Optical filtering device, MEMS shutter

Abstract

Provided is an optical filtering device used as a spatial filter for a dark field optical microscope, wherein the optical filtering device is highly reliable and is capable of controlling a shutter at a desired opening angle without fully opening the shutter. This optical filtering device is characterized in that: the optical filtering device comprises a shutter that can be opened and closed through voltage control, and a substrate having a shutter opening part that is the movable range of the shutter; the substrate has a stopper disposed extending in the thickness direction of the substrate on a side surface of the shutter opening part, and of which any cross sections in the thickness direction of the substrate have substantially the same shape; the shutter has a cut-out part; and the cut-out part abuts on the stopper when the shutter is opened.

Description

Technical Field

[0001] The present invention relates to the structure of an optical filtering device composed of MEMS, and particularly relates to a technology effective when applied to a MEMS shutter mounted on a dark field microscope.

Background Art

[0002] [[ID=]11] A defect observation device includes a scanning electron microscope (SEM) or the like for reviewing and classifying various defects, foreign matters, etc. (hereinafter referred to as "defects, etc.") generated on the surface of a wafer, which is a semiconductor substrate, in a semiconductor manufacturing line or the like.

[0003] The defect observation device preferably further includes an optical microscope. The defect observation device has a function of controlling the optical microscope, automatically detecting defects, etc. on the wafer surface efficiently, and performing coordinate alignment. For minute defects, etc. detected by the optical microscope, the shape can be observed in detail and component analysis can be performed by controlling the SEM. The optical microscope is preferably one that can be used 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 perform observation, classification, and analysis of 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 a defect observation apparatus, an optical microscope and a SEM share a common stage. For a wafer placed on this stage, it is observed with an optical microscope to identify the positions of detected defects and the like, and these defects and the like can be observed with a SEM. For example, according to a defect map having an accuracy of several tens of μm, defects and the like can be searched within a range of several hundred nm using the dark-field microscope of the defect observation apparatus, and the positions of defects and the like can be identified with an accuracy of several μm or less.

[0006] Thereby, the deviation of the coordinate systems between the optical microscope and the SEM can be corrected, the success rate of defect observation can be improved, and high throughput can be maintained. Also, in the manufacturing process of semiconductor devices, defects and the like that cause defects such as poor insulation and short circuits in wiring can be detected at an early stage, the source of the defects can be identified, and the yield reduction can be prevented.

[0007] In a dark-field microscope, a pupil filter corresponding to the type of defects and the like is required, and a minute shutter having a size of 1 mm or less corresponding to various types of defects and the like is demanded. It is considered that various spatial filters can be formed by opening and closing such a shutter.

[0008] In defect detection by a conventional dark-field optical system that does not use such a shutter, the discriminability between a defect and wafer roughness that becomes detection noise is enhanced by a spatial filter and a polarization filter by utilizing the spatial characteristics and polarization characteristics of various defect scattered lights on the pupil plane.

[0009] Since the shape of a spatial filter advantageous for detection varies depending on the type of defects and the like, in order to improve the detection sensitivity for a plurality of types of defects, it is necessary to use a shutter array in which minute shutters are arrayed, and a mechanism for individually switching the opening and closing of the shutters and a switching circuit for controlling it. This is because by using a shutter switching mechanism, the opening and closing positions of the shutter can be selected, and a plurality of types of spatial filters can be configured.

[0010] As a background art in this technical field, for example, there is a technology such as Patent Document 1. Patent Document 1 discloses that “a shutter pattern is two-dimensionally arranged and formed on an optically opaque thin film formed on an SOI wafer, and a portion of the SOI wafer below the shutter pattern is removed to form a hole, and an operating electrode is formed on the remaining portion of the SOI wafer. A shutter array, a glass substrate having an electrode pattern formed on its surface and mounting the shutter array, and a power supply unit for supplying power to the electrode pattern formed on the glass substrate and the operating electrode of the SOI wafer. By controlling the power supplied from the power supply unit to the electrode pattern and the operating electrode, the shutter pattern formed in a two-dimensional arrangement is opened and closed with respect to the hole portion, and the shutter pattern is an optical filtering device having protrusions at its ends.”

