JP6267445B2 - 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 the conventional inspection apparatus, a drive motor manufactured from a non-magnetic material is used as a drive source for moving the stage on which the inspection object (sample) is placed in the XY directions in order to avoid the influence of the electron beam on the magnetic field. It was used. However, a drive motor made of nonmagnetic material is expensive (for example, more expensive than a linear motor), and there is a problem that it is difficult to reduce the cost of the apparatus.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an inspection apparatus capable of reducing the cost of the apparatus.

  The inspection apparatus of the present invention includes a beam generating means for generating either charged particles or electromagnetic waves as a beam, a primary optical system for guiding and irradiating the beam to an inspection object held on a movable stage in the working chamber, A linear motor that detects a secondary charged particle generated from an inspection target, and an image processing system that forms an image based on the detected secondary charged particle; A Helmholtz coil that generates a magnetic field for canceling the magnetic field generated from the linear motor when the stage is driven.

  Thereby, since a linear motor is used as a drive source for driving the movable stage, the cost of the apparatus can be reduced. In this case, the magnetic field generated from the linear motor when driving the movable stage is canceled by the magnetic field generated from the Helmholtz coil. Accordingly, it is possible to suppress the charged particles or the electromagnetic wave beam from being affected by the magnetic field generated from the linear motor.

  The inspection apparatus according to the present invention includes a current detection unit that detects a drive current for driving the linear motor, and a magnetic field control that controls the intensity of the magnetic field generated from the Helmholtz coil according to the drive current detected by the current detection unit. Means.

  Thus, the intensity of the magnetic field generated from the Helmholtz coil is controlled according to the drive current for driving the linear motor. Thereby, it is possible to appropriately control the intensity of the magnetic field generated from the Helmholtz coil so as to cancel the magnetic field generated from the linear motor.

  The inspection apparatus of the present invention further includes position detection means for detecting the position of the movable stage, and the magnetic field control means is in accordance with the driving current detected by the current detection means and the position detected by the position detection means. The intensity of the magnetic field generated from the coil may be controlled.

  Thereby, the intensity of the magnetic field generated from the Helmholtz coil is controlled according to the driving current for driving the linear motor and the position of the movable stage. Thereby, it is possible to appropriately control the intensity of the magnetic field generated from the Helmholtz coil so as to cancel the magnetic field generated from the linear motor.

  According to the present invention, a linear motor can be used as a drive source for driving the movable stage, and the cost of the apparatus can be reduced.

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 showing typically the double tube structure of the semiconductor inspection device concerning one embodiment of the present invention. It is the figure which showed the structure of the electron beam inspection apparatus which concerns on one Embodiment of this invention. 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 the figure which showed the structure of the electronic column type | system | group based on one Embodiment of this invention. It is explanatory drawing (plan view) of the principal part of the inspection apparatus which concerns on one Embodiment of this invention. It is explanatory drawing (side view) of the principal part of the inspection apparatus which concerns on one Embodiment of this invention. It is explanatory drawing of the magnetic field control means which concerns on one Embodiment of this invention. It is explanatory drawing of the magnetic field intensity (magnetic field intensity generate | occur | produced from a linear motor) which concerns on one Embodiment of this invention.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings as a semiconductor inspection apparatus for inspecting a substrate, ie, a wafer, having a pattern formed on the surface as an inspection object. 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 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. 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). Further, zooming at a magnification 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)
<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. 10 is a diagram schematically showing a double tube structure of a semiconductor inspection apparatus according to an embodiment of the present invention. In FIG. 10, the first tube and the second tube are shown in an emphasized manner, but the actual cross sections of the first tube and the second tube are different. As shown in FIG. 10, the electro-optical device 70 including the 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. 10, 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 an insulating component, 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.

"Electronic inspection equipment"
FIG. 11 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 it is possible to increase the transmittance of the mirror electrons. 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.

  FIG. 12 shows an electron beam inspection apparatus to which the present invention is applied. Here, an example of the overall system configuration will be described.

  In FIG. 12, 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. 13 shows an example of the 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. 13, 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. 13, the sample 20 is set 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 ultra-fine foreign matter 10 is inspected with high sensitivity using the aperture 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.

  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.

  FIG. 14 shows the electron column system 100 installed in the main chamber 160 and in the upper part of the main chamber 160. Constituent elements similar to those in FIG. 11 are denoted by the same reference numerals as those in FIG.

