JP2021131946A - Multi-charged particle beam alignment method and multi-charged particle beam inspection device - Google Patents

Abstract

To provide a method capable of aligning a multi-charged particle beam and a secondary electron detector.SOLUTION: A multi-charged particle beam alignment method includes the steps of: retrieving coordinates of two or more detection elements among a plurality of detection elements of a multidetector for detecting a multi-secondary-charged particle beam emitted from a sample surface; rotating the multidetector at a first rotation angle; using a secondary charged particle beam emitted from the sample surface to search coordinates of two or more detection elements after the rotation; using the first rotation angle at which the multidetector is rotated, and the retrieved coordinates of the two or more detection elements before and after the rotation to calculate a rotation center coordinate of the multidetector; using at least one of the retrieved coordinates of the two or more detection elements and the rotation center coordinate of the multidetector to calculate a second rotation angle for aligning the plurality of detection elements to the multi-secondary-charged particle beam; and rotating the multidetector at the second rotation angle.SELECTED DRAWING: Figure 5

Description

The present invention relates to a multi-charged particle beam alignment method and a multi-charged particle beam inspection device.

In recent years, with the increasing integration and capacity of large-scale integrated circuits (LSIs), the circuit line width required for semiconductor devices has become narrower and narrower. Further, improvement of yield is indispensable for manufacturing LSI, which requires a large manufacturing cost. However, as represented by 1-gigabit class DRAM (random access memory), the patterns constituting the LSI are on the order of submicron to nanometer. In recent years, with the miniaturization of LSI pattern dimensions formed on semiconductor wafers, the dimensions that must be detected as pattern defects have become extremely small. Therefore, it is necessary to improve the accuracy of the pattern inspection apparatus for inspecting the defects of the ultrafine pattern transferred on the semiconductor wafer.

As an inspection method, a method of inspecting by comparing a measurement image obtained by imaging a pattern formed on a substrate such as a semiconductor wafer or a lithography mask with design data or a measurement image obtained by imaging the same pattern on the substrate. It has been known. For example, as a pattern inspection method, "die to die inspection" in which measurement image data obtained by imaging the same pattern in different places on the same substrate are compared with each other, or a design image based on pattern-designed design data. There is a "die to database inspection" that generates data (reference image) and compares it with the measurement image that is the measurement data obtained by imaging the pattern. The captured image is sent to the comparison circuit as measurement data. In the comparison circuit, after the images are aligned with each other, the measurement data and the reference data are compared according to an appropriate algorithm, and if they do not match, it is determined that there is a pattern defect.

Defect inspection of semiconductor wafers and photomasks is required to detect defects of smaller sizes. Therefore, in recent inspection devices, the above-mentioned pattern inspection device includes a device that irradiates a substrate to be inspected with laser light and captures a transmitted image or a reflected image thereof, as well as a laser in order to improve the pixel resolution of the image. An inspection device that scans the inspection target substrate with an electron beam having a wavelength shorter than that of light, detects secondary electrons emitted from the inspection target substrate when the electron beam is irradiated, and acquires a pattern image. Development is also in progress. As for the inspection device using the electron beam, the development of the device using the multi-beam is also in progress.

In a multi-beam inspection device, in a system in which the number of multi-beams and the number of elements of the secondary electron detector are the same, the alignment of the two is important. In particular, when the secondary electron detector is mounted on the device as a new or exchanged one, the alignment with the multi-secondary electron beam is important. For example, a method is disclosed in which an aperture plate is arranged between the final stage lens of the secondary optical system lens and the secondary electron detector, and the aperture plate is used for adjusting the position of the secondary electron beam (for example). , Patent Document 1).

Japanese Unexamined Patent Publication No. 2014-026834

Therefore, one aspect of the present invention provides a method capable of aligning a multi-charged particle beam and a secondary electron detector, and an apparatus capable of realizing such a method.

The multi-charged particle beam alignment method of one aspect of the present invention is:
Two or more of the plurality of detection elements of the multi-detector for detecting the multi-secondary charged particle beam including each secondary charged particle beam by using the secondary charged particle beam emitted from the sample surface. The process of searching for the coordinates of the detection element of
The process of rotating the multi-detector at the first rotation angle,
The process of searching the coordinates of two or more detection elements after rotation using each secondary charged particle beam emitted from the sample surface, and
A process of calculating the rotation center coordinates of the multi-detector using the first rotation angle obtained by rotating the multi-detector and the coordinates of two or more detection elements before and after the searched rotation.
Using at least one of each coordinate of the two or more detected elements searched and the rotation center coordinates of the multi-detector, a second rotation angle for aligning the plurality of detection elements with the multi-secondary charged particle beam is determined. The process of calculation and
The process of rotating the multi-detector at the second rotation angle,
It is characterized by being equipped with.

In addition, the process of calculating the corresponding coordinates for the multi-secondary charged particle beam, which has the same positional relationship as the positional relationship of the rotation center coordinates for a plurality of detection elements,
The process of calculating the shift amount for shifting the rotation center coordinates to the coordinates corresponding to the multi-secondary charged particle beam, and
The process of shifting the multi-detector using the shift amount,
It is preferable to further provide.

Further, a step of calculating the coordinates of the remaining detection elements of the plurality of detection elements using each coordinate of the searched two or more detection elements, and a step of calculating the coordinates of the remaining detection elements of the plurality of detection elements.
It is preferable to further provide.

Further, it is preferable to further include a step of selecting three detection elements different from the detection element in the central portion from the plurality of detection elements as the two or more detection elements to be searched.

Further, as two or more detection elements, three detection elements that do not line up in a straight line are used.
Further, the process of performing an operation of decomposing the vector from the coordinates of one detection element to the coordinates of the center of rotation into two vectors from the coordinates of one detection element to the coordinates of the remaining two detection elements among the three detection elements is further performed. Prepare,
The corresponding coordinates are preferably calculated as the coordinates of the composite vector of the two vectors when the two decomposed vectors are applied to the coordinates of the three secondary charged particle beams of the multi-secondary charged particle beam. ..

The multi-charged particle beam inspection apparatus according to one aspect of the present invention is
The stage on which the sample is placed and
A primary electron optics system that irradiates a sample with a multi-primary electron beam,
A multi-detector having a plurality of detection elements and for detecting a multi-secondary electron beam emitted by irradiating a sample with a multi-primary electron beam,
A rotation mechanism that rotates the multi-detector,
A search unit that searches the coordinates of two or more detection elements among a plurality of detection elements before and after rotation that rotates the multi-detector at the first rotation angle using the secondary charged particle beam emitted from the sample surface. When,
A rotation center calculation unit that calculates the rotation center coordinates of the multi-detector using the first rotation angle obtained by rotating the multi-detector and the coordinates of two or more detection elements before and after the searched rotation.
Using at least one of each coordinate of the two or more detected elements searched and the rotation center coordinates of the multi-detector, a second rotation angle for aligning the plurality of detection elements with the multi-secondary charged particle beam is determined. The rotation angle calculation unit to be calculated and
With
The rotation mechanism is characterized by rotating the multi-detector at a second rotation angle.

According to one aspect of the present invention, efficient alignment of the multi-charged particle beam and the secondary electron detector is possible.

