U.S. patent application number 14/323023 was filed with the patent office on 2014-10-23 for titanium-nitride removal.
This patent application is currently assigned to INTERNATIONAL BUSINESS MACHINES CORPORATION. The applicant listed for this patent is INTERNATIONAL BUSINESS MACHINES CORPORATION. Invention is credited to Shyng-Tsong Chen, John A. Fitzsimmons, David L. Rath, Muthumanickam Sankarapandian, Oscar van der Straten.
Application Number | 20140312265 14/323023 |
Document ID | / |
Family ID | 48695143 |
Filed Date | 2014-10-23 |
United States Patent
Application |
20140312265 |
Kind Code |
A1 |
Chen; Shyng-Tsong ; et
al. |
October 23, 2014 |
Titanium-Nitride Removal
Abstract
A chemical solution that removes undesired metal hard mask yet
remains selective to the device wiring metallurgy and dielectric
materials. The present invention decreases aspect ratio by
selective removal of the metal hard mask before the metallization
of the receiving structures without adverse damage to any existing
metal or dielectric materials required to define the semiconductor
device, e.g. copper metallurgy or device dielectric. Thus, an
improved aspect ratio for metal fill without introducing any
excessive trapezoidal cross-sectional character to the defined
metal receiving structures of the device will result.
Inventors: |
Chen; Shyng-Tsong;
(Rensselaer, NY) ; Fitzsimmons; John A.;
(Poughkeepsie, NY) ; Rath; David L.; (Stormville,
NY) ; Sankarapandian; Muthumanickam; (Niskayuna,
NY) ; van der Straten; Oscar; (Mohegan Lake,
NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
INTERNATIONAL BUSINESS MACHINES CORPORATION |
Armonk |
NY |
US |
|
|
Assignee: |
INTERNATIONAL BUSINESS MACHINES
CORPORATION
Armonk
NY
|
Family ID: |
48695143 |
Appl. No.: |
14/323023 |
Filed: |
July 3, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13343190 |
Jan 4, 2012 |
|
|
|
14323023 |
|
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Current U.S.
Class: |
252/79.1 |
Current CPC
Class: |
H01L 21/76804 20130101;
H01L 21/31144 20130101; H01L 21/02063 20130101; C09K 13/00
20130101; H01L 21/32134 20130101; H01L 21/76802 20130101 |
Class at
Publication: |
252/79.1 |
International
Class: |
C09K 13/00 20060101
C09K013/00 |
Claims
1. A chemical composition for removing a metal hard mask and
etching residues from a microelectronic device, said chemical
composition comprising: an oxidizing agent selected from the group
consisting of peroxides and oxidants which do not leave a residue
and do not adversely attack copper; a pH controlling agent selected
from the group consisting of a quaternary ammonium salt and a
quaternary ammonium alkali; and an aqueous solution.
2. The chemical composition of claim 1, further comprising a
sequestering agent selected from the group consisting of amines and
amino acids.
3. The chemical composition of claim 1, further comprising a copper
protectant selected from hetero-organic inhibitors.
4. The chemical composition of claim 1, wherein said chemical
composition has a pH from about 7 to about 14.
5. The chemical composition of claim 1, wherein said chemical
composition has a pH from about 9 to about 10.
6. The chemical composition of claim 1, wherein said oxidizing
agent comprises hydrogen peroxide (H.sub.2O.sub.2), benzoyl
peroxide (C.sub.12H.sub.10O.sub.4) or a mixture thereof.
7. The chemical composition of claim 1, wherein the pH controlling
agent is tetraethylammonium hydroxide (TEAH).
8. The chemical composition of claim 2, wherein the sequestering
agent is at least one of
1,2-cyclohexanediamine-N,N,N',N'-tetraacetic acid (CDTA),
ethyenediaminetetraacetic acid (EDTA) and
diethylenetriaaminopentaacetic acid (DTPA).
9. The chemical composition of claim 3, wherein the copper
protectant is at least one of benzotriazole, 1,2,3 triazole, 1,3,4
triazole, 1,2,4 triazole and imidazole.
10. The chemical composition of claim 1, wherein the aqueous
solution comprises de-ionized water.
