U.S. patent application number 12/241727 was filed with the patent office on 2011-07-14 for demagnification measurement method for charged particle beam exposure apparatus, stage phase measurement method for charged particle beam exposure apparatus, control method for charged particle beam exposure apparatus, and charged particle beam exposure apparatus.
Invention is credited to Shinsuke NISHIMURA.
Application Number | 20110168911 12/241727 |
Document ID | / |
Family ID | 32817966 |
Filed Date | 2011-07-14 |
United States Patent
Application |
20110168911 |
Kind Code |
A1 |
NISHIMURA; Shinsuke |
July 14, 2011 |
DEMAGNIFICATION MEASUREMENT METHOD FOR CHARGED PARTICLE BEAM
EXPOSURE APPARATUS, STAGE PHASE MEASUREMENT METHOD FOR CHARGED
PARTICLE BEAM EXPOSURE APPARATUS, CONTROL METHOD FOR CHARGED
PARTICLE BEAM EXPOSURE APPARATUS, AND CHARGED PARTICLE BEAM
EXPOSURE APPARATUS
Abstract
A method for measuring a demagnification of a charged particle
beam exposure apparatus includes measuring a first stage position
of a mask stage in accordance with a mask stage coordinate system,
irradiating a first charged particle beam to a first irradiation
position on a specimen through the opening portion of the mask,
measuring the first irradiation position in accordance with a
specimen stage coordinate system, moving the mask stage to a second
stage position, measuring the second stage position of the mask
stage, irradiating a second charged particle beam to a second
irradiation position on the specimen through the opening portion of
the mask measuring the second irradiation position in accordance
with the specimen stage coordinate system, and calculating a
demagnification of the charged particle beam exposure apparatus
from the first and second stage positions and the first and second
irradiation positions.
Inventors: |
NISHIMURA; Shinsuke;
(Higashiyamato-shi, JP) |
Family ID: |
32817966 |
Appl. No.: |
12/241727 |
Filed: |
September 30, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11501824 |
Aug 10, 2006 |
7439525 |
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12241727 |
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10742778 |
Dec 23, 2003 |
7095035 |
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11501824 |
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Current U.S.
Class: |
250/400 |
Current CPC
Class: |
H01J 37/28 20130101;
B82Y 10/00 20130101; B82Y 40/00 20130101; H01J 37/3174 20130101;
H01J 2237/282 20130101 |
Class at
Publication: |
250/400 |
International
Class: |
H01J 3/14 20060101
H01J003/14 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 27, 2002 |
JP |
2002-382394 |
Claims
1. A charged particle beam exposure apparatus comprising: a
radiating unit configured to radiate a charged particle beam; an XY
mask stage on which a mask having an opening is placed and which
moves the mask stage in X and Y directions of a mask stage
coordinate system; a mask stage measuring unit configured to
measure a position of the XY mask stage in accordance with the mask
stage coordinate system; a deflector which deflects the charged
particle beam and changes the position of the charged particle beam
on a surface of the mask; an objective lens system which
demagnifies a pattern of the charged particle beam shaped through
the mask and irradiates the specimen with the charged particle
beam; a specimen stage on which the specimen is placed and which
moves the specimen in X and Y directions of a specimen stage
coordinate system; an objective deflector which deflects the
charged particle beam and changes the position of the charged
particle beam on a surface of the specimen; an irradiation position
measuring unit configured to measure an irradiation position of the
charged particle beam on the surface of the specimen in accordance
with the specimen stage coordinate system; and a demagnification
measuring unit configured to measure a demagnification of the
objective lens system on the basis of two positions of the XY mask
stage measured at different opening positions respectively and a
position of the charged particle beam on the surface of the
specimen that was shaped through the opening of each of the opening
positions.
