JPH07183193A - Charged particle beam transfer device - Google Patents

Abstract

PURPOSE:To make it possible to minimize the effect of strain aberration and transfer with high accuracy by deviating a projection lens on a mask side by a specified amount out of a pair of projection lenses and deviating a projection lens on a sample side to the sample side for installation. CONSTITUTION:A pair of projection lenses 10 and 11 projects electron beams passing through a mask 8 with a reduction scale of 1/4 and allow the beams to pass through the opening of an aperture 12 and form an image on a wafer 14 loaded on a wafer stage 13. The aperture 12 is installed at a position at which the optical axial directions of the wafer 14 and the mask 8 are proportionally divided at a reduction ratio of the projection lenses 10 and 11. The projection lens 10 is installed at a position deviated by 12mm in the optical axial direction from the middle between the aperture 12 and the wafer 14. This construction makes it possible to reduce the effect of strain aberration produced when the projection lens is adjusted and transfer a transfer pattern with high accuracy.

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, and more particularly to a charged particle beam transfer apparatus which realizes high accuracy and high throughput.

[0002]

2. Description of the Related Art As a charged particle beam transfer apparatus, an electron beam reduction transfer apparatus, an ion beam reduction transfer apparatus and the like are known, and either of them is the subject of the present invention. Will be described as an example. The electron beam reduction transfer device was configured as follows. That is, the pattern to be transferred onto the wafer is divided into a plurality of areas to be transferred by one irradiation of the electron beam, and is formed on the mask. Irradiation of the electron beams to the plurality of regions has been performed by continuous movement in one direction of the mask stage on which the mask is mounted and deflection around the optical axis of the deflector which is interlocked with this continuous movement. Then, the electron beam transmitted through the mask was applied to a predetermined position on the photosensitive member as follows.
That is, the electron beam is reduced according to the projection ratio of the pair of projection lenses, passes through the aperture of the aperture, and the sample stage on which the photosensitive member is placed is in the opposite direction to the mask stage.
The mask stage is continuously moved at a speed obtained by multiplying the moving speed of the mask stage by the projection ratio of the projection lens. As a result, the electron beam transmitted through the mask was radiated to a predetermined position on the photosensitive member.

The above-mentioned aperture has been arranged at a position that takes into account the optical axis direction of the photosensitive member and the mask by the reduction ratio of the pair of projection lenses. In addition, the projection lens disposed on the mask side of the pair of projection lenses is disposed such that the main surface of the lens is located at an intermediate position between the mask and the aperture. Among the pair of projection lenses, the projection lens arranged on the photosensitive member side is arranged so that the main surface of the lens is located at an intermediate position between the aperture and the wafer.

[0004]

However, there is no problem when transferring a pattern of a mask near the optical axis (the deflection amount of the deflector is small), but it is far from the optical axis (the deflection amount of the deflector is large). When transferring the pattern, there is a problem that spherical aberration generated by the pair of projection lenses becomes large. In addition, if the pair of projection lenses are adjusted so as to correct this spherical aberration, there is a problem that distortion aberration occurs and the transfer accuracy deteriorates.

In order to solve the above problems, the distance from the mask of the electron optical system to the photosensitive member in the optical axis direction is increased, or the pattern area of the mask is decreased to reduce the deflection amount of the deflector. Was being transcribed. Therefore, there are problems that the lens barrel of the electron optical system becomes large and the throughput decreases.

Therefore, it is an object of the present invention to provide a charged particle beam transfer apparatus capable of transferring accurately without being affected by aberration even when a pattern of a mask far from the optical axis is formed on a photosensitive member. .

[0007]

To solve the above problems, an explanation will be given in association with FIG. 1 showing an embodiment.
In the charged particle beam transfer apparatus according to claim 1, an irradiation optical system (1 to 4, 6, for sequentially irradiating a charged particle beam emitted from a charged particle beam source (1) onto a mask (8) having a transfer pattern.
7) and the charged particle beam transmitted through the mask (8) to the sample (1
4) Projection onto the pair of projection lenses (10, 11) arranged on the optical axis and between the sample (14) and the mask (8). In a charged particle beam transfer apparatus including an aperture (12) arranged at a position proportional to the ratio, a main surface of the projection lens (10) of the pair of projection lenses (10, 11) is masked ( 8) and the aperture (12) are displaced from the intermediate position on the mask (8) side by a predetermined amount, and the projection lens (1)
The main surface of 1) is arranged on the side of the sample (14) from the intermediate position between the aperture (12) and the sample (14) by an amount obtained by adding the projection ratio to the predetermined amount.

