Inspection device and inspection method

Abstract

PURPOSE: To provide an inspection device and an inspection method that irradiates a sample with an electron beam, detects the generated electrons to obtain an image, stably applies a desired voltage to the surface of a sample having a pattern formed on an insulating substrate such as a photomask, and obtains a high-resolution and stable image.CONSTITUTION: An inspection device includes an electron gun, an objective lens, a deflection system, a stage, and detection means for generating an image, and also includes potential control means for externally controlling the potential of an electrically isolated pattern present on a sample mounted on the stage, or means for grounding the pattern.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a multi-beam inspection device using a retarding voltage. [Background technology]

[0002] Semiconductor devices are shrinking every year in accordance with Moore's Law, and the minimum feature size of cutting-edge devices is now 20 nm or less. To achieve smaller feature sizes, exposure technology capable of forming smaller patterns is required.

[0003] Conventionally, laser light with a wavelength of 193 nm has been used for exposure, but as this already far exceeds the optical resolution, in recent years there has been vigorous development of exposure technology that utilizes EUV light with a wavelength of 13.5 nm. As a result, TSMC and others have become the first in the world to successfully put this technology into practical use in the logic 7 nano generation.

[0004] Advances in exposure technology mean smaller feature sizes in photomask patterns and an increase in the number of patterns. To perform semiconductor exposure, an insulating quartz plate with a pattern drawn on it called a photomask is used. Fine patterns based on circuit design data are drawn on this quartz plate. The original plate, called the template for nanoimprinting, is also made from quartz.

[0005] In order to check whether the patterns formed on these masks are made with the correct dimensions, electron microscope technology is essential, as optical technology lacks the resolution. In order to obtain high-resolution electron beam images, it is necessary to irradiate the sample surface with electrons of a small beam spot size and detect the signal electrons, but in this case, it is essential that the sample surface does not become charged and adversely affect the irradiated electron beam and the signal electrons. DISCLOSURE OF THEINVENTION [Problem to be solved by the invention]

[0006] Conventionally, the retarding method has been used to inexpensively reduce the aberration of electron beam optical systems. In this method, the energy of the electron beam emitted from the electron gun is first accelerated to a high energy of several tens of KV, then the electron beam is focused using the electron optical system, and the electron energy is reduced to 1 KV or less by a reverse bias voltage applied to the sample before irradiating the sample. This method is characterized by its ability to maintain high resolution despite the low energy when irradiating the sample.

[0007] The higher the energy of the electron beam, the shorter the wavelength, and the more easily the beam can be narrowed down, improving image resolution. However, it has become clear that when a sample such as a semiconductor device is directly scanned with a high-energy electron beam to obtain an image and observe it, the high-energy electrons have a semi-permanent effect on the semiconductor sample, damaging the device. To prevent this, semiconductor CDSEM uses a retarding method to narrow the beam size and reduce the electron beam energy during irradiation.

[0008] In the retarding method, it is necessary that the measurement point potential on the sample surface is the desired potential. However, in the case of a photomask or nanoimprint template made of quartz, which is a dielectric material, unlike a semiconductor wafer, which is usually a conductor, the voltage applied to the electrode provided under the sample used to apply the voltage differs from the potential on the surface of the photomask, making it extremely difficult to always adjust the surface potential to the desired value. In addition, when the sample moves due to the movement of the XY stage, the electric capacitance that constitutes the measurement system changes accordingly, causing a problem in that the retarding voltage actually applied to the sample surface changes.

[0009] Furthermore, in devices that form images by accelerating secondary electrons generated on the sample surface to a predetermined energy, such as multi-beam inspection devices, there was a problem that the retarding voltage became unstable, causing problems in image formation. [Means for solving the problem]

[0010] The present invention has the advantage that a desired retarding voltage can be stably applied to the surface of a sample having a pattern formed on an insulating substrate such as a photomask, as described above, and a high-resolution and stable image can be obtained.

