JP2006114726A - Charged-particle-beam exposure apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charged-particle-beam exposure apparatus whereby such the aberration of the beam of the exposure apparatus as a curvature of field can be reduced without deteriorating the telecentric characteristics possessed by it on both its input and output sides relative to the exposure apparatus. <P>SOLUTION: In the charged-particle-beam exposure apparatus, a main beam 3 obliquely incident on a reticle 1 is so deflected by the action of a fifth deflector 15 as to be made vertically incident on the surface of the reticle 1. Also, the main beam 3 is so emitted vertically from the surface of the reticle 1, and is so deflected by the mutual action generated between a first deflector 10 and the fifth deflector 15 as to be directed to the side of the optical axis of the exposure apparatus in the closer position to the reticle 1 than the position of the first deflector 10, and as to progress more closely to the optical axis than the position shown in Figure 2. Then, although the main beam 3 proceeds obliquely up to the vicinity of a wafer 8, it is so deflected by the mutual action generated between a fourth deflector 13 and a sixth deflector 16 in the closer position to the wafer 8 than the position of the fourth deflector 13 as to become vertical to the wafer 8 and as to be made vertically incident on the wafer 8. As a result, such an aberration of a beam of the exposure apparatus as a curvature of field can be reduced without deteriorating the telecentric characteristics possessed by it on both its input and output sides relative to the exposure apparatus. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a charged particle beam exposure apparatus that uses a charged particle beam to expose and transfer a pattern formed on a reticle onto a sensitive substrate such as a wafer by a projection optical system.

  In recent years, it has become difficult to resolve patterns refined by increasing the integration degree of semiconductor devices by conventional exposure methods using ultraviolet light, and a new exposure method using charged particle beams and extreme ultraviolet rays (EUV). Are beginning to be used. Among them, an exposure apparatus using a charged particle beam has advantages such as good controllability by electric means, and is promising as a next-generation exposure means.

  In a charged particle beam exposure apparatus, a large area cannot be exposed and transferred at a time due to aberrations and distortions of a charged particle beam optical system. For this reason, for example, an area corresponding to one chip is divided into a plurality of areas called subfields (subfields), and a reticle pattern is exposed and transferred to the wafer for each subfield, and the exposed and transferred patterns are joined together. Thus, a divided exposure transfer method for obtaining a pattern of one chip has been adopted.

  FIG. 2 shows an outline of the projection optical system of the electron beam exposure apparatus using the conventional divided exposure transfer system. In FIG. 2, an electron beam emitted from an electron beam source (not shown) illuminates the reticle 1 by an illumination optical system (not shown).

  The reticle is usually divided into approximately 1 mm square, and each divided area is referred to as a reticle side subfield (subfield) 2. The illumination electron beam collectively illuminates the inside of one reticle side subfield 2.

  In FIG. 2, 3 is the principal ray of the deflection trajectory in the projection optical system, and 4 a to 4 c and 5 a to 5 c indicate electron beams emitted from the end of the reticle side subfield 2. These electron beams that have passed through the reticle 1 are adjusted by the first projection lens 6 and the second projection lens 7 so as to form an image of the reticle on the wafer 8 that is the object to be exposed. Usually, the magnification of the projection optical system is set to about 1/4.

  An image formed on the wafer-side subfield 2 on the wafer 8 is called a wafer-side subfield 9. The image of the reticle (wafer side subfield 9) divided on the wafer 8 is connected to form an image of the entire circuit of the semiconductor device.

  The electron beam is adjusted so as to form an image of a shaping aperture (not shown) in the illumination optical system on the reticle 1, and the illumination electron beam is deflected to a desired reticle side subfield 2 by an illumination optical system deflector (not shown). I will do it. The deflection width is about 20 mm on the reticle, and this is called the main field (main field of view). Actual exposure is performed by deflecting the electron beam in the direction of the main field and continuously moving the reticle stage and wafer stage in a direction perpendicular to the main field (the directions of the reticle stage and the wafer stage are usually reversed).

