Apparatus and method for making large area electronic devices, such as flat panel displays and the like, using correlated, aligned dual optical systems

• US 4,769,680 A
• Filed: 10/22/1987
• Issued: 09/06/1988
• Est. Priority Date: 10/22/1987
• Status: Expired

• Current Assignee: Rudolph Technologies Incorporated (Onto Innovation Inc.)
• Original Assignee: MRS Technology, Inc.
• Inventors: Resor, Griffith L. III, Schneider, William C., McEachern, Robert A., Worth, Walter H.
• Primary Examiner(s): WINTERCORN, RICHARD
• Application Number:
  US07/111,427
• Time in Patent Office: 320 Days
• Field of Search: 355/43, 355/46, 355/53, 355/54, 355/45, 356/401, 364/490, 364/559
• US Class Current: 355/43
• CPC Class Codes: G02F 1/13625 Patterning using multi-mask exposure
• CPC Class Codes: G03F 7/70275 Multiple projection paths, e.g. array of projection systems, microlens projection systems or tandem projection systems
• CPC Class Codes: G03F 7/70475 Stitching, i.e. connecting image fields to produce a device field, the field occupied by a device such as a memory chip, processor chip, CCD, flat panel display
• CPC Class Codes: G03F 7/70691 Handling of masks or workpieces
• CPC Class Codes: G03F 7/70791 Large workpieces, e.g. glass substrates for flat panel displays or solar panels
• CPC Class Codes: G03F 7/70875 Temperature, e.g. temperature control of masks or workpieces via control of stage temperature
• CPC Class Codes: G03F 7/70891 Temperature

Abstract

Apparatus for projecting multiple images from a pair of reticles (117) to a photo-sensitive coated substrate (1) to produce large scale electronic devices (2). A pair of parallel and proximate optical systems (29) are used, the optical systems being positioned to project in the z-direction upon a movable stage (11) subject to controlled motion (159, 169) in the x- and y-directions. The apparatus includes means (225) for determining the coordinates of motion of the stage relative to images projected from the reticles, means for using the determined positions to establish a stage transfer function for the apparatus relative to various positions of stage, and means (130) for applying the transfer function to adjust the relative positions of the reticles (117) and substrate (1) for accurate image projection, and for thereafter projecting an image upon the substrate. The stage is then stepped to a position to permit projection of an abutting image, and the transfer function is used to adjust the relative positions of the reticles (117) and substrate (1) for accurate image projection for projecting the abutting image upon the substrate (1). The steps are repeated until sufficient images have been projected upon the substrate to make up one integrated layer of a flat panel display or other large scale electronic device. After treating the photosensitive layer, subsequent layers are produced in a similar manner.

Claims

1. Apparatus to project images from reticles onto the photosensitive surface of a single common substrate to produce a large scale integrated image upon said substrate, said apparatus including

a movable stage for holding said substrate, means for stepping said stage in the x- and y-directions, stage calibration means to calibrate the position of said stage in different stepped positions and to determine a stage transfer function incorporating said calibration data,

a pair of parallel optical systems for concurrently projecting dual images upon said substrate, said systems having optical axes in the z-direction, each said optical system including a projection imaging system, an illumination system, a reticle carrier to carry said reticles, and a reticle chuck positioned to receive said reticles one at a time from said reticle carrier and to hold each said reticle within said illumination system during projection of an image carried by said reticle, each said reticle chuck being capable of individual adjustment movement in at least the x-, y-, z-, and φ

-directions,

reticle calibration means associated with each said reticle chuck to calibrate the position of a said reticle in said chuck relative to said stage and to determine a reticle transfer function incorporating said calibration data,

a computer associated with said stepping means and said optical systems for controlling same, said computer storing said stage transfer function and said reticle transfer functions and utilizing same to adjust said stepping means and said reticle chuck prior to each said image projection,

whereby said projected images will be properly aligned relative to one another to produce a unitary, integrated image on said photosensitive surface.

2. Apparatus to project images from reticles as set forth in claim 1 in which said stage transfer function is an algorithm incorporating the variations of motion of said stage from theoretically true positions.

3. Apparatus to project images from reticles as set forth in claim 1 in which said reticle transfer functions are algorithms incorporating the adjustments required to be made in the positions of said reticle chucks so that the projected image is correct in magnification, rotation, size and position.

4. Apparatus to project images from reticles as set forth in claim 1 in which said reticle chucks are capable of adjustment over six degrees of freedom.

