Maintaining photoresist planarity at hole edges

Maintaining photoresist thickness and uniformity over a substrate that includes various cavities presents problems, such as preventing distortion of features in the resist image close to cavity edges. These problems have been overcome by laying down the photoresist as two separate layers. The first layer is used to eliminate or reduce problems associated with the presence of the cavities. The second layer is processed in the normal way and does not introduce distortions close to a cavity's edge. A first embodiment introduces some liquid into the cavity before laying down the first layer while the second embodiment etches away part of the first layer before applying the second one. Application of the process to the formation of a cantilever that overhangs a cavity is also described.