Further, in the charged particle beam transfer apparatus according to the second aspect, the charged particle beam which has passed through the transfer pattern in the vicinity of the peripheral portion of the mask (8) forms a crossover at substantially the center of the aperture (12), Moreover, a pair of projection lenses (10, 11) are arranged so as to be shifted so as to form an image on the sample (14). Further, in the charged particle beam transfer apparatus according to claim 3, the mask (8) comprises a pair of deflectors (7) for deflecting the charged particle beam emitted from the charged particle beam source (1) from the optical axis.
a, 7b), and when irradiating the transfer pattern on the optical axis side of the vicinity of the peripheral portion, the deflection angle of the deflector (7a) on the charged particle beam source (1) side is set on the mask (8) side. It is set larger than the deflection angle of the deflector (7b).

[0009]

In the present invention, of the pair of projection lenses (10, 11), the projection lens (10) on the mask (8) side is arranged so as to be displaced by a predetermined amount toward the mask (8) side, and the pair of projection lenses (10) The projection lens (11) on the sample (14) side is arranged so as to be shifted to the sample (14) side by an amount obtained by integrating the projection ratios of the projection lenses (10, 11). As a result, the influence of the distortion aberration when the pair of projection lenses (10, 11) is adjusted so as to correct the spherical aberration can be reduced, so that highly accurate transfer can be performed.

Further, the charged particle beam transmitted through the transfer pattern near the peripheral portion of the mask (8) is changed to the aperture (12).
Form a crossover at approximately the center of the
4) A pair of projection lenses (10, 1) for focusing on
When the arrangement 1) is shifted, the transfer pattern in the vicinity of the peripheral portion can be transferred with high accuracy. When the transfer pattern on the optical axis side of the vicinity of the peripheral portion is irradiated, the deflection angle of the deflector (7a) on the charged particle beam source (1) side is set to the mask (8).
By making the deflection angle of the side deflector (7b) larger than that of the other side, the transfer pattern on the mask on the optical axis side of the vicinity of the peripheral portion can be transferred with high accuracy.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a schematic diagram of an electron beam reduction transfer apparatus of the present invention. In FIG. 1, the first condenser lens 2 is
The size of the crossover of the electron beam emitted from the electron gun 1 is adjusted, and the electron beam is allowed to pass through the opening of the aperture 3. The second condenser lens 4 adjusts the position where the crossover 5 of the electron beam that has passed through the opening of the aperture 3 is formed. The third condenser lens 6 turns the electron beam forming the crossover 5 into a parallel light beam, and the pair of deflectors 7 including the deflector 7a and the deflector 7b deflects this parallel light beam from the optical axis.

The mask 8 has a transfer pattern, and the transfer pattern is divided into a plurality of areas to be transferred by one irradiation of the electron beam. In this embodiment, there is a transfer pattern area within a radius of 40 mm from the center of the mask 8 (on the optical axis). By the deflection of the deflector 7 and the continuous movement of the mask stage 9 on which the mask 8 is placed in the Y direction in FIG. 1, the electron beam can be sequentially irradiated onto the transfer pattern area on the mask 8.

The pair of projection lenses 10 and 11 includes a mask 8
The electron beam transmitted through is projected in a reduced size of 1/4, passes through the aperture of the aperture 12, and is imaged on the wafer 14 mounted on the wafer stage 13. The aperture 12 is arranged at a position where the optical axis direction between the wafer 14 and the mask 8 is divided by the reduction ratio of the projection lenses 10 and 11. In this embodiment, the reduction ratio of the projection lenses 10 and 11 is 1.
Therefore, the aperture 12 is arranged at a position where the optical axis direction between the wafer 14 and the mask 8 is divided by 1: 4.

Further, the projection lens 10 is arranged so that the main surface of the lens is located at a position displaced from the middle of the mask 8 and the aperture 12 by 12 mm toward the mask 8 in the optical axis direction. The projection lens 11 is mounted on the wafer 14 by 4 mm in the optical axis direction from the center between the aperture 12 and the wafer 14.
It is arranged so that the main surface of the lens is located at a position displaced to the side.

