WO2004030056A1

WO2004030056A1 - Method for correcting astigmatism, method for determining astigmatic sensitivity and method for exposure in charged particle beam aligner

Info

Publication number: WO2004030056A1
Application number: PCT/JP2003/011879
Authority: WO
Inventors: Hiroyasu Shimizu
Original assignee: Nikon Corporation
Priority date: 2002-09-24
Filing date: 2003-09-18
Publication date: 2004-04-08
Also published as: AU2003264482A1; JPWO2004030056A1

Abstract

While shifting the focal point and varying the current values S1 and S2 of two sets of coil in an astigmatism correcting unit, a combination of current values where focal lines (11, 13, 12, 14) having inclinations of 0°, 45°, 90° and 135° with respect to the x axis is determined. A correction sensitivity of astigmatic blur is determined from the combination of current values according to a specified calculation expressions. The correction sensitivity of astigmatic blur can thereby be determined readily in a charged particle beam aligner.

Description

Description Method for correcting astigmatism in charged particle beam exposure apparatus, method for determining astigmatism sensitivity, and exposure method

The present invention relates to a method for determining astigmatic sensitivity in a charged particle beam exposure apparatus, and an exposure method using the same. Background art

With the increase in the density of semiconductor devices, patterns to be exposed and transferred from a reticle to a wafer in the manufacturing process are becoming finer. In order to expose and transfer such fine patterns, the resolution is insufficient with an optical exposure / transfer device, and as an alternative to the optical exposure / transfer device, exposure transfer using a charged particle beam such as an electron beam is used. Equipment is being developed.

In a charged particle beam exposure apparatus, a charged particle emitted from a charged particle beam source is irradiated onto a reticle through an illumination optical system to illuminate the reticle, and a pattern formed on the reticle is projected through a projection optical system. Exposure transfer is performed by forming an image on a wafer.

FIG. 6 shows an example of a charged particle beam exposure apparatus. The charged particle beam 2 emitted from the charged particle beam source 1 irradiates the shaped aperture 4 by the first irradiation lens 3. The charged particle beam 2 having passed through the forming aperture 4 forms an image on the reticle 7 by the second irradiation lens 5 and the third irradiation lens 6. A pattern to be transferred is formed on the reticle 7, and the charged particle beam 2 that has passed through the reticle 7 is exposed by the first projection lens 8 and the second projection lens 9 on an exposure target 10 such as a resist on a wafer. An image of reticle 7 is formed. Charged particle beam exposure system Usually, the reticle is divided into about 1 mm squares, and the reticle is reduced to about 1/4 on the object to be exposed and transferred. Therefore, the size of the image is about 0.25 mm square. Such an exposure area exposed at one time is called a subfield, and the subfields are connected to form an entire image, for example, a pattern of a semiconductor device.

In such a charged particle beam exposure apparatus, the blur of the image projected on the object 10 is adjusted by adjusting the focal position by using the first projection lens 8, the second projection lens 9, or a dynamic focus corrector. This is done by adjusting the astigmatism blur and astigmatism using the astigmatism corrector SM. For astigmatism blur and astigmatism distortion, the amount of adjustment of the astigmatism corrector that minimizes the amount of aberration according to the optical axis position or each deflection position has been determined by actual exposure or an aerial image sensor (AIS). .

However, as the required exposure transfer accuracy has increased, the exposure current has changed due to the aperture ratio in the subfield, and the blur caused by the space charge effect (space charge blur) has changed. . To cope with this, a method has been adopted in which the amount of space charge blur is calculated by simulation for each subfield, and the focus position is changed correspondingly.

At this time, the focus correction amount (the current flowing through the coil of the focus corrector or the voltage applied to the electrode of the focus corrector) is usually changed by changing the height of the object to be exposed in advance (ie, changing the focus position). The amount of focus change per unit amount of bokeh (the focus correction sensitivity) is determined by measuring the amount of bokeh of the image at that time, and this amount of focus is determined by the amount of bokeh determined by simulation. It can be obtained by multiplying the correction sensitivity.

Furthermore, when the exposure current changes, the astigmatism blur also changes due to the effect of the space charge effect. Therefore, in actual exposure, astigmatism Also need to be dynamically corrected. However, in the case of astigmatism blur, the astigmatism has directionality, and the astigmatism corrector also consists of a combination of multiple coils. It has not been established how to adjust the current flowing through the coil of the astigmatism corrector or the voltage applied to the electrode of the astigmatism corrector with respect to the blur amount. Disclosure of the invention

The present invention has been made in view of such circumstances, and provides a method of correcting astigmatism in a charged particle beam optical system, a method of correcting astigmatism in a charged particle beam exposure apparatus, and a method of correcting astigmatism (astigmatism blur). It is an object of the present invention to provide a method of determining the correction sensitivity of the image and the sensitivity of occurrence of astigmatism blur), and an exposure method using the same. In this specification, the abstract and the claims, the astigmatism blur correction sensitivity refers to a current flowing through an astigmatism corrector for correcting a unit amount of astigmatism blur converted to a focal position. Value means the amount of change in the value or applied voltage. When correcting astigmatism blur in the 0-90 ° direction, the direction in which the astigmatism blur occurs in the 0 ° direction is defined as positive. — When correcting astigmatism blur in the 135 ° direction, the direction in which astigmatism blur occurs in the 45 ° direction shall be positive. In this specification and in the claims, astigmatism blur occurrence sensitivity refers to a focus that occurs when a current value or a voltage value applied to an astigmatism corrector is changed by a unit amount. This means the amount of astigmatism blur converted to the position.For astigmatism blur in the 0-90 ° direction, the direction in which astigmatism blur in the 0 ° direction increases is defined as positive, and in the direction of 45-135 ° Regarding the astigmatism blur, the direction in which the astigmatism blur in the 45 ° direction increases is defined as positive.

Further, in this specification and the claims, unless otherwise specified, "by a coil" means that the current flowing through the coil is adjusted. It is needless to say that “by electrode” means that the voltage applied to the electrode is adjusted. A first invention for achieving the above object is a charged particle beam exposure apparatus having an astigmatism corrector, wherein a focus position is shifted by Ah to change a current value or a voltage value of the astigmatism corrector. Forming at least two different focal lines, obtaining a current value or a voltage value of the astigmatism corrector, shifting the focal position Δh, and calculating the two different sets of focal lines. The astigmatic sensitivity (correction sensitivity of astigmatism blur or astigmatism blur generation sensitivity) of the astigmatism corrector is obtained using a current value or a voltage value of the astigmatism corrector. This is a method for determining the point sensitivity.

In the present invention, since the astigmatism sensitivity of the astigmatism corrector is obtained based on the current or voltage value of the astigmatism corrector when the focal line is formed, the astigmatism can be obtained by a simple method. The astigmatic sensitivity of the corrector can be determined. A second invention for achieving the above object is the first invention, wherein the astigmatism corrector has at least two coil groups or electrode groups.

A third invention for achieving the above object is the first invention, wherein, when the focal position is shifted by Ah, the focal position is shifted by △ h from the normal focus position with respect to the normal focus position. It is characterized by the following.

In this specification and claims, the term “positive focus position” refers to the optical axis of the image plane on which a minimum circle of confusion centered on the optical axis is formed when the imaging state is changed by the projection lens. Directional position (that is, the position of the imaging plane in the optical axis direction where charged particles emitted from one point on the optical axis on the object plane are most narrowed isotropically). Usually, the method of finding the positive focus position is to form a pinhole on the optical axis of the object surface and move the imaging plane in the optical axis direction. Is used to estimate the beam blur in that direction, find the image plane position that minimizes the blur in each direction, and use the midpoint as the focal point position.

In the present invention, since the movement amount Δh of the focal position is determined based on the positive focal position, the astigmatic sensitivity can be easily obtained as described later in the section of the embodiment.

A fourth invention for achieving the above object is the first invention, wherein the astigmatism is a correction sensitivity for astigmatism blur.

A fifth invention for achieving the above object is the first invention, wherein the astigmatism is an astigmatism blur occurrence sensitivity.

A sixth invention for achieving the above object is the fourth invention, wherein the focus position is shifted from the positive focus position by A h and then two sets of coils constituting an astigmatism corrector are provided. The current value of the group (0 ° direction coil and 45 ° direction coil) or the voltage value of the two electrode groups (0 ° direction electrode and 45 ° direction electrode) was changed, and the measurement pattern was used as a reference. 90 ° direction, 0 ° direction, 13.5 ° direction, and 45 ° direction, minimize the blur in each of the two sets of current values or voltage values, and calculate the combination of these current values or voltage values. If it is (S 1 1, S 2 1), (S 1 2, S 2 2) (S 13, S 2 3), (S 14, S 24), at least one of the following expressions Thus, the correction sensitivity of the astigmatism blur in at least one direction is determined.

0 ο

(1) Sensitivity for correcting astigmatism blur when the 0 ° -90 ° direction astigmatism blur is corrected by a 0 ° direction coil or electrode SI 1-512

,

2Ah

(2) Sensitivity for correcting astigmatism blur when correcting astigmatism blur in the 0-90 ° direction using a 45 ° direction coil or electrode

521-522 ^

. "(2)

2Ah)

The (3) 0 ° direction coils or electrodes, the correction sensitivity of astigmatism blur when correcting astigmatism blur of 4 5-135 ° direction 1 ³ -. ¹⁴ .- (3)

2Δ / ι ^}

(4) Sensitivity of astigmatism blur correction when astigmatism blur in the direction of 45-135 ° is corrected by a 45 ° direction coil or electrode

523-524

-^ r- ⁽⁴⁾

Where i in S ij (i = l, 2 j = l 4) indicates a 0 ° direction coil or electrode (i = 1) and a 45 ° direction coil or electrode (i = 2), respectively. j is the direction that minimizes astigmatism blur (j = 1 is 90 ° direction, «] '= 2 is 0 ° direction, j = 3 is 1 35 ° direction, j = 4 is 4 5. Direction)

In this specification and the appended claims, the 0 ° direction with respect to the measurement pattern refers to the reference direction in which the measurement pattern is placed, and is often defined as the reference direction of the charged particle beam exposure system. Matches what was given.

