JP2768344B2 - Pattern inspection apparatus and inspection method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a pattern inspection apparatus and method, and more particularly to a pattern inspection apparatus and method used for pattern inspection of a printed wiring board.

[0002]

2. Description of the Related Art A pattern inspecting apparatus and an inspecting method of this kind perform setting of parameters and pattern comparison for performing image recognition and pass / fail judgment of a printed wiring board before the inspection of the printed wiring board. It is necessary to create master data to perform. The master data is created from image data obtained by automatic creation from pattern original image data of the substrate to be inspected or image data obtained from the substrate to be inspected itself. The parameters and pattern data of the printed wiring board thus obtained are registered as master data of the board to be inspected, and a design rule check (hereinafter abbreviated as DRC) for the board to be inspected is performed based on the master data. In addition, a comparison inspection is performed, and the defect is extracted. When creating the master data, the size of one pixel in image recognition, that is, the resolution is set in advance. As for the resolution in this image recognition, as the size is set to a smaller value, it becomes possible to extract fine defects on the substrate to be inspected, but the amount of image data increases in inverse proportion to the size of this resolution. Therefore, more time is required for image processing, DRC, comparison inspection processing, and the like at the time of pattern inspection, resulting in a delay in the defect extraction processing.

Accordingly, a conventional pattern inspection apparatus and
In the inspection method, the resolution is set to one-several to several tenths of a reference pattern width of the substrate to be inspected in consideration of the inspection accuracy and the inspection time of the printed wiring board, and
The value of the resolution is a fixed value. To change the resolution, it is necessary to recreate the master data.

An example of a printed circuit board pattern inspection apparatus for shortening the inspection time is disclosed in Japanese Patent Laid-Open No. 4-69777.
No. 6,086,045. In this inspection method, the edge of the substrate to be inspected is extracted using a reference printed board determined to be non-defective or a mask film for producing a printed board to be inspected.
Defects are detected around the edge, and defects that occur outside the edge are not important for quality control, and are not extracted. As described above, the target area for detecting the defect is limited to the specific area and selected, thereby reducing the defect extraction processing time, thereby shortening the inspection time.

[0005]

In the above-described conventional pattern inspection apparatus and method, the resolution in image recognition is set to a fixed value in advance when the master data is created. The image data amount is set to a predetermined value, and the processing time required for image processing, DRC, comparison inspection processing, and the like during pattern inspection is also fixed. However, the quality of the substrate to be inspected is fluid at the initial stage of production and defects are liable to occur, and it is necessary to perform the pattern inspection in as much detail as possible even in the early stage of production, but the production is repeated. In the process, the quality of the substrate to be inspected is also stabilized, and the occurrence of the defects follows a decreasing trend. Therefore, even if the inspection function is slightly reduced by changing the resolution to a relatively large value, it is required to reduce the inspection time or the inspection cost.
As described above, the resolution is fixed and cannot be easily changed.

In the pattern inspection apparatus disclosed in Japanese Patent Application Laid-Open No. 4-69777, a means for extracting a pattern edge, a reference printed wiring board determined to be non-defective for extracting the pattern edge, and an inspection method. It has the disadvantage of requiring a mask film to create the target substrate, and furthermore, when a defect that cannot be ignored in quality control suddenly occurs in the area where the defect is not to be detected There was also a disadvantage that it could not be dealt with.

It is an object of the present invention to obtain defect data by comparison inspection with reference inspection data, correct the resolution based on statistics of a predetermined number of inspection results, update the corresponding reference inspection data, and rationally inspect the inspection time. Is to shorten.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide an image signal processing means for outputting, as a digital image signal, an optical image of a printed wiring board on which a conductive pattern is formed on an insulating substrate; An image analysis means for comparing the signal with reference inspection data at a predetermined resolution set in advance and performing quality inspection and outputting detected defect data when a defect is detected; The actual pattern is a real defect, it is not a real defect is determined whether the detected defect was output as a defect, a pattern inspection apparatus having a confirmation station that outputs defect data to distinguish between the real defect and the detected defect, The detected defect data and the actual defect data output from the checking station are recorded in the inspection result database, and the inspection result database is recorded. Referring to the detected defect data and the actual defect data, it is determined whether or not the production quality of the printed wiring board to be inspected is stable, and the resolution is corrected according to the determination result, and the corrected resolution is corrected. Automatically generating and outputting the reference inspection data corresponding to the inspection result processing means for updating the reference inspection data, and the image analysis means is provided by the reference inspection data updated by the inspection result processing means. An apparatus for performing a quality inspection corresponding to the corrected resolution.

