JP2021061096A - Electron gun and electron beam irradiation device - Google Patents

Abstract

PURPOSE: To provide an electron gun that enables efficient baking in the gun and suppresses discharge due to electric field concentration in the gun.CONSTITUTION: An electron gun 201 includes a cathode 10 that radiates an electron beam, multi-stage electrodes 16, 18, 19, 23, 24, 25 arranged in the direction of a central axis of the electron beam, a shield 26 surrounding the multi-stage electrodes, a lamp heater 27 arranged on an inner wall side of the shield, and a conductive half-opening shield 28 arranged between the multi-stage electrodes and the heater to surround the multi-stage electrodes and having a plurality of openings.SELECTED DRAWING: Figure 1

Description

The present invention relates to an electron gun and an electron beam irradiator. For example, the present invention relates to an electron gun in which an electron beam is emitted by passing a heater through a plurality of stages of electrodes arranged in the vicinity, and an electron beam irradiation device using the electron gun.

In recent years, with the increasing integration and capacity of large-scale integrated circuits (LSIs), the circuit line width required for semiconductor elements has become narrower and narrower. Further, improvement of the yield is indispensable for manufacturing an LSI, which requires a large manufacturing cost. However, as represented by 1 gigabit class DRAM (random access memory), the patterns constituting the LSI are on the order of submicron to nanometer. In recent years, with the miniaturization of LSI pattern dimensions formed on semiconductor wafers, the dimensions that must be detected as pattern defects have become extremely small. Therefore, it is required to form an ultrafine pattern on the semiconductor wafer or the exposure mask for transferring the pattern to the semiconductor wafer. Similarly, it is required to inspect the defects of the ultrafine pattern transferred on the semiconductor wafer or the exposure mask. An electron beam having a short wavelength is effective for forming an ultrafine pattern on a semiconductor wafer or an exposure mask. Similarly, an electron beam is also effective for inspecting defects in an ultrafine pattern transferred onto a semiconductor wafer or an exposure mask.

An electron gun is used as an electron source for irradiating such an electron beam. Inside the electron gun, for example, a Schottky type emitter is used. For example, a Schottky type electron gun that emits a multi-beam has been studied (see, for example, Non-Patent Document 1). The electrons emitted from the emitter using the Schottky effect are drawn out by the extractor (extracting electrode) while being suppressed by the suppressor, and are accelerated and focused by the multi-stage electrode. Here, although not limited to the Schottky type, a high vacuum is required around the emitter when emitting electrons in the electron gun. To that end, baking an electron gun is performed. In order to bake efficiently, it is desirable to arrange a built-in type heater in the vicinity of the emitter arranged in the vacuum vessel. However, there is a problem that discharge due to electric field concentration may occur between a multi-stage electrode including a suppressor and an extractor arranged in a vacuum vessel and a built-in type heater.

Ali Mohammadi-Gheidari, 196 Beams in a Scanning Electron Microscope, November 2013, TU Delft

Therefore, one aspect of the present invention provides an electron gun and an electron beam irradiation device that can be efficiently baked in an electron gun and can suppress discharge due to electric field concentration in the electron gun.

The electron gun of one aspect of the present invention is
A source that emits an electron beam and
Multi-stage electrodes arranged in the direction of the central axis of the electron beam,
A shield that surrounds the electrodes in multiple stages,
The heater placed on the inner wall side of the shield and
A conductive tubular body arranged between the multi-stage electrode and the heater so as to surround the multi-stage electrode and having a plurality of openings formed therein.
It is characterized by being equipped with.

Further, it is preferable that the tubular body is controlled to have the same potential as the shield.

Further, it is preferable to further include a molded aperture array substrate in which a plurality of passage holes are formed and a part of the electron beam passes through the plurality of passage holes to form a multi-beam.

Further, it is preferable that a far-infrared heater is used as the heater.

Further, it is preferable that the plurality of openings are formed in either a net shape or a punched shape.

Further, it is preferable that the tubular body is electrically connected to the shield.

The electron beam irradiation device according to one aspect of the present invention is
With the electron gun mentioned above,
The stage on which the sample is placed and
An electron optical system that irradiates a sample with an electron beam emitted from an electron gun,
It is characterized by being equipped with.

According to one aspect of the present invention, baking can be efficiently performed in the electron gun, and discharge due to electric field concentration in the electron gun can be suppressed.

It is a block diagram which shows an example of the structure of the electron gun in Embodiment 1. FIG. It is a figure which shows the structure of the electron gun by the comparative example of Embodiment 1. FIG. It is a figure which shows an example of the half-opening shield in Embodiment 1. FIG. It is a figure which shows another example of the half-opening shield in Embodiment 1. FIG. It is a graph which shows an example of the electric field attenuation rate by a shield in Embodiment 1. FIG. It is a figure which shows an example of the plurality of chip regions formed on the semiconductor substrate in Embodiment 1. FIG. It is a figure which shows an example of the plurality of chip regions formed on the semiconductor substrate in Embodiment 1. FIG. It is a figure for demonstrating the scanning operation of the multi-beam in Embodiment 1. FIG. It is a block diagram which shows an example of the structure in the comparison circuit in Embodiment 1. FIG.

