JP4230838B2 - Inspection recipe setting method and defect inspection method in defect inspection apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a defect inspection apparatus such as a pattern inspection for detecting a defect (such as a short circuit or disconnection) or a foreign substance in a pattern to be inspected, a foreign substance inspection, and the like. The present invention relates to a technique for supporting the setting of an inspection recipe used in a defect inspection apparatus that performs the above and a technique for classifying detected defects.
[0002]
[Prior art]
As semiconductor product life has been shortened and a shift to a multi-product production system centered on system LSIs has progressed, there is an increasing demand for early establishment of mass production process conditions. In each process of semiconductor manufacturing, inspection equipment is extremely important as a tool for inspecting the appearance, obtaining information about the occurrence of defects, obtaining guidelines for adjusting process conditions, or detecting defects in process conditions . Examples of semiconductor appearance inspection devices that have already been put into practical use include optical foreign matter inspection devices, optical or electron beam type pattern inspection devices, and defect review devices.
[0003]
Hereinafter, a parameter setting procedure in the inspection apparatus will be described. Parameters are roughly classified into parameters for setting image acquisition conditions (hereinafter, image acquisition parameters) and parameters for setting image processing conditions (inspection conditions) (hereinafter, inspection parameters). The image acquisition parameter is a parameter for detecting a proper image. For example, in the case of an optical appearance inspection apparatus, the detection magnification (pixel size), the focal position offset amount, the illumination wavelength and the light amount, and various filter settings This corresponds to the optical conditions such as the conditions and the aperture stop. The inspection parameter is a parameter that needs to be set in order to properly process the detected image. For example, a binarization threshold for binarizing and extracting only a defective portion from a detected image, a noise removal size threshold for removing a small area not related to a defect as noise, and sensitivity at an edge A decrease parameter corresponds to this.
[0004]
Conventionally, this type of inspection apparatus has performed an inspection parameter setting procedure as shown in FIG. This will be described below.
[0005]
First, a wafer to be inspected is prepared and set (S2101). Temporarily, image acquisition parameters are set (S2102), an image of an appropriate place in the pattern to be inspected is captured, and the image quality is confirmed (S2103). For example, if the image is dark, the amount of light is increased. If the contrast of the image is low, optical conditions such as a filter and a diaphragm are changed, or focus adjustment is performed. The above parameter setting and image quality confirmation are repeated until a desired image is obtained. At the obtained stage, image acquisition parameters are registered (S2104). Subsequently, using the temporarily set inspection parameters (S2105), a temporary inspection (trial inspection) is executed (S2106). After performing the inspection, the detected defect position is confirmed (reviewed) (S2107), and the setting state of the inspection parameter is verified (S2108). For example, if more false alarms are detected than expected, increase the binarization threshold if the sensitivity is too high, increase the noise removal size if there are more minute defects than necessary, etc. Can be considered.
[0006]
By repeatedly executing the inspection parameter resetting, trial inspection re-execution, and inspection result reconfirmation described above until the desired detection sensitivity is obtained, the setting of the inspection parameter is completed and the parameter is registered ( S2109).
[0007]
Japanese Laid-Open Patent Publication No. 2001-337047 proposes an optimum recipe creation method that creates a simulated defective wafer for obtaining a desired detection sensitivity and does not depend on the skill level of an operator.
[0008]
Regarding defect classification, Japanese Patent No. 3139998 proposes a method of selecting (sampling) an analysis unit that performs classification from detected defects and performing part of defect detection processing and defect classification in parallel. Yes.
[0009]
[Patent Document 1]
JP 2001-337047 A
[Patent Document 2]
Japanese Patent No. 3139998
[0010]
[Problems to be solved by the invention]
In each of the above prior arts, the procedure of performing inspection every time setting inspection conditions and observing (reviewing) the results must be repeated until a desired image and inspection sensitivity are obtained. Since all the steps other than the inspection need to be performed manually by the operator, there is a problem that a great deal of labor and time are required until the recipe is determined. In the review work, there was a waste of reviewing the same defect (or false information) every time the condition was changed. Further, in the setting work, there is a problem that it is difficult to compare the results of the inspection conditions and it is difficult to select the optimum conditions. In particular, the setting of the threshold value depends on the experience of the operator, and trial and error were required.
[0011]
In addition, the method of selecting (sampling) the defect to be classified in the defect classification has a low capability of the classification analysis processing unit and requires time for classification. Therefore, even if the inspection process and the classification process are performed in parallel, the analysis time Although effective when the inspection time is significantly exceeded, since all defects cannot be classified, there is a problem in that a defect (target defect) that the user originally wants to focus on may occur. In addition, there is a problem that the defect distribution state of the entire wafer cannot be accurately grasped and is estimated.
[0012]
An object of the present invention is to provide a defect detection method and apparatus capable of reducing labor and time in setting an inspection recipe in order to solve the above-described problems.
[0013]
Another object of the present invention is to provide a defect detection method and apparatus capable of detecting defects with high accuracy in accordance with a selected inspection recipe.
[0014]
Another object of the present invention is to provide a defect detection method and apparatus for classifying all detected defects almost simultaneously after the inspection process is completed.
[0015]
[Means for Solving the Problems]
To achieve the above object, the present invention provides an image signal acquisition step of sequentially acquiring image signals for each image acquisition condition by changing a plurality of different image acquisition conditions from a predetermined sample in a defect inspection apparatus, and the image Defect candidates for each image acquisition condition (defects determined by the device, including true defects and false reports (pseudo defects)) are detected from the image signals for each image acquisition condition sequentially acquired in the signal acquisition step. A defect detection step for creating the defect candidate OR file for each image acquisition condition based on the position coordinates on the sample of the defect candidate for each image acquisition condition detected by the defect detection step The same defect candidates are reviewed without duplication based on the OR file of defect candidates for each image acquisition condition created by the OR file creation step. An inspection recipe setting method characterized by having a review step. The above processing targets are all defect candidates. In order to finish classification processing for all defect candidates almost at the same time as inspection processing is completed, consider a configuration such as using a processor with sufficiently high processing capacity for the classification analysis unit or operating multiple processors in parallel. There is a need to.
