U.S. patent application number 11/033871 was filed with the patent office on 2005-06-09 for fine particle film forming apparatus and method and semiconductor device and manufacturing method for the same.
This patent application is currently assigned to Kabushiki Kaisha Toshiba. Invention is credited to Hayasaka, Nobuo, Nishino, Hirotaka, Okumura, Katsuya, Sakata, Atsuko, Sasaki, Keiichi.
Application Number | 20050124164 11/033871 |
Document ID | / |
Family ID | 18335285 |
Filed Date | 2005-06-09 |
United States Patent
Application |
20050124164 |
Kind Code |
A1 |
Sakata, Atsuko ; et
al. |
June 9, 2005 |
Fine particle film forming apparatus and method and semiconductor
device and manufacturing method for the same
Abstract
After a barrier film is formed on a pad electrode, Ni particles
having a diameter of 2 .mu.m or less are selectively deposited on
the barrier film, thereby forming a Ni fine particle film. Then, a
bump electrode made of a solder ball is provided on the pad
electrode through the Ni fine particle film. Thereafter, the bump
electrode is melted by a heat treatment to join the Ni fine
particle film to the bump electrode. Thus, a bump electrode
structure is finished.
Inventors: |
Sakata, Atsuko;
(Yokohama-shi, JP) ; Sasaki, Keiichi;
(Yokosuka-shi, JP) ; Hayasaka, Nobuo;
(Yokohama-shi, JP) ; Okumura, Katsuya;
(Yokohama-shi, JP) ; Nishino, Hirotaka;
(Yokohama-shi, JP) |
Correspondence
Address: |
FINNEGAN, HENDERSON, FARABOW, GARRETT & DUNNER
LLP
901 NEW YORK AVENUE, NW
WASHINGTON
DC
20001-4413
US
|
Assignee: |
Kabushiki Kaisha Toshiba
|
Family ID: |
18335285 |
Appl. No.: |
11/033871 |
Filed: |
January 13, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11033871 |
Jan 13, 2005 |
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10314364 |
Dec 9, 2002 |
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10314364 |
Dec 9, 2002 |
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09449941 |
Nov 29, 1999 |
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6538323 |
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Current U.S.
Class: |
438/689 ;
257/E21.508; 257/E23.021 |
Current CPC
Class: |
H01L 2224/0401 20130101;
H01L 2224/11001 20130101; H01L 24/11 20130101; H01L 2924/014
20130101; H01L 2924/05042 20130101; H01L 2224/05022 20130101; H01L
2224/05624 20130101; H01L 2924/01082 20130101; H01L 2924/01322
20130101; H01L 24/13 20130101; H01L 24/05 20130101; H01L 2224/05624
20130101; H01L 2924/01028 20130101; H01L 2924/0105 20130101; H01L
2924/0002 20130101; H01L 2924/01022 20130101; H01L 2924/14
20130101; H01L 2924/01078 20130101; H01L 2924/01005 20130101; H01L
2924/01007 20130101; H01L 2924/01057 20130101; H01L 2924/01014
20130101; H01L 24/03 20130101; H01L 2924/01018 20130101; H01L
2224/13144 20130101; H01L 2924/12042 20130101; H01L 2924/01039
20130101; H01L 2224/13025 20130101; H01L 2224/1147 20130101; H01L
2224/13099 20130101; H01L 24/742 20130101; H01L 2224/0557 20130101;
H01L 2924/00011 20130101; H01L 2924/0002 20130101; H01L 2924/01046
20130101; H01L 2924/00011 20130101; H01L 2924/13091 20130101; H01L
2924/01079 20130101; H01L 2924/12042 20130101; H01L 2924/01004
20130101; H01L 2224/11334 20130101; H01L 2924/01013 20130101; H01L
2224/05571 20130101; H01L 2224/13022 20130101; H01L 23/481
20130101; H01L 2924/01006 20130101; H01L 2924/01033 20130101; H01L
2924/13091 20130101; H01L 2224/1131 20130101; H01L 2924/00
20130101; H01L 2924/00 20130101; H01L 2924/00014 20130101; H01L
2224/81805 20130101; H01L 2224/05552 20130101 |
Class at
Publication: |
438/689 |
International
Class: |
H01L 021/302; H01L
021/461 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 30, 1998 |
JP |
10-340264 |
Claims
1. A fine particle film forming apparatus, comprising: a vessel
having a gas inlet for introducing a gas therein provided on one of
its ends and having a gas blow-off nozzle for blowing off a gas
containing fine particles to an outside provided on another of its
ends; a gas flow forming portion for forming a constant gas flow in
the vessel from the gas inlet toward the gas blow-off nozzle; a
target provided in the vessel for acting as a fine particle source;
a fine particle generating portion for irradiating light on a main
surface of the target, thereby discharging a component of the
target into the gas flow to form the fine particles made of the
component in the gas flow; and a moving portion for moving the
vessel.
2. A fine particle film forming apparatus, comprising: a vessel
having a gas inlet for introducing a gas therein provided on one of
its ends and having a gas blow-off nozzle for blowing off a gas
containing fine particles to an outside provided on another of its
ends; a gas flow forming portion for forming a constant gas flow in
the vessel from the gas inlet toward the gas blow-off nozzle; a
target provided in the vessel for acting as a fine particle source;
a fine particle generating portion for irradiating light on a main
surface of the target, thereby discharging a component of the
target into the gas flow to form the fine particle made of the
component in the gas flow; a moving portion for moving the vessel;
and a magnetic field forming portion for forming a magnetic field
in a region on the substrate.
3. A fine particle film forming apparatus according to claim 1,
wherein the blow-off nozzle has a slit-shaped nozzle or a nozzle
having a plurality of spot-shaped nozzles arranged
rectilinearly.
4. A fine particle film forming apparatus according to claim 2,
wherein the blow-off nozzle has a slit-shaped nozzle or a nozzle
having a plurality of spot-shaped nozzles arranged
rectilinearly.
5. A fine particle film forming apparatus according to claim 1,
wherein the main surface of the target is held in a direction of
the gas flow.
6. A fine particle film forming apparatus according to claim 2,
wherein the main surface of the target is held in a direction of
the gas flow.
7. A fine particle film forming apparatus according to claim 1,
wherein the target has a cylindrical shape, the main surface of the
target is a cylindrical side face, and the target is rotatable
around a rotary shaft parallel with the main surface which is a
symmetry axis of a cylinder.
8. A fine particle film forming apparatus according to claim 2,
wherein the target has a cylindrical shape, the main surface of the
target is a cylindrical side face, and the target is rotatable
around a rotary shaft parallel with the main surface which is a
symmetry axis of a cylinder.
9. A fine particle film forming apparatus according to claim 1,
wherein the target has a disc shape, the main surface of the target
is a bottom face or a top face of a disc, and the target is
rotatable around a rotary shaft which passes through a center of
the main surface and is perpendicular to the main surface.
10. A fine particle film forming apparatus according to claim 2,
wherein the target has a disc shape, the main surface of the target
is a bottom face or a top face of a disc, and the target is
rotatable around a rotary shaft which passes through a center of
the main surface and is perpendicular to the main surface.
11. A fine particle film forming apparatus according to claim 1,
wherein the main surface of the target is divided into at least a
first region and a second region, the first and second regions
being made of different components.
12. A fine particle film forming apparatus according to claim 2,
wherein the main surface of the target is divided into at least a
first region and a second region, the first and second regions
being made of different components.
13. A fine particle film forming apparatus according to claim 1,
further comprising a temperature control portion for controlling a
temperature of an atmosphere around the target in the vessel.
14. A fine particle film forming apparatus according to claim 2,
further comprising a temperature control portion for controlling a
temperature of the target.
15. A fine particle film forming apparatus according to claim 1,
wherein the fine particle forming portion includes a light
irradiating portion for irradiating light, and a light irradiating
portion for simultaneously irradiating light on a plurality of
places on the target in a direction which is substantially
perpendicular to the gas flow or for sequentially irradiating the
light on the places, respectively.
16. A fine particle film forming apparatus according to claim 2,
wherein the fine particle forming portion includes a light
irradiating portion for irradiating the light, and a light
irradiating portion for simultaneously irradiating light on a
plurality of places on the target in a direction which is
substantially perpendicular to the gas flow or for sequentially
irradiating the light on the places, respectively.
17. A method for forming a fine particle film, comprising the steps
of: preparing a target as a fine particle source; irradiating light
on a main surface of the target, thereby discharging a component of
the target to an outside; forming fine particles from the
discharged component; and carrying the fine particles on a gas flow
to a surface of a substrate, thereby forming a fine particle film
made of the fine particle on the substrate.
