Chemistry of resistivity changes in TiTe/Al2O3 conductive-bridge memories

Abstract

We report the chemical phenomena involved in the reverse forming (negative bias on top electrode) and reset of a TaN/TiTe/Al2O3/Ta memory stack. Hard X-ray photoelectron spectroscopy was used to conduct a non-destructive investigation of the critical interfaces between the electrolyte (Al2O3) and the TiTe top and Ta bottom electrodes. During reverse forming, Te accumulates at the TiTe/Al2O3 interface, the TiOx layer between the electrolyte and the electrode is reduced and the TaOx at the interface with Al2O3 is oxidized. These interfacial redox processes are related to an oxygen drift toward the bottom electrode under applied bias, which may favour Te transport into the electrolyte. Thus, the forming processes is related to both Te release and also to the probable migration of oxygen vacancies inside the alumina layer. The opposite phenomena are observed during the reset. TiOx is oxidized near Al2O3 and TaOx is reduced at the Al2O3/Ta interface, following the O2− drift towards the top electrode under positive bias while Te is driven back into the TiTe electrode.

Role of Postdeposition Annealing and Doping with Si and Al Impurities in the Formation of HfxSi1–xO2 at the SiO2/FE:HfO2 Interface in a Ferroelectric Field-Effect Transistor

“…The HAXPES results for the Al 1s spectra of the annealed/unannealed Al-doped samples (Figure ) confirm the separation of the Al 2 O 3 –HfO 2 phases after the annealing of the Al-doped sample. Both spectra of the same FWHM correspond well to Al 2 O 3 or AlO x − and exclude the presence of Hf–Al–O since the energy shift relative to the BE of pure Al 2 O 3 corresponding to hafnium aluminate should have a value of 1–1.5 eV close to that for hafnium silicate due to the almost identical electronegativity of Al and Si. , …”

“…Al 1s HAXPES spectra of samples with Al-doped HfO 2 annealed at 850 °C and unannealed measured at 7 keV photon energy. Reference binding energies of Al 2 O 3 , AlO x , Hf–Al–O, and Al-metal states are shown by dashed vertical lines according to refs − (see comments in the text).…”

Modification and Characterization of Interfacial Bonding for Thermal Management of Ruthenium Interconnects in Next-Generation Very-Large-Scale Integration Circuits

“…The sample sputtered at Ar/N 2 = 19:1 displayed three components located at 1730.9, 1733.1, and 1735.4 eV in Figure c. The first one is very close to the peak of metallic Ta 0 , the second one should be attributed to TaN and tantalum suboxide (TaO x ), and the third one should be the characteristic of Ta 2 O 5 . The Ta oxides may be attributed to either surface oxidation of the top Ta layer or oxidation of TaN by residual oxygen in the sputtering chamber.…”

A new opportunity for the emerging tellurium semiconductor: making resistive switching devices

“…Actually, PCMs have often been utilized as the dielectric layers in EC-RS devices but most of these devices used electrochemically active Ag or Cu electrodes [54][55][56][57] . Recently, the use of Te electrodes has also been found to enable RS [38][39][40][41][42][43] , in which the formation of local Te conducting filaments led to HRS-to-LRS transition while the rupture of filaments led to the reverse transition. In order to confirm whether the RS phenomena in our device are based on such mechanism, we measure the electrode area-dependent resistances of our device in both the NV-RS and V-RS modes.…”

“…Currently, main reported filamentary materials for EC-RS devices are all metals with relatively high thermal conductivities and high melting temperatures 12 . Recently, tellurium (Te), as an emerging semiconductor material for the next-generation transistors [34][35][36][37] , has been found to be electrochemically active [38][39][40][41][42][43] . Associated with its semiconductivity, Te also has low thermal conductivity (1.6 W m −1 K −1 ) 44 compared to those of the metallic filamentary materials (e.g., Cu: 45 .…”