U.S. patent application number 09/449202 was filed with the patent office on 2001-06-14 for alternate steps of imp and sputtering process to improve sidewall coverage.
Invention is credited to DING, PEIJUN, EDELSTEIN, SERGIO, GHOSH, DEBABRATA, GOPALRAJA, PRABURAM, MAITY, NIRMALYA, TEPMAN, AVI.
Application Number | 20010003607 09/449202 |
Document ID | / |
Family ID | 23783296 |
Filed Date | 2001-06-14 |
United States Patent
Application |
20010003607 |
Kind Code |
A1 |
GOPALRAJA, PRABURAM ; et
al. |
June 14, 2001 |
ALTERNATE STEPS OF IMP AND SPUTTERING PROCESS TO IMPROVE SIDEWALL
COVERAGE
Abstract
The present invention provides a method and apparatus for
achieving conformal step coverage on a substrate by PVD. A target
provides a source of material to be sputtered by a plasma and then
ionized. Ionization is facilitated by maintaining a sufficiently
dense plasma using, for example, an inductive coil. The ionized
material is then deposited on the substrate which is biased to a
negative voltage. A signal provided to the target during processing
includes a negative voltage portion and a zero-voltage portion.
During the negative voltage portion, ions are attracted to the
target to cause sputtering. During the zero-voltage portion,
sputtering from the target is terminated while the bias on the
substrate cause reverse sputtering therefrom. Accordingly, the
negative voltage portion and the zero-voltage portion are
alternated to cycle between a sputter step and a reverse sputter
step. The film quality and uniformity can be controlled by
adjusting the frequency of the signal, the chamber pressure, the
power supplied to each of the support member and other process
parameters.
Inventors: |
GOPALRAJA, PRABURAM;
(SUNNYVALE, CA) ; EDELSTEIN, SERGIO; (LOS GATOS,
CA) ; TEPMAN, AVI; (CUPERTINO, CA) ; DING,
PEIJUN; (SAN JOSE, CA) ; GHOSH, DEBABRATA;
(SAN JOSE, CA) ; MAITY, NIRMALYA; (SUNNYVALE,
CA) |
Correspondence
Address: |
PATENT COUNSEL
APPLIED MATERIALS INC
P O BOX 450 A
SANTA CLARA
CA
95052
|
Family ID: |
23783296 |
Appl. No.: |
09/449202 |
Filed: |
November 24, 1999 |
Current U.S.
Class: |
427/569 ;
427/585 |
Current CPC
Class: |
C23C 14/345 20130101;
C23C 14/358 20130101; H01J 37/3408 20130101; C23C 14/046 20130101;
H01J 37/321 20130101 |
Class at
Publication: |
427/569 ;
427/585 |
International
Class: |
C23C 008/00 |
Claims
1. An apparatus, comprising: (a) a processing chamber; (b) a
substrate support member disposed in the processing chamber having
a first power source coupled thereto; (c) a target disposed in the
processing chamber; (d) a second power source coupled to the target
adapted to vary the voltage applied to the target; and (e) an
electromagnetic field source.
2. The apparatus of claim 1, wherein the first power source is an
radio frequency (RF) power source.
3. The apparatus of claim 1, wherein the second power source is
selected from the group of a pulsed direct current (DC) power
source, a pulsed RF power source, a DC power source in combination
with a switch and any combination thereof.
4. The apparatus of claim 1, wherein the second power source is a
pulsed DC power source adapted to provide a signal having a
negative voltage portion and a zero-voltage portion.
5. The apparatus of claim 1, wherein the target comprises a
material selected from the group comprising Ti, Cu, Ta, W, Al and
any combination thereof.
6. The apparatus of claim 1, further comprising a gas source
coupled to the processing chamber to supply a gas for creating a
plasma during processing.
7. The apparatus of claim 1, wherein the electromagnetic field
source is a coil having a power supply coupled thereto.
8. The apparatus of claim 7, wherein the coil is disposed within
the processing chamber.
