JPH1079346A - Charged particle beam transfer apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make illumination characteristics such as a radiation region shape of a charged particle beam to each small region on a mask constant without depending on a deflection amount from a light axis in transferring a mask patron through a division transfer method. SOLUTION: An electron beam EB emitted from an dectron gun 10 is focused by condenser lenses 11A, 11B and reaches an aperture plate 31. The electron beam EB which has passed through an opening of the aperture plate 31 is deflected by a first field of view selecting deflector 12A and made into a parallel beam by a condenser lens 11C, and then deflected back by a second field of view selecting deflector 12B to be incident to a radiation region 33 of one of small regions of a mask 1. An projection image of the opening of the aperture plate 31 is the radiation region 33. A shape, position, current density or the like of the radiation region 33 of the electron beam are corrected by an illumination characteristics correction system 30 placed in the vicinity of the inside the condenser lens 11C.

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 transfer apparatus used in, for example, a lithography process for manufacturing a semiconductor integrated circuit or the like, and more particularly, to irradiation of a charged particle beam such as an electron beam or an ion beam. The present invention relates to a charged particle beam transfer apparatus for transferring a pattern on a mask onto a photosensitive substrate by a division transfer method.

[0002]

2. Description of the Related Art In recent years, studies have been made on a charged particle beam transfer apparatus capable of improving both the resolution of a transfer pattern and the throughput (productivity). As such a transfer apparatus, one die (a pattern corresponding to one integrated circuit formed on one photosensitive substrate) or a pattern for a plurality of dies is collectively transferred from a mask to a photosensitive substrate. Conventionally, a batch transfer type apparatus has been studied.
However, in the batch transfer method, it is difficult to manufacture a mask serving as a transfer master, and a charged particle optical system (hereinafter, simply referred to as an “optical system”) in a large optical field of one die or more.
It is difficult to keep the aberration of the lens below a predetermined value. Therefore, recently, the pattern to be transferred to the photosensitive substrate is divided into a plurality of small areas smaller than the size corresponding to one die on the mask, and the patterns are divided and transferred to the photosensitive substrate respectively. An apparatus of a division transfer system is being studied.

In this division transfer system, transfer can be performed while correcting aberrations such as displacement of a focal position and distortion of a transferred image for each small area. As a result, the resolution and resolution over an optically wider area as compared with the batch transfer method can be improved.
Exposure with good positional accuracy can be performed. FIG.
(A) is an enlarged plan view showing a part of the conventional mask used in the electron beam reduction transfer apparatus of the division transfer system,
In FIG. 10A, a large number of rectangular small areas (sub-fields) 4 are formed by struts 42 serving as boundary areas in which the area inside the mask 41 is formed in a grid pattern vertically and horizontally.
It is divided into three. The small area 43 is, for example, about 1 mm square. FIG. 10B is a cross-sectional view taken along the line AA in FIG. 10A. As shown in FIG.
The strut 42 is formed thick so as to support the weight of the mask 41.

A rectangular pattern forming region 44 is set inside the small region 43, and an original pattern that partially transmits an electron beam is formed in the pattern forming region 44. A skirt region 45 between the strut 42 and the pattern formation region 44 in the small region 43 is a region for blocking an electron beam, and an irradiation region 46 of the electron beam by the illumination system is larger than the pattern formation region 44. , And is set so as not to exceed the skirt region 45. Thus, only the pattern in the pattern forming area 44 inside the skirt area 45 is transferred onto the photosensitive substrate. The electron beam illumination system is generally configured to project an image of a predetermined aperture onto the mask 41. In this case, the image of the aperture is the irradiation area 46 of the electron beam.

[0005] In the normal division transfer system, the transfer by deflecting the electron beam is performed in a row of small areas located substantially across the optical axis of the optical system on the mask in a predetermined direction. Then, in order to transfer a pattern of a small region in a region orthogonal to the predetermined direction, the mask and the photosensitive substrate are mechanically and continuously scanned in a direction orthogonal to the predetermined direction via a stage system. Therefore, the mask 4 shown in FIG.
1 is also continuously scanned in the direction of arrow 47 during exposure, for example, so that the pattern formation region 44 does not deviate from the electron beam irradiation region 46 during transfer.
Is set to be larger than the pattern formation region 44 by a predetermined width.

Further, if the patterns in the respective small areas on the mask are transferred onto the wafer while being joined by the division transfer method, a joining error may occur at the boundary.
In order to reduce such a splicing error, the present inventors blur the outline of the irradiation area of the electron beam, define the area of the pattern to be transferred in each small area by the irradiation area, and define There has been proposed a method of transferring an original pattern in a small area so that contour portions overlap each other (hereinafter, referred to as a “half-shadow overlapping transfer method”). In the penumbra transfer method, an illumination system projects, for example, a defocused image of a predetermined aperture onto a mask, thereby setting an irradiation area whose outline is blurred.

