A heteroepitaxial MIM-Ta/sub 2/O/sub 5/ capacitor with enhanced dielectric constant for DRAMs of G-bit generation and beyond

Abstract

We demonstrate a novel MIM capacitor with a heteroepitaxial Ta20s dielectric, the permittivity of which is as high as 50. The heteroepitaxy of Ta20s on the Ru electrode changes its crystal symmetry from a conventional orthorhombic system to a hexagonal one. One-dimensional Ta-0-Ta chains along the c-axis bring about delocalized electrons, large polarizability and thus enhanced permittivity. This technology is promising for the application of Ta20s to the G-bit DRAMs, eliminating the need to use such exotic materials as BST and STO.

Enhancement of Dielectric Constant due to Expansion of Lattice Spacing in CeO2 Directly Grown on Si(111)

“…The value of ε in ionic oxide is strongly related with crystal structures and/or lattice spacings. Enhancement of ε by changing the crystal structure of Ta 2 O 3 was reported [2], but the crystalline symmetry is unchanged in the CeO 2 case. Anisotropy in ε may not be existent in fluorite structures such as CeO 2 .…”

Development of MIM/Ta2O5 capacitor process for 0.10‐µm DRAM

“…Ta 2 O 5 has a greater relative permittivity of 50 to 60 even for thin films with a thickness of less than 10 nm [10]. The equivalent silicon oxide film thickness (EOT) is about 0.8 nm.…”

“…The authors emphasize technical continuity of the existing MIS/Ta 2 O 5 capacitor process and propose the MIM (metal insulator metal)/Ta 2 O 5 capacitor as a storage capacitance forming technique for the generations after 0.10 µm [4]. Ta 2 O 5 has a greater relative permittivity of 50 to 60 even for thin films with a thickness of less than 10 nm [10]. The equivalent silicon oxide film thickness (EOT) is about 0.8 nm.…”

Effects of an Added Iodine Source (C2H5I) on Ru Metal–Organic Chemical Vapor Deposition

“…[5,6] Recently, a Ta 2 O 5 film grown on a Ru(002) film and annealed at 800 C [7] was found to have a dielectric constant at its highest level of 110, due to the delocalized electrons in the hexagonal crystal structure. [8] Considering process maturity, feasibility, and reliability, [9] Ru±Ta 2 O 5 ±Ru is regarded as an attractive structure for a metal±insulator±metal (MIM) capacitor. Although a Ru thin film grown by physical vapor deposition (PVD) has good material characteristics, [7] it has to be grown by CVD to meet the step coverage required for the bottom electrode of a DRAM capacitor.…”