System and method for inspection of multiple features of patterned objects in manufacture of electrical circuits

Abstract

To provide an improved system and method for inspection of patterned objects in the manufacture of electrical circuits.SOLUTION: A method for inspection of multiple features of patterned objects in the manufacture of electrical circuits includes: using an optical defect detection machine (ODDM) to perform defect detection on the patterned object; and using the ODDM to output at least one of spatial coordinates and physical attributes of at least some of the multiple features.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a system and method for testing electrical circuits, particularly during their manufacture. [Background technology]

[0002] A variety of inspection systems and methods are known in the art. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 7,206,443 [Patent Document 2] U.S. Patent No. 7,388,978 [Patent Document 3] U.S. Patent No. 7,200,259 [Patent Document 4] U.S. Patent No. 7,181,059 Summary of the Invention [Problem to be solved by the invention]

[0004] SUMMARY OF THE PRESENT EMBODIMENT The present invention seeks to provide an improved system and method for inspecting patterned objects during the manufacture of electrical circuits. [Means for solving the problem]

[0005] Thus, in accordance with a preferred embodiment of the present invention, there is provided a method for inspecting a plurality of features of a patterned object during the manufacture of electrical circuits, the method comprising the steps of performing defect detection on the patterned object using an optical defect detection machine (ODDM) and outputting, using the ODDM, spatial coordinates and / or physical attributes of at least some of the plurality of features.

[0006] Preferably, the ODDM comprises a PCB inspection machine.According to a preferred embodiment of the present invention, the ODDM comprises an automated optical inspection machine for electrical circuits.

[0007] According to a preferred embodiment of the present invention, the step of outputting using the ODDM includes improving the spatial accuracy of the measurement of the physical attribute using at least one of a motion sensor, an accelerometer, a distance sensor, a three-dimensional (3D) sensor, and a temperature sensor. Additionally or alternatively, the step of outputting using the ODDM also includes the use of a calibration target.

[0008] Preferably, the step of outputting with ODDM also includes using a plurality of discrete electromagnetic spectrum frequency bands. In accordance with a preferred embodiment of the present invention, the step of outputting with ODDM includes using a plurality of spatially displaced images in a plurality of discrete electromagnetic spectrum frequency bands. The step of outputting with ODDM also includes using a plurality of spatially displaced images in a plurality of discrete electromagnetic spectrum frequency bands to examine how three-dimensional variations of the patterned object appear in the two-dimensional image.

[0009] Preferably, the step of outputting using the ODDM also includes the step of run-time bias compensation using a high precision measurement sensor that detects bias in the ODDM measurements.

[0010] According to a preferred embodiment of the present invention, the step of outputting using the ODDM also includes measuring distortion of measurements of at least some of the physical attributes of the plurality of features as a function of the position of at least some of the plurality of features within the field of view and cropping the field of view to a region having acceptably low distortion. The measurement distortion also occurs during calibration of the ODDM. The step also includes compensating for the measurement distortion that occurs during calibration of the ODDM using a calibration table. Alternatively, the measurement distortion occurs during execution of the ODDM.

[0011] In accordance with a preferred embodiment of the present invention, when inspecting multiple identical patterned objects, the ODDM is operated such that not all of the features of every patterned object are measured in each scan, but each of the features is measured in at least one scan.

[0012] In accordance with a preferred embodiment of the present invention, the ODDM is operated to perform multiple scans at at least two different resolutions, preferably using at least one lower resolution to ensure position accuracy and at least one higher resolution to measure attributes.

[0013] In accordance with a preferred embodiment of the present invention, the method also includes run-time evaluating correspondence between the measurements of the physical attributes and reference computer-aided manufacturing (CAM) data for at least some of the physical attributes to compensate for distortions that may be due to ODDM operation. The method also includes run-time compensating for distortions that may be due to ODDM operation.