A seventh invention for achieving the above object is the fourth invention, wherein a current value of two coil groups (0 ° direction coil and 45 ° direction coil) constituting an astigmatism corrector is provided. Or, change the voltage values of the two electrode groups (0 ° direction electrode and 45 ° direction electrode) to 90 ° direction, 0 ° direction, 135 ° direction, 45 ° direction based on the measurement pattern. 2) where the blur in the ° direction is minimized. A current value or a voltage value of the set is determined respectively, and this is performed at arbitrary positions A and A in the optical axis direction at a position B which is separated by Ah in the optical axis direction from

The combination of these current values is (S11A, S21A;), (S12A, S22A) (S13A, S23A) (S14A, (S24A), (S11B, S21B), (S12B, S22B) _S (S13B, S23B) (S14B, S24) In the case of B), the correction sensitivity for astigmatism blur in at least one direction is determined by at least one of the following expressions.

(1) Sensitivity for correcting astigmatism blur when the 0 ° -90 ° direction astigmatism blur is corrected by a 0 ° direction coil or electrode

511,-12, 11 ^-12 ^)

, 2Δ / ι 2Δ / ι,)

(2) 4 5. Correction sensitivity of astigmatism blur when correcting astigmatism blur in the 0 to 90 ° direction using a directional coil or electrode

(S21 _B -S22 _B _S21 _A -S22 _A )

V 2Ah 2Ah,)

(3) Sensitivity of astigmatism blur when correcting astigmatism blur in the 45-135 ° direction using a 0 ° direction coil or electrode

S13, -S14._513, -S14, ₎

K 2Ah 2Ah)

(4) Sensitivity of astigmatism blur when 45-135 ° direction astigmatism blur is corrected by 45 ° direction coil or electrode

S23 _c -S24 ^Τ Β „_ S23„ -S24,

)-(8)

\ 2Ah 2Ah

Here, i of SijA and SijB (i = l, 2, j = l to 4) are 0 ° direction coil or electrode (i = l), 45 ° direction coil or electrode (i

= 2), where j is the direction in which astigmatism blur is minimized (j = l is the 90 ° direction, | = 2 is the 0 ° direction, j = 3 is the 1 35 ° direction, j = 4 is 4 5 ° direction).

An eighth invention for achieving the object is the fifth invention, wherein the focus position is shifted from the right focus by Ah, and then two sets of coils forming an astigmatism corrector are provided. (0 ° direction coil and 45 ° direction coil) or the voltage value of two sets of electrodes (◦. Direction electrode and 45 ° direction electrode) were changed, and the measured pattern was used as a reference. 90 ° direction, 0 ° direction, 135 ° direction, and 45 ° direction, minimize the blur in each of the above two sets of current values or voltage values, and calculate the combination of these current values or voltage values. That it (S1

1, S 2 1), (S 12, S 2 2), (S 13, S 23), (S 14, S 24) Both are characterized in that the sensitivity of occurrence of astigmatism blur in one direction is determined.

(1) Sensitivity of astigmatism blur that causes astigmatism blur in the 0-90 ° direction by the 0 ° direction coil or electrode

-S12) (S23-24)-(S13-S14XS21-S22)},)

(2) Sensitivity of astigmatism blur that generates astigmatism blur in the 0 ° to 90 ° direction by using a 45 ° direction coil or electrode -2Ah (S13-SU)…

{(511-512XS23-24)-(513 -514) (521 -522)} ¹ ,

(3) Sensitivity of astigmatism blur which generates astigmatism blur in 45 ° -135 ° direction by 0 ° direction coil or electrode -2Ah (S21-S22)

{(S11- S12) (S23-24)-(S13-S14) (S21-S22)}

(4) Sensitivity of occurrence of astigmatism blur that causes astigmatism blur in the direction of 45 ° to 135 ° using a 45 ° direction coil or electrode 2Δ / ι (511-512) ... ₍₁₂₎

{(511-512) (S23-24) 1-1 (513-514) (521-522)} A ninth invention for achieving the above object is the fifth invention, wherein an astigmatism corrector is provided. The current value of the two coil groups (0 ° direction coil and 45 ° direction coil) or the voltage value of the two electrode groups (0. direction electrode and 45 ° direction electrode), The two sets of current or voltage values that minimize the blur in the 90 ° direction, 0 ° direction, 135 ° direction, and 45 ° direction based on the measurement pattern are determined, and this is calculated as the optical axis. At any position A in the direction and at position B that is △ h away from the

The combination of these current values is (S11A, S21A), (S12A, S22A) ヽ (S13A, S23A) ヽ (S14A, (S24A) ヽ (S11B, S21B), (S12B, S22B), (S13B, S23B), (S14B, S24 In the case of B), the sensitivity of occurrence of astigmatism blur in at least one direction is determined by at least one of the following expressions.

(1) Sensitivity of astigmatism blur that causes 0-90 ° direction astigmatism blur by a 0 ° direction coil or electrode

2AA {(S23, -S24 _j? )-(S23 _{/ t} -S24J}… (

Δ

(2) 0 by the 45 ° direction coil or electrode. — Sensitivity of astigmatism blur which causes astigmatism blur in 90 ° direction

-2AA {(S13 _g -S14 _B )-(S13, -S14}

Δ,)

(3) Sensitivity of astigmatism blur that causes astigmatism blur in the 45 ° -135 ° direction by the 0 ° direction coil or electrode

-2 ^ hj (S21 _B -S22 _B )-{S21 _A -S22 _A )}…)

Δ

(4) 45 ° -135 ° astigmatism by 45 ° direction coil or electrode. Sensitivity of astigmatism blur causing blur

2A (^ ll _g- ^ 12 _g )-(Sll _{/ 4} -S12,)}…

Δ ^

Where i of S ij A and S ij B (i = 1, 2, j = 1 to 4) are 0 ° direction coil or electrode (i = 1) and 45 ° direction coil or electrode (i = 2), where j is the direction in which astigmatism blur is minimized (j = l is 90. direction, _< ] '= 2 is 0 ° direction, j = 3 is 135 ° direction, j = 4 is 4

5 ° direction), and △ indicates

A = [{(S11 _B -S12 _B )-(S11 _A -S12 _A )} {(S23 _B -S24 _B )-(S23 _A -S24 _A )} ~ {(S13 _B -SU _B )-(S13 _A -SU _A )} {((S21 _B -S22 _B )-(S21 _A -522,)}].

A tenth invention for achieving the above-mentioned object is the fifth invention, wherein the astigmatism corrector is configured such that the focus position is shifted from the right focus position by △ h, and Current value of coil group (0 ° direction coil and 45 ° direction coil) or voltage value of two sets of electrodes (0 ° direction electrode and 45 ° direction electrode) (S1 and S2 respectively) The current values of the two coil groups or the voltage values of the two electrode groups that minimize the blur in the two directions at which the angles differ by 0 are respectively obtained, and these current values or voltage values are obtained. Are defined as (S 15, S 25) and (S 16, S 26), respectively, and are shown below in the S 1 — S 2 ′ rectangular coordinate system (S 1, S 2.) , A circle passing through (S 15, S 25) and (S 16, S 26) is determined, and this circle is defined as the current or voltage value of the two sets of current values or voltage values forming a focal line. A circle representing astigmatism, wherein the sensitivity of occurrence of astigmatism blur in at least one direction is determined based on a direction in which the astigmatism blur is minimized at a predetermined point on the circle. Things. ₅₁ {(515 + S16) ± (525-526) cot Θ}… S ₂ {(S25 + S26) + (515-S16) cot Θ}… The first invention for achieving the above object is the above-mentioned invention. A fifth invention, in which, after shifting the focal position from the positive focal position by Δh, two sets of coils (0 ° direction coil and 45 ° direction coil) constituting the astigmatism corrector Current value or voltage value of two electrode groups (0 ° direction electrode and 45 ° direction electrode)

(They are S 1 and S 2), respectively, and the angles differ by 6> The current value of the two sets of coils or the voltage of the two sets of electrodes that minimize the blur in the two directions The values of the current and voltage values are defined as (S15, S25) and (S16, S26), respectively. (Sl., S2.)

15, S 25), and (S 16, S 26) on a circle passing through, the astigmatism blur in the 90 ° direction and 135 ° direction with respect to the pattern reference direction is minimized.

Obtain two sets of current or voltage values, and determine the combination of each (S

1 1, S 2 1) and (S 1 3, S 2 3), at least one of the following equations (1 9) to (2 2) It is characterized by determining the sensitivity of occurrence of astigmatism blur.

{(515 + 516) ± (525-26) cot Θ}…

_S2 {(^ 25 + 526) + (515 -516) cot 6>}… ()

(1)) Sensitivity of astigmatism blur which generates astigmatism blur in 90 ° direction by 0 ° direction coil or electrode

AA (S23 * -S2 ₀ )

— (19)

_{{(SI 1 '- Sl 0} ) (S 23' - S 2 n) - (S13 '- S 1 0) (S 2Γ- S 2 0)}'

(2) Astigmatism blur in the ◦ ° — 90 ° direction due to the 45 ° direction coil or electrode Sensitivity of Astigmatism Blurring that Generates

-ΔΛ (513'-51 ₀ )

{(Sir-S1 ₀ ) (S23 ^, -S2 ₀ )-(S13'-S1 ₀ ) (S21 ^, -S2 ₀ )},)

(3) Sensitivity of astigmatism blur that generates astigmatism blur in 45 ° -135 ° direction by 0 ° direction coil or electrode

-(S21'-S2 ₀ )

_{{{S1Y- 51 0) (S} 23 '- S 2 0) - (S13 S1 0) (S 21' - S 2 0)})

(4) Sensitivity of astigmatism blur that generates astigmatism blur in the direction of 45 ° -135 ° using a 45 ° direction coil or electrode

{(S11 ^, -S1 ₀ XS23 ^, -S2 ₀ )-(S13'-S1 ₀ ) (S21 ^, -S2 ₀ )})

A twelfth invention for achieving the above object is the fifth invention, wherein the astigmatism corrector is configured such that the focal position is shifted from the positive focal position by △ h, and The current value of the coil group (0 ° direction coil and 45 ° direction coil) or the voltage value of two sets of electrodes (0 ° direction electrode and 45 ° direction electrode) are changed, and three or more with different angles The current value of the two sets of coils (0 ° direction coil and 45 ° direction coil) or the two sets of electrodes (0 ° direction electrode and 45 ° direction electrode) that minimize astigmatism blur in the direction ) Are calculated (S1 and S2), and the combination of these current or voltage values is calculated as (S11, S21), (S12, S2). 2), ..., (S in, S 2 n) (n is an integer of 3 or more), these points pass through in the S1-S2 Cartesian coordinate system. Is determined by solving an equation or by a statistical fitting method. Based on the direction in which the astigmatism blur is minimized at a given point on the circle, the generation of the astigmatism blur in at least one direction is determined. It is characterized by determining the raw sensitivity. The sign of (S in, S 2 n) used in the present invention may overlap with the sign of other inventions, but it goes without saying that there is no relation between the two. this The same applies to the claims corresponding to the present invention.