[0016]
The present invention also provides an image signal acquisition step for sequentially acquiring image signals for each image acquisition condition by changing a plurality of different image acquisition conditions from a predetermined sample in a defect inspection apparatus, and sequentially acquiring the image signal by the image signal acquisition step. A defect detection step for detecting a defect candidate for each image acquisition condition from the image signals for each image acquisition condition, and position coordinates on the sample of the defect candidates for each image acquisition condition detected by the defect detection step OR file creation step for creating an OR file of defect candidates for each image acquisition condition based on the above, and the same defect candidate based on the OR file of defect candidates for each image acquisition condition created by the OR file creation step Are classified into different types (defects (true defects and their types), false reports, unknowns, etc.) for defect candidates for each image acquisition condition without duplication. And a selection step of selecting and setting an image acquisition condition as an inspection recipe in the defect inspection apparatus according to a condition selection criterion based on a classification result for each image acquisition condition classified by the classification step. This is an inspection recipe setting method characterized by this.
[0017]
Further, the present invention is characterized in that the classification step classifies at least a defect (true defect) and a false alarm.
[0018]
In the defect detection step, the present invention may be configured to detect defect candidates for each of the image acquisition conditions from the sequentially acquired image signals for each of the image acquisition conditions based on set inspection conditions. Features.
[0019]
In the classification step, the classification may include a step of performing the classification by analyzing a generation distribution on a sample. Further, the present invention is characterized in that the classification step includes a step of determining whether the classification is fatal or non-fatal. Further, according to the present invention, in the classification step, defects classified as true defects (particularly foreign matter) by the classification are classified into EDX (Energy Dispersive X-ray Spectroscopy) and EPMA (Electron Probe Microanalyzer: And a step of using a result of defect composition analysis such as an electron beam microanalyzer. The present invention further includes a presentation step of presenting a review sampling rate in accordance with the defect category classified in the classification step. Further, the present invention is characterized in that the image signal acquisition step, the defect detection step, and the classification step are repeated a plurality of times under the same image acquisition conditions.
[0020]
The present invention also provides an image signal acquisition step for acquiring an image signal from a predetermined sample in a defect inspection apparatus, and a defect for detecting a defect candidate based on a desired inspection condition from the image signal acquired by the image signal acquisition step. A detection step, a classification step for classifying the defect candidates detected by the defect detection step into different types, and an inspection recipe as an inspection recipe in the defect inspection apparatus based on a condition selection criterion based on the classification result classified by the classification step It is an inspection recipe setting method characterized by including a selection step of selecting or adjusting conditions.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of a defect inspection apparatus (appearance inspection apparatus) according to the present invention will be described with reference to the drawings. In the present embodiment, setting of an inspection recipe including an image acquisition parameter (image acquisition condition: optical condition) and an inspection parameter (inspection condition) of an inspection pattern in the defect inspection apparatus is facilitated.
[0022]
FIG. 1 shows a system configuration example of a defect inspection apparatus (appearance inspection apparatus) to which a method for setting inspection conditions such as an inspection recipe according to the present invention is applied. FIG. 1 is a diagram showing an embodiment of an optical defect inspection apparatus. The optical system 7 includes an objective lens 8, an optical condition changing unit (such as various filters) 9, an optical condition changing unit (such as various filters) 10, a beam splitter 11, and the like. The light emitted from the light source 12 is reflected by the beam splitter 11, passes through the objective lens 8, and illuminates the sample 1 (semiconductor wafer or the like) of the object to be inspected. Illumination light includes lamp light or laser light, and any wavelength such as visible light, UV, DUV, VUV, or EUV may be used. Of the light reflected, diffracted and scattered by the pattern on the wafer 1, the light propagated in the NA (Numerical Aperture) of the objective lens 8 is captured again by the objective lens 8 and forms an optical image on the image plane. The image signal detected by the detector 13 such as TDI is converted into a digital signal by the A / D conversion circuit 15, and after image correction such as shading correction and dark level correction is performed by the preprocessing unit 16, the image memory Temporarily stored in 17A and 17B. The defect detection unit 18 processes the wafer pattern image stored in the image memory 17A and performs defect detection processing (for example, mismatch processing by die comparison, mismatch processing by cell comparison, or mismatch processing by mixing comparison thereof). , Defect information such as defect coordinates and size is extracted. The defect detection process may be based on a determination binarization threshold value for a defect based on die comparison, cell comparison, and mixed comparison of detected images, and a difference between detected images. The defect information is sent to the defect image extraction unit 19 via a dedicated interface or the network 21. On the basis of this defect information, the defect image extraction unit 19 extracts a defect candidate portion image and a reference portion image to be compared from the wafer pattern image in the image memory 17B, and provides a dedicated interface or network 21 to the defect image processing portion 20. Send through. Similarly, the defect candidate information is also sent from the defect detection unit 18 to the defect image processing unit 20 via the network 18 or from the defect image extraction unit 19 via the dedicated interface or the network 21. In the defect image processing unit 20, the defect portion image and the reference portion image are processed to calculate detailed defect feature amounts. Defect candidate feature quantities include defect size (area, length in X, Y-axis direction, etc.), brightness information (shading value information), defect background pattern information (line width, pattern density, brightness, etc.) ) And so on. In the defect image processing unit 20, a defect classification process is performed based on the acquired feature amount. In order to perform feature amount calculation and classification processing for all defect candidates within the inspection time, a processor with sufficiently high processing capability is used for the defect image processing unit 20 as described above, or a plurality of processors are operated in parallel. , Etc. need to be considered. FIG. 2 shows an embodiment in which N processors are arranged in parallel as the defect image processing unit 20, and the defect image processing unit 1 (201) and the processing unit 2 are sequentially connected from the defect image processing unit 19 via the dedicated interface or the network 21. (202)... Necessary data is sent to the processing unit N (20N), processing is executed in parallel by each processing unit, and the processing result is transferred via the network 21.
