Optical filtering device and defect observation device

Abstract

The present invention provides a highly reliable optical filtering device capable of control whereby a desired opening angle, i.e., shutter aperture, can be obtained to allow light to pass through, without having the shutter come into contact with a wall surface of the shutter aperture even when the shutter opens. The optical filtering device comprises: a shutter 210 that can be opened and closed; a shutter aperture 238 that transmits light when the shutter 210 is open; an electrode 262 disposed in the normal direction when the shutter 210 is closed; wiring 261 that supplies a voltage to the electrode 262; and a wiring board 260 that includes the electrode 262 and the wiring 261, wherein when a potential difference is applied between the shutter 210 and the electrode 262, the shutter 210 opens in the direction of the electrode 262, and the distance (height H) between the shutter 210 and the wiring board 260 is such that the shutter 210 and the wiring board 260 do not come into contact when the shutter 210 opens in the direction of the electrode 262.

Description

Optical filtering device and defect observation apparatus

[0001] The present invention relates to an optical filtering device and a defect observation apparatus.

[0002] The defect observation device is equipped with a scanning electron microscope (SEM) or the like for reviewing, classifying, etc., various defects and foreign matter (hereinafter referred to as "defects, etc.") that occur on the surface of a wafer, which is a semiconductor substrate, in a semiconductor manufacturing line or the like.

[0003] It is desirable that the defect observation device further includes an optical microscope. The defect observation device has the function of controlling the optical microscope to efficiently and automatically detect defects on the wafer surface and perform coordinate alignment. By controlling the SEM, it is possible to observe the shape of minute defects detected by the optical microscope in detail and perform component analysis. It is desirable that the optical microscope be usable as a dark field optical microscope (DFOM).

[0004] In addition, the defect observation device has a function of automatically outputting SEM images, classification data of defects, etc., elemental analysis data, etc., and can also create a defect map from the output data. Furthermore, the defect observation device can also observe, classify, and analyze defects, etc. based on the created defect map. For this reason, the defect observation device is also called a review SEM. It is also called a defect review SEM or a wafer inspection SEM.

[0005] In the defect observation device, the optical microscope and the SEM share a common stage, and a wafer placed on this stage is observed with the optical microscope, the positions of detected defects, etc. are identified, and the defects, etc. are then observed with the SEM. For example, according to a defect map with an accuracy of several tens of μm measured by the defect inspection device, defects, etc. can be searched for within a range of several hundred nanometers using the dark-field microscope of the defect observation device, and the positions of the defects, etc. can be identified with an accuracy of several μm or less.

[0006] This allows for the correction of the deviation between the coordinate system of the defect map generated by the defect inspection device and that of the SEM, improving the success rate of defect observation and maintaining high throughput. Furthermore, in the manufacturing process of semiconductor devices, defects that cause defects such as poor insulation of wiring and short circuits can be detected early, their source identified, and yield reductions can be prevented.

[0007] In a dark-field microscope, pupil filters are required according to the type of defect, etc., and a shutter array consisting of a large number of minute shutters with dimensions of 1 mm or less is required to accommodate a wide variety of defects, etc. It is believed that a variety of spatial filters can be formed by opening and closing such shutters.

[0008] In defect detection using conventional dark-field optical systems that do not use such shutters, the spatial and polarization characteristics of scattered light from various defects at the pupil plane are utilized, and spatial and polarization filters are used to increase the possibility of distinguishing between defects and wafer roughness, which becomes detection noise.

[0009] Since the shape of the spatial filter that is advantageous for detection differs depending on the type of defect, etc., in order to improve the detection sensitivity for multiple types of defects, a shutter array consisting of an array of minute shutters is used, and a mechanism for individually switching the opening and closing of the shutters and a switching circuit for controlling the same are required.By using a shutter switching mechanism, it is possible to select the locations where the shutters are opened and closed, and multiple types of spatial filters can be configured.

[0010] Background art in this technical field includes, for example, technology such as that disclosed in Patent Document 1. Claim 1 of Patent Document 1 discloses "an optical filtering device comprising: a shutter array in which shutter patterns are formed in a two-dimensional arrangement on an optically opaque thin film formed on an SOI wafer, holes are formed by removing portions of the SOI wafer below the shutter patterns, and operating electrodes are formed in remaining portions of the SOI wafer; a glass substrate on whose surface electrode patterns are formed and on which the shutter array is mounted; and a power supply unit that supplies power to the electrode patterns formed on the glass substrate and the operating electrodes of the SOI wafer, wherein the power supplied from the power supply unit to the electrode patterns and the operating electrodes is controlled to open and close the two-dimensionally arranged shutter patterns relative to the holes, and the shutter patterns have protrusions at their edges."

[0011] International Publication No. 2012 / 105705

[0012] A shutter array device (optical filtering device) made of MEMS (Micro Electro Mechanical Systems) generally has a SiO ２ However, when the shutter is fully opened, static electricity and moisture in the air can cause the open shutter to stick to the wall of the shutter opening in the Si substrate, making it impossible to control the opening and closing of the shutter.

[0013] The above-mentioned Patent Document 1 discloses a structure in which the shutter opens toward the inside of the shutter opening as shown in FIG. 6A of Patent Document 1, but does not mention at all the problem of the shutter sticking to the Si substrate as described above or how to solve this problem.

[0014] Furthermore, when the shutter is fully opened, the stress generated in the rotatable beam supporting the shutter increases, shortening its lifespan when the shutter is repeatedly opened and closed.

[0015] Furthermore, in order to prevent the shutter from sticking to the wall of the shutter opening, a control method may be considered in which the shutter is not fully opened from the beginning, but is instead stopped in the space of the shutter opening.

[0016] However, in a shutter that is driven by electrostatic force due to a voltage applied to the shutter and the Si substrate, the degree to which the shutter opens varies depending on the potential difference between the shutter and the opening, i.e., the Si substrate, and as the shutter opens and approaches the wall of the shutter opening, the electric field strength acting on the shutter and the opening increases, causing pull-in, in which the shutter opens suddenly at a certain potential difference, making it difficult to keep the shutter stationary in the space of the shutter opening.

[0017] The problem to be solved by the present invention is to provide a highly reliable optical filtering device and defect observation apparatus that can be controlled to allow light to pass through at a desired opening angle, i.e., shutter opening, without coming into contact with the wall surface of the shutter opening even when the shutter is open.