9. A method of depositing a material on a substrate in a process
chamber, wherein the substrate includes a feature formed therein,
comprising: (a) providing a plasma in the process chamber; (b)
biasing the substrate with a negative voltage; and (c) alternating
between a sputtering and a reverse sputtering step, wherein the
sputtering step comprises applying a bias to a target and the
reverse sputtering step comprises terminating the bias to the
target.
10. The method of claim 9, wherein the sputtering step is adapted
to provide net deposition of material on the substrate and the
reverse sputtering step is adapted to provide net removal of
material from the substrate.
11. The method of claim 9, wherein (a) comprises; (1) supplying a
gas; and (2) supplying a radio frequency (RF) signal to a coil.
12. The method of claim 9, wherein (b) comprises supplying a radio
frequency (RF) signal to the substrate.
13. The method of claim 9, wherein the bias to the target comprises
providing at least one of an RF signal and a DC signal to the
target.
14. A method of depositing a material on a substrate in a process
chamber, comprising: (a) providing a plasma in the processing
chamber; (b) negatively biasing the substrate; (c) energizing a
coil; and (d) biasing the target with a signal having a negative
voltage portion and a zero-voltage portion.
15. The method of claim 14, wherein (c) comprises supplying a radio
frequency (RF) signal to the coil.
16. The method of claim 14, wherein (c) comprises supplying a radio
frequency (RF) signal to the coil at a power between about 100 W
and 6 KW and at a frequency between about 400 KHz and 60 MHz.
17. The method of claim 14, wherein (d) comprises supplying a DC
(direct current) to the target.
18. The method of claim 14, wherein the negative voltage portion is
between about 50 V and 600 V.
19. The method of claim 14, wherein the signal to the target has a
frequency of between about 0.01 Hz and 1 Hz and the negative
voltage portion has a pulse width between about 0.5 seconds and 60
seconds.
20. The method of claim 14, wherein the signal to the target has a
duty cycle between about 10%-80%.
21. The method of claim 14, further comprising providing a device
feature formed in the substrate having an aspect ratio greater than
2:1.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an apparatus and method for
processing substrates. Specifically, the invention relates to a
method for depositing a conformal layer of material on a substrate
using physical vapor deposition process.
[0003] 2. Background of the Related Art
[0004] Sub-quarter micron multi-level metallization represents one
of the key technologies for the next generation of ultra
large-scale integration (ULSI) for integrated circuits (IC). In the
fabrication of semiconductor and other electronic devices,
directionality of particles being deposited on a substrate is
important to improve adequate in filling of electric features. As
circuit densities increase, the widths of vias, contacts and other
features, as well as the dielectric materials between them,
decrease to 0.25 .mu.m or less, whereas the thickness of the
dielectric layer remains substantially constant. Thus, the aspect
ratios for the features, i.e., the ratio of the depth to the
minimum lateral dimension, increases, thereby pushing the aspect
ratios of the contacts and vias to 5:1 and above. As the dimensions
of the features decrease, it becomes even more important to get
directionality in order to achieve conformal coverage of the
feature sidewalls and bottoms.
[0005] Conventionally, physical vapor deposition (PVD) systems have
been used to deposit materials in device features formed on a
substrate. PVD systems are well known in the field of semiconductor
processing for forming metal films. Generally, a power supply
connected to a processing chamber creates an electrical potential
between a target and a substrate support member within the chamber
and generates a plasma of a processing gas in the region between
the target and substrate support member. Ions from the plasma
bombard the negatively biased target and sputter material from the
target which then deposits onto a substrate positioned on the
substrate support member. However, while such processes have
achieved good results for lower aspect ratios, conformal coverage
becomes difficult to achieve with increasing aspect ratios. In
particular, it has been shown that coverage of the bottoms of the
vias decreases with increasing aspect ratios.
