U.S. patent application number 10/995174 was filed with the patent office on 2005-04-07 for plating apparatus and method.
Invention is credited to Inoue, Hiroaki, Karimata, Tsutomu, Kunisawa, Junji, Matsumoto, Moriji, Mishima, Koji, Nakamura, Kenji.
Application Number | 20050074559 10/995174 |
Document ID | / |
Family ID | 26602873 |
Filed Date | 2005-04-07 |
United States Patent
Application |
20050074559 |
Kind Code |
A1 |
Inoue, Hiroaki ; et
al. |
April 7, 2005 |
Plating apparatus and method
Abstract
The present invention relates to an electroless plating
apparatus which can reduce an amount of a plating liquid to be
used, maintain a stable plating process, be downsized, reduce an
apparatus cost, form a film having a uniform thickness over an
entire surface, and prevent a plating liquid from being
deteriorated due to a temperature rise. The present invention
comprises: a holding device for holding a substrate with a surface,
to be plated, facing upwardly; a plating liquid holding mechanism
for sealing a periphery of the surface, to be plated, of the
substrate held by the holding device; an electroless plating
treatment liquid supply device for supplying an electroless plating
liquid to the surface, to be plated, of the substrate sealed by the
plating liquid holding mechanism to allow supplied electroless
plating liquid to be held on the substrate; and a heating apparatus
provided below the substrate.
Inventors: |
Inoue, Hiroaki; (Tokyo,
JP) ; Mishima, Koji; (Fujisawa-shi, JP) ;
Karimata, Tsutomu; (Yokohama-shi, JP) ; Nakamura,
Kenji; (Fujisawa-shi, JP) ; Matsumoto, Moriji;
(Fujisawa-shi, JP) ; Kunisawa, Junji; (Yamato-shi,
JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W.
SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
26602873 |
Appl. No.: |
10/995174 |
Filed: |
November 24, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10995174 |
Nov 24, 2004 |
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09983401 |
Oct 24, 2001 |
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6858084 |
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Current U.S.
Class: |
427/443.1 ;
257/E21.174; 257/E21.585 |
Current CPC
Class: |
H01L 21/76873 20130101;
H01L 21/288 20130101; H01L 2221/1089 20130101; C23C 18/1619
20130101; H01L 21/76849 20130101; H01L 21/76877 20130101; H01L
21/76843 20130101; H01L 21/76874 20130101 |
Class at
Publication: |
427/443.1 |
International
Class: |
B05D 003/12 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 26, 2000 |
JP |
2000-327798 |
Oct 26, 2000 |
JP |
2000-327801 |
Claims
What is claimed is:
1. An electroless plating method comprising: using a transfer
apparatus to transfer a substrate from a load and unload section to
a pretreatment section; at said pretreatment section removing an
oxide film from a metal on a surface of said substrate, using an
electroless plating apparatus to form an electroless-plated film on
said metal on said surface of said substrate so as to form an
electroless-plated substrate; transferring said electroless-plated
substrate from said electroless plating apparatus to a cleaning and
drying treatment section; cleaning and drying said
electroless-plated substrate at said cleaning and drying treatment
section so as to provide a cleaned and dried substrate; and
returning said cleaned and dried substrate to said load and unload
section.
2. The electroless plating method according to claim 1, further
comprising: depositing catalyst on said metal on said surface of
said substrate after removing said oxide film from said metal on
said surface of said substrate; and rinsing said surface of said
substrate.
3. The electroless plating method according to claim 2, further
comprising: neutralizing said surface of said substrate at a
plating pretreatment section after rinsing said surface of said
substrate.
4. The electroless plating method according to claim 1, further
comprising: supplying a cleaning liquid to said electroless-plated
substrate, thereby stopping an electroless plating reaction.
5. The electroless plating method according to claim 1, wherein
said substrate is a semiconductor substrate and said surface of
said substrate comprises said metal and an insulating film.
6. The electroless plating method according to claim 5, wherein
said electroless-plated film on said metal is a protective
film.
7. The electroless plating method according to claim 6, wherein a
thickness of said protective film is in a range of from 0.1 to 500
nm.
8. The electroless plating method according to claim 6, wherein
cleaning said electroless-plated substrate comprises using a sponge
to clean said electroless-plated substrate.
Description
[0001] This application is a Divisional of U.S. Ser. No.
09/983,401, filed Oct. 24, 2001.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to plating apparatus and
method which are preferably used for forming interconnects on a
semiconductor substrate (including forming a seed layer, and
forming a reinforcing seed layer on a seed layer for a purpose of
reinforcing the seed layer), an interconnection-protective film,
and a diffusion-preventive film.
[0004] 2. Description of the Related Art
[0005] Conventionally, aluminum or aluminum alloy have been
generally used as a material for forming interconnect circuits on
semiconductor substrates. As integrated density has increased in
recent years, there is a demand for employing a material having a
higher conductivity as an interconnect material. Thus, there has
been proposed a method in which copper or copper alloy is used as
an interconnect material, and is filled into interconnect pattern
trenches formed in a semiconductor substrate by plating the
substrate.
[0006] There have been known various processes including CVD
(chemical vapor deposition), sputtering, and the like to fill
interconnect pattern trenches with copper or copper alloy. However,
in a case where a metal layer comprises copper or copper alloy,
i.e., a copper interconnect is formed, the CVD process is costly
for forming the copper interconnect, and it is impossible for the
sputtering process to fill copper or copper alloy into interconnect
pattern trenches having a high aspect ratio, i.e., a high ratio of
depth to width. A plating process does not have these drawbacks and
is most effective to fill copper or copper alloy into interconnect
pattern trenches.
[0007] On the other hand, instead of an electroless plating
apparatus for performing electroless plating treatment by providing
a plurality of units for carrying out a plating process, a
pretreatment process associated with plating, and a cleaning
process, there has been proposed an electroless plating apparatus
for performing these various processes by a single unit. FIG. 10 is
a schematic view showing this kind of electroless plating
apparatus. As shown in FIG. 10, the electroless plating apparatus
comprises a holding apparatus (holding device) 81 rotated by a
motor M, and a cover 83 disposed around a periphery of a
semiconductor substrate W placed on and held by the holding
apparatus 81. In the electroless plating apparatus, while the
semiconductor substrate W is rotated by the motor M at a position
indicated by dotted lines in FIG. 10, a plating liquid is supplied
from a plating tank 87 to a central upper surface of the
semiconductor substrate W by a pump P. While the plating liquid is
spreading on an entire upper surface of the semiconductor substrate
W under centrifugal force caused by rotation of the semiconductor
substrate W, for thereby plating the semiconductor substrate W, the
plating liquid which has fallen from the semiconductor substrate W
is returned from a plating liquid recovery section 85 of the cover
83 to the plating tank 87, and is then circulated.
[0008] On the other hand, the semiconductor substrate W which has
been plated is lowered to a position indicated by solid lines in
FIG. 10 and rotated at such position, and cleaning water is
supplied to the semiconductor substrate W from a non-illustrated
cleaning water supply apparatus (cleaning water supply device),
whereby plating liquid is rinsed from the surface of the
semiconductor substrate W, and used cleaning water is collected by
a cleaning liquid recovery section 86 from which collected cleaning
water is drained.
[0009] However, the above conventional electroless plating
apparatus also the following various problems:
[0010] {circle over (1)} Because a plating liquid is always
supplied onto a surface, to be plated, of a semiconductor
substrate, a large amount of plating liquid is circulated and used.
When a large amount of plating liquid is circulated and used, a
large-sized pump is required. Thus, a liquid temperature
maintaining apparatus which prevents a temperature rise of the
liquid due to heat generation of the pump is needed to be provided,
thereby increasing an apparatus cost and enlarging the apparatus,
and hence increasing a cost for a clean room in which this
apparatus is accommodated.
