JP5216307B2 - Semiconductor visual inspection apparatus and inspection method - Google Patents

Description

  The present invention relates to an inspection apparatus and an inspection method using an electron beam for inspecting a semiconductor device having a fine pattern, a substrate, a photomask (exposure mask), a liquid crystal, and the like.

In order to detect abnormalities or defects in the manufacturing process of the semiconductor device at an early stage or in advance, a pattern inspection on the semiconductor wafer is performed at the end of each manufacturing process.
As a method for inspecting this defect, a method and apparatus for inspecting a pattern using an electron beam image with high resolution have been put into practical use. In practical use, in order to perform high-throughput and high-accuracy inspection following the increase in wafer diameter and circuit pattern miniaturization, it is necessary to acquire a high SN image at a very high speed. Furthermore, high-speed and highly efficient detection of secondary electrons and reflected electrons generated from the substrate is essential. Further, a low acceleration electron beam of 2 keV or less is irradiated so that a semiconductor substrate with an insulating film such as a resist is not affected by charging.

  In Patent Document 1 (Japanese Patent Laid-Open No. 5-258703), the substrate is irradiated with an electron beam current 100 times or more (10 nA or more) of a normal SEM, and any of the generated secondary electrons, reflected electrons, or transmitted electrons is irradiated. There has been proposed a method for detecting and detecting a defect from an image obtained from the detection signal. Specifically, the beam deflector is composed of two stages of 20-pole plates, and the beam deflection control circuit is composed of a deflection waveform generator and a high-voltage, low-noise amplifier to generate a ± 180 V ramp waveform. Is disclosed.

  Patent Document 2 (Japanese Patent Laid-Open No. 2000-100322) proposes a digital method in which a digital value is specified stepwise and a staircase wave obtained by DA conversion is used as a basic scanning signal. In this method, scanning control and various corrections can be performed using digital operations based on the scanning signal deflection position, various apparatus error information, irradiation position height information, etc. There is a feature that it is possible to improve the accuracy of the beam irradiation position and the degree of freedom of beam scanning by correcting the position error.

In any of the above systems, an image is acquired by scanning the electron beam at high speed from the inspection start point to the end point in a direction perpendicular to the advancing direction of the stage that moves the sample by the deflection signal of the ramp waveform from the deflection means. The one-time scan performed in the direction perpendicular to the moving direction of the stage is called a line scan.
As shown in FIG. 2A, the conventional line scan method is a one-way line scan method in which an image is acquired by irradiating an electron beam only in one direction indicated by a solid line. When one line scan is completed, the beam moves to the start point of the next line scan as shown by the dotted line in FIG. The time required for this movement is called the beam return time, and usually no image is acquired during this time.
FIG. 2B shows a deflection control signal (deflection voltage signal) waveform of beam scanning in the unidirectional scan mode, and an effective deflection portion (effective scan time T_valid) of this waveform is a predetermined deflection field of view and deflection time. It changes with the inclination decided by. On the other hand, the beam return time is required to convert the voltage value of the deflection control signal from the voltage at the end time to the start voltage required for the next line scan as soon as possible.

However, due to the influence of the response characteristics of the voltage deflection output circuit, there is a phenomenon in which the actual deflection signal does not return to the starting point voltage unless a certain period of time is taken back. When the next line scan starts without the starting point voltage returning to a certain voltage, a position shift occurs in the first part of the acquired image on each line, and due to this position shift, the scan start area of the acquired inspection image Cause degradation of image quality and sensitivity. Actually, the return waveform is as shown by the solid line in FIG. 2B, and there is a deviation from the ideal return waveform indicated by the dotted line.
In order to solve this and satisfy the required specification of the inspection sensitivity, it is conceivable to extend the turn-back time. However, the unnecessary scan time T_invalid shown in FIG. It will cause a problem of degradation. Since the throughput of the inspection device is expressed as the reciprocal of the inspection time per unit area, the length of the wasted time T_invalid, specifically, the length of the settling time required for reversion is a dominant obstacle to improving the device throughput. ing.

