U.S. patent application number 13/455753 was filed with the patent office on 2012-12-20 for methods and apparatus for controlling photoresist line width roughness with enhanced electron spin control.
This patent application is currently assigned to Applied Materials, Inc.. Invention is credited to Ajay Kumar, Omkaram Nalamasu, Kartik Ramaswamy, Banqiu Wu.
Application Number | 20120318773 13/455753 |
Document ID | / |
Family ID | 47352853 |
Filed Date | 2012-12-20 |
United States Patent
Application |
20120318773 |
Kind Code |
A1 |
Wu; Banqiu ; et al. |
December 20, 2012 |
METHODS AND APPARATUS FOR CONTROLLING PHOTORESIST LINE WIDTH
ROUGHNESS WITH ENHANCED ELECTRON SPIN CONTROL
Abstract
The present invention provides methods and an apparatus for
controlling and modifying line width roughness (LWR) of a
photoresist layer with enhanced electron spinning control. In one
embodiment, an apparatus for controlling a line width roughness of
a photoresist layer disposed on a substrate includes a processing
chamber having a chamber body having a top wall, side wall and a
bottom wall defining an interior processing region, a support
pedestal disposed in the interior processing region of the
processing chamber, and a plasma generator source disposed in the
processing chamber operable to provide predominantly an electron
beam source to the interior processing region.
Inventors: |
Wu; Banqiu; (Sunnyvale,
CA) ; Kumar; Ajay; (Cupertino, CA) ;
Ramaswamy; Kartik; (San Jose, CA) ; Nalamasu;
Omkaram; (San Jose, CA) |
Assignee: |
Applied Materials, Inc.
Santa Clara
CA
|
Family ID: |
47352853 |
Appl. No.: |
13/455753 |
Filed: |
April 25, 2012 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61497370 |
Jun 15, 2011 |
|
|
|
Current U.S.
Class: |
216/68 ;
156/345.48; 156/345.51; 216/71 |
Current CPC
Class: |
H01J 37/3244 20130101;
H01J 37/32009 20130101; H01L 21/0273 20130101; H01J 37/32422
20130101; H01L 21/31144 20130101; H01J 37/32669 20130101 |
Class at
Publication: |
216/68 ;
156/345.51; 156/345.48; 216/71 |
International
Class: |
B44C 1/22 20060101
B44C001/22; B05C 13/00 20060101 B05C013/00 |
Claims
1. An apparatus for controlling a line width roughness of a
photoresist layer disposed on a substrate, comprising: a processing
chamber having a chamber body having a top wall, side wall and a
bottom wall defining an interior processing region; a support
pedestal disposed in the interior processing region of the
processing chamber; and a plasma generator source disposed in the
processing chamber operable to provide predominantly an electron
beam source to the interior processing region.
2. The apparatus of claim 1, further comprising: a shield plate
disposed in the processing chamber operable to filter ions from the
plasma and pass electrons.
3. The apparatus of claim 2, further comprising: a control plate
disposed in the processing region between the shield plate and the
support pedestal.
4. The apparatus of claim 3, further comprising: a power source
coupled to the control plate.
5. The apparatus of claim 3, wherein the control plate comprises a
plurality of zones formed therein with at least two zones
comprising different materials or different potential biases.
6. The apparatus of claim 2, further comprising: a power source
coupled to the shield plate.
7. The apparatus of claim 2, wherein the shield plate comprises a
plurality of zones formed therein with at least two zones
comprising different materials or different potential biases.
8. The apparatus of claim 3, wherein the control plate is attached
to the shield plate.
9. The apparatus of claim 3, wherein the control plate has a
plurality of apertures formed therein.
10. The apparatus of claim 1, wherein the shield plate has a
plurality of apertures formed therein.
11. The apparatus of claim 1 further comprising: a magnet or a
group of one or more electromagnetic coils disposed around an outer
circumference of the chamber body adjacent to the interior
processing region of the chamber body.
12. A method for controlling line width roughness of a photoresist
layer disposed on a substrate comprising: providing a substrate
having a patterned photoresist layer disposed thereon into a
processing chamber; supplying a gas mixture into the processing
chamber; generating a plasma in the gas mixture having electrons
moving in a circular mode from the gas mixture; generating a
magnetic field to enhance the electrons in the plasma moving in the
circular mode to a substrate surface; and trimming an edge profile
of the patterned photoresist layer disposed on the substrate
surface with the enhanced electrons.
13. The method of claim 12, wherein generating the plasma further
comprises: filtering ions from the plasma.
14. The method of claim 13, further comprising: directing the
filtered electrons through the magnetic field.
15. The method of claim 12, wherein generating the magnetic field
further comprises: applying a DC or AC power to one or more
electromagnetic coils disposed around the outer circumference of
the processing chamber.
