U.S. patent application number 15/666548 was filed with the patent office on 2017-11-16 for control of the incidence angle of an ion beam on a substrate.
The applicant listed for this patent is Lam Research Corporation. Invention is credited to Ivelin Angelov, Ivan L. Berry, III.
Application Number | 20170330788 15/666548 |
Document ID | / |
Family ID | 58777104 |
Filed Date | 2017-11-16 |
United States Patent
Application |
20170330788 |
Kind Code |
A1 |
Angelov; Ivelin ; et
al. |
November 16, 2017 |
Control Of The Incidence Angle Of An Ion Beam On A Substrate
Abstract
One system includes a chamber, a chuck assembly, and an ion
source. The chuck assembly includes a substrate support and a
precession assembly with a center support coupled to a stationary
center point of an under region of the substrate support. The
precession assembly includes first and second actuators connected
to first and second locations, respectively, that are in the under
region off-set from the center point. The precession assembly
imparts a precession motion to the substrate support when the first
actuator and the second actuator move up and down relative to the
center support, and the precession motion imparted to the substrate
causes a rotating tilt of the substrate support without rotation of
the substrate support. The rotating tilt of the substrate is
configured to cause ions generated by the ion source to impinge
upon a surface of the substrate in continually varying angles of
incidence.
Inventors: |
Angelov; Ivelin; (San Jose,
CA) ; Berry, III; Ivan L.; (San Jose, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Lam Research Corporation |
Fremont |
CA |
US |
|
|
Family ID: |
58777104 |
Appl. No.: |
15/666548 |
Filed: |
August 1, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14956154 |
Dec 1, 2015 |
|
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15666548 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 21/3065 20130101;
H01L 21/68764 20130101; H01L 21/67069 20130101; H01J 2237/334
20130101 |
International
Class: |
H01L 21/687 20060101
H01L021/687; H01L 21/67 20060101 H01L021/67; H01L 21/3065 20060101
H01L021/3065 |
Claims
1. A system for processing a substrate, comprising: a chamber; a
chuck assembly including, a substrate support; and a precession
assembly having a center support that is coupled to a center point
of an under region of the substrate support, the center support
being stationary, wherein the precession assembly further includes
a first actuator and a second actuator, the first actuator being
connected to a first location in the under region off-set from the
center point, the second actuator being connected to a second
location in the under region off-set from the center point, wherein
the precession assembly is programmed to cause a precession motion
to be imparted to the substrate support when the first actuator and
the second actuator move up and down relative to the center
support, such that the first actuator moves up and down in
accordance with a first frequency and the second actuator moves up
and down in accordance with a second frequency, the first frequency
being independent of the second frequency; and an ion source
interfaced with the chamber, the ion source being directionally
oriented toward the substrate support of the chuck assembly,
wherein the ion source is configured to produce ions when a plasma
is struck and the ions are directed toward the substrate support,
wherein the precession motion is imparted to the substrate support
when the substrate is present on the substrate support, the
precession motion causing a rotating tilt of the substrate support
without rotation of the substrate support, the rotating tilt of the
substrate being configured to cause the ions generated by the ion
source to impinge upon a surface of the substrate in continually
varying angles of incidence.
2. The system as recited in claim 1, wherein the first actuator
moves up and down with a first amplitude, and the second actuator
moves up and down with a second amplitude, wherein the first
amplitude is independently controlled from the second
amplitude.
3. The system as recited in claim 1, further including a
controller, wherein the controller is in communication with the
precession assembly to program the precession motion.
4. The system as recited in claim 3, wherein the controller manages
the precession motion to set an angle of incidence of the ions from
the plasma to control how features on the substrate are etched.
5. The system as recited in claim 1, wherein the precession motion
is cyclical, wherein the first location is in an initial position
when the substrate is loaded onto the substrate support, wherein a
distance from the first location to the initial position over time
changes sinusoidally.
6. The system as recited in claim 1, wherein the first location and
the second location are in a periphery of the under region, wherein
the first location is separated 90 degrees from the second location
with reference to the center point.
7. The system as recited in claim 1, wherein the first location and
the second location are near a periphery of the under region.
8. The system as recited in claim 1, wherein the motions up and
down of the first actuator and the second actuator are separately
and independently controlled by the precession assembly to create
the precession motion.
9. The system as recited in claim 1, wherein points on a periphery
of the substrate move up and down during the precession motion.
10. A system for processing a substrate, comprising: a chamber; a
chuck assembly including, a substrate support; and a precession
assembly including a center support, a first rotating cam, and a
second rotating cam, wherein the center support is stationary and
coupled to a center point of a bottom surface of the substrate
support, wherein the first rotating cam is connected to a first
location that is in the bottom surface and off-set from the center
point, wherein the second rotating cam is connected to a second
location that is in the bottom surface and off-set from the center
point, wherein the precession assembly is programmed to cause a
precession motion to be imparted to the substrate support when the
first rotating cam and the second rotating cam move up and down the
first location and the second location, wherein the first rotating
cam moves independently from the second rotating cam; and an ion
source oriented toward the substrate support, the ion source
producing ions when a plasma is struck, wherein the precession
motion causes a rotating tilt of the substrate support without
rotation of the substrate support, the rotating tilt of the
substrate being configured to cause the ions generated by the ion
source to impinge upon a surface of the substrate in continually
varying angles of incidence.