[0011] In order to solve the above-mentioned problems, the present invention provides an electron beam inspection device that generates a high-resolution image by applying a retarding voltage to a sample and irradiating a high-speed electron beam at a slower speed, and is configured to include an electron gun that generates an electron beam of a predetermined high acceleration voltage, an objective lens that narrows the electron beam of a predetermined high acceleration voltage generated by the electron gun and irradiates the sample with it, a deflection system that two-dimensionally scans the electron beam narrowed by the objective lens over the surface of the sample, a retarding voltage application device that applies a predetermined retarding voltage to the sample, a detection device that is provided at the tip of the objective lens facing the sample and detects the potential or capacitance of the sample surface, and a correction device that corrects a first retarding voltage so as to correct the potential of the sample surface to a constant value based on the potential or capacitance of the sample surface detected by the detection device.

[0012] In this case, a sample surface potential control device is provided which controls the second potential on the surface of the sample by applying a voltage from the outside, and based on the potential or capacitance detected by the detector, the sample surface potential control device is instructed to control the second potential, or the correction means is instructed to control the first retarding voltage, or both are controlled.

[0013] In addition, the measurement point corresponding coordinates or the surface of the sample is divided vertically and horizontally to correspond to partial areas of each intersection, and the first retarding voltage, the second potential, or both are corrected according to the movement of the sample based on the potential or capacitance measured in real time.

[0014] In addition, the surface of the sample is divided vertically and horizontally, and a table is provided in which pre-measured potentials or capacitances are registered in correspondence with partial regions of each intersection, and the first retarding voltage, the second potential, or both are corrected according to the movement of the sample based on the table.

[0015] In addition, a black border is electrically isolated by providing a groove in the shape of a strip around the area where the pattern is formed on the surface of the sample, and a claw electrode is provided to electrically connect the internal pattern to the external pattern, so that the potential of the pattern can be controlled from outside by the claw electrode.

[0016] Also, instead of the claw electrodes, conductive connecting parts are formed on the substrate.

[0017] The sample is also designed to form a pattern on an insulating substrate. Effect of the Invention

[0018] The present invention makes it possible to stably apply a desired retarding voltage to the surface of a sample having a pattern formed on an insulating substrate such as a photomask, and to obtain a high-resolution and stable image.

[0019] In addition, the potential or capacitance of the sample surface is measured in real time, and the retarding voltage or the potential of the sample surface is controlled, so that stable, high-resolution images can be obtained even if the sample moves.

[0020] Furthermore, by dividing the sample vertically and horizontally and registering the potential or capacitance of the sample surface in a table in advance, the retarding voltage and the potential of the sample surface can be automatically corrected in accordance with the movement of the sample, making it possible to always obtain stable, high-resolution images. Example 1

[0021] FIG. 1 shows a configuration diagram of one embodiment of the present invention.

[0022] In Fig. 1, the electron gun 1 is a known device that generates electrons, and generates electrons from TFE or LaB6, a field emitter, a photoelectron gun, or the like. After adjusting the acceleration voltage to about several hundred to several tens of KV and the current to about several pA to several hundred nA, for example, through a focusing lens and an aperture (not shown), the beam is narrowed to the order of nm to several hundred nm by an objective lens 5 (described later), and then irradiated onto the surface of a sample 9. A bias voltage (retarding voltage 8) is applied to the substrate (mask) of the sample 9 to optimize the irradiation energy or optimize the energy (about several hundred V to 1 KV) of the electrons generated on the surface of the sample 9.

[0023] The blanking device 2 turns the electrons generated by the electron gun 1 on and off at high speed.

[0024] The blanking aperture 3 is a diaphragm that blocks the electrons deflected by the blanking device 2 .

[0025] The objective aperture 4 limits the electrons that enter the objective lens 5 .

[0026] The objective lens 5 is used to narrow the electron beam and irradiate it onto the sample 9 .

[0027] The deflection device 6 deflects the electron beam and two-dimensionally scans the finely focused electron beam on the sample 9, and is a two-stage deflection system (electrostatic, electromagnetic).

[0028] The surface potential / capacitance detection device 7 is a circular plate with a hole in the center that is attached to the tip of the objective lens 5, and is an electrode for measuring the potential on the surface of the sample 9 and measuring the capacitance (electrostatic capacitance) (the potential or capacitance is measured using a device not shown). The electrode shape does not have to be circular and can be other shapes. It does not necessarily have to be in the center, and a hole is not necessary. The metal that constitutes the objective lens itself can be used as the electrode for measuring capacitance.

