JP5066393B2 - Foreign object / defect inspection / observation system - Google Patents

Description

  The present invention relates to a foreign matter / defect inspection / observation system, for example, a system for detecting and observing foreign matter and pattern defects on the surface of a semiconductor wafer, photomask, magnetic disk, liquid crystal substrate, and the like.

  The current semiconductor device production line aims at cost reduction, short TAT (Turn-around time) and high quality (1) line automation with large diameter wafer, (2) ensuring stable quality, (3) new product Is the main issue. In addition, each company's φ300mm (large-diameter wafer) mass production line is in full operation, and high-efficiency production through automation is in full swing. On the product side, the product group diversified into various segments due to the multi-functionality and high functionality of digital home electronics. It has become an important issue to quickly start up, reduce costs, and ensure quality.

  In the manufacturing process of a semiconductor device, the quality of processing and the generation of foreign matter greatly affect the yield and stabilization of the semiconductor device. For this reason, it is important to detect abnormalities and defects early or in advance and eliminate the cause of defects. This is important for improving the yield of non-defective semiconductor devices, and inspection and analysis of foreign matter and defects after various processes such as lithography and etching. Defect management by

  By the way, as a method of inspecting a defect existing on a circuit pattern formed on a semiconductor substrate, a defect inspection in which a semiconductor wafer is irradiated with white light and the same kind of circuit pattern in a plurality of LSIs is compared using an optical image. The device has been put into practical use. In an inspection method using an optical image, for example, as described in Patent Document 1, an optically illuminated region on a substrate is imaged by a time delay integration sensor, and the image and design information input in advance are provided. There is a method of detecting a defect by comparing with.

  Further, for example, in Patent Document 2, diffracted light or scattered light is detected by irradiating a laser beam, and diffracted light from a regular circuit pattern is discriminated from scattered light from an irregularly shaped foreign substance or defective part. An inspection method for detecting only defects is disclosed.

However, no matter which inspection apparatus is used, it is necessary to set inspection conditions before inspection. In particular, in setting the inspection sensitivity, CMP (C hemical M echanical P olishing) after the micro-scratches, or the like disconnection or short circuit in the wiring process, cause poor in each inspection step DOI (D efect o f I nterest ) High-sensitivity detection and detection of pseudo-defects that do not affect the yield of metal grains used in wiring, etc., and optimize inspection conditions, such as removing pseudo-defects from inspection targets There is a need.

  To optimize inspection conditions, observe and classify actually detected foreign objects and defects, and set parameters based on differences in feature values such as brightness values at the time of detection of DOI and pseudo defects. There is a need. However, due to the rapid miniaturization of semiconductor devices, the size of foreign matter and defects to be managed has also been miniaturized, and the resolution of optical observation cameras attached to conventional inspection equipment has reached its limit. The defect cannot be distinguished.

  There is also a need for new high-resolution observations. Recently, with the latest semiconductor device production line, there has been a need for wafer edge inspection, which was previously inspected at the time of wafer acceptance inspection, for the problem of detecting and managing wafer cracks and yield reduction factors around the wafer. It is growing.

  In addition, automation of inspection / observation increases the operating rate of the apparatus, increasing the risk of physical contact with the wafer due to transfer system misalignment, arm sag, and the like. In particular, care must be taken with respect to aging equipment. On the other hand, batch processing equipment that processes several wafers at a time, mainly heat treatment and cleaning, is used together. However, if a wafer damaged due to the above-mentioned causes is broken in the batch processing equipment, the damage is directly damaged. Considering losses such as equipment start-up time, it is enormous. For these, edge inspection is important for investigating the cause of wafer breakage at an early stage, preventing secondary damage, and preventing detection before the wafer breaks.

  Further, as the diameter of the wafer is increased to 300 mm (large diameter), the yield reduction around the wafer becomes fatal. For example, flakes coming off from the wafer edge and fluctuations in film thickness cause a significant decrease in yield instantly, and edge inspection is effective in analyzing, monitoring and managing the cause. In this regard, various edge processing apparatuses have been introduced as countermeasures for defects caused by wafer edges, but edge inspection is indispensable in determining the conditions of these processing apparatuses and confirming mass production stability.

  However, edge inspection information alone is not enough to investigate the cause of wafer defects and to quickly implement defect countermeasures. The reason is that the optical magnification of the edge inspection is about 50 times, and it is possible to detect a defect and perform a macro analysis, but it is impossible to perform a fatal micro analysis that causes cracks and peeling. When performing preventive detection of wafer cracking, the frequency of 100% inspection is increased, and the time required for analysis and evaluation by observation is greatly increased.

  Therefore, as one of high-resolution observation means, there is an observation method using a scanning electron microscope (SEM). SEM is a technique that scans and irradiates a sample with an electron beam, detects secondary electrons generated from the sample, and displays a secondary electron image of an observation object on the screen of a display device. Observation by an electron beam image is widely adopted for fine structure observation in the field of semiconductor manufacturing because it enables detailed observation of the surface with higher resolution than an optical microscope or laser microscope image. This observation apparatus using an electron beam image is hereinafter referred to as a review SEM.

  The review SEM and the observation method in the review SEM are disclosed in Patent Documents 3 and 4, for example. As described above, for foreign matters or pattern defects detected by the optical appearance inspection and the laser inspection apparatus, the position to be observed can be specified by exchanging position information of these inspection apparatuses, and observed by an electron beam image. By using a review SEM that can be made, it has become possible to observe a detailed shape.

JP-A-3-167456 JP-A-9-138198 JP-A-9-184715 JP-A-10-135288

However, when a review is performed using another device such as a review SEM, it takes time and labor to move the observation sample. In addition, using an apparatus used for product management in setting inspection conditions for an inspection apparatus lowers its operating rate. Furthermore, preparing a plurality of devices for condition setting of the inspection apparatus, or just combine simple apparatus, the cost, would be footprint increases, CoO (C ost o f O wnership) becomes higher End up. When the optical microscope attached to the inspection device is used, the inspection cannot be performed in parallel during the inspection, and the operation rate as the inspection device is lowered, and the sensitivity of the inspection device is set as described above. In addition, since the size of the defect detected at the edge portion is minute, there is a drawback that it is difficult to distinguish DOI and pseudo-defect with an optical microscope.

  The present invention has been made in view of such a situation, and provides a foreign object / defect inspection and observation apparatus capable of appropriately distinguishing DOI and pseudo-defect and further reducing CoO.

