Controlling polymer formation during polysilicon etching in a magnetically enhanced reactive ion etcher

摘要

were conducted in a magnetically enhanced reactive ion etcher to understand the material and process related issues affecting polymer formation during a polysilicon etch. Samples consist of POCl$-3$/ doped and undoped polysilicon which are patterned with two different types of photoresist. Processing is done using a Cl$-2$//HBr chemistry with some of the experiments having oxygen added during the over etch step of the process. Scanning electron microscope results indicate two very distinct structures exist on the various samples. One that exhibits a more uniform polymer and the other that leaves an `ear' shaped polymer formation. These various structures also are analyzed using x-ray photoelectron spectroscopy. This analysis indicates the polymers to be a combination of silicon, oxygen, and carbon. Based on this study it is apparent that the type of material, photoresist, and process variables significantly influence the polymer formation during the etching of undoped and doped polysilicon with an HBr/Cl$-2$/ chemistry.