JP2021182498A - Multi-beam image generation device and multi-beam image generation method - Google Patents

Abstract

PURPOSE: To provide a multi-beam image generation device and a multi-beam image generation method that generate a plurality of primary electron beams, move a sample while irradiating the sample with the primary electron beams, separate a plurality of secondary electron beams emitted at that time by a beam splitter, detect respective pieces of image information by an electron detection device, and combine the pieces of information into a single image to acquire images at high speed.CONSTITUTION: A multi-beam generation device includes a beam splitter, an objective lens, a deflection system, a projection lens, a stage, and an interferometer, and a plurality of primary electron beams generated by the multi-beam generation device are deflected to the axis of the objective lens by a beam splitter, the primary electron beam narrowed down to a sample is irradiated by the objective lens, and the sample is scanned by the deflection system. The secondary electrons emitted from the sample are deflected to the axis of the projection lens by the beam splitter, imaged on an electron detector by the projection lens, and the image information of the plurality of electron beams is output.SELECTED DRAWING: Figure 1

Description

The present invention relates to a multi-beam image generator and a multi-beam image generation method for generating an image by scanning a plurality of primary electron beams on a sample.

Traditionally, the semiconductor industry has been supported by the improved device performance and cost benefits brought about by the advancement of microfabrication technology, which is famous for Moore's Law, but the microfabrication limit of semiconductor devices is determined by exposure technology. Semiconductor exposure technology consists of an original plate called a photomask for creating a pattern, an exposure apparatus, and a resist that forms the pattern. Since the exposure apparatus currently uses a 4: 1 reduction exposure technique, a pattern structure four times as large as the pattern structure on the silicon wafer on which the semiconductor device is actually manufactured is formed on the photomask. ..

The biggest issue in exposure technology is how accurately the pattern created on the photomask based on the semiconductor circuit design data can be transferred to the resist film pattern on the wafer surface. If there is an abnormality in the photomask, it will be transferred to the wafer surface by the exposure apparatus and a defect will occur on the wafer.

In order to prevent exposure defects, it is necessary to inspect at least the entire photomask and correct it to the correct state to obtain the perfect pattern state as designed. Since the microfabrication limit is proportional to the wavelength of light used for exposure, the wavelength of light used for exposure is becoming shorter with the times.

Since a laser light source with a wavelength of 193 nm has been used as an exposure light source since the end of the 20th century, patterns on photomasks have been inspected for a long time using an optical mask pattern inspection device that uses a laser beam of 193 nm or the like as illumination light. rice field.

However, since 2019, the exposure technology using EUV light with a short wavelength of 13.5 nm has been fully introduced, and the limit of microfabrication that can be exposed has become smaller. The pattern on the photomask has also become smaller, from the conventional minimum pattern size of about 100 nm to 50 nm or less, and it has become impossible to perform sufficient inspection with the conventional light of 193 nm.

On the other hand, there is also a so-called actinic inspection device using a wavelength of 13.5 nm, which is the same wavelength as the exposure wavelength. However, when the wavelength is as short as 13.5 nm, it is almost absorbed by the air, so that it is necessary to evacuate the inside of the inspection device, which is very complicated as compared with the conventional device mounted in the atmosphere. Further, since there is no optical lens capable of transmitting light of 13.5 nm, it is necessary to configure all the optical systems with a reflective optical system, which is also complicated and inefficient. For example, an EUV exposure apparatus using a wavelength of 13.5 nm is so inefficient that only about 1% of the total output of the light source can be used.

The resolution of the optical device has the property of being proportional to the aperture ratio NA. For example, in the case of an optical system using a wavelength of 193 nm, a large aperture ratio exceeding 1 can be realized by using immersion or oil immersion, so that the wavelength is as long as 193 nm, but 40 nm in one exposure. It is possible to resolve a degree pattern. It is even possible to create a pattern of about 20 nm by using double patterning.

On the other hand, when EUV light is used, since a reflected optical system is used, only a small aperture ratio such as 0.33 for MA can be realized. Although the light source wavelength is as short as 1/10 of the conventional wavelength, only a resolution of about 13 nm can be obtained at most, and the performance improvement is small for the shorter wavelength. Further, for example, when the detection target is particles, the reflected light weakens in proportion to the sixth power of the particle size, and the reflected light becomes stronger at the square of the wavelength. That is, as the particle size becomes smaller, the signal strength sharply weakens, so that the defect detection sensitivity drops sharply. As described above, the photomask inspection technology using optical technology has reached the technical limit. In addition, since the device using the conventional optical principle operated in the atmosphere, it was easy to manufacture and operate the device, but when the wavelength is shortened, it is absorbed by the air, so a large vacuum chamber is required and it is easy to use for the electron beam device. There is no advantage.

On the other hand, there is an electron microscope as a technology for realizing high resolution on the order of nm. An electron beam type defect inspection technique using an electron beam has been developed for more than 30 years. Although it has been commercialized, it has not been put into practical use as a main inspection device because its throughput is extremely small compared to the optical type. Since it is possible to find electrical defects that cannot be achieved by optical methods, it is gradually becoming widespread in new wafer process development applications.

Unlike a laser beam, an electron beam does not have an electron beam source with a small energy dispersion and high brightness like a laser. Furthermore, since electrons have a negative charge, when they are narrowed down to a small spot with a lens or the like, the electrons repel each other electrostatically. Therefore, when a large current required for high-speed inspection is passed, the minimum beam spot size becomes larger than the optical limit, and the resolution deteriorates. In other words, when using a single electron beam, there is a very tight trade-off between resolution and inspection speed, so there is a principle defect that the speed becomes slower as miniaturization progresses. ..

For example, at present, the maximum inspection speed that can be achieved with one electron beam is at most several hundred Mpixels per second. Since the pattern is written on the photomask in an area of about 10 cm square, it is necessary to inspect the entire area. For example, in order to inspect a pattern on a state-of-the-art photomask with a resolution of 10 nm that can sufficiently resolve it, it is necessary to acquire 10 to the 14th power pixels. For example, if pixels are acquired at 100 Mpixels per second, 10 6 seconds are required. In other words, it takes 277 hours, that is, 10 days or more. In addition, it is necessary to scan many times in order to obtain an image having an SNR of 10 or more required for inspection. Since the conventional optical photomask inspection device can inspect one photomask in about 2 hours, the electron beam type is 100 times slower and cannot be used practically.

On the other hand, in order to improve the speed of the electron beam inspection device, a method called a multi-electron beam inspection device is being studied in which a plurality of electron beams are simultaneously irradiated to a sample in parallel for high-speed inspection. In this method, since scanning is performed by simultaneously irradiating 100 or more small electron beams, the amount of current flowing through one beam can be kept small, and high resolution is maintained without being affected by the electrostatic repulsion of the beam. It is said that the inspection speed can be increased compared to the case where a conventional single electron beam is used.

However, various types of multi-beam inspection equipment have been developed by many companies in the past, and although they are very promising as next-generation high-speed inspection equipment, the speed and resolution are as high as initially thought. It has not been realized and has not yet been commercialized as an inspection device for semiconductors.

The equipment used in the semiconductor industry is an industrial measuring equipment, which is a kind of mission-critical equipment and needs to continue to operate 24 hours a day, 365 days a year without causing problems, so high robustness is essential. It cannot be practically used to the extent that university teachers and students can write a dissertation by chance, as in the case of science and science equipment. It is necessary to withstand various measurement conditions, measurement targets, and changes in the equipment installation environment, and to maintain stable performance for a long period of time.

In the conventional single-beam method high-speed inspection device, the continuous stage method is common, but in the multi-beam method that simultaneously acquires two-dimensional images, the step of increasing the speed by increasing the area that can be acquired by one scan as much as possible. Since the & repeat method has been adopted, there is a problem that the stage movement time becomes dominant and the speed cannot be increased.