[0018] In order to solve the above problem, the optical filtering device of the present invention comprises an openable / closable shutter, a shutter opening that transmits light when the shutter is open, an electrode arranged in the normal direction when the shutter is closed, wiring that supplies voltage to the electrode, and a wiring board having the electrode and the wiring, wherein when a potential difference is applied between the shutter and the electrode, the shutter opens in the direction of the electrode, and there is a distance between the shutter and the wiring board such that the shutter and the wiring board do not come into contact when the shutter opens in the direction of the electrode.

[0019] The defect observation apparatus of the present invention is characterized by including the above-mentioned optical filtering device.

[0020] According to the present invention, it is possible to realize a highly reliable optical filtering device and defect observation apparatus that can control the shutter to pass light at a desired opening angle, i.e., a desired shutter opening, without contacting the wall surface of the shutter opening even when the shutter is open.

[0021] Problems, configurations, and effects other than those described above will become apparent from the following description of the preferred embodiments of the invention.

[0022] 3A is a diagram showing a schematic configuration of a defect observation apparatus of Example 1. FIG. 3B is a diagram showing a schematic configuration of a dark-field microscope that is a defect detection unit of the defect observation apparatus of FIG. 1. FIG. 3C is a diagram showing a schematic enlarged view showing a shutter array device and a microlens array, showing a state in which all of the shutters that constitute the shutter array device are open. FIG. 3A is a diagram showing a schematic enlarged view showing a state in which all of the shutters that constitute the shutter array device of FIG. 3A are closed except for a portion. FIG. 3C is a diagram showing a spatial filter corresponding to the state of the shutter array device of FIG. 3A. FIG. 3B is a diagram showing a spatial filter corresponding to the state of the shutter array device of FIG. 3C. FIG. 3C is a perspective view showing an example (5×5 array) of a shutter array device of Example 1. FIG. 3A is a top view showing one shutter of Example 1. FIG. 3A is a cross-sectional view taken along line A-A of the shutter of FIG. 5A. FIG. 3A is a top view showing a wiring board that faces one shutter of Example 1. FIG. 6A is a cross-sectional view taken along line B-B of the wiring board of FIG. 6A. FIG. 7A is a top view in which a wiring board is arranged on one shutter of Example 1. FIG. 7A is a cross-sectional view taken along line C-C of FIG. 18B. FIG. 18C is a cross-sectional view showing a shutter array manufacturing process of Example 12. FIG. 18A is a cross-sectional view taken along the line D-D in FIG. 8A. FIG. 18B is a cross-sectional view showing a shutter array device of Example 13. FIG. 18C is a cross-sectional view showing a shutter array device of Example 14. FIG. 18C is a cross-sectional view showing a mounting structure of a shutter array device of Example 13. FIG. 18D is a cross-sectional view showing a mounting structure of a shutter array device of Example 14. A cross-sectional view showing the mounting structure of the shutter array and wiring board of Example 15.1 is a diagram showing voltage application states and operations of a shutter array device to explain problems in the past. 2 is a diagram showing voltage application states and operations of a shutter array device to explain problems in the past. 3 is a diagram showing voltage application states and operations of a shutter array device to explain problems in the past.

[0023] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiments are illustrative for explaining the present invention, and some omissions and simplifications have been made as appropriate for clarity of explanation. The present invention can be implemented in various other forms. Unless otherwise specified, each component may be singular or plural.

[0024] In order to facilitate understanding of the invention, the position, size, shape, range, etc. of each component shown in the drawings may not represent the actual position, size, shape, range, etc. Therefore, the present invention is not necessarily limited to the position, size, shape, range, etc. disclosed in the drawings.

[0025] In each drawing and each embodiment, the same or similar components are designated by the same reference numerals, and redundant explanations will be omitted.

[0026] First, a defect observation apparatus 10 and an optical filtering device to which the present invention is applied will be described with reference to Fig. 1 to Fig. 3F. In this embodiment, the defect observation apparatus 10 is provided with a dark-field microscope to which the optical filtering device is applied, and is used to observe and inspect defects and the like on a wafer.

[0027] Fig. 1 is a diagram showing a schematic configuration of a defect observation apparatus of Example 1. Fig. 2 is a diagram showing a schematic configuration of a dark-field microscope which is a defect detection unit of the defect observation apparatus of Fig. 1. Figs. 3A to 3C are schematic enlarged views showing a shutter array device and a microlens array, respectively showing a state in which all shutters are open (Fig. 3A), a state in which all shutters are closed except for a portion (Fig. 3B), and a state in which all shutters are closed (Fig. 3C). Figs. 3D to 3F are diagrams showing spatial filters corresponding to the states of the shutter array device of Figs. 3A to 3C, respectively.

[0028] As shown in FIG. 1 , the defect observation apparatus 10 of this embodiment includes a scanning electron microscope 1002 (SEM), a dark-field microscope 1003 which is a defect detection unit, a control unit 1006, a terminal 1007, a recording device 1008, and a network 1009.

[0029] The scanning electron microscope 1002 is installed in a vacuum chamber 1005 together with a stage 1004. A wafer 1001 is placed on the stage 1004. The wafer 1001 can be moved together with the stage 1004, which is movable in the X and Y axes. This allows any surface of the wafer 1001 to be observed by the scanning electron microscope 1002 and the dark-field microscope 1003.

[0030] The dark-field microscope 1003 is a type of optical microscope, and includes a laser light source 103 , an objective lens 102 , an imaging lens 101 , and an image sensor 100 .

[0031] The objective lens 102 is installed in a vacuum chamber 1005. For this reason, a vacuum sealing window 1014 is provided so that light passing through the objective lens 102 can reach the image sensor 100. A microlens array 107, a shutter array device 200, and a microlens array 106 are installed between the vacuum sealing window 1014 and the imaging lens 101 in this order from the vacuum sealing window 1014 side. A light beam emitted from the laser light source 103 passes through the vacuum sealing window 1011 and is irradiated onto the upper surface of the wafer 1001 via a mirror 1012.

[0032] Light reflected on the top surface of the wafer 1001 passes through the objective lens 102 and the vacuum sealing window 1014 in order, then passes through the microlens array 107, the shutter array device 200 and the microlens array 106 in order, is imaged by the imaging lens 101 and is detected by the imaging element 100.

