Effect of Nitridation for High-K Layers by ALCVDTM in Order to Decrease the Trapping in Non Volatile Memories

Abstract

In non-volatile memories, high-k materials such as Al2O3, HfO2, and hafnium aluminates are good candidates as interpoly layers. In order to decrease the parasitic trapping of the interpoly stack, the effect of post deposition nitridation (PDN) on different high-κ films was investigated. Several characterizations were performed on those films such as Angle Resolved X-ray Photo-electron Spectroscopy (AR-XPS), Auger Electron Spectroscopy (AES), Attenuated Total Reflection - Fourier Transform Infrared spectroscopy (ATR-FTIR) and Vacuum UltraViolet Spectroscopy Ellipsometry (VUV-SE). A correlation between the nitrogen incorporation and the crystallization was demonstrated. Al-rich films remain amorphous after PDN, with an incorporation of nitrogen in the film volume. Meanwhile, Hf-rich films crystallized after PDN, with nitrogen incorporated only at the high-κ / Si substrate interface. Also nitrogen increases the crystallization temperature onset, which leads to a reduction of charge trapping after high temperature spike anneals. Nitrided amorphous hafnium aluminate films are good candidates as interpoly layer.

Compositional Phase Transition of Amorphous AlON

“…Annealed AlON films in group A gave new spectral broad bands at about 590cm -1 and 910cm -1 , respectively. According to several reports (8)(9)(10)(11), high-frequency mode can be assigned to the Al-O and Al-O-N stretching mode in amorphous phase. The position of lower frequency absorption band can be associated with octahedral in amorphous phase of Al 2 O 3 .…”

“…Al-O bond is more flexible against bond angle than nitrogen chemical bond. Sakka and co-workers calculated the potential energy curve of both Si-N-Si and Si-O-Si as a function of the bond angle (11). According to their theoretical studies, the Si-N-Si is a "rigid" bond with narrow and steep potential curves against bond angle, while the change in potential energy for Si-O-Si chemical bond is small when the bond angle varies.…”