Assist Feature for a Photolithographic Process

Patent metadata

Field	Value
Publication number	US-2016011501-A1
Application number	US-201414327834-A
Country	US
Kind code	A1
Filing date	Jul 10, 2014
Priority date	Jul 10, 2014
Publication date	Jan 14, 2016
Grant date	—

Abstract

A photomask having a partial-thickness assist feature and a technique for manufacturing the photomask are disclosed. In an exemplary embodiment, the photomask includes a mask substrate, a reflective structure disposed on the mask substrate, and an absorptive layer formed on the reflective structure. A printing feature region and an assist feature region are defined on the mask. The absorptive layer has a first thickness in the printing feature region and a second thickness in the assist feature region that is different from the first thickness. In some such embodiments, the second thickness is configured such that radiation reflected by the assist feature region does not exceed an exposure threshold of a photoresist of a target.

First claim

1 . A lithographic mask comprising:
a mask substrate; a reflective structure disposed on the mask substrate; and an absorptive layer formed on the reflective structure, wherein the mask includes a printing feature region and an assist feature region defined thereupon, wherein the absorptive layer has a first thickness in the printing feature region and a second thickness in the assist feature region, and wherein the first thickness and the second thickness are different.

2 . The lithographic mask of claim 1 , wherein the printing feature region is substantially free of the absorptive layer.

3 . The lithographic mask of claim 1 , wherein the first thickness is greater than the second thickness.

4 . The lithographic mask of claim 1 , wherein the second thickness is configured such that radiation reflected by the assist feature region does not exceed an exposure threshold of a photoresist of a target.

5 . The lithographic mask of claim 1 , wherein the assist feature region is adjacent to the printing feature region.

6 . The lithographic mask of claim 1 , wherein the absorptive layer includes an upper absorptive layer and a lower absorptive layer.

7 . The lithographic mask of claim 6 , wherein the assist feature region includes a portion of the upper absorptive layer and a portion of the lower absorptive layer.

8 . The lithographic mask of claim 6 , wherein the assist feature region is substantially free of the upper absorptive layer.

9 - 20 . (canceled)

21 . A lithographic mask comprising:
a mask substrate; a reflective structure disposed on the mask substrate; and an absorptive layer formed on the reflective structure, wherein the mask includes a printing feature region with a first feature within a resolution of a radiation to be applied to the lithographic mask, wherein the mask includes a sub-resolution assist feature (SRAF) region with a second feature less than the resolution of the radiation to be applied to the lithographic mask, wherein the absorptive layer has a first thickness in the printing feature region and a second thickness in the SRAF region, and wherein the first thickness and the second thickness are different.

22 . The lithographic mask of claim 21 , wherein the printing feature region is substantially free of the absorptive layer.

23 . The lithographic mask of claim 21 , wherein the first thickness is greater than the second thickness.

24 . The lithographic mask of claim 21 , wherein the SRAF region is adjacent to the printing feature region.

25 . The lithographic mask of claim 21 , wherein the absorptive layer includes an upper absorptive layer and a lower absorptive layer.

26 . The lithographic mask of claim 25 , wherein the SRAF region includes a portion of the upper absorptive layer and a portion of the lower absorptive layer.

27 . The lithographic mask of claim 25 , wherein the SRAF region is substantially free of the upper absorptive layer.

28 . A lithographic mask comprising:
a mask substrate; a reflective structure disposed on the mask substrate; and an absorptive layer formed on the reflective structure, wherein the mask includes a printing feature region, an assist feature region, and a third region that is neither a printing feature region nor an SRAF region, wherein the absorptive layer has a first thickness in the printing feature region, a second thickness in the assist feature region, and a third thickness in the third region, and wherein the first, second, and third thicknesses are different.

29 . The lithographic mask of claim 28 , wherein the printing feature region is substantially free of the absorptive layer.

30 . The lithographic mask of claim 28 , wherein the first thickness is greater than the second thickness.

31 . The lithographic mask of claim 28 , wherein the second thickness is configured such that radiation reflected by the assist feature region does not exceed an exposure threshold of a photoresist of a target.

32 . The lithographic mask of claim 28 , wherein the absorptive layer includes an upper absorptive layer and a lower absorptive layer, and wherein the assist feature region includes a portion of the upper absorptive layer and a portion of the lower absorptive layer.

Assignees

• Taiwan Semiconductor Mfg

Inventors

• Huang Tao-Min
• Chen Chia-Jen
• Lee Hsin-Chang
• Shih Chih-Tsung
• Yu Shinn-Sheng
• Chen Jeng-Horng
• Yen Anthony

Classifications

• H10P76/405

  characterised by their composition, e.g. multilayer masks · CPC title

• H10P76/2041 Primary

  Photolithographic processes · CPC title

• G03F1/24 Primary

  Reflection masks; Preparation thereof · CPC title

• G03F1/38

  Masks having auxiliary features, e.g. special coatings or marks for alignment or testing; Preparation thereof · CPC title

• G03F7/20

  Exposure; Apparatus therefor (photographic printing apparatus for making copies G03B27/00) · CPC title