U.S. patent application number 10/962339 was filed with the patent office on 2005-03-17 for method of fabricating a semiconductor device.
Invention is credited to Maex, Karen, Vanhaelemeersch, Serge.
Application Number | 20050056941 10/962339 |
Document ID | / |
Family ID | 23025835 |
Filed Date | 2005-03-17 |
United States Patent
Application |
20050056941 |
Kind Code |
A1 |
Vanhaelemeersch, Serge ; et
al. |
March 17, 2005 |
Method of fabricating a semiconductor device
Abstract
This invention relates to Integrated Circuit (IC) processing and
fabrication. A device and a method are provided for etching an
opening in an insulating layer while depositing a barrier layer on
the side walls of the opening without essentially depositing a
barrier layer on the bottom of the opening.
Inventors: |
Vanhaelemeersch, Serge;
(Leuven, BE) ; Maex, Karen; (Herent, BE) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET
FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Family ID: |
23025835 |
Appl. No.: |
10/962339 |
Filed: |
October 8, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10962339 |
Oct 8, 2004 |
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10078284 |
Feb 15, 2002 |
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6821884 |
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60269109 |
Feb 15, 2001 |
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Current U.S.
Class: |
257/773 ;
252/79.4; 257/E21.256; 257/E21.577; 257/E23.019; 257/E23.145;
438/629; 438/643; 438/710 |
Current CPC
Class: |
H01L 2924/0002 20130101;
H01L 2924/0002 20130101; H01L 21/76802 20130101; H01L 23/5226
20130101; H01L 2924/00 20130101; H01L 21/76844 20130101; H01L
21/76831 20130101; H01L 21/31138 20130101; H01L 23/485 20130101;
H01L 23/53238 20130101; H01L 21/76865 20130101 |
Class at
Publication: |
257/773 ;
252/079.4; 438/710; 438/629; 438/643 |
International
Class: |
H01L 021/302; H01L
021/28; H01L 023/52 |
Claims
What is claimed is:
1. A device comprising an insulating layer on a substrate, the
insulating layer having an opening, wherein side walls of the
opening are covered with a barrier layer and a bottom of the
opening is essentially not covered with the barrier layer,
characterized in that the device is produced by a method comprising
the steps of: subjecting the substrate to a plasma, wherein the
plasma is generated in a gaseous mixture comprising at least three
components, the components comprising: a first component for
depositing the metal barrier layer on at least the side walls of
the opening, a second component for forming an opening in the
insulating layer, and a third component for removing the barrier
layer formed on the bottom of the opening; etching the insulating
layer with the plasma; and depositing the barrier layer on the side
walls of the opening with the plasma.
2. A device as recited in claim 1, wherein the first component is
selected from the group consisting of 1-methyl silane, 2-methyl
silane, 3-methyl silane, 4-methyl-silane, a mixture of SiH.sub.4
and N.sub.2, and mixtures thereof.
3. A device as recited in claim 1, wherein the second component is
selected from the group consisting of N.sub.xO.sub.y,
C.sub.xF.sub.yH.sub.xO.sub.u, N.sub.2/O.sub.2 mixtures,
N.sub.2/H.sub.2 mixtures, O.sub.2, O.sub.3, and mixtures
thereof.
4. A device as recited in claim 1, wherein the third component
comprises a chemical compound that forms a halogen ion or a radical
in the plasma.
5. A device as recited in claim 4, wherein the third component is
selected from the group consisting of NF.sub.3, SF.sub.6, F.sub.2,
ClF.sub.3, and mixtures thereof.
6. A device as recited in claim 1, wherein the gaseous mixture
further comprises an inert gas.
7. A device as recited in claim 1, wherein the plasma is a
continuous plasma.
8. A device as recited in claim 1, wherein the plasma is a pulsed
plasma.
9. A device as recited in claim 1, wherein the barrier layer is a
metal diffusion barrier layer.
10. A device as recited in claim 9, wherein the barrier layer
comprises silicon carbide.
11. A device as recited in claim 1, wherein the insulating layer
comprises a porous material.
12. A device as recited in claim 1, wherein the insulating is an
organic containing insulating layer.
13. A device as recited in claim 1, wherein the insulating layer is
an inorganic containing insulating layer.
14. A device as recited in claim 1, wherein the opening is a via
hole, the via hole extending through the insulating layer to an
underlying conductive layer or an underlying barrier layer.
15. A device as recited in claim 1, the method for producing the
device further comprising the steps of: covering the insulating
layer with a bilayer, the bilayer comprising a resist hard mask
layer formed on the insulating layer and a resist layer formed on
the hard mask layer; and patterning the bilayer.
Description
RELATED APPLICATION
[0001] This is a division of application Ser. No. 10/078,284, filed
Feb. 15, 2002, now pending, claims priority under 35 U.S.C. .sctn.
119(e) to U.S. Provisional Application No. 60/269,109, filed Feb.
15, 2001.
FIELD OF THE INVENTION
[0002] This invention relates to Integrated Circuit (IC) processing
and fabrication. A device and a method are provided for etching an
opening in an insulating layer while depositing a barrier layer on
the side walls of the opening without essentially depositing a
barrier layer on the bottom of the opening.
BACKGROUND OF THE INVENTION
[0003] Over the years, the demand for higher speed integrated
circuits has been addressed through shrinkage of the device
dimensions and increase of the packing density of the devices in
integrated circuits or on carrier packages. By decreasing the
layout rules of the devices, one can obtain transistors with higher
intrinsic switching speed. In addition, putting the devices closer
to each other reduces the communication time between transistor
devices. Both approaches allow building circuits with increased
overall performance, i.e., higher switching speed combined with
higher functional circuits. Additionally, the integrated circuit
area has increased, leading to circuits with even higher
functionality as more devices can be integrated in a given
area.
