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Claims  |
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What is claimed is:
1. A method for producing a planarized film on a substrate, said method
comprising:
depositing a film of a material onto the substrate;
generating vacancies in the deposited film of material to increase the
mobility of the atoms of the deposited film;
heating the surface of the deposited film to a sufficient degree to cause a
reflow of the material in the deposited film; and
repeating the above sequence of steps until a layer of material is formed
having a predetermined thickness.
2. The method of claim 1 wherein within the sequence of steps, the vacancy
generating step occurs after the film is deposited, and the surface
heating step occurs after generating vacancies within the deposited film
of material and before depositing any more material.
3. The method of claim 2 further comprising using a metal for said material
so that the deposited film is a deposited metal film.
4. The method of claim 3 wherein the step of heating the surface of the
deposited film is performed using a different mechanism from that used to
perform the vacancy generating step.
5. The method of claim 4 wherein the step of depositing comprises using a
plasma to sputter deposit metal from a target onto the substrate to
produce the metal film.
6. The method of claim 5 wherein the step of depositing further comprises
biasing the target to a negative voltage relative to ground.
7. The method of claim 4 wherein the step of generating vacancies comprises
bombarding the deposited film with ions to produce the vacancies.
8. The method of claim 7 wherein the step of generating vacancies further
comprises using a plasma to generate the ions that produce the vacancies.
9. The method of claim 8 wherein the step of generating vacancies further
comprises biasing the wafer to a negative voltage relative to ground.
10. The method of claim 4 wherein the step of heating the surface of the
deposited film of metal comprises bombarding the surface of the deposited
film of metal with electrons.
11. The method of claim 10 wherein the step of heating the surface of the
deposited film of metal comprises using a plasma to generate the electrons
that bombard the surface of the deposited film of metal.
12. The method of claim 11 wherein the step of heating the surface of the
deposited film of metal further comprises biasing the wafer to a positive
voltage relative to ground.
13. The method of claim 3 further comprising performing the depositing,
generating, and heating steps in a plasma chamber.
14. The method of claim 13 further comprising prior to performing the
depositing, generating, and heating steps, evacuating the plasma chamber,
introducing an inert gas into the plasma chamber, and generating a plasma
in the plasma chamber.
15. The method of claim 14 wherein the inert gas is argon.
16. The method of claim 14 wherein the step of depositing comprises sputter
depositing metal from a target onto the substrate to produce the metal
film.
17. The method of claim 16 wherein the step of depositing further comprises
negatively biasing the target relative to ground.
18. The method of claim 17 wherein the step of generating vacancies
comprises bombarding the deposited film with ions to produce the
vacancies.
19. The method of claim 18 wherein the step of generating vacancies further
comprises using the plasma to generate the ions that produce the
vacancies.
20. The method of claim 19 wherein the step of generating vacancies further
comprises reducing the negative bias on the target and negatively biasing
the wafer relative to ground.
21. The method of claim 20 wherein the step of heating the surface of the
deposited film of metal comprises bombarding the surface of the deposited
film of metal with electrons.
22. The method of claim 21 wherein the step of heating the surface of the
deposited film of metal comprises using the plasma to generate the
electrons that bombard the surface of the deposited film of metal.
23. The method of claim 22 wherein the step of heating the surface of the
deposited film of metal further comprises positively biasing the wafer
relative to ground.
24. The method of claim 14 wherein the metal is selected from a group of
metals consisting of aluminum, copper, gold, tin and compounds thereof.
25. The method of claim 24 wherein the metal is aluminum.
26. A method for producing a planarized metal film on a substrate, said
method comprising:
depositing a film of a metal onto the substrate at a first deposition rate;
next, depositing the film of metal at a second deposition rate that is
lower than the first rate while also commencing bombardment of the
deposited film with ions having an energy that is less than the sputter
threshold energy of the deposited film to produce vacancies in the
deposited film of metal and to thereby increase the mobility of the metal
atoms in the deposited film; and
repeating the above-referenced sequence of depositing at a first deposition
rate step followed by the depositing at a second rate while commencing
bombardment step until a metal layer is formed having a predetermined
thickness.
