JP4829542B2 - Film inspection apparatus and film inspection method - Google Patents

Description

  The present invention relates to a film inspection apparatus and an inspection method for inspecting minute defects that can be formed in a film, particularly fish eye (FE).

  There may be a case where a minute defect called “fish eye” occurs during film production. The fish eye is generated when the film material is not completely melted during production of the film or when impurities are mixed into the material (see Patent Document 1).

  Depending on the intended use of the film, fish eyes may impair the function and appearance of the film. For example, there is a film used as a sheet for dicing a semiconductor wafer. If the film has fish eyes, the semiconductor wafer cannot be placed flat on the film, and dicing of the semiconductor wafer may fail.

  Therefore, it is common to determine the size of fish eyes and the number per unit area that are allowed depending on the intended use of the film. Accordingly, various apparatuses for inspecting fish eyes have been developed and disclosed (see Patent Documents 2 to 6). In these apparatuses, a film is photographed by a line sensor, and data obtained by the line sensor is subjected to image processing, and then fish eyes are detected by binarization or the like.

  An example of the flow of image processing is shown in FIG. When an abnormality is detected from the data of the line sensor, the length of the abnormal part is calculated from the traveling direction of the film. If the length is long, it is a scratch or the like, and is judged as a serious defect. If the length is short, it is determined whether or not it is a fish eye. If it is not fisheye, it is determined as noise. If fisheye, classify by size.

  However, the conventional inspection apparatus may not be able to accurately calculate the size of the fish eye depending on the resolution of the line sensor. For example, if the fish eye is very small, it may not be possible to accurately determine the size of the fish eye even if the presence of the fish eye can be confirmed. In such a case, it cannot be determined whether the fisheye is acceptable. In other words, the n-stage classification having the size of FIG. 15 may be restricted by the resolution of the line sensor.

JP 2001-150429 A Japanese Patent No. 3224623 Japanese Patent No. 3224624 JP-A-8-105842 JP-A-6-82385 Japanese Patent No. 2736521

  An object of the present invention is to provide an inspection apparatus and an inspection method for inspecting fish eyes generated during film production.

  An inspection apparatus of the present invention is an apparatus for inspecting a film defect, and includes a light source that emits light transmitted through the film and a sensor in which a plurality of light receiving units are arranged, and the camera that scans the film with the sensor. And a means for converting a charge signal obtained by scanning with the sensor into a voltage signal and analyzing a defective portion of the film from the voltage signal, and a plurality for separating the size of the defective portion of the film from the voltage signal. And means for comparing the analyzed voltage signal with a plurality of magnitude threshold values to determine which magnitude threshold value the voltage signal matches.

  The means for storing the reference number for classifying the size of the defective part of the film is compared with the reference number and the number of the light receiving parts that have scanned the defective part, and the number of the light receiving parts is equal to or more than the reference number. And means for determining whether or not.

  The reference number is different for each threshold.

  The film is manufactured by heat stretching, and includes means for moving the film in a direction perpendicular or oblique to the drawing direction during heat stretching when light is transmitted through the film.

  Means for differentiating the voltage signal; means for storing a judgment threshold value for determining whether or not the film is a defective portion; and the differentiated voltage signal and judgment threshold value. And determining whether or not the film is defective.

  Means for obtaining the length of the defective portion from the number of times the defective portion of the film is scanned, the scanning interval, and the moving speed of the film, and the type of the defective portion from the length of the defective portion and the waveform of the differentiated voltage signal Means for classifying.

  The inspection method of the present invention is a method for inspecting a defect of a film, the step of transmitting light to the film, the step of receiving light transmitted through the film by a sensor in which a plurality of light receiving parts are arranged, Generating a voltage signal in accordance with the light, analyzing a defective portion from the voltage signal, and determining which of the plurality of magnitude thresholds the analyzed voltage signal matches.

  A step of comparing a reference number with the number of light receiving parts that have received the light transmitted through the defective portion.

  The reference number is different for each size threshold.

  The film is manufactured by heat stretching, and includes a step of moving the film in a direction perpendicular or oblique to a drawing direction at the time of heat stretching when light is transmitted through the film.

  The analyzing step includes differentiating the voltage signal, and comparing the differentiated voltage signal with a determination threshold value to determine whether or not the film is defective.

