U.S. patent application number 16/354638 was filed with the patent office on 2020-09-17 for apparatus, system and techniques for mass analyzed ion beam.
This patent application is currently assigned to APPLIED Materials, Inc.. The applicant listed for this patent is APPLIED Materials, Inc.. Invention is credited to Costel Biloiu, Alexandre Likhanskii, Joseph C. Olson, Frank Sinclair.
Application Number | 20200294755 16/354638 |
Document ID | / |
Family ID | 1000005059798 |
Filed Date | 2020-09-17 |
United States Patent
Application |
20200294755 |
Kind Code |
A1 |
Sinclair; Frank ; et
al. |
September 17, 2020 |
APPARATUS, SYSTEM AND TECHNIQUES FOR MASS ANALYZED ION BEAM
Abstract
An apparatus may include a housing including an entrance
aperture, to receive an ion beam. The apparatus may include an exit
aperture, disposed in the housing, downstream to the entrance
aperture, the entrance aperture and the exit aperture defining a
beam axis, extending therebetween. The apparatus may include an
electrodynamic mass analysis assembly disposed in the housing and
comprising an upper electrode assembly, disposed above the beam
axis, and a lower electrode assembly, disposed below the beam axis.
The apparatus may include an AC voltage assembly, electrically
coupled to the upper electrode assembly and the lower electrode
assembly, wherein the upper electrode assembly is arranged to
receive an AC signal from the AC voltage assembly at a first phase
angle, and wherein the lower electrode assembly is arranged to
receive the AC signal at a second phase angle, the second phase
angle 180 degrees shifted from the first phase angle.
Inventors: |
Sinclair; Frank; (Boston,
MA) ; Biloiu; Costel; (Rockport, MA) ; Olson;
Joseph C.; (Beverly, MA) ; Likhanskii; Alexandre;
(Malden, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
APPLIED Materials, Inc. |
Santa Clara |
CA |
US |
|
|
Assignee: |
APPLIED Materials, Inc.
Santa Clara
CA
|
Family ID: |
1000005059798 |
Appl. No.: |
16/354638 |
Filed: |
March 15, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01J 2237/057 20130101;
H01J 37/1472 20130101; H01J 37/3171 20130101; H01J 37/05
20130101 |
International
Class: |
H01J 37/05 20060101
H01J037/05; H01J 37/147 20060101 H01J037/147; H01J 37/317 20060101
H01J037/317 |
Claims
1. An apparatus, comprising: a housing including an entrance
aperture, to receive an ion beam; an exit aperture, disposed in the
housing, downstream to the entrance aperture, the entrance aperture
and the exit aperture defining a beam axis, extending therebetween;
an electrodynamic mass analysis assembly disposed in the housing
and comprising: an upper electrode assembly, disposed above the
beam axis; and a lower electrode assembly, disposed below the beam
axis; and an AC voltage assembly, electrically coupled to the upper
electrode assembly and the lower electrode assembly, wherein the
upper electrode assembly is arranged to receive an AC signal from
the AC voltage assembly at a first phase angle, and wherein the
lower electrode assembly is arranged to receive the AC signal at a
second phase angle, the second phase angle being 180 degrees
shifted from the first phase angle.
2. The apparatus of claim 1, wherein the upper electrode assembly
comprises: an upper entrance electrode, disposed in an entrance
chamber of the housing; a main upper electrode assembly, disposed
in a main chamber of the housing, downstream to the upper entrance
electrode; and an upper exit electrode, disposed in the main
chamber of the housing, downstream to the main upper electrode
assembly; and wherein the lower electrode assembly comprises: a
lower entrance electrode, disposed in the entrance chamber; a main
lower electrode assembly, disposed in the main chamber, downstream
to the lower entrance electrode; and a lower exit electrode,
disposed downstream to the main lower electrode assembly.
3. The apparatus of claim 2, wherein the main upper electrode
assembly and the main lower electrode assembly define a flared
relationship, wherein a separation between the main upper electrode
assembly and the main lower electrode assembly increases between an
upstream position of the main chamber and a downstream position of
the main chamber.
4. The apparatus of claim 2, further comprising a beam blocker, the
beam blocker being disposed in the main chamber and extending
across the beam axis, the beam blocker being set at ground
potential.
5. The apparatus of claim 2, wherein the entrance chamber further
comprises a ground tunnel, disposed downstream of the upper
entrance electrode and the lower entrance electrode, the ground
tunnel having an upper portion disposed above the beam axis and a
lower portion, disposed below the beam axis.
6. The apparatus of claim 1, wherein the AC signal comprises a
frequency of 200 kHz to 100 MHz.
