U.S. patent application number 13/043407 was filed with the patent office on 2011-06-30 for apparatus and method for depositing and planarizing thin films of semiconductor wafers.
This patent application is currently assigned to Lam Research Corp.. Invention is credited to John Boyd, John M. de Larios, Yezdi N. Dordi, Mike Ravkin, Fred C. Redeker.
Application Number | 20110155563 13/043407 |
Document ID | / |
Family ID | 34062291 |
Filed Date | 2011-06-30 |
United States Patent
Application |
20110155563 |
Kind Code |
A1 |
Ravkin; Mike ; et
al. |
June 30, 2011 |
APPARATUS AND METHOD FOR DEPOSITING AND PLANARIZING THIN FILMS OF
SEMICONDUCTOR WAFERS
Abstract
An electroplating apparatus for depositing a metallic layer on a
surface of a wafer is provided. In one example, a proximity head
capable of being electrically charged as an anode is placed in
close proximity to the surface of the wafer. A plating fluid is
provided between the wafer and the proximity head to create
localized metallic plating.
Inventors: |
Ravkin; Mike; (Sunnyvale,
CA) ; Boyd; John; (Atascadero, CA) ; Dordi;
Yezdi N.; (Palo Alto, CA) ; Redeker; Fred C.;
(Fremont, CA) ; de Larios; John M.; (Palo Alto,
CA) |
Assignee: |
Lam Research Corp.
Fremont
CA
|
Family ID: |
34062291 |
Appl. No.: |
13/043407 |
Filed: |
March 8, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11494997 |
Jul 28, 2006 |
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13043407 |
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10607611 |
Jun 27, 2003 |
7153400 |
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11494997 |
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10330843 |
Dec 24, 2002 |
7198055 |
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10607611 |
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10261839 |
Sep 30, 2002 |
7234477 |
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10330843 |
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Current U.S.
Class: |
204/224R |
Current CPC
Class: |
C25D 17/001 20130101;
C25D 17/10 20130101; C25D 5/026 20130101; H01L 21/2885 20130101;
C25D 7/123 20130101; H01L 21/67034 20130101; H01L 21/67028
20130101; H01L 21/67051 20130101; C25D 5/22 20130101 |
Class at
Publication: |
204/224.R |
International
Class: |
C25D 17/10 20060101
C25D017/10 |
Claims
1. An electroplating apparatus for electroplating a surface of a
wafer, the surface of the wafer capable of being electrically
charged as a cathode, comprising: a proximity head capable of being
electrically charged as an anode, the proximity head having a
plurality of inputs and a plurality of outputs, and when the
proximity head is placed close to, but at a separation from the
surface of the wafer, each of the plurality of inputs is capable of
delivering a fluid to the surface of the wafer and each of the
plurality of outputs is capable of removing the fluids from the
surface of the wafer to define a controlled meniscus between the
proximity head and the surface of the wafer, the delivery and
removal of fluids to and from the surface of the wafer enabling a
localized metallic plating when the wafer and proximity head are
charged and contact is made to an edge exclusion region of the
wafer, and the localized metallic plating facilitated at a location
of the controlled meniscus, and the controlled meniscus being
capable of movement when either the proximity head or the wafer are
moved; and an eddy current sensor integrated into the proximity
head for end pointing the localized metallic plating over a region
of the wafer, the eddy current sensor defined in the proximity head
and proximate to a surface of the proximity head that is defined to
face the surface of the wafer when present; wherein the wafer is
electrically charged as the cathode by way of a mechanical contact
to an edge exclusion region of the wafer through a negative bias
power supply.
2. An electroplating apparatus for electroplating a surface of a
wafer as recited in claim 1, wherein the proximity head is
electrically charged as the anode through electrical contact with a
positive bias voltage supply.
3. An electroplating apparatus for electroplating a surface of a
wafer as recited in claim 1, wherein each of the plurality of
inputs on the proximity head are defined as one of circular
conduits, annular rings, and discrete conduits.
4. An electroplating apparatus for electroplating a surface of a
wafer as recited in claim 1, wherein the fluid is defined by one or
more fluids and the fluids are selected from the group comprised of
isopropyl alcohol (IPA), electrolytic solution, a plating chemistry
that enables metallic plating, and an abrasive-free reactive
chemical.
5. An electroplating apparatus for electroplating a surface of a
wafer as recited in claim 5, wherein the plating chemistry is
defined by an aqueous solution for depositing metals including one
of a copper material, a nickel material, a thallium material, a
tantalum material, a titanium material, a tungsten material, a
cobalt material, an alloy material, and a composite metallic
material.
