Physical and electrical characteristics of band-engineered Zr-silicate/SiO2 stacks for tunnel barrier

In this work, we investigated the physical properties of (ZrO2)x(SiO2)1−x such as band-gap, band-offset, structural stability, and the tunneling characteristics of (ZrO2)x(SiO2)1−x/SiO2 tunnel barrier with total EOT of 4.5 nm for the application to charge trap memory devices. It was observed that the band-gap and band-offset of (ZrO2)x(SiO2)1−x can be controlled by changing the composition for (ZrO2)x(SiO2)1−x films. However, the sensitivity of band-gap and band-offset of (ZrO2)x(SiO2)1−x films on ZrO2 content was minimal for the cycle ratio of ZrO2:SiO2 above 1:1. The Zr-silicate film with the ZrO2:SiO2 cycle ratio of 1:7 maintained amorphous even after annealing at 1050 °C. However, and Zr-silicate film with the ZrO2:SiO2 cycle ratio of 1:1 and 3:1 were crystallized after annealing at 950 °C and 850 °C, respectively. The band-engineered tunnel barrier of (ZrO2)x(SiO2)1−x/SiO2 bi-layer showed enhanced tunnel efficiency at high gate bias, while showed smaller tunnel current at low gate bias than a single SiO2 tunnel barrier of the similar EOT.