JP7385493B2 - Multi-charged particle beam alignment method and multi-charged particle beam inspection device - Google Patents

Description

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

In recent years, as large-scale integrated circuits (LSIs) have become more highly integrated and have larger capacities, the circuit line width required for semiconductor devices has become increasingly narrower. Improving yield is essential for manufacturing LSIs, which require a large manufacturing cost. However, as typified by 1 gigabit class DRAM (random access memory), the patterns constituting LSIs are on the order of submicrons to nanometers. In recent years, as the dimensions of LSI patterns formed on semiconductor wafers have become smaller, the dimensions that must be detected as pattern defects have also become extremely small. Therefore, there is a need for higher precision pattern inspection equipment that inspects defects in ultrafine patterns transferred onto semiconductor wafers.

The inspection method is to compare a measurement image of a pattern formed on a substrate such as a semiconductor wafer or lithography mask with design data or a measurement image of the same pattern on a substrate. It has been known. For example, pattern inspection methods include "die to die inspection," which compares measurement image data obtained by capturing images of the same pattern at different locations on the same substrate, and design image inspection based on pattern design data. There is a "die to database inspection" that generates data (reference image) and compares it with a measurement image that is measurement data obtained by capturing a pattern. The captured image is sent to the comparison circuit as measurement data. After aligning the images, the comparison circuit compares the measurement data and reference data according to an appropriate algorithm, and if they do not match, it is determined that there is a pattern defect.

In defect inspection of semiconductor wafers and photomasks, there is a need to detect smaller defects. Therefore, in recent years, the above-mentioned pattern inspection apparatus includes a device that irradiates the substrate to be inspected with laser light and captures a transmitted or reflected image of the same, as well as a device that uses laser light to increase the pixel resolution of the image. An inspection device that scans the substrate to be inspected with an electron beam that has a shorter wavelength than light, detects secondary electrons emitted from the substrate to be inspected as the electron beam irradiates, and obtains a pattern image. Development is also progressing. Among inspection devices that use electron beams, development of devices that use multiple beams is also progressing.

In a multi-beam inspection device, in a system where the number of multi-beams and the number of secondary electron detector elements are the same, alignment of the two is important. In particular, when a new or replacement secondary electron detector is installed in the device, alignment with multiple secondary electron beams is important. For example, a method has been disclosed in which an aperture plate is placed between the final stage lens of the secondary optical system lens and the secondary electron detector, and the aperture plate is used to adjust the position of the secondary electron beam (for example, , see Patent Document 1).

JP2014-026834A

Accordingly, 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 implementing such a method.

A multi-charged particle beam alignment method according to one embodiment of the present invention includes:
Two or more of a plurality of detection elements included in a multi-detector for detecting a multi-secondary charged particle beam including each secondary charged particle beam using each secondary charged particle beam emitted from a sample surface. searching for the coordinates of the detection element;
rotating the multi-detector at a first rotation angle;
searching for the coordinates of the two or more detection elements after rotation using each secondary charged particle beam emitted from the sample surface;
calculating the rotation center coordinates of the multi-detector using the first rotation angle at which the multi-detector was rotated and each coordinate of the two or more detected elements before and after the rotation;
A second rotation angle for aligning the plurality of detection elements with the multi-secondary charged particle beam is determined using at least one of the coordinates of the two or more detected detection elements and the rotation center coordinates of the multi-detector. The process of calculating,
rotating the multi-detector at a second rotation angle;
It is characterized by having the following.

Further, a step of calculating corresponding coordinates for a multi-secondary charged particle beam having a positional relationship similar to the positional relationship of the rotation center coordinates for the plurality of detection elements;
a step of calculating a shift amount for shifting the rotation center coordinates to the corresponding coordinates for the multi-secondary charged particle beam;
Shifting the multi-detector using the shift amount;
It is preferable to further include the following.

Further, a step of calculating the coordinates of the remaining detection elements among the plurality of detection elements using each coordinate of the two or more detected detection elements that have been searched;
It is preferable to further include the following.

Preferably, the method further includes the step of selecting three detection elements different from the central detection element from among the plurality of detection elements as the two or more detection elements to be searched.

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

A multi-charged particle beam inspection device according to one embodiment of the present invention includes:
a stage on which the sample is placed;
a primary electron optical system that irradiates the sample with multiple primary electron beams;
a multi-detector having a plurality of detection elements and for detecting a multi-secondary charged particle 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 for coordinates of two or more detection elements among the plurality of detection elements before and after rotation of rotating the multi-detector at a first rotation angle using secondary charged particle beams emitted from each sample surface; and,
a rotation center calculation unit that calculates rotation center coordinates of the multi-detector using a first rotation angle at which the multi-detector is rotated and each coordinate of the two or more detected elements before and after the rotation;
A second rotation angle for aligning the plurality of detection elements with the multi-secondary charged particle beam is determined using at least one of the coordinates of the two or more detected detection elements and the rotation center coordinates of the multi-detector. a rotation angle calculation unit that calculates;
Equipped 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 a multi-charged particle beam and a secondary electron detector is possible.