  In order to solve the above problems, the foreign matter / defect inspection / observation system of the present invention detects a foreign matter or defect on the wafer and outputs the coordinate information thereof, and observes the detected foreign matter or defect. And an observation unit composed of a review SEM. The observation unit includes a rotation stage that functions as a pre-aligner in the sample chamber and a stage moving unit that moves the rotation stage in one direction perpendicular to the rotation axis. That is, this rotary stage functions as both a pre-aligner stage and an observation sample stage.

  That is, the foreign matter / defect inspection / observation system according to the present invention is a foreign matter / defect inspection / observation system that detects foreign matter and defects of an inspection object and outputs defect information, and detects the foreign matter and defects of the inspection object. The inspection unit that outputs the coordinate information of the foreign object and the defect, the observation unit for observing the foreign object and the defect of the inspection object detected by the inspection unit, and the inspection unit and the observation unit A transport unit that performs mounting and removal, and transports an object to be inspected between the inspection unit and the observation unit, an inspection unit, an observation unit, and a control unit that controls the operation of the transport unit. The observation unit includes a rotation stage on which the inspection object is rotatably mounted, reference position detection means for detecting a reference position of the inspection object mounted on the rotation stage, and the rotation stage perpendicular to the rotation axis. Defect that has stage moving means that moves in one axis direction and an electron optical system that irradiates a charged particle beam to the inspection object mounted on the rotary stage, and detects defect signals by acquiring signals generated from the inspection object An information detection unit and a sample chamber that accommodates the rotary stage are provided. Further, the control unit controls the rotation operation of the rotary stage and the movement operation of the stage moving means based on the coordinate information of the foreign matter and the defect of the inspection object. Furthermore, you may make it provide the vacuum formation means which makes a sample chamber a vacuum state.

  Further, the inspection unit detects foreign matters and defects while distinguishing them from the pseudo defects in the inspection object based on the inspection conditions including the threshold value relating to the set detection signal. As a result of the observation by the observation unit, when the foreign object detected by the inspection unit and the target object that is a defect include a pseudo defect, the system is controlled to change the inspection condition.

  In addition, the electron optical system includes an irradiation unit that irradiates a charged particle beam from at least one of a vertical direction, a horizontal direction, and a tilt direction with respect to an inspection object, and a signal detection unit that detects a signal generated by the irradiation. Have Thereby, observation of the surface and edge part of a to-be-inspected object is enabled.

  Further, when the coordinate information of the foreign matter and the defect is expressed in the XY coordinate system, the coordinate information is converted into the coordinate information of the polar coordinate system with a predetermined point of the inspection object as the origin. Then, based on the coordinate information of the polar coordinate system, the rotary stage and the stage moving means are operated so that the corresponding foreign matters and defects can be observed, and the image represented by the defect information is rotationally corrected. As a means for rotational correction, a method for controlling the scanning direction of the charged particle beam and a method for rotationally correcting an image by image processing are conceivable.

  In addition, the defect information obtained by observation based on the coordinate information of the foreign matter and defect of the first pattern formed on the inspection object, and the foreign matter of the first pattern in the adjacent second pattern And observation information obtained by observing the position in the second pattern corresponding to the coordinate information of the defect may be output so that both can be compared.

  Further, the deviation amount between the polar coordinate system of the object to be inspected and the polar coordinate system of the rotary stage may be calculated and corrected. Furthermore, fine adjustment means for finely adjusting the display position of the image represented by the defect information may be provided. In this case, the fine adjustment result may be registered in the storage unit as an offset amount for display position correction.

  Further features of the present invention will become apparent from the following best mode for carrying out the invention and the accompanying drawings.

  According to the system of the present invention, DOI and pseudo defects can be appropriately distinguished, and CoO can be kept low.

  The foreign matter / defect inspection / observation system according to the present invention sets inspection conditions capable of appropriately distinguishing foreign matters and defects from pseudo-defects that do not affect the yield of metal crystal grains (grains) used for wiring. Thus, when performing simply by high-resolution observation, the hardware of the conventional defect inspection apparatus can be greatly improved without requiring a large increase in footprint.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be noted that this embodiment is merely an example for realizing the present invention, and does not limit the technical scope of the present invention. In each drawing, the same reference numerals are assigned to common components.

<Configuration of foreign matter / defect inspection / observation system>
FIG. 1 is a diagram showing an external configuration of a foreign object / defect inspection / observation system 10 according to an embodiment of the present invention. In FIG. 1, a foreign matter / defect inspection / observation system 10 includes a wafer pod 104 for storing a wafer 099, an opener 105 for opening and closing the lid of the wafer pod 104, and a transfer unit for storing a transfer robot 206 for transferring the wafer. 101, an optical system including a sensor and a light source, a stage, etc., and a main body (optical inspection apparatus) 102 for inspecting the wafer 099, inspection sensitivity (condition) setting calculation, operation of each mechanism, observation unit An observation information / image output (display on a display unit not shown) acquired at 100 and an operation / control unit 103 for performing various controls and an observation unit 100 are provided. In addition to these components, the foreign object / defect inspection / observation system 10 includes a power supply unit for supplying power to each unit, an image processing unit for processing and storing data, and the like (not shown). May be.

  The observation unit 100 is a characteristic part of the present invention, and includes a charged particle beam source that irradiates a charged particle beam to a wafer aligner unit that performs conventional wafer alignment, a detector that detects a signal generated from a sample, and the like. The configuration includes an electron optical system. The charged particle beam source may be an ion beam source such as gallium or a field emission type electron beam source. As a specific example of the present invention, an electron optical device such as an electron gun that can be observed in a low vacuum will be described below. The system configuration will be described based on a configuration using a filament type electron beam source that can be easily miniaturized.

<Internal configuration of observation unit and transport unit>
FIG. 2 is a diagram illustrating a schematic configuration of the inside of the observation unit 100 and the conveyance unit 101 that constitute the foreign object / defect inspection / observation system 10. The observation unit 100 is replaced with a wafer aligner rotation mechanism that performs alignment by detecting the center position and orientation based on the crystal orientation reference, such as a conventional wafer orientation flat (orientation flat) or V notch. The direction perpendicular to the rotation axis (z-axis direction) (x-axis direction, y-axis direction, etc.) may be perpendicular to the z-axis. In FIG. 2, the rθ stage 203 is configured to be movable in the x-axis direction. The rθ stage 203 is operated. Similar to the conventional wafer aligner, the rθ stage 203 includes a wafer chuck 210 that holds the wafer and a wafer reference detector 208 that detects the center position and orientation from the reference of the crystal orientation such as orientation flat and V notch. It follows the function.

