U.S. patent application number 14/163833 was filed with the patent office on 2015-04-23 for dual stage scanner for ion beam control.
This patent application is currently assigned to Varian Semiconductor Equipment Associates, Inc.. The applicant listed for this patent is Varian Semiconductor Equipment Associates, Inc.. Invention is credited to Christopher Campbell, Robert C. Lindberg, Joseph C. Olson, Kenneth H. Purser, Frank Sinclair.
Application Number | 20150108361 14/163833 |
Document ID | / |
Family ID | 52707824 |
Filed Date | 2015-04-23 |
United States Patent
Application |
20150108361 |
Kind Code |
A1 |
Purser; Kenneth H. ; et
al. |
April 23, 2015 |
DUAL STAGE SCANNER FOR ION BEAM CONTROL
Abstract
An ion beam scanner includes a first scanner stage having a
first opening to transmit an ion beam, the first scanner stage to
generate, responsive to a first oscillating deflection signal, a
first oscillating deflecting field within the first opening; a
second scanner stage disposed downstream of the first scanner stage
and having a second opening to transmit the ion beam, the second
scanner stage to generate, responsive to a second oscillating
deflection signal, a second oscillating deflecting field within the
second opening that is opposite in direction to the first
oscillating deflecting field, and a scan controller to synchronize
the first oscillating deflection signal and second oscillating
deflection signal to generate a plurality of ion trajectories when
the scanned ion beam exits the second stage that define a common
focal point.
Inventors: |
Purser; Kenneth H.;
(Gloucester, MA) ; Campbell; Christopher;
(Newburyport, MA) ; Sinclair; Frank; (Boston,
MA) ; Lindberg; Robert C.; (Rockport, MA) ;
Olson; Joseph C.; (Beverly, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Varian Semiconductor Equipment Associates, Inc. |
Gloucester |
MA |
US |
|
|
Assignee: |
Varian Semiconductor Equipment
Associates, Inc.
Gloucester
MA
|
Family ID: |
52707824 |
Appl. No.: |
14/163833 |
Filed: |
January 24, 2014 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61894065 |
Oct 22, 2013 |
|
|
|
Current U.S.
Class: |
250/396R |
Current CPC
Class: |
H01J 37/1475 20130101;
H01J 37/3171 20130101 |
Class at
Publication: |
250/396.R |
International
Class: |
H01J 37/147 20060101
H01J037/147 |
Claims
1. An ion beam scanner, comprising: a first scanner stage having a
first opening to transmit an ion beam in a ribbon beam mode and in
a spot beam mode, wherein in the spot beam mode the first scanner
stage is configured to generate, responsive to a first oscillating
deflection signal, a first oscillating deflecting field within the
first opening; a second scanner stage disposed downstream of the
first scanner stage and having a second opening to transmit the ion
beam in the ribbon beam mode and in the spot beam mode, wherein in
the spot beam mode the second scanner stage is configured to
generate, responsive to a second oscillating deflection signal, a
second oscillating deflecting field within the second opening that
is opposite in direction to the first oscillating deflecting field;
and a scan controller to synchronize the first oscillating
deflection signal and second oscillating deflection signal to
generate a plurality of ion trajectories when the scanned ion beam
exits the second stage that define a common focal point, and
wherein, in the ribbon beam mode the first scanner stage and second
scanner stage are configured to transmit a ribbon beam unperturbed,
wherein the ribbon beam fans out within the first scanner stage and
second scanner stage.
2. The ion beam scanner of claim 1, wherein the first oscillating
deflecting field and the second oscillating deflecting field lie
along a first direction that is perpendicular to a direction of
propagation of the ion beam at the first scanner stage.
3. The ion beam scanner of claim 1, wherein the first and second
scanner stages are magnetic scanners.
4. The ion beam scanner of claim 3, wherein the first oscillating
deflection signal is a first oscillating electric current having a
first oscillation period to generate a first oscillating magnetic
field, wherein the second oscillating deflection signal is a second
oscillating electric current having the first oscillation period to
generate a second oscillating magnetic field, and wherein the scan
controller is operative to synchronize the first and second
oscillating electric currents such that the first oscillating
current exhibits a 180 degrees phase offset from the second
oscillating current.
5. The ion beam scanner of claim 1, wherein the first and second
scanner stage are operative to generate a dog leg shaped trajectory
to a plurality of the ion trajectories, wherein the ion
trajectories converge at a virtual source in the common focal
point.
6. The ion beam scanner of claim 1, wherein the scan controller is
operative to vary a position of the focal point.
7. The ion beam scanner of claim 1, wherein the common focal point
lies upstream of the first scanner stage.
8. The ion beam scanner of claim 1, wherein the ion beam is a spot
ion beam in the spot beam mode.
