JP2019021532A - Electron beam image acquisition device and electron beam image acquisition method - Google Patents

Abstract

To provide an electron beam image acquisition device using electron beams, which is suppressed in occurrence of discharge and is capable of acquiring a high-precision image.SOLUTION: An electron beam image acquisition device includes: an XY stage 105 on which a substrate is placed; an objective lens 207 for focusing electron beams on the substrate; an electrode 220 which is arranged between the substrate and the objective lens, in which a passing hole through which the electron beams pass is formed at a central part thereof, on which negative potential with respect to the objective lens is applied, and which is maintained at such a voltage that does not cause discharge between the substrate and the electrode; a gas supply port 322 supplying gas between the substrate and the electrode; and a detector 222 for detecting secondary electrons including reflected electrons emitted from the substrate due to irradiation of the electron beams onto the substrate.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electron beam image acquisition apparatus and an electron beam image acquisition method. For example, the present invention relates to an inspection apparatus that acquires a secondary electron image of a pattern emitted by irradiating a multi-beam with an electron beam and inspects the pattern.

  In recent years, the circuit line width required for a semiconductor element has been increasingly narrowed as a large scale integrated circuit (LSI) is highly integrated and has a large capacity. These semiconductor elements use an original pattern pattern (also referred to as a mask or a reticle, hereinafter referred to as a mask) on which a circuit pattern is formed, and the pattern is exposed and transferred onto a wafer by a reduction projection exposure apparatus called a stepper. It is manufactured by forming a circuit.

  In addition, improvement in yield is indispensable for manufacturing an LSI that requires a large amount of manufacturing cost. However, as represented by a 1 gigabit class DRAM (Random Access Memory), the pattern constituting the LSI is 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, an imaging apparatus represented by a pattern inspection apparatus that inspects a defect of an ultrafine pattern transferred onto a semiconductor wafer is required to acquire a highly accurate pattern image.

  For example, in an inspection apparatus, which is an example of an apparatus that captures a pattern image, a pattern formed on a substrate such as a semiconductor wafer or a lithography mask is captured at a predetermined magnification using a laser beam by using an enlargement optical system. To obtain an optical image. And the method of test | inspecting by comparing this optical image with the optical data which imaged the design data or the same pattern on a sample is known. For example, as a pattern inspection method, “die to die inspection” in which optical image data obtained by imaging the same pattern at different locations on the same mask is compared, or a pattern is formed using CAD data with a pattern design as a mask. Drawing data (design pattern data) converted into a device input format for the drawing device to input at the time of drawing is input to the inspection device, design image data (reference image) is generated based on this, and the pattern and the pattern are generated. There is a “die to database (die-database) inspection” that compares an optical image that is captured measurement data. In the inspection method in such an inspection apparatus, a substrate to be inspected is placed on a stage, and the stage is moved, so that the light beam scans on the sample and the inspection is performed. The inspection target substrate is irradiated with a light beam by a light source and an illumination optical system. The light transmitted or reflected through the inspection target substrate is imaged on the sensor via the optical system. The image picked up by the sensor is sent to the comparison circuit as measurement data. The comparison circuit compares the measured data and the reference data according to an appropriate algorithm after the images are aligned, and determines that there is a pattern defect if they do not match.

  In the pattern inspection apparatus described above, an optical image is acquired by irradiating the inspection target substrate with a laser beam and capturing a transmission image or a reflection image thereof. On the other hand, development of an inspection apparatus that acquires a pattern image by irradiating a target substrate with an electron beam and detecting secondary electrons corresponding to each beam emitted from the target substrate is also progressing. With respect to an apparatus for imaging a pattern using an electron beam typified by an inspection apparatus, a technique using a multi-beam is being developed in addition to a technique using a single beam. In addition, a scanning electron microscope (SEM) or the like can be given as an apparatus for imaging a pattern using an electron beam.

  In an apparatus for imaging a pattern using an electron beam, the electron beam accelerated with high energy is decelerated immediately before entering the substrate under vacuum, and the low-energy secondary electrons emitted from the substrate are detected on the detector side. A retarding voltage is applied so as to be accelerated (see, for example, Patent Document 1). On the other hand, there is a problem that the upper surface of the substrate is charged by irradiating the substrate with the electron beam. In order to eliminate such charging, it has been studied to flow an ion gas over the substrate. However, in a retarding voltage environment, there is a problem that discharge is easily caused by introduction of gas, and a highly accurate secondary electron image cannot be obtained due to the occurrence of such discharge.

JP2013-0333739A

  In view of the above, an embodiment of the present invention provides an image acquisition apparatus and method using an electron beam that can acquire a highly accurate image in which discharge is suppressed.

An electron beam image acquisition device according to one embodiment of the present invention includes:
A stage on which a substrate is placed;
An objective lens for imaging an electron beam on a substrate;
Located between the substrate and the objective lens, a passage hole through which the electron beam passes is formed in the center, and a negative potential is applied to the objective lens and maintained at a voltage that does not discharge between the substrate and the substrate. Electrodes,
A supply section for supplying a gas between the substrate and the electrode;
A detector for detecting secondary electrons including reflected electrons emitted from the substrate due to irradiation of the electron beam to the substrate;
It is provided with.

In addition, the electrode
A first flow path in the electrode through which gas passes;
A supply port for supplying gas to the substrate in the vicinity of the passage hole from the first flow path;
The supply port is a recovery port for recovering the gas supplied to the substrate in the vicinity of the opposite side of the through hole across the pass hole,
A second flow path in the electrode through which the gas recovered from the recovery port passes;
Is preferably formed.

  The electrode is preferably made of a material that can transmit light.

  The electron beam image acquisition apparatus acquires an image of a substrate using a single beam or a multi-beam as an electron beam.

An electron beam image acquisition method of one embodiment of the present invention includes:
The substrate is placed between the substrate placed on the stage and the objective lens, and a through-hole through which an electron beam passes is formed in the central portion. Using the electrode, a negative potential is applied to the electrode with respect to the objective lens and the substrate. A step of controlling the voltage between the electrode and the electrode so as not to discharge;
Supplying a gas between the substrate and the electrode;
Detecting secondary electrons including reflected electrons emitted from the substrate due to irradiation of the electron beam focused on the substrate using the objective lens, and acquiring an image of the substrate; ,
It is provided with.

  According to one embodiment of the present invention, occurrence of discharge can be suppressed. Therefore, a highly accurate image can be acquired.

1 is a configuration diagram illustrating a configuration of a pattern inspection apparatus according to a first embodiment. FIG. 3 is a conceptual diagram showing a configuration of a molded aperture array substrate in the first embodiment. 6 is a diagram illustrating an example of a state between an objective lens and a substrate in a comparative example of Embodiment 1. FIG. 3 is a cross-sectional view illustrating a configuration between an objective lens and a substrate in Embodiment 1. FIG. FIG. 3 is a top view seen from above the electrode in the first embodiment. It is a figure which shows the relationship between the product of discharge voltage in Embodiment 1, and a spatial distance and a pressure. FIG. 3 is a diagram showing a relationship between gas pressure and electron scattering in the first embodiment. FIG. 3 is a flowchart showing main steps of the inspection method according to Embodiment 1. 3 is a diagram showing an example of a plurality of chip regions formed on the semiconductor substrate in the first embodiment. FIG. 6 is a diagram illustrating an example of a multi-beam irradiation region and a measurement pixel in Embodiment 1. FIG. 3 is an example of an internal configuration diagram illustrating a configuration in a comparison circuit according to Embodiment 1. FIG. 6 is a cross-sectional view showing a configuration between an objective lens and a substrate in Embodiment 2. FIG. 6 is a top view of an electrode in Embodiment 2. FIG. 6 is a right side view of an electrode according to Embodiment 2. FIG. FIG. 10 is a top view of an electrode in a modification of the second embodiment. FIG. 6 is a cross-sectional view illustrating a configuration between an objective lens and a substrate in a third embodiment.