  Above the rθ stage 203, a wafer chamber 099 is inserted by a transfer robot 206, and a sample chamber 202 is provided for maintaining a vacuum around the wafer. An electron optical system 201 including an electron beam source for irradiating an electron beam, a detector for detecting a signal generated from the sample, and the like is provided on the upper portion of the sample chamber 202. Also, the sample chamber 202 and the electron optical system 201 are depressurized at the lower part of the rθ stage 203, and a vacuum exhaust device 204 for creating a vacuum state is removed, and the upper part of the rθ stage 203 is subjected to vibration isolation, thereby disturbing disturbances during electron beam observation. A seismic isolation mechanism 205 is provided.

  FIG. 3 is a diagram showing a comparison of operating ranges of the rθ stage 203 and a general XY stage. Here, a case is considered in which the stage is operated with respect to the fixed observation position and the observation object is moved to the observation position. In the case of the rθ stage 203, in order to observe the entire surface of the wafer 099, the working distance 211 of the wafer chuck 210 may be only a distance corresponding to the radius of the wafer 099. For example, the entire wafer surface can be observed in the operating range 301 of the rθ stage in the operating range of 150 mm for a 300 mm wafer and 100 mm for a 200 mm wafer. On the other hand, when the entire surface of the wafer is observed on the XY stage, the operating range is as the XY stage operating range 302, and one side needs a square that is four times the radius of the wafer, and is approximately 2.7 times the operating range 301 area of the rθ stage 203. It becomes. For this reason, if the rθ stage 203 is adopted, not only the footprint increase of the entire apparatus can be suppressed, but also the size of the sample chamber 202 can be reduced. Therefore, it is possible to reduce the time required for decompression for evacuating the sample chamber 202 when observing the sample after the inspection, and it is possible to reduce the time required for observation.

  FIG. 4 is a diagram illustrating a schematic configuration of the electron optical system 201. The electron optical system 201 includes an electron gun unit 401 that emits an electron beam 400, a condenser lens 404 for focusing the electron beam, an objective lens 406 for focusing, and a deflection coil 405 for scanning an electron beam. A column unit 402 and installed in the upper part of the sample chamber 202.

  The irradiated electron beam 400 is two-dimensionally scanned by a two-stage deflection coil 405 and irradiated onto the wafer 099. The signal generated by the electron beam 400 passes through the signal detector 407 and the amplifier 408, is scanned by the CRT side deflection coil 409, and is projected onto the CRT 410. As described above, in the SEM observation, an image can be obtained by synchronizing the scanning of the electron beam on the sample and the pixel scanning of the CRT. Further, the rotation of the image can be changed by changing the scanning direction of the electron beam on the sample, and the magnification can be changed by changing the scanning range. This rotation and magnification change of the image is realized by the adjuster 411 and the polarization amplifier 412.

<Operation from inspection of foreign matter / defect to observation>
FIG. 5 is a flowchart for explaining an operation example from inspection to observation (review) of foreign matters and defects on the wafer. The operation / control unit 103 controls the operation of the entire system. The steps from S01 to S06 in FIG. 5 are performed up to the output of the inspection result as in the conventional foreign matter / defect inspection system.

(1) First, in step S 01, the wafer 099 is taken out from the wafer pod 104 by the opener 105 and the transfer robot 206 and placed on the wafer chuck 210 on the rθ stage 203.

(2) In step S02, the reference of the crystal direction of the wafer 099, such as orientation flat and V notch, is detected by the detector 208 in the same manner as the wafer aligner, and the direction of the wafer 099 is obtained. Since it is not necessary to evacuate the sample chamber 202 at this stage, priority is given to throughput, and the process is performed under atmospheric pressure as usual.

(3) In step S03, the wafer 099 is transferred again by the transfer robot 206, passes through the main body shutter 207, and is placed on the stage (not shown) of the main body 102 based on the detected wafer direction.

(4) In step S04, conditions for inspection are set. Various conditions can be set from the operation / control unit 103 as in the conventional inspection apparatus. In setting the conditions, the wafer alignment is performed using the pattern of the semiconductor device created on the wafer 099. The alignment method follows the method of the conventional inspection apparatus, and performs rotation correction between the stage coordinate system of the inspection apparatus and the coordinate system of the pattern of the semiconductor device created on the wafer 099. When the inspection object does not have a pattern such as a bare wafer, it is desirable to perform center correction using coordinates of arbitrary three points on the wafer outer periphery and θ correction at two points on the wafer reference such as a V notch. Further, in order to set the inspection conditions, design information such as the die size (circuit size) of the semiconductor device created on the wafer 099 is input in the case of pattern inspection as in the case of a conventional inspection apparatus. At this time, following the function of the conventional inspection apparatus, it is possible to measure the die size based on the information from the observation camera, or to directly input information such as the die size to create a pattern arrangement diagram. It is assumed that high-accuracy inspection can be performed by following the functions and setting methods of the conventional inspection apparatus for the threshold value and other inspection parameters for determining inspection sensitivity.

(5) In step S <b> 05, the foreign body / defect inspection is performed in the main body (optical microscope) 102. In the pattern inspection, a pattern image is acquired in the adjacent dies having the same type of pattern formed on the wafer 099 or in the memory mat of the memory device having the same repeated pattern. Then, while comparing the same patterns, those determined as different patterns are detected as foreign matters / defects. Regarding the detection of foreign matter / defects, the number of defects varies depending on the inspection conditions (including threshold values) set in step S04. Therefore, the present system 10 has a function of confirming how the number of detected defects changes in conjunction with an arbitrarily set inspection condition (including a threshold value).

(6) In step S06, inspection data including design information such as the size of the pattern created on the wafer 099 and coordinate information of the detected defect / foreign matter is output as an inspection result. At this time, it is desirable to output a defect MAP in which the defect position is written on the wafer based on the information. FIG. 6 shows an example of a defective MAP. It is desirable that the display method can be changed for each defect feature, for example, the size, as in the conventional inspection apparatus. If the inspection result obtained in step S06 is expressed in the XY coordinate system, the process proceeds to step S07. On the other hand, when the stage on the inspection apparatus side such as a defect inspection apparatus using scattered light is the rθ stage, the process proceeds to step S08 as it is because it originally has defect / foreign matter coordinate information in polar coordinates.

