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US 2012/0256247 A1Published application
3D Vertical NAND and Method of Making Thereof by Front and Back Side Processing
AssigneeSanDisk Corporation
InventorJohann Alsmeier
Life of this patent
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Abstract
Monolithic three dimensional NAND strings and methods of making. The method includes both front side and back side processing. Using the combination of front side and back side processing, a NAND string can be formed that includes an air gap between the floating gates in the NAND string. The NAND string may be formed with a single vertical channel. Alternatively, the NAND string may have a U shape with two vertical channels connected with a horizontal channel.
Claims22
A method of making a monolithic three dimensional NAND string, comprising:
- forming a stack of alternating layers of a first material and a second material over a substrate, wherein the first material comprises a conductive or semiconductor control gate material and wherein the second material comprises a first sacrificial material;
- etching the stack to form a back side opening in the stack;
- depositing a second sacrificial material in the back side opening;
- etching the stack to form a front side opening in the stack;
- selectively removing the second material through the front side opening to form first recesses;
- forming a first blocking dielectric in the first recesses to partially fill the first recesses;
- forming a plurality of spaced apart dummy layer segments separated from each other in remaining unfilled portions of the first recesses over the first blocking dielectric;
- forming a charge storage material layer over the first blocking dielectric in the front side opening;
- forming a tunnel dielectric layer over the charge storage material layer in the front side opening;
- forming a semiconductor channel layer over the tunnel dielectric layer in the front side opening;
- selectively removing the second sacrificial layer from the back side opening;
- selectively removing the plurality of dummy layer segments through the back side opening to expose the first recesses in the back side opening;
- selectively removing portions of the charge storage material layer through the back side opening and the first recesses to form a plurality of spaced apart charge storage segments;
- and
- forming a second blocking dielectric in the first recesses and between the spaced apart charge storage segments through the back side opening.
12 more elements
A monolithic three dimensional NAND string, comprising:
- a semiconductor channel, at least one end portion of the semiconductor channel extending substantially perpendicular to a major surface of a substrate;
- a plurality of control gate electrodes having a strip shape extending substantially parallel to the major surface of the substrate, wherein the plurality of control gate electrodes comprise at least a first control gate electrode located in a first device level and a second control gate electrode located in a second device level located over the major surface of the substrate and below the first device level;
- a blocking dielectric comprising a plurality of first blocking dielectric segments, wherein each of the plurality of first blocking dielectric segments is located in contact with a respective one of the plurality of control gate electrodes;
- a plurality of spaced apart charge storage segments, wherein the plurality of spaced apart charge storage segments comprise at least a first spaced apart charge storage segment located in the first device level and a second spaced apart charge storage segment located in the second device level, and wherein the first spaced apart charge storage segment is separated from the second spaced apart charge storage segment by an air gap;
- and
- a tunnel dielectric located between each one of the plurality of the spaced apart charge storage segments and the semiconductor channel.
3 more elements
Dependencies are inferred from the claim text.