JP2000067792A - Charged particle beam exposing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enlarge a current amount of a charged particle beam so as to enhance a throughput by reducing blur and distortion caused by coulomb effect. SOLUTION: A shaping aperture 4 is irradiated with an emitted electron beam 2 from an electron source 1 by operation of a first irradiation lens 31. The passed electron beam 2 through the shaping aperture 4 forms an image of the shaping aperture 4 on a reticle 5 by operation of a second irradiation lens 32 and a third irradiation lens 33. The passed electron beam 2 through the reticle 5 passes through a first projection lens 61, is bent in its trajectory by astigmatism correctors 91, 92, 93, 94, and finally, forms an image of the reticle 5 on a wafer 7 by operation of a second projection lens 62. The astigmatism correctors 91, 92, 93, 94 generate astigmatism near a crossover point so as to prevent reduction of an area of the electron beam 2. Thereby, the coulomb effect is reduced, and the current amount can be increased so that the throughput is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charged particle exposure apparatus for irradiating a pattern formed on an object to be transferred with a charged particle beam and exposing and transferring an image of the pattern onto the object to be transferred.

[0002]

2. Description of the Related Art In recent years, fine processing techniques for semiconductors have been progressing year by year. Current exposure apparatuses mainly use light, but in order to carry out further fine processing, a shorter wavelength of light is required. However, there is a limit to shortening the wavelength, and although an exposure apparatus using X-rays has been considered, it has not been put to practical use at the present time because it is not easy to manufacture a reticle. From such a background, attention has been paid to transfer and exposure using a charged particle beam such as an electron beam.

As a conventional example of such a charged particle beam exposure apparatus, an outline of an electron beam exposure apparatus for manufacturing a semiconductor device is shown in FIG.
Shown in In FIG. 3, 1 is an electron source, 2 is an electron beam, 31
33 is an irradiation lens, 4 is a molding aperture, 5 is a reticle, 6
Reference numerals 1 and 62 denote projection lenses, 7 denotes a scattered electron absorption aperture, and 8 denotes a wafer.

[0004] The electron beam 2 emitted from the electron source 1 illuminates the shaped aperture 4 by the first irradiation lens 31. The electron beam 2 that has exited the forming aperture 4 is supplied to the second irradiation lens 32 and the third irradiation lens 33.
Forms a shaped aperture image on the reticle 5. The electron beam exiting the reticle 5 forms an image of the pattern on the reticle 5 on the wafer 8 by the first projection lens 61 and the second projection lens 62. The scattered electron absorbing aperture 7 is
It absorbs the wide-angle electrons scattered by the electron beam and limits the aperture angle of the electron beam.

In a charged particle optical system typified by such an electron beam exposure apparatus, the range in which the curvature of field and astigmatism caused by a lens can be corrected is limited, and therefore, as in a semiconductor exposure apparatus using an optical system, When a pattern of several tens of mm is transferred collectively, the blur becomes very large. For this reason, a method is employed in which a pattern to be transferred is divided and transferred, and the respective patterns are joined on a wafer to form an exposure pattern for manufacturing the entire semiconductor device. The divided pattern is called a subfield and is usually 1 mm on the reticle 5.
Approximately 0.25 mm square on a wafer.

The molding opening 4 is usually a high-melting metal having a square opening formed therein. The dimensions of the opening are when the image is formed on the reticle 5 by the second and third irradiation lenses 32 and 33.
The image is made to match the size of the subfield on the reticle 5. However, the reticle 5 may be formed such that a region where no pattern exists exists between the subfields above the reticle 5, and in this case, the reticle 5 is set to be slightly larger than the size of the subfield. ing.

The reticle 5 has an exposure pattern to be transferred. As the reticle 5, two types are mainly used. First, an exposure pattern is formed as an opening in a silicon thin film of several μm, and an electron beam that passes through the opening forms an image on the wafer 8.
Those not passing through the opening are absorbed by the reticle or scattered even after passing through the reticle, are absorbed by the scattered electron absorption opening 7 on the way, and do not reach the wafer 8. Such a reticle is called a stencil type. Second, a heavy metal pattern is formed at a place other than the exposure pattern on a very thin silicon thin film of 1 μm or less. Electrons hitting the very thin thin film are hardly scattered and form an image on the wafer 8. The electrons hitting the heavy metal pattern are absorbed or scattered, and the scattered electrons are absorbed by the scattered electron absorption aperture 7 so as not to reach the wafer 8. Such a reticle is called a membrane type.

[0008]

In an exposure transfer apparatus, it is required to increase the number of processed wafers or the like per unit time (throughput). In the charged particle exposure apparatus as described above, the most common method of increasing the throughput is to increase the amount of current of the charged particle beam.

