JP5525128B2 - Charged particle beam application apparatus and sample observation method - Google Patents

Description

  The present invention relates to a charged particle beam inspection apparatus and measurement apparatus, and a charged particle beam sample observation method.

  In a semiconductor or magnetic disk manufacturing process, a charged particle beam (hereinafter referred to as a primary beam) such as an electron beam or an ion beam is irradiated on a sample, and secondary charged particles such as secondary electrons generated (hereinafter referred to as a secondary beam). A charged particle beam length measuring device that acquires a signal of a beam) and measures the shape and dimensions of a pattern formed on a sample, a charged particle beam inspection device that checks the presence or absence of defects, and the like are used. In particular, with the miniaturization of sample dimensions, techniques of pattern side wall observation, three-dimensional shape estimation, and high-resolution defect review have become important.

  In such a technique, it is effective to make the primary beam incident on the sample from an oblique direction and use the signal information of the generated secondary charged particles. As a method of acquiring an image by injecting a primary beam in an oblique direction, for example, as described in Patent Document 1, an arbitrary place on a semiconductor wafer can be observed with a scanning electron microscope (SEM). Applying a method of tilting and imaging the stage that moves the semiconductor wafer, a method of mechanically tilting the SEM electron optical system itself, and a method of tilting the incident direction to the observation object by deflecting the irradiated electron beam Has been. Further, Patent Document 2 describes means for selecting and detecting the elevation angle and azimuth angle in the emission direction of the generated secondary electrons, instead of applying a primary beam from an oblique direction, in defect review by a review SEM. Yes.

JP 2000-348658 Japanese Patent Application No. 2006-228999

  In order to make the primary beam incident on the sample from an oblique direction, it is necessary to relatively tilt the electron optical system and the sample or to deflect the primary beam. In order to keep the primary beam arrival point on the sample constant regardless of the tilt, the central axis of the electron optical system and the central axis of the tilt must coincide on the sample, and the primary beam is irradiated from multiple directions. Requires beam adjustment in all directions. In addition, a deceleration electric field is often applied between the electron optical system and the sample from the viewpoint of sample damage reduction and secondary electron efficiency, so it is difficult to tilt the electron optical system and the sample relatively. There is a problem that there is.

  Further, in the means for selecting and detecting the elevation angle and azimuth angle in the emission direction of the generated secondary electrons, the amount of signal to be detected is small for the selection of the generated secondary electrons. There is a problem that it is necessary to have a plurality of items.

  In order to solve the above-described problems, in the first embodiment of the present invention, in the multi-beam type charged particle beam application apparatus, another lens is mounted so as to be focused on the sample even when the lens voltage of the array lens is cut off. By controlling, the primary beam is irradiated to a point on the sample from a plurality of directions, that is, at a plurality of angles to the sample, and the primary beam reaches the sample without tilting the electron optical system and the sample. Provide a means to keep the constant.

  In order to solve the above problem, as another embodiment, a primary optical system for irradiating a charged particle beam on the sample and a secondary charged particle beam generated from the sample by irradiation of the charged particle beam are detected, In a sample observation method for forming an image from a detected signal, a sample observation method including a step of selecting an incident angle and an azimuth angle of a charged particle beam with respect to a sample is provided.

  Further, as a preferred embodiment of the present invention, a primary optical system for irradiating a sample with a charged particle beam and a first signal detection system for detecting a secondary charged particle beam generated from the sample by irradiation of the charged particle beam Means for controlling the primary optical system and the first signal detection system, means for tilting the incident angle of the charged particle beam with respect to the sample, and means for selecting the incident angle of the charged particle beam. A charged particle beam application apparatus having a configuration including the above is provided.

  Furthermore, as another preferred embodiment of the present invention, there is provided a charged particle beam application apparatus including a charged particle beam source that generates a charged particle beam, and a plurality of charged particle beams generated from the charged particle beam source. An irradiation beam forming unit for forming the divided primary beam and a plurality of the divided primary beams formed by the irradiation beam forming unit are incident on a predetermined position on the sample by inclining incident angles with respect to the sample. Observation of the sample using the output of the electron lens system, the signal detection system that detects the secondary beam generated from a predetermined position on the sample by irradiation of the divided primary beam, and the output of the signal detection system corresponding to the secondary beam An image display device that displays an image and a control unit that controls the irradiation beam forming unit and the like. The irradiation beam forming unit selects a plurality of divided primary beams to be formed, and thereby controls the location of the sample. To provide a charged particle beam apparatus including an incident angle selector for selecting the angle of incidence of the primary beam irradiated to the position.

  According to the present invention, it is possible to realize a charged particle beam application apparatus that can achieve both high defect detection sensitivity and high inspection speed.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In all the drawings for explaining the embodiments, the same symbols are attached to the same elements, and the repeated explanation thereof is omitted. Hereinafter, although the Example in the inspection apparatus using an electron beam is shown, the effect of this invention is not lost also in the case of using an ion beam, and the case of a measuring device and a general electron microscope.

  FIG. 1 is a diagram showing a schematic configuration of a multi-beam type electron beam inspection apparatus according to a first embodiment of the present invention.

  First, the apparatus configuration will be described.

  The electron gun 101 includes a cathode 102 made of a material having a low work function, an anode 105 having a high potential with respect to the cathode 102, and an electromagnetic lens 104 that superimposes a magnetic field on an acceleration electric field formed between the cathode and the anode. In this embodiment, a Schottky cathode that can easily obtain a large current and has stable electron emission is used. In the downstream direction in which the primary electron beam 103 is extracted from the electron gun 101, as shown in FIG. 1, a collimator lens 107, an aperture array 108 having a plurality of openings arranged on the same substrate, and a lens array 109 having a plurality of openings , Blanker arrays 116a to 116c arranged at positions corresponding to the respective lens arrays, electron lens groups 140a to 140b, beam separator 111, objective lens 112, scanning optical deflector 113, stage 117, signal detection The secondary beam detectors 121a to 121c and the like which are systems are arranged.

  Further, a current limiting diaphragm, a primary beam center axis (optical axis) adjustment aligner, an aberration corrector, and the like are added to the electron optical system (not shown). The stage 117 moves by placing a wafer 115 as a sample thereon.

  A negative potential (hereinafter referred to as a retarding potential) is applied to the wafer 115 as will be described later. Although not shown, a wafer holder is interposed between the wafer 115 and the stage 117 in a conductive state with the wafer, and a retarding power supply 118a is connected to the wafer holder to apply a desired voltage to the wafer holder and the wafer 115. It is configured to do.

  A surface electric field control electrode 114 is provided on the electron gun 101 direction side from the wafer 115. A scanning signal generator 137 is connected to the scanning deflection deflector 113, and a surface electric field control power source 118b is connected to the surface electric field control electrode 114. Each part of the electron gun 101, collimator lens 107, lens array 109, blanker array 116, electron lens group 140, beam separator 111, objective lens 112, retarding power supply 118a, and surface electric field control power supply 118b includes an optical system control circuit. 139 is connected, and a system control unit 135 is connected to the optical system control circuit 139. A stage controller 138 is connected to the stage 117, and the secondary beam detectors 121 a to 121 c and the scanning deflection deflector 113 are similarly connected to the system controller 135. The system control unit 135 includes a storage device 132, a calculation unit 133, and a defect determination unit 134, and an image display unit 136 is connected thereto. Although not shown, it goes without saying that components other than the control system and the circuit system are disposed in the vacuum vessel and are evacuated to operate. Needless to say, a wafer transfer system for placing the wafer on the stage from outside the vacuum is provided.

  Next, wafer pattern inspection using this apparatus will be described. Hereinafter, the optical conditions and other modes at the time of inspection using this apparatus are described as a multi-beam mode. As will be described later, this mode setting is performed under the control of the system control unit 135 and the like.

  The primary beam 103 emitted from the electron source 102 is accelerated in the direction of the anode 105 while receiving a focusing action by the electromagnetic lens 204, and forms a first electron source image 106 (a point at which the beam diameter is minimized). Although not shown, a diaphragm is arranged in the electron gun 101 as often seen in a general electron gun so that an electron beam in a desired current range passes through the diaphragm. If the operating conditions of the anode 105 and the electromagnetic lens 104 are changed, the current amount of the primary beam passing through the aperture can be adjusted to a desired current amount. Although not shown, an aligner that corrects the optical axis of the primary electron beam is arranged between the electron gun 102 and the collimator lens 107, and the center axis of the electron beam is deviated from the diaphragm or the electron optical system. The configuration can be corrected. Using the first electron source image 106 as a light source, the collimator lens 107 arranges the primary beam substantially in parallel. In this embodiment, the collimator lens 107 is an electromagnetic lens. The aperture array divides the primary beam 103 into a plurality of openings by a plurality of openings. The aperture array 108 and the lens array 109 constitute an irradiation beam forming unit that forms a plurality of beams. In FIG. 1, three beams out of the divided beams are shown for the purpose of illustration. Needless to say, the aperture of the aperture array 108, the corresponding lens array 109, the blanker array 116, and the secondary beam detector 121 are the same, and are not limited to three.

  In the multi-beam mode, the divided primary beams are individually focused by the lens array 109 under the control of the optical system control circuit 139 to form a plurality of second electron source images 110a, 110b, and 110c. It becomes. The lens array 109 is composed of three electrodes each having a plurality of apertures, and acts as an Einzel lens for the primary beam passing through the apertures by applying a voltage to the central electrode among them. . The applicant previously proposed, for example, Japanese Patent Application No. 2006-144934 “Charged Particle Beam Application Device” as a multi-beam type charged particle beam application device having a plurality of beams, and configured the lens array. Disclosure.

  The primary beam 103 passes through the lens array 109 and then enters the blanker array 116. The blanker arrays 116a to 116c are part of the irradiation beam forming unit, each composed of two electrodes, and an on / off selection unit that blocks the beam individually by applying a voltage to one side (turning on the blanker). Function as. That is, by turning on the blankers corresponding to the beams other than the blanker arrays 116a to 116c that are desired to pass, it is possible to select the beam that reaches the sample.

  The primary beam 103 that is not blocked by the blanker array 116 passes through the electron lens group 140. In this embodiment, the electron lens group 140 has two stages 140a and 140b, and the second electron source images 110a to 110c are projected once onto the third electron source images 141a to 141c. Thereafter, the primary beam 103 passes through the beam separator 111. The beam separator 111 is used for the purpose of separating the primary beam 103 and the secondary beam 120, and in this embodiment, generates a magnetic field and an electric field orthogonal to each other in a plane substantially perpendicular to the incident direction of the primary beam. The Wien filter is used to give the deflection angle corresponding to the energy of the passing electrons. In this embodiment, the strength of the magnetic field and the electric field is set so that the primary beam goes straight, and the strength of the electromagnetic field is deflected to a desired angle with respect to the secondary electron beam incident from the opposite direction. Adjust and control. Also, the position of the beam separator 111 is arranged according to the height of the third electron source images 141a, 141b, 141c of the primary beam in order to reduce the influence in consideration of the influence of the aberration on the primary beam. Yes. The objective lens 113 is an electromagnetic lens, and projects the third electron source images 141a, 141b, and 141c in a reduced scale.

  The deflector 113 for scanning deflection is constructed and installed in an electrostatic 8-pole type in the objective lens. When a signal is input to the deflector 113 by the scanning signal generator 137, a plurality of primary beams passing therethrough are deflected in substantially the same direction and at substantially the same angle, and the wafer 115 as a sample is raster scanned. To do.

  A negative potential is applied to the wafer 115 by the retarding power source 118a, and an electric field for decelerating the primary beam is formed. The retarding power supply 118a and the surface electric field control power supply 118b are optical systems similar to other optical elements, that is, the electron gun 101, the collimator lens 107, the lens array 109, the electron lens group 140, the beam separator 111, and the objective lens 112. It is controlled uniformly by the system control unit 135 via the control circuit 139. Stage 117 is controlled by stage controller 138. The scanning signal generator 137 and the stage controller 138 are uniformly controlled so that the system controller 135 inspects a predetermined area on the wafer 115 by one stripe arranged in the stage traveling direction. In the inspection apparatus of the present embodiment, the stage is continuously moved at the time of executing the inspection, and the primary beam is controlled so as to sequentially scan the band-like region by a combination of deflection by scanning and stage movement. This band-like area is obtained by dividing a predetermined inspection area corresponding to a multi-beam, and the entire predetermined inspection area is scanned by the multi-beam scanning each of the plurality of band-like areas. Note that the above-mentioned one stripe corresponds to a range through which a plurality of band-shaped regions corresponding to multi-beams have passed.

  The plurality of primary beams that have reached the surface of the wafer 115 interact with substances near the sample surface. As a result, secondary electrons such as reflected electrons, secondary electrons, Auger electrons, and the like are generated from the sample and become the secondary beam 120.

  The surface electric field control electrode 114 is an electrode for adjusting the electric field intensity near the surface of the wafer 115 and controlling the trajectory of the secondary beam 120. The wafer 115 is placed facing the wafer 115, and a positive potential, a negative potential, or the same potential is applied to the wafer 115 by the surface electric field control power supply 118b. The voltage applied to the surface electric field control electrode 114 by the surface electric field control power supply 118b is adjusted to a value suitable for the type of the wafer 115 and the observation target. For example, when it is desired to positively return the generated secondary beam 120 to the surface of the wafer 115, a negative voltage is applied to the surface electric field control power supply 118b. Conversely, a positive voltage can be applied to the surface electric field control power supply 118b so that the secondary beam 120 does not return to the surface of the wafer 115.

  After passing through the surface electric field control electrode 114, the secondary beam 120 is separated from the trajectory of the primary beam by the beam separator 111 having a focusing action of the objective lens 112 and deflecting the secondary beam. The units 121a, 121b, 121c are reached. The detected signals are amplified by the amplification circuits 130a, 130b, and 130c, digitized by the A / D converter 131, and temporarily stored as image data in the storage device 132 in the system control unit 135. Thereafter, the calculation unit 133 calculates various statistics of the image, and finally determines the presence / absence of a defect based on the defect determination condition previously determined by the defect determination unit 134. The determination result is displayed on the image display device 136. With the above procedure, the area to be inspected in the wafer 115 can be inspected in order from the end.

  Next, a mode in which an electron beam is irradiated on the wafer from an oblique direction and the signal is acquired using the apparatus of FIG. 1 will be described with reference to FIG. Hereinafter, this mode is described as an oblique irradiation mode with respect to the multi-beam mode. This mode switching is executed by control of the system control unit 135, the optical system control circuit 139, and the like.

  FIG. 2 is a schematic diagram of the apparatus and the electron optical system when the electron beam inspection apparatus according to the present embodiment is switched from the multi-beam mode to the oblique irradiation mode. The apparatus configuration in FIG. 2 is the same as that in FIG. 1, and the electro-optical conditions given by the optical system control circuit 139 and the like are different. Due to changes in the electron optical conditions, the primary beam 103 in the multi-beam mode in FIG. 1 and the primary beam 201 in the oblique irradiation mode in FIG. 2 draw different trajectories. The biggest difference between the oblique irradiation mode and the multi-beam mode is the lens intensity of the lens array 109, that is, the voltage applied to the center electrode among the three electrodes constituting the lens array 109.

  In order to switch to the multi-beam mode, a voltage for focusing the primary beam trajectory is applied to the lens array 109. However, in the oblique irradiation mode, the lens array 109 has no lens action and no voltage is applied. For this reason, the primary beam 201 in the oblique irradiation mode follows the same trajectory as the primary beam 103 in the multi-beam mode until it enters the lens array 109, but is not subjected to individual focusing action by the lens array 109, and a plurality of electrons A source image is not formed. For this reason, the primary beam 201 in the oblique irradiation mode is not a multi-beam. Instead, a single second electron source image 202 is formed by the electron lens groups 140a and 140b. In this embodiment, there is no electron source image between the electron lens groups 140a and 140b, and the first electron source image 106 is projected once onto the single second electron source image 202. The primary beam 201 in the oblique irradiation mode receives the focusing action of the objective lens 112, and a single second electron source image 202 is projected onto one point on the wafer 115. The primary beam 201 is divided into a plurality of beams by an aperture array 108 that is an irradiation beam forming unit, and the divided primary beams are incident on a point on the wafer obliquely from different directions. It will be. In other words, in the oblique irradiation mode, the aperture array 108 in which a plurality of apertures included in the primary electron optical system are arranged, the electron lens groups 140a and 140b, and further the objective lens 112 are applied to the wafer of the primary beam divided into a plurality of parts. It functions as a tilting mechanism that tilts the incident angle.

  An angle formed by the central axis of the primary optical system and the center line of each beam when a plurality of divided primary beams are incident on the wafer is referred to as an incident angle. The center line of each beam is projected onto a plane perpendicular to the central axis of the primary optical system, and the angle with respect to the deflection direction by the scanning deflector 113 is called an azimuth angle.

  The secondary beam 203 generated in the oblique irradiation mode is focused by the objective lens 112 in the same manner as in the multi-beam mode, and the secondary beam is separated from the trajectory of the primary beam by the beam separator 111 which has a deflection function for the secondary beam. Is done. However, unlike the multi-beam mode, the secondary beam 203 in the oblique irradiation mode is generated from one point on the wafer, so it cannot be easily separated on the detector, and one of a plurality of detectors 121 (this embodiment Reaches the detector 121b).

  In order to separate and acquire information on the primary beam divided into a plurality of parts, in this embodiment, the system controller 135 issues a command for sequentially turning on / off the blanker arrays 116a to 116c to the optical system control circuit 139. And irradiate the primary beam one by one. In other words, the blanker array 116 functions as an incident angle selector that selects the incident angle of the primary beam on the wafer.

  The system control unit 135 manages the secondary beam signal and the irradiated primary beam together with the incident angle and azimuth angle data. That is, the signal detected by the detector 121b is amplified by the amplification circuit 130b, digitized by the A / D converter 131, and stored as image data in the storage device 132 in the system control unit 135 together with the incident angle and azimuth information. To do. Thereafter, the calculation unit 133 in the system control unit 135 calculates various statistics of the image, and the calculation result is displayed on the image display device 136.

  Regarding the control method of the apparatus other than the above, the oblique irradiation mode is the same as the multi-beam mode. The same applies to the control of the stage, but the signal may be acquired in a stopped state without moving the stage.

  The incident angle θi to the wafer in the oblique irradiation mode is the distance Ra from the center of the aperture of the aperture array 108, the electron optical system from the first electron source image 106 to the wafer (collimator lens 107, electron lens group 140a, b And the angle magnification Ma of the objective lens 113) and the focal length f of the collimator lens 107 are determined as follows.

[Equation 1]
θi ＝ Ma × arctan (Ra / f) ‐‐‐ (1)

Therefore, when selecting beams having the same incident angle and different azimuth angles, the optical system control circuit 139 controls the blanker array 116 so as to select the primary beam corresponding to the aperture of the aperture array 108 having the same Ra. .

  Next, a procedure for acquiring an image in the oblique irradiation mode will be described with reference to FIG. Here, stage 117 is assumed to be stopped. When the operator clicks the oblique irradiation mode start button 302 displayed on the image display device 136 of FIG. 1 (or FIG. 2), the system control unit 135 sends a scanning signal generation device 137, a stage control device 138, and an optical system control circuit 139. A signal is sent to, and the electro-optic condition is switched from the multi-beam mode in FIG. 1 to the oblique irradiation mode in FIG. At the same time, an oblique irradiation mode condition setting screen as shown in FIG. 3 is displayed on the image display device 136.

  The operator selects an incident angle θi from an incident angle selection box 301 which is an incident angle selection screen. In FIG. 3, two types of 0 degrees of # 1 and 5 degrees of # 3 are selected. The number of incident angles θi that can be selected may be any number, but one type of oblique irradiation is usually selected and whether or not there is 0 degree (vertical irradiation) is selected. When the operator presses the oblique irradiation mode start button 302, a signal is captured as described above, and an SEM image corresponding to each beam is displayed on the SEM image display unit 303. In Fig. 3, one type of 0 degree SEM image of # 1 and four types of SEM images of # 3 with different azimuth angles of 5 degrees are displayed. The title of each SEM image window is incident. Angle_azimuth. Based on each SEM image, various parameters such as dimensions and shapes are extracted and displayed on the parameter display unit 304. Alternatively, a stereoscopic image is reconstructed from a plurality of SEM images and displayed on the stereoscopic image display unit 305. In FIG. 3, two dimensions of the observed shape are shown: height (a in FIG. 3) and width (b in FIG. 3). To end the oblique irradiation mode, the end button 306 is pressed to return to the multi-beam mode.

  Note that the oblique irradiation mode condition setting screen shown in FIG. 3 is not limited to the example in FIG. 3, and in addition to the incident angle selection box 301, an azimuth angle selection box that functions as an azimuth angle selection screen. It goes without saying that various modifications can be made, such as further displaying.

  In the first embodiment, the primary beam to be irradiated is sequentially switched by the blanker array to acquire the secondary beam signal one by one. On the other hand, in this embodiment, a primary beam having the same incident angle is collectively irradiated, a secondary beam signal is acquired at the same time, and an SEM image with enhanced edges is acquired. The apparatus configuration and electro-optical conditions in this example are the same as those shown in FIG.

  A procedure for acquiring an image in the oblique irradiation mode in this embodiment will be described with reference to FIG. Here, stage 117 is assumed to be stopped. When the operator clicks the oblique irradiation mode button displayed on the image display device 136 in FIG. 1 or FIG. 2, signals are sent from the system control unit 135 to the scanning signal generation device 137, the stage control device 138, and the optical system control circuit 139. The electron optical conditions are switched from the multi-beam mode in FIG. 1 to the oblique irradiation mode in FIG. At the same time, an oblique irradiation mode condition setting screen as shown in FIG. 4 is displayed on the image display device 136 under the control of the system fresh fish portion 135.

  The operator selects the incident angle θi from the incident angle selection box 301. In FIG. 4, 5 degrees of # 3 is selected. Although the number of incident angles θi that can be selected is not limited, one type of oblique irradiation is usually selected for edge enhancement. When the operator presses the oblique irradiation mode start button 302, a signal is captured as described above, and an SEM image formed by the selected beam is displayed on the SEM image display unit 303. To end the oblique irradiation mode, the end button 306 is pressed to return to the multi-beam mode.

  In the first and second embodiments, the secondary beam is acquired by the same detector in the oblique irradiation mode. In contrast, in this embodiment, the secondary beam is detected separately using different detectors for each incident angle and azimuth angle. This detection method and configuration will be described with reference to FIG.

  FIG. 5 is a schematic diagram of an apparatus and an electron optical system when switched to the oblique irradiation mode according to the third embodiment of the present invention. The apparatus configuration in FIG. 5 is almost the same as in FIGS. 1 and 2, and in the oblique irradiation mode, the primary beam is incident on the wafer 115 from an oblique direction, and a secondary beam is generated, as in the first and second embodiments. . 5 differs from the first and second embodiments in that the beam separator 111 is set so that the reflected electrons 500 of the secondary beam have a desired deflection angle, and the secondary optical system adjustment lens 501. It is a point provided with. The beam separator 111 is set so as to satisfy the Wien condition for the primary beam as in the first and second embodiments. The secondary optical system adjustment lens 501 is an electromagnetic lens in this embodiment.

  The reflected electrons 500 have directivity corresponding to the incident angle and azimuth angle of the primary beam 201 in the oblique irradiation mode, and draw a secondary beam trajectory with the emission angle and the emission azimuth angle corresponding to each irradiation beam. At the position of the pupil of the reflected electrons 500, it is possible to separate for each outgoing angle and outgoing azimuth angle. Therefore, the excitation of the secondary optical system adjustment lens 501 can be detected separately for each incident angle and azimuth angle of the primary beam under the condition that the position of the pupil of the reflected electrons 500 is projected onto the detectors 121a to 121c.

  The angle formed between the central axis of the primary optical system and the center line of each beam when the secondary beam is emitted from the sample is called an exit angle, and the center line of each beam is perpendicular to the central axis of the primary optical system. An angle with respect to the deflection direction by the scanning deflector 113 is called an emission azimuth angle. In this embodiment, when reflected electrons are used as the secondary beam, the incident angle ≈ exit angle, azimuth angle ≈ (180 degrees + exit azimuth angle), and the exit angle and exit azimuth correspond to the incident angle and azimuth angle. To do. Thus, as described above, if the images are acquired separately for each emission angle and emission azimuth angle, an image for each incident angle and azimuth angle can be acquired.

  The procedure for acquiring an image in the oblique irradiation mode in this embodiment is the same as that in the first or second embodiment.

  In the present embodiment, the means for projecting the pupil of the reflected electrons 500 onto the detectors 121a to 121c is adjusted by the excitation of the secondary optical system adjustment lens 501, but the secondary optical system is added to the detectors 121a to 121c. There may be provided a mechanism that can be mechanically adjusted in the traveling direction.

  In Examples 1 to 3, the secondary beam detector used in the multi-beam mode was also applied to the oblique irradiation mode. In this embodiment, a case where a secondary beam detector dedicated to the oblique irradiation mode is provided will be described with reference to FIG.

  FIG. 6 is a schematic diagram of the apparatus and the electron optical system when switched to the oblique irradiation mode according to the fourth embodiment. The apparatus configuration in FIG. 6 is almost the same as that in FIGS. 1 and 2, and in the oblique irradiation mode, the primary beam is applied to the wafer 115 from an oblique direction as in the first embodiment. The primary beam to be irradiated is selected by sequentially switching the blanker arrays 116a to 116c. The generated secondary beam is separated from the trajectory of the primary beam by a beam separator 111 having a deflection action. In the multi-beam mode, it is important to separate the generated secondary beams, so that the deflection angle of the beam separator 111 with respect to the secondary beam needs to be relatively large. On the other hand, in the oblique irradiation mode in the present embodiment, since the separation for each beam is not performed, the deflection angle of the beam separator 111 can be set smaller than that in the multi-beam mode. Since the deflection angle changes in the multi-beam mode and the oblique irradiation mode, the position of the reaching detector also changes. For this reason, a detector 600 for oblique irradiation mode is arranged in FIG. The secondary beam 203 is given a small deflection angle corresponding to the oblique irradiation mode by the beam separator 111 and is detected by the detector 600. Although omitted in FIG. 6, the detector 600 is controlled by the system control unit 135 via an amplifier circuit, an A / D converter, and the like, similarly to the detectors 121a to 121c.

  In this embodiment, the secondary beam 203 is directly detected by the detector 600. However, a tertiary beam generated by colliding the secondary beam 203 with the reflector is placed in front of the detector. It is good also as a structure to detect. In FIG. 6, the multi-beam mode detector 121 and the oblique irradiation mode detector 600 are arranged 180 degrees out of phase, but this arrangement relationship may be any.

  The procedure for acquiring an image in the oblique irradiation mode in the present embodiment is the same as that in the first embodiment.

  In Example 4, one detector for oblique irradiation mode was arranged separately from the detector for multi-beam mode. On the other hand, in the third embodiment, an example in which detection is performed separately by using reflected electrons having directivity at the incident angle is shown. In the present embodiment, with respect to an example in which reflected electrons are used and a detector for oblique irradiation mode is provided separately from the detector for multi-beam mode and the secondary beam is detected separately for each azimuth angle, FIG. To explain.

  FIG. 7 is a schematic diagram of the apparatus and the electron optical system when switched to the oblique irradiation mode according to the fifth embodiment of the present invention. The apparatus configuration in FIG. 7 is almost the same as that in FIGS. 1 and 2, and in the oblique irradiation mode, the primary beam is incident on the wafer from an oblique direction, as in the first embodiment. In the present embodiment, the most different point from Embodiments 1 to 4 is that in the oblique irradiation mode, the beam separator 111 is turned off and no deflection action is given. The reflected electrons 701 generated corresponding to the azimuth angle of each irradiation beam draw a trajectory heading in the direction of the respective emission azimuth angle. An oblique irradiation mode detector 700 is disposed at a position corresponding to the secondary beam trajectory, and is detected separately for each beam. Although omitted in FIG. 7, the detector 700 is controlled by the system control unit 135 via an amplifier circuit, an A / D converter, and the like in the same manner as the detectors 121a to 121c. In this embodiment, the configuration is such that the reflected electrons 701 are directly detected by the detector 700, but a reflecting plate is placed in front of the detector, the reflected electrons 701 collide with the reflecting plate, and the generated tertiary beam is detected. It is good also as a structure.

  The procedure for acquiring an image in the oblique irradiation mode in the present embodiment is the same as that in the first embodiment.

  In Examples 1 to 5, the incident angle θi of the primary beam in the oblique irradiation mode is the distance Ra from the center of the aperture of the aperture array 108, the angle magnification Ma of the electron optical system from the first electron source image 106 to the wafer, And the focal length f of the collimator lens 107 is determined as shown in equation (1). Since the aperture of the aperture array 108 and the focal length f of the collimator lens 107 are determined, there is a limitation that the incident angle θi is selected only from an angle corresponding to the aperture of the aperture array. In this embodiment, a method for eliminating the limitation by changing the angle magnification Ma of the above-described electron optical system will be described with reference to FIG.

  FIG. 8 is a schematic diagram of the trajectory of the primary beam in the oblique irradiation mode, and shows the trajectory from passing through the blanker arrays 116a to 116c in FIGS. 2, 5, 6, and 7 until reaching the wafer 115. . FIG. 8 shows an example of trajectories of two beams having the same incident angle and the azimuth angle shifted by 180 degrees. The primary beam 201 in the oblique irradiation mode forms a single second electron source image 202 by the electron lens groups 140a and 140b, and is focused on one point on the wafer 115 by the objective lens 112. In the angle magnification Ma described above, the incident angle is determined by a combination of excitation conditions of the electron lens groups 140a and 140b and the objective lens 112.

  8 (a) to 8 (c) show that the position of the single second electron source image 202 and the excitation of the objective lens 112 are fixed, the wafer focusing condition is maintained, and the excitation of the electron lens groups 140a and 140b is performed. It is an example of the track | orbit at the time of changing. In FIG. 8A, the excitation of the electron lens 140a is strong, and the incident angle θi of the primary beam 201 with respect to the wafer is small. 8B and 8C, the excitation of the electron lens 140a becomes weaker, and the incident angle θi increases as the excitation of the electron lens 140a becomes weaker. 8 (b), (d), and (e), the excitation of 140a in the electron lens group is fixed, and the excitation of 140b is changed to move the position of the single second electron source image 202. It is an example. At this time, the excitation to be taken by the objective lens 112 is determined as a value for focusing on the wafer. The excitation of the electron lens 140b becomes weaker in the order of FIGS. 8D, 8B, and 8E, and the incident angle θi decreases accordingly. In this way, it is possible to change the angle magnification Ma and change the incident angle θi freely by changing the excitation combination of the lenses constituting the electron optical system while maintaining the condition for focusing on the wafer. Become.

  Next, a procedure for changing the incident angle θi freely by changing the angle magnification Ma will be described with reference to FIG.

  When the operator clicks the oblique irradiation mode lens condition setting button displayed on the image display device 136 of FIG. 1 or FIG. 2, the oblique irradiation mode electro-optical condition setting screen as shown in FIG. 9 is displayed on the image display device 136. Is done. On the left side of the oblique irradiation mode electron optical condition setting screen, an electron optical system schematic diagram 900 of the lens configuration to be adjusted is shown. The operator enters conditions on the lens condition (excitation) setting screen 901 on the right side of the screen based on the information shown in the schematic diagram 900 of the electron optical system. In this embodiment, there are three lenses constituting the electron optical schematic diagram 900, ML1, ML2 (electron lens group 140a, b), and OL (objective lens 112), so in the lens condition setting screen 901 Two lens conditions are entered, and the remaining one condition is determined from the wafer focusing condition. FIG. 9 shows an example in which OL and ML1 are set by themselves. The operator selects OL from the lens selection box 902a under the excitation condition 1, and inputs the excitation to be applied to the OL into the excitation input box 903a. Press the decision button 904a to decide the OL condition. Similarly, the operator selects ML1 from the lens selection box 902b of the excitation condition 2, inputs excitation into the excitation input box 903b, presses the decision button 904b, and determines the condition of ML1. At this time, since the third lens is determined as ML2, ML2 is automatically selected in the lens selection box 902c under the excitation condition 3, and the numerical value in the excitation display box 903c under the excitation condition 3 is adjusted. Since the lens focusing method and procedure are not directly related to the present invention, the description thereof is omitted. From the obtained optical conditions, the angle magnification Ma is determined, and the incident angle θi is calculated. This is displayed in the incident angle display box 905. The operator inputs the name of this condition in the oblique irradiation mode electron optical system condition name box 906 and presses the save button 907. As a result, the conditions are stored in the storage device 132 in the system control unit 135 in FIGS. 1, 2, 5, 6, and 7. Once the condition is set, the set electro-optical condition, that is, the wafer incident angle can be freely called and changed later.

  Subsequently, a procedure for acquiring an image in the oblique irradiation mode in the present embodiment will be described with reference to FIG. Here, stage 117 is assumed to be stopped. When the operator clicks the oblique irradiation mode button displayed on the image display device 136 of FIG. 1, the oblique irradiation mode electro-optical condition selection screen shown in FIG. 10 is displayed on the image display device 136. The operator selects data (# 3 in FIG. 10) having an irradiation angle to be performed from the oblique irradiation mode electro-optical condition selection box 1000 stored in advance. At the same time, a list of electron optical conditions and incident angles in the selected data is displayed in the selection data confirmation box 1001. When the operator presses the OK button 1002, signals are sent from the system controller 135 to the scanning signal generator 137, the stage controller 138, and the optical system controller 139, and the oblique irradiation mode under the electro-optic conditions set by the electro-optic conditions And the oblique irradiation mode condition setting screen shown in FIG. 3 or FIG. 4 is displayed on the image display device 136. The subsequent procedure is the same as in Examples 1 to 5.

  Embodiments 1 to 6 described above take a configuration example in which the function of the multi-beam type electron beam inspection apparatus is switched from the multi-beam mode to the oblique irradiation mode, but the present invention is a multi-beam type inspection apparatus. There is no necessity based on. Therefore, in the present embodiment, the configuration of the embodiment having the electron optical conditions only in the oblique irradiation mode in Embodiments 1 to 6 and not premised on the use as a multi-beam type apparatus will be described with reference to FIG. In the following description, detailed description of the same parts as those in Example 1 is omitted.

  FIG. 11 is a diagram showing a schematic configuration of an electron beam apparatus according to a seventh embodiment of the present invention.

  The apparatus configuration includes an electron gun 101, an electron lens 1100, an aperture array 1101 in which a plurality of apertures are arranged on the same substrate, a movable diaphragm 1102 having one or a plurality of apertures, a deflector 113 for scanning deflection, and a secondary beam detector 1103. And stage 117. A wafer 115 is placed on the stage 117.

  A scanning signal generator 137 is connected to the scanning deflection deflector 113. An optical system control circuit 139 is connected to the electron gun 101 and the electron lens group 1100, and a system control unit 135 that functions as an overall control unit is connected to the optical system control circuit 139. A stage controller 138 is connected to the stage 117, and a secondary beam detector 1103 and a scanning deflection deflector 113 are similarly connected to the system controller 135. In the system control unit 135, a storage device 132 and a calculation unit 133 are arranged, and an image display device 136 is connected.

  The primary beam 1105 exits the electron gun 101, which is a charged particle beam source, passes through the electron lens 1100, and then divides the primary beam 103 into a plurality of parts by a plurality of apertures of an aperture array 1101 that functions as an irradiation beam forming unit. FIG. 11 illustrates three beams among the divided primary beams. The divided primary beam constitutes a part of the irradiation beam forming unit, and is selected to pass or block by matching the opening position of the movable diaphragm 1102 functioning as an on / off selection unit. Of these beams, only the beams that have passed through are subjected to the focusing action by the electron lens system 1100 and are incident on one point on the wafer 115 obliquely from different directions for each beam. A secondary beam 1106 is generated from the wafer, and this is detected by the secondary beam detector 1103 functioning as a signal detection system. An image is formed by the system control unit 135 through the amplifier circuit 1104 and displayed on the image display device 136. The

  In the various embodiments described in detail above, examples related to inspection using an electron beam have been shown. However, when using an ion beam, the effects of the present invention can be achieved even in the case of a measuring device or a general electron microscope. I will not lose. In the embodiments described above, the wafer is taken as an example of the sample to be observed. However, in the case where the wafer is a part of the wafer or a structure other than a semiconductor such as a magnetic disk or a biological sample. However, the effect of the present invention is not lost.

1 is a diagram for explaining the configuration of a multi-beam type electron beam inspection apparatus according to a first embodiment. FIG. The figure explaining the oblique irradiation mode using the multi-beam type electron beam inspection apparatus according to the first embodiment. The figure which shows the diagonal irradiation mode condition setting screen which concerns on a 1st Example. The figure which shows the diagonal irradiation mode condition setting screen which concerns on a 2nd Example. The figure explaining the oblique irradiation mode using the multi-beam type electron beam inspection apparatus which concerns on a 3rd Example. The figure explaining the oblique irradiation mode using the multi-beam type electron beam inspection apparatus which concerns on a 4th Example. The figure explaining the oblique irradiation mode using the multi-beam type electron beam inspection apparatus which concerns on a 5th Example. The primary beam orbit schematic of the oblique irradiation mode which concerns on a 6th Example. The figure which shows the oblique irradiation mode electron optical system condition setting screen which concerns on a 6th Example. The figure which shows the oblique irradiation mode electron optical system selection screen concerning a 6th Example. FIG. 10 is a schematic configuration diagram of an electron beam application apparatus according to a seventh embodiment.

Explanation of symbols

  101 ... electron gun, 102 ... cathode, 103 ... primary beam in multi-beam mode, 104 ... electron gun lens, 105 ... anode, 106 ... first electron source image, 107 ... collimator lens, 108 ... aperture array, 109 ... Lens array, 110a ... second electron source image, 110b ... second electron source image, 110c ... second electron source image, 111 ... beam separator, 112 ... objective lens, 113 ... deflector, 114 ... surface electric field control Electrode, 115 ... wafer, 116 ... blanker array, 116a ... blanker, 116b ... blanker, 116c ... blanker, 117 ... stage, 118a ... retarding power supply, 118b ... surface electric field control power supply, 120 ... secondary beam, 121a ... secondary Beam detector, 121b ... secondary beam detector, 121c ... secondary beam detector, 130a ... amplification circuit, 130b ... amplification circuit, 130c ... amplification circuit, 131 ... A / D converter, 132 ... storage device, 133 ... Calculation unit, 134 ... Defect determination unit, 135 ... System control unit, 136 ... Image table 137 ... Scanning signal generator, 138 ... Stage controller, 139 ... Optical system control circuit, 140 ... Electronic lens group, 140a ... Electronic lens, 140b ... Electronic lens, 141a ... Third electron source image, 141b ... No. Three electron source images, 141c ... third electron source image, 201 ... primary beam in oblique irradiation mode, 202 ... single second electron source image, 203 ... secondary beam generated in oblique irradiation mode, 204 ... Electromagnetic lens 301 ... Incident angle selection box 302 ... Oblique irradiation mode start button 303 ... SEM image display unit 304 ... Parameter display unit 305 ... Stereoscopic image display unit 306 ... End button 500 ... Reflected electron, 501 ... Lens for adjusting secondary optical system, 600 ... Detector for oblique irradiation mode, 700 ... Detector for oblique irradiation mode, 701 ... Reflected electron, 900 ... Schematic diagram of electron optical system subject to incident angle adjustment, 901 ... Lens condition (excitation) Setting screen, 902a ... Lens selection box, 902b ... Lens selection box, 902c ... 903a ... excitation input box, 903b ... excitation input box, 903c ... excitation display box, 904a ... decision button, 904b ... decision button, 905 ... incident angle display box, 906 ... oblique irradiation mode electron optical system condition name box 907 ... Save button 1000 ... Oblique illumination mode Electro-optical condition selection box 1001 ... Selection data confirmation box 1002 ... Decision button 1100 ... Electronic lens 1101 ... Aperture array 1102 ... Movable aperture 1103 ... Secondary beam detection 1104 ... amplifier circuit, 1105 ... primary beam, 1106 ... secondary beam.

Claims (13)

A primary optical system for forming a plurality of divided charged particle beams from a particle beam generated from a charged particle beam source and irradiating the charged particle beam on a sample; and on the sample by irradiation with the charged particle beam A charged particle beam application apparatus comprising a first signal detection system for detecting a secondary charged particle beam generated from a control unit for controlling the primary optical system and the first signal detection system,
The primary optical system includes a selection unit that selects an incident angle of the charged particle beam, an irradiation beam forming unit that forms the plurality of charged particle beams, and one that irradiates the sample with the plurality of charged particle beams. The above lens and a deflector that scans the plurality of charged particle beams on the sample,
The illumination beam forming unit, a second mode of irradiating with a plurality of openings, a plurality of angles of the plurality of charged particle beams on one point of the sample by not the first mode and the voltage is applied a voltage is applied A plurality of lenses, and an on / off selection unit that individually selects passage and blocking of the plurality of charged particle beams,
Charged particle beam application device characterized by that. The charged particle beam application apparatus according to claim 1,
A charged particle beam application apparatus comprising one or more second signal detection systems for detecting the secondary charged particle beam separately from the first signal detection system. The charged particle beam application apparatus according to claim 1 or 2,
Based on the output of the first signal detection system or the second signal detection system, further comprising an image display device for displaying an observation image of the sample,
The charged particle beam application apparatus, wherein the image display device displays an incident angle selection screen for selecting the incident angle. A charged particle beam application device,
A charged particle beam source for generating a charged particle beam;
An irradiation beam forming unit that forms a plurality of divided primary beams from the charged particle beam generated from the charged particle beam source;
An electron lens system that irradiates a predetermined position on the sample by tilting an incident angle of each of the divided primary beams with respect to the sample;
A signal detection system for detecting a secondary beam generated from the sample by irradiation of the divided primary beam;
An image display device for displaying an image of the sample based on the output of the signal detection system corresponding to the secondary beam;
A control unit that controls the irradiation beam forming unit, the electron lens system, the signal detection system, and the image display device;
The illumination beam forming unit, a second mode of irradiating with a plurality of openings, a plurality of angles of the plurality of charged particle beams on one point of the sample by not the first mode and the voltage is applied a voltage is applied A charged particle beam application apparatus comprising a plurality of lenses having The charged particle beam application apparatus according to claim 4,
The irradiation beam forming unit selects at least one of the plurality of divided primary beams,
A charged particle beam application apparatus comprising: an incident angle selection unit that selects an incident angle of the divided primary beam irradiated to the predetermined position. The charged particle beam application apparatus according to claim 5,
The control unit causes the image display device to display an incident angle selection screen for selecting an incident angle of the divided primary beam, and causes the incident angle selection unit to respond to the incident angle selection screen. A charged particle beam application apparatus, wherein the divided primary beam corresponding to the selected incident angle is selected. The charged particle beam application apparatus according to claim 6,
The said control part displays the image of the said sample obtained by irradiation of the said divided | segmented primary beam corresponding to the said incident angle selected on the said image display apparatus, The charged particle beam application apparatus characterized by the above-mentioned. The charged particle beam application apparatus according to claim 7,
When the controller displays the image of the sample on the image display device, the sample is obtained by irradiation with a plurality of the divided primary beams having the selected incident angles and different azimuth angles. A charged particle beam application apparatus, characterized in that it is controlled to simultaneously display the images. A primary optical system for forming a plurality of divided charged particle beams from a particle beam generated from a charged particle beam source and irradiating the charged particle beam on a sample; and from the sample by irradiation with the charged particle beam In a device including a signal detection system for detecting a generated secondary charged particle beam, a sample observation method for forming an image from a signal detected by the signal detection system,
Selecting the presence or absence of inclination of the charged particle beam with respect to the sample by applying or not applying a voltage to a plurality of lenses arranged in the primary optical system;
Selecting an incident angle of the charged particle beam with respect to the sample;
Irradiating the sample with the charged particle beam based on the selected incident angle of the inclination;
And a step of simultaneously displaying a plurality of images having different azimuth angles corresponding to the selected incident angle on an image display device. The sample observation method according to claim 9,
A sample observation method comprising a step of separating the secondary charged particle beam to form an image according to an emission angle and an emission azimuth angle of the secondary charged particle beam. The sample observation method according to claim 9 or 10,
A sample observation method comprising the step of setting the incident angle in advance based on a combination of intensities of electron lenses disposed in the primary optical system. A sample observation method according to any one of claims 9 to 11,
The device further includes a display device,
A method of observing a sample, comprising the step of displaying, on the display device, a screen for selecting an incident angle of the charged particle beam with respect to the sample. A sample observation method according to claim 12, comprising:
Further comprising selecting an azimuth angle of the charged particle beam with respect to the sample;
In the irradiation step, the sample is irradiated with the charged particle beam based on the selected incident angle and azimuth angle of the tilt.

Images