16. The method of claim 12, wherein the gas mixture comprises an
oxygen containing gas.
17. A method for controlling line width roughness of a photoresist
layer disposed on a substrate comprising: supplying a gas mixture
into a processing chamber having a substrate disposed therein,
wherein the substrate has a patterned photoresist layer disposed
thereon; generating a plasma in the processing chamber from the gas
mixture supplied in the processing chamber; applying a voltage to a
shield plate disposed in the processing chamber to filter ions from
the plasma and leave mild reactive species; directing the mild
reactive species through a control plate; applying a DC or AC power
to a group of one or more electromagnetic coils disposed around an
outer circumference of the processing chamber to generate a
magnetic field; enhancing movement of the mild reactive species in
circular mode by passing through the filtered plasma in the
magnetic field; and trimming an edge profile of the patterned
photoresist layer using the mild reactive species.
18. The method of claim 17, wherein directing the filter plasma
further comprises: applying a power to the control plate.
19. The method of claim 17, wherein supplying the gas mixture
further comprises: supplying an oxygen containing gas into the
processing chamber.
20. The method of claim 17, wherein the mild reactive species
include neutral radicals and electrons.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims benefit of U.S. Provisional Patent
Application No. 61/497,370, filed Jun. 15, 2011, which is
incorporated by reference in its entirety.
BACKGROUND
[0002] 1. Field of the Invention
[0003] The present invention generally relates to methods and
apparatus for controlling photoresist line width roughness and,
more specifically, to methods and apparatus for controlling
photoresist line width roughness with enhanced electron spin
control in semiconductor processing technologies.
[0004] 2. Description of the Related Art
[0005] Integrated circuits have evolved into complex devices that
can include millions of components (e.g., transistors, capacitors
and resistors) on a single chip. The evolution of chip designs
continually requires faster circuitry and greater circuit density.
The demands for greater circuit density necessitate a reduction in
the dimensions of the integrated circuit components.
[0006] As the dimensions of the integrated circuit components are
reduced (e.g. to sub-micron dimensions), more elements are required
to be put in a given area of a semiconductor integrated circuit.
Accordingly, lithography processes have become more and more
challenging to transfer even smaller features onto a substrate
precisely and accurately without damage. In order to transfer
precise and accurate features onto a substrate, a desired high
resolution lithography process requires having a suitable light
source that may provide radiation at a desired wavelength range for
exposure. Furthermore, the lithography process requires
transferring features onto a photoresist layer with minimum
photoresist line width roughness (LWR). After all, a defect-free
photomask is required to transfer desired features onto the
photoresist layer. Recently, an extreme ultraviolet (EUV) radiation
source has been utilized to provide short exposure wavelengths so
as to provide a further reduced minimum printable size on a
substrate. However, at such small dimensions, the roughness of the
edges of a photoresist layer has become harder and harder to
control.
[0007] FIG. 1 depicts an exemplary top isometric sectional view of
a substrate 100 having a patterned photoresist layer 104 disposed
on a target material 102 to be etched. Openings 106 are defined
between the patterned photoresist layer 104 readily to expose the
underlying target material 102 for etching to transfer features
onto the target material 102. However, inaccurate control or low
resolution of the lithography exposure process may cause in poor
critical dimension control in the photoresist layer 104, thereby
resulting in unacceptable LWR 108. Large LWR 108 of the photoresist
layer 104 may result in inaccurate feature transfer to the target
material 102, thus, eventually leading to device failure and yield
loss.
[0008] Therefore, there is a need for a method and an apparatus to
control and minimize LWR so as to obtain a patterned photoresist
layer with desired critical dimensions.
SUMMARY
[0009] The present invention provides methods and an apparatus for
controlling and modifying LWR of a photoresist layer with enhanced
electron spin control. In one embodiment, an apparatus for
controlling a line width roughness of a photoresist layer disposed
on a substrate includes a processing chamber having a chamber body
having a top wall, side wall and a bottom wall defining an interior
processing region, a support pedestal disposed in the interior
processing region of the processing chamber, and a plasma generator
source disposed in the processing chamber operable to provide
predominantly an electron beam source to the interior processing
region.
[0010] In another embodiment, a method for controlling line width
roughness of a photoresist includes providing a substrate having a
patterned photoresist layer in a processing chamber, supplying a
gas mixture into the processing chamber, generating a plasma in the
gas mixture having electrons moving in a circular mode from the gas
mixture, generating a magnetic field to enhance the electrons in
the plasma moving in the circular mode to a substrate surface, and
trimming an edge profile of the patterned photoresist layer
disposed on the substrate surface with the enhanced electrons.
