U.S. patent application number 17/647198 was filed with the patent office on 2022-08-25 for cathode mechanism of electron gun, electron gun, and electron beam writing apparatus.
This patent application is currently assigned to NuFlare Technology, Inc.. The applicant listed for this patent is NuFlare Technology, Inc.. Invention is credited to Ryoei KOBAYASHI.
Application Number | 20220270842 17/647198 |
Document ID | / |
Family ID | 1000006107104 |
Filed Date | 2022-08-25 |
United States Patent
Application |
20220270842 |
Kind Code |
A1 |
KOBAYASHI; Ryoei |
August 25, 2022 |
CATHODE MECHANISM OF ELECTRON GUN, ELECTRON GUN, AND ELECTRON BEAM
WRITING APPARATUS
Abstract
A cathode mechanism of an electron gun includes a crystal to
emit a thermal electron from an end surface by being heated, a
holding part to hold the crystal in a state where the end surface
is exposed and at least a part of other surfaces of the crystal is
covered, a first supporting post and a second supporting post each
to support the holding part and extend while maintaining an
unchanged sectional size, a first base part to fix the first
supporting post, and a second base part to fix the second
supporting post, wherein the holding part, the first supporting
post, the second supporting post, the first base part, and the
second base part are formed in an integrated structure made of the
same material, and the crystal is heated by supplying a current to
the integrated structure.
Inventors: |
KOBAYASHI; Ryoei;
(Yokosuka-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NuFlare Technology, Inc. |
Yokohama-shi |
|
JP |
|
|
Assignee: |
NuFlare Technology, Inc.
Yokohama-shi
JP
|
Family ID: |
1000006107104 |
Appl. No.: |
17/647198 |
Filed: |
January 6, 2022 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01J 29/51 20130101;
H01J 29/488 20130101; H01J 29/485 20130101 |
International
Class: |
H01J 29/48 20060101
H01J029/48; H01J 29/51 20060101 H01J029/51 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 25, 2021 |
JP |
2021-029008 |
Claims
1. A cathode mechanism of an electron gun comprising: a crystal
configured to emit a thermal electron from an end surface by being
heated; a holding part configured to hold the crystal in a state
where the end surface is exposed and at least a part of other
surfaces of the crystal is covered; a first supporting post and a
second supporting post each configured to support the holding part
and extend while maintaining an unchanged sectional size; a first
base part configured to fix the first supporting post; and a second
base part configured to fix the second supporting post, wherein the
holding part, the first supporting post, the second supporting
post, the first base part, and the second base part are formed in
an integrated structure made of a same material, and the crystal is
heated by supplying a current to the integrated structure.
2. The mechanism according to claim 1, wherein each of the first
supporting post and the second supporting post has a
cross-sectional configuration in which three sides are straight
lines and one side is a curved line.
3. The mechanism according to claim 1, wherein the crystal is
formed in a shape of at least one of a cylinder and a truncated
cone.
4. The mechanism according to claim 1, wherein the first supporting
post and the second supporting post function as a heater for
heating the crystal through the holding part.
5. The mechanism according to claim 1, wherein crystal orientations
in the end surface are same.
6. The mechanism according to claim 1, wherein as a material of the
integrated structure, one of graphite, tantalum, tungsten, and
iridium is used.
7. The mechanism according to claim 1, wherein a continuous space
having a same width is formed from a back side of the holding part,
between the first supporting post and the second supporting post,
and between the first base part and the second base part.
8. The mechanism according to claim 7, wherein each of the first
supporting post and the second supporting post has a
cross-sectional configuration in which three sides are straight
lines and one side is a curved line.
9. An electron gun comprising: a cathode mechanism of an electron
gun according to claim 1; and an anode electrode configured to be
controlled to have a potential more positive than that of a crystal
and to pull out a thermal electron emitted from the crystal.
10. An electron beam writing apparatus comprising: an electron gun
according to claim 9; and a writing mechanism configured to write a
pattern on a target object using a thermal electron emitted from
the electron gun.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is based upon and claims the benefit of
priority from prior Japanese Patent Application No. 2021-029008
filed on Feb. 25, 2021 in Japan, the entire contents of which are
incorporated herein by reference.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] One aspect of the present invention relates to a cathode
mechanism of an electron gun, an electron gun, and an electron beam
writing apparatus.
Description of Related Art
[0003] The lithography technique that advances miniaturization of
semiconductor devices is extremely important as a unique process
whereby patterns are formed in semiconductor manufacturing. In
recent years, with high integration of LSI, the line width
(critical dimension) required for semiconductor device circuits is
becoming increasingly narrower year by year. The electron beam
writing technique which intrinsically has excellent resolution is
used for writing or "drawing" a mask pattern on a mask blank with
electron beams.
[0004] For example, as a known example of employing the electron
beam writing technique, there is a writing apparatus using multiple
beams. Since it is possible for multi-beam writing to apply
multiple beams at a time, the writing throughput can be greatly
increased in comparison with single electron beam writing. For
example, a writing apparatus employing the multi-beam system forms
multiple beams by letting portions of an electron beam emitted from
an electron gun individually pass through a corresponding one of a
plurality of holes in a mask, performs blanking control for
respective formed beams, reduces by an optical system beams that
were not blocked in the blanking process to reduce a mask image,
and deflects the reduced beams by a deflector to irradiate a
desired position on a target object or "sample".