[0006] One process capable of providing greater directionality to
particles is ionized metal plasma-physical vapor deposition
(IMP-PVD), also known as high density physical vapor deposition
(HDP-PVD). Initially, a plasma is generated by introducing a gas,
such as helium or argon, into the chamber and then biasing a target
to produce an electric field in the chamber, thereby ionizing a
portion of the gas. An energized coil positioned proximate the
processing region of the chamber couples electromagnetic energy
into the plasma to result in an inductively-coupled medium/high
density plasma between the target and a susceptor on which a
substrate is placed for processing. The ions and electrons in the
plasma are accelerated toward the target by the bias applied to the
target causing the sputtering of material from the target. Under
the influence of the plasma, the sputtered metal flux is ionized.
An electric field due to an applied or self-bias, develops in the
boundary layer, or sheath, between the plasma and the substrate
that accelerates the metal ions towards the substrate in a
direction substantially parallel to the electric field and
perpendicular to the substrate surface. The bias energy is
preferably controlled by the application of power, such as RF, to
the susceptor to attract the sputtered target ions in a highly
directionalized manner to the surface of the substrate to fill the
features formed on the substrate.
[0007] One of the problems with HDP-PVD processes is the inability
to achieve conformal step coverage in the increasingly smaller
device features. Conformal coverage of the bottoms and sidewalls of
the features is needed to optimize subsequent processes such as
electroplating. Electroplating requires conformal barrier and seed
layers within the device features in order to ensure uniform
filling of the feature. While conventional HDP-PVD achieves good
bottom coverage due to the directionality of the ions provided by
the bias on the substrate, the sidewall coverage can be less than
conformal. This result is caused in part by the induced high
directionality of ions towards the bottom of the features with
little directionality toward the sidewalls.
[0008] The effects of a bias on film deposition on and into the
features in/on a substrate can be described with reference to FIGS.
1-2 which illustrate the direction of metal ions 12 entering a via
16 formed on a substrate 10. FIG. 1 illustrates a DC magnetron PVD
processing environment wherein no bias is supplied to the substrate
10 (the presence or absence of an applied bias being substantially
irrelevant to traditional planar target DC sputtering). As a
result, the directionality of the ions 12 is determined primarily
by the ejection profile of material (usually atoms) from the target
and by the inelastic collisions with other particles in the
chamber, such as Ar ions which are provided in a plasma. The
angular distribution 22 of the ions in FIG. 1 typically results in
little deposition on the bottom 18 of the via 16. In addition to
the angular distribution of the incoming ions 12, the feature
dimensions also determine the resulting step coverage. Thus, where
the feature opening is wider than the depth of the feature,
deposition material can reach all surfaces of the feature for
relatively uniform deposition. However, where the feature is narrow
compared to the depth, the particles travelling substantially
non-parallel to the feature depth deposit around the feature
opening, resulting in less deposition at the bottom 18 of the via
16.
[0009] FIG. 2 illustrates the processing environment in a HDP-PVD
process wherein the angular distribution of the ions 12 is
influenced by the electrical field E due to interaction between the
charged target material and the applied or self-bias at the surface
of the substrate. The electric field E is oriented perpendicular to
the substrate 10 and the positively charged ions 12 are influenced
into a trajectory parallel to the electric field E toward the
bottom 18 of the via 16. The angular distribution 23 of the ions 12
in FIG. 2 typically results in moderate to lower deposition on the
sidewalls 20 and higher to moderate deposition on the bottom 18
than is possible without ionization of the sputtered material. As
compared to the angular distribution 22 of FIG. 1, the distribution
23 exhibits a tighter distribution indicating more directionality
parallel to the electric field E.
[0010] Therefore, there is a need to provide a technique for
depositing a layer conformally over the surface of features,
particularly sub-half micron and higher aspect ratio features.
SUMMARY OF THE INVENTION
[0011] The present invention generally provides an apparatus and
method for depositing a conformal layer on device features in a
plasma chamber by PVD. In one aspect of the invention, a chamber
having a target, a power supply coupled to the target adapted to
provide a signal having a desired waveform, a substrate support
member, a power supply connected to the substrate support member,
and a magnetic field generator is provided. The target comprises a
material to be sputtered by a plasma formed adjacent to the target
during processing. The signal supplied by the power supply coupled
to the target preferably comprises a negative voltage portion and a
zero-voltage portion. Preferably, the power supply connected to the
substrate support member supplies a substantially constant negative
bias to the substrate.