[0029] The potential / capacity detection signal 71 is a signal (surface potential signal or capacitance detection signal) detected by the surface potential / capacity detection device 7, and is used to detect the potential or capacitance of the surface of the sample 9 in real time using a personal computer (not shown) based on this signal. In the case of a surface potential signal, it is a signal for measuring the potential of the surface of the sample 9 (or the retarding upper electrode 81), and is a well-known signal that generates a minute potential corresponding to the potential of the surface of the sample 9 (retarding upper electrode 81), amplifies this potential, and measures (detects) this potential. In the case of a capacitance detection signal, it is a well-known signal that supplies a minute high-frequency voltage, detects the current that flows at that time, and calculates the capacitance. Other surface potential and capacitance measurement means known in the art can be used.

[0030] The retarding voltage 8 is a retarding voltage applied to the sample 9, and is a deceleration voltage for decelerating a predetermined high voltage electron beam emitted from the electron gun 1, for example, from 5 KV to 35 KV, to about 500 V to 1 KV (in this example, a deceleration voltage that is 500 V to 1 KV lower than 5 KV to 35 KV).

[0031] The retarding upper electrode 81 is an electrode for extracting the potential of the upper surface of the sample 9 to the outside.

[0032] The retarding lower electrode 82 is an electrode for extracting the potential of the lower surface of the sample 9 to the outside. A retarding voltage 8 is usually applied to this retarding lower electrode 82.

[0033] The insulator 10 electrically insulates the retarding lower electrode 82 .

[0034] The sample 9 is a sample such as a mask, which is fixed on an insulator 10 and has a retarding voltage 8 applied to it. An electron beam decelerated by the retarding voltage 8 is irradiated onto the sample 9. After being focused into a small spot by a high voltage in the objective lens 5, the electron beam is decelerated by the retarding voltage 8 and the sample 9 is irradiated with a low-energy electron beam, thereby reducing damage, contamination, etc., and generating a high-resolution image.

[0035] The XYZ stage 11 is a stage that fixes the sample 9 and automatically moves it to any coordinate (X, Y) and further (Z). The sample can be moved while being precisely measured in real time in the X, Y and, if necessary, Z directions by a laser interferometer (not shown). More specifically, there is an insulator on the stage, and on top of that is a photomask holding mechanism made of a conductor called a mask pallet, which can also serve as the lower electrode. Meanwhile, a separate claw electrode is arranged on the pallet, and a voltage can be applied to the top of the photomask from there.

[0036] The vacuum chamber 12 is a container that houses the XYZ stage 11 to which the sample 9 is fixed, etc., in a vacuum.

[0037] The vacuum pump 13 is an oil-less vacuum pumping system such as a dry pump or a TMP that evacuates the vacuum chamber 12 to a vacuum.

[0038] The vibration isolator 14 serves to prevent vibrations from being transmitted from the outside to the vacuum chamber 12 and the like.

[0039] The electron detection device 21 is a known detector that detects secondary electrons emitted when the sample 9 is irradiated with an electron beam and scanned two-dimensionally.

[0040] Next, the operation of the configuration in FIG. 1 will be briefly described. (1) A sample 9 such as a mask (a mask fixed to a holder) is automatically transported to the XYZ stage 11 by a robot and fixed there. (2) The position of the photomask is measured in real time by a laser interferometer according to the design data of the pattern provided on the photomask, and the XYZ stage 11 is moved to the indicated position so that the predetermined position of the sample 9 is irradiated with the electron beam, and the surface potential / capacity detection device 7 measures the potential (or capacitance) of the surface of the sample 9 (or the retarding upper electrode 81) in real time and corrects it to a reference value (or the value of the reference point) (correcting one or both of the retarding voltage 8 and the potential of the retarding upper electrode 81), so that the potential of the surface of the sample 9 is always constant even if the sample 9 is moved. As a result, the surface of the sample 9 always has the same potential even if the sample 9 is moved, and the sample 9 is irradiated and scanned with a low-acceleration electron beam decelerated by the retarding voltage 8, making it possible to always obtain a stable and high-resolution secondary electron image, etc. A detailed description will be given below.

[0041] Fig. 2 shows an example of a sample (mask) of the present invention. Fig. 2 shows the cross-sectional structure of a typical photomask. Fig. 2(a) shows an example of the structure of an EUV mask, and Fig. 2(b) shows an example of the structure of a DUV mask.

