U.S. patent application number 10/779827 was filed with the patent office on 2004-08-19 for electroless plating apparatus and method.
Invention is credited to Hongo, Akihisa, Inoue, Hiroaki, Karimata, Tsutomu, Kimura, Norio, Mishima, Koji.
Application Number | 20040161529 10/779827 |
Document ID | / |
Family ID | 26602874 |
Filed Date | 2004-08-19 |
United States Patent
Application |
20040161529 |
Kind Code |
A1 |
Hongo, Akihisa ; et
al. |
August 19, 2004 |
Electroless plating apparatus and method
Abstract
An plating apparatus which can easily form a plated film having
more uniform thickness on a surface, to be plate, of a material to
be plated. The plating apparatus includes a holding portion having
a heating portion for holding a material to be plated in such a
state that a surface to be plated faces downward, and a plating
bath for introducing an electroless plating liquid having a
predetermined temperature into a plating chamber, and holding the
electroless plating liquid while allowing the electroless plating
liquid to overflow an overflow dam. The material which is by the
holding portion, is brought into contact with the plating liquid in
the plating bath to plate the material.
Inventors: |
Hongo, Akihisa;
(Yokohama-shi, JP) ; Mishima, Koji; (Fujisawa-shi,
JP) ; Inoue, Hiroaki; (Tokyo, JP) ; Kimura,
Norio; (Fujisawa-shi, JP) ; Karimata, Tsutomu;
(Yokohama-shi, JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W.
SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
26602874 |
Appl. No.: |
10/779827 |
Filed: |
February 18, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10779827 |
Feb 18, 2004 |
|
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|
09983399 |
Oct 24, 2001 |
|
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|
6716330 |
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Current U.S.
Class: |
427/58 ;
257/E21.174; 427/443.1 |
Current CPC
Class: |
C23C 18/1619 20130101;
H01L 21/288 20130101; H01L 21/76849 20130101; C23C 18/1678
20130101; H01L 21/76843 20130101; C23C 18/1669 20130101; H01L
21/76874 20130101 |
Class at
Publication: |
427/058 ;
427/443.1 |
International
Class: |
B05D 005/12; B05D
001/18 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 26, 2000 |
JP |
2000-327800 |
Dec 11, 2000 |
JP |
2000-376189 |
Claims
What is claimed is:
1. An electroless plating method comprising: facing a surface, to
be plated, of a substrate downwardly; and processing said surface
to be plated by bringing said surface to be plated into contact
with an electroless plating treatment liquid.
2. An electroless plating method according to claim 1, wherein gas
generated on said surface to be plated is removed from said surface
to be plated by bringing said surface to be plated into contact
with said electroless plating treatment liquid in such a state that
said surface to be plated is inclined.
3. An electroless plating method according to claim 1, wherein gas
generated on said surface to be plated is removed from said surface
to be plated by forming a flow of said electroless plating
treatment liquid in a certain direction on said surface to be
plated and entraining said gas generated on said surface to be
plated with said flow of said electroless plating treatment liquid.
Description
[0001] This is a divisional application of Ser. No. 09/983,399,
filed Oct. 24, 2001.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an electroless plating
apparatus and method which are preferably used for forming
interconnects on a semiconductor substrate (including filling of a
metal such as copper into an interconnection groove or the like,
forming of a seed layer, and forming of a reinforcing seed layer on
a seed layer for the purpose of reinforcing the seed layer), an
interconnection-protective film, and a diffusion-preventive
film.
[0004] 2. Description of the Related Art
[0005] An electroless plating is such a method that a plated film
is formed on a surface of a material to be plated by chemically
reducing metal ions in a plating liquid without supplying any
electric current from the outside, and the electroless plating is
widely used in nickel-phosphorus plating and a nickel-boron plating
for providing corrosion resistance and a wear resistance, and a
copper plating for a printed-wiring substrate.
[0006] As an electroless plating apparatus, there has been
generally known an apparatus comprising a plating bath for holding
an electroless plating liquid while causing the electroless plating
liquid to overflow, and a vertically movable holding portion
disposed above the plating bath for holding a material, to be
plated, such as a substrate so as to face laterally, whereby the
material, to be plated, held by the holding portion is dipped into
the plating liquid in the plating bath (the so-called dipping
(dip)) . Further, there has been also generally known an apparatus
comprising a holding portion for holding a material, to be plated,
such as a substrate so as to face upwardly (face up), and a plating
liquid supply portion for supplying a plating liquid to an upper
surface (surface to be plate) of the material, to be plated, held
by the holding portion, whereby the plating liquid flows along the
upper surface of the material, to be plated, held by the holding
portion. As a face-up type plating apparatus, there is a coater
face-up type plating apparatus in which a plating liquid flows
along an upper surface of a material to be plated by supplying the
plating liquid to the upper surface of the material to be plated
from the plating liquid supply portion and rotating the material to
be plated.
[0007] In recent years, as the processing speed and integration of
a semiconductor chip becomes higher, there has been a growing
tendency to replace aluminum or aluminum alloy with copper having a
low electric conductivity and a high electromigration resistance as
metallic materials for forming interconnection circuits on the
semiconductor substrate. This kind of copper interconnect is
generally formed by filling copper into fine recesses formed in the
surface of the substrate. As a method for forming the copper
interconnect, plating is generally used. In any case, after a
copper film is deposited on the surface of the substrate, the
surface of the substrate is polished to a flat finish by chemical
mechanical polishing (CMP).
