U.S. patent application number 11/547034 was filed with the patent office on 2007-07-12 for dispersion for the chemical-mechanical polishing of metal surfaces containing metal oxide particles and a cationic polymer.
Invention is credited to Menzel Frank, Wolfgang Lortz.
Application Number | 20070157524 11/547034 |
Document ID | / |
Family ID | 34962311 |
Filed Date | 2007-07-12 |
United States Patent
Application |
20070157524 |
Kind Code |
A1 |
Lortz; Wolfgang ; et
al. |
July 12, 2007 |
Dispersion for the chemical-mechanical polishing of metal surfaces
containing metal oxide particles and a cationic polymer
Abstract
Aqueous dispersion for the chemical-mechanical polishing of
metal surfaces, containing a metal oxide powder and a cationic,
surface-active polymer, wherein the metal oxide powder is silicon
dioxide, aluminium oxide or a mixed oxide of silicon dioxide and
aluminium oxide, and the cationic, surface-active polymer is a
polyallyl amine or polydiallyl amine dissolved in the dispersion
and having a weight average molecular weight of less than 100,000
g/mol. The dispersion can be used for the chemical-mechanical
polishing of metallic layers and of metallic films, which are
applied to an insulating barrier layer.
Inventors: |
Lortz; Wolfgang;
(Wachtersbach, DE) ; Frank; Menzel; (Hanau,
DE) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Family ID: |
34962311 |
Appl. No.: |
11/547034 |
Filed: |
March 16, 2005 |
PCT Filed: |
March 16, 2005 |
PCT NO: |
PCT/EP05/02786 |
371 Date: |
October 3, 2006 |
Current U.S.
Class: |
51/298 ; 51/308;
51/309 |
Current CPC
Class: |
C09G 1/02 20130101 |
Class at
Publication: |
051/298 ;
051/308; 051/309 |
International
Class: |
B24D 3/02 20060101
B24D003/02 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 3, 2004 |
DE |
10 2004 016 600.5 |
Claims
1. Aqueous dispersion for the chemical-mechanical polishing of
metal surfaces, containing a metal oxide powder and a cationic,
surface-active polymer, characterised in that the metal oxide
powder is silicon dioxide, aluminium oxide or a mixed oxide of
silicon dioxide and aluminium oxide, and the cationic,
surface-active polymer is a polyallyl amine or polydiallyl amine
dissolved in the dispersion and having a weight-average molecular
weight of less than 100,000 g/mol.
2. Aqueous dispersion for the chemical-mechanical polishing of
metal surfaces according to claim 1, characterised in that the
weight-average molecular weight of the cationic, surface-active
polymer is 2000 to 50,000 g/mol.
3. Aqueous dispersion for the chemical-mechanical polishing of
metal surfaces according to claim 1, characterised in that the
content of cationic, surface-active polymer is between 0.1 and 15
wt. %, relative to the amount of polymer and metal oxide.
4. Aqueous dispersion for the chemical-mechanical polishing of
metal surfaces according to claim 1, characterised in that the
metal oxide powder is produced by flame hydrolysis.
5. Aqueous dispersion for the chemical-mechanical polishing of
metal surfaces according to claim 1, characterised in that the
metal oxide powder is pyrogenically produced silicon dioxide.
6. Aqueous dispersion for the chemical-mechanical polishing of
metal surfaces according to claim 1, characterised in that the
content of aluminium oxide as mixed oxide component of a metal
oxide powder is between 60 and 99.9 wt. % or between 0.01 and 10
wt. %.
7. Aqueous dispersion for the chemical-mechanical polishing of
metal surfaces according to claim 1, characterised in that the
average particle diameter or aggregate diameter of the metal oxide
powder in the dispersion is less than 300 nm.
8. Aqueous dispersion for the chemical-mechanical polishing of
metal surfaces according to claim 1, characterised in that the
content of metal oxide in the dispersion is 1 to 50 wt. %, relative
to the total amount of dispersion.
9. Aqueous dispersion for the chemical-mechanical polishing of
metal surfaces according to claim 1, characterised in that the pH
is 3 to 7.
10. Aqueous dispersion for the chemical-mechanical polishing of
metal surfaces according to claim 1, characterised in that it
contains additives from the group comprising pH-adjusting
substances, oxidising agents, oxidation activators and/or corrosion
inhibitors.
