Inspection equipment and method for generating inspection image data

0001The present invention relates to a technique of irradiating an inspection target with charged particles or electromagnetic waves to generate inspection image data for inspecting a pattern defect or the like formed on the surface of the inspection target.

0002By irradiating an inspection target such as a semiconductor wafer with charged particles or electromagnetic waves, the secondary charged particles obtained according to the surface properties of the inspection target are TDI (Time Delay). An inspection device for inspecting a pattern or the like formed on the surface of an inspection target by detecting with an Integration) sensor and using image data generated based on the detection result is widely known (for example, the following). Patent Documents 1 to 3). In such a method, irradiation of charged particles or electromagnetic waves is performed while moving a moving stage holding an inspection target. The TDI sensor has an image sensor arranged in a predetermined number of stages in the vertical stage direction (corresponding to the moving direction of the moving stage), and transfers the amount of secondary charged particles input by a time-delayed integration method. The integrated detection amount is integrated in the vertical direction in synchronization with the clock, and the integrated detection amount is transferred in synchronization with the transfer clock. The transfer clock is input to the TDI sensor every time required for the moving stage to move a distance corresponding to one pixel of the TDI sensor, assuming that the moving stage moves at a constant speed, for example. According to this method, the amount of secondary charged particles is integrated by a predetermined number of stages, so that high-sensitivity imaging can be performed even when the inspection target is moved at high speed.

0003However, in reality, it is difficult to move the moving stage at a constant speed at all times. This problem is caused by various factors such as the assembly accuracy of the device, the friction between the moving stage and the fixing member (for example, the guide rail), and the control accuracy. When the moving speed of the moving stage fluctuates, the image acquired by the TDI sensor shifts back and forth with respect to the ideal state in which the moving speed does not fluctuate. EO correction technology has been developed to correct such deviations. EO correction is a technology that corrects the position of the image projected on the TDI sensor with a polarizing device based on the difference information between the coordinates of the target position of the predetermined moving stage and the coordinates of the actual position to be measured (). For example, the following patent documents 4 to 6).

<p num="0004"><patcit num="1"><text>International Publication No. 2002/001596</text></patcit><patcit num="2"><text>JP-A-2007-48686</text></patcit><patcit num="3"><text>Japanese Unexamined Patent Publication No. 11-132975</text></patcit><patcit num="4"><text>Japanese Unexamined Patent Publication No. 2012-253007</text></patcit><patcit num="5"><text>Japanese Unexamined Patent Publication No. 2012-119694</text></patcit><patcit num="6"><text>Japanese Unexamined Patent Publication No. 2004-363085</text></patcit></p>

<p num="0005"> However, in the conventional EO correction technology, the coordinates of the target position of the moving stage are set so as to be an ideal constant velocity movement. Since the correction of the position of the projected image based on such a setting is performed in a cycle shorter than the cycle of the transfer clock of the TDI sensor, the projected image moves in the vertical step direction during the exposure period. That is, while the moving stage moves by one pixel, the projected image is projected from the first position projected on only one pixel to only the other pixel adjacent to the pixel in the vertical direction. It will move continuously to the second position. This means that the projected image, which should ideally be maintained in the first position, gradually moves away from the ideal position (first position) toward the second position. For this reason, traditional EO There is still room for improvement in inspection accuracy in the correction technology.</p><p num="0006"> On the other hand, it is also conceivable to input the transfer clock to the TDI sensor every time the actual position of the moving stage is measured and it is detected that the moving stage has moved one pixel. According to such a configuration, even change in the moving speed of the moving stage occurs, transfer clock TDI sensor each time the moving stage moves a distance corresponding to one pixel of the TDI sensor is guaranteed to be input to the Sa To. However, if the moving speed of the moving stage fluctuates, the time required for the moving stage to move a distance of one pixel will fluctuate. This means that the exposure time of the image sensor fluctuates. Fluctuations in the exposure time will affect the accuracy of the image data. Specifically, the detected value that has been exposed and transferred for a relatively short time has a brightness value that is darker than the brightness value that should be originally possessed, and the detected value that has been exposed and transferred for a relatively long time should originally have. The brightness value is brighter than the brightness value. That is, in the obtained image data, luminance unevenness that does not depend on the pattern or the like formed on the surface of the inspection target occurs in the moving direction of the moving stage. If such brightness unevenness occurs, the inspection accuracy will decrease.</p><p num="0007"> For these reasons, it is required to improve the inspection accuracy in the inspection device using the TDI sensor.</p>

<p num="0008"> The present invention has been made to solve at least a part of the above-mentioned problems, and can be realized as the following forms, for example.</p><p num="0009"> The first aspect of the present invention is provided as an inspection device. This inspection device is a primary optical system that irradiates either one of charged particles or electromagnetic waves as a beam, and a moving part that can hold the inspection target, and the inspection target is placed on the irradiation position of the beam by the primary optical system. The amount of secondary charged particles or secondary electromagnetic waves obtained by irradiating the inspection target with a moving unit that moves the moving unit in a predetermined direction and a beam that is performed while moving the moving unit in a predetermined direction is determined by a time delay integration method. A TDI sensor that integrates at the input timing of the transfer clock and sequentially transfers each input timing as an integrated detection amount along the direction of, a position detection unit that detects the position of the moving unit that moves the inspection target, and a detection unit. It is provided with a deflection unit that deflects a secondary charged particle or a secondary electromagnetic wave toward the TDI sensor in a direction that cancels the difference based on the difference between the actual position of the inspection target detected by the above and the target position. The target position is a predetermined time equal to or less than the transfer interval period, which is the period from the input of one transfer clock to the input of the next transfer clock when expressed in a Cartesian coordinate system with the horizontal axis as time and the vertical axis as the target position. After the target position is maintained at the same position for a certain period of time, it is set in a stepped shape that rises by a predetermined distance.</p><p num="0010"> According to such an inspection device, when performing EO correction, it is possible to prevent the projected image from moving away from the ideal position due to the movement of the moving portion while the target position is maintained at the same position. Therefore, the deviation between the ideal position and the actual position of the projected image can be reduced, and as a result, the inspection accuracy is improved.</p><p num="0011"> As a second embodiment of the present invention, in the first embodiment, the target position corresponds to one pixel of the TDI sensor after being maintained at the same position for the same time as the transfer interval period in synchronization with the transfer clock. It may be set in a staircase shape that rises parallel to the vertical axis by the distance. According to this form, the projected image is always maintained at the ideal position, so that the inspection accuracy is further improved.</p><p num="0012"> As a third embodiment of the present invention, in the first or second embodiment, the transfer clock may be input at regular intervals. According to this form, the exposure time in each image sensor becomes constant. Therefore, the inspection accuracy can be improved with a simple configuration.</p><p num="0013"> As a fourth aspect of the present invention, in the first or second embodiment, the transfer clock detects that the moving unit has moved by a distance corresponding to one pixel of the TDI sensor based on the detection result of the position detecting unit. It may be entered each time it is done. According to this form, even if the moving speed of the moving portion fluctuates, the movement of the distance corresponding to one pixel of the moving stage and the transfer clock are completely synchronized, so that the projected image is accurately set to the ideal position. You can get closer. Therefore, the inspection accuracy can be improved.</p><p num="0014"> As a fifth aspect of the present invention, in the fourth aspect, in the inspection device, the moving unit is integrating the image data generation unit that generates image data based on the integrated detection amount and the integrated detection amount or image data. May be provided with a normalization unit that normalizes based on the time required to move a predetermined distance. According to this form, even if the moving speed of the moving portion fluctuates, that is, even if the exposure time of the inspection target fluctuates, it is possible to generate image data in which the influence is mitigated. As a result, the inspection accuracy can be further improved.</p><p num="0015"> As a sixth aspect of the present invention, in the fourth aspect, the inspection device reaches the inspection target side of the beam from one transfer to the next transfer after a certain period of time has elapsed in the transfer interval period. Alternatively, a blocking unit may be provided to prevent the secondary charged particles or the secondary electromagnetic wave from reaching the TDI sensor. According to such an embodiment, the time during which the inspection target is exposed or the time during which the TDI sensor receives the secondary charged particles is constant during the period from one transfer to the next transfer in the TDI sensor. Therefore, even if the moving speed of the moving portion fluctuates, it is possible to suppress the occurrence of luminance unevenness due to the fluctuation in the image data generated based on the integrated detection amount. As a result, the inspection accuracy can be further improved.</p><p num="0016"> As a seventh aspect of the present invention, in any one of the first to sixth forms, the primary optical system may irradiate charged particles. The deflector may include an electronic lens that deflects the secondary charged particles towards the TDI sensor. Such a form can be suitably applied to an inspection device in which a primary optical system irradiates charged particles or electromagnetic waves and detects secondary charged particles with a TDI sensor.</p><p num="0017"> As an eighth aspect of the present invention, in any one of the first to sixth forms, the primary optical system may irradiate electromagnetic waves. The deflector includes a movable lens, and the position of the lens may be moved to shift the focus of the secondary electromagnetic wave toward the TDI sensor. Such a form can be suitably applied to an inspection device in which the primary optical system irradiates electromagnetic waves and the amount of secondary electromagnetic waves is detected by a TDI sensor.</p><p num="0018"> A ninth aspect of the present invention is provided as a method for generating inspection image data. This method involves an irradiation step of irradiating one of charged particles or electromagnetic waves as a beam while moving the inspection target in a predetermined direction, and a secondary charged particle or secondary obtained by irradiating the inspection target with the beam. Using a TDI sensor, the amount of electromagnetic waves is integrated at the input timing of the transfer clock along a predetermined direction by the time delay integration method, and the integrated detection amount is sequentially transferred at each input timing. A secondary charged particle or a secondary electromagnetic wave directed to the TDI sensor based on the difference between the detection process that detects the position of the moving part that moves the object and the actual position of the inspection target detected by the detection process and the target position. Is provided with a deflection step of deflecting the difference in a direction of canceling the difference and a step of generating image data based on the integrated detection amount. The target position is a predetermined time equal to or less than the transfer interval period, which is the period from the input of one transfer clock to the input of the next transfer clock when expressed in a Cartesian coordinate system with the horizontal axis as time and the vertical axis as the target position. After the target position is maintained at the same position for a certain period of time, it is set in a stepped shape that rises by a predetermined distance. According to such a method, the same effect as that of the first embodiment is obtained.</p><p num="0019"> In addition to the above-described embodiment, the present invention generates an inspection image data generator and inspection image data. It can be realized in various forms such as a program for the purpose and a storage medium in which the program is readable by a computer.</p>

