WO2013024472A1

WO2013024472A1 - An inspection/repair/inspection system

Info

Publication number: WO2013024472A1
Application number: PCT/IL2012/000306
Authority: WO
Inventors: Victor RYBALKIN; Ilia Lutsker
Original assignee: Orbotech Ltd.
Priority date: 2011-08-18
Filing date: 2012-08-08
Publication date: 2013-02-21
Also published as: CN103889638A; JP2014529734A; TW201716167A; KR20140058591A; TW201311385A; CN103889638B; CN106862755A; TWI587957B

Abstract

A lens assembly for use in an inspection/repair/inspection system for electrical circuits, the lens assembly including a scan lens operative to correct a laser beam for aberrations at a specific wavelength of the laser beam used for repair and a camera lens operative to receive light from a workpiece through the scan lens and to correct for aberrations at at least one specific wavelength sensed by the camera, which wavelength is other than the specific wavelength of the laser beam used for repair.

Description

AN INSPECTION/REPAIR/INSPECTION SYSTEM

CROSS-REFERENCE TO RELATED APPLICATION

Reference is made to U.S. Provisional Patent Application Serial No. 61/524,995, filed August 18, 201 1 and entitled Inspection/Repair/Inspection system, the disclosure of which is hereby incorporated by reference and priority of which is hereby claimed pursuant to 37 CFR 1.78(a) (4) and (5)(i).

FIELD OF THE INVENTION

The present invention relates to inspection and repair systems for electrical circuits and more particularly to optics used therein.

BACKGROUND OF THE INVENTION

The following publications are believed to represent the current state of the art:

C. Bliton et al., Optical modifications enabling simultaneous confocal imaging with dyes excited by ultraviolet - and visible-wavelength light. Journal of Microscopy, Vol. 169 Pt. 1 January 1993 pp. 15-26; and

Published PCT Application No. WO 2010/100635.

SUMMARY OF THE INVENTION

The present invention seeks to provide improved optics useful in inspection and repair systems for electrical circuits.

There is thus provided in accordance with a preferred embodiment of the present invention a lens assembly for use in an inspection/repair/inspection system for electrical circuits, the lens assembly including a scan lens operative to correct a laser beam for aberrations at a specific wavelength of the laser beam used for repair and a camera lens operative to receive light from a workpiece through the scan lens and to correct for aberrations at at least one specific wavelength sensed by the camera, which wavelength is other than the specific wavelength of the laser beam used for repair.

Preferably, the lens assembly also includes an entrance pupil associated with a scanning mirror upstream of the scan lens. Additionally, the entrance pupil is located at the optical center of the mirror.

In accordance with a preferred embodiment of the present invention the specific wavelength of the laser beam used for repair is 266 nm. Additionally or alternatively, the at least one specific wavelength sensed by the camera is selected from at least one of a range of 460 - 480 nm and a range of 520 - 540 nm.

Preferably, the lens assembly also includes a laser operative to generate the laser beam, the laser being operative at a pulse energy level less than 1 microjoule.

There is also provided in accordance with another preferred embodiment of the present invention a combiner assembly for use in an inspection/repair/inspection system for electrical circuits, the combiner assembly including a first combiner arranged between a scanning mirror and a scan lens for directing laser energy at a first wavelength from the scanning mirror through the scan lens onto a workpiece and for allowing light at a second wavelength, different from the first wavelength to pass therethrough, a second combiner arranged between a first camera and the first combiner for directing light from the workpiece passing through the first combiner to the first camera and a third combiner arranged between the second combiner and an illumination source for directing light from the illumination source through the second combiner and the first combiner to the workpiece and allowing light from the workpiece, passing through the first combiner and the second combiner, to reach a second camera.

Preferably, the illumination source includes at least one of a color LED assembly and a strobe light source. Additionally, the strobe light source includes a flash lamp.

In accordance with a preferred embodiment of the present invention the first camera is a monochrome camera. Additionally or alternatively, the second camera is a color camera.

Preferably, the first wavelength is 266 nm. Additionally or alternatively, the second wavelength is in the range of 460 - 660 nm.

In accordance with a preferred embodiment of the present invention the combiner assembly also includes a laser operative to generate the laser energy, the laser being operative at a pulse energy level less than 1 microjoule.

