JP6017902B2 - Inspection device - Google Patents

Description

  The present invention relates to an inspection apparatus that inspects a defect or the like of a pattern formed on a surface of an inspection target, and more specifically, captures secondary charged particles that change according to the properties of the surface of the inspection target to form image data. The present invention also relates to an inspection apparatus and an inspection method for inspecting a pattern or the like formed on a surface to be inspected with high throughput based on the image data.

  The conventional semiconductor inspection apparatus has been an apparatus and technology corresponding to the 100 nm design rule. However, the samples to be inspected are diversified with wafers, exposure masks, EUV masks, NIL (nanoimprint lithography) masks, and substrates, and currently, there is a need for an apparatus and technology corresponding to the design rule for samples of 5 to 30 nm. ing. That is, it is required to deal with generations in which the node of L / S (line / space) or hp (half pitch) in the pattern is 5 to 30 nm. When inspecting such a sample with an inspection apparatus, it is necessary to obtain high resolution.

  Here, “sample” refers to an exposure mask, EUV mask, nanoimprint mask (and template), semiconductor wafer, optical element substrate, optical circuit substrate, and the like. Some of these have a pattern and some have no pattern. Some of them have a pattern and some do not. Patterns with no irregularities are formed with different materials. Those without a pattern include those coated with an oxide film and those not coated with an oxide film.

  Here, the problems of the conventional inspection apparatus are summarized as follows.

  The first is the problem of lack of resolution and throughput. In the prior art of the mapping optical system, the pixel size is about 50 nm and the aberration is about 200 nm. In order to further improve the high resolution and throughput, it is necessary to reduce aberration, reduce the energy width of the irradiation current, increase the small pixel size, and increase the amount of current.

Second, in the case of the SEM type inspection, the problem of throughput increases as the inspection of the fine structure is performed. This is because image resolution is insufficient unless a smaller pixel size is used. These are due to the fact that SEM mainly performs image formation and defect inspection by edge contrast. For example, in the case of 5 nm Px size and 200 MPPS, it is approximately 6 hr / cm ² . This takes 20 to 50 times as long as the projection method, and is unrealistic in inspection.

International Publication No. 2002/001596 JP 2007-48686 A Japanese Patent Laid-Open No. 11-132975

  In conventional inspection equipment, quartz or synthetic quartz is used as the base material for the photoelectron surface of the photoelectron generator. However, quartz and synthetic quartz have low thermal conductivity, and the heat of the part irradiated with electrons is quickly dissipated. I can't let you. Therefore, in order to increase the resolution of the inspection apparatus and improve the throughput, when trying to increase the power density of the laser that irradiates the photoelectron surface, the photoelectron surface is damaged by the electron irradiation, depending on the decrease in quantum efficiency and the location. There was a problem that unevenness in quantum efficiency occurred.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an inspection apparatus capable of reducing damage to the photoelectron surface caused by electron irradiation.

  The inspection apparatus of the present invention is generated from a beam generating means for generating either charged particles or electromagnetic waves as a beam, a primary optical system for directing and irradiating the beam to the inspection object held in the working chamber, and the inspection object. A secondary optical system for detecting secondary charged particles; and an image processing system for forming an image based on the detected secondary charged particles. The primary optical system includes a photoelectron generator having a photoelectron surface. A material having higher thermal conductivity than quartz is used for the base material of the photoelectron surface.

  In the inspection apparatus of the present invention, sapphire or diamond may be used for the base material of the photoelectron surface. The shape of the photoelectron surface may be a circle having a diameter of 10 μm to 200 μm or a rectangle having a side of 10 μm to 200 μm.

  In the inspection apparatus of the present invention, the photoelectron surface may be coated with a photoelectron material, and ruthenium or gold may be used as the photoelectron material. The thickness of the optoelectronic material may be 5 nm to 100 nm.

  ADVANTAGE OF THE INVENTION According to this invention, the inspection apparatus which can reduce the damage which a photoelectron surface receives by electron irradiation can be provided.

FIG. 3 is an elevational view showing main components of an inspection apparatus according to an embodiment of the present invention, viewed along line AA in FIG. 2. It is the top view of the main components of the inspection apparatus shown in FIG. 1, Comprising: It is the figure seen along line BB of FIG. It is a schematic sectional drawing which shows the other Example of the board | substrate carrying-in apparatus in the test | inspection apparatus which concerns on one Embodiment of this invention. It is sectional drawing which shows the mini-environment apparatus of FIG. 1, Comprising: It is the figure seen along line CC. FIG. 3 is a diagram illustrating the loader housing of FIG. 1, as viewed along line DD in FIG. 2. It is an enlarged view of a wafer rack, [A] is a side view, [B] is a sectional view taken along line EE of [A]. It is a figure which shows the modification of the support method of a main housing. It is a figure which shows the modification of the support method of a main housing. It is a schematic diagram which shows schematic structure of a light irradiation type electron optical apparatus. It is a figure which concerns on one Embodiment of this invention, and is a figure which shows the whole structure of an inspection apparatus. It is a figure concerning one embodiment of the present invention, and is a figure showing an example of an inspection device provided with an electron gun. It is a figure which concerns on one Embodiment of this invention, and is a figure which shows the intensity | strength (amount) and energy state of the irradiation current of the electron beam with which a sample surface is irradiated, and the state of the beam irradiated to the sample surface. It is a figure which concerns on one Embodiment of this invention, and is a figure which shows the example of the primary optical system using UV, EUV, or X-ray | X_line. It is a figure which concerns on one Embodiment of this invention, and is a schematic diagram of formation of the crossover of a primary optical system. It is a figure which concerns on one Embodiment of this invention, and is a figure which shows 2nd Embodiment of a primary optical system. It is a figure which concerns on one Embodiment of this invention, and is a figure which shows an example when light or a laser is guide | induced to a photoelectron surface from the middle position of a primary system by the mirror installed in the column. It is a figure which concerns on one Embodiment of this invention, and is a figure which shows an example when light or a laser is guide | induced to a photoelectron surface from the middle position of a primary system by the mirror installed in the column. It is a figure which concerns on one Embodiment of this invention, and is a figure which shows the example used for the primary optical system which concerns on 2nd Embodiment of a primary optical system by coating the masking material of a pattern on the photoelectron surface. It is a figure which concerns on one Embodiment of this invention, and is a figure which shows the method of reflecting the transmitted light or laser, and irradiating a photoelectron surface again. It is a figure showing typically the double tube structure of the semiconductor inspection device concerning one embodiment of the present invention. It is a figure showing the whole semiconductor inspection device composition concerning one embodiment of the present invention. It is a figure which concerns on one Embodiment of this invention, and is a figure which shows the relationship between the landing energy LE when the sample is irradiated with an electron beam, and the gradation DN. It is a figure which concerns on one Embodiment of this invention, and is a figure which shows the phenomenon of a transition area | region. It is a figure which concerns on one Embodiment of this invention, and is a figure which shows the example of a measurement of the beam shape in the CO position with respect to LE. It is a figure which concerns on one Embodiment of this invention, and is a figure which shows the principle of a 2nd detector. It is a figure which concerns on one Embodiment of this invention, and is the figure which showed the structure of the electron beam inspection apparatus to which this invention is applied. It is a figure which concerns on one Embodiment of this invention, and is a figure which shows the detector which can switch EB-TDI and EB-CCD. It is a figure which concerns on one Embodiment of this invention, and is a figure which shows the electron beam inspection apparatus with which this invention was applied. It is a figure which concerns on one Embodiment of this invention, and is a figure which shows an example of a structure in the case of installing the electronic column of a mapping optical type | mold inspection apparatus, and a SEM type | mold inspection apparatus in the same main chamber. It is a figure which concerns on one Embodiment of this invention, and is a figure which shows the example of the form which united the form which irradiates a sample with light or a laser, and the form which irradiates a sample with an electron beam to a primary system. It is a figure which concerns on one Embodiment of this invention, and is a figure which shows the example of the form which united the form which irradiates a sample with light or a laser, and the form which irradiates a sample with an electron beam to a primary system. It is a figure which concerns on one Embodiment of this invention, and is a figure which shows the example of the form which united the form which irradiates a sample with light or a laser, and the form which irradiates a sample with an electron beam to a primary system.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings as a semiconductor inspection apparatus for inspecting a substrate, that is, a wafer having a pattern formed as an inspection target, that is, a wafer. The following embodiments are examples of the inspection apparatus and the inspection method of the present invention, and are not limited to these.

  1 and 2A, the main components of the semiconductor inspection apparatus 1 of the present embodiment are shown in an elevational plane and a plane.

  The semiconductor inspection apparatus 1 according to the present embodiment includes a cassette holder 10 that holds a cassette that stores a plurality of wafers, a mini-environment device 20, a main housing 30 that defines a working chamber, and a mini-environment device 20. A loader housing 40 disposed between the main housing 30 and defining two loading chambers; a loader 60 for loading a wafer from the cassette holder 10 onto a stage device 50 disposed in the main housing 30; An electron optical device 70 attached to a vacuum housing, an optical microscope 3000, and a scanning electron microscope (SEM) 3002 are provided and are arranged in a positional relationship as shown in FIGS. 1 and 2A. The semiconductor inspection apparatus 1 further includes a precharge unit 81 disposed in the vacuum main housing 30, a potential application mechanism 83 (shown in FIG. 14) for applying a potential to the wafer, an electron beam calibration mechanism 85, And an optical microscope 871 constituting an alignment controller 87 for positioning the wafer on the stage device. The electron optical device 70 includes a lens barrel 71 and a light source tube 7000. The internal structure of the electro-optical device 70 will be described later.

<Cassette holder>
The cassette holder 10 includes a plurality of cassettes c (for example, closed cassettes such as SMIF and FOUP manufactured by Assist) in which a plurality of wafers (for example, 25 wafers) are stored in parallel with each other in the vertical direction. 2 in this embodiment). As this cassette holder, a cassette having a structure suitable for the case where the cassette is transported by a robot or the like and automatically loaded into the cassette holder 10, or an open cassette having a structure suitable for the manual loading is used. Each can be selected and installed. In this embodiment, the cassette holder 10 is a type in which the cassette c is automatically loaded. The cassette holder 10 includes, for example, an elevating table 11 and an elevating mechanism 12 that moves the elevating tail 11 up and down. The cassette c is on the elevating table. 2A can be automatically set in the state shown by the chain line in FIG. 2A, and after the setting, it is automatically rotated to the state shown in the solid line in FIG. 2A to rotate the first transport unit in the mini-environment device. Directed to the axis. Further, the lifting table 11 is lowered to the state shown by the chain line in FIG. As described above, the cassette holder used for automatic loading or the cassette holder used for manual loading may be a known structure as appropriate. Description is omitted.

  In another embodiment, as shown in FIG. 2B, a plurality of 300 mm substrates are accommodated in a grooved pocket (not shown) fixed inside the box body 501, and are transported, stored, etc. It is. The substrate transport box 24 is connected to a rectangular tube-shaped box body 501 and a substrate loading / unloading door automatic opening / closing device, and a substrate loading / unloading door 502 capable of opening and closing a side opening of the box body 501 by a machine, A lid 503 that is positioned on the opposite side and covers an opening for attaching and detaching filters and a fan motor, a groove-type pocket (not shown) for holding the substrate W, a ULPA filter 505, a chemical filter 506, And a fan motor 507. In this embodiment, the substrate is loaded and unloaded by the robot-type first transfer unit 612 of the loader 60.

  The substrate, that is, the wafer housed in the cassette c is a wafer to be inspected, and such inspection is performed after or during the process of processing the wafer in the semiconductor manufacturing process. Specifically, a substrate that has been subjected to a film forming process, CMP, ion implantation, or the like, that is, a wafer having a wiring pattern formed on the surface, or a wafer on which a wiring pattern has not yet been formed is stored in a cassette. Since a large number of wafers accommodated in the cassette c are arranged in parallel in the vertical direction, the first transfer unit can be held by a wafer at an arbitrary position and a first transfer unit described later. The arm can be moved up and down.

<Mini-environment device>
1 to 3, a mini-environment device 20 includes a housing 22 that defines a mini-environment space 21 that is controlled in atmosphere, and a gas such as clean air in the mini-environment space 21. A gas circulation device 23 for circulating and controlling the atmosphere, a discharge device 24 for collecting and discharging a part of the air supplied into the mini-environment space 21, and a mini-environment space 21 are provided. And a pre-aligner 25 for roughly positioning a substrate to be inspected, that is, a wafer.

  The housing 22 has a top wall 221, a bottom wall 222, and a peripheral wall 223 that surrounds the four circumferences, and has a structure that blocks the mini-environment space 21 from the outside. In order to control the atmosphere of the mini-environment space, the gas circulation device 23 is attached to the top wall 221 in the mini-environment space 21 as shown in FIG. 3, and gas (air in this embodiment) is installed. And a gas supply unit 231 for flowing clean air in a laminar flow downwardly through one or more gas outlets (not shown) and disposed on the bottom wall 222 in the mini-environment space A recovery duct 232 that recovers air that has flowed down toward the bottom, and a conduit 233 that connects the recovery duct 232 and the gas supply unit 231 and returns the recovered air to the gas supply unit 231. Yes. In this embodiment, the gas supply unit 231 takes about 20% of the supplied air from the outside of the housing 22 and cleans it. However, the ratio of the gas taken in from the outside can be arbitrarily selected. . The gas supply unit 231 includes a HEPA or ULPA filter having a known structure for producing clean air. The laminar flow of the clean air, that is, the downward flow, is mainly supplied to flow through the transfer surface of the first transfer unit, which will be described later, disposed in the mini-environment space 21, and is generated by the transfer unit. This prevents dust that may be adhered to the wafer. Therefore, it is not always necessary that the downflow jet outlet is located close to the top wall as shown in the drawing, and it is sufficient if it is above the transport surface of the transport unit. Moreover, there is no need to flow over the entire mini-environment space. In some cases, cleanliness can be ensured by using ion wind as clean air. Further, a sensor for observing the cleanliness can be provided in the mini-environment space, and the apparatus can be shut down when the cleanliness deteriorates. An entrance / exit 225 is formed in a portion of the peripheral wall 223 of the housing 22 adjacent to the cassette holder 10. A shutter device having a known structure may be provided in the vicinity of the doorway 225 so that the doorway 225 is closed from the mini-environment device side. The laminar flow downflow created near the wafer may be, for example, a flow rate of 0.3 to 0.4 m / sec. The gas supply unit may be provided outside the mini-environment space.

  The discharge device 24 includes a suction duct 241 disposed below the transfer unit at a position below the wafer transfer surface of the transfer unit, a blower 242 disposed outside the housing 22, a suction duct 241, and a blower 242. And a conduit 243 for connecting the two. The discharge device 24 sucks a gas containing dust that may flow around the transport unit and may be generated by the transport unit through the suction duct 241, and the outside of the housing 22 through the conduits 243 and 244 and the blower 242. To discharge. In this case, the air may be discharged into an exhaust pipe (not shown) drawn near the housing 22.

  The aligner 25 disposed in the mini-environment space 21 is formed on an orientation flat formed on the wafer (referred to as a flat portion formed on the outer periphery of a circular wafer, hereinafter referred to as an orientation flat) or on the outer peripheral edge of the wafer. One or more V-shaped notches or notches are detected optically or mechanically to pre-position the rotational position around the wafer axis OO with an accuracy of about ± 1 degree. It is supposed to keep. The pre-aligner constitutes a part of the mechanism for determining the coordinates of the inspection object of the invention described in the claims, and is responsible for the rough positioning of the inspection object. Since this pre-aligner itself may have a known structure, description of its structure and operation is omitted.

  Although not shown, a recovery duct for a discharge device may be provided at the lower portion of the pre-aligner so that air containing dust discharged from the pre-aligner is discharged to the outside.

<Main housing>
1 and 2A, a main housing 30 that defines a working chamber 31 includes a housing body 32 that is mounted on a vibration isolating device or vibration isolating device 37 disposed on a base frame 36. It is supported by the mounted housing support device 33. The housing support device 33 includes a frame structure 331 assembled in a rectangular shape. The housing main body 32 is disposed and fixed on the frame structure 331, and is connected to the bottom wall 321 mounted on the frame structure, the top wall 322, the bottom wall 321 and the top wall 322, and surrounds the circumference. 323 to isolate the working chamber 31 from the outside. In this embodiment, the bottom wall 321 is made of a relatively thick steel plate so as not to be distorted by weighting by a device such as a stage device placed on the bottom wall 321. Good. In this embodiment, the housing body and the housing support device 33 are assembled in a rigid structure, and vibrations from the floor on which the base frame 36 is installed are prevented from being transmitted to the rigid structure by the vibration isolator 37. It is supposed to be. Of the peripheral wall 323 of the housing body 32, an entrance / exit 325 for taking in and out the wafer is formed in a peripheral wall adjacent to a loader housing described later.

  The vibration isolator may be an active type having an air spring, a magnetic bearing or the like, or a passive type having these. Since any of them may have a known structure, description of its own structure and function is omitted. The working chamber 31 is maintained in a vacuum atmosphere by a known vacuum device (not shown). A control device 2 that controls the operation of the entire apparatus is disposed under the base frame 36.