18.-49. (canceled)
Description
BACKGROUND OF THE INVENTION
[0001] In order to connect an integrated circuit formed in an
element region of a semiconductor substrate to a circuit (an
external circuit) provided on the outside of the substrate, a pad
electrode has been formed in a non-element region in the peripheral
edge portion of the semiconductor substrate. The pad electrode is
electrically connected to the integrated circuit, and furthermore,
is electrically connected to the external circuit through a
lead.
[0002] The connection of the pad electrode and the lead is
performed through a bump (projection) electrode. This kind of bump
electrode has conventionally been formed by electrolytic plating
such as gold, solder and the like.
[0003] FIGS. 18A to 18E are sectional views showing steps of a
method for forming a bump electrode according to the prior art. In
order to form the bump electrode, first of all, a plurality of pad
electrodes 83 (only one of them is shown in the drawing) made of Al
are formed in a non-element region covered with an insulating film
82 in the peripheral edge portion of a semiconductor substrate 81
as shown in FIG. 18A.
[0004] More specifically, for example, an Al film is formed by
using a sputtering method, and the Al film is then processed by
photolithography and RIE, thereby forming the pad electrode 83. The
pad electrode 83 is electrically connected to a semiconductor
device constituting an integrated circuit (not shown) which is
formed on the semiconductor substrate 81.
[0005] As shown in FIG. 18A, next, an interlayer dielectric film 84
is formed over the whole surface of the semiconductor substrate 81,
and the interlayer dielectric film 84 provided on the pad electrode
83 is then removed selectively by etching, thereby forming an
opening.
[0006] As shown in FIG. 18A, then, a Ti film 85, an Ni film 86 and
a Pd film 84 which are conductive films necessary for electrolytic
plating are sequentially formed by using the sputtering method, for
example, so as to cover the exposed pad electrode 83 and the
interlayer dielectric film 84.
[0007] The Ti film 85 is a barrier film of a bump electrode
material, the Ni film 86 is a contact film to perform a contact of
the pad electrode 83 with the bump electrode, and the Pd film 87 is
an oxidation inhibiting film for inhibiting the oxidation of the Ni
film 86.
[0008] As shown in FIG. 18B, thereafter, a photoresist pattern 88
is formed. The photoresist pattern 88 has a thickness of about 20
.mu.m and is provided with an opening in a region where the bump
electrode is to be formed.
[0009] As shown in FIG. 18C, subsequently, the films 85 to 87 are
electrically charged by a current-carrying pin to perform the
electrolytic plating, for example. Thus, a bump electrode 89 made
of gold or solder is selectively formed in the opening. In this
case, it is necessary to previously cover, with an insulator, a
region which should not be subjected to the electrolytic plating,
for example, the back side of the semiconductor substrate 81.
[0010] As shown in FIG. 18D, next, the photoresist pattern 88 is
taken away, and the films 85 to 87 are then subjected to wet
etching by using the bump electrode 89 as a mask. Thus, the films
85 to 87 are caused to remain under the bump electrode 89, thereby
insulating the bump electrodes.
[0011] As shown in FIG. 18E, finally, the bump electrode 89 is
subjected to reflow by performing heating while applying a
flux.
[0012] However, such a method for forming the bump electrode 89 has
the following drawbacks.
[0013] First of all, the electrolytic plating is used for the
formation of the bump electrode 89. The electrolytic plating
requires a large number of steps. For this reason, there is a
problem in that the number of steps is large.
[0014] At a wet etching step for the various films 85 to 87 which
have been subjected to the sputtering prior to the plating, a wet
etching step and a washing step should be performed several times
according to the kind of the film, and a vast amount of water is
required.
[0015] Recently, the pad electrode 83 has also been formed more
finely with an increase in the fineness of the element. Therefore,
there are some cases where an antireflection film such as a TiN
film to prevent reflection during exposure at a lithography step is
formed on an Al film acting as the pad electrode 83.
[0016] Although the TiN film is effective as a barrier metal, it
has poor adhesion to the bump electrode made of metal such as
solder, gold or the like. For this reason, after the Al film is
processed to form the pad electrode 82, the TiN film should be
removed. Consequently, the number of steps tends to be increased
still more.
[0017] Moreover, a resist pattern to be used at the etching step
which is an ordinary semiconductor process has a thickness of
several .mu.m, while the resist pattern 88 to be used at the
plating step has a great thickness of 20 .mu.m as described above.
For this reason, there is a problem in that the photolithography
step for forming the resist pattern 88 will be hard to perform in
the future.
[0018] Moreover, in the case where a semiconductor device having
the resist pattern 88 formed therein is immersed in a strongly
acidic plating bath, the resist pattern 88 is eluted as an organic
impurity into the plating bath at the electrolytic plating step so
that the composition balance of a plating solution is lost.
[0019] As a result, a variation in the reflow reaction temperature
of the bump electrode 89 is generated at a reflow step of the bump
electrode 89 and a mounting connection step thereof. Consequently,
there is a problem in that the reliability and yield of the
connection is deteriorated.
[0020] By the high functionality of the element-and various
mounting steps, a reduction in the size of the pad electrode and an
increase in the number of the pad electrodes are accelerated.
Therefore, a reduction in the above-mentioned variation will be
increasingly significant in the future in order to keep the
reliability of the pad electrode 89.
[0021] In order to eliminate the above-mentioned drawbacks, there
has been known a method in which a metallic ball such as a solder
ball, a gold ball or the like is provided on an Al pad electrode
and is then pressure welded and melted to form a bump
electrode.
[0022] However, in the case where the solder ball is provided on
the Al electrode pad, a barrier film and an adhesion layer are to
be formed in order to prevent Sn constituting the solder ball from
being diffused into the Al electrode pad. In this respect, the
number of steps is increased in the same manner as in plating film
formation.
[0023] As one of metal film forming methods, a fine particle film
forming method has been known and application to a part of the
method to a process has been investigated. As a method for
application to a mounting technique, there has been investigated a
method for forming a bump electrode made of fine particles of gold
(Au) by depositing the Au fine particles on a pad electrode.
[0024] In the case of this method, it is necessary to deposit a
large quantity of Au fine particles in order to form a bump
electrode having a required thickness. Under the existing
conditions, however, a deposition rate or the like is insufficient.
Therefore, there is a problem in that such a method does not
correspond to a real process. In other words, there has not been a
real electrode structure using a conductive fine particle film.
BRIEF SUMMARY OF THE INVENTION
[0025] It is an object of the present invention to provide a
semiconductor substrate having a real electrode structure using a
conductive fine particle film and a method for manufacturing the
semiconductor substrate, and a fine particle film forming apparatus
and method which is effective in the formation of a fine particle
film such as a conductive fine particle film.
[0026] The present invention provides a fine particle film forming
apparatus comprising a vessel having a gas inlet for introducing a
gas therein provided on one of ends thereof and having a gas
blow-off nozzle for blowing off a gas containing fine particles to
an outside provided on the other end thereof, a gas flow forming
portion for forming a constant gas flow in the vessel from the gas
inlet toward the gas blow-off nozzle, a target provided in the
vessel for acting as a fine particle source, a fine particle
generating portion for irradiating light on a main surface of the
target, thereby discharging a component of the target into the gas
flow to form the fine particles made of the component in the gas
flow, and a moving portion for moving the vessel.
[0027] Preferably, the moving portion can cause the gas blow-off
nozzle and the surface of the substrate where the fine particles
are formed to be positioned at a desirable interval, thereby
relatively moving the vessel with respect to the substrate.
Furthermore, it is preferable that the magnetic forming portion for
forming a magnetic field in the region on the substrate should be
provided. A magnetic field may be formed in the region on the
substrate and other regions. In short, it is sufficient that the
magnetic field can affect the formation of the fine particle
film.
[0028] Moreover, the present invention provides a method for
forming a fine particle film, comprising the steps of preparing a
target as a fine particle source, irradiating light on a main
surface of the target, thereby discharging a component of the
target to an outside, forming fine particles from the discharged
component, and carrying the fine particles on a gas flow to a
surface of a substrate, thereby forming a fine particle film made
of the fine particles on the substrate.
[0029] Furthermore, the present invention provides another method
for forming a fine particle film, comprising the steps of preparing
a substrate, and supplying a gas or medium containing fine
particles having a magnetism to the substrate and forming a
magnetic field on the substrate, thereby forming a fine particle
film on the substrate.
[0030] It is desirable that the magnetic field should be formed in
the vicinity of the region on the substrate. The magnetic field can
also be formed in the vicinity of the region on the substrate and
other regions. In short, it is sufficient that the magnetic field
can affect the formation of the fine particle film. More
specifically, it is sufficient that a distribution of the magnetic
field is controlled, thereby increasing an acceleration of the gas
or medium in a direction of the substrate. The increase in the
acceleration means at least one of an increase in the speed of the
gas or medium and an increase in the amount of the gas or medium
running at the same speed in the direction of the substrate.
