JP5372618B2 - Patterned substrate inspection apparatus and patterned substrate inspection method - Google Patents

Description

  The present invention relates to a patterned substrate inspection apparatus and a patterned substrate inspection method, for example, formed on a substrate (for example, a semiconductor wafer or a glass substrate) through a thin film process typified by a semiconductor manufacturing process or a flat panel display manufacturing process. The present invention relates to an apparatus and an inspection method for detecting a defect or a foreign matter of a fine pattern.

  As a conventional substrate inspection apparatus with a pattern, for example, there is JP-A-62-270739. In other words, in order to suppress the erroneous detection of defects due to the influence of scattered light from the normal pattern portion, the inspection device is equipped with a light detection function for detecting only the P-polarized light in the light receiving portion and the light receiving portion. This makes it possible to detect with high sensitivity only foreign matters that really need to be detected.

JP-A-62-70739

  However, the inventor has confirmed that in the above-described prior art, erroneous detection of defects may increase. For example, in a memory product wafer, in the memory cell portion for recording information, the detection function can suppress erroneous detection of defects due to the influence of scattered light from the normal pattern portion, but in a large pattern portion such as an I / O portion. There is a problem that the detection function cannot suppress erroneous detection of defects due to the influence of scattered light from the normal pattern portion, and cannot detect only the defects that need to be detected.

  One object of the present invention is to discriminate between an area where the detection function can suppress erroneous detection of defects due to the influence of scattered light from the normal pattern portion and an area where the detection cannot be suppressed, and the two areas are inspected differently. It is an object of the present invention to provide a patterned substrate inspection apparatus or a patterned substrate inspection method that can detect only defects that really need to be detected with high sensitivity.

  To achieve the above object, one feature of the present invention is generated from an illumination system that illuminates obliquely with a desired light beam on a surface of an object to be inspected placed on a stage, and a portion illuminated by the illumination system. A condensing optical system for condensing scattered light reflected in an arbitrary direction; a detection optical system having photoelectric conversion means for receiving the scattered light collected by the condensing optical system and converting it into a luminance signal; and In a substrate inspection apparatus with a pattern including a determination unit that detects a defect on the inspection object based on a luminance signal detected by a detection optical system, erroneous detection of a defect due to an influence of scattered light from a normal pattern unit In order to suppress, the illumination system is an S-polarized beam, the detection optical system has a light detection function for detecting only P-polarized light, and the inspection area has a defect due to the influence of scattered light from a normal pattern portion. To reduce false positives An area as possible, to discriminate the region can not be suppressed, in carrying out the inspection in the inspection process differently the two regions.

  Here, the inspection area in which erroneous detection of defects is suppressed includes a memory cell portion which is a pattern having a pattern width equal to or smaller than the wavelength of illumination light, and a bare portion having no pattern. The inspection area in which erroneous detection of defects cannot be suppressed is an edge portion of a pattern portion having a pattern width larger than the wavelength of illumination light.

  According to one aspect of the present invention, in a patterned wafer inspection apparatus, it is possible to detect with high sensitivity a pattern defect such as a foreign substance or a short that really needs to be detected.

It is an example of composition of an inspection device of an example of the present invention. It is an example of the wafer circuit pattern of the memory product of the Example of this invention. It is explanatory drawing which misdetects a defect in a comparative example. It is explanatory drawing of an example of the defect detection of the inspection apparatus of the Example of this invention. It is an example of the defect detection flow of the inspection apparatus of the Example of this invention. It is an example of the apparatus operation screen of the inspection apparatus of the Example of this invention. It is an example of the test | inspection flow of the test | inspection apparatus of the Example of this invention.

  An embodiment of a patterned wafer inspection apparatus according to the present invention will be described with reference to the drawings.

