U.S. patent application number 14/479440 was filed with the patent office on 2014-12-25 for apparatus for contamination removal using magnetic particles.
The applicant listed for this patent is Micron Technology, Inc.. Invention is credited to Stephen J. Kramer, Gurtej S. Sandhu, Nishant Sinha.
Application Number | 20140373880 14/479440 |
Document ID | / |
Family ID | 43305320 |
Filed Date | 2014-12-25 |
United States Patent
Application |
20140373880 |
Kind Code |
A1 |
Sinha; Nishant ; et
al. |
December 25, 2014 |
APPARATUS FOR CONTAMINATION REMOVAL USING MAGNETIC PARTICLES
Abstract
Methods and apparatus are provided for cleaning a substrate
(e.g., wafer) in the fabrication of semiconductor devices utilizing
a composition of magnetic particles dispersed within a base fluid
to remove contaminants from a surface of the substrate.
Inventors: |
Sinha; Nishant; (Boise,
ID) ; Kramer; Stephen J.; (Boise, ID) ;
Sandhu; Gurtej S.; (Boise, ID) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Micron Technology, Inc. |
Boise |
ID |
US |
|
|
Family ID: |
43305320 |
Appl. No.: |
14/479440 |
Filed: |
September 8, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12483518 |
Jun 12, 2009 |
8845812 |
|
|
14479440 |
|
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Current U.S.
Class: |
134/94.1 ;
134/184 |
Current CPC
Class: |
C11D 17/0013 20130101;
C11D 3/1206 20130101; B03C 1/01 20130101; B03C 2201/16 20130101;
H01L 21/67028 20130101; B08B 3/10 20130101; H01L 21/6704 20130101;
C11D 3/1213 20130101; B03C 2201/20 20130101; C11D 7/20
20130101 |
Class at
Publication: |
134/94.1 ;
134/184 |
International
Class: |
H01L 21/67 20060101
H01L021/67; B03C 1/01 20060101 B03C001/01 |
Claims
1. An apparatus for cleaning a substrate, the apparatus comprising:
a containment vessel for receiving and containing a fluid
composition therein; a substrate support configured to hold a
substrate, the substrate comprising a semiconductor device
structure; a source of the fluid composition, the fluid composition
comprising magnetic particles having functional reactive groups
formulated to conjugate with contaminants on the substrate; and at
least one magnetic field generator configured to generate a
sufficient magnetic field to draw contaminant-conjugated magnetic
particles from the substrate without causing damage to the
semiconductor device structure.
2. The apparatus of claim 1, wherein the at least one magnetic
field generator comprises a plurality of magnetic field
generators.
3. The apparatus of claim 1, wherein the at least one magnetic
field generator comprises a plurality of magnetic field generators
situated on opposing sides of the containment vessel.
4. The apparatus of claim 2, wherein the plurality of magnetic
field generators at least partially surround the containment
vessel.
5. The apparatus of claim 2, wherein the plurality of magnetic
field generators are situated at a plurality of positions
surrounding the containment vessel.
6. The apparatus of claim 1, wherein the at least one magnetic
field generator is situated beneath a base of the containment
vessel.
7. The apparatus of claim 2, wherein the at least one magnetic
field generator is positioned above the containment vessel.
8. The apparatus of claim 2, wherein the at least one magnetic
field generator is movable about the containment vessel.
9. The apparatus of claim 1, wherein the containment vessel
comprises an outlet for discharging a fluid composition
therefrom.
10. The apparatus of claim 9, further comprising a magnetic field
generator situated proximal to the outlet of the containment
vessel.
11. The apparatus of claim 1, wherein the at least one magnetic
field generator is in communication with a controller comprising a
computer device configured under control of a program to control
the magnetic field.
12. An apparatus for cleaning a substrate, the apparatus
comprising: a substrate support configured to hold a substrate
comprising protruding structures with a recess therebetween; a
containment vessel for receiving and containing a fluid composition
therein; a source of the fluid composition, the fluid composition
comprising magnetic particles having functional reactive groups
formulated to conjugate with contaminants on the substrate; and a
magnetic field generator configured to laterally move
contaminant-conjugated magnetic particles in a single direction
across the substrate and substantially parallel to the protruding
structures.
13. The apparatus of claim 12, further comprising a dispensing
device for applying the fluid composition to the substrate.
14. The apparatus of claim 12, wherein the containment vessel
comprises an inlet and an outlet for passage of the fluid
composition into and out of the containment vessel.
15. The apparatus of claim 12, further comprising an insulator
between the magnetic field generator and the containment vessel or
the substrate to shield the substrate from a magnetic field
generated by the magnetic field generator.
16. The apparatus of claim 12, wherein the magnetic field generator
is incorporated into the containment vessel.
17. An apparatus for cleaning a substrate, the apparatus
comprising: a substrate support configured to hold a substrate
comprising semiconductor structures in linear arrays; a containment
vessel for receiving and containing a fluid composition therein; a
source of the fluid composition, the fluid composition comprising
magnetic particles having functional reactive groups configured to
conjugate with contaminants on the substrate; and a magnetic field
generator perpendicular to the linear arrays of semiconductor
structures, the magnetic field generator configured to move
contaminant-conjugated magnetic particles in a lateral direction
parallel to the linear arrays of semiconductor structures.
18. The apparatus of claim 17, wherein the magnetic field generator
is configured to laterally move contaminant-conjugated magnetic
particles without damaging the semiconductor structures.
19. The apparatus of claim 17, further comprising: an outlet for
discharging the fluid composition; and a collection device within
or proximal to the outlet to isolate and collect the magnetic
particles and the contaminant-conjugated magnetic particles.
