Abstract
Resistive random access memory (RRAM) is considered an attractive candidate for next generation memory devices due to its competitive scalability, low-power operation and high switching speed. The technology however, still faces several challenges that overall prohibit its industrial translation, such as low yields, large switching variability and ultimately hard breakdown due to long-term operation or high-voltage biasing. The latter issue is of particular interest, because it ultimately leads to device failure. In this work, we have investigated the physicochemical changes that occur within RRAM devices as a consequence of soft and hard breakdown by combining full-field transmission x-ray microscopy with soft x-ray spectroscopic analysis performed on lamella samples. The high lateral resolution of this technique (down to 25 nm) allows the investigation of localized nanometric areas underneath permanent damage of the metal top electrode. Results show that devices after hard breakdown present discontinuity in the active layer, Pt inclusions and the formation of crystalline phases such as rutile, which indicates that the temperature increased locally up to 1000 K.
Highlights
Resistive random access memory (RRAM) devices, known as memristors, are typically metal–insulator–metal heterostructures, which are often based on transition-metaloxide thin films
We have investigated the physicochemical changes that occur within RRAM devices as a consequence of soft and hard breakdown by combining full-field transmission x-ray microscopy with soft x-ray spectroscopic analysis performed on lamella samples
We present an atomic-scale chemical investigation of changes that occur along a cross-section of a Pt/TiOx/Pt/Cr/Si/SiO2-based device after SB and hard breakdown (HB) switching underneath a top electrode (TE) defect using soft x-ray spectromicroscopy, a synchrotron-based technique that measures near-edge x-ray absorption fine structure (NEXAFS) spectra at high spatial resolution in a full-field transmission x-ray microscopy (TXM)
Summary
Resistive random access memory (RRAM) devices, known as memristors, are typically metal–insulator–metal heterostructures, which are often based on transition-metaloxide thin films. Between high-resistive states (HRS or OFF) and low-resistive states (LRS or ON) under appropriate biasing. Such ON/OFF cycles can be repeated several times before the device’s eventual failure [2, 3]. Very limited direct experimental evidence of the nanoscale changes that occur in the oxide film, as a consequence of switching, have been reported [7,8,9,10,11]. There is a lack of Nanotechnology 27 (2016) 345705 knowledge of changes that occur in the oxide when the device undergoes permanent failure
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