[0005] In a thermal electron gun emitting electron beams, the
operating temperature of the cathode increases along with achieving
higher luminance of the cathode. The conventional cathode is
assembled by mechanically combining a plurality of parts through
which currents flow. Therefore, there exist a plurality of electric
contact portions, resulting in a problem that resistance of the
entire cathode becomes unstable. Moreover, when a plurality of
parts through which currents flow are fixed within a ceramic
serving as an insulating part, the temperature of the ceramic also
increases at the time of heating, resulting in a problem that
insulation breakdown tends to occur easily.
[0006] There is disclosed a cathode mechanism, integrated from
glassy carbon, composed of a pair of energizing terminals, a pair
of legs each extending from each of the terminals such that the
sectional area of the leg gradually becomes small, and a support
part which connects the pair of legs at the narrowest portions and
on which lanthanum hexaboride (LaB.sub.6) powder is placed (e.g.,
refer to Japanese Patent Application Laid-open (JP-A) No.
2001-084932).
BRIEF SUMMARY OF THE INVENTION
[0007] According to one aspect of the present invention, a cathode
mechanism of an electron gun includes a crystal configured to emit
a thermal electron from an end surface by being heated, a holding
part configured to hold the crystal in a state where the end
surface is exposed and at least a part of other surfaces of the
crystal is covered, a first supporting post and a second supporting
post each configured to support the holding part and extend while
maintaining an unchanged sectional size, a first base part
configured to fix the first supporting post, and a second base part
configured to fix the second supporting post, wherein the holding
part, the first supporting post, the second supporting post, the
first base part, and the second base part are formed in an
integrated structure made of a same material, and the crystal is
heated by supplying a current to the integrated structure.
[0008] According to another aspect of the present invention, an
electron gun includes the cathode mechanism of the electron gun
described above, and an anode electrode configured to be controlled
to have a potential more positive than that of a crystal and to
pull out a thermal electron emitted from the crystal.
[0009] According to yet another aspect of the present invention, an
electron beam writing apparatus includes the electron gun described
above, and a writing mechanism configured to write a pattern on a
target object using a thermal electron emitted from the electron
gun.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a sectional view showing an example of a
configuration of a cathode mechanism of an electron gun according
to a first embodiment;
[0011] FIG. 2 is a top view showing an example of a configuration
of a cathode mechanism of an electron gun according to the first
embodiment;
[0012] FIG. 3 is a perspective view for reference showing an
example of a configuration of a cathode mechanism of an electron
gun according to the first embodiment;
[0013] FIG. 4 is a diagram showing an example of a configuration of
a cathode mechanism according to a comparative example 1 of the
first embodiment 1;
[0014] FIG. 5 is a diagram showing an example of a configuration of
a cathode mechanism according to a comparative example 2 of the
first embodiment;
[0015] FIG. 6 is a diagram showing a configuration of a writing
apparatus according to the first embodiment;
[0016] FIG. 7 is a conceptual diagram showing a configuration of a
shaping aperture array substrate according to the first
embodiment;
[0017] FIG. 8 is a sectional view showing a configuration of a
blanking aperture array mechanism according to the first
embodiment;
[0018] FIG. 9 is a conceptual diagram illustrating an example of a
writing operation according to the first embodiment;
[0019] FIG. 10 is a diagram showing an example of an irradiation
region of multiple beams and a writing target pixel according to
the first embodiment; and
[0020] FIG. 11 is a diagram illustrating an example of a writing
method of multiple beams according to the first embodiment.
DETAILED DESCRIPTION OF THE INVENTION
[0021] Embodiments below describe a cathode mechanism that can heat
a crystal efficiently while providing stability of resistance of a
cathode and prevention of an insulation breakdown.
[0022] Further, Embodiments below describe a configuration using
multiple beams as an electron beam. However, it is not limited
thereto. A configuration using a single beam is also acceptable.
Further, although a writing apparatus is described below, any other
apparatus is also preferable as long as it uses electron beams
emitted from a thermal electronic emission source. For example, it
may be an image acquisition apparatus, an inspection apparatus, or
the like.
First Embodiment
[0023] FIG. 1 is a sectional view showing an example of a
configuration of a cathode mechanism of an electron gun according
to a first embodiment. FIG. 2 is a top view showing an example of a
configuration of a cathode mechanism of an electron gun according
to the first embodiment. FIG. 3 is a perspective view for reference
showing an example of a configuration of a cathode mechanism of an
electron gun according to the first embodiment. The shape of a part
of the cathode mechanism shown in FIG. 3 does not coincide with the
shape shown in FIGS. 1 and 2. A cathode mechanism 222 (negative
electrode mechanism) of the electron gun in FIGS. 1 and 2 includes
a crystal 10, a holding part 12, a pair of supporting posts 14 and
16, and a pair of base parts 18 and 19.
[0024] By being heated, the crystal 10 emits thermal electrons from
an electron emission surface 11 being an end surface. As a material
of the crystal 10, lanthanum hexaboride (LaB.sub.6) is used, for
example. Crystal orientations in the electron emission surface 11
of the crystal 10 are the same. For example, it is preferable to
have a crystal orientation of (100) or (310). The crystal 10 is
formed in the shape of at least one of a cylinder and a truncated
cone. For example, as shown in FIG. 1, it is preferable to form by
combining a cylindrical lower part and a truncated cone upper part.