  Determining the length of the defective portion from the number of times the light transmitted through the defective portion of the film is received, the light receiving interval, and the moving speed of the film, and the failure from the length of the defective portion and the waveform of the differentiated voltage signal Classifying the types of parts.

  According to the present invention, the fish eye of the film is used like a lens, and the presence or absence of the fish eye is detected by the difference between the normal part and the defective part. The size of the fish eye is determined by the difference value. It can also be determined whether or not the fish eye is flowing according to the number of light receiving elements that have received the light transmitted through the fish eye portion.

  Embodiments of a film inspection apparatus and an inspection method according to the present invention will be described with reference to the drawings. The film to be inspected in the present invention is various, including a semiconductor wafer dicing sheet. In addition, although there are various defects (or defects), the present invention particularly inspects fish eyes (FE). In FIG. 1, there are cases where various storage means to be described later are shown as stored contents. Moreover, each waveform after FIG. 2 is an example, and may differ from actual.

  The film inspection apparatus 10 of the present invention shown in FIG. 1 has a light source that emits light to be transmitted through a film and a sensor in which a plurality of light receiving units are arranged, a camera 12 that scans the film with the sensor, and a sensor that scans the film. Analyzing means 14 for converting the obtained charge signal into a voltage signal and analyzing the defective portion of the film from the voltage signal, and a memory for storing a plurality of magnitude threshold values for classifying the size of the defective portion of the film from the voltage signal Means 16 and a comparator 18 for comparing the analyzed voltage signal with a plurality of magnitude thresholds to determine which magnitude threshold the voltage signal matches.

  The film inspection apparatus 10 is controlled by the host computer 11 to operate as a whole. That is, the host computer 11 gives commands to various means.

  The camera 12 is a line sensor camera and is controlled by the camera driving unit 13. For example, a photodiode is used as the light receiving unit, and a CCD (charge coupled device) is used to sequentially extract charges accumulated in the photodiode. The above-described scan is to receive light transmitted through the film by the light receiving unit.

  The analysis means 14 is a means for determining whether or not there is an abnormal signal in the voltage signal. The means is constituted by a circuit, software, or both. The light transmitted through the defective portion becomes a protruding voltage (abnormal signal) as shown in FIG. This is because, for example, the fish eye acts as a lens and is focused on the photodiode. By detecting an abnormal signal, the presence of a defective portion can be obtained.

  The storage means 16 for storing the size threshold is a means for storing data such as a hard disk or memory used in a computer or the like.

  A comparator 18 is provided for each threshold value. By determining which magnitude threshold the analyzed voltage signal matches, the size of the defective portion of the film can be determined. Note that the comparator 18 may binarize the voltage signal and process the voltage signal.

  If it is determined as a defect in the one-scan shape determination, the gate is opened during length measurement, the comparison result is held by the comparator 18 and sent to the correction means 24. The blocks of gate 19a, hold 19b, and size 19c in the figure show the above-described data flow.

  Unlike the prior art, the size can be obtained by a voltage signal, and the size of the defective portion limited by the resolution of the camera 12 can be classified.

  The film inspection apparatus 10 according to the present invention compares the storage means 20 for storing a reference number set in order to classify the size of the defective portion of the film, and the number of the light receiving portions that have scanned the defective portion and the reference number. Means 22 and correction means 24 for determining whether the number of light receiving parts is larger than the reference number by comparison.

  The reference number is the number of light receiving parts that have received the light transmitted through the defective portion. The same voltage signal may be obtained regardless of whether the fish eye is circular or elliptical. This is considered to be because it is proportional to the width of the fisheye scanning direction. In that case, even if the size of the defective portion is different, it is determined that the size is the same. For this reason, a reference number is provided. For example, if the number of photodiodes that have scanned the defective portion is larger than the reference number, the size of the defective portion is increased.

  The storage means 20 for storing the reference number is means for storing data such as a hard disk or memory used in a computer or the like.

  The correcting means 24 is constituted by a circuit, software, or both. As described above, for example, the correction means increases the size of the defective portion if the number of photodiodes that scanned the defective portion is equal to or larger than the reference number. As an example of a method of increasing the size of the defective portion, the size is changed to one size larger than the size obtained by the comparator 18, that is, one size threshold size.

