Quasi-three-dimensional modeling of sub-micron LOCOS structures

A quasi-three-dimensional simulation of local oxidation is presented. The approach employs the solution of three-dimensional oxidant diffusion, a set of analytical solutions which can predict two-dimensional local oxidation of silicon (LOCOS) shape and parameterization to consider the three-dimensional oxidation enhancement effects. A synthesis step is used to combine the three-dimensional oxidant profile and two-dimensional analytical solutions for the creation of full three-dimensional LOCOS shapes. Oxidation characteristics are investigated based on atomic force microscopy (AFM) measurements that produce three-dimensional structural effects such as the bird´s eye phenomena. The narrow window and narrow mask effects on the bird´s beak length are simulated and compared with SEM photographs obtained using AFM measurements. Differences between two- and three-dimensional oxidation effects are shown by the comparison of simulation and experiments