Further, there is a problem that a contrast difference based on a sensitivity difference is clearly generated at the boundary of the scanning region, which makes it difficult to use as an inspection image.

Further, in the case of the single beam method, since there is only one beam, the irradiation position can be easily corrected and the electron beam can be irradiated to a desired position. However, in the case of the multi-beam method, since a plurality of electron beam irradiations are simultaneously performed to acquire a two-dimensional image, there is a problem that it is not easy to strictly control each electron beam irradiation position to a desired position. rice field. In addition, if the stage is run after the acquisition of 2D image information for further speeding up, stage rotation, swell, stage speed fluctuation, height fluctuation, vibration, etc. that occur during running affect the 2D image acquisition. There was a problem that the quality of the image was deteriorated.

Further, there is a problem that an accurate image cannot be acquired because the image is distorted or skipped by simply acquiring an image as in the case of a conventional single beam, and it cannot be used for inspection.

In order to solve the above-mentioned problems, the present invention repeatedly generates a plurality of primary electron beams arranged two-dimensionally, scans them when the sample is stopped, and then repeatedly moves them, and then emits them. A plurality of secondary electron beams are separated by a beam splitter, each image information is detected by an electron detection device and combined into one image, and image acquisition can be performed at high speed.

Therefore, the present invention includes a plurality of beam generators for generating a plurality of primary electron beams arranged in two dimensions in a multi-beam image generator for generating an image by scanning a plurality of primary electron beams on a sample. A plurality of primary electron beams generated by the beam generator are deflected by two steps and incident on the axis of the objective lens, and the secondary electron beam emitted from the sample is deflected by two steps in the direction opposite to the primary electron beam. A beam splitter that is incident on the axis of the projection lens, an objective lens that is two-step deflected by the beam splitter and narrows the primary electron beam incident on the axis, and a primary electron beam that is finely focused by the objective lens. When the sample is stopped by repeatedly moving and stopping the sample, a deflection system that scans on the sample, a projection lens that forms an image of the secondary electron beam that is deflected in two stages by the beam splitter and incident on the axis on the electron detector. It is equipped with a stage for acquiring images and an interferometer that measures the position of the sample in the moving direction and the position in the perpendicular direction in real time. The sample is irradiated with a finely focused primary electron beam with an objective lens and scanned by a deflection system, the secondary electrons emitted from the sample are deflected to the axis of the projection lens with a beam splitter, and the electrons are emitted with the projection lens. A secondary electron beam corresponding to the plurality of primary electron beams arranged in the two dimensions is imaged on the detector, and the image information of the plurality of electron beams is output.

At this time, a compositing means for synthesizing a single image based on the image information of the output plurality of electron beams is provided.

In addition, the movement amount and rotation amount of the stage are corrected based on the image information of the output multiple electron beams and the position in the real-time movement direction of the sample output from the interferometer and the position in the right angle direction, or the stage The image information is moved and rotated by the amount corresponding to the amount of movement and the amount of rotation.

Further, the position in the height direction of the stage is measured in real time, and the height of the stage is corrected based on this, or the height of the stage is corrected electromagnetically so that the autofocus is performed.

Further, the plurality of beam generators irradiate an aperture having a plurality of holes arranged two-dimensionally with one primary electron beam to generate a plurality of primary electron beams.

Further, in the beam splitter, the first stage on the incident side of the primary electrons is an electrostatic deflector, the second stage is an electromagnetic deflector, and the secondary electron beam emitted from the sample by the electromagnetic deflector of the second stage. Is deflected in the opposite direction to the primary electron beam to separate it.

Further, a negative retarding voltage is applied to the sample to reduce the energy while maintaining the high resolution of the primary electron beam to be scanned by irradiating the sample, thereby reducing the damage to the sample.

Further, a deflection system for position correction of the secondary electron beam is provided before or after the projection lens.

In the present invention, a plurality of primary electron beams arranged in two dimensions are generated, these are scanned when the sample is stopped, and then the movement is repeated, and the plurality of secondary electron beams emitted at that time are beamed. It has become possible to separate images with a splitter, detect each image information with an electron detection device, combine them into one image, and acquire images at high speed.

In addition, the contrast difference of the boundary when the images of the plurality of secondary electron beams detected by scanning the sample with a plurality of two-dimensionally arranged primary electron beams are detected by overlapping and combined into one image. Was able to be reduced.

In addition, by acquiring and registering the scanning positions of a plurality of primary electron beams arranged two-dimensionally on the sample in advance, it is possible to correct the center position of the image of the secondary electron beams and synthesize a precise image. It has become possible.

In addition, the position and rotation of the stage on which the sample is mounted during movement are accurately measured and recorded with a laser interferometer in real time, and the amount of movement and rotation of the images of multiple secondary electron beams are corrected for precision. Image information can now be generated.

As a result, in the present invention, not only the position control of each primary electron beam constituting the multi-beam but also the attitude change or velocity change of the stage that occurs during the S & R movement of the stage is measured in real time by the stage position measuring means, and the stage is measured in real time. The positional relationship between the stage and the objective lens and the irradiation state of the primary electron beam are controlled to the ideal or reference state by performing correction, and the position correction processing between each scanned image is performed at high speed by a computer, which is ideal for inspection. You will be able to obtain one large image that is normalized without the targeted boundary effect. Addition processing between arbitrary scanned images can be performed, and the current value of each primary electron beam can be suppressed to a small value to obtain high S & R and high throughput with high resolution. The highest throughput can be achieved despite S & R operation.

First, as an example of the present invention, the multi-beam type inspection apparatus is characterized in that the inspection speed is increased by simultaneously irradiating a sample with 100 or more primary electron beams and acquiring a two-dimensional secondary electron image. Is. Each primary electron beam constituting the multi-beam consists of an electron beam generated by one electron gun divided by an aperture, and in order to realize a small beam spot size, the amount of one primary electron beam is, for example, 1 nA. Although it is small compared to the single beam method, each primary electron beam is scanned at a speed of several tens of MHz or more, so that a detection speed of gigapixel per second or more can be realized as a whole. The position of the primary electron beam irradiated on the sample surface is determined by the relative motion of the stage movement and the multi-electron beam irradiation. Whether or not this relative motion can be ideally realized determines the performance of the high-speed inspection device.

Since it is relative motion, the irradiation position of the primary electron beam can be controlled by controlling the stage or by controlling the irradiation position of the primary electron beam by using the deflection device of the primary electron beam. For the deflection device of the primary electron beam, for example, it is realized by using a two-stage deflection device like the drawing device of the primary electron beam and shifting in the XY horizontal plane while maintaining the irradiation angle of the primary electron beam. can. In the case of the multi-beam inspection device, the individual primary electron beams of each primary electron beam are not deflected, and uniform electric and magnetic fields are applied to all the primary electron beams to scan all at once.

In general, the stage has a large inertial mass, whereas the primary electron beam has almost no mass. Therefore, the position correction using the deflection of the primary electron beam is faster and more accurate in response speed. Is obtained. On the other hand, if the vertical movement of a slow stage with a large time constant is performed with a primary electron beam, the focus control becomes complicated, but if the height is always constant on a Z-axis stage, the control is simple. Can be done. This will be described in detail below.

FIG. 1 shows a structural diagram of an embodiment of the present invention.

In FIG. 1, the electron gun 1 is a known one that generates an electron beam, and generates a primary electron beam accelerated to several hundred V to several tens of KV. The electron gun uses a thermionic source such as W or LaB6, a TFE using ZrO, a cold field emitter, or a photocathode, and the electron gun chamber uses an ion pump, getter pump, or the like to obtain 10 minus 8 Pa. It is maintained in the above ultra-high vacuum or ultra-high vacuum.