0020<figref num="1">It is a schematic elevation view of the inspection apparatus as an Example of this invention.</figref><figref num="2">It is a schematic plan view of the inspection apparatus shown in FIG.</figref><figref num="3">It is explanatory drawing which shows the schematic structure of the electro-optical device.</figref><figref num="4">It is explanatory drawing which shows typically the ideal position and the actual position of the image projected on the TDI sensor.</figref><figref num="5">It is explanatory drawing which shows the actual position of the substrate in the conventional method and 1st Example, and the target position of the substrate in EO correction.</figref><figref num="6">It is explanatory drawing which shows typically the light-receiving amount of each pixel of the TDI sensor as a comparative example (conventional method).</figref><figref num="7">It is explanatory drawing which shows typically the light-receiving amount of each pixel of the TDI sensor as the 1st Example.</figref><figref num="8">It is the schematic which shows the structure for EO correction.</figref><figref num="9">It is the schematic which shows the structure of an EO correction circuit.</figref><figref num="10">It is explanatory drawing which shows the actual position of the substrate and the target position of EO correction in the conventional method and 2nd Example.</figref><figref num="11">It is a schematic elevation view of the inspection apparatus as a 2nd Example.</figref><figref num="12">It is explanatory drawing which shows typically the state of integrating the amount of secondary charge particles in a TDI sensor.</figref><figref num="13">It is explanatory drawing which shows the specific example of normalization.</figref><figref num="14">It is a block diagram which shows an example of the structure for normalizing the integrated detection value.</figref><figref num="15">It is the schematic which shows the schematic structure of the electro-optical device as a 3rd Example.</figref><figref num="16">It is explanatory drawing which shows the schematic structure for controlling the exposure time of an inspection object.</figref><figref num="17">It is a timing chart which shows the timing of irradiating the inspection target with a beam in an Example.</figref><figref num="18">It is a timing chart which shows the timing of irradiating the inspection target with a beam in a comparative example.</figref>

0021A. First Example: 1 and 2 show a schematic configuration of a semiconductor inspection device (hereinafter, also simply referred to as an inspection device) 5 as an embodiment of the inspection device of the present invention. FIG. 1 is a schematic elevation view of the inspection device 5 (AA arrow view of FIG. 2), and FIG. 2 is a schematic plan view of the inspection device 5 (BB arrow view of FIG. 1). The inspection device 5 is a device that inspects a defect of a pattern formed on the surface of the inspection target, the presence of foreign matter on the surface of the inspection target, and the like. Examples of inspection targets include semiconductor wafers, exposure masks, EUV masks, nanoimprint masks (and templates), optical element substrates, optical circuit substrates, and the like. Examples of the foreign matter include particles, cleaning residue (organic matter), reaction products on the surface, and the like. Such foreign matter comprises, for example, an insulator, a conductor, a semiconductor material, or a composite thereof. Hereinafter, the semiconductor wafer (hereinafter, also simply referred to as wafer W) will be inspected by the inspection device 5. Wafer inspection is performed after the wafer processing process has been performed in the semiconductor manufacturing process or during the processing process. For example, the inspection is performed on a wafer having undergone a film forming process, CMP or ion implantation, a wafer having a wiring pattern formed on the surface, a wafer having no wiring pattern yet, and the like.

0022As shown in FIG. 1, the inspection device 5 includes a cassette holder 10, a mini-environment device 20, a main housing 30, a loader housing 40, a stage device 50, an electro-optical device 70, and an image processing device 80. , Equipped with a control device 84. Shown in Figures 1 and 2. As described above, the cassette holder 10 holds a plurality of cassettes C (two in FIG. 2). A plurality of wafers W to be inspected are stored in the cassette C in a state of being arranged in parallel in the vertical direction. In this embodiment, the cassette holder 10 is configured so that the cassette C can be automatically set at the position indicated by the chain line in FIG. 2 on the elevating table. The cassette C set in the cassette holder 10 faces the position shown by the solid line in FIG. 2, that is, the rotation axis OO (see FIG. 1) of the first transport unit 61 in the mini-environment device 20 described later. It is automatically rotated to the position.

0023As shown in FIGS. 1 and 2, the mini-environment device 20 includes a housing 22, a gas circulation device 23, a discharge device 24, and a pre-aligner 25. Inside the housing 22, an atmosphere-controlled mini-environment space 21 is formed. In addition, the first transport unit 61 is installed in the mini-environment space 21. The gas circulation device 23 circulates a clean gas (here, air) in the mini-environment space 21 to control the atmosphere. The discharge device 24 collects a part of the air supplied in the mini-environment space 21 and discharges it to the outside. As a result, even if dust is generated by the first transport unit 61, the gas containing the dust is discharged to the outside of the system. The pre-liner 25 roughly positions the wafer. The pre-liner 25 has an orientation flat formed on the wafer (a flat portion formed on the outer periphery of a circular wafer) and one or more V-shaped notches formed on the outer peripheral edge of the wafer, that is, a notch. It is configured to be optically or mechanically detected so that the position of the wafer in the rotational direction around the axis OO can be pre-positioned.

0024The first transport unit 61 has a multi-node arm that can rotate around the axis OO. This arm is configured to expand and contract in the radial direction. A gripping device for gripping the wafer W, for example, a mechanical chuck, a vacuum chuck, or an electrostatic chuck is provided at the tip of the arm. The arm is movable in the vertical direction. The first transfer unit 61 grips the required wafer W among the plurality of wafers held in the cassette holder 10 and delivers it to the wafer rack 41 in the loader housing 40 described later.

