WO2008044479A1

WO2008044479A1 - Electron beam lithography system and electron beam lithography

Info

Publication number: WO2008044479A1
Application number: PCT/JP2007/068807
Authority: WO
Inventors: Hiroshi Yasuda; Takeshi Haraguchi; Hitoshi Tanaka; Akio Yamada
Original assignee: Advantest Corporation
Priority date: 2006-10-05
Filing date: 2007-09-27
Publication date: 2008-04-17
Also published as: TW200823969A; JP4889431B2; JPWO2008044479A1; JP2008091827A

Abstract

[PROBLEMS] To provide an electron beam lithography system and an electron beam lithography in which re-focus time is shortened and the throughput is enhanced. [MEANS FOR SOLVING PROBLEMS] The electron beam lithography system comprises an electron gun for emitting an electron beam, shaping means having an aperture to shape the electron beam, a projection lens for focusing the electron beam onto a sample surface, a re-focus lens installed above the projection lens and composed of electrostatic multipole lens for correcting the focal point of the electron beam, and 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 re-focus lens. The re-focus lens may have three stages of quadrupole electrostatic electrodes along the beam axis direction of the electron beam. The lengths of the first- and third-stage electrodes may be equal to each other, and the length of the second-stage electrode may be twice the length of the first-stage electrode.

Description

Specification

Electron beam exposure apparatus and electron beam exposure method

Technical field

TECHNICAL FIELD [0001] The present invention relates to an electron beam exposure apparatus and an electron beam exposure method, and in particular, an electron beam exposure apparatus and an electron beam exposure that can change the shape and size of a beam using a variable rectangular opening or a partial collective pattern. Regarding the method.

Background art

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

As such an exposure apparatus, there is an electron beam exposure apparatus that performs partial batch exposure. In partial batch exposure, a beam is irradiated to one pattern area selected by beam deflection from a plurality of patterns arranged on the mask, and the 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 fixed reduction rate determined by the electron optical system, and transferred onto the sample.

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

[0005] On the other hand, when electron beam exposure is performed using a variable rectangular aperture or a partial batch pattern, the beam size of the electron beam varies from shot to shot, and the phenomenon that the beam defocuses due to the defocus of the electron beam occurs. For example, when focusing on the sample surface with a small beam size, exposure with a large beam size increases the total current of the electron beam, increases the focal length, and causes beam blur on the sample surface.

[0006] 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 focusing coil in synchronization with the size of a rectangular beam. [0007] Further, Patent Document 2 discloses a method of measuring and correcting a positional deviation of a beam axis when performing electron beam refocusing.

[0008] As described above, when a variable rectangular opening or a partial collective pattern is used, it is possible to prevent the deviation of the beam focus by moving the focus of the electron beam for each shot.

[0009] Specifically, a refocus coil is installed, and an amount of current proportional to the cross-sectional area of the shaped beam is passed through the refocus 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 that the convergence effect of the electron beam is strengthened.

[0010] However, it takes time to perform refocusing, and it is difficult to improve the exposure throughput even though partial batch exposure is performed!

[0011] For example, although the power and time required for shaping the electron beam are about 50 ns, the refocusing execution time is the time until a predetermined current is passed through the refocusing coil until a stable current is obtained. The time is about 300ns, and the exposure waiting time is long. Patent Document 1: Japanese Patent Laid-Open No. Sho 56-94740

Patent Document 2: JP-A-58-121625

Disclosure of the invention

[0012] The present invention has been made in view of the power and problems of the prior art, and shortens the refocus time and improves the throughput in electron beam exposure that can change the shape and size of the beam. It is an object to provide an electron beam exposure apparatus and an electron beam exposure method capable of achieving the above.

[0013] The above-described problems 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 the projection lens. A focus lens composed of an electrostatic multipole lens that corrects the focus of the electron beam, and a voltage according to the cross-sectional area of the electron beam shaped by the shaping means. This is solved by an electron beam exposure apparatus comprising a control means for applying. 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, and the three stages of quadrupoles. Of the electrostatic electrodes, the first and third electrodes may have the same length, and the length of the second electrode may be twice the length of the second electrode. In addition, the polarity of the voltage applied to the X-direction electrode in the first, second, and third stages is opposite to the polarity of the voltage applied to the y-direction electrode. The applied voltage is opposite in polarity to the voltage applied to the second X-direction electrode, the voltage applied to the first X-direction electrode, and the third X-direction electrode. The polarity of the voltage applied to the electrodes is the same, and the polarity of the voltage applied to the first stage y-direction electrode and the voltage applied to the third stage y-direction electrode may be the same. good.