[0008] An electroless plating is applied to main filling materials
(Cu) for the copper interconnect, the formation of the seed layer
on the barrier metal, or the reinforcement of the seed (Cu),
further the formation of the barrier metal itself, or the formation
of cap material for the copper interconnect (in any case, Ni-P,
Ni-B, Co-P, Ni-W-P, Ni-Co-P, Co-W-P), or the like. In any
electroless plating process, uniformity of the film thickness over
an entire surface of the substrate is required.
[0009] In this case, in the electroless plating, as soon as a
material to be plated is brought into contact with a plating
liquid, a plating metal begins to be deposited on the surface to be
plated, and the deposition velocity of the plating metal varies
with the temperature of the plating liquid. Thus, in order to form
a plated film having a uniform thickness on the surface of the
material to be plated, it is necessary that the temperature of the
plating liquid should be uniform on the entire surface to be plated
from the time when the plating liquid begins to be brought into
contact with the material to be plated, and should be kept constant
during all the plating process of this contact, and the velocity
distribution (thickness of a diffusion layer or a boundary layer
formed along the surface to be plated) of the plating liquid in a
direction perpendicular to the surface to be plated during the
plating process should be uniform over the entire surface to be
plated.
[0010] However, in the conventional dip type and jig fixing type
plating, it has been difficult to make a flow of the plating liquid
on the substrate uniform. Further, in the coater face-up type
plating, there has been problems of a control of flow and a
uniformity of liquid temperature.
[0011] FIG. 11 is a schematic view showing a conventional dip type
electroless plating apparatus. As shown in FIG. 11, this
electroless plating apparatus comprises a plating bath 280 for
storing a plating liquid 281 therein, and a substrate holding
apparatus (substrate holding means) 290 for holding a semiconductor
substrate W.
[0012] In the electroless plating, a good reaction cannot take
place unless the temperature at the contacting portion between a
surface W1, to be plated, of a semiconductor substrate W and a
plating liquid is kept at a predetermined temperature (for example,
60.degree. C.) . Therefore, in order to heat the plating liquid 281
in the plating bath 280 and keep the plating liquid 281 at a
predetermined constant temperature, a pipe 282 is connected to the
plating bath 280 to withdraw the plating liquid in the plating bath
280 and to circulate the plating liquid by a pump P, and there is
provided a heating apparatus (heating means) 283, in the pipe 282,
such as a heater for heating the plating liquid to a predetermined
temperature.
[0013] On the other hand, the substrate holding apparatus 290 is
formed into such a shape that the substrate holding apparatus 290
covers the surface of the semiconductor substrate except for the
surface W1, to be plated, of the semiconductor substrate W, and is
adapted to dip the semiconductor substrate W into the plating bath
280 in such a state the surface W1 to be plated is placed in a
vertical direction. The reason for placing the surface W1, to be
plated, of the semiconductor W in a vertical direction in the
plating bath 280 is that gas is generated on the surface W1 to be
plated by a plating reaction, and if the generated gas remains on a
certain area of the surface W1 to be plated, the plating reaction
is obstructed at such area, and hence such generated gas is
required to be easily separated from the surface W1 to be
plated.
[0014] However, in the above conventional electroless plating
apparatus, because the surface W1, to be plated, of the
semiconductor substrate W must be placed vertically in the plating
bath 280, the plating bath 280 is required to have a large depth,
and thus cannot be downsized. Further, because it is necessary to
provide the heating apparatus 283 outside the plating bath 280, an
overall apparatus cannot be downsized also in this respect.
[0015] On the other hand, in the case where a copper plating is
applied to the semiconductor substrate W, when the temperature of
the plating liquid varies by 1.degree. C. in a plating time of one
minute at, for example, around 60.degree. C., the difference of the
film thickness amounts to approximately 1.8 nm, and hence an
extremely precise temperature control of the plating liquid is
required. However, as described above, the plating bath 280 cannot
be downsized, and thus a large amount of the plating liquid is
required to be contained. Consequently, the temperature of the
plating liquid cannot be precisely controlled, and the amount of
the plating liquid to be used increases to thus increase electric
power consumption for heating the plating liquid and keeping the
plating liquid warm.
SUMMARY OF THE INVENTION
[0016] The present invention has been made in view of the above
drawbacks. It is therefore a first object of the present invention
to provide an electroless plating apparatus which can easily form a
plated film having more uniform thickness on a surface, to be
plate, of a material to be plated.
[0017] A second object of the present invention is to provide
electroless plating apparatus and method in which an overall
apparatus can be downsized, the amount of a plating liquid to be
used can be small, and the temperature of the plating liquid can be
precisely controlled.
[0018] In order to achieve the first object, according to a first
aspect of the present invention, there is provided an electroless
plating apparatus comprising; a holding portion having a heating
portion for holding a material to be plated in such a state that a
surface to be plated faces downward; and a plating bath for
introducing an electroless plating liquid having a predetermined
temperature into a plating chamber, and holding the electroless
plating liquid while allowing the electroless plating liquid to
overflow an overflow dam; wherein the material, to be plated, held
by the holding portion is brought into contact with the plating
liquid in the plating bath to plate the material. The electroless
plating liquid is preferably introduced into the plating bath by an
upward flow.
[0019] In this case, the heating portion may be attached to the
holding portion or may be integrally provided in the holding
portion. The built-in heating portion is preferable because heat
can be effectively and uniformly transferred.