It is a block diagram which shows the structure of the inspection apparatus in Embodiment 1. FIG. It is a conceptual diagram which shows the structure of the molded aperture array substrate in Embodiment 1. FIG. It is a figure which shows an example of the positional relationship between the multi-secondary electron beam and a plurality of detection elements of a multi-detector in the stage before alignment in Embodiment 1. FIG. It is a figure which shows an example of the internal structure of the alignment circuit in Embodiment 1. FIG. It is a flowchart which shows an example of the main part process of the inspection method in Embodiment 1. FIG. It is a figure for demonstrating the method of searching the detection element coordinates in Embodiment 1. FIG. It is a figure which shows the structure of the beam selection aperture substrate in Embodiment 1. FIG. It is a figure for demonstrating an example of the method of scanning a secondary electron beam in Embodiment 1. FIG. It is a figure which shows an example of the scanning range of the secondary electron beam in Embodiment 1. FIG. It is a figure for demonstrating the search method for accurately grasping the position of D11 after identifying the beam near D11. It is a figure which shows the case where one of the two selected detection elements in Embodiment 1 and the secondary electron beam overlap. It is a figure which shows the case where the other of the two selected detection elements in Embodiment 1 and the secondary electron beam overlap. It is a figure which shows an example of the positional relationship between the multi-secondary electron beam before and after rotation in Embodiment 1 and a plurality of detection elements of a multi-detector. It is a figure which shows the case where one of the two selected detection elements in Embodiment 1 and the secondary electron beam overlap. It is a figure which shows the case where the other of the two selected detection elements in Embodiment 1 and the secondary electron beam overlap. It is a figure which shows an example of the coordinates of the plurality of detection elements of the multi-detector before and after rotation in Embodiment 1. FIG. It is a figure which shows the calculation formula for calculating the rotation center coordinates in Embodiment 1. FIG. It is a figure for demonstrating the method of the vector operation of the detection element coordinates in Embodiment 1. FIG. It is a figure which shows the arithmetic expression for calculating the vector coefficient in Embodiment 1. FIG. It is a figure for demonstrating the method of the vector operation of the secondary electron beam coordinates in Embodiment 1. FIG. It is a figure for demonstrating the calculation method of each coordinate of a plurality of detection elements in Embodiment 1. FIG. It is a figure which shows the calculation formula for calculating the alignment angle in Embodiment 1. FIG. It is a figure for demonstrating the mode of shifting a plurality of detection elements in Embodiment 1. FIG. It is a figure for demonstrating the mode of rotating a plurality of detection elements in Embodiment 1. FIG. It is a figure which shows an example of the plurality of chip regions formed on the semiconductor substrate in Embodiment 1. FIG. It is a figure for demonstrating the inspection process in Embodiment 1. FIG. It is a block diagram which shows an example of the structure in the comparison circuit in Embodiment 1. FIG.

Hereinafter, in the embodiment, an electron beam will be described as an example of the charged particle beam. However, it is not limited to this. For example, it may be an ion beam or the like. Further, as an example of the multi-beam image acquisition device, an inspection device using the multi-beam will be described. However, it is not limited to this. Any device may be used as long as it is a device that acquires an image using a secondary electron detector that supports multi-beams.

Embodiment 1.
FIG. 1 is a configuration diagram showing a configuration of an inspection device according to the first embodiment. In FIG. 1, the inspection device 100 for inspecting a pattern formed on a substrate is an example of a multi-electron beam inspection device. The inspection device 100 includes an image acquisition mechanism 150 and a control system circuit 160. The image acquisition mechanism 150 includes an electron beam column 102 (electron lens barrel) and an examination room 103. In the electron beam column 102, an electron gun 201, an electromagnetic lens 202, a molded aperture array substrate 203, a beam selection aperture substrate 232, a drive mechanism 234, an electromagnetic lens 205, a batch blanking deflector 212, a limiting aperture substrate 213, and an electromagnetic lens. 206, electromagnetic lens 207 (objective lens), main deflector 208, sub-deflector 209, beam separator 214, deflector 218, electromagnetic lens 224, alignment coils 225 and 226, detector stage 229 and multi-detector 222 are arranged. ing. Electron optics 201, electromagnetic lens 202, molded aperture array substrate 203, electromagnetic lens 205, batch blanking deflector 212, limiting aperture substrate 213, beam selection aperture substrate 232, electromagnetic lens 206, electromagnetic lens 207 (objective lens), main deflection The primary electron optics system 151 is composed of the device 208 and the sub-deflector 209. Further, the secondary electron optical system 152 is composed of the electromagnetic lens 207, the beam separator 214, the deflector 218, the electromagnetic lens 224, and the alignment coils 225 and 226. The multi-detector 222 is arranged on the detector stage 229 which can move in the x, y direction and the rotation (θ) direction of the secondary coordinate system. The detector stage 229 has a rotary stage 227 and a secondary system x, y stage 228.

A stage 105 that can move at least in the XY directions is arranged in the examination room 103. A substrate 101 (sample) to be inspected is arranged on the stage 105. The substrate 101 includes an exposure mask substrate and a semiconductor substrate such as a silicon wafer. When the substrate 101 is a semiconductor substrate, a plurality of chip patterns (wafer dies) are formed on the semiconductor substrate. When the substrate 101 is an exposure mask substrate, a chip pattern is formed on the exposure mask substrate. The chip pattern is composed of a plurality of graphic patterns. By exposing and transferring the chip pattern formed on the exposure mask substrate to the semiconductor substrate a plurality of times, a plurality of chip patterns (wafer dies) are formed on the semiconductor substrate. Hereinafter, the case where the substrate 101 is a semiconductor substrate will be mainly described. The substrate 101 is arranged on the stage 105, for example, with the pattern forming surface facing upward. Further, on the stage 105, a mirror 216 that reflects the laser beam for laser length measurement emitted from the laser length measuring system 122 arranged outside the examination room 103 is arranged.

Further, the multi-detector 222 is connected to the detection circuit 106 outside the electron beam column 102. The detection circuit 106 is connected to the chip pattern memory 123.

In the control system circuit 160, the control computer 110 that controls the entire inspection device 100 uses the position circuit 107, the comparison circuit 108, the reference image creation circuit 112, the stage control circuit 114, the lens control circuit 124, and the blanking via the bus 120. It is connected to a control circuit 126, a deflection control circuit 128, a detector stage control circuit 130, an alignment circuit 134, a beam selection aperture control circuit 136, a storage device 109 such as a magnetic disk device, a memory 118, and a printer 119. Further, the deflection control circuit 128 is connected to a DAC (digital-to-analog conversion) amplifier 144, 146, 148. The DAC amplifier 146 is connected to the main deflector 208, and the DAC amplifier 144 is connected to the sub-deflector 209. The DAC amplifier 148 is connected to the deflector 218.

Further, the chip pattern memory 123 is connected to the comparison circuit 108 and the alignment circuit 134. Further, the stage 105 is driven by the drive mechanism 142 under the control of the stage control circuit 114. In the drive mechanism 142, for example, a drive system such as a three-axis (XY−θ) motor that drives in the X direction, the Y direction, and the θ direction in the stage coordinate system is configured, and the stage 105 can move in the XYθ direction. It has become. As these X motors, Y motors, and θ motors (not shown), for example, step motors can be used. The stage 105 can be moved in the horizontal direction and the rotational direction by a motor of each axis of XYθ. Then, the moving position of the stage 105 is measured by the laser length measuring system 122 and supplied to the position circuit 107. The laser length measuring system 122 measures the position of the stage 105 by the principle of the laser interferometry method by receiving the reflected light from the mirror 216. In the stage coordinate system, for example, the X direction, the Y direction, and the θ direction of the primary coordinate system are set with respect to the plane orthogonal to the optical axis of the multi-primary electron beam 20.

The detector stage 229 is driven by a drive mechanism 132 under the control of the detector stage control circuit 130. In the drive mechanism 132, for example, a drive system such as a three-axis (xy−θ) motor that drives in the x direction, the y direction, and the θ direction in the stage coordinate system is configured, and the x, y stage is configured in the x, y directions. In 228, the rotary stage 227 can be moved by the θ method. In the example of FIG. 1, the case where the x and y stages 228 are arranged on the rotating stage 227 is shown. As these x motors, y motors, and θ motors (not shown), for example, step motors can be used. The detector stage 229 can be moved in the horizontal direction and the rotational direction by the motor of each axis of xyθ. In the stage coordinate system, for example, the x direction, the y direction, and the θ direction of the secondary coordinate system are set with respect to the plane orthogonal to the optical axis of the multi-secondary electron beam 300.

The electromagnetic lens 202, the electromagnetic lens 205, the electromagnetic lens 206, the electromagnetic lens 207 (objective lens), the electromagnetic lens 224, the alignment coils 226 and 227, and the beam separator 214 are controlled by the lens control circuit 124. Further, the batch blanking deflector 212 is composed of electrodes having two or more poles, and each electrode is controlled by a blanking control circuit 126 via a DAC amplifier (not shown). The sub-deflector 209 is composed of electrodes having four or more poles, and each electrode is controlled by the deflection control circuit 128 via the DAC amplifier 144. The main deflector 208 is composed of electrodes having four or more poles, and each electrode is controlled by a deflection control circuit 128 via a DAC amplifier 146. The deflector 218 is composed of electrodes having four or more poles, and each electrode is controlled by a deflection control circuit 128 via a DAC amplifier 148.

