U.S. patent application number 11/523135 was filed with the patent office on 2008-03-20 for method of reducing oxygen content in ecp solution.
This patent application is currently assigned to Taiwan Semiconductor Manufacturing Co., Ltd.. Invention is credited to Kei-Wei Chen, Hsi-Kuei Cheng, Ming-Yuan Cheng, Ray Chuang, Hsien-Ping Feng, Steven Lin, Jung-Chin Tsao.
Application Number | 20080067076 11/523135 |
Document ID | / |
Family ID | 39187437 |
Filed Date | 2008-03-20 |
United States Patent
Application |
20080067076 |
Kind Code |
A1 |
Cheng; Ming-Yuan ; et
al. |
March 20, 2008 |
Method of reducing oxygen content in ECP solution
Abstract
A novel method, which is suitable to substantially reduce the
presence of oxygen micro-bubbles in an electroplating bath
solution, is disclosed. The method includes the addition of aerobic
bacteria to the electroplating bath solution to consume oxygen in
the solution. Reduction of the oxygen content in the electroplating
bath solution prevents oxygen micro-bubbles from forming in the
solution and becoming trapped between the solution and the surface
of a metal seed layer on a substrate to block the electroplating of
a metal film onto the seed layer. Consequently, the presence of
surface pits and other structural defects in the surface of the
electroplated metal film is substantially reduced.
Inventors: |
Cheng; Ming-Yuan; (Taipei
City, TW) ; Feng; Hsien-Ping; (Yonghe City, TW)
; Cheng; Hsi-Kuei; (Jhubei City, TW) ; Chen;
Kei-Wei; (Taipei, TW) ; Tsao; Jung-Chin;
(Tainan City, TW) ; Lin; Steven; (Hsin-Chu,
TW) ; Chuang; Ray; (Taipei, TW) |
Correspondence
Address: |
TUNG & ASSOCIATES;Suite 120
838 W. Long Lake Road
Bloomfield Hills
MI
48302
US
|
Assignee: |
Taiwan Semiconductor Manufacturing
Co., Ltd.
|
Family ID: |
39187437 |
Appl. No.: |
11/523135 |
Filed: |
September 19, 2006 |
Current U.S.
Class: |
205/261 |
Current CPC
Class: |
C25D 3/02 20130101; C02F
3/34 20130101 |
Class at
Publication: |
205/261 |
International
Class: |
C25D 3/00 20060101
C25D003/00 |
Claims
1. A method of electroplating a thin film onto a substrate,
comprising: providing an electroplating bath solution; providing
aerobic bacteria in said solution; providing a current source in
electrical contact with said substrate; immersing said substrate in
said solution; and plating the thin film onto said substrate by
applying a current to said substrate.
2. The method of claim 1 wherein said aerobic bacteria is a
nitrifying bacterial agent, Bdellovibrio bacteriovorus,
Acinetobacter calcoaceticus, Pseudamonas fluorescens, Arthrobacter
globiformis, or Acetobacter pasteurianus.
3. The method of claim 1 wherein said solution comprises copper
sulfate.
4. The method of claim 3 wherein said aerobic bacteria is a
nitrifying bacterial agent, Bdellovibrio bacteriovorus,
Acinetobacter calcoaceticus, Pseudamonas fluorescens, Arthrobacter
globiformis, or Acetobacter pasteurianus.
5. The method of claim 1 wherein said aerobic bacteria is present
in said solution in a concentration of about 1 ml/l to 5 ml/l.
6. The method of claim 5 wherein said aerobic bacteria is a
nitrifying bacterial agent, Bdellovibrio bacteriovorus,
Acinetobacter calcoaceticus, Pseudamonas fluorescens, Arthrobacter
globiformis, or Acetobacter pasteurianus.
7. The method of claim 5 wherein said solution comprises copper
sulfate.
8. The method of claim 7 wherein said aerobic bacteria is a
nitrifying bacterial agent, Bdellovibrio bacteriovorus,
Acinetobacter calcoaceticus, Pseudamonas fluorescens, Arthrobacter
globiformis, or Acetobacter pasteurianus.
