JPH0745493A - Charged particle beam exposure apparatus and charged particle beam exposure method - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide a charged particle beam exposure apparatus which corrects the rotation of the irradiation surface image due to the field curvature correction and does not cause a deviation in the shot contour portion during the field curvature correction. [Structure] Image forming means 11 for forming an arbitrary irradiation surface image b
A deflection means 12 for deflecting the charged particle beam a, and a field curvature correction coil 13 for correcting the field curvature of the irradiation surface image b.
In the charged particle beam exposure apparatus which has an exposure pattern b on the sample S by projecting the irradiation surface image b, the charged particle beam a is irradiated with the image forming means 11 outside the deflection means 12 on the optical axis O of the charged particle beam a. It is arranged between the formation position of the surface image b and a magnetic field in the direction opposite to the magnetic field direction of the field curvature correction coil 13 is generated to rotate the irradiation surface image b generated by the magnetic field of the field curvature correction coil 13. It has a rotation correction coil 14 for correction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charged particle beam exposure apparatus and a charged particle beam exposure method for irradiating an irradiation surface image formed by a charged particle beam to form an exposure pattern on a sample.

[0002]

2. Description of the Related Art Conventionally, image forming means for passing an irradiated charged particle beam to form an arbitrary irradiation surface image, deflection means for deflecting the charged particle beam, and irradiation surface image generated by the deflection of the charged particle beam. There is known a charged particle beam exposure apparatus which has an image field curvature correction coil for correcting the image field curvature and which forms an exposure pattern on a sample by projecting an irradiation surface image.

In such a charged particle beam exposure apparatus, a pattern formed on a sample is required to have high accuracy in order to cope with an integrated circuit pattern which is required to be further miniaturized in recent years. In the field curvature correction means in the conventional charged particle beam exposure apparatus, as shown in FIG. 10, the field curvature correction coil 2 is provided in the electromagnetic lens 1 for focusing the charged particle beam a, and the field curvature correction coil is provided. A current corresponding to the deflection amount of the charged particle beam a by the deflector 3 is caused to flow in 2 to change the focal length of the electromagnetic lens 1 as a whole according to the deflection amount, and the irradiation surface image b on the sample S is changed. The field curvature that draws an upward arc (see the chain double-dashed line in the figure) was corrected.

That is, assuming that the magnetic field strength of the electromagnetic lens 1 is B and the correction magnetic field strength of the field curvature correction coil 2 is ΔB, the focal length f is 1 / f = k∫ (B + ΔB) with the optical axis O in the Z direction. ) ² dz (1), the field curvature correction coil 2 gives a correction magnetic field strength ΔB according to the deflection amount, and the focal length of the electromagnetic lens 1 as a whole is changed to obtain an image. It is possible to correct the surface curvature.

When the charged particle beam a is focused by the electromagnetic lens 1, the charged particles are focused while rotating spirally. That is, as shown in FIG. 11, charged particles c
However, if the charged particle c is incident on a position slightly distant from the central axis d above the electromagnetic lens 1, the charged particle c receives the force c _{1 in the} circumferential direction from the radial magnetic field of the electromagnetic lens 1 and starts to rotate. Due to this rotation, the charged particles c receive the force c ₂ toward the central axis d from the magnetic field of the electromagnetic lens 1 in the central axis d direction (vertical direction), and then converge.

In the figure, c ₃ is a radial vector, c ₄ is a circumferential vector, and c ₅ is a magnetic field vector. As described above, when the charged particle beam a is incident on the electromagnetic lens 1, the charged particle beam a is subjected to the focusing action and the rotating action by the electromagnetic lens 1. Therefore, when the irradiation surface image b is reduced by the electromagnetic lens 1, the irradiation surface is reduced. The rotation of the image b occurs.

The rotation of the irradiation surface image b by the electromagnetic lens 1 itself does not change if the strength of the magnetic field of the electromagnetic lens 1 does not change. Therefore, it is desired to consider it at the design stage of the optical system in advance. Since it can be set to the rotation angle of, there is no problem. However, when the field curvature correction coil 2 arranged in the electromagnetic lens 1 is used to correct the field curvature, the magnetic field strength of the electromagnetic lens 1 is changed.
In principle, the rotation angle of the irradiation surface image b changes. The rotation angle θ of this irradiation surface image b is the magnetic field strength of the electromagnetic lens 1 is B,
When the correction magnetic field strength of the field curvature correction coil 2 is ΔB, it is expressed by the equation θ = k · ∫ (B + ΔB) dz (2).

In the conventional charged particle beam exposure apparatus of the variable rectangular type for forming the deformable rectangular irradiation surface image b, the correction magnetic field intensity ΔB is a very small value because the deflection amount is small. Since the beam size on the sample S is variable rectangular molding and the length is not so large as about 3 μm at maximum, the rotation of the irradiation surface image b was small, so it was not very noticeable, and also in the shot connection for connecting the shots. It didn't really matter.