(7) In step S07, the coordinate information of the defect / foreign matter expressed in the XY coordinate system is converted into the rθ coordinate system. The defect coordinate information is generally displayed as coordinates from an arbitrary point on the pattern or stage, or from the address of the die on the wafer 099 and the origin of each die. If the coordinates from the origin of each die are x and y, respectively, conversion to the rθ coordinate system can be realized by Equation 1. In this embodiment, the defect coordinate information is provided in a plurality of formats, and each is converted into the rθ coordinate system. Note that the die address is generally expressed as an integer in x and y on the XY coordinate plane with the position of the arbitrarily set reference die 601 as (0, 0) and the reference die as the origin. Further, the converted coordinate information may be stored in a memory unit (not shown) or / and transmitted to another device or system via a network or other medium (not shown).

(8) In step S08, contrary to step S03, the wafer 099 is transferred from the stage of the main body 102 to the observation unit 100 by the transfer robot 206 and mounted on the wafer chuck 210 of the rθ stage 203 of the observation unit 100. Placed.

(9) In step S09, the sample chamber 202 is depressurized by the vacuum exhaust mechanism 204 to a degree of vacuum that can be irradiated with an electron beam. In this embodiment, since the rθ stage 203 is employed, the volume of the sample chamber 202 can be designed to be smaller than that of the XY stage. Therefore, the evacuation time can be shortened. In general, the chuck of the wafer aligner often uses a vacuum suction method, but in this embodiment, since the inside of the sample chamber 202 is depressurized, another method such as an edge grip or the like is desirable.

(10) In step S10, based on the foreign object / defect coordinate information in step S07, the wafer 099 is moved so that the characteristic object (denoted as foreign object / defect) is positioned under the objective lens 406, and the characteristic object is moved. Observe. For observation, coordinate information (orthogonal coordinate system) obtained from the inspection apparatus is converted into a polar coordinate system, and observation is performed by moving the rθ stage 203 to the observation object position. When the wafer 099 is placed on the rθ stage 203, the observation is performed. Coordinate information (orthogonal coordinate system) is converted into a polar coordinate system due to a deviation that occurs, for example, a deviation in the θ direction or a deviation between the rotation axis of the rθ stage 203 (the origin of polar coordinates) and the origin of the wafer coordinates (origin of orthogonal coordinates). In some cases, accurate observation may not be possible.

  Therefore, the amount of deviation between the wafer coordinate system and the rθ stage coordinate system is confirmed and corrected (alignment) every time before observation. For alignment, semiconductor device design information such as die size, die arrangement information (for example, how many dies of 10 mm × 10 mm, etc.), coordinates of the origin, and the like are used. However, if the information input at the time of setting the conditions of the inspection apparatus is diverted, the labor of new input can be saved. Hereinafter, the process of step S10 will be described in detail.

  i) First, with reference to FIG. 13, a description will be given of correction when there is a shift of α in the θ direction and a shift of (a, b) at each coordinate origin in the wafer coordinate system 1301 and the rθ stage coordinate system 1302. An example will be described in which two reference points on the wafer coordinate system 1302 are selected, but points having the same Y coordinate are selected. Further, the reference point is preferably a place where the origin of each die in the wafer coordinate system, an alignment mark or the like can be easily confirmed. The coordinates of the reference points are (Xa1, Y), (Xa2, Y), the coordinates when polar coordinates are converted are (r1, θ1), (r2, θ2), and the rθ stage coordinate system where the reference points actually exist When the above coordinates are (r3, θ3) and (r4, θ4), respectively, the shift amount α in the θ direction of the wafer coordinate system 1301 and the rθ stage coordinate system 1302 can be obtained from Equation 2.

  Since the origin 1303 of the wafer coordinate system is obtained from the main body (inspection apparatus) 102 together with the defect coordinate information, a defect on the rθ stage coordinate system at an arbitrary point (r ′, θ ′) on the wafer coordinate system. The coordinates (r, θ) can be obtained by the coordinate conversion formula of Formula 3.

  Furthermore, by registering the pattern image used for alignment and the coordinate information of the pattern, it is assumed that alignment can be automatically performed as usual. At this time, the rotation of the observation image occurs, for example, the pattern top and bottom is inverted depending on the observation position on the rθ stage 203, but it is assumed that the image to be registered as usual can be minimized by image correction described later.

  In the observation on the rθ stage 203, since the wafer 099 is rotated by the value of θ, an image rotated by the value of θ is displayed when the scanning direction of the electron beam on the sample and the scanning direction on the CRT side are the same. FIG. 7 shows an example in the case of 45 ° rotation. When rotated by 45 °, the pattern on the observation position 702 is rotated by the value of θ as the pattern 703 on the wafer rotated by 45 °. In the case of 704 in which the electron beam 400 is scanned in the horizontal direction in the same manner as the CRT with respect to the pattern 703 on the wafer 099 rotated by 45 °, the pattern is also rotated by 45 ° on the CRT like the observation image 705 in the horizontal scan. Yes. Therefore, the rotation of the image is corrected by changing the scanning direction of the electron beam according to the value of θ of the observation object on the sample, and in the case of 706 scanned in the 45 ° direction, the wafer 099 is always displayed as in the observation image 707. Assume that the top and bottom of the pattern created above can be accurately displayed.

  Image rotation correction can be realized by a method of performing rotation correction on a stored image in software, or by using a confirmation and alignment registration image after automatic observation. As shown in FIG. 7, for example, the observation image 705 in the horizontal scan is stored as electronic data, and the upper and lower sides of the pattern can be accurately adjusted as in 708 by correcting and rotating the software in accordance with the θ value. It can be displayed.

  In addition, as with a conventional electron microscope, a rotation-corrected image can be displayed on a CRT in conjunction with a numerical input method or the rotation of an adjustment knob on an interface. Thus, fine adjustment can be made when there is a shift of θ that cannot be corrected by the rotation correction from the defect coordinate information described above. Furthermore, by providing a function that allows the θ correction amount at the time of fine adjustment to be registered in a memory (not shown) as an θ correction offset amount, it is possible to perform observation with higher accuracy during automatic review (observation). can do.

  ii) Further, when it is difficult to confirm the position of the defect on the screen, the defect may be moved to the same in-die coordinate (x, y) of the adjacent die to confirm whether or not it is a defect. In the case of the XY stage, movement to the same in-die coordinates is performed based on die pitch size information. On the other hand, the rθ stage 203 can also be moved by Expression 4 based on the die pitch in the x and y directions and the destination die address (X, Y).

