Dynamic random-access memory (DRAM) is the main memory in most current computers. The excellent scalability of DRAM has significantly contributed to the development of modern computers. However, DRAM technology now faces critical challenges associated with further scaling toward the ∼10-nm technology node. This scaling will likely end soon because of the inherent limitations of charge-based memory. Much effort has been dedicated to delaying this. Novel cell architectures have been designed to reduce the cell area, and new materials and process technologies have been extensively investigated, especially for dielectrics and electrodes related to charge storage. In this article, the current issues, recent progress in and the future of DRAM materials, and fabrication technologies are discussed.

Strontium titanate (STO) thin films (45-67 % Sr) were deposited by atomic layer deposition using Sr(tBu3Cp)2/Ti(OMe)4/H2O as precursors. The Sr content of the layers is well controlled by the precursor pulse ratio, as indicated by Rutherford backscattering spectroscopy (RBS). The amount of Sr and Ti deposited depends on the Sr:Ti pulse ratio and indicates the enhancement of the Ti precursor reactivity in the presence of Sr-OH. STO compositions that are closer to stoichiometric SrTiO3 result in denser films with correspondingly higher index of refraction. The increase (decrease) of the Sr content over (below) 50 % leads to an expansion (contraction) of the lattice parameter corresponding to cubic SrTiO3 with a perovskite structure. The dielectric constant (extracted from film thickness series) and leakage current strongly depends both on the Sr content and the crystalline state of the films.