A thirteenth invention for achieving the above object is the fifth invention, wherein the focus position is shifted from the positive focus position by Ah, and the astigmatism corrector is constituted by two sets. The current value of the coil group (0 ° direction coil and 45 ° direction coil) or the voltage value of two sets of electrodes (0 ° direction electrode and 45 ° direction electrode) is changed, and three or more angles are different. The current value of the two sets of coils (0 ° direction coil and 45 ° direction coil) or the two sets of electrodes (0 ° direction electrode and 45 ° direction electrode) that minimize astigmatism blur in the direction ) (S1 and S2), and the combination of these current values or voltage values is (S11, S21), (S12, S12) 2 2), ..., (S in, S 2 n) (n is an integer of 3 or more), these points pass through in the SI-S 2 orthogonal coordinate system. A circle is determined by solving an equation or by statistical fitting, and its center is set to (S1, S2,), and '90 ° and 135 ° directions on the circle with respect to the pattern reference direction. The two sets of current values or voltage values that minimize the astigmatism blur of each of them are determined, and the combination of the two values is (Sll ,, S21 '), (S13, S23'). ), At least one of the following equations (19) to (22) is used to determine the sensitivity of occurrence of astigmatism blur in at least one direction. .

The sign of (S 1 n, S 2 n) used in the present invention may overlap with the sign of other inventions, but it goes without saying that there is no relationship between the two. This applies to the claims corresponding to the present invention.

(1) Sensitivity of astigmatic blur that causes astigmatic blur in the 0 to 90 ° direction by a 0 ° direction coil or electrode A (S23'-S2 ₀ )…

{(5ir-Sl ₀ ) (523'-S2 ₀ )-(S13'-S1 ₀ ) (S 2Γ-52 ₀ )}

(2) Sensitivity of astigmatism blur that causes astigmatism blur in the 0 ° to 90 ° direction by using a 45 ° direction coil or electrode

-(513-51 ₀ )

_{{(S1V- S1 Q) (S} 23 '- S 2 0) - (513' - Slo) (S 21'-S 2 0)})

-(S21'-52 ₀ )…

{(SI 1 '-Sl ₀ ) (S 23'-S 2 ₀ )-(S 13 '-S 1 ₀ ) (521'-S 2 ₀ )})

(4) 4 5 ° direction Koiru or electrode, 4 5 ° - 135 ° direction generation sensitivity astigmatism blur to generate astigmatism Bo Ke (S11 '-S1 ₀₎

-(twenty two)

_{{(511 '- Sl 0)} (S 23 S 2 0) - (SI 3' - S 1 0) (S 21 '- S 2 0)},) the invention of the first 4 to achieve the above object In the fifth aspect, two sets of changing the focal position h (where each optical axis direction position is hi (i = l to n)), and configuring the astigmatism corrector Current value of coil group (0 ° direction coil and 45 ° direction coil) or voltage value of two sets of electrode group (0 ° direction electrode and 45. direction electrode) (SI, S 2), and are respectively changed. The angle of the astigmatism blur pattern at that time is denoted by ti. From these data, (h−h.) Changes by a unit amount by a statistical method. When (h. Is the focal position where the positive focus is formed), the set of points (S 1, S 2) forming the focal line indicates the amount of change in the radius of the circle formed by the S 1-S 2 rectangular coordinate plane. The proportional constant r shown and only the 0 ° direction blur with respect to the S1 axis Change direction of such to the corner 2 t. And determining the sensitivity of occurrence of astigmatism blur in at least one direction according to the following equations (23) to (26). . (1) Sensitivity of astigmatism blur that causes astigmatism blur in the direction of 0 to 90 ° by a 0 ° direction coil or electrode

cos (2t ₀ ) / r-(23)

(2) Sensitivity of astigmatism blur that generates astigmatism blur in the 0 ° to 90 ° direction by a 45 ° direction coil or electrode

sin (2t ₀ ) / r-(24)

(3) Sensitivity of astigmatism blur that causes astigmatism blur in 45 ° -135 ° direction by 0 ° direction coil or electrode

-sin (2t ₀ ) / r-(25)

(4) Sensitivity of astigmatism blur that generates astigmatism blur in the direction of 45 ° to 135 ° using a coil or electrode in the direction of 45 °

cos (2t ₀ ) / r — (26)

A fifteenth invention for achieving the above object is the fourteenth invention, wherein the statistical method uses a center point (S 1, S 2) of a circle formed by the focal point. ), Positive focus position h. , The proportionality constant r, and the angle 2t between the direction in which only the 0 ° direction blur changes with respect to the SI axis. Is a method of obtaining the above r and t _D by obtaining these variables so that the following evaluation function minimizes P with the following as variables.

([-SI.-R (-/ ¾) _C0S { ² ft ₊ i.)}

-[52, -52 ₀ -^-/ i ₀ ) sin {2ft ".)}]-(27) A sixteenth invention for achieving the above object is a charged particle beam exposure apparatus, comprising: a reticle; A method for exposing and transferring the image of the astigmatism onto a wafer, wherein the astigmatism blur determined by the method for determining astigmatism sensitivity in the charged particle beam exposure apparatus according to any one of the first to fifteenth inventions. Exposure transfer is performed while adjusting the astigmatism corrector so as to correct astigmatism blur for each subfield using the correction sensitivity or the sensitivity of occurrence of astigmatism blur. This is an exposure method in a charged particle beam exposure apparatus.

A seventeenth invention for solving the above-mentioned problems is the sixteenth means, wherein the astigmatism corrector includes two coil groups (a 0 ° direction coil and a 45 ° direction coil) or 2 A set of electrode groups (0 ° direction electrode and ₄₅ ° direction electrode), and for the astigmatism blur amount △ h ₀ , A h ₄₅ to be corrected, Voltage value ΔΙ of two electrode groups. And it is characterized in that determined by the following equation ΔΙ _45.

Where E, F, G and H are

E is the astigmatism blur correction sensitivity when the 0-90 ° direction astigmatism blur is corrected by the 0 ° direction coil.

F is the sensitivity of astigmatism blur correction when the astigmatism blur in the 0-90 ° direction is corrected by the 45 ° direction coil.

G is the astigmatism blur correction sensitivity when astigmatism blur in the 45-135 ° direction is corrected by the 0 ° direction coil.

H is the astigmatism blur correction sensitivity when the 45-135 ° direction astigmatism blur is corrected by the 45 ° direction coil.

It is. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagram for explaining the principle of the first embodiment of the present invention. FIG. 2 is a diagram for explaining the principle of the second embodiment of the present invention. FIG. 3 is a diagram for explaining the principle of the fourth embodiment of the present invention. FIG. 4 is a diagram for explaining the principle of the fifth embodiment of the present invention. FIG. 5 is a diagram illustrating an example of a coil arrangement of the astigmatism corrector. FIG. 6 is a diagram showing an outline of a charged particle beam exposure apparatus.

FIG. 7 is a diagram illustrating an example of a method for detecting blur. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings. As shown in Fig. 5, a typical astigmatism corrector consists of four coils arranged at 90 ° intervals as shown in (a) as the first set of coils, and as shown in (b). As shown in the figure, the four coil groups arranged at 90 ° intervals in a direction deviated by 45 ° from each other are used as a second set of coils, which are combined and arranged as shown in (c). You. (D) is a sectional view taken along line AA in (c). In the figure, reference numerals 41 a to 41 d and 42 a to 42 d respectively show toroidal coils along the optical axis. Normally, 4 1 a to (! Are connected in series and are excited by the same current. For example, when a certain current flows, 41 1 a and 41 c generate a magnetic field clockwise, and 41 b and 41 d It is wound so as to generate a magnetic field in a counterclockwise direction, and generates a quadrupole field on the optical axis.The same applies to 42 a to 42 d. The flowing current indicates the current flowing through these serially connected coils.Of course, the coils actually used are not limited to the toroidal type.Although not shown in the figure, the electrostatic astigmatism correction is performed. The 0 ° and 180 ° electrodes have the same potential, and the 90 ° and 270 ° electrodes have the opposite potentials. In the present invention, when the voltage applied to the astigmatism compensator is described, the 0 ° direction electrode The voltage applied to the 4 5 °-direction electrodes have a representative value.

The reference direction of the astigmatism corrector is set to 0 °. In this specification and in the claims, according to this direction, the first set of coil groups will be referred to as 0 ° direction coils, and the second set of coil groups will be referred to as 45 ° direction coils. This reference direction Is conceptual to distinguish the two sets of coils. This direction does not always coincide with the 0 ° direction based on the measurement pattern. Of course, if the direction of the astigmatism blur to be corrected matches the direction of the astigmatism blur that can be corrected by the first set of coil groups, the astigmatism correction is performed only by the first set of coil groups. Therefore, the coil group may be a single set, but in this case, the description in this specification is made by ignoring either set of the coil groups (the current flowing through the coil group is 0). As).