6. An electroplating apparatus for electroplating a surface of a
wafer as recited in claim 1, wherein each of the plurality of
outputs on the proximity head are defined as one of circular
conduits, annular rings, and discrete conduits.
7. An electroplating apparatus for electroplating a surface of a
wafer as recited in claim 1, wherein the localized metallic
plating, confines a volume of the fluid within an area beneath the
proximity head, the area being less than an entirety of the wafer
surface.
8. An electroplating apparatus for electroplating a surface of a
wafer, the surface of the wafer capable of being electrically
charged as a cathode, comprising: a proximity head capable of being
electrically charged as an anode, the proximity head having a
plurality of inputs and a plurality of outputs, and when the
proximity head is placed close to, but at a separation from the
surface of the wafer, each of the plurality of inputs is capable of
delivering a fluid to the surface of the wafer, and each of the
plurality of outputs is capable of removing the fluids from the
surface of the wafer to define a controlled meniscus between the
proximity head and the surface of the wafer, the delivery and
removal of fluids to and from the surface of the wafer enabling a
localized metallic plating when the wafer and proximity head are
charged and contact is made to an edge exclusion region of the
wafer, and the localized metallic plating facilitated at a location
of the controlled meniscus, and the controlled meniscus being
capable of movement when either the proximity head or the wafer are
moved; and an eddy current sensor integrated into the proximity
head for end pointing the localized metallic plating over a region
of the wafer, the eddy current sensor defined in the proximity head
and proximate to a surface of the proximity head that is defined to
face the surface of the wafer when present, the eddy current sensor
positioned at about a center location of the proximity head; a
mechanical contact electrically chargeable as a cathode is defined
to contact an edge exclusion region of the wafer when present, the
mechanical contact being coupled to a negative bias power supply,
and the proximity head is electrically charged as the anode through
electrical contact with a positive bias voltage supply.
9. An electroplating apparatus for electroplating a surface of a
wafer as recited in claim 8, wherein each of the plurality of
inputs on the proximity head are defined as one of circular
conduits, annular rings, and discrete conduits.
10. An electroplating apparatus for electroplating a surface of a
wafer as recited in claim 8, wherein the fluid is defined by one or
more fluids and the fluids are selected from the group comprised of
isopropyl alcohol (IPA), electrolytic solution, a plating chemistry
that enables metallic plating, and an abrasive-free reactive
chemical.
11. An electroplating apparatus for electroplating a surface of a
wafer as recited in claim 10, wherein the plating chemistry is
defined by an aqueous solution for depositing metals including one
of a copper material, a nickel material, a thallium material, a
tantalum material, a titanium material, a tungsten material, a
cobalt material, an alloy material, and a composite metallic
material.
12. An electroplating apparatus for electroplating a surface of a
wafer as recited in claim 8, wherein each of the plurality of
outputs on the proximity head are defined as one of circular
conduits, annular rings, and discrete conduits.
13. An electroplating apparatus for electroplating a surface of a
wafer as recited in claim 8, wherein the eddy current sensor is
defined between two inputs.
14. An electroplating apparatus for electroplating a surface of a
wafer as recited in claim 8, wherein the localized metallic
plating, confines a volume of the fluid within an area beneath the
proximity head, the area being less than an entirety of the wafer
surface.
Description
CLAIM OF PRIORITY
[0001] This application is a continuation application and claims
priority under 35 U.S.C. .sctn.120 priority from co-pending U.S.
patent application Ser. No. 11/494,997 filed on Jun. 28, 2006 and
entitled "Apparatus and Method for Depositing and Planarizing Thin
Films of Semiconductor Wafers," which in turn is a continuation and
claims 35 U.S.C. .sctn.120 priority from U.S. Pat. No. 7,153,400
issued on Dec. 26, 2006 and entitled "Apparatus and Method for
Depositing and Planarizing Thin Films of Semiconductor Wafers," and
both are incorporated herein by reference.
[0002] This application is further a continuation-in-part and
claims 35 U.S.C. .sctn.120 priority from U.S. Pat. No. 7,198,055
issued on Apr. 3, 2007 and entitled "Meniscus, Vacuum, IPA Vapor,
Drying Manifold," which is a continuation-in-part of U.S. Pat. No.
7,234,477, issued on Jun. 26, 2007 and entitled "Method and
Apparatus for Drying Semiconductor Wafer Surfaces Using a Plurality
of Inlets and Outlets Held in Close Proximity to the Wafer
Surfaces," both of which are incorporated herein by reference in
their entirety.