7. The apparatus of claim 1, wherein the electrodynamic mass
analysis assembly comprises a plurality of electrodes, the
plurality of electrodes being elongated along an electrode axis,
the electrode axis extending perpendicularly to the beam axis.
8. The apparatus of claim 1, wherein the AC signal comprises a
maximum voltage amplitude of 1 kV to 100 kV.
9. A system, comprising: an ion source, disposed to generate an ion
beam; an electrodynamic mass analysis device, comprising: an
entrance aperture, disposed to receive the ion beam; an exit
aperture, disposed downstream to the entrance aperture, the
entrance aperture and the exit aperture defining a beam axis,
extending therebetween; an upper electrode assembly, disposed above
the beam axis; and a lower electrode assembly, disposed below the
beam axis; and a process chamber, disposed downstream of the exit
aperture, the process chamber comprising a substrate stage; and an
AC voltage assembly, electrically coupled to the upper electrode
assembly and the lower electrode assembly.
10. The system of claim 9, wherein the upper electrode assembly is
arranged to receive an AC signal from the AC voltage assembly at a
first phase angle, and wherein the lower electrode assembly is
arranged to receive the AC signal at a second phase angle, the
second phase angle being 180 degrees shifted from the first phase
angle.
11. The system of claim 9, further comprising an electrostatic
energy filter, disposed between the exit aperture and the process
chamber, wherein the electrostatic energy filter is arranged to
deflect the ion beam from the beam axis to a process axis, over an
angular range of 10 degrees to 60 degrees.
12. The system of claim 10, wherein the upper electrode assembly
comprises: an upper entrance electrode, disposed in an entrance
chamber of the housing; a main upper electrode assembly, disposed
in a main chamber of the housing, downstream to the upper entrance
electrode; and an upper exit electrode, disposed in the main
chamber of the housing, downstream to the main upper electrode
assembly; and wherein the lower electrode assembly comprises: a
lower entrance electrode, disposed in the entrance chamber; a main
lower electrode assembly, disposed in the main chamber, downstream
to the lower entrance electrode; and a lower exit electrode,
disposed downstream to the main lower electrode assembly.
13. The system of claim 12, wherein the main upper electrode
assembly and the main lower electrode assembly define a flared
relationship, wherein a separation between the main upper electrode
assembly and the main lower electrode assembly increases between an
upstream position of the main chamber and a downstream position of
the main chamber.
14. The system of claim 12, further comprising a beam blocker, the
beam blocker being disposed in the main chamber and extending
across the beam axis, the beam blocker being set at ground
potential.
15. The system of claim 12, wherein the entrance chamber further
comprises a ground tunnel, disposed downstream of the upper
entrance electrode and the lower entrance electrode, the ground
tunnel having an upper portion disposed above the beam axis and a
lower portion, disposed below the beam axis.
16. The system of claim 12, wherein the AC signal comprises a
frequency of 200 kHz to 100 MHz and a maximum voltage amplitude of
1 kV to 100 kV.
17. The system of claim 9, wherein the electrodynamic mass analysis
device comprises a plurality of electrodes, the plurality of
electrodes being elongated along an electrode axis, the electrode
axis extending perpendicularly to the beam axis.
18. A method of processing an ion beam, comprising: generating the
ion beam as a continuous ion beam; directing the continuous ion
beam along a beam axis into an electrodynamic mass analysis (EDMA)
device, the EDMA device comprising an upper electrode assembly,
disposed above the beam axis, and a lower electrode assembly,
disposed below the beam axis; and conducting the continuous ion
beam through the EDMA device while applying an AC voltage signal at
a target frequency and a target voltage amplitude to the upper
electrode assembly and to the lower electrode assembly, wherein a
target ion species having a first mass exits the EDMA device along
the beam axis, wherein an impurity ion species having a second
mass, different from the first mass does not exit the EDMA device
along the beam axis, and wherein a mass analyzed ion beam exits the
EDMA device.
19. The method of processing an ion beam of claim 18, further
comprising: directing the mass analyzed ion beam through an energy
filter, wherein a mass analyzed energy filtered ion beam is
generated; and directing the mass analyzed energy filtered ion beam
to a substrate.
Description
FIELD OF THE DISCLOSURE
[0001] The disclosure relates generally to ion beam apparatus and
more particularly to ion implanters having mass analysis.
BACKGROUND OF THE DISCLOSURE
[0002] Ion implantation is a process of introducing dopants or
impurities into a substrate via bombardment. Ion implantation
systems ("ion implanters") may comprise an ion source and a
substrate stage or process chamber, housing a substrate to be
implanted. The ion source may comprise a chamber where ions are
generated. Beamline ion implanters may include a series of
beam-line components, for example, a mass analyzer, a collimator,
and various components to accelerate or decelerate the ion
beam.