[0004] The structures connecting these devices can comprise
multiple metal levels which are, depending upon the aimed
interconnect pattern, either separated one from another by means of
interlevel electrically insulating layers or connected one to the
other by means of a conductive connection through these insulating
layers. These insulating layers also take part in the separation of
interconnect structures defined on the same metal level. Besides
the downscaling of the dimensions of these interconnecting
structures, additional measures are required to be able to meet the
stringent speed specifications.
[0005] For future technologies the increasing impact of the back
end processing in the fabrication of integrated circuits is
recognized. A major change in back end processing is necessitated
by the ever-decreasing feature size of the devices of integrated
circuits that has indicated RC delay-time of the interconnect
structures to be the limiting speed factor of the next generation
of integrated circuits. To address this problem, two major routes
are being explored: introduction of metals with higher conductivity
and introduction of dielectric materials with lower dielectric
constants.
[0006] The introduction of these materials has changed the outlook
of the back end processing schemes where dry etch processes,
cleaning recipes, and barrier requirements all need to be
adapted
[0007] Although aluminum alloys and oxides are still widely used in
interconnect technology, copper and new low-k dielectrics, e.g.,
polymers, are rapidly being implemented in microelectronics as they
are now accepted as the future materials of choice. Copper offers a
lower resistance and, depending on many processing parameters, this
low resistivity can be combined with a better resistance to
electromigration. The introduction of copper requires the
introduction of damascene processing, which is an important change
with respect to classical processing that uses patterning of the
conductive elements. In damascene processing, trenches are formed
in the insulating layers. After the patterning of the trenches,
metal layers are deposited in the trenches and on top of the
insulation layers. Finally, the metal layer is polished down to the
top of the insulating layers, leaving only the via and trenches
filled with metal.
[0008] The use of copper in interconnect structures has some
commonly known disadvantages. Copper can diffuse very fast in the
surrounding insulating layers, such as the low-k materials, which
negatively affects the reliability and the signal delay. Several
solutions have been proposed to solve this problem. The currently
used techniques inhibit the migration of copper ions in the
surrounding layers by depositing, in a non-selective way, diffusion
barrier layers, e.g., refractory metals such as tantalum nitride
(TaN), titanium nitride (TiN) in between the copper and the
insulating layers. The horizontal, i.e. the bottom, as well as the
vertical side walls of an opening in these insulating layers, e.g.
a via or contact hole, are therefore covered with a barrier
material. In case of Chemical Vapor Deposition (CVD) techniques,
the barrier is conformal deposited. In case of Physical Vapor
Deposition (PVD) techniques, the coverage of the vertical side
walls of an opening and the bottom of this opening is less,
compared to the coverage of the top of the opening. However, the
ratio between side wall and horizontal coverage can be tuned to a
certain extent by modifying the process parameters, such as
deposition power and the bias of deposition.
[0009] Several problems are related to the above-mentioned process.
Since a barrier layer is always deposited on both the vertical side
walls and the bottom surface of an opening in the insulating layer,
the presence of a barrier layer on the bottom of the opening causes
several inconveniences. In order to ensure the conductivity of the
metal lines, the barrier on the bottom of the opening must be made
of an electrically conductive material. The adhesion between the
barrier layer and the underlying conductive layer is not always
good, thereby influencing the current flow between the different
conductive levels. When the opening is afterwards filled with a
metal in order to connect the metal layer underneath the insulating
layer, the barrier layer between both metal layers has a
detrimental effect on the electromigration behavior of the
structure.
[0010] In addition, the exposure of the copper layers to the
dielectric etch plasma in the classical scheme leads to the
formation of residues on top of the copper. At the same time,
copper sputtering, even though in very small amounts, and
re-deposition onto the unprotected low-k side walls can not be
avoided. Therefore, one has to make use of after-etch cleaning
methods to remove the copper from the side walls of the opening
etched in the insulating low-k material in order to prevent copper
diffusion into the low-k material. After etching of the barrier,
further cleaning methods are needed to clean up the residues on top
of the copper in order to obtain a good via resistance. The
different cleaning methods that are used must be compatible with
the presence of the low-k material and must avoid sputtering of
copper onto the side walls of the opening.
[0011] In the damascene metallization scheme, the first step is a
pre-clean of the copper surface, which can be an in-situ pre-clean.
This step includes the high risk of having re-deposition of copper
on the low-k side wall, which may lead to its subsequent diffusion
into the low-k material during the following barrier sputter
process at higher temperature. In addition, it is clear that the
pre-clean process step may also change the low k material
properties leading to, e.g., an increased k value after the full
process integration. The formation of TaN barrier layers with PVD
techniques is difficult for high aspect ratio features, due to the
intrinsic limited step coverage of such a process. Bad quality TaN
barriers or layers which are too thin may lead to local breakdown
of the copper barrier film and thus create a diffusion path for the
copper.
[0012] The CMP process step makes use of two different slurries
for, respectively, the CMP removal of copper and of the TaN. This
makes the CMP process very difficult, very complex and very
time-consuming and slurry-consuming, resulting in a high cost of
ownership with medium process quality only.
[0013] When an opening is formed in a porous insulating material,
the pores of the insulating material at the side wall of the
opening are intersected, resulting in a rough side wall.
Subsequently, the barrier layer is deposited by, e.g., PVD on the
side walls of the opening, resulting in a barrier layer with the
same profile as the rough side wall of the opening. This has a
detrimental effect on the final device performance.