Hereinafter, in the embodiment, an inspection device using an electron beam will be described as the electron beam irradiation device. However, it is not limited to this. The electron beam irradiating device may be, for example, a device such as a drawing device that irradiates the target substrate or the like with an electron beam emitted from an electron gun. Further, the electron beam may be a single beam or a multi-beam.

Embodiment 1.
FIG. 1 is a configuration diagram showing an example of the configuration of the electron gun according to the first embodiment. In FIG. 1, the electron gun 201 according to the first embodiment has a cathode 10 as an emitter, a suppressor 12, an extractor 14 (drawer electrode), and a plurality of stages of electrodes 16, 18, 19, 23, 24 in a vacuum vessel 11. , 25, shield 26, lamp heater 27, and half-opening shield 28 are arranged. Further, a heater 31 is separately arranged around the vacuum container 11. In the example of FIG. 1, as the electron gun 201, for example, an example of a Schottky type electron gun is shown.

The cathode 10, suppressor 12, extractor 14, and multi-stage electrodes 16, 18, 19, 23, 24, 25 are non-contactly supported by a laminated holder 13 made of an insulating material such as ceramic. The cathode 10, suppressor 12, extractor 14, and multi-stage electrodes 16, 18, 19, 23, 24, 25 as a whole supported by the stacking holder 13 in a state of being stacked / arranged in the central axis direction of the electron beam 200. An electron gun stack is constructed. Further, as the cathode 10, for example, it is preferable to use a ZrO / W emitter in which a tungsten (W) <100> single crystal is coated with zirconium oxide (ZrO).

An opening through which the electron beam 200 can pass is formed in the central portion of the suppressor 12, the extractor 14, and the electrodes 16, 18, 19, 23, 24, and 25 in a plurality of stages, respectively. The suppressor 12, the extractor 14, and the multi-stage electrodes 16, 18, 19, 23, 24, 25 are formed of a conductive material. For example, it is made of a metal material. Alternatively, the surface of the insulating material may be coated with a conductive material. The suppressor 12, the extractor 14, and the multi-stage electrodes 16, 18, 19, 23, 24, 25 are composed of, for example, disc-shaped electrodes. However, the shapes of the suppressor 12, the extractor 14, and the electrodes 16, 18, 19, 23, 24, and 25 in the plurality of stages are not limited to the disc shape. Other shapes may be used.

The shield 26 is arranged so as to surround the suppressor 12, the extractor 14, and the multi-stage electrodes including the multi-stage electrodes 16, 18, 19, 23, 24, 25. The shield 26 is made of a conductive material. For example, it is made of a metal material. Alternatively, the surface of the insulating material may be coated with a conductive material. In FIG. 1, for the sake of simplified illustration, the side surface is connected at a right angle to the bottom surface, but at least the inner surface side is connected by a gentle curved surface in order to avoid electric field concentration. The upper end of the shield 26 is connected to and supported by, for example, the laminated holder 13.

A lamp heater 27 (an example of a far-infrared heater) is arranged on the inner wall side of the shield 26. In the example of FIG. 1, a plurality of (for example, three) lamp heaters 27 are arranged. Each lamp heater 27 goes around along the inner wall surface of the shield 26. Alternatively, it is preferable that one lamp heater 27 is arranged in a spiral shape.

The semi-opening shield 28 (cylindrical body) is formed between the suppressor 12, the extractor 14, and the multi-stage electrode including the multi-stage electrodes 16, 18, 19, 23, 24, 25 and the lamp heater 27. It is arranged so as to surround the multi-stage electrode including 12, the extractor 14, and the multi-stage electrodes 16, 18, 19, 23, 24, 25. The half-opening shield 28 is formed in a tubular shape with a thickness of, for example, about 200 to 500 μm. Depending on the outer diameter shape of the multi-stage electrodes including the suppressor 12, the extractor 14, and the multi-stage electrodes 16, 18, 19, 23, 24, 25, the shape may be cylindrical or square cylinder. There may be. When it is formed in a square tube shape, it is preferable to bend the corner portion by a gentle curved surface such as an arc shape without bending it at an acute angle. The semi-opening shield 28 is made of a conductive material. For example, it is made of a metal material such as titanium (Ti) or stainless steel (SUS steel material). Alternatively, the surface of the insulating material may be coated with a conductive material. A plurality of openings are formed in the half-opening shield 28.

