The effects of C on the low-temperature formation and the properties of the spin-on dielectric films used for sub-50 nm technology and beyond

Abstract

Precursor films based on polysilazane and polymethylsilazane were deposited on Si-substrates or on stacked TiN/Ti/tetraethyl orthosilicate/Si-substrates by spin-coating, subsequently annealed at 150–850°C or at 150–400°C, and physicochemically characterized or integrated further to form a top electrode and pad. They were then electrically characterized. Compared to perhydro-polysilazane, annealing the precursor films of hydro-polymethylsilazane led to a more difficult formation of good-quality spin-on dielectric films by evaporating smaller amounts of N, H, and C and gaining a smaller amount of O at 400°C, whereas evaporating and gaining larger amounts at 850°C, results in a shrink ratio of 14.5% less than the 15.6% ratio of perhydro-polysilazane at 400°C but 37.4% more than that of 19.4% at 850°C. Fourier-transform infrared spectroscopy indicated that C induced fewer SiO bonds, a non-uniform property, and lower resistance to chemical etching. Electrical measurements indicated that a larger capacitance of 2.776×10−11F compared to 9.457×10−12F and a lower leakage current of 0.4pA from the polysilazane-based dielectric films compared to the value of 2.4pA from a polymethylsilazane based film were obtained at less than 0.6MV/cm, giving therefore higher dielectric constant of 5.48 compared to 3.96. Better electrical properties are directly correlated with larger numbers of SiO bonds and better bonding structures of spin-on dielectric films as derived from a precursor without C.