[0003] A useful function of an ion implanter beamline is to
separate ions of different masses so that an ion beam may be formed
having the desired ions for treating the work piece or substrate,
while undesirable ions are intercepted in a beamline component and
do not reach the substrate. In known systems, this mass analysis
function is provided by an analyzing magnet, which component bends
a beam of ions that all have the same energy in a curve whose
radius depends on the ion mass, thus achieving the required
separation. Magnets of this kind, however, are large, expensive and
heavy and represent a significant fraction of the cost and power
consumption of an ion implanter.
[0004] For relatively lower energy ion implantation, such as energy
below approximately 50 keV, compact ion beam systems have been
developed. These ion beam systems may include a plasma chamber
acting as ion source, and placed adjacent a process chamber,
housing the substrate to be implanted. An ion beam may be extracted
from the plasma chamber using an extraction grid or other
extraction optics to provide an ion beam to the substrate, with a
desired beam shape, such as a ribbon beam. In these latter systems,
mass analysis may be omitted because of size/space considerations
for installing a magnetic analyzer, as discussed above, as well as
cost. Thus, the use of such compact ion beam systems may be limited
to applications where purity of implanting species is not a strict
requirement.
[0005] With respect to these and other considerations, the present
disclosure is provided.
BRIEF SUMMARY
[0006] In one embodiment, an apparatus may include a housing
including an entrance aperture, to receive an ion beam, and an exit
aperture, disposed in the housing, downstream to the entrance
aperture, where the entrance aperture and the exit aperture define
a beam axis, extending therebetween. The apparatus may include an
electrodynamic mass analysis assembly disposed in the housing and
comprising an upper electrode assembly, disposed above the beam
axis, as well as a lower electrode assembly, disposed below the
beam axis. The apparatus may include an AC voltage assembly,
electrically coupled to the upper electrode assembly and the lower
electrode assembly. The upper electrode assembly may be arranged to
receive an AC signal from the AC voltage assembly at a first phase
angle, and the lower electrode assembly may be arranged to receive
the AC signal at a second phase angle, the second phase angle being
180 degrees shifted from the first phase angle.
[0007] In another embodiment, a system may include an ion source,
disposed to generate an ion beam and an electrodynamic mass
analysis device. The electrodynamic mass analysis device may
include an entrance aperture, disposed to receive the ion beam and
an exit aperture, disposed downstream to the entrance aperture,
where the entrance aperture and the exit aperture define a beam
axis, extending therebetween. The electrodynamic mass analysis
device may further include an upper electrode assembly, disposed
above the first axis; and a lower electrode assembly, disposed
below the first axis. The system may also include a process
chamber, disposed downstream of the exit aperture, the process
chamber comprising a substrate stage, and an AC voltage assembly,
electrically coupled to the upper electrode assembly and the lower
electrode assembly.
[0008] In a further embodiment, a method of processing an ion beam
may include generating the ion beam as a continuous ion beam and
directing the continuous ion beam along a beam axis into an
electrodynamic mass analysis (EDMA) device. The EDMA device may
include an upper electrode assembly, disposed above the beam axis,
and a lower electrode assembly, disposed below the beam axis. The
method may include conducting the continuous ion beam through the
EDMA device while applying an AC voltage signal at a target
frequency and a target voltage amplitude to the upper electrode
assembly and to the lower electrode assembly. As such, a target ion
species having a first mass may exit the EDMA device along the
first axis, wherein an impurity ion species having a second mass,
different from the first mass does not exit the EDMA device along
the first axis, and wherein a mass analyzed ion beam exits the EDMA
device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1A shows an exemplary apparatus, according to
embodiments of the disclosure;
[0010] FIG. 1B depicts the geometry for mass analysis of an ion
beam using the apparatus of FIG. 1A;
[0011] FIG. 2A shows the trajectories of a target ion species
according to one scenario for operating the apparatus of FIG. 1A,
according to other embodiments of the disclosure;
[0012] FIG. 2B shows the trajectories of an impurity ion species
according to the scenario of FIG. 2A;
[0013] FIG. 2C shows the trajectories of another impurity ion
species according to the scenario of FIG. 2A;
[0014] FIG. 2D shows a calculated filter profile for the apparatus
of FIG. 1A;
[0015] FIG. 2E illustrates simulated 11 amu target ion trajectories
for operating an apparatus in accordance with embodiments of the
disclosure;
[0016] FIG. 2F illustrates simulated 3 amu impurity ion
trajectories for operating under the conditions of FIG. 2E;
[0017] FIG. 2G illustrates simulated 19 amu impurity ion
trajectories for operating under the conditions of FIG. 2E;
[0018] FIG. 3A, FIG. 3B, and FIG. 3C illustrate simulated 11 amu, 3
amu, and 19 amu ion trajectories, respectively, for operating
another apparatus in accordance with embodiments of the
disclosure;
[0019] FIG. 4 depicts an exemplary system, arranged in accordance
with embodiments of the disclosure; and
[0020] FIG. 5 depicts an exemplary process flow according to some
embodiments of the disclosure.
