U.S. patent number RE33,193 [Application Number 07/022,059] was granted by the patent office on 1990-04-03 for ion beam processing apparatus and method of correcting mask defects.
This patent grant is currently assigned to Hitachi, Ltd.. Invention is credited to Mikio Hongo, Tateoki Miyauchi, Akira Shimase, Hiroshi Yamaguchi.
United States Patent |
RE33,193 |
Yamaguchi , et al. |
April 3, 1990 |
Ion beam processing apparatus and method of correcting mask
defects
Abstract
Disclosed is an ion beam processing apparatus comprising within
a vacuum container a specimen chamber with a table for mounting a
specimen provided therein, a high intensity ion source, such as a
liquid metal ion source or an electric field ionizing ion source
which operates in ultra-low temperature, confronting the specimen
chamber, an extraction electrode for extracting an ion beam out of
the ion source, a charged-particle optical system for focusing the
ion beam to a spot, and an aperture for adjusting the spot
diameter.
Inventors: |
Yamaguchi; Hiroshi (Fujisawa,
JP), Miyauchi; Tateoki (Yokohama, JP),
Shimase; Akira (Yokohama, JP), Hongo; Mikio
(Yokohama, JP) |
Assignee: |
Hitachi, Ltd. (Tokyo,
JP)
|
Family
ID: |
26482323 |
Appl.
No.: |
07/022,059 |
Filed: |
March 5, 1987 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
427584 |
Sep 29, 1982 |
04503329 |
Mar 5, 1985 |
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Current U.S.
Class: |
250/309;
250/492.2 |
Current CPC
Class: |
G03F
1/74 (20130101); H01J 37/3007 (20130101); H01J
37/3053 (20130101) |
Current International
Class: |
G03F
1/00 (20060101); H01J 37/30 (20060101); H01J
37/305 (20060101); G01N 023/00 () |
Field of
Search: |
;250/309,492.21,358,492.2 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
"A High-Intensity Scanning Ion Probe with Submicrometer Spot Size",
Seliger et al., Appl. Phy. Lett., 34 (5), Mar. 1979, pp.
310-312..
|
Primary Examiner: Anderson; Bruce C.
Attorney, Agent or Firm: Antonelli, Terry & Wands
Claims
We claim:
1. An ion beam processing apparatus provided within a vacuum
container with a specimen chamber with a table for mounting a work
piece or specimen provided therein comprising: a high .[.density.].
.Iadd.intensity .Iaddend.ion source confronting said specimen
chamber, an extraction electrode for extracting an ion beam out of
said ion source, a grid electrode for controlling energy and
stability of the ion beam, a first aperture controlling the focused
spot diameter and the spot current, at least a set of electrostatic
lenses for focusing the ion beam which is outputted through said
first aperture to form a spot, X-axis and Y-axis deflection
electrodes which cause the beam spot to scan over the specimen, a
secondary charged-particle detector which detects the intensity of
secondary charged-particles emitted from the specimen as it is
exposed to a low-power ion beam and transduces the intensity of
emission into an electrical signal, a TV monitor which receives the
output of said detector and deflection signals applied to said
deflection electrodes and performs the scanning of a spot having an
intensity in proportion to the output of said secondary
charged-particle detector in synchronization with the ion beam
which scans the specimen so as to follow the observation of the
surface of the specimen, setting means for setting the range of
processing to said TV monitor, a second aperture for interrupting a
projection of the ion beam to the specimen and provided between at
least a portion of said set of electrostatic lenses and said
deflection electrodes, a beam blanking electrode disposed above
said second aperture, said beam blanking electrode being operated
by a signal produced by said setting means in correspondence to the
deflection signal for deflecting the ion beam out of said second
aperture, and switching means for switching the power supplies for
detecting a .[.deflect.]. .Iadd.defect .Iaddend.on the specimen by
said detector and for processing said defect on said specimen by
sputtering.
2. An ion beam processing apparatus according to claim 1, wherein
said first aperture is an aperture of variable dimensions between
said ion source and said lenses, said lenses focusing an image of
said first aperture produced by the ion beam on the surface of the
specimen.
3. An ion beam processing apparatus according to claim 1, further
comprising electron shower means for electrically neutralizing the
ion beam and provided between said deflection electrodes and the
specimen.
4. An ion beam processing apparatus according to claim 1,
comprising a conductive prober which comes into contact with a
conductive pattern formed on the specimen so that charges generated
during processing are removed by said prober.
5. An ion beam processing apparatus provided within a vacuum
container with a specimen chamber with a table for mounting a work
piece or specimen provided therein comprising: a high intensity ion
source confronting said specimen chamber, an extraction electrode
for extracting an ion beam out of said ion source, a grid electrode
for controlling energy and stability of the ion beam, an aperture
member with an aperture of variable dimensions for controlling the
focused spot diameter and the spot current, at least a set of
electrostatic lenses for focusing the ion beam which is outputted
through said aperture to form a spot in the image of said aperture
on the surface of the specimen, a beam blanking electrode, X-axis
and Y-axis deflection electrodes which cause the beam spot to scan
over the specimen, a secondary charged-particle detector which
detects the intensity of secondary charged-particles emitted from
the specimen as it is exposed to a low-power ion beam transduces
the intensity of emission into an electrical signal, a TV monitor
which receives the output of said detector and deflection signals
applied to said deflection electrodes and performs the scanning of
a spot having an intensity in proportion to the output of said
secondary charged-particle detector in synchronization with the ion
beam which scans the specimen so as to allow the observation of the
surface of the specimen, a setting means for setting the range of
processing to said TV monitor, and setting means producing signals
for setting the dimensions and position of said aperture, and
switching means for switching the power supplies for detecting a
defect on the specimen by said detector and for processing said
defect on the specimen by sputtering.
6. An ion beam processing apparatus comprising:
a vacuum container installed on a bed,
a table for mounting a specimen disposed on the bed within a
specimen chamber of said vacuum container,
a drive controller means for controlling the movement of said
table,
a high intensity ion source provided within said vacuum
container,
an ion beam extraction electrode for extracting an ion beam out of
said ion source,
a grid electrode for controlling energy and stability of the ion
beam,
an aperture for controlling the focused spot diameter and the spot
current.
electrostatic lenses for focusing the ion beam which is outputted
through said aperture to form a spot,
a beam blanking electrode,
X-axis and Y-axis deflection electrodes which cause the beam spot
to scan over the specimen,
a secondary charged-particle detector for detecting the intensity
of secondary charged-particles emitted from the specimen as it is
exposed to a low-power ion beam and transduces the intensity of
emission into an electrical signal,
a defect detecting means for detecting a defect by comparing the
output binary signal of said secondary charged-particle detector
with binary signal information on the original pattern read out of
a memory means, and
a switching means for switching the power supplies for detecting a
defect on the specimen and for correcting said defect on the
specimen by sputtering.
7. An ion beam processing apparatus according to claim 1, wherein
said second aperture is rectangular.
8. An ion beam processing apparatus according to claim 1, further
comprising electron shower means for electrically neutralizing the
ion beam on the specimen.
9. An ion beam processing apparatus according to claim 5, wherein
said aperture member with an aperture of variable dimensions for
controlling the focus spot diameter and the spot current includes a
first aperture, a second aperture being provided between at least a
portion of said set of electrostatic lenses and said deflection
electrodes for interrupting a projection of the ion beam to the
specimen, said beam blanking electrode being located above said
second aperture for deflecting the ion beam out of said second
aperture.
10. An ion beam processing apparatus according to claim 9, wherein
at least a portion of said electrostatic lenses are disposed
between said second aperture and said ion source for transforming
the ion beam from said ion source into a parallel beam or for
focusing the ion beam to have a beam diameter on the plane of said
second aperture slightly larger than the dimensions of said second
aperture.
