JP2014194982A - Charged particle beam deflection apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charged particle beam deflection apparatus capable of suppressing occurrence of additional aberration when correcting astigmatism after deflecting the charged particle beam.SOLUTION: A charged particle beam deflection apparatus 100 includes a multipole 13 of electrostatic type or magnetic field type, and a control part 21 for applying a deflection signal for deflecting a charged particle beam 1 to the multipole 13. The control part 21 superposes n-time astigmatic correction signal V(θ) for canceling n-time astigmatism (n=2, 3, ..., N, N is integer of three or larger) on a deflection signal V(θ), so that for every deflection coordinates in which a charged particle beam deflected under application of the deflection signal V(θ) enters, 2, 3, ..., n-1-time astigmatic correction signal for canceling 2, 3, ..., n-1-time astigmatism occurring at superposition of the n-time astigmatic correction signal V(θ) is superposed on the deflection signal V(θ).

Description

  The present invention relates to a charged particle beam deflection apparatus.

  The charged particle beam deflection apparatus is a charged particle beam apparatus such as an electron beam drawing apparatus or a scanning electron microscope, which is used to scan a drawing material or an observation sample with a charged particle beam. It is a device that deflects by applying a magnetic field.

  As a charged particle beam apparatus provided with a charged particle beam deflection apparatus, for example, a variable shaped electron beam drawing apparatus is known. The variable shaped electron beam drawing apparatus is an electron beam drawing apparatus in which the cross-sectional area of the electron beam on the drawing material is increased and the cross-sectional shape and dimensions thereof are variable for the purpose of improving the drawing throughput. The variable shaped electron beam drawing apparatus is mainly used for drawing a photomask for manufacturing a semiconductor device.

  For example, Patent Document 1 discloses a variable shaped electron beam drawing apparatus having an optical system as shown in FIG. The optical system shown in FIG. 14 includes an irradiation lens 1002, a first molded aperture plate 1003, a molded lens 1006, a second molded aperture plate 1007, a reduction lens 1008, an objective lens 1009, a molded deflector 1012, an objective deflector 1013, Blankers 1014 and 1015 and a blanking aperture plate 1017 are included.

  Hereinafter, the basic operation of the variable shaped electron beam drawing apparatus will be described with reference to FIG.

  The variable shaped electron beam drawing apparatus shapes the cross section of the electron beam 1 and reduces and projects an image of the cross section (projected figure 11) onto the material 10. Here, the shaping of the cross section of the electron beam 1 and the reduction projection of the image of the cross section (projected figure 11) are the second shaping aperture plate 1007, the optical system above it, and the second shaping aperture plate 1007, respectively. By lower optical system. A resist (photosensitive material) is applied on the material 10.

  As a result of the molding and the reduction projection, the resist on the material 10 is exposed, and the projection figure 11 is transferred to the resist. Therefore, a desired pattern can be drawn on the material 10 by controlling the shape, size, position, and exposure time of the projected figure 11. The projection figure 11 controlled in this way is exposed, or the projection figure 11 itself is called a shot.

  A shaping deflector 1012 is used to control the shape and dimensions of the projection figure 11. The shaping deflector 1012 deflects the electron beam 1, and a figure (the figure generated by the overlap between the image of the opening of the first shaping aperture plate 1003 on the second shaping aperture plate 1007 and the opening of the second shaping aperture plate 1007). This is a deflector for changing the shape and dimension of the cross section of the electron beam 1.

  In order to control the position of the projection figure 11, an objective deflector 1013 and a material stage (not shown) are used in combination. Since there is a limit to the deflectable region, that is, the deflection field of the objective deflector 1013, first, the material 10 is moved by the material stage, a large step positioning is performed, and then the electron beam 1 is deflected by the objective deflector 1013. Perform small positioning of.

The limitation of the deflection field depends on the rated output of the amplifier, the deflection sensitivity of the objective deflector 1013 (the deflection distance per unit applied voltage at the height of the material 10), and the allowable deflection aberration. The deflection field is preferably large in order to improve the drawing throughput. This is because the movement speed of the material stage is slower than the deflection speed of the objective deflector 1013, and the number of movements of the material stage is inversely proportional to the square (area) of the size of the deflection field.

  Blankers 1014 and 1015 are used to control the exposure time of the projected figure 11. The blankers 1014 and 1015 are deflectors for deflecting the electron beam 1 and blocking (blanking) the electron beam 1.

The exposure time of the projected figure 11 is called a shot time. The shot time is determined by dividing the necessary exposure [μC / cm ² ] by the beam current density on the material 10, that is, the current density [A / cm ² ] of the projection pattern 11. That is, the shot time is inversely proportional to the current density of the projected figure 11. In order to improve the drawing throughput, it is preferable to shorten the shot time by increasing the current density of the projected figure 11.

  Here, the necessary exposure amount is an exposure amount at which the dimension of the figure transferred to the resist on the material 10 becomes equal to a desired value. Further, the current density of the projected figure 11 is expressed by the following equation (1), where B is the brightness of the electron gun and ψ is the opening angle of the electron beam 1 on the material 10.

J = πBψ ² (1)

  Hereinafter, important problems in the development of the variable shaped electron beam drawing apparatus will be described. This important issue is to increase the throughput and resolution of the variable shaped electron beam drawing apparatus. Both of these are not easy and require careful consideration.

  First, in order to increase the throughput of the variable shaped electron beam drawing apparatus, it is preferable to increase the current density J of the projection figure 11 and increase the deflection field of the objective deflector 1013 as described above.

  In order to increase the current density J of the projected figure 11, as can be seen from the equation (1), the brightness B of the electron gun is increased, or the opening angle ψ of the electron beam 1 on the material 10 is increased.

  However, it is necessary to pay attention to aberrations (axial aberrations and deflection aberrations seen on the material 10) that increase with the opening angle ψ. This is because these aberrations cause beam blur on the material 10 and reduce the resolution. From this point of view, in order to increase the current density J of the projected figure 11, it is required to increase the luminance B instead of increasing the opening angle ψ.

  On the other hand, in order to increase the deflection field of the objective deflector 1013, the deflection voltage or the deflection sensitivity applied to the objective deflector 1013 may be increased. However, in that case, it is necessary to pay attention to the response speed of the amplifier that drives the objective deflector 1013. This is because when the rated voltage of the amplifier that drives the objective deflector 1013 is increased, the response speed of the amplifier is decreased. From this point of view, in order to expand the deflection field of the objective deflector 1013, it is required to increase the deflection sensitivity instead of increasing the deflection voltage of the objective deflector 1013.

In order to expand the deflection field of the objective deflector 1013, in addition to the deflection aberration accompanying the deflection of the electron beam 1 by the objective deflector 1013, that is, distortion aberration, field curvature aberration, astigmatism, coma aberration, and chromatic aberration, It is necessary to keep in mind. This is because these deflection aberrations reduce the drawing accuracy. More specifically, among these deflection aberrations, distortion aberration causes the positional deviation of the electron beam 1 on the material 10 and reduces the positional accuracy. Further, the field curvature aberration, astigmatism, coma aberration, and chromatic aberration contribute to the blurring of the electron beam 1 and reduce the resolution. In general, a variable shaped electron beam drawing apparatus corrects (removes) distortion, field curvature, and astigmatism among these aberrations in order to improve positional accuracy and resolution.

  The correction of these aberrations does not reduce the correction object, that is, the aberration itself, but generates deflection (positional deviation) or aberration (blur) of the same size but opposite direction, thereby becoming the correction object. This is done by canceling out the aberration. More specifically, the distortion aberration is corrected by the positional deviation generated by superimposing the distortion correction voltage on the deflection voltage, and the field curvature aberration is applied to the focus correction device (not shown). Thus, astigmatism is corrected by the astigmatism generated by applying an astigmatism correction voltage to an astigmatism corrector (not shown).

  Here, the focus corrector is a cylindrical electrode provided in the magnetic field of the reduction lens 1008 or the objective lens 1009, that is, an electrostatic corrector. The focus is corrected by the focus corrector because the electron beam 1 is accelerated or decelerated as a result of voltage application to the focus corrector, and the intensity of the lenses 1008 and 1009 with respect to the electron beam 1 changes. Further, the astigmatism corrector is an electrostatic multipole as in the case of the objective deflector 1013. The reason why these correctors are electrostatic is to have these correctors have a response speed equivalent to that of the objective deflector 1013.

  Next, in order to increase the resolution of the variable shaped electron beam writing apparatus, the above problem, in addition to the blur due to the deflection aberration, the blur on the axis, that is, the blur in the state where the electron beam 1 is not deflected. Need to be reduced. For this purpose, the Coulomb effect in the section from the first molded aperture plate 1003 to the material 10 (suppression of the electron beam 1 due to the Coulomb force acting between electrons) is suppressed, and the axial aberration related to the objective lens 1009 That is, it is required to reduce spherical aberration and longitudinal chromatic aberration.

  In order to suppress the Coulomb effect in the section from the first molded aperture plate 1003 to the material 10, the optical path length in the section may be shortened. On the other hand, in order to reduce the above-described axial aberration, the distance from the main surface of the objective lens 1009 to the material 10 may be reduced in order to reduce the spherical aberration coefficient and the axial chromatic aberration coefficient of the objective lens 1009.

  However, when the distance from the main surface of the objective lens 1009 to the material 10 is reduced, the deflection sensitivity of the objective deflector 1013 is reduced and the deflection field is reduced. As a result, the drawing throughput decreases. Therefore, it is required to increase the deflection sensitivity of the objective deflector 1013 in order to secure the deflection field while reducing the distance. In order to satisfy this requirement, the length of the objective deflector 1013 may be increased or the inner diameter thereof may be decreased. However, as described above, since the optical path length is shortened to reduce the Coulomb effect, the length of the objective deflector 1013 is limited accordingly. Therefore, in order to satisfy this requirement, it is required to reduce the inner diameter of the objective deflector 1013 instead of increasing the length.

  However, when the inner diameter of the objective deflector 1013 is reduced, the higher-order component of the potential in the objective deflector 1013, that is, the potential n-order component related to the integer n of 2 or more is increased. The potential n-order component causes n-fold astigmatism and causes m-fold astigmatism with respect to the integer m satisfying 2 ≦ m ≦ n−1. These astigmatisms contribute to the blur of the electron beam 1 and reduce the resolution.

As described above, the potential n-order component increases as the inner diameter of the objective deflector 1013 decreases, because the potential n-order component is inversely proportional to the n-th power of the inner diameter of the objective deflector 1013. The potential n-order component is also proportional to the electrode applied voltage, proportional to the nth power of the radius from the center of the objective deflector 1013, and has a period of 2π / n in the circumferential direction.

  Here, the n-fold astigmatism is an aberration that draws an n-fold symmetry, that is, an aberration figure with a 2π / n period. As an example, FIG. 15 shows two-fold astigmatism and three-fold astigmatism aberration diagrams in a state in which the observation surface, that is, the surface defining the aberration diagram is displaced from the image plane. FIG. 15A is an aberration diagram of two-fold astigmatism, and FIG. 15B is a three-fold astigmatism diagram.

  These aberration diagrams are circular when the observation surface is coincident with the image plane, that is, when Δz = 0, but are n-fold symmetric when they are not coincident, that is, when Δz ≠ 0. Here, Δz represents the distance from the image plane of the observation plane. As can be seen from FIG. 15, these figures are apparently turned in the circumferential direction by the sign of Δz.

  Conventionally, as the astigmatism of n times in the variable shaped electron beam writing apparatus, the astigmatism of 2 times is a problem, and n times of astigmatism related to n of 3 or more can be ignored. For this reason, the n-fold astigmatism that has been conventionally corrected in the variable shaped electron beam drawing apparatus is the 2-fold astigmatism. Among the n-fold astigmatisms, low-order ones are likely to be problematic because the potential n-th order component is inversely proportional to the n-th power of the deflector inner diameter as described above and the radius from the center of the deflector ( Is proportional to the nth power of the deflection), that is, proportional to the ratio of the radius from the deflector center to the deflector inner diameter.

  However, in recent years, not only the two-fold astigmatism but also the n-fold astigmatism related to n of 3 or more is reduced to such an extent that the inner diameter of the objective deflector 1013 cannot be ignored. It has become necessary to increase the ratio of the radius from the center of 1013. This is because the demand for the drawing throughput and the resolution of the variable shaped electron beam drawing apparatus has increased as a result of the progress in scale and miniaturization of semiconductor devices.

  In principle, n-th astigmatism can be corrected by a 4n-pole astigmatism corrector. For example, 2-fold astigmatism can be corrected by an 8-pole astigmatism corrector, and 3-fold astigmatism can be corrected by a 12-pole astigmatism corrector. However, in order to apply such an astigmatism corrector to the optical system shown in FIG. 14, it is necessary to provide a spatial margin for that purpose before or after the objective deflector 1013. Such a spatial margin prevents the optical path length from being shortened for higher resolution.

  In order to correct the astigmatism n times without providing a new astigmatism corrector, the objective deflector may be used also as an astigmatism corrector.

  For example, Patent Document 2 discloses a technique in which an objective deflector also serves as an astigmatism corrector twice. More specifically, the method described in Patent Document 2 performs twice astigmatism correction by superimposing a twice astigmatism correction signal on a deflection signal applied to the objective deflector. However, at that time, the focus correction is also performed by superimposing the focus correction signal together. According to this method, not only the focus corrector and the astigmatism corrector itself but also an amplifier for driving them becomes unnecessary.

  Further, for example, Patent Document 3 discloses a technique in which one octupole or 12 pole astigmatism corrector (magnetic field type) is responsible for both twice and three times astigmatism correction. More specifically, the method described in Patent Document 3 sets the control parameters for astigmatism correction twice or three times as the quadrupole or hexapole field, that is, the strength and phase angle of the second or third magnetic component. Direction).

JP 2007-67192 A JP-A-1-258347 JP 2002-42707 A

  If the objective deflector 1013 is, for example, an octupole deflector, the technique described in Patent Document 2 may be used to perform only two astigmatism corrections. However, another means is required to perform astigmatism correction three times by the objective deflector 1013 shown in FIG.

  As such means, it is conceivable to apply the method described in Patent Document 3 to the objective deflector 1013. However, the technique described in Patent Document 3 is intended to be applied to an electron microscope, not an electron beam drawing apparatus, and therefore requires a function of acquiring a microscope image. More specifically, the method described in Patent Document 3 refers to the optimum values of the intensity and the phase angle, that is, these values that minimize the astigmatism twice or three times by trial and error while referring to a microscope image. I needed to find it. In addition, the object of the method described in Patent Document 3 is only an astigmatism corrector. For this reason, it has not been shown what kind of problem occurs and what kind of countermeasure is required when performing astigmatism correction three times after deflecting the electron beam.

  According to the detailed study of the present inventors, in such a case, a new aberration is generated as a by-product. Accordingly, a device for suppressing or correcting such aberration is required.

  The present invention has been made in view of the above problems, and one of the objects according to some aspects of the present invention is to correct astigmatism after deflecting a charged particle beam. Another object of the present invention is to provide a charged particle beam deflection apparatus that can suppress the occurrence of new aberrations.

(1) A charged particle beam deflection apparatus according to the present invention comprises:
An electrostatic or magnetic multipole;
A controller for applying a deflection signal for deflecting a charged particle beam to the multipole;
Including
The controller is
n times astigmatism correction signal for canceling n times astigmatism (n = 2, 3,..., N, N is an integer of 3 or more) is superimposed on the deflection signal;
.., N-1 times astigmatism generated by superimposing the n times astigmatism correction signal for each deflection coordinate on which the charged particle beam deflected by application of the deflection signal is incident. 2, 3,..., N-1 times astigmatism correction signal is superimposed on the deflection signal.

  According to such a charged particle beam deflection apparatus, when the astigmatism correction signal is superimposed n times on the deflection signal in order to reduce the blur (aberration) of the charged particle beam, 2, 3,. .., occurrence of n-1 astigmatism can be suppressed. That is, it is possible to suppress the occurrence of new aberrations (2, 3,..., N−1 times astigmatism) when correcting the n times astigmatism after deflecting the charged particle beam. . Thereby, the blur of the charged particle beam does not become large due to 2, 3,..., N-1 times astigmatism. Therefore, when the n-time astigmatism correction signal for minimizing the n-time astigmatism is determined for each deflection coordinate, the n-time astigmatism correction signal is determined 2, 3,..., N-1 times. Not disturbed by astigmatism.

(2) In the charged particle beam deflection apparatus according to the present invention,
An angle around the central axis of the multipole representing the position of each pole of the multipole is θ,
Two components constituting the n-time astigmatism correction signal are V _nA and V _nB ,
Distribution functions representing voltage distribution for each electrode of the multipole element or current distribution for each coil of the multipole element with respect to the V _nA and the V _nB are expressed as f _nA (θ) and f _nB , respectively.
(Θ)
The controller is
Using V _nA and V _nB as parameters, and superimposing V _n (θ) = V _nA f _nA (θ) + V _nB f _nB (θ) as the n-time astigmatism correction signal, The values of V _nA and V _nB may be determined for each deflection coordinate, and V _n (θ) into which the determined V _nA and V _nB are substituted may be used as the n-time astigmatism correction signal.

(3) In the charged particle beam deflection apparatus according to the present invention,
The potential n-order component or magnetic potential n-order component generated according to the V _nA and the potential n-order component or magnetic potential n-order component generated according to the V _nB may be orthogonal to each other.

(4) In the charged particle beam deflection apparatus according to the present invention,
The 2, 3, ..., n-1 astigmatism correction signals for canceling the 2, 3, ..., n-1 astigmatism generated by the superposition of the n times astigmatism correction signals. , M times astigmatism correction signal (m = 2, 3,..., N−1),
When the two components constituting the m-time astigmatism correction signal are V _mA and V _mB ,
The controller is
2,3 generated according to a predetermined variation [Delta] V _nA of the _{V nA,} ···, n-1 times for canceling each of the astigmatism, the two components _{V mA} of the m-fold astigmatism correction signal And the ratio ρ _mAnA and ρ _{mBnA of the} amount of change in V _{mB to} the ΔV _nA ,
2,3 generated according to a predetermined variation [Delta] V _nB of the _{V nB,} ···, n-1 times for canceling each of the astigmatism, the two components _{V mA} of the m-fold astigmatism correction signal And a ratio ρ _mAnB and ρ _mBnB of the change amount of V _{mB to} the ΔV _nB are determined for each deflection coordinate,
The ratio _{ρ mAnA, ρ mBnA, ρ mAnB} , and [rho _MBnB and the _{V nA} and the product [rho _MANA V _nA of said _{V nB} for each of the deflection _{coordinates, ρ mBnA V nA, ρ mAnB} V nB, and _ρ mBnB V _nB To calculate
Laminate _{ρ mAnA V nA, ρ mBnA V} nA, ρ mAnB V nB, and _ρ mBnB V sum of _{nB ρ mAnA V nA + ρ mAnB} V nB, and _{ρ mAnB V nB + ρ mBnB V} nB, wherein m times astigmatic correction The two components V _mA and V _mB of the signal may be used.

(5) In the charged particle beam deflection apparatus according to the present invention,
The control unit distributes the voltage distribution to each electrode of the multipole element or the current distribution to each coil of the multipole element with respect to the n-th astigmatism correction signal, except for the case of n = N, the n-th astigmatism correction signal. , N-order components, or magnetic potentials n + 1, n + 2,..., N-order components may be suppressed.

(6) In the charged particle beam deflection apparatus according to the present invention,
The controller may determine a distortion correction signal for canceling the distortion aberration after determining the n-time astigmatism correction signal.

(7) In the charged particle beam deflection apparatus according to the present invention,
When ΔV _1An and ΔV _1Bn are two components constituting a distortion correction signal for canceling distortion aberration generated in response to the n-th astigmatism correction signal among the distortion correction signals,
The controller is
Two components ΔV _1AnA and ΔV _1BnA constituting a distortion correction signal for canceling distortion aberration generated according to V _nA ;
Two components ΔV _1AnB and ΔV _1BnB constituting a distortion correction signal for canceling distortion aberration generated according to V _nB are determined for each deflection coordinate,
Four components of the distortion correction signal ΔV _1AnA , ΔV _1BnA , ΔV _1AnB , and ΔV _{1B
From nB} , the sum ΔV _1AnA + ΔV _1AnB and ΔV _1BnA + ΔV _1BnB of two components for correcting distortion aberration in the same direction are calculated,
The sums ΔV _1AnA + ΔV _1AnB and ΔV _1BnA + ΔV _1BnB of the two components may be _used as the two components ΔV _1An and ΔV _1Bn of the distortion correction signal, respectively.