The electron gun 201 is controlled by a high voltage power supply circuit (not shown). When the acceleration voltage (for example, -15 kV) from the high-voltage power supply circuit is applied to the cathode 10, the electron beam 200 emitted from the cathode 10 (emission source) by utilizing the Schottky effect is biased from the high-voltage power supply circuit. While the spread is suppressed by the suppressor 12 to which the potential (for example, -15.5 kV) is applied, the extractor 14 (extract electrode) to which the withdrawal potential (for example, -10 kV) is applied from the high-voltage power supply circuit draws out. Then, the extracted electron beam 200 travels toward the electrodes 16, 18, 19, 23, 24, 25 in a plurality of stages. A desired control potential (for example, -4 kV) is applied to the electrode 16 from the high voltage power supply circuit. A desired control potential (for example, -10.5 kV) is applied to the electrode 18 from the high voltage power supply circuit. A desired control potential (for example, -13 kV) is applied to the electrode 19 from the high voltage power supply circuit. A desired control potential (for example, -13 kV) is applied to the electrode 23 from the high voltage power supply circuit. A desired control potential (for example, -11.5 kV) is applied to the electrode 24 from the high voltage power supply circuit. A desired control potential (for example, −9 kV) is applied to the electrode 25 from the high voltage power supply circuit. The electron beam 200 is expanded and decelerated by the electric fields of the electrodes 16, 18 and 19, and is refracted so as to change its direction in the focusing direction by the electric field provided by the electrodes 23. Then, the multi-primary electron beam 20 that has passed through the electrodes 23 is further focused while being accelerated by the electric field provided by the electrodes 24 and 25, and is emitted from the electron gun 201.

A desired potential (for example, -15.5 kV) is applied to the shield 26 from the high voltage power supply circuit. Here, for example, the same potential as the control potential of the suppressor 12 having the largest absolute value is applied. This suppresses, for example, corona discharge from each electrode to which a high voltage potential is applied.

Here, a high vacuum is required to emit the electron beam 200 from the cathode 10. Therefore, the inside of the vacuum vessel 11 is evacuated by a vacuum pump (not shown). However, if only evacuation is performed by a vacuum pump, the degree of vacuum decreases because the molecules adsorbed when the temperature near the cathode 10 is low are gasified by the heating of the cathode 10. Therefore, before irradiating the electron beam 200, the inside of the vacuum vessel 11 is evacuated by the vacuum pump and the inside of the vacuum vessel 11 is baked by the heater 31 from the outside of the vacuum vessel 11. Heating by the heater 31 is difficult to bake sufficiently to transfer heat to the electron gun stack by heat conduction. Therefore, the lamp heater 27 is arranged on the inner wall surface of the shield 26, and heat is transferred to the electron gun stack, particularly the vicinity of the cathode 10, by radiant heat by far infrared rays. As a result, baking can be performed efficiently.

FIG. 2 is a diagram showing a configuration of an electron gun according to a comparative example of the first embodiment. In the electron gun in the comparative example of the first embodiment, a cathode, a suppressor, an extractor, a shield, and a lamp heater are arranged in a vacuum container. A heater is arranged on the outside of the vacuum vessel. A plurality of stages of electrodes may be arranged under the extractor. In the comparative example of FIG. 2, a lamp heater is arranged on the inner wall surface of the shield as in the case described above, and heat is transferred to the electron gun stack, particularly near the cathode, by radiant heat from far infrared rays. As a result, baking can be performed efficiently. However, if a protrusion or the like is present in the parts constituting the lamp heater, when a high potential is applied to the suppressor and the extractor, the space between the suppressor or the extractor and the protrusion of the built-in type lamp heater There was a problem that a discharge was generated due to the concentration of the electric field. When a discharge occurs, the potential applied to the suppressor or extractor becomes unstable. As a result, it affects the orbit of the electron beam. Therefore, it is necessary to suppress the concentration of electrodes in the vacuum vessel. In a space where the installation space in the vacuum vessel is limited, it is difficult to increase the distance between the extractor and the built-in type lamp heater to a sufficient distance where electric discharge does not occur.

Therefore, in the first embodiment, as shown in FIG. 1, a plurality of stages of electrodes including a suppressor 12, an extractor 14, and a plurality of stages of electrodes 16, 18, 19, 23, 24, 25 and a lamp heater 27 are provided. A semi-opening shield 28 is placed between them. Then, the half-opening shield 28 is controlled to have the same potential as the shield 26. When, for example, a potential of -15.5 kV is applied to the shield 26, the same potential (for example, -15.5 kV) is also applied to the half-opening shield 28 from the high-voltage power supply circuit. Alternatively, it is preferable to electrically connect the half-opening shield 28 and the shield 26 without applying the voltage from the high-voltage power supply circuit. In the example of FIG. 1, the lower end of the half-opening shield 28 is connected (shorted) to the shield 26 to have the same potential. As a result, there is no potential difference between the half-opening shield 28 and the shield 26. Therefore, even if there is a protrusion or the like in the parts constituting the lamp heater 27 arranged between the half-opening shield 28 and the shield 26, there is no potential difference, so that discharge can be avoided. Further, there is no problem even if the half-opening shield itself is heated.

