Precision automatic mask-wafer alignment system
AssigneeHughes Aircraft Company
InventorsJohn L. Bartelt, Ross D. Oleny
Life of this patent
Estimating the term…
Abstract
An interferometric alignment and position detector system for determining relative location of an object is provided. A composite diffraction grating is provided with the object. A laser can provide a collimated coherent light beam directed so as to impinge on the composite diffraction grating. A beam splitter can collect at least two pairs of diffracted light beams from the composite diffraction grating and can combine the pairs of diffracted light beams to provide interference fringe patterns. Apparatus is provided for detecting the interference fringe patterns to provide a measurement of the intensity distribution from which the relative location can be established.
Claims33
An interferometric alignment system for permitting a reproduction of an image from a mask onto a substrate comprising:
- a substrate having a first diffraction grating formed thereon;
- a mask having a second diffraction grating different from the first diffraction grating, the mask and substrate being provided in close proximity to one another so as to substantially superimpose mask and substrate gratings;
- means for providing a collimated coherent light beam directed so as to impinge on the mask and substrate gratings;
- a unitary optical member for collecting and recombining at least a pair of diffracted light beams from the mask and the substrate to provide an interference pattern;
- and
- a detector array, positioned such that the interference pattern is realized on the detector array to provide a measurement of the intensity distribution of the interference pattern from which relative alignment of the substrate and mask can be determined.
An interferometric alignment measurement system for the precision alignment of a first element and a second element comprising:
- a transmissive first diffraction grating associated with the first element;
- a second diffraction grating associated with the second element;
- means for positioning the first and second elements such that the gratings are superimposed over each other;
- means for providing collimated coherent light directed so as to impinge on the grating of the first element and therethrough onto the grating of the second element;
- a unitary optical member for selecting and redirecting at least two pair of diffraction beams of a given diffraction order from the gratings to provide a mutually coherent interference pattern of the beams;
- a detector array, positioned such that the interference pattern is realized on the detector array to provide a measurement of the intensity distribution of the interference pattern;
- and
- means for determining the relative alignment of the first and second element from the intensity distribution.
An interferometric alignment and control system for reproducing an image from a mask onto a substrate comprising:
- a substrate having a composite diffraction grating formed thereon;
- a mask having a composite diffraction grating different from said first diffraction grating formed thereon, the mask and substrate being provided in close proximity to one another so as to substantially superimpose the mask and substrate gratings in parallel planes;
- means for providing a collimated coherent lightbeam directed so as to impinge on and be diffracted from each of the mask and substrate gratings at acute angles to the parallel planes;
- detector arrays for providing a measurement of intensity distributions impacting each array;
- and
- a single optical element positioned to select and redirect diffracted light of a predetermined diffraction order from each set of gratings to realize an interference pattern on the detector array whereby the relative alignment of the substrate and mask can be determined from the intensity distributions of the interference patterns.
An interferometric alignment measurement system for the precision alignment of a first element and a second element comprising:
- first composite diffraction grating associated with the first element;
- a second composite diffraction grating associated with the second element;
- means for positioning the first and second elements such that the gratings are superimposed over each other;
- means for providing collimated coherent light directed so as to impinge at an acute angle on the gratings of the first element and therethrough onto the gratings of the second element;
- means for selecting and redirecting the plus and minus diffraction beams of a given diffraction order from the gratings to provide mutually coherent interference patterns of the beams;
- detector array positioned such that the interference pattern is realized on the detector array to provide a measurement of the intensity distribution of the interference pattern;
- and
- means for automatically determining the relative alignment of the first and second element from the intensity distributions
A position detector for determining relative location of an object, comprising:
- a composite diffraction grating provided with the object;
- means for providing a collimated coherent light beam directed so as to impinge on the composite diffraction grating;
- a unitary optical means for collecting at least two pair of diffracted light beams from the composite diffraction grating;
- means for coherently combining the pairs of diffracted light beams to provide an interference fringe pattern;
- and
- means for detecting the interference fringe pattern to provide a measurement of the intensity distribution from which the relative location can be established.
An improved lithography system for permitting a reproduction of an image from a mask onto a substrate comprising:
- means for providing and directing a source of exposure energy towards the mask and substrate;
- and
- means for aligning the mask and substrate including at least one composite diffraction grating provided on both the mask and substrate, means for providing a collimated coherent light beam directed so as to impinge on the composite diffraction gratings, means for collimating at least two pair of diffracted light beams from each composite diffraction grating, means for coherently combining the pairs of diffracted light beams to provide an interference fringe patterns, and means for detecting the measurement of the intensity distribution from which the relative location of the mask and substrate can be established.
A position detector for determining relative location of an object, comprising;
- a composite diffraction grating provided with the object;
- means for providing a collimated coherent light beam directed so as to impinge on the composite diffraction grating;
- means for collecting at least two pairs of diffracted light beams from the composite diffraction grating;
- means for coherently combining the pairs of diffracted light beams to provide interference fringe patterns;
- and
- means for detecting the interference fringe patterns to provide a measurement of the intensity distribution from which the relative location can be established.
Dependencies are inferred from the claim text.