9. A method for forming a metal film onto a substrate by: providing
an electroplating bath solution comprising a metal; providing
aerobic bacteria in a concentration of from about 1 ml/l to about 5
ml/l; providing a current source in electrical contact with said
substrate; immersing said substrate in said solution; and applying
a current of from about 0.2 mA/cm.sup.2 to about 20 mA/cm.sup.2 to
said substrate.
10. The metal film of claim 9 wherein said aerobic bacteria is a
nitrifying bacterial agent, Bdellovibrio bacteriovorus,
Acinetobacter calcoaceticus, Pseudamonas fluorescens, Arthrobacter
globiformis, or Acetobacter pasteurianus.
11. The metal film of claim 9 wherein said electroplating bath
solution comprises copper sulfate.
12. An electrochemical plating solution comprising: an electrolyte
solution comprising metal; and an aerobic bacteria provided in said
electrolyte solution.
13. The electrochemical plating solution of claim 12 wherein said
metal is copper, aluminum, nickel, chromium, zinc, tin, gold,
silver, lead, or cadmium.
14. The electrochemical plating solution of claim 12 wherein said
aerobic bacteria is a nitrifying bacterial agent, Bdellovibrio
bacteriovorus, Acinetobacter calcoaceticus, Pseudamonas
fluorescens, Arthrobacter globiformis, or Acetobacter
pasteurianus.
15. The electrochemical plating solution of claim 12 wherein said
aerobic bacteria is present in said electroplating bath solution in
a concentration of about 1 ml/l to 5 ml/l.
16. The electrochemical plating solution of claim 12 wherein said
electroplating bath solution comprises copper sulfate.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to electrochemical plating
(ECP) processes used to deposit metal layers on semiconductor wafer
substrates in the fabrication of semiconductor integrated circuits.
More particularly, the present invention relates to a method of
reducing the oxygen content of an electroplating bath solution by
adding aerobic bacteria to the solution in order to enhance the
quality of an electroplated metal film.
BACKGROUND OF THE INVENTION
[0002] When a copper layer is deposited on a substrate, such as by
electrochemical plating, the copper layer must be deposited on a
metal seed layer such as copper, which is deposited on the
substrate prior to the copper ECP process. Conventional
electrochemical plating techniques typically use copper sulfate
(CuSO.sub.4) for the main electrolyte in the electroplating bath
solution. The solution may further include additives such as
chloride ion and levelers, as well as accelerators and suppressors,
which increase and decrease, respectively, the rate of the
electroplating process. The rate of deposition of copper on the
substrate, and the quality and resulting electrical and mechanical
properties of the metallization, are critically dependent on the
concentration of these organic additives in the electroplating bath
solution.
[0003] Throughout the electroplating process, the electroplating
bath solution is continually circulated from and back to the bath
container, respectively. This circulation of the solution often
induces the formation of oxygen micro-bubbles in the solution. The
micro-bubbles tend to become trapped at various locations on the
seed layer deposited on the wafer and block deposition of the metal
film onto the seed layer at those locations. As a result, the metal
film is unevenly plated on the seed layer. During subsequent
chemical mechanical planarization (CMP) of the electroplated metal
film, this phenomenon is manifested by the presence of defects in
the form of pits, voids, broken metal lines and other defects in
device features on the wafer. The presence of pits, voids and
broken metal lines in device features leads to unreliable,
unpredictable and unuseable electronic devices in the electronic
circuit containing the features. Accordingly, a novel method is
needed to reduce the oxygen content in an electrochemical plating
bath solution in order to prevent or at least reduce the formation
of bubble-induced defects in a metal film or line electroplated
onto a wafer.
