FORFARANDE FOR FRAMSTELLNING AV MONOLITISKA, KOMPLEMENTERA TRANSISTORER

1525247 Integrated circuits WESTERN ELECTRIC CO Inc 19 Sept 1975 [19 Sept 1974] 38498/75 Heading H1K Complementary bipolar transistors of similar characteristics are provided in a semiconductor body comprising a moderately-doped n-type epitaxial layer 13 on a lightly-doped p-type substrate 12. The pnp transistor 10 comprises a lightly phosphorus-doped n-type buried isolation region 14 preferably formed by diffusion of ion-implanted phosphorus atoms, a heavilydoped (preferably with boron) P+ type buried collector region 15 within the isolation region 14, a part 24 of the epitaxial layer 13 overlying the region 15 and converted to p-type conductivity, e.g. by boron or aluminium ion implantation, an n-type base region 16 and a p-type emitter region 17, preferably phosphorus implanted and boron diffused respectively. Highly doped contact regions 19, 18, 20 may also be provided. The npn transistor 11 comprises a heavily arsenic or antimony doped n+ type buried collector region 30, either diffused or implanted, a heavily doped p+-type buried isolation region 31 laterally surrounding the region 30, a p-type base region 32 within the epitaxial layer 13 above the region 30 and an n-type emitter region 33 within the region 32. Once again heavily-doped contact regions 37, 34, 35 may be provided. The invention requires the regions 14, 30 and 15/31 to be formed in that order, and preferably the regions 16, 32, 17 and 33 are subsequently formed in that order. The various heat treatments preferably occur at successively lower temperatures in order that the first-formed regions are not disrupted during the later heating steps.