20. The apparatus of claim 17, further comprising a device for
applying a dilute ammonium hydroxide/hydrogen peroxide (SC1)
solution or a dilute hydrofluoride solution to the substrate.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional of U.S. patent application
Ser. No. 12/483,518, filed Jun. 12, 2009, pending, the disclosure
of which is hereby incorporated herein in its entirety by this
reference.
TECHNICAL FIELD
[0002] Embodiments of the invention relate to methods and
apparatuses for cleaning surfaces of a substrate.
BACKGROUND OF THE INVENTION
[0003] A common occurrence during semiconductor device fabrication
is the accumulation of particulate contaminants on semiconductor
device surfaces. Various processes and cleaning solutions have been
used for the removal of small residual particles and other
contaminants from surfaces, such as a wafer surface in the
fabrication of semiconductor-based structures and devices. A
post-process clean is typically conducted to remove contaminants
remaining on a surface after a processing step such as etching,
planarization, polishing, sawing, film deposition, etc., prior to
performing another device fabrication step such as a metallization,
gate or device formation, etc. If residues or contaminants
remaining from a process step are not effectively removed, various
fabrication problems and defects in the finished integrated circuit
device can result. For example, metal contaminants that remain on a
surface feature can cause shorts between capacitor electrodes or
other electrical failures, and non-conductive contaminants on a
feature such as particles (e.g., SiO.sub.2, polysilicon, nitride,
polymers, etc.) remaining after a chemical-mechanical planarization
or polishing (CMP) or other process can cause the failure in
adhesion of subsequent layers, a loss of critical dimension of the
formed feature, or pattern deformation in that area leading to
yield loss. Current technology nodes (e.g., 65 nm and smaller)
require a high level of surface cleaning, including the removal of
remnant particles, residues and other contaminants while
maintaining other surface materials intact.
[0004] One example of a known cleaning technique used to remove
unwanted surface materials is an RCA clean, which conventionally
includes first applying an aqueous alkaline cleaning solution known
as a Standard Clean 1 (SC1) to remove particle contaminants. SC1
typically consists of a dilution of ammonium hydroxide/hydrogen
peroxide (NH.sub.4OH/H.sub.2O.sub.2) followed by a deionized (DI)
water rinse. An example of a cleaning technique to remove metal
contaminants is an aqueous acidic cleaning solution known as a
Standard Clean 2 (SC2) composed of a hydrochloric acid/hydrogen
peroxide (HCl/H.sub.2O.sub.2) dilution followed by a second DI
water rinse. Other wet cleaning methods used for cleaning residues
from structures include, for example, a piranha clean using a
sulfuric acid-based mixture (e.g., H.sub.2SO.sub.4/H.sub.2O.sub.2),
a buffered oxide etch solution, and fluorine-based aqueous
chemistries.
[0005] Small particles or other contaminants resulting from
fabrication steps can be held to a surface by electrostatic and/or
other forces and can become adhered, typically requiring relatively
large forces to remove them. Cleaning solutions are often applied
in conjunction with acoustic energy (i.e., ultrasonic or megasonic
energy), high pressure spraying techniques, mechanical scrubbing
techniques with a pad or brush, etc., to enhance the cleaning
action of the solution. However, acoustic cleaning and spraying
techniques apply cleaning forces in a manner that is difficult to
control, which can cause damage to surface structures or alter
critical dimensions without effectively removing all of the
particulate contaminants from the substrate. In addition, many
cleaning solutions can attack and/or dissolve the structures formed
in the fabrication step.
[0006] Other techniques involve forcing solid particles (e.g.,
salts of fatty acid solids, paraffin, wax, polymers, etc.)
dispersed within a continuous phase to a substrate surface to
disengage surface contaminants, which can damage to line elements
and other surface structures. For example, some techniques apply a
chemical or foam that contains salts of fatty acid solids (e.g.,
crystals of stearic acid salts) by dispensing from a rotary head or
proximity cleaning head. However, stearic acid crystal size and its
velocity in a dynamic foam are difficult to control, resulting in
damage to surface structures (e.g., line elements) by poorly
controlled parameters within the foam.
[0007] It would be desirable to provide a process for removing
contaminants from a surface without adversely affecting structures
and/or surface materials on a substrate that overcomes these
problems.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Embodiments of the present disclosure are described below
with reference to the following accompanying drawings, which are
for illustrative purposes only. Throughout the following figures,
reference numerals will be used in the drawings, and the same
reference numerals will be used throughout the several figures and
in the description to indicate same or like parts.
[0009] FIG. 1 is a diagrammatic elevational cross-sectional view of
an apparatus for removing contaminants from a substrate according
to an embodiment of the invention.
[0010] FIG. 2 is a cross-sectional view of the apparatus shown in
FIG. 1 at a subsequent processing stage showing the application of
a magnetic field; FIG. 2A is a top plan view of the apparatus of
FIG. 2, taken along line 2A-2A.
[0011] FIG. 3 is a diagrammatic top plan view of an apparatus for
removing contaminants from a substrate according to another
embodiment of the invention, showing multiple magnetic field
generators positioned about a containment vessel.
[0012] FIG. 4 is a diagrammatic elevational cross-sectional view of
an apparatus for removing contaminants from a substrate according
to another embodiment of the invention, showing magnetic field
generators situated at each side, above and/or below a containment
vessel.
[0013] FIG. 5 is a cross-sectional view of the apparatus shown in
FIG. 2 at a subsequent processing stage.
[0014] FIG. 6 is a cross-section view of the substrate shown in
FIG. 5 at a subsequent processing stage.
