JPH0778742A - Charged particle beam transfer device - Google Patents

Abstract

PURPOSE:To eliminate the necessity for correcting the conditions of capacitor lenses when small areas on a mask are selected. CONSTITUTION:An electron beam from an electron gun 1 is formed into parallel beams by capacitor lenses 2 and 3 and thereafter, the electron beam indicates one of small regions on a mask 7 by two-stage deflectors 4 and 5. The electron beam transmitted through the small region on the mask 7 forms a pattern of the small region on a photosensitive substrate 10 conjugated with the mask 7 by projection lenses 8 and 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for transferring a pattern formed on a mask by a charged particle beam onto a photosensitive substrate such as a semiconductor wafer, and particularly suitable for application to lithography after 1 Gbit DRAM. Is.

[0002]

2. Description of the Related Art Conventionally, a pattern surface of one mask is divided into a plurality of small areas, and the positions of charged particle beams of such a size that the small areas can be collectively exposed are deflected by a deflector. There has been proposed a charged particle beam transfer apparatus which sequentially exposes a plurality of areas to transfer a pattern of a small area onto a photosensitive substrate.

Conventionally, in this type of apparatus, a deflector for selecting a sub-field of view is provided at a crossover position formed by a condenser lens, and a parallel charged particle beam is formed by another condenser lens provided after the deflector to form a mask. The charged particle beam transmitted through the mask was focused on the photosensitive substrate by the two projection lenses, and the mask pattern was transferred onto the photosensitive substrate.

[0004]

In the prior art as described above, the final condenser lens (charged particle beam) is selected depending on whether a small area near the optical axis is selected or a small area away from the optical axis is selected. Since the position where the light passes through the mask and the mask is made parallel to each other is different, spherical aberration occurs in this lens. Therefore, the Z-direction position of the crossover formed in the middle of the two projection lenses moves. In order to correct this, it was necessary to make a correction such as changing the excitation of the final condenser lens.

The present invention has been made in view of the conventional problems, and an object of the present invention is to provide a charged particle beam transfer apparatus which does not need to correct the conditions of the condenser lens when selecting a small area.

[0006]

In order to solve the above problems, according to the present invention, the pattern surface of one mask is divided into one or more small areas (sub-fields of view), and these small areas are collectively exposed. In the charged particle beam transfer apparatus, a small area is selected by a two-stage deflector provided between the final condenser lens and the mask.

Further, the projection lens system is composed of at least two stages of projection lenses, and an astigmatism correction device is provided at the position of the final crossover formed between the projection lenses, whereby the astigmatism of each small area is corrected. I made a correction.

[0008]

In the present invention, since there is no condenser lens between the mask and the deflector for selecting a small area (subfield of view), spherical aberration of the condenser lens does not occur. In other words,
No matter which small region is selected, the charged particle beam passes through the same orbit in the condenser lens unit, and therefore no extra correction is necessary.

[0009]

1 is a sectional view of only one side of an optical system of an electron beam reduction transfer apparatus which is an embodiment of a charged particle beam transfer apparatus of the present invention. The electron beam emitted from the electron gun 1 forms a crossover at the position 11 by the condenser lens 2. The electron beam that has passed through this crossover is made into a parallel beam 12 by the final condenser lens 3 and enters the deflectors 4 and 5 having the core 6. Since the deflectors 4 and 5 have the same amount of deflection but opposite deflection directions, they function to translate the electron beam. The pattern surface of the mask 7 is divided into one or more main visual fields, and the main visual field is further divided into a plurality of sub visual fields. The relationship between the main visual field and the sub visual field of the mask 7 is shown in FIG. 2, and the function thereof will be described in detail later. The electron beam made into the parallel beam 12 by the final condenser lens 3 illuminates one of the deflected sub-fields of view. That is, the cross-sectional shape of the parallel beam 12 substantially matches the outer shape of the sub-field of view. The electron beam passing through one sub-field of view makes a crossover between the two projection lenses 8 and 9 by the projection lens 8 as shown by the trajectory 13. An astigmatism correction coil 14 is provided at this crossover position to perform astigmatism correction on each sub-field of view. After that, the pattern of the sub-field of the mask is reduced and projected on the photosensitive substrate 10 by the projection lens 9, and exposure is performed.

As shown in FIG. 2, the mask 7 has a main field of view M.
The main visual field MF is further divided into a plurality of rectangular regions called F, and the main visual field MF is further divided into a plurality of rectangular regions called sub visual field SF, and the sub visual field SF is collectively exposed. In the above-described transfer device, the exposure of the photosensitive substrate 7 is repeated while adjusting the exposure condition for each sub-field of view SF in response to the enlargement of the photosensitive substrate 7 and the miniaturization of the circuit pattern.

