U.S. patent application number 10/718897 was filed with the patent office on 2005-05-12 for structure and process of metal interconnects.
Invention is credited to Hu, Shao-Chung, Huang, Chien-Chung, Yang, Yu-Ru.
Application Number | 20050098892 10/718897 |
Document ID | / |
Family ID | 34546493 |
Filed Date | 2005-05-12 |
United States Patent
Application |
20050098892 |
Kind Code |
A1 |
Hu, Shao-Chung ; et
al. |
May 12, 2005 |
Structure and process of metal interconnects
Abstract
A process of metal interconnects and a structure of metal
interconnect produced therefrom are provided. An opening is formed
in a dielectric layer. A metal layer is formed over the dielectric
layer filling the opening. A film layer is formed on the metal
layer and the dielectric layer. The film layer is reacted with the
metal layer during a thermal process, and a protective layer is
formed on the surface of the metal layer. The portion of the film
layer not reacted with the metal layer is removed to avoid short
between the metal layers. The protective layer can protect the
surface of the metal layer from being oxidized and thus the
stability and the reliability of the semiconductor device can be
effectively promoted.
Inventors: |
Hu, Shao-Chung; (Taipei,
TW) ; Yang, Yu-Ru; (Ilan City, TW) ; Huang,
Chien-Chung; (Taichung Hsien, TW) |
Correspondence
Address: |
J C PATENTS, INC.
4 VENTURE, SUITE 250
IRVINE
CA
92618
US
|
Family ID: |
34546493 |
Appl. No.: |
10/718897 |
Filed: |
November 20, 2003 |
Current U.S.
Class: |
257/758 ;
257/762; 257/E21.591; 438/618 |
Current CPC
Class: |
H01L 21/76805 20130101;
H01L 21/76856 20130101; H01L 21/76867 20130101; H01L 21/76886
20130101; H01L 21/76849 20130101; H01L 21/76855 20130101 |
Class at
Publication: |
257/758 ;
257/762; 438/618 |
International
Class: |
H01L 023/48 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 11, 2003 |
TW |
92131480 |
Claims
What is claimed is:
1. A process of forming metal interconnects, comprising: forming a
first opening in a first dielectric layer; filling a first metal
layer in the first opening; forming a first film layer over the
first dielectric layer and the first metal layer; performing a
thermal process to induce a reaction between the first metal layer
and the first film layer to form a first protective layer on the
surface of the first metal layer; and removing an unreacted portion
of the first film layer.
2. The process according to claim 1, wherein the first metal layer
is comprised of copper.
3. The process according to claim 1, wherein the first film layer
is comprised of a conductive material or a non-conductive
material.
4. The process according to claim 3, wherein the conductive
material is selected from a group consisting of stannum (Sn),
aluminum (Al), and stannum-lead alloy (Sn--Pb).
5. The process according to claim 1, wherein the first film layer
has a thickness of between 10.ANG..about.500 .ANG..
6. The process according to claim 1, wherein the thermal process is
performed at a temperature lower than 400.degree. C.
7. The process according to claim 1, further comprising a step of
forming a first stop layer on the surface of the first dielectric
layer before the step of forming the first opening in the first
dielectric layer.
8. The process according to claim 1, after the step of removing
unreacted portion of the first film layer, further comprising:
forming a second dielectric layer over the first dielectric layer
to cover the first protective layer; forming a second opening in
the second dielectric layer to cut through the first protective
layer and expose the first metal layer; filling a second metal
layer in the second opening to electrically contact the first metal
layer; forming a second film layer over the second dielectric layer
and the second metal layer; performing a thermal process to induce
a reaction between the second metal layer and the second film layer
to form a second protective layer on the surface of the second
metal layer; and removing an unreacted portion of the second film
layer.
9. The process according to claim 8, wherein the second metal layer
is comprised of copper.
10. The process according to claim 8, wherein the second film layer
is comprised of a conductive material or a non-conductive
material.