  Hereinafter, as an example of an apparatus for acquiring an image of a substrate in an embodiment, an inspection apparatus that irradiates a substrate to be inspected with a multi-beam by an electron beam and captures a secondary electron image will be described. However, the present invention is not limited to this. As another example of an apparatus that acquires an image of a substrate, for example, an apparatus that captures a secondary electron image by irradiating the substrate with a single beam of one electron beam may be used. Further, the inspection apparatus may not be used.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram showing the configuration of the pattern inspection apparatus according to the first embodiment. In FIG. 1, an inspection apparatus 100 that inspects a pattern formed on a substrate is an example of an electron beam image acquisition apparatus. The inspection apparatus 100 includes an image acquisition mechanism 150 and a control system circuit 160 (control unit). The image acquisition mechanism 150 includes an electron beam column 102 (an electron column), an examination room 103, a detection circuit 106, a chip pattern memory 123, a stage drive mechanism 142, a gas supply device 134, and a laser length measurement system 122. In the electron beam column 102, there are an electron gun 201, an illumination lens 202, a shaping aperture array substrate 203, a reduction lens 205, a limiting aperture substrate 206, an objective lens 207, a main deflector 208, a sub deflector 209, and a batch blanking deflector. 212, a beam separator 214, an electrode 220, a gas supply port 322, a gas recovery port 324, projection lenses 224 and 226, a deflector 228, and a multi-detector 222 are arranged.

  An XY stage 105 that can move at least on the XY plane is disposed in the examination room 103. A substrate 101 to be inspected is disposed on the XY stage 105. The substrate 101 includes a mask substrate for exposure 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 formed on the mask substrate for exposure is exposed and transferred a plurality of times onto the semiconductor substrate, whereby a plurality of chip patterns (wafer dies) are formed on the semiconductor substrate. Hereinafter, a case where the substrate 101 is a semiconductor substrate will be mainly described. For example, the substrate 101 is disposed on the XY stage 105 with the pattern formation surface facing upward. On the XY stage 105, a mirror 216 for reflecting laser length measurement laser light emitted from a laser length measurement system 122 arranged outside the examination room 103 is arranged. 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. The electron beam column 102 and the inspection chamber 103 are evacuated by a vacuum pump (not shown) to form a vacuum state.

  In the control system circuit 160, a control computer 110 that controls the entire inspection apparatus 100 is connected via a bus 120 to 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 blanking. The control circuit 126, deflection control circuit 128, retarding control circuit 129, gas control circuit 132, storage device 109 such as a magnetic disk device, monitor 117, memory 118, and printer 119 are connected.

  The chip pattern memory 123 is connected to the comparison circuit 108. The XY 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 is configured, and the XY stage 105 is movable. As these X motor, Y motor, and θ motor (not shown), for example, step motors can be used. The XY stage 105 can be moved in the horizontal direction and the rotation direction by motors of XYθ axes. The moving position of the XY stage 105 is measured by the laser length measurement system 122 and supplied to the position circuit 107. The laser length measurement system 122 receives the reflected light from the mirror 216, and measures the position of the XY stage 105 based on the principle of laser interferometry.

  A high voltage power supply circuit (not shown) is connected to the electron gun 201, and an acceleration voltage is applied from a high voltage power supply circuit between a filament (not shown) in the electron gun 201 and the extraction electrode (anode) together with a predetermined extraction electrode (Wernert). The electron group emitted from the cathode is accelerated by the application of the above voltage and the heating of the cathode at a predetermined temperature, and the electron beam 200 is emitted. The illumination lens 202, the reduction lens 205, the objective lens 207, and the projection lenses 224 and 226 are, for example, electromagnetic lenses, and are controlled by the lens control circuit 124. The beam separator 214 is also controlled by the lens control circuit 124. The collective blanking deflector 212 and the deflector 228 are each composed of an electrode group of at least two poles, and are controlled by the blanking control circuit 126. The main deflector 208 and the sub deflector 209 are each composed of an electrode group having at least four poles, and are controlled by a deflection control circuit 128. The electrode 220 is configured on a disk in which a through hole penetrating in the center is formed, and is controlled together with the substrate 101 by a retarding control circuit 129.

  Here, FIG. 1 shows a configuration necessary for explaining the first embodiment. The inspection apparatus 100 may normally have 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, a two-dimensional horizontal (x direction) m ₁ row × vertical (y direction) n ₁ stage (m ₁ , n ₁ is an integer of 2 or more) hole (opening) is formed in the molded aperture array substrate 203. ) 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 of a rectangle having the same size and shape. Alternatively, it may be a circle having the same outer diameter. When a part of the electron beam 200 passes through each of the plurality of holes 22, the multi-beam 20 is formed. Here, an example is shown in which two or more holes 22 are arranged in both horizontal and vertical directions (x and y directions), but the present invention is not limited to this. For example, one of the horizontal and vertical directions (x and y directions) may be a plurality of rows and the other may be only one row. Further, the arrangement of the holes 22 is not limited to the case where the horizontal and vertical directions are arranged in a grid pattern as shown in FIG. For example, the holes in the vertical direction (y direction) k-th row and the (k + 1) -th row may be arranged so as to be shifted in the horizontal direction (x direction) by a dimension a. Similarly, the holes in the vertical (y direction) k + 1-th row and the k + 2-th row may be arranged so as to be shifted in the horizontal direction (x direction) by a dimension b. Next, the operation of the image acquisition mechanism 150 in the inspection apparatus 100 will be described.

  The electron beam 200 emitted from the electron gun 201 (emission source) illuminates the entire shaped aperture array substrate 203 almost vertically by the illumination lens 202. As shown in FIG. 2, a plurality of rectangular holes 22 (openings) are formed in the molded aperture array substrate 203, and the electron beam 200 illuminates a region including all of the plurality of holes 22. Each part of the electron beam 200 irradiated to the positions of the plurality of holes 22 passes through the plurality of holes 22 of the shaped aperture array substrate 203, for example, a plurality of rectangular electron beams (multi-beams) 20a to 20a. 20d (solid line in FIG. 1) is formed.

