MNOS Memory device and method of manufacture
AssigneeRCA Corporation
InventorHeshmat Khajezadeh
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Abstract
A metal nitride oxide semiconductor (MNOS) memory device having improved memory retention capability is described. Improved memory retention is obtained by ion implanting a non-doping material, such as argon or nitrogen, or a low concentration of an N type dopant, such as phosphorus, into the oxide before depositing the nitride layer. It is believed that the ion implantation results in a nitride-oxide interface conducive to charge storage. The MNOS device produced has a considerably improved memory retention characteristic when compared with an MNOS device which did not have the ion implantation.
Claims12
An improved method of forming an MNOS device of the type comprising the steps of:
- (a) selecting a substrate having a first impurity type;
- (b) forming a spaced source and drain of opposite conductivity type extending into said substrate from a surface thereof;
- (c) forming a silicon dioxide layer on the surface of said substrate at least between said source and said drain;
- (d) forming a silicon nitride layer over the surface of said silicon dioxide layer;
- and
- (e) forming a continuous conductive gate over said silicon nitride layer at least overlying a portion of said source and said drain;
- wherein the improvement comprises implanting ions selected from the group consisting of a non-dopant and a dopant having the same impurity type as said substrate into said silicon dioxide layer, said step of implanting occurring immediately prior to said step of forming a silicon nitride layer.
An improved MNOS device of the type comprising:
- (a) a substrate having a first impurity type;
- (b) a source and a drain spaced from said source, both being of conductivity type opposite to said substrate and extending into said substrate from a surface thereof;
- (c) a silicon dioxide layer on the surface of said substrate extending at least between said source and said drain, said silicon dioxide layer having a central portion which is substantially thinner than the portions adjacent either said source or said drain;
- (d) a silicon nitride layer formed on the surface of said silicon dioxide layer;
- and
- (e) a continuous conductive gate overlying said silicon nitride layer and at least a portion of said source and said drain;
- wherein the improvement comprises damage to said silicon dioxide layer at its interface with said silicon nitride layer caused by ion implantation of ions into said silicon dioxide layer.
Dependencies are inferred from the claim text.