Alternatively, it may be formed in a cylinder from the lower part
to the upper part. Alternatively, it may be formed in a truncated
cone or a prism from the lower part to the upper part.
[0025] The holding part 12 holds the crystal 10 in a manner such
that the electron emission surface 11 of the crystal 10 is exposed
and at least a part of the other surfaces of the crystal 10 is
covered. A hole of a predetermined depth is formed in the center of
the top surface of the cylindrical holding part 12. The size of the
hole is matched with the size of the crystal 10. The crystal 10 is
held by being inserted into the hole from the lower part. Thereby,
in the example of FIG. 1, the bottom surface and the side surface
at the lower part of the crystal 10 are covered. The holding part
12 contacts the crystal 10 at the covered surfaces to heat the
crystal 10 and applies an acceleration voltage to the crystal 10.
When the crystal 10 is a cylinder, a truncated cone, or a
combination of them, the shape of the hole of the holding part 12
may be a cylinder. When the crystal 10 is a prism, the shape of the
hole of the holding part 12 may be a prism.
[0026] The pair of supporting posts, 14 (first supporting post) and
16 (second supporting post), supports the holding part 12. Each of
the pair of supporting posts 14 and 16 extends while maintaining an
unchanged sectional size substantially. The pair of supporting
posts 14 and 16 is arranged with a space width W therebetween. The
pair of supporting posts 14 and 16 functions as a heater for
heating the crystal 10 through the holding part 12.
[0027] The pair of base parts 18 and 19 fixes the pair of
supporting posts 14 and 16. Specifically, the base part 18 fixes
the bottom end of the supporting post 14, and the base part 19
fixes the bottom end of the supporting post 16. The base part 18 is
connected to a metal electric wire 50 supported by an insulator 54,
and is supported by the electric wire 50. The base part 19 is
connected to a metal electric wire 52 supported by the insulator
54, and is supported by the electric wire 52.
[0028] The holding part 12, the pair of supporting posts 14 and 16,
and the pair of base parts 18 and 19 are formed in an integrated
structure made of the same material. As a material of the
integrated structure, one of graphite, tantalum, tungsten, and
iridium can be used. When forming the holding part 12, the pair of
supporting posts 14 and 16, and the pair of base parts 18 and 19 in
an integrated structure, first, a base material is formed in the
shape in which a cylinder is upright in the center of the tabular
base part. A width L of the base part is preferably sufficiently
larger than a diameter .phi. of the cylinder. For example, the
width L is equal to or greater than twice the diameter .phi.. In
the cases of FIGS. 2 and 3, the width L is about three times the
diameter .phi., for example. Then, the width W is notched at the
center with respect to the longitudinal direction of the base part
and at the position passing through the center axis of the
cylinder. The width W is notched such that the portion
corresponding to the holding part 12 is left, the base parts 18 and
19 are separated, and the supporting posts 14 and 16 are separated.
Thereby, a current flow can be formed in series in order of the
base part 18, the supporting post 14, the holding part 12, the
supporting post 16, and the base 19. Further, thereby, a continuous
space having the same width W is formed from the back side of the
holding part 12, between the two supporting posts 14 and 16, and
between the two base parts 18 and 19. Moreover, a hole of a
predetermined depth is formed in the center of the top surface of
the cylindrical holding part 12. The diameter size of the hole is
matched with the size of the crystal 10. The depth of the hole is
preferably equal to or less than the length of the crystal 10.
Thereby, the holding part 12, the pair of supporting posts 14 and
16, and the pair of base parts 18 and 19 can be formed in an
integrated structure.
[0029] Since the current flowing into the base part 18 of the width
L through the electric wire 50 has a large sectional area,
resistance can be suppressed small, and therefore, the amount of
heat generation can be suppressed. Then, since the supporting post
14 whose sectional area rapidly becomes small from that of the base
part 18 has a high resistance, the amount of heat generation can be
increased. For example, in the case of the shape whose sectional
area gradually becomes small, since the portion having a high
resistance is small, a large electric power is needed for obtaining
a necessary heat generation amount. On the other hand, according to
the first embodiment, since the supporting post 14 extends toward
the holding part 12 while maintaining a small sectional area, the
high resistance state can be maintained. Therefore, when obtaining
a necessary amount of heat generation, a small electric power is
sufficient for generating heat efficiently. The same applies to the
supporting post 16.
[0030] As described above, the pair of supporting posts 14 and 16
is carved out from the cylindrical portion having the diameter
.phi.. The cylindrical portion having the diameter p is carved into
halves by performing width-W notching at the center while leaving
the portion corresponding to the holding part 12. Further, as shown
in the top view of the pair of supporting posts, illustrated at the
upper right of FIG. 1, portions 2, 3, 4, and 5 at the both sides of
the halved portions are carved such that the outer sides of the
sectional surfaces of the pair of supporting posts 14 and 16, each
width being D, are circular arcs. Thereby, each of the supporting
posts 14 and 16 has a cross-sectional configuration in which three
sides are straight lines and one side is a curved line. The
sectional areas of the supporting posts 14 and 16 can be made
smaller by further carving the portions 2, 3, 4, and 5 at the both
sides of the halved portions. By making the sectional area small,
resistance is increased, and therefore, when a current flows, the
temperature can be raised efficiently.