(8) In the charged particle beam deflection apparatus according to the present invention,
The controller is
The variable range of the deflection coordinates is a deflection field,
For canceling the distortion aberration generated in accordance with a predetermined change amount [Delta] V _nA of the _{V nA,} the change amount of the two components [Delta] V _1A and [Delta] V _1B of the distortion correction signal, and the ratio [rho _1AnA and [rho _1BnA for the [Delta] V _nA,
For canceling the distortion aberration generated in accordance with a predetermined change amount [Delta] V _nB of the _{V nB,} the change amount of the two components [Delta] V _1A and [Delta] V _1B of the distortion correction signal, and a ratio [rho _1AnB and [rho _1BnB for [Delta] V _nB ,
Measured at deflection coordinate points of predetermined n (n + 1) / 2 points or more included in the deflection field,
By interpolating the measured values of the ratios ρ _1AnA , ρ _1BnA , ρ _1AnB , and ρ _1BnB , the ratios ρ _1AnA , ρ _1BnA , in each deflection coordinate to which the values of V _nA and V _nB are allocated, determine the values of ρ _1AnB , and ρ _1BnB ,
The ratio _{ρ 1AnA, ρ 1BnA, ρ 1AnB} , and [rho value of _1BnB, the _{V nA} and the product ρ _1AnA V _nA between the value of the _{V nB, ρ 1BnA V nA,} ρ 1AnB V nB, and ρ _1BnB V _nB To calculate
The _products ρ _1AnA V _nA , ρ _1BnA V _nA , ρ _1AnB V _nB , and ρ _1BnB V _nB are also _used as the four components ΔV _1AnA , ΔV _1BnA , ΔV _1AnB , and _B of the distortion correction signal, respectively.

(9) In the charged particle beam deflection apparatus according to the present invention,
The controller is
The deflection field is divided into a plurality of sections, and the n-th astigmatism correction signal for the coordinates of the point representing the section and a distortion correction signal for distortion aberration generated by the n-th astigmatism correction are assigned to each section. ,
The coordinates and size of each of the sections may be common to the n times astigmatism correction signal and the distortion correction signal.

(10) In the charged particle beam deflection apparatus according to the present invention,
The control unit may determine the N, N-1,..., Twice astigmatism correction signals in the order of N, N-1,.

(11) In the charged particle beam deflection apparatus according to the present invention,
The control unit may repeat the determination of the value of the component constituting the N, N-1,..., Twice astigmatism correction signal until the value converges.

The figure which shows typically the structure of the variable shaping | molding electron beam drawing apparatus which concerns on this embodiment. The figure which shows the structure of the objective deflector of the variable shaping electron beam drawing apparatus of this embodiment. The figure which shows the distribution function showing the electrode voltage distribution of the objective deflector of this embodiment. Table showing an and b _n for _n from 0 to 7. 5 is a flowchart showing an example of a flow of aberration correction in the present embodiment. The figure which shows typically the structure of the variable shaping | molding electron beam drawing apparatus which concerns on this embodiment. The figure which shows the structure of the objective deflector of the variable shaping electron beam drawing apparatus of a 1st modification. The figure which shows the distribution function showing the electrode voltage distribution of the objective deflector of a 1st modification. The figure which shows the structure of the objective deflector of the variable shaping electron beam drawing apparatus of a 2nd modification. The figure which shows the distribution function showing the electrode voltage distribution of the objective deflector of a 2nd modification. The figure which shows the distribution function showing the electrode voltage distribution of the objective deflector of a 3rd modification. The figure which shows the structure of the variable shaping electron beam drawing apparatus which concerns on a 6th modification. The flowchart which shows an example of the flow of the aberration correction in the 7th modification. The figure which shows typically the structure of the conventional variable shaping | molding electron beam drawing apparatus. The figure which shows the aberration figure of (a) 2 times astigmatism and (b) 3 times astigmatism.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. The embodiments described below do not unduly limit the contents of the present invention described in the claims. In addition, not all of the configurations described below are essential constituent requirements of the present invention.

1. Configuration of Variable Shaped Electron Beam Drawing Apparatus First, a variable shaped electron beam drawing apparatus according to this embodiment will be described with reference to the drawings. FIG. 1 is a diagram schematically illustrating a configuration of a variable shaped electron beam drawing apparatus 100 according to the present embodiment.

  The variable shaped electron beam drawing apparatus 100 includes a charged particle beam deflection apparatus according to the present invention. Here, the case where the charged particle beam deflection apparatus according to the present invention is the charged particle beam deflection apparatus 100a according to the present embodiment will be described.

  As shown in FIG. 1, the variable shaped electron beam drawing apparatus 100 includes an irradiation lens 2, a first shaped aperture plate 3, an electron beam supply unit 4, a shaped lens 6, a second shaped aperture plate 7, a reduction lens 8, The objective lens 9, the shaping deflector 12, the blankers 14 and 15, the blanking aperture plate 17, the material stage 30, and the charged particle beam deflecting device 100a are configured. The charged particle beam deflecting device 100a includes an objective deflector 13, a knife edge 18, a current detector (Faraday cup) 19, a drive amplifier 20, a control device (control unit) 21, and a storage device (storage unit) 22. It consists of

  In the illustrated example, the optical system 101 of the variable shaped electron beam drawing apparatus 100 includes an irradiation lens 2, a first shaped aperture plate 3, an electron beam supply unit 4, a shaped lens 6, a second shaped aperture plate 7, and a reduction lens. 8, an objective lens 9, a shaping deflector 12, an objective deflector 13, blankers 14 and 15, and a blanking aperture plate 17. The components 14, 15, 2, 3, 12, 6, 7, 17, 8, 9 (and 13) of the optical system 101 are arranged in this order along the Z axis (in the traveling direction of the electron beam 1). Yes. In the illustrated example, it is assumed that the electron beam 1 travels in the positive direction of Z.

  The electron beam supply unit 4 emits the electron beam 1. The electron beam supply unit 4 is, for example, an electron gun. In the electron beam supply unit 4, a crossover 4a is formed. This crossover 4 a is a substantial light source of the optical system 101.

  The irradiation lens 2 is a lens that connects an image of a crossover (light source) 4 a, that is, an image 5 of the light source, below the first shaping aperture plate 3. The irradiation lens 2 is, for example, a magnetic field type electron lens.

The first molded aperture plate 3 has, for example, a rectangular aperture. The 1st shaping | molding aperture plate 3 makes the cross-sectional shape of the electron beam 1 rectangular shape by allowing the electron beam 1 to pass through this opening.

  The molded lens 6 is a lens for projecting an image of the first molded aperture plate 3 onto the second molded aperture plate 7. The molded lens 6 is, for example, a magnetic field type electron lens.

  The 2nd shaping | molding opening board 7 has a rectangular-shaped opening, for example. The second molded aperture plate 7 partially blocks the electron beam 1 due to the overlap between the image of the aperture of the first molded aperture plate 3 and the aperture of the second molded aperture plate 7, and the second molded aperture plate The cross-sectional shape of the electron beam 1 passing through the aperture 7 is changed.

  The reduction lens 8 and the objective lens 9 project onto the material 10 an image of a figure (logical product) generated by the overlap of the image of the opening of the first molded aperture plate 3 and the aperture of the second molded aperture plate 7. The optical system for this is comprised. The reduction lens 8 and the objective lens 9 are, for example, magnetic field type electron lenses.

  The shaping deflector 12 deflects the electron beam 1 that has passed through the first shaping aperture plate 3 in a two-dimensional direction. Thereby, the shaping deflector 12 can change the projection position of the image of the opening of the first shaping aperture plate 3 on the second shaping aperture plate 7. The shaping deflector 12 is a multipole, for example, a quadrupole deflector. The shaping deflector 12 is, for example, an electrostatic type. Thereby, the response speed can be increased and the drawing throughput can be improved.

  The objective deflector 13 controls the projection position on the material 10 by deflecting the electron beam 1 in a two-dimensional direction within the objective lens 9. The objective deflector 13 is a multipole element, for example, an octupole deflector. The objective deflector 13 is, for example, an electrostatic type for the purpose of increasing the response speed.

  FIG. 2 is a diagram showing a configuration of the objective deflector 13 and is an XY sectional view of the objective deflector 13. Note that the X axis and the Y axis are orthogonal to each other, and the X axis and the Y axis are orthogonal to the Z axis, respectively.

  As shown in FIG. 2, the center of the objective deflector 13 is on the Z axis. The objective deflector 13 is composed of a conductive hollow cylinder equally divided into eight at intervals of π / 4 (45 °). When the angle around the Z-axis (circumferential direction) is θ, the eight-pole electrode of the objective deflector 13 has E1 to E8 in order counterclockwise from the electrode positioned at θ = 0 (0 °). Assign a name. However, the positions (angles) of the electrodes E1 to E8 are the center positions of the electrodes E1 to E8. For example, the positions of the electrode E1 and the electrode E2 are 0 and π / 4, respectively, from FIG. In FIG. 2, the positive direction of Z is the front direction from the paper surface. That is, the electron beam 1 travels in that direction.

  A voltage (analog amount) output from the drive amplifier 20 is applied to each of the electrodes E1 to E8. Different voltages can be applied to the electrodes E1 to E8, and the drive amplifier 20 is provided for each of the electrodes E1 to E8 of the objective deflector 13. That is, a total of eight drive amplifiers 20 are provided.

  The output (digital quantity) of the control device 21 is input to each drive amplifier 20. The output of the control device 21 is a result of the control device 21 reading data (digital quantity) stored in the storage device 22 and performing a predetermined calculation on the data.

The blankers 14 and 15 are deflectors for deflecting the electron beam 1 and blocking (blanking) the electron beam 1. The blankers 14 and 15 are also electrostatic deflectors for the purpose of increasing the response speed, similarly to the shaping deflector 12 and the objective deflector 13. However, since the deflection direction by the blankers 14 and 15 may be a one-dimensional direction, the number of poles of the blankers 14 and 15 is, for example, two.

  The knife edge 18 is mounted on the material stage 30. More specifically, the knife edge 18 is provided in a region different from the region where the material 10 is mounted.

  The current detector (Faraday cup) 19 detects the current of the electron beam 1. The current detector 19 is mounted on the material stage 30. More specifically, the current detector 19 is provided below the knife edge 18.

  Prior to drawing on the material 10, the knife edge 18 and the current detector 19 measure the size and position of the electron beam 1 used for drawing or the blur of the electron beam 1 by the knife edge method, and based on the measurement result. And used to adjust the electron beam 1. Here, the knife edge method refers to the electron beam 1 from the current waveform (waveform of the beam current flowing into the current detector 19 without being blocked by the knife edge 18) obtained when the knife edge 18 is scanned by the electron beam 1. A technique for quantifying the size, position, beam blur, etc.

  The control device 21 performs processing for controlling the objective deflector 13. Specifically, the control device 21 uses the objective signal based on the deflection signal, distortion correction signal, focus correction signal, two-time astigmatism correction signal, and three-time astigmatism correction signal stored as digital data in the storage device 22. The applied voltage for each of the electrodes E1 to E8 of the deflector 13 is determined. Further, the control device 21 determines a deflection signal, a distortion correction signal, a focus correction signal, a two-time astigmatism correction signal, and a three-time astigmatism correction signal based on the measurement result by the knife edge method. The function of the control device 21 can be realized by, for example, hardware (dedicated circuit) or a personal computer (PC).

  The storage device 22 stores programs, data, and the like for the control device 21 to perform various calculation processes and control processes. This includes a deflection signal, a distortion correction signal, a focus correction signal, a two-time astigmatism correction signal, and a three-time astigmatism correction signal determined by the control device 21. The storage device 22 is also used as a work area for the control device 21 for temporarily storing calculation results and the like.

  The material stage 30 can move the material 10. For example, the material stage 30 can move the material 10 in a certain step in accordance with exposure and drawing. The material stage 30 can move the knife edge 18 and the current detector (Faraday cup) 19.

2. Operation of Variable Shaped Electron Beam Drawing Apparatus Next, the operation of the variable shaped electron beam drawing apparatus 100 will be described. However, first, exposure and drawing operations will be described as basic operations, and then deflection and correction operations will be described as operations characterizing the apparatus.

  First, the electron beam 1 is irradiated onto the first shaped aperture plate 3 through the irradiation lens 2 as shown in FIG. As a supply source of the electron beam 1, that is, a light source, a crossover 4a formed in an electron gun may be considered. An image 5 of a light source is formed under the first shaping aperture plate 3. The image of the light source in the optical system 101 including the image 5 of the light source is connected to the position where the light beams represented by the dotted lines in FIG. 1 intersect.

  Next, an image of the first molded aperture plate 3 is projected onto the second molded aperture plate 7 by the molded lens 6. Including this image, the image of the aperture of the shaped aperture plates 3 and 7 in the optical system 101 is connected to the position where the light beams represented by the solid lines in FIG. 1 intersect.

  An image of a figure (logical product) generated by the overlap of the image of the opening of the first molded aperture plate 3 and the aperture of the second molded aperture plate 7 is converted into a resist (photosensitive material) by the reduction lens 8 and the objective lens 9. ) Is projected onto the coated material 10. That is, the material 10 is exposed.

  As a result, the resist is exposed. That is, the projected figure 11 is transferred to the resist on the material 10. Therefore, a desired pattern can be drawn on the material 10 by controlling the shape, size, position, and exposure time of the projected figure 11.

  A shaping deflector 12 is used to control the shape and dimensions of the projection figure 11. If the electron beam 1 is deflected by the shaping deflector 12, the shape and size of the figure generated by the overlap change, and the shape and size of the projection figure 11 also change.

  In order to control the position of the projection figure 11, the objective deflector 13 and the material stage 30 in the charged particle beam deflection apparatus 100a are used in combination. Among these, first, the material 10 is moved by the material stage 30 to perform positioning with a large step, and then the electron beam 1 is deflected by the objective deflector 13 to perform positioning with a small step.

  Blankers 14 and 15 are used to control the exposure time of the projected figure 11. While the blankers 14 and 15 are not operated, the electron beam 1 is incident on the material 10 and the material 10 is exposed. However, when the blankers 14 and 15 are operated, the electron beam 1 is interrupted halfway and the material 10 is not exposed. . That is, the exposure time is the time from once releasing the operation of the blankers 14 and 15 to starting again. Here, the operation of the blankers 14 and 15 interrupts the electron beam 1 as a result of the deflection of the electron beam 1 by the operation of the blankers 14 and 15 so that the image 16 of the light source is in the non-opening portion of the blanking aperture plate 17. By entering.

  The charged particle beam deflecting device 100a deflects the electron beam 1 by the objective deflector 13, and also provides distortion aberration, field curvature aberration, 2-fold astigmatism, and 3-fold astigmatism accompanying the deflection by the objective deflector 13. In order to remove, distortion correction, field curvature correction, twice astigmatism correction, and three times astigmatism correction are performed. These corrections are performed by superimposing a distortion correction voltage, a focus correction voltage, a two-fold astigmatism correction voltage, and a three-fold astigmatism correction voltage on the deflection voltage applied to the objective deflector 13, that is, adding these voltages. By applying this to the objective deflector 13.

  For this purpose, the charged particle beam deflection apparatus 100a firstly stores the deflection signal, distortion correction signal, and focus correction stored in the storage device 22 as digital data for each deflection coordinate (incidence position of the electron beam 1 on the material 10). The signal, the two-fold astigmatism correction signal, and the three-fold astigmatism correction signal are input to the control device 21. Then, the control device 21 performs multiplication and addition operations on these signals for each of the electrodes E1 to E8 of the objective deflector 13, and outputs a digital amount calculation result V (θ) to the drive amplifier 20. Then, the drive amplifier 20 converts V (θ) from digital to analog, and outputs an analog amount of electrode voltage V (θ) (vs. ground voltage) to the objective deflector 13. As a result, the electron beam 1 is deflected to a predetermined deflection coordinate, and the electron beam 1 is subjected to distortion correction, field curvature correction, twice astigmatism correction, and three times astigmatism correction. However, V (θ) represents a voltage distributed (applied) to the electrodes located at the angle θ, that is, the electrodes E1 to E8. Hereinafter, all the signals and voltages are treated as voltages. That is, no distinction is made between digital quantities and analog quantities.

  The correction voltage stored in the storage device 22 is determined by the control device 21 for each finite number of measurement points in the deflection field. The correction voltage is determined based on beam blur measurement (knife edge method) by scanning the knife edge 18 with the electron beam 1. Details of the determination of the correction voltage will be described later.

Of the deflection voltage and the correction voltage stored in the storage device 22, the deflection voltage is two components of V _1A and V _1B (X and Y components, respectively), and the distortion correction voltage is two components of ΔV _1A and ΔV _1B (X and Y, respectively). Y component), a component of the focus correction voltage _{V 0A,} the two components of the 2-fold astigmatism correction voltage _{V 2A} and _{V 2B,} astigmatic correction voltage 3 times consists of two components _{V 3A} and _{V 3B.} Of these, the deflection voltage and the distortion correction voltage are each composed of two components. The X and Y components of deflection are generated from the two components, and these are linearly combined to perform omnidirectional deflection and correction. This is because of the purpose of applying. In addition, the two-time and three-time astigmatism correction voltages are composed of two components, respectively, by generating two components of two and three times astigmatism from each of the two components, and by linearly combining them, This is for the purpose of performing astigmatism correction twice and three times. In the following description, for the sake of convenience, these voltage components are simply referred to as voltages unless particularly required.

The electrode voltage V (θ) includes deflection voltage V ₁ (θ) = V _1A f _1A (θ) + V _1B f _1B (θ), distortion correction voltage ΔV ₁ (θ) = ΔV _1A f _1A (θ) + ΔV _1B f _1B (θ), focus correction voltage V ₀ (θ) = V _0A f _0A (θ), twice astigmatism correction voltage V ₂ (θ) = V _2A f _2A (θ) + V _2B f _2B (θ), and Three-time astigmatism correction voltage V ₃ (θ) = V _3A f _3A (θ) + V _3B f _3B (θ) is the total sum. That is, V (θ) = V ₁ (θ) + ΔV ₁ (θ) + V ₀ (θ) + V ₂ (θ) + V ₃ (θ). As shown in FIG. 1, the control device 21 performs an operation based on these mathematical expressions in order to output V (θ).

In the above formula, f _1A (θ) and f _1B (θ) are deflection voltages, f _0A (θ) is a focus correction voltage, and f _2A (θ) and f _2B (θ) are twice astigmatism correction voltages. F _3A (θ) and f _3B (θ) are distribution functions representing the electrode voltage distribution of the three-fold astigmatism correction voltage. More specifically, these distribution functions are the dimensionless voltages (vs. ground voltage) distributed to the electrodes E1 to E8 located at the angle θ. Of these, f _1A (θ) and f _1B (θ) are common to the deflection voltage and the distortion correction voltage.

FIG. 3 shows distribution functions f _1A (θ), f _1B (θ), f _0A (θ), f _2A (θ), f _2B (θ), f _3A (θ), and f _3B (θ), It is a figure shown with the XY cross section of the objective deflector. In FIG. 3, symbols f _1A , f _1B , f _0A , f _2A , f _2B , f _3A , and f _3B written near the center of the objective deflector 13 represent the distribution functions, and The numbers attached to the electrodes represent the values of these distribution functions at each electrode.

For convenience, among the distribution functions, f _1A (θ), f _2A (θ), and f _3A (θ) are listed in the respective electrodes, as shown in FIG. 3, f _1A (0) = 1, f _1A (π / 4) = 1 / √2, f _1A (π / 2) = 0, f _1A (3π / 4) = − 1 / √2, f _1A (π) = − 1, f _1A (5π / 4) = − 1 / √2, f _1A (3π / 2) = 0, f _1A (7π / 4) = 1 / √2, f _2A (0) = 1, f _2A (π / 4) = 0 , F _2A (π / 2) = − 1, f _2A (3π / 4) = 0, f _2A (π) = 1, f _2A (5π / 4) = 0, f _2A (3π / 2) = − 1 , F _2A (7π / 4) = 0, f _3A (0) = 1, f _3A (π / 4) = − 1 / √2, f _3A (π / 2) = 0, f _3A (3π / 4) = 1 / √2, f _3A (π) =-1, f _3A (5π / 4) = 1 / √2, f _3A (3π / 2) = 0, and f _3A (7π / 4) = − 1 / √2.

