Characterization of dielectric breakdown behavior by in situ transmission electron microscopy

Dielectric breakdown (BD) is the loss of capacitance upheld by an insulating material through defect formation and charge trapping. Dielectric BD is well-studied in the framework of reliability physics for semiconductor applications, and presents itself as a viable mechanism during materials processing by electric field assisted sintering (EFAS). So far a mechanistic understanding of dielectric BD is incomplete due to the limitations in nanoscale defect characterization techniques. The recent development of novel in situ transmission electron microscopy (TEM) capabilities enables the atomic-scale characterization of dielectric BD mechanisms, which was the subject of this dissertation.;As the technology of semiconductor devices moves toward the sub-25 nm technology the electronic properties of gate oxide layers are affected eventually leading to device failure by dielectric BD. This study aimed to provide a systematic approach of simultaneous imaging and local application of electrical stress using in situ TEM by contacting an electrically biased Scanning Tunnelling Microscopy (STM) probe directly to the TEM sample. This experimental setup therefore allows a correlation of electrical signatures with defect structure evolution. In situ TEM experiments carried out with a single SiO2-based field effect transistor resulted to catastrophic failure of the dielectric layer consistent with descriptions of soft dielectric breakdown (SBD) and hard dielectric breakdown (HBD).;A variety of in situ TEM techniques was further utilized to investigate whether electric field induced dielectric breakdown may contribute to densification of metallic powder particles during EFAS. In situ heating and STM-TEM experiments were systematically applied to separately study thermal and athermal effects during densification, respectively. Nanometric metal powders used for sintering typically possess surface oxides that affect the thermodynamics and kinetics of neck formation during the initial stage of sintering. The thermal effects were found to be driven by reduction-oxidation reactions of nickel oxide with carbon. The presence of carbon promotes the removal of surface oxides at lower temperatures and, therefore, can accelerate densification. By the controlled application of electrical bias, EFAS conditions were reproduced during in situ TEM and revealed reduction of ultra-thin nickel oxide surface layers by electric field-induced dielectric breakdown. The results provide evidence for previously suggested effects of local electric field amplification at inter-particle contact areas, which, hence, triggers surface cleaning through electric field-induced dielectric breakdown.