Extreme ultraviolet lithography process and mask

Patent metadata

Field	Value
Publication number	US-2016306272-A1
Application number	US-201615194072-A
Country	US
Kind code	A1
Filing date	Jun 27, 2016
Priority date	Oct 7, 2013
Publication date	Oct 20, 2016
Grant date	—

Abstract

An extreme ultraviolet lithography (EUVL) system is disclosed. The system includes an extreme ultraviolet (EUV) mask with three states having respective reflection coefficient is r 1 , r 2 and r 3 , wherein r 3 is a pre-specified value that is a function of r1 and r2. The system also includes a nearly on-axis illumination (ONI) with partial coherence a less than 0.3 to expose the EUV mask to produce diffracted light and non-diffracted light. The system further includes a projection optics box (PUB) to remove a portion of the non-diffracted light and to collect and direct the diffracted light and the remaining non-diffracted light to expose a target.

First claim

What is claimed is:

1 . An extreme ultraviolet lithography (EUVL) system, comprising:
an extreme ultraviolet (EUV) mask with three states having reflection coefficients r 1 , r 2 , and r 3 , respectively, wherein r 3 is a pre-specified value that is a function of r 1 and r 2 ; an on-axis illumination (ONI) with partial coherence σ less than 0.3 to expose the EUV mask to produce diffracted light and non-diffracted light; and a projection optics box (POB) to remove a portion of the non-diffracted light and to collect and direct the diffracted light and the remaining non-diffracted light to expose a target.

2 . The system of claim 1 , wherein the EUV mask comprises:
a low thermal expansion material (LTEM) layer; a reflective multilayer (ML) over one surface of the LTEM layer; a conductive layer over an opposite surface of the LTEM layer; a capping layer over the reflective ML; a buffer layer over the capping layer; and an absorption stack over the buffer layer, wherein the absorption stack comprises multiple layers.

3 . The system of claim 2 , wherein the absorption stack includes a top layer, a middle layer, and a bottom layer.

4 . The system of claim 3 , wherein the top and the bottom layers include molybdenum (Mo).

5 . The system of claim 3 , wherein the middle layer includes material from a group consisting of tantalum (Ta), tantalum nitride (TaN), and tantalum boron nitride (TaBN).

6 . The system of claim 1 , wherein r 3 is a function of the product of r 1 and r 2 .

7 . The system of claim 2 , wherein the first state is configured as (from top to bottom) the buffer layer/the capping layer/the reflective ML/the LTEM layer.

8 . The system of claim 2 , wherein the second state is configured as (from top to bottom) the bottom layer of the absorption stack/the buffer layer/the capping layer/the reflective ML/the LTEM layer.

9 . The system of claim 2 , wherein the portion of the non-diffracted light is at least 70%.

10 . The system of claim 2 , wherein the capping layer and the buffer layer can be replaced by a single layer.

11 . The system of claim 1 , wherein the first and the second states are assigned to adjacent polygons, while the third state is assigned to a field (a region without polygons).

12 . An extreme ultraviolet lithography (EUVL) process, comprising:
fabricating an extreme ultraviolet (EUV) mask, including:
forming an absorption stack comprising two or more layers;
removing a first portion of the absorption stack; and
removing a second portion of the absorption stack, the second portion being different than the first portion;
wherein the forming. the removing the first portion, and removing the second portion result in the EUV mask having a first state, a second state, and a third state with respective pre-specified reflection coefficients r 1 , r 2, and r 3 , wherein r 3 is a function of r 1 and r 2 ;
exposing the EUV mask by an on-axis illumination (ONI) with partial coherence σ less than 0.3 to produce diffracted light and non-diffracted light; and collecting and directing the diffracted light and the not removed non-diffracted light by a projection optics box (POB) to expose a semiconductor wafer.

13 . The process of claim 12 , wherein fabricating the EUV mask further comprises:
forming a first polygon; forming a second polygon adjacent to the first polygon; wherein the first state is assigned to the first polygon, the second state is assigned to the second polygon, and the third state is assigned to a field region free of the first and second polygons.

14 . The process of claim 13 , wherein the first polygon and the second polygon are circuit patterns.

15 . The process of claim 12 , wherein r 3 is (r 1 +r 2 )/2.

16 . The process of claim 12 , wherein the absorption stack includes a top layer, a middle layer, and a bottom layer.

17 . An extreme ultraviolet lithography (EUVL) system, comprising:
an extreme ultraviolet (EUV) mask with three states having reflection coefficients r 1 , r 2 , and r 3 , respectively, wherein r 3 is approximately an average of r 1 and r 2 ; an on-axis illumination (ONO with partial coherence σ less than 0.3 to expose the EUV mask to produce diffracted light and non-diffracted light; and a projection optics box (POB) to remove a portion of the non-diffracted light and to collect and direct the diffracted light and the remaining non-diffracted light to expose a target.

18 . The system of claim 17 , wherein the EUV mask comprises:
a low thermal expansion material (LTEM) layer; a reflective multilayer (ML) over one surface of the LTEM layer; a conductive layer over an opposite surface of the LTEM layer; a capping layer over the reflective ML; a buffer layer over the capping layer; and an absorption stack over the buffer layer, wherein the absorption stack comprises multiple layers.

19 . The system of claim 17 , wherein the first and the second states are assigned to adjacent polygons, while the third state is assigned to a field (a region without polygons).

20 . The system of claim 19 , wherein the adjacent polygons are circuit patterns.

Assignees

• Taiwan Semiconductor Mfg Co Ltd

Inventors

• Lu Yen-Cheng
• Chen Jeng-Horng
• Yu Shinn-Sheng
• Yen Anthony

Classifications

• G03F7/70091

  Illumination settings, i.e. intensity distribution in the pupil plane or angular distribution in the field plane; On-axis or off-axis settings, e.g. annular, dipole or quadrupole settings; Partial coherence control, i.e. sigma or numerical aperture [NA] · CPC title

• G03F1/24 Primary

  Reflection masks; Preparation thereof · CPC title

• G03F7/2004

  characterised by the use of a particular light source, e.g. fluorescent lamps or deep UV light · CPC title

• G03F7/70283 Primary

  Mask effects on the imaging process · CPC title

• G03F1/54

  Absorbers, e.g. of opaque materials · CPC title