High-k Materials in Flash Memories

Abstract

The scaling down of Flash memories can be pursued using theconventional stacked gate architecture only with major changesof the active dielectrics, mainly the inter-poly dielectric(IPD).The required 4-6 nm EOT thickness for the IPD cannot beachieved by the conventional ONO (Oxide-Nitride-Oxide)technology which starts failing in the 10-12 nm range in termsof charge retention properties. Therefore high-k materials arecurrently investigated for IPD formation in future Flashmemories. It is worth noticing that the requirements for IPD arevery different from those of the gate dielectrics used inlogics. Alumina and alumina based materials (like hafniumaluminates) are among the possible candidates. Promising andtunable electrical and structural properties are achieved forthese materials by varying the high-k stack chemicalcompositions and post- deposition thermal treatments. Differentmaterial combinations have been selected as potential solutionsfor the replacement of the conventional ONO(Oxide-Nitride-Oxide) stack

Structural and Chemical Investigation of Annealed Al2O3 Films for Interpoly Dielectric Application in Flash Memories

“…By the correlation between physical and electrical thickness we can obtain the dielectric constant of the material, since: EOT = (k SiO2 /k IL ) * t IL + (k SiO2 /k HK ) * t HK , [1] where EOT is the electrical thickness of the film as achieved by the non-contact measurement, k SiO2 is the silicon dioxide dielectric constant (3.9), k IL is the inter-layer dielectric constant, t IL is the inter-layer thickness, k HK is the high-k material dielectric constant and t HK is the high-k material physical thickness. Plotting the high-k physical thickness vs the EOT we obtain both the dielectric constant and the inter-layer EOT.…”

“…The evolution upon high temperature thermal treatments of both as deposited and annealed samples has been studied by means of N 2 RTP at 1030ºC for 15 seconds. The high temperature RTP is mandatory in order to fully crystallize the alumina film (1,4). Chemical characterization has been performed by Time of Flight-Secondary Ion Mass Spectrometry (ToF-SIMS), whereas morphological and structural characterizations have been carried out by (Scanning) Transmission Electron Microscopy ((S)TEM) with analytical complements performed via Energy Dispersive X-Ray Spectroscopy (EDX), X-ray Diffraction (XRD), X-ray Reflectivity (XRR) and Atomic Force Microscope (AFM).…”

“…Among the potential candidates for the ONO replacement, Al 2 O 3 deposited by ALD is attractive for IPD applications in flash memories since it guarantees excellent film conformality, a feasible dielectric constant, large bandgap and low leakage current (1). In this work we report the physical and structural evolution of Al 2 O 3 films deposited by ALCVD TM after 1030°C Rapid Thermal Processing (RTP) in N 2 .…”

“…The scaling down of flash memories is less aggressive as compared to logics; therefore a high-k dielectric with a dielectric constant in the 10÷20 range can fulfil the 45nm node EOT requirements (4÷6nm). Moreover, the integration issues are different from those of the gate dielectrics in logics devices: the IPD is exposed to several thermal Among the potential candidates for the ONO replacement, Al 2 O 3 deposited by ALD is attractive for IPD applications in flash memories since it guarantees excellent film conformality, a feasible dielectric constant, large bandgap and low leakage current (1). In this work we report the physical and structural evolution of Al 2 O 3 films deposited by ALCVD TM after 1030°C Rapid Thermal Processing (RTP) in N 2 .…”

Evaluation of HfLaOx as Blocking Layer for Innovative Nonvolatile Memory Applications

“…In principle, materials with a dielectric constant in the 10÷20 range can fulfill these requirements. Due to its excellent conformality, very good thermal stability, moderately high dielectric constant (k~10 after crystallization), large band-gap and good leakage currents (10), Al 2 O 3 is a very strong candidate for integration as blocking oxide in 32nm TANOS memories. For 22nm node, dielectric materials with higher k values are currently under investigation.…”