U.S. patent application number 12/036887 was filed with the patent office on 2008-06-19 for device having contact pad with a conductive layer and a conductive passivation layer.
Invention is credited to Tongbi Jiang, Li Li.
Application Number | 20080142983 12/036887 |
Document ID | / |
Family ID | 22972649 |
Filed Date | 2008-06-19 |
United States Patent
Application |
20080142983 |
Kind Code |
A1 |
Jiang; Tongbi ; et
al. |
June 19, 2008 |
DEVICE HAVING CONTACT PAD WITH A CONDUCTIVE LAYER AND A CONDUCTIVE
PASSIVATION LAYER
Abstract
A method and apparatus is disclosed for sequential processing of
integrated circuits, particularly for conductively passivating a
contact pad with a material which resists formation of resistive
oxides. In particular, a tank is divided into three compartments,
each holding a different solution: a lower compartment and two
upper compartments divided by a barrier, which extends across and
partway down the tank. The solutions have different densities and
therefore separate into different layers. In the illustrated
embodiment, integrated circuits with patterned contact pads are
passed through one of the upper compartments, in which oxide is
removed from the contact pads. Continuing downward into the lower
compartment and laterally beneath the barrier, a protective layer
is selectively formed on the insulating layer surrounding the
contact pads. As the integrated circuits are moved upwardly into
the second upper compartment, a conducting monomer selectively
forms on the contact pads prior to any exposure to air. The
integrated circuits can then be transferred to an ozone chamber
where polymerization results in a conductive passivation layer on
the contact pad.
Inventors: |
Jiang; Tongbi; (Boise,
ID) ; Li; Li; (Meridian, ID) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET, FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Family ID: |
22972649 |
Appl. No.: |
12/036887 |
Filed: |
February 25, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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|
11234000 |
Sep 23, 2005 |
7358185 |
|
|
12036887 |
|
|
|
|
10634134 |
Aug 4, 2003 |
6967164 |
|
|
11234000 |
|
|
|
|
09854292 |
May 9, 2001 |
6630400 |
|
|
10634134 |
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09256548 |
Feb 24, 1999 |
6303500 |
|
|
09854292 |
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Current U.S.
Class: |
257/765 ; 118/75;
257/773; 257/E21.476; 257/E23.01; 257/E23.02; 438/652 |
Current CPC
Class: |
H01L 21/76826 20130101;
H01L 21/288 20130101; H01L 2924/19043 20130101; H01L 24/03
20130101; H01L 2924/01322 20130101; H01L 21/76834 20130101; H01L
2924/01005 20130101; H01L 2924/014 20130101; H01L 21/76838
20130101; H01L 2224/131 20130101; H01L 21/02052 20130101; H01L
21/7685 20130101; H01L 2924/01011 20130101; H01L 2924/01029
20130101; H01L 2224/131 20130101; H01L 2924/19041 20130101; H01L
24/05 20130101; Y10S 134/902 20130101; H01L 2924/01006 20130101;
H01L 2924/01033 20130101; H01L 21/76828 20130101; H01L 2924/01079
20130101; H01L 2924/05042 20130101; H01L 2924/01013 20130101; H01L
2924/01016 20130101; H01L 2924/01014 20130101; H01L 2924/01078
20130101; H01L 2924/014 20130101; H01L 2924/14 20130101; H01L
2224/0401 20130101; H01L 2924/01075 20130101 |
Class at
Publication: |
257/765 ;
257/773; 438/652; 118/75; 257/E23.01; 257/E21.476 |
International
Class: |
H01L 23/48 20060101
H01L023/48; H01L 21/44 20060101 H01L021/44; B05C 11/00 20060101
B05C011/00 |
Claims
1. A contact pad of an integrated circuit die, the contact pad
adapted to provide electrical connection between the integrated
circuit die and an electrical system, the contact pad comprising: a
conductive layer; and a conductive passivation layer directly on
the conductive layer.
2. The contact pad of claim 1, wherein the conductive layer
comprises aluminum.