[0014] In accordance with another preferred embodiment of the present invention, there is also provided a system for inspecting a plurality of features of a patterned object during the manufacture of electrical circuits, the system including an inspection subsystem operative to detect defects in the patterned object and a physical attribute measurement subsystem operative to output at least some of the plurality of features.

[0015] Preferably, the system also includes at least one of a motion sensor, an accelerometer, a distance sensor, a 3D sensor and a temperature sensor.

[0016] In accordance with a preferred embodiment of the present invention, the system also includes a high precision measurement sensor.

[0017] In accordance with a preferred embodiment of the present invention, the system also includes at least one high precision encoder.

[0018] The invention will be understood and appreciated from the following detailed description. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a simplified schematic diagram of an optical defect detector (ODDM) useful in the manufacture of electrical circuits, retrofitted to measure physical attributes of multiple features of a patterned object. [Diagram 2] FIG. 1 is a simplified flow diagram illustrating the operation of an optical defect inspection machine useful in the manufacture of electrical circuits that measures physical attributes of multiple features of a patterned object. [Figure 3A] FIG. 1 is a detailed flow diagram outlining operational portions of an optical defect inspection machine useful in the manufacture of electrical circuits that measure physical attributes of multiple features of a patterned object. [Figure 3B] FIG. 1 is a detailed flow diagram outlining operational portions of an optical defect inspection machine useful in the manufacture of electrical circuits that measure physical attributes of multiple features of a patterned object. [Figure 4] 1 is a simplified diagram of a portion of a patterned object having various typical features whose physical attributes may be measured; [Diagram 5] 1 is a simplified diagram of measuring spatial coordinates of selected features of a patterned object relative to a reference point. [Figure 6A] FIG. 3C is a simplified diagram of a detailed flow diagram of some of the operational portions of an optical defect inspection machine useful in fabricating electrical circuits that measure physical attributes of multiple features of the patterned object shown in FIG. 3B. [Figure 6B] FIG. 3C is a simplified diagram of a detailed flow diagram of some of the operational portions of an optical defect inspection machine useful in fabricating electrical circuits that measure physical attributes of multiple features of the patterned object shown in FIG. 3B. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Reference is now made to Figure 1, which is a simplified schematic diagram of an optical defect detector (ODDM) useful in the manufacture of electrical circuits, retrofitted to measure physical attributes of multiple features of a patterned object. For purposes of this patent application, the term "optical defect detector" refers to machines such as the Orbotech DISCOVERY or Orbotech FUSION machines sold by Orbotech Ltd. of Yavne, Israel, which have spatial inaccuracies of greater than 25 microns.

[0021] It will be appreciated that the ODDM shown in FIG. 1 is a modification of a commercially available optical inspection machine useful for inspecting printed circuit boards.

[0022] 1, the system preferably includes a workstation 100 and an inspection subsystem 102. The workstation 100 preferably includes a computer 150 that includes a user input interface 152 and a display 154.

[0023] The inspection subsystem 102 preferably includes a patterned object placement assembly 156 that includes a chassis 160 preferably mounted to a conventional optical stand 162. The chassis 160 defines a patterned object support 164 on which a patterned object 166, typically an electrical circuit to be inspected and / or repaired, such as a printed circuit board (PCB), flexible printed circuit (FPC), electrical circuit artwork, or flat panel display (FPD), may be placed. The patterned object 166 typically includes one or more conductors 104. The patterned object 166 typically has one or more defects of various kinds, such as defects due to missing conductors, e.g., cuts 106.

[0024] The patterned object placement assembly 156 also preferably includes a bridge 170 arranged for linear movement relative to the support 164 along a first inspection axis 174 defined with respect to the chassis 160. Alternatively, the bridge 170 may be fixed and the patterned object 166 may be displaced relative to the bridge, such as in roll-to-roll processing. As a further alternative, the bridge 170 may be fixed and the chassis 160 may be displaced by any suitable axial movement or movements.