2. The charged particle beam exposure apparatus according to claim
1, further comprising: a .theta. mask stage which rotates the mask
in an XY plane of the mask stage coordinate system; a rotation
angle measuring unit configured to measure a rotation angle of the
pattern of the charged particle beam in the objective lens system;
a .theta. mask stage driving unit configured to drive the .theta.
mask stage corresponding to the measured rotation angle; a phase
difference measure unit configured to measure a phase difference
between the specimen stage coordinate system and the mask stage
coordinate system from a position of the XY mask stage measured at
two opening positions respectively and a position of the charged
particle beam on the surface of the specimen that was shaped
through the opening of each of the opening positions; and a driving
unit configured to drive the XY mask stage and the .theta. mask
stage corresponding to the measured phase difference.
3. A charged particle beam exposure apparatus comprising: a radiate
unit configured to radiate a charged particle beam; an XY mask
stage on which a mask having an opening is placed and which moves
the mask in X and Y directions of a mask stage coordinate system; a
.theta. mask stage which rotates the mask in an XY plane of the
mask stage coordinate system; an opening position measuring unit
configured to measure a position of the opening in accordance with
the mask stage coordinate system; a deflector which deflects the
charged particle beam and changes the position of the charged
particle beam on a surface of the mask; an objective lens system
which demagnifies a pattern of the charged particle beam shaped
through the mask and irradiates a specimen with the charged
particle beam; a specimen stage on which the specimen is placed and
which moves the specimen in X and Y directions of a specimen stage
coordinate system; an objective deflector which deflects the
charged particle beam and changes the position of the charged
particle beam on a surface of the specimen; an irradiation position
measuring unit configured to measure an irradiation position of the
charged particle beam on the surface of the specimen in accordance
with the specimen stage coordinate system; a rotation angle
measuring unit configured to measure a rotation angle of the
pattern of the charged particle beam in the objective lens system;
a phase measuring portion configured to measure a phase of the mask
stage coordinate system with respect to the specimen stage
coordinate system based on a position of the XY mask stage measured
at two opening positions respectively and a position of the charged
particle beam on the surface of the specimen that was shaped
through the opening of each of the opening positions; and a driving
unit configured to drive the XY mask stage and the .theta. mask
stage corresponding to the measured phase.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 11/501,824, filed Aug. 10, 2006, which is a divisional of
U.S. patent application Ser. No. 10/742,778 filed Dec. 23, 2003,
now U.S. Pat. No. 7,095,035, and claims the benefit of priority
from Japanese Patent Application No. 2002-382394, filed Dec. 27,
2002. The entire contents of these applications are incorporated
herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates to lithography using a charged
particle beam. More specifically, the invention relates to a stage
phase measurement method for a charged particle beam exposure
apparatus for measuring the phase of a mask stage coordinate system
for a specimen stage coordinate system of a charged particle beam
exposure apparatus; a demagnification measurement method for a
charged particle beam exposure apparatus for measuring the
demagnification for image projection onto a mask specimen surface;
a control method for a charged particle beam exposure apparatus for
performing control corresponding the measured phase and
demagnification; and a charged particle beam exposure
apparatus.
[0004] 2. Description of the Related Art
[0005] With increasingly fined semiconductor devices, studies and
research are being made regarding charged particle beam exposure
apparatuses for exposure patterns.
[0006] Demagnification lenses and objective lenses are used to
demagnify and transferring a mask pattern onto a specimen. The mask
pattern is demagnified by these lenses and the pattern is rotated
by a magnetic field, so that the phase of the pattern to be
transferred onto the surface of the specimen is varied concurrently
with deflection in demagnification. The apparatus is designed by
taking both the rotation and the demagnification into account, and
the apparatus is designed so that the rotation is performed at a
desired demagnification. Practically, however, design errors and
manufacture errors disable obtaining the condition concurrently
allowing the desired demagnification and the desired rotation to be
exhibited. A process for measuring the demagnification and pattern
rotation angle is disclosed in Jpn. Pat. Appln. KOKAI Publication
No. 7-22349.