3. The contact pad of claim 1, wherein the conductive layer
comprises an aluminum alloy formed with copper, silicon, or both
copper and silicon.
4. The contact pad of claim 1, wherein the conductive layer
comprises an aluminum-copper alloy with about 0.5% copper
content.
5. The contact pad of claim 1, wherein the conductive layer
comprises a portion of a conductive line of the integrated circuit
die.
6. The contact pad of claim 1, wherein the contact pad is
integrally connected to a conductive line of the integrated circuit
die, the conductive line comprising a metallic material.
7. The contact pad of claim 6, wherein the metallic material
comprises aluminum, aluminum-silicon eutectic, or aluminum-copper
alloy.
8. The contact pad of claim 1, wherein the contact pad is
integrally connected to a conductive line of the integrated circuit
die, the conductive line comprising polysilicon.
9. The contact pad of claim 1, wherein the contact pad comprises no
intervening oxide material between the conductive layer and the
conductive passivation layer.
10. The contact pad of claim 1, wherein the conductive passivation
layer comprises a conductive polymer material.
11. An integrated circuit die comprising: a substrate; a conductive
line on or within the substrate; and a contact pad electrically
coupled to the conductive line, the contact pad comprising a
conductive layer and a conductive passivation layer directly on the
conductive layer.
12. The integrated circuit die of claim 1, wherein the substrate
comprises a semiconductor layer.
13. The integrated circuit die of claim 12, wherein the
semiconductor layer comprises gallium arsenide or silicon.
14. The integrated circuit die of claim 11, further comprising an
insulating layer comprising a dielectric material, the insulating
layer over the conductive layer and having a hole which exposes a
portion of the conductive layer.
15. The integrated circuit die of claim 14, wherein the dielectric
material comprises silicon dioxide, silicon nitride, or silicon
oxynitride.
16. A method of making an integrated circuit, comprising: providing
a substrate; forming electrical devices on the substrate; immersing
the substrate in a cleaning fluid; and transferring the substrate
from the cleaning fluid to a separate plating fluid while keeping
the substrate immersed in fluid.
17. A method of making an integrated circuit die, comprising:
providing a substrate comprising a metal surface; forming
electrical devices on the substrate; immersing the integrated
circuit die in a container holding a plurality of solutions,
wherein each of said plurality of solutions is in contact with at
least one other of said plurality of solutions, thereby allowing
direct transfer of said integrated circuit die between said
plurality of solutions in said container; exposing the metal
surface to an oxide cleaning solution within the container;
preferentially forming a layer comprising a conducting monomer
after exposing the metal surface to the oxide cleaning solution and
prior to removing the integrated circuit die from the container;
and polymerizing said conducting monomer layer.
18. A contact pad of an integrated circuit die, the contact pad
adapted to provide electrical connection between the integrated
circuit die and an electrical system, the contact pad comprising:
means for conducting electricity from an integrated circuit die to
at least one outside circuit; and means for passivating the
conducting means.
19. The contact pad of claim 18, wherein the conducting means
comprises a conductive layer.
20. The contact pad of claim 18, wherein the passivating means
comprises a conductive passivation layer directly on the conducting
means.
21. An apparatus for sequential in situ cleaning and formation of a
conductive passivation layer on a conductive element in an
integrated circuit, the apparatus comprising: means for cleaning
the integrated circuit; means for forming a protective layer on the
integrated circuit; means for forming a monomer layer on the
integrated circuit; means for separating the cleaning means, the
protective layer forming means, and the monomer layer forming
means, wherein the separating means is positioned to separate the
cleaning means from the monomer layer forming means; and means for
containing the cleaning means, the protective layer forming means,
and the monomer layer forming means, wherein the cleaning means is
above and in contact with the protective layer forming means, and
the monomer layer forming means is above and in contact with the
protective layer forming means, such that the integrated circuit
can be transferred from the cleaning means to the protective layer
forming means, and then to the monomer layer forming means, while
keeping the substrate immersed in fluid.
22. The apparatus of claim 21, wherein the cleaning means comprises
a cleaning solution.