11. The system as recited in claim 10, wherein the first location
moves up and down with a first amplitude, and the second location
moves up and down with a second amplitude, wherein the first
amplitude is independently controlled from the second
amplitude.
12. The system as recited in claim 10, further including a
controller, wherein the controller is in communication with the
precession assembly to program the precession motion.
13. The system as recited in claim 12, wherein the controller
manages the precession motion to set an angle of incidence of the
ions from the plasma to control how features on the substrate are
etched.
14. The system as recited in claim 10, wherein the precession
motion is cyclical, wherein the first location is in an initial
position when the substrate is loaded onto the substrate support,
wherein a distance from the first location to the initial position
over time changes sinusoidally.
Description
CLAIM OF PRIORITY
[0001] The present patent application is a Divisional of and claims
the benefit of and priority, under 35 U.S.C. .sctn.120, to U.S.
patent application Ser. No. 14/956,154, filed on Dec. 1, 2015, and
entitled "Control of the Incidence Angle of an Ion Beam on a
Substrate", which is incorporated by reference herein in its
entirety.
BACKGROUND
1. Field of the Invention
[0002] The present embodiments relates to methods, systems, and
programs for improving etching on a semiconductor manufacturing
chamber, and more particularly, methods, systems, and computer
programs for controlling the direction of an ion beam on the
surface of the substrate.
2. Description of the Related Art
[0003] In semiconductor manufacturing, etching processes are
commonly and repeatedly carried out. As is well known to those
skilled in the art, there are two types of etching processes: wet
etching and dry etching. One type of dry etching is plasma etching
performed using an inductively coupled plasma etching
apparatus.
[0004] Plasma contains various types of radicals, as well as
positive and negative ions. The chemical reactions of the various
radicals, positive ions, and negative ions are used to etch
features, surfaces and materials of a substrate.
[0005] In some chambers, the substrate is supported by a chuck that
spins in order to control how the ions coming from the plasma
impinge on the surface of the substrate. Keeping the substrate at a
constant or controlled temperature requires liquid or gas cooling
of the rotating substrate, and may also require electrostatic
clamping of the substrate to the rotating fixture. To get the
liquid or gas, and the electrical utilities to the rotating fixture
requires a rotating journal and rotating slip rings. Such journals
and slip rings have limited lifetime due to rotating-seal failure
or contactor failure. The lifetime is usually a function of the
number of rotations, and faster rotations generally result in
shorter journal lifetime.
[0006] What is desired is to eliminate the rotating journals while
still achieving uniform etching. It is in this context that
embodiments arise.
SUMMARY
[0007] Methods, devices, systems, and computer programs are
presented for controlling the angle of incidence of an ion beam on
a substrate. It should be appreciated that the present embodiments
can be implemented in numerous ways, such as a method, an
apparatus, a system, a device, or a computer program on a computer
readable medium. Several embodiments are described below.
[0008] A system for processing a substrate includes a chamber, a
chuck assembly, and an ion source. The chuck assembly includes a
substrate support and a precession assembly. The precession
assembly has a center support that is coupled to a center point of
an under region of the substrate support, the center support being
stationary. The precession assembly further includes a first
actuator and a second actuator, the first actuator being connected
to a first location in the under region off-set from the center
point, and the second actuator being connected to a second location
in the under region off-set from the center point. The precession
assembly is programmed to cause a precession motion to be imparted
to the substrate support when the first actuator and the second
actuator move up and down relative to the center support, such that
the first actuator moves up and down in accordance with a first
frequency and the second actuator moves up and down in accordance
with a second frequency, the first frequency being independent of
the second frequency. The ion source is interfaced with the
chamber, and the ion source is directionally oriented toward the
substrate support of the chuck assembly, where the ion source is
configured to produce ions when the plasma is struck and the ions
are directed toward the substrate support. The precession motion is
imparted to the substrate support when the substrate is present on
the substrate support, the precession motion causing a rotating
tilt of the substrate support without rotation of the substrate
support. The rotating tilt of the substrate is configured to cause
the ions generated by the ion source to impinge upon a surface of
the substrate in continually varying angles of incidence.
[0009] Another system for processing a substrate includes a
chamber, a chuck assembly, and an ion source. The chuck assembly
includes a substrate support and a precession assembly. The
precession assembly includes a center support, a first rotating
cam, and a second rotating cam, where the center support is
stationary and coupled to a center point of the bottom surface of
the substrate support. The first rotating cam is connected to a
first location that is in the bottom surface and off-set from the
center point, and the second rotating cam is connected to a second
location that is in the bottom surface and off-set from the center
point. Further, the precession assembly is programmed to cause a
precession motion to be imparted to the substrate support when the
first rotating cam and the second rotating cam move up and down the
first location and the second location. The first rotating cam
moves independently from the second rotating cam. The ion source is
oriented toward the substrate support, and the ion source produces
ions when the plasma is struck. The precession motion causes a
rotating tilt of the substrate support without rotation of the
substrate support, the rotating tilt of the substrate being
configured to cause the ions generated by the ion source to impinge
upon a surface of the substrate in continually varying angles of
incidence.
[0010] A method for processing a substrate includes an operation
for loading a substrate on a substrate support within a chamber.