  On the other hand, between the reticle side subfields 2, there are reinforcing members called struts (beams) and portions without patterns called skirts. Therefore, when the reticle side subfield 2 is projected onto the wafer 8 as it is, a continuous pattern is obtained. I can't. Therefore, a deflector is also provided in the projection optical system in order to adjust that portion. Furthermore, aberrations caused by deflection can be reduced by adjusting the deflector. In FIG. 2, a first deflector 10, a second deflector 11, a third deflector 12, and a fourth deflector 13 are installed for this purpose. In FIG. 2, reference numeral 14 denotes a contrast aperture for cutting the electron beam scattered by the reticle 1.

  The projection optical system is an input / output telecentric optical system. The reason is that if the position of the reticle 1 in the optical axis direction and the position of the wafer 8 in the optical axis direction fluctuate, the image formation position changes to prevent image distortion.

  However, if the resolution is improved while inheriting the charged particle beam projection optical system as in the conventional example shown in FIG. 2, aberrations such as field curvature become a problem. An effective method for improving the field curvature is to bring the deflection trajectory as close to the optical axis as possible as shown in FIG. In FIG. 3, the same components as those shown in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted.

  However, as can be seen from FIG. 3, when the deflection trajectory is brought closer to the vicinity of the optical axis, the deflection trajectory has an inclination on the reticle 1 surface and the wafer 8 surface. When the inclination of the deflection trajectory is large, the image position shifts due to the height fluctuation of the reticle 1 or the wafer 8. Typically, the inclination of the deflection trajectory on the reticle 1 surface and the wafer 8 surface is several degrees. For example, when the wafer stage fluctuates by 1 μm, an imaging position change of 17 nm or more occurs.

  In order to reduce this, it is necessary to suppress the height variation of the reticle stage and wafer stage, or to detect the height variation and correct it with the charged particle beam projection optical system. However, increasing the accuracy of each stage is very expensive. Further, when correction is performed by the charged particle beam projection optical system, there is a problem that the correction range increases, the response speed becomes slow, and the processing time is long.

  The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a charged particle beam exposure apparatus capable of reducing aberrations such as field curvature without deteriorating entry / exit telecentricity. To do.

  A first means for achieving the above object is a charged particle beam exposure apparatus that uses a charged particle beam to expose and transfer a pattern formed on a reticle onto a sensitive substrate such as a wafer by a projection optical system, A charged particle beam exposure apparatus (Claim 1), wherein at least one of the deflectors for the projection optical system is provided downstream of the imaging plane in the traveling direction of the charged particle beam. .

  The magnetic field of the deflector provided on the downstream side of the imaging plane spreads to the upstream side of the imaging plane and contributes to the deflection of the trajectory until the charged particle beam reaches the imaging plane. Therefore, it becomes possible to deflect the trajectory at a position closer to the imaging plane, and for example, the second means described later can be realized.

  The second means for solving the problem is the first means, wherein the principal ray of the charged particle beam is in the traveling direction of the charged particle beam in the deflector of the projection optical system. On the upstream side of the imaging plane and downstream of the position of the deflector closest to the imaging plane, and on the upstream side of the imaging plane, substantially perpendicular to the imaging plane, It is designed to be incident on the image plane (claim 2).

  In this means, due to the action of the deflector provided on the downstream side of the imaging surface, the principal ray of the charged particle beam is upstream of the imaging surface and from the position of the deflector closest to the imaging surface. On the downstream side and on the upstream side of the imaging plane, it can be made substantially incident on the imaging plane and incident on the imaging plane. That is, when the exit-side telecentricity is ensured, the chief ray can be incident obliquely to a position closer to the imaging plane than before, and accordingly, the deflection trajectory can pass near the optical axis. And aberrations such as field curvature can be reduced.

  In this section and the claims, “substantially vertical” means that it may not be completely vertical, but may not be completely vertical as long as it does not affect the exposure transfer accuracy. The range can be appropriately determined by those skilled in the art according to the required projection accuracy of the projection optical system, the aberration, the magnitude of the position variation of the reticle or wafer in the optical axis direction, and the like.

  A third means for solving the above problem is a charged particle beam exposure apparatus that uses a charged particle beam to expose and transfer a pattern formed on a reticle onto a sensitive substrate such as a wafer by a projection optical system, A charged particle beam exposure apparatus (Claim 3), wherein at least one of the deflectors for the projection optical system is provided upstream of the reticle surface in the traveling direction of the charged particle beam. .

