U.S. patent application number 13/054331 was filed with the patent office on 2011-07-21 for film formation method and storage medium.
This patent application is currently assigned to TOKYO ELECTRON LIMITED. Invention is credited to Shuji Azumo, Yasuhiko Kojima.
Application Number | 20110174630 13/054331 |
Document ID | / |
Family ID | 43758525 |
Filed Date | 2011-07-21 |
United States Patent
Application |
20110174630 |
Kind Code |
A1 |
Kojima; Yasuhiko ; et
al. |
July 21, 2011 |
FILM FORMATION METHOD AND STORAGE MEDIUM
Abstract
A film formation method includes preparing a substrate formed a
Co film as a seed layer on a surface of the substrate, applying a
negative voltage to the substrate such that a surface potential of
Co is lower than an oxidation potential of the Co, and in a state
when the negative voltage is applied to the substrate, dipping the
Co film in a plating solution mainly containing copper sulfate
solution, thereby a Cu film is formed on the Co film of the
substrate by electroplating.
Inventors: |
Kojima; Yasuhiko;
(Nirasaki-shi, JP) ; Azumo; Shuji; (Nirasaki-shi,
JP) |
Assignee: |
TOKYO ELECTRON LIMITED
Tokyo
JP
|
Family ID: |
43758525 |
Appl. No.: |
13/054331 |
Filed: |
August 27, 2010 |
PCT Filed: |
August 27, 2010 |
PCT NO: |
PCT/JP2010/064572 |
371 Date: |
January 14, 2011 |
Current U.S.
Class: |
205/186 ;
205/183 |
Current CPC
Class: |
C25D 3/38 20130101; H01L
21/76873 20130101; C25D 17/001 20130101; C25D 5/34 20130101; C25D
7/123 20130101; H01L 21/2885 20130101; H01L 21/28556 20130101 |
Class at
Publication: |
205/186 ;
205/183 |
International
Class: |
C23C 28/02 20060101
C23C028/02 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 17, 2009 |
JP |
2009-215415 |
Claims
1. A film formation method comprising: preparing a substrate formed
a Co film as a seed layer on a surface of the substrate; applying a
negative voltage to the substrate such that a surface potential of
Co is lower than an oxidation potential of the Co; and in a state
when the negative voltage is applied to the substrate, dipping the
Co film in a plating solution mainly containing copper sulfate
solution, thereby a Cu film is formed on the Co film of the
substrate by electroplating.
2. The film formation method of claim 1, wherein the Co film is
formed by CVD.
3. The film formation method of claim 1, wherein a thickness of the
Co film ranges from 1.5 to 5 nm.
4. The film formation method of claim 1, wherein a voltage is
applied before the substrate is dipped in the plating solution such
that a potential difference between the substrate and the plating
solution is equal to or greater than 0.3 V at a time when the Co
film on the surface of the substrate is dipped in the plating
solution.
5. A film formation method comprising: forming a Co film to become
a seed layer on a substrate by CVD; applying a negative voltage to
the substrate such that a surface potential of Co is lower than an
oxidation potential of the Co; and in a state when the negative
voltage is applied to the substrate, dipping the Co film in a
plating solution mainly containing copper sulfate solution, thereby
a Cu film is formed on the Co film of the substrate by
electroplating.
6. The film formation method of claim 5, wherein a thickness of the
Co film ranges from 1.5 to 5 nm.
7. The film formation method of claim 5, wherein a voltage is
applied before the substrate is dipped in the plating solution such
that a potential difference between the substrate and the plating
solution is equal to or greater than 0.3 V at a time when the Co
film on the surface of the substrate is dipped in the plating
solution.
8. A storage medium operating on a computer, having stored thereon
a program for controlling a film formation apparatus and
controlling the film formation apparatus on the computer, wherein
the program performs, when the program is executed, a film
formation method comprising preparing a substrate formed a Co film
as a seed layer on a surface of the substrate, applying a negative
voltage to the substrate such that a surface potential of Co is
lower than an oxidation potential of the Co, and in a state when
the negative voltage is applied to the substrate, dipping the Co
film in a plating solution mainly containing a copper sulfate
solution, thereby a Cu film is formed on the Co film of the
substrate by electroplating.
