On the role of Ti adlayers for resistive switching in HfO2-based metal-insulator-metal structures: Top versus bottom electrode integration

The authors demonstrate bipolar resistive switching in TiN/HfO2/Ti(top)/TiN devices using a (Bi) complementary metal-oxide semiconductor (CMOS) compatible technology process. The device performance includes a cycling endurance in dc sweeping mode >10(3). The results suggest that HfO2-based metal-insulator-metal devices with Si CMOS compatible metal electrodes may be well suited for future embedded nonvolatile memory applications. However, hysteretic current-voltage characteristics were only observed for a Ti top adlayer, whereas a Ti bottom adlayer integration did not show any resistive switching effect. Using x-ray photoelectron spectroscopy, the authors examined the interface chemistry of the Ti/HfO2 interface. It is clearly observed that Ti top adlayer deposition results in an increased nitrogen- and oxygen-gettering activity in contrast to Ti bottom adlayer. It follows that the formation of a nonstoichiometric HfO2 layer at the Ti/HfO2 interface is crucial for resistive switching. (C) 2011 American Vacuum Society. [DOI: 10.1116/1.3536524]