JP4520905B2 - Analysis device, probe control method, and analysis system - Google Patents

Description

  The present invention relates to an analysis apparatus having a charged beam apparatus and a probe, for example, an analysis apparatus that cuts out a minute sample including a defective portion from a sample and performs an observation image, element analysis, or the like.

  In semiconductor manufacturing, it is required to produce good products in large quantities with a high yield. On the other hand, there are several hundred semiconductor manufacturing processes, and if the manufacturing process is advanced without knowing that a defect has occurred in a certain process, a large number of defective products will be produced, resulting in a huge loss. In order to prevent this, careful inspection is performed for each process, and the cause of the defect is investigated and countermeasures are taken at an early stage.

  In the inspection, circuit pattern dimension measurement, circuit pattern defect inspection, foreign matter analysis, and the like are performed, and various inspection apparatuses are used for this purpose. As such an inspection apparatus, a critical dimension scanning electron microscope (hereinafter referred to as a CDSEM) that measures a production pattern dimension, an optical inspection apparatus that optically inspects foreign matters and defects, and an electron beam are used. There are SEM type inspection devices, nanoprober inspection devices for inspecting electrical defects such as circuit breaks and short circuits.

  In particular, when a defective part is present in the product, fine processing observation is performed by combining a focused ion beam (hereinafter referred to as FIB) apparatus and a scanning electron microscope (hereinafter referred to as SEM). A device is used.

  In the “micro sample processing observation method and apparatus” disclosed in Japanese Patent Application Laid-Open No. 2002-150990, a micro area of micron order (hereinafter referred to as a micro sample) including a defective portion is cut out by FIB, and the micro sample is removed from the needle. It is extracted with a manipulator including a probe. While holding the microsample, adjust the position and orientation of the microsample, modify it to the optimum shape, and observe and analyze it.

  When a microsample having a micron order size including an observation site is extracted with a manipulator including a needle-like probe, it is necessary to bring the probe into contact with the microsample at high speed and stably. When the probe is brought into contact with the microsample, if the probe collides with the microsample, the probe and the microsample are damaged. In this case, it is necessary to redo the work, and quick failure analysis, analysis, and countermeasure feedback are not possible. As a result, the productivity of the line is reduced.

  In the “probe driving method and probe apparatus” disclosed in Japanese Patent Application Laid-Open No. 2002-40107, in order to bring the probe into contact with the sample, for example, by detecting the shadow of the probe generated in the SIM image, the height of the probe relative to the sample is increased. The speed of the probe is controlled quickly and reliably based on the information.

  When the probe is brought close to the sample by the probe controller, the probe becomes an obstacle for secondary electrons, reflected electrons, etc. emitted from the region behind the probe as viewed from the secondary electron detector. Therefore, the amount of secondary electrons and reflected electrons that reach the secondary electron detector decreases, and the shadow of the probe appears. The appearance of this shadow reduces the moving speed of the probe, and recognizes the contact of the probe by a sudden increase in luminance.

JP 2002-150990 A JP 2002-40107 A

  When there is an insulator on the sample surface, the insulator surface is often positively or negatively charged by irradiation with a charged particle beam such as a focused ion beam or an electron beam. For example, when a focused ion beam is irradiated to an insulator formed on a silicon wafer that is a semiconductor, the insulator is positively charged. This is due to the accumulation of positive charges on the insulator surface and the accumulation of more positive charges equivalently due to secondary electron emission. For example, when an insulator is irradiated with an electron beam and the ratio α of the amount of secondary electrons to the amount of primary electrons is smaller than 1, the insulator is negatively charged. On the contrary, when α is larger than 1, the surface of the insulator is positively charged. α also varies depending on the observation target and the energy value of the incident primary electron beam.

  If the microsample including the defective portion is charged positively or negatively, when the probe is brought close, the change in luminance near the probe at the position where the probe comes into contact becomes small, and it becomes difficult to recognize the approach of the probe.

  For example, when the observation position is positively charged, the secondary electrons are pushed back to the sample side by the positive electric field of the sample, and the amount of secondary electrons incident on the electron detector is reduced. Therefore, the SIM image becomes dark overall. In this state, when a probe to which a ground potential is applied is approached, the luminance in the vicinity of the probe becomes an obstacle when viewed from the electron detector, and the amount of signals of secondary electrons and the like further decreases to lower the luminance. Therefore, it becomes difficult to detect the approach of the probe due to a change in luminance.