However, a charged particle beam has a phenomenon called Coulomb effect, which causes blurring and distortion of an image. The Coulomb effect is a phenomenon in which the trajectory of charged particles is bent by the effect of repulsive force due to charges between charged particles.
When the current is large, the accelerating voltage is low, the lens barrel length is long, and the beam diameter is small, it becomes large. The present invention considers the Coulomb effect due to the small beam diameter, and assumes that other factors are constant.

FIG. 4 shows an electronic track in a conventional transfer optical system.
It is a figure showing an example of a road. Deflector for easy explanation
Is not considered. Figure 4
And z _oIs the object surface (eg, reticle surface), z_iIs the image plane (for example
100 is a crossover point. Electron beam
Of the image point z_iCrossover
Point 100 is also narrowed down. The crossover point is
Electrons emitted from the electron beam source have a narrowed beam diameter
At this point, some appear in the optical path by the electron optics.

In a scanning electron microscope or an exposure apparatus using a spot beam, a small image is required, so that this crossover point is made to coincide with a target imaging plane. However, in an electron beam apparatus such as a transfer type electron beam exposure apparatus, a uniform current density is required in a wide area, so that the crossover point is not located on the wafer but the other current densities are uniform. The distribution area is located on the wafer, so-called Koehler illumination.
In some cases, an electron beam source having a wide electron emission surface and a uniform emission current density is used, and critical Koehler illumination for forming an image of the electron emission surface on a wafer surface is employed.

As can be seen from FIG. 4, the size of the crossover point 100 corresponds to the angular distribution of the reticle image on the wafer. That is, as the size of the crossover point increases, the opening angle of the reticle image on the wafer increases. Thus, at the crossover point 100,
Originally the spread of the electron beam is small. Further, for the purpose of suppressing aberration, the smaller the opening angle of the reticle image on the wafer, the smaller the size of the crossover point. However, as the size of the crossover point becomes smaller, the Coulomb effect becomes larger due to the concentration of current, which causes a problem that image blur and distortion become larger. Therefore, in order to keep the aberration, blur, and distortion within a predetermined range, the current amount of the electron beam cannot be increased unnecessarily, and the throughput cannot be increased. Such a situation is the same in an exposure transfer apparatus using a charged particle beam other than the electron beam.

The present invention has been made in view of such circumstances, and a charged particle beam exposure apparatus capable of increasing the amount of current of a charged particle beam and increasing the throughput by reducing blur and distortion due to the Coulomb effect. The task is to provide

[0014]

The gist of the present invention is to use an astigmatism corrector and to change the performance (aberration, blur, distortion, deflection position, etc.) on the image plane near the crossover point without changing the performance. By generating astigmatism, the spread of the charged particle beam in a portion where the charged particle beam becomes narrow between reticle wafers is increased, and the Coulomb effect is reduced.

[0015] That is, the first to solve the above-mentioned problem.
The means is a charged particle exposure apparatus that irradiates a pattern formed on an object to be transferred with a charged particle beam, and exposes and transfers an image of the pattern onto a transfer object, astigmatism blur on an image plane, A charging device having an astigmatism corrector that generates astigmatism near a crossover point of a charged particle beam without deteriorating at least one of distortion, change in incident angle, deflection position, and change in deflection incident angle. This is a particle beam exposure apparatus (Claim 1).

In this means, astigmatism is generated near the crossover point using an astigmatism corrector.
As a result, the charged particle beam spreads in the y-axis direction where it converges in the x-axis direction, and spreads in the x-axis direction where it converges in the y-axis direction. Therefore, the point where the trajectory of the charged particle beam becomes extremely thin is eliminated, and the average distance between the charged particles is widened, and blur and distortion due to the Coulomb effect can be reduced. In generating such astigmatism, an astigmatism corrector is used so as not to deteriorate at least one of astigmatism blur, distortion, incident angle change, deflection position shift, and deflection incident angle change on the image plane. , The transfer performance is not deteriorated.

A second means for solving the above-mentioned problems is as follows:
The first means, wherein the optical axis of the charged particle beam exposure apparatus is a z-axis, and coordinates on an xy plane in an orthogonal coordinate system having the z-axis as one axis are represented by complex coordinates where w = x + iy, Z
_o , the image plane z _i , w _a [z], w _a [z _o ] = 0, w _a '[z _o ] =
1. The trajectory of the charged particle represented by complex coordinates, where w _a [z _i ] = 0, _expressed by the lens, w _b [z], and the charged particle represented by complex coordinates, where w _b [z _o ] = 1 Orbit by the lens of
_Let these complex conjugate orbits be w _ac [z] and w _bc [z], and the electromagnetic astigmatism field on the axis in the case of the electromagnetic astigmatism corrector and the static electromagnetic field on the axis in the case of the electrostatic astigmatism corrector. When f [z] is obtained by dividing the electric non-point field by the square root of the on-axis potential,

[0018]

[Equation 14]

[0019]

(Equation 15) (Claim 2). Here, 'indicates a differential value by z, and the same applies to the following description.