27. An apparatus for producing a planarized metal layer on a substrate
using a metal target; said apparatus comprising:
a sputter deposition chamber including a source assembly adapted to hold
the target during processing;
a platform within the chamber, said platform adapted to hold the substrate
during processing;
a first power supply generating a first voltage on the target, said first
voltage varying as a function of time;
a second power supply generating a second voltage on the platform, said
second voltage varying as a function of time; and
a control unit controlling both the first and second power supplies, said
control unit programmed to cause the first and second voltages to have
predetermined characteristics, said predetermined characteristics being
that:
during a first period, the first voltage is V.sub.11, said value V.sub.11
being sufficiently negative to sputter the metal target;
during a second period following the first period, the first voltage is
V.sub.12 and the second voltage is V.sub.22, wherein the magnitude of
V.sub.12 is substantially lower than the magnitude of V.sub.11 so as to
produce a significantly reduced target sputtering rate, and wherein
V.sub.22 is sufficiently negative to produce an ion bombardment of the
substrate; and
during a third period following the second period, the first voltage is
V.sub.13 and the second voltage is V.sub.23, wherein the magnitude of
V.sub.13 is substantially lower than the magnitude of V.sub.11 so as to
produce a significantly reduced target sputtering rate, and wherein
V.sub.23 is sufficiently positive to produce an electron bombardment of
the substrate.
28. The apparatus of claim 27 wherein one cycle of operation is defined as
a sequence made up of the first, second and third periods, and wherein the
control unit is programmed to repeat said cycle of operation many times.
29. A method for producing a planarized metal film on a substrate, said
method comprising:
heating the substrate to a predetermined temperature;
depositing a film of a metal onto the substrate, wherein the depositing
step is performed on a heated substrate;
after the film is deposited, bombarding the deposited film with ions to
produce vacancies in the deposited film of metal and to thereby increase
the mobility of the metal atoms in the deposited film, wherein the
bombarding ions have an energy that is less than the sputter threshold
energy of the deposited film; and
repeating the above-referenced sequence of the depositing step followed by
the bombarding step until a metal layer is formed having a predetermined
thickness.
30. The apparatus of claim 27 further comprising:
an RF antenna within said chamber located between the source assembly and
the platform; and
an RF power supply connected to the RF antenna and for providing RF power
to the RF antenna.
31. The method of claim 26, wherein the second deposition rate is
substantially less than the first deposition rate.
32. The method of claim 31, wherein the second deposition rate is less than
about 5% of the first deposition rate.
33. The apparatus of claim 27, wherein the electron bombardment heats the
substrate sufficiently to enhance reflow of the metal layer.
34. The apparatus of claim 27, wherein the bombarding ions have an energy
that is less than the sputter threshold energy of the metal in the metal
layer. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
The invention relates to a method for planarizing metal films that are
deposited on substrates, such as semiconductor wafers which are used for
fabricating integrated circuits.
The semiconductor fabrication of VLSI (Very Large Scale Integration)
circuits generally involves many stages of processing. One or more of
those stages of processing typically involve depositing a metal layer onto
an insulating layer (e.g. SiO.sub.2) that partially covers the surface of
the wafer. The insulating layer, which was produced during earlier stages
of processing, includes an array of contact holes that extend down to
devices that have been formed in the underlying semiconductor wafer. The
metal layer serves, among other things, to provide conductive
interconnects between devices within the integrated circuit. To achieve
good electrical contact to the underlying devices, the deposited metal
layer must fill the contact holes.
As the capabilities of semiconductor fabrication technology advanced,
device size dramatically decreased and, not surprisingly, the dimensions
of the openings to the contact holes also decreased. This created certain
problems for the metalization stage of processing. The contact holes,
which due to their smaller openings now had higher aspect ratios (i.e.,
ratio of depth to width), were more difficult to fill with metal. Because
of the shadowing effect of the walls of the contact holes, the rate of
metal deposition on the bottom of the holes was not as high as on the top
surface of the wafer. In addition, deposited metal tends to accumulate
near the rim of the contact hole at the surface of the insulating layer
thereby further masking the hole from receiving metal during deposition.
The reduced device dimensions and the more complex multi-layered device
structures which came with the advances in technology also produced other
problems. The surface of a deposited metal layer tends to follow the
contours of the insulating layer on which it is deposited. The surface of
the insulating layer, in turn, tends to follow the contours of underlying
structures such as previously deposited metal conducting lines and contact
openings formed in lower insulating layers during earlier stages of
processing. In other words, the surface of the deposited metal layer
contains irregularities, which, if not removed, will interfere with
efforts to fabricate the submicron structures on the wafer.