1 is a configuration diagram showing the configuration of an inspection device in Embodiment 1. FIG. 2 is a conceptual diagram showing the configuration of a molded aperture array substrate in Embodiment 1. FIG. FIG. 3 is a diagram showing an example of the positional relationship between the multiple secondary electron beams and multiple detection elements of the multiple detector at a stage before alignment in Embodiment 1; 3 is a diagram showing an example of an internal configuration of a positioning circuit in Embodiment 1. FIG. FIG. 2 is a flowchart diagram illustrating an example of essential steps of the inspection method in Embodiment 1. FIG. FIG. 3 is a diagram for explaining how to search for detection element coordinates in the first embodiment. 3 is a diagram showing the configuration of a beam selection aperture substrate in Embodiment 1. FIG. FIG. 3 is a diagram for explaining an example of how to scan a secondary electron beam in the first embodiment. 5 is a diagram showing an example of a scanning range of a secondary electron beam in the first embodiment. FIG. FIG. 7 is a diagram for explaining a search method for accurately determining the position of D11 after identifying a beam close to D11. FIG. 3 is a diagram showing a case where one of two selected detection elements and a secondary electron beam overlap in the first embodiment. FIG. 6 is a diagram showing a case where the other of the two selected detection elements and the secondary electron beam overlap in the first embodiment. FIG. 3 is a diagram showing an example of the positional relationship between the multi-secondary electron beam and a plurality of detection elements of a multi-detector before and after rotation in Embodiment 1; FIG. 3 is a diagram showing a case where one of two selected detection elements and a secondary electron beam overlap in the first embodiment. FIG. 6 is a diagram showing a case where the other of the two selected detection elements and the secondary electron beam overlap in the first embodiment. FIG. 3 is a diagram showing an example of coordinates of a plurality of detection elements of the multi-detector before and after rotation in Embodiment 1; FIG. 3 is a diagram showing an arithmetic expression for calculating rotation center coordinates in the first embodiment. FIG. 3 is a diagram for explaining how to calculate vectors of detection element coordinates in the first embodiment. FIG. 3 is a diagram showing an arithmetic expression for calculating vector coefficients in the first embodiment. FIG. 3 is a diagram for explaining how to calculate vectors of secondary electron beam coordinates in the first embodiment. FIG. 3 is a diagram for explaining a method of calculating each coordinate of a plurality of detection elements in the first embodiment. 5 is a diagram showing an arithmetic expression for calculating a positioning angle in the first embodiment. FIG. FIG. 3 is a diagram for explaining how a plurality of detection elements are shifted in the first embodiment. FIG. 3 is a diagram for explaining how a plurality of detection elements are rotated in the first embodiment. 3 is a diagram showing an example of a plurality of chip regions formed on a semiconductor substrate in Embodiment 1. FIG. FIG. 3 is a diagram for explaining inspection processing in the first embodiment. FIG. 2 is a configuration diagram showing an example of a configuration inside a comparison circuit in Embodiment 1. FIG.

In the following embodiments, an electron beam will be used as an example of a charged particle beam. However, it is not limited to this. For example, an ion beam or the like may be used. Furthermore, as an example of a multi-beam image acquisition device, an inspection device using multi-beams will be described. However, it is not limited to this. Any device that acquires an image using a secondary electron detector compatible with multi-beams may be used.

Embodiment 1.
FIG. 1 is a configuration diagram showing the configuration of an inspection device according to the first embodiment. In FIG. 1, an inspection apparatus 100 that inspects a pattern formed on a substrate is an example of a multi-electron beam inspection apparatus. 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 chamber 103. Inside the electron beam column 102, there are an electron gun 201, an electromagnetic lens 202, a shaped aperture array substrate 203, a beam selection aperture substrate 232, a drive mechanism 234, an electromagnetic lens 205, a bulk blanking deflector 212, a limiting aperture substrate 213, and an electromagnetic lens. 206, an electromagnetic lens 207 (objective lens), a main deflector 208, a sub-deflector 209, a beam separator 214, a deflector 218, an electromagnetic lens 224, alignment coils 225, 226, a detector stage 229, and a multi-detector 222 are arranged. ing. Electron gun 201, electromagnetic lens 202, shaped aperture array substrate 203, electromagnetic lens 205, bulk 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 optical system 151 is composed of the deflector 208 and the sub-deflector 209. Further, the electromagnetic lens 207, the beam separator 214, the deflector 218, the electromagnetic lens 224, and the alignment coils 225 and 226 constitute the secondary electron optical system 152. The multi-detector 222 is arranged on a detector stage 229 that is movable in the x, y directions and the rotational (θ) direction of the secondary coordinate system. The detector stage 229 includes a rotation stage 227 and a secondary x, y stage 228.

A stage 105 movable at least in the X and Y directions is arranged within the examination room 103. A substrate 101 (sample) to be inspected is placed 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 die) 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. A plurality of chip patterns (wafer die) are formed on the semiconductor substrate by exposing and transferring the chip pattern formed on the exposure mask substrate a plurality of times onto the semiconductor substrate. The case where the substrate 101 is a semiconductor substrate will be mainly described below. For example, the substrate 101 is placed on the stage 105 with the pattern formation surface facing upward. Further, a mirror 216 is arranged on the stage 105 to reflect a laser beam for laser length measurement irradiated from a laser length measurement system 122 arranged outside the examination room 103.

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

In the control system circuit 160, a control computer 110 that controls the entire inspection apparatus 100 controls a position circuit 107, a comparison circuit 108, a reference image creation circuit 112, a stage control circuit 114, a lens control circuit 124, and a blanking circuit via a 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. The deflection control circuit 128 is also connected to DAC (digital-to-analog conversion) amplifiers 144, 146, and 148. DAC amplifier 146 is connected to main deflector 208 , and DAC amplifier 144 is connected to sub-deflector 209 . DAC amplifier 148 is connected to 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 a drive mechanism 142 under the control of a stage control circuit 114. The drive mechanism 142 includes, for example, a drive system such as a 3-axis (X-Y-θ) motor that drives in the X direction, Y direction, and θ direction in the stage coordinate system, so that the stage 105 can move in the XYθ directions. It has become. For these X motor, Y motor, and θ motor (not shown), for example, a step motor can be used. The stage 105 is movable in the horizontal direction and rotational direction by motors for each of the XYθ axes. The moving position of the stage 105 is then measured by the laser length measurement system 122 and supplied to the position circuit 107. The laser length measurement system 122 measures the position of the stage 105 using the principle of laser interferometry by receiving the reflected light from the mirror 216. In the stage coordinate system, for example, the X direction, Y direction, and θ direction of the primary coordinate system are set with respect to a plane perpendicular to the optical axis of the multi-primary electron beam 20.