BACKGROUND OF THE INVENTION
[0003] 1. Field of the Invention
[0004] The present invention relates to semiconductor wafer
deposition and planarization and, more particularly, to apparatuses
and techniques for more effectively depositing thin films using
localized deposition and for enabling localized planarization.
[0005] 2. Description of the Related Art
[0006] Electroplating is a well-established deposition technology.
In the semiconductor fabrication arts, electroplating is typically
performed in a single-wafer processor, with the wafer immersed in
an electrolyte. During electroplating, the wafer is typically held
in a wafer holder, at a negative, or ground potential, with respect
to a positively charged plate (also immersed in the electrolyte)
which acts as an anode. To form a copper layer, for example, the
electrolyte is typically between about 0.3M and about 0.85M
CuSO.sub.4, pH between about 0 and about 2 (adjusted by H2SO4),
with trace levels (in ppm concentrations) of proprietary organic
additives as well as Cl.sup.- to enhance the deposit quality.
During the plating process the wafer is typically rotated to
facilitate uniform plating. After a sufficient film thickness has
been achieved during the plating process, the wafer is moved from
the plating chamber to another chamber where it is rinsed in
de-ionized (DI) water, to remove residual electrolyte from the
wafer surface. Next the wafer is subjected to additional wet
processing, to remove unwanted copper from the backside and bevel
edge, and then another DI water rinse removes wet processing
chemical residues. Then the wafer is dried and annealed before it
is ready for the chemical mechanical planarization (CMP)
operation.
[0007] Unlike vacuum processing of wafers, each "wet" processing
step during wafer processing today is followed by an overhead step
of a DI water rinse. Due to electrolyte dilution concerns and
increased hardware design complexity, DI water rinsing is typically
not done within the plating chamber. Today, approximately fifty
percent of the wet processing stations on a wafer plating tool are
dedicated to plating, having a significant negative impact on wafer
throughput and increasing processing cost. In addition, to enable
direct copper plating on the barrier layer, minimizing time between
surface activation and plating is critical. The additional time, to
rinse after surface activation and to transport the wafer to the
plating module, significantly limits the effectiveness of the
surface activation step. What is needed is a way of eliminating DI
water rinses between wet processing steps.
[0008] During the plating process, the wafer acts as a cathode,
which requires that the power supply be electrically connected to
the wafer. Typically, numerous discrete contacts on the wafer
holder connect the wafer holder electrically to the edge of the
wafer. The current utilized to electroplate the wafers is provided
through these contacts. Plating current must be evenly distributed
around the perimeter of the wafer to provide uniform deposition.
Maintaining consistent contact resistance with the wafer, through
the resistive seed layer, is critical for uniform deposition.
Therefore, in an effort to provide uniform deposition, cleanliness
of the contacts is preferred. In some cases, cleaning of the
contacts requires additional steps further limiting the
productivity of the plating operation.
[0009] Another challenge in copper electroplating is a bipolar
effect, observed when the contact resistance is very high. This
effect induces etching of the copper seed layer directly under the
contacts, thereby severing as the electrical contact between the
wafer and the power supply during electroplating. Prior art
approaches have attempted to resolve this issue by sealing the
contacts from the electrolyte, thereby preventing plating on the
contacts and eliminating the bipolar effect. Unfortunately, seals
are not perfect and contacts become contaminated and current
distribution in the contacts along the wafer periphery results in
non-uniform plating. Consequently, contact resistance must be
controlled by some other way of active monitoring during the
plating process.
[0010] Additional adverse physical challenges occur when applying
the contacts to the surface of the wafer. While the contacts are
typically placed in the exclusion area (e.g., a 1-3 mm outer region
of the wafer) of the wafer, some amount of force must be applied to
maintain consistent electrical contact with the wafer. Application
of such force can, in some cases cause defects on the wafer due to
mechanical stresses on certain materials, such as porous low-k
dielectric films.
[0011] As feature dimensions on semiconductor wafers continue to
shrink, the copper seed layer thickness is also expected to
decrease, from approximately 1000 angstroms today to less than
about 400 angstroms. Thickness reduction of the seed layer is
necessary to ensure a reasonable sized opening at the top of the
features so as to enable void free gap fill during the copper
electroplating process. Since the role of the seed layer is to
distribute the plating current over the entire wafer during
electroplating, a thinner more resistive seed layer introduces a
significant challenge in chambers designed for uniform plating near
contacts on the wafer periphery. Known as the terminal effect, this
effect is more pronounced on larger wafers, such as today's 300 mm
wafers.