[0020] With this arrangement, while holding the material, to be
plated, by the holding portion and heating the material, to be
plated, to the same temperature as that of the plating liquid by
the heating portion provided in the holding portion, the material
to be plated is dipped in the plating liquid having a predetermined
temperature to perform a plating treatment, thereby preventing the
surface of the material, to be plated, from becoming nonuniform
temperature distribution and preventing the plating temperature
from being changed during a plating process. Further, by creating a
stable flow of the plating liquid flowing upwardly and spreading
outwardly in the plating chamber, the velocity distribution
(thickness of a diffusion layer or a boundary layer) of the plating
liquid in a direction perpendicular to the surface of the material
to be plated can be more uniform over an entire area of the surface
to be plated during the plating process.
[0021] The temperature of the plating liquid to be introduced into
the plating bath is in the range of, for example, 25 to 90.degree.
C., preferably 55 to about 80.degree. C., and the flow rate of the
plating liquid is in the range of, for example, 1 to 30 l
(liter)/min, preferably 1 to 20 l/min, and more preferably 1 to
about 10 l/min. However, the optimal flow rate of the plating
liquid varies with process temperature and reducing reaction
state.
[0022] According to a preferable aspect of the present invention,
the holding portion is adapted to be freely rotatable. With this
arrangement, by holding and rotating the material to be plated by
the holding portion, the velocity distribution of the plating
liquid in a direction perpendicular to the surface, to be plated,
of the material during a plating process can be more uniform. This
rotational speed is in the range of, for example, 0 to 100 rpm (0
to 100 min.sup.-1), preferably 0 to about 50 rpm (0 to 50
min.sup.-1). However, these optimal rotational speeds vary with
reducing reaction state and required uniformity of the film
thickness on the surface.
[0023] According to a preferable aspect of the present invention,
at least an area of a bottom surface of the plating chamber which
faces the material, to be plated, held by the holding portion has a
quadratic curved surface spreading upwardly and outwardly.
[0024] With this arrangement, in the area having a quadratic curve
on the bottom surface of the plating chamber, the plating liquid
flows smoothly in a laminar flow along the bottom surface of the
plating chamber without generating vortex locally while
flowing.
[0025] According to a preferable aspect of the present invention, a
heating portion for heating the plating liquid held by the plating
bath or a heat insulating material for heat insulation of the
plating liquid from the outside is provided in the plating bath.
Thus, the plating liquid having, for example, a high temperature
can be prevented from being gradually cooled while flowing in the
plating bath.
[0026] According to a preferable aspect of the present invention,
the holding portion is adapted to hold the substrate by a vacuum
chuck or an electrostatic chuck.
[0027] In the case where a uniform flow of the plating liquid on
the substrate is considered to be formed, the seal located at the
outer peripheral portion of the substrate becomes a factor to
disturb the flow of the plating liquid. In order to further improve
accuracy of uniformity of the surface, it is desirable that there
is no seal on the surface, to be plated, of the substrate. Thus,
the chuck should hold the backside of the substrate, the vacuum
chuck or the electrostatic chuck should be used, and the seal
should be performed at the outer periphery of the backside of the
substrate.
[0028] According to an aspect of a substrate processing apparatus
of the present invention, the substrate processing apparatus
comprises the electroless plating apparatus for forming a plated
film on a surface of the substrate, and an apparatus for forming a
catalyst layer before applying electroless plating to the surface
of the substrate by the electroless plating apparatus.
[0029] In order to achieve the above second object, according to a
second aspect of the present invention, there is provided an
electroless plating method comprising: facing a surface, to be
plated, of a substrate downwardly; and processing the surface to be
plated by bringing the surface to be plated into contact with an
electroless plating treatment liquid.
[0030] With this arrangement, the surface to be plated can be
easily brought into contact with the plating treatment liquid.
Further, the amount of the plating treatment liquid to be used can
be reduced and the temperature of the plating liquid can be
accurately and easily controlled, and the electric power
consumption for heating the plating treatment liquid and keeping
the plating treatment liquid warm can be decreased.
[0031] In this case, by bringing the surface to be plated into
contact with the electroless plating treatment liquid in such a
state that the surface to be plated is inclined, gas generated on
the surface to be plated can be effectively removed from the
surface to be plated.
[0032] Further, gas generated on the surface to be plated is
removed from the surface to be plated by forming a flow of the
electroless plating treatment liquid in a certain direction on the
surface to be plated and entraining the gas generated on the
surface to be plated with the flow of the electroless plating
liquid.
[0033] According to a second aspect of the present invention, there
is provided an electroless plating apparatus, comprising: a plating
treatment liquid holding apparatus for storing a plating treatment
liquid while maintaining the plating treatment liquid at a
predetermined plating treatment temperature; and a substrate
holding apparatus for holding a substrate in such a state that a
surface, to be plated, of the substrate faces downwardly, and
bringing the surface, to be plated, of the substrate into contact
with the plating treatment liquid.
[0034] With this arrangement, the plating treatment liquid holding
apparatus can be downsized, and an overall apparatus can be
downsized.