11. An ion beam processing apparatus according to claim 9, further
comprising a conductive prober for contacting a conductive pattern
formed on the specimen so that charges generated during the
processing are removed by said prober.
12. A method of correcting defects on a mask comprising the steps
of: extracting an ion beam out of a high intensity ion source;
controlling energy and stability of the extracted ion beam by a
grid electrode;
focusing the ion beam into a fine spot by an optical system for
charged-particles;
detecting the intensity of secondary charge particles emitted from
the mask as it is exposed to a low-power ion beam and transduced
into an electrical signal by a secondary charged-particle
detector;
detecting a defect on the mask by comparing the output binary
signal of the secondary charged-particle detector with binary
signal information on the original pattern read out of a memory
means;
electrically neutralizing an electric charge charged on the mask by
an electron shower;
switching the power supplies for detecting a defect on the mask and
for removing the defect on the mask by sputtering; and
removing an existing defect on the mask by projecting and
sputtering the ion beam to the existing defect. .Iadd.
13. An ion beam processing apparatus provided within a vacuum
container with a speciimen chamber with a table for mounting a work
piece or specimen provided therein comprising:
a high intensity ion source confronting said specimen chamber,
an extraction electrode for extracting an ion beam out of said ion
source,
a first aperture controlling the focused spot diameter and the spot
current,
at least a set of electrostatic lenses for focusing the ion beam
which is outputted through said first aperture to form a spot,
X-axis and Y-axis deflection electrodes which cause the beam spot
to scan over the specimen,
a secondary charged-particle detector which detects the intensity
of secondary charged-particles emitted from the specimen as it is
exposed to the ion beam and transduces the intensity of emission
into an electrical signal,
display means for receiving the output of said secondary
charged-particle detector and deflection signals applied to said
deflection electrodes for performing the scanning of a spot having
an intensity proportional to the output of said secondary
charged-particle detector in synchronization with the ion beam
which scans the specimen so as to enable the observation of the
surface of the specimen including a portion to be corrected,
setting means for setting a range of processing to said display
means,
a second aperture for interrupting a projection of the ion beam to
the specimen and provided between at least a portion of said set of
electrostatic lenses and said deflection electrodes,
a beam blanking electrode disposed above said second aperture, said
beam blanking electrode being operated by a signal produced by said
setting means in correspondence to the deflection signal for
deflecting the ion beam out of said second aperture, and
means for controlling a power supply for detecting the specimen by
said secondary charged-particle detector and for processing a
portion of the range set by said setting means to remove the
portion to be corrected and obtain a corrected specimen..Iaddend.
.Iadd.
14. An ion beam processing apparatus according to claim 13, further
comprising means for controlling current of the ion beam..Iaddend.
.Iadd.15. An ion beam processing apparatus according to claim 14,
wherein said current controlling means comprises a control
electrode..Iaddend. .Iadd.16. An ion beam processing apparatus
according to claim 13, wherein said first aperture is an aperture
of variable dimensions between said ion source and said lenses,
said lenses focusing an image of said first aperture produced by
the ion beam on the surface of the specimen..Iaddend.
7. An ion beam processing apparatus according to claim 13, further
comprising electron shower means for electrically neutralizing the
ion beam and provided between said deflection electrodes and the
specimen.
An ion beam processing apparatus according to claim 13, comprising
a conductive prober which comes into contact with a conductive
pattern formed on the specimen so that charges generated during
processing are
removed by said prober. 19. An ion beam processing apparatus
according to claim 13, wherein said controlling means enables
processing for removing a
portion of the specimen by sputtering. .Iadd.20. An ion beam
processing apparatus according to claim 13 wherein the specimen is
a mask and the portion to be corrected is a defect
thereof..Iaddend. .Iadd.21. An ion beam processing apparatus
according to claim 13, wherein the specimen is a substrate having a
fine circuit pattern thereon and the portion to be corrected is a
portion of the fine circuit pattern..Iaddend. .Iadd.22. An ion beam
processing apparatus according to claim 13, wherein said display
means displays a SIM image for enabling observation of a wide
scanning area of the specimen, and said setting means sets a narrow
scanning range
for enabling removal of the portion to be corrected..Iaddend.
.Iadd.23. An ion beam processing apparatus provided within a vacuum
container with a specimen chamber with a table for mounting a
workpiece or specimen provided therein comprising:
a high intensity ion source confronting said specimen chamber;
an extraction electrode for extracting an ion beam out of said ion
sources;
a first aperture controlling the focused spot diameter and the spot
current;
at least a set of electrostatic lenses for focusing the ion beam
which is outputted through said first aperture to form a spot;
X-axis and Y-axis deflection means which cause the beam spot to
scan over the specimen;
a secondary charged-particle detector which detects secondary
charged-particles emitted from the specimen and provides an
electrical signal indicative thereof;
display means for displaying an SIM image so as to enable
observation of a wide scanning of the substrate including a portion
to be corrected;
setting means for setting a narrow scanning area for enabling
removal of the portion to be corrected to said display means;
a second aperture for interrupting a projection of the ion beam to
the specimen and provided between at least a portion of said set of
electrostatic lenses and said deflection means;
a beam blanking electrode disposed above said second aperture, said
beam blanking electrode being operated by a signal produced by said
setting in correspondence with a deflection signal for deflecting
the ion beam out of said second aperture; and
means for controlling ion beam being irradiated to the specimen in
accordance with observation of the wide scanning area and with
removal of the portion to be corrected in the narrow scanning area
and for controlling said beam blanking electrode and said
deflection means so that the portion to be corrected is removed by
irradiating the scanning ion beam in the narrow scanning area set
by said setting means..Iaddend. .Iadd.24. An ion beam processing
apparatus according to claim 25, wherein said specimen having a
portion to be corrected comprises a substrate having a fine circuit
pattern..Iaddend. .Iadd.25. An ion beam processing apparatus
according to claim 23, wherein said specimen having a portion to be
corrected is a mask with a defect..Iaddend. .Iadd.26. An ion beam
processing apparatus provided with a vacuum container with a
specimen chamber with a table for mounting a workpiece or specimen
provided therein, comprising:
a high intensity ion source confronting said specimen chamber;
an extraction electrode for extracting an ion beam out of said ion
source;
a first aperture controlling the focused spot diameter and a spot
current;
at least a set of electrostatic lenses for focusing the ion beam
which is outputted through said first aperture to form a spot;
X-axis and Y-axis deflection means which cause the beam spot to
scan over the specimen;
a secondary charged-particle detector which detects secondary
charged-particles emitted from the specimen and provides an
electrical signal indicative thereof;
display means for receiving the output of said secondary
charged-particle detector and deflection signals applied to said
deflection means for performing the scanning of a spot having an
intensity proportional to the output of said secondary
charged-particle detector in synchronization with the ion beam
which scans the specimen so as to enable observation of a wide
scanning area of the specimen including a portion to be
corrected;
setting means for setting a narrow scanning area for enabling
removal of the portion to be corrected to said display means;
a second aperture for interrupting a projection of the ion beam to
the specimen and provided between at least a portion of said set of
electrostatic lenses and said deflection means;
a beam blanking electrode disposed above said second aperture, said
beam blanking electrode being operated by a signal produced by said
setting means in correspondence to the deflection signal for
deflecting the ion beam out of said second aperture;
and means for controlling the ion beam being irradiated to the
specimen for observing the wide scanning area by the display means
and for removing the
portion to be corrected set by said setting means..Iaddend.