[0015] FIG. 7 is diagrammatic elevational cross-sectional view of
an apparatus for removing contaminants from a substrate according
to another embodiment of the invention; FIG. 7A is a top plan view
of the apparatus of FIG. 7, taken along line 7A-7A.
DETAILED DESCRIPTION
[0016] The following description, with reference to the drawings,
provides illustrative examples of apparatus and methods according
to embodiments of the present disclosure. Such description is for
illustrative purposes only and not for purposes of limiting the
same.
[0017] The terms "wafer" and "substrate" are interchangeable and
are to be understood as a semiconductor-based material including
silicon, silicon-on-insulator (SOI) or silicon-on-sapphire (SOS)
technology, doped and undoped semiconductors, epitaxial layers of
silicon supported by a base semiconductor foundation, and other
semiconductor structures. Furthermore, when reference is made to a
"wafer" and/or "substrate" in the following description, previous
process steps may have been utilized to form regions or junctions
in or over the base semiconductor structure or foundation.
Additionally, when reference is made to a "substrate assembly" in
the following description, the substrate assembly may include a
wafer with materials including dielectrics and conductors, and
features such as transistors, formed thereover, depending on the
particular stage of processing. In addition, the semiconductor need
not be silicon-based, but may be based on silicon-germanium,
silicon-on-insulator, silicon-on-sapphire, germanium, or gallium
arsenide, among others.
[0018] In embodiments of the invention, the composition is a fluid
suspension composed of magnetic particles dispersed in a carrier or
base fluid that is chemically compatible with the materials to be
treated. In embodiments, the carrier fluid is a continuous phase
selected so as not to damage or adversely affect surface materials
and/or structures situated on a substrate, with suitable chemical
and thermal stability over the temperature range of the
application. The carrier fluid should have a wide temperature range
with a low freezing point and a high boiling point (e.g., from
about -40.degree. C. to about +200.degree. C.). The pH of the
composition can be from about 1 to about 13, or any value or
sub-range therebetween.
[0019] The carrier fluid can be an aqueous solution, for example,
water or a buffer such as saline, phosphate, borate, acetate,
citrate, carbonate, bicarbonate or other buffer, with a pH of about
3-11, or a value or sub-range therebetween. In other embodiments,
the carrier fluid can be water with appropriate surfactants to
stabilize the magnetic particles in suspension.
[0020] In other embodiments, the carrier fluid can be a non-aqueous
liquid, including, for example, silicone oils such as polyalkyl-,
polyaryl-, polyalkoxy-, or polyaryloxysiloxane oils and silicate
oils (e.g., polydimethyl siloxanes, liquid methyl phenyl siloxanes,
tetraethyl silicate, etc.); mineral oils; vegetable oils (e.g.,
sunflower oils, rapeseed oil, soybean oil, etc.); hydrocarbon oils
including paraffin oils, naphthalenes, chlorinated paraffins,
olefin oligomers and hydrogenated olefin oligomers (e.g.,
polyisobutylene, ethylene-propylene copolymers, etc.);
polyphenylethers; polyesters (e.g., perfluorinated polyesters,
etc.); dibasic acid esters; neopentylpolyol esters; phosphate
esters; glycol esters and ethers (e.g., polyalkylene glycol, etc.);
aromatic-type oils (e.g., benzoic acid, phthalic acid, etc.);
alkylene oxide polymers and interpolymers, and derivatives thereof
(e.g., methylpolyisopropylene glycol, etc.); carbon tetrachloride;
fluorocarbons; chlorofluorocarbons; ketones; and alcohols, among
others.
[0021] The carrier fluid should have a viscosity that permits
movement of the magnetic particles within the suspension when
applied to a substrate in the presence of a magnetic field. The
viscosity of the carrier fluid can be varied according to the type
and concentration of the magnetic particles from a relatively low
viscosity carrier fluid, such as isopropyl alcohol (IPA), acetone
and propanol, to a relatively high viscosity carrier fluid, such as
an ethylene glycol/sulfuric acid mixture. The viscosity of the
carrier fluid can be determined according to known techniques, for
example, using a viscometer.
[0022] The magnetic particles are typically composed of a
ferromagnetic, ferrimagnetic, paramagnetic, or superparamagnetic
material combined with and/or coated with a material that is
functionalized to have surface functional reactive groups to bind
with or repel contaminants on the surface of a substrate. The
composition of the magnetic particles determines characteristics
including hydrophobicity/hydrophilicity and charge
(positive/negative), which can affect coupling to or repulsion of
contaminants.
[0023] Methods for producing magnetic particles are known in the
art, as described, for example, in U.S. Pat. No. 5,091,206 to Wang
et al. (assigned to Baxter Diagnostics Inc.), U.S. Pat. No.
6,133,047 to Elaissari et al. (assigned to Bio Merieux), U.S. Pat.
No. 6,682,660 to Sucholeiki et al. (assigned to MDS Proteomics,
Inc.), U.S. Pat. No. 7,186,398 to Andres et al. (assigned to Purdue
Research Foundation), and U.S. Pat. No. 7,214,427 to Huang et al.
(assigned to Aviva Biosciences Corporation).
[0024] In embodiments of the invention, the magnetic particles can
be composed of a magnetic material dispersed in a polymer matrix
that includes ligands or reactive functional groups presented on
the surface of the magnetic particle such that binding moieties are
available for interaction with a target contaminate(s). In other
embodiments, the magnetic material can be combined with a polymeric
material, ceramic material, semiconductive material, etc., to form
a core particle and then surface coated with a polymeric material
that provides surface reactive functional groups.
