# US 2014/0193969 A1 · Semiconductor structures and methods of fabrication of same

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- Number: US 2014/0193969 A1
- Document ID: US20140193969A1
- Status: Published application
- Kind: A1
- Application number: 13/738,457
- Filed: 2013-01-10
- Published: 2014-07-10
- Earliest claimed: 2013-01-10
- Assignees: Micron Technology, Inc.
- Inventors: Jeffery B. Hull; John M. Meldrim
- Web page: https://patentgrep.com/patent/US20140193969A1

## CPC

- H10D 30/0411: {of FETs having floating gates}
- H10B 41/27: the channels comprising vertical portions, e.g. U-shaped channels
- H10D 30/689: {Vertical floating-gate IGFETs}
- H10D 30/6891: {characterised by the shapes, relative sizes or dispositions of the floating gate electrode}
- H10D 64/01306: {the conductor comprising a layer of silicon contacting the insulator, e.g. polysilicon}
- H10D 64/035: {comprising conductor-insulator-conductor-insulator-semiconductor structures}
- H10D 64/661: {the conductor comprising a layer of silicon contacting the insulator, e.g. polysilicon having vertical doping variation (having lateral variation in the gate structure H10D64/671)}
- H10D 64/681: {having a compositional variation, e.g. multilayered}
- H10D 64/691: {comprising metallic compounds, e.g. metal oxides or metal silicates (insulators comprising nitrogen H10D64/693)}
- H10D 64/693: {the insulator comprising nitrogen, e.g. nitrides, oxynitrides or nitrogen-doped materials}
- H10P 14/69391: {the material containing aluminium, e.g. Al2O3}
- H10P 50/283: {by chemical means}
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
- H10B: ELECTRONIC MEMORY DEVICES
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10

## Abstract

Semiconductor structure including an etch stop material between a substrate and a stack of alternating insulating materials and first conductive materials, wherein the etch stop material comprises an amorphous aluminum oxide on the substrate and a crystalline aluminum oxide on the amorphous aluminum oxide; a channel material extending through the stack; and a second conductive material between the channel material and at least one of the first conductive materials in the stack of alternating insulating materials and first conductive materials, wherein the second conductive material is not between the channel material and the etch stop material. Also disclosed are methods of fabricating such semiconductor structures.

## Claims

### Claim 1

A method of fabricating a semiconductor structure, the method comprising:
forming an etch stop material between a substrate and a stack of alternating insulating materials and first conductive materials, the etch stop material comprising an amorphous aluminum oxide on the substrate and a crystalline aluminum oxide on the amorphous aluminum oxide;
forming an opening through the stack of alternating insulating materials and first conductive materials;
removing a portion of each of the first conductive materials to form a plurality of first recesses adjacent each of the first conductive materials;
extending a depth of the opening into the crystalline aluminum oxide and the amorphous aluminum oxide to form a second recess in the amorphous aluminum oxide;
filling the second recess with an oxide material and a nitride material;
filling the plurality of first recesses with a second conductive material; and
forming a channel material extending through the stack of alternating insulating materials and first conductive materials and into at least a portion of the etch stop material,
wherein filling the plurality of first recesses with the second conductive material comprises forming the second conductive material between the channel material and at least one of the first conductive materials in the stack of alternating insulating materials and first conductive materials, without forming the second conductive material between the channel material and the etch stop material.

### Claim 2 (depends on 1)

The method of claim 1, wherein forming an etch stop material between a substrate and a stack of alternating insulating materials and first conductive materials comprises forming the amorphous aluminum oxide over the substrate at a temperature of up to about 450° C.

### Claim 3 (depends on 1)

The method of claim 1, wherein removing a portion of each of the first conductive materials to form a plurality of first recesses adjacent each of the first conductive materials comprises laterally recessing each of the first conductive materials relative to the insulating materials.

### Claim 4 (depends on 1)

The method of claim 1, wherein removing a portion of each of the first conductive materials to form a plurality of first recesses adjacent each of the first conductive materials comprises selectively removing the portion of each of the first conductive materials without removing a portion of each of the insulating materials.

### Claim 5 (depends on 4)

The method of claim 4, wherein removing a portion of each of the first conductive materials to form a plurality of first recesses adjacent each of the first conductive materials comprises selectively removing the portion of each of the first conductive materials using a solution of tetramethylammonium hydroxide (TMAH).

### Claim 6 (depends on 1)

The method of claim 1, further comprising selectively forming a dielectric material over the first conductive materials.

### Claim 7 (depends on 1)

The method of claim 1, wherein extending the depth of the opening into the crystalline aluminum oxide and the amorphous aluminum oxide to form a second recess in the amorphous aluminum oxide comprises exposing the crystalline aluminum oxide and the amorphous aluminum oxide to an aqueous solution of hydrofluoric acid at a 2000:1 ratio (deionized water:HF).