Among the distribution functions, the values of f _1A (θ), f _0A (θ), f _2A (θ), and f _3A (θ) at the respective electrode positions coincide with cos (nθ). That is, these distribution functions can be expressed as f _nA (θ) = cos (nθ), respectively, when θ is an integral multiple of π / 4 (f _nA (θ) intersects with cos (nθ)). Further, the values of f _1B (θ), f _2B (θ), and f _3B (θ) at the respective electrode positions coincide with sin (nθ). That is, these distribution functions can be expressed as f _nB (θ) = sin (nθ) = cos (nθ−π / 2) when θ is an integral multiple of π / 4, where f _nB (θ) is sin ( nθ)).

Therefore, there is a phase difference of π / 2 between f _nA (θ) and f _nB (θ). As will be described later, this phase difference is equal to the phase difference relating to the potential n-order component generated by the n-time astigmatism correction voltages V _nA and V _nB .

If all the above distribution functions are reflected in the electrode voltage V (θ) = V ₁ (θ) + ΔV ₁ (θ) + V ₀ (θ) + V ₂ (θ) + V ₃ (θ), the electrode voltage is as follows: It is expressed in

V _E1 = V (0) = V _1A + ΔV _1A + V _0A + V _2A + V _3A (2)
V _E2 = V (π / 4) = (V _1A + V _1B + ΔV _1A + ΔV _1B ) / √2 + V _0A + V _2B + (− V _3A + V _3B ) / √2 (3)
V _E3 = V (π / 2) = V _1B + ΔV _1B + V _0A −V _2A −V _3B (4)
V _E4 = V (3π / 4) = (− V _1A + V _1B −ΔV _1A + ΔV _1B ) / √2 + V _0A −V _2B + (V _3A + V _3B ) / √2 (5)
V _E5 = V (π) = − V _1A −ΔV _1A + V _0A + V _2A −V _3A (6)
V _E6 = V (5π / 4) = (− V _1A −V _1B −ΔV _1A −ΔV _1B ) / √2 + V _0A + V _2B + (V _3A −V _3B ) / √2 (7)
V _E7 = V (3π / 2) = − V _1B −ΔV _1B + V _0A −V _2A + V _3B (8)
V _E8 = V (7π / 4) = (V _1A −V _1B + ΔV _1A −ΔV _1B ) / √2 + V _0A −V _2B + (− V _3A −V _3B ) / √2 (9)

However, in the formulas (2) to (9), V _E1 , V _E2 , V _E3 , V _E4 , V _E5 , V _E6 , V _E7 , and V _E8 are electrodes E1, E2, E3, E4, E5, respectively. , E6, E7, and E8 (voltage against ground).

Electrode voltage V (θ) = V ₁ (θ) + ΔV ₁ (θ) + V ₀ (θ) + V ₂ (θ) + V ₃ (θ), that is, V _E1 , V _E2 , V _E3 , V _E4 , V _E5 , V _E6 , V _E7 , and V _E8 generate a potential n (≧ 0) order component (formula (11) below) that constitutes the potential in the objective deflector 13 (formula (10) below).

_{φ n (V E, r,} θ) = (a n / R n) V E r n cos (nθ) + (b n / R n) V E r n sin (nθ) ··· (11)
In equation (11), a _n and b _n are real coefficients, r is the center of the objective deflector 13, that is, the radius from the Z axis, R is the inner radius of the objective deflector 13, and V _E is the electrode voltage V _E1 , V _A value of any one of _E2 , V _E3 , V _E4 , V _E5 , V _E6 , V _E7 , and V _E8 is not zero. However, the coefficient a _n and b _n are the number of poles of the objective deflector 13 depends electrode voltage distribution, and the size and position of each electrode. The coefficients _{a n} and _{b n,} also, since although _{V E} depends on whether representing the voltage value of any of the electrode (non-zero), the coefficients _{a n} and _{b n} is inversely proportional to _{V E, φ n (V E} , r, θ) does not depend on this.

As can be seen from the equation (11), the potential n-order component φ _n is composed of two components, and each of the two components is inversely proportional to R _n and proportional to V, and r ⁿ cos (nθ) or r ⁿ sin ( nθ). That is, in the direction θ with proportional to r ⁿ has a period of 2 [pi / n. Further, as can be seen by substituting the equation (11) into a two-dimensional Laplace equation (see the following equation), φ _n is a solution of the two-dimensional Laplace equation.

  That is, equation (11) represents the distribution of potential n-order components that can appear inside the deflector that can be regarded as being sufficiently long in the Z-axis direction.

Coefficients _{a n} and _{b n} can be regarded as the Fourier coefficients of the dimensionless V (theta) was distribution function f (θ) = V (θ ) / V E. That is, the following relationship exists between these coefficients and f (θ).

This is because, firstly, φ (V _E , r, θ) in equation (10) matches the electrode voltage V (θ) when r = R (see the following equation), and secondly due to the fact that the equation (11) is likewise r = phi _n when _{R (V E, R, θ} ) = a n V E cos (nθ) + b n V E sin (nθ).

  However, V (θ) and f (θ) have values not only in the angle region corresponding to the electrode region but also in the angle region corresponding to the gap between the electrodes.

For these reasons, namely the coefficients a _n and b _n since it can be regarded as a Fourier coefficient of f (theta), these coefficients, the following equation (12), can be calculated if Nottore to the definition of the Fourier coefficients shown in equation (13) .

  However, when n = 0, these definitions are the following expressions (12 ′) and (13 ′), respectively.

The potential n-order component φ _n represented by the equation (11) can also be expressed as a superposition of n-order components derived from the deflection voltage, the focus correction voltage, the 2-fold astigmatism correction voltage, and the 3-fold astigmatism correction voltage. That is, φ _n is
φ _n =
(A _n1A / R ⁿ ) V _1A r ⁿ cos (nθ) + (b _n1A / R ⁿ ) V _1A r ⁿ sin (nθ)
+ (A _n1B / R ⁿ ) V _1B r ⁿ cos (nθ) + (b _n1B / R ⁿ ) V _1B r ⁿ sin (nθ)
+ (A _n0A / R ⁿ ) V _0A r ⁿ cos (nθ) + (b _n0A / R ⁿ ) V _0A r ⁿ sin (nθ)
^{_{+ (A n2A / R n)}} V 2A r n cos (nθ) + (b n2A / R n) V 2A r n sin (nθ)
^{_{+ (A n2B / R n)}} V 2B r n cos (nθ) + (b n2B / R n) V 2B r n sin (nθ)
+ (A _n3A / R ⁿ ) V _3A r ⁿ cos (nθ) + (b _n3A / R ⁿ ) V _3A r ⁿ sin (nθ)
^{_{+ (A n3B / R n)}} V 3B r n cos (nθ) + (b n3B / R n) V 3B r n sin (nθ)
= {(A _n1A V _1A + a _n1B V _1B + a _n0A V _0A + a _n2A V _2A
+ A _n2B V _2B + a _n3A V _3A + a _n3B V _3B ) / R ⁿ } r ⁿ cos (nθ)
+ {(B _n1A V _1A + b _n1B V _1B + b _n0A V _0A + b _n2A V _2A
+ B _n2B V _2B + b _n3A V _3A + b _n3B V _3B ) / R ⁿ } r ⁿ sin (nθ) (14)
It can also be expressed.

However, in the equation (14), the deflection voltages V _1A and V _1B include distortion correction voltages ΔV _1A and ΔV _1B , respectively. The coefficient _{a n1A} and _{b n1A, a n1B} and _{b n1B, a N0a} and _{b N0a, a n2A} and _{b n2A, a N2b} and _{b N2b, a N3A} and _{b N3A, a N3B} and _{b N3B} are _{respectively, V 1A , V 1B, V 0A, V} 2A, V 2B, V 3A, corresponding to _{a n} and _{b n} about _{V 3B.} As can be seen by comparing the equations (11) and (14) between these coefficients and voltage, and the coefficients a _n , b _n , and voltage V,
_{a n V E = a n1A V} 1A + a n1B V 1B + a n0A V 0A + a n2A V 2A + a n2B V 2B + a n3A V 3A + a n3B V 3B ··· (15)
_{b n V E = b n1A V} 1A + b n1B V 1B + b n0A V 0A + b n2A V 2A + b n2B V 2B + b n3A V 3A + b n3B V 3B ··· (16)
There is a relationship.

In the equations (15) and (16), V _E is any one of the electrode voltages V _E1 , V _E2 , V _E3 , V _E4 , V _E5 , V _E6 , V _E7 , and V _E8 as described above. , That is, the actual electrode voltage value, but V _1A , V _1B , V _0A , V _2A , V _2B , V _3A , and V _3B are control parameters and do not necessarily represent the actual electrode voltage value. Not represented. The relationship between these control parameters and the actual electrode voltage is the definition of the deflection voltage, the focus correction voltage, the twice astigmatism correction voltage, and the three times astigmatism correction voltage described above, that is, V ₁ (θ) = V _1A f _1A (θ) + V _1B f _1B (θ), V ₀ (θ) = V _0A f _0A (θ), V ₂ (θ) = V _2A f _2A (θ) + V _2B f _2B (θ), V ₃ ( θ) = V _3A f _3A (θ) + V _3B f _3B (θ) and the definition of the sum of these V (θ) = V ₁ (θ) + ΔV ₁ (θ) + V ₀ (θ) + V ₂ (θ) + V _{3 As} represented by (θ).

  Generalizing equations (14), (15), and (16) gives the following results.

  However, in the equations (14 '), (15'), and (16 '), N is the maximum number of n times astigmatism to be corrected. In this embodiment, N = 3.

Coefficients _{a n1A, b n1A, a n1B} , b n1B, a n0A, b n0A, a n2A, b n2A, a n2B, b n2B, a n3A, b n3A, a n3B, and _{b N3B} also coefficients _{a n} and b Similar to _n, it can be calculated according to the above definition, that is, the equations (12), (12 ′), (13), and (13 ′). However, at that time, the distribution function f (θ) corresponding to the coefficient to be obtained (subscripts are the same), that is, f _1A (θ), f _1B (θ), f _0A (θ), f _2A (Θ), f _2B (θ), f _3A (θ), or f _3B (θ).

Here, the distribution function f (θ) (= V ( θ) / V E) , as well as the coefficient _{a n} and _{b n,} or represents a voltage value of _{V E} is one of the electrodes E1~E8 (other than zero) Distribution function f _1A (θ), f _1B (θ), f _0A (θ), f _2A (θ), f _2B (θ), f _3A (θ), and f _3B (θ) , the coefficient _{a n1A, b n1A, a n1B} , b n1B, a n0A, b n0A, a n2A, b n2A, a n2B, b n2B, a n3A, b n3A, a n3B, and _{b N3B} also _{respectively, V 1A} , V _1B , V _0A , V _2A , V _2B , V _3A , and V _3B do not depend on which of the electrodes E1 to E8 represents a voltage value (other than zero). As described above, V _E represents the actual electrode voltage value, but V _1A , V _1B , V _0A , V _2A , V _2B , V _3A , and V _3B are control parameters, and are not necessarily actual parameters. By not representing the electrode voltage value. In other words, these distribution functions may be freely multiplied by a constant (other than zero). Where the coefficients a _n1A , b _n1A , a _n1B , b _n1B , a _n0A , b _n0A , a _n2A , b _n2A , a _n2B , b _n2B , a _n3A , b _n3A , a _n3B , and b _n values V _E is dependent on the multiplier at that time.

(12), (12 ′), (13) and (13 ′) a _n1A , b _n1A , a _n1B , b _n1B , a _n0A , b _n0A , a _n2A , b _n2A , a _n2B , b _{n2B, a n3A, b n3A,} among _{a N3B,} and _{b N3B,} those relating to n from 0 to 7, are shown in Table 1 of FIG.

However, 1A, 1B, 0A, 2A, 2B, 3A, and 3B in Table 1 indicate some of the subscripts of these coefficients. For example, a _11A is a ₁ obtained from f _1A (θ), and its value is 0.973. In the following, for convenience, these coefficients related to n of 8 or more will not be treated. Similarly, the potential n-order component and n-th astigmatism relating to n of 8 or more are ignored.

In the calculation of the coefficient, a gap is provided between the electrodes E1 to E8 on the assumption that the electrode dimensional error is zero, and the angle at which both ends of each gap are viewed from the center of the objective deflector 13 is 10 °, that is, the objective. The angle at which both ends of the electrodes E1 to E8 are viewed from the center of the deflector 13 is set to 35 °. Further, in an angle region corresponding to the gap between the electrodes E1 to E8, the distribution functions f _1A (θ), f _1B
(Θ), f _0A (θ), f _2A (θ), f _2B (θ), f _3A (θ), and f _3B (θ) were approximated to change linearly with respect to θ.

Under the above assumption, as can be seen from Table 1, although a zero number of coefficients, n = 1 and 7 relates to _{a n1A} and _b n1B, n = 0 regarding _{a n0A,} n = 2 and 6 about _{a n2A And} a _n3A and b _n3B for b _n2B , n = 3 and 5, have non-zero values. That is, V _1A and V _1B have a potential primary component φ ₁ and a seventh component φ ₇ , V _0A has a zero-order component φ ₀ , V _2A and V _2B have a secondary component φ ₂ and a sixth component φ ₆ , V _3A and V _3B generate a third-order component φ ₃ and a fifth-order component φ ₅ .

Except for b ₀ (by definition, zero), the reason why the coefficient becomes zero or does not become n by n is as a result of superposition of potential n-order components derived from each of the eight-pole electrodes E1 to E8. is there. However, if the electrode dimensional error is not zero contrary to the above assumption, among the coefficients whose values are zero in Table 1, those that are not zero may appear.

Similarly, as can be seen from Table 1, when V _2A and V _2B generate the potential secondary component φ ₂ , the potential tertiary component φ ₃ does not occur. Conversely, when V _3A and V _3B generate the potential tertiary component φ ₃ , the potential secondary component φ ₂ does not occur. In the present embodiment, among these, the former, ie phi ₂ of the generator with phi ₃ is important not to occur. In the present invention, when the n-time astigmatism correction voltages V _nA and V _nB generate the potential n-order component, the potentials n + 1, n + 2,..., N (N = 3 in the present embodiment) are also generated. It is important that no secondary components are generated. This will be described later.

Of the potential n-order components relating to n from 0 to 7, the potential zero-order component φ ₀ is focus correction, the primary component φ ₁ is deflected, the secondary component φ ₂ and the tertiary component φ ₃ are each twice and Used for 3 times astigmatism correction. That is, these four components are useful components in this embodiment.

On the other hand, the remaining components, that is, the potential seventh-order component φ ₇ , the sixth-order component φ ₆ , and the fifth-order component φ ₅ are unnecessary components, and n (= 7, 6, or 5) times generated by these three components and m (2 ≦ m ≦ n−1) astigmatism is a correction target of this embodiment. However, the necessity for these corrections depends on their size.

The Among the unnecessary components, potential seventh order component phi ₇ tends to become a problem. This is because the potential seventh-order component φ ₇ is a component that is primarily generated with application of the deflection voltages V _1A and V _1B . For the same reason, a potential n (≧ 2) order component φ _n (not reflected in Table 1) derived from an electrode dimensional error, which also occurs when the deflection voltages V _1A and V _{1B are} applied, is likely to be a problem. In an objective deflector machined with actual machining accuracy, the latter n (≧ 2) times rather than the n (= 7) times and m (2 ≦ m ≦ 6) times astigmatism produced by the former. And m (2 ≦ m ≦ n−1) times astigmatism, particularly n (≧ 2) times and m (2 ≦ m ≦ n−1) times astigmatism generated by the latter with respect to small n.

On the other hand, the other components, that is, the sixth-order component φ ₆ and the fifth-order component φ ₅ are normally negligible. First, the two components are astigmatism correction voltages V _2A , V _2B , V _3A , V _3B (2 from the deflection voltage) superimposed according to astigmatism derived from the deflection voltages V _1A and V _1B. Second order and third order components (proportional to r ³ or r ² ), and secondly the second component is proportional to r ⁶ or r ⁵ It is because it becomes an order of magnitude smaller than. Hereinafter, n (= 6) times and m (2 ≦ m ≦ 5) times astigmatism generated by the 6th-order potential component derived from V _2A and V _2B and the 5th-order potential derived from V _3A and V _3B. N (= 5) times and m (2 ≦ m ≦ 4) times astigmatism generated by the component are ignored.

It can be derived from equation (11) that the potential n (≧ 2) order component φ _n including the above-mentioned unnecessary components produces astigmatism n times and m (2 ≦ m ≦ n−1) times as described above. . This will be confirmed below.

For this purpose, first, cos (nθ) and sin (nθ) in the expression (11) are respectively changed to real and imaginary parts of exp (inθ), that is, Re (exp (inθ)) and Im (exp (inθ)). replace. Then the equation is
^{_{φ n = (a n V E}} / R n) Re (r n exp (inθ)) + (b n V E / R n) Im (r n exp (inθ))
_{^{= (A n V E / R}} n) Re (U n) + (b n V E / R n) Im (U n) ··· (11 ')
It becomes. However, in the expression (11 ′), U = rexp (iθ).

Next, the deflection voltage is a complex deflection voltage V _1C (= V _1A + iV _1B ), and the complex deflection trajectory of the principal ray (the ray located at the beam center) of the electron beam 1 with respect to the unit deflection voltage V _1C = 1 is represented by u ₁ ( z), and the deflection trajectory U (z, θ) = V _1C u ₁ (z) + r _B (z) exp (iθ _B ) for the principal ray of the electron beam 1 and its surrounding rays (iθ _B ) ( 17)
Is substituted into the equation (11 ′), the following equation (18) is obtained.

However, in the equations (17) and (18), θ _B represents the angle around the principal ray, and _n C _m represents the number of combinations. Further, a _n V _E and b _n V _{E in the} formula (18) are those in the formulas (15) and (16) or the formulas (15 ′) and (16 ′), respectively.

If the equation (18) is expressed as the following equation (18 ′), φ _mn in the equation (18 ′) can be expressed as the following equation (19).

Equation (19) is a potential m (0 ≦ m ≦ n) order component around the principal ray of the electron beam 1 derived from a potential n (≧ 0) order component around the central axis (Z axis) of the objective deflector 13. , that it represents a component proportional to ^{_{r B m (z) cos (}} mθ B) and ^{_{r B m (z) sin (}} mθ B).

As can be seen from the equation (19), when V _1C = 0, φ _mn regarding m = n, that is, φ _nn can have a non-zero value, but φ _mn regarding m ≠ n is zero. That is, the potential n (≧ 0) order component φ _n around the central axis of the objective deflector 13 similarly produces only the potential n order component around the principal ray of the electron beam 1 when V _1C = 0. Therefore, when V _1C = 0, the potential n (≧ 2) order component generated by the objective deflector 13 produces only n-fold astigmatism. This is the same as the principle that the 4n pole astigmatism corrector produces n times astigmatism.

However, as can be seen from the equation (19), when V _1C ≠ 0, not only φ _{mn for} m = n but also φ _{mn for} m ≠ n can have non-zero values. That is, when V _1C ≠ 0, the same component φ _n generates a potential m-order component for m satisfying 0 ≦ m ≦ n−1 in addition to the potential n-order component around the principal ray. Therefore, when V _1C ≠ 0, the potential n (≧ 2) order component generated by the objective deflector 13 is not limited to n times astigmatism but also m times astigmatism with respect to m satisfying 2 ≦ m ≦ n−1. Produces aberrations.

The potential n-order component φ _n around the central axis of the objective deflector 13 causes m-fold astigmatism in this way. First of all, an unnecessary potential n-order component φ such as the seventh-order component φ ₇ is used. _means that astigmatism occurs from _n , 2, 3, ..., n-1 times, and therefore may need to be corrected, but secondly, n times astigmatism correction This also means that the potential n-th order component φ _n generated for this reason causes 2, 3,..., N−1 times astigmatism, and therefore measures against them may be required.

  In the present embodiment, when such 2, 3,..., N-1 astigmatisms occur with n times astigmatism correction, the optimum value of n times astigmatism correction voltage, that is, n times astigmatism. , N times astigmatism, not n-th astigmatism correction voltage, and n times astigmatism The astigmatism correction voltage n times that minimizes the combination of is obtained. That is, there is a problem that the n-th astigmatism is not minimized despite the attempt to minimize the n-th astigmatism. When these different astigmatisms, ie, 2, 3,..., N times astigmatism are mixed, the beam blur measurement in this embodiment, that is, the beam blur measurement based on knife edge scanning is simply performed. Then, it is because each of these astigmatism cannot be separated and evaluated.

  However, since the n-fold astigmatism correction performed in the present embodiment is specifically limited to the two-fold and three-fold astigmatism corrections, 2, 3,..., N−1 astigmatism as described above. As described above, the problem in this embodiment is limited to the two-fold astigmatism that occurs with the three-fold astigmatism correction. Therefore, hereinafter, the object of explanation is limited to the two-fold astigmatism.

