JP5391172B2 - Foreign object inspection apparatus and alignment adjustment method - Google Patents

Description

  The present invention relates to a foreign substance inspection apparatus that detects foreign substances existing on the surface of an object to be inspected after alignment adjustment is performed during inspection, such as a semiconductor defect inspection apparatus.

  As a foreign matter inspection device that detects foreign matter, scratches, defects, dirt, etc. (hereinafter simply referred to as foreign matter) present on the surface of an inspection object such as a semiconductor wafer, a light beam such as a laser beam is applied to the surface of the inspection object. It is known to detect the presence or absence of foreign matter on the surface of an object to be inspected by detecting reflected light or scattered light generated on the surface at the time of irradiation.

  For example, in the case of a semiconductor defect inspection apparatus, a semiconductor wafer on which a large number of IC chips originally having the same pattern are formed is irradiated with a light beam, and an image signal is obtained from the intensity of reflected or scattered light detected from each chip. The generated signal is compared with an image signal obtained from an adjacent chip or an image signal of a good chip prepared in advance.

  In such foreign matter inspection, when collecting image signals of chips formed on a semiconductor wafer, which is an object to be inspected, chips arranged in parallel on the surface of the semiconductor wafer are scanned with a light beam. It must be placed parallel to the direction. This is because in such foreign matter inspection, since the deviation signal is collected by comparing the image signal of the detected chip with the image signal of the adjacent chip or non-defective chip, the semiconductor wafer should be parallel to the scanning direction of the light beam. This is because the deviation signal varies depending on the type and density of the pattern included in the detection area, such as the wiring layout in the chip and the scribe line between the chips, and the inspection result is affected.

  Therefore, in such a foreign substance inspection apparatus, as an alignment method for placing the inspection object in parallel with the scanning direction of the light beam, an alignment mark formed in the chip on the surface of the inspection object is used as a reference. Then, the coordinates (X, Y) of two points in the inspection object are sampled, and the inspection stage on which the inspection object is placed is moved based on the deviation amount of the inspection object calculated from the coordinates. Corrections have been made.

  On the other hand, with the recent high integration and miniaturization of semiconductors, it is necessary to detect finer foreign substances. In order to correctly detect reflected light or scattered light from a minute foreign matter, the foreign matter inspection apparatus needs to set a low threshold for determining the foreign matter described above. However, if the threshold value is set low, there is a concern that noise is erroneously detected as a foreign substance due to variations in the deviation signal. Therefore, in the foreign substance inspection apparatus, it is desired to improve both sensitivity and prevent erroneous detection.

  Therefore, in the apparatus described in Patent Document 1, the threshold value is added from the image signal of the good chip prepared in advance, the upper threshold image to which the expansion process is added, and the threshold value is subtracted, and the contraction process is added. Create a lower threshold image and compare the image signal detected by each chip with both the upper threshold image and the lower threshold image to prevent false detection due to misalignment near the edge of the pattern doing.

  In the apparatus described in Patent Document 2, the alignment detection processing between chips is performed after the image is acquired, and the sensitivity of foreign object detection is improved by calculating and determining a plurality of feature amounts calculated in the image.

  In Patent Document 3, contraction / expansion processing is performed on an image after foreign object determination (a binary image in which a place where it is determined that there is a foreign object is 1 and a place where it is determined that there is no foreign object is 0). Thus, the false foreign substance detected erroneously is erased.

  Furthermore, in order to improve sensitivity and prevent erroneous detection, as described in Patent Documents 1 to 3 described above, in addition to performing these processes after obtaining an image signal, further alignment when an inspection object is placed is performed. Although it is effective to reduce variations in deviation signals by improving accuracy, alignment is becoming difficult due to miniaturization of alignment marks and a decrease in contrast caused by manufacturing processes.

  With regard to such an alignment method of inspection positions, for example, in Patent Document 4, a projection waveform of a reticle substrate is prepared as reference image data (hereinafter referred to as a template), and a projection actually obtained from a reticle substrate for position adjustment is prepared. An apparatus for obtaining a deviation amount from pattern matching with a waveform is disclosed.

As for the pattern matching method, Patent Document 5, detects an image signal from the object to be inspected, the image is normalized, it is also disclosed that to calculate the correlation values and the normalized template normalized correlation method Yes.

  In Patent Document 6, a predetermined feature amount is extracted from an image signal to form an abstract pattern, and this and the abstract pattern obtained from the reference image (template) are matched to calculate the degree of coincidence. An apparatus is disclosed.

JP 2010-91360 A JP 2008-39533 A JP 2000-180377 A Japanese Patent Laid-Open No. 10-106941 JP 2006-107046 A JP 11-340115 A

However, the above-described conventional technology has the following problems.
The technique disclosed in Patent Document 1 does not take into account variations in deviation signals due to misalignment, and cannot be expected to be effective except near the edges of the pattern.

  In addition, the technique disclosed in Patent Document 2 is basically based on the premise of correction in units of pixels, and the accuracy of interpolation (fitting) processing performed for correction in units of pixels or less is not guaranteed. .

  In addition, the technique disclosed in Patent Document 3 may be erased as an erroneous detection even if there is actually a minute foreign object in the image after the determination. Not.

In addition, in the case of alignment using pattern matching as in the techniques disclosed in Patent Documents 4 to 6, in the case of a pattern formed with a double frame as shown in FIG. Even if the position is shifted by about 5 mm, a high degree of coincidence is shown, and there is a possibility that correct matching cannot be obtained. Further, in the case of an alignment mark having a low contrast, no consideration is given to the fact that the matching degree is low and matching cannot be performed.