[0011] In another embodiment, a method for controlling line width
roughness of a photoresist layer disposed on a substrate includes
providing a substrate having a patterned photoresist layer disposed
thereon into a processing chamber, supplying a gas mixture into the
processing chamber, generating a plasma in the gas mixture,
extracting electrons out of the plasma, generating a magnetic field
to enhance the electrons moving in a circular mode to a substrate
surface, and trimming an edge profile of the patterned photoresist
layer disposed on the substrate surface with the enhanced
plasma.
[0012] In yet another embodiment, a method for controlling line
width roughness of a photoresist layer disposed on a substrate
includes supplying a gas mixture into a processing chamber having a
substrate disposed therein, wherein the substrate has a patterned
photoresist layer disposed thereon, generating a plasma in the
processing chamber from the gas mixture supplied in the processing
chamber, applying a voltage to a shield plate disposed in the
processing chamber to filter ions from the plasma and leaving mild
reactive species, directing the mild reactive species through a
control plate, applying a DC or AC power to a group of one or more
electromagnetic coils disposed around an outer circumference of the
processing chamber to generate a magnetic field, enhancing movement
of the mild reactive species in circular mode by passing the mild
reactive species through the magnetic field, and trimming an edge
profile of the patterned photoresist layer using the mild reactive
species.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] So that the manner in which the above recited features of
the present invention are attained and can be understood in detail,
a more particular description of the invention, briefly summarized
above, may be had by reference to the embodiments thereof which are
illustrated in the appended drawings.
[0014] FIG. 1 depicts a top isometric sectional view of an
exemplary structure of a patterned photoresist layer disposed on a
substrate conventionally in the art;
[0015] FIG. 2A depicts a schematic cross-sectional view of an
inductively coupled plasma (ICP) reactor with enhanced electron
spin control used according to one embodiment of the invention;
[0016] FIG. 2B depicts an electron trajectory diagram according to
one embodiment of the invention;
[0017] FIG. 3 depicts an electron trajectory diagram passing
through a beam control plate disposed in the ICP reactor depicted
in FIG. 2;
[0018] FIG. 4 depicts a flow diagram of one embodiment of
performing a photoresist line width roughness control process
according to one embodiment of the present invention;
[0019] FIG. 5 depicts a top view of electron trajectories traveled
adjacent to a photoresist layer according to one embodiment of the
present invention; and
[0020] FIG. 6 depicts a profile of a line width roughness of a
photoresist layer disposed on a substrate according to one
embodiment of the invention.
[0021] FIG. 7 depicts one embodiment of a control plate and/or a
shield plate;
[0022] FIG. 8 depicts another embodiment of a control plate and/or
a shield plate; and
[0023] FIG. 9 depicts yet another embodiment of a control plate
and/or a shield plate.
[0024] To facilitate understanding, identical reference numerals
have been used, where possible, to designate identical elements
that are common to the figures. It is contemplated that elements
and features of one embodiment may be beneficially incorporated in
other embodiments without further recitation.
[0025] It is to be noted, however, that the appended drawings
illustrate only exemplary embodiments of this invention and are
therefore not to be considered limiting of its scope, for the
invention may admit to other equally effective embodiments.
DETAILED DESCRIPTION
[0026] Embodiments of the present invention include methods and
apparatus for controlling LWR of a photoresist layer disposed on a
substrate. The LWR of a photoresist layer may be controlled by
performing an ICP process with enhanced electron spin control on a
photoresist layer after an exposure/development process. The ICP
process is performed to provide a chemical and electron grinding
process on a nanometer scale with enhanced electron spin control to
smooth the edge of the photoresist layer pattern with sufficient
electron spin momentum, thereby providing a smooth pattern edge of
the photoresist layer with minimum pattern edge roughness for
subsequent etching processes. The ICP process with enhanced
electron spin control may also be used to etch a target material
disposed underneath the photoresist layer on the substrate
subsequent to the photoresist line edge roughness minimization
process.
[0027] FIG. 2A depicts a schematic, cross-sectional diagram of one
embodiment of an ICP reactor 200 suitable for performing plasma
processing with enhanced electron spin control according to the
present invention. One such etch reactor that may be adapted for
performing the invention may be available from Applied Materials,
Inc., of Santa Clara, Calif. It is contemplated that other suitable
plasma processing chambers may also be employed herein, including
those from other manufacturers.
[0028] The plasma reactor 200 includes a processing chamber 248
having a chamber body 210. The processing chamber 248 is a high
vacuum vessel having a vacuum pump 228 coupled thereto. The chamber
body 210 of the processing chamber 248 includes a top wall 222, a
sidewall 224 and a bottom wall 226 defining an interior processing
region 212 therein. The temperature of the sidewall 224 is
controlled using liquid-containing conduits (not shown) that are
located in and/or around the sidewall 224. The bottom wall 226 is
connected to an electrical ground 230.
[0029] The processing chamber 248 includes a support pedestal 214.