23. The apparatus of claim 21, wherein the protective layer forming
means comprises a siliconizing solution.
24. The apparatus of claim 21, wherein the monomer layer forming
means comprises a plating solution.
25. The apparatus of claim 21, wherein the separating means
comprises a water-tight barrier.
26. The apparatus of claim 21, wherein the containing means
comprises a tank.
Description
REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 11/234,000, filed Sep. 23, 2005, which is a
continuation of U.S. patent application Ser. No. 10/634,134, filed
Aug. 4, 2003, issued as U.S. Pat. No. 6,967,164, which is a
continuation of U.S. patent application Ser. No. 09/854,292, filed
May 9, 2001, issued as U.S. Pat. No. 6,630,400, which is a
continuation of U.S. patent application Ser. No. 09/256,548, filed
Feb. 24, 1999, issued as U.S. Pat. No. 6,303,500. Each of these
applications is incorporated in its entirety by reference
herein
FIELD OF THE INVENTION
[0002] The invention relates generally to contact pads in
integrated circuits, and more particularly to oxide-free bond
pads.
BACKGROUND OF THE INVENTION
[0003] Bond pads are electrical terminals which connect an
integrated circuit die or chip to the electrical system outside of
the chip. The electrical connection is normally made by bonding
electrical leads to the bond pad. The chip can then be connected to
a larger circuit, such as a printed circuit board (PCB), with the
leads making contact with the outside system.
[0004] The bond pads are integrally connected to metal lines or
runners within the die, which are typically formed of a metal such
as aluminum, aluminum-silicon eutectic, aluminum-copper alloys, or
polysilicon. The bond pads themselves are also typically formed of
aluminum or an aluminum alloy, which is highly conductive and
relatively inexpensive. Unfortunately, aluminum or aluminum alloy
readily oxidizes to form aluminum oxide. The aluminum oxide is not
conductive, and it therefore increases the overall resistivity of
the system. Increased resistivity, in turn, leads to slower signal
propagation.
[0005] Conventionally, aluminum oxide is removed with a reducing
agent in several separate steps. The chip is exposed to atmosphere
between steps, and the exposed metal spontaneously oxidizes,
impairing the conductive connection. Even the short exposure
between oxide cleaning and sealing the bond pad results in aluminum
oxide formation between the metal and sealant.
[0006] There is thus a need for a method of avoiding oxide on the
surface of a contact pad.
SUMMARY OF THE INVENTION
[0007] In view of this need, the present invention provides a
method and apparatus for providing conductive passivation on
contact pads, such as bond pads.
[0008] In accordance with one aspect of the invention, a method is
provided for plating a conductive layer in an integrated circuit.
The method includes immersing the integrated circuit in a cleaning
fluid. The integrated circuit is then transferred from the cleaning
fluid to a plating fluid, without exposing the integrated circuit
to air.
[0009] In an illustrative embodiment, such transfer is performed
directly from one liquid phase to another. The cleaning fluid
represents a first liquid phase, preferably an oxide etch bath, and
the second liquid phase forms a protective layer over the
insulating material which surrounds the contact pad. The plating
fluid is in yet a third liquid phase, containing a conducting
monomer in solution. This forms a monomer layer over the conductive
layer, which is later polymerized to form a conductive polymer. The
integrated circuit sequentially moves between the first and second
phases, and between the second and third phases, without passing
through air. As will be understood by the skilled artisan, such an
arrangement enables sealing the underlying conductive layer of the
contact pad, which may be susceptible to oxidation, immediately
after oxide removal. Nether oxide nor other contaminants have the
opportunity to form on the conductive layer between steps, which
would hinder electrical contact between the contact pad and outside
circuits.
[0010] In accordance with another aspect of the invention, an
apparatus is provided for sequential processing with two or more
liquid solutions. The apparatus includes a water-tight tank with an
upper portion and a lower portion. The upper portion is divided
into at least a first side and a second side by a water-tight
barrier. The lower portion is open to and extends beneath both the
first side and the second side.