FIG. 3 is a diagram showing an example of a half-opening shield according to the first embodiment.
FIG. 4 is a diagram showing another example of the half-opening shield according to the first embodiment. As shown in FIG. 3, the half-opening shield 28 is formed in a net-like cylinder, and a plurality of net-like openings 17 are formed. Alternatively, as shown in FIG. 4, it is preferable that a plurality of punched openings 15 are formed on the outer peripheral surface of the half-opening shield 28, for example, by punching. By forming these plurality of openings 17 (or 15), the radiant heat from the lamp heater 27 can be transferred to the electron gun stack arranged inside the half-opening shield 28. Therefore, the heat from the lamp heater 27 is transferred to the electron gun stack, particularly in the vicinity of the cathode 10, by radiant heat by far infrared rays. As a result, baking can be performed efficiently.

FIG. 5 is a graph showing an example of the electric field attenuation factor due to the shield in the first embodiment. In FIG. 5, the vertical axis shows the attenuation rate, and the horizontal axis shows the arrangement pitch of the openings. The example of FIG. 5 shows a case where an opening mesh knitted in a net shape using a 1 mmφ stainless steel wire is formed on a shield plate. As shown in FIG. 5, for example, in order to attenuate the electric field strength to 1/10, it can be seen that 1 mmφ stainless steel wires may be arranged at a pitch of about 2 mm. In other words, in order to attenuate the electric field strength to 1/10 or less, it can be seen that the aperture ratio should be 50% or less. Therefore, if the aperture ratio of the opening formed in the half-opening shield 28 is 50% or less, a potential different from that of the shield 26 is applied even when the opening is formed in the half-opening shield 28. The electric field generated between the extractor 14 and the multi-stage electrodes including the multi-stage electrodes 16, 18, 19, 23, 24, 25 can be sufficiently attenuated. Therefore, even when an opening is formed in the half-opening shield 28, the discharge can be suppressed.

By arranging the half-opening shield 28 as described above, the electron gun stack can be directly heated without generating an electric discharge between the electron gun stack and the lamp heater 27. Therefore, the degree of vacuum in the vicinity of the cathode 10 can be improved, and the life of the cathode 10 can be extended.

Next, an inspection device equipped with the electron gun 201 will be described.

FIG. 6 is a configuration diagram showing an example of the configuration of the pattern inspection device according to the first embodiment. In FIG. 6, the inspection device 100 for inspecting the pattern formed on the substrate is an example of the multi-electron beam inspection device. The inspection device 100 includes an image acquisition mechanism 150 (secondary electronic image acquisition mechanism) and a control system circuit 160. The image acquisition mechanism 150 includes an electron gun 201, an electron beam column 102 (electron lens barrel), and an examination room 103. The electron gun 201 is mounted on the electron beam column 102.

In the example of FIG. 6, the case where the molded aperture array substrate 21 is arranged on the electrode 19 in the electron gun 201 is shown. A plurality of through holes are formed in the molded aperture array substrate 21. Then, as will be described later, a part of the electron beam 200 passes through the plurality of passage holes to form the multi-beam 20.

In the electron beam column 102, an electromagnetic lens 205, a batch blanking deflector 212, a limiting aperture substrate 213, 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, and a multi-detector 222 are arranged. In the example of FIG. 6, the electromagnetic lens 205, the batch blanking deflector 212, the limiting aperture substrate 213, the electromagnetic lens 206, the electromagnetic lens 207 (objective lens), the main deflector 208, and the sub-deflector 209 are multi-primary electrons. A primary electron optical system that irradiates the substrate 101 with the beam 20 is configured. The electromagnetic lens 207, the beam separator 214, the deflector 218, and the electromagnetic lens 224 constitute a secondary electron optical system that irradiates the multi-detector 222 with the multi-secondary electron beam 300.

In the examination room 103, a stage 105 that can move at least in the XYθ direction is arranged. A substrate 101 (sample) to be inspected is arranged on the stage 105. The substrate 101 includes an exposure mask substrate and a semiconductor substrate such as a silicon wafer. When the substrate 101 is a semiconductor substrate, a plurality of chip patterns (wafer dies) are formed on the semiconductor substrate. When the substrate 101 is an exposure mask substrate, a chip pattern is formed on the exposure mask substrate. The chip pattern is composed of a plurality of graphic patterns. By exposing and transferring the chip pattern formed on the exposure mask substrate to the semiconductor substrate a plurality of times, a plurality of chip patterns (wafer dies) are formed on the semiconductor substrate. Hereinafter, the case where the substrate 101 is a semiconductor substrate will be mainly described. The substrate 101 is arranged on the stage 105, for example, with the pattern forming surface facing upward. Further, on the stage 105, a mirror 216 that reflects the laser beam for laser length measurement emitted from the laser length measuring system 122 arranged outside the examination room 103 is arranged. The multi-detector 222 is connected to the detection circuit 106 outside the electron beam column 102.

