| 摘要 |
1,048,475. Field effect transistors. RADIO CORPORATION OF AMERICA. Aug. 20, 1963 [Sept. 7, 1962], No. 32977/63. Heading H1K. A field effect transistor consists of a semiconductor substrate with a low-resistivity surface inversion layer of opposite conductivity type provided with two electrodes and a control electrode disposed on an insulating layer overlying the surface layer between the two electrades. A typical arrangement (Fig. 3) is made from a monocrystalline 500 ohm. cm. P-type silicon wafer 23a by chemically etching its surface, depositing thereon heavily donordoped silica by decomposition of a doped oxysilane, and selectively removing it by etching using photoresist techniques to expose certain portions. The wafer is next heated in dry oxygen for an hour to form thin pure silica layers 25a on the exposed portions with N-type inversion layers 27a beneath them and to form beneath the doped silica N-type regions 31a, 33a &c. making ohmic connection to the ends of the inversion layers. Apertures are etched in the doped oxide layers by conventional photoresist techniques, and aluminium vapour deposited over the entire surface and subsequently selectively removed to leave source and drain contacts 35a, 37a on the N regions and gate contacts 45 overlying the pure silica layers 25a. The gate contacts may be confined to the original apertures in the doped layer as shown or may extend slightly beyond them. The resulting devices are suitable for series connection. In an alternative arrangement (Fig. 8, not shown) every third gate electrode is omitted and the remaining ones connected together in pairs to provide a plurality of devices each with two source electrodes and a central drain electrode. The thickness and hence resistance of the inversion layers is determined by the duration and temperature of the heating step but the channel resistance may be further modified by baking the wafer in a dry inert atmosphere immediately before the electrodes are deposited. Characteristics of devices subjected to such treatments are given to illustrate their effect. An alternative device with a disc-shaped drain and concentric annular gate and source electrodes is also described (Fig. 1, not shown). |