<Loader housing>
1, 2 </ b> A, and 4, the loader housing 40 includes a housing body 43 that defines a first loading chamber 41 and a second loading chamber 42. The housing main body 43 includes a bottom wall 431, a top wall 432, a peripheral wall 433 that surrounds the four circumferences, and a partition wall 434 that partitions the first loading chamber 41 and the second loading chamber 42. Can be isolated from the outside. The partition wall 434 has an opening, that is, an entrance / exit 435 for exchanging wafers between both loading chambers. In addition, entrances 436 and 437 are formed in a portion of the peripheral wall 433 adjacent to the mini-environment device and the main housing. The housing main body 43 of the loader housing 40 is placed on and supported by the frame structure 331 of the housing support device 33. Therefore, the floor vibration is not transmitted to the loader housing 40. A shutter device for selectively preventing communication between the mini-environment space 21 and the first loading chamber 41 is aligned with the entrance / exit 436 of the loader housing 40 and the entrance / exit 226 of the housing 22 of the mini-environment device. 27 is provided. The shutter device 27 surrounds the doorways 226 and 436 and seals 271 fixed in close contact with the side wall 433, and a door 272 that blocks air flow through the doorway in cooperation with the sealant 271. And a driving device 273 for moving the door. Further, the entrance / exit 437 of the loader housing 40 and the entrance / exit 325 of the housing main body 32 are aligned with each other, and there is a shutter device 45 that selectively blocks the communication between the second loading chamber 42 and the working chamber 31. Is provided. The shutter device 45 surrounds the entrances and exits 437 and 325, closely contacts the side walls 433 and 323, and cooperates with the sealing material 451 and the sealing material 451 that are fixed to the side walls 433 and 323. It has a door 452 for blocking and a driving device 453 for moving the door. Further, the opening formed in the partition wall 434 is provided with a shutter device 46 which is closed by a door 461 and selectively prevents communication between the first and second loading chambers. These shutter devices 27, 45 and 46 are adapted to hermetically seal each chamber when in the closed state. Since these shutter devices may be known ones, detailed description of their structure and operation will be omitted. The support method of the housing 22 of the mini-environment device 20 and the support method of the loader housing are different, and in order to prevent vibration from the floor from being transmitted to the loader housing 40 and the main housing 30 via the mini-environment device. In addition, an anti-vibration cushion material may be disposed between the housing 22 and the loader housing 40 so as to airtightly surround the doorway.

  In the first loading chamber 41, a wafer rack 47 is disposed that supports a plurality (two in this embodiment) of wafers in a horizontal state with a vertical separation. As shown in FIG. 5, the wafer rack 47 includes support columns 472 that are fixed upright at four corners of a rectangular substrate 471, and two support portions 473 and 474 are formed on each support column 472. Then, the periphery of the wafer W is placed on and held on the support portion. Then, the tips of arms of first and second transfer units, which will be described later, are brought close to the wafer from between adjacent columns, and the wafer is held by the arm.

The loading chambers 41 and 42 can be controlled in a high vacuum state (the degree of vacuum is 10 ⁻⁵ to 10 ⁻⁶ Pa) by an evacuation apparatus (not shown) having a known structure including a vacuum pump (not shown). It has become. In this case, the first loading chamber 41 can be maintained as a low vacuum chamber in a low vacuum atmosphere, and the second loading chamber 42 can be maintained as a high vacuum chamber in a high vacuum atmosphere to effectively prevent wafer contamination. By adopting such a structure, a wafer which is accommodated in the loading chamber and to be inspected next can be transferred into the working chamber without delay. By adopting such a loading chamber, the throughput of defect inspection is improved, and the degree of vacuum around the electron source that is required to be kept in a high vacuum state is made as high as possible. Can do.

  The first and second loading chambers 41 and 42 are connected to a vacuum exhaust pipe and a vent pipe (not shown) for an inert gas (for example, dry pure nitrogen), respectively. Thereby, the atmospheric pressure state in each loading chamber is achieved by an inert gas vent (injecting an inert gas to prevent oxygen gas other than the inert gas from adhering to the surface). Since the apparatus for performing such an inert gas vent itself may have a known structure, a detailed description thereof will be omitted.

<Stage device>
The stage device 50 includes a fixed table 51 disposed on the bottom wall 321 of the main housing 30, a Y table 52 that moves in the Y direction (a direction perpendicular to the paper surface in FIG. 1) on the fixed table, and a Y table. An X table 53 that moves in the X direction (left-right direction in FIG. 1), a rotary table 54 that can rotate on the X table, and a holder 55 that is arranged on the rotary table 54 are provided. The wafer is releasably held on the wafer placement surface 551 of the holder 55. The holder may have a known structure capable of releasably gripping the wafer mechanically or by an electrostatic chuck method. The stage apparatus 50 uses a servo motor, an encoder, and various sensors (not shown) to operate the plurality of tables as described above, thereby causing the wafer held by the holder on the mounting surface 551 to be electro-optically. It can be positioned with high accuracy in the X direction, Y direction, and Z direction (up and down direction in FIG. 1) with respect to the electron beam irradiated from the apparatus, and further in the direction around the vertical axis (θ direction) on the wafer support surface. It has become. For positioning in the Z direction, for example, the position of the mounting surface on the holder may be finely adjusted in the Z direction. In this case, the reference position of the mounting surface is detected by a position measuring device (laser interference distance measuring device using the principle of an interferometer) using a fine-diameter laser, and the position is controlled by a feedback circuit (not shown). Instead, the position of the notch or orientation flat of the wafer is measured to detect the planar position and the rotational position of the wafer with respect to the electron beam, and the rotary table is rotated by a stepping motor capable of controlling a minute angle or the like. In order to prevent the generation of dust in the working chamber as much as possible, the servomotors 521 and 531 for the stage device and the encoders 522 and 532 are arranged outside the main housing 30. Note that the stage device 50 may have a known structure used in, for example, a stepper, and the detailed description of the structure and operation is omitted. Also, since the laser interference distance measuring device may have a known structure, detailed description of the structure and operation is omitted.

  It is also possible to standardize a signal obtained by inputting the rotation position of the wafer with respect to the electron beam and the X and Y positions in advance to a signal detection system or an image processing system described later. Further, the wafer chuck mechanism provided in the holder is adapted to apply a voltage for chucking the wafer to the electrode of the electrostatic chuck, and has three points (preferably equally spaced in the circumferential direction) on the outer periphery of the wafer. It is designed to press and hold (separated). The wafer chuck mechanism includes two fixed positioning pins and one pressing crank pin. The clamp pin can realize automatic chucking and automatic release, and constitutes a conduction point for voltage application.

  In this embodiment, the table that moves in the horizontal direction in FIG. 2A is the X table and the table that moves in the vertical direction is the Y table. However, the table that moves in the horizontal direction in FIG. The moving table may be an X table.

<Loader>
The loader 60 includes a robot-type first transfer unit 61 arranged in the housing 22 of the mini-environment device 20 and a robot-type second transfer unit 63 arranged in the second loading chamber 42. I have.

The first transport unit 61 has a multi-node arm 612 that is rotatable about the axis O ₁ -O ₁ with respect to the drive unit 611. As the multi-node arm, an arbitrary structure can be used, but in this embodiment, the multi-node arm has three portions which are rotatably attached to each other. One portion of the arm 612 of the first transport unit 61, that is, the first portion closest to the drive unit 611 is a shaft that can be rotated by a drive mechanism (not shown) having a known structure provided in the drive unit 611. 613 is attached. The arm 612 can be rotated around the axis O ₁ -O ₁ by the shaft 613, and can expand and contract in the radial direction with respect to the axis O ₁ -O ₁ as a whole by relative rotation between the parts. A gripping device 616 for gripping a wafer such as a mechanical chuck or an electrostatic chuck having a known structure is provided at the tip of the third portion farthest from the shaft 613 of the arm 612. The drive unit 611 can be moved in the vertical direction by an elevating mechanism 615 having a known structure.

  In the first transfer unit 61, the arm extends in one direction M1 or M2 of the two cassettes c in which the arm 612 is held by the cassette holder, and one wafer is stored in the cassette c. It is taken out by holding it on an arm or holding it with a chuck (not shown) attached to the tip of the arm. Thereafter, the arm contracts (as shown in FIG. 2A), and the arm rotates to a position where it can extend in the direction M3 of the pre-aligner 25 and stops at that position. Then, the arm extends again and the wafer held by the arm is placed on the pre-aligner 25. After receiving the wafer from the pre-aligner in the reverse direction, the arm further rotates and stops at a position (direction M4) where the arm can extend toward the second loading chamber 41, and the wafer receiver 47 in the second loading chamber 41. Deliver the wafer. When the wafer is mechanically gripped, the peripheral edge of the wafer (in the range of about 5 mm from the peripheral edge) is gripped. This is because a device (circuit wiring) is formed on the entire surface of the wafer except for the peripheral portion, and if this portion is gripped, the device is broken or a defect is generated.

  The second transfer unit 63 is basically the same in structure as the first transfer unit, and is different only in that the wafer is transferred between the wafer rack 47 and the mounting surface of the stage apparatus. Therefore, detailed description is omitted.

  In the loader 60, the first and second transfer units 61 and 63 transfer the wafer from the cassette held in the cassette holder onto the stage device 50 disposed in the working chamber 31 and vice versa. The arm of the transfer unit is moved up and down while maintaining the state. The wafer unit is simply taken out from the cassette and inserted into the cassette, placed on the wafer rack and taken out from the wafer rack, and the wafer stage device. Only when placed on and taken out of. Therefore, a large wafer, for example, a wafer having a diameter of 30 cm can be moved smoothly.

<Wafer transfer>
Next, the transfer of the wafer from the cassette c supported by the cassette holder to the stage device 50 disposed in the working chamber 31 will be described in order.

  As described above, the cassette holder 10 has a structure suitable for manually setting a cassette, and has a structure suitable for automatically setting a cassette. In this embodiment, when the cassette c is set on the lifting table 11 of the cassette holder 10, the lifting table 11 is lowered by the lifting mechanism 12 and the cassette c is aligned with the entrance / exit 225.

  When the cassette is aligned with the entrance / exit 225, a cover (not shown) provided on the cassette is opened, and a cylindrical cover is disposed between the cassette c and the entrance / exit 225 of the mini-environment, so Block the environment space from the outside. Since these structures are publicly known, detailed description of the structure and operation is omitted. When a shutter device that opens and closes the entrance / exit 225 is provided on the mini-environment device 20 side, the shutter device operates to open the entrance / exit 225.

  On the other hand, the arm 612 of the first transport unit 61 is stopped in a state facing in either the direction M1 or M2 (in this description, the direction of M1). One of the wafers stored in the wafer is received. In this embodiment, the vertical position adjustment between the arm and the wafer to be taken out from the cassette is performed by the vertical movement of the driving unit 611 and the arm 612 of the first transfer unit 61. It may be performed up and down or both.

  When the reception of the wafer by the arm 612 is completed, the arm contracts and operates the shutter device to close the entrance / exit (if there is a shutter device), and then the arm 612 rotates around the axis O1-O1 in the direction M3. It will be in the state where it can extend toward. Then, the arm extends and is placed on the tip or held by the chuck, the wafer is placed on the pre-aligner 25, and the pre-aligner sets the rotation direction of the wafer (the direction around the central axis perpendicular to the wafer plane) to a predetermined value. Position within range. When the positioning is completed, the transfer unit 61 receives the wafer from the pre-aligner 25 at the tip of the arm and then contracts the arm so that the arm can be extended in the direction M4. Then, the door 272 of the shutter device 27 moves to open the entrances 226 and 436 and the arm 612 extends to place the wafer on the upper stage side or the lower stage side of the wafer rack 47 in the first loading chamber 41. Note that the opening 435 formed in the partition wall 434 is closed in an airtight state by the door 461 of the shutter device 46 before the shutter device 27 is opened and the wafer is transferred to the wafer rack 47 as described above.

  In the wafer transfer process by the first transfer unit, clean air flows in a laminar flow (as a downflow) from the gas supply unit 231 provided on the housing of the mini-environment device, and dust is generated during transfer. Prevents adhesion to the upper surface of the wafer. A part of the air around the transport unit (in this embodiment, air mainly contaminated with about 20% of the air supplied from the supply unit) is sucked from the suction duct 241 of the discharge device 24 and discharged out of the housing. The remaining air is recovered via a recovery duct 232 provided at the bottom of the housing and returned to the gas supply unit 231 again.

  When a wafer is loaded on the wafer rack 47 in the first loading chamber 41 of the loader housing 40 by the first transfer unit 61, the shutter device 27 is closed and the loading chamber 41 is sealed. Then, after the inert gas is expelled in the first loading chamber 41 and the air is expelled, the inert gas is also discharged and the inside of the loading chamber 41 is made a vacuum atmosphere. The vacuum atmosphere of the first loading chamber may be a low vacuum level. When the degree of vacuum in the loading chamber 41 is obtained to some extent, the shutter device 46 operates to open the doorway 434 that has been sealed by the door 461, the arm 632 of the second transfer unit 63 extends, and the wafer is held by the gripping device at the tip. One wafer is received from the receiver 47 (mounted on the tip or held by a chuck attached to the tip). When the receipt of the wafer is completed, the arm contracts, and the shutter device 46 operates again to close the doorway 435 with the door 461. Note that before the shutter device 46 is opened, the arm 632 can be extended in advance in the direction N1 of the wafer rack 47. In addition, as described above, the doors 437 and 325 are closed by the door 452 of the shutter device 45 before the shutter device 46 is opened, thereby preventing communication between the second loading chamber 42 and the working chamber 31 in an airtight state. The inside of the second loading chamber 42 is evacuated.

When the shutter device 46 closes the entrance / exit 435, the inside of the second loading chamber is evacuated again, and is evacuated at a higher degree of vacuum than in the first loading chamber. Meanwhile, the arm of the second transfer unit 61 is rotated to a position where it can extend toward the stage device 50 in the working chamber 31. On the other hand, in the stage apparatus in the working chamber 31, the Y table 52 has an X axis X ₁ -X in which the center line X ₀ -X ₀ of the X table 53 passes through the rotation axis O ₂ -O ₂ of the second transport unit 63. 2 moves upward in FIG. 2A to a position substantially coincident with _1, and the X table 53 moves to a position closest to the leftmost position in FIG. 2A and stands by in this state. When the second loading chamber becomes substantially the same as the vacuum state of the working chamber, the door 452 of the shutter device 45 moves to open the entrances 437 and 325, and the tip of the arm that holds the wafer by extending the arm is in the working chamber 31. Approach the stage device. Then, a wafer is placed on the placement surface 551 of the stage apparatus 50. When the placement of the wafer is completed, the arm contracts and the shutter device 45 closes the entrances 437 and 325.

  The above description is about the operation until the wafer in the cassette c is transported onto the stage device. However, in order to return the wafer that has been placed on the stage device and has been processed into the cassette c from the stage device, the reverse of the above. Perform the operation and return. Further, in order to place a plurality of wafers on the wafer rack 47, the cassette and the wafer rack are used in the first transfer unit while the wafer is transferred between the wafer rack and the stage apparatus in the second transfer unit. The wafer can be transferred between the two and the inspection process can be performed efficiently.

Specifically, when there are already processed wafers A and unprocessed wafers B in the wafer rack 47 of the second transfer unit,
(1) First, an unprocessed wafer B is moved to the stage apparatus 50, and processing is started. (2) During this process, the processed wafer A is moved from the stage device 50 to the wafer rack 47 by the arm, and the unprocessed wafer C is extracted from the wafer rack by the arm and positioned by the pre-aligner. The wafer rack 47 is moved.
In this way, in the wafer rack 47, the processed wafer A can be replaced with the unprocessed wafer C while the wafer B is being processed.

  Further, depending on how to use such an apparatus for performing inspection and evaluation, a plurality of stage apparatuses 50 are placed in parallel, and a plurality of wafers are transferred by moving wafers from one wafer rack 47 to each apparatus. The same processing can be performed.

  FIG. 6 shows a modification of the main housing support method. In the modification shown in FIG. 6, the housing support device 33a is formed of a thick and rectangular steel plate 331a, and the housing body 32a is placed on the steel plate. Therefore, the bottom wall 321a of the housing body 32a has a thin structure as compared with the bottom wall of the above embodiment. In the modification shown in FIG. 7, the housing body 32b and the loader housing 40b are suspended and supported by the frame structure 336b of the housing support device 33b. Lower ends of the plurality of vertical frames 337b fixed to the frame structure 336b are fixed to four corners of the bottom wall 321b of the housing main body 32b, and the peripheral wall and the top wall are supported by the bottom wall. The vibration isolator 37b is disposed between the frame structure 336b and the base frame 36b. The loader housing 40 is also suspended by a suspension member 49b fixed to the frame structure 336. In the modification shown in FIG. 7 of the housing main body 32b, since it is supported in a suspended manner, the center of gravity of the main housing and the various devices provided therein can be lowered. In the main housing and loader housing support methods including the above-described modifications, vibrations from the floor are not transmitted to the main housing and the loader housing.

  In another variant not shown, only the main housing exterior of the main housing is supported from below by the housing support device, and the loader housing can be placed on the floor in the same way as the adjacent mini-environment device. In yet another variant, not shown, only the housing body of the main housing is supported in a suspended manner on the frame structure, and the loader housing can be placed on the floor in the same manner as the adjacent mini-environment device.

According to the above embodiment, the following effects can be obtained.
(A) An overall configuration of a mapping projection type inspection apparatus using an electron beam is obtained, and an inspection object can be processed with high throughput.
(B) Inspecting the inspection object while monitoring the dust in the space by providing a sensor for observing the cleanliness by supplying a clean gas to the inspection object in the mini-environment space to prevent the adhesion of dust. Can do.
(C) Since the loading chamber and the working chamber are integrally supported via the vibration preventing device, it is possible to supply and inspect the inspection target to the stage device without being affected by the external environment.

<Electronic optical device>
The electron optical device 70 includes a lens barrel 71 fixed to the housing main body 32, and includes a primary light source optical system (hereinafter simply referred to as “primary optical system”) 72 and a secondary electron optical system (hereinafter referred to as “first optical system”). An optical system provided with a "secondary optical system" 74) and a detection system 76 are provided. FIG. 8 is a schematic diagram showing a schematic configuration of a “light irradiation type” electron optical device. As an electron optical device according to an embodiment of the present invention, an “electron irradiation type” electron optical device described later is used. In the electron optical device of FIG. 8 (light irradiation type electron optical device), the primary optical system 72 is an optical system that irradiates the surface of the wafer W to be inspected, a light source 10000 that emits light, and a light beam. And a mirror 10001 for changing the angle of. In this light irradiation type electro-optical device, the optical axis of the light beam 10000A emitted from the light source is inclined with respect to the optical axis of the photoelectrons emitted from the wafer W to be inspected (perpendicular to the surface of the wafer W). Yes.

  The detection system 76 includes a detector 761 and an image processing unit 763 arranged on the image plane of the lens system 741.

<Light source (light source)>
In the electro-optical device of FIG. 8, a DUV laser light source is used as the light source 10000. A DUV laser beam is emitted from the DUV laser light source 10000. Other light sources may be used as long as they emit light electrons from a substrate irradiated with light from the light source 10000, such as UV, DUV, EUV light and laser, and X-ray and X-ray laser.