  The present invention has been made in view of the above-described problems, and by performing pattern matching so as not to be unrecognizable or erroneously recognized even when the alignment mark of the target inspection object is in a condition that makes pattern matching difficult. Another object of the present invention is to provide a foreign substance inspection apparatus and an alignment adjustment method capable of realizing highly accurate sample positioning and high sensitivity inspection.

The present invention irradiates a surface of an inspection object with a light beam, obtains an image signal from the received light intensity of reflected light or scattered light, and compares the surface of the inspection object with an image signal obtained from an adjacent inspection object Image data including a pattern image of an alignment mark formed on the surface of the object to be inspected and contoured with multiple frame lines including double frame lines. a device for collecting, analyzing means for obtaining a luminance distribution of each pixel of the image data the collected, based on the bright distribution obtained by the analysis means, of the alignment marks in the pattern image of the alignment marks the collected shape measures the frame distance between multiple border give contour is subjected to a replacement process of the luminance values for the pixels surrounding the border at the determined processing width on the basis of the inter the frame distance, next if After making the pattern image of the single frame alignment mark connecting the frame lines, the frame thickness of the pattern image of the single frame alignment mark is measured, and the single frame with the processing width determined based on the frame thickness And processing means to convert the brightness value to the frame edge pixels to make the pattern image of the thin single-line alignment mark, and perform pattern matching after processing the image data It is characterized by that.

  According to the present invention, highly accurate sample alignment can be performed, and high-sensitivity inspection can be realized.

It is a schematic block diagram of the foreign material inspection apparatus which concerns on one embodiment of this invention. It is a flowchart of the test | inspection operation | movement by the foreign material inspection apparatus which concerns on this Embodiment. It is a flowchart of a pattern image formation process in the case of re-registering a pattern image whose shape is outlined with a double frame line as a single frame thin line pattern image. It is the figure which represented typically progress of the formation process of the pattern image which concerns on 1st Example which an alignment calculation process part performs. It is a flowchart of the pattern image formation process in the case of re-registering the pattern image of a unclear alignment mark as the pattern image of a clear alignment mark. It is the figure which represented typically progress of the formation process of the pattern image which concerns on 2nd Example which an alignment calculation process part performs. It is a flowchart of the pattern image formation process in the case of re-registering a pattern image of an unclear alignment mark as a thinned alignment mark pattern image. It is the figure which represented typically progress of the formation process of the pattern image which concerns on the 3rd Example which an alignment calculation process part performs.

  Hereinafter, a foreign substance inspection apparatus according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a foreign matter inspection apparatus according to an embodiment of the present invention.
The foreign matter inspection apparatus 1 according to the present embodiment includes an illumination unit 10 of a foreign matter detection system, a detection unit 20 of the same foreign matter detection system including an imaging unit 20a and a light receiving unit 20b, an X scale 30, and a Y scale 40. And an illumination unit 50 of a surface height position detection system separate from the foreign matter detection system, a detection unit 60 of the same surface height position detection system including a pair of detectors 60a and 60b, An inspection stage 70 on which an inspection object is mounted and movable, an alignment detection system 80 separate from the foreign matter detection system and the surface height position detection system, and the processing apparatus 100 are included.

  When the wafer 2 having the chip 3 formed on the surface thereof as an object to be inspected is mounted on a wafer table (not shown in FIG. 1) and conveyed to the inspection stage 70, first, an alignment detection system 80 including an alignment detection system 80, which will be described later. The alignment apparatus 200 is used to correct the offset in the X and Y directions and the angle deviation θ between the wafer coordinate system of the wafer 2 described later and the movement coordinate system of the inspection stage 70.

  The illuminating unit 10 of the foreign matter detection system generates laser light having a predetermined wavelength as inspection light, and irradiates the surface of the wafer 2 as an inspection object with the light beam. At that time, the irradiation position of the light beam on the surface of the wafer 2 is relatively moved by moving the inspection stage 70 in the X direction or the Y direction, and the light beam irradiated from the laser device 10 scans the surface of the wafer 2. It will be. That is, the inspection stage 70 is moved in the vertical / horizontal direction (XY direction) in a horizontal plane, and the entire surface of the wafer 2 or a desired region (desired cell or die) therein is scanned with the inspection light. Irradiation can be performed.

  The detection unit 20 of the foreign object detection system receives light reflected or scattered from the surface of the wafer 2 by irradiating the surface of the wafer 2 from the illumination unit 10 with the inspection light, and detects the light intensity. The light receiving means 20b is composed of, for example, a TDI (Time Delay and Integration) sensor, a CCD sensor, a photomultiplier tube (photomultiplier), etc., and the reflected light or scattered light generated on the surface of the wafer 2 is passed through the imaging means 20a. The light intensity is converted into an electrical signal and output to the processing apparatus 100 as an image signal.

  The X scale 30 and the Y scale 40 are configured by, for example, a laser scale, and detect the X-direction position and the Y-direction position of the inspection stage 70, respectively, and output them to the processing apparatus 100. Thereby, in the processing apparatus 100, the irradiation position of the light beam on the wafer coordinate system of the wafer 2 mounted on the inspection stage 70 can be obtained based on the X-direction position and the Y-direction position of the inspection stage 70. At the same time, a desired position on the wafer coordinate system on the surface of the wafer 2 can be irradiated with the light beam.