  The electric field or magnetic field of the deflector provided upstream from the reticle surface extends to the downstream side of the reticle surface, and contributes to the deflection of the trajectory after the charged particle beam is emitted from the reticle surface. Accordingly, the trajectory can be deflected at a position closer to the reticle surface, and for example, the fourth means described later can be realized.

  A fourth means for solving the above-mentioned problem is the third means, wherein the principal ray of the charged particle beam emitted substantially perpendicularly from the reticle surface is within the deflector of the projection optical system, In the traveling direction of the charged particle beam, it is deflected in the optical axis direction on the downstream side of the reticle surface and upstream of the position of the deflector closest to the reticle surface and on the downstream side of the reticle surface. (Claim 4).

  In this means, the chief ray of the charged particle beam emitted substantially perpendicularly from the reticle surface by the action of the deflector provided on the upstream side of the reticle surface causes the charged particle beam of the projection optical system to In the advancing direction, the light is deflected in the optical axis direction on the downstream side of the reticle surface and upstream of the position of the deflector closest to the reticle surface and on the downstream side of the reticle surface. In other words, when the entrance-side telecentricity is ensured, the principal ray can be deflected toward the optical axis at a position closer to the reticle surface than in the past, so that the deflection trajectory can pass near the optical axis, Aberrations such as field curvature can be reduced.

  According to the present invention, it is possible to provide a charged particle beam exposure apparatus that can reduce aberrations such as field curvature without deteriorating entry / exit telecentricity.

  Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an outline of a projection optical system of an electron beam exposure apparatus according to an embodiment of the present invention. In FIG. 1, an electron beam emitted from an electron beam source (not shown) illuminates the reticle 1 by an illumination optical system (not shown).

  The reticle is usually divided into approximately 1 mm square, and each divided area is referred to as a reticle side subfield (subfield) 2. The illumination electron beam collectively illuminates the inside of one reticle side subfield 2.

  In FIG. 1, 3 is a principal ray of a deflection trajectory in the projection optical system, and 4 a to 4 c and 5 a to 5 c indicate electron beams emitted from the end of the reticle-side subfield 2. These electron beams that have passed through the reticle 1 are adjusted by the first projection lens 6 and the second projection lens 7 so as to form an image of the reticle on the wafer 8 that is the object to be exposed. Usually, the magnification of the projection optical system is set to about 1/4.

  An image formed on the wafer-side subfield 2 on the wafer 8 is called a wafer-side subfield 9. The image of the reticle (wafer side subfield 9) divided on the wafer 8 is connected to form an image of the entire circuit of the semiconductor device.

  The electron beam is adjusted so as to form an image of a shaping aperture (not shown) in the illumination optical system on the reticle 1, and the illumination electron beam is deflected to a desired reticle side subfield 2 by an illumination optical system deflector (not shown). I will do it. The deflection width is about 20 mm on the reticle, and this is called the main field (main field of view). Actual exposure is performed by deflecting the electron beam in the direction of the main field and continuously moving the reticle stage and wafer stage in a direction perpendicular to the main field (the directions of the reticle stage and the wafer stage are usually reversed).

  On the other hand, between the reticle side subfields 2, there is a portion having no pattern called a reinforcing material called a strut (beam) or a skirt, and when the reticle side subfield 2 is projected onto the wafer 8 as it is, a continuous pattern is obtained. I can't. Therefore, a deflector is also provided in the projection optical system in order to adjust that portion. Furthermore, aberrations caused by deflection can be reduced by adjusting the deflector. In FIG. 1, a first deflector 10, a second deflector 11, a third deflector 12, and a fourth deflector 13 are installed for this purpose. In FIG. 1, reference numeral 14 denotes a contrast aperture for cutting an electron beam scattered by the reticle 1.

  The above configuration is the same as that of the conventional projection optical system shown in FIG. 2, but in the projection optical system shown in FIG. 1, the fifth deflection is made upstream of the reticle 1 (upstream of the electron beam flow). A difference is that a device 15 is provided and a sixth deflector 16 is provided downstream of the wafer 8.

