U.S. patent application number 10/761784 was filed with the patent office on 2004-08-05 for integrated circuit structure with copper interconnect.
This patent application is currently assigned to Sharp Laboratories of America, Inc.. Invention is credited to Evans, David R., Hsu, Sheng Teng, Pan, Wei.
Application Number | 20040152307 10/761784 |
Document ID | / |
Family ID | 29269684 |
Filed Date | 2004-08-05 |
United States Patent
Application |
20040152307 |
Kind Code |
A1 |
Pan, Wei ; et al. |
August 5, 2004 |
Integrated circuit structure with copper interconnect
Abstract
A method of adhering copper thin film to a substrate in an
integrated circuit structure includes preparing a substrate,
including forming active regions and trenches for interconnect
structures; depositing a metal barrier layer on the substrate;
depositing an ultra thin film layer of tungsten over the barrier
metal layer; depositing a copper thin film on the tungsten ultra
thin film layer; removing excess copper and tungsten to the level
of the metal barrier layer; and completing the integrated circuit
structure. An integrated circuit having a copper interconnect
therein formed over a layer of barrier metal includes a substrate,
including active regions, vias and trenches for interconnect
structures; a metal barrier layer formed on the substrate, wherein
said metal barrier layer is taken from the group of materials
consisting of Ta, TiN, TaN, TaSiN and TiSiN, and formed to a
thickness of between about 5 nm to 10 nm; an ultra thin film layer
of tungsten formed on the barrier metal layer, said tungsten ultra
thin film layer having a thickness of between about 1 nm to 5 nm;
and a copper thin film layer formed on the tungsten ultra thin film
layer to a thickness sufficient to fill the vias and trenches.
Inventors: |
Pan, Wei; (Vancouver,
WA) ; Evans, David R.; (Beaverton, OR) ; Hsu,
Sheng Teng; (Camas, WA) |
Correspondence
Address: |
David C. Ripma, Patent Counsel
Sharp Laboratories of America, Inc.
5750 N.W. Pacific Rim Boulevard
Camas
WA
98607
US
|
Assignee: |
Sharp Laboratories of America,
Inc.
|
Family ID: |
29269684 |
Appl. No.: |
10/761784 |
Filed: |
January 21, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10761784 |
Jan 21, 2004 |
|
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10140460 |
May 6, 2002 |
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6716744 |
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Current U.S.
Class: |
438/687 ;
257/E21.17; 257/E21.171; 438/643; 438/644 |
Current CPC
Class: |
H01L 23/53238 20130101;
H01L 2924/00 20130101; H01L 21/76846 20130101; H01L 2924/0002
20130101; H01L 21/28556 20130101; H01L 21/28562 20130101; H01L
2924/0002 20130101 |
Class at
Publication: |
438/687 ;
438/643; 438/644 |
International
Class: |
H01L 021/4763; H01L
021/44 |
Claims
We claim:
1. A method of adhering copper thin film to a substrate in an
integrated circuit structure comprising: preparing a substrate,
including forming active regions, vias and trenches for
interconnect structures; depositing a metal barrier layer on the
substrate; depositing an ultra thin film layer of tungsten over the
barrier metal layer; depositing a copper thin film on the tungsten
ultra thin film layer; removing excess copper and tungsten to the
level of the metal barrier layer; and completing the integrated
circuit structure.
2. The method of claim 1 wherein said depositing an ultra thin film
layer of tungsten includes depositing a tungsten layer having a
thickness of between about 1 nm to 5 nm.
3. The method of claim 1 wherein said depositing an ultra thin film
layer of tungsten includes depositing the tungsten by a deposition
method taken from the group of methods consisting of MOCVD and
ALD.
4. The method of claim 1 wherein said depositing an ultra thin film
layer of tungsten includes depositing the tungsten from a precursor
taken from the group of precursors consisting of WF.sub.6 and
W(CO).sub.6.
5. The method of claim 1 wherein said depositing a barrier metal
layer includes depositing a layer of material taken from the group
of materials consisting of Ta, TiN, TaN and TiSiN.
6. The method of claim 1 wherein said depositing a barrier metal
layer includes depositing a layer of material to a thickness of
between about 5 nm to 10 nm.