  The illumination unit 50 of the surface height position detection system generates inspection light (laser light) having a predetermined wavelength and angle as inspection light (laser light) for detecting the surface height position of the inspection object.

  The detection unit 60 of the surface height position detection system includes a pair of detectors 60a and 60b whose detection center positions are different from each other in the vertical direction of the inspection object. The light reflected from the surface of the wafer 2 by irradiating the surface of the wafer 2 from the illumination unit 50 is received by the detectors 60a and 60b to detect the light intensity, and the surface height of the object to be inspected. The signal is supplied to the processing apparatus 100 as a position detection signal. As a result, the processing apparatus 100 adjusts the focal position of the foreign object detection system according to the surface height position of the object to be inspected based on the detection signals supplied from the detectors 60a and 60b.

  The alignment detection system 80 includes a light source 81, an illumination optical system that condenses the illumination light emitted from the light source 81 onto the alignment marks 4 (4 a and 4 b) of the wafer 2, and a reflected light from the wafer 2 as a CCD camera 87. And an imaging optical system for focusing the light. In the illustrated example, the illumination light emitted from the light source 81 is converted into parallel light by the projection lens 82, reflected by the half mirror 83, condensed by the first objective lens 84, and a certain point on the wafer 2, for example, an alignment mark 4a is irradiated. The reflected light reflected by the wafer 2 is converted into parallel light by the first objective lens 84, then passes through the half mirror 83 and passes through the second objective lens 85 and the imaging lens 86, and the image sensor of the CCD camera 87. Is imaged. The CCD camera 87 converts the light intensity into an electric signal and outputs it to the processing apparatus 100 as an image signal.

  The processing device 100 is configured by using a computer device having an input / output device and a device connection interface, such as a PC. The processing device 100 includes an A / D converter 110 (111, 112), an image processing device 120 (121, 122), a foreign matter determination processing unit 130, a coordinate management device 140, an inspection result storage device 150, a stage. It has a control device 160, an alignment calculation processing unit 170, an alignment storage device 180, and a user interface device 190.

  The A / D converter 111 converts the analog image signal supplied from the light receiving means 20b of the detection unit 20 of the foreign substance detection system into a digital image signal and outputs the digital signal.

  The image processing device 121 includes, for example, a delay circuit and a difference detection circuit. The delay circuit inputs the image signal from the A / D converter 111 and delays it, so that the irradiation of the light beam immediately before the chip currently irradiated with the light beam in the scanning of the inspection light is completed. The image signal is output. The difference detection circuit includes an image signal from the A / D converter 111 of the chip that is currently irradiated with the light beam in the scanning of the inspection light, and a delay circuit for the chip that has been irradiated with the previous light beam. The difference from the image signal is generated. From the image processing device 121, the difference between the image signal from the A / D converter 111 and the image signal generated by the difference detection circuit is supplied to the foreign matter determination processing unit 130. The image processing apparatus 121 includes a memory that stores image data of a good chip image prepared in advance instead of the delay circuit, compares the image signal with a good chip image signal, and determines the difference between the image signals as a foreign matter determination. You may make it supply to the process part 130. FIG.

  The foreign matter determination processing unit 130 includes a determination circuit 131 and coefficient tables 132 and 133. The coefficient tables 132 and 133 call the coefficient stored in association with the coordinate information based on the coordinate information input from the coordinate management device 140 described later, and output the coefficient to the determination circuit 131. When the coefficients stored in the coefficient tables 132 and 133 are called up based on the coordinate information and output to the determination circuit 131, the determination circuit 131 uses the corresponding coordinates set in advance in the image processing apparatus 121. It is multiplied by the reference threshold. Therefore, the determination circuit 131 enables flexible adjustment depending on whether the threshold value used for defect determination is created by multiplying the coefficient from the coefficient table 132 or 133.

  A difference between image signals between adjacent chips is input to the determination circuit 131 from the image processing device 121, and a coefficient for changing to a threshold value for determination is input from the coefficient tables 132 and 133. The determination circuit 131 selectively multiplies the reference threshold value of the corresponding coordinates for foreign object determination by a coefficient supplied from the coefficient tables 132 and 133 according to a preset condition. Then, a threshold value for determination applied to the difference signal of the corresponding pixel from the image processing device 121 is created. Here, the preset condition is set based on, for example, accumulation of past inspection / analysis data obtained by inspecting a large number of identical or similar products. For example, an image input from the image processing apparatus 120 Conditions such as whether or not the signal difference is between chips located in the vicinity of the edge of the wafer 2 are applicable.

  Then, the determination circuit 131 compares the difference between the image signals and the created threshold value for determination. If the difference is equal to or greater than the threshold value for determination, the difference signal of the pixel is determined as a foreign object or It is determined that the light is based on scattered light from the defect. In this way, the determination circuit 131 can accurately determine foreign matter regardless of the difference in irradiation position on the semiconductor wafer 2 irradiated with the light beam.

  Then, the determination circuit 131 outputs the determination result to the inspection result storage device 150 for storage. At that time, the determination circuit 131 also outputs information such as the threshold size used for the determination to the inspection result storage device 150 and stores the information in the inspection result storage device 150 in association with the determination result. It has become.

  As described above, the illumination unit 10 of the foreign object detection system, the detection unit 20 of the foreign object detection system, and the A / D converter 111, the image processing device 121, and the foreign object determination processing unit 130 in the processing apparatus 100 are included in the foreign object inspection apparatus 1. Functions as a foreign matter determination device.

