# US 6,720,251 B1 · Applications and methods of making nitrogen-free anti-reflective layers for semiconductor processing

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- Number: US 6,720,251 B1
- Document ID: US6720251B1
- Status: Granted
- Kind: B1
- Application number: 09/990,197
- Filed: 2001-11-21
- Granted: 2004-04-13
- Earliest claimed: 2001-06-28
- Assignees: Novellus Systems, Inc.
- Inventors: Bart van Schravendijk; Ming Li; Jason Tian; Tom Mountsier; M. Zlaul Karim
- Web page: https://patentgrep.com/patent/US6720251B1

## CPC

- H10P 14/6922: {the material containing Si, O and at least one of H, N, C, F or other non-metal elements, e.g. SiOC, SiOC:H or SiONC}
- C23C 16/401: {containing silicon}
- G03F 7/091: {characterised by antireflection means or light filtering or absorbing means, e.g. anti-halation, contrast enhancement}
- H10P 50/73: {using masks for insulating materials}
- H10P 76/2043: {using an anti-reflective coating}
- H10P 14/6336: {in the presence of a plasma [PECVD]}
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
- C23C: COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04)
- G03F: PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR; (phototypographic composing devices B41B; photosensitive materials or processes for photographic purposes G03C; electrophotography, sensitive layers or processes therefor G03G)

## Abstract

A nitrogen-free anti-reflective layer for use in semiconductor photolithography is fabricated in a chemical vapor deposition process, optionally plasma-enhanced, using a gaseous mixture of carbon, silicon, and oxygen sources. By varying the process parameters, acceptable values of the refractive index n and extinction coefficient k can be obtained. The nitrogen-free anti-reflective layer produced by this technique eliminates the mushrooming and footing problems found with conventional anti-reflective layers.

## Claims

### Claim 1

A method of fabricating an anti-reflective layer of a dual damascene device in a chemical vapor deposition chamber, the method comprising the steps of:
forming a first layer of dielectric that is to be patterned;
forming an anti-reflective layer over the first layer using a source comprising a silane and a carbon oxide, wherein the anti-reflective layer is substantially nitrogen-free and comprises between about 20% and 80% oxygen;
patterning the first layer to define a dual damascene via; and
filling said via with photoresist that contacts the anti-reflective layer.

### Claim 2 (depends on 1)

The method of claim 1 wherein forming an anti-reflective layer comprises introducing gas or liquid sources of carbon, hydrogen, silicon, and oxygen.

### Claim 3 (depends on 2)

The method of claim 2 wherein oxygen source comprises elemental oxygen, carbon monoxide, or carbon dioxide.

### Claim 4 (depends on 2)

The method of claim 2 wherein forming an anti-reflective layer comprises introducing carbon dioxide at a flow rate of from 2.5 sccm to 25 sccm per square centimeter of the surface of the anti-reflective layer.

### Claim 5 (depends on 2)

The method of claim 2 wherein forming an anti-reflective layer comprises introducing silane at a flow rate of from 0.01 sccm to 0.5 sccm per square centimeter of the surface of the anti-reflective layer.

### Claim 6 (depends on 2)

The method of claim 2 wherein forming an anti-reflective layer comprises introducing carbon dioxide at a flow rate of from 2.5 sccm to 25 sccm per square centimeter of the surface of the anti-reflective layer and silane at a flow rate of from 0.01 sccm to 0.5 sccm per square centimeter of the surface of the anti-reflective layer.

### Claim 7 (depends on 2)

The method of claim 2, wherein forming an anti-reflective layer further comprises applying radio frequency power in the chemical vapor deposition chamber at a power intensity of from 0.05 W to 5.5 W per square centimeter of the surface of the anti-reflective layer.

### Claim 8 (depends on 1)

The method of claim 1, further comprising:
depositing a photoresist on top of the anti-reflective layer;
exposing the photoresist to radiation defining a pattern to be imposed on the first layer; and
developing the photoresist.

### Claim 9 (depends on 1)

The method of claim 1 wherein forming the anti-reflective layer comprises introducing the gas reactants into the chemical vapor deposition chamber to between about 0.1 mTorr and 100 Torr.

### Claim 10 (depends on 1)

The method of claim 1 wherein forming the anti-reflective layer comprises using plasma enhanced chemical vapor deposition (PECVD) methods.

### Claim 11 (depends on 1)

The method of claim 1 wherein forming the anti-reflective layer comprises using a substrate deposition temperature between about 200 and 900 degrees Celsius.

### Claim 12 (depends on 1)

The method of claim 1 wherein the total gas flow rate is about 5.2 sccm per square centimeter area of processed wafer.

### Claim 13 (depends on 1)

The method of claim 1 wherein the extinction coefficient for the anti-reflective layer is between about 0 and 1.3 at 248 nm.

### Claim 14 (depends on 1)

The method of claim 1 wherein the dual damascene device comprises a low k dielectric layer.

### Claim 15

A method for improving a damascene process for metallization, said method comprising:
forming a low-k dielectric layer on a semiconductor substrate;
forming an anti-reflective layer on said low-k dielectric layer using a source comprising a silane and a carbon oxide, wherein said anti-reflective layer comprises substantially no nitrogen and comprises between about 20% and 80% oxygen;
patterning said low-k dielectric layer, thereby forming interconnect line regions in said low-k dielectric layer; and
forming a conductive layer in said interconnect line regions.

### Claim 16 (depends on 15)

The method of claim 15, wherein the forming of the anti-reflective layer is performed in a high density plasma chemical vapor deposition reactor.

### Claim 17 (depends on 15)

The method of claim 15 wherein forming the anti-reflective layer comprises using a substrate deposition temperature between about 200 and 900 degrees Celsius.

### Claim 18

A method of fabricating an anti-reflective layer in a chemical vapor deposition chamber, the method comprising the steps of:
forming a first layer of dielectric that is to be patterned;
forming an anti-reflective layer over the first layer using a source comprising a silane and a carbon oxide, wherein the anti-reflective layer is substantially nitrogen-free and comprises between about 20% and 80% oxygen.