U.S. patent application number 12/887332 was filed with the patent office on 2011-06-16 for surface treatment apparatus and method for semiconductor substrate.
Invention is credited to Shinsuke KIMURA, Tatsuhiko KOIDE, Yoshihiro OGAWA, Hisashi OKUCHI, Hiroshi TOMITA.
Application Number | 20110139192 12/887332 |
Document ID | / |
Family ID | 44141534 |
Filed Date | 2011-06-16 |
United States Patent
Application |
20110139192 |
Kind Code |
A1 |
KOIDE; Tatsuhiko ; et
al. |
June 16, 2011 |
SURFACE TREATMENT APPARATUS AND METHOD FOR SEMICONDUCTOR
SUBSTRATE
Abstract
In one embodiment, a surface treatment apparatus for a
semiconductor substrate includes a holding unit, a first supply
unit, a second supply unit, a third supply unit, a drying treatment
unit, and a removal unit. The holding unit holds a semiconductor
substrate with a surface having a convex pattern formed thereon.
The first supply unit supplies a chemical solution to the surface
of the semiconductor substrate, to perform cleaning and oxidation.
The second supply unit supplies pure water to the surface of the
semiconductor substrate, to rinse the semiconductor substrate. The
third supply unit supplies a water repelling agent to the surface
of the semiconductor substrate, to form a water repellent
protective film on the surface of the convex pattern. The drying
treatment unit dries the semiconductor substrate. The removal unit
removes the water repellent protective film while making the convex
pattern remain.
Inventors: |
KOIDE; Tatsuhiko;
(Yokkaichi-Shi, JP) ; KIMURA; Shinsuke;
(Yokkaichi-Shi, JP) ; OGAWA; Yoshihiro;
(Yokkaichi-Shi, JP) ; OKUCHI; Hisashi;
(Yokkaichi-Shi, JP) ; TOMITA; Hiroshi;
(Yokohama-Shi, JP) |
Family ID: |
44141534 |
Appl. No.: |
12/887332 |
Filed: |
September 21, 2010 |
Current U.S.
Class: |
134/94.1 |
Current CPC
Class: |
H01L 21/67028 20130101;
H01L 21/31116 20130101; H01L 21/31 20130101; H01L 21/324 20130101;
H01L 21/02057 20130101; H01L 21/3065 20130101 |
Class at
Publication: |
134/94.1 |
International
Class: |
B08B 3/00 20060101
B08B003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 15, 2009 |
JP |
2009-284347 |
Claims
1. A surface treatment apparatus for a semiconductor substrate,
comprising: a holding unit which holds a semiconductor substrate
with a surface having a convex pattern formed thereon; a first
supply unit which supplies a chemical solution to the surface of
the semiconductor substrate, to perform cleaning and oxidation; a
second supply unit which supplies pure water to the surface of the
semiconductor substrate, to rinse the semiconductor substrate; a
third supply unit which supplies a water repelling agent to the
surface of the semiconductor substrate, to form a water repellent
protective film on the surface of the convex pattern; a drying
treatment unit which dries the semiconductor substrate; and a
removal unit which removes the water repellent protective film
while making the convex pattern remain.
2. The surface treatment apparatus for a semiconductor substrate
according to claim 1, wherein the first supply unit has a heating
unit for heating the chemical solution.
3. The surface treatment apparatus for a semiconductor substrate
according to claim 1, further comprising a fourth supply unit which
supplies alcohol to the surface of the semiconductor substrate, to
rinse the semiconductor substrate.
4. The surface treatment apparatus for a semiconductor substrate
according to claim 2, further comprising a fourth supply unit which
supplies alcohol to the surface of the semiconductor substrate, to
rinse the semiconductor substrate.
5. A surface treatment apparatus for a semiconductor substrate,
comprising: a holding unit which holds a semiconductor substrate
with a surface having a convex pattern formed thereon; a first
supply unit which supplies a chemical solution to the surface of
the semiconductor substrate, to perform cleaning and oxidation; a
second supply unit which supplies pure water to the surface of the
semiconductor substrate, to rinse the semiconductor substrate; a
third supply unit which supplies a water repelling agent to the
surface of the semiconductor substrate, to form a water repellent
protective film on the surface of the convex pattern; a drying
treatment unit which dries the semiconductor substrate; and a
removal unit which irradiates the semiconductor substrate with
light, to oxidize the semiconductor substrate surface and remove
the water repellent protective film while making the convex pattern
remain.
6. The surface treatment apparatus for a semiconductor substrate
according to claim 5, wherein the drying treatment unit is included
in the holding unit, and the holding unit performs spin drying
treatment on the semiconductor substrate.
7. The surface treatment apparatus for a semiconductor substrate
according to claim 6, wherein the removal unit has an outlet for
discharging pure water at the time of oxidation of the
semiconductor substrate surface.
8. A surface treatment method for a semiconductor substrate,
comprising forming a plurality of convex patterns on a
semiconductor substrate, washing the surface of the convex pattern
with use of a chemical solution, rinsing the semiconductor
substrate with use of pure water after washing, irradiating the
convex pattern surface with light after rinsing, forming a water
repellent protective film on the convex pattern surface, irradiated
with the light, with use of a water repelling agent, rinsing the
semiconductor substrate with use of pure water after formation of
the water repellent protective film, drying the semiconductor
substrate, and removing the water repellent protective film while
the convex pattern is made remain.
9. The surface treatment method for a semiconductor substrate
according to claim 8, wherein the convex pattern is formed by a
side-wall transfer process.
10. The surface treatment method for a semiconductor substrate
according to claim 8, wherein the convex pattern has a first side
face that forms a first angle with respect to the surface of the
semiconductor substrate, and a second side face that is located on
the first side face and forms a second angle, different from the
first angle, with respect to the surface of the semiconductor
substrate.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is based upon and claims benefit of
priority from the Japanese Patent Application No. 2009-284347,
filed on Dec. 15, 2009, the entire contents of which are
incorporated herein by reference.
FIELD
[0002] Embodiments described herein relate generally to a surface
treatment apparatus and a surface treatment method for a
semiconductor substrate.
