# US 7,745,332 B1 · PVD-based metallization methods for fabrication of interconnections in semiconductor devices

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- Number: US 7,745,332 B1
- Document ID: US7745332B1
- Status: Granted
- Kind: B1
- Application number: 12/074,168
- Filed: 2008-02-29
- Granted: 2010-06-29
- Earliest claimed: 2008-02-29
- Assignees: Novellus Systems, Inc.
- Inventors: Roey Shaviv; Alexander Dulkin; Neil Mackie; Daniel Juliano; Robert Rozbicki
- Web page: https://patentgrep.com/patent/US7745332B1

## CPC

- H10W 20/056: {by filling conductive material into holes, grooves or trenches}
- H10P 14/44: Physical vapour deposition [PVD]
- H10W 20/054: {by selectively removing parts thereof (H10W20/034 takes precedence)}
- H10W 20/0552: {by diffusing metallic dopants to react with dielectrics}
- H10W 20/057: {by selectively depositing, e.g. by using selective CVD or plating}
- H10W: GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10

## Abstract

Recessed features on a Damascene substrate are filled with metal using plasma PVD. Recessed features having widths of less than about 300 nm, e.g., between about 30-300 nm can be filled with metals (e.g., copper and aluminum), without forming voids. In one approach, the deposition is performed by exposing the substrate to a high-density plasma characterized by high fractional ionization of metal. Under these conditions, the metal is deposited within the recess, without forming large overhang at the opening of the recess. In some embodiments, the metal is deposited within the recess, while diffusion barrier material is simultaneously etched from the field region. In a second approach, recessed features are filled by performing a plurality of profiling cycles, wherein each cycle includes a net etching and a net depositing operation. Etching and depositing parameters are adjusted such that the recessed features are filled without forming overhangs and voids.

## Claims

### Claim 1

A method of filling a recessed feature on a semiconductor substrate with a metal-containing material, the method comprising:
(a) depositing a layer of the metal-containing material on the semiconductor substrate, to coat at least a bottom portion of the recessed feature; and
(b) performing a plurality of profiling cycles, wherein each profiling cycle comprises a net etching operation removing a first portion of a material residing at the bottom of the recessed feature and a net deposition operation depositing a second portion of a material at the bottom of the recessed feature, wherein the net etching operation comprises redistributing the metal-containing material from the bottom portion of the recessed feature to the sidewalls of the recessed feature in at least some profiling cycles, and wherein performing the plurality of profiling cycles fills the recessed feature with the metal-containing material, wherein removing the first portion of a material residing at the bottom of the recessed feature comprises resputtering the material using high density plasma resputtering in at least some profiling cycles.

### Claim 2 (depends on 1)

The method of claim 1, wherein the net etching operation reduces overhang material residing at the opening of the recessed feature during at least some of the profiling cycles.

### Claim 3 (depends on 1)

The method of claim 1, wherein (b) fills at least about 80% of the volume of the recessed feature.

### Claim 4 (depends on 1)

The method of claim 1, wherein (b) completely fills the recessed feature without forming a void.

### Claim 5 (depends on 1)

The method of claim 1, wherein the metal-containing material comprises aluminum.

### Claim 6 (depends on 1)

The method of claim 1, wherein the semiconductor substrate comprises a Damascene structure.

### Claim 7 (depends on 1)

The method of claim 1, wherein (b) is performed in a plasma physical vapor deposition (PVD) process chamber.

### Claim 8 (depends on 1)

The method of claim 1, wherein the method comprises performing at least some of the etching operations in a process chamber not having a metal target and performing at least some of the deposition operations in a plasma physical vapor deposition (PVD) process chamber equipped with a metal target.

### Claim 9 (depends on 1)

The method of claim 1, wherein the recessed feature has a width of less than about 300 nm.

### Claim 10 (depends on 1)

The method of claim 1, wherein (a) comprises depositing a layer of copper under the following conditions:
Substrate temperature
−50-400° C.
Pressure
0.005-0.5 mTorr
External RF substrate
0-300 W
bias power
DC target power
20-100 kW
Argon flow rate
0-10 sccm

### Claim 11 (depends on 1)

The method of claim 1, wherein in (b) the sidewalls of the recessed feature are exposed to alternating metal fluxes, wherein the first flux is directed from a metal target and the second flux is directed from the bottom of the recessed feature.

### Claim 12 (depends on 1)

The method of claim 1, wherein (b) comprises performing between about 5-50 profiling cycles.

