Precision automatic mask-wafer alignment system

Claim 2

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.

Claim 3

The invention of claim 1 further including means for automatically adjusting the relative position of the substrate and mask from the measurement of the intensity distribution.

Claim 4

The invention of claim 1 wherein the optical member for collecting and recombining is a single beam splitter.

Claim 5

The invention of claim 1 wherein the detector array comprises a plurality of light receiving members positioned to receive the interference pattern.

Claim 6

The invention of claim 2 further including means for comparing the measured relative position of the substrate and mask with a predetermined standard.

Claim 7

The invention of claim 2 further including composite gratings as the diffraction grating on the substrate and mask with different component periodicities.

Claim 8

The invention of claim 2 wherein the means for providing a collimated coherent light beam and a unitary optical member are offset from a perpendicular plane normal to the diffraction gratings of the mask and substrate.

Claim 9

The invention of claim 7 further including a computer means for determining the relative alignment of the substrate and mask and means for automatically adjusting one of the mask and substrate to a position within an acceptable tolerance for reproducing an image.

Claim 10

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.

Claim 11

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.

Claim 12

The invention of claim 9 further including means for comparing the measured relative position of the first and second elements with a predetermined standard.

Claim 13

The invention of claim 9 further including composite gratings as the diffraction gratings on the first and second elements with different component periodicities on each diffraction gratings.

Claim 14

The invention of claim 10 wherein the means for providing a collimated coherent light beam and a unitary optical member are offset from a perpendicular plane normal to the diffraction gratings of the first and second elements.

Claim 15

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.

Claim 16

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.

Claim 17

The invention of claim 13 further including means for comparing the measured relative position of the substrate and mask with a predetermined standard.

Claim 18

The invention of claim 13 wherein the means for providing a collimated coherent light beam and the single optical element are offset from a perpendicular plane normal to the diffraction gratings of the mask and substrate.

Claim 19

The invention of claim 13 further including a computer means for determining the relative alignment of the substrate and mask and means for automatically adjusting one of the mask and substrate to a position within an acceptable tolerance for reproducing an image.

Claim 20

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

Claim 21

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

Claim 22

The invention of claim 17 further including means for automatically adjusting the relative alignment until the first and second elements are positioned within predetermined tolerances.

Claim 23

The invention of claim 18 wherein each composite diffraction grating is a composite of two gratings of two different periods superimposed on each other.

Claim 24

The invention of claim 18 wherein the means for selecting and redirecting includes a single beamsplitter for receiving the plus and minus diffraction beams from the first and second composite diffraction gratings.

Claim 25

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.

Claim 26

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.

Claim 27

The invention of claim 21 wherein the means for detecting the interference fringe pattern includes a linear detector array of photodetector elements.

Claim 28

The invention of claim 21 wherein the optical means is a single beamsplitter.

Claim 29

The invention of claim 21 wherein the collimated coherent light beam is directed at an acute angle to the surface of the composite diffraction grating and the optical means is spatially positioned to receive the two pairs of diffracted light beams extending at acute angles from the surface of the composite diffraction grating.

Claim 30

The invention of claim 21 wherein the composite diffraction grating is a composite of two gratings of two different periods superimposed on the object.

Claim 31

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.

Claim 32

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.

Claim 33

The invention of claim 26 further including means for automatically adjusting the relative position of the substrate and mask from the measurement of the intensity distribution.

Claim 34

The invention of claim 26 further including means for comparing the measured relative position of the substrate and mask with a predetermined standard.

Claim 35

The invention of claim 26 wherein the means for collecting and the means for coherently combining is a unitary optical member.

Claim 36

The invention of claim 29 wherein the means for providing a collimated coherent light beam and the unitary optical member are offset from a perpendicular plane normal to the composite diffraction gratings of the mask and substrate.

Claim 37

The invention of claim 29 wherein the optical member is a single beam splitter.

Claim 38

The invention of claim 26 further including a computer means for determining the relative alignment of the substrate and mask and means for automatically adjusting one of the mask and substrate to a position within an acceptable tolerance for reproducing an image.

Claim 39

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.

Claim 40

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.