Detector stage 229 is driven by drive mechanism 132 under the control of detector stage control circuit 130. The drive mechanism 132 includes, for example, a drive system such as a 3-axis (x-y-θ) motor that drives in the x direction, y direction, and θ direction in the stage coordinate system, and drives the x and y stages in the x and y directions. 228, the rotation stage 227 is movable in the θ direction. The example in FIG. 1 shows a case where an x, y stage 228 is placed on a rotation stage 227. These x motors, y motors, and θ motors (not shown) may be, for example, step motors. The detector stage 229 is movable in the horizontal direction and rotational direction by motors for each of the xy and θ axes. In the stage coordinate system, for example, the x direction, y direction, and θ direction of the secondary coordinate system are set with respect to a plane perpendicular 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, 227, and the beam separator 214 are controlled by the lens control circuit 124. The collective blanking deflector 212 is composed of two or more electrodes, and each electrode is controlled by the blanking control circuit 126 via a DAC amplifier (not shown). The sub-deflector 209 is composed of four or more electrodes, and each electrode is controlled by the deflection control circuit 128 via the DAC amplifier 144. The main deflector 208 is composed of four or more electrodes, and each electrode is controlled by the deflection control circuit 128 via the DAC amplifier 146. The deflector 218 is composed of four or more electrodes, and each electrode is controlled by the deflection control circuit 128 via the DAC amplifier 148.

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

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

Here, FIG. 1 shows a configuration necessary for explaining the first embodiment. The inspection apparatus 100 may normally include other necessary configurations.

FIG. 2 is a conceptual diagram showing the configuration of the molded aperture array substrate in the first embodiment. In FIG. 2, the molded aperture array substrate 203 has two-dimensional holes (openings) in m horizontal (x direction) x ₁ column x vertical (y direction) n ₁ stage (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. The example in FIG. 2 shows a case where 23×23 holes (openings) 22 are formed. Each hole 22 is formed in a rectangular shape with the same size and shape. Alternatively, they may be circular with the same outer diameter. When a portion of the electron beam 200 passes through each of these holes 22, a multi-primary electron beam 20 is formed. Next, the operation of the image acquisition mechanism 150 when acquiring a secondary electron image will be described. The primary electron optical system 151 irradiates the substrate 101 with multiple primary electron beams 20 . Specifically, it operates as follows.

An electron beam 200 emitted from an electron gun 201 (emission source) is refracted by an electromagnetic lens 202 and illuminates the entire shaped aperture array substrate 203. As shown in FIG. 2, a plurality of holes 22 (openings) are formed in the shaped aperture array substrate 203, and the electron beam 200 illuminates a region including all the plurality of holes 22. A 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 shaped aperture array substrate 203.

The formed multi-primary electron beam 20 is refracted by an electromagnetic lens 205 and an electromagnetic lens 206, and while repeating intermediate images and crossovers, the intermediate image plane (image plane) of each beam of the multi-primary electron beam 20 is The beam passes through a beam separator 214 placed at a conjugate position (I.I.P.) and advances to an electromagnetic lens 207 (objective lens).

When the multiple primary electron beams 20 enter the electromagnetic lens 207 (objective lens), the electromagnetic lens 207 focuses the multiple primary electron beams 20 onto the substrate 101 . The multi-primary electron beams 20 focused on the substrate 101 (sample) surface by the objective lens 207 are collectively deflected by the main deflector 208 and the sub-deflector 209. Irradiation is applied to each irradiation position above. Note that when the entire multi-primary electron beam 20 is deflected at once by the collective blanking deflector 212, the position of the multi-primary electron beam 20 is shifted from the center hole of the limiting aperture substrate 213, and the multi-primary electron beam 20 is deflected by the limiting aperture substrate 213. The entire beam 20 is blocked. On the other hand, the multi-primary electron beam 20 that has not been deflected by the collective blanking deflector 212 passes through the center hole of the limited aperture substrate 213, as shown in FIG. Blanking control is performed by turning ON/OFF the collective blanking deflector 212, and ON/OFF of the beam is collectively controlled. In this way, the limited aperture substrate 213 shields the multi-primary electron beam 20 that has been deflected by the collective blanking deflector 212 so as to turn the beam OFF. A multi-primary electron beam 20 for image acquisition is formed by a group of beams that have passed through the limiting aperture substrate 213 and are formed from when the beam is turned on until when the beam is turned off.

When a desired position of the substrate 101 is irradiated with the multi-primary electron beam 20, a beam corresponding to each of the multi-primary electron beams 20 is emitted from the substrate 101 due to the irradiation of the multi-primary electron beam 20. , a bundle of secondary electrons (multiple secondary electron beam 300) including reflected electrons is emitted.

Multi-secondary electron beam 300 emitted from substrate 101 passes through electromagnetic lens 207 and advances to beam separator 214 .

Here, the beam separator 214 generates an electric field and a magnetic field in orthogonal directions on a plane perpendicular to the direction in which the central beam of the multi-primary electron beam 20 travels (trajectory center axis). The electric field exerts a force in the same direction regardless of the direction in which the electrons travel. On the other hand, a magnetic field exerts a force according to Fleming's left-hand rule. Therefore, the direction of the force acting on the electrons can be changed depending on the direction in which the electrons enter. For the multi-primary electron beam 20 entering the beam separator 214 from above, the force due to the electric field and the force due to the magnetic field cancel each other out, and the multi-primary electron beam 20 travels straight downward. On the other hand, the force due to the electric field and the force due to the magnetic field act in the same direction on the multiple secondary electron beam 300 that enters the beam separator 214 from below, and the multiple secondary electron beam 300 is directed diagonally upward. Can be bent.