[0007]

In the above-described conventional divided transfer method, a pattern of a small area located at a position distant from the optical axis in a row of small areas (subfields) on a mask is transferred onto a photosensitive substrate. In this case, in the illumination system, the electron beam is largely deflected from the optical axis to irradiate the small area. However, when the electron beam is deflected from the optical axis in this way,
Compared to irradiating the electron beam to a small area almost on the optical axis,
The state of the aberration of the electron beam changes, and the shape, position, current density, and the like of the irradiation area of the electron beam on the small area slightly change.

More specifically, for example, in the case where the irradiation area 46 in FIG. 10A becomes a larger irradiation area 46A due to a shift (defocus) of the focal position, the skirt area 45 is set with a certain margin in advance. You have to set it widely. However, since the skirt region 45 is essentially a wasteful region, there is a disadvantage that the mask and the mask stage become large as a whole. If the shape of the irradiation area 46 changes or the position of the irradiation area 46 shifts, a part of the pattern formation area 44 deviates from the irradiation area 46, resulting in a pattern that is not transferred onto the photosensitive substrate. Further, when the current density changes, the exposure amount on the photosensitive substrate changes. Further, even when the shape of the irradiation area 46 changes with a constant current, the current density also changes.

Further, particularly in the case of the division transfer system and the semi-shadow overlap transfer system, when the shape, position, current density, etc. of the electron beam irradiation area on a small area away from the optical axis on the mask changes. In addition, there is an inconvenience that when the projected image of the pattern of each small area on the mask is exposed while the outline is overlapped on the photosensitive substrate, the connecting portion is not smooth. Since the degree of integration of semiconductor devices is increasing, smoothness at such joints is also becoming a problem. Further, there is also a disadvantage that the exposure amount on the photosensitive substrate becomes uneven due to a change in the shape or the like of the irradiation area.

In view of the above, the present invention deflects the illumination characteristics such as the shape of the irradiation area of the charged particle beam with respect to each small area on the mask from the optical axis when transferring the mask pattern by the division transfer method. It is an object of the present invention to provide a charged particle beam transfer device that can be constant regardless of the amount.

[0011]

A charged particle beam transfer apparatus according to the present invention comprises a plurality of small areas (2A, 2A) in which patterns to be transferred are separated from each other, as shown in FIGS.
B, 2C,...), The mask (1) formed in a divided manner is provided with a deflection illumination system (10, 11A, 11) for selecting a visual field.
B, 11C, 12A, 12B, and 31) are sequentially irradiated with a charged particle beam having a predetermined cross-sectional shape in units of these small regions, and an image forming system (1)
In a charged particle beam transfer apparatus for transferring an image of a pattern to be transferred onto a substrate (5) by transferring the images obtained by the methods (4, 15) on a substrate (5) to be transferred substantially in contact with each other. And illumination characteristics (such as the shape and position of the irradiation area or the current density of the charged particle beam) relating to the cross-sectional shape of the charged particle beam irradiated on the small area on the mask (1) by the deflection illumination system for selecting the field of view. An illumination characteristic correcting means (30) for correcting a variation of the charged particle beam from the optical axis (AX) according to the deflection amount is provided.

According to the present invention, the illumination characteristic correcting means (30) is arranged on the charged particle beam source side with respect to the mask (1). Then, via the illumination characteristic correction means (30),
By dynamically correcting the illumination characteristics related to the cross-sectional shape of the charged particle beam in accordance with the amount of deflection of the small area to be transferred on the mask (1) from the optical axis (AX), each of the areas on the mask (1) is corrected. The illumination characteristics relating to the cross-sectional shape of the charged particle beam irradiated to the small area are made constant irrespective of the amount of deflection from the optical axis (AX).

In this case, one example of the deflection illumination system for selecting the field of view is to focus and deflect the charged particle beam that has passed through the aperture (31) having a predetermined shape, thereby forming the mask (1).
This is an imaging type illumination system in which an image of the aperture (31) is sequentially formed on the above small areas, and the illumination characteristic of the imaging system depends on the amount of deflection of the charged particle beam from the optical axis (AX). The fluctuation is a shift of the focal position of the image of the aperture (31),
At least one of astigmatism, rotation error, and position error
One. At this time, for example, the shift of the focal position is corrected by an electromagnetic lens or an electrostatic lens, the astigmatism is corrected by an electromagnetic or electrostatic astigmatism corrector, and the rotation error is corrected by an electromagnetic lens or an electrostatic lens. The position error is corrected by an electromagnetic or electrostatic deflector.

