# US 12,191,328 B2 · Photodetector with reduced dark current sensitivity and methods of forming the same

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- Number: US 12,191,328 B2
- Document ID: US12191328B2
- Status: Granted
- Kind: B2
- Application number: 17/458,676
- Filed: 2021-08-27
- Published: 2023-03-02
- Granted: 2025-01-07
- Earliest claimed: 2021-08-27
- Assignees: Taiwan Semiconductor Manufacturing Company, Ltd.
- Applicants: Taiwan Semiconductor Manufacturing Company Limited
- Inventors: Yeh-Hsun Fang; Zhi-Wei Zhuang; Li-Hsin Chu
- Web page: https://patentgrep.com/patent/US12191328B2

## CPC

- H10F 39/8033: {Photosensitive area}
- G01J 1/44: Electric circuits {(for command of an exposure part G03B7/02)}
- H10F 39/018: {of hybrid image sensors}
- H10F 39/8053: {Colour filters}
- H10F 39/8063: {Microlenses}
- H10F 39/809: {of hybrid image sensors}
- H10F 39/811: {Interconnections}
- H10W 20/0245: {comprising use of blind vias during the manufacture}
- H10W 20/2134: {TSVs extending from the semiconductor wafer into back-end-of-line layers}
- H10W 20/20: Interconnections within wafers or substrates, e.g. through-silicon vias [TSV]
- H10W 80/312: {characterised by the direct bonding of electrically conductive pads}
- H10W 80/327: {characterised by the direct bonding of insulating parts, e.g. of silicon oxide layers}
- H10W 90/792: {between multiple chips}
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
- G01J: MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY (light sources F21, H01J, H01K, H05B; investigating properties of materials by optical means G01N)
- H10W: GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10

## Abstract

A method of forming a semiconductor device includes: forming a patterned hard mask layer on a semiconductor substrate; performing a first etching process to form a recess in an exposed portion of the semiconductor substrate, using a first etchant that includes a first halogen species; performing a second etching process using a second etchant that includes a second halogen species, such that the second halogen species forms a barrier layer in the semiconductor substrate, surrounding the recess; and growing a detection region in the recess using an epitaxial growth process. The barrier layer is configured to reduce diffusion of the first halogen species into the detection region.

## Claims

### Claim 1

A method of forming a semiconductor device, comprising:
forming a patterned hard mask layer on a semiconductor substrate;
performing a first etching process to form a recess in an exposed portion of the semiconductor substrate, using a first etchant comprising a first halogen species;
performing a second etching process using a second etchant comprising a second halogen species, such that the second halogen species forms a barrier layer in the semiconductor substrate, surrounding the recess; and
growing a detection region in the recess using an epitaxial growth process,
wherein the barrier layer is configured to reduce diffusion of the first halogen species into the detection region.

### Claim 2 (depends on 1)

The method of claim 1, wherein the first halogen species has a smaller atomic radius than the second halogen species.

### Claim 3 (depends on 1)

The method of claim 1, wherein the first halogen species has a higher diffusion coefficient with respect to silicon than the second halogen species.

### Claim 4 (depends on 1)

The method of claim 1, wherein:
the semiconductor substrate comprises silicon (Si); and
the detection region comprises single-crystal germanium (Ge).

### Claim 5 (depends on 1)

The method of claim 1, wherein a peak concentration of the first halogen species in the detection region is less than 10 atomic percent (at %).

### Claim 6 (depends on 1)

The method of claim 1, wherein a peak concentration of the first halogen species in the detection region is less than 5 atomic percent (at %).

### Claim 7 (depends on 1)

The method of claim 1, wherein:
the first halogen species comprises fluorine (F) or chlorine (Cl); and
the second halogen species comprises bromine (Br).

### Claim 8 (depends on 1)

The method of claim 1, wherein:
the first halogen species comprises fluorine (F) or chlorine (Cl); and
the second atomic species comprises iodine (I).

### Claim 9 (depends on 1)

The method of claim 1, wherein the first etching process and the second etching process are performed such that a peak concentration of the second halogen species in the semiconductor substrate occurs closer to the recess than a peak concentration of the first halogen species in the semiconductor substrate.

### Claim 10 (depends on 1)

The method of claim 1, wherein the second etching process is an etching process that does not increase an etching depth of the recess by more than 5%.

### Claim 11 (depends on 1)

The method of claim 1, wherein the first etching process and the second etching process comprise reactive ion etching processes.

### Claim 12 (depends on 11)

The method of claim 11, wherein the first etching process comprises applying a higher bias voltage than the second etching process.

### Claim 13

A method of forming a photodetector, comprising:
forming a patterned hard mask layer on a front side of a first semiconductor substrate;
performing a first etching process to form recesses in exposed portions of the front side of the first semiconductor substrate, using a first etchant comprising a first halogen species;
performing a second etching process using a second etchant comprising a second halogen species, such that the second halogen species forms barrier layers in the first semiconductor substrate, surrounding the recesses;
growing detection regions comprising single-crystal germanium (Ge) in the recesses using an epitaxial growth process,
forming a passivation layer on the detection regions;
forming a first interconnect structure over the front surface of the first semiconductor substrate;
forming a second interconnect structure on a second semiconductor substrate, the second semiconductor substrate comprising photodetector sensing circuits; and
bonding the first interconnect structure and the second interconnect structure, wherein,
the first etching process comprises implanting the first halogen species in the first semiconductor substrate to a first depth,
the second etching process comprises implanting the second halogen species in the first semiconductor substrate to a second depth that is less than the first depth, and
the first halogen species has a higher diffusion coefficient with respect to silicon than the second halogen species.

### Claim 14 (depends on 13)

The method of claim 13, wherein:
the first halogen species comprise fluorine (F) or chlorine (Cl); and
the second halogen species comprise bromine (Br) or iodine (I).

### Claim 15 (depends on 13)

The method of claim 13, further comprising:
forming through-substrate via structures in the first semiconductor substrate;
thinning a backside of the first semiconductor substrate to expose the through-substrate via structures;
forming external bonding pads on exposed portions of the through-substrate via structures;
forming a filter layer on the backside of the first semiconductor substrate; and
forming a lens layer on the filter layer.

### Claim 16

A photodetector comprising:
a first semiconductor substrate;
detection regions comprising epitaxial germanium (Ge) and disposed in recesses formed in a front side surface of the first semiconductor substrate;
a first halogen species implanted in the first semiconductor substrate around the recesses; and
barrier layers surrounding the recesses and comprising a second halogen species, wherein the barrier layers are configured to reduce diffusion of the first halogen species into the detection regions from the first semiconductor substrate,
wherein the first halogen species has a smaller atomic radius than the second halogen species.

### Claim 17 (depends on 16)

The photodetector of claim 16, further comprising:
a second semiconductor substrate comprising photodetector sensing circuits; and
an interconnect structure electrically connecting the detection regions to the photodetector sensing circuits.

### Claim 18 (depends on 16)

The photodetector of claim 16, wherein a peak concentration of the second halogen species in the first semiconductor substrate occurs closer to each recess than a peak concentration of the first halogen species in the semiconductor substrate.

### Claim 19 (depends on 16)

The photodetector of claim 16, wherein:
the first halogen species comprise fluorine (F) or chlorine (Cl); and
the second halogen species comprise bromine (Br) or iodine (I).

### Claim 20 (depends on 16)

The photodetector of claim 16, wherein the first halogen species is implanted at a greater depth in the first semiconductor substrate than the second halogen species.