The multi-secondary electron beam 300 bent obliquely upward is further bent by a deflector 218 and projected onto a multi-detector 222 while being refracted by an electromagnetic lens 224 . The multiple detector 222 detects the projected multiple secondary electron beams 300. The multi-detector 222 has a plurality of detection elements (for example, a diode-type two-dimensional sensor, not shown). Each beam of the multiple primary electron beams 20 collides with a detection element corresponding to each secondary electron beam of the multiple secondary electron beams 300 on the detection surface of the multiple detector 222 to amplify and generate electrons, Secondary electronic 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 into a sub-irradiation area surrounded by the inter-beam pitch in the x direction and the inter-beam pitch in the y direction on the substrate 101 where its own beam is located, and scans within the sub-irradiation area ( scan operation).

As described above, the secondary electron image is obtained by irradiating the multi-primary electron beam 20 and collecting the multi-secondary electrons including reflected electrons emitted from the substrate 101 due to the irradiation of the multi-primary electron beam 20. Beam 300 is detected by multi-detector 222. The detection data of secondary electrons for each pixel in the individual irradiation area (sub-irradiation area) of each primary electron beam detected by the multi-detector 222 (measured image data: secondary electron image data: image data to be inspected) is , are 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. 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 within the sub-irradiation area 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 where 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 alignment is important.

FIG. 3 is a diagram illustrating an example of the positional relationship between the multiple secondary electron beams and the multiple detection elements of the multiple detector at a stage before alignment in the first embodiment. Here, for example, the positional relationship after rough adjustment is shown. In the example of FIG. 3, a secondary coordinate system is shown with the center position of the multiple secondary electron beam 300 on the detection surface of the multiple detector 222 as the origin. In the example of FIG. 3, for example, 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. The multi-detector 222 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, 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 position of each detection element (D11 to D33) is adjusted to the corresponding secondary electron beam (B11 to B33). ) position.

FIG. 4 is a diagram showing an example of the internal configuration of the alignment circuit in the first embodiment. In FIG. 4, the alignment circuit 134 includes a search section 60, a rotation center calculation section 61, a vector calculation section 62, a center corresponding coordinate calculation section 63, a shift amount calculation section 64, a coordinate calculation section 65, and a rotation angle calculation section 66. , a rotation processing section 67, a shift processing section 68, and a selection section 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, Each "section" such as the selection section 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, or the like. Further, each "~ section" may use a common processing circuit (the same processing circuit). 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, Input data or calculated results required in the selection section 69 are stored in a memory (not shown) or in the memory 118 each time.

FIG. 5 is a flowchart showing an example of main steps of the inspection method in the first embodiment. In FIG. 5, the main steps of the inspection method in Embodiment 1 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 process (S108), detection element coordinate search process (S110), rotation center calculation process (S112), vector calculation process (S114), center corresponding coordinate calculation process (S116), and shift amount calculation process (S118) ), remaining detection element coordinate calculation step (S120), rotation angle calculation step (S122), shift step (S124), rotation step (S126), and inspection processing step (S130). Implement.

The multi-electron beam alignment method in the first embodiment includes, among these steps, a secondary electron beam coordinate measurement step (S102), a detection element selection step (S104), a detection element coordinate search step (S106), Detector rotation step (S108), detection element coordinate search step (S110), rotation center calculation step (S112), vector calculation step (S114), center corresponding coordinate calculation step (S116), and shift amount calculation step (S118), the remaining detection element coordinate calculation process (S120), the rotation angle calculation process (S122), the shift process (S124), and the rotation process (S126). It does not matter which one of the shift step (S124) and the rotation step (S126) comes first. Alternatively, they may be performed at the same time.

In the secondary electron beam coordinate measuring step (S102), first, the position of the multi-secondary electron beam 300 on the detection surface is measured. First, an electron beam detection image sensor (hereinafter referred to as EDIS) (not shown) is attached in place of the multi-detector 222, 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 much smaller than the beam size are arranged two-dimensionally, and for example, one in which 4000 x 3000 pixels of 10 μm square are arranged is useful. Each pixel may be sensitive to electron beams, or may be one that detects electron beams through a phosphor. By directing the electron beam, it is possible to set a secondary coordinate system with the origin at the center position of the multiple secondary electron beam 300 on the detection surface of the multiple detector 222. Thereafter, the direct detection device will be removed and the multi-detector 222 will be installed. In the example of FIG. 3, the position of each detection element (D11 to D33) is shown as an example, but in reality, the position of each detection element (D11 to D33) in the secondary coordinate system is not known. It is. For 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 beam 20 may be irradiated one by one. Then, the positions of the corresponding secondary electron beams may be measured. Stage 105 may be performed in a stopped state. Furthermore, instead of the substrate 101, a mark, an evaluation substrate, or the like (not shown) may be irradiated with the primary electron beam.

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

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

FIG. 6 is a diagram for explaining how to search for detection element coordinates in the first embodiment. As shown in FIG. 6, the multiple secondary electron beams 300 are scanned one by one by selection with the beam selection aperture board 232, and the secondary electron beams near the selected detection elements D11, D31 (, D33) are scanned one by one. Understand each. In order to focus on one secondary electron beam, multiple primary electron beams 20 are selected one by one. The example in FIG. 6 shows a case where the detection element D11 can be searched by the secondary electron beam B21. Similarly, a case is shown in which the detection element D31 can be searched by the secondary electron beam B31.

