A system for aligning a semiconductor wafer with a mask bearing a pattern to be formed on the wafer, in which both the wafer and the mask bear an alignment mark, and in which light used for alignment is filtered to transmit only in a selected bandwidth, uses a reflector system to gather light reflected from edges of the alignment mark on the wafer. In order to minimize the effect of erroneous alignment signals from standing waves generated when the alignment signal is reflected from a wafer coated with a layer of photoresist, a second filter is placed in the path of light after it has reflected from the target. This second filter transmits a range of the reflected light which does not produce standing waves.
Techniques for identifying and determining the orientation, magnitude, and direction of slip plane dislocations transecting semiconductor dies are described, whereby a four point alignment pattern is examined for "squareness" and size integrity. Lack of squareness or significant change in apparent size of various aspects of the alignment pattern indicate slip-plane dislocations. The magnitude, orientation and direction of the dislocations are determined geometrically from measurement of the alignment pattern. Various other aspects of the invention are directed to optimal alignment of a photolithographic mask to a die which has experienced a slip-plane dislocation, and to discrimination between slip-plane dislocation and die-site rotation.
A wafer alignment system aligns a wafer by checking the alignment marks formed on the back surface of the wafer. A number of guiding rays are used to determine the corresponding alignment mark on the back of the wafer to ensure that the wafer is properly aligned. The alignment system of the invention also includes a wafer stage and a fixed base, wherein the wafer stage and the fixed base contains a number of apertures that allow the guiding rays to pass through and strike on the alignment marks on the wafer.
A precision placement apparatus comprises an improved probe for aligning a component and a substrate based upon features on the inner surfaces arranged in facing, spaced relationship, prior to assembling the component to the substrate. The probe comprises a dual prism assembly having a first face for viewing the componenet surface and a second face for viewing the substrate surface. The dual prism assembly superposes the images of the surfaces to permit an operator to accurately align the elements. A liquid crystal shutter is mounted onto one face of the dual prism assembly to exclude the image of the corresponding surface and thereby allow the operator to quickly determine the features of the other surface in order to make the appropriate adjustments.
A reduction projection type aligner in a reduction projection exposing device for exposing a circuit pattern on a mask through a reduction projection lens onto a wafer by the step and repeat of the wafer, which comprises: a light source for irradiating coherent irradiation light, a reflection mirror for reflecting the coherent irradiation light irradiated from the light source, a detection optical system for detecting an interference pattern by optically causing interference between an alignment pattern reflection light obtained by entering the coherent irradiation light irradiated from the light source through the reduction projection lens to the alignment pattern portion of the wafer, which is then reflected at the alignment pattern portion and then passed through the reduction projection lens and a reflection light reflected at the reflection mirror, and means for aligning a mask and a wafer relatively by detecting the position of the wafer by the video image signals in the interference pattern detected by the detection optical system.
An aerial image produced by a mask having transmissive portions is simulated by dividing the transmissive portions of the mask into primitive elements and obtaining a spatial frequency function corresponding to each of the primitive elements. The spatial frequency functions corresponding to the primitive elements are combined to obtain a transformed mask transmission function, and the transformed mask transmission function is utilized to generate a simulation of the aerial image.