  It is possible to adjust the brightness of the SIM image before approaching the probe by adjusting the contrast and brightness, but the brightness change due to the approach of the probe is insufficient, and the approach of the probe to the sample is difficult to recognize.

  Also, when the probe is brought into contact with the micro sample by automatic control, the probe tip image is registered, the probe position when the probe is approaching is recognized, and the probe position deviation is recognized by the image comparison when the registered contact is completed. Perform position correction and contact. However, when the contrast between the probe and the sample including the microsample is insufficient and the tip of the probe cannot be recognized, the probe may collide with the microsample, and defects such as probe damage and microsample damage may occur.

  In addition, when the defective portion is negatively charged, secondary electrons are accelerated to the secondary electron detector side by the negative electric field of the sample, and the amount of secondary electrons increases because the amount of emission increases. The brightness of the entire SIM image increases and becomes brighter. Although the brightness near the probe decreases due to the approach of the probe to which the ground potential is applied, the change is small and it is difficult to visually recognize the approach of the probe. This phenomenon is the same even when visual contrast and brightness adjustment is performed.

  In addition, when the charging state changes with time and discharge of the power storage and the ground potential portion is repeated on the surface of the insulator, the entire SIM image may become brighter or darker. That is, when the sample is no longer positively charged, the number of secondary electrons incident on the secondary electron detector increases, so the image becomes brighter, and when the amount of positive charge on the sample increases, the secondary electron incident on the secondary electron detector. As the number of electrons decreases, the image becomes darker. In such a state, when the probe is brought close to the sample, the brightness of the shadow of the probe changes greatly, and it is very difficult to visually recognize the approach of the probe to the sample.

  A similar problem occurs when a microsample is mounted on a sample stage. When a micro sample mechanically bonded to the probe by a deposition film (hereinafter referred to as a deposition film) is brought close to the sample stage, the approach cannot be recognized, and the micro sample collides with the sample stage. As a result, the probe and the micro sample are damaged, and problems such as the micro sample cannot be accurately bonded to the sample table at a predetermined angle occur.

  When such a problem occurs, probe replacement work occurs and sampling work needs to be redone, which consumes a great deal of time. When a micro sample is taken out of the apparatus together with the sample stage and analyzed with a STEM (Scanning Transmission Electron Microscope), TEM (Transmission Electron Microscope), etc. to perform higher resolution analysis, the waiting time of the STEM and TEM apparatuses is long. Occurs and has a greater impact on a series of analysis and analysis operations. In such a situation, a series of failure analysis flows are changed, affecting the manufacturing process, and failure feedback cannot be performed, so that the temporary manufacturing process may be stopped.

  An object of the present invention is to provide an apparatus and a method capable of quickly and accurately performing a work of cutting out a micro sample from a sample, and capable of performing a work of arranging a micro sample on a sample stage quickly and accurately. There is to do.

  The present invention relates to an analysis apparatus having a charged particle beam apparatus and a probe. A negative voltage is applied to the probe, and the brightness of the sample is measured. When cutting out a small sample from a sample with a probe, it is determined that the probe has approached the sample when the luminance decreases, and it is determined that the probe has come into contact with the sample when the luminance increases rapidly after further decreasing in luminance. . Thus, the probe can be brought into rapid contact with the sample without colliding with the sample.

  When a micro sample connected to the probe is placed on the sample stage, the brightness of the sample stage is measured, and when the brightness decreases, it is determined that the micro sample connected to the probe has approached the sample stage. When the value rapidly increases after further decreasing, it is determined that the micro sample connected to the probe has contacted the sample stage. In this way, the micro sample can be quickly placed on the sample stage without the micro sample connected to the probe colliding with the sample stage.

  According to the present invention, the work of cutting out a micro sample from a sample can be performed quickly and accurately. Moreover, the operation | work which arrange | positions a micro sample on a sample stand can be performed rapidly and correctly.

An example of an analysis apparatus according to the present invention will be described with reference to FIG. The analysis device includes a focused ion beam device 7 (hereinafter abbreviated as FIB device) and a scanning electron microscope device 18 (hereinafter referred to as SEM device), which are attached to a vacuum chamber 23. The inside of the vacuum chamber 23 is exhausted by a vacuum exhaust system having a vacuum pump or the like (not shown) so that the pressure becomes 10 ⁻⁶ Pa level.