[0035] The plating treatment liquid holding apparatus preferably
has a heater at a bottom surface of the plating treatment liquid
holding apparatus, and a dam for holding the plating treatment
liquid over a periphery of the heater.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] FIG. 1A through FIG. 1C are views showing an example of a
plating process;
[0037] FIG. 2 is a cross-sectional view showing an electroless
plating apparatus according to a first embodiment of a first aspect
of the present invention;
[0038] FIG. 3 is a cross-sectional view showing an electroless
plating apparatus according to a second embodiment of a first
aspect of the present invention;
[0039] FIG. 4 is a plan view showing a layout of a substrate
processing apparatus having the electroless plating apparatus shown
in FIG. 2;
[0040] FIG. 5 is a cross-sectional view showing a modified example
of the electroless plating apparatus shown in FIG. 2;
[0041] FIG. 6 is a schematic view showing a basic structure of an
electroless plating apparatus according to a second aspect of the
present invention;
[0042] FIG. 7 is a schematic view showing another embodiment of an
electroless plating apparatus according to the second aspect of the
present invention;
[0043] FIG. 8 is a schematic view showing still another embodiment
of an electroless plating apparatus according to the second aspect
of the present invention;
[0044] FIG. 9 is a schematic view showing still another embodiment
of an electroless plating apparatus according to the second aspect
of the present invention;
[0045] FIG. 10 is a schematic view showing still another embodiment
of an electroless plating apparatus according to the second aspect
of the present invention; and
[0046] FIG. 11 is a schematic view of a conventional electroless
plating apparatus.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0047] Embodiments of the present invention will be described below
with reference to drawings. In the following examples, the
following cases will be described: An electroless copper plating is
applied to a surface of a substrate, such as a semiconductor wafer,
in which a via hole or a trench for an interconnect is formed,
thereby filling copper into the via hole or the trench for the
interconnect, and then a CMP process is applied to the surface of
the substrate to polish the surface of the substrate, thus forming
a copper interconnect on the surface of the substrate.
[0048] An example of this plating process will be described with
reference to FIGS. 1A through 1C.
[0049] As shown in FIG. 1A, an insulating film 2 of Sio.sub.2 is
deposited on a conductive layer 1a of a substrate 1 on which
semiconductor devices are formed, and a via hole 3 and a trench 4
for an interconnect are formed by lithography and etching
technology. Thereafter, a barrier layer 5 of TiN or the like is
formed thereon, and then a seed layer 7 is formed on the barrier
layer 5 by electroless copper plating. In some cases, the seed
layer 7 is formed in advance by sputtering, and a reinforcing seed
layer is formed by the copper electroless plating on the seed layer
7 for reinforcing the seed layer. Further, as shown in FIG. 1B,
copper plating is applied to a surface of the semiconductor
substrate W to fill the via hole 3 and the trench 4 with copper and
to deposit a copper layer 6 on the insulating film 2. Thereafter,
the copper layer 6 on the insulating film 2 is removed by chemical
mechanical polishing (CMP) to make the surface of the copper layer
6 filled into the via hole 3 and the trench 4 for the interconnect
lie substantially flush with the surface of the insulating film 2,
and then an interconnection-protective film 8 is formed on an
exposed metal surface.
[0050] FIG. 2 shows an electroless plating apparatus according to a
first embodiment of the present invention. This electroless plating
apparatus has a substrate holding portion 10 for holding a
substrate W (material to be plated), such as a semiconductor wafer,
having a surface S (surface to be plated) in which a via hole or a
trench for an interconnect is formed, in such a manner that the
surface S faces downward (facedown). The substrate holding portion
10 is housed in a housing 12 so as to be movable vertically, and
rotatable in unison with the housing 12 which is open downwardly.
By using the electroless plating apparatus shown in FIG. 2, the
seed layer 7 shown in FIG. 1A can be formed by copper plating,
copper alloy plating, or cobalt alloy plating, the seed layer 7 can
be reinforced by copper plating, the copper layer 6 shown in FIG.
1B can be formed by copper plating, and the
interconnection-protective film 8 shown in FIG. 1C can be formed by
cobalt alloy plating, nickel alloy plating, or copper alloy
plating. A copper plating liquid used in copper plating comprises a
copper sulfate liquid to which a reducing agent such as sodium
hypophosphite or glyoxylic acid, a complexing agent, a pH buffer
agent, a pH regulating agent, and the like are added. A nickel
plating liquid used in the nickel alloy plating comprises nickel
chloride or nickel sulfate to which sodium hypophosphite as a
reducing agent in the case for Ni-P film, sodium borohydride as a
reducing agent in the case for Ni-B film, and other agents, such as
a complexing agent and a pH buffer agent are added.
[0051] Inside the substrate holding portion 10, there is provided a
heating portion (heater) 14 for heating the substrate W over an
area slightly larger than an entire area of the surface S of the
substrate W in such a state that the lower surface of the heating
portion 14 is exposed, and the substrate W is held on the lower
surface of the heating potion 14 such that the substrate W is held
by a seal 18. Thus, the substrate W is held by the lower surface of
the heating portion 14 and heated by the heating portion 14 so as
not to become nonuniform with regard to temperature distribution on
the substrate W. In addition, the heating portion 14 has a
temperature controlling function so that the substrate W can be
heated to a desired temperature.
[0052] The housing 12 is connected to a lower end of a main shaft
16 which is vertically movable and rotatable, and has a lower end
which projects inwardly and forms a seal claw 18 for sealing an
outer peripheral portion of the substrate W, and a circumferential
wall having an opening 20 for allowing the substrate W to be
carried in or out.
[0053] A plating bath 24 for holding an electroless plating liquid
22 is disposed below the housing 12. In order to reduce a friction
against the plating liquid 22, the plating bath 24 is made of, for
example, TEFLON (polytetrafluorethylene), and has a plating chamber
28 therein which holds the plating liquid 22 and communicates with
a plating liquid supply passage 26 extending upwardly from a
central bottom portion of the plating bath 24. The periphery of the
plating chamber 28 is surrounded by an overflow dam 30, and a
plating liquid discharge passage 32 is formed outwardly of the
overflow dam 30. Thus, the plating liquid 22 flows upwardly through
the plating liquid supply passage 26 and is introduced into the
plating chamber 28, overflows the overflow dam 30, and is then
discharged through the plating liquid discharge passage 32 to the
outside.