  On the other hand, the coordinate management device 140, based on the position coordinates in the moving coordinate system of the inspection stage 70 supplied from the X scale 30 and the Y scale 40, the wafer coordinates on the semiconductor wafer 2 corresponding to the current light beam irradiation position. The position coordinates by the system are calculated and the coordinate information is output. The coordinate management device 140 calculates the position coordinates in the wafer coordinate system on the semiconductor wafer 2 based on the alignment information supplied from the alignment calculation processing unit 170 when performing foreign object inspection, and the position coordinates in the movement coordinate system and the wafer. Correction of coordinate deviations in the X direction, Y direction, and rotation direction θ that occur between the position coordinates by the coordinate system and the position coordinates by the wafer coordinate system on the semiconductor wafer 2 corresponding to the current irradiation position of the light beam Is calculated. The calculated position coordinates in the wafer coordinate system are supplied to the coefficient tables 132 and 133 and the inspection result storage device 150 of the foreign matter determination processing unit 130. As a result, the inspection result storage device 150 also stores position coordinates based on the corresponding wafer coordinate system in association with the determination result, the threshold value size, and the like.

  The stage control device 160 performs inspection based on the position coordinates of the inspection stage 70 supplied from the X scale 30 and the Y scale 40 according to the set stage movement conditions during alignment adjustment, foreign object inspection, and the like. The movement of the stage 70 in the X direction and the Y direction is controlled. At that time, for example, when a foreign object is inspected, a desired area (desired cell or die) on the wafer coordinate system is designated as a target area using the user interface device 190, and the stage movement condition is determined from the coordinates on the wafer coordinate system. In this case, the stage control device 160 determines the movement coordinate system of the inspection stage 70 from the position coordinates on the designated wafer coordinate system for the target region based on the alignment information supplied from the alignment calculation processing unit 170. And the movement of the inspection stage 70 in the X and Y directions is controlled.

  Further, the stage control device 160 moves the mounting surface of the inspection object of the inspection stage 70 up and down in the Z direction as necessary based on the detection result of the surface height position of the inspection object by the detection unit 60, The focus position is also adjusted for the inspection light from the illumination unit 10 of the foreign object detection system.

  The user interface device 190 includes an image display unit 191 as an output unit, and an input unit 192 such as a keyboard and a mouse. The image display unit 191 includes a detection image based on an image signal output from the image processing device 120 (121, 122), a foreign matter determination result or alignment result by the foreign matter determination processing unit 130 or the alignment processing unit 170, or an alignment adjustment or foreign matter. A setting / operation screen related to the inspection is displayed. The input unit 192 is operated when various setting operations are performed based on the setting / operation screen displayed on the image display unit 191.

  On the other hand, the A / D converter 112 converts an analog image signal supplied from the CCD camera 87 of the alignment detection system 80 into an image signal of a digital signal and outputs the digital image signal. The image processing device 122 generates image information of a portion captured by the CCD camera 87 based on the image signal from the A / D converter 112, that is, a detected image. If the CCD camera 87 of the alignment detection system 80 can directly output a detection image, the A / D converter 112 and the image processing device 122 can be omitted.

  The alignment calculation processing unit 170 performs image processing on the image information input from the image processing device 122 in the set values and order stored in advance, and forms a pattern image. If the processing method is not stored, new registration is performed using the user interface unit 190 by a method described later. After the pattern image is formed, the alignment calculation processing unit 170 performs pattern matching with a reference alignment mark image stored in the alignment storage device 180 described below, using the formed pattern image as a measurement image.

  When a matching shape portion is found between the measurement image and the reference alignment mark image and the pattern matching of the alignment mark 4 is obtained, the matching shape portion is used as the actual coordinates of the alignment mark 4 for which the pattern matching has been taken. The coordinates of the moving coordinate system of the inspection stage 70 are acquired. This actual coordinate is the X direction of the inspection stage 70 that is instructed to the stage controller 160 to acquire the measurement image when the pattern matching of the alignment mark 4 is obtained between the measurement image and the reference alignment mark image. And it is calculated based on the coordinate value of the movement coordinate system for the movement destination in the Y direction. In this way, the alignment calculation processing unit 170 acquires the actual coordinates of the alignment marks 4a and 4b for two different chips 3a and 3b in the wafer 2, and the actual coordinates of the acquired alignment marks 4a and 4b are obtained. The reference coordinate mark stored in advance in association with the reference alignment mark image, from the position coordinates of the corresponding matching part in the wafer coordinate system, the movement coordinate system of the inspection stage 70 and the wafer 2 as the inspection object. The coordinate deviation in the X direction, the Y direction, and the rotation direction θ with respect to the wafer coordinate system is calculated. The alignment calculation processing unit 170 supplies the coordinate deviations in the X direction, the Y direction, and the rotation direction θ as correction values to necessary units such as the coordinate management device 140 and the stage control device 160.

  The alignment storage device 180 is necessary for the processing of the alignment calculation processing unit 170, for example, the reference alignment image, the position coordinates of the reference alignment mark in the wafer coordinate system, the processing order, and the movement of the inspection stage 70 for acquiring the measurement image. Alignment information such as a specified range is stored. The alignment information stored in the alignment storage device 180 indicates that the foreign object inspection device 1 itself is a foreign object of a predetermined inspection object when connected to a device such as a data management server related to the foreign object inspection via the network. Registration and updating may be performed by these external devices at the start of the inspection.

  As described above, the alignment detection system 80, the A / D converter 112 in the processing device 100, the image processing device 122, the alignment calculation processing unit 170, and the alignment storage device 180 function as the alignment device 200 in the foreign matter inspection apparatus 1.