The beam selection aperture substrate 232 is driven by the drive mechanism 234, and the drive mechanism 234 is controlled by the beam selection aperture control circuit 136.

A high-voltage power supply circuit (not shown) is connected to the electron gun 201, and an acceleration voltage is applied from the high-voltage power supply circuit between the filament (cathode) and the extraction electrode (anode) in the electron gun 201 (not shown), and another extraction electrode is used. By applying a voltage of (Wenert) and heating the cathode at a predetermined temperature, a group of electrons emitted from the cathode is accelerated and emitted as an electron beam 200.

Here, FIG. 1 describes a configuration necessary for explaining the first embodiment. The inspection apparatus 100 may usually have other necessary configurations.

FIG. 2 is a conceptual diagram showing the configuration of the molded aperture array substrate according to the first embodiment. In FIG. 2, the molded aperture array substrate 203 has _{holes (openings) of two-dimensional horizontal (x direction) m 1} row × vertical (y direction) n ₁ step (m ₁ and n ₁ are integers of 2 or more). ) 22 are formed at a predetermined arrangement pitch in the x and y directions. In the example of FIG. 2, a case where a 23 × 23 hole (opening) 22 is formed is shown. Each hole 22 is formed by a rectangle having the same dimensions and shape. Alternatively, it may be a circle having the same outer diameter. A part of the electron beam 200 passes through each of these plurality of holes 22, so that the multi-primary electron beam 20 is formed. Next, the operation of the image acquisition mechanism 150 in the case of acquiring a secondary electronic image will be described. The primary electron optics system 151 irradiates the substrate 101 with the multi-primary electron beam 20. Specifically, it operates as follows.

The electron beam 200 emitted from the electron gun 201 (emission source) is refracted by the electromagnetic lens 202 to illuminate the entire molded aperture array substrate 203. As shown in FIG. 2, a plurality of holes 22 (openings) are formed in the molded aperture array substrate 203, and the electron beam 200 illuminates an area including all the plurality of holes 22. The multi-primary electron beam 20 is formed by each part of the electron beam 200 irradiated to the positions of the plurality of holes 22 passing through the plurality of holes 22 of the molded aperture array substrate 203.

The formed multi-primary electron beam 20 is refracted by the electromagnetic lens 205 and the electromagnetic lens 206, respectively, and the intermediate image plane (image plane) of each beam of the multi-primary electron beam 20 is repeated while repeating the intermediate image and the crossover. It passes through the beam separator 214 arranged at the conjugate position (IP) and proceeds to the electromagnetic lens 207 (objective lens).

When the multi-primary electron beam 20 is incident on the electromagnetic lens 207 (objective lens), the electromagnetic lens 207 focuses the multi-primary electron beam 20 on the substrate 101. The multi-primary electron beam 20 focused (focused) on the surface of the substrate 101 (sample) by the objective lens 207 is collectively deflected by the main deflector 208 and the sub-deflector 209, and the substrate 101 of each beam is deflected collectively. Each of the above irradiation positions is irradiated. When the entire multi-primary electron beam 20 is collectively deflected by the batch blanking deflector 212, the position is displaced from the central hole of the limiting aperture substrate 213, and the multi-primary electrons are displaced by the limiting aperture substrate 213. The entire beam 20 is shielded. On the other hand, the multi-primary electron beam 20 not deflected by the batch blanking deflector 212 passes through the central hole of the limiting aperture substrate 213 as shown in FIG. By turning ON / OFF of the batch blanking deflector 212, blanking control is performed, and ON / OFF of the beam is collectively controlled. In this way, the limiting aperture substrate 213 shields the multi-primary electron beam 20 deflected so that the beam is turned off by the batch blanking deflector 212. Then, the multi-primary electron beam 20 for image acquisition is formed by the beam group that has passed through the limiting aperture substrate 213 formed from the time when the beam is turned on to the time when the beam is turned off.

When the multi-primary electron beam 20 is irradiated to a desired position of the substrate 101, it corresponds to each beam of the multi-primary electron beam 20 from the substrate 101 due to the irradiation of the multi-primary electron beam 20. , A bundle of secondary electrons including backscattered electrons (multi-secondary electron beam 300) is emitted.

The multi-secondary electron beam 300 emitted from the substrate 101 passes through the electromagnetic lens 207 and proceeds to the beam separator 214.

Here, the beam separator 214 generates an electric field and a magnetic field in a direction orthogonal to the direction (center axis of the orbit) in which the central beam of the multi-primary electron beam 20 travels. The electric field exerts a force in the same direction regardless of the traveling direction of the electron. On the other hand, the magnetic field exerts a force according to Fleming's left-hand rule. Therefore, the direction of the force acting on the electron can be changed depending on the invasion direction of the electron. The force due to the electric field and the force due to the magnetic field cancel each other out to the multi-primary electron beam 20 that invades the beam separator 214 from above, and the multi-primary electron beam 20 travels straight downward. On the other hand, in the multi-secondary electron beam 300 that invades the beam separator 214 from below, both the force due to the electric field and the force due to the magnetic field act in the same direction, and the multi-secondary electron beam 300 is obliquely upward. Can be bent.

The multi-secondary electron beam 300 bent obliquely upward is further bent by the deflector 218 and projected onto the multi-detector 222 while being refracted by the electromagnetic lens 224. The multi-detector 222 detects the projected multi-secondary electron beam 300. The multi-detector 222 has a plurality of detection elements (for example, a diode type two-dimensional sensor (not shown)). Then, each beam of the multi-primary electron beam 20 collides with a detection element corresponding to each secondary electron beam of the multi-secondary electron beam 300 on the detection surface of the multi-detector 222 to amplify and generate electrons. Secondary electron image data is generated for each pixel. The intensity signal detected by the multi-detector 222 is output to the detection circuit 106. Each primary electron beam is irradiated in a sub-irradiation region surrounded by an inter-beam pitch in the x direction and an inter-beam pitch in the y direction in which its own beam is located on the substrate 101, and scans the sub-irradiation region ( Scan operation).

As described above, the secondary electron image is obtained by irradiating the multi-primary electron beam 20 with the multi-secondary electrons including backscattered electrons emitted from the substrate 101 due to the irradiation of the multi-primary electron beam 20. The beam 300 is detected by the multi-detector 222. The detection data of secondary electrons (measured image data: secondary electron image data: inspected image data) for each pixel in the individual irradiation region (sub-irradiation region) of each primary electron beam detected by the multi-detector 222 is , It is output to the detection circuit 106 in the order of measurement. In the detection circuit 106, analog detection data is converted into digital data by an A / D converter (not shown) and stored in the chip pattern memory 123. Then, the obtained secondary electronic image data (data of the secondary electronic image 1) is output to the comparison circuit 108 together with information indicating each position from the position circuit 107.

In order to obtain an image in the sub-irradiation region of each primary electron beam, it is necessary to detect the secondary electron beam corresponding to each primary electron beam with the corresponding detection element of the multi-detector 222. Therefore, in a system in which the number of multi-primary electron beams 20 and the number of detection elements of the multi-detector 222 are the same, the multi-secondary electron beam 300 corresponding to the multi-primary electron beam 20 and the plurality of detection elements of the multi-detector 222 are used. Alignment is important.

FIG. 3 is a diagram showing an example of the positional relationship between the multi-secondary electron beam and the plurality of detection elements of the multi-detector in the stage before alignment in the first embodiment. Here, for example, the positional relationship after rough adjustment is shown. In the example of FIG. 3, it is shown by a secondary coordinate system with the center position of the multi-secondary electron beam 300 on the detection surface of the multi-detector 222 as the origin. In the example of FIG. 3, for example, a case where a 3 × 3 multi-secondary electron beam 300 (B11 to B33) is detected by 3 × 3 detection elements (D11 to D33) arranged in an array is shown. It is installed so that the center of the multi-detector 222 approaches the center position of the multi-secondary electron beam 300. However, as shown in FIG. 3, in the stage before alignment, each detection element (D11 to D33) is displaced from the corresponding secondary electron beam (B11 to B33). Therefore, it is difficult to obtain an image of the substrate 101 as it is. Therefore, in the first embodiment, by moving the multi-detector 222 in the x, y, and θ directions from this state, the positions of the respective detection elements (D11 to D33) are corresponding to the secondary electron beams (B11 to B33). ) Align.

