Lanthanum diffusion in the TiN/LaOx/HfSiO/SiO2/Si stack

Band edge Complementary Metal Oxide Semiconductor (CMOS) devices are obtained by insertion of a thin LaOx layer between the high-k (HfSiO) and metal gate (TiN). High temperature post deposition anneal induces Lanthanum diffusion across the HfSiO towards the SiO2 interfacial layer, as shown by Time of Flight Secondary Ions Mass Spectroscopy (ToF-SIMS) and Atom Probe Tomography (APT). Fourier Transform Infrared Spectroscopy in Attenuated Total Reflexion mode (ATR-FTIR) shows the formation of La–O–Si bonds at the high-k/SiO2 interface. Soft X-ray Photoelectron Spectroscopy (S-XPS) is performed after partial removal of the TiN gate. Results confirm La diffusion and changes in the La chemical environment.

Advanced nFET devices are studied at three steps of the gate elaboration. After anneal at 1065 °C, Lanthanum diffusion is observed towards the bottom SiO2 interface by ToF-SIMS, as well as Lanthanum silicate formation by ATR-FTIR.Figure optionsDownload as PowerPoint slide