Next, in the above-described charged particle beam transfer apparatus, as shown in FIGS. 7 to 9, for example, a small area (2) on a mask (1A) is irradiated via a deflection illumination system for selecting a field of view. The intensity distribution at the contour of the cross-sectional shape of the charged particle beam is set so as to decrease monotonically outward, and the image of the pattern in those small regions with respect to the substrate (5) is set to the image of the adjacent pattern. The contour portions (7Ma to 7Md) may be overlapped. This means that the penumbra transfer method is used together. In the semi-shadow transfer method, the transfer target region in each small region is defined by the cross-sectional shape of the charged particle beam. The smoothness at the connecting portion is improved, and the exposure amount distribution becomes constant.

In these cases, one example of the illumination characteristic correcting means (30) is an electromagnetic compensator or an electrostatic compensator.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a charged particle beam transfer apparatus according to the present invention will be described below with reference to FIGS. In this embodiment, the present invention is applied to an electron beam reduction transfer apparatus that transfers a mask pattern by a division transfer method. FIG. 1 shows a schematic configuration of an electron beam reduction transfer apparatus used in the present embodiment. In FIG. 1, a Z axis is taken in parallel with an optical axis AX of an electron optical system, and FIG. The description will be made by taking the X axis perpendicular to the paper surface and the Y axis parallel to the paper surface of FIG. First, in the deflection illumination system of the present example, the electron beam EB emitted from the electron gun 10 is applied to the first condenser lens 11A.
Is focused once, and then focused again by the second condenser lens 11B. An aperture plate 31 is arranged near the second condenser lens 11B, and the electron beam EB that has passed through the opening of the aperture plate 31 is deflected mainly in the Y direction by the first field-of-view selection deflector 12A.
After being converted into a parallel beam at C, the second field-of-view selection deflector 12
It is turned back by B and guided to the irradiation area 33 on one small area of the mask 1. Field-of-view selection deflectors 12A, 12B
Is an electromagnetic deflector, and the amount of deflection in the field-of-view selection deflectors 12A and 12B is set by a main controller 19 which controls the overall operation of the apparatus via a deflection correction amount setting device 25.
In FIG. 1, the locus indicated by the solid line of the electron beam EB indicates the conjugate relationship of the crossover, and the locus indicated by the dotted line indicates the conjugate relationship of the mask pattern.

In this embodiment, the arrangement surface of the aperture plate 31 is conjugate with the arrangement surface of the mask 1, and the projected image of the opening of the aperture plate 31 is the irradiation area 33 of the electron beam on the mask 1. Further, near the inside of the third condenser lens 11C in the deflection illumination system of the present example, an illumination characteristic correction system 30 for correcting the shape, position, current density and the like of the irradiation area 33 of the electron beam is arranged. I have. The illumination characteristic correction system 30 includes a focus correction coil 30a, an astigmatism correction coil 30b, a deflection correction coil 30c, and a rotation correction coil 30d. Among them, the focus correction coil 30a is composed of, for example, a spiral wound air-core coil,
The focal position of the projection image of the irradiation area 33, that is, the opening of the aperture plate 31 can be corrected by 0a. The focal position may be corrected by using an electrostatic lens instead of the electromagnetic lens such as the focus correction coil 30a.

The astigmatism correction coil 30b is, for example, an eight-pole saddle type coil 50A as shown in FIG.
-50H are arranged at equal angular intervals around the optical axis to generate mutually repelling magnetic fields between the opposed pairs of coils. In FIG. 3A, opposed coils 50A,
As shown by arrows 51A and 51E, a repulsive magnetic field is generated between 50E, and a magnetic field in the opposite direction is generated between coils 50C and 50G arranged in a direction orthogonal to the magnetic field. Two sets of coils that generate magnetic fields in mutually opposite directions are thus arranged. The astigmatism of the irradiation area 33 can be corrected by the astigmatism correction coil 30b. Note that an electrostatic astigmatism corrector may be used instead of an electromagnetic astigmatism corrector such as the astigmatism correction coil 30b.

The deflection correction coil 30c is, for example, a quadrupole saddle type coil 52 as shown in FIG.
A to 52D are arranged at equal angular intervals around the optical axis to generate a magnetic field in the same direction between each pair of coils facing each other. In FIG. 3B, the opposing coils 52A,
A magnetic field in the same direction is generated between 52C as shown by an arrow 53, and a magnetic field in the same direction is generated between other opposing coils. The position of the irradiation area 33 in the X and Y directions can be corrected by the deflection correction coil 30c. An electrostatic deflector may be used instead of the electromagnetic deflector such as the deflection correction coil 30c.

The rotation correction coil 30d is, for example, a spiral air core coil long in the optical axis direction, and the rotation angle of the irradiation area 33 can be corrected by the rotation correction coil 30d. The correction amounts of the focus correction coil 30a, the astigmatism correction coil 30b, the deflection correction coil 30c, and the rotation correction coil 30d are determined by the main controller 19 via the deflection correction amount setting unit 25 for each small area on the mask 1. It is configured so that it can be set to.