### Claim 13 (depends on 1)

The method of claim 1, wherein in (b) the net deposition operation deposits between about 50-600 Å of metal-containing material in a field region of the substrate and wherein the net etch operation removes at least about 40% of the deposited material from the field region at least in some of the profiling cycles.

### Claim 14 (depends on 1)

The method of claim 1, wherein at least some etching operations have an E/D ratio of at least about 2 in the field region.

### Claim 15 (depends on 1)

The method of claim 1, wherein the net etching operation removes material at a net etch rate of at least about 5 Å/second at least in some profiling cycles.

### Claim 16 (depends on 1)

The method of claim 1, wherein (b) comprises performing a first profiling cycle having a first net etching operation followed by a second profiling cycle having a second net etching operation, wherein the second net etch operation removes a larger fraction of the deposited material than the first net etch operation.

### Claim 17 (depends on 1)

The method of claim 1, wherein in at least some of the net etching operations, a resputtering process gas comprises neon or helium.

### Claim 18 (depends on 1)

The method of claim 1, wherein at least some net etching operations are performed under the following conditions:
Substrate temperature
−50-400° C.
Pressure
0.5-5 mTorr
External RF substrate
500-2000 W
bias power
DC target power
0.5-10 kW
Argon flow rate
10-200 sccm

### Claim 19 (depends on 1)

The method of claim 1, wherein the net deposition operation is performed under conditions which minimize formation of overhang for at least some of the profiling cycles.

### Claim 20 (depends on 1)

The method of claim 1, wherein the metal-containing material comprises copper.

### Claim 21 (depends on 20)

The method of claim 20, wherein the metal-containing material comprises a copper alloy, wherein said alloy is an electromigration resistance improving alloy or a diffusion barrier self-forming alloy.

### Claim 22 (depends on 1)

The method of claim 1, wherein the high density plasma has a density of at least about 1010 electrons/cm3 proximate to the substrate, and a mean ion energy of between about 100-700 eV.

### Claim 23 (depends on 22)

The method of claim 22, wherein net etch is performed under the following conditions:
Substrate temperature
−50-400° C.
Pressure
0.5-5 mTorr
External RF substrate
200-500 W
bias power
DC target power
0.5-10 kW
Argon flow rate
10-200 sccm

### Claim 24 (depends on 23)

The method of claim 23, wherein the net deposition operation comprises applying an RF bias to the semiconductor substrate.

### Claim 25

A method of processing a layer of material on a semiconductor substrate having a recessed feature, the method comprising:
(a) depositing a layer of material on the semiconductor substrate, to coat at least a bottom portion of the recessed feature; and
(b) performing a plurality of profiling cycles, wherein each profiling cycle comprises a net etching operation removing a first portion of a material residing at the bottom of the recessed feature and a net deposition operation depositing a second portion of a material at the bottom of the recessed feature, the deposited portion of the material being greater than the etched portion of the material for at least one of the profiling cycles, and wherein performing the plurality of profiling cycles achieves net material deposition at the bottom portion of the recessed feature, wherein the net etching operation comprises resputtering the material from the bottom of the recessed feature using high density plasma resputtering in at least some profiling cycles.

### Claim 26 (depends on 25)

The method of claim 25, wherein the high density plasma has a density of at least about 1010 electrons/cm3 proximate to the substrate, and a mean ion energy of between about 100-700 eV.

### Claim 27 (depends on 25)

The method of claim 25, wherein net etch is performed under the following conditions:
Substrate temperature
−50-400° C.
Pressure
0.5-5 mTorr
External RF substrate
200-500 W
bias power
DC target power
0.5-10 kW
Argon flow rate
10-200 sccm

### Claim 28 (depends on 25)

The method of claim 25, wherein (b) comprises performing between about 5-50 profiling cycles.

### Claim 29

A method of processing a layer of material on a semiconductor substrate having a recessed feature, the method comprising:
(a) depositing a layer of material on the semiconductor substrate to coat at least some portions of the substrate residing above the bottom of the recessed feature; and
(b) performing at least one profiling cycle, wherein the profiling cycle comprises a first operation and a second operation, said first operation comprising removing a first portion of a material residing above the bottom of the recessed feature and redistributing at least some of said material to the bottom of the recessed feature such that no net etching occurs at the bottom of the feature by resputtering the material residing above the bottom of the recessed feature under a pressure that is sufficient to reflect at least some of said material to the bottom of the recessed feature, said second operation comprising depositing a second portion of a material at least onto some portions of the substrate residing above the bottom of the recessed feature, wherein performing the at least one profiling cycle achieves net material deposition at the bottom of the recessed feature.

