Abstract
With the continuous scaling of resistive random access memory (RRAM) devices, in-depth understanding of the physical mechanism and the material issues, particularly by directly studying integrated cells, become more and more important to further improve the device performances. In this work, HfO2-based integrated 1-transistor-1-resistor (1T1R) RRAM devices were processed in a standard 0.25 μm complementary-metal-oxide-semiconductor (CMOS) process line, using a batch atomic layer deposition (ALD) tool, which is particularly designed for mass production. We demonstrate a systematic study on TiN/Ti/HfO2/TiN/Si RRAM devices to correlate key material factors (nano-crystallites and carbon impurities) with the filament type resistive switching (RS) behaviours. The augmentation of the nano-crystallites density in the film increases the forming voltage of devices and its variation. Carbon residues in HfO2 films turn out to be an even more significant factor strongly impacting the RS behaviour. A relatively higher deposition temperature of 300 °C dramatically reduces the residual carbon concentration, thus leading to enhanced RS performances of devices, including lower power consumption, better endurance and higher reliability. Such thorough understanding on physical mechanism of RS and the correlation between material and device performances will facilitate the realization of high density and reliable embedded RRAM devices with low power consumption.
Highlights
Future mass production of related devices[9]
The electrical characteristics of 1 transistor-1 resistor (1T1R) integrated Resistive random access memories (RRAM) devices with HfO2 films grown at 150 °C and 300 °C have been examined by current-voltage (I-V) measurements
Nm-size HfO2-based 1T1R integrated RRAM devices were fabricated in a standard 0.25 μm CMOS process line by employing the batch atomic layer deposition (ALD) tool designed for mass production
Summary
Future mass production of related devices[9]. Despite of a bunch of detailed studies focusing on unveiling the RS mechanism (normally on μm-size devices10,11) and on attempting to improve the cell-performances (with different methods like doping[12,13,14,15], filament confinement[16,17] and bilayers[18,19,20,21] etc.), a fundamental but indispensable study correlating the material properties (e.g. the crystallinity and the carbon impurity, etc.) and device performances, for integrated RRAM devices in nm scale, is still missing. The TiN/Ti/HfO2/TiN MIM structures, acting as the resistor, were fabricated by depositing HfO2 at two different temperatures (150 °C and 300 °C) by employing the batch ALD approach (with 100 process-wafer loading capability) with a metal organic precursor (which is more suitable for the batch ALD process thanks to its liquid form[22]). Both electrical and material properties of devices were systematically studied and correlated. The theoretical simulation using the Quantum Point Contact (QPC) model confirms that the 300 °C samples have much more stable confinement of leakage current paths (i.e. filaments)
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