The image signal processing means converts an image signal of a printed circuit board to be tested obtained by a predetermined camera into a digital signal and outputs the digital signal. A binarization circuit for converting the image into a signal and outputting the signal; and a preprocessing circuit for outputting the binarized image signal after performing a correction process, wherein the image analysis means is output from the preprocessing circuit. An image memory for temporarily storing a digital image signal, a digital image signal output from the pre-processing circuit, and the reference inspection data output from the image memory are input, and the two digital image signals are compared and analyzed. A comparison inspection circuit that outputs an inspection result; and a design rule check that outputs a digital image signal output from the preprocessing circuit and outputs the result. And a circuit, and the test result database the test result processing means, for storing the defect and real defect data output from said check station,
A statistical analysis circuit for statistically analyzing the defect data stored in the inspection result database; and referring to an analysis result by the statistical analysis circuit, to determine whether or not the production quality of the printed wiring board to be tested is stable. When the resolution determination circuit determines that the production quality of the printed wiring board to be tested is stable in the resolution determination circuit, the determination result is received and stored in the database of the printed wiring board reference inspection data. Inspection data generation for retrieving the reference inspection data set in a certain step, appropriately correcting the resolution set for the optical image data extraction, and outputting and updating the reference inspection data based on the corrected resolution. A pattern inspection apparatus having a circuit is also a preferred embodiment of the pattern inspection apparatus of the present invention.

Further, it is appropriate to have means for performing the statistical analysis for every 100 inspections, and the first 10 inspections for every 100 inspections from the second 100 inspections to the initial resolution. It is desirable to check the quality stability by performing a corresponding check.

According to the pattern inspection method of the present invention, a first step of optically generating an image signal of a printed wiring board to be inspected, and converting the image signal into a digital image signal,
A second step of correcting and outputting the digital image signal, analyzing the digital image signal output in the second step, inspecting the digital image signal for defects, and detecting an inspection result defect Then, a third step of outputting defect data and a fourth step of confirming whether the defect indicated by the defect data is an actual defect that is an actual defect or a detected defect that is not an actual defect but has been detected as a defect When,
In a pattern inspection method including a fifth step of registering defect data while distinguishing between an actual defect and a detected defect, when a predetermined number of printed wiring boards are inspected in the first to fifth steps, a fifth step is performed. A sixth step of statistically analyzing the defect data registered in the step and outputting a defect occurrence rate and a standard deviation of the defect; and determining whether the defect occurrence rate and the standard deviation of the defect meet predetermined conditions, respectively. A seventh step of determining whether
When the actual defect detection rate and the standard deviation of the defect conform to the predetermined standard values, the resolution set for the inspection of the optical image data is corrected to the resolution corresponding to the standard value. And automatically updating and setting the reference inspection data corresponding to the corrected resolution.

[0012]

Next, an embodiment of the present invention will be described.

FIG. 1 is a block diagram of an embodiment of a pattern inspection apparatus according to the present invention.

The pattern inspection apparatus corresponds to a printed wiring board 21 to be inspected, and includes an image signal processing section 3, an image analysis section 4, an inspection result processing section 5, a CCD camera 6, a pair of illuminations 7, And an optical inspection device section 1 including an inspection table 8 and a confirmation station 2. The image signal processing unit 3 includes an A / D converter 9, a binarization circuit 10, and a pre-processing circuit 11, and the image analysis unit 4
An RC circuit 12, a comparison circuit 13, an image memory 14,
An inspection result output circuit 15 is provided. The inspection result processing unit 5
An inspection result database 16, a statistical analysis circuit 17, a decomposition ability determination circuit 18, an inspection database 19, and an inspection data generation circuit 20 are provided.