FIG. 7 is a diagram showing the configuration of the beam selection aperture substrate 232 in the first embodiment. In FIG. 7, a beam selection aperture substrate 232 has a large aperture 11 that allows the entire multi-primary electron beam 20 to pass through, and a small aperture 13 that is sized to allow only one primary electron beam to pass through. Ru. Under the control of the beam selection aperture control circuit 136, the drive mechanism 234 horizontally moves the beam selection aperture substrate 232 to selectively pass one primary electron beam among the multiple primary electron beams 20. . The primary electron beam that has passed through the beam selection aperture substrate 232 is irradiated onto the substrate 101 and emits a corresponding secondary electron beam. The emitted secondary electron beam is deflected by the beam separator 214 and advances to 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 in the first embodiment. The secondary electron beams 301, which have been narrowed down one by one, are deflected by an alignment coil 225 so that the center orbit is slanted, and then an alignment coil 226 changes the slanted trajectory to an orbit axis parallel to the original orbit axis. Turn it back. This allows for axial movement without changing the incident angle. By such axis movement, the position where the multi-detector 222 is irradiated is scanned. Note that although the case where scanning is performed using two alignment coils 225 and 226 is shown here, the invention is not limited to this. For example, it is preferable to scan the secondary electron beam 301 using a deflector composed of four or more electrodes.

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, the scanning range of each secondary electron beam is preferably set to a rectangular area (±0.5 beam pitch in the x and y directions) surrounded by the beam pitch between the secondary electron beams. The example in FIG. 9A shows a case where some of the secondary electron beams are arranged at a pitch larger than the designed beam pitch due to various error factors (processing accuracy of steel members, assembly accuracy, etc.). ing.

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

FIG. 10 is a diagram showing a case where one of the two selected detection elements and the secondary electron beam overlap in the first embodiment. In the example of FIG. 10, the secondary electron beam detected by the detection element D11 is searched. The example in FIG. 10 shows a case where the secondary electron beam B21 is detected by the detection element D11. 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 maximum is added to the position of the secondary electron beam B21. The position can be searched (detected) using 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 and the secondary electron beam overlap in the first embodiment. The secondary electron beam detected by the detection element D31 is searched for by performing the same operation as when detecting the coordinates (x1, y1) of the detection element D11. The example in FIG. 11 shows a case where the secondary electron beam B31 is detected by the detection element D31. 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 maximum is added. The position can be searched (detected) using the coordinates (x2, y2) of the detection element D31.

Note that when three detection elements are selected, the coordinates (x3, y3) of the third detection element D33 are similarly searched (detected).

As the detector rotation step (S108), the detector stage control circuit 130 controls the drive mechanism 132 to rotate the rotation stage 227. Thereby, 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 multiple secondary electron beams and the multiple detection elements of the multiple detector before and after rotation 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 center (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 were detected before the rotation after the rotation are unknown. The example in FIG. 12 shows a state in which the detection element D11 has moved to the detection element D11' by rotating the multi-detector 222 by the rotation angle φ. Similarly, a state in which the detection element D31 has been moved to the detection element D31' is shown.

As the detection element coordinate search step (S110), the search unit 60 uses each secondary electron beam emitted from the surface of the substrate 101 to search for the coordinates of two or more detection elements after rotation. Specifically, the rotated coordinates of the selected two or more detection elements D11, D31 (, D33) are searched using one of the secondary electron beams.

FIG. 13 is a diagram showing a case where one of the two selected detection elements and the secondary electron beam overlap in the first embodiment. 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 for. The example in FIG. 13 shows a case where the secondary electron beam B11 is detected by the detection element D11'. 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 maximum is added to the position of the secondary electron beam B11. The position can be searched (detected) using 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 and the secondary electron beam overlap in the first embodiment. The secondary electron beam detected by the detection element D31' is searched for by performing the same operation as in the case of detecting the coordinates (X1, Y1) of the detection element D11'. The example in FIG. 14 shows a case where the secondary electron beam B31 is detected by the detection element D31'. 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 maximum is added. The position can be searched (detected) using the coordinates (X2, Y2) of the detection element D31'.

FIG. 15 is a diagram showing an example of 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') rotates from the coordinates (x1, y1) before rotation to the coordinates (X1, Y1) after rotation around the unknown rotation center coordinates (rx, ry). It's moving. Similarly, the detection element D31 (D31') is moving from the coordinates (x2, y2) before rotation to the coordinates (X2, Y2) after rotation around the unknown rotation center coordinates (rx, ry). .

As the rotation center calculation step (S112), the rotation center calculation unit 61 calculates the rotation angle φ at which the multi-detector 222 is rotated, and the searched two or more detection elements D11 (D11') and D31 (D31') before and after the rotation. ), the rotation center coordinates (rx, ry) of the multi-detector 222 are calculated using the coordinates (x1, y1), (x2, y2), (X1, Y1), (X2, Y2) of the multi-detector 222.

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

By the above processing, each coordinate (x1, y1), (x2, y2), (X1, Y1), (X2, Y2) before and after rotation of at least two detection elements D11 (D11') and D31 (D31') and rotation center coordinates (rx, ry). Furthermore, when three detection elements are selected, the coordinates (x3, y3) of the third detection element D33 before rotation can be similarly obtained. If three detection elements are not selected, the third detection element is selected and the coordinates (x3, y3) before rotation are searched. When selecting the third detection element, it is a detection element different from the detection element D22 in the center, and the three detection elements are not aligned on a straight line in relation to the previous two detection elements D11 and D31. Select a detection element.

As the vector calculation step (S114), the vector calculation unit 62 calculates a vector from the coordinates of one detection element to the rotation center coordinates (rx, ry) among the three detection elements from the coordinates of the one detection element to the remaining one. An operation is performed to decompose the coordinates of the two detection elements into two vectors.