[0031] The present invention provides a semiconductor device
comprising a semiconductor substrate, and an electrode structure
provided on the semiconductor substrate and constituted by a first
electrode provided on the semiconductor substrate, a conductive
fine particle film provided on the first electrode and made of
conductive fine particles, and a second electrode provided on the
conductive fine particle film.
[0032] Moreover the present invention provides another
semiconductor device comprising a semiconductor substrate, and an
electrode structure provided on the semiconductor substrate and
constituted by a first electrode provided on the semiconductor
substrate, a barrier film provided on the first electrode, a
conductive fine particle film provided on the barrier film and made
of conductive fine particles, and a second electrode provided on
the conductive fine particle film.
[0033] Furthermore, the present invention provides yet another
semiconductor device comprising a semiconductor substrate, and a
bump electrode structure provided on the semiconductor substrate
and constituted by a first electrode provided on the semiconductor
substrate, a conductive fine particle film acting as a barrier film
and an adhesion layer which is provided on the first electrode and
is made of conductive fine particles, and a second electrode
provided on the conductive fine particle film.
[0034] The present invention provides a method for manufacturing a
semiconductor device comprising the steps of forming a pad
electrode on a semiconductor substrate, forming an insulating film
on the semiconductor substrate on a side where the pad electrode is
formed, removing the insulating film provided on the pad electrode,
thereby forming, on the insulating film, an opening reaching the
pad electrode, forming, on a bottom of the opening, a conductive
fine particle film as an adhesion layer and a barrier film that is
made of conductive fine particles, providing a bump electrode on
the conductive fine particle film, and joining the bump electrode
to the conductive fine particle film.
[0035] The present invention provides another method for
manufacturing a semiconductor device comprising the steps of
forming, on a semiconductor substrate, a pad electrode having a top
face covered with a barrier film, forming an insulating film on the
semiconductor substrate on a side where the pad electrode is
formed, removing the insulating film provided on the barrier film,
thereby forming, on the insulating film, an opening reaching-the
barrier film, forming, on a bottom of the opening, a conductive
fine particle film as an adhesion layer that is made of conductive
fine particles, providing a bump electrode on the conductive fine
particle film, and joining the bump electrode to the conductive
fine particle film.
[0036] The present invention provides yet another method for
manufacturing a semiconductor device comprising the steps of
forming a pad electrode on a semiconductor substrate, forming an
insulating film on the semiconductor substrate on a side where the
pad electrode is formed, removing the insulating film provided on
the pad electrode, thereby forming, on the insulating film, an
opening reaching the pad electrode, forming a barrier film on a
whole surface of the substrate on a side where the opening is
formed, forming, on the barrier film in the opening, a conductive
fine particle film as an adhesion layer which is made of conductive
fine particles, providing a bump electrode on the conductive fine
particle film, joining the bump electrode to the conductive fine
particle film, and removing the barrier film on an outside of the
opening.
[0037] It is preferable that the method for manufacturing a
semiconductor device should further comprise the step of removing a
natural oxide film formed on the conductive fine particle film or a
natural oxide film formed on the conductive fine particle film and
the bump electrode.
[0038] The natural oxide film formed on the conductive fine
particle film may be removed during or after the formation of the
conductive fine particle film or during and after the formation of
the conductive fine particle film.
[0039] Moreover, the conductive fine particle film and the natural
oxide film of the bump electrode may be removed at separate steps
respectively or may be removed at the same time.
[0040] Furthermore, the natural oxide film is removed by a heat
treatment (a heating treatment), for example.
[0041] More specifically, the removal is carried out by the heat
treatment in a vacuum atmosphere, an inactive gas atmosphere, a
reducing gas atmosphere, or a gas atmosphere containing H.sub.2 and
a flux. Examples of other removing methods include a method using a
reverse sputtering method.
[0042] Similarly, it is preferable that the natural oxide film
formed on the pad electrode, the barrier film or both of them
should be removed.
[0043] The natural oxide film formed on the pad electrode and the
barrier film may be removed before or during the formation of the
conductive fine particle film, or before and during the formation
of the conductive fine particle film. Moreover, the same removing
method as that of the conductive fine particle film is used, for
example.
[0044] According to the present invention (claims 21 to 44), the
conductive fine particle film is not used for the electrode but is
utilized as the contact film and the barrier film to be inserted
between the electrodes. Since such films are much thinner than the
electrode, they do not make troubles on a deposition rate but
correspond to a real process. Accordingly, it is possible to
implement a real electrode structure using the conductive fine
particle film.
[0045] According to the present invention (claims 1 to 16),
furthermore, the fine particles can selectively be deposited more
easily in the predetermined region. Therefore, the fine particle
film can selectively be formed easily in the predetermined region.
According to the present invention (claims 1 to 16), therefore, it
is possible to prevent the number of steps from being increased
when forming the electrode structure according to the present
invention (claims 21 to 44).
[0046] According to the present invention (claims 16 to 20),
moreover, the kinetic energy of the fine particles colliding with
the substrate can be increased by utilizing the magnetic field. As
a result, it is possible to form fine particles film having a
higher density.
[0047] Additional objects and advantages of the invention will be
set forth in the description which follows, and in part will be
obvious from the description, or may be learned by practice of the
invention. The objects and advantages of the invention may be
realized and obtained by means of the instrumentalities and
combinations particularly pointed out hereinafter.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0048] The accompanying drawings, which are incorporated in and
constitute a part of the specification, illustrate presently
preferred embodiments of the invention, and together with the
general description given above and the detailed description of the
preferred embodiments given below, serve to explain the principles
of the invention.
[0049] FIG. 1 is a sectional view showing a main part (a fine
particle exhaust nozzle) of a fine particle film forming apparatus
according to a first embodiment of the present invention;
[0050] FIG. 2 is a view showing a more specific structure of the
fine particle film forming apparatus;
[0051] FIG. 3 is a view showing a variant of a target of the fine
particle film forming apparatus;
[0052] FIG. 4 is a sectional view showing a main part (a fine
particle exhaust nozzle) of a fine particle film forming apparatus
according to a second embodiment of the present invention;
[0053] FIGS. 5A and 5B are plan views showing an annular target
comprising first and second targets made of different materials
from each other;
[0054] FIGS. 6A and 6B are sectional views showing a variant of the
fine particle exhaust nozzle according to the second
embodiment;
[0055] FIGS. 7A and 7B are views showing a target to be used for
the fine particle exhaust nozzle;
[0056] FIGS. 8A to 8E are sectional views showing the steps of a
method for forming a pad electrode of a semiconductor device
according to a third embodiment of the present invention;
[0057] FIGS. 9A and 9B are sectional views illustrating the steps
according to a variant of the third embodiment;
[0058] FIGS. 10A to 10C are views showing an example of a fine
particle exhaust nozzle to be used in the third embodiment;
[0059] FIGS. 11A to 11E are sectional views showing the steps of a
method for forming a bump electrode structure according to a fourth
embodiment of the present invention;
[0060] FIG. 12 is a sectional view illustrating a variant of the
fourth embodiment;
[0061] FIG. 13 is a chart showing a relationship between a heat
treating time and a heat treating temperature at a heat treating
step according to the fourth embodiment;
[0062] FIGS. 14A to 14C are sectional views showing the steps of a
method for forming a bump electrode structure according to a
seventh embodiment of the present invention;
[0063] FIGS. 15A to 15D are sectional views showing the steps of a
method for manufacturing a chip for a multi-chip semiconductor
device according to a ninth embodiment of the present
invention;
[0064] FIGS. 16A and 16B are sectional views showing the steps of a
method for manufacturing a multi-chip semiconductor device
according to a tenth embodiment of the present invention;
[0065] FIGS. 17A and 17B are sectional views showing the steps
according to a variant of the tenth embodiment;
[0066] FIGS. 18A to 18E are sectional views showing the steps of a
method for forming a bump electrode according to the prior art;
[0067] FIG. 19 is a chart showing a temperature dependency in a
heat treating atmosphere of the amount of Ni nitride for a Ni fine
particle film; and
[0068] FIGS. 20A and 20B are views illustrating a method for
forming a Ni fine particle film having a high density utilizing a
magnetic field.
DETAILED DESCRIPTION OF THE INVENTION
[0069] Preferred embodiments of the present invention will be
described below with reference to the drawings.
FIRST EMBODIMENT
[0070] FIG. 1 is a sectional view showing a main part (a fine
particle exhaust nozzle) of a fine particle film forming apparatus
according to a first embodiment of the present invention. The fine
particle film forming apparatus according to the present embodiment
is broadly divided into the fine particle exhaust nozzle shown in
FIG. 1, a carrier gas supply source which is not shown, an external
light source which is not shown, and moving means of the fine
particle exhaust nozzle which is not shown.