<Primary optical system>
A portion where a primary light beam is formed by a light beam emitted from the light source 10000 and is irradiated with a rectangular or circular (may be elliptical) beam on the wafer W surface is referred to as a primary optical system. The light beam emitted from the light source 10000 passes through the objective lens optical system 724 and is irradiated on the wafer WF on the stage apparatus 50 as a primary light beam.

<Secondary optical system>
A two-dimensional image by photoelectrons generated by light rays irradiated on the wafer W passes through a hole formed in the mirror 10001, and is connected at a field stop position through a numerical aperture 10008 by electrostatic lenses (transfer lenses) 10006 and 10009. The image is magnified and projected by the lens 741 at the subsequent stage, and detected by the detection system 76. This imaging projection optical system is called a secondary optical system 74.

At this time, a negative bias voltage is applied to the wafer. Photoelectrons generated from the sample surface are accelerated by the potential difference between the electrostatic lens 724 (lenses 724-1 and 724-2) and the wafer, and the effect of reducing chromatic aberration is obtained. The extraction electric field in the objective lens optical system 724 is 3 kV / mm to 10 kV / mm, which is a high electric field. Increasing the extraction electric field has the effect of reducing aberrations and improving the resolution. On the other hand, when the extraction electric field is increased, the voltage gradient becomes large and discharge is likely to occur. Therefore, it is important to select an appropriate value for the extraction electric field. The electrons expanded to the specified magnification by the lens 724 (CL) are converged by the lens (TL1) 10006 to form a crossover (CO) on the numerical aperture 10008 (NA). In addition, zooming can be performed by combining the lens (TL1) 10006 and the lens (TL2) 10009. Thereafter, the image is magnified and projected by a lens (PL) 741 and formed on an MCP (Micro Channel Plate) in the detector 761. In this optical system, TL1-TL
An optical system capable of reducing off-axis aberrations is configured by arranging an NA between the two and optimizing the NA.

<Detector>
A photoelectron image from a wafer imaged by the secondary optical system is first amplified by a microchannel plate (MCP) and then converted to a light image by hitting a fluorescent screen. The principle of MCP is a bundle of millions of very thin conductive glass capillaries having a diameter of 6 to 25 μm and a length of 0.24 to 1.0 mm, which are shaped into a thin plate and applied with a predetermined voltage. Thus, each capillary functions as an independent electronic amplifier and forms an electronic amplifier as a whole.

The image converted into light by this detector is one-to-one on a TDI (Time Delay integration) -CCD (Charge Coupled Device) in a FOP (Fiber Optical Plate) system placed in the atmosphere through a vacuum transmission window. Is projected. As another method, a fluorescent material-coated FOP is connected to the TDI sensor surface, and a signal that has been subjected to electronic / optical conversion in a vacuum is introduced into the TDI sensor. This is more efficient for transmittance and MTF (Modulation Transfer Function) than when placed in the atmosphere. For example, high values of x5 to x10 can be obtained in transmittance and MTF. At this time, as described above, MCP + TDI may be used as the detector, but EB (Electron Bombardment) -TDI or EB-CCD may be used instead. When EB-TDI is used, photoelectrons generated from the sample surface and forming a two-dimensional image are directly incident on the EB-TDI sensor surface, so that an image signal can be formed without degradation in resolution. For example, in the case of MCP + TDI, after electronic amplification by MCP, electron / light conversion is performed by a fluorescent material, a scintillator or the like, and information on the optical image is delivered to the TDI sensor. On the other hand, in EB-TDI and EB-CCD, there are no electronic / optical conversion and light-enhanced information transmission parts / losses, so there is no image degradation and the signal reaches the sensor. For example, when MCP + TDI is used, the MTF and contrast are ½ to １ ／ compared to when EB-TDI or EB-CCD is used.

  In this embodiment, it is assumed that a high voltage of 10 to 50 kV is applied to the objective lens system 724 and the wafer W is installed.

<Relationship between main functions of map projection method and explanation of its overall image>
FIG. 9 shows an overall configuration diagram of the present embodiment. However, a part of the configuration is omitted.

  In FIG. 9, the inspection apparatus has a lens barrel 71, a light source cylinder 7000, and a chamber 32. A light source 10000 is provided inside the light source tube 7000, and the primary optical system 72 is disposed on the optical axis of the light beam (primary light beam) emitted from the light source 10000. A stage device 50 is installed inside the chamber 32, and a wafer W is placed on the stage device 50.

  On the other hand, inside the lens barrel 71, on the optical axis of the secondary beam emitted from the wafer W, a cathode lens 724 (724-1 and 724-2), transfer lenses 10006 and 10009, and a numerical aperture (NA). 10008, a lens 741 and a detector 761 are arranged. The numerical aperture (NA) 10008 corresponds to an aperture stop, and is a thin plate made of metal (such as Mo) having a circular hole.

  On the other hand, the output of the detector 761 is input to the control unit 780, and the output of the control unit 780 is input to the CPU 781. The control signal of the CPU 781 is input to the light source control unit 71a, the lens barrel control unit 71b, and the stage drive mechanism 56. The light source control unit 71a controls the power source of the light source 10000, and the lens barrel control unit 71b controls the lens voltage of the cathode lens 724, the lenses 10006 and 10009 and the lens 741, and the voltage control (deflection amount) of the aligner (not shown). Control).

  The stage driving mechanism 56 transmits stage position information to the CPU 781. Further, the light source cylinder 7000, the lens barrel 71, and the chamber 32 are connected to a vacuum exhaust system (not shown), and are exhausted by a vacuum pump of a vacuum exhaust system to maintain a vacuum state inside. In addition, a roughing vacuum exhaust system using a dry pump or a rotary pump is installed downstream of the turbo pump.

  When the sample is irradiated with the primary light, photoelectrons are generated as a secondary beam from the light irradiation surface of the wafer W.

  The secondary beam passes through the cathode lens 724, the TL lens groups 10006 and 10009, and the lens (PL) 741 and is guided to the detector to form an image.

  Incidentally, the cathode lens 724 is composed of three electrodes. The bottom electrode is designed to form a positive electric field with the potential on the sample W side, draw electrons (especially secondary electrons with small directivity), and efficiently guide them into the lens. Yes. Therefore, it is effective that the cathode lens is both telecentric. The secondary beam imaged by the cathode lens passes through the hole of the mirror 10001.

  If the secondary beam is imaged with only one stage of the cathode lens 724, the lens action becomes strong and aberrations are likely to occur. Therefore, a two-stage doubled lens system is used to form an image once. In this case, the intermediate image formation position is between the lens (TL 1) 10006 and the cathode lens 724. At this time, as described above, using both telecentrics is very effective in reducing aberrations. The secondary beam is converged on the numerical aperture (NA) 10008 by the cathode lens 724 and the lens (TL1) lens 10006 to form a crossover. An image is formed once between the lens 724 and the lens (TL1) 10006, and then the intermediate magnification is determined by the lens (TL1) 10006 and the lens (TL2) 10009, and is magnified by the lens (PL) 741 and is enlarged to the detector 761. Imaged. That is, in this example, the image is formed three times in total.

  The lenses 10006, 10009 and the lens 741 are all rotationally symmetric lenses called unipotential lenses or einzel lenses. Each lens has a configuration of three electrodes. Usually, the outer two electrodes are set to zero potential, and the lens action is performed with a voltage applied to the center electrode. In addition to this lens structure, the lens 724 has a focus adjustment electrode on the first stage, the second stage, or both, or a focus adjustment electrode that performs dynamically, and has four poles or 5 May be poles. It is also effective to use a 4-pole or 5-pole for the PL lens 741 in order to add a field lens function to reduce off-axis aberrations and enlarge magnification.

  The secondary beam is enlarged and projected by the secondary optical system, and forms an image on the detection surface of the detector 761. The detector 761 includes an MCP that amplifies electrons, a fluorescent plate that converts electrons into light, a relay between the vacuum system and the outside, and a lens and other optical elements for transmitting an optical image, and an image sensor (CCD or the like). It consists of. The secondary beam forms an image on the MCP detection surface and is amplified, and the electrons are converted into an optical signal by the fluorescent plate and converted into a photoelectric signal by the imaging device.

  The control unit 780 reads the image signal of the wafer W from the detector 761 and transmits it to the CPU 781. The CPU 781 performs a pattern defect inspection from the image signal by template matching or the like. The stage device 50 can be moved in the XY directions by a stage drive mechanism 56. The CPU 781 reads the position of the stage device 50, outputs a drive control signal to the stage drive mechanism 56, drives the stage device 50, and sequentially detects and inspects images.

  Further, when the magnification is changed, a uniform image can be obtained on the entire field of view on the detection side even if the set magnification of the lens conditions of the lenses 10006 and 10009 is changed. In the present embodiment, a uniform image without unevenness can be acquired. However, usually, when the enlargement magnification is increased, the brightness of the image is lowered. Therefore, in order to improve this, when changing the magnification ratio by changing the lens condition of the secondary optical system, the lens condition of the primary optical system is set so that the amount of electrons emitted per unit pixel becomes constant. .

<Precharge unit>
As shown in FIG. 1, the precharge unit 81 is disposed adjacent to the lens barrel 71 of the electron optical device 70 in the working chamber 31. Since this inspection apparatus is a type of apparatus that inspects the device pattern formed on the wafer surface by irradiating the substrate to be inspected, that is, the wafer, with the electron beam, the photoelectron information generated by the irradiation of the light beam As information, the wafer surface may be charged (charged up) depending on conditions such as the wafer material, the light to be irradiated, the wavelength and energy of the laser, and the like. In addition, there may be places where the wafer surface is strongly charged and weakly charged. If the charge amount on the wafer surface is uneven, the photoelectron information is also uneven, and accurate information cannot be obtained. Therefore, in this embodiment, in order to prevent this unevenness, a precharge unit 81 having a charged particle irradiation unit 811 is provided. Before irradiating light or a laser to a predetermined portion of a wafer to be inspected, charged particles are irradiated from the charged particle irradiation unit 811 of the precharge unit to eliminate uneven charging, thereby eliminating uneven charging. This charge-up of the wafer surface is detected by forming an image of the wafer surface to be detected in advance, evaluating the image, and operating the precharge unit 81 based on the detection.

(Embodiment 1)
<Electron Optical Device with Primary Optical System Using Electron Irradiation Instead of Primary System Using Light Irradiation>
What has been described so far has described the form in which light, laser, etc. irradiate the sample surface, thereby generating photoelectrons from the sample surface. Hereinafter, as an embodiment of the present invention, an “electron irradiation type” primary system that irradiates an electron beam instead of irradiating light will be described. First, an example of an inspection apparatus provided with a general electron gun is shown in FIG. FIG. 10A shows the overall configuration, and FIG. 10B is an enlarged schematic view of the electron gun portion. However, a part of the configuration is omitted.

10A, the inspection apparatus has a primary column 71-1, a secondary column 71-2, and a chamber 32. An electron gun 721 is provided inside the primary column 71-1, and a primary optical system 72 is disposed on the optical axis of an electron beam (primary beam) emitted from the electron gun 721. A stage device 50 is installed inside the chamber 32, and the sample W is placed on the stage device 50. On the other hand, inside the secondary column 71-2, the cathode lens 724, the numerical aperture NA-2, the Wien filter 723, the second lens 741-1, the pneumatic lens are arranged on the optical axis of the secondary beam generated from the sample W 1. A reical aperture NA-3, a third lens 741-2, a fourth lens 741-3, and a detector 761 are arranged. The numerical aperture NA-3 corresponds to an aperture stop, and is a metal (Mo or the like) thin plate with a circular hole. The numerical aperture NA-2 is arranged so that the opening is at the primary beam focusing position and the focal position of the cathode lens 724. Therefore, the cathode lens 724 and the numerical aperture NA-2 constitute a telecentric electron optical system. In particular, there may be a case where the cathode lens 724 is a doublet doublet lens and the first intermediate image forming point is formed in the vicinity of the E × B center to form a telecentric electron optical system. This can reduce aberrations and achieve high resolution imaging of a two-dimensional electronic image with a wide field of view as compared with a case where it is not one-telecentric or non-telecentric. That is, aberrations 1/2 to 1/3 can be realized.

  On the other hand, the output of the detector 761 is input to the control unit 780, and the output of the control unit 780 is input to the CPU 781. The control signal of the CPU 781 is input to the primary column control unit 71a, the secondary column control unit 71b, and the stage drive mechanism 56. The primary column control unit 71a performs lens voltage control of the primary optical system 72, and the secondary column control unit 71b performs lens voltage control of the cathode lens 724, the second lens 741-1 to the fourth lens 741-3, and Wien. The electromagnetic field applied to the filter 723 is controlled. The stage driving mechanism 56 transmits stage position information to the CPU 781. Further, the primary column 71-1, the secondary column 71-2, and the chamber 32 are connected to an evacuation system (not shown) and are evacuated by a turbo molecular pump of the evacuation system, and the inside is maintained in a vacuum state. doing.

(Primary beam)
The primary beam from the electron gun 721 is incident on the Wien filter 723 while receiving a lens action by the primary optical system 72. Here, as the tip of the electron gun, one having a rectangular shape, a circular flat shape, a curved surface (for example, about r = 50 μm) can be used, and LaB6 that can extract a large current is used. The primary optical system 72 uses a rotation axis asymmetric quadrupole or octupole electrostatic (or electromagnetic) lens. This can cause convergence and divergence in the X-axis and Y-axis as in the so-called cylindrical lens. By constructing this lens in two or three stages and optimizing each lens condition, the beam irradiation area on the sample surface can be made into an arbitrary rectangular or elliptical shape without irradiating irradiation electrons. Can be shaped. Specifically, when an electrostatic lens is used, four cylindrical rods are used. Opposing electrodes are equipotential, and opposite voltage characteristics are given. In addition, as a quadrupole lens, a lens having a shape obtained by dividing a generally used circular plate into four by an electrostatic deflector may be used instead of a cylindrical shape. In this case, the lens can be reduced in size.

  The orbit of the primary beam that has passed through the primary optical system 72 is bent by the deflection action of the Wien filter 723. The Wien filter 723, when the magnetic field and the electric field are orthogonal to each other, when the electric field is E, the magnetic field is B, and the velocity of the charged particles is v, only the charged particles satisfying the Wien condition of E = vB travel straight. Bend the trajectory. For the primary beam, a force FB caused by a magnetic field and a force FE caused by an electric field are generated, and the beam trajectory is bent. On the other hand, since the force FB and the force FE work in opposite directions with respect to the secondary beam, they cancel each other, so the secondary beam goes straight. The lens voltage of the primary optical system 72 is set in advance so that the primary beam forms an image at the opening of the numerical aperture NA-2. This numerical aperture NA-2 prevents an extra electron beam scattered in the apparatus from reaching the sample surface and prevents charge-up and contamination of the sample W. Further, since the field aperture NA-2 and the cathode lens 724 (two-stage doublet lens (not shown)) form a telecentric electron optical system, the primary beam transmitted through the cathode lens 724 becomes a parallel beam, The sample W is irradiated uniformly and uniformly. That is, Koehler illumination referred to as an optical microscope is realized.

(Secondary beam)
When the sample is irradiated with the primary beam, secondary electrons, reflected electrons, or backscattered electrons are generated as a secondary beam from the beam irradiation surface of the sample. Alternatively, mirror electrons are formed depending on the irradiation energy. The secondary beam passes through the lens while receiving the lens action of the cathode lens 724. Incidentally, the cathode lens 724 is composed of three or four electrodes. The bottom electrode forms a positive electric field with the potential on the sample W side, and electrons (particularly,
It is designed to draw secondary emission electrons and mirror electrons with small directivity and efficiently guide them into the lens. The lens action is performed by applying a voltage to the first and second electrodes of the cathode lens 724 to bring the third electrode to zero potential. Alternatively, a voltage is applied to the first, second, and third electrodes, and the fourth electrode is set to zero potential. The third electrode in the case of four electrodes is used for focus adjustment. On the other hand, the numerical aperture NA-2 is disposed at the focal position of the cathode lens 724, that is, the back focus position from the sample W. Therefore, the electron beam emitted from the center of the field of view (off-axis) also becomes a parallel beam and passes through the center position of the numerical aperture NA-2 without being distorted. The numerical aperture NA-3 plays a role of suppressing the lens aberration of the cathode lens 724 and the second lens 741-1 to the fourth lens 741-3 for the secondary beam. The secondary beam that has passed through the numerical aperture NA-2 passes straight through without being subjected to the deflection action of the Wien filter 723. Note that by changing the electromagnetic field applied to the Wien filter 723, only electrons having specific energy (for example, secondary electrons, reflected electrons, or backscattered electrons) are guided to the detector 761 from the secondary beam. it can. The cathode lens 724 is an important lens that determines the aberration of secondary emission electrons generated from the sample surface. Therefore, a very large magnification cannot be expected. Therefore, in order to reduce aberrations, a double telecentric structure is adopted as a cathode lens having a double-stage doublet lens structure. Further, in order to reduce the aberration (such as astigmatism) generated by the Wien filter formed by E × B, the intermediate image is set near this E × B intermediate position. As a result, the effect of suppressing the increase in aberration is very large. Then, the beam is converged by the second lens 741-1 to form a crossover in the vicinity of the numerical aperture NA-3. In addition, the second lens 741-1 and the third lens 741-2 have a zoom lens function, and magnification control is possible. In the subsequent stage, there is a fourth lens 741-3, which forms an enlarged image on the detector surface. The fourth lens has a five-stage lens structure, and the first, third, and fifth stages are GND. A positive high voltage is applied to the second and fourth stages, and a high voltage is applied to form a lens. At this time, the second stage has a field lens function, and the second intermediate image is formed in the vicinity thereof. At this time, the off-axis aberration can be corrected by the field lens function. An enlarged image is formed by the lens function of the fourth stage. In this way, the image is formed three times in total here. The cathode lens and the second lens 741-1 may be combined to form an image on the detection surface (two times in total). Further, all of the second lens 741-1 to the fourth lens 741-3 may be rotational axis symmetric lenses called unipotential lenses or Einzel lenses. Each lens may have a configuration of three electrodes. Normally, the outer two electrodes are set to zero potential, and the lens action is performed with the voltage applied to the center electrode. Further, a field aperture FA-2 may be arranged at an intermediate image point (not shown). This field aperture FA-2 is installed near the second stage when the fourth lens 741-3 is a five-stage lens, and is installed near the first stage when the fourth lens 741-3 is a three-stage lens. This field aperture FA-2 limits the field of view to the necessary range, similar to the field stop of an optical microscope. However, in the case of an electron beam, the extra beam is blocked to prevent the detector 761 from being charged up or contaminated. It is preventing. The secondary beam is enlarged and projected by the secondary optical system, and forms an image on the detection surface of the detector 761. The detector 761 includes an MCP that amplifies electrons, a fluorescent plate that converts electrons into light, a relay between the vacuum system and the outside, and a lens and other optical elements for transmitting an optical image, and an image sensor (CCD or the like). It consists of. The secondary beam forms an image on the MCP detection surface and is amplified, and the electrons are converted into an optical signal by the fluorescent plate and converted into a photoelectric signal by the imaging device. The control unit 780 reads the image signal of the sample from the detector 761 and transmits it to the CPU 781. The CPU 781 performs a pattern defect inspection from the image signal by template matching or the like. The stage device 50 can be moved in the XY directions by a stage drive mechanism 56. The CPU 781 reads the position of the stage device 50, outputs a drive control signal to the stage drive mechanism 56, drives the stage device 50, and sequentially detects and inspects images.