Description
TECHNICAL FIELD
[0001] The present invention relates to a film formation method for
forming a Cu film on a Co seed by electroplating, and a storage
medium.
BACKGROUND ART
[0002] Recently, as semiconductor devices have higher speed and
wiring patterns get smaller, Cu having higher conductivity than Al
and also having high electromigration resistance and the like has
been in the spotlight as the wiring. Conventionally, a Cu wiring
layer has been formed by electroplating, and Cu has been used as a
seed of Cu wiring formed by electroplating. However, as wiring
patterns get smaller, better embedding characteristic is required.
Accordingly, studies have been made to use Co instead of Cu, which
has been conventionally used, because Co has good embedding
characteristic. Also, Co has the advantages of low resistance and
high adhesion to Cu.
[0003] However, when a Cu film is formed by electroplating, a
copper sulfate has been conventionally used as a plating solution.
However, since Co is soluble in a sulfuric acid, if the Co is used
as a plating seed, the Co is eluted into the plating solution.
DISCLOSURE OF THE INVENTION
Technical Problem
[0004] Recently, as a wiring pattern gets smaller, a plating seed
gets thinner to a thickness of equal to or less than 5 nm. If a Co
film having such a small thickness is used as a plating seed, since
the Co film is eluted into a plating solution during a plating
process, the Co film is lost, and thus a portion where Cu plating
is not formed may be generated or the adhesion of a Cu film may be
deteriorated.
[0005] Accordingly, an objective of the present invention is to
provide a film formation method for forming a Cu film having high
uniformity and high adhesion on a Co seed by preventing Co from
being eluted when a Cu film is to be formed using Co as a plating
seed by electroplating.
[0006] Also, another objective of the present invention is to
provide a storage medium having stored thereon a program for
executing the film formation method.
Technical Solution
[0007] According to a first aspect of the present invention, there
is provided a film formation method including: preparing a
substrate formed a Co film as a seed layer on a surface of the
substrate; applying a negative voltage to the substrate such that a
surface potential of Co is lower than an oxidation potential of the
Co; and in a state when the negative voltage is applied to the
substrate, dipping the Co film in a plating solution mainly
containing copper sulfate solution, thereby a Cu film is formed on
the Co film of the substrate by electroplating.
[0008] According to a second aspect of the present invention, there
is provided a film formation method including: forming a Co film to
become a seed layer on a substrate by CVD; applying a negative
voltage to the substrate such that a surface potential of Co is
lower than an oxidation potential of the Co; and in a state when
the negative voltage is applied to the substrate, dipping the Co
film in a plating solution mainly containing copper sulfate
solution, thereby a Cu film is formed on the Co film of the
substrate by electroplating.
[0009] According to a third aspect of the present invention, there
is provided a storage medium operating on a computer, having stored
thereon a program for controlling a film formation apparatus and
controlling the film formation apparatus on the computer, wherein
the program performs, when the program is executed, a film
formation method including preparing a substrate formed a Co film
as a seed layer on a surface of the substrate, applying a negative
voltage to the substrate such that a surface potential of Co is
lower than an oxidation potential of the Co, and in a state when
the negative voltage is applied to the substrate, dipping the Co
film in a plating solution mainly containing a copper sulfate
solution, thereby a Cu film is formed on the Co film of the
substrate by electroplating.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a schematic cross-sectional view showing an
embodiment of a film formation apparatus for performing a film
formation method according to the present invention.
[0011] FIG. 2 is a flowchart for explaining a film formation method
according to an embodiment of the present invention.
[0012] FIG. 3A is a schematic view showing a state when a voltage
is applied to a wafer before a surface of the wafer is dipped in a
plating solution.
[0013] FIG. 3B is a schematic view showing a state when the surface
of the wafer is dipped in the plating solution after the state of
FIG. 3A.
[0014] FIG. 4 is a schematic view showing an embodiment of a CVD
apparatus for forming a Co film as a plating seed.
[0015] FIG. 5 is a schematic view showing a structure of another
embodiment of a film formation apparatus for performing a film
formation method according to the present invention.