Prior Art Documents

Patent Documents

[0011]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0012] By the way, a shutter array device (optical filtering device) composed of MEMS (Micro Electro Mechanical Systems) is generally formed using an SOI substrate (Silicon On Insulator) in which SiO2 is inserted between a Si substrate and a surface Si layer. However, when the shutter is fully opened, due to the influence of static electricity and moisture in the air, the opened shutter may stick to the wall surface of the shutter opening provided on the Si substrate, and thereafter, the opening and closing control of the shutter may become impossible.

[0013] The above Patent Document 1 does not mention anything about the problem of the shutter sticking to the Si substrate and its solution as described above.

[0014] In addition, when the shutter is fully opened, the stress generated in the rotatable beam that supports the shutter increases, and the lifespan when opening and closing are repeated is shortened.

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

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

[0017] Therefore, an object of the present invention is to provide a highly reliable optical filtering device that can control a shutter at a desired opening angle without fully opening the shutter in an optical filtering device used as a spatial filter of a dark-field microscope.

Means for Solving the Problems

[0018] In order to solve the above problems, the present invention includes a shutter that can be opened and closed by voltage control, and a substrate having a shutter opening that is a movable range of the shutter. The substrate has a stopper that extends in the thickness direction of the substrate on the side surface of the shutter opening, and any cross-section in the thickness direction of the substrate has a substantially the same shape. The shutter has a notch, and when the shutter is opened, the notch abuts against the stopper.

Effects of the Invention

[0019] According to the present invention, in an optical filtering device used as a spatial filter of a dark-field microscope, a highly reliable optical filtering device capable of controlling a shutter at a desired opening angle without fully opening the shutter can be realized.

[0020] As a result, since the shutter is not fully opened, it is possible to prevent the shutter from sticking to the wall surface of the shutter opening and to reduce the stress generated in the beam portion that supports the shutter, thereby improving the reliability of a defect inspection device, a dark-field microscope, an optical inspection device, and a review SEM.

[0021] Problems, configurations, and effects other than those described above will be clarified by the description of the following embodiments.

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

Figure 3A

Figure 3B

Figure 3C

Figure 3D

Figure 3E

Figure 3F

Figure 4

Figure 5A

Figure 5B

Figure 5C

Figure 5D

Figure 6A

Figure 6B

Figure 6C

Figure 7

Figure 8

Figure 9

Figure 10A

Figure 10B

Figure 10C

Figure 10D

Figure 11

Figure 12

BEST MODE FOR CARRYING OUT THE INVENTION

[0023] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that detailed descriptions of overlapping parts will be omitted.

EMBODIMENTS

[0024] First, with reference to FIGS. 1 to 3F, a review SEM, an optical inspection device, a dark-field microscope, and an optical filtering device to which the present invention is applicable will be described. In this embodiment, as an example of the dark-field microscope, a defect observation device for observing and inspecting defects such as those on a wafer will be used for the description.

[0025] FIG. 1 is a diagram showing a schematic configuration of the defect observation device according to this embodiment. FIG. 2 is a diagram showing a schematic configuration of an optical microscope which is a defect detection unit of the defect observation device of FIG. 1. FIGS. 3A to 3C are schematic enlarged views showing a shutter array device and a microlens array, showing a state where all shutters are open (FIG. 3A), a state where part of the shutters are closed except for a part (FIG. 3B), and a state where all shutters are closed (FIG. 3C), respectively. FIGS. 3D to 3F are diagrams showing spatial filters corresponding to FIGS. 3A to 3C, respectively.

[0026] As shown in FIG. 1, the defect observation device 10 of this embodiment includes a scanning electron microscope (SEM) 1002, 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.

[0027] 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-axis and Y-axis directions. Thereby, it is possible to observe any surface of the wafer 1001 by the scanning electron microscope 1002 and the dark-field microscope 1003.

[0028] The dark-field microscope 1003 includes a laser light source 1010, an objective lens 1013, an imaging lens 1015, and an image sensor 1016.