11. The chemical composition of claim 1, wherein said oxidizing
agent is hydrogen peroxide (H.sub.2O.sub.2), said pH controlling
agent is tetraethylammonium hydroxide (TEAH) and said aqueous
solution is de-ionized water, and wherein the chemical composition
has a pH in the range of about 9 to about 10.
12. The chemical composition of claim 1, wherein said aqueous
solution comprises 25% isoproponal and 75% deionized water.
13. The chemical composition of claim 1, wherein said oxidizing
agent is present in amount of 9% per weight, said pH controlling
agent is present in an amount of 0.8%, and said aqueous solution is
present in an amount of 90.2%.
14. The chemical composition of claim 2, wherein said oxidizing
agent is present in amount of 9% per weight, said pH controlling
agent is present in an amount of 0.8%, said sequestering agent is
present in an amount of 10 ppm, and said remainder of said chemical
composition, up to 100% per weight, is comprised of said aqueous
solution.
15. The chemical composition of claim 3, wherein said oxidizing
agent is present in an amount of 9% per weight, said pH controlling
agent is present in an amount of 0.8%, said sequestering agent is
present in an amount of 10 ppm, said copper protectant is present
in an amount of 100 ppm, and said remainder of said chemical
composition, up to 100% per weight, is comprised of said aqueous
solution.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional of U.S. patent application
Ser. No. 13/343,190, filed Jan. 4, 2012, the entire content and
disclosure of which is incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to removal of metal hard mask
materials for microelectronic devices. More particularly, the
present invention relates to a chemical solution for removing metal
hard mask selective to device wiring and dielectric materials.
DESCRIPTION OF THE RELATED ART
[0003] Interconnect circuitry in semiconductor circuits consists of
conductive metallic circuitry surrounded by insulating dielectric
material. Silicate glass vapor deposited from
tetraethylorthosilicate (TEOS) was widely used as the dielectric
material, while alloys of aluminum were used for metallic
interconnects.
[0004] Demand for higher processing speeds has led to smaller
sizing of circuit elements, along with the replacement of TEOS and
aluminum alloys by higher performance materials. Aluminum alloys
have been replaced by copper or copper alloys due to the higher
conductivity of copper. TEOS and fluorinated silicate glass (FSG)
have been replaced by the so called low-k dielectrics, including
low-polarity materials such as organic polymers, hybrid organic,
inorganic materials, organosilicate glass (OSG), and carbon-doped
oxide (CDO) glass. The incorporation of porosity, i.e. air-filled
pores, in these materials further lowers the dielectric constant of
the material.
[0005] During dual-damascene processing of integrated circuits,
photolithography is used to image a pattern on a device wafer.
Photolithography techniques comprise the steps of coating, exposure
and development. A wafer is coated with a positive or negative
photoresist substance and subsequently covered with a mask that
defines patterns to be retained or removed in subsequent processes.
Following the proper positioning of the mask, the mask has directed
there through a beam of monochromatic radiation, such as
ultraviolet (UV) light or deep UV (DUV) light (.about.250 nm or 193
nm), to make the exposed photoresist material more or less soluble
in a selected rinsing solution. The soluble photoresist material is
then removed, or "developed," thereby leaving behind a pattern
identical to the mask.
[0006] Thereafter, gas-phase plasma etching is used to transfer the
patterns of the developed photoresist coating to the underlying
layers, which may include hard mask, inter-level dielectric (ILD),
and/or etch stop layers. Post-plasma etch residues are typically
deposited on back-end-of-the-line (BEOL) structures and if not
removed, may interfere with subsequent silicidation, proper
metallization or contact formation. Post-plasma etch residues
typically include chemical elements present on the substrate and in
the plasma gases. For example, if a TiN hard mask is employed, e.g.
as a metal hard mask over a dielectric hard mask or as a layer over
ILD, the post-plasma etch residues include titanium-containing
species, which are difficult to remove using conventional wet
cleaning chemistries.
