Abstract: The reflective projection system has a relatively wide field of view that comprises two concave and two convex spherical mirrors, situated in certain non-light-blocking positions with respect to one another, for deriving, with negligible image aberrations, a projected magnified or demagnified image over at least one of a range of magnification or demagnification power values between 3 and infinity that may be zoomed over this range. Such a reflective projection system, utilizing a high-power excimer laser radiation source, may be employed for ablating the surface of a substrate, such as the surface of the coating of a coated wafer, with a demagnified image of an object pattern defined by a mask, the radiation intensity of the demagnified image being sufficiently high to effect this ablation.

Abstract: An alignment system for a unit magnification system (such as a Half-Field Dyson system) for use in microlithography is provided. The alignment system provides for aligning a pattern on a reticle with a complementary pattern on a wafer.

Abstract: By providing redundant interferometer laser-metering devices, either one of which is capable by itself of providing measurement data of the angular value .theta. of rotation of the X-Y movable stage of a wafer stepper about a vertical Z axis for use by a computer-controlled servo devices that controls the operation of the X-Y movable stage, the servo devices, in a calibration mode, may receive data of specific measurements defining the respective values of undesired departures from flatness or straightness of the nominally-plane mirror surfaces of the the X-Y movable stage. These specific measurements, which may be made quickly at any time without disturbing the stage's mirrors, will also include those departures induced only at the point of use of the mirror and permit the stored control data used by the computer-controlled servo devices to be modified in order to compensate for these undesired departures from flatness or straightness of the nominally-plane mirror surfaces of the X-Y movable stage.

Abstract: Disclosed is tilt-sensing means that employs a point source of alternate 1st or 2nd divergent light beams which, after passing through collimating lenses of the Half-Field Dyson projection optics of the stepper, are separately incident on and reflected from a reflective pattern disposed on the surface of a reticle and from a reflective surface of a wafer, together with two-dimensional position detection means responsive to the position of each of the reflected alternate 1st or 2nd divergent light beams, for independently sensing the angular position of the surface of the reticle and the angular position of the surface of the wafer to determine thereby whether or not the surface of the reticle and the surface of the wafer are substantially parallel to one another.

Abstract: An illumination system for use in a unit magnification optical projection system (such as a Half-Field Dyson system) is provided. In a Half-Field Dyson system, a reticle and a wafer are parallel to each other with a window being provided on the reticle to allow for projection of the reticle pattern onto the wafer. The present invention provides uniform bright illumination over the reticle pattern with little or no spill over through the reticle window.

Abstract: A microlithographic stepper, employing a Half-Field Dyson projection optical system, achieves focusing of an image of a first-layer reticle pattern on a completely unpatterned reflective wafer surface by including a repetitive diffraction pattern on the reticle which has a configuration in which a particular ordinal diffraction order is normally missing. In response to being simultaneously illuminated with each of two incident monochromatic beams of light, diffraction orders generated by the repetitive diffraction pattern are imaged on the reflective wafer surface and then reflected back to and reimaged on the repetitive diffraction pattern on the reticle. Diffraction orders generated on the first encounter with the repetitive diffraction pattern generate light in the originally missing ordinal diffraction order on the second encounter.