Volatile Nickel Aminoalkoxide Complexes as Liquid Precursors for Non-volatile Memory Device of NiO Films by ALD

Abstract

Recently, NiO film of metal-oxide-metal (MOM) structure 1a has drawn much attention because it shows reproducible resistance switching phenomena applicable to next generation nonvolatile resistive random access memory (ReRAM) device. The resistance switching phenomenon, that is, a drastic change in resistance between a high-resistance state (OFFstate) and low resistance state (ON-state) in current-voltage (I-V) characteristic of MOM structure, has been observed in binary oxides such as NiO, 1 TiO2, 2 Nb2O5, 3 Cr-doped SrZrO3, 4 Pr1-xCaMnO3, 5 and chalcogenide semiconductors although exact origin was unsolved. Among these materials, the binary oxide is the first consideration for the application due to the relatively simple fabrication process. In the case of a device fabrication, the self-limiting process of atomic layer deposition (ALD) may be very important for the growth of NiO films because the expected structure of ReRAM device requires the filling process of NiO on the hole or trench-patterned 3-dimensional substrates. Therefore, it is worthwhile to find the optimal ALD process for NiO film growth by using suitable Ni precursors. In general, most of Ni compounds are in solid state at room temperature although highly volatile liquid precursor is highly desirable to obtain conformal film qualities in ALD processes. A number of nickel precursors have been synthesized and examined for preparing Ni and NiO films using metal organic chemical vapor deposition (MOCVD) and ALD during the past years. The ligands for the nickel precursors are carbonyl, 6 β-diketonates, 7 cycolpentadienyl, 8 and alkoxides, 9 N,N'-dialkyl