[0014] U.S. Pat. No. 5,818,071 discloses interconnect structures
incorporating a silicon carbide layer as a diffusion barrier layer,
more specifically a layer between a dielectric and a highly
conductive metal layer with a resistivity less than about 2.5
microhm-centimeters. U.S. Pat. No. 5,818,071 does not disclose how
to pattern or to remove the silicon carbide layer selectively to
expose the underlying layer, more particularly a metal layer.
[0015] U.S. Pat. No. 5,904,565 discloses a method for selectively
forming barrier layers in a via or damascene structure after
patterning these vias and damascene structures.
[0016] U.S. Pat. No. 5,176,790 discloses an improved process for
forming a via in an integrated circuit by etching through an
insulating layer while inhibiting the sputtering of the underlying
metal. The process is performed by, e.g., using in the gaseous
etchant one or more 3-6 carbon atom fluorinated hydrocarbons having
the chemical formula C.sub.xH.sub.yF.sub.z.
SUMMARY OF THE INVENTION
[0017] A method for etching an opening in an insulating layer while
depositing a barrier layer on the side walls of the opening without
essentially depositing a barrier layer on the bottom of the opening
is therefore desirable.
[0018] In a first embodiment, a method is disclosed for forming at
least one opening in an insulating layer on a substrate while
depositing a barrier layer on the side walls of the opening without
essentially depositing the barrier layer on the bottom of the
opening, comprising the steps of: subjecting the substrate to a
plasma, the plasma being generated in a gaseous mixture comprising
at least three components: a first component for depositing the
metal barrier layer on at least the side walls of the opening, a
second component for forming an opening in the insulating layer,
and a third component for removing the barrier layer being formed
on the bottom of the opening; etching the insulating layer with the
plasma; and depositing the barrier layer on the side walls of the
opening with the plasma.
[0019] The steps of etching and depositing are performed by
controlling the plasma in a manner that while creating an opening
in an insulating layer, a barrier layer is formed on the side walls
of the opening without essentially forming a barrier layer on the
bottom on the opening.
[0020] In an aspect of the first embodiment, the first component
comprises at least one of the group consisting of 1-methyl silane,
2-methyl silane, 3-methyl silane, 4-methyl silane, a mixture of
SiH.sub.4 and N.sub.2, a mixture of WF.sub.6 and N.sub.2, and
combinations thereof.
[0021] In a further aspect of the first embodiment, the second
component comprises at least one of the group consisting of
N.sub.xO.sub.y, C.sub.xF.sub.yH.sub.zO.sub.u, N.sub.2/O.sub.2,
N.sub.2/H.sub.2, O.sub.2, O.sub.3, NH.sub.3, CO, CO.sub.2,
CH.sub.4, and combinations thereof.
[0022] In a further aspect of the first embodiment, the third
component comprises at least a chemical compound that form halogen
ions or radicals in the etching plasma.
[0023] In a further aspect of the first embodiment, the third
component is at least one of the group consisting of NF.sub.3,
SF.sub.6, F.sub.2, CiF.sub.3, and C.sub.xF.sub.yH.sub.z.
[0024] In a further aspect of the first embodiment, the gaseous
mixture further comprises an inert gas.
[0025] In a further aspect of the first embodiment, the plasma is a
continuous plasma. In a further aspect of the first embodiment, a
method as recited in the first aspect of a preferred embodiment is
disclosed wherein the plasma is a pulsed plasma.
[0026] In a further aspect of the first embodiment, the barrier
layer is a metal diffusion barrier layer. Preferably, the barrier
layer is a copper diffusion barrier layer. The barrier layer can be
selected from the group consisting of Ti, TiN, Ta, TaN,
Ta.sub.xSi.sub.yN.sub.z, W.sub.xN.sub.y, W.sub.xC.sub.yN.sub.z,
SiC, SiOC, hydrogenated SiC, hydrogenated SiOC, and combinations
thereof.
[0027] In a further aspect of the first embodiment, the insulating
layer comprises at least a porous material. The insulating layer
can be an organic containing insulating layer or an inorganic
containing insulating layer.
[0028] In a further aspect of the first embodiment, the opening is
a via hole, the via hole extending through the insulating layer to
an underlying conductive layer or an underlying barrier layer.
[0029] In a further aspect of the first embodiment, the method
further comprises, prior to the step of subjecting the substrate,
the steps of covering the insulating layer with a bilayer, the
bilayer comprising a resist hard mask layer being formed on the
insulating layer and a resist layer being formed on the hard mask
layer; and patterning the bilayer.
[0030] In a second embodiment, a device is provided, the device
comprising an insulating layer on a substrate, the insulating layer
having an opening, wherein side walls of the opening are covered
with a barrier layer and a bottom of the opening is essentially not
covered with the barrier layer, characterized in that the device is
produced by a method comprising the steps of: subjecting the
substrate to a plasma, wherein the plasma is generated in a gaseous
mixture comprising at least three components, the components
comprising: a first component for depositing the metal barrier
layer on at least the side walls of the opening, a second component
for forming an opening in the insulating layer, and a third
component for removing the barrier layer formed on the bottom of
the opening; etching the insulating layer with the plasma; and
depositing the barrier layer on the side walls of the opening with
the plasma.
[0031] In a first aspect of the second embodiment, the first
component is selected from the group consisting of 1-methyl silane,
2-methyl silane, 3-methyl silane, 4-methyl-silane, a mixture of
SiH.sub.4 and N.sub.2, and combinations thereof.
[0032] In a further aspect of the second embodiment, the second
component is selected from the group consisting of N.sub.xO.sub.y,
C.sub.xF.sub.yH.sub.xO.sub.u, N.sub.2/O.sub.2 mixtures,
N.sub.2/H.sub.2 mixtures, O.sub.2, O.sub.3, and combinations
thereof.
[0033] In a further aspect of the second embodiment, the third
component comprises a chemical compound that forms a halogen ion or
a radical in the plasma.