[0011] {circle over (2)} Because plating liquid is always
circulated and used, by-products are accumulated in a system
performing electroless plating, and a stable plating process cannot
be maintained. In order to perform a stable plating process, an
apparatus for analyzing and adjusting a plating liquid is needed to
be installed, thus increasing an apparatus cost and a clean room
cost.
[0012] {circle over (3)} Because a large amount of plating liquid
is circulated and used, particles tend to be generated from
respective components of the apparatus. Thus, it is necessary to
install a filter F in a circulation path so as to increase an
apparatus cost and a clean room cost.
[0013] {circle over (4)} When plating is performed in such a state
that plating liquid is always supplied only to a certain portion of
the surface to be plated, a thickness of plated film at the portion
where the plating liquid has been supplied is smaller than a
thickness of plated film at other portions, as confirmed by
experiments. Thus, uniformity of a film thickness on the surface
deteriorates. A reason for this is that flow rate and thickness of
the plating liquid, and the like at the portion where the plating
liquid has been supplied is different from those at other portions,
and hence plating reaction states are different from each
other.
[0014] {circle over (5)} In order to perform electroless plating, a
temperature of a reaction surface between the surface to be plated
and plating liquid is required to be maintained at a predetermined
constant temperature. Therefore, a device for constantly heating a
large amount of the plating liquid to a temperature optimum for a
plating reaction is required to be provided, thus increasing an
apparatus cost and a clean room cost. Further, since a temperature
rise of plating liquid is necessary at all times, deterioration of
the plating liquid is hastened.
[0015] {circle over (6)} A semiconductor substrate is always
rotated, and hence heat dissipation due to peripheral speed of the
semiconductor substrate causes a remarkable temperature drop,
resulting in a failure to obtain a stable plating process.
[0016] {circle over (7)} In a case where a plating liquid is
supplied to the surface to be plated not by dropping but by
spraying, temperature control of the plating liquid becomes
uncertain, and a stable plating process cannot be obtained.
[0017] Further, if an interconnect pattern having a uniform
thickness should be formed on the semiconductor substrate by
electroless copper plating, it is essential to maintain a plating
temperature at respective plating reaction portions of the
semiconductor substrate at a predetermined high temperature. In
this case, FIG. 1 is a view showing measured results, obtained by
experiments, of relationships between plating liquid temperature
and film thickness in electroless copper plating.
[0018] Plating conditions in the experiments are as follows:
[0019] {circle over (1)} Specifications of the plating liquid
1 CuSO.sub.4.5H.sub.2O 2.5 g/l EDTA.2Na 20 g/l NaOH 4 g/l HCHO
(37%) 5 ml/l
[0020] {circle over (2)} Samples used in plating
[0021] Semiconductor substrate having a diameter of 8 inches
wherein a barrier layer of TaN (20 nm) and a Cu seed layer (full
plating) are formed on silicone.
[0022] {circle over (3)} Plating Time
[0023] 60 seconds
[0024] An electroless plating was applied to semiconductor
substrates under the above plating conditions. As a result, as
shown in FIG. 11, it was found that when a temperature of the
plating liquid varied by 1.degree. C. during a plating time period
of one minute, a difference of film thickness amounted to
approximately 1.8 nm, and as plating temperature increased,
thickness of plated film increased. Therefore, as described above,
in order to perform electroless plating so as to form a plated film
having a desired thickness and a uniform thickness over an entire
surface of the semiconductor substrate, the plating liquid must be
maintained at a predetermined high temperature, and temperatures at
respective portions of the semiconductor substrate must be
controlled to be uniform during plating reaction.
[0025] Thus, in the conventional plating apparatus, there has been
employed a mechanism for bringing a plating liquid, whose
temperature has been increased in advance to a plating treatment
temperature or higher, into contact with a surface, to be plated,
of a semiconductor substrate and keeping a surface of plating
reaction warm by virtue of a heater or a lamp.
[0026] However, in the conventional method, it has been difficult
to keep the surface of plating reaction of the semiconductor
substrate warm at a predetermined temperature accurately at all
times during plating reaction. Particularly, in a case of a single
wafer processing plating apparatus in which semiconductor
substrates are plated one by one, a temperature of the
semiconductor substrates must be increased one by one. In this
case, it has been difficult to heat a semiconductor substrate to a
predetermined temperature accurately and quickly and keep the
semiconductor substrate at the predetermined temperature.
SUMMARY OF THE INVENTION
[0027] 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 reduce an
amount of a plating liquid to be used, maintain a stable plating
process, be downsized, reduce an apparatus cost, form a film having
a uniform thickness over an entire surface, and prevent a plating
liquid from being deteriorated due to a temperature rise.
[0028] Further, a second object of the invention is to provide
plating apparatus and method which can accurately keep a surface of
plating reaction of a substrate warm at a predetermined temperature
at all times during plating reaction, perform stable and reliable
plating, and improve throughput.
[0029] In order to achieve the first object, according to an aspect
of the present invention, there is provided an electroless plating
apparatus comprising: a holding device for holding a substrate with
a surface, to be plated, facing upwardly; a plating liquid holding
mechanism for sealing a periphery of the surface, to be plated, of
the substrate held by the holding device; an electroless plating
treatment liquid supply device for supplying an electroless plating
liquid to the surface, to be plated, of the substrate sealed by the
plating liquid holding mechanism to allow supplied electroless
plating liquid to be stored on the substrate; a heating device
provided below the substrate; and a gap (space) formed between the
heating device and the substrate. This gap (space) constitutes a
uniform temperature forming section by being filled with gas or
liquid.
[0030] With this arrangement, treatment of the surface to be plated
can be performed using a small amount of electroless plating
treatment liquid, a pump of a small size can be used as a pump for
supplying the electroless plating treatment liquid, the electroless
plating apparatus can be made compact, and cost for a clean room
housing the apparatus can be reduced. Since a small amount of
electroless plating treatment liquid is used, heating and warmth
retention of the electroless plating treatment liquid can be easily
and promptly performed.
[0031] Further, because the gap (uniform temperature forming
section) which can be filled with gas or liquid is provided between
the heating device and the substrate, even if a heating device
having a non-uniform surface temperature distribution, for example,
a wire-like heater arranged in a ring (spiral) shape is used, the
gap (uniform temperature forming section) can have the same
temperature at an entire plane, and a heating temperature at
respective portions of the substrate can be made uniform. In the
electroless plating apparatus, a pretreatment liquid, a catalytic
treatment liquid, an electroless plating liquid or the like can be
used as an electroless plating treatment liquid while switching any
of these liquids, and hence a series of electroless plating steps
can be carried out in a single cell.
[0032] According to an aspect of the present invention, there is
provided an electroless plating apparatus comprising: a holding
device for holding a substrate with a surface, to be plated, facing
upwardly; a plating liquid holding mechanism for sealing a
periphery of the surface, to be plated, of the substrate held by
the holding device; an electroless plating treatment liquid supply
device for supplying an electroless plating liquid to the surface,
to be plated, of the substrate sealed by the plating liquid holding
mechanism to allow supplied electroless plating liquid to be stored
on the substrate; a heating device provided in the vicinity of the
substrate for heating the substrate in its entirety; and a
temperature control device for controlling a temperature of the
heating device; wherein the heating device has a plurality of
divided zones and temperatures in respective zones are controlled
respectively by the temperature control device .