11. The method of using the aqueous dispersion according to claim 1
for the chemical-mechanical polishing of metal layers.
12. The method of using the aqueous dispersion according to claim 1
for the chemical-mechanical polishing of metal layers applied to an
insulating barrier layer.
Description
[0001] The application concerns a dispersion for the
chemical-mechanical polishing of metal surfaces.
[0002] A process for the production of semiconductors generally
includes a chemical-mechanical polishing (CMP) step.
[0003] Excess metal, for example copper or tungsten, is removed in
such a step. In special embodiments the conductive metal is not
directly to an insulating layer, which generally consists of
silicon dioxide, because reactions can occur between these layers
that are undesirable. In order to prevent this, a barrier layer is
applied between the metal and the silicon dioxide layer. The
barrier layer can consist for example of titanium nitride (TiN),
titanium (Ti), tantalum (Ta), tantalum nitride (TaN) or
combinations consisting thereof. It causes the metal layer to
adhere to the silicon dioxide layer. In a subsequent polishing step
it is then important that the abrasive in the form of a dispersion
displays a high selectivity of metal to barrier layer.
[0004] Numerous dispersions for polishing metal surfaces are
described. These dispersions generally contain abrasive particles
in the form of metal oxides. Such dispersions can additionally also
contain agents for pH adjustment, oxidising agents, corrosion
inhibitors and surface-active substances.
[0005] Although such dispersions often display good selectivity,
the metal removal rates are too low. Alternatively, the metal
removal rates are adequate but the selectivity is not. Furthermore,
a dispersion that displays good removal rates and good selectivity
values may display only low stability, in terms of settling of the
abrasive, for example.
[0006] The object of the invention is to provide a dispersion for
the chemical-mechanical polishing of metal surfaces that displays a
high removal rate for metals combined with good selectivity to a
barrier layer and at the same time has good stability.
[0007] The invention provides an aqueous dispersion for the
chemical-mechanical polishing of metal surfaces, containing a metal
oxide powder and a cationic, surface-active polymer, characterised
in that [0008] the metal oxide powder is silicon dioxide, aluminium
oxide or a mixed oxide of silicon dioxide and aluminium oxide, and
[0009] the cationic, surface-active polymer is a polyallyl amine or
polydiallyl amine dissolved in the dispersion and having a
weight-average molecular weight of less than 100,000 g/mol.
[0010] The cationic, surface-active polymer in the dispersion
according to the invention can preferably be one based on a diallyl
ammonium compound. Polymers starting from a dialkyl diallyl
compound, which can be obtained by a radical cyclisation reaction
of diallyl amine compounds and displays the structure 1 or 2, are
particularly preferred here.
[0011] Cationic, surface-active polymers having structures 3 and 4
can likewise be particularly preferred. They are copolymers
starting from dialkyl diallyl compounds. R1 and R2 here are a
hydrogen atom, a methyl, an ethyl, an n-propyl, an isopropyl, an
n-butyl, an isobutyl or a tert-butyl group, wherein R1 and R2 can
be the same or different. A hydrogen atom from the alkyl group can
further be substituted by a hydroxyl group. Y represents a free
radical-polymerisable monomer unit, such as e.g. sulfonyl,
acrylamide, methacrylamide, acrylic acid, methacrylic acid. X.sup.-
represents an anion. ##STR1##
[0012] The weight-average molecular weight of the cationic,
surface-active polymer can preferably be 2000 to 50,000 g/mol.
[0013] The content of cationic, surface-active polymer can be
between 0.1 and 15, particularly preferably between 0.5 and 10, and
most particularly preferably between 0.8 and 5 wt. %, relative to
the amount of cationic polymer and mixed oxide particles.
[0014] Particularly suitable cationic, surface-active polymers are
obtainable under the name polyDADMAC.
[0015] There is no restriction on the type of metal oxide powders
in the dispersion according to the invention. They can be powders
obtained by precipitation, by sol-gel processes, hydrothermal
processes, plasma processes, aerogel processes and by pyrogenic
processes, such as flame hydrolysis and flame oxidation.
[0016] Metal oxide powders obtained from a flame hydrolysis process
can preferably be present in the dispersion according to the
invention, however.