There is further provided in accordance with yet another preferred embodiment of the present invention an inspection/repair/inspection system for electrical circuits including a laser ablator operative for ablating metals, organic materials, silicon oxides and metal oxides in electrical circuits, the laser ablator including a laser emitting at a wavelength of 266 nanometers at a pulse energy level less than 1 microjoule.

There is yet further provided in accordance with still another preferred embodiment of the present invention an inspection/repair/inspection system for electrical circuits including a laser welder operative for welding metals to each other or to metal oxides, the laser welder including a laser emitting at a wavelength of 266 nanometers at a pulse energy level less than 1 microjoule.

There is even further provided in accordance with another preferred embodiment of the present invention a laser writing system including a UV laser producing an output beam having a generally Gaussian energy distribution along a first axis perpendicular to a propagation axis of the output beam and having a non-Gaussian energy distribution along a second axis perpendicular to the first axis, the second axis being perpendicular to the propagation axis and beam correction optics operative to correct the energy distribution of the output beam to be generally Gaussian along the second axis. There is also provided in accordance with still another preferred embodiment of the present invention an inspection/repair/inspection system for electrical circuits including an acousto-optical modulator, a fast steering mirror and a control assembly operative to precisely coordinate the acousto-optical modulator and the fast steering mirror.

Preferably, the inspection/repair/inspection system for electrical circuits also includes control lines interconnecting the mirror and the acousto-optical modulator with the control assembly.

In accordance with a preferred embodiment of the present invention the control assembly is operative to position the mirror relative to the acousto-optical modulator so that a laser beam output from the acousto-optical modulator impinges precisely at a desired point on a workpiece being inspected/repaired/inspected by the system.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood and appreciated more fully from the following detailed description in which:

Fig. 1 is a simplified illustration of an inspection/repair/inspection system for electrical circuits constructed and operative in accordance with a preferred embodiment of the present invention;

Fig. 2 is a schematic illustration of the system of Fig. 1;

Fig. 3 is a simplified flow chart illustrating the operation of the system of Figs. 1 and 2; and

Fig. 4 is a simplified flow chart illustrating the operation of a defect repair process utilizing the system of Figs. 1 and 2.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Reference is now made to Fig. 1, which is a simplified illustration of a system for inspecting, repairing and reinspecting electrical circuits.

As seen in Fig. 1, the system preferably comprises a chassis 101 which is preferably mounted on a conventional optical table 102. The chassis 101 defines an electrical circuit inspection/repair location 104 onto which an electrical circuit, such as a flat panel display (FPD) 106, to be inspected and repaired may be placed. The FPD 106 typically has one or more of various types of defects, typically defects in the formation of conductors, such as excess material defects and missing material defects.

A bridge 112 is arranged for linear motion relative to inspection/ repair location 104 along a first inspection/repair axis 114, defined with respect to chassis 101. An optical head assembly 116 is arranged for linear motion relative to bridge 112 along a second inspection/repair axis 118, perpendicular to first inspection/repair axis 114.

In accordance with an embodiment of the present invention, the optical head assembly 116 preferably includes an inspection/repair subassembly 120.

The system preferably also includes a control assembly 124, preferably including a computer 126 having a user interface 128 and including software modules operative to operate the inspection/repair subassembly 120. Control assembly 124 preferably receives a defect location input from an automated optical inspection system, not shown, such as a Supervision™ system, commercially available from Orbotech Ltd. of Yavne, Israel.

Inspection/repair subassembly 120 preferably includes a base 130, on which is supported a color camera 132, such as a Dalsa CMOS camera Model Falcon 4M60 Color, and a monochromatic camera 134, such as a Dalsa CMOS camera Model Falcon 4M60. Alternatively, a pair of monochromatic cameras may be supported on base 130. Both the color and the monochromatic cameras are commercially available from Teledyne DALSA of Waterloo, Ontario, Canada.

Camera 132 views an imaging location 135 on FPD 106 along an optical axis 136 through a tube lens 138, having a typical focal length of 200 - 250mm, a beam splitter assembly 140 and an objective lens assembly 142. Camera 134 views imaging location 135 on FPD 106 along optical axes 143 and 136 through a tube lens 144, having a typical focal length of 400-600 mm, beam splitter assembly 140 and a scan lens 146.

