U.S. patent application number 14/510381 was filed with the patent office on 2015-01-22 for cleaning composition and process for cleaning semiconductor devices and/or tooling during manufacturing thereof.
The applicant listed for this patent is International Business Machines Corporation. Invention is credited to Vishal Chhabra, Laertis Economikos, John A. Fitzsimmons, James Hannah, Mahmoud Khojasteh, Jennifer Muncy.
Application Number | 20150024989 14/510381 |
Document ID | / |
Family ID | 50622887 |
Filed Date | 2015-01-22 |
United States Patent
Application |
20150024989 |
Kind Code |
A1 |
Chhabra; Vishal ; et
al. |
January 22, 2015 |
CLEANING COMPOSITION AND PROCESS FOR CLEANING SEMICONDUCTOR DEVICES
AND/OR TOOLING DURING MANUFACTURING THEREOF
Abstract
Cleaning solutions and processes for cleaning semiconductor
devices or semiconductor tooling during manufacture thereof
generally include contacting the semiconductor devices or
semiconductor tooling with an acidic aqueous cleaning solution free
of a fluorine containing compound, the acidic aqueous cleaning
solution including at least one antioxidant and at least one
non-oxidizing acid.
Inventors: |
Chhabra; Vishal; (Fishkill,
NY) ; Economikos; Laertis; (Wappingers Falls, NY)
; Fitzsimmons; John A.; (Poughkeepsie, NY) ;
Hannah; James; (Ossining, NY) ; Khojasteh;
Mahmoud; (Poughkeepsie, NY) ; Muncy; Jennifer;
(Ridgefield, CT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
International Business Machines Corporation |
Armonk |
NY |
US |
|
|
Family ID: |
50622887 |
Appl. No.: |
14/510381 |
Filed: |
October 9, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13669627 |
Nov 6, 2012 |
|
|
|
14510381 |
|
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|
Current U.S.
Class: |
510/175 ;
134/42 |
Current CPC
Class: |
C11D 3/042 20130101;
C11D 11/0047 20130101; C11D 7/267 20130101; C11D 3/2086 20130101;
C11D 7/08 20130101; C11D 3/2079 20130101; H01L 21/02057 20130101;
C11D 7/265 20130101 |
Class at
Publication: |
510/175 ;
134/42 |
International
Class: |
H01L 21/02 20060101
H01L021/02; C11D 7/08 20060101 C11D007/08; C11D 7/26 20060101
C11D007/26 |
Claims
1. A process for cleaning a semiconductor device or tooling during
manufacture thereof, the process comprising: contacting the
semiconductor device or tooling with an acidic aqueous solution
that is free of a fluorine containing compound for a period of time
and at a temperature effective to remove residues from the
semiconductor device or tooling, wherein the acidic aqueous
solution comprises at least one antioxidant and at least one
non-oxidizing acid.
2. The process of claim 1, wherein the at least one antioxidant
comprises ascorbic acid, citric acid, lactic acid, erythorbic acid,
derivatives thereof, and mixtures thereof.
3. The process of claim 1, wherein the at least one non-oxidizing
comprises sulfuric acid, hydrochloric acid, hydroiodic acid,
hydrobromic acid, hydrofluoric acid, phosphoric acid, methane
sulfonic acid, acetic acid, formic acid, butyric acid, propionic
acid, and mixtures thereof.
4. The process of claim 1, wherein the period of time will range
from about 10 seconds to about 60 minutes and the temperature from
10.degree. C. to 100.degree. C.
5. The process of claim 1, wherein the residue comprises compounds
containing a rare earth element of the lanthanide series.
6. The process of claim 5, wherein the rare earth element is
ceria.
7. The process of claim 1, wherein the semiconductor tool is a
chemical mechanical planarization pad.
8. The process of claim 1, wherein the antioxidant is ascorbic acid
in an amount from 0.5 to 10% (w/w) and the non-oxidizing acid is
sulfuric acid at greater than 0% (w/w) to 10% (w/w), wherein the
aqueous cleaning solution has a pH less than 5.