[0017] Flame hydrolysis is understood to be the hydrolysis of metal
compounds, generally metal chlorides, in the gas phase in a flame
generated by the reaction of hydrogen and oxygen. In this process,
highly dispersed, non-porous primary particles are initially
formed, which as the reaction continues coalesce to form aggregates
which in turn can congregate to form agglomerates. The BET surface
area of these primary particles is between 5 and 600 m.sup.2/g. The
surfaces of these particles can display acid or basic centres.
[0018] Metal oxides within the meaning of the invention are silicon
dioxide, aluminium oxide or a mixed oxide of silicon dioxide and
aluminium oxide. Mixed oxide is understood to be the intimate
mixture of the metal oxide components at an atomic level. The
powder particles here display Si--O--Al. In addition there can also
be regions of silicon dioxide next to aluminium oxide.
[0019] The mixed oxide powders can be produced for example by means
of a "co-fumed" process, wherein the precursors of silicon dioxide
and aluminium oxide are mixed and then burned in a flame. The mixed
oxide powder described in DE-A-19847161 is also suitable. Silicon
dioxide powders partially coated with aluminium oxide or aluminium
oxide powders partially coated with silicon dioxide are also
suitable for the dispersion according to the invention. The
production of these powders is described in US-A-2003/22081.
[0020] The mixed oxide powders of the dispersion according to the
invention preferably have a content of aluminium oxide as mixed
oxide component of a metal oxide powder of between 60 and 99.9 wt.
% or between 0.01 and 10 wt. %.
[0021] The following mixed oxide powders are particularly suitable:
silicon dioxide doped with 0.1 to 0.5 wt. % aluminium oxide and
having a BET surface area of 50 to 70 m.sup.2/g, according to
DE-A-19847161. Furthermore, silicon dioxide partially coated with
Al.sub.2O.sub.3, having an aluminium oxide content of 3.5 to 7 wt.
% and a BET surface area of 40 to 60 m.sup.2/g, according to
US-A-2003/22081. Furthermore, a mixed oxide powder produced by a
"co-fumed" process, having a content of aluminium oxide of 85 to 95
wt. % and a BET surface area of 85 to 110 m.sup.2/g. Furthermore, a
mixed oxide powder produced by a "co-fumed" process, having a
content of aluminium oxide of 60 to 70 wt. % and a BET surface area
of 85 to 110 m.sup.2/g.
[0022] The optimum diameter of the particles or aggregates of the
metal oxide powders present in the dispersion depends on the
polishing task. In the specific case of the polishing of metal
surfaces having an underlying barrier layer, it has proved to be
advantageous if the average particle or aggregate diameter of the
metal oxide powder in the dispersion is less than 300 nm. Values of
less than 150 nm are particularly preferred. Depending on the
origin of the metal oxide powder, it can be in the form of
isolated, largely spherical particles or, as in the case of the
preferred metal oxides produced by flame hydrolysis, in the form of
aggregates. The particle or aggregate size can be determined by
means of dynamic light scattering.
[0023] The content of metal oxide powder can be varied within broad
limits. For instance, dispersions having a high content of metal
oxide powder can be advantageous for transport, whilst
significantly lower contents are used in the actual polishing
process. The content of metal oxide powder in the dispersion
according to the invention can be 1 to 50 wt. %, relative to the
total amount of dispersion. In polishing applications the content
is generally between 1 and 10 wt. %.
[0024] The pH of the dispersion according to the invention can
preferably be between 3 and 7, a range between 4 and 6 being
particularly preferred.
[0025] The dispersion according to the invention can also contain
additives from the group comprising oxidising agents, pH-adjusting
substances, oxidation activators and/or corrosion inhibitors.
[0026] Suitable oxidising agents can be: hydrogen peroxide, a
hydrogen peroxide adduct, such as e.g. the urea adduct, an organic
per-acid, an inorganic per-acid, an imino per-acid, persulfates,
perborate, percarbonate, oxidising metal salts or mixtures of the
above. Hydrogen peroxide can particularly preferably be used.
[0027] Due to the reduced stability of some oxidising agents
towards other constituents of the dispersion according to the
invention, it can be useful to add it only just before the
dispersion is used.