[0031] Thus, theater can be easily fabricated by scraping off the
slit portion (W) and the portions 2, 3, 4, and 5 from the cylinder
made of graphite by a lathe operation, for example. That is, the
configuration is easily made. Further, since the cylinder is
equally formed by the lathe operation and has a little stress
because of being formed with a light load, a crack etc. seldom
occurs on the cylinder itself. Further, the resistance can be
increased since the sectional area is small, and the structure
intensity is improved more than that of a quadrangle.
[0032] FIG. 4 is a diagram showing an example of a configuration of
a cathode mechanism according to a comparative example 1 of the
first embodiment 1. In FIG. 4, in the comparative example 1, two
lead wires 350 which vertically penetrate a disc-like ceramic base
354 from the outside to be fixed are bent and extending mutually
toward inside after penetrating the ceramic base 354, for example.
Then, at the ends of the two lead wires 350, a crystal 310 is put
between tabular pyrolytic graphite (PG) portions 312. In this
configuration, there are a mechanical and electrical contact
portion between each lead wire 350 and each PG portion 312, and a
mechanical and electrical contact portion between the two PG
portions 312 and the crystal 310. In particular, the crystal 310
contacts, for junction, the tip of each tabular PG portion 312.
Therefore, there is a problem that the contact resistance at these
contact portions tends to change easily.
[0033] FIG. 5 is a diagram showing an example of a configuration of
a cathode mechanism according to a comparative example 2 of the
first embodiment. In FIG. 5, in the comparative example 2, for
example, two base pins 450 and 452 extend diagonally toward inside
from the upper surface peripheral part of a disc-like ceramic base
454, and a leaf spring 418 is connected to the end part of the base
pin 450. Similarly, a leaf spring 419 is connected to the end part
of the base pin 452. The leaf springs 418 and 419 extend, toward
the center part, in parallel to the upper surface of the ceramic
base 454, and are fixed inside a small insulating insulator block
453 disposed at the center part. In the insulator block 453, a
heater rod 414 is connected to the leaf spring 418. Similarly, in
the insulator block 453, a heater rod 416 is connected to the leaf
spring 419. The two heater rods 414 and 416 centered by the
insulator block 453 extend vertically to be connected to a holding
part 412. A crystal 410 is fittingly inserted into the upper
surface of the holding part 412. In this configuration, there are
mechanical and electrical contact portions between the edge portion
of the base pin 450 and the leaf spring 418, and between the edge
portion of the base pin 452 and the leaf spring 419. Moreover, in
the insulator block 453, there are mechanical and electrical
contact portions between the heater rod 414 and the leaf spring
418, and between the heater rod 416 and the leaf spring 419.
Therefore, there is a problem that the contact resistances at these
contact portions tend to change easily. Further, since the
temperatures of the heater rods 414 and 416 become high, the
temperature of the insulator block 453 itself also becomes high. As
a result, although the material of the insulator block 453
originally has excellent insulation, an insulation failure occurs
in the insulator block 453. Consequently, there is a problem that
insulation breakdown occurs between the heater rods 414 and 416 in
the insulator block 453, resulting in that resistance of the whole
cathode mechanism changes.
[0034] Furthermore, in the comparative example 2, there is a
problem that since contamination accumulates on the insulator block
453 and electrically connects between the heater rods 414 and 416,
insulation breakdown occurs between the heater rods 414 and 416,
resulting in that resistance of the whole cathode mechanism
changes.
[0035] On the other hand, according to the first embodiment, since
the holding part 12, the pair of supporting posts 14 and 16, and
the pair of base parts 18 and 19 are formed in an integrated
structure made of the same material, there is no mechanical and
electrical contact portion. Therefore, no contact resistance change
occurs. Further, while each end of the pair of supporting posts 14
and 16 is connected to one of the separated base parts 18 and 19,
since no insulator block exists, it is possible to prevent
contamination accumulation. Thus, no insulation breakdown occurs
between the supporting posts 14 and 16, and therefore, there is no
change of resistance of the whole cathode mechanism.
[0036] As described above, according to the first embodiment, it is
possible to provide stability of resistance of the cathode
mechanism 222, and prevention of insulation breakdown, and to heat
the crystal 10 efficiently. By stabilizing the electrical
resistance of the cathode mechanism 222, temperature change of the
crystal 10 can be prevented, thereby emitting stable thermal
electrons.
[0037] FIG. 6 is a schematic diagram showing a configuration of a
writing or "drawing" apparatus according to the first embodiment.
As shown in FIG. 6, a writing apparatus 100 includes a writing
mechanism 150 and a control system circuit 160. The writing
apparatus 100 is an example of a multiple electron beam writing
apparatus. The writing mechanism 150 includes an electron beam
column 102 (multiple electron beam column) and a writing chamber
103. In the electron beam column 102, there are disposed an
electron gun 201, an illumination lens 202, a shaping aperture
array substrate 203, a blanking aperture array mechanism 204, a
reducing lens 205, a limiting aperture substrate 206, an objective
lens 207, a deflector 208, and a deflector 209. In the writing
chamber 103, an XY stage 105 is disposed. On the XY stage 105,
there is placed a target object or "sample" 101 such as a mask
blank on which resist has been applied serving as a writing target
substrate when writing is performed. The target object 101 is, for
example, an exposure mask used when fabricating semiconductor
devices, or a semiconductor substrate (silicon wafer) for
fabricating semiconductor devices. Further, on the XY stage 105, a
mirror 210 for measuring the position of the XY stage 105 is
placed.