0025As shown in FIGS. 1 and 2, a wafer rack 41 and a second transfer unit 62 are installed inside the loader housing 40. The housing 22 of the mini-environment device 20 and the loader housing 40 are separated by the shutter device 27, and the shutter device 27 is opened only when the wafer W is delivered. The wafer rack 41 supports a plurality of wafers (two in FIG. 1) in a horizontal state by separating them vertically. The second transport unit 62 has basically the same configuration as the first transport unit 61 described above. The second transfer unit 62 transfers the wafer W between the wafer rack 41 and the holder 55 of the stage device 50, which will be described later. The inside of the loader housing 40 is in a high vacuum state (vacuum degree is 10).^-5~10^-6The atmosphere is controlled in Pa), and an inert gas (for example, dry pure nitrogen) is injected.

0026As shown in FIGS. 1 and 2, a stage device 50 is provided in the main housing 30 as an example of a moving portion for moving the wafer W. The stage device 50 includes a fixed table 51 arranged on the bottom wall, a Y table 52 that moves in the Y direction on the fixed table, an X table 53 that moves in the X direction on the Y table, and a rotation on the X table. It includes a possible turntable 54 and a holder 55 placed on the turntable 54. The Y table 52 is moved in the Y direction by a servomotor 56, which is an actuator provided outside the main housing 30. The X table 53 is moved in the X direction by a servomotor 57, which is an actuator provided outside the main housing 30. The holder 55 holds the wafer W on its mounting surface so that it can be released by a mechanical chuck or an electrostatic chuck. The position of the wafer W held in the holder 55 in the Y direction is detected by the position detector (position sensor) 58. Be known. The position detection unit 58 is a laser interference distance measuring device that uses the principle of an interferometer, and detects the reference position of the mounting surface of the holder 55 with a fine-diameter laser. In FIGS. 1 and 2, the positions of the position detection unit 58 are shown schematically. The position detection unit 58 irradiates the laser toward the mirror plate fixed to the Y table 52 (or holder 55), for example, and the laser interferometer measures the position of the incident wave of the laser and the reflected wave from the mirror plate. Based on the phase difference, the coordinates of the wafer W, more precisely the Y table 52 (or holder 55), are detected. The laser interferometer may be provided inside the main housing 30 or may be provided outside. Further, the laser interferometer may be connected to an optical pickup provided in the optical path of the laser via an optical cable and may be provided at a position away from the main housing 30.

0027The electro-optical device 70 uses either one of the charged particles or the electromagnetic wave as a beam to irradiate the wafer W moving in the Y direction (see FIG. 2), and detects the amount of the secondary charged particles obtained thereby. The movement of the wafer W is performed by the stage device 50. Details of the electro-optical device 70 will be described later.

0028The image processing device 80 shown in FIG. 1 functions as an image data generation unit 81, and generates image data based on the amount of secondary charged particles detected by the electro-optical device 70. The generated image data has a luminance value as a gradation value. In this embodiment, the image processing device 80 includes a memory and a CPU, and realizes an image data generation function by executing a program stored in advance. At least a part of each functional unit of the image processing apparatus 80 may be composed of a dedicated hardware circuit.

0029The image data generated by the image processing apparatus 80 is used for inspecting the presence or absence of defects and foreign substances in the pattern formed on the surface of the wafer W by an arbitrary method. This inspection may be automatically performed using an information processing device or the like. For example, the information processing apparatus may detect a region in which the brightness value is higher than the threshold value, or may perform pattern matching between the generated image data and the reference image data prepared in advance. Alternatively, the inspection may be performed by an inspector based on the image represented by the image data or the gradation value of each pixel constituting the image data.

0030The control device 84 shown in FIG. 1 controls the overall operation of the inspection device 5. For example, the control device 84 sends a movement command to the stage device 50 to move the holder 55 holding the wafer W in the Y direction at a predetermined moving speed. The control device 84 includes a memory and a CPU, and may realize a required function by executing a program stored in advance. Alternatively, the control device 84 may realize at least a part of the required functions by a dedicated hardware circuit in addition to or instead of realizing the functions by software.

0031FIG. 3 shows a schematic configuration of the electro-optical device 70. As shown in the figure, the electro-optical device 70 includes a primary optical system 72, a secondary optical system 73, a TDI sensor 75, and a deflection electrode 91. The primary optical system 72 generates charged particles as a beam, and irradiates the wafer W held in the holder 55 with the beam. The primary optical system 72 includes a light source 71, lenses 72a, 72d, apertures 72b, 72c, an E × B filter 72e, lenses 72f, 72h, 72i, and aperture 72g. The light source 71 is, in this embodiment, an electron gun that produces an electron beam. However, the light source 71 may be any means for generating either charged particles or electromagnetic waves, such as a UV (Ultraviolet) laser, a DUV (Deep Ultraviolet) laser, an EUV (Extreme Ultraviolet) laser, an X-ray laser, and the like. it can. The configuration of the primary optical system 72 and the configuration of the secondary optical system 73, which will be described later, are appropriately changed according to the type of the light source 71.

0032By irradiating the wafer W with charged particles, the state of the wafer W (pattern formation state, Secondary charged particles can be obtained according to the state of attachment of foreign matter. As used herein, a secondary charged particle is one of secondary emitted electrons, mirror electrons and photoelectrons, or a mixture of at least two of these. The secondary emitted electrons are either secondary electrons, backscattered electrons, or backscattered electrons, or a mixture of at least two of them. Secondary emitted electrons are generated when the surface of the wafer W is irradiated with charged particles such as an electron beam, and the charged particles collide with the surface of the wafer W. Mirror electrons are generated when a charged particle such as an electron beam is irradiated on the surface of the wafer W, and the irradiated charged particle is reflected in the vicinity of the surface of the wafer W without colliding with the surface of the wafer W. Photoelectrons are generated from the surface of the wafer W when it is irradiated with electromagnetic waves.

0033The lenses 72a, 72d and apertures 72b, 72c shape the electron beam generated by the light source 71, control the direction of the electron beam, and guide the electron beam to the E × B filter 72e so that the electron beam is incident from an oblique direction. The electron beam incident on the E × B filter 72e is deflected vertically downward under the influence of the Lorentz force due to the magnetic field and the electric field, and is guided toward the wafer W through the lenses 72f, 72h, 72i and the aperture 72g. Be taken. The lenses 72f, 72h, 72i control the direction of the electron beam and perform appropriate deceleration to adjust the landing energy.

0034By irradiating the wafer W with an electron beam, foreign matter on the wafer W is charged up, so that some of the incident electrons are bounced off without contacting the wafer W. As a result, the mirror electrons are guided to the TDI sensor 75 via the secondary optical system 73. Further, when some of the incident electrons come into contact with the wafer W, the secondary emitted electrons are emitted.

0035Secondary charged particles (here, mirror electrons and secondary emitted electrons) obtained by irradiation with an electron beam pass through the objective lens 72i, the lens 72h, the aperture 72g, the lens 72f and the E × B filter 72e again, and then pass through the objective lens 72i, the lens 72h, the aperture 72g, and then the E × B filter 72e. It is guided to the secondary optical system 73. The secondary optical system 73 guides the secondary charged particles obtained by irradiation with the electron beam to the TDI sensor 75. The secondary optical system 73 includes lenses 73a and 73c, an NA aperture 73b, and an aligner 73d. In the secondary optical system 73, the secondary charged particles are collected by passing through the lens 73a, the NA aperture 73b, and the lens 73c, and are arranged by the aligner 64. The NA aperture 73b has a role of defining the transmittance and aberration of the secondary system.