[0028] The pH can be adjusted by means of acids or bases. Inorganic
acids, organic acids or mixtures of the aforementioned can be used
as acids.
[0029] In particular, phosphoric acid, phosphorous acid, nitric
acid, sulfuric acid, mixtures thereof and their acid-reacting salts
can be used as inorganic acids.
[0030] Carboxylic acids having the general formula
C.sub.nH.sub.2n+1CO.sub.2H, where n=0-6 or n=8, 10, 12, 14, 16, or
dicarboxylic acids having the general formula
HO.sub.2C(CH.sub.2).sub.nCO.sub.2H, where n=0-4, or
hydroxycarboxylic acids having the general formula
R.sub.1R.sub.2C(OH)CO.sub.2H, where R.sub.1.dbd.H,
R.sub.2.dbd.CH.sub.3, CH.sub.2CO.sub.2H, CH(OH)CO.sub.2H, or
phthalic acid or salicylic acid, or acid-reacting salts of the
aforementioned acids or mixtures of the aforementioned acids and
salts thereof are preferably used as organic acids.
[0031] The pH can be raised by the addition of ammonia, alkali
hydroxides or amines. Ammonia and potassium hydroxide are
particularly preferred.
[0032] Suitable oxidation activators can be the metal salts of Ag,
Co, Cr, Cu, Fe, No, Mn, Ni, Os, Pd, Ru, Sn, Ti, V and mixtures
thereof. Carboxylic acids, nitrites, ureas, amides and esters are
also suitable. Iron(II) nitrate can be particularly preferred. The
concentration of the oxidation catalyst can be varied in a range
between 0.001 and 2 wt. %, depending on the oxidising agent and the
polishing task. The range between 0.01 and 0.05 wt. % can be
particularly preferred.
[0033] Suitable corrosion inhibitors, which can be present in the
dispersion according to the invention in a proportion of 0.001 to 2
wt. %, comprise the group of nitrogen-containing heterocyclic
compounds, such as benzotriazole, substituted benzimidazoles,
substituted pyrazines, substituted pyrazoles, glycine and mixtures
thereof.
[0034] The dispersion according to the invention can be produced by
means of dispersing and/or grinding devices, which give rise to an
energy input of at least 200 kJ/m.sup.3. These include systems
based on the rotor-stator principle, for example Ultra-Turrax
machines, or attrition mills. Higher energy inputs are possible
with a planetary kneader/mixer. The effectiveness of this system is
dependent on an adequately high viscosity in the mixture to be
processed, however, in order to incorporate the high shear energies
needed to break down the particles.
[0035] Using high-pressure homogenisers, dispersions can be
obtained in which the particles or aggregates of the metal oxide
powder display a size of less than 150 nm and particularly
preferably of less than 100 nm.
[0036] In these devices, two predispersed streams of suspension
under high pressure are decompressed through a nozzle. The two jets
of dispersion hit each other exactly and the particles grind
themselves. In another embodiment the predispersion is likewise
placed under high pressure, but the particles collide against
armoured sections of wall. The operation can be repeated any number
of times to obtain smaller particle sizes.
[0037] The dispersing and grinding devices can also be used in
combination. Oxidising agents and additives can be added at any
point of the dispersing operation. It can also be advantageous not
to incorporate the oxidising agents and oxidation activators until
the end of the dispersing operation, for example, optionally with a
lower energy input.
[0038] The invention also provides the use of the dispersion
according to the invention for the chemical-mechanical polishing of
metallic surfaces. These can be layers consisting of copper,
aluminium, tungsten, titanium, molybdenum, niobium, tantalum and
alloys thereof.
[0039] The invention also provides the use of the dispersion
according to the invention for the chemical-mechanical polishing of
metallic surfaces that are applied to an insulating barrier layer.
The metal surfaces comprise the metals copper, aluminium, tungsten,
titanium, molybdenum, niobium, tantalum and alloys thereof. The
barrier layers can consist of titanium nitride or tantalum nitride,
for example.
[0040] Dispersions containing cationic, surface-active polymers
have until now been used primarily in the paper industry for the
stabilisation of dispersions (cf. EP-A-1331254). These are
dispersions containing a solid which in the desired acid pH range
displays little or no stability due to its negative surface charge.