The electron beam EB that has passed through the mask 1 is deflected by a predetermined amount by a deflector 13A composed of a two-stage electromagnetic deflector, and once connected to a crossover CO by a projection lens 14, and then passed through an objective lens 15. The pattern is focused on the wafer 5 on which the electron beam resist is applied, and a pattern in one small area of the mask 1 is formed at a predetermined position on the wafer 5 by a predetermined reduction ratio β.
An image reduced by (for example, 1/4) is transferred. The projection lens 14 and the objective lens 15 of this example constitute an imaging system of a symmetric magnetic doublet (SMD) system, and an aperture stop 32 is arranged at a position where a crossover CO is formed. . Also, the objective lens 1
A deflector 13B composed of a two-stage electromagnetic deflector is also arranged between the vicinity of the wafer 5 and the wafer 5, and the amount of deflection in the deflectors 13A and 13B is set by the main controller 19 via a deflection amount setting device 26. I do. In the split transfer method, each small area on the mask 1 is arranged with a strut in between, while each small area on the corresponding wafer 5 is arranged closely, so that the deflectors 13A, 13B is used to shift the electron beam laterally by the amount of the strut, and to correct a synchronization error between the mask 1 and the wafer 5.

Further, a backscattered electron detector 29 for detecting electrons from the wafer side is disposed near the bottom surface of the objective lens 15, and a backscattered electron signal RE from the backscattered electron detector 29 is supplied to the main controller 19. ing. Then, the mask 1 is mounted on the mask stage 16 in parallel with the XY plane. The mask stage 16 is continuously moved in the X direction by the driving device 17 and is stepwise moved in the Y direction. The position of the mask stage 16 in the XY plane is detected by the laser interferometer 18 and output to the main controller 19.

On the other hand, the wafer 5 is held on a wafer stage 21 on a sample stage 20 in parallel with the XY plane. The wafer stage 21 can be continuously moved by the driving device 22 in the direction opposite to the direction of continuous movement of the mask stage 16 along the X axis, and can be step-moved in the Y direction. The direction opposite to the X direction is because the mask pattern image is inverted by the lenses 14 and 15. Wafer stage 21
Are detected by the laser interferometer 23 and output to the main controller 19.

The main controller 19 controls the visual field selection deflectors 12A, 12A based on the exposure data input from the input device 24 and the position information of the mask stage 16 and the wafer stage 21 detected by the laser interferometers 18, 23. 12B and the amount of deflection of the electron beam EB by the deflectors 13A and 13B, and the mask stage 16 and the wafer stage 2
The information (for example, the position and the moving speed) necessary for controlling the operation 1 is calculated. The calculation result of the deflection amount is output to the deflection correction amount setting device 25 and the deflection amount setting device 26, and these setting devices use the field-of-view selection deflectors 12A and 12A, respectively.
B and the amount of deflection by the deflectors 13A and 13B are set. Further, the illumination characteristic correction system 30 is driven via the deflection correction amount setting device 25 in accordance with the amount of deflection of the electron beam EB from the optical axis AX by the field-of-view selection deflectors 12A and 12B, so that the electron beam on the mask 1 is Is controlled so that the shape and the like of the irradiation area 33 are always constant.

The calculation results relating to the operations of the mask stage 16 and the wafer stage 21 are output to drivers 27 and 28, respectively. The drivers 27 and 28 operate the driving device 1 so that the stages 16 and 21 operate according to the calculation results.
7 and 22 are controlled. As the input device 24, a device for reading magnetic recording information created by an exposure data creating device, a device for reading exposure data registered in the mask 1 and the wafer 5 when these are loaded, and the like may be appropriately selected.

Next, referring to FIGS. 2 and 6, the pattern arrangement of the mask 1 of this embodiment and the arrangement of the corresponding transferred image on the wafer 5 will be described. FIG. 2 is a perspective view showing the correspondence between the mask 1 and the wafer 5 of the present example. In FIG. 2, the mask 1 is rectangular with a predetermined pitch in the X direction and the Y direction by struts 3 as boundary regions. Are divided into a number of small areas 2A, 2B, 2C,..., And the electron beam EB is applied to the irradiation area 33 in the small area to be transferred (small area 2A in FIG. 2).
Is irradiated.

FIG. 6 shows a small region 2A,
One small area 2 representing 2B, 2C,... Is shown. In FIG. 6, an electron beam transmitting portion corresponding to a pattern to be transferred is provided in a rectangular pattern forming area 34 inside the small area 2. The skirt region 35 between the contour of the pattern forming region 34 and the strut 3 and the strut 3
These are regions that block or diffuse an electron beam, respectively. In addition,
As a mask 1 for electron beam transfer, silicon nitride (Si
N) or the like, a so-called scattering mask in which a transparent portion of an electron beam is formed by a thin film such as N) and a scattering portion made of tungsten is appropriately provided on the surface thereof, and a hole formed in a scattering portion made of silicon (Si) are formed in the thin film. There is a so-called perforated stencil mask or the like serving as a transmission portion, but any of them may be used in this example.