The blanking device 2 turns on or off the primary electron beam emitted from the electron gun 1 at high speed, and turns the voltage on or off to deflect the primary electron beam and pass or cut it off. be.

The illumination lens 3 focuses the electron beam generated and accelerated by the electron gun 1 so as to be a predetermined beam shown in FIG. 4, which will be described later.

The multi-beam aperture 3-1 is generated by dividing (for example, 100 divisions) from an irradiated primary electron beam into a plurality of two-dimensionally arranged primary electron beams (see FIG. 2).

The objective aperture 4 passes through the central portion of each of the plurality of primary electron beams, and each of the passed primary electron beams is finely focused on the surface of the sample 8 by an objective lens 6 described later and irradiated. It is for doing.

The beam splitter 5 separates primary electrons and secondary electrons traveling in opposite directions, and the upper stage is composed of an electrostatic deflector 5-1 and the lower stage is composed of an electromagnetic deflector 5-2. be. The primary electron beam is deflected to the right by the electrostatic deflector 5-1 and to the left by the electromagnetic deflector 5-2, swung back onto the axis of the objective lens 6, and the objective. It is finely focused and imaged on the sample 8 by the lens 6. As shown in FIG. 1, the secondary electrons emitted from the sample 8 are deflected to the right by the electromagnetic deflector 5-2, deflected to the left by the electrostatic deflector 5-1 and swing on the axis of the projection lens 12. After being returned, the projection lens 12 forms an image of a plurality of secondary electron beams two-dimensionally arranged on the electron detection device 14, and outputs a plurality of secondary electron images (secondary electron signals).

The electrostatic deflector 5-1 is a deflector on the side close to the electron gun 1 constituting the beam splitter 5, and is an electrostatic deflector here.

The electromagnetic deflector 5-2 is a deflector on the side away from the electron gun 1 constituting the beam splitter 5, and is an electromagnetic deflector here.

The objective lens 6 narrows down a plurality of primary electron beams and irradiates the sample 8 with the target lens 6.

The deflection device 7 scans a plurality of primary electron beams on the surface of the sample 8, and usually scans two-dimensionally (scans in the X and Y directions) with the stage 9 moved and stopped. (See FIGS. 6, 7, etc.).

Sample 8 is a sample for which a plurality of images such as masks and wafers are acquired and combined into one.

The mirror 8-1 is a reflecting mirror for actually measuring the position with a laser interferometer.

The stage (XYZθ stage) 9 is a stage on which a sample is mounted and capable of XYZ and further θ (rotation), and XYZ and θ can be actually measured and recorded in real time by an interferometer (not shown), and further real-time correction is possible. It is a possible configuration.

The vacuum chamber 10 is a container that houses the sample 8, the stage 9, and the like and can be evacuated.

The vacuum pump 10-1 evacuates the inside of the vacuum chamber 10 with an oil-free pump.

The alignment 11 aligns a plurality of secondary electron beams deflected on the axis of the projection lens 12 from the electrostatic deflector 5-1 constituting the beam splitter 5.

The projection lens 12 forms an image of a plurality of secondary electron beams emitted from the sample 8 on the detection surface of the electron detection device 14.

In the reverse scanning device 13, the plurality of secondary electron beams emitted when the plurality of primary electron beams arranged in two dimensions are finely focused on the sample 8 and scanned are predetermined on the detection surface of the electron detecting device 14. It reverse scans (backward or corrects) so that each stays in the area.

The electron detection device 14 detects each of a plurality of secondary electron beams emitted from the sample 8. For example, an avalanche photodiode, a CCD, a CMOS sensor, a TDI camera, or the like can be used. The electrons may be once collided with the scintillator to be converted into light and then detected by the above-mentioned device, or the electrons may be directly injected into the above-mentioned device for detection. In any case, it suffices if a plurality of secondary electron beams, each of which is imaged in a predetermined region of the detection surface, can be independently detected.

Next, the operation of the structure of FIG. 1 will be described.

(1) The primary electron beam emitted from the electron gun 1 irradiates the multi-beam aperture 3-1 to generate a plurality of two-dimensionally arranged primary electron beams (see FIG. 2). The generation of a plurality of two-dimensionally arranged primary electron beams is not limited to this method, and a plurality of two-dimensionally arranged two-dimensionally arranged electron beam sources may be provided on the surface of the emitter of the electron gun 1. A primary electron beam may be generated.

(2) A plurality of two-dimensionally arranged primary electron beams divided and generated by the beam aperture 3-1 pass through the central portion thereof by the objective aperture 4, and the static electricity in the upper stage constituting the beam splitter 5 is formed. The deflector 5-1 deflects to the right and the electromagnetic deflector 5-2 deflects to the left to enter on the axis of the objective lens 6.

(3) A state in which a plurality of two-dimensionally arranged primary electron beams incident on the axis of the objective lens 6 are finely focused by the objective lens 6 and the sample 8 moves and stops on the surface of the sample 8. At this time, after two-dimensional scanning, it is repeatedly moved and stopped. As a result, when the movement of the sample 8 is stopped, a plurality of primary electron beams arranged two-dimensionally are surface-scanned on the sample 8 in a rectangular shape or the like. At this time, although not shown, a negative retarding voltage is applied to the sample 8 to set the energy of the plurality of primary electron beams to, for example, 1 KV and irradiate the sample 8 (for example, negative retarding to the energy of the plurality of primary electron beams of 15 KV). A voltage of 14 KV is applied to make a 1 KV primary electron beam, and the sample 8 is irradiated).

(4) Secondary electrons, backscattered electrons, light, X-rays and the like are emitted from the regions of the plurality of primary electron beams surface-scanned in a rectangular shape or the like in (3).

(5) The secondary electrons emitted in (4) travel spirally in the opposite direction on the axis of the objective lens 6 due to the magnetic field of the objective lens 6, and the lower electromagnetic deflector 5 constituting the beam splitter 5 is formed. Here, it is deflected to the right by −2 (deflected in the direction opposite to the deflection of the plurality of primary electron beams), deflected to the left by the electrostatic deflector 5-1 and incident on the axis of the projection lens 12. ..

(6) After correcting with alignment 11 as necessary on the axis of the projection lens 12, a plurality of secondary electron beams emitted from the sample 8 are imaged on the electron detection device 14, and the electron detection device 14 is formed. The imaging region of each of the plurality of secondary electron beams is irradiated. When it protrudes from the imaging region, the reverse scanning device 13 synchronizes with the scanning (deflection) of a plurality of primary electron beams on the sample 8 and supplies a voltage (or current) to the reverse scanning device 13. Correct so that it fits within the image area. Then, the secondary electron images (secondary electron signals) obtained by detecting each of the plurality of secondary electron beams are output from the electron detection device 14.

As described above, a plurality of primary electron beams arranged two-dimensionally are generated, these are finely narrowed by an objective lens 6 via a beam splitter 5, and surface scanning into a rectangular shape or the like with the sample 8 stopped at the stage 9. Then, the movement is repeated, and the surface region such as a rectangular shape is scanned by a plurality of primary electron beams. Then, the plurality of secondary electron beams emitted at that time are separated via the beam splitter 5, and the plurality of secondary electron beams are imaged on the respective detection surfaces of the electron detection device 14 by the projection lens 12. It is possible to output secondary electron images (secondary electron signals) of each of a plurality of secondary electron beams.

FIG. 2 shows an example of a schematic array of multi-beam apertures of the present invention. This shows an example of the type of hole arrangement of the multi-beam aperture 3-1 of FIG. 1 described above. Although the hole is schematically rectangular in FIG. 2, a hole (circular hole) is actually desirable.