SUMMARY OF THE INVENTION
[0004] In accordance with these and other objects and advantages,
the present invention is generally directed to a novel method,
which is suitable to substantially reduce the presence of oxygen
micro-bubbles in an electroplating bath solution. The method
includes the addition of aerobic bacteria to the electroplating
bath solution to consume oxygen in the solution. Reduction of the
oxygen content in the electroplating bath solution prevents oxygen
micro-bubbles from forming in the solution and becoming trapped
between the solution and the surface of a metal seed layer on a
substrate to block the electroplating of a metal film onto the seed
layer. Consequently, the presence of surface pits and other
structural defects in the surface of the electroplated metal film
is substantially reduced.
[0005] The present invention is further directed to a metal film
having a substantially reduced number of surface pits, voids and
other defects. The metal film is plated onto a substrate by
providing an electrochemical plating solution, adding aerobic
bacteria to the solution, immersing the substrate in the solution,
and carrying out an electroplating process in the solution.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] The invention will be better understood, by way of example,
with reference to the accompanying drawings, in which:
[0007] FIG. 1 is a schematic of an electrochemical plating system
in implementation of the present invention;
[0008] FIG. 1A is a cross-sectional view of a wafer substrate with
a metal film electroplated thereon according to the method of the
present invention;
[0009] FIG. 2 is a flow diagram illustrating a typical flow of
process steps carried out according to the method of the present
invention; and
[0010] FIG. 3 is a graph in which the concentration of dissolved
oxygen (DO) in an electroplating bath solution to which aerobic
bacteria have been added is compared to the concentration of
dissolved oxygen in an electroplating bath solution devoid of
aerobic bacteria.
DETAILED DESCRIPTION OF THE INVENTION
[0011] The present invention has particularly beneficial utility in
the electrochemical plating of a high-quality copper film on a
copper seed layer deposited on a semiconductor wafer substrate in
the fabrication of semiconductor integrated circuits. However, the
invention is more generally applicable to the electrochemical
plating of metals including but not limited to copper on substrates
in a variety of industrial applications including but not limited
to semiconductor fabrication.
[0012] The present invention is generally directed to a novel
method for substantially reducing the presence of oxygen
micro-bubbles in an electroplating bath solution used to
electroplate a metal film on a seed layer provided on a substrate.
The method facilitates the electroplating of a metal film which is
substantially devoid of voids and surface pits onto the seed layer.
According to the method, an aerobic bacteria is added to the
electroplating bath solution. The aerobic bacteria consumes all or
most of the oxygen in the solution to prevent or reduce the
formation of oxygen micro-bubbles in the solution typically as the
solution is circulated through the bath container. Consequently,
micro-bubble blockage of metal electroplated onto the seed layer is
prevented or at least substantially reduced.
[0013] The present invention is further directed to a metal film
having a substantially reduced number of surface pits, voids and
other defects. The metal film is plated onto a substrate by
providing an electrochemical plating solution, adding aerobic
bacteria to the solution, immersing the substrate in the solution,
and carrying out an electroplating process in the solution.
[0014] The method of the present invention may be used with any
formulation for the electrochemical plating bath solution, such as
copper, aluminum, nickel, chromium, zinc, tin, gold, silver, lead
and cadmium electrochemical plating baths. The present invention is
also suitable for use with electrochemical plating baths containing
mixtures of metals to be plated onto a substrate.
[0015] It is preferred that the electroplating bath be a copper
alloy electroplating bath, and more preferably, a copper
electroplating bath. Typical copper electroplating bath
formulations are well known to those skilled in the art and
include, but are not limited to, an electrolyte and one or more
sources of copper ions. Suitable electrolytes include, but are not
limited to, sulfuric acid, acetic acid, fluoroboric acid, methane
sulfonic acid, ethane sulfonic acid, trifluormethane sulfonic acid,
phenyl sulfonic acid, methyl sulfonic acid, p-toluenesulfonic acid,
hydrochloric acid, phosphoric acid and the like. The acids are
typically present in the bath in a concentration in the range of
from about 1 to about 300 g/L. The acids may further include a
source of halide ions such as chloride ions.