[0042] In FIG. 2(a), as shown, an EUV mask generally comprises an insulating substrate 31 made of ultra-low thermal expansion quartz, on which a conductive reflective film 32 such as MoSi is provided, and on which a Ta-based absorption layer having a pattern 33 formed thereon is provided, so that the area in which the pattern is formed has electrical conductivity overall.

[0043] 2(b), in the case of the illustrated DUV mask, there may be no conductive film below the layer of the pattern 34, so the pattern 34 often becomes an island-like floating state that is not electrically connected anywhere. When such a mask is irradiated with an electron beam, the surface potential changes due to charging, making it impossible to obtain a stable and high-resolution secondary electron image.

[0044] Figure 3 shows an example of the black border of the present invention, where (a) of Figure 3 shows a side view and (b) of Figure 3 shows a top view.

[0045] In FIG. 3, photomask 35 is an example of sample 9.

[0046] The bias electrode 36 is an electrode for applying a potential to the rear surface of the photomask 35 .

[0047] The black border 37 is provided to reduce the effects of flare generated by an EUV exposure tool, and as a result, the surrounded area has a structure that electrically isolates it from the surrounding area.

[0048] The claw electrode 38 is an electrode for electrically connecting to apply the bias voltage 1 to the surface of the photomask 35. The shape of the electrode is arbitrary, but it may be a needle-shaped electrode to break through the insulator on the surface.

[0049] The bias voltage 1 is a voltage applied to the nail electrodes 38 (the surface of the photomask 35).

[0050] The bias voltage 2 is a voltage applied to the rear surface of the photomask 35 .

[0051] Next, the configuration will be described. (1) In Fig. 3, as already described, the EUV mask in Fig. 2(a) is formed by providing about 50 layers of reflective film material such as MoSi on a quartz substrate, and then forming an absorbing layer for forming the pattern 33. In this state, the entire surface of the photomask can be set to the desired potential by applying a voltage to the periphery from the outside. (2) However, since EUV exposure equipment uses a short wavelength of 13.5 nm and many mirrors, and the light source is not necessarily high performance, a defect phenomenon called flare occurs, and the light scatters in directions other than the intended direction, reducing the quality of the light source. As a result, the EUV light reaches adjacent areas that should not be exposed, causing defects. In order to prevent this, an electrically insulating boundary area called a black border 37 is provided as shown in the figure, surrounding the area where the main pattern of the photomask is written.

[0052] The boundary called the black border 37 is formed by engraving the MoSi conductor that forms the reflective layer down to the quartz glass substrate, so that the area surrounded by the black border 37 is electrically isolated from the surrounding area and becomes an insulator.

[0053] If the mask is insulated, the area surrounded by the insulator will not reach the desired potential even if a voltage is applied from the periphery of the mask surface. In addition, when observing by irradiating an electron beam such as with an SEM, electric charges gradually accumulate in the observation area, causing the image to deteriorate. To avoid this, in the present invention, as shown in FIG. 3, a special claw electrode 38 is provided to pass electricity to the area surrounded by the black border 37. This allows electrical conduction between the periphery and the inside of the mask, allowing the charge to escape and making the surface potential the same. The claw electrode 38 used in this case is as thin and flat as possible, and the surface is covered with an insulator with high insulation voltage such as Teflon (registered trademark) to prevent discharge from occurring between the opposing objective lens 5 (the distance between the objective lens 5 is about several mm (e.g., 3 mm)). Not only one claw electrode 38 may be provided, but multiple claw electrodes 38 may be provided on the periphery of the photomask. In addition, since there may be multiple insulating areas separated by black borders, the voltages applied to the multiple claw electrodes 38 may be controlled independently. Furthermore, it is desirable to be able to apply independent voltages to the inside and outside of the black border.

[0054] FIG. 4 shows an example of the black border of the present invention.

[0055] In FIG. 4, as described above, the black border 41 is formed by engraving the MoSi conductor forming the reflective layer down to the quartz glass substrate.

[0056] The peripheral region 42 is a peripheral region electrically isolated by a black border 41 .

[0057] The measurement target area 43 is an area to be measured that is separated by a black border 41 .