As a technique for shortening the dead time T_invalid, there is a bidirectional scan mode. As shown in FIG. 3 (a), for example, (i) 'th scan from left to right, (ii)' th from right to left, and (iii) 'th still Scanning is performed by repeatedly switching the scanning direction from left to right.
The beam scanning deflection control signal (deflection voltage signal) waveform in the bidirectional scan mode is as shown in FIG. 3B, and an effective deflection part (effective scan time T_valid) for acquiring an image is a unidirectional scan. Similarly, it changes with an inclination determined by a predetermined deflection visual field and deflection time. After one line scan is completed, the deflection voltage is changed to a voltage required by the start point of the next line scan. However, in the case of bidirectional scanning, the end point of the previous line and the start point of the next line are basically the same area along the scanning direction, and the difference between them is very small. The change in deflection voltage is small, and the useless time T_invalid can be shortened. That is, compared with the unidirectional scan, the entire inspection time can be reduced, and the throughput can be improved.

However, in the unidirectional scan, the charging condition of the sample at each starting point at the time of line scanning was almost the same. In the case of bidirectional scanning, the beam scanning direction between the front and rear lines depends on the charging characteristics of the inspection sample. The charging situation resulting from the difference between the images differs, and a new problem arises that the image quality of the acquired images does not match. Since this difference in image quality is seen as noise, it will affect the inspection sensitivity as a result.
In the case of bidirectional scanning, the voltage value conversion between the end points and start points of the front and rear lines is small, but the direction of voltage change is reversed, and the rate of change between the points may differ greatly. Since the rate of change of the analog voltage can only change continuously, a certain pause time is also required between line scans.

  On the other hand, in Patent Document 3 (Japanese Patent Application Laid-Open No. 2002-251975), in a scanning electron beam apparatus with a variable scanning speed, when the scanning speed is high, performance deterioration due to image quality change or deflection distortion near both ends of the scanning area is described. In order to prevent this, a technique for comparing and inspecting defects based on an image signal that has been deleted by controlling the blanking signal at both ends of the scanning area has been disclosed. Request downtime.

JP-A-5-258703 Japanese Patent Laid-Open No. 2000-10032 JP 2002-251975 A

Therefore, in order to achieve high sensitivity and high throughput of the inspection apparatus, it is necessary to minimize the extra downtime between line scans for each scan mode. In particular, the turn-back time of the deflection control signal is an obstacle to increasing the inspection time and improving the image quality of the inspection image, and it is essential to shorten it.
For actual inspection, it is effective to be able to switch the scan mode according to the characteristics of the sample to be inspected in order to use each advantage of the unidirectional line scan method and bidirectional line scan method effectively. is there.

  Furthermore, since the setting of the scanning sequence for controlling the scanning of the electron beam based on this pause time, the stage speed, etc. greatly affects the inspection throughput or inspection sensitivity, it is necessary to set it as accurately as possible. Conventionally, in order to set the pause time as small as possible, the scan is actually performed with the pause time set to a certain value, and it is checked whether the noise amount at the start part is within the allowable value. If so, it was necessary to repeat the work of shortening the pause time and resetting the pause time longer if the allowable value was exceeded. However, since the pause time is different for each inspection condition, the conventional setting method has a problem that a huge amount of time is required for setting.

The present invention reduces the settling time of the deflection signal between the scan lines with respect to the deflection signal for controlling the scanning of the electron beam, and improves the problem of throughput reduction and image quality degradation due to the settling time, The present invention provides a high throughput and high sensitivity of an electron beam scanning device.
In addition, the present invention provides means for visually recognizing a necessary rest time on a GUI screen according to various inspection conditions when the scan mode is switched.
Furthermore, the present invention quantitatively calculates and displays the relationship between the length of the pause time and the amount of deviation that can be generated in the scan start area according to various inspection conditions for each scan mode. In addition, a method for efficiently setting the inspection sensitivity and throughput to optimum values is provided.