[0025] In another embodiment, a magnetic material (e.g., metal
oxide) can be mixed with monomer(s) and coated onto a polymeric
core particle (e.g., polystyrene particles), ceramic material core
particle, semiconductive material core particle, etc., which can be
coated with a layer of functionalized polymer to provide functional
groups such as carboxyl, amino or hydroxyl groups for covalent
coupling of contaminant materials. Magnetic particles (or core
particles) can be overcoated with the same or a different polymer
than used for forming a polymer/magnetic material core particle. In
yet other embodiments, a magnetic material (e.g., a metal oxide)
can be formed as a core particle and coated with a polymeric
material that provides surface reactive functional groups.
[0026] Non-limiting examples of magnetic materials that can be
utilized include iron, iron oxides, iron nitrides, iron carbides,
silanized iron oxides, carbonyl iron, chromium dioxide, low carbon
steel, silicon steel, nickel, cobalt, etc., or combinations or
alloys of such materials, for example, Fe--Co compounds and alloys
(e.g., CoFe), Fe--Ni compounds and alloys (e.g., Ni.sub.3Fe),
Mn--Zn ferrite, Ni--Zn ferrite, AlNiCo alloys, and ceramic ferrites
such as magnetite (Fe.sub.3O.sub.4), maghemite (Fe.sub.2O.sub.3)
magnesioferrite (MgFe.sup.3+.sub.2O.sub.4), jacobsite
(MnFe.sub.2O.sub.4), trevorite (NiFe.sup.3+.sub.2O.sub.4),
pyrrohite (Fe.sub.(1-x)S (x=0 to 0.2)), greigite
(Fe(II)Fe(III).sub.2S.sub.4), and rare earth magnets such as
neodymium magnet (NdFeB magnet or Neo magnet) and samarium cobalt
magnet alloys (generally SmCo.sub.5), etc., among others.
[0027] The reactive functional groups can be incorporated onto the
surface of the magnetic particles, for example, by using a
functionalized monomer or a mixture of monomers and functionalized
monomers with a magnetic material during formation of magnetic
particles composed of a polymeric and magnetic material. In other
embodiments, a magnetic material or a polymer/magnetic material
core particle can be coated with a thin layer of functionalized
monomer (or monomer/functionalized monomer mixture) to form a
polymeric outer layer. Inclusion of an effective amount or
percentage of functionalized monomers can eliminate adding
materials having functionalized groups after formation of the
particles.
[0028] Polymeric materials can be produced using monomers having
reactive functional groups including, for example, groups
containing C--O bonds, such as carboxyl groups, aldehyde groups,
carbonyl (ketone) groups, ether groups, ester groups, peroxy
groups, etc.; hydroxyl functional groups; hydrazide functional
groups; hydrocarbon functional groups, such as alkyl (methyl)
groups, alkenyl (alkene) groups, alkynyl (alkyne) groups, vinyl
groups, phenyl groups, benzyl groups, etc.; nitrogen-containing
functional groups, such as amide groups, amine (amino) groups,
imine groups, azo groups, nitrile (cyano) groups, nitro groups,
nitroso groups, pyridyl groups, isocyanate groups, isothiocyanate
groups, etc.; functional groups containing a carbon-halogen bond,
such as halide groups, fluoro groups, chloro groups (e.g.,
chloromethyl groups), etc.; sulfur-containing functional groups,
such as sulfate groups, etc.; and groups containing phosphorus and
sulfur, such as phosphodiester groups, sulfhydryl (thiol) groups,
phosphorus sulfide groups, etc.; and combinations thereof.
[0029] The polymeric material can be produced by conventional
methods including emulsion polymerization, suspension
polymerization or other polymerization process, with or without the
use of a cross-linking agent (e.g., divinyl benzene, etc.).
Monomers that can be utilized to produce the polymeric material
include vinyl monomers such as styrene, vinyl toluene, and
substituted styrenes (e.g., chloromethyl styrene), acrylates and
methacrylates (e.g., methylmethacrylate, 2-hydroxyethyl
methacrylate, 2-aminoethyl methacrylate, etc.), among others,
including copolymers and multiblock copolymers (e.g.,
styrene-divinylbenzene copolymer, styrene/butadiene copolymer,
styrene/vinyltoluene copolymer, etc.).
[0030] In other embodiments, a ligand having a reactive functional
group can be attached to the surface of the magnetic particles, for
example, through covalent attachment, non-covalent binding,
chemical coupling, or adsorption by hydrophobic (van der Waals)
attraction, hydrophilic attraction or ionic interaction, according
to conventional methods for surface functionalization. Metal and
ceramic material can generally be functionalized through covalent
bonds such as a metal-oxygen bond, a metal-sulfur bond, or a
metal-carbonyl bond according to conventional methods. Ligands can
also be attached to metal surfaces electrostatically. See for
example, Baraton, Marie-Isabelle (ed.), Synthesis,
Functionalization and Surface Treatment of Nanoparticles, American
Scientific Publishers, Valencia, Calif., 323 pp. (2003), and
Sigma-Aldrich, Inc., Surface Functionalized Nanoparticles at
www.sigmaaldrich.com/materials-science/material-science-products.html?Tab-
lePage=16377718.
[0031] Ligands can be attached to the magnetic particles, for
example, using an absorption buffer (e.g., phosphate buffered
saline (PBS), borate buffer, acetate buffer, citrate phosphate
buffer, carbonate-bicarbonate buffer, MES buffer, etc.).