[0021] The drawings are not necessarily to scale. The drawings are
merely representations, not intended to portray specific parameters
of the disclosure. The drawings are intended to depict exemplary
embodiments of the disclosure, and therefore are not be considered
as limiting in scope. In the drawings, like numbering represents
like elements.
DETAILED DESCRIPTION
[0022] An apparatus, system and method in accordance with the
present disclosure will now be described more fully hereinafter
with reference to the accompanying drawings, where embodiments of
the system and method are shown. The system and method may be
embodied in many different forms and are not be construed as being
limited to the embodiments set forth herein. Instead, these
embodiments are provided so this disclosure will be thorough and
complete, and will fully convey the scope of the system and method
to those skilled in the art.
[0023] As used herein, an element or operation recited in the
singular and proceeded with the word "a" or "an" are understood as
potentially including plural elements or operations as well.
Furthermore, references to "one embodiment" of the present
disclosure are not intended to be interpreted as precluding the
existence of additional embodiments also incorporating the recited
features.
[0024] Provided herein are approaches for mass analyzed ion
implantation systems, using a novel mass analysis device. In
various embodiments the mass analysis device may be implemented in
beamline ion implanters or in compact ion beam systems.
[0025] FIG. 1A depicts an apparatus 100, according to various
embodiments of the disclosure. The apparatus 100 may generally act
as a mass filter, referred to herein as an electrodynamic mass
analysis (EDMA) device. According to various embodiments, the
apparatus 100 may be deployed in a compact ion beam system, or
alternatively, in a beamline ion implantation system (ion
implanter). For purposes of clarity, the structure of the apparatus
100 may be shown in somewhat idealized form, where the relative
dimensions of various portions or parts of the apparatus 100 may or
may not be drawn to scale.
[0026] As shown in FIG. 1A the apparatus 100 may include an
enclosure 103 including an entrance aperture 106, to receive an ion
beam, as well as an exit aperture 108, disposed downstream to the
entrance aperture 106. The entrance aperture 106 and the exit
aperture 108 may define a beam axis 101, extending between the
entrance aperture 106 and the exit aperture 108. In the example of
FIG. 1A, the beam axis 101 lies parallel to the Z-axis of the
Cartesian coordinate system shown. As detailed with respect to the
various figures to follow, the apparatus 100 may be operated in a
manner where select ions of a desired mass enter through entrance
aperture 106 having trajectories generally parallel to the beam
axis 101 and exit through the exit aperture generally parallel to
the beam axis 101, while being deflected along different
trajectories within the interior of the apparatus 100.
[0027] To perform mass analysis, the apparatus 100 may include an
electrodynamic mass analysis assembly, including an upper electrode
assembly 102, disposed above the beam axis 101, and a lower
electrode assembly 104, disposed below the beam axis 101.
[0028] In some embodiments, the upper electrode assembly 102 and
the lower electrode assembly 104 may include a plurality of
electrodes, where the plurality of electrodes are elongated along
an electrode axis (represented by the X-axis) where the electrode
axis extends perpendicularly to the beam axis. This configuration
may be especially suitable for treating ribbon beams, where the
ribbon beam is characterized by a long axis in cross-section
extending along the X-axis. However, in other embodiments the
electrodes of the apparatus 100 may treat a spot or pencil beam
having a more equiaxed shape in cross-section.
[0029] The upper electrode assembly 102 may include an upper
entrance electrode 112, disposed in an entrance chamber 110, a main
upper electrode assembly 122, disposed in a main chamber 120,
downstream to the upper entrance electrode 112, and an upper exit
electrode 132, disposed downstream to the main upper electrode
assembly 122.
[0030] The lower electrode assembly 104 may include a lower
entrance electrode 114, disposed in the entrance chamber 110, a
main lower electrode assembly 124, disposed in the main chamber
120, and a lower exit electrode 134, disposed downstream to the
main lower electrode assembly 124.
[0031] According to various embodiments, the main upper electrode
assembly 122 and the main lower electrode assembly 124 may define a
flared relationship, wherein a separation between the main upper
electrode assembly and the main lower electrode assembly increases
between an upstream position of the main chamber and a downstream
position of the main chamber. This flared relationship may aid in
reducing ion impacts from an ion beam traveling through the
enclosure 103.
