U.S. patent application number 12/654295 was filed with the patent office on 2010-04-22 for pattern forming method and method of manufacturing semiconductor device.
This patent application is currently assigned to Kabushiki Kaisha Toshiba. Invention is credited to Shinichi Ito, Daisuke Kawamura.
Application Number | 20100099036 12/654295 |
Document ID | / |
Family ID | 36780375 |
Filed Date | 2010-04-22 |
United States Patent
Application |
20100099036 |
Kind Code |
A1 |
Kawamura; Daisuke ; et
al. |
April 22, 2010 |
Pattern forming method and method of manufacturing semiconductor
device
Abstract
A pattern forming method includes forming a resist film on a
substrate, coating the resist film with a coating solution which
forms a cover film on the resist film to form the cover film on the
resist film, transferring a pattern onto the resist film by an
immersion lithography method using a liquid immersion fluid to form
a latent image on the resist film, removing the cover film after
the formation of the latent image, conducting a first inspection to
inspect whether or not the cover film has a defect between said
forming the latent image and said removing the cover film,
performing predetermined processing when the defect is found in the
first inspection, and developing the resist film to form a resist
pattern on the substrate after said removing the cover film.
Inventors: |
Kawamura; Daisuke;
(Yokohama-shi, JP) ; Ito; Shinichi; (Yokohama-shi,
JP) |
Correspondence
Address: |
FINNEGAN, HENDERSON, FARABOW, GARRETT & DUNNER;LLP
901 NEW YORK AVENUE, NW
WASHINGTON
DC
20001-4413
US
|
Assignee: |
Kabushiki Kaisha Toshiba
|
Family ID: |
36780375 |
Appl. No.: |
12/654295 |
Filed: |
December 16, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11350080 |
Feb 9, 2006 |
7662543 |
|
|
12654295 |
|
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Current U.S.
Class: |
430/30 ; 430/319;
430/325 |
Current CPC
Class: |
Y10S 430/162 20130101;
G03F 7/70958 20130101; G03F 7/11 20130101; G03F 7/7065 20130101;
G03F 7/70341 20130101 |
Class at
Publication: |
430/30 ; 430/325;
430/319 |
International
Class: |
G03F 7/20 20060101
G03F007/20 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 10, 2005 |
JP |
2005-034540 |
Claims
1.-6. (canceled)
7. A method of pattern forming comprising: forming a resist film on
a substrate; transferring a pattern onto the resist film by an
immersion lithography method using a liquid immersion fluid to form
a latent image on the resist film; conducting a first inspection to
inspect whether or not the liquid immersion fluid remains on the
resist film after said forming the latent image; developing the
resist film after the first inspection; and performing
predetermined processing when residual of the liquid immersion
fluid is found in the first inspection.
8. The method according to claim 7, wherein the predetermined
processing includes: collecting the residual of the liquid
immersion fluid; and removing the resist film to return to said
forming a resist film on a substrate.
9. The method according to claim 7, wherein the predetermined
processing includes: conducting, after said developing, a
predetermined second inspection corresponding to a case where the
liquid immersion fluid remains, for a substrate on which the liquid
immersion fluid remains; and removing the resist film from the
substrate which is judged to be abnormal as a result of the second
inspection, to return to said forming a resist film on a
substrate.
10. The method according to claim 9, wherein positional information
of the residual of the liquid immersion fluid is obtained during
the first inspection; and the second inspection is conducted in
accordance with the positional information.
11. The method according to claim 7, further comprising
implementing processing to remove the liquid immersion fluid
remaining on the resist film.
12. The method according to claim 7, further comprising forming a
cover film on the resist film before said forming the latent
image.
13. The method according to claim 7, further comprising rinsing the
surface of the cover film by use of a rinsing liquid between the
formation of the latent image and the post exposure bake; and
removing the rinsing liquid on the cover film.
14. The method according to claim 7, wherein post exposure bake is
implemented for the resist film during a period after the first
inspection and before said developing.
15. A method of manufacturing a semiconductor device, comprising:
forming a resist film on a semiconductor substrate; transferring a
semiconductor device pattern onto the resist film by an immersion
lithography method using a liquid immersion fluid to form a latent
image on the resist film; conducting a first inspection to inspect
whether or not the liquid immersion fluid remains on the resist
film after the formation of the latent image; implementing post
exposure bake for the resist film after the first inspection;
developing the resist film after the post exposure bake; and
performing predetermined processing when residual of the liquid
immersion fluid is found in the first inspection.
16. The method according to claim 15, wherein the predetermined
processing includes: collecting the residual of the liquid
immersion fluid; and removing the resist film to return to said
forming a resist film on a semiconductor substrate.
17. The method according to claim 15, wherein the predetermined
processing includes: conducting, after said developing, a
predetermined second inspection corresponding to a case where the
liquid immersion fluid remains, for a substrate on which the liquid
immersion fluid remains; and removing the resist film from the
substrate which is judged to be abnormal as a result of the second
inspection to return to said forming a resist film on a
semiconductor substrate.
18. The method according to claim 17, wherein positional
information of the residual of the liquid immersion fluid is
obtained in the first inspection; and the second inspection is
conducted in accordance with the positional information.
19. The method according to claim 15, further comprising
implementing processing to remove the liquid immersion fluid
remaining on the resist film.
20. The method according to claim 15, further comprising forming a
cover film on the resist film before the formation of the latent
image.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from prior Japanese Patent Application No. 2005-034540,
filed Feb. 10, 2005, 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 a pattern forming method
based on immersion lithography, and a method of manufacturing a
semiconductor device.
[0004] 2. Description of the Related Art
[0005] Development of exposure tools has been in progress along
with shrinkage of semiconductor devices. A 157 nm-lithography tool
has been developed as a next-generation lithography tool, which
replaces a tool presently in practical use to 193 nm lithography.
However, due to delays in development of exposure tools and resist
materials, a 193 nm-immersion lithography exposure tool is regarded
as reliable at present. In the immersion lithography exposure tool,
a solvent such as water which is a medium having a refractive index
greater than that of air is filled between an objective lens and
resist films targeted for image formation to increase a critical
angle of an interface between the objective lens and the medium or
an interface between the medium and the resist films, and an
appropriate lens is used to enable image formation of a small
pattern with a larger diffraction angle (refer to pamphlet for
International publication No. WO99/49504).