FIG. 2A shows an example of a quadrangle (rectangle), and FIG. 2B shows an example of a hexagon.

FIG. 2A shows an example of a quadrangle (rectangle). This schematically shows an example in which the aperture of the multi-beam aperture 3-1 in FIG. 1 is provided with holes (actually, a round shape is good) arranged in two dimensions as shown in the figure. For example, if 9 × 9 holes are provided in a quadrangle (rectangle), a total of 81 primary electron beams can be generated. As shown in the figure, the hole size is Ax × Ay, the distance between holes in the horizontal (X) direction is Sx, and the distance between holes in the vertical (Y) direction is Sy.

FIG. 2B shows an example of a hexagon. This schematically shows an example in which the aperture of the multi-beam aperture 3-1 in FIG. 1 is provided with holes (actually, a round shape is good) arranged in two dimensions as shown in the figure. For example, if holes are provided as shown in the figure, the number will be as follows, for a total of 73 holes.

・ 1st row: 5 ・ 2nd row: 8 ・ 3rd row: 9 ・ 4th row: 10 ・ 5th row: 9 ・ 6th row: 10 ・ 7th row: 9 ・8th row: 8 pieces ・ 9th row: 5 pieces Total: 73 pieces
Therefore, a total of 73 primary electron beams can be generated. As shown in the figure, the hole size is Ax × Ay, the hole-to-hole spacing in the horizontal (X) direction is Sx, and the hole-hole spacing in the vertical (Y) direction is Sy, and they are arranged in a staggered pattern as shown in the figure. do.

It should be noted that each of the multi-beam apertures 3-1 in FIGS. 2 (a) to 2 (b) has a function of independently turning on / off each primary electron beam, so that the apertures have physically different arrangements. Instead of preparing a large number as shown in the figure, it may be created so that only the electron beam at an arbitrary position selected among all the multi-beams can be controlled to reach the sample.

FIG. 3 shows an example of a data table of the present invention (FIG. 2). In FIG. 3, as described and described later, under the structure of FIG. 1, the position XYZ, rotation θ, etc. of the stage 9 on which the sample 8 (for example, a mask) is mounted are measured in real time by a laser interferometer. After stopping the stage 9 and scanning the primary electron beam on the sample 8 to acquire a secondary electron image, when the movement is repeated, the stage shift amount, the stage rotation amount, and the stage correspond to the stage position. It is a record of the height.

In FIG. 3, the stage position indicates the position when the XYZθ stage (hereinafter referred to as the stage) 9 on which the sample 8 of FIG. 1 is mounted is moved and stopped, and the primary electron beam is surface-scanned on the sample 8, and the laser interferometry occurs. It was measured in real time with a meter (described later). The stage position is measured and recorded in real time, for example, in steps (intervals) corresponding to the distance between pixels of the image to be acquired. For example, when trying to acquire an image of 1000 pixels × 1000 pixels for a 100 μm rectangular area, one entry of information (stage position, stage shift amount, stage rotation amount, stage height) is measured in real time every 0.1 μm. And record. Further, every 0.01 μm corresponding to a 10 μm, 1 μm rectangular area. Real-time measurement and recording are performed every 0.001 μm. If the same value is continuous, the difference may be recorded. Further, each stop position of the stage 9 may be recorded.

The stage deviation amount is the deviation amount at the stage position (the deviation amount from the ideal position), and is a record of the value measured in real time by the laser interferometer (described later).

The stage rotation amount is the rotation amount at the stage position (rotation amount θ from the ideal no rotation), and is a recording of the rotation amount of the stage measured in real time by a laser interferometer (described later).

The stage height is the height Z (the amount of deviation in the Z direction from the ideal height) at the stage position, and is a recording of the amount of deviation of the height measured in real time by a laser interferometer (described later). ).

As described above, when the stage 9 in FIG. 1 is moved and stopped, the amount of deviation from the ideal value of the stage 9 (stage deviation amount (XY)), stage rotation amount θ, and stage height. It is possible to precisely measure and record each deviation amount of Z) in real time with a laser interferometer. Then, by correcting the position of the stage 9 or the acquired image in real time based on each recorded deviation amount, the error due to the movement of the stage 9 is corrected, and a plurality of primary electron beams are used as a sample. It is possible to synthesize each image of a plurality of secondary electron beams obtained by irradiation to generate one precise image. This will be described in detail below.

FIG. 4 shows an example of creating a multi-beam of the present invention. FIG. 4 schematically shows an example of creating a multi-beam using the multi-beam aperture 3-1 of FIG. 1 described above.

In FIG. 4, the primary electron beam emitted from the electron gun 1 just irradiates a plurality of two-dimensionally arranged holes (see FIG. 2) of the multi-beam aperture 3-1 here as shown by the illumination lens 3. Project to do. The plurality of primary electron beams (multi-electron beam 3-2) generated by passing through the multi-beam aperture 3-1 and being divided are placed on the surface of the sample 8 by the objective lens 6 of FIG. 1 (not shown in FIG. 4). It is squeezed finely and irradiated. Here, since the sample 8 is scanned in a plane when the sample 8 is stopped by the stage 9, as a result, the surface of the sample 8 is scanned in a plane with a multi-electron beam 3-2 on a plane such as a rectangular shape. Then, the emitted secondary electron beam is detected by the electron detection device 14 in FIG. 1, the secondary electron images are acquired respectively, and the secondary electron images are combined into one image (see FIGS. 6 and 7), and sample 8 2 is used. It becomes possible to generate a secondary electronic image.

FIG. 5 shows an explanatory diagram of multi-beam detection of the present invention. This shows a detailed explanatory view of the projection lens 12, the reverse scanning device 13, and the electron detection device 14 of FIG.

In FIG. 5, a plurality of secondary electron beams emitted from the sample 8 are separated via the beam splitter 5, and when they are incident downward from the top of FIG. 4, the projection lens 12 hits the detection surface of the electron detection device 14 respectively. It is imaged. At this time, the imaging region in which a plurality of secondary electron beams are imaged has no problem when it is in its own imaging region, but if it protrudes into another region, it is not detected and the secondary image is missing. Will be. In order to prevent this, the reverse scanning device 13 synchronizes with the scanning of the primary electron beam on the sample 8 (scanning by the deflection of the plurality of primary electron beams by the deflection device 7) and within a predetermined imaging region. It is corrected and deflected so that it enters, and it is corrected so that it is surely within its own imaging region.

As described above, each of the plurality of secondary electron beams emitted from the sample 8 is imaged in each imaging region of the electron detection device 14, and the secondary electron images of the plurality of secondary electron beams are surely obtained. It can be detected and output.

FIG. 6 shows a multi-beam image acquisition / synthesis explanatory diagram (quadrangle) of the present invention. Here, the horizontal direction represents the X direction, and the vertical direction represents the Y direction. The numbers 1, 2, 3, and 4 represent image 1, image 2, image 3, and image 4.

In FIG. 6, images 1, image 2, image 3, and image 4 are samples of a plurality of primary electron beams generated by using the square multi-beam aperture 3-1 of FIG. 2 (a) in a stopped state. 8 is irradiated, and then the movement of a predetermined distance is repeated four times to obtain four images (secondary electronic images) in which adjacent portions overlap each other as shown in the figure, and these four images are known. It is schematically shown how the images were combined into one image using the composition software of. This will be described in detail below.

(1) In FIG. 6, each primary electron beam is two-dimensionally performed on the surface of the sample 8 in the XY directions, and the stage 9 moves by S & R by a predetermined distance in an arbitrary direction. The stage movement amount corresponds to the width of the area that can be covered by one scanning surface. In reality, since an overlapping area for alignment is provided in the corner, the stage moves instantaneously by a distance smaller than the scanning surface width by the overlap.

