Title: Wet cleaning process and wet cleaning equipment
Abstract: A wet treatment method useful in one of a chemical processing and a rinsing step performed upon fabrication of semiconductor devices. A substrate is treated with a desired liquid while revolving the substrate around an axis of rotation outside the substrate such that the liquid flowing on a surface of the substrate is maintained flowing under a centrifugal force greater than gravitation. The substrate is treated while supplying the liquid at a flow rate at least equal to a discharge rate of the liquid only in a direction conforming with that of the centrifugal force or with that of a flow of the liquid flowing on the surface of the substrate under the centrifugal force. The substrate surface is evenly treated with the liquid while avoiding flows of the liquid running against each other or a flow of the liquid stagnating on the surface of the substrate.
Patent Number: 6,866,723 Issued on 03/15/2005 to Ueda, et al.
| Inventors:
|
Ueda; Takeji (Okayama, JP);
Oka; Koji (Okayama, JP);
Sumi; Sanae (Okayama, JP)
|
| Assignee:
|
m.FSI Ltd. (Tokyo, JP)
|
| Appl. No.:
|
921555 |
| Filed:
|
August 6, 2001 |
Foreign Application Priority Data
| Aug 09, 2000[JP] | 2000-241168 |
| Current U.S. Class: |
134/33; 134/2; 134/25.1; 134/26; 134/29; 134/34; 438/906; 510/175 |
| Intern'l Class: |
B08B 007//00 |
| Field of Search: |
134/2,25.1,26,29,33,34,3,6,8,17,19,27,28,32,36,42,153,157,198,200,902
438/906
510/175
132/2,3,26,32,33,34
252/79.3,79.4
|
References Cited [Referenced By]
U.S. Patent Documents
| 3769992 | Nov., 1973 | Wallestad | 134/138.
|
| 3990462 | Nov., 1976 | Elftmann et al. | 134/102.
|
| 4132567 | Jan., 1979 | Blackwood | 134/1.
|
| 4197000 | Apr., 1980 | Blackwood | 354/323.
|
| 4609575 | Sep., 1986 | Burkman | 427/426.
|
| 4682615 | Jul., 1987 | Burkman et al. | 134/102.
|
| 4694852 | Sep., 1987 | Grant | 137/501.
|
| 4750505 | Jun., 1988 | Inuta et al. | 134/153.
|
| 4801335 | Jan., 1989 | Burkman et al. | 134/25.
|
| 4815630 | Mar., 1989 | Jenson et al. | 220/378.
|
| 5132038 | Jul., 1992 | Kukanskis et al. | 252/139.
|
| 5320709 | Jun., 1994 | Bowden et al. | 438/745.
|
| 5888308 | Mar., 1999 | Sachdev et al. | 134/1.
|
| Foreign Patent Documents |
| 2 154 434 | Sep., 1985 | GB.
| |
| 52-12774 | Jan., 1977 | JP.
| |
Other References
Handbook of semiconductor wafer cleaning technology. Edited by W.Kem, 1993
by Noyes Publications, pp. 3, 137-141.*
Kern, W. J.Electrochem. Soc. 137(6): 1887-1892 (1990).*
Burkman, D.C. Semiconductor International, 4(7):109-111 (1984).*
Menon, V.B. and Donavan, R.P. Microcontamination, 8(11):29-34.
|
Primary Examiner: Kornakov; M.
Attorney, Agent or Firm: Oblon, Spivak, McClelland, Maier & Neustadt, P.C.
Claims
What is claimed is:
1. A wet treatment method useful in at least one of a chemical processing
step and a rinsing step performed upon fabrication of semiconductor
devices, which comprises a sub-step in which:
a substrate under treatment is treated with a desired liquid while causing
said substrate to revolve around an axis of rotation outside said
substrate such that said desired liquid flowing on a surface of said
substrate is maintained flowing under a centrifugal force greater than
gravitation, the surface of the substrate disposed on a horizontal plane
perpendicular to the axis of rotation, and
said substrate is treated while supplying an additional amount of said
desired liquid at a flow rate at least equal to a discharge rate of said
desired liquid, the additional amount of the desired liquid provided to
the substrate only in a direction perpendicular to the axis of rotation,
while
directly spraying with the desired liquid only a top cover of a chamber in
which the desired liquid is supplied to the substrate,
whereby said substrate is evenly treated at said surface thereof with said
desired liquid while avoiding development of such a situation that flows
of said desired liquid run against each other on said surface of said
substrate or a flow of said desired liquid stagnates on said surface of
said substrate.
2. The wet treatment method according to claim 1, wherein said desired
liquid has a high viscosity, a high adhesion, or contains an organic
substance.
3. The wet treatment method according to claim 1, wherein said sub-step is
conducted before a final treatment in at least one of said chemical
processing step and said rinsing step.
4. The wet treatment method according to claim 3, wherein said wet
treatment method is used in said rinsing step such that the desired liquid
is used to rinse a chemical employed in said chemical processing step; and
said chemical employed in the chemical processing step has a high
viscosity, high adhesion, contains an organic substance, or has an etching
rate that increases when mixed with water.
5. The wet treatment method according to claim 2, wherein said wet
treatment method is used in said rinsing step such that the desired liquid
is used to rinse a chemical employed in said chemical processing step; and
said chemical used in the chemical processing step comprises a solution of
at least one of amines and ammonium fluoride dissolved as an effective
component in an organic solvent or a water-containing organic solvent.
6. A wet treatment method according to claim 1, wherein said desired liquid
comprises pure water.
7. The wet treatment method according to claim 1, wherein a nozzle sprays
the top cover of the chamber, the nozzle disposed on a rotating table on
which the substrate is disposed.
8. The wet treatment method according to claim 1, wherein directly spraying
comprises directly spraying the desired liquid from a nozzle, the nozzle
configured to directly spray only the top cover of the chamber.