FIG. 2 is a flowchart showing a processing procedure of the pattern inspection method of the present invention. The operation of the present embodiment will be described below with reference to FIGS.

Projected light by the illumination 7 is applied to the printed wiring board 21 to be inspected, and the reflected light of the projected light from the printed wiring board 21 is received by the CCD camera, and an image signal is output. In the converter 9, the image signal is converted into a digital image signal, input to the binarization circuit 10, and converted into a binarization signal in the binarization circuit 10. This binarized signal is supplied to the preprocessing circuit 11
, Is output after preprocessing including image correction and the like is performed, and is sent to the image analysis unit 4. In the image analysis unit 4, the image signal on which the preprocessing has been performed is converted into the DRC circuit 1.
2. Input to the comparison inspection circuit 13 and the image memory 14 and stored in the image memory 14. In the comparison inspection circuit 13, the image signal input from the preprocessing circuit 11
The printed wiring board is compared with master data (hereinafter referred to as reference data) output from the image memory 14 and analyzed.
The comparison inspection result is input to the inspection result output circuit 15. The DRC circuit 12 performs DRC on the input image signal, and the inspection result is input to the inspection result output circuit 15. Then, the inspection result output circuit 1
5, the comparison inspection circuit 13 and the DRC circuit 1
2 is transmitted to the confirmation station 2 (step 101). At confirmation station 2,
Confirmation of these inspection results is performed (step 10).
2). At this time, a defect detected by the inspection result (including a defect which is not actually a defect but is detected as a defect on inspection)
Is determined as an actual defect (actually a defect), and is classified into a detected defect and an actual defect, and is inputted and registered in the inspection result database 16 (step 103).

In this way, every time the printed wiring board 21 is inspected, data including the defects detected by the CCD camera 6, the image signal processing unit 3, and the image analysis unit 4 and the actual defects are stored in the inspection result database 16. Stored. When the above process is performed on the printed wiring board having 100 surfaces to be inspected (step 104), if the inspection of the printed wiring board 21 having 100 surfaces is not completed, step 10 is executed.
Returning to step 2, the processing means after the "confirmation" in step 102 is performed again, and if the inspection of the 100 printed wiring boards 21 has been completed, the inspection of the 100 printed wiring boards 21 has been completed. In the first case, the statistical analysis circuit 17 inputs the data including the defects and the actual defects accumulated in the inspection result database 16 and statistically analyzes the number of detected defects, the number of actual defects, and the distribution of occurrence of the 100 lots. An analysis is performed (step 105).

Through the above processing procedure, the value of the actual defect detection rate (t) and the standard deviation (σ _x , σ _y ) given by the following equations are obtained each time the printed wiring board 21 of 100 surfaces is inspected. .

(1) Assuming that the actual defect detection rate is t, t = (the actual number of defects per N surface / the total number of defects per N surface) × 1
00% (2) Actual defect coordinate values (X _i , Y _i ) (i = 1, 2,...)
• Standard deviation of X coordinate = σ _x Standard deviation of Y coordinate = σ _y in all coordinates with respect to n) Then, in response to the statistical analysis result, in the resolution determination circuit 18, the actual defect detection rate t ≤ 1% ( It is determined whether or not the condition A) and the standard deviations are σ _x ≧ 120 and σ _y ≧ 120 (condition B) (step 106).

Generally, in the early stage of the inspection of the printed wiring board 21, since the production quality of the printed wiring board 21 is not yet stable, the actual defect detection rate t has a high value. The standard deviations σ _x and σ _y are small values because defects are likely to occur in the specified range due to the pattern formed on the wiring board 21. However, when a printed wiring board of the same line is continuously supplied, the manufacturing quality of the printed wiring board is gradually stabilized, and the value of the actual defect occurrence rate t becomes a gradually lower value, and the standard deviation σ _x , The value of σ _y also changes to a large value.

