JP4889431B2 - Electron beam exposure apparatus and electron beam exposure method - Google Patents

Description

  The present invention relates to an electron beam exposure apparatus and an electron beam exposure method, and more particularly to an electron beam exposure apparatus and an electron beam exposure method that can change the shape and size of a beam using a variable rectangular aperture or a partial collective pattern.

  In recent years, in order to improve throughput in an electron beam exposure apparatus, a variable rectangular opening or a plurality of mask patterns are prepared in a mask, and these are selected by beam deflection and transferred and exposed to a sample.

  As such an exposure apparatus, there is an electron beam exposure apparatus that performs partial batch exposure. In partial collective exposure, a beam is irradiated to one pattern region selected by beam deflection from a plurality of patterns arranged on a mask, and a beam cross section is formed into a pattern shape. Further, the beam that has passed through the mask is deflected back by a subsequent deflector, reduced at a constant reduction rate determined by the electron optical system, and transferred onto the sample.

  If a frequently used pattern is prepared on the mask in advance in partial batch exposure, the number of exposure shots required is greatly reduced and the throughput is improved as compared with the case of only a variable rectangular aperture.

  On the other hand, when electron beam exposure is performed using a variable rectangular aperture or a partial collective pattern, the beam size of the electron beam varies from shot to shot, and the phenomenon that the focus of the electron beam shifts and the beam is blurred occurs. For example, when focusing on the sample surface with a small beam size, if exposure is performed with a large beam size, the total current of the electron beam increases, the focal length increases, and beam blur occurs on the sample surface.

  In order to prevent such defocusing of the electron beam, a method of correcting the current flowing through the refocusing coil for each shot from the area of the variable rectangular opening has been studied. Patent Document 1 discloses a method for controlling a converging coil in synchronization with the size of a rectangular beam.

Japanese Patent Application Laid-Open No. H10-228688 discloses a method of measuring and correcting a beam axis misalignment when performing electron beam refocusing.
JP-A-56-94740 JP 58-121625 A

  As described above, when a variable rectangular opening or a partial collective pattern is used, the focus of the electron beam is moved for each shot, so that it is possible to prevent the deviation of the beam focus.

  Specifically, a refocusing coil is installed, and an amount of current proportional to the cross-sectional area of the shaped beam is passed through the refocusing coil to adjust the focus of the beam. For example, when the beam size is large, a larger current is passed through the refocusing coil in proportion to the cross-sectional area of the beam so as to strengthen the electron beam convergence effect.

  However, it takes time to execute the refocus, and there is a disadvantage that the exposure throughput cannot be improved despite the partial batch exposure.

  For example, although the time required to shape the electron beam is about 50 ns, the refocusing execution time is about 300 ns until a predetermined current is passed through the refocusing coil and becomes a stable current. The exposure waiting time has become longer.

  The present invention has been made in view of the problems of the prior art, and in electron beam exposure capable of changing the shape and size of a beam, an electron capable of shortening the refocus time and improving the throughput. An object is to provide a beam exposure apparatus and an electron beam exposure method.

The problems described above include an electron gun that emits an electron beam, shaping means having an opening for shaping the electron beam, a projection lens that forms an image of the electron beam on a sample surface, and an upper part of the projection lens. A refocusing lens comprising an electrostatic multipole lens installed to correct the focus of the electron beam, and a control means for applying a voltage corresponding to the cross-sectional area of the electron beam shaped by the shaping means to the refocusing lens The refocusing lens has three stages of quadrupole electrostatic electrodes in the beam axis direction of the electron beam, and the first and third stages of the three stages of quadrupole electrostatic electrodes. This is solved by an electron beam exposure apparatus characterized in that the length of the electrodes of the second stage is the same, and the length of the second stage electrode is twice the length of the first stage and third stage electrodes .

  In the electron beam exposure apparatus according to this aspect, the refocusing lens may have three stages of quadrupole electrostatic electrodes in the beam axis direction of the electron beam, or the three stages of quadrupole electrostatic electrodes. Of these, the lengths of the first and third electrodes may be the same, and the length of the second electrode may be twice the length of the first electrode. In addition, the polarity of the voltage applied to the x-direction electrode of the first stage, the second stage, and the third stage is opposite to the polarity of the voltage applied to the y-direction electrode. The applied voltage and the voltage applied to the second stage x-direction electrode have opposite polarities, and the voltage applied to the first stage x-direction electrode and the third stage x-direction electrode The polarity of the voltage applied to the first and second electrodes in the y direction may be the same as the voltage applied to the first and second electrodes in the y direction. .

  In the present invention, in order to perform refocusing for adjusting the focus of the electron beam, an electron beam refocusing lens composed of an electrostatic electrode is provided. This refocusing lens has a structure in which three quadrupole lenses are stacked so that the electron beam passing between them is converged. The voltage applied to each electrode constituting the refocus lens is adjusted according to the cross-sectional area of the shaped electron beam. This makes it possible to focus on the sample surface even if the amount of electrons of the irradiated electron beam changes. In addition, since the electric field is adjusted by the voltage using the electrostatic electrode, the refocusing speed can be increased and the exposure throughput can be improved.

  Embodiments of the present invention will be described below with reference to the drawings.

  First, the configuration of the electron beam exposure apparatus will be described. Next, a refocus lens that performs electron beam refocus will be described. Finally, an electron beam exposure method will be described.

(Configuration of electron beam exposure system)
FIG. 1 is a block diagram of an electron beam exposure apparatus according to the present embodiment.

  The electron beam exposure apparatus is roughly divided into an electron optical system column 100 and a control unit 200 that controls each part of the electron optical system column 100. Among these, the electron optical system column 100 includes an electron beam generating unit 130, a mask deflecting unit 140, and a substrate deflecting unit 150, and the inside thereof is decompressed.

  In the electron beam generator 130, the electron beam EB generated from the electron gun 101 is converged by the first electromagnetic lens 102, then passes through the rectangular aperture 103 a of the beam shaping mask 103, and the cross section of the electron beam EB is rectangular. To be shaped.

  Thereafter, the electron beam EB is imaged on the exposure mask 110 by the second electromagnetic lens 105 of the mask deflection unit 140. The electron beam EB is deflected to a specific pattern S formed on the exposure mask 110 by the first and second electrostatic deflectors 104 and 106, and the cross-sectional shape thereof is shaped into the pattern S.

  Although the exposure mask 110 is fixed to the mask stage 123, the mask stage 123 is movable in a horizontal plane, and the deflection range (beam deflection region) of the first and second electrostatic deflectors 104 and 106 is set. In the case of using the pattern S in the portion exceeding, the pattern S is moved into the beam deflection region by moving the mask stage 123.

Further, instead of the exposure mask 110, an opening capable of changing the electron beam into a predetermined shape may be arranged.
The third and fourth electromagnetic lenses 108 and 111 arranged above and below the exposure mask 110 play a role of forming an image of the electron beam EB on the substrate W by adjusting their current amounts.

  The size of the electron beam EB that has passed through the exposure mask 110 is returned to the optical axis (beam axis) C by the deflection action of the third and fourth electrostatic deflectors 112 and 113, and then the size is adjusted by the fifth electromagnetic lens 114. Reduced.

  The mask deflection unit 140 is provided with first and second correction coils 107 and 109, which correct beam deflection aberrations generated by the first to fourth electrostatic deflectors 104, 106, 112, and 113. Is done.

  Thereafter, the electron beam EB passes through the aperture 115a of the shielding plate 115 constituting the substrate deflecting unit 150, and the focus is adjusted according to the cross-sectional area of the electron beam EB by the refocus lens 128. Two projection electromagnetic lenses 116 and 121 project the image onto the substrate W. As a result, the pattern image of the exposure mask 110 is transferred to the substrate W at a predetermined reduction ratio, for example, a reduction ratio of 1/10.

  The substrate deflecting unit 150 is provided with a fifth electrostatic deflector 119 and an electromagnetic deflector 120, and the electron beam EB is deflected by these deflectors 119 and 120, and an exposure mask is formed at a predetermined position on the substrate W. The pattern image is projected.

  Further, the substrate deflection unit 150 is provided with third and fourth correction coils 117 and 118 for correcting the deflection aberration of the electron beam EB on the substrate W.

  The substrate W is fixed to a wafer stage 124 that can be moved in the horizontal direction by a driving unit 125 such as a motor. By moving the wafer stage 124, it is possible to expose the entire surface of the substrate W.