  Even if the fish eye flows in the film drawing direction when the film is manufactured (even if the major axis of the ellipse faces the drawing direction), the fish eye can be classified into an appropriate size.

  The reference number is made different for each size threshold. This is because the number of light receiving parts that receive light transmitted through the fish eye differs depending on the size of the fish eye.

  The present invention includes a film feeding apparatus that moves a film in a direction perpendicular to a drawing direction at the time of heat stretching when the film is manufactured by heat stretching and light is transmitted through the film. By making the moving direction of the film as described above, the major axis of the elliptical fish eye becomes a direction perpendicular to the moving direction of the film. This is because the fish eye flows in the drawing direction of the film when the film is manufactured. Therefore, if the number of photodiodes that have scanned the defective portion is equal to or larger than the reference number, the correcting unit 24 increases the size classification, for example, by increasing the size classification of the defective portion by one rank.

  The analyzing unit 14 includes a differentiating unit 26 for differentiating the voltage signal, a storage unit 28 for storing a determination threshold value for determining whether or not the film is a defective portion, a differentiated voltage signal and a determination threshold value. And determining means 30 for determining whether the film is defective or not.

  Differentiating means 26 is constituted by a circuit, software, or both. By differentiating the voltage signal, the difference between the normal part and the defective part can be changed from an absolute difference to a relative difference. By being a relative difference, it is not necessary to consider the difference in light transmission by the film.

  The storage means 28 for storing the determination threshold is a means for storing data such as a hard disk and a memory used in a computer or the like, like the other storage means.

  The determination means 30 is a means for determining a failure if the abnormal signal in the differentiated voltage signal is larger or smaller than the determination threshold. The determination means is constituted by a circuit, software, or both, like other means.

  The film inspection apparatus 10 includes means 32 for obtaining the length of the defective portion from the number of times the defective portion of the film has been scanned, the scanning time interval, and the moving speed of the film, and the waveform shape of the voltage signal differentiated from the length of the defective portion. And means 34 for classifying the type of defective portion. Further, a means 31 for determining the waveform shape of one scan from the differentiated signal waveform is included.

  The film inspection apparatus 10 has a constant time interval for scanning the film, and can determine the length of the defective portion from the number of scans and the moving speed of the film. The number of light receiving portions per unit length is the resolution in the width direction of the film, but the resolution in the movement direction of the film is determined by the scanning time interval and the moving speed of the film. In the present invention, the determination of the size of the defective portion is not affected by this resolution.

  The defective part is not only a fish eye but also a defect and a scratch with different colors. From the waveform of the differentiated signal, as shown in FIGS. 4 to 7, defects that can be recognized from the signal of one scan can be classified into four. The type of the defective portion can be determined from this classification and the length of the defective portion. Various waveforms are stored in arbitrary storage means of the film inspection apparatus 10.

  Further, if the shape of the defective portion is finally displayed on a computer display or the like, defect image generating means 35 is provided. An encoder is provided, and synchronization signals in the X and Y directions of the film are input to the defect image generating means 35, and defect images are generated in synchronization with the signals. The X direction and the Y direction of the film are the width direction and the traveling direction of the film.

  Furthermore, a means for counting the number of fish eyes detected by each means described above may be provided in the inspection apparatus 10. Whether or not the number of fish eyes is within an allowable range is determined based on the number of fish eyes formed on the film. Means (circuit and / or program) for automatically performing this determination may be provided in the inspection apparatus 10. In addition, a means (circuit and / or program) for counting the number of fish eyes per unit area may be provided in the inspection apparatus 10. Furthermore, the number of fish eyes may be counted for each fish eye size, and means (circuit and / or program) for that purpose may be provided in the inspection apparatus 10.

  Next, a film inspection method using the above-described film inspection apparatus 10 will be described.

  The inspection method includes the following steps (1) to (4). (1) Light is transmitted through the film. (2) Light transmitted through the film is received by a sensor in which a plurality of light receiving portions are arranged. (3) A voltage signal is generated according to the received light, and a defective portion is analyzed from the voltage signal. (4) Find out which of the plurality of magnitude thresholds the analyzed signal matches.

  In step (1), the film is moved. This is because the type of sensor is a line sensor. If the sensor scans the film sequentially, the sensor may move instead of the film.

  If there is a defective part on the film when light is received in the step (2), a part protruding in the voltage signal is generated in the step (3) as shown in FIG. It can be seen that there is a defective portion in the film by this protruding portion.

  The analysis of (3) includes a step of differentiating the voltage signal and a step of comparing the differentiated voltage signal with a determination threshold value to determine whether or not the film is defective.

  As shown in FIG. 3, the voltage difference between the defective portion and the normal portion is changed from an absolute value to a relative value by differentiating the voltage signal. Eliminates the effects of light transmission and other differences due to film differences.

  As shown in FIG. 3, an upper limit value and a lower limit value are set as the determination threshold. In the differentiated voltage signal, if there is a portion that exceeds the upper limit value of the threshold for determination or breaks the lower limit value, it is determined that there is a defective portion on the film.

  Since the defective part of the film is not only fisheye, it is also necessary to classify the type of defect. Therefore, the inspection method includes the steps of obtaining the length of the defective portion from the number of times the light transmitted through the defective portion of the film is received, the received time interval, and the moving speed of the film, and a voltage signal differentiated from the length of the defective portion. And classifying the type of the defective portion from the waveform.

  Since the sensor receives light at regular intervals, the length of the defective portion can be obtained from the number of times the defective portion is received and the moving speed of the film.

  The waveform of the differentiated voltage signal differs depending on the type of defective portion. For example, FIGS. 4 to 7 show the difference in waveform depending on the type of defective portion. FIG. 4 shows that the light transmitted through the defective portion is bright and has a narrow width. If the length of the defective portion is short, it is a fish eye (see FIG. 9A). FIG. 9A shows that the fish 50 has a fish eye 52a. If it is a fish eye, the above step (4) is performed.

  FIG. 5 shows that the light transmitted through the defective portion is dark and narrow, which is a defect due to coloring generated in the film due to impurities mixed during the purification of the film (see FIG. 9B). FIG. 9B shows that the film 50 has a colored defect 52b. Even if it is such a defect, the process may move to the step (4) and the size may be classified.

  If the light transmitted through the defective portion is bright or dark, the width of the defective portion is narrow, and the length of the defective portion is long, it is determined as a streak-like defect 52c as shown in FIG. The value of the size is invalidated even if the process does not proceed to the step (4) or has proceeded. This is because if it is a streak-like defect, it usually occurs several millimeters continuously, and the area may not be calculated.

  In FIG. 6, the light transmitted through the defective portion is bright and wide. In FIG. 7, the light transmitted through the defective portion is dark and wide. If the brightness of the light transmitted through the defective portion is bright or dark, the width of the defective portion is wide, and the length of the defective portion is long, it is determined that the defective portion is considerably large (see FIG. 9D). FIG. 9D shows that the film 50 has a large defect 52d. The value of the size is invalidated even if the process does not proceed to the step (4) or has proceeded.

  As shown in FIGS. 10A and 10B, the size of the defective portion can be determined by determining to which size threshold the signal analyzed in step (4) matches. When the maximum value of the differentiated signal voltage value is not less than the magnitude threshold value n and less than n + 1, it is assumed that it matches the magnitude threshold value n (n is an integer of 1 or more). That is, the size threshold value for obtaining the size of the defective portion is a value having a certain width. In the case of FIG. 10A, since there is a differentiated signal voltage between the magnitude thresholds 1 and 2, the magnitude threshold 1 is matched. The width of the size threshold and the number of size thresholds described above are arbitrary. The width of the size threshold and the number of size thresholds are determined according to the accuracy required for the fish eye inspection.

  It does not occur when the brightness of light is bright or dark, the width of the defective portion is wide, and the length of the defective portion is short. Further, if the waveform is as shown in FIG. 8, it is determined as noise, this signal is ignored, and the subsequent processing is not performed. Although noise can be determined by only one scan, it may be determined from a signal of several scans to increase the accuracy of determining noise.

  In the step (4), a plurality of size threshold values are stored in the storage unit 16. This magnitude threshold has a certain width as described above. As shown in FIGS. 10A and 10B, the magnitude of the defective portion can be easily obtained by obtaining which magnitude threshold range the differentiated voltage signal falls within.