  “Secondary charged particles” include secondary emission electrons, mirror electrons, and some or a mixture of photoelectrons. When electromagnetic waves are irradiated, photoelectrons are generated from the sample surface. When the sample surface is irradiated with charged particles such as an electron beam, “secondary emission electrons” are generated from the sample surface or “mirror electrons” are formed. “Secondary emission electrons” are generated when an electron beam collides with the sample surface. That is, “secondary emission electrons” indicate a part or a mixture of secondary electrons, reflected electrons, and backscattered electrons. Also, what is reflected by the irradiated electron beam in the vicinity of the surface without colliding with the sample surface is called “mirror electron”.

  As described above, in the inspection apparatus according to the present embodiment, the numerical aperture NA-2 and the cathode lens 724 constitute a telecentric electron optical system. Can be irradiated. That is, Kohler illumination can be easily realized. Further, for the secondary beam, all the principal rays from the sample W are incident on the cathode lens 724 perpendicularly (parallel to the lens optical axis) and pass through the numerical aperture NA-2, so that the ambient light is also The image brightness at the periphery of the sample does not decrease. Further, a so-called chromatic aberration of magnification occurs in which the image formation position varies depending on the energy variation of the electrons (particularly, the secondary electron has a large chromatic aberration of magnification due to the large energy variation), but the focal position of the cathode lens 724 In addition, the chromatic aberration of magnification can be suppressed by arranging the numerical aperture NA-2.

  Further, since the enlargement magnification is changed after passing through the numerical aperture NA-2, the field of view on the detection side can be changed even if the setting magnification of the lens conditions of the third lens 741-2 and the fourth lens 741-3 is changed. A uniform image can be obtained on the entire surface. In the present embodiment, a uniform image without unevenness can be acquired. However, usually, when the enlargement magnification is increased, the brightness of the image is lowered. Therefore, in order to improve this, when changing the magnification condition by changing the lens condition of the secondary optical system, the effective field of view on the sample surface determined accordingly, and the electron beam irradiated on the sample surface, The lens conditions of the primary optical system are set so as to have the same size.

  That is, if the magnification is increased, the field of view is narrowed accordingly, but at the same time the irradiation energy density of the electron beam is increased, so that the signal density of the detected electrons is increased even if it is enlarged and projected by the secondary optical system. It is always kept constant and the brightness of the image does not decrease. In the inspection apparatus according to the present embodiment, the Wien filter 723 that bends the trajectory of the primary beam and travels the secondary beam straight is used. However, the invention is not limited thereto, and the trajectory of the secondary beam travels straight. An inspection apparatus using a Wien filter that bends the wire may be used. In this embodiment, the rectangular beam is formed from the rectangular cathode and the quadrupole lens. However, the present invention is not limited to this. For example, a rectangular beam or an elliptical beam may be created from the circular beam, or the circular beam may be passed through the slit. The rectangular beam may be taken out.

  In this example, two numerical apertures, a numerical aperture NA-2 and a numerical aperture NA-3, are installed. This can be properly used according to the amount of irradiated electrons. When the amount of irradiated electrons on the sample is small, for example, at 0.1 to 10 nA, an appropriate diameter for selecting the beam diameter, for example, φ30, is used to reduce the aberration of the primary beam and the secondary beam by the numerical aperture NA-2. Use ~ φ300 μm. However, when the amount of irradiated electrons increases, the numerical aperture NA-2 may be charged up due to contamination and adversely deteriorate the image quality. At this time, a numerical aperture NA-2 having a relatively large hole diameter, for example, φ500 to φ3000 μm, is used for cutting the surrounding stray electrons. Then, it is used to determine the aberration and transmittance of the secondary beam by the numerical aperture NA-3. Since the numerical aperture NA-3 is not irradiated with the primary beam, there is little contamination and there is no image deterioration due to charge-up. Therefore, it is very efficient to select and use the numerical aperture diameter depending on the amount of irradiation current.

  In the semiconductor inspection apparatus 1 that uses an electron gun as the primary optical system 72 of the electron optical device 70 when electron irradiation is performed on the primary beam in such a form, when a large irradiation current is to be obtained, However, there is a problem that the energy width of the widened area increases. This will be described in detail below with reference to the drawings. FIG. 10B is a schematic diagram of the primary optical system 72 of the electron optical apparatus 70 provided with a general electron gun 2300.

In the electron gun 2300, a heating current is supplied to the cathode 2310 from a heating power source 2313 for generating thermoelectrons. Further, an acceleration voltage Vacc is set to the cathode 2310 by an acceleration power source 2314. On the other hand, a voltage is applied to the anode 2311 so as to have a relatively positive voltage with respect to the cathode 2310, for example, to have a voltage difference of 3000 to 5000V. When the cathode 2310 is −5000V, the anode 2311 may be 0V. At this time, the amount of emission is controlled by the voltage applied to the Wehnelt 2312. Wehnelt 2312 is superimposed on the acceleration voltage Vacc. For example, the superimposed voltage is 0 to −1000V. If the voltage difference from Vacc is large, the amount of emission becomes small, and if it is small, the emission becomes large. Also, the first crossover (first crossover: 1stCO) position that can be generated by the Wehnelt voltage is shifted in the axial direction. Also, if the cathode center and Wehnelt and anode centers are misaligned, misalignment also occurs in the x and y directions perpendicular to the z axis. The emitted emissions are spreading. Of these, the field aperture FA 2320 selects an effective beam and determines the beam shape. The transmittance with respect to the emission at that time is usually 0.1 to 0.5%. For example, the emission current is 5 to 25 nA at an emission of 5 μA.
Therefore, for example, if an irradiation current of 1 μA is to be obtained, an emissin of 200 μA to 1 mA is required. At this time, as the emission increases, the energy width of electrons spreads due to the Bersch effect in the trajectory from the cathode to the first crossover and from the first crossover to the field aperture FA. For example, it expands from 1.2 eV to 10 to 50 eV at the FA position.

  The energy width becomes a problem particularly at low LE. This is because the electron trajectory in the vicinity of the sample surface becomes larger in the z direction. This will be described with reference to the drawings. FIG. 11 is a diagram showing the intensity (amount) and energy state of the irradiation current of the electron beam irradiated on the sample surface and the state of the beam irradiated on the sample surface. FIG. 11A shows the intensity and energy state of the irradiation current of the beam applied to the sample surface, and FIG. 11B shows the state of the beam applied to the sample surface. The beam when the energy of the irradiation current of the beam irradiated on the sample is optimum is a beam c, the beam when the energy of the irradiation current of the beam is low is the beam a, and the beam when the irradiation current of the beam is maximum is the beam. Let b. Further, a beam when the energy of the irradiation current of the beam is high is referred to as a beam d. The relationship between the energy of the electron beam and the intensity (amount) of the irradiation current is as shown in FIG. 11A according to the Maxell distribution in the thermoelectron forming method such as LaB6. At this time, as described above, the electron beams having characteristics depending on the level of energy were designated as beams a to d.

  As an example, FIG. 11B shows a case where a high-energy beam d just collides with the sample surface. At this time, the beam d collides with the surface and does not reflect (no formation of mirror electrons). On the other hand, the beam c, the beam b, and the beam a are each reflected at the reflection potential point. That is, mirror electrons are formed. The axial positions where the beams c, b, and a having different energies are reflected, that is, the Z positions are different. This Z position difference ΔZ occurs. As this ΔZ is larger, the blur of the image formed by the secondary optical system becomes larger. That is, the mirror electrons formed at the same surface position cause a positional shift on the imaging plane. Especially in the mirror electrons, the energy shift causes a shift of the reflection point and a shift of the orbit on the way, so that the influence is great. The same can be said for an image formed by mirror electrons or an image formed by mirror electrons + secondary emission electrons. Further, when the energy width of the electron beam to be irradiated is large, such an adverse effect is increased (ΔZ is increased). Therefore, it is very effective to have a primary beam that can irradiate the sample surface with a narrow energy width. For that purpose, the electron generation source and the primary optical system as shown in FIGS. 12 to 18 described later are invented. Compared to the conventional type, these can not only narrow the energy width of the electron beam but also dramatically increase the transmittance of the primary beam, so that a large current can be applied to the sample surface with a narrow energy width. Can be irradiated. That is, since the above-described ΔZ can be reduced, the positional deviation on the imaging surface in the secondary optical system is reduced, and low aberration, high resolution, large current, and high throughput can be realized. Usually, a thermoelectron electron source (Gun) such as LaB6 has an energy width of about 2 eV in the electron generator. As the amount of generated current increases, the energy width further increases due to the Bersch effect due to Coulomb repulsion or the like. For example, when the emission current of the electron source is changed from 5 μA to 50 μA, the energy width increases, for example, from 0.6 eV to 8.7 eV. In other words, when the current value is increased 10 times, the energy width increases about 15 times. Furthermore, the energy width such as the space charge effect is widened during the passage of the primary optical system on the way. In view of these characteristics, in order to allow an electron beam with a narrow energy width to reach the sample, the electron generation source is made by reducing the energy width at the electron generation source and increasing the transmittance of the primary optical system. It is most important to reduce the emission current. Until now, there was no means for realizing it, but the present invention realizes them. The effects and explanations of these will be described later in the embodiments shown in FIGS.

  Further, the intensity of the electron beam (when the amount is high, the beam b) is not necessarily optimal for imaging. For example, when the energy distribution conforms to the Maxell distribution, the maximum beam intensity (amount) is often present at a low energy portion (beam b). At this time, since there are many beams with higher energy than the beam b, the image quality may be different from the image formed by them. That is, when the beam d collides with the sample to form a secondary emission electron image, and the energy of the beam b is relatively low, mirror electrons are easily formed with little influence on the unevenness of the sample surface. In other words, mirror electrons are formed with little influence on the surface unevenness and potential difference, and the overall image quality is likely to be an image with low contrast or a blurred image. Empirically, it is difficult to obtain an image with high resolution. In particular, when an oxide film is present at the uppermost part of the surface, the influence of the amount of electrons colliding with the surface is increased. For example, when the emission is increased (for example, 10 times) compared to when the emission current is small, the energy width is thereby increased. Will spread more than 10 times. At this time, when the sample surface is irradiated with the electron beam with the same landing energy LE, an absolute amount of a portion having a higher energy than the beam b, for example, the beam d, collides with the sample surface increases. growing. Due to the effect of the charge-up, the trajectory of the mirror electrons and the imaging conditions may be disturbed and normal imaging may not be possible. This was one of the reasons why the irradiation current could not be increased. In such a situation, it is possible to use an energy beam c that can reduce the amount of collision of the beam d with the sample surface and suppress the potential change of the oxide film to be small (a beam of optimum energy). As a result, it is possible to obtain a stable image while suppressing the amount of the beam colliding with the sample. However, as can be seen from FIG. 11A, the beam c has lower intensity (amount) than the beam b. If the beam c having the optimum energy can be brought close to the beam b having the maximum intensity, the amount of electrons contributing to image formation is increased correspondingly, and the throughput can be increased. For this purpose, it is important to reduce the number of electrons that collide with the sample surface with a narrow energy width. The present invention realizes this, and an embodiment thereof will be described with reference to FIGS.

  In FIG. 11B, when LE is gradually increased, the beam d collides with the sample surface, then the beam c collides, and when the colliding electron beams increase, 2 is generated thereby. Secondary emission electrons increase. Such a region where mirror electrons and secondary emission electrons are mixed is called a transition region. When all the primary beams collide with the sample surface, the mirror electrons disappear and only secondary emission electrons exist. When there are no colliding electrons, all become mirror electrons.

  Further, when the emission is changed by changing the Wehnelt voltage, the first crossover position also changes, so that it is necessary to adjust the aligner and the lens downstream each time.

  Further, in the inspection of semiconductors, 10 nm level defect inspection such as EUV mask inspection (inspection of extreme ultraviolet lithography mask) and NIL inspection (mask inspection for nanoimprint lithography) is required corresponding to a new technology. Yes. For this reason, the semiconductor inspection apparatus is required to increase the resolution by reducing the aberration.

  In order to reduce the aberration and increase the resolution, it is particularly necessary to reduce the aberration of the secondary optical system. However, the factors that degrade the mapping system are so-called energy aberration (also referred to as chromatic aberration) and Coulomb buler. Therefore, in order to improve the aberration of the secondary optical system, it is required to increase the acceleration energy in a short time.

  In order to solve such problems, the present inventors have invented a primary optical system having a new photoelectron generator and an electron optical device having the primary optical system. This primary optical system uses DUV light or a DUV laser as a light source. However, the light source is not limited to this, and UV, EUV, or X-ray may be used. The contents will be described below with reference to FIG.

  As shown in FIG. 12, this primary optical system 2000 is roughly composed of a light source (not shown), a field aperture (FA) 2010, a photoelectron generator 2020, an aligner 2030, an E × B deflector (Wien filter) (see FIG. 12). Not shown), an aperture 2040, and a cathode lens (CL) 2050.

  The field aperture 2010 is disposed between a photoelectron surface 2021 of a photoelectron generator 2020 described later and a light source, and is provided with a hole having a predetermined shape. The light or laser irradiated from the light source toward the field aperture 2010 passes through the hole of the field aperture 2010 and is irradiated to the photoelectron surface 2021 as light or laser in the shape of a hole. That is, the light or laser emitted from the light source generates photoelectrons having the same shape as the hole shape from the photoelectron surface 2021. As the light source, light such as DUV (deep ultraviolet), UV (ultraviolet), EUV (extreme ultraviolet), X-ray or the like having a wavelength that generates photoelectrons or a laser is used. In this case, in particular, DUV light or laser having a wavelength λ ≦ 270 nm (that is, E ≧ 4.8 eV) is preferably used.

  In the photoelectron generator 2020, the first stage lens 2022, the second stage lens 2023, and the third stage lens 2024, which are three-stage extraction lenses, constitute one extraction lens. Further, a numerical aperture 2025 is provided. This extraction lens uses a magnetic lens or an electrostatic lens. When a magnetic lens is used, a magnetic field corrector is provided in the vicinity of a numerical aperture 2025 described later. It is also effective to provide it near the downstream of the field lens (not shown) of the secondary optical system or near the objective lens (not shown). This is because the image may be bent due to the influence of the magnetic field, and this is to be corrected. Further, the number of steps of the drawing lens is not limited to this.

The optoelectronic surface 2021 is obtained by coating a base material made of a light transmitting member such as sapphire or diamond with a photoelectron material, and has a flat surface portion. Note that the structure of the photoelectron surface 2021 having a planar portion is also referred to as a planar cathode. In this case, a material having high thermal conductivity such as sapphire or diamond is particularly preferably used as the base material of the photoelectron surface 2021. The thermal conductivity of sapphire and diamond (sapphire: 30 to 40 W / (K · m), diamond: 50 to 100 W / (K · m)) is the thermal conductivity of quartz and synthetic quartz (1 to 2 W / (K · m). Since it is higher than m)), it is possible to quickly dissipate the heat of the portion irradiated with the electrons. Therefore, the damage received by the photoelectron surface 2021 can be reduced, and the quantum efficiency can be prevented from being lowered and the occurrence of unevenness in the quantum efficiency depending on the location. And since the damage which the photoelectron surface 2021 receives can be reduced, the spot size of electron irradiation can be made small (power density can be made high), and the thickness of an optoelectronic material can be made thin. For example, if a synthetic quartz as a base material, the quantum efficiency when irradiated with CW laser with a wavelength of 266nm at a power density of 8000W / cm ² optoelectronic surface, quantum when irradiated at a power density of 1000W / cm ² Whereas the efficiency decreased to 1/5 of the efficiency, when sapphire was used as a base material, the quantum efficiency was not decreased. In addition, as for sapphire and diamond, not only a natural thing but an artificial thing can also be used. As the optoelectronic material, a material having a low work function such as ruthenium or gold (a material having high photoelectron generation efficiency) is preferably used. For example, in this embodiment, a base material coated with a photoelectron material such as ruthenium or gold with a thickness of 5 nm to 100 nm, preferably 5 nm to 30 nm is used. Further, the shape of the photoelectron surface 2021 is such that the base material has a diameter of, for example, about 5 to 50 mm, and there is a region where the photoelectron material is coated in the central region. The coating area has, for example, a diameter of 2 to 10 mm, preferably 3 to 5 mm. A conductive film such as Cr is coated on the outside of the photoelectronic material, and voltage can be applied to the photocathode through this film. In addition, this Cr film has a low transmittance of the DUV laser, shields and passes through, and is irradiated on unnecessary members to reduce noise generated therefrom. Also, Cr is more than the above-mentioned optoelectronic materials such as Au and Ru. Since the photoelectron generation efficiency is orders of magnitude smaller, noise generated therefrom is also reduced.

