Conformal step coverage of (Ba,Sr)TiO3 films prepared by liquid source CVDusing Ti(t-BuO)(2)(DPM)(2)

Citation
T. Kawahara et al., Conformal step coverage of (Ba,Sr)TiO3 films prepared by liquid source CVDusing Ti(t-BuO)(2)(DPM)(2), JPN J A P 1, 38(4B), 1999, pp. 2205-2209
Citations number
16
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science
Volume
38
Issue
4B
Year of publication
1999
Pages
2205 - 2209
Database
ISI
SICI code
Abstract
We study the application of(Ba,Sr)TiO3 (BST) films prepared by chemical vap or deposition (CVD) method to similar to 0.13-mu m-scale devices, for examp le, 4Gbit dynamic random access memories (DRAMs), whose minimum feature siz e and height of storage nodes are around 0.13 and 0.36 mu m, respectively. It is necessary for these devices to obtain a conformal step coverage of th e BST films of more than 80% at an aspect ratio of 3-5, along with an equiv alent SiO2 thickness (t(eq)) of 0.5 nm. Recently, a new Ti source, Ti(t-BuO )(2)(DPM)(2) [bis (t-butoxy) bis (dipivaloylmethanato) titanium], whose Ti ion is surrounded by four large organic ligands, was developed. It is more stable in THF (tetrahydrofuranl C4H8O) solution and in the vapor phase than conventional Ti sources such as TiO(DPM)(2) [oxo bis (dipivaloylmethanato) titanium]. In fact, the step coverages of the BST films using Ti(t-BuO)(2) (DPM)(2) were found to be 80% and 70% at aspect ratios of 3.3 and 5, respec tively, which were much better than those of films using TiO(DPM)(2). Moreo ver, the electrical properties of the BST films using Ti(t-BuO)(2)(DPM)(2) were r(eq) = 0.44 nm and a leakage current J(L) Of 2.8 x 10(-8) A/cm(2) (+1 .1 V) for a film of 24 nm thickness after post-annealing. These characteris tics meet the requirements of the 4Gbit DRAM capacitors.