# US 9,437,499 B2 · Semiconductor device including merged-unmerged work function metal and variable fin pitch

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- Number: US 9,437,499 B2
- Document ID: US9437499B2
- Status: Granted
- Kind: B2
- Application number: 14/830,829
- Filed: 2015-08-20
- Published: 2015-12-10
- Granted: 2016-09-06
- Earliest claimed: 2014-03-26
- Assignees: International Business Machines Corporation
- Applicants: International Business Machines Corporation
- Inventors: Veeraraghavan S. Basker; Zuoguang Liu; Tenko Yamashita; Chun-chen Yeh
- Web page: https://patentgrep.com/patent/US9437499B2

## CPC

- H10D 84/038: {using silicon technology, e.g. SiGe}
- H10D 30/024: {of fin field-effect transistors [FinFET]}
- H10D 30/6217: {having non-uniform gate electrodes, e.g. gate conductors having varying doping}
- H10D 64/01318: {the conductor comprising a layer of alloy material, compound material or organic material contacting the insulator, e.g. TiN (comprising a layer of alloys of Si, Ge or C H10D64/01314)}
- H10D 84/014: {the gate conductors having different materials or different implants}
- H10D 84/0142: {the gate conductors having different shapes or dimensions}
- H10D 84/0151: {Manufacturing their isolation regions}
- H10D 84/0158: {the components including FinFETs}
- H10D 84/83135: {the IGFETs characterised by having different gate conductor materials or different gate conductor implants}
- H10D 84/834: {comprising FinFETs}
- H10D 84/84: Combinations of enhancement-mode IGFETs and depletion-mode IGFETs
- H10D 89/10: Integrated device layouts
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES

## Abstract

A method of varying a threshold voltage of a semiconductor device includes forming plural first semiconductor fins atop a substrate and which are separated from one another according to a first fin pitch to define first fin trenches having a first width. At least one second semiconductor fin is formed atop the substrate and is separated from the plural first semiconductor fins by a second fin pitch to define second fin trenches having a second width. The method further includes forming a work function metal layer in the first and second fin trenches. The second trenches have a first cavity formed therein such that at least one second semiconductor fin has a different concentration of work function metal layer with respect to the first plural semiconductor fins so as to vary the threshold voltage of the at least one second semiconductor fin with respect to the first plural semiconductor fins.

## Claims

### Claim 1

A method of varying a threshold voltage of a semiconductor device, the method comprising:
forming plural first semiconductor fins atop a substrate, the plural first semiconductor fins separated from one another according to a first fin pitch to define first fin trenches having a first width;
forming at least one second semiconductor fin separated from the plural first semiconductor fins by a second fin pitch to define second fin trenches having a second width; and
forming at least one work function metal layer in the first and second fin trenches, wherein the second trenches have a first cavity formed therein such that at least one second semiconductor fin has a different concentration of work function metal layer with respect to the first plural semiconductor fins so as to vary the threshold voltage of the at least one second semiconductor fin with respect to the first plural semiconductor fins.

### Claim 2 (depends on 1)

The method of claim 1, wherein the at least one work function metal layer has a second cavity formed in at least one of the first fin trenches.

### Claim 3 (depends on 2)

The method of claim 2, further comprising defining a first threshold voltage of the first plural semiconductor fins based on a first portion of the at least one work function metal layer and the second cavity, and defining a second threshold voltage of the at least one second semiconductor based on a second portion of the at least one work function metal layer and the second cavity.

### Claim 4 (depends on 3)

The method of claim 3, wherein a first thickness of the first portion formed in the second cavity is less than a second thickness of the second portion formed in the first cavity.

### Claim 5 (depends on 4)

The method of claim 4, wherein the at least one work function metal layer includes first and second work function metal layers.

### Claim 6 (depends on 5)

The method of claim 5, wherein the first work function metal layer comprises a first material and the second work function metal layer comprises a second material different from the first material.

### Claim 7 (depends on 6)

The method of claim 6, wherein the first work function metal layer comprises titanium nitride (TiN), and the second work function metal layer comprises titanium carbide (TiC).

### Claim 8 (depends on 4)

The method of claim 4, wherein the first thickness defines the first threshold voltage and the second thickness defines the second threshold voltage.

### Claim 9 (depends on 8)

The method of claim 8, wherein the first thickness is greater than the second thickness.

### Claim 10 (depends on 8)

The method of claim 8, wherein the first thickness is less than the second thickness.

### Claim 11

A method of tuning a threshold voltage of a semiconductor device, the method comprising:
forming a plurality of semiconductor fins on an upper surface of a substrate, the semiconductor fins including at least one isolated semiconductor fin having a first fin pitch (dif) that is different from a second fin pitch (df) of the remaining semiconductor fins,
wherein a first trench separates the at least one isolated semiconductor fin from the remaining semiconductor fins, and second trenches separate the remaining semiconductor fins from one another, the second trenches sized differently from the first trench; and
depositing at least one work function metal (WFM) layer in the first trench and the second trenches so as to cover the at least one isolated semiconductor fin and the remaining semiconductor fins,
wherein a threshold voltage differential of the at least one isolated semiconductor fin and the remaining semiconductor fins is tuned based on a thickness of the at least one WFM layer.

### Claim 12 (depends on 11)

The method of claim 11, wherein depositing the at least one WFM layer comprises:
depositing a first WFM layer that completely fills the second trenches while partially filling the first trench so as to define a cavity in the first trench located between the at least one isolated semiconductor fin and the remaining semiconductor fins; and
depositing a second WFM layer that fills the cavity such that a first thickness of the first WFM layer deposited in the first trench is different than a combination of the first and second work function metal layers deposited in the second trenches so as to tune the threshold voltage of the at least one isolated semiconductor fin and the remaining semiconductor fins with respect to each other.

### Claim 13 (depends on 12)

The method of claim 12, wherein the first fin pitch of the at least one isolated semiconductor fin is greater than the second fin pitch (df) of the remaining semiconductor fins.

### Claim 14 (depends on 12)

The method of claim 12, wherein the first fin pitch of the at least one isolated semiconductor fin is less than the second fin pitch (df) of the remaining semiconductor fins.

### Claim 15 (depends on 12)

The method of claim 12, wherein an amount of the second WFM layer surrounding one or more of the remaining semiconductor fins is less than the amount of the first WFM layer.

### Claim 16 (depends on 15)

The method of claim 15, wherein the threshold voltage (Vt) of the remaining semiconductor fins is essentially tuned according to the first WFM layer.

### Claim 17 (depends on 12)

The method of claim 12, wherein an amount of the second WFM layer surrounding the at least one isolated semiconductor fin is greater than the amount of the first WFM layer.

### Claim 18 (depends on 17)

The method of claim 17, wherein the threshold voltage (Vt) of the at least one isolated semiconductor fin is tuned according to the second WFM layer.

### Claim 19 (depends on 12)

The method of claim 12, wherein the first work function metal layer comprises a first material and the second work function metal layer comprises a second material different from the first material.

### Claim 20 (depends on 19)

The method of claim 19, wherein the first work function metal layer comprises titanium nitride (TiN), and the second work function metal layer comprises titanium carbide (TiC).