SINGLE LAYER DOPED POLY-SILICON GATE STRUCTURE FOR CHARGE-COUPLED DEVICES

摘要

1528923 Charge-coupled devices RCA CORPORATION 19 Jan 1976 [3 Feb 1975] 4544/75 Heading H1K In a CCD comprising a single layer semiconductor gate structure preferably of polysilicon, on an insulated substrate 10, transfer electrodes 14, 16, 18 &c. are separated by regions 20, 22 of a conductivity type opposite to that of the electrodes, and in use the leakage current between adjacent electrodes is reduced by properly biasing the substrate relative to the electrodes. In case of a buried-channel device, Fig. 4 (not shown), the transfer electrodes are of the same conductivity type as the substrate provided with a thin layer of the opposite conductivity type in between the substrate and an insulating layer, e.g. of silicon dioxide. Diffusion regions, Fig. 5 (not shown), in the substrate, of the same conductivity type as but of higher impurity concentration than the substrate are provided to define the boundaries of the CCD channels. When used as a two-phase device, a fixed charge either in the insulation layer or in the substrate beneath the same edge of each electrode is provided. The polysilicon layer, preferably vapour deposited by pyrolitic decomposition of silane, is doped by using diborane during growth or subsequently by ion implanatation, whereas N+ regions are formed using an oxide diffusion mask and using conventional phosphorous doping sources. Aluminium is used for contacting the transfer electrodes. Upper and lower limits of three-phase voltage waveforms imposed on the electrodes and the bias voltage of the substrate are disclosed.