[0034] In a further aspect of the second embodiment, the third
component is selected from the group consisting of NF.sub.3,
SF.sub.6, F.sub.2, ClF.sub.3, and mixtures thereof.
[0035] In a further aspect of the second embodiment, the gaseous
mixture further comprises an inert gas.
[0036] In a further aspect of the second embodiment, the plasma is
a continuous plasma. In a further aspect of the second embodiment,
the plasma etching is a pulsed plasma.
[0037] In a further aspect of the second embodiment, the barrier
layer is a metal diffusion barrier layer. The barrier layer may
comprise silicon carbide.
[0038] In a further aspect of the second embodiment, the insulating
layer may comprise a porous material. Alternatively, the insulating
may organic containing insulating layer or an inorganic containing
insulating layer.
[0039] In a further aspect of the second embodiment, the opening is
a via hole, the via hole extending through the insulating layer to
an underlying conductive layer or an underlying barrier layer.
[0040] In a further aspect of the second embodiment, the method for
producing the device further comprising the steps of: covering the
insulating layer with a bilayer, the bilayer comprising a resist
hard mask layer formed on the insulating layer and a resist layer
formed on the hard mask layer; and patterning the bilayer.
[0041] In a third embodiment, a gaseous mixture is provided for use
in a method for forming at least one opening in an insulating layer
on a substrate while depositing a barrier layer on side walls of
the opening without essentially depositing the barrier layer on a
bottom of the opening, wherein a plasma is generated from the
gaseous mixture, and wherein the gaseous mixture comprises a first
component, a second component, and a third component, wherein the
first component deposits a barrier layer on the side wall of the
opening, wherein the second component forms the opening in the
insulating layer, and wherein the third component removes the
barrier layer formed on the bottom of the opening.
[0042] In a first aspect of the third embodiment, the first
component is selected from the group consisting of 1-methyl silane,
2-methyl silane, 3-methyl silane, 4-methyl-silane, a mixture of
SiH.sub.4 and N.sub.2, a mixture of WF.sub.6 and N.sub.2, and
mixtures thereof.
[0043] In a further aspect of the third embodiment, the second
component is selected from the group consisting of N.sub.xO.sub.y,
C.sub.xF.sub.yH.sub.xO.sub.u, N.sub.2/O.sub.2 mixtures,
N.sub.2/H.sub.2 mixtures, O.sub.2, O.sub.3, NH.sub.3, CO, CO.sub.2,
CH.sub.4, and mixtures thereof.
[0044] In a further aspect of the third embodiment, the third
component comprises a chemical compound that forms a halogen ion or
a radical in the plasma. The third component may be selected from
the group consisting of NF.sub.3, SF.sub.6, F.sub.2, ClF.sub.3, and
mixtures thereof.
[0045] In a further aspect of the third embodiment, the gaseous
mixture further comprises an inert gas.
BRIEF DESCRIPTION OF THE DRAWINGS
[0046] FIG. 1 illustrates the prior method for forming an opening
in an insulating layer and depositing a barrier layer on the side
walls of the opening according to the prior art.
[0047] FIG. 2 illustrates a method for forming an opening in an
insulating layer while depositing a barrier layer on the side walls
of the opening without essentially depositing a barrier layer on
the bottom of the opening. The dashed arrows illustrate the
anisotropic aspect of the plasma etching
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0048] The following description and examples illustrate preferred
embodiments of the present invention in detail. Those of skill in
the art will recognize that there are numerous variations and
modifications of this invention that are encompassed by its scope.
Accordingly, the description of preferred embodiments should not be
deemed to limit the scope of the present invention.
[0049] In a first aspect of a preferred embodiment, a method is
disclosed for forming at least one opening in an insulating layer
on a substrate while depositing a barrier layer on the side walls
of the opening without essentially depositing the barrier layer on
the bottom of the opening, the method comprising the steps of:
[0050] subjecting the substrate to a plasma, the plasma being
generated in a mixture comprising at least three components
including:
[0051] a first component for depositing the metal barrier layer on
at least the side walls of the opening,
[0052] a second component for forming the opening in the insulating
layer, and
[0053] a third component for removing the barrier layer being
formed on the bottom of the opening;
[0054] etching the insulating layer with the plasma; and
[0055] depositing the barrier layer on the side walls of the
opening with the plasma.
[0056] As referred to herein, the steps as disclosed in the first
aspect of this preferred embodiment are also called plasma etching
or plasma etch process, thus including at least the subjecting
step, etching step, and depositing step.
[0057] The steps of etching and depositing are performed by
controlling the plasma in a manner that, while creating an opening
in an insulating layer, a barrier layer is formed on the side walls
of the opening without essentially forming a barrier layer on the
bottom of the opening. The term "essentially" as used in this
context means that the barrier layer on the bottom of the opening
can be formed but is substantially removed by the plasma.
[0058] The term "barrier layer" should be understood as any layer
being present on at least a part of the side walls of the opening.
If the opening is filled with a material, the barrier layer should
be understood to be a layer between the insulating layer and the
material filling the opening. The barrier layer should essentially
prevent the diffusion of the material filling the opening into the
insulating layer.
[0059] The term "layer" should be understood to include any layer
having a thickness of at least one molecule. Examples of a layer
include, but are not limited to, a monolayer, a stack of
monolayers, a film with a thickness less than 50 nm, or a film with
a thickness greater than 50 nm.