  The part coated with the optoelectronic material is irradiated with a DUV laser or the like. The diameter is 10 μm to 300 μm, preferably 20 μm to 150 μm, or the side is 10 μm to 300 μm, preferably 10 μm to 150 μm. Although used, the scope of the present invention is not limited thereto. Light or laser is introduced through the viewport of the base material and reaches the photocathode, where photoelectrons are generated.

  The extraction lens (extraction electrode) including the first-stage lens 2022, the second-stage lens 2023, and the third-stage lens 2024 extracts photoelectrons generated from the photoelectron surface 2021 in the opposite direction from the light source, and accelerates the extracted photoelectrons. To act. An electrostatic lens is used as these drawer lenses. The extraction lenses 2022, 2023 and 2024 do not use Wehnelt, and the extraction electric field is constant. Note that it is preferable to use a one-side telecentric structure or a double tele-line trick structure for the first extraction electrode 2022, the second extraction electrode 2023, and the third extraction electrode 2024. This is because a very uniform extraction electric field region can be formed and the generated photoelectrons can be transported with low loss.

  The applied voltage of each extraction lens is, for example, V2 when the voltage on the photoelectron surface is V1, and the voltages of the first extraction electrode 2022, the second extraction electrode 2023, and the third extraction electrode 2024 are V2, V3, and V4, respectively. And V4 are set to V1 + 3000 to 30000V, and V3 is set to V4 + 10000 to 30000V. However, it is not limited to this.

  A numerical aperture 2025 is disposed between the third extraction electrode 2024 of the photoelectron generator 2020 and an aligner 2030 described later. The numerical aperture 2025 selects an effective beam such as a crossover formation position, beam amount, and aberration.

  The aligner 2030 includes a first aligner 2031, a second aligner 2032, and a third aligner 2033, and is used for adjusting the optical axis condition. The first aligner 2031 and the second aligner 2032 are aligners that perform a static operation, and play a role of tilt and shift used when adjusting the optical axis condition. On the other hand, the third aligner 2033 is an aligner used when a dynamic deflector performs a high-speed operation, and is used, for example, for a dynamic blanking operation.

  An aperture 2040 is disposed downstream of the aligner 2030 (the sample side; hereinafter, the light source side is referred to as upstream and the sample side is referred to as downstream in the positional relationship with each member). The aperture 2040 receives a beam during blanking, and is used for, for example, stray electron cut and beam centering. Further, the amount of electron beam can be measured by measuring the absorption current of the aperture 2040.

  Downstream of the aperture 2040 is an E × B region that is a region intersecting with the secondary optical system, and an E × B deflector (Wien filter) (not shown) is provided here. The E × B deflector deflects the primary electron beam so that its optical axis is perpendicular to the surface of the sample.

  A cathode lens 2050 is provided downstream of the E × B region. The cathode lens 2050 is a lens in which a primary optical system and a secondary optical system coexist. The cathode lens 2050 may be composed of two stages of the first cathode lens 2051 and the second cathode lens 2052, or may be composed of one sheet. When the cathode lens 2050 is composed of two stages, a crossover is formed between the first cathode lens 2051 and the second cathode lens 2052, and in the case of a single cathode lens, between the cathode lens 2050 and the sample. Form a crossover.

  The amount of photoelectrons is determined by the intensity of light or laser irradiated on the photoelectron surface. Therefore, a system for further adjusting the output of the light source or the laser light source may be applied to the primary optical system 2000. Although not shown, an output adjustment mechanism such as an attenuator or a beam separator may be further provided between the light source or the laser light source and the base material.

  For example, in the present embodiment, an aging procedure may be executed when performing electron irradiation. The aging procedure is as follows: (1) electron irradiation for 5 hours with a large beam size (1-2 mm), then (2) electron irradiation for 2 hours with a medium beam size (100-300 μm). Then, the procedure of (3) performing electron irradiation with a small beam size (10 to 100 μm) is sequentially performed. As a result, dirt and contamination attached to the photoelectron surface can be removed, and a stable heat condition can be created. Dirt and contamination adhering to the photoelectron surface are, for example, carbon, hydrocarbon, moisture and the like. By creating a stable thermal condition, the uniformity of the thermal state can be obtained, and damage to the photoelectron surface at the time of heat rise can be reduced. The beam size (3) is a size (use size) when used as a photoelectron source. Therefore, it can be said that the beam size of (2) is 3 to 10 times the use size, and the beam size of (1) is 500 to 1000 times the use size.

  Here, the formation of the crossover of the primary optical system 2000 according to the present invention will be described with reference to the drawings. FIG. 13 is a schematic view of the formation of the crossover of the primary optical system 2000 according to the present invention. In FIG. 13, the photoelectrons generated on the photoelectron surface are schematically expressed as being irradiated perpendicularly to the sample, but in actuality, they are deflected by the E × B deflector.

  As shown in FIG. 13, light or laser light is irradiated from the light source or laser light source through the field aperture 2010 to the photoelectron surface 2021. As a result, the photoelectrons generated on the photoelectron surface 2021 form a first crossover at the position of the numerical aperture 2025, and are further deflected perpendicularly to the sample by the E × B deflector via the aperture 2040. A crossover is formed between 2051 and the second cathode lens 2052. The photoelectrons forming the crossover are irradiated onto the sample surface as a surface beam. Therefore, the electron emission shape of the photoelectron surface 2021 and the electron beam shape irradiated onto the sample surface are conjugate. On the other hand, in a primary optical system equipped with a general electron gun, as shown in FIG. 10B, photoelectrons generated from the cathode 2310 have a fast crossover between the cathode 2310 and the anode 2311. Then, the sample surface is irradiated via the anode 2311 and the field aperture 2320. Therefore, the shape of the field aperture 2320 and the shape of the electron beam applied to the sample surface are conjugate.

  The setting of the applied voltage of the primary optical system 2000 according to the present invention will be described. The present invention has a different configuration from a general electron gun, irradiates light or a laser onto the photoelectron surface 2021, and extracts the generated photoelectrons with a subsequent extraction lens for acceleration. Since there is no Wehnelt or suppressor and acceleration is performed with a uniform electric field, the setting of the voltage applied to each component is different from that of a general electron gun.

  Hereinafter, a description will be given with reference to FIG. The voltage applied to each component is as follows. The voltage of the photoelectron surface 2021 is V1, the voltage of the electrode constituting the extraction lens is V2, the voltage of the first extraction electrode 2022 is V2, the voltage of the second extraction electrode 2023 is V3, and the voltage 2024 of the third extraction electrode is V4, the voltage of the numerical aperture 2025 is V5, and the voltage of the aperture 2040 is V6. The wafer surface voltage (also referred to as retarding voltage) is assumed to be RTD. In the primary optical system 2000 of the present invention, the voltage is applied to each component as described below based on the voltage V1 of the photoelectron surface 2021. That is, in the case of low LE, V1 = RTD-10V to RTD + 5V. V2, V4 = V1 + 3000-30000V. V3 = V4 + 10000 to 30000V. V5, V6 = reference potential. In one embodiment of the primary optical system according to the present invention, RTD = −5000V, V1 = −5005V, V2, V4 = GND, and V3 = + 20000V. By applying the voltage as described above, high throughput with high resolution can be realized with low LE. However, this is an example, and the applied voltage to each component is not limited to this.

When the reference potential is represented as V0, and the voltage on the surface where the detector electrons enter is represented as DV, the applied voltage relationship with the RTD in the primary optical system 2000 according to the present invention is set as shown in Table 1 below. Preferably used.

  The primary optical system 2000 according to the present invention having the above-described configuration and the electron optical apparatus including the primary optical system 2000 according to the present invention can obtain the following effects.

  First, the primary optical system 2000 of the present invention can achieve very high transmittance. The transmittance is 5 to 50%, and the transmittance of 10 to 100 times can be ensured with respect to the transmittance of 0.1 to 0.5% of the primary optical system provided with a general electron gun. First, because a very uniform extraction electric field region can be formed by the configuration of the flat cathode surface and the new extraction lens, the formed photoelectrons can be transported with low loss. This configuration realizes that the extracted electric field distribution is kept constant by increasing or decreasing the amount of generated photoelectrons, thereby realizing a stable operation with high transmittance. In a primary optical system equipped with a general electron gun, a Wehnelt or suppressor mechanism is required, so that the electric field distribution changes depending on the amount of generated electrons, that is, the amount of emission, so that the uniform extraction electric field portion is reduced and the effective beam area is reduced. Therefore, although it is difficult to increase the transmittance, the primary optical system 2000 according to the present invention does not require a Wehnelt or suppressor mechanism, and thus can increase the transmittance. Second, the primary optical system 2000 according to the present invention has a first crossover position downstream of the lens, so that it is easy to install a numerical aperture or the like. This is because an optical system that is easy to perform can be realized. In a primary optical system equipped with a general electron gun, since the first crossover position is in the vicinity of Wehnelt, it is difficult to install a numerical aperture or the like at that position, and the position is shifted due to emission. Even if a numerical aperture or the like can be installed at this position, it is difficult to use it effectively. This is because the primary optical system 2000 according to the present invention can solve this problem because the position of the first crossover can be placed downstream of the lens.

  Secondly, the primary optical system 2000 according to the present invention can realize high resolution and high throughput. As described above, since a high transmittance can be realized, a very small amount of cathode emission current of 2 to 10 μA is required to obtain a high throughput, for example, an electron irradiation amount of 1 μA. Therefore, the Bersch effect can be very small. For example, the energy width is 0.5 to 1.2 eV at the numerical aperture position. Therefore, since the electron irradiation amount can be increased with a small energy width, the positional deviation of the beam formed by the secondary optical system is small, and high resolution can be maintained. As a result, high throughput and high throughput can be realized.

  Thirdly, the primary optical system 2000 according to the present invention can always maintain a stable optical system. This is because the first optical system 2000 according to the present invention does not cause a first crossover misalignment.

  Next, the effect of the electro-optical device including the primary optical system 2000 according to the present invention will be described in detail below.

  First, since the primary optical system 2000 having the above-described configuration is used, the electron beam shape irradiated on the sample surface can be set to a magnification x10 to x0.1 times the electron emission shape of the photoelectron surface. Is possible. In particular, since it can be used at a scale of 1 × magnification or less, it is not necessary to reduce the size of the photoelectron surface, and the generated photoelectron density can be kept low. As a result, the electron optical device including the primary optical system 2000 of the present invention can reduce the Bersch effect and suppress the spread of the energy width.

  Secondly, the photoelectron generator can be easily formed at the center position formed by the extraction lens with respect to the axial center of the electron generator on the photoelectron surface. This can be achieved by irradiating the axial center position with light or laser. Although the position of the light source is not shown in FIGS. 12 and 13, it can be easily achieved by using a lens, a mirror, or the like regardless of the position of the light source. The primary optical system 2000 according to the present invention is arranged in a lens barrel fixed to the main housing. However, since light or a laser is used to generate photoelectrons, the light source does not necessarily need to be arranged in the lens barrel. For example, it can be installed outside the lens barrel and guided to the axial center of the electron generating portion of the photoelectron surface by a mirror lens or the like. Accordingly, since it can be arranged on the atmosphere side, the center position of the electron optical device using the primary optical system 2000 according to the present invention can be easily adjusted. In the inspection apparatus using the general electron gun shown in FIG. 10B, the center positions of the cathode 2310, Wehnelt 2312, anode 2311, and field aperture 2320 are shifted due to assembly. Further, a positional shift due to baking performed after opening to the atmosphere, that is, a positional variation after assembly due to a process of thermal expansion and cooling due to a temperature change also occurs. In order to correct these deviations, a normal aligner is provided upstream of the field aperture 2320, and correction is performed by this aligner. If the misalignment is severe, it is necessary to repeat disassembly, assembly, adjustment, and baking. On the other hand, in the electro-optical device using the primary optical system 2000 according to the present invention, the photoelectron generator can be easily formed at the center position formed by the electrostatic lens by simply irradiating the axial center position with light or laser. Therefore, even if a deviation due to assembly occurs, it can be easily adjusted. Further, since the light source can be arranged on the atmosphere side, it is difficult to be subjected to a position change after assembly, and can be easily adjusted when a position change after assembly occurs. Therefore, the work process can be greatly shortened and the cost can be reduced. Further, since the field aperture 2010 that determines the electron generation shape of the photoelectron surface can be arranged on the atmosphere side, the field aperture 2010 can be easily replaced. In this respect, the work process is greatly shortened and the cost is reduced. Can be achieved. If there is a field aperture on the vacuum side, replacement requires operations such as vacuum break, column disassembly, assembly, adjustment, vacuum disposal, baking, and optical axis adjustment, but this operation is eliminated.

  Third, the electron optical device including the primary optical system 2000 according to the present invention has an improved beam size freedom. Since the electron generation shape of the photoelectron surface is determined by the field aperture 2010, the shape is not limited to a circle or a rectangle, but a shape asymmetric with respect to a rectangle or an axis is possible. In the inspection apparatus including the primary optical system 2000 according to the present invention, as an example, a circular shape of φ100 μm on the photoelectron surface, a circular shape of φ50 μm to 100 μm on the sample surface, and a rectangular shape of 100 × 100 μm on the photoelectron surface, A rectangle of 50 × 50 μm to 100 × 100 μm is possible on the sample surface.

  Fourth, the electron optical device including the primary optical system 2000 according to the present invention can greatly reduce the number of parts in vacuum. In an electron optical device equipped with a general electron gun, an aligner is required in front of the field aperture 2320 shown in FIG. 10B in order to correct misalignment of the cathode center, Wehnelt, anode, and field aperture center. In addition, in order to form an image of the beam shape formed by the field aperture 2320 on the sample surface, one to three lenses are required. Since the electron optical device including the primary optical system 2000 according to the present invention does not require these components, the number of components in a vacuum can be greatly reduced.

  If the electron optical device including the primary optical system according to the present invention described above is applied to a semiconductor inspection device, high resolution and high throughput can be achieved, which is suitable for EUV mask inspection and NIL mask inspection. Also, high resolution can be achieved even in the case of low LE (landing energy).

(Embodiment 2)
<Second Embodiment of Primary Optical System>
A second embodiment of the primary optical system according to the present invention will be described. FIG. 14 is a diagram showing a second embodiment of a primary optical system according to the present invention. This primary optical system 2100 is roughly composed of a light source (not shown), a field aperture (FA) 2110, a photoelectron generator 2120, an aligner 2130, an E × B deflector (Wien filter) (not shown), an aperture 2140, A cathode lens (CL) 2150, a first tube 10071, and a second tube (not shown) for housing these primary optical systems are provided. The second embodiment of the primary optical system according to the present invention is characterized in that the reference potential is a high voltage. Hereinafter, the difference from the above-described primary optical system according to the present invention will be mainly described.

  The present embodiment has a double structure including a first tube 10071 and a second tube, and the photoelectron generator 2120 includes a photoelectron surface 2121, a single extraction lens 2122, and a numerical aperture 2125.

  The first tube 10071 is a tube for producing a reference voltage when the reference voltage is a high voltage, and a high voltage is applied to the first tube. The first tube 10071 is disposed inside the hole for passing the primary beam provided in each of the extraction lens 2122, the numerical aperture 2125, and the aligner 2130 so as to be inscribed in the hole. A large diameter is formed, and a cathode lens 2150 is disposed inside a portion where the diameter is large.

  The material of the first tube 10071 is not particularly limited as long as it is not a magnetic material, but a thin copper tube, a thin titanium tube, or a copper-plated or titanium-plated plastic is preferably used. Thus, when a high voltage is applied to the first tube 10071, a magnetic field is formed inside the first tube 10071, and the primary electron beam generated on the photoelectron surface 2121 irradiated with light or laser light is highly accelerated. Is done.

  On the other hand, although not shown in FIG. 14, the second tube includes the above-described field aperture (FA) 2110, photoelectron generator 2120, aligner 2130, E × B deflector (Wien filter) (not shown), aperture. 2140, the cathode lens (CL) 2150, and the first tube 10071 are covered and set to GND. Since this is the outermost configuration of the column device, this portion is held at GND, and is configured for conductor connection with other device portions, prevention of electric shock when a person touches, and the like.

  One extraction lens is used, and an electromagnetic lens is used in the second embodiment of the primary optical system according to the present invention. Other configurations are the same as those of the above-described embodiment, and thus description thereof is omitted.

  By using such a double-structured tube, the primary optical system 2100 according to the present invention sets the sample surface voltage to GND, and applies a high voltage to the first tube 10071 which is a tube inside the double-tube structure. By adding, the electron beam generated on the photoelectron surface 2121 can be highly accelerated. Therefore, the primary optical system according to the present invention can be called a high acceleration column.

  In the primary optical system 2100 according to the present invention (see FIG. 14), voltages applied to each component are as follows. The voltage of the photoelectron surface 2121 is V1, the voltage of the first tube 10071 is V2, the voltage of the numerical aperture NA2025 is V5, and the voltage of the aperture 2140 is V6. The wafer surface voltage (also referred to as retarding voltage) is assumed to be RTD. Under low LE conditions, V1 = RTD-10V to RTD + 5V. V2, V5, and V6 are reference potentials. In one embodiment of the present invention, RTD = 0, V1 = −5V, and reference potential = 40000V were set. By applying the voltage as described above, high throughput with high resolution can be realized with low LE.

  At this time, if a magnetic lens is used, beam rotation occurs due to a standing magnetic field (residual magnetic field in the optical axis direction). Therefore, the two-dimensional photoelectron generation shape formed on the photoelectron surface may rotate after passing through the generation unit and the magnetic lens. In order to correct this, a rotation correction lens is installed near the NA or downstream of the magnetic field lens to correct the influence. The correction lens at the downstream position of the magnetic lens may be installed at a position (immediately after) as close as possible to the magnetic lens to perform rotation correction.