[0025] Preferably, the inspection subsystem 102 also includes an optical assembly 176 that is preferably configured for linear motion relative to the bridge 170 along a second inspection axis 178 that is perpendicular to the first inspection axis 174. Alternatively, the optical assembly 176 may be a stationary optical assembly and the chassis 160 may be a moveable chassis that operates to move the patterned object 166 relative to the optical assembly 176 in the X and / or Y directions.

[0026] According to a preferred embodiment of the present invention, the optical assembly 176 is provided with one or more of the following measurement accuracy enhancement (MAE) sensors: an accelerometer 180, such as a VN-100 IMU sensor available from VectorNav Technologies, Inc., Dallas, Texas, USA, a temperature sensor 182, such as an ACCU-CURVE thermistor available from Ametherm, Inc., Carson City, Nevada, USA, a distance sensor 184, such as an LK-G series sensor available from Keyence Corporation USA, Itasca, Illinois, USA, and a three-dimensional (3D) camera 186, such as a white light interferometer with 3D camera available from Heliotis, Lucerne, Switzerland. Preferably, at least one additional accelerometer 190 and at least one additional temperature sensor 192 are mounted on the chassis 160 and / or bridge 170.

[0027] A high precision metrology sensor 194, preferably an ALTERA coordinate measuring machine (CMM) available from LK Metrology of Derby, England, may be provided and integrated into the optical assembly 176 or may be separate from the inspection machine. Alternatively, the high precision metrology sensor 194 may include a high resolution camera with suitable illumination and high quality collection optics.

[0028] Preferably, the inspection machine includes at least one high precision encoder 196, such as the MS15 available from RSF Elektronik of Talsdorf, Austria, which may be provided in addition to an existing encoder or in place of one or more existing encoders.

[0029] The MAE sensor is useful for improving the accuracy of measurements made with the optical assembly 176 of physical features of the patterned object 166 being inspected and / or spatial coordinates in which such physical features are located. Preferably, the spatial coordinates are measured in a known coordinate system established relative to at least one reference point, which may be a unique reference point or a feature designated as a reference point. Some examples of such physical features include the width and / or thickness of conductors, the spacing between conductors, the diameter of pads, and the dimensions of via holes.

[0030] Workstation 100 preferably also includes software modules that operate to operate optical assembly 176 and patterned object placement assembly 156. Workstation 100 preferably receives at least one image of patterned object 166 produced by optical assembly 176, as well as being capable of receiving reference CAM data from a CAM data source (not shown). Workstation 100 preferably also receives input from MAE sensors, such as sensors 180, 182, 184, 186, 190, 192, and 194, several examples of which are shown in FIG. 1 and its enlarged view A.

[0031] As also shown in Close Up A, a schematic side block diagram of optical assembly 176, optical assembly 176 preferably also includes at least one camera 200 that views patterned object 166, preferably through a lens arrangement 202, and passes an image of patterned object 166 to display 154 of workstation 100. Optical assembly 176 also preferably includes an illumination assembly 204.

[0032] Reference is now made to FIG. 2, which is a simplified flow diagram illustrating the operation of an optical defect detector useful in the manufacture of electrical circuits that measures physical attributes of multiple features of a patterned object.

[0033] 2, in a first step 210, the measurement capabilities of the defect detector are calibrated, preferably using a machine calibration target, optionally formed on a glass, ceramic or other suitable surface. The calibration result is provided to the ODDM as a calibration output.

[0034] Subsequently, as shown in a next step 220, during the defect detection inspection, the ODDM measures the spatial coordinates of the features of the patterned object in a known coordinate system established by the physical attributes of the features of the patterned object and at least one reference point, which may be an inherent reference point or a physical feature designated as a reference point.

[0035] Optionally, as shown in a next step 230, the system can later or simultaneously sense at least one of the current environmental, spatial and kinematic characteristics during operation of the ODDM using one or more sensors that provide sensor output to the ODDM.