[0023]
On the other hand, when selecting (sampling) the target for feature value calculation and classification processing from all defect candidates, the processor capacity can be reduced and the number of parallel units can be reduced, which simplifies the unit configuration. There is an effect of cost reduction. On the other hand, when the configuration of the defect image processing unit 20 is limited, it is necessary to set the sampling rate so that the number of objects to be processed matches the capability.
[0024]
The defect candidate part image obtained from the defect image processing unit 20 and the defect information such as the coordinates, the feature amount, and the classification process result are transferred to the inspection information management unit 23 via the network 21. The data is stored and saved in the storage device 24 and transferred to the operation control unit 26 at the same time. The operation control unit 26 processes the input defect information, and points the defect position on the wafer map displayed on the display 27 or displays a defect image or the like. The θ stage 5, the Z stage 4, the Y stage 3, and the X stage 2 on which the sample 1 is mounted are controlled by the mechanism control unit 22. In addition to the above, the mechanism control unit 22 controls the optical system 7 such as the light amount control of the light source 12 (for example, using an ND filter), the wafer height measuring device 6, various filters (spatial filter, wavelength filter, diaphragm, etc.) Also do. By controlling the Z stage 4 and moving the sample 1 in the height direction based on the signal from the height measuring device 6, an image with a predetermined focus can be acquired with respect to the pattern on the sample 1 such as a wafer. .
[0025]
The operation control unit 26 includes a user interface for instructing control of the pattern inspection system. The user uses an input device 25 such as a keyboard, a mouse, a joystick, etc., and an inspection parameter setting screen for setting an image processing condition (inspection condition) or a parameter (optical) for setting an image acquisition condition (optical condition). Condition) Basic data such as the type and process of the wafer to be inspected, optical conditions, image processing parameters, and inspection area are set via the setting screen. As an inspection parameter (inspection condition), for example, a determination binarization threshold for binarizing and extracting only a defective portion from a detected (acquired) image as shown in FIGS. Equivalent to a noise removal size threshold that removes a small area not related to the defect as noise, a sensitivity reduction parameter at the edge, and a threshold that discriminates a defect or false alarm based on the feature amount of the defect To do. The image acquisition parameter (optical condition) is a parameter for acquiring an appropriate image. For example, if it is an optical appearance inspection device (defect inspection device) as shown in FIGS. This corresponds to the magnification (pixel size), the offset amount of the focal position, the illumination wavelength and light amount, the setting conditions of various filters, and the optical conditions such as the aperture stop. In the case of the SEM type as the appearance inspection apparatus, the acceleration conditions, the beam current, the beam spot, the scanning speed, etc. are related as the optical conditions.
[0026]
Further, the distribution identification unit 28 uses the defect coordinate information (chip address and in-chip defect coordinate) and classification information (category information) detected, transferred to the information management unit 23 and stored in the storage device 24, and the wafer is recorded. Analyzes the distribution status of individual defects or all defects in the die, and determines whether the distribution of the analyzed individual defect categories or the distribution of all defects is similar to a known pattern By doing so, it becomes possible to specify the defect cause process and the apparatus. For example, the distribution identification unit 28 can estimate that defects have occurred in the CMP process when defects (scratches) are distributed on an arc.
[0027]
Further, the layout conversion calculation unit 29 acquires the circuit layout data of the sample 1 from the layout CAD 30 via the network 21, and generates the pattern layout in the chip from the acquired circuit layout data of the sample. The chip pattern information (pattern density, line width, etc.) at the defect detection position stored in 24 can be obtained, and the defect is a fatal defect (disconnection or short circuit), or a non-fatal defect (disconnection or short circuit is not directly related). It is possible to determine whether or not the defect has occurred. In some cases, it is possible to specify the cause of the defect. At this time, the layout data to be referred to is mainly the layer, but there may be a case where a plurality of layer information of the previous process is required. For example, since the defect occurrence cause identification is usually targeted for the layer, the layer in which the defect exists is examined, only the layer that is the relevant layer is extracted, and the defect that has occurred in the previous process layer is removed. Or the usage of setting as a defect not to be analyzed can be considered.
[0028]
Further, a composition analyzer (EDX such as a mass spectrometer or a spectroscopic analyzer) 31 acquires defect composition information of each defect and analyzes it along with the defect classification information of the inspection apparatus obtained from the storage device 24. Therefore, the cause of the defect can be identified more accurately. For example, by analyzing the composition of the generated foreign matter, it may be possible to determine which material is used in which process, or whether a gas component is contained, or in which part of which apparatus it is generated.
[0029]
In the above description, the defect classification processing is performed by the defect image processing unit 20, and the process of causing the defect and the specific analysis of the device are performed by the distribution identification unit 28, the layout conversion calculation unit 29, and the composition analysis device 31. However, any processing may be performed by the information management unit 23 or the operation control unit 26.
