Illuminating device

An illumination device usable in a projection exposure system having an imaging optical system for forming an image of a circuit pattern of a reticle on a wafer, for illuminating the reticle, said device comprising:

• a light source for supplying coherent light;
• optical-path-difference applying means for dividing the coherent light into plural light fluxes and for applying an optical path difference or optical path differences to the light fluxes to provide plural light fluxes each of which is coherent in itself but which are mutually incoherent;
• an optical system for converging the light fluxes from said optical-path-difference applying means to form a plurality of point light sources at an entrance pupil of the imaging optical system, and for illuminating the reticle by use of the light fluxes;
• and
• scanning means disposed to receive the light fluxes from said optical-path-difference applying means, for scanningly deflecting the light fluxes to scan said point light sources at the entrance pupil of the imaging optical system.

An illumination method, comprising the steps of:

• providing a coherent beam;
• dividing the coherent beam into plural beams and applying a mutual optical path difference or optical path differences to the plural beams to provide plural mutually incoherent beams;
• forming plural mutually incoherent beam spots distributed in a plane by using the mutually incoherent beams;
• scanning the plane with the beam spots;
• and
• superposing beams from the beam spots one upon another on a surface to be illuminated.

An illumination method comprising the steps of:

• dividing a coherent beam into plural beams and applying an optical path difference or optical path differences to the plural beams to provide plural mutually incoherent beams;
• projecting the mutually incoherent beams toward a surface to be illuminated in different respective directions, wherein the mutually incoherent beams are deflected to scan a pupil plane of a projection lens;
• wherein the step of projecting the mutually incoherent beams further comprises receiving the mutually incoherent beams by the projection lens;
• respectively forming a plurality of beam spots through the mutually incoherent beams on the pupil plane;
• scanning the pupil plane with the beam spots;
• and superposing beams from the beam spots one upon another on the surface to be illuminated.

An exposure apparatus, comprising:

• p1 a laser;
• means for dividing a laser beam from said laser into plural beams and for applying an optical path difference or optical path differences to the beams to provide plural mutually incoherent laser beams;
• and
• an optical system having a pupil plane, for directing the incoherent laser beams in different directions to a mask so that a wafer is exposed to a pattern of the mask, said optical system comprising scanning means for scanning the pupil plane with the incoherent laser beams.