| 摘要 |
1524685 Charge coupled devices PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 19 Sept 1975 [24 Sept 1974] 38587/75 Heading H1K The transfer electrode structure of a charge transfer device is made by first forming lower and upper layers of insulation over the channels material, the upper layer being impervious to oxygen and selectively etchable with respect to that of the lower layer, forming first electrodes of an oxidizable material from a deposited layer and providing them with an insulating layer by surface oxidation, and then etching away the parts of the upper layer between the electrodes and depositing further electrodes over the exposed parts of the lower layer to interlace with and partially overlap the first electrodes. In one device so formed (Fig. 1), packets of majority carriers are injected from source diffusion 7 into an N-type silicon channel capable of being completely depleted [of such carriers by sub-breakdown fields and isolated by back-biasing of its junctions with P-type substrate 5 and the isolating ring 16, which optionally extends to the substrate, and are read out at diffusion 9. The diffused or implanted regions 7, 9, 16 are formed before provision of the lower insulating layer 12 of genetic oxide 800A thick and the upper layer 13 of deposited silicon nitride 350Š thick. The first electrodes 10 of boron- or phosphorus-doped polycrystalline silicon (or aluminium or tantalum) are heated at 1000‹ C. in an oxidizing ambient to provide a 0À3 Á thick oxide coating 14 and are then used to mask etching of the nitride in hot phosphoric acid. After providing contact windows in the oxide aluminium is deposited and patterned by photoetching to define the second transfer electrodes 11 and contacts 6, 8, 19 to the diffusions, and the device annealed in hydrogen at 450‹ C. In another embodiment, after removal of the nitride between electrodes 10, a layer of alumina, or silicon nitride alone or coated with silica is applied on the electroded face and a gettering layer of phosphorus-doped silica deposited on both faces, the layers applied to the electroded face etched off again and the device heated at 1000‹ C. in an oxidizing medium to complete gettering and to increase the oxide thickness, except under electrodes 10, by 200Š. The remaining electrodes are formed as before. Variations include provision of a highly doped skin on the surface of lightly doped channel 3, interconnection of electrodes 10 and 11 and use of the same electrode structure in BBDs and minority carrier CCDs. |
