High aspect ratio and reduced undercut trench etch process for a semiconductor substrate

摘要

A hydrofluorocarbon gas is employed as a polymer deposition gas in an anisotropic etch process employing an alternation of an etchant gas and the polymer deposition gas to etch a deep trench in a semiconductor substrate. The hydrofluorocarbon gas can generate a thick carbon-rich and hydrogen-containing polymer on sidewalls of a trench at a thickness on par with the thickness of the polymer on a top surface of the semiconductor substrate. The thick carbon-rich and hydrogen-containing polymer protects sidewalls of a trench, thereby minimizing an undercut below a hard mask without degradation of the overall rate. In some embodiments, an improvement in the overall etch rate can be achieved.

主权项

1. A semiconductor structure comprising:
a stack of a semiconductor substrate and a mask layer having an opening therein; a trench located within said semiconductor substrate and underlying said opening and having a vertically modulated width; and a hydrofluorocarbon polymer layer contiguously extending from a top surface and sidewalls of said mask layer, through sidewalls of said trench, and to a bottom surface of said trench, wherein said hydrofluorocarbon polymer layer has a first composition at said bottom surface of said trench, said hydrofluorocarbon polymer layer has a second composition at said sidewalls of said trench, and said second composition is different from said first composition, wherein said first composition includes hydrogen at first hydrogen atomic percentage, and said second composition includes hydrogen at a second hydrogen atomic percentage that is greater than said first hydrogen atomic percentage.