MOS integrated circuit mfr. - using local oxidn. of silicon to separate active transistor zone in silicon semiconductor substrate

摘要

In the circuits, the active transistor zones in a p- or n- doped semiconductor substrate(1) are sepd. by silica layers obtd. by LOCOS (local oxidn. of silicon); and the usable voltage is increased by field ion implantation in the field oxide. The substrate is first coated with thermal oxide (2), which is implanted with nitrogen ions to form an implanted oxide (4). The N-ion concn. (C-N) in the substrate must remain below its dopant concn. A photolacquer mask(5) is used to define the active transistor zones; and layer(4) is etched off where field oxide is to be formed. Field ions are then implanted, followed by removing mask(5) and creating the field oxide zones. Layer (4) is next removed and gate oxidn. employed. Alternatively, layer (4) may be used as the gate oxide. Used in very large scale integration technology, to achieve min. dimensions without "birds' beaks".