5. Apparatus to project images from reticles as set forth in claim 4, said apparatus including an asymmetric lens in each said optical system, each said projection imaging system having magnification adjustment capability on its reticle side and telecentric focus adjustment capability on its substrate side, and

each said optical system including means for adjusting the spacing between said lens and said substrate,

whereby adjustment of said spacing focusses said lens and z-adjustment of said reticle chuck relative to said lens adjusts said magnification and each projected image can be adjusted for size, shape, angular orientation, and position.

6. Apparatus to project images from reticles as set forth in claim 1, each said illumination system including a folding mirror to alter the direction of light before it enters each said lens, whereby said projection imaging systems may be positioned proximate to one another.

7. Apparatus to project images from reticles as set forth in claim 1 including means to measure the distance between each said projection imaging systems and the surface of said substrate and to vary said distance prior to the projection of each image, whereby said spacing can be adjusted to maintain said image in focus regardless of unevenness of said surface.

8. Apparatus to project images from reticles as set forth in claim 1 in which said stage stepping means includes a pair of linear motors, one of which is positioned to move the stage in one direction and the other of which is positioned to move the stage in an orthogonal direction.

9. Apparatus to project images from reticles as set forth in claim 1 in which said stage includes banking pins and a vacuum chuck to receive and position said substrate, said vacuum chuck being biased to press said substrate towards said banking pins,

whereby said substrate can be initially positioned in said stage.

10. Apparatus to project images from reticles as set forth in claim 1 including means to vary the spacing between said two optical axes.

11. Apparatus to project images from reticles as set forth in claim 1 including means for measuring the intensity of the said image projected from each said reticle and for varying the exposure to provide equal exposure dosages to said photosensitive surface from each said reticle.

12. Apparatus to project images from reticles onto the photosensitive surface of a single common substrate to produce a large scale integrated image upon said substrate, said apparatus including

a movable stage for holding said substrate, means for stepping said stage in orthogonal directions in the plane of said substrate,

a pair of parallel optical systems mounted proximate to said substrate for concurrently projecting dual images upon said glass substrate, said systems having optical axes perpendicular to said substrate, each said optical system including a reticle carrier to carry said reticles and a reticle chuck positioned to receive said reticles one at a time from said reticle carrier and to hold each said reticle during projection of an image carried by said reticle, each said reticle chuck being capable of individual adjustment movement in six degrees of freedom,

a computer associated with said stepping means and said optical systems for controlling same, said computer storing data pertaining to the relative positions of said stage and each said reticle and utilizing same to adjust said stepping means and said reticle chuck prior to each said image projection,

whereby said projected images will be properly aligned relative to one another to produce a unitary, integrated image on said photosensitive surface.

13. Apparatus to project images from reticles as set forth in claim 12 in which each said optical system includes mirror means for altering the light path, whereby projection lenses may be positioned more proximate to one another.

14. Apparatus to project images from reticles as set forth in claim 12 including alignment marks on said reticles and sensing means in said stage for sensing said alignment marks as they are projected from said reticles.

15. Apparatus to project images from reticles as set forth in claim 14 in which said sensing means is a pop-up sensor adapted to move between a position corresponding to the level of the upper surface of substrate and a level below the lower surface of said substrate.

16. Apparatus to project images from reticles as set forth in claim 12 including a reflective alignment microscope associated with at least one of said optical columns, whereby said substrate can be aligned prior to projecting a second layer of images thereupon.

17. Apparatus to project images from reticles as set forth in claim 12 including means for adjusting the positions of said reticles to compensate for variations in magnification and/or focus caused by variations in the index of refraction of the surrounding air affecting the velocity of light.

18. Apparatus to produce large scale integrated images on the photosensitive surface of a substrate, said apparatus including

a movable stage, means for stepping said stage in the x-and y-directions,

a pair of parallel and proximate optical systems having axes in the z-direction and positioned above said stage for projection of images thereupon, said optical systems including a reticle chuck operatively associated with each said optical system, for carrying reticles bearing alignment marks to be projected upon said stage,

sensing means for comparing the position of said projected alignment marks on said stage as said stage is stepped throughout its movement range beneath said optical systems and for determining and recording the extent of variation of said stage from its theoretically true x-, y-, and φ

-positions throughout said range,

and means for varying the stepping of said stage from theoretical stepping distances to compensate for said variation in each position of said stage within said range,

whereby images formed upon said photosensitive surface will accurately abut with one another.

19. Apparatus to produce large scale integrated images as set forth in claim 18 in which said sensing means includes a plurality of sensors mounted in said stage.