The method further include an operation for causing, by a
precession assembly, a precession motion of the substrate support,
where the precession motion is imparted when the substrate is on
the substrate support. The precession motion causes a rotating tilt
of the substrate support without rotation of the substrate support,
the rotating tilt of the substrate being configured to cause ions,
generated by an ion source above the chamber, to impinge upon a
surface of the substrate continually varying angles of incidence.
The precession assembly includes a center support, a first
actuator, and a second actuator. The center support is stationary
and coupled to a center point of an under region of the substrate
support, the first actuator is connected to a first location that
is in the under region of the substrate support and off-set from
the center point, and the second actuator is connected to a second
location that is in the under region of the substrate support and
off-set from the center point. The precession motion is created
when the first actuator and the second actuator move up and down
relative to the center support, such that the first actuator moves
up and down in accordance with a first frequency and the second
actuator moves up and down in accordance with a second frequency,
the first frequency being independent of the second frequency.
[0011] Other aspects will become apparent from the following
detailed description, taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The embodiments may best be understood by reference to the
following description taken in conjunction with the accompanying
drawings.
[0013] FIG. 1 is a schematic cross-section diagram showing a plasma
processing system utilized for etching operations, in accordance
with one embodiment.
[0014] FIG. 2 illustrates the chamber during operation, according
to one embodiment.
[0015] FIG. 3 illustrates a plurality of substrate positions when
the substrate is tilted during processing, according to one
embodiment.
[0016] FIGS. 4A-4B illustrate a chamber where the precession motion
applied to the chuck/substrate is performed by two actuators,
according to one embodiment.
[0017] FIG. 5A illustrates the precession motion of the substrate
by moving two peripheral points up and down, according to one
embodiment.
[0018] FIG. 5B is a chart showing the changes in height of the two
peripheral points over time, according to one embodiment.
[0019] FIG. 5C shows the substrate after the two peripheral points
have changed their respective height, according to one
embodiment.
[0020] FIG. 5D illustrates the change of the angle of incidence of
the ion beam depending on the tilting of the substrate, according
to one embodiment.
[0021] FIG. 6A illustrates a chamber where the precession motion
applied to the chuck/substrate is performed by two rotating cams,
according to one embodiment.
[0022] FIG. 6B illustrates a chamber where the precession motion
applied to the chuck/substrate is performed by three pushrods
connected to the bottom of the chuck, according to one
embodiment.
[0023] FIG. 6C illustrates a chamber where the precession motion
applied to the chuck/substrate is performed by two axis motors,
according to one embodiment.
[0024] FIG. 7 is a flowchart of an algorithm for processing the
substrate by applying a precession motion that changes over time,
according to one embodiment.
[0025] FIG. 8 is a simplified schematic diagram of a computer
system for implementing embodiments.
DETAILED DESCRIPTION
[0026] Embodiments provide a wobbling motion to a chuck in order to
change the position of the substrate supported by the chuck. By
changing the position of the substrate, the angle of the ion beams
from the plasma can be controlled. This allows the substrate to
change position without having to spin the substrate, which results
in savings in manufacturing by avoiding expensive components
required to rotate the substrate.
[0027] The following embodiments describe methods, devices,
systems, and computer programs for controlling the angle of
incidence of an ion beam on a substrate. It will be apparent, that
the present embodiments may be practiced without some or all of
these specific details. In other instances, well-known process
operations have not been described in detail in order not to
unnecessarily obscure the present embodiments.
[0028] FIG. 1 is a schematic cross-section diagram showing a plasma
processing system utilized for etching operations, in accordance
with one embodiment. The system includes a transport module 110
that carries the substrate, a gate valve, and chamber 114. The
substrate 112 enters the chamber through a substrate load 154, with
the substrate 112 being in a horizontal position when the substrate
enters the chamber 114. The chamber includes chuck assembly 115 and
position actuator 136. Chuck assembly 115 includes substrate
support 116 and precession assembly 140. In some embodiments a
dielectric window 106 is also present (not shown) in the
chamber.
[0029] The substrate support 116 can be an electrostatic chuck for
supporting substrate 112. Precession assembly 140 applies a
precession motion to the substrate support during operation to
change the angle of incidence of ions from the plasma when striking
the wafer, as discussed in more detail below.
[0030] Position actuator 136 rotates the chuck assembly 90.degree.
after the substrate has been loaded, in order to perform the
processing of the substrate while the substrate is in the vertical
position. Although the embodiment shown in FIG. 1 is for processing
substrates in the vertical position, the principles presented
herein to apply motion to the wafer/chuck may also be utilized in
chambers that process the substrate in the horizontal position.
[0031] Facilities 104 are connected to the chuck assembly to
provide electrical power to the substrate support, or to provide
liquid or gas to cool the substrate during operation. An ion source
134 generates the plasma for processing the substrate. In some
embodiments, an internal faraday shield (not shown) is disposed
inside the chamber 100. In some embodiments, the ion source 134 is
a TCP coil connected to match circuitry 102.
[0032] Further shown is a bias RF generator 120, which can be
defined from one or more generators. If multiple generators are
provided, different frequencies can be used to achieve various
tuning characteristics. A bias match 118 is coupled between the RF
generator 120 and a conductive plate of the assembly that defines
the substrate support 116. The substrate support 116 also includes
electrostatic electrodes to enable the chucking and dechucking of
the substrate. Broadly, a filter and a DC clamp power supply can be
provided. Other control systems for lifting the substrate off of
the substrate support 116 can also be provided.