Next, the inspection operation by the foreign matter inspection apparatus 1 according to the present embodiment will be described.
FIG. 2 is a flowchart of the inspection operation performed by the foreign matter inspection apparatus according to the present embodiment.

  At the start of foreign matter inspection, the processing apparatus 100 operates a transfer unit (not shown) to transfer one wafer 2 to be inspected this time from a wafer cassette containing a plurality of wafers 2 to be inspected. It is conveyed to the stage (S201).

  The processing apparatus 100 detects the position of the outer periphery of the wafer 2 placed on the pre-alignment stage and the position of the V notch (or orientation flat) using a pre-alignment detector. The processing apparatus 100 moves and rotates the pre-alignment stage based on the detection result, and after performing coarse adjustment so that the rotational deviation θ of the wafer 2 is within a certain range (S202), the transfer unit is moved. Operate and transport and place from the pre-alignment stage to the inspection stage 70 (S203). Therefore, when the wafer 2 is placed on the inspection stage 70, the rotational adjustment θ of the wafer 2 is roughly adjusted so as to be within a certain range. Thereafter, the processing apparatus 100 causes the alignment calculation processing unit 170 or the like as the alignment apparatus 200 to execute the alignment operation shown in steps S204 to S216.

  First, the alignment calculation processing unit 170 sets the irradiation position of the illumination light by the alignment detection system 80 to the chip (first chip) 3a specified in advance on the wafer based on the alignment information stored in the alignment storage device 180. Thus, the inspection stage 70 is moved (S204). After the movement, the alignment calculation processing unit 170 further changes the position where the alignment detection system 80 is supposed to have an alignment mark to the irradiation position of the illumination light by the alignment detection system 80 based on the alignment information stored in the alignment storage device 180. Thus, the inspection stage 70 is moved based on the movement designation range (S205), and the image information of the place is collected (S206). The alignment calculation processing unit 170 executes a pattern image forming process, which will be described later, in the set values and order stored in advance for the collected image information, and acquires a pattern image for the collected image information (S207). ). Then, the alignment calculation processing unit 170 performs pattern matching with the reference alignment mark image stored in the alignment storage device 180 using the acquired pattern image as a measurement image (S208). The alignment calculation processing unit 170 finds a matching shape portion between the measurement image and the reference alignment image, and when the pattern matching of the alignment mark 4a is obtained, as the actual coordinates of the alignment mark 4a obtained by pattern matching, The coordinates of the moving coordinate system of the inspection stage 70 for the matching shape location are acquired (S209). On the other hand, when this pattern matching cannot be obtained, the alignment calculation processing unit 170 determines that there is no alignment mark 4a in the acquired pattern image, and executes steps S205 to S208 again.

  On the other hand, if the alignment calculation processing unit 170 detects the alignment mark 4a in the first chip 3a (S209), this time, the alignment detection system 80 uses the alignment information stored in the alignment storage device 180. The inspection stage 70 is moved so that the irradiation position of the illumination light is a predesignated chip (second chip) 3b on the wafer (S210). Then, the alignment calculation processing unit 170 is similar to the processing of steps S205 to S208 performed on the first chip 3a, and the alignment mark 4b around the chip 3b based on the movement designation range of the inspection stage 70 is considered to be a place. The pattern image includes search processing (S211), image information collection processing (S212) of the alignment mark 4b at that location, pattern image formation processing (S213), and pattern matching processing (S214) between the pattern image and the reference alignment mark image. And the reference alignment mark image are repeatedly performed in the movement designation range of the inspection stage 70 until a matching shape portion is found and the pattern matching of the alignment mark 4b is obtained.

  Then, the alignment calculation processing unit 170 finds a matching shape portion between the pattern image and the reference alignment mark image in the pattern matching processing in step S214, and if the matching of the alignment mark 4b is obtained, the matching shape is obtained. The coordinate values of the movement coordinate system for the movement destination of the inspection stage 70 in the X direction and the Y direction are acquired as the actual coordinates of the location of the alignment mark 4b (S215).

  Based on the actual coordinates of the locations of the acquired alignment marks 4a and 4b, the alignment calculation processing unit 170 performs X and Y directions between the wafer coordinate system of the wafer 2 and the movement coordinate system of the inspection stage 70. The offset and the angle deviation θ are calculated (S216). Then, the alignment calculation processing unit 170 supplies these as correction values to necessary units such as the coordinate management device 140 and the stage control device 160.

  When the alignment operation described above by the alignment apparatus 200 including the alignment calculation processing unit 170 is completed, the processing apparatus 100 performs the above-described wafer inspection process as a foreign matter determination apparatus including the foreign matter determination processing unit 130 (S217). Then, when the execution of the wafer inspection process described above is completed, the processing apparatus 100 unloads the wafer 2 that has been inspected from the inspection stage 70 (S218), and transports the wafer 2 back to the wafer cassette storage.

In addition, in the foreign matter inspection apparatus 1 according to the present embodiment, when the alignment calculation processing unit 170 performs pattern matching between the measurement image and the reference alignment mark image, the reference alignment mark on the reference alignment mark image is displayed. For example, even if the shape is outlined by a multiple frame line such as a double frame line or a thick single frame, or the reference alignment mark image itself is unclear, the same pattern as in steps S207 and S213 described above An image forming process is performed to form a pattern image of a reference alignment mark that has been thinned or sharpened with a single frame. Then, instead of the reference alignment mark or the unclear original reference alignment mark image whose shape is outlined by multiple frame lines or a thick single frame, the pattern image of the reference alignment mark thinned or sharpened by this single frame and it is capable to be registered and noted to be as standard alignment mark image.