  Moreover, in the primary optical system 2000 (see FIG. 12) of the present invention of an electrostatic lens, when the example of the double tube structure is described based on the photoelectron surface 2021 voltage V1, a voltage is applied to each component as follows. Apply. That is, in the case of low LE, V1 = RTD-10V to RTD + 5V. V2, V5, and V6 are reference potentials, and V3 = reference voltage + 10 to 100 kV. In one embodiment of the present invention, RTD = 0, V1 = −5V, V2 = reference potential + 40000V, and V3 = 65000V were set. Further, there is a tube 1 in which these lenses are incorporated so that the reference voltage becomes a reference space voltage, and the lens, aperture, and aligner of FIG. 12 are incorporated in the tube 1 in which this reference voltage is ignited. And the pipe | tube 2 which has a GND electric potential is installed in the outer side. Between the pipe 1 and the pipe 2 is fixed by an insulating part. (Tube 1 and tube 2 are not shown). By applying the voltage as described above, high throughput with high resolution can be realized with low LE.

  The primary optical system 2100 according to the present invention can obtain an effect of being able to inspect while keeping the sample surface voltage RTD at 0V. Furthermore, the primary optical system 2100 according to the present invention can obtain the same effects as those of the above-described primary optical system 2000 according to the present invention. The effect of the electron optical device including the primary optical system according to the present invention is also the same, and the description thereof is omitted.

<Modification of Photoelectron Generator in Primary Optical System>
Another example of the photoelectron generator in the primary optical system according to the present invention is shown. FIG. 15 and FIG. 16 are examples when light or laser is guided to the photoelectron surface from a midway position of the primary system by a mirror installed in the column.

  FIG. 15 is an example when the reference voltage is a high voltage, for example, 40 kV. That is, this is an example applied to the second embodiment of the primary optical system 2000 according to the present invention. At this time, a voltage of V2 = 40 kV is applied to the tube 10071 to which a high voltage is applied in order to form a reference voltage. The inside of the tube 10071 is the same voltage space. Therefore, in this example, DUV light or a UV laser is introduced through a hole provided in a tube 100071 (not shown) using a mirror having a hole through which photoelectrons pass in the center, for example, a triangular mirror 2170, and this triangular mirror 2170 The photoelectron surface 2121 is irradiated after reflection. Then, photoelectrons are generated from the irradiated surface, and the photoelectrons pass through the EX lens 2120 and NA 2125 and the downstream aligner and are irradiated onto the sample surface. At this time, a specified voltage is applied to the photoelectron surface 2121 in order for the generated photoelectrons to form a primary orbit. LE = RTD voltage −V1.

  On the other hand, FIG. 16 shows an example of the reference voltage GND in which the photoelectron surface is irradiated with light or a laser that generates photoelectrons by the triangular mirror 2070 as in the example shown in FIG. That is, this is an example applied to one embodiment of the primary optical system 2000 according to the present invention. At this time, for example, V2, V4, and V5 are GND, and the vicinity thereof is a reference voltage space. Then, it becomes possible to install a mirror similar to that shown in FIG. At this time, since the amount of generated photoelectrons is determined by the irradiation intensity of light or laser, the irradiation intensity is controlled. For this, the above-described intensity control method is used. At this time, the mirror surface and the entire structure are coated with a conductor or a conductor. The potential is the same as the reference potential. They are the same potential so as not to disturb the space potential. Further, a hole is formed in the center of the optical axis of the mirror so that the primary beam can pass without being affected by the mirror, and the primary beam passes through the hole. A conductor material or a conductor is coated and connected to the reference voltage portion so that the same potential as the reference voltage is provided inside the hole.

  In addition, two methods are shown for the shape of photoelectron generation. This will be described with reference to FIG. One is to use an FA aperture 2010 that defines the beam system before the incidence of the mirror in the column. A beam having a shape of a field aperture (FA) 2010 is formed, and the photocathode is irradiated with the beam to generate photoelectrons having the shape. At this time, the projection size of the field aperture (FA) 2010 is controlled by the lens position upstream of the field aperture (FA) 2010.

  The other method is to coat a pattern masking material on the photoelectron surface. FIG. 17 is a diagram showing an example in which an example in which a photomask is coated with a pattern masking material is used for the primary optical system 2100 according to the second embodiment of the primary optical system according to the present invention. As shown in FIG. 17, the photoelectron surface 2121 is coated with a masking material 2122. The masking material 2122 has a pattern-shaped hole, and the hole portion is not coated with the masking material. By this coating, photoelectrons are not generated from the site, but photoelectrons are generated from the site without the masking material. That is, when the DUV light is irradiated, pattern-shaped photoelectrons are generated from a pattern-shaped photocathode region that is not masked. At this time, as the masking material, a material that does not generate photoelectrons may be coated. A material having a large work function or a material having low generation efficiency may be used. For example, carbon, Pt, Cr and the like. However, when charged up, a potential non-uniformity is formed and the emitted electron trajectory is bent, so that a conductive material is used.

FIG. 18 is a diagram showing a method of reflecting the transmitted light or laser and irradiating the photoelectron surface again to improve efficiency. The light / laser incident from the photoelectron surface 2121 side is reflected in the light / laser transmitting member having the reflective surface structure (reflective surface 2123), returns to the photoelectron surface 2121 and is irradiated again. According to this method, the photoelectron surface 2121 is irradiated with light or a laser a plurality of times, so that the efficiency is increased. For example, when the light / laser transmittance of the photoelectron surface 2121 is 60%, an increase in the amount of photoelectrons generated according to the number of irradiations can be obtained by irradiating the transmitted 60% light / laser again. Not limited to this example, a method of irradiating a plurality of times is effective. In particular, 2 to 5 irradiations can achieve its effectiveness. Beyond that, the light / laser intensity drops, so the effectiveness is greatly reduced. Thus, when irradiation can be performed a plurality of times, it is possible to expect an effect that the intensity of incident light / laser can be 1/2 to 1/5 that of a single irradiation. For example, when 1 W of irradiation light / laser intensity is required, 0.2 to 0.5 W is sufficient. In particular, when a light source with a large output is required, there may be a case where the light source itself is not present or the operation management cost is large. At this time, if a low-output light source can be used, the cost, efficiency, influence of heat, influence of deterioration of the light introduction system, and the like can be reduced, which is very effective.

  Note that the examples described in FIGS. 17 and 18 are examples applied to the primary optical system 2100 according to the second embodiment of the primary optical system according to the present invention, but are not limited thereto. Instead, the present invention may be applied to the primary optical system 2000 according to another embodiment.

(Embodiment 3)
<Semiconductor inspection device with double tube structure>
As described above, in the electro-optical device 70 including the primary optical system 2100 shown in the second embodiment of the primary optical system according to the present invention, the voltage applied to each component is set as a general electron. Different from a gun. That is, the reference potential V2 is set to a high voltage (for example, +40000 V). Therefore, the semiconductor inspection apparatus 1 including the electron optical device 70 according to the present invention has a double tube structure first.

  This will be described with reference to FIG. FIG. 19 is a diagram schematically showing a double tube structure of a semiconductor inspection apparatus according to an embodiment of the present invention. In FIG. 19, the first tube and the second tube are shown with emphasis, but the actual cross sections of the first tube and the second tube are different. As shown in FIG. 19, an electro-optical device 70 including a primary optical system 2000 according to the present invention includes two tubes, a first tube 10071 and a second tube 10072 provided outside the first tube 10071. Consists of In other words, a double pipe structure is used. A light source, a primary optical system, a secondary optical system, and a detector are accommodated in the double tube structure. Then, a high voltage (for example, +40000 V.) is applied to the first tube 10071, and the second tube 10072 is set to GND. A high-voltage space reference potential V0 is secured by the first tube 10071, and GND is enclosed by the second tube. Thereby, the implementation of the GND connection of the apparatus and the electric shock are prevented. The tube 10071 is fixed to the tube 10072 with insulating parts. This tube 10072 is GND and is attached to the main housing 30. A primary optical system 2000, a secondary optical system, a detection system 76, and the like are disposed inside the first tube 10071.

  The internal partition walls of the first tube 10071 and the second tube 10072 are made of a non-magnetic material so as not to affect the magnetic field until reaching a member such as a screw, and the magnetic field does not act on the electron beam. I am doing so. Although not shown in FIG. 19, a space is provided on the side surface of the second tube 10072, and a protruding portion in which a part of the primary optical system 2000 such as a light source and a photoelectron generator is disposed is provided. Connected. Similarly, the first tube 10071 is provided with a space similar to the space provided in the second tube 10072, and the sample is irradiated with the photoelectrons generated in the photoelectron generator through these spaces. Note that the light source is not necessarily provided inside the second tube 10072, and may be disposed on the atmosphere side and introduced into a photoelectron generator housed in the second tube 10072 on the vacuum side. However, the primary optical system and the secondary optical system are necessarily accommodated in the double tube structure. The detector may be installed in the first tube 10071 or may be installed at an independent potential independent of the first and second tubes. This is characterized in that the potential of the detection surface of the detector is arbitrarily set and the energy of electrons incident on the detector is controlled to an appropriate value. In a state where the potential is separated from the tube 1 and the tube 2 by the insulating parts, the detection sensor surface potential of the detector can be operated by applying an arbitrary voltage. At this time, assuming that the sensor surface potential is VD, the energy incident on the sensor surface is determined by VD-RTD. When EB-CCD or EB-TDI is used for the detector, it is effective to use incident energy at 1 to 7 keV in order to reduce damage to the sensor and use it for a long time.

  Further, another configuration of the semiconductor inspection apparatus 1 including the electron optical device 70 according to the present invention will be described. FIG. 20 is a diagram showing an overall configuration of a semiconductor inspection apparatus 1 according to an embodiment of the present invention. As shown in FIG. 20, the semiconductor inspection apparatus 1 according to an embodiment of the present invention secondly has a second vacuum chamber 900. That is, the second vacuum chamber 900 is disposed in the semiconductor inspection apparatus 1, the power source 910 that generates a high voltage is disposed in the second vacuum chamber 900, and the first tube and the second tube are accommodated. The lens barrel 71 and the second vacuum chamber 900 are connected by a connection pipe 920, and wiring is provided in the connection pipe 920. This is because, as described above, the electron optical device 70 according to the present invention makes the reference potential V0 a high voltage unlike the conventional one. In order to set the reference potential V0 to a high voltage, the semiconductor inspection apparatus 1 including the electron optical device 70 according to the present invention has a double tube structure. Then, a high voltage is applied to the inner first tube 10071. When such a high voltage is applied, the feedthrough between the atmosphere and the vacuum requires a large feedthrough in order to ensure the creeping withstand voltage because the withstand pressure on the atmosphere side is low. For example, if the withstand voltage of 1 kV / mm is 40 kV, an insulating component having an insulation creepage distance of 40 mm or more and a large connector for the insulating component are required. When there are a large number of such large connectors, the occupied part of providing the installation portion in the lens barrel accounts for a large proportion, which increases the lens barrel size and its cost. Therefore, in the present invention, a vacuum chamber dedicated to the power source is provided. This eliminates the need for feed-through from the output, so the wiring may be connected to the electrodes. At this time, since the gas generated from the power source becomes a contamination contamination factor, it is effective to insulate the vacuum chamber for the power source and the lens barrel from the insulating parts in order to cut off the vacuum in the middle of the wiring. Further, when the voltage is high, the wiring becomes thick. In the semiconductor inspection apparatus 1, when the sample application voltage is increased, a large number of thick wires need to be installed around the stage. If such a large-diameter wiring is arranged inside the working chamber, a large torque is required because the wiring is moved during the stage operation. For example, the force with which the wiring rubs against the wall surface becomes large, and particle generation due to it becomes a big problem. . Therefore, a method in which the sample potential is set to GND and the reference voltage is set to a high voltage is very effective. At this time, it is more effective to reduce the sensor damage by controlling the voltage on the detector surface. The sample potential, the reference space potential, and the sensor surface potential are set to different values. At that time, for example, if the sample potential is GND, the reference voltage is 10 to 50 kV, and the sensor surface potential is 3 to 7 kV, it is very effective. Further, as described above, the second vacuum chamber 900 is provided to accommodate the power source 910, connected to the lens barrel or the like by the connecting pipe 920, and the wiring is provided in the connecting pipe 920 to realize the vacuum wiring. ing. A power supply (AC100V or DC24V or the like) is introduced from the outside as a power source, and an optical communication method is used for communication. If it is about this power supply, a small feedthrough is sufficient, so connection from the atmosphere side is easy.

Further, as described above, since it has a double tube structure, the inner tube (tube 1) is in a high vacuum, and an atmospheric pressure state is possible between the outer tube (tube 2) and the inner tube (tube 1). It is. In such a case, installing an electrostatic electrode in the tube 1 may not be practical due to the large number of connections made by the walls of the conduit tube 1 and the increased feedthrough of vacuum / atmosphere. . At this time, a lens, aligner, and corrector using a magnetic field are used as the lens, aligner, and corrector. This eliminates the need to install a feedthrough in the tube 1 and is effective in forming a high-voltage reference space. Use of this structure can also be applied to the first to ninth embodiments.

  According to the above-described invention of the present application, the structure of the above-described lens barrel, the second vacuum chamber for power supply, and the connection pipe for vacuum wiring connecting the lens barrel and the second vacuum chamber are all made double. A semiconductor inspection apparatus 1 including the next optical system 2000 is provided. However, this is an example, and the semiconductor inspection apparatus 1 including the primary optical system 2000 according to the present invention is not limited to this. Further, the embodiments described so far, for example, the primary system and the secondary system shown in the first to ninth embodiments can also be performed by using the double pipe structure of the present embodiment. .

(Embodiment 4)
<Beam measurement method at crossover position, primary irradiation electron beam and NA position adjustment method using the method, and semiconductor inspection apparatus using the adjustment method>
A semiconductor inspection method using the above-described electron optical device including the primary optical system according to the present invention will be described. The following method can also be applied to a semiconductor inspection apparatus using an electron optical apparatus equipped with a general electron gun.

  In the present embodiment, a sample is observed using a mapping projection observation apparatus (an electron beam observation apparatus having a mapping projection optical system). This type of electron beam observation apparatus includes a primary optical system and a secondary optical system. The primary optical system 2000 irradiates the sample with an electron beam emitted from the photoelectron generator, and generates electrons obtained from information such as the structure of the sample. The secondary optical system has a detector and generates an image of electrons generated by irradiation with an electron beam. In the projection type observation apparatus, a large-diameter electron beam is used, and a wide range of images can be obtained. That is, irradiation is performed with a surface beam instead of a spot beam focused as in a normal SEM.

  When the sample is irradiated with an electron beam, a plurality of types of electrons are detected by the secondary optical system. The plural types of electrons are mirror electrons, secondary electrons, reflected electrons, and backscattered electrons. In the present embodiment, secondary electrons, reflected electrons, and backscattered electrons are referred to as secondary emission electrons. Then, the sample is observed using the characteristics of mirror electrons and secondary emission electrons. Mirror electrons are electrons that do not collide with the sample and bounce immediately before the sample. The mirror electron phenomenon is caused by the action of the electric field on the sample surface.

  As described above, secondary electrons, reflected electrons, and backscattered electrons are referred to as secondary emission electrons. Even when these three types of electrons are mixed, the term secondary emission electrons is used. Of the secondary emission electrons, secondary electrons are typical. Therefore, secondary electrons may be described as representative of secondary emission electrons. For both mirror electrons and secondary emission electrons, expressions such as “emitted from the sample”, “reflected from the sample”, and “generated by electron beam irradiation” may be used.

  FIG. 21 is a diagram showing the relationship between the landing energy LE and the gradation DN when the sample is irradiated with an electron beam. The landing energy LE is energy applied to the electron beam irradiated on the sample. Assume that an acceleration voltage Vacc is applied to the electron gun and a retarding voltage Vrtd is applied to the sample. In this case, the landing energy LE is represented by the difference between the acceleration voltage and the retarding voltage.

  In FIG. 21, the gradation DN on the vertical axis represents the luminance in an image generated from electrons detected by the detector of the secondary optical system. That is, the gradation DN represents the number of detected electrons. As more electrons are detected, the gradation DN increases.

  FIG. 21 shows gradation characteristics in a small energy region near 0 [eV]. As shown in the figure, in a region where LE is greater than LEB (LEB <LE), the gradation DN shows a relatively small constant value. In a region where LE is equal to or lower than LEB and equal to or higher than LEA (LEA ≦ LE ≦ LEB), the gradation DN increases as LE decreases. In the region where LE is smaller than LEA (LE <LEA), the gradation DN shows a relatively large constant value.

  The gradation characteristics are related to the type of electrons detected. In the region of LEB <LE, almost all detected electrons are secondary emission electrons. This region can be called a secondary emission electron region. On the other hand, in the region of LE <LEA, almost all detected electrons are mirror electrons. This region can be called a mirror electron region. As shown in the figure, the gradation of the mirror electron region is larger than that of the secondary emission electron region. This is because the range of distribution of mirror electrons is smaller than that of secondary emission electrons. Since the distribution range is small, more electrons can reach the detector, and the gradation becomes large.

  The region of LEA ≦ LE ≦ LEB is a transition region from the secondary emission electron region to the mirror electron region (or vice versa). This region is a region where mirror electrons and secondary emission electrons are mixed, and can also be referred to as a mixed region. In the transition region (mixed region), the smaller the LE is, the more mirror electrons are generated and the gradation is increased.

  LEA and LEB mean the lowest landing energy and the highest landing energy in the transition region. Specific values of LEA and LEB will be described. According to the research results of the present inventors, LEA is −5 [eV] or more and LEB is 5 [eV] or less (that is, −5 [eV] ≦ LEA ≦ LEB ≦ 5 [eV]).

  The advantages of the transition area are as follows. In the mirror electron region (LE <LEA), all electrons generated by beam irradiation become mirror electrons. Therefore, regardless of the shape of the sample, all the detected electrons are mirror electrons, and the difference in gradation is reduced in both the concave and convex portions of the sample, and the S / N and contrast of the pattern and defect are reduced. Therefore, it may be difficult to use the mirror electron region for inspection. In contrast, in the transition region, mirror electrons are generated characteristically and specifically at the edge portion of the shape, and secondary emission electrons are generated at other portions. Therefore, the S / N and contrast of the edge can be increased. Therefore, the transition region is very effective when performing inspection. Hereinafter, this point will be described in detail.

