Localized characterization of charge transport and random telegraph noise at the nanoscale in HfO2 films combining scanning tunneling microscopy and multi-scale simulations

Abstract

Charge transport and Random Telegraph Noise (RTN) are measured successfully at the nanoscale on a thin polycrystalline HfO2 film using room temperature Scanning Tunneling Microscopy (STM). STM is used to scan the surface of the sample with the aim of identifying grains and grain boundaries, which show different charge transport characteristics. The defects responsible for charge transport in grains and grain boundaries are identified as positively charged oxygen vacancies by matching the localized I-V curves measured at the nanoscale with the predictions of physics-based multi-scale simulations. The estimated defect densities at grains and grain boundaries agree with earlier reports in the literature. Furthermore, the current-time traces acquired by STM at fixed bias voltages on grains show characteristic RTN fluctuations. The high spatial resolution of the STM-based RTN measurement allows us to detect fluctuations related to individual defects that typically cannot be resolved by the conventional device-level probe station measurement. The same physical framework employed to reproduce the I-V conduction characteristics at the grains also successfully simulates the RTN detected at the nanoscale. We confirm that charge trapping at defects not directly involved in charge transport can induce significant current fluctuations through Coulombic interactions with other defects in the proximity that support charge transport

Half-volt operation of IGZO thin-film transistors enabled by ultrathin HfO2 gate dielectric

“…The breakdown electric field strength is comparable to other reports about HfO2. 29,30 There are a few possible electron transport mechanisms including direct tunneling, Poole-Frenkel (P-F) emission, Fowler-Nordheim (F-N) tunneling, and Schottky emission, etc.…”

Random Telegraph Noise in Resistive Random Access Memories: Compact Modeling and Advanced Circuit Design

“…Semiconductor (CMOS) technology is increasing the importance of phenomena associated with charge trapping/detrapping at discrete defect sites (either pre-existing in the virgin device or induced by stress), such as Stress-Induced Leakage Current (SILC) [1][2][3], Bias Temperature Instability (BTI) [4][5][6], and Random Telegraph Noise (RTN) [7][8][9][10]. Particularly, RTN represents a major reliability issue for conventional devices such as MOS transistors and their evolutions (e.g.…”

“…In fact, RTN variability in RRAM can be wide enough to significantly shrink the read margin [9][10], especially in devices operated at low current levels for lowpower circuits. As RRAM technology is approaching the industrial stage, RTN mechanisms must be understood [7][8][9][10] and, possibly, mastered. This is essential to evaluate the technology potential and limitations for specific applications Francesco Maria Puglisi, Nicolò Zagni, and Paolo Pavan are with the Dipartimento di Ingegneria "Enzo Ferrari", Università di Modena e Reggio Emilia, Via Vivarelli 10/1, 41125 Modena -Italy (phone: +39-059-2056324; fax: +39-059-2056329; e-mail: francescomaria.puglisi@unimore.it).…”

Material-Inherent Noise Sources in Quantum Information Architecture

“…Even though the purity of materials has been greatly improved, many defects and impurities still exist in bulk semiconductors and oxides. Furthermore, the material’s surface and interface are significantly involved since more charge trap centers or defects tend to exist and they likely interact with charge carriers through the aforementioned capture and release [ 52 , 53 ]. Indeed, the quality of a material is revealed in its noise.…”