  First, FIG. 1 shows an example of a wafer inspection apparatus with a pattern for realizing the embodiment. A wafer 113 which is an object to be inspected placed on a stage 114 whose position coordinates are measured and controlled to travel in the XY directions, a light source 102 composed of a light source obtained by polarizing an Ar laser having a wavelength of 488 nm, for example, into S-polarized light, and a reflecting mirror 103, an oblique illumination optical system 101, a condenser lens 106 that illuminates illumination light 104 onto the wafer 113 and collects scattered light reflected from the wafer 113, a photomultiplier, a CCD camera, a CCD sensor, The scattered light received and received from at least one of the TDI sensor and the like is converted into an analog luminance signal by the photoelectric converter 108 and the polarizing plate 107 that transmits only the P-polarized light component in the scattered light reflected from the wafer 113. An analog luminance signal output from the configured detection optical system 105 and the photoelectric converter 108 is converted into a digital luminance signal. An A / D converter 109 for conversion, a stage controller 112 for controlling the travel of the stage 114 based on the position coordinates measured from the stage 114, and a luminance signal for detecting a defective portion in synchronization with the travel of the stage 114. And a general control unit 111 that controls the stage controller 112 and further controls the determination unit 110 and receives a test result obtained from the determination unit 110.

  As the determination unit 110, for example, a dedicated digital signal circuit that can perform pipeline processing in synchronization with the scan clock of the photoelectric converter 108 that scans in synchronization with the travel of the stage 114 can be used.

  As a processing method of the determination unit 110, there is also a method in which the output of the A / D conversion unit 109 is temporarily stored in a memory and processed asynchronously, for example, without performing the synchronous processing as described above. When processing asynchronously, the inspection speed is generally slow, but a dedicated signal processing circuit is not required, and the circuit scale can be reduced. In addition, although not shown, a registration unit that stores past data as experience values may be included in the determination unit 110 or in the inspection apparatus.

  Next, it will be described how the signal processed by the A / D conversion unit 109 of such an inspection apparatus looks when it is an image arranged two-dimensionally by the determination unit 110.

  The BF image (bright field image) on the upper side of FIG. 2 shows how a wafer circuit pattern of a normal memory product can be seen with a bright field microscope. The circuit pattern is roughly divided into the following three parts. That is, an L / S (line and space) pattern 204 of a memory cell portion having a pattern width pattern equal to or smaller than the wavelength of the light source 102, a pattern portion 205 having a pattern width pattern larger than the wavelength of the light source 102, and any pattern. There is no bear part 206. The L / S pattern 204 of the memory cell portion is a bit portion for recording information. A large pattern portion 205 is an I / O portion for controlling a memory address or the like. The bare portion 206 is a portion where no circuit is formed.

  A dark field image in which such a circuit pattern is two-dimensionally arranged by the determination unit 110 of the patterned substrate inspection apparatus is shown as a DF image on the lower side of FIG. The L / S pattern 204 in the memory cell portion often has an L / S pitch that is less than or equal to the wavelength of the light source 102, and in that case, it looks dark. In the pattern portion 205 having a pattern with a pattern width larger than the wavelength of the light source 102, the edge and the elbow portion appear bright. The bear portion 206 having no pattern looks dark. Further, the foreign matter or short 201 on the L / S pattern 204 of the memory cell portion appears as a bright luminescent spot. This foreign object or short 201 is a defect that needs to be detected. If hillock or grain 202 is detected, it is a pattern that is determined to be a false detection of detection, but does not shine due to the detection function of detection optical system 105. The foreign matter 203 on the bare part 206 appears as a bright luminescent spot.

  FIG. 3 compares the DF image of the circuit pattern of the first die on the wafer to be inspected as seen above with the DF image of the corresponding circuit pattern on the adjacent second die on the same wafer. As a comparative example of the embodiment, a state in which the determination unit 110 determines that a defect is detected if a difference of more than a certain luminance remains.

  As shown in FIG. 3, a DF image (see the upper left portion of FIG. 3) of the large pattern portion edge 306 of the die A301 corresponding to the first die and a large pattern portion edge 306 of the die B302 corresponding to the second die. In the DF image (see the upper right part in FIG. 3), a difference in luminance appears. This is because there is a slight difference in the BF image, and even in a portion where the defect detection is not required, a large difference is caused in the DF image viewed with scattered light. The inventor has confirmed that this tendency is further increased by the elbow portion 307 having a 90 ° angle of the large pattern portion edge 306 having a pattern having a pattern width larger than the wavelength of the light source 102 by the light detection function of the detection optical system 105. . Accordingly, when the difference image 303 (see the lower part of FIG. 3) is calculated and a portion larger than the set threshold value is determined as a defect, not only the foreign matter or short 304 or foreign matter 305 to be originally detected but also a pattern portion larger than the wavelength of the light source 102 The elbow part 307 which is a part of the edge 306 is erroneously detected. This is the reason why the false detection of defects sometimes increases in the technique of the comparative example.

