Abstract:
Conventionally, defect data outputted by an inspection system comprised only characteristic quantitative data, such as coordinate data, area, and projected length, and only the coordinate data for moving to a defect location could be utilized effectively. By contrast, by using image data in addition to characteristic quantitative data as the defect data for an inspection system, the retrieval of image data via an outside results confirmation system is made possible. Further, for defect data of a plurality of substrates, it is possible to display a defect image during inspection by the fact that similar defects are retrieved via images and retrieval results are displayed as trends, which makes it possible to display a defect image during inspection by searching similar defects on images and displaying them as a trend, and designating a substrate on the trend, thereby displaying the defect map thereof and designating a defect on the defect map.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This is a continuation of application Ser. No. 10/062,666, filed Feb. 5, 2002, entitled “PATTERN INSPECTION METHOD AND SYSTEM THEREFOR”, by T. HIROI, the contents of which are incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   The present invention is related to a system for the manufacture of a substrate having a circuit pattern, such as a semiconductor device or liquid crystal display; and, more particularly, the invention relates to technology for inspecting a substrate pattern during fabrication. 
   Conventional optical or electron beam pattern inspection systems are described in Japanese Patent Laid-open No. H5-258703 and Japanese Patent Laid-open No. H11-160247. 
     FIG. 1  shows the constitution of a system disclosed in Japanese Patent Laid-open No. H5-258703 as an example of an electron beam pattern inspection system. In this system, an electron beam  2  from an electron beam source  1  is deflected in the X direction by a deflector  3  and is irradiated onto a target substrate  5  via an object lens  4 , while a stage  6  is simultaneously made to move continuously in the Y direction. Secondary electrons  7  from the target substrate  5  are detected by a detector  8 , and the detected signal is converted from analog to digital by an analog-to-digital (A/D) converter  9  to form a digital image, which is compared in an image processing circuit  10  to a digital image of a place that can be expected to be the same as the original, a place that differs is detected as a pattern defect  11 , and the location of the defect is established. 
     FIG. 2  shows the constitution of the system disclosed in Japanese Patent Laid-open No. H11-160247 as an example of an optical inspection system. In this system, a light from a light source  21  is irradiated onto a target substrate  5  via an object lens  22 , and a reflected light is detected by an image sensor  23  at that time. By repeatedly detecting the reflected light while a stage  6  moves at a constant speed, an image is detected as a detected image  24 , and this image  24  is stored in memory  25 . The detected image  24  is compared with a memory stored image  27 , which can be expected to have the same pattern as the detected image  24 , and if the patterns are identical, the detected image  24  is determined to be a normal portion. However, but if the patterns differ, this difference is detected as a pattern defect  11 , and the defect location is established. 
   As an example,  FIG. 3  shows a layout of a wafer  31  which represents a target substrate  5 . Dies  32 , which are ultimately cut apart to yield individual products of the same variety, are formed on wafer  31 . Stage  6  is moved along a scanning line  33 , and an image of the stripe region  34  is detected. When the present detection location A is at  35 , an image of detection location B  36  in memory  25  is extracted as a stored image  27 , and the two images are compared. Thereby, detection location A  35  is compared against a pattern that can be expected to be an identical pattern. Here, memory  25  possesses a capacity capable of holding an image that can be expected to be an identical pattern, that is used repeatedly in a ring shape to form an actual circuit. 
   In the case of both inspection systems, to confirm the results of the inspection, the inspected data is outputted to a review system. Thereafter, the wafer is transferred to and set on a table of the review system to review defects detected by the inspection system. In the review system, the defect to be reviewed is placed in a viewing field of the review system by using the inspected data outputted from the inspection system. Then, the image is visually observed to judge whether or not it has an actual defect or to infer what could have caused it. In such a reviewing method, a vast amount of image data acquired during the inspection is not effectively used. 
   SUMMARY OF THE INVENTION 
   The present invention is constituted such that an image of a defect portion, which is similar to an image of a defect portion specified on the basis of inspection results outputted by an inspection system, and the defect portion image data thereof, is retrieved, and the conditions for the occurrence of a specific mode defect, which have occurred in the past, can be identified by displaying the retrieval results, so as to enable identification. 
