# US 2020/0286907 A1 · Three-dimensional memory device with mobility-enhanced vertical channels and methods of forming the same

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- Number: US 2020/0286907 A1
- Document ID: US20200286907A1
- Status: Published application
- Kind: A1
- Application number: 16/882,957
- Filed: 2020-05-26
- Published: 2020-09-10
- Earliest claimed: 2019-01-18
- Assignees: SanDisk Technologies LLC
- Applicants: Sandisk Technologies LLC
- Inventors: Chun GE; Yanli ZHANG; Fei ZHOU; Raghuveer S. MAKALA
- Web page: https://patentgrep.com/patent/US20200286907A1

## CPC

- H10B 43/30: characterised by the memory core region
- H10D 64/037: {comprising charge-trapping insulators}
- H10B 43/27: the channels comprising vertical portions, e.g. U-shaped channels
- H10B 51/30: characterised by the memory core region
- H10D 30/63: Vertical IGFETs (H10D30/66 {, H10D30/6728, H10D30/689, H10D30/693} take precedence)
- H10D 30/6893: {wherein the floating gate has multiple non-connected parts, e.g. multi-particle floating gate}
- H10D 30/69: IGFETs having charge trapping gate insulators, e.g. MNOS transistors
- H10D 30/701: {IGFETs having ferroelectric gate insulators, e.g. ferroelectric FETs}
- H10D 30/796: {having memorised stress for introducing strain in the channel regions, e.g. recrystallised polysilicon gates}
- H10D 64/033: {comprising ferroelectric layers}
- 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}
- H10B: ELECTRONIC MEMORY DEVICES
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES

## Abstract

A combination of an alternating stack and a memory opening fill structure is provided over a substrate. The alternating stack includes insulating layers and electrically conductive layers. The memory opening fill structure vertically extends through the alternating stack, and includes a memory film, a vertical semiconductor channel, and a core structure comprising a core material. A phase change material is employed for the core material. A volume expansion is induced in in the core material by performing an anneal process that induces a microstructural change within the core material. The volume expansion in the core material induces a lateral compressive strain and a vertical tensile strain within the vertical semiconductor channel. The vertical tensile strain enhances charge mobility in the vertical semiconductor channel, and increases the on-current of the vertical semiconductor channel.

## Claims

### Claim 1

A three-dimensional memory device comprising:
an alternating stack of insulating layers and electrically conductive layers overlying a substrate;
a memory opening fill structure that vertically extends through the alternating stack, wherein the memory opening fill structure comprises a memory film, a vertical semiconductor channel, and a core structure comprising a polycrystalline core material, wherein the polycrystalline core material induces a lateral compressive strain and a vertical tensile strain to the vertical semiconductor channel.

### Claim 2 (depends on 1)

The three-dimensional memory device of claim 1, wherein:
the polycrystalline core material is a phase change material including an amorphous phase having a first density and a polycrystalline phase having a second density that is less than the first density;
the polycrystalline core material is in the polycrystalline phase of the phase change material; and
the second density is in a range from 90% of the first density to 98% of the first density.

### Claim 3 (depends on 1)

The three-dimensional memory device of claim 1, wherein:
the polycrystalline core material has electrical conductivity less than 1.0×10−5 S/m; and
the core structure has a vertical-to-lateral dimension ratio in a range from 3 to 300.

### Claim 4 (depends on 1)

The three-dimensional memory device of claim 1, wherein:
the vertical semiconductor channel is under lateral compressive strain having a magnitude in a range from 0.1% to 2.0%; and
the vertical semiconductor channel is under vertical tensile strain having a magnitude in a range from 0.01% to 0.2%.

### Claim 5 (depends on 2)

The three-dimensional memory device of claim 2, wherein the core material includes a compound comprising germanium, tellurium, and oxygen.

### Claim 6 (depends on 5)

The three-dimensional memory device of claim 5, wherein the core material comprises oxygen at an atomic percentage in a range from 6.0% to 14%.

### Claim 7 (depends on 1)

The three-dimensional memory device of claim 1, wherein:
the three-dimensional memory device comprises a two-dimensional array of NAND strings vertically extending through the alternating stack, wherein the memory opening fill structure comprises one of the NAND strings;
the electrically conductive layers comprise, or are electrically connected to, a respective word line for the two-dimensional array of NAND strings;
the substrate comprises a silicon substrate;
at least one memory cell in a first device level of the two-dimensional array of NAND strings is located over another memory cell in a second device level of two-dimensional array of NAND strings;
the electrically conductive layers comprise a plurality of control gate electrodes for the two-dimensional array of NAND strings,
the electrically conductive layers have a respective strip shape extending substantially parallel to the top surface of the substrate; and
each NAND string within the two-dimensional array of NAND strings comprises a respective memory film, a respective vertical semiconductor channel, and a respective core structure.