U.S. patent application number 14/736322 was filed with the patent office on 2016-12-15 for method for euv power improvement with fuel droplet trajectory stabilization.
The applicant listed for this patent is Taiwan Semiconductor Manufacturing Co., Ltd.. Invention is credited to Jaw-Jung Shin, Tsiao-Chen Wu.
Application Number | 20160366756 14/736322 |
Document ID | / |
Family ID | 57516095 |
Filed Date | 2016-12-15 |
United States Patent
Application |
20160366756 |
Kind Code |
A1 |
Wu; Tsiao-Chen ; et
al. |
December 15, 2016 |
METHOD FOR EUV POWER IMPROVEMENT WITH FUEL DROPLET TRAJECTORY
STABILIZATION
Abstract
The present disclosure relates to an extreme ultraviolet (EUV)
radiation source that generates charged tin droplets having a
trajectory controlled by an electromagnetic field, and an
associated method. In some embodiments, the EUV radiation source
has a laser that generates a laser beam. A charged fuel droplet
generator provides a plurality of charged fuel droplets having a
net electrical charge to an EUV source vessel. An electromagnetic
field generator generates an electric field and/or a magnetic
field. The net electrical charge of the charged fuel droplets
causes the electric or magnetic field to generate a force on the
charged fuel droplets that controls a trajectory of the charged
fuel droplets to intersect the laser beam. By using the electric or
magnetic field to control a trajectory of the charged fuel
droplets, the EUV system is able to avoid focus issues between the
laser beam and the charged fuel droplets.
Inventors: |
Wu; Tsiao-Chen; (Jhudong
Township, TW) ; Shin; Jaw-Jung; (Hsinchu City,
TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Taiwan Semiconductor Manufacturing Co., Ltd. |
Hsin-Chu |
|
TW |
|
|
Family ID: |
57516095 |
Appl. No.: |
14/736322 |
Filed: |
June 11, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G03F 7/70033 20130101;
H05G 2/008 20130101; H05G 2/005 20130101; H05G 2/006 20130101 |
International
Class: |
H05G 2/00 20060101
H05G002/00; G03F 7/20 20060101 G03F007/20 |
Claims
1. An extreme ultraviolet (EUV) radiation source, comprising: a
charged fuel droplet generator configured to provide a plurality of
charged fuel droplets having a net positive or negative electrical
charge to an EUV source vessel; a laser configured to generate a
laser beam having a sufficient energy to ignite a plasma from the
charged fuel droplets, wherein the plasma emits extreme ultraviolet
radiation; and an electromagnetic field generator configured to
generate an electric field or a magnetic field that stabilizes a
trajectory of the charged fuel droplets within the EUV source
vessel, prior to ignition of the charged fuel droplets, along a
path intersecting the laser beam.
2. The EUV radiation source of claim 1, further comprising: a fuel
droplet generator configured to provide a plurality of un-charged
fuel droplets to an EUV source vessel; and an ion species injector
configured to generate a beam of charged ion species that is
incident upon the plurality of un-charged fuel droplets, wherein
upon hitting the plurality of un-charged fuel droplets, the charged
ion species attach to the plurality of un-charged fuel droplets to
generate the plurality of charged fuel droplets.
3. The EUV radiation source of claim 2, wherein the ion species
injector comprises an electron gun configured to generate an
electron beam, wherein the electron gun comprises: a hot cathode
configured to generate electrons via thermionic emission; a
collimator lens configured to form a beam of electrons; an aperture
lens and a condenser lens configured to focus the beam of
electrons; and a downstream blanker configured to remove electrons
that are outside of the beam of electrons to form the electron
beam.
4. The EUV radiation source of claim 2, wherein the beam of charged
ion species has a lower energy than the laser beam, and the beam of
charged ion species is configured to deform the plurality of
charged fuel droplets to increase a size of the charged fuel
droplets as viewed from the laser.
5. The EUV radiation source of claim 2, further comprising: a
control element configured to selective adjust one or more
characteristics of the ion species injector; and a measurement unit
configured to measure a position of the un-charged fuel droplets
and to provide a control signal to the control element that causes
the control element to adjust a shape or a size of the beam of
charged ion species.
6. (canceled)
7. The EUV radiation source of claim 1, further comprising: a
pre-pulse laser configured to generate a pre-pulse laser beam,
having a lower energy than the laser beam, which is configured to
deform the plurality of charged fuel droplets, wherein the
pre-pulse laser is arranged so that the pre-pulse laser beam hits
the plurality of charged fuel droplets prior to the laser beam
hitting the plurality of charged fuel droplets.
