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Write Once Read Only Store

IP.com Disclosure Number: IPCOM000077579D
Original Publication Date: 1972-Aug-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 59K

Publishing Venue

IBM

Related People

Herrell, DJ: AUTHOR [+2]

Abstract

A metal oxide device, such as niobium oxide or tantalum oxide, can be electrically formed to produce an avalanche state. Using devices which are formed in the avalanche state to represent the binary "1", or not formed to represent the binary "0", a memory can be provided which does not require a series diode connected to each metal oxide device in order to prevent sneak paths.

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Write Once Read Only Store

A metal oxide device, such as niobium oxide or tantalum oxide, can be electrically formed to produce an avalanche state. Using devices which are formed in the avalanche state to represent the binary "1", or not formed to represent the binary "0", a memory can be provided which does not require a series diode connected to each metal oxide device in order to prevent sneak paths.

Fig. 1 shows the current vs. voltage characteristics for the metal oxide devices of this improvement. A device which has been formed to have an avalanche state represents a binary 1, while a device which is unformed represents a binary 0. The forming voltage necessary for creating the avalanche state is no greater than three times the threshold voltage (V(T)), of a metal oxide device having an avalanche state. This requirement is met with a niobium oxide device having a forming voltage of 3.6 volts, and is met with a tantalum oxide device having a forming voltage as high as 11.5 volts. If the device when formed passes directly into a low-resistance state, the avalanche state can be regenerated by passing a current through the device in the reverse direction (base electrode to counter electrode).

Representative threshold voltages for metal oxide devices are represented by the following: TiO(2) - 0.4V Nb(2)O(5) - 1.2V Ta(2)O(5) - 3.5V. Fig. 2 shows an electrical layout of a read-only storage in which the metal oxide elements are represented by the circles labeled 11...