9. The wet treatment method according to claim 8, wherein the nozzle is
disposed on a table on which the substrate is disposed.
10. The wet treatment method according to claim 1, wherein a plurality of
nozzles configured to clean the top cover with the desired liquid spray
only the top cover of the chamber.
11. A method of treating a substrate, comprising:
rotating the substrate about an axis disposed apart from the substrate, a
surface of the substrate disposed on a horizontal plane perpendicular to
the axis;
supplying a liquid to treat the surface of the substrate in a direction
only perpendicular to the axis; and
directly spraying with the liquid only a top cover of a chamber in which
the liquid is supplied to the substrate,
whereby said substrate is evenly treated at said surface thereof with said
liquid while avoiding development of such a situation that flows of said
liquid run against each other on said surface of said substrate or a flow
of said liquid stagnates on said surface of said substrate.
12. The method according to claim 11, wherein the substrate is rotated such
that a centrifugal force is greater than a gravitational force.
13. The method according to claim 11, wherein supplying comprises supplying
the liquid at a rate at least equal to a rate of removal of the liquid
from the substrate due to a centrifugal force.
14. The method according to claim 11, wherein rotating comprises rotating
the substrate such that the supplied liquid flows in a direction of liquid
flow from the substrate due to a centrifugal force.
15. The method according to claim 14, wherein the liquid comprises water.
16. The method according to claim 15, wherein the liquid comprises chemical
etchant.
17. The method according to claim 11, wherein a nozzle sprays the top cover
of the chamber, the nozzle disposed on a rotating table on which the
substrate is disposed.
18. The method according to claim 11, wherein directly spraying comprises
directly spraying the liquid from a nozzle, the nozzle configured to
directly spray only the top cover of the chamber.
19. The method according to claim 18, wherein the nozzle is disposed on a
table on which the substrate is disposed.
20. The method according to claim 11, wherein a plurality of nozzles
configured to clean the top cover with the liquid spray only the top cover
of the chamber.
Description
BACKGROUND OF THE INVENTION
a) Field of the Invention
This invention relates to a wet treatment method and apparatus effective
for use in a fabrication process of semiconductor devices.
b) Description of the Related Art
RIE (reactive ion etching) has long been used in a metallization step for
semiconductor devices. In such a step, deposits of a reaction product
called, "polymer" or "wall pieces" remains on a surface of an etched
substrate. A polymer stripper treatment step has, therefore, been needed
to remove the deposits after the etching. Many of chemicals useful in the
polymer stripper treatment step have high viscosity and are expensive, and
a significant load is required for the treatment of waste water. Such
chemicals are, therefore, circulated and reused in many instances. To
permit effective handling of a chemical the composition of which tends to
vary due to evaporation or the like, the treatment with the chemical as a
polymer stripper is widely conducted by suitably supplying the chemical
from a circulating tank onto a surface of a substrate only when the
treatment is conducted rather than a bath-type treatment that a substrate
is dipped in the chemical. To meet requirements for this treatment, a
variety of treatment apparatuses have been developed, including
single-wafer or batch processing apparatuses and apparatuses equipped with
a mechanism for spraying a chemical onto plural substrates while causing
the substrates to rotate (or eccentrically rotate) or to revolve U.S. Pat.
No. 4,132,567 that issued on Jan. 2, 1979, U.S. Pat. No. 4,682,615 (Ser.
No. 626,702 filed on Jul. 2, 1984). and U.S. Pat. No. 4,609,575 (Ser. No.
626,640 filed on Jul. 2, 1984)).
As examples of chemicals effective for the removal of the above-mentioned
polymer, solutions containing an amine and ammonium fluoride dissolved as
effective components in a solvent called a "semi-aqueous solvent" are used
widely. These chemicals often use, as a solvent, an organic solvent in
combination with water to reduce dissociation of such effective components
because, if these effective components are simply added to water, they
ionize or otherwise dissociate and exhibit unduly high reactivity.
Accordingly, the solvent employed in such a chemical is a water-containing
organic solvent having high viscosity in many instances. The solvent,
hence, tends to remain on each substrate subsequent to its treatment with
a polymer stripper, thereby giving a rise to a need for rinsing.
Therefore, rinsing is often conducted using water.
The rinsing of a substrate subsequent to its treatment with a chemical
effective for the removal of the above-mentioned polymer is, however,
accompanied by a problem in that mixing of the chemical with water as a
rinsing liquid results in a quick increase in etching rate and causes
corrosion of metallization patterns and/or interconnections formed on the
substrate. According to an investigation by the present inventors, this
problem has been ascertained to markedly arise especially in a situation
where the chemical is gradually mixed with water. To cope with this
problem, it has thus been a rather common, conventional practice that
intermediate or provisional rinsing is conducted to wash off the chemical
once with a water-soluble solvent, followed by finish rinsing with water.
In view of the environment, however, there is an increasing demand toward
performing the rinsing with water alone without conducting the
intermediate or provisional rinsing with such a solvent. As a result of an
investigation on those removed by such rinsing, they have been found to
include a polymer in a dissolved form and a polymer lift off and existing
as particles (i.e., a residue). Upon rinsing, it is thus essential to
achieve efficient dilution of the solvent and at the same time, effective
elimination of these particles from the surface of the substrate.
In the conventional art, the etching rate tended to drop as an inorganic
chemical was diluted. The conventional art has, therefore, been developed
with a view to minimizing the supply flow rates of a polymer stripper
chemical and rinsing water as much as possible in order to minimize the
consumption of the inorganic chemical. In the conventional art, a polymer
stripper chemical and rinsing water are supplied in small amounts in many
instances. As their flow rates are low, the post-etching treatment has
been conducted in such a way that, as a measure to meet the
above-mentioned desire, a substrate under treatment is treated while
rotating it at a low speed or the polymer stripper chemical or rinsing
water is once caused to stand up on the surface of a substrate at a low
rotation speed and the rotation speed of the substrate is then increased
to a high speed to promptly spin it off in its entirety.