8-9. (canceled)
10. The EUV radiation source of claim 1, further comprising: a
vapor shield source configured to provide a gas into the EUV source
vessel that mitigates accumulation of residue from the charged fuel
droplets, which have not been completely vaporized when struck by
the laser beam, on a collector mirror.
11. The EUV radiation source of claim 1, wherein the
electromagnetic field generator comprises a conductive coil wrapped
around the EUV source vessel and configured to control the
trajectory of the plurality of charged fuel droplets by way of the
electric field or the magnetic field.
12. The EUV radiation source of claim 1, wherein the plurality of
charged fuel droplets comprise tin.
13. An EUV radiation source, comprising: a tin droplet generator
configured to generate a plurality of un-charged tin droplets; an
electron gun configured to generate an electron beam of electrons
that is incident upon the plurality of un-charged tin droplets,
wherein upon hitting the plurality of un-charged tin droplets
electrons from the electron beam attach to the plurality of
un-charged tin droplets to generate a plurality of charged tin
droplets having a net negative electrical charge, wherein the
electron gun comprises: a hot cathode configured to generate
electrons via thermionic emission; a collimator lens configured to
form a beam of electrons; an aperture lens and a condenser lens
configured to focus the beam of electrons; and a downstream blanker
configured to remove electrons that are outside of the beam of
electrons to form the electron beam; a carbon dioxide (CO.sub.2)
laser configured to generate a laser beam having a sufficient
energy to ignite a plasma from the plurality of charged tin
droplets within an EUV source vessel, wherein the plasma emits
extreme ultraviolet radiation; and an electromagnetic field
generator configured to generate an electric field or a magnetic
field that controls a trajectory of the plurality of charged tin
droplets.
14. The EUV radiation source of claim 13, further comprising: a
collector mirror having a concave curvature configured to focus the
extreme ultraviolet radiation to a downstream optical system
comprising a plurality of mirrors configured to convey the extreme
ultraviolet radiation to a semiconductor workpiece; and a pre-pulse
laser configured to generate a pre-pulse laser beam, having a lower
energy than the laser beam, which is configured to deform the
plurality of charged tin droplets, wherein the pre-pulse laser is
arranged so that the pre-pulse laser beam hits the plurality of
charged tin droplets prior to the laser beam hitting the plurality
of charged tin droplets.
15. The EUV radiation source of claim 14, further comprising: a
vapor shield source configured to provide a gas into the EUV source
vessel that mitigates accumulation of residue from the charged tin
droplets, which have not been completely vaporized when struck by
the laser beam, on the collector mirror.
16. The EUV radiation source of claim 13, further comprising: a
control element configured to selective adjust one or more
characteristics of the electron gun; and a measurement unit
configured to measure a position of the un-charged tin droplets and
to provide a control signal to the control element that causes the
control element to adjust the one or more characteristics of the
electron gun.
17. The EUV radiation source of claim 13, wherein the
electromagnetic field generator comprises a conductive coil wrapped
around the EUV source vessel and configured to control the
trajectory of the plurality of charged tin droplets.
18. The EUV radiation source of claim 13, wherein the electron beam
has a lower energy than the laser beam, and the electron beam is
configured to deform the plurality of charged tin droplets.
19. A method of generating extreme ultraviolet (EUV) radiation,
comprising: generating a plurality of charged fuel droplets having
a net positive or negative electrical charge; generating an
electric field or a magnetic field configured to stabilize a
trajectory of the plurality of charged fuel droplets; focusing a
laser beam on the plurality of charged fuel droplets to generate
extreme ultraviolet (EUV) radiation; and wherein the electric field
or the magnetic field stabilizes the trajectory of the plurality of
charged fuel droplets, prior to ignition of the charged fuel
droplets, along a path intersecting the laser beam.
20. The method of claim 19, wherein generating the plurality of
charged fuel droplets comprises: generating a plurality of
un-charged fuel droplets; and hitting the plurality of un-charged
fuel droplets with a beam of ion species to form the plurality of
charged fuel droplets.
21. The EUV radiation source of claim 2, wherein the un-charged
fuel droplets have a diameter of less than or equal to
approximately 20 microns so as to provide for a charge-to-mass
ratio that improves controllability of the charged fuel droplets by
the electric field or the magnetic field.
