A poly-Si/Al,O,/poly-Si capacitor is developed for the simple integration of 256Mb DRAM and beyond.The oxide equivalent thickness (Tow) of AI,O, capacitor was achieved as small as 2 8 m , which is about 1.7 times smaller than that of advanced NO capacitor. Especially, the pre-treatment before the deposition of A1,03 f i l m plays crucial role for stable device performance. Moreover, one of the distinguished characteristics of A1,0, capacitor is that the capacitance was even enhanced by performing the conventional DRAM processes, including high temperature planarization known as BPSG flow, without degrading the leakage characteristics.suffer fiom the lack of the required capacitance even with the stacked storage node with rugged surface. The storage capacitor integration with TqO, and BST requires the major modification of the electrode materials, which produces many difficulties during the full integration. Therefore, it is highly desirable to develop new capacitors with conventional poly-Si as both storage and plate electrodes, which provide sufficient capacitance in a limited area. In this paper, the excellent physical and dielectric properties of Al,O, film as well as its applicability to conventional 256Mb DRAM and beyond are presented.[ 11
Capacitor Fabrication IntroductionFor the 0.21 pm DRAMS and beyond, the conventional storage capacitors, consisting of Nitride/Oxide (NO) dielectrics and poly-Si electrodes, As shown in Fig. 1 (a), the simple stacked Al,O, capacitors with 1 .Opm-height storage node were integrated into a 256Mb DRAM with a feature size of 0.2 1 pm. Fig. 1. (a) A vertical view of the simple stacked A1,0, capacitors integrated into a 256 Mb DRAM with a feature size of 0.26pm. (b) TEM micrograph of A1,0, storage capacitor.