BACKGROUND
[0003] The process of manufacturing a semiconductor device includes
various processes, such as a lithography process, an etching
process and an ion implantation process. After completion of each
process, a cleaning process and a drying process for removing
impurities and residues remaining on a wafer surface to clean the
wafer surface are performed before the transfer to the next
process.
[0004] In recent years, as progress has been made in
miniaturization of elements, a problem has arisen in that, during
development and drying of resist patterns after the lithography
process (exposure and development), the resist patterns are
collapsed due to capillarity. To solve such a problem, a method of
making the surfaces of resist patterns water-repellent to decrease
capillary forces acting between the resist patterns and developer
as well as between the resist patterns and pure water for rinsing
has been proposed (see, e.g., Japanese Patent Application Laid-Open
No. 7-142349). Under this method, an organic matter is adhered onto
the surfaces of resist patterns; however, the organic matter is
removed together with the resist patterns in the etching process
after the lithography process.
[0005] For example, in cleaning treatment of a wafer after the
etching process, a chemical for the cleaning treatment is supplied
onto the surface of the wafer, and then pure water is supplied to
perform rinsing. After the rinsing, drying is performed which
removes the pure water remaining on the wafer surface and dries the
wafer.
[0006] As the method of performing the drying, there is known a
method which uses isopropyl alcohol (IPA) and substitutes IPA for
pure water on a wafer to dry the wafer (see, e.g., Japanese Patent
No. 3866130). However, there has been a problem in that, during the
drying, the actual device patterns formed on the wafer are
collapsed by the surface tension of a liquid. Even with
hydrofluoroether (HFE) having lower surface tension than IPA, it
has been difficult to restrain the pattern collapse.
[0007] To solve such problems, supercritical drying in which the
surface tension becomes zero has been proposed. However, it is
difficult to apply the supercritical drying to mass production
processes. Further, the supercritical drying has had a problem in
that, when moisture or the like is carried into a chamber which
provides a supercritical atmosphere, collapse of patterns cannot be
prevented.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a diagram showing a schematic configuration of a
surface treatment apparatus of a semiconductor substrate according
to a first embodiment of the present invention;
[0009] FIG. 2 is a flowchart explaining a surface treatment method
of a semiconductor substrate according to the first embodiment;
[0010] FIG. 3 is a view showing a surface tension of liquid to the
pattern;
[0011] FIG. 4A is a view showing a state of a pattern after a
drying process in case where a water repellent protective film is
not formed;
[0012] FIG. 4B is a view showing a state of a pattern after a
drying process in case where a water repellent protective film is
formed;
[0013] FIG. 5 is a diagram showing a schematic configuration of a
surface treatment apparatus of a semiconductor substrate according
to a second embodiment of the present invention;
[0014] FIG. 6 is a flowchart explaining a surface treatment method
of a semiconductor substrate according to the second
embodiment;
[0015] FIG. 7 is a diagram showing a schematic configuration of a
surface treatment apparatus of a semiconductor substrate according
to a third embodiment of the present invention;
[0016] FIG. 8 is a flowchart explaining a surface treatment method
of a semiconductor substrate according to the third embodiment;
[0017] FIG. 9 is a schematic constitutional view of a water
repelling film removal unit provided in a surface treatment
apparatus for a semiconductor substrate according to a fourth
embodiment of the present invention;
[0018] FIG. 10 is a flowchart explaining a surface treatment method
of a semiconductor substrate according to the fourth
embodiment;
[0019] FIG. 11A is a sectional view explaining a surface treatment
method for a semiconductor substrate according to a
modification;
[0020] FIG. 11B is a sectional view showing a step subsequent to
FIG. 11A;
[0021] FIG. 11C is a sectional view showing a step subsequent to
FIG. 11B;
[0022] FIG. 11D is a sectional view showing a step subsequent to
FIG. 11C;
[0023] FIG. 12A is a sectional view showing a step subsequent to
FIG. 11D;
[0024] FIG. 12B is a sectional view showing a step subsequent to
FIG. 12A;
[0025] FIG. 12C is a sectional view showing a step subsequent to
FIG. 12B;
[0026] FIG. 13A is a sectional view showing a side-wall transfer
process;
[0027] FIG. 13B is a sectional view showing a step subsequent to
FIG. 13A;
[0028] FIG. 13C is a sectional view showing a step subsequent to
FIG. 13B;
[0029] FIG. 13D is a sectional view showing a step subsequent to
FIG. 13C;
[0030] FIG. 14A is a sectional view showing a step subsequent to
FIG. 13D;
[0031] FIG. 14B is a sectional view showing a step subsequent to
FIG. 14A;
[0032] FIG. 14C is a sectional view showing a step subsequent to
FIG. 14B;
[0033] FIG. 15A is a view showing a surface tension of liquid to
the pattern; and
[0034] FIG. 15B is a view showing a configuration in which the
whole pattern is tilted.
DETAILED DESCRIPTION
[0035] In one embodiment, a surface treatment apparatus for a
semiconductor substrate includes a holding unit, a first supply
unit, a second supply unit, a third supply unit, a drying treatment
unit, and a removal unit. The holding unit holds a semiconductor
substrate with a surface having a convex pattern formed thereon.
The first supply unit supplies a chemical solution to the surface
of the semiconductor substrate, to perform cleaning and oxidation.
The second supply unit supplies pure water to the surface of the
semiconductor substrate, to rinse the semiconductor substrate. The
third supply unit supplies a water repelling agent to the surface
of the semiconductor substrate, to form a water repellent
protective film on the surface of the convex pattern. The drying
treatment unit dries the semiconductor substrate. The removal unit
removes the water repellent protective film while making the convex
pattern remain.
[0036] An object to be performed in the washing process in the
manufacturing process of a semiconductor device is to return a
semiconductor substrate surface to a clean surface state without
generating any defect (missing pattern, scratch, thinned pattern,
dug substrate, or the like) in a fine pattern structure formed on a
semiconductor substrate. Specifically, target matters to be washed
includes resist material used in a lithography process, a reaction
by-product (residue) remaining on a semiconductor wafer surface in
a dry etching process, and metallic impurity, organic contaminant
or the like, these processes are generally employed in a
semiconductor manufacturing process. If the wafer is flown to the
following manufacturing process while leaving the target materials
to be washed, a device manufacturing yield ratio has to be
lowered.