Optionally, a blocker can be adsorbed onto the magnetic particles
to reducenon-specific binding between the magnetic particle and
non-target molecules and self-aggregation of the magnetic or core
particles (e.g., BSA, non-ionic surfactants such as TWEEN.RTM. 20
and TRITON.RTM. X-100, polyethylene glycol, etc.). In some
embodiments, a linker molecule (e.g., a cleavable linker) that
includes difunctional groups can be used to covalently couple a
ligand having a reactive functional group to a magnetic material,
and/or to a polymer magnetic material core particle, etc. A linker
(e.g., BSA, polylysine, or molecule having an alkane, alkene,
ester, ether or other group, etc.) can also function as a spacer to
extend a small molecule with a reactive functional group from the
magnetic particle and reduce steric hindrance.
[0032] In other embodiments of the invention, the magnetic
particles can be fanned without ligands or reactive functional
groups. An additive material bearing a ligand having a reactive
functional group (e.g., a functionalized monomer,
monomer/functionalized monomer mixture, etc.) can be added to the
carrier fluid with the non-functionalized magnetic particles,
wherein the additive material will react, for example, to
covalently couple the magnetic particles with the contaminants. For
example, the magnetic particles can be composed of a magnetic
material with a core of a polymeric material, a ceramic material, a
semiconductive material, etc. In other embodiments, the magnetic
particles are composed of a magnetic material combined with a
polymeric material, a ceramic material, a semiconductive material,
etc., to form a composite particle. In other embodiments, the
magnetic particles are composed of a core of a magnetic material
overcoated with a polymeric material, a ceramic material, a
semiconductive material, etc.
[0033] Magnetic particles can be prepared, for example, from an
aqueous suspension of a magnetic material and monomer(s), with or
without a cross-linking agent such as divinylbenzene (e.g.,
ferrofluid (magnetite)/styrene/divinylbenzene) that is polymerized
to trap the magnetic materials (e.g., magnetite) in a polymer
matrix to form a core particle. The core particle can be
encapsulated by a polymer material with reactive functional groups,
for example, carboxyl (--COOH) or amine groups that are available
on the surface of the magnetic particle to react with contaminants
on the substrate. Such magnetic particles are commercially
available, for example, as COMPEL.TM. superparamagnetic particles,
composed of a magnetite/polymer matrix coated with a polymer with
carboxyl (--COOH) surface groups (mean diameter of about 3-8 .mu.m;
density of about 1.1-1.2 g/cm.sup.3) available from Bangs
Laboratories, Inc., (Fishers, Ind., USA).
[0034] The size and shape(s) of the magnetic particles can be
varied according to the contaminant to be removed and for effective
substrate cleaning without damaging the substrate or the structures
and materials on the substrate. In embodiments of the invention,
the magnetic particles can have an average particle size (particle
diameter) of about 1-100 times the size of the contaminant to be
removed, for example, about 0.01-100 .mu.m (as measured by
transmission electron microscopy (TEM)), or any value or sub-range
therebetween, e.g., about 0.1-40 .mu.m, about 1-10 .mu.m, etc. The
shape of the magnetic particles can be regular or irregular,
spherical or non-spherical, and can be in the form of a powder,
fibers, spheres, rods, plates, core-shell structures, and the like,
including, nano-sized rods (e.g., 10 nm to 100 nm) and
microspheres.
[0035] The volume fraction (concentration) of magnetic particles in
the composition should be sufficient to provide the desired effect
or performance. The concentration of magnetic particles is such
that the particles can be maintained as a dispersion in the base
fluid without settling, and to allow the composition to maintain a
relatively low viscosity for application onto the substrate.
Generally, the concentration of magnetic particles in the base
fluid can be in a range of about 0.1-30% by weight of the total
composition, or any value or sub-range therebetween, and in some
embodiments at about 20-30% by weight, about 10-30% by weight,
about 1-10% by weight, etc. The weight percentage of the magnetic
particles can be adjusted according to the density of the fluid
phase and/or the amount of contaminants to be removed. In other
embodiments, the density of the particles can be matched with a
base fluid for dispersion of the magnetic particles within the
composition. The magnetic particle loading in the dispersion can be
varied according to the desired weight % or according to the
dispersion of the magnetic particles in the fluid carrier (loading
before flocculation), which is dependent, at least in part, on
particle surface chemistry, the fluid carrier or dispersion medium,
particle size, and/or additives.
[0036] Optionally, the composition can contain typically used
additives, generally at about 0.1-10% by weight of the total
composition, or about 0.5-6% by weight. Typical additives include,
for example, co-solvents, pH modifiers, chelating agents,
antioxidants, rheology modifiers (e.g., polymers, particulates,
polypeptides, etc.), polar solvents, and surfactants or dispersing
agents (dispersants) to enhance the dispersion stability of the
suspension against sedimentation and aggregation or agglomeration
of the magnetic particles. Examples of surfactants include block
copolymers, dedecyl alcohol, fatty acids and amines, glycerol,
glycerol esters, glycerol monooleates, hydrocarbon polymers, sodium
oleate, and tin oxide, among others. The composition can also
include a chemical compound to modify or bind to the available
reactive group on the magnetic particle, for example, a
cross-linking agent to activate groups having a low reactivity to
the contaminant (e.g., carbodiimide for binding to COOH groups) or
to join non-reactive groups. The composition should not contain
compounds or additives that will interfere with or compete with the
binding reaction of the magnetic particles with contaminants.
[0037] In some embodiments, an additive material bearing a ligand
having a reactive functional group (e.g., a functionalized monomer,
monomer/functionalized monomer mixture, etc.) that is not bound to
the magnetic particles can be added to the carrier fluid with
magnetic particles that have not been functionalized and/or with
functionalized magnetic particles.
[0038] An embodiment of a method according to the invention for
removing contaminants from a substrate to be processed is described
with reference to FIGS. 1-2A.