[0033] Gas sources 128 include a plurality of gas sources that can
be mixed through manifolds 122. The gas sources include one or more
reactant gases (also referred to herein as main gases) and one or
more tuning gases. A reactant gas is an active gas used for
etching, and the reactant gas is a source of the species necessary
for etching over the substrate. Examples of reactant gases include
Cl.sub.2, HBr, and SF.sub.6, but other reactant gases may also be
used. It should be appreciated that multiple gas supplies may be
provided for supplying different gases to the chamber for various
types of operations, such as process operations on substrates,
substrate-less auto-cleaning operations, and other operations.
[0034] A vacuum pump 130 is connected to the chamber 114 to enable
vacuum pressure control and removal of gaseous byproducts from the
chamber during operational plasma processing. A valve 126 is
disposed between exhaust 124 and the vacuum pump 130 to control the
amount of vacuum suction being applied to the chamber.
[0035] The chamber 114 will also operate at vacuum conditions in
the range of between about 1 m Torr (mT) and about 500 m Torr (mT).
Although not all specifically shown, chamber 114 is typically
coupled to facilities when installed in a clean room, or a
fabrication facility. Facilities include plumbing that provide
processing gases, vacuum, temperature control, and environmental
particle control.
[0036] A programmable controller 108 is provided for controlling
the operation of the chamber 114 and its associated components.
Broadly speaking, the controller 108 can be programmed to execute a
chamber operation defined by a recipe. A given recipe may specify
various parameters for the operation, such as the application of
power to the TCP coils, the flow of gas into the chamber, and the
application of vacuum. It should be appreciated that the timing,
duration, magnitude, or any other adjustable parameter or
controllable feature can be defined by a recipe and carried out by
the controller to control the operation of the chamber 114 and its
associated components. Additionally, a series of recipes may be
programmed into the controller 108.
[0037] In one embodiment, the controller includes, or has access
to, plurality of precession motion profiles 152, where each
procession motion profiles includes instructions for generating the
procession motion in a particular operation in the chamber. The
precession motions vary the type of motion applied to the chuck,
such as frequency or amplitude of the motion, as discussed in more
detail below.
[0038] FIG. 2 illustrates the chamber during operation, according
to one embodiment. In one embodiment, the substrate 112 is loaded
into the substrate support 116, and after the substrate is loaded,
the position actuator rotates substrate support 116 90.degree. to
place substrate support 116 and substrate 112 in a vertical
position before the plasma is ignited. The ion source 134 is
disposed on the side of the chamber in a vertical orientation. It
is noted that embodiments may be implemented in chambers that
operate with the chuck in a vertical position or in a horizontal
position.
[0039] In prior solutions, the substrate is rotated (e.g., 10-120
revolutions per minute (RPM)) to change the angle of the substrate
with reference to the plasma, i.e., the ion beam striking the
substrate. The chuck holds the substrate, and the chuck has to have
a high voltage connection (e.g., facilities 104) and water cooling
to control the temperature of the substrate, so the substrate does
not become too hot due to the proximity to the plasma.
[0040] The problem with rotating the substrate is how to get
electrical, water, and even gas (in some embodiments) to the chuck.
Water, gas, and electrical connections must be connected, and these
connections require custom-built (or expensive) mechanical unions
that can transport those facilities through a spindle. The problem
is that rotating mechanical unions fail over time, and the
time-to-failure usually depends on the number of rotations. The
more the chuck spins, the sooner the spinning parts fail. Further,
failure can be catastrophic, because failure may cause water in the
chamber, or gases in a place where the gases can cause harm.
[0041] FIG. 3 illustrates a plurality of substrate positions when
the substrate is tilted during processing, according to one
embodiment. FIG. 3 illustrates the positions of the substrate when
processing the substrate in a horizontal initial position. Instead
of rotating the chuck, the chuck and the substrate are moved around
without actually rotating the chuck/substrate. The chuck is subject
to a precession motion, and the precession moves in a circular
fashion, but without spinning the chuck. The precession motion
could be described as a controlled wobble effect on the substrate,
where the highest point of the substrate changes over time, where
any of the points on the periphery of the substrate could be the
highest point of the substrate at some time. That is, the tilt axis
of the substrate changes over time, while the center of the
substrate remains substantially stationary. In one embodiment,
there is a rotating tilt of the surface of the substrate as the
precession motion is applied. It is similar to a planetary-type
oscillation. However, it is noted that the precession motion does
not include rotation (e.g., spinning) of the chuck/wafer.
[0042] It is contemplated that in other embodiments, the center of
the chuck may also move up and down to produce the same precession
effect, but still without rotating the chuck.
[0043] Such a motion achieves the same effect as tilting and
360.degree. rotation of the chuck without requiring fixture
rotation. All water, air, and electrical connections can be made by
flexible wires, or tubes. FIG. 3 illustrates different positions of
the substrate over time. The different positions show that the
highest point of the substrate changes over time, the angle of the
top surface of the substrate with reference to the plasma also
changes over time, and the tilt of the top surface of the substrate
rotates over time, without having chuck rotation.