[0054] In this case, at least an area of the bottom surface 28a of
the plating chamber 28 which faces the substrate W held by the
substrate holding portion 10 is streamlined, for example,
trumpet-funnel-shaped, and has a quadratic curved surface spreading
upwardly and outwardly. In this manner, in the area having a
quadratic curve on the bottom surface 28a of the plating chamber
28, the plating liquid 22 flows smoothly in a laminar flow along
the bottom surface 28a of the plating chamber 28 without generating
vortex locally while flowing.
[0055] Further, a heating portion 34 having such a shape as to be
along the quadratic curved surface of the bottom surface 28a is
embedded at a location close to the bottom surface 28a of the
plating chamber 28 within the plating bath 24. Thus, even if the
plating liquid 22 which has been heated and is introduced through
the plating liquid supply passage 26 into the plating chamber 28 is
cooled during conveyance, the plating liquid 22 is heated to a
fixed temperature by the heating portion 34. A heat insulating
material may be provided instead of the heating portion 34.
Further, the heating portion or the heat insulating material may be
omitted, if the temperature of the plating liquid is not so
high.
[0056] In the electroless plating apparatus according to this
embodiment, the substrate W is first introduced through the opening
20 into the housing 12, the substrate holding portion 10 is lowered
in such a state that the substrate W is placed on and held by the
seal claw 18, and hence the substrate W is pressed and held by the
substrate holding portion 10. In such a state, the entire area of
the substrate W is heated to the same fixed temperature as that of
the plating liquid 22 to be introduced into the plating chamber 28
by the heating portion 14 incorporated in the substrate holding
portion 10.
[0057] On the other hand, the plating liquid 22 heated to a fixed
temperature is introduced through the plating liquid supply passage
26 into the plating chamber 28, and is caused to overflow the
overflow dam 30. The temperature of the plating liquid 22 to be
introduced into the plating bath 24 is in the range of, for
example, 25 to 90.degree. C., preferably 55 to about 80.degree. C.,
and the flow rate of the plating liquid 22 is in the range of, for
example, 1 to 30 l(liter)/min, preferably 1 to 20 l/min, and more
preferably 1 to about 10 l/min.
[0058] In such a state, the substrate W is lowered while it is
rotated at a rotational speed of, for example, 0 to 100 rpm (0 to
100 min.sup.-1), preferably 0 to 50 rpm (0 to 50 min.sup.-1), more
preferably 0 to about 20 rpm (0 to 20 min.sup.-1), whereby the
substrate W is dipped in the plating liquid 22 in the plating
chamber 28 to apply copper plating to a surface of the substrate W.
Optimal values of the temperature and the flow rate of the plating
liquid, and the rotational speed of the substrate vary with
respective processes.
[0059] In this manner, while holding the substrate W by the
substrate holding portion 10 and heating the substrate W to the
same temperature as that of the plating liquid 22 by the heating
portion 14 provided in the substrate holding portion 10, the
substrate W is dipped in the plating liquid having a predetermined
temperature to perform a plating process, thereby preventing the
surface S of the substrate W from having a nonuniform temperature
distribution and preventing the plating temperature from being
changed during the plating process.
[0060] Further, by creating a stable flow of the plating liquid 22
flowing upwardly and spreading outwardly in the plating chamber 28,
the velocity distribution (thickness of a diffusion layer or a
boundary layer) of the plating liquid 22 in a direction
perpendicular to the surface S of the substrate W can be more
uniform over an entire area of the surface S during the plating
process. Thus, it is possible to deposit a plated copper film
having a uniform thickness so as not to cause problems in a
subsequent CMP process or a lithography process. Further, for the
purpose of formation of a seed layer, it is possible to form the
seed layer having a uniform thickness, and hence to stabilize
embeddability in a subsequent process.
[0061] After a plating process of a predetermined time finishes,
the substrate W is raised, and the liquid is removed from the
substrate W, if necessary. Thereafter, the substrate W which has
been plated is transferred to the outside of the housing 12 in the
reverse operations of the above operations. If the seal claw on the
substrate disturbs the flow of the plating liquid and a uniform
thickness of the film cannot be maintained, a vacuum chuck or an
electrostatic chuck 38 is attached to the lower surface of the
substrate holding portion 10 as shown in FIG. 5. In this case, the
substrate W is attracted and held by the vacuum chuck or the
electrostatic chuck 38, and the seal is attached at the side of the
backside surface of the substrate W for sealing this side. Thus,
the seal claw can be omitted.
[0062] FIG. 3 shows an electroless plating apparatus according to a
second embodiment of the present invention. In the electroless
plating apparatus of the present embodiment, the plating bath 24
has a laminated structure composed of a core member 40 and a cover
member 42 for covering the surface of the core member 40, and a
pipe 44 is provided between the core member 40 and the cover member
42 and a heating medium 46 is introduced into the pipe 44, thereby
constituting a heating portion 48 having a jacket structure. In
this example, the heating medium 46 is introduced into the pipe 44
from the outside of the plating bath 24 and flows through the pipe
44 toward the interior of the plating bath 24. Other constitutions
are substantially the same as those shown in FIG. 2.
[0063] According to this embodiment, as the plating liquid 22 flows
outwardly in the plating chamber 28, the plating liquid 22 is
gradually cooled. By effectively heating the plating liquid 22,
which has been cooled most, with the heating medium 46, the
temperature of the plating liquid 22 can be more constant.