[0006] In an optical lithography step where the immersion
lithography exposure tool is used to transfer a pattern to a resist
film, there is concern over the elution of an inclusion from the
resist film into a liquid immersion fluid. This arises from the
fear that a photo-acid generator contained in the resist film and
its photoproducts which are photo-generated acids, basic materials
and other low-molecular components elute into the immersion fluid
and contaminate the element of the projection optics which contacts
with the liquid immersion fluid, a shower head, a wafer stage, and
so forth. The adsorption of the eluting substances onto the
projection optics or corrosion thereof emerges as an optical path
difference, and therefore influences imaging performance as
aberration and flare, and it is presumed that this influence
accumulatively increases due to an increase in processing for the
resist processes of the same kind. On the other hand, the elusion
of the substance into the immersion fluid changes the refractive
index of the immersion fluid and thus changes the optical path
length, which causes aberration of a projected image and affects
the imaging performance.
[0007] Furthermore, in an immersion lithography exposure tool which
selectively fills the liquid immersion fluid between a downstream
surface of an optical axis of the objective lens and a substrate
upper surface targeted for image projection, the following problems
occur in a case where the liquid immersion fluid remains on the
substrate when the substrate is loaded after completion of an
exposure step.
[0008] 1. If the liquid immersion fluid leaks into the exposure
tool and a coating tool and touches electric systems therein,
trouble occurs in the operation of the tools. This results in a
reduction in productivity and generation of costs due to the
stoppage and repair of the tools, and a loss due to the
reprocessing and damage of a wafer.
[0009] 2. If the liquid immersion fluid leaks into the exposure
tool and the coating tool and is left as it is, microorganisms such
as bacteria are grown in the leaking solution, which increases the
concentration of a chemical species such as a base in the air
inside the exposure tool and coating tool. This leads to a decrease
in productivity due to deterioration of lithographic performance,
stops the tools and generates repair cost.
[0010] 3. If drying is performed before post exposure bake (PEB)
with the liquid immersion fluid remaining on the substrate surface
or if the PEB step is implemented with the remaining liquid
immersion fluid, watermarks are produced on the resist film. In a
relevant part, there are caused non-resolution of the resist
pattern, a T-topped shape and a size change. Defects are produced
in a process pattern using this resist pattern as a mask. This
results in a productivity decrease.
[0011] 4. If the PEB is carried out with the liquid immersion fluid
remaining on the substrate surface, the temperature of the resist
film changes due to latent heat in the vicinity of the part where
the liquid immersion fluid remains, and the size of the resist
pattern changes. This results in a productivity decrease.
[0012] 5. If the PEB is carried out with the liquid immersion fluid
remaining on the substrate surface, the amount of a substance
volatizing from the film on the substrate increases, or a substance
is generated by a reaction between the volatilizing substance and
the liquid immersion fluid. As a result, adherents on the inner
wall of a baking unit in the PEB step increase, and the adherents
act on a wafer as dust to cause a pattern defect, leading to a
productivity decrease and a loss.
[0013] 6. If the PEB is carried out with the liquid immersion fluid
remaining on the substrate surface, a surface state change is
caused in the resist film or a cover film in the vicinity of the
part where the liquid immersion fluid remains. This causes the
removal of the cover film, an insufficient removal of the cover
film due to occurrence of parts of different development
characteristics, or a loss from a productivity decrease due to
occurrence of development defects.
[0014] Therefore, there has been a demand to realize a pattern
forming method and a method of manufacturing a semiconductor device
which can restrain the occurrence of the problems caused by the
liquid immersion fluid used during the immersion lithography
exposure.
BRIEF SUMMARY OF THE INVENTION
[0015] According to a first aspect of the invention, there is
provided a method of pattern forming, which includes:
[0016] forming a resist film on a substrate;
[0017] coating the resist film with a coating solution which forms
a cover film on the resist film to form the cover film on the
resist film;
[0018] transferring a pattern onto the resist film by an immersion
lithography method using a liquid immersion fluid to form a latent
image on the resist film;
[0019] removing the cover film after the formation of the latent
image;
[0020] conducting a first inspection to inspect whether or not the
cover film has a defect between said forming the latent image and
said removing the cover film;
[0021] performing predetermined processing when the defect is found
in the first inspection; and
[0022] developing the resist film to form a resist pattern on the
substrate after said removing the cover film.
[0023] According to a second aspect of the invention, there is a
method of pattern forming, which includes:
[0024] forming a resist film on a substrate;
[0025] transferring a pattern onto the resist film by an immersion
lithography method using a liquid immersion fluid to form a latent
image on the resist film;
[0026] conducting a first inspection to inspect whether or not the
liquid immersion fluid remains on the resist film after said
forming the latent image;
[0027] developing the resist film after the first inspection;
and
[0028] performing predetermined processing when residual of the
liquid immersion fluid is found in the first inspection.
[0029] According to a third aspect of the invention, there is
provided a method of manufacturing a semiconductor device, which
includes:
[0030] forming a resist film on a semiconductor substrate;
[0031] transferring a semiconductor device pattern onto the resist
film by an immersion lithography method using a liquid immersion
fluid to form a latent image on the resist film;
[0032] conducting a first inspection to inspect whether or not the
liquid immersion fluid remains on the resist film after the
formation of the latent image;
[0033] implementing post exposure bake for the resist film after
the first inspection; developing the resist film after the post
exposure bake; and
[0034] performing predetermined processing when residual of the
liquid immersion fluid is found in the first inspection.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0035] FIG. 1 shows a flowchart to explain a manufacturing process
of a semiconductor device according to a first embodiment;
[0036] FIGS. 2A and 2B are schematic diagrams to explain rinsing in
the first embodiment, wherein FIG. 2A is a plan view and FIG. 2B is
a side view;
[0037] FIGS. 3A and 3B are schematic diagrams to explain another
rinsing in the first embodiment, wherein FIG. 3A is a plan view and
FIG. 3B is a side view;
[0038] FIGS. 4A and 4B are schematic diagrams to explain removal
processing after rinsing in the first embodiment, wherein FIG. 4A
is a plan view and FIG. 4B is a side view;
[0039] FIG. 5 is a schematic sectional view of an exposure tool
according to the first embodiment;
[0040] FIG. 6 is a plan view representing the arrangement of
exposure fields formed on a wafer in the first embodiment;
[0041] FIGS. 7A to 7C are schematic diagrams used to explain
scan/exposure according to the first embodiment;
[0042] FIGS. 8A to 8C are schematic diagrams used to explain
another scan/exposure according to the first embodiment;
[0043] FIG. 9 is a plan view representing one example of an
exposure sequence when the respective exposure fields are
sequentially scanned/exposed;
[0044] FIG. 10 is a plan view showing droplets remaining on a
substrate after the scan/exposure according to the first
embodiment;
[0045] FIG. 11 shows a flowchart to explain a manufacturing process
of a semiconductor device according to [Modification 1-1] of the
first embodiment;
[0046] FIG. 12 shows a flowchart to explain a manufacturing process
of a semiconductor device according to [Modification 1-2] of the
first embodiment;
[0047] FIG. 13 shows a flowchart to explain a manufacturing process
of a semiconductor device according to a second embodiment;
[0048] FIG. 14 is a schematic sectional view of an exposure tool
according to the second embodiment;
[0049] FIG. 15 shows a flowchart to explain a manufacturing process
of a semiconductor device according to a third embodiment;
[0050] FIG. 16 shows a flowchart to explain a manufacturing process
of a semiconductor device according to [Modification 3-1] of the
third embodiment;
[0051] FIG. 17 shows a flowchart to explain a manufacturing process
of a semiconductor device according to [Modification 3-2] of the
third embodiment;
[0052] FIG. 18 shows a flowchart to explain a manufacturing process
of a semiconductor device according to [Modification 3-3] of the
third embodiment;
[0053] FIG. 19 shows a flowchart to explain a manufacturing process
of a semiconductor device according to [Modification 3-4] of the
third embodiment; and
[0054] FIG. 20 shows a flowchart to explain a manufacturing process
of a semiconductor device according to [Modification 3-5] of the
third embodiment.
