Projection exposure method and apparatus
AssigneeNikon Corporation
InventorNaomasa Shiraishi
Life of this patent
Estimating the term…
Abstract
In order to effect projection exposure at a great depth of focus without spoiling transfer fidelity even for a plurality of isolated patterns relatively close to one another, provision is made of a coherence reducing member CCM for reducing the coherency between imaging light in a central circular transmitting portion FA on or near the pupil plane (Fourier transform plane) of a projection optical system and imaging light in a marginal zonal transmitting portion FB, and a double focalizing member DFM for making the in-focus position of light passing through the circular transmitting portion FA and the in-focus position of light passing through the zonal transmitting portion FB differ in the direction of the optical axis of the projection optical system.
Claims8
A projection exposure apparatus comprising:
- an illuminating system for irradiating a mask with illuminating light;
- a projection optical system for projecting the image of a pattern formed on said mask to a photosensitive substrate;
- a first optical member for reducing the coherency between imaging light distributed in a first area comprising at least one of a circular area and an annular area centering around the optical axis of said projection optical system in or near an optical Fourier transform plane in said projection optical system for the pattern surface of said mask and imaging light distributed in a second area other than said first area in or near said Fourier transform plane;
- and
- a second optical member for making the in-focus position of the light passing through said first area and the in-focus position of the light passing through said second area differ by a predetermined amount in the direction of the optical axis of said projection optical system.
A projection exposure method comprising:
- the step of disposing a mask having an isolated pattern on the object surface side of a projection optical system;
- and
- the step of disposing in said projection optical system a first optical member for reducing the coherency between imaging light distributed in a first area comprising at least one of a circular area and an annular area centering around the optical axis of said projection optical system in or near an optical Fourier transform plane in said projection optical system for the pattern surface of said mask, and a second optical member for making the in-focus position of the light passing through said first area and the in-focus position of the light passing through said second area differ by a predetermined amount in the direction of the optical axis of said projection optical system.
Dependencies are inferred from the claim text.