# US 10,872,898 B2 · Embedded non-volatile memory device and fabrication method of the same

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- Number: US 10,872,898 B2
- Document ID: US10872898B2
- Status: Granted
- Kind: B2
- Application number: 15/848,439
- Filed: 2017-12-20
- Published: 2019-01-24
- Granted: 2020-12-22
- Earliest claimed: 2017-07-19
- Assignees: Cypress Semiconductor Corporation
- Applicants: Cypress Semiconductor Corporation
- Inventors: Chun Chen; James Pak; Unsoon Kim; Inkuk Kang; Sung-Taeg Kang; Kuo Tung Chang
- Web page: https://patentgrep.com/patent/US10872898B2

## CPC

- H10B 43/35: with cell select transistors, e.g. NAND
- H10B 43/40: characterised by the peripheral circuit region
- H10D 30/696: {having at least one additional gate, e.g. program gate, erase gate or select gate}
- H10D 30/0212: {using self-aligned silicidation}
- H10D 30/0215: {using self-aligned selective metal deposition simultaneously on gate electrodes and the source regions or drain regions}
- H10D 64/017: {using dummy gates in processes wherein at least parts of the final gates are self-aligned to the dummy gates, i.e. replacement gate processes}
- H10B: ELECTRONIC MEMORY DEVICES
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES

## Abstract

Systems and methods of forming such include method, forming a memory gate (MG) stack in a first region, forming a sacrificial polysilicon gate on a high-k dielectric in a second region, wherein the first and second regions are disposed in a single substrate. Then a select gate (SG) may be formed adjacent to the MG stack in the first region of the semiconductor substrate. The sacrificial polysilicon gate may be replaced with a metal gate to form a logic field effect transistor (FET) in the second region. The surfaces of the substrate in the first region and the second region are substantially co-planar.

## Claims

### Claim 1

A method, comprising:
forming a memory gate (MG) polysilicon layer in first and second regions;
patterning the MG polysilicon layer in the first region to form a MG stack;
depositing a select gate (SG) polysilicon layer in the first region and the second region;
concurrently removing at least the SG polysilicon layer completely in the second region and above a top surface of the MG stack in the first region;
after removing at least the SG polysilicon layer, removing the MG polysilicon layer in the second region;
forming a sacrificial polysilicon gate on a high-k dielectric in the second region, wherein the first and second regions are disposed in a single semiconductor substrate;
forming a select gate (SG) stack adjacent to the MG stack in the first region of the semiconductor substrate; and
replacing the sacrificial polysilicon gate with a metal gate to form a logic field effect transistor (FET) in the second region, and
wherein surfaces of the substrate in the first region and the second region are substantially co-planar.

### Claim 2 (depends on 1)

The method of claim 1, wherein forming the MG stack comprises:
forming a charge trapping layer in the first region of the semiconductor substrate;
forming a MG polysilicon layer over the charge trapping layer; and
patterning at least the MG polysilicon layer to form a memory gate (MG).

### Claim 3 (depends on 2)

The method of claim 2, wherein forming the SG stack comprises:
forming a gate oxide layer underneath the SG polysilicon layer in the first region of the semiconductor substrate;
depositing an SG polysilicon layer over the gate oxide layer; and
patterning at least the SG polysilicon layer remaining in the first region to form a select gate (SG) such that the SG stack is disposed adjacent to the MG stack.

### Claim 4 (depends on 1)

The method of claim 1, further comprising forming at least two dielectric layers between the MG stack and the SG stack.

### Claim 5 (depends on 1)

The method of claim 1 further comprising forming a silicide on at least one of the MG or the SG.

### Claim 6 (depends on 3)

The method of claim 3, wherein forming the SG stack further comprises:
planarizing the SG polysilicon layer, wherein the planarizing stops at a thin dielectric layer overlying the MG stack such that the MG and SG stacks have an approximately same height.

### Claim 7 (depends on 6)

The method of claim 6, wherein the thin dielectric layer has a thickness in an approximate range of 20 angstrom to 500 angstrom.

### Claim 8 (depends on 1)

The method of claim 1, wherein a first surface of the first region and a second surface of the second region of the substrate are within 200 angstrom of co-planar of one another.

### Claim 9 (depends on 1)

The method of claim 1, wherein a first upper surface of the SG, a second upper surface of the MG, and a third upper surface of the logic FET are within 300 angstroms of co-planar of one another.

### Claim 10 (depends on 1)

The method of claim 1, prior to replacing the sacrificial polysilicon gate with the metal gate, further including comprising:
forming a protection film overlying at least the SG and MG stacks in the first region.