(2) The amount of movement of the primary electron beam, the position of the stage, and the luminance information of the image on the scanning surface are recorded. A plurality of images of the scanning surface are formed each time S & R is repeated. In order to scan the sample 8 thoroughly, about 5 to 10% of the scanning width of the scanning surface is overlapped. As a result, scanning omissions are eliminated, and at the same time, a common image exists in the images of the adjacent scanning surfaces. Therefore, using the position sheet and pattern matching obtained by the laser interferometer, the images of the adjacent scanning surfaces are used. It is possible to correct the positional relationship of and make one large image.

(3) Since the overlap region is scanned twice, a high SNR can be obtained due to the image addition effect, so that more accurate alignment can be realized. For example, in the example of FIG. 6, the images 1, 2, 3, and 4 of each scanning surface are aligned, and the images are combined to form one large image region from the images of four independent scanning surfaces. NS. The image processed in this way is used as an inspection image. When the inspection target is formed without straddling the images of the respective scanning surfaces, the inspection can be realized using the images of one scanning surface, so that it is not always necessary to combine them into one image.

FIG. 7 shows a multi-beam image acquisition / synthesis explanatory diagram (hexagon) of the present invention. Here, the horizontal direction represents the X direction, and the vertical direction represents the Y direction. The numbers 1, 2, 3, and 4 represent image 1, image 2, image 3, and image 4.

In FIG. 7, images 1, image 2, image 3, and image 4 are samples in which a plurality of primary electron beams generated by using the hexagonal multi-beam aperture 3-1 of FIG. 2 (b) are stopped. 8 is irradiated, and then the movement of a predetermined distance is repeated four times to obtain four images (secondary electronic images) in which adjacent portions overlap each other as shown in the figure, and these four images are known. It is schematically shown how the images were combined into one image using the composition software of. This will be described in detail below.

Here, similar to (1) to (4) in FIG. 6 in the case of a quadrangle, in the case of a hexagon in FIG. 7, when an aperture arranged in a honeycomb shape ((b) in FIG. 2) is provided. As shown in the examples of the images 1, 2, 3, and 4 of the scanning surface generated in the above, the electron beam column is generally columnar, and the characteristics change or deteriorate concentrically when the electron beam is scanned. If the hexagon is shaped like a honeycomb, deterioration is suppressed and many images with the same characteristics can be obtained.

As in the case of FIG. 6, in FIG. 7, since the secondary electron images generated by scanning the respective primary electron beams are independent of each other, the images 1, 2, 3, and 4 of the respective scanning surfaces are shown. It is a completely independent image. Since the positional relationship with each other is known, one image can be obtained by performing image processing using the positional relationship and superimposing the images of the respective scanning surfaces. Image superimposition is obtained by pattern matching the overlapping parts.

As described above, when the S & R method of the present invention is used, the same place can be scanned many times to add images. Therefore, when one electron beam current is the same, the SNR is higher than that in the case of one scan. You can get an image. There is also the effect of averaging sampling by scanning the electron beam at very slightly different locations.

FIG. 8 shows an operation explanatory flowchart (acquisition of center coordinates of a multi-beam image) of the present invention.

In FIG. 8, S1 prepares a pattern having a known interval dimension. It prepares a reference sample with a pattern whose pattern spacing and shape dimensions are precisely known. A photomask or a silicon substrate having conductivity in which the same pattern is created in advance is preferable. The size and arrangement interval of the pattern are measured in advance by CDSEM or an optical measuring device. Since the deflection center coordinates of the electron beam are known as design values in advance for simplification of measurement, it can be easily calibrated by using a reference sample in which a pattern is placed at the location of the design deflection center coordinates. The pattern size is arbitrary, but a symmetrical pattern is desirable so that the center position can be accurately obtained even if process fluctuations occur.

S2 acquires an image while the stage is stopped. This scans a plurality of primary electron beams with respect to the pattern prepared in S1 with the stage stopped, and acquires an image of each pattern.

S3 compares the acquired image with the pattern with known spacing dimensions.

S4 calculates the center coordinates of each electron beam scan. In these S3 and S4, each image acquired in S2 and an image (or design data) of a reference sample are compared by using pattern matching or the like, and the deviation of the center position is calculated in S4. The deflection center coordinates of each primary electron beam are calculated from the amount of misalignment of the center position and the design data of the reference sample, and stored.

As described above, it is possible to calculate (measure) the center coordinates on the sample 8 scanned by the plurality of primary electron beams divided and generated by the multi-beam aperture of FIG. 2 arranged in two dimensions. After that, based on the center coordinates of these plurality of primary electron beams, it is possible to perform plane scanning and combine the acquired images to generate one image. This will be described in detail below.

FIG. 9 shows an operation explanatory flowchart (calibration) of the present invention. This shows an example of a procedure for automatically correcting an error (XY, Z) due to the movement of the stage 9.

In FIG. 9, S11 is set to the stage movement start position. This is set at the stage movement start position of the stage 9 in FIG. 1, for example, the movement start position (home position) on the sample 8 for which an image is to be acquired.

S12 moves the stage by a desired distance and issues a stop command.

S13 feeds back the difference between the target position and the current position to the electron beam deflector.

S14 matches the center coordinates of the electron beam scan with the target position. These S12, S13, and S14 move the stage 9 by a predetermined distance from the stage movement start position set in S11 (for example, move from the stage movement start position to the center position where the image is acquired, or move from the center position of the image already acquired to the next. Move to the center position of the image), issue a stop command, and stop. Then, the electron of FIG. 1 is used to correct the difference (ΔX, ΔY) between the stopped current position (current position (X, Y) measured in real time by a laser interferometer described later) and the designated target position. It feeds back to the beam deflection device 7, corrects it, and corrects it so that the stage 9 stops at a designated position (corrects the irradiation position of a plurality of primary electron beams).

S15 makes the stage height match the target value. Similarly, the height Z of the stage 9 is corrected in real time so that the height Z currently measured in real time of the stage 9 and the target height match (see FIG. 14 and the like described later).

S16 acquires an image. This corrects the position and height of the stage to match the target position and height in S11 to S15, and then acquires an image (described later with reference to FIGS. 10 and 11).

As described above, the position and height of the stay 9 are measured in real time while the stage 9 is moved and stopped, and the target position and height are matched (corrected), and then an image is acquired, which is accurately desired. It is possible to acquire images of the positions of (multi-beam images). Then, a plurality of acquired images are combined to generate one image.

FIG. 10 shows an operation explanatory flowchart (acquiring a multi-beam image (quadrangle)) of the present invention. This is an operation explanation flowchart when acquiring the quadrilateral multi-beam image of FIG.

In FIG. 10, S21 acquires an image of the stage stop position. This acquires an image of the position where the stage 9 is stopped. For example, a plurality of primary electron beams divided by the square multi-beam aperture of FIG. 2 (a) described above are irradiated on the surface of the sample 8 and surface-scanned, and the secondary electrons emitted at that time are electrons. Each of them is detected by the detection device 14, and the secondary electron images are acquired and combined, and for example, one image 1 shown in FIG. 6 is acquired.

S22 moves the stage by the scanning surface width X-overlap width x. As shown in FIG. 6, when moving from the image 1 acquired in S21 to the position of the image 2, the stage 9 is moved to the position obtained by subtracting the “overlap width x” from the “scanning surface width X”. do.

S23 acquires an image. This stops at the moved position with the overlap width x of S22, and acquires the image 2. As a result, the overlap width x overlaps with the images 1 and 2 in FIG. 6, and the overlapping portion can be used to accurately combine the images into one image.

S24 determines whether it is finished. If YES, the process proceeds to S25. If NO, it returns to S22 and repeats.

