| 摘要 |
1,264,209. Semi-conductor memory elements. WESTINGHOUSE ELECTRIC CORP. 9 April, 1969 [19 April, 1968], No. 18135/69. Heading H1K. In a memory element comprising a dielectric disposed between a semi-conductor body and a metal electrode, the dielectric is capable of storing charges injected from the body or electrode so that the graph of net charge versus electrode-semi-conductor voltage exhibits a reproducible hysteresis loop. The preferred embodiment consists of a silicon IGFET, the gate insulation of which consists of a silicon nitride layer superposed on a layer of silica, with a further silica layer between the nitride and the electrode if desired. Alternative dielectrics are a single layer of silicon nitride or of a mixture of oxide and nitride, a layer of silica and alumina preferably coated with silicon nitride, or for operation at liquid nitrogen temperatures, a single layer of tantalum oxide. With gate voltages below a threshold level the preferred IGFET behaves conventionally but at higher voltages carriers tunnelling from the silicon to the dioxide-nitride interface are captured in deep traps in the nitride to provide the hysteresis effect. At normal temperatures the charges can be stored for several months, but can be removed by application of a reverse voltage above a threshold value or by irradiation. The insulating layers which should be amorphous or monocrystalline may be prepared by pyrolytic deposition though the oxide may instead be thermally grown. Aluminium is the usual gate electrode metal though a transparent tin oxide layer is preferred where irradiation erasure is to be used. In alternative embodiments the charge storing dielectric is disposed over the collector junction of a bipolar transistor to control its amplification or over the junction of a diode to control its breakdown voltage. |