[0036] The system then adjusts the measurements of the spatial coordinates of the physical attributes and features based on the calibration output and / or the sensor output, as shown in next step 240.

[0037] The ODDM then outputs at least one of defect information and patterned object information, as shown in next step 250. The defect information preferably includes the defect location, and may include the spatial coordinates of the defect location. The defect information may also include the type of defect and any other relevant information about the defect. The patterned object information preferably includes at least measurements of physical attributes of features of the patterned object, and may also include the spatial coordinates of the physical attributes being measured.

[0038] Reference is now made to FIG. 3A, which is a detailed flow diagram outlining the calibration step 210 of FIG. 2 that forms part of the operation of an ODDM useful in the manufacture of electrical circuits that measure multiple physical attributes of patterned objects.

[0039] As shown in FIG. 3A, the first step 310 is to provide a machine calibration target suitable for correcting systematic errors related to the measurement functionality.

[0040] The ODDM tests the calibration target during installation of the machine and periodically thereafter, as shown in the next step 320. Optionally, the ODDM uses an MAE sensor during testing of the calibration target. The results of the test are provided to the ODDM as a target calibration test output.

[0041] The spatial coordinates of each selected feature of the calibration target are then preferably automatically identified in a next step 340. The physical attributes of the given measured calibration features may also be ascertained.

[0042] The spatial coordinates of each selected feature are measured with respect to at least one reference point of the calibration target, as shown in the next step 350. The at least one reference point may be an inherent reference point or a feature designated as a reference point.

[0043] The measured physical attributes of the predetermined calibration features and spatial coordinates of the predetermined calibration features of the calibration target are then compared to their design value specified physical attributes and spatial coordinates, as shown in the next step 360. Optionally, the measured spatial coordinates of the predetermined calibration features of the calibration target are compared to spatial coordinates specified in the reference CAM data for the calibration target. Optionally, the measurements are adjusted based on the MAE sensor output.

[0044] Optionally, as shown in a next step 370, prior to a particular initial inspection of a particular patterned object, and perhaps periodically thereafter, the ODDM is operated to inspect the particular patterned object using a high precision data source, which may be an external high precision data source, such as an image data source, a profiler or a coordinate measuring machine (CMM). Optionally, the ODDM uses an MAE sensor during the inspection. The results of the inspection are provided to the ODDM as a calibrated output specific to the patterned object.

[0045] Finally, as shown in step 380, a machine calibration output is generated in the form of a correction table based on the comparison of steps 360 and 370.

[0046] Reference is now made to FIG. 3B, which is a detailed flow diagram outlining the measurement step 220 of FIG. 2, which forms part of the operation of a defect detector useful in the manufacture of electrical circuits that measure multiple physical attributes of patterned objects.

[0047] 3B, prior to a particular initial inspection of a particular patterned object, the features and attributes of the particular patterned object that are to be measured, and the features whose spatial coordinates are to be ascertained, are selected, as shown in a first step 410. Based on this selection, an appropriate measurement algorithm is executed.

[0048] In a subsequent step 420, at least one image of the particular patterned object is obtained using the ODDM with at least one illumination setting suitable for measuring physical attributes of the features of the patterned object.

[0049] As shown in step 430, simultaneously with or subsequent to step 420, at least one image of the particular patterned object is obtained using an ODDM with at least one illumination setting suitable for defect detection.

[0050] Subsequently, at least one of the images produced in step 420, and optionally the image produced in step 430, are processed using image processing techniques including edge detection, image smoothing, etc. as shown in step 440.

[0051] Finally, as shown in step 450, appropriate measurements are made using appropriate measurement algorithms for each feature being measured and the attributes and spatial coordinates of each feature being measured.

[0052] Reference is now made to FIG. 4, which is a simplified diagram of a portion of a patterned object annotated to indicate various typical features for which physical attributes may be measured.