[0007] A rotational error of the pattern is correctable by using a
rotation stage that carries the mask. However, since no means is
provided to correct the movement direction of a mask stage X and
the movement direction of a mask stage Y, the system phase of the
mask stage coordinate system remains mismatched with the specimen
stage coordinate system.
[0008] Because of assembly errors, design errors, and lens system
adjustment errors, the mask stage coordinate system has errors for
the specimen stage coordinate system; and generally, it does not
have means for adjusting the errors. While an XY mask stage should
be mounted to one more .theta. stage to adjust the phase of an XY
mask stage, since the construction is thereby complexed and free
space in an electrooptical housing is insufficient, it is difficult
to mount the XY mask stage. When moving a desired mask pattern with
the mask stage to the vicinity of the beam, if such errors as those
described above are zero, the movement position can be determined
in accordance with pattern design values. However, a problem arises
in that an accurate movement position of the pattern cannot be
known, so that accurate movement cannot be implemented.
[0009] Regarding a demagnification measurement method, using a
design distance D between two opening portions provided in the mask
and a distance d between individual beam specimen surface positions
formed in the opening portions, the demagnification has been
obtained by way of "demagnification M=d/D". However, errors such as
those occurring in the manufacture of the opening portions and
distortion undesirably influence the calculation result. In a case
where the manufacture error is 50 nm and the distance between the
opening portions is 500 .mu.m, the case results in causing an error
of 0.01% (50 nm/500 .mu.m.times.100). When performing scan-exposure
of a 300 .mu.m mask pattern by using the demagnification, there
arises the problem of causing an image-dimensional error of as
large as 30 nm (i.e., 300 .mu.m.times.0.01%=30 nm).
[0010] Further, a problem arises in that an accurate pattern cannot
be imaged onto the specimen since no method is available to measure
the phase of the mask stage coordinate system with respect to the
problem of demagnification measurement errors and the specimen
stage coordinate system.
BRIEF SUMMARY OF THE INVENTION
[0011] A demagnification measurement method for a charged particle
beam exposure apparatus, according to an aspect of the present
invention, comprises: measuring a first stage position of a mask
stage of the charged particle beam exposure in accordance with a
mask stage coordinate system with an opening portion of a mask
placed on the mask stage being situated in a first opening
position; irradiating a first charged particle beam to a first
irradiation position on a surface of a specimen through the opening
portion of the mask, the first charged particle beam being shaped
through the opening portion and then passing through an objective
lens system; measuring the first irradiation position in accordance
with a specimen stage coordinate system; moving the mask stage to a
second stage position to situate the opening portion of the mask in
a second opening position different from the first opening
position; measuring the second stage position of the mask stage in
accordance with the mask stage coordinate system; irradiating a
second charged particle beam to a second irradiation position on
the surface of the specimen through the opening portion of the mask
moved together with the mask stage, the second charged particle
beam being shaped through the opening portion situated in the
second opening position and then passing through an objective lens
system; measuring the second irradiation position in accordance
with the specimen stage coordinate system; and calculating a
demagnification of the objective lens system from the first and
second stage positions and the first and second irradiation
positions.
[0012] A stage phase measurement method for a charged particle beam
exposure apparatus, according to another aspect of the present
invention, comprises: measuring a rotation angle of a pattern of a
charged particle beam shaped through a mask placed on a mask stage
of the charged particle beam exposure apparatus and then irradiated
on a surface of a specimen through an objective optical system;
correcting rotation of the pattern by rotating the mask
corresponding to the measured rotation angle; measuring a first
stage position of the mask stage in accordance with a mask stage
coordinate system after correcting the rotation with an opening
portion of the mask being situated in a first opening position;
irradiating a first charged particle beam to a first irradiation
position on the surface of the specimen through the opening portion
of the mask, the first charged particle beam being shaped through
the opening portion and then passing through an objective lens
system; measuring the first irradiation position in accordance with
a specimen stage coordinate system; moving the mask stage to a
second stage position to situate the opening portion in a second
opening position different from the first opening position;
measuring the second stage position of the mask stage in accordance
with the mask stage coordinate system; irradiating a second charged
particle beam to a second irradiation position on the surface of
the specimen through the opening of the mask moved together with
the mask stage, the second charged particle beam shaped through the
opening portion situated in the second opening position and then
passing through the objective lens system; measuring the second
irradiation position in accordance with a specimen stage coordinate
system; and calculating a phase difference between the specimen
stage coordinate system and the mask stage coordinate system from
the first and second stage positions and the first and second
irradiation positions.