[0037] Accordingly, the cleaning process has an important role of
forming a clean semiconductor wafer surface after cleaning without
generating any defect (missing pattern, scratch, thinned pattern,
dug substrate, or the like) in a fine pattern structure formed on
the semiconductor substrate. As an element is miniaturized,
cleanliness demanded in the cleaning process becomes higher.
[0038] On the other hand, in a recent structure in which a convex
fine pattern of high aspect is provided (for example, a structure
having pattern size of 30 nm or less, and an aspect ratio of 10 or
more), since hydrophobicity is insufficient only by applying
hydrophobic technique which is used in the resist process, it has
been difficult to suppress collapse of the pattern. Further, there
has been a problem with this method that the pattern surface is
contaminated. In accordance with the following embodiments, it is
possible to achieve higher hydrophobic surface than the
conventional one and to suppress the pattern collapse, while
keeping the pattern surface clean, with respect to the structure
having the convex fine pattern of high aspect.
First Embodiment
[0039] FIG. 1 shows a schematic configuration of a surface
treatment apparatus for a semiconductor substrate according to a
first embodiment of the present invention. The surface treatment
apparatus includes a treatment bath 101, a carrier unit 102, a
chemical solution supply unit 103, a pure water supply unit 104, an
IPA supply unit 105, a water repelling agent supply unit 106, a gas
supply unit 107, and a water repelling film removal unit 108. This
surface treatment apparatus is a batch type apparatus that washes
and dries a plurality of semiconductor substrates in block.
[0040] The carrier unit 102 holds and carries a semiconductor
substrate W on the surface of which a convex pattern is formed. For
example, the carrier unit 102 introduces the semiconductor
substrate W into the treatment bath 101, and carries the
semiconductor substrate W to the water repelling film removal unit
108.
[0041] The chemical solution supply unit 103 supplies the treatment
bath 101 with a chemical solution for washing the semiconductor
substrate W. The chemical solution supply unit 103 supplies a
highly oxidative chemical solution, such as a solution obtained by
increasing a temperature of a mixed solution (SPM) of sulfuric acid
and hydrogen peroxide to 80.degree. C. or higher, or sulfuric acid.
The chemical solution supply unit 103 may be provided with a
heating mechanism (e.g. heater, etc.) for increasing a temperature
of the chemical solution.
[0042] The pure water supply unit 104 supplies the treatment bath
101 with pure water for rinsing the semiconductor substrate W.
[0043] The IPA supply unit 105 supplies the treatment bath 101 with
IPA (isopropyl alcohol) for rinsing the semiconductor substrate
W.
[0044] The water repelling agent supply unit 106 supplies the
treatment bath 101 with a water repelling agent for forming a water
repellent protective film on the surface of a convex pattern formed
on the semiconductor substrate W. The water repelling agent is, for
example, a silane coupling agent. The silane coupling agent has a
hydrolytic group having an affinity for and reactivity to an
inorganic material in a molecule, and an organic functional group
that forms a chemical bond with an organic material, and for
example, hexamethyldisilazane (HMDS), tetramethyl silyl
diethylamine (TMSDEA), or the like can be applied. Generation of an
ester-reaction of the silane coupling agent leads to formation of a
water repellent protective film.
[0045] The gas supply unit (drying treatment unit) 107 can supply
dry air so as to dry the semiconductor substrate W.
[0046] The treatment bath 101 can reserve and discharge a liquid
supplied from the chemical solution supply unit 103, the pure water
supply unit 104, the IPA supply unit 105, the water repelling agent
supply unit 106, or the like. The treatment bath 101 is preferably
made up of a Teflon (registered trademark)-based material in order
to be capable of treating the highly oxidative chemical solution
supplied from the chemical solution supply unit 103.
[0047] The water repelling film removal unit 108 can remove the
water repellent protective film formed on the convex pattern
surface on the semiconductor substrate W, and for example, a dry
ashing, ozone-gas treatment, UV light irradiation, or the like is
performed.
[0048] A method for performing surface treatment on a semiconductor
substrate with use of such a surface treatment apparatus will be
described using a flowchart shown in FIG. 2.
[0049] (Step S101) The carrier unit 102 introduces the
semiconductor substrate W processed with the convex pattern into
the treatment bath 101. This convex pattern is, for example, a
line-and-space pattern. The convex pattern is, for example, a high
aspect ratio structure having an aspect ratio of 10 or more. The
convex pattern is formed, for example, by RIE (Reactive Ion
Etching) method.
[0050] (Step S102) A highly oxidative chemical solution is supplied
from the chemical solution supply unit 103 to the treatment bath
101, and the semiconductor substrate W is washed. Thereby, a
residue generated due to the processing of the convex pattern on
the semiconductor substrate W can be removed, and also, the surface
can be oxidized.
[0051] (Step S103) Pure water is supplied from the pure water
supply unit 104 to the treatment bath 101, and the semiconductor
substrate W is rinsed so that the chemical solution component used
in Step 102 is removed.
[0052] (Step S104) IPA is supplied from the IPA supply unit 105 to
the treatment bath 101, to perform alcohol rinsing treatment for
replacing pure water by IPA.
[0053] (Step S105) A silane coupling agent is supplied from the
water repelling agent supply unit 106 to the treatment bath 101,
and a protective film with low wettability (water repellent
protective film) is formed on the semiconductor substrate W (convex
pattern) surface.
[0054] Generation of a silylation reaction between an OH group of
the semiconductor substrate W (convex pattern) and R--Si--OH of the
silane coupling agent leads to formation of R--Si--O on the
semiconductor substrate W (convex pattern) surface. The water
repellent protective film is obtained by a molecular structure with
an R group turned outward among R--Si--O.
[0055] Therefore, the larger the number of OH groups on the
semiconductor substrate W (convex pattern), the easier the water
repellent protective film is to form and the higher the water
repellency of the semiconductor substrate W (convex pattern)
surface becomes. In the present embodiment, with the highly
oxidative chemical solution used at the time of washing treatment
in Step S102, the number of OH groups on the semiconductor
substrate W (convex pattern) is large.
