# US 10,483,393 B2 · Method to induce strain in 3-D microfabricated structures

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- Number: US 10,483,393 B2
- Document ID: US10483393B2
- Status: Granted
- Kind: B2
- Application number: 15/798,976
- Filed: 2017-10-31
- Published: 2018-03-08
- Granted: 2019-11-19
- Earliest claimed: 2013-07-29
- Assignees: STMicroelectronics S.r.l.
- Applicants: STMicroelectronics, Inc.
- Inventors: Nicolas Loubet; Pierre Morin
- Web page: https://patentgrep.com/patent/US10483393B2

## CPC

- H10D 30/797: {being in source or drain regions, e.g. SiGe source or drain}
- H10D 30/024: {of fin field-effect transistors [FinFET]}
- H10D 30/62: Fin field-effect transistors [FinFET]
- H10D 30/6211: {having fin-shaped semiconductor bodies integral with the bulk semiconductor substrates}
- H10D 30/751: {having composition variations in the channel regions}
- H10D 30/798: {being provided in or under the channel regions}
- H10D 62/8164: {comprising only semiconductor materials (potential variation in long-range structurally-disordered materials H10D62/8163)}
- H10D 62/822: comprising only Group IV materials heterojunctions, e.g. Si/Ge heterojunctions
- H10D 62/83: being Group IV materials, e.g. B-doped Si or undoped Ge
- H10D 62/832: being Group IV materials comprising two or more elements, e.g. SiGe
- H10D 62/8325: {Silicon carbide}
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES

## Abstract

Methods and structures for forming strained-channel finFETs are described. Fin structures for finFETs may be formed in two epitaxial layers that are grown over a bulk substrate. A first thin epitaxial layer may be cut and used to impart strain to an adjacent channel region of the finFET via elastic relaxation. The structures exhibit a preferred design range for increasing induced strain and uniformity of the strain over the fin height.

## Claims

### Claim 1

A device, comprising:
a substrate having a first portion and a second portion extending away from the first portion, the second portion having a first length in a first direction and a first width in a second direction orthogonal to the first direction;
a microfabricated structure on the substrate, the microfabricated structure having a fin including:
the second portion of the substrate;
a strain-inducing layer on the second portion of the substrate, the strain-inducing layer having a second length in the first direction and a second width in the second direction, the first length approximately equal to the second length and the first width approximately equal to the second width; and
a semiconductor layer on the strain-inducing layer.

### Claim 2 (depends on 1)

The device of claim 1 wherein the semiconductor layer includes a strained channel.

### Claim 3 (depends on 1)

The device of claim 1 wherein the strain-inducing layer includes at least one of silicon germanium and silicon carbide.

### Claim 4 (depends on 1)

The device of claim 1 wherein the microfabricated structure includes an insulating layer on a portion of the semiconductor layer.

### Claim 5 (depends on 4)

The device of claim 4 wherein the microfabricated structure includes a gate electrode on the insulating layer.

### Claim 6 (depends on 5)

The device of claim 5 wherein the gate electrode includes a first portion and a second portion, the first portion of the gate electrode on a first side of the second portion of the substrate and a second portion of the gate electrode on a second side of the second portion of the substrate, the first side opposite the second side.

### Claim 7 (depends on 1)

The device of claim 1 wherein the semiconductor layer has a third length in the first direction and a third width in the second direction, the first length approximately equal to the third length and the first width approximately equal to the third width.

### Claim 8

A device, comprising:
a substrate having a first portion with a first surface and a second portion with a second surface spaced apart from the first surface; and
a semiconductor structure extending away from the second surface of the substrate, the semiconductor structure including:
a strain-inducing layer having a first surface on the second surface of the substrate and a second surface; and
a semiconductor layer having a first surface on the second surface of the strain-inducing layer and a second surface,
wherein the second portion of the substrate has the same length and width as the strain-inducing layer and the semiconductor layer.

### Claim 9 (depends on 8)

The device of claim 8 wherein a distance between the first surface of the semiconductor layer and the second surface of the semiconductor layer is less than a distance between the first surface of the strain-inducing layer and the second surface of the strain-inducing layer.

### Claim 10 (depends on 8)

The device of claim 8 wherein the strain-inducing layer includes silicon germanium or silicon carbide.

### Claim 11 (depends on 8)

The device of claim 8 further including an insulating layer on a portion of the semiconductor layer.

### Claim 12 (depends on 11)

The device of claim 11 further including a gate electrode on the insulating layer.

### Claim 13 (depends on 12)

The device of claim 12 wherein a portion of the gate electrode is on the first surface of the substrate.

### Claim 14

A device, comprising:
a substrate having a raised portion;
a fin on the raised portion of the substrate, the fin including:
a first semiconductor layer on the raised portion of the substrate; and
a second semiconductor layer that is strained on the first semiconductor layer; and
a gate insulator contacting sidewalls of the first semiconductor layer and the second semiconductor layer.

### Claim 15 (depends on 14)

The device of claim 14 wherein the first semiconductor layer is relaxed.

### Claim 16 (depends on 14)

The device of claim 14 further including a dielectric layer adjacent to at least a portion of the fin and the raised portion of the substrate.

### Claim 17 (depends on 16)

The device of claim 16 further including a gate electrode adjacent to the dielectric layer.

### Claim 18 (depends on 14)

The device of claim 14 wherein the second semiconductor layer includes a strained channel.

### Claim 19 (depends on 14)

The device of claim 14 wherein the first semiconductor layer includes silicon germanium or silicon carbide.

### Claim 20

A device, comprising:
a substrate having a raised portion;
a dielectric layer over the substrate and surrounding the raised portion;
a fin on the raised portion of the substrate, the fin including:
a first semiconductor layer on the raised portion of the substrate, wherein the first semiconductor layer is protruded above the dielectric layer; and
a second semiconductor layer that is strained on the first semiconductor layer; and
a gate structure adjacent to sidewalls of the first semiconductor layer and the second semiconductor layer.

### Claim 21 (depends on 20)

The device of claim 20, wherein the raised portion of the substrate has a width the same as a width of the first semiconductor layer.