Photomask and methods for manufacturing and correcting photomask

• US 9,519,211 B2
• Filed: 01/28/2015
• Issued: 12/13/2016
• Est. Priority Date: 02/16/2009
• Status: Active Grant

• Current Assignee: Dai Nippon Printing Company Limited
• Original Assignee: Dai Nippon Printing Company Limited
• Inventors: Nagai, Takaharu, Mohri, Hiroshi, Morikawa, Yasutaka, Hayano, Katsuya
• Primary Examiner(s): Rosasco, Stephen
• Application Number:
  US14/607,541
• Publication Number:
  US 20150140480A1
• Time in Patent Office: 685 Days
• Field of Search: 430/5
• US Class Current: 1/1
• CPC Class Codes: G03F 1/28 with three or more diverse phases on the same PSM; Preparation thereof
• CPC Class Codes: G03F 1/30 Alternating PSM, e.g. Levenson-Shibuya 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
• CPC Class Codes: G03F 1/36 Masks having proximity correction features; Preparation thereof, e.g. optical proximity correction [OPC] design processes
• CPC Class Codes: G03F 1/38 Masks having auxiliary features, e.g. special coatings or marks for alignment or testing; Preparation thereof
• CPC Class Codes: G03F 1/44 Testing or measuring features, e.g. grid patterns, focus monitors, sawtooth scales or notched scales
• CPC Class Codes: G03F 1/68 Preparation processes not covered by groups G03F1/20 - G03F1/50
• CPC Class Codes: G03F 1/72 Repair or correction of mask defects
• CPC Class Codes: G03F 1/80 Etching

Abstract

The present invention provides a halftone mask comprising an assist pattern and a manufacturing method of the halftone mask, which uses an ArF excimer laser as an exposing source, is used for a projection exposure by an off axis illumination, does not resolve the assist pattern while keeping the focal depth magnification effect as the assist pattern, and may form a transferred image having high contrast of a main pattern. A photomask is a photomask comprising the main pattern which is transferred to a transfer-target surface by the projection exposure and the assist pattern which is formed nearby the main pattern and not transferred, characterized in that the main pattern and the assist pattern are each constituted from a semi-transparent film made of the same material, a retardation of 180° is generated between the light transmitting through the main pattern and the light transmitting through a transparent region of a transparent substrate, and a predetermined retardation within the scope of 70° to 115° is generated between the light transmitting through the assist pattern and the light transmitting through the transparent region of the transparent substrate.

Claims

1. A correcting method of a photomask using an ArF excimer laser as an exposing source, being used for a projection exposure by an off axis illumination, and comprising on a principal plane of a transparent substrate a main pattern transferred to a transfer-target surface by the projection exposure and an assist pattern formed nearby the main pattern, in which a minimum pattern pitch of the main pattern on the transfer-target surface is 120 nm or less, in a case where the assist pattern is resolved on the transfer-target surface by the projection exposure;

wherein a surface of the assist pattern to be resolved is etched to make a film thickness of the assist pattern to be resolved thinner than a film thickness of the main pattern until the assist pattern is not resolved on the transfer-target surface.

2. The correcting method of a photomask according to claim 1, wherein a film thickness difference between a film thickness of the assist pattern after being corrected by etching to thin and a film thickness of the assist pattern before being corrected is within a scope of 1 nm to 40 nm.

3. The correcting method of a photomask according to claim 1, wherein the etching is a gas-assisted etching by using an electron beam of an electron beam mask correcting device.

4. The correcting method of a photomask according to claim 1, wherein the main pattern and the assist pattern are each constituted from a semi-transparent film, and a film thickness of the main pattern is a film thickness for generating a retardation of 180°

between a light transmitting through the main pattern and a light transmitting through a transparent region of the transparent substrate.

5. The correcting method of a photomask according to claim 1, wherein the main pattern is constituted from a light shielding film, and the assist pattern is constituted from a semi-transparent film.

6. The correcting method of a photomask according to claim 1, wherein the main pattern and the assist pattern are each constituted from a light shielding film.

7. The correcting method of a photomask according to claim 1, wherein both the main pattern and the assist pattern are line patterns, and the main pattern is an isolated pattern or a periodic pattern.

8. A photomask wherein the assist pattern is corrected by the correcting method of a photomask according to claim 1, and a film thickness of the assist pattern after being corrected is thinner than a film thickness of the assist pattern before being corrected.