Reinhard Johannes Stengl

High pressure oxidation induced stress in submicron trench structures

The maximum stress induced by high pressure oxidation (wet and dry) in the vertical bird’s beak of submicron trench structures has been investigated experimentally. The oxidation induced stress was measured via wafer bow on wafers that were patterned with a special trench mask featuring a pattern factor of 50%. For wet high pressure oxidations above 850 °C, the stress drops from 2×1010 dyne/cm2 at 850 °C to a value below 1×109 dyne/cm2 at 1000 °C. At oxidation temperatures between 700 and 900 °C, dry pressure oxidations show lower stress than wet oxidations.

Dislocation Formation in Trench-Based Dynamic Random Access Memory (DRAM) Chips

This paper reports on our studies of dislocation formation in trench capacitor DRAM structures. Experimental results on process dependence and layout dependence of dislocation formation in cell layouts with minimum feature sizes from 0.5 μm to 0.25 μm are compared to two-dimensional stress simulations. It is shown that the nucleation and spatial distribution of dislocations can be explained by considering stress fields which are influenced by the overlay of deep trench and shallow trench isolation structures.