U.S. patent application number 13/408066 was filed with the patent office on 2012-06-21 for immersion multiple-exposure method and immersion exposure system for separately performing multiple exposure of micropatterns and non-micropatterns.
This patent application is currently assigned to Kabushiki Kaisha Toshiba. Invention is credited to Takehiro Kondoh.
Application Number | 20120154771 13/408066 |
Document ID | / |
Family ID | 40132668 |
Filed Date | 2012-06-21 |
United States Patent
Application |
20120154771 |
Kind Code |
A1 |
Kondoh; Takehiro |
June 21, 2012 |
IMMERSION MULTIPLE-EXPOSURE METHOD AND IMMERSION EXPOSURE SYSTEM
FOR SEPARATELY PERFORMING MULTIPLE EXPOSURE OF MICROPATTERNS AND
NON-MICROPATTERNS
Abstract
This invention discloses an immersion multiple-exposure method
including a first exposure step of performing, using a first mask,
immersion exposure of a photoresist film formed on a substrate, a
cleaning step of clearing the surface of the substrate, and a
second exposure step of performing immersion exposure of the
photoresist film using a second mask. No heating process is
performed between the first exposure step and the second exposure
step.
Inventors: |
Kondoh; Takehiro;
(Yokkaichi-shi, JP) |
Assignee: |
Kabushiki Kaisha Toshiba
Tokyo
JP
|
Family ID: |
40132668 |
Appl. No.: |
13/408066 |
Filed: |
February 29, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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12140653 |
Jun 17, 2008 |
8148054 |
|
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13408066 |
|
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Current U.S.
Class: |
355/30 |
Current CPC
Class: |
G03F 7/70466 20130101;
G03F 7/091 20130101; G03F 7/70283 20130101; G03F 7/70925 20130101;
G03F 7/70341 20130101; H01L 21/0276 20130101 |
Class at
Publication: |
355/30 |
International
Class: |
G03B 27/52 20060101
G03B027/52 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 18, 2007 |
JP |
2007-160467 |
Claims
1.-10. (canceled)
11. An immersion exposure system comprising: a cleaning unit
configured to clean a substrate between exposure steps of an
immersion multiple-exposure process.
12. The system according to claim 11, wherein the cleaning unit
cleans the substrate after first immersion exposure is performed
using a first mask, and second immersion exposure is performed
using a second mask after the substrate is cleaned.
13. The system according to claim 11, wherein the cleaning unit
cleans the substrate while rotating the substrate and spraying pure
water.
14. An immersion exposure system comprising: an immersion exposure
apparatus; a coater/development apparatus; and a cleaning unit
provided between the immersion exposure apparatus and the
coater/development apparatus to clean a substrate between exposure
steps of an immersion multiple-exposure process.
15. The system according to claim 14, wherein the immersion
exposure apparatus comprises an illumination light source, a
condenser optical system configured to condense irradiation light
from the illumination light source, a reticle stage arranged on an
exit side of the condenser optical system to accept a photomask, a
projection optical system arranged under the reticle stage, and a
wafer stage arranged under the projection optical system to accept
a wafer.
16. The system according to claim 14, wherein the
coater/development apparatus applies a resist to the substrate to
form a photoresist film.
17. The system according to claim 14, wherein the cleaning unit
cleans the substrate while rotating the substrate and spraying pure
water.
18. The system according to claim 14, wherein the cleaning unit
cleans the substrate by spraying pure water after the immersion
exposure apparatus performs first immersion exposure using a first
mask, and the immersion exposure apparatus performs second
immersion exposure using a second mask after the substrate is
cleaned.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from prior Japanese Patent Application No. 2007-160467,
filed Jun. 18, 2007, the entire contents of which are incorporated
herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an immersion exposure
technique used in manufacturing a semiconductor device and, for
example, to an immersion multiple-exposure method and immersion
exposure system for separately performing multiple exposure of
micropatterns and non-micropatterns.
[0004] 2. Description of the Related Art
[0005] In a recently proposed technique, in forming a highly
integrated semiconductor circuit device, patterns to be exposed are
divided into micropatterns and non-micropatterns and double-exposed
to a photoresist film under illumination conditions optimum for the
respective patterns (e.g., Jpn. Pat. Appln. KOKAI Publication No.
2000-349010). Immersion exposure will be described as an example.