9. An ion implanter, comprising: an ion source; beamline components
to generate a spot ion beam; and a dual stage scanner system
operative to scan the spot ion beam over a plurality of ion
trajectories to generate a scanned ion beam, wherein the dual stage
scanner system is operative to generate a first oscillating
deflecting field at a first scanner stage that has a first opening
to transmit an ion beam in a ribbon beam mode and in a spot beam
mode, and a second oscillating deflecting field at a second scanner
stage that is opposite in direction to the first oscillating
deflecting field, the second scanner stage having a second opening
to transmit the ion beam in a ribbon beam mode and in the spot beam
mode, wherein the plurality of ion trajectories define a plurality
of lines that converge at a focal point that is disposed upstream
of the dual stage scanner system, wherein the dual stage scanner
system is configured to switch from the spot beam mode in which the
dual stage scanner system scans the spot beam, and the ribbon beam
mode, and wherein, in the ribbon beam mode the first scanner stage
and second scanner stage are configured to transmit a ribbon beam
unperturbed, wherein the ribbon beam fans out within the first
scanner stage and second scanner stage.
10. The ion implanter of claim 9, further comprising a mass
resolving slit, wherein the focal point is located at the mass
resolving slit.
11. The ion implanter of claim 9, further comprising a collimator
located downstream of the dual stage scanner system and configured
to receive the scanned ion beam and generate a collimated ion beam
from therefrom, wherein the focal point is located at an object
point of the collimator.
12. The ion implanter of claim 9, wherein the first oscillating
deflecting field and the second oscillating deflecting field lie
along a first direction that is perpendicular to a direction of
propagation of the ion beam at the first scanner stage.
13. The ion implanter of claim 9, wherein the first and second
scanner stages are magnetic scanners.
14. The ion implanter of claim 9 wherein the dual stage scanner
system comprises a scan controller configured to: output a first
and second oscillating deflection signal that generate the
respective first and second oscillating deflection fields; and
synchronize the first oscillating deflection signal and second
oscillating deflection signal to generate the plurality of ion
trajectories.
15. The ion implanter of claim 14 wherein the scan controller is
operative to generate a 180 degree phase offset between the first
and second oscillating deflection signals.
16. (canceled)
17. A method of controlling a spot ion beam in a beamline ion
implanter, comprising; generating in a spot beam mode a first
oscillating deflecting field along a first direction perpendicular
to a direction of propagation of the spot ion beam when the spot
ion beam passes through a first region; generating in the spot beam
mode a second oscillating deflecting field along the first
direction when the spot ion beam passes through a second region
downstream to the first region, wherein the first and second
oscillating deflecting fields are interoperative to fan the spot
ion beam out over a plurality of trajectories that are not parallel
to the direction of propagation of the spot ion beam, and wherein
the plurality of trajectories have a common focal point; switching
from the spot beam mode to a ribbon beam mode; and in the ribbon
beam mode, transmitting unperturbed the ion beam as a ribbon beam
through the first region and the second region, wherein the ribbon
beam fans out within the first region and the second region.
18. The method of claim 17, further comprising synchronizing the
first and second oscillating deflecting fields wherein the first
oscillating deflecting field exhibits a 180 degrees phase offset
from the second oscillating deflecting field.
19. The method of claim 17, wherein the generating the first and
second oscillating deflecting fields comprises generating a first
and second oscillating magnetic field.
Description
RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional Patent
Application Ser. No. 61/894,065 , filed Oct. 22, 2013.
FIELD
[0002] The present embodiments relate to ion beam apparatus, and
more particularly, to scanners to control ion beams.
BACKGROUND
[0003] In the present day, ion implanters are often constructed to
optimize implantation according to a specific set of applications.
In current applications, for example, some beamline ion implanters
are configured to generate high current ribbon beams in which the
beam cross section that intercepts a substrate has a beam width
that is much greater than the beam height. In some configurations
the beam width is slightly larger than the size of a substrate at
the substrate plane e.g., 200, 300, or 400 mm, while the beam
height is on the order of 10 mm, 20 mm, or 30 mm, for example. By
scanning the substrate with respect to the ribbon beam in the
direction of the beam height, the entire substrate may be implanted
by the ion beam.
[0004] For other ion implantation applications, it may be
preferable to use a spot beam ion beam in which the beam height and
beam width are more equal. One advantage afforded by spot beam ion
implantation is the better control of dose uniformity afforded by
spot beams. In a spot beam ion implantation application, the spot
beam may be scanned along a first direction to cover the dimension
of a substrate in that direction that is being implanted. At the
same time, the substrate may be scanned in a direction
perpendicular to that of the scan direction of the spot beam. The
local ion dose concentration can be modified by adjusting the speed
of the ion beam along the direction of spot beam scanning This can
be accomplished under computer control in a manner that allows the
spot beam scanning to be carefully controlled to optimize ion dose
uniformity.