When the pattern in the small area 2 is transferred, an electron beam is applied to a rectangular irradiation area 33 covering the pattern forming area 34. In this case, in this example, the mask 1 is moved by the mask stage 16 in, for example, the -X direction indicated by the arrow A. However, in this example, the illumination characteristic correction system 30 of FIG.
Is provided, even if the small region 2 is located at a position distant from the optical axis AX, the shape of the irradiation region 33 is corrected by correcting the shift of the focal position, astigmatism, the shift of the position, and the change of the rotation angle. Is a shape obtained by accurately projecting an opening in the aperture plate 31 of FIG.
Is maintained in a rectangular shape with a margin of a predetermined width outside. Therefore, the skirt region 35 around the pattern forming region 34
It is not necessary to have that much time. Therefore, as compared with the case where a mask having a large skirt region is used as in the related art, if a mask pattern having the same area is transferred, the size of the mask 1 can be reduced as a whole.

Returning to FIG. 2, the electron beam EB that has passed through the small area 2A on the mask 1 passes through the projection lens 14 and the objective lens 15 of FIG.
And the reduced image of the pattern in the small area 2A is
The image is projected on the small transfer area 7A. At the time of transfer, the irradiation of the electron beam EB is repeated for each of the small areas 2A, 2B, 2C,.
Are sequentially transferred to different upper small transfer areas 7A, 7B, 7C,. At this time, by driving the deflectors 13A and 13B of FIG. 1 to shift the electron beam EB laterally by the width of the strut 3 separating each small region, the small transfer regions 7A, 7B, 7C, Are arranged without gaps.

Next, the overall operation in the case of transferring the pattern of the mask 1 in this embodiment will be described. First, in this example, the mask stage 16 is controlled under the control of the main controller 19.
And via the wafer stage 21 as shown in FIG.
The wafer 5 is moved in the + X direction at a speed VW in synchronization with the continuous movement (mechanical scanning) of the mask 1 at a predetermined speed VM in the -X direction.
To move continuously. Using the reduction ratio β of the projection lens 14 and the objective lens 15 from the mask to the wafer in FIG. 1, the width in the X direction of the pattern forming region 34 in each small region on the mask 1 is L1, and the width of the pattern forming region 34 is The distance in the X direction is L2
Then, the speed VW of the wafer 5 is expressed by the following equation.

VW = β · {L1 / (L1 + L2)} · VM (1) Then, in many small areas on the mask 1, the optical axis AX
The electron beams are sequentially transmitted to a plurality of small regions (small regions 2A, 2B,... In FIG. 2) arranged in a line in the Y direction reaching a position crossing the position through the visual field selection deflectors 12A and 12B in FIG. The EB is radiated, and the pattern in each small area is sequentially set on the wafer 5.
Is transferred without gaps in the transfer area 6A for one die. Then, as the mask 1 and the wafer 5 move in the X direction, the operation of sequentially transferring the patterns in the plurality of small areas in a row reaching the position crossing the optical axis AX onto the wafer 5 is repeated. When the pattern in all the small areas on the mask 1 is transferred onto the wafer, the transfer of the pattern to the transfer area 6A on the wafer 5 ends. Thereafter, the pattern of the mask 1 is similarly transferred to another transfer region 6B for one adjacent die on the wafer 5.

At this time, as shown in FIG. 6, in this example, the shape of the electron beam irradiation area 33 is constant regardless of the amount of deflection of the small area 2 on the mask 1 from the optical axis AX. The skirt area 35, which is a useless area in the small area 2 of the mask 1, is reduced, and the mask 1 is downsized. Therefore, there is an advantage that the mask stage 16 of FIG. 1 can be reduced in size and the manufacturing cost of the entire apparatus can be reduced. Furthermore, if the shape of the irradiation area 33 is constant, the current density is also constant, and therefore, the exposure amount unevenness on the wafer 5 is eliminated.

In order to correct the shape and the like of the irradiation area 33 via the illumination characteristic correction system 30 as described above, the irradiation area 3 is adjusted according to the distance of the irradiation area 33 from the optical axis AX.
It is necessary to measure the shape and the like of No. 3. Therefore, an example of a method for measuring the shape and the like of the electron beam irradiation area 33 on the mask 1 will be described. Here, assuming that the aberration of the imaging system including the projection lens 14 and the objective lens 15 is negligible, the shape of the projection image of the irradiation area 33 onto the wafer 5 is measured.