  Furthermore, the setting values and order for obtaining a pattern image of a reference alignment mark that has been thinned or sharpened with a single frame, acquired in the pattern image forming process, is the pattern image of the alignment mark taken from the inspection object. It can be used to get.

  Hereinafter, the pattern image forming process for the reference alignment mark and the alignment mark collected from the inspection object executed by the alignment calculation processing unit 170 in the above-described steps S207 and S213 will be described in detail.

  Here, as a first embodiment, for a reference alignment mark whose shape is contoured by a double frame line, a pattern image forming process similar to the above-described steps S207 and S213 is stored in advance. A pattern image forming process executed by the alignment calculation processing unit 170 when a pattern image of a reference alignment mark image that has been executed in the set values and in the order described above and has been thinned with a single frame will be described.

  FIG. 3 is a flowchart of a pattern image forming process in a case where a pattern image of a reference alignment mark whose shape is outlined with a double frame line is registered again as a single frame thin line pattern image.

  FIG. 4 is a diagram schematically showing the progress of the pattern image forming process according to the first embodiment executed by the alignment calculation processing unit at that time.

  First, the user operates the input unit 192 of the user interface unit 190, and a reference whose shape is outlined by a double frame line saved in the alignment storage device 180 as shown in FIG. The pattern image 400 of the alignment mark is collected and displayed on the image display unit 191 of the user interface unit 190 (S301).

Next, on the screen of the image display unit 191 of the user interface unit 190, the user sets the distance between the double frame lines (interline) from the original pattern image 400 of the double frame line of the reference alignment mark. point of measuring, in example embodiment, the two portions in the X direction 40 1, Y direction 402, selectively set by operating the input unit 192 of the user interface unit 190 (S302).

Thus, the alignment processing unit 170 acquires a cross-sectional profile of the alignment storage device 180 in the selected portions 401, 402 of the original reference alignment mark pattern image 400, the frame of the measurement point 40 1,402 therefrom The distances dx1 and dy1 are measured (S303).

  The alignment calculation processing unit 170 calculates based on the measured interframe distances dx1 and dy1 according to the formulas (1) and (2), and minimizes the double frame lines connected in the x direction and the y direction. The widths ex1 and ey1 of the shrinking process are determined.

  Here, the inter-frame distances dx1 and dy1 are taken in based on the number of pixels on the pattern image 400 of the original reference alignment mark. If the inter-frame distances dx1 and dy1 are an even number, double frame lines are connected. When the minimum extensibility widths ex and ey are determined as dx1 / 2 and dy1 / 2 based on the formula (1) and the number of pixels of the interframe distances dx1 and dy1 is an odd number, double frame lines are connected. The minimum contraction processing widths ex and ey are determined as (dx1 + 1) / 2 and (dy1 + 1) / 2 based on the equation (2).

  Subsequently, the alignment calculation processing unit 170 performs image information contraction processing on the pattern image 400 of the original reference alignment mark within the determined contraction range (contraction processing widths ex1 and ey1) (S304).

  Here, the contraction process is a process of replacing the luminance value of each pixel in the contraction range of the pattern image 400 with the minimum luminance value in neighboring pixels.

  For example, when the neighboring pixels are defined as eight pixels surrounding the pixel, the luminance value replacement processing is expressed by an equation (3).

  The expression (3) sets the pixel represented by the position (i, j) within the contraction range as the target pixel, and the brightness of the target pixel is eight positions (i−1, j−1) surrounding itself and itself. A method of replacing the luminance value of the pixel having the lowest luminance among the pixels of (i + 1, j + 1) is shown.

  In Expression (3), i and j are pixel positions, Dest is the luminance of the target pixel after processing, and Img is the luminance of the original target image.

  FIG. 4B shows an example in which an appropriate contraction process is added to the pattern image of the original reference alignment mark shown in FIG.

  By the contraction process within the determined contraction range, the region between the double frame lines of the original reference alignment mark pattern image 400 is filled, and a single frame thick reference alignment mark pattern image 410 is formed. At the same time, bright isolated points within the contraction range in the pattern image 400 of the original reference alignment mark can be removed.

  After the contraction process, the alignment calculation processing unit 170 measures the pattern width (dx2, dy2) of the pattern image 410 of the formed single-frame thick reference alignment mark (S305).

  At this time, the same locations 401 and 402 as in the case of the measurement of the distance between the frames of the double frame lines may be used as the measurement locations, or new different locations 411 and 412 are used in the same manner as the processing in step S302 described above. Then, the user may make a selection.

  Then, the alignment calculation processing unit 170 calculates based on the measured pattern widths dx2 and dy2 according to the formulas (4) and (5), and the pattern width (frame size) of the single frame in each of the x direction and the y direction. The maximum expansion processing widths fx2 and fy2 that minimize the line thickness) are determined.

Here, when the number of pixels of the measured pattern width dx2, dy2 is an even number, the maximum expansion processing width fx2, fy2 is the maximum expansion processing width fx2, fy2, so that the single frame is not lost. When {dx2 / 2} -1 and {dy2 / 2} -1 are determined based on Expression (4) and the number of pixels of the pattern widths dx2 and dy2 is an odd number, the maximum expansion is performed so that the single frame is not lost. The processing widths fx2 and fy2 are determined as {dx2 + 1} / 2 and {dy2 + 1} / 2 based on the equation (5).