[0016] FIG. 6 is a view for explaining a state when a voltage is
applied without dipping a wafer in a plating solution in the
apparatus of FIG. 5.
[0017] FIG. 7 are photographs showing results of embodiments of the
present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0018] (Mode for Carrying Out the Invention)
[0019] Hereinafter, embodiments of the present invention will be
explained with reference to the attached drawings.
[0020] <Embodiment of a Film Formation Apparatus for Performing
Film Formation Method According to the Present Invention>
[0021] FIG. 1 is a schematic cross-sectional view showing an
embodiment of a film formation apparatus for performing a film
formation method according to the present invention. The film
formation apparatus is constituted as an impregnation-type
electroplating apparatus for forming a Cu film by
electroplating.
[0022] The film formation apparatus 100 includes a support member 1
which holds a semiconductor wafer (hereinafter simply referred to
as a wafer) W, which is a substrate to be processed, on a surface
of which a Co film is formed as a seed layer. The support member 1
is rotatable by a rotating device (not shown), and the wafer W is
rotated in a plane by rotating the support member 1. An edge seal
member 2 having a cylindrical shape is liquid sealed with respect
to the wafer W along an edge of a top surface of the wafer W which
is to be processed. And, a plating solution L is stored in a
container formed by the surface of the wafer W and the edge seal
member 2, and the wafer W and the edge seal member 2 constitute a
lower chamber. Also, an electrode contact point 4 is formed on an
outside portion of the edge seal member 2 of the surface of the
wafer W.
[0023] A plating head 10 having a substantially cylindrical shape
is disposed over the wafer W held by the support member 1 to be
vertically movable by an elevating device 17. The plating head 10
includes an upper chamber 11 in which the plating solution L is
received, an anode electrode 12 which is formed in the upper
chamber 11 to face the wafer W, and an impregnation member 13 which
is formed of a porous ceramic to constitute a bottom of the upper
chamber 11. A plating solution supply hole 14 is formed in a
central portion of a top of the upper chamber 11. The plating
solution L is supplied from a plating solution supply device 16
into the upper chamber 11 through the plating solution supply hole
14. A plurality of plating solution passing holes 15 through which
the plating solution L passes are vertically formed in the anode
electrode 12.
[0024] A direct current power source 5 is connected between the
anode electrode 12 and the wafer W that becomes a cathode
electrode. A negative pole of the direct current power source 5 is
connected through the electrode contact point 4 to the wafer W, and
a positive pole of the direct current power source 5 is connected
to the anode electrode 12. An output voltage of the direct current
power source 5 is variable.
[0025] In order to perform a plating process, the plating head 10
is moved near to the surface of the wafer W, and the plating
solution L is supplied from the plating solution supply hole 14 to
the upper chamber 11. The plating solution L passes through the
impregnation member 13 and is stored in the container formed by the
surface of the wafer W and the edge seal member 2 constituting the
lower chamber, and is additionally stored in the upper chamber 11.
A surface of the plating solution L at this time is high enough to
dip the anode electrode 12 in the plating solution L. Also, the
supplied plating solution can be drained by a drainage device (not
shown).
[0026] The film formation apparatus 100 includes a control unit 20,
and the control unit 20 controls each of elements, for example, the
direct current power source 5, the elevating device 17, the plating
solution supply device 16, a driving device of the support member 1
of the wafer W, and so on. The control unit 20 includes a process
controller 21 including a microprocessor (computer), a user
interface 22, and a memory unit 23. The process controller 21 is
electrically connected to each element of the film formation
apparatus 100 to send a control signal to the elements. The user
interface 22 is connected to the process controller 21, and
includes a keyboard with which an operator executes an input
operation of a command, or the like in order to manage each element
of the film formation apparatus 100, a display on which an
operating state of each element of the film formation apparatus 100
is visually displayed, and so on. The memory unit 23 is also
connected to the process controller 21, and a control program for
implementing various processes performed in the film formation
apparatus 100 under the control of the process controller 21 or a
control program for implementing a predetermined process in each
element of the film formation apparatus 100 according to process
conditions, that is, process recipes, various data bases, and the
like are stored in the memory unit 23. The process recipes are
stored in a storage medium (not shown) in the memory unit 23. The
storage medium may be a stationary medium, such as a hard disk or
the like, or a portable medium such as a CD ROM, a DVD, a flash
memory, or the like. Also, the recipes may be appropriately
transmitted from another device through, for example, a dedicated
line.