[0029] The objective lens 1013 is installed inside the vacuum chamber 1005. Therefore, a vacuum sealing window 1014 is provided so that the light passing through the objective lens 1013 reaches the imaging device 1016. Between the vacuum sealing window 1014 and the imaging lens 1015, a microlens array 1103, a shutter array device 1101, and a microlens array 1102 are installed in order from the side of the vacuum sealing window 1014. The light beam irradiated from the laser light source 1010 is configured to pass through the vacuum sealing window 1011 and irradiate the upper surface of the wafer 1001 via the mirror 1012.

[0030] The light reflected from the upper surface of the wafer 1001 passes through the objective lens 1013 and the vacuum sealing window 1014 in order, passes through the microlens array 1103, the shutter array device 1101, and the microlens array 1102 in order, is imaged by the imaging lens 1015, and is detected by the imaging device 1016.

[0031] As the imaging device 1016, a two-dimensional CCD sensor, a line CCD sensor, a TDI sensor group in which a plurality of TDIs are arranged in parallel, a photodiode array, etc. are used. Here, CCD is an abbreviation for Charge-Coupled Device. Also, TDI is an abbreviation for Time Delay Integration.

[0032] The scanning electron microscope 1002 and the dark field microscope 1003 are fixed so as to maintain an accurate distance.

[0033] The control unit 1006 includes a stage control circuit 1018, a SEM imaging system control circuit 1019, an image processing circuit 1020, an external input / output interface 1021, a central processing unit 1022 (CPU), and a memory 1023.

[0034] The stage control circuit 1018, the SEM imaging system control circuit 1019, and the image processing circuit 1020 are connected to the external input / output interface 1021, the central processing unit 1022, and the memory 1023 via the bus 1024.

[0035] The stage control circuit 1018, the SEM imaging system control circuit 1019, and the image processing circuit 1020 are circuits for moving the wafer 1001, observing defects and the like on the surface of the wafer 1001, and performing other operations. The image processing circuit 1020 integrates the signals of the images acquired by the imaging device 1016, performs data conversion and the like, and discriminates the types of defects and the like, specifies their positions and dimensions, and the like. Information regarding the results of discrimination, specification, and the like will be referred to as "defect information" in this specification.

[0036] The defect information is input to the recording device 1008 or the memory 1023. The memory 1023 is mainly used for temporary storage. On the other hand, the recording device 1008 can be used to accumulate and store the acquired defect information.

[0037] In the control unit 1006, based on the defect information, the stage control circuit 1018 controls the stage 1004, and the SEM imaging system control circuit 1019 controls the scanning electron microscope 1002. Then, in the control unit 1006, some or all of the defects and the like detected by the dark field microscope 1003 are observed in detail, and classification of the defects and the like, analysis of the causes of their occurrence, and the like are performed. Also, in the control unit 1006, control of the focus and output of the SEM image, control of the analysis, analysis of the data obtained by the scanning electron microscope 1002, position correction of the defects and the like obtained by the dark field microscope 1003, and the like are also performed. Further, in the control unit 1006, display on the terminal 1007, data transfer via the network 1009, and the like can also be performed.

[0038] At the terminal 1007, conditions for observing defects and the like are set. Also, at the terminal 1007, parameter settings for controlling the scanning electron microscope 1002, the dark-field microscope 1003, and the stage 1004 are performed. Further, at the terminal 1007, settings regarding the opening and closing operation of the shutter (described later) of the shutter array device 1101 are also made. Furthermore, at the terminal 1007, the speed at which the shutter is opened can be adjusted. In this case, the speed at which the shutter is opened can be adjusted by adjusting the shape of the voltage curve applied to the shutter or the slope in the case of a straight line, and furthermore, a sequence for applying voltages in multiple steps can be set. The open / closed state of the shutter can be confirmed at the terminal 1007 by converting the image obtained by the imaging device 1016 into an image of the pupil image, and furthermore, a method of adjusting the voltage applied to the shutter array device 1101 while observing the image converted into the pupil image may be adopted. Thereby, it is possible to prevent the voltage value applied to the shutter from being too large, and it is possible to prevent dielectric breakdown of the shutter portion, breakage or failure of the shaft portion of the shutter.