[0033] In many cases, cooling rates of a heated substrate held by
the holding device are different at respective portions of the
substrate, and the substrate normally begins to be cooled from an
outer periphery of the substrate. In such a case, as in the present
invention, it is desirable that the heating device be divided into
a plurality of zones, and temperatures in respective zones are
controlled, respectively. For example, the heating device is
divided into a zone facing a central portion of the substrate and a
zone facing an outer peripheral portion of the substrate, and a
temperature in the zone facing the outer peripheral portion of the
substrate is caused to be higher than a temperature in the zone
facing the central portion of the substrate for thereby making
uniform a temperature of the substrate in its entirety.
[0034] According to an aspect of the present invention, there is
provided an electroless plating apparatus comprising: a holding
device for holding a substrate with a surface, to be plated, facing
upwardly; a plating liquid holding mechanism for sealing a
periphery of the surface, to be plated, of the substrate held by
the holding device; an electroless plating treatment liquid supply
device for supplying an electroless plating treatment liquid to the
surface, to be plated, of the substrate sealed by the plating
liquid holding mechanism to allow supplied electroless plating
liquid to be stored on the substrate; a heating device provided in
the vicinity of the substrate; and a lid member for covering the
substrate to which the electroless plating treatment liquid has
been supplied.
[0035] By placing the lid member over the substrate during an
electroless plating treatment, evaporation of electroless plating
treatment liquid and heat dissipation caused by generation of air
current can be suppressed, and hence plating of the substrate can
be more effectively performed. The lid member may be or may not be
brought into contact with a liquid surface of the electroless
plating treatment liquid.
[0036] According to a preferred aspect of the present invention,
the electroless plating treatment liquid supply device is provided
above a surface, to be plated, of a substrate, and has such a shape
that the electroless plating treatment liquid supply device covers
the surface, to be plated, of the substrate to which electroless
plating treatment liquid is supplied, thus serving also as the lid
member.
[0037] If the electroless plating treatment liquid supply device
serves also as the lid member, the apparatus can be compact and
reduced in cost.
[0038] According to a preferred aspect of the present invention,
the electroless plating apparatus has a mechanism for sucking and
recovering electroless plating treatment liquid remaining on a
surface, to be plated, of a substrate.
[0039] Further, in order to achieve the second object, according to
an aspect of the present invention, there is provided a plating
apparatus comprising a plating treatment chamber including a
holding device for holding a substrate with a surface, to be
plated, facing upwardly; a plating treatment liquid holding
mechanism for sealing a periphery of the surface, to be plated, of
the substrate held by the holding device; and a device for
supplying plating treatment liquid to the surface, to be plated, of
the substrate sealed by the plating treatment liquid holding
mechanism; wherein the plating treatment chamber constitutes a
thermostatic chamber for maintaining an inner space of the plating
treatment chamber at a temperature higher than an exterior
temperature. With this arrangement, plating can be stably and
reliably performed, and throughput can be improved.
[0040] According to a preferred aspect of the present invention, a
plating treatment chamber is provided for applying plating
treatment to a surface, to be plated, of a substrate by bringing a
plating treatment liquid into contact with the surface, to be
plated, of the substrate, and an inner space of the plating
treatment chamber constitutes a thermostatic chamber for
maintaining the inner space of the plating treatment chamber at a
temperature substantially equal to a plating treatment
temperature.
[0041] According to a preferred aspect of the present invention, a
substrate to be carried into a plating treatment chamber and
plating treatment liquid are preheated to a temperature
substantially equal to a temperature in the plating treatment
chamber. With this arrangement, optimum plating treatment reaction
can be instantaneously obtained only by supplying a plating
treatment liquid to the semiconductor substrate which has been
carried into the plating treatment chamber, and throughput can be
improved.
[0042] According to a preferred aspect of the present invention, a
substrate storage chamber is provided adjacent to a plating
treatment chamber for housing plural substrates to be treated and
supplying them to the plating treatment chamber, and an inner space
of the substrate storage chamber constitutes a substrate preheating
area for maintaining an inner space of the substrate storage
chamber at a temperature substantially equal to a temperature in
the plating treatment chamber.
[0043] According to a preferred aspect of the present invention, a
plating treatment liquid storage chamber is provided adjacent to a
plating treatment chamber for storing a plating treatment liquid,
and an inner space of the plating treatment liquid storage chamber
constitutes a plating treatment liquid preheating area for
maintaining an inner space of the plating treatment liquid storage
chamber at a temperature substantially equal to a temperature in
the plating treatment chamber.
[0044] According to the present invention, there is provided a
substrate plating method comprising: using a holding device to hold
a substrate with a surface, to be plated, facing upwardly; and
supplying a plating liquid to the surface, to be plated, of the
substrate and performing a plating treatment while a periphery of
the surface, to be plated, of the substrate is sealed by a plating
liquid holding mechanism; wherein the plating treatment is
performed in a thermostatic chamber.
BRIEF DESCRIPTION OF THE DRAWINGS
[0045] FIGS. 1A through 1C are views showing an example of a
plating process;
[0046] FIG. 2 is a schematic view showing an electroless plating
apparatus according to a first embodiment of the present
invention;
[0047] FIG. 3 is a plan view of a backside heater;
[0048] FIG. 4 is a schematic view showing an electroless plating
apparatus according to another embodiment of the present
invention;
[0049] FIG. 5 is a schematic view showing an electroless plating
apparatus according to another embodiment of the present
invention;
[0050] FIG. 6 is a schematic view showing an electroless plating
apparatus according to another embodiment of the present
invention;
[0051] FIG. 7 is a plan view showing an example of a plating
treatment apparatus having the electroless plating apparatus shown
in FIG. 2;
[0052] FIG. 8 is a plan view showing another example of a plating
treatment apparatus having the electroless plating apparatus shown
in FIG. 2;
[0053] FIG. 9 is a schematic view showing a plating apparatus
according to a second embodiment of the present invention;
[0054] FIG. 10 is a schematic view showing a conventional
electroless plating apparatus; and
[0055] FIG. 11 is a view showing measured results of relationships
between temperature of a plating liquid and thickness of plated
film formed by electroless copper plating.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0056] Embodiments of the present invention will be described below
with reference to drawings. An electroless plating apparatus
according to a first embodiment of the present invention is used
for, for example, forming a seed layer or an interconnect
comprising a copper layer by applying electroless copper plating
onto a surface of a semiconductor substrate W. An example of this
plating process will be described with reference to FIGS. 1A
through 1C.
[0057] As shown in FIG 1A, an insulating film 2 of SiO.sub.2 is
deposited on a conductive layer la of a substrate I on which
semiconductor devices are formed, and a via hole 3 and a trench 4
for an interconnect are formed by performing lithography and
etching technology. Thereafter, a barrier layer 5 of TiN or the
like is formed on the insulating layer 2 and conductive layer 1a,
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
preformed by sputtering or the like, and a reinforcing seed layer
is formed by electroless copper 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 a surface of the copper 6 filled into the
via hole 3 and the trench 4 for the interconnect lie substantially
flush with a surface of the insulating film 2, and then an
interconnection-protective film 8 is formed on an exposed metal
surface.
[0058] FIG. 2 is a schematic view showing an electroless plating
apparatus according to an embodiment of the present invention. 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 for 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 for the nickel
alloy plating comprises nickel chloride or nickel sulfate to which
sodium hypophosphite as a reducing agent in a case for Ni--P film,
sodium borohydride as a reducing agent in a case for Ni--B film,
and other agents, such as a complexing agent and a pH buffer agent
are added.
[0059] As shown in FIG. 2, this electroless plating apparatus 10
comprises a holding apparatus (holding device ) 11 for holding a
semiconductor substrate W to be plated on its upper surface, a dam
member (plating liquid holding mechanism) 31 for contacting a
peripheral edge portion of a surface to be plated (upper surface)
of the semiconductor substrate W held by the holding apparatus 11
to seal the peripheral edge portion, and a shower head (electroless
plating treatment liquid (scattering) supply device ) 41 for
supplying a plating liquid (electroless plating treatment liquid)
to the surface, to be plated, of the semiconductor substrate W
having the peripheral edge portion sealed with the dam member 31.