[0012] In another aspect of the invention, a plasma is supplied to
a chamber to sputter a material from a target. A coil is energized
proximate the chamber to enhance ionization of the sputtered
material. During processing, a modulated signal is provided to the
target. In one embodiment, the modulated signal is varied between a
negative voltage portion during which the target material is
sputtered onto a substrate and a zero-voltage portion during which
the deposited material is re-sputtered from the substrate. A bias
is provided to the substrate to influence the direction of ions in
the chamber during processing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] So that the manner in which the above recited features,
advantages and objects of the present invention are attained and
can be understood in detail, a more particular description of the
invention, briefly summarized above, may be had by reference to the
embodiments thereof which are illustrated in the appended
drawings.
[0014] It is to be noted, however, that the appended drawings
illustrate only typical embodiments of this invention and are
therefore not to be considered limiting of its scope, for the
invention may admit to other equally effective embodiments.
[0015] FIG. 1 is a cross-section of a substrate having a via formed
therein and illustrates cosine distribution of sputtered
material.
[0016] FIG. 2 is a cross-section of a substrate having a via formed
therein and illustrates over-cosine distribution of sputtered
material.
[0017] FIG. 3 is a cross-section of a simplified processing chamber
of the invention having a coil disposed therein.
[0018] FIG. 4 is a graphical illustration of a signal applied to a
target.
[0019] FIG. 5 is a graphical illustration of a signal applied to a
substrate.
[0020] FIG. 6 is a cross section of a substrate and a target
illustrating sputtering.
[0021] FIG. 7 shows the substrate and target of FIG. 6 and
illustrates re-sputtering of a material from the substrate.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0022] The embodiments described below preferably use a modified
ionized metal plasma (IMP) process that can be carried out using
process equipment, such as an Endura.RTM. platform, available from
Applied Materials, Inc., located in Santa Clara, Calif. with
modifications as described below. The equipment preferably includes
an integrated platform having a preclean chamber, an IMP-PVD
barrier layer chamber, a PVD chamber, an IMP-PVD seed layer
chamber, and a CVD chamber. One ion metal plasma (IMP) processing
chamber, known as an IMP VECTRA.TM./ELECTRA.TM. Chamber is
available from Applied Materials, Inc., of Santa Clara, Calif.
[0023] FIG. 3 is a schematic cross-sectional view of an IMP chamber
100 according to the present invention. The chamber 100 includes
walls 101, lid 102, and bottom 103. A target 104 comprising the
material to be sputtered is mounted to the lid 102 and disposed in
the chamber 100 to define an upper boundary to a processing region
107. Magnets 106 are disposed behind the lid 102 and are part of a
rotatable magnetron which traps electrons during operation and
increases the density of a plasma adjacent to the target 104.
[0024] A substrate support member 112 supports the substrate 110
and defines the lower boundary to the processing region 107. The
substrate support member 112 is movably disposed in the chamber 100
and provides an upper support surface 105 for supporting a
substrate 110. The support member 112 is mounted on a stem 109
connected to a motor assembly 114 that raises and lowers the
substrate support 112 between a lowered loading/unloading position
and a raised processing position. An opening 108 in the chamber 100
provides access for a robot (not shown) to deliver and retrieve
substrates 110 to and from the chamber 100 while the substrate
support member 112 is in the lowered loading/unloading
position.
[0025] A coil 122 is mounted in the chamber 100 between the
substrate support member 112 and the target 105 and, when an AC
current is passed therethrough, provides electromagnetic fields in
the chamber 100 during processing to assist in generating and
maintaining a plasma between the target 104 and substrate 110. The
electromagnetic fields produced by the coil 122 induces currents in
the plasma to densify the plasma, i.e., to increase the ionization
of the gas and the sputtered target material. The ionized material
is attracted toward the substrate 110 by virtue of the electrical
attraction between the positively charged ions and the negatively
biased substrate support member 112 (which is biased either with a
power supply or is self biased). By virtue of this "attraction" the
sputtered material ions reaching the substrate are aligned more
parallel to the depth access of the features. In addition, the coil
122 itself attains a negative self-bias causing the coil 122 to be
sputtered.