[0039] At the shaft portion of the shutter that supports and rotates the shutter, a force acts as an elastic body that tries to return to the closed state against the stress in the open state of the shutter. The opening angle is determined by the balance between this force and the electrostatic force that tries to open the shutter generated by the above voltage application. Therefore, by adjusting the application curve of the above voltage, the opening speed can be adjusted. Also, the opening angle of the shutter is determined by the voltage value applied.

[0040] Using FIG. 2, the dark-field microscope 1003, which is the defect detection unit of the defect observation apparatus 10 in FIG. 1, will be described in detail. In FIG. 2, the dark-field microscope is indicated by reference numeral 20, etc., which is shown by a different reference numeral from FIG. 1, but the configuration and function of each part are the same as those in FIG. 1.

[0041] As shown in Fig. 2, the dark-field microscope 20 of this embodiment includes an imaging device (sensor) 100, an imaging lens 101, and an objective lens 102. Micro-lens 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 micro-lens arrays 106 and 107. The micro-lens arrays 106 and 107 and the shutter array device 200 are installed near the pupil plane of the dark-field microscope 20.

[0042] The objective lens 102 is configured such that the light beam 300 irradiated from the laser light source 103 onto the wafer 104 is reflected from the surface of the wafer 104, and the reflected light 301 is incident thereon. 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 imaging device 100, and is detected as an electrical signal. Note that the light beam 300 irradiated from the laser light source 103 passes through the vacuum sealing window 351, is reflected by the mirror 352, and is irradiated onto the wafer 104.

[0043] When there is a defect 108 on the wafer 104, the light beam 300 that hits the defect 108 is reflected, and reflected light 301 different from normal is generated. This reflected light 301 is detected by the imaging device 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 105, the defect 108 existing on the surface of the wafer 104 can be found.

[0044] The shutter array device and the micro-lens arrays in Figs. 1 and 2 will be described in detail with reference to Figs. 3A to 3F.

[0045] Figure 3A shows the state where all the shutters 220 of the shutter array device 200 are open. In Figure 3A, the shutter array device 200 is installed between the microlens arrays 106 and 107. All the shutters 220 of the shutter array device 200 are open. Therefore, the reflected light 302 passing through the shutter array device 200 from below the paper surface as shown in Figure 2 converges at the shutter aperture 304 to form a focus and becomes light 303.

[0046] Figure 3B shows the state where all but some of the shutters 220 of the shutter array device 200 are closed. Also, Figure 3C shows the state where all the shutters 210 of the shutter array device 200 are closed. Thus, the plurality of shutters (closed) 210 and shutters (open) 220 have a configuration in which each can be independently opened and closed.

[0047] Figures 3D to 3F show the spatial filters corresponding to the states shown in Figures 3A to 3C respectively. Figures 3D to 3F are views seen from above or below the shutter array device 200.

[0048] In these figures, the shutter closed state 211 is represented in black, and the shutter open state 221 is represented in white. By individually controlling ON / OFF for each pixel of the shutter array device 200, a plurality of types of spatial filters (spatial masks) can be configured.

[0049] In Figures 3A to 3C, the shutters 210, 220 of the shutter array device 200 and the lenses of the microlens arrays 106, 107 are arranged in a 3 - row and 3 - column pattern, but this is just an example, and a larger - scale matrix may be formed as needed.

[0050] Next, with reference to FIGS. 6A to 6C, the problems to be solved by the present invention described above will be described in detail. FIGS. 6A to 6C are longitudinal sectional views of one shutter within the shutter array device 200, and all show the operation of the shutter. FIGS. 6A to 6C show a potential (+) and a potential (-) schematically indicating the voltage application state of the shutter array.

[0051] As shown in FIG. 6A, a positive potential (V1) is applied to the shutter 212 via the shutter support portion 203, and a negative potential or a potential of 0 (V2) is applied to the substrate 201. Due to the resulting potential difference, an electrostatic force is generated, and the shutter 212 opens. Note that even if the potentials of V1 and V2 are set in reverse, the operating behavior of the shutter is the same.

[0052] As shown in this figure, the lower surface of the shutter 212 is positively charged, and the inner wall surface 282 of the substrate 201 is negatively charged. As a result, the shutter 212 rotates around the shaft portion (torsion beam 232), moves the shutter opening 264, and as a result, the shutter opens. When the application of the voltage is stopped, the shutter returns to the closed state due to the restoring force of the shaft portion (torsion beam 232).

