IMPROVEMENT OF MEMORY RETENTION IN METAL-FERROELECTRIC-INSULATOR-SEMICONDUCTOR STRUCTURE BY SrBi₂Ta₂O₉ SURFACE MODIFICATION INDUCED BY NITROGEN AND OXYGEN RADICAL IRRADIATION

ABSTRACT

A Pt/SrBi₂Ta₂O₉(SBT)/SiO₂/n-Si metal–ferroelectric–insulator–semiconductor (MFIS) structure has been prepared with SrBi₂Ta₂O₉ thin film whose surface was modified by irradiation of nitrogen or oxygen radical. The leakage current is reduced by irradiation treatment and C-V characteristic shows clear memory window and sharp slopes corresponding to good interface layer. It is estimated from X-ray Photoelectron Spectroscopy and Ultraviolet Photoyield Spectroscopy that the SBT thin films with nitrogen treatment have exhibited the higher threshold energy than that without the irradiation. Memory window of the MFIS structures are in the range of 1–2 V when the gate voltage is varied from 3–6 V. Retention time of ON and OFF states is 1 week in the structure irradiated with oxygen radical and 12 days in that with nitrogen radical although that without the irradiation is only 3 hours.

Keywords:

• MFIS
• SBT
• SrBi₂Ta₂O₉
• XPS
• UV-PYS
• memory window
• SEM