DETAILED DESCRIPTION OF THE INVENTION
[0055] According to embodiments of the present invention
hereinafter described, a coating liquid film or a cover film is
inspected to determine whether or not it is defective during a
period after the formation of the coating liquid film for the
formation of the cover film and before the removal of the cover
film. If the film is defective, predetermined processing for
implementing a predefined treatment is performed to enable the
restraint of the elution of an inclusion from a resist film into a
liquid immersion fluid.
[0056] Furthermore, after the formation of a latent image by
immersion lithography, a first inspection is conducted to see
whether a liquid immersion fluid remains on the resist film, such
that problems caused by an optical path medium remaining on a
substrate can be avoided. Alternatively, if adjustment of a tool,
or rinsing or wafer reprocessing is implemented in early stages, it
is possible to avoid the spread of the problems to next steps or
subsequent lots. This improves production efficiency.
[0057] The embodiments of the present invention will hereinafter be
described referring to the drawings.
First Embodiment
[0058] FIG. 1 shows a flowchart to explain a pattern forming method
of a semiconductor device according to a first embodiment of the
present invention.
[0059] First, a bottom-layer antireflection film is formed on a
semiconductor substrate. In the present embodiment, for example, a
coating-type bottom-layer antireflection film is formed (step
ST101).
[0060] Then, a chemically amplified positive resist film is formed
on the antireflection film (step ST102). In forming the resist
film, the resist film at the edge of a wafer is selectively
removed.
[0061] In a separately conducted surface analysis of some ArF
chemically amplified resist films, it has been proved that
photo-acid generators and acid trap agents (such as amine) are
distributed on the film surface. In order to remove the photo-acid
generators and the acid trap agents on the resist film surface,
pure water is supplied to the resist for rinsing (step ST103). This
rinsing removes the photo-acid generators and the acid trap agents
on the resist film surface. It is to be noted that a cover film may
be additionally formed on the resist film to eliminate the
influence of the photo-acid generators and the acid trap agents
remaining on the film surface after baking. The photo-acid
generators and the acid trap agents can exist on the cover film
depending on the heating state, and similar rinsing may be
required.
[0062] FIGS. 2A and 2B are diagrams showing a state where the
rinsing according to the first embodiment of the present invention
is carried out. FIGS. 2A and 2B are a schematic plan view and side
view of the state during a period the rinsing is carried out,
respectively.
[0063] As shown in FIGS. 2A and 2B, a semiconductor substrate 10 is
held on a substrate support part 11. The substrate support part 11
is rotated by a drive part 12. Pure water (third chemical agent) 14
which is a rinsing liquid is supplied from a rinsing nozzle 13 to
the semiconductor substrate 10 while the semiconductor substrate is
being rotated. In the rinsing, as shown in FIG. 2A, the rinsing
nozzle 13 reciprocates between one end and the opposite end on the
circumference of the substrate 10. The movement speed of the
rinsing nozzle 13 is lower in a state where the rinsing nozzle 13
is located on the circumference of the substrate 10 than in a state
where the rinsing nozzle 13 is located over the center of the
substrate 10. As a result, the rinsing liquid supplied per unit
area of the substrate 10 will be equal, and effects of rinsing can
be enhanced. It is to be noted that when the nozzle 13 performs
uniform motion, similar effects can be obtained if the rotation
number of the substrate is changed in inverse proportion to a
distance from the center of the substrate with respect to the
nozzle position.
[0064] Furthermore, any chemical agent may be utilized as long as
it can easily remove these substances, and it is not limited to the
pure water described in the present embodiment. When the rinsing
requires a long time, oxygen dissolved water, hydrogen dissolved
water, carbonic acid dissolved water or the like can be used as the
rinsing liquid to enable short-time processing. When the oxygen
dissolved water is used, rinsing at 10 ppm or lower can cause no
damage to the film surface. When the hydrogen water is used, it is
preferably used substantially in a saturated state (about 1.2 ppm).
The selection from these chemical agents is preferably carried out
under a condition where the photo-acid generators and the acid trap
agents are easily let free from the film surface, depending on a
potential produced when the film surface is exposed to the chemical
agent and on potentials in the solution of the photo-acid
generators and the acid trap agents.
[0065] Moreover, as shown in FIGS. 3A and 3B, the nozzle 13 may be
moved back and forth between the center of the substrate 10 and the
one end on the circumference of the substrate 10. FIGS. 3A and 3B
are diagrams showing a state where the rinsing is carried out in
the first embodiment of the present invention. FIGS. 3A and 3B are
a schematic plan view and side view, respectively, of the state
while the rinsing is carried out. In FIGS. 3A and 3B, identical
numbers are assigned to parts identical to those in FIGS. 2A and
2B, and the duplicated explanation of these parts are omitted.