To address these problems, a planarizing step was introduced into the
fabrication process. Typically, after depositing a metal layer, or even
during the metal deposition step itself, the entire wafer is heated to a
temperature near the flow point of the metal that was or is being
deposited. The higher wafer temperature causes the deposited metal to flow
over the surface of the wafer and into the contact holes. The reflow of
metal on the wafer fills the contact holes and reduces the irregularities
on the surface of the metal. For aluminum, that temperature that is
required to achieve effective reflow is around 525.degree.-530.degree. C.,
for other materials such as copper, it can be much higher (e.g. above 800
.degree. C.).
However, as fabrication technology advances even further and devices
continue to decrease in size, it is also becoming important to reduce the
temperature extremes to which the wafer is exposed and the amount of time
that the wafer spends at elevated temperatures during processing.
Prolonged exposure to high temperatures and the repeated cycling to high
temperatures generate stresses in the wafer. The stresses, in turn, tend
to produce defects which can destroy the extremely small devices. In
addition, long times spent at elevated temperatures during processing also
tend to increase unwanted migration of material within the devices. All of
this can drastically reduce circuit yields on a wafer. Because of this,
integrated circuit manufacturers have begun to impose a tight thermal
budgets on their fabrication processes and on the equipment which they
use. These thermal budgets are sure to become even tighter in the future
as the limits of the technology are pushed even further.
SUMMARY OF THE INVENTION
In general, the invention is an apparatus and method for depositing a
planarized metal layer on a substrate without exposing the substrate to
the high temperatures that are typical of conventional planarization
techniques. The planarization is performed during the deposition process.
The method includes three phases of operation which are repeated in
sequence until the total desired metal thickness is achieved. During a
first phase, a thin metal layer is deposited on the surface of the
substrate. During a second phase, the mobility of the metal atoms is
enhanced by introducing vacancies or holes into the Just-deposited metal
layer. During a third phase, the surface of the mobility-enhanced metal
layer is heated (e.g. by using an electron beam) to reflow the metal,
thereby redistributing it into the contact holes to form interconnects and
also reducing irregularities on the surface of the deposited metal layer.
In general, in one aspect, the invention is a method for producing
planarized metal films on a substrate. The method includes the steps of
depositing a thin film of a metal onto the substrate; generating vacancies
in the deposited thin film of metal to increase the mobility of the metal
atoms of the deposited thin film; after generating vacancies within the
deposited thin film of metal and before depositing any more metal, heating
the surface of the deposited thin film to cause a reflow of the metal in
the thin metal film; and repeating the above sequence of steps until a
metal layer is formed having a predetermined thickness.
Preferred embodiments include the following features. The process is
performed in a plasma chamber using a plasma to sputter deposit metal from
a target onto the substrate to produce the thin metal film. The metal
deposition step involves biasing the target to a negative voltage relative
to ground. The next vacancy generating step involves biasing the wafer to
a negative voltage relative to ground and bombarding the deposited thin
film with plasma-generated ions to produce the vacancies. The heating
phase involves biasing the wafer to a positive voltage relative to ground
and bombarding the surface of the deposited thin film of metal with
electrons.
In general, in another aspect, the invention is a method for producing
planarized metal films on a substrate that includes heating the substrate
to a predetermined temperature; depositing a thin film of a metal onto the
substrate; after depositing the thin film, bombarding the deposited thin
film with ions to produce vacancies in the deposited thin film of metal
and to thereby increase the mobility of the metal atoms in the deposited
thin film; and repeating the above depositing step followed by the
bombarding step until a metal layer is formed having a predetermined
thickness. In this method, the bombarding ions have an energy that is less
than the sputter energy threshold of the deposited thin film.