  One aspect of the present invention switches the scan mode on the GUI screen according to the charging characteristics of the test sample, and conventionally, according to the specific test conditions such as the scan mode and the inspection field of view, pixel size, optical conditions, etc. As for the return time of the deflection signal for which no image has been acquired, an image obtained by irradiating a sample having a registered pattern is acquired. Then, the analog waveform of the return is converted from the obtained deflection signal, the correction data extracted by comparing the analog waveform with the ideal return waveform is input to the deflection waveform data generation unit, and the actual waveform is input. By generating the deflection waveform data so that the waveform approaches the ideal waveform, the settling time at the time of reversing can be shortened and high throughput can be realized.

  According to another aspect of the present invention, first, an image in which a conventional image is deleted is obtained by irradiating a sample having a registered pattern in accordance with each specific inspection condition for each scan mode, and a GUI screen is obtained. Displayed above. Subsequently, an analog waveform signal to which the deflection voltage signal is returned is converted from the acquired image, and based on the analog output waveform, the information is paused for each information such as optical conditions, pixel size, number of pixels, and scan cycle variation set by the user. The amount of scan start area noise that can be generated with time is calculated and displayed on the GUI screen. Based on the relationship between the displayed pause time and scan start area noise, it is possible to select the optimum inspection conditions for detection sensitivity and throughput.

In addition, the outline of a representative one of the inventions disclosed in the present application will be briefly described as follows.
(1) A sample stage for holding a sample to be inspected, an irradiating unit for irradiating the sample to be inspected with an electron beam, a deflecting unit for deflecting the electron beam, and outputting a deflection control signal to the deflecting unit to output the deflection. An inspection apparatus comprising: deflection control means for controlling the means; and detection means for detecting secondary electrons from the specimen to be inspected by the electron beam deflected by the controlled deflection means, wherein the deflection The control means is an inspection apparatus characterized in that the deflection means is controlled by a deflection control signal in which a portion of the deflection control signal waveform corresponding to the return time of the electron beam is corrected.
(2) A stage for holding the sample to be inspected, an electron source for irradiating the sample to be inspected with an electron beam, lens means for focusing the irradiated electron beam, and deflecting means for deflecting the focused electron beam A deflection control means for controlling the deflection means, a detection means for detecting electrons secondarily generated from the sample to be inspected by the irradiated electron beam, and a detection signal obtained by the detection means as an image. An image signal obtained by irradiating the sample having a specific registered pattern with the electron beam, the conversion means for converting into a signal and a display means for displaying the inspection result based on the image signal. Using a waveform conversion means for converting a deflection control signal from the correction data, a correction data extraction means for extracting correction data from the converted waveform of the deflection control signal, and the extracted correction data An inspection apparatus characterized by having a deflection waveform data generating means for generating a deflection control signal having a reduced settling time of the return swing.

According to the present invention, the return waveform of the deflection signal that controls the scanning of the electron beam is detected and corrected, and the settling time of the return is reduced, thereby reducing the throughput and image quality degradation caused by the settling time. Can be improved, and high sensitivity and high throughput of the electron beam scanning apparatus can be provided.
In addition, the relationship between the length of the pause time and the amount of deviation that can occur in the scan start area is quantitatively calculated and displayed according to various inspection conditions in each scan mode. Based on the display result, the user can check the inspection sensitivity and throughput. It is possible to easily perform the optimal setting.

  Hereinafter, specific embodiments of the present invention will be described.

  A first embodiment of an inspection apparatus according to the present invention will be described with reference to FIG. FIG. 1 is a schematic block diagram showing a configuration example of an electron beam scanning apparatus, which is an application example to an automatic inspection apparatus for wafers and the like. In accordance with the command, the deflection of the electron beam 31 irradiated from the electron gun 30 to the specimen 33 placed on the stage 34 through the deflecting means constituted by the focusing lens 36 and the electrostatic electrode plate 32 and the objective lens 37 is controlled. The deflection controller 2, the detector 35 for detecting the product generated by the electron beam 31 irradiated on the sample 33, the signal processor 4 for processing the signal from the product obtained by the detector 35, And a GUI screen 5 for displaying the inspection result.