[0033] The imaging element 100 may be a two-dimensional CCD sensor, a line CCD sensor, a TDI sensor group in which multiple TDIs are arranged in parallel, a photodiode array, or other sensor. Here, CCD is an abbreviation for Charge-Coupled Device. TDI is an abbreviation for Time Delay Integration.

[0034] The scanning electron microscope 1002 and the dark field microscope 1003 are fixed so as to maintain an accurate distance between them.

[0035] The control unit 1006 has a stage control circuit 1018 , an SEM imaging system control circuit 1019 , an image processing circuit 1020 , an external input / output interface 1021 , a central processing unit (CPU) 1022 , and a memory 1023 .

[0036] The stage control circuit 1018 , the SEM imaging system control circuit 1019 , and the image processing circuit 1020 are connected to an external input / output interface 1021 , a central processing unit 1022 , and a memory 1023 via a bus 1024 .

[0037] The stage control circuit 1018, SEM imaging system control circuit 1019, and image processing circuit 1020 are circuits for moving the wafer 1001, observing defects on the surface of the wafer 1001, and performing other operations. The image processing circuit 1020 calculates the image signals acquired by the image sensor 100, performs data conversion, etc., and determines the type of defect, etc., and specifies its position and size, etc. Information related to the results of determination, identification, etc. will be referred to as "defect information" in this specification.

[0038] The defect information is input to the recording device 1008 or the memory 1023. The memory 1023 is mainly used for temporary storage, while the recording device 1008 can be used to accumulate and store the acquired defect information.

[0039] In the control unit 1006, based on the defect information, a stage control circuit 1018 controls the stage 1004, and an SEM imaging system control circuit 1019 controls the scanning electron microscope 1002. The control unit 1006 then observes in detail some or all of the defects detected by the dark-field microscope 1003, classifies the defects, analyzes their causes, etc. The control unit 1006 also controls the focus and output of the SEM image, controls analysis, analyzes data obtained by the scanning electron microscope 1002, and corrects the positions of defects obtained by the dark-field microscope 1003. The control unit 1006 can also display data on a terminal 1007, transfer data via a network 1009, etc.

[0040] The terminal 1007 is used to set conditions for observing defects, etc. The terminal 1007 also sets parameters for controlling the scanning electron microscope 1002, the dark-field microscope 1003, and the stage 1004. The terminal 1007 also sets the opening and closing operation of the shutter (described below) of the shutter array device 200. Furthermore, the terminal 1007 is capable of adjusting the shutter opening speed. The shutter opening speed can be determined by adjusting the shape of the voltage curve applied to the shutter, or the slope if the voltage curve is linear, and can also set a sequence for applying voltage in multiple stages. The shutter open / close state can be confirmed on the terminal 1007 by converting the image obtained by the image sensor 100 into a pupil image. Furthermore, a method of adjusting the voltage applied to the shutter array device 200 while viewing the converted pupil image may be adopted. This prevents the voltage applied to the shutter from being too high, thereby preventing dielectric breakdown of the shutter portion and damage or malfunction of the shutter shaft.

[0041] The shutter shaft, which supports and rotates the shutter, acts as an elastic body, resisting the stress when the shutter is in the open state and attempting to return to the closed state. The opening angle is determined by the balance between this force and the electrostatic force that attempts to open the shutter, which is generated by the application of the voltage. Therefore, the opening speed can be adjusted by adjusting the voltage application curve. The opening angle of the shutter is also determined by the applied voltage value.

[0042] The dark-field microscope 1003, which is the defect detection unit of the defect observation device 10 in FIG. 1, will be described in detail with reference to FIG.

[0043] 2 , the dark-field microscope 1003 of this embodiment includes an image sensor 100, an imaging lens 101, and an objective lens 102. Microlens arrays 106 and 107 are installed between the imaging lens 101 and the objective lens 102. A shutter array device 200 (optical filtering device) is installed between the microlens arrays 106 and 107. The microlens arrays 106 and 107 and the shutter array device 200 are installed near the pupil plane of the dark-field microscope 1003.

[0044] The objective lens 102 is configured so that a light beam 300 irradiated onto the wafer 1001 from the laser light source 103 is reflected by the surface of the wafer 1001, and the reflected light 301 is incident on the objective lens 102. The light that has passed through the objective lens 102 passes through the pupil plane (Fourier transform plane) and the imaging lens 101, reaches the image sensor 100, and is detected as an electrical signal. The light beam 300 irradiated from the laser light source 103 passes through a vacuum sealing window 1011, is reflected by a mirror 1012, and is irradiated onto the wafer 1001.

[0045] If a defect 108 is present on the wafer 1001, a light beam 300 that strikes the defect 108 is reflected, generating an unusual reflected light 301. This reflected light 301 is detected by the image sensor 100, and data corresponding to the image of the defect 108 can be acquired by the image processing circuit 1020 in FIG. 1 . By moving the stage 1004, the defect 108 present on the surface of the wafer 1001 can be found. At this time, a pattern can be formed by opening or closing any shutter in the shutter array device 200, which functions as an optical filtering device, to block scattered light due to wafer roughness and the like, thereby improving the detection sensitivity of the defect 108. Furthermore, the detection sensitivity of the defect 108 can be improved by changing the opening / closing pattern of the shutter array device 200 depending on the shape, size, and type of the defect 108. The shutter array device 200 can change the opening / closing pattern in a variety of ways, allowing it to form a variety of optical filters and accommodate a wide variety of defects.

[0046] The shutter array device 200 and the microlens arrays 106 and 107 of FIGS. 1 and 2 will be described in detail with reference to FIGS. 3A to 3F.

[0047] 3A shows a state in which all of the shutters 210 of the shutter array device 200 are open. In Fig. 3A, the shutter array device 200 is placed between the microlens arrays 106 and 107. All of the shutters 210 of the shutter array device 200 are open, resulting in a shutter-open state 212. Therefore, as shown in Fig. 2, reflected light 301 passing through the shutter array device 200 from below the paper surface converges and focuses at the shutter opening 238, becoming light 303.

[0048] Fig. 3B shows a state in which all but a portion of the shutters 210 of the shutter array device 200 are closed. Fig. 3C shows a state in which all of the shutters 210 of the shutter array device 200 are closed. In areas where the shutters 210 are closed to form a shutter closed state 211, reflected light 301 is blocked by the shutters 210, and light 303 does not pass through. In this way, the multiple shutters 210 are configured to be able to open and close independently.

