WO1997027467A9

WO1997027467A9 - Revisit station for an optical scanner

Info

Publication number: WO1997027467A9
Application number: PCT/US1997/000992
Authority: WO
Filing date: 1997-01-27
Publication date: 1997-12-31

Abstract

An optical scanner (22) scanning disks (2) or other materials connected to a microscope (32, 35-38) or other inspection device, providing the location of defects, flaws and events to the microscope (32, 35-38), facilitating defect location and analysis. In some embodiments, the microscope (32, 35-38) may be replaced with an electron microscope or an atomic force microscope, or other advanced image analysis. In some embodiments, information regarding the defect is provided to a manufacturing function automatically and quickly, thus preventing problems that might arise due to delays in communication. In some embodiments the disks (2) on which defects are found are physically moved to a remote microscope location, while in other embodiments the scanner (22) and microscope (32, 35-38) are located along the path (57) on which all disks (2) are transported.

Description

REVISIT STATION FOR AN OPTICAL SCANNER

FIELD OF THE INVENTION

The present invention relates to the field of inspection control; more particularly, the present invention relates to inspection processes.

BACKGROUND OF THE INVENTION

Optical inspection of disks, silicon wafers, or magnetic media require specialized skills different from those used in manufacturing. Inspection of optical disks often requires a first scan through a magnetic or optical defect detector, producing electronic pulses when a defect is discovered. These pulses are often presented to an inspection engineer, who makes an initial determination of the nature of the defect that caused the electronic pulse. The determination, however, is based solely on observation of the electronic pulse on a monitor. If the inspection engineer believes that a defect of a reparable or irreparable nature is present on the disk, the inspection engineer removes the disk from the manufacturing stream, and carries the disk to a microscope. The inspection engineer often makes note of the radius of the defect from the center of the disk, and, using this information, begins to locate the defect on the disk using the microscope. The inspector then locates the defect and determines, based on experience, whether the defect can be removed through burnishing or cleaning, or whether the defect is of an irreparable nature. In either case, the inspection engineer often reports the defect to the manufacturing engineer, who may vary the manufacturing means according to his understanding of the inspection engineers report.

The delay between the initial electronic discovery of the defect and the subsequent changes implemented by the manufacturing engineer can result in the manufacture of disks having the same defect, manufactured before the manufacturing engineer learns of the defect. Also, time may be lost in carrying the disks, placing the disks under the scanning electron microscope, and adjusting the scanning electron microscope to the vicinity of the defect. Computer control of the conveyor system allows efficient delivery of the disks to the optical scanner and to the subsequent inspection device, and removal of inspected disks. Additionally, the microscope may be located in an ambient environment, not in the clean room environment in which the disks are manufactured, and therefore can become contaminated by being carried through the ambient environment. Communication problems between the inspection engineers and the manufacturing engineers can create further manufacturing problems. Also, the subjectivity of the inspection creates inaccuracy in determining the reparability of the defect, and in determining its size and nature. The subjectivity of the inspection also makes more difficult the archiving of information for subsequent statistical analysis of both the manufacturing and inspection steps.

Therefore, it is desirable to implement an optical scanner that can determine the nature and reparability of defects. It is also desirable to implement an optical scanner that determines whether defects are embedded or loose. It is further desirable for an optical scanner to provide objective information and a means for providing objective information to the manufacturing process to allow improved performance in the future. It would also be desirable to have archived information of previous defect frequencies, so that improved statistical analysis may be performed and manufacturing and error detection performance may result. Video presentation and archiving of defect analysis, rather than mere electronic pulse traces, allows for improved communication between manufacturing and quality control. It is desirable to have non-invasive means of inspecting disks, especially when the non-invasive methods can be implemented quickly, because fast inspection of optical disks allows for greater through-put.