On the other hand, an increasing number of polymer strippers has been
developed with a view to permitting rinsing with water only. Even with
such polymer strippers, it is still impossible to completely avoid the
above-mentioned increase in etching rate, which takes place upon rinsing.
As a consequence, the etching rate is observed to reach a peak in the
course of dilution with rinsing water. Even when a chemical permitting
rinsing with only water is used as mentioned above, there is still a
demand for the development of a solution regarding how to dilute the
chemical quickly with only water to such a low concentration as causing no
corrosion, in other words, how to achieve the liquid/liquid replacement
with a high efficiency. Especially under a situation that metals of
different kinds are in contact with each other and galvanic corrosion
hence tends to occur, the conventional rinsing method of a substrate
surface with water at such a low flow rate as mentioned above has
difficulty in completely avoiding corrosion, leading to an outstanding
desire for the development of a method which can achieve the liquid/liquid
replacement with a high efficiency.
In general, an inefficient rinsing method requires a longer rinsing time
and results in a greater consumption of rinsing water. Such an inefficient
rinsing method is, therefore, undesired not only from the standpoint of
cost but also from the standpoint of influence to the environment. In all
wet treatments, it is thus widely required to heighten the efficiency of
rinsing.
In rinsing, particles which have been lifted off have to be removed from
the surface of a substrate as mentioned above. A polymer stripper such as
that described above or its diluted solution, however, does not
necessarily have such a pH as causing the particles to electrically repel
in the solution from the substrate. In some instances, these particles may
be readily adsorbed on the surface of the substrate, thereby making it
difficult to remove them. As a method for permitting removal of particles
under any pH conditions, it is necessary to apply a physical external
force. Toward this direction, wet treatment methods making use of various
physical forces have been under investigation in recent years. Use of a
physical force such as ultrasonic waves or brushing, for example, can
certainly improve the efficiency of particle removal, but on the other
hand, the use of such a physical force has been reported to develop
another problem in that semiconductor devices are damaged. It is,
therefore, desired to develop a method which does not damage semiconductor
devices while heightening the efficiency of a liquid/liquid replacement
such as between a chemical and rinsing water. This desire is common to
every general wet cleaning.
SUMMARY OF THE INVENTION
An object of the present invention is, therefore, to provide a wet
treatment method and apparatus, which with a small supply of a treatment
liquid, can promptly achieve an even liquid/liquid replacement with high
efficiency on a surface of a substrate without allowing the liquids to
remain locally.
Another object of the present invention is to provide a wet treatment
method and apparatus, which can minimize corrosion of metallization
patterns, interconnections and/or the like or the amount of a polymer
remaining as particles on a surface of a substrate especially in water
rinsing which is a rinsing treatment applied subsequent to treatment with
a chemical and is known to result in marked occurrence of deleterious
effect to the surface of the substrate due to an increase in etching rate
by dilution with water.
A further object of the present invention is to provide a wet treatment
method and apparatus which, when applied to rinsing in such a situation
that the viscosity or adhesion of a used chemical is high and its
remaining on a surface of a substrate causes a problem or when supplying a
chemical or supplying a rinsing liquid to remove the chemical, can achieve
a liquid/liquid replacement with high efficiency by reducing the supply
rate of the liquid or chemical as much as possible and feeding a fresh
supply of the liquid or chemical as fast as possible.
A still further object of the present invention is to provide a wet
treatment method and apparatus, which can be effectively used especially
upon conducting rinsing after treatment with a chemical containing an
organic substance and employed in a removal step of residues from resist
stripping or etching or upon conducing rinsing after treatment with a
chemical containing an organic substance and employed in a removal step of
residues (particles) from resist stripping or etching when a metal is
exposed as a ground on a substrate.
The above-described objects can be achieved by the present invention to be
described hereinafter. Specifically, in one aspect of the present
invention, there is a wet treatment method useful in at least one of a
chemical processing step and a rinsing step performed upon fabrication of
semiconductor devices, which comprises a sub-step in which:
a substrate under treatment is treated with a desired liquid while causing
the substrate to revolve around an axis of rotation outside the substrate
itself instead of allowing the substrate to rotate about the axis of
rotation such that the liquid flowing on a surface of the substrate is
maintained flowing under a centrifugal force greater than gravitation, and
the substrate is treated while supplying a fresh liquid of the same kind as
the desired liquid at a flow rate at least equal to a discharge rate of
the desired liquid only in a direction conforming with that of the
centrifugal force or with that of a flow of the liquid flowing on the
surface of the substrate under the centrifugal force,
whereby the substrate is evenly treated at the surface thereof with the
desired liquid while avoiding development of such a situation that flows
of the liquid run against each other on the surface of the substrate or a
flow of the liquid stagnates on the surface of the substrate.
In another aspect of the present invention, there is also provided a wet
treatment apparatus useful in at least one of a chemical processing step
and a rinsing step performed upon fabrication of semiconductor devices,
wherein:
the wet treatment apparatus is constructed such that a substrate under
treatment is wet-treated with a desired liquid while being caused to
revolve around an axis of rotation outside itself instead of being allowed
to rotate about the axis of rotation; and
the wet treatment apparatus is provided with a control system for
maintaining the liquid, which is flowing on a surface of the substrate, to
flow at a high speed under a centrifugal force greater than gravitation
and also supplying a fresh liquid of the same kind as the desired liquid
at a flow rate at least equal to a discharge rate of the desired liquid
only in a direction conforming with that of the centrifugal force or with
that of a flow of the liquid flowing on the surface of the substrate under
the centrifugal force such that the substrate is evenly treated at the
surface thereof with the desired liquid while avoiding development of such
a situation that flows of the liquid run against each other on the surface
of the substrate or a flow of the liquid stagnates on the surface of the
substrate.
