Semiconductor memory array of floating gate memory cells with vertical control gate sidewalls and insulation spacers
View Patent ↗A self aligned method of forming a semiconductor memory array of floating gate memory cells in a semiconductor substrate having a plurality of spaced apart isolation regions and active regions on the substrate substantially parallel to one another in the column direction. Floating gates are formed in each of the active regions. Control gates are each formed with a substantially vertical face portion by covering a portion of a conductive layer with a protective layer, and performing an anisotropic etch to remove the exposed portion of the conductive layer. An insulation sidewall spacer is formed against the vertical face portion. The control gates have protruding portions that extend over the floating gates.
1. An electrically programmable and erasable memory device comprising:
a substrate of semiconductor material of a first conductivity type;
first and second spaced-apart regions in the substrate of a second conductivity type, with a channel region therebetween;
a first insulation layer disposed over said substrate;
an electrically conductive floating gate disposed over said first insulation layer and extending over a portion of the channel region and over a portion of the first region;
a second insulation layer having a first portion disposed over said first insulation layer and said substrate, a second portion disposed adjacent the floating gate and a third portion disposed over the floating gate, wherein the second insulation layer has a thickness permitting Fowler-Nordheim tunneling of charges therethrough;
an electrically conductive control gate having a first portion disposed over the second insulation layer first portion and adjacent to the second insulation layer second portion, and a second portion extending over the second insulation layer third portion, the control gate having a substantially vertical sidewall portion; and
an insulation spacer formed adjacent to the substantially vertical sidewall portion of the control gate;
wherein the second region has an edge that is aligned with the substantially vertical sidewall portion.
2. The device of claim 1 , further comprising:
a third insulation layer formed over a top surface of the control gate.
3. The device of claim 1 , wherein the floating gate includes a sharp edge portion that extends toward the control gate.
4. The device of claim 3 , the first and second portions of the control gate form a notch into which the sharp edge portion of the floating gate extends.
5. The device of claim 1 further comprising:
a layer of metalized silicon formed on the second region and aligned to the insulation spacer.
6. An array of electrically programmable and erasable memory devices comprising:
a substrate of semiconductor material of a first conductivity type;
spaced apart isolation regions formed on the substrate which are substantially parallel to one another and extend in a first direction, with an active region between each pair of adjacent isolation regions;
each of the active regions including a column of memory cells extending in the first direction, each of the memory cells including:
first and second spaced-apart regions formed in the substrate having a second conductivity type, with a channel region formed in the substrate therebetween,
a first insulation layer disposed over said substrate including over said channel region,
an electrically conductive floating gate disposed over said first insulation layer and extending over a portion of the channel region and over a portion of the first region, and
a second insulation layer having a first portion disposed over said first insulation layer and said substrate, a second portion disposed adjacent the floating gate and a third portion disposed over the floating gate, wherein the second insulation layer has a thickness permitting Fowler-Nordheim tunneling of charges therethrough; and
a plurality of electrically conductive control gates each extending across the active regions and isolation regions in a second direction substantially perpendicular to the first direction and having a first portion and a second portion, wherein each of the control gates intercepts one of the memory cells in each of the active regions such that the control gate first portion is positioned over the second insulation layer first portion and adjacent to the second insulation layer second portion and the control gate second portion extends over the second insulation layer third portion, and wherein each of the control gates has a substantially vertical sidewall portion; and
a plurality of insulation spacers each formed adjacent to one of the substantially vertical sidewall portions of the control gates;
wherein the second region has an edge that is aligned with the substantially vertical sidewall portion.
7. The device of claim 6 , further comprising:
a third insulation layer formed over a top surface of each of the control gates.
8. The device of claim 6 , wherein each of the floating gates includes a sharp edge portion that extends toward one of the control gates.
9. The device of claim 8 , wherein for each of the control gates, the first and second portions form a notch into which the sharp edge portion of the floating gate extends.
10. The device of claim 6 , further comprising:
a layer of metalized silicon formed on each of the second regions and aligned to the corresponding insulation spacer.