[0007] In addition to the need to remove post-plasma residues, it
is often desirable to remove or partially etch back the metal hard
mask such as a titanium-containing hard mask and/or
titanium-containing post plasma etch residue, additional materials
that are deposited during the post-plasma etch process such as
polymeric residues on the sidewalls of the patterned device and
copper-containing residues in the open via structures of the device
are also preferably removed. No single wet cleaning composition has
successfully removed all of residue and/or hard mask material while
simultaneously being compatible with the ILD, other low-k
dielectric materials, and metal interconnect materials.
Compositions in the art claim to act in such a manner but are
extremely less effective than the claims indicate.
[0008] The integration of new materials, such as low-k dielectrics,
into microelectronic devices places new demands on cleaning
performance. At the same time, shrinking device dimensions reduces
the tolerance for changes in critical dimensions and damage to
device elements. Etching conditions can be modified in order to
meet the demands of the new materials Likewise, post-plasma etch
cleaning compositions must be modified. Importantly, the cleaner
should not damage the underlying dielectric material or corrode
metallic interconnect materials, e.g. sensitive ILD materials such
as carbon-doped oxides and metal structures such as copper,
tungsten, cobalt, aluminum, ruthenium and silicides thereof, on the
device.
[0009] Typical trench first metal hard mask integration removes the
metal hard mask during the chemical mechanical polish process that
removes excess device metallurgy. As integration tolerances
tighten, the limited ability to correctly fill the defined metal
receiving structures has been clearly demonstrated.
[0010] Additional complications arise when a self-aligned via (SAV)
process that requires enhanced metal hard mask stability is used to
provide additional lithographic process window. While it may be
beneficial for metal fill to add trapezoidal cross-sectional
character to an integration structure, line to line integration
space can suffer if an excessive trapezoidal cross-sectional design
is used to enhance metal fill of very high aspect structures. A
metal hard mask can be designed such that the lithographic transfer
into the metal hard mask will define the desired future trench
structure and yet be resistant to undesired damage during reactive
ion etch transfer operations into the ILD structures such that a
metal fill definition structure may be constructed without
significant trapezoidal character. An unfortunate byproduct of this
aforementioned process is an increase in aspect ratio, which may
further impede proper metallization.
[0011] What is needed to advance new technologies is a method to
improve the aspect ratio for metal deposition while still
maintaining the desired line to line integration spaces. U.S. Pat.
No. 7,922,824 suggests the use of quaternary ammonium salts and
quaternary ammonium alkali as part of a chemical composition for
removing metal hard masks and post-plasma etch residues. However,
it teaches away from the use of quaternary ammonium salts and
quaternary ammonium alkali without the addition of an acid
modifying agent, such as citric acid, and by this teaching as well
as the direct omission of quaternary ammonium salts in the list of
oxidizing agent stabilizers indicates that quaternary ammonium
salts and quaternary ammonium alkali cannot be used alone.
SUMMARY OF THE INVENTION
[0012] The present invention is a chemical solution that removes
undesired metal hard mask yet remains selective to the device
wiring metallurgy and dielectric materials. The present invention
decreases aspect ratio by removal of the metal hard mask before the
metallization of the receiving structures without adverse damage to
any existing metal or dielectric materials required to define the
semiconductor device, e.g. copper metallurgy or device
dielectric.
[0013] According to an embodiment of the present invention, a
chemical composition for removing a metal hard mask and etching
residues from a microelectronic device is provided. The chemical
composition includes: an oxidizing agent selected from a group
comprised of peroxides and oxidants which do not leave a residue or
adversely attack copper; a pH controlling agent selected from a
group comprised of quaternary ammonium salts and quaternary
ammonium alkali; and an aqueous solution.
[0014] According to a further embodiment of the present invention,
a method of removing a metal hard mask and etching residues from a
microelectronic device is provided. The method includes steps of:
etching a trench in an interconnect structure selective to a
dielectric capping layer by a reactive ion etching process (RIE);
applying a wet chemical composition for removing at least a portion
of layers on the interconnect structure selective to the dielectric
capping layer, said chemical composition comprising an oxidizing
agent selected from a group comprised of peroxides and oxidants
which do not leave a residue or adversely attack copper, a pH
controlling agent selected from a group comprised of quaternary
ammonium salts and quaternary ammonium alkali and an aqueous
solution, wherein the composition has a pH in the range of about 7
to about 14; and etching the interconnect structure to open the
dielectric capping layer above a copper device layer for filling
the trench.