[0012] What is needed therefore, is an electroplating system that
limits rinsing processes and provides sufficient electrical contact
without applying excessive surface force while producing uniform
electroplating on wafers with little or no seed layer.
SUMMARY OF THE INVENTION
[0013] Broadly speaking, the present invention is an apparatus that
provides local electroplating using a meniscus based plating
process. In the claimed invention, the plating and planarization
process proceeds on either the entire wafer surface, or in the case
of sub-aperture plating, a plating head of smaller size than the
wafer scans the wafer and provides localized plating.
[0014] It should be appreciated that the present invention can be
implemented in numerous ways, including as a process, an apparatus,
a system, a device or a method. Several inventive embodiments of
the present invention are described below.
[0015] In one embodiment, an electroplating apparatus for
electroplating a surface of a wafer is provided. The surface of the
wafer is capable of being electrically charged as a cathode. A
proximity head capable of being electrically charged as an anode is
included. The proximity head has a plurality of inputs and a
plurality of outputs, and when the proximity head is placed close
to the surface of the wafer, each of the plurality of inputs is
capable of delivering a fluid to the surface of the wafer and each
of the plurality of outputs is capable of removing the fluids from
the surface of the wafer. The delivery and removal of fluids to and
from the surface of the wafer enables localized metallic plating
when the wafer and proximity head are charged.
[0016] In another embodiment of the present invention, a first
fluid electrically charged as an anode is generated between a first
proximity head and the surface of the wafer for depositing a
metallic layer. A second fluid electrically charged as a cathode
for enabling a non-consumable chemical reaction over the surface of
the wafer is capable of being generated between a second proximity
head and the surface of the wafer. An electrical connection is
defined between the first fluid and the second fluid when
depositing the metallic layer over the surface of the wafer.
[0017] In yet another embodiment of the present invention, a first
fluid electrically charged as an anode is generated between a first
proximity head and the surface of the wafer for depositing a
metallic layer. A second fluid electrically charged as a cathode
for enabling a non-consumable chemical reaction over the surface of
the wafer is capable of being generated between a second proximity
head and the surface of the wafer. An electrical connection is
defined between the first fluid and the second fluid when
depositing the metallic layer over the surface of the wafer. The
second proximity head is placed in physical contact with the
deposited layer by way of a pad to enable removal of at least a
portion of the metal layer.
[0018] The advantages of the present invention are numerous, most
notably; the embodiments enable localized plating thereby reducing
the active area of plating and improving chemical exchange.
Localized metallic plating reduces the total plating current that
must be distributed over the seed layer, thereby significantly
reducing the resistive seed layer effect and improving deposit
uniformity. In-situ film thickness control and planarization
produce increased productivity by reducing the number of wafer
transfers during processing, and consolidating several applications
on one piece of equipment. Other aspects and advantages of the
present invention will become apparent from the following detailed
description, taken in conjunction with the accompanying drawings,
illustrating by way of example the principles of the present
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The present invention will be readily understood by the
following detailed description in conjunction with the accompanying
drawings. To facilitate this description, like reference numerals
designate like structural elements.
[0020] FIG. 1A illustrates an electroplating apparatus.
[0021] FIG. 1B illustrates an electroplating apparatus shown during
localized metallic plating.
[0022] FIG. 1C provides a bottom view of a proximity head of the
electroplating apparatus.
[0023] FIG. 1D illustrates a prospective view of an electroplating
apparatus equipped with a polishing pad for planarization.
[0024] FIG. 2A illustrates an electroplating apparatus without
mechanical contacts to a wafer.
[0025] FIG. 2B illustrates an electrolytic reaction used by the
electroplating apparatus without mechanical contacts to the wafer
for an electroplating operation.
[0026] FIG. 2C provides a cross sectional view of the
electroplating apparatus without mechanical contacts, showing an
electroplating head and a second head at an interface of the wafer
surface.
[0027] FIG. 2D provides a cross sectional view of the
electroplating apparatus without mechanical contacts, showing the
progression of the deposited layer as a electroplating head and a
second head are applied over the surface of the wafer.
[0028] FIG. 3 provides a cross sectional view of an electroplating
and planarization apparatus, showing the electroplating and
electrolytic heads at the interface with the wafer surface, where
the second head is equipped with a polishing pad for
planarization.
[0029] FIG. 4 is a flowchart for operation of the electroplating
apparatus.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0030] An invention, for methods and apparatuses for electroplating
surfaces of a substrate, is disclosed. In the following
description, numerous specific details are set forth in order to
provide a thorough understanding of the present invention. It will
be understood, however, by one of ordinary skill in the art, that
the present invention may be practiced without some or all of these
specific details. In other instances, well known process operations
have not been described in detail in order not to unnecessarily
obscure the present invention.