[0016] Suitable sources of copper ions include, but are not limited
to, copper sulfate, copper chloride, copper acetate, copper
nitrate, copper fluoroborate, copper methane sulfonate, copper
phenyl sulfonate and copper p-toluene sulfonate. Such copper ion
sources are typically present in a concentration in the range of
from about 10 to about 300 g/L of electroplating solution.
[0017] Aerobic bacteria which are suitable for implementation of
the present invention include nitrifying bacterial agents,
Bdellovibrio bacteriovorus, Acinetobacter calcoaceticus,
Pseudamonas fluorescens, Arthrobacter globiformis, and Acetobacter
pasteurianus. In a preferred embodiment of the present invention,
the aerobic bacteria is a nitrifying bacterial agent. Preferably,
the aerobic bacteria are present in the electroplating bath
solution in a concentration of from typically about 1 ml/l to about
5 ml/l.
[0018] Other electrochemical plating process conditions suitable
for implementation of the present invention include a plating rpm
of from typically about 0 rpm to about 500 rpm; a plating current
of from typically about 0.2 mA/cm.sup.2 to about 20 mA/cm.sup.2;
and a bath temperature of from typically about 10 degrees C. to
about 35 degrees C. In cases in which planarity of the
electroplated metal through chemical mechanical planarization (CMP)
is necessary, a leveling agent may be added to the electroplating
bath solution at a concentration of from typically about 5 mmol/L
to about 5 mol/L.
[0019] Referring to FIG. 1, an electrochemical plating (ECP) system
10 which is suitable for implementation of the present invention is
shown. The system 10 may be conventional and includes a standard
electroplating cell having an adjustable current source 12, a bath
container 14, a typically copper anode 16 and a cathode 18, which
cathode 18 is the semiconductor wafer substrate that is to be
electroplated with copper. The anode 16 and cathode/substrate 18
are connected to the current source 12 by means of suitable wiring
38. The bath container 14 holds an electrolyte electroplating bath
solution 20. The system 10 may further include a mechanism for
rotating the substrate 18 in the bath 20 during the electroplating
process, as is known by those skilled in the art.
[0020] The ECP system 10 may further include a pair of bypass
filter conduits 24, a bypass pump/filter 30, and an electrolyte
holding tank 34. The bypass filter conduits 24 typically extend
through the anode 16 and open to the upper, oxidizing surface 22 of
the anode 16 at opposite ends of the anode 16. The bypass filter
conduits 24 connect to the bypass pump/filter 30 located outside
the bath container 14, and the bypass pump/filter 30 is further
connected to the electrolyte holding tank 34 through a tank inlet
line 32. The electrolyte holding tank 34 is, in turn, connected to
the bath container 14 through a tank outlet line 36. It is
understood that the ECP system 10 heretofore described represents
just one example of a possible system which is suitable for
implementation of the present invention, and other systems of
alternative design may be used instead.
[0021] Referring to FIGS. 1, 1A and 2, according to the method of
the present invention, a metal seed layer 19, such as copper, is
deposited on a wafer substrate 18, as indicated in step S1 of FIG.
2. The metal seed layer 19 may be deposited on the substrate 18
using conventional chemical vapor deposition (CVD) or physical
vapor deposition (PVD) techniques, for example, according to the
knowledge of those skilled in the art. The seed layer 19 has a
thickness of typically about 50.about.1500 angstroms.
[0022] As indicated in step S2 of FIG. 2, the electrochemical
plating (ECP) electrolyte bath solution 20 is prepared in the bath
container 14. The electroplating bath solution 20 may include an
accelerator having a concentration of from typically about 5 mmol/L
to about 5 mol/L, and may include a leveling agent or additive in a
concentration of from typically about 5 mmol/L to about 5 mol/L, as
heretofore noted.
[0023] Next, as indicated in step S3 and shown in FIG. 1, the
aerobic bacteria 25 of the present invention is added to the
electroplating bath solution 20, which is then circulated from the
bath container 14, through the electrolyte holding tank 34 and back
to the bath container 14, by operation of the pump 30, to achieve
an aerobic bacteria concentration of from typically about 1 ml/l to
typically about 5 ml/l in the electroplating bath solution 20. The
anode 16 and substrate 18 are then immersed in the bath solution 20
and connected to the adjustable current source 12, typically
through wiring 38. Accordingly, the seed layer 19 on the substrate
18 contacts the bath solution 20. The entire surface of the seed
layer 19, as well as gap features on the substrate 18, is
thoroughly wetted by the bath solution 20.
