High Resolution, Steep Profile, Resist Patterns

High resolution and steep profile patterns have been generated in a 2.6-μm thick organic layer which conforms to the steps on a wafer surface and is planar on its top. This thick organic layer (a photoresist in the present experiments) is covered with an intermediate layer of SiO2and a top, thin layer of X-ray or photoresist. After exposure and development of the top resist layer, the intermediate layer is etched by CHF3reactive ion etching. The thick organic layer is then etched by O2reactive ion etching. Submicron resolution with essentially vertical walls in the thick organic material was achieved. The technique is also applicable to photo- and electron lithography. It reduces the need for thick resist patterns for the lithography step and, at the same time, ensures high resolution combined with good step coverage.