Therefore, as shown in FIG. 4, a reference pattern 54 made of a rectangular thin film of tantalum (Ta) for reflecting an electron beam is formed on a part of the silicon wafer by using a part of the silicon wafer. It is formed. The reference member on which the reference pattern 54 is formed is fixed on the wafer stage 21 in FIG. In FIG. 1, with the mask 1 removed, the visual field selection deflectors 12A, 12B
The electron beam irradiation area 33 is set at a position away from the optical axis AX by a predetermined amount via the. Next, the wafer stage 21 is driven, and an edge 54a in the + Y direction of the reference pattern 54 in FIG. 4 is arranged at a position conjugate with the center of the irradiation region 33 in the Y direction in terms of design.

Thereafter, as shown by the arrows in FIG. 4, the deflectors 13A and 13B shown in FIG.
Is scanned in the Y direction so as to cross the edge 54a, and the main controller 19 captures the reflected electron signal RE from the backscattered electron detector 29 in FIG. Further, a conversion coefficient for converting the amount of deflection of the image 33 by the deflectors 13A and 13B into a displacement y on the Y coordinate is obtained in advance, and the reflected electron signal RE is stored as a function of the displacement y of the image 33. The origin of the displacement y is a position where the amount of deflection by the deflectors 13A and 13B is zero.

FIG. 5A shows the reflected electron signal RE thus stored as a function of the displacement y, and by differentiating the reflected electron signal RE with the displacement y, as shown in FIG. , A differential signal dRE / dy that changes greatly at the position of the edge in the Y direction of the image 33W of the irradiation area is obtained.
Then, when the width DY of the region where the differential signal dRE / dy exceeds a predetermined threshold value and the displacement ΔY of the center of the region are obtained, the width DY is the width of the image 33W of the irradiation region in the Y direction, and the displacement ΔY is , The amount of displacement in the Y direction from the designed position of the center of the image 33W. Similarly, by using the edge of the reference pattern 54 in the X direction, the width in the X direction of the image 33W of the irradiation area and the amount of displacement can be measured. Then, the shape and position of the irradiation area 33 to be measured can be obtained from these measurement results and the reduction ratio β from the mask to the wafer.

Also, for example, while operating the focus correction coil 30a in the illumination characteristic correction system 30 of FIG. 1 to shift the focus position of the irradiation area 33, the differentiation of the image 33W of the irradiation area as shown in FIGS. When the signal dRE / dy is measured, the rising and falling edges of the waveform become sharpest when the irradiation area 33 is at the best focus position, so that the correction amount of the focus correction coil 30a can be determined. Similarly, when the rotation correction coil 30d is operated to shift the rotation angle of the irradiation area 33 and the differential signal dRE / dy of the image 33W of the irradiation area is measured as shown in FIGS. When the edge of the image 33W is parallel to the edge of the reference pattern 54, the rising and falling edges of this waveform are sharpest, so that the amount of correction by the rotation correction coil 30d can be determined.

Next, another example of the embodiment of the present invention will be described with reference to FIGS. In this embodiment, the present invention is applied to an electron beam reduction transfer apparatus of a split transfer system and a half-shadow overlap transfer system. In this example, the electron beam reduction transfer device shown in FIG. 1 is used almost as it is, but the aperture plate 31 is disposed on a surface defocused by a predetermined amount from the conjugate surface with the mask 1. Further, the pattern arrangement of the mask and the transfer method are different. The following mainly describes the differences.

First, FIG. 7A shows a mask 1A used in this embodiment. In FIG. 7A, a large number of masks 1A are also formed at predetermined pitches in the X and Y directions by struts 3 as boundary regions. The pattern to be transferred is formed in a pattern forming area (effective pattern area) 36 in the small area 2 which is divided into the small areas 2. However, in this example, since the transfer is performed by the penumbra overlay transfer method, the pattern formation region 3
An image of the opening of the aperture plate 31 in FIG. 1 is projected on an electron beam irradiation area 37 having the same size as 6. In other words, the contour of the pattern formation region 36 is substantially defined by the electron beam irradiation region 37. Then, an area of a predetermined width (hereinafter, referred to as an area) inside the contour of the pattern formation area 36.
In the emissive area 36e), the intensity distribution of the electron beam decreases almost linearly, and the intensity is 0 at the contour.

That is, FIG. 7B shows an electron beam intensity distribution E along the Y direction at the center of the irradiation area 37 in FIG. 7A.
FIG. 7C shows the irradiation area 37 of FIG.
Intensity distribution E (X) of the electron beam along the X direction at the center of
As shown in FIGS. 7B and 7C, the electron beam intensity distributions E (X) and E (Y) decrease linearly in the regions 38X and 38Y respectively corresponding to the penumbra region 36e. Therefore, the distribution is trapezoidal. As an example, if the pattern formation area 36 is 1 mm square, the penumbra area 36
The width of e is about 0.1 mm.