11. The process according to claim 10, wherein the conductive
material is selected from a group consisting of stannum (Sn),
aluminum (Al), and stannum-lead alloy (Sn--Pb).
12. The process according to claim 8, wherein the second film layer
has a thickness of between 10 .ANG..about.500 .ANG..
13. The process according to claim 8, wherein the thermal process
is performed at a temperature lower than 400.degree. C.
14. The process according to claim 8, further comprising a step of
forming a second stop layer on the surface of the second dielectric
layer before forming the second opening in the second dielectric
layer.
15. A structure of metal interconnects, comprising: a first
dielectric layer, having a first opening therein; a first metal
layer, formed in the first opening; and a first protective layer,
formed on the surface of the first metal layer not covered by the
first dielectric layer.
16. The structure according to claim 15, wherein the first metal
layer is comprised of copper.
17. The structure according to claim 15, further comprising a first
stop layer on the surface of the first dielectric layer with the
first opening formed in the first dielectric layer and the first
stop layer.
18. The structure according to claim 15, further comprising: a
second dielectric layer, formed over the first dielectric layer,
wherein the second dielectric layer has a second opening therein
cutting through the first protective layer to expose the first
metal layer; a second metal layer, being filled into the second
opening; and a second protective layer, formed on the surface of
the second metal layer not covered by the second dielectric
layer.
19. The structure according to claim 18, wherein the second metal
layer is comprised of copper.
20. The structure according to claim 18, further comprising a
second stop layer on the surface of the second dielectric layer,
wherein the second opening is formed in the second dielectric layer
and the second stop layer.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the priority benefit of Taiwan
application serial no. 92131480, filed Nov. 11, 2003.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a structure and a process
of a semiconductor. More particularly, the present invention
relates to a structure and a process of metal interconnects.
[0004] 2. Description of the Related Art
[0005] After semiconductor fabrication processes reach to a deep
sub-micron generation, integration of integrated circuit devices
has been greatly enhanced. Deep sub-micron processes, however, has
encountered certain problems arising from characteristics of the
devices and properties of the materials. Certain characteristics,
such as the resistance of the material and electromigration
resistivity of aluminum interconnects, are unable to meet the needs
of the deep sub-micron processes, which represents one of the
pressing problems that need to be solved for fabricating integrated
circuits.
[0006] In processes of fabricating integrated circuits,
technologies of using aluminum to form metal interconnects have
become rather mature. In a deep sub-micron process of semiconductor
fabrication, however, copper is often used in place of aluminum to
form interconnects. This is because copper has an electromigration
resistivity 30 to 100 times higher than that of aluminum, a
dielectric resistivity 10 to 20 times lower than that of aluminum,
and an electric resistivity 30% lower than that of aluminum. Thus,
the formation of inter-metal dielectrics by using copper to form
metal interconnects in company with use of a material with low
dielectric constant (low K) inter-metal can effectively lower
resistivity-capacitance delay (RC delay) and increase
elelectromigration resistivity.
[0007] Referring to FIG. 1, since copper is not easy to be etched,
metal interconnects using copper are mostly fabricated by using a
method of damascene. In other words, as shown in FIG. 1, a
substrate 100 having many preformed devices (not shown) thereon is
first provided. A dielectric layer 102a is then formed over the
substrate 100 to cover the foregoing devices. The dielectric layer
102a has a damascene opening 108a of a wiring region for connecting
with the substrate 100. In the damascene opening 108a is formed a
barrier layer 104a, and subsequently a copper metal layer 110a to
fill in the damascene opening 108a. The excess portion of the
copper metal layer 110a that is outside of the damascene opening
108a is removed through a chemical mechanical polishing method.
Over the dielectric layer 102a and the copper metal layer 110a,
another dielectric layer 102b is formed having a damascene opening
108b for connecting with the copper metal layer 110a. A barrier
layer 104b is formed in the damascene opening 108b, and then a
copper metal layer 110b is filled into the damascene opening 108b.
