Bi1–x–yTixSiyOz (BTSO) Thin Films for Dynamic Random Access Memory Capacitor Applications

Bi 1-x-y Ti x Si y O z (BTSO) thin films were grown on eight inch diameter Ru/SiO 2 /Si or bare Si wafers by atomic layer deposition (ALD) method using Bi(mmp) 3 , Ti(mmp) 4 , and Si(OEt) 4 [mmp= 1-methoxy-2-methyl-2-propoxide (OCMe 2 CH 2 OMe, Me = methyl); Et = ethyl] as metal alkoxide precursors and ozone (O 3 ) as the oxidant gas. Transmission electron microscopy (TEM) and Rutherford backscattering spectrometry (RBS) analysis showed that the as-deposited films are amorphous and the cation compositional ratio of Bi:Ti:Si is 0.38:0.37:0.25 of films deposited at 325°C on Ru/SiO 2 /Si Ru substrates. X-ray photoelectron spectroscopy (XPS) shows that the BTSO films are homogeneously dispersed without any phase-separation of the components. The BTSO films show excellent step coverage on a high aspect ratio (4) contact hole structure with a diameter of 300 nm. The leakage current density of BTSO films is on the order of 10 -8 A cm -2 at 1 V, meeting present dielectric requirements for a dynamic random access memory storage capacitor with an equivalent oxide thickness of 2.1 nm. From the capacitance-voltage characteristics at 10 kHz of the Pt/BTSO/Ru capacitor, the estimated dielectric constant of amorphous BTSO films is ∼24.