FIG. 17 is a diagram for explaining how to calculate vectors of detection element coordinates in the first embodiment. Among 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 expressed as the coordinates of the detection element D31 ( 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. . Among the three detection elements D11, D31, and D33, the remaining one detection element D31 has two detection elements D11 and D33 located separately on both sides with respect to the vector to the rotation center coordinates (rx, ry). It is preferable to use this as a reference. Vector R can be defined by the following equation (2) using vector P and vector Q. In equation (2), the symbol (-) indicating a vector is omitted.
(2) R=αP+βQ

FIG. 18 is a diagram showing arithmetic expressions for calculating vector coefficients in the first embodiment. The unknown vector coefficients α and β can be obtained using equation (3).

In the center correspondence coordinate calculation step (S116), the center correspondence coordinate calculation unit 63 calculates multi-secondary electrons that have a positional relationship similar to the positional relationship of the rotation center coordinates (rx, ry) with respect to the plurality of detection elements D11, D31, D33. Corresponding coordinates Bc for beams B11, B31, and B33 are calculated.

FIG. 19 is a diagram for explaining how to calculate vectors of secondary electron beam coordinates in the first embodiment. In FIG. 19, the corresponding coordinate Bc is a combination of two vectors when the two decomposed vectors αP and βQ are applied to the coordinates of three secondary electron beams B11, B31, and B33 of the multi-secondary electron beams. Calculated as vector coordinates. Specifically, the center correspondence 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 a vector coefficient α. The composite vector R' is calculated 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' with the secondary electron beam B31 as the starting point as the corresponding coordinate Bc.

As the shift amount calculation step (S118), the shift amount calculation unit 64 calculates a shift amount (dx, dy) for shifting the rotation center coordinates (rx, ry) to the corresponding coordinates Bc for 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 among the plurality of detection elements D11 to D33 using the respective coordinates of the two or more detected detection elements that have been searched. .

FIG. 20 is a diagram for explaining a method of calculating each coordinate of a plurality of detection elements in 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 through 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 arrayed at the same pitch along two orthogonal axes. Therefore, if each coordinate of at least two detection elements is known, each coordinate of the remaining detection elements can be calculated. In the example of FIG. 20, when each coordinate (x1, y1), (x2, y2), (x3, y3) of three detection elements D11, D31, D33 is known, each coordinate of the remaining detection elements is An example of a calculation method is shown.

For example, the coordinates (x4, y4) of the detection element D21 are calculated as the center position of a 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 a 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 a 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 the coordinates (x1, y1) of the detection element D11, and the vector from the coordinates (x2, y2) of the detection element D31 to the coordinates (x3, y3) of the detection element D33. Calculated as the position of the added value. Alternatively, the coordinates (x7, y7) of the detection element D13 are obtained by adding the vector from the coordinates (x2, y2) of the detection element D31 to the coordinates (x1, y1) of the detection element D11 to the coordinates (x3, y3) of the detection element D13. 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 (x2, y2) of the detection element D31 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 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 a 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 a straight line connecting the coordinates of the detection elements D13 and D33.

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

As the rotation angle calculation step (S122), the rotation angle calculation unit 66 uses at least one of the coordinates of the two or more detected detection elements and the rotation center coordinates (rx, ry) of the multi-detector 222 to A rotation angle θ (second rotation angle) for aligning the detection elements D11 to D33 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. Among the coordinates (X1', Y1') to (X9', Y9') of the detection elements D11 to D33 after alignment of the multiple detection elements D11 to D33 to 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 rotation center coordinates (rx, ry), and the unknown rotation angle θ. can be defined as equation (4) shown in FIG. The same applies when another detection element is used instead of the detection element D11. By transforming Equation (4), the unknown rotation angle θ can be determined. In order to further improve accuracy, it is preferable to find the unknown rotation angle θ using each coordinate (x1, y1) to (x9, y9) of all nine 3×3 detection elements D11 to D33. .

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

In the above manner, the shift amount (dx, dy) and rotation angle θ for alignment 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 to obtain the rotation center coordinates (rx, ry) are ) was used to find the rotation angle θ, but the rotation angle θ is not limited to this. The rotation angle θ' for alignment may be determined 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. do not have. In such a case, in addition to the coordinates (X1, Y1) and (X2, Y2) of the two searched detection elements D11 and D31 after rotation, the remaining coordinates (X3, Y3) to (X9, Y9 ). Alternatively, using at least one of the coordinates (X1, Y1) and (X2, Y2) of the two searched detection elements D11 and D31 after rotation, equation (4) is applied to align the position. You may also find the rotation angle θ'. In such a case, (x1, y1) in equation (4) may be replaced with (X1, Y1), and θ may be replaced with 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 a plurality of detection elements are shifted in the first embodiment. In FIG. 22, the multi-detector 222 is shifted so that the rotation center Dc of the multi-detector 222, which was 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 stage 228 by the drive mechanism 132 under the control of the detector stage control circuit 130.

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

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

As an inspection processing step (S130), the substrate 101 is inspected using the inspection apparatus 100 that has been aligned.

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

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

In the example of FIG. 25, for example, a case of 5×5 arrays of multi-primary electron beams 20 is shown. The irradiation area 34 that can be irradiated by one irradiation with the multi-primary electron beam 20 is (x-direction calculated by multiplying the inter-beam pitch in the x-direction of the multi-primary electron beams 20 on the surface of the substrate 101 by the number of beams in the x-direction). size)×(y-direction size obtained by multiplying the inter-beam pitch in the y-direction of the multi-primary electron beams 20 on the surface of the substrate 101 by the number of beams in the y-direction). The irradiation area 34 becomes the field of view of the multi-primary electron beam 20. Each primary electron beam 10 constituting the multi-primary electron beam 20 is irradiated into a sub-irradiation area 29 surrounded by the inter-beam pitch in the x direction and the inter-beam pitch in the y direction, where its own beam is located. , scan the inside of the sub-irradiation area 29 (scanning operation). Each primary electron beam 10 will be in charge of one of the different sub-irradiation areas 29. Then, during each shot, each primary electron beam 10 irradiates the same position within the assigned sub-irradiation area 29. Movement of the primary electron beam 10 within the sub-irradiation area 29 is performed by deflecting the entire multi-primary electron beam 20 at once by the sub-deflector 209. This operation is repeated to sequentially irradiate one sub-irradiation area 29 with one primary electron beam 10.