[0060] The method as described herein is performed in such a way as
to obtain the formation of a barrier layer on at least a part of at
least one of the side walls of the opening while etching an opening
in the insulating layer. Preferably, the plasma is controlled in
such a way that the barrier layer is formed as a permanent,
adhesive layer on the side walls of the opening in the insulating
material. This means that specific conditions of the plasma, such
as the ion energy and bias, the temperature, and the pressure and
the composition of the etching gas should be selected. Thus, the
barrier layer on the side walls of the opening is essentially not
etched during the process. Preferably, the composition of the
gaseous mixture and the conditions are chosen so as to obtain
removal of the barrier material that builds up at the bottom of the
opening. To create an opening in the insulating layer, a plasma is
used. Etching using a plasma typically results in anisotropic
etching. To obtain plasma etching, the spontaneous etching is
preferably negligible while the etch reaction is effectively
stimulated by the ion bombardment. In other words, the lateral etch
should be negligibly small compared to the vertical etch rate.
Furthermore, the plasma should be controlled such that an opening
is created in such a manner that while creating an opening, a
barrier layer is formed on the side walls of the opening without
essentially forming a barrier layer on the bottom of the opening.
For the purpose of this invention, plasma etching is understood as
plasma-assisted etching, reactive ion etching (RIE), or reactive
ion beam etching (RIBE).
[0061] The gaseous etching mixture for plasma etching comprises at
least three components: a first component for depositing the
barrier layer on at least the side walls of the opening, a second
component for forming an opening in the insulating layer, and a
third component for removing the barrier layer being formed on the
bottom of the opening. The first, second, and third component can
be different chemical species. The gaseous mixture can also
comprise one or two components. If the gaseous component comprises
one component, this component is for depositing the barrier layer
on at least the side walls of the opening, for forming an opening
in the insulating layer, and for removing the barrier layer being
formed on the bottom of the opening. This means that the chemical
composition and the corresponding physical behavior in a plasma
should be pre-selected. If the gaseous mixture comprises at least
two components, the first component should be defined as being
selected (i) for depositing the barrier layer on at least the side
walls of the opening and for forming an opening in the insulating
layer, or (ii) for depositing the barrier layer on at least the
side walls of the opening and for removing the barrier layer being
formed on the bottom of the opening, or (iii) for forming an
opening in the insulating layer and for removing the barrier layer
being formed on the bottom of the opening. The second component is
(i) for depositing the barrier layer on at least the side walls of
the opening, or (ii) for forming an opening in the insulating
layer, or (iii) for removing the barrier layer being formed on the
bottom of the opening.
[0062] Various combinations of the first and the second component
are possible.
[0063] The substrate can be a partly processed or pristine wafer or
slice of semi-conductive material, like Si, GaAs, Ge, or an
insulating material, e.g. a glass slice or a conductive material.
The substrate can comprise a patterned conductive layer.
Particularly, when the substrate is a partly processed wafer or
slice, at least a part of an active and/or passive device can
already be formed and/or at least a part of the structures
interconnecting these devices can be formed.
[0064] The insulating layer can be an organic-containing insulating
layer or an inorganic insulating layer.
[0065] The invention as described in the first aspect of this
invention is particularly relevant for semiconductor
processing.
[0066] In a first aspect of a preferred embodiment, a method is
disclosed for forming at least one opening in an insulating layer
on a substrate while depositing a barrier layer on the side walls
of the opening without essentially depositing the barrier layer on
the bottom of the opening, the method comprising the steps of:
[0067] subjecting the substrate to a plasma, the plasma being
generated in a mixture comprising at least three components:
[0068] a first component for depositing the barrier layer on at
least the side walls of the opening,
[0069] a second component for forming an opening in the insulating
layer,
[0070] a third component for removing the barrier layer being
formed on the bottom of the opening;
[0071] etching the insulating layer with the plasma; and
[0072] depositing the barrier layer on the side walls of the
opening with the plasma.
[0073] The method can further comprise the step of filling the
opening, the side walls of which are covered with a barrier layer,
with a conductive material.
[0074] The substrate can be a substrate used in semiconducting
processing including, but not limited to, e.g., silicon substrates
and germanium substrates. The substrate can be a wafer, a structure
in the process of IC fabrication, any layer on a substrate in the
process of IC fabrication, a semiconducting layer, or a
semiconducting layer in the process of IC fabrication.
[0075] The term "fabrication" refers to the patterning of
structures. More particularly, the substrates can be subjected to
damascene processing, dual damascene processing, or front-end
processing, where front-end processing means providing contacting
on the source, drain, or gate regions.
[0076] The term "opening" should be understood to include a via
hole, trench, groove, or contact hole made in a substrate used in
semiconductor manufacturing. If the opening is a via hole, the
opening extends through the insulating layer to an underlying
conductive layer or an underlying barrier layer. If the opening is
a contact hole, the opening extends through the insulating layer to
contact the underlying source, drain, or gate regions.
[0077] The term "insulating layer" refers to a layer or a stack of
layers made of non-conductive material used to electrically isolate
layers made of conductive material from each other. The insulating
layer may include silicon oxide, silicon nitride, and silicon
oxynitride. The insulating layer can also comprise silicon
oxycarbide, with varying concentrations of oxygen, carbon and
silicon, as well as hydrogenated silicon oxycarbide. The insulating
layer can also be an organic-containing material, including, but
not limited to, organic containing materials containing benzyl
groups, saturated carbon-carbon bounds, and the like. The
insulating layer can be made of porous material.
[0078] The barrier layer can be a layer or a stack of layers
preventing the diffusion of conductive material (which fills the
opening) into the insulating layer. The nature of the barrier layer
is determined by the conductive material filling the opening. When
the metal is copper, the barrier layer may include, but is not
limited to, Ti, TiN, Ta, TaN, Ta.sub.xSi.sub.yN.sub.z,
W.sub.xN.sub.y, W.sub.xC.sub.yN.sub.z, SiC, SiOC, hydrogenated SiC,
hydrogenated SiOC, and combinations thereof. The thickness of the
deposited barrier layer can be lower than 50 nm, lower than 20 mm,
and preferably lower than 10 nm. In the most preferred embodiment,
the thickness of the barrier layer is between 1 and 5 nm. The
barrier layer is a permanent barrier layer; this means that the
barrier layer remains essentially on the side walls of the opening
after filling the opening. The barrier layer should have a good
adhesion to the side walls of the opening.
