| 摘要 |
1497499 Semi-conductor devices INTERNATIONAL BUSINESS MACHINES CORP 13 Oct 1976 [28 Nov 1975] 42466/76 Heading H1K A localized dielectric region is produced in the surface of a silicon substrate by forming a corresponding region of porous silicon in the surface, completely oxidizing the porous silicon at a high temperature so that the oxide extends above the substrate surface and then raising the temperature further for a time sufficient to densify the oxide so that its surface is flush with that of the substrate. In the described embodiments, in which the dielectric region is used to isolate sections of an epitaxial layer overlying heavily doped buried regions on an N type body, a masking layer of thermal or pyrolytic silicon, optionally coated with silicon nitride, is apertured at the site of the dielectric region and the exposed silicon diffused or implanted with acceptor impurity to form a P+ network extending to the body. The network is then subjected to anodic action in hydrofluoric acid to produce 40-80% porosity, and the porous silicon heated in steam or oxygen at 970‹ C. to oxidize it and optionally form a dense silica layer beneath it. After densifying by heating, e.g. at 1150‹ C. or above in nitrogen or other inert gas or in an oxidizing gas, transistor structures are conventionally formed in the isolated sections of the epitaxial layer. Typically a strip of densified porous oxide is formed within each section to provide a laterally isolated collector contact region. |
