# US 8,568,964 B2 · Flood exposure process for dual tone development in lithographic applications

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- Number: US 8,568,964 B2
- Document ID: US8568964B2
- Status: Granted
- Kind: B2
- Application number: 12/430,203
- Filed: 2009-04-27
- Published: 2010-10-28
- Granted: 2013-10-29
- Earliest claimed: 2009-04-27
- Assignees: Tokyo Electron Limited
- Applicants: Carlos A. Fonseca; Mark Somervell; Steven Scheer; Wallace P. Printz
- Inventors: Carlos A. Fonseca; Mark Somervell; Steven Scheer; Wallace P. Printz
- Web page: https://patentgrep.com/patent/US8568964B2

## CPC

- G03F 7/30: Imagewise removal using liquid means
- G03F 7/095: having more than one photosensitive layer (G03F7/075 takes precedence)
- G03F 7/70466: {Multiple exposures, e.g. combination of fine and coarse exposures, double patterning or multiple exposures for printing a single feature (stitching G03F7/70475)}
- 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 method and system for patterning a substrate using a dual tone development process is described. The method and system comprise a flood exposure of the substrate to improve process latitude for the dual tone development process.

## Claims

### Claim 1

A method of patterning a substrate, comprising:
forming a layer of radiation-sensitive material on a substrate;
performing a patterned exposure of said layer of radiation-sensitive material using a mask having a mask critical dimension to form first radiation-sensitive material portions having a high radiation exposure, second radiation-sensitive material portions having a low radiation exposure, and third radiation-sensitive material portions having an intermediate radiation exposure;
performing a first post-exposure bake following said performing said patterned exposure;
performing positive-tone developing of said layer of radiation-sensitive material to remove said first radiation-sensitive material portions from said substrate;
performing a flood exposure of said layer of radiation-sensitive material;
performing a second post-exposure bake following said performing said flood exposure; and
performing negative-tone developing of said layer of radiation-sensitive material to remove said second radiation-sensitive material portions from said substrate,
wherein said third radiation-sensitive material portions remain after performing said positive-tone and negative-tone developing.

### Claim 2 (depends on 1)

The method of claim 1, further comprising:
adjusting a critical dimension of said third radiation-sensitive material portions having said intermediate radiation exposure by altering said patterned exposure, said first post-exposure bake, said positive-tone developing, said flood exposure, or said second post-exposure bake, or any combination of two or more thereof.

### Claim 3 (depends on 2)

The method of claim 2, wherein said adjusting comprises adjusting said mask critical dimension for said patterned exposure, an exposure dose for said patterned exposure, an exposure intensity for said patterned exposure, an exposure wavelength of said patterned exposure, a first post-exposure temperature for said first post-exposure bake, a time said substrate is elevated to said first post-exposure temperature, a heating rate for achieving said first post-exposure temperature, a cooling rate for reducing said first post-exposure temperature, a pressure of a gaseous environment surrounding said substrate during said elevation of said substrate to said first post-exposure temperature, a composition of a gaseous environment surrounding said substrate during said elevation of said substrate to said first post-exposure temperature, a second post-exposure temperature for said second post-exposure bake, a time said substrate is elevated to said second post-exposure temperature, a heating rate for achieving said second post-exposure temperature, a cooling rate for reducing said second post-exposure temperature, a pressure of a gaseous environment surrounding said substrate during said elevation of said substrate to said second post-exposure temperature, a composition of a gaseous environment surrounding said substrate during said elevation of said substrate to said second post-exposure temperature, a composition of a first developing chemistry for said positive-tone developing, a time duration for applying said first developing chemistry, a temperature of said first developing chemistry, a composition of a second developing chemistry for said negative-tone developing, a time duration for applying said second developing chemistry, a temperature of said second developing chemistry, an exposure dose for said flood exposure, an exposure intensity for said flood exposure, an exposure wavelength of said flood exposure, or a composition of the layer of radiation-sensitive material, or any combination of two or more thereof.

### Claim 4 (depends on 1)

The method of claim 1, wherein said performing said flood exposure comprises exposing said substrate to electromagnetic (EM) radiation having a wavelength in the visible spectrum, or EM radiation having a wavelength in the ultraviolet spectrum, or a combination thereof.

### Claim 5 (depends on 1)

The method of claim 1, wherein said performing said flood exposure comprises exposing said substrate to continuous EM radiation, pulsed EM radiation, poly-chromatic EM radiation, mono-chromatic EM radiation, broad-band EM radiation, or narrow-band radiation, or a combination thereof.

