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Field Effect Transistor Storage

IP.com Disclosure Number: IPCOM000082394D
Original Publication Date: 1974-Nov-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Fowler, AB: AUTHOR [+2]

Abstract

The sloshistor or storage field-effect transistor (FET) is an alternative to the metal-nitride-oxide semiconductor (MNOS) or metal-alumina-oxide semiconductor (MAOS) memory PET which operates by injecting charge from a silicon substrate, in order to shift the threshold of the FET. These devices "fatigue" (loss of retention time). It is believed that the fatigue is the result of repeated injection of charge through insulator.

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Field Effect Transistor Storage

The sloshistor or storage field-effect transistor (FET) is an alternative to the metal-nitride-oxide semiconductor (MNOS) or metal-alumina-oxide semiconductor (MAOS) memory PET which operates by injecting charge from a silicon substrate, in order to shift the threshold of the FET. These devices "fatigue" (loss of retention time). It is believed that the fatigue is the result of repeated injection of charge through insulator.

The sloshistor consists of a silicon FET structure 1 having an insulating layer 2, consisting of sandwiches of SiO 3 and 5 and an intermediate insulator 4. The SiO(2) layers 3 and 5 must be about 75 Angstroms to prevent charge injection. The intermediate insulator 4 must be one that has a resistance that is highly nonlinear in an applied field. The flat band voltage or the threshold of the FET is switched by "sloshing" electrons in the intermediate insulator 4, by applying switching voltages to the gate 6. Positive switching voltage will move the electrons toward the gate 6; negative voltage moves the electrons toward the substrate 7.

The threshold shift resulting is given by the equation; Delta V(E) = nq Delta
(N) over K(n) Epsilon (o). where n is the number of electrons moved, q the electronic charge, Delta the insulator thickness, and K(n)Epsilon (o) the insulator permittivity. (For example, if Si(3)N(4) is used as the insulator 4 and Delta (n) = 750 Angstroms (o), to achieve a Triangle V(t) = 5V, about 2.7 x 10/12/ electrons/cm/2/ would have to...