U.S. patent application number 14/753311 was filed with the patent office on 2016-10-13 for method for forming cobalt barrier layer and metal interconnection process.
The applicant listed for this patent is Shanghai Huali Microelectronics Corporation. Invention is credited to Jingxun Fang, Tong Lei.
Application Number | 20160300758 14/753311 |
Document ID | / |
Family ID | 53560069 |
Filed Date | 2016-10-13 |
United States Patent
Application |
20160300758 |
Kind Code |
A1 |
Lei; Tong ; et al. |
October 13, 2016 |
METHOD FOR FORMING COBALT BARRIER LAYER AND METAL INTERCONNECTION
PROCESS
Abstract
The present invention provides a method for forming a cobalt
barrier layer and a metal interconnection process. The method is
performed on a surface of a semiconductor device substrate on which
metal interconnection lines and an inter-line dielectric layer are
formed, and comprises: depositing a dielectric material film on a
surface of the inter-line dielectric layer by atomic layer
deposition, to densify the surface of the inter-line dielectric
layer; removing the deposited dielectric material film, to expose
the metal interconnection lines and the densified surface of the
inter-line dielectric layer; selectively depositing cobalt on
surfaces of the metal interconnection lines to form a cobalt
barrier layer. In the present invention, deposition selectivity of
cobalt on surfaces of the metal interconnection lines and the
inter-line dielectric layer is improved, thus reducing leakage
current between metal interconnection lines and improving yield and
reliability of the product.
Inventors: |
Lei; Tong; (Shanghai,
CN) ; Fang; Jingxun; (Shanghai, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Shanghai Huali Microelectronics Corporation |
|
|
|
|
|
Family ID: |
53560069 |
Appl. No.: |
14/753311 |
Filed: |
June 29, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 21/02274 20130101;
H01L 21/76829 20130101; H01L 21/76849 20130101; H01L 21/76883
20130101; H01L 2221/1047 20130101; H01L 21/76843 20130101; H01L
21/76826 20130101; H01L 21/76865 20130101; H01L 21/28562
20130101 |
International
Class: |
H01L 21/768 20060101
H01L021/768; H01L 21/02 20060101 H01L021/02; H01L 21/285 20060101
H01L021/285 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 13, 2015 |
CN |
201510173198.8 |
Claims
1. A method for forming a cobalt barrier layer, which is performed
on a surface of a semiconductor device substrate on which metal
interconnection lines and an inter-line dielectric layer are
formed, comprising the following steps in order: Step 01:
depositing a dielectric material film on a surface of the
inter-line dielectric layer and surfaces of the metal
interconnection lines by atomic layer deposition, to densify the
surface of the inter-line dielectric layer and increase a
deposition selectivity of cobalt between the surfaces of the metal
interconnection lines and the densified surface of the inter-line
dielectric layer; Step 02: removing the deposited dielectric
material film, to expose the metal interconnection lines and the
densified surface of the inter-line dielectric layer; then treating
the surfaces of the metal interconnection lines and the surface of
the inter-line dielectric layer with reducing plasma treatment;
Step 03: selectively depositing cobalt on the surfaces of the metal
interconnection lines to form a cobalt barrier layer.
2. (canceled)
3. The method for forming a cobalt barrier layer of claim 1,
wherein the inter-line dielectric layer is formed by a porous low-k
dielectric material.
4. The method for forming a cobalt barrier layer of claim 3,
wherein, in step 01, the dielectric material film penetrates the
porous low-k dielectric material, and a surface of the porous low-k
dielectric material is densified.
5. The method for forming a cobalt barrier layer of claim 1,
wherein, in step 01, the atomic layer deposition is plasma enhanced
atomic layer deposition.
6. The method for forming a cobalt barrier layer of claim 5,
wherein the temperature range of the substrate in the process of
the plasma enhanced atomic layer deposition is 50 to 400.degree.
C.
7. The method for forming a cobalt barrier layer of claim 6,
wherein, the temperature of the substrate is decreased, radio
frequency energy is decreased, and a reactant gas of low
oxidability is adopted during the atomic layer deposition.
