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Substrate Current Memory Cell

IP.com Disclosure Number: IPCOM000087350D
Original Publication Date: 1977-Jan-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 56K

Publishing Venue

IBM

Related People

Abbas, SA: AUTHOR [+2]

Abstract

The value of the substrate current Isx during a read operation is used to determine the presence or absence of negative charge in the silicon nitride-silicon dioxide layer at the drain end of the channel. Electrons are injected into the gate by hot electron injection (write operation). A read operation involves sensing Isx, which is the hole current flow produced by avalanche multiplication at the drain end of the channel.

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Substrate Current Memory Cell

The value of the substrate current Isx during a read operation is used to determine the presence or absence of negative charge in the silicon nitride- silicon dioxide layer at the drain end of the channel. Electrons are injected into the gate by hot electron injection (write operation). A read operation involves sensing Isx, which is the hole current flow produced by avalanche multiplication at the drain end of the channel.

Isx will be increased for a given gate voltage V(g), drain voltage V(d) and substrate voltage V(sx) or, equivalently, lower terminal voltages are necessary in the improved structure, as shown.

The P region around the drain increases avalanche multiplication effects. This reduces the write voltage and write time, and lowers the read voltages.

The cell, shown in the figure, can be made as follows:

1. Starting with a high resistivity <100> P type silicon substrate,

2. Deposit silicon dioxide, silicon nitride and pyrolytic silicon dioxide layers. The silicon dioxide and silicon nitride can be used as the gate insulator layer.

3. Open source and drain windows in the pyrolytic silicon dioxide.

4. Block out the source window.

5. Ion implant boron through the window and drive in by heat treatment to form the P region.

6. Ion implant N+ (P or As) source and drain regions.

7. Strip pyrolytic silicon dioxide from field region.

8. Ion implant boron in the field regions, then strip pyrolytic silicon dioxide from gate.

9. Grow...