  Therefore, the inventor uses hillocks or grains such as the L / S (line and space) pattern 204 of the memory cell portion which is a pattern having a pattern width equal to or smaller than the wavelength of the light source 102 and the bare portion 206 having no pattern. The inspection area such as 202, where the erroneous detection is suppressed, and the inspection area where the erroneous detection of the defect such as the elbow part 307, such as the pattern edge 306 larger than the wavelength of the light source 102, are discriminated. Invented a technology to inspect two areas with different inspection methods. An example of this will be described with reference to FIGS.

  A die A401 in FIG. 4 is an inspection die, a die B402 is the right adjacent die, and a die C403 is the same circuit pattern portion of the left adjacent die. Focusing on the same pixel among the three dies, if two or more dies are dark portions, they are set as luminance determination areas 407 and 408. At this time, the darkness that is the determination criterion is approximately equal to or less than a value obtained by adding a margin of several gradations to the darkness when the photoelectric converter 108 is shielded from light. Generally, it is a margin of 2 to 3 gradations, and it is desirable to widen the margin, such as a margin of 5 to 6 gradations, in the case of an inspection target with a lot of noise. The other non-dark parts are designated as die comparison areas 409 and 410. The state of this processing is shown as processing 501 to processing 503 in the flow of FIG.

  In the luminance determination areas 407 and 408, for example, a portion of the image of the die A401 that is equal to or greater than the set threshold value X is determined as a defect. This state is shown in the process 505 of the flow in FIG.

  Further, in the die comparison areas 409 and 410, for example, a portion of the difference image 406 that is equal to or larger than the set threshold Y is determined as a defect. The setting threshold values X and Y may be registered in advance in the apparatus as experience values, or may be reset for each examination. The set threshold values X and Y are determined according to the inspection object.

  In this way, since different defect determination thresholds can be set for the luminance determination areas 407 and 408 and the die comparison areas 409 and 410, only defects that really need to be detected can be detected with high sensitivity. This determination is performed on all the pixels of the inspection die A. This state is shown in processing 506 to processing 507 in FIG.

  As described above, FIG. 5 is an example of a defect detection flow of the inspection apparatus, and the contents thereof are as follows. That is, when the process of FIG. 5 is started (START), image data reading processing 501 and reading of pixels (or areas) corresponding to the same position of each image of the inspection die A, the right adjacent die B, and the left adjacent die C are read. If the pixel (or area) is dark on all three dies based on the image, processing 502 for determining that the pixel (or area) is a “luminance determination area”, processing 503 for determining whether or not it is a luminance determination area, and luminance determination If it is an area (YES), the threshold value X of the luminance determination area is compared with the luminance of the corresponding portion of the die A image. The comparison area threshold Y is compared with the brightness of the corresponding part of the difference image, and if the brightness of the corresponding part is high, the process 504 determines that all pixels (or pre-detection). It is determined whether or not the defect determination has been completed for a predetermined pixel (target pixel) 506, and if it has not been completed (NO), the process returns from the process 507 that makes the determination of the next pixel (or area) to the process 501. If the defect determination is finished (YES), the process of FIG. 5 is finished (END).

  In the examples of FIGS. 4 and 5, the example in which the inspection die and the three right and left adjacent dies are used has been described, but any three dies including the inspection die may be used. Also, in the three dies, if it is a dark part with two or more dies paying attention to the same pixel, it is determined as the luminance judgment areas 407 and 408. However, in any M dies, N or more dies are dark parts. If there are, the luminance determination areas 407 and 408 may be determined. Here, N is an integer smaller than M. In general, N = M−1, but N may be two or more smaller than M.

  Next, an example of the operation of the operator who operates the apparatus and the inspection process in the embodiments of FIGS. 4 and 5 will be described with reference to FIGS.

  First, the inspection mode 601 is set on the inspection condition setting screen 603 in FIG. If the setting threshold values X and Y are registered in the apparatus in advance, “false detection deletion mode” or the like is set. The state of this inspection flow is shown in process 701 in FIG.

  Next, the inspection start button 602 is pressed. The apparatus starts an inspection scan of the wafer, automatically inspects the wafer according to the flow of FIG. 5, ends inspection of all dies, and ends inspection of the wafer. This state is shown in processing 702 to processing 705 in FIG.