The electroless plating apparatus 10 further comprises a cleaning
liquid supply apparatus (cleaning liquid supply device ) 51
disposed near an upper outer periphery of the holding apparatus 11
for supplying a cleaning liquid to the surface, to be plated, of
the semiconductor substrate W, a recovery vessel 61 for recovering
a cleaning liquid or the like (plating waste liquid) discharged, a
plating liquid recovery nozzle 65 for sucking in and recovering
plating liquid held on the semiconductor substrate W, and a motor
(rotational drive device ) M for rotationally driving the holding
apparatus 11. These respective members will be described below.
[0060] The holding apparatus 11 is adapted to be rotated by the
motor M and is movable vertically by a non-illustrated raising and
lowering apparatus (raising and lowering device ). The holding
apparatus 11 has a substrate placing portion 13 on its upper
surface for placing and holding the semiconductor substrate W.
[0061] The substrate placing portion 13 is adapted to place and fix
the semiconductor substrate W thereon, and has a uniform
temperature forming section 17, at its portion where the
semiconductor substrate W is placed, which comprises a circular
recess having an inner diameter slightly smaller than a diameter of
the semiconductor substrate W. Temperature sensors 14 are embedded
respectively in predetermined positions of a central portion and a
peripheral portion of the uniform temperature forming section 17.
These temperature sensors 14 are composed of, for example, infrared
ray sensors for detecting a temperature of a backside surface of
the semiconductor substrate which faces these sensors. On the other
hand, backside heaters (heating apparatus (heating device )) 15-1,
15-2 for heating a surface, to be plated, of the semiconductor
substrate W from an underside thereof are provided below the
uniform temperature forming section 17. As shown in FIG. 3, the
backside heater 15-1 comprises a circular backside heater centrally
disposed, and the backside heater 15-2 comprises a ring-like
backside heater disposed so as to surround the backside heater
15-1. These backside heaters 15-1, 15-2 are composed of, for
example, a rubber heater and are controlled at respective
predetermined temperatures by a temperature control apparatus
(temperature controlling device) 20 shown in FIG. 3. Temperature
detection signals from respective temperature sensors 14 are
inputted to the temperature control apparatus 20.
[0062] The dam member 31 is tubular, has a seal portion 33 provided
in a lower portion thereof for sealing the outer peripheral edge of
the semiconductor substrate W, and is installed so as not to move
vertically from its illustrated position.
[0063] The shower head (electroless plating treatment liquid
(scattering) supply device) 41 is of a structure having many
nozzles provided at a front end for scattering supplied plating
liquid in a shower form and supplying the liquid substantially
uniformly to the surface, to be plated, of the semiconductor
substrate W. Thus, it is desirable that the plating liquid to be
supplied is heated to a temperature (for example, 50.degree. C.)
suitable for plating. Therefore, it is desirable for a piping
extending from a plating liquid supplying source to the shower head
(plating liquid supply device) 41 to use a material having a high
heat retaining property. For example, the piping has a double-tube
structure in which a plating liquid flows through a central passage
and a heat insulating medium (warmth retention means) is filled
into an outer passage defined between the tubes of the double-tube
structure. The heat insulating medium comprises, for example, gas
such as air or liquid such as water or warm water heated to a
predetermined temperature (for example, 50.degree. C.). When heated
gas or liquid is filled into the outer passage, even if a
temperature of the plating liquid is low in the plating liquid
supply source, the plating liquid is heated in the piping, thus
making it possible to increase a temperature of the plating liquid
suitable for plating when the plating liquid reaches the shower
head 41. On the other hand, the cleaning liquid supply apparatus 51
has a structure for ejecting a cleaning liquid from a nozzle
53.
[0064] The plating liquid recovery nozzle 65 is adapted to be
movable upwardly and downwardly and is swingable, and a front end
of the plating liquid recovery nozzle 65 is adapted to be lowered
inwardly of the dam member 31 located on the upper peripheral edge
portion of the semiconductor substrate W and suck in plating liquid
on the semiconductor substrate W.
[0065] Next, peration of the electroless plating apparatus will be
described. First, the holding apparatus 11 is lowered from its
illustrated state to provide a gap of a predetermined dimension
between the holding apparatus 11 and the dam member 31, and
semiconductor substrate W is placed on and fixed to the substrate
placing portion 13. At this time, the uniform temperature forming
section 17 is closed. An 8 inch wafer, for example, is used as the
semiconductor substrate W.
[0066] Then, the holding apparatus 11 is raised to bring its upper
surface into contact with a lower surface of the dam member 31 as
illustrated, and an outer periphery of the semiconductor substrate
W is sealed with the seal portion 33 of the dam member 31. At this
time, a surface of the semiconductor substrate W is in an open
state.
[0067] Then, the semiconductor substrate W itself is heated through
the uniform temperature forming section 17, comprising an air
layer, by the backside heaters 15-1, 15-2 to render a temperature
of the semiconductor substrate W, for example, 70.degree. C.
(maintained until termination of plating). Then, plating liquid
heated, for example, to 50.degree. C. is ejected from the shower
head 41 to pour the plating liquid over substantially an entire
surface of the semiconductor substrate W. H eating temperatures of
the backside heaters 15-1, 15-2 are controlled by the temperature
control apparatus 20 shown in FIG. 3 according to temperatures of
respective portions of the semiconductor substrate detected by
respective temperature sensors 14. For example, the semiconductor
substrate W normally tends to be cooled more at its outer
peripheral edge than at its central portion. In such a case, a
heating temperature of the backside heater 15-2 is slightly higher
than that of the backside heater 15-1 for thereby keeping
respective portions of the semiconductor substrate at a uniformly
warm temperature.
[0068] Since the surface of the semiconductor substrate W is
surrounded by the dam member 31, all the poured plating liquid is
held on the surface of the semiconductor substrate W. An amount of
supplied plating liquid may be a small amount which will become 1
mm thick (about 30 ml) on the surface of the semiconductor
substrate W. A depth of the plating liquid held on the surface to
be plated may be 10 mm or less, and may be even 1 mm as in this
embodiment. If a small amount of the supplied plating liquid is
sufficient as in the present embodiment, a heating apparatus for
heating the plating liquid may be of a small size. In this
embodiment, a temperature of the semiconductor substrate W is
raised to 70.degree. C., and a temperature of the plating liquid is
raised to 50.degree. C. by heating. Thus, the surface, to be
plated, of the semiconductor substrate W becomes, for example,
60.degree. C., and hence a temperature optimal for a plating
reaction in this embodiment can be achieved. If the semiconductor
substrate W itself is adapted to be heated as described above, to
raise a temperature of the plating liquid much electric power
consumption is not required. This is preferred, because electric
power consumption can be decreased, and a change in a property of
the plating liquid can be prevented. Electric power consumption for
heating the semiconductor substrate W itself may be small, and an
amount of plating liquid held on the semiconductor substrate W may
be also small. Thus, heat retention of the semiconductor substrate
W by the backside heaters 15-1, 15-2 can be performed easily, a
capacity of the backside heaters can be small, and the apparatus
can be made compact. If a device for directly cooling the
semiconductor substrate W itself is used, switching between heating
and cooling may be performed during plating to change plating
conditions. Since plating liquid held on the semiconductor
substrate is in a small amount, temperature control can be
performed with good sensitivity.
