Browse Prior Art Database

Programmable Read Only Memory

IP.com Disclosure Number: IPCOM000083736D
Original Publication Date: 1975-Jul-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Haug, W: AUTHOR [+2]

Abstract

The illustrated read-only.memory with field-effect transistors (FET's), in this case transistors T1, utilizes the hot electron effect, by means of which the transistor characteristics, in particular the threshold voltage, can be changed considerably. At high gate and drain voltages, the hot electron effect causes charges to be injected into the gate dielectric of the respective FET. These charges may form a space charge, causing the threshold of the respective transistor to be changed. This effect is particularly pronounced when the FET has a silicon oxide/ silicon nitride sandwich gate dielectric.

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Programmable Read Only Memory

The illustrated read-only.memory with field-effect transistors (FET's), in this case transistors T1, utilizes the hot electron effect, by means of which the transistor characteristics, in particular the threshold voltage, can be changed considerably. At high gate and drain voltages, the hot electron effect causes charges to be injected into the gate dielectric of the respective FET. These charges may form a space charge, causing the threshold of the respective transistor to be changed. This effect is particularly pronounced when the FET has a silicon oxide/ silicon nitride sandwich gate dielectric.

The proposed read-only memory requires one FET T1 for storing one bit. Writing proceeds as follows: The common gate terminal VGS is raised to a high voltage VHH. For writing a 1, the appertaining drain terminals VD are temporarily subjected to voltage VHH. The threshold voltage of the FET remains permanently increased, i.e., a 1 is written into the nonvolatile memory. For writing a 0, no voltage VHH is applied to the appertaining drain terminals VD, so that the threshold voltage remains unchanged.

In a memory into which information has been written as described, the 1's are represented by FET's T1 with a high-threshold voltage and the 0's by FET's T1 with a low-threshold voltage. The difference between the two threshold voltages is about 1 volt, so that the sense amplifier shown in the drawing should be used. Depending on the state of storing FET's T1, this circuit must permit or inhibit the transfer of a signal from S to SG.

In order to...