  FIG. 22 shows the phenomenon of the above transition region. FIG. 22 is a diagram illustrating the phenomenon of the transition region. In FIG. 22, in the mirror electron region (LE <LEA), all electrons become mirror electrons without colliding with the sample. In contrast, in the transition region, some electrons collide with the sample, and the sample emits secondary emission electrons. As LE increases, the proportion of secondary emission electrons increases. Although not shown, when LE exceeds LEB, only secondary emission electrons are detected.

  In the present invention, a secondary optical system that forms an image with an irradiated electron beam including a secondary emission electron region, a transition region, a mirror electron region, and a pattern having a concavo-convex structure and a pattern having no concavo-convex structure. Invented an electron beam condition creation and adjustment method. According to the present invention, highly accurate adjustment and condition creation can be achieved remarkably efficiently. This is shown below.

A major feature of the present invention is that the position and shape of a beam coming to a crossover position (hereinafter referred to as CO position) in the middle of the secondary optical system are measured. Conventionally, without measuring the beam coming to the CO position, the NA is moved, an image is taken, and the contrast of the image is evaluated. This takes an enormous amount of time. The conventional procedure is as follows.
a. Form imaging conditions with a lens between the CO position and the detector.
b. If there is NA, use a large aperture. Or remove it.
It is better to observe the entire CO. For example, φ1000 to φ5000 μm
c. Imaging the beam at the CO position.

  In the present invention, in order to efficiently perform such imaging and adjustment, and to improve deterioration and replacement / maintenance due to contamination, the configuration of the device will be described later. Characteristically, the movable numerical aperture (NA) 10008 is provided. Thus, an example of measuring the beam shape at the CO position with respect to LE is shown in FIG. FIG. 23 is a diagram illustrating a measurement example of the beam shape at the CO position with respect to LE. In FIG. 23, the shape of the beam coming to the CO position is shown in the upper stage, and the phenomenon in the mirror region, transition region, and secondary emission electron region of the beam irradiated on the sample surface is shown in the lower stage. In the upper stage, mirror electrons are indicated by black dots, and secondary emission electrons are indicated by circles. In contrast to LE, only mirror electrons are observed in the mirror electron region. In the transition region, mirror electrons and secondary emission electrons are observed. In the secondary emission electron region, only secondary emission electrons are observed, and mirror electrons are not observed. Using the image data obtained by this imaging, the position, size, and intensity of mirror electrons and the size and intensity of secondary emission electrons are measured.

  In addition, this observation makes it possible to immediately determine which of the three states is present when the irradiated electron beam is applied to the target sample. Conventionally, an ambiguous prediction has been made from the irradiation conditions and the obtained image. Such an accurate situation judgment could not be made. Moreover, the error due to the power setting accuracy and the influence due to the optical axis condition could not be accurately determined. This is because the formation of the mirror electron region and the transition region is sensitive to the LE and optical axis conditions, and is also affected by errors in equipment and conditions that control them. For example, the power supply setting accuracy is generally about 0.1%. The setting error of the 5000V setting power supply is 5V. When a change of 5 V occurs, the transition region → mirror region or the transition region → secondary emission electron region may be sufficient. Since the confirmation could not be made, only a vague prediction such as the mirror electron region or the transition region could be made depending on the set value.

  Furthermore, the present invention describes a method for setting the NA position for adjusting the primary irradiation electron beam and performing image formation using the method for performing this measurement. It is assumed that the direction of a sample such as a mask or wafer has been adjusted with the coordinates and position of the secondary optical system (column).

(Photoelectron cathode primary system)
FIG. 14 shows an example used when the reference voltage is not GND but is a high voltage. In this example, the reference voltage is + 40000V. The tube is cylindrical so that its reference voltage can be unified within the column to form an electric field. This tube is referred to as tube 1. Then, 40,000 V is applied to form a reference voltage. Further, the portion close to the photoelectron surface is parallel to the equipotential line (distribution) photocathode. For this reason, a magnetic lens is used as the lens. As the aligner, an electromagnetic aligner is used. NA and other apertures are reference potentials and are installed in the tube structure. Since this tube 1 is applied with a high voltage, there is another tube 2 on the outside. This pipe 2 is GND, and a GND connection is possible as a device. The tube 1 and the tube 2 are insulated by an insulator having a withstand voltage, and the necessary applied voltage is even maintained. Although not described here, the reference voltage of the primary system is controlled in order to make the reference voltage of the secondary optical system high. Therefore, in the secondary optical system, the tube is a double-structured column as in the primary optical system. A high voltage is applied to the inner tube, and the outer tube is GND. The voltage difference is maintained as in the primary system. Further, the tube 1 may be a conductor, and the outer peripheral portion of the tube 1 may be coated with a resin material such as polyimide or epoxy. Furthermore, a conductive material may be coated on the outer peripheral portion of the resin material, and the coated conductive material may be GND. Thereby, the inside of the resin material is a high-voltage reference voltage, and the outside is GND, so that it is possible to assemble other GND connections and components that can be GND-installed. In addition, a conductor shield tube 2 may be provided on the outside. The tube 2 is a magnetic material such as permalloy or pure iron, and can block an external magnetic field. In addition, this embodiment is applicable also to Embodiment 1-25 mentioned above and Embodiment which is not numbered.

"Second detector"
As a means for measuring the position and shape of the beam at the CO position and adjusting the optical axis without requiring frequent replacement of the detector, and as a detector for measuring the beam at the CO position, for inspection A second detector is provided immediately before the detector. FIG. 24 is a diagram showing the principle of the second detector according to the present invention. FIG. 24A is a diagram showing a secondary optical system of the present invention, and FIG. 24B is a diagram illustrating an electron beam of secondary emission electrons and mirror electrons at a numerical aperture (NA) 10008 position through a lens. It is a figure which shows making it image on the 2nd detector 76-2. A second detector 76-2 according to an embodiment of the present invention is provided between the numerical aperture 10008 and the detection system 76 shown in FIG. 24B, and the movable numerical aperture (NA) 10008 is moved. Then, the position and shape of the beam at the CO position may be imaged with the second detector. Here, the beam shape and position at the CO position (or NA position) only need to be able to capture a still image. The adjustment is repeated based on the information captured by the second detector 76-2, and the inspection is performed after the adjustment.

  Secondary emission electrons and mirror electrons that have passed through the numerical aperture (NA) 10008 form an image on the sensor surface of the detector. The imaged two-dimensional electronic image is acquired by the second detector 76-2, converted into an electrical signal, and sent to the image processing unit. A transfer lens or an electrostatic lens for magnifying projection is used between the numerical aperture 10008 and the second detector 76-2 so that the electron beam image at the CO position can be captured by the second detector 76-2. May be.

  As the second detector 76-2, an EB-CCD or a C-MOS type EB-CCD can be used. The element size may be 1/2 to 1/3 of the element size of EB-TDI which is the first detector (detector 761). As a result, imaging with a Px size smaller than that of the first detector becomes possible. The Px size is a value obtained by dividing the element size by the optical magnification, and is the image division size on the sample surface. For example, when the element size is 10 μm and the magnification is 1000 times, Px size = 10 μm / 1000 times = 10 nm. If the second detector has an element size smaller than that of the first detector, surface observation with a Px size smaller than that of the first detector becomes possible. The EB-TDI of the first detector, the EB-CCD of the second detector, or the C-MOS type EB-CCD does not require a photoelectron conversion mechanism and a light transmission mechanism. The electrons are directly incident on the EB-TDI sensor surface or the EB-CCD sensor surface. Therefore, there is no deterioration in resolution, and a high MTF (Modulation Transfer Function) and contrast can be obtained. Compared to the conventional EB-CCD, the C-MOS type EB-CCD can significantly reduce the background noise, so it is very effective in reducing the noise caused by the detector. Also, contrast and S / N can be improved. This is particularly effective when the number of acquired electrons is small. There is an effect of about 1/3 to 1/20 of the conventional EB-CCD in reducing noise.

  The beam formed on the detector surface through the numerical aperture (NA) 10008 is detected by the second detector 76-2, and the electron beam condition creation and the numerical aperture (NA) 10008 are determined according to the position and shape of the detected beam. Adjust the position of etc. After various adjustments are made according to the detection results of the second detector 76-2, the sample is inspected using the detection system 76. Therefore, since the detection system 76 is used only at the time of inspection, the replacement frequency of the detection system 76 can be suppressed. In addition, since the second detector 76-2 captures only a still image, even if deterioration occurs, the inspection is not affected. In order to achieve such an imaging condition, for example, a condition for forming an electron image on the first detector, a condition for forming an image on the second detector, and a CO position for observing the beam at the CO position. In the conditions for imaging the beam shape coming to the second detector, etc., these adjustments are made by adjusting the lens intensity of the transfer lens 10009 and referring to the first detector and the second detector with reference to the example of FIG. In some cases, an imaging condition for which an optimum condition for two detectors is obtained is used. Further, a lens 741 may be used instead of the transfer lens 10009. Since the distance between the lens center and the detector changes, the magnification changes when the transfer lens 10009 and the lens 741 are used. Therefore, a suitable lens and magnification may be selected.

  The second detector 76-2 described above is effective when used in combination with the adjustment method according to the present invention in which the beam position and shape at the CO position described above are measured to create the condition of the electron beam and perform high-precision adjustment. Is obtained. The second detector 76-2 may be applied not only to an electron optical device including a new photoelectron generator according to the present invention but also to an electron optical device including a general electron gun. This example is also applicable to the devices described in the first to eleventh embodiments. In the example of the beam and NA position adjustment method described above, an example in which the primary beam is an electron beam has been described, but the present invention can also be applied when the irradiation system is light or laser. Photoelectrons are generated from the sample surface by irradiation with a laser or light, and can be used when the crossover size of the photoelectrons and the relationship between the center position and the NA installation position are appropriately set. This makes it possible to form a photoelectron image with good resolution.

"Electronic inspection equipment"
FIG. 25 is a diagram showing a configuration of an electron beam inspection apparatus to which the present invention is applied. In the above description, the principle part of the foreign matter inspection method has been mainly described. Here, a foreign substance inspection apparatus applied to execute the above-described foreign substance inspection method will be described. Therefore, all the foreign substance inspection methods described above can be applied to the following foreign substance inspection apparatus.

  The inspection object of the electron beam inspection apparatus is the sample 20. The sample 20 is a silicon wafer, a glass mask, a semiconductor substrate, a semiconductor pattern substrate, a substrate having a metal film, or the like. The electron beam inspection apparatus according to the present embodiment detects the presence of the foreign matter 10 on the surface of the sample 20 made of these substrates. The foreign material 10 is an insulator, a conductive material, a semiconductor material, or a complex thereof. The types of the foreign matter 10 are particles, cleaning residues (organic matter), reaction products on the surface, and the like. The electron beam inspection apparatus may be an SEM system apparatus or a mapping projection apparatus. In this example, the present invention is applied to a mapping projection inspection apparatus.

  The projection type electron beam inspection apparatus forms a primary optical system 40 that generates an electron beam, a sample 20, a stage 30 on which the sample is placed, and an enlarged image of secondary emission electrons or mirror electrons from the sample. Secondary optical system 60 to be detected, a detector 70 for detecting those electrons, an image processing device 90 (image processing system) for processing a signal from the detector 70, an optical microscope 110 for alignment, and a review SEM120. The detector 70 may be included in the secondary optical system 60 in the present invention. Further, the image processing apparatus 90 may be included in the image processing unit of the present invention.

  The primary optical system 40 is configured to generate an electron beam and irradiate the sample 20. The primary optical system 40 includes an electron gun 41, lenses 42 and 45, apertures 43 and 44, an E × B filter 46, lenses 47, 49 and 50, and an aperture 48. An electron beam is generated by the electron gun 41. The lenses 42 and 45 and the apertures 43 and 44 shape the electron beam and control the direction of the electron beam. In the E × B filter 46, the electron beam is affected by the Lorentz force due to the magnetic field and the electric field. The electron beam enters the E × B filter 46 from an oblique direction, is deflected vertically downward, and travels toward the sample 20. The lenses 47, 49, and 50 adjust the landing energy LE by controlling the direction of the electron beam and appropriately decelerating.

  The primary optical system 40 irradiates the sample 20 with an electron beam. As described above, the primary optical system 40 irradiates both the precharge charging electron beam and the imaging electron beam. According to the experimental results, the difference between the precharge landing energy LE1 and the imaging electron beam landing energy LE2 is preferably 5 to 20 eV.

  In this regard, it is assumed that when there is a potential difference between the foreign material 10 and the surrounding area, the precharge landing energy LE1 is irradiated in the negatively charged region. The charge-up voltage varies depending on the value of LE1. This is because the relative ratio of LE1 and LE2 changes (LE2 is the landing energy of the imaging electron beam as described above). When LE1 is large, the charge-up voltage becomes high, whereby a reflection point is formed at a position above the foreign material 10 (position closer to the detector 70). Depending on the position of this reflection point, the trajectory and transmittance of the mirror electrons change. Therefore, an optimum charge-up voltage condition is determined according to the reflection point. On the other hand, if LE1 is too low, the efficiency of forming mirror electrons decreases. The present invention has found that the difference between LE1 and LE2 is preferably 5 to 20 [eV]. The value of LE1 is preferably 0 to 40 [eV], more preferably 5 to 20 [eV].

  In the primary optical system 40 of the mapping projection optical system, the E × B filter 46 is particularly important. The primary electron beam angle can be determined by adjusting the electric field and magnetic field conditions of the E × B filter 46. For example, the condition of the E × B filter 46 can be set so that the primary electron beam and the secondary electron beam are incident on the sample 20 substantially perpendicularly. In order to further increase the sensitivity, for example, it is effective to tilt the incident angle of the primary electron beam with respect to the sample 20. An appropriate inclination angle is 0.05 to 10 degrees, preferably about 0.1 to 3 degrees.

  As described above, by irradiating the foreign material 10 with the electron beam at a predetermined angle θ, the signal from the foreign material 10 can be strengthened. As a result, it is possible to form a condition in which the orbit of the mirror electrons does not deviate from the center of the secondary system optical axis, and therefore the transmittance of the mirror electrons can be increased. Therefore, when the foreign material 10 is charged up and the mirror electrons are guided, the tilted electron beam is very advantageously used.

  Returning to FIG. The stage 30 is a means for placing the sample 20 and is movable in the xy horizontal direction and the θ direction. Further, the stage 30 may be movable in the z direction as necessary. A sample fixing mechanism such as an electrostatic chuck may be provided on the surface of the stage 30.

  The sample 20 is on the stage 30, and the foreign material 10 is on the sample 20. The primary optical system 40 irradiates the sample surface 21 with an electron beam with landing energy LE-5 to -10 [eV]. The foreign material 10 is charged up, and incident electrons of the primary optical system 40 are bounced back without contacting the foreign material 10. Thereby, the mirror electrons are guided to the detector 70 by the secondary optical system 60. At this time, secondary emission electrons are emitted in a direction extending from the sample surface 21. Therefore, the transmittance of secondary emission electrons is a low value, for example, about 0.5 to 4.0%. On the other hand, since the direction of the mirror electrons is not scattered, the mirror electrons can achieve a high transmittance of almost 100%. The mirror electrons are formed by the foreign material 10. Therefore, only the signal of the foreign material 10 can cause high luminance (a state in which the number of electrons is large). The brightness difference / ratio with the surrounding secondary emission electrons is increased, and high contrast can be obtained.

  Further, as described above, the mirror electron image is magnified at a magnification larger than the optical magnification. The enlargement ratio ranges from 5 to 50 times. Under typical conditions, the magnification is often 20 to 30 times. At this time, foreign matter can be detected even if the pixel size is three times or more the foreign matter size. Therefore, it can be realized at high speed and high throughput.

  For example, when the size of the foreign material 10 is 20 [nm] in diameter, the pixel size may be 60 [nm], 100 [nm], 500 [nm], or the like. As in this example, it is possible to image and inspect a foreign object using a pixel size that is three times or more that of the foreign object. This is a feature that is remarkably superior for increasing the throughput as compared with the SEM method or the like.

  The secondary optical system 60 is a means for guiding the electrons reflected from the sample 20 to the detector 70. The secondary optical system 60 includes lenses 61 and 63, an NA aperture 62, an aligner 64, and a detector 70. The electrons are reflected from the sample 20 and pass through the objective lens 50, the lens 49, the aperture 48, the lens 47 and the E × B filter 46 again. Then, the electrons are guided to the secondary optical system 60. In the secondary optical system 60, electrons are collected through the lens 61, the NA aperture 62, and the lens 63. The electrons are arranged by the aligner 64 and detected by the detector 70.

  The NA aperture 62 has a role of defining the transmittance and aberration of the secondary system. The size and position of the NA aperture 62 are selected so that the difference between the signal from the foreign object 10 (mirror electron etc.) and the signal at the surrounding (normal part) becomes large. Alternatively, the size and position of the NA aperture 62 are selected so that the ratio of the signal from the foreign object 10 to the surrounding signal is increased. Thereby, S / N can be made high.

  For example, it is assumed that the NA aperture 62 can be selected in the range of φ50 to φ3000 [μm]. It is assumed that mirror electrons and secondary emission electrons are mixed in the detected electrons. In order to improve the S / N of the mirror electron image in such a situation, the selection of the aperture size is advantageous. In this case, it is preferable to select the size of the NA aperture 62 so as to reduce the transmittance of secondary emission electrons and maintain the transmittance of mirror electrons.

  For example, when the incident angle of the primary electron beam is 3 °, the reflection angle of the mirror electrons is approximately 3 °. In this case, it is preferable to select a size of the NA aperture 62 that allows the trajectory of mirror electrons to pass. For example, a suitable size is φ250 [μm]. Since it is limited to the NA aperture (diameter φ250 [μm]), the transmittance of secondary emission electrons is lowered. Therefore, the S / N of the mirror electron image can be improved. For example, when the aperture diameter is changed from φ2000 to φ250 [μm], the background gradation (noise level) can be reduced to ½ or less.

Returning to FIG. The detector 70 is means for detecting electrons guided by the secondary optical system 60. The detector 70 has a plurality of pixels on its surface. Various two-dimensional sensors can be applied to the detector 70. For example, the detector 70 includes a CCD (Charge Coupled).
Device) and TDI (Time Delay Integration) -CCD may be applied. These are sensors that detect signals after converting electrons to light. Therefore, means such as photoelectric conversion are necessary. Therefore, electrons are converted into light by using photoelectric conversion or scintillator. The image information of light is transmitted to TDI that detects light. In this way, electrons are detected.

