| AVS 65th International Symposium & Exhibition | |
| Electronic Materials and Photonics Division | Thursday Sessions |
| Session EM-ThP |
| Session: | Electronic Materials and Photonics Division Poster Session |
| Presenter: | Jeffrey Chang, University of California, Los Angeles |
| Authors: | K. Fitzell, University of California, Los Angeles J. Chang, University of California, Los Angeles A. Acosta, University of California, Los Angeles H. Ma, University of California, Los Angeles X. Li, University of California, Los Angeles K.L. Wang, University of California, Los Angeles J.P. Chang, University of California, Los Angeles |
| Correspondent: | Click to Email |
In contrast to manipulating magnetization with applied current, using an applied electric field can significantly reduce the required energy and result in less heat generation, leading to increased ene rgy density. This can be accomplished using the voltage-controlled magnetic anisotropy (VCMA) effect, which forms the basis of next-generation magnetoelectric MRAM devices. Specifically, applying an electric field across a CoFeB/MgO interface can decrease the perpendicular magnetic anisotropy field as a result of the altered electron density at the interface, thus destabilizing the magnetization state and allowing for its efficient and deterministic reorientation with a small applied magnetic field. This op eration principle stands in contrast to that of STT-RAM, which uses upwards of 100 fJ to write a single bit (300,000 times more energy than the actual energy barrier to switching).
Previous research on CoFeB/oxide interfaces has shown that increasing the dielectric constant of the oxide layer also increases the sensitivity of the interfacial magnetic anisotropy energy to an applied electric field (Kita et al., 2012). Our previous work involving MgO/PZT/MgO composite tunneling barriers showed a 40% increase in the VCMA effect upon addition of PZT to the tunneling barrier. However, the ferroelectric order of PZT is very weak at such small dimensions, and the leakage current and high annealing temperatures required of PZT prevent this technology from being industrially relevant. On the other hand, the orthorhombic phase of HfO2 has been shown to possess desirable ferroelectric properties even in ultrathin films. In addition, ferroelectric HfO2 boasts superior compatibility with CMOS technology as well as desirable electrical properties for device integration.
In this work, a method for depositing orthorhombic phase HfO2 (FE-HfO2)-based thin films via a radical-enhanced atomic layer deposition process is described. These ferroelectric thin films were subsequently incorporated into the tunneling junctions of CoFeB/MgO-based magnetic tunnel junction in an effort to enhance the VCMA effect and introduce ferroelectric functionality into magnetoelectric random-access memory devices.