Auto focus alignment and measurement system and method

Claim 2

Apparatus for focusing on an object plane, said apparatus comprising: first imaging means (18), movably disposed along an optical axis, for providing a first focal plane disposed toward the object plane; second imaging means (30), disposed along the optical axis on the opposite side of the first imaging means from the object plane, for providing a second focal plane disposed away from the object plane: illumination means (46) for illuminating the object plane; an array of photodiodes (36) disposed along the optical axis at the second focal plane, each photodiode being operable for producing an electrical signal proportional to the intensity of light incident thereon; processing means, coupled to the array of photodiodes, for analyzing the signals therefrom to indicate the focus of an image of the object plane at the second focal plane; and control means, coupled to the processing means, for moving the first imaging means along the optical axis to position the first focal plane in coincidence with the object plane.

Claim 3

Apparatus for positioning a first planar object with respect to a second planar object separated from the first plane object by a finite distance, said apparatus comprising: first imaging means (18), movably disposed along an optical axis, for providing a first focal plane disposed toward the planar objects; second imaging means (30), disposed along the optical axis on the opoposite side of the first imaging means from the planar objects, for providing a second focal plane disposed away from the planar objects; illumination means (46) for illuminating the planar objects; an array of photodiodes (36) disposed along the optical axis at the second focal plane, each photodiode being operable for producing an electrical signal proportional to the intensity of light incident thereon; processing means, coupled to the array of photodiodes, for analyzing the signals therefrom to indicate the focus of images of the planar objects; and control means, coupled to the processing means, for moving the first imaging means from one position to another along the optical axis to position the first focal plane alternately in coincidence with adjacent surfaces of the planar objects; said processing means also being operable for determining the displacement between the aforementioned positions of the first imaging means to determine the separation distance between the adjacent surfaces of the planar objects along the optical axis.

Claim 4

Apparatus for positioning a first planar object with respect to a second planar object separated from the first plane object by a finite distance, said apparatus comprising: first imaging means (18), movably disposed along an optical axis, for providing a first focal plane disposed toward the planar objects; second imaging means (30), disposed along the optical axis on the opoposite side of the first imaging means from the planar objects, for providing a second focal plane disposed away from the planar objects; illumination means (46) for illuminating the planar objects; an array of photodiodes (36) disposed along the optical axis at the second focal plane, each photodiode being operable for producing an electrical signal proportional to the intensity of light incident thereon; processing means, coupled to the array of photodiodes, for analyzing the signals therefrom to indicate the focus of images of the planar objects; and control means, coupled to the processing means, for moving the first imaging means from one position to another along the optical axis to position the first focal plane alternately in coincidence with adjacent surfaces of the planar objects; said processing means also being operable for determining the displacement between the aforementioned positions of the first imaging means to determine the separation distance between the adjacent surfaces of the planar objects along the optical axis.

Claim 5

Apparatus as in claim 2 further comprising: displacement means for moving the first planar object in a direction parallel to the optical axis; and control means, coupled to the displacement means, for adjusting the separation distance between the adjacent surfaces of the planar object to a preselected value.

Claim 6

Apparatus as in claim 2 further comprising: displacement means for moving the planar objects together in a plane perpendicular to the optical axis to allow determination of the separation distance between the adjacent surfaces of the planar objects at several locations; and rotation means for rotating the first planar object about orthogonal axes perpendicular to the optical axis to position the adjacent surfaces of the planar objects in parallel planes by equalizing the separation distances determined at the aforementioned locations.

Claim 7

Apparatus as in claim 3 or 4 further comprising: displacement means for translating and rotating the first planar object relative to the second planar object in a plane perpendicular to the optical axis; alignment sensing means for measuring the alignment between the two planar objects; and control means, coupled to the alignment sensing means and the last-mentioned displacement means, for controlling the translation and rotation of the first planar object to position the first planar object in alignment with respect to the second planar object.