  In order to solve the above problem, the determination of the twice astigmatism correction voltage and the three times of the astigmatism correction voltage may be repeated alternately. With this measure, although there is a possibility that the measurement time becomes long, both the three-fold astigmatism and the two-fold astigmatism may converge to zero.

  However, if the increase in beam blur due to the above-mentioned 2nd astigmatism accompanying the 3rd astigmatism correction is larger than the decrease in beam blur due to the 3rd astigmatism reduction due to the 3rd astigmatism correction, the above countermeasures are taken. Even if the 2nd astigmatism can be converged to zero, the 3rd astigmatism cannot be converged to zero. Even if the increase in the former is smaller than the decrease in the latter, if the increase in the former is not small enough, the convergence of both is slow, that is, the number of measurements required for the convergence of both increases and the measurement time increases. To do.

  Therefore, in the above countermeasure, the determination of the two-fold astigmatism correction voltage and the three-fold astigmatism correction voltage are not simply repeated, but the two-fold astigmatism accompanying the three-fold astigmatism correction is minimized. Well, ideally it should be completely removed. For this purpose, when changing the three-fold astigmatism correction voltage for three-fold astigmatism correction, in order to cancel the two-fold astigmatism, that is, a new two-fold astigmatism opposite to the two-fold astigmatism. Therefore, an appropriate two-fold astigmatism correction voltage may be superimposed on the deflection voltage in conjunction with the three-fold astigmatism correction voltage.

  In addition to this, when the third-order potential component is generated in order to correct the three-fold astigmatism in this embodiment, the second-order potential component is generated, thereby generating the second astigmatism. However, the two-fold astigmatism can be canceled by this method together with the two-fold astigmatism accompanying the three-fold astigmatism correction. However, when generating a second-order potential component to cancel the two-fold astigmatism, if a third-order potential component is generated, resulting in three-fold astigmatism, depending on the magnitude, the second-order astigmatism Neither astigmatism nor three-fold astigmatism can converge to zero. As can be seen from this, in the present embodiment, it is more important that the potential tertiary component is not generated when the potential secondary component is generated than the potential secondary component is not generated when the potential tertiary component is generated. .

  In order to cancel the two-fold astigmatism accompanying the three-fold astigmatism correction as described above, the two-fold astigmatism correction voltage to be superimposed on the deflection voltage in conjunction with the three-fold astigmatism correction voltage, The ratio to the three-fold astigmatism correction voltage may be appropriately determined. If the ratio is obtained, the product of the ratio and the three-time astigmatism correction voltage can be used as a two-time astigmatism correction voltage to be superimposed on the deflection voltage in conjunction with the three-time astigmatism correction voltage. Hereinafter, this ratio is referred to as a correction voltage ratio.

More specifically, the correction voltage _{ratio, V 3A} and _{V 3B} of the predetermined change amount [Delta] V _3A and [Delta] V _3B becomes twice required to cancel the astigmatism produces a 2-fold astigmatism correction voltage _{V 2A} and V _This is the ratio of the amount of change of _{2B to} ΔV _3A and ΔV _3B . In addition, the two-time astigmatism correction voltage to be superimposed on the deflection voltage in conjunction with the three-time astigmatism correction voltage is the same ratio and the n-time astigmatism correction voltage required for n-time astigmatism correction for each deflection coordinate. It is the sum of products with V _nA and V _nB .

  In order to obtain the correction voltage ratio, in the state where the electron beam 1 is deflected for each deflection coordinate, first, the optimum value of the two-fold astigmatism correction voltage, that is, the two-fold astigmatism that minimizes the two-fold astigmatism. Determine the correction voltage, and then change the 3 times astigmatism correction voltage intentionally to generate 2 times astigmatism along with 3 times astigmatism and then optimize the 2 times astigmatism correction voltage. What is necessary is just to determine a value. That is, the optimum value of the two-fold astigmatism correction voltage may be determined for each different three-fold astigmatism correction voltage.

  If the amount of change in the optimum value of the twice astigmatism correction voltage obtained in this way is divided by the amount of change in the three times astigmatism correction voltage, the quotient at that time is the target correction voltage ratio, that is, for each deflection coordinate. This is the correction voltage ratio. The reason why the correction voltage ratio is obtained for each deflection coordinate is because the correction voltage ratio depends on the deflection coordinates.

Using the correction voltage ratio, the twice astigmatism correction voltages V _2A (x, y) and V _2B (x, y) for each deflection coordinate (x, y) are
V _2A (x, y) = V _2Ai (x, y) + ρ _2A3A (x, y) V _3A (x, y) + ρ _2A3B (x, y) V _3B (x, y) (20)
_{V 2B (x, y) =} V 2Bi (x, y) + ρ 2B3A (x, y) V 3A (x, y) + ρ 2B3B (x, y) V 3B (x, y) ··· (21)
It can be expressed. By making V _2A (x, y) and V _2B (x, y) follow the formulas (20) and (21), the two-fold astigmatism generated by the three-fold astigmatism correction is removed.

However, in the equations (20) and (21),
ρ _2A3A (x, y) = (V _2A (x, y, V _3A + ΔV _3A , V _3B ) −V _2A (x, y, V _3A , V _3B )) / ΔV _3A (22)
ρ _2B3A (x, y) = (V _2B (x, y, V _3A + ΔV _3A , V _3B ) −V _2B (x, y, V _3A , V _3B )) / ΔV _3A (23)
ρ _2A3B (x, y) = (V _2A (x, y, V _3A , V _3B + ΔV _3B ) −V _2A (x, y, V _3A , V _3B )) / ΔV _3B (24)
ρ _2B3B (x, y) = (V _2B (x, y, V _3A , V _3B + ΔV _3B ) −V _2B (x, y, V _3A , V _3B )) / ΔV _3B (25)
_{Represents the} correction voltage ratio, and V _2Ai (x, y) and V _2Bi (x, y) are V _2A independent of either V _3A (x, y) or V _3B (x, y), respectively. Represents the components of (x, y) and V _2B (x, y). In the equations (22)-(25), V _2A (x, y, V _3A , V _3B ) and V _2B (x, y, V _3A , V _3B ) are respectively corrected three times by the correction voltage V _3A , _Represent the optimal values of V _2A (x, y) and V _2B (x, y) determined with V _3B superimposed on the deflection voltage, ie those values that minimize double astigmatism, ΔV _3A and ΔV _3B represent the amount of change in V _3A and V _3B , respectively. ΔV _3A and ΔV _3B may be fixed regardless of the deflection coordinates.

  Such a contrivance, that is, a contrivance that independently corrects a plurality of aberrations, is not only in the relationship between n-th astigmatism and m (≠ n) -th astigmatism, but also constitutes n-th astigmatism. This is also necessary in the relationship between the components. Here, a plurality of aberrations or aberration components being independent from each other means that correcting a certain aberration or aberration component does not increase or decrease other aberrations or aberration components as a side effect.

In other words, the optimum values of the n-time astigmatism correction voltage components V _nA and V _nB , that is, these values that minimize the n-time astigmatism are obtained under the condition that the n-time astigmatism components generated by them are independent of each other. It is necessary to decide. Even if the determination of the optimum values of the two components V _nA and V _nB is alternately repeated without satisfying this condition, the two n-fold astigmatism components produced by the two components V _nA and V _nB are in principle Finally, it can converge to zero, but because of the other component that occurs as one component is corrected, their convergence is slow. Therefore, in the following, the above condition, that is, a condition in which the n-time astigmatism components generated by V _nA and V _nB are independent of each other is derived.

Therefore, first, an aberration diagram of n (≧ 2) times astigmatism is represented by S _n = [C _n ψ ⁿ⁻² exp {−in (θ−γ _n )} + Δz] φ exp (iθ).
= [T _n ψ ⁿ⁻² + Δz] ψexp (iθ) (26)
It expresses. However, in the equation (26), C _n is a real number coefficient, ψ is the opening angle of the electron beam 1 on the material 10, and γ ⁿ is the circumference of an aberration figure exhibiting n-fold astigmatism with θ = 0 as a reference. The direction angle, Δz, represents the position of the observation plane with respect to the image plane. Hereinafter, the angle of the n-th astigmatism or the aberration figure exhibited by the component thereof is simply referred to as the n-th astigmatism angle. In addition, T _n in the equation (26) is
T _n = C _n exp {−in (θ−γ _n )} (27)
It is an amount that characterizes the n-fold astigmatism or the aberration pattern exhibited by the component regardless of ψ or Δz.

Equation (26) shows that the radius of the aberration figure increases / decreases n times as θ increases in the range of 0 ≦ θ ≦ 2π in the observation plane deviated from the image plane, that is, Δz ≠ 0. However, when Δz = 0, the equation (26) is
S _n = C _n ψ ⁿ⁻¹ exp [−i {(n−1) θ−nγ _n }]
It becomes. That is, the aberration diagram is circular.

  If the observation surface is made coincident with the paraxial image surface (Gauss image surface), the equation (26) can be interpreted as an equation representing an aberration figure for n-th astigmatism plus field curvature aberration. If the observation plane, that is, the paraxial image plane is used as a reference, the field curvature related to the field curvature aberration can be expressed as -Δz using the Δz.

Next, it expressed using aberration figures, namely the _{S n,} 2 one n-fold astigmatism correction voltage components _{V nA} and _{V nB} represented by equation (26). However, for convenience, T _n represented by the equation (27) is represented using V _nA and V _nB . T _n is obtained by using real voltages V _nA and V _nB ,
_{T n = D nA V nA exp} {-in (θ-α n)} + D nB V nB exp {-in (θ-β n)} ··· (28)
It can be expressed. However, in the equation (28), D _nA and D _nB represent real coefficients, and α _n and β _n represent the angles of n-time astigmatism components derived from V _nA and V _nB , respectively.

Representing T _n defined by the equation (27) by the equation (28) is an n-fold astigmatism having an arbitrary angle γ _n and an n-fold astigmatism having an angle α _n and proportional to V _nA. This corresponds to a linear combination of a component and an n-fold astigmatism component having an angle β _n and proportional to V _nB . When these two n-fold astigmatism components are generated, a potential n-order component φ _n derived from V _nA and V _nB is generated around the central axis of the objective deflector 13.

Here, γ _n , α _n, and β _n represent the aberration or the angle of the component constituting it, as described above, and the potential component φ _n in the objective deflector 13 or the component constituting it. It does not directly represent the angle of the component. There is a certain gap between the former angle and the latter, which is derived from the rotation of the ray trajectory by the magnetic field of the objective lens 9.

Next, the equation (27) is modified, and T _n of the equation (27) is changed to T _n = C _n exp {in (γ _n −α _n )} exp {−in (θ−α _n )}
= C _n [cos {n (γ _n −α _n )} + isin {n (γ _n −α _n )}] exp {−in (θ−α _n )} (27 ′)
Together represent a, (28) by modifying the formula, the _{T n} of the equation _{T n = [D nA V nA} + D nB V nB exp {in (β n -α n)}] exp {-in (θ-α _n )}
_{= [D nA V nA + D} nB V nB {cos (nδ n) + isin (nδ n)}] exp {-in (θ-α n)} ··· (28 ')
It expresses. However, in the equation (28 ′), δ _n = β _n −α _n . Since δ _n is an angle difference, it is common to both the aberration and the potential component φ _n in the objective deflector 13.

Next, when comparing the right sides of Equations (27 ′) and (28 ′), the former real and imaginary components are equal to those of the latter, respectively.
C _n cos {n (γ _n −α _n )} = D _nA V _nA + D _nB V _nB cos (nδ _n ) (29)
C _n sin {n (γ _n −α _n )} = D _nB V _nB sin (nδ _n ) (30)
The relationship is obtained. And if V _nA and V _nB are derived from the equations (29) and (30),
_{V nA = (C n / D} nA) cos {n (γ n -α n)} - (D nB / D nA) V nB cos (nδ n) ··· (31)
_{V nB = (C n / D} nB) sin {n (γ n -α n)} / sin (nδ n) ··· (32)
It becomes.

As can be seen from the equation (31), V _nA depends on V _nB depending on the value of δ _n . Further, as can be understood by substituting the subscripts A and B and the angles α _n and β _n in the equation (28) and deriving the equations (31) and (32) from the equations, the values of δ _n V _nB also depends on V _nA .

For the purposes, namely in order to independently n times astigmatism produce the V _nA and V _nB is, V _nA and V _nB may be so as not to depend this manner to each other. The condition for this is that cos (nδ _n ) = 0 is satisfied, that is,
δ _n = (2L _n +1) π / (2n) (33)
Is to be satisfied. However, in the equation (33), L _n is an integer. In formula (33), δ _n is simply set to L _n = 0,
δ _n = π / (2n) (33 ′)
And it is sufficient.

That is, the above condition is that δ _n is an odd multiple of π / (2n). At this time, δ _n is represented by an equidistant series of initial terms π / (2n) and tolerance π / n (or −π / n). When this condition is satisfied, that is, when equation (33) is satisfied, equations (31) and (32) are respectively
_{V nA = (C n / D} nA) cos {n (γ n -α n)} ··· (31 ')
_{V nB = (C n / D} nB) sin {n (γ n -α n)} / cos (L n π)
= ± (C _n / D _nB ) sin {n (γ _n −α _n )} (32 ′)
It becomes.

(33) the angle difference [delta] _n of, to be provided for the purpose of _{(V nA} and _{V nB} one another and independently of the n-fold astigmatism component _produce), n-fold astigmatism produce the _{V nA} and _{V nB} It represents the angular difference regarding the aberration component, and also represents the angular difference regarding the n-th order component of the potential generated by V _nA and V _nB that should be provided for the above purpose. This is because δ _n is common to both the astigmatism component and the potential component as described above. [delta] _n it is _also the angular difference relates electrode voltage distribution _{V nA} and _{V nB,} i.e. also the angular difference of the distribution function _{f nA} (theta) and _{f nB} (theta) representing the electrode voltage distribution _{V nA} and _{V nB.} The reason why δ _n is an angular difference related to these distribution functions is that the electrodes E1 to E8 of the objective deflector 13 are equally divided.

The angle difference δ _n corresponds to the phase difference ± π / 2 related to the potential n-order component generated by V _nA and V _nB . That is, the potential n-order components generated by V _nA and V _nB are orthogonal to each other. This is obtained by shifting the potential n-order component φ _n (V _E , r, θ) represented by the equation (11) by an angle δ _n .
φ _n (V _E , r, θ−δ _n )
^{_{= (A n / R n)}} V E r n cos {n (θ-δ n)} + (b n / R n) V E r n sin {n (θ-δ n)}
^{_{= (A n / R n)}} V E r n cos (nθ ± π / 2) + (b n / R n) V E r n sin (nθ ± π / 2)
It can be expressed as That is, the phase difference between φ _n (V _E , r, θ) and φ _n (V _E , r, θ−δ _n ) is equal to nδ _n = ± π / 2. However, here, to limit the scope of Enuderuta _n to -π ≦ nδ _n ≦ π. The angle difference δ _n also corresponds to the phase difference ± π / 2 between the distribution functions f _nA (θ) and f _nB (θ). That is, these distribution functions are orthogonal to each other.

The angle difference δ _n and the phase difference ± π / 2 also apply to the distribution functions f _nA (θ) and f _nB (θ) shown in FIG. From FIG. _{3, f 2B} (θ) Since _{f 2A} a _{(θ) π / 4, f} 3B (θ) is equal to the rotated _{f 3A} the (theta) by _{-π / 2, f 2A (θ} ) And f _2B (θ) is δ ₂ = π / 4, and the angle difference between f _3A (θ) and f _3B (θ) is δ ₃ = −π / 2. These angular differences satisfy the equation (33). The phase difference between f _2A (θ) and f _2B (θ) is 2δ ₂ = π / 2, and the phase difference between f _3A (θ) and f _3B (θ) is 3δ ₃ = -3π. / 2, i.e., _{3 [} delta] ₃ = [pi] / 2 in the range of-[pi] ≤3 [delta] 3≤ [pi]. That is, both of these phase differences are π / 2.

Assuming that the angle differences δ ₂ and δ ₃ are π / 4 and −π / 2 as described above, the aberration patterns S ₂ and S ₃ are obtained from the equations (26) and (28), respectively.
S ₂ = D _2A V _2A ψexp {−i (θ−2α ₂ )} + D _2B V _2B ψexp {−i (θ
-2 (α ₂ + π / 4))}
= D ₂ (V _2A + iV _2B ) ψexp {−i (θ-2α ₂ )} (34)
S ₃ = D _3A V _3A ψ ² exp {−i (2θ-3α ₃ )} + D _3B V _3B ψ ² exp {−i (2θ-3 (β ₃ −π / 2))}
= D ₃ (V _3A + iV _3B ) φ ² exp {−i (2θ-3α ₃ )} (35)
It can be expressed. However, in the equations (34) and (35), Δz = 0 is set for convenience. Therefore, it can be considered that the observation surface of the aberration pattern represented by the equations (34) and (35) coincides with the paraxial image surface. For simplicity, D _n = D _nA = D _nB .

In order to represent the state of astigmatism correction by the 2nd and 3rd astigmatisms expressed by the equations (34) and (35), the astigmatism to be corrected, that is, the electron beam 1 is expressed in the equations (34) and (35). If the 2 times and 3 times astigmatism generated by the deflection of ## EQU3 ## are respectively included, the equations (34) and (35) are
_{S 2 = C 2 ψexp {-i} (θ-2γ 2)} + D 2 (V 2A + iV 2B) ψexp {-i (θ-2α 2)} ··· (34 ')
^{_{S 3 = C 3 ψ 2 exp}} {-i (2θ-3γ 3)} + D 3 (V 3A + iV 3B) ψ 2 exp {-i (2θ-3α 3)} ··· (35 ')
It becomes. Equations (34 ′) and (35 ′) respectively represent aberration diagrams that are presented after the two-time and three-time astigmatisms generated with the deflection of the electron beam 1 have been corrected. However, the first term on the right side of the equations (34 ′) and (35 ′) is an aberration diagram exhibiting two-fold and three-fold astigmatism generated with the deflection of the electron beam 1, respectively.

Similarly to these, if the aberration figure corresponding to the curvature of field aberration and the defocus is expressed by a mathematical formula,
S ₀ = −Δzψexp (iθ) −D ₀ V _0A ψexp (iθ) (36)
It becomes. Expression (36) represents an aberration diagram that is exhibited after the field curvature aberration that has occurred along with the deflection of the electron beam 1 has been corrected. However, the first term on the right side of Equation (36) represents the field curvature aberration with respect to the field curvature Δz that occurs with the deflection of the electron beam 1. That is, the observation surface of the aberration pattern represented by Equation (36) coincides with the paraxial image surface. On the other hand, the second term represents a focus shift _{caused by} the focus correction voltage _V0A .

For the sake of convenience, S ₂ , S ₃ and S ₀ in the formula (34 ′)-(36)
S ₂ = C ₂ 'ψexp {-i (θ-2γ ₂ )} (34 ″)
S ₃ = C ₃ ′ ψ ² exp {−i (2θ-3γ ₃ )} (35 ″)
S ₀ = −Δz′ψexp (iθ) (36 ′)
When these aberration figures are combined, the aberration figure after the combination is
S ₂ + S ₃ + S _{0
= [C 2 'ψexp {-i2} (θ-γ 2)} + C 3' ψ 2 exp {-i3 (θ-γ 3)} - Δz'ψ] exp (iθ)
= R _s exp (iθ) (37)
It can be expressed. However, the observation surface of the aberration pattern represented by the equation (37) coincides with the paraxial image surface.

Measuring the beam blur by knife edge scanning in this embodiment, be less it, (37) to evaluate the expression of r _s, C ₂ it to decrease ', C _3', zero Delta] z ' It is equivalent to approaching. However, in the formula (34 ″) − (37),
C ₂ ′ = C ₂ + D ₂ (V _2A + iV _2B ) exp {i2 (α ₂ −γ ₂ )}
C ₃ '= C ₃ + D ₃ (V _3A + iV _3B ) exp {i3 (α ₃ −γ ₃ )}
Δz ′ = Δz + D ₀ V _0A
r _s = C ₂ ′ ψexp {−i2 (θ−γ ₂ )} + C ₃ ′ ψ ² exp {−i3 (θ−γ ₃ )} − Δz′ψ
Where C ₂ ′, C ₃ ′, and Δz ′ represent C ₂ , C ₃ , and Δz changed due to the two-time astigmatism correction, the three-time astigmatism correction, and the focus correction, respectively, and r _s Represents the radius (including the imaginary component) of the combined aberration diagram.