[0066] In addition, water is injected to the main surface of the
substrate 10 in a direction perpendicular to this main surface in
the present embodiment, but the present invention is not limited
thereto. For example, water may be injected in the same direction
as the rotation direction of the substrate 10. In this way, the
impact of the pure water 14 is reduced when it collides with the
film surface, and rinsing can be achieved without damaging the film
surface. Further, if the water is injected in a direction reverse
to the rotation direction of the substrate, the photo-acid
generators and the acid trap agents adhering to the film surface
can be efficiently removed. Moreover, if the water is injected
toward the circumference of the substrate, the photo-acid
generators and the acid trap agents removed from the film surface
can be efficiently ejected to the outside of the substrate.
[0067] Then, the resist film surface is dried (step ST104). For the
drying, as shown in FIGS. 4A and 4B, a gas 22 from which an acid
and alkali are filtered is blown to the main surface of the
substrate 10 through an air knife 21. An area of the substrate onto
which the air knife 21 blows air is only a part of the substrate
surface. In order to blow air all over the surface of the substrate
10, the air knife 21 scans the surface of the substrate 10 from one
end to the other end on the circumference of the substrate. In this
case, the substrate 10 may be rotated or stationary.
[0068] FIGS. 4A and 4B are diagrams showing a state where the
removal of the rinsing liquid according to the first embodiment of
the present invention is carried out. FIGS. 4A and 4B are a plan
view and side view, respectively, showing the state where the
removal of the rinsing liquid is carried out. The pure water 14 may
be removed to such a degree that adsorbed water remains on the film
surface. The air 22 blown from the air knife 21 is desirably
oriented in a moving direction of the air knife 21. Making
directions same with respect to the blowing and moving can realize
efficient and short-time removal of water. The point of the removal
of the pure water 14 in this step lies in the fact that baking or
drying under reduced pressure is not conducted. If the baking or
drying under reduced pressure is conducted, the photo-acid
generators and the acid trap agents are extracted from the inside
of the resist film and again emerge on the film surface, thus
losing the preceding rinsing effects. In the case of a substrate
with a small diameter, the substrate may be rotated without using
the air knife to accomplish drying.
[0069] Then, the resist film is coated with a coating solution by a
spin coater to form a cover film thereon, thus forming an coating
liquid film (step ST105). After the formation of the coating liquid
film, the substrate is continuously rotated, and the coating
solution is dried by spin drying, thereby forming a coated film
(step ST106). The substrate is continuously rotated, and an etching
solution is sprayed onto a rear surface of the wafer to remove the
coated film clinging to the rear surface of the wafer (step ST107).
During edge/back rinsing, the surface of the coated film is
inspected for a coating defect (step ST108).
[0070] When the inspection is conducted during the rotation of the
substrate, information in the rotation direction for each point of
the radial direction of the substrate is averaged to detect a
coating defect. Thus, it is possible to judge whether or not the
coating defect exists. However, with respect to identification of
the position of the coating defect, position determination accuracy
in the circumference of the substrate slightly decreases because
the movement speed thereof is higher even if the rotation is
performed at a low speed.
[0071] The following techniques can be considered as detection
methods, but are not limited thereto.
[0072] (A) Reflection of Detection Light
[0073] Detection light strikes on the substrate in a vertical or
oblique direction, and the intensity or phase of the detection
light is detected by a detector provided at a position conjugate
with the detection light source. This detection is conducted by
scanning substantially the entire area on the substrate. In this
case, it is desirable to optimize a scanning interval in a
detection area in accordance with the area of the detection light
on the substrate (and a valid detector area of the detector). When
there is a part where the detected light is out of a predetermined
limit, the upper layer cover film is judged to have the coating
defect. In this case, influence of a substrate edge portion and an
underlying step of the substrate may be taken into
consideration.
[0074] (B) Image Processing
[0075] An image of the upper portion of the substrate is obtained,
and the image abnormality at the inspection position is judged. In
accordance with a tint change or a template based on an original
image or CAD information corresponding to a laminated structure and
an inspection position of the substrate, an image abnormality at
the inspection position is judged. When it is judged that an
abnormality exists, this is recognized as the coating defect.
[0076] (C) Capacitance Meter
[0077] When the upper layer cover film is a dielectric, a
capacitance meter is considered to be effective. The following two
forms can be contrived.
[0078] The first one is a scanning form wherein a scan on the
substrate is possible and a relative position of the coating defect
of the upper layer cover film on the substrate can be detected.
[0079] The second one is a form wherein capacitance meters are
disposed in a predetermined arrangement on a flat plate having an
area larger than that of the substrate, and the capacitance meters
are opposed to the exposed substrate, and the position of the
coating defect of the upper layer cover film is read from the
detected arrangement information with respect to the capacitance
meters.
[0080] Then, the coated film is baked to remove a solvent remaining
in the coated film (step ST109). A cover film is completed by the
removal of the solvent.
[0081] Then, wafer edge exposure is conducted (step ST110). This
wafer edge exposure is conducted to remove, in the course of the
development, a slightly lifted rim portion during the selective
removal of the edge portion of the resist film. Since the resist
film is positive, it is removed during the development by exposing
the wafer edge.
[0082] Then, the wafer is loaded to an immersion lithography scan
and repeat type exposure tool (step ST111). It is then judged
whether or not the loaded substrate has a coating defect in a
coating inspection step (step ST112). A step and repeat type
exposure tool can be used instead.
[0083] When there is no coating defect, various alignment
adjustments are made, and then a pattern is transferred to form a
latent image in the resist film (step ST113).
[0084] The exposure tool used in the present embodiment is a liquid
immersion type. FIG. 5 schematically shows the exposure tool. FIG.
5 is a diagram showing a schematic configuration of the exposure
tool according to one embodiment of the present invention. A
reticle stage 31 is disposed under unshown illumination optics. A
reticle 32 is disposed on the reticle stage 31. The reticle stage
31 is capable of translating. A projection lens system 33 is
disposed under the reticle stage 31. A wafer stage 34 is disposed
under the projection lens system 33. The semiconductor substrate 10
which has been subjected to the above-mentioned processing is
disposed on the wafer stage 34. The wafer stage 34 translates
together with the semiconductor substrate 10. A support plate 37 is
provided on the periphery of the semiconductor substrate 10.
[0085] A liquid film 35 of the pure water (liquid immersion fluid)
is formed under the projection lens system 33. A pair of water
supply/drain devices 36 to supply and drain water is provided
beside the projection lens system 33 to form the liquid film 35.