[0079] In the first aspect of a preferred embodiment, the mixture
comprises at least three components. The mixture can be a gaseous
mixture. The term "components" should be understood to include the
chemical molecules present in the reaction chamber and exposed to
the plasma. By bringing at least those three components into the
plasma, an opening is formed in the insulating layer. Further, a
barrier layer is formed on the side walls of the opening.
[0080] A first component contains the chemistries accounting for
the in-situ deposition of the barrier layer. For a SiC barrier
layer, examples of the first component include, but are not limited
to, 1-methyl silane (1MS), 2-methyl silane (2MS), 3-methyl silane
(3MS), and 4-methyl-silane (4MS). For a W.sub.xN.sub.y barrier
layer, the first component may include, but is not limited to, a
mixture of WF.sub.6 and N.sub.2. For a Si.sub.3N.sub.4 barrier
layer, the first component can be a mixture of SiH.sub.4 and
N.sub.2.
[0081] A second component contains the chemistries accounting for
the anisotropic etching of the insulating dielectric, thereby
creating the opening. Examples of the third component are
N.sub.xO.sub.y, C.sub.xF.sub.yH.sub.zO.sub.u, N.sub.2/O.sub.2,
N.sub.2/H.sub.2, O.sub.2, O.sub.3, NH.sub.3, CO, CO.sub.2,
CH.sub.4, and combinations thereof.
[0082] A third component contains the chemistries accounting for
the anisotropic etching of this barrier layer according to another
embodiment of the invention. The second component is able to form
ions or radicals in a plasma and is able to react with the barrier
layer on the bottom of the opening, such that volatile reaction
products are formed. Examples of the second component are fluorine
containing chemistries, e.g., NF.sub.3, SF.sub.6, F.sub.2,
ClF.sub.3, and chlorine containing chemistries, with or with
additives such as oxygen.
[0083] These etching plasmas can further comprise inert gasses such
as helium and argon.
[0084] Various combinations of the above-mentioned first component,
second component, and third component are possible.
[0085] The gaseous mixture can also comprise one or two components.
If the gaseous component comprises one component, this component is
for depositing the barrier layer on at least the side walls of the
opening, for forming an opening in the insulating layer and for
removing the barrier layer being formed on the bottom of the
opening. If the gaseous mixture comprises at least two components,
the first component should be defined as being selected (i) for
depositing the barrier layer on at least the side walls of the
opening and for forming an opening in the insulating layer, or (ii)
for depositing the barrier layer on at least the side walls of the
opening and for removing the barrier layer being formed on the
bottom of the opening, or (iii) for forming an opening in the
insulating layer and for removing the barrier layer being formed on
the bottom of the opening. The second component is (i) for
depositing the barrier layer on at least the side walls of the
opening, or (ii) for forming an opening in the insulating layer or
(iii) for removing the barrier layer being formed on the bottom of
the opening. Various combinations of the first and the second
component are possible.
[0086] By subjecting the substrate to a plasma, etching of the
insulating layer with the plasma and deposition of the barrier
layer on the side walls of the opening with the plasma occurs. The
plasma is selected so as to obtain an opening in the insulating
layer and so as to obtain a deposition of the barrier layer on the
side walls of the opening. This means that the etching gases, the
temperature, the pressure, the ion energy and bias of the etching
gases are pre-selected. Furthermore, the electron density of the
plasma is selected by adjusting the power applied to the plasma,
the frequency of the power, and the nature of the walls of the
reactor and the inert gases. The gaseous etching mixture can
comprise three components. The components are preferably volatile
and contain the chemical atoms necessary for the formation of the
barrier layer.
[0087] In plasma etching, the etched surface is subjected to an ion
flux, oriented vertically to the wafer surface. In a plasma,
radicals are also generated, but the radicals have a random
distribution. This ion flux is present in a plasma that aims to
obtain a high degree of anisotropy. The origin of the vertically
oriented ion flux is found in the existence of the sheath potential
between the bulk of the plasma and the wafer surface, whereas the
bulk of the plasma is at a more positive potential than the wafer
surface. In the bulk of the plasma, ions move in randomly
distributed directions. Whenever they approach the sheath, however,
the potential difference induces the ions to collide onto the wafer
surface orthogonal to the wafer surface, as implied by the
electrical field. The purpose of anisotropic etching is to induce
etch reactions to occur in the presence of this ion flux and
prevent etching, or cause deposition, on the surfaces that are not
subjected to this ion flux. While etching the insulating layer, the
insulating material is removed such that an opening is created. The
opening is formed by a physical process (ion flux) and a chemical
reaction. The ion flux accounts also for the immediate removal of
the barrier layer on the bottom of the opening. The ion flux
essentially avoids the build-up of a barrier layer on the bottom of
the opening. The vertical side walls of the etched openings are
preferably not subjected to this ion flux, and hence, etching will
not occur.
[0088] The etching plasma can be a continuous plasma, meaning that
the excitation power is continuously applied to the mixture. The
plasma can also be interrupted. Therefore, the power applied to the
gaseous mixture is applied for a defined period, e.g., in the range
of from 1 ms to 10 ms. The time between the pulses (duty cycle)
depends on the specific plasma conditions.
[0089] It is also possible to apply a continuous low power and to
apply a pulsed plasma.