[0053] For example, when V1 is a positive potential of +10 to +200 V and V2 is a negative potential of -10 to -200 V, the applied voltage is 20 to 400 V. When the voltage applied to the shutter is increased, the opening angle 250 of the shutter increases according to the applied voltage. However, the voltage applied to the shutter also varies depending on the size of the shutter 212, and the present invention is not limited to the above example.

[0054] On the other hand, as shown in FIG. 6B, when the opening angle 251 of the shutter 212 reaches a certain angle, the distance between the shutter 212 and the substrate 201 becomes close, and the electrostatic force inversely proportional to the square of the distance becomes larger than the reaction force of the torsion beam 232 supporting the shutter 212 with respect to the shutter rotation, and a pull-in occurs in which the shutter 212 fully opens at once, resulting in the state of the shutter 212 shown in FIG. 6C.

[0055] As shown in FIG. 6C, when the shutter 212 is fully opened, due to the influence of static electricity or moisture in the air, the opened shutter 212 may stick to the inner wall surface 282 of the shutter opening 264 provided on the substrate 201, and then the opening and closing control of the shutter 212 may become impossible. In order to prevent such sticking of the shutter, it is preferable to stop the shutter 212 in the space of the shutter opening 264 without fully opening it. When the shutter 212 is opened halfway and stopped in the air, there is a concern about the occurrence of pull-in. Therefore, in the present invention, a stopper structure described below is proposed.

[0056] Next, with reference to FIGS. 4 to 5D, the optical filtering device of the present embodiment will be described. FIG. 4 is a perspective view showing an example (5×5 array) of the shutter array device of the present embodiment. FIG. 5A is a perspective view showing one shutter array of the present embodiment, and FIG. 5B is a top view thereof. FIG. 5C is a perspective view showing a state where the shutter is open, and FIG. 5D is a top view thereof. Note that in FIGS. 5A to 5D, the electrodes are shown omitted.

[0057] The optical filtering device of the present embodiment is configured as a 5×5 array in which 25 shutter arrays are arranged 5 by 5 vertically and horizontally as shown in FIG. 4. Each of the shutter arrays is provided with an electrode pad 240, and by applying a voltage through the electrode pad 240, the opening and closing of the shutter 210 are controlled as described above.

[0058] Here, in the optical filtering device of the present embodiment, as shown in FIGS. 5A and 5B, a hinge 233 is provided on the shutter 222, and the hinge 233 and the shutter support portion 203 are connected by a torsion beam 232. Further, a stopper 230 is provided on the side wall surface 253 of the shutter opening 264. The stopper 230 is a quadrangular prism having substantially the same shape in the cross section in the thickness direction of the substrate 201 and is formed integrally with the substrate 201. Furthermore, a notch portion 231 is provided in a state where a part of the shutter 222 is removed and recessed. Due to this notch portion 231, the shutter 222 becomes polygonal at portions other than the hinge 233 and the torsion beam 232.

[0059] With the above configuration, as shown in FIGS. 5C and 5D, even when the shutter 222 is opened, the notch 231 abuts against the stopper 230 at the abutting portion 234 and can stop in the space of the shutter opening 264.

[0060] As a result, even when a pulling voltage is applied, the shutter 222 does not fully open and stops halfway. The positions where the stopper 230 and the notch 231 are provided are set so that the shutter 222 stops at a desired opening angle 251 (see FIG. 6B).

[0061]

[0062] As described above, the optical filtering device of the present embodiment includes a shutter 210 (222) that can be opened and closed by voltage control, and a substrate 201 having a shutter opening 264 that is a movable range of the shutter 210 (222). The substrate 201 is disposed on the side surface of the shutter opening 264 so as to extend over the whole or a part of the thickness direction of the substrate 201, and has a stopper 230 in which any cross section in the thickness direction of the substrate 201 has substantially the same shape. The shutter 210 (222) has a notch 231 and is configured such that the notch 231 abuts against the stopper 230 when the shutter 210 (222) is opened.