.Iadd.27. An ion beam processing apparatus according to claim 26,
wherein the specimen comprises a substrate having a fine circuit
pattern and the portion to be corrected is a part of the circuit
pattern..Iaddend. .Iadd.28. An ion beam processing apparatus
according to claim 29, wherein said current controlling means
comprises a control electrode..Iaddend. .Iadd.29. An ion beam
processing apparatus according to claim 27, wherein said first
aperture is an aperture of variable dimensions between said ion
source and said lenses, said lenses focusing an image of said first
aperture produced
by the ion beam on the surface of the specimen..Iaddend. .Iadd.30.
An ion beam processing apparatus according to claim 27, further
comprising electron shower means for electrically neutralizing the
ion beam and provided between said deflection electrodes and the
specimen..Iaddend. .Iadd.31. An ion beam processing apparatus
according to claim 27, comprising a conductive prober which comes
into contact with a conductive pattern formed on the specimen so
that charges generated during processing are removed by said
prober..Iaddend. .Iadd.32. An ion beam processing apparatus
according to claim 27, wherein said controlling means enables
processing for removing a portion of the specimen by
sputtering..Iaddend. .Iadd.33. An ion beam processing apparatus
according to claim 28, wherein said current controlling means
comprises a control electrode..Iaddend. .Iadd.34. An ion beam
processing apparatus according to claim 26, wherein the specimen is
a mask and the portion to be corrected is a defect of the
mask..Iaddend. .Iadd.35. A method for processing a predetermined
range of a workpiece or specimen provided in a specimen chamber of
a vacuum container, comprising the step of:
extracting an ion beam out of a high intensity ion source by an
extraction electrode;
focusing the ion beam into a fine spot by an optical system for
charged-particles including a first aperture and electrostatic
lenses for focusing the ion beam which is passed through the first
aperture;
deflecting the ion beam spot for scanning over the specimen in
X-axis and Y-axis directions by X-axis and Y-axis deflection
electrodes;
detecting by a secondary charged-particle detector secondary
charged particles emitted from the specimen and providing an
electrical signal indicative thereof;
displaying on a display means an image so that a spot having an
intensity proportional to the output of the secondary
charged-particle detector is scanned on the display means in
synchronization with the ion beam which scans the specimen in
accordance with deflection signals applied to the deflection
electrodes and enabling observation of a wide scanning area of the
specimen including a portion to be corrected;
setting a narrow scanning area for enabling removal of the portion
to be corrected to the display means by a setting means;
providing a second aperture between at least part of the
electrostatic lenses and the deflection electrodes for interrupting
a projection of the ion beam to the specimen;
providing a beam blanking electrode above the second aperture and
blanking the ion beam by deflecting the ion beam out of the second
aperture in accordance with a signal produced by the setting
means;
controlling a power supply for detecting a specimen by the
secondary charged-particle detector and for removing the portion to
be corrected in accordance with the narrow scanning area set by the
setting means; and
removing the portion of the specimen to be corrected so as to
obtain a
corrected specimen..Iaddend. .Iadd.36. A method according to claim
35, wherein the specimen is a mask, and the portion to be corrected
is a defect of the mask removed by sputtering..Iaddend. .Iadd.37. A
method according to claim 35, wherein the specimen comprises a
substrate having a fine circuit pattern, and the portion to be
corrected is a part of the circuit pattern..Iaddend.
Description
The present invention relates to an ion beam processing apparatus
which performs superfine machining on the mask of a semiconductor
integrated circuit.
It has conventionally been difficult to perform micromachining for
a work piece by projecting a high energy ion beam to a small area
of the work piece. Recently, semiconductor integrated circuits
(ICs) have advanced significantly in miniaturization and packing.
The dimension of wiring patterns is changing from 3 .mu.m to 2
.mu.m, and it is expected that wiring patterns having a width of
1-1.5 .mu.m will come out few years later. This will requires
advanced technology for correcting defects created on the mask.
However, reduction in the spot diameter of the laser beam is
limited to above 0.5 .mu.m due to the diffraction limit. This is
the limit of focusing by the laser, and it means that more fine
patterns cannot be handled by mask correcting technology by the
laser. Therefore, for integrated circuits having wiring patterns
1-1.5 .mu.m or less, mask defects of 0.3-0.5 .mu.m or more are
determined as being defective, and the minimum unit of correction
smaller than that value is required. However, due to the focusing
limit as mentioned above, the conventional laser processing
technologies cannot meet the requirement.
The above explanation is for the correction of a photomask used for
the exposure to visible rays and ultraviolet rays. As the
miniaturization of wiring patterns further advances, satisfactory
micromachining cannot be achieved by photoetching technology using
a light beam having problems of diffraction and scattering, and
exposure by use of X-rays with less diffraction and scattering or
parallel ion beam is considered.
FIGS. 1A through 1E show an example of fabricating a mask for the
X-rays exposure. First, as shown in FIG. 1A, a parylene film 24
with a thickness of a few .mu.m is formed on a silicon substrate 23
having a thickness of about 100 .mu.m and a thin film of chrome 25
having a thickness of 100 .ANG. is formed on the parylene film 24.
Then a thin film of gold 26 having a thickness of 1000 .ANG. is
formed as an X-rays absorber on the chrome film 25, and further a
PMMA resist 27 having a thickness of about 1000 .ANG. is coated on
the gold film 26. An electron beam exposing apparatus is used to
project circuit patterns on the PMMA resist 27. After the substrate
has been treated under the development process, grooves 28 and 29
as shown in FIG. 1B are formed in the PMMA resist 27. Using the
grooves 28 and 29 in the PMMA resist 27, patterns of chrome 30
having a thickness of about 1000 .ANG. are formed as shown in FIG.
1C. In more detail, in the state shown in FIG. 1B, chrome is
deposited from the top surface for a thickness of about 1000 .ANG.,
and the PMMA resist 27 is removed by an etchant. Then chrome coated
on the PMMA resist 27 is removed together with the PMMA resist 27,
and the chrome resist patterns 30 are produced. Thereafter, ion
beam etching is performed so as to remove the thin gold film 26 in
portions where the thin chrome resist 30 is absent, and the
structure shown in FIG. 1D is formed. Finally, the silicon
substrate 23 is etched deeply from the bottom, leaving only
portions necessary for the support. Then, as shown in FIG. 1E, an
X-rays resist made up of the thin gold film 26 of about 1000 .ANG.
for absorbing X-rays only in the necessary portions and the thin
chrome resist film 30 of about 1000 .ANG. which does not absorb
X-rays, and parylene film 24 in the remaining portions are produced
on supporting sections 23'.
Next, an example of the mask for collimated ion beam exposure will
be described with reference to FIG. 2. This mask is made up of a
supporting film 31, an ion absorber 32 and a spacer 33. The
supporting film is formed of a material which makes the scattering
of the transmitted ion beam as small as possible. For example, this
is a monocrystalline silicon film having a vertical crystal axis,
utilizing the fact that if the incident direction of the ion beam
coincides with the crystal axis of the silicon supporting film,
most of the incident ion beam is transmitted by channeling,
resulting in less scattering of ions. In another example, a
supporting film of a very thin and hard material is used. For
example, an ion beam is transmitted by the thin film of Al.sub.2
O.sub.3 having a thickness of several hundreds to several thousands
.ANG. extended in a mold of pyrex. Under the supporting film 31, a
thin film of gold, for example, is formed as an ion absorber 32,
and patterns are formed on it. The method of formation is similar
to that of the X-rays mask, including electron beam exposure to the
resist such as PMMA and etching following the exposure.
In the foregoing, the X-rays exposure mask and the collimated ion
beam exposure mask have been described. In fabricating these masks,
the processes of exposure and development for the resist such as
PMMA are required, and the occurrence of defects caused by foreign
matters during the processes cannot be avoided.