Here, as described above, the condition A is set to t
≦ 1% and condition B are set as σ _x ≧ 120 and σ _y ≧ 120, and when both of these conditions A and B are satisfied (hereinafter, this condition is referred to as condition C), the resolution determination circuit 18 performs printing. The production quality of wiring board 21 is determined to be stable. In response to this determination result, the inspection data generation circuit 20 searches the inspection database 19 for inspection data of the printed wiring board 21, and usually sets the resolution, that is, the size of one image to 7 to 12 μm □. The created inspection data indicates that the resolution is doubled over the entire inspection range, that is, the size of one pixel is 14 to 24 μm.
It is automatically created as new inspection data of m □ (step 110). Also, in step 106,
If the condition C is not satisfied, the optical inspection with the original resolution is continued (step 101). When the condition C is satisfied as described above, the new inspection data is transmitted to the comparison inspection circuit 13 included in the image analysis unit 4, and accordingly, as an optical inspection for the printed wiring board 21, In the comparative inspection circuit 13, an inspection including a comparative analysis is performed based on the new inspection data in which the size of the pixel is 14 to 24 μm (step 10).
1) Then, as described above, the confirmation processing in step 102, the registration processing of the actual defect in step 103, and the 100-page inspection completion determination processing in step 104 are performed. When the inspection of the printed wiring board 21 is performed, with respect to the subsequent inspection of the ten printed wiring boards, the process proceeds to step 107, where the resolution of one time the original (the size of one pixel is 7 to 12).
Inspection is performed on the basis of the inspection data according to μm □), and then confirmation processing (Step 108) and real defect registration processing (Step 109) similar to Steps 102 and 103 are performed, respectively. The process proceeds to perform a statistical analysis of the corresponding defect occurrence (step 105). Next, when the determination based on the condition A is made and the condition A is not satisfied, the inspection is performed by returning to the inspection data with the original resolution of 1 time. The subsequent processing procedure is as described above.

As described above, each time the inspection of the 100 printed wiring boards 21 is completed, the inspection of the printed wiring boards 21 is continuously performed through a process in which the inspection data is automatically reviewed and verified. Done.

As described above, according to the present invention, each time the inspection of a printed wiring board having 100 surfaces is completed, a statistical analysis process is performed based on the inspection result, and the resolution at the time of optical inspection is determined with reference to the analysis result. By automatically setting the size per pixel to be set to a value of n times, the inspection time required for recognizing an image based on the obtained inspection data and extracting the inspection result is reduced to 1 / n. There is an effect that the processing speed capability of the pattern inspection apparatus can be improved.

As a measure against quality deterioration due to fluctuations in the manufacturing process of the printed wiring board, the use inspection data is automatically reviewed and verified every time the inspection of 100 printed wiring boards is completed. In accordance with the quality state, the defect detection accuracy is maintained according to the quality of the printed wiring board by performing inspection based on inspection data with different resolutions as appropriate, with emphasis on defect detection accuracy, This has the effect of significantly shortening the inspection time.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of a pattern inspection apparatus according to the present invention.

FIG. 2 is a flowchart of an embodiment of a pattern inspection method according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical inspection apparatus part 2 Confirmation station 3 Image signal processing part 4 Image analysis part 5 Inspection result processing part 6 Camera 7 Lighting 8 Inspection bleed 9 A / D converter 10 Binarization circuit 11 Preprocessing circuit 12 DRC circuit 13 Comparison inspection circuit 14 Image Memory 15 Test Result Output Circuit 16 Test Result Database 17 Statistical Analysis Circuit 18 Resolution Judgment Circuit 19 Test Database 20 Test Data Generation Circuit

Claims (7)