[0032] As shown in FIG. 1A, the apparatus 100 may also include a
beam blocker 109, disposed in the main chamber 120, and extending
across the beam axis 101. The beam blocker 109 may be set at ground
potential, where the operation of beam blocker 109 is further
detailed below.
[0033] The apparatus 100 may include a ground tunnel in the
entrance chamber 110, disposed downstream of the upper entrance
electrode 112 and the lower entrance electrode 114. As shown in
FIG. 1A, the ground tunnel may include an upper portion 116,
disposed above the beam axis 101 and a lower portion 118, disposed
below the beam axis 101. In various embodiment, the ground tunnel
may also be characterized by a flared shape in the Y-Z plane, as
shown in FIG. 1.
[0034] The apparatus 100 may include an AC voltage assembly 160,
electrically coupled to the upper electrode assembly 102 and the
lower electrode assembly 104. As described in more detail below,
the upper electrode assembly 102 may be arranged to receive an AC
signal from the AC voltage assembly 160 at a first phase angle,
while the lower electrode assembly 104 is arranged to receive the
AC signal at a second phase angle, the second phase angle being 180
degrees shifted from the first phase angle.
[0035] In brief, the provision of an AC voltage signal (see AC
voltage assembly 160 of FIG. 1) to the electrodes of apparatus 100
facilitates deflection of ions along different trajectories
according to their mass and arrival time in the entrance aperture
106. In various non-limiting embodiments, the AC signal may have a
frequency of 200 kHz to 100 MHz. Moreover, in some embodiments, the
AC signal may have a voltage where a maximum voltage amplitude is
between 1 kV to 100 kV. As detailed below, within such energy range
and frequency range, ions having different mass may be conveniently
filtered when traveling through an electrodynamic mass analysis
device, such as the apparatus 100.
[0036] FIG. 1B illustrates general features of the geometry for
mass filtering performed by the apparatus of FIG. 1A, showing the
various components inside enclosure 103, as well as an ion beam
150. The ion beam 150 may enter the enclosure 103 from the left
through entrance aperture 106 (see FIG. 1A). The ion beam 150 may
include process ions 154, shown as curved trajectories, and
representing ions of a targeted mass for use in implantation, for
example. Other impurity species may be present in the ion beam 150
before entering the enclosure 103. These impurities are represented
by the ions 152. By application of an AC voltage signal having an
appropriate frequency, as well as voltage amplitude, the process
ions 154 are deflected in the trajectories shown in the solid
curves, and exit the enclosure 103 via the exit aperture 108 (see
FIG. 1A), generally parallel to the beam axis 101 and close enough
to the beam axis 101 to exit through the exit aperture 108, as
shown. Upon exit along the beam axis, such ions may then be
transported downstream to a substrate to be processed.
[0037] The ions 152 have a different mass than the mass of process
ions 154. Again, by appropriate selection of various parameters,
the ions 152 may be deflected along trajectories that cause the
ions 152 to be captured within the enclosure 103, or may be caused
to exit through exit aperture 108 along trajectories that are not
parallel to the beam axis 101, and thus to not strike a substrate
to be processed. These various parameters may include frequency of
the applied AC voltage, voltage amplitude, as well as the
geometrical arrangement of various components within the enclosure
103.
[0038] FIG. 2A shows one scenario for operating the apparatus 100
of FIG. 1A, according to other embodiments of the disclosure. In
this scenario, a 20 keV .sup.11B.sup.+ ion beam enters the
apparatus 100 from the left. The boron ions represent the targeted
ions to be transported through the apparatus 100, with minimal
filtering loss. The ion beam 202 is made of individual ions
traveling with a velocity determined by their energy and mass,
generally along the beam axis 101 during entry into the enclosure
103. The scenario of FIG. 2A represents the simulation of the
trajectories of various different ions that enter the enclosure at
different instances. An AC signal is applied to generate a 2 MHz
sinusoidally varying time-dependent field in the vertical direction
(Y-axis) with a maximum amplitude of 2E5V/m. The AC signal is
applied in a manner so that at any given instance, electrodes of
the upper electrode assembly 102 are driven by a first voltage
signal that is 180 degrees out of phase with a second voltage
signal at the lower electrode assembly 104. This phase shift
establishes the time-dependent electric field along the Y-axis. The
electric fielded is shielded in portions of the enclosure 103 that
are grounded, such as between upper portion 116 and lower portion
118 of the ground tunnel, and also in a region just upstream of the
upper exit electrode 132 and lower exit electrode 134. As shown by
the various trajectories, representing different arrival times,
corresponding to different phases of the AC signal, the ion beam
202 returns to the original line of flight and the original angle,
oriented along the beam axis 101, regardless of the phase (arrival
time) for different ions. In the example of FIG. 2A, the dimensions
(shown in meters) are such that the ions of ion beam 202 traverse
through the enclosure 103 in approximately one cycle (360
degrees).
