Photomask alignment system

Claim 2

An automatic apparatus for aligning a photomask with a substrate comprising: (a) a substrate having a diffraction pattern formed thereon; (b) a monochromatic light source adapted to have a beam directed onto said diffraction pattern; (c) a completely opaque key on the photomask, said completely opaque key being adapted to block portions of said diffraction pattern from the beam of said monochromatic light source; (d) at least two photosensitive elements adapted to receive light from said monochromatic light source after it has been reflected from said diffraction pattern; (e) mounting means for mounting said substrate and said photomask such that the photomask and substrate can be moved relative to one another; and (f) a feedback mechanism including said photosensitive elements and said mounting means for aligning said photomask to said substrate by relative movement between said photomask and said substrate in response to the intensities of light detected by said photosensitive elements.

Claim 3

The apparatus of claim 1 wherein said monochromatic light source comprises a laser.

Claim 4

The apparatus of claim 1 wherein said diffraction pattern is comprised of a photoresist pattern formed on a semiconductor substrate.

Claim 5

The apparatus of claim 1 wherein said substrate comprises a silicon wafer and said diffraction pattern is comprised of a silicon dioxide pattern formed on said substrate.

Claim 6

The apparatus of claim 1 wherein said diffraction pattern comprises a series of diffraction gratings which provide x-axis, y-axis and rotational information regarding the relative alignment of said photomask and said substrate.

Claim 7

The apparatus of claim 1 wherein said photosensitive elements comprise photodiodes.

Claim 8

The apparatus of claim 1 wherein said mounting means comprises a movable stage.

Claim 9

The apparatus of claim 7 wherein said photomask mounts on said stage.

Claim 10

The apparatus of claim 7 wherein said substrate mounts on said stage.

Claim 13

The method of claim 10 wherein said step of transmitting a monochromatic beam comprises the step of transmitting a beam from a laser.

Claim 14

The method of claim 11 further comprising chopping said beam before it is transmitted through said key.

Claim 15

The method of claim 12 further comprising splitting said beam into two beams before it is transmitted through said key.

Claim 16

The method of claim 13 further comprising measuring the intensity of beams of light reflected from at least two of said diffraction patterns, which reflected beams are representative of the displacement of the key with respect to each of said diffraction patterns along the x-axis and y-axis, whereby the intensities of the reflected beams are representative of the rotation of the key with respect to said diffraction patterns.

Claim 17

The method of claim 14 further comprising moving said photomask relative to said substrate in response to signals determined by the intensities of said beams.

Claim 18

The method of claim 14 further comprising moving said substrate relative to said photomask in response to signals determined by the intensities of said beams.

Claim 19

An automatic apparatus for aligning a photomask with a substrate comprising: (a) a substrate having a diffraction pattern formed thereon; (b) a monochromatic light source adapted to have a beam directed onto said diffraction pattern; (c) an opaque key on the photomask, said opaque key being adapted to block portions of said diffraction pattern from the beam of said monochromatic light source; (d) at least two photosensitive elements adapted to receive light from said monochromatic light source after it has been reflected from said diffraction pattern; (e) mounting means for mounting said substrate and said photomask such that the photomask and substrate can be moved relative to one another; (f) a feedback mechanism including said photosensitive elements and said mounting means for aligning said photomask to said substrate by relative movement between said photomask and said substrate in response to the intensities of light detected by said photosensitive elements; and (g) means for vibrating said substrate in a direction substantially perpendicular to the planes of said substrate and said photomask.

Claim 20

An automatic apparatus for aligning a photomask with a substrate comprising: (a) a substrate having a diffraction pattern formed thereon; (b) a monochromatic light source adapted to have a beam directed onto said diffraction pattern; (c) an opaque key on the photomask, said opaque key being adapted to block portions of said diffraction pattern from the beam of said monochromatic light source; (d) at least two photosensitive elements adapted to receive light from said monochromatic light source after it has been reflected from said diffraction pattern; (e) mounting means for mounting said substrate and said photomask such that the photomask and substrate can be moved relative to one another; (f) a feedback mechanism including said photosensitive elements and said mounting means for aligning said photomask to said substrate by relative movement between said photomask and said substrate in response to the intensities of light detected by said photosensitive elements; and (g) means for vibrating said substrate in a direction substantially perpendicular to the planes of said substrate and said photomask.

Claim 21

The apparatus of claim 17 wherein said means for vibrating comprises a piezoelectric element on which said substrate is mounted.

Claim 22

The apparatus of claim 18 wherein said piezoelectric element is a PZT element and said apparatus further comprises means for providing an alternating voltage across said piezoelectric element.

Claim 23

The apparatus of claim 17 wherein said photosensitive elements comprise photodiodes.

Claim 24

The apparatus of claim 17 wherein said mounting means comprises a movable stage.

Claim 25

The apparatus of claim 21 wherein said photomask mounts on said stage.

Claim 26

The apparatus of claim 21 wherein said substrate mounts on said stage.