It is preferable that the width of each stripe area 32 is set to be the same as the y-direction size of the irradiation area 34, or to a size narrower by the scan margin. The example in FIG. 25 shows a case where the irradiation area 34 has the same size as the rectangular area 33. However, it is not limited to this. The irradiation area 34 may be smaller than the rectangular area 33. Or it doesn't matter if it's big. Each primary electron beam 10 constituting the multi-primary electron beam 20 is irradiated into the sub-irradiation area 29 where its own beam is located, and scans (scanning operation) within the sub-irradiation area 29. When scanning of one sub-irradiation area 29 is completed, the entire multi-primary electron beam 20 is collectively deflected by the main deflector 208, so that the irradiation position moves to an adjacent rectangular area 33 within the same stripe area 32. This operation is repeated to sequentially irradiate the inside of the stripe area 32. When scanning of one stripe area 32 is completed, the irradiation area 34 is moved to the next stripe area 32 by movement of the stage 105 and/or collective deflection of the entire multi-primary electron beam 20 by the main deflector 208. As described above, by irradiating each primary electron beam 10, a scanning operation and acquisition of a secondary electron image are performed for each sub-irradiation area 29. By combining these secondary electron images for each sub-irradiation area 29, a secondary electron image of the rectangular area 33, a secondary electron image of the striped area 32, or a secondary electron image of the chip 332 is constructed. Furthermore, when actually performing image comparison, the sub-irradiation area 29 within each rectangular area 33 is further divided into a plurality of frame areas 30, and the frame images 31 of each frame area 30 are compared. The example in FIG. 8 shows a case where the sub-irradiation area 29 scanned by one primary electron beam 10 is divided into four frame areas 30 formed by dividing the sub-irradiation area 29 into two in each of the x and y directions, for example. .

Here, when the multi-primary electron beam 20 is irradiated onto the substrate 101 while the stage 105 is continuously moving, the main deflector 208 deflects the multi-primary electron beam 20 at once so that the irradiation position follows the movement of the stage 105. Tracking operation is performed by Therefore, the emission position of the multiple secondary electron beams 300 changes every moment with respect to the orbit center axis of the multiple primary electron beams 20. Similarly, when scanning the sub-irradiation area 29, the emission position of each secondary electron beam changes momentarily within the sub-irradiation area 29. The deflector 218 collectively deflects the multiple secondary electron beams 300 so that each of the secondary electron beams whose emission positions have changed in this way is irradiated into the corresponding detection area of the multiple detector 222.

As described above, the image acquisition mechanism 150 advances 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 with the multi-primary electron beam 20 is detected by the multi-detector 222. . The detected multi-secondary electron beam 300 may include reflected electrons. Alternatively, the reflected electrons may diverge and be separated while moving through the secondary electron optical system 152 and may not reach the multi-detector 222. The detection data of secondary electrons for each pixel in each sub-irradiation area 29 detected by the multi-detector 222 (measurement image data: secondary electron image data: image data to be inspected) is output to the detection circuit 106 in the order of measurement. Ru. 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. The obtained measurement image data is then transferred to the comparison circuit 108 together with information indicating each position from the position circuit 107.

FIG. 26 is a configuration diagram showing an example of the internal configuration of the comparison circuit in the first embodiment. In FIG. 26, in the comparison circuit 108, storage devices 50, 52, and 56 such as magnetic disk devices, a frame image creation section 54, a positioning section 57, and a comparison section 58 are arranged. Each "section" such as the frame image creation section 54, the alignment section 57, and the comparison section 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. Includes equipment, etc. Further, each "~ section" may use a common processing circuit (the same processing circuit). Alternatively, different processing circuits (separate processing circuits) may be used. Input data or calculated results necessary for the frame image creation section 54, alignment section 57, and comparison section 58 are stored in a memory (not shown) or in the 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 of the plurality of frame regions 30 obtained 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. Note that it is preferable that each frame area 30 is configured so that the margin areas overlap each other so that no image is 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 area 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, 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 multivalued image data.

As mentioned above, the shapes defined in the design pattern data are basic shapes such as rectangles and triangles, and include the coordinates (x, y) at the reference position of the shape, the length of the sides, the rectangle, triangle, etc. Graphic data is stored that defines the shape, size, position, etc. of each pattern graphic using information such as a graphic code serving as an identifier for distinguishing the graphic type.

When design pattern data serving as such graphic data is input to the reference image creation circuit 112, it is developed into data for each graphic, and the graphic code, graphic dimensions, etc. indicating the graphic shape of the graphic data are interpreted. Then, it is expanded into binary or multivalued design pattern image data as a pattern arranged in a grid with a grid of a predetermined quantization size as a unit, and output. In other words, read the design data, calculate the occupancy rate occupied by the figure in the design pattern for each square created by virtually dividing the inspection area into squares with predetermined dimensions as units, and calculate the n-bit occupancy data. Output. For example, it is preferable to set one square as one pixel. If one pixel has a resolution of ^1/28 (=1/256), a small area of 1/256 is allocated for the area of the figure placed within the pixel, and the occupancy rate within the pixel is calculated. calculate. This results in 8-bit occupancy data. Such squares (inspection pixels) may be aligned with pixels of measurement data.

Next, the reference image creation circuit 112 performs filter processing on the design image data of the design pattern, which is the image data of the figure, using a predetermined filter function. Thereby, the design image data, which is image data on the design side in which the image intensity (gradation value) is a digital value, can be matched to the image generation characteristics obtained by irradiation with 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 serving as the image to be inspected and the reference image corresponding to the frame image 31, and aligns both images in units of sub-pixels smaller than pixels. For example, alignment may be performed using the least squares method.