22. The EUV radiation source of claim 14, wherein the electron gun
is arranged between the pre-pulse laser and the tin droplet
generator.
23. The method of claim 19, further comprising: operating a
conductive coil wrapped around an EUV source vessel to generate the
electric field or the magnetic field configured to control the
trajectory of the plurality of charged fuel droplets prior to
ignition of the charged fuel droplets.
Description
BACKGROUND
[0001] Photolithography is a process by which a reticle having a
pattern is irradiated with light to transfer the pattern onto a
photosensitive material overlying a semiconductor substrate. Over
the history of the semiconductor industry, smaller integrated chip
minimum features sizes have been achieved by reducing the exposure
wavelength of optical lithography radiation sources to improve
photolithography resolution. Extreme ultraviolet (EUV) lithography,
which uses extreme ultraviolet (EUV) light having an exposure
wavelength of between 10 nm and 130 nm, is a promising
next-generation lithography solution for emerging technology nodes
(e.g., 32 nm, 22 nm, 14 nm, etc.).
BRIEF DESCRIPTION OF THE DRAWINGS
[0002] Aspects of the present disclosure are best understood from
the following detailed description when read with the accompanying
figures. It is noted that, in accordance with the standard practice
in the industry, various features are not drawn to scale. In fact,
the dimensions of the various features may be arbitrarily increased
or reduced for clarity of discussion.
[0003] FIG. 1 illustrates a block diagram of some embodiments of an
extreme ultraviolet (EUV) radiation source for an EUV
photolithography system.
[0004] FIG. 2 illustrates a block diagram of some additional
embodiments of an extreme ultraviolet (EUV) radiation source for an
EUV photolithography system.
[0005] FIG. 3 illustrates some embodiments of cross-sectional views
showing a tin droplet being hit with a beam of ion species
configured to both charge the un-charged tin droplets and to deform
the tin droplet.
[0006] FIG. 4 illustrates a block diagram of some embodiments of an
extreme ultraviolet (EUV) radiation source for an EUV
photolithography system.
[0007] FIG. 5 illustrates a block diagram of some additional
embodiments of an EUV radiation source.
[0008] FIG. 6 illustrates a block diagram of some embodiments of an
EUV photolithography system.
[0009] FIG. 7 illustrates a flow diagram of some embodiments of a
method of performing an EUV photolithography process.
DETAILED DESCRIPTION
[0010] The following disclosure provides many different
embodiments, or examples, for implementing different features of
the provided subject matter. Specific examples of components and
arrangements are described below to simplify the present
disclosure. These are, of course, merely examples and are not
intended to be limiting. For example, the formation of a first
feature over or on a second feature in the description that follows
may include embodiments in which the first and second features are
formed in direct contact, and may also include embodiments in which
additional features may be formed between the first and second
features, such that the first and second features may not be in
direct contact. In addition, the present disclosure may repeat
reference numerals and/or letters in the various examples. This
repetition is for the purpose of simplicity and clarity and does
not in itself dictate a relationship between the various
embodiments and/or configurations discussed.
[0011] Further, spatially relative terms, such as "beneath,"
"below," "lower," "above," "upper" and the like, may be used herein
for ease of description to describe one element or feature's
relationship to another element(s) or feature(s) as illustrated in
the figures. The spatially relative terms are intended to encompass
different orientations of the device in use or operation in
addition to the orientation depicted in the figures. The apparatus
may be otherwise oriented (rotated 90 degrees or at other
orientations) and the spatially relative descriptors used herein
may likewise be interpreted accordingly.
[0012] Typically, extreme ultraviolet (EUV) photolithography
systems use extreme ultraviolet radiation having a 13.5 nm
wavelength. One method of producing 13.5 nm wavelength radiation
that has recently emerged is to shot a carbon dioxide (CO.sub.2)
laser at droplets of tin (Sn). The tin droplets are typically
dropped into an EUV source vessel. As the droplets fall into the
EUV source vessel, the CO.sub.2 laser hits the tin droplets and
heats the tin droplets to a critical temperature that causes atoms
of tin to shed their electrons and become a plasma of ionized tin
droplets. The ionized tin droplets emit photons having a wavelength
of approximately 13.5 nm, which is provided as EUV radiation to a
downstream optical lithography system.