[0044] FIGS. 4A-4B illustrate a chamber where the precession motion
applied to the chuck/substrate is performed by two actuators,
according to one embodiment. FIG. 4A is a side view of a chamber
for processing substrate 112. Precession assembly 140 includes two
actuators 404a and 404b that are connected to the bottom surface of
substrate support 115 at locations 403a and 403b, which are away
from the center of substrate support 115.
[0045] In general, an actuator is a type of motor that is
responsible for moving or controlling a mechanism or system. A
mechanical actuator functions by converting rotary motion into
linear motion to execute movement. It may involve gears, rails,
pulleys, chains or other devices to create the linear motion. An
example is a rack and pinion actuator that includes a pair of gears
which convert rotational motion into linear motion. A circular gear
called the pinion engages teeth on a linear gear bar called the
rack. The rotational motion applied to the pinion causes the rack
to move relative to the pinion, thereby translating the rotational
motion of the pinion into linear motion. Actuators 404a and 404b
move racks 402a and 402b under the substrate support 115 to create
the precession motion of the substrate support.
[0046] In addition, precession assembly 140 includes a fixed
support 406, which makes contact at point 405 with the bottom
surface of substrate support 115. In one embodiment, substrate
support rests on top of point 408, but other embodiments may
include different couplings between fixed support 406 and substrate
support 115, as long as substrate support 115 is able to pivot
around point 408 when the precession motion is applied.
[0047] In one embodiment, actuator racks 402a and 402b are
connected to the bottom surface of substrate support 115 in the
periphery of the bottom surface of substrate support 115. The
contact points for actuator racks 402a and 402b are separated a
certain angle with reference to the center point of the substrate
support. FIG. 4B illustrates a top view of substrate support 115,
which includes a contact point 408 in the center of the bottom
surface of the substrate support 115, and actuator racks 402a and
402b connected at the periphery of the substrate support at points
403a and 403b, respectively. In the exemplary embodiment of FIG.
4B, actuator racks 402a and 402b are separated 90.degree. with
reference to the center of the bottom surface of the substrate
support 115, but in other embodiments other separation angles are
possible, such as 30.degree., 135.degree., or any angle in the
range between 10.degree. and 350.degree..
[0048] As actuator racks 402a and 402b move up and down, the
corresponding contact points 403a and 403b also move up and down,
which causes the precession motion of the chuck. The orientation of
the surface of the substrate is the same as the orientation of the
substrate support, which is defined by the plane that includes the
three points 408, 403a and 403b.
[0049] Each of the actuator racks may go up and down a configurable
height, also referred to as amplitude, and may go up and down at a
certain frequency. Both the amplitudes and frequencies of the
actuators are independently controlled and are independent from
each other, thus the controller 108 is able to generate different
precession effects based on the frequencies and amplitudes. For
example, in some operations the precession effect is fast, but in
other operations the precession effect is slow, depending on the
desired effect on the substrate. This provides flexibility because
the processing recipe can change the frequencies and amplitudes of
the actuators depending on each processing step (e.g., depending on
the aspect ratio).
[0050] In this embodiment, precession assembly 140 includes the two
actuators 404a, 404b with the respective actuator racks 402a and
402b, and the fixed support 406. It is noted that the embodiments
illustrated in FIGS. 4A-4B are exemplary. Other embodiments may
connect the actuators on different parts of the chuck, as long as
the precession motion is generated, or the fix point on the bottom
of the chuck is away from center, etc. The embodiments illustrated
in FIGS. 4A-4B should therefore not be interpreted to be exclusive
or limiting, but rather exemplary or illustrative.
[0051] FIG. 5A illustrates the precession motion of the substrate
support by moving two peripheral points up and down, according to
one embodiment. In the embodiment of FIG. 5A, two points on the
periphery of the bottom of the substrate support are moved up and
down to generate the precession effect. For example, points P.sub.1
and P.sub.2 may be controlled by the two actuators of FIG. 4A, or
the rotating cams of FIG. 6A described below. In the exemplary
embodiment of FIG. 5A, points P.sub.1 and P.sub.2 are separated by
90.degree. with reference to the center of the substrate support,
but other embodiments may have different angular separations for
points P.sub.1 and P.sub.2.
[0052] Over time, the center of the substrate support remains
stationary and each of the points P.sub.1 and P.sub.2 moves up and
down with a certain defined amplitude. Therefore, the position of
the bottom surface of the substrate support, at any point in time,
is determined by three points: the center, point P.sub.1, and point
P.sub.2.
[0053] Points P.sub.1 and P.sub.2 move independently from each
other, and are controlled separately and independently by the
controller. Therefore, the position of the substrate with reference
to the plasma can change over time, allowing for infinite
possibilities for the orientation of the surface of the substrate
as the points move up and down. The embodiment of FIG. 5A shows
substrate support 115 in a horizontal position.
[0054] FIG. 5B is a chart showing the changes in height of the two
peripheral points over time, according to one embodiment. In one
embodiment, the height of each point P.sub.1 and P.sub.2, when
tracked over time, shows a cyclical sinusoidal shape, which depends
on the amplitude of the change (e.g., the maximum and minimum
heights) as well as the frequency. Because of the sinusoidal
movement, the motion of the substrate is smooth, without jerky
moves that may damage the substrate. In other embodiments, the
height profile of the points is not sinusoidal and may follow other
cyclical or non-cyclical motion patterns.