[0038] The electron gun 201 (electron beam emission source)
includes the above-described cathode mechanism 222. The electron
gun 201 includes a Wehnelt 224 (Wehnelt electrode) and an anode 226
(anode electrode) in addition to the cathode mechanism 222.
Further, the anode 226 is controlled to have a potential more
positive than that of the crystal 10 of the cathode mechanism 222,
and pulls out thermal electrons emitted from the crystal 10. For
example, the anode 226 is grounded.
[0039] The control system circuit 160 includes a control computer
110, a memory 112, an electron gun power supply 120, a deflection
control circuit 130, DAC (digital-analog converter) amplifier units
132 and 134, a stage position detector 139, and a storage device
140 such as a magnetic disk drive. The control computer 110, the
memory 112, the electron gun power supply 120, the deflection
control circuit 130, the DAC amplifier units 132 and 134, the stage
position detector 139, and the storage device 140 are connected to
each other through a bus (not shown). The DAC amplifier units 132
and 134 and the blanking aperture array mechanism 204 are connected
to the deflection control circuit 130. Outputs of the DAC amplifier
unit 132 are connected to the deflector 209. Outputs of the DAC
amplifier unit 134 are connected to the deflector 208. The
deflector 208 is composed of at least four electrodes (or "poles"),
and each electrode is controlled by the deflection control circuit
130 through the DAC amplifier 134. The deflector 209 is composed of
at least four electrodes (or "poles"), and each electrode is
controlled by the deflection control circuit 130 through the
corresponding DAC amplifier unit 132. The stage position detector
139 emits laser lights to the mirror 210 on the XY stage 105, and
receives a reflected light from the mirror 210. The stage position
detector 139 measures the position of the XY stage 105, based on
the principle of laser interferometry which uses information of the
reflected light.
[0040] Information input/output to/from the control computer 110
and information being operated are stored in the memory 112 each
time.
[0041] In the electron gun power supply 120, there are arranged an
acceleration voltage power circuit 236, a bias voltage power
circuit 234, a filament power supply circuit 231 (filament power
supply unit), and an ammeter 238.
[0042] The negative electrode (-) side of the acceleration voltage
power circuit 236 is connected to the electric wires 50 and 52 of
both the poles of the cathode mechanism 222 in the electron beam
column 102. The positive electrode (+) side of the acceleration
voltage power circuit 236 is grounded through the ammeter 238
connected in series. Further, the negative electrode (-) of the
acceleration voltage power circuit 236 branches to be also
connected to the positive electrode (+) of the bias voltage power
circuit 234. The negative electrode (-) of the bias voltage power
circuit 234 is electrically connected to the Wehnelt 224 disposed
between the cathode mechanism 222 and the anode 226. In other
words, the bias voltage power circuit 234 is arranged to be
electrically connected between the negative electrode (-) of the
acceleration voltage power circuit 236 and the Wehnelt 224. Then,
the filament power supply circuit 231 supplies a current between
the electric wires 50 and 52 of both the electrodes of the cathode
mechanism 222 in order to heat the crystal 10 in the cathode
mechanism 222 to a predetermined temperature. In other words, the
filament power supply circuit 231 supplies a filament power to the
cathode mechanism 222. The filament power and the cathode
temperature T (heating temperature of the crystal 10) can be
defined by a certain relation, and the cathode can be heated to a
desired temperature by the filament power. Thus, the cathode
temperature T is controlled by the filament power. The filament
power is defined by the product of a current flowing between both
the electrodes of the cathode mechanism 222 and a voltage applied
between both the electrodes of the cathode mechanism 222 by the
filament power supply circuit 231. The acceleration voltage power
circuit 236 applies an acceleration voltage between the cathode
mechanism 222 and the anode 226. The bias voltage power circuit 234
applies a negative bias voltage to the Wehnelt 224.
[0043] Writing data is input from the outside of the writing
apparatus 100, and stored in the storage device 140. The writing
data generally defines information on a plurality of figure
patterns to be written. Specifically, it defines a figure code,
coordinates, size, and the like of each figure pattern.
[0044] FIG. 6 shows a configuration necessary for describing the
first embodiment. Other configuration elements generally necessary
for the writing apparatus 100 may also be included therein.