3. Flow of determination of focus correction voltage, correction voltage ratio, 2 times and 3 times astigmatism correction voltage, and distortion correction voltage Next, focus correction voltage, correction voltage ratio, 2 times and 3 times astigmatism correction voltage in this embodiment The flow of determining the distortion correction voltage will be described. FIG. 5 is a flowchart showing an example of the flow of determining the focus correction voltage, the correction voltage ratio, the second and third astigmatism correction voltages, and the distortion correction voltage in the present embodiment.

  In the variable shaped electron beam drawing apparatus 100, the control device 21 performs processing for determining the focus correction voltage, the correction voltage ratio, the second and third astigmatism correction voltages, and the distortion correction voltage shown in FIG.

FIG. 6 is a diagram showing a configuration of the variable shaped electron beam drawing apparatus 100 when determining the focus correction voltage, the correction voltage ratio, the second and third astigmatism correction voltages, and the distortion correction voltage. Note that the deflection voltages V _1A and V _1B always include the focus correction voltage V _0A , the two-time astigmatism correction voltages V _2A and V _2B , and the three-time astigmatism correction voltage V _throughout the flow of the processing shown in FIG. _3A and V _3B , and distortion correction voltages ΔV _1A and ΔV _1B are superimposed, and these values are changed as necessary. The initial values of these correction voltages and correction voltage ratios are zero.

(1) Focus correction voltage determination process First, the control device 21 determines a focus correction voltage. That is, the focus correction voltage V _0A that sets Δz ′ in the equation (37) to zero is obtained. The determination is made based on beam blur measurement by scanning the knife edge 18. Beam blur measurement by scanning the knife edge 18 is performed at a predetermined finite number of measurement points or deflection coordinates within the deflection field.

More specifically, the control device 21 first applies deflection voltages V _1A and V _1B to the objective deflector 13 to deflect the electron beam 1 so that the electron beam 1 is incident on a target measurement point, and the deflection thereof. The knife edge 18 is moved according to the above. Then, while changing the value of V _0A scan the knife edge 18 at the electron beam 1, the relationship between V _0A and the beam blur obtained from the detection result of the current detector 19, the optimum value of V _0A, i.e. focus The value that minimizes the beam blur due to deviation is determined (S10).

When the optimum value of V _{0A at} each measurement point is obtained in this way, the control device 21 determines approximate functions V _0A (x, y) representing these distributions (S11). Then, a focus correction voltage for each deflection coordinate is determined from the approximate function, and this is stored in the storage device 22.

By this series of processes, the field curvature aberration at an arbitrary deflection coordinate is corrected. More specifically, the field curvature aberration derived from the magnetic field of the objective lens 9 is corrected together with the field curvature aberration derived from the electric potential in the objective deflector 13. Here, the curvature of field due to the electric potential in the objective deflector 13 is generated when the deflection voltage is not zero, that is, when V _1C ≠ 0, as can be seen from the equation (19). This is because the potential n-order component φ _n around the central axis of 13 generates the potential m-order component φ _mn related to m = 0 around the principal ray of the electron beam 1, that is, φ _0n .

(2) Correction Voltage Ratio Determination Processing Next, the control device 21 determines the correction voltage ratio, that is, the 3 times astigmatism of the 2 times astigmatism correction voltage necessary for canceling the 2 times astigmatism accompanying the 3 times astigmatism correction. Measure the ratio to the correction voltage. This measurement is also performed based on a beam blur measurement by scanning the knife edge 18 at a predetermined measurement point.

More specifically, the control device 21 first applies deflection voltages V _1A and V _1B to the objective deflector 13 to deflect the electron beam 1 so that the electron beam 1 is incident on a target measurement point. The knife edge 18 is moved in accordance with the deflection. Then, while keeping V _3A and V _3B at the current values, the knife edge 18 is scanned with the electron beam 1 while changing the values of V _2A and V _2B , and V _2A obtained from the detection result of the current detector 19 And the optimum values of V _2A and V _2B , that is, those values that minimize the beam blur due to double astigmatism are determined from the relationship between V _2B and beam blur. _Then, while adding the [Delta] V _3A to _{V 3A, likewise,} it determines the optimum value of _{V 2A} and _{V 2B, then} returned to the original value of _{V 3A,} while adding the [Delta] V _3B to _{V 3B} Similarly, the optimum values of V _2A and V _2B are determined. Finally, the optimum values of V _2A and V _2B obtained by these measurements and ΔV _3A and ΔV _3B are substituted into the equations (22)-(25), and the corrected voltage ratios ρ _2A3A , ρ _2B3A , Ρ _2A3B , ρ _2B3B are obtained (S12). However, when determining the optimum values of V _2A and V _2B , they converge alternately.

Thus, if ρ _2A3A , ρ _2B3A , ρ _2A3B , ρ _{2B3B at} each measurement point is obtained, the control device 21 approximates ρ _2A3A (x, y), ρ _2B3A (x, y) representing these distributions. y), ρ _2A3B (x, y), and ρ _2B3B (x, y) are determined (S13). Then, from the approximate functions ρ _2A3A (x, y), ρ _2B3A (x, y), ρ _2A3B (x, y), and ρ _2B3B (x, y), the correction voltage ratio for each deflection coordinate is determined, The data is stored in the storage device 22.

(3) 2nd and 3rd Astigmatism Correction Voltage Determination Processing Next, the control device 21 determines the 2nd and 3rd astigmatism correction voltage. That is, the astigmatism correction voltages V _2A , V _2B , V _3A , and V _3B are _calculated twice and three times with C ₂ ′ and C ₃ ′ in equation (37) being zero. These determinations are also made based on beam blur measurement by scanning the knife edge 18 at a predetermined measurement point.

However, at each measurement point, among these correction voltages, the three-fold astigmatism correction voltage is determined first and the two-fold astigmatism correction voltage is determined later. This (19) As can be seen from the equation, but 2-fold astigmatism from potential tertiary component phi ₃ about the central axis of the objective deflector 13 may occur, three times from the potential secondary component phi ₂ This is because astigmatism cannot occur.

More specifically, the control device 21 first applies deflection voltages V _1A and V _1B to the objective deflector 13 to deflect the electron beam 1 so that the electron beam 1 is incident on a target measurement point, and the deflection thereof. The knife edge 18 is moved according to the above. _Then, by scanning the knife edge 18 at the electron beam 1 while changing the value of _{V 3A} and _{V 3B,} the relationship between _{V 3A} and _{V 3B} and the beam blur results from the current detector _{19, V 3A} and Determine the optimum value of V _3B , that is, those values that minimize beam blur due to 3-fold astigmatism. At that time, V _2A and V _2B are made to follow V _3A and V _3B based on the correction voltage ratio. Further, V _3A and V _3B are converged alternately. Next, the values of V _2A and V _2B are changed, and the knife edge 18 is scanned with the electron beam 1 for each of these values. From the resulting relationship between V _2A and V _2B and beam blur, V _2A and V _2A optimum value of V _2B, i.e. to determine these values to minimize the beam blur twice astigmatism (S14). At that time, V _2A and V _2B are converged alternately.

However, these optimum values are not determined by performing the above convergence, that is, the convergence of the pair of V _2A and V _2B and the convergence of the pair of V _3A and V _3B at each measurement point. It is desirable to determine after repeating these convergences alternately. In that case, if the correction voltage ratios ρ _2A3A , ρ _2B3A , ρ _2A3B , and ρ _2B3B include an error, two-fold astigmatism occurs due to the three-fold astigmatism correction. Alternatively, even if a small amount of 3 times astigmatism occurs due to correction of 2 times astigmatism, both 2 times astigmatism and 3 times astigmatism can be converged to zero.

When the optimum values of V _2A , V _2B , V _3A , and V _3B at the respective measurement points are obtained in this way, the control device 21 approximates V _2A (x, y), V _2B ( x, y), V _3A (x, y), and V _3B (x, y) are determined (S15). Then, the astigmatism correction voltage is determined twice and three times for each deflection coordinate from the approximate function, and is stored in the storage device 22.

  As a result of these series of processes, astigmatism is corrected twice and three times at an arbitrary deflection coordinate. More specifically, the 2 and 3 times astigmatism derived from the magnetic field of the objective lens 9 are corrected together with the 2 and 3 times astigmatism derived from the potential in the objective deflector 13.

(4) Distortion Correction Voltage Determination Process Next, the control device 21 determines distortion correction voltages ΔV _1A and ΔV _1B . The distortion correction voltages ΔV _1A and ΔV _1B are determined based on the measurement of the beam incident position by scanning the knife edge 18. Here, the measurement of the incident position by scanning the knife edge 18 refers to extracting the beam incident position from the waveform of the beam current flowing into the current detector (Faraday cup) 19.

More specifically, the control device 21 first applies deflection voltages V _1A and V _1B to the objective deflector 13 to deflect the electron beam 1 so that the electron beam 1 is incident on a target measurement point, and the deflection thereof. The knife edge 18 is moved according to the above. Next, the knife edge 18 is scanned with the electron beam 1 to measure the positional deviation. Then, after changing the distortion correction voltages ΔV _1A and ΔV _1B to cancel the misalignment, the misalignment is measured again to confirm that it becomes zero, and ΔV _1A and ΔV _1B at that time are The optimum values of ΔV _1A and ΔV _{1B at} the measurement point are set (S16).

  However, this measurement does not necessarily need to be performed by scanning the knife edge 18, and may be performed by scanning a fine structure made of heavy metal. In this case, instead of detecting the beam current flowing into the current detector (Faraday cup) 19, reflected electrons from the fine structure made of heavy metal are detected.

When the optimum values of ΔV _1A and ΔV _1B at the respective measurement points are obtained in this way, that is, these values that minimize the positional deviation are obtained, the control device 21 approximates the distribution ΔV _1A (x, y) and ΔV _1B (x, y) are determined (S17). Then, a distortion correction voltage for each deflection coordinate is determined from the approximate function, and these are stored in the storage device 22.

Through a series of these processes, distortion aberration at an arbitrary deflection coordinate is corrected. More specifically, the result of focus correction, two-time astigmatism correction, and three-time astigmatism correction, together with distortion aberration derived from the electric potential in the objective deflector 13 and distortion aberration derived from the magnetic field of the objective lens 9. Distortion is corrected. Here, distortion aberration occurs as a result of focus correction because the zero-order potential component generated for correction accelerates or decelerates electrons of the electron beam 1 and changes the deflection amount of the electron beam 1. On the other hand, as a result of the astigmatism correction twice and three times, the distortion is generated when the deflection voltage is not zero, that is, when V _1C ≠ 0, as can be seen from the equation (19). This is because the potential secondary component φ ₂ and the tertiary component φ ₃ around the central axis generate a potential m-order component φ _mn for m = 1 around the principal ray of the electron beam 1, that is, φ ₁₂ and φ ₁₃ .

Through the above steps S10 to S17, the field curvature aberration, the second and third astigmatisms, and the distortion aberration at any deflection coordinate are all corrected. Strictly speaking, as can be seen from the equation (19), when the deflection voltage is not zero, that is, when V _1C ≠ 0, the astigmatism of the objective deflector 13 is corrected for 2 times astigmatism correction, 3 times astigmatism correction, and distortion correction. A potential secondary component φ ₂ , a tertiary component φ ₃ , and a primary component φ ₁ generated around the central axis are respectively converted into potential zero-order components φ ₀₂ , φ ₀₃ , and around the principal ray of the electron beam 1, and φ ₀₁ is produced, and these components produce curvature of field aberration, which can be ignored. This is because the astigmatism correction voltage and the distortion correction voltage are generally orders of magnitude smaller than the deflection voltage.

  The charged particle beam deflection apparatus 100a according to this embodiment has the following features, for example.

  In the charged particle beam deflection apparatus 100a, the control device 21 deflects an n-fold astigmatism correction signal for canceling n-fold astigmatism (n = 2, 3,..., N, N is an integer of 3 or more). 2, 3,..., N−1 times astigmatism generated by superimposing n times astigmatism correction signals for each deflection coordinate on which the electron beam 1 deflected by application of the deflection signal is superimposed. The astigmatism correction signal for superimposing 2, 3,..., N-1 times is superimposed on the deflection signal. As a result, when the astigmatism correction signal is superimposed n times on the deflection signal to reduce the blur (aberration) of the electron beam, 2, 3,. Can be suppressed. That is, it is possible to suppress the occurrence of new aberrations (2, 3,..., N−1 times astigmatism) when correcting the n times astigmatism after deflecting the charged particle beam. . Thereby, for example, the blur of the electron beam 1 does not increase due to the astigmatism of 2, 3,..., N−1 times. Therefore, when the n-time astigmatism correction signal for minimizing the n-time astigmatism is determined for each deflection coordinate, the n-time astigmatism correction signal is determined 2, 3,..., N-1 times. Not disturbed by astigmatism. However, in the present embodiment, N = 3, and the 2nd and 3rd astigmatisms that are caused by the deflection of the electron beam 1 by the objective deflector 13, that is, the octupole deflector, are corrected.

  In the charged particle beam deflection apparatus 100a, the control device 21 distributes the voltage distribution to each electrode of the multipole element (objective deflector 13) related to the n-time astigmatism correction signal n times astigmatism correction signals except when n = N. , N-order components, or magnetic potentials n + 1, n + 2,..., N-order components are suppressed. For this reason, when the astigmatism correction signal is superimposed n times to reduce the blur of the electron beam 1, the occurrence of n + 1, n + 2,..., N astigmatism is suppressed regardless of the deflection coordinates. That is, the blur of the electron beam 1 does not increase due to these aberrations. Therefore, when the n-time astigmatism correction signal that minimizes the n-th astigmatism is determined for each deflection coordinate, the determination of the n-time astigmatism correction signal is not hindered by these aberrations.

In the charged particle beam deflection apparatus 100a, an angle around the central axis of the multipole element (objective deflector 13) representing the position of each pole of the multipole element (objective deflector 13) is θ, and an n-fold astigmatism correction signal is constructed. When the two components to be performed are V _nA and V _nB, and the distribution functions representing the voltage distribution to the electrodes E1 to E8 with respect to V _nA and V _nB are f _nA (θ) and f _nB (θ), respectively, the control device 21 V _nA and V _nB are parameters, and n times astigmatism correction signal V _n (θ) = V _nA f _nA (θ) + V _nB f _nB (θ) is superimposed on the deflection signal, V _nA and V _n The value of _nB is determined for each deflection coordinate, and V _n (θ) into which V _nA and V _nB determined in this way are substituted is used as an n-time astigmatism correction signal for each deflection coordinate. As a result, n times astigmatism is evaluated by evaluating n times astigmatism, that is, the size of beam blur, by knife edge scanning without observing the aberration figure as a microscope image (2 in this embodiment). Astigmatism correction and 3 astigmatism correction) can be performed. That is, astigmatism correction can be performed n times even in a charged particle beam apparatus that does not have a function of observing an aberration pattern as a microscope image.

In the charged particle beam deflection apparatus 100a, the potential n-order component generated according to V _nA and the potential n-order component generated according to V _nB are orthogonal to each other, and therefore one of V _nA and V _nB is obtained. Increasing or decreasing does not increase or decrease the other. Therefore, when determining these values that minimize n-time astigmatism, the determination of one value does not interfere with the determination of the other value.

In the charged particle beam deflecting device 100a, 2, 3,..., N−1 times for canceling 2, 3,..., N−1 times astigmatism generated by superimposing n times astigmatism correction signals. The astigmatism correction signal is an m-time astigmatism correction signal (2 ≦ m ≦ n−1, where m is an integer) regarding an integer m satisfying 2 ≦ m ≦ n−1, and two components constituting the m-time astigmatism correction signal the when the _{V mA} and _{V mB,} the control device _21, 2,3 generated in response to a predetermined change amount [Delta] V _nA of _{V nA,} ···, n-1 times for canceling each of astigmatism of, m times of 2 variation component _{V mA} and _{V mB} of astigmatism correction signal, and the ratio [rho _MANA and [rho _MBNA for [Delta] V _nA, 2,3 generated according to the predetermined change amount [Delta] V _nB of _{V nB,} ... 2 component V _{mA of} m times astigmatism correction signal to cancel each of n-1 times astigmatism. The amount of change and _{V mB,} and a ratio [rho _manB and [rho _MBnB for [Delta] V _nB, determined for each deflection coordinates, said ratio _{ρ mAnA, ρ mBnA, ρ mAnB} , and [rho _MBnB and _{V nA} and V for each deflection coordinates product [rho _MANA V _nA and _{nB, ρ mBnA} V _nA, to calculate the _ρ mAnB V _nB, and _ρ mBnB V _nB, laminate _{ρ mAnA V nA, ρ mBnA V} nA, ρ mAnB V nB, and _ρ mBnB V _nB sum _{ρ mAnA V nA + ρ mAnB V} nB, and _{ρ mAnB V nB + ρ mBnB V} nB, and 2-component _{V mA} and _{V mB} of m-fold astigmatism correction signal. Thereby, the astigmatism correction signal can be determined 2, 3, ..., n-1 times. That is, the astigmatism of 2, 3,..., N−1 times that can occur with n times astigmatism correction can be removed.

  In the charged particle beam deflection apparatus 100a, the control device 21 repeats the determination of the values of the components constituting the astigmatism correction signal N, N-1,... Twice until the values converge. Thereby, the correction residual can be reduced.

  In the charged particle beam deflection apparatus 100a, the control device 21 determines a distortion correction signal for canceling distortion aberration after determining the n-point astigmatism correction signal. As a result, N, N−1,... Distortion aberrations that can occur due to astigmatism correction twice are collectively corrected. Even if the distortion correction signal is determined before the astigmatism correction is completed and the distortion correction is performed based on the distortion correction signal, it is necessary to determine the distortion correction signal again and perform the distortion correction based on the distortion correction signal.

4). Modified Example Next, a modified example of the variable shaped electron beam drawing apparatus 100 according to the present embodiment will be described. Hereinafter, differences from the above-described variable shaped electron beam drawing apparatus 100 will be described, and description of similar points will be omitted.

(1) First Modification First, a first modification will be described. FIG. 7 is a diagram showing a configuration of the objective deflector 13 of the charged particle beam deflection apparatus according to the first modification. FIG. 8 is a diagram illustrating a distribution function of the objective deflector 13 of the charged particle beam deflector according to the first modification, together with an XY cross section of the objective deflector 13.

  As shown in FIG. 7, the objective deflector 13 of the charged particle beam deflection apparatus according to the first modification is π / 8 (22.22) relative to the objective deflector 13 of the charged particle beam deflection apparatus 100a shown in FIG. 5 °). That is, there are no electrodes E1 to E8 on the X and Y axes.

FIG. 8 shows a distribution function representing the electrode voltage distribution of the deflection voltage, distortion correction voltage, focus correction voltage, twice astigmatism correction voltage, and three times astigmatism correction voltage in the first modification. Of the distribution functions shown in FIG. 8, the values of f _1A (θ), f _0A (θ), f _2A (θ), and f _3A (θ) at the respective electrode positions are cos (nθ) / cos (nπ / 8). ). That is, these distribution functions can be expressed as f _nA (θ) = cos (nθ) / cos (nπ / 8), respectively, when θ is an odd multiple of π / 8. Further, the values of f _1B (θ), f _2B (θ), and f _3B (θ) at the respective electrode positions coincide with sin (nθ) / cos (nπ / 8). That is, these distribution functions can be expressed as f _nB (θ) = sin (nθ) / cos (nπ / 8), respectively, when θ is an odd multiple of π / 8.

The right-side denominator cos (nπ / 8) of the above expression representing f _nA (θ) and f _nB (θ) is set so that the value of f _nA (θ) at the electrode E1, that is, f _nA (π / 8) is 1. Is not necessarily required. That is, the above f _nA (θ) and f _nB (θ) may be set to f _nA (θ) = cos (nθ) and f _nB (θ) = sin (nθ), respectively. This is because, as described above, these distribution functions may be freely multiplied by a constant (other than zero).

(2) Second Modification Next, a second modification will be described. FIG. 9 is a diagram showing a configuration of the objective deflector 13 of the charged particle beam deflection apparatus according to the second modification. FIG. 10 is a diagram illustrating a distribution function of the objective deflector 13 of the charged particle beam deflector according to the second modification, together with an XY cross section of the objective deflector 13.

  The number of poles of the objective deflector 13 of the charged particle beam deflection apparatus 100a shown in FIG. 2 described above was 8.

