Investigation of charge trap and loss characteristics for charge trap memory by electrostatic force microscopy

In this work, we employ the electrostatic force microscopy (EFM) technique to investigate the charge trapping and loss properties of Hf-based trapping structures by contact potential differences (CPDs) measurement. For different samples, the electron densities after injection and after 2 hours retention time are extracted from the measured CPDs. The HfO₂ material shows higher charge trapping capability to Al₂O₃ under the same condition of charge injection. The charge decay phenomenon is effectively inhibited in high-k materials with post deposition anneal (PDA) process. Meanwhile, by the introduction of the Al₂O₃/HfO₂ interface, the bi-layer structure exhibits significantly improved charge trapping capability along with acceptable charge loss. The structure dependence and process dependence of the high-k materials properties are investigated.