[0056] (Step S106) IPA is supplied from the IPA supply unit 105 to
the treatment bath 101, and the silane coupling agent is replaced
by IPA.
[0057] (Step S107) Pure water is supplied from the pure water
supply unit 104 to the treatment bath 101, and an IPA residue is
rinsed off.
[0058] (Step S108) The carrier unit 102 pulls up the semiconductor
substrate W from the treatment bath 101, and the gas supply unit
107 supplies the semiconductor substrate W with dry air for
evaporation-drying.
[0059] Since the pattern formed on the semiconductor substrate W is
covered by the water repellent protective film, a contact angle
.theta. of pure water is large (close to 90.degree.).
[0060] FIG. 3 shows a state where a part of patterns 4 formed on
the semiconductor substrate W is wet with a liquid 5. When a space
between the patterns 4 is taken as "Space" and a surface tension of
the liquid 5 as .gamma., power P that is applied to the pattern 4
is:
P=2.times..gamma..times.cos .theta.H/Space (Equation 1)
[0061] It is found that, with .theta. being close to 90.degree.,
cos .theta. is close to zero, and hence the power P of the liquid,
which acts on the pattern at the time of drying treatment, is
small. It is thereby possible to prevent collapse of the pattern at
the time of the drying treatment.
[0062] (Step S109) The carrier unit 102 carries the semiconductor
substrate W to the water repelling film removal unit 108. The water
repelling film removal unit 108 removes the water repellent
protective film formed on the convex pattern surface on the
semiconductor substrate W while making the convex pattern
remain.
[0063] FIG. 4A shows states of the pattern after the drying
treatment in the case of not forming the water repellent protective
film, and FIG. 4B shows states of the pattern after the drying
treatment in the case of forming the water repellent protective
film as thus described. Surface treatment was performed on patterns
with three kinds of line heights: 150 nm, 170 nm and 200 nm, and
three kinds of pattern widths: normal, fine and extra-fine
(normal>fine>extra-fine).
[0064] As seen from FIG. 4A, in the case of not forming the
protective film, pattern collapse occurred in the pattern with the
extra-fine line width and the line heights of any of 150 nm, 170 nm
and 200 nm. Further, the pattern collapse also occurred in the
pattern with the fine line width and the 200-nm line height.
[0065] On the other hand, as seen from FIG. 4B, when the water
repellent protective film was formed, it was possible to prevent
pattern collapse except for the pattern with the extra-fine line
width and the 200-nm line height. It is found that formation of the
water repellent protective film can prevent pattern collapse due to
washing/drying even in a pattern with a high aspect ratio, so as to
improve a collapse margin.
[0066] As thus described, forming (and forcibly oxidizing) the
semiconductor substrate surface with use of the highly oxidative
chemical solution and then forming the water repellent protective
film on the substrate surface can prevent collapse of the
extra-fine pattern at the time of the drying treatment.
Second Embodiment
[0067] FIG. 5 shows a schematic configuration of a surface
treatment apparatus for a semiconductor substrate according to a
second embodiment of the present invention. The surface treatment
apparatus includes a substrate holding/rotation unit 200, a
chemical solution supply unit 210, a pure water supply unit 211, an
IPA supply unit 212, a water repelling agent supply unit 213, and a
water repelling film removal unit 214. This surface treatment
apparatus is a single type apparatus that supplies a semiconductor
substrate with a treatment solution, to treat the substrate on a
one-by-one basis.
[0068] The substrate holding/rotation unit 200 has a spin cup 201,
which constitutes a process chamber, a rotation axis 202, a spin
base 203, and a chuck pin 204. The rotation axis 202 extends in a
substantially vertical direction, and the spin base 203 in disc
shape is mounted on the top of the rotation axis 202. The rotation
axis 202 and the spin base 203 can be rotated by a motor not shown
in the figure.
[0069] The chuck pin 204 is provided around the edge of the spin
base 203. By the chuck pin 204 nipping a substrate (wafer) W, the
substrate holding/rotation unit 200 can rotate the substrate W
while holding it almost horizontally
[0070] When a liquid is supplied from the chemical solution supply
unit 210, the pure water supply unit 211, the IPA supply unit 212
or the water repelling agent supply unit 213, the liquid expands in
a radial direction of semiconductor the substrate W to the vicinity
of the rotational center of the substrate W. Further, the substrate
holding/rotation unit 200 can perform spin-drying on the
semiconductor substrate W. An extra liquid scattered in the radial
direction of the substrate W is captured in the spin cup 201, and
discharged through a waste tube 205.
[0071] The chemical solution supply unit 210 supplies the
semiconductor substrate W held in the substrate holding/rotation
unit 200 with a chemical solution for washing the semiconductor
substrate W. The chemical solution supply unit 210 supplies a
highly oxidative chemical solution, such as a solution obtained by
heating a temperature of a mixed solution (SPM) of sulfuric acid
and hydrogen peroxide to 80 (C or higher, or sulfuric acid.
[0072] The pure water supply unit 211 supplies the semiconductor
substrate W held in the substrate holding/rotation unit 200 with
pure water for rinsing the semiconductor substrate W.
[0073] The IPA supply unit 212 supplies the semiconductor substrate
W held in the substrate holding/rotation unit 200 with IPA for
rinsing the semiconductor substrate W.
[0074] The water repelling agent supply unit 213 supplies the
semiconductor substrate W held in the substrate holding/rotation
unit 200 with a water repelling agent. The water repelling agent is
a chemical solution that forms a water repellent protective film on
the surface of a convex pattern, formed on the surface of the
semiconductor substrate W, to make the pattern surface water
repellent, and for example, hexamethyldisilazane (HMDS),
tetramethyl silyl diethylamine (TMSDEA), or the like can be
applied.
[0075] The water repelling film removal unit 214 can remove the
water repellent protective film while making the convex pattern
remain. The water repelling film removal unit 214 removes the water
repellent protective film, for example, by UV-light irradiation.
The water repelling film removal unit 214 is provided above the
substrate holding/rotation unit 200, and is vertically movable.