The support pedestal 214 extends through the bottom wall 226 of the
processing chamber 248 into the interior processing region 212. The
support pedestal 214 may receive a substrate 250 to be disposed
thereon for processing.
[0030] A plasma generator source 202 is attached to top of the
chamber body 210 configured to supply electrons to the interior
processing region 212. A plurality of coils 208 may be disposed
around the plasma generator source 202 to insist creating
inductively coupled plasma from the plasma generator source
202.
[0031] Processing gases may be introduced to the interior
processing region 212 from a gas source 206 coupled to the
processing chamber 248. The processing gases from the gas source
206 are supplied to the interior processing region 212 through the
plasma generator source 202. Current is applied to the coil 208
from a power source which creates an electric field that
dissociates the processing gases. The processing gases dissociated
by the coils 208 form an electron beam 249 to be delivered to the
interior processing region 212 for processing.
[0032] A group of one or more coil segments or electromagnetic
coils 221 (shown as 221A and 221B) are disposed around an outer
circumference of a lower portion 211 of the chamber body 210
adjacent to the interior processing region 212. Power to the coil
segment(s) or magnets 221 is controlled by a DC power source or a
low-frequency AC power source (not shown). The electromagnetic
coils 221 generate a magnetic field in a direction perpendicular to
the substrate surface where the electron beam 249 is introduced
into the processing chamber 248. As the electrons from the electron
beam 249 may not have sufficient momentum to reach down to the
interior processing region 212 further down to an upper surface 253
of the substrate 250, the group of the coil segments or
electromagnetic coils 221 may be disposed at the lower portion 211
of the chamber body 210 (e.g., close to the interior processing
region 212) to enhance spinning and/or whirling of the electrons
down to the upper surface 253 of the substrate 250. The interaction
between the electric field and magnetic field generated from the
group of the coil segments or electromagnetic coils 221 causes the
electron beam 249 having enhanced electron spinning and/or whirling
momentum to reach down to the surface of the substrate 250. It is
noted that other magnetic field sources capable of generating
sufficient magnetic field strength to promote an electron beam
(e-beam) source may also be used.
[0033] In one embodiment, a shield plate 262 is disposed in the
processing chamber 248 above the support pedestal 214. The shield
plate 262 is a substantially flat plate comprising a plurality of
apertures 270. The shield plate 262 may be made of a variety of
materials compatible with processing needs, comprising one or more
apertures 270 that define desired open areas in the shield plate
262. In one embodiment, the shield plate 262 may be fabricated from
a material selected from a group consisting of copper or copper
coated ceramics. The open areas of the shield plate 262 (i.e., the
size and density of the apertures 270) assist in controlling the
amount of ions/electrons which mainly consist of an electron beam
and small amounts of ions formed from the plasma generator source
202 to the interior processing region 212 above the upper surface
253 of the substrate 250. Accordingly, the shield plate 262 acts as
an ion/electron filter (or electron controller) that controls the
electron density and/or ion density in the volume passing through
the shield plate 262 to the upper surface 253 of the substrate
250.
[0034] During processing, a voltage from a power source 260 may be
applied to the shield plate 262. The voltage potential applied on
the shield plate 262 may attract ions from the plasma, thereby
efficiently filtering the ions from the plasma, while allowing only
neutral species, such as radicals and electrons, to pass through
the apertures 270 of the shield plate 262. Thus, by
reducing/filtering the amount of ions through the shield plate 262,
grinding or smoothing of the structures formed on the substrate by
neutral species, radicals, or electrons, i.e., mild reactive
species, can be processed in a more controlled manner. Therefore,
the mild reactive species may reduce the likelihood of undesired
erosion sputter, or overly aggressive ion bombardment that may
cause to the substrate surface to roughen, thereby resulting in
precise smoothing performance and critical dimension uniformity.
The voltage applied to the shield plate 262 may be supplied at a
range sufficient to attract or retain ions from the plasma, thereby
repelling the neutral species, radicals, or electrons from the ions
generated in the plasma. Thus, the mild reactive species are
extracted from the plasma by the shield plate 262. In one
embodiment, the voltage is applied to the shield plate 262 from the
power source 260 between about 50 volts DC and about 200 volts DC.
In another embodiment, the mild reactive species are extracted from
the plasma by the shield plate 262 are predominantly electrons.
[0035] A control plate 264 is disposed below the shield plate 262
and above the support pedestal 214. The control plate 264 has a
plurality of apertures 268 that allow the neutral species,
radicals, or electrons filtered through the shield plate 262 to
pass therethrough into the interior processing region 212. The
control plate 264 is positioned in a spaced-apart relationship with
the shield plate 262 at a predetermined distance 266. In another
embodiment, the control plate 264 is attached to the shield plate
262 with minimum space in between. In one embodiment, the distance
266 between the shield plate 262 and the control plate 264 is less
than about 20 mm.