[0063] Thereby, in an optical filtering device used as a spatial filter for a dark field microscope or an optical inspection device, a highly reliable optical filtering device capable of controlling the shutter at a desired opening angle without fully opening the shutter can be realized.

[0064] Since the shutter does not fully open, it is possible to prevent the shutter from sticking to the wall surface of the shutter opening, and the stress generated in the beam portion that supports the shutter is reduced, improving the reliability of the defect inspection device, the dark field microscope, the optical inspection device, and the review SEM.

Example

[0065] Referring to FIG. 7, the optical filtering device according to Embodiment 2 of the present invention will be described. FIG. 7 is a top view of the shutter array of this embodiment, showing the state where the shutter is closed. Note that the electrodes are not shown.

[0066] In this embodiment, as shown in FIG. 7, the upper surface of the stopper 235 is nearly semi-circular in shape. That is, the stopper 235 is substantially semi-cylindrical in shape, and the cross-section in the thickness direction of the substrate 201 is substantially the same shape. Further, the shutter 222 has a shape in which a part thereof is cut off, and a curve is provided in the recessed notch portion 236. Therefore, when the shutter 222 opens and the notch portion 236 abuts against the stopper 235, the contact becomes a point contact, and the contact portion is smaller than the line contact between the stopper 230 and the notch portion 231 of the shutter 222 shown in FIGS. 5A to 5D, and it becomes more difficult to stick.

[0067] It is preferable to provide both the stopper 235 and the notch portion 236, but either one may be sufficient. The shapes of the curved surface of the stopper 235 and the curve of the notch portion 236 are not limited to arcs, and may be provided so that the contact portion between the stopper and the notch portion becomes small.

[0068] For example, the stopper 235 may have a curve in a part of the cross-section in the thickness direction of the substrate 201, and the notch portion 236 may be configured to have a curve in a part thereof.

Embodiment

[0069] Referring to FIG. 8, the optical filtering device according to Embodiment 3 of the present invention will be described. FIG. 8 is a top view of the shutter array of this embodiment, showing the state where the shutter is closed. Note that the electrodes are not shown.

[0070] In this embodiment, as shown in FIG. 8, a tapered portion 237 is provided on the surface where the notch portion 231 of the stopper 230 abuts.

[0071] By using the stopper 230 provided with the tapered portion 237 as in this embodiment, the contact portion with the notch portion 231 of the shutter 222 becomes smaller, and sticking can be prevented.

[0072] Also, the taper may be provided not on the stopper 230 side but on the side of the recessed notch portion obtained by cutting out a part of the shutter 222.

Example

[0073] Referring to FIG. 9, the optical filtering device according to Embodiment 4 of the present invention will be described. FIG. 9 is a top view of the shutter array of this embodiment, showing the state where the shutter is closed. Note that the electrodes are not shown.

[0074] In this embodiment, as shown in FIG. 9, the stopper 230 is provided at the corner of the shutter support portion 204 and is integrated therewith. That is, a part of the shutter support portion 204 around the shutter 222 is removed to form a recess, and the shutter opening 238 has a polygonal shape. The shutter 222 extends within the range of the shutter convex portion 239 in a direction perpendicular to the movable direction, that is, on the side surface of the shutter opening. Therefore, the shutter 222 has a polygonal shape.

[0075] The difference from Embodiment 1 (FIGS. 5A to 5D) is that the width of the shutter support portion 204 is narrower where the shutter 222 protrudes in the direction of the shutter support portion 204.

[0076] Note that a curved surface portion or a curved portion may be provided on the stopper 230 and the notch portion 231 as in Embodiment 2 (FIG. 7), or a tapered portion may be provided as in Embodiment 3 (FIG. 8).

[0077] As described above, in the optical filtering device of this embodiment, the stopper 230 is provided at the inner corner of the shutter support portion 204, and the shutter 222 is connected to the notch portion 231 and is configured to have a wide portion protruding in a direction perpendicular to the thickness direction of the substrate 201.

[0078] As in this embodiment, by providing the stopper 230 on the side wall surface of the shutter opening 238 and providing the notch portion 231 in the shutter 222, the shutter 222 can be stopped halfway without being fully opened, and adhesion can be prevented.