[0013] A control method for a charged particle beam exposure
apparatus, according to another aspect of the present invention,
comprises: measuring a first stage position of a mask stage of the
charged particle beam exposure apparatus in accordance with a mask
stage coordinate system with an opening portion of a mask placed on
the mask stage being situated in a first opening position;
irradiating a first charged particle beam to a first irradiation
position on a surface of a specimen through the opening portion of
the mask, the first charged particle beam being shaped through the
opening portion situated in the first opening position and then
passing through an objective lens system of the exposure apparatus;
measuring a first irradiation position in accordance with a
specimen stage coordinate system; moving the mask stage to a second
stage position to situate the opening portion in a second opening
position different from the first opening position; measuring the
second stage position of the mask stage in accordance with the mask
stage coordinate system; irradiating a second charged particle beam
to a second irradiation position on the surface of the specimen
through the opening portion of the mask moved together with the
mask stage, the second charged particle beam being shaped through
the opening portion situated in the second opening position and
then passing through the objective lens system; measuring the
second irradiation position in accordance with a specimen stage
coordinate system; and obtaining a demagnification of the objective
lens system from the first and second stage positions and the first
and second irradiation positions; adjusting the demagnification of
the objective lens system corresponding to the obtained
demagnification; measuring a rotation angle of a pattern of the
charged particle beam shaped through the mask and then irradiated
on the surface of the specimen via the objective optical system,
after the adjusting; correcting the rotation of the pattern by
rotating the mask corresponding to the measured rotation angle;
measuring a third stage position of the mask stage in accordance
with a mask stage coordinate system after correcting the rotation
with the opening portion of the mask being situated in a third
opening position; irradiating a third charged particle beam to a
third irradiation position on the surface of the specimen through
the opening portion situated in the third opening position, the
third charged particle beam being shaped through the opening
portion situated in the third opening position and then passing
through an objective lens system; measuring the third irradiation
position in accordance with a specimen stage coordinate system;
moving the mask stage to a fourth stage position to situate the
opening portion in a fourth opening position different from the
third opening position; measuring the fourth stage position of the
mask stage in accordance with the mask stage coordinate system;
irradiating a fourth charged particle beam to a fourth irradiation
position on the surface of the specimen through the opening portion
situated in the fourth opening position, the fourth charged
particle beam being shaped through the opening portion situated in
the fourth opening position and then passing through the objective
lens system; measuring the fourth irradiation position in
accordance with a specimen stage coordinate system; and obtaining a
phase difference between the specimen stage coordinate system and
the mask stage coordinate system from the third and fourth stage
positions and the third and fourth irradiation positions; and
moving the mask stage by correction in accordance with the phase
difference.