S25 moves the stage by the scanning surface width Y-overlap width y. As shown in FIG. 6, when moving to the position of the image 4 from the image 2 of the illustrated figure obtained by the image, the stage 9 is moved to the position obtained by subtracting the “overlap width y” from the “scanning surface width Y”. do.

S26 acquires an image. This stops at the downward position where the image 4 is moved with the overlap width y of S25, and the image 4 is acquired. As a result, the overlap width y exists overlapping with the images 2 and 4 in FIG. 6, and it is possible to accurately combine the images into one image by using this overlapping portion.

S27 determines whether it is finished. If YES, the process ends. If NO, it returns to S25 and repeats.

As described above, a plurality of primary electron beams are generated using the square multi-beam aperture of FIG. 2 (a), and the surface of the sample 8 is irradiated with these and surface-scanned to acquire an image of the sample 8. At that time, as shown in FIG. 6, by moving the stage so as to have overlapping overlap widths x and y between the images, partially overlapping images 1, 2, 3, 4 and the like are generated. It is possible to accurately and quickly combine these overlapping portions into a single image.

FIG. 11 shows an operation explanatory flowchart (acquiring a multi-beam image (hexagon)) of the present invention. This is an operation explanation flowchart when acquiring the hexagonal multi-beam image of FIG. 7.

In FIG. 11, S31 acquires an image of the stage stop position. This acquires an image of the position where the stage 9 is stopped. For example, a plurality of primary electron beams divided by the hexagonal multi-beam aperture of FIG. 2 (b) described above are irradiated on the surface of the sample 8 and surface-scanned, and the secondary electrons emitted at that time are electrons. Each of them is detected by the detection device 14, and the secondary electron images are acquired and combined, and for example, one image 1 shown in FIG. 7 is acquired.

S32 moves the stage by the scanning surface width X-overlap width x. As shown in FIG. 7, when moving from the image 1 acquired in S31 to the position of the image 2, the stage 9 is moved to the position obtained by subtracting the “overlap width x” from the “scanning surface width X”. do.

S33 acquires an image. This stops at the moved position with the overlap width x of S32, and acquires the image 2. As a result, the overlap width x overlaps with the images 1 and 2 in FIG. 7, and it is possible to accurately combine the images into one image by using this overlapping portion.

S34 determines whether it is finished. If YES, the process proceeds to S35. If NO, it returns to S32 and repeats.

S35 moves the stage by the scanning surface width Y-overlap width y. As shown in FIG. 7, when moving from the position of the image 2 acquired as an image to the position of the image 4, the stage 9 is moved to a position obtained by subtracting the “overlap width y” from the “scanning surface width Y”. do.

S36 acquires an image. This stops at the downward position where the image 4 is moved with the overlap width y of S35, and the image 4 is acquired. As a result, the overlap width y exists overlapping with the images 2 and 4 in FIG. 7, and it is possible to accurately combine the images into one image by using this overlapping portion.

S37 determines whether it is finished. If YES, the process ends. If NO, it returns to S35 and repeats.

As described above, a plurality of primary electron beams are generated using the hexagonal multi-beam aperture shown in FIG. 2B, and the surface of the sample 8 is irradiated with the surface scan to obtain an image of the sample 8. At that time, as shown in FIG. 7, by moving the stage so as to have overlapping overlap widths x and y between the images, partially overlapping images 1, 2, 3, 4 and the like are generated. It is possible to accurately and quickly combine these overlapping portions into a single image.

FIG. 12 shows an operation explanatory view (measurement of a deviation amount and a rotation amount of stage movement) of the present invention.

FIG. 12A shows an example of the positional relationship of the laser interferometer 31 for XY position measurement, and FIG. 12B shows an example of the positional relationship of the laser interferometer 31 for rotation measurement.

In (a) of FIG. 12, the interferometer X1 is arranged as shown in the figure so that the distance of the position of the stage 9 in the X direction can be accurately measured, and a mirror is arranged on the stage side.

The interferometer Y1 is arranged as shown in the figure so that the distance between the positions of the stage 9 in the Y direction can be accurately measured, and the mirror is arranged on the stage side.

By arranging the interferometers X1 and Y1 as described above, it is possible to accurately measure and record the distances (positions) in the X and Y directions of the stage 9 in real time (see FIG. 3).

In FIG. 12B, the interferometer X1 is arranged as shown so that the distance between the positions of the stage 9 in the X direction can be accurately measured, and the mirrors are arranged on the stage side and the mirrors are arranged on the stage side. do.

As shown in the figure, the interferometers Y1 and Y2 are arranged so that the rotation angle can be actually measured at a distance so that the distance between the positions of the stage 9 in the Y direction can be accurately measured, and the mirror is arranged on the stage side.

By arranging the interferometers X1, Y1 and Y2 as described above, it is possible to accurately measure the rotation of the stage 9 in real time (see FIG. 3).

FIG. 13 shows an explanatory diagram of tilt correction of the stage of the present invention. This shows an example of the stage 9 of FIG. 1 described above, and shows an example of a stage supported at three points of stage Z1 (cone), stage Z2 (cone), and stage Z3 (flat). Each stage that supports three points contracts by applying a voltage to the piezo element, and has a structure that can be arbitrarily adjusted from the outside to an arbitrary distance.

More specifically, FIG. 13 is composed of three independent piezo actuators having the same performance and arranged so as to support three points with respect to the center of the sample.

One end of the three piezo actuators has a support point on the surface of the moving part of the XY stage, and the other end is connected to a holder that supports the sample. The connection portion is molded so that three-point support is accurately performed. As an example, a ruby ball surface-treated to prevent slipping can be used, or a conical metal or plastic can be used. It is desirable to surface-treat the friction coefficient as large as possible. At least one of the three supports is conductive to form the circuit required to apply the bias voltage to the sample.

It has three independent control circuits to drive three piezo actuators, processes signals from height sensors 151 and 152 by a PC, and uses the processing results to command from a PC or the like to obtain a desired distance. You can change the height. Each actuator has a built-in displacement sensor such as a capacitance sensor, which monitors and feeds back the amount of displacement that actually occurs, and can correct the non-linearity of the piezo element. Positional accuracy can be obtained on the order of nm (see FIG. 20 described later).

The stroke required for Z-axis control is in the range of several microns to 1000 microns. It is necessary to have high rigidity so that the sample does not vibrate by being supported by the Z-axis stage. Since the support system using the piezo actuator with displacement expansion mechanism including the sample holder has a high response speed of ms and a large mechanical rigidity, it has a high resonance frequency of several hundred Hz or more and unnecessary vibration can be avoided. It is made up. Therefore, even a heavy sample weighing nearly 1 kg, such as a photomask, can be instantly maintained horizontally.

FIG. 14 shows a meandering explanatory view of the stage of the present invention.

FIG. 14 (a) schematically shows the state of the stage without meandering, FIG. 14 (b) shows the state when the meandering is on the left, and FIG. 14 (c) shows the state of the stage where the meandering is on the right. The situation of the case is shown schematically. Here, the vertical direction indicates the stage moving direction, and the horizontal direction indicates the electron beam scanning method.

In FIG. 14A, the stage 9 schematically shows a state in which there is no meandering with respect to the stage moving direction in a fixed direction (vertical direction), and shows a case where correction is not necessary.

In FIG. 14B, the stage 9 schematically shows how the meandering is to the left with respect to the stage moving direction in a certain direction (vertical direction), and shows a case where correction is necessary. In this case, the meandering is corrected to the right (see the amount of stage shift in FIG. 3).

In (c) of FIG. 14, the stage 9 schematically shows how the meandering is to the right with respect to the stage moving direction in a certain direction (vertical direction), and shows a case where correction is necessary. In this case, the meandering is corrected to the left (see the amount of stage shift in FIG. 3).