[0013] It has been appreciated that the power of the EUV radiation
generated by such a method depends upon how well a laser beam can
be focused onto the tin droplets. For example, if the laser beam is
properly focused, a desirable EUV power is achieved. However,
forces within the EUV source vessel may cause the tin droplets to
deviate from an expected trajectory causing the CO.sub.2 laser to
be out of focus with some of the tin droplets. For example, thermal
waves from the CO.sub.2 laser and/or a buoyancy of a medium within
the EUV source vessel can result in changes in the position of the
tin droplets falling into EUV source vessel. If the CO.sub.2 laser
is out of focus (i.e., focused to a position that is not hitting
the tin droplet), a power of the resulting EUV radiation will be
reduced. Since EUV radiation is typically formed from multiple tin
droplets, which may have different trajectories within the EUV
source, focus issues can lead to inconsistency in EUV power that
can cause non-uniformities in exposure over the surface of a
workpiece. For example, dose errors may range from less than 1% to
greater than 10% over a single wafer.
[0014] Accordingly, the present disclosure relates to an EUV
radiation source configured to generate charged tin droplets having
a trajectory controlled by an electromagnetic field, and an
associated method. In some embodiments, the EUV radiation source
comprises a laser configured to generate a laser beam. A charged
fuel droplet generator is configured to provide a plurality of
charged fuel droplets to an EUV source vessel. The plurality of
charged fuel droplets have a net positive or negative electrical
charge. An electromagnetic field generator is configured to
generate an electric field or a magnetic field. Therefore,
trajectory remote control of the charged fuel droplets is enabled
with the force exerted by the electric or magnetic field on the
charged fuel droplets. Accordingly, by using the electric or
magnetic field to control a trajectory of the charged fuel
droplets, the EUV system is able to stabilize the trajectory and to
avoid focus issues between the laser beam and the charged fuel
droplets (e.g., to provide maximized and consistent EUV power that
avoids non-uniformities in exposure over the surface of a
substrate).
[0015] FIG. 1 illustrates a block diagram of some embodiments of an
extreme ultraviolet (EUV) radiation source 100 for an EUV
photolithography system.
[0016] The EUV radiation source 100 comprises a charged fuel
droplet generator 102 configured to generate charged fuel droplets
104 having a net positive or negative electrical charge. In some
embodiments, the charged fuel droplet generator 102 comprises a
droplet generator 106 and a charging element 108. The droplet
generator 106 is configured to generate un-charged fuel droplets.
The charging element 108 is configured to impart a charge onto the
un-charged fuel droplets to generate the charged fuel droplets 104
comprising a target material that has been ionized to have a
positive or negative net charge. In some embodiments, the charged
fuel droplets 104 may comprise tin (Sn). In other embodiments, the
charged fuel droplets 104 may comprise a different metal
material.
[0017] A laser 112 is configured to generate a laser beam 114 that
is incident upon the charged fuel droplets 104. In some
embodiments, the laser 112 may comprise a carbon dioxide (CO.sub.2)
laser. In other embodiments, the laser 112 may comprise alternative
types of lasers. The laser beam 114 is configured to have a
critical energy that is sufficient to ignite a plasma from the
charged fuel droplets 104.
[0018] The EUV radiation source 100 further comprises an
electromagnetic field generator 110 configured to generate an
electric field and/or a magnetic field. The electric field and/or
the magnetic field is configured to interact with the charged fuel
droplets 104 generated by the charged droplet generator 102. For
example, because of the net positive or negative charge of the
charged fuel droplets 104, the electric and/or magnetic field will
generate a force on the charged fuel droplets 104 (i.e., according
to Coloumb's law). Therefore, the profile and strength of the
electric and/or magnetic field may be selected to control a
trajectory of the charged fuel droplets 104 (e.g., to control the
trajectory of the charged fuel droplets to account for forces from
thermal waves induced by plasma generation).
[0019] During operation of the EUV radiation source 100, the
charged fuel droplets 104 fall from the charged fuel droplet
generator 102. The charged fuel droplets 104 fall along a
trajectory that is influenced by the electric field and/or a
magnetic field generated by the electromagnetic field generator 110
to intersect a focal point of the laser beam 114. When the laser
beam 114 hits the charged fuel droplets 104, the laser beam 114
heats the charged fuel droplets 104 to a critical temperature. At
the critical temperature, the charged fuel droplets 104 shed their
electrons and become a plasma 115 comprising ions. The ions of the
plasma emit photons 116 having a wavelength of approximately 13.5
nm. The photons 116 are provided to a downstream optical system 118
that directs the photons 116 onto a workpiece 120.
