Photomask and pattern formation method using the same

• US 8,278,014 B2
• Filed: 07/07/2011
• Issued: 10/02/2012
• Est. Priority Date: 09/03/2007
• Status: Active Grant

• Current Assignee: Pannova Semic, LLC (Vector Capital Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Irie, Shigeo, Misaka, Akio, Nonami, Yuji, Nakamura, Tetsuya, Harada, Chika
• Primary Examiner(s): Huff, Mark F
• Assistant Examiner(s): JELSMA, JONATHAN G
• Application Number:
  US13/178,256
• Publication Number:
  US 20110262849A1
• Time in Patent Office: 453 Days
• Field of Search: 430/5, 430/22, 430/311
• US Class Current: 430/5
• CPC Class Codes: G03F 1/29 Rim PSM or outrigger PSM; Preparation thereof
• CPC Class Codes: G03F 1/32 Attenuating PSM [att-PSM], e.g. halftone PSM or PSM having semi-transparent phase shift portion,; Preparation thereof

Abstract

A photomask includes a transparent substrate having a transparent property against exposing light, a semi-light-shielding portion formed on the transparent substrate, a first opening formed in the semi-light-shielding portion and having a first dimension and a second opening formed in the semi-light-shielding portion and having a second dimension lager than the first dimension. A phase-shifting portion which transmits the exposing light in an opposite phase with respect to the first opening is formed on the transparent substrate around the first opening. A light-shielding portion is formed on the transparent substrate around the second opening.

Claims

1. A photomask comprising:

a transparent substrate having a transparent property against exposing light,

a semi-light-shielding portion formed on the transparent substrate;

an opening formed in the semi-light-shielding portion; and

a light-shielding portion formed on the transparent substrate and surrounding the opening, wherein;

the semi-light-shielding portion transmits the exposing light in an identical phase with respect to the opening, and

the light-shielding portion has a width not more than a maximum width with which an unexposed region is not formed by the exposing light having passed through the opening and diffracting at an edge of the opening to round to a back of the light-shielding portion.

2. The photomask of claim 1, wherein the light-shielding portion is disconnected at a corner of the opening.

3. The photomask of claim 2, wherein each disconnected part of the light-shielding portion has a length shorter than a corresponding side of the opening.

4. The photomask of claim 1, wherein the light-shielding portion has a width not less than a minimum width with which light intensity of a side lobe caused by diffraction, at an edge of the opening, of the exposing light having passed through the opening is not sufficient for sensitizing a resist.

5. The photomask of claim 1, wherein:

the photomask is designed for a specific reduction projection optical system, and is included in such a system along with an exposure apparatus, and

the light-shielding portion of the photomask has a width not less than (0.12×

λ

/NA)×

M, where λ

is a wavelength of the exposing light, NA is numerical aperture of a reduction projection optical system of an aligner and M is a reduction ratio of the reduction projection optical system.

6. The photomask of claim 1, wherein:

the photomask is designed for a specific reduction projection optical system, and is included in such a system along with an exposure apparatus, and

the light-shielding portion of the photomask has a width not more than (1.74×

λ

/NA)×

M, where λ

is a wavelength of the exposing light, NA is numerical aperture of a reduction projection optical system of an aligner and M is a reduction ratio of the reduction projection optical system.

7. The photomask of claim 1, wherein the light-shielding portion is in contact with the opening.

8. The photomask of claim 1, wherein a part of the semi-light-shielding portion is present between the opening and the light-shielding portion.

9. The photomask of claim 8, wherein:

the photomask is designed for a specific reduction projection optical system, and is included in such a system along with an exposure apparatus, and

the part of the semi-light-shielding portion of the photomask present between the opening and the light-shielding portion has a width not more than (0.10×

λ

/NA)×

M, where λ

is a wavelength of the exposing light, NA is numerical aperture of a reduction projection optical system of an aligner and M is a reduction ratio of the reduction projection optical system.

10. A pattern formation method using the photomask of claim 1, the method comprising steps of:

(a) forming a resist film on a substrate;

(b) irradiating the resist film with the exposing light through the photomask; and

(c) patterning the resist film by developing the resist film having been irradiated with the exposing light.

11. The pattern formation method of claim 10, wherein an ArF excimer laser is used as an exposing light source in the step (b).

12. The pattern formation method of claim 11, wherein an immersion exposure process is employed in the step (b).

13. The pattern formation method of claim 12, wherein the step (a) includes coating of the resist film with a top coat.