[0015] According to another embodiment of the present invention, a
method of removing a metal hard mask and etching residues from a
microelectronic device is provided. The method includes steps of:
etching a trench in an interconnect structure selective to a copper
device layer by a reactive ion etching process (RIE); and applying
a wet chemical composition for removing at least a portion of
layers on the interconnect structure selective to the copper device
layer, said chemical composition comprising an oxidizing agent
selected from a group comprised of peroxides and oxidants which do
not leave a residue or attack copper, a pH controlling agent
selected from a group comprised of quaternary ammonium salts and
quaternary ammonium alkali and an aqueous solution, wherein the
composition has a pH in the range of about 7 to about 14.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The features and elements of the present invention are set
forth with respect to the appended claims and illustrated in the
drawings.
[0017] FIG. 1 illustrates a microelectronic device prior to imaging
and etching.
[0018] FIG. 2 illustrates the microelectronic device with an imaged
lithographic stack.
[0019] FIG. 3 illustrates the microelectronic device after removal
of the lithographic stack and etched metal hard mask.
[0020] FIG. 4A illustrates the microelectronic device post reactive
ion etch selective to the dielectric cap (partial RIE) with etch
residue according to the present invention.
[0021] FIG. 4B illustrates the microelectronic device post reactive
ion etch selective to the dielectric cap (partial RIE) without etch
residue according to the present invention.
[0022] FIG. 4C illustrates the partially etched microelectronic
device after a full wet strip of the metal hard mask and etch
residue according to the present invention.
[0023] FIG. 4D illustrates the partially etched microelectronic
device after a partial wet strip of the metal hard mask and etch
residue according to the present invention.
[0024] FIG. 4E illustrates the partially etched microelectronic
device post final reactive ion etch chamfer and clean according to
the present invention.
[0025] FIG. 5A illustrates the microelectronic device post reactive
ion etch selective to the copper line (full RIE) with etch
residue.
[0026] FIG. 5B illustrates the microelectronic device post reactive
ion etch selective to the copper line (full RIE) without etch
residue.
[0027] FIG. 5C illustrates the fully etched microelectronic device
after a full wet strip of the metal hard mask and etch residue
according to the present invention.
[0028] FIG. 5D illustrates the fully etched microelectronic device
after a partial wet strip of the metal hard mask and etch residue
according to the present invention.
[0029] FIG. 5E illustrates the fully etched microelectronic device
post final reactive ion etch chamfer and clean according to the
present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0030] The following describes embodiments of the present invention
with reference to the drawings. The embodiments are illustrations
of the invention, which can be embodied in various forms. The
present invention is not limited to the embodiments described
below, rather representative for teaching one skilled in the art
how to make and use it. Some aspects of the drawings repeat from
one drawing to the next. The aspects retain their same numbering
from their first appearance throughout each of the preceding
drawings.
[0031] The present invention is a chemical solution that removes
undesired metal hard mask yet remains selective to the device
wiring metallurgy and dielectric materials. The present invention
decreases aspect ratio by selective removal of the metal hard mask
before the metallization of the receiving structures without
adverse damage to any existing metal or dielectric materials
required to define the semiconductor device, e.g. copper metallurgy
or device dielectric. Thus, an improved aspect ratio for metal fill
without introducing any excessive trapezoidal cross-sectional
character to the defined metal receiving structures of the device
will result.
[0032] Compositions of the invention may be embodied in a wide
variety of specific formulations, as hereinafter more fully
described. In all such compositions, wherein specific components of
the composition are discussed in reference to weight percentage
ranges including a zero lower limit, it will be understood that
such components may be present or absent in various specific
embodiments of the composition, and that in instances where such
components are present, they may be present at concentrations as
low as 0.0001 weight percent, based on the total weight of the
composition in which such components are employed.
[0033] The compositions of the invention may be formulated to
substantially remove the titanium-containing residue, the polymeric
sidewall reside and/or the copper-containing residue from the
surface of the microelectronic device without substantially
damaging the underlying inter level dielectric, metal interconnect
materials and any dielectric hard mask, if present. The composition
may be formulated to remove the metal hard mask layer from the
surface of the microelectronic device without substantially
damaging the underlying low-k dielectric and metal interconnect
materials.