  The chief ray 3 of the electron beam will be described. The chief ray 3 incident on the reticle 1 from an oblique direction is deflected by the action of the fifth deflector 15 and enters the reticle 1 surface perpendicularly and from the reticle 1 surface. 2 is emitted perpendicularly to the reticle 1 and is deflected toward the optical axis at a position closer to the reticle 1 than the position of the first deflector 10 by the interaction between the first deflector 10 and the fifth deflector 15. It advances from the optical axis rather than the position shown in FIG.

  Then, although it proceeds obliquely to the vicinity of the wafer 8, it is perpendicular to the wafer 8 at a position closer to the wafer 8 than the fourth deflector 13 due to the interaction between the fourth deflector 13 and the sixth deflector 16. The light is deflected and vertically incident on the wafer 8.

  In this way, the principal ray 3 of the electron beam passing through the deflection trajectory exits from the reticle 1 surface perpendicularly to the reticle and enters the wafer 8 surface perpendicularly, so that this projection optical system is an input / output telecentric optical system. ing. Further, after the principal ray 3 exits the reticle 1, the point deflected in the optical axis direction is on the reticle 1 side from the first deflector 10, and the principal ray 3 directed from the optical axis direction to the wafer 8 is reflected on the wafer 8. Since the point deflected in the direction perpendicular to the fourth deflector 13 is closer to the wafer 8 than the fourth deflector 13, the deflection trajectory can be made from the optical axis, and as a result, aberrations such as field curvature can be reduced. .

  As is clear from FIG. 1, the deflection directions of the first deflector 10 and the fifth deflector 15 are the same, and the deflection directions of the fourth deflector 13 and the sixth deflector 16 are the same.

It is a figure which shows the outline | summary of the projection optical system of the electron beam exposure apparatus which is embodiment of this invention. It is a figure which shows the outline | summary of the projection optical system of the electron beam exposure apparatus by the conventional division | segmentation exposure transfer system. FIG. 3 is a diagram showing a state in which the deflection trajectory is brought close to the optical axis in the projection optical system shown in FIG. 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Reticle, 2 ... Reticle side subfield, 3 ... Main beam, 4a, 4b, 4c ... Electron beam emitted from edge part of reticle side subfield, 5a, 5b, 5c ... From edge part of reticle side subfield Emitted electron beam, 6 ... first projection lens, 7 ... second projection lens, 8 ... wafer, 9 ... wafer side subfield, 10 ... first deflector, 11 ... second deflector, 12 ... third deflection 13 ... 4th deflector, 14 ... Contrast aperture, 15 ... 5th deflector, 16 ... 6th deflector

Claims (4)

A charged particle beam exposure apparatus that exposes and transfers a pattern formed on a reticle to a sensitive substrate such as a wafer by a projection optical system using a charged particle beam, wherein at least one of the deflectors for the projection optical system includes: A charged particle beam exposure apparatus, wherein the charged particle beam exposure apparatus is provided downstream of the imaging plane in the traveling direction of the charged particle beam. 2. The charged particle beam exposure apparatus according to claim 1, wherein a principal ray of the charged particle beam is upstream of the imaging plane in a traveling direction of the charged particle beam in a deflector of the projection optical system. So that it is substantially perpendicular to the imaging plane on the downstream side of the deflector position closest to the imaging plane and the upstream side of the imaging plane, and is incident on the imaging plane. A charged particle beam exposure apparatus. A charged particle beam exposure apparatus that exposes and transfers a pattern formed on a reticle to a sensitive substrate such as a wafer by a projection optical system using a charged particle beam, wherein at least one of the deflectors for the projection optical system includes: A charged particle beam exposure apparatus, wherein the charged particle beam exposure apparatus is provided upstream of the reticle surface in the traveling direction of the charged particle beam. 4. The charged particle beam exposure apparatus according to claim 3, wherein a principal ray of the charged particle beam emitted substantially perpendicularly from the reticle surface is a traveling direction of the charged particle beam in a deflector of the projection optical system. In the optical axis direction on the downstream side of the reticle surface and upstream of the position of the deflector closest to the reticle surface and on the downstream side of the reticle surface. Charged particle beam exposure apparatus.

Images