9. The process of claim 1, wherein the aqueous cleaning solution
further comprises a surfactant, a pH buffer, a chelating agent, or
mixtures thereof.
10. The process of claim 6, wherein the surfactant comprises a
quaternary ammonium salt surfactant, a water soluble
perfluorocarboxylic acid, a perfluorocarboxylic acid sulfate,
heptafluorobutyric acid. heptafluorobutyric sulfate, or mixtures
thereof.
Description
DOMESTIC PRIORITY
[0001] This Application is a DIVISIONAL of and claims priority to
U.S. application No. 13/669,627, filed Nov. 6, 2012, the contents
of which are incorporated by reference in its entirety.
BACKGROUND
[0002] The present disclosure generally relates to semiconductor
device manufacturing and, more particularly, to the cleaning and
removal of residues and/or contaminants formed on the semiconductor
device during manufacture.
[0003] The integrated circuit manufacturing process can generally
be divided into front end of line (FEOL) and back end of line
(BEOL) processing. The FEOL processes are focused on fabrication of
the different devices that make up the integrated circuit, whereas
BEOL processes are focused on forming metal interconnects between
the different devices of the integrated circuit. In the FEOL
processes, shallow trench isolation structures and gate or memory
stacks are typically formed. These structures are fragile due to
their increasingly small dimensions and the types of materials used
to form the structures. BEOL processes may also have fragile
structures such as dual damascene etched openings in low k
dielectric materials or polysilicon interconnect lines. Often BEOL
processing includes one or more chemical mechanical planarization
(CMP) process steps, which are inherently very dirty processes.
[0004] The number of photoresist cleaning or stripping steps
employed in the semiconductor manufacturing process has grown
greatly in the last few years. The increasing number of ion
implantation steps has contributed greatly to this increase.
Current high current or high energy implant operations are the most
demanding in that they require a high degree of wafer cleanliness
to be obtained while minimizing or eliminating photoresist popping,
surface residues, and metal contamination while requiring
substantially no substrate/junction loss or oxide loss. Likewise,
the semiconductor manufacturing process will typically include one
or more CMP processes that typically employ abrasive slurries and
rotating pads/brushes to effect surface planarization. Defect
minimization during semiconductor manufacture is of great interest
to the overall success as devices are scaled to smaller dimensions.
For example, ceria nanoparticles are often used as the CMP slurry
for next generation technology nodes because defect levels are at
or below the more traditional silica-abrasive slurries and also
because very low concentrations can effectively be used, which
translates to lower levels of contamination. However, the
semiconductor devices as well as the CMP pads/brushes are often
contaminated with particles of ceria that require removal for
successful and efficient device manufacture.
[0005] Because of the extraordinarily high levels of cleanliness
that are generally required during the fabrication of semiconductor
substrates, multiple cleaning steps are typically required to
remove impurities from the surfaces of the substrates before
subsequent processing. A typical surface preparation procedure may
include etch, clean, rinse and dry steps. During a typical cleaning
step, the substrates may be exposed to a cleaning solution that can
include mixtures of hydrogen peroxide and ammonium hydroxide,
and/or hydrochloric acid, and/or sulfuric acid, and/.or
hydrofluoric acid with a surfactant. These solutions are commonly
referred by those in the art to as SC1, SC2, HPM, APM and IMEC
cleaning solutions. After cleaning, the substrates are rinsed using
ultra-pure water and then dried using one of several known drying
processes. In some instances, the cleaning solutions may be in
combination with acoustical cleaning methods, e.g., ultrasonics,
megasonics, and the like.
[0006] In various advanced development processes required for
semiconductor device manufacture, either rare earth metals or
transition metals are required to be selectively removed in the
presence of very similar metallurgy. In addition, reactive ions
etch (RIE) or CMP processes may leave modified residues related to
these rare earth or transition metallurgy. In FEOL processes, the
typical cleaning chemistries are not selective enough to
differentiate between some of these residues that must be removed
or metals and the metals required to remain. For example, SC1 is
commonly used to remove FEOL residue, but is also known to attack
TiN surfaces. TiN is used as a component of some metal gate
structures and any loss of TiN in these metal gate structures can
result in an undesirable decrease or change in device
performance.
