Method of controlling outdiffusion in doped three-dimensional film by using angled implants

摘要

A solid state fabrication technique for controlling the amount of outdiffusion from a three-dimensional film is comprised of the step of providing a first layer of insitu doped film in a manner to define an upper portion and a lower portion. A second layer of undoped film is provided on top of the first layer to similarly define an upper portion and a lower portion. The first and second layers are etched according to a predetermined pattern. The second layer is doped to obtain a desired dopant density which decreases from the upper portion to the lower portion. Outdiffusion of the dopant from the upper portion of the second layer results in the dopant migrating to the lower portion of the second layer. Thus, outdiffusion into the substrate, and the problems caused thereby, are eliminated or greatly reduced.