In the embodiments of the invention described below, the astigmatism corrector will be described as being constituted by such a coil group, but the astigmatism corrector uses a coil as described above, In addition to the method of correcting astigmatism by the Lorentz force, there is also a method of applying a voltage to the electrode and correcting the astigmatism by the electrostatic force. The operation of such an astigmatism corrector using a coil and an astigmatism corrector using an electrode are basically the same. Therefore, those skilled in the art can easily read the embodiment of the present invention in an astigmatism corrector using an electrode by reading the coil in the following embodiment as an electrode and the current flowing through the coil as a voltage applied to the electrode. Can be inferred. It goes without saying that the astigmatism corrector described in the claims includes both a device using a coil and a device using an electrode. First, the principle of the first embodiment of the present invention will be described with reference to FIG. Figure 1 shows that astigmatism blur changes the current flowing in the 0 ° direction coil (actually, the magnetic field is a problem, so the unit is AT.) S1, the current S2 flowing in the 45 ° direction coil is changed. in FIG. a is _c Figure 1 showing how the changes by the horizontal axis the current S 1 flows to the first set of coil group, the current S 2 flowing through the second set of co-I le group vertical An orthogonal coordinate system as an axis is shown. That is, it is a coordinate system for explaining the excitation of the astigmatism corrector.

However, in FIG. 1, the shape of the image shown is It is a shape (shape on the X-y plane) indicated by a rectangular coordinate system (X-y coordinate system) with the reference direction set to 0 °. In Fig. 1, the figure is drawn so that the S1 axis and the X axis coincide with each other, and the S2 axis and the y axis coincide with each other, but this is only displayed for convenience for easy understanding. It is. Since the X-y coordinate system and the S 1-S 2 coordinate system are completely different, there is no special meaning in giving them the same representation. Also, the origins of the S1-S2 coordinate system and the X-y coordinate system need not coincide. The circle shown by the broken line in FIG. 1 is on the S1-S2 plane.

In this figure, it is assumed that the focal position is shifted from the normal focal position by Δh. The focal position may be shifted by operating the charged particle beam optical system, but a simpler method can be realized by changing the height of the object to be exposed.

Reference numeral 15 indicates a beam shape in a state where astigmatism blur does not occur.

By changing S l and S 2, the beam shape changes as shown in the figure according to the respective values of S l and S 2. Then, a focal line is formed on a circle centered at 15. Of these focal lines, 11 is at 0 ° to the axis, 12 is at 90 ° to the X-axis, 13 is 45 ° to the X-axis, and 14 is at X-axis. It is tilted 135 ° to it. In the present embodiment, a set of S 1 and S 2 giving these focal lines 11 to 14 is found, and the correction sensitivity of astigmatism blur is determined based on the set. In other words, the coordinates of 11 are (S11, S21), the coordinates of 12 are (S12, S22), the coordinates of 13 are (S13, S23), and the coordinates of 14 Let (S14, S24) be the current flowing through the 0 ° directional coil from the state where there is no astigmatism blur at the same focal position as the measurement point and the 45 ° directional coil, as is clear from the figure. The current flowing through 512-511

Two

522-521

Two

By changing only the astigmatism blur in the 45 ° -135 ° direction, only the astigmatism blur in the 0 ° -90 ° direction is adjusted, and the astigmatism blur in the 0 ° direction is adjusted. It can be minimized (state 1 and 2 in Figure 1). Conversely, when the sign of these equations is changed by as much as the sign is changed, the astigmatism blur in the 90 ° direction can be minimized (state 11 in FIG. 1).

Since this is the value when the focal position changes by △ h in the optical axis direction, when astigmatism blur is converted into a focal position deviation in the optical axis direction, astigmatism with respect to defocus per unit length is obtained. The blur correction sensitivity is as shown in Equations (1) and (2). Here, the dimensions of equations (1) and (2) are expressed, for example, as [AT / mm] (voltage is expressed as [V / mm]). 511-512

-(1)

2Δ / ι

521-522

~ (2)

Similarly to 2Ah, the current flowing through the 0 ° directional coil and the current flowing through the 45 ° directional coil from the same focal position as the measurement point and no astigmatism blur,

S14-S13

Two

524-S23

Two

If only the astigmatism blur is changed, the astigmatism blur in the 0-90 ° direction is not changed, and only the astigmatism blur in the 45 ° -135 ° direction is adjusted. Astigmatism blur can be minimized (14 in Fig. 1). or, When the sign of the above equation is changed, the astigmatism blur in the 135 ° direction can be minimized (state 13 in Fig. 1).

Since this is the value when the focal position changes by △ h in the optical axis direction, the correction sensitivity of the astigmatism blur for the defocus per unit length is expressed by the equations (3) and (4), respectively. become that way. Here, the dimensions of equations (3) and (4) are expressed, for example, as [mm / AT] (for voltage, they are expressed as [V / mm]).

S13-SU

-(3)

2Ah

523-524

•••(Four)

2Δ / ι Further, in the present specification, the magnitude of the astigmatism blur is represented by being converted into the magnitude of the focal position shift in the optical axis direction. The absolute value of these two components of astigmatism blur is the absolute value of the amount of deviation of the imaging plane position, which becomes the focal line when there is astigmatism, from the positive focal point. It is expressed by the combination of the direction blur and the 45-degree direction blur. The 0-degree direction component and the 45-degree direction component are the 0-degree direction blur for the astigmatism blur (9 if the 0-degree direction blur is negative). Contribution of 0 degree directional blur), 45 degree directional blur (If 45 degree directional blur is negative, it indicates that 135 degree directional blur is occurring) Is shown. Of course, when there is no astigmatism blur, both the 0-degree component and the 45-degree direction component become 0. Then, the current or voltage applied to the astigmatism corrector is calculated by applying the astigmatism bog to be corrected (inversion of the sign of the generated astigmatism blur) to the correction sensitivity matrix of the astigmatism blur. The astigmatism blur is corrected by changing the current or voltage of the astigmatism corrector by that amount.

In the above explanation, the current values S 1 and S 2 that give a focal line in each direction were found As described, it is not necessary to actually find the focal line. That is, for example, if a combination of the current values S 1 and S 2 that minimizes the blur in the X-axis direction is found, it corresponds to the focal line 12. If a combination of the current values S l and S 2 that minimizes the blur in the y-axis direction is found, it corresponds to the focal line 11. If a combination of the current values S 1 and S 2 that minimizes the blur in the 45 ° direction with respect to the X axis is found, it corresponds to the focal line 14. If a combination of the current values S 1 and S 2 that minimizes the blur in the 135 ° direction with respect to the X axis is found, it corresponds to the focal line 13.

An example of a method for finding the combination of S1 and S2 that minimizes the blur in each direction will be described later.

Hereinafter, a second embodiment of the present invention will be described. This embodiment is different from the first embodiment in that the focus position is changed to determine the correction sensitivity for astigmatism blur. The principle of this method will be described with reference to FIG. In Fig. 2, the concept of S1-S2 axis and X-y axis is the same as Fig.1. The shape of the image is on the X-y plane, and the circle shown by the broken line is on the SI-S2 plane.

In FIG. 2, a focal line is detected at a certain focal position in the same manner as in the first method, and the focal line in the X-axis direction (0 ° direction) is inclined at 11 A and 90 ° with respect to the X-axis. The focal line is 12 A, the focal line inclined at 45 ° to the X axis is 13 A, and the focal line inclined at 135 ° to the x axis is 14 A. Next, the focal position is shifted Ah from this position, and the focal line is detected in the same manner. To shift the focal point, the focal point may be shifted by operating the charged particle beam optical system, but a simpler method can be realized by changing the height of the object to be exposed.

After defocusing, the focal line in the X-axis direction is 1 1 B, the focal line inclined 90 ° to the X axis is 12 B, and the focal line inclined 45 ° to the X axis is 13 B, the focal line inclined by 135 ° with respect to the x-axis is defined as 14B. And the coordinates of each point are 1 1 A (SI 1 A, S 2 1 A) _s 1 2 A (S 12 A, S 22 A) 13 A (S 13 AS 23 A), 14 A (S 14 A, S 2 4 A), 1 1 B (S 1 1 B, S 2 1 B) 1 2 B (S 1 2 B, S 2 2 B), 1 3 B (S 1 3 B, S 2 3 B), 1 4 B (S14B, S24B).

Then, by differentially using the principle described with reference to FIG. 1, the correction sensitivity of astigmatism blur in the 0 ° -90 ° direction and the 45 ° -135 ° direction can be obtained as follows. Can be determined.

(1) Sensitivity for correcting astigmatism blur when correcting astigmatism blur in the 0 to 90 ° direction using a 0 ° direction coil or electrode

11 _B -S12 _B Sll.-S12 _A

(^ 1 ~~ ^ά

2Ah 2Ah,

S2 \ _B -S12 _B _S2 \ _A -S12 _A )

, 2Ah 2Ah)

S13 _B -S14, _S13, -S14, ₎

, 2Ah 2Ah)

(S23 _B -S2A _B _S23 _A -S24 _A)

2Ah 2Ah)

Where i in S ij AS ij B (i = 1, 2j = 14) indicates a 0 ° directional coil (i = l) and a 45 ° directional coil (i = 2), respectively, and j Is the direction in which astigmatism blur is minimized (j = 1 is 90 ° direction, j = 2 is 0 ° direction, j = 3 is 13.5 ° direction, j = 4 is 45 ° direction) Is shown. Hereinafter, a third embodiment of the present invention will be described. The sensitivity of the astigmatism corrector (correction sensitivity for astigmatism blur) is different from the one described above. When the current flowing through the coil of a certain astigmatism corrector is changed, how much is 0 to 90 ° If you want to know if the astigmatism blur in the direction changes, as well

Five

There is. In this sense, the sensitivity of astigmatism blur, which represents astigmatism blur (conversion in the optical axis direction) that occurs when the current flowing through the coil of the astigmatism corrector is changed by a unit amount, is For example, it is represented by a dimension such as [mm / AT]. The occurrence sensitivity of such astigmatism blur is as described in the above (1).

It can be easily obtained from Eq. (4).