[0064] FIG. 4 shows a whole structure of the substrate processing
apparatus having the electroless plating apparatus shown in FIGS. 2
and 3. The substrate processing apparatus is placed on a
rectangular installation floor 50, and comprises load and unload
units 52a, 52b, cleaning apparatuses 54, 56 for pretreatment, an
activation treatment apparatus 58 for performing an activation
treatment using SnCl.sub.2 liquid or the like serving as an
activating agent in plating, a catalyst imparting apparatus 60 for
performing a catalyst imparting treatment, i.e., a Pd imparting
treatment using PdCl.sub.2 liquid or the like serving as catalyst
in electroless plating, and an electroless plating apparatus 62.
Further, the substrate processing apparatus comprises cleaning and
drying apparatuses 64, 66 for performing a post-treatment after
plating, two transfer apparatuses (transfer robots) 68, 70 for
transferring the substrate W between the above apparatuses, and a
temporary storage stage 72.
[0065] Here, in this example, the cleaning and drying apparatus 64
comprises a roll cleaning unit, and the cleaning and drying
apparatus 66 comprises a spin dry unit having a pencil-type sponge.
The transfer apparatus 68 located at the side of the load and
unload units 52a, 52b comprises a dry robot, and the transfer
apparatus 70 located at the opposite side of the units 52a, 52b
with respect to the temporary storage stage 72 comprises a wet
robot having a reversing mechanism. The dry robot transfers dry
(dried) substrates W and the wet robot transfers wet (wetted)
substrates W.
[0066] Next, a series of plating processes by the substrate
processing apparatus having the above structure will be described.
First, the substrate W held by the load and the unload units 52a,
52b is taken out by the transfer apparatus 68 and placed on the
temporary storage stage 72. The substrate W is transferred by the
transfer apparatus 70 to the cleaning apparatus 54 where a
pre-cleaning is applied to the substrate W, and then the substrate
W is transferred to the activation treatment apparatus 58. In the
activation treatment apparatus 58, an activation treatment is
performed by a treatment liquid containing an activating agent such
as SnCl.sub.2. Next, the substrate W is transferred to the catalyst
imparting apparatus 60 adjacent to the activation treatment
apparatus 58. In the catalyst imparting apparatus 60, a catalyst
imparting treatment is performed by a catalyst such as PdCl.sub.2
liquid or the like, and then the substrate W is rinsed.
[0067] During the above processes, in the activation treatment
apparatus 58, ions Sn.sup.2+ generated from the activating agent
SnCl.sub.2 are adsorbed on the surface of the substrate W, these
ions Sn.sup.2+ are oxidized to Sn.sup.4+ by Pd.sup.2+ generated
from PdCl.sub.2 in the catalyst imparting apparatus 60, and
conversely Pd.sup.2+ is reduced to metal Pd. This metal Pd is
deposited on the surface of the substrate W to become a catalyst
layer in the subsequent electroless plating process. This process
can be performed by using one liquid catalyst of Pd/Sn colloid.
Although the above catalyst imparting process can be performed in
the activation treatment apparatus 58 and the catalyst imparting
apparatus 60 as in this example, this process may be performed by
another apparatus, and then the substrate W may be transferred.
Further, in some cases, the activation treatment and/or the
catalyst imparting treatment may be omitted depending on the
material and state of the inner surface of the recess of the
semiconductor substrate.
[0068] The substrate W is further transferred by the transfer
apparatus 70 to the cleaning apparatus 56 where a pre-cleaning is
performed, and then the substrate W is transferred to the
electroless plating apparatus 62. In the electroless plating
apparatus 62, the electroless plating treatment is performed by the
use of a predetermined reducing agent and a predetermined plating
liquid. In this case, electrons generated by decomposition of the
reducing agent at a solid-liquid interface are given through the
catalyst on the surface of the substrate to Cu.sup.2+, thus causing
Cu to be deposited on the catalyst as metal Cu and forming a plated
copper film. As this catalyst, Fe, Co, Ni, Cu, Ag, and the like
which are transition metals can be used other than Pd.
[0069] Next, the substrate W which has been plated is taken out
from the electroless plating apparatus 62 and transferred to the
cleaning and drying apparatus 64 by the transfer apparatus 68. In
the cleaning and drying apparatus 64, the substrate W is cleaned
with water by a roll, and dried. Then, the substrate is transferred
by the transfer apparatus 68 to the cleaning and drying apparatus
66 where a finish cleaning of the substrate is performed by a
pencil-type sponge and a spin-dry of the substrate is performed.
Thereafter, the substrate is returned to the load and unload units
52a, 52b. The substrate is then transferred to a plating apparatus
or an oxide film forming apparatus.
[0070] As another example of the treatment processes, a
pre-cleaning treatment for imparting catalyst is performed in the
cleaning apparatus 54, a catalyst imparting process is performed in
the activation treatment apparatus 58, a post-treatment for
imparting catalyst is performed in the catalyst imparting apparatus
60, a pre-treatment cleaning before plating is performed in the
cleaning apparatus 56, a plating treatment process is performed in
the electroless plating apparatus 62, and a cleaning after plating
is then performed promptly in the electroless plating apparatus 62
to stop a growth of the plating.
[0071] In this example, the plated copper film is formed by the
electroless plating. However, as a plated film formed by the
electroless plating, besides copper, there are nickel--boron,
nickel--phosphorous, cobalt--phosphorous,
nickel--tungsten--phosphorous, nickel--cobalt--phosphorous,
cobalt--tungsten--phosphorous, and the like.
[0072] As described above, according to the present invention, the
surface, to be plated, of the material is prevented from becoming
nonuniform temperature distribution and the plating temperature is
prevented from being changed during the plating process. Further,
the velocity distribution (thickness of a diffusion layer or a
boundary layer) of the plating liquid in a direction perpendicular
to the surface, to be plated, of the material can be more uniform
on the entire area of the surface to be plated, and hence the
plated film having a more uniform thickness can be formed on the
surface, to be plated, of the material to be plated.