  On the other hand, the control unit 200 includes an electron gun control unit 202, an electron optical system control unit 203, a mask deflection control unit 204, a mask stage control unit 205, a blanking control unit 206, a substrate deflection control unit 207, a wafer stage control unit 208, and A refocus control unit 209 is included. Among these, the electron gun control unit 202 controls the electron gun 101 to control the acceleration voltage of the electron beam EB, beam emission conditions, and the like. Further, the electron optical system control unit 203 controls the amount of current to the electromagnetic lenses 102, 105, 108, 111, 114, 116 and 121, and the magnification and focus of the electron optical system in which these electromagnetic lenses are configured. Adjust the position. The blanking control unit 206 controls the voltage applied to the blanking electrode 127 to deflect the electron beam EB generated before the start of exposure onto the shielding plate 115, and onto the substrate W before exposure. Prevents EB from being irradiated.

  The substrate deflection control unit 207 controls the voltage applied to the fifth electrostatic deflector 119 and the amount of current to the electromagnetic deflector 120 so that the electron beam EB is deflected to a predetermined position on the substrate W. To. The wafer stage control unit 208 adjusts the driving amount of the driving unit 125 to move the substrate W in the horizontal direction so that the desired position of the substrate W is irradiated with the electron beam EB.

  The refocus control unit 209 supplies a necessary voltage to each electrode constituting the refocus lens according to the cross-sectional area of the electron beam EB that is shaped through the exposure mask 110.

  The above-described units 202 to 209 are controlled in an integrated manner by an integrated control system 201 such as a workstation.

(Refocus lens)
FIG. 2 shows the configuration of the refocus lens used in this embodiment. FIG. 2A shows a plan view of the refocus lens 128 installed above the projection lenses 116 and 121 on the electron gun 101 side. FIG. 2B shows a cross-sectional view of the refocus lens 128 as seen from the front.

  As shown in FIG. 2, the refocus lens 128 is configured by overlapping an electrostatic quadrupole lens using four electrostatic electrodes at a predetermined interval in the beam axis direction (Z-axis direction).

  The electrostatic quadrupole lens has the first, second, and third stages from the side closer to the electron gun along the electron beam irradiation direction. The quadrupole lenses are denoted by LS1, LS2, and LS3, respectively.

  The electrostatic quadrupole lens LS1 is composed of four electrostatic electrodes P11, P12, P13, and P14, and two are arranged at equal intervals around the beam axis (Z axis) in the X axis direction and the Y axis direction. Is done. For example, the length L1 of each electrode is 10 mm.

  The electrostatic quadrupole lens LS2 includes four electrostatic electrodes P21, P22, P23, and P24, and is arranged in the lower stage of LS1. The four electrodes of the electrostatic quadrupole lens LS2 are arranged so as to overlap the four electrodes of LS1 with a predetermined gap G1 in the Z-axis direction. This predetermined gap G1 is, for example, 5 mm. The length L2 of each electrode of the electrostatic quadrupole lens LS2 is twice as long as the length L1 of each electrode of the electrostatic quadrupole lens LS1. For example, when L1 is 10 mm, Ll2 is 20 mm.

  The electrostatic quadrupole lens LS3 is composed of four electrostatic electrodes P31, P32, P33, P34, and is arranged in the lower stage of LS2. The four electrodes of the electrostatic quadrupole lens LS3 are arranged so as to overlap the four electrodes of LS2 with a predetermined gap G2 in the Z-axis direction. The predetermined gap G2 is 5 mm, for example.

  The length of each electrode of the electrostatic quadrupole lens LS3 is the same as that of LS1.

  Next, it will be described that the focus of electrons can be adjusted by the refocus lens configured as described above. First, the amount of deflection of electrons after passing through a single-stage electrostatic quadrupole lens will be described.

FIG. 3 shows a plan view of a one-stage electrostatic quadrupole lens. The potential distribution φ of this lens is expressed as φ = A (x ² −y ² ) / r ₀ ² . Here, r ₀ = 2 mm.

Electrons that pass through in the Z-axis direction travel by receiving forces in the X-axis direction and the Y-axis direction.
The electric field at a point where x = 1 mm is E (x = 1) = − dφ / dx = 40/9 [V / mm]. Here, the amount of polarization at a position where electrons passing through a distance of 1 mm from the beam axis are separated by 5000 mm in the Z-axis direction will be examined.