[0030]
Although one embodiment of the system configuration has been described with reference to FIG. 1, the present invention is of course not limited thereto. As shown in FIG. 20, the optical system 7 (7A, 7B), the illumination light source 12 (12A, 12B), and the detection A method of switching a plurality of devices 13 (13A, 13B) and using them is also conceivable. As the illumination light source 12, for example, a UV or DUV light source and a white light source (broadband) are switched so as to switch the wavelength of light, and the magnification is high in order to detect a fine defect of several tens of nm in the case of a white light source. Need to scale. Thus, when the wavelength of the light source is different, it is necessary to switch the detector 13 to a detector suitable for a different wavelength of light.
[0031]
The detector 13A and the detector 13B can also acquire images from different illumination light sources 12A and 12B without switching the detector by combining the beam splitter 11C and the lens 14.
[0032]
Further, as shown in FIG. 21, based on the wafer pattern image detected by the optical system 7 and stored in the image memory 17, the defect detection unit 18 performs defect candidate detection processing, and the defect candidate coordinates, size, etc. If the defect candidate information and the reference part image are extracted and sent to the defect image processing unit 20 at the same time, a plurality of image memories 17 are not required, and the defect image extraction unit 19 is also unnecessary. .
[0033]
Next, an embodiment of an inspection recipe automatic generation method in the appearance inspection apparatus as shown in FIG. 1 will be described with reference to FIGS. As described above, the appearance inspection apparatus performs high-sensitivity and high-speed inspection so that a defect of about 50 nm or less can be detected as the pattern to be inspected is miniaturized (0.1 μm or less, further 80 nm or less). It has been requested to do. On the other hand, when trying to perform a high-sensitivity inspection, a lot of flaws and unknown defects are naturally detected, which increases the possibility of misjudging that the pattern to be inspected is defective. become.
[0034]
In the case of semiconductor wafers and the like, they are manufactured through a number of manufacturing processes, so that in the process where fatal defects greatly affect the operating characteristics of semiconductor elements, priority is given to sensitivity so that defective products are not manufactured. In a process where fatal defects do not significantly affect the operating characteristics of semiconductor elements, defective products are manufactured even though non-defective products are manufactured with priority given to reducing false alarms and unknown errors. It is required to prevent wrong judgment that the product is manufactured, and to make sensitivity and wrong answer intermediate in the intermediate process. In any case, it is necessary to optimally set optical conditions (image acquisition parameters) and inspection conditions (inspection parameters) in accordance with the types such as the density and line width of the pattern to be inspected and the manufacturing process steps.
[0035]
Therefore, an inspection recipe in the appearance inspection apparatus described below is set for each type of pattern to be inspected, line width, and the like, and for each manufacturing process step.
[0036]
Therefore, FIG. 3 is used for the first embodiment of the processing flow for selecting and setting the optical condition based on the optical condition setting standard, which is performed by the operation control unit 26 using the input device 25 before the actual inspection. I will explain.
[0037]
First, the operation control unit 26 displays the screen shown in FIG. 5 on the display 27, sets and registers N (plurality) optical conditions using the input device 25, and stores them in the storage device 24 (S301). In FIG. The case of 3 is shown. Optical conditions to be set include the type of the detector 13 (camera), the pixel size (which depends on the detection magnification), the wavelength filter, the spatial filter, the ND filter, the aperture, the type of light source (lamp), and the focus offset. There is quantity. Of course, if the SEM method is adopted, the optical conditions to be set also change.
[0038]
Next, the set optical conditions are sequentially changed, and the defect determination binarization threshold value in the defect detection unit 18, the noise removal filter size in the preprocessing unit 16 and the sensitivity reduction parameter at the edge, and the defect image processing unit 20 Inspection parameters (inspection conditions) such as determination threshold values for determining defects and false reports based on the feature values are set (S302), and inspection processing is performed by the defect detection unit 18 (S303). It is determined whether or not the number of processes has reached N (S304). If the number is not satisfied, the number is incremented (S305), and the inspection process is further continued under the next condition (optical condition / inspection parameter). When the number of processes reaches N, a defect OR file is created (S306). Details of the OR file will be described later. Using this defect OR file, the defect image extraction unit 19 calculates the feature amount of the defect candidate from the defect candidate part image / reference part image for all defect candidates without duplication, and the defect image processing unit 20 In step S307, it is determined whether it is a defect or a false report based on the feature amount. The types of feature values used for classification are the defect candidate area calculated from the image, the defect candidate size such as the X and Y projection lengths, the brightness of the defect candidate area, the density difference between the defect candidate area image and the reference area image, There is a pattern density of the background of the defect. In the defect image processing unit 20, the determination of the defect and the false information is automatically performed using a rule set in advance by using these feature amounts or a determination rule generated from a database in which the defect and the false information are collected. Condition selection is performed based on the classification result and a preset condition selection criterion (S308). The condition selection criterion mentioned here can be considered variously, for example, a condition in which the largest number of defects are detected, that is, a condition with high sensitivity, or a condition in which defects may be overlooked to some extent and false information is minimized. That is, as the condition selection criteria, there are at least a criterion (mode) that prioritizes sensitivity and a criterion (mode) that minimizes false alarms. Furthermore, you may have the reference | standard (mode) of these. By executing the above method, it is possible to automatically select a condition that can obtain a desired result most desired by the production manager.