Embodiment

[0079] With reference to FIGS. 10A to 10D, the manufacturing process of the optical filtering device according to Embodiment 5 of the present invention will be described. FIGS. 10A to 10D show longitudinal sections in each step when processing one shutter in the optical filtering device (shutter array device).

[0080] In this embodiment, as shown in FIG. 10A, an SOI wafer 500 is used. The SOI wafer 500 has a three-layer structure of a device layer 501, a BOX (Buried Oxide) layer 502, and a handle layer 503, and the respective thicknesses are about 0.1 μm to 10 μm, 0.1 μm to 10 μm, and 30 μm to 1000 μm.

[0081] First, a photoresist is applied to the device layer 501, and the shape of the shutter 510 (222) is patterned by photolithography. Then, as shown in FIG. 10B, the shape of the shutter 510 (222) is processed by etching. At this time, an opening pattern 520 is formed in the device layer 501. Then the photoresist is removed.

[0082] Next, a photoresist is applied to the handle layer 503, and the pattern of the shutter opening 521 is formed by photolithography. Then, as shown in FIG. 10C, etching is performed up to the BOX layer 502 to form the shutter opening 521. Then, the resist is removed.

[0083] Finally, as shown in FIG. 10D, the BOX layer 502 exposed in the shutter opening 521 is removed by etching to expose the back surface 522 of the shutter. In this step, the shutter 510 (222) is separated from the shutter support portion 203 except for the portion connected to the torsion beam 232 (see FIG. 5B), and a gap 523 is formed.

[0084] As in this embodiment, by processing the SOI wafer 500 from both sides, a shutter can be formed.

[0085] Note that for the etching described above, either dry etching or wet etching may be used.

[0086] Also, although FIGS. 10A to 10D show the processing steps for one shutter, in a shutter array in which a plurality of shutters are arranged in an array, each shutter is processed simultaneously.

Embodiment

[0087] Referring to FIG. 11, the mounting structure of the shutter array device according to Embodiment 6 of the present invention will be described. FIG. 11 is a perspective view showing the mounting structure of the shutter array device of this embodiment.

[0088] The optical filtering device described in Embodiments 1 to 5 can be mounted in a form as shown in FIG. 11, for example.

[0089] The mounting structure of the shutter array device of this embodiment includes, as shown in FIG. 11, a shutter array 205 in which shutters are arrayed, and a wiring substrate 400 having wiring 401 that mounts the shutter array 205 and supplies a voltage for opening and closing each shutter of the shutter array 205.

[0090] The wiring 401 is connected to a flexible substrate 403 different from the wiring substrate 400 via a bonding wire 402, and is electrically connected to an external control device (not shown) via a connector 404 of the flexible substrate 403.

[0091] With the mounting structure as in this embodiment, a voltage supplied from an external control device can be applied to the electrode pads 240 (see FIG. 4) of each shutter array to control the opening and closing of the shutter 210.

[0092] Note that the flexible substrate 403 may be a printed wiring board, and it is also possible to connect electrodes to each other using bumps or solder by facing the electrodes instead of the bonding wire 402, or to connect them via an anisotropic conductive film.

Example

[0093] Referring to FIG. 12, the mounting structure of the shutter array device according to Example 7 of the present invention will be described. FIG. 12 is a perspective view showing the mounting structure of the shutter array device of this example.

[0094] In this example, a quartz glass (protective cover) 405 covering the shutter array 205 is further provided in the mounting structure of the shutter array device of Example 6 (FIG. 11).

[0095] For example, by attaching and sealing the quartz glass 405 to the upper surface of the shutter array 205 by adhesion with an adhesive or other joining means, the shutter array 205 can be protected from dust and moisture in the air.

[0096] The optical filtering device (shutter array device) described in each of the above examples operates such that the shutter rotates about the torsion beam by electrostatic force, and the notch portion of the shutter collides with the stopper to stop the shutter midway. By stopping the shutter midway, the stress generated in the torsion beam is smaller than when fully opened, the load applied to the torsion beam is reduced, and the concern of breakage can be reduced to improve reliability.