[0026] The chamber 100 optionally includes a process kit comprising
a process shield 128 and a shadow ring 129. The process shield 128
is an annular member suspended from the lid 102 between the coil
122 and the body 101. An upwardly turned wall 131 of the process
shield 128 is adapted to support the shadow ring 129 while the
support member 112 is in a lowered position. To provide a return
path for RF currents in the chamber 100 the process shield is
preferably coupled to ground.
[0027] One or more plasma gases are supplied to the chamber 100
through a gas inlet 136 from gas sources 138, 140 as metered by
respective mass flow controllers 142, 144. One or more vacuum pumps
146 are connected to the chamber 100 at an exhaust port 148 to
exhaust the chamber 100 and maintain the desired pressure in the
chamber 100. Preferably the vacuum pumps 146 include a cryopump and
a roughing pump and are capable of sustaining a base pressure of
about 10.sup.-8 mTorr.
[0028] Three power supplies are preferably used to bias elements of
the chamber 100. A first power supply 130 delivers a modulated or
oscillating power signal to the target 104. The first power supply
130 may be a direct current (DC) or radio frequency (RF) power
supply capable of providing a signal to the target 104 having a
desired waveform. However, the particular arrangement used to
provide the signal to the target 104 is not limiting of the present
invention and may include any conventional components known in the
art, such as switches, pulse generators, microprocessors and the
like. A second power source 132, preferably a RF power source,
supplies electrical power in the megahertz range to the coil 122 to
increase the density of the plasma. A third power source 134
supplies an RF power signal to bias the substrate support member
112 with respect to the plasma and provides an electric field
adjacent a substrate to attract the ionized sputtered material
toward the substrate 110.
[0029] In operation, a robot delivers a substrate 110 to the
chamber 100 through the opening 108. After placing the substrate
110 upon the upper surface 105 of the support member 112 the robot
retracts from the chamber 100 and the opening 108 is sealed. The
substrate support member 112 then raises the substrate 110 into a
processing position. During the upward movement of the support
member 112 the shadow ring 129 is lifted from the process shield
128. During processing, the shadow ring 129 covers a perimeter
portion (usually less than 3 millimeters) of the substrate 110.
Preferably, the space between the target 104 and the substrate
support member 112 in a raised processing position is between about
90 mm and 199 mm.
[0030] One or more plasma gases are then introduced into the
chamber 100 from the gas sources 138, 140 to stabilize the chamber
100 at a processing pressure. The target receives a negative DC
bias which, in conjunction with magnets 106, facilitates the
formation of a plasma adjacent the target 104. The power supply 130
provides a periodic bias which attracts the charged particles of
the plasma toward the target 104 to cause sputtering therefrom.
[0031] The coil 122 is energized by the third signal generator 132
and operates to increase the density of the plasma, thereby
facilitating ionization of sputtered target material. A portion of
the ions formed from the sputtered target material continue to
traverse the space between the target 104 and the support member
112 and deposit on the substrate 110 which is biased by the third
power supply 134. The biases to the target 104 and support member
112 are controlled according to the processes described in detail
below.
[0032] Following the deposition cycle, the substrate support member
112 is lowered to a loading/unloading position. The robot is then
extended into the chamber 100 through the opening 108 and the
substrate 110 is placed on the robot for removal from the chamber
100 and delivery to a subsequent location. Subsequent locations
include various processing chambers, such as electroplating
chambers, where the substrate 110 undergoes additional
processing.
[0033] The present invention utilizes alternating steps of
sputtering and reverse sputtering to achieve conformal coverage of
the feature formed on the substrate. Good step coverage on the
device features of the substrate 110 is achieved by ensuring proper
proportions of bottom coverage and sidewall coverage of the
features. According to one aspect of the present invention, the
proportions of coverage are controlled by adjusting the sputtering
and reverse sputtering steps and other process parameters.