[0039]
FIG. 4A shows an example showing the relationship of the defect OR file. The defect OR file determines whether or not defect candidates detected under different conditions are the same from defect coordinates, size, etc., for a plurality of (N times; three times in FIG. 4) defect detection results. It is a file representing all defect candidates without duplication detected by the inspection process. In the example shown in FIG. 4, 130 (401), 52 (402), and 100 (403) defects are detected in three inspection results with different optical conditions. As described above, there are some defects (true defects) detected in duplicate. Therefore, the operation control unit 26 can display all defect candidates without duplication on the display 27 based on the defect OR file and perform a batch review. As a result of the defect / false report determination in the subsequent review, the number of defects (α) in each inspection is 100 (404), 50 (405), 90 (as shown in FIG. 4B). 406), and the total number of defects excluding duplication is 120 (407) in total. Assuming that this total number is all defects on the sample 1, out of 120 total defects in the optical condition 1, the least missed (β) is the smallest, and 100 can be detected and sensitivity is maximized. As a result of increasing the sensitivity in this way, the number of false reports (γ) increases to 30 and the number of erroneous answers (β + γ) becomes 50 (408). Under optical condition 2, 70 out of 120 defects are the most common miss (β), and only 50 can be detected, and the sensitivity is minimized. As a result of reducing the sensitivity in this way, only two false reports (γ) are detected, and the number of wrong answers (β + γ) is almost missed to be 72 (409). In optical condition 3, out of 120 defects, the number of missed misses (β) is small, and 90 defects can be detected, and the sensitivity is medium. As a result of the medium sensitivity, the number of false reports (γ) is detected as 10 and the number of incorrect answers (β + γ) is 40 including oversight (410).
[0040]
If the optical condition 1 is used as a reference (missing is set to 0) as the number of erroneous answers, the inspection condition 1 can be 30, the inspection condition 2 can be 52, and the inspection condition 3 can be 20.
[0041]
If the criterion for selecting the optical condition is set in advance, for example, with the maximum sensitivity “maximum number of detected actual defects”, the optical condition 1 having the smallest number of misses and the largest number of defects and the largest number of false alarms is the sensitivity. If “minimum number of false alarms” is set to the minimum, the optical condition 2 with the smallest number of false alarms is set to medium sensitivity, and if “minimum number of false answers” is set, the number of false alarms is medium. Also, the intermediate optical condition 3 is selected. For this pattern to be inspected, which should not overlook ultra-fine defects, optical condition 1 is selected, and some patterns to be inspected that allow some oversight of ultra-fine defects but dislike false alarms (false detections) For the above, the optical condition 2 is selected, and the optical condition 3 is selected for the pattern to be inspected located in the middle.
[0042]
An example of a reference setting screen for selecting conditions is shown in FIG. In this example, the “minimum sensitivity” check (radio) button (412) is selected for the displayed setting standard list (411).
[0043]
FIG. 5 shows an example of the optical condition setting screen.
[0044]
First, the number of the optical condition to be set is input in the box (501). As shown in FIG. 20, when the apparatus has a plurality of imaging means (detectors 13A and 13B), the type of camera used under the conditions is selected using a pull-down menu (502). Subsequently, if there is a pixel size (503) to be used and a filter, selection of those (504, 505, 506), selection of an aperture (507), selection of illumination type (508), and optimum focus for inspection A focus offset amount or the like for setting the position is selected (509). If it is OK, an “OK” button is pressed (510), and the setting data is saved. When not saving, the “Cancel” button is pressed (511). The above procedure is performed for each set condition, and a plurality of optical conditions are set. For example, a method of automatically selecting an ND filter for adjusting the amount of illumination light so as to obtain a desired brightness according to the brightness of an acquired image can be considered even if the optical conditions are not manually selected. .
[0045]
FIG. 6 shows an example of a confirmation screen for optical condition selection. As a result of the processing of FIG. 3, a list of optical conditions finally automatically selected is displayed (601). If the setting is acceptable after confirmation, pressing the “OK” button (602) will confirm the setting. If the setting is not selected, a “cancel” button is pressed (603). When the “standard” button is pressed (604), data registered as default in the apparatus is set. When the user wants to redo the setting, the user presses the “reset” button (605), returns to the process of FIG. 5, and repeats the flow of FIG.
[0046]
Next, a procedure for setting an inspection recipe including the optical conditions and the inspection conditions by setting the inspection parameters (inspection conditions) used for inspection after selecting and setting the optical conditions as described above will be described with reference to FIG. . First, initial values of inspection parameters are set (S701). As the initial value, for example, a high sensitivity is set so that a false alarm is included as much as possible as a test result as indicated by a test threshold value 803 in FIG. An inspection is executed using the inspection parameters (S702), and the detected defect is classified as a true defect or a false information (S703). This classification may be performed manually by visually displaying a defect image on the display 27 and the like, or by using an automatic defect classification function for automatically classifying according to a determination rule using the above-described feature amount in the defect image processing unit 20. You may use and set automatically. Using this classification result, automatic parameter adjustment is performed by a method described later (S704). When confirming whether the setting result is appropriate, by performing the inspection process (test inspection) again using the obtained parameters (S705), by visually reviewing the detected defect and confirming the defect / false information (S706) An inspection recipe is set (S707). If the initial value setting (S701) is set to a fixed value or automatic setting, defect / false report classification (S703) is automatically performed, and a visual review (S706) is not performed, a series of settings can be automated.
[0047]
An example of automatic parameter adjustment is shown in FIG. FIG. 8A is an example of a graph used when the determination binarization threshold value is set in the defect detection unit 18. The threshold value is plotted on the horizontal axis, and the number of defects detected by the threshold value is plotted on the vertical axis, and plotted based on the classification result, which are divided into defects (801) and false reports (802). In other words, the number of defects detected at each threshold is the sum of the number of defects and the number of false reports. The operation control unit 26 can create this graph by leaving information such as the maximum value of the density difference of the defect inspection from the defect image extraction unit 19 at the time of inspection. For example, the lower the threshold value for the difference image between the defect portion image and the reference portion image, the greater the number of detections for both defects and false alarms. Maximum number of detections. The threshold value is selected based on a criterion set in advance using a setting screen as shown in FIG. In other words, if you do not want to detect false alarms, you can use a high threshold A (804) with reduced sensitivity. If you want to detect the maximum number of defects (there are as few false alarms as possible), you can increase the sensitivity to a low threshold. When it is desired to set the value C (806) to the intermediate value (number of defects + number of false reports), an intermediate threshold value B (805) is selected.