The present invention provides a wet treatment method and apparatus, which
with a small supply of a treatment liquid, can promptly achieve an even
liquid/liquid replacement with high efficiency on a surface of a substrate
without allowing the liquids to remain locally.
The present invention also provides a wet treatment method and apparatus,
which can minimize corrosion of metallization patterns, interconnections
and/or the like or the amount of a polymer remaining as particles on a
surface of a substrate especially in water rinsing which is a rinsing
treatment applied subsequent to treatment with a chemical and is known to
result in marked occurrence of deleterious effect to the surface of the
substrate due to an increase in etching rate by dilution with water.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a fragmentary schematic perspective view of a treatment chamber
in a wet treatment apparatus according to a first embodiment of the
present invention;
FIG. 2 is a schematic top plan view of the treatment chamber of FIG. 1;
FIG. 3 is a schematic top plan view of a treatment chamber in a wet
treatment apparatus according to a second embodiment of the present
invention, in which the treatment chamber is provided with four substrate
containers;
FIG. 4 is a simplified schematic view showing an illustrative fundamental
construction of a wet treatment apparatus according to a third embodiment
of the present invention;
FIG. 5 is a simplified schematic view of a wet treatment apparatus
according to a fourth embodiment of the present invention, which is of the
large flow-rate and unidirectional spray type;
FIG. 6 is a diagram explaining differences among centrifugal forces applied
to a liquid at indicated points, respectively, when a substrate is caused
to revolve, in other words, to turn around an axis of rotation outside the
substrate itself; and
FIG. 7 is a diagram explaining differences among centrifugal forces applied
to a liquid at indicated points, respectively, when a substrate is caused
to rotate about an axis of rotation inside the substrate itself.
DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS
The present invention will hereinafter be described in detail based on
certain preferred embodiments.
The present inventors have proceeded with an extensive investigation to
solve the above-described problems of the conventional art. As a result,
it has been found that to prevent or reduce an increase in etching rate in
water rinsing, said increase having remained as a most detrimental problem
and being not soluble by the efficiency of a replacement with rinsing
water available in any one of the above-described conventional rinsing
methods, the achievement of a high-speed replacement of a chemical with
the rinsing water on the surface of a substrate is needed. It has also
been found effective for the achievement of such a high-speed replacement
to produce a centrifugal force greater than gravitation in a predetermined
specific direction on the entire surface of the substrate and further, to
include in an initial stage of the rinsing step a sub-step to supply
rinsing water at a high speed in a direction conforming with a flow of the
chemical produced under the centrifugal force on the surface of the
substrate. It has also been found that these measures can avoid a
reduction in the efficiency of rinsing and can hence achieve a high-speed,
even replacement of the chemical with the rinsing water without allowing
neither the chemical nor the rinsing water to remain. These findings have
led to the completion of the present invention. According to the
investigation by the present inventors, it has-also been found that the
above-described centrifugal force and the flow of the rinsing water
produced under this centrifugal force can bring about effects comparable
with a physical external force and can be used effectively, for example,
for the removal of particles from the surface of the substrate.
According to the investigation by the present inventors, it has also been
found that an apparatus of the rotation type that a substrate under
treatment rotates around an axis of rotation inside itself cannot produce
sufficient centrifugal force in the vicinity of the axis of rotation and
has difficulty in making a flow of a fresh supply of rinsing liquid
conforming with a flow of liquid produced on a surface of the substrate
under such insufficient centrifugal force. It has also been found that,
even with an apparatus of the revolution type that a substrate does not
have an axis of rotation inside itself, a flow of liquid on a surface of
the substrate and a flow of a fresh supply of liquid on the surface of the
substrate run against each other and causes corrosion of metallization
patterns and/or interconnections formed on the substrate if the apparatus
is constructed such that rinsing liquid is also supplied from the outside
toward the axis of rotation as has been conventionally practiced to
enhance the effect of rinsing.
According to the wet treatment method of the present invention, on the
other hand, a substrate is firstly caused to revolve such that a
centrifugal force greater than gravitation is produced by the revolution.
As a result, a fresh supply of liquid to the surface of the substrate is
provided with such a high flow velocity that would be unavailable unless
the centrifugal force is applied, resulting in a liquid-to-liquid
replacement with improved efficiency on the surface of the substrate.
Further, the revolution of the substrate rather than its rotation has made
it possible to allow the substrate to receive sufficient centrifugal force
over the entire surface thereof, leading to a further improvement in the
efficiency of the liquid-to-liquid replacement on the surface of the
substrate. The wet treatment method according to the present invention is
usable in at least one of a chemical processing step and a rinsing step,
both of which are conducted upon fabrication of semiconductor devices. The
wet treatment method is conducted such that a liquid flowing on the
surface of the substrate is maintained flowing under a centrifugal force
greater than gravitation to avoid development of such a situation that the
flow of the liquid stagnates on the surface of the substrate. This has
made it possible to prevent the liquid from remaining on the surface of
the substrate and also to prevent corrosion of metallization patterns,
inter-connections and/or the like formed on the substrate. In addition to
the above-described requirements, the substrate is treated while supplying
a fresh liquid at a flow rate at least equal to a discharge rate of the
liquid only-in a direction conforming with that of the centrifugal force
or with that of a flow of the liquid flowing on the surface of the
substrate under the centrifugal force. This allows the liquid to always
flow in a specific direction on the surface of the substrate, and the
resulting flow of the liquid achieves a situation where the liquid flows
over the entire surface of the substrate without causing such a situation
that flows of the liquid run against each other. As a result, the
substrate can be evenly treated at the entire surface thereof while
preventing corrosion of metallization patterns, interconnections and/or
the like formed on the substrate and also preventing the liquid from
remaining on the surface of the substrate due to formation of dry areas
there.