Further, the excess portion of the copper metal layer 110b that is
outside of the damascene opening 108b is removed to form a
structure of metal interconnects.
[0008] However, since copper is easy to be oxidized, in the
foregoing fabrication processes of a damascene structure, copper
oxide is easily formed on the surface of the copper metal layers
110a/110b, which increases electric resistivity of the copper metal
layers 110a/110b, and lowers efficiency of the metal interconnects.
In addition, copper is a relatively soft metal and the copper oxide
formed on the surface of the copper is rather loose, and thus the
surface properties of copper are difficult to be controlled, which
will induce formation of undercut profile on the copper metal
layers 110a/110b, as shown at A and B in FIG. 1, during a process
of wet etching or wash with a solvent. Moreover, the formation of
copper oxide on the surface of the copper metal layers 110a/110b
may also have negative effects to adhesion between the copper metal
layers 110a/110b and the barriers layers 104a/104b.
SUMMARY OF THE INVENTION
[0009] Accordingly, an object of the present invention is to
provide a structure and a process of metal interconnects for
avoiding oxidation on the surface of a metal layer and enhancing
electric resistivity.
[0010] Another object of the present invention is to provide a
structure and a process of metal interconnects for increasing
process margin so as to enhance the efficiency of metal
interconnection.
[0011] In accordance to the above objects and other advantages of
the present invention, as broadly embodied and described herein,
the present invention provides a structure of metal interconnects.
The structure comprises a substrate, a dielectric layer, a metal
layer and a protective layer. Wherein, the dielectric layer has an
opening, a metal layer is filled in the opening, and the protective
layer is formed on the portion of the surface of the metal layer
not covered by the dielectric layer.
[0012] The present invention provides a process of metal
interconnects. During the process, a dielectric layer is formed to
cover a plurality of devices preformed on a substrate. An opening
is formed in the dielectric layer, a barrier layer and a metal
layer are formed over the opening filling the opening, and a film
layer is subsequently formed over the dielectric layer and the
metal layer. A thermal process is performed to induce a reaction at
the interface between the film layer and the metal layerto form a
protective layer on the surface of the metal layer. Subsequently,
the portion of the film layer not reacted with the metal layer is
removed.
[0013] As shown in the foregoing, the present invention provides a
structure of metal interconnects comprising a protective layer over
the metal layer, so as to avoid negative effects on either the
efficiency of the entire devices or the stability of the process
due to unexpected oxidation reactions occurring on the metal layer
during the subsequent process steps.
[0014] It is to be understood that both the foregoing general
description and the following detailed description are exemplary,
and are intended to provide further explanation of the invention as
claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The accompanying drawings are included to provide a further
understanding of the invention, and are incorporated in and
constitute a part of this specification. The drawings illustrate
embodiments of the invention and, together with the description,
serve to explain the principles of the invention.
[0016] FIG. 1 is a schematic sectional view of a structure of the
conventional metal interconnects.
[0017] FIGS. 2A.about.2J are schematic sectional views showing a
process of metal interconnects according to one preferred
embodiment of the present invention.
[0018] FIGS. 3A.about.3K are schematic sectional views showing a
process of metal interconnects according to another preferred
embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0019] FIGS. 2A.about.2J are schematic sectional views showing a
process of metal interconnects according to one preferred
embodiment. Referring to FIG. 2A, the process first provides a
substrate 200, whereon many devices (not shown) are preformed. A
dielectric layer 202 is formed on the surface of the substrate 200
to cover the foregoing devices. An opening 208 is formed in the
dielectric layer 202. The opening 208 is, for example, a damascene
opening for constructing a structure of dual damascene or a trench
for constructing a metal wiring, or a dielectric via or a
contacting opening for constructing a plug, or any opening for
constructing metal interconnects (the opening 208 is shown in the
figures only as a trench for constructing a metal wiring). The
process to form the opening 208 is, for example, photolithographic
etching.
