Reach-through isolation etching method for silicon-on-insulator devices

摘要

A method and the resulting product for isolating lightly doped silicon islands from each other and from a common substrate. The substrate (1) is covered with a first heavily doped epi layer (3). The first epi layer is covered with a lightly doped second epi layer (4). A pair of spaced deep trenches (6, 17) are provided which extend from the top surface of the second layer, through the first layer and into the substrate. The interior walls of the trenches are lined with an oxide layer (8). A pair of heavily doped reach-through diffusion regions (14, 15) extending from said top surface to the first layer is oriented perpendicularly to the deep trenches and fully extends between the trenches. The heavily doped reach-through diffusion regions (14, 15) and the contiguous first layer are then removed by a single anisotropic etching step to yield silicon islands isolated by air except where the islands contact the oxide-lined deep trenches. The air isolation preferably is partially replaced with other dielectric material (10, 11).