Low-temperature preparation of SrxBi2+yTa2O9 ferroelectric thin film by pulsed laser deposition and its application to a metal-ferroelectric-nitride-oxide-semiconductor structure
Preferentially (105)-oriented SrxBi2+yTa2O9 (SBT) thin films on SiN/SiO2/p-Si(100) prepared by the pulsed laser deposition (PLD) method at a temperature as low as 400 °C, which is the lowest process temperature for growing SBT ferroelectric thin films on a silicon nitride film. Excess Bi promotes crystallization of the SBT film. A metal-ferroelectric-nitride-oxide-semiconductor (MFNOS) structure, which is very important in ferroelectric gate memory FET, has been fabricated by depositing the SBT film on silicon nitride-oxide-silicon. The MFNOS structures show capacitance-voltage (C-V) hysteresis corresponding to ferroelectric hysteresis. A memory window of the C-V hysteresis is improved, to be as high as 3.5 V in the SBT(400 nm)/SiNx(7 nm)/SiO2(18 nm)/Si compared with the window of 2.7 V in the SBT(400 nm)/SiO2(27 nm)/Si (MFOS), where the thicknesses of their insulator layers are nearly the same. Little degradation is induced in the C-V characteristics of the SiNx/SiO2/p-Si structure when depositing the SBT film by PLD at low temperature. It is also found that the SiNx layer acts as a diffusion barrier against component atoms in the SBT film during its deposition. Finally, the MFNOS structure prepared at the low temperature is very promising for a next-generation ferroelectric gate memory FET.
Applied Physics A: Materials Science & Processing
- Pub Date:
- PACS: 81.15.Fg;
- 68.55. -a