Also in this example, in FIG.
A moves in the −X direction indicated by arrow A, for example. At this time, it is desirable to move the electron beam irradiation area 37 in the −X direction via the visual field selection deflectors 12A and 12B in FIG. Also in this example, regardless of the amount of deflection of the small region on the mask 1A from the optical axis, the shape, position, current density, etc. of the irradiation region 37 on the small region are determined by the illumination characteristic correction system 30 of FIG. Keep constant. Therefore, the pattern formation region 36 or the irradiation region 37 can be extended substantially over the entire small region 2, and the region (also called the “skirt region”) 38 between the pattern formation region 36 and the strut 3 can be almost ignored. As a result, the mask 1A
Can be reduced in size.

Further, the mask 1A shown in FIG.
In the penumbra area 36e of the pattern formation area 36, the same pattern as that of the penumbra area of the adjacent small area overlaps. The duplication of this pattern will be described with reference to FIG. FIG. 8 shows a plurality of small areas of the mask 1A of the present example. In FIG. 8, the pattern forming area 36M in the central small area 2M is left and right and up and down, respectively,
6Ma, 36Mb, 36Md, and 36Mc are set. In the left half (+ Y direction) penumbra area 36Ma, a pattern formation area 36L in a small area adjacent to the left side is formed.
The same pattern as that in the right penumbra area 36Lb is formed in the right penumbra area 36Mb, and in the right penumbra area 36Mb, the left penumbra area 36N in the pattern formation area 36N in the small area adjacent to the right.
The same pattern as in Na is formed. Similarly, the penumbra area 36 above and below (X direction) the pattern formation area 36M.
Md and 36Mc respectively include penumbra areas 36T of pattern formation areas 36T and 36G in vertically adjacent small areas.
The same pattern as in Tc and 36Gd is formed.

Then, the mask pattern shown in FIG.
When transferred onto the upper surface, the patterns of the pattern forming regions 36L to 36N, 36T, and 36G in the small region on the mask 1A are respectively transferred to the small transfer regions 7L to 7N,
It is transferred into 7T and 7G. In this case, the small transfer area 7L
7N, 7T, and 7G are arranged such that the patterns of the penumbra area (36 Ma or the like) in FIG. 8 overlap each other. That is,
Taking the small transfer region 7M corresponding to the small region 2M in FIG. 8 as an example, a contour portion 7M having a predetermined width on the right side of the small transfer region 7M in FIG.
The pattern of the penumbra areas 36Ma and 36Lb in FIG. 8 is duplicated and transferred to a, and the pattern of the penumbra areas 36Mb and 36Na is duplicated and transferred to the left contour 7Mb. Similarly, the upper and lower contour portions 7 of the small transfer area 7M in FIG.
Mc and 7Md respectively have a penumbra area 36M in FIG.
The patterns of c, 36Gd and the penumbra areas 36Md, 36Tc are transferred in an overlapping manner.

As described above, in this example, in each of the small transfer areas 7L, 7M,... On the wafer 5, the pattern on the mask corresponding to the outline is transferred in an overlapping manner. The joint error is reduced as compared with. In addition, as shown in FIG. 7, since the intensity of the electron beam irradiation area 37 on the mask 1A is linearly reduced in the penumbra area, the exposure amount in the overlapping portion on the wafer 5 is reduced in other parts. And there is no unevenness in exposure. Furthermore, since the shape and the like of the irradiation area 37 are constant, the connection (contour) between the small transfer areas on the wafer 5 is smooth, and a desired pattern can be obtained with high accuracy. Further, the intensity distribution of the electron beam in the pattern formation area 36 in the small area 2 is always constant, and the exposure amount does not become uneven even on the wafer 5.
Transfer is always performed at a high resolution.

It is apparent that the present invention can be applied not only to an electron beam transfer apparatus but also to a transfer apparatus using an ion beam or the like. As described above, the present invention is not limited to the above-described embodiment, and can take various configurations without departing from the gist of the present invention.

[0046]

According to the charged particle beam transfer apparatus of the present invention,
Since the illumination characteristic correction means for correcting the variation of the illumination characteristic related to the cross-sectional shape of the charged particle beam irradiated to each small area on the mask from the optical axis of the charged particle beam is provided, the division is performed. When the mask pattern is transferred by the transfer method, there is an advantage that the illumination characteristics such as the shape of the irradiation area of the charged particle beam with respect to each small area on the mask can be made constant irrespective of the amount of deflection from the optical axis. As a result, the skirt region of each small region on the mask can be narrowed, and the size of the mask and the mask stage can be reduced. Further, it is possible to prevent the occurrence of a pattern that is not partially transferred, and to reduce the unevenness of the exposure amount.

An imaging system in which a deflection illumination system for selecting a visual field focuses and deflects a charged particle beam passing through an aperture of a predetermined shape, thereby sequentially forming an image of the aperture on a small area on the mask. In the illumination system, the variation of the illumination characteristics according to the amount of deflection from the optical axis of the charged particle beam, the shift of the focal position of the image of the aperture, astigmatism,
In the case of at least one of a rotation error and a position error, there is an advantage that these variations in the illumination characteristics can be easily and individually corrected by an electromagnetic or electrostatic corrector.