The treatment sub-step is conducted in at least one of the chemical
processing step and the rinsing step under conditions that the liquid
flowing on the surface of the substrate is maintained flowing and that a
fresh supply of a liquid of the same kind as the liquid is fed at a flow
rate at least equal to a discharge rate of the liquid only in a direction
conforming with that of the centrifugal force or with that of the flow of
the liquid flowing on the surface of the substrate under the centrifugal
force. This sub-step may be conducted in any stage of at least one of the
chemical processing step and the rinsing step. According to a detailed
investigation by the present invention, it has been found that
advantageous effects of the present invention, which will be mentioned
subsequently herein, can be more markedly brought about especially when
the treatment sub-step is conducted in an initial stage of at least one of
the chemical processing step and the rinsing step.
According to the wet treatment method of this invention including the
treatment sub-step of the above-described features, it is possible, for
example, to avoid a reduction in the efficiency of rinsing although such a
reduction has heretofore occurred due to stagnation of liquid on the
substrate as a result of running of a flow of the liquid and a flow of the
fresh supply of the liquid against each other on the surface of the
substrate in the conventional method in which the rinsing liquid is also
supplied from the outside toward the axis of rotation. This has made it
possible to promptly replace the chemical, which is remaining on the
surface of the substrate, with the rinsing liquid and hence, to avoid
corrosion of metallization patterns, interconnections and/or the like
formed on the substrate. In addition, the wet treatment method of this
invention including the treatment sub-step can also avoid an increase in
etching rate although such an increase in etching rate may take place when
the liquid is caused to stand up on the surface of the substrate. This has
also made it possible to avoid corrosion of metallization patterns,
interconnections and/or the like formed on the substrate. During the
treatment, it is possible to always maintain a flow of liquid at a high
speed over the entire surface of the substrate. This has made it possible
to prevent occurrence of localized dry areas on the surface of the
substrate in the course of the treatment, so that no liquid is allowed to
remain on the surface of the substrate and the substrate can be evenly
treated over the entire surface thereof. Described specifically, it is
possible to evenly replace a liquid such as a chemical with another liquid
such as another chemical or a rinsing liquid on the surface of the
substrate in at least one of the chemical processing step and the rinsing
step. Here, it is possible to allow the liquid to flow at a high speed
comparable with a physical force so that particles can be removed from the
surface of the substrate.
With reference to the accompanying drawings, the wet treatment apparatuses
according to the first to fourth embodiments of the present invention will
be described hereinafter.
As is illustrated in FIGS. 1 and 2, a treatment chamber unit of the
treatment apparatus according to the first embodiment of the present
invention is constructed of a closed treatment chamber 1 and, arranged in
this treatment chamber 1, a rotary shaft 2 driven by an unillustrated
motor, a rotating table 3 supported on the rotary shaft 2 and rotatable in
a substantially horizontal position in the treatment chamber 1, a
substrate container 4 mounted on the rotating table 3 at a position close
to an inner wall of the treatment chamber 1, a nozzle 5 arranged around
the rotary shaft 2, and fluid supply sources (see FIG. 4) provided with
change-over devices for selectively supplying plural liquids and at least
one gas (which may hereinafter be collectively called "fluids") to the
nozzle 5. Further, a balancer 6 may be arranged optionally at a position
diametrically opposite to the substrate container 4 with the rotary shaft
2 located therebetween to smoothen rotation of the rotating table 3. In
addition, an enclosure 7 is also arranged so that each fluid sprayed or
otherwise fed out from the nozzle 5 can be supplied at a desired constant
flow rate onto the substrate. It is to be noted that the balancer 6 and
the enclosure 7 are omitted in FIG. 1.
Upon using the apparatus shown in FIGS. 1 and 2, plural substrates 8 to be
treated are stored in the substrate container 4, and the substrate
container 4 with the substrates 8 stored therein is fixedly secured by a
fixture 9. Subsequent to the fixing of the substrates 8, the treatment
chamber 1 is brought into a closed state, the rotating table 3 is caused
to turn at an appropriate speed, and a desired liquid is sprayed fed out
in a direction of arrow A (toward the substrates) from the nozzle 5. The
liquid makes the substrates 8 wet, and under a centrifugal force (arrow B)
produced by the turning of the rotating table 3, the liquid flows in the
direction of arrow B on the surfaces of the substrates 8. The liquid is
sprayed for a predetermined time in this state. During this time, the
liquid flows in the direction of arrow B on the surfaces of the
substrates, hits the inner wall of the treatment chamber 1, downwardly
flows on and along the inner wall, and is then discharged out of the
system through an unillustrated passage. Mixing of the chemical and the
rising water can be limited to minimum extent, for example, by firstly
spraying the chemical for a time as much as needed and then spraying the
rinsing water.
In the present invention, the supply of the chemical, the supply of rinsing
water, and the drive of the motor M for rotating the rotary shaft (and if
necessary, the supply of an inert gas) are controlled through a control
panel to achieve the above-described conditions for the treatment.
In the above-described first embodiment, the closed treatment chamber 1 is
provided with the substrate container 4 alone, that is, only one substrate
container. The plural substrates 8 are held in a form stacked one over the
other with equal intervals therebetween such that the liquid, the rinsing
water and further, the gas are allowed to smoothly pass between the
substrates 8. The intervals may preferably be set, for example, at 3 mm or
greater.
Referring next to FIG. 3, a description will be made of the treatment
chamber in the wet treatment apparatus according to the second embodiment
of the present invention. In the second embodiment, a nozzle 5 having many
spray openings is arranged around the rotary shaft 2. On the rotary table
3, four substrate containers 4 are mounted around the rotary shaft 2 as a
center. In each of the containers 4, plural substrates 8 can be stored.