[0031] FIG. 1A is a drawing of an exemplary electroplating
apparatus 100 in accordance with one embodiment of the present
invention. A wafer 104 with a seed layer 106 is placed on a support
130. A negative bias power supply 124 charges the wafer 104 to
function as a cathode by way of electrical contact 132. Electrical
contact 132 may be established in the form of a single ring
surrounding the wafer 104, an individual mechanical contact, or a
plurality of individual contacts. In a preferred embodiment, the
electrical contact 132 is applied to a periphery of the wafer 104,
such that contact is made with an edge exclusion region 133. The
edge exclusion region 133 is typically between 1 to 3 mm, for 200
and 300 mm wafers.
[0032] A proximity head 102 charged as an anode by a positive power
supply 122 is suspended above the wafer 104 by an arm 103. The arm
103 can contain a conduit channel 105 for holding one or more
conduits for delivery and removal of fluids utilized in the
electroplating operation. Of course, the conduit channel 105 can be
coupled to the proximity head 102 by any other suitable technique,
such as strapped to the arm 103, etc. In one embodiment, the arm
103 is part of system that facilitates movement of the proximity
head 102 across the wafer 104 in a direction 120.
[0033] Movement of the proximity head 102 can be programmed to scan
the wafer 104 in any number of ways. It should be appreciated that
the system is exemplary, and that any other suitable type of
configuration that would enable movement of the head(s) into close
proximity to the wafer may be utilized. For example, when the wafer
is rotated, the proximity head 102 can start at the center of the
wafer 104 and progressively move linearly to the outer edge. In
another embodiment, the proximity head 102 could navigate a fixed
wafer while circling in an orbital fashion or otherwise move over
the wafer in a fashion that enables processing of all portions of
the wafer. In another embodiment, the proximity head 102 may scan
the wafer using reciprocating movement, move in a linear fashion
from one edge of the wafer to another diametrically opposite edge
of the wafer, or other non-linear movements may be utilized such
as, for example, in a radial motion, in a circular motion, in a
spiral motion, in a zigzag motion, etc. The motion may also be any
suitable specified motion profile as desired by a user. During this
movement, it is desired that the plating operation deliver a
uniform layer of metallic material to the surface of the wafer 104.
Details regarding the functionality of the proximity head 102 and
the plating techniques will be described in greater detail
below.
[0034] Localized metallic plating of the electroplating apparatus
is shown in FIG. 1B. As used herein, localized metallic plating is
meant to define an area beneath the proximity head 102 where a
metallic material is deposited. As shown in the drawings, the area
beneath the proximity head 102 is less than the surface area of the
wafer 104. Thus, localized metallic plating will occur only under
the proximity head 102 at a given point in time. To accomplish more
metallic plating over the surface of the wafer 104, the proximity
head 102 will need to move over another surface area of the wafer
104. In exemplary embodiments, the proximity head 102 will be
coupled to an arm 103 as shown in FIG. 1A. Although any number of
movement patterns can be used to ensure that the desired areas of
the wafer 104 are adequately plated with a particular metallic
material, one way is to move the arm 103 while the wafer 104 is
rotated in a controlled environment. In addition, an arm 103 is
only one exemplary way of moving the proximity head 102. For
instance, the wafer 104 can be moved instead of moving the
proximity head 102.
[0035] Returning to FIG. 1B, the proximity head 102 is placed over
the wafer 104 having a seed layer 106. The seed layer 106 is
optional, however, some embodiments may benefit from having the
seed layer 106 formed thereon before an electroplating operation is
performed. When copper is the material being plated, the seed layer
is typically a thin layer of copper that may be sputtered or
deposited using known techniques. Thereafter, a deposited layer 108
is formed over the seed layer 106 as the proximity head 102
proceeds in a direction 120 across the wafer 104. The deposited
layer 108 is formed by way of an electrochemical reaction
facilitated by an electrolyte 110 contained in a meniscus 116 that
is defined between the proximity head 102 and the seed layer 106.
In an alternative embodiment, the deposited layer 108 can be formed
over a layer that is not a seed layer. An example of such layer may
be a barrier layer or some other layer material.
