Interference system and semiconductor exposure apparatus having the same

A Fizeau interference system for causing interference between reflection lights from a reflection surface and a semi-transmission surface, respectively, disposed along one and the same optical axis, comprising:

• a light source;
• an interference optical system for causing reflection of light from said light source at corresponding one of the reflection surface and the semi-transmission surface to produce interference;
• and
• an optical path difference applying optical system disposed between said light source and said interference optical system, for dividing light from said light source into two lights to be directed to the reflection surface and the semi-transmission surface, respectively, and also for re-combining them and directing them to said interference optical system, wherein said optical path difference applying optical system applies to the two lights an optical path difference effective to reduce the optical path difference applied to the two lights by said interference optical system, to be not greater than the coherence length of the light from said light source;
• and
• a spatial filter disposed between said optical path difference applying optical system and said interference optical system, for reducing the differences in wavefront between the two lights.

A projection exposure apparatus, comprising:

• a projection exposure system for printing an original pattern on a photosensitive member via a projection optical system;
• a light source;
• an optical path difference applying optical system for dividing light from said light source into two lights and for re-combining them;
• and
• an interference optical system for causing reflection of the two lights passed through said optical path difference applying optical system, at corresponding one of a reflection surface and a semi-transmission surface, and to cause interference of them,
• wherein a difference ΔF in optical path length of the light reflected by said reflection surface and with respect to the light reflected by the semi-transmission surface satisfies the following relation, where the optical path difference between the two lights as applied by said optical path difference applying optical system is ΔD, and the coherence length of the light from said light source is ΔL:
• |ΔD−ΔF|<ΔL;
• and
• a spatial filter disposed between said optical path difference applying optical system and said interference optical system, for reducing the difference in wavelength between the two lights.

A projection exposure apparatus, comprising:

• a projection exposure system for printing an original on a photosensitive member, via a projection optical system;
• a light source;
• an interference optical system for causing reflection of light from said light source at corresponding one of the reflection surface and the semi-transmission surface to produce interference;
• and
• an optical path difference applying optical system disposed between said light source and said interference optical system, for dividing light from said light source into two lights to be directed to the reflection surface and the semi-transmission surface, respectively, and also for re-combining them and directing them to said interference optical system, wherein said optical path difference applying optical system applies to the two lights an optical path difference effective to reduce the optical path difference applied to the two lights by said interference optical system, to be not greater than the coherence length of the light from said light source;
• and
• a spatial filter disposed between said optical path difference applying optical system and said interference optical system, for reducing the difference between the two lights.