Ten

That is, the amount of change in the current flowing through the 0 ° direction coil is △ I. , 4 5 ° the amount of change current flowing in the direction coil and delta 1 _{4 5,} the time of 0-9 0 those converted in the optical axis direction position astigmatism blur of ° direction A h. And those obtained by converting the astigmatism blur of 4 5-135 ° direction in the optical axis direction position and delta 1 _{4 5,}

From (1) to (4),

Because

Δn

Ah ■ 45

The two

2 /, Δ ₄₅ no

Where A ii represents the current flowing through the 0 ° Generating sensitivity astigmatism blur, A _{1 2} 4 against to current flow in 4 5 generation sensitivity astigmatism blur of ° 0- 9 0 ° direction with respect to the current flowing in the direction coil, A ₂ i is 0 ° direction coil generating sensitivity astigmatism blur of 5-135 ° direction, the occurrence sensitivity astigmatism blur of 4 5-135 ° direction with respect to the current a _{2 2} shed to 4 5 °-direction coil. A i have AA ₂ have A _{2 2} is determined easy by calculating the inverse matrix of (2 9). That is,

2ΔΑ (523-524)

^ 11 =

{(--512) (523-24) one (513-four) (521 -522)}

-2Ah (S13-S14)

A {^ 11- -S12) (S23 -24)-(SL3 -SL4) (S21 -S22)}

-2Δ / ι (521-522)

{(Sll- -512) (523 -24)-(513 -514) (Sll-《22)}

It becomes.

Similarly, the current value of the two sets of coils or the voltage value of the two sets of electrodes constituting the astigmatism compensator are varied respectively, and the 0 ° direction, 90 ° direction, 45 The two sets of current values or voltage values that minimize the blur in the 135 ° direction and 135 ° direction are calculated accordingly, and these are determined as arbitrary positions A and A in the optical axis direction at positions △ h away from the arbitrary optical axis directions in the optical axis direction. Done in B,

The combination of these current values is (S11A, S21A), (SI2A, S22A), (S13A, S23A) ヽ (S14A, S 2 4 A) _s (S 11 B, S 21 B), (S 12 B, S 22 B), (S 13 B, S 23 B) _S (S 14 B, S 2 4B), when determining the sensitivity of occurrence of astigmatism blur in at least one direction by at least one of the following equations, by taking the difference,

(1) 0-90 ° direction astigmatism blur is generated by the 0 ° direction coil Sensitivity of astigmatism blur

2 ^ {{S23 _B -S2 ^ _B )-(S2 _A -S2A _A )}… (

Δ

(2) Sensitivity of astigmatism blur which generates astigmatism blur in the 0 ° to 90 ° direction by the 45 ° direction coil

-2AA {(S13 _g -S14,)-(S13, -S14J}

Δ,)

(3) Sensitivity of astigmatism blur that generates astigmatism blur in the 45 ° -135 ° direction by the 0 ° direction coil

(15) Minus at the beginning & Close at the end}

-2Ah {(S21 _B -S22 _B )-(S2 \ _A -S22J}

ー (15)

Δ

(4) Sensitivity of astigmatism blur which generates astigmatism blur in the direction of 45 °-135 ° by the 45 ° direction coil

Remove the minus sign at the beginning of equation (16)

2 ^ {{S1 \ _B -S12 _B )-{SY1 _A -S12 _A )}

• (16)

Δ

Can be obtained.

However, i of SijA and SijB (i2, j = 1 to 4) are 0 ° direction coils (i = l) and 45, respectively. Indicates the direction coil (i = 2), j is the direction in which astigmatism blur is minimized (j = 1 is 90 ° direction, j = 2 is 0 ° direction, j = 3 is 1 35 ° Direction, j = 4 indicates 45 ° direction), and △ indicates

Δ = [{(^ 11, -S \ 2 _B )-{Sn _A -S12 _A )} {(S23 _B -S2 _B )-{S23 _A -S2 _A )}-{{S13 _B -514 _β )- (513 _Λ -S _A )} {((S21 _B -S22 _B )-{S21 _A -S22 _A )}].

Also, from the equations (5) to (8) shown in the second embodiment, the above-mentioned (2) 8) The expression corresponding to the expression is

511.-512, _ SH _A -S12 _A ), 513 _Β -14 S13, -S _t

2ΔΛ 2ΔΛ 2ΔΛ 2ΔΛ

■ (31)

ΑΙ '45 521 „_- 522 _β- one S21 _A -522, S23 _B -S24 _B 523.-Ξ24 _Λ 45,

2Δ / ι 2ΔΛ 2ΔΛ 2ΔΛ

Therefore, if A, A ₁₂ , A _{2 and} A ₂₂ corresponding to the equation (30) are obtained,

_{_{2ΔΑ {(523 β - S24 B}} ) - (S23 A - - • 524,)}

Δ

-2Ah {(S13 _B -su _B )-(^ 13, -514,)}

Δ

-2Ah {(S21 _B -522-(^ 21,

1 =

Δ

A i 2Ah {(Sll _B -512 _β )-(^ ιι.i S12 _A )

^Λ 22 ―

Δ

It becomes. However

Δ = [{(S11 _B -512,)-(511, -S12 _A )} {{S23 _B -S24 _B )-(S23 _A -S24 _A )}

-{(^ 13, -S _B )-(S13 _A -S _A )} {((S21 _B -S22 _B )-(S21 _A -S22 _A )}].

FIG. 3 is a diagram for explaining a fourth embodiment of the present invention, and is similar to FIG. In this figure, it is assumed that the focal position is shifted from the normal focal position by Δh. Note that 0 indicates the excitation condition in a state where astigmatism blur does not occur.

In the example shown in FIG. 3, the combination of S 1 and S 2, which forms a long focal line in a direction shifted by 45 ° from the reference direction of the measurement pattern, is set to the position of point 22 (S 15, S 2 5), The combination of S1 and S2, which forms a long focal line in a direction shifted 90 ° from the reference direction of the measurement pattern, is defined as the position of point 23 (S16, S26) . In the figure, these focal lines are indicated by lines. That is, points 22 and 23 respectively correspond to the reference direction of the measurement pattern. This is a point at which astigmatism blur in directions shifted by 135 ° and 0 ° is minimized. That is, at point 22 and point 23, the angle difference 0 in the direction that minimizes astigmatism blur is

4 5 degrees.

By the way, in general, when the focal point deviates from the right focal point position, the combination of S 1 and S 2 that forms a focal line on the image forming plane can draw a circular locus on the S 1—S 2 plane. Are known. It is known that the direction of the focal line at the point at which the center angle of the circle changes by ø changes by +2 or one-two. Using this, the center point 0 of the circle 21, that is, the position where astigmatism blur does not occur is obtained. The position of point 0 is defined as (S1,

52. ).

First, it is clear that point 0 is on the perpendicular bisector 24 of points 22 and 23 because points 22 and 23 are points on the circle 21. The equation of this vertical bisector is

(S1- ^{S15 + S16} (S15 -S16) + (S2- ^{S2:> + S2} (S25 -S26) = 0… (32)

M

To be satisfied. Also, as described above, the direction of the focal line at the point where the center angle of the circle where the combination of (S1, S2) forming the focal line exists changes by ø changes by 0/2. It has been known. Conversely, since the direction of the focal line is shifted by 0 at points 2 2 and 2 3, the line connecting the center 0 of circle 2 1 and point 2 2 (or point 2 3) and this vertical 2 The angle formed by the bisectors 24 is 0.

From this, using the inner product of the vector

(51-S15XS1-S16) + (52-S25) (S2-S26)

= (51-S15) ² + (S2-S25) ² -S16) ² + (S2-S26) ² cos 2Θ-<33)

Therefore, the position of point 0 is obtained as a solution (S1, S2) obtained by simultaneously solving equations (32) and (33) for S1 and S2. That is,

_ {(S15 ₊ S16) ± (S25-S26) cote}…

M

_S2 {(525 + 526) + (515-516) cot Θ}… hi ₈₎ Since two sets of solutions (S1, S2.) Are obtained, it is important to decide which one to use. Become. However, this can be easily determined. The simplest method is to excite the astigmatism compensator under the conditions (S 1 D, S 2) that were found, and to adopt the one that has astigmatism blur close to zero. In general, the tendency of astigmatism blur generated by each current of each astigmatism corrector is known from the design, so that the one that matches the tendency may be adopted. For example, it is assumed that when S1 is excited to the positive side, the astigmatism blur is designed so that the 0-90 ° direction becomes stronger in the 0 ° direction. The focal line in the 0 ° direction is symmetrical to point 23 with respect to zero. If it is 0 in Fig. 3, if S1 is excited positively, the blur in the 0 ° direction becomes stronger, but the other solution is reversed, so that it is easy to determine.

In this way, when the center 0 of the circle 21 is determined, the circle connecting the points forming the focal line is determined as a circle centered on the point 0 and passing through the points 22 and 23. The radius of the circle indicates the magnitude of astigmatism blur caused by the shift of the focal position by Δh.

When this circle is obtained, the astigmatism blur in the direction of 0 ° to 90 ° and the astigmatism blur in the direction of 45 ° to 135 ° with respect to the reference direction of the pattern, and the astigmatic blur in the direction of The sensitivity at the time of correction by the 45 ° directional coil (Sl) and the 45 ° directional coil (S2) can be obtained.

First, the point where the astigmatism blur in the 90 ° direction is minimized on this circle is determined, and the combination of the currents of the 0 ° direction coil and the 45 ° direction coil of the astigmatism corrector at that time is (S ll , S 2 1 '). Also, on this circle, 135 ° Find the point where the astigmatism blur in the azimuth is minimized. Then, the 0 ° direction coil of the astigmatism corrector, 45. The combination of the currents in the direction coils is (S13, S23 ').

In general, for example, the excitation current or voltage of the astigmatism corrector that minimizes the blur in the 0i direction is (S15S25), and the astigmatism that minimizes the blur in the 6> ₂ direction. The excitation current or voltage of the compensator is (S16 ', S26')

The point on the general focal line circle is the focal line radius S,

_ _v (S15 'One S16J + (S 25' ― S 26 J cos ec ^

Two

The point (S1, S2) on this focal line circle is a straight line parallel to the S1 axis, centered on the center of the circle (S1, S2) in (SI—S2) coordinates. If the angle formed is ø,

51- S1. = S cos0

52- S2. = S sin ^

And thus

tan = (S2-S2 ₀ ) bar S1-S1 ₀ )

It becomes.

0 Rotation angle in the S 1—S 2 coordinate system that minimizes blur in the i direction ø i is φ J = tan " ¹ ((S25 *-S2 ₀ ) / (S15 *-Sl ₀ ))

Therefore,

φ: ± 2 (0-6>)) + φ!