[0036] A voltage from a power source 251 may be applied to the
control plate 264, so as to create a voltage potential (e.g., an
electrical potential) that interacts with the magnetic field
generated from the group of the coil segments or electromagnetic
coils 221 (shown as 221A and 221B). The electrical potential
generated by the control plate 264 along with the magnetic field
generated by the group of the coil segments or electromagnetic
coils 221 assist and enhance maintaining sufficient momentum and
energy to keep the neutral species, radicals, or electrons spinning
down to the upper surface 253 of the substrate 250. Furthermore,
the neutral species, radicals, or electrons passing through the
apertures 268 of the control plate 264 may be directed in a
predetermined path, thereby confining the trajectory of the neutral
species, radicals, or electrons in a predetermined path to reach to
a desired area on the upper surface 253 of the substrate 250. When
passing through the control plate 264, the magnified field may
cause the neutral species, radicals, or electrons passing through
to keep moving in a circular mode and spinning toward to the upper
surface 253 of the substrate 250. The spin electrons have to grid
the structures with sufficient momentum to bottoms of the
structures formed on the upper surface 253 of the substrate
250.
[0037] In one embodiment, the control plate 264 may have different
materials or different characteristics. The control plate 264 may
comprise more than one zone or segments having at least one
characteristic that is different from each other. For example, the
control plate 264 may have a number of zones with different
configurations including various geometries (e.g., sizes, shapes
and open areas) and the zones may be made of the same or different
materials, or be adapted to have different potential bias or
different powers. By providing combinations of zone configurations,
materials, powers, and/or potential bias, the spatial distribution
of the neutral species, radicals, and electrons in the plasma may
be modified in a localized manner, allowing customization of
process characteristics, such as smoothing uniformity or locally
enhanced or reduced smoothing rates (e.g., to tailor to different
pattern densities in different parts of a substrate) and so on.
Such a multi-zone control plate 264 may be used to actively control
the neutral species, radicals, and electrons distribution, and
thus, allow for enhanced process control. More embodiment of the
control plate 264 will be further discussed below with reference to
FIGS. 7-9.
[0038] During substrate processing, gas pressure within the
interior of the processing chamber 248 may be controlled in a
predetermined range. In one embodiment, the gas pressure within the
interior processing region 212 of the processing chamber 248 is
maintained at about 0.1 to 999 mTorr. The substrate 250 may be
maintained at a temperature of between about 10 to about 500
degrees Celsius.
[0039] Furthermore, the processing chamber 248 may include a
translation mechanism 272 configured to translate the support
pedestal 214 and the control plate 264 relative to one another. In
one embodiment, the translation mechanism 272 is coupled to the
support pedestal 214 to move the support pedestal 214 laterally
relative to the control plate 264. In another embodiment, the
translation mechanism 272 is coupled to the plasma generator source
202 and/or the control plate 264 and/or the shield plate 262 to
move the plasma generator source 202 and/or the control plate 264
and/or the shield plate 262 laterally relative to the support
pedestal 214. In yet another embodiment, the translation mechanism
272 moves one or more of plasma generator source 202, the control
plate 264 and shield plate 262 laterally relative to the support
pedestal 214. Any suitable translation mechanism may be used, such
as a conveyor system, rack and pinion system, an x/y actuator, a
robot, electronic motors, pneumatic actuators, hydraulic actuators,
or other suitable mechanism.
[0040] The translation mechanism 272 may be coupled to a controller
240 to control the scan speed at which the support pedestal 214 and
plasma generator source 202 and/or the control plate 264 and/or the
shield plate 262 move relative to one another. In addition,
translation of the support pedestal 214 and the plasma generator
source 202 and/or the control plate 264 and/or the shield plate 262
relative to one another may be configured to be along a path
perpendicular to the predetermined trajectory 274 of the neutral
species, radicals, or electrons the upper surface 253 of the
substrate 250. In one embodiment, the translation mechanism 272
moves at a constant speed, of approximately 2 millimeters per
seconds (mm/s). In another embodiment, the translation of the
support pedestal 214 and the plasma generator source 202 and/or the
control plate 264 and/or the shield plate 262 relative to one
another may be moved along other paths as desired.
[0041] The controller 240, including a central processing unit
(CPU) 244, a memory 242, and support circuits 246, is coupled to
the various components of the reactor 200 to facilitate control of
the processes of the present invention. The memory 242 can be any
computer-readable medium, such as random access memory (RAM), read
only memory (ROM), floppy disk, hard disk, or any other form of
digital storage, local or remote to the reactor 200 or CPU 244. The
support circuits 246 are coupled to the CPU 244 for supporting the
CPU 244 in a conventional manner. These circuits include cache,
power supplies, clock circuits, input/output circuitry and
subsystems, and the like. A software routine or a series of program
instructions stored in the memory 242, when executed by the CPU
244, causes the reactor 200 to perform a plasma process of the
present invention.
[0042] FIG. 2A only shows one exemplary configuration of a plasma
reactor that can be used to practice the invention. For example,
other types of reactors may utilize different types of plasma power
and magnetic power coupled into the plasma chamber using different
coupling mechanisms. In some applications, different types of
plasma may be generated in a different chamber from the one in
which the substrate is located, e.g., remote plasma source, and the
plasma subsequently guided into the chamber using techniques known
in the art.
[0043] FIG. 3 depicts an electron trajectory diagram passing
through the control plate 264 depicted in FIG. 2 according to one
embodiment of the invention. As the filtered neutral species,
radicals, and electrons (e.g., electron beam source) passing
through the shield plate 262 are accelerated toward the upper
surface 253 of the substrate 250, the filtered neutral species,
radicals, and electrons (e.g., electron beam source) subsequently
passing through the control plate 264 may be confined to pass
through the apertures 268 formed in the control plate 264. As the
group of electromagnetic coils 221 are disposed around the control
plate 264, the neutral species, radicals, and electrons (e.g.,
electron beam source) passing therethrough may keep orbiting around
and travelling down in the predetermined trajectory 274 confined by
the apertures 268 of the control plate 264 and reach desired
regions on the upper surface 253 of the substrate 250. By
utilization of the control plate 264, the trajectory 274 of the
neutral species, radicals, and electrons (e.g., electron beam
source) may be efficiently controlled in a manner with enhanced
electron spinning momentum so as to enable electrons to travel deep
down to the bottom of the structures formed on the substrate while
continuing to spin around the horizontal plane so that the
electrons grind and smooth the roughness from the edge of the
structures formed on the substrate 250.
[0044] FIG. 4 illustrates a flow diagram of one embodiment of
performing a photoresist LWR control process 400 according to one
embodiment of the invention. The process 400 may be stored in
memory 242 as instructions that executed by the controller 240 to
cause the process 400 to be performed in an ICP processing chamber,
such as the ICP reactor 200 depicted in FIG. 2A or other suitable
reactors.
[0045] The process 400 begins at a block 402 by transferring a
substrate, such as the substrate 250 depicted in FIG. 2A, into the
processing chamber 248 for processing. The substrate 250 may have a
target material 512 to be etched disposed thereon, as shown in FIG.
6, disposed under a photoresist layer 514. In one embodiment, the
target material 512 to be etched using the photoresist LWR control
process 400 may be a dielectric layer, a metal layer, a ceramic
material, or other suitable material. In one embodiment, the target
material 512 to be etched may be a dielectric material formed as a
gate structure or a contact structure or an inter-layer dielectric
structure (ILD) utilized in semiconductor manufacturing. Suitable
examples of the dielectric material include SiO.sub.2, SiON, SiN,
SiC, SiOC, SiOCN, amorphous-carbon (a-C), or the like. In another
embodiment, the target material 512 to be etched may be a metal
material formed as an inter-metal dielectric structure (IMD) or
other suitable structures. Suitable examples of metal layers
include Cu, Al, W, Ni, Cr, or the like.
[0046] At block 404, a photoresist LWR control process 400 may be
performed on the substrate 250 to grind, modify and trim edges 516
of the photoresist layer 514, as shown in FIG. 5. The photoresist
LWR control process 400 is performed providing a source of
electrons. In one embodiment, the electrons are providing by
generating an ICP in the processing chamber 248. The ICP is
generated by the plasma generator source 202 disposed in the
processing chamber 248. As discussed above, the plasma as generated
may include different types of reactive species, such as electrons,
charges, ions, neutral species, and so on either with positive or
negative charges. The excited plasma is used to extract electrons
which are moved and accelerated in a circular motion toward the
upper surface 253 of the substrate 250.
[0047] At block 406, as the plasma is advanced toward the substrate
surface, the plasma then passes through the shield plate 262
disposed in the processing chamber 248. A voltage is applied to the
shield plate 262 to create a voltage potential, so as to attract
ions from the plasma, thereby efficiently filtering ions from the
plasma, while allowing only neutral species, such as radicals and
electrons (e.g., electron beam source), to pass through the
apertures 270 of the shield plate 262 to the substrate surface. In
one embodiment, the voltage is applied to the shield plate 262 from
power source 260 between about 50 volts DC and about 200 volts
DC.
