# US 10,312,107 B2 · Forming interconnect structure using plasma treated metal hard mask

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- Number: US 10,312,107 B2
- Document ID: US10312107B2
- Status: Granted
- Kind: B2
- Application number: 13/228,011
- Filed: 2011-09-08
- Published: 2013-03-14
- Granted: 2019-06-04
- Earliest claimed: 2011-09-08
- Assignees: Taiwan Semiconductor Manufacturing Company, Ltd.
- Applicants: Chung-Chi Ko; Chia-Cheng Chou; Shing-Chyang Pan; Keng-Chu Lin; Shwang-Ming Jeng
- Inventors: Chung-Chi Ko; Chia-Cheng Chou; Shing-Chyang Pan; Keng-Chu Lin; Shwang-Ming Jeng
- Web page: https://patentgrep.com/patent/US10312107B2

## CPC

- H10P 50/73: {using masks for insulating materials}
- H10P 95/00: Generic processes or apparatus for manufacture or treatments not covered by the other groups of this subclass
- H10W 20/087: {involving multiple stacked pre-patterned masks}
- H10W 20/088: {involving partial etching of via holes}
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
- H10W: GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10

## Abstract

A method includes forming a metal hard mask over a low-k dielectric layer. The step of forming the metal hard mask includes depositing a sub-layer of the metal hard mask, and performing a plasma treatment on the sub-layer of the metal hard mask. The metal hard mask is patterned to form an opening. The low-k dielectric layer is etched to form a trench, wherein the step of etching is performed using the metal hard mask as an etching mask.

## Claims

### Claim 1

A method comprising:
forming a metal hard mask over a low-k dielectric layer, wherein the step of forming the metal hard mask comprises:
depositing a first layer of the metal hard mask comprising horizontal grains and vertical grains;
performing a plasma treatment on the first layer of the metal hard mask, wherein the first layer of the metal hard mask has a first thickness, and wherein after the plasma treatment, the metal hard mask is substantially free from vertical grains;
depositing a second layer of the metal hard mask, wherein the second layer of the metal hard mask has a second thickness different from the first thickness of the first layer of the metal hard mask; and
performing a plasma treatment on the second layer of the metal hard mask;
patterning the metal hard mask to form an opening;
etching the low-k dielectric layer to form a trench, wherein the step of etching is performed using the metal hard mask as an etching mask;
forming a diffusion barrier layer in the trench;
filling a metallic material into the trench, wherein the metallic material is over the diffusion barrier layer, and the diffusion barrier layer and the metallic material comprise portions overlapping the metal hard mask; and
performing a chemical mechanical polish (CMP) to remove excess portions of the metallic material over the metal hard mask.

### Claim 2 (depends on 1)

The method of claim 1, wherein the step of forming the metal hard mask further comprises a plurality of deposition-treatment cycles, and wherein each of the deposition-treatment cycles comprises:
depositing a first additional layer of the metal hard mask;
performing a plasma treatment on the first additional layer of the metal hard mask; depositing a second additional layer of the metal hard mask; and
performing a plasma treatment on the second additional layer of the metal hard mask.

### Claim 3 (depends on 2)

The method of claim 2, wherein the additional layer and the layer are formed of a same material.

### Claim 4 (depends on 1)

The method of claim 1, wherein the low-k dielectric layer is over a substrate having a major surface, wherein the horizontal grains have slant angles smaller than 45 degrees with the major surface, and the vertical grains have slant angles greater than 45 degrees with the major surface.

### Claim 5 (depends on 1)

The method of claim 1, wherein the CMP is performed until the metal hard mask is fully removed.

### Claim 6 (depends on 1)

The method of claim 1, wherein the plasma treatment lasts between about 1 second and about 10 seconds, and wherein during the plasma treatment, a wafer comprising the metal hard mask and the low-k dielectric layer is at a temperature between about 200° C. and about 450° C.

### Claim 7 (depends on 1)

The method of claim 1, wherein the metal hard mask comprises a material selected from the group consisting essentially of boron nitride.

### Claim 8 (depends on 1)

The method of claim 1 further comprising:
forming a via opening in the low-k dielectric layer, wherein the via opening is underlying the trench, and wherein a location and a size of the via opening is limited by the metal hard mask during the step of forming the via opening, wherein the diffusion barrier layer and the metallic material are also filled into the via opening.