The wet treatment apparatus according to the second embodiment is operated
in a similar manner as the wet treatment apparatus according to the first
embodiment illustrated in FIGS. 1 and 2, so that a number of substrates 8
can be treated together. In the second embodiment, the supply of a
chemical, the supply of rinsing water, and the drive of a motor for
rotating the rotary shaft (and if necessary, the supply of an inert gas)
are also controlled through a control panel to achieve the above-described
conditions for the treatment.
FIG. 4 illustrates the outline of the wet treatment apparatus according to
the third embodiment of the present invention, which is provided with two
substrate containers 4. In particular, FIG. 4 illustrates control of
supplies of a chemical, rinsing water and a gas such as nitrogen gas and
control of rotation of a rotary shaft by a motor. Described specifically,
the starts, ends and rates of supplies of a chemical 10 and rinsing water
11 (and an inert gas 12) and the rotation of a rotating table 3 by a motor
M are all controlled by a program stored in a control panel 100 to achieve
the above-described conditions for treatment, which are needed for the
present invention. The substrates 8 are treated in a similar manner as in
the first and second embodiments depicted in FIGS. 1 to 3. The substrates
8 are treated by operating the wet treatment apparatus in a similar manner
as described above, purging the interiors of the treatment chambers 1, for
example, with nitrogen gas or the like, and then opening a directional
control valve for the chemical 10 to spray the chemical 10 for a
predetermined time. After that, the directional control valve for the
chemical is closed, and a directional control valve for the rinsing water
is then opened to spray the rinsing water through the nozzle 5.
With reference to FIG. 5, a description will next be made of the wet
treatment apparatus according to the fourth embodiment of the present
invention. The wet treatment apparatus outlined in this diagram is of the
large flow-rate and unidirectional spray type. Different from the wet
treatment apparatus depicted in FIG. 4, the wet treatment apparatus
according to the fourth embodiment has a nozzle 5 arranged pendant from a
cover (top) of a treatment chamber 1. A chemical 10, rinsing water 11 or
nitrogen gas 12 is selectively supplied to the nozzle 5 under control by a
control panel 100 and sprayed or otherwise fed out in only one direction
from the nozzle 5. The substrates 8 are moved by the rotating table 3 and
treated with the chemical 10, the rinsing water 11 or the nitrogen gas 12
sprayed or otherwise fed out in the one direction from the nozzle 5. To
spray off dust or the like which may adhere to the cover (top) of the
treatment chamber 1, cover cleaning nozzles 13 are also arranged on the
rotating table 3 in communication with a cleaning solution tank 15 via a
suitable line 14. These cover cleaning nozzles 13 are provided with spray
openings for spraying the cleaning solution toward the cover (top).
Whenever the rotating table 3 is caused to turn, the cover cleaning
nozzles 13 turn so that the cover (top) is cleaned with the cleaning
solution sprayed from the nozzles 13. The treatment chamber 1 is
sufficiently cleaned by the chemical, the rinsing water and the like
except for the cover (top). The cover cleaning nozzles 13 are, therefore,
arranged to clean off dust or the like adhered to the inner wall of the
cover (top) when the top (cover) is opened or closed and hence to prevent
contamination of the substrates. In the fourth embodiment, the supply of
the chemical 10, the supply of rinsing water 11, and the drive of a motor
M for rotating the rotary shaft 2 (and if necessary, the supply of the
nitrogen gas) are also controlled through a control panel 100 to achieve
the above-described conditions for the treatment.
As one of features of the wet treatment apparatus according to the present
invention, the wet treatment apparatus has such a construction that, upon
wet-treating the surfaces of the substrates 8 held as described above,
each container 4 with its corresponding substrates 8 stored therein is
arranged on the rotating table 3 at a position, said position being as
apart as possible from the rotary shaft 2, in the treatment chamber 1
without allowing the substrates to rotate about axes of rotation inside
themselves (i.e., without rotation of the substrates) and the substrates 8
are caused to revolve (see FIG. 2). The chemical remaining on the
substrates 8 is exposed to a centrifugal force owing to the revolution,
and is caused to fly out of the substrates. Here, the centrifugal force
applied to droplets on the surface of each substrate 8 is greater than
that applied when the substrate 8 is rotated, because the distance of the
substrate 8 from the rotary shaft 2 is greater than the distance of the
substrate 8 from the rotary shaft 2 when the substrate 8 is rotated. When
a substrate is rotated, on the other hand, a centrifugal force applied
around a rotary shaft is smaller than that applied on an outer side.
Droplets around the rotary shaft are, therefore, applied only with weak
outward energy. In the wet treatment apparatus according to the present
invention, on the other hand, droplets on the surface of each substrate 8
are applied with sufficient centrifugal force over the entire surface.
Further, the wet treatment apparatus according to the present invention is
usable in at least one of the chemical processing step and the rinsing
step for the chemical upon fabrication of semiconductor devices. The wet
treatment apparatus according to the present invention is characterized in
that it is provided with the control system for, irrespective of the step,
maintaining the liquid, which is flowing on a surface of the substrate, to
flow at a high speed under a centrifugal force greater than gravitation
and also supplying a fresh liquid of the same kind as the above-mentioned
liquid at a flow rate at least equal to a discharge rate of the desired
liquid only in a direction conforming with that of the centrifugal force
or with that of a flow of the liquid flowing on the surface of the
substrate under the centrifugal force such that the substrate is evenly
treated at the surface thereof with the desired liquid while avoiding
development of such a situation that flows of the liquid run against each
other on the surface of the substrate or a flow of the liquid stagnates on
the surface of the substrate. In this case, it is also preferred to design
the control system such that the above-described treatment sub-step is
conducted especially in an initial stage of the treatment. This makes it
possible to perform high-speed cleaning by effecting an even
liquid-to-liquid replacement exclusively on the surface of the substrate,
for example, in the initial stage of the rinsing.