In general, in yet another aspect, the invention is an apparatus for
producing a planarized metal layer on a substrate from a target made of a
preselected metal. The apparatus includes a sputter deposition chamber
including a source assembly adapted to hold the target during processing,
a platform adapted to hold the substrate during processing, and an RF
antenna located between the source assembly and the platform. There is
also an RF power supply connected to the RF antenna, a first power supply
generating a target voltage that varies as a function of time, a second
power supply generating a platform voltage also varying as a function of
time, and a control unit controlling both the first and second power
supplies. The control unit is programmed to cause the first and second
voltages to have the following characteristics: (1) during a first period,
the first voltage is V.sub.11, where V.sub.11 is sufficiently negative to
sputter the target; (2) during a second period following the first period,
the first voltage is V.sub.12 and the second voltage is V.sub.22, wherein
the magnitude of V.sub.12 is substantially lower than the magnitude of
V.sub.11 so as to produce a significantly reduced target sputtering rate,
and wherein V.sub.22 is Sufficiently negative to produce an ion
bombardment of the substrate; and (3) during a third period following the
second period, the first voltage is V.sub.13 and the second voltage is
V.sub.23, wherein the magnitude of V.sub.13 is substantially lower than
the magnitude of V.sub.11 so as to produce a significantly reduced target
sputtering rate, and wherein V.sub.23 is sufficiently positive to produce
an electron bombardment of the substrate. In this system, one cycle of
operation is defined as a sequence made up of the first, second and third
periods, and the control unit is programmed to repeat that cycle of
operation many times.
The invention eliminates the need for a subsequent reflow or anneal step to
achieve planarization. It also significantly reduces the temperatures to
which the wafer must be exposed during the planarization phase of
processing.
The preferable electron beam heating has the further advantage that it
primarily heats the surface of the deposited metal layer rather than the
underlying structures and substrate. Since the temperature increase is
concentrated at the surface of the recently deposited metal layer, where
it advantageously enhances the reflow of metal, less damage is done to the
rest of the wafer by avoiding thermal stresses associated with cycling to
high temperatures.
Other advantages and features will become apparent from the following
description of the preferred embodiment and from the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a sputtering system in which the invention is carried out;
FIG. 2 illustrates the three phases of the planarization method; and
FIG. 3 shows the power that is supplied to the target and the voltage
waveform that is applied to the wafer/platform (both as a function of
time) to produce the three phases of operation.
DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
1. Hardware
The planarization method which is the subject of this invention can be
carried out in any of a variety of commercially available sputter
deposition systems. For the described embodiment, an Endura 5500 PVD
(physical vapor deposition) system which is manufactured and sold by
Applied materials, Inc., of Santa Clara, Calif. is used. The sputtering
chamber that normally comes with that system is modified to accommodate an
internal RF coil. The principle components of the sputter deposition
system are shown schematically in FIG. 1.
The sputter deposition system includes a chamber body 10, an adapter 12,
and a source assembly 14 containing a sputtering target 16. In the
described embodiment, the sputtering source is a magnetron which includes
a set of magnets (not shown) positioned behind an aluminum sputtering
target. The source assembly (including the sputtering target) is
electrically isolated from the rest of the chamber by an insulator ring
20. The adapter 12 extends the upper part of the chamber to make room for
an internal RF coil antenna 22, which is made from copper tubing. Around
the inside circumference of the chamber above the wafer pedestal, there is
a grounded metal shield 24 which confines the plasma that is formed within
the chamber to the region above the wafer and prevents the sputtered atoms
from reaching the chamber body.
A movable platform 26 within the chamber holds a wafer 28 on which material
sputtered from target 16 is deposited. The platform can be raised and
lowered by a mechanical lift mechanism 30. After the wafer is placed on
the platform, the lift mechanism raises the wafer until it contacts a
clamping ring 32. The clamping ring, which has a central aperture 34 that
is slightly smaller than the diameter of the wafer, shields the platform
from deposition material during processing.
A vacuum pump 36, which is connected to the chamber, is used to evacuate
the chamber for a process run. Gas control circuitry 38 is used to control
the flow of inert gas (e.g. Ar) in and out of the chamber during
processing and to thereby achieve the desired gas pressure during
sputtering.
The system also includes a conventional RF power source 40 and two
conventional modulated DC power supplies 42 and 44, whose output voltages
can be controlled by a control signal. The RF power source, which
generates a selectable frequency within the range of 400 KHz to 60 MHz, is
connected through a matching network 46 to coil 22. Voltage feed throughs
48 are provided in the side of the chamber to allow an electrical
connection to made to the RF antenna inside the chamber. Power supply 42
is connected between the target and ground potential. Power supply 44,
which has a controllable output polarity, is connected between the
pedestal/wafer and ground potential. A conventional microcontroller 50
generates the control signals that control the operation of both DC power
supplies 42 and 44 to generate and synchronize the voltage waveforms that
are required to perform the deposition/planarization process as described
below.