[0034] The chemical composition of the present invention includes
an oxidizing agent and a pH controlling agent in an aqueous
solution. De-ionized water is the principle solvent in the aqueous
solution. The solvent must be at least free of any detrimental ions
or other materials that could interfere with the cleaning action of
the chemical composition or degrade the cleanliness or future
performance of the semiconductor circuit. While de-ionized water is
the most preferred solvent for the chemical composition, it is
understood that other solvent systems with similar salvation
properties to de-ionized water may also act as a possible solvent
for the present invention. Thus, an aqueous solution is most
preferred. However, it is understood that other solvent systems
similar to water may also act suitably for the present invention.
For example, a 25% isopropanol, 75% de-ionized water solvent system
may also produce satisfactory results.
[0035] The oxidizing agent is preferably a peroxide, for example
hydrogen peroxide and organic peroxides such as benzoyl peroxide.
However, oxidizing agents may also include a non-metal with the
ability to oxidize titanium nitride (TiN) to a soluble compound
without leaving a metallic residue and oxidants that do not leave a
residue or adversely attack copper (Cu). It is very important that
the oxidant/oxidizing agent, when dissolved in the chemical
process, does not attack copper (Cu). For example, an oxidant may
have an activity against copper when used without the modifying
agents in the present chemical composition. However, when so mixed
with the other agents of the present chemical composition, the
activity of the oxidant is modified such that copper is not
detrimentally attacked. More specifically, the pH may be adjusted
such that copper oxidation is minimized, and/or a surface
adsorption action may occur due to agents in the present invention
such that the copper is protected from oxidation. The
tetraethylammonium (TEA) ion may act as a passavating adsorbent on
a copper surface at the pH value of the present chemical
composition as it is so designed.
[0036] The pH stabilizer adjusts the pH level in the chemical
composition to a range of about 7 to about 14. Preferably, the pH
stabilizer adjusts the pH level to a range of about 9 to about 10.
Quaternary ammonium salts and quaternary ammonium alkalis are
preferred for use as a pH stabilizer in the present invention.
Tetramethylammonium hydroxide (TMAH) is the quaternary ammonium
that is primarily used in the industry. However, TMAH is toxic; it
causes severe and typically unexpected health problems from
exposure. Unlike typical strong bases where an unprotected acute
exposure generally results in a caustic burn, TMAH may also
introduce a complication of decreased respiratory function. Thus, a
quaternary ammonium that does not cause unexpected health side
effects is preferable. Tetraethylammonium hydroxide (TEAH) is the
most preferred pH stabilizer in the present invention. In addition
to the ability to adjust pH without the introduction of extraneous
undesirable metal ions, such as alkaline earth or alkali metal
ions, the TEA ion may also act as a passavating adsorbent on a
copper surface at the pH value of the present chemical composition
as it is also designed.
[0037] Regardless of whether the passavation action by TEA ions
occur, the ability to adjust pH without the introduction of
extraneous undesirable metal ions and the decreased hazard of TEAH
makes TEAH the most preferred pH stabilizer for the present
invention. It is understood that other quaternary ammonium salts
may also act as pH stabilizing agents without the additional
passavation action towards a copper surface as long as the
resultant solution does not have detrimental activity towards a
copper surface; such a resultant solution is within the purview of
the present invention.