0036The TDI sensor 75 has image pickup elements arranged in a predetermined number of stages (s) in the Y direction, and detects the amount of secondary charged particles guided by the secondary optical system 73. In this embodiment, the image sensor of the TDI sensor 75 is also arranged in the X direction. For detection by the TDI sensor 75, the stage device 50 moves the wafer W along the Y direction, irradiates the wafer W with an electron beam, and integrates the amount (charge) of the secondary charged particles obtained by the electron beam with a time delay. It is performed by accumulating the number of steps in the Y direction along the Y direction according to the method. The moving direction of the wafer W and the integrating direction by the TDI sensor 75 are the same direction. The amount of secondary charged particles is integrated one step at a time each time a transfer clock is input to the TDI sensor 75. In other words, the charge stored in one pixel of the TDI sensor 75 is transferred to the next pixel in the Y direction each time the transfer clock is input. Then, the detected amount integrated for the number of stages in the Y direction, that is, the detected amount integrated up to the final stage (also referred to as integrated detection amount) is transferred to the image processing device 80 each time the transfer clock is input. .. The integration direction of the TDI sensor 75 is not limited to the Y direction, but may be the X direction. In this case, the wafer W is moved in the X direction.

0037The integrated detection amount (luminance data) obtained in this way preferably reflects, for example, the presence or absence of foreign matter on the wafer W. This is because the mirror electrons described above do not scatter, whereas the secondary emission electrons scatter, so that the amount of secondary charged particles obtained from the region where foreign matter exists on the wafer W is the other region. Much more than the amount of secondary charged particles obtained from Because. That is, the region in which the foreign matter exists is imaged as a region having higher brightness than the region in which the foreign matter does not exist.

0038In this embodiment, the transfer clock is input to the TDI sensor 75 at regular time intervals. This fixed time is set to the time required for the wafer W (holder 55) to move by one pixel in an ideal state, that is, in a state where the moving speed of the holder 55 is completely constant. However, it is practically difficult to keep the moving speed of the wafer W strictly constant during the integration of the amount of secondary charged particles by the TDI sensor 75. Therefore, the actual projection position of the projected image represented by the secondary charged particles on the TDI sensor 75 deviates from the ideal position. The deflection electrode (electrostatic lens) 91 is provided to suppress the influence of the misalignment of the projected image on the image data by EO correction. Specifically, on the deflection electrode 91, the difference between the coordinates of the predetermined target position of the holder 55 (wafer W) and the coordinates of the actual position of the holder 55 (wafer W) detected by the position detection unit 58. The voltage corresponding to is applied. As a result, the deflection electrode 91 deflects the secondary charged particles in the direction of canceling the difference by electrostatic deflection. The configuration for deflecting the secondary charged particles can be various electronic lenses. For example, an electromagnetic lens can be used instead of the electrostatic lens. Hereinafter, the EO correction in this embodiment will be described.

0039FIG. 4 schematically shows the ideal position and the actual position of the projected image projected on the TDI sensor 75. FIG. 4A shows an array of pixels included in the TDI sensor 75. FIG. 4 (b) shows the pattern P1 formed on the wafer W to be inspected. In this example, the width of the pattern P1 in the Y direction is one pixel. FIG. 4C shows the ideal position and the actual position of the pattern P1 at the timing when the transfer clock is input when the pattern P1 moves along the Y direction. As shown in the figure, the ideal positions of the pattern P1 are positions Y1 to Y4 separated by one pixel along the Y direction. That is, the pattern P1 moves accurately one pixel at a time each time the transfer clock is input (every time a certain period of time elapses). On the other hand, the actual position of the pattern P1 is displaced back and forth in the Y direction from the ideal position due to the fluctuation of the moving speed of the holder 55. EO correction is introduced to correct such an ideal position and an actual position of the wafer W.

0040FIG. 5 shows the actual position of the wafer W and the target position of the wafer W in the EO correction in a Cartesian coordinate system. The horizontal axis is time, and the vertical axis is the position of the wafer W in the Y direction. Each of the periods T1 to T4 is the time from the input of one transfer clock to the input of the next transfer clock. In this embodiment, since the transfer clock is input at regular time intervals as described above, the periods T1 to T4 are equal to each other. The positions Y2 to Y4 of the wafer W in the Y direction are positions advanced by one pixel from the position Y1. As shown in the figure, the actual position AP of the wafer W is represented as a complicated curve by changing the moving speed in the Y direction. As shown in the figure, the target position TP0 in the conventional EO correction is linearly set so that the wafer W advances by one pixel each time the transfer clock is input. That is, the conventional target position TP0 corresponds to the case where the moving speed of the wafer W in the Y direction is always constant.

0041On the other hand, the target position TP1 in the EO correction of this embodiment is set in a stepped shape as shown in the figure. Specifically, the target position TP1 is a predetermined distance after the target position is maintained at the same position for a predetermined time equal to or less than the period from the input of one transfer clock to the input of the next transfer clock (for example, period T1). It is set in a staircase shape that only stands up. In this embodiment, the target position TP1 is maintained at the same position for the same time as the period from the input of one transfer clock to the input of the next transfer clock in synchronization with the transfer clock, and then on the vertical axis. In parallel, it stands up by a distance equivalent to one pixel of the TDI sensor 75.

00426 and 7 schematically show the amount of light received by each pixel of the TDI sensor 75. Figure 6 shows Figure 5 The case where the EO correction based on the conventional target position TP0 shown in FIG. 5 is performed is shown, and FIG. 7 shows the case where the EO correction based on the target position TP1 of the present embodiment shown in FIG. 5 is performed. FIG. 6 (a) shows the transfer clock input to the TDI sensor 75. This transfer clock is input at regular intervals. As shown in FIG. 6 (b), in the conventional EO correction, the projected image is positioned in the period T1 corresponding to one cycle of the transfer clock input to the TDI sensor 75 based on the preset target position TP0. It moves continuously from Y1 to position Y2. Similarly, during period T2, the projected image moves from position Y2 to position Y3. Note that the position control of the projected image by EO correction is a feedback control based on the difference between the actual position and the target position, so that there is actually a slight time delay, but in FIG. 6, it is assumed that there is no time delay. Shown.

0043When the projected image moves in this way, the projected image is projected over two pixels adjacent to each other in the Y direction. For example, as shown in FIG. 6 (c), the light receiving amount of the two pixels adjacent to the TDI sensor in the Y direction during the periods T11 to T14 obtained by dividing the period T1 into four equal parts is the light receiving amount L1 of the pixel in the bottom row. And the light receiving amount L2 of the pixel one line above it is expressed as (L1, L2), and if the total light receiving amount in each of the periods T11 to T14 is "10", then (10) at position Y1. It changes from, 0) to (8,2), (5,5), (2,8), and finally becomes (0,10) at position Y2. FIG. 6 (d) shows the integrated light receiving amount when the light receiving amount of each pixel is transferred according to the transfer clock. For example, in the period T11, the received light received in the period T0 before the period T1 (10,0) is transferred (after the transfer, the received amount becomes (0,10)), and the light is received in the period T11. The amount of light received (8,2) is added to obtain the amount of light received (8,12) at the end point of the period T11. Then, at the end of the period T2, the amount of light received (L2, L3) in the second and third rows from the bottom is (30,60). This means that the pattern P1 having a width of 1 pixel is imaged as a pattern having a width of 2 pixels, and an image blurred in the Y direction can be obtained.

0044On the other hand, as shown in FIG. 7B, in the EO correction of this embodiment, during the period T1 corresponding to one cycle of the transfer clock input to the TDI sensor 75 based on the preset target position TP1. , The projected image is maintained at position Y2. Similarly, during period T2, the projected image is maintained at position Y3. In this case, the amount of light received by each pixel during the periods T1 and T2 is received by only one of the plurality of pixels arranged in the Y direction, as shown in FIG. 7 (c). Therefore, at the end of the period T2, the light receiving amount (L2, L3) in the second and third rows from the bottom is (0,90). This means that the pattern P1 having a width of 1 pixel is accurately imaged as a pattern having a width of 1 pixel.

0045FIG. 8 shows an example of the configuration for realizing the EO correction of the present embodiment described above. The deflection unit 90 of the inspection device 5 includes an EO corrector 92 and an EO correction circuit 94. The EO corrector 92 includes the deflection electrode 91 described above and an amplifier (not shown). The EO correction circuit 94 controls the voltage applied to the deflection electrode 91, that is, the deflection gain.