  Here, an example in which EB-TDI is applied to the detector 70 will be described. EB-TDI does not require a photoelectric conversion mechanism / light transmission mechanism. Electrons enter the EB-TDI sensor surface directly. Therefore, there is no deterioration in resolution, and a high MTF (Modulation Transfer Function) and contrast can be obtained. Conventionally, detection of the small foreign material 10 has been unstable. On the other hand, when EB-TDI is used, it is possible to increase the S / N of the weak signal of the small foreign material 10. Therefore, higher sensitivity can be obtained. The improvement in S / N reaches 1.2 to 2 times.

  In addition to the EB-TDI, an EB-CCD may be provided. EB-TDI and EB-CCD are interchangeable and may be switched arbitrarily. It is also effective to use such a configuration. For example, a usage method as shown in FIG. 26 is applied.

  FIG. 26 shows a detector 70 capable of switching between the EB-TDI 72 and the EB-CCD 71. The two sensors can be exchanged depending on the application, and both sensors can be used.

  In FIG. 26, the detector 70 includes an EB-CCD 71 and an EB-TDI 72 installed in a vacuum vessel 75. The EB-CCD 71 and the EB-TDI 72 are electronic sensors that receive an electron beam. The electron beam e is directly incident on the detection surface. In this configuration, the EB-CCD 71 is used for adjusting the optical axis of the electron beam, and is used for adjusting and optimizing image capturing conditions. On the other hand, when the EB-TDI 72 is used, the EB-CCD 71 is moved to a position away from the optical axis by the moving mechanism M. Then, imaging is performed by the EB-TDI 72 using or referring to the conditions obtained by using the EB-CCD 71. Evaluation or measurement is performed using the image. The moving mechanism M is configured to be movable not only in the direction in which the EB-CCD 71 is moved (X direction) but also in three axes (for example, in the X, Y, and Z directions), and the center of the EB-CCD 71 is the center of the electron optical system. You may comprise so that fine adjustment can be carried out with respect to the optical axis center.

  In this detector 70, the foreign substance detection of the semiconductor wafer by the EB-TDI 72 can be performed by using or referring to the electro-optical condition obtained by using the EB-CCD 71.

  After the foreign substance inspection by the EB-TDI 72, review imaging may be performed using the EB-CCD 71, and defect evaluation such as a foreign substance type and a foreign substance size may be performed. The EB-CCD 71 can integrate images. Noise can be reduced by integration. Therefore, it is possible to perform review imaging of a defect detection site with high S / N. Furthermore, it is effective that the pixels of the EB-CCD 71 are smaller than the pixels of the EB-TDI 72. That is, the number of pixels of the image sensor can be increased with respect to the size of the signal enlarged by the mapping projection optical system. Therefore, an image having higher resolution can be obtained. This image is used for classification and determination of inspection, defect type, and the like.

  The EB-TDI 72 has a configuration in which pixels are two-dimensionally arranged, and has, for example, a rectangular shape. As a result, the EB-TDI 172 can directly receive the electron beam e and form an electronic image. The pixel size is, for example, 12 to 16 [μm]. On the other hand, the pixel size of the EB-CCD 71 is, for example, 6 to 8 [μm].

  The EB-TDI 72 is formed in the form of a package. The package itself serves as a feedthrough FT. The package pins 73 are connected to the camera 74 on the atmosphere side.

  The configuration shown in FIG. 26 can solve various drawbacks. Disadvantages to be solved are optical conversion loss due to FOP, hermetic optical glass, optical lenses, and the like, aberrations and distortion during light transmission, resulting in image resolution degradation, poor detection, high cost, large size, and the like.

  FIG. 27 shows an electron beam inspection apparatus to which the present invention is applied. Here, an example of the overall system configuration will be described.

  27, the foreign matter inspection apparatus includes a sample carrier 190, a mini-environment 180, a load lock 162, a transfer chamber 161, a main chamber 160, an electron beam column system 100, and an image processing apparatus 90. The mini-environment 180 is provided with a transfer robot in the atmosphere, a sample alignment device, a clean air supply mechanism, and the like. The transfer chamber 161 is provided with a transfer robot in vacuum. Since the robot is always placed in the transfer chamber 161 in a vacuum state, it is possible to minimize the generation of particles and the like due to pressure fluctuations.

  The main chamber 160 is provided with a stage 30 that moves in the x direction, the y direction, and the θ (rotation) direction, and an electrostatic chuck is installed on the stage 30. The sample 20 itself is installed on the electrostatic chuck. Or the sample 20 is hold | maintained at an electrostatic chuck in the state installed in the pallet or the jig.

  The main chamber 160 is controlled by the vacuum control system 150 so that a vacuum state is maintained in the chamber. Further, the main chamber 160, the transfer chamber 161, and the load lock 162 are placed on the vibration isolation table 170 so that vibration from the floor is not transmitted.

  In addition, an electronic column 100 is installed in the main chamber 160. The electron column 100 includes columns of the primary optical system 40 and the secondary optical system 60 and a detector 70 that detects secondary emission electrons or mirror electrons from the sample 20. The signal from the detector 70 is sent to the image processing device 90 for processing. Both on-time signal processing and off-time signal processing are possible. On-time signal processing is performed during the inspection. When performing off-time signal processing, only an image is acquired and signal processing is performed later. Data processed by the image processing apparatus 90 is stored in a recording medium such as a hard disk or memory. Moreover, it is possible to display data on the monitor of the console as necessary. The displayed data includes, for example, an inspection area, a foreign matter number map, a foreign matter size distribution / map, a foreign matter classification, a patch image, and the like. In order to perform such signal processing, system software 140 is provided. An electron optical system control power supply 130 is provided to supply power to the electron column system. Further, the main chamber 160 may be provided with the optical microscope 110 and the SEM type inspection device 120.

  FIG. 28 shows an example of a configuration when the electronic column 100 of the mapping optical inspection apparatus and the SEM inspection apparatus 120 are installed in the same main chamber 160. As shown in FIG. 28, it is very advantageous if the mapping optical inspection device and the SEM inspection device 120 are installed in the same chamber 160. The sample 20 is mounted on the same stage 30, and the sample 20 can be observed or inspected by both the mapping method and the SEM method. The usage and advantages of this configuration are as follows.

  First, since the sample 20 is mounted on the same stage 30, when the sample 20 moves between the mapping type electronic column 100 and the SEM type inspection apparatus 120, the coordinate relationship is uniquely obtained. Therefore, when specifying a foreign matter detection location or the like, the two inspection devices can easily specify the same location with high accuracy.

  Assume that the above configuration is not applied. For example, the mapping optical inspection device and the SEM inspection device 120 are configured separately as separate devices. Then, the sample 20 is moved between the separated devices. In this case, since it is necessary to place the sample 20 on different stages 30, it is necessary for the two apparatuses to perform alignment of the sample 20 separately. Further, when the alignment of the sample 20 is performed separately, the specific error at the same position is 5 to 10 [μm]. In particular, in the case of the sample 20 having no pattern, since the position reference cannot be specified, the error is further increased.

  On the other hand, in the present embodiment, as shown in FIG. 28, the sample 20 is placed on the stage 30 of the same chamber 160 in two types of inspection. Even when the stage 30 moves between the mapping-type electronic column 100 and the SEM inspection apparatus 120, the same position can be specified with high accuracy. Therefore, even in the case of the sample 20 without a pattern, the position can be specified with high accuracy. For example, the position can be specified with an accuracy of 1 [μm] or less.

  Such high-precision identification is very advantageous in the following cases. First, the foreign substance inspection of the sample 20 without a pattern is performed by a mapping method. Then, identification and detailed observation (review) of the detected foreign matter 10 are performed by the SEM type inspection apparatus 120. Since an accurate position can be specified, it is possible not only to determine the presence or absence of the foreign material 10 (pseudo detection if there is no foreign material), but also to perform detailed observation of the size and shape of the foreign material 10 at high speed.

  As described above, if the electronic column 100 for foreign matter detection and the SEM inspection device 120 for review are provided separately, it takes a lot of time to identify the foreign matter 10. In the case of a sample having no pattern, the degree of difficulty increases. Such a problem is solved by this embodiment.

  As described above, in the present embodiment, the ultrafine foreign matter 10 is inspected with high sensitivity using the imaging condition of the foreign matter 10 by the mapping optical method. Further, the mapping optical type electronic column 100 and the SEM type inspection device 120 are mounted in the same chamber 160. Thereby, in particular, the inspection of the ultrafine foreign material 10 of 30 [nm] or less and the determination and classification of the foreign material 10 can be performed very efficiently and at high speed. In addition, this embodiment is applicable also to Embodiment 1-28 mentioned above and embodiment which does not attach | subject the number.

  Next, another example of inspection using both the projection type inspection apparatus and the SEM will be described.

  In the above description, the projection type inspection apparatus detects a foreign object, and the SEM performs a review inspection. However, the present invention is not limited to this. Two inspection devices may be applied to different inspection methods. By combining the characteristics of each inspection apparatus, an effective inspection can be performed. Another inspection method is as follows, for example.

  In this inspection method, the projection type inspection apparatus and the SEM inspect different areas. Furthermore, "cell to cell" inspection is applied to the projection type inspection apparatus, and "die to die" inspection is applied to the SEM, so that high-accuracy inspection can be realized efficiently as a whole. Is done.

  More specifically, the mapping projection inspection apparatus performs “cell-to-cell” inspection on an area having a large number of repeated patterns in the die. Then, the SEM performs “die-to-die” inspection on an area where there are few repetitive patterns. Both of the inspection results are combined to obtain one inspection result. “Die-to-die” is an inspection in which images of two dies obtained sequentially are compared. A “cell to cell” is an inspection that compares images of two cells obtained sequentially, and the cell is a part of the die.

  In the inspection method described above, a high-speed inspection is performed using a mapping projection method in a repetitive pattern portion, while an inspection is performed with an SEM with high accuracy and less pseudo in an area where the repetitive pattern is small. SEM is not suitable for high-speed inspection. However, since the region with few repeating patterns is relatively narrow, the SEM inspection time does not become too long. Therefore, the entire inspection time can be reduced. Thus, this inspection method can make the most of the merit of the two inspection methods and perform a highly accurate inspection in a short inspection time.

  Next, returning to FIG. 27, the transport mechanism of the sample 20 will be described.

  A sample 20 such as a wafer or mask is transferred from the load port into the mini-environment 180, and alignment work is performed therein. The sample 20 is transferred to the load lock 162 by a transfer robot in the atmosphere. The load lock 162 is exhausted from the atmosphere to a vacuum state by a vacuum pump. When the pressure becomes a certain value (about 1 [Pa]) or less, the sample 20 is transferred from the load lock 162 to the main chamber 160 by the transfer robot in vacuum arranged in the transfer chamber 161. Then, the sample 20 is placed on the electrostatic chuck mechanism on the stage 30.

(Light + EB irradiation type)
An embodiment in which there are two types of primary systems will be described.

  It is also very effective to form an image by a combination of a photoelectron image by light or laser irradiation and secondary emission electrons and / or mirror electrons (which may or may not have mirror electrons) by electron beam irradiation. Here, secondary emission electrons refer to a state in which secondary electrons, reflected electrons, and backscattered electrons are partially or mixed. In particular, at low LE, it is difficult to distinguish them.

  It is the form which united the form which irradiates a sample with the light or laser of FIGS. 7-9, and the form which irradiates a sample with an electron beam to the primary system of FIGS. 10a-19. Examples of the embodiment are shown in FIG. 29, FIG. 30, and FIG. An example in the case where the sample is uneven is described below.

  In this example, laser irradiation (or light) and electron beam irradiation are simultaneously performed as a primary beam. As an irradiation method, irradiation can be performed simultaneously and alternately in time. The characteristics of laser irradiation and electron beam irradiation at this time are described, and the effects and actions that occur when they are fused are described.

  When the top layer (convex part) has a large amount of photoelectrons when the laser irradiation is performed and a white signal is emitted, and when the electron beam is irradiated, the top layer has a large number of secondary emission electrons and a white signal, the photoelectron image and the secondary emission electrons are generated. By combining the images, the amount of electrons in the top layer can be increased (photoelectron white + secondary emission electrons and / or mirror electron white), that is, an image in which the top layer (convex portion) is white and the concave portion is black can be formed. The contrast and S / N can be increased.

  On the other hand, when the concave portion has many photoelectrons and the concave portion is observed with a white signal and the amount of secondary emitted electron concave portions is large and the concave portion is observed with a white signal, if laser irradiation and electron beam irradiation are performed simultaneously (combination), the concave portion Can increase the contrast and S / N of an image formed with white (photoelectron white + secondary tail-exposed electrons and / or mirror electron white) and top layer (convex portion) black. At this time, the white signal means that the number of electrons detected is larger than that of other parts and the luminance is relatively high, that is, it is possible to capture white.

  As shown in FIG. 10 (a), when an electron beam is used, it is separated from the secondary beam (using Wien filter conditions for linearly traveling the secondary beam, etc.), so that an electron beam separator such as E × B is used. Is absolutely necessary. Therefore, such an electron beam separator is also required in a form in which an electron beam and a laser or light beam are fused. Examples thereof are shown in FIG. 29, FIG. 30, and FIG.

  The difference between FIG. 29, FIG. 30 and FIG. 31 is as follows. 29 and 30 have a mechanism for introducing a laser (or light) closer to the sample side than E × B. FIG. 31 has a mechanism for introducing a laser (or light) closer to the detector than E × B. For example, in FIGS. 29 and 30, a laser introduction hole is provided in the cathode lens, and a laser is irradiated onto the sample in a state where alignment is adjusted by a mirror or the like outside the chamber, or a fiber + lens or the like is used as the cathode lens. In this case, laser irradiation can be performed. Further, in FIG. 31, a mirror member is installed in a secondary column, and a laser can be introduced from outside the column to irradiate the sample with laser (or light). FIG. 31 shows the case where the amount of electrons in the convex portion due to laser irradiation and electron beam irradiation is large (white signal), but the case where the amount of electron in the opposite concave portion is large (white signal) is also performed in the same manner as in FIG. It is possible.

  For the primary electron beam, it is more effective to use the electron beam described in the embodiment as shown in FIGS. Since an electron beam having a narrow band energy can be irradiated with a large current, the energy of secondary emission electrons and mirror electrons formed is narrow, and a high resolution image with less aberration and blur can be realized. In addition, since the energy of photoelectrons by laser irradiation is narrower than that of secondary emission electrons, it is possible to maintain a narrow band of energy even if fusion / combination is performed, so that the amount of electrons increases but the energy width increases. There is a merit that it is not necessary. This is very effective and useful because it can be realized without degrading the image quality when the number of lasers or electron beams to be irradiated is increased in order to increase the throughput.

  Conversely, a combination in which photoelectrons are white and secondary emission electrons are black is also possible. In this case, the combined image is gray, that is, an intermediate color between white and black, and the resolution and contrast of the pattern are lowered. At this time, it becomes possible to perform an observation in which only a defect has a strong white signal or black. At this time, for example, if the defect is highly sensitive to light irradiation, a white or black signal can be formed by increasing or decreasing the amount of photoelectrons. In addition, if the defect has high sensitivity due to electron irradiation, white or black signal formation can be performed by increasing or decreasing the amount of secondary emitted electrons.

  A combination in the case where the photoelectrons are black and the secondary emission electrons are white is also possible. In the example of the EUV mask, the following combinations can be performed on TaBO of the top layer and Ru of the recess.

(Combination of Ru white / TaBO black photoelectron image and secondary emission electron and / or mirror electron image / Ru black / TaBO white photoelectron image and secondary emission electron and / or mirror electron image)
As a result, high contrast and S / N can be realized, and it is possible to perform highly sensitive pattern defect inspection and foreign matter inspection.

  For the low LE image, the oxide film potential is stabilized by light irradiation. This is particularly effective for low LE images where the electron irradiation energy is -5 eV <LE <10 eV, particularly when the top layer is made of an oxide film. When the top layer is an oxide film, the oxide film is charged to a negative voltage due to low LE electron beam irradiation. As a result, the image quality deteriorates and the current density cannot be increased. At this time, irradiation with light such as UV, DUV, EUV, and X-rays or laser can be performed to control the potential of the oxide film. When these lights are irradiated, photoelectrons are generated, so that positive charging can be caused. Therefore, the potential of the oxide film can be controlled to be constant by performing the low LE and the light or laser light simultaneously or intermittently. By being kept constant, the image quality is stable, and even if the current density is increased, stable image formation is possible, so that throughput can be improved.

  The embodiments of the present invention have been described above by way of example, but the scope of the present invention is not limited to these embodiments, and can be changed or modified according to the purpose within the scope of the claims. is there.

  As described above, the inspection apparatus according to the present invention is useful as a semiconductor inspection apparatus or the like for inspecting a defect or the like of a pattern formed on a surface to be inspected.

Claims (5)

Beam generating means for generating either charged particles or electromagnetic waves as a beam;
A primary optical system for directing and irradiating the beam onto an inspection object held in a working chamber;
A secondary optical system for detecting secondary charged particles generated from the inspection object;
An image processing system for forming an image based on the detected secondary charged particles;
With
Said primary optical system,
A precharge unit for irradiating the inspection object with a charging beam before irradiating the inspection object with an imaging beam;
A photoelectron generator having a photoelectron surface for generating the imaging beam and the charging beam ;
Have
An inspection apparatus characterized in that a material having higher thermal conductivity than quartz is used for the base material of the photoelectron surface.   The inspection apparatus according to claim 1, wherein sapphire or diamond is used as a base material of the photoelectron surface.   3. The inspection apparatus according to claim 1, wherein a shape of the photoelectron surface is a circle having a diameter of 10 μm to 200 μm or a rectangle having a side of 10 μm to 200 μm.   4. The inspection apparatus according to claim 1, wherein the photoelectron surface is coated with a photoelectron material, and ruthenium or gold is used as the photoelectron material. The inspection apparatus according to claim 4, wherein the thickness of the optoelectronic material is 5 nm to 100 nm.