The formed multi-beams 20a to 20d then form a crossover (C.O.), pass through a beam separator 214 arranged at the crossover position of the multi-beam 20, and then reduced by a reduction lens 205. , Proceed toward the central hole formed in the limiting aperture substrate 206. Here, when the entire multi-beams 20a to 20d are deflected collectively by the collective blanking deflector 212 disposed between the shaping aperture array substrate 203 and the reduction lens 205, the center of the limiting aperture substrate 206 is obtained. The position is deviated from the hole and is shielded by the limiting aperture substrate 206. On the other hand, the multi-beams 20a to 20d that have not been deflected by the collective blanking deflector 212 pass through the central hole of the limiting aperture substrate 206 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 manner, the limiting aperture substrate 206 shields the multi-beams 20a to 20d deflected so as to be in the beam OFF state by the collective blanking deflector 212. Then, the inspection multi-beams 20a to 20d are formed by the beam group that has passed through the limiting aperture substrate 206 formed from when the beam is turned on to when the beam is turned off. The multi-beams 20a to 20d that have passed through the limiting aperture substrate 206 are focused on the surface of the substrate 101 by the objective lens 207, and images the multi-beams 20a to 20d (electron beams) on the substrate 101. At this time, the multi-beams 20a to 20d become pattern images (beam diameters) having a desired reduction ratio, and the entire multi-beams 20 that have passed through the limiting aperture substrate 206 are collectively bundled in the same direction by the main deflector 208 and the sub-deflector 209. Then, the light is deflected, passes through the passage hole in the center of the electrode 220, and is irradiated to each irradiation position on the substrate 101 of each beam. In such a case, the main deflector 208 deflects the entire multi-beam 20 in a lump to the reference position of the mask die scanned by the multi-beam 20. When scanning is performed while continuously moving the XY stage 105, tracking deflection is further performed so as to follow the movement of the XY stage 105. Then, the sub-deflector 209 collectively deflects the entire multi-beam 20 so that each beam scans the corresponding area. The multi-beams 20 irradiated at a time are ideally arranged at a pitch obtained by multiplying the arrangement pitch of the plurality of holes 22 of the shaped aperture array substrate 203 by the desired reduction ratio (1 / a) described above. As described above, the electron beam column 102 irradiates the substrate 101 with a two-dimensional m ₁ × n _single multi-beam 20 at a time. A bundle of secondary electrons (multi-secondary electrons 300) including reflected electrons corresponding to each beam of the multi-beam 20 from the substrate 101 due to the irradiation of the multi-beam 20 on a desired position of the substrate 101 (FIG. 2). 1 dotted line) is emitted.

  The multi-secondary electrons 300 emitted from the substrate 101 are refracted toward the center of the multi-secondary electrons 300 by the objective lens 207 after passing through the passage hole of the electrode 220, and are formed on the limiting aperture substrate 206. Proceed toward the hole. The multi-secondary electrons 300 that have passed through the limiting aperture substrate 206 are refracted almost parallel to the optical axis by the reduction lens 205 and proceed to the beam separator 214.

  Here, the beam separator 214 generates an electric field and a magnetic field in a direction orthogonal to a direction orthogonal to the traveling direction (optical axis) of the multi-beam 20. The electric field exerts a force in the same direction regardless of the traveling direction of the electrons. In contrast, the 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 of the electron penetration. The multi-beam 20 (primary electron beam) that enters the beam separator 214 from the upper side cancels out the force due to the electric field and the force due to the magnetic field, and the multi-beam 20 goes straight downward. On the other hand, the force due to the electric field and the force due to the magnetic field both act in the same direction on the multi-secondary electrons 300 that enter the beam separator 214 from below, and the multi-secondary electrons 300 are bent obliquely upward. .

  The multi-secondary electrons 300 bent obliquely upward are projected onto the multi-detector 222 while being refracted by the projection lenses 224 and 226. The multi-detector 222 detects the projected multi-secondary electrons 300. The multi-detector 222 includes, for example, a diode-type two-dimensional sensor (not shown). Then, at the diode-type two-dimensional sensor position corresponding to each beam of the multi-beam 20, each secondary electron of the multi-secondary electrons 300 collides with the diode-type two-dimensional sensor to generate electrons, and secondary electrons. Image data is generated for each pixel described later. When the multi-detector 222 does not detect the multi-secondary electrons 300, the multi-secondary electrons 300 may be prevented from reaching the light receiving surface by blanking and deflecting the multi-secondary electrons 300 with the deflector 228.

  FIG. 3 is a diagram illustrating an example of a state between the objective lens and the substrate in the comparative example of the first embodiment. As shown in FIG. 3, in the comparative example of the first embodiment, the electron beam accelerated with high energy is decelerated immediately before entering the substrate (wafer) under vacuum, and the low energy emitted from the substrate is reduced. In order to accelerate the secondary electrons toward the detector, a retarding voltage is applied so that the substrate has a negative potential with respect to the objective lens. On the other hand, when the electron beam is irradiated onto the substrate, multi-secondary electrons are emitted as described above. Depending on the difference between the number of electrons emitted to the substrate and the number of electrons emitted from the substrate, the upper surface of the substrate is charged positively or negatively. In order to eliminate such a charging situation, gas or ion gas is supplied to the space between the objective lens and the substrate. However, the introduction of gas increases the pressure in the space between the objective lens and the substrate, which makes it easy to discharge in a retarding voltage environment. Therefore, due to the occurrence of such discharge, noise components are included in the multi-secondary electrons, and a highly accurate secondary electron image may not be obtained. If the degree of discharge increases, it will also lead to equipment failure. Therefore, in the first embodiment, such discharge is suppressed.

FIG. 4 is a cross-sectional view showing a configuration between the objective lens and the substrate in the first embodiment.
FIG. 5 is a top view seen from above the electrodes in the first embodiment. 4 and 5, in the first embodiment, an electrode 220 having a passage hole 221 through which multi-beams 20 a to 20 d (electron beams) pass is disposed between the substrate 101 and the objective lens 207. To do. The electrode 220 is formed using a conductive material. Alternatively, it is also preferable to form a thin film of a conductive material on the surface of the insulating material. Between the objective lens 207 and the electrode 220, a negative potential is applied to the electrode 220 with respect to the objective lens 207 by the power supply 130 disposed in the retarding control circuit 129. In the example of FIG. 4, a ground potential is applied to the objective lens 207 and a negative potential is applied to the electrode 220. Further, the retarding control circuit 129 controls the voltage so as not to discharge (voltage that does not induce discharge) between the electrode 220 and the substrate 101. For example, the same potential is applied to the electrode 220 and the substrate 101. Alternatively, it may be configured such that a voltage that does not induce discharge is applied between the electrode 220 and the substrate 101 by the power supply 131 disposed in the retarding control circuit 129. Needless to say, when the same potential is applied to the electrode 220 and the substrate 101, the power supply 131 is unnecessary.