  As described above, the size of the defective portion is determined using the differentiated voltage signal and is not affected by the resolution of the sensor. It is possible to determine the size of the defective portion that could not be determined by the sensor resolution in the past.

  Fish eyes may become elliptical when the film is manufactured by heat stretching. In this case, there is a possibility that the determination of size is erroneous only by the above-described process. As shown in FIGS. 11A and 11B, the voltage signal changes according to the width of the fish eye 52a scanned by the sensor. As shown in FIGS. 12A and 12B, if the fisheye 52a has the same width in the scanning direction of the sensor, the maximum signal voltage is the same regardless of whether it is circular or elliptical. End up. This is presumably because the magnitude of the signal voltage is influenced by the scanning width direction of the fish eye 52a. Therefore, the oval fish eye 52a is determined to be smaller than the actual size. Therefore, the inspection method of the present invention includes, after the step (4), a step of comparing the number of light receiving portions that have received the light transmitted through the defective portion with the reference number. If the number is larger than the reference number, the size is set to the size of one larger threshold. A flow of size classification is simply shown in FIG. FIG. 13 newly shows the n-stage classification of the size of FIG. 15 shown in the prior art. 11 and 12, the circled numbers indicate the light receiving units, the vertical axis indicates the voltage, and the horizontal axis indicates the time, but shows how the respective light receiving units change. .

  Further, when light is transmitted through the film, the film is moved in a direction perpendicular to the drawing direction during heating and stretching. This is because the major axis of the elliptical fish eye is parallel to the light receiving portion of the sensor. By matching the arrangement direction of the long axes and the light receiving parts, the number of light receiving parts that receive light transmitted through the fish eye is larger than that of a circular fish eye if it is elliptical. Therefore, the size of the fish eye can be determined to be one larger by the comparing step described above.

  The reference number is made different for each size threshold. This is because the size of the fish eye is different.

  As described above, the present invention can determine the size of the fish eye without being affected by the resolution of the sensor, and can classify the size even if the fish eye is elliptical.

  Finally, if necessary, an image of the defective portion is generated and displayed on a computer display or the like. A signal obtained by differentiating the signal voltage is input to the image generation means 35 as a defect signal, and an image is generated in synchronization with synchronization signals in the X and Y directions.

  The inspection method of the present invention may include a step of counting the number of fish eyes detected in the above-described steps. This is because the allowable number of fish eyes varies depending on the purpose of use of the film. A step of counting the number of fish eyes per unit area may be included. Furthermore, the above-described count of fish eyes may be performed for each size of fish eyes.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the above-mentioned embodiment. For example, when light is transmitted through the film, the film may be moved in an oblique direction with respect to the drawing direction during heat stretching. By moving the film in an oblique direction, the voltage signals of the circular and elliptical fish eyes become different. Therefore, it is not necessary to perform the step of comparing the number of light receiving parts that have received the light transmitted through the defective part with the reference number. In this case, as shown in FIGS. 14 (a) and 14 (b), since the magnitude of the signal voltage differs between the circular fish eye and the elliptical fish eye, the comparison means and the correction means are not included, and the direct comparison is not performed. Ensure that the size is entered into the host computer.

    In addition, the present invention can be carried out in a mode in which various improvements, modifications, and changes are added based on the knowledge of those skilled in the art without departing from the spirit of the present invention.