  As described above, FIG. 7 is an example of the inspection flow of the inspection apparatus, and the contents thereof are as follows. That is, when the process of FIG. 7 is started (START), a process 701 for inputting an inspection mode on the inspection setting screen, a process 702 for pressing an inspection start button, a process 703 for executing a scan for inspecting a wafer to be inspected. The processing in FIG. 7 is completed through processing 704 in which the determination unit of the patterned substrate inspection apparatus performs defect determination in accordance with the processing flow shown in FIG. 5 and processing 705 in which the wafer inspection is completed (END).

  According to the above, the operator does not need to set an inspection area or the like, and is not bothered by the trouble.

  In addition, as described above, the inspection area is discriminated into an area where the light detection function can suppress erroneous detection of defects and an area where the detection cannot be suppressed, and the two areas are inspected by different inspection processes. Only defects that really need to be detected can be detected with high sensitivity.

DESCRIPTION OF SYMBOLS 101 Oblique illumination optical system 102 Light source 103 Reflection mirror 104 Illumination light 105 Detection optical system 106 Condensing lens 107 Polarizing plate 108 Photoelectric converter 109 A / D conversion part 110 Judgment part 111 Overall control part 112 Stage controller 113 Wafer 114 Stage 201 , 304, 404 Foreign matter or short 202 Hillock or grain 203, 305, 405 Foreign matter 204 L / S pattern 205 of memory cell portion Large pattern portion 206 Bare portion 301, 401 Die A
302,402 Die B
303,406 Difference image 306 Large pattern portion edge 307 Elbow portion 403 Die C
407, 408 Luminance judgment area 409, 410 Die comparison area 601 Inspection mode 602 Inspection start button 603 Inspection condition setting screen

Claims (8)

An illumination unit that illuminates a portion of the surface of the inspection object with desired light; and
A condensing optical system for condensing scattered light from the inspection object;
A light receiving unit that receives the scattered light collected by the condensing optical system and converts it into a luminance signal;
A detection unit for detecting a defect on the inspection object based on the luminance signal;
The illumination light is an S-polarized beam;
The light receiving unit includes a light detecting unit for detecting P-polarized light,
In the detection unit, the inspection area is discriminated into an inspection area in which the light detection unit can suppress erroneous detection of defects, and an inspection area that cannot be suppressed,
These two areas are processed separately,
The inspection area in which erroneous detection of the defect is suppressed is a memory cell portion that is a pattern having a pattern width equal to or smaller than the wavelength of illumination light, and a bare portion without a pattern,
An inspection area in which erroneous detection of defects cannot be suppressed is an elbow portion having an angle of 90 ° at an edge portion of a pattern portion having a pattern width larger than the wavelength of illumination light. In claim 1,
A substrate inspection apparatus with a pattern, wherein the inspection area is discriminated based on a predetermined standard. In claim 2,
The patterned substrate inspection apparatus, wherein the predetermined reference is created based on at least some images of three inspection dies. In claim 2,
A substrate inspection apparatus with a pattern, comprising: a registration unit that stores an experience value that is past data, wherein the predetermined reference is created based on the experience value that is past data. Illuminate the area on the surface of the object under test with the desired light,
Condensing the scattered light from the inspection object,
Receiving the collected scattered light and converting it into a luminance signal;
A patterned substrate inspection method for detecting a defect on the inspection object based on the luminance signal,
The illumination light is an S-polarized beam, and the received light detects P-polarized light. In the detection, the inspection area on the inspection object is made into an inspection area that can suppress erroneous detection of defects and an inspection area that cannot be suppressed. Discriminate,
In these two areas, perform separate inspection processes,
The inspection area in which erroneous detection of the defect is suppressed is a memory cell portion that is a pattern having a pattern width equal to or smaller than the wavelength of illumination light, and a bare portion without a pattern,
An inspection area in which erroneous detection of defects cannot be suppressed is an elbow portion having an angle of 90 ° at an edge portion of a pattern portion having a pattern width larger than the wavelength of illumination light. In claim 5,
A substrate inspection method with a pattern, wherein the inspection area is discriminated based on a predetermined standard. In claim 6,
The patterned substrate inspection method, wherein the predetermined reference is created based on at least some images of three inspection dies. In claim 6,
Memorize experience data that is past data,
The method for inspecting a substrate with a pattern, wherein the predetermined reference is created based on an experience value which is past data.

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