[0011] This apparatus is particularly useful for the illustrated
process, where one side of the upper portion holds an oxide
cleaning agent (e.g., 1% NaOH, density about 1.0 g/cm.sup.3) and
the other side of the upper portion holds a conducting monomer in
solution (e.g., pyrrole, density less than about 0.99 g/cm.sup.3).
The barrier separates the cleaning solution from the monomer
solution. The lower portion holds a relatively more dense solution
for forming a protective layer (e.g., siliconizing solution,
density about 1.09 g/cm.sup.3), ensuring that the phases are
naturally separated by gravity.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a partial cross-sectional view of partially
fabricated integrated circuit, showing a bond pad covered with an
oxide layer.
[0013] FIG. 2 illustrates the integrated circuit of FIG. 1 after
the oxide layer has been removed, exposing the conductive
layer.
[0014] FIG. 3 illustrates the integrated circuit of FIG. 2 after a
protective layer has been formed on the dielectric layer.
[0015] FIG. 4 illustrates the integrated circuit of FIG. 3 after
formation of a passivation precursor on the conductive layer.
[0016] FIG. 5 illustrates the integrated circuit of FIG. 4 after
treatment of the precursor layer, forming a conductive passivation
layer on the conductive layer.
[0017] FIG. 6 is a process flow diagram showing the process steps
and movement of the integrated circuit while forming the conductive
passivation on the bond pad.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0018] The present application describes a method of cleaning and
passivating a conductive surface with a conductive layer without
exposing the surface to air between the process steps. While
illustrated in the context of conductive passivation of aluminum
bond pads, the skilled artisan will recognize many other
applications for the methods and structures disclosed herein. In
particular, contact pads formed of other metals, while less
susceptible to oxidation, will also benefit from the conductive
passivation of the illustrated embodiment. Furthermore, sequential
cleaning and conductive passivation, without allowing re-oxidation,
will have utility for a great many applications beyond integrated
bond pads.
[0019] Initially, an integrated circuit is formed on a substrate.
The substrate includes a semiconductor layer or wafer, such as
silicon or gallium arsenide, in which active or operable portions
of electrical devices are formed. Through a series of mask, etch
and deposition steps, electrical devices such as transistors,
capacitors and resistors are integrally formed and interconnected
by metal layers separated by insulating layers. Typically, a
plurality of chips or dies are formed in a single wafer.
[0020] Upper levels of the metal interconnections are terminated in
integral bond pads for forming connections between the chips or
dies and outside circuits. The bond pads comprise conductive layers
surrounded by insulating layers. Similar contact pads, typically
referred to as "probe pads," are often formed in lower layers for
testing circuits at intermediate steps in fabrication.
[0021] The conductive layers can be metal, silicide, or other
suitable conductive material. Some examples of conductive layers
include, but are not limited to, copper, gold, aluminum, doped
silicon and the like. Mixtures of metals are also suitable for
forming a conducting layer. Some suitable mixtures of metals
include, but are not limited to, aluminum alloys formed with copper
and/or silicon.
[0022] FIG. 1 illustrates such a conductive layer 10 formed and
patterned into a bond pad over metal layers and devices formed in a
substrate (not shown). A window 15 is formed in a surrounding
insulating layer 20 to expose the conductive layer 10. The
illustrated insulating layer 20 is a dielectric material suitable
for final passivation, such as silicon dioxide, silicon nitride or
silicon oxynitride. In the illustrated embodiment, the insulating
layer comprises silicon nitride (Si.sub.3N.sub.4), which is known
to have good moisture barrier qualities.
[0023] The conductive layer 10 of the illustrated embodiment
comprises aluminum, and particularly aluminum mixed with copper. In
a preferred embodiment, the conductive layer comprises aluminum
with about 0.5% copper content. The illustrated conductive layer 10
is particularly susceptible to oxidation. An oxide layer 30 thus
naturally forms on the surface of the conductive layer 10, as shown
in FIG. 1, upon exposure to air, such as after deposition of the
conductive layer 10. The illustrated oxide layer 30 comprises
aluminum oxide, which prevents or hinders electrical conduction
from the conductive layer 10 to contacts formed thereupon, such as
wire bonds or solder balls. It is therefore preferred to remove the
oxide layer 10 before attaching a conductive contact (e.g., pins,
wires, solder balls, etc.) to the bond pad.