[0020] Then, referring to FIG. 2B, a barrier layer 204 is formed on
the surfaces of the opening 208 and the dielectric layer 202. The
material of the barrier layer 204 is, for example, tantalum
nitride, titanium oxide, or nitride of titanium-silicon. When the
material is tantalum nitride, the process of forming the barrier
layer 204 is, for example, first depositing a tantalum layer to
cover the dielectric layer 202 via a magnetron DC sputtering, then
nitrifying tantalum to form tantalum nitride at a high temperature
and under an atmosphere of nitrogen or ammonia. In addition,
methods of forming the barrier layer 204 also include a step of
reactive sputtering, wherein tantalum is used as a metal target,
and ions in the gaseous mixture of argon and nitrogen bombard the
metal target. Tantalum sputtered from ion bombardment will react
with nitrogen atom generated from decomposition reactions occurred
in plasma to form tantalum nitride. The resulting tantalum nitride
then deposits on and covers the dielectric layer 202.
[0021] Further, referring to FIG. 2C, a metal layer 206 is formed
over the barrier layer 204 filling the opening 208. The metal layer
206 is comprised of, for example, copper. The method of forming the
copper metal layer 206 is, for example, physical vapor deposition
(PVD) or chemical vapor deposition (CVD).
[0022] Referring to FIG. 2D, a portion of the copper metal layer
206 and a portion of the barrier layer 204 outside the opening 208
are removed by performing a chemical mechanical polishing (CMP) or
etching. Referring to FIG. 2E, a film layer 210 is deposited on the
dielectric layer 202 and the copper metal layer 206. The film layer
210 has a thickness of, for example, 10 .ANG..about.500 .ANG., and
can be made of, for example, a conductive or non-conductive
material. Examples of the conductive material are, but not limited
to, stannum (Sn), aluminum (Al), or stannum-lead alloy
(Sn--Pb).
[0023] FIG. 2F shows a protective layer 212 formed via a reaction
between the film layer 210 and the copper metal layer 206 in a
thermal process. During the thermal process, the film layer 210
reacts with the copper metal layer 206, but not with the dielectric
layer 202, via either dissolution or chemical reactions. Thus, the
protective layer 212 is formed on the surface of the copper metal
layer 206 to protect the copper metal layer 206 from being
oxidized. In addition, the protective layer 212 is formed from a
mixture of copper and the material of the film layer 210, such as a
solid solution or compound of copper. Moreover, the temperature of
the thermal process is controlled within an appropriate range, such
as below 400.degree. C., to avoid negative effect on other portions
of the structure due to excessively high temperature and to lower
costs of thermal supply in the process.
[0024] Referring to FIG. 2G, the portion of the film layer 206 not
reacted with the copper metal layer 206 is removed. The removal
process is accomplished through chemical mechanical polishing (CMP)
or dry/wet etching by using the dielectric layer 202 as CMP stop
layer or etch stop layer. Thus the process of forming a conductive
structure is completed. The conductive structure is of, for
example, a plug, a trench, or a dual damascene.
[0025] Further referring to FIG. 2G, the conductive structure
formed according to the foregoing method comprises the dielectric
layer 202, the barrier layer 204, the metal layer 206 and the
protective layer 212. Wherein, the dielectric layer 202 is formed
over the substrate 200, and has an opening 208 therein to expose
part of devices on the substrate 200. In addition, the barrier
layer 204 is disposed on the surface of the opening 208, and the
metal layer 206 is disposed over the barrier layer 204. The barrier
layer 204 is provided to prevent the metal layer 206 from diffusing
via ion diffusion during a thermal process into, for example, the
dielectric layer 202, and thus avoid the problem of depth energy
level. On the other hand, the metal layer 206 is provided to form
electrical connections with other metal layers in a subsequent
process. Further, the protective layer 212 is formed over the metal
layer 206 to prevent the metal layer 206 from the surface being
oxidized and thus avoid the increase of resistivity of the metal
layer 206.
[0026] After the formation of the conductive structure as shown in
FIG. 2G, another conductive structure can be subsequently formed
over and in electric contact with the foregoing conductive
structure. Referring to FIG. 2H, a dielectric layer 202a with an
opening 208a therein is formed over the dielectric layer 202 and
the protective layer 212. The opening 208a cuts through the
protective layer 212 to expose a portion of the copper metal layer
206. Depending on the structure of the opening 208, the opening
208a can be in the form of a dual damascene, a trench, a dielectric
layer opening, a contact opening, or an opening for forming a
damascene structure. A barrier layer 204a is then formed on the
surface of the opening 208a, and a metal layer 206a is formed over
the barrier layer 204a filling the opening 208a. Subsequently,
portions of the copper metal layer 206a and the barrier layer 204a,
which are outside of the opening 208a, are removed via chemical
mechanical polishing, whereas the other portions of the copper
metal layer 206a and the barrier layer 204a, which are inside of
the opening 208a, remain intact.
[0027] Referring to FIG. 2I, a film layer 210a is deposited over
the dielectric layer 202a and the metal layer 206a. A thermal
process is performed to induce a reaction on the interface between
the film layer 210a and the copper metal layer 206a to form a
protective layer 212a for protecting the copper metal layer 206a
from the surface being easily oxidized. Referring to FIG. 2J, a
process of chemical mechanical polishing or dry/wet etching is
subsequently performed using the dielectric layer 202a as the
chemical mechanical polishing stop layer or etch stop layer. The
portion of the film layer 210a not reacted with the copper metal
layer 206a is removed, and thus the conductive structure is
constructed.
[0028] In the foregoing description, materials and fabrication
methods of the metal layers 206 and 206a can be similar or
identical. Materials and fabrication methods of the barriers layers
204 and 204a can be also similar or identical. Furthermore,
materials and fabrication methods of the film layers 210 and 210a
can be also similar or identical.
[0029] Further referring to FIG. 2J, the structure constructed
according to the foregoing processes comprises the dielectric layer
202, the barrier layer 204, the metal layer 206, the protective
layer 212, the dielectric layer 202a, the barrier layer 204a, the
metal layer 206a and the protective layer 212a. Wherein, the
dielectric layer 202 is formed over the substrate 200 and the
dielectric layer 202 has an opening 208 therein to expose part of
devices on the substrate 200. In addition, the barrier layer 204 is
formed on the surface of the opening 208, and the metal layer 206
is formed over the barrier layer 206. The barrier layer 204 is
provided to prevent the metal layer 206 from diffusing via ion
diffusion during a thermal process into, for example, the
dielectric layer 202, and thus avoid the problem of depth energy
level. Whereas, the protective layer 212 is formed over the metal
layer 206 to prevent the surface of the metal layer 206 from being
oxidized and thus avoid the increase of resistivity of the metal
layer 206. In addition, the dielectric layer 202a with an opening
208a therein is formed over the dielectric layer 202 and the
protective layer 212. The opening 208a cuts through the protective
layer 212 to expose a portion of the copper metal layer 206.
Further, the protective layer 212a is formed on the surface of the
metal layer 206a to prevent the metal layer 206a from the surface
being easily oxidized and thus avoid the increase of resistivity of
the metal layer 206a.
[0030] Another preferred embodiment of the present invention
further comprises a stop layer formed on the dielectric layer. The
stop layer is, for example, chemical mechanical polishing stop
layer or etch stop layer to prevent the dielectric layer and the
copper metal layer from excessive wear or etch.
[0031] FIGS. 3A.about.3K are schematic sectional views showing a
process to form metal interconnects according to another preferred
embodiment of the present invention. For clarity and simplicity in
this preferred embodiment, structures and layers similar to those
in the foregoing preferred embodiment are marked with identical
numerical labels, and descriptions of materials or processes of the
structures and layers are not further described.
[0032] Referring to FIG. 3A, a substrate 200 having many preformed
devices (not shown) thereon is first provided. A dielectric layer
202 is formed over the substrate 200 to cover the foregoing
devices. A stop layer 300 is than formed over the dielectric layer
202. The stop layer 300 is, for example, a chemical mechanical
polishing stop layer or an etch stop layer. Referring to FIG. 3B,
an opening 308 is formed cutting through both the stop layer 300
and the dielectric layer 202 to expose a portion of the foregoing
devices on the substrate 200. Referring to FIG. 3C, a barrier layer
204 is formed on the surfaces of the stop layer 300 and the opening
308. Referring to FIG. 3D, a metal layer 206 is formed over the
barrier layer 204. Referring to FIG. 3E, the portions of the metal
layer 206 and the barrier layer 204, which are outside the opening
308, are removed via chemical mechanical polishing process or etch
process until the stop layer 300 is exposed, whereas the portions
of the metal layer 300 and the barrier layer 204, which are inside
the opening, remain intact. The chemical mechanical polishing
process or etch process stops upon the exposure of the stop layer
300, such that the stop layer 300 can be used to avoid excessive
polishing or etching and thus prevent the dielectric layer 202 and
the metal layer 206 form being damaged.
[0033] Referring to FIG. 3F, film layer 210 is formed over the
metal layer 206 and the barrier layer 204. Then referring to FIG.
3G, a thermal process is performed, wherein the film layer 210
reacts with the copper metal layer 206, but not with the dielectric
layer 202, via either dissolution or chemical reactions to form a
protective layer 212. Thus, the protective layer 212 is formed on
the surface of the copper metal layer 206 to prevent the copper
metal layer 206 from being oxidized and avoid the increase of
resistivity of the metal layer 206. Moreover, the temperature of
the thermal process is controlled within an appropriate range, such
as below 400.degree. C., to avoid negative effect on other portions
of the structure due to excessively high temperature and to lower
costs of thermal supply in the process. Referring to FIG. 3H, the
removal of the portion of the film layer 210 not reacted with the
metal layer 206 is accomplished via a chemical mechanical polishing
or dry/wet etching, whereupon the construction of the conductive
structure is completed.
[0034] Further referring to FIG. 3H, the conductive structure
formed according to the foregoing method comprises the dielectric
layer 202, the CMP stop layer 300, the barrier layer 204, the metal
layer 206 and the protective layer 212. Wherein, the dielectric
layer 202 is formed over the substrate 200, and the stop layer 300
is over the dielectric layer 202. The stop layer 300 is comprised
of, for example, silicon dioxide (SiO.sub.2), silicon nitride
(SiN), silicon oxynitride (SiON), silicon carbide (SiC), silicon
carboxide (SiCO) or silicon oxycarbonitride (SiOCN). In addition,
an opening 308 is formed in the stop layer 300 and the dielectric
layer 202 to expose a portion of devices preformed on the substrate
200, the barrier layer 204 is formed on the surface of the opening
308 and the metal layer 206 is formed over the barrier layer 204.
Further, the protective layer 212 is formed on the metal layer 206
to prevent it from being oxidized and avoid the increase of its
resistivity.