SUMMARY OF THE INVENTION

An optical scanner for scanning disks or other materials is disclosed. The scanner system includes a microscope or other inspection device, a means for providing the location of defects, flaws and events to the microscope, and a means for facilitating defect location and analysis. In some embodiments, the microscope may be replaced with an electron microscope or an atomic force microscope, or other advanced image analysis. Information regarding the defect is provided to a manufacturing function automatically and quickly, thus preventing problems that might arise due to delays in communication. In some embodiments the disks on which defects are found are physically moved to a remote microscope location, while in other embodiments the scanner and microscope are located along the path on which all disks are transported.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood more fully from the detailed description given below and from the accompanying drawings of various embodiments of the invention, which, however, should not be taken to limit the invention to the specific embodiments, but are for explanation and understanding only.

Figure 1 shows an overview of a manufacturing and inspection according to the present invention process;

Figure 2A, 2B, 2C and 2D show inspection systems according to several embodiments of the present invention, using a robotic control system, respectively;

Figure 3 shows an optical scanner;

Figure 4A shows an inspection system according to an embodiment of the present invention in which each optical scanner is associated with a distinct subsequent inspection device;

Figure 4B shows an inspection system according to an embodiment of the present invention in which disks are transported from a plurality of optical scanners to a single subsequent inspection device;

Figures 5A, 5B, and 5C show embodiments of the present invention in which disks are transported by an air-bearing conveyor system.

Figure 6 shows a subsequent processing device;

DETAILED DESCRIPTION A revisit station for detecting and classifying defects in smooth substrates and disks 2 and for examining defects in detail is described. In the following description, numerous details are set forth, such as distances between components and type of materials. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without these specific details. In other instances, well- known structures and devices are shown in block diagram form, rather than in detail, in order to avoid obscuring the present invention.

Referring now to Figure 1, an overview of a manufacturing and inspection process according to several embodiments of the present invention is shown. A manufacturing function 60 provides disks 2 or other substrates to a conveyor system 50. Although the embodiments described herein refer to disks 2, it will be understood that any substrate having a substantially smooth surface may be inspected. The conveyor system 50 may include any of a number of delivery or conveyor systems 50 that carry disks 2 from the manufacturing function 60 to an optical scanning function 20. An optical scanning function 20 receives the disks 2 from the conveyor system 50 and inspects the surfaces of the disks 2 for defects. Disks 2 on which defects are found are delivered to a subsequent inspection system 30 by the conveyor system 50, the subsequent inspection system 30 receiving information regarding the location of the defects found by the optical scanning function 20 and providing further information regarding the defects. A host computer 40 receives information regarding the status of the optical scanning function 20, the subsequent inspection, and the conveyor system 50, and controls the conveyor system 50 such that disks 2 may be inspected efficiently by the optical scanning function 20 and the subsequent inspection function. The host computer 40 also communicates with a nonvolatile archival memory 42 that allows the host computer 40 to perform statistical analyses of the occurrence of defects. The host computer 40 efficiently provides information to the manufacturing function 60, so that the manufacturing function 60 can respond quickly to defects detected by the optical scanning function 20 and the subsequent inspection system 30. Thus, evaluation of defects may be accomplished without manual handling of disks 2. Once detected, a disk having a defect may be moved by a subsequent inspection device 31 automatically and efficiently, without physical handling by personnel and without removal from the clean room environment. The subsequent inspection system 30 receives the location of defects from the optical scanning function 20 and thus may move the disk or may move the subsequent inspection device to a location and orientation such that the subsequent inspection device may inspect the exact location of defects, saving time.