Conventionally, a charged particle beam is projected on a tantalum chip provided on a holder to form an irradiation surface image, and this irradiation surface image is scanned to detect and detect backscattered electrons from the tantalum chip. Charged particle beam exposure that forms an exposure pattern on the sample held in the holder in the optimum projection state of the irradiation surface image by correcting the irradiation surface image formed on the tantalum chip based on the reflected electrons The method is known.

This charged particle beam exposure method is used in a charged particle beam exposure apparatus such as an electron beam exposure apparatus used in an LSI manufacturing process, and an optimum projection state is obtained by correcting an irradiation surface image. . That is, FIG.
As shown in FIG. 5, the edge of the charged particle beam a forming a rectangular irradiation surface image b having a vertical and horizontal length of about 3 × 3 μm is scanned with respect to the fine dots 4 provided on the tantalum chip (FIG. By referring to the middle arrow), the rotation (tilt) amount corresponding value from the detection data is obtained, and the rotation of the irradiation surface image b is corrected based on this corresponding value to obtain the optimum projection state.

FIG. 13 shows the detection data.
A rotation amount corresponding value θ corresponding to the rotation amount of the charged particle beam a with respect to is converted into an actual rotation angle α of the irradiation surface image b (see FIG. 12), and a lens optical system for adjusting the rotation of the charged particle beam a is provided. Feedback is applied so that α = 0, and the rotation of the charged particle beam a is adjusted.

[0012]

However, in the charged particle beam exposure apparatus, recently, as a new method for improving the throughput in the charged particle beam exposure, a block exposure or a blanking aperture array (B) is used.
With the introduction of the large beam collective irradiation method such as the AA method, the shift in shot connection due to the minute rotation of the charged particle beam a cannot be ignored.

For example, in the block exposure, as shown in FIG. 14, the charged particle beam a shaped by the block mask 5 is irradiated as one shot on the sample S so that the vertical and horizontal lengths thereof are both about 4.5 μm. (See (a))
Since the shot charged particle beam a has a large vertical and horizontal length of 4.5 μm, even if the metaphor rotation angle is small, the deviation at the shot contour portion where the pattern is connected becomes large.

In addition, the exposure pattern in one shot is
For example, a line width of 0.2 μm for 256M DRAM
Since it is very thin, even if the rotation angle θ of the irradiation surface image b by the field curvature correction coil 2 is small, there is a possibility that the joint portion of the pattern e pattern of each shot may be displaced ((b)). reference). Further, as shown in FIG. 15, in the blanking aperture array method, the blanking aperture array 6 that is capable of shaping the charged particle beam a into an arbitrary shape by arranging small holes for individually turning on / off the charged particle beam a is provided. However, since the shaped charged particle beam a is used as a shot having a larger vertical and horizontal length of about 3 × 10 μm on the sample S (see (a)), the same problem as in the block exposure is more remarkable. (See (b)).

Separately from this, in the block exposure, it is necessary to make the correction magnetic field intensity ΔB by the field curvature correction coil 2 strong. That is, in the block exposure, it is desirable that the pattern has a reduction ratio of about 100: 1 with respect to the block mask 5 in view of manufacturing restrictions of the block mask 5 and required accuracy of the exposure pattern. This means that the vertical and horizontal lengths on the sample S are both 4.5 μm.
In order to obtain a pattern e of a certain degree, the size of one pattern e on the block mask 5 is 450 μm in both vertical and horizontal lengths.
It is necessary to some extent.

By the way, in the block exposure, in order to increase the throughput as a whole, a mask pattern of as many kinds as possible is provided on the block mask 5, and the desired particle pattern is selected by deflecting the charged particle beam a. However, if the number of selectable mask patterns is about 100, one mask pattern is about 500 as described above.
Since it is μm, the selection range, that is, the deflection range of the charged particle beam a is very large, which is 5 mmφ or more.

Therefore, as the deflection range becomes very large, the field curvature also becomes very large, so that it becomes necessary to make the magnetic field of the field curvature correction coil 2 strong. Therefore, the magnetic field of the field curvature correction coil 2 is a deflector that forms the irradiation surface image b on the sample S (main deflector, see FIGS. 14 and 15).
When correcting the field curvature for the deflection of No. 3, roughly 6 to 8
While AT (ampere turn) is sufficient, in the field curvature correction for the deflection of the deflector (mask deflector, see FIG. 16) 3 that deflects the charged particle beam a and scans the block mask 5, It also requires 20 to 30 AT.

As a result, as shown in FIG. 16, the rotation of the irradiation surface image b (see the arrow in the figure) accompanying the correction of the field curvature cannot be ignored. Therefore, at the time of beam exposure by large-beam collective irradiation, the pattern e is generated by minute rotation of the irradiation surface image b.
There is a problem in that the deviation in the shot contour portion that is connected to becomes so large that it cannot be ignored.

Further, in the block exposure, by making the magnetic field of the field curvature correction coil 2 strong, the rotation of the irradiation surface image b due to the field curvature correction becomes too large to be ignored. there were. Further, in the charged particle beam exposure method, when the rotation of the irradiation surface image b is corrected and the optimum projection state is obtained, an accurate rotation amount correspondence value may not always be obtained if the detection data to noise ratio is poor. There was a problem.

Furthermore, the charged particle beam a must be scanned so that the edge of the charged particle beam a exactly overlaps the fine dots 4, and a technique is required for the scanning, and it is necessary to calculate the amount of rotation from the detected data. There was also. The present invention has been made in view of the above problems, and an object thereof is to correct the rotation of the irradiation surface image due to the field curvature correction during the field curvature correction, thereby causing a deviation in the shot contour portion. It is an object of the present invention to provide a charged particle beam exposure apparatus that does not have a beam.

Further, the purpose thereof is to be able to correct the rotation of the charged particle beam forming the irradiation surface image without needing to calculate the amount of rotation of the irradiation surface image which significantly affects the exposure accuracy. An object is to provide an exposure method.

[0022]

The above-mentioned object is to provide an image forming means for passing an irradiated charged particle beam to form an arbitrary irradiation surface image, a deflecting means for deflecting the charged particle beam, and the charged particle. A charged particle beam exposure apparatus, comprising: a field curvature correction coil that corrects a field curvature of the irradiation surface image caused by deflection of a beam, and forming an exposure pattern on a sample by projecting the irradiation surface image. It is arranged on the optical axis of the particle beam between the image forming means outside the deflecting means and the position where the irradiation surface image is formed, and generates a magnetic field in a direction opposite to that of the magnetic field of the field curvature correction coil. And a rotation correction means for correcting the rotation of the irradiation surface image caused by the magnetic field of the field curvature correction coil.

In the charged particle beam exposure apparatus,
The rotation correction means is achieved by a charged particle beam exposure apparatus, which is formed by a rotation correction coil having the same number of coil turns as that of the field curvature correction coil. Further, in the charged particle beam exposure apparatus, the deflection means comprises a main deflector for deflecting the charged particle beam to a desired position on the sample, and the rotation correction means corresponds to the deflection amount of the main deflector. It is achieved by a charged particle beam exposure apparatus characterized by having a corrected rotation amount.

In the charged particle beam exposure apparatus,
The deflection means comprises a mask deflector for deflecting the charged particle beam to a desired position of the mask forming means during block exposure, and the rotation correction means has a correction deflection amount corresponding to the deflection amount of the mask deflector. Is achieved by a charged particle beam exposure apparatus. Further, the charged particle beam is projected to have a rectangular shape distributed along the line of the chip formed on the holding portion for holding the sample, and an adjusted irradiation surface image with the distribution surface facing the line is formed. And an image forming step of rotating the charged particle beam with respect to the line at a predetermined angle, detecting backscattered electrons from the line at each rotation, and storing the signal intensity obtained by the detection as detection data. From the detection data, the maximum value data obtained when the distribution surface is positioned parallel to the line is determined and selected, and the maximum value data is the adjustment irradiation surface image formed on the chip. A correction step of correcting to the obtained optimum projection state, wherein the charged particle beam is projected in the optimum projection state of the adjusted irradiation surface image to form an exposure pattern on the sample. That is achieved by the charged particle beam exposure method.

[0025]

According to the present invention, on the optical axis of the charged particle beam,
The magnetic field of the field curvature correction coil is arranged by the rotation correction means which is arranged between the image forming means outside the deflecting means and the position where the irradiation surface image is formed and which generates a magnetic field in the direction opposite to the direction of the magnetic field of the field curvature correction coil. Since it is possible to correct the rotation of the irradiation surface image caused by, the rotation of the irradiation surface image is prevented by correcting the change in the magnetic field strength due to the field curvature correction, so that the shift of the shot joint portion does not occur, and the image Even if the magnetic field of the surface curvature correction coil is made strong, the rotation of the irradiation surface image can be corrected.

In the image forming step, the charged particle beam is projected to have a rectangular shape distributed along the line of the chip formed on the holding portion for holding the sample, and the distribution surface is opposed to the line. An adjusted irradiation surface image is formed, and in the detection process, the charged particle beam is rotated at a predetermined angle with respect to the line, the reflected electrons from the line at each rotation are detected, and the signal intensity obtained by the detection is used as detection data. Optimum to obtain maximum value data of the adjusted irradiation surface image formed on the chip by saving and correcting and selecting the maximum value data obtained when the distribution surface is parallel to the line from the detected data By correcting to the projection state, it is possible to correct the rotation of the charged particle beam by projecting the charged particle beam in the optimum projection state of the adjusted irradiation surface image to form an exposure pattern on the sample. Kill.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A charged particle beam exposure apparatus according to an embodiment of the present invention will be described below with reference to the drawings. (First Embodiment) As shown in FIG. 1, a charged particle beam exposure apparatus 10 includes an image forming means 11 and a deflector (deflecting means) 1.
2 and a field curvature correction coil (field curvature correction means) 13
And a rotation correction coil (rotation correction means) 14.

The image forming means 11 has an opening through which the charged particle beam a emitted from an electron gun (not shown) passes, and the charged particle beam a passes through this opening to form a rectangular shape. To form an arbitrary irradiation surface image b, for example, a block mask or a blanking aperture array (BAA). Deflector 12
Is formed by, for example, an electromagnetic deflection coil and is arranged between the electromagnetic lens 15 that focuses the charged particle beam a and the position where the irradiation surface image b is formed. The charged particle beam a is deflected by deflecting the charged particle beam a. The irradiation position of a is controlled.

The field curvature correction coil 13 is for correcting the field curvature of the irradiation surface image b caused by the deflection of the charged particle beam a, and is arranged in the electromagnetic lens 15. That is, the field curvature correction coil 13 provided in the electromagnetic lens 15
By passing a current in accordance with the deflection amount of the charged particle beam a, the focal length of the electromagnetic lens 15 as a whole is changed in accordance with the deflection amount, so that the irradiation surface image b causes a curvature of field that draws an upward arc. Correcting.

The rotation correction coil 14 has a charged particle beam a.
Is disposed between the deflector 12 and the position where the irradiation surface image b is formed on the optical axis O of the field curvature correction coil 13 and generates a magnetic field in the direction opposite to the direction of the magnetic field of the field curvature correction coil 13 to generate the field curvature. The rotation of the irradiation surface image b caused by the magnetic field of the correction coil 13 is corrected. The position of the rotation correction coil 14 may be any position on the optical axis O of the charged particle beam a between the image forming means 11 outside the deflector 12 and the position where the irradiation surface image b is formed.

The rotation correction coil 14 has the same number of coil turns as the field curvature correction coil 13, and the rotation correction coil 14 has the field curvature correction coil 13.
The magnetic field strength is the same as the magnetic field strength generated by. Here, an outline of the correction of the field curvature of the irradiation surface image b by the field curvature correction coil 13 and the correction of the rotation of the irradiation surface image b by the rotation correction coil 14 will be shown. The positions of the field curvature correction coil 13 and the rotation correction coil 14 are determined as follows.

First, from the above equation (1), when the magnetic field strength is B, the focal length f becomes 1 / f = k · ∫B ² dz with the optical axis O in the z direction and the magnetic field strength B becomes Since the field curvature correction coil 13 is arranged in the electromagnetic lens 15, since it is proportional to the square, 1 / f = k · ∫ (B + ΔB) ² when the correction magnetic field strength of the field curvature correction coil 13 is ΔB. dz = k · [∫B ² dz + ∫ (2BΔB + ΔB ² ) dz], and the focal length can be corrected most efficiently under the influence of the magnetic field strength B.

Therefore, it is preferable to arrange the field curvature correction coil 13 in the electromagnetic lens 15. Next, the position of the rotation correction coil 14 is determined. Here, the field curvature correction coil 1
Consider a case where both 3 and the rotation correction coil 14 are arranged in the electromagnetic lens 15. The magnetic field strength of the electromagnetic lens 15 is B, and the correction magnetic field strength of the field curvature correction coil 13 is Δ.
B ₁ and the correction magnetic field strength of the rotation correction coil are ΔB ₂ .
From equations (1) and (2), 1 / f = k · ∫ (B + ΔB ₁ + ΔB ₂ ) ² dz (3) f = k · ∫ (B + ΔB ₁ + ΔB ₂ ) dz (4), but the field curvature In order for the rotation of the irradiation surface image b by the correction coil 13 and the rotation of the irradiation surface image b by the rotation correction coil 14 to cancel each other, the condition of ΔB ₁ + ΔB ₂ = 0 (5) occurs from the equation (4). . When this conditional expression (5) is substituted into the expression (3), the expression (3) becomes 1 / f = k · ∫B ² dz, and the field curvature correction coil 13 does not work at all. Therefore, it is not desirable to arrange the rotation correction coil 14 in the electromagnetic lens 15.

For the above reasons, the field curvature correction coil 1
3 is arranged inside the electromagnetic lens 15, and the rotation correction coil 14 is arranged at an arbitrary position outside the electromagnetic lens 15. Now, as to the principle of rotation correction, as described above, when the charged particles c are incident on the magnetic field as shown in FIG. 11, the charged particles c are rotated and focused. Even if the direction of the magnetic field is reversed, the charged particles c will be focused, but the direction of rotation will be opposite. Therefore, the rotation correction coil 14 can reverse the rotation of the irradiation surface image b by the field curvature correction coil 13 by making the direction of the magnetic field opposite to the direction of the magnetic field of the field curvature correction coil 13. is there.

When the magnetic field strength by the electromagnetic lens 15 is B and the corrected magnetic field strength by the field curvature correction coil 13 is ΔBdf, when the field curvature correction coil 13 is arranged in the electromagnetic lens 15, the value of the corrected magnetic field strength ΔBdf is changed. It is assumed that the field curvature is just corrected. The rotation angle Δθdf by the field curvature correction coil 13 at this time is given by the equation (2).
Therefore, Δθdf = k · ∫ΔBdfdz.

On the other hand, when the correction magnetic field strength of the rotation correction coil 14 is ΔBrc, the rotation angle Δθrc of the rotation correction coil 14 similarly becomes Δθrc = k · ∫ΔBrcdz, which cancels this rotation angle Δθdf. Rotation angle Δ
By generating the correction magnetic field intensity ΔBrc that generates θrc by the rotation correction coil 14, the irradiation surface image b
Correct the rotation of.

The change in the focal length f due to the correction magnetic field strength ΔBrc generated by the rotation correction coil 14 can be considered. The change Δfrc in the focal length f is calculated by the equation (1) as follows: 1 / Δfrc = k · ∫ ( ΔBrc) ² dz, which is much smaller than the change in the focal length f by the field curvature correction coil 13, and is considered to be negligible.

Therefore, by correcting the change in the magnetic field strength associated with the correction of the field curvature to prevent the irradiation surface image b from rotating,
Even if the magnetic field of the field curvature correction coil 13 is strengthened, the shot connecting portion is not displaced, and the rotation of the irradiation surface image b can be corrected. (Second Embodiment) This embodiment shows a case where the rotation correction of the charged particle beam a is applied when the field curvature correction is performed by the deflection of the mask deflector in the block exposure. The mask deflector deflects the charged particle beam a to a desired position on the block mask (mask forming means).

As shown in FIG. 2, a charged particle beam exposure apparatus 20 by block exposure is provided with a pair of mask deflectors 22a and 22b sandwiching a block mask 21 arranged on the way of passage of a charged particle beam a. A field curvature correction coil 23 for correcting the field curvature by the mask deflector 22b and a rotation correction coil 24 for dealing with the field curvature correction are provided.

First, the charged particle beam a emitted from the electron gun 25 passes through the first A lens 26a, the first slit 27 and the first B lens 26b in this order, and then the mask deflector 2
The light is deflected by 2a and is focused by the second A lens 28a and passes through the block mask 21. The charged particle beam a is deflected by the mask deflector 22a and the desired position of the block mask 21 is irradiated with the charged particle beam a, and a desired mask pattern can be selected from the block mask 21.

The charged particle beam a which has passed through the block mask 21 and has a desired irradiation surface shape is focused by the second B lens 28b and deflected by the mask deflector 22b, and passes through the third lens 29 and the aperture 30. Be focused on. Further, the charged particle beam a that has passed through the aperture 30 is shaped and passes through the fourth lens 31. A rotation correction coil 24 is provided between the aperture 30 and the fourth lens 31 through which the charged particle beam a formed in a desired irradiation surface shape passes, and further, an image is provided in the fourth lens 31. A surface curvature correction coil 23 is provided.

The rotation correction coil 24 has a magnetic field direction opposite to that of the field curvature correction coil 23 and the same magnetic field strength, and has a correction deflection amount corresponding to the deflection amount of the mask deflector 22b. Therefore, the rotation of the charged particle beam a by the field curvature correction coil 23 can be restored. Therefore, the field curvature correction coil 23 corrects the field curvature of the irradiation surface image b caused by the deflection of the charged particle beam a, and the rotation correction coil 24 corrects the rotation accompanying the field curvature correction. Therefore, in the charged particle beam exposure by the large beam collective irradiation, the minute rotation of the irradiation surface image b is corrected, and the deviation in the shot contour portion where the pattern is connected does not occur.

Subsequently, the charged particle beam a which has passed through the fourth lens 31 is focused by the fifth lens 32, and the sample S
A desired irradiation surface image b is projected on the surface to form a pattern. (Third Embodiment) This embodiment is similar to the second embodiment in that the rotation correction of the charged particle beam a is applied when the field curvature is corrected by the deflection of the mask deflector in the block exposure. In particular, the case where the correction magnetic field strength itself by the field curvature correction coil is made strong is shown.

As shown in FIG. 3, in the charged particle beam exposure apparatus 35 by block exposure, the field curvature correction coil 36 for correcting the field curvature by the mask deflector 22a and the rotation correction for coping with the field curvature correction. Except that the coil 37 is provided, it has the same configuration and operation as the charged particle beam exposure apparatus 20. Between the first B lens 26b and the second A lens 28a, through which the charged particle beam a passes,
The rotation correction coil 37 is provided, and further, the field curvature correction coil 36 is provided in the second A lens 28a.

By the way, in the block exposure, it is desirable that the pattern has a sufficient reduction ratio with respect to the block mask 21 in view of manufacturing restrictions of the block mask 21 and required accuracy of the exposure pattern. In order to increase the throughput, it is necessary to increase the deflection amount of the charged particle beam a, and the field curvature correction coil 36
The correction magnetic field strength due to is increased.

The rotation correction coil 37 has the same magnetic field direction and the same magnetic field strength as the field curvature correction coil 36, and has a correction deflection amount corresponding to the deflection amount of the mask deflector 22a. Therefore, the rotation of the charged particle beam a by the field curvature correction coil 36 can be restored. Therefore, the field curvature correction coil 36 corrects the field curvature of the irradiation surface image b caused by the deflection of the charged particle beam a, and the rotation correction coil 37 corrects the rotation accompanying the field curvature correction. Therefore, during the charged particle beam exposure by the large beam collective irradiation, the rotation of the irradiation surface image b is corrected due to the strong magnetic field of the field curvature correction coil 36, and the deviation in the shot contour portion where the pattern is connected does not occur. .

(Fourth Embodiment) This embodiment shows a case where the rotation correction of the charged particle beam a is applied when the field curvature is corrected by the deflection of the main deflector in the blanking aperture array system. There is. The blanking aperture array method individually turns on the passage of the charged particle beam a.
By using a blanking aperture array in which small holes that can be turned on / off are arranged, the charged particle beam a can be shaped into an arbitrary irradiation surface shape. The main deflector deflects the charged particle beam a to a desired position on the sample.

As shown in FIG. 4, a charged particle beam exposure apparatus 40 of the blanking aperture array system is provided with a blanking aperture array 41 while the charged particle beam a is passing, and the charged particle beam a is on the sample S. The main deflector 42 is provided immediately before the image is projected on the image plane, and the field curvature correction coil 43 that corrects the field curvature by the main deflector 42 and the rotation correction coil 44 that corresponds to the field curvature correction are provided. Has been.

First, the charged particle beam a emitted from the electron gun 45 is emitted from the first slit 46, the first lens 47, and the second lens 46.
After passing through the lens 48 in order, the blanking aperture array 41 is passed to form a rectangular irradiation surface shape, for example. Blanking aperture array 41
The charged particle beam a which has passed through is focused on the aperture 50 by the third lens 49, and the charged particle beam a which has been shaped through the aperture 50 passes through the fourth lens 51.

Subsequently, the charged particle beam a which has passed through the fourth lens 51 is focused by the fifth lens 52 and is deflected by the main deflector 42 provided in the fifth lens 52, and then is placed on the sample S. A desired irradiation surface image b is projected to form a pattern. A rotation correction coil 44 is provided between the aperture 50 and the fourth lens 51 through which the charged particle beam a formed in a desired irradiation surface shape passes, and further,
A field curvature correction coil 43 is provided in the fourth lens 51.

The rotation correction coil 44 has a magnetic field direction opposite to that of the field curvature correction coil 43 and the same magnetic field strength, and has a correction deflection amount corresponding to the deflection amount of the main deflector 42. Therefore, the field curvature correction coil 43
The rotation of the charged particle beam a due to can be restored. Therefore, the field curvature correction coil 43 corrects the field curvature of the irradiation surface image b caused by the deflection of the charged particle beam a, and the rotation correction coil 44 corrects the rotation accompanying the field curvature correction. Therefore, when the charged particle beam exposure is performed by the large beam collective irradiation, the irradiation surface image b
Is corrected so that no deviation occurs in the shot contour portion where the patterns are connected.

As described above, according to each of the above-described embodiments, the rotation of the irradiation surface image b exposed on the sample S caused by the rotation of the charged particle beam a at the time of correcting the field curvature is corrected, and the pattern between the shots is corrected. Since the connection can be made more accurate, the charged particle beam a can be exposed with higher accuracy. (Fifth Embodiment) FIG. 5 shows a step of forming an exposure pattern by the charged particle beam exposure method.

In the charged particle beam exposure method, an image forming step 60 for forming the adjusted irradiation surface image d by the image forming means, and a detecting step 6 for obtaining and storing the detection data by the detecting means.
1 and a correction step 62 for correcting the optimum projection state in which the maximum value data is obtained by the correction means, and the exposure pattern can be formed on the sample in the optimum projection state of the adjusted irradiation surface image.

As shown in FIG. 6, a wafer W as a sample is fixedly held by a holder (holding portion) 63, and the holder 63 has a rectangular tantalum (Ta) chip whose vertical and horizontal lengths are both about 15 mm. A (chip) 64 is formed (see (a)). On the upper surface of this tantalum chip 64,
Fine lines L each having a width of about 0.2 μm are formed vertically and horizontally with an interval of about 30 μm, and fine dots 4 are provided in the divided screen divided by the lines L ((b ), (C)).

The holder 63 holding the wafer W
Are mounted on a movable stage (not shown). First, in the image forming step 60, the charged particle beam a is irradiated to form an adjusted irradiation surface image, which is projected on the tantalum chip 64. The charged particle beam a, after being formed into an arbitrary adjusted irradiation surface image, passes through a lens optical system for reducing and irradiating the wafer W and a lens optical system for adjusting the rotation of the beam, passes through a deflector, and is transferred onto the wafer W. It is deflected and irradiated to a desired position.

The adjusted irradiation surface image has a width wider than the width of the line L of the wafer W and has a rectangular shape distributed along the line L, and the distribution surface of the adjusted irradiation surface image is opposed to the line L. There is. As shown in FIG. 7, this adjustment irradiation surface image is formed by a block mask (image forming means) 66 having various mask patterns 65, and an arbitrary adjustment mask 67 selected from the mask patterns 65. By the block beam that has passed through, two blocks are formed apart from each other on the same line (see FIG. 8). In addition to this, the adjustment irradiation surface image is formed in various shapes by an adjustment mask used as necessary, such as being formed vertically by a rectangular beam that has passed through the adjustment mask 68 (see FIG. 9).

Subsequently, in the detection step 61, the reflected electrons from the wafer W due to the projection of the charged particle beam a are detected, and the signal intensity of the reflected electrons is stored as detection data. The charged particle beam a is projected onto each line L on the wafer W by rotating at a predetermined angle in a direction in which the distribution surface faces the line L and approaches and separates from the line L. The reflected electrons are reflected from the wafer W when the charged particle beam a is projected on the line L to form an adjusted irradiation surface image at each rotation of the charged particle beam a.

When the backscattered electrons are detected by a backscattered electron detector (not shown), a backscattered electron signal is sent out from the backscattered electron detector, and the signal intensity corresponding to the address reflecting the projection position of the charged particle beam a. Is stored in a memory (not shown). Therefore, the charged particle beam a is rotated by a predetermined angle by using a lens optical system that adjusts the rotation of the beam, and scanning in the X direction and the Y direction on the wafer W is repeated by a predetermined angle. (Fig. 6 (c)
The maximum value data of the signal strength is obtained. Further, the maximum value of the maximum value data group is obtained, and it is recognized that the scanning direction and the line L intersect at the most right angle depending on the state of the lens optical system at that time, and the state is stored in the memory as a current value and a register. Hold as a value.

Then, in the correction step 62, the maximum value data obtained when the distribution surface is located parallel to the line L is judged and selected from the detected data, and the adjusted irradiation surface image formed on the wafer W is maximized. The projection state of the charged particle beam a is corrected so as to obtain the value data. That is, as shown in FIG. 8, the detection data g has the height h of the input signal in accordance with the rotation amount (tilt) with respect to the line L of the distribution plane of the adjusted irradiation surface image i formed by the projection of the block beam. The heights h are changing such that h ₁ <h ₂ <h ₃ ((a), (b),
(See (c)), h ₄ <h ₃ (see (d)), and h ₃
Is the highest, and when this maximum value data is obtained, the distribution surface is in the state of being most parallel to the line L ((c)).
reference). Here, h ₁ is when the inclination of the block beam is large, h ₂ is when the inclination of the block beam is small, h ₃
Is a height when the block beam has almost no inclination, and h ₄ is a height when the block beam has an opposite inclination.

Incidentally, FIG. 8 shows detection data g by the block beam which has passed through the adjustment mask 67.
The same applies to the case of the adjusted irradiation surface image i by the rectangular beam that has passed through the adjustment mask 68 shown in FIG. By this correction step 62, the adjusted irradiation surface image i formed on the wafer W can be corrected to the optimum projection state.

As described above, when the line L on the wafer W and the charged particle beam a intersect at a substantially right angle, the fact that the detection data has the maximum value is used to adjust irradiation which significantly affects the exposure accuracy. The rotation can be corrected without obtaining the accurate rotation amount of the surface image i with respect to the line L by calculation. The present invention is not limited to the above embodiment, and various modifications are possible. For example, the rotation amount correction including the rotation correction coil is not limited to the charged particle beam exposure apparatus that forms the exposure pattern on the sample, and the field curvature correction is performed. It can be applied to various cases where the field curvature is corrected by the coil.

[0062]

As described above, according to the present invention, even if the magnetic field of the field curvature correction coil is made strong, the image plane of the irradiation surface image does not rotate due to the field curvature correction, and the deviation of the shot joint is not caused. Does not happen. Further, it is possible to correct the rotation of the charged particle beam forming the irradiation surface image without requiring the calculation of the rotation amount of the irradiation surface image that significantly affects the exposure accuracy.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of a charged particle beam exposure apparatus according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a schematic configuration of a charged particle beam exposure apparatus according to a second embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a schematic configuration of a charged particle beam exposure apparatus according to a third embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a schematic configuration of a charged particle beam exposure apparatus according to a fourth embodiment of the present invention.

FIG. 5 is a process explanatory diagram of a charged particle beam exposure method according to a fifth embodiment of the present invention.

6A and 6B show a wafer and a tantalum chip held by a holder, FIG. 6A is an overall explanatory diagram, FIG. 6B is an enlarged explanatory diagram of a tantalum chip, and FIG. 6C is an enlarged explanatory diagram of a line.

7A and 7B show block masks, FIG. 7A is an overall explanatory view, and FIG. 7B is an enlarged explanatory view of an adjustment mask.

8A and 8B show detection data by a block beam, FIG. 8A is an explanatory diagram when the inclination of the block beam is large, FIG. 8B is an explanatory diagram when the inclination of the block beam is small, and FIG. 8C is a block beam. Is an explanatory diagram when there is almost no inclination, and (d) is an explanatory diagram when the inclination of the block beam is opposite to that of (a).

FIG. 9 shows detection data with a rectangular beam,
(A) is an explanatory view when the inclination of the rectangular beam is large,
(B) is an explanatory view when the inclination of the rectangular beam is small,
(C) is an explanatory diagram when the rectangular beam has almost no inclination,
(D) is an explanatory view when the inclination of the rectangular beam is opposite to that of (a).

FIG. 10 is a schematic explanatory diagram of field curvature correction by a conventional charged particle beam exposure apparatus.

FIG. 11 is an explanatory diagram showing an example of a force received by a charged particle in a magnetic field.

FIG. 12 is a schematic explanatory diagram showing rotation correction of an irradiation surface image by a conventional charged particle beam exposure method.

13 is an explanatory diagram showing a rotation amount of detection data in the rotation correction shown in FIG.

14A and 14B show conventional problems in block exposure, in which FIG. 14A is a schematic configuration explanatory diagram of block exposure, and FIG.
FIG. 4 is a schematic explanatory diagram of the influence of field curvature correction on a shot.

15A and 15B show a conventional problem in the blanking aperture array system, FIG. 15A is a schematic configuration explanatory diagram of the blanking aperture array system, and FIG. 15B is a schematic explanatory diagram of the influence of field curvature correction on a shot. Is.

FIG. 16 shows another conventional problem in block exposure, in which (a) is a schematic explanatory diagram of a mask selection state,
(B) is a schematic explanatory view of the influence of field curvature correction.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Charged particle beam exposure apparatus 11 ... Image forming means 12 ... Deflector (deflecting means) 13 ... Field curvature correction coil 14 ... Rotation correction coil (rotation correction means) 15 ... Electromagnetic lens 20 ... Charged particle beam exposure apparatus 21 ... Block masks 22a, 22b ... Mask deflector 23 ... Field curvature correction coil 24 ... Rotation correction coil 25 ... Electron gun 26a ... First A lens 26b ... First B lens 27 ... First slit 28a ... Second A lens 28b ... Second B lens 29 ... Third lens 30 ... Aperture 31 ... Fourth lens 32 ... Fifth lens 35 ... Charged particle beam exposure device 36 ... Field curvature correction coil 37 ... Rotation correction coil 40 ... Charged particle beam exposure device 41 ... Blanking aperture array 42 ... Main deflector 43 ... Field curvature correction coil 44 ... Rotation correction coil 45 ... Electron gun 46 First slit 47 ... First lens 48 ... Second lens 49 ... Third lens 50 ... Aperture 51 ... Fourth lens 52 ... Fifth lens 60 ... Image forming step 61 ... Detection step 62 ... Correction step 63 ... Holder 64 ... Tantalum Chip 65 ... Mask pattern 66 ... Block mask (image forming means) 67 ... Adjustment mask 68 ... Adjustment mask a ... Charged particle beam b ... Irradiation surface image c ... Charged particle d ... Central axis e ... Pattern g ... Detection data h … Height i… Adjusted irradiation surface image S… Sample W… Wafer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akio Takemoto 2-1844, Kozoji-cho, Kasugai-shi, Aichi Prefecture Fujitsu Viels E Ltd. (72) Inventor Manabu 2-1844-2 Kozoji-cho, Kasugai-shi, Aichi Inside VIEL S Co., Ltd. (72) Inventor Kiichi Sakamoto 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited

Claims (5)

[Claims] 1. An image forming unit for passing an irradiated charged particle beam to form an arbitrary irradiation surface image, a deflection unit for deflecting the charged particle beam, and the irradiation surface generated by the deflection of the charged particle beam. In a charged particle beam exposure apparatus having an image field curvature correction coil for correcting an image field curvature of an image, and forming an exposure pattern on a sample by projecting the irradiation surface image, on the optical axis of the charged particle beam, The field curvature correction coil is disposed between the image forming unit outside the deflection unit and the irradiation surface image forming position, and generates a magnetic field in a direction opposite to the direction of the magnetic field of the field curvature correction coil. A charged particle beam exposure apparatus having a rotation correction means for correcting the rotation of the irradiation surface image caused by the magnetic field. 2. The charged particle beam exposure apparatus according to claim 1, wherein the rotation correction means is formed by a rotation correction coil having the same number of coil turns as the field curvature correction coil. Charged particle beam exposure apparatus. 3. The charged particle beam exposure apparatus according to claim 1, wherein the deflection means comprises a main deflector for deflecting the charged particle beam to a desired position on the sample, and the rotation correction means comprises the main correction means. A charged particle beam exposure apparatus having a correction rotation amount corresponding to a deflection amount of a deflector. 4. The charged particle beam exposure apparatus according to claim 1, wherein the deflecting means comprises a mask deflector for deflecting the charged particle beam to a desired position of the mask forming means during block exposure, and the rotation correcting means. A charged particle beam exposure apparatus having a correction deflection amount corresponding to the deflection amount of the mask deflector. 5. An adjusted irradiation surface having a rectangular shape which projects a charged particle beam and is distributed along a line of a chip formed on a holding portion for holding a sample, and a distribution surface of which faces the line. An image forming step of forming an image, rotating the charged particle beam with respect to the line at a predetermined angle, detecting backscattered electrons from the line at each rotation, and detecting the signal intensity obtained by the detection as detection data. In the detection step of storing, the maximum value data obtained when the distribution surface is positioned parallel to the line is determined and selected from the detection data, and the adjusted irradiation surface image formed on the chip is set to the maximum value. And a correction step for correcting to an optimum projection state in which value data is obtained, and projecting the charged particle beam in the optimum projection state of the adjusted irradiation surface image to form an exposure pattern on the sample. A charged particle beam exposure method characterized.