[0076] A carrier unit 215 carries the semiconductor substrate W to
the substrate holding/rotation unit 200.
[0077] A method for performing surface treatment on a semiconductor
substrate with use of such a surface treatment apparatus will be
described using a flowchart shown in FIG. 6. It is to be noted that
operations of the substrate holding/rotation unit 200, the chemical
solution supply unit 210, the pure water supply unit 211, the IPA
supply unit 212, the water repelling agent supply unit 213 and the
water repelling film removal unit 214 can be controlled by a
controlling unit not shown in the figure.
[0078] (Step S201) A semiconductor substrate W to be treated,
having a plurality of convex patterns in a predetermined area of
its surface, is carried by the carrier unit (not shown), and held
in the substrate holding/rotation unit 200. The convex pattern is,
for example, a line-and-space pattern. At least part of the convex
pattern may be formed by a silicon-containing film. The convex
pattern is formed, for example, by RIE (Reactive Ion Etching)
method.
[0079] (Step S202) The semiconductor substrate W is rotated at a
predetermined rotational speed, and the chemical solution is
supplied from the chemical solution supply unit 210 to the vicinity
of the rotational center of the semiconductor substrate W surface.
The chemical solution is a highly oxidative chemical solution. Upon
receipt of centrifugal force generated by rotation of the
semiconductor substrate W, the chemical solution reaches all parts
of the semiconductor substrate W surface, and chemical-solution
(washing) treatment is performed on the semiconductor substrate
W.
[0080] (Step S203) Pure water is supplied from the pure water
supply unit 211 to the vicinity of the rotational center of the
semiconductor substrate W surface. Upon receipt of centrifugal
force generated by rotation of the semiconductor substrate W, the
pure water reaches all parts of the semiconductor substrate W
surface. Thereby, pure-water rinsing treatment is performed in
which the chemical solution remaining on the semiconductor
substrate W surface is rinsed off by the pure water. This can
remove the processing residue and oxidize the substrate
surface.
[0081] (Step S204) Alcohol such as IPA is supplied from the IPA
supply unit 212 to the vicinity of the rotational center of the
semiconductor substrate W surface. Upon receipt of centrifugal
force generated by rotation of the semiconductor substrate W, IPA
reaches all parts of the semiconductor substrate W surface.
Thereby, alcohol rinsing treatment is performed in which the pure
water remaining on the semiconductor substrate W surface is
replaced by IPA.
[0082] (Step S205) A water repelling agent is supplied from the
water repelling agent supply unit 213 to the vicinity of the
rotational center of the semiconductor substrate W surface. The
water repelling agent is, for example, a silane coupling agent.
[0083] Upon receipt of centrifugal force generated by rotation of
the semiconductor substrate W, the silane coupling agent reaches
all parts of the semiconductor substrate W surface. Thereby, a
protective film with low wettability (water repellent protective
film) is formed on the convex pattern surface. This water repellent
protective film is formed by generation of an ester-reaction of the
silane coupling agent.
[0084] As described in the above first embodiment, the larger the
number of OH groups on the semiconductor substrate W (convex
pattern), the higher the water repellency of the semiconductor
substrate W (convex pattern) surface becomes. In the present
embodiment, with the highly oxidative chemical solution used at the
time of the washing treatment in Step S202, the number of OH groups
on the semiconductor substrate W (convex pattern) is large.
[0085] (Step S206) Alcohol such as IPA is supplied from the IPA
supply unit 212 to the vicinity of the rotational center of the
semiconductor substrate W surface. Upon receipt of centrifugal
force generated by rotation of the semiconductor substrate W, IPA
reaches all parts of the semiconductor substrate W surface.
Thereby, alcohol rinsing treatment is performed in which the silane
coupling agent remaining on the semiconductor substrate W surface
is replaced by IPA.
[0086] (Step S207) Pure water is supplied from the pure water
supply unit 211 to the vicinity of the rotational center of the
semiconductor substrate W surface. Upon receipt of centrifugal
force generated by rotation of the semiconductor substrate W, the
pure water reaches all parts of the semiconductor substrate W
surface. Thereby, pure-water rinsing treatment is performed in
which the pure water remaining on the semiconductor substrate W
surface is replaced by IPA.
[0087] (Step S208) The substrate holding/rotation unit 200
increases the rotational speed of the semiconductor substrate W to
a predetermined spin dry rotational speed, to perform spin dry
treatment in which the pure water remaining on the semiconductor
substrate W surface is spun off and dried.
[0088] Since the convex pattern on the semiconductor substrate W is
covered by the water repellent protective film, a contact angle
.theta. of pure water is large (close to 90.degree.). Thereby, cos
.theta. in above Equation 1 is close to zero and power of the
liquid, which acts on the pattern at the time of drying treatment,
is small so that collapse of the pattern can be prevented.
[0089] (Step S209) The water repelling film removal unit 214 moves
down to the vicinity of the semiconductor substrate W. Then, the
water repelling film removal unit 214 removes the water repellent
protective film formed on the convex pattern surface on the
semiconductor substrate W while making the convex pattern
remain.
[0090] Performing the surface treatment on a semiconductor
substrate according to the present embodiment also makes it
possible to obtain a similar effect to the effect of the above
first embodiment (cf. FIG. 4).
[0091] As thus described, forming the semiconductor substrate
surface with use of the highly oxidative chemical solution and then
forming the water repellent protective film on the substrate
surface can prevent collapse of the extra-fine pattern at the time
of the drying treatment.
Third Embodiment
[0092] Although the number of OH groups on the semiconductor
substrate W (convex pattern) is increased by the washing treatment
with use of the highly oxidative chemical solution in the above
first embodiment, it may be increased by irradiating the substrate
surface with UV light after being washed with a normal washing
chemical solution to further oxidize the substrate surface.
[0093] FIG. 7 shows a schematic configuration of a surface
treatment apparatus according to the present embodiment. This
apparatus is different from the surface treatment apparatus
according to the above first embodiment shown in FIG. 1 in that a
UV light irradiation unit 111 is provided. Further, the chemical
solution supply unit 103 supplies a normal washing chemical
solution, such as SPM, SC-1 (Standard Clean 1), or SC-2. The
chemical solution supply unit 103 may supply one kind of chemical
solution, or may supply a plurality of chemical solutions
simultaneously or sequentially. In FIG. 7, the same portions as
those in the first embodiment shown in FIG. 1 are provided with the
same numerals, and descriptions thereof will not be repeated.