[0036] FIG. 1C illustrates a generic bottom view of the proximity
head 102, in accordance with one embodiment of the present
invention. The proximity head 102 has a plurality of inputs 112a
and 112b and outputs 112c. The plurality of inputs 112a and 112b,
and the plurality of outputs 112c can be defined by one or more
individual conduits. Each conduit can be machined or form-made
during the manufacture of the proximity head 102 body. In another
embodiment, the plurality of inputs 112a and 112b and outputs 112c
can be defined by annular rings that enable fluids to be
transported in a similar way as would the conduits. The selection
of the particular structure for the plurality of inputs 112a and
112b and outputs 112c, as will be appreciated by those skilled in
the art, can take on many physical forms and shapes. However, it is
important for the selected form or shape to be able to functionally
deliver fluids by way of inputs and remove fluids by way of
outputs. Consequently, in one embodiment, the wafer 104 remains dry
in all regions except for in regions below the proximity head
102.
[0037] As shown, a plating chemistry is supplied by way of the
plurality of inputs 112b that enable localized metallic plating
beneath the proximity head 102. Plating chemistry may be designed
for deposition of copper, however other plating chemistries may be
substituted depending on the particular application (i.e., the type
of metallic material needed). The plating chemistry could be
defined by an aqueous solution for depositing metals, alloys, or
composite metallic materials. In one embodiment, deposited metals
can include, but not limited to, one of a copper material, a nickel
material, a thallium material, a tantalum material, a titanium
material, a tungsten material, a cobalt material, an alloy
material, a composite metallic material, etc.
[0038] The plating chemistry is preferably confined in a meniscus
116 that is defined as a thin layer of fluid lying over the seed
layer 106 beneath the proximity head 102. To further confine and
define the meniscus 116, an isopropyl alcohol (IPA) vapor supplied
by way of the plurality of inputs 112a. The thickness of the
meniscus 116 may vary based on the desired application. In one
example, the thickness of the meniscus may range between about 0.1
mm and about 10 mm. Thus, the proximity head 102 is placed close to
the wafer surface. As used herein, the term "close" defines a
separation between the undersurface of the proximity head 102 and
the surface of the wafer 104, and that separation should be
sufficient to enable the formation of a fluid meniscus. A plurality
of outputs 112c provide vacuum to remove the fluid byproducts of
the plating reaction delivered by the plurality of inputs 112b and
112a.
[0039] In accordance with the invention, the deposited plating
material is formed by a chemical reaction taking place in an
electrolyte 110 supplied by the plurality of inputs 112b. Charging
the proximity head 102 as an anode facilitates the chemical
reaction. In one example, the proximity head is electrically
coupled to a positive bias voltage supply 122. To enable the
plating, a reduction of ions in the chemistry is performed at the
seed layer 106, which is charged as a cathode through the
electrical contact 132 to the negative bias power supply 124. The
chemical reaction causes a metallic layer to be formed as deposited
layer 108. Reaction byproducts and depleted reactant fluids are
removed via the plurality of outputs 112c.
[0040] In another embodiment, an eddy current sensor 114 is
integrated into the proximity head 102. The eddy current sensor 114
is used to determine the presence and thickness of a metallic layer
and to determine when a particular process is complete (e.g., end
pointing). In one embodiment, the thickness of the deposited layer
108 can be sensed during the deposition process. In this manner,
controlled application of metallic materials can be attained. Of
course, other techniques for measuring the thickness of the
deposited layer 108 can be used. For a more detailed description of
the functionality of eddy current sensors, reference can be made to
U.S. patent application Ser. No. 10/186,472, entitled "Integration
of Sensor Based Metrology into Semiconductor Processing Tools",
filed on Jun. 28, 2002, and which is incorporated herein by
reference.
[0041] FIG. 1D illustrates, in accordance with another embodiment,
an electroplating and polishing system 101. In this embodiment, the
proximity head 102 has been equipped with a polishing pad 150,
which assists by planarizing the deposited layer 108. An
abrasive-free reactive chemical supplied by the plurality of inputs
112a and 112b is applied to the polishing pad 150 facilitating a
planarized layer 108'. The polishing pad 150 can be made from any
number of materials, so long as channels in the pad material allow
passage of chemical fluids. In one example, the material can be
porous polymer material, similar to those materials commonly used
in chemical mechanical polishing (CMP) equipment. Other materials
can include, for example, polyurethane compounds, fixed abrasive
materials such as MWR64 or MWR69 from 3M, of Minneapolis Minn.,
etc. In one exemplary operation, a deposition of metallic material
will occur almost simultaneously with the polishing operation that
is facilitated by the polishing pad 150. In another embodiment, the
polishing can be performed using the same proximity head 102 used
to deposit metallic material. In another embodiment, the plating
head and polishing head can be independent workpieces, with the
polishing head trailing the plating head. However, polishing can
occur at a later point in time after deposition is completed. As
can be appreciated, the actual combination of deposition and
polishing operations can be selected depending on the desired
application. By alternating plating and planarization steps or by
performing simultaneous plating and planarization, topographic
variation and undesired overburden material is removed.