Claim 8

Apparatus for measuring the degree of flatness of a generally planar object, said apparatus comprising: first imaging means, movably disposed along an optical axis, for providing a first focal plane disposed toward the planar object; second imaging means, disposed along the optical axis on the opposite side of the first imaging means from the planar object, for providing a second focal plane disposed away from the planar object; illumination means for illuminating a surface of the planar object; an array of photodiodes disposed along the optical axis at the second focal plane, each photodiode being operable for producing an electrical signal proportional to the intensity of light incident thereon; processing means, coupled to the array of photodiodes, for analyzing the signals from the array of photodiodes to indicate focus of an image of the surface of the planar object at the second focal plane; displacement means for moving the planar object in a plane parallel to the first focal plane to successively position different areas of the surface of the planar object within the field of view of the first imaging means; and control means, coupled to the processing means, for moving the first imaging means to successively position the first focal plane in coincidence with the aforementioned surface areas of the planar object; said processing means also being operable for determining the displacement range of the first imaging means for the aforementioned surface areas of the planar object to determine the degree of flatness of the surface of the planar object.

Claim 9

Apparatus for measuring the degree of flatness of a generally planar object, said apparatus comprising: first imaging means, movably disposed along an optical axis, for providing a first focal plane disposed toward the planar object; second imaging means, disposed along the optical axis on the opposite side of the first imaging means from the planar object, for providing a second focal plane disposed away from the planar object; illumination means for illuminating a surface of the planar object; an array of photodiodes disposed along the optical axis at the second focal plane, each photodiode being operable for producing an electrical signal proportional to the intensity of light incident thereon; processing means, coupled to the array of photodiodes, for analyzing the signals from the array of photodiodes to indicate focus of an image of the surface of the planar object at the second focal plane; displacement means for moving the planar object in a plane parallel to the first focal plane to successively position different areas of the surface of the planar object within the field of view of the first imaging means; and control means, coupled to the processing means, for moving the first imaging means to successively position the first focal plane in coincidence with the aforementioned surface areas of the planar object; said processing means also being operable for determining the displacement range of the first imaging means for the aforementioned surface areas of the planar object to determine the degree of flatness of the surface of the planar object.

Claim 10

Apparatus for aligning a semiconductor substrate with respect to a circuit mask separated from the substrate by a finite distance, said apparatus comprising: first imaging means, movably disposed along a first optical path, for providing a first focal plane disposed toward the mask and the substrate; second imaging means, disposed along the first optical path on the opposite side of the first imaging means from the mask and the substrate, for providing a second focal plane disposed away from the mask and the substrate; beam splitting means, disposed along the first optical path between the first imaging means and the second imaging means, for providing a second optical path: third imaging means, disposed along the second optical path, for providing an image of the mask and the substrate: illumination means for illuminating the mask and the substrate; an array of photodiodes disposed along the first optical path at the second focal plane, each photodiode being operable for producing an electrical signal proportional to the intensity of light incident thereon; processing means, coupled to the array of photodiodes, for analyzing the signals therefrom to indicate the focus of images of the mask and the substrate; and control means, coupled to the processing means, for moving the first imaging means from one position to another along the first optical path to position the first focal plane alternately in coincidence with a surface of the mask and an adjacent surface of the substrate.

Claim 11

Apparatus for aligning a semiconductor substrate with respect to a circuit mask separated from the substrate by a finite distance, said apparatus comprising: first imaging means, movably disposed along a first optical path, for providing a first focal plane disposed toward the mask and the substrate; second imaging means, disposed along the first optical path on the opposite side of the first imaging means from the mask and the substrate, for providing a second focal plane disposed away from the mask and the substrate; beam splitting means, disposed along the first optical path between the first imaging means and the second imaging means, for providing a second optical path: third imaging means, disposed along the second optical path, for providing an image of the mask and the substrate: illumination means for illuminating the mask and the substrate; an array of photodiodes disposed along the first optical path at the second focal plane, each photodiode being operable for producing an electrical signal proportional to the intensity of light incident thereon; processing means, coupled to the array of photodiodes, for analyzing the signals therefrom to indicate the focus of images of the mask and the substrate; and control means, coupled to the processing means, for moving the first imaging means from one position to another along the first optical path to position the first focal plane alternately in coincidence with a surface of the mask and an adjacent surface of the substrate.