  A sample stage 21 that holds the sample 20 is disposed in the vacuum chamber 23. The sample stage 21 is tilted by the sample stage control unit 37 with respect to the sample 20 in the X-axis direction (left-right direction), Y-axis direction (depth direction), Z-axis direction (top and bottom direction), R-axis direction (rotation direction), and inclination. It can be driven with respect to five axes in the axial direction.

  The FIB apparatus 7 includes a gallium liquid metal ion source 1, an extraction electrode 2, a condenser lens 3, a movable diaphragm 4, a deflection coil 5, an objective lens 6, and an ion beam control unit 8 for controlling them. The FIB apparatus 7 is arranged so that the optical axis is perpendicular to the surface of the sample 20. By the FIB apparatus 7, a focused ion beam 9 having a beam current of several tens of nanoamperes to 0.1 picoamperes and a diameter of several nanometers to several micrometers is formed on one side of the sample 20 from several millimeters to several micrometers. The irradiation range is irradiated. Thus, micron-order holes can be formed on the sample 20 by sputtering by irradiation of the focused ion beam 9.

  The SEM device 18 efficiently causes a Schottky emission type electronic chip 10, an anode 11, a focusing lens 12, a diaphragm 13, a deflection coil 14, a secondary electron from a sample, and the like to efficiently enter the electron detector 35 by an electric field and a magnetic field. × B15, an objective lens 17, and an electron beam control unit 19 for controlling them. The optical axis of the SEM device 18 is inclined with respect to the optical axis of the FIB device 7. The SEM device 18 irradiates an electron beam 22 having an electron beam current of several picoamperes to several hundred picoamperes and a diameter of at least several nanometers in an irradiation range of one millimeter on the sample 20 from several millimeters to several micrometers. Is done.

  The vacuum chamber 23 is further provided with an electron detector 35, a charge detector 25, a probe 30, and a probe driver 31.

  The electron detector 35 is composed of a scintillator and a photomultiplier tube to which a positive potential of about 10 kV is applied. The detection signal from the electron detector 35 is sent to the detected electron analyzer 36 where it is analyzed. A signal from the detection electron analysis unit 36 is processed by the central control unit 38 in synchronization with the scanning of the focused ion beam 9, and a SIM image is obtained. This SIM image is displayed on the monitor 39.

  An energy filter made of a copper mesh is provided on the front surface of the electron detection unit 35, and a predetermined voltage is applied to the energy filter. Secondary electrons having energy smaller than the potential applied to the energy filter are pushed back by this electric field and cannot reach the electron detector 35. Therefore, the amount of secondary electrons incident on the electron detector 35 can be controlled by changing the voltage value applied to the energy filter. When a graph is plotted with the voltage applied to the energy filter on the horizontal axis and the signal amount of secondary electrons detected by the electron detector 35 on the vertical axis, the voltage applied to the energy filter is increased and becomes larger than a predetermined boundary value. It can be observed that the amount of secondary electrons detected by the electron detector 35 is extremely reduced. This boundary value represents the magnitude of energy of secondary electrons incident on the electron detector 35. By obtaining this boundary value, the magnitude of the energy of the secondary electrons can be detected.

  When the sample 20 is positively charged, in order for the secondary electrons emitted from the sample 20 to reach the electron detection unit 35, the influence of the positive electric field due to the charging of the sample surface must be shaken out. Therefore, the number of electrons incident on the electron detector 35 is remarkably reduced. When the sample 20 is negatively charged, secondary electrons emitted from the sample 20 are accelerated by obtaining energy by a negative electric field generated by charging the sample surface. Accordingly, the number of electrons incident on the electron detector 35 increases. Therefore, the charged state of the sample 20 can be measured by the increase or decrease of the energy of the secondary electrons detected by the electron detection unit 35.

  The probe 30 has a tapered needle shape with a tip made of tungsten having a diameter of several micrometers. The probe driving unit 31 controlled by the probe control unit 32 performs the X-axis direction (left-right direction) and Y-axis direction (depth). Direction) and Z axis direction (vertical direction) each move several millimeters. The positioning accuracy of the probe 30 is several micrometers.

  The operations of the charge detector 25, the charge measuring unit 26, and the probe voltage calculator 27 will be described later with reference to FIG.