Referring now to Figures 2A and 2B, an inspection system according to a first and second embodiment of the present invention is shown. Disk 2 arrives from the conveyor system 50 either individually or in containers 4. As shown in Figure 2A and Figure 2B, the disk 2 may be placed on a table 6 by the conveyor system 50. Alternatively, as shown in Figures 2C and 2D, the disks may be moved directly from the conveyor system 50 to the optical scanners 22. It will be recognized that other conveyor and delivery systems are possible. In the embodiment shown in Figures 2A and 2B, the inspection system uses a robotic control device 51 with a robotic arm 52 to mechanically lift a disk 2 from the containers 4 and place the disk 2 onto air bearing spindle about which the disk 2 is free to rotate in a horizontal plane. The robotic arm 52 places the disk 2 in an optical scanner 22, shown in greater detail in Figure 3, in which a pair of optical scanning heads 24, one above and one below the surface of the disk 2, within the optical scanner 22 project a beam of light onto the surface of the disk. As will be discussed with respect to Figure 3, the optical scanner 22 detects the presence of defects, contaminants, scratches, bumps, and pits on the surface of the disk. After inspection, the robotic control device places the disk 2 onto conveyor system 50. In parallel with the placement of the disk onto conveyor system 50, data is communicated to the host computer 40, indicating that the disk has been inspected, as well as indicating the presence and nature of any defects. A single robot may operate on more than one first and second conveyor, or several conveyor systems 50 may operate on disk 2 while a single robot removes defective disk 2 and transports the defective disk 2 to a remote microscope or other image analysis apparatus for review. Referring now to Figure 3, the optical scanner operates by projecting a beam of light substantially normally onto the surfaces of /27467 PC17US97/00992

the disk. The light is of a frequency reflected by the disk, and the reflected beam is projected onto a photodetector. A scanning recorder sensitive to a signal received from the photodetector, and sensitive to the position of the arm carrying two optical scanning heads 24 and angular position (or rotation time) of the disk, communicates the position of each nonspecular point on either surface of the disk to a subsequent inspection device. Information obtained by the optical scanner 22 is automatically communicated to a computer system 80 having a memory that stores the information and a processor that provides statistical information of defects. The statistical information produced by the processor in such embodiments is generally useful to the manufacturing function 60 to identify and classify the causes of the defects. Computer interface with the manufacturing function 60 advantageously provides analyses and defect reports that may be used dynamically and automatically to correct manufacturing defects, thus avoiding delays inherent in other forms of communication such as verbal communication between inspection and manufacturing personnel.

The optical scanners 22 include two optical scanning heads 24, positioned parallel with the plane of the disks 2, that scan the two planar faces of each disk. The heads are mounted on a moving arm 26 that translates radially inward toward the center of the disk. While the arm translates, the disk spins about the spindle 8 such that the path taken by the optical scanning heads 24 with respect to the disk defines a spiral path inward from the outer edge of the disk.

Figures 4-5 show various other embodiments of the conveyer system in accordance with the present invention. As shown in Figure 4A, disks 2 arrive substantially horizontally and individually along a plurality of paths, each path including an optical scanner and a subsequent inspection device. Data lines couple the optical scanners with the host computer 40 and with the subsequent inspection devices, allowing the nature and location of defects detected by the optical scanner to be communicated to the subsequent inspection device and to the host computer 40. Thus, the conveyor system 50, and not a robotic control device, moves disks 2 from the optical scanner to the subsequent inspection device. Once the optical scanner 22 detects a /27467 PC17US97/00992

defect, the location of the defect is communicated to a subsequent inspection device located at a revisit station.

Referring now to Figure 4B, an alternate conveyor system 50 is shown. In the embodiment shown in Figure 4B, disks 2 on which no defect is detected, or on which defects are sufficiently examined by the optical scanning device, avoid subsequent inspection by the subsequent inspection device. A deverter 53 redirects such disks 2 onto an alternate path. Thus, only those disks 2 on which subsequent inspection by a subsequent inspection device is advantageous are so examined.

In Figure 4B, each disk on which the optical scanners 22 detect a defect is transported to a remote revisit station 31 on which the subsequent inspection device resides, while the optical scanner continues to inspect the next disk. A control device 54 directs disks 2 on which the optical scanner has detected a defect to a conveyor moving toward the subsequent inspection device, while defect-free disks 2 are directed away from the subsequent inspection device. The subsequent inspection device receives from the optical scanner 22 information regarding the general nature of any defects and the location of the defects, and is able to concentrate inspection on the specific location of the defects.