7. The method of claim 1 wherein said depositing a barrier metal
layer includes depositing a layer of material by PVD, ALD or
MOCVD.
8. The method of claim 1 wherein said depositing a copper thin film
includes depositing a layer of copper to a thickness sufficient to
fill vias and trenches in the structure.
9. The method of claim 8 wherein said depositing a copper thin film
includes depositing a layer of copper to a thickness sufficient to
fill vias and trenches in the structure includes depositing a layer
of copper to a thickness of between about 10 nm to 20 nm.
10. The method of claim 1 wherein said depositing a copper thin
film includes depositing a layer of copper by PVD, ALD or
MOCVD.
11. A method of adhering copper thin film to a substrate in an
integrated circuit structure comprising: preparing a substrate,
including forming active regions, vias and trenches for
interconnect structures; depositing a metal barrier layer on the
substrate; depositing an ultra thin film layer of tungsten over the
barrier metal layer to a thickness of between about 1 nm to 5 nm
from a precursor taken from the group of precursors consisting of
WF.sub.6 and W(CO).sub.6; depositing a copper thin film on the
tungsten ultra thin film layer; removing excess copper and tungsten
to the level of the metal barrier layer; and completing the
integrated circuit structure.
12. The method of claim 11 wherein said depositing an ultra thin
film layer of tungsten includes depositing the tungsten by a
deposition method taken from the group of methods consisting of
MOCVD and ALD.
13. The method of claim 11 wherein said depositing a barrier metal
layer includes depositing a layer of material taken from the group
of materials consisting of Ta, TiN, TaN TaSiN and TiSiN.
14. The method of claim 11 wherein said depositing a barrier metal
layer includes depositing a layer of material to a thickness of
between about 5 nm to 10 nm.
15. The method of claim 11 wherein said depositing a barrier metal
layer includes depositing a layer of material by PVD, ALD or
MOCVD.
16. The method of claim 11 wherein said depositing a copper thin
film includes depositing a layer of copper to a thickness
sufficient to fill vias and trenches in the structure.
17. The method of claim 16 wherein said depositing a copper thin
film includes depositing a layer of copper to a thickness
sufficient to fill vias and trenches in the structure includes
depositing a layer of copper to a thickness of between about 10 nm
to 20 nm.
18. The method of claim 11 wherein said depositing a copper thin
film includes depositing a layer of copper by PVD, ALD or
MOCVD.
19. An integrated circuit having a copper interconnect therein
formed over a layer of barrier metal comprising: a substrate,
including active regions, vias and trenches for interconnect
structures; a metal barrier layer formed on the substrate, wherein
said metal barrier layer is taken from the group of materials
consisting of Ta, TiN, TaN and TiSiN, and formed to a thickness of
between about 5 nm to 10 nm; an ultra thin film layer of tungsten
formed on the barrier metal layer, said tungsten ultra thin film
layer having a thickness of between about 1 nm to 5 nm; and a
copper thin film layer formed on the tungsten ultra thin film layer
to a thickness to sufficient to fill the vias and trenches in the
structure
20. The integrated circuit of claim 19 wherein said ultra thin film
layer of tungsten is formed from a precursor taken from the group
of precursors consisting of WF.sub.6 and W(CO).sub.6.
21. The method of claim 19 wherein said depositing a copper thin
film includes depositing a layer of copper to a thickness
sufficient to fill the vias and trenches in the structure includes
depositing a layer of copper to a thickness of between about 10 nm
to 20 nm.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional of application Ser. No.
10/140,465, filed May 6, 2002, entitled Ultra Thin Tungsten Metal
Films Used as Adhesion Promoter Between Barrier Metals and Copper,
invented by Pan et al.
RELATED APPLICATIONS
[0002] This application is related to Ser. No. 09/940,739, filed
Aug. 27, 2001, for Thermal densification in the early stage of
Copper MOCVD for depositing high quality Cu films with good
adhesion and trench filling characteristics.
FIELD OF THE INVENTION
[0003] This invention relates to MOCVD of barrier and copper thin
films for interconnects in semiconductor IC high-speed devices, and
specifically to a method of enhancing adhesion properties of CVD
copper.