[0045] FIG. 7 is a conceptual diagram showing a configuration of
the shaping aperture array substrate 203 according to the first
embodiment. As shown in FIG. 7, holes (openings) 22 of p rows long
(length in the y direction) and q columns wide (width in the x
direction) (p.gtoreq.2, q.gtoreq.2) are formed, like a matrix, at a
predetermined arrangement pitch in the shaping aperture array
substrate 203. In the case of FIG. 7, for example, holes 22 of
512.times.512, that is 512 (rows of holes arrayed in the y
direction).times.512 (columns of holes arrayed in the x direction),
are formed. Each of the holes 22 is rectangular, including square,
having the same dimension and shape as each other. Alternatively,
each of the holes 22 may be a circle with the same diameter as each
other. The shaping aperture array substrate 203 (beam forming
mechanism) forms multiple beams 20. Specifically, the multiple
beams 20 are formed by letting portions of an electron beam 200
individually pass through a corresponding one of a plurality of
holes 22. The method of arranging the holes 22 is not limited to
the case of FIG. 7 where the holes are arranged like a grid in the
width and length directions. For example, with respect to the
x-direction kth and (k+1)th rows which are arrayed in the length
direction (in the y direction), each hole in the kth row and each
hole in the (k+1)th row may be arranged mutually displaced in the
width direction (in the x direction) by a dimension "a". Similarly,
with respect to the x-direction (k+1)th and (k+2)th rows which are
arrayed in the length direction (in the y direction), each hole in
the (k+1)th row and each hole in the (k+2)th row may be arranged
mutually displaced in the width direction (in the x direction) by a
dimension "b".
[0046] FIG. 8 is a sectional view showing a configuration of a
blanking aperture array mechanism 204 according to the first
embodiment. With regard to the configuration of the blanking
aperture array mechanism 204, a semiconductor substrate 31 made of
silicon, etc. is placed on a support table 33 as shown in FIG. 8.
The central part of the substrate 31 is shaved, for example, from
the back side into a membrane region 330 (first region) having a
thin film thickness h. The periphery surrounding the membrane
region 330 is an outer peripheral region 332 (second region) having
a thick film thickness H. The upper surface of the membrane region
330 and the upper surface of the outer peripheral region 332 are
formed to be flush or substantially flush in height with each
other. At the back side of the outer peripheral region 332, the
substrate 31 is supported on the support table 33. The central part
of the support table 33 is open, and the membrane region 330 is
located at this opening region.
[0047] In the membrane region 330, passage holes 25 (openings)
through each of which a corresponding one of the multiple beams 20
passes are formed at positions each corresponding to each hole 22
in the shaping aperture array substrate 203 shown in FIG. 7. In
other words, in the membrane region 330 of the substrate 31, there
are formed a plurality of passage holes 25, in an array state,
through each of which a corresponding one of the multiple electron
beams 20 passes. Further, in the membrane region 330 of the
substrate 31, there are arranged a plurality of electrode pairs
each composed of two electrodes being opposite to each other with
respect to a corresponding one of the plurality of passage holes
25. Specifically, in the membrane region 330, as shown in FIG. 8,
each pair (blanker: blanking deflector) of a control electrode 24
and a counter electrode 26 for blanking deflection is arranged
close to a corresponding passage hole 25 in a manner such that the
electrodes 24 and 26 are opposite to each other across the passage
hole 25 concerned. Further, close to each passage hole 25 in the
membrane region 330, inside the substrate 31, there is arranged a
control circuit 41 (logic circuit) which applies a deflection
voltage to the control electrode 24 for the passage hole 25
concerned. The counter electrode 26 for each beam is grounded.
[0048] In the control circuit 41, there is arranged an amplifier
(an example of a switching circuit) (not shown) such as a CMOS
inverter circuit. The output line (OUT) of the amplifier is
connected to the control electrode 24. On the other hand, the
counter electrode 26 is applied with a ground electric potential.
As an input (IN) of the amplifier, either an L (low) potential
(e.g., ground potential) lower than a threshold voltage, or an H
(high) potential (e.g., 1.5 V) higher than or equal to the
threshold voltage is applied as a control signal. According to the
first embodiment, in a state where an L potential is applied to the
input (IN) of the amplifier, the output (OUT) of the amplifier
becomes a positive potential (Vdd), and then, a corresponding beam
is deflected by an electric field due to a potential difference
from the ground potential of the counter electrode 26 so as to be
blocked by the limiting aperture substrate 206, and thus it is
controlled to be in a beam OFF condition. On the other hand, in a
state (active state) where an H potential is applied to the input
(IN) of the amplifier, the output (OUT) of the amplifier becomes a
ground potential, and therefore, since there is no potential
difference from the ground potential of the counter electrode 26, a
corresponding beam is not deflected, and controlled to be in a beam
ON condition by passing through the limiting aperture substrate
206.
[0049] A pair of the control electrode 24 and the counter electrode
26 individually provides blanking deflection of a corresponding
beam of the multiple beams 20 by an electric potential switchable
by the amplifier which serves as a corresponding switching circuit.
Thus, each of a plurality of blankers performs blanking deflection
of a corresponding beam in the multiple beams having passed through
a plurality of holes 22 (openings) in the shaping aperture array
substrate 203.
[0050] Next, operations of the writing mechanism 150 of the writing
apparatus 100 will be described. The writing mechanism 150 writes a
pattern on the target object 101, using thermal electrons emitted
from the electron gun 201. Specifically, it operates as follows.
The electron beam 200 emitted from the electron gun 201 (electron
emission source) illuminates the whole of the shaping aperture
array substrate 203 by the illumination lens 202. A plurality of
rectangular (including square) holes 22 (openings) are formed in
the shaping aperture array substrate 203. The region including all
of the plurality of holes 22 is irradiated with the electron beam
200. For example, a plurality of rectangular (including square)
electron beams (multiple beams 20) are formed by letting portions
of the electron beam 200, which irradiate the positions of the
plurality of holes 22, individually pass through a corresponding
hole of the plurality of holes 22 in the shaping aperture array
substrate 203. The multiple beams 20 individually pass through
corresponding blankers (first deflector: individual blanking
mechanism) of the blanking aperture array mechanism 204. Each
blanker deflects (provides blanking deflection) an electron beam
passing therethrough individually.