X-rays exposure and ion beam exposure are expected to be applied to
the fabrication of patterns of 1 .mu.m or less, however, defects
still exist in the mask used in these exposures, and a correction
accuracy of 0.2 .mu.m or less is required. It is obvious from the
foregoing that correction by the laser machining method cannot be
applied to these processors. As an example of the prior art, see R.
L. Seliger et al "A high-intensity scanning ion probe with
submicrometer spot size" Appl. Phys. Lett. 34 (5); Mar. 1, 1979,
pp. 310-312.
It is an object of the present invention to overcome the foregoing
prior art drawbacks and provide an ion beam processing apparatus
which is capable of correcting superfine defects occurring in the
photomask, X-rays exposure mask and ion beam exposure mask used in
fabricating integrated circuits with wiring patterns of 1-1.5 .mu.m
or smaller than 1 .mu.m, with a sufficient accuracy and practical
productivity.
The ion beam processing apparatus according to the present
invention has the following features. There is formed a specimen
chamber within a vacuum container, with a tray for mounting a mask
provided within the specimen chamber, and a high-intensity ion
source such as a liquid metal ion source or an electric
field-ionizing ion source which operates in ultra-low temperature
is provided within the vacuum container so that it confronts the
specimen chamber. The arrangement includes an electrode for
extracting an ion beam out of the ion source, electrostatic lenses
for focusing the ion beam into a spot, an aperture for the ion
beam, a blanking electrode for deflecting the ion beam out of the
aperture, deflection electrodes for making the ion beam spot to
scan the work piece in a specified pattern, power supplies for the
above-mentioned electrodes and electrostatic lenses, a secondary
charged-particle detector which detects secondary charged-particles
emitted on the work piece as it is exposed to the ion beam and
provides a signal representing the amount of secondary
charged-particles, and a monitor display for displaying a luminance
signal from the secondary charged-particle detector. The machining
position on the work piece displayed on the monitor is set by
electronic lines or the like, and the blanking electrode is
operated or a rectangular opening of the aperture is adjusted so as
to project and sputter the ion beam to the machining position.
The ion beam processing apparatus according to the present
invention has also such a feature that the ion beam projecting over
the work piece is neutralized electrically to prevent the position,
size and shape of the ion beam spot from being disturbed by
electric charge of the correcting specimens.
The present invention also relates to a method of correcting
defects on the mask, wherein an ion beam is extracted out of a
high-intensity ion source such as a liquid metal ion source or an
electric field ionizing ion source which operates in the ultra-low
temperature, the ion beam is focused into a fine spot by the
optical system for charged-particles, and the ion beam spot is
projected and sputtered to a back spot defect on the mask so that
it is removed.
FIGS. 1A through 1E are illustrations showing, as an example, the
fabricating process of an X-rays mask;
FIG. 2 is a longitudinal cross-sectional view showing an example of
the ion beam exposure mask;
FIG. 3 is a block diagram showing an embodiment of the apparatus
for carrying out the method of correcting a mask defect according
to the present invention;
FIG. 4 is an enlarged perspective view showing an embodiment of the
liquid metal ion source used in the apparatus shown in FIG. 3;
FIG. 5 is an enlarged cross-sectional view showing an embodiment of
means for preventing the spot disturbance caused by charges of the
ion beam;
FIGS. 6A through 6D are illustrations showing the specific forms of
the present invention performed by use of the apparatus shown in
FIG. 3;
FIG. 7 is an enlarged cross-sectional view of another example of
the ion source of the ultra-low temperature electric field
ionization type;
FIGS. 8A through 8D are illustrations of various embodiments where
the lens of the charged-particle optical system and the aperture
for focusing the ion beam on the work piece are combined in various
ways;
FIGS. 9A and 9B are enlarged longitudinal and side views of the
aperture having variable opening dimensions;
FIGS. 10A through 10C and FIGS. 11A through 11C are illustrations
showing the defect correcting processes performed by use of the
aperture having variable opening dimensions;
FIG. 12 is a block diagram of the device for displaying the
positional and dimensional adjustments between the black spot
defect and the opening of the aperture having the variable opening
dimensions;
FIG. 13 is a cross-sectional view of a means for preventing the
spot disturbance caused by charges of the ion beam, in contrast to
that shown in FIG. 5;
FIGS. 14A and 14B are front view and plan view showing still
another example of the spot disturbance preventing means
respectively;
FIG. 15 is a longitudinal cross-sectional view of still another
example of the spot disturbance preventing means; and
FIG. 16 is a diagram of saw tooth waves supplied to the deflection
electrode power supply.
FIG. 3 shows an embodiment of the mask defect modification
apparatus according to the present invention. The arrangement of
FIG. 3 includes a bed 37, a column 39 and a specimen chamber 40,
both constituting a vacuum container, a specimen exchanging chamber
41 provided adjacent to the specimen chamber 40, a pumping system,
a mask table 55 for mounting a specimen, a liquid-metal ion source
65, a control (bias) generating electrode 66, an ion beam
extracting electrode 67, an aperture (circular opening) 69,
electrostatic lenses 70, 71 and 72, a blanking electrode 73, an
aperture (rectangular opening) with micrometer 74, a pair of
deflection electrodes 75 and 76, a filament power supply 77, a
control electrode power supply 78, an extracting electrode power
supply 79, electrostatic lens power supplies 80 and 81, a high
voltage power supply 82, a blanking electrode power supply 83, a
deflection electrode power supply 84, a power supply controller 85,
a secondary charged-particle detect 86 inserted in the specimen
chamber 40, a scanning ion microscope (SIM) observation unit 87,
and a means 89 for preventing the spot disturbance causes by
charges of the ion beam.
The bed 37 is proof against dusts by provision of air support 38.
The specimen chamber 40 and specimen exchange chamber 41 are
located over the bed 37, and the mirror tube 39 is located over the
specimen chamber 40. The specimen chamber 40 is separated from the
column 39 and the specimen exchange chamber 41 by gate valves 42
and 43, respectively.
The pumping system is arranged including an oil rotary pump 47, an
oil trap 48, an ion pump 49, a turbo molecular pump 50, and valves
51, 52, 53 and 54. The pumping system is connected to the column
39, the specimen chamber 40 and the specimen exchange chamber 41
through pipes 44, 45 and 46, respectively, so that the mirror tube
39, specimen chamber 40 and specimen exchange chamber 41 are
evacuated to the extent of 10.sup.-5 torr or less.
The table 55 is provided with feed micrometers 56, 57 and 58 for
the X, Y and Z directions through rotary feedthroughs 61, 62 and
63, respectively, and further provided with a travelling ring 59
for the .theta. direction, so that the table 55 can be moved finely
in the X, Y and Z directions and around the vertical axis.
On the table 55, there is disposed a specimen tray 60 on which a
specimen mask is placed. The specimen tray 60 can be moved between
the specimen chamber 40 and the specimen exchange chamber 41 by a
specimen drawing (taking) bar 64. When the specimen is replaced,
the gate valve 43 is opened, the specimen tray 60 is taken out into
the specimen chamber 40, the gate valve 43 is closed, the door of
the specimen exchange chamber 41 is opened, the specimens are
changed, the door is closed, the specimen exchange chamber 41 is
evacuated preliminarily, the gate valve 43 is opened, and then the
specimen tray 60 is placed within the specimen chamber 40. In FIG.
3, the specimen is shown by a reference numeral 90.