[0042] FIG. 2A is an illustration of an exemplary contact-less
electroplating apparatus 200 in accordance with one embodiment of
the present invention. A contact-less electroplating apparatus as
used herein is an apparatus that utilizes electrolytic contact. In
this embodiment, the proximity head 102 is supported in a close
relationship to the wafer 104 by the arm 103 so as to create the
meniscus 116. In this illustration, the seed layer 106 is exposed
to the meniscus 116 while the wafer 104 is held on the support 130,
as described above. The proximity head 102 is charged electrically
to perform as an anode by connecting to the positive power supply
122. Additionally, a second proximity head 102' is supported by an
arm 103, and acts as a facilitator to enable plating by the
proximity head 102, while at the same time not removing material
from the surface of the wafer 104. The arm 103 could be an
extension of the arm holding the proximity head 102 or a separate
arm. In this alternative embodiment, the second proximity head 102'
is charged as a cathode by a negative bias power supply 124. A
meniscus 116' is defined between the second proximity head 102' and
the seed layer 106. The facilitating enabled by the meniscus 116'
is a result of the chemistry that defines the meniscus 116' itself.
Exemplary chemical characteristics of the meniscus 116' are
provided below.
[0043] FIG. 2B illustrates an exemplary electrolytic reaction used
by the contact-less electroplating apparatus 200 for metallic
plating of the deposited layer 108. As previously discussed,
beneath the proximity head 102, the meniscus 116 contains an
electrolytic plating chemistry that is charged by the anode through
the positive bias voltage supply 122.
[0044] The meniscus 116 includes IPA vapor supplied by way of the
plurality of inputs 112a and an electrolyte 110 plating chemistry
supplied by way of the plurality of inputs 112b, as shown in FIG.
2C. In an exemplary embodiment, the plurality of inputs 112b
beneath the proximity head 102 provides an electrolytic solution
whereby the reaction at the surface of the wafer 104 is
Cu.sup.+2+2e.sup.-Cu when the proximity head 102 has been charged a
positive bias voltage supply 122. As this is a REDOX reaction, the
reaction away from the wafer 102 surface is
Cu.fwdarw.Cu.sup.+2+2e.sup.- if a consumable Cu electrode is used,
or 2H.sub.2O--O.sub.2+2e.sup.- if a non-consumable electrode is
used.
[0045] Similarly the second proximity head 102', which serves as
the counter electrode is charged by the negative bias voltage
supply 124. A second meniscus 116' formed beneath the second
proximity head 102' contains electrolytic chemistry. The second
meniscus 116' includes IPA vapor supplied by way of the plurality
of inputs 112a and an electrolyte 110' as supplied through the
plurality of inputs 112b'. In an exemplary embodiment, the
plurality of inputs 112b', provide an electrolytic solution at the
second proximity head 102' whereby the reaction at the surface of
the wafer 104 is of the form Me.sup.X [complex].fwdarw.Me.sup.X+1
[complex]+e.sup.-. In this case, Me can be a metal ion such as Cu,
and x is 2. The complexing agent can be ethylene diamine or ammonia
(NH3). The reaction away from the surface of the wafer 104 can be
the reverse, for example Me.sup.X+1 [complex]+e.sup.-Me.sup.X
[complex]. Other chemistries may provide a similar function; the
chemistry is selected such that the counter electrode chemistry is
at a lower potential than the Cu.fwdarw.Cu.sup.+2+2e.sup.-
potential, thus suppressing the dissolution of Cu at the counter
electrode. Additionally, the electrolyte 110' beneath the second
proximity head 102' can be tailored with other additives, such as
ethylene glycol, to assist in the suppression of Cu dissolution. An
electrical connection 136 is established between the proximity head
102 and the second proximity head 102' through the seed layer 106.
Through this electrical connection 136, the electrolyte 110 and the
electrolyte 110' will be connected completing the REDOX couple and
enabling plating by the proximity head 102. It is important to note
that the second proximity head 102' provides the link to a cathode
(i.e., negative bias voltage supply), and thus, no physical contact
with the wafer 104 is needed. The combination of the proximity head
102 and the second proximity head 102' defines a contact-less
connection to the wafer 104 providing more efficient and uniform
plating of desired metallic materials.