[0051] The multiple beams 20 having passed through the blanking
aperture array mechanism 204 are reduced by the reducing lens 205,
and go toward the hole formed in the center of the limiting
aperture substrate 206. Then, the electron beam in the multiple
beams 20 which was deflected by the blanker of the blanking
aperture array mechanism 204 deviates (shifts) from the hole in the
center of the limiting substrate 206 and is blocked by the limiting
aperture substrate 206. On the other hand, the electron beam which
was not deflected by the blanker of the blanking aperture array
mechanism 204 passes through the hole in the center of the limiting
aperture substrate 206 as shown in FIG. 6. Blanking control is
provided by ON/OFF of the individual blanking mechanism so as to
control ON/OFF of beams. Then, for each beam, one shot beam is
formed by a beam which has been made during a period from becoming
beam ON to becoming beam OFF and has passed through the limiting
aperture substrate 206. The multiple beams 20 having passed through
the limiting aperture substrate 206 are focused by the objective
lens 207 so as to be a pattern image of a desired reduction ratio.
Then, respective beams having passed (all of the multiple beams 20
having passed) through the limiting aperture substrate 206 are
collectively deflected in the same direction by the deflectors 208
and 209 in order to irradiate respective beam irradiation positions
on the target object 101. Ideally, the multiple beams 20
irradiating at a time are aligned at pitches obtained by
multiplying the arrangement pitch of a plurality of holes 22 in the
shaping aperture array substrate 203 by a desired reduction ratio
described above.
[0052] FIG. 9 is a conceptual diagram illustrating an example of a
writing operation according to the first embodiment. As shown in
FIG. 9, a writing region 30 of the target object 101 is virtually
divided, for example, by a predetermined width in the y direction
into a plurality of stripe regions 32 in a strip form. First, the
XY stage 105 is moved to make an adjustment such that an
irradiation region 34 which can be irradiated with one shot of the
multiple beams 20 is located at the left end of the first stripe
region 32 or at a position further left than the left end, and then
writing is started. When writing the first stripe region 32, the XY
stage 105 is moved, for example, in the -x direction, so that the
writing may relatively proceed in the x direction. The XY stage 105
is moved, for example, continuously at a constant speed. After
writing the first stripe region 32, the stage position is moved in
the -y direction to make an adjustment such that the irradiation
region 34 is located at the right end of the second stripe region
32 or at a position further right than the right end to be thus
located relatively in the y direction. Then, by moving the XY stage
105 in the x direction, for example, writing proceeds in the -x
direction. That is, writing is performed while alternately changing
the direction, such as performing writing in the x direction in the
third stripe region 32, and in the -x direction in the fourth
stripe region 32, thereby reducing the writing time. However, the
writing operation is not limited to the writing while alternately
changing the direction, and it is also preferable to perform
writing in the same direction when writing each stripe region 32. A
plurality of shot patterns maximally up to as many as the number of
the holes 22 are formed at a time by one shot of multiple beams
having been formed by passing through the holes 22 in the shaping
aperture array substrate 203. Further, although FIG. 9 shows the
case where writing is performed once for each stripe region 32, it
is not limited thereto. It is also preferable to perform multiple
writing which writes the same region multiple times. In performing
the multiple writing, preferably, the stripe region 32 of each pass
is set while shifting the position.
[0053] FIG. 10 is a diagram showing an example of an irradiation
region of multiple beams and a pixel to be written (writing target
pixel) according to the first embodiment. In FIG. 10, in the stripe
region 32, there are set a plurality of control grids 27 (design
grids) arranged in a grid form at the beam size pitch of the
multiple beams 20 on the surface of the target object 101, for
example. Preferably, they are arranged at a pitch of around 10 nm.
The plurality of control grids 27 serve as design irradiation
positions of the multiple beams 20. The arrangement pitch of the
control grid 27 is not limited to the beam size, and may be any
size that can be controlled as a deflection position of the
deflector 209 regardless of the beam size. Then, a plurality of
pixels 36, each of which is centering on each control grid 27, are
set by virtually dividing into a mesh form by the same size as that
of the arrangement pitch of the control grid 27. Each pixel 36
serves as an irradiation unit region per beam of the multiple
beams. FIG. 10 shows the case where the writing region of the
target object 101 is divided, for example, in the y direction, into
a plurality of stripe regions 32 by the width size being
substantially the same as the size of the irradiation region
(writing field) which can be irradiated by one irradiation with the
multiple beams 20. The x-direction size of the irradiation region
34 can be defined by the value obtained by multiplying the beam
pitch (pitch between beams) in the x direction of the multiple
beams 20 by the number of beams in the x direction. The y-direction
size of the irradiation region 34 can be defined by the value
obtained by multiplying the beam pitch in the y direction of the
multiple beams 20 by the number of beams in the y direction. The
width of the stripe region 32 is not limited to this. Preferably,
the width of the stripe region 32 is n times (n being an integer of
one or more) the size of the irradiation region 34. FIG. 10 shows
the case where the multiple beams of 512.times.512
(rows.times.columns) are simplified to 8.times.8
(rows.times.columns). In the irradiation region 34, there are shown
a plurality of pixels 28 (beam writing positions) which can be
irradiated with one shot of the multiple beams 20. In other words,
the pitch between adjacent pixels 28 is the pitch between beams of
the design multiple beams. In the example of FIG. 10, one
sub-irradiation region 29 is a region surrounded by beam pitches.
