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Exposure apparatus that compensates for spherical aberration of an image forming device
| Details |
Inventors: Torigoe, Makoto; Suzuki, Akiyoshi;
Assignee: Canon Kabushiki Kaisha (Tokyo, JP)
Primary Examiner: Allen; Stephone
Assistant Examiner:
Attorney, Agent or Firm: Fitzpatrick, Cella, Harper & Scinto
An exposure apparatus wherein an image forming system forms an image of a pattern upon a photosensitive layer, and a detecting system detects a spherical aberration of the image forming system. The detected spherical aberration of the image forming system is adjusted or controlled in a suitable way, whereby correct pattern transfer operation is assured. |
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DETAILED DESCRIPTION It is an object of the present invention to provide an improved projection exposure apparatus, by which the inconveniences described above can be reduced satisfactorily.
In accordance with an aspect of the present invention, there may be provided a projection exposure apparatus wherein, in lithographic projection of a pattern of a first object such as a reticle as illuminated with light from an illumination optical system onto a surface of a second object such as a wafer through a projection optical system, a spherical aberration of the projection optical system is measured by use of a spherical aberration measuring means and wherein, in response to a signal from the aberration measuring means, a control means controls the spherical aberration of the projection optical system to a predetermined level.
The control means may move an optical element or elements of the projection optical system to control the spherical aberration of the projection optical system.
The or each optical element may comprise one lens element and it may be moved along the optical axis.
The optical elements may comprise two optical wedges disposed opposed to each other to provide in combination a parallel flat plate, and these optical wedges may be moved relative to each other in a direction perpendicular to the optical axis to change the thickness in the direction of the optical axis.
The control means may interchangeably insert/retract an optical element or elements of the projection optical system, such as, for example, plural parallel flat plates of different thicknesses, to control the spherical aberration of the projection optical system.
The control means may change the refractive index of a gas in a space between optical elements of the projection optical system to control the spherical aberration of the projection optical system On that occasion, for example, the pressure of the gas between optical elements may be changed to change the refractive index.
Alternatively, the gas between optical elements may consist of mixed different gaseous fluids and the ratio of mixture of the gaseous fluids may be changed to change the refractive index of the gas
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LCD 