As described above, the upper surface of the substrate 101 is positively or negatively charged depending on the difference between the number of electrons irradiated on the substrate 101 and the number of electrons emitted from the substrate 101. The sign of charging changes depending on the incident energy of the multi-beam 20 (electron beam). Therefore, under the control of the gas control circuit 132, a gas supply port 322 (supply unit) connected to a gas supply device 134 arranged outside the examination chamber 103 by a pipe (not shown) is connected between the substrate 101 and the electrode 220. The charged neutralizing gas is supplied. The charge neutralizing gas supplies positive or negative ion gas in accordance with the charged state of the upper surface of the substrate 101. However, the present invention is not limited to this, and non-ionized gas may be supplied as long as charging can be eliminated. For example, an inert gas such as nitrogen (N ₂ ) gas or argon (Ar) gas is preferably used. Alternatively, the atmosphere may be used. The charged neutralizing gas supplied between the substrate 101 and the electrode 220 passes between the substrate 101 and the electrode 220 and is connected to a vacuum pump (not shown) disposed outside the inspection chamber 103 by a pipe (not shown). The gas is recovered by the gas recovery port 324 and exhausted to the outside of the inspection chamber 103. The gas recovery port 324 recovers the charged neutralized gas without diffusing upward (or diffusing as much as possible) by differential exhaust with a pressure lower than the pressure in the inspection chamber 103. Further, as shown in FIG. 5, it is preferable that the gas supply port 322 and the gas recovery port 324 are arranged at positions facing each other with the substrate 101 and the electrode 220 interposed therebetween. As a result, the charge neutralization gas can be advanced in one direction from the gas supply port 322 to the gas recovery port 324, and the amount of gas leaking upward from the electrode 220 can be reduced. As described above, the gas supply port 322, the gas recovery port 324, and the electrode 220 constitute a differential exhaust mechanism. Further, it is preferable that the charging neutralization gas is supplied in a width size that allows the entire region of the substrate 101 exposed by the passage hole 221 at the center of the electrode 220 to be in contact with the charging neutralization gas. Thereby, charging of the region where the electron beam is irradiated and the secondary electrons are emitted during the period of irradiation with the electron beam can be eliminated.

  Here, the electrode 220 is formed on a disk, for example. However, it is not limited to this, and it may be a rectangle or a polygon. The electrode 220 is preferably formed with a size larger than that of the lower substrate 101. In other words, the electrode 220 is formed in a size that can cover the lower substrate 101 when viewed from above except for a part of the substrate 101 exposed by the passage hole 221, in other words, the substrate 101 is not exposed. It is preferable. With this configuration, it is possible to prevent the charged neutralizing gas flowing between the substrate 101 and the electrode 220 from diffusing upward. Further, it is possible to prevent a direct electric field from being formed between the substrate 101 and the objective lens 207.

FIG. 6 is a diagram showing the relationship between the discharge voltage and the product of the spatial distance and the pressure in the first embodiment. In FIG. 6, the vertical axis represents the discharge voltage (unit: AU: arbitration unit), and the horizontal axis represents the product of the spatial distance and pressure (unit: AU: arbitration unit). Further, the graph of FIG. 6 is a logarithmic graph. If the spatial distance L between the object (electrode) and the object (electrode) where the potential difference occurs is constant, the discharge voltage (discharge start voltage) when the gas pressure in the space between the object and the object is within a certain range. Obtains the minimum value (part A). In other words, when the space distance L between the objects causing the potential difference is constant, the discharge is most easily performed when the gas pressure in the space between the objects is within a certain range. It is known that the curve trajectory of such a graph shows almost the same tendency although it slightly differs depending on the gas species existing in the space (Paschen's law). Discharge can occur under conditions above the Paschen curve. In the comparative example shown in FIG. 3, when the spatial distance L2 between the objective lens and the substrate is constant, the gas pressure in the space between the objective lens and the substrate increases due to the gas supply, as shown by the arrow in FIG. , Approaching the condition near the minimum value. Therefore, discharge occurs between the objective lens (electrode) and the substrate (electrode). Therefore, in order to suppress the discharge, the discharge voltage can be kept high by reducing the condition on the left side of the Paschen curve near the minimum value (A portion), in other words, by reducing the product of the spatial distance L and the pressure P, It can be made difficult to discharge. Or it can make it hard to discharge by making the electric potential difference between electrodes smaller than discharge voltage. Or it can make it difficult to discharge by providing both of these conditions. Therefore, in the first embodiment, the inspection apparatus 100 is configured to satisfy the conditions for suppressing the discharge. Here, it is difficult to change the distance L2 between the objective lens 207 and the substrate 101 from the conditions of the electron optical system. Therefore, in Embodiment 1, as shown in FIG. 4, the electrode 220 is disposed between the object lens 207 and the substrate 101. Then, a gas is allowed to flow between the electrode 220 and the substrate 101. As a result, the pressure P2 between the electrode 220 and the substrate 101 rises, but the differential pumping mechanism suppresses (or reduces) gas leakage above the electrode 220, so that the objective lens 207 having a potential difference is generated. An increase in pressure P1 in the space between the electrodes 220 can be suppressed (or reduced). Therefore, the discharge between the objective lens 207 and the electrode 220 can be suppressed. Further, in the first embodiment, the distance L1 between the electrode 220 and the substrate 101 can be made sufficiently smaller than the distance L2 between the objective lens 207 and the substrate 101. Therefore, even when the pressure P2 between the electrode 220 and the substrate 101 increases, the product of the spatial distance L1 and the pressure P2 can be kept small. Therefore, a decrease in the discharge start voltage can be avoided, and the discharge between the electrode 220 and the substrate 101 can be suppressed. Further, in Embodiment 1, since the electrode 220 and the substrate 101 are controlled to have the same negative potential, there is substantially no potential difference between the electrode 220 and the substrate 101. Therefore, it is possible to make the discharge more difficult. In the above-described example, the electrode 220 and the substrate 101 are controlled to have the same negative potential. However, the present invention is not limited to this, and it is sufficient that the voltage between the electrode 220 and the substrate 101 can be controlled so as not to discharge.

  FIG. 7 is a diagram showing the relationship between gas pressure and electron scattering in the first embodiment. FIG. 7A to FIG. 7D show the scattering range of incident electrons due to the difference in gas pressure in the space when the spatial distance L is constant. 7A shows a case of 100 Pa, FIG. 7A shows a case of 10 Pa, FIG. 7A shows a case of 1 Pa, and FIG. 7A shows a case of 0.1 Pa. As shown in FIGS. 7A to 7D, the smaller the gas pressure, the smaller the collision between electrons and gas molecules, so the scattering range can be reduced. Similarly, the shorter the spatial distance L, the smaller the scattering range. In the first embodiment, for the distance between the objective lens 207 and the substrate 101 where it is difficult to reduce the distance L2, the pressure P1 is kept low, and the distance L1 between the electrode 220 and the substrate 101 at which the pressure P2 increases. Make it smaller. As a result, it is possible to form an environment in which the incident primary electron beam (multi-beam 20) does not collide with gas molecules in any space. As described above, according to the first embodiment, the scattering range of the primary electron beam (multi-beam 20) can be controlled to be small. Therefore, the scattered electrons that are noise components of the secondary electron image can be reduced. If the distance L1 between the electrode 220 and the substrate 101 can be reduced, the speed of the primary electron beam (multi-beam 20) colliding with the substrate 101 is reduced and the emitted secondary electrons (multi-secondary electrons 300) are reduced. ) Can be accelerated toward the multi-detector 222 side.

  Thus, in Embodiment 1, the charging of the substrate 101 can be suppressed without discharging, and the noise of the secondary electron image can be reduced. Therefore, a highly accurate secondary electron image can be obtained.

  FIG. 8 is a flowchart showing main steps of the inspection method according to the first embodiment. In FIG. 8, the inspection method in the first embodiment includes a voltage control step (S102), a gas supply step (S104), a measurement image acquisition step (S112), a division step (S114), and a reference image creation step ( A series of steps of S116), an alignment step (S120), and a comparison step (S122) are performed.