FIG. 2 shows an excitation condition (dotted line) for forming a crossover at the center of the aperture 12 by the pair of projection lenses 10 and 11 for the electron beam transmitted through the mask 8 and the wafer 1.
4 is a diagram showing an excitation condition (solid line) for forming an image on FIG.
In the figure, the vertical axis represents the exciting current applied to the projection lenses 10 and 11, the horizontal axis represents the distance between the optical axis and the mask 8, and the pattern in which the horizontal axis is 0 is on the optical axis. Is.

In FIG. 2, when α = 0, the conventional arrangement of a pair of projection lenses 10 and 11 is used.
The main lens surface of the projection lens 11 is disposed in the middle of the mask 8 and the aperture 12, and the main lens surface of the projection lens 11 is set to the aperture 1
2 and the wafer 14 are arranged in the middle. In the present embodiment, when α = 12, the lens main surface of the projection lens 10 is arranged so as to be displaced from the middle of the mask 8 and the aperture 12 by 12 mm toward the mask 8 side. The lens main surface of the projection lens 11 is arranged so as to be shifted to the wafer 14 side by an amount obtained by adding a projection ratio to an amount obtained by shifting the lens main surface of the projection lens 10 from the middle of the aperture 12 and the wafer 14.
That is, since the projection ratio is 1/4, the wafer 14
It is arranged to be shifted to the side.

The case where α = 13 is a modification described later, and
The lens main surface of the projection lens 10 is displaced from the center between the mask 8 and the aperture 12 by 13 mm toward the mask 8 side, and the lens main surface of the projection lens 11 is moved from the center between the aperture 12 and the wafer 14 toward the wafer 14 side by 3.25 mm. They are arranged in a staggered manner. A pair of projection lenses 1 of this embodiment
In the arrangements of 0 and 11, the excitation condition for forming the crossover and the condition for forming an image on the wafer 14 coincide with each other in the transfer pattern region 30 mm away from the optical axis.

Since the light beam transmitted through the mask 8 is inverted by the projection lenses 10 and 11, the wafer stage 13 continuously moves in the direction opposite to the mask stage 9. The position correction deflector 15 corrects the position of the electron beam imaged on the wafer 14 by deflecting the electron beam transmitted through the mask 8. The CPU 16 performs various calculations for transferring the transfer pattern on the mask 8 onto the wafer 14, and also performs electron optical system (electron gun 1, lenses 2, 4, 6, 10, 11,
It controls the deflectors 7 and 15) and the stage driving device 17.

The stage driving device 17 controls the mask stage 9 and the wafer stage 13 so as to synchronize with each other via a motor (not shown). The operation of the electron beam reduction transfer device configured as described above will be described below. Figure 3 CPU
16 is a flowchart of FIG. 16, and the transfer operation of this embodiment will be described below using this flowchart.

The CPU 16 recognizes the irradiation position on the mask 8. (Step 101) Here, the pattern area on the mask 8 which is 40 mm away from the optical axis is recognized as the next irradiation position. CPU16
Adjusts the electron optical system so as to transfer the pattern area on the mask 8 which is 40 mm away from the optical axis. (Step 1
02) Next, the CPU 16 performs transfer. (Step 103) That is, the pair of deflectors 7 deflects the electron beam so as to irradiate the pattern area on the mask 8 which is 40 mm away from the optical axis. That is, the deflector 7a deflects so that the deflection angle becomes large, and the deflector 7b deflects at the same deflection angle in the opposite direction so as to cancel the deflection angle of the deflector 7a. As a result, the electron beam irradiating the mask 8 becomes a substantially parallel light beam.

An electron beam transmitted through a pattern area on the mask 8 40 mm away from the optical axis is reduced to 1/4 by the projection lenses 10 and 11 and transferred onto the mask by the continuous movement of the mask stage 9 described above. . The projection lenses 10 and 1
In No. 1, the exciting current is set so as to form an image on the wafer 14 in order to correct the spherical aberration. That is, as shown in FIG. 2, an exciting current corresponding to a position 40 mm away from the (α = 12) optical axis is applied to the projection lenses 10 and 11. Therefore, an exciting current smaller than the exciting current for forming the crossover at the center of the aperture 12 is flowing through the pair of projection lenses, so that the crossover is on the optical axis on the wafer 14 side from the center of the aperture 12. It is formed. This causes distortion, but
As compared with the conventional case, the displacement of the position where the crossover is formed is smaller, so that the amount of distortion aberration is small and transfer is possible. This makes it possible to accurately transfer the transfer pattern area far from the optical axis.