[0020] The reticle as the optical axis of the z-axis and the object surface z _o to the wafer and the image plane z _i. Then, the charged particle beam trajectory is represented by w
= X + iy (x = x [z], y = y [z])
Indicated by Orbit shift dw caused by astigmatism corrector
[z] is the axis of the astigmatism on the axis (per unit voltage) for the electromagnetic astigmatism corrector (per unit current) in the case of the electromagnetic astigmatism corrector. The value divided by the square root of the upper potential (in proportion to r ² · cos 2θ in cylindrical coordinates) is f [z]
Then

[0021]

(Equation 16) Is represented by Here w _a [z] _{is, w a [z o] =} 0, w a '
[z _o ] = 1, w _a [z _i ] = 0, the trajectory of the charged particle represented by complex coordinates by the lens, and w _b [z] is w
_b is the trajectory of the charged particle represented by complex coordinates, represented by complex coordinates, where [z _o ] = 1. W _c [z], w _ac [z],
w _bc [z] is w [z], respectively, w _a [z], it denotes the complex conjugate orbit w _b [z].

[0022] w [z] is when any of the orbit of the opening angle of the trajectory of the on the reticle α in _o, a position leaving the object plane and _{w bo, w [z] =} α o · w a [z] + w _bo · w _b [z] (17) Equation (6) above is

[0023]

[Equation 17]

[0024]

(Equation 18) And these derivatives are

[0025]

[Equation 19]

[0026]

(Equation 20) Becomes

The values at these image points are:

[0028]

(Equation 21)

[0029]

(Equation 22)

[0030]

(Equation 23)

[0031]

(Equation 24) Becomes Equation (12) is the astigmatism blur on the image plane, Equation (13) is the astigmatism distortion on the image plane, and Equations (14) and (15) are the changes in the incident angle on the image plane in each case. Is represented. (12) ~
Equation (15) is all 0, that is,

[0032]

(Equation 25)

[0033]

(Equation 26)

[0034]

[Equation 27] Then, the trajectory on the image plane by the astigmatism corrector does not change.

However, depending on the conditions of the charged particle exposure apparatus, the change in the incident angle may not be a problem. In this case, the expression (3) can be ignored, and if the astigmatism corrector is controlled so that the expressions (1) and (2) are satisfied, the charged particle beam is controlled by the astigmatism corrector. Even if astigmatism is generated in the vicinity of the crossover point, the astigmatism blur on the image plane and the astigmatism distortion on the image plane can be reduced to zero. In this means, the astigmatism corrector is controlled so that such a condition is satisfied.

A third means for solving the above-mentioned problem is:
The first means or the second means, comprising a one-stage astigmatism corrector having performance equivalent to that of two or more astigmatism correctors (Claim 3) It is.

In order to reduce astigmatism blur on the image plane and astigmatism distortion on the image plane to zero while generating astigmatism near the crossover point, usually, an astigmatism corrector having two or more stages is used. is necessary. However, by devising the shape of the astigmatism corrector and the winding method of the coil, the function of the astigmatism corrector having two or more stages can be provided to one astigmatism corrector. This means has such a feature, and has the feature that only one astigmatism corrector is required.

A fourth means for solving the above problem is as follows.
The first means, wherein the optical axis of the charged particle beam exposure apparatus is a z-axis, and coordinates on an xy plane in an orthogonal coordinate system having the z-axis as one axis are represented by complex coordinates where w = x + iy, Z
_o , the image plane z _i , w _a [z], w _a [z _o ] = 0, w _a '[z _o ] =
1. The trajectory of the charged particle represented by complex coordinates, where w _a [z _i ] = 0, _expressed by the lens, w _b [z], and the charged particle represented by complex coordinates, where w _b [z _o ] = 1 Orbit by the lens of
_Let these complex conjugate orbits be w _ac [z] and w _bc [z], and the electromagnetic astigmatism field on the axis in the case of the electromagnetic astigmatism corrector and the static electromagnetic field on the axis in the case of the electrostatic astigmatism corrector. When f [z] is obtained by dividing the electric non-point field by the square root of the on-axis potential,

[0039]

[Equation 28]

[0040]

(Equation 29)

[0041]

[Equation 30] (Claim 4).

As described in the description of the second means, astigmatism is generated near the crossover point of the charged particle beam by the astigmatism corrector, and the astigmatism blur on the image plane is reduced.
In order to make the astigmatism distortion on the image plane and the change in the incident angle on the image plane zero, the astigmatism corrector is controlled so as to satisfy the expressions (1), (2) and (3). It is necessary. This means has such an effect, and has a feature that, in addition to the second means, the change in the incident angle on the image plane becomes zero.