That is, at the time of exposure, the arrow Fm,
As shown by Fw, the mask 7 and the photosensitive substrate 10 are continuously and synchronously moved in opposite directions by a mask driving device and a photosensitive substrate driving device (not shown) (actually, a control device for controlling the two driving devices). There is). At this time, the mask 7
The irradiation position of the charged particle beam with respect to (1) is stepwise changed by the deflectors 5 and 6 in the direction perpendicular to the relative movement direction of the mask 7 and the photosensitive substrate 10 by one sub-field SF. Therefore, if the mask 7 in FIG. 2 is moved in the direction of arrow Fm in the figure by a mask driving device (not shown), each sub-field of view SF is irradiated with the charged particle beam in the order shown by arrow E in the figure. The pattern is transferred onto the photosensitive substrate 10.

With this structure, the electron beam emitted from the electron gun 1 is made into a parallel beam 12 by the two condenser lenses 2 and 3, and then the mask 7 is selected by the two deflectors 4 and 5. It is translated in accordance with the position of the subfield of view. Therefore, the electron beam passing through the condenser lenses 2 and 3 does not deflect its path even if the excitation conditions of the two deflectors 4 and 5 change, so that spherical aberration of the condenser lenses 2 and 3 occurs. There is no.
The electron beam irradiating one of the sub-fields of the mask 7 is transmitted through, for example, a portion where a pattern is formed, is condensed by the projection lens 8 to form a crossover, and then is projected onto the mask 7 by the projection lenses 8 and 9. On the photosensitive substrate 10 arranged at a conjugate position,
A reduced image of the pattern of the mask 7 is formed.

In the embodiment described above, the electron beam reduction transfer device using an electron beam which is one of the charged particle beams has been taken as an example, but the reduction transfer device using another charged particle beam such as an ion beam. It goes without saying that the present invention can be applied to. Further, in the above embodiments, the mask 7 and the exposure substrate 10
Since the electron beam (charged particle beam) was deflected in the direction orthogonal to the moving direction of the mask 7 while moving and in the opposite direction, it is possible to expose a large area with a small lens diameter. The present invention is also applied to a transfer device having a large lens diameter so as to select a sub-field of view by deflecting an electron beam (charged particle beam) two-dimensionally by a deflector without moving the substrate 10. It goes without saying that it can be applied.

[0014]

As described above, according to the present invention, since it is not necessary to correct the condenser lens when a small area (subfield of view) is selected, the following effects can be obtained. (1) Since the condenser lens can be made of metal such as iron or permalloy instead of ferrite, the cost can be reduced. (2) Since the aperture image that irradiates a small area (sub-field of view) does not rotate, the irradiation area can be a minimum size, and the mask is not heated more than necessary. (3) Dummy area between small areas (sub-fields of view) Since the joint area for preventing the irradiation beam from protruding to the adjacent small area can be made small in width, the deflector that corrects the beam position can have a small ability. High-precision drawing can be performed even if the accuracy is low. (4) Since the crossover position is the same regardless of which small area (sub-field of view) is selected, when the astigmatism correction is performed by the astigmatism correction device, there is no beam position movement and the like, and highly accurate drawing is possible.

[Brief description of drawings]

FIG. 1 is a half cross-sectional view of an electron optical system of an electron beam reduction transfer apparatus of an embodiment of a charged particle beam reduction transfer apparatus of the present invention.

FIG. 2 is a diagram showing an example of field division of a mask.

FIG. 3 is a diagram illustrating movement of a mask and a photosensitive substrate during exposure.

[Explanation of symbols]

 1 Electron Gun 2, 3 Condenser Lens 4, 5 Deflector 7 Mask 8, 9 Projection Lens 10 Photosensitive Substrate

Claims (2)

[Claims] 1. A charged particle beam transfer apparatus using a mask in which a pattern surface is divided into a plurality of small areas, wherein the charged particle beam from a charged particle beam source irradiates one of the small areas in parallel. A condenser lens system for forming a beam, a two-stage deflector for selecting an irradiation position of the parallel beam on the mask, and a projection lens system for conjugating the mask and a photosensitive substrate are provided at least. In the charged particle beam transfer apparatus, the deflector is composed of two-stage deflector, and
A charged particle beam transfer apparatus, wherein the two-stage deflector is provided between the condenser lens system and the mask. 2. The charged particle beam transfer apparatus according to claim 1, wherein the projection lens system is composed of at least two stages of projection lenses, and a final crossover is formed between the projection lenses. An astigmatism correction device is provided at the position of the final crossover, and astigmatism correction is performed for each of the small areas.