Next, the case of transferring a transfer pattern region in the vicinity of the optical axis 10 mm away from the optical axis will be described. The transfer is started after the electron optical system is adjusted. That is, the deflector 7a deflects so that the deflection angle becomes smaller, and the deflector 7b deflects at the same deflection angle in the opposite direction so as to cancel the deflection angle of the deflector 7a. As a result, the electron beam irradiating the mask 8 becomes a substantially parallel light beam.

As described above, the electron beam transmitted through the pattern area on the mask 8 near the optical axis is projected onto the projection lenses 10 and 11.
Is reduced to 1/4 and is transferred onto the mask by the continuous movement of the mask stage 9 described above. The projection lens 10,
In 11, the exciting current is set so as to form an image on the wafer 14 in order to correct the spherical aberration. Therefore, as shown in FIG. 2, since an exciting current larger than the exciting current for forming the (α = 12) crossover in the center of the aperture 12 is flowing to the pair of projection lenses, the crossover is caused. , Is formed on the optical axis closer to the mask 8 than the center of the aperture 12. Further, the displacement of the position where the crossover is formed is larger than that in the conventional case, and the amount of distortion aberration is also large, but since the distortion aberration occurs in proportion to the cube of the distance from the optical axis, the optical axis The effect of distortion aberration in the vicinity is small. Therefore, the transfer pattern area on the mask 8 near the optical axis can be transferred without any problem. Therefore, the entire transfer pattern area can be transferred more accurately than in the past.

Next, a modified example of this embodiment will be described below. In this modification, only the positions where the projection lenses 10 and 11 are arranged are changed, and the other configurations are the same as those of the electron beam transfer apparatus of FIG. In the present modification, the main surface of the lens of the projection lens 10 is displaced by 13 mm from the middle position between the mask 8 and the aperture 13 toward the mask 8 side.
Along with this, the principal surface of the lens of the projection lens 11 is 3.25 m from the intermediate position between the aperture 13 and the wafer 16.
It is arranged so as to be shifted by m toward the wafer 16 side.

As shown in FIG. 2, in this modification (α = 13), at the position 40 mm away from the optical axis, the excitation condition for forming a crossover and the condition for forming an image on the wafer 14 match. Therefore, the vicinity of the peripheral portion on the mask 8 can be accurately transferred. In addition, as described above, the mask 8
Since the influence of distortion is small in the vicinity of the upper optical axis, the mask 8
The entire upper transfer pattern area can be accurately transferred.

Next, a second modification of this embodiment will be described below. The second modification has the same device configuration as that of this embodiment. FIG. 4 is a drawing showing the pair of deflectors 7 and below in FIG. 1, and the same reference numerals are given. A locus EB1 of the electron beam is a locus of the electron beam irradiating a position on the mask 8 which is 40 mm away from the optical axis, and is the same as the above-mentioned embodiment. The electron beam locus EB2 is a locus of the electron beam that irradiates a position on the mask 8 which is 40 mm away from the optical axis in the opposite direction to the electron beam locus EB1. The projection lenses 10 and 1
1 is supplied with a current that forms an image on the mask 8 when the trajectories EB1 and EB2 of either electron beam pass.

As shown in FIG. 2 (α = 12), the locus EB1 of the electron beam has a current value for forming the center of the crossover 12 that is larger than the current value for forming an image on the wafer 14. Therefore, the crossover is formed on the optical axis on the wafer 14 side with respect to the center of the aperture.
In the trajectory EB2 of the electron beam of this modification, the deflection angles of the deflectors 7a and 7b of the pair of deflectors 7 are adjusted as follows. That is, the deflector 7a makes the deflection angle smaller than that of the deflector 7b and irradiates the mask 8 which is 40 mm away from the optical axis. Therefore, the electron beam having an angle approaching the optical axis irradiates the mask 8. The position of the crossover formed by the electron beam that has passed through the mask 8 is closer to the optical axis of the center of the aperture than the locus EB1 of the electron beam. Thereby, the influence of distortion aberration can be further reduced.