In the present invention, in order to perform refocusing for adjusting the focus of the electron beam, an electron beam refocusing lens constituted by an electrostatic electrode is provided. This refocusing lens has a configuration 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 in 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.

Brief Description of Drawings

FIG. 1 is a block diagram of an electron beam exposure apparatus according to the present invention.

FIG. 2 is a configuration diagram of a refocus lens in the electron beam exposure apparatus according to the present invention.

FIG. 3 is a diagram illustrating electron deflection control in a single-stage quadrupole electrode.

FIG. 4 is a diagram for explaining electron trajectories of a three-stage quadrupole electrostatic electrode.

FIG. 5 is a diagram showing a connection relationship of each electrode of the refocus lens.

FIG. 6 is a diagram illustrating a refocus circuit.

FIG. 7 is a diagram for explaining a refocus amount.

FIG. 8 is a diagram (part 1) illustrating calculation of a refocus coefficient. FIG. 9 is a diagram (part 2) illustrating calculation of a refocus coefficient.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

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

[0019] (Configuration of electron beam exposure apparatus)

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

This 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 generation unit 130, a mask deflection unit 140, and a substrate deflection unit 150, and the inside thereof is decompressed.

[0021] In the electron beam generator 130, the electron beam EB generated from the electron gun 101 is converged by the first electromagnetic lens 102, and then passes through the rectangular aperture 103a of the beam shaping mask 103 to be transmitted to the electron beam EB. The cross section is shaped into a rectangle.

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

Note that the exposure mask 110 has a force to be fixed to the mask stage 123. The mask stage 123 can be moved in a horizontal plane, and the deflection range (beam) of the first and second electrostatic deflectors 104 and 106 can be When using the pattern S in the portion exceeding the deflection area), the pattern S is moved into the beam deflection area 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.

[0025] The third and fourth electromagnetic lenses 108 and 111 disposed 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.

[0026] Electron beam EB passing through exposure mask 110 is deflected by third and fourth electrostatic deflectors 112 and 113. After being returned to the optical axis (beam axis) C by the action, the size is reduced by the fifth electromagnetic lens 114.

[0027] The mask deflector 140 is provided with first and second correction coils 107 and 109, and the beams generated by the first to fourth electrostatic deflectors 104, 106, 112, and 113 by them. Deflection aberration is corrected.

[0028] 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. The first and second projection electromagnetic lenses 116 and 121 are projected onto the substrate W. As a result, the image power of the pattern of the exposure mask 110 is transferred to the substrate W at a predetermined reduction ratio, for example, a reduction ratio of 1/10.

[0029] The substrate deflecting unit 150 is provided with a fifth electrostatic deflector 119 and an electromagnetic deflector 120, and the deflector 119, 120 deflects the electron beam EB so that the substrate W has a predetermined position. An image of the pattern of the exposure mask is projected onto the screen.

In addition, the substrate deflecting unit 150 is provided with third and fourth corrective coins 117 and 118 for correcting the deflection aberration of the electron beam EB on the substrate W.

[0031] 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, the entire surface of the substrate W can be exposed. It becomes.

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 206, and a wafer. A stage control unit 208 and a refocus control unit 209 are 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. The electron optical system control unit 203 controls the amount of current to the electromagnetic lenses 102105, 108, 111, 114, 116, and 121, and the magnification, focal position, etc. of the electron optical system in which these electromagnetic lenses are configured. Adjust. The blanking control unit 20 controls the voltage applied to the blanking electrode 127 to deflect the electron beam EB generated from before the start of exposure onto the shielding plate 115, and onto the substrate W before exposure. Prevent EB irradiation. 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 to deflect the electron beam EB onto a predetermined position on the substrate W. To be. Wafer stage control unit 208 adjusts the driving amount of driving unit 125 to move substrate W in the horizontal direction so that a desired position on substrate W is irradiated with 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.

Each of the above-described units 202 to 209 is controlled in an integrated manner by an integrated control system 201 such as a workstation.

[0036] (Refocus lens)

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

[0037] 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).

[0038] The electrostatic quadrupole lens has a first stage, a second stage, and a third stage from the side closer to the electron gun along the electron beam irradiation direction, and the first stage, the second stage, and the third stage. These electrostatic quadrupole lenses are LSI and LS 2, LS3, respectively.

[0039] The electrostatic quadrupole lens LS I is composed of four electrostatic electrodes Pl l, P12, P13, and P14, and is centered on the beam axis (Z axis) in the X axis direction, the Y axis direction, etc. Two are arranged at intervals. For example, the length L1 of each electrode is 10mm.