[0027] And if necessary, a desired process is performed in the film
formation apparatus 100 under the control of the process controller
21 by reading a predetermined process recipe from the memory unit
23 in response to an instruction or the like from the user
interface 22 and executing the process recipe in the process
controller 21.
[0028] <Film Formation Method According to Embodiment of the
Present Invention>
[0029] Next, a film formation method performed by using the film
formation apparatus constructed as described above according to an
embodiment of the present invention will be explained.
[0030] FIG. 2 is a flowchart for explaining a film formation method
according to an embodiment of the present invention.
[0031] First, the wafer W on a surface of which a Co film is formed
as a plating seed is prepared (operation 1). It is preferable that
a thickness of the Co film ranges from 1.5 to 5 nm. Next, the wafer
W is transferred to the film formation apparatus 100 for forming a
Cu film by electroplating (operation 2), and is held by the support
member 1.
[0032] Next, the plating head 10 is lowered to be in a processing
state, and the plating solution L mainly containing copper sulfate
is supplied into the upper chamber 11 (operation 3). And, as shown
in a schematic view of FIG. 3A, the anode electrode 12 is dipped in
the plating solution L, and in a state when the plating solution
does not reach the wafer W, a negative voltage is applied to the
wafer W, which becomes a cathode electrode, from the direct current
power source 5 such that a surface potential of a Co film 31 is
lower than an oxidation potential (or an oxidation reduction
potential) of Co (operation 4).
[0033] In this state, the plating solution L is additionally
supplied, and as shown in FIG. 3B, the surface of the wafer W, that
is, the Co film 31 is dipped in the plating solution L (operation
5). At this time, since the surface potential of the Co film 31 is
lower than the oxidation potential of the Co, even though the
plating solution L mainly containing the copper sulfate contacts
the Co film formed on the surface of the wafer W, the Co is
prevented from being eluted into the plating solution L. That is,
the Co is electrochemically stable.
[0034] Since the oxidation potential of the Co is -0.28 V, it is
preferable that a voltage is applied before the surface of the
wafer W is dipped in the plating solution L, so that a potential
difference between the wafer W (Co film) and the plating solution
is equal to or greater than 0.3 V at a time when the surface of the
wafer W is dipped in the plating solution L.
[0035] As such, after the surface of the wafer W is dipped in the
plating solution, a Cu plating process is performed by adjusting a
voltage output from the direct current power source 5 to a voltage
for actual Cu plating (operation 6). This voltage is preferably
about 0.1 to 3 V. Accordingly, Cu is educed on the Co film of the
surface of the wafer W, thereby a Cu film is formed.
[0036] After the plating process is finished, the plating head 10
is raised to drain the plating solution L on the surface of the
wafer W, and the wafer W is taken transferred out (operation
7).
[0037] Since the Co has a stronger tendency to be ionized than the
Cu and is soluble in a sulfuric acid, if the plating solution
mainly containing the copper sulfate is brought into contact with
the Co film of the surface of the wafer W without any manipulation,
the Co is converted into Co.sup.+ and is eluted into the plating
solution L. In particular, as a wiring pattern of a semiconductor
device gets smaller, a film thickness of a plating seed layer is
required to be equal to or less than 5 nm. However, if the Co film
having such a small thickness is used as a plating seed layer,
since the Co is eluted and the Co film is thinned or lost when the
Co film is dipped in the plating solution L, a portion where a Cu
plating film is not formed may be generated or the adhesion of the
Cu film may be deteriorated.
[0038] To solve the problems, in the present embodiment, before the
surface of the wafer W is dipped in the plating solution L, a
negative voltage is applied to the wafer W which becomes the
cathode electrode such that the surface potential of the Co film is
lower than the oxidation potential of the Co. At this time, since
the Co is prevented from being eluted into the plating solution, a
portion where Cu plating is not formed is prevented from being
generated, and the adhesion of the Cu film is prevented from being
deteriorated, thereby forming the Cu film having high uniformity
and high adhesion.
