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Nonvolatile MIS Charge Storage Devices

IP.com Disclosure Number: IPCOM000086243D
Original Publication Date: 1976-Aug-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Kurylo, A: AUTHOR [+3]

Abstract

This nonvolatile MIS charge storage device is a metal-insulator-silicon field-effect transistor (MISFET) consisting of a pyrolytic SiO(2)-thin Si(3)N(4)-thermal SiO(2) gate structure. The structure of the device is illustrated in Fig. 1.

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Nonvolatile MIS Charge Storage Devices

This nonvolatile MIS charge storage device is a metal-insulator-silicon field- effect transistor (MISFET) consisting of a pyrolytic SiO(2)-thin Si(3)N(4)-thermal SiO(2) gate structure. The structure of the device is illustrated in Fig. 1.

The operation of such a memory device is as follows. Let the device have an initial "on" voltage of V(T)(V(T)= threshold voltage,~ 1V). When a positive voltage in excess of V(I)(V(I) = injection voltage ~45 volts for a 300 Angstroms - 50 Angstroms - 300 Angstroms dielectric structure) is applied to th gate, electrons will be injected from the silicon substrate toward the thin Si(3)N(4)layer through Fowler-Nordheim tunneling. Many injected electrons are trapped in the Si(3)N(4) film.

These trapped electrons induce a field across the dielectric and change the "on" voltage from V(T) to a more positive voltage V(T)'. Therefore, the device is at its "off" state when V(T) is applied on the gate. For example, for a 300 Angstroms - 50 Angstroms - 300 Angstroms dielectric structure, approxima 4X10/12/electrons/cm/2/is needed to change the threshold voltage from +1 volt to +7 volts.

After the injection voltage is removed, the electrons will remain trapped in the Si(3)N(4) film for a very long period of time (on the order of years), because the nitride layer is sandwiched between two layers of high resistivity and high-energy barrier SiO(2). The charge movement in the nitride also does not affect the ...