[0005] In many beamline ion implanters, after exiting a mass
resolving slit, the ion beam may propagate as a wide beam of
diverging ions to a collimator, which form a collimated ion beam
that is directed to the substrate being processed. In order to
provide the correct collimation of the ion beam, the collimator is
often set to collimate ions that originate from an object that is
placed at the plane of the mass resolving slit (MRS). This feature
makes it more difficult to operate the same beamline in both spot
beam mode and ribbon mode. In ribbon beam mode, the ion
trajectories generated by an analyzer magnet may focus at the MRS
to fan out into the collimator situated downstream. However in a
conventional ion implanter in a spot beam mode the ion beam may
pass through the mass resolving slit as a small beam having more
parallel ion trajectories. After exiting the mass resolving slit,
the spot beam is then deflected back and forth in a scanner by a
deflecting field oriented generally perpendicularly to the
direction of propagation of the spot beam. This scanning of the
spot beam forms a diverging fan of ion trajectories over time that
enters the collimator. The object location in this spot beam
configuration is within the scanner that is located downstream of
the mass resolving slit. The object location of a spot beam
generated from a scanner may therefore vary too much from the
object location of a ribbon beam for a collimator to properly
collimate both types of beams without extensive reconfiguration.
Accordingly, it is common practice for a ribbon beam ion implanter
to be employed for certain ion implantation steps or for certain
substrates, such as high dose implantation, while a separate spot
beam ion implanter is employed for other ion implantation steps
that require better dose control. It is with respect to these and
other considerations that the present improvements have been
needed.
SUMMARY
[0006] This Summary is provided to introduce a selection of
concepts in a simplified form that are further described below in
the Detailed Description. This Summary is not intended to identify
key features or essential features of the claimed subject matter,
nor is it intended as an aid in determining the scope of the
claimed subject matter.
[0007] In one embodiment, an ion beam scanner includes a first
scanner stage having a first opening to transmit an ion beam, the
first scanner stage to generate, responsive to a first oscillating
deflection signal, a first oscillating deflecting field within the
first opening; a second scanner stage disposed downstream of the
first scanner stage and having a second opening to transmit the ion
beam, the second scanner stage to generate, responsive to a second
oscillating deflection signal, a second oscillating deflecting
field within the second opening that is opposite in direction to
the first oscillating deflecting field , and a scan controller to
synchronize the first oscillating deflection signal and second
oscillating deflection signal to generate a plurality of ion
trajectories when the scanned ion beam exits the second stage that
define a common focal point.
[0008] In a further embodiment a ion implanter includes an ion
source; beamline components to generate a spot ion beam; and a dual
stage scan system operative to scan the spot ion beam over a
plurality of ion trajectories to generate a scanned ribbon beam,
wherein the dual stage scan system is operative to generate a first
oscillating deflecting field at a first stage, and a second
oscillating deflecting field at a second stage that is opposite in
direction to the first oscillating deflecting field, and wherein
the plurality of ion trajectories define a respective plurality of
lines that converge at a focal point that is disposed upstream of
the dual stage scan system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 depicts a top plan view in block form of a ion
implanter according to the present embodiments;
[0010] FIG. 2 depicts a top isometric view of a dual stage scanner
consistent with various embodiments;
[0011] FIG. 3A depicts the general relationship between an
exemplary dual stage scanner and ion beam shape;
[0012] FIG. 3B depicts in schematic form the geometrical
relationship of dual stage scanner and real and projected ion
trajectories in accordance with some embodiments;
[0013] FIGS. 3C and 3D depict exemplary oscillating deflection
signals;
[0014] FIG. 4 presents details of a magnetic scanner stage
according to various embodiments; and
[0015] FIGS. 5A and 5B depicts a top plan view in block form of
another embodiment of an ion implanter operating is ribbon beam and
spot beam modes, respectively.
DETAILED DESCRIPTION
[0016] The present embodiments will now be described more fully
hereinafter with reference to the accompanying drawings, in which
some embodiments are shown. The subject matter of the present
disclosure, however, may be embodied in many different forms and
should not be construed as limited to the embodiments set forth
herein. Rather, these embodiments are provided so that this
disclosure will be thorough and complete, and will fully convey the
scope of the subject matter to those skilled in the art. In the
drawings, like numbers refer to like elements throughout.
[0017] The embodiments described herein provide a novel dual stage
scanner to perform scanning of an ion beam. The dual stage scanner
may be used to scan the ion beam into a fan shape that has a range
of ion trajectories that are received by a collimator, while at the
same time establishing a common focal point of the scanned ion beam
that lies outside the dual stage scanner. In particular, as
detailed herein, the dual stage scanner provides a novel apparatus
and operation principle that allows the focal point to be set at a
desired location upstream to the dual stage scanner, such as at a
plane of the mass resolving slit of a beamline ion implanter. The
present embodiments facilitate, among other things, the ability to
operate a beamline ion implanter in both a ribbon beam and spot
beam mode without extensive reconfiguration between operating
modes. In addition, the present embodiments provide a new "control
knob" to adjust the location of the focal point of a scanned ion
beam as desired.
