Dielectric and electrical characteristics of titanium-modified Ta2O5 thin films deposited on nitrided polysilicon by metalorganic chemical vapor deposition

Titanium-modified tantalum oxide thin films with a composition of (TaZO(5)) (0.922)-(TiO2)(0.078), and pure Ta2O5 thin films of 12 nm thickness were pr epared on a nitrided poly-Si electrode by liquid source delivery metalorgan ic chemical vapor deposition at 390 degrees C. The effective dielectric con stant of the Ti-modified Ta2O5 thin films is higher than that of the pure T a2O5 thin films whether they were crystallized or not. The highest value of the effective dielectric constant is 30.2 for the Ti-modified Ta2O5 thin f ilms after being subjected to rapid thermal oxygen annealing (RTO) at 800 d egrees C fur 30 s, but that of the pure Ta2O5 is only 22.4 under the same h eat treatment conditions. Moreover, the former also has a high and stable i nsulating characteristic against bias voltage, i.e., a low leakage current of 1 x 10(-8) A/cm(2) can be maintained at 2.5 MV/cm after RTO at 850 degre es C for 90s, However, that of pure Ta2O5 only reaches 1 x 10(-7) A/cm(2) u nder the same treatment conditions. The relationship of current versus time (I-t) measured at room temperature also reveals the superior insulating pr operty of Ti-modified Ta2O5 compared to that of pure Ta2O5 thin films. An e xcellent leakage current characteristic along with high capacitance suggest s that the Ti-modified Ta2O5 thin film is a more promising material than th e pure Ta2O5 film for use in the fabrication of capacitors for G-bit dynami c random access memories.