During exposure, a space between the substrate 10 and the
projection lens system 33 is filled with the liquid film 35 of
water. Exposure light emitted from the projection lens system 33
passes through a layer of the liquid film 35 to reach an
irradiation area. An image of a mask pattern (not shown) on the
reticle 32 is projected on a photoresist on the substrate surface
corresponding to the irradiation area, whereby a latent image is
formed.
[0086] FIG. 6 is a plan view representing the arrangement of
exposure fields formed on the wafer. A mask pattern drawn on one
sheet of reticle is projected and transferred onto rectangular
exposure fields 41 on the substrate 10 by scan-exposure. During the
scan-exposure, for example, as shown in FIGS. 7A to 7C, an exposure
slit area 51 scans the exposure field 41 from the upper side to
lower side of the drawing. Alternatively, as shown in FIGS. 8A to
8C, the exposure slit area 51 scans the exposure field 41 from the
lower side to upper side of the drawing. FIGS. 7A to 7C and 8A to
8C are diagrams used to explain the scan-exposure according to the
first embodiment of the present invention.
[0087] FIG. 9 is a plan view representing one example of an
exposure sequence when the respective exposure fields are
sequentially scan-exposed. Upward arrows and downward arrows in
FIG. 9 indicate directions in which the exposure slit area moves.
As shown in FIG. 9, one exposure field is scan-exposed, and then
the next exposure field is scanned/exposed in an opposite scanning
direction. Such an operation is repeated to expose the entire
surface of the substrate.
[0088] When it is judged in step ST112 that the coating defect is
present, the substrate is put on standby in the exposure tool (step
ST114). A standby time change may cause pattern dimension change,
so that it is preferable this standby time is the same as the time
required for the alignment and pattern transfer.
[0089] After the formation of the latent image or after the
standby, the substrate is unloaded from the exposure tool (step
ST115).
[0090] During the scan-exposure, the water supply/drain units 36
collect water so that no water remains on the substrate. However,
for example, when the cover film on the substrate easily repels
water (the contact angle of the cover film with water is great),
when the movement speed of the stage is high, or when an absolute
value of acceleration/deceleration of the stage is high, residual
water 71 is produced on the substrate 10, as shown in FIG. 10. If
next baking (PEB) is implemented in a state where the water partly
remains on the resist film after the exposure as above, an amount
of heat supplied to the resist film is smaller in a part where the
water remains and absorbs heat than in other parts. Thus, it is not
possible to cause a sufficient reaction from the baking in the
resist film, which leads to an abnormal line width. When the resist
is a positive resist, unopened defects are produced. When the
resist is a negative resist, there arises a problem of occurrence
of defects having an opening trouble.
[0091] To solve these problems, it is desired in the present
embodiment that the residual water 71 on the substrate be removed
after the immersion lithography. Spin drying is often used to
remove the residual water on the substrate 10. However, since the
residual water 71 is dotted on the substrate 10, it is difficult to
remove the residual water 71 by the spin drying.
[0092] In the present embodiment, the following processing is
implemented to remove the residual water 71. That is, the substrate
on which the latent image is formed is loaded to a water processing
unit where residual water removal processing is carried out. To
carry out the removal of the residual water, pure water is supplied
to the entire surface of the substrate to form a liquid film
substantially on the entire surface of the substrate (step ST116).
The liquid film of the pure water is removed by use of the spin
drying or the air knife, as in the drying after the rinsing in step
ST103 (step ST117). In the above processing, water (the residual
water and the liquid film) on the film surface is completely
removed. If the water cannot be completely removed, it is possible
to create a state in which water is similarly absorbed between
exposure shots. When the water is similarly absorbed between
exposure shots, a dimensional difference produced in subsequent
baking is fed back in advance as a dimensional conversion
difference to a mask used during exposure such that a desired
resist pattern can finally be obtained. It is to be noted that
water is used here, but this is not a limitation. It is also
possible to use chemical agents such as alcohols and ethers which
have a good affinity with water and which do not damage the resist
film and whose vaporization heat is lower than that of droplets
(water in this embodiment: vaporization heat=583 cal/g at
100.degree. C.). Alternatively, it is possible to use these
chemical agents-dissolved in a solvent having the same components
as those of the droplets. The chemical agent used will be better if
it is quick-drying. The above processing is effective not only in
the resist film surface but also in the cover film surface when the
cover film is used.
[0093] The substrate which has been subjected to the processing
described above is loaded into a baker where the substrate to be
processed (resist film) is baked (PEB) (step ST118). An acid
produced in the resist film at the stage of exposure is diffused
and reacted with the protection-unit of resist polymer by the
baking. Further, an exclusive solvent different from a developing
solution is used to remove the cover film (step ST119). After the
removal of the cover film, the substrate is loaded to a development
unit where development is implemented to form a resist pattern
(step ST120). It is to be noted that an alkali-soluble cover film
which dissolves in a tetra-methylammoniumhydroxide (TMAH) may be
used as the cover film. Note that the TMAH solution is used for the
development of the resist. Therefore, there is no need for a step
of removing the cover film by the exclusive solvent, and it is
possible to continuously implement the steps of removing the cover
film and developing the resist film by the TMAH solution.
[0094] Then, it is judged whether or not there is a coating defect
to sort out the substrates depending on the existence of the
coating defect in the coating inspection (step ST121). If there is
no coating defect, the substrate is brought to an ordinary
inspection step (step ST122). If there is a coating defect, the
resist film is removed (step ST123). Then, the lithography steps
(step ST102 to step ST120) are again implemented (rework).
[0095] However, atmosphere control needs to be performed in at
least the steps ranging from an exposure unit to the baker unit
through the post-exposure water processing unit. It has been found
out that the concentration of a basic substance needs to be 10 ppb
or lower to restrain the acid loss to such an extent that the
formation of the resist pattern is not affected. In addition,
experimental results have been obtained which indicate that
processing time including loading time is desirably managed in a
range of .+-.10%.
[0096] According to the present embodiment, water is supplied to
the cover film after the immersion lithography and then the water
is removed, so that the residual water on the cover film surface
can be removed. As a result, the occurrence of defective pattern
formation can be restrained.
[0097] It is to be noted that after the immersion lithography, the
pure water supply (step ST116) and the pure water removal (step
ST117) have been carried out to remove the residual water 71 dotted
on the substrate. However, the air knife 21 which blows a gas from
a slit-like nozzle to a part of the substrate may scan the
substrate to remove the residual water 71, as in the drying in step
ST103. Moreover, an air gun may scan the substrate instead of the
air knife. The capacity to remove the residual water is higher when
the air knife is used than when the air gun is used. Therefore, it
is preferable to remove the residual water 71 by use of the air
knife rather than the air gun.
