Abstract: An improved pattern of lines (26, 28) is placed on a wedged substrate (18) used to locate the focal plane of a scanning projection aligner. This pattern replaces the conventional array of microscopic resolution targets with large regions of microscopic lines and spaces. When printed, in- and out-of-focus conditions are macroscopically apparent due to the presence or absence of photoresist (14). Desired quantities conventionally determined from microscopic data, such as location of the best focus plane, astigmatism, mask-to-wafer parallelism, mirror aberrations and misalignments, are macroscopically determined in accordance with the invention.

Abstract: A reticle design is provided for step and repeat projection aligners which, when patterned on a wafer (10), allows quick macroscopic evaluation of best focus for used in fabricating integrated circuits. The reticle pattern consists of opaque lines and spaces of widths slightly above the resolution limit of the resist/aligner system. The macroscopic determination of best focus, being macroscopically visible, eliminates the need for microscopic determination, thereby providing a quick and easy method. The best focus determination is made by forming an array (22) of resist fields (14') on the wafer, subjecting each field to a different focus and exposure. Upon development, those fields away from the best focus and at the larger exposure doses will be removed, leaving a parabola (24) of fields whose apex (26) is at high exposure. Best focus is the focus setting used to print the row of fields (B) containing the apex.