[0048]
Furthermore, a method of setting a plurality of parameters at the same time is also conceivable. FIG. 8B shows an example of a graph used when setting a threshold value for discriminating between defects and false reports in the defect image processing unit 20. The graph is plotted for each detected defect, with the horizontal axis representing the maximum density difference of the defect and the vertical axis representing the defect area. It is difficult to draw the boundary line (threshold value) between the defect and the false alarm by using the maximum density difference or the area alone as in the threshold line (807, 808) shown in FIG. It is possible to draw a boundary line (809) that does not include a boundary line or a boundary line (810) that detects a defect maximum. Alternatively, there is a possibility that a quadratic curve (811) that separates defects and false information may be drawn. This can be realized by taking the parameters that make the boundary well drawn on the vertical and horizontal axes.
[0049]
FIG. 9 shows an example of a confirmation screen for selecting inspection conditions. As a result of the processing of FIG. 7, a list of inspection conditions that are finally automatically selected is displayed (901). If the setting is acceptable after confirmation, pressing the “OK” button (902) will confirm the setting. If the setting is not selected, a “cancel” button is pressed (903). When the “standard” button is pressed (904), data registered as default in the apparatus is set. When it is desired to redo the setting, when the “reset” button is pressed (905), the process returns to the setting process of FIG. 4C, and the flow of FIG. 7 is repeated again. Alternatively, a numerical value may be directly input into the input box (906).
[0050]
As described above, the inspection condition setting method based on the two classifications of defect and false alarm has been described. However, the setting in the case where the number of classifications is further increased may be considered.
[0051]
Next, FIG. 10 shows a second embodiment of a processing flow for selecting and setting the optical conditions based on the optical condition setting criteria performed by the operation control unit 26 using the input device 25 before the actual inspection. It explains using. The basic process of the second embodiment is the same as that of the first embodiment shown in FIG. 3, but the defect classification process (S307 ′) is different. Perform classification. Hereinafter, a condition setting method when the operation control unit 26 performs fine classification will be described.
[0052]
FIG. 11 shows an example of a detection result in this method in the operation control unit 26. The number of detected defects for each category is displayed for a plurality of optical conditions (1101) set in advance by the same method as described above. In addition to the classification of defect and false information, here, defect 1 (for example, foreign object defect), defect 2 (for example, short defect), defect 3 (for example, scratch defect), and unknown classification are performed (1102). A specific defect name may be displayed in this column. The ON / OFF description shown below the defect indicates whether the defect distribution map (1201) on the wafer as shown in FIG. 12 is to be scored, that is, whether the defect is necessary for the user. Further, the right column also shows the total value (1103) of the number of defects displayed ON and the total value (1104) of the OFF defects. An optical condition selection criterion is set in advance, and an optical condition that meets the criterion is selected. For example, if the total number of required defects, that is, the condition with the largest ON total is set as the reference, the optical condition 2 with the maximum ON total (highest sensitivity to defects 1, 2, and 3) is OFF. If the total minimum condition is set (minimum of false reports and unknowns that are erroneously determined as defective products), the optical condition 5 or the specific defect 2 (for example, the category of short defects that are fatal defects) is the most. In the case where a condition for detecting many (a reference for giving priority to a specific category) is set, the optical condition 1 is selected.
[0053]
FIG. 13 shows an example of a list of defect classification conditions set for the operation control unit 26. For each defect category, the defect name (1301), ON / OFF setting of the result display (1302), etc. are performed in advance. The result display ON / OFF setting is used to determine whether or not to make a dot on the wafer map as described above, or to change the shape and color of the dot on the wafer map (1401) as shown in FIG. In FIG. 14, the inspection condition (1402) including the inspection recipe, the inspection state (1403), and the display condition (1404) on the wafer map are also displayed. The result display ON / OFF setting may be performed on this display condition (1404). On this display screen, further, the ID number (1405) of the inspected apparatus, the status (1406) of the display screen, the lot number (1407) of the wafer to be inspected, and the wafer processing time or inspection time information (1408) Is also displayed. Since classification processing is performed for all detected defects, it is not necessary to estimate defects with no classification, and it is possible to accurately grasp the distribution status of defects.
[0054]
FIG. 15 shows an example of a display screen on the display 27 of the defect classification result classified by the operation control unit 26 or the like.
[0055]
In this embodiment, defect images (1501 to 1503) classified by category are classified into defect type (foreign matter 1504, isolated defect 1505, short-circuit defect (pattern short) 1506) that is a fatal defect and the number of detections ( 1507 to 1509) and the total number of detected defects (1510). Further, the ID number (1511) of the inspection apparatus that inspected the defect, the status (1512) of the display screen, the lot number (1513) of the wafer to be inspected, and the wafer processing time or inspection time information (1514) are also displayed.
[0056]
Next, another embodiment for identifying a defect and a false alarm resulting from the apparatus will be described using the processing flows shown in FIGS. In the method of this embodiment, the detected defect candidate is an actual defect by performing inspection multiple times under the same conditions and determining whether the defect detection is reproducible, that is, how many times it is detected. It is to judge whether it is false information. If it is a true defect, it should be detected every time or multiple times, and conversely, for example, in the case of a false alarm caused by a malfunction during imaging such as illumination fluctuation or stage running failure, the imaging conditions are the same each time. If there is no deficiency, it will not be detected many times.