It is a block diagram which shows the structure of the test | inspection apparatus of this invention. It is a figure in which the abnormal part has generate | occur | produced in the signal voltage when there exists a defective part in a film. It is the figure which differentiated the signal voltage. It is the figure which differentiated the signal voltage when the light which permeate | transmitted the defective part is bright, and the width | variety of a defective part is narrow. It is the figure which differentiated the signal voltage when the light which permeate | transmitted the defective part is dark, and the width | variety of a defective part is narrow. It is the figure which differentiated the signal voltage when the light which permeate | transmitted the defective part is bright and the width | variety of a defective part is wide. It is the figure which differentiated the signal voltage in case the light which permeate | transmitted the defective part is dark, and the width | variety of a defective part is wide. It is the figure which differentiated the signal voltage when noise generate | occur | produces. It is a figure which shows the defective part of a film, (a) is a figure of a fish eye, (b) is a figure of the defect with which color was attached to the film, (c) is a line-shaped wound of the film It is a figure and (d) is a figure of the big fault made into the film. It is a figure which determines the magnitude | size of a fish eye, (a) is a figure in the case of the size threshold value 1, (b) is a figure in the case of the size threshold value 2. It is a figure which shows that a signal voltage changes with the magnitude | sizes of a fish eye, (a) is a case where three light-receiving parts receive the light which permeate | transmitted the fish eye, (b) is a case where five light-receiving parts are fish eyes. In this case, the light that has passed through is received. It is a figure which shows that a signal voltage becomes the same even if the magnitude | sizes of a fish eye differ, (a) is a circular fish eye, (b) is an elliptical fish eye. It is a figure which shows the flow for determining the magnitude | size of a fish eye. It is a figure at the time of scanning a fish eye diagonally, (a) is a case where five light-receiving parts receive the light which permeate | transmitted fish eye, (b) is the light which seven light-receiving parts permeate | transmitted fish eye Is received. It is a figure which shows the flow of the test | inspection method of the conventional fish eye.

Explanation of symbols

10: inspection device 11: host computer 12: camera 13: camera drive unit 14: analysis means 16: size threshold storage means 18: comparator 20: reference number storage means 22: comparator 24: correction means 26: differentiation means 28: Determination threshold storage means 30: Determination means 32: Length measuring means 34: Defect portion type determination means

Claims (8)

An apparatus for inspecting film defects,
A light source that emits light to be transmitted through the film and a sensor in which a plurality of light receiving units are arranged, and a camera that scans the film with the sensor;
A means for differentiating the voltage signal in order to convert a charge signal obtained by scanning with the sensor into a voltage signal and analyzing the defective portion of the film from the voltage signal. Means for storing a threshold value for determination for determination, and means for analyzing including a means for comparing the differentiated voltage signal with the threshold value for determination and determining whether or not the film is defective ,
Means for storing a plurality of size thresholds for separating the size of the defective portion of the film from the voltage signal;
Means for comparing the analyzed voltage signal with the plurality of magnitude thresholds to determine which magnitude threshold the voltage signal matches;
Means for determining the length of the defective portion from the number of times the defective portion of the film has been scanned, the scan interval, and the moving speed of the film;
Means for classifying the type of the defective portion from the length of the defective portion and the waveform of the differentiated voltage signal;
Including film inspection equipment. Means for storing a reference number for separating the size of the defective portion of the film;
Means for comparing the number of light-receiving portions that have scanned the defective portion with a reference number, and determining whether the number of light-receiving portions is equal to or greater than a reference number;
The film inspection apparatus according to claim 1 comprising: The film inspection apparatus according to claim 2, wherein the reference number is different for each threshold value. The film according to claim 1, wherein the film is manufactured by heat stretching, and includes means for moving the film in a direction perpendicular or oblique to a drawing direction at the time of heat stretching when light is transmitted through the film. Any film inspection device. A method for inspecting film defects,
Transmitting light through the film;
Receiving light transmitted through the film with a sensor in which a plurality of light receiving units are arranged; and
In order to generate a voltage signal according to the received light and analyze the defective portion from the voltage signal , the voltage signal is differentiated, the differentiated voltage signal is compared with a judgment threshold value, and the film is defective. Analyzing the defective portion by determining whether or not
Determining which of the plurality of magnitude thresholds the analyzed voltage signal matches;
Determining the length of the defective part from the number of times the light transmitted through the defective part of the film is received, the light receiving interval, and the moving speed of the film;
Classifying the type of defective part from the length of the defective part and the waveform of the differentiated voltage signal;
A film inspection method including: The film inspection method according to claim 5 , further comprising a step of comparing the number of light receiving parts that have received light transmitted through the defective portion with a reference number. The film inspection method according to claim 6 , wherein the reference number is different for each size threshold. The film is intended that is manufactured by hot drawing, when the transmitting light to the film at the time of heat stretching a film according to claim 5 to 7 comprising the step of moving in a vertical direction or oblique direction with respect to the drawing direction Either film inspection method.

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