| 摘要 |
1509949 Integrated circuits RCA CORPORATION 28 Oct 1975 [13 Jan 1975] 44375/75 Heading H1K Mutual isolation of circuit components formed in a semiconductor layer epitaxially grown on an insulating substrate is achieved by providing a field electrode on an insulating layer overlying parts of the layer between the components and connecting it to the layer, the difference in work function of the electrode and layer materials providing an electric field sufficient to deplete said parts of the layer of carriers. A pair of mutually perpendicular FETs thus isolated are formed in an epitaxial N-type silicon layer on a sapphire, spinel, or titania substrate by first forming successive layers of thermal oxide, polysilicon and boron glass, etching the glass so that it overlies the inter-device regions, heating to drive boron in to dope the underlying polysilicon, removing the glass and etching in a mixture of caustic potash and N-propanol to preferentially remove the undoped polysilicon and thus define the field electrode. After a thermal oxidation step, a born-doped polysilicon layer forming the gates of the two FETs is formed as before. The sites of the FET source and drain regions are then exposed by etching, a layer of phosphorus-doped polysilicon deposited to cover those of one of the FETs and a layer of boron doped polysilicon to cover those of the other and the structure heated to form the regions by diffusion from the doped polysilicon. Contact areas on the source and drain regions and field electrode are then exexposed by etching and aluminium deposited and etched to form the contacts. Details of processing steps and alternative materials are given. |