[0038] The approximate bath life of the chemical composition is in
the range of about 18 hrs to about 22 hrs. When the chemical bath
drops below 10-15% fresh bath, the bath is no longer useful. It is
understood that typical methods used to extend solution bath life
such as replenishment of the consumed oxidizer in a recirculated
solution may be used to extend usable bath life. Additionally, it
is known that trace contamination such as minute amounts of some
metal ions may also dramatically decrease bath life. As such, the
chemical composition of the present invention may be of single use
(i.e., dispensed on the wafer for cleaning and sent to drain) or
multiple use (i.e., reclaimed after initial processing use and
stored for additional use). It is recognized that reclamation may
decrease the usable life of a reclaimed chemical bath. The use of a
sequestering agent (oxidant stabilizer) in the chemical bath can
increase the life of the bath during reclamation process use. A
sequestering agent may be added to an un-reclaimed chemical
composition; this sequestering agent may extend the usable bath
life of such a composition beyond that of a solution without the
sequestering agent. Through the use of a sequestering agent, the
oxidizer concentration may be controlled such that excessive
oxidant concentration addition to the chemical composition of the
present invention is not necessary to compensate for oxidant
consumption by undesired decomposition due to contamination, rather
than by the normal consumption that occurs during the desired
cleaning action of the present chemical composition. Thereby, the
sequestering agent optimizes the concentration to further minimize
the chemical composition's attack on the copper device layer by
enabling a minimization of required oxidizer concentration in the
present chemical composition.
[0039] Sequestering agents that can be used in the present
invention are amines and amino acids. The preferred sequestering
agents are 1,2-cyclohexanediamine-N,N,N',N'-tetraacetic acid
(CDTA), ethyenediaminetetraacetic acid (EDTA) and
diethylenetriaaminopentaacetic acid (DTPA). The preferential use of
complex sequestering agents, such as CDTA, versus a simple
sequestering agent, such as EDTA, is based on the possibility of
degradation of a simple sequestering agent over time and at
extended exposure to certain temperatures. However, it is
understood that for some methods of application a simple
sequestering agent such as EDTA may be suitable. For example, a
single use system where heating occurs just before the solution
dispenses on a wafer for chemical cleaning.
[0040] For further copper protection, a copper protectant can be
added to the chemical composition. The preferred copper protectants
for the present invention are hetero-organic inhibitors such as
azoles. Preferably, at least one of benzotriazole, 1,2,3 triazole,
1,3,4 triazole, 1,2,4 triazole and imidazole are used in the
chemical composition. The use of hetero-organic inhibitors as
opposed to simple organic compounds is based on the possibility of
degradation of organic compounds over time and at extended exposure
to certain temperatures. Azoles are organic compounds containing
nitrogen atoms with free electron pairs that are potential sites
for bonding with copper and that enable inhibiting action. Also,
there is a possibility of introduction of other heteroatoms and
groups in molecules of these compounds so there is a wide range of
derivatives that exhibit good inhibition characteristics. For
example, it is understood that thiols produce active protection on
copper surfaces.
[0041] Preferred formulations for the chemical composition are:
[0042] 1. 9% per wt oxidizing agent, 0.8% per wt pH stabilizer,
90.2% aqueous solution; [0043] 2. 9% per wt oxidizing agent, 0.8%
per wt pH stabilizer, 10 ppm sequestering agent, remainder aqueous
solution; [0044] 3. 9% per wt oxidizing agent, 0.8% per wt pH
stabilizer, 10 ppm sequestering agent, 100 ppm copper protectant,
remainder aqueous solution.
[0045] The preferred formulation of the chemical composition is
hydrogen peroxide and TEAH in an aqueous solution, wherein the
composition has a pH in the range of about 9 to about 10. The
chemical composition is designed to remove at least some titanium
nitride (TiN). However, the chemical composition is also intended
to remove at least some etching residues.
[0046] Accordingly, it is intended to be a full clean. It is
understood that in some cases a full clean by a single solution may
be too aggressive and a sequential clean using multiple chemical
systems may be less aggressive with respect to copper or sensitive
ILD structures. Performing a full clean with a single solution is
not to be done at the expense of the copper device layer or
sensitive ILD structures.
[0047] The chemical composition can be applied to a microelectronic
device in multiple ways. Referring now to FIG. 1, the
microelectronic device may include protective layers including a
lithographic stack layer 160, a metal hard mask layer 150, such as
titanium nitride, a dielectric hard mask layer 140, such as
tetraethyl orthosilicate (TEOS), an inter-level dielectric 130, and
a dielectric capping layer 120, such as NBlock, above a copper
device layer (copper line) 110 and another inter-level dielectric
115. Prior to application of the chemical composition, the
lithographic stack layer 160 is imaged, as shown in FIG. 2,
creating an opening in the lithographic stack layer 160 exposing a
portion of the metal hard mask 150. In FIG. 3, the lithographic
stack layer 160 is removed during etch of metal hard mask layer
150. The metal hard mask layer 150 is etched in such a way as to
create an opening thus exposing a portion of the dielectric hard
mask layer 140. Another etch is performed for forming a trench in
the microelectronic device. The etching processes are most likely a
reactive ion etching. The etching process often leaves a residue on
the microelectronic device and the protective layers, as well as
leaving a portion of the protection layers intact.