A fifth means for solving the above problem is as follows.
The first means, wherein the optical axis of the charged particle beam exposure apparatus is a z-axis, and coordinates on an xy plane in an orthogonal coordinate system having the z-axis as one axis are represented by complex coordinates where w = x + iy, Z
_o , the image plane z _i , w _a [z], w _a [z _o ] = 0, w _a '[z _o ] =
1. The trajectory of the charged particle represented by complex coordinates, where w _a [z _i ] = 0, _expressed by the lens, w _b [z], and the charged particle represented by complex coordinates, where w _b [z _o ] = 1 Orbit by the lens of
Let w _m [z] be the trajectory of the deflector expressed in complex coordinates,
These complex conjugate orbitals are _expressed as w _ac [z], w _bc [z], w
_mc [z], the electromagnetic astigmatism on the axis for the electromagnetic astigmatism corrector and the electrostatic astigmatism on the axis for the electrostatic astigmatism corrector were divided by the square root of the on-axis potential When the thing is f [z]

[0044]

(Equation 31)

[0045]

(Equation 32)

[0046]

[Equation 33] (Claim 5).

In the description so far, the orbit of the charged particle beam is considered only by w _a [z] and w _b [z] determined by the lens.
The present means is extended to include a deflector. That is, instead of the equation _{(7), w [z] = α o} · w a [z] + w bo · w b [z] + d · w m [z] ... Change (16) (6) What is necessary is just to substitute in an expression. Where w
_m [z] is the deflection trajectory per unit current or voltage, and d is the current or voltage applied to the deflector. Performing the same calculation as above and corresponding to equations (12) to (15)

[0048]

(Equation 34)

[0049]

(Equation 35) And the condition that these become 0 is

[0050]

[Equation 36]

[0051]

(37) It is. Of these, equation (4) corresponds to blur and distortion on the image plane, and equation (5) corresponds to a change in the incident angle on the image plane.

This means is employed when the incident angle can be changed, and is the same as the second means. Therefore, a combination of the expressions (1), (2) and (4) in the second means is a control condition in which the astigmatism corrector and the deflector in the present means are combined. Thus, even when a deflector is used, even when astigmatism is generated near the crossover point of the charged particle beam by the astigmatism corrector, astigmatism blur on the image plane and Astigmatism distortion can be reduced to zero.

A sixth means for solving the above-mentioned problem is:
The fourth means or the fifth means, comprising a one-stage or two-stage astigmatism corrector having a performance equivalent to that of three or more stages of astigmatism corrector (claim) Item 6).

In the fourth means or the fifth means, since there are three equations, usually three or more stages of astigmatism correctors are required. By devising one method, the function of two or more astigmatism correctors can be provided to one astigmatism corrector. This means has such a feature, and has an advantage that the number of astigmatism correctors is small.

A seventh means for solving the above problem is as follows.
The first means, wherein the optical axis of the charged particle beam exposure apparatus is a z-axis, and coordinates on an xy plane in an orthogonal coordinate system having the z-axis as one axis are represented by complex coordinates where w = x + iy, Z
_o , the image plane z _i , w _a [z], w _a [z _o ] = 0, w _a '[z _o ] =
1. The trajectory of the charged particle represented by complex coordinates, where w _a [z _i ] = 0, _expressed by the lens, w _b [z], and the charged particle represented by complex coordinates, where w _b [z _o ] = 1 Orbit by the lens of
Let w _m [z] be the trajectory of the deflector expressed in complex coordinates,
These complex conjugate orbitals are _expressed as w _ac [z], w _bc [z], w
_mc [z], the electromagnetic astigmatism on the axis for the electromagnetic astigmatism corrector and the electrostatic astigmatism on the axis for the electrostatic astigmatism corrector were divided by the square root of the on-axis potential When the thing is f [z]

[0056]

(38)

[0057]

[Equation 39]

[0058]

(Equation 40)

[0059]

[Equation 41]

[0060]

(Equation 42) (Claim 7).

As described in the description of the fifth means, when the deflector is used, blurring, distortion,
In order to reduce the change in the incident angle to 0, a new equation (4) is used.
It is necessary to satisfy the relationship of equation (5). In this means, in the formulas (1) to (3) of the third means,
Equations (4) and (5) are added. By satisfying these relations, in this means, even when a deflector is used, the crossover point of the charged particle beam can be controlled by the astigmatism corrector. Even if astigmatism is generated in the vicinity, astigmatism blur on the image plane, astigmatism distortion on the image plane, and change in the incident angle on the image plane can be reduced to zero.

Eighth means for solving the above-mentioned problem is:
The seventh means, further comprising a one-stage to four-stage astigmatism corrector having a performance equivalent to that of five or more stages of astigmatism corrector (Claim 8). is there.