The liquid metal ion source 65 is located at the top of the column
39 so that it confronts the specimen chamber 40. The liquid metal
ion source 65 shown in FIG. 4 includes an insulating base 650,
filaments 651 and 652 assembled in V-shape on the base 650, an
acute needle 653 made of tungsten or the like and spot-welded
between the tips of the filaments 651 and 652, and a metal piece
654 attached on the needle 653 so as to serve as an ion source. For
the ion source metal 654, Ga, In, Au, Bi, Sn, or Cu is used. The
filaments 651 and 652 are connected through terminals 651' and 652'
to the filament power supply 77 which is connected to the high
voltage power supply 82.
The control electrode 66 is located below the liquid metal ion
source 65 and connected electrically to the control electrode power
supply 78 which is connected to the high voltage power supply 82. A
low positive or negative voltage is applied to the control
electrode 66 so as to control the ion beam current.
The ion beam extraction electrode 67 is located below the control
electrode 66 and connected electrically to the extraction electrode
power supply 79 which is connected to the high voltage power supply
82. With a current supplied to the filaments 651 and 652 of the
liquid metal ion source 65 so as to melt the metal in the vacuum of
10.sup.-5 torr or less, and with a negative voltage of several kV
to several deca-kV applied to the extraction electrode 67, an ion
beam is drawn out of a very narrow area at the tip of the needle
653 in the liquid metal ion source 65. In FIG. 3, the ion beam is
shown by a reference numeral 68 and its spot is shown by 68'.
The circular aperture 69 is located below the extraction electrode
67, and serves to pass only the central portion of the ion beam
which has been extracted by the extraction electrode 67.
The electrostatic lenses 70, 71 and 72 are aligned below the
aperture 69 and connected electrically to the lens power supplies
80 and 81 which are connected to the high voltage power supply 82.
These lenses 70, 71 and 72 serve to focus the ion beam which is fed
through the aperture 69.
The blanking electrode 73 is located below the electrostatic lens
72 and connected electrically to the blanking electrode power
supply 83 which is connected to the controller 85. The blanking
electrode 73 swings the ion beam very quickly so as to deflect the
beam out of the rectangular aperture 74 located below the blanking
electrode 73, so that projection of the ion beam to the specimen is
interrupted quickly.
The pair of deflection electrodes 75 and 76 are located below the
aperture 74 and connected electrically to the deflection electrode
power supply 84 which is connected to the controller 85. The
deflection electrodes 75 and 76 deflect the ion beam spot, which
has been focused by the electrostatic lenses 70, 71 and 72, in the
X and Y directions so that the beam spot is positioned to a black
spot defect on the specimen.
The high voltage power supply 82 supplied a high voltage of several
deca-kV to the filament power supply 77 for the liquid metal ion
source 65, the control electrode power supply 78, the ion beam
extraction electrode power supply 79, and the lens power supplies
80 and 81.
The controller 85 operates on the blanking electrode power supply
83 and the deflection electrode power supply 84 to operate the
blanking electrode 73 and the deflection electrodes 75 and 76 in
accordance with the specified scanning pattern.
The secondary charged-particle detector 86 is located within the
specimen chamber 40 so that it confronts the specimen. The detector
86 catches secondary electrons or secondary ions emitted from the
specimen as it is exposed to the ion beam, tranduces the intensity
of emission into a signal of electric current, and sends the signal
to the SIM observation unit 87.
The SIM observation unit 87 receives from the deflection electrode
power supply 84 signals representing the ion beam deflection in the
X and Y directions and performs the scanning of its cathode ray
tube (CRT) 88 in synchronization with the signals, and at the same
time, varies the intensity of the CRT spot in accordance with the
secondary emission signal provided by the secondary
charged-particle detector 86, whereby the image of the specimen
representing the amount of secondary electron emission at each
point of the specimen is displayed. Owing to the function of the
SIM (scanning ion microscope), the specimen surface can be observed
on magnified scale.
The inspection system for the specimen 90 has a memory 113, a
comparison circuit 114 and a magnetic disk 110. The memory 113
records a binary image signal produced by the SIM observation unit
87 based on signals detected from the secondary charged-particle
detector 86. The magnetic disk 110 stored original pattern
information supplied through a magnetic tape 111. The comparison
circuit 114 retrieves in the memory 113 the image data of the
specimen 90 at the position specified by the positional information
of the image supplied from the controller 115 and compares it with
the original pattern data retrieved on the magnetic disk 110, then
determines to be defective with both patterns do not coincide with
each other.
The inspection system for the specimen 90 is connected with control
system 112, which in turn is connected to the high voltage power
supply 82, the controller .[.84.]..Iadd.85.Iaddend., and the lens
power supplies 80 and 81. The control system 112 is arranged such
that it switches the power supplies connected to the high voltage
power supply 82 and the controller 85 to provide a small current
and low acceleration voltage for producing an ion beam for a wide
scanning area when the specimen 90 is observed or inspected for
defects, and to provide a large current and high acceleration
voltage for producing an ion beam for a narrow scanning area when
the detected defect is removed or corrected.
In FIG. 3, reference numerals 116 and 117 denote linear encoders.
There is disposed between the deflection electrode 76 and the
specimen 90 a means 89 for preventing the spot disturbance caused
by charges of the ion beam. The means 89 for preventing the spot
disturbance as shown in FIG. 5 includes a pair of electron shower
unit 890 and 891 which confront with each other on the axis
intersecting the ion beam path, and each of the electron shower
units 890 and 891 is made up of a cup-shaped main body 892, a
filament 893 provided within the body, and a grid-shaped extraction
electrode 894 attached at the opening section of the body 892. The
electron shower units 890 and 891 take out streams of electrons 895
from the filament 893 by an acceleration voltage of around 100 V
applied to the extraction electrode 894, and release the electron
streams 895 into the space where the ion beam goes through, thereby
charging the ion beam negatively for neutralization. In FIG. 5,
reference numeral 68 denotes the ion beam, 75 and 76 are deflection
electrodes, and 90 is the specimen.
The following will describe in connection with FIG. 3 and FIGS.
6A-6D the performance of the foregoing embodiment of the defect
correcting apparatus and one specific form of the defect correcting
method according to the present invention. The foregoing apparatus
is used for inspecting a defect on the mask and correcting the
defect.
Before placing a specimen 90 in the specimen chamber 40, the entire
vacuum container 39 is evacuated by a vacuum pump means. The
specimen tray 90 is drawn out into the specimen exchange chamber 41
by means of the drawing bar 64 provided on the tray 60. The gate
valve 43 is closed, the door of the specimen exchange chamber 41 is
opened, and the specimen 90, i.e., a mask, is placed on the
specimen tray 60. After preliminary evacuation for the specimen
exchange chamber 41, the tray 60 is entered into the specimen
chamber 40 and the tray 60 is placed at the specified position on
the table 55. Subsequently, the pumping system is activated to
evacuate the column 39 and the specimen chamber 40 to the extent of
10.sup.-6 torr. The X-axis and Y-axis drive motors 56 and 57 are
operated through the controller 115 to move the table 55 so that
the inspection start position on the specimen 90 is set. The Z-axis
fine feeding micrometer 58 and the .theta.-axis rotating ring 59
are operated so that the specimen position is finely adjusted in
the Z-axis direction and on the horizontal plane.
Subsequently, the control system 112 is operated to switch the high
voltage power supply 82, controller 85 and the lens power supplies
80 and 81 so that a small current and low acceleration voltage for
producing an ion beam having a wide scanning range are supplied to
the electrodes 77-81, 83 and 84. Then, observation and inspection
for defects on the specimen 90 are started.
The filament in the liquid metal ion source 65 is heated by being
supplied with a current from the power supply 77, and when a
negative voltage of several kV to several deca-kV from the power
supply 79 is applied to the extraction electrode 67, an ion beam 68
is extracted out of a very narrow area on the tip of the filament
in the liquid metal ion source 65. At the same time, a low positive
or negative voltage from the power supply 78 is applied through the
control electrode 66 to the portion near the tip of the filament in
the liquid metal ion source 65 to thereby control the ion beam
current.