Throughout the following discussion, periodic reference is made to
FIG. 3 where necessary.
[0034] During the deposition process, the power supply 130 delivers
a signal 200 to the target 104 having a desired waveform. The
signal 200, shown in FIG. 4, is a square wave or step function and
includes a negative voltage portion 202 and a zero-voltage portion
204. Although shown here as a square wave, any waveform oscillated
between a negative voltage portion and a less negative or zero
voltage portion may be used to advantage. During the negative
voltage portion 202, the positively charged ions supplied by the
plasma gas, such as Ar, bombard the target 104 causing ejection of
material therefrom. The energy with which the Ar ions strike the
target 104, can be controlled by adjusting the bias to the target
104, i.e., a greater bias resulting in greater ion energy.
Preferably, the negative voltage portion 202 is between about -50 V
and -600 V. The metal flux produced during the negative voltage
portion 202 of the signal 200 is then ionized by the plasma
maintained by the coil bias and the target bias and subsequently
forms a layer on the substrate 110.
[0035] During the subsequent zero-voltage portion 204 of the signal
200, the direction of the positively charged Ar ions is determined
primarily by the negative bias on the substrate 110 supplied by the
third power supply 134. Preferably, the bias to the substrate 110
remains constant throughout the deposition cycle so that a constant
voltage drop is established across a region between the plasma and
the substrate 110 known as the sheath or dark space. Due to the
resulting voltage drop in the sheath, an electric field is
generated substantially perpendicular to the substrate 110, thereby
causing the ions to accelerate toward the substrate. As in the
sputtering step described above, the ions strike the substrate with
sufficient energy to cause reverse sputtering, or re-sputtering, of
the material previously deposited onto the substrate from the
target 104. Thus, during the zero-voltage portion 202 of the signal
200, sputtering from the target 104 is substantially terminated and
the previously deposited material on the substrate 110 is
re-sputtered therefrom. The result of the reverse sputtering step
is to redistribute and planarize the deposited material on the
substrate, thereby achieving greater uniformity and superior step
coverage. It should be noted that impinging ions will sputter the
substrate 110 during the negative voltage portion 202 as well as
the zero-voltage portion 204 due to the constant bias applied to
the substrate 110. However, the flux of sputtered material will be
substantially less during zero-voltage portion 204 since only the
coil 122 will be sputtered. As a result, negative voltage portion
202 provides for net deposition on the substrate 110, while
zero-voltage portion 204 provides for net re-sputtering of material
with only a little deposition onto the substrate 110. The effects
of the oscillating signal 200 on deposition will be described below
with reference to FIGS. 8-9.
[0036] Preferably, the negative voltage portion 202 and the
zero-voltage portion 204 are sequentially alternated to result in a
series of sputtering steps (or high deposition rate steps) and
reverse sputtering steps (or low deposition rate steps). The
frequency and duty cycle of the signal 200 can be adjusted to
increase the sputtering step or the reverse sputtering step to
achieve the desired results. Preferably, the frequency of the
signal 200 is between about 0.01 Hz and 1 Hz. As defined herein,
the duty cycle is the ratio of the width, t1, of the negative
voltage portion 202 to the signal period T1, shown in FIG. 4.
Preferably, the duty cycle is between about 10% and about 80%,
wherein the negative voltage portion width t1 is between about 0.55
seconds and about 60 seconds.
[0037] Although the voltage applied to the substrate 110 may be
modulated in a manner similar to the signal 200 provided to the
target 104, preferably the voltage is maintained at a substantially
constant value throughout a deposition cycle. FIG. 5 shows an RF
signal 201 provided to the substrate 110 by the third power supply
134. In the presence of a plasma, the signal 201 is shifted
downward into the negative voltage region resulting in an induced
DC bias (Vdc) on the substrate 110. The Vdc, shown in FIG. 5 as a
signal 206, is maintained at a substantially constant value. In one
embodiment, the power from the third power supply 134 is sufficient
to produce an applied bias on the substrate 110 between about 0 V
and -300 V. The particular values for power and voltage may be
adjusted to achieve the desired result.