[0094] The UV light irradiation unit 111 irradiates the
semiconductor substrate inside the processing bath 101 with UV
light. The water repelling film removal unit 108 may be the UV
light irradiation unit 111. The carrier unit 102 or another
movement mechanism, not shown in the figure, carries the UV light
irradiation unit 111 above the processing bath 101.
[0095] A method for performing surface treatment on a semiconductor
substrate with use of such a surface treatment apparatus will be
described using a flowchart shown in FIG. 8.
[0096] (Step S301) The carrier unit 102 introduces the
semiconductor substrate W processed with the convex pattern into
the treatment bath 101.
[0097] (Step S302) A chemical solution is supplied from the
chemical solution supply unit 103 to the treatment bath 101, and
the semiconductor substrate W is washed. Thereby, a residue
generated due to the processing of the convex pattern on the
semiconductor substrate W can be removed.
[0098] (Step S303) Pure water is supplied from the pure water
supply unit 104 to the treatment bath 101, the semiconductor
substrate W is rinsed so that the chemical solution component used
in Step S302 is removed.
[0099] (Step S304) The UV light irradiation unit 111 is carried
above the processing bath 101. The UV light irradiation unit 111
then irradiates the semiconductor substrate W with UV light.
Thereby, the substrate surface is further oxidized.
[0100] (Step S305) IPA is supplied from the IPA supply unit 105 to
the treatment bath 101, and alcohol rinsing treatment is performed
in which pure water is replaced by IPA.
[0101] (Step S306) A silane coupling agent is supplied from the
water repelling agent supply unit 106 to the treatment bath 101,
and a protective film with low wettability (water repellent
protective film) is formed on the semiconductor substrate W (convex
pattern) surface.
[0102] As described in the above first embodiment, the larger the
number of OH groups on the semiconductor substrate W (convex
pattern), the higher the water repellency of the semiconductor
substrate W (convex pattern) surface becomes. In the present
embodiment, due to the UV light irradiation treatment in Step S304,
the number of OH groups on the semiconductor substrate W (convex
pattern) is large.
[0103] (Step S307) IPA is supplied from the IPA supply unit 105 to
the treatment bath 101, and the silane coupling agent is replaced
by IPA.
[0104] (Step S308) Pure water is supplied from the pure water
supply unit 104 to the treatment bath 101, and an IPA residue is
rinsed off.
[0105] (Step S309) The carrier unit 102 pulls up the semiconductor
substrate W from the treatment bath 101, and the gas supply unit
107 supplies the semiconductor substrate W with dry air for
evaporation-drying.
[0106] Since the pattern formed on the semiconductor substrate W is
covered by the water repellent protective film, a contact angle
.theta. of a liquid is large (close to 90.degree.). Liquid force
which acts on the pattern at the time of the drying treatment is
thus small, and hence collapse of the pattern at the time of drying
treatment can be prevented.
[0107] (Step S310) The carrier unit 102 carries the semiconductor
substrate W to the water repelling film removal unit 108. The water
repelling film removal unit 108 removes the water repellent
protective film formed on the convex pattern surface on the
semiconductor substrate W while making the convex pattern
remain.
[0108] As thus described, irradiating the semiconductor substrate
surface with UV light to promote an oxidation reaction and then
forming the water repellent protective film on the substrate
surface can prevent collapse of the extra-fine pattern at the time
of the drying treatment, as in above first embodiment.
Fourth Embodiment
[0109] Although the number of OH groups on the semiconductor
substrate W (convex pattern) is increased by the washing treatment
with use of the highly oxidative chemical solution in the above
second embodiment, it may be increased by irradiating the substrate
surface with UV light after being washed with a normal washing
chemical solution to further oxidize the substrate surface. The
water repelling film removal unit 214 performs UV-light
irradiation.
[0110] The surface treatment apparatus according to the present
embodiment has a similar configuration to that of the surface
treatment apparatus according to the above second embodiment shown
in FIG. 5. However, the water repelling film removal unit 214 needs
the semiconductor substrate W surface to be in a wet state at the
time of irradiation of the substrate surface with UV light for
oxidization. Therefore, as shown in FIG. 9, the water repelling
film removal unit 214 includes an outlet 214a for discharging pure
water.
[0111] Further, the chemical solution supply unit 210 supplies a
normal washing chemical solution, such as SPM, SC-1 (Standard Clean
1), or SC-2. The chemical solution supply unit 210 may supply one
kind of chemical solution, or may supply a plurality of chemical
solutions simultaneously or sequentially.
[0112] A method for performing surface treatment on a semiconductor
substrate with use of the surface treatment apparatus according to
the present embodiment will be described using a flowchart shown in
FIG. 10.
[0113] (Step S401) A semiconductor substrate W to be treated,
having a plurality of convex patterns in a predetermined area of
its surface, is carried and held in the substrate holding/rotation
unit 200. The convex pattern is, for example, a line-and-space
pattern. At least part of the convex pattern may be formed by a
silicon-containing film. The convex pattern is formed, for example,
by RIE (Reactive Ion Etching) method.
[0114] (Step S402) The semiconductor substrate W is rotated at a
predetermined rotational speed, and the chemical solution is
supplied from the chemical solution supply unit 210 to the vicinity
of the rotational center of the semiconductor substrate W surface.
Upon receipt of centrifugal force generated by rotation of the
semiconductor substrate W, the chemical solution reaches all parts
of the semiconductor substrate W surface, and chemical-solution
(washing) treatment is performed on the semiconductor substrate W.
It is possible by this treatment to remove a residue generated by
processing of the convex pattern on the semiconductor substrate
W.