[0071] In the drawing, the reference numeral 1 denotes a vessel. A
target 2 acting as a fine particle source is provided in the vessel
1. The target 2 is held on the internal wall of the vessel 1. More
specifically, the main surface of the target 2 is held in parallel
with a direction of a gas flow fed in the vessel 1.
[0072] One of ends of the vessel 1 is provided with a gas inlet 4
for introducing a carrier gas 3 and the other end of the vessel 1
is provided with a gas blow-off nozzle 5 for blowing off the
carrier gas 3 containing fine particles to the outside.
[0073] An external light source which is not shown is provided on
the outside of the vessel 1, and a light 6 emitted from the
external source is irradiated on the main surface of the target 2
through an optical window 7 provided on the side wall of the vessel
1.
[0074] Next, a method for forming fine particles using the fine
particle film forming apparatus having such a structure will be
described.
[0075] First of all, the carrier gas 3 is introduced from the gas
inlet 4, thereby forming a constant gas flow along the main surface
of the target 2. The carrier gas 3 flowing over the surface of the
target 2 is blown off from the gas blow-off nozzle 5 and is
irradiated on the surface of a wafer (or substrate) 8. In a state
of such a gas flow, the light 6 is irradiated on the surface of the
target 2 from the external light source through the optical window
7.
[0076] At this time, the light intensity of the light 6 is properly
selected, thereby evaporating or ablating a component (target
material) 9 from the surface of the target 2 to discharge the
target material 9 into the gas flow. The configuration of the
target material 9 is an atom, a molecule or a particle.
[0077] Furthermore, a pressure in the vessel 1 is relatively
raised, thereby causing the target material 9 discharged into a gas
phase by the evaporation or the ablation to collide with the
carrier gas 3 to lose the kinetic energy of the target material 9.
Thus, aggregation of the target materials is caused to form fine
particles made of the target material 9.
[0078] The fine particles are carried by the gas flow of the
carrier gas 3. The carrier gas 3 containing the fine particles is
blown off from the gas flow-off nozzle 5, and is sprained on the
surface of the wafer 8. Thus, the fine particles are deposited to
form a fine particle film 10.
[0079] The light 6 is continuously or intermittently irradiated on
the main surface of the target 2 while moving the vessel 1 in a
direction of an arrow m shown in the drawing by means of moving
means which is not shown. Consequently, a line-shaped or
spot-shaped fine particle film 10 can be formed on the wafer 8.
[0080] FIG. 2 shows a more specific structure of the fine particle
film forming apparatus. The fine particle exhaust nozzle is shown
in a sectional perspective view.
[0081] Herein, a laser beam source is used as the external light
source. The light (laser beam) 6 emitted from the laser beam source
is reflected by a rotating mirror 11 and is then irradiated on the
surface of the target 2 through the optical window 7.
[0082] By controlling the rotating angle of the rotating mirror 11,
the laser beam 6 can be irradiated like a spot in a desired
position on the main surface of the target 2. For this reason, in
the case where the fine particle exhaust nozzle is fixed, the fine
particles are deposited like a spot on the surface of the wafer 8
positioned under a laser beam irradiating portion so that the
spot-shaped fine particle film 10 is formed.
[0083] Accordingly, the fine particle film 10 having an optional
pattern can be formed on the wafer 8 by controlling the irradiating
timing of the laser beam 6, the irradiating time thereof, and the
movement (scan) of the fine particle exhaust nozzle.
[0084] Next, description will be given to an example in which a
fine particle film is actually formed by using the fine particle
film forming apparatus according to the present embodiment.
[0085] Ni was used as the target material, and KrF excimer laser
(having a wavelength of 248 nm) was used as the light to be
irradiated.
[0086] A laser spot diameter was 100 .mu.m.phi. on a target
surface, a laser power was 1 to 10 J/cm.sup.2, and a laser pulse
width was about 10 nsec.
[0087] An Ar gas is used as the carrier gas 3, which has a flow
rate to generate a constant gas flow. A higher pressure than a
pressure on the outside provided with the wafer was kept in the
vessel 1. The gas exhaust nozzle 5 was a slit-shaped, and had an
opening width of 100 .mu.m and a length of 50 mm. Fused quartz was
used for the optical window 7.
[0088] The fine particle film is formed as follows. First of all,
the fine particle exhaust nozzle was fixed to irradiate the laser
beam 6 on a plurality of places over the surface of the target 2.
Next, the fine particle exhaust nozzle was moved by a constant
distance and was then fixed again to irradiate the laser beam 6 on
a plurality of places over the main surface of the target 2.
[0089] As a result, as shown in FIG. 2, the fine particle film 10
formed by depositing the fine particles like a spot could be
arranged on the wafer 8. Moreover, the spot size of the fine
particle film 10 can be set to 100 to 200 .mu.m.phi. by controlling
the flow rate of the gas.
[0090] The present embodiment can variously be changed in the
following manner. For example, while Ni has been used as the target
material in the present embodiment, various materials such as
metals, alloys, semiconductors and insulators can be used by
selecting a proper laser power.
[0091] Moreover, while the Ar gas has been used as the carrier gas
3 in the present embodiment, a gas having a high reactivity can
also be used. For example, a SiO.sub.2 film can be formed by using
Si as the target material and an oxygen gas as the carrier gas 3.
Furthermore, a silicon nitride film can also be formed by
introducing a nitrogen gas. By such a method, a film such as
metals, oxide of semiconductors, nitride or the like can also be
formed.
[0092] Furthermore, although Ni has been used as the target
material in any portion in the present embodiment, a lamination
film having different materials can be formed by using other target
materials 12a and 12b on the upstream and the downstream in the
flow direction of the gas and shaking the laser beam 6 vertically
to alternately irradiate the laser beam 6.
[0093] Moreover, while the rotating mirror 10 has been used for
controlling the irradiation position of the laser beam 6 in the
present embodiment, the control may be performed by other
methods.
[0094] Furthermore, although the KrF excimer laser beam has been
used as the laser beam 6 in the present embodiment, other laser
beams may be used. For example, fundamental waves of a CO.sub.2
laser and a YAG laser, harmonics thereof and the like or a laser
beam in a longer wavelength region (from an infrared region to a
ultraviolet region) can be used. Moreover, while the pulse laser
beam has been used in the present embodiment, a continuous (CW)
laser beam may be used.
SECOND EMBODIMENT
[0095] FIG. 4 is a sectional view showing a main part (a fine
particle exhaust nozzle) of a fine particle film forming apparatus
according to a second embodiment of the present invention. FIG. 4
is a sectional view in which the fine particle exhaust nozzle is
seen from above. Corresponding portions to the fine particle
exhaust nozzle in FIG. 1 have the same reference numerals as in
FIG. 1 and their detailed description will be omitted.
[0096] In the present embodiment, a cylindrical target 2 is used.
The cylindrical target 2 is held in a vessel 1 eccentrically from
the side (a region A) on which the laser beam 6 is irradiated
toward the opposite side (a region B).
[0097] As a result, a conductance between the vessel 1 in the
region A and the target 2 is greater than that between the vessel 1
in the region B and the target 2, and the gas flow of the carrier
gas 3 is mainly formed on the laser beam irradiation side.
Consequently, a target material discharged into a vapor phase by
evaporation or ablation can be blown off more efficiently toward
the surface of a wafer.
[0098] FIGS. 5A and 5B are plan views showing an annular target 2
comprising first and second targets 2.sub.1 and 2.sub.2 made of
different materials from each other.
[0099] As shown in FIG. 5A, in the case where the target 2 is
divided into two portions, a half of the target 2 being formed by
the first target 2.sub.1 and the other half being formed by the
second target 2.sub.2, a fine particle film having two lamination
films can be formed by irradiating a laser beam on the target
material 2.sub.1 (2.sub.2) for a constant period and then
irradiating the laser beam on the target material 2.sub.1 (2.sub.2)
for a constant period.
[0100] Moreover, a fine particle film (a mixed film) obtained by
mixing different materials from each other can be formed by
rotating the target 2 at a high speed. Furthermore, a fine particle
film can be formed in the shape of an alloy film by rotating the
target 2 at a high speed and controlling a temperature in the
vessel 1.
[0101] As shown in FIG. 5B, furthermore, the target 2 is divided
into more portions, and the first target 2.sub.1 and the second
target 2.sub.2 are alternately formed. Consequently, a lamination
film, a mixed film and an alloy film which have more uniform
qualities can be formed.
[0102] Besides, the number of the targets made of different
materials from each other is not always two but may be three or
more. By increasing the number of the targets made of different
materials, it is possible to form a lamination film, a mixed film
and an alloy film which are made of various materials. Furthermore,
a division ratio is not always equal.
