Method of configuring extreme ultra-violet (euv) illumination system, and euv exposure method using the euv illumination system

Patent metadata

Field	Value
Publication number	US-2025138434-A1
Application number	US-202418806848-A
Country	US
Kind code	A1
Filing date	Aug 16, 2024
Priority date	Oct 31, 2023
Publication date	May 1, 2025
Grant date	—

Abstract

Provided are a method of configuring an optimized extreme ultraviolet (EUV) illumination system, and an EUV exposure method using the EUV illumination system. The method of configuring the EUV illumination system includes calculating an aerial image by performing an optical simulation with respect to each of EUV point sources, summing up the aerial images based on EUV mapping, searching for a combination of the EUV point sources by using a fitness value with respect to the summed aerial image, and configuring the EUV illumination system as a combination of the EUV point sources, which has a maximum fitness value.

First claim

What is claimed is:

1 . A method of configuring an extreme ultraviolet (EUV) illumination system, the method comprising:
generating aerial images by performing an optical simulation with respect to each of a plurality of EUV point sources; summing up the aerial images based on EUV mapping; searching for a combination of the EUV point sources using a fitness value with respect to the summed aerial images; and configuring the EUV illumination system as a combination of the EUV point sources which has a maximum fitness value.

2 . The method of claim 1 , wherein
each of the plurality of EUV point sources is a minimum unit that is configured to be individually turned on/off, and EUV light from the plurality of EUV point sources at different locations has incoherence with each other.

3 . The method of claim 1 , wherein the aerial images are represented as graphs of an intensity of a cutline with respect to a mask pattern.

4 . The method of claim 1 , wherein
the EUV mapping corresponds to a restricted condition of selecting optical paths from M field facet mirrors (FFMs) to N pupil facet mirrors (PFMs) and M represents a positive integer and N represents an integer greater than M.

5 . The method of claim 4 , wherein the aerial images, with respect to N EUV point sources, are generated through the optical simulation.

6 . The method of claim 4 , wherein, in the searching of the combination of the EUV point sources, a genetic algorithm is used.

7 . The method of claim 6 , wherein,
in the summing up of the aerial images, P combinations of the EUV point sources are generated, with P representing a positive integer, and the aerial images are summed with respect to each of the combinations of the EUV point sources; wherein the searching of the combination of the EUV point sources comprises
determining the fitness value with respect to each of the P combinations of the EUV point sources,
selecting Q combinations of the EUV point sources, which are set in an order of large fitness values, with Q representing a positive integer less than P, and
partially changing the EUV mappings in the Q combinations of the EUV point sources,
wherein, after the changing of the EUV mappings partially, the summing up of the aerial images is performed; wherein transition to the summing up of the aerial images is repeatedly performed a number of times; and wherein, in the configuring of the EUV illumination system, after the performance of the transition the number of times, the EUV illumination system is configured using the EUV point sources included in the combination having the maximum fitness value.

8 . The method of claim 7 , wherein the fitness value includes at least one of a critical dimension (CD) longer axis, a CD shorter axis, a CD aspect ratio that is a ratio between the CD longer axis and the CD shorter axis, a longer axis normalized image log slope (NILS), a shorter axis NILS, and dose as a factor, and is calculated by applying a weight value to the factor.

9 . The method of claim 4 , wherein, in the searching of the combination of the EUV point sources, a Lagrange multiplier method is used.

10 . The method of claim 9 , wherein, in the Lagrange multiplier method,
a function L, representing the restricted condition, is defined by Equation 1 below in order to find a combination of the EUV point sources based on normalized image log slopes (NILS) including NILSx and NILSy,
L ( I i ,λ)=NILS−λ( I tot −I 0 )  (1),

the NILSx of the NILS is expressed as

∑

i
=
1

M

CD
x

I
tot

⁢

dI
i

dx

,

the NILSy of the NILS is expressed as

∑

i
=
1

M

CD
y

I
tot

⁢

dI
i

dy

,

and
I tot is

∑

i
=
1

M

I
i

and represents a total intensity of the aerial images in a target critical dimension (CD) and I 0 denotes a value used in implementing the target CD, and
under a condition of I tot =I 0 , a problem of finding the optimal combination of the EUV point sources is changed into a problem of maximizing the NILS.

11 . The method of claim 10 , wherein
the NILS corresponds to a slope of an intensity at a point where the target CD is defined, and the NILS has a characteristic in which the CD is less changed with respect to a change in processes as a value of the NILS increases.

12 . The method of claim 4 , wherein the method is applied to a mask pattern to which a bias is applied or to a plurality of mask patterns.

13 . A method of configuring an extreme ultraviolet (EUV) illumination system, the method comprising:
generating aerial images, indicated as an intensity of a cutline with respect to a mask pattern, by performing an optical simulation on each of a plurality of EUV point sources that are individually configured to turn on/off incoherent light; performing an EUV mapping for selecting optical paths from M field facet mirrors (FFMs) to N pupil facet mirrors (PFMs) in order to configure an illumination system of the EUV point sources, with M representing a positive integer and N representing an integer greater than M; summing up the aerial images based on the EUV mapping; searching for a combination of the EUV point sources using a fitness value with respect to the summed aerial images; selecting a combination of the EUV point sources, which has a maximum fitness value; and configuring the EUV illumination system using the selected combination of the EUV point sources.

14 . The method of claim 13 , wherein the aerial images with respect to N EUV point sources are generated through the optical simulation.

15 . The method of claim 13 , wherein,
in the summing up of the aerial images, P combinations of the EUV point sources are generated, with P representing a positive integer, and the aerial images are summed with respect to each of the combinations of the EUV point sources; w

Assignees

• Samsung Electronics Co Ltd

Inventors

• Cho Yeongchan
• Kim Minjae
• Nam Sungmin
• Yang Seunghune

Classifications

• G03F7/70058

  Mask illumination systems · CPC title

• G03F7/70504 Primary

  Optical system modelling, e.g. lens heating models · CPC title

• G03F7/70125

  Use of illumination settings tailored to particular mask patterns (details of setting means G03F7/70091) · CPC title

• G03F7/70075

  Homogenization of illumination intensity in the mask plane by using an integrator, e.g. fly's eye lens, facet mirror or glass rod, by using a diffusing optical element or by beam deflection · CPC title

• G03F7/705

  Modelling or simulating from physical phenomena up to complete wafer processes or whole workflow in wafer productions · CPC title