[0035] After the formation of the conductive structure as shown in
FIG. 3H, another conductive structure can be subsequently formed
over and in electrical contact with the foregoing conductive
structure. Referring to FIG. 31, another dielectric layer 202a is
further formed over the stop layer 300 and the protective layer
212, and another stop layer 300a is formed over the dielectric
layer 202a. An opening 308a is formed in the stop layer 300a and
further through the dielectric layer 202a and the protective layer
212 for exposing a portion of the copper metal layer 206. Depending
on the structure of the opening 308, the opening 308a can be in the
form of a dual damascene, a trench, a dielectric layer opening, a
contact opening, or a opening for forming a damascene structure. A
barrier layer 204a is then formed on the surface of the opening
308a, and a metal layer 206a is formed over the barrier layer 204a
filling the opening 308a. Subsequently, portions of the copper
metal layer 206a and the barrier layer 204a, which are outside of
the opening 308a, are removed via chemical mechanical polishing
until the stop layer 300a is exposed, whereas the remaining
portions of the copper metal layer 206a and the barrier layer 204a,
which are within the opening 308a remain intact. Referring to FIG.
3J, a film layer 210a is deposited over the dielectric layer 300a
and the metal layer 206a. Referring to FIG. 3K, a thermal process
is performed to cause the film layer 210 to react with the copper
metal layer 206a, but not with the stop layer 300a, via either
dissolution or chemical reactions to form a protective layer 212a.
Thus, the protective layer 212 is formed on the surface of the
copper metal layer 206a to prevent the copper metal layer 206 from
being oxidized and avoid the increase of resistivity of the metal
layer 206. Subsequently, for example, a chemical mechanical
polishing or dry/wet etching is performed to remove the portion of
the film layer 210a not reacted with the copper metal layer 206a,
whereupon the construction of a conductive structure is
completed.
[0036] Further referring to FIG. 3K, the structure formed in the
foregoing process comprises the dielectric layer 202, the stop
layer 300, the barrier layer 204, the metal layer 206, the
protective layer 212, the dielectric layer 202a, the stop layer
300a, the barrier layer 204a, the metal layer 206a and the
protective layer 212a. Wherein, the dielectric layer 202 is formed
over the substrate 200, and the stop layer 300 is formed over the
dielectric layer 202. The opening 208 is formed in the stop layer
300 and the dielectric layer 202 to expose a portion of devices on
the substrate 200. Besides, the barrier layer 204 is formed on the
surface of the opening 308, and the metal layer 206 is formed over
the barrier layer 204. The protective layer 212 is formed on the
surface of the metal layer 206 to prevent the metal layer 206 from
its surface being oxidized and avoid the increase of the
resistivity of the metal layer 206. In addition, the dielectric
layer 202a with an opening 308a therein is formed over the stop
layer 300 and the protective layer 212. The opening 308a cuts
through the dielectric layer 202a and the protective layer 212 to
expose a portion of the metal layer 206. Moreover, the barrier
layer 204a is formed on the surface of the opening 308a, and the
metal layer 206a is formed over the barrier layer 204a. Further,
the protective layer 212a is formed on the surface of the metal
layer 206a to prevent the metal layer 206a from its surface being
oxidized and to avoid the increase of the resistivity of the metal
layer 206a.
[0037] In the foregoing descriptions of preferred embodiments,
copper is used as an example. The method of the present invention,
however, is applicable to a process where other oxidizable metal is
used, and thus is not limited to process of metal interconnects
with copper as the material.
[0038] According to the present invention, the surface
non-oxidizable protective layer is formed on the metal layer. The
protective layer is provided to protect the metal layer to avoid
the occurrence of undercut profile during a metal layer etching
process, and to keep the original adhesion between the metal layer
and the barrier layer by avoiding the decrease of the adhesion due
to oxidation on the surface of the metal layer and thereby the
metal layer is protected from any adverse effects affecting the
material and electrical properties thereof. Therefore, the
structure and process of the present invention is capable of
enhancing the reliability of oxidizable metals and increase the
process margin.
[0039] It will be apparent to those skilled in the art that various
modifications and variations can be made to the structure of the
present invention without departing from the scope or spirit of the
invention. In view of the foregoing, it is intended that the
present invention covers modifications and variations of this
invention provided they fall within the scope of the following
claims and their equivalents.
* * * * *