[0014] A charged particle beam exposure apparatus according to
another aspect of the present invention, comprises: a radiating
unit configure to radiate a charged particle beam; an XY mask stage
on which a mask having an opening is placed and which moves the
mask stage in X and Y directions of a mask stage coordinate system;
a mask stage measuring unit configured to measure a position of the
XY mask stage in accordance with the mask stage coordinate system;
a deflector which deflects the charged particle beam and changes
the position of the charged particle beam on a surface of the mask;
an objective lens system which demagnifies a pattern of the charged
particle beam shaped through the mask and irradiates the specimen
with the charged particle beam; a specimen stage on which the
specimen is placed and which moves the specimen in X and Y
directions of a specimen stage coordinate system; an objective
deflector which deflects the charged particle beam and changes the
position of the charged particle beam on a surface of the specimen;
an irradiation position measuring unit configure to measure an
irradiation position of the charged particle beam on the surface of
the specimen in accordance with the specimen stage coordinate
system; and a demagnification measuring unit configure to measure a
demagnification of the objective lens system on the basis of two
positions of the XY mask stage measured at different opening
positions respectively and a position of the charged particle beam
on the surface of the specimen that was shaped through the opening
of each of the opening positions.
[0015] A charged particle beam exposure apparatus according to
another aspect of the present invention, comprises: a radiate unit
configure to radiate a charged particle beam; an XY mask stage on
which a mask having an opening is placed and which moves the mask
in X and Y directions of a mask stage coordinate system; a .theta.
mask stage which rotates the mask in an XY plane of the mask stage
coordinate system; an opening position measuring unit configure to
measure a position of the opening in accordance with the mask stage
coordinate system; a deflector which deflects the charged particle
beam and changes the position of the charged particle beam on a
surface of the mask; an objective lens system which demagnifies a
pattern of the charged particle beam shaped through the mask and
irradiates a specimen with the charged particle beam; a specimen
stage on which the specimen is placed and which moves the specimen
in X and Y directions of a specimen stage coordinate system; an
objective deflector which deflects the charged particle beam and
changes the position of the charged particle beam on a surface of
the specimen; an irradiation position measuring unit configure to
measure an irradiation position of the charged particle beam on the
surface of the specimen in accordance with the specimen stage
coordinate system; a rotation angle measuring unit configure to
measure a rotation angle of the pattern of the charged particle
beam in the objective lens system; a phase measuring portion
configure to measure a phase of the mask stage coordinate system
with respect to the specimen stage coordinate system based on a
position of the XY mask stage measured at two opening positions
respectively and a position of the charged particle beam on the
surface of the specimen that was shaped through the opening of each
of the opening positions; and a driving unit configure to drive the
XY mask stage and the .theta. mask stage corresponding to the
measured phase.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0016] FIG. 1 is a schematic configuration diagram showing an
electron beam exposure apparatus according to an embodiment of the
present invention;
[0017] FIG. 2 is a view showing in detail a portion of the electron
beam exposure apparatus shown in FIG. 1;
[0018] FIG. 3 is a plan view showing the construction of a marking
table of the electron beam exposure apparatus shown in FIG. 1;
[0019] FIGS. 4A and 4B are views used to explain a mask stage phase
measurement method and a demagnification measurement method for an
objective lens system;
[0020] FIG. 5 is a view showing phases of a mask stage coordinate
system for a specimen stage coordinate system;
[0021] FIG. 6 is a flowchart showing a control method for a charged
particle beam exposure apparatus; and
[0022] FIG. 7 is a view used to explain a method of measuring an
irradiation position of an electron beam.
DETAILED DESCRIPTION OF THE INVENTION
[0023] An embodiment according to the present invention will be
described herein below with reference to the drawings.
[0024] FIG. 1 is a schematic configuration diagram showing an
electron beam exposure apparatus according to the embodiment of the
present invention. A beam emitted from an electron gun 1 is imaged
through an illumination lens 2, a projection lens 19, and a
demagnification lens (objective lens system) 8, and is finally
imaged on a main surface of an objective lens (objective lens
system) 9. An image of a first shaping aperture 4 is formed onto a
mask 6, and an image thus formed is created on the specimen surface
through the demagnification lens 8 and the objective lens 9.
[0025] An opening portion 21 is provided in the first shaping
aperture 4. The dimensional shape of the opening portion 21 is a
rectangle having one side of 80 .mu.m, for example. The electron
beam emitted from the electron gun 1 can be deflected through a
blanking deflector 3, and the beam position on the first shaping
aperture 4 can thereby be changed.
[0026] Referring to FIG. 2, the mask 6 is mounted over a .theta.
stage 20, and the .theta. stage 20 is mounted on an X stage 14 and
a Y stage 15, whereby the mask 6 can be moved. The mask 6 is moved
by the X stage 14 and the Y stage 15 in X and Y directions. The
positions of the X stage 14 and the Y stage 15 are under positional
control of a laser measurement apparatus (laser interferometer) 31.
An opening portion 22 is provided in the mask 6, as shown in FIG.
2. In accordance with programs stored in a storage medium 35, a CPU
34 acquires the position of the opening portion 22 from the
measurement result of the laser measurement device 31. The
dimensional shape of the opening portion 22 is smaller than the
size of the first shaping aperture image formed on the mask 6. The
dimensional shape of the opening portion 22 is a rectangle having
one side of 40 .mu.m, for example. The electron beam shaped through
the opening portion 21 of the first shaping aperture can be
deflected through a shaping deflector 5, and the beam position on
the mask 6 can thereby be changed. The beam passed through the
objective lens 9 can be deflected by an objective deflector 18. A
marking table 10 is provided on an XY specimen stage 11 and is
movable in the X and Y directions in the specimen stage coordinate
system. The position of the XY specimen stage 11 is under
positional control of a laser measurement device (laser
interferometer) 32. As shown in FIG. 3, a cross mark 17 provided on
the marking table 10 is made from a beam-reflecting material
different from a material of a base 24. For example, the base 24 is
made of silicon, whereas the mark 17 is made of a material such as
gold or tungsten, for example. The beam position on the marking
table 10 can be changed by the objective deflector 18. A beam
detector 23 detects electrons reflected from the marking table 10
and secondary electrons.
[0027] A function is provided that moves the mark 17 to the optical
axis position, scans the electron beam to be projected onto the
mark 17 by using the objective deflector 18, and then detects the
irradiation position of the electron beam in accordance with the
distance between the mark and the electron beam, which has been
obtained through calculation performed by taking a signal detected
by the beam detector 23 into a mark signal processor 33 and a stage
position measurement value of the laser measurement device 32. The
CPU 34 executes the above-described function in accordance with
programs stored in the storage medium 35. In FIG. 1, reference
numeral 17 denotes an objective aperture, reference numeral 12
denotes a lens imaging system, and reference numeral 13 denotes a
shaped-image imaging system 13.
[0028] A mask stage phase measurement method and an
objective-lens-system demagnification measurement method according
to the present embodiment will now be described hereinbelow by
using FIGS. 4A, 4B, and 5. The mask stage phase measurement and the
objective-lens-system demagnification measurement are executed by
the CPU 34 in accordance with programs stored in the storage medium
35. Also, control of the X, Y, and .theta. mask stages 14, 15, and
20 corresponding to the measurement results is executed by the CPU
34 in accordance with programs stored in the storage medium 35.
[0029] When measuring a mask stage phase, a rotation angle
.theta.mp of the mask pattern formed through the demagnification
lens 8 and the objective lens 9 is preliminarily measured. The
.theta. stage 20 is driven in accordance with the measurement
result to bring the mask pattern into to the state in which it is
not rotated on the specimen. A method of measuring a mask-pattern
rotation angle as .theta.mp is described in, for example, Jpn. Pat.
Appln. KOKAI Publication No. 7-22349. However, the measurement of
the rotation angle .theta.mp is not necessary in the event of
obtaining only the demagnification.
[0030] The opening portion 22 on the mask 6 is moved to a position
A by using the shaping deflector. The positions of the X mask stage
14 and the Y mask stage 15 are measured by a laser measurement
device in accordance with the mask stage coordinate system, and the
position A of the opening portion 22 is measured from the results
thereof. The electron beam shaped through the first shaping
aperture opening portion 21 is deflected by the shaping deflector 5
to the opening portion 22 on the mask. The electron beam is
deflected to a position where the opening portion 22 is covered
overall, as shown in FIG. 4A. The electron beam shaped through the
opening portion 22 arrives at a position "a", as shown in FIG. 4B.
