Abstract: Misalignment errors in a lithographic system resulting from the effect of environmental changes on the lens system itself are detected and corrected. A fiducial on the reticle adjacent to its working area is projected through the lens. A metrology plate carried by the lens holds reference mirrors and detectors The reference mirrors receive the resultant image and reflect it to detectors in a reflected image plane. This provides feedback to the reticle alignment system as to the extent of misalignment, if any. Correction is made by moving the reticle until alignment is achieved and detected. This motion is achieved by using a reticle chuck with linear motors.

Abstract: A focus shift sensor includes a light source which directs light through a first grating to form a pattern of light. The pattern is directed through the lens which images the pattern at a second grating. The two gratings have different periods such that the second grating generates a pattern of Moire fringes which are projected onto a CCD array. The second grating is preferably tilted with respect to the plane of the image of the pattern from the first grating such that only a portion of the second grating is within the range of focus of the lens. As a result, a pattern of shortened Moire fringes is produced. As the range of focus shifts along the second grating, the Moire fringes move along the CCD array. The movement of the fringes is tracked and the system is adjusted to maintain the location of the focal plane of the lens at a desired location.

Abstract: A lithographic stage is carried by a platen formed of a plurality of tiles containing a uniformly spaced grid of teeth and having low reluctance and high resistivity. The teeth have been formed by powder metal technology using as powder particles of a ferromagnetic material, the particles being of high resistivity or coated with an insulating material. The space between the teeth is filled with non-magnetic material, such as epoxy, and the entire platen finished such that it has a smooth and uniform flat upper surface.

Abstract: A non-contact substrate alignment system for a lithography system is disclosed that comprises three substrate edge detectors. Each edge detector comprises a projector, preferably located above the substrate, that projects a light field down onto a substrate and a stage. The light field has a predetermined shadow line that is straight and runs perpendicularly to the direction of the substrate's edge. A camera is also located above the substrate and detects the light from the light field. The height differential between the substrate and stage causes a shift in the shadow line from the perspective of the camera. A controller connected to the camera utilizes this shift to locate the edge of the substrate. The problems associated with the mechanical banking techniques are thus avoided. Moreover, the technique uses detectors and projectors that can be located entirely above the substrate; specially designed stages with incorporated detectors or projectors are not required.

Abstract: Two lithographic substrate stages are used in a single lithographic system. While a substrate on one stage is being exposed, a second substrate is being loaded, unloaded, or aligned on a second stage. After exposure, the first stage is unloaded, reloaded, and the newly-loaded substrate is aligned, while the second substrate on the second stage is being exposed. The two stages are thus used alternately in different steps of the process. One of the steps is being performed on one stage while a different step is being performed on the other stage. The substrates on both stages are, therefore, being acted upon simultaneously. The two stages are carried on a single linear motor platen, and moved about the platen by use of linear motors. The two stages alternately both move in clockwise directions about the platen, or both move in counterclockwise directions. When both move in clockwise directions, the first stage is moving to the exposure position, and the second stage is moving to the unload/load/align station.

Abstract: A system for aligning substrates when preparing flat panel displays by lithography. A spherical reflector (imaging mirror) is used to focus a small geometric object, such as a cross, etched at the center of the reflector. The cross is projected toward a beam splitter and is then reflected onto the mirror which, in turn, images it on the surface of the substrate being used in the lithographic process. This optical system, which has a numerical aperture of about 0.05 radians, provides maximum depth of field with essentially no aberrations, and produces a relatively large probe image on a large alignment mark.The surface of the substrate carries a grid of stepped patterns as an alignment mark. The steps diffract the light received, and the diffracted light passes through a lens system to a sensor associated with the lens system. The amount of light diffracted is dependent upon where the image strikes the steps in the grid.

Abstract: A direct reticle reference alignment system for use in photolithography for use with substrates having optical transmissivity. The system includes a movable stage (14), a transmissive substrate (11) held by the stage and bearing at least one plate mark (15) upon its upper surface, an optical system having a light source (1) for illuminating and projecting a reticle alignment image (4) upon the substrate (11) for alignment with the plate mark (15), a sensor (17) mounted in the stage (14) below the substrate (11) and the plate mark (15) to receive light from the projected alignment image (4), the sensor (17) producing an electrical signal related to the degree of alignment, and a stage control actuated by the signal to position the stage (14) and, so, align the substrate (11) with the reticle (4). The sensor (17) includes a light channel (19), such as a fiber optic rod, positioned to receive images from the lower surface (13) of said substrate ( 11) and carry them to the photocell.

Abstract: Apparatus for projecting multiple images from a pair of reticles (117) to a photo-sensitive coated substrate (1) to produce large scale electronic devices (2). A pair of parallel and proximate optical systems (29) are used, the optical systems being positioned to project in the z-direction upon a movable stage (11) subject to controlled motion (159, 169) in the x- and y-directions. The apparatus includes means (225) for determining the coordinates of motion of the stage relative to images projected from the reticles, means for using the determined positions to establish a stage transfer function for the apparatus relative to various positions of stage, and means (130) for applying the transfer function to adjust the relative positions of the reticles (117) and substrate (1) for accurate image projection, and for thereafter projecting an image upon the substrate.

Abstract: Apparatus for projecting multiple images from a pair of reticles (117) to a photo-sensitive coated substrate (1) to produce large scale electronic devices (2). A pair of parallel and proximate optical systems (29) are used, the optical systems being positioned to project in the z-direction upon a movable stage (11) subject to controlled motion (159, 169) in the x- and y-directions. The apparatus includes means (225) for determining the coordinates of motion of the stage relative to images projected from the reticles, means for using the determined positions to establish a stage transfer function for the apparatus relative to various positions of stage, and means (130) for applying the transfer function to adjust the relative positions of the reticles (117) and substrate (1) for accurate image projection, and for thereafter projecting an image upon the substrate.