In the seventh means, since there are five equations, five or more stages of astigmatism correctors are required.
By devising the shape of the astigmatism corrector and the winding method of the coil, the function of two or more astigmatism correctors can be substituted by one astigmatism corrector. This means has such a feature, and has an advantage that the number of astigmatism correctors is small.

A ninth means for solving the above-mentioned problem is:
In any one of the first to eighth means, the astigmatism corrector changes the intensity according to the amount of current of the charged particle beam (Claim 9). ).

The Coulomb effect increases as the amount of current of the charged particle beam increases. On the other hand, when the intensity (current, voltage) of the astigmatism corrector is increased, aberration occurs due to this. Therefore, the optimal intensity of the astigmatism corrector is determined according to the current amount of the charged particle beam in consideration of these factors. In this means, blur, distortion, and aberration of the entire image can be minimized by keeping the intensity of the astigmatism corrector at an optimum value corresponding to the current of the charged particle beam.

A tenth means for solving the above-mentioned problem is any one of the first to eighth means, wherein the astigmatism corrector comprises: a current amount of a charged particle beam; Wherein the intensity is changed in accordance with the current or voltage of the power supply (claim 10).

Since the aberration of the image also changes depending on the amount of deflection, in order to minimize the blur, distortion, and aberration of the entire image, the intensity of the astigmatism corrector is determined together with the amount of current of the charged particle beam. , It is necessary to consider the current or voltage of the deflector. In this means, the intensity of the astigmatism corrector is determined according to both of these values, so that blur, distortion, and aberration of the entire image can be minimized.

[0068]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view showing a transfer type electron beam exposure apparatus which is an example of an embodiment of the present invention. In FIG. 1, 1 is an electron source, 2 is an electron beam, 31 is a first irradiation lens, 32 is a second irradiation lens, 33 is a third irradiation lens,
Is a molding aperture, 5 is a reticle, 61 is a first projection lens, 6
2 is a second projection lens, 7 is a scattered electron absorption aperture, 8 is a wafer, 91 is a first astigmatism corrector, 92 is a second astigmatism corrector, 93 is a third astigmatism corrector, 94 is 4 shows a fourth astigmatism corrector.

The electron beam 2 emitted from the electron source 1 illuminates the shaping aperture 4 by the first irradiation lens 31. The electron beam 2 that has exited the forming aperture 4 is supplied to the second irradiation lens 32 and the third irradiation lens 33.
Forms a shaped aperture image on the reticle 5. After passing through the first projection lens 61, the trajectory of the electron beam 2 exiting the reticle 5 is bent by the astigmatism correctors 61, 62, 63, 64, and the reticle image is formed on the wafer 7 by the second projection lens 62. Form an image. The scattered electron absorption aperture 7 limits the aperture angle of the electron beam.

The astigmatism corrector is usually composed of two sets of four electrodes or coils.
Each set has the same electric potential on the opposite side to the optical axis or the same magnetic field direction with respect to the optical axis, and the orthogonal direction has the opposite electric potential or the direction of the opposite magnetic field with respect to the optical axis. They are installed rotated 45 degrees from each other with respect to the optical axis.

The astigmatism corrector is usually for correcting astigmatism. Astigmatism is an aberration in which the focal point of a charged particle beam changes depending on the direction. The astigmatism is caused by mechanical tolerance, electrical precision, charging, and the like of components of the charged particle optical system. The astigmatism corrector changes the trajectory of the charged particle beam depending on the direction, and can give directionality to the focal position. This action corrects the astigmatism of the device.

In the present invention, the astigmatism corrector is used to positively generate astigmatism, thereby reducing the Coulomb effect. That is, when the current of the electron beam transmitted through the reticle 5 is large, a current is supplied to the astigmatism corrector or a voltage is applied to generate astigmatism so that astigmatism occurs near the crossover point. .

FIG. 2 shows an example of a trajectory in the electron beam optical system having the astigmatism corrector set as described above.
In (X), the dashed line indicates the state where no current or voltage is applied to the astigmatism corrector, and the solid line indicates the state where the current or voltage is applied to the astigmatism corrector from the x-axis of the object plane. The orbit excluding the rotation of the electron beam is shown. Further, in (Y), the broken line indicates the state where no current or voltage is applied to the astigmatism corrector, and the solid line indicates the state when the current or voltage is applied to the astigmatism corrector from the y-axis of the object plane. The orbit excluding the rotation of the electron beam is shown.

The trajectory on which the astigmatism corrector is operated is the object surface,
Both trajectories near the image plane have the same trajectory in which the astigmatism corrector is not operated, but are different trajectories in the middle. A point 100 surrounded by a broken-line circle represents a crossover point, and points 101 and 102 surrounded by a solid-line circle represent points where the beam diameter becomes minimum in each direction.
Point 101 is closer to the image point z _i than the crossover point 100, and point 102 is the object point z _o compared to the crossover point 100.
It is shifted toward.