The pressure and flow rates that are used are typical of those which would
be used during a conventional sputter deposition process. For example, the
pressure of Ar is typically set to less than about 100 mTorr and often as
low as 0.5 mTorr or even lower. For such pressures, typical Ar flow rates
may be between about 10 to 140 sccm (standard cubic centimeters per
minute). Of course, these parameters may be adjusted to optimize the
process for the particular power levels, gas atmosphere, and chamber
geometries that are used.
2. The Three Phase Process
The deposition/planarization process has three phases of operation referred
to below as Phase I, Phase II, and Phase III. During Phase I, a thin layer
of Al is sputter deposited on the surface of the wafer (e.g. 10-50 .ANG.).
During Phase II the surface of the wafer is bombarded with low energy
Ar.sup.+ ions (e.g. 100 eV) to generate vacancies or holes within the
just-deposited thin layer of Al. During Phase III, the surface of the
wafer is bombarded by electrons which excite the surface of the wafer to
facilitate a reflow of the metal layer. The three phase sequence is
repeated many times until the desired overall thickness of metalization is
achieved.
The three phases of operation are generated by the particular voltage
waveforms that are applied to the target and the wafer. The voltage
applied to the target is shown in the upper half of FIG. 3 and the voltage
that is applied to the wafer/platform is shown in the lower half of FIG.
3. Throughout the process, RF supply 40 is set to deliver a constant power
(e.g. between 300-2500 watts) to the RF antenna to inductively generate an
RF plasma within the chamber. The inductively generated RF plasma serves
to enhance sputtering during Phase I, to provide the source of Ar.sup.+
ions for vacancy generation during Phase II, and to provide the source of
electrons during Phase III. In the described embodiment, processing a
wafer that is about 200 mm in diameter is done using an RF frequency of
400 KHz and RF power of about 300-400 watts.
During Phase I, the target voltage is set to a negative 500 volts to
generate a sputtering plasma above the target while the RF power supplied
to the internal antenna is generating a second Ar plasma. The RF induced
plasma acts to enhance sputtering efficiency during this phase of
operation by increasing the amount of Ar.sup.+ ions that are produced.
While sputtering is taking place, the wafer voltage is either set to zero
or allowed to float at a voltage level that is dictated by the plasma. To
enable the wafer voltage to float, the DC power supply 44 is adapted to
disconnect from the platform during this phase of operation. Under these
operating conditions, the current to the target is about 20 amperes (i.e.,
about 10 KWatts of power is being supplied to the target) which yields a
deposition rate of about 10,000 .ANG./minute. The duration of Phase I
(i.e., time t.sub.1 in FIG. 4) is between about 10-100 msec, the precise
value depending, of course, on how much metal one wants to deposit. If,
for example, t.sub.1 is set to about 60 msec, about 10 .ANG. of Al will be
deposited during Phase I. The optimum thickness for the Al layer deposited
during Phase I is the maximum depth to which the ion bombardment will
penetrate during Phase II, as will be explained below.
During Phase II, the RF power to the antenna remains at the same level and
the power to the target is reduced sufficiently to effectively stop the
sputtering process. However, it is preferable to avoid shutting off the
target power completely so as to maintain some minimal deposition rate
(e.g. a few .ANG./min). The minimal deposition rate serves to keep a fresh
surface during this phase of operation. If the sputter deposition were to
be completely turned off, the surface of the Al layer would be more likely
to collect contaminants (e.g. oxygen and/or nitrogen atoms) which would
have a deleterious effect on the quality of the metal layer and would tend
to interfere with reflow.
In the described embodiment, the background power level to the target
during Phase II (and continued during Phase III) is reduced to about 500
Watts by dropping the target voltage to about -250 volts. Thus, the
resulting deposition rate during Phase II is about 5% of the rate achieved
at full power operation.
At the same time the target power is reduced at the beginning of Phase II,
the microcontroller 50 causes the power supply 44 to switch the voltage on
the wafer from its zero voltage (or alternatively, its free floating
condition) to a voltage sufficiently negative to attract argon ions so
they bombard the wafer, preferably between -20 to -150 volts (e.g. -100
volts). Thus, the positively charged Ar.sup.+ ions that are being
generated by the RF induced plasma within the chamber cavity are drawn
toward and bombard the surface of the negatively charged wafer. The
resulting current is about 5-10 amperes.