  The sample 20 is placed on a stage 30 that can move in the x, y, z, and θ directions. High precision alignment is performed by the stage 30 and the optical microscope 110. Then, the mapping projection optical system performs foreign matter inspection and pattern defect inspection of the sample 20 using the electron beam. Here, the potential of the sample surface 21 is important. In order to measure the surface potential, a surface potential measuring device capable of measuring in vacuum is attached to the main chamber 160. This surface potential measuring device measures a two-dimensional surface potential distribution on the sample 20. Based on the measurement result, focus control is performed in the secondary optical system 60a that forms an electronic image. A focus map of the two-dimensional position of the sample 20 is produced based on the potential distribution. Using this map, the inspection is performed while changing and controlling the focus during the inspection. As a result, blurring and distortion of the image due to changes in the surface circular potential depending on the location can be reduced, and accurate and stable image acquisition and inspection can be performed.

  Here, the secondary optical system 60 a is configured to be able to measure the detection current of electrons incident on the NA aperture 62 and the detector 70, and further configured to be able to install an EB-CCD at the position of the NA aperture 62. Yes. Such a configuration is very advantageous and efficient. In FIG. 14, the NA aperture 62 and the EB-CCD 65 are installed on an integral holding member 66 having openings 67 and 68. The secondary optical system 60a includes a mechanism that can independently perform the current absorption of the NA aperture 62 and the image acquisition of the EB-CCD 65, respectively. In order to realize this mechanism, the NA aperture 62 and the EB-CCD 65 are installed on an X and Y stage 66 operating in a vacuum. Therefore, the position control and positioning of the NA aperture 62 and the EB-CCD 65 are possible. Since the stage 66 is provided with openings 67 and 68, mirror electrons and secondary emission electrons can pass through the NA aperture 62 or the EB-CCD 65.

  The operation of the secondary optical system 60a having such a configuration will be described. First, the EB-CCD 65 detects the spot shape of the secondary electron beam and its center position. Then, voltage adjustments of the stigmeter, the lenses 61 and 63, and the aligner 64 are performed so that the spot shape is circular and minimized. With respect to this point, conventionally, the spot shape and astigmatism at the position of the NA aperture 62 cannot be directly adjusted. Such direct adjustment is possible in the present embodiment, and astigmatism can be corrected with high accuracy.

  In addition, the center position of the beam spot can be easily detected. Therefore, the position of the NA aperture 62 can be adjusted so that the hole center of the NA aperture 62 is arranged at the beam spot position. In this regard, conventionally, the position of the NA aperture 62 cannot be directly adjusted. In the present embodiment, the position of the NA aperture 62 can be directly adjusted. This enables highly accurate positioning of the NA aperture, reduces the aberration of the electronic image, and improves uniformity. Further, the transmittance uniformity is improved, and an electronic image with high resolution and uniform gradation can be acquired.

  In the inspection of the foreign material 10, it is important to efficiently acquire the mirror signal from the foreign material 10. The position of the NA aperture 62 is very important because it defines the transmittance and aberration of the signal. Secondary emission electrons are emitted from the sample surface in a wide angle range according to the cosine law, and reach a uniformly wide region (for example, φ3 [mm]) at the NA position. Therefore, the secondary emission electrons are insensitive to the position of the NA aperture 62. On the other hand, in the case of mirror electrons, the reflection angle on the sample surface is approximately the same as the incident angle of the primary electron beam. Therefore, the mirror electrons show a small spread and reach the NA aperture 62 with a small beam diameter. For example, the spreading region of mirror electrons is 1/20 or less of the spreading region of secondary electrons. Therefore, the mirror electrons are very sensitive to the position of the NA aperture 62. The spreading region of the mirror electrons at the NA position is usually a region of φ10 to 100 [μm]. Therefore, it is very advantageous and important to obtain the position where the mirror electron intensity is the highest and arrange the center position of the NA aperture 62 at the obtained position.

  In order to realize the installation of the NA aperture 62 at such an appropriate position, in the preferred embodiment, the NA aperture 62 is x, y with an accuracy of about 1 [μm] in the vacuum of the electron column 100. Moved in the direction. The signal intensity is measured while the NA aperture 62 is moved. Then, the position with the highest signal intensity is obtained, and the center of the NA aperture 62 is set at the obtained coordinate position.

  The EB-CCD 65 is very advantageously used for signal intensity measurement. Thereby, two-dimensional information of the beam can be known, and the number of electrons incident on the detector 70 can be obtained, so that quantitative signal strength evaluation can be performed.

  Alternatively, the aperture arrangement may be determined so that the position of the NA aperture 62 and the position of the detection surface of the detector 70 are conjugated, and the condition of the lens 63 between the aperture and the detector is May be set. This configuration is also very advantageous. Thereby, an image of the beam at the position of the NA aperture 62 is formed on the detection surface of the detector 70. Therefore, the beam profile at the position of the NA aperture 62 can be observed using the detector 70.

  The NA size (aperture diameter) of the NA aperture 62 is also important. Since the signal region of the mirror electrons is small as described above, the effective NA size is about 10 to 200 [μm]. Further, the NA size is preferably a size larger by +10 to 100% than the beam diameter.

