Capacitance Enhancement by Mesopore Formation for sub 100nm Deep Trench DRAM Technology

We have successfully applied the electro-chemical method of mesopore formation in deep trenches (DTs) to increase the surface of deep-trench capacitors for DRAMs. The length of the mesopores is controlled by the etching time and was up to 60 nm. Subsequently, the diameter of the mesopores, was increased to above 20 nm by an isotropic wet etch. By sufficient tuning of the arsenic doping concentration of the trench side-walls, the density of the mesopores was adjusted to 400/μm2. Thus, a surface area increase of the DTs of up to 150% was achieved.