The ion beam 68 extracted from the liquid metal ion source 65 is
passed through the circular aperture 69 so that only the central
portion of the beam is extracted. Then the ion beam is focused to a
spot 68' having a diameter of 0.5 .mu.m or less by means of the
electrostatic lenses 70 and 71 with voltages from the power
supplies 80 and 81 applied thereto and another electrostatic lens
72. Then, the ion beam is deflected in the X and Y directions by
the deflection electrodes 75 and 76 with a voltage from the power
supply 84 applied thereto, and the ion beam spot 68' is focused on
the surface of the specimen 90.
As mentioned previously, when the ion beam 68 is projected onto the
surface of the specimen 90, secondary charged-particles are emitted
from the specimen 90. The secondary charged-paticles, i.e.,
secondary electrons or secondary ions, are caught by the secondary
charged-particle detector 86, which then transduces the intensity
of emission into an electric current and supplies the current to
the SIM observation unit 87. The SIM observation unit 87 receives
from the deflection electrode power supply 84 the signals
indicating the amount of ion beam deflection in the X and Y
directions, and swings the spot of the CRT (TV monitor display) in
sychronization with the signals. At the same time, the intensity of
the CRT spot is varied in accordance with the current signal from
the secondary charged-particle detector 86, and the image of the
specimen 90 is displayed.
Subsequently, the image signal of the specimen 90 obtained by the
SIM observation unit 87 is converted to a binary signal by the
binary circuit (not shown), and the binary signal is stored by the
memory 113 in the inspection system for the specimen 90. The binary
signal represents whether or not a Cr pattern exists on a mask as a
specimen.
The comparison circuit 114 is the specimen inspection system takes
out the binary image signal of the specimen 90 from the memory 113
and takes out the pattern information corresponding to the binary
image signal from the original pattern information stored in memory
means comprising the magnetic disk 110 in accordance with the image
positional information given by the controller 115 for driving the
table 55, then compares the specimen image with the original
pattern information and determines to be defective if both data do
not coincide with each other.
In this way, by use of the secondary electron image or secondary
ion image produced by the scanning of the ion beam 68 having a
diameter of 0.5 .mu.m or less, pattern defects of smaller than 0.5
.mu.m can be inspected.
When a defect is detected on the specimen 90, the table 55 is
positioned by turning manually the feed micrometers 56 and 57 and
the .theta.-direction feed cylinder 59 which are provided outside
of the specimen chamber 40 through the rotary feedthroughs 61, 62
and 63, such that the defect 96 is positioned to substantially the
center of the CRT (TV monitor display) 88, i.e., in the middle of
the deflection electrodes 75 and 76, as shown in FIG. 10A. In FIG.
10A reference numerals 94 and 95 denote wiring patterns on the
mask, and 96 shows the defective portion.
In order to remove the defect, first, the control electrode 66 and
extraction electrode 67 are operated to take out an ion beam 68
with a low acceleration voltage of several kV or less from the ion
source metal 654 through the needle 653 of the liquid metal ion
source 65. The spot 68' of the ion beam is manipulated to scan the
surface of the specimen 90, and the surface of the specimen is
displayed on a magnified scale on the CRT (TV monitor display) 88
of the SIM observation unit 87 in accordance with the deflection
signal (saw tooth wave) from the deflection electrode power supply
84 and the signal from the secondary charged-particle detector
86.
As shown in FIG. 12, four electronic lines X.sub.1, X.sub.2,
Y.sub.1 and Y.sub.2 are displayed on the screen of the TV monitor
display 697 (88). The operator moves the displayed electronic lines
by operating an electronic line generator 696 by application of
signals 698 from potentiometers or the like, so that the defect 694
(shown in FIG. 10B) is enclosed within a rectangle formed by the
four electronic lines X.sub.1, X.sub.2, Y.sub.1 and Y.sub.2.
After the observation and inspection for the specimen 90, the
blanking electrode 83 is operated so as to swing the ion beam 68
quickly out of the aperture 74, thereby halting the exposure of the
specimen 90 to the ion beam 68 quickly.
Subsequently, a negative voltage of several deca-kV is applied to
the ion beam extraction electrode 67 so as to extract an ion beam
68 out of a very narrow area of the tip of the needle 653 in the
liquid metal ion source 65, and the ion beam current is controlled
by application of a much lower positive or negative voltage to the
control electrode 66. The ion beam 68 is entered through the
aperture 69 to allow only the central portion of the beam to pass
through, then the ion beam is focused by the electrostatic lenses
70, 71 and 72 and its spot 68' is projected to a black spot defect
92 on the specimen 90 while being deflected in the X and Y
directions by the deflection electrodes 75 and 76, whereby the
defective portion of the specimen can be processed by sputtering.
In correcting the black spot defect 92, the ion beam spot 68' on
row Y.sub.1 is swung in the X-axis direction, as shown in FIG. 6C,
and in this case when the beam spot has come to X.sub.1 on the X
coordinate, the blanking electrode 73 is operated so that the ion
beam reaches the specimen, and when the beam spot has come to
X.sub.m, the blanking electrode is operated so that the ion beam is
deflected from the specimen. Then, the beam spot is shifted in the
Y-direction by .DELTA.Y, and on the row of Y=Y.sub.2 the ion beam
is swung in the X-direction in the same manner. This operation is
repeated until the row of Y-Y.sub.n has been scanned. Thus the area
of X.sub.1 .ltoreq.X.ltoreq.X.sub.n and Y.sub.1
.ltoreq.Y.ltoreq.Y.sub.n is exposed to the ion beam, and defects
are removed by the sputtering process.
In this way, the area of X.sub.1 .ltoreq.X.ltoreq.X.sub.m and
Y.sub.1 .ltoreq.Y.ltoreq.Y.sub.n enclosed by the electronic lines
X.sub.1, X.sub.2, Y.sub.1 and Y.sub.2 is exposed to the ion beam,
and the defect is removed by the sputtering process.
The controller 84 supplies the blanking signal to the power supply
82 before and after voltage levels 701 and 702 of the saw tooth
waves supplied to the deflection electrode power supply 84 become
equal to voltage signals V.sub.X1, V.sub.X2, V.sub.Y1 and V.sub.Y2
obtained from potentiometers 700, as shown in FIG. 16(a) and (b),
so as to operate on the blanking electrode 73 to deflect the ion
beam out of the aperture 74. In consequence, only the area enclosed
by the electronic lines is subjected to the sputtering process.
When a defect on the pattern of the specimen 90 has been detected
by the comparison circuit 114 in the inspection system for the
specimen 90 and when the defect is removed by the sputtering
process, the control system 112 is switched to provide a large
current and high acceleration voltage for producing an ion beam 68
having a narrow scanning range which is suitable for the correction
process. A large current ion beam 68 is extracted out of the liquid
metal ion source 65 and it is subjected to a high acceleration
voltage by the control electrode 66, then it is concentrated to a
spot of 0.5 .mu.m or less in diameter by the electrostatic lenses
70, 71 and 72. The ion beam 68, with its scanning range limited by
the deflection electrodes 75 and 76, is projected to the defective
portion of the pattern, whereby the defect is removed by
sputtering. The ion beam 68 may be focused on the defective portion
so that the defect is removed by sputtering.
Thus, correction by use of the micro ion beam allows the removal
and correction of a small defect of 0.5 .mu.m or less.
After the defect on the pattern of the specimen 90 has been
corrected, the control system is restored to the conditions
suitable for observation and inspection, and the corrected pattern
on the specimen 90 can be checked by taking the same operating
procedures as described above.