[0020] Thus, by using the electric field and/or a magnetic field
generated by the electromagnetic field generator 110 to stabilize
and/or control the trajectory of the charged fuel droplets 104, EUV
radiation source 100 avoids focus issues between the laser beam 114
and the charged fuel droplets 104. By avoiding focus issues, the
power output from the EUV radiation source 100 can be maximized and
non-uniformities in exposure over the surface of a workpiece 120
due to inconsistencies in EUV power can be mitigated.
[0021] FIG. 2 illustrates a block diagram of some additional
embodiments of an extreme ultraviolet (EUV) radiation source 200
for an EUV photolithography system.
[0022] The EUV radiation source 200 comprises a CO.sub.2 laser 202
configured to generate a pulsed laser beam 204 comprising a
plurality of pulses of infrared light. In some embodiments, the
pulsed laser beam 204 may have principal wavelength bands centered
around a range of between approximately 9 um and approximately 11
um. The pulsed laser beam 204 is provided within a housing of an
EUV source vessel 206. In some embodiments, the EUV source vessel
206 may be held under vacuum.
[0023] A charged tin droplet generator 208 is configured to
generate charged tin droplets 212, which are provided to the EUV
source vessel 206. In some embodiments, the charged tin droplet
generator 208 may comprise a tin droplet generator 210 and an ion
species injector 214. The tin droplet generator 210 is configured
to generate un-charged tin droplets 211. The ion species injector
214 is configured to generate a beam of charged ion species 216.
Ions from the beam of charged ion species 216 adhere to the
un-charged tin droplets 211 to form the charged tin droplets 212
that are introduced into the EUV source vessel 206. In some
embodiments, the ion species injector 214 may comprise an electron
beam configured to propel a beam of electrons at the un-charged tin
droplets 211. In such embodiments, the resulting charged tin
droplets 212 have a net negative charge.
[0024] The beam of charged ion species 216 output from the ion
species injector 214 has an energy that is less than the critical
energy of the un-charged tin droplets 211 (i.e., the energy needed
to ignite a plasma from the un-charged tin droplets 211). For
example, the beam of charged ion species 216 may have an energy of
less than 11.9 MeV. In some embodiments, the beam of charged ion
species 216 may have an energy that is between approximately 10
kilo-electron volts (KeV) and 200 approximately KeV, so as to form
ions without producing significant amounts of photons. In some
embodiments, the un-charged tin droplets 211 may have a size of
between approximately 10 microns and approximately 30 microns. In
some embodiments, the un-charged tin droplets 211 may be selected
to have a size that gives a charge-to-mass ratio that provides for
improved controllability of a charged tin droplet by electric
and/or magnetic fields generated by electromagnetic field generator
110. For example, in some embodiments, the tin droplet generator
210 is configured to provide un-charged tin droplets 211 having a
diameter of less than or equal to approximately 20 microns.
[0025] In some embodiments, the EUV radiation source 200 may
further comprise a pre-pulse laser 218. The pre-pulse laser 218 is
configured to generate a pre-pulse laser beam 220 that may be
incident on the charged tin droplets 212 or the un-charged tin
droplets 211. The pre-pulse laser beam 220 has an energy that is
less than the CO.sub.2 laser 202. The energy is insufficient to
ignite a plasma from the tin droplets (e.g., is less than 11.9
MeV), but does deform the tin droplets (e.g., increase a target
size/diameter of the tin droplets). In some embodiments, the
pre-pulse laser 218 may comprise a carbon-dioxide (CO.sub.2) laser
that has a lower energy than the CO.sub.2 laser 202.
[0026] In some embodiments, the ion species injector 214 may be
separate from the pre-pulse laser 218. In other embodiments, the
ion species injector 214 and the pre-pulse laser 218 may comprise a
same element, such that the beam of charged ion species 216 (e.g.,
beam of electrons) can be combined with the pre-pulse laser beam
220. In such embodiments, the beam of charged ion species 216 is
configured to both charge the un-charged tin droplets 211 and to
deform a shape of the tin droplets. By having the beam of charged
ion species 216 act to both charge the un-charged tin droplets 211
and to deform a shape of the tin droplets, the ion species injector
214 replaces the pre-pulse laser 218 (i.e., resulting in an EUV
radiation source 200 that can cause ionization and deformation of
tin droplets without a pre-pulse laser).
[0027] FIG. 3 illustrates some embodiments of cross-sectional views
showing a tin droplet being hit with a beam of charged ion species
configured to both charge the un-charged tin droplet and to deform
the tin droplet.