  In this regard, an electron image is formed by mirror electrons and secondary emission electrons. By setting the aperture size, the ratio of mirror electrons can be further increased. Thereby, the contrast of mirror electrons can be increased, that is, the contrast of the foreign material 10 can be increased.

  More specifically, when the aperture hole is made smaller, the secondary emission electrons decrease in inverse proportion to the aperture area. Therefore, the gradation of the normal part becomes small. However, the mirror signal does not change and the gradation of the foreign material 10 does not change. Therefore, the contrast of the foreign material 10 can be increased by the reduction of the surrounding gradation, and a higher S / N can be obtained.

  Further, an aperture or the like may be configured so that the position of the aperture can be adjusted not only in the x and y directions but also in the z axis direction. This configuration is also advantageous. The aperture is preferably installed at a position where the mirror electrons are most narrowed. Thereby, the aberration of the mirror electrons can be reduced and the secondary emission electrons can be reduced very effectively. Therefore, it is possible to obtain a higher S / N.

  As mentioned above, mirror electrons are very sensitive to NA size and shape. Therefore, proper selection of the NA size and shape is very important to obtain a high S / N. Hereinafter, an example of a configuration for selecting such an appropriate NA size and shape will be described. Here, the shape of the aperture (hole) of the NA aperture 62 will also be described.

  Here, the NA aperture 62 is a member (part) having a hole (opening). Generally, the member is sometimes called an aperture, and the hole (opening) is sometimes called an aperture. In the following description related to the aperture, the member is referred to as an NA aperture in order to distinguish the member (part) from its hole. And the hole of a member is called an aperture. The aperture shape generally means the shape of the hole.

<Inspection device>
Hereinafter, an inspection apparatus according to an embodiment of the present invention will be described with reference to the drawings. In this embodiment, a case where the present invention is applied to a semiconductor inspection apparatus or the like is illustrated.

  As described above, the inspection apparatus according to the present embodiment includes a beam generation unit that generates either charged particles or electromagnetic waves as a beam, and a primary that irradiates the inspection target held on a movable stage in the working chamber. An optical system, a secondary optical system that detects secondary charged particles generated from the inspection target, and an image processing system that forms an image based on the detected secondary charged particles are provided.

  First, terms such as secondary charged particles and mirror electrons will be described. “Secondary charged particles” include secondary emission electrons, mirror electrons, and some or a mixture of photoelectrons. When an electromagnetic wave is 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”.

  Next, the configuration of the inspection apparatus according to the present embodiment will be described in detail with reference to FIGS. 15 and 16. As shown in FIGS. 15 and 16, the inspection apparatus 1501 includes a linear motor 1503 that moves the movable stage 1502 in the X direction and a linear motor 1504 that moves the movable stage 2 in the Y direction. Further, the inspection apparatus 1501 uses a Helmholtz coil 1505 that generates a magnetic field in the X direction and a magnetic field in the Y direction in order to cancel (cancel) the magnetic field generated from the linear motors 3 and 4 when the movable stage 2 is driven. A Helmholtz coil 1506 to be generated and a Helmholtz coil 1507 to generate a magnetic field in the Z direction are provided.

  The inspection apparatus 1501 includes a current detection unit 1508 that detects a drive current that drives the linear motor 1503 in the X direction, and a current detection unit 1509 that detects a drive current that drives the linear motor 1504 in the Y direction.

  Further, the inspection apparatus 1501 includes a laser oscillator 1510, a mirror 1511, an X-direction stage mirror 1512, and an interferometer 1513 as a configuration for detecting the X-direction stage position of the movable stage. Further, the inspection apparatus 1501 includes a laser oscillator 1510, a mirror 1514, a stage mirror 1515 in the Y direction, and an interferometer 1516 as a configuration for detecting the stage position in the Y direction of the movable stage.

  The inspection apparatus 1501 includes a magnetic field control unit 1517. The magnetic field control unit 1517 controls the strength of the magnetic field generated from the Helmholtz coils 1505, 1506, 1507 according to the drive current detected by the current detection units 1508, 1509 and the stage position detected by the interferometers 1513, 1516. .

  Here, the configuration of the magnetic field control unit 1517 will be described in detail with reference to FIG. The magnetic field controller 1517 is provided with a lookup table 1518. The lookup table 1518 receives the drive currents IX and IY detected by the current detectors 1508 and 1509 and the stage positions PX and PY detected by the interferometers 1513 and 1516. The lookup table 1518 stores compensation values CX, CY, and CZ corresponding to the drive currents IX and IY and the stage positions PX and PY.

  The compensation values CX, CY, and CZ are obtained by installing a three-axis (three-dimensional) magnetic field sensor in the vicinity of the beam center position on the movable stage 1502, moving the movable stage 1502, and generating a magnetic field intensity (phase It is obtained in advance by measuring the magnetic field intensity to be killed (see FIG. 18).