8. The method for forming a cobalt barrier layer of claim 7,
wherein the reactant gas is carbon dioxide.
9. The method for forming a cobalt barrier layer of claim 7,
wherein the temperature of the substrate is 50.degree. C.
10. The method for forming a cobalt barrier layer of claim 5,
wherein, the reactant gas during the atomic layer deposition is
carbon dioxide.
11. The method for forming a cobalt barrier layer of claim 1,
wherein, the dielectric material film is a silicon oxide film.
12. The method for forming a cobalt barrier layer of claim 11,
wherein, the thickness of the silicon oxide is 10 to 50
Angstroms.
13. The method for forming a cobalt barrier layer of claim 1,
wherein, in step 03, the cobalt barrier layer is deposited by
chemical vapor deposition.
14. The method for forming a cobalt barrier layer of claim 1,
wherein the thickness of the cobalt barrier layer is 20 to 100
Angstroms.
15. A metal interconnection process, comprising the following steps
in order: forming front end metal interconnection lines and an
inter-line dielectric layer; forming a cobalt barrier layer on
surfaces of the front end metal interconnection lines by the method
of claim 1; forming a diffusion barrier layer on surfaces of the
cobalt barrier layer and the inter-line dielectric layer; forming
back end metal interconnection lines on the diffusion barrier
layer.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the priority benefit of China patent
application serial No. 201510173198.8, filed Apr. 13, 2015, The
entirety of each of the above-mentioned patent applications is
hereby incorporated by reference herein and made a part of this
specification.
FIELD OF THE INVENTION
[0002] The present invention relates to the field of semiconductor,
and particularly to a method for forming a cobalt barrier layer and
a metal interconnection process.
BACKGROUND OF THE INVENTION
[0003] With the development of fabricating process for CMOS
integrated circuits and the reduction in critical dimension, novel
materials and processes have been applied to device fabricating
processes to improve the performance of devices. In a back end
process of integrated circuits, Copper (Cu) lines are used to
replace Aluminum (Al) lines, and the interconnection resistance is
greatly reduced. At the same time, the use of a porous low-k
dielectric material can realize a dielectric constant of 2.5 or
less. These techniques can effectively reduce RC delay in
integrated circuits.
[0004] Since Cu is prone to diffuse, a Cu diffusion barrier layer
is deposited after a chemical mechanical polishing of a back end Cu
layer, and then a low-k dielectric material is deposited, so as to
avoid the Cu diffusion into the low-k dielectric material. In
technology nodes of 28 nm or larger, this Cu diffusion barrier
layer is usually formed by a thin nitrogen-doped silicon carbide
(NDC, k.about.5.3) In technology nodes of 28 nm or less, a
diffusion barrier layer of cobalt film is introduced which is
formed by CVD. The diffusion barrier layer of cobalt can not only
block the diffusion of Cu, but also prevent the moisture in air
from penetrating the Cu layer during fabrication. The introduction
of the cobalt film indicates that the thickness of the
nitrogen-doped silicon carbide (NDC) film is reduced, which
facilitates reducing the overall effective k value. Besides, cobalt
has excellent adhesion ability with respect to Cu, and the
reliability of products can be significantly improved.
[0005] However, a more amount of cobalt deposited on the dielectric
layer means a larger leakage current of between Cu interconnection
lines. Thus, it is urgent to explore a method for depositing
cobalt, in which the amount of cobalt deposited on a porous
dielectric layer is as small as possible, namely, deposition
selectivity is as much as possible.
BRIEF SUMMARY OF THE DISCLOSURE
[0006] To overcome the problems as mentioned above, it is an object
of the present invention to improve deposition selectivity of
cobalt on surfaces of metal interconnection lines and a surface of
inter-line dielectric layer, thus reducing the amount of the cobalt
deposited on the dielectric layer.