[0028] As shown in cross-sectional view 300a, an incident beam of
charged ion species 302 hits an un-charged tin droplet 211. As
illustrated, the beam of charged ion species 302 comprises
electrons having a negative charge.
[0029] As shown in cross-sectional view 300b, ions 304 from the
beam of charged ion species 302 attach to the un-charged tin
droplet 211, causing the un-charged tin droplet 211 to become a
charged tin droplet 212 having a net negative charge.
[0030] As shown in cross-sectional view 300c, the energy of the
beam of charged ion species 302 also causes the charged tin droplet
212 to become deformed. In some embodiments, deformation of the tin
droplet may cause a height of the charged tin droplet 212 to
increase and a width of the charged tin droplet 212 to decrease. In
such embodiments, the deformation of the tin droplets increases a
target size that a subsequent laser beam hits to ignite a plasma
from the tin droplets.
[0031] FIG. 4 illustrates a block diagram of some additional
embodiments of an extreme ultraviolet (EUV) radiation source 400
for an EUV photolithography system.
[0032] The EUV radiation source 400 comprises a CO.sub.2 laser 202
configured to generate a pulsed laser beam 204. Pulses from the
CO.sub.2 laser 202 illuminate charged tin droplets 212, causing the
charged tin droplets 212 to radiate extreme ultraviolet (EUV)
radiation 402 having a wavelength of approximately 13.5 nm.
[0033] A collector mirror 404 is positioned around the intersection
of the charged tin droplets 212 and the pulsed laser beam 204. The
collector mirror 404 has a surface with a concave curvature that is
configured to focus the extreme ultraviolet radiation 402 emitted
from the charged tin droplets 212 into a downstream optical system
118 that directs the extreme ultraviolet radiation 402 onto a
workpiece 120.
[0034] In some embodiments, a vapor shield source 406 is configured
to provide a gas 408 into the EUV source vessel 206. The gas 408 is
configured to prevent residue from the charged tin droplets 212,
which have not completely vaporized during plasma generation, from
accumulating on the collector minor 404. In some embodiments, the
gas 408 may comprise hydrogen gas (H.sub.2) or nitrogen gas
(N.sub.2), for example. It will be appreciated that the gas 408 may
add additional turbulence within the EUV source vessel 206, which
can disrupt the trajectory of the charged tin droplets 212. The
electric and/or magnetic field generated by the electromagnetic
field generator 110 reduces the effect of the turbulence on the
plurality of charged tin droplets 212, thereby increasing the
efficiency of the EUV radiation source 400 and decreasing
contamination of the collector mirror 404.
[0035] In some embodiments, the EUV radiation source 400 may
further comprise a control element 410 configured to adjust one or
more characteristics of the beam of charged ion species 216 and/or
the electromagnetic field generator 110. For example, in some
embodiments, the control element 410 may be configured to generate
a control signal S.sub.CTR that is provided to the ion species
injector 214 to adjust a voltage, a current, a frequency, a beam
shape, and/or a size of the beam of charged ion species 216. In
some embodiments, the control element 410 may be configured to
adjust the one or more characteristics of the beam of charged ion
species 216 and/or the electromagnetic field generator 110 based
upon one or more operating conditions of the EUV radiation source
400. In various embodiments, the one or more operating conditions
may comprise a size of the tin droplets, a pressure of an EUV
source vessel, a flow of gas 408 from the vapor shield source 406,
etc.
[0036] In other embodiments, the control element 410 may comprise a
control unit 412 and a measurement element 414. In some
embodiments, the measurement element 414 may be configured to
measure a position of the charged tin droplets 212. For example,
the measurement element 414 may measure a position of the charged
tin droplets 212 by an optical measurement tool (not shown). In
other embodiments, the measurement element 414 may be configured to
measure a power of the extreme ultraviolet radiation 402. Based
upon a measured position of the charged tin droplets 212 and/or a
power of the extreme ultraviolet radiation 402, the control unit
412 may generate a control signal S.sub.CTR that varies one or more
characteristics of the charged tin droplet generator 210 and/or the
electromagnetic field generator 110.
[0037] FIG. 5 illustrates a block diagram of some additional
embodiments of an EUV radiation source 500.
[0038] The EUV radiation source 500 comprises a CO.sub.2 laser 202
configured to generate a laser beam 204 to a beam transport and
focusing system 502. The beam transport and focusing system 502
comprises one or more lenses 502a, 502b arranged within a beam line
and configured to focus the pulsed laser beam 204. The pulsed laser
beam 204 is output from the beam transport and focusing system 502
to the EUV source vessel 206.