  Here, Dx: x direction die pitch, Dy: y direction die pitch, X: die address X, Y: die address Y.

  Moreover, the movement to the adjacent die is also necessary when performing observation automatically. In the automatic observation, an image of the defect coordinate portion (defect image) and an image of the coordinates in the same die of the adjacent die (reference image) are acquired, and the defect position is specified from the difference (difference image). Note that it is desirable that the observation position can be moved (moved to the adjacent die) by inputting a move button or a die address to the adjacent die, clicking on the wafer map, or the like, as in the past. Furthermore, the movement to any point on the wafer can be performed by inputting the die address on the die matrix and the coordinates in the die in the XY coordinate system, as in the movement on the XY stage. It is assumed that it can be converted to

  When observing a wafer that has no pattern, such as a bare wafer, the wafer center calculation / correction using the coordinates of any three points on the wafer periphery, and two points on the wafer reference, such as a V-notch, as in the inspection. It is desirable to perform θ correction. This operation can be performed manually or automatically as in the conventional review SEM.

  iii) Next, the observation of the wafer edge portion will be described with reference to FIGS. FIG. 8 is a diagram illustrating a configuration example in the case where the electron beam 400 is irradiated from the vertical direction to the wafer 099. As shown in FIG. 8, when the electron beam 400 is irradiated vertically, the electron gun unit 401 and the column unit 402 that perform the electron beam irradiation are in the r operation direction of the rθ stage 203 in order to observe the entire surface of the wafer 099. Installed on the line. In addition, one or both of the backscattered electron detector 801 and the secondary electron detector 803 are installed above or above the wafer 099. The number to be installed is determined based on the high yield of reflected electrons and secondary electron signals, the arrangement space, and the like. When a plurality of sensors are arranged, the information obtained by switching the detectors changes, so the optical system 201 has the same function as a conventional electron microscope.

  The movement to the observation position in the case of FIG. 8 is executed based on the defect coordinate information of the rθ coordinate system, similarly to the observation of the patterned wafer.

  In the case of FIG. 8, the irradiation of the electron beam 400 from the vertical direction with respect to the wafer 099 is the most general method, but the observable range is only the front bevel and the surface. If the front bevel can be observed, it is possible to check for cracks, scratches, etc. that cause the wafer to crack. However, when observing in more detail, it is desirable to use together with the method mentioned later.

  FIG. 9 is a diagram showing an example in which the electron optical system 201 is installed in the horizontal direction. In this case, the backscattered electron detector 802 is installed at a horizontal position where the electron beam 400 is irradiated. Accordingly, in FIGS. 1 and 2, the electron optical system 201 is in a normal state protruding in the y-axis direction. The secondary electron detector 803 is installed above or below the wafer 099. Similarly to the irradiation from the vertical direction, one or both of the backscattered electron detector 802 and the secondary electrons 803 are installed as single or plural. The number to be installed is determined based on the high yield of reflected electrons and secondary electrons, the arrangement space, and the like. When a plurality of sensors are arranged, information obtained by switching detectors changes, and therefore the electron optical system 201 has the same function as a conventional electron microscope.

  When the electron optical system 201 is installed in the horizontal direction (in the case of FIG. 9), the observable range is the back bevel portion, the top portion, and the front bevel portion. In the case of the configuration of FIG. 9, the electron gun unit 401 and the column unit 402 that perform electron beam irradiation so that the distance (WD: Working Distance) between the objective lens of the electron optical system 201 and the wafer 099 can be changed by the operation of r, The rθ stage 203 is installed in the same direction as the r operation direction. By shortening the WD, high-resolution observation is possible, and by widening the WD, the scan width of the electron beam can be increased, and a wide range observation similar to an optical image is possible. In addition, when the WD of the electron optical system 201 and the wafer 099 installed at the horizontal position is set, the coordinates of the observation object are converted corresponding to the set value.

  Further, when the electron optical system 201 is installed in the horizontal direction (FIG. 9), alignment between the rotation center of the rθ stage 203 and the center of the observation object can also be performed from the values of θ and r at the time of observation. In particular, with respect to r, the deviation between the rotation center of the rθ stage 203 and the center of the wafer 099 appears as an eccentricity when the stage 203 is rotated. It becomes a gap. Therefore, the center position of the wafer can be obtained from the relationship between the focus value set in advance of the observation position and the distance between the observation objects. Similarly, in the rotation correction, the θ correction amount can be calculated from the position of two points on the reference of the wafer, such as a V notch, and the focus shift amount.

  FIG. 10 is a diagram illustrating a configuration example of the electron optical system 201 when the wafer 099 is irradiated with the electron beam 400 inclined. In this case, it is desirable that the backscattered electron detector 802 is installed at a position where the electron beam 400 is irradiated and the secondary electron detector 803 is installed above the wafer 099. In addition, as in the case of irradiation from the vertical direction (FIG. 8), one or both of the detectors are respectively installed in a single or a plurality. The number of detectors to be installed and the irradiation angle of the electron beam are determined based on the high yield of reflected electrons and secondary electrons, the arrangement space, and the like, as described above. When a plurality of detectors are arranged, information obtained by switching the detectors changes, so the electron optical system 201 has the same function as a conventional electron microscope.

  When the electron beam 400 is tilted and irradiated, the top portion, the front bevel portion, and the surface can be observed as shown in FIG. Note that the back bevel portion and the back surface can be observed by using a mechanism for reversing the wafer 099 and a chuck that does not touch the back surface, such as a side chuck, as in the conventional wafer back surface inspection apparatus.

  Further, when the electron beam 400 is tilted and irradiated, a shadow image is obtained, so that three-dimensional observation is possible, and it is suitable for observation of fine unevenness, for example, micro scratches. Thus, when the electron optical system 201 is realized only by the configuration in which the electron beam is inclined and irradiated, the obtained image is only a shadow image, and the rθ stage 203 has a plurality of images although the direction of the shadow varies depending on the observation place. By registering, automatic alignment can also be supported.