  On the other hand, the number of poles of the objective deflector 13 of the charged particle beam deflection apparatus according to the first modification is 12 as shown in FIG. Therefore, the interval between the electrodes E1 to E8 is π / 6.

  In the present modification, the control device 21 performs astigmatism correction four times and five times in addition to two times and three times astigmatism correction as n times astigmatism correction. That is, the astigmatism correction voltage is superimposed twice, three times, four times, and five times as the n-fold astigmatism correction voltage on the deflection voltage applied to the objective deflector 13.

In this modification, the electrode voltage distribution of the deflection voltage, the distortion correction voltage, the focus correction voltage, the 2-fold astigmatism correction voltage, the 3-fold astigmatism correction voltage, the 4-fold astigmatism correction voltage, and the 5-fold astigmatism correction voltage is represented. The distribution function is shown in FIG. Among the distribution functions shown in FIG. 10, f _1A (θ), f _0A (θ), f _2A (θ), f _3A (θ), f _4A (θ), and f _5A (θ) are values at the respective electrode positions. Corresponds to cos (nθ). That is, these distribution functions can be expressed as f _nA (θ) = cos (nθ), respectively, when θ is an integer multiple of π / 6. Further, the values of f _1B (θ), f _2B (θ), f _3B (θ), f _4B (θ), and f _5B (θ) at the respective electrode positions coincide with sin (nθ). That is, these distribution functions can be expressed as f _nB (θ) = sin (nθ), respectively, when θ is an integer multiple of π / 6.

However, if the astigmatism correction is performed three times in a state in which the electron beam 1 is deflected by the objective deflector 13 in the present modification, a second astigmatism is newly generated as described above. In addition, if astigmatism correction is performed four times or five times in the state where the electron beam 1 is deflected by the objective deflector 13 as well, three times and two times astigmatism, or four times and three times, respectively. And two new astigmatisms. Therefore, when the astigmatism correction is performed three times, four times, and five times in this modification, it is necessary to remove these newly generated astigmatisms.

Therefore, m = 2, 3, or 4, and N = 5, and V _2A , V _2B , V _3A , V _3B , V _4A , V _4B are made to follow the following formulas (38) and (39).

  The expressions (38) and (39) are also generalized expressions of the above expressions (20) and (21). Assuming that m = 2 and N = 3, the equations (38) and (39) match the equations (20) and (21), respectively.

However, in the expressions (38) and (39), V _mAi (x, y) and V _mBi (x, y) are V _nA (x, y) and V _nB related to n satisfying m + 1 ≦ n ≦ N, respectively. _Represents components of V _mA (x, y) and V _mB (x, y) that do not depend on any of (x, y), and correction voltage ratios ρ _mAnA (x, y), ρ _mBnA (x, y), ρ _mAnB (x, y) and ρ _mBnB (x, y) are
ρ _mAn (x, y) = (V _mA (x, y, V _nA + ΔV _nA , V _nB ) −V _mA (x, y, V _nA , V _nB )) / ΔV _nA (40)
ρ _mBnA (x, y) = (V _mB (x, y, V _nA + ΔV _nA , V _nB ) −V _mB (x, y, V _nA , V _nB )) / ΔV _nA (41)
ρ _mAnB (x, y) = (V _mA (x, y, V _nA , V _nB + ΔV _nB ) −V _mA (x, y, V _nA , V _nB )) / ΔV _nB (42)
ρ _mBnB (x, y) = (V _mB (x, y, V _nA , V _nB + ΔV _nB ) −V _mB (x, y, V _nA , V _nB )) / ΔV _nB (43)
Follow.

In the equations (40)-(43), V _mA (x, y, V _nA , V _nB ) and V _mB (x, y, V _nA , V _nB ) are n times astigmatism correction voltages V _nA and V _{nB. Represents} the optimum values of m-th astigmatism correction voltages V _mA and V _mB determined in a state in which is superimposed on the deflection voltage, that is, these values that minimize m-th astigmatism, and ΔV _nA and ΔV _nB are , And represents the amount of change in V _nA and V _nB , respectively. However, when the n-time astigmatism correction voltages V _nA and V _nB are changed by ΔV _nA and ΔV _nB , respectively, other astigmatism correction voltages, that is, n ′ (≠ n) times astigmatism correction voltages V _n′A and V n _n′B is fixed. That is, the correction voltage ratio corresponds to a partial differentiation of V _mA and V _mB by V _nA or V _nB . At that time, ΔV _nA and ΔV _nB may be fixed irrespective of the deflection coordinates.

  As a result of the above device, 4 times, 3 times, and 2 times astigmatism that occur with 5 times astigmatism correction, 3 times and 2 times astigmatism with 4 times astigmatism correction, and 3 times astigmatism The double astigmatism generated with the correction can be removed. That is, astigmatism can be corrected independently of each other by 2, 3, 4, and 5 times. Here, a plurality of aberrations being independent of each other means that increasing or decreasing a certain aberration does not increase or decrease other aberrations as a side effect.

However, the determination of these astigmatism correction voltages is carried out successively in the order of 5, 4, 3, 2, and 2 astigmatism, that is, from the largest n. By doing so, these astigmatism corrected earlier can be determined without increasing later. Then, if this series of determinations is repeated until each astigmatism correction voltage converges, the astigmatism derived from the error included in the correction voltage ratio can be converged to zero.

  As described above, in the present modification, the control device 21 performs astigmatism correction twice, three times, four times, and five times. However, at that time, the control device 21 determines that N, N−1,..., Twice astigmatism correction signal (N = 5 in this modification) in the order of N, N−1,. A point correction signal is determined. Therefore, even if an error is included in the astigmatism correction signal for removing 2, 3,... Astigmatism that has not yet been corrected (n-1, n-2,..., Without newly generating corrected astigmatism (N, N-1,..., N-th astigmatism).・ Twice astigmatism can be corrected. As a result, the correction residual when the astigmatism correction is performed twice is reduced. If, for example, these astigmatisms are corrected in the order of 2, 3,..., N times astigmatism, for example, astigmatism already corrected with the superposition of n times astigmatism correction signals ( (2, 3,..., N-1 astigmatism) newly occurs, the correction residual at the time when N times astigmatism is corrected becomes large.

(3) Third Modification Next, a third modification will be described. FIG. 11 is a diagram illustrating a distribution function of the objective deflector 13 of the charged particle beam deflector according to the third modification, together with an XY section of the objective deflector 13. As can be seen from FIG. 11, the number of poles of the objective deflector 13 in this modified example is eight.

  In this modification, the control device 21 performs four astigmatism corrections in addition to the two and three astigmatism corrections.

  FIG. 11 shows the electrode voltage distribution of the four-fold astigmatism correction voltage in this modification. If the electrode voltage distribution of FIG. 11 (a) or (b) is applied to the objective deflector 13 of the present embodiment and the first modified example, respectively, only one component of the two components of the four-fold astigmatism. Can be generated.

Although the four-fold astigmatism cannot be completely corrected by the one component, correcting the four-fold astigmatism while being incomplete contributes to the improvement of the resolution. In order to perform such correction, one of V _4A and V _{4B in} the equations (38) and (39) is set to zero, and the other is set to V _2A , V 4 based on the electrode voltage distribution in FIG. _What is necessary is _just to superimpose on deflection voltage _V1A and _V1B with _2B , _V3A , _V3B .

(4) Fourth Modification Next, a fourth modification will be described.

  The electrodes of the objective deflector 13 shown in FIGS. 2, 7, 9, and 11 described above are equally divided, but in the present modification, the electrodes of the objective deflector 13 are not equally divided.

In the embodiment described above, the distribution functions f _nA (θ) and f _nB (θ) representing the electrode voltage distribution are expressed as f _nA (θ) = cos (nθ) and f _nB (θ) = sin (nθ) at the respective electrode positions. ), But this is not possible in this modification. Further, the distribution functions (n ≧ 1) representing the electrode voltage distribution are not necessarily orthogonal to each other, as will be described later.

If the electrode voltage distribution based on the above equation is followed in this modification, first, potential n + 1, n + 2,. Second, the two components constituting the potential n-order component, that is, the components proportional to V _nA and V _nB are not independent of each other. That is, increasing or decreasing one component can increase or decrease the other component as a side effect. These results from the fact that the electrodes of the objective deflector 13 in this modification are not equally divided.

In order to appropriately determine the electrode voltage distribution for V _nA and V _{nB in} this modification, first, the Fourier coefficient for a specific electrode, that is, the voltage of the specific electrode is set to a non-zero value, and the rest What is necessary is just to obtain | require the Fourier coefficient when the voltage of the electrode of this is made into zero. This Fourier series can be interpreted as the contribution of the specific electrode to the potential n-order component. Secondly, from the conditional expression indicating that an unnecessary component among potential n-order components obtained by linearly combining electrode voltages using a Fourier coefficient is canceled (required components remain), the conditional expression It is only necessary to find a combination of electrode voltages V _E1 , V _{E2 ,.} That is, the simultaneous equations relating to these electrode voltages may be solved.

In the following, only the method for determining the electrode voltage distribution for V _nA , that is, f _nA (θ) will be described for the time being. Further, the number of poles of the objective deflector 13 is set to K (≧ 1).

To find the Fourier coefficient for a particular electrode of the objective deflector 13, set r = R, the voltage of the electrode Ek (k is an integer satisfying 1 ≦ k ≦ K), ie, V _Ek to a non-zero value, and the remaining After making the voltage of the electrode zero, V _E = V _Ek and f (θ) = V (θ) / V _Ek (simply V _E = V _Ek = 1 and f (θ) = V ( θ)) is applied to the above definition of Fourier coefficients, ie, the equations (12), (12 ′), (13), and (13 ′).

  The potential n-order component obtained by linearly combining the electrode voltages using the Fourier coefficient can be expressed by the following equation (44).

(44) in _{equation a NeK} and _{b NeK} are the Fourier coefficients, phi _nA and phi _nB, respectively, the following equation (45), a (46) below.

Further, the value of V _Ek is not fixed to the value when the Fourier coefficients an _nEk and b _nEk are determined by the equations (12), (12 ′), (13), and (13 ′), To be determined.

The above conditional expression, that is, a conditional expression indicating that unnecessary components among the potential components are canceled out, requires a total of K−1 expressions. This means that, for example, if the electrode E1 is selected as one of the K pole electrodes and the electrode voltage is V _E1 = 1, the remaining electrode voltages V _E2 , V _E3 ,. , V _EK is uniquely determined.

If these electrode voltages are determined from the above total K-1 equation, f _nA (θ) at each electrode position.
_Can be expressed as f _nA (2π (k−1) / K) = V _Ek . However, f _0A (θ) can always be expressed as f _0A (θ) = 1 as obvious.

The breakdown of the above total K-1 expression is as follows. If n is n ′ regarding the target f _nA (θ), 0 ≦ n ≦ N and n ≠ n ′ when K is odd, and 0 when K is even. For n satisfying ≦ n ≦ N + 1 and n ≠ n ′, a conditional expression (equation (47) below) (total N or N + 1 expression) for making φ _nA represented by expression (45) zero, and 1 ≦ n ≦ For n satisfying N, it is a conditional expression (formula (48) below) (total formula N) for making φ _nB represented by formula (46) zero.

Supplementing this, φ _nB related to n = 0, that is, φ _0B, is always zero _{based on} the definition of b _0Ek (b _0Ek = 0).

Here, N is the maximum number of n times astigmatism to be corrected as described above, and is also the maximum number of n times astigmatism that can be corrected in all directions. If N is expressed using K,
N = (K−1) / 2 (49)
It is. In equation (49), N is rounded down.

  For example, when K = 8 and 12, the total number of the conditional expressions is 7 and 11, respectively. The breakdown of the conditional expressions is, for example, if n ′ = 2, the equation (47) relating to n = 0, 1, 3, 4 and the equation (48) relating to n = 1, 2, 3, and n = 0, 1 (47) related to 3, 4, 5, 6 and (48) related to n = 1, 2, 3, 4, 5 At this time, N becomes N = 3 and 5 from the equation (49), respectively. This corresponds to the fact that, in the embodiment and the second modification described above, up to n astigmatism corrections can be performed for n = 3 and 5 at the maximum, respectively. In other words, in order to enable n-fold astigmatism correction for n = 3 or 5 at the maximum, the number of poles K may be at least 7 or 11, respectively.

The above is the method for determining the electrode voltage distribution related to V _nA in this modification, that is, f _nA (θ) when the electrodes of the objective deflector 13 are not _equally divided. In a similar manner, the electrode voltage distribution for V _nB , ie, f _nB (θ) can also be determined.

Based on the electrode voltage distribution obtained by the above method, that is, the distribution functions f _nA (θ) and f _nB (θ), the potential n-order components φ _nA and φ _nB are obtained by V _nA and V _nB (1 ≦ n ≦ N). If generated, the phase difference between the two components becomes ± π / 2. That is, the potential n-order components generated by V _nA and V _nB (1 ≦ n ≦ N) are orthogonal to each other.

However, the above f _nA (θ) and f _nB (θ) are not necessarily orthogonal to each other. This will be described below.

For the explanation, first, let n ′ be n ′ related to the focused f _nA (θ) and f _nB (θ) (1 ≦ n ≦ N), and V _n′A related to n ′ (1 ≦ n ′ ≦ N) and The potential n (n ≧ 0) order component generated by V _n′B is _expressed as φ _n = {(a _nn′A V _n′A + a _nn′B V _n′B ) / R ⁿ } r ⁿ cos (nθ)
+ {(B _nn′A V _n′A + b _nn′B V _n′B ) / R ⁿ } r ⁿ sin (nθ)
= Φ _nA + φ _nB (50)
It expresses. Equation (50) is obtained by removing the summation symbol from Equation (14 ′). However, in the formula (50), φ _nA and φ _nB are respectively
φ _nA = (r / R) ⁿ {a _nn′A cos (nθ) + b _nn′A sin (nθ)} V _n′A (51)
φ _nB = (r / R) ⁿ {a _nn′B cos (nθ) + b _nn′B sin (nθ)} V _n′B (52)
V _n′A and V _n′B represent potential n-order components generated by V _n′A and V _n′B , respectively.

Equations (50)-(52) are related to n satisfying 0 ≦ n ≦ N.
φ _n = (a _nn′A V _n′A / R ⁿ ) r ⁿ cos (nθ) + (b _nn′B V _n′B / R ⁿ ) r ⁿ sin (nθ) (53)
φ _nA = (r / R) ⁿ a _nn′A cos (nθ) V _n′A (54)
φ _nB = (r / R) ⁿ b _nn′B sin (nθ) V _n′B (55)
It becomes. For n satisfying 0 ≦ n ≦ N, f _n′A (θ) and f _n′B (θ) in the equations (50)-(52), that is, f _{n ′} obtained by the above method. _This is because a _nn′B and b _nn′A derived from _A (θ) and f _n′B (θ) become zero. In other words, with respect to n satisfying 0 ≦ n ≦ N, φ _nA and φ _nB do not include components proportional to r ⁿ sin (nθ) and r ⁿ cos (nθ), respectively.

However, among φ _nA and φ _nB represented by the equations (54) and (55), those relating to n satisfying n ≠ n ′ are zero as described above. This corresponds to the fact that a _nn′A and b _nn′B relating to n satisfying 0 ≦ n ≦ N and n ≠ n ′ become zero in the equations (54) and (55), respectively.

(51), (52), (54), and (55) Using the equation, _{V n'a} and _{V N'b} an electrode voltage, i.e. _{V n'a} and _{V N'b} the objective deflector 13 The potential φ generated when r = R is applied
φ (V _n′A , R, θ) = V _n′A f _n′A (θ) (56)
φ (V _n′B , R, θ) = V _n′B f _n′B (θ) (57)
Can be represented by the following equations (58) and (59), respectively.

Next, from these equations, f _n′A (θ) and f _n′B (θ) in the equations (56) and (57) are derived. f _n′A (θ) and f _n′B (θ) are _{expressed by the following} formulas (60) and (61) from formulas (56) and (58) and formulas (57) and (59), respectively. It becomes.

According to the equations (60) and (61), unless b _nn′A = a _nn′B = 0, the constant for determining the orthogonality between f _n′A (θ) and f _n′B (θ) is determined. It can be seen that the equation (62) does not become zero.

That is, f _n′A (θ) and f _n′B (θ) are not necessarily orthogonal to each other.

In this modification, the above method is applied when the electrode of the objective deflector 13 is not equally divided. However, this method can also be applied when the electrode of the objective deflector 13 is equally divided. That is, the electrode voltage V _Ek (1 ≦ k ≦ K) represented by f _nA (θ) shown in FIGS. 3, 8, and 10 as f _nA (θ) in the above-described embodiment is 0 ≦ n ≦ N + 1. In addition, the expression (47) is satisfied for n satisfying n ≠ n ′, and the expression (48) is satisfied for n satisfying 1 ≦ n ≦ N. The electrode voltage V _Ek represented by f _nB (θ) shown in FIGS. 3, 8, and 10 satisfies the equation (48) for n satisfying 1 ≦ n ≦ N and n ≠ n ′, and 0 ≦ Equation (47) is satisfied with respect to n satisfying n ≦ N + 1.

Supplementing the above, in the latter case, f _nA (θ) and f _nB (θ) are orthogonal to each other. This is because the symmetry of the electrodes in this case becomes zero not only when b _nn′A and a _nn′B are 1 ≦ n ′ ≦ N but also when n ′ ≧ N + 1. That is, in the equations (60) and (61), b _nn′A = a _nn′B = 0, and I in the equation (62) becomes zero.

(5) Fifth Modification Next, a fifth modification will be described.

  In this modification, the number K of poles of the objective deflector 13 is set larger than K = 2N + 1 determined from the equation (49).

  Here, the relationship between K and N satisfies the expression (49) in the above-described embodiment, but does not satisfy the expression (49) in the present modification. For example, when K = 16, N = 7 according to equation (49), but in this modification, for example, only 12 of the 16 electrodes are used, and N = 5. That is, the astigmatism correction is performed 2, 3, 4, and 5 times as n astigmatism correction for n satisfying 2 ≦ n ≦ N. At this time, it can be considered that K = 12.

  In other words, in the above-described embodiment, N is the maximum number of n-time astigmatisms to be corrected and the maximum number of n-time astigmatisms that can theoretically be corrected in all directions. In the present modification, although the maximum number of n-fold astigmatisms to be corrected is not the maximum number of n-fold astigmatisms that can theoretically be corrected in all directions, it is smaller than that.

  The method of obtaining the electrode voltage distribution in this modification is in accordance with the method shown in the fourth modification. However, the voltage of electrodes other than the electrode to be used (12 poles in the above example) is always zero.

(6) Sixth Modification Next, a sixth modification will be described. FIG. 12 is a diagram showing a configuration of a variable shaped electron beam drawing apparatus 200 according to the sixth modification.

  In the variable shaped electron beam drawing apparatus 200 according to this modification, an objective deflector 13 ′ is provided separately from the objective deflector 13 as shown in FIG. 12.

  In this modification, the charged particle beam deflection apparatus 100a applies a deflection voltage to the objective deflector 13 'without applying the deflection voltage to the objective deflector 13. In other words, the electron beam 1 is deflected by the objective deflector 13 ′, and field curvature correction, n-time astigmatism correction (two-time astigmatism, three-time astigmatism), and distortion correction are performed by the objective deflector 13. However, among these, the field curvature correction and the distortion correction may be performed by the objective deflector 13 ′ instead of the objective deflector 13.

  Also in this modified example, in the case of n-time astigmatism correction, an n-time astigmatism correction signal for canceling 2, 3,... 2, 3,..., N−1 times astigmatism correction signal is superimposed. In the present modification, astigmatism is generated n times as many as 2, 3,..., N-1 times astigmatism, that is, even if the electron beam 1 is not deflected by the objective deflector 13. Astigmatism can occur because the axis of the objective deflector 13 and the axis of the electron beam 1 do not necessarily match in the actual optical system 101. This discrepancy comes from the fact that the processing and assembly errors of actual lenses, deflectors, and correctors are not zero.

(7) Seventh Modification Next, a seventh modification will be described.

  In this modification, distortion aberration is corrected together with curvature of field aberration and n-th astigmatism, as in the above-described embodiment. However, in the present modification, the distortion that occurs due to n-fold astigmatism correction and other distortion aberrations are distinguished from each other and corrected. Specifically, the distortion correction voltage (distortion correction signal) for the distortion generated by the n-time astigmatism correction is determined from the n-time astigmatism correction voltage, and the distortion correction voltages for other distortion aberrations are described above. This is determined by the method in the embodiment (S16 in FIG. 5).