  As the voltage control step (S102), as described above, the retarding control circuit 129 is disposed between the substrate 101 placed on the XY stage 105 and the objective lens 207, and the multi-beam 20 (electron beam) is arranged at the center. ) Is formed, and a negative potential is applied to the electrode 220 with respect to the objective lens 207 and controlled to a voltage that does not discharge between the substrate 101 and the electrode 220. As described in FIG. 4, the power supply 130 in the retarding control circuit 129 applies a ground potential to the objective lens 207. Then, the same negative potential is applied to the electrode 220 and the substrate 101. The voltage applied between the electrode 220 and the substrate 101 and the objective lens 207 may be set as appropriate through experiments or the like.

  As the gas supply step (S104), the gas supply device 134 supplies the charged neutralizing gas between the substrate 101 and the electrode 220 via the gas supply port 322 as described above. The supply amount may be set according to the charge amount charged on the substrate 101.

  In the measurement image acquisition step (S112), the image acquisition mechanism 150 causes the substrate 101 to be irradiated with the multi-beam 20 (electron beam) focused on the substrate 101 using the objective lens 207. An image of the substrate 101 is acquired by detecting multi-secondary electrons 300 including reflected electrons emitted from the substrate 101. The operation of the image acquisition mechanism 150 operates as follows in addition to the contents described above.

FIG. 9 is a diagram showing an example of a plurality of chip regions formed on the semiconductor substrate in the first embodiment. In FIG. 9, a plurality of chips (wafer dies) 332 are formed in a two-dimensional array in an inspection region 330 of a semiconductor substrate (wafer) 101. A mask pattern for one chip formed on the exposure mask substrate is transferred to each chip 332 after being reduced to, for example, ¼ by an exposure apparatus (stepper) (not shown). Each chip 332 is divided into, for example, a plurality of mask dies 33 each having two-dimensional horizontal (x direction) m ₂ rows × vertical (y direction) n ₂ stages (m ₂ and n ₂ are integers of 2 or more). The In the first embodiment, the mask die 33 is a unit inspection region.

  FIG. 10 is a diagram illustrating an example of a multi-beam irradiation region and a measurement pixel in the first embodiment. In FIG. 10, each mask die 33 is divided into a plurality of mesh regions in a mesh shape, for example, with a multi-beam beam size. Each mesh region is a measurement pixel 36 (unit irradiation region). In the example of FIG. 10, the case of 8 × 8 multi-beams is shown. The irradiation region 34 that can be irradiated by one irradiation of the multi-beam 20 is (the x-direction size obtained by multiplying the multi-beam 20 in the x-direction pitch between the beams in the x-direction) × (the multi-beam 20 in the y-direction. Y-direction size obtained by multiplying the pitch between beams by the number of beams in the y-direction). In the example of FIG. 10, the irradiation area 34 has the same size as the mask die 33. However, the present invention is not limited to this. The irradiation area 34 may be smaller than the mask die 33. Or it may be large. In the irradiation area 34, a plurality of measurement pixels 28 (beam irradiation positions at one shot) that can be irradiated by one irradiation of the multi-beam 20 are shown. In other words, the pitch between the adjacent measurement pixels 28 is the pitch between the beams of the multi-beam. In the example of FIG. 10, one sub-irradiation region 29 is configured by a square region that is surrounded by four adjacent measurement pixels 28 and includes one measurement pixel 28 among the four measurement pixels 28. In the example of FIG. 10, each sub-irradiation region 29 is configured with 4 × 4 pixels 36.

In the scanning operation in the first embodiment, scanning is performed for each mask die 33. In the example of FIG. 10, an example in which a certain mask die 33 is scanned is shown. When all the multi-beams 20 are used, m ₁ × n ₁ sub-irradiation regions 29 are arranged in the x and y directions (two-dimensionally) in one irradiation region 34. . The XY stage 105 is moved to a position where the first mask die 33 can be irradiated with the multi-beam 20. The main deflector 208 collectively deflects the entire multi-beam 20 to the reference position of the mask die 33 scanned by the multi-beam 20. At that position, the XY stage 105 is stopped, and the inside of the mask die 33 is scanned (scanning operation) using the mask die 33 as the irradiation region 34. When scanning is performed while continuously moving the XY stage 105, the main deflector 208 performs tracking deflection so as to follow the movement of the XY stage 105. Each beam constituting the multi-beam 20 is in charge of one of the different sub-irradiation areas 29. In each shot, each beam irradiates one measurement pixel 28 corresponding to the same position in the assigned sub-irradiation area 29. In the example of FIG. 10, each beam is deflected by the sub deflector 209 so as to irradiate the first measurement pixel 36 from the bottom right in the assigned sub irradiation region 29 in the first shot. Then, the first shot is irradiated. Subsequently, the sub-deflector 209 collectively shifts the entire multi-beam 20 in the y direction by one measurement pixel 36 and shifts the beam deflection position by the second measurement from the bottom in the assigned sub-irradiation region 29 in the second shot. The first measurement pixel 36 from the right is irradiated. Similarly, the third measurement pixel 36 from the right in the third row from the bottom in the assigned sub-irradiation region 29 is irradiated in the third shot. In the fourth shot, the first measurement pixel 36 from the right in the fourth row from the bottom in the assigned sub-irradiation region 29 is irradiated. Next, the sub-deflector 209 collectively shifts the entire multi-beam 20 and shifts the beam deflection position to the position of the second measurement pixel 36 from the bottom right, and similarly, the measurement pixel toward the y direction. 36 are sequentially irradiated. Such an operation is repeated, and all the measurement pixels 36 in one sub-irradiation region 29 are sequentially irradiated with one beam. In one shot, secondary electrons 300 corresponding to a plurality of shots having the same number as each hole 22 are detected at a time by the multi-beam formed by passing through each hole 22 of the shaped aperture array substrate 203. The

  As described above, the entire multi-beam 20 is scanned (scanned) using the mask die 33 as the irradiation region 34, but each beam scans one corresponding sub-irradiation region 29. When the scanning of one mask die 33 is completed, the next adjacent mask die 33 moves so as to be the irradiation region 34, and the next adjacent mask die 33 is scanned (scanned). Such an operation is repeated to advance scanning of each chip 332. Each time the multi-beam 20 is shot, secondary electrons 300 are emitted from the irradiated measurement pixel 36 and detected by the detector 222. In the first embodiment, the unit detection area size of the detector 222 detects the secondary electrons 300 emitted upward from each measurement pixel 36 for each measurement pixel 36 (or for each sub-irradiation area 29).

  As described above, scanning using the multi-beam 20 enables a scanning operation (measurement) at a higher speed than when scanning with a single beam. Note that each mask die 33 may be scanned by a step-and-repeat operation, or each mask die 33 may be scanned while the XY stage 105 is continuously moved. When the irradiation area 34 is smaller than the mask die 33, the scanning operation may be performed while moving the irradiation area 34 in the mask die 33.

  When the substrate 101 is an exposure mask substrate, the chip area for one chip formed on the exposure mask substrate is divided into a plurality of stripe areas in a strip shape with the size of the mask die 33 described above, for example. Then, each mask die 33 may be scanned for each stripe region by the same scanning as that described above. Since the size of the mask die 33 on the exposure mask substrate is the size before transfer, it is four times the size of the mask die 33 on the semiconductor substrate. Therefore, when the irradiation region 34 is smaller than the mask die 33 on the exposure mask substrate, the scanning operation for one chip increases (for example, four times). However, since the pattern for one chip is formed on the exposure mask substrate, the number of scans can be reduced as compared with a semiconductor substrate on which more than four chips are formed.