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

Note that in the above example, the die-database inspection was explained, but the present invention is not limited to this. It may also be a case of performing a die-to-die inspection. When performing a die-to-die inspection, there is a difference between the target frame image 31 (die 1) and the frame image 31 (die 2) on which the same pattern as the frame image 31 is formed (another example of a reference image). , the alignment and comparison processing described above may be performed.

As described above, according to the first embodiment, it is possible to efficiently align the multi-charged particle beam and the secondary electron detector.

In the above description, a 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, each "circuit" may use a common processing circuit (the same processing circuit). Alternatively, different processing circuits (separate processing circuits) may be used. A program for executing a 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, the position circuit 107, the comparison circuit 108, the reference image creation circuit 112, the stage control circuit 114, the lens control circuit 124, the blanking control circuit 126, the deflection control circuit 128, the detector stage control circuit 130, the alignment circuit 134, and Beam selection aperture control circuit 136 may be comprised of at least one processing circuit described above. For example, the processing within these circuits may be performed by the control computer 110.

The embodiments have been described above with reference to specific examples. However, the present invention is not limited to these specific examples. The example in FIG. 1 shows a case where a multi-primary electron beam 20 is formed by a shaping aperture array substrate 203 from one beam irradiated from an electron gun 201 serving as one irradiation source, but the present invention is not limited to this. isn't it. An embodiment may be adopted in which the multi-primary electron beam 20 is formed by irradiating primary electron beams from a plurality of irradiation sources, respectively.

In addition, descriptions of parts not directly necessary for the explanation of the present invention, such as the device configuration and control method, have been omitted, but the necessary device configuration and control method can be selected and used as appropriate.

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

10 Primary electron beam 11 Large aperture 13 Small aperture 17 Re-search 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 section 57 Alignment section 58 Comparison section 60 Search section 61 Rotation center calculation section 62 Vector calculation section 63 Center corresponding coordinate calculation section 64 Shift amount calculation section 65 Coordinate calculation section 66 Rotation angle calculation section 67 Rotation processing section 68 Shift processing Section 69 Selection section 100 Inspection device 101 Substrate 102 Electron beam column 103 Inspection chamber 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 Positioning circuit 136 Beam selection aperture control circuit 142 Drive mechanism 144, 146, 148 DAC Amplifier 150 Image acquisition mechanism 151 Primary electron optical system 152 Secondary electron optical 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-deflector device 212 collective blanking deflector 213 limiting aperture substrate 214 beam separator 216 mirror 218 deflector 222 multi-detector 225, 226 alignment coil 227 rotation 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 a plurality of detection elements included in a multi-detector for detecting a multi-secondary charged particle beam including each of the secondary charged particle beams, each using a secondary charged particle beam emitted from a sample surface. a step of searching for the coordinates of the above detection element;
rotating the multi-detector at a first rotation angle;
searching for coordinates of the two or more detection elements after rotation using each secondary charged particle beam emitted from the sample surface;
calculating the rotation center coordinates of the multi-detector using the first rotation angle at which the multi-detector was rotated and the searched coordinates of the two or more detection elements before and after rotation;
A second method for aligning the plurality of detection elements with the multi-secondary charged particle beam using at least one of the searched coordinates of the two or more detection elements and the rotation center coordinates of the multi-detector. a step of calculating the rotation angle of
rotating the multi-detector at the second rotation angle;
A multi-charged particle beam alignment method characterized by comprising: calculating corresponding coordinates for the multi-secondary charged particle beam that have a positional relationship similar to the positional relationship of the rotation center coordinates with respect to the plurality of detection elements;
calculating a shift amount for shifting the rotation center coordinates to the corresponding coordinates for the multi-secondary charged particle beam;
Shifting the multi-detector using the shift amount;
The multi-charged particle beam alignment method according to claim 1, further comprising:. calculating the coordinates of the remaining detection elements of the plurality of detection elements using each coordinate of the two or more detected detection elements that have been searched;
The multi-charged particle beam alignment method according to claim 1 or 2, further comprising:. 4. The method according to claim 3, further comprising the step of selecting three detection elements different from a central detection element from among 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 are not arranged in a straight line are used,
Among the three detection elements, a calculation is performed to decompose a vector from the coordinates of one detection element to the rotation center coordinates into two vectors from the coordinates of the one detection element to the coordinates of the remaining two detection elements. With further processes,
The corresponding coordinates are calculated as the coordinates of a composite vector of the two vectors when the two decomposed vectors are applied to the coordinates of three secondary charged particle beams of the multi-secondary charged particle beams. 3. The multi-charged particle beam alignment method according to claim 2 . a stage on which the sample is placed;
a primary electron optical system that irradiates the sample with a multi-primary electron beam;
a multi-detector having a plurality of detection elements for detecting a multi-secondary charged particle beam emitted by irradiating the sample with the multi-primary electron beam;
a rotation mechanism that rotates the multi-detector;
searching for coordinates of two or more of the plurality of detection elements before and after rotation of rotating the multi-detector at a first rotation angle using secondary charged particle beams emitted from the sample surface; The exploration department and
a rotation center calculation unit that calculates rotation center coordinates of the multi-detector using the first rotation angle at which the multi-detector is rotated and the searched coordinates of the two or more detection elements before and after rotation; and,
A second method for aligning the plurality of detection elements with the multi-secondary charged particle beam using at least one of the searched coordinates of the two or more detection elements and the rotation center coordinates of the multi-detector. a rotation angle calculation unit that calculates the rotation angle of the
Equipped with
A multi-charged particle beam inspection apparatus, wherein the rotation mechanism rotates the multi-detector at the second rotation angle.

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