[0055] In the exemplary embodiment of FIG. 5B, the trajectory of
point P.sub.1 is tracked on line 504 and the trajectory of point
P.sub.2 is tracked on line 502. In this embodiment, the frequencies
are different and the amplitudes also are different, but in other
embodiments the amplitudes might be the same and the frequency may
also be the same. Although, if both frequencies are equal, the
substrate may teeter totter without changing the precession of the
substrate circularly.
[0056] In one embodiment, the frequency of the motion for one point
is determined by an actuator that cycles at 120 times per minute,
but other values are also possible. For example, the actuator may
cycle at a frequency in the range from 5-200 times per minute, or
in the range between 30-150 times per minute. In one embodiment,
the frequencies of the actuators are not multiple of each other in
order to avoid resonance patterns.
[0057] The controller is able to obtain the desired
precession/circular effect on the substrate by controlling
independently both points, P.sub.1 and P.sub.2. In other
embodiments, different combinations are possible. For example,
point P.sub.1 may move very slowly while point P.sub.2 moves very
fast, causing a teeter totter like effect on the substrate, where
the teeter totter changes the angle slowly over time. In other
embodiments, both frequencies are low, resulting in a slow change
of the orientation of the surface of the substrate, and in another
embodiment, both frequencies are fast, resulting in quick changes
of the orientation of the surface of the substrate with reference
to the plasma.
[0058] FIG. 5C shows the substrate after the two peripheral points
have changed their respective height, according to one embodiment.
FIG. 5C shows the position of the substrate support 115 after
points P.sub.1 and P.sub.2 have moved. Here, point P.sub.1 is about
one third of the distance between the stationary position and the
maximum height, and point P.sub.2 is about one quarter of the
distance from the stationary position to the bottom possible
height.
[0059] The center of the bottom surface of the substrate support
remains stationary, and the position of the bottom surface is
determined by the center, point P.sub.1, and point P.sub.2, as
three points define the plane of the bottom surface of the
substrate support. As points P.sub.1 and P.sub.2 move, so will the
plane defined by the bottom surface of the substrate support. In
some embodiments, the tilt of the surface may go up and to
80.degree. with respect to horizontal, but in other embodiments it
may be as low as 5.degree.. Therefore, the tilt created by the
motion of any point P.sub.1 or P.sub.2 may be in the range from
3.degree. to 85.degree., although other values are also
possible.
[0060] FIG. 5D illustrates the change of the angle of incidence of
the ion beams depending on the precession motion of the substrate,
according to one embodiment. Etching starts with a mask. If an ion
comes in at a certain angle, the ion will etch some region, but not
another one. The angle is a function of the aspect ratio of the
structure, and when the angle of the ion beam is increased, it is
possible to increase the aspect ratio.
[0061] In some etching patterns, there is a plurality of features
that follow a regular pattern, such as in a memory chip.
Controlling the angle of incidence allows the control of the aspect
ratio. However, as the substrate tilts, it is possible that shadows
to the ion flow are created. In the exemplary embodiment of FIG.
5D, the ion direction changes depending on the tilt of the surface
of the substrate. Sometimes, the ion direction will allow the ions
to hit features 515, such as ion beam 522. But other times, the ion
direction will be such that the ions will not hit features 515,
such as in ion direction 510.
[0062] In summary, the ion incidence angle changes depending on the
position of the substrate, and some features are blocked at certain
angles, while ions will reach the features at other angles.
[0063] If the pattern on the substrate is uniform, the controller
controls how fast or how slow the tilt changes over time in order
to take advantage of the channels that allow the ions to hit the
substrate features. This way, some ions come preferentially through
these channels.
[0064] In one embodiment, the speed of change is not uniform. For
example, at times the substrate tilts slowly when the ions are
hitting the desired features, but the substrate tilts faster when
there are shadows that block the ions from reaching the desired
features. In addition to the rate of change of the surface of the
substrate, the angle of the precession motion may also be
controlled to enhance the incidence of ions on the surface of the
substrate based on the process recipe.
[0065] Therefore, in one embodiment, the controller determines the
rate of change of the precession/tilt of the surface of the
substrate based on the angle of incidence of the ions. The
controller makes the amount of time that the substrate is in a
desired position as large as possible, while the controller makes
the amount of time that the substrate is in an undesirable position
as low as possible. This improves the aspect ratio and decreases
the amount of time required to etch deep features on the
substrate.
[0066] FIG. 6A illustrates a chamber where the precession motion
applied to the chuck/substrate is performed by two rotating cams,
according to one embodiment. Substrate support 116 in chamber 608
is connected to two rotating cams 622 and 624. As the rotating cams
rotate, each rotating cam moves up and down a point of the
substrate support, such as a point on the periphery of the chuck,
although other locations are also possible. In one embodiment, the
two points moved up and down by the rotating cams are separated
90.degree. with reference to the center of the substrate/chuck, but
in other embodiments other degrees of separation are also possible,
such as 45.degree., 135.degree., or any value in the range from
45.degree. to 180.degree..
[0067] Each of the rotating cams has a cam pin which is attached to
a point on the chuck. Depending on the height of the pin, the
corresponding point on the chuck will get a different
elevation.