[0049] Figures 3D to 3F show spatial filters corresponding to the states shown in Figures 3A to 3C, respectively, and are views of the shutter array device 200 from above or below.

[0050] In these figures, the shutter closed state 211 is shown in black, and the shutter open state 212 is shown in white. By individually controlling the ON / OFF of each pixel of the shutter array device 200, multiple types of spatial filters (spatial masks) can be configured.

[0051] 3A to 3C, the shutters 210 of the shutter array device 200 and the lenses of the microlens arrays 106 and 107 are arranged in 3 rows and 3 columns, but this is just an example, and a larger matrix may be formed as needed. In practice, optical filters are produced using arrays of 10 x 10 shutters, 32 x 32 shutters, or even 100 x 100 shutters. Furthermore, if the optical filtering device only requires the overall ON / OFF function, it is not limited to the array-shaped shutter array device 200, and may be configured with only one shutter.

[0052] Next, the problems of the conventional technology will be described in detail with reference to Fig. 22A to Fig. 22C. Fig. 22A to Fig. 22C are diagrams showing the voltage application state and operation of a shutter array device to explain the problems of the conventional technology. Fig. 21A to Fig. 21C are longitudinal cross-sectional views of one shutter 2210 in a shutter array device 2000. Fig. 22A to Fig. 22C show potentials (+) and potentials (-) that schematically show the voltage application state of the shutter array device 2000.

[0053] As shown in Figure 22A, a voltage is applied to the shutter 2210 via the shutter support member 2203 so that it has a positive potential (V1), and to the substrate 2201 so that it has a negative potential or zero potential (V2). The resulting potential difference generates an electrostatic force, which opens the shutter 2210. Note that the operating behavior of the shutter 2210 is the same even if the potentials of V1 and V2 are reversed. The shutter support member 2203 and the substrate 2201 are insulated from each other by an insulating layer 2234.

[0054] As shown in this figure, the underside of the shutter 2210 is positively charged, and the inner wall surface 2282 of the substrate 2201 is negatively charged. This causes the shutter 2210 to rotate around the shaft (torsion beam 2232) and move within the shutter opening 2238, resulting in the shutter being open. When the application of voltage is stopped, the restoring force of the shaft (torsion beam 2232) returns the shutter to the closed state.

[0055] For example, if V1 is set to a positive potential of +10 to +200 V and V2 is set to a negative potential of -10 to -200 V, the applied voltage is 20 to 400 V. When the voltage applied to the shutter 2210 is increased, the opening angle 2250 of the shutter 2210 increases in accordance with the applied voltage. However, the voltage applied to the shutter 2210 also varies depending on the size of the shutter 2210, and is not limited to the above example.

[0056] On the other hand, as shown in FIG. 22B , when the opening angle 2250 of the shutter 2210 reaches a certain angle, the distance between the shutter 2210 and the substrate 2201 becomes shorter, and the electrostatic force, which is inversely proportional to the square of the distance, becomes greater than the reaction force of the torsion beam 2232 supporting the shutter 2210 against the shutter rotation, causing a pull-in in which the shutter 2210 opens fully in one go, resulting in the state shown in FIG. 22C .

[0057] 22C , when the shutter 2210 is fully opened, static electricity or moisture in the air can cause the open shutter 2210 to stick to the inner wall surface 2282 of the shutter opening 2238 provided in the substrate 2201, making it impossible to subsequently control the opening and closing of the shutter 2210. In order to prevent this type of sticking of the shutter 2210, it is preferable to not open the shutter 2210 fully but to allow it to stand still in the space of the shutter opening 2238. However, if the shutter 2210 is opened partway and left to stand still in the air, there is a concern that pull-in may occur.

[0058] Therefore, in this embodiment, instead of opening the shutter 2210 by the potential difference with the inner wall surface 2282 of the shutter opening 2238 as in the conventional case, a structure is proposed in which a separate electrode 262 is arranged opposite the shutter 210, and the shutter 210 is opened by the potential difference with the electrode 262, as will be described below.

[0059] Next, the optical filtering device of this embodiment will be described with reference to Figs. 4 to 7B. Fig. 4 is a perspective view showing an example (5x5 array) of a shutter array device of Example 1. Fig. 5A is a top view showing one shutter of Example 1. Fig. 5B is an A-A cross-sectional view of the shutter of Fig. 5A. Fig. 6A is a top view showing a wiring board arranged opposite one shutter of Example 1. Fig. 6B is a B-B cross-sectional view of the wiring board of Fig. 6A. Fig. 7A is a top view in which a wiring board is arranged on one shutter of Example 1. Fig. 7B is a C-C cross-sectional view of Fig. 7A.

[0060] The optical filtering device of this embodiment is a shutter array device 200, and as shown in FIG. 4 , it includes a shutter array 205 configured as a 5×5 array in which five shutters 210 are arranged vertically and horizontally, and a wiring board 260 disposed opposite the shutter array 205. The wiring board 260 is provided with electrodes 262 facing each shutter 210, and opening and closing of the shutters 210 is controlled by applying a voltage between the electrodes 262 and the shutters 210. Note that the number of shutters 210 in the shutter array 205 is not limited to 25, and any necessary number may be used. Furthermore, the optical filtering device of this embodiment is not limited to an array, and may be configured with one shutter 210 and one electrode 262.

[0061] 5A and 5B, a shutter unit 206 having one shutter 210 has a hinge 233 provided on the shutter 210, and the hinge 233 and the shutter support portion 203 are connected by a torsion beam 232. Also, as shown in Fig. 5B, the shutter unit 206 has an insulating layer 234 below the shutter support portion 203, and a substrate 201 further below that. A shutter opening 238 is formed in the substrate 201, and is structured so that light can pass through when the shutter 210 is open.