[0018] The term "focal point" refers to a point at which a
plurality of non-parallel ion trajectories converge or appear to
converge. As detailed below, to a collimator the focal point of a
scanned spot beam produced by a dual stage scanner may appear as a
source of the scanned spot beam that lies upstream of the dual
stage scanner. However, as detailed below, and in accordance the
present embodiments, such a source is a virtual source. This is
because the ion trajectories of the scanned ions do not fan out
until passing through the dual stage scanner which lies downstream
of this virtual source. In some embodiments, the dual stage scanner
may be configured to place the focal point of scanned ions at an
object point of a collimator that receive the scanned spot beam. In
this manner, the scanned spot beam may mimic geometry of a ribbon
beam that has its focus at the object point of the collimator.
Accordingly, an ion implanter that employs the dual stage scanner
may generate a same or similar beam geometry as received by the
collimator whether operating in a ribbon beam or spot beam
mode.
[0019] FIG. 1 depicts a top plan view in block form of an ion
implanter 100 according to the present embodiments. The ion
implanter 100 includes an ion source 102 used to generate ions,
analyzer magnet 104, vacuum chamber 106, dual stage scanner 108,
collimator 110, and substrate stage 112. The ion implanter 100 is
configured to generate an ion beam 120 and deliver the ion beam 120
to a substrate 114. For simplicity, the ion beam 120 is depicted
merely as a central ray trajectory of the ion beam. In various
embodiments, the ion source 102 may be an indirectly heated cathode
(IHC) ion source, an RF ion source, a microwave ion source or other
ion source. The analyzer magnet 104 may alter the trajectory of
ions extracted from the ion source 102 as in conventional analyzer
magnets. The vacuum chamber 106 may include a mass resolving slit
(not shown in FIG. 1) which may function as a conventional mass
resolving slit to screen out ions of undesired mass. In various
embodiments the dual stage scanner 108 may be a magnetic scanner or
an electrostatic scanner. The collimator 110 may be a magnetic
collimator that functions at least to generate a collimated ion
beam to be conducted to the substrate 114. The ion implanter 100
may include other beamline components including apertures,
dithering components, acceleration/deceleration lenses, each of
whose operation is well known. For clarity, further discussion of
such components is omitted herein.
[0020] As further illustrated in FIG. 1 the ion implanter 100
includes a scan controller 116 whose function is to control
scanning of an ion beam 120. Further details of operation of the
scan controller 116 and similar scan controllers are disclosed with
respect to the figures to follow. However, in brief, the scan
controller 116 may send signals to the two stages of the dual stage
scanner 108 to that generate of extinguish deflection fields within
the dual stage scanner 108. The scan controller 116 may also send
signals to adjust deflection fields in both stages of the dual
stage scanner 108 in a manner that sets a focal point of the
scanned ion beam 120 outside of the dual stage scanner. The scan
controller 116 may comprise one or more hardware elements as well
as software elements, such as switches, circuits, power supplies,
computer programs or routines, user interfaces, and the like.
[0021] For convenience in the discussion to follow, different
coordinate systems are employed to describe operation of the
present embodiments as shown in FIG. 1. At the dual stage scanner
108 a first Cartesian coordinate system whose components are
labeled Y, Xsc, and Zsc, is used. At the substrate 114 a second
Cartesian coordinate system whose components are labeled Y, Xs, and
Zs, is used. In each coordinate system, the Y-axis is parallel to
the same absolute direction. The Z-axis for the different
coordinate systems is in each case along the direction of central
ray trajectory of ion beam propagation at a particular point. Thus,
the absolute direction of the Zsc axis differs from that of the Zs
axis. Similarly Xsc differs from Xs.
[0022] In some embodiments, the ion implanter 100 may operate in
both ribbon beam and spot beam modes. In various embodiments, the
ribbon beam may have a relatively smaller aspect ratio defined by a
ratio of ion beam height along a direction parallel to the Y-axis
to ion beam width along a direction parallel to the Xsc axis. For a
ribbon beam this ratio may be less than one third and is in some
examples less than one tenth. For example, a ribbon beam provided
to the substrate 114 whose ions have trajectories along the Zs axis
may have a width along the Xs axis of 300 to 400 mm and a height
along the Y axis of 20 mm at the substrate 114, yielding an aspect
ratio of less than 0.1. The embodiments are not limited in this
context. In various embodiments, the spot beam may have a
relatively larger aspect ratio such as greater than 1/2 and in some
cases greater than one. For example, a spot beam provided to the
substrate 114 may have a width along the Xs axis of 20 mm and a
height along the Y axis of 30 mm. The embodiments are not limited
in this context. It is to be noted that the aforementioned spot
beam dimensions apply to the instantaneous dimension of a spot
beam, and that the overall treatment area of a scanned spot beam
may be the same or similar to that of a ribbon beam.