FIG. 4 is a diagram showing an example of the internal configuration of the alignment circuit according to the first embodiment. In FIG. 4, the alignment circuit 134 includes a search unit 60, a rotation center calculation unit 61, a vector calculation unit 62, a center-corresponding coordinate calculation unit 63, a shift amount calculation unit 64, a coordinate calculation unit 65, and a rotation angle calculation unit 66. , The rotation processing unit 67, the shift processing unit 68, and the selection unit 69 are arranged. Search unit 60, rotation center calculation unit 61, vector calculation unit 62, center-corresponding coordinate calculation unit 63, shift amount calculation unit 64, coordinate calculation unit 65, rotation angle calculation unit 66, rotation processing unit 67, shift processing unit 68, and Each "~ part" such as the selection part 69 includes a processing circuit, and the processing circuit includes an electric circuit, a computer, a processor, a circuit board, a quantum circuit, a semiconductor device, and the like. Further, a common processing circuit (same processing circuit) may be used for each “~ part”. Alternatively, different processing circuits (separate processing circuits) may be used. Search unit 60, rotation center calculation unit 61, vector calculation unit 62, center-corresponding coordinate calculation unit 63, shift amount calculation unit 64, coordinate calculation unit 65, rotation angle calculation unit 66, rotation processing unit 67, shift processing unit 68, and The necessary input data or the calculated result in the selection unit 69 is stored in a memory (not shown) or a memory 118 each time.

FIG. 5 is a flowchart showing an example of a main part process of the inspection method according to the first embodiment. In FIG. 5, the main steps of the inspection method according to the first embodiment are a secondary electron beam coordinate measurement step (S102), a detection element selection step (S104), a detection element coordinate search step (S106), and a detector. Rotation step (S108), detection element coordinate search step (S110), rotation center calculation step (S112), vector calculation step (S114), center correspondence coordinate calculation step (S116), shift amount calculation step (S118). ), The remaining detection element coordinate calculation step (S120), the rotation angle calculation step (S122), the shift step (S124), the rotation step (S126), and the inspection processing step (S130). To carry out.

The multi-electron beam alignment method according to the first embodiment includes a secondary electron beam coordinate measurement step (S102), a detection element selection step (S104), a detection element coordinate search step (S106), and the like. Detector rotation step (S108), detection element coordinate search step (S110), rotation center calculation step (S112), vector calculation step (S114), center correspondence coordinate calculation step (S116), shift amount calculation step (S118), the remaining detection element coordinate calculation step (S120), the rotation angle calculation step (S122), the shift step (S124), and the rotation step (S126) are performed. Either the shift step (S124) or the rotation step (S126) may come first. Alternatively, it may be carried out at the same time.

As the secondary electron beam coordinate measurement step (S102), first, the position of the multi-secondary electron beam 300 on the detection surface is measured. First, instead of the multi-detector 222, an electron beam detection image sensor (Electron Detecting Image Sensor, hereinafter referred to as EDIS) (hereinafter referred to as EDIS) (not shown) is attached, and the multi-secondary electron beam 300 is detected by a direct detection device. The position of the multi-secondary electron beam 300 on the detection surface is measured. EDIS is an image sensor in which pixels sufficiently smaller than the beam size are arranged in a two-dimensional manner. For example, one in which 4000 x 3000 pixels having a size of 10 μm square are arranged is useful. Each pixel may have sensitivity to an electron beam, or may detect an electron beam via a phosphor. Directly using the electron beam This makes it possible to set a secondary coordinate system with the center position of the multi-secondary electron beam 300 on the detection surface of the multi-detector 222 as the origin. After that, the direct detection device will be removed and the multi-detector 222 will be installed. In the example of FIG. 3, the positions of the detection elements (D11 to D33) are shown as an example, but in reality, the positions of the detection elements (D11 to D33) in the secondary coordinate system cannot be grasped. Is. For the measurement with EDIS, the multi-primary electron beam 20 may be irradiated to measure the entire multi-secondary electron beam 300 emitted from the substrate 101, or the multi-primary electron beams 20 may be irradiated one by one. The positions of the corresponding secondary electron beams may be measured. The stage 105 may be performed in a stopped state. Further, instead of the substrate 101, a mark (not shown), an evaluation substrate, or the like may be irradiated with a primary electron beam.

As the detection element selection step (S104), the selection unit 69 selects two or more detection elements from the plurality of detection elements (D11 to D33). When selecting, two or more detection elements different from the detection element D22 in the central portion are selected. For example, two detection elements D11 and D31 different from the detection element D22 in the central portion are selected. As will be described later, since the coordinates of the three detection elements are required in the vector calculation step (S114), it is preferable to select three detection elements different from the detection element D22 in the central portion. In such a case, three detection elements that do not line up on a straight line are selected. For example, three detection elements D11, D31, and D33 are selected. Alternatively, two detection elements D11 and D31 may be selected first, and each step before the subsequent vector calculation step (S114) may be performed, and then another detection element may be selected.

As the detection element coordinate search step (S106), the search unit 60 detects a multi-secondary electron beam including each secondary electron beam by using the secondary electron beams emitted from the surface of the substrate 101 (sample). The coordinates of two or more detection elements among the plurality of detection elements included in the multi-detector 222 for the purpose are searched. Specifically, the coordinates of the two or more selected detection elements D11 and D31 (, D33) are searched by using any of the secondary electron beams.

FIG. 6 is a diagram for explaining how to search for the detection element coordinates in the first embodiment. As shown in FIG. 6, the multi-secondary electron beams 300 are scanned one by one by selecting the beam selection aperture substrate 232 to obtain secondary electron beams close to the selected detection elements D11, D31 (, D33). Grasp each. The multi-primary electron beams 20 are selected one by one in order to narrow down to one secondary electron beam. In the example of FIG. 6, the case where the detection element D11 can be searched by the secondary electron beam B21 is shown. Similarly, the case where the detection element D31 can be searched by the secondary electron beam B31 is shown.

FIG. 7 is a diagram showing the configuration of the beam selection aperture substrate 232 according to the first embodiment. In FIG. 7, the beam selection aperture substrate 232 has a large aperture 11 through which the entire multi-primary electron beam 20 can pass and a small aperture 13 having a size that allows only one primary electron beam to pass through. NS. Under the control of the beam selection aperture control circuit 136, the drive mechanism 234 selectively passes one of the primary electron beams 20 of the multi-primary electron beams 20 by horizontally moving the beam selection aperture substrate 232. .. The primary electron beam that has passed through the beam selection aperture substrate 232 irradiates the substrate 101 and emits the corresponding secondary electron beam. The emitted secondary electron beam is deflected by the beam separator 214 and proceeds to the alignment coils 225 and 226 of the secondary electron optical system 152.

FIG. 8 is a diagram for explaining an example of how to scan the secondary electron beam according to the first embodiment. The secondary electron beams 301 narrowed down one by one are deflected by the alignment coil 225 and the central orbit is oscillated diagonally, and then the orbit oscillated by the alignment coil 226 is made into an orbital axis parallel to the original orbital axis. Look back. As a result, the axis can be moved without changing the incident angle. By such axial movement, the position to be irradiated to the multi-detector 222 is scanned. Here, the case of scanning with two alignment coils 225 and 226 is shown, but the case is not limited to this. For example, it is also preferable to scan the secondary electron beam 301 using a deflector composed of electrodes having four or more poles.

FIG. 9A is a diagram showing an example of the scanning range of the secondary electron beam in the first embodiment. As shown in FIG. 9, it is preferable to set the scanning range of each secondary electron beam to a rectangular region (± 0.5 beam pitch in the x and y directions) surrounded by the beam pitch between the secondary electron beams. The example of FIG. 9A shows a case where some secondary electron beams are arranged at a pitch larger than the design beam pitch due to various error factors (machining accuracy of steel members, assembly accuracy, etc.). ing.

