Tantalum oxide thin films for microelectronic applications

Over the last several years, tantalum pentoxide (Ta2O5) thin films have received much attention as chip integrated high permittivity, high breakdown strength dielectrics for storage capacitors for ULSI DRAMs. We have studied the properties of reactively sputtered films of Ta2O5 on silicon wafers. These films have been characterized for refractive index. X-ray diffraction studies on films annealed in oxygen ambient at 800°C show the films to crystallize into an orthorhombic phase with an increase in refractive index with respect to the bulk value. Various capacitor configurations such as MIM, MIS (on p-type and n-type Si substrates) have been fabricated to study the nature of the Ta2O5/Si interface. The capacitors fabricated on p-type Si exhibit lower leakage. The reactive ion etching behavior of Ta2O5 is investigated in CF4+O2 and CHF3. It is observed that these films show lower etch rate as compared to Si and SiO2, however in CHF3 the etch rates of Si and Ta2O5 are comparable