The beam diameter in each direction at the crossover point is larger than the crossover image, and is substantially circular. Therefore, the influence of the Coulomb effect at this point is smaller than when the astigmatism corrector is not operated. Further, at the point 101, the beam diameter in the x direction is small but the beam diameter in the y direction is large, and the beam has an elliptical beam shape. Also in this case, the distance between the electrons is larger than when the astigmatism corrector is not operated, and the influence of the Coulomb effect is smaller. The same can be said for point 102.

As described above, by intentionally producing astigmatism near the crossover point by operating the astigmatism corrector, the minimum area of the charged particle beam can be reduced as compared with the case where the astigmatism corrector is not operated. Can be increased,
Coulomb effect can be reduced.

However, by operating the astigmatism corrector, if the blur, distortion, and change in the incident angle on the image plane increase, another problem arises that the transfer accuracy deteriorates. In the present invention, such a problem does not occur because astigmatism is created near the crossover point without changing the performance on these image planes.
Specifically, claim 2, claim 4, claim 5, and claim 7
The astigmatism corrector is operated under conditions such that the equation shown in (1) is satisfied, and astigmatism is generated near the crossover point.

Hereinafter, an example of a specific control method of the astigmatism corrector, that is, a method of determining a current or a voltage applied thereto will be described. First, an example of an embodiment corresponding to claim 4 will be described. In this case, a satisfactory equation is (1),
Since there are three (2) and (3), three astigmatism correctors are used.

Since there are three conditional expressions, three astigmatism correctors are provided, and the astigmatism field due to the unit current or voltage in each of them is represented by f ₁ [z], f ₂ [z], f ₃ [z], respectively. a current or voltage applied to the _{w 1, w 2, w 3} ,

[0080]

[Equation 43]

[0081]

[Equation 44]

[0082]

[Equation 45] If (i = 1 to 3), the expressions (1), (2) and (3) are determinants, and

[0083]

[Equation 46] It is represented as W ₁ ,
If w ₂ and w ₃ are controlled, the electron beam trajectory is deformed without astigmatism blur, distortion, and change in the incident angle on the image plane, and no crossover is formed. Blur and distortion can be reduced.

(22) is that the determinant of the matrix on the left side is 0
Only when, w ₁ , w ₂ , and w ₃ have nonzero solutions. In order to satisfy this condition with three stages of the astigmatism corrector, the position and shape of the astigmatism corrector must be strictly set. In order to avoid such a situation, usually, a four-stage astigmatism corrector is used. Then the equation to be satisfied is

[0085]

[Equation 47] And rewriting this gives

[0086]

[Equation 48] When the determinant on the left side is not 0, w ₁ , w ₂ , and w ₃ have a solution with w ₄ as a parameter, and when the determinant is 0, w ₄
If = 0, it becomes the same as the case of three stages. If w ₁ , w ₂ , w ₃ , and w ₄ are controlled so as to satisfy this condition, the electron beam trajectory is deformed on the image plane without astigmatism blur, distortion, and change in the incident angle, and the crossover is imaged. In addition, since it does not become a minute spot, blur and distortion due to the Coulomb effect can be reduced.

Further, an arbitrary two-stage astigmatism corrector is provided by (2
It is also possible to combine them so as to satisfy the condition of the expression 4) and operate as a three-stage astigmatism corrector due to the configuration. Furthermore, it is also possible to perform further coupling to form two stages and one stage in configuration. Conversely, by dividing an arbitrary astigmatism corrector into two or more stages so as to satisfy the condition of Expression (24), the astigmatism corrector having five or more stages may be configured.

As described above, the invention according to claim 4 satisfies the condition that the change of the incident angle on the image plane is 0. Can eliminate the expression (3),
And the number of astigmatism correctors can be reduced by reducing the number of equations.

Next, an example of an embodiment corresponding to claim 7 will be described. In this case, since the equations become five of equations (1) to (5), five astigmatism correctors are used, and the astigmatism field due to the unit current or voltage is f ₁ [z _{], f 2 [z],} f 3 [z], f 4 [z], f 5 [z],
The current or voltage to be given to each of them is represented by w ₁ , w ₂ , w ₃ ,
Let w ₄ and w ₅ be the same as in equations (19), (20) and (21),

[0090]

[Equation 49]

[0091]

[Equation 50]

Then, corresponding to the equations (1) to (5),
The condition of the astigmatism corrector when including the deflector is:

[0093]

(Equation 51) Becomes Do it by controlling the w ₅ from w ₁ so as to satisfy this condition, astigmatism blur on the image plane distortion, to deform the electron beam trajectories in the angle of incidence without changing, without imaging the crossover,
Since it does not become a minute spot, blur and distortion due to the Coulomb effect can be reduced. In the equation (27), only when the determinant of the matrix on the left is 0, with a solution from w ₁ w ₅ is not zero. In order to satisfy this condition with five stages of the astigmatism corrector, the position and shape of the astigmatism corrector must be strictly set. In order to avoid such a situation, usually, a four-stage astigmatism corrector is used. Then the equation to be satisfied is

[0094]

(Equation 52) And rewriting this gives

[0095]

(Equation 53) When the determinant on the left side is not 0, w ₁ to w ₅ have a solution using w ₆ as a parameter, and when the determinant is 0, w ₆
If = 0, it becomes the same as the case of five stages. Astigmatism blur on the image plane by controlling the w ₆ from w ₁ so as to satisfy this condition, distortion, to deform the electron beam trajectories in the angle of incidence without changing, without imaging the crossover, the minute spot Since it is not, blur and distortion due to the Coulomb effect can be reduced.

Further, an arbitrary two-stage astigmatism corrector is provided by (2
It is also possible to combine them so as to satisfy the condition of the expression 9) and operate as a five-stage astigmatism corrector due to the configuration. Further, it is possible to perform further coupling to reduce the number of stages to four or less. Conversely, by dividing an arbitrary astigmatism corrector into two or more stages so as to satisfy the condition of Expression (29), the astigmatism corrector having seven or more stages may be operated.

As described above, the invention according to claim 7 satisfies the condition that the change of the incident angle on the image plane is 0. Can eliminate equations (3) and (5),
According to the fifth aspect of the present invention, the number of astigmatism correctors can be reduced by reducing the number of equations.

The Coulomb effect increases as the amount of current of the charged particle beam increases. On the other hand, when the intensity (current, voltage) of the astigmatism corrector is increased, aberration occurs due to this. Therefore, the optimal intensity of the astigmatism corrector is determined according to the current amount of the charged particle beam in consideration of these factors. In this means, blur, distortion, and aberration of the entire image can be minimized by keeping the intensity of the astigmatism corrector at an optimum value corresponding to the current of the charged particle beam.

Since the aberration of the image also changes depending on the amount of deflection, in order to minimize blur, distortion and aberration of the entire image, the intensity of the astigmatism corrector must be determined by determining the current of the charged particle beam. Along with the quantity, the current or voltage of the deflector must be considered. In this means, the intensity of the astigmatism corrector is determined according to both of these values, so that blur, distortion, and aberration of the entire image can be minimized.

In the above description of the embodiment, an electron beam exposure apparatus has been described as an example. However, these descriptions also apply to a charged particle beam apparatus such as an ion beam exposure apparatus.
The same is true.

[0101]

As described above, in the present invention, astigmatism is generated by using an astigmatism corrector so that a crossover image is not formed on the optical path. The distance between the particles can be increased,
This can reduce blur and distortion due to the Coulomb effect. At the same time, on the image plane, there is no blur, distortion, and deviation of the incident angle due to the astigmatism corrector, so the current of the charged particle beam can be increased without reducing the overall optical performance of the charged particle beam. As a result, the processing capability of the charged particle beam device can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a transfer type electron beam exposure apparatus which is an example of an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a trajectory in the electron beam optical system according to the embodiment of the present invention.

FIG. 3 is a diagram showing an outline of a conventional electron beam exposure apparatus.

FIG. 4

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electron source, 2 ... Electron beam, 31 ... First irradiation lens, 32
... second irradiation lens, 33 ... third irradiation lens, 4 ... molding aperture, 5 ... reticle, 61 ... first projection lens, 62 ... second
Projection lens, 7: scattered electron absorption aperture, 8: wafer, 91
... First astigmatism corrector, 92 ... Second astigmatism corrector, 9
3: a third astigmatism corrector, 94: a fourth astigmatism corrector,
100: crossover image point, 101: point of minimum beam diameter in X direction, 102: point of minimum beam diameter in Y direction

Claims (10)