[0073] FIG. 6 is a schematic view showing a basic structure of an
electroless plating apparatus according to a second aspect of the
present invention. As shown in FIG. 6, the electroless plating
apparatus comprises a semiconductor substrate W, a substrate
holding apparatus (substrate holding means) 110 for holding the
semiconductor substrate W, and a plating liquid holding apparatus
(plating liquid holding means) 120 for holding a plating liquid
(plating treatment liquid) 125. By using the electroless plating
apparatus shown in FIG. 6, the seed layer 7 shown in FIG. 1A can be
formed by copper plating, copper alloy plating, or cobalt alloy
plating, the seed layer 7 can be reinforced by copper plating, the
copper layer 6 shown in FIG. 1B can be formed by copper plating,
and the interconnection-protective film 8 shown in FIG. 1C can be
formed by cobalt alloy plating, nickel alloy plating, or copper
alloy plating. A copper plating liquid used in copper plating
comprises a copper sulfate liquid to which a reducing agent such as
sodium hypophosphite or glyoxylic acid, a complexing agent, a pH
buffer agent, a pH regulating agent, and the like are added. A
nickel plating liquid used in the nickel alloy plating comprises
nickel chloride or nickel sulfate to which sodium hypophosphite as
a reducing agent in the case for Ni-P film, sodium borohydride as a
reducing agent in the case for Ni-B film, and other agents, such as
a complexing agent and a pH buffer agent are added.
[0074] In this case, the substrate holding apparatus 110 has a
structure for holding a semiconductor substrate W such that a
surface W1, to be plated, of the substrate W faces just downward
(downward). At this time, the surface of the semiconductor
substrate W except the surface W1 to be plated is covered with the
substrate holding apparatus 110 so as not to cause the plating
liquid to be attached to the surface of the semiconductor substrate
W except the surface W1 to be plated. A rotation drive shaft 111
for rotatably supporting the substrate holding apparatus 110 is
attached to a central upper surface of the substrate holding
apparatus 110. The rotation drive shaft 111 is coupled to a
rotation drive apparatus (rotation drive means) such as a motor
(not shown in the drawing).
[0075] On the other hand, the plating liquid holding apparatus 120
comprises a heater holding portion 121 serving as a bottom surface
in which a heater H is provided, and a ring-shaped dam 123
extending upwardly from the periphery of the heater holding portion
121 for holding a plating liquid 125.
[0076] The electroless plating liquid 125 is filled inside the dam
123 of the plating liquid holding apparatus 120, and is heated by
the heater H to a predetermined temperature (electroless plating
treatment temperature, for example, 60.degree. C.) optimum for the
electroless plating and kept warm at a fixed temperature.
[0077] Next, the surface W1, to be plated, of the semiconductor
substrate W is held on the lower surface of the substrate holding
apparatus 110 in such a state that the surface W1 to be plated
faces downwardly, and the surface W1 to be plated is dipped in and
brought into contact with the plating liquid 125. At the same time,
the substrate holding apparatus 110 is rotated (may not be
necessarily rotated). In this manner, a copper plating is applied
to the surface W1, to be plated, of the semiconductor substrate
W.
[0078] As described above, according to the present invention,
because the surface W1, to be plated, of the semiconductor
substrate W is brought into contact with the plating liquid 125 in
such a state that the surface W1 to be plated faces downwardly, the
depth of the plating liquid 125 can be small in structure. Thus,
the plating liquid 125 should be held in minimum and necessary
quantity in the plating liquid holding apparatus 120, and hence the
plating liquid holding apparatus 120 can be downsized. Further,
since the heater H is provided in the heater holding portion 121,
the plating liquid holding apparatus 120 can be smaller than the
conventional plating treatment tank 280 shown in FIG. 11.
Furthermore, since the amount of the plating liquid to be used is
small, the temperature of the plating liquid can be accurately
controlled. The electric power consumption for heating the plating
liquid can be reduced.
[0079] On the other hand, as described above, gas (H.sub.2 gas) is
normally generated at the time of electroless plating reaction.
Therefore, in the basic structure of the electroless plating
apparatus shown in FIG. 6, the gas tends to stay at the lower
surface of the semiconductor substrate. Even if the substrate
holding apparatus 110 is rotated, a part of the gas is collected at
a portion of the rotation center located at the central portion of
the lower surface of the semiconductor substrate W and is difficult
to be removed. Therefore, in order to remove such gas effectively,
the following measures were taken by the present inventors.
[0080] (Method for dissolving the generated gas into the plating
liquid)
[0081] In this method, composition of the electroless plating
liquid is selected to reduce the amount of the gas generated in the
electroless plating reaction to such a degree as to allow the
generated gas to be dissolved entirely in the plating liquid. In
this case, the structure of the electroless plating apparatus may
be the same as that shown in FIG. 6.
[0082] Gas such as hydrogen gas is dissolved in the plating liquid
in a certain solubility. Thus, by reducing the amount of gas
generated, the entire amount of the generated gas should be
dissolved in the plating liquid for thereby preventing the
generated gas from remaining on the surface W1 to be plated.
