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 SiO
2
and a top, thin layer of X-ray or photoresist. After exposure and development of the top resist layer, the intermediate layer is etched by CHF
3
reactive ion etching. The thick organic layer is then etched by O
2
reactive 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.