The inspection/repair subassembly 120 preferably includes a pulsed laser source 152, such as a Fiber coupled Q-switch laser, commercially available from Quantel Corporation of2 bis Avenue due Pacifique, ZA de Courtaboeuf, France (http://www.quantel-laser.com ),

a passive Q-switch microchip laser available from Concepts Research Corporation of Charlotte, NC or a picoseconds fiber laser available from Toptica Photonics of 82166 Graefelfing (Munich) · Germany. Pulsed laser source 152 is operative to generate a pulsed laser beam 154

Pulsed beam 154 passes through collimating and beam shaping optics 158, operative to shape and collimate the laser beam 154 to a desired beam size, preferably between 1.5 - 2.5 mm. Collimating and beam shaping optics 158 preferably include a modulator 160, Examples of suitable modulators 160 includes an acousto-optical modulator (AOM), such as an AOM available from Crystal Technology of Palo Alto, CA and an electro-optic modulator such as Picoseconds Pockel Cells, commercially available from Key Photonics Ltd of Cambridge, UK. Laser beam 154 is then optionally adjusted to a specific diameter, preferably between 8 - 15 mm, by a beam expander 170 including multiple lenses placed and adjusted for the required size of the collimated output beam.

Laser beam 154 is then directed by a mirror 180 to impinge on a two-axis fast steering mirror (FSM) 182, such as the one which is described in Figs. 7 and 8 of U.S. Patent No. 7,598,688, the disclosure of which is hereby incorporated by reference, and then passes through beam splitter assembly 140, which directs beam 154 through scan lens 142 along axis 136.

Illumination is preferably provided by a selected one of either a strobe light source, such as a flash lamp 184, via a moving mirror 186, or a color LED assembly 188. Light from flash lamp 184 or from LED assembly 188 is directed through an illumination homogenizer 190, whose exit plane is imaged by a lens assembly 192 and either of objective lens assembly 142 and scan lens 146 onto FPD 106 at location 135 thereof. Reference is now made to Fig. 2, which is a schematic illustration of the system of Fig. 1, to emphasize particular novel features of the present invention. As seen in Fig. 2, it is seen that tube lens 144, which serves as the camera lens of monochromatic camera 134, receives light from imaging location 135 on FPD 106 via scan lens 146, which is operative to correct laser beam 154 for aberrations at a specific wavelength of the laser beam used for repair, preferably 266 nm.

The use of a wavelength of 266 nm is a particular feature of the present invention since it provides ablation of metals, organic materials, silicon oxides and metal oxides in electrical circuits. It is appreciated that a wavelength of 266 nm is also operative for welding of metals to each other as well as welding of metals to metal oxides in electrical circuits.

It is a further particular feature of the present invention that laser 152 operates at a pulse energy level less than 1 microjoule.

It is a particular feature of the present invention that tube lens 144 corrects for aberrations at at least one specific wavelength, here between 460 - 480 or 520 - 540 nm, sensed by monochromatic camera 134, which wavelength is different from the specific wavelength of laser beam 154 used for repair, which wavelength is preferably 266 nm.

It is further seen in Fig. 2 that scan lens 146 has an entrance pupil 194 associated with mirror 182 upstream of scan lens 146 and more particularly, preferably at the optical center of mirror 182.

Fig. 2 also illustrates a further particular feature of the present invention, namely the structure and operation of beam splitter assembly 140. As seen with particularity in Fig. 2, beam splitter assembly 140 preferably includes:

a first combiner 200 arranged between mirror 182 and scan lens 146 for directing laser beam 154 at a first wavelength, preferably 266 nm, from mirror 182 through scan lens 146 onto imaging location 135 on FPD 106 and for allowing light at a second wavelength, different from the first wavelength, in the visible range, here preferably between 460 - 660 nm to pass therethrough; a second combiner 202, arranged between the monochromatic camera 134 and the first combiner 200 for directing light from imaging location 135 on FPD 106 passing through first combiner 200 to the monochromatic camera 134; and

a third combiner 204, arranged between the second combiner 202 and an illumination source, here preferably color LED assembly 188 and flash lamp 184 for directing light from the illumination source through the second combiner 202 and the first combiner 200 to imaging location 135 on FPD 106 and allowing light from imaging location 135 on FPD 106, passing through first combiner 200 and second combiner 202 to reach color camera 132.