The Ar.sup.+ ions bombarding the surface of the wafer penetrate into and
generate vacancies within that metal layer. It is desirable to set the
voltage on the wafer to a sufficiently high negative voltage so that the
Ar.sup.+ ions penetrate the just-deposited metal layer and produce
vacancies distributed throughout it (i.e. above 20 eV for Al). However, it
is also desirable to avoid setting the voltage so high as to cause reverse
sputtering of the wafer (i.e., sputter etching off of the wafer some of
the material deposited on the wafer during Phase I) or to cause the ions
to penetrate through the metal layer and into the underlying substrate
where they may damage devices. In other words, the bombarding ions will
have an energy that is less than the threshold energy that is required to
sputter metal atoms off of the surface (referred to hereinafter as the
sputtering energy threshold).
During Phase II, the production of vacancies within the deposited layer
reduces the density of the deposited Al layer and increases the mobility
of the Al atoms within that layer. Thus, the effective diffusion
coefficient of the Al atoms within that layer is increased sufficiently so
as to produce significant reflow of Al at temperatures well below the flow
point temperature for Al (i.e., 525.degree.-530.degree. C.).
In the described embodiment, the ion bombardment which occurs during Phase
II is allowed to continue for about 1-5 msec. The objective is to generate
a vacancy concentration in the range of about 1-10% (i.e., for every 100
Al atoms within that layer, one Al atom is displaced by the bombarding
ions). That is, the concentration of vacancies is raised sufficiently so
as to increase the mobility of the Al atoms enough to cause an appreciable
reflow of material during Phase III. If the vacancy concentration is too
low, reflow will not be enhanced significantly and/or higher temperatures
will be required during Phase III. On the other hand, if the vacancy
concentration is increased too much, the metal will become amorphous which
may be undesirable.
Note also that it is desirable to limit the amount of metal that is
deposited during Phase I. If the deposited layer is too thick, the ion
bombardment of Phase II will not be able to produce vacancies throughout
the just-deposited layer.
During Phase III, the RF power to the antenna remains on, the target power
remains at its reduced level, and the voltage on the wafer is switched to
a positive value between about 100-200 volts (e.g. see 150 volts in FIG.
3) to cause electron bombardment of the wafer. The voltage should be set
high enough so that the electron bombardment heats the just-deposited
metal layer sufficiently to promote diffusion and reflow of the aluminum.
However, the voltage should not be set so high as to cause the electrons
to penetrate the metal layer where they will heat up the underlying wafer
and/or possibly cause radiation damage to the devices. At about 150 volts
the resulting current is about 15-20 amperes.
It is desirable to select the duration of Phase III (i.e., t.sub.3
-t.sub.2) to be long enough relative to the entire three-phase cycle to
achieve a high enough surface temperature on the metal layer to produce an
effective reflow of metal. In the described embodiment, the duration of
Phase III is set to between 20-50 msec. It is believed that the resulting
duty cycle causes the surface layer to heat up to about
300.degree.-350.degree. C. Though this is still well below the flow point
of Al, due to the enhanced mobility of Al atoms in the layer, it
nevertheless achieves effective diffusion and redistribution (i.e.,
planarization) of the deposited metal layer. Thus, the electron beam
heating which occurs during Phase III causes the deposited layer of Al to
diffuse into the contact holes and corners.
Typically, the desired thickness of the Al metalization is about 6000
.ANG.. Given the operating conditions described above, the three phase
sequence must be repeated about 600 times to achieve this thickness.
Other embodiments are within the following claims. For example, sputter
sources other than a magnetron source could be used and other target
materials can be used for the target (e.g. Cu, Au, and Sn, to name a few).
In addition, heating techniques other than electron beam can be used to
heat the surface of the wafer, e.g. a laser could be used. Also, the
phases may be overlapped; for example, if a laser is used to heat the
surface of the deposited metal in Phase III, that heating may be performed
concurrently with al or part of Phase II. In yet other embodiments, Phase
III can be eliminated and a heater element 60 in the platform 26 5 used to
heat the wafer to a high enough temperature to achieve appreciable reflow
and diffusion of the vacancy enhanced metal layer.
Also note that the process parameters described above were for illustrative
purposes. It is anticipated that they can vary widely depending upon the
particular system in which the process is being performed, the metal that
is being deposited, and the characteristics of the deposited layer that
are desired. For example, it may be desirable to deposit a thicker layer
of metal during Phase I, or it may be desirable to change the duty cycle
to control the amount of heating that occurs during Phase III. All such
modifications fall within the scope of the claimed invention.
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