[0024] Traditionally, removal of the oxide layer 30 and formation
of a contact comprise several process steps, and even brief
exposure to air between steps results in re-oxidation and/or other
contamination of the conductive layer 10. For the illustrated
conductive layer 10, oxidation of the aluminum in the presence of
air is almost instantaneous. The embodiments of the present
invention provide a method of removing the oxide layer 30 and
passivating the exposed conductive layer 10 with a conductive
polymer in situ, without exposing the conductive layer 10 to air or
other contaminants.
[0025] The oxide layer 30 can be removed in a variety of ways.
Typically, the oxide layer 30 is exposed to a reducing agent. In
the illustrated embodiment, the substrate is immersed in a dilute
base solution (e.g., between about 8 pH and 14 pH). An exemplary
solution for removing the oxide layer comprises approximately 1%
NaOH in water. The bath is preferably between about 20.degree. C.
and 50.degree. C., more preferably between about 20.degree. C. and
30.degree. C. The wafer is preferably immersed in the solution for
between about 0.2 and 30 minutes, more preferably between about 1
and 10 minutes.
[0026] FIG. 2 shows the integrated circuit after removal of the
metal oxide 30 from the top of the conductive layer 10. Removal of
the metal oxide 30 exposes the conductive layer 10, as shown. If
exposed to air, the metal in the conductive layer 10 would
spontaneously reoxidize, forming a new metal oxide layer. In
accordance with the preferred method, however, the conductive layer
10 is not exposed to air or other contaminants after removal of the
oxide 30, as will be apparent from FIG. 6 and the accompanying
text.
[0027] With reference to FIG. 3, a protective layer 40 is then
formed on the insulating layer 20. The protective layer 40 is
selectively formed on the insulating layer 20 without forming on
the exposed conductive layer 10. In the illustrated embodiment,
such selectivity is accomplished by immersing the integrated
circuit in a siliconizing agent. The siliconizing agent can
comprise a wide variety of compounds. An exemplary siliconizing
agent is dichloro-octamethyl-tetrasiloxane, commercially available
from SurfaSil.TM. of Rockville, Ill.
[0028] Chlorine ions in the preferred siliconizing agent are
attracted to silanol groups on the surface of the preferred silicon
nitride insulating layer 20, essentially forming a monolayer of the
siliconizing agent. The siliconizing agent however, does not bond
to the metal in the conductive layer 10. The siliconizing agent
also has the advantage of continuing to clean the surface of the
conductive layer 10. Moreover, exposed methyl tails of the
illustrated protective layer 10 are hydrophobic, which facilitates
later selective formation of the conductive passivation, as will be
understood better from the discussion below.
[0029] With reference to FIG. 4, a passivation precursor layer 50
is then deposited onto the exposed surface of the conductive layer
10. The illustrated precursor layer 50 comprises a conducting
monomer, and particularly pyrrole (C.sub.4H.sub.5N), though other
monomers such as acetylene or aniline can also be used. The pyrrole
does not deposit onto the surface of the dielectric layer 20 due to
the intervening protective layer 40. In particular, the hydrophobic
upper surface of the protective layer 40 prevents pyrrole from
depositing on the nitride 20, while hydrophilic interactions cause
deposition on the conductive layer 10.
[0030] With reference to FIG. 5, the precursor layer 50 is then
treated to result in a conductive passivation layer 60 directly on
the surface of the conductive layer 10, with no intervening oxide.
In the illustrated embodiment, such treatment comprises
polymerizing the monomer of the preferred precursor layer 50,
leaving a conductive polymer in its place. As will be readily
appreciated by the skilled artisan, polymerization of the preferred
precursor can be accomplished by exposure to an oxidation agent,
such as ozone or permanganate.
[0031] As also shown in FIG. 5, the protective layer 40 can be
removed at this point. The illustrated protective layer 40 can be
removed by application of heat, which evaporates the monolayer on
the surface of the insulating layer 20. The flash point for
evaporation of dichloro-octamethyl-tetrasiloxane is about
78.degree. F.
[0032] The resulting polymer 60 is non-oxidizing and therefore
passivates the surface of the conductive layer 10, completing the
electroless bond pad plating. At the same time, the conductive
polymer 60 serves to provide a conductive surface to which wires,
pins or solder balls can be attached prior to die encapsulation.
The bond pad can be thereby electrically connected to outside
circuitry, such as the motherboard of a personal computer.
[0033] FIG. 6 schematically illustrates a preferred process and
apparatus for forming conductive passivation for integrated contact
pads. For simplicity, reference numeral 70 will be utilized to
refer to an integrated circuit in which the contact pad is
integrally formed. The described process begins after the
integrated circuit 70 has been fabricated to the point of having
windows opened in an insulating layer to expose an underlying
conductive layer. The conductive layer has preferably already been
patterned into a contact pad, as shown and discussed with respect
to FIG. 1, though such patterning may also be conducted after
forming the conductive passivation of the present invention. As
also discussed above, the illustrated conductive layer 10 includes
metal, particularly aluminum, and has a resistive oxide 30 formed
thereover.
[0034] It will be understood that the integrated circuit 70 may be
an individual die, or it may represent a wafer with a plurality of
dies prior to separation. In either case, the process is most
efficiently performed simultaneously on a plurality of dies or
wafers in a boat or other carrier.
[0035] Both the process flow and the physical movement of the
integrated circuit are illustrated in FIG. 6 by a path 72. The
integrated circuit 70 is lowered into a water-tight tank or
container 75, which holds a plurality of treatment phases. The
container 75 is preferably formed of a robust material which can
withstand the chemicals in each of the treatment phases, and is
preferably made of or lined with Teflon.TM.. Movement through the
phases is preferably accomplished by known robotic mechanisms.
[0036] A water-tight barrier 80 divides the container 75 into at
least two compartments, and preferably greater than two, each
holding a different treatment phase. Preferably, the phases are
liquid solutions which are immiscible, differ in density, and are
arranged for sequential processing of the integrated circuit 70.
Immiscible solutions, as that term is employed herein, refers to
solutions which do not dissolve in one another. Aqueous solutions,
for example, tend to be immiscible with solutions having organic
solvents, although many other solutions are also immiscible. It
will be apparent to the skilled artisan, in view of the present
disclosure, that immiscible gaseous phases of differing densities,
devoid of intermediate contaminating media, can also be
arranged.
[0037] In the illustrated embodiment, the container 75 and barrier
80 define three compartments. A first compartment 85, in the upper
portion of the container on a first side of the barrier 80, holds a
cleaning agent for cleaning the surface of the contact pad. A
second compartment 90, below the first compartment 85 and extending
below the barrier 80, holds a solution for selectively forming a
protective layer over the insulating layer surrounding the contact
pad. A third compartment 95, extending above the second compartment
on a second side of the barrier 80, holds a third solution for
selectively forming a precursor layer on the contact pad.
Desirably, the third compartment leads to a chamber in which the
precursor layer can be treated to form the conductive passivation
for the contact pad.
[0038] It will be understood that, in other arrangements, the
protective layer may be unnecessary. For example, some precursor
materials or final conductive passivation materials can be formed
on the contact pad selectively without forming on the surrounding
insulating material. Furthermore, a precursor layer need not be
employed where the conductive passivation material can be formed
directly, without curing or polymerizing treatments.
[0039] Returning to the illustrated embodiment, the preferred
cleaning agent in the first compartment 85 comprises an oxide
etchant to clean the metal oxide from the conductive layer and
expose the underlying conductive layer. In other arrangements, the
cleaning agent may remove other contaminants, such as carbon or
sulfur. As discussed above, aluminum oxide is preferably removed by
a reducing agent, and in the preferred embodiment the first
compartment 85 holds a dilute base solution such as 1% aqueous
NaOH, which has a density of about 1.0 g/cm. The integrated circuit
70 is lowered into first compartment 85, cleaning the oxide from
the surface of the conductive layer. It will be understood that the
term "lowered" is meant in encompass movement of the container 75
relative to a stationary integrated circuit 70.