[0039] As the ions enter the enclosure 103, the electric field
appears on for approximately 65.degree. adjacent the upper entrance
electrode 112 and lower entrance electrode 114. The electric field
appears off for approximately 65.degree., adjacent the ground
tunnel, on for approximately 175.degree., in the left portion of
the main chamber 120, off for approximately 65.degree. and then on
for approximately 65.degree., toward the right of the main chamber
120 and left of the exit chamber 130. This arrangement causes the
trajectory of any given ion to be bent initially in the entrance
chamber 110, to drift in a straight line adjacent the ground
tunnel, to be bent again in the initial portion of the main chamber
120, to drift in a straight line while exiting the main chamber
120, and to again be bent in the exit chamber 130.
[0040] FIG. 2B shows the trajectories of impurity ions having a
mass of 1 amu, according to the scenario for operating the
apparatus 100 of FIG. 2A. Thus, the same AC voltage signal is
applied to deflect the ions 204, as the AC voltage signal used to
deflect the ions 202. Because the mass of the ions 204 is much
lighter than for ions 202, the ions 204 travel through the
enclosure 103 much faster, and after being deflected in an initial
direction, off of the beam axis 101, are collected in the interior
walls, because the electric field does not switch rapidly enough to
reverse the initial deflection.
[0041] FIG. 2C shows the trajectories of impurity ions having a
mass of 40 amu, according to the scenario for operating the
apparatus 100 of FIG. 2A. In this example, the much heavier ions,
ions 206, travel much more slowly than ions 202, will experience
less transverse deflection along the Y-axis, and may be deflected
through multiple cycles while traveling through the enclosure 103.
The ions 206 thus tend to travel along more overall linear
trajectories as shown, while some ions, depending upon their
arrival time in the apparatus 100, may tend to travel along the
beam axis 101 or close to the beam axis 101. To ensure that such
heavier ions are properly screened, the beam blocker 109 may be
provided to extend across the beam axis 101 and to intercept any
ions traveling along the beam axis 101. Notably any of the ions
206, tending to exit through exit aperture 108 will exhibit
trajectories that are not parallel to the beam axis 101, and may be
intercepted at different components downstream, before striking a
substrate.
[0042] FIG. 2D shows a calculated filter profile for the apparatus
of FIG. 1A, based upon filtering for mass in the range of 10-11 amu
(boron).
[0043] In accordance with various embodiments of the disclosure,
the dimensions and the operation of the apparatus 100 may be
engineered to accommodate a wide variety of ion beam sizes, ion
energies, ion masses and AC frequencies. These parameters are
related by the simple equation
L = n f 2 E m Eq 1 ##EQU00001##
where L is the length from the entrance to the exit of the
enclosure 103, n is the number of cycles of the AC voltage of
frequency f, E is the ion energy and m is the ion mass. The
parameter n depends on the detailed trajectory chosen, and may in
general be an integer or non-integer value. In the arrangement of
FIG. 2A, n is chosen to be 1. Table 1 shows a sample of the
possible masses, energies, frequencies and lengths that may be used
to filter different ions. The minimum length may be limited by the
geometry of the incoming ion beam: in order to achieve good
separation, the length has to be more than approximately 10 times
the height of the ion beam along the Y-axis. If the incoming ion
beam has a wide range of angles, the length should be short enough
that the initial angle spread does not overcome the mass
separation. As dimensions of enclosure 103 on the order of several
centimeters to less than one meter may accommodate many well-known
implant species for mass filtering, using frequencies in the range
of hundreds of kHz to less than 10 MHz. The embodiments are not
limited in this context. In view of the above, according to some
embodiments, the enclosure 103 may be constructed to have a
targeted length for a given implant species. Thus, given an AC
voltage assembly operating at 2 MHz, for 10 KeV energy, an
enclosure 103 having a length of 0.21 M may be to construct an EDMA
device appropriate for transmitting boron ions, while an EDMA
device using enclosure 103 having a length of 0.12 m may be
appropriate for transmitting 10 keV phosphorous ions.
TABLE-US-00001 TABLE I Ion H B P As Mass (amu) 1 1 1 11 11 11 31 31
31 75 75 75 Energy (keV) 1 5 10 10 10 20 10 10 30 10 30 30
Frequency (kHz) 6780 6780 2000 2000 6780 2000 1200 2000 2000 800
1200 2000 Length (m) 0.06 0.14 0.69 0.21 0.06 0.30 0.21 0.12 0.22
0.20 0.23 0.14
[0044] Notably, in other embodiments, a given EDMA device having a
given length of enclosure 103 (along the Z-axis), may be used to
transmit different ion species by changing the frequency applied to
the electrodes or the energy of the incoming beam, as appropriate.