  As described above, the image acquisition mechanism 150 uses the multi-beam 20 to scan the inspection substrate 101 on which the graphic pattern is formed, and from the inspection substrate 101 due to the irradiation of the multi-beam 20. The emitted secondary secondary electrons 300 are detected. Detection data (secondary electron image) of secondary electrons from each measurement pixel 36 detected by the multi-detector 222 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, for example, at the stage where the detection data for one chip 332 is accumulated, it is transferred as chip pattern data to the comparison circuit 108 together with information indicating each position from the position circuit 107.

  FIG. 11 is an example of an internal configuration diagram illustrating a configuration in the comparison circuit according to the first embodiment. In FIG. 11, storage devices 50, 52, 56 such as a magnetic disk device, a division unit 54, an alignment unit 68, and a comparison unit 70 are arranged in the comparison circuit 108. Each “˜ unit” such as the division unit 54, the alignment unit 68, and the comparison unit 70 includes a processing circuit. The processing circuit includes an electric circuit, a computer, a processor, a circuit board, a quantum circuit, a semiconductor device, and the like. Is included. In addition, each “˜unit” may use a common processing circuit (the same processing circuit). Alternatively, different processing circuits (separate processing circuits) may be used. Necessary input data or calculated results in the dividing unit 54, the alignment unit 68, and the comparison unit 70 are stored in a memory (not shown) each time.

  FIG. 11 shows a configuration capable of performing both die-database inspection and die-die inspection. In the case where only the die-database inspection is performed, only the die-die inspection is performed, and the die-database inspection is not performed, the storage device 52 in the configuration of FIG. 11 and the reference image creation circuit 112 in FIG. . First, the die-database inspection will be described. The specific operation of the image acquisition mechanism 150 is as described above. Chip pattern data as an example of a measurement image is transferred to the comparison circuit 108 as described above. The data is stored in the storage device 50 in the comparison circuit 108.

  As a dividing step (S114), the dividing unit 54 divides the chip pattern data into a plurality of mask die images (an example of a measurement image) with the size of the mask die 33 serving as a unit inspection region. Each mask die image (an example of a measurement image) is stored in the storage device 56.

  As the reference image creation step (S116), the reference image creation circuit 112 performs the mask die 33 for each mask die 33 based on the design pattern data on which the pattern is formed on the substrate 101 or the exposure image data of the pattern formed on the substrate 101. Next, a reference image is created. Specifically, it operates as follows. First, design pattern data (exposure image 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.

  Here, the figure defined in the design pattern data is, for example, a rectangle or triangle as a basic figure. For example, the coordinates (x, y) at the reference position of the figure, the length of the side, a figure such as a rectangle or a triangle Stored is graphic data that defines the shape, size, position, etc. of each pattern graphic with information such as a graphic code serving as an identifier for distinguishing species.

When design pattern data as such graphic data is input to the reference image creation circuit 112, it is expanded to data for each graphic, and graphic codes, graphic dimensions, etc. indicating the graphic shape of the graphic data are interpreted. Then, it is developed into a binary or multi-value design pattern image data as a pattern arranged in a grid having a grid of a predetermined quantization size as a unit, and is output. In other words, the design data is read, the occupancy ratio of the figure in the design pattern is calculated for each grid formed by virtually dividing the inspection area as a grid with a predetermined size as a unit, and the n-bit occupancy data is calculated. Output. For example, it is preferable to set one square as one pixel. If a resolution of 1/2 ⁸ (= 1/256) is given to one pixel, 1/256 small areas are allocated by the figure area arranged in the pixel, and the occupation ratio in the pixel is set. Calculate. Then, it is output to the reference circuit 112 as 8-bit occupation ratio data. Such squares (inspection pixels) may be aligned with the pixels of the measurement data.

  Next, the reference image creation circuit 112 performs an appropriate filter process on the design image data of the design pattern, which is graphic image data. Since the optical image data as the measurement image is in a state in which the filter is applied by the optical system, in other words, in an analog state that continuously changes, the image intensity (light / dark value) is changed to the design image data that is the image data on the design side of the digital value. Also, it can be adjusted to the measurement data by applying the filtering process.

  When the exposure image data is stored as gradation data for each pixel, the exposure image data of the target mask die may be used as a reference image. If the exposure image data is graphic data in which the shape, size, position, etc. of each pattern graphic is defined by information such as coordinates (x, y), side length, and graphic code, the same as the above-described design pattern data A reference image may be created by a technique. The image data of the created reference image is output to the comparison circuit 108. In the comparison circuit 108, the image data of the reference image is stored in the storage device 52.

  As the alignment step (S120), the alignment unit 68 aligns the image of the mask die 33 (mask die image) serving as the measurement image and the reference image corresponding to the measurement image. The alignment is preferably performed by, for example, the least square method.

  As a comparison process (S122), the comparison unit 70 compares the measurement image and the reference image for each pixel. Both are compared for each pixel according to a predetermined determination condition using a predetermined determination threshold value, and the presence or absence of a defect such as a shape defect is determined. For example, if the gradation value difference for each pixel is larger than the determination threshold Th, it is determined as a defect. Then, the comparison result is output. The comparison result may be output to the storage device 109, the monitor 117, or the memory 118. Alternatively, it may be output from the printer 119.

  Alternatively, the contour lines of the graphic patterns in the images may be generated from the measurement image and the reference image, respectively, and the deviations between the contour lines of the matching graphic patterns may be compared. For example, if the deviation between the contour lines is larger than the determination threshold Th ′, it is determined as a defect. Then, the comparison result is output. The comparison result may be output to the storage device 109, the monitor 117, or the memory 118. Alternatively, it may be output from the printer 119.

  Next, the case of performing die-die inspection will be described. In such a case, the image comparison compares, for example, images on the mask die 33.

  As the alignment step (S120), the alignment unit 68 reads from the storage device 56 the image of the mask die 33 (mask die image) (die 1) that becomes the inspection image and the image of the mask die 33 that becomes the reference image corresponding to the inspection image. (Mask die image) (Die 2) is read out, and both images are aligned. The alignment is preferably performed by, for example, the least square method.

  The content of the comparison step (S122) may be the same as the content described above. Then, the comparison result is output. The comparison result may be output to the storage device 109, the monitor 117, or the memory 118. Alternatively, it may be output from the printer 119.

  As described above, according to the first embodiment, the occurrence of discharge can be suppressed. Therefore, a highly accurate image can be acquired.

Embodiment 2. FIG.
In Embodiment 1 described above, the case where the charge neutralizing gas is caused to flow between the substrate 101 and the electrode 220 across the both ends of the substrate 101 in the diameter direction of the substrate 101 has been described, but the present invention is not limited to this. In the second embodiment, the case where the charged neutralizing gas is allowed to flow only in the central portion of the substrate 101 will be described. The configuration of the inspection apparatus 100 is the same as that in FIG. Further, the main steps of the inspection method are the same as those in FIG. Hereinafter, the contents other than those described in particular may be the same as those in the first embodiment.