By the addition of cationic, surface-active substances such a
dispersion can be stabilised in the acid to neutral pH range.
[0041] In our view, the use of such dispersions, in which a
polyallyl amine or polydiallyl amine having a weight-average
molecular weight of less than 100,000 g/mol is dissolved in the
dispersion as cationic, surface-active component, for use in the
chemical-mechanical polishing of metal surfaces, is not a part of
the prior art.
[0042] It is surprising that the dispersion according to the
invention gives rise to markedly better metal layer/barrier layer
selectivity values than corresponding dispersions without the
cationic, surface-active component. The effect of this component
has not yet been explained. It is surprising, however, that the
positive effect also occurs in dispersions which inherently already
display a positive surface charge in the acid range, such as an
aluminium oxide dispersion, for example, or a dispersion of a
silicon-aluminium mixed oxide powder having an aluminium oxide
content of 90 wt. % or more.
EXAMPLES
[0043] A silicon-aluminium mixed oxide powder having a content of
66 wt. % Al.sub.2O.sub.3 and a BET surface area of 90 m.sup.2/g is
used in Example 1.
[0044] A silicon-aluminium mixed oxide powder having a content of
90 wt. % Al.sub.2O.sub.3 and a BET surface area of 90 m.sup.2/g is
used in Examples 2 and 3.
[0045] Example 1
[0046] 33.5 kg of demineralised water and 500 g of Catiofast.RTM.
PR 8153 (BASF) are placed in a 60 l stainless steel batch
container. 5 kg of the powder are sucked in and coarsely
predispersed with the aid of a dispersing and suction mixer (at
4500 rpm) supplied by Ystral. Following the introduction of the
powder, dispersion is completed with an Ystral Z 66 continuous
rotor/stator homogeniser with four machining rings, a stator slot
width of 1 mm and a speed of 11,500 rpm. During the introduction of
the powder, a pH of 4.0+/-0.3 is maintained by the addition of
acetic acid (100% glacial acetic acid). An abrasive body
concentration of 12.5 wt. % is established by the addition of
further demineralised water. This "predispersion" is ground with a
wet-jet mill, Ultimaizer system from Sugino Machine Ltd., model
HJP-25050, under a pressure of 250 MPa and with a diamond nozzle
diameter of 0.3 mm and two grinding cycles.
[0047] Example 2 is performed in the same way as Example 1.
[0048] Example 3 is also performed in the same way as Example 1,
but without the cationising agent Catiofast.RTM.. TABLE-US-00001
Polishing tool and polishing parameters Polishing machine: MECAPOL
E460 (STEAG) with 46 cm platen and 6'' wafer carrier Polishing pad:
IC1400 (RODEL Corp); pad conditioning with diamond segment after
each polished wafer Slurry quantity: 120 ml/min for all experiments
Polishing p.sub.A Operating pressure: 10-125 kPa = 1.45-18.13 psi
parameters: Default 45 and 60 kPa p.sub.R Rear pressure 10 kPa
.omega..sub.p = .omega..sub.c = 40 rpm (constant for all
experiments) Sweep = 4 cm (constant for all experiments) Polishing
time: 2 min Aftercleaning: After polishing, the wafer was rinsed
for 30 s in deionised water and then cleaned on both sides in a
scouring unit with a spray jet and megasonic support and dried in a
centrifugal dryer.
[0049] Starting from the dispersions from examples 1 to 3, suitable
polishing slurries for the Cu CMP process are produced by dilution
to a powder content of 5 wt. %, addition of 1.3 wt. % of glycine as
complexing agent and addition of 7.5 wt. % of hydrogen peroxide as
oxidising agent. The pH was adjusted to 4 with acetic acid. The
polishing results obtained with these slurries are shown in Table
1. TABLE-US-00002 TABLE 1 Polishing results Removal Removal nm
Cu/min nm TaN/min Selectivity Rq* Example 60 kPa 60 kPa Cu:TaN 60
kPa 1 455 3 152 14 2 210 2 105 13 3 205 4 51 35 *Rq = square mean
roughness on Cu; the Rq value for the unpolished Cu wafer was 11 nm
The polishing results demonstrate the advantages of using a
cationised mixed oxide slurry with regard to selectivity and Rq
value.
* * * * *