  Hereinafter, detailed explanations and specific operations of each part will be described while showing a simple inspection operation of the inspection apparatus. In FIG. 1, the system control means 10 provided in the overall control unit 1 determines an inspection sequence, and transfers various scanning parameters and commands to the deflection control unit 2 through the deflection scanning control unit 11. In the deflection control unit 2, the electron beam 31 is deflected by controlling the voltage applied to the deflecting means composed of the electrostatic electrode plate 32 according to the parameters, and the target position on the sample 33 such as a wafer or mask is scanned. . The product generated at that time is taken in as information on the sample 33 by the detector 35 and the detection circuit 41 provided in the signal processing unit 4, and the image processing means 42 further sends the information on this product to the beam deflection position. By processing as pixel data, image data of the sample 33 is obtained. The acquired image data is compared with the image or design data having the same pattern on the sample in the image processing means 42, and the result is used for evaluation of the difference in pattern and process management by the system control means 10. Inspection is performed by performing the above data processing, and the inspection result is displayed on the GUI screen 5.

  The deflection waveform data generating means 21 of the deflection control unit 2 is a ramp type so that the electron beam 31 can be linearly scanned from the start point to the end point of the scan line according to the scan control parameter from the deflection scan control unit 11 of the overall control unit 1. The digital data of the deflection control signal having the following waveform is generated. The deflection waveform generation means 22 converts an analog waveform from the generated waveform data, and then controls the deflection means constituted by the electrostatic electrode plate 32 based on the deflection control signal amplified by the output circuit 23 to control the electron beam. Controls 31 deflections. At the same time, the stage 34 on which the sample is placed moves at a low speed in the direction perpendicular to the electron beam 31 based on a command instruction from the system control unit 10. When the scanning of one line from the start point to the end point of the electron beam 31 is completed, the stage 34 is moved during that time, and the scanning start area is arranged on the next scanning target line on the sample 33, and the next line is continuously moved. The scan starts.

  As the line continuous scan mode, there are a one-way scan mode and a two-way scan mode as shown in FIG. When an actual inspection is performed, a scan mode switching function is required according to the specimen charging characteristics of the inspection object. In this inspection apparatus, the scan mode control means 13 capable of switching the scan mode according to a user instruction is provided. This is realized by arranging in the overall control unit 1, and the result is confirmed on the GUI screen 5.

  On the other hand, in order to realize high-speed inspection, it is necessary to return the beam to the scanning start point as soon as possible, and it is necessary to correct the return signal in consideration of the settling time of the response characteristic of the deflection system circuit. Furthermore, since the amplitude, period, etc. of the deflection signal change depending on the inspection conditions, the scanning signal, for example, when the scan mode is switched from bidirectional scan to unidirectional scan, accurately and appropriately. A correction means capable of performing correction is required.

Here, in the above operation, the deflection control signal swing-back correction processing is roughly divided into two stages. The first stage is a stage of measuring the actual waveform of the swing-back waveform and extracting correction data from the comparison with the ideal swing-back waveform. In the normal inspection mode, the blanking signal that is turned on because the image is not acquired during turning back of the deflection signal is turned off, and image data of the time for turning back the sample having a known pattern registered in advance is stored. By acquiring, the return waveform of the change control signal is measured, and the correction parameter used to correct the settling time is extracted.
The second stage is a stage in which the extracted correction parameters are used to correct the back-up during normal inspection, and appropriate corrections are made based on the relationship with the scanning parameters for each scan, and each inspection condition is met. A deflection control signal is generated.

  In the first step of measuring the actual waveform of the return waveform and extracting the correction data, first, for the purpose of measuring the return characteristic of the deflection circuit, a sample having a pre-registered pattern (even if it is a dedicated wafer). Image data may be acquired using a special pattern embedded in a wafer used for normal inspection. Similar to the normal inspection, various scanning parameters are transferred from the system control means 10 to the deflection control means 2, and a lamp deflection control signal is generated as in the normal inspection. However, as described above, in the case of a normal inspection as shown in FIG. 4, the blanking signal is turned off at the ramp portion of the deflection control signal, the beam is irradiated onto the sample, an image is acquired, and the deflection signal is returned. In the meantime, the blanking signal is turned on and no image is taken, but in the above-mentioned mode of measuring the return waveform, contrary to the normal inspection, it is necessary to turn off the blanking signal when acquiring the deflection signal and acquire the image. is there. On the other hand, the blanking signal is turned on at the ramp portion of the deflection signal and no image is acquired.