   A first system according to the present invention will be explained. A constitution of a system that uses an electron beam will be considered, but there is substantially identical to a system which utilizes another type of charged particle. 
   As seen in  FIG. 4 , the system is constituted from an electron beam source  1  for generating an electron beam  2 ; a deflector  3  for deflecting the electron beam  2 ; an object lens  4  for converging the electron beam  2  onto a target substrate  5 ; and a stage  6  for holding, scanning and positioning the target substrate  5 . A detector  8  is grounded for detecting secondary electrons  7  emitted from the target substrate  5 ; and, an A/D converter  9  operates to convert a detected signal from analog to digital to form a digital image. An image processing circuit  110  compares the digital image against a digital image of a location that can be expected to be substantially identical and detects a location that is different as a pattern defect  11 . Defect data storing means  201  operates to store defect data  200  comprising the defect location and image data of the pattern defect  11 ; and data outputting means  203  outputs the stored defect data  202  to either a network or a storage medium. An inputting means  205  is provided for inputting defect data  202  related to a plurality of wafers, which was outputted to data transferring means  204  by data outputting means  203 ; and defect data storing means  206  stores the inputted defect data. A defect map  207  operates to display defect location data of the wafer on a display screen and selecting means  208  selects a specific defect on the defect map  207 . Image displaying means  209  displays the image of the selected defect data in an image format. Search command means  210  is provided for issuing a command for retrieving, from the defect data group a defect image that is similar to a displayed image; and image retrieving means  211  operates to retrieve an image having image data that is similar to a displayed image. 
   The electron beam  2  from electron beam source  1  is irradiated onto target substrate  5  via object lens  4 , and generated secondary electrons  7  are detected by the detector  8 . In this operation, the electron beam  1  is deflected by deflector  3 , image data is formed by using stage  6  for scanning target substrate  5 , the image data detected by the detector is converted from analog to digital by A/D converter  9 , so that a digital image is formed. Image processing circuit  110  compares this digital image with a digital image which is expected to be substantially identical, and detects a difference between the two images as a pattern defect  11 . Defect data  200 , comprising the defect location and image data of the detected pattern defect  11 , is stored in defect data storing means  201 , and stored defect data  202  is outputted by data outputting means  203  as necessary to information transferring means  204  in the form of either a network or a storage medium. 
   Defect data  202  of a plurality of wafers, which is outputted from outputting means  203 , is inputted by inputting means  205  and is stored in a storing means  206 , and the defect location data of the inputted defect data is displayed on defect map  207 . When a specific defect on the defect map is selected by selecting means  208 , an image of the selected specific defect is displayed on image displaying means  209 . When a command is issued by search command means  210 , a defect image similar to the displayed image is retrieved from among the stored defect data stored in the storing means  206  by image retrieving means  211 , and the retrieval results are reflected in defect map  207 . Retrieval results can be checked as needed by issuing a command via selecting means  208 . The frequency at which similar defects occur can be checked by displaying in the time-series format shown in  FIG. 5 , a display format of defect map  207 . In accordance therewith, the image data acquired at inspection time can be utilized effectively. 
   These and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic diagram showing a simplified constitution of a conventional electron beam-type pattern inspection system; 
       FIG. 2  is a schematic diagram showing a simplified constitution of a conventional optical-type pattern inspection system; 
       FIG. 3  is a plan view showing a wafer layout; 
       FIG. 4  is a schematic block diagram showing a simplified constitution of solution means of the present invention; 
       FIG. 5  is a graph showing an example of the occurrence frequency trends of defects; 
       FIG. 6  is a diagram showing the overall constitution of a pattern inspection system according to the present invention; 
       FIG. 7  is a schematic diagram showing a simplified constitution of an inspection system according to the present invention; and 
       FIG. 8  is a diagram of a display screen showing an example of a results confirmation system according to the present invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The embodiments of the present invention will be explained hereinbelow using specific figures. The overall system will be explained first, and then the respective parts of the system will be explained. 