0046When a movement command is given from the control device 84 to the stage device 50 (servo motor 56), the Y table 52 is moved in the Y direction. The amount of movement of the Y table 52 is detected by the position detection unit 58. Then, the position information detected by the position detection unit 58 is input to the TDI clock generator 74 and the EO correction circuit 94. The TDI clock generator 74 starts generating a clock at regular time intervals (corresponding to the period T1 shown in FIG. 5) at the timing when the position of the Y table 52 becomes a predetermined initial position. This clock is input to the TDI sensor 75 as a transfer clock. This clock is also input to the EO correction circuit 94. The EO correction circuit 94 controls the EO correction device 92 so that the projected image on the TDI sensor 75 is corrected from the actual position AP to the target position TP1 based on the input clock.

0047FIG. 9 shows an example of the EO correction circuit 94. The EO correction circuit 94 includes a comparator 95, an adder / subtractor 96, a register 97, an adder 98, and a subtractor 99. The EO correction process is executed by the EO correction circuit 94 as follows. First, when the user inputs an imaging command for the wafer W to the control device 84, the control device 84 inputs the imaging start Y coordinate, that is, the initial position of imaging to the comparator 95 and the adder 98, and 1 The amount of pixel movement, that is, the distance corresponding to one pixel is input to the adder / subtractor 96.

0048The position detection unit 58 inputs the detected current Y coordinate, that is, the actual position of the wafer W, to the comparator 95 and the subtractor 99 at any time. The comparator 95 sends a reset signal to the adder / subtractor 96 and the register 97 when the input Y coordinate for starting imaging and the current Y coordinate match. Such processing performs zero point correction of the wafer W as an imaging target.

0049After the reset signal is input, the adder / subtractor 96 inputs the input 1-pixel movement amount to the register 97. The transfer clock is input to the register 97 from the TDI clock generator 74. The register 97 outputs the value input from the adder / subtractor 96 to the adder 98 each time this transfer clock is input. The output of register 97 is input to adder 98 and at the same time fed back to adder 96. After that, the adder / subtractor 96 adds the amount of movement of one pixel to the returned value and outputs it to the register 97. As a result, the register 97 sequentially outputs values that increase by N, such as N, 2N, 3N, and 4N, in synchronization with the TDI transfer clock, assuming that the amount of movement per pixel is N. The adder 98 adds the value input from the register 97 and the imaging start Y coordinate value input from the control device 84, and outputs the sum to the subtractor 99.

0050The subtractor 99 calculates the difference between the value input from the adder 98 and the current Y coordinate value input from the position detector 58, and outputs it to the EO corrector 92 as the deflection gain in the Y direction in the EO correction. .. As is clear from the above explanation, the EO correction circuit 94 generates the target position TP1 and outputs the difference between the target position TP1 and the actual position AP to the EO corrector 92. The EO corrector 92 deflects the secondary charged particles toward the TDI sensor 75 in a direction in which the difference between the target position TP1 and the actual position AP is canceled out based on the deflection gain input from the EO correction circuit 94. In other words, the EO corrector 92 deflects the secondary charged particles toward the TDI sensor 75 so that the projected image of the wafer W at the real position AP matches the projected image of the wafer W at the target position TP1. With such control, accurate imaging as shown in FIG. 7 becomes possible.

0051According to the inspection device 5 of the present embodiment described above, the projected image is ideal because the projected image does not move while the target position TP1 of the wafer W is maintained at the same position when performing EO correction. It is possible to prevent the projected image of the position, that is, the region corresponding to one pixel to be imaged, from moving away from the position projected on only one pixel to be projected by the TDI sensor 75. Therefore, the deviation between the ideal position of the projected image and the actual position AP can be reduced, and as a result, the inspection accuracy is improved. In particular, in this embodiment, since the projected image of the wafer W of the actual position AP completely matches the projected image of the wafer W of the target position TP1, the projected image is always maintained at the ideal position, and the inspection accuracy is further improved.

0052Further, according to the inspection device 5, since the transfer clock is input to the TDI sensor 75 at regular time intervals, the exposure time in each image sensor of the TDI sensor 75 becomes constant. Therefore, even if the moving speed of the wafer W fluctuates, the exposure time in each image sensor does not fluctuate, so that the brightness unevenness due to the fluctuation of the exposure time is added to the image data generated by the image processing device 80. It does not occur. As a result, the inspection target can be inspected with high accuracy with a simple configuration.

0053B. Second Example: FIG. 10 is an explanatory diagram showing the actual position of the wafer W and the target position of the wafer W in the EO correction in the second embodiment, and corresponds to FIG. 5 described above. In the second embodiment, the transfer clock is input to the TDI sensor 75 every time the wafer W moves in the Y direction by a distance corresponding to one pixel. Also in the second embodiment, the target position TP2 for EO correction is set in a stepped manner as shown in FIG. Specifically, the target position TP2 is maintained at the same position for the same time as the period from the input of one transfer clock to the input of the next transfer clock in synchronization with the transfer clock, and then on the vertical axis. In parallel, it stands up by a distance equivalent to one pixel of the TDI sensor 75. As is clear from FIG. 10, when the transfer speed of the wafer W fluctuates, that is, when the actual position AP has a curved shape, the time required for the wafer W to move one pixel (periods T21 to T24 in the figure). ) Are different times. In FIG. 10, the difference between the periods T21 to T24 is emphasized.

0054FIG. 11 shows a schematic configuration of the inspection device 205 as the second embodiment. In FIG. 11, the same components as those in the first embodiment (FIG. 1) among the components of the inspection device 205 are designated by the same reference numerals as those in FIG. 1, and the description thereof will be omitted. The inspection device 205 includes an image processing device 280. This image processing device 280 is different from the image processing device 80 of the first embodiment in that it also functions as a normalization unit 282. The function of the normalization unit 282 will be described later.

0055FIG. 12 schematically shows how the TDI sensor 75 integrates the amount of secondary charged particles. Here, for convenience of explanation, the TDI sensor 75 will be described assuming that the TDI sensor 75 has five pixels arranged in the Y direction and not arranged in the X direction. In FIG. 12, P1 to P5 indicate each image sensor (pixel) arranged in the Y direction. In the illustrated example, the wafer W moves in the direction from pixels P1 to P5 during detection by the TDI sensor 75. In FIG. 12, T11 to T15 indicate the time (period) actually required for the wafer W to move by one pixel. For example, the time T11 is the time required to move the distance corresponding to the pixel P1, and the time T12 is the time required to move the distance corresponding to the pixel P2.

0056As shown in FIG. 12, in the detection by the TDI sensor 75, first, during the time T11, the charge Q1 corresponding to the amount of the detected secondary charged particles is accumulated in the pixel P1. This charge Q1 is transferred to the pixel P2 adjacent to the pixel P1 according to the transfer clock input to the TDI sensor 75 at the timing immediately after the lapse of the time T11. During the time T12 following the time T11, the charge Q2 is accumulated in the pixel P2 in addition to the charge Q1 transferred from the pixel P1. As a result, when the time T12 elapses, the charges Q1 + Q2 are accumulated in the pixel P2. This charge Q1 + Q2 is transferred to the pixel P3 at the timing immediately after the lapse of time T12. During the time T13 following the time T12, the charge Q3 is accumulated in the pixel P3 in addition to the charges Q1 + Q2 transferred from the pixel P2. As a result, when the time T13 elapses, the charges Q1 + Q2 + Q3 are accumulated in the pixel P3. By sequentially accumulating the charges in this way, after the lapse of time T11 to T15, the charges Q1 + Q2 + Q3 + Q4 + Q5 are accumulated in the pixels P5 and transferred to the image processing device 280.