Referring now to Figures 5A and 5B, other embodiments of the conveyor system 50 according to the present invention is shown in which disks 2 are transported to the optical scanner, and from the optical scanner to the subsequent inspection device, by a conveyor system 50 using compressed air to reduce friction between the disks 2 and the conveyor surface 55. The embodiments shown are similar to Figures 2A-2D, and 4A-4B, respectively. A stainless steel platen 58 comprised of a substantially horizontal conveyor surface and having a large number of pin holes 56 through which compressed air may be released, supports disks 2 sliding along a cushion of air. Compressed air is delivered to a chamber below the platen 58 surface, and the air is slowly released through the pin holes 56 , creating a cushion of air on which the disks 2 are maintained, preventing the surface of the disks 2 from coming in contact with the potentially contaminating surface of the platen 58. Thus, the disks 2 slide frictionlessly from the manufacturing function 60 to the optical scanner 22, and subsequently from the optical scanner 22 to the subsequent inspection device 31. The conveyor system 50 transports disks 2 from the manufacturing function 60 to an optical scanner. In some embodiments, solid railings 57 prevent disks 2 from sliding off the lateral edges of the platen 58. In some embodiments the railings 57 have pin holes 56 similar to the pin holes 56 in the platen 58 surface, preventing the disks 2 from coming in contact with the railings 57 and further helping to propel the disks 2 along the platen 58 surface to the optical scanner. Although in some embodiments the air bearing frictionless delivery and conveyor system 50 transports disks 2 directly to the optical scanner and to the subsequent inspection device, in other embodiments the air bearing delivery system merely delivers the disks 2 to a temporary holding area from which a robotic arm similar to the robotic arm described above lifts the disks 2 and places the disks 2 in the optical scanner or the subsequent inspection device. In one embodiment, both the direction and pressure of the air delivered throvigh the pin holes 56 in the platen 58, as well as the pressure and direction of air delivered through the holes in the railing, as well as the operation of the robotic arm, are all controlled by the host computer 40. Thus, the host computer 40, receiving information from the optical scanner 22 and the subsequent inspection device 31, can control the delivery of disks 2 thereto.

In some embodiments, the present invention, provides for complete computer control of all facets of the inspection of the disks 2, in that disks 2 delivered from the manufacturing function 60 are efficiently transported to the optical scanner, which determines the location and general nature of any defects on the disks 2. In some embodiments, the present invention also provides a human user an opportunity to inspect a computer-enhanced visual image of any defects, without removing the disks 2 from the clean room environment. The host computer 40 may contain a processor that automatically provides a detailed statistical analysis of defect at currents and nature to the manufacturing function 60. The host computer 40 stores details analyses of each defect in a data storage medium 42, archives the data, and provides statistical analyses to the manufacturing function 60, automatically, quickly, and without contamination. Human users may visually inspect defects using a scanning electron microscope or other advanced analyses. The manufacturing function 60 can respond rapidly to defects, in some embodiments ignoring loose particular defects while responding promptly to scratches, bumps, and pits. Defects caused strictly by communication time delays are also avoided, in that direct digital communication is possible between the host computer 40 and a computer controlling the manufacturing function 60.

