Memory operation of Pt-SrBi₂Ta₂O₉-Y ₂O₃-Si field-effect transistor with damage-free selective dry etching process

Metal-ferroelectric-insulator-semiconductor field-effect transistor (MFISFET) with Pt-SrBi₂Ta₂O₉ (SBT)-Y ₂O₃-Si gate structure was fabricated with a selective dry etching of SBT and Y₂O₃. The etching characteristics of SBT, Y₂O₃, and silicon were investigated with various Ar/Cl₂ gas mixing ratios. Inductively coupled plasma (ICP) Powers, and RF bias powers and the surface condition after the etching was analyzed by using the scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoemission spectroscopy (XPS), and Rutherford back scattering (RBS) measurement. The etch-stop process was successfully achieved at the condition of 50% Cl₂ concentration with the ICP power of 900 W and the RF bias power of 100 W where the selectivity of SBT to Y₂O₃ was 4. The fabricated MFISFET with the etch-stop process showed good memory operation with 1.2 V threshold voltage difference and more than three orders of drain current difference in the on/off drain current ratio at the operating voltage of 7 V. These results meant that the etch-stop process was successfully carried out and applied to MFISFET fabrication without degradation of the ferroelectric characteristics and damage on silicon surface.