### Claim 30 (depends on 29)

The method of claim 29, wherein the first operation comprises resputtering the material residing above the bottom of the recessed feature with a plasma comprising ions having atomic weight of greater than about 40.

### Claim 31 (depends on 29)

The method of claim 29, wherein (b) fills at least about 80% of the volume of the recessed feature.

### Claim 32 (depends on 29)

The method of claim 29, wherein (b) completely fills the recessed feature without forming a void.

### Claim 33 (depends on 29)

The method of claim 29, wherein the first operation of the at least one profiling cycle comprises resputtering the material residing above the bottom of the recessed feature at a pressure of at least about 20 mTorr.

### Claim 34 (depends on 29)

The method of claim 29, wherein the first operation of the at least one profiling cycle comprises resputtering the material residing above the bottom of the recessed feature at a pressure of between about 40-80 mTorr.

### Claim 35 (depends on 29)

The method of claim 29, wherein the semiconductor substrate comprises a Damascene structure.

### Claim 36 (depends on 29)

The method of claim 29, wherein the method comprises performing at least some of the etching operations in a process chamber not having a metal target and performing at least some of the deposition operations in a plasma physical vapor deposition (PVD) process chamber equipped with a metal target.

### Claim 37 (depends on 29)

The method of claim 29, wherein the recessed feature has a width of less than about 300 nm.

### Claim 38 (depends on 29)

The method of claim 29, wherein (a) comprises depositing a layer of copper under the following conditions:
Substrate temperature
−50-400° C.
Pressure
0.005-0.5 mTorr
External RF substrate
0-300 W
bias power
DC target power
20-100 kW
Argon flow rate
0-10 sccm

### Claim 39 (depends on 29)

The method of claim 29, wherein (b) comprises performing between about 5-50 profiling cycles.

### Claim 40 (depends on 29)

The method of claim 29, wherein the deposited material comprises copper.

### Claim 41 (depends on 40)

The method of claim 40, wherein the deposited material comprises a copper alloy, wherein said alloy is an electromigration resistance improving alloy or a diffusion barrier self-forming alloy.

### Claim 42

An apparatus for filling recessed features on a wafer substrate, comprising:
(a) a process chamber configured to hold a metal target;
(b) a wafer support for holding the wafer in position during deposition of a metal-containing material; and
(c) a controller comprising program instructions for
(i) depositing a layer of the metal-containing material on the semiconductor substrate, to coat at least a bottom portion of a recessed feature; and
(ii) performing a plurality of profiling cycles, each cycle comprising a net etching and a net deposition operation at the bottom of the recessed feature, to fill the recessed feature with the metal-containing material, wherein program instructions for performing the plurality of profiling cycles comprise instructions for resputtering the metal-containing material using high density plasma resputtering in the net etching operation of at least some profiling cycles.

### Claim 43 (depends on 42)

The apparatus of claim 42, wherein the apparatus comprises a planar magnetron.

### Claim 44 (depends on 42)

The apparatus of claim 42, wherein the apparatus comprises a hollow cathode magnetron (HCM).

### Claim 45 (depends on 42)

The apparatus of claim 42, wherein program instructions for high density plasma resputtering comprise instructions for generating a high density plasma having a density of at least about 1010 electrons/cm3 proximate to the substrate, and a mean ion energy of between about 100-700 eV.

### Claim 46 (depends on 42)

The apparatus of claim 42, wherein program instructions for high density plasma resputtering comprise instructions for setting the following process conditions:
Substrate temperature
−50-400° C.
Pressure
0.5-0.5 mTorr
External RF substrate
200-500 W
bias power
DC target power
0.5-10 kW
Argon flow rate
10-200 sccm

### Claim 47

An apparatus for filling recessed features on a wafer substrate, comprising:
(a) a process chamber configured to hold a metal target;
(b) a wafer support for holding the wafer in position during deposition of a metal-containing material; and
(c) a controller comprising program instructions for
(i) depositing a layer of the metal-containing material on the semiconductor substrate, to coat at least some portions of the substrate residing above the bottom of the recessed feature; and
(ii) performing at least one profiling cycle, wherein the profiling cycle comprises a first operation and a second operation, said first operation comprising removing a first portion of the metal-containing material residing above the bottom of the recessed feature and redistributing at least some of said material to the bottom of the recessed feature such that no net etching occurs at the bottom of the feature by resputtering the material residing above the bottom of the recessed feature under a pressure that is sufficient to reflect at least some of said material to the bottom of the recessed feature, said second operation comprising depositing a second portion of a material at least onto some portions of the substrate residing above the bottom of the recessed feature, wherein performing the at least one profiling cycle achieves net material deposition at the bottom of the recessed feature.