[0103] FIGS. 6A and 6B are sectional views showing a fine particle
exhaust nozzle according to a variant of the present embodiment. In
FIG. 6A, a rotary shaft is different from the rotary shaft of the
cylindrical target 2 shown in FIG. 4. In FIG. 6B, a disc-shaped
target 2 is used. With such a device structure, the same effects
can also be obtained. FIG. 7 is a view corresponding to FIG. 5.
FIG. 7 is a plan view seen in parallel with the rotary shaft 13 of
the target 2 in the structure of the device illustration in FIG.
6.
THIRD EMBODIMENT
[0104] FIGS. 8A to 8E are sectional views showing the steps of a
method for forming a pad electrode of a semiconductor device
according to a third embodiment of the present invention.
[0105] First of all, as shown in FIG. 8A, an interlayer dielectric
film 23 is formed on a semiconductor substrate 20 where an element
such as a MOS transistor is formed. In the drawing, the reference
numeral 21 denotes an element isolation film and the reference
numeral 22 denotes a MOS transistor having an LDD structure.
[0106] As shown in FIG. 8B, next, a source/drain electrode and a
multilayer interconnection are formed according to a known method.
In the drawing, the reference numeral 25 denotes an interlayer
dielectric film. Portions in the interlayer dielectric film 25
which are shown in different oblique lines denote wiring of the
multilayer interconnection or a connecting plug.
[0107] As shown in FIG. 8B, subsequently, a pad electrode 26 made
of Al which is covered with a barrier film 27 having a surface made
of TiN is formed on the semiconductor substrate 20. The materials
of the barrier film 27 and the pad electrode 26 are not restricted
to TiN and Al, respectively.
[0108] The barrier film 27 and the pad electrode 26 are formed in
the following manner, for example.
[0109] First of all, an Al film acting as the pad electrode 26 and
a TiN film acting as the barrier film 27 are sequentially formed on
the interlayer dielectric film 25. Then, the TiN film and the Al
film are processed by using lithography and RIE. Thus, the pad
electrode 26 and the barrier film 27 are formed. At this time, the
TiN film serves as an antireflection film at the lithography
step.
[0110] In the case where a thin (damascene type) pad electrode is
to be formed, a liner film such as a TiN film for covering the
internal face of a trench is formed, and an Al film and the barrier
film 27 are then formed. While the case of the pad electrode has
been described above, the same effects can be obtained in the case
where a substrate is a wiring.
[0111] As shown in FIG. 8B, next, a protective insulating film 28
is deposited over the whole surface. Then, the protective
insulating film 28 provided on the pad electrode 26 is selectively
removed by etching, thereby forming an opening (a pad opening) on
the pad electrode 26. At this time, the etching is stopped with the
surface of the barrier film 27 exposed.
[0112] Examples of another method for forming a structure in which
the barrier film 27 is present on the bottom of the pad opening
include a method for forming a pad opening, then forming a TiN film
acting as the barrier film 27 by an ordinary sputtering or CVD
method, or an anisotropic sputtering or CVD method, thereby
removing the unnecessary TiN film provided on the protective
insulating film 28 by CMP. FIG. 9A shows a structure obtained by
using the ordinary sputtering or CVD method, and FIG. 9B shows a
structure obtained by using the anisotropic sputtering or CVD
method.
[0113] As shown in FIG. 8C, subsequently, Ni particles having a
diameter of 1 to 2 .mu.m or less are selectively deposited on the
barrier film 27, thereby forming a Ni fine particle film 29.
Sectional views of FIG. 8C and succeeding drawings show a region C
of FIG. 8B. A specific method for forming the Ni fine particle film
29 is as follows.
[0114] More specifically, Ni fine particles previously formed by
using an evaporating method are introduced into a chamber having a
semiconductor substrate 20 housed therein and having a lower
pressure than a carrier gas, desirably a carrier gas containing a
reducing gas (for example, a gas containing hydrogen) by means of
the gas. By utilizing a difference between the pressure of the gas
and the internal pressure of the chamber, the gas is sprayed on the
surface of the semiconductor substrate 20 with high rectilinearity
to deposit the Ni fine particles. Thus, the Ni fine particle film
29 is formed.
[0115] At this time, the Ni fine particle film 29 is deposited on a
desired pad electrode 26 with an area having a diameter of about 50
.mu.m, for example, through the barrier film 27 by using a pencil
type fine particle exhaust nozzle 15 having a nozzle exhaust
diameter of about 50 .mu.m, for example, as shown in FIG. 10A in
such a manner that the Ni fine particles can be deposited like a
dot with a diameter which is equal to or smaller than the size of
the pad electrode 26.
[0116] As shown in FIG. 10B, a plurality of fine particle exhaust
nozzles 15 may be used. As shown in FIG. 10C, moreover, a mask 17
is provided between the fine particle exhaust nozzle 15a capable of
exhausting the Ni fin particles like a line or a face and the
semiconductor substrate 20. The fine particle exhaust nozzle 15a is
caused to scan the whole surface of the substrate while exhausting
the Ni fine particles. Thus, the Ni fine particle film 29 can be
deposited and formed on the desired pad electrode 26.
[0117] Examples of other methods for forming the Ni fine particle
film 29 include a method for forming a Ni fine particle 16 by arc
discharge and depositing the Ni fine particle 16 on the surface of
the barrier film 27, thereby forming the Ni fine particle film 29,
for example.
[0118] Also in this case, the Ni fine particle 16 is formed in a
gas including a reducing atmosphere. Consequently, the Ni fine
particle film 29 having high adhesion can be deposited and formed
on the barrier film 27. As a matter of course, high adhesion can
also be obtained by the method for forming the Ni fine particle
film 29 described above.
[0119] As shown in FIG. 8D, next, a bump electrode 30 made of a
solder ball is provided on the pad electrode 26 through the Ni fine
particle film 29.
[0120] As shown in FIG. 8E, finally, the bump electrode 30 is
melted by a heat treatment, thereby joining the Ni fine particle
film 29 to the bump electrode 30. Thus, a bump electrode structure
is formed.
[0121] It is preferable that the heat treatment should be performed
in the reducing atmosphere. The reason is that a natural oxide film
of the Ni fine particle film 29 and a natural oxide film of the
bump electrode 30 are removed, resulting in an enhancement in the
adhesion of the bump electrode 30 to the Ni fine particle film 29
and the adhesion of the Ni fine particle film 29 to the protective
film (TiN film) 28.
[0122] Moreover, the Ni fine particle film 29 and the natural oxide
film of the solder ball 30 can also be removed by a heat treatment
in a vacuum atmosphere and an inactive gas atmosphere such as a
N.sub.2 atmosphere, an Ar atmosphere or the like. The natural oxide
film can effectively be removed by performing the heat treatment
under a pressure reduction.
[0123] Furthermore, the natural oxide film of the Ni fine particle
film 29 can be removed by a heat treatment to be performed in a
vacuum at a temperature of about 150.degree. or more. Therefore,
the solder ball 30 can also be dissolved after the heating is fully
performed at a temperature which is less than the melting point of
the solder ball 30.
[0124] In the conventional method, the adhesion of the solder ball
to the TiN film (barrier film) is poor. Therefore, after the TiN
film is removed by RIE at the time of the formation of the pad
opening, lamination films having a Ti film, an Ni film and a Pd
film as a barrier film, an adhesion film and an antioxidant film
are continuously formed by using a sputtering method, for
example.
[0125] According to the present embodiment, however, the TiN film
(barrier film) 27 is caused to remain at the time of the formation
of the pad opening, and can be used as the barrier film of the
solder ball. Therefore, the process can be simplified.
[0126] In general, there has been known that the fine particles
have active surfaces and are easily reacted at a lower temperature
than a reaction temperature in an equilibrium state differently
from the contact of bulk materials.
[0127] Accordingly, the reaction is performed more easily at the
same temperature by using the Ni fine particle film 29 for the
adhesion layer to the solder ball 30 than by using a conventional
adhesion layer (for example, a Ni layer). If a reaction amount
having the same extent is enough, a heat treating temperature can
be more reduced.
FOURTH EMBODIMENT
[0128] FIG. 11 is a sectional view showing the steps of a method
for forming a bump electrode structure according to a fourth
embodiment of the present invention, which is a sectional view
corresponding to the region C of FIG. 8B.
[0129] First of all, as shown in FIG. 11A, an interlayer dielectric
film 31 is formed, according to a known method, on a semiconductor
substrate 30 where an element and the like (not shown) are formed,
and subsequently, a pad electrode 32 made of Al, for example, is
formed on the interlayer dielectric film 31. A wiring which is not
shown exists in the interlayer dielectric film 31.
