Catadioptric projection printer

Claim 1

In a projection printer for printing a circuitry pattern from a reticle onto a wafer and including an ultra violet source of radiant energy, a beam splitter, a focusing mirror and means for mounting and optically registering said reticle and said wafer respectively in input and output regions of said beam splitter, the improvement comprising: a. said beam splitter is a polarizing beam splitter directing a polarized portion of said radiant energy toward said focusing mirRor; b. means between said polarizing beam splitter and said focusing mirror for altering said polarization of said radiant energy so said polarization of said radiant energy reflected from said focusing mirror is oriented to pass straight through said polarizing beam splitter to said wafer; c. a multi-element corrective lens arranged between said polarizing beam splitter and said focusing mirror for correcting chromatic and spherical aberration, astigmatism and field curvature and directing said radiant energy reflected from said focusing mirror substantially telecentrically onto said wafer; d. said polarizing beam splitter, said polarization altering means and said lens being selected for substantially transmitting said radiant energy throughout the near ultra violet and visible spectrum; e. said optical registering means including a source of polarized visible radiant energy and a microscope arranged for observing said reticle; f. means for directing said polarized visible radiant energy toward said polarizing beam splitter to pass through said polarization altering means so the polarization of said visible radiant energy is oriented to pass straight through said polarizing beam splitter to be substantially telecentrically incident on said wafer, said visible radiant energy being reflected to said focusing mirror from said wafer and said visible radiant energy reflected back from said focusing mirror being oriented by said polarization altering means to be split by said polarizing beam splitter for imaging said wafer on said reticle for viewing through said microscope; and g. adjustable means for varying the optical length of the path between said focusing mirror and said wafer to accommodate different wavelengths of said radiant energy from said ultra violet source and said source of visible radiant energy.