[0046] In another embodiment, an eddy current sensor 114 is
integrated into the proximity head 102. The eddy current sensor 114
is used to determine the presence and thickness of a metallic layer
and to determine when a particular process is complete. In one
embodiment, the thickness of the deposited layer 108 can be sensed
by the eddy current sensor 114 during the deposition process. In
this manner, controlled application of metallic materials can be
attained. FIG. 2D shows the progression as the deposited layer 108
is applied over the surface of the wafer 104, where the second
proximity head 102' is now sitting over the deposited layer
108.
[0047] FIG. 3 illustrates an electroplating and planarizing
apparatus 300 in accordance with one embodiment of the present
invention. The proximity head 102 operates in the manner previously
discussed. The second head 102' provides an electrical path for the
plating operation as described above. Additionally, in this
embodiment the second head 102' is equipped with a polishing pad
150. The polishing pad 150 provides for leveling of the deposited
layer 108 resulting in a planarized layer 108'. The presence of the
polishing pad 150 does not inhibit electrical connectivity 136 of
the second head 102'. An abrasive-free reactive chemical may also
be delivered by way of the plurality of inputs 112a and 112b' to
assist in the leveling process. The planarized layer 108' can be
achieved under the second proximity head 102' simultaneously to the
deposition process beneath the proximity head 102.
[0048] In another embodiment, planarization is accomplished beneath
a third head that operates independently of the first proximity
head 102 and second proximity head 102'. Fluid delivered via
meniscus formation and confinement with IPA can be of an
abrasive-free chemistry that facilitates planarization in concert
with a polishing pad integrated on the head.
[0049] In another embodiment a second proximity head 102' with a
polishing pad 150 is equipped with a scatterometer system 156,
which provides planarization control by way of sensing backscatter
parameters from the topography of the deposited layer 108.
[0050] FIG. 4 is a flow chart diagram that provides an exemplary
method of operation for an electroplating and planarizing apparatus
400 in accordance with the present invention. Given the
electroplating apparatus as described in FIGS. 1-3 above, an
operator must provide a wafer with a seed layer 402. In an
alternative embodiment, the wafer may not have a seed layer yet
formed thereon. The wafer may be transported to the wafer support
in a number of ways. Wafer transport may include a series of manual
or automated robotic movements assisted by mechanical, vacuum,
electrostatic or other ways of holding the wafer. Once the wafer is
placed on the support the operator must select the material desired
for deposition 404. Next the proximity head is placed over the
desired deposition region 406. Placement of the proximity head may
be predefined and facilitated by an automated routine. A voltage
bias may be applied to the proximity head responsible for
deposition 408 at any time prior to deposition including during the
wafer and arm movements or when the fluid is provided through the
plurality of inputs described above. Once the proximity has a bias
voltage applied, the selected fluid inputs and vacuum outputs are
applied 410 beneath the proximity head and the material is
deposited 412.
[0051] In-situ measurement of the deposited layer 414 ensures that
the desired thickness is achieved 416. The proximity head will
remain in its current position until the desired thickness is
achieved by way of the feedback provided from the in-situ
measurement system 414. In one embodiment the measurement system
may be one of the eddy current sensor system described above. Of
course, other thickness measuring techniques may also be used. Once
desired deposition thickness is achieved, the proximity head
responsible for deposition will discontinue fluid delivery and
removal 420. The system will then be setup for the next wafer 422.
In one embodiment the proximity head is removed from the plane of
the wafer while in other embodiments the wafer itself may be
transported while the head remains above the wafer. Once the wafer
is removed another wafer may be placed on the support for
subsequent deposition.
[0052] If the system is equipped with a planarization component as
described in FIG. 1D and FIG. 3 above, the deposited material will
be leveled to assist uniform deposition across the desired area.
In-situ measurement techniques may be used to ensure that the
deposited layer is planarized 424. When the sufficient planarity is
achieved, the fluid delivery and removal system can be discontinued
420 and the system can be setup for the next wafer 422. In one
embodiment, the proximity heads are removed from the plane of the
wafer, while in other embodiments, the wafer itself may be
transported while the heads remain above the wafer. Once the wafer
is removed, another wafer may be placed on the support for
subsequent deposition and planarization.
[0053] While this invention has been described in terms of several
preferred embodiments, it will be appreciated that those skilled in
the art upon reading the preceding specifications and studying the
drawings will realize various alterations, additions, permutations
and equivalents thereof. For instance, the electroplating system
described herein may be utilized on any shape and size of
substrates such as for example, 200 mm wafers, 300 mm wafers, flat
panels, etc. It is therefore intended that the present invention
includes all such alterations, additions, permutations, and
equivalents as fall within the true spirit and scope of the claimed
invention.
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