[0068] Each of the rotating cams can be controlled separately by
the controller, and the control includes both the amplitude of the
change in elevation as well as the frequency of the rotating cam.
The frequencies and amplitudes of each of the rotating cams are
independent from each other, and the controller is able to generate
different precession effects based on the rotating frequencies of
the cams. For example, in some operations the precession effect is
fast, but in other operations the precession effect is slow,
depending on the desired effect on the substrate. This provides
flexibility because the processing recipe can change the
frequencies and amplitudes of the rotating cams depending on each
processing step (e.g., depending on the aspect ratio).
[0069] In this embodiment, precession assembly 140 includes the two
rotating camps with the respective actuators, as well as a center
support that is fixed (not shown because it is behind rotating cam
624), similar to the fixed support 406 of FIG. 4A.
[0070] FIG. 6B illustrates a chamber 640 where the precession
motion applied to the chuck/substrate is performed by three
pushrods connected to the bottom of the chuck, according to one
embodiment. In one embodiment, substrate support 116 is moved by
three push rods 606a, 606b, and 606c, connected to the bottom of
the chuck. The push rods 606a, 606b, and 606c are connected to
respective actuators 612a, 612b, and 612c, which are in
communication with controller 108. For clarity of description, some
of the elements in the chamber have been omitted, including a
substrate being held by substrate support 116.
[0071] Ion source 604 is above the vacuum chamber 608 and the ion
beams from the ion source 604 travel downwards. The three push rods
move up and down causing the change in orientation of the surface
of the substrate, e.g., the tilting and wobbling of the substrate,
i.e., the precession motion. The controller controls the motions of
the three push rods 606a, 606b, and 606c in order to produce the
desired movement of the chuck. In this embodiment, precession
assembly 140 includes the three push rods and their respective
actuators.
[0072] In another embodiment, one of the push rods is stationary
while the other two push rods move up and down, which means that
one push rod could be replaced by a fixed joint and the solution
could be implemented with just two push rods. For example, in one
embodiment a push rod is coupled to the center of the chuck and the
other two push rods are connected to other points underneath the
chuck. The center rod will be substantially stationary, while the
other two push rods move up and down.
[0073] In another embodiment, the three push rods are connected to
the chuck in a position near the periphery of the chuck and the
three points where the pushrods are connected form a equilateral
triangle whose center is underneath the center of the
substrate.
[0074] It is noted that the embodiments illustrated in FIG. 6B are
exemplary. Other embodiments may utilize different positions for
the push rods, as long as the controller may control the
orientation of the surface of the substrate. The embodiments
illustrated in FIG. 6B should therefore not be interpreted to be
exclusive or limiting, but rather exemplary or illustrative.
[0075] FIG. 6C illustrates a chamber where the precession motion
applied to the chuck/substrate is performed by two axis motors,
according to one embodiment. FIG. 6C is a top view of chamber 640,
which includes two axis motors 642 and 644. The two axis motors
combined produced the desired precession on the chuck/substrate. A
first axis motor 644 creates a teeter-totter effect that lifts the
second axis motor 642 up and down. The second axis motor 642
rotates to generate a precession effect on the chuck/substrate.
[0076] The combined effect produces the desire rotating precession
on the surface of the substrate. The controller of chamber 640
controls independently each of the two axis motors to obtain the
desired precession effect on the substrate. For example, the
precession effect may be smooth and slowly changing the orientation
of the surface of the substrate, or the precession effect may
produce fast changes on the orientation of the surface of the
substrate.
[0077] In one embodiment, first axis motor 644 is outside the
chamber while the second axis motor 642 is inside the chamber, but
in other embodiments both axis motors may be situated inside the
chamber (at vacuum) or outside the chamber. Further, in another
embodiment, the motor may be inside the chamber but encased in a
mini-chamber at atmospheric pressure under the chuck.
[0078] In the embodiments illustrated in FIGS. 4A, 6A, 6B and 6C,
there is no need for special spinning connectors. All that is
needed are flexible connectors that move with the motion of the
chuck. For example's, the flexible connectors may include flexible
tubing, flexible pipes, or flexible cables, etc. In addition, in
some embodiments, casing may be installed around the connectors to
lower the wear on the connectors.
[0079] It is noted that the embodiments illustrated in FIGS. 4A,
6A, 6B and 6C are exemplary. Other embodiments may utilize
different rotating devices, situate the motors or cams in different
locations, combine a motor with a pushing rod, etc., that enable
the precession effect without having to spin the chuck. The
embodiments illustrated in FIGS. 4A, 6A, 6B and 6C should therefore
not be interpreted to be exclusive or limiting, but rather
exemplary or illustrative.
[0080] FIG. 7 is a flowchart of an algorithm for processing the
substrate by applying a precession motion that changes over time,
according to one embodiment. While the various operations in this
flowchart are presented and described sequentially, one of ordinary
skill will appreciate that some or all of the operations may be
executed in a different order, be combined or omitted, or be
executed in parallel.
[0081] Operation 702 is for loading a substrate on a substrate
support within a chamber. From operation 702, the method flows to
operation 704 where a precession assembly in the chamber receives a
precession motion profile from a controller. The precession motion
profile identifies a precession motion to be applied to a chuck
during operation of the chamber. The precession assembly includes a
center support that is stationary and coupled to a center point of
an under region of the substrate support.