### Claim 6 (depends on 1)

The method of claim 1, wherein said performing said flood exposure comprises exposing said substrate to 436 nm (nanometer) EM radiation, 365 nm EM radiation, 248 nm EM radiation, 193 nm EM radiation, 157 nm EM radiation, or deep ultraviolet (DUV) EM radiation, or any combination of two or more thereof.

### Claim 7 (depends on 1)

The method of claim 1, wherein said layer of radiation-sensitive material comprises a positive-tone photo-resist, a dual tone photo-resist, or a photo-resist having one or more photo-acid generators.

### Claim 8 (depends on 7)

The method of claim 7, wherein:
said layer of radiation-sensitive material comprises a first photo-acid generator and a second photo-acid generator;
said first photo-acid generator generates acid in said layer of radiation-sensitive material when exposed to EM radiation at a first wavelength or first range of wavelengths; and
said second photo-acid generator generates acid in said layer of radiation-sensitive material when exposed to EM radiation at a second wavelength or second range of wavelengths.

### Claim 9 (depends on 8)

The method of claim 8, wherein said performing said patterned exposure is configured for exposing said layer of radiation-sensitive material to said first wavelength or first range of wavelengths, and said performing said flood exposure is configured for exposing said layer of radiation-sensitive material to said second wavelength or second range of wavelengths.

### Claim 10 (depends on 8)

The method of claim 8, said performing said flood exposure is configured for exposing said layer of radiation-sensitive material to said first wavelength or first range of wavelengths and to said second wavelength or second range of wavelengths.

### Claim 11 (depends on 1)

The method of claim 1, wherein said layer of radiation-sensitive material comprises a photo-resist that switches solubility due to a change in polarity upon said performing said patterned exposure, said performing said flood exposure, said performing said first post-exposure bake following said patterned exposure, or said performing said second post-exposure bake following said flood exposure, or any combination of two or more thereof, or wherein said layer of radiation-sensitive material comprises a photo-resist that provides acid-catalyzed deprotection upon said performing said patterned exposure, said performing said flood exposure, said performing said first post-exposure bake following said patterned exposure, or said performing said second post-exposure bake following said flood exposure, or any combination of two or more thereof.

### Claim 12

A method of patterning a substrate, comprising:
forming a layer of radiation-sensitive material on a substrate;
performing a patterned exposure of said layer of radiation-sensitive material using a mask having a mask critical dimension to form first radiation-sensitive material portions having a first radiation exposure level that is one of high or low exposure and a first critical dimension, second radiation-sensitive material portions having a second radiation exposure level that is the other of high or low exposure and a second critical dimension, and third radiation-sensitive material portions having a third radiation exposure level intermediate the first and second radiation exposure levels and a third critical dimension;
performing a first post-exposure bake following said performing said patterned exposure;
performing a first development of said layer of radiation-sensitive material to remove said first radiation-sensitive material portions from said substrate;
performing a flood exposure of said layer of radiation-sensitive material to further expose said second and third material portions to radiation;
performing a second post-exposure bake following said performing said flood exposure, wherein said flood exposure and said second post-exposure bake are effective to adjust a de-protection gradient across said second and third material portions and thereby adjust said second and third critical dimensions; and
performing a second development of said layer of radiation-sensitive material to remove said second radiation-sensitive material portions from said substrate,
wherein one of said first or second developments is a positive-tone development for removing the respective first or second radiation-sensitive material portions having the high radiation exposure level and the other of said first or second developments is a negative-tone development for removing the respective first or second radiation-sensitive material portions having the low radiation exposure level, and
wherein said third radiation-sensitive material portions having said adjusted third critical dimension remain after performing said first and second developments.

### Claim 13 (depends on 12)

The method of claim 12, wherein said flood exposure is at a wavelength capable of generating acid in said second and third material portions, and wherein said second post-exposure bake causes acid-catalyzed de-protection using said generated acid from said flood exposure to increase said de-protection gradient.

### Claim 14 (depends on 13)

The method of claim 13, wherein:
said layer of radiation-sensitive material comprises a first photo-acid generator and a second photo-acid generator;
said first photo-acid generator generates acid in said layer of radiation-sensitive material proportional to said high, intermediate and low radiation exposure levels when exposed to EM radiation at a first wavelength or first range of wavelengths during said patterned exposure; and
said second photo-acid generator generates acid in said layer of radiation-sensitive material proportional to said high or low and said intermediate radiation exposure levels when exposed to EM radiation at a second wavelength or second range of wavelengths during said flood exposure.