It is an additional particular feature of the invention described hereinabove and illustrated in Figs. 1 and 2 that a laser writing system is provided wherein:

laser 152 is a UV laser and output beam 154 has a generally Gaussian energy distribution along one axis 208, perpendicular to a propagation axis 210 of beam 154;

output beam 154 preferably has a non-Gaussian energy distribution along an axis 212 perpendicular to axis 208, where axis 212 is also perpendicular to propagation axis 210; and

beam correction optics 158 is operative to correct the energy distribution of output beam 154 to be generally Gaussian also along axis 212.

It is a further particular feature of the invention that due to the enhanced ablation quality parameters achieved by embodiments of the invention removal of excess material is done without harming the other layers.

It is an additional particular feature of the present invention that the operation of mirror 182 is precisely coordinated with that of the modulator 160, preferably by means of control lines interconnecting mirror 182 and modulator 160 with control assembly 124. Control assembly 124 preferably ensures that the position of mirror 182 is such that the laser beam output from modulator 160 impinges precisely at a desired point at location 135 on FPD 106.

Reference is now made to Fig. 3, which is a simplified flow chart illustrating the operation of the system of Figs. 1 and 2. As seen in Fig. 3, in step 300, a defect location input is acquired by an automated optical inspection system.

As noted hereinabove, control assembly 124 preferably receives the defect location input from the automated optical inspection system. As seen in Fig. 3, control assembly 124 is operative, in step 302, to position the optical head assembly 116 over the input defect location of the electrical circuit being inspected and/or repaired. In step 304, control assembly 124 is operative to register the position of the defect location. Subsequently, in step 306, a defect classification is generated.

Control assembly 124 is then operative to check, in step 308, if the defect is classified as a repairable defect. If the defect is classified as non-repairable, the process returns to step 300 to consider the next defect location.

If the defect is classified as repairable, the process continues, at step 310, to allow the user to select either manual or automatic definition of the area to be repaired. When manual definition is selected, as seen in step 312, the user defines the repair area. When automatic definition is selected, as seen in step 314, control assembly 124 is operative, utilizing the imaging functionality associated with color camera 132, to automatically define the repair area.

The control assembly 124 is then operative, in step 316, to calculate a movement plan for FSM 182. In step 318, control assembly 124, preparatory to running a defect repair process, is operative to change the imaging functionality to utilize the monochrome camera 134 and associated optics and the defect position registration from step 304.

In step 320, control assembly 124 is operative to run the defect repair process. Following the defect repair process, in step 322, control assembly 124 is operative to re-inspect the input defect location to determine if the repair process successfully repaired the defect. As seen in step 324, if the defect was successfully repaired, the process continues, at step 300, by considering the next defect location. If the defect was not successfully repaired, the process returns at step 320, to run the defect repair process again. Reference is now made to Fig. 4, which is a simplified flow chart illustrating the operation of a preferred embodiment of a defect repair process utilizing the system of Figs. 1 and 2.

As seen in Fig. 4, control assembly 124 is operative, in step 402, to position beam expander 170 to provide a required laser spot size, in step 404, to position an energy attenuator to provide a required laser energy range, and in step 406 to set an amplitude of AOM 160 to provide a required laser energy level.

The defect repair process continues with switching on the laser, in step 408, and, in step 410, starting execution of the FSM movement plan.

In step 412, control assembly 124 is operative to check if FSM 182 is suitably positioned over the repair area. If FSM 182 is suitably positioned over the repair area, in step 414, FSM 182 is operative to set an "ON" trigger to AOM 160 to allow laser beam 154 to reach the target repair area and thus perform the repair in the target repair area. If FSM 182 is not suitably positioned over the repair area, in step 416, FSM 182 is operative to set an "OFF" trigger to AOM 160 to block laser beam 154 from reaching the target area.

In step 418, control assembly 124 is operative to check if the end of the FSM movement plan has been reached. If the end of the FSM movement plan has not been reached, the process returns to step 412. If the end of the FSM movement plan has been reached, the process terminates at step 420.

Alternatively or additionally, other operation plans may be utilized. For example, any one or more of the parameters defined in steps 402, 404, 406 in Fig. 4 may be changed during the performance of a defect repair process, such as precisely setting the energy range to be used (block 404 in Fig. 4) at any point in time during the repair period. Additionally or alternatively, the defect repair routine of block 320 in Fig. 3 may be run more than once before proceeding to step 322. In another alternative method of operation, the scanning velocity of FSM 182 may be reset between as well as during repair routines.