FIG. 12 is a cross-sectional view showing a configuration between the objective lens and the substrate in the second embodiment.
FIG. 13 is a top view of electrodes in the second embodiment.
FIG. 14 is a right side view of the electrode according to the second embodiment. FIG. 14 corresponds to the view of arrow A in FIG.
In acquiring an image, the region on the substrate 101 that should be de-charged may be any region that includes the irradiable regions of the multi-beams 20a to 20d (electron beams) exposed by the passage holes 221 of the electrode 220. Therefore, in the second embodiment, as shown in FIGS. 12 to 14, for example, on a disk in which the passage 220 221 through which the multi-beams 20 a to 20 d (electron beams) pass is formed in the center. On the electrode plate 40, with the passage hole 221 sandwiched, the flow path 42 for flowing the charged neutralizing gas with the three-side surfaces other than the upper and lower surfaces and the inlet closed, and the three-way side surfaces other than the upper and lower surfaces and the outlet are closed And a flow path 44 through which the charged neutralizing gas flows. Then, a through groove 46 connected to the flow path 42 is formed in the electrode plate 40 at the back end of the flow path 42 in front of the passage hole 221 of the electrode plate 40. Similarly, a through groove 48 connected to the flow path 44 is formed in the electrode plate 40 at the end of the flow path 44 before the passage hole 221 of the electrode plate 40.

  The charged neutralized gas supplied from the gas supply port 322 (supply unit) passes through the flow path 42 (first flow path) in the electrode 220. Then, the charged neutralizing gas is supplied to the upper surface of the substrate 101 from the flow path 42 through the through groove 46 (supply port) in the vicinity of the passage hole 221 of the electrode plate 40. The charged neutralizing gas that has flowed through the multibeam 20a to 20d (electron beam) irradiation area of the substrate 101 exposed by the passage hole 221 of the electrode 220 is opposite to the through groove 46 across the passage hole 221. Then, it is recovered from the through groove 48 (recovery port). Then, the gas recovered from the through groove 48 (recovery port) passes through the flow path 44 (second flow path) in the electrode 220, is recovered by the gas recovery port 324, and is exhausted outside the inspection chamber 103. . When the charged neutralizing gas flows through the flow paths 42 and 44 whose upper and lower side surfaces are closed, it is possible to prevent the charged neutralized gas from diffusing upwards through the flow path. Furthermore, since no gas flows between the electrode plate 40 and the substrate 101 in the entire diametrical direction, the amount of charging neutralization gas leaking from the periphery of the electrode 220 can be greatly reduced.

  The electrode 220 is preferably formed to a size that can cover the lower substrate 101 when viewed from above except for a portion of the substrate 101 exposed by the passage hole 221, in other words, not to expose the substrate 101. This is the same as in the first embodiment. In the second embodiment, since no gas flows between the electrode plate 40 and the substrate 101 in the entire diameter direction, the distance L3 between the bottom surface of the electrode plate 40 and the top surface of the substrate 101 can be reduced. Therefore, since the conductance with respect to the gas between the electrode plate 40 and the substrate 101 can be reduced, the amount of the charge neutralizing gas leaking from the periphery of the electrode 220 can be further reduced. If the amount of gas leaking from the periphery of the electrode 220 can be reduced, an increase in the pressure P1 in the space between the objective lens 207 and the electrode 220 can be further suppressed, and the risk of discharge can be further reduced.

  In addition, in the example of FIG. 12, although the flow paths 42 and 44 are arrange | positioned on the electrode plate 40, it does not restrict to this. Although the conductance between the electrode plate 40 and the substrate 101 becomes large, the case where the flow paths 42 and 44 are arranged below the electrode plate 40 is not excluded.

  Further, as in Embodiment 1, the electrode 220 is formed using a conductive material or a thin film of a conductive material is formed on the surface of an insulating material. Between the objective lens 207 and the electrode 220, a negative potential is applied to the electrode 220 with respect to the objective lens 207 by the power supply 130 disposed in the retarding control circuit 129. The electrode 220 and the substrate 101 is the same as that of the first embodiment in that the retarding control circuit 129 is controlled so as to maintain a voltage that does not discharge.

  FIG. 15 is a top view of an electrode in a modification of the second embodiment. In the modification of the second embodiment, as shown in FIG. 15, an electrode plate on a disk, for example, having a passage hole 221 through which multi-beams 20 a to 20 d (electron beams) pass is formed at the center. The size of 40 is made smaller than the size of the substrate 101. Then, on the electrode plate 40 smaller than the size of the substrate 101, the passage 42, and the flow path 42 for flowing the charged neutralized gas with the three-side surfaces other than the upper and lower surfaces and the inlet closed, the upper and lower surfaces and the outlet And a flow path 44 through which the charged neutralized gas is closed with the other three-direction side surfaces closed. Then, a through groove 46 connected to the flow path 42 is formed in the electrode plate 40 at the back end of the flow path 42 in front of the passage hole 221 of the electrode plate 40. Similarly, a through groove 48 connected to the flow path 44 is formed in the electrode plate 40 at the end of the flow path 44 before the passage hole 221 of the electrode plate 40. In the modification of the second embodiment, the inlet of the channel 42 whose three-side surfaces other than the upper and lower surfaces and the inlet are closed is configured to be outside the outer periphery of the substrate 101. In other words, the flow path 42 extends from the outside of the outer periphery of the substrate 101 to the front of the passage hole 221. Similarly, the outlet of the flow path 44 whose three-side surfaces other than the upper and lower surfaces and the outlet are closed is configured to be outside the outer periphery of the substrate 101. In other words, the flow path 44 extends from the front of the passage hole 221 to the outside of the outer periphery of the substrate 101.

  In the example of FIG. 15, the charged neutralized gas supplied from the gas supply port 322 (supply unit) passes through the flow path 42 (first flow path) in the electrode 220. Then, the charged neutralizing gas is supplied to the upper surface of the substrate 101 from the flow path 42 through the through groove 46 (supply port) in the vicinity of the passage hole 221 of the electrode plate 40. The charged neutralizing gas that has flowed through the multibeam 20a to 20d (electron beam) irradiation area of the substrate 101 exposed by the passage hole 221 of the electrode 220 is opposite to the through groove 46 across the passage hole 221. Then, it is recovered from the through groove 48 (recovery port). Then, the gas recovered from the through groove 48 (recovery port) passes through the flow path 44 (second flow path) in the electrode 220, is recovered by the gas recovery port 324, and is exhausted outside the inspection chamber 103. . Thus, the gas flow is the same as in FIGS. However, even when the size of the electrode plate 40 is made smaller than the size of the substrate 101 by flowing the charged neutralizing gas through the flow paths 42 and 44 whose upper and lower side surfaces are closed, the charged neutralizing gas is passing through the flow path. It is possible to prevent the electrode 220 from being diffused upward. Furthermore, since no gas flows between the electrode plate 40 and the substrate 101 in the entire diametrical direction, the amount of leakage of the charged neutralizing gas from the periphery of the electrode 220 can be greatly reduced as in the case of FIGS. It is.