[0048] At block 408, after passing through the shield plate 262,
the filtered plasma (e.g., electron beam source) then travels
through the control plate 264. The control plate 264 may confine
the filtered plasma passing therethrough to a predetermined path so
as to increase collimation of the filtered plasma (e.g., electron
beam source) such that the mild reactive species fall on certain
regions of the upper surface 253 of the substrate 250. The filtered
plasma (e.g., electron beam source) is accelerated to maintain a
substantially helical movement circulated by the magnetic field
generated from the group of the electromagnetic coils 221 such that
the mild reactive species have sufficient momentum to maintain a
spinning motion down to the upper surface 253 of the substrate 250.
A power supplied to the control plate 264 may generate an electric
field to interact with the magnetic field generated from the group
of the electromagnetic coils 221 to enhance/maintain the helical
motion of the mild reactive species such that sufficient momentum
and energy is provided to keep the mild reactive species spinning
down to the upper surface 253 of the substrate 250. The spin
electrons may, thus, grind the structures with sufficient momentum
all the way to bottoms of the structures formed on the upper
surface 253 of the substrate 250.
[0049] At block 410, the LWR of the photoresist layer 514 may be
adjusted, grinded, modified, controlled during the plasma-induced
process. As depicted in FIG. 5, the circular movement 504 of the
electrons may smoothly grind, collide, and polish away the uneven
edges 516 of the photoresist layer 514. The process may be
continuously performed until a desired degree of roughness, e.g.,
straightness, (as shown by imaginary line 510) of photoresist layer
514 is achieved. By a good control of the electron momentum, the
uneven surfaces and protrusions from edges 516 of the photoresist
layer 514 may be gradually flattened out, thereby efficiently
controlling the photoresist LWR within a desired minimum range. The
electron momentum or neutral species concentration may be
controlled by the power generated from the interaction between the
magnetic field and the electric field and the gases supplied
thereto. In one embodiment, by adjusting the power supplied to
generate the plasma power and the magnetic field, different
electron momentum or mobility may be obtained.
[0050] In one embodiment, the distribution of the electrons and/or
neutral species (e.g., electron beam source) may be controlled by
using a different control plate 264 with different materials or
different characteristics. More embodiments of the control plate
264 with different materials or different characteristics will be
further discussed below with reference to FIGS. 7-9.
[0051] During processing, at block 410, several process parameters
may be controlled to maintain the LWR of the photoresist layer 514
at a desired range. In one embodiment, the plasma power may be
supplied to the processing chamber between about 50 watts and about
2000 watts. The magnetic field generated in the first group of
coils or magnetic segments 208 in the processing chamber may be
controlled between about 500 Gauss (G) and about 1000 G. A DC
and/or AC power between about 100 watts and about 2000 watts may be
used to generate a magnetic field in the processing chamber. The
magnetic field generated in the group of electromagnetic coils 221
in the processing chamber may be controlled between about 100 G and
about 200 G. A DC and/or AC power may be applied to the control
plate 264 between about 100 watts and about 2000 watts to generate
a magnetic field in the processing chamber. The voltage between
about 50 volts DC and about 200 volts DC is applied to the shield
plate 262 to filter the plasma as generated from the plasma
generator 202. The pressure of the processing chamber may be
controlled at between about 0.5 milliTorr and about 500 milliTorr.
A processing gas may be supplied into the processing chamber to
assist modifying, trimming, and controlling the edge roughness of
the photoresist layer 514. As the materials selected for the
photoresist layer 514 are often organic materials, an oxygen
containing gas may be selected as the processing gas to be supplied
into the processing chamber to assist gridding and modifying the
roughness and profile of the photoresist layer 514. Suitable
examples of the oxygen containing gas include O.sub.2, N.sub.2O,
NO.sub.2, 0.sub.3, H.sub.2O, CO, CO.sub.2, and the like. Other
types of processing gas may also be supplied into the processing
chamber, simultaneously or individually, to assist in modifying the
roughness of the photoresist layer 514. Suitable examples of the
processing gas include N.sub.2, NH.sub.3, Cl.sub.2 or inert gas,
such as Ar or He. The processing gas may be supplied into the
processing chamber at a flow rate between about 10 sccm to about
500 sccm, for example, about between about 100 sccm to about 200
sccm. The process may be performed between about 30 seconds and
about 200 seconds. In one particular embodiment, the O.sub.2 gas is
supplied as the processing gas into the processing chamber to react
with the photoresist layer 514 so as to trim and modify the LWR of
the photoresist layer 514 disposed on the substrate 250.
[0052] The photoresist LWR control process 400 may be continuously
performed until a desired minimum roughness of the photoresist
layer 514 is achieved. In one embodiment, line width roughness 513
of the photoresist layer 514 may be controlled in a range less than
about 3.0 nm, such as between about 1.0 nm and about 1.5 nm. The
photoresist LWR control process 400 may be terminated after
reaching an endpoint signal indicating that a desired roughness of
the photoresist layer 514 is achieved. Alternatively, the
photoresist LWR control process 400 may be terminated by a preset
time mode. In one embodiment, the photoresist LWR control process
400 may be performed for between about 100 seconds and between
about 500 seconds.