[0062] As shown in FIGS. 6A and 6B , the wiring board 260 includes an electrode 262 and a wiring 261 that supplies a voltage to the electrode 262. In this embodiment, the electrode 262 is rectangular. The wiring board 260 also includes another electrode 262 that faces the shutter 210 of the other shutter unit 206, and a wiring 264 that supplies a voltage to the other electrode 262. Multiple wirings 264 may be provided to match the arrangement of the electrodes 262. The wiring board 260 is required to be transparent in order to transmit light. Therefore, the wiring board 260 includes a transparent plate 263. The transparent plate 263 can be made of glass, such as quartz, lead glass, soda glass, or borosilicate glass, or transparent resins, such as acrylic resin, ABS resin, polycarbonate resin, silicone resin, fluorine-based resin, or cycloolefin resin. Furthermore, to reduce light reflection, it is preferable to form an anti-reflective coating on these transparent materials. Furthermore, if there is an effect of heat generation due to transmitted light, glass-based materials are preferred, and quartz, which has high transmittance, is suitable.

[0063] 7A and 7B , a wiring board 260 is installed facing the shutter 210 of the shutter unit 206 shown in FIGS. 5A and 5B , and an electrode 262 is arranged in the normal direction when the shutter 210 is in a closed state 211. In this embodiment, the wiring board 260 is arranged on the opposite side of the shutter opening 238 with respect to the shutter 210, so that when a potential difference is applied between the shutter 210 and the electrode 262, the shutter 210 opens in the direction opposite the shutter opening 238. Specifically, as shown in FIG. 7B , a voltage is supplied from a power source 265 to the electrode 262 via wiring 261, and a voltage is supplied to the shutter 210 via the shutter support portion 203 and the torsion beam 232, thereby generating a potential difference between the electrode 262 and the shutter 210. An electrostatic force is generated by the electric field due to this potential difference, and shutter 210 is attracted toward electrode 262 of wiring board 260, but because one end of shutter 210 is stopped by torsion beam 232, shutter 210 rotates around torsion beam 232 and opens, resulting in shutter open state 212. Here, height H is set so that shutter 210 does not come into contact with wiring board 260 including electrode 262 in shutter open state 212.

[0064] That is, the optical filtering device of this embodiment comprises an openable / closable shutter 210, a shutter opening 238 that transmits light when the shutter 210 is open, an electrode 262 arranged in the normal direction when the shutter 210 is closed, wiring 261 that supplies voltage to the electrode 262, and a wiring board 260 having the electrode 262 and wiring 261, and is configured so that when a potential difference is applied between the shutter 210 and the electrode 262, the shutter 210 opens in the direction of the electrode 262, and there is a distance (height H) between the shutter 210 and the wiring board 260 such that the shutter 210 and the wiring board 260 do not come into contact with each other when the shutter 210 opens in the direction of the electrode 262.

[0065] 7A and 7B , even when the shutter 210 is open, it does not come into contact with the wiring board 260, and can remain stationary in the open state in the space between the shutter unit 206 and the wiring board 260. Therefore, even when the shutter 210 is open, it does not come into contact with the inner wall surface 282 of the shutter opening 238, and a highly reliable optical filtering device and defect observation apparatus 10 can be realized that are capable of obtaining a desired opening angle, i.e., a shutter opening, and capable of controlling light to pass through.

[0066] The optical filtering device of this embodiment also includes a shutter array 205 in which a plurality of shutters 210 and a plurality of shutter openings 238 are arranged in an array, and a wiring board 260 has a plurality of electrodes 262 arranged in an array and a plurality of wirings 261 that independently supply voltages to each electrode 262, and the opening and closing of each shutter 210 can be independently controlled by the electrodes 262 arranged corresponding to each shutter 210. This makes it possible to configure a plurality of types of spatial filters (spatial masks).

[0067] 7A shows spot 310 of light passing through when shutter 210 is open. The size of spot 310 of light depends on the design of the optical system, but it is necessary to take into consideration misalignment of shutter array 205 and wiring board 260 when assembled, and misalignment between shutter opening 238 and spot 310 of light, and it is therefore desirable to set spot 310 of light with a diameter smaller than the path of light obtained when shutter 210 is opened.

[0068] As a result, even when a pull-in voltage is applied, the shutter 210 can be opened without coming into contact with the wiring board 260 including the electrode 262. As will be explained below, the opening angle of the shutter in the open state 212 varies depending on the shape, position, and height H of the electrode 262, as well as the applied voltage. The higher the voltage, the larger the opening angle of the shutter 210, and the lower the voltage, the smaller the opening angle. Furthermore, the larger the area of ​​the electrode 262, the greater the electrostatic force, allowing the voltage to be reduced. Furthermore, the higher the height H, the smaller the electrostatic force, so a larger voltage is required.

[0069] According to this embodiment, it is possible to realize a highly reliable optical filtering device that can control the opening and closing of the shutter 210 without the shutter 210 sticking, in an optical filtering device used as a spatial filter in an optical inspection apparatus such as the dark-field microscope 1003. Furthermore, even when the shutter 210 is fully open, there is no portion to which the shutter 210 sticks, so there is no problem with opening and closing the shutter 210 due to sticking or damage due to contact, and this improves the reliability of the defect observation apparatus 10.

[0070] Fig. 8A is a top view showing one shutter and a wiring board according to Example 2. Fig. 8B is a cross-sectional view taken along line DD in Fig. 8A. Figs. 8A and 8B show the shutter 210 in an open state.

[0071] In this embodiment, as shown in FIG. 8A , the electrode 262 has a notch 266 in the area overlapping the shutter opening 238. The notch 266 is rectangular in shape. Therefore, the electrode 262 is U-shaped and includes the notch 266 and an arm 267. The formation of the notch 266 allows for a wider area through which light passes, thereby increasing the effective area of ​​the shutter opening. The shutter 210 opens when a voltage is applied to the electrode 262 and the shutter 210. However, the electrode area is larger due to the arm 267 than when the arm 267 is not present, resulting in a stronger electrostatic force. Therefore, a lower voltage can be set compared to when the arm 267 is not present. Setting a lower voltage reduces leakage current in the shutter unit 206. Furthermore, the load on the power supply and circuitry can be reduced, and the withstand voltage of electronic components can be reduced, resulting in cost and installation space savings.

[0072] Fig. 9 is a top view showing one shutter and a wiring board according to Example 3. Fig. 9 shows a state in which the shutter 210 is closed.

[0073] In this embodiment, as shown in Fig. 9, electrode 262 has a notch 266 in the region overlapping with shutter opening 238, and arm 267 is longer than arm 267 of embodiment 2 shown in Fig. 8A. This makes the effective area of ​​the shutter opening even larger than in embodiment 2 shown in Fig. 8A, and also increases the area to which a potential is applied, i.e., the area of ​​electrode 262, which increases the electrostatic force, allowing the drive voltage of shutter 210 to be set low.