[0039] An ion species injector 506 is configured to generate a beam
of charged ion species 507. In some embodiments, the ion species
injector 506 may comprise one or more electron guns, respectively
configured to generate a beam of electrons. In some embodiments,
the electron gun may operate to generate electrons at a frequency
of approximately 50,000 electrons or more per second. In other
embodiments, the electron gun may operate to generate electrons at
a frequency of less than 50,000 electrons per second. The electron
gun may comprise an electron source 508 configured to generate a
plurality of electrons. In some embodiments, the electron source
508 may comprise a hot cathode configured to generate electrons via
thermionic emission. A collimator lens 510 is configured to form a
beam of electrons. An aperture lens and condenser lens 512 are
configured to focus the beam of electrons, and a downstream blanker
514 is configured to remove electrons that are outside of the beam.
A beam deflector 516 receives the beam from the blanker 514 and
directs the beam to a position intersecting un-charged tin droplets
211 output from a tin droplet generator 210. Electrons from the
electron beam attach to the un-charged tin droplets 211 to generate
charged tin droplets 212.
[0040] The EUV radiation source 500 further comprises an
electromagnetic field generator 518. In some embodiments, the
electromagnetic field generator 518 may comprise a conductive coil
wrapped around an outer surface of the EUV source vessel 206. In
various embodiments, the conductive coil may comprise a single
coil, a double coil, a quadrapole coil, etc. The conductive coil is
coupled to a current source (not shown) configured to provide a
current to the conductive coil. As current passes through the
conductive coil a magnetic field is generated within the EUV source
vessel 206. In some embodiments, the electromagnetic field
generator 518 may be configured to generate a magnetic field having
a magnetic field strength in a range of between approximately 1 mT
and approximately 5 T.
[0041] FIG. 6 illustrates an EUV photolithography system 600 having
a disclosed EUV radiation source. Although the EUV photolithography
system 600 is illustrated as having a certain configuration of
components, it will be appreciated that the disclosed EUV radiation
source may be implemented in EUV photolithography systems having
additional components (e.g., additional minors) or having less
components (e.g., less minors).
[0042] The EUV photolithography system 600 comprises EUV radiation
source 500 configured to supply EUV radiation 601 (i.e., with
wavelengths in a range of between about 10 nm and about 130 nm) to
a reticle 602. The EUV radiation source 500 is configured to
generate the EUV radiation by hitting charged fuel droplets with a
laser to generate a plasma of ions that emit photons at a
wavelength of between approximately 10 nm and approximately 130
nm.
[0043] The EUV radiation 601 output from the EUV radiation source
500 is provided to a condenser 606. In some embodiments, the
condenser 606 comprises first and second surfaces, 608a and 608b,
configured to focus the EUV radiation 601, and a reflector 610
configured to reflect the EUV radiation 612 towards the reticle
602. The reticle 602 is configured to reflect the EUV radiation 612
to form a pattern on a surface of a semiconductor workpiece 604. To
produce the pattern, the reticle 602 comprises a plurality of
absorptive features 614A-614C arranged on a front surface of the
reticle 602. The plurality of absorptive features 614A-614C are
configured to absorb the EUV radiation 612, such that the reflected
rays of radiation 616 conveys a patterned defined by the reticle
602.
[0044] The EUV radiation 616 is filtered through reduction optics
comprising a series of first through fourth mirrors 618a-618d,
which serve as lenses to reduce a size of the pattern carried by
the EUV radiation 616. The fourth mirror 618d conveys the EUV
radiation 616 onto a on a layer of photoresist disposed on a
surface of the semiconductor workpiece 604. The EUV radiation
patterns the layer of photoresist so that subsequent processing can
be performed on selected regions of the semiconductor workpiece
604.
[0045] FIG. 7 illustrates a flow diagram of some embodiments of a
method 700 of performing an EUV photolithography process.
[0046] While the disclosed method 700 is illustrated and described
herein as a series of acts or events, it will be appreciated that
the illustrated ordering of such acts or events are not to be
interpreted in a limiting sense. For example, some acts may occur
in different orders and/or concurrently with other acts or events
apart from those illustrated and/or described herein. In addition,
not all illustrated acts may be required to implement one or more
aspects or embodiments of the description herein. Further, one or
more of the acts depicted herein may be carried out in one or more
separate acts and/or phases.