  Suppose that the amount of polarization of electrons when they pass between parallel plates is considered. If the disturbance of the electric field at both ends of the parallel plate is ignored, the deflection amount D at a position 1 away from the electrode by the length l is expressed by the following equation.

D = (lb / 2d) × (Xd / V0) (1)
Here, b is the length of the parallel plates, Vd is a voltage applied between the plates, and V0 is an electron incident voltage (for example, 50 kV).

  In this equation, since 2Vd / d is the electric field E, D = 1bE / 4V0.

  In equation (1), when b = 10 [mm], E = 40/9 [V / m], V0 = 50000 [V], and l = 5000 [mm], the deflection distance D is 1.11 [mm]. It becomes.

  That is, in order to make the focal point on the beam axis, it is only necessary to deflect by 1 [mm]. Therefore, the purpose can be achieved by adjusting the voltage applied to the electrode. In this way, the focus of electrons can be adjusted by a single-stage quadrupole lens.

  Therefore, even when the quadrupole lens is configured in multiple stages, the focus of electrons can be adjusted.

  FIG. 4 is a diagram for explaining the trajectory of electrons of the three-stage quadrupole electrostatic electrode. Assume that the Z axis in FIG. 4 is the beam axis, and the electron beam travels from the left to the right in the figure.

  The x-axis side in FIG. 4 shows the trajectory C1 of the electron beam in the X direction, and the y-axis side shows the trajectory C2 in the Y direction of the electron beam. As shown in FIG. 4, when paying attention to the trajectory C1 in the x direction, the first-stage quadrupole lens functions as a convex lens, and the second-stage quadrupole lens functions as a concave lens. The quadrupole lens functions as a convex lens. When attention is paid to the orbit C2 in the y direction, the first quadrupole lens functions as a concave lens, the second quadrupole lens functions as a convex lens, and the third quadrupole lens Acts as a concave lens. The incident angle to the final focal point z2 can be made almost the same in both the x direction and the y direction. Therefore, by using this three-stage quadrupole electrostatic electrode, it is possible to easily adjust the focus.

  A predetermined voltage is applied to each electrode of the refocus lens configured as shown in FIG. 2 by the refocus control unit 209 so that the refocus lens 128 as a whole generates an electric field necessary for refocus. In the present embodiment, a voltage having a polarity as shown in FIG. 5 is applied. FIG. 5 shows the plan views of the electrostatic quadrupole lenses LS1, LS2, and LS3 side by side for convenience.

  As shown in FIG. 5, a voltage of −Vy is supplied to the electrostatic electrodes P11 and P13, and a voltage of + Vx is supplied to P12 and P14.

  A voltage is applied to each electrode of LS2 in the next stage so that the potential is opposite to that of each electrode of LS1. That is, + Vy ′ is applied to P21 and P23, and −Vx ′ is applied to P22 and P24.

  The same voltage as LS1 is applied to each electrode of the third stage LS3.

  Thus, four values of voltage are used for the 12 electrostatic electrodes. These voltages are calculated by multiplying the cross-sectional area of the electron beam shaped by the refocus control unit 209 by the refocus coefficient and supplied to each electrode.

  FIG. 6 is a diagram illustrating a configuration of a refocus circuit that applies a predetermined voltage to each electrode of the refocus lens.

  The refocus circuit 42 converts the four voltage values (digital values) designated by the refocus control unit 209 to perform refocusing into analog data through the DAC 43, and the above-described voltage value via the voltage amplifier 44. An analog voltage converted to a predetermined electrode is supplied.

  The cross-sectional area of the electron beam to be shaped is calculated from the exposure mask data stored in the storage unit 41 and the electron beam deflection amount data. For example, as shown in FIG. 7, the opening 110a of the exposure mask is selected, and a cross section in which the deflected electron beam EB is irradiated onto the exposure mask 110 is EBS. At this time, the cross-sectional area Fcs of the electron beam to be shaped is the area of the portion where the opening 110a and the cross-section EBS of the electron beam overlap.

  The refocus coefficient is calculated by a known method as described below.

  An electron beam having two beam sizes is used, and a refocus amount that minimizes the blur of the beam edge is obtained for each of the electron beams.

  Since the beam current passing through the rectangular aperture 103a is constant and the refocus amount is substantially proportional to the current of the beam passing through the exposure mask 110, the exposure mask 110 and the electron beam image at this position overlap. A voltage proportional to the area, that is, a voltage corresponding to the deflection amount in the deflectors 104 and 106 is supplied to each electrode of the refocus lens as a refocus amount.

