Effects of Boron and Phosphorous on Isotropic etch of Borophosphosilicate Glass by Wet Chemical and Down Stream Plasma Etch Systems

摘要

In fabrication of standard CMOS devices, isotropic etch is used in conjunction with anisotropic etch to create an interconnect between first layer metal and poly-silicon or substrate (contacts) in the shape of a wine glass. The first step in creating the wine glass profile is to etch the bowl or the isotropic portion in a process that is solely driven by chemical reactions. A true isotropic (chemical) etch removes oxide in all directions at the same rate. Therefore the amount of etch in the vertical direction would equal the amount of etch in the horizontal direction (aspect ratio of 1:1). To perform an isotropic etch there are two well-known options. First option is in a wet sink (wet etch) with a chemical reactant, and second is in a down stream plasma etcher (dry etch). For a wet sink the mechanism is to simply use an acidic solution to contact the oxide film and chemically react to remove the oxide film. For a down stream plasma etcher the mechanism is different. A plasma generates reactive species a distance away from the oxide surface and gas flow through the chamber caries reactive spices to the oxide surface to react with and remove the oxide film.