[0058] The connecting portion 44 is a conductive portion formed to electrically connect the measurement target area 43 and the surrounding area 42 that is electrically separated by the black border 41 .

[0059] Next, FIG. 4 will be described in detail. (1) In FIG. 4, the black border itself is very large compared to the size of the pattern that is actually formed. Therefore, a pattern (connecting portion 44) is formed in which the peripheral and inner regions are connected somewhere, leaving a portion of the border so that the performance of the black border 41 is not restricted. In this way, electrical conduction occurs between the peripheral region of the mask separated by the black border 41 and the inside, so the potential of the two regions can be made the same. In addition, it becomes possible to release the charge generated by the electron beam irradiation, and image distortion due to the charge-up phenomenon is eliminated. It is sufficient to apply a voltage using the claw electrodes to the region on the outer periphery of the mask. (2) On the other hand, there are cases where it is not always possible to form the above pattern (connecting portion 44). In such cases, it is possible to form wiring on the black border 41 with a conductive material such as Ta or W that has the property of absorbing EUV light using an FIB or electron beam mask repair device used for mask repair, to obtain electrical continuity. Multiple electrical continuity points can be obtained. Since the mask repair device can also form wiring in a three-dimensional form, it is easy to wire across the black border 41. This connects the area separated by the black border 41 to the outer periphery, and electrical continuity can be obtained by contacting the outer periphery with an electrode from the outside, so that the mask surface has the desired potential anywhere, and it is possible to prevent the EUV mask from charging up.

[0060] FIG. 5 is a schematic explanatory diagram of the surface potential of the present invention.

[0061] In FIG. 5, C1 represents the capacitance between the lower surface of the objective lens 5 and the surface of the mask (retarding upper electrode 81).

[0062] C2 represents the capacitance between the surface of the mask (retarding upper electrode 81) and the bias electrode (retarding lower electrode 82).

[0063] E represents the retarding voltage 8.

[0064] Next, the operation will be described. (1) In FIG. 5, the principle of determining the potential generated in the internal region separated by the black border in an insulating state or the surface of a floating DUV photomask placed in an electron beam inspection device is shown. Photomasks do not necessarily have a conductive reflective layer like EUV masks, so the entire surface is not necessarily conductive. In that case, the surface potential when an external voltage of the floating region is applied from the substrate lower electrode is determined by capacitance. Opposite to the photomask surface (surface of sample 9), an objective lens 5 made of metal is present inside the chamber of the electron beam inspection device. Since the photomask surface and the objective lens 5 are close to each other, it is the same as if two metal electrodes exist, forming a large capacitance C1. On the other hand, since a dielectric such as quartz exists between the photomask surface and the photomask back surface, a large capacitance C2 is formed between the pattern on the photomask surface and the photomask lower electrode 82.

[0065] Therefore, the potential of the surface of the photomask located between them is roughly determined by the ratio of the magnitudes of the two capacitances. (2) When the photomask is moved by the XYZ stage 11 during measurement, the distance from the objective lens 5 and the distance from the surrounding components change, causing a change in the capacitance C1 of the measurement system described above. The bias voltage (retarding voltage 8) applied to the substrate is distributed as this changes, so that when the same voltage is applied, the surface potential changes with the movement of the XYZ stage 11. In other words, if measurements are performed while a constant retarding voltage is applied, the bias potential generated on the substrate surface differs depending on the location, resulting in completely different measurements being performed, or, in the case of a measurement device that is sensitive to the surface potential, the image may not be formed at worst, or the position at which the image is formed may fluctuate, making the measurement unstable. (3) Therefore, if the potential of the bias electrode (retarding voltage 8) or the potential of the mask surface (first potential) is corrected so that the potential of the mask surface (potential distributed by capacitance C1 and capacitance C2) is always constant even when the XYZ stage 11 moves, and automatic control is performed so that the potential of the mask surface is constant, the potential of the mask surface will be constant even when the XYZ stage is moved, making it possible to acquire stable, high-resolution secondary electron images.

[0066] FIG. 6 shows an example of a map table of capacitance and potential of the mask of the present invention.

[0067] FIG. 6(a) shows an example of a capacitance map table, and FIG. 6(b) shows an example of a surface potential map table.