For example, the compensation values CX, CY, and CZ are expressed by the following equations. Here, ± A to ± F are coefficients (mixing ratios) that are variable according to the stage positions PX and PY.
CX = ± A ・ IX ± B ・ IY
CY = ± C ・ IX ± D ・ IY
CZ = ± E ・ IX ± F ・ IY

  Next, how to create a lookup table (how to determine a lookup table value) will be described.

  The strength of the magnetic field at the observation center is determined by the magnitude of the coil current of the linear motor that is the source of the magnetic field, the magnetic force of the linear motor (the magnetic force of the linear motor magnet), and the position from the magnet of the linear motor. .

  Although the magnetic force of the linear motor changes macroscopically depending on time, temperature, etc., in that case, the calibration may be performed each time, so it is considered to be almost constant. On the other hand, the coil current varies depending on the speed and load conditions. The magnetic field generated from the coil is proportional to the coil current.

  The magnetic field acting on the observation point is the sum of the magnetic field generated from the magnet of the linear motor and the magnetic field generated from the coil.

  For example, a magnetic field sensor having sensitivity in the XYZ directions is arranged near the observation center. First, the stage coordinates are divided at multiple points in the XY directions, and the stage is moved to that position and stopped. And the magnetic field of XYZ direction is measured in the state which interrupted | blocked coil current. From this measurement a), the magnetic field strength a 'at each point due to the magnetic field of the linear motor is obtained.

  Next, the stage is moved at a constant speed in the XY directions, or acceleration / deceleration is performed at the multipoint positions. Then, a drive current is passed through the XY linear motor, and the magnetic field at each point (each coordinate) is measured. In this measurement b), the influence of the coil current is superimposed on the result obtained in measurement a) in the measurement result of the magnetic field at the same coordinates as in measurement a). Therefore, the result of subtracting the value obtained in measurement a) from the value obtained in measurement b) is the influence of the coil current at each point. Thereby, the magnetic field intensity b 'at each point due to the influence of the coil current is obtained. At the same time, the coil current I 'at this time is recorded. The magnetic field strength b ′ is proportional to the coil current I ′ (b ′ = b ″ × I ′).

As described above, the magnetic fields X, Y, and Z of the respective points on the stage are obtained, and correction values at the respective points are obtained. For example, the correction value at the coordinates X0, Y0 is a ′ _{X0, Y0} ± I · b ″ _{X0, Y0} . Here, a ′ _{X0, Y0} is the value of a ′ at the coordinates X0, Y0, Is the coil current value (current value), b ″ _{X0, Y0} is the value of b ″ at the coordinates X0, Y0. The lookup table shows these values of a ′ _{X0, Y0} and b ″ _{X0, Y0} . Is remembered.

  When actual measurement is performed, the value of the lookup table is read for each stage coordinate, the current value flowing through the linear motor is substituted into I, and the current is passed through the Helmholtz coil so as to cancel the magnetic field.

  In addition, in coordinates other than the point (measurement point) where the magnetic field is measured in advance, the coordinates may be supplemented based on the data of the observation point close to that point. Moreover, the measurement of a magnetic field can be performed at the time of shipment of an inspection apparatus, a maintenance, etc., for example.

  According to such an inspection apparatus of the embodiment of the present invention, since a linear motor is used as a drive source for driving the movable stage, the cost of the apparatus can be reduced. In this case, the magnetic field generated from the linear motor when driving the movable stage is canceled by the magnetic field generated from the Helmholtz coil. Accordingly, it is possible to suppress the charged particles or the electromagnetic wave beam from being affected by the magnetic field generated from the linear motor.

  In the embodiment of the present invention, the strength of the magnetic field generated from the Helmholtz coil is controlled according to the drive current for driving the linear motor and the position of the movable stage. Thereby, it is possible to appropriately control the intensity of the magnetic field generated from the Helmholtz coil so as to cancel the magnetic field generated from the linear motor.

  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 has an effect that the cost of the apparatus can be reduced, and is useful as a semiconductor inspection apparatus or the like.

Claims (2)

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 on a movable stage 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;
A linear motor for driving the movable stage;
A Helmholtz coil for generating a magnetic field for canceling the magnetic field generated from the linear motor when driving the movable stage;
Current detection means for detecting a driving current of the linear motor for driving the movable stage,
Magnetic field control means for controlling the intensity of the magnetic field generated from the Helmholtz coil in accordance with the drive current of the linear motor detected by the current detection means;
An inspection apparatus comprising: Comprising position detecting means for detecting the position of the movable stage;
The inspection according to claim 1, wherein the magnetic field control means controls the intensity of the magnetic field generated from the Helmholtz coil according to the drive current detected by the current detection means and the position detected by the position detection means. apparatus.