Generally, the XY stage is a combination of direct motors, servo motors, stepping motors, ultrasonic motors, linear motors, etc. for moving at high speeds with a large driving force of micron or more, and piezo actuators and brakes capable of fine movements on the order of micron or less. There are many things.

The XY stage has a function of moving to a designated coordinate point with a degree of freedom of movement in the XY direction by combining an X-axis movement mechanism and a Y-axis movement mechanism that are independent of each other. For example, suppose that a movement command is given to the XY stage to move along the Y axis. If it is a perfect stage, it does not move in the X direction but moves only in the Y-axis direction, but as shown in FIG. 14, in an actual stage, movement also occurs in the X direction.

The guide rail that regulates the moving accuracy of the stage is made of ceramic or the like, and is machined with extremely high precision, but there is a mechanical accuracy error of about micron. When the stage moves from (X1, Y1) to (X1, Y2) along the Y axis, for example, the center coordinates of the stage meander to the left and right in the X-axis direction while the stage is moving. In the multi-beam method, a group of primary electron beams arranged in a two-dimensional manner in which the interval between each electron beam is predetermined is used. If the stage meanders during the continuous inspection, the place where the primary electron beam is irradiated is different from the intended place, and the primary electron beam is unevenly irradiated, causing a defect in the inspection.

FIG. 15 shows an explanatory diagram of meandering correction of the stage of the present invention.

FIG. 15A schematically shows an example of an image before correction, and FIG. 15B schematically shows an example of an image after correction. Here, the vertical direction represents the stage moving direction, and the horizontal direction represents the scanning direction of the primary electron beam.

In FIG. 15A, each image schematically shows how the image of the rectangular region shown in the figure meanders to the left and right for each meandering of the stage.

In FIG. 15B, each image schematically shows the state after the image of the rectangular region shown in the figure is corrected for each meandering of the stage. There is no meandering in the image, and it can be seen that the images are scanned with the same width in the direction of stage movement.

As described above, as described with reference to FIG. 14 described above, when there is meandering of the stage 9 (the amount of deviation in the direction perpendicular to the stage moving direction, and further, the amount of deviation in the stage moving direction) (when detected). Is corrected to move the stage (or move the detected image) by the amount of these meanders, and it is possible to make corrections so that there is no apparent meander as shown in FIG. 15 (b).

FIG. 16 shows an explanatory diagram of stage rotation of the present invention.

FIG. 16 (a) schematically shows a state where there is no horizontal rotation, FIG. 16 (b) schematically shows a state when the horizontal rotation is on the right, and FIG. 16 (c) shows a state where the horizontal rotation is on the right. The situation in the case on the left is schematically shown. Here, the vertical direction indicates the stage moving direction, and the horizontal direction indicates the electron beam scanning method.

In FIG. 16A, the stage 9 schematically shows a state in which there is no horizontal rotation with respect to the stage moving direction in a fixed direction (vertical direction), and shows a case where correction is not necessary.

In FIG. 16B, the stage 9 schematically shows a state in which the horizontal rotation is to the right with respect to the stage moving direction in a fixed direction (vertical direction), and shows a case where correction is necessary. In this case, the horizontal rotation is corrected to the left (see the stage rotation amount in FIG. 3).

In FIG. 16 (c), the stage 9 schematically shows a state in which the horizontal rotation is to the left with respect to the stage moving direction in a fixed direction (vertical direction), and shows a case where correction is necessary. In this case, the horizontal rotation is corrected to the right (see the stage rotation amount in FIG. 3).

Generally, the stage 9 is placed on two rails symmetrically with a movable part in between. Since the characteristics of the left and right rails are not necessarily the same and the friction is different, when the stage 9 is moved along the rails, the amount of movement differs between the left and right rails. Therefore, the movable portion of the stage 9 causes a slight rotational sway in the XY plane. This is corrected in the present invention.

FIG. 17 shows an explanatory diagram of rotation correction of the stage of the present invention.

FIG. 17A schematically shows an example of the image before correction, and FIG. 17B schematically shows an example of the image after correction. Here, the vertical direction represents the stage moving direction, and the horizontal direction represents the scanning direction of the primary electron beam.

In FIG. 17A, each image schematically shows how the image in the rectangular region shown in the figure rotates left or right with each horizontal rotation of the stage.

In FIG. 17B, each image schematically shows a state after the image of the rectangular region shown in the figure is corrected for each horizontal rotation of the stage. It can be seen that the image is scanned in the same direction as the stage moves without horizontal rotation.

As described above, as described with reference to FIG. 16 described above, when there is horizontal rotation of the stage 9 (amount of deviation in the rotation direction with respect to the stage movement direction) (when detected), these horizontal directions are used. Correction is performed to rotate the stage in the opposite direction (or rotate the detected image) by the amount of rotation, and correction is made so that there is no horizontal rotation with respect to the movement direction of the stage, as shown in FIG. 17 (b). It becomes possible to do.

FIG. 18 shows an explanatory diagram of tilt correction of the stage of the present invention (height control by the Z stage and automatic leveling).

FIG. 18A schematically shows the state before the correction, and FIG. 18B schematically shows the state after the correction. Here, the horizontal axis represents the moving directions Y1 to Y2 of the stage, and the vertical axis represents the height Z at that time.

In FIG. 18A, the convex curve shown in the figure shows an example of the curve before correction, and the change in the coordinates of the height Z when the stage 9 moves from the coordinates Y1 to the coordinates Y2 at a constant speed. Is schematically shown. Here, it is found that the height Z changes in a convex shape (actually measured (see the stage height in FIG. 3)).

In FIG. 18B, the illustrated curve shows an example of the corrected curve, and shows the state after the height Z of the stage 9 is corrected. This is when the coordinates of the height Z when the stage 9 moves from the coordinates Y1 to the coordinates Y2 at a constant speed change like the convex curve shown in FIG. 18A before the correction (FIG. 3). The height Z is automatically corrected according to the height Z detected in real time.

As described above, when the stage 9 moves in a certain direction at a constant speed, the height Z can be detected in real time and the height of the stage can be automatically corrected by the change in the height (see the figure to be described later). 19).

It should be noted that the movement of the stage 9 in the Z direction is automatically focused by controlling the objective lens 6 (or an auxiliary objective lens (not shown)) without performing the correction in the Z direction of the stage 9 described with reference to FIG. 18 described above. And a method of performing automatic magnification correction may be adopted.

FIG. 19 shows an explanatory diagram of height correction of the stage of the present invention.

FIG. 19A schematically shows a state without correction, and FIG. 19B schematically shows a state with correction. Here, the vertical direction is the electron beam scanning direction, and the horizontal direction is the moving direction of the stage.

In FIG. 19A, each image of the front end portion, the center portion, and the rear end portion without the correction shown is the movement of the stage 9 (from the coordinate Y1 (tip portion) in FIG. 18 to the coordinate Y2 (rear end portion). ), Which is a schematic representation of the blurring of the image due to the change in height Z.

In FIG. 19B, each image of the front end portion, the center portion, and the rear end portion with the correction shown is the movement of the stage 9 (from the coordinate Y1 (tip portion) of FIG. 18 to the coordinate Y2 (rear end portion). ) Is a schematic representation of the image (without blurring) after the height correction is performed due to the change in the height Z generated.

As described above, with respect to the uncorrected blurred image of FIG. 19 (a), the height Z is detected in real time to automatically correct the height of the stage 9, and the corrected image of FIG. 18 (b) is obtained. Can be automatically corrected.

FIG. 20 shows a sample height and tilt correction explanatory diagram of the present invention. This shows an example of an example structural diagram in which the stage of FIG. 13 is incorporated in FIG. 1 described above.