[0068] FIG. 6(a) shows that the XYZ stage 11 (or mask) is divided into i pieces in the X direction and j pieces in the Y direction, and the capacitance C1(i,j) at the intersection position (i,j) is measured and registered.

[0069] FIG. 6B shows that the XYZ stage 11 (or mask) is divided into i parts in the X direction and j parts in the Y direction, and the potential V(i,j) at the intersection position (i,j) is measured and registered.

[0070] Here, the capacitance C1 and the potential V are measured as follows. (1) Sample surface potential V: There are various methods for finding the sample surface potential V. The surface potential can be found using commercially available surface potential meters of various principles and types. The surface potential meter can be placed at the tip of the objective lens 5 to measure the potential at the measurement point on the mask. The voltage applied to the substrate (retarding voltage 8 or potential of retarding upper electrode 81 in FIG. 1) while the XYZ stage 11 is moving or stopped is automatically adjusted so that the measured potential becomes a constant value. (2) The same result can be obtained by measuring the electrical capacitance generated between the objective lens and the sample surface. The capacitance is measured at a specific coordinate on the XY coordinate system. The sample 9 is moved using the XYZ stage 11 and the capacitance is measured. Since the capacitance difference represents a change in the surface potential, the voltage applied to the sample 9 (the retarding voltage 8 or the potential of the retarding upper electrode 81 in FIG. 1) is changed by the amount of the change in capacitance, and the surface potential is adjusted to be substantially the desired value. (3) The surface potential V can also be determined by examining the energy of secondary electrons generated by actually irradiating an electron beam. Specifically, a mesh grid or the like is provided on the surface of the secondary electron detection device, a specified voltage is applied, and the energy of the secondary electrons can be determined by examining the amount of secondary electrons that pass through the mesh and are detected. By changing the grid voltage, the energy distribution can be determined, and as a result, the change in the sample surface potential V, which is the source of the energy shift of the secondary electrons, can be detected. The surface potential can be maintained at the desired value by automatically adjusting the bias voltage applied to the substrate (retarding voltage 8 or potential of retarding upper electrode 81 in Figure 1) so that there is no change in the measured value. (4) The change in surface potential or capacitance due to the movement of the XYZ stage 11 obtained as described above is a quantity specific to a particular apparatus, and is constant unless the inside of the apparatus is changed.

[0071] Therefore, once data on the change in surface potential V or capacitance change accompanying the movement of the XYZ stage is acquired and registered, the amount of correction can be estimated by inputting the position coordinates thereafter. Therefore, by storing such data on the surface potential or capacitance change corresponding to the measurement point coordinates XY in a storage device as a map table as shown in (b) and (a) of Figure 6, during actual measurement, the voltage applied to the mask (sample 9) is automatically adjusted based on the map table, thereby making it possible to keep the surface potential constant at a desired value.

[0072] FIG. 7 is a flowchart showing a mask surface potential setting process according to the present invention.

[0073] 7, S1 moves the XY stage. Here, the coordinates of the movement position are (Xi, Yj).

[0074] S2 measures the surface potential or capacitance. This is done by measuring the potential Vij of the mask surface facing the objective lens 5, or measuring the capacitance Cij between the objective lens 5 and the opposing mask surface, while the XY stage is moved to the coordinates (i, j).

[0075] S3 calculates a correction value based on the surface potential Vij or capacitance Cij measured in S2 so that the correction value coincides with either a reference value, the potential (capacity) at a specific location, or an arbitrary specified value.

[0076] S4 sets the applied voltage, which is to set the potential of the retarding lower electrode 82 or the retarding upper electrode 81 in FIG. 1 to a predetermined value and correct the surface potential or capacitance to be always constant.

[0077] In step S5, it is determined whether the measurement is complete. If the answer is YES, the measurement is completed. If the answer is NO, the steps from S1 onwards are repeated.

[0078] As described above, by measuring the surface potential or capacitance every time the XYZ stage 11 moves and correcting it so that it is always constant (correcting the potential of the retarding lower electrode 82 or the retarding upper electrode 81 in FIG. 1), the surface potential of the mask (sample 9) can be kept constant, making it possible to obtain a stable and high-resolution secondary electron image. When correcting in real time, the surface potential or capacitance can be measured at any measurement point and the retarding voltage value to be applied can be corrected.