[0023] Because the ion implanter 100 may operate in either ribbon
beam mode or spot beam mode, the ion implanter 100 provides
convenience and process flexibility for processing substrates when
a succession of implantation operations for a set of substrates or
for different sets of substrates may require different implantation
modes. This avoids the requirement to direct substrates to be
processed by ribbon beam ion implantation or spot beam ion
implantation to a respective ion implanter dedicated for ribbon
beam or spot beam implantation.
[0024] When a ribbon beam mode is set for the ion implanter 100 a
ribbon beam may be generated at the ion source 102 and focused at
an MRS (not shown) provided in the vacuum chamber 106. In ribbon
beam mode the dual stage scanner 108 may remain inactive or the
scan controller 116 may deactivate any scan signals from being sent
to the dual stage scanner 108. In this manner the dual stage
scanner may transmit the ribbon beam unperturbed. The ribbon beam
may then fan out as it propagates into the collimator 110. The
collimator 110 may be adjusted to provide collimation to such a
ribbon beam. As such the collimator 110 may be set to collimate a
beam having a focal point at the MRS.
[0025] In the present embodiments, ion implanter 100 may also be
operated in spot beam mode, which entails activating the dual stage
scanner 108 so that a spot beam emerging from the vacuum chamber
106 is scanned such that the ion trajectories fan out over a range
of angles before entering the collimator 110. Consistent with the
present embodiments, and as detailed below, the dual stage scanner
108 may be set to scan a spot beam in a manner that creates a
virtual source of the spot beam at an MRS within the vacuum chamber
106. This allows the ion implanter 100 to be operated in spot beam
mode without reconfiguration of the collimator 110, since the spot
beam may appear to emanate from the same position as a ribbon beam
generated when the ion implanter is operated in ribbon beam mode.
As detailed below, this is accomplished by the manner in which the
dual stage scanner generates a first oscillating deflection signal
in a first scanner stage and a second oscillating deflection signal
in a second scanner stage. These oscillating deflection signals are
synchronized so that in concert they produce respective first and
second oscillating deflection fields that alter ion trajectories
when a spot beam is scanned through the dual stage scanner 108 in a
manner that creates a virtual source at an appropriate location
such as the mass resolving slit.
[0026] FIG. 2 depicts an isometric top view of a dual stage scanner
200 consistent with various embodiments. In the example shown in
FIG. 2 the dual stage scanner 200 includes a first scanner stage
202 and a second scanner stage 204 disposed downstream from the
first scanner stage. The second scanner stage 204 is "downstream"
of the first scanner stage 202 in that the ion beam 206 enters the
first scanner stage 202 before entering the second scanner stage
204 as it propagates towards a substrate (not shown). For clarity
several components of each scanner stage of the dual stage scanner
200 are removed in the example of FIG. 2. Details of an exemplary
scanner stage are provided in FIG. 4 discussed below.
[0027] The dual stage scanner 200 is configured to accept an ion
beam 206 that travels generally in the direction to the right as
indicated by the arrow. In the example shown in FIG. 2, the dual
stage scanner 200 is a magnetic scanner that generates a set of
deflecting fields that exert a force on the ion beam 206 along the
Xsc axis so as to change the trajectory of an ion in the ion beam
206, trajectory may lie along the Zsc axis before entering the dual
stage scanner 200. In particular, as discussed below, the first
scanner stage 202 is configured to generate a first oscillating
deflecting field within the region 208 through which the ion beam
206 may travel. The second scanner stage 204 is configured to
generate a second oscillating deflecting field in the region 210
that is also configured to transmit the ion beam 206. Each of these
oscillating deflecting fields is time dependent such that the
strength and direction of a respective oscillating deflecting field
varies over time, with a result that the a series of deflected ion
beams 212 exit the dual stage scanner 200 over a range of
trajectories as shown in FIG. 2.
[0028] As explained further below the first scanner stage and
second scanner stage of a dual stage scanner may act in concert to
generate a series of ion beam trajectories that exit the dual stage
scanner as generally shown in FIG. 2, where the ion beam
trajectories appear to originate from a common focal point as shown
by the virtual source 214 at a location that is upstream of the
dual stage scanner.
[0029] FIG. 3A and FIG. 3B depict operation of a dual stage scanner
system 300 that illustrate principles of operation of various
embodiments. In particular, FIGS. 3A and 3B depict one example of
the manner that two stages of a dual stage scanner act in concert
to generate a virtual source 305 that lies outside the dual stage
scanner. The view presented in FIGS. 3A and 3B is parallel to the
Xsc-Zsc plane for the Cartesian coordinate system shown. As
illustrated a portion of an ion implanter is shown in relation to a
first scanner stage 304 and second scanner stage 306 of a dual
stage scanner system 300. The view presented in FIG. 3A shows
general features of the geometry associated with scanning a spot
beam, while FIG. 3B depicts additional details of the geometry of
ion trajectories produced by the dual stage scanner. For clarity of
illustration, in FIG. 3B the orientation of the first scanner stage
304 and second scanner stage 306 is partially rotated around an
axis along the Zsc axis in comparison to their actual positions.
Moreover, the scanner stages depicted in FIGS. 3A and 3B are
schematic and omit details of components of a scanner stage, which
are provided below for an exemplary scanner stage with respect to
FIG. 4.
[0030] Turning now to FIG. 3A, an ion beam envelope 302 is shown in
solid lines that illustrates the space occupied by a spot ion beam
as it propagates from a mass resolving slit 312 through the first
scanner stage 304 and second scanner stage 306 to a collimator 316.
The ion beam envelope 302 represents the trajectories and positions
of ions over time as a spot beam is scanned using the dual stage
scanner system 300. In some embodiments, a spot beam may be scanned
back and forth at a rate of 10 s of Hz to thousands of Hz. Before
entering the first scanner stage 304, the ion beam envelop 302
defines a narrow spot beam where ions have trajectories parallel to
Zsc. The trajectories then fan out as shown such that the ion beam
envelope 302 is wide when it intercepts the collimator 316.
[0031] Notably, although the ion beam envelope 302 does not expand
until it reaches the first scanner stage 304, the ion beam
trajectories that fan out from the second scanner stage 306 to be
intercepted by the collimator 316 appear to originate from a
virtual source 305 as defined by the virtual envelope 307 shown in
dotted lines.
[0032] Turning now to FIG. 3B there are shown details of operation
of the dual stage scanner system 300. In FIG. 3B the first scanner
stage 304 and second scanner stage 306 may be magnetic scanners
that each generate a magnetic field that provides a deflecting
force to an ion beam passing through the dual stage scanner system
300. In the present embodiments, the first scanner stage 304 and
second scanner stage 306 are each configured to generate a
oscillating magnetic field responsive to a time-varying signal,
such as an oscillating electric current that travels in a loop and
generates a magnetic field. For clarity of illustration, the first
scanner stage 304 and second scanner stage 306 are merely
represented by electric current-carrying loops. In particular, the
first scanner stage 304 and second scanner stage 306 are configured
to generate an electric current that varies in strength and
direction with time. Examples of such currents include a
sinusoidally varying electric current, an oscillating electric
current having a triangular or sawtooth variation of current over
time (waveform), or a composite-shaped oscillating electric
current.
[0033] In the embodiment of FIGS. 3A and 3B the shape and
orientation of the electric current loops of the first scanner
stage 304 and second scanner stage 306 are arranged such that
respective magnetic fields generated by oscillating electric
currents create oscillating deflecting forces that act along the
Xsc axis. Accordingly when an ion beam traverses the dual stage
scanner system 300 the ion beam is subject to an oscillating
deflecting force along the Xsc axis from both the first scanner
stage 304 and second scanner stage 306. At any given instant,
depending upon the magnitude and direction of the deflecting forces
generated by the first scanner stage 304 and second scanner stage
306, an ion beam may be deflected to a greater or lesser extent
from its initial trajectory. Over the duration of one oscillation
cycle or multiple oscillation cycles the dual stage scanner system
300 may generate the ion beam envelope 302 as shown.
[0034] One notable feature provided by the dual stage scanner of
the present embodiments is the synchronization or alignment of the
oscillating deflecting fields generated by the first and second
scanner stages. In FIG. 3B, a scan controller 340 is provided to
align the electric current signal 308, which represents oscillating
electric current of a given oscillation cycle provided to the first
scanner stage 304, with an electric current signal 310, which
represents an oscillating electric current of the given oscillation
period provided to the second scanner stage 306. The alignment is
such that the waveform of the electric current signal 308 exhibits
a 180 degree phase offset with respect to that of the electric
current signal 310. In this manner, at any given instant an ion
beam traversing the dual stage scanner system 300 is subject to
deflecting forces that act in opposite directions, except when the
respective electric current signals 308, 310 are both zero.
[0035] In FIG. 3B, the trajectory of a single ion beam 314 is shown
as a solid line, which may represent the trajectory of a spot beam
at a particular instance in time. As shown, the ion beam 314 has a
trajectory that is parallel to the Zsc axis during propagation of
the ion beam 314 through the mass resolving slit 312 until it
reaches the first scanner stage 304. At this point the ion beam is
deflected towards the left in the example shown, and subsequently
towards the right as it passes through the second scanner stage
306. The overall ion beam path forms a "dog-leg" shape after the
ion beam 314 exits the second scanner stage 306. This overall
trajectory is the result of the instantaneous generation of a first
deflecting force from first scanner stage 304 that acts upwardly in
FIG. 3B along the Xsc axis, and a second deflecting force from the
second scanner stage 306 that acts downwardly along the Xsc axis.