  Although not shown in FIG. 1, the vacuum chamber 23 is provided with a deposition gas gun. The deposition gas gun has a tungsten carbide gas source whose temperature is controlled to about 60 ° C., a gas nozzle, a nozzle drive unit, and a control unit. When the target on the sample is irradiated with the gas from the deposition gas gun and the focused ion beam 9 of several tens of picoamperes is scanned there, the gas decomposes and reacts. As a result, a tungsten deposition film having a diameter of several micrometers can be formed in a few minutes.

  Hereinafter, a silicon wafer will be described as an example of the sample 20. A silicon wafer on which wiring, protective film formation, and the like are formed includes defects or defects such as adhesion of foreign matter and contact failure. The coordinate positions of these defective portions are detected in advance by an optical inspection device, an SEM inspection device, or the like. The sample stage 21 is positioned with an accuracy of about submicron by the sample stage control unit 37. Therefore, the sample stage 21 can be positioned on the order of several micrometers so that the focused ion beam 9 and the electron beam 22 intersect at the coordinate position of the defective portion detected by the inspection apparatus.

  A method for driving the probe 30 will be described with reference to FIG. FIG. 2 shows a state in which the microsample 40 is formed on the surface of the sample 20. A groove 43 having a depth of 5 micrometers is formed by sputtering by irradiating a focused ion beam 9 around a rectangle including a defective portion having a long side of 10 micrometers and a short side of 5 micrometers. The groove on the long side is formed to be inclined. Thereby, a microsample 40 having a wedge-shaped cross section is formed. Diagonal grooving is performed by inclining the sample stage 21. In this example, the sample stage 21 is inclined 45 °.

  Note that the lower end portion 42 of the micro sample 40 is still connected to the sample 20 only by forming the groove. Therefore, it is necessary to completely separate the microsample 40 from the sample. First, the probe 30 is brought close to the micro sample 40 and the tip thereof is brought into contact with the micro sample 40. Next, the tip of the probe 30 and the surface of the micro sample 40 are bonded together by generating a tungsten deposition film. Finally, the lower end portion 42 of the micro sample 40 is cut off. A method of transporting the microsample 40 thus separated to a high-resolution STEM or TEM sample stage will be described later with reference to FIG.

  When the tip of the probe 30 is brought into contact with the microsample 40, if the driving speed of the probe 30 is high, the probe 30 cannot be stopped at a desired position due to the inertial force of the probe 30. The tip of the probe 30 collides with the microsample 40, and the probe 30 and the microsample 40 are damaged. Therefore, as described below, it is necessary to accurately detect when the probe 30 approaches and contacts the microsample 40 and control the movement of the probe 30 based on the detection.

  A measurement area 41 of several micrometers angle is set on the surface of the micro sample 40. The electrification detector 25 detects energy of secondary electrons and reflected electrons generated when the focused ion beam 9 scans the measurement region 41 through an energy filter.

  The charge measuring unit 26 obtains the charged potential of the measurement region 41 from the detection signal from the charge detector 25. The probe voltage calculator 27 calculates an optimum probe voltage value based on the charged potential and sends the calculation result to the probe voltage control unit 28. The probe voltage control unit 28 generates a probe voltage based on the probe voltage value from the probe voltage calculator 27 and applies it to the probe 30. The operation of the probe voltage calculator 27 will be described with reference to FIG.

  As a method for measuring the charged potential of the micro sample 40, in addition to the method described here, a method using a surface potentiometer using electrostatic induction, a light beam is irradiated on the electro-optic crystal, and its polarization, phase, refraction There is a method of measuring the charging potential by changing the rate.

  With reference to FIG. 3, the operation of the probe voltage calculator 27 of the analyzer according to the present invention will be described. FIG. 3 shows the relationship between the charging potential in the measurement region 41 and the probe voltage value. The horizontal axis represents the charging potential, and the vertical axis represents the probe voltage value. FIG. 3A shows a case where the probe voltage is continuously changed by a linear expression, and FIG. 3B shows a case where the applied voltage is changed stepwise. As described above, the charging potential of the measurement region 41 is measured by the charge measuring unit 26. When the charged potential in the measurement region 41 is obtained, the probe voltage calculator 27 calculates the probe voltage value using the graph of FIG.

  According to the present invention, a negative voltage is applied to the probe 30. When the absolute value of the charging potential is small, the negative probe voltage value is decreased, and when the absolute value of the charging potential is large, the negative probe voltage value is increased. In this way, by applying a negative voltage to the probe 30 and increasing the negative voltage value applied to the probe 30 when the absolute value of the charging potential is large, the change in the brightness of the SIM image becomes significant, and the probe 30 Although it is possible to accurately detect when the micro sample 40 is approached and contacted, details will be described below.