[0079] Fig. 8 shows a flowchart (part 2) for setting the mask surface potential of the present invention. In Fig. 8, instead of measuring the surface potential and capacitance in real time as in Fig. 7, the surface potential and capacitance at the coordinates of the mask are read out and corrected from the surface potential map table in Fig. 6(b) or the capacitance map table in Fig. 6(a), which are measured and registered in advance.

[0080] 8, S11 moves the XY stage. Here, the moved position is set to coordinates (Xi, Yj).

[0081] In step S12, the correction value is read out. As described above, the surface potential or capacitance at the coordinates of the mask is read out from the preregistered surface potential map table in FIG. 6(b) or capacitance map table in FIG. 6(a). If there is no matching coordinate in the table, the values ​​(potential or capacitance) of multiple neighboring coordinates are read out.

[0082] In step S13, a correction value is calculated based on the surface potential Vij or capacitance Cij read in step S12 so that the correction value coincides with either a reference value, the potential (capacity) at a specific location, or an arbitrary specified value.

[0083] S14 sets the applied voltage, which is to set the potential of the retarding lower electrode 82 or the retarding upper electrode 81 in Fig. 1 to a predetermined value and correct the surface potential or capacitance to be always constant.

[0084] In S15, it is determined whether the measurement is finished. If the answer is YES, the measurement is finished. If the answer is NO, S11 and subsequent steps are repeated.

[0085] As described above, by reading the surface potential or capacitance from the preregistered table each time the XYZ stage 11 is moved and correcting it so that it is always constant (by correcting the potential of the retarding lower electrode 82 or the retarding upper electrode 81 in FIG. 1), the surface potential of the mask (sample 9) can be kept constant, making it possible to acquire a stable, high-resolution secondary electron image. Note that since the Z-axis height affects the capacitance value, it is desirable to automatically control the height to a desired constant height (the distance between the sample surface and the objective lens).

[0086] Fig. 9 shows a configuration diagram of another embodiment of the present invention. Fig. 9 shows an external view of a multi-electron beam inspection device. The multi-electron beam inspection device is a device that can achieve ultra-high speed two-dimensional image acquisition by irradiating multiple electron beams onto a sample 9 in a planar manner at once and re-accelerating secondary electrons generated on the sample 9 to form an image. In this device, it is very important to uniformly accelerate the secondary electrons generated on the surface of the sample 9, and control of the surface potential is very important because any variation in the surface potential will cause problems with the operation of the beam splitter 541 and prevent the image from being formed at the desired position.

[0087] In general, inspection devices perform high-speed, large-volume measurements, so they may move step-by-step like a normal SEM or review device, or the XYZ stage 11 may move continuously. Even in such cases, the present invention can be used. Specifically, it is as follows. (1) In the case of step-by-step, it is sufficient to have a correction value for each step as a map (see Figure 6). On the other hand, in the case of continuous movement of the stage 11, the following method is used. For example, as shown in Figure 6, the area of ​​the photomask is divided into approximately 100 equal parts, and the surface potential or capacitance of the sample 9 is measured at the center coordinates of each area. This is then stored as a map (see Figure 6). Since the surface potential or capacitance value has the property of changing gradually as the photomask moves, it is possible to estimate the correction value at coordinates that cannot be measured directly by interpolation. (2) For example, for intermediate coordinates not included in the table in Fig. 6, the surface potential or capacitance at the measurement point coordinates can be estimated by performing least squares, spline, Lagrange interpolation, or other interpolation calculations, or Gaussian filter or other two-dimensional weighting calculations, using the measurement point coordinates and map data output from a laser interferometer. From this value, a correction value at any coordinate can be estimated. When the stage is moved continuously, the XYZ coordinates of the measurement point are captured and corrections are made in real time. (3) On the other hand, the globally applied retarding potential in the measurement target area is determined by the above-mentioned principle, but when local capacitance changes are also taken into consideration, the area of ​​the pattern that contributes to the formation of the capacitance directly below the objective lens 55 is calculated using pattern design data (CAD data such as GDI) written on the photomask, and the capacitance is calculated, so that the surface potential can be estimated. By calculating and controlling the correction amount from the capacitance thus estimated (controlling the potential of the retarding upper electrode 81 or the retarding lower electrode 82), the potential of the measurement point on the surface of the sample 9 can be set to a desired value. [Brief description of the drawings]