[0007] Accordingly, it would be desirable to have a process and
chemistry that is capable of removing undesired residue without
producing a undesired decrease or change in device performance.
BRIEF SUMMARY
[0008] Disclosed herein are compositions and processes for cleaning
semiconductor devices and/or semiconductor tooling. In one
embodiment, an aqueous cleaning solution for cleaning semiconductor
devices and/or semiconductor tooling, the aqueous cleaning solution
comprises at least one antioxidant; at least one non-oxidizing
acid; and water, wherein the aqueous cleaning solution is acidic
and is free of a fluorine containing compound.
[0009] In another embodiment, a process for cleaning a
semiconductor device or tooling during manufacture thereof, the
process comprises contacting the semiconductor device or tooling
with an acidic aqueous solution that is free of a fluorine
containing compound for a period of time and at a temperature
effective to remove residues from the semiconductor device or
tooling, wherein the acidic aqueous solution comprises at least one
antioxidant and at least one non-oxidizing acid.
[0010] The disclosure may be understood more readily by reference
to the following detailed description of the various features of
the disclosure and the examples included therein.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0011] Referring now to the figures wherein the like elements are
numbered alike:
[0012] FIG. 1 is a scanning electron micrograph of a ceria
contaminated polishing pad;
[0013] FIG. 2 graphically illustrates electron dispersive
spectroscopy data for the ceria contaminated pad of FIG. 1;
[0014] FIG. 3 is a scanning electron micrograph of the contaminated
polishing pad after cleaning with a dAS aqueous cleaning solution
in accordance with the present disclosure; and
[0015] FIG. 4 graphically illustrates electron dispersive
spectroscopy data for the cleaned pad of FIG. 3.
DETAILED DESCRIPTION
[0016] Disclosed herein are aqueous cleaning processes and
compositions for cleaning substrates during semiconductor
manufacturing. The processes generally include exposing the
substrate to an acidic aqueous cleaning solution free of a fluorine
containing compound having a composition that generally including
an antioxidant, a non-oxidizing acid, and water. Surprisingly and
advantageously, the process and composition provide effective
removal of particles and residues without the need for a fluorine
containing compound while not damaging underlying material in
contact therewith during processing such as, but not limited to,
Si, SiO.sub.2, TEOS, Si.sub.3N.sub.4, TiN, TaN, TaAlN, TiAlN, and
the like. Likewise, the aqueous cleaning process and composition
can be utilized to effectively clean the semiconductor tooling
associated with semiconductor manufacture. For example, the aqueous
cleaning process and composition can be used to remove rare earth
lanthanides such as ceria particles that may be entrained in the
brushes and/or pads used in chemical mechanical processing to
effect surface planarization.
[0017] As used herein, the terms residues and particles generally
refer to post ash, post etch, and post CMP materials and may
byproducts thereof that may be formed on the device and tooling
surfaces. For example, post CMP residue generally refers to
particles from the polishing slurry, e.g., ceria containing
particles, silica containing particles, and the like; chemicals
present in the slurry; reaction byproducts of the polishing slurry;
carbon rich particles; polishing pad particles; brush deloading
particles; tooling materials of construction particles; copper;
copper oxides; copper containing materials; aluminum; aluminum
oxides; aluminum containing materials; orrganic residues; and any
other materials that are byproducts of the CMP process.
[0018] While not wanting to be bound by theory, it is believed the
antioxidant in the acidic aqueous cleaning composition provides
antioxidant properties, i.e., inhibits oxidation, and also a ligand
effect to provide significant and unexpected cleaning action.
Suitable antioxidants are soluble in water at an acidic pH.