[0090] The process as described herein protects the insulating
layer from the etching plasma and, equally important, copper
sputtering onto the side walls of the insulating layers becomes
less likely because the copper diffusion barrier is already
deposited. Furthermore, the process as disclosed in this aspect of
the preferred embodiment has the advantage in that the cleaning
after barrier etch is facilitated as the insulating material is
protected and there is no need for removal of the copper from the
side walls of the opening.
[0091] The method of a preferred embodiment can, prior to the
plasma etching step, further comprise the steps of (i) covering the
insulating layer with a bilayer, the bilayer comprising a resist
hard mask layer being formed on the insulating layer and a resist
layer being formed on the hard mask layer, and (ii) patterning the
bilayer. After the plasma etching process as described in the
preferred embodiment is conducted, the opening can be cleaned and
subsequently filled with a conductive material. The conductive
material may include, but is not limited to, a metal such as
copper, aluminum, gold, tungsten, and combinations thereof.
[0092] FIG. 2 illustrates a method of a preferred embodiment. There
is provided a process for the formation of a opening (4) in an
insulating layer (3) while forming a copper barrier layer (5) on
the side walls (7) of the opening (4) without essentially forming a
barrier layer on the bottom (8) of the opening. The opening is a
via hole in an insulating layer. The insulating layer covers an
underlying conductive layer (2). The trench extends to the
conductive layer. The conductive layer is formed on a substrate (1)
subject to back-end IC processing.
[0093] According to a preferred embodiment, the copper-barrier
layer comprises a silicon carbide layer. For the purpose of this
invention, silicon carbide is understood to include a layer
composed of at least Si and C, e.g., SiC, or of at least Si, C, and
O, i.e., a silicon oxycarbide, e.g., SiOC, or at least Si, C, and
H, e.g., an amorphous hydrogenated silicon carbide such as SiC:H.
The substrates are introduced into a pressurized chamber of a
plasma-etch tool, such as a reactive ion etch (RIE) plasma tool,
and then processed. The temperature in the chamber is preferably
600 degrees C. or below, even more preferably below 400 degrees C.
This temperature can also be in the range of from 100 to 600
degrees C.
[0094] The process is performed using plasma etching with a gaseous
mixture comprising at least three components.
[0095] A first component contains the chemistries accounting for
the in-situ deposition of the barrier layer. For SiC, examples of
the first component include, but are not limited to, 1-methyl
silane (1MS), 2-methyl silane (2MS), 3-methyl silane (3MS), and
4-methyl-silane (4MS).
[0096] A second component contains the chemistries accounting for
the anisotropic etching of this barrier layer according to another
embodiment of the invention. Examples of the second component
include halogen-containing chemistries, e.g., NF.sub.3, SF.sub.6,
F.sub.2, ClF.sub.3, and chlorine containing chemistries, with or
without additives.
[0097] A third component contains the chemistries accounting for
the anisotropic etching of the insulating dielectric, thereby
creating the opening. Examples of the third component include
N.sub.xO.sub.y, C.sub.xF.sub.yH.sub.xO.sub.u, N.sub.2/O.sub.2,
N.sub.2/H.sub.2, O.sub.2, O.sub.3, and equivalent chemistries.
[0098] The amount of each component is preferably at least 0.1% of
the total mixture.
[0099] Typical ratios of these mixtures include, but are not
limited to, 25/50/25.
[0100] These etching plasmas can further comprise inert gasses such
as helium and argon.
[0101] The optimized process conditions, such as temperature, ion
energy and bias, pressure, and composition of the plasma depend on
the barrier layer to be deposited and on the insulation layer to be
simultaneously etched. The type of barrier layer depends on the
kind of metal used in the metallization process, e.g., copper,
aluminum, and the like.
[0102] FIG. 1 illustrates the process as known in the prior art.
Compared to the prior art, the method of preferred embodiments
minimizes the sputtering of copper onto the side walls of the
insulating layers, since the side walls are protected by the
deposited barrier layer. The process of preferred embodiments
facilitates cleaning after the formation of the opening and there
is no need for removal of the copper from the side walls of the
opening.
[0103] In another embodiment of the present invention, the method
as disclosed is used for the formation of a copper-barrier layer
while etching a porous insulating material present on a substrate.
The substrates that are to be etched can be silicon substrates
subject to damascene processing. In a first step, the substrate is
subjected to a plasma, the plasma being generated in a gaseous
mixture comprising three components: a first component for
depositing a SiC barrier layer, a second component for creating an
opening in the porous SILK layer, and a third component for
removing the SIC barrier layer being formed on the bottom of the
opening.
[0104] By subjecting the substrate to the plasma, an opening is
created in the porous insulating layer, and a SiC barrier layer is
formed on the side wall of the opening. Since the insulating layer
is made of a porous material, the side walls are rough. By using
the method of the preferred embodiments, the opening in the side
walls is filled in the first part of the insulating layer, and a
barrier layer is formed on the side walls. This results in smooth
side walls. In the prior art, when the opening is formed and
subsequently the barrier layer is deposited by, e.g., PVD, the
barrier layer has the same profile as the rough side wall of the
opening. This has a detrimental effect on the final device
performance.
[0105] According to a preferred embodiment of the invention, the
copper-barrier layer comprises a silicon carbide layer. This
silicon carbide is understood to be a layer composed of at least Si
and C, e.g., SiC, or of at least Si, C, and O, i.e., a silicon
oxycarbide, e.g., SiOC, or at least Si, C, and H, such as, e.g.,
amorphous hydrogenated silicon carbide, SiC:H.
[0106] The insulating material is a porous low k dielectric,
commercially available as porous SiLK.TM. (Dow Chemical). The
substrate comprises a wafer subjected to back-end IC processing.