  In order to determine the refocus amount, the beam edge blur amount is measured as follows. That is, as shown in FIG. 8A, a tantalum film 82 having an electron reflectivity higher than that of silicon Si is formed on a silicon Si wafer 81. The beams are scanned by the deflectors 104 and 106 so that the electron beam 83 crosses the tantalum film 82. At this time, the reflected electrons 84 from the irradiation point are detected by the electron detector. Then, an electron detection amount as shown in FIG. The electron detection amount is differentiated with respect to the beam scanning position to obtain a waveform as shown in FIG. 8C, and the distance at which the maximum value changes from 90% to 10% is obtained as the beam edge blur amount δ.

  G1 to G4 are obtained by adjusting the voltage applied to each electrode so as to minimize the beam edge blur.

  The above processing is performed for two electron beams having different cross-sectional areas.

  Next, as shown in FIG. 9, the relationship between the cross-sectional area of the electron beam and the refocus amount (refocus coefficients G1 to G4) is linearly approximated. If the refocus coefficient when the cross-sectional area is S1 is GS1 and the refocus coefficient when the cross-sectional area is S2 is GS2, the correlation between the cross-sectional area and the refocus coefficient is a straight line passing through the two points. Ask for. Correlation is similarly obtained for the four refocus coefficients. Based on this, a refocus coefficient is determined from the area of an arbitrarily shaped block pattern.

(Electron beam exposure method)
Next, an exposure method using the above-described electron beam exposure apparatus will be described.

  When performing electron beam exposure, every time an exposure mask is selected, a refocus coefficient is determined in order to adjust the focus of the electron beam.

  As described with reference to FIGS. 8 and 9, the refocus coefficient is determined by measuring the beam blur for two electron beams having different cross-sectional areas, and determining the refocus coefficients G1 to G4 so that the beam blur is minimized. To do.

  The size of the cross-sectional area of the irradiated electron beam is extracted from the storage unit 41 in which exposure data is stored. A voltage value to be applied to each electrode is determined by applying refocus coefficients G1 to G4 according to the size.

  The calculation of the voltage value is performed simultaneously with the application of a voltage to the deflectors 104 and 106. Conventionally, since the time until the voltage is stabilized after the voltage is applied to the deflector is 50 [ns], the refocus current is stabilized for about 300 [ns]. It was over. In this embodiment, since the voltage is applied to the electrostatic electrode, the voltage stabilization time for focus correction is as short as 50 [ns], and the voltage value to be applied to each electrode is determined from the size of the electron beam. Even if time is taken into consideration, the exposure waiting time is about 100 [ns], and the exposure can be started in a short time about three times as compared with the conventional case, so that the exposure throughput can be improved.

  As described above, in the present embodiment, a refocus lens including an electrostatic electrode is provided in order to perform refocus for adjusting the focus of the electron beam. This refocusing lens has a structure in which three quadrupole lenses are stacked so that the electron beam passing between them is converged. In this case, the voltage applied to each electrode constituting the refocus lens is adjusted according to the cross-sectional area of the electron beam. This makes it possible to focus even if the amount of electrons in the electron beam changes according to the size of the cross-sectional area of the electron beam. In addition, since the electric field is adjusted simply by applying a voltage using the electrostatic electrode, the refocusing speed can be increased and the exposure throughput can be improved.

  In the present embodiment, the case where four values are used as the voltages applied to the respective electrodes of the refocus lens in order to perform refocus has been described. However, the present invention is not limited to this. A voltage may be separately applied to each of the electrostatic electrodes. In this case, it becomes possible to perform refocusing with higher accuracy.

  In the present embodiment, a refocus lens having a configuration in which three stages of quadrupole lenses are stacked has been described. However, the present invention is not limited to this, and the number of stages may be greater than three.