Exemplary antioxidants include ascorbic acid, citric acid, lactic
acid, erythorbic acid, derivatives, and mixtures thereof. In one
embodiment, the antioxidant is in the aqueous cleaning solution in
an amount within a range of 0.5% to 10% weight by weight (w/w), and
in other embodiments, within a range of 1 to 5 (% w/w), and in
still other embodiments, within a range of 1 to 3% (w/w).
[0019] As generally defined herein, the term "non-oxidizing acid"
generally refers to an acid that cannot act as an oxidizing agent.
Suitable non-oxidizing acids include both inorganic and organic
acids. Exemplary non-oxidizing inorganic acids include, without
limitation, sulfuric acid, hydrochloric acid, hydroiodic acid,
hydrobromic acid, hydrofluoric acid, phosphoric acid, mixtures
thereof and the like. Exemplary non-oxidizing organic acids
include, without limitation, methane sulfonic acid, acetic acid,
formic acid, butyric acid, propionic acid, mixtures thereof and the
like. In one embodiment, the non-oxidizing acid is in the aqueous
cleaning solution in an amount within a range of 0.1 to 10% weight
by weight (w/w), and in other embodiments, within a range of 1 to
8% (w/w), and in still other embodiments, within a range of 2 to 5%
(w/w).
[0020] The cleaning solution is an aqueous solution, wherein the
water component can be deionized water. The aqueous cleaning
solution can be free of any other solvents. Additionally, the
aqueous cleaning solution can be free of a fluorine containing
compound and provide effective cleaning while not damaging
underlying material in contact therewith during processing.
[0021] The aqueous cleaning solution is acidic and has a pH less
than 7; in other embodiments, the aqueous cleaning solution has a
pH less than 5 and in still other embodiments, aqueous cleaning
solution has a pH less than 2, and in yet other embodiments,
aqueous cleaning solution has a pH of less than 1. An acidic pH is
generally preferred because the residue can be thoroughly removed
without damaging the underlying structure and solubility of the
antioxidant and/or the antioxidant residue complex is generally
enhanced. The pH may be measured by using a known pH meter or other
techniques generally suitable to measure pH within the suggested pH
range that do not have interference in measurement of an acidic
reducing solution.
[0022] In an exemplary embodiment, the cleaning solution includes
an acidic aqueous solution of ascorbic acid and sulfuric acid.
[0023] Optionally, the aqueous cleaning solutions may further
contain a surfactant, a chelating agent, a pH buffer, and the
like.
[0024] Exemplary surfactants that may be used include a nonionic
surfactant, an anionic surfactant, a cationic surfactant, an
ampholytic surfactant, and combinations thereof. The surfactant
improves residue removal by effectively minimizing agglomeration
and re-deposition of particles/residues from substrates, tooling
surfaces, and solutions.
[0025] Examples of the nonionic surfactant that may be used include
polyalkylene oxide alkyl phenyl ether surfactants, polyalkylene
oxide alkyl ether surfactants, polyethylene oxide-polypropylene
oxide block copolymer surfactants, polyoxyalkylene distyrenated
phenyl ether surfactants, polyalkylene tribenzyl phenyl ether
surfactants and acetylene polyalkylene oxide surfactants. Exemplary
polyalkylene oxide (hereinafter abbreviated as "PAO") alkyl ether
surfactant include, without limitation, PAO decyl ether, PAO lauryl
ether, PAO tridecyl ether, PAO alkylene decyl ether, PAO sorbitan
monolaurate, PAO sorbitan monooleate, PAO sorbitan monostearate,
polyethylene oxide sorbitol tetraoleate, PAO alkylamine, and PAO
acetylene glycol, mixtures thereof, and the like.
[0026] A cationic surfactant can also be used in the present
disclosure and has been found to provide an increase in the
removability of the residues and the resistance to corrosion of the
substrate and the dielectric film Preferred examples of the
cationic surfactant include a quaternary ammonium salt
surfactant.