[0074] Fig. 10 is a top view showing one shutter and a wiring board according to Example 4. Fig. 10 shows a state in which the shutter 210 is closed.

[0075] 10 , when viewed from the normal direction when the shutter 210 is closed, the electrode 262 has an area that overlaps the shutter opening 238 and an area that does not overlap the shutter opening 238. The electrode 262 is rectangular, but is narrower than the electrode 262 described in Example 1, which increases the area of ​​the opening region through which light passes and makes it easier to mitigate the effects of misalignment of the light spot 310. On the other hand, by lengthening the length of the long side of the electrode 262 so that it overlaps with the shutter support portion 203 to compensate for the narrower width of the electrode 262, it has the effect of mitigating the decrease in the strength of the electric field, i.e., the electrostatic force.

[0076] Fig. 11 is a top view showing one shutter and a wiring board according to Example 5. Fig. 11 shows a state in which the shutter 210 is closed.

[0077] In this embodiment, as shown in Fig. 11, the electrode 262 has a notch 266 in a region overlapping the shutter opening 238. The difference from the electrode 262 of embodiment 3 shown in Fig. 9 is that in this embodiment, the electrode 262 is enlarged so as to overlap the shutter support portion 203, and also covers the torsion beam 232. In other words, when viewed from the normal direction when the shutter 210 is closed, a portion of the electrode 262 is positioned so as to overlap the opening / closing axis (torsion beam 232) of the shutter 210. This increases the electrode area, increasing the electrostatic force and allowing the voltage to be set low.

[0078] Fig. 12 is a top view showing one shutter and a wiring board according to Example 6. Fig. 12 shows a state in which the shutter 210 is closed.

[0079] 12, the electrode 262 has an arc-shaped notch 266 in the region overlapping the shutter opening 238. The difference from the rectangular notch 266 is that the area of ​​the notch 266 can be made smaller, so the electrode area is wider than in the case of the rectangular notch 266, which increases the electrostatic force and allows the voltage to be set lower.

[0080] Fig. 13 is a top view showing one shutter and a wiring board according to Example 7. Fig. 13 shows a state in which the shutter 210 is closed.

[0081] In this embodiment, as shown in Fig. 13, the electrode 262 has a semi-elliptical cutout 266 in the region overlapping the shutter opening 238. The difference from the electrode 262 of Example 6 shown in Fig. 12 is that the arm portion 267, which is the straight portion of the semi-ellipse, is longer. This makes the electrode area larger than in the case of the arc-shaped cutout 266, increasing the electrostatic force and allowing the voltage to be set lower.

[0082] Fig. 14 is a top view showing one shutter and a wiring board according to Example 8. Fig. 14 shows a state in which the shutter 210 is closed.

[0083] In this embodiment, as shown in Figure 14, the electrode 262 is frame-shaped and has an opening 268 in the area that overlaps the shutter opening 238. In this embodiment, the shape of the opening 268 is rectangular. Therefore, the electrode 262 is square-shaped. The opening 268 serves as a path for light. The electrode 262 overlaps the shutter support portion 203, and the electrode area is widened, which increases the electrostatic force and allows the voltage to be set low.

[0084] As explained above with reference to Figures 7A to 14, the larger the size of the electrode 262, the stronger the electric field strength and the greater the electrostatic force. However, the electric field also spreads, causing crosstalk, in which adjacent shutters 210 also open. Crosstalk must be prevented as much as possible, and the size, installation position, height, and voltage of the electrode 262 must be adjusted so that the opening angle of adjacent shutters 210 caused by crosstalk is approximately 20 degrees. It is most desirable that adjacent shutters 210 are not affected by crosstalk.

[0085] 6A is laid out between adjacent shutters 210, the thickness of the wires 264 also has an effect, and if the wires 264 are too thick, the adjacent shutters 210 may open due to the effect of the electric field generated in the wires 264. Therefore, the wires 264 should be thin, preferably 5 micrometers or less. Furthermore, as the number of parallel wires 264 increases, the electric field generated in the wires 264 increases, so the number of parallel wires 264 also needs to be adjusted appropriately.

[0086] 15 is a diagram showing voltage application to one shutter and a wiring board in Example 9. The configuration of the shutter unit 206 and wiring board 260 is the same as that of Example 1 shown in FIG. 7B, and shows a state in which the shutter 210 is open. In FIG. 15, the shutter 210 is grounded, and a positive voltage is applied to the electrode 262.

[0087] As shown in FIG. 15 , the shutter 210 is grounded and therefore at 0 V, and the electrode 262 is at a positive voltage, which creates an electrostatic field between the shutter 210 and the electrode 262, generating an electrostatic force. This electrostatic force causes the shutter 210 to be drawn to the electrode 262 and open. On the other hand, when the power supply is turned off and the voltage is removed, the electric field disappears, the electrostatic force disappears, and the shutter 210 returns to the closed state due to the restoring force of the torsion beam 232. Here, the polarity of the voltage applied to the electrode 262 when the shutter 210 is grounded may be negative. Alternatively, the shutter 210 can be opened by grounding the electrode 262 and applying a positive or negative voltage to the shutter 210. Alternatively, the shutter 210 may be positive and the electrode 262 may be negative. In other words, any combination of voltages may be applied as long as a potential difference is generated between the shutter 210 and the electrode 262.

[0088] FIG. 16 is a diagram showing voltage application to one shutter and a wiring board in Example 10. The difference from Example 9 shown in FIG. 15 is that the electrode 262 is grounded and a negative voltage is applied to the substrate 201. The shutter 210 is also negatively charged due to the dielectric effect caused by the voltage applied to the substrate 201. In other words, polarization occurs inside the insulating layer 234, and the shutter 210 becomes negative. Similarly, when a positive voltage is applied to the substrate 201, the shutter 210 also becomes positively charged.