These forces are generated in turn by the respective electric
current signal 308 which travels in a clockwise fashion, and the
electric current signal 310 which travels in a counterclockwise
fashion in the instance shown in FIG. 3B. The relative magnitude of
the deflecting forces is arranged so that the final ion beam
trajectory of ion beam 314 as it enters the collimator 316 can be
linearly projected back to the virtual source 305 located at the
aperture 336 of mass resolving slit 312, as illustrated by the
apparent trajectory 314A. The final ion beam trajectory represents
a trajectory of the ion beam after leaving the dual stage scanner
where no further deflecting forces are experienced resulting in the
final trajectory defining a straight line.
[0036] At other instances in time, the magnitude and direction of
deflecting forces produced by the first scanner stage 304 and
second scanner stage 306 vary in concert with one another such that
other final ion beam trajectories are generated. In FIG. 3B a
series of additional solid lines represent the final ion beam
trajectories 318, 320, 322, 324, 326, 328, and 330 of ion beams
produced at other instances in time over a scan cycle, which
collectively form the ion beam envelope 302. Each of these final
ion beam trajectories defines a respective line that projects back
(upstream) to the aperture 336 of mass resolving slit 312 to
collectively form the virtual source 305, meaning that a straight
line drawn through each final ion beam trajectory intercepts the
aperture 336 at the plane 334 of the mass resolving slit 312. Thus,
from the perspective of collimator 316, the ions that travel along
the final ion beam trajectories 318, 320, 322, 324, 326, 328, and
330 appear to diverge from the virtual source 305. For clarity, the
actual trajectories of ion beams corresponding to the final ion
beam trajectories 318-330 are not shown, but it may be understood
that each trajectory may have a dog leg shape similar to that of
ion beam 314 while traversing the dual stage scanner system
300.
[0037] FIGS. 3C and 3D depict exemplary oscillating deflection
signals 350, 352 that may be sent to the respective first scanner
stage 304 and second scanner stage 306 to generate oscillating
deflection fields. As illustrated the oscillating deflection
signals 350, 352 share a common oscillation period 354. However,
the oscillating deflection signals 350, 352 have a 180 degree phase
offset such that when the oscillating deflection signal 350 is
positive the oscillating deflection signal 352 is negative, and
vice versa. Moreover, a positive peak in one oscillating deflection
signal 350, 352 corresponds to a negative peak in the other
oscillating deflection signal 352, 350.
[0038] It is to be noted, that although the oscillation period of
oscillating current signals conducted within the first scanner
stage 304 and second scanner stage 306 may be equal and while their
relative phase offset may be 180 degrees, the amplitude of
oscillating electric current signals need not be equal. Thereby the
magnitude of electric currents conducted within the first scanner
stage 304 and second scanner stage 306 at any given time need not
be equal. Rather, the relative amplitudes of the respective
oscillating current signals may be set so that the final ion beam
trajectories project back to the plane of the mass resolving slit
312 for all ion beam trajectories, regardless of the relative
current amplitudes in the first scanner stage 304 and second
scanner stage 306.
[0039] FIG. 4 provides further details of a scanner stage 400
consistent with various embodiments. The scanner stage 400 may be
used either as a first or second scanner stage in a dual stage
scanner. The scanner stage 400 is a magnetic scanner in which the
scanner body 402 may be composed of thin silicon steel sheets such
as 0.5 mm thick sheets. A set of high current windings 406 are
provided to act as scanning coils to generate an oscillating
magnetic field to be used as a deflecting field to deflect an ion
beam 404. In particular, the high current windings 406 are coupled
to a current source that may generate an electric current that
oscillates in polarity as discussed above with respect to FIGS. 3A,
3B. This serves to generate the oscillating magnetic field within a
gap defined by the opening 410 that transmits the ion beam 404. In
order to provide the appropriate deflection force in the opening
410 the current conducted through the high current windings 406 may
be controlled using drive circuitry which may incorporate elements
of conventional drive circuitry used to drive magnetic
scanners.
[0040] Moreover, as further shown in FIG. 4, a set of zero-field
effect avoidance windings are provided that wrap around a portion
of the scanner body 402. These may act as secondary coils to
produce a secondary magnetic field superimposed on the main
oscillatory magnetic field component, which acts to substantially
eliminate fluctuations in the beam size of ion beam 404.
[0041] In addition, a scan controller such as scan controller 340
may synchronize an oscillating current conducted through the high
current windings 406 of scanner stage 400 with that of a like
scanner stage so that a phase offset exists between the two scanner
stages to produce the desired final ion trajectory of the ion beam
404 as discussed above with respect to FIGS. 3A, 3B.
[0042] FIG. 5A and 5B depicts operation of an ion implanter 500
consistent with further embodiments. In this case, the ion
implanter 500 may have similar components as the ion implanter 100.