0057The luminance data transferred to the image processing device 280 in this way is normalized by the processing of the normalization unit 282 of the image processing device 280. The normalization here means that the influence on the integrated detection value (brightness unevenness) caused by the variation in the moving speed of the wafer W (Y table 52), that is, the variation in the exposure time of the wafer W is alleviated. As described above, it is a process of correcting the integrated detection amount. This normalization process is performed based on the time required for the wafer W to move along the Y direction by a distance corresponding to one pixel during integration by the TDI sensor 75. More specifically, the normalization process is performed by the following equation (1) using the normalization coefficient K, which is the ratio of the actual travel time Tn and the target travel time T0. IV0 is the integrated detection amount before normalization, and IV1 is This is the integrated detection amount after normalization. IV1 = K × IV0 (1)

0058The normalization coefficient K is calculated by the following equation (2). Tn is the time actually required to move the wafer W by a predetermined distance (hereinafter, also referred to as the actual moving time). In this embodiment, the predetermined distance is a distance corresponding to the number of pixels in the Y direction of the TDI sensor 75 (in the example of FIG. 12, a distance corresponding to 5 pixels). Therefore, the actual travel time Tn is equal to the exposure time corresponding to the integrated detection amount transferred from the TDI sensor 75. The target movement time T0 is a time estimated in advance as the time required to move a predetermined distance (hereinafter, also referred to as a target movement time). The target movement time T0 may be regarded as a design value of the time required for the wafer W to move a predetermined distance. K = T0 / Tn (2)

0059The integrated detection amount normalized by the normalization unit 282 in this way is output to the image data generation unit 81. The image data generation unit 81 synthesizes the integrated detection values received from the normalization unit 282 to generate image data composed of pixel values (brightness values) arranged in the Y direction and the X direction. The order of the normalization process and the image data generation process may be reversed. That is, even if the image data generation unit 81 synthesizes the data transferred from the TDI sensor 75 to generate image data, and then the normalization unit 282 performs normalization processing on the generated image data. Good.

0060FIG. 13 shows a specific example of the normalization process. In this example, the image data is generated first, and then the normalization is performed. FIG. 13A shows the pixel arrangement of the image data before normalization. The pixel group with Y = 1 is the pixel group first transferred to the image processing device 280 by the TDI sensor 75. The pixel group of Y = 2 is the pixel group transferred next to the pixel group of Y = 1. That is, the sequence of numbers in the Y direction represents the order of transfer from the TDI sensor 75. FIG. 13 (b) shows the total exposure time for each pixel group along the X direction. For example, the exposure time T1 is the total value of the times T11 to T15 shown in FIG. That is, the exposure time T1 corresponds to the above-mentioned actual movement time Tn. FIG. 13 (c) shows the pixel value of each pixel of the image data generated by synthesizing the integrated detection values. That is, FIG. 13 (c) shows the integrated detection amount IV0 before normalization. The integrated detection amount IV0 (pixel value) before normalization is a luminance value of 256 gradations here. FIG. 13 (d) shows the normalization coefficient K applied to each pixel group of Y = n (here, n is an integer of 1 to 8). FIG. 13 (e) shows the normalization calculated by Eq. (2) based on the pre-normalization integrated detection amount IV0 shown in FIG. 13 (c) and the normalization coefficient K shown in FIG. 13 (d). Post-integrated detection amount IV1.

0061FIG. 14 shows an example of the configuration for realizing such normalization processing. The illustrated example is a configuration in which image data is generated after normalization. As shown in the figure, the normalization unit 282 includes a normalization clock generator 285, a counter 286, a division unit 287, and a multiplication unit 288. When a movement command is given from the control device 84 to the stage device 50 (servo motor 56), the Y table 52 is moved in the Y direction. The amount of movement of the Y table 52 is detected by the position detection unit 58. Then, the position information detected by the position detection unit 58 is input to the TDI clock generator 74. Based on the received position information, the TDI clock generator 74 inputs the TDI clock (transfer clock) to the TDI sensor 75 each time the Y table 52 moves one pixel in the Y direction. The TDI sensor 75 integrates electric charges according to this TDI clock, and transfers the electric charges integrated up to the final stage to the built-in A / D converter (not shown). The pre-normalization integrated detection amount IV0 converted into a digital value by the A / D conversion unit is input to the multiplication unit 288. Further, each time the TDI sensor 75 transfers the amount (charge) of the secondary charged particles, the TDI sensor 75 inputs a transfer signal indicating that the transfer has been performed to the counter 286.

0062On the other hand, in the normalization unit 282, the counter 286 measures the actual travel time Tn using the time measurement clock generated by the normalization clock generator 285. Specifically, the counter 286 measures the time required to receive the transfer signal only the most recent predetermined number of times (5 times in the example of FIG. 12) using the time measurement clock, and the measured time. Is input to the division unit 287 as the actual travel time Tn. The division unit 287 calculates the normalization coefficient K using the above equation (2) based on the target travel time T0 input from the control device 84 and the actual travel time Tn input from the counter 286. .. The calculated normalization coefficient K is input to the multiplication unit 288, and the normalization process in the multiplication unit 288, that is, the calculation by the above equation (1) is performed. The calculation result of the multiplication unit 288, that is, the integrated detection amount IV1 after normalization is input to the image data generation unit 81.

0063Although not shown, the image data generation unit 81 synthesizes the data transferred from the TDI sensor 75 to generate image data, and then the normalization unit 282 normalizes the generated image data. In the case of performing, the normalization unit 282 can perform the normalization process as follows, for example. First, the normalization unit 282 sequentially measures the actual travel time Tn or calculates the normalization coefficient K sequentially, and stores each actual travel time Tn or the normalization coefficient K in the buffer, as in FIG. Keep it. Next, the normalization unit 282 sequentially extracts data groups received from the TDI sensor 75 in one transfer from the image data generated by the image data generation unit 81 in the order in which they are received. Then, the extracted data group is subjected to normalization processing.

0064According to the inspection device 205 described above, even if the moving speed of the wafer W fluctuates, the movement of the wafer W at a distance corresponding to one pixel and the transfer clock are completely synchronized, so that the moving speed of the wafer W is completely synchronized with the TDI sensor 75. The projected image can be brought close to the ideal position with high accuracy. Therefore, the wafer W can be inspected with high accuracy. Moreover, the pre-normalization integrated detection amount IV0 integrated by the TDI sensor 75 is normalized based on the actual exposure time (actual movement time Tn) of the wafer W. Therefore, even if the moving speed of the wafer W, that is, the exposure time varies, it is possible to generate image data in which the brightness unevenness caused by the variation in the exposure time is alleviated. As a result, the accuracy of the inspection using the image data can be further improved.

0065In the above-mentioned normalization process, the actual moving time Tn used in the above equation (2) is that the wafer W moves by a part of the distance corresponding to the number of pixels in the Y direction of the TDI sensor 75. It may be the time required to do so. In this case, the target travel time T0 may be set as the time corresponding to the part of the distance. For example, when the number of stages in the Y direction of the TDI sensor 75 is 2048, the actual movement time Tn may be the time required for the wafer W to move by the distance corresponding to the pixels of 2047. According to such a configuration, the generation speed of image data can be increased without significantly affecting the accuracy of normalization.

0066The above-mentioned normalization process may include operations other than the above. For example, in addition to the calculations of the above equations (1) and (2), a process of subtracting a predetermined offset amount from the pre-normalization integrated detection amount IV0 or the post-normalization integrated detection amount IV1 may be performed. Such subtraction processing is performed to remove dark current noise. As the offset amount, the integrated detection value obtained by preliminarily taking an image with the TDI sensor 75 in a state where the wafer W is not irradiated with the beam may be used. The offset amount may be set at the time of starting the inspection device 205, or may be set every time a predetermined number of wafers W are inspected. According to such a configuration, it is possible to generate highly accurate image data in which the influence of dark current noise is reduced. As a result, the accuracy of the inspection using the image data can be improved.

0067Alternatively, in the normalization process, in addition to the above calculations (1) and (2), a predetermined increase / decrease ratio is integrated for each image sensor group composed of image sensors arranged along the Y direction. Inspection You may perform the process of multiplying the output. Such multiplication processing is performed in order to correct variations in light receiving sensitivity for each image sensor group. The increase / decrease ratio to be multiplied may be set so that the same light source is applied to each element of the TDI sensor 75 to perform imaging in advance, and the variation in the integrated detection value obtained thereby is alleviated in the X direction. Further, in the normalization process, instead of using the normalization coefficient K, a coefficient obtained by multiplying the normalization coefficient K and the increase / decrease ratio in advance may be used. According to such a configuration, since the variation in the light receiving sensitivity for each image sensor group is corrected, the accuracy of the inspection using the image data can be improved.