In the control system circuit 160, the control computer 110 that controls the entire inspection device 100 uses the high-voltage power supply circuit 121, the position circuit 107, the comparison circuit 108, the reference image creation circuit 112, the stage control circuit 114, and the lens control via the bus 120. It is connected to a circuit 124, a blanking control circuit 126, a deflection control circuit 128, a retarding high-voltage power supply circuit 130, a storage device 109 such as a magnetic disk device, a monitor 117, a memory 118, and a printer 119. Further, the deflection control circuit 128 is connected to a DAC (digital-to-analog conversion) amplifier 144, 146, 148. The DAC amplifier 146 is connected to the main deflector 208, and the DAC amplifier 144 is connected to the sub-deflector 209. The DAC amplifier 148 is connected to the deflector 218.

Further, the detection circuit 106 is connected to the chip pattern memory 123. The chip pattern memory 123 is connected to the comparison circuit 108. Further, the stage 105 is driven by the drive mechanism 142 under the control of the stage control circuit 114. In the drive mechanism 142, for example, a drive system such as a three-axis (XY−θ) motor that drives in the X direction, the Y direction, and the θ direction in the stage coordinate system is configured and can move in the XYθ direction. .. For these X motors, Y motors, and θ motors (not shown), for example, stepping motors can be used. Then, the moving position of the stage 105 is measured by the laser length measuring system 122 and supplied to the position circuit 107. The laser length measuring system 122 measures the position of the stage 105 by the principle of the laser interferometry method by receiving the reflected light from the mirror 216.

The electron gun 201 is controlled by the high voltage power supply circuit 121. The electromagnetic lens 205, the electromagnetic lens 206, the electromagnetic lens 207 (objective lens), the electromagnetic lens 224, and the beam separator 214 are controlled by the lens control circuit 124. Further, the batch blanking deflector 212 is composed of electrodes having two or more poles, and each electrode is controlled by a blanking control circuit 126 via a DAC amplifier (not shown). The sub-deflector 209 is composed of electrodes having four or more poles, and each electrode is controlled by the deflection control circuit 128 via the DAC amplifier 144. The main deflector 208 is composed of electrodes having four or more poles, and each electrode is controlled by a deflection control circuit 128 via a DAC amplifier 146. The deflector 218 is composed of electrodes having four or more poles, and each electrode is controlled by a deflection control circuit 128 via a DAC amplifier 146. Further, the substrate 101 is electrically insulated from the stage 105, and a retarding voltage optimum for inspection is applied from the retarding high-voltage power supply circuit 130.

Here, FIG. 6 describes a configuration necessary for explaining the first embodiment. The inspection apparatus 100 may usually have other necessary configurations.

As described above, desired potentials are applied from the high-voltage power supply circuit 121 to the cathode 10, the suppressor 12, the extractor 14, and the electrodes 16, 18, 19, 23, 24, and 25 in the plurality of stages, respectively. In the example of FIG. 6, the electron beam 200 emitted from the cathode 10 is extracted by the extractor 14 (extraction electrode) while being suppressed from spreading by the suppressor 12. Then, the extracted electron beam 200 is expanded and decelerated by the electric field formed by the electrodes 16 and 18, and is irradiated to a region including the entire plurality of passage holes formed in the molded aperture array substrate 21. Then, a part of the electron beam 200 passes through each of the plurality of passage holes to form the multi-primary electron beam 20. In the formed multi-primary electron beam 20, an intermediate image plane of each beam is formed at the height position of the next electrode 23 by the electric field (electric field) generated by the electrode 19, and the electric field provided by the electrode 23 forms an intermediate image plane in the focusing direction. It is refracted to turn around. Then, the multi-primary electron beam 20 that has passed through the electrodes 23 is further focused while being accelerated by the electric field provided by the electrodes 24 and 25, emitted from the electron gun 201, and advances into the electron beam column 102.