When irradiating the transfer pattern area distant from the mask 8 on the optical axis where the excitation condition for forming the crossover and the condition for forming an image on the wafer 14 are the same, as described above. The deflection angle of the deflector 7a may be smaller than that of the deflector 7b. Also,
When irradiating a transfer pattern near the optical axis on the mask 8 on which the excitation condition for forming the crossover and the image forming condition on the wafer 14 are the same, the deflection angle of the deflector 7a is set to that of the deflector 7b. It suffices if the deflection is made larger than the deflection angle.

That is, since the electron beam having an angle away from the optical axis irradiates the mask 8, the position of the crossover formed by the electron beam transmitted through the mask 8 approaches the optical axis at the center of the aperture. There is. Thereby, the influence of distortion aberration can be further reduced. Even when a transfer pattern on the mask 8 in which the excitation condition for forming the crossover does not match the imaging condition on the wafer 14 is irradiated, the deflection angles of the deflectors 7a and 7b are adjusted as described above. By doing so, the influence of the distortion aberration can be further reduced, so that highly accurate transfer is possible. Further, as described above, by reducing the effects of spherical aberration and distortion,
Since the transfer pattern area on the mask 8 can be expanded, higher throughput than before can be realized.

[0030]

As described above, according to the present invention, in the present invention, of the pair of projection lenses, the projection lens on the mask side is arranged so as to be shifted to the mask side by a predetermined amount, and the projection lens on the mask side The projection lens on the sample side is arranged shifted to the wafer side by an amount obtained by integrating the projection ratio of the projection lens.
As a result, the influence of the distortion aberration generated when the pair of projection lenses is adjusted is reduced, so that the transfer pattern area can be transferred with high accuracy.

Further, the charged particle beam that has passed through the transfer pattern near the periphery of the mask forms a crossover at approximately the center of the aperture, and is arranged with the pair of projection lenses displaced so that it forms an image on the sample. When provided, the transfer pattern near the peripheral portion can be transferred with high accuracy. Further, when irradiating the transfer pattern area on the optical axis side from the vicinity of the peripheral portion, by setting the deflection angle of the deflector on the charged particle beam source side larger than the deflection angle of the mask side deflector, The transfer pattern area on the shaft side can be transferred with high accuracy.

Further, since the influence of the distortion aberration is reduced, the transfer pattern area on the mask can be expanded, and the throughput is also improved.

[Brief description of drawings]

FIG. 1 is an electron beam reduction transfer apparatus that is an embodiment of the present invention.

FIG. 2 is a diagram showing an exciting current that forms a crossover and an exciting current that forms an image on a wafer.

FIG. 3 is a flowchart of a CPU 16.

FIG. 4 is a diagram showing a second modification of the present invention.

[Explanation of symbols]

 1 Electron Gun 2 1st Condenser Lens 3, 12 Aperture 4 2nd Condenser Lens 6 3rd Condenser Lens 7 Deflector 8 Mask 10, 11 Projection Lens 14 Wafer

Claims (3)

[Claims] 1. An irradiation optical system for sequentially irradiating a mask having a transfer pattern with a charged particle beam emitted from a charged particle beam source, and projecting the charged particle beam transmitted through the mask onto a sample.
Charged particle beam comprising a pair of projection lenses arranged in the optical axis direction, and an aperture arranged between the sample and the mask at a position determined by the projection ratio of the pair of projection lenses In the transfer device, of the pair of projection lenses, the main surface of the projection lens on the mask side is arranged so as to be displaced from the intermediate position between the mask and the aperture to the mask side by a predetermined amount, and the projection lens on the sample side. The charged particle beam transfer apparatus is characterized in that the main surface of is shifted from the intermediate position between the aperture and the sample to the sample side by an amount obtained by integrating the projection ratio with the predetermined amount. 2. The charged particle beam transfer apparatus according to claim 1, wherein the charged particle beam that has passed through the transfer pattern in the vicinity of the peripheral portion of the mask forms a crossover at approximately the center of the aperture, and the sample. A charged particle beam transfer apparatus, wherein the pair of projection lenses are arranged so as to be shifted so as to form an image on the top. 3. The charged particle beam transfer apparatus according to claim 2, wherein the mask is sequentially irradiated with a pair of deflectors for deflecting a charged particle beam emitted from a charged particle beam source from an optical axis, and the peripheral portion. When irradiating the transfer pattern on the optical axis side from the vicinity, the deflection angle of the deflector on the charged particle beam source side is made larger than the deflection angle of the deflector on the mask side. .