0068The normalization process is not limited to the configuration performed on the integrated detection amount of the digital value, and may be performed on the integrated detection amount of the analog value. A real-time analog computing unit may be used to normalize the analog values. In this case, the integrated detection amount will be A / D converted after normalization. According to such a configuration, the normalization is performed in a state where the quantization error is not included, so that the accuracy of the image data can be improved.

0069In this embodiment, the normalization unit 282 is shown as a configuration included in the image processing device 280, but the normalization unit 282 may be provided at an arbitrary location as the entire inspection device 205. For example, the normalization unit 282 may be configured as an intermediate processor provided between the TDI sensor 75 and the image processing device 280. Alternatively, the normalization unit 282 may be configured as a signal processing unit (for example, FPGA (Field Programmable Gate Array)) included in the TDI sensor 75.

0070C. Third Example: In the third embodiment, the same EO correction as in the second embodiment described above is performed. That is, the target position in the EO correction is set as shown as the target position TP2 in FIG. 10, and the transfer clock is input to the TDI sensor 75 every time the wafer W moves in the Y direction by a distance corresponding to one pixel. To. Further, the inspection device as the fourth embodiment includes an electro-optical device 370 in place of the electro-optical device 70 (see FIG. 3) of the first embodiment.

0071FIG. 15 shows a schematic configuration of the electro-optical device 370. In FIG. 15, the same components as those in the first embodiment (FIG. 3) are designated by the same reference numerals as those in FIG. The electro-optical device 370 includes a blocking unit 378 in addition to the configuration shown in FIG. The blocking unit 378 includes a blanking electrode 376 and a blanking aperture 377. The blanking electrode 376 blanks an electron beam that is irradiated from the light source 71 and has passed through the lens 72d. Specifically, the blanking electrode 376 deflects the electron beam to the outside of the opening of the blanking aperture 377 at high speed by electrostatic deflection, and controls the electron beam so that it does not reach the E × B filter 72e. .. According to the blocking unit 378, even when the moving speed of the wafer W is not constant, the exposure time of the wafer W can be uniformly controlled for each interval in which the integrated detection amount is transferred from the TDI sensor 75.

0072FIG. 16 shows an example of a configuration for controlling the exposure time. In FIG. 16, the configurations of the stage device 50 and the electro-optical device 370 described above are shown in a simplified manner. Further, in this example, a linear motor 356 is used instead of the servomotor 56 as an actuator for moving the wafer W in the Y direction. As shown in the figure, the wafer W moves in the Y direction when the Y table 52 is moved by the linear motor 356. The amount of movement of the wafer W is measured by the position detection unit 58 as described above. Specifically, the position detection unit 58 includes a laser oscillator 58a as a light source, a laser interferometer 58b, a mirror plate 58c fixed to a Y table 52 (or holder 55), and a coordinate detection unit 58d. There is. The light emitted from the laser oscillator 58a is emitted to the mirror plate 58c through the laser interferometer 58b, and the reflected light returns to the laser interferometer 58b. The laser interferometer 58b is a combination of an incident wave from the laser oscillator 58a and a reflected wave from the mirror plate 58c. The phase difference is detected and input to the coordinate detection unit 58d. The coordinate detection unit 58d detects the coordinates of the wafer W, strictly speaking, the Y table 52 (or holder 55) based on the input phase difference.

0073The coordinate values detected by the coordinate detection unit 58d are fed back to the stage control unit 385 that controls the stage device 50, and are input to the coordinate difference value detection unit 386. The coordinate difference value detection unit 386 calculates the difference between the newly input coordinate value and the previously input coordinate value, and inputs the difference to the parallel / serial conversion unit 387. The parallel / serial conversion unit 387 inputs a serial transfer pulse to the TDI sensor 75 at the timing when the wafer W moves by a distance corresponding to one pixel of the TDI sensor 75 based on the coordinate values input as the parallel digital value. .. This transfer pulse is also input to the constant pulse generation unit 388.

0074The constant pulse generator 388 inputs a blanking signal to the amplifier 389 each time a transfer pulse is input. A blanking signal is a single pulse having a pulse width of a certain period of time. This blanking signal is input to the blanking electrode 376 after the high (H) level and the low (L) level are inverted by the amplifier 389. When a high level is applied to the blanking electrode 376, the blanking electrode 376 deflects the electron beam to the outside of the opening of the blanking aperture 377. That is, during the period when the blanking signal is at a high level, the electron beam is emitted toward the wafer W, but during the period when the blanking signal is at a low level, the electrons are emitted by the blanking electrode 376 and the blanking aperture 377. The beam is blocked from reaching the wafer W side. In this embodiment, the stage control unit 385, the coordinate difference value detection unit 386, the parallel / serial conversion unit 387, and the constant pulse generation unit 388 are included in the control device 84 (see FIG. 1). However, at least some of these functions may be separate from the control device 84.

0075FIG. 17 shows the timing of irradiating the wafer W with the electron beam in the inspection apparatus of the fourth embodiment. It is assumed that the wafer W here is free from defects and foreign matter. That is, it is assumed that the secondary charge amount obtained from the wafer W is uniform over the entire region of the wafer W. As shown in the figure, in the period T1 from the generation of the first transfer clock to the generation of the subsequent second transfer clock, that is, in the period in which the wafer W moves by a distance corresponding to one pixel, the first The blanking signal becomes high level during the period T11 from the timing when the transfer clock rises. During this period T11, since the electron beam is irradiated toward the wafer W, the amount of charge accumulated in the first pixel of the TDI sensor 75 increases at a constant rate from zero to charge Q1. After that, in the remaining period T12 of the period T1, the blanking signal becomes low level, so that the electron beam is prevented from reaching the wafer W side. Therefore, during the period T12, the amount of charge accumulated in the first pixel of the TDI sensor 75 is maintained as the charge Q1. When the second transfer clock is generated, this charge Q1 is transferred to the second pixel adjacent to the first pixel, so that the second transfer clock is generated and the third transfer clock is generated thereafter. With the start of T2, the amount of charge is reset to zero. In this example, period T2 is shorter than period T1. That is, the moving speed of the wafer W varies.

0076Next, in the period T2, the blanking signal becomes high level from the timing when the second transfer clock rises to the period T21. As described above, since the pulse width of the blanking signal is constant, the period T11 and the period T21 are the same time. Therefore, in the period T12, the amount of charge accumulated in the first pixel increases at a constant rate from zero to the charge Q1 as in the period T11. After that, in the remaining period T22 of the period T2, the blanking signal becomes low level, so that the electron beam is prevented from reaching the wafer W side. Therefore, the amount of charge accumulated in the first pixel is maintained as the charge Q1 and is transferred to the second pixel when the period T2 elapses. Although the explanation is omitted, the period T3 that follows the period T2 and is shorter than the period T2. However, the electric charge Q1 is accumulated in the first pixel. In the above example, the rise of the transfer clock and the rise of the blanking signal have been described as being the same, but the blanking signal may rise after a certain period of delay from the rise of the transfer clock. As described above, in this embodiment, the time for irradiating the wafer W with the electron beam is constant regardless of the moving speed of the wafer W.

0077On the other hand, when the blocking unit 378 is not provided, as shown in FIG. 18, the charges Q2, Q3, and Q4 accumulated in the first pixel during the periods T1, T2, and T3 are proportional to the exposure time. , Q2&gt; Q3&gt; Q4. That is, even when there is no region distribution in the surface characteristics of the wafer W, the amount of electric charge is not constant due to the variation in the moving speed of the wafer W.

