Oxidation-induced defect generation in advanced DRAM structures

Structures containing deep-trenched storage capacitors and shallow-trench isolation were examined in patterns suitable for future generation dynamic RAMs (DRAMs). These same effects were also examined in similar structures which included only the shallow isolation trenches. Observed was a strong interaction between the deep and shallow trenches, which makes structures which incorporate both types much more susceptible to oxidation-induced defect generation than those without deep trenches. It was observed that at higher oxidation temperatures, more oxide can be grown before defects are generated. This is interpreted as a combination of more-efficient visco-elastic relaxation in the oxide and a lower differential oxidation rate between the {110} trench sidewalls and the {100} planar surface at higher temperatures. It was also observed that substantial defect immunity can be obtained by incorporating an oxidation barrier in the trench structures. An overall processing strategy to eliminate defect generation in these advanced structures is suggested