[0048] In one embodiment of the present invention, the etching
process forms the trench down to the dielectric capping layer 120,
as shown in FIGS. 4A-4D. This is called a partial etch. The
dielectric capping layer 120 is left in this embodiment of the
present invention as a barrier for the copper device layer to
protect against the wet etching process, that is, application of
the chemical composition of the present invention. FIG. 4A shows
the microelectronic device after a partial etch with residual etch
residue 170. FIG. 4B shows the microelectronic device after a
partial etch without the residual etch residue for clarity.
Likewise, the residue is removed from FIGS. 4C-4E for clarity.
[0049] FIG. 4C shows the microelectronic device after a full wet
etch process, that is, after application of the chemical
composition of the present invention removing the entire metal hard
mask layer 150. The chemical composition is applied to the
microelectronic device at a temperature in the range of about
25.degree. C. to about 80.degree. C. Preferably, the chemical
composition is applied at about 60.degree. C. For total removal,
the chemical composition is applied to the microelectronic device
for about 1 minute to about 5 minutes.
[0050] It has been observed that there is a pattern density
relationship to the wet removal of metal hard masks such as
titanium nitride (TiN). This is not surprising based both on the
incoming variation induced by prior reactive ion etch operations as
well as possible chemical kinetic relationships. It is noted that
in dense areas of the microelectronic device, an application of the
chemical composition of the present invention for about 2 minutes
is sufficient to achieve total removal of a titanium nitride (TiN)
metal hard mask with a deposited thickness of about 300 A to about
400 A. Whereas, in blanket areas of the microelectronic device, the
chemical composition is applied for about 4 minutes to achieve
total removal. Total removal would remove all layers above the
dielectric hard mask or inter-level dielectric layer if no
dielectric hard mask layer is present.
[0051] A partial wet etch process can be performed as opposed to a
total wet etch process as shown in FIG. 4D. A partial wet etch
would clean and taper at least a part of the microelectronic device
for future metallization of the device, which would help the aspect
ratio of the device and as such improve metallization. In FIG. 4D,
a portion of the metal hard mask layer 150 is removed after the
partial wet etch process exposing a portion of dielectric hard mask
140. This helps to mitigate any potential damage to the copper
device layer 110. In order to perform a partial etch, the chemical
composition is applied for about 1 minute to about 2 minutes at
about 60.degree. C. The wet etch, whether total or partial, is
followed by an etching process to open the dielectric capping layer
120 and perform any additional tapering/hard mask chamfering
necessary as shown in FIG. 4E. A cleaning process may also be
performed after the etching process to remove any additional
residues from the etching process.
[0052] FIGS. 5A-5E show another embodiment of the present invention
where the trench etching process forms the trench down to the
copper device layer 110. FIG. 5A shows the microelectronic device
after a full etch with residual etch residue 170. FIG. 5B shows the
microelectronic device after a full etch without the residual etch
residue for clarity. Likewise, the residue is removed from FIGS.
5C-5E for clarity.
[0053] FIG. 5C shows the microelectronic device after a full wet
etch process, that is, after application of the chemical
composition of the present invention removing the entire metal hard
mask 150. The chemical composition is applied to the
microelectronic device at a temperature in the range of about
25.degree. C. to about 80.degree. C. Preferably, the chemical
composition is applied at about 60.degree. C. For total removal,
the chemical composition is applied to the microelectronic device
for about 1 minute to about 5 minutes. Total removal would remove
the entire metal hard mask layer above the dielectric hard mask or
inter-level dielectric layer if no dielectric hard mask layer is
present.