Claim 12

Apparatus as in claim 7 wherein the illumination means is coupled to the processing means and responsive thereto for illuminating the aforementioned surface of the mask when that surface is in coincidence with the first focal plane and for illuminating the aforementioned adjacent surface of the substrate when that surface is in coincidence with the first focal plane.

Claim 13

Apparatus as in claim 8 further comprising first substrate displacement means for translating and rotating the substrate relative to the mask in a plane parallel to the first focal plane to move the substrate into alignment with respect to the mask.

Claim 14

Apparatus as in claim 9 wherein the processing means is operable for determining the displacement between the aforementioned positions of the first imaging means to determine the separation distance between the aforementioned adjacent surfaces of the mask and the substrate along the first optical path.

Claim 15

Apparatus as in claim 10 further comprising: second substrate displacement means for moving the substrate in a direction perpendicular to the first focal plane: and control means, coupled to the second substrate displacement means and the processing means, for adjusting the separation distance between the aforementioned adjacent surfaces of the mask and the substrate to a preselected value.

Claim 16

Apparatus for aligning a semiconductor substrate with respect to a circuit mask separated from the substrate by a finite distance, said apparatus comprising: right first imaging means, movably disposed along a right first optical path, for providing a right first focal plane disposed toward the mask and the substrate: left first imaging means, movably disposed along a left first optical path parallel to the right first optical path, for providing a left first focal plane disposed toward the mask and the substrate; right second imaging means, disposed along the right first optical path on the opposite side of the right first imaging means from the mask and the substrate, for providing a right second focal plane disposed away from the mask and the substrate;. left second imaging means, disposed along the left first optical path on the opposite side of the left first imaging means from the mask and the substrate, for providing a left second focal plane disposed away from the mask and the substrate; right beam splitting means, disposed along the right first optical path between the right first imaging means and the right second imaging means, for providing a right second optical path separate from the right first optical path: left beam splitting means, disposed along the left first optical path between the left first imaging means and the left second imaging means, for providing a left second optical path separate from the left first optical path; right third imaging means, disposed along the right second optical path, for providing an image of a right area of a surface of the mask and a corresponding right area of an adjacent surface of the substrate; left third imaging means,disposed along the left second optical path, for providing an image of a left area of a surface of the mask and a corresponding left area of an adjacent surface of the substrate; right illumination means for illuminating the right surface areas of the mask and the substrate; left illumination means for illuminating the left surface areas of the mask and the substrate; a right array of photodiodes disposed along the right first optical path at the right second focal plane, each of those photodiodes being operable for producing an electrical signal proportional to the intensity of light incident thereon; a left array of photodiodes disposed along the left first optical path at the left second focal plane, each of those photodiodes also being operable for producing an electrical signal proportional to the intensity of light incident thereon; processing means, coupled to the right and left arrays of photodiodes, for analyzing the signals from the right array of photodiodes to indicate the focus of images of the right surface areas of the mask and the substrate and for analyzing the signals from the left array of photodiodes to indicate the focus of images of the left surface areas of the mask and the substrate: right control means, coupled to the processing means, for moving the right first imaging means from one position to another along the right first optical path to position the right first focal plane alternately in coincidence with the corresponding right surface areas of the mask and the substrate; and left control means, coupled to the processing means, for moving the left first imaging means from one position to another along the left first optical path to position the left first focal plane alternately in coincidence with the corresponding left surface areas of the mask and the substrate.