First, an ArF organic anti-reflection material is applied to the
element formation surface (major surface) of a wafer by spin
coating and baked at 215.degree. C. for 1 minute, thereby forming
an 80-nm-thick anti-reflection film. Then, an ArF positive resist
is applied to the anti-reflection film by spin coating and baked at
90.degree. C. for 1 minute, thereby forming a 400-nm-thick
photoresist film. Next, an immersion exposure protective film is
applied to the photoresist film by spin coating and baked at
90.degree. C. for 1 minute.
[0006] An ArF excimer laser immersion exposure apparatus exposes
the wafer having the stacked structure of the anti-reflection film,
photoresist film, and immersion protective film using a halftone
mask having a transmittance of 6% under conditions of NA=0.78 and
2/3 annular illumination. The wafer is exposed again using a
halftone mask having a transmittance of 6% under conditions of
NA=0.92 and .sigma.0.97. The wafer is baked at 100.degree. C. for 1
minute and developed in a 2.38-wt % aqueous solution of
tetramethylammonium hydroxide (TMAH), thereby forming a resist
pattern.
[0007] When the resist pattern formed by the above-described
double-exposure was inspected by an optical defect inspection
apparatus (2360 available from KLA), a number of defects were
found, and the defect density was about 0.7 pieces/cm.sup.2. These
defects are presumably produced upon double-exposure in immersion
exposure because dust particles produced in the first exposure step
stick to the immersion protective film and shield the irradiation
light in the second exposure step.
BRIEF SUMMARY OF THE INVENTION
[0008] According to an aspect of the present invention, there is
provided an immersion multiple-exposure method of performing
immersion exposure twice or more for a photoresist film formed on a
substrate, in which at least one step of cleaning the surface of
the substrate is inserted between the exposure steps of the
immersion multiple-exposure process.
[0009] According to another aspect of the present invention, there
is provided an immersion exposure system for performing immersion
exposure twice or more for a photoresist film, comprising a
cleaning unit which cleans the substrate between the exposure steps
of the immersion multiple-exposure process.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0010] FIG. 1 is a process flowchart illustrating the procedure of
loading a wafer to an exposure step and delivering it after a
development step so as to explain an immersion multiple-exposure
method and immersion exposure system according to an embodiment of
the present invention;
[0011] FIG. 2 is a sectional view showing a wafer as a target of
immersion double-exposure so as to explain the immersion
multiple-exposure method and immersion exposure system according to
the embodiment of the present invention;
[0012] FIG. 3 is a block diagram showing the schematic arrangement
of an immersion exposure system so as to explain the immersion
multiple-exposure method and immersion exposure system according to
the embodiment of the present invention;
[0013] FIG. 4 is a plan view showing a result obtained by
inspecting, using an optical defect inspection apparatus, a pattern
formed by the immersion multiple-exposure method according to the
embodiment of the present invention;
[0014] FIG. 5 is a plan view showing a result obtained by
inspecting, using an optical defect inspection apparatus, a pattern
formed by a conventional immersion multiple-exposure method;
and
[0015] FIG. 6 is a sectional view showing a wafer as a target of
immersion double-exposure so as to explain another embodiment of
the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0016] FIGS. 1 to 3 are views for explaining an immersion
multiple-exposure method and immersion exposure system according to
an embodiment of the present invention. FIG. 1 is a process
flowchart illustrating the procedure of loading a wafer
(semiconductor substrate) to an exposure step and delivering it
after a development step. FIG. 2 is a sectional view of the wafer
as a target of immersion double-exposure. FIG. 3 is a block diagram
showing the schematic arrangement of the immersion exposure
system.
[0017] First, an ArF organic anti-reflection material is applied to
the element formation surface (major surface) of a wafer 11 by spin
coating (STEP 1) and heated (STEP 2), e.g., baked at 215.degree. C.
for 1 minute, thereby forming an anti-reflection film 12 having a
thickness of about 80 nm.
[0018] The wafer 11 is loaded into a coater/development apparatus
100. An ArF positive resist is applied to the anti-reflection film
12 by spin coating (STEP 3) and heated (STEP 4), e.g., baked at
90.degree. C. for 1 minute, thereby forming a photoresist film 13
having a thickness of about 400 nm.
[0019] Next, an immersion exposure protective material is applied
to the photoresist film 13 by spin coating (STEP 5) and heated
(STEP 6), e.g., baked at 90.degree. C., for 1 minute, thereby
forming an immersion protective film 14.
