Process for producing integrated circuit devices by ion implantation

Claim 1

An improved process for making an integrated circuit semiconductor device in a monocrystalline semiconductor substrate comprising: forming a subcollector region of a first conductivity type in a monocrystalline semiconductor substrate of a second opposite conductivity type, depositing an epitaxial layer of semiconductor material on said substrate, oxidizing the surface of said epitaxial layer to form a layer of thermally grown SiO 2 having a thickness in the range of 500 to 2500 A, forming an annular shaped isolation means that at least encompasses the region of said epitaxial layer overlying said subcollector region, depositing a first layer of photoresist over the layer of SiO 2 , exposing, developing and removing a portion of said first layer of photoresist to define a window for a base region overlying in part said subcollector, ion implanting an impurity of a second conductivity through the window to form a base region, removing said first layer of photoresist, depositing a second layer of photoresist over the layer of SiO 2 , exposing, developing and removing portions of said second layer of photoresist to define windows for the collector contact, the base contact, and the emitter contact, removing the exposed areas of said layer of SiO 2 to define the collector contact, the base contact and the emitter contact, removing said second layer of photoresist, depositing a third layer of photoresist, exposing, developing and removing portions of said third layer of photoresist to redefine the collector contact and the emitter contact, ion implanting an impurity of a first conductivity to form the collector contact region and the emitter region, removing said third layer of photoresist, heating the resultant device at a temperature in the range of 900° to 1100° C. to activate the implanted first and second type impurities, and to drive in the ion implanted first impurity in said emitter region, deposit the metallurgy system.