[0069] On the other hand, in the present embodiment, there is
provided the uniform temperature forming section 17, having a gap
(space) between the backside heaters 15-1, 15-2 and semiconductor
substrate W for filling gas therein. Because the uniform
temperature forming section 17 has a large heat capacity, even if
surfaces of the backside heaters 15-1, 15-2 have non-uniform
temperature distribution, respective portions of the uniform
temperature forming section 17 become uniform in temperature, and
thus a backside surface of the semiconductor substrate W can be
heated to a uniform temperature with high accuracy. Although air is
used as gas in this embodiment, various other kinds of gas such as
inert gas may be used.
[0070] The semiconductor substrate W is instantaneously rotated by
the motor M to perform uniform liquid wetting of the surface to be
plated, and then plating of the surface to be plated is performed
in such a state that the semiconductor substrate W is in a
stationary state. Specifically, the semiconductor substrate W is
rotated at 100 rpm (100 min.sup.-1) or less for only 1 second to
uniformly wet the surface, to be plated, of the semiconductor
substrate W with the plating liquid. Then, the semiconductor
substrate W is kept stationary, and electroless plating is
performed for 1 minute. An instantaneous rotating time is at most
10 seconds or less.
[0071] After completion of the plating treatment, the front end of
the plating liquid recovery nozzle 65 is lowered to an area near an
inside of the dam member 31 on the peripheral edge portion of the
semiconductor substrate W to suck in plating liquid. At this time,
if the semiconductor substrate W is rotated at a rotational speed
of, for example, at least 100 rpm (100 min.sup.-1), plating liquid
remaining on the semiconductor substrate W can be gathered at a
portion of the dam member 31 on the peripheral edge portion of the
semiconductor substrate W via centrifugal force, so that recovery
of the plating liquid can be performed with good efficiency and a
high recovery rate. The holding apparatus 11 is lowered to separate
the semiconductor substrate W from the dam member 31. The
semiconductor substrate W is started to be rotated, and a cleaning
liquid (ultrapure water) is jetted at the plated surface of the
semiconductor substrate W from the nozzle 53 of the cleaning liquid
supply apparatus 51 to cool the plated surface and simultaneously
perform dilution of plating liquid and cleaning of the
semiconductor substrate W, thereby stopping an electroless plating
reaction. At this time, the cleaning liquid jetted from the nozzle
53 may be supplied to the dam member 31 to perform cleaning of the
dam member 31. Plating waste liquid at this time is recovered into
the recovery vessel 61, and then discarded.
[0072] Plating liquid once used is not reused, but thrown away. As
described above, since the amount of the plating liquid used in
this apparatus can be made very small, compared with that in the
prior art, an amount of plating liquid which is discarded is small,
even without reuse. In some cases, the plating liquid recovery
nozzle 65 may not be installed, and plating liquid which has been
used may be recovered as a plating waste liquid into the recovery
vessel 6 1, together with a cleaning liquid.
[0073] Then, the semiconductor substrate W is rotated at a high
speed by the motor M for spin-drying, and then the semiconductor
substrate W is removed from the holding apparatus 11.
[0074] FIG. 4 is a schematic view showing an electroless plating
apparatus according to another embodiment of the present invention.
The cleaning liquid supply apparatus 51 and the plating liquid
recovery nozzle 65 shown in FIG. 2 are not shown in FIG. 4 for
convenience of explanation. This embodiment is different from the
embodiment shown in FIG. 2 only in that a lid member 25 for
covering semiconductor substrate W is provided. The lid member 25
is adapted to be movable between a position where the lid member 25
covers an upper surface of dam member 31 and a position where the
lid member 25 does not cover the upper surface of the dam member
31. The lid member 25 is normally located at a position where the
lid member 25 does not cover the upper surface of the dam member
31, and after plating liquid is supplied onto the semiconductor
substrate W by shower head 41, the lid member 25 moves to the
position, shown in FIG. 4, where the lid member 25 covers the upper
surface of the dam member 31.
[0075] By locating the lid member 25 over the semiconductor
substrate W to which plating liquid has been supplied so as to
cover the semiconductor substrate W, evaporation of the plating
liquid and heat dissipation caused by generation of an air current
can be suppressed, and hence temperature control during electroless
plating can be easily performed with high accuracy. In this
embodiment, although a space is defined between plating liquid on
the semiconductor substrate W and the lid member 25, the plating
liquid and the lid member 25 may contact each other (in order to
prevent a temperature of the plating liquid from changing, though
it is normally desirable for the lid member and the liquid to not
contact each other).
[0076] FIG. 5 is a schematic view showing an electroless plating
apparatus according to still other embodiment of the present
invention. In FIG. 5 also, illustration of the cleaning liquid
supply apparatus 51 and the plating liquid recovery nozzle 65 shown
in FIG. 2 is omitted. This embodiment is different from the
embodiment shown in FIG. 4 in that shower head 41 serves also as
lid member 25, without providing the lid member as an independent
and separate member. Specifically, the shower head 41 placed over a
surface, to be plated, of a semiconductor substrate W is adapted to
be movable vertically, and by providing a plate-like projecting
portion 26 on an outer periphery of the shower head 41, the shower
head 41 itself serves as the lid member 25 which is positioned over
the semiconductor substrate W so as to cover the semiconductor
substrate W. With this arrangement, because the lid member 25 is
not required to be provided separately, the apparatus can be
compact and can be manufactured at a low cost.
[0077] FIG. 6 is a schematic view showing an electroless plating
apparatus according to still another embodiment of the present
invention. The embodiment shown in FIG. 6 is different from the
embodiment shown in FIG. 2 in that a hollow uniform temperature
forming section 17 is provided inside holding apparatus 11, instead
of providing a recess-like uniform temperature forming section, and
liquid (for example, water) is filled into the hollow uniform
temperature forming section 17. With this arrangement also, since
the uniform temperature forming section 17, comprising a clearance
(space) for filling liquid having a large heat capacity therein, is
formed between backside heaters 15-1, 15-2 and semiconductor
substrate W, even if surfaces of the backside heaters have
non-uniform temperature distribution, a temperature at respective
portions in the uniform temperature forming section 17 can be
uniform, and a backside surface of the semiconductor substrate W
can be heated to a uniform temperature with high accuracy. Although
liquid such as water is filled into the uniform temperature forming
section 17 in this embodiment, gas such as air may be filled
therein. By providing a piping and a pump for withdrawing liquid
from the hollow uniform temperature forming section 17 to the an
exterior, replacement of liquid or the like may be performed. In
this case, a temperature of the liquid to be supplied is preferably
raised to a predetermined temperature in advance.
[0078] Although embodiments of the present invention have been
described, the present invention is not limited to the above
embodiments, and various modifications may be made within the scope
of the claims and the scope of the technical ideas described in the
specification and drawings. For example, the electroless plating
apparatus according to the present invention is not limited to
formation of a seed layer and a copper layer for interconnects, and
can be used for formation of an interconnection-protective film and
a diffusion-preventive film.
[0079] Further, the electroless plating apparatus according to the
present invention can also be used in a pretreatment step and a
catalyst treatment step for electroless plating. That is, in the
above embodiments, for example, electroless plating was performed
by supplying an electroless plating liquid from shower head 41 to a
surface, to be plated, of a semiconductor substrate W. However,
other electroless plating treatment liquid for use in a
pretreatment step or a catalyst treatment step, for electroless
plating, may be supplied from the shower head 41 before a step of
supplying an electroless plating liquid. Thus, these other
treatment steps can also be performed by this electroless plating
apparatus, together with an electroless plating step.
[0080] In the above embodiments, plating is carried out in such a
state that plating liquid is held on a surface to be plated, and a
substrate is kept stationary. However, the substrate may be rotated
slowly to such a degree that uneven plating does not occur.