The multi-primary electron beam 20 emitted from the electron gun 201 and formed proceeds to the primary electron optics system, and the primary electron optics system is the multi-primary electron beam 20 (electron beam) emitted from the electron gun 201. Irradiates the substrate 101 with. Specifically, it operates as follows. The multi-primary electron beam 20 emitted from the electron gun 201 and formed is refracted by the electromagnetic lens 205 and the electromagnetic lens 206, respectively, to form a crossover and an intermediate image, and each of the multi-primary electron beams 20 is formed. It passes through the beam separator 214 arranged at the intermediate image plane (IP) position of the beam and proceeds to the electromagnetic lens 207 (objective lens). Then, the electromagnetic lens 207 focuses (focuses) the multi-primary electron beam 20 on the substrate 101. The multi-primary electron beam 20 focused (focused) on the surface of the substrate 101 (sample) by the electromagnetic lens 207 (objective lens) is collectively deflected by the main deflector 208 and the sub-deflector 209. Each beam is irradiated to each irradiation position on the substrate 101. When the entire multi-primary electron beam 20 is collectively deflected by the batch blanking deflector 212, the multi-primary electron beam 20 is displaced from the center hole of the limiting aperture substrate 213, and the limiting aperture 20 is displaced. It is shielded by the substrate 213. On the other hand, the multi-primary electron beam 20 not deflected by the batch blanking deflector 212 passes through the central hole of the limiting aperture substrate 213 as shown in FIG. By turning ON / OFF of the batch blanking deflector 212, blanking control is performed, and ON / OFF of the beam is collectively controlled. In this way, the limiting aperture substrate 213 shields the multi-primary electron beam 20 deflected so that the beam is turned off by the batch blanking deflector 212. Then, the multi-primary electron beam 20 for inspection (for image acquisition) is formed by the beam group formed from the time when the beam is turned on to the time when the beam is turned off and passed through the limiting aperture substrate 213.

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

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

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

The multi-secondary electron beam 300, which is bent obliquely upward and separated from the multi-primary electron beam 20, is further bent by the deflector 218 and projected onto the multi-detector 222 while being refracted by the electromagnetic lens 224. The multi-detector 222 detects the projected multi-secondary electron beam 300. Backscattered electrons and secondary electrons may be projected onto the multi-detector 222, or the backscattered electrons may be diverged on the way and the remaining secondary electrons may be projected. The multi-detector 222 has a two-dimensional sensor. Then, each secondary electron of the multi-secondary electron beam 300 collides with the corresponding region of the two-dimensional sensor to generate electrons, and secondary electron image data is generated for each pixel. In other words, in the multi-detector 222, a detection sensor is arranged for each primary electron beam of the multi-primary electron beam 20. Then, the corresponding secondary electron beam emitted by the irradiation of each primary electron beam is detected. Therefore, each detection sensor of the plurality of detection sensors of the multi-detector 222 detects the intensity signal of the secondary electron beam for the image caused by the irradiation of the primary electron beam 301 in charge of each. The intensity signal detected by the multi-detector 222 is output to the detection circuit 106.

FIG. 7 is a diagram showing an example of a plurality of chip regions formed on the semiconductor substrate according to the first embodiment. In FIG. 7, when the substrate 101 is a semiconductor substrate (wafer), a plurality of chips (wafer dies) 332 are formed in a two-dimensional array in the inspection region 330 of the semiconductor substrate (wafer). A mask pattern for one chip formed on an exposure mask substrate is transferred to each chip 332 by being reduced to, for example, 1/4 by an exposure device (stepper) (not shown). The region of each chip 332 is divided into a plurality of stripe regions 32 with a predetermined width in the y direction, for example. The scanning operation by the image acquisition mechanism 150 is performed, for example, for each stripe region 32. For example, while moving the stage 105 in the −x direction, the scanning operation of the stripe region 32 is relatively advanced in the x direction. Each stripe region 32 is divided into a plurality of multi-scan unit regions 33 in the longitudinal direction. The movement of the beam to the target multi-scan unit region 33 is performed by batch deflection of the entire multi-primary electron beam 20 by the main deflector 208.