[0039] Since the risk of the problems is low if a thickness of the
Co film is greater than 5 nm, the method of the present embodiment
is effective when the thickness of the Co film is equal to or less
than 5 nm. Meanwhile, if a Cu film is formed on the Co film by
electroplating, since the Co film is first etched by as much as 1
nm due to immersion plating, it is preferable that a thickness of
the Co film is determined in consideration of the etched portion.
Accordingly, it is preferable that a thickness of the Co film
ranges from 1.5 to 5 nm.
[0040] A method of forming the Co film is not limited to a specific
method, and may be physical vapor deposition (PVD), such as
sputtering, or chemical vapor deposition (CVD). However, in order
to form the Co film having a small thickness equal to or less than
5 nm even in a micro hole as a wiring pattern gets smaller, it is
preferable that CVD having good step coverage is used. The wafer W
for forming the Co film may have a surface on which an organic
insulating film or a SiOxCy insulating film (x and y are integers)
is formed as a base.
[0041] FIG. 4 is a schematic view showing an embodiment of a CVD
film formation apparatus for forming a Co film by CVD. The CVD film
formation apparatus 200 includes a chamber 41, and a susceptor 42
for horizontally holding a wafer W, which is a substrate to be
processed, is formed in a bottom of the chamber 41. A heater 43 is
embedded in the susceptor 42, and as electric current flows through
the heater 43, the wafer W placed on the susceptor 42 is
heated.
[0042] A shower head 45 is formed to protrude downward from a
ceiling wall in a top of the chamber 41. A gas introduction hole 46
through which a process gas is introduced is formed at a central
portion of a top of the shower head 45 for ejecting the process gas
for film formation into the chamber 41. As gas diffusing space 47
is formed in the shower head 45, and a plurality of gas ejection
holes 49 are formed in a bottom plate 48 of the shower head 45. A
gas supply pipe 51 is connected to the gas introduction hole 46,
and a process gas supply device 52 is connected to the gas supply
pipe 51. And, the process gas for forming a Co film introduced from
the process gas supply device 52 into the gas diffusing space 47
through the gas supply pipe 51 and the gas introduction hole 46 is
ejected from the gas ejection holes 49 into the chamber 41.
[0043] An exhaust port 55 is formed in the bottom of the chamber
41, and an exhaust pipe 56 is connected to the exhaust port 55. A
pressure regulating valve and a vacuum pump (both not shown) are
formed at the exhaust pipe 56. An inlet/outlet 57 for transferring
the wafer W and a gate valve 58 for opening/closing the
inlet/outlet 57 are formed at a side wall of the chamber 41.
[0044] The CVD film formation apparatus 200 includes the same
control unit 60 as the control unit 20 of the film formation
apparatus 100, and the control unit 60 controls the CVD film
formation apparatus 200 in completely the same manner as that of
the control unit 20.
[0045] In the CVD film formation apparatus constructed as described
above, the wafer W is transferred to the chamber 41, vacuum exhaust
is performed in a inner part of the chamber 41 until a pressure in
the chamber 41 reaches a predetermined pressure, a process gas is
introduced from the process gas supply device 52 into the chamber
41 through the gas supply pipe 51 and the shower head 45, and a
film formation reaction occurs on the wafer W that is heated to a
predetermined temperature, thereby a Co film is formed on the
wafer.
[0046] This process gas is not limited to a specific gas as long as
the process gas can be practically used to form a Co film. For
example, a reducing agent and cobalt amindinate such as
bis(N-tert-butyl-N'-ethyl-propionamidinate) cobalt (II)
(Co(tBu-Et-Et-amd).sub.2) may be used. The reducing agent may be a
H.sub.2 gas, a NH.sub.3 gas, or a carbonic acid gas. Also, cobalt
carbonyl (CO.sub.2(CO).sub.8) may be used, and in this case,
pyrolysis may be performed on the wafer W to form a Co film. It is
preferable that a temperature of a film formation is 100 to
300.degree. C. in the former case and is 120 to 300.degree. C. in
the latter case.