[0081] Furthermore, the shower head is not restrictive, if the
plating liquid can be supplied in a scattered manner to the surface
to be plated. For example, there may be provided a nozzle which
supplies the plating liquid while performing a swinging motion or a
translational motion.
[0082] In the above embodiments, cleaning is performed during a
cleaning step, after plating, by supplying cleaning liquid while
holding apparatus 11 is separated from dam member 31. However,
cleaning may be performed by supplying cleaning liquid while the
holding apparatus 11 is not separated from the dam member 31, and
by causing the cleaning liquid to overflow from an upper edge of
the dam member 31. When plating liquid remaining is diluted by
supplying the cleaning liquid, a liquid temperature is
simultaneously lowered, whereupon an electroless plating reaction
comes to an end. Incidentally, the holding apparatus 11 and the dam
member 31 may be separated by raising the dam member 31, instead of
lowering the holding apparatus 11.
[0083] During heating of the semiconductor substrate W by the
backside heaters 15-1, 15-2 (especially during a period from start
of heating to contact of plating liquid with a surface of the
substrate), it is desirable to blow an inert gas such as an argon
(Ar) gas onto the surface, to be plated, of the semiconductor
substrate W in order to prevent oxidation. If a seed layer formed
by sputtering or the like is exposed at the surface of the
semiconductor substrate W, heating of the seed layer may result in
oxidation of a surface of the seed layer. Thus, blowing of such
inert gas is particularly effective when it is attempted to prevent
oxidation of the seed layer and form a plated layer of more uniform
film thickness on the seed layer.
[0084] In the above embodiments, the backside heaters 15-1, 15-2
are used as a heating apparatus for semiconductor substrate W, but
a heater may be provided at other positions close to the substrate.
Moreover, in addition to the use of this heater, a temperature of
surroundings for performing electroless plating may be made
substantially equal to an electroless plating treatment temperature
(a temperature suitable for plating of the surface, to be plated,
which is a reaction surface), whereby heat dissipation can be
prevented to maintain a treatment temperature constant. In this
case, a heated gas may be supplied to surroundings of the
substrate, for example.
[0085] In the above embodiments, a step of instantaneously rotating
a substrate is used as a step of bringing electroless plating
treatment liquid supplied onto a surface, to be plated, of the
substrate into contact with the surface to be plated. Other steps
may include spreading the electroless plating treatment liquid all
over the surface to be plated, by moving the substrate, or moving
the supplied electroless plating treatment liquid. That is, the
step of moving the substrate is, for example, to vibrate or swing
(shakingly move) the substrate to which the electroless plating
treatment liquid is supplied. The step of moving the supplied
electroless plating treatment liquid is, for example, to rake the
supplied electroless plating treatment liquid by using a raking
member, or to blow gas onto a surface of the liquid.
[0086] In the above embodiments, electroless plating on a
semiconductor substrate is illustrated. However, the above
electroless plating apparatus are applicable to many substrates
other than a semiconductor substrate.
[0087] According to the present invention, as described above, the
following excellent effects can be obtained:
[0088] {circle over (1)} Electroless plating treatment liquid is
stored and held on a surface, to be plated, of a substrate for a
predetermined time to treat the surface to be plated. Thus,
treatment of the surface to be plated can be performed using a
small amount of the electroless plating treatment liquid, so that a
cost reduction can be achieved. Further, a pump of a small size can
be used as a pump for supplying electroless plating treatment
liquid, the electroless plating apparatus can be made compact, and
a cost for a clean room housing the apparatus can be reduced. Since
a small amount of electroless plating treatment liquid is used,
heating and warmth retention of the electroless plating treatment
liquid can be easily and promptly performed. Furthermore, there is
no need to constantly heat a large amount of electroless plating
treatment liquid, and hence deterioration of the electroless
plating treatment liquid is not promoted.
[0089] {circle over (2)} Since an amount of electroless plating
treatment liquid used may be small, discarding this liquid as it is
does not lead to a cost increase. A fresh electroless plating
treatment liquid can always be used, and composition of the
treatment liquid can be made constant. By-products generated when
the liquid is used in a circulated manner are not deposited in the
system, and stable treatment such as plating can be carried out
easily. A liquid analyzer or a liquid adjustor for plating liquid
becomes unnecessary, and a decrease in equipment cost and a
decrease in clean room cost can be achieved. Since a large amount
of the electroless plating treatment liquid is not used in a
circulated manner, particles are difficult to be generated from
constituent members of the apparatus, thus obviating a need for a
filter.
[0090] {circle over (3)} Because treatment is performed in such a
state that electroless plating treatment liquid is held on a
surface, to be plated, of a substrate treatment conditions for
respective portions of the surface to be plated can be equalized,
in comparison with a case in which treatment is performed in such a
state that electroless plating treatment liquid is dripped onto a
surface to be plated. Consequently, in-plane uniformity of a
thickness of a resulting plated film can be achieved. Particularly,
when treatment is performed in such a state that a substrate is in
a stationary state, heat dissipation due to peripheral speed of the
substrate does not take place, a reaction temperature can be
uniformized without a fall in the temperature, and a stable process
can be obtained, in comparison with a case in which treatment is
performed in such a state that a substrate is rotated.
[0091] {circle over (4)} Because a gap (uniform temperature forming
section) is provided between a heating apparatus and a substrate,
even if a heating apparatus having non-uniform surface temperature
distribution is used, an entirety of the gap (uniform temperature
forming section) can have the same temperature, and a heating
temperature at respective portions of the substrate can be made
uniform.
[0092] {circle over (5)} Because a heating apparatus is used which
has a plurality of divided zones and temperature control can be
performed in each of the zones, temperature of an entire substrate
can be made uniform.
[0093] {circle over (6)} Because a lid member is provided so as to
cover a substrate to which electroless plating treatment liquid is
supplied, evaporation of the electroless plating treatment liquid
and heat dissipation caused by generation of an air current can be
suppressed, and hence plating of the substrate can be more
effectively performed. Specifically, if an electroless plating
treatment liquid supply apparatus serves also as the lid member,
the apparatus can be made compact and reduced in cost.
[0094] {circle over (7)} A pretreatment liquid, a catalytic
treatment liquid, an electroless plating liquid or the like can be
used as an electroless plating treatment liquid while switching any
of these liquids, and hence a series of electroless plating steps
can be carried out in a single cell, and the apparatus can be made
compact.
[0095] FIG. 7 shows an entire structure of a plating treatment
apparatus in which a series of plating treatments is performed by
electroless plating apparatus 10 shown in FIGS. 1 through 6. This
plating treatment apparatus comprises: a pair of electroless
plating apparatuses 10; load and unload sections 70; plating
pretreatment apparatuses 72 for performing plating pretreatment
such as a catalyst treatment for imparting, for example, Pd
catalyst, or an oxide film removal treatment for removing an oxide
film formed on a surface of an exposed interconnect; temporary
storage sections 74 capable of performing rough cleaning; and
post-cleaning apparatuses 76. The plating treatment apparatus
further comprises a first transfer apparatus 78a for transferring a
substrate between the load and unload sections 70, the
post-cleaning apparatuses 76, and the temporary storage sections
74; and a second transfer apparatus 78b for transferring the
substrate between the plating pretreatment apparatuses 72 and the
temporary storage sections 74.
[0096] Next, a series of plating processes performed by the plating
treatment apparatus having the above structure will be described.
First, a semiconductor substrate held by load and unload section 70
is removed by the first transfer apparatus 78a and placed on
temporary storage section 74. The second transfer apparatus 78b
transfers the semiconductor substrate to plating pretreatment
apparatus 72 in which a plating pretreatment such as a catalyst
imparting treatment of a catalyst such as PdCl.sub.2 liquid, or an
oxide film removal treatment for removing an oxide film formed on a
surface of an exposed interconnect, is performed, and then the
semiconductor substrate is rinsed.