  The registered dedicated pattern is characterized in that the deflection voltage of the beam can be converted from information such as the gradation value / position of the image data that can be detected along the scanning direction and the image data capture frequency. For example, a pattern having a unique gradation value according to the distance from the scanning start point or a periodic gradation value according to the distance from the scanning start point shown in FIG.

  In the inspection apparatus according to the present invention, as shown in FIG. 1, a deflection waveform conversion means 43 is provided in the signal processing unit 4 to measure the actual waveform of the return waveform, and is registered in advance detected by the above method. Waveform data is obtained from the image data of the known pattern obtained by the procedure shown in FIG. Specifically, the gradation value of the image data obtained from the image processing means 42 is checked (step 601), and the actual image is obtained from the gradation value and the positional information of the image data that should be obtained when the known pattern is scanned. Is calculated (step 602), and the voltage amount of the corresponding deflection return signal is calculated (step 603). Further, the timing corresponding to the deflection voltage is calculated from the ID number of the image data and the image capture frequency (step 604), and voltage / time information of the deflection return signal is obtained. If there is unprocessed image data at this time, the process returns to step 601 and the same processing is repeated for other image data (step 605). When all the image data has been processed, approximation / interpolation is performed. Processing is performed to obtain a deflection return waveform (step 606).

  Further, in order to extract correction data from the comparison between the deflection return waveform obtained as described above and the ideal return waveform, correction data extraction means 12 is provided in the overall control unit 1 as shown in FIG. The correction data is extracted and registered according to the steps of FIG. Specifically, measurement conditions and parameters are set on the GUI screen (step 701), and the return waveform is measured as described above under the conditions (step 702). It is confirmed whether the return waveform obtained here is the shortest (step 703). If it is not the shortest, the settling time is measured (step 704), and the comparison between the return waveform and the ideal return waveform is performed again. The difference data is extracted from (step 705), the difference data is processed with a constant weighting factor and added to the original return waveform data, and the deflection waveform data is updated (step 706). Using the updated deflection waveform data, a deflection signal is generated again, and the return waveform is measured (step 702), and it is confirmed again whether the settling time is the shortest (step 703). In this way, correction data is generated using the difference between the measured actual return waveform information and the ideal return waveform as a feedback input signal, the adjustment of the return part of the deflection data is performed, and the measured return waveform and the ideal return waveform are adjusted. Correction data when the return waveform is closest or when the main settling time is minimized is registered as final correction data (step 707). When correction data for other inspection conditions is also necessary, the same steps are repeated (step 708), whereby optimum correction data for each inspection condition can be extracted and registered.

The above-described measurement of the return waveform and the extraction of the correction data are performed based on commands such as inspection conditions and parameters designated on the GUI screen by the user in accordance with the scan mode switching work, and the calculated correction data is An apparatus constant corresponding to each inspection condition is registered in the system control means 10 or the deflection scanning control means 11 (FIG. 1 shows an example of registration in the deflection scanning control means 11).
In this way, by providing the deflection waveform conversion means 43 and the correction data extraction means 12 for measuring the return waveform from the image data of the sample having the pattern to be registered and extracting the correction data, it is possible to easily measure the return waveform. In addition, this measurement can measure the characteristics of the deflection circuit in the same operating state as that at the time of inspection, and thus an accurate value can be obtained.

  In addition, although the example which used image data was shown above as a return waveform measurement method, if this can calculate the deflection voltage amount at the time of return, it can also be replaced with another form. For example, even if the known pattern is a linear pattern or dot pattern arranged at equal intervals and the time crossing between the patterns is measured based on a signal detected during scanning, the difference in deflection voltage at that timing is approximate. A pattern having these characteristics may be used as a registered pattern.