[0097] On the other hand, in order to prevent the shutter from being damaged by the impact caused by the notch portion of the shutter colliding with the stopper, an arbitrary voltage curve such as a sine curve or a trapezoidal curve, which is the voltage value curve when applying a voltage, is set, and the speed is slowed down immediately before the notch portion of the shutter contacts the stopper, thereby preventing the shutter from being damaged by the collision.

[0098] Note that the present invention is not limited to the above-described embodiments, and includes various modifications. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Also, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, for a part of the configuration of each embodiment, addition, deletion, or replacement with other configurations is possible.

Explanation of Reference Numerals

[0099] 10…Defect observation device, 20, 1003…Dark field microscope (defect detection unit), 100, 1016…Image sensor (sensor), 101, 1015…Imaging lens, 102, 1013…Objective lens, 103, 1010…Laser light source, 104, 1001…Wafer, 105, 1004…Stage, 106, 107, 1102, 1103…Micro lens array, 108…Defect, 200, 1101…Shutter array device, 201…Substrate, 203, 204…Shutter support part, 205…Shutter array, 210, 220, 212, 222, 510…Shutter, 211…Shutter closed state, 213…Gap, 221…Shutter open state, 230, 235…Stopper, 231, 236…Notch part, 232…Twisted beam, 233…Hinge, 234…Contact part, 237…Taper part, 238, 264, 521…Shutter opening, 239…Shutter convex part, 240…Electrode pad, 250, 251, 252…Opening angle, 253…Side wall surface, 282…Inner wall surface (of substrate 201), 300…Light ray, 301, 302…Reflected light, 303…Light, 304…Shutter opening, 351, 1011, 1014…Vacuum sealing window, 352, 1012…Mirror, 400…Wiring board, 401…Wiring, 402…Bonding wire, 403…Flexible board, 404…Connector, 405…Quartz glass, 500…SOI wafer, 501…Device layer, 502…BOX layer, 503…Handle layer, 520…Opening pattern, 522…Back surface of shutter, 523…Gap, 1002…Scanning electron microscope (SEM), 1005…Vacuum chamber, 1006…Control unit, 1007…Terminal, 1008…Recording device, 1009…Network, 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.

Claims

1. A shutter that can be opened and closed by voltage control, and a substrate having a shutter opening that is the movable range of the shutter, and is provided with, The substrate has a stopper that extends in the thickness direction of the substrate and is disposed on the side surface of the shutter opening, and any cross section in the thickness direction of the substrate has substantially the same shape, The shutter has a notch, An optical filtering device, characterized in that when the shutter is opened, the notch abuts against the stopper.

2. The optical filtering device according to claim 1, wherein the stopper has a substantially semi-cylindrical shape.

3. The optical filtering device according to claim 1, wherein a part of the notch has a curve.

4. The optical filtering device according to claim 1, wherein the stopper has a curve in a part of the cross section in the thickness direction of the substrate, and the notch has a curve in a part thereof.

5. The optical filtering device according to claim 1, wherein the stopper has a taper at the contact portion with the notch.

6. The optical filtering device according to claim 1, a torsion beam that serves as an axis for rotating the shutter, and a shutter support portion provided around the shutter and connected to the torsion beam to support the shutter. An optical filtering device, characterized by having.

7. The optical filtering device according to claim 6, wherein the stopper is provided at an inner corner portion of the shutter support portion, and the shutter has a wide portion that is connected to the notch and protrudes in a direction perpendicular to the thickness direction of the substrate.

8. The optical filtering device according to claim 1, a shutter array in which the shutters are arrayed, a wiring substrate on which the shutter array is mounted and having wiring for supplying a voltage for opening and closing each shutter of the shutter array, and a protective cover that covers the shutter array. An optical filtering device, characterized by comprising.

9. The optical filtering device according to claim 1, An optical filtering device, characterized in that it is mounted on any one of an optical inspection device, a dark-field optical microscope, a defect inspection device, and a review SEM.

10. A shutter that can be opened and closed by voltage control, A substrate having a shutter opening that is the movable range of the shutter, and The substrate has a stopper that extends in the thickness direction of the substrate and is disposed on a side surface of the shutter opening, and any cross section in the thickness direction of the substrate has substantially the same shape. The shutter has a notch, A MEMS shutter, characterized in that when the shutter is opened, the notch abuts against the stopper.

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