[0038] As described above, the invention provides a method of
controlling the deposition of a material deposited on a substrate
and may be illustrated with reference to FIGS. 8-9. FIG. 6 is a
schematic side view of a substrate 110 and a target 104 during
application of the negative voltage portion 202 of the signal 200
thereto. The substrate 110 has a feature 218 such as a via, formed
therein. A plasma 220 is maintained between the substrate 110 and
the target 104. Preferably, the plasma is generated using argon due
to argon's low sticking coefficient which reduces the potential for
poisoning the target 104 or the resulting film formed on the
substrate 110 with substantial argon. However, other non-reactive
gases such as He, N.sub.2, Xe, Kr and Ne may be used to advantage.
Subsequent to the formation of the plasma 220, Ar ions are
attracted to the target 104 under the influence of the negative
bias provided by the power supply 130. The Ar ions then strike the
target 104 with sufficient energy to dislodge, or sputter, material
from the target 104. The target 104 may comprise one or more of Cu,
Al, W, Ti, and Ta, among other materials. The metal flux ejected
from the target 104 traverses the processing region 107, where at
least a portion of it is ionized by the plasma 220. The
directionality of the ionized target material is then affected by
the voltage drop across the sheath 226. The voltage drop can be
modified by application of a bias to the substrate 110 using the
third power supply 134. The result of the deposition step during
the negative voltage portion 202 of the signal 200 is to form a
layer 228 on the substrate 110. Due to the bias applied to the
substrate 110, the angular distribution of the ionized target
material results in proportionately more deposition at the bottom
232 of the feature 218.
[0039] The negative bias on the substrate 110 also attracts the Ar
ions to cause some re-sputtering of deposited material. However,
the rate of deposition is higher than the rate of re-sputtering,
thereby achieving net deposition.
[0040] Once the applied bias to the target 104 is terminated during
the zero-voltage portion 202 of the signal 200, sputtering from the
target 104 ceases. Without a target bias, the substrate 110
experiences deposition resulting only from sputtering of the coil
122. However, as a result of applied negative bias provided by the
third power supply 134, the substrate 110 continues to experience
re-sputtering due to Ar ion bombardment. FIG. 7 shows a schematic
representation of the re-sputtering of layer 228 caused by the Ar
ions. In particular, the bias to the substrate 110 causes the Ar
ions to strike the bottom 232 of the feature 218 (as well as the
field of the substrate) causing re-sputtering of the deposited
layer 228 onto the sidewalls 231. Accordingly, material can be
redistributed from the bottom 232 onto the sidewalls 231 to ensure
sidewall coverage. Further, overhangs, are etched during the
re-sputtering step and result in opening of the features. Thus, the
potential for the formation of voids is minimized. In addition, the
layer 228 formed on the field 230 of the substrate 110 is
re-sputtered and redistributed into the feature 218, thereby
providing more deposition onto the sidewalls 231 and the bottom
232.
[0041] As a result, in tandem with other process parameters, such
as the pressure, substrate bias power and coil power, the invention
can modify step coverage and film thickness uniformity over prior
art methods. The invention has particular application in barrier
layer and seed layer deposition wherein film quality is
particularly important to ensure good results in subsequent
processes, such as electroplating. Table I provides exemplary
materials and ranges for various process parameters. However, Table
I is merely illustrative and the invention contemplates other
process recipe as well.
1 TABLE I Materials: Ti, Cu, Ta, W, Al Bias Power to Support
Member: 0W to 1000W Bias Voltage induced on Support 0V to -300V
Member: Coil Power: 100W to 6000W Coil Frequency: 400Khz to 60MHz
Target Power: 0V to -600V Pressure 0.1 mTorr to 100 mTorr
[0042] While the foregoing is directed to the preferred embodiment
of the present invention, other and further embodiments of the
invention may be devised without departing from the basic scope
thereof, and the scope thereof is determined by the claims that
follow.
* * * * *