It is a block diagram of the electron beam exposure apparatus which concerns on this invention. It is a block diagram of the refocusing lens in the electron beam exposure apparatus which concerns on this invention. It is a figure explaining the deflection control of the electron in a 1 step | paragraph quadrupole electrode. It is a figure explaining the trajectory of the electron of a 3 step | paragraph quadrupole electrostatic electrode. It is a figure which shows the connection relation of each electrode of a refocus lens. It is a figure explaining a refocusing circuit. It is a figure explaining the amount of refocusing. FIG. 6 is a diagram (part 1) for explaining calculation of a refocus coefficient. FIG. 6 is a diagram (part 2) illustrating calculation of a refocus coefficient.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Electro-optic system column, 101 ... Electron gun, 102 ... 1st electromagnetic lens, 103 ... Beam shaping mask, 103a ... Rectangular aperture, 104 ... 1st electrostatic deflector, 105 ... 2nd electromagnetic lens, 106 ... 1st 2 electrostatic deflector 107 107 first correction coil 108 third electromagnetic lens 109 second correction coil 110 exposure mask 111 fourth electromagnetic lens 112 third electrostatic deflector 113 ... fourth electrostatic deflector, 114 ... fifth electromagnetic lens, 115 ... shielding plate, 115a ... aperture, 116 ... first projection electromagnetic lens, 117 ... third correction coil, 118 ... fourth correction coil, 119 ... first 5 electrostatic deflectors, 120 ... electromagnetic deflectors, 121 ... second projection electromagnetic lenses, 123 ... mask stage, 124 ... wafer stage, 125 ... drive unit, 127 ... blanking electrode, 12 ... re-focus lens.

Claims (4)

An electron gun that emits an electron beam;
Shaping means having an aperture for shaping the electron beam;
A projection lens for imaging the electron beam onto the sample surface;
Disposed above the projection lens, and refocus lens consisting of electrostatic multipole lens for correcting the focus of the electron beam,
Control means for applying a voltage corresponding to the area of the cross section of the electron beam shaped by the shaping means to the refocus lens ,
The refocus lens has three stages of quadrupole electrostatic electrodes in the beam axis direction of the electron beam, and the length of the first and third stages of the three stages of quadrupole electrostatic electrodes. The electron beam exposure apparatus is characterized in that the length of the second-stage electrode is twice the length of the first-stage and third-stage electrodes . The polarities of the voltage applied to the x-direction electrode of the first stage, the second stage, and the third stage are opposite to the polarity of the voltage applied in the y direction,
The voltage applied to the first-stage x-direction electrode and the voltage applied to the second-stage x-direction electrode have opposite polarities,
The polarity of the voltage applied to the first-stage x-direction electrode and the voltage applied to the third-stage x-direction electrode are the same,
A voltage applied to the y direction of the electrode of the first stage, the polarity of the voltage applied to the y direction of the electrode of the third stage electron beam exposure apparatus according to claim 1, characterized in that the same. A first voltage amplifier for applying a first voltage to the first-stage and third-stage electrodes in the x direction;
A second voltage amplifier that applies a second voltage having a polarity different from that of the first voltage to the first-stage and third-stage electrodes in the y direction;
A third voltage amplifier for applying a third voltage having a polarity different from that of the first voltage to the second-stage electrode in the x direction;
A fourth voltage amplifier that applies a fourth voltage having the same polarity as the first voltage to the second-stage electrode in the y direction;
With
The first to fourth voltages are obtained by calculating four refocus coefficients obtained from the correlation between a predetermined beam cross-sectional area calculated in advance and the refocus amount to the cross-sectional area of the electron beam. electron beam exposure apparatus according to claim 1 or 2, characterized in that each calculated by multiplying the area. An electron gun for irradiating an electron beam, a shaping means having an opening for shaping the electron beam, and a projection lens for forming the electron beam onto the sample surface, is disposed above the projection lens, quadruple There are three stages of polar electrostatic electrodes in the direction of the beam axis of the electron beam, and among the three stages of quadrupole electrodes, the first and third stage electrodes have the same length, and the second stage electrode The first voltage is applied to the refocusing lens whose length is twice the length of the first and third stage electrodes and the first and third stage electrodes in the x direction. A second voltage amplifier for applying a second voltage to the first and third stage y-direction electrodes, and a third voltage to the second stage x-direction electrode. A third voltage amplifier; a fourth voltage amplifier that applies a fourth voltage to the second stage y-direction electrode; In an electron beam exposure apparatus comprising a control means,
The control means calculates four refocus coefficients from a correlation between a predetermined beam cross-sectional area and a refocus amount according to the cross-sectional area of the electron beam shaped by the shaping means, An electron beam exposure method, wherein the first to fourth voltages are calculated by multiplying a cross-sectional area by the refocus coefficient.

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