[0047] At 702, a plurality of charged fuel droplets are generated.
The plurality of charged fuel droplets may have a net electrical
charge that is positive or negative. In some embodiments, the
plurality of electrically charged fuel droplets may comprise tin
droplets.
[0048] In some embodiments, the plurality of charged fuel droplets
may be generated according to acts 704-706. At 704, a plurality of
un-charged fuel droplets are generated. At 706, the plurality of
un-doped fuel droplets are hit with a beam of charged ion species.
Ions from the beam of charged ion species will attach to the
un-charged fuel droplets to form the plurality of charged fuel
droplets.
[0049] At 708, an electric field and/or a magnetic field configured
to control a trajectory of the electrically charge fuel droplets is
generated. The electric field and/or the magnetic field are
generated at a position that interacts with the charged fuel
droplets.
[0050] At 710, a laser beam is focused on the charged fuel droplets
to generate extreme ultraviolet (EUV) radiation. In some
embodiments, the laser beam may comprise a laser beam generated by
a carbon dioxide (CO.sub.2) laser. The laser beam may excite atoms
within the charged fuel droplets to ignite a plasma having ions
that output photons having a wavelength in the extreme ultraviolet
spectrum.
[0051] At 712, the EUV radiation is provided to a workpiece via an
EUV photomask.
[0052] At 714, the electric field, the magnetic field, and/or the
beam of ion species may be adjusted. The electric field, the
magnetic field, and/or the beam of ion species may be adjusted
based upon a measured position of the charged droplets of tin, a
power of the EUV radiation, and/or one or more parameters of the
EUV system (e.g., a size of the tin droplets, a pressure of an EUV
source vessel, etc.).
[0053] Therefore, the present disclosure relates to an extreme
ultraviolet (EUV) radiation source that generates charged tin
droplets having a trajectory controlled by an electric field and/or
a magnetic field, and an associated method.
[0054] In some embodiments, the present disclosure relates to an
extreme ultraviolet (EUV) radiation source. The EUV radiation
source comprises a charged fuel droplet generator configured to
provide a plurality of charged fuel droplets having a net positive
or negative electrical charge to an EUV source vessel. The EUV
radiation source further comprises a laser configured to generate a
laser beam having a sufficient energy to ignite a plasma from the
charged fuel droplets, which emits extreme ultraviolet radiation.
The EUV radiation source further comprises an electromagnetic field
generator configured to generate an electric field or a magnetic
field that controls a trajectory of the charged fuel droplets
within the EUV source vessel.
[0055] In other embodiments, the present disclosure relates to an
EUV radiation source. The EUV radiation source comprises a tin
droplet generator configured to generate a plurality of un-charged
tin droplets. The EUV radiation source further comprises an
electron gun configured to generate a beam of electrons that is
incident upon the plurality of un-charged tin droplets, wherein
upon hitting the plurality of un-charged tin droplets the electrons
attach to the plurality of un-charged tin droplets to generate the
plurality of charged tin droplets having a net negative electrical
charge. The EUV radiation source further comprises a carbon dioxide
(CO.sub.2) laser configured to generate a laser beam having a
sufficient energy to ignite a plasma from the plurality of charged
tin droplets within an EUV source vessel, wherein the plasma emits
extreme ultraviolet radiation. The EUV radiation source further
comprises an electromagnetic field generator configured to generate
an electric field or a magnetic field that controls a trajectory of
the plurality of charged tin droplets.
[0056] In yet other embodiments, the present disclosure relates to
a method of generating extreme ultraviolet (EUV) radiation. The
method comprises generating a plurality of charged fuel droplets
having a net positive or negative electrical charge. The method
further comprises generating an electric field or a magnetic field
configured to control a trajectory of the plurality of charged fuel
droplets. The method further comprises focusing a laser beam on the
plurality of charged fuel droplets to generate extreme ultraviolet
(EUV) radiation.
[0057] The foregoing outlines features of several embodiments so
that those skilled in the art may better understand the aspects of
the present disclosure. Those skilled in the art should appreciate
that they may readily use the present disclosure as a basis for
designing or modifying other processes and structures for carrying
out the same purposes and/or achieving the same advantages of the
embodiments introduced herein. Those skilled in the art should also
realize that such equivalent constructions do not depart from the
spirit and scope of the present disclosure, and that they may make
various changes, substitutions, and alterations herein without
departing from the spirit and scope of the present disclosure.
* * * * *