In the case of FIG. 10, each sub-irradiation region 29 is composed
of 4.times.4 pixels.
[0054] FIG. 11 is a diagram illustrating an example of a writing
method of multiple beams according to the first embodiment. FIG. 11
shows a portion of the sub-irradiation region 29 to be written by
each of beams at the coordinates (1, 3), (2, 3), (3, 3), . . . ,
(512, 3) in the y-direction third row from the bottom in the
multiple beams for writing the stripe region 32 shown in FIG. 10.
In the example of FIG. 11, while the XY stage 105 moves the
distance of eight beam pitches, four pixels are written (exposed),
for example. In order that the relative position between the
irradiation region 34 and the target object 101 may not be shifted
by the movement of the XY stage 105 while these four pixels are
written (exposed), the irradiation region 34 is made to follow the
movement of the XY stage 105 by collective deflection of all of the
multiple beams 20 by the deflector 208. In other words, tracking
control is performed. In the case of FIG. 11, one tracking cycle is
executed by writing (exposing) four pixels while shifting, per
shot, the irradiation target pixel 36 in the y direction during a
movement by the distance of eight beam pitches.
[0055] Specifically, the writing mechanism 150 irradiates each
control grid 27 with a corresponding beam in an ON state in the
multiple beams 20 during a writing time (irradiation time or
exposure time) corresponding to each control grid 27 within a
maximum irradiation time Ttr of the irradiation time of each beam
of the multiple beams of the shot concerned. The maximum
irradiation time Ttr is set in advance. Although the time obtained
by adding a settling time of beam deflection to the maximum
irradiation time Ttr actually serves as a shot cycle, the settling
time of beam deflection is omitted here to indicate the maximum
irradiation time Ttr as the shot cycle. After one tracking cycle is
completed, the tracking control is reset so as to swing back
(return) the tracking position to the starting position of a next
tracking cycle.
[0056] Since writing of the pixels in the first column from the
right of each sub-irradiation region 29 has been completed, in the
next tracking cycle after resetting the tracking, first, the
deflector 209 performs deflection such that the writing position of
each corresponding beam is adjusted (shifted) to the control grid
27 of the pixel at the bottom row in the second column from the
right of each sub-irradiation region 29.
[0057] As described above, in the state where the relative position
of the irradiation region 34 to the target object 101 is controlled
by the deflector 208 to be the same (unchanged) position during the
same tracking cycle, each shot is carried out while performing
shifting from a control grid (a pixel 36) to another control grid
27 (another pixel 36) by the deflector 209. Then, after finishing
one tracking cycle and returning the tracking position of the
irradiation region 34, the first shot position is adjusted to the
position shifted by, for example, one control grid (one pixel) as
shown in the lower part of FIG. 10, and each shot is performed
shifting from one control grid (one pixel) to another control grid
(another pixel) by the deflector 209 while executing a next
tracking control. By repeating this operation during writing the
stripe region 32, the position of the irradiation region 34 is
shifted sequentially, such as from 34a to 34o, to perform writing
of the stripe region concerned.
[0058] Based on the writing sequence, it is determined which beam
of the multiple beams irradiates which control grid 27 (pixel 36)
on the target object 101. Supposing that the sub-irradiation region
29 is a region composed of n.times.n pixels, n control grids (n
pixels) are written by one tracking operation. Then, by the next
tracking operation, other n pixels in the same n.times.n pixel
region are similarly written by a different beam from the one used
above. Thus, writing is performed for each n pixels by a different
beam each time in n-time tracking operations, thereby writing all
of the pixels in one region of n.times.n pixels. With respect also
to other sub-irradiation regions 29 each composed of n.times.n
pixels in the irradiation region of multiple beams, the same
operation is executed at the same time so as to perform writing
similarly.
[0059] As described above, since the resistance of the cathode
mechanism 222 is stabilized, a stable electron beam 200 can be
emitted. Thus, writing can be performed with high precision.
[0060] Embodiments have been explained referring to specific
examples described above. However, the present invention is not
limited to these specific examples.
[0061] While the apparatus configuration, control method, and the
like not directly necessary for explaining the present invention
are not described, some or all of them can be appropriately
selected and used on a case-by-case basis when needed. For example,
although description of the configuration of the control unit for
controlling the writing apparatus 100 is omitted, it should be
understood that some or all of the configuration of the control
unit can be selected and used appropriately when necessary.
[0062] Further, any other cathode mechanism of electron guns,
electron gun, and electron beam writing apparatus that include
elements of the present invention and that can be appropriately
modified by those skilled in the art are included within the scope
of the present invention.
[0063] Additional advantages and modification will readily occur to
those skilled in the art. Therefore, the invention in its broader
aspects is not limited to the specific details and representative
embodiments shown and described herein. Accordingly, various
modifications may be made without departing from the spirit or
scope of the general inventive concept as defined by the appended
claims and their equivalents.
* * * * *