Determination of focal plane for a scanning projection aligner
AssigneeHewlett-Packard Company
InventorCatherine G. Kroko
Life of this patent
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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.
Claims10
A method of determining the location of the best focus surface of a scanning projection resist/aligner system having minimum resolvable features, comprising:
- (a) exposing an image in a resist layer formed on a polished side of a wafer through a wedged mask patterned with a plurality of opaque lines and clear spaces of widths nearly the size of the minimum resolvable features of the resist/aligner system;
- (b) developing the resist;
- and
- (c) determining the location of the best focus "plane" or surface by selecting the center of the resulting patterns.
A mask pattern arrangement to be placed on a conventional wedged mask substrate for use in a scanning projection aligner having minimum resolvable features and a condenser/optics system, which when patterned in a resist layer on a wafer, allows quick macroscopic evaluation of the optical condition of the aligner, the mask pattern comprising:
- (a) a plurality of opaque lines and clear spaces of width nearly the size of the minimum resolvable feature of the aligner;
- and
- (b) wherein the pattern is arranged in stripes across the wedged mask so that each stripe will provide information about one segment of the aligner condenser/optics system.
A method of diagnosing and characterizing a lens in a scanning projection aligner comprising (a) forming a plurality of stripes of resist on a polished side of a flat wafer, said stripes comprising alternating strips of sagittal and tangential lines or horizontal and vertical lines formed by exposure through a similarly-patterned wedges mask;
- (b) developing the resist to macroscopically define a region in each stripe at best focus, (c) determining the centers of each said region;
- and (d) comparing the location of said centers with a predetermined specification for each stripe and with the location of centers of other stripes.
Dependencies are inferred from the claim text.