Browse Prior Art Database

Nonvolatile Imaging Devices

IP.com Disclosure Number: IPCOM000078650D
Original Publication Date: 1973-Feb-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 25K

Publishing Venue

IBM

Related People

Agusta, B: AUTHOR [+3]

Abstract

A nonvolatile random-access memory device which can be switched optically and can be used as an imaging device is described.

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Nonvolatile Imaging Devices

A nonvolatile random-access memory device which can be switched optically and can be used as an imaging device is described.

The field-effect transistor (FET) of the figure uses a stacked dual gate 11 disposed on the surface 12 of an N-type silicon substrate 10, into which P-type source and drain diffusions 14 and 15 are made. The gate structure 11 disposed over the channel region 13, between the source and drain diffusions, consists of a layer of silicon dioxide 16 overcoated with a first polysilicon gate 17, which is electrically isolated by a silicon dioxide layer 18 from a second polysilicon gate
19. The first gate 17 is electrically floating and can be charged while the second gate 19 serves as a control.

The FET described has states or threshold voltages determined by the presence or absence of charge in the floating gate 17. Charging and discharging of the floating gate 17 is performed electrooptically. The floating gate 17 is charged by biasing the control gate 19, the source diffusion 14, the drain diffusion 15 and the substrate 10 to a negative voltage, such that when light is directed into the floating gate 17 charge accumulation will occur therein. The gate 17 is selectively discharged by irradiating the device while the control gate 19, the substrate 10, and the source and drain diffusions 14 and 15 are held at ground.

The state of the charge in the floating gate 17 can be determined by applying a bias between the source a...