[0097] Then, the second transfer apparatus 78b transfers the
substrate to electroless plating apparatus 10 in which an
electroless plating treatment is performed using a predetermined
reducing agent and a predetermined plating liquid. Next, the
semiconductor substrate, which has been plated, is removed from the
electroless plating apparatus 10 and is transferred to temporary
storage section 74 by the second transfer apparatus 78b. Rough
cleaning of the substrate is performed in the temporary storage
section 74. Then, the first transfer apparatus 78a transfers the
substrate to post-cleaning apparatus 76 where finish-cleaning of
the substrate is performed by a pencil-type sponge and spin-drying
of the substrate is also performed, and then the first transfer
apparatus 78a returns the substrate to the load and unload section
70. Thereafter, the substrate is transported to a plating apparatus
or an oxide film forming apparatus.
[0098] FIG. 8 shows an entire structure of a plating treatment
apparatus for performing a series of plating treatments (cap
plating treatment) for forming the protective film 8 as shown in
FIGS. 1A through 1C. This plating treatment apparatus comprises
load and unload sections 80, a pretreatment section 82, a Pd
depositing section 84, a plating pretreatment section 86, an
electroless plating apparatus 10, and a cleaning and drying
treatment section 88. The plating treatment apparatus further
comprises a transfer apparatus 92 which is movable freely along a
transfer path 90 and transfers a substrate between these
sections.
[0099] Next, a series of plating processes (cap plating treatment)
by the plating treatment apparatus having the above structure will
be described. First, a substrate held by load and unload section 80
is removed by the transfer apparatus 92 and transferred to the
pretreatment section 82 where pretreatment such as another cleaning
of a surface of the substrate is performed. Thereafter, by
depositing Pd on a surface of copper layer 6 (see FIG. 1A) in the
Pd depositing section 84, an exposed surface of the copper layer 6
is activated, and then a plating pretreatment such as a
neutralization treatment is performed in the plating pretreatment
section 86. Next, the substrate is transferred to the electroless
plating apparatus 10 where selective electroless plating is
applied, for example, Co--W--P to a surface of the activated copper
layer 6, and hence an exposed surface of the copper layer 6 is
protected by a Co--W--P film (protective film) 8 as shown in FIG.
1C. This electroless plating liquid comprises, for example, cobalt
salt and tungsten salt to which a reducing agent, a complexing
agent, a pH buffer agent, and a pH regulating agent are added.
[0100] After polishing, electroless Ni--B plating may be applied to
form a protective film (plated film) 8 comprising an Ni--B alloy
film selectively on a surface, of interconnect 6, exposed to an
exterior for thereby protecting the interconnect. A film thickness
of the protective film is in the range of from 0.1 to 500 nm,
preferably 1 to 200 nm, more preferably 10 to about 100 nm.
[0101] The electroless Ni--B plating liquid for forming the
protective film 8 contains, for example, nickel ions, a complexing
agent of nickel ions, and alkylamine borane or borohydride as a
reducing agent for nickel ions, and a pH of the electroless Ni--B
plating liquid is adjusted to be within the range of from 5 to 12
by use of TMAH (tetramethylammonium hydroxide).
[0102] Next, after the cap plating treatment, the substrate is
transferred to the cleaning and drying treatment section 88 where a
cleaning and drying treatment of the substrate is performed. The
substrate which has been cleaned and dried is returned to a
cassette in the load and unload section 80 by the transfer
apparatus 92.
[0103] In the above example, as the cap plating treatment, before
the electroless Co--W--P plating treatment is applied, the exposed
surface of the copper layer 6 which has been activated by
depositing Pd is covered selectively with the Co--W--P film.
However, the cap plating treatment is not limited to the above
example.
[0104] FIG. 9 is a schematic view showing a second embodiment of
the plating apparatus (electroless plating apparatus) according to
the present invention. By using the electroless plating apparatus
shown in FIG. 9, seed layer 7 shown in FIG. 1A can be formed by
copper plating, copper alloy plating, or cobalt alloy plating, the
seed layer can be reinforced by copper plating, copper layer 6
shown in FIG. 1B can be formed by copper plating, and
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 for 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 nickel alloy plating comprises nickel
chloride or nickel sulfate to which sodium hypophosphite as a
reducing agent in a case for Ni-P film, sodium borohydride as a
reducing agent in a case for Ni--B film, and other agents, such as
a complexing agent and a pH buffer agent are added.
[0105] As shown in FIG. 9, the electroless plating apparatus
comprises a plating treatment chamber 40 for performing electroless
plating treatment, a substrate storage chamber 30 for storing
substrates to be treated, and a plating treatment liquid storage
chamber 50 for storing a plating liquid and other plating treatment
liquids, and these chambers are integrally combined.
[0106] The plating treatment chamber 40 comprises a holding
apparatus 11 for holding a semiconductor substrate W to be plated
on its upper surface, a dam member (plating treatment liquid
holding mechanism) 31 for contacting a peripheral edge portion of a
surface, to be plated (upper surface), of the semiconductor
substrate W held by the holding apparatus 11 to seal the peripheral
edge portion, and a shower head (plating treatment liquid supply
device) 41 for supplying a plating liquid to the surface, to be
plated, of the semiconductor substrate W having the peripheral edge
portion sealed with the dam member 31. The plating treatment
chamber 40 further comprises a cleaning liquid supply apparatus 51
disposed near an upper outer periphery of the holding apparatus 11
for supplying a cleaning liquid to the surface, to be plated, of
the semiconductor substrate W, a recovery vessel 61 for recovering
a discharged cleaning liquid or the like (plating waste liquid), a
plating liquid recovery nozzle 65 for sucking in and recovering
plating liquid held on the semiconductor substrate W, and a motor M
for rotationally driving the holding apparatus 11.
[0107] The holding apparatus 11 holds the semiconductor substrate W
by having the semiconductor substrate W placed on the upper surface
of the holding apparatus 11. The holding apparatus 11 has a vacuum
attraction mechanism (not shown) for holding the semiconductor
substrate W under vacuum. The holding apparatus 11 is rotated by
the motor M and is vertically movable by a non-illustrated raising
and lowering apparatus (raising and lowering device). A position
shown by solid lines in FIG. 9 is a position where the
semiconductor substrate W is attached or detached, position A,
located above the above-mentioned position, is a position where the
semiconductor substrate W is cleaned, and position B, located above
position A, is a position where the semiconductor substrate W is
brought into contact with the dam member 31 and is plated.
[0108] The dam member 31 is tubular, has a seal portion provided at
a lower portion thereof for sealing the outer peripheral edge of
the semiconductor substrate W, and is installed so as not to move
vertically from its illustrated position. The shower head (plating
treatment liquid supply device) 41 is of a structure having many
nozzles provided at a front end for scattering supplied plating
liquid in a shower form and supplying the liquid substantially
uniformly to the surface, to be plated, of the semiconductor
substrate W. The cleaning liquid supply apparatus 51 has a
structure for ejecting a cleaning liquid from a nozzle.
[0109] The plating liquid recovery nozzle 65 is adapted to be
movable upwardly and downwardly and is swingable, and a front end
of the plating liquid recovery nozzle 65 is adapted to be lowered
inwardly of the dam member 31 located on the upper peripheral edge
portion of the semiconductor substrate W to suck in plating liquid
on the semiconductor substrate W.