  In the example of FIG. 15, the substrate 220 is not covered by the electrode 220 (electrode plate 40), and many exposed portions are generated. Therefore, when a negative potential is applied to the electrode 220 and the substrate 101 with respect to the objective lens 207, a direct electric field is formed between the exposed portion of the substrate 101 and the objective lens 207. However, the region in which the pressure is increased by the gas is limited to the region that can be irradiated with the multi-beams 20a to 20d (electron beams) of the substrate 101 exposed by the passage hole 221 of the electrode 220. Therefore, a pressure increase in the space between the exposed portion of the substrate 101 and the objective lens 207 is suppressed. As a result, even if a direct electric field is formed between the exposed portion of the substrate 101 and the objective lens 207, the pressure condition does not induce discharge, and discharge can be avoided. Further, by reducing the distance L3 between the bottom surface of the electrode plate 40 and the top surface of the substrate 101, the conductance with respect to the gas between the electrode plate 40 and the substrate 101 can be reduced. ) The amount of leakage from the surroundings can be reduced. If the amount of gas leaking from the periphery of the electrode plate 40 can be reduced, an increase in the pressure P1 in the space between the objective lens 207 and the electrode 220 can be further suppressed, and the risk of discharge can be further reduced.

  As described above, according to the second embodiment, the possibility of occurrence of discharge can be further reduced as compared with the first embodiment.

Embodiment 3 FIG.
In Embodiment 3, a structure in which the electrode 220 of each of the above-described embodiments is formed using a material that can transmit light will be described.

  FIG. 16 is a cross-sectional view showing a configuration between the objective lens and the substrate in the third embodiment. In the example of FIG. 16, in the electrode 220, the substrate 41 on the disk is formed of a material that can transmit light (laser light) such as glass and quartz. If it is left as it is, it becomes an insulating substrate and cannot function as an electrode. Therefore, a thin film 43 is formed which covers the exposed surface of the substrate 41 with a conductive material such as mesa coat or ITO. The function as the electrode 220 is exhibited by the thin film 43 of the conductive material. With this configuration, in the inspection apparatus 100 according to the third embodiment, an optical lever type height displacement measuring device (Z sensor) that measures the height displacement of the substrate 101 can be arranged.

  In the example of FIG. 16, the case where the electrode 220 of the first embodiment is configured to transmit light is described. However, the electrode 220 of the second embodiment is configured to transmit light similarly. Also good.

  Other configurations of the inspection apparatus 100 according to the third embodiment are the same as those in FIG. Further, the main steps of the inspection method are the same as those in FIG. Hereinafter, contents other than those specifically described may be the same as those in the first or second embodiment.

  The Z sensor has a projector 140 and a light receiver 144. The projector 140 and the light receiver 144 are disposed on the inspection chamber 103 or in the inspection chamber 103 with the electron beam column 102 interposed therebetween. In FIG. 15, when laser light 143 is output from the oblique direction with an angle θ toward the surface of the substrate 101 by the projector 140, the laser light 143 passes through the electrode 220 and is irradiated onto the surface of the substrate 101 from the oblique direction with the angle θ. Is done. The laser beam 143 irradiated on the surface of the substrate 101 is reflected from the substrate 101 at an angle θ, and the reflected light of the laser beam 143 is output. The reflected light passes through the electrode 220 and enters the light receiver 144 from an oblique direction with an angle θ, and is received. Here, when the surface of the substrate 101 is displaced by Δz in the height direction, the laser beam 143 irradiated from the same position hits the substrate 101 by a displacement x before the previous time, and is reflected from the substrate 101 at an angle θ, Reflected light is output. Therefore, before and after the height position of the surface of the substrate 101 is displaced by Δz, the optical axis (center of gravity) of the reflected light is displaced by ΔL in a direction orthogonal to the optical axis. Therefore, the height displacement Δz of the substrate 101 can be calculated by measuring the distance ΔL between the centers of gravity of the optical axes with a sensor (not shown) in the light receiver 144 in a state where the incident angle θ of light is fixed in advance.

  As described above, according to the third embodiment, in addition to the effects of the first or second embodiment, the height displacement of the substrate 101 can be measured by the optical lever principle.

  In the above description, a series of “˜circuit” 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 device. Further, a common processing circuit (the same processing circuit) may be used for each “˜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, and the like may be configured by at least one processing circuit described above.

  The embodiments have been described above with reference to specific examples. However, the present invention is not limited to these specific examples. In the electrode 220 of Embodiment 2 described above, the flow paths 42 and 44 are formed on one electrode plate 40, but the present invention is not limited to this. For example, a flow path may be formed in a space sandwiched between two electrode plates. Or you may utilize the inside of the electrode plate of a hollow structure as a flow path.

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

  In addition, all pattern inspection methods and pattern inspection apparatuses that include the elements of the present invention and that can be appropriately modified by those skilled in the art are included in the scope of the present invention.

20 Multibeam 22 Hole 28 Pixel 29 Sub irradiation region 33 Mask die 34 Irradiation region 36 Pixel 40 Electrode plate 41 Substrate 42, 44 Channel 43 Thin film 46, 48 Through groove 50, 52, 56 Storage device 54 Dividing unit 68 Positioning unit 70 Comparison unit 100 Inspection device 101 Substrate 102 Electron beam column 103 Inspection room 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 measurement Long system 123 Chip pattern memory 124 Lens control circuit 126 Blanking control circuit 128 Deflection control circuit 129 Retarding control circuit 130, 131 Power supply 132 Gas control circuit 134 Gas supply device 140 Projector 142 Step 143 Drive mechanism 143 Light 144 Light receiver 150 Image acquisition mechanism 160 Control system circuit 200 Electron beam 201 Electron gun 202 Illumination lens 203 Molding aperture array substrate 205 Reduction lens 206 Restriction aperture substrate 207 Objective lens 208 Main deflector 209 Sub deflector 212 Collective Blanking deflector 214 Beam separator 216 Mirror 220 Electrode 221 Passing hole 222 Multi detectors 224 and 226 Projection lens 228 Deflector 300 Secondary electron 322 Gas supply port 324 Gas recovery port 330 Inspection region 332 Chip

Claims (5)

A stage on which a substrate is placed;
An objective lens for imaging an electron beam on the substrate;
Disposed between the substrate and the objective lens, a passage hole through which the electron beam passes is formed in the center, and a negative potential is applied to the objective lens and no discharge occurs between the substrate and the substrate. An electrode maintained at a voltage;
A supply unit for supplying a gas between the substrate and the electrode;
A detector for detecting secondary electrons including reflected electrons emitted from the substrate due to the electron beam being applied to the substrate;
An electron beam image acquisition apparatus comprising: The electrode includes
A first flow path in the electrode through which the gas passes;
A supply port for supplying the gas from the first flow path to the substrate in the vicinity of the passage hole;
The supply port is a recovery port for recovering the gas supplied to the substrate in the vicinity of the opposite side of the passage hole across the passage hole,
A second flow path in the electrode through which the gas recovered from the recovery port passes;
The electron beam image acquisition apparatus according to claim 1, wherein:   3. The electron beam image acquisition apparatus according to claim 1, wherein the electrode is made of a material that can transmit light.   The electron beam image acquisition apparatus according to claim 1, wherein the electron beam image acquisition apparatus acquires an image of the substrate using a single beam or a multi-beam as the electron beam. A through hole is formed between the substrate placed on the stage and the objective lens, through which an electron beam passes at the center, and a negative potential is applied to the electrode using the electrode. And controlling the voltage so as not to discharge between the substrate and the electrode,
Supplying a gas between the substrate and the electrode;
Secondary electrons including reflected electrons emitted from the substrate due to irradiation of the electron beam focused on the substrate using the objective lens are detected, and Acquiring an image;
An electron beam image acquisition method comprising: