JP5042282B2 - Ion beam equipment - Google Patents

Description

  The present invention relates to a charged particle beam technology for irradiating a charged particle beam to a sample for observation, analysis, and processing.

  A charged particle beam apparatus for irradiating a sample with a charged particle beam and observing, analyzing, and processing the sample is widely used. When the sample includes an insulating material, when charged particles are scanned and irradiated on the sample surface, the sample surface may be charged. Charging hinders observation, analysis, and processing due to drift of the irradiation beam and a decrease in the amount of secondary particles emitted. Therefore, a method for preventing this charging becomes important.

  Conventional antistatic methods include a method of neutralizing charging by irradiating the sample surface with charged particles, a method of releasing a charged charge by forming a conductive layer on the sample surface by irradiating with ultraviolet rays or charged particle beams, a conductive film There are a method of releasing the charged charge by covering the sample surface and a method of releasing the charged charge by a conductive foil, paste or terminal.

  As a prior art 1, there is a “charged beam processing apparatus and method (Japanese Patent Laid-Open No. 8-138617)” as a method for neutralizing charging by irradiation with charged particles. In the prior art 1, when neutralizing the sample charged by the ion beam with the electron beam, the secondary electron detector is arranged near the surface of the sample with the tip of the neutralizing electron gun in the form of a nozzle so that the secondary electron detector is neutralized electrons. An apparatus and method for detecting secondary electrons from a sample surface without drawing electrons from a gun is disclosed.

  As a conventional technique 2, a method of forming a conductive layer on the sample surface by irradiation of ultraviolet rays or charged particle beams to release the charge is disclosed as “Secondary electron image detection method and apparatus thereof, and processing method and apparatus thereof by focused charged particle beam ( 11-154479) and "charged beam processing apparatus and method (Japanese Patent Laid-Open No. 8-138617)". Prior art 2 uses a method of inducing a conductive layer to release charges by irradiating positive ion beam to the area including the focused charged particle beam irradiation area on the surface of the sample, thereby stably charging regardless of the state and type of the sample. Avoiding, real-time detection of secondary electron images of the sample with high resolution, realizing the pattern observation of the sample and positioning of the focused charged particle beam with high accuracy, and an apparatus that realizes processing of 1.0 μm or less, and A method is disclosed.

  As a method of covering the sample surface with a conductive film, there is "Conductive resist film and semiconductor device manufacturing method (Japanese Patent Laid-Open No. 7-74076)" as Prior Art 3. Prior art 3 performs a pattern exposure with high accuracy by reducing the charged particle beam bending irradiation phenomenon by suppressing the charging as much as possible by forming a conductive film below the resin film sensitive to charged particles. A method is disclosed.

  As a prior art 4, there is a “sample charge removing device (Japanese Patent Laid-Open No. 2000-173525)” as a method for releasing the charge by using a conductive terminal. In the prior art 4, the terminal is contacted so as to surround at least 180 degrees in the vicinity of the observation / analysis / processing area by remote control, and the charge generated in the process of observation / analysis / processing is discharged through the ground wire. Disclosed is a device that eliminates obstacles in observation, analysis, and processing due to phenomena and realizes high sensitivity, high resolution, and high precision work.

  As a prior art 5, there is a “fine pattern measuring device (Japanese Patent Laid-Open No. 7-94562)” as a method for capturing a charged charge with a conductive probe. In the prior art 5, the negative charge due to the electron beam is brought into direct contact with the fine pattern or separated from the fine pattern by 30 μm, and a positive voltage of 5000 V is applied to the probe to catch the charged charge in advance. An apparatus for measuring a fine pattern to be prevented is disclosed.

JP-A-8-138617 Japanese Patent Laid-Open No. 11-154479 JP-A-8-138617 JP 7-74076 A JP 2000-173525 A Japanese Unexamined Patent Publication No. 7-94562

  The above-described prior art removes the charge generated when a charged particle beam is irradiated by a method of coating or contacting a conductive material on a sample surface or a method of irradiating charged particles.

  In the antistatic method shown in prior art 1 or prior art 2, electrification occurs when the irradiation amount of the electron or ion beam used for antistatic does not match the charged particle beam used for observation / analysis / processing. In this case, the neutralization condition for charging is based on the improvement of the resolution of the observation image by improving the irradiation position accuracy of the charged particle beam and the improvement of the observation image contrast by the increase of the emission amount of secondary electrons generated by the irradiation of the charged particle beam. It is necessary to control the irradiation amount of the electron beam or ion beam by means for detecting. Furthermore, the dose control by the neutralization condition detection means requires the experience of the operator.

  Further, secondary electrons emitted by irradiation with electrons or ion beams are drawn into the secondary electron detector. At this time, since it overlaps with secondary electrons emitted from the surface of the sample by the charged particle beam, the secondary electrons due to irradiation with electrons or ion beams significantly deteriorate the observation image. Therefore, in order to suppress the amount of secondary electron emission due to electron or ion beam irradiation, it is necessary to limit the irradiation amount. When the amount of charge on the sample surface is large, the antistatic method by electron or ion beam irradiation is not effective. .