20. Apparatus to produce large scale integrated images as set forth in claim 19 in which at least one of said sensing means is adapted to move between a position corresponding to the upper surface of said substrate and a retracted position.

21. Apparatus to produce large scale integrated images as set forth in claim 18 including

control means for each of said reticle chucks, said control means being adapted to vary the position of said chuck to adjust the position of said image to compensate for said variation in the said positions of said stage.

22. Apparatus to produce large scale integrated images as set forth in claim 18 in which said reticle chucks have six degrees of freedom of movement.

23. Apparatus to produce large scale integrated images as set forth in claim 18 including

a sensor for each said optical system to detect the distance of the lens in said system from said photosensitive surface and means to maintain said lens at a constant distance from said surface,

whereby said lenses in said optical system will be maintained in focus as said stage is moved regardless of variations in height of said surfaces.

24. Apparatus for making large area electronic devices utilizing horizontal alignment of images from two optical systems, said apparatus including

a movable stage adapted for motion in x- and y-directions,

a pair of parallel and proximate optical systems having axes in the z-direction and positioned to receive reticles in their object planes and to project images from said reticles upon said stage,

a reticle carrier associated with each said optical system and a reticle alignment chuck associated with each said reticle carrier and adapted to receive a reticle from its respective said carrier and to hold said reticle in the object plane of its respective said optical system, and

alignment means associated with said optical systems including

(i) control means associated with each said reticle chuck for adjusting same in any of six degrees of freedom,

(ii) means for varying the distance between said optical axes, and

(iii) means for varying the magnification of said optical systems,

whereby images projected by each said optical systems may be butted with one another and with images from the other of said system to produce large scale images suitable for said displays.

25. Apparatus for making large area electronic displays as set forth in claim 24 in which each said optical system includes an asymmetric telecentric lens.

26. Apparatus for making large area electronic displays as set forth in claim 24 in which said reticle carriers are adapted to carry a plurality of said reticles, and means for individually interchanging said reticles in said chuck.

27. Apparatus for making large area electronic displays as set forth in claim 24 including step and repeat means to move said stage distances equal to one dimension of said projected images, and means for so aligning said reticle alignment chucks during each said step that immediately preceding projected said images will abut with images projected in each said new position.

28. Apparatus for forming abutting images upon the photosensitive surface of a substrate, said images serving to form a display, said apparatus including

a movable stage for holding said substrate, said stage including preliminary alignment means for said substrate,

a pair of reticle chucks adapted to receive and hold reticles for projection upon said substrate, a light source and an optical system associated with each said chuck positioned to simultaneously project an image from each of said reticles held by said chucks upon different portions of said substrate, said optical systems having parallel optical axes, and

means for adjusting the relative positions of said chucks and said optical systems so that multiples of said images are abutting and in alignment upon said substrate,

whereby said images form a continuum with one another upon said substrate.

29. Apparatus for forming abutting images as set forth in claim 28 in which said continuum is a single integrated image on said substrate.

30. Apparatus for forming abutting images as set forth in claim 28 including a stepper associated with said stage adapted to move said stage in a direction paralleling a line connecting said optical axes for a distance commensurate with said images sizes, whereby said images may be repeated upon portions of said photosensitive surface contiguous with said first images.

31. Apparatus for forming abutting images as set forth in claim 30 in which the line between said optical axes is in the x-direction and said stepper operates in both the x- and y-directions.

32. Apparatus for forming abutting images as set forth in claim 28 in which said means for adjusting the relative positions of said carriers and said stage include step and repeat means to move said stage a distance substantially equal to one dimension of said projected images.

33. Apparatus for forming abutting images as set forth in claim 28 in which the spacing between the images of said optical systems leaves a remainder space and including a reticle image to fill and abut said space

34. Apparatus for forming abutting images as set forth in claim 28 including reticle carriers to carry a plurality of reticles and means for transferring said reticles between said carriers and said chucks.

35. Apparatus for forming abutting images as set forth in claim 28 including means associated with said optical systems for adjusting the distances of the respective said optical systems from said substrate to maintain constant distances from the surfaces of said substrate.

36. Apparatus for forming abutting images as set forth in claim 28 including laser interferometer means for determining the axial spacing between said optical systems.