  Next, in the second stage in which the correction waveform extracted and registered as described above is used to correct the return waveform during the normal inspection, the deflection waveform data generating means 21 included in the deflection control unit 2 is The system control means 10 and the deflection scanning control means 11 provide scanning parameters for each scan and correction data corresponding to the scanning parameters, thereby forming a deflection control signal that has been corrected according to the inspection conditions.

Next, a second embodiment of the inspection apparatus according to the present invention will be described with reference to FIG. 8, FIG. 9, and FIG.
The basic configuration of the apparatus of the second embodiment according to the present invention is substantially the same as that of the first embodiment as shown in FIG. The part will be mainly described. This different part is that, after converting the return waveform of the deflection control signal, the predicted noise value is calculated for each inspection condition by the scan start area noise calculation means 14 and displayed on the GUI screen 5 as follows. Details will be described.

First, as in the first embodiment, the conversion analog waveform of the deflection control signal is converted, and the magnitude of the scan start area noise that can be generated at every fixed pause time is predicted based on the converted deflection waveform shape. .
Here, the cause of occurrence of the scan start area noise will be described with reference to FIGS. The cause of noise in the scan start area is the start position shift of each line scan. Since the start position of each line scan is determined by the start voltage of the corresponding deflection voltage waveform, the cause of noise occurs due to variations in the start voltage of each line scan start point. The starting point voltage of the starting point is determined based on the inclination at the time of convergence of the deflection return waveform and the variation in the start timing (line scan period) of each of the scans. FIG. 9 shows the relationship between the tilt at the time of convergence of the deflection return waveform, the variation in the start timing of each of the scans, and the start area noise of the acquired image. The horizontal axis represents time, and the vertical axis represents voltage. The waveform of the deflection voltage signal for controlling the represented scan is displayed. The right side of the figure shows the image obtained by scanning the beam based on the deflection signal shown on the left side, with the stage moving direction in the horizontal direction and the line scanning method of the beam in the vertical direction. This pattern is a standard pattern of lines and spaces arranged at equal intervals parallel to the stage moving direction and perpendicular to the line scanning direction.

  The waveform of the deflection voltage signal (deflection control signal) shown in FIG. 9 does not converge to the next start voltage, and the line scan start time varies. As shown in the figure, when the next scan start time comes, the deflection waveform does not converge to the next start voltage, so line line scans started at different start timings are due to differences in the start voltage values of the scans. The irradiation position on the sample is also different, and the position of each line is displaced along the scanning direction.

  Therefore, in the present embodiment, the magnitude of noise generated in the line scan start region is determined based on the degree of convergence (slope) of the deflection waveform toward the next start voltage and the range of variation in the line scan start time. Optical conditions such as beam current and acceleration voltage, inspection pixel size, number of inspection pixels, sampling speed for acquiring images, etc. when the scan mode is switched from bidirectional scanning to unidirectional scanning according to the charging characteristics of the sample After inputting the inspection conditions from the GUI screen, an image during the deflection voltage return time under the actual inspection conditions is acquired using the registered pattern. The return waveform of the deflection voltage is converted by the waveform conversion means from the acquired image and the registered information of the pattern used in advance. Based on the converted shape of the return waveform (slope before convergence), the scan start area noise that can be generated for each variation range of the assumed line scan start time is calculated.

  Here, the calculation method will be specifically described below. As shown on the left side of FIG. 10, on the convergence waveform of the deflection voltage control signal, the voltage change amount ΔV of the convergence waveform within a certain time corresponding to the variation range ΔT of the scan cycle centered on the predetermined pause time t. Calculate (t, ΔT). From the deflection voltage range corresponding to the number of inspection pixels and the inspection visual field, the deflection voltage sensitivity per pixel can be converted by the following (Equation 1).

(Expression 1) δV_per_pixel = V_pp / number of pixels Further, the start region deviation noise δN_start that can be generated with respect to a variation range ΔT between a certain pause time t and a certain scan start time can be calculated by the following (Expression 2). is there.

(Formula 2) δN_start (t, ΔT) = ΔV (t, ΔT) / δV_per_pixel
If calculation is performed by shifting the pause time t and the start time variation range to selectable regions, the noise in the scan start region corresponding to these parameters can be calculated quantitatively.