Then, the multi-primary electron beams 20 are selected one by one, and the secondary electron beam close to the detection element D11 is grasped by scanning the scanning range. Specifically, the beam having the maximum output from D11 is specified as a beam close to D11.
Next, a search method for accurately grasping the position of D11 after identifying a beam close to D11 will be described with reference to FIG. 9B. The coordinates (Xmax, Ymax) (maximum output coordinates) at which the output from D11 by the beam B21 is maximized are recorded, and the search range (research range 17) is redefined around the coordinates. For example, ± 0.5 beam pitch. The output of D11 is recorded while scanning B21 within the re-search range 17, and the coordinates of the center of gravity are calculated from the data of the output value and the scanning coordinate value. The coordinates of the center of gravity are specified as the final coordinates of D11.

FIG. 10 is a diagram showing a case where one of the two selected detection elements in the first embodiment and the secondary electron beam overlap each other. In the example of FIG. 10, the secondary electron beam detected by the detection element D11 is searched. In the example of FIG. 10, the case where the secondary electron beam B21 is detected by the detection element D11 is shown. Since the position of the secondary electron beam B21 is measured by EDIS, the relative scanning position from the position of the secondary electron beam B21 to the position where the detected intensity is maximized is added. The position can be searched (detected) as the coordinates (x1, y1) of the detection element D11.

FIG. 11 is a diagram showing a case where the other of the two selected detection elements in the first embodiment and the secondary electron beam overlap each other. By performing the same operation as when detecting the coordinates (x1, y1) of the detection element D11, the secondary electron beam detected by the detection element D31 is searched. In the example of FIG. 11, the case where the secondary electron beam B31 is detected by the detection element D31 is shown. Since the position of the secondary electron beam B31 is measured by EDIS, the relative scanning position from the position of the secondary electron beam B31 to the position where the detected intensity is maximized is added. The position can be searched (detected) as the coordinates (x2, y2) of the detection element D31.

When three detection elements are selected, the coordinates (x3, y3) of the third detection element D33 are searched (detected) in the same manner.

In the detector rotation step (S108), the detector stage control circuit 130 controls the drive mechanism 132 to rotate the rotation stage 227. As a result, the rotation stage 227 rotates the multi-detector 222 at a preset rotation angle φ (first rotation angle).

FIG. 12 is a diagram showing an example of the positional relationship between the multi-secondary electron beam before and after rotation and the plurality of detection elements of the multi-detector in the first embodiment. As shown in FIG. 12, the centers of the plurality of detection elements D11 to D33 are not necessarily the rotation centers (rx, ry) of the multi-detector 222. Therefore, when the multi-detector 222 is rotated by the rotation angle φ, the positions of the detection elements D11, D31, and D33 whose coordinates are detected before the rotation are unknown. In the example of FIG. 12, the detection element D11 is moved to the detection element D11'by rotating the multi-detector 222 by the rotation angle φ. Similarly, it shows a state in which the detection element D31 has moved to the detection element D31'.

In the detection element coordinate search step (S110), the search unit 60 searches for the coordinates of two or more detection elements after rotation by using the respective secondary electron beams emitted from the surface 101 of the substrate. Specifically, the coordinates after rotation of the two or more selected detection elements D11 and D31 (, D33) are searched by using any of the secondary electron beams.

FIG. 13 is a diagram showing a case where one of the two selected detection elements in the first embodiment and the secondary electron beam overlap each other. The search method is the same as the search method before rotation. In the example of FIG. 13, the secondary electron beam detected by the detection element D11'is searched. In the example of FIG. 13, the case where the secondary electron beam B11 is detected by the detection element D11'is shown. Since the position of the secondary electron beam B11 is measured by EDIS, the relative scanning position from the position of the secondary electron beam B11 to the position where the detected intensity is maximized is added. The position can be searched (detected) as the coordinates (X1, Y1) of the detection element D11'.

FIG. 14 is a diagram showing a case where the other of the two selected detection elements in the first embodiment and the secondary electron beam overlap each other. By performing the same operation as when detecting the coordinates (X1, Y1) of the detection element D11', the secondary electron beam detected by the detection element D31' is searched. In the example of FIG. 14, the case where the secondary electron beam B31 is detected by the detection element D31'is shown. Since the position of the secondary electron beam B31 is measured by EDIS, the relative scanning position from the position of the secondary electron beam B31 to the position where the detected intensity is maximized is added. The position can be searched (detected) as the coordinates (X2, Y2) of the detection element D31'.

FIG. 15 is a diagram showing an example of the coordinates of a plurality of detection elements of the multi-detector before and after rotation in the first embodiment. As shown in FIG. 15, the detection element D11 (D11') changes from the coordinates before rotation (x1, y1) to the coordinates after rotation (X1, Y1) about the unknown center of rotation coordinates (rx, ry). I'm moving. Similarly, the detection element D31 (D31') moves from the coordinates before rotation (x2, y2) to the coordinates after rotation (X2, Y2) about the unknown center of rotation coordinates (rx, ry). ..

In the rotation center calculation step (S112), the rotation center calculation unit 61 has the rotation angle φ obtained by rotating the multi-detector 222 and two or more detection elements D11 (D11') and D31 (D31') before and after the searched rotation. ), (X1, y1), (x2, y2), (X1, Y1), (X2, Y2) are used to calculate the rotation center coordinates (rx, ry) of the multi-detector 222.

FIG. 16 is a diagram showing an arithmetic expression for calculating the rotation center coordinates in the first embodiment. It can be obtained by Eq. (1) from the relationship of coordinates before and after rotation.

By the above processing, the coordinates (x1, y1), (x2, y2), (X1, Y1), (X2, Y2) before and after the rotation of at least two detection elements D11 (D11') and D31 (D31') And the coordinates of the center of rotation (rx, ry) can be obtained. Further, when the three detection elements are selected, the coordinates (x3, y3) before the rotation of the third detection element D33 can be obtained in the same manner. When the three detection elements are not selected, the selection of the third detection element and the search for the coordinates (x3, y3) before rotation are performed. When the third detection element is selected, the detection elements are different from the detection element D22 in the central portion, and the three detection elements are not arranged in a straight line in relation to the two detection elements D11 and D31. Select a detection element.

In the vector calculation step (S114), the vector calculation unit 62 applies a vector from the coordinates of one detection element to the coordinates of the center of rotation (rx, ry) among the three detection elements, and the rest from the coordinates of the one detection element. The operation of decomposing into two vectors to the coordinates of the two detection elements is performed.

FIG. 17 is a diagram for explaining how to perform vector calculation of the detection element coordinates in the first embodiment. Of the three detection elements D11, D31, and D33 before rotation described above, the vector R from the coordinates (x2, y2) of one detection element D31 to the rotation center coordinates (rx, ry) is the coordinate of the detection element D31 (. It is decomposed into a vector P from x2, y2) to the coordinates (x3, y3) of the detection element D33 and a vector Q from the coordinates (x2, y2) of the detection element D31 to the coordinates (x1, y1) of the detection element D11. .. Of the three detection elements D11, D31, and D33, the remaining one detection element D31 in which the two detection elements D11 and D33 are separately located on both sides with respect to the vector to the rotation center coordinates (rx, ry). It is preferable to use as a reference. The vector R can be defined by the following equation (2) using the vector P and the vector Q. In the equation (2), the symbol (-) indicating the vector is omitted.
(2) R = αP + βQ

FIG. 18 is a diagram showing an arithmetic expression for calculating the vector coefficient in the first embodiment. The unknown vector coefficients α and β can be obtained by Eq. (3).

In the center-corresponding coordinate calculation step (S116), the center-corresponding coordinate calculation unit 63 has a multi-secondary electron having the same positional relationship as the rotational center coordinates (rx, ry) with respect to the plurality of detection elements D11, D31, and D33. The corresponding coordinates Bc for the beams B11, B31, and B33 are calculated.

FIG. 19 is a diagram for explaining how to perform vector calculation of secondary electron beam coordinates in the first embodiment. In FIG. 19, the corresponding coordinates Bc are the composite of the two vectors when the two decomposed vectors αP and βQ are applied to the coordinates of the three secondary electron beams B11, B31 and B33 of the multi-secondary electron beams. Calculated as vector coordinates. Specifically, the center-corresponding coordinate calculation unit 63 multiplies the vector P'from the secondary electron beam B31 corresponding to the reference detection element D31 to the secondary electron beam B33 corresponding to the detection element D33 by the vector coefficient α. Calculate the composite vector R ′ of αP ′ and βQ ′ obtained by multiplying the vector Q ′ from the secondary electron beam B31 corresponding to the detection element D31 to the secondary electron beam B11 corresponding to the detection element D11 by the vector coefficient β. do. Then, the center corresponding coordinate calculation unit 63 calculates the coordinates of the composite vector R'starting from the secondary electron beam B31 as the corresponding coordinates Bc.

