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ENHANCED STORAGE DYNAMIC CELL USING COMPOSITE SILICON-RICH SiO2 AND THERMAL SiO2 LAYERS

IP.com Disclosure Number: IPCOM000041978D
Original Publication Date: 1984-Mar-01
Included in the Prior Art Database: 2005-Feb-03
Document File: 3 page(s) / 48K

Publishing Venue

IBM

Related People

DiMaria, DJ: AUTHOR [+3]

Abstract

This article relates generally to one-device memory cells and more particularly to an enhanced storage dynamic FET memory cell using a composite silicon-rich silicon dioxide and thermal silicon dioxide layers in its storage capacitor. A dynamic memory cell using Si-rich SiO2 and pure SiO2 composite layers for storage capacitors is disclosed whose storage capacitance is enhanced by injection of electrons into and out of the Si-rich oxide with respect to the counter electrode (field plate). Furthermore, the dielectric strength of the underlying SiO2 (adjacent to Si substrate) is significantly improved because of the Si-rich SiO2 . For an appropriate composition of Si-rich SiO2, the process is reversible and rapid. Hence, it allows charge storage enhancement by virtue of an increased effective field across the pure SiO21ayer.

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ENHANCED STORAGE DYNAMIC CELL USING COMPOSITE SILICON-RICH SiO2 AND THERMAL SiO2 LAYERS

This article relates generally to one-device memory cells and more particularly to an enhanced storage dynamic FET memory cell using a composite silicon-rich silicon dioxide and thermal silicon dioxide layers in its storage capacitor. A dynamic memory cell using Si-rich SiO2 and pure SiO2 composite layers for storage capacitors is disclosed whose storage capacitance is enhanced by injection of electrons into and out of the Si-rich oxide with respect to the counter electrode (field plate). Furthermore, the dielectric strength of the underlying SiO2 (adjacent to Si substrate) is significantly improved because of the Si-rich SiO2 . For an appropriate composition of Si-rich SiO2, the process is reversible and rapid. Hence, it allows charge storage enhancement by virtue of an increased effective field across the pure SiO21ayer. The same composite layer can also be used for the gate oxide of a switching FET so that no extra masking step is needed during fabrication. This composite layer enhances the transconductance of the transfer FET because of the increased capacitance. The reliability of the gate insulator is also enhanced because of the silicon-rich oxide. The Si-rich oxide and pure SiO2 composite layer sandwiched between conductive layers, which form the storage capacitor, has the following properties. When the field across the structure is low (N<2 MV/cm), the Si-rich oxide behaves like an insulator with a dielectric constant of 7.5 and there is little or no charge stored in it. The composite layer is thus like an insulator with thickness (wox1 + wox2) with a dielectric constant of: When the field across the structure is higher (N 2 MV/cm), the Si-rich oxide begins to conduct and electrons are injected and stored in the Si-rich oxide. If d is the centroid of the injected charge in the Si-rich oxide measured from the Si-rich oxide and pure SiO2 interface, the effective dielectric constant is: The process is reversed when the field is lowered. At that time the electrons are dumped from the Si-rich SiO2 by field reversal. The field across the structure should be limited to less than 4 MV/cm. At higher fields, electrons are actually injected into the pure SiO2 layer. Fig. 1 shows...