[0007] To realize the above object, the present invention provides
a method for forming a cobalt barrier layer, which is performed on
a surface of a semiconductor device substrate on which metal
interconnection lines and an inter-line dielectric layer are
formed, and which comprises the following steps:
[0008] Step 01: depositing a dielectric material film on a surface
of the inter-line dielectric layer by atomic layer deposition, to
densify the surface of the inter-line dielectric layer;
[0009] Step 02: removing the deposited dielectric material film, to
expose the metal interconnection lines and the densified surface of
the inter-line dielectric layer;
[0010] Step 03: selectively depositing cobalt on surfaces of the
metal interconnection lines to form a cobalt barrier layer.
[0011] Preferably, after step 02 and before step 03, the method
comprises: treating the surfaces of the metal interconnection lines
and the surface of the inter-line dielectric layer with reducing
plasma treatment.
[0012] Preferably, the inter-line dielectric layer is formed by a
porous low-k dielectric material.
[0013] Preferably, in step 01, the dielectric material film
penetrates the porous low-k dielectric material, and a surface of
the porous low-k dielectric material is densified.
[0014] Preferably, in step 01, the atomic layer deposition is a
plasma enhanced atomic layer deposition,
[0015] Preferably, the temperature of the substrate is decreased,
the radio frequency energy is decreased, and a reactant gas of low
oxidability is adopted during the atomic layer deposition.
[0016] Preferably, the carbon dioxide is adopted as the reactant
gas during the atomic layer deposition.
[0017] Preferably, the dielectric material film is silicon oxide
film, the thickness of the silicon oxide is 10.about.50 .ANG.A.
Preferably, in step 03, the cobalt barrier layer is deposited by
chemical vapor deposition, the thickness of cobalt barrier layer is
20.about.100 .ANG.. To realize the above object, the present
invention further provides a metal interconnection process, which
comprises: [0018] forming front end metal interconnection lines and
an inter-line dielectric layer; [0019] forming a cobalt barrier
layer on surfaces of the front end metal interconnection lines by
the method of claim I; [0020] forming a diffusion barrier layer on
surfaces of the cobalt barrier layer and the inter-line dielectric
layer; [0021] forming back end metal interconnection lines on the
diffusion barrier layer.
[0022] The method for forming a cobalt barrier layer and the metal
interconnection process of the present invention are based on the
principle that cobalt shows a relatively high deposition
selectivity with respect to a surface of a dense dielectric
material In view of this, a dielectric material film is deposited
on the surface of the inter-line dielectric layer by atomic layer
deposition, so that the surface of the inter-line dielectric layer
is densified. As a result, deposition selectivity of cobalt on
surfaces of the metal interconnection lines and the surface of the
inter-line dielectric layer is improved, leakage current between
metal interconnection lines is reduced, and yield and reliability
of the product are improved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a flow chart for illustrating a method for forming
a cobalt barrier layer in a preferred embodiment of the present
invention.
[0024] FIGS. 2, 3, 4 are schematic views for illustrating each step
in a method for forming a cobalt barrier layer in a preferred
embodiment of the present invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0025] The present invention will be described in further details
hereinafter by referring to the accompanying drawings, so as to
provide a better understanding of the present invention. However,
the present invention is not limited to these embodiments. All
equivalent modifications and substitutions without departing from
the spirit and scope of the present invention should be covered by
the present invention.
[0026] In a method for forming a cobalt barrier layer of the
present invention, a dielectric material film is deposited on a
surface of an inter-line dielectric layer by atomic layer
deposition. As a result, the surface of the inter-line dielectric
layer is densified, on that the cobalt is selectively deposited on
surfaces of metal interconnection lines, and hardly deposited on
the surface of the inter-line dielectric layer. The underlying
principle follows. During atomic layer deposition, the dielectric
material will penetrate a skin layer of the inter-line dielectric
layer so that the. skin layer is densified. In addition, the amount
or thickness of the deposited cobalt is different for various
substrate surfaces, i.e., more cobalt is deposited on a dense
substrate surface, while less cobalt is deposited on a loose or
porous substrate surface. In other words, the cobalt is prone to be
selectively deposited on a dense substrate surface. The present
invention intends to inhibit deposition of cobalt on the surface of
the inter-line dielectric layer, and promote selective deposition
of cobalt on surfaces of metal interconnection lines. Thus, in the
present invention, a dielectric material film is formed on the
surface of the inter-line dielectric layer to improve a density of
the surface of the inter-line dielectric layer, so as to improve
deposition selectivity of cobalt on the surfaces of metal
interconnection lines and the surface of inter-line dielectric
layer.