The porous insulating layer is covered with a hardmask material,
e.g., SiO.sub.2, SiC, or a combination of SiO.sub.2 and SiC, or a
spin-on hardmask, on top of which photoresist is spun. The
substrates are introduced into a pressurized chamber of a
plasma-etch tool, such as a reactive ion etch (RIE) plasma tool,
and then processed. The temperature in the chamber is in the range
of from 15 to 40 degrees C. RF power settings range from 200 to
2200 W for both electrodes. Operating pressure is typically between
50 and 250 mTorr. The process is performed using plasma etching
with a gaseous mixture comprising at least three components. The
first component contains the chemistries for the in-situ deposition
of the barrier layer. For SiC, 3-methyl-silane (3MS) or
4-methyl-silane (4MS) is used.
[0107] The second component contains the chemistries accounting for
the anisotropic etching of this barrier layer. Fluorine-containing
gases such as CF.sub.4, CHF.sub.3, CH.sub.2F.sub.2, or CHF.sub.3
are used. An inorganic hardmask opening is also performed using
these gases in combination with an inert gas such as argon in
combination with O.sub.2 and/or CO.
[0108] The third component contains the chemistries for the
anisotropic etching of the insulating dielectric whereby the
opening is created. Preferred chemistries for this third component
are N.sub.2/O.sub.2, N.sub.2/H.sub.2, and O.sub.2, optionally
combined with CH.sub.4 or C.sub.2H.sub.4 for enhanced side wall
passivation and hardmask selectivity.
[0109] The first step in the processing sequence is the hardmask
opening. The second step is etching of the porous insulating
material while a SiC layer is deposited on the side walls. To
propagate the etching, it is preferred to continuously remove the
SiC at the bottom of the etched feature, until the SiC copper
diffusion barrier is reached. Finally, this barrier is etched
anisotropically, so as not to remove the SiC on the side walls.
[0110] In another preferred embodiment, a method is disclosed for
forming at least one opening in an insulating layer on a substrate
while depositing a barrier layer on the side walls of the opening,
the method comprising the steps of:
[0111] subjecting the substrate to a plasma, the plasma being
generated in a mixture comprising at least two components:
[0112] a first component for depositing the barrier layer on at
least the side walls of the opening, and
[0113] a second component for forming an opening in the insulating
layer;
[0114] etching the insulating layer with the plasma; and
[0115] depositing the barrier layer on the side walls of the
opening with the plasma.
[0116] Contrary to the preferred embodiments described previously,
in this embodiment it is not necessary to remove the barrier layer
from the bottom of the opening. This is particularly relevant when
the barrier layer is made of a conductive material.
[0117] The various aspects of this preferred embodiment are similar
to those of previously described preferred embodiments, with the
exception that the gaseous mixture does not comprise a third
component.
[0118] In a second aspect of a preferred embodiment, a device is
disclosed. The device comprises an insulating layer on a substrate,
the insulating layer having an opening, the side walls of the
opening being covered with a barrier layer, wherein the bottom of
the opening is essentially not covered with the barrier layer. The
device is obtainable by a method comprising the steps of:
[0119] subjecting the substrate to a plasma, the plasma being
generated in a gaseous mixture comprising at least three
components:
[0120] a first component for depositing the metal barrier layer on
at least the side walls of the opening,
[0121] a second component for forming an opening in the insulating
layer, and
[0122] a third component for removing the barrier layer being
formed on the bottom of the opening;
[0123] etching the insulating layer with the plasma; and
[0124] depositing the barrier layer on the side walls of the
opening with the plasma.
[0125] The scope of the method is determined by the disclosure of
the first aspect of a preferred embodiment.
[0126] In an embodiment of the second aspect of the preferred
embodiment, a device is disclosed, the device comprising a porous
insulating layer on a substrate, the porous insulating layer having
an opening, the side walls of the opening being covered with a
barrier layer wherein the bottom of the opening is essentially not
covered with the barrier layer. The device is obtainable by a
method comprising the steps of:
[0127] subjecting the substrate to a plasma, the plasma being
generated in a gaseous mixture comprising at least three
components:
[0128] a first component for depositing the metal barrier layer on
at least the side walls of the opening,
[0129] a second component for forming an opening in the insulating
layer, and
[0130] a third component for removing the barrier layer being
formed on the bottom of the opening;
[0131] etching the insulating layer with the plasma; and
[0132] depositing the barrier layer on the side walls of the
opening with the plasma.
[0133] In the prior art, etching an opening in an insulating
material would result in rough openings, since the pores of the
insulating material are intersected by the plasma. When the barrier
layer is subsequently deposited by a technique known in the prior
art, e.g., PVD, the barrier layer has the same profile as the rough
side wall of the opening. This has a detrimental effect on the
final device performance. By applying the method as described
above, the opening in the side walls are filled in the first part
of the insulating layer, and a barrier layer will be formed on the
side walls. This results in smooth side walls.
[0134] The device as disclosed in the second aspect of a preferred
embodiment is characterized in that the pores that are intersected
by the plasma during the formation of the opening are filled with
material forming the barrier layer and that a barrier layer,
preferably a thin layer, is formed on the side walls such that the
side walls are essentially smooth.
[0135] The above description discloses several methods and
materials of the present invention. This invention is susceptible
to modifications in the methods and materials. Such modifications
will become apparent to those skilled in the art from a
consideration of this disclosure or practice of the invention
disclosed herein. Consequently, it is not intended that this
invention be limited to the specific embodiments disclosed herein,
but that it cover all modifications and alternatives coming within
the true scope and spirit of the invention as embodied in the
attached claims. The disclosures of all references cited herein are
hereby incorporated by reference in their entireties.
* * * * *