[0088] [Figure 1] FIG. 1 is a configuration diagram of one embodiment of the present invention. [Diagram 2] 1 is an example of a sample (mask) of the present invention. [Diagram 3] 1 is an example of a black border according to the present invention. [Figure 4] 1 is an example of a black border according to the present invention. [Diagram 5] FIG. 4 is a schematic diagram illustrating a mask surface potential according to the present invention. [Figure 6] 1 is an example of a map table of capacitance and potential of a mask of the present invention. [Figure 7] 4 is a flowchart for setting a mask surface potential according to the present invention. [Figure 8] 13 is a flowchart (part 2) of a mask surface potential setting process according to the present invention. [Figure 9] FIG. 11 is a configuration diagram of another embodiment of the present invention. [Explanation of symbols]

[0089] 1: Electron gun 2: Blanking device 3: Blanking aperture 4: Objective aperture 5: Objective lens 6: Deflection device 7: Surface potential and capacitance detection device 71: Potential / capacity detection signal 8: Retarding voltage 81: Retarding upper electrode 82: Retarding lower electrode 83: First potential 9: Sample 10: Insulator 11: XYZ Stage 12: Vacuum chamber 13: Vacuum pump 14: Vibration isolator 21: Electronic submission 31: Insulating substrate 32: Conductive reflective layer 33: Absorption layer (pattern) 34: Pattern 35: Photomask 36: Bias electrode 37: Black Border 38: Claw electrode 41: Black Border 42: Surrounding area 43: Measurement area 44:Connection part

Claims

1. In an inspection device that irradiates an electron beam onto a sample and detects the electrons generated to obtain an image, an electron gun that generates an electron beam; an objective lens for narrowing the electron beam generated by the electron gun and irradiating the sample with the narrowed electron beam; a deflection system that performs two-dimensional scanning of the electron beam narrowed by the objective lens on the surface of the sample; a stage for mounting the sample and moving it to a predetermined position; a detection means for irradiating a surface of the sample with a narrow electron beam and detecting emitted secondary electrons or reflected electrons to generate an image; A potential control means for externally controlling the potential of the electrically separated pattern present on the sample mounted on the stage or a means for grounding the pattern, An inspection device characterized by:

2. 2. The inspection device according to claim 1, wherein said potential control means or said earthing means is a claw electrode that is in electrical contact with said pattern.

3. 2. The inspection apparatus according to claim 1, wherein said potential control means or said grounding means is a wiring that provides electrical continuity to said pattern.

4. 4. The inspection device according to claim 3, wherein the wiring for electrical continuity is formed by either an FIB or an electron beam.

5. 5. An inspection device according to claim 2, wherein the potential control means or the means for grounding is a claw electrode or wiring for providing electrical continuity between the pattern and a mask pallet carrying the sample mask.

6. In an inspection method for obtaining an image by detecting electrons generated by irradiating an electron beam onto a sample, an electron gun that generates an electron beam; an objective lens for narrowing the electron beam generated by the electron gun and irradiating the sample with the narrowed electron beam; a deflection system that performs two-dimensional scanning of the electron beam narrowed by the objective lens on the surface of the sample; a stage for mounting the sample and moving it to a predetermined position; a detection means for irradiating a surface of the sample with a narrow electron beam and detecting emitted secondary electrons or reflected electrons to generate an image; The potential control means or the grounding means externally controls the potential of the electrically isolated pattern present on the sample mounted on the stage or grounds it.

13. An inspection method comprising:

7. 7. The inspection method according to claim 6, wherein the potential control means or the earthing means is a claw electrode that is in electrical contact with the pattern.

8. 7. The inspection method according to claim 6, wherein the potential control means or the grounding means is a wiring that provides electrical continuity to the pattern.

9. 9. The inspection method according to claim 8, wherein the wiring for electrical continuity is formed by either an FIB or an electron beam.

10. 10. An inspection method according to claim 6, wherein the potential control means or the means for grounding is a claw electrode or wiring for providing electrical continuity between the pattern and a mask pallet carrying the sample mask.

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