Next, the intensity distribution at the contour of the cross-sectional shape of the charged particle beam irradiated to the small area on the mask via the deflection illumination system for selecting the field of view is monotonously reduced outward. When the image of the pattern in the small area with respect to the substrate to be transferred is set to overlap with the image of the adjacent pattern and the contour portion, the transfer is performed by the semi-shadow overlay transfer method. At this time, the illumination characteristic correction means makes the illumination characteristics such as the shape of the irradiation region of the charged particle beam with respect to each small region on the mask constant without depending on the amount of deflection from the optical axis, so that it can be displayed on the substrate. There is an advantage that the joint between the images of the patterns in each of the small areas can be made smooth and the unevenness of the exposure amount on the substrate can be reduced.

In these cases, the use of an electromagnetic compensator or an electrostatic compensator as the illumination characteristic correcting means has the advantage that the illumination characteristics can be easily corrected with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an electron beam reduction transfer apparatus as an example of an embodiment of a charged particle beam transfer apparatus according to the present invention.

FIG. 2 is a perspective view showing an arrangement of small areas on a mask 1 of FIG. 1 and a corresponding arrangement of a small transfer area on a wafer 5;

3A is a perspective view illustrating an example of an astigmatism correction coil 30b in the illumination characteristic correction system 30, and FIG. 3B is a perspective view illustrating an example of a deflection correction coil 30c.

FIG. 4 is an explanatory diagram of a method of measuring a shape of an irradiation area of an electron beam on a mask.

FIG. 5A is a diagram showing a backscattered electron signal RE obtained when an image of an irradiation area is scanned with respect to a reference pattern;
(B) is a diagram showing a differential signal of the reflected electron signal RE.

FIG. 6 is an enlarged plan view showing a pattern forming region and an electron beam irradiation region in a typical small region 2 on the mask 1 of FIG.

FIG. 7 is a diagram showing a pattern forming region, an electron beam irradiation region, and the like in a representative small region on a mask 1A used in another example of the embodiment of the present invention.

FIG. 8 shows a mask 1 used in another example of the embodiment.
FIG. 3 is an enlarged plan view showing a plurality of small areas in A.

9 is an enlarged plan view showing a plurality of small transfer regions on the wafer 5 corresponding to the plurality of small regions of the mask 1A in FIG.

FIG. 10A is an enlarged plan view showing a small area of a mask used in a conventional split transfer type electron beam reduction transfer apparatus,
FIG. 11B is a sectional view taken along the line AA in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mask 2, 2A, 2B, 2C Small area 3 Strut 5 Wafer 7A, 7B, 7C Small transfer area 12A, 12B Field selection deflector 13A, 13B Deflector 14 Projection lens 15 Objective lens 16 Mask stage 19 Main control unit 21 Wafer Stage 25 Deflection correction amount setting device 26 Deflection amount setting device 33 Electron beam irradiation area 34 Pattern formation area 37 Electron beam irradiation area

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location H01L 21/30 541V

Claims (4)

[Claims] 1. A mask having a pattern to be transferred divided into a plurality of small areas separated from each other is sequentially provided with a predetermined cross section in units of said small areas via a deflection illumination system for selecting a field of view. The pattern to be transferred onto the substrate is irradiated by irradiating a charged particle beam having a shape, and transferring the image of the pattern in the small area by an imaging system so as to substantially contact each other on the substrate to be transferred. A charged particle beam transfer device for transferring an image of the charged particle beam, wherein the deflection characteristics of the charged particle beam are applied to the small area on the mask by the deflection illumination system for selecting the field of view. A charged particle beam transfer apparatus comprising an illumination characteristic correction unit for correcting a variation according to a deflection amount from an axis. 2. The charged particle beam transfer apparatus according to claim 1, wherein the deflection illumination system for selecting a visual field focuses and deflects the charged particle beam that has passed through an aperture having a predetermined shape, thereby forming the mask. An imaging system illumination system that sequentially forms an image of the aperture on the small area above, wherein the variation of the illumination characteristics according to the amount of deflection from the optical axis of the charged particle beam is the image of the aperture. Shift of the focal position of
At least one of astigmatism, rotation error, and position error
A charged particle beam transfer device, comprising: 3. The charged particle beam transfer device according to claim 1, wherein a cross section of the charged particle beam irradiated on the small area on the mask via the deflection illumination system for selecting a field of view. The intensity distribution at the contour of the shape is set to decrease monotonically outward, and the image of the pattern in the small region with respect to the substrate overlaps the image of the adjacent pattern with the contour. Charged particle beam transfer device. 4. The charged particle beam transfer device according to claim 1, wherein the illumination characteristic correction means is an electromagnetic corrector or an electrostatic corrector. apparatus.