[0057]
For example, in the operation control unit 26, as shown in FIG. 16, first, one optical condition is set (S1701). At this time, the number of inspections (N) and the number of times (M) for determining how many times of those detected are regarded as defects are set simultaneously. An inspection process is executed (S1702), and it is determined whether the number of processes has reached N (S1703). If not, the number is incremented (S1704), and the inspection process is further continued under the same conditions. When the number of processes reaches N, a defective OR file is created as described above (S306). A defect candidate is checked how many times the candidate has been detected in N inspections (S1706). If it exceeds M times, it is determined as a true defect (S1707), and if it does not exceed it, it is determined as a false report (S1708). ). It is checked whether all the defect candidates have been completed (S1709), and the defect candidates (S1710) are sequentially judged until the completion.
[0058]
It is conceivable that the cause of erroneous detection is an optically erroneous detection such as lens aberration. In particular, aberrations tend to occur around the lens, and false information tends to be generated. In such a case, the optical conditions can be changed by shifting the position of the visual field. FIG. 17 shows a processing flow. The difference from the flow of FIG. 16 is that inspection is performed (S1802), the visual field position is changed at the time of re-examination, an image is retaken (S1803), and a plurality of inspections (S1804) are performed. According to the result, as in FIG. 16, it is determined whether it is a defect or a false alarm (S1706). In addition to this, the visual field position is moved to a position with the best optical conditions (for example, the visual field center) and re-inspected. If the defect is still detected, it is determined as a defect, and if it is not detected, it is determined as a false alarm. Is. Further, for example, the visual field position when the defect detection unit 18 detects the defect candidate is stored in, for example, the storage device 24, and the mechanism control unit 22 moves the stages 2 and 3 only for the defect candidate detected around the visual field ( A method is also conceivable in which the optical system 7 and the detector 13 are used again to re-examine and re-inspect the image at the center of the field of view by controlling the traveling). As described above, the optical condition as the inspection recipe that is selected and set includes a detection position in the field of view related to the lens aberration.
[0059]
Next, a method for removing the influence of brightness unevenness (color unevenness) due to thin film interference or the like will be described. This method is also basically the same as the above-described method, and the flow is shown in FIG. When inspection is performed with short wavelength illumination (S1901) such as UV and DUV (S1902), the sensitivity of these wavelengths is high, but false alarms due to thin film interference are likely to occur. In order to confirm whether or not the defect is truly a defect, the inspection is executed several times (S1904) by using a different illumination system such as white broadband illumination this time (S1903). Although white illumination is not easily affected by brightness unevenness, defect detection sensitivity seems to be lower than that for short wavelength illumination, so it is necessary to devise high sensitivity detection such as setting a high magnification. The same applies if the optical system is changed instead of changing the illumination system. As described above, the optical conditions as the inspection recipe selected and set include the illumination wavelength and the imaging magnification.
[0060]
As described above, by repeating the inspection several times, not only when an inspection recipe consisting of optical conditions and inspection conditions is obtained, but also the accuracy of defect detection is improved at the time of actual inspection, and at the same time Reliability can be improved.
[0061]
Next, an inspection flow when automatic defect classification is performed after an inspection recipe is set as described above in an inspection apparatus such as an appearance inspection apparatus will be described with reference to FIG. First, an inspection recipe including optical conditions and inspection parameters (inspection conditions) for performing inspection is set for the inspection apparatus body (S1601). Classification conditions are set for the automatic defect classification (ADC) unit (S1602).
[0062]
The inspection apparatus main body inspects the inspection target similar to the sample for which the inspection recipe is set (S1603). For example, when a defect is detected by the defect image extraction unit 19 (S1604), the inspection result is obtained. The obtained defect data (1620) such as defect part coordinates, defect area, and defect size is transferred to the ADC unit. For example, in the case of the defect image processing unit 20 and the comparison inspection, the defect image processing unit 20 acquires the image of the reference unit to be compared (with an appropriate size) (S1605) and transfers it to the ADC unit (S1606). ). The ADC unit calculates feature amounts based on the transferred defect data and image (1621), automatically classifies defects based on the result and preset classification conditions (S1606), and inspects the classification results. The data is transferred to the apparatus main body (1622). This procedure is repeated until the inspection is completed. When the inspection is completed (S1607, S1608), for example, the distribution identification unit 28 identifies the distribution of defects based on the coordinates of all the obtained defects or for each defect category. (S1609). This process may be performed by the inspection apparatus main body or the ADC unit. The results obtained by the above processing are displayed on the display screen of the inspection apparatus main body or the ADC unit as shown in FIGS. 12, 14, and 15 (S1610).
[0063]
In the above, the case where the present invention is applied to an optical semiconductor pattern inspection apparatus has been described. However, the present invention is not limited to this, and a combination of a foreign substance inspection apparatus and an electronic pattern inspection apparatus, or other liquid crystal display inspection The present invention can be applied to setting conditions of various inspection apparatuses such as an apparatus and a photomask inspection apparatus.
[0064]
【The invention's effect】
According to the present invention, it is possible to support an operator's condition setting work at the time of setting an inspection recipe, and it is possible to reduce setting labor and time.
Further, according to the present invention, defect classification is performed for all defects, so that classification omission does not occur and the defect distribution can be accurately grasped.
In addition, according to the present invention, an effect of improving the operating rate by reducing the occupation time required for setting the conditions of the apparatus can be expected.
[0065]
Similarly, according to the present invention, since classification of all defects is completed almost simultaneously with the completion of the inspection, an effect of improving the operation rate by reducing the defect classification time can be expected.
Further, according to the present invention, the reliability of the detected defect can be improved.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of a system configuration of a defect inspection apparatus (appearance inspection apparatus) according to the present invention.
FIG. 2 is a diagram showing an embodiment of a part of a system configuration of a defect inspection apparatus (appearance inspection apparatus) according to the present invention.
FIG. 3 is a diagram showing an example of a flow of setting an image acquisition parameter (image acquisition condition: optical condition) as an inspection recipe according to the present invention.