[0089] On the other hand, when the substrate 201 is grounded, a positive or negative voltage is applied to the electrode 262, but because the substrate 201 is at 0 V, the shutter 210 also remains at 0 V, creating a potential difference between the electrode 262 and the substrate 201, allowing the shutter 210 to be opened by electrostatic force. In this way, the shutter 210 can be opened by applying a voltage to the substrate 201 via the insulating layer 234 or by grounding the substrate 201, rather than applying a voltage directly to the shutter 210. One advantage of applying a voltage to the substrate 201 is that it is easier to manufacture the structure by drawing an electrode for applying a voltage to the substrate 201 from the substrate 201, rather than drawing an electrode for applying a voltage to the shutter support portion 203 from the space between the wiring board 260 and the shutter 210.

[0090] FIG. 17 is a cross-sectional view of the wiring board of the eleventh embodiment arranged on the substrate side of the shutter.

[0091] 17 , since the wiring board 260 is disposed on the same side of the shutter 210 as the shutter opening 238, when a potential difference is applied between the shutter 210 and the electrode 262, the shutter 210 opens toward the inside of the shutter opening 238. In this embodiment, although the shutter 210 is configured to open toward the inside of the shutter opening 238, the shutter 210 opens due to the electrostatic force caused by the potential difference between the shutter 210 and the electrode 262, rather than the electrostatic force caused by the potential difference between the shutter 210 and the inner wall surface 282 of the substrate 201. Therefore, even if the shutter 210 is fully open, it stops halfway inside the shutter opening 238, and it is possible to prevent the shutter 210 from sticking to the inner wall surface 282 of the substrate 201.

[0092] Furthermore, the wiring board 260 can be arranged in contact with the substrate 201 via an insulating layer (not shown) that is separately provided on the substrate 201. This eliminates the need to ensure a space between the wiring board 260 and the substrate 201, i.e., the shutter unit 206, making it easier to mount the wiring board 260 and the shutter unit 206.

[0093] The twelfth embodiment is an example of a method for manufacturing the shutter array 205 used in the optical filtering device of the first to eleventh embodiments.

[0094] 18A to 18D are cross-sectional views showing the shutter array manufacturing process of Example 12. Figures 18A to 18D show vertical cross sections in each step when processing a shutter unit 206 corresponding to one shutter 210 in a shutter array 205.

[0095] In this example, an SOI wafer 500 is used, as shown in Fig. 18A. The SOI wafer 500 has a three-layer structure consisting of a device layer 501, a BOX layer 502 (BOX: Buried Oxide), and a handle layer 503, each of which has a thickness of approximately 0.1 µm to 10 µm, 0.1 µm to 10 µm, and 30 µm to 1000 µm. The device layer 501 and the handle layer 503 can be made of a semiconductor such as Si. The BOX layer 502 can be made of, for example, SiO２ An oxide film such as the above can be used.

[0096] First, photoresist is applied to the device layer 501, and the shape of the shutter 210 is patterned by photolithography, and then the shape of the shutter 210 is processed by etching, as shown in Fig. 18B. At this time, an opening pattern 504 is formed in the device layer 501. The photoresist is then removed.

[0097] Next, photoresist is applied to the handle layer 503, and a pattern of the shutter opening 238 is formed by photolithography, and then etching is performed down to the BOX layer 502 to form the shutter opening 238, as shown in Fig. 18C. The remaining handle layer 503 becomes the substrate 201. The photoresist is then removed.

[0098] 18D, the BOX layer 502 exposed in the shutter opening 238 is removed by etching to expose the back surface of the shutter 210. In this process, the shutter 210 is separated from the shutter support portion 203 except for the portion connected to the torsion beam 232 (see FIG. 5B). The remaining BOX layer 502 becomes the insulating layer 234.

[0099] As in this embodiment, the shutter unit 206 can be formed by processing the SOI wafer 500 from both sides.

[0100] The etching described above may be either dry etching or wet etching.

[0101] 18A to 18D show the processing steps for one shutter 210, but in the shutter array 205 in which a plurality of shutters 210 are arranged in an array, each shutter 210 is processed simultaneously.

[0102] The thirteenth embodiment is an example of a mounting structure of the optical filtering device described in the first to eleventh embodiments.

[0103] FIG. 19 is a perspective view showing a mounting structure of a shutter array device according to a thirteenth embodiment.

[0104] As shown in Fig. 19, the shutter array 205 is mounted on a wiring board 260. Note that in Fig. 19, the shutter arrays 205 of Examples 1 to 10 are upside down, with the shutters 210 provided on the underside of the shutter array 205 in Fig. 19. A portion of the wiring 401 provided on the wiring board 260 is connected to wiring 261, 264 for supplying a voltage to the electrode 262. Another portion of the wiring 401 is used to supply a voltage to the shutter array 205, and the details of the structure for supplying a voltage to the shutter array 205 will be explained in detail in Example 15 below.

[0105] The wiring 401 is connected via bonding wires 402 to a flexible substrate 403 different from the wiring board 260, and is electrically connected via a connector 404 of the flexible substrate 403 to an external control device (not shown).

[0106] By using the mounting structure of this embodiment, a voltage supplied from an external control device can be applied to the electrodes 262 facing each shutter 210 and to the shutters 210, thereby controlling the opening and closing of the shutters 210 (see Figure 7B).

[0107] A printed wiring board may be used instead of the flexible substrate 403. Also, instead of the bonding wires 402, a method of connecting electrodes facing each other using bumps or solder, or a method of connecting via an anisotropic conductive film may be used.

[0108] FIG. 20 is a perspective view showing the mounting structure of the shutter array device of Example 14.

[0109] In this embodiment, as shown in Fig. 20, the mounting structure of the shutter array device 200 of Example 13 shown in Fig. 19 is further provided with a transparent protective cover 405 that covers the shutter array 205. The protective cover 405 is disposed on the opposite side to the wiring board 260. The protective cover 405 may be made of, for example, quartz glass.

[0110] For example, by attaching and sealing the protective cover 405 to the shutter array 205 by means of adhesive or other joining means, the shutter array 205 can be protected from dust and moisture in the atmosphere.

[0111] FIG. 21 is a cross-sectional view showing the mounting structure of the shutter array and the wiring board according to the fifteenth embodiment.

[0112] Example 15 is an example having an interposer plate 600, and will be described assuming the structures of Examples 1 to 9, but can also be applied to Examples 10 and 11 by changing the arrangement appropriately. Note that Figure 21 is upside down compared to the diagrams of Examples 13 and 14.