  FIG. 4 is a schematic diagram of a SIM image of a part of the sample 40 including the microsample 40 when the sample 20 is positively charged. The processing groove 43 is formed around the microsample 40 as shown in FIG. 2, but is omitted here in order to avoid complication of the drawing. As shown in FIG. 1, since the FIB apparatus 7 is arranged so that the optical axis is perpendicular to the sample 20, the SIM image appears as an image obtained by observing the surface of the sample 20 from vertically above.

  4A to 4D are screens 500 showing SIM images when the probe 30 is brought close to the microsample 40 when the probe voltage is 0 and FIGS. 4E to 4H are when the probe voltage is −2V. 4A and 4E, a part of the image 530 of the probe 30 appears. In the SIM images of FIGS. 4B and 4F, the tip of the image 530 of the probe 30 becomes an image 540 of the microsample 40. You are approaching. 4C and 4G, the tip of the image 530 of the probe 30 is at the center of the screen 500.

  As shown, probe shadow images 545 appear on either side of the probe 30 image 530. When the probe 30 approaches the sample 20 and the distance between the two becomes smaller than several tens of micrometers, a shadow image 545 appears. In this shadow image 545, secondary electrons and reflected electrons emitted from the region behind the probe 30 when viewed from the electron detection unit 35 are blocked by the probe 30, and are prevented from reaching the electron detection unit 35. Further, in this region, since the positive electric field by the electron detection unit 35 does not reach, it is difficult for secondary electrons, reflected electrons, etc. emitted from this region to reach the electron detection unit 35. The shadow image 545 of the probe increases with the image of the probe 30. The probe shadow image 545 approaches the measurement region image 541, overlaps the measurement region image 541, and is separated from the measurement region image 541.

  The SIM images in FIG. 4D and FIG. 4H show a state where the tip of the probe 30 is in contact with the microsample 40. In the SIM image of FIG. 4D, since the charged electrons on the surface of the sample 20 flow to the probe 30, the SIM image becomes bright overall. The shadow image 545 of the probe is also small but small.

  FIG. 5 shows a change in the brightness of the SIM image in the measurement region 41 of the microsample 40 when the sample 20 is positively charged. The vertical axis represents the luminance of the SIM image in the measurement region 41, and the horizontal axis represents time. A curve 51 in FIG. 5A corresponds to FIGS. 4A to 4D and shows a change in luminance when the probe voltage is 0, and a curve 52 in FIG. 5B corresponds to FIGS. 4E to 4H and the probe voltage is −2V. The change of the brightness | luminance in the case of is shown. The method of measuring luminance is known and will not be described in detail here.

  In the SIM images shown in FIGS. 4A and 4B and FIGS. 4E and 4F, the luminance does not change. This is because the probe 30 and the microsample 40 are sufficiently separated from each other, and the shadow image 545 of the probe does not enter the measurement region 41. In the SIM images shown in FIG. 4C and FIG. 4G, the distance between the probe 30 and the microsample 40 approaches, and the shadow image 545 of the probe enters the measurement region 41, so the luminance decreases. In the SIM images shown in FIG. 4D and FIG. 4H, the shadow image 545 of the probe contained in the measurement area 41 is small, and the luminance of the entire screen 500 is high, so that the luminance in the measurement area 41 is high.

  In order to contact the microsample 40 without damaging the probe 30, it is necessary to stop or decelerate the probe 30 at a position a predetermined distance before the position where the tip of the probe 30 contacts the microsample 40. If the probe 30 is stopped or decelerated immediately before the tip of the probe 30 contacts the microsample 40, the planned stop position is shifted due to the inertial force of the probe 30, and the probe 30 collides with the microsample 40.

  As shown by the curve 51 in FIG. 5A and the curve 52 in FIG. 5B, the luminance becomes the minimum value immediately before t2 when the tip of the probe 30 contacts the microsample 40. Therefore, when the luminance value becomes smaller than the predetermined threshold value, it can be determined that the tip of the probe 30 is a position that is a predetermined distance before the position where the tip of the probe 30 contacts the microsample 40.