37. Apparatus for producing large area electronic devices and having rapid throughput, said apparatus including

a frame,

a stage carried by said frame for motion in x- and y-directions, said stage being adapted to hold a substrate,

a pair of parallel and proximate optical systems having lenses with their axe in the z-direction and positioned to project images upon said substrate held by said stage,

sensors associated with said stage for determining the x-, y-, and φ

-positions of said stage relative to said optical systems,

a pair of reticle alignment chucks mounted on said frame, each said chuck being operatively associated with one of said optical systems, said reticle chucks being capable of adjustment in six degrees of freedom,

a stage alignment function providing coordinates of motion of said stage relative to each said reticle chuck,

stepping means for said stage, and

control means to adjust the position of said reticle chucks in accordance with said stage alignment function,

whereby multiple abutting images can be projected through said optical systems to create a uniform, integral image upon said substrate.

38. Apparatus for producing large area electronic devices as set forth in claim 37 including sensors for determining the relative axial positions of said lenses whereby said control means can adjust the position of said reticle chucks in accordance with said relative positions.

39. Apparatus for producing large area devices as set forth in claim 38 in which said lens position detectors are laser interferometers.

40. In an apparatus adapted to project simultaneous images, from reticles carried by a pair of parallel optical columns, upon a common substrate, to produce a single unified image, said columns being mounted with axes perpendicular to a stage carrying a substrate, said stage being adapted for stepping motion in x- and y- directions orthogonal to the axes of said columns, that improvement including

an asymmetric projecting lens in each said optical column for projecting said images, each said lens having magnification adjustment capability on its reticle side and focus adjustment capability on its substrate side, and separate means for each said lens for adjusting the axial spacing between said lenses and said substrate and separate means for each said lens for adjusting the spacing between said lenses and said reticles,

whereby the focus and magnification of each said lens can be independently adjusted for better alignment of said projected images.

41. In an apparatus adapted to project simultaneous images as set forth in claim 40, that further improvement including means for measuring the velocity of light and further means for adjusting the spacing of the lens from the substrate to adjust for focus changes based upon changes in said velocity of light.

42. In an apparatus adapted to project simultaneous images as set forth in claim 41 in which said means for adjusting for focus changes is an alignment chuck adapted to carry said reticle and having six degree of freedom of movement.

43. In an apparatus as set forth in claim 40, a folding mirror within said optical columns whereby light therein will be redirected permitting said axes to be positioned adjacent to one another.

44. In an apparatus adapted to project simultaneous images upon a common substrate, from reticles carried by a pair of optical columns having illuminators and lenses therein, to produce a unified image, said lenses being mounted with their axes parallel and perpendicular to a stage carrying said substrate, said stage being orthogonal to the axes of said lenses, that improvement including a folding mirror within said optical columns between said lenses and said condensers to redirect the light from said illuminator to said lenses, whereby said lenses may be positioned proximate to one another.

45. In an apparatus adapted to project simultaneous images, from reticles carried by a pair of parallel optical columns, upon a common substrate, to produce a single unified image, said columns being mounted with axes perpendicular to a stage carrying a substrate, said stage being adapted for stepping motion in orthogonal directions perpendicular to the axes of said columns, that improvement including

an asymmetric projecting lens in each said optical column for projecting said images, each said lens having magnification adjustment capability on its reticle side and focus adjustment capability on its substrate side,

a reticle chuck in each said optical column positioned to hold a reticle during projection of a said image, each said reticle chuck being independently adjustable in six degrees of freedom to permit positioning of said reticle for control of magnification, rotation, size and shape, and

control means to control the adjustment of each said reticle,

whereby images from each said optical column can be adjusted independently to permit proper alignment for the creation of a single integral image on said substrate formed from multiple simultaneous images projected from said two columns.

46. In an apparatus as set forth in claim 45 in which said reticles chucks are adjusted prior to each exposure.

47. In an apparatus as set forth in claim 45 in which said reticles chucks are adjusted upon power-up.

48. In an apparatus adapted to project simultaneous images as set forth in claim 45, that improvement in which said control means adjusts the said reticles during the period between each said simultaneous projection and each stepping of said stage.

49. The method of making displays on a photo-sensitive coated substrate carried by a movable stage, and using a pair of parallel optical columns with axes perpendicular to said stage, including the steps of

positioning said substrate on said stage,

simultaneously projecting a pair of aligned images, one from each of said optical systems upon said stage,

stepping said stage a predetermined distance in a given direction and thereafter again projecting said images upon said substrate, each of said new images being in abutting and aligned relationship with one of said previously projected images, and

repeating said stepping and projecting steps until said substrate carries an integral image layer formed of a plurality of said abutting images,

whereby one layer of an integral display has been projected upon said photosensitive substrate.

