# US 12,224,347 B2 · P-type field effect transistor (PFET) on a silicon germanium (Ge) buffer layer to increase Ge in the PFET source and drain to increase compression of the PFET channel and method of fabrication

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- Number: US 12,224,347 B2
- Document ID: US12224347B2
- Status: Granted
- Kind: B2
- Application number: 17/180,219
- Filed: 2021-02-19
- Published: 2022-08-25
- Granted: 2025-02-11
- Earliest claimed: 2021-02-19
- Assignees: QUALCOMM Incorporated
- Applicants: QUALCOMM Incorporated
- Inventors: Bin Yang; Xia Li; Haining Yang
- Web page: https://patentgrep.com/patent/US12224347B2

## CPC

- H10D 30/797: {being in source or drain regions, e.g. SiGe source or drain}
- H10D 62/822: comprising only Group IV materials heterojunctions, e.g. Si/Ge heterojunctions
- H10D 30/021: {of FETs having insulated gates [IGFET]}
- H10D 62/021: {Forming source or drain recesses by etching e.g. recessing by etching and then refilling}
- H10D 62/832: being Group IV materials comprising two or more elements, e.g. SiGe
- H10D 84/017: {Manufacturing their source or drain regions, e.g. silicided source or drain regions}
- H10D 84/038: {using silicon technology, e.g. SiGe}
- H10D 84/8311: {the IGFETs characterised by having different channel structures}
- H10D 84/85: Complementary IGFETs, e.g. CMOS
- H10D 84/0167: {Manufacturing their channels}
- H10D 84/8312: {the IGFETs characterised by having different source or drain region structures, e.g. IGFETs having symmetrical source or drain regions integrated with IGFETs having asymmetrical source or drain regions}
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES

## Abstract

An exemplary high performance P-type field-effect transistor (PFET) fabricated on a silicon (Si) germanium (Ge)(SiGe) buffer layer with a SiGe source and drain having a Ge percentage higher than a threshold that causes dislocations at a Si substrate interface is disclosed. A source and drain including a Ge percentage above a 45% threshold provide increased compressive strain in the channel for higher performance of the PFET. Dislocations are avoided in the lattices of the source and drain by forming the PFET on a SiGe buffer layer rather than directly on a Si substrate and the SiGe buffer layer has a percentage of Ge less than a percentage of Ge in the source and drain. In one example, a lattice of the buffer layer is relaxed by implanting dislocations at an interface of the buffer layer and the Si substrate and annealing the buffer layer.

## Claims

### Claim 1

A semiconductor device, comprising:
a silicon substrate;
a buffer layer disposed on the silicon substrate, the buffer layer comprising a first percentage of germanium;
a silicon layer comprising a semiconductor material disposed on the buffer layer;
a first transistor comprising:
a first channel region of the silicon layer comprising the semiconductor material doped with a pentavalent impurity;
a first gate disposed on the first channel region;
a first source disposed on a first side of the first channel region on the buffer layer; and
a first drain disposed on a second side of the first channel region on the buffer layer;
wherein:
the first source and the first drain each comprise a silicon germanium (SiGe) composite comprising a second percentage of germanium, and the second percentage is greater than the first percentage; and
a second transistor comprising:
a second channel region of the silicon layer comprising the semiconductor material doped with a trivalent impurity;
a second gate disposed on the second channel region;
a second source disposed on a first side of the second gate and recessed into the silicon layer on the first side of the second gate; and
a second drain disposed on a second side of the second gate opposite the first side and recessed into the silicon layer on the second side of the second gate,
wherein:
a first portion of the silicon layer is disposed between the second source and the buffer layer; and
a second portion of the silicon layer is disposed between the second drain and the buffer layer.

### Claim 2 (depends on 1)

The semiconductor device of claim 1, wherein the second percentage of germanium is at least forty-six percent (46%).

### Claim 3 (depends on 1)

The semiconductor device of claim 1, wherein the second percentage of germanium is greater than sixty percent (60%).

### Claim 4 (depends on 1)

The semiconductor device of claim 1, wherein the first source and the first drain are doped with a trivalent impurity.

### Claim 5 (depends on 1)

The semiconductor device of claim 1, wherein the first percentage of germanium is fifteen percent (15%).

### Claim 6 (depends on 1)

The semiconductor device of claim 1, wherein the buffer layer comprises a thickness of at least one (1) micron.

### Claim 7 (depends on 1)

The semiconductor device of claim 1, wherein:
the semiconductor material of the first channel region comprises a thickness of 100 to 500 angstroms; and
the first source and the first drain each comprise a thickness equal to or greater than the thickness of the semiconductor material of the first channel region.

### Claim 8 (depends on 1)

The semiconductor device of claim 1, wherein:
the first transistor comprises a P-type field-effect transistor (FET) (PFET); and
the second transistor comprises an N-type FET (NFET).

### Claim 9 (depends on 1)

The semiconductor device of claim 1, wherein:
the second source and the second drain of the second transistor comprise silicon and phosphorous.

### Claim 10 (depends on 1)

The semiconductor device of claim 1, integrated into a radio-frequency (RF) front-end module.

### Claim 11 (depends on 1)

The semiconductor device of claim 1 integrated into a device selected from the group consisting of: a set-top box; an entertainment unit; a navigation device; a communications device; a fixed location data unit; a mobile location data unit; a global positioning system (GPS) device; a mobile phone; a cellular phone; a smartphone; a session initiation protocol (SIP) phone; a tablet; a phablet; a server; a computer; a portable computer; a mobile computing device; a wearable computing device; a desktop computer; a personal digital assistant (PDA); a monitor; a computer monitor; a television; a tuner; a radio; a satellite radio; a music player; a digital music player; a portable music player; a digital video player; a video player; a digital video disc (DVD) player; a portable digital video player; an automobile; a vehicle component; avionics systems; a drone; and a multicopter.