# US 12,218,240 B2 · Source/drain regions of FinFET devices and methods of forming same

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- Number: US 12,218,240 B2
- Document ID: US12218240B2
- Status: Granted
- Kind: B2
- Application number: 18/346,511
- Filed: 2023-07-03
- Published: 2023-11-02
- Granted: 2025-02-04
- Earliest claimed: 2019-06-14
- Assignees: Taiwan Semiconductor Manufacturing Company, Ltd.
- Applicants: Taiwan Semiconductor Manufacturing Co., Ltd.
- Inventors: Kun-Mu Li; Heng-Wen Ting; Yen-Ru Lee; Hsueh-Chang Sung
- Web page: https://patentgrep.com/patent/US12218240B2

## CPC

- H10D 30/62: Fin field-effect transistors [FinFET]
- H10D 30/024: {of fin field-effect transistors [FinFET]}
- H10D 30/0243: {using dummy structures having essentially the same shapes as the semiconductor bodies, e.g. to provide stability}
- H10D 30/797: {being in source or drain regions, e.g. SiGe source or drain}
- H10D 62/151: {of IGFETs (of IGFETs having LDD or DDD structure H10D30/601; of thin film transistors H10D30/6713)}
- H10D 62/822: comprising only Group IV materials heterojunctions, e.g. Si/Ge heterojunctions
- 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}
- H10P 14/3411: {Silicon, silicon germanium or germanium}
- H10P 14/6923: {the material being boron or phosphorus doped silicon oxides, e.g. BPSG, BSG or PSG}
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10

## Abstract

A method includes forming a semiconductor fin over a substrate, etching the semiconductor fin to form a recess, wherein the recess extends into the substrate, and forming a source/drain region in the recess, wherein forming the source/drain region includes epitaxially growing a first semiconductor material on sidewalls of the recess, wherein the first semiconductor material includes silicon germanium, wherein the first semiconductor material has a first germanium concentration from 10 to 40 atomic percent, epitaxially growing a second semiconductor material over the first semiconductor material, the second semiconductor material including silicon germanium, wherein the second semiconductor material has a second germanium concentration that is greater than the first germanium concentration, and epitaxially growing a third semiconductor material over the second semiconductor material, the third semiconductor material including silicon germanium, wherein the third semiconductor material has a third germanium concentration that is smaller than the second germanium concentration.

## Claims

### Claim 1

A device comprising:
a first fin and a second fin extending from a substrate;
an isolation region over the substrate, the isolation region being between the first fin and the second fin;
a gate stack over the first fin and the isolation region;
a first source/drain region in the first fin adjacent the gate stack and in the substrate, wherein a bottom surface of the first source/drain region is below a bottom surface of the isolation region, the first source/drain region comprising:
a first source/drain material comprising silicon germanium having a first concentration of germanium and a first concentration of boron;
a second source/drain material over the first source/drain material, the second source/drain material comprising silicon germanium having a second concentration of germanium and a second concentration of boron, wherein the second concentration of germanium is greater than the first concentration of germanium, wherein the second concentration of boron is greater than the first concentration of boron; and
a third source/drain material over the second source/drain material, the third source/drain material comprising silicon germanium having a third concentration of germanium and a third concentration of boron.

### Claim 2 (depends on 1)

The device of claim 1, wherein a thickness of the first source/drain material at a bottom of the first source/drain material is in a range between 3 nm and 20 nm.

### Claim 3 (depends on 1)

The device of claim 1, further comprising:
a second source/drain region having a same structure as the first source/drain region, wherein the third source/drain material extends continuously from over the second source/drain material of the first source/drain region to over the second source/drain material of the second source/drain region.

### Claim 4 (depends on 1)

The device of claim 1, wherein an upper surface of the first source/drain material is higher than the bottom surface of the isolation region.

### Claim 5 (depends on 1)

The device of claim 1, wherein an upper surface of the first source/drain material is higher than an upper surface of the second source/drain material.

### Claim 6 (depends on 1)

The device of claim 1, wherein the first source/drain material extends from an upper surface of a channel region to below the channel region.