(57) [Claims] An image signal processing means for outputting, as a digital image signal, an optical image of a printed wiring board on which a conductive pattern is formed on an insulating substrate, and a predetermined resolution for converting the digital image signal to a predetermined resolution Image analysis means for performing a quality inspection compared with the reference inspection data and outputting detected defect data when a defect is detected, and whether the defect indicated by the detected defect data is an actual defect which is an actual defect,
A pattern inspection apparatus that determines whether the detected defect is not a real defect but has been output as a defect, and that outputs a defect data by distinguishing between the real defect and the detected defect. The data and the actual defect data are recorded in the inspection result database, and by referring to the detected defect data and the actual defect data in the inspection result database, it is determined whether or not the production quality of the inspection target printed wiring board is stable. In accordance with the determination result, the resolution is corrected, the inspection result processing means for automatically creating and outputting reference inspection data corresponding to the corrected resolution, and updating the reference inspection data, The inspection result processing unit performs the quality inspection corresponding to the corrected resolution based on the updated reference inspection data. Pattern inspection apparatus according to claim. 2. An A / D converter, wherein said image signal processing means converts an image signal of a test target printed wiring board obtained by a predetermined camera into a digital signal and outputs the digital signal, and converts the digital image signal into a binary image. A binarization circuit for converting the image into a signal and outputting the signal, and a preprocessing circuit for performing image correction after adding the correction processing to the binarized image signal, and outputting the image. An image memory for temporarily storing a digital image signal output from the circuit; a digital image signal output from the preprocessing circuit; and the reference inspection data output from the image memory. A comparison / inspection circuit for outputting an inspection result by signal comparison analysis; and a design rule for checking a digital image signal output from the pre-processing circuit for design rules and outputting the result. A check result circuit, wherein the inspection result processing means statistically analyzes the defect data stored in the inspection result database, wherein the inspection result database stores defects and actual defect data output from the confirmation station. A statistical analysis circuit, a resolution determination circuit for determining whether or not the production quality of the printed wiring board to be tested is stable with reference to the analysis result by the statistical analysis circuit, and a print of the test target in the resolution determination circuit. If it is determined that the production quality of the wiring board is stable, the result of the determination is received, and the reference inspection data at a predetermined stage stored in the database of the printed wiring board reference inspection data is searched. Inspection that corrects the resolution set for dynamic image data extraction to a predetermined value and outputs and updates reference inspection data based on the corrected resolution Pattern inspection apparatus according to claim 1, further comprising a chromatography data generating circuit. 3. The pattern inspection apparatus according to claim 1, further comprising means for performing the statistical analysis every 100 inspections. 4. The pattern inspection apparatus according to claim 3, wherein the statistical analysis performs an inspection corresponding to an initial resolution for the first 10 inspection numbers every 100 inspection numbers from the second 100 inspection numbers. 5. A first step of optically generating an image signal of a printed wiring board to be inspected, and a second step of converting the image signal into a digital image signal, correcting and outputting the digital image signal. Analyzing the digital image signal output in the second step, inspecting the digital image signal for defects, and outputting defect data upon detecting an inspection result defect; and A fourth step of checking whether the defect indicated by the defect data is a real defect that is an actual defect or a detected defect that is not a real defect but has been detected as a defect; And a fifth step of registering the number of printed wiring boards. When a predetermined number of printed wiring boards are inspected by the first to fifth steps, the fifth step A sixth step of statistically analyzing the registered defect data to output the defect occurrence rate and the standard deviation of the defect, and whether the actual defect inspection rate and the standard deviation of the defect meet predetermined conditions, respectively. A seventh step of determining whether or not the defect occurrence rate and the standard deviation of the defect conform to predetermined standard values, the inspection is set to the optical image data. An eighth step of correcting the resolution to a resolution corresponding to the standard value, and automatically updating and setting reference inspection data corresponding to the corrected resolution. 6. The pattern inspection method according to claim 5, wherein the predetermined number is 100. 7. The first one for every second 100 inspections
7. The pattern inspection method according to claim 6, wherein the zero inspection includes a step of performing an inspection corresponding to an initial resolution.