Periodic structure of the shallow trench isolation type ULSI cells was generally used for the latest semiconductor devices. However, dislocations sometimes accumulate in the electron channel when the device size became small, and they have an enormous effect on the electronic state and obstruct the device from normal operation. The periodic structure of the shallow trench isolation type ULSI cells was numerically modeled here, and the plastic slip that takes place during the oxidation process of oxide film area was analyzed. The slip deformation was analyzed by a crystal plasticity analysis software, which was developed on the basis of finite element technique, and the accumulation of dislocations that accompanied plastic slip was evaluated. The results exhibited stress concentrations at the shoulder part of the device area and the bottom corners of the trench for the device isolation, and the high stresses at these area cause plastic slip and dislocation accumulation. The direction of these dislocation lines were shown to be mostly parallel to the trench direction and dislocations were approximately 60° mixed type.

Simulation of Dislocation Accumulation in ULSI Cells with STI Structure. T.Ohashi, M.Sato, T.Maruizumi, I.Kitagawa: Applied Surface Science, 2003, 216[1-4], 340-6