[0130] As shown in FIG. 11A, next, a protective insulating film 33
is deposited over the whole surface. Then, the protective
insulating film 33 provided on the pad electrode 32 is selectively
removed by etching, thereby forming an opening (a pad opening) on
the pad electrode 32. Then, a barrier film 34 made of TiN is
deposited over the whole surface as shown in FIG. 11A.
[0131] As shown in FIG. 11B, subsequently, a Ni fine particle film
35 is selectively formed on the bottom of the pad opening by the
method described in the first embodiment.
[0132] In the drawing is shown a state in which the selective
formation of the Ni fine particle film 35 is incompletely performed
and a Ni fine particle film 35' is also formed on the barrier film
34 other than the pad opening.
[0133] As shown in FIG. 11C, next, a bump electrode 36 made of a
solder ball is provided on the pad electrode 32 through the barrier
film 34 and the Ni fine particle film 35.
[0134] As shown in FIG. 11D, then, the bump electrode 36 is melted
by a heat treatment, and the Ni fine particle film 35 and the bump
electrode 36 are joined together, thereby forming a bump electrode
structure in the same manner as in the first embodiment.
[0135] As shown in FIG. 11E, thereafter, the unnecessary barrier
film (TiN film) 34 existing between the pad electrodes is removed
by using the bump electrode 36 as a mask. As a result, the Ni fine
particle film 35' formed on the barrier film 34 other than the pad
opening is removed together with the unnecessary barrier film 34 at
the time of the formation of the Ni fine particle film 35.
Consequently, also in the case where the pad electrode 32 becomes
finer, a short circuit between the pad electrodes can be
prevented.
[0136] The barrier film (TiN film) 34 is removed by wet etching
using a mixed solution containing NH.sub.4OH, H.sub.2O.sub.2 and
H.sub.2O, for example.
[0137] In the case of lift-off using the wet etching, there is a
possibility that a substrate wiring layer might be damaged by the
wraparound of drugs. In order to prevent such a drawback, it is
sufficient that the barrier film (TiN) film 34 is not largely
formed on the side wall of the pad opening in such a manner that
the top of the substrate wiring layer can fully be covered with the
bump electrode.
[0138] More specifically, a barrier film 34' having a structure
shown in FIG. 12 is formed by a film forming method in which a
barrier film (TiN film) 24 is not largely formed on the side wall,
for example, an anisotropic film forming method in such a manner
that the top of the wiring is fully covered with the bump
electrode.
[0139] Examples of another method include a method for selectively
removing the unnecessary barrier film (TiN film) 34 by RIE using a
gas system capable of selectively removing TiN by etching with the
bump electrode 36 used as a mask.
[0140] As yet another method, first of all, a resist pattern for
covering the bump electrode. 36 is formed, the unnecessary barrier
film (TiN film) 34 is then removed by the RIE using the resist
pattern as a mask, and the resist pattern is thereafter taken
away.
FIFTH EMBODIMENT
[0141] The present embodiment is different from the above-mentioned
embodiments in respect of a heat treating step to be performed
after a solder ball is formed.
[0142] More specifically, a semiconductor substrate is housed in a
vessel in a vacuum atmosphere or an inactive gas atmosphere such as
a N.sub.2 gas atmosphere, an Ar gas atmosphere or the like, a heat
treating temperature is held at a temperature that is equal to or
higher than a temperature at which the natural oxide film of a Ni
fine particle film is removed and that is equal to or lower than
the melting point of the solder ball. After the natural oxide film
of the Ni fine particle film is removed, the heat treating
temperature is raised to the melting point of the solder ball to
join the Ni fine particle film to the solder ball. Thus, a bump
electrode is formed.
[0143] By performing the step of removing the natural oxide film of
the Ni fine particle film and the step of forming the bump
electrode in the same atmosphere by means of the same vessel, the
process can be shortened.
[0144] As a matter of course, the step of removing the natural
oxide film of the Ni fine particle film and the step of forming the
bump electrode may be performed in separate vessels (devices),
respectively. In this case, a substrate is carried without breaking
a vacuum.
[0145] The natural oxide film of the Ni fine particle film may be
removed at the same time during the formation of the Ni fine
particle film (in this case, the formation of the Ni fine particle
film is also performed in the same vessel), or after the formation
of the Ni fine particle film (in this case, the formation of the Ni
fine particle film is performed in the same vessel or a separate
vessel).
[0146] FIG. 13 shows a specific relationship between a heat
treating time and a heat treating temperature at the heat treating
step. Although the temperature that is equal to or higher than the
temperature at which the natural oxide film of the Ni fine particle
film is removed and that is equal to or lower than the melting
point of the solder ball also depends on the solder composition of
the solder ball, it is equal to or higher than about 150.degree. C.
and is lower than 183.degree. C. in the case where an eutectic
solder is used. The natural oxide film of the Ni fine particle film
can be removed more effectively at the same heat treating
temperature in a reducing gas atmosphere in place of the inactive
gas atmosphere.
[0147] FIG. 19 shows a temperature dependency in the heat treating
atmosphere of a Ni nitride amount for the Ni fine particle film,
indicating the rate of a Ni oxide amount for a Ni fine particle
amount which is obtained by performing the heat treatment, wherein
a Ni oxide amount for an initial Ni fine particle before the heat
treatment is set to 1.
[0148] In the drawing, a white circle represents the rate of the Ni
oxide amount obtained when the heat treatment is performed at a
degree of vacuum of 5.times.10.sup.-8 Torr or less and a black
circle represents the rate of the Ni oxide amount obtained when the
heat treatment is performed in an atmosphere with a steam partial
pressure of 152.times.10.sup.-3.
[0149] As is apparent from the drawing, if the same temperature is
set, more Ni oxide can be removed by the heat treatment in the
reducing atmosphere than the heat treatment in the vacuum.
Moreover, it is apparent that more Ni oxide can be removed at a
lower temperature by the heat treatment in the reducing atmosphere
than the heat treatment in the vacuum when the same amount of Ni
oxide is to be removed. Furthermore, it has been confirmed that the
Ni oxide film can be removed at a temperature of 280.degree. C. in
an amount shown by a black square in the drawing by selecting a
proper heat treating time and a hydrogen partial pressure.
[0150] A surface treatment is carried out by such a heat treatment
in the reducing atmosphere. Consequently, it is possible to remove
sufficient Ni oxide at a temperature which is equal to or lower
than a temperature necessary for the step of melting and bonding a
solder. More specifically, as in the present embodiment, the heat
treating step for removing the oxide film provided on the surface
of the fine particle film and the heat treating step for melting
and connecting the solder ball can be continuously carried out by
simply changing the heat treating temperature in the same device,
and, as a matter of course, it can be performed in chambers having
different heat treating temperatures, for example.
SIXTH EMBODIMENT
[0151] The present embodiment is different from the above-mentioned
embodiments in respect of a method for forming a Ni fine particle
film.
[0152] At the step of forming a Ni fine particle film on a barrier
film (TiN film) by deposition, a Ni fine particle film having a
high density is formed by deposition in the early stage and a Ni
fine particle film having a low density is subsequently formed by
deposition.
[0153] More specifically, the kinetic energy of Ni fine particles
colliding with a substrate is changed by the following method,
thereby forming, by deposition, a Ni fine particle film having a
density gradient in which the density of the Ni fine particles is
continuously reduced as the Ni fine particle film is more deposited
on the barrier (TIN) film.
[0154] Alternatively, the kinetic energy of the Ni fine particles
colliding with the substrate is changed by the following method,
thereby forming, by deposition, a Ni fine particle film having a
density gradient in which the density of the Ni fine particles is
discontinuously reduced as the Ni fine particle film is more
deposited on the barrier (TiN) film. In other words, there is
formed, by deposition, the Ni fine particle film having a
lamination structure having at least two layers with different
densities in which a portion closer to the barrier film (TiN film)
has a higher density.
[0155] The kinetic energy of the Ni fine particles colliding with
the substrate is controlled in the following manner.
[0156] More specifically, the Ni fine particles are formed, thereby
continuously or intermittently changing a distance between a nozzle
for exhausting the Ni fine particles and the substrate. If the
distance is smaller, the kinetic energy loss of the Ni fine
particle is more reduced. Therefore, the kinetic energy of the Ni
fine particles colliding with the substrate is great. Thus, a Ni
fine particle film having a higher density can be formed by
deposition.
[0157] As another effective method, a gas pressure at which the
fine particles are exhausted from the nozzle is changed
continuously or intermittently. If the gas pressure is higher, the
kinetic energy of the Ni fine particles colliding with the
substrate is more increased. Consequently, a Ni fine particle film
having a higher density can be formed by deposition.