[Claims] 1. A charged particle exposure apparatus for irradiating a pattern formed on an object to be transferred with a charged particle beam, and exposing and transferring an image of the pattern onto a transferred object, comprising: Having at least one astigmatism corrector that generates astigmatism near the crossover point of the charged particle beam without deteriorating at least one of distortion, incident angle change, deflection position shift, and deflection incident angle change. Charged particle beam exposure equipment. 2. The charged particle beam exposure apparatus according to claim 1, wherein an optical axis of the charged particle beam exposure apparatus is a z-axis, and coordinates on an xy plane in an orthogonal coordinate system having the axis as one axis. To w = x +
expressed in complex coordinates as iy, the object plane is z _o , the image plane is z _i , w
the _{a [z], w a [} z o] = 0, w a '[z o] = 1, w a [z i] = 0
The trajectory of the charged particle represented by the complex coordinate represented by the lens, w _b [z], and the trajectory of the charged particle represented by the complex coordinate represented by w _b [z _o ] = 1, and the complex conjugate trajectory thereof _Let w _ac [z] and w _bc [z] be the electromagnetic astigmatism field on the axis in the case of the electromagnetic astigmatism corrector, and the electrostatic astigmatism field on the axis in the case of the electrostatic astigmatism corrector. When f [z] is the value obtained by dividing the square root of the on-axis potential, (Equation 2) A charged particle beam exposure apparatus comprising an astigmatism corrector that satisfies the following. Here, 'indicates a differential value by z. 3. The charged particle beam exposure apparatus according to claim 1, further comprising a one-stage astigmatism corrector having performance equivalent to that of two or more astigmatism correctors. A charged particle beam exposure apparatus characterized in that: 4. The charged particle beam exposure apparatus according to claim 1, wherein an optical axis of the charged particle beam exposure apparatus is a z-axis, and coordinates on an xy plane in an orthogonal coordinate system having the z-axis as one axis. To w = x +
expressed in complex coordinates as iy, the object plane is z _o , the image plane is z _i , w
the _{a [z], w a [} z o] = 0, w a '[z o] = 1, w a [z i] = 0
The trajectory of the charged particle represented by the complex coordinate represented by the lens, w _b [z], and the trajectory of the charged particle represented by the complex coordinate represented by w _b [z _o ] = 1, and the complex conjugate trajectory thereof _Let w _ac [z] and w _bc [z] be the electromagnetic astigmatism field on the axis in the case of the electromagnetic astigmatism corrector, and the electrostatic astigmatism field on the axis in the case of the electrostatic astigmatism corrector. When f [z] is the value obtained by dividing the square root of the on-axis potential, (Equation 4) (Equation 5) A charged particle beam exposure apparatus comprising an astigmatism corrector that satisfies the following. Here, 'indicates a differential value by z. 5. The charged particle beam exposure apparatus according to claim 1, wherein an optical axis of the charged particle beam exposure apparatus is a z-axis, and coordinates on an xy plane in an orthogonal coordinate system having the z-axis as one axis. To w = x +
expressed in complex coordinates as iy, the object plane is z _o , the image plane is z _i , w
the _{a [z], w a [} z o] = 0, w a '[z o] = 1, w a [z i] = 0
The trajectory of the charged particle represented by the complex coordinate represented by the lens, w _b [z], is represented by the following formula: The trajectory of the charged particle represented by the complex coordinate represented by w _b [z _o ] = 1, w _m [z] Are the orbits by a deflector expressed in complex coordinates, and these complex conjugate orbits are w _ac [z], w _bc [z], and w _mc [z]. In the case of an astigmatism and electrostatic astigmatism corrector, f [z] is obtained by dividing the on-axis electrostatic astigmatism by the square root of the on-axis potential. (Equation 7) (Equation 8) A charged particle beam exposure apparatus comprising an astigmatism corrector that satisfies the following. Here, 'indicates a differential value by z. 6. The charged particle beam exposure apparatus according to claim 4, wherein the one-stage or two-stage astigmatism corrector has performance equivalent to that of three or more stages of astigmatism corrector. Charged particle beam device characterized by having 7. A charged particle beam exposure apparatus according to claim 1, wherein an optical axis of the charged particle beam exposure apparatus is a z-axis, and coordinates on an xy plane in a rectangular coordinate system having the axis as one axis. To w = x +
expressed in complex coordinates as iy, the object plane is z _o , the image plane is z _i , w
the _{a [z], w a [} z o] = 0, w a '[z o] = 1, w a [z i] = 0
The trajectory of the charged particle represented by the complex coordinate represented by the lens, w _b [z], is represented by the following formula: The trajectory of the charged particle represented by the complex coordinate represented by w _b [z _o ] = 1, w _m [z] Are the orbits by a deflector expressed in complex coordinates, and these complex conjugate orbits are w _ac [z], w _bc [z], and w _mc [z]. In the case of an astigmatism and electrostatic astigmatism corrector, f [z] is obtained by dividing the on-axis electrostatic astigmatism by the square root of the on-axis potential. (Equation 10) [Equation 11] (Equation 12) (Equation 13) A charged particle beam exposure apparatus comprising an astigmatism corrector that satisfies the following. Here, 'indicates a differential value by z. 8. The charged particle beam exposure apparatus according to claim 7, further comprising a one-stage to four-stage astigmatism corrector having a performance equivalent to that of a five-stage or more astigmatism corrector. A charged particle beam exposure apparatus. 9. One of claims 1 to 8
Item 3. The charged particle beam exposure apparatus according to Item 1, wherein the astigmatism corrector changes the intensity according to the amount of current of the charged particle beam. 10. The charged particle beam exposure apparatus according to claim 1, wherein the astigmatism corrector includes a charged particle beam current amount and a deflector current amount. A charged particle beam exposure apparatus wherein the intensity is changed according to a voltage.