The electrostatic quadrupole lens LS2 is composed of 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 LS I with a predetermined gap G1 in the Z-axis direction. This predetermined interval G1 is 5 mm, for example. The length L2 of each electrode of the electrostatic quadrupole lens LS2 is twice the length L1 of each electrode of the electrostatic quadrupole lens LS I. For example, if L1 is 10mm, L12 is 20mm And

[0041] The electrostatic quadrupole lens LS3 includes four electrostatic electrodes P31, P32, P33, and 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. This predetermined gap G2 is, for example, 5 mm.

[0042] The length of each electrode of the electrostatic quadrupole lens LS 3 is the same as that of LS 1.

[0043] Next, the fact that the focus of electrons can be adjusted by the refocus lens configured as described above will be described. First, the amount of deflection of the 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 φ =

A (x'-y ') / r ² Here, r = 2mm.

0 0

[0045] 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 the point of x = 1 mm is E (x = 1) = — dφ / dx = 40/9 [V / mm]. Here, we examine the amount of polarized light at a position 5000 mm away in the Z-axis direction, which passes the distance of lmm from the beam axis.

[0046] It is assumed that the amount of polarization of electrons when electrons pass between parallel flat plates corresponds to the amount of polarization. If the disturbance of the electric field at both ends of the parallel plate is ignored, the deflection amount D at a distance of 1 distance from the electrode is expressed by the following equation.

[0047] D = (lb / 2d) X (Xd / VO)

Here, b is the length of the parallel plates, Vd is the voltage applied between the plates, and V0 is the incident voltage of electrons (for example, 50 kV).

[0048] In this equation, 2Vd / d is the electric field E, so D = lbE / 4V0.

[0049] Formula (1), b = 10 [mm], E = 40/9 [V / m], V0 = 50000 [V],

If l = 5000 [mm], the deflection distance D is 1. l l [mm].

[0050] That is, in order to make the focal point on the beam axis, it is only necessary to deflect l [mm]. Therefore, the purpose can be achieved by adjusting the voltage applied to the electrode. In this way, it is possible to adjust the focal point of electrons by using a single quadrupole lens.

[0051] Therefore, even when the quadrupole lens is configured in multiple stages, the focus of electrons is adjusted. It becomes possible.

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

In FIG. 4, the X-axis side 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, focusing on the X-direction trajectory C1, the first quadrupole lens acts as a convex lens, the second quadrupole lens acts as a concave lens, and the third step The quadrupole lens works as a convex lens. Looking at the orbit C2 in the y direction, the first quadrupole lens acts as a concave lens, the second quadrupole lens acts 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 almost the same in both the X and y directions. 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 entire refocus lens 128 generates an electric field necessary for refocus. I have to. In this 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.

[0055] As shown in FIG. 5, a voltage of −Vy is supplied to the electrostatic electrodes P11 and P13, and + V is supplied to P12 and P14.

Supply X voltage.

[0056] 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 the LSI. That is, P21 and P23 are marked with + Vy, and P22 and P24 are marked with Vx '.

[0057] The same voltage as the LSI is applied to each electrode of the third-stage LS3.

Thus, four values of voltage are used for 12 electrostatic electrodes. These voltages are

Then, the refocus control unit 209 multiplies the cross-sectional area of the shaped electron beam by the refocus coefficient, and supplies it to each electrode.

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

[0060] The refocusing circuit 42 converts four voltage values (digital values) specified by the refocusing control unit 209 for performing refocusing through the DAC 43 to analog de- duction. The analog voltage converted to the predetermined electrode is supplied through the voltage amplifier 44.

The cross-sectional area of the electron beam to be shaped is calculated from exposure mask data and electron beam deflection data stored in the storage unit 41. For example, as shown in FIG. 7, the opening 110a of the exposure mask is selected, and the 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 Fes of the shaped electron beam is the area where the opening 110a and the cross-section EBS of the electron beam overlap.

[0062] The refocus coefficient is calculated by a known method as described below.

[0063] 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.

[0064] 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 at this position A voltage proportional to the area where the image overlaps, that is, a voltage force corresponding to the amount of deflection in the deflectors 104 and 106, is supplied to each electrode of the refocus lens as a refocus amount.

Yes

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 the silicon silicon 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, the amount of detected electrons is obtained as shown in FIG. This electron detection amount is differentiated with respect to the beam scanning position to obtain the waveform shown in Fig. 8 (c), and the distance at which the maximum value changes from 90% to 10% is obtained as the beam edge blur amount δ. .

[0066] The voltage applied to each electrode is adjusted so as to minimize the beam edge blurring amount, and G ;! to G4 are obtained.

[0067] The above processing is performed on 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 coefficient G;! To G4) is linearly approximated. The refocus coefficient when the cross-sectional area is S1 is GS1 If the refocus coefficient is GS2 when the cross-sectional area is S2, the correlation between the cross-sectional area and the refocus coefficient is obtained by a straight line passing through the two points. The correlation is similarly obtained for the four refocus coefficients. Based on this, the refocus coefficient is determined from the area of the block pattern of arbitrary shape.