[0098] It is to be noted that the deaerated pure water is used for
the water disposed between the lens and the substrate to be
processed during exposure in the present embodiment, but this is
not a limitation. It is also possible to use a liquid to which
ions, salt or minute particles uniformly dispersed in the liquid
are added to increase a refractive index. When use is made of an
exposure tool having a small absorption coefficient for the
exposure light wave length and adapted to a particular refractive
index, any liquid may be used as long as it has the particular
refractive index and does not damage a lens system or the like
Modification 1-1
[0099] It is to be noted that in the embodiment described above, it
is decided whether or not to transfer the semiconductor device
pattern after the substrate is loaded to the exposure tool
depending on the existence of the coating defect (step ST112).
However, as shown in FIG. 11, the semiconductor device pattern may
be transferred (step ST113) even if there is a coating defect
without implementing the judgment processing in step ST112.
Modification 1-2
[0100] In addition, a flowchart of a modification of Modification
1-1 above (modification 1-2) is shown in FIG. 12. After the
development (step ST120), an ordinary inspection (first inspection)
is conducted (step ST122). A wafer which has passed the first
inspection is judged as to whether it has a coating defect (step
ST130). A wafer without a coating defect is brought to next
processing (step ST131). A second inspection is conducted for a
wafer with a coating defect (step ST133).
[0101] The kinds of second inspection include an optical defect
inspection, dimensional measurement by a CD-SEM or the like, a
macro inspection, and so forth. Items include non-resolution of a
pattern due to the formation of watermarks which can be produced by
the coating defect of a cover film, a change in water content, and
a change in antireflection effects, a pattern formation defect such
as T-top, and abnormal pattern dimensions, and so forth. Any
inspection device other than the above-mentioned device may be used
as long as it is capable of quantitative measurement of the
dimensions, shape and the like of the pattern, or watermark
detection.
[0102] It is to be noted that the second inspection may be
conducted for the entire surface of the relevant wafer. In
addition, during the inspection of the coating defect, information
on the position of the coating defect may be stored, and the second
inspection may be conducted for the position of the coating defect
referring to the stored positional information.
[0103] Furthermore, in the second embodiment, it is considered
whether or not a defect due to the detected coating defect of the
cover film affects the operation of circuits, on the basis of
pattern arrangement or design data with regard to a relevant layer
and a shot map on the wafer during exposure. This consideration may
be utilized to omit the second inspection or to judge results of
the second inspection step.
[0104] It is to be noted that the second inspection may not only be
conducted after the resist pattern formation but also be conducted,
as required, for a pattern processed using the above-mentioned
resist pattern as a mask.
[0105] It is judged whether or not an abnormality has been found in
the second inspection (step ST133). A wafer without an abnormality
is brought to next processing (step ST131). The resist film is
removed from the wafer having an abnormality (step ST123), and
rework is performed (step ST102 to step ST120).
[0106] A rework rate is lower in the case of [Modification 1-2]
than in the case described in [Modification 1-1]. As a result, when
costs and processing time are reduced in the above-mentioned
additional inspection time as compared with the rework and repeated
lithography processes, improvements are especially made in
productivity and yield. Moreover, when heat resisting properties of
an unprocessed layer or durability properties to the rework process
are low, unnecessary rework can be reduced to improve the
yield.
[0107] A mask pattern obtained in the manner as described above is
transferred to a semiconductor wafer. Then, although not described
in detail and not shown in the drawings, a semiconductor device can
be manufactured through a well-known dicing step, mounting step,
bonding step and packaging step.
Second Embodiment
[0108] In the present embodiment, an example will be described in
which a coating defect inspection is conducted after a substrate is
loaded to an exposure tool.
[0109] FIG. 13 is a flowchart to explain a method of forming a
resist pattern according to the second embodiment of the present
invention.
[0110] As in the first embodiment, processing from step ST201 to
step ST206 is similar to that from step ST101 to step ST110
described in the first embodiment referring to FIG. 1, and
therefore duplicated explanation is omitted.
[0111] Then, the substrate is loaded to the exposure tool (step
ST207). In recent years, a twin-stage type exposure tool equipped
with two stages to hold the substrate has appeared. The exposure
tool used in the present embodiment is schematically described
referring to FIG. 14. FIG. 14 is a diagram schematically showing
the exposure tool according to the second embodiment of the present
invention.
[0112] The twin-stage type exposure tool comprises first and second
substrate stages 34a and 34b independently movable on a base 42.
Moreover, the twin-stage type exposure tool has an exposure station
A and a measurement/exchange station B. The measurement/exchange
station B is equipped with a focus detection system 40 having a
projection portion 40a and a light-receiving portion 40b.
[0113] In a basic operation of such a twin-stage type exposure
tool, an exposed substrate 10.sub.0 (not shown) and a substrate
10.sub.2 on the second substrate stage 34b are exchanged and
measured in the measurement/exchange station B, for example, during
the exposure of the substrate on the first substrate stage 34a in
the exposure station A. Then, when the respective operations have
finished, the first substrate stage 34a moves to the
measurement/exchange station B. In parallel with this, the second
substrate stage 34b moves to the exposure station A. In turn, a
substrate 10.sub.1 and a next substrate 10.sub.3 (not shown) are
exchanged and the substrate. 10.sub.3 is measured in the first
substrate stage 34a, and the substrate 10.sub.2 on the second
substrate stage 34b is exposed.
[0114] In other words, information on the surface position of a
substrate 10 is detected by the focus detection system 40 in the
measurement/exchange station B (step ST208), and this detection
result is stored in a controller (not shown).
[0115] Furthermore, a detection signal of a focus detection system
40 is used to inspect the substrate for a coating defect (step
ST209). The focus detection system 40 is disposed to detect a focus
position in a scan direction of an exposure area. When scan
directions exist in both directions, a switch is made to a coating
defect detector disposed in the direction corresponding to a change
in the scan direction, thus detecting a coating defect. This focus
detection system is different from ordinary focus detection systems
in the following point. In an ordinary scan-and-repeat focus
detection system, the detectors have only to be disposed in the
scan directions of the exposure area, that is, both directions of
one axis on a substrate plane surface. On the other hand, in a
coating defect detection device based on the present invention,
movement between shots includes movement in a direction different
from the scan directions of the exposure area, which is typically a
direction perpendicular to the scan directions. Thus, it is also
necessary to dispose a similar coating defect detection device in
the perpendicular direction.