Table II provides a set of ion energies corresponding to a length L
(see Eq. 1) of 0.3 m for enclosure 103, as a function of AC voltage
frequency for hydrogen (amu=1), boron (amu=11), phosphorous
(amu=31), and arsenic (amu=75).
TABLE-US-00002 TABLE II L(m) = 0.3 M(amu) 1 11 31 75 Energy (keV)
Frequency 800 0.3 3.3 9.3 23 (kHz) 1200 0.7 7.4 21 50.7 2000 1.9 21
58 141 6780 22 237 669 1619
[0045] As shown in table II., for a given ion energy (e.g. 22
keV+/-1 eV), the frequency of the AC voltage decreases with
increasing mass (showing a square root dependence), but well within
the range of commercially available RF supplies. Thus, different AC
voltage (RF voltage in this case) supplies may be used as
appropriate to drive the same enclosure having a given length L, in
order to transmit ions of different masses for a given ion
energy.
[0046] More generally, the dimensions of drift regions, deflection
regions, and number of different regions may be tailored to
optimize EDMA device performance.
[0047] FIG. 2E illustrates simulated 11 amu target ion trajectories
for operating an apparatus 240 in accordance with embodiments of
the disclosure. In this example, the ion trajectories are simulated
trajectories for 20 keV .sup.11B.sup.+ ion beam by a 2 MHz
sinusoidally varying time dependent field in the Y-axis direction
with a maximum amplitude of 2E5V/m. The apparatus is generally
arranged as in apparatus 100, while no beam blocker is present.
Again, the ions 250 travel from left to right with different
trajectories representing different ion arrival times. The
apparatus is divided into different sections according to whether a
deflecting electric field is present, including deflection region
252, drift region 254, deflection region 256, drift region 258, and
deflection region 260. As with FIG. 2A, the ion trajectories all
diverge and then reconverge on a beam axis (0.00 in the
Z-direction). Thus, boron ions will tend to proceed through the
apparatus 240.
[0048] FIG. 2F illustrates simulated 3 amu impurity ion
trajectories for operating under the conditions of FIG. 2E. In this
example, the lighter ions, ions 270, are again collected off the
beam axis and do not complete a cycle, showing divergent paths to
the right of the apparatus 240
[0049] FIG. 2G illustrates simulated 19 amu impurity ion
trajectories for operating under the conditions of FIG. 2E. In this
case, the heavier ions, ions 280, are deflected through more than
one cycle, but again do not converge along the beam axis.
[0050] FIG. 3A, FIG. 3B, and FIG. 3C illustrate simulated 11 amu, 3
amu, and 19 amu ion trajectories, respectively, for operating
another apparatus in accordance with embodiments of the disclosure.
In this example, the apparatus 300 is arranged with a first
deflection region 304, drift region 306, and second deflection
region 308. Thus, the powered electrodes (not shown) in the
apparatus 300 may be arranged toward the entrance of an enclosure
and toward the exit of the enclosure, while a grounded region is
disposed in the middle of the enclosure.
[0051] In FIG. 3A, a transverse deflection of a 20 keV
.sup.11B.sup.+ ion beam by a 2 MHz sinusoidally varying time
dependent field in the vertical direction with a maximum amplitude
of 2E5V/m. The apparatus 300 is shown in very schematic form where
the dimensions along the Z-axis for various regions are sized to
treat the ion beam over 2.5 AC cycles (n=5/2) for the given
frequency of the AC field. The field is shielded in the regions
marked "drift". The various curves represent trajectories of
different ions of the ion beam, entering the apparatus 300 at
different times. The trajectories of the different ions of the ion
beam returns to the original line of flight (beam axis) and
original angle regardless of the phase with which the particular
ion of the ion beam enters the system. In region first deflection
region 304, the field is on for a full cycle, then shielded for a
half cycle in drift region 306, and then on again for a full cycle
in second deflection region 308. The ions 302 diverge and then
converge along a beam axis as shown.
[0052] In FIG. 3B, the 3 amu ions, ions 312, travel much more
rapidly through apparatus 300 and are not deflected through a full
cycle, with divergent trajectories as shown. In FIG. 3C, the 19 amu
ions, ions 322, are deflected in the apparatus 300 through more
than one cycle, while generally diverging away from the beam axis,
or in some occasions exiting along non-parallel directions. Thus,
just 20 keV .sup.11B.sup.+ ions propagate through the apparatus 300
and exit at the proper position and along the proper direction.