[0039] FIG. 1 depicts an embodiment of an apparatus, designated
generally as 10, which can be utilized in methods of the invention.
The apparatus 10 generally includes a containment vessel (or
container) 12 for receiving and containing a fluid, and a magnetic
field generator 14. As shown, a substrate 16 to be treated, which
is a wafer in the present example, can be placed onto a substrate
support 18 within the containment vessel 12. The containment vessel
12 can be composed of an insulating material such as glass,
plastic, polyvinylidene fluoride (PVDF), etc.
[0040] The apparatus 10 can be connected to other processing
units/systems, for example, by a conveyor mechanism (not shown) for
conducting the substrate 16 through a processing system, including
a pre-cleaning apparatus and/or a post-cleaning apparatus (not
shown). The various processing units can be electrically coupled to
a microprocessor, which may be programmed to carry out particular
functions as is known in the art. A pre-cleaning apparatus can be
designed to physically loosen up particles from the substrate 16 by
means of undercutting or etching of the substrate 16, which can be
performed, for example, by a Standard Clean 1 (SC1) clean or dilute
hydrofluoric acid (DHF) clean, followed by a rinse (e.g., DI
rinse). This can serve to reduce the treatment required for removal
of contaminants. A post-cleaning can be applied to remove remaining
particles.
[0041] As depicted in FIG. 1, the substrate 16 to be treated is
contacted by a composition 20, according to the invention, composed
of magnetic particles 22 in a base fluid 24. The substrate 16 can
comprise structures 26 such as conductive or insulative lines,
shallow trench isolation (STI) structures, bond pads, contacts and
interconnects, among other elements, exposed at a surface 28 of the
substrate 16. Contaminants 30 composed of conductive, insulative
and/or semiconductive materials such as oxides, nitrides, silicon
materials, carbon, polymer resist, metals and metal-containing
materials (e.g., W, WSi.sub.x, TiN, Ta.sub.2O.sub.5, etc.), among
others, can remain adhered to the structures 26 and/or the surface
28 of the substrate 16 as a result of earlier processing (e.g., an
SC1 clean, etc.).
[0042] The composition 20 can be applied to the substrate 16, for
example, from a dispensing device 32. In some embodiments, the
dispensing device 32 can be structured to deliver the composition
20 under pressure onto the surface 28 of the substrate 16. In other
embodiments, the containment vessel 12 can include an inlet and an
outlet for passage of the composition 20 into and out of the vessel
12.
[0043] In embodiments of the invention, the magnetic particles 22
are allowed to react with contaminants 30 for a time and at a
temperature to permit substantial interaction to form
contaminant-conjugated magnetic particles 34. Optionally, the
composition 20 can be mixed (continuously or intermittently) during
the reaction period. Reaction time can vary, for example, according
to the nature and concentration of contaminants 30, the mechanism
by which binding occurs, and the affinities of the reactive
functional groups 36 that are used.
[0044] Reactive functional group(s) 36 on the surface of the
magnetic particles 22 can chemically and/or physically interact
with one or more contaminants 30, for example, by adsorption,
covalent bonding, or a non-covalent interaction (e.g., hydrogen
bond, ionic bond, van der Waals forces, etc.) to form
contaminant-conjugated magnetic particles 34. In some embodiments,
the reactive functional group(s) 36 on surfaces of the magnetic
particles can provide a repelling force to cause contaminants 30 to
be displaced and/or separated from the surface 28 of the substrate
16 and structures 26. The magnetic particles 22 are structured with
reactive functional groups 36 that will provide an interaction with
contaminants 30 that is stronger than the interactive force of the
surface 28 of the substrate 16 or structures 26 with the target
contaminant. The chemical composition of the contaminants 30 and
the surface 28 of the substrate 16 and structures 26 will
determine, at least in part, the ultimate strength of adhesion of
contaminants 30 to the substrate 16 and surface structures. The
interaction of magnetic particles 22 with contaminants 30 can be
enhanced, for example, by the inclusion of a surfactant or
dispersing agent to maintain the magnetic particles as a dispersion
in the composition 20, by adjusting the pH, by application of the
magnetic field, and/or by the inclusion of a chemical agent to
enhance reactivity of the surface functional groups.
[0045] Referring to FIGS. 2 and 2-A, a magnetic field (arrows
<.apprxeq.) is applied to attract (or repel)
contaminant-conjugated magnetic particles 34 (and non-conjugated,
magnetic particles 22) at a low force to draw and disengage the
contaminants 30 from the surface 28 of the substrate 16 and
structures 26. The interaction of the magnetic particles 22 with
the contaminants 30 and movement of magnetic particles 22 in
response to the magnetic field(s) provides removal of contaminants
30 without damage to the device structures (e.g., lines, etc.) on
the surface 28 of the substrate 16. Devices for magnetic separation
of particles in solution are generally described, for example, in
U.S. Pat. No. 6,562,239 (Foy et al.), U.S. Pat. No. 6,572,778
(Sterman et al.), U.S. Pat. No. 6,689,615 (Murto et al.), U.S. Pat.
No. 7,258,799 (Ras et al.), and Bangs Laboratories, Inc., TechNote
102, Rev. 005, Jan. 6, 2004 (at www.bangslabs.com).
[0046] In any of the described embodiments, the magnetic field
generator 14 can be a permanent magnet, electromagnet (connected to
a power source) or superconducting magnet, and can be composed, for
example, of ferromagnetic or rare earth magnets. An insulator (not
shown) can be positioned between the magnetic field generator 14
and the containment vessel 12 or the substrate 16 to block or
shield the substrate from a magnetic field. In some embodiments,
the magnetic field generator can be incorporated into a containment
vessel, e.g., embedded in a sidewall of the vessel.