Claim 17

Apparatus for aligning a semiconductor substrate with respect to a circuit mask separated from the substrate by a finite distance, said apparatus comprising: right first imaging means, movably disposed along a right first optical path, for providing a right first focal plane disposed toward the mask and the substrate: left first imaging means, movably disposed along a left first optical path parallel to the right first optical path, for providing a left first focal plane disposed toward the mask and the substrate; right second imaging means, disposed along the right first optical path on the opposite side of the right first imaging means from the mask and the substrate, for providing a right second focal plane disposed away from the mask and the substrate;. left second imaging means, disposed along the left first optical path on the opposite side of the left first imaging means from the mask and the substrate, for providing a left second focal plane disposed away from the mask and the substrate; right beam splitting means, disposed along the right first optical path between the right first imaging means and the right second imaging means, for providing a right second optical path separate from the right first optical path: left beam splitting means, disposed along the left first optical path between the left first imaging means and the left second imaging means, for providing a left second optical path separate from the left first optical path; right third imaging means, disposed along the right second optical path, for providing an image of a right area of a surface of the mask and a corresponding right area of an adjacent surface of the substrate; left third imaging means,disposed along the left second optical path, for providing an image of a left area of a surface of the mask and a corresponding left area of an adjacent surface of the substrate; right illumination means for illuminating the right surface areas of the mask and the substrate; left illumination means for illuminating the left surface areas of the mask and the substrate; a right array of photodiodes disposed along the right first optical path at the right second focal plane, each of those photodiodes being operable for producing an electrical signal proportional to the intensity of light incident thereon; a left array of photodiodes disposed along the left first optical path at the left second focal plane, each of those photodiodes also being operable for producing an electrical signal proportional to the intensity of light incident thereon; processing means, coupled to the right and left arrays of photodiodes, for analyzing the signals from the right array of photodiodes to indicate the focus of images of the right surface areas of the mask and the substrate and for analyzing the signals from the left array of photodiodes to indicate the focus of images of the left surface areas of the mask and the substrate: right control means, coupled to the processing means, for moving the right first imaging means from one position to another along the right first optical path to position the right first focal plane alternately in coincidence with the corresponding right surface areas of the mask and the substrate; and left control means, coupled to the processing means, for moving the left first imaging means from one position to another along the left first optical path to position the left first focal plane alternately in coincidence with the corresponding left surface areas of the mask and the substrate.

Claim 18

Apparatus as in claim 12 wherein: the right illumination means is coupled to the processing means and responsive thereto for illuminating the right surface area of the mask when that surface area is in coincidence with the right first focal plane and for illuminating the right surface area of the substrate when that surface area is in coincidence with the right first focal plane; and the left illumination means is also coupled to the processing means and responsive thereto for illuminating the left surface area of the mask when that surface area is in coincidence with the left first focal plane and for illuminating the left surface area of the substrate when that surface area is in coincidence with the left first focal plane.

Claim 19

Apparatus as in claim 13 further comprising first substrate displacement means for translating and rotating the substrate relative to the mask in a plane perpendicular to the right and left first optical paths to move the substrate into alignment with respect to the mask.

Claim 20

Apparatus as in claim 14 wherein the processing means is operable for determining the displacement between the aforementioned positions of the right first imaging means to determine the right separation distance between the corresponding right surface areas of the mask and the substrate and for determining the displacement between the aforementioned positions of the left first imaging means to determine the left separation distance between the corresponding left surface areas of the mask and the substrate; second substrate displacement means for rotating the substrate about an axis perpendicular to the right and left first optical paths; and control means, coupled to the second substrate displacement means and the processing means, for positioning the substrate to equalize the right and left separation distances.

Claim 21

Apparatus as in any of the preceding claims 1, 2, 6, and 12 wherein each first imaging means comprises a single convergent lens.

Claim 22

Apparatus as in claim 16 wherein each second imaging means comprises a convergent lens.

Claim 23

Apparatus as in claim 17 wherein each second imaging means further comprises a convergent magnifying lens.

Claim 24

Apparatus as in any of the preceding claims 1, 2, 6, 7 and 12 wherein each control means comprises: a piezoelectric transducer, coupled to the respective first imaging means, for displacing that first imaging means in proportion to the magnitude of an applied voltage; and drive means, coupled to the piezoelectric transducer and the processing means, for driving the piezoelectric transducer with an applied voltage of a magnitude for effecting displacement of the respective first imaging means to a position at which the processing means indicates focus of an image.