  Generally, secondary electrons generated by irradiation with a charged particle beam are emitted 10 to 100 times more than secondary ions. Therefore, the resolution of the observation image based on the secondary electron signal is better than that of the secondary ion. However, when irradiating an electron or ion beam to neutralize the charge, the resolution of the observed image based on the secondary electron signal is lower than that of the secondary ion because of generation of secondary electrons. End up. Therefore, secondary ion detectors are widely used in charged particle beam devices.

  In the antistatic method shown in Prior Art 3, an antistatic film is produced on the sample surface. If the surface of the sample is covered, the surface structure cannot be observed with the charged particle beam, which causes inconvenience in determining the position of observation / analysis / processing with the charged particle beam. Furthermore, in order to avoid sample contamination, the antistatic film formed on the sample surface must be removed after observation / analysis / processing with a charged particle beam.

  In the method of releasing the charge by the conductive terminal shown in the prior art 4, the terminal must be brought into contact by remote operation so as to surround at least 180 degrees around the observation / analysis / processing area. By contacting the terminal so as to surround the observation / analysis / processing area of 180 degrees or more, it is difficult to confirm the terminal contact, and at the same time, the positional accuracy at the time of contact of the terminal is lowered. Furthermore, a larger area than the observation / analysis / processing area irradiated with the charged particle beam is contaminated by contact with the terminal.

  In the method of capturing charged charges with the conductive probe shown in the prior art 5, when the probe is in contact, the probe hides a part of the fine pattern and cannot be observed, and when the probe is not in contact, the charged electrons are probed. The observation image is distorted by a strong electric field when captured by

  When a sample is prepared using a charged particle beam without using an antistatic method, the operator must perform observation, analysis, and processing on the basis of a drifting observation image. In order to confirm these operations and settings by visual observation, observation, analysis, and processing without using the antistatic method are work requiring skill. At this time, the operator destroys the sample if the processing fails, and causes sample destruction or probe tip damage if the probe operation fails.

  In these methods, the contamination of the sample is reduced, the work of coating or contacting the surface of the conductive material is reduced, the charge newly generated by irradiation of the charged particle beam on the sample surface, and observation / analysis using secondary electrons It has problems such as reducing the influence of terminals on processing and eliminating skilled techniques when extracting sample pieces directly from the sample.

  The present invention has been made in view of the above points, and provides a highly reliable charge neutralization control method that eliminates experience and skilled skill steps for suppressing charging on the surface of a sample. Another object of the present invention is to provide a charged particle beam apparatus with good analysis and sample preparation efficiency.

  As means for achieving the above object, the present invention controls charging generated when a sample is irradiated with a charged particle beam (ion beam, electron beam, etc.) by a neutralizing electrode adjacent to or in contact with the irradiation region. A method based on the new knowledge is provided.

  Even if the neutralization electrode and the irradiation region are in an electrically insulated state, the charged particle beam is exchanged between the charged irradiation region and the neutralization electrode as a result of the irradiation of the charged particle beam. . The cause of this is that near-charge exchange occurs between the neutralizing electrode and the irradiation region by efficiently drawing the secondary particles generated from the surface of the sample charged by irradiation of the charged particle beam to the neutralizing electrode. If the neutralizing electrode is adjacent to or in contact within, for example, 300 μm from the irradiation region, a proximity current flows between the charged irradiation region and the neutralizing electrode due to the irradiation of the charged particle beam. .

  When the operator performs high-precision observation / analysis / processing / probe operation, it is necessary to further reduce the distance between the neutralizing electrode and the irradiation region. As the interval is narrowed, the charging potential is lowered by proximity charge exchange or proximity current with the irradiation region, and at the same time, the electric field in the vicinity of the irradiation region due to charging can be confined in a narrower space. As a result, the irradiation position of the charged particle beam on the surface of the insulator sample can be controlled with a position accuracy of about 1/50 times the interval. At the same time, the amount of secondary particles detected by the secondary particle detector is not affected by charging, and a clear observation image can be obtained.

  Using the above-described method for controlling charging, a typical configuration example of a charge neutralization control method of the present invention that realizes highly accurate observation / analysis / processing / probe operation and a charged particle beam apparatus using the same, Listed below.

  First, as a charge neutralization control method, the present invention irradiates a sample mounted on a sample stage with a charged particle beam emitted from a charged particle source, and charges generated in the irradiation region of the sample are The neutralization control of the charging is performed by applying a predetermined voltage to the neutralizing electrode placed near the surface and generating a charge exchange with the charged irradiation region without contact with the sample. It is characterized by having comprised as follows.

  In the present invention, the charged particle beam emitted from the charged particle source is irradiated to the sample mounted on the sample table, and the charge generated in the irradiation region of the sample is installed near the surface of the sample table. The neutralization control of the charging is performed by applying a predetermined voltage to the neutralizing electrode, bringing it into contact with the sample, and generating a current with the charged irradiation region. To do.

  Next, as a charged particle beam apparatus, the present invention includes a charged particle source, a charged particle optical system for focusing and deflecting the charged particle beam emitted from the charged particle source, and irradiating a sample with the charged particle beam. In a charged particle beam apparatus comprising a detector for detecting secondary particles from a sample and a sample stage on which the sample is mounted, neutralization provided movably with respect to the surface of the sample stage An electrode, and a neutralization electrode control device that controls the voltage applied to the neutralization electrode and the movement, and an irradiation region on the sample that is charged by irradiation with the charged particle beam and the neutralization electrode It is characterized in that the charge is neutralized and controlled by generating a charge exchange or current with the electrode.

  The present invention also provides a charged particle source, a lens that focuses the charged particle beam emitted from the charged particle source, a deflector, and a detection for detecting secondary particles by irradiating the sample with the charged particle beam. A charged particle beam apparatus comprising: a sampler; a sample stage for holding the sample; and a sample position control device for controlling the position of the sample stage. The charged particle beam irradiation region on the sample and the lens A first electrode that is movably provided with respect to the sample and generates charge exchange or current with the charged particle beam irradiation region, controls the first electrode, and the sample stage position control device An electrode control device that is driven independently; and a second electrode that is driven independently of the sample stage position control device and generates a current between the charged particle beam irradiation region, the first and the The charged particles charged using the second electrode Characterized by being configured to perform neutralization control line illumination area.

  The present invention eliminates the experience and skilled skill in the antistatic technology in the charged particle beam device, improves the reliability of the control of the charged particle beam and the probe, and performs the charging with a comprehensive analysis and sample preparation efficiency. A particle beam device is realized.

The figure which shows the 1st Example of the charged particle beam apparatus by this invention. The figure which shows the sample charge and beam drift at the time of ion beam irradiation. The figure which shows the ion beam irradiation time dependence of the charging potential of a sample surface. The figure which shows the beam current dependence of the beam vibration period by charging vibration. The circuit diagram which shows the method of controlling charging by the electrode for neutralization. The figure which shows the irradiation current dependence of the electric current which flows into the electrode for neutralization. The figure which shows the height between the electrode tip for neutralization, and a sample. The figure which shows the tip height dependence of the electric current which flows into the electrode for neutralization with an ion beam. The figure explaining the 2nd Example of the charged particle beam apparatus by this invention. The figure which shows the method of producing a highly accurate analysis sample from an insulator. The figure explaining the 3rd Example of the charged particle beam apparatus by this invention. The figure which shows the tip height dependence of the electric current which flows into the electrode for neutralization with an electron beam. The figure which shows the control method of the electrode for neutralization by a sample height recording part. The figure which shows the control method of the electrode for neutralization by the electric current which flows into the electrode for neutralization. The figure which shows the control method of the electrode for neutralization by the setting value of an objective lens. The figure which shows the control method of the electrode for neutralization by the setting value of a deflector. Explanatory drawing which compares the prior art 2 and the Example of this invention.

Example 1
FIG. 1 shows a basic configuration of a charged particle beam apparatus according to a first embodiment of the present invention.

  In the charged particle beam apparatus of the present invention, an ion beam 11 is extracted from the ion source 1 by the extraction electrode 2, the ion beam is focused by the condenser lens 3, the ion beam is narrowed by the beam limiting aperture 4, and the sample 8 is focused by the objective lens 6. A charged particle optical system for focusing the ion beam 11 on the surface, a movable sample stage 7 on which a sample is placed, a secondary particle detector 9, a deflector 5, a control device 10, and a neutralizing electrode 20 It consists of.

  The neutralizing electrode 20 is composed of an electrode made of a conductive material. The tip of the neutralizing electrode 20 is brought close to the ion beam irradiation position of the sample 8 by means of an in-plane position measuring means for observing by scanning with an ion beam and a height position measuring means based on a set value of the objective lens 6 at this time. approach.

  During ion irradiation of the sample, the ion beam is elastically scattered or inelastically scattered. Inelastic scattering generates secondary electrons from the sample. Most of the secondary electrons have an energy of only a few eV, and when the potential on the surface of the ion beam irradiation region is positively charged by several volts with respect to the surroundings, the low-speed secondary electrons cannot leave the sample and return to the sample. When the ion beam irradiation current is equal to the total current flowing out of the sample, the surface potential of the sample reaches equilibrium.

  FIG. 2 shows how the ion beam drifts in the direction of the arrow due to the bias in the potential distribution of the sample. In the figure, 31 indicates an equipotential line. As a result of the irradiation position of the ion beam 11 and the dielectric constant distribution on the surface of the sample 8, the surface potential is distributed with a bias with respect to the ion beam. The charged electric charge flows out to the sample stage through the insulation resistance. This insulation resistance is considered to be related to the volume resistance and surface resistance of the sample. In an insulator, the surface resistance is often smaller than the volume resistance.

  The time change dVc / dt of the positively charged charging potential Vc in the ion beam irradiation region is expressed by the following equation, assuming that the effective capacitance C, the insulation resistance R, and the beam current Ip on the sample surface.

dVc / dt = Ip / C-Vc / RC
FIG. 3 shows the time dependence of the charged potential at the ion beam irradiation position assuming an ion beam irradiation amount (beam current) of 10 nA, an effective electrostatic capacitance of 1 nF on the sample surface, and an insulation resistance of 5 GΩ. As time passes, the charging potential increases and becomes approximately in equilibrium after about 10 seconds.

  If charged and balanced, there is almost no effect on the ion beam forming process. If the surface potential changes with time during ion beam irradiation, beam drift occurs. The beam drift is caused by the deviation of the surface potential distribution due to the structure and physical properties of the sample surface. For example, when a time change of an observation image is evaluated by a method of detecting a secondary particle by irradiating the surface of a cover glass (30 mm × 20 mm thickness 0.1 mm) with a scanning ion beam, a SIM image is observed. The observation area was repeatedly moved. If the potential of the sample is in an equilibrium state after a certain time of ion beam irradiation, the observation region should not move. However, since the observation region movement is actually repeated, it can be said that a time change occurs in the sample surface potential due to repeated discharge and charging.

  FIG. 4 shows the beam current dependence of the frequency of observation region movement. The discharge frequency f increases with the beam current Ip. When the beam current increases, the beam drift increases as vibration due to charging increases.

  FIG. 5 is a circuit diagram showing a method of controlling the charging 33 by ion beam irradiation by the neutralizing electrode 20. The proximity charge exchange 32 can be performed by bringing the tip of the neutralizing electrode 20 close to the surface of the sample that is charged by ion beam irradiation. The tip of the neutralizing electrode 20 is a needle-like electrode formed of a conductive material. The current flowing in the proximity charge exchange 32 by the neutralizing electrode 20 is 60% or more of the current of the ion beam when the tip of the neutralizing electrode 20 is fixed at a position of 30 μm in the horizontal direction and 30 μm in the vertical direction from the irradiation region to the sample surface. become.

  The neutralizing electrode 20 always supplies electrons in order to neutralize positive charges charged by ion beam irradiation. FIG. 6 shows the beam current dependency of the current flowing through the neutralizing electrode 20 (hereinafter referred to as supply current) when charging of the cover glass is performed.

  The tip of the neutralizing electrode 20 was adjacent to the position about 16 μm from the ion beam irradiation position, and the supply current was measured by changing the beam current in the range of 20 pA to 8 nA. In the figure, the measurement results are indicated by ■. A straight line when the supply current I is equal to the beam current Ip is indicated by a thin line. Most of the beam current Ip flows from the two straight lines in FIG. 6 to the neutralizing electrode 20, and the amount thereof is proportional to the beam current Ip, and flows out of the sample through the insulation resistance in a path other than the neutralizing electrode 20. It was confirmed that the current was also substantially proportional to Ip. At this time, the insulation resistance does not seem to depend on the beam current.

FIG. 7 shows the height between the tip of the neutralizing electrode and the sample. When a 32 × 32 μm ² region was irradiated with a beam current of 8.0 nA, the tip of the neutralizing electrode 20 was set at 2 μm in height and 16 μm in the lateral direction from the irradiation position center, and only the height 40 was changed. When the height of the neutralizing electrode 20 is changed, the amount of displacement in the lateral direction is about 100 μm at the maximum due to the influence of the control device.

  FIG. 8 shows the measurement results of the height dependence of the current flowing through the neutralizing electrode. The current flowing through the neutralizing electrode varies in the range of 4.4 to 5.1 nA, but has no height dependency up to 100 μm.

  On the other hand, most of the secondary electrons emitted from the sample surface by the irradiation of the ion beam 11 have an energy of only a few eV. At this time, the secondary particle detector 9 cannot detect the secondary electrons from the sample because the low-speed secondary electrons cannot leave the sample and return to the sample due to the electric field generated by the charging and neutralizing electrode 20. End up. Further, the ion beam 11 is shifted by the neutralizing electrode 20 and the electric field generated by charging.

  In order to solve the above problems, a voltage source for applying a voltage to the neutralization electrode itself and a neutralization electrode 20 having a long and narrow conductive needle shape are provided. As shown in FIG. 5, when a negative potential is applied to the neutralizing electrode 20 while the sample surface is positively charged, the amount of secondary electrons 34 emitted is increased in addition to charge exchange with the charged region. Therefore, when the neutralization electrode 20 is applied with a positive potential of about +2 V to reduce the pulling back due to charging of secondary electrons, the accuracy of ion beam scanning is improved and the detection of secondary particles of secondary electrons emitted from the sample surface is performed. Due to the improvement of the collection rate in the vessel 9, the resolution of the observation image was improved twice as compared with the case where 0 V was applied to the neutralizing electrode 20.

(Example 2)
FIG. 9 shows a basic configuration of a second embodiment of the charged particle beam apparatus according to the present invention. In the present embodiment, a charged particle beam apparatus that forms a sample of several to sub-μm order is configured by combining the mechanical probe 21.

  After the ion beam is extracted from the ion source 1 by the extraction electrode 2, the ion beam is focused by the condenser lens 3, the ion beam is focused by the beam limiting aperture 4, and the ion beam is focused on the surface of the sample 8 by the objective lens 6. It comprises an optical system, a movable sample stage 7 on which a sample is placed, a secondary particle detector 9, a deflector 5, a control device 10, a neutralizing electrode 20, and a mechanical probe 21.

  The tip of the neutralizing electrode 20 is composed of a conductive needle having a radius of curvature of about 100 μm and is brought close to the surface of the sample 8. The neutralizing electrode 20 is fixed at a position of about 30 μm in the horizontal direction of the sample surface and about 30 μm in the vertical direction from the ion beam irradiation region. When the sample contains an insulator and is positively charged in the irradiation region, the charge is suppressed by exchanging charges with the irradiation region charged by the neutralizing electrode 20. When scanning with a 30 μA ion beam, a clear observation image can be obtained from the signal from the secondary particle detector 9.

  However, when a 10 nA ion beam is irradiated to process a sample, the charging position increases, and the ion beam irradiation position cannot be controlled. Therefore, the tip of the mechanical probe 21 is brought into contact with the sample surface rather than scanning the ion beam of 30 μA to form an observation image. At this time, even when the ion beam of 10 nA is irradiated, the mechanical probe 21 suppresses charging by the proximity current flowing between the charged irradiation region and the ion beam irradiation position can be accurately controlled.

  FIG. 10 shows a method for producing a high-precision analytical sample from an insulator.

  In a state where the tip of the mechanical probe 21 is in contact with the sample surface, the posture of the substrate 51 is maintained so that the ion beam 52 is irradiated at a right angle to the surface of the sample substrate 51, and the substrate 51 is not overlapped with the mechanical probe 21. Then, the ion beam 52 is scanned in a rectangular shape to form a square hole 53 having a required depth on the sample surface (FIG. 10A). At this time, when a voltage of +1 V was applied to the probe 11, the desired sample position in the observed image was clearly observed, the molding process was accurately set, and a sample piece could be produced with high accuracy.

  Next, the vertical groove 54 is formed (FIG. 10B). After the tip of the mechanical probe 21 is separated from the substrate 51, the substrate 51 is tilted so that the axis of the ion beam 52 with respect to the surface of the substrate 51 is tilted by about 30 ° to form the tilted groove 55. The posture change of the inclination angle of the substrate 51 is performed by the sample stage (FIG. 10-c). Again, after the substrate 51 is placed in a state in which the surface of the substrate 51 is perpendicular to the ion beam 52, the tip of the mechanical probe 21 is brought into contact with the portion of the substrate 51 that becomes the sample (FIG. 10-d). ). In the apparatus of FIG. 9, the tip of the neutralization electrode 20 is composed of a conductive needle having a radius of curvature of about 100 μm, and the neutralization electrode 20 forms a gas nozzle that supplies a deposition gas at the same time and approaches the surface of the sample 8. Let A deposition gas is supplied from a gas nozzle, and an ion beam 52 is locally irradiated onto a region including the tip of the mechanical probe 21 to form an ion beam assisted deposition (hereinafter abbreviated as IBAD) film 56. The sample piece 57, which is a separated part of the substrate 51 in contact, and the tip of the mechanical probe 21 are connected by an IBAD film 56 (FIG. 10-e).

  The remaining portion is cut out with the ion beam 52, and the separated sample piece 57 is cut out from the substrate 51. The separated sample piece 57 cut out is in a state of being supported by the connected mechanical probe 21 (FIG. 10-f). The separated specimen 57 is moved to the sample mesh 58 (FIG. 10-g). The deposition gas is supplied from the gas nozzle, and the ion beam 52 is locally irradiated to the boundary region where the separated specimen piece and the sample mesh are in contact to form the IBAD film 59 (FIG. 10-h). The region adjacent to the IBAD film 56 is locally irradiated with the ion beam 52, and the mechanical probe 21 is separated from the separated sample piece 57 (FIG. 10-i). The observation region in the separated sample piece 57 is thinned by using the ion beam 52 so as to leave a thickness of about 100 nm, and this sample can be observed and analyzed with sub-nm resolution by a transmission electron microscope ( FIG. 10-j).

(Example 3)
FIG. 11 shows a basic configuration of a third embodiment of the charged particle beam apparatus of the present invention.

  The charged particle beam apparatus of the present invention extracts an electron beam 82 from an electron source 80 by an extraction electrode 81, focuses the electron beam by a condenser lens 83, and then focuses the electron beam on the surface of a sample 85 by an objective lens 84. The optical system includes a movable sample stage 86 on which a sample 85 is placed, a secondary electron detector 87, a deflector 88, a control device 89, and a neutralizing electrode 90.

  When the sample 85 includes an insulator, the irradiation region of the electron beam 82 may be charged. Most of the secondary electrons emitted from the surface of the sample by irradiation with the electron beam 82 have an energy of only a few eV. However, when the secondary electrons are positively charged, the sample cannot be detached and returns to the sample, and is negatively charged. Since it is sometimes accelerated, the secondary electron detector 87 cannot detect secondary electrons from the sample 85. Furthermore, the irradiation position of the electron beam 82 cannot be controlled due to a shift caused by an electric field generated by charging.

The resolution of the observation image on the insulator sample (SiO ₂ ) was significantly reduced by scanning with an electron beam 82 (700 pA) with an acceleration voltage of ₂ kV. The reason for this is the negative charging of the irradiated area.

FIG. 12 shows a current that flows due to charge exchange between the neutralizing electrode 90 and the charged irradiation region. At this time, the tip of the neutralizing electrode 90 was moved in the vertical direction to a distance of 0 to about 360 μm away from the irradiation region 3 × 3 μm ^{2 in the} horizontal direction by 9 μm. At this time, when it was brought into contact with the insulator surface of the sample, a current of about 200 pA flowed between the neutralizing electrode 90 and the charged irradiation region. When a current of 100 pA or more flows through the neutralizing electrode 90, the resolution of the observation image has reached 1 nm.

  Furthermore, when a voltage of +5 V was applied to the neutralization electrode 90, a current of about 300 pA flowed at a position where the tip of the neutralization electrode 90 was 500 pA at the position of the sample surface and a distance of 360 μm in the vertical direction. When a positive voltage is applied when the irradiation region is negatively charged, the neutralizing electrode takes in secondary electrons emitted from the sample surface by irradiation of the electron beam 82. As a result, since the secondary electron detector 87 cannot detect the secondary electrons, the S / N of the observed image decreases. In order for the neutralizing electrode 90 to avoid taking in and accelerating secondary electrons, a negative voltage of 0 V to −5 V may be applied to the neutralizing electrode 90. As a result, the S / N of the observed image was improved, and the resolution reached 1 nm.

(Example 4)
FIG. 13 shows a charge control method when the surface of the sample 8 is not parallel to the sample stage 7 in the first, second, and third embodiments. In this case, when the sample stage 7 is moved rightward, the tip of the neutralizing electrode 20 interferes with the sample surface. The tip of the neutralizing electrode 20 is destroyed by the collision with the sample 8, or the surface of the sample 8 is broken by the collision with the neutralizing electrode 20. Unless this interference is avoided, the charge control by the neutralizing electrode 20 does not work effectively. Therefore, a method for achieving both charge exchange and interference between the irradiation region of the sample 8 and the neutralizing electrode 20 will be described below.

First, FIG. 13 shows a first example of a method for achieving both charge exchange and interference between the irradiation region of the sample 8 and the neutralizing electrode 20. Before irradiating the charged particle beam, the height distribution of the entire surface of the sample 8 is recorded in the recording unit 61 of the control device 10. For example, when the tip distance 62 of the neutralizing electrode 20 is set to 100 μm, the accuracy of the height distribution needs to be ± 50 μm. In order to shorten the tip distance 62, the accuracy of the height distribution must be improved. The height change that occurs when the sample stage 7 is moved is calculated by the recording unit 61, and the tip electrode distance 62 is made constant by moving the neutralizing electrode 20 by the change amount. For example, when the tip distance 62 is 100 μm, the charged particle beam irradiation area is 100 × 100 μm ² and the observation accuracy is 1 μm. In order to improve the observation accuracy, it is necessary to control charging by the neutralizing electrode 20 with the tip distance 62 set short.

FIG. 14 shows a second example of a method for achieving both charge exchange and interference between the irradiation region of the sample 8 and the neutralizing electrode 20. Unlike the above example, the second method measures the current flowing between the irradiation region and the neutralizing electrode 20 by the ammeter 63 during the charge control. The current depends on the tip distance 62. When approaching the sample 8 and reducing the tip distance 62, the current flowing through the neutralizing electrode 20 increases. Therefore, during or after moving the sample, the current is monitored so that the tip of the neutralizing electrode 20 does not interfere with the sample surface, the tip distance 62 is calculated by the calculation unit 64, and the tip distance 62 is made constant. The neutralizing electrode 20 is controlled. For example, when the tip distance 62 is 1 μm, the charged particle beam irradiation area is 1 × 1 μm ² and the observation accuracy is 10 nm. In order to improve the observation accuracy, it is necessary to control charging by the neutralizing electrode 20 by shortening the tip distance 62 or by contacting the periphery of the irradiation region.

  FIG. 15 shows a third example of a method for achieving both charge exchange and interference between the irradiation region of the sample 8 and the neutralizing electrode 20. Unlike the two examples described above, the third method uses the set value of the objective lens 6. When the neutralizing electrode 20 is at the retracted position (for example, the tip distance 62 is 100 μm), the set value of the objective lens 6 is changed to adjust the focused point of the charged particle beam to the surface of the sample 8. At this time, the control device 10 calculates the tip distance 62 by the calculation unit 65 from the amount of change in the set value of the objective lens 6, and brings the neutralizing electrode 20 closer to the sample surface. The control accuracy of the tip distance 62 according to the set value of the objective lens 6 was 30 μm.

FIG. 16 shows a fourth example of a method for achieving both charge exchange and interference between the irradiation region of the sample 8 and the neutralizing electrode 20. The neutralizing electrode 20 holds a uniaxial movable mechanism in a direction of 20 to 80 degrees with respect to the irradiation angle of the charged particle beam. The control device 10 sets the scanning range of the charged particle beam in the deflector 5 and simultaneously calculates the tip distance 62 corresponding to the scanning range by the calculation unit 65 to control the neutralization electrode. For example, when the tip distance 62 is set to 30 μm, the observation accuracy is 0.3 μm and the processing accuracy is 0.5 μm when the scanning range is 30 × 30 μm ² .

  When the scanning range is narrowed and high-precision observation is performed, and when high-precision processing is performed while referring to the observation image, the tip distance is automatically adjusted to improve the observation and processing accuracy when changing the scanning range. 62 is shortened. For example, when the tip distance 62 is set to 1 μm, if the sample 8 is moved, the neutralizing electrode 20 and the sample 8 interfere with each other. Therefore, the range in which the sample 8 can be moved on the sample stage 7 is set to 10 μm or less in the horizontal direction. .

This method can be combined with the method of achieving both charge exchange and interference between the irradiation region of the sample 8 and the neutralizing electrode 20 shown in FIGS. 13, 14, and 15. When the scanning range is narrow (for example, smaller than 30 × 30 μm ² ), the neutralizing electrode 20 is controlled by the method shown in FIG. 16, and when the scanning range is wide, the method shown in FIGS. The summing electrode 20 is controlled. This dramatically improved the accuracy of observation and processing of charged particle beams.

  FIG. 17 is an explanatory diagram comparing (a) showing the prior art 2 and (b) showing an example of the present invention. According to Japanese Patent Laid-Open No. 8-138617 of Prior Art 2, when an ion beam is applied to an insulating layer of a sample, a very thin conductive layer 70 is formed in the vicinity of the irradiation region on the sample surface, and this conductive layer is contacted. Discloses a method of avoiding charge-up by flowing charge to ground through the probe 71.

  In this method, when the ion beam irradiation region is narrower than the tip radius of the probe, when the ion beam 11 is in direct contact with the conductive layer formed by the ion beam, the probe 71 moves to the ion beam 11 irradiation region as shown in FIG. Overlap. However, in this embodiment, as shown in (b), it is not necessary to directly contact the conductive layer 70, and the probe (neutralization electrode 20) does not overlap the ion beam irradiation region.

  As described above, according to the charged particle beam apparatus of the present invention, the charged particle beam is controlled with high accuracy by controlling the charging with the neutralizing electrode adjacent to or in contact with the surface of the sample. By eliminating experience and skilled skill steps to suppress charging on the sample surface, and eliminating secondary ion detectors and electron guns or ion guns, improving the reliability of charging control technology, reducing equipment costs, Accurate observation, analysis, processing, and probe operation can be realized.