[0024] As indicated in step S4 of FIG. 2, the bath 20 is
continually circulated from the bath container 14 through the
bypass filter conduits 24, electrolyte holding tank 34 and back
into the bath container 14, respectively, by operation of the pump
30. This maintains the copper sulfate or other electrolyte in a
dissolved state in the electroplating bath solution 20, and
prevents or minimizes precipitation of the electrolyte onto the
sides, bottom and other surfaces of the bath container 14,
throughout the electroplating process.
[0025] During circulation of the bath solution 20 throughout the
ECP system 10, as heretofore described, dissolved oxygen normally
forms oxygen micro-bubbles (not shown) in the bath solution 20.
Accordingly, the aerobic bacteria 25, having been previously added
to the bath solution 20 at step S3 of FIG. 2, consume all or most
of the oxygen present in the bath solution 20. This eliminates or
substantially reduces the quantity of oxygen micro-bubbles which
form in the solution 20. Consequently, the presence of
micro-bubbles between the bath solution 20 and the seed layer 19 on
the substrate 18 is eliminated or substantially reduced during the
subsequent electroplating process, which will be hereinafter
described.
[0026] As the electroplating bath solution 20 is circulated through
the system 10, a metal film 21 is electroplated onto the seed layer
19, as shown in FIG. 1A and indicated in step S5 of FIG. 2,
typically as follows. The electroplating bath solution 20 is
maintained at a temperature of from typically about 10 degrees C.
to about 35 degrees C. The plating rpm for the substrate 18 is
typically about 0-500 rpm.
[0027] During the electrochemical plating process, the current
source 12 applies a selected voltage potential, typically at room
temperature, between the anode 16 and the cathode/substrate 18.
This voltage potential creates a magnetic field around the anode 16
and the cathode/substrate 18, which magnetic field affects the
distribution of the copper ions in the bath solution 20. In a
typical copper electroplating application, a voltage potential of
about 2 volts may be applied for about 2 minutes, and a plating
current of from typically about 0.2 mA/cm.sup.2 to about 20
mA/cm.sup.2 flows between the anode 16 and the cathode/substrate
18.
[0028] Consequently, copper is oxidized typically at the oxidizing
surface 22 of the anode 16 as electrons harvested from the copper
anode 16 flow through the wiring 38 and reduce the ionic copper in
the typically copper sulfate solution bath solution 20 to form a
copper electroplate (not illustrated) at the interface between the
cathode/substrate 18 and the copper sulfate bath 20. Due to the
absence or paucity of oxygen micro-bubbles between the bath
solution 20 and the surface of the seed layer 19, the electroplated
metal film 21 deposited onto the seed layer 19 is substantially
continuous and devoid of structural deformities such as voids, pits
and broken metal lines. Accordingly, the electroplated metal film
21 on the substrate 18 contributes to the fabrication of
high-quality IC devices that are characterized by high structural
and operational integrity.
[0029] Referring next to the graph of FIG. 3, which illustrates a
graph in which the concentration of dissolved oxygen (DO) in an
electroplating bath solution to which aerobic bacteria have been
added is compared to the concentration of dissolved oxygen in an
electroplating bath solution devoid of aerobic bacteria. From a
consideration of the graph, it can be seen that the addition of
aerobic bacteria to an electroplating bath solution is capable of
reducing the concentration of dissolved oxygen (DO) in the solution
from about 5 mg/l to about 2 mg/l.
[0030] While the preferred embodiments of the invention have been
described above, it will be recognized and understood that various
modifications can be made in the invention and the appended claims
are intended to cover all such modifications which may fall within
the spirit and scope of the invention.
* * * * *