[0083] (Method for forming a flow of a plating liquid in a certain
direction so as to remove the gas)
[0084] In this method, for example, as shown in FIG. 7, a magnetic
stirrer S rotatable by a magnetic force applied from the outside is
placed in the vicinity of a bottom surface of the plating liquid
125, and is rotated to create a flow of the plating liquid as shown
by arrows in FIG. 7 (flow directed from a central portion of the
surface W1 to be plated to an outer periphery of the surface W1 to
be plated), whereby the gas generated at the lower surface W1 to be
plated is discharged in an outer peripheral direction. As a means
for creating a flow of a plating liquid, besides the magnetic
stirrer S, a method for rotating an impeller by a motor, a method
for injecting the plating liquid from a nozzle, or various other
methods are conceivable.
[0085] (Method for bringing the surface W1 to be plated into
contact with the plating liquid in such a state that the surface W1
to be plated is inclined)
[0086] In this method, for example, as shown in FIG. 8, the surface
W1 to be plated is dipped in the plating liquid 125 in such a state
that the substrate holding apparatus 110, the semiconductor
substrate W held by the substrate holding apparatus 110 and the
rotation drive shaft 111 are inclined altogether at a certain angle
to horizontal, whereby the gas generated at the lower surface W1 to
be plated is caused to ascend along the inclined surface W1 to be
plated, and is removed.
[0087] (Method for rotating the semiconductor substrate W about a
shaft other than a shaft perpendicular to the surface of the
substrate W, while making the surface W1 to be plated be
inclined)
[0088] In this method, for example, as shown in FIG. 9, only the
rotation drive shaft 111 is vertically provided in such a state
that both the substrate holding apparatus 110 and the semiconductor
substrate W held by the substrate holding apparatus 110 are
inclined at a predetermined angel to horizontal (namely, the
rotation drive shaft 111 is attached so as to be inclined to a
plane of the substrate holding apparatus 110), and in this state,
the rotation drive shaft 111 is rotated. With this arrangement, the
gas generated at the lower surface W1 to be plated can be caused to
ascend along the surface W1 to be plated and the plating liquid is
stirred by swinging the substrate holding apparatus 110 and the
semiconductor substrate W up and down, thereby effectively removing
the gas.
[0089] (Method for rotating the semiconductor substrate W about a
shaft other than a shaft perpendicular to the surface of the
substrate W, while making the surface W1 to be plated be inclined,
and further positioning the rotation center at a location other
than a center of the semiconductor substrate W)
[0090] In this method, for example, as shown in FIG. 10, only the
rotation drive shaft 111 is vertically provided in such a state
that both the substrate holding apparatus 110 and the semiconductor
substrate W held by the substrate holding apparatus 110 are
inclined at a predetermined angel to horizontal (namely, the
rotation drive shaft 111 is attached so as to be inclined to a
plane of the substrate holding apparatus 110), and the rotation
drive shaft 111 is attached at the position other than a center of
the semiconductor substrate W, and the rotation drive shaft 111 is
rotated. With this arrangement, the gas generated at the lower
surface W1 to be plated can be caused to ascend along the surface
W1 to be plated and the plating liquid is stirred by rotating the
substrate holding apparatus 110 and the semiconductor substrate W
eccentrically, while swinging the substrate holding apparatus 110
and the semiconductor substrate W up and down, thereby removing the
gas more effectively.
[0091] Although the embodiments of the present invention have been
described with reference to FIGS. 6 through 10, the present
invention is not limited to the above embodiments and may be
modified within the scope of technical ideas described in the
claims, specification and drawings. Further, even if any shape,
structure and material are not described directly in the
specification and drawings, if they have the same function and
effect as the present invention, then they are encompassed within
the scope of the technical ideas of the present invention. For
example, the electroless plating apparatus according to the present
invention is used not only for forming a seed layer or a copper
layer for an interconnect, but also for forming an
interconnection-protective film and a diffusion-preventive film.
Further, the electroless plating apparatus according to the present
invention can be used for a pretreatment process of the electroless
plating and a catalyst treatment process. Specifically, instead of
the electroless plating liquid, by using other electroless plating
treatment liquids used for the pretreatment process and the
catalyst treatment process, these treatment processes can be
performed by this electroless plating apparatus. Further, in the
above embodiments, the examples in which the electroless plating is
applied to the semiconductor substrate W are described. However,
the present invention is applicable to the electroless plating for
various substrates other than the semiconductor substrate.
[0092] As described above in detail, according to the second aspect
of the present invention, the following excellent effects can be
obtained.
[0093] {circle over (1)} Since the surface, to be plated, of the
semiconductor substrate can be brought into contact with the
plating liquid in such a state that the surface to be plated faces
downward, the depth of the plating treatment liquid can be small,
and hence the plating treatment liquid holding apparatus for
storing the plating treatment liquid can be downsized, and the
whole apparatus can be downsized.
[0094] {circle over (2)} Since the surface, to be plated, of the
semiconductor substrate can be brought into contact with the
plating liquid in such a state that the surface to be plated faces
downwardly, the depth of the plating treatment liquid can be small,
and the amount of the plating treatment liquid to be used can be
small, and the temperature of the plating treatment liquid can be
accurately controlled. In addition, the electric power consumption
for heating and retaining warmth can be reduced.
[0095] {circle over (3)} Since the surface to be plated is brought
into contact with the electroless plating treatment liquid in such
a state that the surface to be plated is inclined, the gas
generated at the surface to be plated can be easily removed from
the surface to be plated.
[0096] {circle over (4)} In the case where a flow of the
electroless plating treatment liquid is formed in a predetermined
direction on the surface to be plated, the gas generated at the
surface to be plated can be entrained by the flow of the
electroless plating treatment liquid and can be easily removed from
the surface to be plated.
[0097] {circle over (5)} In the case where the heater is provided
in the plating treatment liquid holding apparatus itself, the
apparatus can be downsized.
* * * * *