Simulation study of micro-loading phenomena in silicon dioxide hole etching

A new surface reaction model for a dry-etching topography simulator is propose. First, two types of radical adsorptions are introduced. One is a nondepositive type (Langmuir type) radical adsorption which plays an important role for ion-assisted etching. The other is a depositive type radical adsorption which results in polymer deposition as an etching inhibitor. Secondly, direct and indirect radical transport inside the enclosure of a geometry is self-consistently taken into account based on the present radical adsorption model. Complicated etching/deposition profile evolution is well described by a newly revised string model based on Boolean logical operation. The simulator is applied to study the etching rate, the profile and the selectivity in SiO₂ contact hole etching as a function of depth/diameter or aspect ratio A. Etching rate shows its maximum at an intermediate A, and becomes smaller with increase or decrease of A in the present process condition. The etching profile becomes more vertical as A increases. Etching selectivity to underlying Si becomes lower as A increases. The variations of the etching profile and the selectivity are strongly related to the surface coverage of depositive type radicals on the sidewall and on the bottom of the hole geometry, respectively