Ultrahigh density vertical NAND memory device
A monolithic three dimensional NAND string includes a semiconductor channel having at least one end extending substantially perpendicular to a major surface of a substrate, a plurality of control gates extending substantially parallel to the major surface of the substrate, including a first control gate located in a first device level and a second control gate located in a second device level, a charge storage material located in the first device level and in the second device level, a blocking dielectric located between the charge storage material and the plurality of control gates, and a tunneling dielectric located between the charge storage material and the semiconductor channel. The tunneling dielectric has a straight sidewall, portions of the blocking dielectric have a clam shape, and each of the plurality of control gates is located at least partially in an opening in the clam-shaped portion of the blocking dielectric.
1. A monolithic three dimensional NAND string, comprising:
a semiconductor channel located over a substrate, at least one end of the semiconductor channel extending substantially perpendicular to a major surface of the substrate;
a plurality of control gates extending substantially parallel to the major surface of the substrate, wherein the plurality of control gates comprise at least a first control gate located in a first device level and a second control gate located in a second device level located over the substrate and below the first device level;
a charge storage material located in the first device level and in the second device level;
a blocking dielectric located between the charge storage material and the plurality of control gates; and
a tunneling dielectric located between the charge storage material and the semiconductor channel;
wherein:
the tunneling dielectric has a straight sidewall;
portions of the blocking dielectric have a clam shape; and
each of the plurality of control gates is located at least partially in an opening in the clam-shaped portion of the blocking dielectric.
2. The NAND string of claim 1 , wherein the tunneling dielectric has the straight sidewall and a uniform thickness throughout the NAND string.
3. The NAND string of claim 1 , further comprising one of a source or drain electrode which contacts the semiconductor channel from above, and another one of a source or drain electrode which contacts the semiconductor channel from below.
4. The NAND string of claim 1 , wherein the charge storage material comprises a charge storage dielectric material or conductive nanoparticles.
5. The NAND string of claim 1 , wherein the charge storage material comprises a floating gate material.
6. The NAND string of claim 5 , wherein the floating gate material comprises polysilicon, metal, metal alloy or metal silicide.
7. The NAND string of claim 1 , wherein the plurality of control gates comprise conductive or semiconductor control gate material.
8. The NAND string of claim 7 , wherein the plurality of control gates comprise tungsten, copper, aluminum, tantalum, titanium, cobalt, titanium nitride or alloys thereof.
9. The NAND string of claim 8 , wherein the plurality of control gates comprise tungsten.
10. The NAND string of claim 1 , further comprising an insulating fill material located in a central part of an opening in the semiconductor channel.
11. A monolithic, three dimensional array of memory devices located over a silicon substrate, comprising an array of vertically oriented NAND strings in which at least one memory cell in a first device level of the array is located over another memory cell in a second device level, wherein at least one vertically oriented NAND string of the array of vertically oriented NAND strings comprises:
a semiconductor channel located over the silicon substrate, at least one end of the semiconductor channel extending substantially perpendicular to a major surface of the silicon substrate;
a plurality of control gates extending substantially parallel to the major surface of the silicon substrate, wherein the plurality of control gates comprise at least a first control gate located in the first device level and a second control gate located in the second device level located over the silicon substrate and below the first device level;
a charge storage material located in the first device level and in the second device level;
a blocking dielectric located between the charge storage material and the plurality of control gates;
a tunneling dielectric located between the charge storage material and the semiconductor channel; and
an integrated circuit comprising a driver circuit for the memory array located on the silicon substrate;
wherein:
the tunneling dielectric has a straight sidewall;
portions of the blocking dielectric have a clam shape; and
each of the plurality of control gates is located at least partially in an opening in the clam-shaped portion of the blocking dielectric.
12. The array of claim 11 , wherein the tunneling dielectric of the at least one NAND string has the straight sidewall and a uniform thickness throughout the NAND string.
13. The array of claim 11 , wherein the at least one NAND string further comprises one of a source or drain electrode which contacts the semiconductor channel from above, and another one of a source or drain electrode which contacts the semiconductor channel from below.
14. The array of claim 11 , wherein the charge storage material of the at least one NAND string comprises a charge storage dielectric material or conductive nanoparticles.
15. The array of claim 11 , wherein the charge storage material of the at least one NAND string comprises a floating gate material.
16. The array of claim 15 , wherein the floating gate material comprises polysilicon, metal, metal alloy or metal silicide.
17. The array of claim 11 , wherein the plurality of control gates of the at least one NAND string comprise conductive or semiconductor control gate material.
18. The array of claim 17 , wherein the plurality of control gates comprise tungsten, copper, aluminum, tantalum, titanium, cobalt, titanium nitride or alloys thereof.
19. The array of claim 18 , wherein the plurality of control gates comprise tungsten.
20. The array of claim 11 , wherein the at least one NAND string further comprises an insulating fill material located in a central part of an opening in the semiconductor channel.