[0047] As such, after the Co film is formed on the wafer W by CVD,
a Cu film is formed on the Co film by electroplating as described
above. Accordingly, after the Co film having good step coverage is
thinly formed even in a micro pattern, a Cu film having high
adhesion can be formed without losing the Co film.
[0048] <Another Embodiment of a Film Formation Apparatus for
Performing Film Formation Method of the Present Invention>
[0049] While the film formation apparatus 100 is an impregnation
type electroplating apparatus in the above embodiment, a film
formation apparatus in this present embodiment is a type of an
electroplating apparatus that simply dips an anode electrode and a
wafer, on a surface of which a Co film is formed, in a plating
solution.
[0050] FIG. 5 is a schematic view showing a structure of another
embodiment of a film formation apparatus for performing a film
formation method according to the present invention. The film
formation apparatus 100' includes a plating bath 71 in which a
plating solution L is stored, and an anode electrode 72 is dipped
in the plating solution L. And, a wafer W is dipped as a cathode
electrode in the plating solution L. The wafer W is movable by a
driving device (not shown) between a state where the wafer W is
dipped in the plating solution L as shown in FIG. 5 and a state
where the wafer W is raised above the plating solution L. A direct
current power source 73 is connected between the anode electrode 72
and the wafer W.
[0051] In the film formation apparatus 100' constructed as
described above, as shown in FIG. 6, in a state where the wafer W
is raised above the plating solution L, a negative voltage is
applied to the wafer W, which is the cathode electrode, from the
direct current power source 73 such that a surface potential of a
Co film is lower than an oxidation potential of Co. Accordingly,
since then, even though the wafer W is lowered to be dipped in the
plating solution L, since the surface potential of the Co film is
lower than the oxidation potential of the Co, the Co is prevented
from being eluted into the plating solution L.
[0052] Next, a Cu plating process is performed by adjusting a
voltage output from the direct current power source 73 to a voltage
for actual Cu plating, thereby Cu film is formed on the Co
film.
[0053] As described above, according to the present embodiment,
since the negative voltage is applied to the wafer W such that the
surface potential of the Co film is lower than the oxidation
potential of the Co before the wafer W on the surface of which the
Co film, which is a plating seed is formed, is dipped in the
plating solution, the Co is prevented from being eluted into the
plating solution, and thus a portion where Cu plating is not formed
is prevented from being generated and the adhesion of the Cu film
is prevented from being deteriorated, thereby enabling to form the
Cu film having high uniformity and high adhesion.
Embodiments
[0054] Next, embodiments will be explained.
[0055] A sample in which a Co film was formed as a plating seed to
a thickness of 10 nm on a substrate and two samples in each of
which a Co film was formed as a plating seed to a thickness of 5 nm
on a substrate were prepared. First, no voltage was applied to the
sample in which the Co film was formed to the thickness of 10 nm
and one of the samples in which the Co film was formed to the
thickness of 5 nm before the samples were dipped in plating
solutions, and Cu films are formed by electroplating. Also, a
voltage of -20 V was applied to the other sample in which the Co
film was formed to the thickness of 5 nm before the sample was
dipped in a plating solution, thereby a Cu film is formed by
electroplating.
[0056] FIG. 7 are photographs showing plating states of the samples
as time passes. As shown in FIG. 7, it was found that in the sample
in which the Co film was formed to the thickness of 10 nm, the Cu
film was formed satisfactorily although no voltage was applied
before the electroplating. Meanwhile, it was found that in the
sample in which the Co film was formed to the thickness of 5 nm, Co
was lost and no Cu film was formed when no voltage was applied
before the electroplating. However, it was found that in the sample
in which the Co film was formed to the thickness of 5 nm, the Cu
film was formed satisfactorily when the voltage of -20 V was
applied before the electroplating.
[0057] <Another Application of the Present Invention>
[0058] Also, the present invention may be modified in various ways
without being limited to the above-described embodiments. For
example, a film formation apparatus constituted as an
electroplating apparatus is not limited to that in the embodiment
and may be any of various apparatuses.
[0059] Also, although a semiconductor wafer is used as a substrate
to be processed, the present invention is not limited thereto and
another substrate, such as a flat panel display (FPD) substrate or
the like may be used.
* * * * *