BACKGROUND OF THE INVENTION
[0004] Copper films which are formed by metal organic chemical
vapor deposition (MOCVD) on metal nitride barriers, such as TiN or
TaN, for example, which are also formed by MOCVD, do not exhibit
good adhesive integrity, especially when the copper layer is grown
in situ on a nitride layer or structure. The exhibited adhesion
properties have prevented the application of copper CVD technology
in IC manufacturing.
[0005] A great deal of research has been done in this area in order
to improve the adhesion of copper to underlying barrier films. The
related application and the cited prior art identify some
improvements which have been made in this field, and include water
vapor injection, barrier surface oxidation, barrier surface
pre-treatment, and thermal densification. Of these improvements,
only thermal densification has been shown to have practical
application in providing reasonable throughput when copper is to be
deposited in narrow trenches and vias. However, as thermal
densification requires additional steps, thermal densification in
copper CVD is relatively complex, and has lower throughput compared
to conventional CVD.
[0006] Atomic Layer CVD (ALD) is a relatively new technology that
has been adopted in semiconductor research, and is now being
adopted for commercial IC production. ALD uses rapidly operating
valves to deliver individual reactants into a deposition chamber.
Each reactant deposits a mono-layer of material on the IC surface
through chemical absorption, and reacts with a previously deposited
mono-layer species to form the desired compound. The as-formed
compound has a much higher density than could ever be achieved by
conventional CVD. The ALD process also provides excellent step
coverage. By carefully selecting precursors, multi-layered, or
alternating layered, barrier metal films are formed, e.g.,
alternating TaN/SiN, TaN/TiN and TiN/SiN thin films, or other
combinations thereof, may be easily formed. An entire film stack
formed by ALD may be only 50 .ANG. thick, and also exhibits
excellent barrier properties.
[0007] The application of ALD is particularly useful in the
fabrication of a barrier layer, such as a multi-layered TaN/TiN
thin film stack. TaN thin films exhibit better barrier properties
than does a stack of TiN, but does not provide adequate adhesion
for subsequent layers, particularly copper thin film layers. Single
thin film layers also have a grain structure that allows some
diffusion along the grain boundaries. Thus, a TaN/TiN multi-layer
thin film stack is desirable, provided that copper can be made to
adhere to such a thin film stack.
[0008] U.S. Pat. No. 5,744,192, for Method of using water vapor to
increase the conductivity of copper deposited with Cu(Hfac)TMVS, to
Nguyen et al., granted Apr. 28, 1998, describes the use of water
vapor to enhance the adhesive properties of copper thin films.
[0009] Nuesca et al., Surface effects in the MOCVD of copper, Mat.
Res. Soc. Symp. Proc. Vol. 337, 1994, pp177-188, describes the use
of hydrogen to enhance the adhesive properties of copper thin
films.
SUMMARY OF THE INVENTION
[0010] A method of adhering copper thin film to a substrate in an
integrated circuit structure includes preparing a substrate,
including forming active regions and trenches for interconnect
structures; depositing a metal barrier layer on the substrate;
depositing an ultra thin film layer of tungsten over the barrier
metal layer; depositing a copper thin film on the tungsten ultra
thin film layer; removing excess copper and tungsten to the level
of the metal barrier layer; and completing the integrated circuit
structure.
[0011] An integrated circuit having a copper interconnect therein
formed over a layer of barrier metal includes a substrate,
including active regions and trenches for interconnect structures;
a metal barrier layer formed on the substrate, wherein said metal
barrier layer is taken from the group of materials consisting of
Ta, TiN, TaN, TaSiN and TiSiN, and formed to a thickness of between
about 5 nm to 10 nm; an ultra thin film layer of tungsten formed on
the barrier metal layer, said tungsten ultra thin film layer having
a thickness of between about 1 nm to 5 nm; and a copper thin film
layer formed on the tungsten ultra thin film layer to a thickness
required to fill the vias and trenches, which is usually a
thickness of between about 10 nm to 20 nm.
[0012] It is an object of the invention is to increase the adhesive
properties of copper thin films on metal and metal nitride
substrates.
[0013] Another object of the invention is to provide a method of
depositing tungsten on a metal or metal nitride substrate to
enhance the adhesion of a copper thin film to the substrate.