[0020] The wafer 11 having the stacked structure of the
anti-reflection film 12, photoresist film 13, and immersion
protective film 14 is transferred into an exposure apparatus 200
and exposed using a first halftone mask having a transmittance of
6% under conditions of NA=0.78 and 2/3 annular illumination (STEP
7). The exposure apparatus 200 is, e.g., an ArF excimer laser
immersion exposure apparatus including an illumination light source
210, condenser optical system 220, reticle stage 230, projection
optical system 240, and wafer stage 250. The condenser optical
system 220 condenses irradiation light from the illumination light
source 210. The reticle stage 230 is arranged on the exit side of
the condenser optical system 220 to accept a photomask. The
projection optical system 240 is arranged under the reticle stage
230. The wafer stage 250 is arranged under the projection optical
system 240 to accept the wafer 11.
[0021] The wafer 11 that has undergone immersion exposure is
transferred into a cleaning unit 300 to clean the surface using
pure or ultrapure water (referred to as ultrapure water
hereinafter) (STEP 8). The cleaning unit 300 is provided at the
interface portion between the coater/development apparatus and the
exposure apparatus 200. The cleaning unit 300 cleans the wafer 11
while rotating it and spraying ultrapure water.
[0022] The wafer 11 that has undergone surface cleaning is
transferred into the exposure apparatus 200 again and loaded on the
wafer stage 250. The wafer 11 is exposed using a second halftone
mask (having a pattern different from that of the first halftone
mask) having a transmittance of 6% under conditions of NA=0.92 and
.sigma.0.97 (STEP 9) and heated (STEP 10), e.g., baked at
100.degree. C. for 1 minute. The exposed wafer 11 is transferred
into the coater/development apparatus 100 and developed in a
2.38-wt % aqueous solution of tetramethylammonium hydroxide (TMAH),
thereby forming a resist pattern (STEP 11).
[0023] A workpiece is processed, e.g., an oxide film or metal film
is etched using the resist pattern as at least part of a mask,
thereby forming various semiconductor elements, interconnections,
and the like. According to the above-described immersion
multiple-exposure method, it is possible to remove dust particles
that are produced in the first exposure step and stick to the
immersion protective film 14 by surface cleaning using ultrapure
water. This allows pattern defects to be reduced.
[0024] According to the above-described immersion exposure system,
the cleaning unit 300 is provided at the interface portion between
the coater/development apparatus 100 and the exposure apparatus
200. It is therefore possible to efficiently clean the photoresist
film and also minimize contamination during transfer between the
apparatuses.
[0025] According to the above-described semiconductor device
manufacturing method, it is possible to reduce pattern defects in
the photoresist film. This suppresses a decrease in the yield.
[0026] The pattern formed by the above-described manufacturing
method was subjected to defect inspection by an optical defect
inspection apparatus. The defect density was about 0.3
pieces/cm.sup.2, as shown in FIG. 4. That is, the number of defects
obviously decreased as compared to the defect density (0.7
pieces/cm.sup.2) in the conventional manufacturing method shown in
FIG. 5.
[0027] In the above-described embodiment, the immersion protective
film 14 is formed on the photoresist film 13. However, the
immersion protective film is unnecessary if a protective film-less
type photoresist film 13' is used, as shown in FIG. 6. The
remaining manufacturing methods and manufacturing conditions are
the same as in the above embodiment.
[0028] In the above embodiment, immersion double-exposure has been
explained. However, the present invention is also applicable to
immersion multiple exposure that performs exposure of a single
resist surface three times or more. The effects are obtained by
performing the cleaning process at least once between two of the
plurality of exposure processes. The cleaning process may be done
between the respective exposure processes, as a matter of
course.
[0029] In the above-described embodiment, the first and second
halftone masks have different patterns. However, the present
invention is also applicable to multiple exposure using a single
mask having a single pattern, and almost the same functions and
effects can be obtained.
[0030] As described above, according to one aspect of the present
invention, it is possible to obtain an immersion multiple-exposure
method and immersion exposure system capable of reducing pattern
defects in multiple exposure.
[0031] Additional advantages and modifications will readily occur
to those skilled in the art. Therefore, the invention in its
broader aspects is not limited to the specific details and
representative embodiments shown and described herein. Accordingly,
various modifications may be made without departing from the spirit
or scope of the general inventive concept as defined by the
appended claims and their equivalents.
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