As the shift amount calculation step (S118), the shift amount calculation unit 64 calculates the shift amount (dx, dy) for shifting the rotation center coordinates (rx, ry) to the coordinates Bc corresponding to the multi-secondary electron beam.

As the remaining detection element coordinate calculation step (S120), the coordinate calculation unit 65 calculates the coordinates of the remaining detection elements of the plurality of detection elements D11 to D33 using the coordinates of the two or more detected detection elements searched for. ..

FIG. 20 is a diagram for explaining a method of calculating the coordinates of each of the plurality of detection elements according to the first embodiment. In the above example, the coordinates (x1, y1), (x2, y2), and (x3, y3) of the three detection elements D11, D31, and D33 are already known by the search. Further, it is assumed that the plurality of detection elements D11 to D33 of the multi-detector 222 are 3 × 3 detection elements arranged in an array at the same pitch along two orthogonal axes. Therefore, if the coordinates of at least two detection elements are known, the coordinates of the remaining detection elements can be calculated. In the example of FIG. 20, when the coordinates (x1, y1), (x2, y2), (x3, y3) of the three detection elements D11, D31, and D33 are known, the coordinates of the remaining detection elements are used. An example of the calculation method is shown.

For example, the coordinates (x4, y4) of the detection element D21 are calculated as the center position of the straight line connecting the coordinates (x1, y1) and (x2, y2) of the detection elements D11 and D31. For example, the coordinates (x5, y5) of the detection element D32 are calculated as the center position of the straight line connecting the coordinates (x2, y2) and (x3, y3) of the detection elements D31 and D33. For example, the coordinates (x6, y6) of the detection element D22 are calculated as the center position of the straight line connecting the coordinates (x1, y1) and (x3, y3) of the detection elements D11 and D33.

For example, the coordinates (x7, y7) of the detection element D13 are a vector from the coordinates (x2, y2) of the detection element D31 to the coordinates (x3, y3) of the detection element D33 at the coordinates (x1, y1) of the detection element D11. It is calculated as the position of the added value. Alternatively, for the coordinates (x7, y7) of the detection element D13, a vector from the coordinates (x2, y2) of the detection element D31 to the coordinates (x1, y1) of the detection element D11 is added to the coordinates (x3, y3) of D33. Calculated as the position of the value. Alternatively, the coordinates (x7, y7) of the detection element D13 are obtained by adding twice the vector from the coordinates of the detection element D31 (x2, y2) to the coordinates of the detection element D22 to the coordinates (x2, y2) of the detection element D31. Calculated as the position of the value. Alternatively, it is more preferable to calculate as the average value of these three equations.

For example, the coordinates (x8, y8) of the detection element D12 are calculated as the center position of the straight line connecting the coordinates of the detection elements D11 and D13. For example, the coordinates (x9, y9) of the detection element D23 are calculated as the center position of the straight line connecting the coordinates of the detection elements D13 and D33.

As described above, the coordinates (x1, y1) to (x9, y9) of all nine detection elements D11 to D33 of 3 × 3 of the multi-detector 222 can be acquired.

As the rotation angle calculation step (S122), the rotation angle calculation unit 66 uses at least one of the coordinates of each of the two or more detected elements searched and the rotation center coordinates (rx, ry) of the multi-detector 222, and a plurality of them. The rotation angle θ (second rotation angle) for aligning the detection elements D11 to D33 of the above with the multi-secondary electron beams B11 to B33 is calculated.

FIG. 21 is a diagram showing an arithmetic expression for calculating the alignment angle in the first embodiment. Of the coordinates (X1', Y1') to (X9', Y9') of the detection elements D11 to D33 after the alignment in which the plurality of detection elements D11 to D33 are aligned with the multi-secondary electron beams B11 to B33. The coordinates (X1', Y1') of one detection element D11 are the coordinates (x1, y1) of the detection element D11 before alignment, the coordinates of the center of rotation (rx, ry), and the unknown rotation angle θ. By using it, it can be defined as the equation (4) shown in FIG. The same applies when another detection element is used instead of the detection element D11. By modifying the equation (4), an unknown rotation angle θ can be obtained. In order to further improve the accuracy, it is preferable to obtain the unknown rotation angle θ by using the coordinates (x1, y1) to (x9, y9) of all nine detection elements D11 to D33 of 3 × 3. ..

Specifically, it can be obtained from the equations (4) and (5) shown in FIG.

As described above, the shift amount (dx, dy) for alignment and the rotation angle θ can be obtained.

In the above example, the coordinates (x1, y1) to (x9, y9) of the detection elements D11 to D33 before the multi-detector 222 is rotated by the rotation angle φ in order to obtain the rotation center coordinates (rx, ry). ) Was used to determine the rotation angle θ, but the present invention is not limited to this. The rotation angle θ'for alignment may be obtained using the coordinates (X1, Y1) to (X9, Y9) of the detection elements D11 to D33 after rotating the multi-detector 222 by the rotation angle φ. No. In such a case, in addition to the coordinates (X1, Y1) and (X2, Y2) of the two detected detection elements D11 and D31 searched after being rotated, the remaining coordinates (X3, Y3) to (X9, Y9). ) Should be sought. Alternatively, for alignment, the equation (4) is applied using at least one of the coordinates (X1, Y1) and (X2, Y2) of the two detected elements D11 and D31 searched after being rotated. The rotation angle θ'of may be obtained. In such a case, (x1, y1) in the equation (4) may be read as (X1, Y1), and θ may be read as θ ′.

As a shift step (S124), the shift processing unit 68 shifts the multi-detector 222 using the shift amount (dx, dy).

FIG. 22 is a diagram for explaining how the plurality of detection elements in the first embodiment are shifted. In FIG. 22, the multi-detector 222 is shifted so that the rotation center Dc of the multi-detector 222 located at the rotation center coordinates (rx, ry) is aligned with the corresponding coordinates Bc of the multi-secondary electron beams B11 to B33. The multi-detector 222 is shifted by moving the x, y stages 228 by the drive mechanism 132 under the control of the detector stage control circuit 130.

As a rotation step (S126), the rotation processing unit 67 rotates the multi-detector 222 at a rotation angle θ.

FIG. 23 is a diagram for explaining how the plurality of detection elements according to the first embodiment are rotated. In FIG. 23, the multi-detector 222 is rotated by a rotation angle θ around the rotation center Dc of the multi-detector 222 aligned with the corresponding coordinates Bc of the multi-secondary electron beams B11 to B33. The multi-detector 222 is rotated by rotating the rotary stage 227 by the drive mechanism 132 under the control of the detector stage control circuit 130.

By the above operation, the plurality of detection elements D11 to D33 of the multi-detector 222 can be aligned with the multi-secondary electron beams B11 to B33.

As the inspection processing step (S130), the substrate 101 is inspected using the aligned inspection device 100.

FIG. 24 is a diagram showing an example of a plurality of chip regions formed on the semiconductor substrate according to the first embodiment. In FIG. 24, when the substrate 101 is a semiconductor substrate (wafer), a plurality of chips (wafer dies) 332 are formed in a two-dimensional array in the inspection region 330 of the semiconductor substrate (wafer). A mask pattern for one chip formed on an exposure mask substrate is transferred to each chip 332 by being reduced to, for example, 1/4 by an exposure device (stepper) (not shown). The mask pattern for one chip is generally composed of a plurality of graphic patterns.

FIG. 25 is a diagram for explaining the inspection process according to the first embodiment. As shown in FIG. 25, the region of each chip 332 is divided into a plurality of stripe regions 32 with a predetermined width in the y direction, for example. The scanning operation by the image acquisition mechanism 150 is performed, for example, for each stripe region 32. For example, while moving the stage 105 in the −x direction, the scanning operation of the stripe region 32 is relatively advanced in the x direction. Each stripe region 32 is divided into a plurality of rectangular regions 33 in the longitudinal direction. The movement of the beam to the rectangular region 33 of interest is performed by batch deflection of the entire multi-primary electron beam 20 by the main deflector 208.