[0053] 4, the patterned object 166 is implemented as a panel 466 that includes a plurality of exemplary structures having physical attributes to be measured. The exemplary plurality of structures of the panel 466 to be measured includes, among others, at least one conductor 470 having a width 472 to be measured, at least one space 474 having a width 476 to be measured, at least one via or bore hole 480 having a top diameter 482, a bottom diameter 484, and an aspect ratio to be measured, at least one substantially rectangular pad 490 having a width 492 and a length 494 to be measured, and at least one substantially circular pad 500 having a bottom diameter 502, a top diameter 504, and an aspect ratio to be measured. As is known in the art, aspect ratio typically refers to the ratio of a first feature, such as a top diameter or width, of a structure to a second feature, such as a bottom diameter or width, of the structure, where "top" and "bottom" refer to different positions along the height of the structure.

[0054] Reference is now made to Figure 5, which is a simplified diagram of the measurement of spatial coordinates of a given feature 510 of patterned object 566, one embodiment of patterned object 166, relative to a given reference point 570. In the example shown in Figure 5, feature 510 is located at location 580 having x,y coordinates (x1,y1). It will be appreciated that the x,y coordinates of a feature, such as feature 510 of patterned object 566, indicate its respective distance in directions indicated by x-axis 592 and y-axis 594 from a given reference point 570, which for ease of calculation is typically considered to have x,y coordinates (0,0).

[0055] Reference is now made to FIG. 6A, which is a detailed flow diagram outlining the feature selection step 410 of FIG. 3B which forms part of the operation of a defect detector useful in the manufacture of electrical circuits that measure physical attributes of a plurality of features of a patterned object.

[0056] As shown in Figure 6A, in a first step 610, various features of the printed circuit to be inspected and measured, such as the features shown in Figure 4, are designated for measurement. This designation can be done in a variety of ways, such as pre-designated in the CAM data or designated by feature type using a graphical user interface (GUI). Some examples of feature types include all lines with a width between 30 and 50 microns, all circular pads with a radius less than 100 microns, all lines within a designated area on the printed circuit board, and all lines that terminate in a circular pad.

[0057] Then, as shown in a next step 620, an appropriate algorithm for measuring the indicated characteristic is selected from a database of stored algorithms, such as those described in U.S. Patent Nos. 7,206,443, 7,388,978, 7,200,259, and 7,181,059.

[0058] Reference is now made to FIG. 6B, which is a detailed flow diagram outlining the algorithm-utilizing step 450 of FIG. 3B that forms part of the operation of a defect detector useful in the manufacture of electrical circuits that measure physical attributes of multiple features of a patterned object.

[0059] As shown in FIG. 6B, in a first step 650, each selected feature and reference point specified in step 610 (FIG. 6A) is identified.

[0060] Subsequently, as shown in the next step 660, the spatial coordinates of each selected feature relative to each reference point are ascertained.

[0061] As shown in the next step 670, the spatial coordinates of the selected features are then adjusted according to the correction table of step 380 (FIG. 3A).

[0062] Those skilled in the art will appreciate that the present invention is not limited to what has been particularly shown and described above, but rather the scope of the present invention includes both combinations and subcombinations of the various features of the present invention and modifications thereof which would occur to one skilled in the art upon reading and understanding the above description and which do not exist in the prior art.

Claims

1. 1. A method for inspecting a plurality of features of a patterned object during the manufacture of an electrical circuit, comprising: performing defect detection on the patterned object using an optical defect detector (ODDM), the patterned object being a printed circuit board, a flexible printed circuit (FPC), or a flat panel display; outputting at least one of spatial coordinates and physical attributes of at least some of the plurality of features using the ODDM; Measuring distortion of measurements of at least some of the physical attributes of the plurality of features as a function of positions of at least some of the plurality of features within the field of view; cropping the field of view to a region with acceptably low distortion; The method includes:

2. The method of inspecting multiple features of a patterned object of claim 1 , wherein the ODDM comprises a printed circuit board inspection machine and the patterned object is the printed circuit board.