[0158] As yet another method, a magnetic field is formed between
the nozzle and the substrate, and the intensity of the magnetic
field is controlled. If the intensity of the magnetic field is
higher, the Ni fine particles receive greater force so that the
kinetic energy of the Ni fine particles colliding with the
substrate is more increased. Consequently, a Ni fine particle film
having a higher density can be formed by deposition. A method
utilizing the magnetic field will further be described in a ninth
embodiment.
[0159] Subsequent steps are the same as in the above-mentioned
embodiments.
[0160] According to the present embodiment, the density of the Ni
fine particle film on the side in contact with the barrier film
(TiN film) is high. Therefore, the contact area of the barrier film
(TiN film) with the Ni fine particle film is increased.
Consequently, the adhesion strength of the barrier film (TiN film)
to the Ni fine particle film is increased.
[0161] On the other hand, the density of the Ni fine particle film
on the side in contact with the solder ball is low. At the step of
dissolving the solder ball to form the bump electrode, therefore,
the melted solder easily enters the Ni fine particle film so that
the contact area of the bump electrode with the Ni fine particle
film is increased. Consequently, the adhesion strength of the bump
electrode to the Ni fine particle film is increased.
SEVENTH EMBODIMENT
[0162] FIG. 14 is a sectional view showing the steps of a method
for forming a bump electrode structure according to a seventh
embodiment of the present invention.
[0163] As shown in FIG. 14A, first of all, a pad electrode 42 made
of Al, for example, is formed on an interlayer dielectric film 41
having the same multilayer interconnection as in the third
embodiment of FIG. 8 formed thereon. A semiconductor substrate (not
shown) having an element formed as in the third embodiment is
present under the interlayer dielectric film 41.
[0164] As shown in FIG. 14A, next, a protective insulating film 43
is deposited, and the protective insulating film 43 provided on the
pad electrode 42 is selectively removed by etching. Thus, an
opening (a pad opening) is formed on the pad electrode 42.
[0165] As shown in FIG. 14A, subsequently, an adhesion/barrier film
44 made of fine particles or a film 44 serving as both of them is
selectively formed by deposition on the bottom of the pad
opening.
[0166] It is also possible to use an adhesion/barrier film made of
Ti fine particles, NiTi.sub.x alloy fine particles or NiTi.sub.x
mixed fine particles in place of Ni fine particles.
[0167] It is apparent that the adhesion/barrier film made of the Ti
fine particles, the NiTi.sub.x alloy fine particles or the
NiTi.sub.x mixed fine particles as well as the Ni fine particles
described in the above-mentioned embodiments may be used or the
film serving as both of them may be used, or a plural kinds of fine
particles may be combined.
[0168] Furthermore, it is also possible to use an adhesion/barrier
film made of at least one of fine particles selected from a fine
particle group comprising the Ni fine particles, the Ti fine
particles, the NiTi.sub.x alloy fine particles and the NiTi.sub.x
mixed fine particles and at least one of fine particles selected
from another fine particle group. In this case, the forming method
described in the first embodiment, for example, is used for a
method for forming an alloy fine particle film and a mixed fine
particle film.
[0169] As shown in FIG. 14B, next, a bump electrode 45 made of a
solder ball is provided on the pad electrode 42 through the
adhesion/barrier film 44.
[0170] As shown in FIG. 14C, finally, the bump electrode 45 made of
the solder ball is melted by a heat treatment, the adhesion/barrier
film or the film 44 serving as both of them is joined to the bump
electrode 45. Thus, a bump electrode structure is completed. In the
drawing, the reference numeral 46 denotes a conductive layer
obtained by the reaction of the adhesion/barrier film 45 with the
bump electrode 45.
[0171] Also in the present embodiment, the same effects as in the
third embodiment can be obtained. According to the present
embodiment, furthermore, it is not necessary to previously form a
barrier film. Therefore, the number of steps can be more
reduced.
[0172] Also in the case where a gold ball is used in place of the
solder ball, a Au ball can be provided on the adhesion/barrier film
44, thereby performing melting connection. At this time, the Au
ball is not oxidized. Therefore, it is sufficient that the step of
pressure welding and melding the Au ball and the adhesion layer,
the barrier film or the film 44 serving as the adhesion layer and
the barrier film is carried out after a natural oxide film made of
the fine particles is removed.
[0173] Moreover, in the case where the Au ball is combined with an
Al wiring (a substrate wiring), gold and Al are alloyed so that an
alloy layer is formed. Therefore, it is possible to prevent the
gold from being diffused into an insulating film in the Al wiring
and around the Al wiring. Under the existing conditions, therefore,
the barrier film is not used.
[0174] However, if a Au ball having a diameter of several tens nm,
for example, is formed, a very small amount of gold is actually
diffused. Such gold diffusion makes troubles together with an
increase in the fineness of the element. Also in such a case, the
barrier film made of the fine particles described above can be
used.
EIGHT EMBODIMENT
[0175] The present embodiment is different from the above-mentioned
embodiments in respect of a method for forming a Ni fine particle
film. More specifically, the present embodiment is characterized in
that a paste (a Ni fine particle paste) having Ni fine particles
dispersed therein is used as a Ni fine particle film.
[0176] More specifically, a pad opening is first formed. Then, the
Ni fine particle paste is applied to the whole surface of a
substrate. Thereafter, the Ni fine particle paste is subjected to
patterning, thereby removing the Ni fine particle paste in a region
other than the pad opening. Subsequently, a solder ball is provided
on the Ni fine particle paste (a Ni fine particle film) over the
pad opening.
[0177] The patterning of the Ni fine particle paste may be
performed after the solder ball is provided. In this case, however,
there is a possibility that the solder ball might be damaged by the
patterning. Therefore, it is preferable that the patterning should
be performed before the solder ball is provided.
[0178] Moreover, if the Ni fine particle paste is applied by screen
printing, the application and the patterning can be performed at
the same time. Therefore, the steps can be shortened.
[0179] Furthermore, the Ni fine particle paste may be a burning
type or a curing type.
[0180] It is preferable that a treating temperature should be
450.degree. C. or less in such a manner that the Ni fine particle
paste becomes a conductive Ni fine particle film after a burning
treatment or a curing treatment is carried out.
[0181] For example, if the diameter of the Ni fine particle is 0.1
.mu.m.phi. or less, it is possible to obtain conductiveness by the
burning treatment and the curing treatment at a temperature of
450.degree. C. or less. Moreover, also in the case where a vacuum
atmosphere and a reducing atmosphere, for example, a hydrogen
atmosphere are used as a burning treatment atmosphere and a curing
treatment atmosphere, the treating temperatures for the burning
treatment and the curing treatment can be lowered and the
conductiveness can be obtained at a temperature of 350.degree. C.,
for example. By performing the burning treatment or the curing
treatment at a temperature of 450.degree. C. with the atmosphere
controlled, it is possible to obtain a Ni fine particle film having
a lower resistivity than in the case where the atmosphere is not
controlled.
[0182] As a method for applying (forming) the Ni fine particle
paste, moreover, dipping can also be used in addition to the
above-mentioned screen printing. If the Ni fine particle paste has
a Ni fine particle diameter of 0.1 .mu.m.phi. or less, patterning
of 1 .mu.m or less can be carried out.
[0183] Examples of other methods include a spin coating method. In
this case, however, a viscosity should be regulated. In the case
where the Ni fine particle paste is applied over the whole surface
of the substrate as in a spin coater, there is a possibility that
the burning treatment or the curing treatment might cause the Ni
fine particle film (Ni fine particle paste) to be peeled off
because the coefficient of thermal expansion of the Ni fine
particle paste is different from that of the substrate. Therefore,
it is desirable that the patterning should be carried out before
the burning treatment or the curing treatment.
[0184] If the dispersion paste having a polarity (+ or -) is used,
the dispersion paste can initially be formed selectively on the
bottom of the pad opening by applying a voltage having a reverse
polarity to the above-mentioned polarity to the pad electrode.
[0185] At the subsequent steps, a solder ball is provided on the
pad electrode and is then melted by a heat treatment, and the Ni
fine particle film is joined to the solder ball, thereby forming a
bump electrode in the same manner as in the other embodiments. The
heat treating step may be carried out simultaneously with the
burning step.
[0186] While the Ni fine particle paste has been used for the
adhesion layer to the solder ball and the pad electrode in the
present embodiment, it can also be used as an embedded metal
material of a connecting hole such as a contact hole, a through
hole or the like.
NINTH EMBODIMENT
[0187] FIG. 15 is a sectional view showing the steps of a method
for manufacturing a chip for a multi-chip semiconductor device
according to a ninth embodiment of the present invention. The
present embodiment is characterized in that a fine particle film is
formed by a film forming method using a solution (a Ni dispersing
solution) turbid with Ni fine particles. The case where the film
forming method is applied to a through plug will be described
below.