  As is apparent from a comparison between the curve 51 in FIG. 5A and the curve 52 in FIG. 5B, when the tip of the probe 30 approaches the microsample 40, when the probe voltage is 0, the decrease in luminance is gradual. When the voltage is −2 V, the decrease in luminance is abrupt. In the case of the curve 51 in FIG. 5A, since the slope of the curve 51 is gentle, it is difficult to set the threshold value so that it can be detected that the tip of the probe 30 has reached a desired position. In the case of the curve 52 in FIG. 5B, since the slope of the curve 52 is steep, it is easy to set the threshold value so that it can be detected that the tip of the probe 30 has reached a desired position.

  Therefore, in this example, as shown in FIG. 5B, by setting a predetermined threshold, it is possible to detect a time t1 that is a predetermined time before t2 immediately before the tip of the probe 30 contacts the microsample 40. .

  FIG. 6 is a schematic diagram of an SEM image of a part of the sample 40 including the microsample 40 when the sample 20 is negatively charged. The processing groove 43 is formed around the microsample 40 as shown in FIG. 2, but is omitted here in order to avoid complication of the drawing. Since the SEM apparatus 18 shown in FIG. 1 is arranged so that the optical axis is inclined to the sample 20, the SEM image should appear as a three-dimensional image observed from the direction in which the surface of the sample 20 is inclined. However, here, for convenience of explanation, the SEM apparatus 18 is arranged so that the optical axis is perpendicular to the sample 20 and is shown as a planar image observed from a direction perpendicular to the surface of the sample 20.

  6A to 6D are screens 600 showing SEM images when the probe 30 is brought close to the micro sample 40 when the probe voltage is 0 and FIGS. 6E to 6H are when the probe voltage is −2V. 6A and 6E, a part of the image 630 of the probe 30 appears. In the SEM images of FIGS. 6B and 6F, the tip of the image 630 of the probe 30 becomes an image 640 of the microsample 40. You are approaching. 6C and 6G, the tip of the image 630 of the probe 30 is at the center of the screen 600.

  As shown, probe shadow images 645 appear on either side of the probe 30 image 630. The shadow image 645 of the probe increases with the image of the probe 30. The probe shadow image 645 approaches the measurement region image 641, overlaps the measurement region image 641, and is separated from the measurement region image 641.

  The SEM images in FIG. 6D and FIG. 6H show a state in which the tip of the probe 30 is in contact with the microsample 40. Since the charged electrons on the surface of the sample 20 flow to the probe 30, the SEM image becomes bright overall. The probe shadow image 645 is also small but small.

  In the case of this example, as compared with FIG. 4, when the tip of the probe 30 is not in contact with the microsample 40, the overall brightness of the screen showing the SEM image is high. Other than that is the same as FIG.

  FIG. 7 shows a change in luminance of the SEM image in the measurement region 41 of the micro sample 40 when the sample 20 is negatively charged. The vertical axis represents the luminance of the SEM image in the measurement region 41, and the horizontal axis represents time. A curve 53 in FIG. 7A corresponds to FIGS. 6A to 6D and shows a change in luminance when the probe voltage is 0, and a curve 54 in FIG. 7B corresponds to FIGS. 6E to 6H and the probe voltage is −2V. The change of the brightness | luminance in the case of is shown.

When the sample 20 is SiO ₂ , the sample 20 is negatively charged by irradiation with the electron beam 22 and generates a negative electric field on the sample surface. Secondary electrons emitted from the sample 20 gain energy by a negative electric field and are pushed out to the opposite side of the sample. Accordingly, the amount of secondary electrons emitted increases. For this reason, the SEM image is generally bright.

  In the SEM images shown in FIGS. 6A and 6B and FIGS. 6E and 6F, since the shadow image 645 of the probe does not enter the measurement region 41, the luminance does not change. In the SEM images shown in FIGS. 6C and 6G, since the shadow image 645 of the probe enters the measurement region 41, the luminance decreases. In the SEM images shown in FIGS. 6D and 6H, the shadow image 645 of the probe contained in the measurement region 41 is small and the luminance of the entire screen 600 is high, so that the luminance in the measurement region 41 is high.

  As shown by the curve 53 in FIG. 7A and the curve 54 in FIG. 7B, the luminance reaches the minimum value immediately before t2 when the tip of the probe 30 contacts the microsample 40. Therefore, when the luminance value becomes smaller than the predetermined threshold value, it can be determined that the tip of the probe 30 is a position that is a predetermined distance before the position where the tip of the probe 30 contacts the microsample 40.