Referring now to Figure 6, a subsequent inspection device is shown. The subsequent inspection device is located at a revisit station and may comprise an electron microscope, atomic force microscope, or any apparatus using advanced image analysis. It will readily apparent to one of ordinary skill in the art upon inspection of this disclosure that other inspection devices may be substituted for the microscope. The microscope is directed to the location of any nonspecular points on the disk surface by information received from the host computer 40, optical scanning function 20, or from a scanning recorder. The subsequent inspection device shown in Figure 6 receives a disk 2 placed below a microscope objective 33. A motorized microscope carriage 34receives the location of defects from either the optical scanner 22 or host computer 40 and positions the disk and microscope objective 33 correspondingly, and provides illumination from an illuminator 32. An observation tube 35 allows a human user to visually inspect the defect through eyepieces 36, and a CCD camera 37 carries an optical image to a viewing monitor (not shown). Information generated by the subsequent inspection device is also carried by a fiber guide 38 to a host computer 40. A focusing mechanism 39 allows a human user to focus the subsequent inspection device, or focusing may be accomplished automatically. Eyepieces 36 or a video monitor may present a visual image of the defect, or the subsequent inspection device may connect to the host computer 40 system and provide further statistical data. In some embodiments, a processor performs real-time statistical analysis on defects, generating information useful to the manufacturing function 60. In some embodiments, a database is maintained storing the location and parameters of defects for subsequent batch processing. In some embodiments, a video /audio, or other monitor presents the defects in a manner that conveys information regarding the defects to human users. For example, a video monitor may present a computer- enhanced and magnified section of the disk showing a defect. Because both the optical scanner 22 and the subsequent inspection device are located within the clean room, there is no risk of contamination in the transportation of the disks 2 from the optical scanner 22 to the subsequent inspection device. Furthermore, data collected by the inspection means or computed within the computer system may be provided automatically and instantaneously to the manufacturing function 60, and thus the time delay between detecting a manufacturing problem and communicating the problem to the manufacturing function 60 is significantly reduced. The general nature of the defect is also evaluated, and thus defects that can be repaired through burnishing or cleaning may be ignored by the communication to the manufacturing function 60. The instantaneous nature of the communication prevents additional disks 2 being manufactured after the defect has been discovered. The clean room environment protects the disks 2 from additional contamination in route to the subsequent inspection device, and thus ensures that the defects discovered by the subsequent inspection device were actually present when the disks 2 left the manufacturing function 60. In some embodiments video monitors are provided by both the optical scanner 22 and the subsequent device to present a variety of information relating to the defects, and a video monitor connected to the host computer 40 provides a presentation of the statistical results.

In several embodiments of the system implementing the present invention, the manufacturing function 60 responds automatically to signals received from the inspection system. Thus, in such embodiments the system is "closed loop" in that defects detected by the optical scanner 22 are evaluated in detail by the subsequent inspection device, analyzed by the host computer 40, and corrective measures indicated where necessary are automatically implemented by the manufacturing function 60.

Claims

CLAIMSWe claim:

1. An inspection method for detecting and correcting defects on optical arm magnetic disks, comprising the steps of: manufacturing one or more disks; optically inspecting the disks; providing the results of the inspection to the manufacturing step automatically.

2. The inspection method is set forth in Claim 1, further comprising the step of microscopically inspecting the disks, using either a scanning electron microscope, an atomic force microscope, or advanced image analysis.

3. The inspection method is set forth in Claim 2, wherein the step of microscopically inspecting the disk further comprises moving the disk from an optical inspector to a microscopic inspector.

4. The inspection method is set forth in Claim 2, further comprising the step of controlling the step of microscopically inspecting the disk using information from the step of optically inspecting the disk.

5. The inspection method as set forth in Claim 2, wherein the steps of optically and microscopically inspecting the substrate produce information relating to the size, number, and nature of defects on the substrate.

6. The inspection method as set forth in Claim 1, further comprising the step of presenting information to a human user by use of a human user interface.

7. The inspection method as set forth in Claim 6, wherein the human user interface includes a monitor or video printer, and a means for storing information relating to defects on substrate in an archival form. 121461 PC17US97/00992

12

8. The inspection method as set forth in Claim 5, further comprising the step of analyzing information and providing analyzed information to a manufacturing function.

9. The inspection method as set forth in Claim 7, further comprising the step of analyzing information and providing analyzed information to a manufacturing function.

10. The inspection method as set forth in Claim 1, further comprising the step of moving a carriage holding a surface of the substrate to a microscopic inspector.

11. The inspection method as set forth in Claim 1, wherein the step of microscopically inspecting and the step of optically inspecting further comprising the step of rotating the substrate about an axis.

12. The inspection method as set forth in Claim 7, wherein information obtained is such that a host computer or an observer may detect and distinguish irreparable defects from other defects eligible for repair.

13. An inspection apparatus for detecting and correcting defects on the surface of a smooth substrate, comprising: an optical scanner, scanning the surface of the substrate; an inspection device, further inspecting defects on the surface of the substrate detected in the an optical scanner step;

an output device, coupled to the optical scanner and to the inspection device, providing first signals indicative of the nature of defects on the substrate.

