The Simplest Stacked BST Capacitor For The Future DRAMs Using A Novel Low Temperature Growth Enhanced Crystallization

Abstract

The simplest stacked capacitor with BST thinner films (about 50nm-thick) grown by a novel low temperature growth [ 11 was demonstrated. The storage node without sidewall spacer was constructed by thinner Ru-layer, sputtered-TiN diffusion barrier, TiSix electrical contact layer and poly-Si plug. The low temperature BST growth prevented the leakage current increase of BST films as thin as 25nm. Therefore, 50% step coverage BST-capacitor was performed as sidewall-less simple stacked capacitors with large storage charge. Introduction(Ba, Sr)TiO, film with high dielectric constant has been extensively investigated in view of its applications to simple stacked capacitors for high density DRAMS. Recently, Ru and/ or RuO, as storage node has been applied on the capacitor structure, on the point of view in dry-etching and electrical conduction [2]. However, Ru is not so stable for oxygen at high temperatures which causes of increase in roughness at the surface. Therefore, low temperature BST growth processes has been required for the capacitor fabrications. Chemical vapor deposition using metalorganic sources [2] or mist sources [3] have recently been proposed for the low temperature deposition with excellent step coverage, however, the deposition temperature was considered higher for Ru-layer. Therefore, in the case of CVD process for BST deposition, RuO,/Ru multilayer must be used [2].This paper is to demonstrate the simplest stacked capacitor with Ru storage node using a novel lower temperature BST growth enhanced crystallization by reactive sputtering.