The position "a" is measured by a mark scan process performed in
accordance with the specimen stage coordinate system. The mark scan
process is described in, for example, reference document (S.
Nishimura: Jpn. J. Appl. Phys. Vol. 36 (1997), pp. 7517-7522:
Evaluation of Shaping Gain Adjustment Accuracy Using Atomic Force
Microscope in Variably Shaped Electron-Beam Writing Systems) and
Jpn. Pat. Appln. KOKAI Publication No. 10-270337.
[0031] Subsequently, the opening portion 22 of the mask 6 is moved
to a position B (FIG. 4A). The positions of the X mask stage 14 and
the Y mask stage 15 are measured by a laser measurement device in
accordance with the mask stage coordinate system, and the position
B is measured from the results thereof. The electron beam is
deflected by the shaping deflector to the opening portion 22 in the
position B. The beam shaped through the opening portion 22 is then
irradiated to a position b (FIG. 4B) on the specimen. In a manner
similar to the above, the position b is measured by the mark scan
process in accordance with the specimen stage coordinate system.
The electron beam is irradiated to the two positions without
altering the settings of the demagnification lens 8, the objective
lens 9, and the objective deflector 18.
[0032] The distance between the position A and the position B of
the opening portion on the mask 6 is represented by L. Likewise,
the distance between the beam position "a" and the beam position b
of each specimen surface is represented by l. In this case, the
relationship can be expressed as "demagnification .eta.=1/L."
[0033] In addition, the phase difference between a line segment
connecting between the position A and the position B and an Xm axis
of the mask stage coordinate system is represented by .theta.1.
Likewise, the phase difference between a line segment connecting
between the position "a" and the position b and the X axis of the
specimen stage coordinate system is represented by .theta.2. In
this case, a phase .theta. of the mask stage coordinate system for
the specimen stage coordinate system can be expressed as
".theta.2-.theta.1" (FIG. 5).
[0034] The phase differences .theta.1 and .theta.2 are thus
obtained based on the Xm axis and the X axis. However, the phase
differences .theta.1 and .theta.2 may be obtained based on a Ym
axis and the Y axis. Still alternatively, the phase differences
.theta.1 and .theta.2 may be obtained based on straight lines
having the same tilts in the individual coordinate systems. In
addition, according to the above description, the opening positions
A and B are individually obtained. However, only the positions of
the X mask stage 14 and the Y mask stage 15 may be measured by the
laser measurement device in the state in which the opening portions
are individually situated in the opening positions A and B. The
positional relationship between the two opening positions can be
known and the distances and phase differences can be obtained from
the X mask stage 14 and the Y mask stage 15 in the individual
opening positions.
[0035] The positions of the X mask stage 14 and the Y mask stage 15
can be accurately obtained. In the present embodiment, the
measurement is performed by way of measurement of the positions of
the X mask stage 14 and the Y mask stage 15, so that the
measurements are each obtained with a measurement accuracy of 1 nm
or less (accuracy of an actual measurement device recently used).
Accordingly, also the measurement accuracy of the distance L of
each of the positions A and B is 1 nm or less. When the distance L
is 500 .mu.m, the error is 50 nm in the conventional case. However,
in the present invention, the measurement can be implemented with
the accuracy of 1 nm or less, so that the demagnification
measurement error is 0.0002% (1 nm/500 .mu.m.times.100). Therefore,
in the case where a pattern of 300 .mu.m is imaged on the mask, a
linewidth accuracy or positional accuracy of 0.6 nm (i.e., 300
.mu.m.times.0.0002.times.0.01=0.6 nm) can be implemented.