[0027] The method for forming a cobalt barrier layer of the present
invention will be described hereinafter with reference to FIG. 1-4
and specific embodiments. It is noted that the accompanying
drawings are drawn in a simplified manner and not to scale, and
that the accompanying drawings are only used to illustrate
embodiments in a convenient and clear manner.
[0028] Referring to FIG. 1, in an embodiment of the present
invention, forming a cobalt barrier layer belongs to a back end
metal interconnection process, and the method for forming a cobalt
barrier layer is performed on a semiconductor device substrate on
which metal interconnection lines and an inter-line dielectric
layer are formed, and comprises the following steps.
[0029] Step 01: referring to FIG. 2, a dielectric material film 03
is deposit on a surface of an inter-line dielectric layer 01 by
atomic layer deposition, so that the surface of the inter-line
dielectric layer 01 is densified.
[0030] In particular, in this embodiment, the dielectric material
film 03 is deposited by atomic layer deposition after chemical
mechanical polishing process of metal interconnection lines. The
dielectric material film 03 is also deposited on surfaces of metal
interconnection lines 02. Due to limits in temperature during back
end metal interconnection process, a plasma enhanced atomic layer
deposition is adopted, and the deposition temperature is
50-400.degree. C. The deposition comprises but is not limited to a
cyclic process of adsorption of precursors on the surface of the
inter-line dielectric layer, purging the deposited dielectric
material with an inert gas, and plasma cleaning the deposited
dielectric material. In order to reduce damage to the inter-line
dielectric layer due to plasma, during the atomic layer deposition,
a temperature of the substrate can be reduced, e.g., a substrate
temperature of 50.degree. C.; the radio frequency energy can be
decreased; and a reactant gas of low oxidability, e.g., carbon
dioxide, can be adopted. The material of the deposited dielectric
film can be silicon oxide, and a thickness of the silicon oxide
film is 10.about.50 .ANG.. In this process, since the precursors
may enter voids in the surface of the inter-line dielectric layer,
and the dielectric material grows in these voids, so that a skin
layer of the inter-line dielectric layer is densified. The
densified portion has an increased k value. However, since the
densified skin layer is very thin, the overall k value of the
inter-line dielectric layer will not increase significantly. Of
course, other dielectric materials can be deposited by atomic layer
deposition, and all those dielectric materials which will not lead
to significant increase in k value of the inter-line dielectric
layer can be adopted in the present invention,
[0031] In this embodiment, the material of the inter-line
dielectric layer 01 is a porous low-k dielectric. The dielectric
material film 03 penetrates the porous low-k dielectric material,
so that the porous low-k dielectric material surface is
densified.
[0032] Step 02: referring to FIG. 3, the deposited dielectric
material 03 is removed, the densified surface of the inter-line
dielectric layer 01 and the metal interconnection lines 02 are
exposed.
[0033] In particular, the method for removing the dielectric
material comprises but is not limited to plasma dry etching
process. When the deposited dielectric material film is removed,
the densified surface of the inter-line dielectric layer is
retained. in this embodiment, the deposited dielectric material
film is silicon oxide film. In this case, a silicon-cobalt-nickel
process can be used to etch and remove the silicon oxide thin film.