[0188] As shown in FIG. 15A, first of all, an interlayer dielectric
film 55 is formed on a silicon substrate 51 where an element such
as a MOS transistor is formed. In the drawing, the reference
numeral 52 denotes an element isolation film, the reference numeral
53 denotes a gate portion of the MOS transistor (a gate oxide film,
a gate electrode, a gate cap insulating film, a gate sidewall
insulating film), and the reference numeral 54 denotes a
source/drain diffusion layer having an LDD structure.
[0189] As shown in FIG. 15B, next, the interlayer dielectric film
55 and the silicon substrate 51 are subjected to etching, thereby
forming a trench. Then, a uniform thin insulating film 56 is formed
on the internal face of the trench.
[0190] As shown in FIG. 15C, subsequently, a through plug 57 made
of Ni fine particles is formed in the trench. A method for forming
the through plug 57 is as follows.
[0191] First of all, a Ni dispersing solution is applied onto the
silicon substrate 51. As the Ni dispersing solution; for example,
10% of Ni fine particles are mixed in a pure water, and ultrasonic
waves are irradiated to disperse the Ni fine particles in the pure
water. Moreover, the Ni dispersing solution is applied by using a
spin coater, for example.
[0192] Then, the silicon substrate 51 is heated to a temperature of
80.degree. C., thereby evaporating the water in the Ni dispersing
solution. Consequently, a film made of the Ni fine particles (a Ni
fine particle film) is formed.
[0193] Finally, the silicon substrate 51 is heated in a hydrogen
atmosphere at a temperature of 450.degree. C., thereby sintering
the Ni fine particles. Thus, the through plug 57 made of the Ni
fine particle film is obtained.
[0194] If a polycrystalline silicon film is formed as the substrate
of the Ni fine particle film at the above-mentioned steps, the
through plug 57 made of a Ni silicide film can be formed.
[0195] While the Ni fine particles have been used as conductive
fine particles, the through plug 57 can be formed by the same
method with a metal fine particle having a diameter of 4 .mu.m.phi.
or less.
[0196] While the water has been used as a solvent, alcohol and
thinner can also be used. The capability of dispersing the
conductive fine particles is enhanced in order of water, alcohol
and thinner.
[0197] Moreover, while the concentration of the conductive fine
particles is 10%, it may be higher. As the concentration is raised,
the fineness of the film is basically increased. By repeating
application and drying, the fineness of the film can be
increased.
[0198] Although a sintering temperature has been 450.degree. C., a
lower sintering temperature is sufficient if the Ni fine particle
has a diameter of 0.1 .mu.m or less.
[0199] As shown in FIG. 15C, next, a source/drain electrode and a
multilayer interconnection are formed according to a known method.
In the drawing, the reference numerals 55 and 59 to 61 denote an
interlayer dielectric film. Portions shown in different oblique
lines in the interlayer dielectric films 55 and 59 to 61 denote a
wiring of the multilayer interconnection or a connecting plug
58.
[0200] As shown in FIG. 15D, finally, the back face of the silicon
substrate 51 is ground, thereby exposing the through plug 57 on the
bottom of a trench. Thus, it is possible to finish a chip for a
multi-chip semiconductor device having a connecting plug having
such a structure that the through plug 57 is embedded in a through
hole through an insulating film 56.
TENTH EMBODIMENT
[0201] FIG. 16 is a sectional view showing the steps of a method
for manufacturing a multi-chip semiconductor device according to a
tenth embodiment of the present invention.
[0202] As shown in FIG. 16A, first of all, an element and a wiring
(a multilayer interconnection) which are not shown are formed on a
first semiconductor substrate 71, and a first pad electrode 72 and
a first Ni fine particle film 73 are then formed on the first
semiconductor substrate 71 according to the above-mentioned
embodiments, for example, the third embodiment. Thus, a chip for a
first mulch-chip semiconductor device (which will be hereinafter
referred to as a "chip") is finished. Although the first Ni fine
particle film 73 is an adhesion layer in the present embodiment,
the adhesion layer may be formed after a barrier metal film is
formed if the barrier metal film is not formed on a pad
electrode.
[0203] Similarly, an element and a wiring (multilayer
interconnection) which are not shown, and a second pad electrode 75
and a second Ni fine particle film 76 are formed on a second
semiconductor substrate 74. Thus, a second chip is finished.
[0204] As shown in FIG. 16A, next, a bump electrode 77 made of a
solder ball is provided on the Ni fine particle film 73 of the
first chip, thereby confirming a position. Then, the Ni fine
particle film 76 of the second chip is provided above the first
chip through a bump electrode 77.
[0205] As shown in FIG. 16B, subsequently, the Ni fine particle
films 73 and 76 and the natural oxide film of the bump electrode 77
are removed. Then, the bump electrode 77 is melted by a heat
treatment, thereby joining (melting and connecting) the Ni fine
particle films 73 and 76 to the bump electrode 77. Consequently,
the first chip and the second chip are electrically connected to
each other.
[0206] While the case where two chips are connected has been
described in the present embodiment, three or more chips can also
be connected in the same manner. The chips to be provided have the
connecting plug (the insulating film 56 and the through plug 57)
shown in FIG. 15. FIG. 17 is a sectional view showing the steps
corresponding to FIG. 16 in which three chips are used. In the
drawing, the reference numeral 78 denotes a third semiconductor
substrate, the reference numeral 79 denotes a third pad electrode,
the reference numeral 80 denotes a third Ni fine particle film, and
the reference numeral 81 denotes a connecting plug. Herein, there
as been described an example in which the connecting plug 81 is
provided on the second and third chips.
ELEVENTH EMBODIMENT
[0207] There has been described that examples of the method for
forming a Ni fine particle film having a high density include a
method for increasing the kinetic energy of the Ni fine particles
colliding with the substrate. A method using a magnetic field will
further be described below.
[0208] FIGS. 20A and 20B are typical views showing the
above-mentioned method. As shown, a line of magnetic force (a
magnetic field B) is formed in parallel with an axis on which Ni
fine particles 16 are exhausted from a fine particle exhaust
nozzle. A source for generating a magnetic field may be a permanent
magnet or an electromagnet.
[0209] In the case where the fine particle exhaust nozzle is
provided in such a manner that an axial direction is perpendicular
to the surface of a substrate 8, it is further desirable that the
axial direction should be set to cause the line of magnetic force
to enter perpendicularly to the surface of the substrate 8.
[0210] Moreover, it is further desirable that the magnetic field B
should be uniform in at least the face of the substrate 8 as shown
in FIG. 20A. Alternatively, it is also effective in the formation
of a Ni fine particle film having a high density that a local
magnetic field B having almost the same size as a film forming spot
is formed as shown in FIG. 20B.
[0211] Furthermore, in the case where the fine particle has a
paramagnetic material or a ferromagnetic material, they are
magnetized by the magnetic field B in the same direction as the
magnetic field B. At this time, induction magnetic charges are
generated in the direction according to the magnetic charges of the
source for generating the magnetic field. Therefore, the fine
particles receive attraction in the direction of the substrate
8.
[0212] In the case where the source for generating the magnetic
field is provided below the substrate 8 and the magnetic field B
perpendicular to the surface of the substrate 8 is generated, the
kinetic energy (collision energy) of the Ni fine particles 16
toward the substrate 8 is increased in order for the Ni fine
particles 16 exhausted from the fine particle exhaust nozzle to
receive force in the direction of the substrate 8. Consequently,
the Ni fine particle film having a high density can be formed on
the substrate 8.
[0213] Although the magnetic field B turns downward from the
substrate 8 in FIGS. 20A and 20B, the same effects can be obtained
even if the magnetic field B turns upward from the substrate 8. The
reason is as follows. In this case, the fine particles having the
paramagnetic material or the ferromagnetic material are magnetized
in the same direction as the magnetic field B so that magnetic
charges are generated corresponding to the magnetic charges of the
source for generating a magnetic field. Therefore, attraction is
generated in the direction of the source for generating a magnetic
field irrespective of the direction of the magnetic field B.
[0214] In the case where an induction coil acting as the source for
generating a magnetic field is provided below the substrate 8, the
intensity of the magnetic field B can be varied by changing the
amount of a flowing coil current on a time basis. In addition, it
is also possible to cause the density of the fine particle film to
be formed to have a desirable density distribution. It is apparent
that the source for generating a magnetic field is provided above
the substrate 8 when a material having a predominant diamagnetism
is to be formed.
[0215] The present invention is not restricted to the
above-mentioned embodiments but can variously be changed without
departing from the scope of the invention.
[0216] Additional advantages and modifications will readily occur
to those skilled in the art. Therefore, the invention in its
broader aspects is not limited to the specific details and
representative embodiments shown and described herein. Accordingly,
various modifications may be made without departing from the spirit
or scope of the general inventive concept as defined by the
appended claims and their equivalents.
* * * * *