[0047] In the embodiment illustrated in FIGS. 1-2A, a magnetic
field generator 14 is positioned along one side of the containment
vessel 12 such that a magnetic field is applied in a single
direction relative to the substrate 16. When the composition 20 is
exposed to a sufficiently high magnetic field from the magnetic
field generator 14, the magnetic particles (both unbound,
non-conjugated magnetic particles 22 and conjugated magnetic
particles 34) will move in response to the magnetic field that is
generated, i.e., attracted toward the magnetic field (arrows
.rarw.) as shown in FIG. 2, or repulsed away. The velocity at which
the contaminant-conjugated magnetic particles 34 are moved can be
varied, for example, by adjusting the strength of the magnetic
field and/or the position of the magnetic field generator 14 with
respect to the substrate 16.
[0048] The magnetic field generator 14 can be positioned relative
to the substrate 16 to apply a magnetic field to draw magnetic
particles 22 in a lateral direction (arrows .rarw..fwdarw.) across
the substrate 16. For example, a magnetic field generator can be
situated at one location as depicted in FIG. 2A, or one or more
magnetic field generators can surround a substrate (partially or
completely) as illustrated in FIGS. 3 and 4. In embodiments of the
invention, a plurality of magnetic field generators (e.g.,
14a.sub.1' to 14a.sub.8' in FIG. 3; 14a.sub.1'', 14a.sub.2'' in
FIG. 4) can be positioned around the substrate at multiple
locations to apply a magnetic field in more than one direction
relative to the substrate. As further illustrated in FIG. 4, in
some embodiments, a magnetic field generator can be situated above
(as shown by magnetic field generator 14b'') and/or below (as shown
by magnetic field generator 14c'') the substrate 16'' to draw
magnetic particles in an upward (.uparw.) or a downward (.dwnarw.)
direction relative to the substrate 16.
[0049] Multiple magnetic field generators can be independently
controlled, for example, using a dedicated power supply in the case
of electromagnets, by the positioning of an insulator to shield one
or more of the magnetic field generators from the substrate, or by
using a field generator control by connecting the magnetic field
generator(s) in communication with a controller comprising a
computer device configured under control of a program to control
the magnetic field, e.g., when the magnets are turned off and
on.
[0050] In embodiments of the invention, a magnetic field can be
applied in a single direction relative to the substrate to draw (or
repel) the magnetic particles including the contaminant-conjugated
magnetic particles, laterally in a single direction, which can
reduce damage to the substrate and/or structures on the
substrate.
[0051] In other embodiments, a magnetic field can be applied in
multiple directions to enhance contact and interaction of magnetic
particles with contaminants and the removal of contaminants from
the substrate. Two or more magnetic field generators can be
activated simultaneously, in succession, in an alternating
sequence, in pairs, or in other combinations or sequences. For
example, referring to FIG. 3, magnetic field generators 14a.sub.1',
14a.sub.2' and 14a.sub.5', 14a.sub.6' on opposing sides of a
substrate 16' can be activated to generate magnetic fields (arrows
.apprxeq.>) to attract and draw magnetic particles 22' in a
lateral direction (arrows .rarw..fwdarw.) to opposite sides of the
substrate 16' and containment vessel 12'.
[0052] In some embodiments, a magnetic field can be applied in a
first direction and then in a second direction. In yet other
embodiments of the invention, the magnetic field can be oscillated,
for example, by pulsing the magnetic field(s), by cyclically or
repeatedly applying and terminating the magnetic field(s) and/or by
increasing and decreasing the strength of the magnetic field(s),
which can cause the magnetic particles and contaminant-conjugated
magnetic particles to move (e.g., rock or oscillate) with a low
force to enhance the interaction of magnetic particles with
contaminants.
[0053] In yet other embodiments, the magnetic field generator(s)
can be movable to vary its position relative to the substrate. For
example, a magnetic field generator 14c'' (FIG. 4) can be first
positioned below a containment vessel 12'' to draw magnetic
particles downward (arrows .dwnarw.) relative to a surface 28'' of
a substrate 16'' then moved to above the substrate 16'' (e.g.,
magnetic field generator 14b'') to draw magnetic particles upward
(arrows .uparw.) relative to the substrate surface, then moved to
one side of the containment vessel 12'' (e.g., 14a'') to draw
magnetic particles in a lateral direction (arrows .rarw.), and/or
to a second position at another side of the containment vessel 12''
(e.g., magnetic field generator 14a.sub.2'') to draw magnetic
particles in a second lateral direction (arrow .fwdarw., or other
combination or sequence.
[0054] The magnetic particles will accumulate in response to the
magnetic field. For example, in the embodiment depicted in FIGS. 2
and 2A, magnetic particles 22 and contaminant-conjugated magnetic
particles 34 will accumulate at the side of the containment vessel
12 in proximity to the magnetic field generator 14. The accumulated
magnetic particles 22 and contaminant-conjugated magnetic particles
34 can then be removed, for example, by terminating the magnetic
field and discharging the liquid composition 20 from the
containment vessel 12, for example, through a discharge outlet 38,
as shown in FIG. 2.