[0036] Where the measurement accuracy of the irradiation position
"a" and the irradiation position b is 1 nm (measurement accuracy of
a recent exposure apparatus) and the distance is 50 .mu.m, the
phase measurement error is 1/50,000 rad (=0.02 mrad). Where the
movement amount of the mask stage is 100 mm, the difference at both
ends is as extremely small as 2 .mu.m (100 mm.times.0.02/1,000). As
such, the positional movement accuracy of the pattern on the mask 6
is exhibited with a high value of 2 .mu.m. Further, since the
differing phase is corrected and the mask stage is moved, when
exposure is performed while the mask stage is being moved, the
overall deflection range of Y of the shaping deflection becomes
effectively usable as a scan width.
[0037] A control method for the charged particle beam exposure
apparatus, which is configured by combining the above-described
demagnification measurement and the stage phase measurement will
now be described hereinbelow with reference to FIG. 6.
[0038] Using the method described above, processing is performed to
measure a demagnification .eta. (step S101). Then, the measured
demagnification .eta. is compared with a desired demagnification
.eta..sub.0 (step S102). If the result is not .eta.=.eta..sub.0,
the lens system is adjusted so that the desired demagnification can
be obtained (step S103). If the measured demagnification .eta. has
become the demagnification .eta..sub.0, processing proceeds to next
step S104. The arrangement may be such that if a required
demagnification has reached an allowable error range, processing
shifts to next step S104.
[0039] Using a well known process, processing is performed to
measure a rotation angle .theta.mp of a pattern of an electron beam
that has been shaped through a mask and has traveled through the
objective lens system (step S104). The process to be used to
measure the rotation angle .theta.mp is selected from those of the
type that does not rely on the phase difference between the mask
stage coordinate system and the specimen stage coordinate system.
Then, the .theta. stage 20 is driven corresponding to the rotation
angle Amp, and the rotation of the pattern is thereby corrected
(step S105).
[0040] Subsequently, using the above-described method, processing
is performed to measure a phase .theta. of the specimen stage
coordinate system for the mask stage coordinate system (step
S106).
[0041] When moving the mask stage, after correction is made
corresponding to the phase .theta., and the mask stage is moved
(step S107). Where the mask pattern coordinate system is based on
(Xm, Ym) and the mask stage coordinates are based on (X, Y), moving
the mask stage to satisfy the following relationship enables the
mask stage to be moved in conformity with the phase of the specimen
stage:
.DELTA.X=.DELTA.Xm.times.cos .theta.+.DELTA.Ym.times.sin
.theta.
.DELTA.Y=.DELTA.Ym.times.cos .theta.-.DELTA.Xm.times.sin
.theta.
[0042] By performing the movement correction of the XY mask stage,
the mask can be moved to an accurate position. Then, by performing
adjustment of the demagnification, correction of the rotation angle
of the pattern, and movement correction of the mask stage according
to the phase .theta., the pattern can be accurately imaged on the
specimen.
[0043] The present invention is not limited to the embodiment
described above. While having been described by reference to the
exemplified electron beam exposure apparatus, the present invention
can be adapted also to an ion beam exposure apparatus. In addition,
while the stage position is measured by the laser interferometer,
there is no limitation thereto; and any other devices may be used
as long as they are capable of defining the stage coordinates with
high accuracy.
[0044] The process of measuring the irradiation position of the
electron beam is not limited to the mark scan process. For example,
as shown in FIG. 7, a process is available in which scan is
performed with an electron beam over a mark M sized smaller than a
scan range, and the center of gravity of a screen-image object is
obtained to thereby measure the beam position. The mark M may be
arbitrary, as shown in FIG. 7. A range R larger than the mark M is
beam-scanned to thereby obtain data of the screen-image object. The
beam position can be obtained by obtaining the data of the
screen-image object. The present invention can be practiced by
making various other changes without departing from the scope of
the invention.
[0045] Additional advantages and modifications 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.
* * * * *