[0113] The shutter array device 200, which is the optical filtering device of this embodiment, is provided with an interposer plate 600 between the shutter array 205 and the wiring board 260, which ensures a distance (height H in Figure 7B) between the shutter 210 and the wiring board 260, and the shutter array 205 is supplied with voltage from the wiring board 260 via the interposer plate 600.

[0114] Specifically, as shown in Fig. 21 , in order to mount the shutter array 205 and the wiring board 260 while ensuring a height H, an interposer board 600 is sandwiched between the shutter array 205 and the wiring board 260. The interposer board 600 has an insulating plate 601, through-hole wiring 602 that penetrates the insulating plate 601, and bond pads 603 and 604 provided on the front and back sides of the insulating plate 601. The through-hole wiring 602 electrically connects the bond pad 603 and the bond pad 604. Meanwhile, the shutter array 205 has a bond pad 605 on the shutter support portion 203. The wiring board 260 also has a bond pad 606 that is connected to wiring 401 (not shown) (see Fig. 19 ). Bonding pads 604 of interposer board 600 are soldered to bonding pads 605 of shutter array 205, and bonding pads 603 of interposer board 600 are soldered to bonding pads 606 of wiring board 260. Note that bonding may be achieved by methods other than soldering, such as activated bonding or resin bonding. This allows voltage to be supplied from wiring board 260 to shutter 210 via wiring 401, bonding pads 606 and 603, through-wire 602, bonding pads 604 and 605, and shutter support portion 203.

[0115] Furthermore, wiring board 260 is provided with alignment mark 610, interposer board 600 is provided with alignment marks 611 and 612, and shutter array 205 is provided with alignment mark 613. In the mounting process, alignment mark 610 of wiring board 260 is aligned using alignment mark 611 or 612 of interposer board 600 for bonding, and then alignment mark 612 of interposer board 600 is aligned using alignment mark 613 of shutter array 205 for bonding and mounting. As for how to use the alignment marks, when storing an image, it is also possible to store the alignment mark 610 of the wiring board 260, align the alignment mark 611 or 612 of the interposer board 600 with the alignment mark 610 of the wiring board 260, and then align the alignment mark 613 of the shutter array 205 with the stored alignment mark 610 of the wiring board 260.

[0116] The present invention is not limited to the above-described embodiments, but includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

[0117] 10...Defect observation device 100...Image capture element 101...Imaging lens 102...Objective lens 103...Laser light source 106, 107...Microlens array 108...Defect 200...Shutter array device 201...Substrate 203...Shutter support portion 205...Shutter array 206...Shutter unit 210...Shutter 211...Shutter closed state 212...Shutter open state 213...Gap 232...Torsional beam 233...Hinge 234...Insulating layer 238...Shutter opening 260...Wiring board 261, 264...Wiring 262...Electrode 263...Transparent plate 265...Power supply 266...Notch portion 267...Arm portion 268...Opening 282...Inner wall surface 300...Light ray 301...Reflected light 303...Light 310...Light spot 401...Wiring 402...Bonding wire 403...Flexible substrate 404...Connector 405...Protective cover 500...SOI wafer 501...Device layer 502...BOX layer 503...Handle layer 504...Aperture pattern 600...Interposer plate 601...Insulating plate 602...Through-through wiring 603, 604, 605, 606...Bonding pads 610, 611, 612, 613...Alignment mark 1001...Wafer 1002...Scanning electron microscope 1003...Dark-field microscope 1004...Stage 1005...Vacuum chamber 1006...Control unit 1007...Terminal 1008...Recording device 1009...Network 1011, 1014...Vacuum sealing window 1012...Mirror 1018...Stage control circuit 1019...SEM imaging system control circuit 1020...Image processing circuit 1021...External input / output interface 1022...Central processing unit 1023...Memory 1024...Bus 2000...Shutter array device 2201...Substrate 2203...Shutter support portion 2210...Shutter 2232...Torsion beam 2238...Shutter opening 2234...Insulating layer 2250...Opening angle 2282...Inner wall surface

Claims

1. An optical filtering device comprising: an openable / closable shutter; a shutter opening that transmits light when the shutter is open; an electrode arranged in the normal direction when the shutter is closed; wiring that supplies voltage to the electrode; and a wiring board having the electrode and the wiring, wherein when a potential difference is applied between the shutter and the electrode, the shutter opens in the direction of the electrode, and there is a distance between the shutter and the wiring board such that the shutter and the wiring board do not come into contact when the shutter opens in the direction of the electrode.

2. An optical filtering device according to claim 1, wherein the electrode has an area that overlaps the shutter opening and an area that does not overlap the shutter opening when viewed from the normal direction.

3. An optical filtering device according to claim 2, wherein the electrode is positioned so that a portion of the electrode overlaps with the opening / closing axis of the shutter when viewed from the normal direction.

4. The optical filtering device according to claim 1, wherein the electrode is rectangular.

5. An optical filtering device according to claim 1, wherein the electrode has a notch in the area overlapping the shutter opening.

6. An optical filtering device according to claim 1, wherein the electrode has a semi-elliptical cutout in a region overlapping the shutter opening.

7. An optical filtering device according to claim 1, wherein the electrode is frame-shaped and has an opening in a region that overlaps the shutter opening.

8. An optical filtering device according to claim 1, wherein when the potential difference is applied between the shutter and the electrode, the shutter opens in a direction opposite to the shutter opening.

9. An optical filtering device according to claim 1, wherein when the potential difference is applied between the shutter and the electrode, the shutter opens toward the inside of the shutter opening.

10. An optical filtering device according to claim 1, comprising a shutter array in which a plurality of the shutters and a plurality of the shutter openings are arranged in an array, the wiring board having a plurality of the electrodes arranged in the array and a plurality of the wirings that independently supply voltage to each of the electrodes, and the opening and closing of each of the shutters can be independently controlled by the electrodes arranged corresponding to each of the shutters.

11. An optical filtering device according to claim 10, further comprising an interposer plate between the shutter array and the wiring board, which can ensure the distance between the shutters and the wiring board, and wherein the shutter array is supplied with voltage from the wiring board via the interposer plate.

12. An optical filtering device according to claim 11, further comprising a transparent protective cover that covers the shutter array and is disposed on the opposite side from the wiring board.

13. An optical filtering device according to claim 1, wherein the shutter is made of a semiconductor.

14. A defect observation apparatus comprising an optical filtering device according to any one of claims 1 to 13.

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