Multi-layer tunnel barrier (Ta 2 O 5 /TaO x /TiO 2 ) engineering for bipolar RRAM selector applications

Abstract

Ultrathin stoichiometric Ta2O5 layer, which was formed by thermal oxidation of Ta layer on ALD TiO2, exhibits excellent selector characteristics. To maximize the selector performance, we adopted various interface engineering techniques such as Ta2O5 thickness, control of oxygen profile in TaOx layer, top electrode materials, and band gap of bottom insulating oxide layer. By optimizing process conditions, we obtained outstanding selector performances such as high current density (>107A/cm2), high selectivity (~104), better off-current (<;100nA) and excellent reliabilities. Furthermore, the selector was fabricated in 1K cross-point array and vertically-integrated with Conductive-Bridge RAM (CBRAM).