### Claim 11

A method of fabricating a semiconductor device, comprising:
forming a split-gate memory cell in a first region of a substrate, further comprising;
depositing a memory gate (MG) polysilicon layer overlying a charge trapping layer in the first region and a second region;
patterning at least the MG polysilicon layer to form an MG in the first region;
depositing a select gate (SG) polysilicon layer overlying an SG oxide layer and the MG in the first region and the second region;
planarizing the SG polysilicon layer such that top surfaces of the MG and SG polysilicon layer are substantially coplanar and parallel to a surface of the substrate in the first region, wherein planarizing the SG polysilicon layer concurrently removes the SG polysilicon layer completely in the second region; and
removing portions of the SG polysilicon layer and SG oxide layer in the first region to form an SG adjacent to the MG, and the SG polysilicon layer completely in the second region;
after planarizing the SG polysilicon layer, removing the MG polysilicon layer in the second region; and
forming a logic field-effect transistor (FET) including comprising a metal gate disposed over a high-K dielectric in the second region of the substrate, wherein the logic FET and the split-gate memory cell have a substantial same height.

### Claim 12 (depends on 11)

The method of claim 11, further comprising:
depositing a thin dielectric layer overlying the MG polysilicon layer, wherein planarizing the SG polysilicon layer stops at the thin dielectric layer.

### Claim 13 (depends on 11)

The method of claim 11, wherein removing portions of the SG polysilicon layer includes:
removing a first portion of the SG polysilicon layer on one side of the MG; and
patterning a second portion of the SG polysilicon layer on another side of the MG to form the SG.

### Claim 14 (depends on 13)

The method of claim 13, wherein removing the first portion of the SG polysilicon layer includes performing at least one of wet etch or dry etch.

### Claim 15 (depends on 11)

The method of claim 11, further comprising forming at least two dielectric layers overlying at least two side surfaces of the MG prior to depositing the select gate (SG) polysilicon layer.

### Claim 16 (depends on 11)

The method of claim 11, wherein a first upper surface of the SG, a second upper surface of the MG, and a third upper surface of the logic FET are within 300 angstroms of co-planar of one another.

### Claim 17 (depends on 11)

The method of claim 11, further comprising depositing a cap layer overlying the MG polysilicon layer, wherein depositing the cap layer further comprises depositing one or more of a dielectric film, an amorphous silicon film, or a polysilicon film.

### Claim 18

A method to fabricate a semiconductor device, comprising:
depositing a memory gate (MG) polysilicon layer overlying a charge trapping layer in first and second regions of a substrate;
patterning at least the MG polysilicon layer to form an MG in the first region;
depositing a select gate (SG) polysilicon layer overlying an SG oxide layer and the MG in the first region and the second region;
planarizing the SG polysilicon layer such that top surfaces of the MG and the SG polysilicon layer are substantially co-planar in the first region;
removing the SG polysilicon layer completely in the second region concurrently with planarizing the SG polysilicon layer in the first region;
after removing the SG polysilicon layer, removing the MG polysilicon layer in the second region;
depositing a high-k dielectric layer over the substrate in the second region, and a sacrificial polysilicon gate layer overlying the high-k dielectric layer;
patterning the sacrificial polysilicon gate layer and the high-k dielectric layer;
removing portions of the SG polysilicon layer to form an SG adjacent to the MG;
depositing an inter-layer dielectric (ILD) to encapsulate the MG, the SG, and a logic field-effect transistor (FET);
planarizing the ILD;
removing the sacrificial polysilicon gate layer; and
depositing a metal gate overlying the high-K dielectric layer to form the logic FET field-effect transistor (FET) in the second region.

### Claim 19 (depends on 18)

The method of claim 18, further comprising:
depositing a cap layer overlying the MG polysilicon layer, wherein the cap layer includes at least one layer of dielectric material, polysilicon, or a combination thereof.

### Claim 20 (depends on 18)

The method of claim 18, further comprising:
forming inter-gate dielectric layers, each including comprising at least two dielectric layers, overlying at least two side walls of the MG.

### Claim 21 (depends on 18)

The method of claim 18, wherein planarizing the SG polysilicon layer comprises includes performing a chemical mechanical planarization (CMP) process, a dry etch-back process, or a combination thereof.

### Claim 22 (depends on 18)

The method of claim 18, further comprising:
performing metal polish such that top surfaces of the MG, the SG and the logic FET are substantially co-planar.

### Claim 23 (depends on 18)

The method of claim 18, wherein depositing the MG polysilicon layer comprises includes performing one of:
depositing a doped polysilicon layer; or
depositing an undoped polysilicon layer and subsequently doping the undoped polysilicon layer.

### Claim 24 (depends on 18)

The method of claim 18, wherein depositing the SG polysilicon layer comprises includes performing one of:
depositing a doped polysilicon layer; or
depositing an undoped polysilicon layer and subsequently doping the undoped polysilicon layer.

### Claim 25 (depends on 18)

The method of claim 18, wherein prior to removing the sacrificial polysilicon gate layer, the method further including comprising:
forming a protection film overlying at least the MG and the SG.