It is appreciated that the defect repair functionality of the present invention, as described in Figs. 3 and 4 above, may include removal of excess material, such as by laser ablation, redistribution of existing material, such as by laser welding, It is appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described hereinabove. Rather the scope of the present invention includes both combinations and subcombinations of various features described hereinabove as well as variations and modifications thereto which would occur to a person of skill in the art upon reading the above description and which are not in the prior art.

Claims

1. For use in an inspection/repair/inspection system for electrical circuits, a lens assembly comprising:

a scan lens operative to correct a laser beam for aberrations at a specific wavelength of the laser beam used for repair; and

a camera lens operative to receive light from a workpiece through said scan lens and to correct for aberrations at at least one specific wavelength sensed by said camera, which wavelength is other than the specific wavelength of said laser beam used for repair.

2. A lens assembly according to claim 1 and also comprising an entrance pupil associated with a scanning mirror upstream of said scan lens.

3. A lens assembly according to claim 2 wherein said entrance pupil is located at the optical center of said mirror.

4. A lens assembly according to claim 1 wherein said specific wavelength of the laser beam used for repair is 266 nm.

5. A lens assembly according to claim 1 wherein said at least one specific wavelength sensed by said camera is selected from at least one of a range of 460 - 480 nm and a range of 520 - 540 nm.

6. A lens assembly according to claim 1 also comprising a laser operative to generate said laser beam, said laser being operative at a pulse energy level less than 1 microjoule.

7. For use in an inspection/repair/inspection system for electrical circuits, a combiner assembly comprising: a first combiner arranged between a scanning mirror and a scan lens for directing laser energy at a first wavelength from said scanning mirror through said scan lens onto a workpiece and for allowing light at a second wavelength, different from said first wavelength to pass therethrough;

a second combiner arranged between a first camera and said first combiner for directing light from said workpiece passing through said first combiner to said first camera; and

a third combiner arranged between said second combiner and an illumination source for directing light from said illumination source through said second combiner and said first combiner to said workpiece and allowing light from said workpiece, passing through said first combiner and said second combiner, to reach a second camera.

8. A combiner assembly according to claim 7 wherein said illumination source comprises at least one of a color LED assembly and a strobe light source.

9. A combiner assembly according to claim 8 wherein said strobe light source comprises a flash lamp.

10. A combiner assembly according to claim 7 wherein said first camera is a monochrome camera.

11. A combiner assembly according to claim 7 wherein said second camera is a color camera.

12. A combiner assembly according to claim 7 wherein said first wavelength is 266 nm.

13. A combiner assembly according to claim 7 wherein said second wavelength is in the range of 460 - 660 nm.

14. A combiner assembly according to claim 7 also comprising a laser operative to generate said laser energy, said laser being operative at a pulse energy level less than 1 microjoule.

15. An inspection/repair/inspection system for electrical circuits comprising:

a laser ablator operative for ablating metals, organic materials, silicon oxides and metal oxides in electrical circuits, said laser ablator comprising a laser emitting at a wavelength of 266 nanometers at a pulse energy level less than 1 microjoule.

16. An inspection/repair/inspection system for electrical circuits comprising:

a laser welder operative for welding metals to each other or to metal oxides, said laser welder comprising a laser emitting at a wavelength of 266 nanometers at a pulse energy level less than 1 microjoule.

17. A laser writing system comprising:

a UV laser producing an output beam having a generally Gaussian energy distribution along a first axis perpendicular to a propagation axis of said output beam and having a non-Gaussian energy distribution along a second axis perpendicular to said first axis, said second axis being perpendicular to said propagation axis; and

beam correction optics operative to correct the energy distribution of said output beam to be generally Gaussian along said second axis.

18. An inspection/repair/inspection system for electrical circuits comprising:

at least one of an acousto-optical modulator and an electro-optic modulator;

a fast steering mirror; and

a control assembly operative to precisely coordinate said at least one of an acousto-optical modulator and an electro-optic modulator and said fast steering mirror.

19. An inspection/repair/inspection system for electrical circuits according to claim 18 and also comprising control lines interconnecting said mirror and said acousto- optical modulator with said control assembly.

20. An inspection/repair/inspection system for electrical circuits according to claim 18 wherein said control assembly is operative to position said mirror relative to said acousto-optical modulator so that a laser beam output from said acousto-optical modulator impinges precisely at a desired point on a workpiece being inspected/repaired/inspected by said system.