[0027] An example of a suitable quaternary ammonium salt surfactant
includes a compound represented by general formula (I)
##STR00001##
wherein X.sup.- represents a hydroxide ion, a chlorine ion, a
bromine ion sulfate ion or a nitrate ion; R.sub.1 to R.sub.4
independently represents an alkyl group and/or an aralkyl group
having 1 to 24 carbon atoms.
[0028] Non-limiting examples of the compound represented by general
formula (I) include ammonium octyl sulfate, ammonium lauryl
sulfate, and the like. The counter anion of these illustrated
compounds is not limited to sulfate ion but may be chloride ion,
bromine ion, hydroxide ion, or nitrate ion.
[0029] Additionally, anionic surfactant agents have been found to
have utility especially in low pH formulations. We have observed
that water soluble perfluorocarboxylic acids or sulfate esters such
as heptafluorobutyric acid, or heptafluorobutyric acid sulfate can
act as surfactant/dispersant agents at pH values below pH 2. While
there are known industry restrictions on perfluorooctanoic acid
sulfates (PFOAS), perfluorooctanoic acids (PFOA), there remain some
lower molecular weight compounds in this family of chemistries that
have not demonstrated the undesired behavior of PFOAS and still
retain the desired behaviors: heptafluorobutyric acid is an example
of this type of compound and included as an example of such a
potential candidate. Any anionic surfactant used in the present
formulations preferably is within EPA guidelines and functions as a
surfactant/dispersant within the formulation pH range.
[0030] The surfactant is incorporated in the aqueous cleaning
solution in an amount of preferably 0.0001 to 5 wt % and more
preferably 0.0001 to 1 wt % with respect to the total weight of the
aqueous cleaning solution. The addition of the surfactant to the
aqueous cleaning solution enables viscosity to be adjusted to
improve the wettability of the liquid with respect to the object to
be cleaned. In general, such surfactants are commercially
available. These surfactants may be used singly or in combination
of two or more. Advantageously, residue removal is generally
improved form some applications relative cleaning solutions without
the surfactant(s).
[0031] As noted above, the aqueous cleaning solution may further
include a chelating agent, which can enhance removal of metal ions,
for example. Examples of a suitable chelating agent include a group
of aminopolycarboxylic acid salts such as, but not limited to,
ethylenediaminetetraacetate (EDTA), diethylenetriaminepentaacetate
(DTPA), 1,2-cyclohexylene-aminotetraacetic acid (CDTA),
hydroxyethylethylenediaminetriacetate (HEDTA),
dihydroxyethylethylenediaminetetraacetate (DHEDDA), nitrilo
triacetate (NTA), hydroxyethyliminodiacetate (HIDA), .beta.-alanine
diacetate, aspartic acid diacetate, methylglycine diacetate,
iminodisuccinate, serine diacetate, hydroxyiminodisuccinate,
dihydroxyethylglycine salt, aspartate, glutamate, and the like; a
group of hydroxycarboxylic acid salts such as, but not limited to,
hydroxyacetate, tartrate, citrate, gluconate, and the like; a group
of cyclocarboxylic acid salts such as, but not limited to,
pyromellitate, benzopolycarboxylate, cyclopentane tetracarboxylate,
and the like; a group of ether carboxylic acid salts such as, but
not limited to, carboxymethyl tartronate, carboxymethyloxy
succinate, oxydisuccinate, tartaric acid monosuccinate, tartaric
acid disuccinate, and the like; a group of other carboxylic acid
salts such as, but not limited to, maleic acid derivative, oxalate,
and the like; a group of organic carboxylic acid (salt) polymers
such as, but not limited to, acrylic polymers and copolymers (such
as acrylic acid-allyl alcohol copolymer, acrylic acid-maleic acid
copolymer, hydroxyacrylic acid polymer, polysaccharide-acrylic acid
copolymer, and the like; a group of polyvalent carboxylic acid
polymers and copolymers such as, but not limited to, polymers and
copolymers of monomers such as maleic acid, itaconic acid, fumaric
acid, tetramethylene-1,2-dicarboxylic acid, succinic acid, aspartic
acid and glutamic acid, and the like; glyoxylic acid polymers; a
group of polysaccharides such as, but not limited to, starch,
cellulose, amylose, pectin, carboxymethyl cellulose, and the like;
a group of phosphonic acid salts such as, but not limited to,
methyl diphosphonic acid salt, aminotrismethylene phosphonic acid
salt, ethylidene diphosphonic acid salt,
1-hydroxyethylidene-1,1-diphosphonic acid salt,
ethylaminobismethylene phosphonic acid salt,
ethylenediaminebismethylene phosphonic acid salt,
ethylenediaminetetramethylene phosphonic acid salt,
hexamethylenediaminetetramethylene phosphonic acid,
propylenediaminetetramethylene phosphonic acid salt,
diethylenetriaminepentamethylene phosphonic acid salt,
triethylenetetraminehexamethylene phosphonic acid salt,
tetraethylenepentamineheptamethylene phosphonic acid salt, and the
like; dimercaporal (BAL); various combinations thereof; and the
like.