  Subsequently, the alignment calculation processing unit 170 performs image information expansion processing on the pattern image 410 within the expansion range (expansion processing widths fx2, fy2) determined based on the pattern image 410 of the single frame thick reference alignment mark. Is performed (S306).

  Here, the expansion process is a process of replacing the luminance value of each pixel in the expansion range of the pattern image 410 with the maximum luminance value in neighboring pixels.

  For example, when the neighboring pixels are defined as eight pixels surrounding the pixel, the luminance value replacement process is expressed by an equation (6).

  In the expression (6), the pixel represented by the position (i, j) within the expansion / contraction range is set as the target pixel, and the brightness of the target pixel is set to eight positions (i−1, j−1) surrounding itself and itself. ) To (i + 1, j + 1), a method of replacing with the luminance value of the pixel having the highest luminance is shown.

  In Expression (6), i and j are pixel positions, Dest is the luminance of the target pixel after processing, and Img is the luminance of the original target image.

  FIG. 4C shows an example in which an appropriate expansion process is added to the pattern image of the single frame thick reference alignment mark shown in FIG.

  By the expansion / contraction process within the determined expansion range, the pattern width of the pattern image 410 of the single frame thick reference alignment mark is reduced, and the pattern width of the single frame line reference alignment mark having the smallest pattern width, for example, 1 to 2 pixels is reduced. A pattern image 420 is formed. At the same time, dark isolated points in the expansion range in the image can be removed.

  By adding the pattern image forming process consisting of a series of shrinkage process and expansion process as described above, a single frame thin reference alignment mark pattern can be obtained from the original double frame reference alignment mark pattern image 400. An image 420 can be created and registered.

The alignment calculation processing unit 170 has the same range as the range of the contraction process and the expansion process determined at the time of image registration of the pattern image 420 of the reference alignment mark when executing the alignment in steps S205 to S208 and steps S211 to S214 in FIG. , for the collected pattern image in step S 206 and step S212, the shrinkage treatment in the formation process of the pattern image shown in step S207 and step S213, after performing the expansion processing, the pattern image consisting of a series of contraction process and expansion process the pattern image 420 of the reference alignment mark added forming process, a pattern matching process shown in step S 208 and step S214 in FIG. 2 performed (S307).

If performed in step S 207 and step S213, the order of the time of forming the pattern image 420 of the reference alignment mark, the configuration performs formation processing for the pattern image taken from the object to be inspected, a result of the contraction and expansion process , (S308) if a part is lost pattern, in performing repeatedly steps S 304 following treatment, as necessary, or widen the range of shrinkage treatment, or to or narrow the scope of the expansion process If the pattern remains thick, the expansion process range can be expanded.

Next, a second embodiment, the formation process of the pattern image shown in step S 207 and step S213 in FIG. 2, in the case of clarity blurred pattern, formation of a pattern image alignment processing unit 170 executes Processing will be described.

  FIG. 5 is a flowchart of the pattern image forming process when the pattern image of the unclear alignment mark is registered again as the pattern image of the clear alignment mark.

  FIG. 6 is a diagram schematically showing the progress of the pattern image forming process according to the second embodiment executed by the alignment calculation processing unit at that time.

  For example, when the pattern is formed of another material on the wafer, the blurred pattern is generated when the optical characteristics of the pattern material are close to those of the wafer. At this time, for example, after obtaining a blurred pattern image of an alignment mark as shown in FIG. 6A (S501), the user first performs an S / N improvement process of the pattern image (S502).

  In the S / N improvement processing, images may be acquired a plurality of times in order to reduce random noise, and integration processing may be performed. In order to reduce the influence of uneven sensitivity of the CCD camera, there is no pattern such as wiring. The pattern image may be acquired at the place and the subtraction process may be performed, or both processes may be applied.

  Subsequently, the alignment calculation processing unit 170 acquires the luminance distribution of the pattern image of the alignment mark (S503).

For example, as shown in FIG. 6B, the luminance distribution has a peak at a luminance value that differs for each material, and an optimum value (a valley portion between luminance peaks) is determined as a threshold value. Then, for example, as shown in FIG. 6C, the image is binarized ( S505 ).

  By adding the above-described series of processing, the pattern image of the unclear alignment mark can be made clear, and the alignment success probability can be improved.

Formation process of the pattern image of the present embodiment, to the time of registration only of standard alignment mark pattern images may be applied to the reference alignment mark pattern image, when the alignment performed, and step S 206 shown in FIG. 2 the pattern image taken from the object to be inspected in step S212 may be applied in step S 207 and step S213. Regarding the application, at the time of registration or collection of the pattern image, the threshold value is automatically determined based on the pattern image registered or collected by the alignment calculation processing unit 170 and binarized. It is also possible to adopt a configuration in which the interface device 190 is used to make the user confirm the threshold value determination or the like (S506). When applied only at the time of reference alignment mark image registration, an increase in alignment time can be prevented.

  If an appropriate threshold value cannot be determined from the luminance distribution (S507), the S / N improvement processing may be performed again, or pattern matching is applied to the image before binarization while actually shifting the threshold value. A value that maximizes the degree of matching may be used as the threshold value.

  In addition, when the alignment mark and its peripheral part are formed of three or more kinds of materials, a plurality of threshold values are prepared to be multi-valued (for example, three kinds of materials are represented by three threshold values. (Value).