-

It is considered that the focal line becomes 0 degree direction when 6> = 0, ^ iBJ) S13 'Two S cos0 o ⁺ Sl ₀

S23 * = S sin ø o + S2 ₀

Similarly, the 45 ° directional focal line is considered to be 0 = ττ / 4 when φ ₅ = + 2Θ, Satichi + tan ¹ ¾

5 ¹ 2 15 '-Sl ₀ no

S23 'two S sin ø ₄ ε + S2.

It can be expressed as.

In this way, from the geometric relationship shown in Figure 3,

(1)) 0 ° -90 ° direction astigmatism blur caused by 0 ° direction coil

AA (S23'-S2 ₀ )

{(SI 1 '-S1 ₀ ) (S 23'-S 2 ₀ )-(513 '-51 ₀ ) (S 21'-S 2 ₀ )})

- (S13'-S1 ₀₎ ...

{(511 Sl ₀ ) (S 23 S 2 ₀ )-(SI 3 '-S 1 ₀ ) (S 21' -S 2 ₀ )},)

(3) Sensitivity of astigmatism blur that causes astigmatism blur in the 45 ° -135 ° direction by the 0 ° direction coil

-(S21'-S2 ₀ )

{(SI 1 Sl ₀ ) (S 23 S 2 ₀ )-(S 13 '-S 1 ₀ ) (S 21 52 ₀ )},)

(4) Sensitivity of astigmatism blur which generates astigmatism blur in the direction of 45 ° to 135 ° by the 45 ° direction coil

Ah (SlV-Sl ₀ )

{(S1V- S1 _Q ) (S 23 '-S 2 ₀ )-(S13'-Sl ₀ ) (521 '-S 2 ₀ )}'

It becomes.

In the above embodiment, two points at which the astigmatism blur in the different directions is minimized are found on the S 1 —S 2 plane, and these are the focal lines on the S 1 —S 2 plane. If the center angle in the circle where the combination of (S1, S2) forms the focal line changes by ø, the direction of the focal line will change by 0/2. Was used to find a circle forming a focal line. However, if three points at which the astigmatism blur in the different directions is minimized on the S 1 -S 2 plane are obtained, each of these points is on a circle forming a focal line on the S 1-S 2 plane. By taking advantage of this fact, a simultaneous equation can be solved to obtain a circle. After obtaining the circle, the same processing as described above is performed, and the generation sensitivity of the astigmatism corrector can be obtained.

The above discussion has been based on the assumption that there is no determination error at a point on the S 1—S 2 plane that minimizes astigmatism blur in a predetermined direction. However, if there are errors in determining these points, they will appear as errors in the sensitivity of the astigmatism corrector.

FIG. 4 is a diagram for explaining a fifth embodiment of the present invention using a method for removing the influence of such an error as much as possible when there is such an error. In this embodiment, the points (combinations of the current values of the two coils) on the S1-S2 surface that minimize astigmatism in many directions (eight in the figure) are obtained. The points are represented by 25-32. The shape of the focal line at each point is indicated by a line. In this example as well, for the sake of explanation, the pattern direction is set to 0 ° in the S1 direction.

As in FIG. 3, circle 21 is the circle connecting the points where the focal line is formed, and point 0 is the center. As is clear from the figure, points 25 to 32 are not on the circle 21. This is because there is an error in the determination of points 25-32. In this embodiment, the circle 21 is estimated by the least squares method using these eight points. In other words, if the coordinates of points 25-32 are different (Sli, S2) (i = 25-32),

S l such that is minimized. , S2. , R can be obtained.

When the circle 21 is obtained in this manner, the generation sensitivity of the astigmatism corrector can be obtained by the same method as the embodiment shown in FIG.

In order to implement the above-described embodiment, it is necessary to find a combination of currents of the astigmatism corrector that minimizes blur in a predetermined direction. This is performed by the method shown in FIG.

In the figure, the blur detection charged particle beam image 51 is scanned by a scanning deflector, and passes over the charged particle beam blur detection mark 52. Then, a signal is obtained by a signal detector (not shown) (for example, a backscattered electron detector). This signal is proportional to the area of the overlapping portion of the charged particle beam blur detection mark 52 and the blur detection charged particle beam image 51, but the blurred charged particle beam image 51 If there is, it becomes a figure that is blurred by the amount of the blur. Therefore, this detection signal usually has a shape as shown in 53, and by differentiating it, a waveform like 54 is obtained. Usually, the scanning distance of a portion from 12% to 88% of the rising portion in the differential signal is defined as a blur 55.

While changing the combination of the current values S 1 and S 2 of the astigmatism corrector, scan in the X-axis direction and measure the blur as described above, and find the combination that minimizes the blur. Corresponds to a focal line parallel to the y-axis. As described above, by measuring the blur while changing the scanning direction of the charged current particle beam, it is possible to find the combination of the current values of the astigmatism corrector that minimizes the blur in the predetermined direction. .

Hereinafter, an example of the charged particle beam exposure method using the sensitivity of occurrence of astigmatism blur determined in this way will be described. In this exposure method, the Coulomb effect is corrected in consideration of the aperture ratio of the pattern for each subfield. This is performed for each subfield. That is, the focal position of the projection optical system is changed for each subfield so as to correct the Coulomb effect.

First, the astigmatism blur correction sensitivity is determined from the obtained astigmatism blur occurrence sensitivity. That is,

A is the sensitivity of astigmatism blur which causes astigmatism blur in the 0-90 ° direction by the 0 ° direction coil (that is, when the current flowing through the 0 ° direction coil is increased per unit, 0 ° directional blur increase)

B, the sensitivity of astigmatism blur which causes astigmatism blur in the 0 ° -90 ° direction by the 45 ° direction coil (that is, the current flowing through the 45 ° direction coil was increased per unit) 0 ° direction bokeh increase in case)

C is the sensitivity of astigmatism blur which causes astigmatism blur in the 45 ° -135 ° direction by the 0 ° direction coil (that is, when the current flowing through the 0 ° direction coil is increased per unit, 90 ° increase in direction blur)

D, the sensitivity of the astigmatism blur which causes 45 ° -135 ° direction astigmatism blur by the 45 ° direction coil (that is, the current flowing through the 45 ° direction coil was increased per unit) In the case, the amount of increase in the 45 ° direction blur), the astigmatism blur occurrence sensitivity matrix [X] is (AB \

[X} =

^{11 1} , C and Du), and find the inverse sensitivity matrix of the correction sensitivity matrix [Y] for astigmatism blur. That is

It becomes. here,

E is the astigmatism blur correction sensitivity when the 0 ° -90 ° direction astigmatism blur is corrected by the 0 ° direction coil. F is the sensitivity of astigmatism blur correction when the astigmatism blur in the 0-90 ° direction is corrected by the 45 ° direction coil.

G is the astigmatism blur correction sensitivity when correcting the astigmatism blur in the 45-135 ° direction using the 0 ° direction coil.

H is the astigmatism blur correction sensitivity when the 45-135 ° direction astigmatism blur is corrected by the 45 ° coil.

It is.

Due to changes in the influence of the Coulomb effect and changes in the deflection position, astigmatism blur in the 0-90 ° direction is _ △ h. Only occurs at 45 ° -135. Square astigmatism blur countercurrent is - △ If only occurs h _45, astigmatic blur quantity to be corrected (Δΐΐο, Δ1ι ₄₅₎ becomes, the exciting current flowing in the 0 ° direction coils, a 45 ° direction co I le The exciting current that flows is

ΔI calculated by It may be changed by △ I _{4 5.}

In this way, a good imaging pattern with small astigmatism can be obtained.

In the above description, the sensitivity of occurrence of astigmatism blur was obtained with the focus position changed from the normal focus position by △ h, but astigmatism correction in which focal lines are formed at a plurality of focus positions is performed. The current values S 1 and S 2 of the detector may be obtained, and the occurrence sensitivity of astigmatism blur may be obtained by a statistical method. An example is shown below.

Assuming that the focal position h is hi (i = l to n) and is changed by n steps, the combination of the current values of the astigmatism corrector when a focal line is formed at each focal position is described above. Expressed as (S 1 or S 2, the angle of the astigmatism blur pattern at that time is ti. Note that ti is usually a design value, The measured value may be used.

Then, an estimation equation such as the following equations (35) and (36) is considered. 51-51 ₀ = r (/ i- / i ₀ ) cos {2 (i + i ₀ )} '' (35)

<S2-52. = — / ¾) sin {2 (i + i ₀ )} '· (36)

Where (SI, S 2) is the combination of the exciting current as described above, t is the angle of the astigmatic blur pattern (the angle between the focal line and the X axis and the angle in the direction perpendicular to the X axis), and the variable together with h It is.

On the other hand, (S1, S2.) Is the center point of the circle created by the above-mentioned focal point, h. Is the focus position, and r is the proportional constant, which is the radius of the circle that changes when (h—]!) Changes by a unit amount, t. Is the half of the angle with respect to the S1 axis that only the 0 ° direction blur changes, and these are all unknowns. And these unknowns are

A known statistical method may be selected and used as a method of obtaining an unknown that minimizes the evaluation function P by minimizing the evaluation function P expressed by:

Thus, (S l., S 2.), h. , T. , R, the astigmatism blur correction sensitivity matrix is

frcos [it _Q ) rsin (2 ₀ ),

rsiru i _Q ) rcos (2t ₀ )

The reciprocal of the astigmatism blur occurrence sensitivity matrix is

It becomes. Therefore, ', the equation corresponding to equation (34) is

The astigmatism blur in the 0 to 90 ° direction is Δh due to changes in the influence of the Coulomb effect and changes in the deflection position. Only it occurs, 4 5 ° - 135 If the astigmatism blur of ° direction occurs only A h _{4 5,} the excitation current flowing in the direction of 0 ° to Koi Le, the exciting current applied to 4 5 ° direction coils, it it , Δ 計算 calculated by equation (37). , ΔI ₄₅ may be changed.