Claim 25

Apparatus as in claim 7 or 12 wherein each third imaging means comprises first and second convergent lenses for providing a focused and magnified view of the mask and the substrate.

Claim 26

Apparatus as in claim 7 or 12 wherein each third imaging means comprises a television camera and an associated television monitor for providing a focused and magnified view of the mask and the substrate.

Claim 27

Apparatus as in claim 7 or 12 wherein each illumination means comprises a strobe light timed to flash when a first focal plane coincides with the aforementioned surface of the mask or the aforementioned adjacent surface of the substrate.

Claim 28

Apparatus as in any of the preceding claims 1, 2, 6, 7 and 12 wherein the processing means is responsive to the rate of signal transition from photodiodes sensing a relatively light area of an image to photodiodes sensing a relatively dark area of the same image in determining the focus of that image.

Claim 29

Apparatus as in any of the preceding claims 1, 2, 6, 7 and 12 wherein the processing means is responsive to the difference in signal strength from photodiodes sensing a relatively light area of an image and from photodiodes sensing a relatively dark area of the same image in determining the focus of that image.

Claim 30

Apparatus for measuring the dimensions of surface features of a planar object, said apparatus comprising: imaging means for focusing an image of a surface of the planar object onto a focal plane; illumination means for illuminating the surface of the planar object; an array of photodiodes disposed at the focal plane, each photodiode being operable for producing an electrical signal proportional to the intensity of light incident thereon; and processing means, coupled to the array of photodiodes, for analyzing the signals therefrom to indicate the dimensions of surface features of the planar object by determining the extent of photodiodes sensing the same intensity of light.

Claim 31

Apparatus for measuring the dimensions of surface features of a planar object, said apparatus comprising: imaging means for focusing an image of a surface of the planar object onto a focal plane; illumination means for illuminating the surface of the planar object; an array of photodiodes disposed at the focal plane, each photodiode being operable for producing an electrical signal proportional to the intensity of light incident thereon; and processing means, coupled to the array of photodiodes, for analyzing the signals therefrom to indicate the dimensions of surface features of the planar object by determining the extent of photodiodes sensing the same intensity of light.

Claim 32

Apparatus as in claim 25 wherein the imaging means comprises: first imaging means, disposed along an optical axis between the aforementioned focal plane and the planar object, for providing another focal plane at the surface of the planar object; and second imaging means disposed along the optical axis on the opposite side of the first imaging means from the planar object, for providing the first-mentioned focal plane.

Claim 37

A method as in claim 27 or 28 wherein the focus signal is computed from the difference in magnitude of output signals produced by photodiodes sensing a relatively light area of the image and photodiodes sensing a relatively dark area of the same image.

Claim 38

A method as in claim 27 or 28 wherein the focus signal is computed from the transition rate between output signals produced by photodiodes sensing a relatively light area of the image and photodiodes sensing a relatively dark area of the same image.

Claim 41

A method as in claim 31 further comprising the step of measuring the displacement of the first optical lens from a position at which the image of the first planar object is focused onto the array of photodiodes at the focal plane of the second optical lens to a postion at which the image of the second planar object is focused onto the array of photodiodes at the focal plane of the second optical lens to determine the separation distance between the first and second planar objects.

Claim 42

A method as in claim 32 further comprising the step of moving the first planar object in a direction parallel to the optical axis of the first optical lens to adjust the separation distance between the first and second planar objects to a preselected value.

Claim 43

A method as in claim 32 or 33 further comprising the steps of: measuring the separation distance between the first and second planar objects at a plurality of spaced-apart locations; and rotating the first planar object about orthogonal axes perpendicular to the optical axis of the first optical lens to equalize the separation distances measured at the aforementioned locations.

Claim 46

A method as in claim 31, 32, 33 or 35 wherein: the first planar object comprises a semiconductor substrate; and the second planar object comprises a circuit mask.