[0032] Exemplary salts of these compounds include ammonium salts
and salts of alkanolamines (such as monoethanolamine and
triethanolamine). These may be used singly or in combination of two
or more.
[0033] The chelating agent is preferably used in the aqueous
cleaning solution at a concentration of 0 to 10 wt % with respect
to the total weight of the aqueous cleaning solution.
[0034] Exemplary optional pH buffering agents include, but are not
limited to, hydroxides, quaternary ammonium hydroxides, glycines,
hydrogen phthalates, acetates, oxalates, carbonates, carbamates,
citrates, methyl diethanolamine (MDEA), salicylic acid, boric acid,
sulfosalicylic acid, ethane-l-hydroxy-1,1-diphosphoinic acid
(HEDP), sulfamic acid, sulfonic acids, choline hydroxide,
monoethanolamine, acetylacetone, and combinations thereof. When the
pH is within a range of about 2 to 7, the pH buffer is typically in
an amount effective to maintain the pH at a range of -1.0 to 0.9
relative to the target pH. At pHs lower than 2, effective buffering
agents are relatively limited. We note that water soluble perfluoro
carboxcylic acids such as heptafluorobutyric acid by virtue of
their pKa values may act as effective buffering agents within these
lower pH ranges and as dictated by the Henderson-Hasselbalch
equation may be used to construct a buffering agent within this pH
region. Again the use of Perfluoro alkane chemicals may be
restricted by EPA findings and these recommendations are respected
and followed. However, as previously discussed, there remain some
lower molecular weight compounds in this family of chemistries that
have not demonstrated the undesired behavior of PFOA or PFOAS; and
as such, acids with pKa values of 2 or less may employed to enhance
buffering behavior below pH 2.
[0035] The process for cleaning the semiconductor device and/or
tooling during manufacture generally includes containing the
aqueous cleaning solution with the semiconductor device and/or
tooling to be cleaned. The type of contact is not intended to be
limited and may include immersion, dipping, spraying, spin coating,
combinations thereof, and the like. The cleaning step may be
repeated as may be desired for different applications. The
temperature of the aqueous cleaning solution can be within a range
from about 10.degree. C. to about 100.degree. C. in most
embodiments, with a temperature within a range of 15.degree. C. to
80.degree. C. in other embodiments, and a temperature of 20 to
50.degree. C. in still other embodiments.
[0036] The period of time for which the cleaning solution contacts
the semiconductor device will generally depend on the preceding
manufacturing step. Typically, the period of of time will range
from about 10 seconds to about 60 minutes in most embodiments, with
a period of time within a range of about 10 seconds to about 30
minutes in other embodiments, and with a period of time within a
range of about 1 minute to about 15 minutes in still other
embodiments.
[0037] The present process can be used in individually or in
combination with one or more other cleaning processes such as the
SC1 and/or SC2 cleaning processes. If such a combination is used,
the order of performance is not intended to be limited to any
particular order. Likewise, where appropriate, the present process
can be used in combination with acoustical and/or mechanical
energy.