  The result is displayed on the GUI screen as shown on the right side of FIG. 10, and when the user sets the inspection condition such as the stage speed in accordance with the switching of the scan mode, the scan start that can be generated corresponding to each inspection condition is started. It becomes possible to visually predict the amount of noise in the region. In order to satisfy the inspection sensitivity that requires this amount of noise, it is possible to efficiently set the pause time or stage moving speed to an optimum value.

Next, a third embodiment of the inspection apparatus according to the present invention will be described with reference to FIG. Since the configuration of the inspection apparatus of the present embodiment is substantially the same as that of the first embodiment, only different points will be described.
When bi-directional scanning is performed, a deflection voltage waveform having a flat voltage level is ideal as shown by a broken line during a pause time, but in reality, a waveform like a solid line is obtained. As shown in the figure, normally, in the time between the target end point voltage and the start point voltage, in order to prevent deterioration in performance due to image quality change or deflection distortion near the both ends of the scanning area, The defect is comparatively inspected based on the image signal deleted by the control of the blanking signal. However, since the range of image quality change and deflection distortion near the both ends of the scanning region changes depending on the inspection conditions such as the optical conditions and the inspection visual field, it is necessary to delete an appropriate region according to each condition.

  In this embodiment, by using a previously registered pattern, both end portions of the inspection area are appropriately deleted by blanking signal control as in case 1 in FIG. 11, and the blanking signal in the effective image area is turned on. The image is acquired by the control of Case 2 which is OFF during the downtime, and is displayed on the GUI screen. If the image information of the registered pattern is compared with the actually acquired image, the image area that can be accurately acquired is divided, and the signal area to be deleted is also divided by the blanking signal. By calculating the necessary blanking signal timing based on the sampling speed to acquire the image and the image information of the pattern registered in advance, when the scan mode is switched, the areas that need to be cut at both ends of the inspection image during bidirectional scanning The timing can be confirmed visually.

  Here, FIG. 11 shows the blanking signal of case 2 that obtains an image during a pause time in an area slightly larger than the area originally deleted in case 1 as an example. It is easy to check. Other forms of blanking signals may be used as long as the image portion during the pause time can be confirmed. For example, the blanking signal may be turned OFF for all scanning areas, and an image of all scanning areas may be acquired.

Next, a fourth embodiment of the inspection apparatus according to the present invention will be described with reference to FIG. Also in this embodiment, part of the description common to the first embodiment is omitted, and different points are mainly described.
In this embodiment, the part different from the first embodiment is the configuration of the measuring means for the swing back waveform. In this embodiment, as shown in FIG. 12, at the output part of the amplified deflection control signal, the digitizer, A configuration is adopted in which a waveform is directly detected using a deflection waveform detector 61 such as an analog / digital conversion circuit. If it is difficult to measure the high voltage signal as it is, the resistance voltage may be used to reduce the detection means to a measurable range.

Similar to the first embodiment, the processing after the measurement of the return waveform is performed by comparing the measured return waveform with the ideal waveform signal, calculating correction data so as to shorten the settling time, and adding the deflection waveform and the addition processing. Then, the measurement flow of measurement is repeated again, and correction data that has the shortest settling time or satisfies a predetermined specification is extracted and registered in the apparatus database as a correction parameter for the same inspection condition. In addition, by using the same value during actual inspection, it is possible to shorten the settling time for the swingback and realize high throughput.
Compared with the image data conversion method of the first embodiment, the measurement method is effective in that the waveform can be directly measured and corrected.

  As described above, by configuring the deflection control system using the present invention, the return waveform of the deflection signal that controls the scanning of the electron beam is detected and corrected, and the settling time of the return is shortened. It is possible to improve the problem of throughput reduction and image quality deterioration due to settling time, and provide high sensitivity and high throughput of the electron beam scanning apparatus.