  FIG. 14 is an example of an outline of alignment. Alignment (wafer alignment) refers to correction of displacement between coordinate systems to enable movement to a singular point on the wafer coordinate system in a coordinate system different from the wafer coordinate system (here, the stage coordinate system). . In terms of hardware, there is a position correction of the wafer and the stage, and in terms of software, a coordinate conversion equation is calculated, and both are usually performed.

  The correction is performed by calculating a deviation amount from the coordinates of a designated point (alignment point) such as the die origin and the coordinates where the alignment point actually exists. When the alignment is performed automatically, the alignment point is identified from the positional relationship between the characteristic pattern created on the wafer and the alignment point. Further, the pattern is specified by superimposing the characteristic pattern image registered in advance and the actual image on the wafer, and the most coincident portion is specified as a registered location.

  Differences in alignment between the rθ stage coordinate system and the XY stage coordinate system will be described with reference to FIG. FIG. 15 shows an example in which a characteristic pattern at the positions of two points a and b existing with the same X coordinate and across the rotation axis of the rθ stage 203 is observed from the direction of A. Since the stage moves in parallel on the XY stage, there is no difference in the direction of shadow. Therefore, if an image is registered at the position a, it can also be used for alignment at the position b.

  However, the rθ stage 203 apparently changes the direction of irradiation (the shadow direction is different), so a plurality of images need to be registered.

  FIG. 16 is an example of a case where two points a and b are extracted without interposing the rotation axis of the rθ stage 203 with the same X coordinate. In this example, when the characteristic pattern is tilted from the direction A, the shadow direction does not differ, and if an image is registered at the position a, it can also be used for alignment at the position b. . If the number of images to be registered is small, the labor required for creating automatic observation conditions is reduced and the storage area required for image storage is reduced. On the other hand, there is a concern that the correction accuracy is low because the alignment is performed in the vicinity.

  Further, when the operating range in the r direction is equal to or larger than the radius of the wafer, the translation can be performed across the rotation axis. If the operating range in the r direction is the same as the diameter of the wafer, the entire wafer can be translated on the same X coordinate.

  However, when the operating range in the r direction is the same as the radius of the wafer, the stage operating range is 4/3 times when the operating range in the r direction is the same as the diameter of the wafer (1/2 for the XY stage). Times). In the present embodiment, an optimum method can be selected from the above-mentioned three means according to the situation.

  By combining the configuration (irradiation method) of the electron optical system shown in FIGS. 8 to 10 alone or in combination, an apparatus configuration suited to the purpose can be realized. Furthermore, when other detectors such as EDS (Energy Dispersion X-ray Spectrometry) are combined, analysis according to different purposes can be performed as in the conventional SEM.

  iV) The observation in step S10 can be automatically performed by comparison with adjacent dies in the same manner as in a conventional semiconductor SEM observation apparatus. In this case, it is necessary to move not only to the coordinates of the feature detected in the automatic observation but also to the coordinates within the same die of the adjacent die, but in this embodiment, only the coordinates of the observation object are converted to polar coordinates. Instead, polar coordinate conversion of the coordinates in the same die of adjacent dies is performed. Since the polar coordinate information of the coordinates in the same die of the adjacent die can be used during manual observation, it is effective when it is difficult to determine the defect position with only the observation object such as a pattern defect. Therefore, also in this embodiment, it is preferable to be able to move to the same in-die coordinates by selecting a specific die on the defect map, as in the conventional observation apparatus.

  V) The order of feature observation in automatic observation is generally calculated by calculating the shortest distance from the defect ID output from the inspection apparatus and the coordinate information of the feature in the XY coordinate system, and in order of the distance. Done along. In the present embodiment, the order in which movement is possible at the shortest distance is calculated from the defect coordinate information in polar coordinates calculated in step S07, and observation is performed in an order that enables efficient automatic review. In addition, in the rθ stage 203, performance differences are expected in the speed and stop systems due to operation in the r and θ directions, so it is desirable to take into account the order setting according to the performance difference.

(11) In step S11, it is determined whether the observed inspection result (determined as a foreign object / defect) includes a pseudo defect. If a pseudo defect is included, the process proceeds to step S03, and condition setting (threshold value setting) is executed again. More specifically, in step S03, the wafer is transferred again by the transfer robot 206, passes through the main body shutter 207, and is placed on the stage of the main body 102 based on the detected wafer direction. If it is determined in step S11 that the agenda defect is not included, the process ends. In this case, the wafer 099 is returned to the wafer pod 104 by the transfer robot 206.

<Application example>
As shown in FIG. 11, high-speed inspection / review can be realized by installing a plurality of observation units 100 and processing automatic reviews in parallel. The review process by the observation unit 100 takes more time than the process of the main body unit (inspection apparatus) 102. Therefore, the throughput is improved by increasing the number of observation units 100.

  Further, as shown in FIG. 12, by specializing in the observation function and executing a plurality of review processes in parallel, the throughput can be significantly improved as compared with the conventional review SEM.

<Summary>
In the foreign substance / defect inspection / observation system according to the present embodiment, a foreign substance or defect on a wafer is detected, coordinate information is output, and the detected foreign substance or defect is observed by an observation unit including a review SEM. The observation unit includes a rotation stage that functions as a pre-aligner in the sample chamber and a stage moving unit that moves the rotation stage in one direction perpendicular to the rotation axis. That is, this rotary stage functions as both a pre-aligner stage and an observation sample stage. By doing so, it is possible to prevent the deterioration of CoO due to the increased footprint without significantly changing the size of the conventional defect inspection apparatus. Further, it becomes possible to perform high-resolution observation of a fine foreign matter / defect that cannot be discriminated by an optical observation function mounted on a conventional foreign matter / defect inspection apparatus without using another observation device.

  Further, based on a threshold value relating to the set detection signal, foreign matter and defects are detected while being distinguished from pseudo defects in the wafer. Then, as a result of observation by the observation unit, if the foreign object detected by the optical inspection unit and the target object as a defect include a pseudo defect, the threshold value is set high again, and the foreign object Perform defect inspection and observation. Thereby, it is possible to optimize the condition setting for defect detection, and thus it is possible to compensate for the defect of defect inspection using an optical microscope that cannot accurately distinguish between DOI and pseudo defects.

