Radiant energy – Irradiation of objects or material – Irradiation of semiconductor devices
Reexamination Certificate
2000-03-15
2003-05-20
Berman, Jack (Department: 2881)
Radiant energy
Irradiation of objects or material
Irradiation of semiconductor devices
Reexamination Certificate
active
06566664
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a charged-particle beam exposure apparatus such as an electron beam exposure apparatus or ion beam exposure apparatus used to expose a semiconductor integrated circuit or the like and, more particularly, to a charged-particle beam exposure apparatus for drawing a pattern by using a plurality of charged-particle beams, and a device manufacturing method using this apparatus.
BACKGROUND OF THE INVENTION
Multi charged-particle beam exposure apparatuses using a plurality of charged-particle beams include electron beam exposure apparatuses disclosed in Japanese Patent Laid-Open Nos. 9-248708 and 9-288991.
FIG. 25
is a schematic view of such an apparatus.
In
FIG. 25
, an electron beam from an electron source ES which emits electrons is almost collimated by a collimator lens CL. The almost collimated beam enters an aperture array AA having a plurality of apertures where the beam is split into a plurality of electron beams. The split electron beams enter element electrooptic systems EL
1
to EL
3
and form intermediate images img
1
to img
3
of the electron source ES on the almost front focal positions of the respective element electrooptic systems. The intermediate images are projected on a wafer W as a surface to be exposed via a projection electrooptic system DO. At this time, the electron beams of the intermediate images scan the surface of the wafer W via a common deflector. Blankers B
1
to B
3
and stoppers S
1
to S
3
separately control irradiation of the respective electron beams on the wafer W, and a pattern is drawn on the wafer W.
As the feature of this apparatus, the optical characteristics of the element electrooptic systems are individually set for the curvature of field (deviation between an actual imaging position and an ideal imaging position on the wafer W along the optical axis of the projection electrooptic system DO), and the intermediate image formation position along the optical axis is changed for each element electrooptic system so as to correct the curvature of field, in order to correct aberration generated when a plurality of intermediate images are projected on a surface to be exposed via the projection electrooptic system DO. For distortion (deviation between an actual imaging position and an ideal imaging position on the wafer W in directions perpendicular to the optical axis of the projection electrooptic system DO), the element electrooptic systems are located at positions where distortion is corrected.
Aberration of the projection electrooptic system DO varies owing to thermal/mechanical deformation of the projection electrooptic system DO. It is easy to electrically reset the optical characteristics of the element electrooptic systems in correspondence with varied curvature of field. However, it is difficult in terms of precision to mechanically relocate each element electrooptic system in correspondence with varied distortion.
SUMMARY OF THE INVENTION
The present invention has been made to overcome the conventional drawbacks, and has as its object to provide a charged-particle beam exposure apparatus capable of easily correcting distortion of a projection electrooptic system.
It is another object of the present invention to enable obtaining a higher-precision device than a conventional device by manufacturing the device by using the charged-particle beam exposure apparatus which achieves the above object.
To achieve the above objects, according to the present invention, there is provided a charged-particle beam exposure apparatus for exposing a surface to be exposed by using a plurality of charged-particle beams, comprising a charged-particle source for emitting a charged-particle beam, a substrate having a plurality of apertures, an irradiation electrooptic system for irradiating the substrate with the charged-particle beam emitted by the charged-particle source, element electrooptic systems for forming a plurality of intermediate images of the charged-particle source by forming the intermediate images of the charged-particle source by charged-particle beams having passed through the apertures of the substrate, a projection electrooptic system for projecting the plurality of intermediate images on the surface to be exposed, and adjustment means for adjusting incident angles of the charged-particle beams incident on the element electrooptic systems in order to adjust positions where the plurality of intermediate images are projected on the surface to be exposed.
It is preferable that the apparatus further comprise information acquisition means for obtaining information about the positions where the plurality of intermediate images are projected on the surface to be exposed, and the adjustment means adjust the incident angles of the charged-particle beams incident on the element electrooptic systems on the basis of the information. This is because distortion can be properly corrected in accordance with the electrooptic system.
According to another aspect of the present invention, the adjustment means adjusts the incident angles to move formation positions of the plurality of intermediate images in a direction parallel to a surface perpendicular to an optical axis of the projection electrooptic system.
Another aspect of the adjustment means adjusts the incident angles by changing a positional relationship between a front focal position of the irradiation electrooptic system and a position of the charged-particle source. Adjustment is easy because of a small number of control targets (adjustment targets), and systematic distortion (distortion of the projection electrooptic system) can be corrected.
It is preferable that the irradiation electrooptic system has a plurality of electron lenses, and the adjustment means changes the front focal position by adjusting electrooptic powers of at least two electron lenses of the irradiation electrooptic system. Since distortion can be corrected by adjusting the electrooptic powers, easy, high-precision correction can be implemented.
It is also possible that the apparatus further comprises deflectors which are arranged in correspondence with the apertures of the substrate and deflect charged-particle beams from the apertures, and the adjustment means adjusts the incident angles by deflecting the charged-particle beams by using the deflectors. The number of adjustment items increases owing to a larger number of control targets (adjustment targets). However, both systematic distortion (distortion of the projection electrooptic system) and random distortion can be corrected, and higher-precision correction can be realized.
The deflectors preferably function as shielding deflectors for giving shielding deflection amounts to charged particles so as to prevent the charged particles from corresponding intermediate images from being incident on the projection electrooptic system. The construction can be simplified.
The adjustment means may comprise first adjustment means for adjusting the incident angles by changing a positional relationship between a front focal position of the irradiation electrooptic system and a position of the charged-particle source, and second adjustment means for adjusting the incident angles by deflecting charged-particle beams by using the deflectors.
When the adjustment means has the first and second adjustment means, it is also possible that the apparatus further comprises information acquisition means for obtaining information about the positions where the plurality of intermediate images are projected on the surface to be exposed via the projection electrooptic system, and that the adjustment means executes the first adjustment means on the basis of the information, newly acquires information from the information acquisition means after execution of the first adjustment means, and executes the second adjustment means on the basis of the newly acquired information. If distortion can be satisfactorily corrected by only the first adjustment means, the adjustment means does not execute the second adjustment means. This can shorten the
Berman Jack
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Smith II Johnnie L
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