In the present invention, the distortion is caused by the n-fold astigmatism correction, as described in the case of n = 2 or 3 in the above-described embodiment, in the objective deflector 13 for the n-fold astigmatism correction. This is because the generated potential n-order component φ _n generates a potential m-order component φ _mn related to m = 1, that is, φ _1n around the principal ray of the electron beam 1 deflected by the objective deflector 13.

If it rewrites, this will be understood from the equation (19). However, V _1C = (V _1A + iV _1B ) in the equation (19) includes ΔV _1A and ΔV _1B . Similarly, V _1A and V _1B in the equations (15) and (16), or (15 ′) and (16 ′) include distortion correction voltages ΔV _1A and ΔV _1B , respectively.

  Hereinafter, the correction for distortion aberration associated with n-time astigmatism correction will be described in detail. Therefore, first, the distortion aberration associated with n-time astigmatism correction is derived from the equation (19), and then the distortion correction voltage is derived from the distortion aberration associated with n-time astigmatism correction.

In order to derive the distortion aberration from the equation (19), first, the independent variable for φ _{mn in the} equation (19) is set to n times astigmatism correction voltages V _nA and V _nB, and φ _mn is fully differentiated. This total differentiation is expressed by the following equation (63).

In the equation (63), ΔV _nA and ΔV _nB represent minute change amounts of V _nA and V _nB , respectively. However, when the electron beam 1 is not deflected by the objective deflector 13, that is, when the n (≧ 2) times astigmatism correction voltages V _nA and V _nB when the deflection voltage V _1C is zero, ΔV _nA and ΔV _nB may be replaced with V _nA and V _nB , respectively. As described above, this is because the n-time astigmatism correction voltages V _nA and V _nB are orders of magnitude smaller than the deflection voltages V _1A and V _1B . Hereinafter, according to this replacement, the expression (63) is re-expressed as the following expression (63 ′).

  The two partial derivatives in the right side of the equation (63 ′) are expressed by the following (64) and (16) from the equations (15) and (16), or (15 ′) and (16 ′), and the equation (19). 65).

  Using the expressions (64) and (65), the expression (63 ') can be expressed as the following expression (66).

From Equation (66), φ _1n , that is, the potential primary component around the principal ray of the electron beam 1 derived from the potential n-order component around the central axis of the objective deflector 13 is expressed by the following Equation (67).

When r _B (z) cos θ _B and r _B (z) sin θ _B in the expression (67) are expressed as x (z) and y (z), respectively, the expression (67) becomes the following expression (68).

Next, the electric fields in the X-axis and Y-axis directions derived from φ _1n , that is, the following expressions (69) and (70) are obtained from the expression (68), and the expressions (69) and (70) are combined into one. .

Thereby, the complex electric field derived from φ _1n , that is, the following expression (71) is obtained.

However, in the formula (71), E _1n = E _1xn + iE _1yn , c _nnA = a _nnA + ib _nnA , and c _nnB = a _nnB + ib _nnB .

The complex electric field E _{1n of the} equation (71) deflects the electron beam 1 and changes the incident position of the electron beam 1 on the material 10. That is, distortion aberration is generated. The aberration (complex number) is expressed by the following equation (72).

However, in the equation (72), w (z) (complex number) is the material of the electron beam 1 of the deflection of the electron beam 1 caused by applying the unit electric field E _1n = 1 to the minute interval dz in the coordinate z. contribution to the incident position deviation of 10, i.e. representing a contribution to distortion aberration U _n. Distortion aberration contribution w to _{U n} (z) is a constant that regardless of the deflection track _V 1C _u 1 (z). Z ₁ and z ₂ represent Z coordinates at the light source side end and the material side end of the objective deflector 13, respectively. The potential generated by the objective deflector 13 follows the equation (18) when z ₁ ≦ z ≦ z ₂ , but is zero regardless of the equation (18) when z <z ₁ and z> z ₂ .

If the equation (71) is substituted into the equation (72), the distortion aberration U _1n becomes the following equation (73).

However, when deriving the equation (73), Re (V ₁ C ⁿ⁻¹ u ₁ ⁿ⁻¹ (z)) = Re (V ₁ C ⁿ⁻¹ ) Re (u ₁ ⁿ⁻¹ (z)) − Im The relationship (V ₁ C ^n-1 ) Im (u ₁ ^n-1 (z)) was used.

From U _1n represented by the equation (73), the X component U _1xn = Re (U _1n ) and the Y component U _1yn = Im (U _1n ) are represented by the following equations (74) and (75), respectively.

The integrand in equations (74) and (75) is a real number. The function is also only for the complex deflection trajectory u ₁ (z) for the unit deflection voltage V _1C = 1 and the coefficients c _nnA = a _nnA + ib _nnA and c _nnB = a _nnB + ib _nnB specific to the objective deflector 13. It depends on the deflection voltage V _1C and the n-time astigmatism correction voltages V _nA and V _nB . Therefore, the integration of the function does not depend on the deflection voltage V _1C or the n-time astigmatism correction voltages V _nA and V _nB . Therefore, the integral of the function can be regarded as a real constant. In the formulas (74) and (75), Re (V _1C ^n-1 ) and Im (V _1C ^n-1 ) can be expressed by the following formulas (76) and (77), respectively.

That is, Re (V _1C ⁿ⁻¹ ) and Im (V _1C ⁿ⁻¹ ) are binary n−1 order or binary n−2 order functions of V _1A and V _1B . However, the decimal parts of (n-1) / 2 and (n-2) / 2 are rounded down in the expressions (76) and (77).

From the above, n times X component _{U 1Xn} and Y components _{U 1Yn} distortion aberration due to astigmatism correction, real constants _{F 1XnAm} that does not depend on the deflection voltage _{V 1C} and n-fold astigmatism correction voltage _{V nA} and _{V nB '} , F _{1xnBm ′} , F _{1ynAm ′} , and F _{1ynBm ′} can be expressed by the following formulas (78) and (79).

(78) and (79) a distortion correction voltage component [Delta] V _1an and [Delta] V _1bn for _{U 1Xn} and _{U 1Yn} represented by formula, respectively, distortion aberration _U 1n _{= U} 1xn _{+ iU 1yn} deflection voltage to produce the micro-deflection _{-U 1n} counteract As the real and imaginary components of the change ΔV _1Cn = ΔV _1An + iΔV _1Bn = −U _1n / u ₁ (z _s )
ΔV _1An = − (Re (u ₁ (z _s )) U _1xn + Im (u ₁ (z _s )) U _1yn ) / | u ₁ (z _s ) | ² (80)
ΔV _1Bn = − (Re (u ₁ (z _s )) U _1yn −Im (u ₁ (z _s )) U _1xn ) / | u ₁ (z _s ) | ² (81)
It can be expressed. Here, z _s is the Z coordinate of the incident surface of the electron beam 1, that is, the upper surface of the material 10. In addition, the distortion aberration newly generated due to the distortion correction was ignored. These formulas indicate that Re (u ₁ (z _s )) = u ₁ (z _s ), that is, Im (u ₁ (z _s )) = 0, the mounting angle of the objective deflector 13 (around the Z axis) If you decide
ΔV _1An = −U _1xn / u ₁ (z _s ) (80 ′)
ΔV _1Bn = −U _1yn / u ₁ (z _s ) (81 ′)
And become easy. At this time, u ₁ (z _s ) is a real number. Hereinafter, the distortion correction voltage components ΔV _1An and ΔV _1Bn follow the equations (80 ′) and (81 ′).

From the expressions (78), (79), (80 ′), and (81 ′), ΔV _1An and ΔV _1Bn are _{expressed by the following} expressions (82) and (83).

When the following formulas (84) to (87) are introduced into the formulas (82) and (83) as the coefficients of V _nA and V _nB , the formulas (82) and (83) are represented by the following formulas (88) and (89). It is expressed as an expression.

In the equations (88) and (89), ΔV _1AnA = ρ _1AnA V _nA and ΔV _1AnB = ρ _1AnA V _nB are distortion aberration correction voltage components with respect to the X component of the distortion aberration generated by V _nA and V _nB , respectively. ΔV _1BnA = ρ _1BnA V _nA and ΔV _1BnB = ρ _1BnB V _nB represent distortion aberration correction voltage components with respect to the Y component of distortion aberration generated by V _nA and V _nB , respectively. That is, among these a total of four strain aberration correction voltage component, the sum ΔV _1AnA + ΔV _1AnB and ΔV _1BnA + ΔV _1BnB of the two components with each other to correct the distortion aberration of the same direction, respectively, and [Delta] V _1an and [Delta] V _1bn.

  If the equations (88) and (89) are used, the distortion correction voltage required to correct all distortion aberrations derived from the 2, 3,..., N times astigmatism correction voltage is the following (90), (91)

Equations (88) and (89) are the total derivatives of V _1An and V _1Bn , respectively, and _equations (90) and (91) are none other than the total derivatives of V _1A and V _1B , respectively. That is, the coefficients ρ _1AnA , ρ _1BnA , ρ _1AnB , ρ _1BnB can be expressed by the following equations (84 ′), (85 ′), (86 ′), and (87 ′), respectively.

Hereinafter, these coefficients ρ _1AnA , ρ _1BnA , ρ _1AnB , and ρ _1BnB are referred to as correction voltage ratios.

As can be seen from the above description, the components ΔV _1An and ΔV _1Bn of the distortion correction voltage with respect to the distortion aberration associated with the n-time astigmatism correction are n times astigmatic with the correction voltage ratios ρ _1AnA , ρ _1BnA , ρ _1AnB , ρ _1BnB It can be determined from the correction voltages V _nA and V _nB . Here, since V _nA and V _nB are determined at the stage where n-point astigmatism correction has been performed, it is not necessary to newly obtain these for determining ΔV _1A and ΔV _1B .

The correction voltage ratios ρ _1AnA , ρ _1BnA , ρ _1AnB , ρ _1BnB do not depend on any of ΔV _nA and ΔV _nB as can be seen from the equations (84)-(87). More specifically, the correction voltage ratio is a binary n-1 linear function of V _1A and V _1B . V _1A and V _1B can be expressed as binary linear functions of the deflection coordinates x and y if the distortion correction voltages ΔV _1A and ΔV _1B are ignored.

For these two reasons, the correction voltage ratio can be approximately expressed as a binary n-1 order function of x and y. Specifically, for example, if N = 3, the correction voltage ratio is approximately a binary linear function of x and y when n = 2, that is, when astigmatism correction is performed twice. When n = 3, that is, when astigmatism correction is performed three times, a binary quadratic function of x and y is approximately obtained.

  The above approximation is effective in a general variable shaped electron beam drawing apparatus. This is because, in a variable shaped electron beam writing apparatus, the maximum deflection is several hundred microns, whereas the distortion is at most several hundred nm, that is, 0.1% of the deflection. This is because the distortion correction voltage is as small as about 0.1% of the deflection voltage.

To determine the distribution of the correction voltage ratios ρ _1AnA , ρ _1BnA , ρ _1AnB , ρ _1BnB , that is, to determine these values at each deflection coordinate, first, a predetermined field within the deflection field of the objective deflector 13 is determined. The correction voltage ratio may be measured at a point. Then, these values may be interpolated to determine the correction voltage ratio value at an arbitrary deflection coordinate.

  At that time, the number of the predetermined points, that is, the number of measurement points of the correction voltage ratio may be at least n (n + 1) / 2 points. This means that the correction voltage ratio is expressed by a binary n−1 linear function as described above, and the number of coefficients of the binary n−1 linear function is n (n + 1) / 2. It depends. Specifically, the number of measurement points of the correction voltage ratio is at least 3 when n = 2, that is, when the astigmatism correction is performed twice, and when n = 3, that is, the astigmatism correction is performed 3 times. In some cases, the minimum score is 6.

If the determination of the distortion correction voltage for the distortion aberration associated with the n-fold astigmatism correction is not based on the above method, for example, by directly measuring the distortion aberration (S16 in FIG. 5), the n-fold astigmatism. When the distribution of the correction voltage is expressed by a binary j (≧ 1) degree function of x and y, it is necessary to measure distortion aberration at at least (j + n) (j + n + 1) / 2 measurement points. Become. This is because the n-time astigmatism correction voltage distribution is a binary j (≧ 1) order function of x and y, and a binary n−1 order function of ρ _1AnA , ρ _1BnA , ρ _1AnB , ρ _1BnB is x and y. As can be seen from the equations (32) and (33), the distortion distribution is represented by a binary j + n−1 linear function, and the number of coefficients of the binary j + n−1 linear function. Is (j + n) (j + n + 1) / 2. Specifically, for example, when the distribution of the n-time astigmatism correction voltage is expressed by a binary 6th-order function of x and y, the number of measurement points of the correction voltage ratio is n = 2, that is, twice astigmatism. When correction is performed, a minimum of 36 points is required, and when n = 3, that is, when astigmatism correction is performed three times, a minimum of 45 points is required.

As can be seen from the above, when determining the distortion correction voltage by this method, when n is small (for example, n = 2 or 3), the correction voltage ratios ρ _1AnA , ρ _1BnA , ρ _1AnB , ρ _1BnB are measured. The score is small. If the number of measurement points is reduced, the distortion correction voltages ΔV _1A and ΔV _1B can be determined in a short time. However, it is conceivable that the measurement result of the correction voltage ratio includes an error. If necessary, the number of measurement points of the correction voltage ratio may be larger than the number of points n (n + 1) / 2 in order to smooth the measurement result.

  In many cases, the n-th astigmatism decreases as n increases. That is, n astigmatism with respect to a small n can be so large as to require correction. Therefore, in many cases, it is only necessary to correct distortion aberration associated with n-time astigmatism correction for a small n, and as a result, the number of measurement points for the correction voltage ratio is small.

The fact that n-fold astigmatism decreases in many cases as n increases as described above, that is, increases as n decreases, can be explained using equation (19). Here, n corresponds to m in the equation (19), and n-fold astigmatism is m-fold astigmatism in the following description, that is, a potential around the central axis (Z-axis) of the objective deflector 13. This corresponds to m-th astigmatism _{caused by} the potential m-order component φ _mn around the principal ray of the electron beam 1 derived from the n-order component φ _n .

According to the equation (19), the beam radius r _B direction generated by the potential m-order component φ _mn around the principal ray of the electron beam 1 derived from the potential n-order component around the central axis (Z axis) of the objective deflector 13. The electric field is expressed by the following equation (92).

However, G _mn in the equation (92) is the amplitude of the electric field,
_{G mn = (| c n |} V E r B n-1 (z) / R n) n C m m (| V 1C u 1 (z) | / r B (z)) n-m ··· ( 93)
It is.

From equation (93), it can be seen that G _mn is proportional to (| V _1C u ₁ (z) | / r _B (z)) ^nm . That is, by increasing the deflection voltage V _1C , the deflection trajectory V _1C u ₁ (z) of the electron beam 1 increases, and as a result | V _1C u ₁ (z) |> r _B (z), m As G becomes smaller, G _mn increases exponentially, and therefore m-th astigmatism _produced by E _mrn also increases. This property of the m-th astigmatism becomes conspicuous as the deflection trajectory V _1C u ₁ (z) of the electron beam 1 increases. However, in the formula (92), γ _mn = arcsin (Im (V _1C ^n−m u ₁ ^n−m (z)) / | V _1C ^n−m u ₁ ^n−m (z) |) and γ _n = arcsin (b _n / | c _n |), where c _n = a _n + ib _n .

  Next, the flow of aberration correction in this modification will be described. FIG. 13 is a flowchart showing an example of the flow of aberration correction in this modification. However, in FIG. 13, N = 3. That is, astigmatism correction n times, astigmatism correction is performed twice and three times.

As shown in FIG. 13, the flow of aberration correction in this modification is as follows: focus correction (field curvature correction) voltage determination processing (steps S20 and S21) by the control device 21 shown in FIG. It consists of a correction voltage determination process (steps S22, S23), a first distortion correction voltage determination process (steps S24, S25, S26), and a second distortion correction voltage determination process (steps S27, S28). Among these, the first distortion correction voltage determination processing is correction for distortion aberrations generated by n-time astigmatism correction, specifically, distortion aberrations derived from V _2A , V _2B , V _3A , and V _3B. The second distortion correction voltage determination process is correction for other distortion aberrations, specifically distortion aberrations derived from V _0A , V _1A , and V _1B and distortion aberrations derived from the magnetic field of the objective lens 9. Further, the focus correction (field curvature correction) voltage determination processing (steps S20 and S21) is the same as steps S10 and S11 of FIG. 5 described above, and the astigmatism correction voltage determination processing (step S22, S22) twice and three times. S23) corresponds to steps S12, S13, S14, and S15 of FIG. Throughout the flow shown in FIG. 13, the deflection voltages V _1A and V _1B always include the focus correction voltage V _0A , the twice astigmatism correction voltages V _2A and V _2B , the three times astigmatism correction voltage V _3A and It is assumed that V _3B , distortion correction voltages ΔV _1A and ΔV _1B are superimposed, and these values change as necessary. The initial values of these correction voltages and correction voltage ratios are zero.

(1) Focus Correction Voltage Determination Processing First, the control device 21 performs the same processing as S10 and S11 shown in FIG. 5 described above, optimizes the focus correction voltage V _0A at each deflection coordinate (S20), and distributes these. An approximate function V _0A (x, y) representing is determined (S21). Then, a focus correction voltage for each deflection coordinate is determined from the approximate function, and this is stored in the storage device 22.

  For this purpose, the deflection field of the objective deflector 13 is divided into a finite number of partitions, and the focus correction voltage in each partition is stored in each of the memory with the same finite address number provided in the storage device 22. . Then, the value stored in the memory is referred to according to the deflection coordinates. That is, the focus correction voltage is a discontinuous function with respect to the deflection coordinates because the section is finitely small.

  This method of storing and referring to the correction voltage is applied not only to the focus correction voltage but also to the second and third correction voltages and the distortion correction voltage. Therefore, the second and third correction voltages and the distortion correction voltage are also discontinuous functions with respect to the deflection coordinates.

(2) Two-time and three-time astigmatism correction voltage determination processing Next, the control device 21 performs the same processing as S12 to S15 shown in FIG. 5 described above, and performs the two-time astigmatism correction voltage V _{2A at} each deflection coordinate. And V _2B and the three-time astigmatism correction voltages V _3A and V _3B are optimized (S22), and approximate functions V _2A (x, y), V _2B (x, y), V _3A (x , Y) and V _3B (x, y) are determined (S23). Then, the astigmatism correction voltage is determined twice and three times for each deflection coordinate from the approximate function, and is stored in the storage device 22.

(3) First distortion correction voltage determination process (correction of distortion aberration caused by n-time astigmatism correction)
Next, at a predetermined deflection coordinate, the control device 21 first changes the astigmatism correction voltage V _2A twice by a predetermined change amount ΔV _2A to generate distortion aberration, and the electron beam is scanned by scanning the knife edge 18. Measure the position of 1. Then, the distortion correction voltage components ΔV _1A and ΔV _1B are changed by a change amount necessary to cancel the distortion aberration, and ratios ρ _1A2A and ρ _1B2A of the change amounts with respect to ΔV _2A are calculated. Next, V _2B is changed by a predetermined change amount ΔV _2B to generate distortion, and the position of the electron beam 1 is measured in the same manner. Then, the distortion correction voltage components ΔV _1A and ΔV _1B are changed by a change amount necessary to cancel the distortion aberration, and ratios ρ _1A2B and ρ _1B2B of the change amounts with respect to ΔV _2B are calculated (S24). Further, ρ _1A3A , ρ _1B3A , ρ _1A3B , and ρ _1B3B are calculated by the same method. However, the number of the predetermined deflection coordinates is n (n + 1) / 2 points.

  The distortion aberration measurement does not necessarily need to be performed by scanning the knife edge 18, but may be performed by scanning a heavy metal microstructure as described above. In that case, instead of detecting the beam current flowing into the current detector 19, the reflected electrons from the heavy metal microstructure are detected.