[0040] The integrated circuit 70 is further lowered to the second
compartment 90, where the second solution selectively forms a
protective layer on the insulating material surrounding the contact
pad. In the preferred embodiment, the surrounding insulating
material comprises silicon nitride, and the second solution
comprises a siliconizing agent. The preferred siliconizing agent
forms the protective layer with a hydrophobic upper surface, while
continuing to clean the metal of the contact pad.
[0041] The preferred solution (dichloro-octamethyl-tetrasiloxane,
commercially available under from SurfaSil.TM. of Rockville, Ill.)
is an organic solution having a density of about 1.09 g/cm.sup.3.
The second solution does not mix with the overlying aqueous NaOH in
the first compartment 85, and naturally rests below the aqueous
NaOH, and no physical barrier or intermediate chamber is required
to separate the phases. The integrated circuit 70 thus passes from
a first phase in the first compartment 85 to a second phase in the
second compartment 90, without exposure to air or other
contaminants.
[0042] After moving laterally through the illustrated second
compartment 90, the integrated circuit 70 is then moved upwardly
into the third compartment 95. In this phase, the preferred
precursor layer is formed on the cleaned conductive layer of the
contact pad. As described above, the solution in the third
compartment 95 comprises a conducting monomer to be later treated
to form a conductive polymer. The monomer deposits on the
conductive layer through hydrophilic interactions, while the
protective layer over the surrounding insulating material prevents
monomer deposition thereover.
[0043] The preferred monomer comprises pyrrole, having a density of
less than about 0.99 g/cm.sup.3. Accordingly, the pyrrole
preferably floats above the preferred siliconizing agent in the
underlying second compartment 90. As with the transfer from the
first compartment 85 to the second compartment 90, the integrated
circuit 70 need not pass through intermediate contaminating media,
such as air, prior to forming the precursor layer.
[0044] Note that, in the illustrated embodiment, the phase in the
third compartment 95 need not be immiscible with or of a different
density than the phase in the first compartment 85, since the
barrier 80 physically separates these phases. To ensure physical
separation of the cleaning solution in the first compartment 85
from the monomer solution in the third compartment 95, the
siliconizing agent in the lower compartment 90 preferably overfills
the lower compartment 90 and extends into each of the upper
compartments 85, 95, as illustrated.
[0045] As illustrated, the integrated circuit 70 is then raised out
of the third compartment 95 into a fourth phase, where the
precursor layer is treated to form the conductive passivation. As
discussed above, the illustrated treatment comprises polymerization
of the conducting monomer, and the preferred fourth phase comprises
an ozone chamber. Desirably, heat treatment is also applied, which
serves to evaporate the illustrated protective layer from over the
surrounding insulating material.
[0046] Various modifications of the embodiment of FIG. 6 may be
made without departing from the spirit of the invention. For
example, the density of the phases can be reversed, such that the
densities of the cleaning solution and the conducting monomer can
be greater than the density of the solution forming the protective
layer.
[0047] It will be understood that the integrated circuit 70 can
pass through intermediate media prior to the polymerization or
evaporation steps, if desired. Moreover, the integrated circuit may
be passed through intermediate phases between the first and second
or second and third phases, though such intermediate phases are
preferably devoid of oxidizing or other contaminants. For example,
an intermediate liquid phase can be added between the cleaning
agent phase and the phase in which the protective layer is formed.
Such an intermediate phase could perform additional cleaning of the
conductive layer surface without exposing the same to air or other
contaminants.
[0048] Though described in terms of certain preferred embodiments,
the skilled artisan will readily appreciate that various
modifications and alterations may be made to the described
processes and structures, without departing from the scope and
spirit of the invention. Accordingly, the invention is not meant to
be limited to the embodiments disclosed herein, but should rather
be defined by reference to the appended claims.
* * * * *