[0055] In some embodiments, the composition 20 including the
magnetic particles 22 and contaminant-conjugated magnetic particles
34 can be passed through the outlet 38 by gravity, optionally by
applying force or a pressure differential (e.g., vacuum or
suction). In other embodiments, as illustrated in FIG. 2, a
magnetic field generator 40 can be positioned at the outlet to
generate a magnetic field to attract and draw the magnetic
particles 22 and contaminant-conjugated magnetic particles 34
toward and into the outlet 38. The apparatus 10 can further include
a collection device 42 for receiving and collecting the magnetic
particles 22 and contaminant-conjugated magnetic particles 34 of
the discharged composition 20. The collection device 42 can be
structured, for example, with a filter 43 that can be positioned
within or proximal to the outlet 38 to isolate and collect the
magnetic particles 22 and contaminant-conjugated magnetic particles
34, for example, a glass fiber filter, porous membrane, paper
filter, woven fabric filter, etc. The magnetic particles 22 and
contaminant-conjugated magnetic particles 34 can also be recovered
from the discharged composition 20 by centrifugation or other known
method.
[0056] In embodiments of the invention, a collected material can
then be processed to separate and recover the magnetic particles 22
from contaminants 30, particulates and other components. In some
embodiments, the magnetic particles 22 can be separated or cleaved
off from the contaminants 30 by an optical, chemical or other
suitable cleavage method. For example, the magnetic particles 22
can be separated from contaminants 30 by applying an appropriate
elution buffer, applying a magnetic field to draw off the magnetic
particles 22, and removing the supernatant containing the
contaminants 30.
[0057] As illustrated in FIG. 5, a rinse water or other aqueous
medium 44 can then be applied (arrows .dwnarw..dwnarw.) to remove
the composition 20, including magnetic particles 22 and/or
contaminant-conjugated magnetic particles 34, from the substrate
16. The aqueous medium 44 can be applied, for example, from a
dispensing device 46 under non-damaging conditions by dispensing,
by aerosol spraying, by megasonic rinsing, etc.
[0058] Referring now to FIG. 6, a post-clean procedure (arrows
.dwnarw..dwnarw.) can then be conducted to apply a cleaning agent
to remove remaining residual material (e.g., remaining composition,
magnetic particles, etc.) from the substrate 16 leaving a cleaned
surface 28. For example, a post-clean can be conducted through the
use of an SC1 clean or DHF clean (e.g., about 500:1 water:HF) in
conjunction with a spray or megasonic system, followed by a water
rinse. Subsequent processing of the substrate 16 and features 26
can then be conducted as desired.
[0059] In another embodiment of a method of the invention
illustrated in FIGS. 7 and 7A, a composition 20''' according to the
invention containing magnetic particles 22''' can be applied to
remove contaminants 30''' from a substrate 16''' having a
non-planar topography, for example, one or more structures 26'''
that project or protrude from the surface 28'''. In some
embodiments, the substrate 16''' can comprise a plurality of
structures 26''' that protrude from the surface 28''' and extend
over the substrate 16''' separated by a channel or recess 48'''.
The structures 26''' can be, for example, a gate runner, wordline,
bit line, conductive line (e.g., conductive metal trace line,
interconnect, etc.), insulative line, spacer line, etc., of a
material (e.g., conductive, semiconductive, insulative, etc.), such
as oxides, nitrides, silicon materials, carbon materials, resists,
metals, metal-containing materials, etc. The substrate 16''' can
comprise a plurality of elements, for example, contacts, bond pads,
ball pads, ball contacts, transistors, isolation structures (e.g.,
shallow trench isolation (STI) structures), etc., that project from
the surface 28''' of the substrate 16''', and, in some embodiments,
can be situated in generally parallel-aligned linear arrays.
[0060] Contaminants 30''' composed of conductive, insulative and/or
semiconductive materials such as oxides, nitrides, silicon
materials, carbon, polymer resist, metals and metal-containing
materials, among others, can remain adhered to the structures 26'''
and/or the surface 28''' of the substrate 16''' as a result of
earlier processing. A composition 20''' can be applied to the
substrate 16''' by delivery from a dispensing device or, as
illustrated, by flowing into the containment vessel 12''' through
an inlet, as shown in FIG. 7.
[0061] In some embodiments, contaminants 30''' can be removed from
the non-planar surface 28''' of the substrate by applying a
composition according to the invention and applying one or more
magnetic fields to draw and remove the contaminant-conjugated
magnetic particles 34''' using a low force in a lateral direction
across the substrate (and/or in an upward or downward direction),
as previously described with respect to FIGS. 1-4.
[0062] In another embodiment of the invention, magnetic field
generators 14a.sub.1''', 14a2''' can be positioned on opposing
sides as shown in FIG. 7A, or on one side of the substrate 16''',
at or about a perpendicular orientation relative to the axis of
line element structures 26'''. Upon the application of a magnetic
field (arrows from one or both magnetic field generators
14a.sub.1''', 14a.sub.2''', the magnetic particles 22''' and
contaminant-conjugated magnetic particles 34''' can be drawn in a
lateral direction (arrows ) within and along the channels 48''' and
relatively parallel to the line element structures 26'''. This
arrangement and application of magnetic field(s) from magnetic
field generators 14a.sub.1''' and/or 14a.sub.2''' in a parallel
direction relative to the axis of elevated structures 26''' (e.g.,
lines) on the surface 28''' of the substrate 16''' can reduce
contact by the magnetic particles 22''' and contaminant-conjugated
magnetic particles 34''' that can result in damage to the
structures 26'''.
[0063] Although specific embodiments have been illustrated and
described herein, it will be appreciated by those of ordinary skill
in the art that any arrangement that is calculated to achieve the
same purpose may be substituted for the specific embodiments shown.
This application is intended to cover any adaptations or variations
that operate according to the principles of this disclosure as
described herein. It is therefore intended that such changes and
modifications be covered by the appended claims and the equivalents
thereof. The disclosures of patents, references and publications
cited in the application are incorporated by reference herein.
* * * * *
References