In FIG. 20, the primary electron beam 1-1 represents a plurality of primary electron beams.

The secondary electron beam 1-2 represents a plurality of secondary electron beams emitted when the sample 51 is irradiated with the plurality of primary electron beams 1-1.

The height sensors 151 and 152 are devices that measure and output the height of the sample 51 in real time, such as a laser interferometer.

The sample holder 52 holds the sample 8.

The piezo piezoelectric elements (Z1) 51, (Z2) 52, and (Z3) 55 correspond to the stage Z1 (cone), stage Z2 (cone), and stage Z3 (flat) of FIG. 12 described above. The sample holder 52 is supported by three-point support.

Under the above structure, as described with reference to FIG. 13, the control voltage is applied to any of the piezo piezoelectric elements (Z1) 51, (Z2) 52, and (Z3) 55 that support the sample holder 52 at three points. Can be applied to automatically correct the height and inclination of the sample holder 52 to a desired height Z in real time and at ultra-high speed. By correcting the tilt, the incident angle of the electron beam can be kept constant with respect to the sample.

It is a structural drawing of 1 Example of this invention. This is an example of a schematic array of multi-beam apertures of the present invention. It is an example of a data table of the present invention (FIG. 2). This is an example of creating a multi-beam of the present invention. It is a multi-beam detection explanatory diagram of this invention. It is a multi-beam image acquisition / synthesis explanatory view (quadrilateral) of this invention. It is a multi-beam image acquisition / synthesis explanatory view (hexagon) of this invention. It is the operation explanation flowchart (the center coordinate acquisition of a multi-beam image) of this invention. It is an operation explanation flowchart (calibration) of this invention. It is an operation explanation flowchart of this invention (the multi-beam image (quadrilateral) is acquired). It is an operation explanation flowchart of this invention (the multi-beam image (hexagon) is acquired). It is an operation explanatory drawing (measurement of the deviation amount and the rotation amount of a stage movement) of this invention. It is an inclination correction explanatory view of the stage of this invention. It is a meandering explanatory view of the stage of this invention. It is a meandering correction explanatory diagram of the stage of this invention. It is a rotation explanatory drawing of the stage of this invention. It is a rotation correction explanatory diagram of the stage of this invention. It is an inclination correction explanatory drawing of the stage of this invention. It is a height correction explanatory drawing of the stage of this invention. It is a sample height and inclination correction explanatory drawing of this invention.

1: Electron gun 1-1: 1st-order electron beam 1-2: Secondary electron beam 2: Blanking device 3: Illumination lens 3-1: Multi-beam aperture 3-2: Multi-electron beam 4: Objective aperture 5: Beam Splitter 5-1: Electrostatic deflector 5-2: Electromagnetic deflector 6: Objective lens 7: Deflection device 8: Sample 8-1: Mirror 9: XYZθ stage (stage)
10: Vacuum chamber 10-1: Vacuum pump 11: Alignment 12: Projection lens 13: Reverse scanning device 14: Electronic detection device 52: Sample holder 53, 54, 55; Piezo piezoelectric element 151, 152: Height sensor

Claims (10)

In a multi-beam image generator that scans a sample with multiple primary electron beams to generate an image.
A multi-beam generator that generates multiple primary electron beams arranged in two dimensions,
A plurality of primary electron beams generated by the multiple beam generator are deflected in two stages and incident on the axis of the objective lens, and the secondary electron beam emitted from the sample is 2 in the direction opposite to the primary electron beam. A beam splitter that is step-biased and incident on the axis of the projection lens,
An objective lens that narrows down the primary electron beam that is split in two stages by the beam splitter and is incident on the axis.
A deflection system that deflects a primary electron beam finely focused by the objective lens and scans it on a sample.
A projection lens that images a secondary electron beam that is split in two stages by the beam splitter and incident on the axis on an electron detector.
A stage that repeatedly moves and stops the sample and acquires an image when it stops,
Equipped with an interferometer that measures the position of the sample in the moving direction and the position in the right angle direction in real time.
A plurality of primary electron beams generated by the plurality of beam generators are deflected to the axis of the pair lens by the beam splitter, and the sample is irradiated with the primary electron beam narrowed down by the objective lens and the deflection system. 2. The secondary electrons emitted from the sample are deflected to the axis of the projection lens by the beam splitter, and the projection lens corresponds to the plurality of primary electron beams arranged in the electron detector in the two dimensions. A multi-beam image generator characterized by forming an image of a secondary electron beam and outputting image information of a plurality of electron beams. The multi-beam image generation apparatus according to claim 1, further comprising a synthesizing means for synthesizing a single image based on the output image information of the plurality of electron beams. The movement amount and rotation amount of the stage are corrected based on the image information of the output plurality of electron beams and the position in the real-time movement direction and the position in the right angle direction of the sample output from the interference meter. The multi-beam image generation device according to any one of claims 1 to 2, wherein the image information is moved and rotated by the amount corresponding to the movement amount and the rotation amount of the stage. Claims 1 to claim 1, wherein the position in the height direction of the stage is measured in real time, the height of the stage is corrected based on the measurement, or the height of the stage is corrected electromagnetically to automatically focus. 3. The multi-beam image generator according to any one of 3. The present invention is claimed from claim 1, wherein the plurality of beam generators generate a plurality of primary electron beams by irradiating an aperture having a plurality of holes arranged two-dimensionally with one primary electron beam. Item 4. The multi-beam image generator according to any one of Items 4. In the beam splitter, the first stage on the incident side of the primary electron is an electrostatic deflector, the second stage is an electromagnetic deflector, and the secondary electron beam emitted from the sample by the electromagnetic deflector of the second stage is used. The multi-beam image generator according to any one of claims 1 to 5, wherein the beam is deflected in the opposite direction to the primary electron beam and separated. A claim characterized in that a negative retarding voltage is applied to the sample to reduce the energy while maintaining the high resolution of the primary electron beam to be scanned by irradiating the sample to reduce the damage of the sample. The multi-beam image generator according to any one of claims 1 to 6. The multi-beam image generation apparatus according to any one of claims 1 to 7, wherein a deflection system for correcting the position of the secondary electron beam is provided before or after the projection lens. In a multi-beam image generation method in which a plurality of primary electron beams are scanned into a sample to generate an image.
A multi-beam generator that generates multiple primary electron beams,
A plurality of primary electron beams generated by the multiple beam generator are deflected in two stages and incident on the axis of the objective lens, and the secondary electron beam emitted from the sample is 2 in the direction opposite to the primary electron beam. A beam splitter that is step-biased and incident on the axis of the projection lens,
An objective lens that narrows down the primary electron beam that is split in two stages by the beam splitter and is incident on the axis.
A deflection system that deflects a primary electron beam finely focused by the objective lens and scans it in a plane on a sample.
A projection lens that forms an image of a secondary electron beam that is split in two stages by the beam splitter and incident on the axis on an electron detector, a stage that repeatedly moves and stops the sample, and an image acquisition when the sample stops.
An interferometer that measures the position of the sample in the moving direction and the position in the right angle direction in real time is provided.
A plurality of primary electron beams generated by the plurality of beam generators are deflected to the axis of the pair lens by the beam splitter, and the sample is irradiated with the primary electron beam narrowed down by the objective lens and the deflection system. 2. The secondary electrons emitted from the sample are deflected to the axis of the projection lens by the beam splitter, and the projection lens corresponds to the plurality of primary electron beams arranged in the electron detector in the two dimensions. A multi-beam image generation method characterized by forming an image of a secondary electron beam and outputting image information of a plurality of electron beams. The multi-beam image generation method according to claim 9, further comprising a synthesizing means for synthesizing a single image based on the output image information of the plurality of electron beams.

Images