  Moreover, the vacuum forming means which makes the sample chamber of an observation part a vacuum state is provided. As described above, since the pre-aligner stage and the sample observation stage are shared, the sample chamber of the observation unit can be reduced in size. Therefore, the time for evacuating the sample chamber can be shortened, and the observation preparation time can be shortened. This is also a feature that contributes to throughput improvement.

  Furthermore, the electron optical system includes an irradiation unit that irradiates the object to be inspected with a charged particle beam from at least one of a vertical direction, a horizontal direction, and a tilt direction. Thereby, observation of the surface and edge part of a to-be-inspected object is enabled. By adopting such a configuration, it will be possible to meet the needs of high-resolution observation of the edge portion of the semiconductor substrate, and to cope with the problem of detecting and managing cracks in the semiconductor substrate and the cause of yield reduction around the semiconductor substrate. .

  When the coordinate information of the foreign matter and the defect is expressed in the XY coordinate system, the coordinate information is converted into the coordinate information of the polar coordinate system with a predetermined point on the wafer as the origin. Then, based on the coordinate information of the polar coordinate system, the rotary stage and the stage moving means are operated so that the corresponding foreign matters and defects can be observed, and the image represented by the defect information is rotationally corrected. As a means for rotational correction, a method for controlling the scanning direction of the charged particle beam and a method for rotationally correcting an image by image processing are conceivable. This makes it possible to observe foreign matter / defects in a polar coordinate system. Therefore, since the wafer can be observed evenly while minimizing the operating range of the stage, the sample chamber and thus the system can be downsized as compared with the stage of the XY coordinate system.

  Defect information (defect image, etc.) obtained by observation based on the coordinate information of the foreign matter and defect on one pattern formed on the wafer, and the adjacent pattern corresponding to the coordinate information of the foreign matter and defect of the pattern Observation information (observation image) obtained by observing the position is output so that both can be compared. Thereby, the defect position can be specified when it is difficult to determine the defect position with only the observation object due to a pattern defect or the like.

  Further, by irradiating the wafer with a charged particle beam (electron beam) from an inclined direction, defect information (defect image) relating to the surface of the wafer, the oblique surface of the end portion, and the top surface of the end portion is detected. At this time, the coordinates of the rotary stage and the coordinates on the wafer may not coincide with each other due to the wafer placement error. In order to observe defects accurately, the coordinate system must be aligned. For this purpose, the coordinate system can be aligned by previously registering a characteristic pattern on the wafer and executing matching with the characteristic pattern registered on the actually mounted wafer. When an electron beam is irradiated from an oblique direction on a stage that can only be rotated, the shadow of the characteristic pattern is different and pattern matching cannot be performed accurately. However, the rotary stage of the present invention moves not only in the rotation but also in the r direction. Since it is possible, pattern matching can be executed without making a difference in the direction of shadow. Therefore, accurate pattern matching is possible, and thus accurate coordinate correction is possible.

  In addition, by installing multiple observation units and processing automatic reviews in parallel, high-speed inspection / review can be realized. Furthermore, specializing in the observation function, it is possible to realize a significant throughput improvement over the conventional review SEM by parallel processing of reviews.

It is a figure which shows an example of the external appearance of the foreign material / defect inspection / observation system by embodiment of this invention. It is a figure which shows the schematic structural example inside the observation part of a system by embodiment of this invention, and a conveyance part. It is a figure which compares the operating range of an rθ stage and an XY stage. It is a block diagram which shows an example of an electron optical system. It is a flowchart for demonstrating the operation example of a foreign material / defect inspection and observation. It is a figure which shows an example of a defect map. It is a comparison figure which shows the example of an observation at the time of rotating counterclockwise. It is a block diagram which shows the example of arrangement | positioning of the detector at the time of irradiating an electron beam to a perpendicular direction. It is a block diagram which shows the example of arrangement | positioning of the detector at the time of irradiating an electron beam to a horizontal direction. It is a block diagram which shows the example of arrangement | positioning of the detector at the time of making it incline and irradiate an electron beam. It is a block diagram which shows the example of the test | inspection / observation system which mounts multiple observation parts. It is a block diagram which shows the example of the observation system which mounts multiple observation parts. It is a figure which shows an example of the positional relationship of a r (theta) stage coordinate system and a wafer coordinate system. It is a figure of an example which shows the outline of alignment. It is a figure which shows the difference in alignment of r (theta) stage coordinate system and XY stage coordinate system. It is a figure which shows an example in the case of aligning with a single image by r (theta) stage coordinate system.

Explanation of symbols

099: Wafer, 100: Observation section, 101: Transfer section, 102: Main body section, 103: Operation section, 104: Wafer pod, 105: Opener, 201: Electron optical system, 202: Sample chamber, 203: rθ stage, 204 : Vacuum evacuation device, 205: vibration removal mechanism, 206: transfer robot, 207: main body shutter unit, 208: wafer reference detector, 210: wafer chuck, 211: wafer chuck operating range, 301: rθ stage operating range, 302 : XY stage operating range, 400: electron beam, 401: electron gun unit, 402: column unit, 403: electron beam source, 404: condenser lens, 405: deflection coil, 406: objective lens, 407: signal detector, 408: Signal amplifier, 409: CRT side deflection coil, 410: CRT, 411: Deflection adjuster, 41 2: deflection amplifier, 413: pattern on wafer, 414: scanning direction on wafer, 415: CRT display image, 416: CRT scanning direction, 600: wafer defect map with pattern, 601: reference die, 602: large foreign matter / defect, 603: Medium foreign matter / defect, 604: Small foreign matter / defect, 605: Unpatterned wafer defect map, 702: Observation position,
703: Pattern on wafer rotated by 45 °, 704: Horizontal scan on pattern, 704: Horizontal scan on pattern, 705: Observation image during horizontal scan, 706: 45 ° scan on pattern, 707: 45 ° direction Observation image during scanning, 708: Observation image after soft rotation correction, 801: Wafer edge portion, 802: Backscattered electron detector, 803: Secondary electron detector, 804: Chuck during vertical irradiation of electron beam and Detector position, 805: chuck and detector position when electron beam is irradiated horizontally, 806: chuck and detector position when electron beam is tilted, 1001: bird's-eye view of an inspection apparatus equipped with a plurality of observation mechanisms, 1101: observation Top view showing an example of an inspection apparatus equipped with a plurality of mechanisms, 1301: Wafer coordinate system, 1302: rθ stage coordinate system, 130 : Wafer coordinate system origin