4A and 4B are diagrams showing an example of a defect detection result for each optical condition according to the present invention, FIG. 4A is a diagram showing a relationship of a defect OR file, and FIG. 4B is a breakdown of defects for each optical condition. (C) is a figure which shows the reference | standard setting screen of optical condition selection.
FIG. 5 is a diagram showing an example of an optical condition setting screen according to the present invention.
FIG. 6 is a diagram showing an example of an optical condition selection result confirmation screen according to the present invention.
FIG. 7 is a diagram showing an example of a flow for setting an inspection parameter (inspection condition) as an inspection recipe according to the present invention.
FIG. 8 is a diagram showing an example of setting criteria for inspection parameters (for example, determination threshold values, determination threshold values for feature amounts) according to the present invention.
FIG. 9 is a diagram showing an embodiment of a setting result display screen for inspection parameters (for example, determination threshold value) according to the present invention.
FIG. 10 is a diagram showing another embodiment of a setting flow of an image acquisition parameter as an inspection recipe according to the present invention.
FIG. 11 is a diagram showing another example of the defect detection result for each optical condition according to the present invention.
FIG. 12 is a diagram showing an example of a defect classification result display screen according to the present invention.
FIG. 13 is a diagram showing an example of defect classification conditions according to the present invention.
FIG. 14 is a diagram showing an example of a defect classification result display screen according to the present invention.
FIG. 15 is a diagram showing an example of a defect classification result display screen according to the present invention.
FIG. 16 is a diagram showing an example of a processing flow in the case of executing defect determination according to the present invention.
FIG. 17 is a diagram showing an example of a processing flow in the case of executing defect determination according to the present invention.
FIG. 18 is a diagram showing an example of a processing flow when executing defect determination according to the present invention.
FIG. 19 is a diagram showing an example of a processing flow when executing defect classification according to the present invention.
FIG. 20 is a diagram showing another embodiment of the system configuration of the defect inspection apparatus (appearance inspection apparatus) according to the present invention.
FIG. 21 is a diagram showing still another embodiment of the system configuration of the defect inspection apparatus (visual inspection apparatus) according to the present invention.
FIG. 22 is a flowchart showing a conventional inspection condition setting method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Sample (object to be inspected), 2 ... X stage, 3 ... Y stage, 4 ... Z stage, 5 ... θ stage, 6 ... Height measuring instrument, 7, 7A, 7B ... Optical system, 8 ... Objective lens , 9: Optical condition changing unit (various filters, etc.), 10: Optical condition changing unit (various filters, etc.), 11 ... Beam splitter, 12, 12A, 12B ... Light source, 13, 13A, 13B ... Detector, 14 ... Lens , 15, 15A, 15B ... A / D conversion circuit, 16 ... pre-processing unit, 17, 17A, 17B ... image memory, 18 ... defect detection unit, 19 ... defect image extraction unit, 20 ... defect image processing unit, 21 ... Network, 22 ... Mechanism control unit, 23 ... Information management unit, 24 ... Storage device, 25 ... Input device (keyboard, mouse, joystick, etc.), 26 ... Operation control unit, 27 ... Display, 28 ... Distribution identification unit, 29 Layout conversion calculation unit, 30 ... layout CAD, 31 ... defect composition analysis device (EDX).

Claims (7)

An image signal acquisition step of acquiring an image signal of sequential said picture image for each acquisition condition by changing the plurality of different image acquisition condition from a given sample in the defect inspection apparatus,
A defect detecting step of detecting a defect candidate of the image signal acquisition step by each desired the image acquisition condition based on inspection condition set from the image signal of each sequentially acquired the image acquisition condition from the predetermined sample,
Represents the non-overlapping defect candidate defect candidates detected for each detected images acquired conditions by the defect detection step is detected over a plurality of image acquisition condition to determine whether the same on the sample OR file creation step for creating an OR file;
Non- overlapping defect candidates detected over the plurality of image acquisition conditions using an OR file representing non-overlapping defect candidates detected over the plurality of image acquisition conditions created by the OR file creation step A classification step for classifying at least flaws and false alarms,
An inspection recipe in the defect inspection apparatus according to a condition selection criterion having a criterion that prioritizes at least sensitivity, a criterion that minimizes false alarms, and an intermediate criterion based on the classification result for each image acquisition condition classified in the classification step And a selection step of selecting and setting an image acquisition condition or an inspection condition as an inspection recipe setting method in a defect inspection apparatus. 2. The defect according to claim 1, wherein in the classification step, the classification of at least the defect and the false report is performed based on a review with respect to a non-overlapping defect candidate detected over the plurality of image acquisition conditions. Inspection recipe setting method in inspection apparatus . In the classification step, the classification of at least the defect and the false information about the defect candidate without duplication detected over the plurality of image acquisition conditions is automatically performed based on the feature amount of the defect candidate for each image acquisition condition. The inspection recipe setting method in the defect inspection apparatus according to claim 1, wherein the inspection recipe setting method is performed automatically . 4. The classification according to claim 1, wherein in the classification step, the classification of the defect with respect to the non-overlapping defect candidate detected over the plurality of image acquisition conditions includes a plurality of types of defect categories. 5. The inspection recipe setting method in the defect inspection apparatus as described in one . 5. The inspection recipe setting method in the defect inspection apparatus according to claim 4, wherein, in the selection step, the condition selection criterion further includes a criterion for giving priority to the specific category to be classified . 5. The inspection recipe setting method in the defect inspection apparatus according to claim 1, further comprising a presentation step of presenting the classification result classified in the classification step as a defect map on a screen . A defect inspection is performed on an object to be inspected similar to the sample in accordance with an inspection recipe set by an inspection recipe setting method in the defect inspection apparatus according to claim 1. A defect inspection method in a defect inspection apparatus.

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