Next, as a third embodiment, pattern image formation executed by the alignment arithmetic processing unit 170 when the unclear pattern is clarified in the pattern image formation processing shown in steps S 207 and S 213 of FIG. Processing will be described.

  FIG. 7 is a flowchart for registering an unclear alignment pattern image as a thinned alignment mark pattern image.

  FIG. 8 is a diagram schematically showing the progress of the pattern image forming process according to the second embodiment executed by the alignment calculation processing unit at that time.

  When the luminance peaks between the materials are close or noise cannot be sufficiently reduced, as shown in FIG. 8A, a large number of isolated points (both in the pattern portion and the background portion in the alignment mark pattern image) Noise) may get on.

  Such an unclear pattern occurs, for example, when a pattern of different materials is formed on a wafer, when luminance peaks between the materials are close, or when noise cannot be sufficiently reduced.

  At this time, after obtaining the pattern image of the alignment mark (S701), the user first performs an S / N improvement process on the image (S702).

  The user first binarizes the pattern image subjected to S / N improvement processing (S703), and then uses the user interface device 190 to use the pattern portion (alignment mark) and background portion (alignment mark) of the image. If the pattern area is lighter, the shrinking process described above is selected as the first process, and if it is dark, the expansion process described above is selected as the first process. The second process is selected (S704). This binarization process selection process can be automatically executed by the apparatus-side alignment calculation processing unit 170 based on information stored in advance in the alignment storage device 180.

FIG. 8A shows an example of an image binarized in step S703 described above.
In this case, since the pattern part is brighter than the background part, the expansion process is selected as the first process and the contraction process is selected as the second process. Subsequently, processing is performed according to the selected order.

  The range of the first processing may be set by the user so that the noise (isolated point) inside the pattern image can be erased while checking the processed image using the user interface device 190, or on the device side. The alignment calculation processing unit 170 may detect the largest noise (isolated point) in the pattern image and determine the processing width therefrom.

  When the first processing is added (S704), for example, an image having no noise in the pattern as shown in FIG. 8B can be obtained. Thereafter, a second process is added to this image (S706).

  The range of the second processing may be set by the user so that the background noise (isolated point) can be erased. As in the first embodiment, the pattern width is measured on the apparatus side to determine the pattern. You may set so that a width | variety may become the minimum.

  By adding the above-described series of processing, it is possible to create and register a fine pattern image that is thinned from an unclear pattern image.

  When the alignment is executed, if the processing range is the same as that at the time of registration as in the first embodiment, and the first and second processes are performed on the pattern image collected by the alignment calculation processing unit 170 in the same manner as described above. If there is a problem such as noise remaining as a result of contraction and expansion processing (S707), or a part of the pattern is missing (S708), the processing range and the binarization threshold value are changed on the apparatus side. Alternatively, the user interface device 190 may be used to change the user.

1 Foreign matter inspection device,
2 Wafer 3 Chip 4 Alignment mark 10 Illumination part (foreign matter detection system),
20 detection unit (foreign matter detection system),
30 X scale,
40 Y scale,
50 Illumination unit (surface height position detection system),
60 detector (surface height position detection system),
70 Inspection stage 80 Alignment detection system,
100 processing equipment,
110 (111, 112) A / D converter,
120 (121, 122) image processing apparatus,
130 foreign matter determination processing unit,
131 judgment circuit 132, 133 table
140 coordinate management device,
150 test result storage device,
160 stage controller,
170 Alignment Calculation Processing Unit 180 Alignment Storage Device 190 User Interface Device 191 Image Display Unit 192 Input Unit 200 Alignment Measuring Device 400 Reference Alignment Mark

Claims (2)

Foreign matter present on the surface of the inspection object by irradiating the surface of the inspection object with a light beam, obtaining an image signal from the received light intensity of reflected light or scattered light, and comparing with an image signal obtained from an adjacent inspection object In foreign matter inspection equipment that inspects the presence or absence of
An apparatus for collecting image data including a pattern image of an alignment mark formed on the surface of the object to be inspected and contoured with multiple frame lines including a double frame line ;
An analysis means for obtaining a luminance distribution for each pixel of the collected image data ;
Based on Brightness distribution obtained by the analysis means, measures a frame distance between multiple border attaching outline the shape of the alignment marks in the pattern image of the alignment marks the collected, is determined on the basis of inter the frame distance After applying a luminance value replacement process to the pixels surrounding each frame line with the processed width to form a single frame alignment mark pattern image that connects adjacent frame lines, the single frame alignment mark pattern A single-frame alignment mark pattern that is thinned by measuring the frame thickness in the image and performing a luminance value substitution process on the frame edge pixels of the single frame with a processing width determined based on the frame thickness. A foreign matter inspection apparatus comprising processing means for converting an image . A sampling step for collecting image data including a pattern image of an alignment mark formed on the surface of the object to be inspected and contoured with multiple frame lines including a double frame line ,
Analysis step you get a luminance distribution of each pixel of the image data the collected,
Based on Brightness distribution obtained by the analysis process, to measure the frame distance between multiple border attaching outline the shape of the alignment marks in the pattern image of the alignment marks the collected, is determined on the basis of inter the frame distance After applying a luminance value replacement process to the pixels surrounding each frame line with the processed width to form a single frame alignment mark pattern image that connects adjacent frame lines, the single frame alignment mark pattern A single-frame alignment mark pattern that is thinned by measuring the frame thickness in the image and performing a luminance value substitution process on the frame edge pixels of the single frame with a processing width determined based on the frame thickness. An alignment adjustment method including a processing step for converting an image .

Images