[0115] (Step S403) Pure water is supplied from the pure water
supply unit 211 to the vicinity of the rotational center of the
semiconductor substrate W surface. Upon receipt of centrifugal
force generated by rotation of the semiconductor substrate W, the
pure water reaches all parts of the semiconductor substrate W
surface. Thereby, pure-water rinsing treatment is performed in
which the chemical solution remaining on the semiconductor
substrate W surface is rinsed off by the pure water.
[0116] (Step S404) The water repelling film removal unit 214 moves
down, and irradiates the semiconductor substrate W surface with UV
light while discharging pure water. Thereby, the substrate surface
is further oxidized.
[0117] (Step S405) Alcohol such as IPA is supplied from the IPA
supply unit 212 to the vicinity of the rotational center of the
semiconductor substrate W surface. Upon receipt of centrifugal
force generated by rotation of the semiconductor substrate W, IPA
reaches all parts of the semiconductor substrate W surface.
Thereby, alcohol rinsing treatment is performed in which the pure
water remaining on the semiconductor substrate W surface is
replaced by IPA.
[0118] (Step S406) A water repelling agent is supplied from the
water repelling agent supply unit 213 to the vicinity of the
rotational center of the semiconductor substrate W surface. The
water repelling agent is, for example, a silane coupling agent.
[0119] Upon receipt of centrifugal force generated by rotation of
the semiconductor substrate W, the silane coupling agent reaches
all parts of the semiconductor substrate W surface. Thereby, a
protective film with low wettability (water repellent protective
film) is formed on the convex pattern surface. This water repellent
protective film is formed by generation of an ester-reaction of the
silane coupling agent.
[0120] As described in the above first embodiment, the larger the
number of OH groups on the semiconductor substrate W (convex
pattern), the higher the water repellency of the semiconductor
substrate W (convex pattern) surface becomes. In the present
embodiment, due to the UV light irradiation treatment in Step S404,
the number of OH groups on the semiconductor substrate W (convex
pattern) is large.
[0121] (Step S407) Alcohol such as IPA is supplied from the IPA
supply unit 212 to the vicinity of the rotational center of the
semiconductor substrate W surface. Upon receipt of centrifugal
force generated by rotation of the semiconductor substrate W, IPA
reaches all parts of the semiconductor substrate W surface.
Thereby, alcohol rinsing treatment is performed in which the silane
coupling agent remaining on the semiconductor substrate W surface
is replaced by IPA.
[0122] (Step S408) Pure water is supplied from the pure water
supply unit 211 to the vicinity of the rotational center of the
semiconductor substrate W surface. Upon receipt of centrifugal
force generated by rotation of the semiconductor substrate W, the
pure water reaches all parts of the semiconductor substrate W
surface. Thereby, pure-water rinsing treatment is performed in
which the pure water remaining on the semiconductor substrate W
surface is replaced by IPA.
[0123] (Step S409) The substrate holding/rotation unit 200
increases the rotational speed of the semiconductor substrate W to
a predetermined spin dry rotational speed, to perform spin dry
treatment in which the pure water remaining on the semiconductor
substrate W surface is spun off and dried.
[0124] Since the convex pattern on the semiconductor substrate W is
covered by the water repellent protective film, a contact angle
.theta. of pure water is large (close to 90.degree.). Thereby, cos
.theta. in above Equation 1 is close to zero and power of the
liquid, which acts on the pattern at the time of drying treatment,
is small so that collapse of the pattern can be prevented.
[0125] (Step S410) The water repelling film removal unit 214 moves
down to the vicinity of the semiconductor substrate W. Then, the
water repelling film removal unit 214 irradiates the semiconductor
substrate W with UV light, to remove the water repellent protective
film formed on the convex pattern surface on the semiconductor
substrate W while making the convex pattern remain.
[0126] Performing the surface treatment on a semiconductor
substrate according to the present embodiment also makes it
possible to obtain a similar effect to the effect of the above
first embodiment (cf. FIG. 4).
[0127] As thus described, irradiating the semiconductor substrate
surface with UV light to promote an oxidation reaction and then
forming the water repellent protective film on the substrate
surface can prevent collapse of the extra-fine pattern at the time
of the drying treatment.
[0128] In the above first to forth embodiments, in the case of the
silane coupling agent being replaceable by pure water, it is
possible to omit the alcohol rinsing treatment before and after the
water repelling treatment.
[0129] It is known that, when added with IPA having a hydroxyl
group and H.sub.2O, the silane coupling agent used for the water
repelling treatment undergoes hydrolysis and the water repellent
ability decreases. Degradation of the water repellent ability
causes reduction in pattern collapse preventing effect.
[0130] For this reason, after the pure-water rinsing and the IPA
replacement and before the water repelling treatment, thinner
treatment may be performed to replace IPA by a thinner not
containing a hydroxyl group. As the thinner used can be a solvent
having no hydroxyl group in a compound itself, such as toluene, a
solvent that does not generate a hydroxyl group as an intermediate
product, or cyclohexanone. When the thinner is replaceable by
water, the IPA replacement (alcohol rinsing) after the pure-water
rinsing may be omitted.
[0131] Although the water repelling treatment is performed using
the silane coupling agent in the above first to fourth embodiments,
a surfactant (aqueous surfactant) may be used. In the case of using
the surfactant, the IPA replacement (alcohol rinsing) before and
after the water repelling treatment can be omitted, thereby
eliminating the need to provide the IPA supply units 105, 212 in
the surface treatment apparatus.
[0132] Although each of the surface treatment apparatuses according
to the first and third embodiments is an overflow type apparatus
using a single treatment bath, a plurality of treatment baths
respectively reserving a chemical solution, pure water, a water
repelling agent, and the like may be provided, and the substrate
holding/carrier unit 102 may sequentially soak the semiconductor
substrate in the respective baths.
[0133] Although the semiconductor substrate is dried using the
evaporation-drying method in the above first and third embodiments,
a depressurization-drying method, a spin-drying method, or the like
may be used. Further, pure water may be replaced by a solvent
containing IPA or HFE, and the solvent may be subjected to
evaporation-drying.
[0134] In the above second and fourth embodiments, the water
repelling film removal unit may be provided in each of the
plurality of substrate holding/rotation units 200, or one water
repelling film removal unit may be made movable above the plurality
of substrate holding/rotation units 200.