Firstly, by arranging the control system to apply a centrifugal force at
least equal to gravitation at every location on the surface of the
substrate, the liquid flowing on the surface of the substrate can be
maintained to have a high velocity. In other words, droplets of the liquid
on the surface of the substrate is exposed to an outward centrifugal force
greater than gravitation which is acting to allow them to stay there, so
that the liquid flows on the surface of the substrate. A specific method
for achieving this varies depending, for example, upon the diameter of a
rotating table to be used, the density of liquid droplets remaining on the
surface of the substrate, and the viscosity of a liquid to be used. In
essence, however, this can be achieved by controlling the turning speed of
the rotating table by the control system such that the substrate is caused
to revolve at a high speed. Described specifically, when the diameter of
the rotating table 4 on which the substrates are mounted is 60 cm, for
example, the turning speed of the rotating table 4 may be set in a range
of from 300 to 500 rpm or so, preferably from 500 to 700 rpm or so by also
taking economy and the like into consideration.
With respect to the model shown in FIG. 6 where each substrate was caused
to revolve around an axis of rotation outside itself and the model
illustrated in FIG. 7 where each substrate was caused to rotate around an
axis of rotation inside itself, centrifugal forces applied to individual
positions on the substrates were calculated. The results are presented in
Table 1. As is clearly envisaged from the results, when the diameter of
the rotating table 3 is 60 cm, setting of the turning speed of the
rotating table at 300 rpm or higher makes it possible to apply a
centrifugal force at least equal to gravitation at all the points A to C
on the substrate 8 in the case of FIG. 6 in which the substrate 8 is
arranged on an outer side farther from the axis of rotation and is caused
to revolve. In the case of the rotation type in FIG. 7 in which the
substrate 8 rotates around an axis of rotation inside itself, no
substantial centrifugal force is applied to a central area where the axis
of rotation is located, and even in other areas, centrifugal forces
applied are smaller than those applied in the case of FIG. 6.
TABLE 1
Centrifugal Forces Applied to Individual Points When Revolved at
Different Rotational Speeds
Centrifugal acceleration (m/
S.sup.2 ; a centrifugal force
is proportional to a
Rotational speed centrifugal acceleration)
R (rpm) R/60 (rps) Point A Point B Point C
20 0.33 0.438 0.876 1.315
60 1 3.944 7.888 11.832
120 2 15.775 31.551 47.326
160 2.66 28.045 56.090 84.135
200 3.33 43.821 87.641 131.461
300 5 98.596 197.192 295.788
500 8.33 273.88 547.756 821.633
Centrifugal Forces Applied to Individual Points When Rotated at
Different Rotational Speeds
Centrifugal acceleration* (m/
S.sup.2 ; a centrifugal force
is proportional to a
Rotational speed centrifugal acceleration)
R (rpm) R/60 (rps) Point A Point B Point C
60 1 0 1.972 3.944
120 1.66 0 5.478 10.955
500 8.33 0 136.939 273.878
1000 16.66 0 547.756 1095.511
1500 25.00 0 1232.45 2464.9
2000 33.33 0 2191.022 4382.044
*Centrifugal acceleration a at distance r (m) from the axis of rotation: a
= r.omega..sup.2 (.omega.: angular speed, .omega. = 2.pi. .times.
rotational speed = .pi.R/30 (rad/sec))
The wet treatment apparatus according to the present invention is
constructed such that, upon performing rinsing treatment subsequent to
processing with a chemical to remove the chemical under conditions
required for the present invention and established by the control system,
the rinsing treatment is conducted while feeding a fresh supply of a
liquid (for example, rinsing water) only in a direction conforming with a
flow of a liquid produced on the surface of the substrate as described
above. At this time, it is also controlled such that the rinsing treatment
is conducted while the fresh supply of the liquid is fed at a rate at
least equal to a discharge rate of the liquid.
As has been described above, use of the wet treatment apparatus according
to the present invention makes it possible to accelerate the replacement
with the fresh supply of the liquid. It is, therefore, possible to
effectively avoid a phenomenon such as an increase in chemical etching
rate which, as mentioned above, takes place if the rinsing water is
gradually mixed to the chemical (for example, if the rinsing water was
caused to stand up on the surface of the substrate). In particular, the
inclusion of the above-described treatment sub-step in an initial stage of
the treatment makes it possible to replace the chemical on the surface of
the substrate with the rinsing water in a stage that the rinsing water has
been used only in a small amount and, therefore, to decrease the overall
consumption of the rinsing water and the overall time required for the
rinsing. Further, as the rinsing water swiftly flows off from the surface
of the substrate, a still further advantageous effect can be brought about
in that even the inner wall of the treatment chamber is cleaned in the
above-described sub-step. Accordingly, the chemical adhered on the inner
wall of the treatment chamber can also be replaced with the fresh supply
of rinsing water at the same time. This makes it extremely easier to clean
the interior of the treatment chamber after the treatment compared with
the conventional apparatuses.
As a specific method for feeding the fresh supply of rinsing water only in
the direction conforming with the flow of liquid on the surface of the
substrate, the nozzle 5 may be arranged with its spray openings aligned in
a similar vertical direction as the rotary shaft, and the rinsing water
may be sprayed from the spray openings toward the inner wall of the
treatment chamber (see FIGS. 1 and 2).
The wet treatment method and apparatus of the present invention as
described above are usable in at least one of a chemical processing step
and a rinsing step, both of which are conducted upon fabrication of
semiconductor devices. These method and apparatus are used especially to
evenly and promptly perform the liquid-to-liquid replacement which is
effected in the step. These method and apparatus can be used most suitably
when the chemical employed in the chemical processing step is, for
example, one having such a high viscosity and/or adhesion as tending to
allow it to remain on the surface of the substrate, one with an organic
substance contained therein, or one having such a property that its
etching rate quickly increases when mixed with water. Illustrative of the
chemical which tends to remain abundantly on the surface of the substrate
are sulfuric acid, SPM (sulfuric acid-hydrogen peroxide mixture), and
tartaric acid. When the wet treatment method according to the present
invention is used, for example, upon rinsing such a chemical with water,
the chemical remaining on the surface of the substrate is promptly and
evenly replaced with water supplied in the rinsing step.