   (Overall System) 
   The constitution of a first embodiment of the present invention is shown in  FIG. 6 . This first embodiment is constituted from a server  151 , which is arranged on a network  150  and which manages and stores various information; an SEM (scanning electron microscope) type pattern inspection system, an optical type pattern inspection system, an extraneous material inspection system, a length-measuring SEM, and other such inspection systems A  152  and inspection systems B  153 , which treat a target substrate  5  as an object, and inspect patterns and measure dimensions; a review system  154  for receiving inspection results from inspection system A  152  and inspection system B  153 , fir positioning target substrate  5  at a specified defect location, and for visually checking this specified defect; and a defect checking system  155  for receiving and checking either inspection or measurement data at inspection time. The respective parts satisfy their functionality by operating as described hereinbelow. 
   That is, a target substrate is loaded, and either a pattern inspection or an extraneous material inspection is carried out, or pattern dimensions are measured by inspection system A  152  and inspection system B  153 . Measurement results, together with image data of defective parts and measured portions are stored when inspection and measurement are performed, and the measurement results and image data are outputted over network  150 . This data is stored in server  151  at one time. 
   Information of the measurement results and image data of a plurality of target substrate stored in server  151  is transmitted to defect review system  154 , and measurement results are displayed on defect confirmation system  155 . Based on the displayed results, image data of a defective portion, which is similar to the image of a specific defect, is retrieved using a method which will be explained hereinbelow, and the retrieval results are reflected on a display. 
   A first variation of this embodiment will be explained. That is, instead of executing a search via a defect checking system  155 , a search can be executed via either inspection system A  152 , or inspection system B  153 , or server  151 , or review system  154 . Or, instead of the checking system  155 , a search server  156 , which is connected to the network  150 , is provided, a search is executed by the search server  156 , and only the results are displayed via a system other than defect checking system  155  or search server  156 . Further, a search can be executed by an arbitrary system without the need to provide search server  156  independently. 
   (Inspection System) 
   The constitution of a SEM-type pattern inspection system is shown in  FIG. 7 . This system comprises an electron beam source  1  having an electron gun for generating an electron beam  2 ; and an electron optical system  64  for accelerating and extracting the electron beam  2  from electron beam source  1  by means of an electrode, and which creates a virtual light source in a fixed location by means of an electrostatic or magnetic field superimposed lens. The electron optical system  64  includes a condenser lens  60  for converging the electron beam  2  from the virtual light source in a fixed location; a blanking plate  104 , which is set near the convergence location, and which effects ON/OFF control of the electron beam  2  emitted from the electron gun; a deflector  105  for deflecting an electron beam  2  in XY directions; and an object lens  4  for converging the electron beam  2  onto a target substrate  5 . A sample chamber  107  is evacuated for maintaining a wafer  31 , which is the target substrate  5 , in a vacuum; a stage  6 , on which the wafer  31  is mounted, is located in the sample chamber  107 , and a retarding voltage  108  is applied thereto for making it possible to detect an image of an arbitrary location. A detector  8  detects secondary electrons  7  emitted from target substrate  5 ; and an A/D converter  9  is provided for converting a signal detected by detector  8  from analog to digital and producing a digital image. A memory  109  is connected to the converter  9  for storing the digital image; and an image processing circuit  110  operates to compare data image stored in memory  109  with an A/D converted digital image and to detect the difference between the compared images as a pattern defect  11 . A pattern defect storage portion  201 , is provided for storing defect data  200 , such as pattern defect  11  coordinates, projected length, area, critical threshold value DD (the threshold value at which, when the threshold value is lower than this value, a defect is detected), differential image average value, differential image distribution, maximum image difference, defect image texture, reference image texture, image of a defect portion, and a reference image having a pattern that is identical to that of the defect portion. Data outputting means  203  is connected to the pattern defect storage portion  201  for outputting stored defect data  200  to either a network or a storage medium. A system controller  100  is provided for controlling the entire system (control lines from system controller  100  are omitted from the figure); and a display unit is connected to the system controller  100 . The display unit includes an operating screen  45  for performing various operations, a keyboard (not shown), a mouse (not shown)and a knob (not shown) for specifying operations. A Z sensor  113  is provided for maintaining the focal point position of a detected digital image constant by measuring the height of a wafer  31  and adding and controlling an offset  112  to the current value of object lens  4 . A loader (not shown) is provided for loading and unloading wafers  31  carried in a cassette  114  into sample chamber  107 ; and an orientation flat detector (not shown) is provided for positioning the wafer  31  using the outline shape of the wafer  31  as a reference. An optical microscope  118  is provided for observing a pattern on the wafer  31 ; and a standard sample  119  is provided on stage  6 . 