[0116] The controller moves the substrate from which the surface
position information has been detected to the exposure station A.
The substrate is judged as to whether it has a coating defect (step
ST210). When the substrate has no coating defect, a semiconductor
device pattern is transferred while a positional relation between
an image surface of a projection lens system 33 and the surface of
a substrate 10 are being adjusted on the basis of the stored
surface position information (step ST211). When the substrate has a
coating defect, it is put on standby (step ST212).
[0117] Processing from step ST213 to step ST221 that follow is
similar to that from step ST115 to step ST123 described in the
first embodiment referring to FIG. 1, and therefore duplicated
explanation is omitted.
Modification 2-1
[0118] It is to be noted that in the embodiment described above, it
is decided whether or not to transfer a semiconductor device
pattern after the substrate is loaded to the exposure tool
depending on the existence of the coating defect (step ST210).
However, as in [Modification 1-1] of the first embodiment, the
semiconductor device pattern may be transferred (step ST211) even
if there is a coating defect without implementing the judgment
processing in step ST210.
Modification 2-2
[0119] In addition, processing similar to that in
[Modification-1-2] of the first embodiment may be performed. After
the development, a first inspection is conducted. A wafer which has
passed the first inspection is judged as to whether it has a
coating defect. A wafer without a coating defect is brought to next
processing. A second inspection is conducted for a wafer having a
coating defect. It is judged whether or not an abnormality has been
found in the second inspection. A wafer without an abnormality is
brought to next processing. The resist film is removed from the
wafer with an abnormality, and rework is performed.
[0120] In the present embodiment as well, a mask pattern obtained
in the manner as described above is transferred to a semiconductor
wafer. Then, although not described in detail and not shown in the
drawings, a semiconductor device can be manufactured through a
well-known dicing step, mounting step, bonding step and packaging
step.
Third Embodiment
[0121] FIG. 15 is a flowchart to explain a manufacturing process of
a semiconductor device according to a third embodiment of the
present invention.
[0122] First, an antireflection film is formed on a semiconductor
substrate. In the present embodiment, for example, a coating-type
antireflection film is formed (step ST301). Then, a chemically
amplified positive resist film is formed on the antireflection film
(step ST302). A cover film is formed on the resist film (step
ST303). Wafer edge exposure is conducted (step ST304). The wafer is
loaded to an immersion lithography scan and repeat type exposure
tool (step ST305). After various alignments are made, a
semiconductor device pattern is transferred by immersion
lithography to form a latent image in the resist film (step
ST306).
[0123] Then, an inspection is conducted to know whether or not a
liquid immersion fluid used during the immersion lithography
remains on the cover film (step ST307). As detection mechanisms of
the residual liquid immersion fluid, methods mentioned below are
conceivable. A plurality of methods may be used together at the
same time. Moreover, since the effects of the present invention are
not changed depending on the detection method, any other method not
mentioned below may be used. It is to be noted that the method
which performs optical detection needs to use a wavelength at which
the resist is not exposed.
[0124] (A) Reflection of Detection Light
Detection light strikes the substrate in a vertical or oblique
direction, and the intensity or phase of the detection light is
detected by a detector provided at a conjugate position. This
detection is conducted by scanning substantially the entire area on
the substrate. In this case, it is desirable to optimize a scanning
interval in a detection area in accordance with the area of the
detection light on the substrate (and a valid detector area of the
detector). When there is a part having an unacceptable change of
the detection light, it is judged that the liquid immersion fluid
remains. In this case, influence of a substrate edge portion and an
underlying step of the substrate may be taken into consideration.
Moreover, a focus detection system installed in the exposure tool
may be utilized.
[0125] (B) Incidence of Detection Light
[0126] A detection light source and a detector are provided in a
direction substantially parallel with the substrate surface, and
the intensity or phase of the detection light is monitored. When
there is a part having an unacceptable change of the detection
light, it is judged that the liquid immersion fluid remains.
[0127] (C) Utilization of Characteristic Absorption or Light
Emission of Liquid Immersion Fluid
[0128] Detection light strikes the substrate in a vertical or
oblique direction, and the characteristic absorption or light
emission of the liquid immersion fluid in reflected light is
detected. There is a possibility that the liquid immersion fluid is
adsorbed onto or immersed into the resist or the cover film. Thus,
it is judged that the liquid immersion fluid remains in a part
having a predetermined intensity or more of characteristic
absorption or light emission.
[0129] (D) Image Processing
[0130] An image of the upper portion of the substrate is obtained.
In accordance with a tint change or a template based on an original
image or CAD information corresponding to a laminated structure and
an inspection position of the substrate, an image abnormality at
the inspection position is judged. When it is judged that the
abnormality exists, this is recognized that the liquid immersion
fluid remains.
[0131] (E) Capacitance Meter
[0132] Two kinds of forms can be devised.
[0133] The first one is a scanning form wherein a scan on the
substrate is possible and a relative position of the residual
liquid immersion fluid on the substrate can be detected.
[0134] The second one is a form wherein the capacitance meters are
disposed in a predetermined arrangement on a flat plate having an
area larger than that of the substrate, and the capacitance meters
are opposed to the exposed substrate, and the position of the
residual liquid immersion fluid is read from the detected
information of the capacitance meter arrangement. Specifically, the
flat plate is disposed above the exposed substrate for a time that
allows the detection of the liquid immersion fluid. The capacitance
meters are dispose under the flat plate, and a predetermined
distance is maintained between the flat plate and the exposed
substrate, such that the residual of the liquid immersion fluid can
be detected by the capacitance meters. The capacitance meters may
be provided on the top of a wafer handling arm to transfer the
exposed substrate from the wafer stage.
[0135] After the inspection in step ST307, the wafer is unloaded
from the exposure tool (step ST308). The wafer is loaded to a baker
where the substrate to be processed (resist film) is baked (post
exposure bake, PEB) (step ST309). An acid produced in the resist
film at the stage of exposure is diffused and reacted with the
protection-unit of resist polymer by the baking. Further, an
exclusive solvent different from a developing solution is used to
remove the cover film (step ST310). After the removal of the cover
film, the substrate is loaded to a development unit where
development is implemented to form a resist pattern (step ST311).
