Ion-implanted treatment of (Ba,Sr)TiO3 films for DRAM applications

The effects of ion implantation on the properties of spin-on sol–gel Ba0.7Sr0.3TiO3 (BST) thin films were studied by implanted Ar+, N+, and F+ doses. The F+-implanted BST samples present leakage current density <10−6 A/cm2 at 2.5 V and dielectric constant ∼450. The leakage current of F+-implanted BST samples was reduced about one order of magnitude as compared with that of samples with implanted Ar+, N+ or without implantation. The thickness shrinkage from 135 to 115 nm was observed in F+-implanted BST films (before annealing treatment) and a respective increase in the refractive index from 1.84 to 2.05 was measured. After annealing the implanted samples, the changes of thickness and refractive index depend on the concentration of implanted dose. Based on an infrared transmission study of the samples we suggest that the ion-implanted samples with smaller dose (5×1014 cm−2) have fewer −OH contaminants than the non-implanted or implanted samples with the larger doses (⩾1×1015 cm−2). Based on the results presented, we conclude that suitable ion implantation densifies the spin-on sol–gel BST films and reduces the −OH contaminants in the films.