   The operation of the inspection system will be explained. When an inspection is started by a command from a user, stage  6  moves and the region to-be-inspected on the wafer  31  mounted on the stage  6  is moved to the scanning start position. A wafer-specific offset measured beforehand is added and set in offset  112 , Z sensor  113  is made operative, stage  6  scans in the Y direction along scanning line  33  shown in  FIG. 3 , deflector  105  scans in the X direction in synchronization with the scan of the stage, the voltage of blanking plate  104  is shut off at the effective scanning time, and an electron beam  2  is irradiated onto the wafer  31  and scanning is performed. Either reflected electrons or secondary electrons generated from wafer  31  are detected by detector  8 , a digital image of stripe region  34  is produced by A/D converter  9 , and this digital image is then stored in memory  109  and inputted in image processing circuit  110  in parallel. Upon termination of the scan of stage  6 , Z sensor  113  is made inoperative. 
   An inspection of all required regions is carried out by repeating the scanning of the stage  6 . When the detection is carried out in the location A  35  (Refer to  FIG. 3 ), image processing circuit  110  compares a detected image of the location A  35  with an image of detection location B  36  (Refer to  FIG. 3 ) stored in memory  109 , and extracts a discrepancy between both images as a pattern defect  11 , and the image of detection location A  36  is stored in defect data storage means  201 . Defect data  200 , such as extracted pattern defect  11  coordinates, projected length, area, critical threshold value DD (the threshold value at which, when the threshold value is lower than this value, a defect is detected), differential image average value, differential image distribution, maximum image difference, defect image texture, reference image texture, and image data, is stored in defect data storage means  201 . And, from data outputting means  203 , data is outputted as needed to data transferring means  204 , which is either a network or an MO (magneto-optical disk), CDR (compact disk-recordable), DVD (digital video disk), FD (floppy disk) or other storage medium. 
   (Results Confirmation System) 
   Outputted defect data  202  is inputted via inputting means  205  (See  FIG. 4 ) of results confirmation system  155  either via a network or from a storage medium, and defect location data from among the inputted defect data is displayed on defect map  207 . When a specific item on the defect map is selected by selecting means  208 , image data of the defect data is displayed in a image format on image displaying means  209 . When a command is issued by search command means  210 , a defect image similar to the display image is retrieved by image retrieving means  211  from among the defect data group, and retrieval results are reflected on defect map  207 . Retrieval results can be checked as needed by issuing a command via selecting means  208 . The frequency at which similar defects occur can be checked by displaying in the time-series format shown in  FIG. 5 , a display format of the defect map  207 . In accordance therewith, the image data acquired at inspection time can be utilized effectively. 
   An example of a display screen of the results confirmation system  155  is shown in  FIG. 8 . The location on a substrate (wafer) of each detected defect is displayed on map display portion  55 , which corresponds to defect map  207  of  FIG. 4 . 
   Further, an image of a defect specified from among the defects displayed on the map display portion  55  is displayed on image display portion  56 , which corresponds to image displaying means  209  of  FIG. 4 . Specifying a defect for displaying this image is effected by operating a mouse operation command button  140 . That is, a current location symbol  59  is displayed on the screen using the mouse operation command button  140  to select a selection mode  145  from among a selection mode  145  and a zooming mode  146 , the current location display  59  is moved with the mouse (not shown in the figure), and the image of a defect that a user wishes to see is displayed on image display portion  56  by clicking on the location of the defect to be viewed. 
   Further, when the zooming mode  146  is selected with the mouse operation command button  140 , a display on map display portion  55  of the distribution of defects on a substrate can be either enlarged or reduced. 
   According to the present invention, an image of a defect portion, which is similar to an image of a defect portion specified on the basis of inspection results outputted by an inspection system and the defect portion image data thereof, is retrieved, and the conditions for the occurrence of a specific mode defect, which occurred in the past, can be identified by displaying the retrieval results so as to enable identification. Further, the present invention is characterized in that it enables the provision of functions for sounding an alarm in response to a future specific mode-generated defect by setting retrieval conditions in the inspection system. 
   The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.