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Programming a Static Random-Access Memory Cell With Hot Electrons

IP.com Disclosure Number: IPCOM000061488D
Original Publication Date: 1986-Aug-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Beilstein, KE: AUTHOR

Abstract

By injecting hot electrons into the gate region of a field-effect transistor (FET) structure, a simple technique for personalizing chips for redundancy, architecture, organization or initial shadow programs can be provided. A CMOS FET static random-access memory (SRAM) cell with matched devices will, in the ideal case, assume random states upon the application of voltage to the cell. Through the injection of hot electrons into the gate insulator of an FET SRAM cell, it is possible to cause a threshold voltage shift so that each time the cell is powered on it will assume a preferred state. In actual use, a normal gate input signal will override the preferred state when the cell is addressed and can be set to either binary state. Fig.

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Programming a Static Random-Access Memory Cell With Hot Electrons

By injecting hot electrons into the gate region of a field-effect transistor (FET) structure, a simple technique for personalizing chips for redundancy, architecture, organization or initial shadow programs can be provided. A CMOS FET static random-access memory (SRAM) cell with matched devices will, in the ideal case, assume random states upon the application of voltage to the cell. Through the injection of hot electrons into the gate insulator of an FET SRAM cell, it is possible to cause a threshold voltage shift so that each time the cell is powered on it will assume a preferred state. In actual use, a normal gate input signal will override the preferred state when the cell is addressed and can be set to either binary state. Fig. 1 shows a six-device CMOS SRAM cell with matched n-channel devices A and B, matched p-channel devices A' and B' and n-channel transfer devices C. The cell has two stable states with either A and A' devices on and B and B' devices off or vice versa. By electronically altering the threshold shift of one of the n-channel devices (A or B) to a threshold shift above the expected process generated threshold, the cell will assume the preferred preprogrammed state each time the cell is powered up. Fig. 2 shows a schematic presentation of the n-channel devices (A and B) surrounded by an N+ diffusion. By forward biasing the Ndiffusion around the cell in a P substrate through the application of voltage Vp, hot electrons can be made available for injection into the insulator of A or B. The value of Vp and the a...