3. The method of inspecting multiple features of a patterned object of claim 1 , wherein the ODDM comprises an automated optical inspection machine for electrical circuits.

4. 2. The method of inspecting multiple features of a patterned object of claim 1, wherein the step of outputting using the ODDM includes the step of improving spatial accuracy of the measurement of the physical attribute using at least one of a motion sensor, an accelerometer, a distance sensor, a 3D sensor, and a temperature sensor.

5. The method of claim 1 , wherein the step of outputting using the ODDM further comprises the step of using a calibration target.

6. 2. The method of inspecting multiple features of a patterned object of claim 1, wherein the step of outputting using the ODDM comprises using a plurality of discrete electromagnetic spectrum frequency bands.

7. 7. The method of inspecting multiple features of a patterned object of claim 6, wherein the step of outputting using the ODDM comprises the step of using a plurality of spatially offset images in the plurality of discrete electromagnetic spectrum frequency bands.

8. 8. The method of inspecting multiple features of a patterned object of claim 7, wherein the step of outputting using the ODDM includes using the multiple spatially offset images in the multiple discrete electromagnetic spectrum frequency bands to determine how three-dimensional variations in the patterned object appear in a two-dimensional image.

9. 2. The method of inspecting multiple features of a patterned object of claim 1, wherein the step of outputting using the ODDM further comprises the step of detecting bias in measurements by the ODDM using a measurement sensor and compensating for the bias on-the-fly.

10. The method of inspecting multiple features of a patterned object of claim 1 , wherein measuring the distortion occurs during calibration of the ODDM.

11. 11. The method of inspecting multiple features of a patterned object of claim 10, wherein measuring the distortion occurring during calibration of the ODDM comprises compensating with a calibration table.

12. The method of inspecting multiple features of a patterned object of claim 1 , wherein the step of measuring the distortion occurs during execution of the ODDM.

13. 2. The method of inspecting multiple features of a patterned object of claim 1, wherein the ODDM is operated such that, when inspecting multiple identical patterned objects, not all of the multiple features of all of the patterned objects are measured in each scan, but each of the multiple features is measured in at least one scan.

14. The method of claim 1 , further comprising operating the ODDM to perform multiple scans at at least two different resolutions.

15. 15. The method of inspecting multiple features of a patterned object of claim 14, further comprising using at least one lower resolution to ensure positional accuracy and using at least one higher resolution for the measurement of the attribute.

16. 2. The method for inspecting multiple features of a patterned object of claim 1, further comprising: evaluating, on-the-fly, a correspondence between the physical attributes and at least some reference CAM data of the physical attributes to compensate for distortions that may be caused by the operation of the ODDM.

17. 20. The method of inspecting multiple features of a patterned object of claim 16, further comprising: run-time compensation for distortions that may result from operation of the ODDM.

18. 1. A system for inspecting a plurality of features of a patterned object during manufacturing of an electrical circuit, comprising: an inspection subsystem operative to detect defects in the patterned object, the patterned object being a printed circuit board, a flexible printed circuit (FPC), or a flat panel display; and a physical attribute measurement subsystem operative to output measurements of at least one of physical attributes and spatial coordinates of at least some of the plurality of features; a workstation configured to measure distortion of measurements of at least some of the physical attributes of the plurality of features as a function of position of at least some of the plurality of features within a field of view and to crop the field of view to a region having acceptably low distortion; Including, the system.

19. 20. The system of claim 18, further comprising at least one of a motion sensor, an accelerometer, a distance sensor, a 3D sensor, and a temperature sensor.

20. 20. The system of claim 18, further comprising a high accuracy sensor.

21. 20. The system of claim 18, further comprising at least one encoder.

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