Hybrid illumination system for use in photolithography

Details Hybrid illumination system for use in photolithography Hybrid illumination system for use in photolithography

H - Electricity

01

L

H01L 21/268 (2006.01) G03F 7/20 (2006.01)

Patent

CA 2177196

An illumination system for use in photolithography having an array optical element near the formation of a desired illumination field. Light or electromagnetic radiation from an illumination source is expanded and received by a multi-image optical element forming a plurality of secondary illumination sources in a plane. A condenser receives the light from the plurality of illumination sources. A array or diffractive optical element is placed on or near the focal point of the condenser. The illumination plane formed at the focal point of the condenser is within the near field diffraction pattern of the array or diffractive optical element. There is no condenser following the array or diffractive optical element. The use of the array or diffractive optical element permits the use of a condenser between the multi-image optical element and the array or diffractive optical element having a smaller numerical aperture than the emergent numerical aperture of the diffractive optical element, and generates a desired angular distribution with little dependance on the illumination source profile. When a relay is used, intermediate illumination planes may be spatially separated to form separate X and Y planes that facilitate the formation of a rectangular illumination field. The relay, unlike a condenser, simply conjugates the illumination plane with another plane or a reticle. Additionally, the use of a diffractive optical element makes possible an illumination field that has a substantially uniform illumination intensity profile along one axis and a trapezoidal illumination profile along a perpendicular axis. This illumination field profile being particularly advantageous in a scanning photolithography operation. In one embodiment, a plurality of optical multiplexers are used to condition the beam prior to being directed through the multi-image optical element. Multiplexing to create secondary beams with small lateral coherence and no mutual coherence enhances the uniformity of spacial and angular profiles. This permits efficient use of the electromagnetic radiation.

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