[0053] As noted, an EDMA device arranged according to the present
embodiments may be used to replace a magnetic mass analyzer, such
as a known magnetic mass analyzer, used in beamline ion implanters.
Moreover, the EDMA devices of the present embodiments may be used
to construct a novel compact ion implantation apparatus having mass
analysis capabilities. FIG. 4 depicts a novel ion implantation
system, shown as system 400. In this embodiment, the apparatus 100
includes an ion source 402. According to some variants, the ion
source 402 may include a plasma chamber, excited by any suitable
method, to generate a given ion species. The system 400 may include
extraction optics 404, coupled to a suppression supply 420 and an
extraction supply 422, to extract an ion beam 430A, such as a
ribbon beam (having a long axis along the X-axis).
[0054] The apparatus 100, including enclosure 103, having an
electrode assembly disposed therein, and generally configured as
described above with respect to FIG. 1, is disposed downstream of
extraction optics 404. The enclosure 103 is coupled to receive the
ion beam 430A, where the ion beam 430A includes unanalyzed ions,
where targeted ions for implantation may be mixed with impurity
ions. The enclosure 103 is coupled to receive an AC voltage signal
from AC voltage assembly 160, to perform mass analysis, as
described above. Notably, the AC voltage assembly may include known
components, including generators, resonators, and circuitry to
provide phase delay between voltage signals applied to the upper
electrode assembly 102 and the lower electrode assembly 104.
Accordingly, a mass analyzed ion beam 430B is directed out of the
enclosure 103.
[0055] The system 400 further includes a process chamber 410,
disposed downstream of the enclosure 103, to receive a mass
analyzed ion beam and expose a substrate 412 to the mass analyzed
ion beam. In some embodiments, a substrate stage 414 may be
provided in the process chamber 410, to scan the substrate 412, for
example, along the Y direction, where the mass analyzed ion beam
may be elongated along the X-direction. In this manner, the
entirety of the substrate 412 may be exposed to the mass analyzed
ion beam 430B. As suggested in FIG. 4, and according to optional
embodiments, the system 400 may include an energy filter 406,
arranged according to known electrostatic energy filters, to filter
out ions an energetic neutrals that do not have the targeted final
ion energy. To accomplish this energy filtering, the energy filter
406 may be coupled to a voltage source 408, arranged to deflect the
mass analyzed ion beam 430B from a first axis, such as the beam
axis in the enclosure 103, to a process axis, which axis may be
perpendicular to the plane of the substrate 412. The energy filter
may also include an accelerating or decelerating voltage to control
the final energy of the beam.
[0056] Thus, a mass analyzed, energy filtered ion beam 430C may be
provided to the substrate 412. Notably, in embodiments where the
enclosure 103 has the dimensions on the order of several tenths of
one meter, the entire distance between ion source 402 and process
chamber 410 may be on the order of 1 meter or less.
[0057] FIG. 5 depicts an exemplary process flow 500 according to
some embodiments of the disclosure. At block 502, an ion beam is
generated as a continuous ion beam. The ion beam may be generated
by any convenient means according to various embodiments.
[0058] At block 504, the continuous ion beam is directed along a
beam axis into an electrodynamic mass analysis (EDMA) device. The
EDMA device may include an upper electrode assembly and lower
electrode assembly, where the upper electrode assembly is disposed
above the beam axis and lower electrode assembly is disposed below
the beam axis.
[0059] At block 506, the continuous ion beam is conducted through
the EDMA device while applying an AC voltage at a target frequency
and target amplitude. The target frequency may be tuned according
to the energy of the continuous ion beam and the target ion species
to be transmitted through the EDMA device. As such, the target ion
species having a first mass and a target energy exits the EDMA
device along the beam axis, while ion species having a second mass,
different from the target mass does not exit the EDMA device along
the beam axis. In this manner, the impurity ion species may be
filtered from continuing to propagate along the beam axis toward a
substrate to be implanted.
[0060] In view of the foregoing, at least the following advantages
are achieved by the embodiments disclosed herein. A first advantage
is realized by providing a more compact mass analysis component for
mass analyzing an ion beam. A second advantage is expense saved in
providing an EDMA type system for mass analysis. A third advantage
is provided in that high frequency AC fields used to perform mass
analysis according to the present embodiments will probably not
transport particles, and thus reduce particle contamination. A
further advantage is the relatively higher throughput of the mass
analyzer according to the present embodiments, simulated to be
above 50% and in some cases as high as 70%.
[0061] While certain embodiments of the disclosure have been
described herein, the disclosure is not limited thereto, as the
disclosure is as broad in scope as the art will allow and the
specification may be read likewise. Therefore, the above
description are not to be construed as limiting. Those skilled in
the art will envision other modifications within the scope and
spirit of the claims appended hereto.
* * * * *