It is a schematic block diagram which shows the structural example of the electron beam scanning-type apparatus of this invention. It is explanatory drawing of the time breakdown of a unidirectional scanning mode and a deflection | deviation scanning signal. It is explanatory drawing of the time breakdown of a bidirectional | two-way scan mode and a deflection | deviation scanning signal. It is a figure which shows the control blanking signal at the time of a normal test | inspection at the time of a one-way scan, and a turning-back waveform measurement. It is explanatory drawing of the example of conversion of the return waveform from the detection image data of a registration pattern. It is explanatory drawing of the conversion procedure of a return waveform. It is explanatory drawing of the extraction procedure of the return waveform correction data. It is a schematic block diagram which shows the structural example of 2nd Embodiment of the inspection apparatus which concerns on this invention. It is a figure which shows the relationship of a return waveform convergence state, scan start time dispersion | variation, and noise. It is a figure which shows an example of the detection result in the test | inspection apparatus of 2nd Embodiment which concerns on this invention. It is a figure which shows the control blanking signal at the time of confirming a normal test | inspection and rest time at the time of a bidirectional | two-way scan. It is a schematic block diagram which shows the structural example of 4th Embodiment of the inspection apparatus which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 General control part, 2 Deflection control part, 4 Signal processing part, 5 GUI screen, 10 System control means, 11 Deflection scanning control means, 12 Correction data extraction means, 13 Scan mode control means, 14 Scan start area | region noise calculation means, 21 deflection waveform data generation means, 22 deflection waveform generation means, 23 output circuit, 30 electron gun, 31 electron beam, 32 electrostatic electrode plate, 33 sample, 34 stage, 35 detector, 36 focusing lens, 37 objective lens, 41 Detection circuit, 42 Image processing means, 43 Deflection waveform conversion means, 61 Deflection waveform detection means

Claims (7)

A stage for holding a sample to be inspected;
An electron source that irradiates the specimen with an electron beam;
Lens means for focusing the irradiated electron beam;
Deflection means for deflecting the focused electron beam;
Deflection control means for controlling the deflection means;
Detecting means for detecting electrons secondarily generated from the sample to be inspected by the irradiated electron beam;
Conversion means for converting the detection signal obtained by the detection means into an image signal;
Display means for displaying the inspection result based on the image signal,
The deflection control means includes
Waveform conversion means for converting a deflection control signal from the image signal acquired by irradiating the electron beam, correction data extraction means for extracting correction data from the converted waveform of the deflection control signal, and extracted correction data And a deflection waveform data generating means for generating a deflection control signal that shortens the settling time of the swingback using,
The waveform conversion means, the correction data extraction means, and the deflection waveform data using an image signal acquired by irradiating the electron beam during the retraction time when moving the electron beam in scanning a sample having a specific registered pattern An inspection apparatus characterized in that a deflection control signal is generated by a generation means . The inspection apparatus according to claim 1,
It has a control unit, and the control unit turns off the blanking signal during the back-up time when moving the electron beam in the sample scan, and irradiates the electron beam during the back-up time when moving the electron beam to acquire the image signal An inspection apparatus characterized by: The inspection device according to claim 1,
The deflection control means converts a deflection control signal from an image signal obtained by irradiating an electron beam using a dedicated wafer having a clear physical boundary capable of converting a deflection voltage or a dedicated pattern embedded in a user's wafer. Inspection device characterized by The inspection device according to claim 1,
And a means for calculating the amount of noise that can be generated in the start area of the inspection image corresponding to the length of the pause time based on the analog waveform converted by the waveform conversion means and the variation time of the scanning scan period. Inspection device. The inspection device according to claim 4,
The inspection apparatus is characterized in that the correction data extraction means extracts optimal correction data so that the amount of noise that can be generated during a fixed setback time is less than a required target . The inspection apparatus according to any one of claims 1 to 5,
Furthermore, a one-way scanning mode in which the electron beam is scanned in one direction to acquire an image based on the object to be inspected, and a bidirectional scanning in which an image based on the object to be inspected is alternately scanned in two directions. inspection apparatus characterized by have a mode control means for switching a mode. The inspection apparatus according to claim 6,
The inspection apparatus, wherein the one-way scanning mode and the bidirectional scanning mode can be switched on a GUI screen .

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