It is to be noted that an alkali-dissoluble protection film, which
dissolves in a TMAH solution used for the developing of the resist
film, may be used as the cover film. In this case, there is no need
for a step of removing the cover film by the exclusive solvent, and
it is possible to continuously implement the steps of removing the
cover film and developing the resist film by the TMAH solution.
[0136] Then, it is judged whether or not the liquid immersion fluid
remains to sort out the substrates depending on whether or not the
liquid immersion fluid remains in the inspection in step ST307
(step ST312). If there is no coating defect, the substrate is
subjected to an ordinary inspection (step ST313). If there is a
coating defect, the resist film is removed (step ST314), and then,
the lithography steps (step ST302 to step ST311) are again
implemented (rework).
[0137] According to the present invention, it is possible to avoid
problems caused by the liquid immersion fluid. This improves
production efficiency. In the immersion lithography, the liquid
immersion fluid remains on the substrate and the liquid immersion
fluid dries, with the result that so-called watermarks are
produced, which leads to an abnormal resist shape or a pattern
defect such as non-resolution of a pattern.
Modification 3-1
[0138] It is to be noted that processing may also be performed in
accordance with a flowchart shown in FIG. 16. That is, after the
development (step ST311), an ordinary inspection (first inspection)
is conducted. A wafer which has passed the inspection is judged as
to whether it has the residual of the liquid immersion fluid (step
ST320). A wafer without any residual liquid is brought to next
processing (step ST321).
[0139] A second inspection is conducted for a wafer with the
residual liquid immersion fluid (step ST133). The kinds of second
inspection include an optical defect inspection, dimensional
measurement by a CD-SEM or the like, a macro inspection, and so
forth. Items include non-resolution of a pattern due to the
formation of watermarks which can be produced by the residual
liquid immersion fluid, a change in water content, a change in
antireflection effects, a pattern formation defect such as T-top,
abnormal pattern dimensions, and so forth. Any device other than
the above-mentioned device may be used as long as it is capable of
quantitative measurement of the dimensions, shape and the like of
the pattern, or watermark detection.
[0140] It is to be noted that the second inspection may be
conducted for the entire surface of the relevant wafer. In
addition, during the inspection of the residual liquid immersion
fluid, information on the position of the residual liquid may be
stored, and the second inspection may be conducted for the position
of the residual liquid referring to the stored positional
information.
[0141] Furthermore, in the implementation of the second inspection,
it may be considered whether or not a defect due to the detected
residual of the cover film affects the operation of circuits, on
the basis of pattern arrangement or design data with regard to a
relevant layer and a shot map on the wafer during exposure. This
consideration may be utilized to omit the second inspection or to
judge results of the second inspection step.
[0142] It is to be noted that the second inspection may not only be
conducted after the resist pattern formation but also be conducted,
as required, for a pattern processed using the above-mentioned
resist pattern as a mask.
[0143] It is judged whether or not an abnormality has been found in
the second inspection (step ST323). A wafer without an abnormality
is brought to next processing (step ST321). The resist film is
removed from the wafer having an abnormality (step ST324), and
rework is performed (step ST302 to step ST313).
[0144] A rework rate is decreased in this manner. As a result, when
costs and processing time are reduced in the above-mentioned
additional inspection time as compared with the rework and repeated
lithography processes, improvements are especially made in
productivity and yield. Moreover, when heat resisting properties or
durability properties to the rework process of an unprocessed layer
is low, unnecessary rework can be reduced to improve the yield.
Modification 3-2
[0145] In addition, processing may also be performed in accordance
with a flowchart of in FIG. 17. That is, rinsing (step ST331) and
drying (step ST332) are performed which are similar to steps ST103
and ST104 described referring to a flowchart shown in FIG. 1 in the
first embodiment. Moreover, pure water supply (step ST333) and
drying (step ST334) are performed which are similar to steps ST116
and ST117 described referring to the flowchart shown in FIG. 1 in
the first embodiment. It is to be noted that any one pair of
processing of steps ST331 and ST332 and steps ST333 and ST334 may
be performed.
Modification 3-3
[0146] In addition, processing may also be performed in accordance
with a flowchart shown in FIG. 18. After the inspection of the
residual liquid immersion fluid (step ST307), it is judged whether
the liquid immersion fluid remains (step ST340). If no liquid
remains, the wafer is unloaded from the exposure tool (step ST308).
Then, processing of steps ST310 to 311 and ST313 is sequentially
performed. If the fluid remains, the residual liquid on the cover
film in the exposure tool is collected (step ST341). The residual
liquid is preferably collected by suction. The collection by
suction makes it possible to prevent the residual liquid from
scattering in the exposure tool. After the collection of the
residual liquid, the wafer is unloaded from the exposure tool (step
ST342). The resist film is removed (step ST343). Then, the
lithography steps are again implemented (rework).
Modification 3-4
[0147] It is to be noted that after the collection of the residual
liquid, processing similar to that for the case where no liquid
remains may be performed, as shown in FIG. 19.
Modification 3-5
[0148] Furthermore, as shown in FIG. 20, it may be judged whether
the liquid remains (step ST350) after the wafer is unloaded from
the exposure tool. For the wafer having the residual liquid,
processing (steps ST309 to 311 and ST313) similar to that for the
wafer without any residual liquid is performed after the collection
of the residual liquid (step ST351).
[0149] A mask pattern obtained in the manner as described above is
transferred to a semiconductor wafer. Then, although not described
in detail and not shown in the drawings, a semiconductor device can
be manufactured through a well-known dicing step, mounting step,
bonding step and packaging step.
[0150] It is to be noted that the present invention is not limited
to the embodiments described above. For example, pure water having
a refractive index of about 1.44 has been used as the liquid
immersion fluid, but a liquid immersion fluid with a higher
refractive index may be used to increase the resolution of the
exposure tool. Specifically, salt, ions and surfactant may be added
to the pure water. Moreover, an organic solvent, fluorine oil or
the like may be used as the liquid immersion fluid.
[0151] A proper amount of edge cutting may be set for the
bottom-layer antireflection film and the resist film in accordance
with a loading system in a substrate processing step or with the
convenience of the tool.
[0152] In addition, when the bottom-layer antireflection film
includes a material eluting into the liquid immersion fluid, such
as an acid or a photo-acid generator, a base or a surfactant, it is
desirable to form a cover film to cover the bottom-layer
antireflection film located on the substrate flat surface which can
contact the liquid immersion fluid in at least the immersion
lithography exposure tool.
[0153] 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.
* * * * *