The ion implanter 500 includes an ion source 502, analyzer magnet
506, vacuum chamber 508 that includes a mass resolving slit 510,
dual stage scanner system 300, including scan controller 340,
collimator 110, and substrate stage 112. The ion implanter 500 is
operative to generate a spot ion beam or ribbon ion beam at the
mass resolving slit 510. This provides the advantages that both
modes of ion beam are produced within a single ion implanter. The
switching between ribbon beam and spot beam operation may take
place by changing ion sources or using other components to change
the shape of an ion beam before entering the mass resolving slit.
However, in order to reduce the complexity and time from switching
between ribbon beam and spot beam modes, it may be desirable to
avoid reconfiguration of the collimator 110 as noted previously.
This is accomplished by the dual stage scanner system 300.
[0043] In FIG. 5A there is shown a scenario of operation of the ion
implanter in ribbon beam mode in which the ion source 502 generates
a ribbon beam 504. The ribbon beam 504 propagates through the ion
implanter 500 where it is focused at the mass resolving slit 510
and conducted to the collimator 110. In this scenario the dual
stage scanner system 300 is not active and merely transmits the
ribbon beam 504. In FIG. 5B, the ion implanter generates a spot
beam 520, which is conducted to the mass resolving slit 510.
Although the ion source 502 is shown as generating the spot beam
520, in some instances a different ion source may be used to
generate the spot beam 520. In any case, in the example shown in
FIG. 5B the collimator 110 may be configured as in the scenario of
FIG. 5A so that its collimating components are set to collimate a
diverging set of ions that emanates from a source at the mass
resolving slit 510. As previously discussed, when a spot beam is
conducted through a mass resolving slit 510, the spot beam is not
scanned into a fan shape until entering a scanner that is disposed
downstream. Thus, the spot beam 520 remains as a narrow beam of
parallel ion trajectories until entering the dual stage scanner
system 300 at point 512. The spot beam 520 may be scanned as
described above with respect to FIGS. 3A and 3B. A set of ion beams
514 that exit the second scanner stage 306 are generated over time
in a fan shape that enters the collimator 110. The ion trajectories
of the ion beams 514 are such that they project linearly back as a
virtual envelope 516 to a focal point that defines a virtual source
(not separately shown) that is located at the mass resolving slit
510. Accordingly, since the collimator 110 is configured to
collimate a diverging ion beam emanating from the mass resolving
slit 510, collimator 110 may properly collimate ion beams 514 to
produce a collimated ion beam 518 at the substrate 114 without
adjustment to the collimator 110.
[0044] In particular embodiments, when operating in spot beam mode,
the dual stage scanner system 300 may be configured so that the on
beams 514, in addition to appearing to emanate from a virtual
source at the mass resolving slit 510, also define the same width
W.sub.2 at the entrance to the collimator 110 as that of the ribbon
beam 504. In this manner, a scanned spot beam may appear to
collimator 110 to define the same geometry as that of a ribbon
beam, therefore facilitating the ability to generate the same width
W in the collimated ion beam 518 and collimated ion beam 509.
[0045] Although the aforementioned embodiments have provided
details of magnetic scanners, the present embodiments include dual
scan stage electrostatic scanners. In these latter embodiments, a
first electrostatic scan stage and second electrostatic scanner
stage may each include opposing plates that define an electrostatic
field therebetween when an electric potential is applied to the
opposing plates. The first and second electrostatic scanner stages
may be driven with oscillating voltage signals that are 180 degrees
out of phase in order to generate final ion trajectories in a
scanned ion beam that define a virtual source upstream of the
actual electrostatic scanner stages, such as in the plane of a mass
resolving slit.
[0046] Moreover, in some embodiments, a dual stage scanner may be
configured to generate the appropriate deflection signals to
produce a scanned ion beam that has a virtual source located at any
desired position upstream of the dual stage scanner. This may be
accomplished by appropriate choice of amplitude of signals provided
to the scanner stages, gaps between components of a scanner stage,
separation of scanner stages. In various embodiments, for a given
configuration of scanner stages, control circuitry such as a scan
controller may be used to set the relative signal strengths
supplied to the scanner stages in order to adjust the position of a
virtual source.
[0047] The present disclosure is not to be limited in scope by the
specific embodiments described herein. Indeed, other various
embodiments of and modifications to the present disclosure, in
addition to those described herein, will be apparent to those of
ordinary skill in the art from the foregoing description and
accompanying drawings. Thus, such other embodiments and
modifications are in the tended to fall within the scope of the
present disclosure. Furthermore, although the present disclosure
has been described herein in the context of a particular
implementation in a particular environment for a particular
purpose, those of ordinary skill in the art will recognize that its
usefulness is not limited thereto and that the present disclosure
may be beneficially implemented in any number of environments for
any number of purposes. Thus, the claims set forth below should be
construed in view of the full breadth and spirit of the present
disclosure as described herein.
* * * * *