The present invention is summarized as follows.
(1) The sample mounted on the sample stage is irradiated with the charged particle beam emitted from the charged particle source, and the charge generated in the irradiation region of the sample is neutralized installed near the surface of the sample stage. Charging characterized in that neutralization control of the charging is performed by applying a predetermined voltage to the electrode and generating charge exchange with the irradiation region charged without contact with the sample. Neutralization control method.
(2) Neutralization is performed near the surface of the sample table by irradiating the sample mounted on the sample table with the charged particle beam emitted from the charged particle source and generating the charge generated in the irradiation region of the sample. The charging is characterized in that neutralization control of the charging is performed by applying a predetermined voltage to the electrode and generating a current between the irradiation region and the charged region in contact with the sample. Sum control method.
(3) In the configuration of (1) or (2), by observing the surface of the sample with the charged particle beam, the neutralization electrode is brought into contact with the vicinity of the irradiation region, thereby neutralizing the charge. A charge neutralization control method characterized by being configured to perform control.
(4) The charging neutralization control method according to (1) or (2), wherein the neutralizing electrode is configured to be movable with respect to the surface of the sample.
(5) The charging neutralization control method according to (1) or (2), wherein a voltage of −5 V to +5 V is applied to the neutralizing electrode.
(6) The charge neutralization control method according to (1), (2), or (3), wherein the sample includes an insulator.
(7) A charged particle beam emitted from a charged particle source is irradiated on a sample including an insulator mounted on the sample table, and the charge generated in the irradiation region of the sample is installed near the surface of the sample table. A charge neutralization control method, wherein a predetermined voltage is applied to the neutralization electrode and the charge neutralization control is performed without contact with the sample.
(8) A charged particle source, a charged particle optical system for focusing and deflecting a charged particle beam emitted from the charged particle source, and detecting secondary particles from the sample by irradiating the sample with the charged particle beam In a charged particle beam apparatus including a detector for performing the above and a sample stage on which the sample is mounted, the neutralizing electrode provided movably with respect to the surface of the sample stage, and applied to the neutralizing electrode A neutralizing electrode control device for controlling the voltage and the movement, and exchanging charges or current between the irradiation region on the sample charged by irradiating the charged particle beam and the neutralizing electrode. A charged particle beam apparatus configured to neutralize and control the charge by generating the charge.
(9) In the configuration of (8), the neutralization electrode is provided between the charged particle optical system and the sample stage, and is movable with respect to the surface of the sample stage. Charged particle beam device.
(10) The charged particle beam apparatus according to (8), wherein the neutralization electrode is formed of a needle-shaped electrode having a tip with a curvature of 100 μm or less made of a conductive material. .
(11) The charged particle beam apparatus according to (8), wherein a voltage of −5 V to +5 V is applied to the neutralizing electrode.
(12) In the configuration of (8), the neutralization electrode control device is configured to detect the neutralization based on a change in current flowing between the irradiation region and the neutralization electrode during the neutralization control of the charge. A charged particle beam apparatus comprising a calculation unit that calculates a control value of a position or a voltage of a working electrode.
(13) In the configuration of (8), the neutralization electrode control device includes a calculation unit that calculates a distance or voltage between the neutralization electrode and the sample from a set value of the lens or the deflector. A charged particle beam apparatus comprising:
(14) a charged particle source, a lens that focuses a charged particle beam emitted from the charged particle source, a deflector, a detector for irradiating the sample with the charged particle beam to detect secondary particles, In a charged particle beam apparatus comprising a sample stage for holding the sample and a sample position control device for controlling the position of the sample stage, the charged particle beam irradiation area on the sample and the lens are disposed on the sample. A first electrode (e.g., a neutralization electrode) that is movably provided and generates charge exchange or current between the charged particle beam irradiation region and the first electrode; An electrode controller that is driven independently of the position controller and a second electrode that is driven independently of the sample stage position controller and generates a current between the charged particle beam irradiation region (for example, a mechanical probe) ), And the first and Using said second electrode, charged the charged particle beam apparatus characterized by being configured to perform the neutralization control of the charged particle beam irradiation region.

  DESCRIPTION OF SYMBOLS 1 ... Ion source, 2 ... Extraction electrode, 3 ... Condenser lens, 4 ... Beam limiting aperture, 5 ... Deflector, 6 ... Objective lens, 7 ... Sample position control apparatus, 8 ... Sample, 9 ... Secondary particle detector, DESCRIPTION OF SYMBOLS 10 ... Control apparatus, 11 ... Ion beam, 20 ... Electrode for neutralization, 21 ... Mechanical probe, 31 ... Equipotential line, 32 ... Proximity charge exchange, 33 ... Charging, 34 ... Secondary electron, 35 ... Leakage current, 40 ... height between neutralization electrode and sample, 50 ... protective film, 51 ... substrate, 52 ... ion beam, 53 ... square hole, 54 ... bottom hole, 55 ... groove, 56 ... IBAD film, 57 ... sample piece, 58 ... sample mesh, 59 ... IBAD film, 60 ... thin film, 61 ... calculation unit, 62 ... tip distance, 63 ... ammeter, 64 ... calculation unit, 65 ... calculation unit, 70 ... conductive layer, 71 ... probe, 80 ... Electron source, 81 ... extraction electrode, 82 ... electron beam, 8 ... condenser lens, 84 ... objective lens, 85 ... sample, 86 ... sample stage 87 ... secondary electron detector, 88 ... deflector, 89 ... controller, 90 ... neutralizing electrode.

Claims (4)

An ion source;
A sample stage on which the sample is placed;
An ion beam irradiation optical system for focusing and deflecting the ion beam emitted from the ion source;
A detector for irradiating the sample with the ion beam to detect secondary particles from the sample;
By supplying electrons to the sample while being electrically connected to the sample stage and at the same potential as the sample stage, the positive charge of the sample caused by the irradiation of the ion beam is not different from the sample. ion beam apparatus comprising: a, a neutralization electrode to neutralize the contact. The ion beam apparatus according to claim 1, wherein said tip of neutralizing electrode, an ion beam apparatus which is a needle-shaped electrode formed of a conductive material. The ion beam apparatus according to claim 1, the ion beam and wherein the radius of curvature of the tip portion of the neutralizing electrode is 100μm or less. The ion beam apparatus according to claim 3, wherein the neutralizing electrode is connected to the ammeter, the distance between the tip and the sample of the neutralizing electrode by monitoring the amount of current measured by the ammeter An ion beam apparatus characterized by calculating.

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