[0135] Although the semiconductor substrate W is irradiated with
ultraviolet light so as to be oxidized in the above third and
fourth embodiments, another light such as infrared light may be
applied.
[0136] Ultraviolet-light irradiation for oxidizing the
semiconductor substrate W surface may be performed in the middle of
the convex pattern processing. FIGS. 11A, 11B, 11C, 11D, 12A, 12B,
12C show an example of such a surface treatment method.
[0137] First, as shown in FIG. 11A, a silicon-based member layer
11, a silicon nitride film 12 and a silicon oxide film 13 are
sequentially formed on the semiconductor substrate W. The
silicon-based member layer 11 is formed using silicon oxide,
polysilicon or the like. The silicon-based member layer 11 may be
made up of a plurality of films.
[0138] Next, as shown in FIG. 11B, a resist layer 14 having a
line-and-space pattern is formed on the silicon oxide film 13 by
means of a photolithography technique.
[0139] Next, as shown in FIG. 11C, dry etching is performed, to
pattern the silicon oxide film 13.
[0140] Next, as shown in FIG. 11D, the resist layer 14 is
peeled.
[0141] Next, as shown in FIG. 12A, dry etching is conducted, to
pattern the silicon nitride film 12. Herein, the silicon-based
member layer 11 under the silicon nitride film 12 is not processed.
Washing is then performed using a chemical solution such as SC-1,
SC-2 or SPM, to remove a residue generated due to the dry
etching.
[0142] Next, as shown in FIG. 12B, UV-light irradiation is
performed. Therewith, oxidation proceeds on the surface of the
silicon oxide film 13, the side faces of the silicon nitride film
12, and the like. It is to be noted that the silicon oxide film 13
may be removed before the UV-light irradiation.
[0143] Next, as shown in FIG. 12C, dry etching is conducted, to
pattern the silicon-based member layer 11.
[0144] To the semiconductor substrate W formed with a convex
pattern 15 in the manner as thus described, the surface treatment
method according to the above third and fourth embodiments (except
for Steps S304, S404) are applied. The side faces of the silicon
nitride film 12 has been forcibly oxidized by the UV-light
irradiation, thereby to facilitate formation of the water repellent
protective film and improve a water repellency, thus making it
possible to prevent collapse of the extra-fine pattern at the time
of the drying treatment.
[0145] Each of the surface treatment apparatuses in the above first
to fourth embodiments is suitable for washing/drying of a
semiconductor substrate having a convex pattern formed by side-wall
transfer process. The side-wall transfer process is performed in
such a manner that, as shown in FIG. 13A, first, a second film 502
is formed on a first film 501 formed on a semiconductor substrate
(not shown). A resist 503 having a line-and-space pattern is then
formed on the second film 502.
[0146] Next, as shown in FIG. 13B, the second film 502 is etched
using the resist 503 as a mask, to transfer the pattern.
[0147] Next, as shown in FIG. 13C, the second film 502 is subjected
to slimming treatment, to be reduced in width by the order of one
half so as to be processed into core members 504. It is to be noted
that the resist 503 is removed before or after the slimming
treatment. The slimming treatment is preformed by wetting treatment
or drying treatment, or in combination of the wetting treatment and
the drying treatment.
[0148] Next, as shown in FIG. 13D, a third member 505 is formed so
as to cover the upper faces and the side faces of the core members
504 by means of CVD (Chemical Vapor Deposition), or the like. The
third member 505 is formed of a material capable of taking a large
etching selection ratio with respect to the core member 504.
[0149] Next, as shown in FIG. 14A, the third member 505 is
dry-etched until the upper face of the core member 504 is exposed.
Dry-etching is performed on an etching condition having selectivity
with respect to the core member 504. Thereby, the third member 505
remains in the shape of a spacer along the side faces of the core
member 504. In the third member 505 that remains at this time, a
top end 505a is located in contact with the top of the side face of
the core member 504, and an upper side part takes a shape
projectingly curved toward the outside of the core member 504.
[0150] Next, as shown in FIG. 14B, the core member 504 is removed
by wet etching treatment. The third member 505 is formed in an
asymmetric shape where spaces with a distance between the tops of
adjacent two patterns (opening width size of the space pattern)
being small and spaces with the distance being large are
alternately present.
[0151] In the case of washing and drying the pattern in such an
asymmetric shape as the third member 505, as shown in FIG. 14C,
fluid level lowering speeds of space portions significantly differ,
to cause application of large force to the pattern, and it has thus
been difficult to prevent collapse of the pattern.
[0152] However, with use of the surface treatment apparatuses in
the above first to fourth embodiments, even in the case of the
pattern in the asymmetrical shape formed by the side-wall transfer
process, performing forcible oxidation and water repelling
treatment on the pattern surface can lead to washing and drying of
the substrate while preventing collapse of the pattern.
[0153] As seen from above Equation 1 and FIG. 3, the force P
applied to the pattern 4 depends on a vertical component of the
surface tension .gamma.. Therefore, as shown in FIG. 15A, by making
a structure such that the top of the pattern is inclined, namely an
angle formed by the side face of the top of the pattern with
respect to the substrate surface is different from an angle formed
by the side face of the bottom of the pattern with respect to the
substrate surface, it is possible to make the vertical component of
the surface tension .gamma. small, so as to reduce the force
applied to the pattern.
[0154] Such a structure can be formed by making a temperature low
at the time of performing RIE treatment on the pattern. Further, as
shown in FIG. 15B, in a case where the pattern is configured of a
mask material 1501 and a pattern material 1502, a similar
configuration can be obtained by performing RIE treatment on the
condition of a selectivity between the mask material 1501 and the
pattern material 1502 being low or on the condition of the
selectivity being the same.
[0155] While certain embodiments have been described, these
embodiments have been presented by way of example only, and are not
intended to limit the scope of the inventions. Indeed, the novel
methods and systems described herein may be embodied in a variety
of other forms; furthermore, various omissions, substitutions and
changes in the form of the methods and systems described herein may
be made without departing from the spirit of the inventions. The
accompanying claims and their equivalents are intended to cover
such forms or modifications as would fall within the scope and
spirit of the inventions.
* * * * *