After defects of the pattern on the specimen 90 have been corrected
completely, all power supplies are turned off, the gate valve 42 to
the upper half specimen chamber 40 in the vacuum container 39 is
closed, and another gate valve 43 is opened. Then the specimen tray
60 is drawn out into the specimen exchange chamber 41 using the
drawing bar 64, and the corrected mask is taken out.
In the arrangement of the present invention, voltage division
resistors may be used in place of the high voltage power supply
82.
Arrangement may also be made such that a threshold circuit is
connected to the secondary charged-particle detector 86, which then
provides binary signal having a 0's level and a 1's level for the
SIM observation unit depending on whether the secondary emission is
higher than or lower than the reference level.
A black spot defect and a pattern connected to the black spot
defect on the mask which the present invention concerns are made of
metal or metal compound, and they exist separately and are not
grounded. Therefore, when the charged ion beam is projected to the
pattern, charges are accumulated on the pattern, that effects the
path of the ion beam coming succeeding. This causes the ion beam 68
to make a larger spot 68' or deviate from the scanning locus, and
cause the deformation at the edge of the focused image of the
aperture 74, resulting in an unsatisfactory processing.
On this account, the means 89 for preventing the spot disturbance
caused by charges of the ion beam has electron shower units 890 and
891, which release electrons streams 895 to the ion beam 68 so as
to charge the ion beam negatively for neutralization. In
consequence, spreading of the ion beam 68 by the space charge
effect, deflection of the scanning locus of the beam spot 68' and
deformation at the edge of the image of the aperture 74 can be
prevented, whereby the accuracy of correcting black spot defects
can further be improved.
For taking out the mask which has been corrected through the
foregoing process, the gate valve 42 between the column 39 and the
specimen chamber 40 is closed, the gate valve 43 between the
specimen chamber 40 and the specimen exchange chamber 41 is opened,
the specimen tray 60 is drawn out into the specimen exchange
chamber 41 using the specimen drawing bar 64, the gate valve 43 is
closed, the door of the specimen exchange chamber 41 is opened, and
the corrected mask is taken out. The corrected mask is then
transferred to the subsequent process.
A satisfactory processing result of the removal of a black spot
defect was obtained under the processing conditions that, for a
black spot defect on the chrome mask having a thickness of 600
.ANG., an ion beam is extracted out of the liquid metal ion source
of gallium with an acceleration voltage of 45 kV, and the ion beam
is focused to a spot of 0.2 .mu.m in diameter by the electrostatic
lenses, which scans the mask surface at a speed of 20 .mu.m/sec by
the operation of the deflection electrodes.
The following will describe other embodiments of the present
invention.
First, the pumping system is not limited to that shown in FIG. 3,
but instead the system may be arranged by combination of an oil
rotary pump, a diffusion pump and an oil trap. Still another
arrangement is the combination of an oil rotary pump, a cryo pump,
an ion pump and a titanium pump.
The ion source is not limited to the liquid metal ion source 65
shown in FIGS. 3 and 4, but instead an ion source of the ultra-low
temperature electric field ionization type operating in th vacuum
of 10.sup.-9 torr or less can also be used. FIG. 7 shows such an
ion source of the ultra-low temperature electric field ionization
type. The arrangement shown in FIG. 7 includes a supporter 655
having a gas releasing hole 656, a metallic needle 657 attached on
the supporter 655, and an extraction electrode 658 which is
insulated electrically from the supporter 655 by means of an
insulator 659 made of sapphire or the like. The supporter 655 is
conducted to a liquid helium refrigerator so that the supporter 655
and the needle 657 are cooled to the liquid helium temperature.
Ionizing gas 600 of a rare gas, e.g., helium, is introduced through
the hole 656 formed in the supporter 655, and gas atoms are
deposited densely on the surface of the needle 657. With a high
voltage applied to the extraction electrode 658, the gas atoms are
ionized in the very narrow area on the tip of the needle 657 and
they are extracted out as an ion beam 661. The ion source of the
ultra-low temperature electric field ionization type provides a
very high deposition density of gas atoms at the tip of the needle
as compared with the ion source of the normal temperature electric
ionization type, thereby serving as a high intensity ion
source.
The charged-particle optical system for focusing the ion beam is
not limited to the set of three electrostatic lenses 70, 71 and 72
shown in FIG. 3, but Eintzeln lenses can also be used, and further
the number of lenses is not limited to three.
The spatial relationship among the lenses of the charged-particle
optical system, the blanking electrode, the aperture, and the
deflection electrodes is not limited to that shown in FIG. 3, but
many variations are possible.
FIGS. 8A through 8D show various embodiments for the lenses of the
charged-particle optical system and the aperture. The arrangement
of FIG. 8A has an aperture 681 located below ion source 680, and a
set of lenses 700, 701 and 702 is disposed below the aperture 681,
so that the image of the aperture 681 is focused by the lenses 700,
701 and 702 on the specimen 90.
In the arrangement of FIG. 8B, a set of first-stage lenses 703, 704
and 705 and a pair of second-stage lenses 706 and 707 are disposed
at a certain interval below the ion source 680, and an aperture 682
is interposed between the first-stage lenses 703, 704 and 705 and
the second-stage lenses 706 and 707. The ion beam generated by the
ion source 680 is transformed into a parallel beam by the
first-stage lenses 703, 704 and 705, and the central portion of the
parallel beam is extracted by the aperture 682, then the image of
the aperture 682 is focused on the specimen 90 by the second-stage
lenses 706 and 707. This arrangement allows the use of much part of
the ion beam for projecting the specimen as compared with the
arrangement shown in FIG. 8A.
In the arrangement shown in FIGS. 8C and 8D, a set of first-stage
lenses 708, 709 and 710 constituting a zoom lens set is disposed
below the ion source 680, an aperture 683 with a variable opening
area is disposed below the zoom lens set, and a set of second-stage
lenses 711, 712 and 713 is disposed below the aperture 683. In FIG.
8C, the opening of the aperture 683 is adjusted to have a small
dimension b and the ion beam is focused by the first-stage zoom
lens set 708, 709 and 710 to a dimension of c which is slightly
larger than the opening dimension b, and the image of the aperture
683 is projected in a dimension of a on the specimen 90 by the
second-stage lens set 711, 712 and 713. In FIG. 8D, the opening of
the aperture 683 is adjusted to have a dimension b' which is
slightly larger than the dimension b in FIG. 8C, and the ion beam
is focused by the first-stage lens set 708, 709 and 710 to a
dimension of c' which is slightly larger than the dimension b', and
the image of the aperture is projected in a dimension of a' on the
specimen 90 by the second-stage lens set 711, 712 and 713.
According to the arrangements shown in FIGS. 8C and 8D, further
large part of the ion beam can be projected on the specimen 90. The
opening of the aperture may be formed in arbitrary shape such as
circle, polygon and the like, however, a square with variable
dimensions allows the easiest use.
FIGS. 9A and 9B, FIGS. 10A through 10C, FIGS. 11A through 11C, and
FIG. 12 show apertures with variable opening dimensions, the
methods of using these apertures, and the device for positioning
and scaling the opening of the aperture to a black spot defect.