14. The inspection apparatus is set forth in Claim 13, wherein the inspection device microscopically inspecting the surface of the substrate comprises either a scanning electron microscope, an atomic force microscope, or advanced image analysis.

15. The inspection apparatus is set forth in Claim 14, further comprising a translation device, moving the substrate from an optical scanner to the inspection device.

16. The inspection apparatus is set forth in Claim 14, wherein the inspection device microscopically inspecting the surface of the substrate inspects only those defects identified by information from the optical scanner.

17. The inspection apparatus as set forth in Claim 14, wherein the optical scanner and the output device provides information relating to the size, number, and nature of defects on the substrate.

18. The inspection apparatus as set forth in Claim 13, wherein the output device human user interface includes a human user that presents information to a human user.

19. The inspection apparatus as set forth in Claim 18, wherein the human user interface includes a monitor or video printer, and a data storage device storing information relating to defects on substrate in an archival form.

20. The inspection apparatus as set forth in Claim 17, wherein the output device analyzes information and provides analyzed information to a manufacturing function.

21. The inspection apparatus as set forth in Claim 19, wherein the output device analyzes information and provides analyzed information to a manufacturing function.

22. The inspection apparatus as set forth in Claim 13, wherein the translation device moves substrates from the optical scanner to the inspection device.

23. The inspection apparatus as set forth in Claim 13, wherein the optical scanner and the inspection device rotate the substrate about an axis.

24. The inspection apparatus as set forth in Claim 19, further comprising a host computer that receives information from the output device, and distinguishes irreparable defects from other defects eligible for repair.

25. The inspection apparatus as set forth in Claim 19, wherein the output device presents information pertaining to defects on the substrate to a human user such that the human user may distinguish irreparable defects from other defects eligible for repair.

26. An inspection means for detecting and correcting defects on the surface of a smooth substrate, comprising: an optical scanning means for scanning the surface of the substrate; an subsequent inspection means for further inspecting defects on the surface of the substrate detected in the an optical scanning means step;

an output means, coupled to the optical scanning means and to the subsequent inspection means, for providing first signals indicative of the nature of defects on the substrate.

27. The inspection means is set forth in Claim 26, wherein the subsequent inspection means microscopically inspecting the surface of the substrate comprises either a scanning electron microscope, an atomic force microscope, or advanced image analysis.

28. The inspection means as set forth in Claim 27, further comprising a translation means for moving the substrate from an optical scanning means to the subsequent inspection means.

29. The inspection means is set forth in Claim 27, wherein the subsequent inspection means microscopically inspecting the surface of the substrate inspects only those defects identified by information from the optical scanning means.

30. The inspection means as set forth in Claim 27, wherein the optical scanning means and the output means provide information relating to the size, number, and nature of defects on the substrate.

31. The inspection means as set forth in Claim 26, wherein the output means includes a means for interfacing with a human user, that presents information to a human user.

32. The inspection means as set forth in Claim 31, wherein the output means includes a monitor or video printer, and further includes a data storage means for storing information relating to defects on substrate in an archival form.

33. The inspection means as set forth in Claim 30, wherein the output means analyzes information and provides analyzed information to a manufacturing function.

34. The inspection means as set forth in Claim 32, wherein the output means analyzes information and provides analyzed information to a manufacturing function.

35. The inspection means as set forth in Claim 26, wherein the translation means moves the substrate from the optical scanning means to the subsequent inspection means.

36. The inspection means as set forth in Claim 26, wherein the optical scanning means and the subsequent inspection means rotate the substrate about an axis.

37. The inspection means as set forth in Claim 32, further comprising a host computer that receives information from the output means and distinguishes irreparable defects from other defects eligible for repair.

38. The inspection means as set forth in Claim 32, wherein the output means presents information pertaining to defects on the substrate to a human user such that the human user may distinguish irreparable defects from other defects eligible for repair.