Reference can be made to the existing process for specific etching
steps of the silicon-cobalt-nickel process, which are not repeated
here for simplicity. Of course, other etching methods can also be
applied in other embodiments of the present invention,
[0034] In this embodiment, after step 02 and before step 03, the
method comprises: treating the surfaces of the metal
interconnection lines and the surface of the inter-line dielectric
layer by reducing plasma. The reducing plasma can be H plasma (for
example, H2 plasma), so that oxidized metal on the surfaces of the
metal interconnection lines can be reduced. In addition, the
inter-line dielectric layer can be repaired to a certain extent, so
that k value of the inter-line dielectric layer is decreased. For
example, Cu metal interconnection lines may be oxidized into copper
oxide during the preceding deposition or removing processes, and
treating surfaces of Cu metal interconnection lines with H plasma
can reduce copper oxide into Cu metal. Besides, by treating porous
the surface of the low-k dielectric material with H plasma, damage
to the porous low-k dielectric material during the above-mentioned
deposition or removing processes can be repaired, so that k value
is further reduced.
[0035] Step 03: referring to FIG. 4, the cobalt is selectively
deposited on the surfaces of the metal interconnection line 02, so
that a cobalt barrier layer 04 is formed.
[0036] In particular, the cobalt barrier layer is deposited by
chemical vapor deposition. Since the surface of the inter-line
dielectric layer is densified, the deposition of the cobalt will
exhibit excellent selectivity. As a result, the cobalt is
selectively deposited on the surfaces of the metal interconnection
lines, while is hardly deposited on the surface of the inter-line
dielectric layer, thus improving deposition selectivity of the
cobalt. The cobalt barrier layer can have a thickness of
20.about.100 .ANG..
[0037] The present invention further provides a metal
interconnection process, which comprises the following steps.
[0038] Firstly, front end metal interconnection lines and an
inter-line dielectric layer are formed. Conventional processes can
be used in this case, which are not repeated here for
simplicity.
[0039] Then, a cobalt barrier layer is formed on the surfaces of
the front end metal interconnection lines by the above-mentioned
method for forming a cobalt barrier layer.
[0040] Then, a diffusion barrier layer is formed on surfaces of the
cobalt barrier layer and of the inter-line dielectric layer. The
diffusion barrier layer can be made from nitrogen-doped silicon
carbide, and can have a thickness of 50.about.200 .ANG.,
Conventional processes can be used in this case, which are not
repeated here for simplicity.
[0041] Finally, back end metal interconnection lines are formed on
the diffusion barrier layer.
[0042] In an embodiment of the present invention, the method for
forming metal interconnection lines comprises the following
steps.
[0043] Step 201: a first barrier layer and a low-k dielectric
material are deposited in sequence on the semiconductor device
substrate.
[0044] In particular, the semiconductor device substrate comprises
but is not limited to substrates which have been subject to front
end interconnection processes. The semiconductor device substrate
comprises a porous low-k dielectric material formed in a front end
interconnection process, a first trench, and a filling metal in the
first trench. A diffusion barrier layer of e.g. Ta/TaN is formed on
an inner wall of the first trench, and the filling metal is formed
on a surface of the diffusion barrier layer. In step 201, the low-k
dielectric material is formed in a PECVD reactor chamber, and the
reactants comprise methyldiethoxysilane (mDEOS) and .alpha.-
terpinene (ATRP). The ATRP acts as a pore-foaming agent, the
reaction temperature is 200.about.400.degree. C., and the deposited
low-k dielectric material has a thickness of 1000.about.5000 .ANG..
It is noted that, the substrate of the semiconductor device in the
present invention can be any semiconductor substrate, and all those
substrates of the semiconductor device which are subject to
interconnection processes of porous low-k dielectric material can
be applied in the present invention.
[0045] Step 202: the deposited low-k dielectric material is subject
to a first ultraviolet curing process.
