cu) from an electrochemically active electrode onto a passive (electrochemically stable) electrode and formation of conductive filaments bridging the oxide under application of a positive electrical bias (with respect to the electrochemically active electrode); a bias of the opposite polarity (negative electrical bias) triggers the dissolution of the conductive filament by removing metal ions from the oxide. Air stable switching is typically seen in moderately thick oxides (30-40nm), it can be observed in even thinner, chemically produced oxides[31,40] if the microstructure is appropriate
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