GB1379269A - Semiconductor device manufacturing process - Google Patents

Abstract

1379269 Semi-conductor devices INTERSIL Inc 4 Oct 1972 [13 July 1972] 45765/72 Heading H1K A method for diffusing impurities of the same conductivity type into different regions of a semiconductor body to produce different dopant concentrations using a single accurately aligned mask comprises producing an apertured mask 13 on an oxide layer on a semi-conductor body surface, etching the oxide to a predetermined depth, Fig. 1c, marking some of the holes, and continuing etching of the remaining holes, Fig. 1E until a desired oxide thickness remains on the body surface. Further holes may then be masked and the remaining holes may be extended, by etching, to the body surface, Fig. 1G, where a heavy dopant concentration may be produced by diffusion into the body to form, for example, an isolation region. The masking may then be removed, and the previously masked holes extended until they also reach the body surface. A lighter doping concentration may then be diffused into the newly-exposed region and also into the heavily doped first region. Three apertures 21, 22, 23 may be used to produce respectively an isolation region, a base region and a resistive region. The depth at which etching is stopped may be determined by the colour of the oxide thereat. The advantage of small masks, e.g. 24, covering the unfinished holes is that alignment is not critical. A further region of the opposite conductivity type may be diffused into the isolation region, through the same aperture, to form a conductive strip for interconnection purposes as described and claimed in Specification 1,379,270. The body may be of silicon, the oxide silicon oxide, and aluminium may be used to interconnect regions to form an integrated circuit for memory applications.