Claims (16)

A foreign matter / defect inspection / observation system that detects foreign matter and defects in an inspection object and outputs defect information.
An inspection unit for detecting foreign matter and defects of the inspection object and outputting coordinate information of the foreign matter and defects;
An observation unit for observing foreign matter and defects of the inspection object detected by the inspection unit;
For the inspection unit and the observation unit, the loading and unloading of the inspection object is performed, and a conveyance unit that conveys the inspection object between the inspection unit and the observation unit,
The inspection unit, the observation unit, and a control unit that controls the operation of the transport unit,
The observation unit is
A rotating stage on which the inspection object is rotatably mounted;
A reference position detecting means for detecting a reference position of the inspection object mounted on the rotary stage;
Stage moving means for moving the rotary stage in a uniaxial direction perpendicular to the rotation axis;
A defect information detection unit that has an electron optical system that irradiates a charged particle beam to the inspection object mounted on the rotation stage, detects a signal generated from the inspection object, and acquires defect information;
A sample chamber for housing the rotary stage,
The foreign matter / defect inspection / observation system, wherein the control unit controls the rotation operation of the rotary stage and the movement operation of the stage moving means based on coordinate information of the foreign matter and defects of the inspection object.   The foreign matter / defect inspection / observation system according to claim 1, further comprising a vacuum forming unit configured to vacuum the sample chamber.   The electron optical system is configured to irradiate the charged particle beam from at least one of a vertical direction, a horizontal direction, and an inclination direction with respect to the inspection object, and a signal detection for detecting a signal generated by the irradiation. 2. The foreign object / defect inspection / observation system according to claim 1, further comprising: means for observing a surface and an end of the inspection object.   When the coordinate information of the foreign matter and the defect is expressed in an XY coordinate system, the control unit converts the coordinate information into coordinate information of a polar coordinate system with a predetermined point of the inspection object as an origin. The foreign matter / defect inspection / observation system according to claim 1.   The control unit operates the rotary stage and the stage moving unit based on the coordinate information of the polar coordinate system so that corresponding foreign matters and defects can be observed, and rotationally corrects the image represented by the defect information. The foreign matter / defect inspection / observation system according to claim 4.   The control unit controls a scanning direction of the charged particle beam in the electron optical system based on coordinate information of the polar coordinate system, and rotationally corrects an image represented by the defect information. 5. Foreign matter / defect inspection / observation system according to 5.   The foreign matter / defect inspection / observation system according to claim 5, wherein the control unit rotationally corrects an image represented by the defect information by image processing based on coordinate information of the polar coordinate system. The control unit includes defect information obtained by observation based on the coordinate information of the foreign matter and the defect of the first pattern formed on the inspection object, and the second pattern adjacent to the first pattern. a is, and outputs the first pattern and the second observation information position obtained by observing the inside pattern corresponding to the coordinate information of the foreign matter and defect, to ensure that comparable both The foreign matter / defect inspection / observation system according to claim 4.   The control unit is based on polar coordinate information of at least two places on the inspection object and polar coordinate information on the stage of the at least two places when the inspection object is placed on the rotary stage. 5. The foreign object / defect inspection / observation system according to claim 4, wherein a deviation amount between the polar coordinate system of the inspection object and the polar coordinate system of the rotary stage is calculated and corrected. Furthermore, a fine adjustment means for finely adjusting the display position of the image represented by the defect information,
The foreign matter / defect inspection / observation system according to claim 5, wherein the control unit registers the fine adjustment result as a display position correction offset amount in a storage unit. When the electron optical system irradiates the object to be inspected with the charged particle beam from the horizontal direction, the irradiation direction of the charged particle beam is the same as the moving direction realized by the stage moving means of the rotary stage. Yes,
The control unit changes a scanning distance defined by a distance between an objective lens included in the electron optical system and an end of the inspection object in accordance with an input instruction. Foreign matter / defect inspection / observation system described in 1.   The control unit calculates a deviation amount between the focal point set in the electron optical system and the actually measured scanning distance, changes the scanning distance based on the deviation amount, and sets the origin of the rotary stage. 12. The foreign object / defect inspection / observation system according to claim 11, wherein a deviation amount from the origin of the inspection object is corrected.   When the electron optical system irradiates the object to be inspected with the charged particle beam from an inclination direction, the defect information detection unit is configured to detect the surface of the object to be inspected, the oblique surface of the end, and the top of the end The defect / defect inspection / observation system according to claim 3, wherein defect information relating to a surface is detected. The control unit corrects a deviation between the coordinates of the rotary stage and the coordinates on the inspection object,
The defect information detection unit detects defect information related to a surface of the inspection object, an oblique surface of an end portion, and a top surface of the end portion after the coordinate deviation is corrected. Foreign matter / defect inspection / observation system described in 1. The inspection unit detects the foreign matter and the defect while distinguishing it from the pseudo defect in the inspection object based on an inspection condition including a threshold regarding the set detection signal,
As a result of observation by the observation unit, the control unit changes the inspection condition when the foreign object detected by the inspection unit and the target object that is a defect include the pseudo defect. The foreign matter / defect inspection / observation system according to claim 1. A foreign matter / defect inspection / observation system that detects foreign matter and defects in an inspection object and outputs defect information.
An inspection unit for detecting foreign matter and defects of the inspection object and outputting coordinate information of the foreign matter and defects;
A plurality of observation units for observing foreign objects and defects of the inspection object detected by the inspection unit;
For the inspection unit and the observation unit, the loading and unloading of the inspection object is performed, and a conveyance unit that conveys the inspection object between the inspection unit and the observation unit,
The inspection unit, the observation unit, and a control unit that controls the operation of the transport unit,
Each of the plurality of observation units is
A rotating stage on which the inspection object is rotatably mounted;
A reference position detecting means for detecting a reference position of the inspection object mounted on the rotary stage;
Stage moving means for moving the rotary stage in a uniaxial direction perpendicular to the rotation axis;
A defect information detection unit that has an electron optical system that irradiates a charged particle beam to the inspection object mounted on the rotation stage, detects a signal generated from the inspection object, and acquires defect information;
A sample chamber for housing the rotary stage,
The foreign matter / defect inspection / observation system, wherein the control unit controls the rotation operation of the rotary stage and the movement operation of the stage moving means based on coordinate information of the foreign matter and defects of the inspection object.

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