0078In the above-described inspection device, the pulse width of the blanking signal does not exceed the minimum value of the fluctuation range in consideration of the fluctuation of the time required for the wafer W to move by the distance corresponding to one pixel of the TDI sensor 75. It is desirable to set as large as possible. By doing so, the exposure time can be lengthened within the range in which the exposure time at each position of the wafer W can be kept uniform, and as a result, the TDI sensor 75 can perform highly sensitive imaging. Normally, the speed variation of the stage device 50 is in the range of 1% to 0.1%. The value of this speed fluctuation is often defined by the maximum speed, and increases when the speed becomes low. For example, when the moving speed is 30 mm / s and the speed fluctuation rate is 1%, in many stage devices, the speed fluctuation rate is about 10% when the moving speed is 3 mm / s. .. One of the reasons for this is that the loop gain of the servo is constant regardless of the speed. In order to keep the brightness constant regardless of this velocity fluctuation rate, it is desirable to determine the pulse width of the blanking signal in consideration of the period of the transfer pulse of the TDI sensor 75 shortened by the velocity fluctuation. Further, in order to secure the number of secondary charges to be detected, it is desirable to lengthen the irradiation time in one cycle as much as possible. Assuming that the average transfer pulse period at low speed is t1, t1 ± 10% is the range of the transfer pulse period. If the transfer pulse period is long, there is no problem, but if it is short, there is a possibility that fluctuations cannot be absorbed. In addition, it is desirable to consider the rise and fall times of the pulse, the response time of the blanking mechanism, and the like. Therefore, for example, it is conceivable to allocate about 80% of the average transfer pulse period to the irradiation time in one cycle, that is, to use the pulse width of the blanking signal and the remaining 20% to the fluctuation absorption allowance. Of course, this is a value that applies the stage volatility, etc. as a predetermined example in order to make it possible to absorb fluctuations, and when using a stage with a smaller volatility, each value is based on the same idea. Should be applied.

0079According to the inspection device described above, even if the moving speed of the wafer W fluctuates, the movement of the wafer W at a distance corresponding to one pixel and the transfer clock are completely synchronized, so that the image is projected onto the TDI sensor 75. The image can be brought closer to the ideal position with high accuracy. Therefore, the wafer W can be inspected with high accuracy. Moreover, since the time for irradiating the wafer W with the electron beam is constant regardless of the moving speed of the wafer W, if there is no region distribution in the surface characteristics of the wafer W, it is accumulated in the pixels of the TDI sensor 75. The amount of charge is always constant. Therefore, even if the moving speed of the wafer W, that is, the exposure time varies, it is possible to generate image data in which the brightness unevenness caused by the variation in the exposure time is alleviated. As a result, the accuracy of the inspection using the image data can be further improved.

0080The inspection apparatus described above may include a monitoring unit that monitors the moving speed of the wafer W, in other words, the holder 55 or the Y table 52. The moving speed can be easily grasped by using the measurement result of the position detection unit 58. Further, the inspection device may include a setting unit for setting the pulse width of the blanking signal based on the monitoring result of the moving speed by the monitoring unit. This setting unit may move the Y table 52 on a trial basis before imaging the wafer W, and set the pulse width of the blanking signal based on the monitoring result by the monitoring unit at that time. With such a configuration, when mass-producing inspection equipment, a bra is used according to individual differences in the movement characteristics of the Y table 52. The pulse width of the linking signal can be set to a suitable value. Alternatively, the pulse width of the blanking signal may be reset based on the monitoring results of the monitoring unit up to that point every time the imaging of a predetermined number of wafers W is performed at a predetermined timing, for example, every predetermined period. With such a configuration, the pulse width of the blanking signal can be set to a suitable value even when the movement characteristics of the Y table 52 fluctuate. The monitoring unit and the setting unit may be configured as a part of the control device 84.

0081The position of the blocking portion 378 is not limited to the above example, and may be a position capable of achieving either the beam reaching the wafer W side or the secondary charged particles reaching the TDI sensor 75. For example, the blocking unit 378 may be provided between the TDI sensor 75 and the secondary optical system 73, or may be provided between the stage device 50 and the secondary optical system 73.

0082The blocking unit 378 is not limited to the blanking means, and may have any configuration capable of blocking the beam from reaching the wafer W side or the secondary charged particles from reaching the TDI sensor 75. For example, when an electromagnetic wave is emitted from the light source 71, the blocking unit 378 may be an openable / closable shutter that blocks the electromagnetic wave.

0083D. Modification example: D-1. Modification 1: Modification 1: The target position in EO correction is not limited to the above example, and when expressed in a Cartesian coordinate system with the horizontal axis as time and the vertical axis as the target position, from the input of one transfer clock to the input of the next transfer clock. It may be set in a stepped shape in which the target position is maintained at the same position for a predetermined time equal to or less than the period (hereinafter, also referred to as a transfer interval period) and then rises by a predetermined distance. For example, the target position is maintained at the same position with respect to the conventional target position TP0 shown in FIG. 5 for a shorter period of time than the transfer interval period (for example, period T2 in FIG. 5), and then on the vertical axis. It may be set to stand up in parallel and return to the line of the target position TP0. Further, the step-like is not limited to a configuration in which the stairs rise parallel to the vertical axis, and may have an inclination with respect to the vertical axis. Even with these configurations, as compared with the conventional EO correction in which the target position is set to the target position TP0, it is possible to suppress the projection image of the wafer W from moving away from the ideal position, and the inspection accuracy can be improved.

0084D-2. Deformation example 2: The inspection device described above may irradiate the inspection target with an electromagnetic wave (light) and capture the secondary electromagnetic wave reflected on the inspection target, that is, the reflected light with the TDI sensor 75. In this case, the secondary optical system that guides the reflected light to the TDI sensor 75 may include a deflection portion that shifts the focus of the secondary electromagnetic wave. This deflection unit corresponds to the deflection unit 90 of the first embodiment, and includes, for example, a movable lens and an actuator. The deflection unit shifts the focus of the secondary electromagnetic wave by driving an actuator to move the movable lens in a direction orthogonal to the optical axis of the secondary electromagnetic wave. Such a deflection unit realizes the same function as the EO correction of the first embodiment, and the deflection amount can be determined by the same configuration as the EO correction circuit 94 of the first embodiment.

0085Although the embodiments of the present invention have been described above based on some examples, the above-described embodiments of the invention are for facilitating the understanding of the present invention and limit the present invention. It's not a thing. The present invention can be modified and improved without departing from the spirit thereof, and it goes without saying that the present invention includes an equivalent thereof. In addition, any combination or omission of the claims and the components described in the specification is possible within the range in which at least a part of the above-mentioned problems can be solved, or in the range in which at least a part of the effect is exhibited. Is.

00865,205 ... Inspection equipment 10 ... cassette holder 20 ... Mini Environment Device 21 ... Mini environment space 22 ... housing 23 ... Gas circulation device 24 ... Discharge device 25 ... Pre-aligner 27 ... Shutter device 30 ... Main housing 40 ... loader housing 41 ... Wafer rack 50 ... Stage equipment 51 ... Fixed table 52 ... Y table 53 ... X table 54 ... turntable 55 ... holder 56,57 ... Servo motor 58 ... Position detector 58a ... laser oscillator 58b ... Laser interferometer 58c ... mirror plate 58d ... Coordinate detector 61 ... 1st transport unit 62 ... 2nd transport unit 64 ... Aligner 70,170,370 ... Electron optics 71,171 ... Light source 72,172 ... Primary optical system 72a, 72d, 72f, 72h, 72i ... lens 72b, 72c, 72g ... Aperture 72e ... E × B filter 73,173 ... Secondary optical system 73a, 73c ... lens 73b ... NA Aperture 73d ... Aligner 74 ... TDI clock generator 75 ... TDI sensor 80,280 ... Image processing equipment 81 ... Image data generator 84 ... Control unit 90 ... deflection part 91 ... Deflection electrode 92 ... EO corrector 94 ... EO correction circuit 95 ... Comparator 96 ... adder / subtractor 97 ... Register 98 ... adder 99 ... subtractor 282 ... Normalization Department 285 ... Clock generator for normalization 286 ... counter 287 ... Division 288 ... Multiplication part 356 ... Linear motor 376 ... Branking electrode 377 ... Branking Aperture 378 ... Block 385 ... Stage control unit 386 ... Coordinate difference value detector 387 ... Serial converter 388 ... Constant pulse generator 389 ... amp W ... Wafer C ... cassette AP ... real position TP0, TP1, TP2 ... Target position