### Claim 7 (depends on 1)

The device of claim 1, wherein a distance between a bottom of the first source/drain material and the bottom surface of the isolation region is between 0 nm and 10 nm.

### Claim 8

A device comprising:
a first fin extending from a substrate;
an isolation region along sidewalls of the first fin;
a gate stack over the first fin;
a source/drain region adjacent the first fin under the gate stack, the source/drain region comprising:
a first source/drain material comprising silicon germanium having a first concentration of germanium and a first concentration of boron, wherein the first source/drain material extends into the substrate;
a second source/drain material over the first source/drain material, the second source/drain material comprising silicon germanium having a second concentration of germanium and a second concentration of boron, wherein the second concentration of germanium is greater than the first concentration of germanium, wherein the second concentration of boron is greater than the first concentration of boron, wherein the first source/drain material extends above an upper surface of the second source/drain material; and
a third source/drain material over the second source/drain material, the third source/drain material comprising silicon germanium having a third concentration of germanium and a third concentration of boron, wherein the third source/drain material extends from the second source/drain material to above an upper surface of the first source/drain material.

### Claim 9 (depends on 8)

The device of claim 8, wherein the third source/drain material contacts the first source/drain material and the second source/drain material.

### Claim 10 (depends on 8)

The device of claim 8, wherein an upper surface of the second source/drain material is lower than an upper surface of the first fin.

### Claim 11 (depends on 8)

The device of claim 8, wherein a thickness of the first source/drain material is in a range between 3 nm and 20 nm.

### Claim 12 (depends on 8)

The device of claim 8, further comprising:
a second fin, wherein the gate stack extends over the second fin;
a fourth source/drain material comprising silicon germanium having the first concentration of germanium and the first concentration of boron, wherein the fourth source/drain material extends into the substrate; and
a fifth source/drain material over the fourth source/drain material, the fifth source/drain material comprising silicon germanium having the second concentration of germanium and the second concentration of boron, wherein the third source/drain material extends over the second source/drain material and the fifth source/drain material.

### Claim 13 (depends on 8)

The device of claim 8, wherein the substrate comprises a silicon substrate having an n-type dopant concentration between 1E16 atoms/cm3 and about 1E18 atoms/cm3, wherein the first source/drain material contacts the silicon substrate.

### Claim 14 (depends on 8)

The device of claim 8, wherein the first concentration of germanium is between 10% and 40%.

### Claim 15 (depends on 14)

The device of claim 14, wherein the second concentration of germanium is between 20% and 80%.

### Claim 16

A device comprising:
a fin extending from a substrate, the fin having a first height above a surface of the substrate, the fin having a recess, the recess having a depth greater than the first height of the fin; and
a source/drain region in the recess, wherein the source/drain region comprises:
a first semiconductor material in the recess, wherein a portion of the first semiconductor material extends below a bottom of the fin, wherein the first semiconductor material comprises doped silicon germanium;
a second semiconductor material over the first semiconductor material, wherein the second semiconductor material comprises doped silicon germanium having a greater dopant concentration and a greater atomic percent of germanium than the first semiconductor material, wherein the first semiconductor material extends a greater height above the surface of the substrate than the second semiconductor material; and
a third semiconductor material over the second semiconductor material, wherein the third semiconductor material comprises doped silicon germanium having a smaller dopant concentration and a smaller atomic percent of germanium than the second semiconductor material, wherein the third semiconductor material overlaps the first semiconductor material.

### Claim 17 (depends on 16)

The device of claim 16, wherein the doped silicon germanium of the first semiconductor material has a dopant concentration in a range between 1×1019 atoms/cm3 and 1×1021 atoms/cm3.

### Claim 18 (depends on 17)

The device of claim 17, wherein the doped silicon germanium of the first semiconductor material is doped with a p-type dopant.

### Claim 19 (depends on 16)

The device of claim 16, wherein the first semiconductor material has a first p-type dopant concentration, the second semiconductor material has a second p-type dopant concentration, wherein the second p-type dopant concentration is 10 times the first p-type dopant concentration.

### Claim 20 (depends on 16)

The device of claim 16, further comprising forming a contact to the source/drain region, wherein the contact extends through the third semiconductor material.