[0110] Further, the substrate storage chamber 30 has a substrate
holding apparatus (substrate holding device) 32 therein, and allows
the substrate holding apparatus 32 to hold a plurality of
semiconductor substrates W vertically arranged at a predetermined
interval. The substrate holding apparatus 32 has such a structure
that the substrate holding apparatus 32 holds the semiconductor
substrates W, and lifts and lowers the semiconductor substrates W
in an elevator manner, and when a semiconductor substrate W held by
a substrate transfer mechanism (not shown) at an upper portion of
the substrate holding apparatus is transferred to the holding
apparatus 11, a subsequent semiconductor substrate W is raised to a
transfer position.
[0111] Further, the plating treatment liquid storage chamber 50 has
a plating treatment liquid storage unit 52 therein, and a plating
liquid and other plating treatment liquids are stored respectively
in the plating treatment liquid storage unit 52, and supplied to
the shower head 41, as required.
[0112] The plating treatment chamber 40 constitutes a thermostatic
chamber in which gas (inert gas, for example, argon gas or the like
is preferable) therein can always be kept at a temperature equal to
a temperature (plating treatment temperature, for example,
60.degree. C.) optimum for electroless plating. With this
arrangement, not only an atmosphere in the plating treatment
chamber 40, but also various members such as the holding apparatus
11 can be kept warm and maintained at a temperature equal to a
plating treatment temperature.
[0113] Furthermore, in this embodiment, both the substrate storage
chamber 30 and the plating treatment liquid storage chamber 50 also
constitute a preheating area (thermostatic chamber) in which gas,
in the respective entire chambers, can be kept at a temperature
equal to a temperature (for example, 60.degree. C.) optimum for an
electroless plating treatment, whereby a number of stored
semiconductor substrates and a plating liquid or the like are
preheated and maintained at a temperature equal to a plating
treatment temperature.
[0114] In order to keep the plating treatment chamber 40, the
substrate storage chamber 30 and the plating treatment liquid
storage chamber 50 warm at the same temperature, gas (warm current
of gas) such as inert gas heated to, for example, a temperature
equal to a plating treatment temperature, is introduced from an
exterior into the substrate storage chamber 30 as shown by an arrow
represented by dotted lines in FIG. 9, and the gas is circulated
between the plating treatment chamber 40 and the plating treatment
liquid storage chamber 50, and then discharged from the plating
treatment chamber 40. Temperature, humidity, and an amount of gas
to be introduced are controlled by, for example, a temperature
sensor and a humidity sensor installed in the plating treatment
chamber 40 so that temperature and humidity in the plating
treatment chamber 40 becomes optimum. As an apparatus for raising a
temperature in the chambers 30, 40 and 50 to a predetermined value
and maintaining such temperature at this value, a heater or a lamp
or the like may be used instead of a warm current of gas. In short,
any heating apparatus (heating device) for raising a temperature in
the chambers 30, 40 and 50 to a predetermined value and maintaining
such temperature at this valve may be used.
[0115] Next, operations of the plating apparatus will be described
below. First, by keeping the plating treatment chamber 40, the
substrate storage chamber 30 and the plating treatment liquid
storage chamber 50 warm at the same temperature as described above,
respective members therein are also kept warm at the same
temperature. Then, a semiconductor substrate W held in the
substrate holding apparatus 32 and placed at a highest position
therein is transferred to the holding apparatus 11 by a substrate
transfer mechanism (not shown), and then the holding apparatus 11
is raised to position B to bring an outer periphery of the
semiconductor substrate W into contact with a lower surface of the
dam member 31, and the outer periphery of the semiconductor
substrate W is sealed with the dam member 31.
[0116] Next, plating liquid is ejected from the shower head 41 to
pour the plating liquid over a surface of the semiconductor
substrate W. Since the surface of the semiconductor substrate W is
surrounded by the dam member 31, all the poured plating liquid is
held on the surface of the semiconductor substrate W and
electroless plating is performed. In the present invention, a
temperature of the semiconductor substrate W and the plating liquid
is raised to a plating treatment temperature (for example,
60.degree. C.) in advance, and an atmosphere inside the plating
treatment chamber 40 and respective members, such as the holding
apparatus 11, are heated to and maintained at substantially the
same temperature as above. Therefore, the semiconductor substrate W
is not required to be heated, and optimum plating of the
semiconductor substrate W is started only by supplying plating
liquid onto the semiconductor substrate W.
[0117] After completion of a plating treatment, a front end of the
plating liquid recovery nozzle 65 is lowered to a position near the
surface of the semiconductor substrate W to suck in the plating
liquid. The holding apparatus 11 is lowered to separate the
semiconductor substrate W from the dam member 31 (position A). The
semiconductor substrate W is started to be rotated, and cleaning
liquid (ultrapure water) is jetted at a plated surface of the
semiconductor substrate W from the cleaning liquid supply apparatus
51 to cool the plated surface, and simultaneously perform dilution
of plating liquid and cleaning of the semiconductor substrate W,
thereby stopping an electroless plating reaction. Plating waste
liquid at this time is recovered into the recovery vessel 61 and
discarded.
[0118] Plating liquid once used is not reused, but thrown away
because an amount of the plating liquid used in this embodiment can
be made very small, compared with that in the prior art.
[0119] Then, the semiconductor substrate W is rotated at a high
speed by the motor M for spin-drying, and then the holding
apparatus 11 is lowered to the position shown by the solid lines
and the semiconductor substrate W is removed from the holding
apparatus 11 to an exterior.
[0120] Although the embodiments of the present invention have been
described, the present invention is not limited to the above
embodiments and may be modified within the scope of claims and the
scope of technical ideas described in the 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 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 plating apparatus according to the present invention
can be used for a pretreatment process of electroless plating, and
also for a catalyst treatment process. Specifically, instead of
electroless plating liquid, by using other 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, structure of a
mechanism for performing electroless plating inside the plating
treatment chamber 40, structure of a mechanism for housing a
plurality of semiconductor substrates W inside the substrate
storage chamber 30, and structure of a mechanism for storing
various kinds of plating treatment liquids inside the plating
treatment liquid storage chamber 50 may be modified in various
ways.
[0121] Further, in the above embodiments, examples in which
electroless plating is applied to semiconductor substrate W are
described. However, the present invention is applicable to
electroless plating for various substrates other than semiconductor
substrates.
[0122] Furthermore, the present invention may be applied to an
electroplating apparatus. A temperature of a plating treatment is
20.degree. C. in a case of chromium electroplating, which is a kind
of the electroplating, 20.degree. C. in a case of Sn
electroplating, and 5 to 20.degree. C. in a case of Sn--Pd solder
bump plating. A temperature of a plating treatment is 60 to
90.degree. C. in a case of electroless Ni plating. Therefore, it
goes without saying that a temperature inside the plating treatment
chamber is changed variously corresponding to a type of plating
being performed.
[0123] In an above embodiment, a temperature in the plating
treatment chamber is kept at a temperature substantially equal to a
temperature optimum for a plating treatment.
[0124] However, in a case where a plating treatment temperature is
higher than an exterior temperature (there are many cases of such
with regard to electroless plating), only by keeping a temperature
in the plating treatment chamber at a temperature higher than an
exterior temperature, can a preferable electroless plating be
performed.
[0125] As described above in detail, according to the present
invention, because a plating treatment chamber constitutes a
thermostatic chamber for maintaining temperature therein at a
temperature substantially equal to a plating treatment temperature
(or temperature higher than an exterior temperature), a surface of
a plating reaction can be accurately kept warm at a predetermined
temperature all during the plating reaction of the substrate, and
hence plating can be stably and reliably performed. Further, by
constructing the apparatus such that a substrate to be carried into
the plating treatment chamber, and the plating treatment liquid are
preheated to a temperature substantially equal to a temperature in
the plating treatment chamber in advance, optimum plating treatment
reaction can be instantaneously obtained only by supplying a
plating treatment liquid to the substrate which has been carried in
the plating treatment chamber, and throughput can be improved.
* * * * *