FIG. 8 is a diagram for explaining a multi-beam scanning operation according to the first embodiment. In the example of FIG. 8, for example, the case of a multi-primary electron beam 20 in a 5 × 5 row is shown. The irradiation region 34 that can be irradiated by one irradiation of the multi-primary electron beam 20 is (the x-direction obtained by multiplying the x-direction beam-to-beam pitch of the multi-primary electron beam 20 on the substrate 101 surface by the number of beams in the x-direction. Size) × (size in the y direction obtained by multiplying the pitch between beams in the y direction of the multi-primary electron beam 20 on the surface of the substrate 101 by the number of beams in the y direction). It is preferable that the width of each stripe region 32 is set to a size similar to the y-direction size of the irradiation region 34 or narrowed by the scan margin. In the examples of FIGS. 7 and 8, the case where the irradiation area 34 has the same size as the multi-scan unit area 33 is shown. However, it is not limited to this. The irradiation area 34 may be smaller than the multi-scan unit area 33. Alternatively, it may be large. Then, each beam of the multi-primary electron beam 20 is irradiated in the sub-irradiation region 29 surrounded by the inter-beam pitch in the x direction and the inter-beam pitch in the y direction in which the own beam is located, and the sub-irradiation region 29 is irradiated. Scan inside (scan operation). Each primary electron beam 301 constituting the multi-primary electron beam 20 is in charge of any of the sub-irradiation regions 29 different from each other. Then, at each shot, each primary electron beam 301 irradiates the same position in the responsible sub-irradiation region 29. The movement of the primary electron beam 301 within the sub-irradiation region 29 is performed by batch deflection of the entire multi-primary electron beam 20 by the sub-deflector 209. This operation is repeated to sequentially irradiate the inside of one sub-irradiation region 29 with one primary electron beam 301. Then, when the scan of one sub-irradiation region 29 is completed, the main deflector 208 moves to the adjacent multi-scan unit region 33 in the stripe region 32 having the same irradiation position by batch deflection of the entire multi-primary electron beam 20. To do. This operation is repeated to irradiate the inside of the stripe region 32 in order. When the scan of one stripe region 32 is completed, the irradiation position is moved to the next stripe region 32 by the movement of the stage 105 and / and the collective deflection of the entire multi-primary electron beam 20 by the main deflector 208. As described above, the secondary electron images for each sub-irradiation region 29 are acquired by the irradiation of each primary electron beam 301. By combining the secondary electron images for each of the sub-irradiation regions 29, a secondary electron image of the multi-scan unit region 33, a secondary electron image of the stripe region 32, or a secondary electron image of the chip 332 is configured.

It is also preferable that, for example, a plurality of chips 332 arranged in the x direction are grouped into the same group, and each group is divided into a plurality of stripe regions 32 with a predetermined width in the y direction, for example. The movement between the stripe regions 32 is not limited to each chip 332, and may be performed for each group.

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

To acquire the image, as described above, the multi-primary electron beam 20 is irradiated, and the multi-secondary electron beam 300 emitted from the substrate 101 due to the irradiation of the multi-primary electron beam 20 is detected by the multi-detector 222. Detect with. The secondary electron detection data (measured image data: secondary electron image data: inspected image data) for each pixel in each sub-irradiation region 29 detected by the multi-detector 222 is output to the detection circuit 106 in the order of measurement. To. In the detection circuit 106, analog detection data is converted into digital data by an A / D converter (not shown) and stored in the chip pattern memory 123. Then, the obtained measurement image data is transferred to the comparison circuit 108 together with the information indicating each position from the position circuit 107.

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

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

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

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

FIG. 9 is a configuration diagram showing an example of the configuration in the comparison circuit according to the first embodiment. In FIG. 9, storage devices 50, 52, 56 such as a magnetic disk device, a frame image creation unit 54, an alignment unit 57, and a comparison unit 58 are arranged in the comparison circuit 108. Each "-part" such as the frame image creation unit 54, the alignment unit 57, and the comparison unit 58 includes a processing circuit, and the processing circuit includes an electric circuit, a computer, a processor, a circuit board, a quantum circuit, or a semiconductor. Devices and the like are included. Further, a common processing circuit (same processing circuit) may be used for each “~ part”. Alternatively, different processing circuits (separate processing circuits) may be used. The input data or the calculated result required in the frame image creation unit 54, the alignment unit 57, and the comparison unit 58 are stored in a memory (not shown) or a memory 118 each time.

In the first embodiment, the sub-irradiation region 29 acquired by the scanning operation of one primary electron beam 301 is further divided into a plurality of frame regions, and the frame region is used as a unit region of the image to be inspected. It is preferable that the frame regions are configured so that the margin regions overlap each other so that the image is not omitted. The frame region is set to, for example, a region having a size of 1/4 of the sub-irradiation region 29 obtained by dividing the sub-irradiation region 29 into two in the x and y directions.

In the comparison circuit 108, the transferred image data (image to be inspected) for each stripe area 32 is temporarily stored in the storage device 50. Similarly, the transferred reference image data is temporarily stored in the storage device 52 as a reference image for each frame area.

The frame image creation unit 54 reads image data from the storage device 50 and creates a frame image for each frame area. The created frame image is stored in the storage device 56.

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

The comparison unit 58 compares the frame image (secondary electronic image) with the reference image. In other words, the comparison unit 58 compares the reference image data and the frame image for each pixel. The comparison unit 58 compares the two for each pixel according to a predetermined determination condition, and determines the presence or absence of a defect such as a shape defect. For example, if the gradation value difference for each pixel is larger than the determination threshold value Th, it is determined as a defect. Then, the comparison result is output. The comparison result may be output to the storage device 109, the monitor 117, or the memory 118, or may be output from the printer 119.

In the above-mentioned example, the case where the die database inspection is performed has been described, but the present invention is not limited to this. It may be the case of performing a die-die inspection. A case of performing a die-die inspection will be described.

When performing a die-die inspection, the alignment unit 57 reads out the frame image of the die 1 and the frame image of the die 2 on which the same pattern is formed, and aligns both images in units of sub-pixels smaller than pixels. .. For example, the alignment may be performed by the method of least squares.

Then, the comparison unit 58 compares the frame image of the die 1 (the image to be inspected) with the frame image of the die 2 (the image to be inspected). The comparison unit 58 compares the two for each pixel according to a predetermined determination condition, and determines the presence or absence of a defect such as a shape defect. For example, if the gradation value difference for each pixel is larger than the determination threshold value Th, it is determined as a defect. Then, the comparison result is output. The comparison result is output to the storage device 109, the monitor 117, or the memory 118.

As described above, according to the first embodiment, it is possible to efficiently bake in the electron gun 201 and suppress the discharge due to the electric field concentration in the electron gun 201. Therefore, it is possible to prevent device troubles due to electric discharge and shorten the downtime of the inspection device 100.

In the above description, the series of "~ circuits" includes a processing circuit, and the processing circuit includes an electric circuit, a computer, a processor, a circuit board, a quantum circuit, a semiconductor device, and the like. Further, a common processing circuit (same processing circuit) may be used for each “~ circuit”. Alternatively, different processing circuits (separate processing circuits) may be used. The program for executing the processor or the like may be recorded on a recording medium such as a magnetic disk device, a magnetic tape device, an FD, or a ROM (read-only memory). For example, 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, and the deflection control circuit 128 are composed of at least one of the processing circuits described above. Is also good.

The embodiment has been described above with reference to a specific example. However, the present invention is not limited to these specific examples. In the example of FIG. 1, a case where a Schottky type cathode is used as the cathode 10 of the electron gun 201 has been described, but the present invention is not limited to this. For example, another cathode such as a thermal cathode may be used.

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

In addition, all electron guns and electron beam irradiators that have the elements of the present invention and can be appropriately redesigned by those skilled in the art are included in the scope of the present invention.

10 Cathode 11 Vacuum vessel 12 Suppressor 13 Laminated holder 14 Extractors 15, 17 Openings 16, 18, 19, 23, 24, 25 Electrodes 20 Multi-primary electron beam 21 Molded aperture array substrate 26 Shield 27 Lamp heater 28 Half-opening shield 29 Sub-irradiation area 31 Heater 32 Stripe area 33 Multi-scan unit area 34 Irradiation area 50, 52, 56 Storage device 54 Frame image creation unit 57 Alignment unit 58 Comparison unit 100 Inspection device 101 Substrate 102 Electron beam column 103 Inspection room 105 Stage 106 Detection circuit 107 Position circuit 108 Comparison circuit 109 Storage device 110 Control computer 112 Reference image creation circuit 114 Stage control circuit 117 Monitor 118 Memory 119 Printer 120 Bus 121 High-voltage power supply circuit 122 Laser length measurement system 123 Chip pattern memory 124 Lens control circuit 126 Blanking control circuit 128 Deflection control circuit 130 Returning high-voltage power supply circuit 142 Drive mechanism 144, 146,148 DAC amplifier 150 Image acquisition mechanism 160 Control system circuit 201 Electron gun 205, 206, 207, 224 Electromagnetic lens 208 Main deflector 209 Sub Deviator 212 Bulk Branking Deviator 213 Restriction aperture substrate 214 Beam separator 216 Mirror 218 Deviator 222 Multi detector 300 Multi secondary electron beam 301 Primary electron beam 330 Inspection area 332 Chip

Claims (7)

A source that emits an electron beam and
A plurality of stages of electrodes arranged in the direction of the central axis of the electron beam,
A shield surrounding the multi-stage electrodes and
The heater arranged on the inner wall side of the shield and
A conductive tubular body arranged between the plurality of stages of electrodes and the heater so as to surround the plurality of stages of electrodes and having a plurality of openings formed therein.
An electron gun characterized by being equipped with. The electron gun according to claim 1, wherein the tubular body is controlled to have the same potential as the shield. The first or second aspect of claim 1 or 2, wherein a plurality of passage holes are formed, and a molded aperture array substrate that forms a multi-beam by passing a part of the electron beam through the plurality of passage holes is further provided. Electronic gun. The electron gun according to any one of claims 1 to 3, wherein a far-infrared heater is used as the heater. The electron gun according to any one of claims 1 to 4, wherein the plurality of openings are formed in either a net shape or a punched shape. The electron gun according to any one of claims 1 to 5, wherein the tubular body is electrically connected to the shield. The electron gun according to any one of claims 1 to 6.
The stage on which the sample is placed and
An electron optical system that irradiates the sample with an electron beam emitted from the electron gun, and
An electron beam irradiation device characterized by being equipped with.

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