### Claim 8 (depends on 1)

The method of claim 1, wherein filling the second recess with an oxide material and a nitride material comprises filling the second recess prior to filling the plurality of first recesses with the second conductive material.

### Claim 9 (depends on 1)

The method of claim 1, wherein extending the depth of the opening into the crystalline aluminum oxide and the amorphous aluminum oxide to form a second recess in the amorphous aluminum oxide comprises forming the second recess at an interface between the amorphous aluminum oxide and the crystalline aluminum oxide.

### Claim 10 (depends on 1)

The method of claim 1, wherein extending the depth of the opening into the crystalline aluminum oxide and the amorphous aluminum oxide to form a second recess in the amorphous aluminum oxide comprises forming the second recess laterally adjacent the amorphous aluminum oxide.

### Claim 11 (depends on 1)

The method of claim 1, wherein extending the depth of the opening into the crystalline aluminum oxide and the amorphous aluminum oxide to form a second recess in the amorphous aluminum oxide comprises recessing the amorphous aluminum oxide relative to the crystalline aluminum oxide.

### Claim 12 (depends on 1)

The method of claim 1, wherein the first and second conductive materials are independently selected from the group consisting of n-doped polysilicon, p-doped polysilicon, and undoped polysilicon.

### Claim 13

A method of fabricating a flash memory device, the method comprising:
forming an etch stop material between a substrate and a stack of alternating insulating materials and first conductive materials, the etch stop material comprising an amorphous aluminum oxide on the substrate and a crystalline aluminum oxide in contact with the stack, wherein the stack of alternating insulating materials and first conductive materials is a stack of alternating first oxide materials and first polysilicon materials;
forming an opening through the stack and the etch stop material;
removing portions of the first polysilicon materials to create a plurality of first recesses adjacent the first polysilicon materials;
selectively removing a portion of the amorphous aluminum oxide to form a second recess adjacent the amorphous aluminum oxide;
forming a second oxide material on sidewalls of the first polysilicon material in the plurality of first recesses;
forming a nitride material substantially conformally in the opening and forming a third oxide material over the nitride material to fill the second recess;
filling the plurality of first recesses with a second conductive material to form a plurality of floating gates, the second conductive material comprising polysilicon; and
forming a channel material extending through the stack of alternating insulating materials and first conductive materials and into at least a portion of the etch stop material,
wherein filling the plurality of first recesses with the second conductive material comprises forming the second conductive material between the channel material and at least one of the first conductive materials in the stack of alternating insulating materials and first conductive materials, without forming the second conductive material between the channel material and the etch stop material.

### Claim 14 (depends on 13)

The method of claim 13, wherein forming a nitride material substantially conformally in the opening and forming a third oxide material over the nitride material comprises filling the second recess with the nitride material and the third oxide material, and partially filling the plurality of first recesses with the nitride material and the third oxide material.

### Claim 15 (depends on 13)

The method of claim 13, wherein forming an opening through the stack and the etch stop material comprises forming the opening having an aspect ratio of at least 20:1.

### Claim 16

A semiconductor structure, comprising:
an etch stop material between a substrate and a stack of alternating insulating materials and first conductive materials, the etch stop material comprising an amorphous aluminum oxide on the substrate and a crystalline aluminum oxide on the amorphous aluminum oxide;
a channel material extending through the stack and into at least a portion of the etch stop material; and
a second conductive material between the channel material and at least one of the first conductive materials in the stack of alternating insulating materials and first conductive materials, wherein the second conductive material is not between the channel material and the etch stop material.

### Claim 17 (depends on 16)

The semiconductor structure of claim 16, further comprising at least one of silicon oxide and silicon nitride between the channel material and the etch stop material.

### Claim 18 (depends on 16)

The semiconductor structure of claim 16, further comprising an oxide-nitride-oxide (ONO) structure material between the second conductive material and the at least one of the first conductive materials in the stack of alternating insulating materials and first conductive materials.

### Claim 19 (depends on 16)

The semiconductor structure of claim 16, wherein the first and second conductive materials are independently selected from the group consisting of n-doped polysilicon, p-doped polysilicon, and undoped polysilicon.

### Claim 20 (depends on 16)

The semiconductor structure of claim 16, wherein the channel material comprises a pillar of conductively doped polysilicon.

### Claim 21 (depends on 16)

The semiconductor structure of claim 16, wherein the stack of alternating insulating materials and first conductive materials comprises a stack of alternating oxide-based materials and polysilicon-based materials, and the second conductive material comprises a polysilicon-based material.

### Claim 22 (depends on 16)

The semiconductor structure of claim 16, wherein the semiconductor structure comprises a three-dimensional NAND flash memory device.