In the example of FIG. 25, for example, the case of a 5 × 5 row multi-primary electron beam 20 is shown. The irradiation region 34 that can be irradiated by one irradiation of the multi-primary electron beam 20 is (the x-direction obtained by multiplying the x-direction beam-to-beam pitch of the multi-primary electron beam 20 on the substrate 101 surface by the number of beams in the x-direction. Size) × (size in the y direction obtained by multiplying the pitch between beams in the y direction of the multi-primary electron beam 20 on the surface of the substrate 101 by the number of beams in the y direction). The irradiation region 34 becomes the field of view of the multi-primary electron beam 20. Then, each of the primary electron beams 10 constituting the multi-primary electron beam 20 is irradiated in the sub-irradiation region 29 surrounded by the inter-beam pitch in the x-direction and the inter-beam pitch in the y direction in which the own beam is located. , Scan (scan operation) in the sub-irradiation area 29. Each primary electron beam 10 is responsible for any of the sub-irradiation regions 29 that are different from each other. Then, at each shot, each primary electron beam 10 irradiates the same position in the responsible sub-irradiation region 29. The movement of the primary electron beam 10 in the sub-irradiation region 29 is performed by batch deflection of the entire multi-primary electron beam 20 by the sub-deflector 209. This operation is repeated to sequentially irradiate the inside of one sub-irradiation region 29 with one primary electron beam 10.

It is preferable that the width of each stripe region 32 is set to a size similar to the y-direction size of the irradiation region 34 or narrowed by the scan margin. In the example of FIG. 25, the case where the irradiation area 34 has the same size as the rectangular area 33 is shown. However, it is not limited to this. The irradiation area 34 may be smaller than the rectangular area 33. Alternatively, it may be large. Then, each of the primary electron beams 10 constituting the multi-primary electron beam 20 is irradiated in the sub-irradiation region 29 in which its own beam is located, and scans (scans) in the sub-irradiation region 29. Then, when the scanning of one sub-irradiation region 29 is completed, the main deflector 208 moves to the adjacent rectangular region 33 in the stripe region 32 having the same irradiation position by the collective deflection of the entire multi-primary electron beam 20. This operation is repeated to irradiate the inside of the stripe region 32 in order. After scanning one striped region 32 is complete, the irradiated region 34 moves to the next striped region 32 by moving the stage 105 and / or batch deflection of the entire multi-primary electron beam 20 by the main deflector 208. As described above, by irradiating each of the primary electron beams 10, the scanning operation for each sub-irradiation region 29 and the acquisition of the secondary electron image are performed. By combining the secondary electron images for each of the sub-irradiation regions 29, a secondary electron image of the rectangular region 33, a secondary electron image of the stripe region 32, or a secondary electron image of the chip 332 is formed. Further, when actually performing image comparison, the sub-irradiation region 29 in each rectangular region 33 is further divided into a plurality of frame regions 30, and the frame image 31 for each frame region 30 is compared. The example of FIG. 8 shows a case where the sub-irradiation region 29 scanned by one primary electron beam 10 is divided into four frame regions 30 formed by dividing the sub-irradiation region 29 into two in the x and y directions, for example. ..

Here, when the substrate 101 is irradiated with the multi-primary electron beam 20 while the stage 105 continuously moves, the main deflector 208 collectively deflects the irradiation position of the multi-primary electron beam 20 so as to follow the movement of the stage 105. Tracking operation is performed by. Therefore, the emission position of the multi-secondary electron beam 300 changes every moment with respect to the orbital central axis of the multi-primary electron beam 20. Similarly, when scanning the inside of the sub-irradiation region 29, the emission position of each secondary electron beam changes every moment in the sub-irradiation region 29. The deflector 218 collectively deflects the multi-secondary electron beam 300 so that each secondary electron beam whose emission position has changed is irradiated into the corresponding detection region of the multi-detector 222.

As described above, the image acquisition mechanism 150 promotes the scanning operation for each stripe area 32. As described above, the multi-secondary electron beam 300 emitted from the substrate 101 due to the irradiation of the multi-primary electron beam 20 by irradiating the multi-primary electron beam 20 is detected by the multi-detector 222. .. The detected multi-secondary electron beam 300 may contain backscattered electrons. Alternatively, the backscattered electrons may be diverged and separated while moving through the secondary electron optics system 152, and may not reach the multi-detector 222. The secondary electron detection data (measured image data: secondary electron image data: inspected image data) for each pixel in each sub-irradiation region 29 detected by the multi-detector 222 is output to the detection circuit 106 in the order of measurement. NS. In the detection circuit 106, analog detection data is converted into digital data by an A / D converter (not shown) and stored in the chip pattern memory 123. Then, the obtained measurement image data is transferred to the comparison circuit 108 together with the information indicating each position from the position circuit 107.

FIG. 26 is a configuration diagram showing an example of the configuration in the comparison circuit according to the first embodiment. In FIG. 26, storage devices 50, 52, 56 such as a magnetic disk device, a frame image creation unit 54, an alignment unit 57, and a comparison unit 58 are arranged in the comparison circuit 108. Each "-part" such as the frame image creation unit 54, the alignment unit 57, and the comparison unit 58 includes a processing circuit, and the processing circuit includes an electric circuit, a computer, a processor, a circuit board, a quantum circuit, or a semiconductor. Devices and the like are included. Further, a common processing circuit (same processing circuit) may be used for each “~ part”. Alternatively, different processing circuits (separate processing circuits) may be used. The input data or the calculated result required in the frame image creation unit 54, the alignment unit 57, and the comparison unit 58 are stored in a memory (not shown) or a memory 118 each time.

The measurement image data (beam image) transferred into the comparison circuit 108 is stored in the storage device 50.

Then, the frame image creation unit 54 creates a frame image 31 for each frame region 30 of a plurality of frame regions 30 by further dividing the image data of the sub-irradiation region 29 acquired by the scanning operation of each primary electron beam 10. .. Then, the frame area 30 is used as a unit area of the image to be inspected. It is preferable that the frame regions 30 are configured so that the margin regions overlap each other so that the image is not omitted. The created frame image 31 is stored in the storage device 56.

On the other hand, the reference image creation circuit 112 creates a reference image corresponding to the frame image 31 for each frame region 30 based on the design data that is the basis of the plurality of graphic patterns formed on the substrate 101. Specifically, it operates as follows. First, the design pattern data is read from the storage device 109 through the control computer 110, and each graphic pattern defined in the read design pattern data is converted into binary or multi-valued image data.

As described above, the figure defined in the design pattern data is, for example, a basic figure of a rectangle or a triangle. For example, the coordinates (x, y) at the reference position of the figure, the length of the side, the rectangle or the triangle, etc. Graphical data that defines the shape, size, position, etc. of each pattern graphic is stored with information such as a graphic code that serves as an identifier that distinguishes the graphic types of.

When the design pattern data to be the graphic data is input to the reference image creation circuit 112, it is expanded to the data for each graphic, and the graphic code, the graphic dimension, etc. indicating the graphic shape of the graphic data are interpreted. Then, it is developed into binary or multi-valued design pattern image data as a pattern arranged in a grid having a grid of predetermined quantization dimensions as a unit and output. In other words, the design data is read, the inspection area is virtually divided into squares with a predetermined dimension as a unit, the occupancy rate of the figure in the design pattern is calculated for each square, and the n-bit occupancy rate data is obtained. Output. For example, it is preferable to set one square as one pixel. Then, when to have a resolution of 1/2 8 ^{(= 1/256)} to 1 pixel, the occupancy rate of the pixel allocated the small area region amount corresponding 1/256 of figures are arranged in a pixel Calculate. Then, it becomes 8-bit occupancy rate data. Such squares (inspection pixels) may be matched with the pixels of the measurement data.

Next, the reference image creation circuit 112 filters the design image data of the design pattern, which is the image data of the figure, by using a predetermined filter function. Thereby, the design image data in which the image intensity (shade value) is the image data on the design side of the digital value can be matched with the image generation characteristics obtained by the irradiation of the multi-primary electron beam 20. The image data for each pixel of the created reference image is output to the comparison circuit 108. The reference image data transferred into the comparison circuit 108 is stored in the storage device 52.