[0082] From operation 704, the method flows to operation 706 to
determine, based on the precession motion profile, a first
frequency and a first amplitude for the motion of a first actuator
in the precession assembly. The first actuator is connected to a
first location that is in the under region of the substrate support
and off-set from the center of the bottom surface of the substrate
support.
[0083] From operation 706, the method flows to operation 708 to
determine, based on the precession motion profile, a second
frequency and a second amplitude for the motion of a second
actuator in the precession assembly. The second actuator is
connected to a second location that is in the under region of the
substrate support and off-set from the center of the bottom surface
of the substrate support.
[0084] From operation 708, the method flows to operation 710 to
activate the first actuator and the second actuator with the
determined respective frequency and amplitude to generate the
precession motion of the substrate support. In operation 712, the
plasma is stricken in the chamber.
[0085] The precession motion is imparted when the substrate is on
the substrate support, the precession motion causing a rotating
tilt of the substrate support without rotation of the substrate
support. Further, the rotating tilt of the substrate is configured
to cause ions, generated by an ion source above the chamber, to
impinge upon a surface of the substrate continually varying angles
of incidence.
[0086] The precession motion is created when the first actuator and
the second actuator move up and down relative to the center
support, such that the first actuator moves up and down in
accordance with a first frequency and the second actuator moves up
and down in accordance with a second frequency, the first frequency
being independent of the second frequency.
[0087] FIG. 8 is a simplified schematic diagram of a computer
system for implementing embodiments. It should be appreciated that
the methods described herein may be performed with a digital
processing system, such as a conventional, general-purpose computer
system. Special purpose computers, which are designed or programmed
to perform only one function may be used in the alternative. The
computer system includes a central processing unit (CPU) 804, which
is coupled through bus 810 to random access memory (RAM) 806,
read-only memory (ROM) 812, and mass storage device 814. System
controller program 808 resides in random access memory (RAM) 806,
but can also reside in mass storage 814.
[0088] Mass storage device 814 represents a persistent data storage
device such as a floppy disc drive or a fixed disc drive, which may
be local or remote. Network interface 830 provides connections via
network 832, allowing communications with other devices. It should
be appreciated that CPU 804 may be embodied in a general-purpose
processor, a special purpose processor, or a specially programmed
logic device. Input/Output (I/O) interface provides communication
with different peripherals and is connected with CPU 804, RAM 806,
ROM 812, and mass storage device 814, through bus 810. Sample
peripherals include display 818, keyboard 822, cursor control 824,
removable media device 834, etc.
[0089] Display 818 is configured to display the user interfaces
described herein. Keyboard 822, cursor control 824, removable media
device 834, and other peripherals are coupled to I/O interface 820
in order to communicate information in command selections to CPU
804. It should be appreciated that data to and from external
devices may be communicated through I/O interface 820. The
embodiments can also be practiced in distributed computing
environments where tasks are performed by remote processing devices
that are linked through a wire-based or wireless network.
[0090] Embodiments may be practiced with various computer system
configurations including hand-held devices, microprocessor systems,
microprocessor-based or programmable consumer electronics,
minicomputers, mainframe computers and the like. The embodiments
can also be practiced in distributed computing environments where
tasks are performed by remote processing devices that are linked
through a network.
[0091] With the above embodiments in mind, it should be understood
that the embodiments can employ various computer-implemented
operations involving data stored in computer systems. These
operations are those requiring physical manipulation of physical
quantities. Any of the operations described herein that form part
of the embodiments are useful machine operations. The embodiments
also relates to a device or an apparatus for performing these
operations. The apparatus may be specially constructed for the
required purpose, such as a special purpose computer. When defined
as a special purpose computer, the computer can also perform other
processing, program execution or routines that are not part of the
special purpose, while still being capable of operating for the
special purpose. Alternatively, the operations may be processed by
a general purpose computer selectively activated or configured by
one or more computer programs stored in the computer memory, cache,
or obtained over a network. When data is obtained over a network
the data may be processed by other computers on the network, e.g.,
a cloud of computing resources.
[0092] One or more embodiments can also be fabricated as computer
readable code on a computer readable medium. The computer readable
medium is any data storage device that can store data, which can be
thereafter be read by a computer system. Examples of the computer
readable medium include hard drives, network attached storage
(NAS), read-only memory, random-access memory, CD-ROMs, CD-Rs,
CD-RWs, magnetic tapes and other optical and non-optical data
storage devices. The computer readable medium can include computer
readable tangible medium distributed over a network-coupled
computer system so that the computer readable code is stored and
executed in a distributed fashion.
[0093] Although the method operations were described in a specific
order, it should be understood that other housekeeping operations
may be performed in between operations, or operations may be
adjusted so that they occur at slightly different times, or may be
distributed in a system which allows the occurrence of the
processing operations at various intervals associated with the
processing, as long as the processing of the overlay operations are
performed in the desired way.
[0094] Although the foregoing embodiments have been described in
some detail for purposes of clarity of understanding, it will be
apparent that certain changes and modifications can be practiced
within the scope of the appended claims. Accordingly, the present
embodiments are to be considered as illustrative and not
restrictive, and the embodiments are not to be limited to the
details given herein, but may be modified within the scope and
equivalents of the appended claims.
* * * * *