### Claim 9

A method comprising:
forming a low-k dielectric layer over a semiconductor substrate;
forming a metal hard mask over the low-k dielectric layer, wherein the metal hard mask comprises a plurality of sub-layers distinguishable from each other, with the plurality of sub-layers comprising boron nitride, wherein the forming the metal hard mask is performed at least in part with an atomic layer deposition, wherein a first sub-layer of the plurality of sub-layers of the metal hard mask is formed directly over the low-k dielectric layer prior to forming the remainder of the plurality of sub-layers of the metal hard mask, wherein the first sub-layer of the plurality of sub-layers of the metal hard mask has a first thickness, and wherein at least one of the plurality of sub-layers of the metal hard mask has a second thickness different from the first thickness of the first sub-layer of the plurality of sub-layers of the metal hard mask;
patterning the metal hard mask to form an opening in the metal hard mask;
etching the low-k dielectric layer to form a trench using the metal hard mask as an etching mask;
etching the low-k dielectric layer to form a via opening in the low-k dielectric layer; and
forming a metal line and a via in the trench and the via opening, respectively, wherein the forming the metal line and the via comprises:
filling a conductive material into the trench and the openings; and
performing a planarization to remove excess portions of the conductive material and the metal hard mask, with remaining portions of the conductive material forming the metal line and the via.

### Claim 10 (depends on 9)

The method of claim 9, wherein the step of forming the metal hard mask comprises a plurality of deposition-treatment cycles, and wherein each of the deposition-treatment cycles comprises:
depositing one of the plurality of sub-layers of the metal hard mask; and
bombarding the one of the plurality of sub-layers to convert vertical grains to horizontal grains.

### Claim 11 (depends on 10)

The method of claim 10, wherein in the bombarding, substantially all vertical grains in the one of the plurality of sub-layers are converted to horizontal grains.

### Claim 12 (depends on 10)

The method of claim 10, wherein the metal hard mask comprises grains, and a percentage of vertical grains to all grains is smaller than about 20 percent.

### Claim 13

A method comprising:
forming a metal hard mask over a low-k dielectric layer, wherein the forming the metal hard mask comprises:
depositing a first sub layer of the metal hard mask comprising horizontal grains and vertical grains, wherein the first sub layer of the metal hard mask has a first thickness;
modifying directions of longitudinal axis of grains in the first sub layer of the metal hard mask, wherein substantially all vertical grains are converted to horizontal grains;
depositing a second sub layer of the metal hard mask comprising horizontal grains and vertical grains, wherein the second sub layer of the metal hard mask has a second thickness different from the first thickness of the first sub layer of the metal hard mask; and
modifying directions of longitudinal axis of grains in the second sub layer of the metal hard mask, wherein substantially all vertical grains are converted to horizontal grains;
patterning the metal hard mask to form an opening;
etching the dielectric layer to form a trench, wherein the etching is performed using the metal hard mask as an etching mask;
filling the trench with a conductive material, wherein the conductive material comprises:
a first portion in the trench;
a second portion extending into the metal hard mask; and
a third portion higher than the metal hard mask; and
performing a planarization to remove the metal hard mask and the second portion and the third portion of the conductive material.

### Claim 14 (depends on 13)

The method of claim 13, wherein the metal hard mask comprises boron nitride.

### Claim 15 (depends on 13)

The method of claim 13, wherein the modifying directions comprises bombarding the metal hard mask.

### Claim 16 (depends on 13)

The method of claim 13, wherein the modifying directions is performed after the depositing.

### Claim 17 (depends on 13)

The method of claim 13 further comprising a plurality of deposition-treatment cycles to increase a thickness of the metal hard mask, wherein each of the deposition-treatment cycles comprises:
depositing an additional sub layer of the metal hard mask; and
performing a plasma treatment on the additional sub layer of the metal hard mask.

### Claim 18 (depends on 17)

The method of claim 17, wherein the additional sub layers of the plurality of deposition-treatment cycles are formed of a same material.

### Claim 19 (depends on 1)

The method of claim 1, wherein the forming the metal hard mask is performed at least in part with an atomic layer deposition.

### Claim 20 (depends on 9)

The method of claim 9, wherein the forming the metal hard mask is performed such that a total thickness of the metal hard mask is between about 100 Å and about 400 Å.