### Claim 48 (depends on 47)

The apparatus of claim 47, wherein program instructions for the first operation of the at least one profiling cycle comprise instructions for resputtering the material residing above the bottom of the recessed feature with a plasma comprising ions having atomic weight of greater than about 40.

### Claim 49 (depends on 47)

The apparatus of claim 47, wherein program instructions for the first operation of the at least one profiling cycle comprise instructions for resputtering the material residing above the bottom of the recessed feature at a pressure of at least about 20 mTorr.

### Claim 50 (depends on 47)

The apparatus of claim 47, wherein program instructions for the first operation of the at least one profiling cycle comprise instructions for resputtering the material residing above the bottom of the recessed feature at a pressure of between about 40-80 mTorr.

### Claim 51 (depends on 47)

The apparatus of claim 47, wherein the apparatus comprises a planar magnetron.

### Claim 52 (depends on 47)

The apparatus of claim 47, wherein the apparatus comprises a hollow cathode magnetron (HCM).

### Claim 53

An apparatus for filling recessed features on a wafer substrate, comprising:
(a) a first process chamber configured to hold a metal target and configured for depositing a metal-containing material;
(b) a second process chamber without a metal target and configured for material etching; and
(c) a controller comprising program instructions for
(i) depositing a layer of the metal-containing material on the semiconductor substrate, to coat at least a bottom portion of a recessed feature in the first process chamber; and
(ii) performing a plurality of profiling cycles, each cycle comprising a net etching and a net depositing operation at the bottom of the recessed feature, to fill the recessed features with the metal-containing material, wherein program instructions for performing the plurality of profiling cycles comprise instructions for resputtering the metal-containing material using high density plasma resputtering in the net etching operation of at least some profiling cycles, and for performing at least some of net etching operations in the second process chamber without a target.

### Claim 54 (depends on 53)

The apparatus of claim 53, wherein the first chamber comprises a planar magnetron.

### Claim 55 (depends on 53)

The apparatus of claim 53, wherein the first chamber comprises a hollow cathode magnetron (HCM).

### Claim 56 (depends on 53)

The apparatus of claim 53, wherein program instructions for high density plasma resputtering comprise instructions for generating a high density plasma having a density of at least about 1010 electrons/cm3 proximate to the substrate, and a mean ion energy of between about 100-700 eV.

### Claim 57

An apparatus for filling recessed features on a wafer substrate, comprising:
(a) a first process chamber configured to hold a metal target and configured for depositing a metal-containing material;
(b) a second process chamber without a metal target and configured for material etching; and
(c) a controller comprising program instructions for
(i) depositing a layer of the metal-containing material on the semiconductor substrate, to coat at least some portions of the substrate residing above the bottom of the recessed feature, in the first process chamber; and
(ii) performing at least one profiling cycle, wherein the profiling cycle comprises a first operation and a second operation, said first operation comprising removing a first portion of the metal-containing material residing above the bottom of the recessed feature and redistributing at least some of said material to the bottom of the recessed feature such that no net etching occurs at the bottom of the feature by resputtering the material residing above the bottom of the recessed feature under a pressure that is sufficient to reflect at least some of said material to the bottom of the recessed feature in the second process chamber; said second operation comprising depositing a second portion of the metal-containing material at least onto some portions of the substrate residing above the bottom of the recessed feature in the first process chamber, wherein performing the at least one profiling cycle achieves net material deposition at the bottom of the recessed feature.

### Claim 58 (depends on 57)

The apparatus of claim 57, wherein program instructions for the first operation of the at least one profiling cycle comprise instructions for resputtering the material residing above the bottom of the recessed feature with a plasma comprising ions having atomic weight of greater than about 40.

### Claim 59 (depends on 57)

The apparatus of claim 57, wherein program instructions for the first operation of the at least one profiling cycle comprise instructions for resputtering the material residing above the bottom of the recessed feature at apressure of at least about 20 mTorr.

### Claim 60 (depends on 57)

The apparatus of claim 57, wherein program instructions for the first operation of the at least one profiling cycle comprise instructions for resputtering the material residing above the bottom of the recessed feature at a pressure of between about 40-80 mTorr.

### Claim 61 (depends on 57)

The apparatus of claim 57, wherein the first chamber comprises a planar magnetron.

### Claim 62 (depends on 57)

The apparatus of claim 57, wherein the first chamber comprises a hollow cathode magnetron (HCM).