The wet treatment method and apparatus according to the present invention
are also effective when a chemical contains an organic solvent such as
DMSO (dimethyl sulfoxide), NMP (N-methylpyrrolidone) or DMF
(N,N-dimethylformamide). When one containing an acid or alkali dissolved
in such an organic solvent is used as a chemical, subsequent rinsing with
water promotes dissociation of the acid or alkali and leads to a
substantial change in pH. As a result, the etching rate increases, and in
some instances, corrosion of AlCu patterns and/or interconnections formed
on the surface of the substrate may occur. In contrast, use of the wet
treatment apparatus according to the present invention can prevent or
substantially reduce the occurrence of corrosion of such metallization
patterns and/or interconnections although rinsing with water is conducted.
For example, in a polymer stripping step which is conducted subsequent to
the formation of AlCu patterns and/or interconnections on a surface of a
substrate, unnecessary polymer is stripped with a stripper solution
containing ammonium fluoride, and then, rinsing is performed using water
as a rinsing liquid to remove the stripper solution and polymer residues
still remaining on the surface of the substrate. For such rinsing
treatment, the wet treatment apparatus according to the present invention
is suited. When gradually mixed with water, the stripper solution with
ammonium fluoride contained therein quickly increases in etching rate and
may cause corrosion of AlCu patterns and/or interconnections formed on the
surface of the substrate. Use of the wet treatment apparatus according to
the present invention, however, makes it possible to prevent or otherwise
substantially reduce the occurrence of corrosion of metallization patterns
and/or interconnections although rinsing with water is conducted without
performing intermediate or provisional rinsing. Further, the
above-described chemical remaining on the surface of the substrate is
promptly and evenly replaced with water in an initial stage of the rinsing
treatment. As a result, it is possible to reduce the overall time and
water consumption required for the rinsing treatment. As the rinsing water
swiftly flows off from the surface of the substrate, a still further
advantageous effect can be brought about in that the inner wall of the
treatment chamber is also cleaned at the same time and the chemical
adhered on the inner wall can also be replaced with the fresh supply of
rinsing water.
Use of the wet treatment apparatus according to the present invention is by
no means limited to the rinsing method in the above-described specific
case, but it can be applied to general wet treatments. Irrespective of the
wet treatment, the wet treatment apparatus according to the present
invention can feed a fresh supply of liquid to a treated surface and can
achieve a liquid-to-liquid replacement with high efficiency.
The present invention will next be described in further detail based on
Examples and Comparative Examples.
EXAMPLES 1-2 & COMPARATIVE EXAMPLES 1-2
Subsequent to an etching treatment conducted upon formation of AlCu
patterns and/or interconnections on surfaces of silicon wafers, residues
were treated with a stripper containing ammonium fluoride and then, the
surfaces of the silicon wafers were washed with water by using a modified
model (FIGS. 4 and 5) of "MERCURY" (trade name; manufactured by FSI
International, Inc.). This apparatus can be effectively used for
pre-cleaning of substrates, post-etch stripping of a resist and other
cleaning treatments upon fabrication of semiconductor devices. In a closed
chamber (treatment chamber 1) purged with nitrogen gas, substrates 8 can
be subjected at surfaces thereof to a series of treatments including
chemical processing, rinsing for the chemical and subsequent drying. As is
illustrated in FIG. 5, the modified model is provided in the chamber with
a rotating table, and around a rotary shaft, containers are arranged to
hold substrates. A nozzle is arranged with its spray openings aligned in a
similar vertical direction as the rotary shaft. The apparatus is
constructed such that a chemical or a rinsing liquid can be sprayed from
the nozzle toward the substrates while being controlled by the
above-described control system.
Substrates, which had been subjected to etching and carried AlCu patterns
and/or interconnections thereon, were placed in the substrate containers
mounted on the rotating table. After spraying a stripper with ammonium
fluoride contained therein against the substrates and treating them with
the stripper, water was sprayed through the nozzle to conduct rinsing.
Conditions for the rinsing treatment conducted in an initial stage of
rinsing in Examples 1-2 and Comparative Examples 1-2, respectively, are
presented in Table 2.
(Ranking)
(1) Extent of Corrosion
To investigate the efficiency of the rinsing treatment under the respective
conditions, the extent of corrosion of AlCu patterns and/or
interconnections on the surfaces of the substrates after the rinsing
treatment was determined. Described specifically, the surfaces of the
substrates were observed under a microscope and were ranked in accordance
with the following ranking standard. The results of the ranking are
presented in Table 2.
A: Absolutely no corrosion is observed on any of metallization patterns
and/or interconnections.
B: Only slight corrosions are observed on some of metallization patterns
and/or interconnections.
C: Corrosions are observed to such extent as making side walls of
metallization patterns and/or interconnections uneven.
D: Substantial corrosion-related reductions in width are observed on
metallization patterns and/or Interconnections.
(2) Amount of Residues (Particles)
To investigate the efficiency of the rinsing treatment under the respective
conditions, the amount of residues lifted off onto the surfaces of the
substrates after the rinsing treatment was determined by SEM observation.
The results of the observation were ranked in accordance with the
following ranking standard. The results of the ranking are presented in
Table 2.
A: Absolutely no particle is observed anywhere on the surface of the
substrate.
B: Particles are observed.
TABLE 2
Corrosion Preventing Ability
Ranking
results
Supply Dischar
