US 5,636,004 A · Projection exposure method and apparatus

Abstract

In a projection exposure method of irradiating illumination light from an illumination light source onto a photomask made of a transparent substrate with a periodic mask pattern, and projecting the resultant transmitted light from the photomask on a wafer through a projection system, thereby forming an optical image of the mask pattern on the wafer, projection/exposure with respect to the wafer is performed by a main exposure operation and a sub-exposure operation to be performed after the main exposure operation. The main exposure operation is performed by irradiating the photomask with the illumination light whose coherency becomes 0.3 or less when a period L of the mask pattern on the image plane of the optical system is not more than a value obtained by doubling an exposure wavelength .lambda. of the illumination light source, and dividing the resultant value by a numerical aperture of the projection system. The sub-exposure operation is performed by irradiating the photomask with the illumination light having a coherency of 0.3 or less at at least one of positions separated from a position in the main exposure operation in the optical axis direction by .DELTA.=.lambda./[2{1-(1-.lambda..sup.2 /L.sup.2).sup.1/2 }], thereby forming a periodic pattern having a period 1/2 the period L on the wafer.

Claims16

Dependent claims

A projection exposure method of irradiating illumination light from an illumination light source onto a photomask made of a transparent substrate having a periodic mask pattern formed thereon, and projecting the resultant transmitted light from said photomask on a wafer through a projection system, thereby forming an optical image of the periodic mask pattern on the wafer,

wherein projection and exposure with respect to the wafer are performed by a main exposure operation and a sub-exposure operation to be performed after the main exposure operation,
the main exposure operation is performed by irradiating said photomask with the illumination light whose coherency becomes not more than 0.3 when a period L of the periodic mask pattern on an image plane of said projection system is not more than a value obtained by doubling an exposure wavelength .lambda. of said illumination light source, and dividing the resultant value by a numerical aperture of said projection system, and
the sub-exposure operation is performed by irradiating said photomask with the illumination light whose coherency is not more than 0.3 at at least one of a plurality of positions separated from a position in the main exposure operation in an optical axis direction by .DELTA.=.lambda./[2{1-(1-.lambda..sup.2 /L.sup.2).sup.1/2 }],
thereby forming a periodic pattern having a period 1/2 the period L on the wafer.

1 more element

A projection exposure apparatus for irradiating illumination light from an illumination light source onto a photomask made of a transparent substrate having a periodic mask pattern formed thereon, and projecting/exposing the resultant transmitted light from said photomask onto a wafer through a projection system, thereby forming an optical image of the periodic mask pattern on the wafer, comprising:

an illumination light source having a coherency of not more than 0.3;
and
optical control means for calculating a value .DELTA.=.lambda./[2{1-(1-.lambda..sup.2 /L.sup.2).sup.1/2 }] from a period L of the periodic mask pattern on the image plane and a wavelength .lambda. of said illumination light source, and performing control to set an image projection plane on the wafer and the image plane of said projection system at positions separated from each other by a predetermined distance so as to set a first positional relationship in a main exposure operation, and to make the respective planes have a positional relationship different from the first positional relationship in the main exposure operation by the value .DELTA. on an optical axis in a sub-exposure operation,
wherein exposure is performed while the image projection plane on the wafer and the image plane of said projection system have a plurality of positional relationships with respect to the first positional relationship.

1 more element

Dependencies are inferred from the claim text.

Projection exposure method and apparatus

Life of this patent

Projection exposure method and apparatus

Life of this patent

Abstract

Claims16