In order to _obtain the correction voltage ratios ρ _1AnA , ρ _1BnA , ρ _1AnB , ρ _1BnB (n = 2 or 3), instead of using the equation (84)-(87), (84 ′) − (87 ′) An approximate expression of
ρ 1 _AnA (x, y) = (V _1A (x, y, V _nA + ΔV _nA , V _nB ) −V _1A (x, y, V _nA , V _nB )) / ΔV _nA (84 ″)
ρ _1BnA (x, y) = (V _1B (x, y, V _nA + ΔV _nA , V _nB ) −V _1B (x, y, V _nA , V _nB )) / ΔV _nA (85 ″)
ρ _1AnB (x, y) = (V _1A (x, y, V _n A, V _nB + ΔV _nB ) −V _1A (x,
y, V _nA , V _nB )) / ΔV _nB (86 ″)
ρ _1BnB (x, y) = (V _1B (x, y, V _nA , V _nB + ΔV _nB ) −V _1B (x, y, V _nA , V _nB )) / ΔV _nB (87 ″)
Should be used. However, in the equation (84 ″) − (87 ″), V _1A (x, y, V _nA , V _nB ) and V _1B (x, y, V _nA , V _nB ) are astigmatized n times. It represents the deflection voltages V _1A and V _1B determined to cancel out distortion aberration caused by the voltages V _nA and V _nB . Further, when the n-time astigmatism correction voltages V _nA and V _nB are changed by ΔV _nA and ΔV _nB , respectively, other astigmatism correction voltages, that is, n ′ (≠ n) times astigmatism correction voltage V _n′A and V _n′B is fixed. At this time, the change amounts ΔV _nA and ΔV _nB of the n-fold astigmatism correction voltage may be fixed regardless of the deflection coordinates.

When the optimum values of ρ _1AnA , ρ _1BnA , ρ _1AnB , ρ _1BnB (n = 2 or 3) at each deflection coordinate are _obtained in this way, the control device 21 calculates the approximate function ρ _1AnA (x , Y), ρ _1BnA (x, y), ρ _1AnB (x, y), and ρ _1BnB (x, y) are determined (S25). These functions and the approximate function of the n-time astigmatism correction voltages V _nA and V _nB obtained in S23 are reflected in the equations (90) and (91), and the distortion correction voltage ΔV _{1A at} each deflection coordinate and ΔV _1B is determined (S26), and these are stored in the storage device 22.

However, when determining the [Delta] V _1A and [Delta] V _1B, the value of _{V nA} and _{V nB,} the value of _{V nA} and _{V nB} in each compartment in the deflection field of the objective deflector 13, that is stored in the aforementioned memory value And ρ _1AnA , ρ _1BnA , ρ _1AnB , and ρ _1BnB are the values in each section. Furthermore, the size and coordinates of each section are common to V _nA and V _nB and ΔV _1A and ΔV _1B . That is, the sections corresponding to these are made to correspond one-to-one.

  In this way, only one distortion correction voltage value exists for the twice and three times astigmatism correction voltage values in each section. As a result, the distortion correction residual resulting from the fact that the divisions for the 2nd and 3rd astigmatism correction voltages are finitely small, that is, the nth astigmatism correction voltage changes discontinuously with respect to the coordinates in the deflection field. Is resolved. In other words, it is possible to remove distortion aberration that occurs due to the second and third astigmatism corrections from the stage of generation.

(4) Second distortion correction voltage determination processing (correction of other distortion aberration)
Next, the control device 21 measures the position of the electron beam 1 by scanning the knife edge 18 (or a heavy metal microstructure) at a predetermined deflection coordinate. Then, the distortion correction voltage components are changed by an amount necessary to cancel the distortion aberration, and the optimum values of the distortion correction voltages ΔV _1A and ΔV _{1B at} the respective deflection coordinates are determined (S27). The number of the predetermined deflection coordinates is appropriately determined according to the distortion distribution.

When the optimum values of the distortion correction voltages ΔV _1A and ΔV _1B at the respective deflection coordinates are obtained in this way, approximate functions ΔV _1A (x, y) and ΔV _1B (x, y) representing these distributions are determined ( S28). Then, a distortion correction voltage for each deflection coordinate is determined from the approximate function, and these are stored in the storage device 22.

However, these distortion correction voltages, that is, the distortion correction voltage determined in the second distortion correction voltage determination processes S27 and S28 and the distortion correction voltage determined in the first distortion correction voltage determination processes S24, S25, and S26 are as follows. These are stored separately and added before being superimposed on the deflection voltage (not shown in FIG. 6). Also, the deflection field section for the former is made finer than the deflection field section for the latter, that is, the deflection field section for the latter and the n-th astigmatism correction voltage. This is because, in the variable shaped electron beam drawing apparatus, the tolerance for the correction error of the beam position deviation is smaller than that for the correction error of the beam blur.

  Conversely, the section for the n-th astigmatism correction voltage may be rougher than the section for the distortion correction voltage determined in the second distortion correction voltage determination processes S27 and S28. For the same reason, the section for the focus correction voltage may be rougher than the section for the distortion correction voltage. If the section for the n-fold astigmatism correction voltage and the focus correction voltage is made rough in this way, the capacity of the memory provided in the storage device 22 can be reduced.

  The above is the flow of aberration correction in this modification. Through the above steps S20 to S28, the field curvature aberration, the second and third astigmatisms, and the distortion aberration at any deflection coordinate are all corrected.

  Of these steps, even if steps S24, S25, and S26 are omitted, the distortion aberration can be corrected theoretically. In this case, however, the section for the n-time astigmatism correction voltage is finitely small. That is, a distortion aberration residual that can be generated when the n-fold astigmatism correction voltage is a discontinuous function with respect to the deflection coordinates becomes a problem. Although it is possible to reduce the correction residual, in order to do so, it is necessary to increase the number of predetermined deflection coordinates for measuring the position of the electron beam 1 in steps S27 and S28. That is, the measurement time increases.

  As described above, in the present modification, the control device 21 determines and corrects the distortion occurring due to the n-fold astigmatism correction from the n-fold astigmatism correction voltage. For this purpose, it is necessary to measure the correction voltage ratio, but the number of measurement points does not need to be increased even if the distribution of the n-fold astigmatism correction voltage in the deflection field becomes complicated. That is, even when the distribution of the n-fold astigmatism correction voltage becomes complicated, the time required to determine the correction voltage ratio and to correct the distortion occurring due to the correction of the n-fold astigmatism varies. Absent.

  The charged particle beam deflection apparatus according to this modification has the following features, for example.

In the charged particle beam deflection apparatus according to this modification, the control device 21 includes two components ΔV _1AnA and ΔV _1BnA that constitute a distortion correction signal for canceling distortion aberration generated according to the n-time astigmatism correction signal V _nA , Two components ΔV _1AnB and ΔV _1BnB constituting a distortion correction signal for canceling distortion aberration generated according to the n-time astigmatism correction signal V _nB are determined for each deflection coordinate, and the four components ΔV _1AnA and ΔV of the distortion correction signal are determined. _1BnA, ΔV _1AnB, and [Delta] V from _1BnB, calculates the sum ΔV _1AnA + ΔV _1AnB and ΔV _1BnA + ΔV _1BnB of the two components with each other to correct the distortion aberration of the same direction, the two sum of components between ΔV _1AnA + ΔV _1AnB and ΔV _1BnA + ΔV _{Let 1BnB be} the two components ΔV _1An and ΔV _{1Bn of the} distortion correction signal, respectively. As a result, it is possible to remove distortion aberration that may occur with n-time astigmatism correction.

In the charged particle beam deflection apparatus according to this modification, the control device 21 uses the variable range of the deflection coordinates as a deflection field, and cancels distortion aberration that occurs in response to a predetermined change amount ΔV _nA of the n-time astigmatism correction signal V _nA. for, the change amount of the two components [Delta] V _1A and [Delta] V _1B of the distortion correction signal, and the ratio [rho _1AnA and [rho _1BnA for the [Delta] V _nA, for canceling the distortion aberration generated in accordance with a predetermined change amount [Delta] V _nB of _{V nB} The ratios ρ _1AnB and ρ _1BnB of the change amounts of the two components ΔV _1A and ΔV _1B of the distortion correction signal to ΔV _nB are defined as deflection coordinate points of predetermined n (n + 1) / 2 points or more included in the deflection field. And interpolating the values of the measured ratios ρ _1AnA , ρ _1BnA , ρ _1AnB , and ρ _{1BnB assigned} the values of V _nA and V _nB The _values of the ratios ρ _1AnA , ρ _1BnA , ρ _1AnB , and ρ _1BnB at each deflection coordinate are determined, the values of the ratios ρ _1AnA , ρ _1BnA , ρ _1AnB , and ρ _1BnB and the n-time astigmatism correction signals V _nA and V product ρ _1AnA V _nA and the value of _nB, ρ _1BnA V _nA, to calculate the ρ _1AnB V _nB, and ρ _1BnB V _nB, laminate ρ _1AnA V _n
Let _A , ρ _1BnA V _nA , ρ _1AnB V _nB , and ρ _1BnB V _{nB be} the four components ΔV _1AnA , ΔV _1BnA , ΔV _1AnB , and ΔV _1BnB of the distortion correction signal, respectively. Thereby, the four components ΔV _1AnA , ΔV _1BnA , ΔV _1AnB , and ΔV _1BnB of the distortion correction signal can be determined. That is, it is possible to remove distortion aberration that may occur with n times astigmatism correction. For this purpose, the ratio needs to be measured, but the number of measurement points does not need to be increased even if the distribution of the n-fold astigmatism correction signal in the deflection field becomes complicated. That is, even if the distribution of the n-th astigmatism correction signal is complicated, the time required to determine the ratio and to correct the distortion occurring due to the correction of the n-th astigmatism based on the ratio remains unchanged. .

  There is no need to increase the number of measurement points of the ratio regardless of the complexity of the distribution of n-fold astigmatism because the number of measurement points n (n + 1) / 2 is a function representing the distribution of the ratio in the deflection field, ie, deflection. This is equal to the number of coefficients of the binary n-1 linear function of the coordinates x and y, and does not depend on the distribution of the n times astigmatism correction signal in the deflection field. If, for example, the distortion aberration is directly measured for correcting the distortion aberration (S16 in FIG. 5 and S27 in FIG. 13), the distribution of the nth astigmatism correction signal is the jth order of the coordinates in the deflection field. When expressed by a function, it is necessary to measure the distortion aberration at at least (j + n) (j + n + 1) / 2 measurement points.

  In the charged particle beam deflection apparatus according to this modification, the control device 21 divides the deflection field into a plurality of sections, and each section has an n-time astigmatism correction signal and a n-time non-point correction signal with respect to the coordinates of a point representing the section. A distortion correction signal for distortion aberration generated by point correction is assigned, and the coordinates and size of each section are made common to the n-time astigmatism correction signal and the distortion correction signal. Thereby, the value of the distortion correction signal and the n-time astigmatism correction signal for each section can be made to correspond one-to-one. Therefore, it is possible to eliminate the distortion correction residual caused by the fact that the section for the n-time astigmatism correction signal is finitely small, that is, the n-time astigmatism correction signal changes discontinuously with respect to the coordinates in the deflection field. In other words, it is possible to remove distortion aberration that occurs due to n times astigmatism correction from the stage of generation.

(8) Eighth Modification Next, an eighth modification will be described.

  In the charged particle beam deflection apparatus 100a described above, the objective deflector 13 is an electrostatic type. On the other hand, the objective deflector 13 may be a magnetic field type. That is, in the present modification, the objective deflector 13 includes a plurality of coils for generating a magnetic field. When the objective deflector 13 is a magnetic field type, the electrode of the objective deflector 13 in the above-described embodiment and the above-described first to seventh modifications corresponds to a coil, and the electrode voltage distribution (voltage distribution) is Coil current distribution (current distribution). Therefore, the electrode in the embodiment described above and the first to seventh modifications described above can be read as a coil, and the electrode voltage distribution can be read as a coil current distribution.

(9) Ninth Modification Next, a ninth modification will be described.

  In the charged particle beam deflection apparatus 100a described above, the case where the opening of the second shaped aperture plate 7 is rectangular has been described. However, the shape of the opening of the second shaped aperture plate 7 is not particularly limited, and is given. It can have the shape of Thereby, character projection can be implemented.

(10) Tenth Modification Next, a tenth modification will be described.

  In the embodiment described above, the case where the charged particle beam deflection apparatus 100a is used in a variable shaped electron beam drawing apparatus as shown in FIG. 1 has been described. However, the charged particle beam deflection apparatus 100a is used as a spot electron beam drawing apparatus. It may be used. That is, the optical system 101 shown in FIG. 1 connects the images of the first molded aperture plate 3 and the second molded aperture plate 7 on the material 10, but the optical system of this modification is an optical source of the light source (crossover 4a). The image is tied onto the material 10. That is, the electron beam 1 is not a variable shaped beam but a spot beam.

(11) Eleventh Modification Next, an eleventh modification will be described.

  In the embodiment described above, the variable shaped electron beam drawing apparatus 100 uses the electron beam 1, but an ion beam may be used instead of the electron beam 1.

  The above-described embodiments are examples and are not limited to these. For example, it is possible to combine the above-described embodiment and each modification as appropriate.

  The present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations that have the same functions, methods, and results, or configurations that have the same objects and effects). In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that exhibits the same operational effects as the configuration described in the embodiment or a configuration that can achieve the same object. Further, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

DESCRIPTION OF SYMBOLS 1 ... Electron beam (charged particle beam), 2 ... Irradiation lens, 3 ... 1st shaping | molding aperture plate, 4 ... Electron beam supply part, 6 ... Molding lens, 7 ... 2nd shaping | molding aperture plate, 8 ... Reduction lens, DESCRIPTION OF SYMBOLS 9 ... Objective lens, 12 ... Molding deflector, 13, 13 '... Objective deflector, 14, 15 ... Blanker, 17 ... Blanking aperture plate, 18 ... Knife edge, 19 ... Current detector (Faraday cup), 20 ... Drive amplifier, 21 ... control device, 22 ... storage device, 30 ... material stage, 100 ... variable shaping electron beam drawing device, 100a ... charged particle beam deflection device, 200 ... variable shaping electron beam drawing device

Claims (11)

An electrostatic or magnetic multipole;
A controller for applying a deflection signal for deflecting a charged particle beam to the multipole;
Including
The controller is
n times astigmatism correction signal for canceling n times astigmatism (n = 2, 3,..., N, N is an integer of 3 or more) is superimposed on the deflection signal;
.., N-1 times astigmatism generated by superimposing the n times astigmatism correction signal for each deflection coordinate on which the charged particle beam deflected by application of the deflection signal is incident. A charged particle beam deflecting device that superimposes the astigmatism correction signal 2, 3, ..., n-1 times on the deflection signal. In claim 1,
An angle around the central axis of the multipole representing the position of each pole of the multipole is θ,
Two components constituting the n-time astigmatism correction signal are V _nA and V _nB ,
When f _nA (θ) and f _nB (θ) are distribution functions representing the voltage distribution for each electrode of the multipole or the current distribution for each coil of the multipole with respect to V _nA and V _nB , respectively.
The controller is
Using V _nA and V _nB as parameters, V _n (θ) = V _nA f _nA (θ) + V _nB f _nB (θ) is superimposed on the deflection signal as the n-time astigmatism correction signal, and the V _A charged particle beam deflection apparatus, wherein values of _nA and V _nB are determined for each deflection coordinate, and V _n (θ) into which the determined V _nA and V _nB are substituted is used as the n-time astigmatism correction signal. In claim 2,
A charged particle beam deflecting device in which a potential n-order component or magnetic potential n-order component generated according to V _nA and a potential n-order component or magnetic potential n-order component generated according to V _nB are orthogonal to each other . In claim 2 or 3,
The 2, 3, ..., n-1 astigmatism correction signals for canceling the 2, 3, ..., n-1 astigmatism generated by the superposition of the n times astigmatism correction signals. , M times astigmatism correction signal (m = 2, 3,..., N−1),
When the two components constituting the m-time astigmatism correction signal are V _mA and V _mB ,
The controller is
2,3 generated according to a predetermined variation [Delta] V _nA of the _{V nA,} ···, n-1 times for canceling each of the astigmatism, the two components _{V mA} of the m-fold astigmatism correction signal And the ratio ρ _mAnA and ρ _{mBnA of the} amount of change in V _{mB to} the ΔV _nA ,
2,3 generated according to a predetermined variation [Delta] V _nB of the _{V nB,} ···, n-1 times for canceling each of the astigmatism, the two components _{V mA} of the m-fold astigmatism correction signal And a ratio ρ _mAnB and ρ _mBnB of the change amount of V _{mB to} the ΔV _nB are determined for each deflection coordinate,
The ratio _{ρ mAnA, ρ mBnA, ρ mAnB} , and [rho _MBnB and the _{V nA} and the product [rho _MANA V _nA of said _{V nB} for each of the deflection _{coordinates, ρ mBnA V nA, ρ mAnB} V nB, and _ρ mBnB V _nB To calculate
Laminate _{ρ mAnA V nA, ρ mBnA V} nA, ρ mAnB V nB, and _ρ mBnB V sum of _{nB ρ mAnA V nA + ρ mAnB} V nB, and _{ρ mAnB V nB + ρ mBnB V} nB, wherein m times astigmatic correction A charged particle beam deflection apparatus that uses the two components V _mA and V _{mB of the} signal. In any one of Claims 1 thru | or 4,
The control unit distributes the voltage distribution to each electrode of the multipole element or the current distribution to each coil of the multipole element with respect to the n-th astigmatism correction signal, except for the case of n = N, the n-th astigmatism correction signal. , N-order components, or magnetic potentials n + 1, n + 2,..., N-order components are suppressed when they are superimposed. In any one of Claims 2 thru | or 5,
The said control part is a charged particle beam apparatus which determines the distortion correction signal for negating a distortion aberration after determining the said n times astigmatism correction signal. In claim 6,
When ΔV _1An and ΔV _1Bn are two components constituting a distortion correction signal for canceling distortion aberration generated in response to the n-th astigmatism correction signal among the distortion correction signals,
The controller is
Two components ΔV _1AnA and ΔV _1BnA constituting a distortion correction signal for canceling distortion aberration generated according to V _nA ;
Two components ΔV _1AnB and ΔV _1BnB constituting a distortion correction signal for canceling distortion aberration generated according to V _nB are determined for each deflection coordinate,
From the four components ΔV _1AnA , ΔV _1BnA , ΔV _1AnB , and ΔV _{1BnB of the} distortion correction signal, the sums ΔV _1AnA + ΔV _1AnB and ΔV _1BnA + ΔV _1BnB of the two components that correct distortion aberration in the same direction are calculated,
A charged particle beam deflecting device in which the sums ΔV _1AnA + ΔV _1AnB and ΔV _1BnA + ΔV _1BnB of the two components are used as the two components ΔV _1An and ΔV _{1Bn of the} distortion correction signal, respectively. In claim 7,
The controller is
The variable range of the deflection coordinates is a deflection field,
For canceling the distortion aberration generated in accordance with a predetermined change amount [Delta] V _nA of the _{V nA,} the change amount of the two components [Delta] V _1A and [Delta] V _1B of the distortion correction signal, and the ratio [rho _1AnA and [rho _1BnA for the [Delta] V _nA,
For canceling the distortion aberration generated in accordance with a predetermined change amount [Delta] V _nB of the _{V nB,} the change amount of the two components [Delta] V _1A and [Delta] V _1B of the distortion correction signal, and a ratio [rho _1AnB and [rho _1BnB for [Delta] V _nB ,
Measured at deflection coordinate points of predetermined n (n + 1) / 2 points or more included in the deflection field,
By interpolating the measured values of the ratios ρ _1AnA , ρ _1BnA , ρ _1AnB , and ρ _1BnB , the ratios ρ _1AnA , ρ _1BnA , in each deflection coordinate to which the values of V _nA and V _nB are allocated, determine the values of ρ _1AnB , and ρ _1BnB ,
The ratio _{ρ 1AnA, ρ 1BnA, ρ 1AnB} , and [rho value of _1BnB, the _{V nA} and the product ρ _1AnA V _nA between the value of the _{V nB, ρ 1BnA V nA,} ρ 1AnB V nB, and ρ _1BnB V _nB To calculate
The _products ρ _1AnA V _nA , ρ _1BnA V _nA , ρ _1AnB V _nB , and ρ _1BnB V _nB are the four components ΔV _1AnA , ΔV _1BnA , ΔV _1AnB , and ΔV _1B of the distortion correction signal, respectively. Beam deflection device. In claim 8,
The controller is
The deflection field is divided into a plurality of sections, and the n-th astigmatism correction signal for the coordinates of the point representing the section and a distortion correction signal for distortion aberration generated by the n-th astigmatism correction are assigned to each section. ,
A charged particle beam deflection apparatus in which the coordinates and size of each section are common to the n-time astigmatism correction signal and the distortion correction signal. In any one of Claims 1 thru | or 9,
The control unit determines the N, N-1,..., Twice astigmatism correction signals in the order of N, N-1,. In claim 10,
The charged particle beam deflection apparatus, wherein the control unit repeats the determination of the values of the components constituting the N, N-1,..., Twice astigmatism correction signals until the values converge.

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