Conversely, the excitation current flowing through the coil in the 0 ° direction and the excitation current flowing through the 45 ° direction coil are Δ Δ. , △ I of _{4 5} only when changing, 0 - 9 0 astigmatism blur of ° direction △, 4 5 ° - 135 astigmatism blur of ° direction △ h ₄

5 is

_{_{Ah 0 \ (cos (2t 0}} ) / r sin (2/0) / (Δ /.,

• (38)

Ah ₄₅ JI-sin (2i ₀ ) I r cos (2i ₀ ) / rj Δ ₄₅ no

Will be given by

The charged particle beam exposure apparatus to which the embodiment of the present invention is applied is the same as that shown in FIG. In the present embodiment, the correction sensitivity of astigmatism blur in each direction is obtained by the method described above, and the amount of change in astigmatism blur due to the space charge effect (positive focus) is determined by simulation. The current value of each coil may be changed by the value obtained by multiplying the amount of change in astigmatism blur by the correction sensitivity of astigmatism blur in each direction. Hereinafter, an example of the charged particle beam exposure method using the correction sensitivity for astigmatism blur determined as described above will be described. In this exposure method, the Coulomb effect is corrected for each subfield in consideration of the aperture ratio of the pattern for each subfield. That is, the focal position of the projection optical system is changed for each subfield so as to correct the Coulomb effect. At the same time, the amount of astigmatism that occurs due to the change in the deflection position is converted into a change in the focal position, and the resulting value is multiplied by the correction sensitivity for astigmatism blur determined by the method described above, and the resulting value is calculated as the astigmatism. The astigmatism associated with the deflection is also corrected by changing the current flowing through the 0 ° direction coil and the current flowing through the 45 ° direction coil of the astigmatism corrector. In this way, a good imaging pattern with small astigmatism can be obtained.

Claims

The scope of the claims

1. In a charged particle beam exposure apparatus having an astigmatism corrector, at least two different focal lines are formed by shifting a focal position by h and changing a current value or a voltage value of the astigmatism corrector. A current value or a voltage value of the astigmatism corrector, the shift amount Δh of the focal position, and a current value or a voltage value of the astigmatism corrector forming the two different sets of focal lines. A method for determining astigmatic sensitivity, wherein the astigmatic sensitivity of the astigmatism corrector (the astigmatic blur correction sensitivity or the astigmatic blur occurrence sensitivity) is obtained using the following formula.

2. The method for determining astigmatism according to claim 1, wherein the astigmatism corrector has at least two coil groups or electrode groups.

3. The method for determining astigmatism sensitivity according to claim 1, wherein, when the focal position is shifted by Δh, the focal position is shifted by △ h from the positive focal position with reference to the positive focal position.

4. The method for determining astigmatism according to claim 1, wherein the astigmatism is a correction sensitivity for astigmatism blur.

5. The method for determining astigmatism according to claim 1, wherein the astigmatism is an astigmatism blur occurrence sensitivity.

6. The method for determining astigmatism according to claim 4, wherein the astigmatism corrector is configured after shifting the focal position from the positive focal position by 正 h.

The current value of the two coil groups (0 ° direction coil and 45 ° direction coil) or the voltage value of the two electrode groups (0 ° direction electrode and 45 ° direction electrode) is varied, and the measurement pattern is changed. The two sets of current values or voltage values that minimize the blur in the 90 ° direction, 0 ° direction, 135 ° direction, and 45 ° direction as the reference are obtained, and these current values or voltage values are obtained. (S11, S21), (S12, S22), (S13, S23), (S1, S24) A method for determining astigmatism in a charged particle beam exposure apparatus, wherein the sensitivity for correcting astigmatism blur in at least one direction is determined by at least one of the following expressions.

(1) Sensitivity for correcting astigmatism blur when correcting 0-90 ° direction astigmatism blur using a 0 ° direction coil or electrode

511-512

2Δ / ι

521-522 ^

· '· (2)

2Ah,

(3) by 0 ° direction Koiru or electrodes, correction sensitivity 1 ³ astigmatism blur when correcting astigmatism blur of 45- 135 ° direction - ¹⁴ ... (3)

(4) Sensitivity of astigmatic blur correction when 45-135 ° astigmatic blur is corrected by a 45 ° coil or electrode

523-524

•(Four)

2Δ / ι

However, i of S i j (i = 1, 2, j = 1 to 4) is 0 for each. A directional coil or electrode (i2 1) indicates a 45 ° directional coil or electrode (i = 2), and j indicates the direction in which astigmatism blur is minimized (j = 1 is 90 ° direction). , = 2 is 0 ° direction, j = 3 is 135. direction, j = 4 is 45. direction).

7. The method for determining astigmatism according to claim 4, wherein the currents of two sets of coils (0 ° direction coil and 45 ° direction coil) constituting the astigmatic error compensator are set. Value or the voltage value of the two sets of electrodes (0 ° direction electrode and 45 ° direction electrode), respectively, to change the 90 ° direction with respect to the measurement pattern. Determine the two sets of current values or voltage values that minimize the blur in the 0 ° direction, the 135 ° direction, and the 45 ° direction, and determine whether these are arbitrary positions A and A in the optical axis direction. At the position B, which is △ h away from the optical axis direction,

Each combination of these current values (S1 1A S2 1A), (S1

2 AS 2 2 A) (S 13 A, S 23 A) (S 14 A, S ₂₄ A) _s (S

1 1 B, S 2 1 B), (S 1 2 B S 2 2 B), (S 13 B, S 23 B) (S

14B, S24B), the charged particle beam exposure apparatus characterized in that the correction sensitivity of at least one direction of astigmatism blur is determined by at least one of the following equations: Method for determining astigmatism sensitivity in

(1) Sensitivity of astigmatism blur correction when astigmatism blur in the 0-90 ° direction is corrected by a 0 ° direction coil or electrode

sn _B -si2 _B _sn _A -si2 _A )

, 2Ah 2Ah)

(2) Sensitivity for correcting astigmatism blur when correcting astigmatism blur in the 0 to 90 ° direction using a 45 ° direction coil or electrode

_/ S2L-S22 „S21.-S22.

(^ ^ ^, (6)

2ΔΛ 2Ah

(3) Sensitivity for correcting astigmatism blur when correcting astigmatism blur in the direction of 45-135 ° using a 0 ° direction coil or electrode

, S13. — S14 „S13. -S14,

-)… (F)

, 2Ah 2Ah

(4) Sensitivity of astigmatic blur correction when astigmatic blur in the direction of 45-135 ° is corrected with a 45 ° directional coil or electrode

523.ー 24. One S23 S24

■) .-. (8)

2Ah 2Ah

However, i of S ij A and S ij B (i 2 1,2, j 2 1 to 4) is 0 for each. Indicates the direction coil or electrode (i = 1), 45 ° direction coil or electrode (i = 2), and j is the direction in which astigmatism blur is minimized (j = l). Is 90. Direction, ( _] '= 2 indicates 0 ° direction, j = 3 indicates 135 ° direction, j = 4 indicates ⁴⁵⁰ direction).

8. The method for determining astigmatism according to claim 5, wherein the focus position is shifted from the positive focus by Ah, and then two sets of coils forming the astigmatism corrector ( The current value of the 0 ° directional coil and 45. directional coil) or the voltage value of two sets of electrodes (0. directional electrode and 45 ° directional electrode) are varied, and 90 ° based on the measurement pattern. direction, 0 ° direction, 1 3 5 ° directions, the 4 5 ⁰ the direction of the blur is minimum two pairs of current value or voltage value which it asked, each a combination of these current values or voltage values (S 1 1, S 21), (S 12, S 22), (S 13, S 23), (S 14, S 24), by at least one of the following equations: A method for determining astigmatism in a charged particle beam exposure apparatus, wherein the method determines the sensitivity of occurrence of astigmatism blur in at least one direction.

(1) Sensitivity of astigmatism blur that causes astigmatism blur in the 0-90 ° direction by a 0 ° direction coil or electrode-1AA (S23-S24)

{(Sll-SI 2) (S23-24)-(S13-S14) (S21-522)} ()

(2) Sensitivity of astigmatism blur that generates astigmatism blur in the 0 ° to 90 ° direction using a 45 ° direction coil or electrode -2 (S13- ^ 14)

{(511-S12) (523-24)-(513-S14XS21-S22)},) (3) Astigmatism that causes astigmatism blur in the 45 ° -135 ° direction by the 0 ° direction coil or electrode Occurrence sensitivity of aberration blur

{(SI1-S12) (S23-24)-(S13-S14) (S21-S22)} (4) 45 ° with a directional coil or electrode. 135 ° astigmatism Sensitivity of astigmatism blur causing blur

2 (511-512)

• (12)

{(511-512) (523-24,-(513-514) (S21 -522)}

9. The method for determining astigmatism sensitivity according to claim 5, wherein the two groups of coils (0 ° direction coil and 45 ° direction coil) constituting the astigmatic error compensator are provided. The current value or the voltage value of the two sets of electrodes (0 ° direction electrode and 45 ° direction electrode) is changed, and the 90 ° direction, 0 ° direction, 135 ° direction, 45 The two sets of current values or voltage values at which the blur in the 5 ° direction is minimized are determined, and these are determined as arbitrary positions A and A in the optical axis direction at a position B that is △ h away from the arbitrary optical axis direction in the optical axis direction. Done in

The combination of these current values is (S11A, S21A), (S12A, S22A) _S (S13A, S23A) ヽ (S14A , S 24 A) ヽ (S 11 B, S 21 B) ヽ (S 12 B, S 22 B) s (S 13 B, S 23 B), (S 14 B, S 24 B), the sensitivity of occurrence of astigmatism blur in at least one direction is determined by at least one of the following expressions. Decision method.

2Ah {(S23 _B -S24 _B )-(S23 _A -S24 _A )}…)

Δ

-2 h {(S13 _B -SU _B )-(S13 _A -SU _A )}

Δ,)

-2Ahj (S21 _B -S22 _B )-(S21 _A -S22 _A )}…)

Δ (4) Sensitivity of astigmatic blur that causes 45 ° to 135 ° astigmatic blur by 45 ° directional coil or electrode

2 h {(Sll _B -S12 _B )-(Sll _A -S12 _A )}

Δ

Here, i of SijA and SijB (i = 1, 2, j = 1 to 4) are 0 ° direction coil or electrode (i = 1), 45 ° direction coil or electrode (i

= 2) where j is the direction in which the astigmatism blur is minimized (j = l is the 90 ° direction, '= 2 is the 0. direction, j = 3 is the 135 ° direction, and j = 4 is the Four

5 ° direction).