The aperture shown in FIGS. 9A and 9B includes the first and second
slide plates 685 and 686 placed in series along the X-axis on the
horizontal plane, the third and fourth slide plates 687 and 688
placed in series along the Y-axis, and the first, second, third and
fourth fine manual feed means of the micrometer type 689, 690, 691
and 692 connected to the first, second, third and fourth side
plates, respectively, and mounted on the wall 684 of the vacuum
container so that they can be operated outside the container. The
confronting edges of the first and second slide plates 685 and 686
and the third and fourth slide plates 687 and 688 are shaped in
knife-edge. The first and second slide plates 685 and 686 and the
third and fourth slide plates 687 and 688 are assembled in a
back-to-back relationship through sliding surfaces 693. In this
aperture, the first and second slide plates 685 and 686 are moved
in the X-direction by operating the first and second fine feed
means 689 and 690 so that the dimension and position of the opening
in the X-direction is adjusted, and the third and fourth slide
plates 687 and 688 are moved in the Y-direction by operating the
third and fourth fine feed means 691 and 692 so that the dimension
and position of the opening in the Y-direction is adjusted.
FIGS. 10A through 10C illustrate the application of the aperture
shown in FIGS. 9A and 9B to the removal of a black spot defect
which is deposited within a narrow gap between contiguous patterns.
As shown in FIG. 10A, the first, second, third and fourth slide
plates 685, 686, 687 and 688 of the aperture shown in FIGS. 9A and
9B are moved so as to adjust the position and dimensions of the
aperture to those of the black spot defect 96 deposited on pattern
94, so that the black spot defect 96 is enclosed inside a
rectangular frame 694, as shown in FIG. 10B, which defines the
range of the projected image. Then, the ion beam is projected
inside the frame 694 so as to remove the black spot defect 96 and
the pattern 94 is corrected as shown in FIG. 10C. In this case of
processing, the deflection electrodes 75 and 76 are not
activated.
FIGS. 10A through 11C illustrate the application of the aperture
having variable opening dimensions shown in FIGS. 9A and 9B to the
removal of a large black spot defect 99 deposited on pattern 97.
The processing of this case is the same as that shown in FIGS. 10A
through 10C, except that the rectangular frame 965 is formed to
match the position and dimensions of the large black spot defect
99.
FIG. 12 shows the system using a TV monitor display 88 for setting
the position and dimensions of the aperture with variable opening
dimensions to those of a black spot defect on the pattern. The
system includes an electronic line generator 696 and a TV monitor
display 697 (88). In this system, potentiometers and the like are
coupled to the first, second, third and fourth fine feed means 689,
690, 691 and 692 of the variable opening aperture shown in FIG. 9,
and signals 698 from these potentiometers are supplied to the
electronic line generator 696. The electronic line generator 696
provides for the TV monitor display 697 a signal 699 representing
the positions of the first, second, third, and fourth slide plates
685, 686, 687 and 688, so that the frame of the aperture is
displayed on the TV monitor screen 697 by electronic lines X.sub.1
and X.sub.2 for the X-direction and Y.sub.1 and Y.sub.2 for the
Y-direction. Using this system, the opening of the aperture can be
adjusted accurately and easily so as to match the position and
dimensions of the black spot defect.
The arrangement of the present invention may be modified to use
voltage division resistors in place of the power supply 79 for the
ion beam electrode and the power supplies 79 and 80 for the
lenses.
FIG. 13, FIGS. 14A and 14B and FIG. 15 show other examples of a
means for preventing the spot disturbance caused by charges of the
ion beam, as against the arrangement shown in FIG. 5.
The arrangement shown in FIG. 13 is the same as shown in FIG. 5
with the exception that the electron shower units 896 and 897 are
directed to the surface of the specimen 90 so that electron streams
898 are projected to the surface of the specimen 90 thereby to
prevent the specimen 90 from being charged by the ion beam.
The arrangement shown in FIGS. 14A and 14B has an arm 898 which can
be moved in the X-, Y- and Z-directions, with a prober 899 attached
to the end of the grounded arm 898. In operation, the prober 899
comes in contact with a pattern 100 having a black spot defect 101,
and when the ion beam 68 is projected to the specimen 90, charges
on the pattern 100 are discharged through the prober 899 and arm
898 to the ground. In consequence, accumulation of charges on the
specimen 90 can be prevented.
In the arrangement shown in FIG. 15, a mask substrate 901 is placed
on the specimen tray 60 and fixed with a clamper 904 made of
conductive material. The entire surface of the mask substrate 901
is coated with a thin film 903 of metal or conductive compound such
as In.sub.2 O.sub.3 or SnO.sub.2 by evaporation. In this
arrangement, charges on the pattern 902 can be discharged through
the clamper 904 and specimen tray 60 to the ground without changing
the transmittivity of the specimen mask for the light, X-rays or
ion beams, whereby accumulation of charges caused by the exposure
to the ion beam can be prevented.
The present invention is summarized as follows.
According to the first aspect of the present invention, an ion beam
is extracted from a high intensity ion source, which is focused to
a fine spot by an optical system for charged-particles, and the
spot is projected on a black spot defect of a specimen mask so as
to remove the defect. The invention can effectively be applied with
satisfactory productivity to the high accuracy correction of black
spot defects which occur on a photomask, X-rays exposure mask and
ion beam exposure mask used in fabricating IC patterns having a
width of 1-1.5 .mu.m or less than 1 .mu.m.
According to the second aspect of the present invention, a black
spot defect of the mask is exposed to the ion beam produced in the
arrangement of the first aspect of invention while the beam spot is
prevented from being disturbed by charges of the ion beam, whereby
mask defects can be corrected more accurately.
According to the third aspect of the present invention, the
arrangement comprises a specimen chamber within a vacuum container,
a table for mounting a mask thereon within the specimen chamber, a
high intensity ion source such as a liquid-metal ion source or an
electric field ionizing ion source which operate in ultra-low
temperature disposed within the vacuum container so that it
confront the specimen chamber, a means for extracting an ion beam
out of the ion source, a charged-particle optical system for
focusing the extracted ion beam to a spot, and a means for
controlling the energy, stability, spot diameter and projection
direction of the ion beam and for projecting the beam spot to a
black spot defect on the mask, whereby the invention as described
as the first aspect can surely be practiced.
According to the fourth aspect of the present invention, a means
for preventing spot disturbance caused by charges of the ion beam
is added to the arrangement of the third aspect of the invention,
whereby the invention as described in the second aspect can surely
be practiced.
According to the method of the present invention, an ion beam
derived from a high intensity ion source is focused to a fine area
of 0.5 .mu.m or less in diameter by an optical system for
charged-particles, the beam spot is projected onto a mask which is
used for manufacturing semiconductor integrated circuits and the
like, the intensity of the resultant secondary charged-particles is
measured, the measured value is compared with information of the
original pattern so as to detect a mask defect, and when a defect
has been detected, the ion beam is concentrated to scan or focus on
the defective portion, and the ion beam is now provided with an
micro ion beam current and an acceleration voltage suitable for the
removal of the defect by sputtering, whereby inspection and
corrections of mask defects can be performed with a resolution and
accuracy of 0.5 .mu.m or less.
Moreover, according to the inventive apparatus comprising a vacuum
container installed on a bed and having a pumping means, a table
for a mask disposed on a bed within the vacuum container, a drive
controller for the table, a high intensity ion source provided
within the vacuum container, an ion beam extracting electrode, an
ion beam control electrode, electrostatic lenses for focusing the
ion beam, an ion beam aperture, a blanking electrode for deflecting
the ion beam out of the aperture, deflection electrodes for causing
the beam spot to scan the mask pattern, power supplies for the
electrodes and electrostatic lenses, a secondary charged-particle
detector which detects secondary charged-particles emitted on the
mask as it is exposed to the ion beam and transduces the intensity
of emission into an electrical signal, a comparison circuit which
compares the output of the secondary charged-particle detector with
information on the original pattern and determines the presence or
absence of a defect, and a control system for switching the power
supplies for observation and inspection of the mask and for
correcting a defect on the mask, inspection and correction of a
mask can be performed effectively by the single apparatus, whereby
the work efficiency can be improved significantly and redundant
facilities can be avoided.
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