[0014] This summary and objectives of the invention are provided to
enable quick comprehension of the nature of the invention. A more
thorough understanding of the invention may be obtained by
reference to the following detailed description of the preferred
embodiment of the invention in connection with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIGS. 1 to 5 depict steps in the method of the invention and
fabrication of a copper thin film integrated circuit device
according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0016] In this invention, an ultra thin layer of tungsten, of
between about 1 nm to 5 nm thick, is formed on any conventional
barrier layers. Copper is then deposited by CVD. The adhesion
between as-deposited tungsten and copper has been demonstrated to
be excellent. In this way, barrier films, thin tungsten films, and
copper films may be deposited in a smooth streamline CVD process
with excellent adhesive integrity, and without the requirement of
additional steps which result in a more complex fabrication
process.
[0017] The ultra thin tungsten film, may be deposited by metal
organic chemical vapor deposition (MOCVD) or atomic layer
deposition (ALD), and acts as an adhesion promoter between the
copper thin film and the metal barrier layers. Compared with other
adhesion enhancing methods, the method of the invention provides a
simple, easy, and straightforward way to fabricate copper
interconnects in high-speed IC devices, and to provide adequate
filling of vias and trenches with copper having adequate adhesive
properties to the underlying IC structures.
[0018] Practice of the method of the invention begins with
preparation of a substrate, and now referring to FIG. 1, shown
generally at 10. The substrate is prepared by formation of active
regions therein, such as source 12, drain 14, gate 16, and may
include a gate stack 18. The substrate and structures thereon are
covered with oxide 20, and the substrate and structures are
patterned, and interconnect trenches, such as trench 21, formed
therein. Patterning and trenching any be performed by any of the
methods which are well know to those of skill in the art.
[0019] Referring now to FIG. 2, a layer of metal or metal nitride
barrier film 22 is deposited on to the substrate and follows any
patterning or trenching structures. By way of example, the barrier
metal may be taken from the group of materials comprising Ta, TiN,
TaN, TiSiN, and the metal may be deposited by physical vapor
deposition (PVD) or MOCVD to a thickness of between about 5 nm to
10 nm.
[0020] As shown in FIG. 3, a tungsten thin film 24, actually, an
ultra thin film, is deposited either in situ or ex situ on the
barrier metal thin films by MOCVD, using either WF.sub.6 or
W(CO).sub.6 as a precursor, to a thickness of between about 1 nm to
5 nm. The precursor is either gaseous WF.sub.6, or a solid
substance, such as W(CO).sub.6. The precursor is fed into, or
transported by a carrier gas into, a CVD chamber at a temperature
of between about 350.degree. C. to 450.degree. C., and the
deposition takes between about one minute to two minutes to
establish the tungsten ultra thin film of the desired
thickness.
[0021] Turning now to FIG. 4, a copper thin film 26 is deposited
onto the tungsten thin film by MOCVD to a thickness of between
about 10 nm to 20 nm. Copper may be deposited by use of
CupraSelect.TM. Blend precursor, as provided by Schumacher,
introduced into the CVD chamber at a temperature of between about
180.degree. C. to 250.degree. C., and the deposition takes between
about twelve seconds to ten minutes to establish the copper thin
film of the desires thickness.
[0022] The structure is then ready for further copper electrical
plating or chemical mechanical polishing (CMP), in the case of a
CVD fill-up, to the level of the barrier film, as shown in FIG. 5.
Additional IC structures and metallization may then be added to
complete the copper thin film IC device, such as the filling of
trench 28 by copper 30, by CVD or some other deposition
technique.
[0023] The barrier metal, tungsten and copper may all be deposited
by ALD, or any of the layers may be deposited by ALD and the
remaining layers formed by CVD or MOCVD. As feature size decreases,
particularly below 100 nm, it is advantageous to use ALD. A
particularly good protocol is to form the barrier layer of TiN by
ALD, ALD the tungsten layer, and deposit the copper by CVD.
[0024] Thus, a method for using ultra thin tungsten metal films as
an adhesion promoter between CVD TiSiN, TaN, TaSiN and Cu has been
disclosed. It will be appreciated that further variations and
modifications thereof may be made within the scope of the invention
as defined in the appended claims.
* * * * *