[0038] By way of example, the aqueous cleaning solution and process
can be used to clean the polishing pads/brushes used during
chemical mechanical planarization (CMP). A CMP system typically
includes components for handling and polishing the semiconductor
substrates. Such components can include an orbital pad. In
operation, the pad is put in motion and then a slurry material is
applied and spread over the surface of the pad. Slurries typically
used for CMP can include rare earth elements in the lanthanide
series such as ceria in the form of nanoparticles to effect
planarization. Once the pad is rotating at the desired speed, the
semiconductor substrate is placed in contact with the pad. The
substrate is then sent to be cleaned in a substrate cleaning
system. It is important to clean the substrate after CMP because
particles, particulates and residues can remain on the substrate.
These residues can cause damage to the semiconductor substrate
during subsequent processing.
[0039] Better cleaning in the substrate cleaning system can be
achieved by improving the processes used in the CMP. In this
regard, pad conditioning is often performed to remove excess slurry
and residue build-up. Advantageously, it has been found that the
acidic aqueous cleaning solution including an antioxidant such as
ascorbic acid and a non-oxidizing acid such as sulfuric acid
effectively removed ceria deposits from the pad.
[0040] The following examples are presented for illustrative
purposes only, and are not intended to limit the scope of the
invention.
EXAMPLE 1
[0041] In this example, a comparison was made between prior art
cleaning chemistries and a cleaning process with an aqueous
cleaning solution in accordance with the present disclosure. A
cleaning solution in accordance with the present disclosure,
referred to herein as dAS, was compounded in aqueous solution and
included 1% (w/w) ascorbic acid in 2% (w/w) sulfuric acid as active
agents. The dAS solution was used to clean a substrate including a
TiN surface having a defined thickness at room temperature
(25.degree. C.) for two different immersion times: 60 seconds and
300 seconds. Following immersions, the substrates were rinsed with
deionized water and dried. Thickness of the TiN layer was measured
before and after cleaning. The results are shown in Table 1
below.
TABLE-US-00001 TABLE 1 dAS Cleaning Process Pre- Immersion Post
Thickness Thickness Time Thickness of Difference Etch Rate Sample
of TiN (.ANG.) (seconds) TiN (.ANG.) (.ANG.) (.ANG./minute) A 94.88
60 94.50 0.38 0.08 B 57.92 300 57.63 0.29 0.29
[0042] The results indicate that neither dAS exposure removed TiN
material within the noise limit of the measurement. The noise limit
of the measurement is less than 1 angstrom.
[0043] A prior art cleaning processes were compared to our dAS
process with respect to TiN etch using an industry standard
cleaning process referred to as SC1, in a process chemistry design
space generally selected to minimize TiN etch. The composition
included a solution of NH.sub.4OH (ammonium hydroxide),
H.sub.2O.sub.2 (hydrogen peroxide), H.sub.2O (water), at a ratio of
1:1.5:50 respectively at 25.degree. C. for various immersion times
The results are reported in table 2 below.
TABLE-US-00002 TABLE 2 SC1 Prior art Cleaning Process Immersion
Time Etch Rate Sample (Seconds) Thickness Difference (.ANG.)
(.ANG./minute) C* 300 14.80 2.96 D* 600 29.60 2.96 E* 900 37.40
2.49 F* 1200 65.40 3/27 *comparative examples
[0044] The results indicate an average etch rate of 2 to 3
angstroms per minute with a loss of about 10-15 Angstroms for a 600
second immersion. It is important to note that while more
concentrated solutions of SC1 may improve cleaning, the additional
aggressiveness against TiN is detrimental and contraindicated for
the purposes of non-destructive cleaning. More concentrated
solutions of SC1 are known to etch titanium nitride with more
aggressive etching rates such as is disclosed in U.S. Pat. No.