[0069] (Electron beam exposure method)

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

[0070] When performing electron beam exposure, a refocus coefficient is determined in order to adjust the focus of the electron beam every time an exposure mask is selected.

[0071] As described with reference to FIGS. 8 and 9, the refocus coefficient is measured by measuring the beam blur for two electron beams having different cross-sectional areas, and the refocus coefficient G1 so that the beam blur is minimized. To determine G4.

[0072] The size of the cross-sectional area of the irradiated electron beam is extracted from the storage unit 41 in which the exposure data is stored. The voltage value applied to each electrode is determined by applying the refocus coefficients G1 to G4 according to the size.

The voltage value is calculated at the same time as the voltage is applied to the deflectors 104 and 106. Conventionally, the time until the voltage is stabilized after applying a voltage to the deflector is 50 [ns], but the refocus current is stabilized for about 300 [ns]. It was over. In this embodiment, since a voltage is applied to the electrostatic electrodes, the voltage stabilization time for focus correction is 50 [ns], which is a short time until 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 long as the conventional method, so that the exposure throughput can be improved.

As described above, in this embodiment, in order to perform refocusing for adjusting the focus of the electron beam, a refocusing lens including an electrostatic electrode is provided. This refocus 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. As a result, the focus is adjusted even if the amount of electrons in the electron beam changes according to the cross-sectional area of the electron beam It becomes possible. In addition, since the electric field is adjusted simply by applying a voltage using an electrostatic electrode, the refocusing speed can be increased and the exposure throughput can be improved.

In the present embodiment, the force S described for the case where the voltage applied to each electrode of the refocusing lens uses four values to perform the refocusing is not limited to this, and the three-stage quadrupole is not limited thereto. A voltage may be separately applied to each of the 12 electrostatic electrodes constituting the lens. In this case, it becomes possible to perform refocusing with higher accuracy.

Further, in the present embodiment, the refocus lens having a configuration in which the quadrupole lens is stacked in three stages has been described! However, the present invention is not limited thereto, and may be configured with more stages than three stages. good.

Claims

The scope of the claims

[1] 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;

A refocusing lens that is installed above the projection lens and is made of an electrostatic multipole lens that corrects the focus of the electron beam;

Control means for applying a voltage according to the cross-sectional area of the electron beam shaped by the shaping means to the refocus lens;

An electron beam exposure apparatus comprising:

2. The electron beam exposure apparatus according to claim 1, wherein the refocus lens has three stages of quadrupole electrostatic electrodes in the beam axis direction of the electron beam.

[3] Of the three-stage quadrupole electrostatic electrodes, the first-stage and third-stage electrodes have the same length, and the second-stage electrode has the same length as the first-stage electrode. 3. The electron beam exposure apparatus according to claim 2, wherein the electron beam exposure apparatus is doubled.

[4] The polarity of the voltage applied to the first, second and third stage X-direction electrodes and the voltage applied to the y-direction electrode is opposite,

The voltage applied to the first X-direction electrode and the voltage applied to the second X-direction electrode are opposite in polarity.

The polarity of the voltage applied to the first X-direction electrode and the voltage applied to the third X-direction electrode are the same,

4. The electron beam according to claim 2, wherein the polarity of the voltage applied to the first-stage y-direction electrode and the voltage applied to the third-stage y-direction electrode are the same. Exposure equipment.

[5] The voltages applied to the electrodes of the refocus lens are four refocus values obtained from the correlation between the cross-sectional area of the electron beam and the pre-calculated cross-sectional area of the predetermined beam and the refocus amount. 5. The electron beam exposure apparatus according to claim 2, wherein a coefficient is calculated by multiplying an area of a cross section of the electron beam.

[6] having an electron gun that emits an electron beam and an opening for shaping the electron beam A shaping lens, a projection lens that forms an image of the electron beam on the sample surface, a refocus lens comprising an electrostatic multipole lens that is installed above the projection lens and corrects the focal point of the electron beam, and a control unit. In an electron beam exposure system equipped with

The control means calculates four refocus coefficients from the correlation between the pre-calculated cross-sectional area of the predetermined beam and the refocus amount according to the cross-sectional area of the electron beam shaped by the shaping means, An electron beam exposure method, wherein the exposure is performed by multiplying the cross-sectional area by the refocus coefficient and applying a voltage to each electrode of the refocus lens.

7. The electron beam exposure method according to claim 6, wherein the refocus lens has three stages of quadrupole electrostatic electrodes in the beam axis direction of the electron beam.