A = [{(S11 _B -S12 _B )-(S11 _A -S12 _A )} {(S23 _B -S24 _B )-(S23 _A -S24 _A )} ~ {(S13 _B -S14 _B )-(S13 _A - S14 _a)} - is the value represented by _{_{{(S21 B -S22 B) {}} S2 \ a -S22 a)}}.

10. The method for determining astigmatism according to claim 5, wherein a focus position is shifted from a positive focus position by Δh, and then two coils constituting the astigmatism corrector are provided. The current value of the group (0 ° directional coil and 45 ° directional coil) or the voltage value of the two electrode groups (0 ° directional electrode and 45 ° directional electrode) (these shall be SI and S2), respectively. The current value of the two sets of coils or the voltage value of the two sets of electrodes, which minimize the blur in the two directions where the angles differ by 0, are determined, and a combination of these current values or voltage values is obtained. Are defined as (S 15, S 25) and (S 16, S 26), respectively, and in the SI—S 2 rectangular coordinate system, centered on (S 1, S 2.) 5, S25) and a circle passing through (S16, S26) are obtained, and this circle is defined as a circle representing the combination of the two sets of current values or voltage values forming the focal line. A charged particle beam exposure method for determining the sensitivity of occurrence of astigmatism blur in at least one direction based on a direction in which astigmatism blur is minimized at a predetermined point of the circle. A method for determining astigmatism in an apparatus. {(515 + 516) ± (525- S26) cot Θ}…? )

_S2 {(525 + 526) + (515-516) cot Θ}…)

^0-1 2

1 1. The method for determining astigmatism according to claim 5, wherein the astigmatism corrector is configured such that a focus position is shifted from a positive focus position by Δh, and Current value of coil group (0 ° direction coil and 45 ° direction coil) or voltage value of two sets of electrodes (0 ° direction electrode and 45 ° direction electrode) (S1 and S2 respectively) ), And the angle differs by Θ

The current value of the two sets of coils or the voltage value of the two sets of electrodes that minimizes the blur in the two directions is determined, and the combination of these current values or voltage values is determined as (S15, S 2 5), (S 16, S 26), and in the SI-S 2 rectangular coordinate system, centered on (31., 32.) shown below, (3 15, S 25), On a circle passing through (S16, S26), the two sets of current or voltage values that minimize astigmatism blur in the 90 ° direction and 135 ° direction with respect to the pattern reference direction are deviated. When (S 1 1 ', S 21) and (S 13 S 2 3') are combined, at least one of the following equations (1 9) to (2 2) A method for determining astigmatic sensitivity in a charged particle beam exposure apparatus, comprising determining sensitivity to occurrence of astigmatism blur in at least one direction.

_S1 ― {(515 + ± (525 -526) cot Θ}… "

M

_S2 _ {(525 + 526) + (515 -516) cot 6>}… "^

(1) Sensitivity of astigmatism blur which causes astigmatism blur in 0-90 ° direction by 0 ° direction coil or electrode

- (S13'-S1 ₀₎ ...

(rSll ^, -Sl ₀ ) (S23'-S2 ₀ )-(S13 ^, -Sl ₀ XS21 ^, -S2 ₀ )})

-(S21'-S2 ₀ )

_{{(S11'-S1 0) (} S23, -S2 0) - (S13, -S1 0) (S21, -S2 0)}

(4) Sensitivity of astigmatism blur that generates astigmatism blur in the direction of 45 ° -135 ° using a 45 ° direction coil or electrode ^ IV-S ^) ... ₍₂₂₎

_{{(511 '- Sl 0)} (523' - S 2 0) - (S 13 '- 51 0) (521' - 52 0)} 1 2. Determination of astigmatism sensitivity according to claim 5 After shifting the focus position from the positive focus position by Δh, the current values of the two coil groups (0 ° direction coil and 45. direction coil) constituting the astigmatism corrector are obtained. Alternatively, the voltage values of the two electrode groups ( ^0.0 ° direction electrode and 450 direction electrode) are varied, and the astigmatism blur in three or more directions at different angles is minimized. The current value of the coil group (0 ° direction coil and 45 ° direction coil) or the voltage value of two sets of electrodes (0 ° direction electrode and 45 ° direction electrode) (S1 and S2, respectively) (S ll, S 21), (S 12, S 22), ..., (S ln, S 2 n) (Η is an integer of 3 or more), S 1 — S 2 In a co-ordinated coordinate system, a circle passing through these points is determined by solving an equation or by a statistical fitting method, and based on the direction at which the astigmatism blur at a given point on this circle is minimized. A method for determining astigmatism in a charged particle beam exposure apparatus, comprising determining a sensitivity of occurrence of astigmatism blur in at least one direction.

1 3. The method for determining astigmatism according to claim 5, wherein the focus position is shifted from the positive focus position by Ah, and then the astigmatism corrector is configured. The current value of the coil group (0. directional coil and 45 ° directional coil) or the voltage value of two sets of electrode groups (0 ° directional electrode and 45 ° directional electrode) are changed, and three angles are different. The current values of the two sets of coils (0. direction coil and 45 ° direction coil) or the two sets of electrode groups (0 ° direction electrode and 45 ° direction) that minimize astigmatism blur in the above directions The voltage value of the electrode is determined as SI, S2, and the combination of these current values or voltage values is determined as (S11, S21), (S12, S12). 2 2),..., (S ln, S 2 n) (n is an integer of 3 or more), the circle passing through these points in the S 1—S 2 orthogonal coordinate system is Solve the equations or find them by statistical fitting, center them at (S 1, S 2), and on the circle, 90 ° and 135 ° directions with respect to the pattern reference direction The two sets of current values or voltage values that minimize the astigmatism blur of each of them are determined, and the combinations thereof are defined as (Sll ,, S21,), (S13, S23 '). ), The charged particle beam exposure characterized in that the sensitivity of occurrence of astigmatism blur in at least one direction is determined by at least one of the following equations (19) to (22). A method for determining astigmatism in an apparatus.

h (S23'-S2 ₀ )

_{{(Sir-S1 0) (} S23'-S2 0) - (S13, -S1 0) (S21, -S2 0)} ^ '

-(513'-S1 ₀ )…

{(Sir-Sl ₀ ) (S23 ^, -S2 ₀ )-(S13 ^, -51 ₀ ) (S2r-S2 ₀ )},)

(3) 45 ° -135 ° astigmatism blur due to 0 ° coil or electrode Sensitivity of Astigmatism Blurring that Generates

-Ah (S2V-S2 ₀ )…

{(S11 '-S1.) (S23'-S2.)-(S13 '-S1 ₀ ) (S21, -S2 ₀ )}

(4) Sensitivity of astigmatism blur which causes astigmatism blur in the direction of 45 ° -135 ° by 45 ° direction coil or electrode

, A ^ Sll'-Slo)

{(S11'-S1 ₀ ) (S23'-S2 ₀ )-(513'_S1 ₀ ) (S21 ^, -S2 ₀ )}

1 4. The method for determining astigmatism according to claim 5, wherein a plurality of focal positions h are changed (each optical axis direction position is hi (i = l ~! 1)). In addition, the current values of two sets of coils (0 ° direction coil and 45 ° direction coil) constituting the astigmatism corrector or two sets of electrode groups (0 ° direction electrode and 45. 0 direction electrode) ), Which are assumed to be SI and S 2, respectively, and the angle of the astigmatism-blur evaluation pattern at that time is assumed to be ti. When (h-h.) Changes by a unit amount (h is the focus position where a positive focus is formed), the set of points (S1, S2) forming the focal line is the S1-S2 rectangular coordinates. The proportional constant r indicating the amount of change in the radius of the circle formed by the plane, and the angle 2t between the S1 axis and the direction in which only the 0 ° direction blur changes. The charged particle beam is characterized by determining the sensitivity of occurrence of astigmatism blur in at least one direction by the following equations (23) to (26). A method for determining astigmatic sensitivity in an exposure apparatus.

(1) Sensitivity of astigmatism blur that causes astigmatism blur in the direction of 0 to 90 ° by a 0 ° direction coil or electrode

cos (2t ₀ ) / r — (23)

sin (2t ₀ ) / r-(24) (3) Sensitivity of astigmatism blur that causes astigmatism blur in 45 ° -135 ° direction by 0 ° direction coil or electrode

-sin (2t ₀ ) / r 〜 (25)

(4) 4 5. Sensitivity of astigmatism blur which causes astigmatism blur in 45 ° -135 ° direction by directional coil or electrode

cos (2t ₀ ) / r-"(26)

15 5. The statistical method calculates the center point (S 1, S 2) of the circle formed by the point serving as the focal line, the positive focus position h ₀ , the proportionality constant r, and the 0 ° direction axis with respect to the S 1 axis. The angle 2t between the directions in which only ケ changes. The variables r and t are determined by determining these variables so that the following evaluation function P is minimized. 15. The method for determining astigmatism according to claim 14, wherein the method is a method for determining the astigmatism.

16. A method for exposing and transferring an image of a reticle onto a wafer in a charged particle beam exposure apparatus, wherein the astigmatism correction of the astigmatism corrector in the charged particle beam exposure apparatus according to claim 1 is performed. Using the astigmatism blur correction sensitivity or astigmatism blur generation sensitivity determined by the determination method, the exposure is adjusted while adjusting the astigmatism corrector to correct the astigmatism blur for each subfield. An exposure method in a charged particle beam exposure apparatus, wherein transfer is performed.

17. The astigmatism corrector has two sets of coils (0 ° direction coil and 45 ° direction coil) or two sets of electrodes (0. direction electrode and 45 ° direction electrode), astigmatism blur delta 1Iota to be corrected ₀ for a h _{4 5,} the two pairs of voltage values ΔΙ the current value or the two sets of electrode groups of the coil group. The exposure method in luggage鼋粒Ko beam exposure apparatus according to the first item 6 claims, characterized in that determined by the following equation ΔΙ _{4 5.}

Where E, F, G and H are

G is the sensitivity of astigmatism blur correction when astigmatism blur in the direction of 4 5-135 ° is corrected by a 0 ° direction coil.

H is the sensitivity of astigmatism blur correction when correcting astigmatism blur in the direction of 45-135 ° using a 45 ° direction coil.

It is.