[0054] It has been observed that there is a pattern density
relationship to the wet removal of metal hard masks such as
titanium nitride (TiN). This is not surprising based both on the
incoming variation induced by prior reactive ion etch operations as
well as possible chemical kinetic relationships. It is noted that
in dense areas of the microelectronic device, an application of the
chemical composition of the present invention for about 2 minutes
is sufficient to achieve total removal of a titanium nitride (TiN)
metal hard mask with a deposited thickness of about 300 A to about
400 A. Whereas, in blanket areas of the microelectronic device, the
chemical composition is applied for about 4 minutes to achieve
total removal. Total removal would remove all layers above the
dielectric hard mask or inter-level dielectric layer if no
dielectric hard mask layer is present. Partial removal would leave
some metal hard mask structures, but modify the structures by a
partial removal of the structures while preserving all layers below
the dielectric hard mask such as the dielectric hard mask or
inter-level dielectric layers if no dielectric hard mask layer is
present.
[0055] A partial wet etch process can be performed as opposed to a
total wet etch process as shown in FIG. 5D. A partial wet etch
would clean and taper the microelectronic device, which would help
the aspect ratio of the device. In FIG. 5D, a portion of the metal
hard mask layer 150 is removed after the partial wet etch process
exposing a portion of dielectric hard mask 140. This helps to
mitigate any potential damage to the copper device layer 110. In
order to perform a partial etch the chemical composition is applied
for about 1 minute to about 2 minutes at about 60.degree. C. The
partial wet etch may be followed by an etching process to perform
any additional tapering/hard mask chamfering necessary as shown in
FIG. 5E. A cleaning process may also be performed after the etching
process to remove any additional residues from the etching
process.
[0056] The chemical composition and its accompanying methods can be
used for 64 nm pitch copper single and dual damascene interconnects
using pitch split double patterning scheme to enable sub 80 nm
pitch patterning, for example. After the trench pattern is formed,
the trenches are to be filled with metal. The metallization process
has become a challenge for recent technology generations with
narrow width trenches patterned in low-k dielectric material with
hard masks on top of the dielectric film. The trenches often have a
high aspect ratio with undercut under the hard mask. To prevent
metal fill defects, the metal hard mask can be removed using the
chemical composition of the present invention using one of the
methods described herein. This will significantly improve the metal
fill process.
[0057] Trapezoidal structures in FIGS. 4E and 5E are exaggerated to
illustrate possible chamfering of a structure by selective design,
not by the lack of degrees of freedom to time a desired sidewall
angle. A sidewall angle approximating 90 degrees to the copper
plane may be constructed using the present invention. However, the
present invention enables the construction of a trapezoidal
cross-section, if such a structure is desired. A main difference is
that this construction of a trapezoidal cross-section is by
conscious design, rather than by an uncontrolled process side
effect.
[0058] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the invention. As used herein, the singular forms "a", "an" and
"the" are intended to include the plural forms as well, unless the
context clearly indicates otherwise. It will be further understood
that the terms "comprises" and/or "comprising," when used in this
specification, specify the presence of stated features, integers,
steps, operations, elements, and/or components, but do not preclude
the presence or addition of one or more other features, integers,
steps, operations, elements, components, and/or groups thereof.
[0059] The corresponding structures, materials, acts, and
equivalents of all means or step plus function elements in the
claims below are intended to include any structure, material, or
act for performing the function in combination with other claimed
elements as specifically claimed. It is well known that different
deposition conditions may result in metal films such as titanium
nitride (TiN) hard mask films with different properties.
Accordingly, the chemical ratios and/or contact times may be
adjusted to produce similar results with varying titanium nitride
(TiN) or other metal hard mask films. Thus, the description of the
present invention has been presented for purposes of illustration
and description, but is not intended to be exhaustive or limited to
the invention in the form disclosed.
[0060] The description of the present invention has been presented
for purposes of illustration and description, but is not intended
to be exhaustive or limited to the invention in the form disclosed.
Many modifications and variations will be apparent to those of
ordinary skill in the art without departing from the scope and
spirit of the invention. The embodiment was chosen and described in
order to best explain the principles of the invention and the
practical application, and to enable others of ordinary skill in
the art to understand the invention for various embodiments with
various modifications as are suited to the particular use
contemplated.
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