[0053] FIG. 6 depicts an exemplary embodiment of a cross sectional
view of the photoresist layer 514 already having the photoresist
LWR control process 400 performed thereon. After the photoresist
LWR control process 400 is performed, a smooth edge surface is
obtained. The roughness of the photoresist layer 514 is smoothed
out and trimmed in a manner to minimize the edge roughness and
smooth the edge morphology of the photoresist layer 514. The smooth
edge surface formed in the photoresist layer 514 defines a sharp
and well defined opening 604 in the patterned photoresist layer 514
to expose the underlying target material 512 for etching, thereby
etching a precise and straight opening width 606 to be formed as a
mask layer. In one embodiment, the width 606 of the openings 604
may be controlled between about 15 nm and about 35 nm.
[0054] In one embodiment, the underlying target material 512 may be
etched by an etching process performed in the same chamber used to
perform the LWR control process, such as the processing chamber 248
depicted in FIG. 2. In another embodiment, the underlying target
material 512 may be etched by an etching process performed in any
other different suitable etching chamber integrated in a cluster
system where the LWR processing chamber may be incorporated
thereto. In yet another embodiment, the underlying target material
512 may be etched by an etching process performed in any other
different suitable etching chambers, including a stand-alone
chamber separated from the LWR process chamber or separated from a
cluster system where the LWR processing chamber may be incorporated
thereto.
[0055] In one embodiment, the gas mixture utilized to perform the
LWR process is configured to be different from the gas mixture
utilized to etch the underlying target material 512. In one
embodiment, the gas mixture utilized to perform the LWR process
includes an oxygen containing gas, such as O.sub.2, and the gas
mixture utilized to etch the underlying target material 512
includes a halogen containing gas, such as fluorine carbon gas,
chlorine containing gas, bromide containing gas, fluorine
containing gas, and the like.
[0056] FIG. 7 depicts one embodiment of a plate 700 having
different zones in various arrangements. In the embodiment depicted
in FIG. 7, the plate 700 has different zones, 702, 704, 706
arranged in concentric rings. The plate 700 may be used as one or
both of a control plate or shield plate in the embodiment of FIG.
2A. The concentric ring configuration, for example, may be useful
in compensating for plasma non-uniformities (in a radial direction)
that may arise from non-uniform gas flow patterns in the
chamber.
[0057] FIG. 8 depicts another embodiment of a plate 800 having
different zones in various arrangements. The plate 800 may be used
as one or both of a control plate or shield plate in the embodiment
of FIG. 2A. In the embodiment depicted in FIG. 8, the plate 800 is
configured to have zones or segments based on the specific mask
patterns in order to achieve different smoothing rate resulted on
the substrate surface. The plate 800 is divided into two zones 802,
804, whose spatial configurations correspond to or correlate with
respective regions on a mask having different pattern densities.
For example, if zone 802 corresponds to a region on the mask
requiring a relatively higher smoothing rate than the rest of the
mask, then zone 802 may be provided with a larger diameter of
apertures 806. Alternatively, zones 802, 804 may be made of
materials with different dielectric contacts and/or different
potential biases, so as to provide different electron (and/or
neutral species) spinning or rotating rates.
[0058] FIG. 9 depicts yet another embodiment of a plate 900 having
different zones in various arrangements. The plate 900 may be used
as one or both of a control plate or shield plate in the embodiment
of FIG. 2A. In the embodiment depicted in FIG. 9, the plate 900 is
configured to have a plurality of zones or segments 902, 904, 906,
908. At least two zones are made of different materials compatible
with process chemistries. At least two zones may be independently
biased to maintain a potential difference between the biased zones.
The use of materials having different dielectric constants or
different potential biases allows users to tune the plasma
characteristics or different rotating speeds and momentums.
Additionally, the sizes of apertures 910, 912, 914, 916 located in
different zones 902, 904, 906, 908 of the plate 900 may be arranged
in any combinations or configurations.
[0059] Thus, the present invention provides methods and an
apparatus for controlling and modifying LWR of a photoresist layer
with enhanced electron spinning momentum. The method and apparatus
can advantageously control, modify and trim the profile, line width
roughness and dimension of the photoresist layer disposed on a
substrate after a light exposure process, thereby providing
accurate critical dimension control of an opening in the
photoresist layer so the subsequent etching process may accurately
transfer critical dimensions to the underlying layer being etched
through the opening.
[0060] While the foregoing is directed to embodiments of the
present invention, other and further embodiments of the invention
may be devised without departing from the basic scope thereof, and
the scope thereof is determined by the claims that follow.
* * * * *