6,200,910. Thus, if more aggressive SC1 solutions are used to
improve cleaning performance, additional TiN material loss will
likely result. As demonstrated above, the dAS cleaning solution
that can clean surfaces without the negative aspects of TiN
attack.
EXAMPLE 2
[0045] In this example, we have studied the use of hot sulfuric
acid as a pre-step to remove organic contamination prior to dAS
cleaning. This sequence of hot sulfuric followed by dAS was also
evaluated with respect to TiN loss. The process included immersing
a substrate including TiN to sulfuric acid at 55.degree. C. for 600
seconds followed by immersion to dAS at 25.degree. C. with a
subsequent deionized water rinse and drying process. The results
are shown in Table 3 below.
TABLE-US-00003 TABLE 3 Hot Sulfuric Acid/dAS Cleaning Sequence Hot
sulfuric acid dAS Total TiN Hot sulfuric exposure exposure Removal
acid TiN dAS TiN Sample (seconds) (seconds) (.ANG.) Removal (.ANG.)
Removal (.ANG.) G 600 300 10.65 10.57 0.08
[0046] As demonstrated above, the exposure of the hot sulfuric acid
dominates and/or dictates the TiN removal in this process sequence.
The measured TiN loss from only the hot sulfuric acid step is about
10.57 Angstroms and is similar to that observed from the soft SC1
in Example 1 that had a loss of about 10 to 15 angstroms. Thus, a
combined hot sulfuric acid/dAS cleaning sequence can be employed
for more aggressive cleaning than a single SC1 step with a similar
TiN loss. If the hot sulfuric acid/dAS cleaning sequence was
replaced by an analogous hot sulfuric acid (10 minutes, 55.degree.
C.) soft SC1 (5 minutes) sequence, the combination of these
processes would be expected to double the amount of TIN loss. In
view of the foregoing, the combination of the hot sulfuric acid or
the soft SC1 may be employed with the dAS for conditions requiring
more aggressive cleaning and yet provide minimal TIN losses
compared to combinations of prior art cleaning processes, e.g., hot
sulfuric acid/soft SC1.
[0047] The cleaning solution provided effective removal of
undesired residue whereas the typical industrial alternatives were
unable to produce a similar reduction in particles from the
surface.
EXAMPLE 3
[0048] In this example, the cleaning solution was used to remove
ceria from CMP contaminated pads. The pads were exposed to an
aqueous solution of dAS as in example 1 for a period of 600 seconds
followed by a 30 second deionized rinsing step.
[0049] FIGS. 1 and 2 provide scanning electron microscopy-energy
dispersive spectroscopic (SEM-EDS) data, respectively, of the
contaminated pad. As shown, significant deposits of ceria and ceria
derivatives on the pad are clearly evident. FIGS. 3 and 4 provide
SEM-EDS data, respectively, after cleaning the pad with the aqueous
cleaning solution. As clearly demonstrated, no ceria signature is
evident indicating that the aqueous cleaning solution was highly
effective for removing ceria and ceria derivatives from the
contaminated pads.
EXAMPLE 4
[0050] In this example, solubility of a ceria containing
precipitate was measured as a function of concentration of the
ascorbic acid/sulfuric acid within the cleaning solution. Grams of
the ceria containing precipitate were added to the same volume of
solution. It was found that solubility (and cleaning efficiency)
was effectively increased by increasing the concentration of the
aqueous cleaning solution from 1% (w/w) ascorbic acid in 2% (w/w)
sulfuric acid to 5% (w/w) ascorbic acid in 5% (w/w) sulfuric acid.
Thus, the cleaning solution can be tailored to the residues being
removed from the substrate.
[0051] This written description uses examples to disclose the
invention, including the best mode, and also to enable any person
skilled in the art to make and use the invention. The patentable
scope of the invention is defined by the claims, and may include
other examples that occur to those skilled in the art. Such other
examples are intended to be within the scope of the claims if they
have structural elements that do not differ from the literal
language of the claims, or if they include equivalent structural
elements with insubstantial differences from the literal languages
of the claims.
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