Westinghouse Electric Corporation

Michael D Fitzpatrick

James R Cricchi

Franklyn C Blaha

A non-volatile memory and method is described incorporating an array of variable threshold transistors, a row decoder, a buffer circuit positioned between the array and row decode circuitry, column decode circuitry, and a sense amplifier. The non-volatile memory overcomes the problem of high voltages in the memory array during READ operation. During READ operation the variable threshold transistors operate in the common source mode. A buffer circuit with level shift capability is described incorporating P and N channel transistors. A sense amplifier with decoupling during sensing or lock out is described incorporating P and N channel transistors.

Electrically alterable non-volatile memory

A radiation hardened drain-source protected MNOS transistor is disclosed. A layer of silicon oxide overlies the channel and the junctions formed by the intersections of the drain and source regions with the channel. Drain and source protection is provided by relatively thick portions of the silicon oxide layer which overlie the junctions formed by the drain and source regions and the channel. The portion of the silicon oxide layer overlying the central section of the channel is thinner than the remainder of this layer. A silicon nitride layer and an electrically conductive layer forming the gate electrode overlie the thinner portion of the silicon oxide layer to complete the MNOS transistor. The conductive layer forming gate electrode of the transistor is in electrical contact with both the silicon nitride and the silicon oxide layers. This provides a convenient method for electrons generated at the interface of the silicon and the silicon-oxide layer during irradiation to be transported to the gate, thereby preventing charge build-up in the silicon oxide which causes shifts in the characteristics of the transistor.

Radiation hardened drain-source protected MNOS transistor

A complementary MOS voltage level shift circuit which can be used as a memory buffer circuit, for example, is disclosed. The circuit utilizes both N-channel depletion mode devices and P-channel enhancement mode MOS devices preferably fabricated on silicon-on-sapphire. Both types of devices are operated with only negative or zero gate-source voltage in order to minimize threshold voltage shifts in radiation environments. A capacitive voltage level shifting technique is used to obtain push-pull operation with driver type devices in order to reduce power consumption and increase switching speed while feeding into a capacitive load. Load type devices are used to prevent discharge of a capacitive load.

High speed, radiation hard complementary MOS capacitive voltage level

A complementary MOS logic circuit is disclosed. The circuit utilizes two stages with a coupling network comprising a capacitor and a diode used to couple the first stage to the second stage. This results in a circuit with the logic signal coupled to the input being inverted at the output without introducing substantial loss in signal amplitude.

Complementary MOS logic circuit

An MOS transistor constructed using silicon on sapphire technology in which the channel region can be electrically connected either to the source or drain terminal is disclosed. The transistor is advantageous in that the shift of the threshold voltage of the transistor in the presence of radiation is substantially decreased. Connecting the channel region of the transistor to the source terminal also substantially reduces what is normally referred to as the 'kink' effect in MOS transistors utilizing floating substrate channel regions. Reducing the sensitivity to radiation and the kink effect results in a transistor having improved electrical characteristics.

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Glen Burnie, MD, United States of America

Michael D Fitzpatrick