[0046] In particular, the low-k dielectric material is formed by
the first ultraviolet curing process. hi the first ultraviolet
curing process, a curing temperature is 300.about.400.degree. C.,
and a curing time is determined on basis of the thickness of the
low-k dielectric material and is for example 100-1000 seconds. In
the present invention, a high porosity, a low k value, and a high
mechanical strength of the low-k dielectric material are realized
by means of the first ultraviolet curing process. These effects
cannot be obtained if the duration of the first ultraviolet curing
process is too short. Thus, in some embodiments of the present
invention, the curing time of the first ultraviolet curing process
is larger than that of the second ultraviolet curing process. In
this embodiment, the curing time of the first ultraviolet curing
process makes up 80%-95% of the total curing time of the first and
second ultraviolet curing processes. In this way, in this
embodiment, the low-k dielectric material will still shrink in the
first ultraviolet curing process. However, the low-k dielectric
material will shrink in the first ultraviolet curing process to an
extent less than the extent to which the low-k dielectric material
will shrink, in a single curing process. The first ultraviolet
curing process can comprise a plurality of ultraviolet curing
processes in which, for example, different curing temperatures are
adopted.
[0047] Step 203: a second trench is formed in the low-k dielectric
material by photolithography and etching processes, and the first
barrier layer at a bottom of the second trench is etched away to
expose the filling metal in the first trench.
[0048] In particular, firstly, the second trench is formed by
photolithography and etching; then a diffusion barrier layer of
e.g. Ta/TaN is deposited on an inner wall and a bottom of the
formed second. trench; then, a portion of the first barrier layer
at the bottom of the second trench is etched away. Conventional
processes can be used in this case, which are not repeated here for
simplicity.
[0049] Step 204: a metal is filled in the second trench., and the
filled metal is subject to chemical mechanical polishing up to the
surface of the low-k dielectric material.
[0050] In particular, the copper can be deposited in the second
trench by copper plating process. In this step, the low-k
dielectric material is removed partially by chemical mechanical
polishing, In this embodiment, after chemical mechanical polishing,
the low-k dielectric material has a thickness of 1200.about.1800
.ANG.. Here, the first trench and the filling metal therein as well
as the second trench and the filling metal therein constitute
interconnection through holes.
[0051] Step 205: the low-k dielectric material is subject to a
second ultraviolet curing process to form a porous low-k dielectric
material.
[0052] In particular, in the second ultraviolet curing process, the
curing temperature is 300.about.400.degree. C. In the second
ultraviolet curing process, the pore-foaming agent in the low-k
dielectric material is discharged completely. The interconnection
through holes functions to support the low-k dielectric material to
prevent it from shrinking, while precipitation and crosslinking of
the pore-foaming agent will still proceed, This means that the
low-k dielectric material will have an even higher porosity and
lower k value. this embodiment, the second ultraviolet curing
process has a duration which makes up 5.about.20% of the total
duration of the first and second ultraviolet curing processes. The
second ultraviolet curing process can comprise a plurality of
ultraviolet curing processes in which, for example, different
curing temperatures can be adopted,
[0053] Step 206: a second barrier layer is deposited on the surface
of the porous low-k dielectric material and the surface of the
filled metal.
[0054] In particular, the material of the second barrier layer can
be, but is not limited to, nitrogen-doped silicon carbide.
[0055] To sum up, the method for forming a cobalt barrier layer and
the metal interconnection process of the present invention are
based on the principle that the cobalt shows a relatively high
deposition selectivity with respect to a surface of a dense
dielectric material. In view of this, a dielectric material film is
deposited on the surface of the inter-line dielectric layer by
atomic layer deposition, so that the surface of the inter-line
dielectric layer is densified. As a result, the deposition
selectivity of the cobalt on surfaces of the metal interconnection
lines and the. surface of the inter-line dielectric layer is
improved, the leakage current between metal interconnection lines
is reduced, and the yield and reliability of the product are
improved.
[0056] While the invention has been described in connection with
preferred embodiments, it will be understood that modifications
thereof within the principles outlined above will be evident to
those skilled in the art, and thus the invention is not limited to
the preferred embodiments but is intended to encompass such
modifications. The invention resides in each and every novel
characteristic feature and each and every combination of
characteristic features. Reference numerals in the claims do not
limit their protective scope.
* * * * *