50. The method of making displays as set forth in claim 49 including the step of moving said stage in a direction orthogonal to said given direction.

51. The method of making displays as set forth in claim 49 including the step of adjusting the size of said aligned images such that no remainder space remains between the totalities of images projected by the two said optical systems.

52. The method of making displays as set forth in claim 49 including the step of projecting a remainder image.

53. The method of making displays a set forth in claim 49 including the step of adjusting the exposures of the two said images to make them equal.

54. The method of making displays as set forth in claim 49 including the steps of etching said photoresist and recoating it, positioning said substrate upon said stage, aligning it to receive a second image, and

thereafter simultaneously projecting said second image on said substrate, stepping and repeating it as before, to create a second integral image layer on said substrate.

55. The method of making displays a set forth in claim 49 including the step of panel scaling, aligning it to receive a second image, and

thereafter simultaneously projecting said second image on said substrate, stepping and repeating it as before, to create a second integral image layer on said substrate.

56. The method of correcting for variations in translatory movement of a movable stage used in apparatus for making displays, said apparatus including a pair of parallel and proximate optical columns to project images upon a substrate carried by said stage, said method including

determining the actual positions of said stage as it is moved throughout its range of movement,

determining the apparent position of said stage as determined by projecting images from said optical columns to sensors on said stage,

comparing the differences between said actual and apparent positions and recording them as a transfer function, and

varying the position of said stage relative to said optical columns in accordance with said transfer function,

whereby images projected by said optical columns upon said substrate will accurately abut.

57. The method of aligning multiple images being projected from a reticle to a photo-sensitive coated substrate using a pair of parallel and proximate optical systems, said systems being positioned to project in the z-direction upon a movable stage subject to controlled motion in the x-, y-, and φ

directions, said method including the steps of

determining the coordinates of motion of said stage relative to images projected from said reticles,

determining the reticle coordinates of each said reticle by projection of images upon sensors positioned in known locations in said stage,

using said determined coordinates of said stage and said determined reticle coordinates to determine a first transfer function for said system relative to positions of said stage,

positioning a said substrate in said stage and applying said first transfer function to adjust the relative positions of said reticles and said substrate for accurate image projection, and thereafter projecting an image upon said substrate,

stepping said stage to a position to permit projection of an abutting image, and again applying said first transfer function to adjust the relative positions of said reticles and said substrate for accurate image projection, and thereafter projecting an image upon said substrate, and

repeating the steps of stepping said stage, applying said first transfer function, and projecting said image until sufficient images have been projected upon said substrate to make up an integrated level of a display.

58. The method of aligning multiple images, as set forth in claim 57, including the steps of

determining second reticle coordinates for a second reticle for each said optical system,

developing said first layer of photo-resist and recoating said substrate,

positioning said recoated substrate in said stage and determining the difference in alignment of said substrate on said stage relative to the initial alignment of said substrate to said stage to provide an alignment transfer function,

using said determined stage coordinates, said determined second reticle coordinates, and said alignment transfer function to create a second transfer function for said system relative to positions of said stage,

applying said second transfer function to adjust the relative positions of said second reticle and said substrate for accurate image projection, and thereafter projecting an image upon said substrate,

stepping said stage to a position to permit projection of an abutting image on said substrate, and again applying said second transfer function to adjust the relative positions of said reticles and said substrate for accurate image projection, and thereafter projecting an image upon said substrate, and

repeating the steps of stepping said stage, applying said second transfer function, and projecting said image until sufficient images have been projected upon said substrate to make up a second level of a display.

59. A flat panel display containing a multiplicity of repetitive stitched images and a plurality of layers, said display including

a substrate,

a plurality of aligned, etched layers formed using photoresist material upon said substrate, each of said layers having been formed by simultaneous projection of images upon said photoresist material from a reticle carried in each of at least a pair of optical columns, said images each covering a small portion of said substrate but having been repeatedly stepped and reprojected from each said optical column over said substrate so as to form a continuum of interfitting images to form a total, unitary image on said photoresist of said layer,

said images from each of said optical columns having been separately adjusted before each stepping and projection to match and abut one another in respect to size, shape, rotation, and magnification,

whereby said flat panel display is formed of a plurality of unitary, integral layer of circuitry.

60. A flat panel display as set forth in claim 59 in which the dimensions of the images projected on layers of said photoresist after said first layer have been scale adjusted to compensate for dimensional changes in said preceding layer.