Next, the alignment unit 57 reads out the frame image 31 to be the image to be inspected and the reference image corresponding to the frame image 31, and aligns both images in sub-pixel units smaller than the pixels. For example, the alignment may be performed by the method of least squares.

Then, the comparison unit 58 compares the frame image 31 and the reference image for each pixel. The comparison unit 58 compares the two for each pixel according to a predetermined determination condition, and determines the presence or absence of a defect such as a shape defect. For example, if the gradation value difference for each pixel is larger than the determination threshold value Th, it is determined as a defect. Then, the comparison result is output. The comparison result may be output to the storage device 109 or the memory 118, or may be output from the printer 119.

In the above-mentioned example, the die-database inspection has been described, but the present invention is not limited to this. It may be the case of performing a die-die inspection. When performing a die-die inspection, between the target frame image 31 (die 1) and the frame image 31 (die 2) (another example of the reference image) in which the same pattern as the frame image 31 is formed. , The above-mentioned alignment and comparison processing may be performed.

As described above, according to the first embodiment, the multi-charged particle beam and the secondary electron detector can be efficiently aligned.

In the above description, the series of "~ circuits" includes a processing circuit, and the processing circuit includes an electric circuit, a computer, a processor, a circuit board, a quantum circuit, a semiconductor device, and the like. Further, a common processing circuit (same processing circuit) may be used for each “~ circuit”. Alternatively, different processing circuits (separate processing circuits) may be used. The program for executing the processor or the like may be recorded on a recording medium such as a magnetic disk device, a magnetic tape device, an FD, or a ROM (read-only memory). For example, position circuit 107, comparison circuit 108, reference image creation circuit 112, stage control circuit 114, lens control circuit 124, blanking control circuit 126, deflection control circuit 128, detector stage control circuit 130, alignment circuit 134, and The beam selection aperture control circuit 136 may be composed of at least one processing circuit described above. For example, the processing in these circuits may be performed by the control computer 110.

The embodiment has been described above with reference to a specific example. However, the present invention is not limited to these specific examples. In the example of FIG. 1, a case is shown in which a multi-primary electron beam 20 is formed by a molded aperture array substrate 203 from one beam emitted from an electron gun 201 as one irradiation source, but the present invention is limited to this. is not it. The multi-primary electron beam 20 may be formed by irradiating the primary electron beams from a plurality of irradiation sources.

In addition, although the description of parts that are not directly necessary for the description of the present invention, such as the device configuration and control method, is omitted, the required device configuration and control method can be appropriately selected and used.

In addition, all multi-charged particle beam alignment methods and multi-charged particle beam inspection devices that include the elements of the present invention and can be appropriately redesigned by those skilled in the art are included in the scope of the present invention.

10 Primary electron beam 11 Large opening 13 Small opening 17 Research range 20 Multi-primary electron beam 22 Hole 29 Sub-irradiation area 30 Frame area 31 Frame image 32 Stripe area 33 Rectangular area 34 Irradiation area 50, 52, 56 Storage device 54 Frame image creation unit 57 Alignment unit 58 Comparison unit 60 Search unit 61 Rotation center calculation unit 62 Vector calculation unit 63 Center-corresponding coordinate calculation unit 64 Shift amount calculation unit 65 Coordinate calculation unit 66 Rotation angle calculation unit 67 Rotation processing unit 68 Shift processing Part 69 Selection part 100 Inspection device 101 Board 102 Electron beam column 103 Inspection room 105 Stage 106 Detection circuit 107 Position circuit 108 Comparison circuit 109 Storage device 110 Control computer 112 Reference image creation circuit 114 Stage control circuit 117 Monitor 118 Memory 119 Printer 120 Bus 122 Laser length measurement system 123 Chip pattern memory 124 Lens control circuit 126 Blanking control circuit 128 Deflection control circuit 130 Detector stage control circuit 132 Drive mechanism 134 Alignment circuit 136 Beam selection aperture control circuit 142 Drive mechanism 144, 146, 148 DAC Amplifier 150 Image acquisition mechanism 151 Primary electron optics system 152 Secondary electron optics system 160 Control system circuit 201 Electron gun 202 Electromagnetic lens 203 Molded aperture array substrate 205, 206, 207, 224,226 Electromagnetic lens 208 Main deflector 209 Sub-deflection Instrument 212 Collective blanking deflector 213 Limitation aperture substrate 214 Beam separator 216 Mirror 218 Deflector 222 Multi detector 225, 226 Alignment coil 227 Rotating stage 228 x, y Stage 229 Detector stage 232 Beam selection aperture substrate 234 Drive mechanism 300 Multi Secondary electron beam 330 Inspection area 332 Chip

Claims (6)

Two of the plurality of detection elements of the multi-detector for detecting the multi-secondary charged particle beam including the respective secondary charged particle beam by using the secondary charged particle beam emitted from the sample surface. The process of searching for the coordinates of the above detection elements and
The process of rotating the multi-detector at the first rotation angle and
A step of searching for the coordinates of the two or more detection elements after rotation using each secondary charged particle beam emitted from the sample surface, and a step of searching for the coordinates of the two or more detection elements after rotation.
A step of calculating the rotation center coordinates of the multi-detector using the first rotation angle obtained by rotating the multi-detector and the coordinates of the two or more detection elements before and after the searched rotation.
A second for aligning the plurality of detection elements with the multi-secondary charged particle beam by using at least one of the coordinates of each of the two or more detection elements searched and the rotation center coordinates of the multi-detector. The process of calculating the rotation angle of
The step of rotating the multi-detector at the second rotation angle and
A multi-charged particle beam alignment method characterized by being equipped with. A step of calculating the corresponding coordinates for the multi-secondary charged particle beam, which has the same positional relationship as the positional relationship of the rotation center coordinates with respect to the plurality of detection elements.
A step of calculating the shift amount for shifting the rotation center coordinates to the corresponding coordinates with respect to the multi-secondary charged particle beam, and
The step of shifting the multi-detector using the shift amount and
The multi-charged particle beam alignment method according to claim 1, further comprising. A step of calculating the coordinates of the remaining detection elements of the plurality of detection elements using each coordinate of the two or more detection elements searched for, and a step of calculating the coordinates of the remaining detection elements of the plurality of detection elements.
The multi-charged particle beam alignment method according to claim 1 or 2, further comprising. 3. The third aspect of claim 3, further comprising a step of selecting three detection elements different from the central detection element from the plurality of detection elements as the two or more detection elements to be searched. Multi-charged particle beam alignment method. As the two or more detection elements, three detection elements that do not line up in a straight line are used.
Of the three detection elements, the operation of decomposing the vector from the coordinates of one detection element to the coordinates of the center of rotation into two vectors from the coordinates of the one detection element to the coordinates of the remaining two detection elements is performed. With more processes
The corresponding coordinates are calculated as the coordinates of the composite vector of the two vectors when the decomposed two vectors are applied to the coordinates of the three secondary charged particle beams of the multi-secondary charged particle beam. The multi-charged particle beam alignment method according to claim 3 or 4, characterized in that. The stage on which the sample is placed and
A primary electron optics system that irradiates the sample with a multi-primary electron beam,
A multi-detector having a plurality of detection elements and for detecting a multi-secondary electron beam emitted by irradiating the sample with the multi-primary electron beam.
A rotation mechanism that rotates the multi-detector,
Using the secondary charged particle beam emitted from the sample surface, the coordinates of two or more of the plurality of detection elements before and after the rotation of rotating the multi-detector at the first rotation angle are searched for. Search department and
A rotation center calculation unit that calculates the rotation center coordinates of the multi-detector using the first rotation angle obtained by rotating the multi-detector and the coordinates of the two or more detection elements before and after the searched rotation. When,
A second for aligning the plurality of detection elements with the multi-secondary charged particle beam by using at least one of the coordinates of each of the two or more detection elements searched and the rotation center coordinates of the multi-detector. Rotation angle calculation unit that calculates the rotation angle of
With
The rotation mechanism is a multi-charged particle beam inspection device characterized by rotating the multi-detector at the second rotation angle.

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