Ta2O5/TaOx heterostructure has become a leading oxide layer in memory cells and/or a bidirectional selector for resistive random access memory (RRAM). Although atomic layer deposition (ALD) was found to be uniquely suitable for depositing uniform and conformal films on complex topographies, it is hard to use ALD to grow suboxide TaOx layer. In this study, tantalum oxide films with a composition of Ta2O5 were grown by ALD. Using Ar+ ion irradiation, the suboxide was formed in the top layer of Ta2O5 films by observing the Ta core level shift toward lower binding energy with angle-resolved X-ray photoelectron spectroscopy. By controlling the energy and irradiation time of an Ar+ ion beam, Ta2O5/TaOx heterostructure can be reliably produced on ALD films, which provides a way to fabricate the critical switching layers of RRAM.
In this letter, we report analog switching characteristics in an analog resistive random access memory device based on a TiW/Al2O3/Ta2O5/Ta stack. For this device, both oxides were grown by using an atomic layer deposition system and the oxygen vacancies were found to exist at the interface of these oxides by using angle-resolved X-ray Photoelectron Spectroscopy. The device exhibits analog switching behaviors. Multiple states were achieved by applying 128 consecutive identical pulses of <20 μs duration and stable for at least 104 s. These characteristics show that the TiW/Al2O3/Ta2O5/Ta device is a promising candidate for synaptic applications.
A forming-free TaO x based RRAM cell is demonstrated with low operation voltage and large resistance window. RRAM devices with Pt/TaO x /TiN and Pt/TaO x /Ta film-stacks are investigated in this work. For devices with TiN as top electrode (TE), the initial resistance is at OFF state, thus a forming process is needed prior to subsequent switching operations. For devices with Ta as TE, the initial resistance is at ON state, negating the need for a forming process. This is attributed to the dielectric thinning effect caused by the interfacial reaction between the TaO x and Ta layers during forming gas anneal process. In addition, with Ta as TE, smaller |V SET | and |V RESET | and wider OFF/ON ratio window are observed. Thermal stability up to 400 • C during post deposition annealing process with N 2 and O 2 are studied in this work, electrical results suggested excellent thermal stability for this TaO x based RRAM devices.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.