  As is clear from comparison between the curve 53 in FIG. 7A and the curve 54 in FIG. 7B, when the tip of the probe 30 approaches the microsample 40, when the probe voltage is 0, the decrease in luminance is gradual. When the voltage is −2 V, the decrease in luminance is abrupt. In the case of the curve 53 in FIG. 7A, since the slope of the curve 53 is gentle, it is difficult to set the threshold value so that it can be detected that the tip of the probe 30 has reached a desired position. In the case of the curve 54 in FIG. 7B, since the slope of the curve 54 is steep, it is easy to set the threshold value so that it can be detected that the tip of the probe 30 has reached the desired position.

  Therefore, in this example, as shown in FIG. 7B, by setting a predetermined threshold, it is possible to detect a time t1 that is a predetermined time before t2 immediately before the tip of the probe 30 contacts the microsample 40. .

  The voltage applied to the probe 30 will be described with reference to FIG. Here, as shown in FIG. 3, the reason for applying a negative voltage to the probe 30 and the reason for increasing the negative voltage of the probe when the absolute value of the charged potential on the surface of the sample 20 increases will be described.

  First, the reason for applying a negative voltage to the probe 30 will be described. 8A shows a case where the surface of the sample 20 is positively charged, and FIG. 8B shows a case where the surface of the sample 20 is negatively charged. The probe 30 is connected to a power source 82 that can be changed to several tens of volts through a resistance 81 of 1 megaohm. A positive or negative electric field is formed by a positive or negative voltage applied to the probe 30.

  A positive electric field is generated by the electron detector 35. A dotted line 83 represents an equipotential surface showing a positive electric field. The current value of the focused ion beam 9 is 10 pA, and the magnification is 3000 times. The secondary electrons 85, 86 and 87 emitted from the sample 20 by irradiation of the focused ion beam 9 have a predetermined energy width, and the average value thereof is, for example, several electron volts.

  When the distance between the probe 30 and the sample 20 is larger than several hundred micrometers, the electric field of the probe 30 does not affect the secondary electrons 85, 86, 87 emitted from the sample 20. Therefore, this is the same as when the probe voltage is 0V. The secondary electrons 85, 86 and 87 emitted from the sample 20 are captured by the positive electric field by the electron detector 35 without being disturbed by the probe 30.

  When the probe 30 approaches the sample 20, the electric field of the probe 30 affects the secondary electrons 85, 86, 87 emitted from the sample 20.

  As shown in the figure, when a negative voltage is applied to the probe 30 to form a negative electric field, a part 87 of the secondary electrons 85, 86, 87 is moved to the sample 20 side by the negative electric field of the probe 30. Pushed back. The positive electric field generated by the electron detector 35 is blocked by the probe 30 and cannot capture a part 87 of the secondary electrons 85, 86, 87 emitted from the sample 20.

  Therefore, secondary electrons detected by the electron detector 35 are reduced, the SIM image becomes dark as a whole, and the luminance of the probe shadow image 545 is lowered. Thus, by applying a negative voltage to the probe 30, the amount of change in the luminance of the measurement region 41 is increased, and the approach of the probe 30 can be reliably recognized.

  When a positive voltage is applied to the probe 30 to form a positive electric field, the secondary electrons 85, 86, 87 are drawn out by the positive electric field of the probe 30 and supplemented by the positive electric field from the electron detector 35. Therefore, even if the tip of the probe 30 is brought close to the microsample 40, the amount of change in the luminance of the measurement region 41 does not increase, and it is difficult to reliably recognize the approach of the probe 30.

  Although the case where the sample 20 is positively charged has been described here, the above discussion holds true even when the sample 20 is negatively charged as shown in FIG. 8B.

  Next, the reason why the negative voltage of the probe is increased when the absolute value of the charged potential on the surface of the sample 20 is increased will be described. When the charged potential on the surface of the sample 20 is increased, the influence of the negative electric field of the probe 30 is relatively reduced. Therefore, the amount of change in the brightness of the measurement region 41 is reduced, and it is difficult to reliably recognize the approach of the probe 30. In this case, the negative voltage value applied to the probe 30 may be increased. Thereby, the influence of the negative electric field of the probe 30 is increased, and the amount of change in the luminance of the measurement region 41 is increased. Thereby, the approach of the probe 30 can be reliably recognized.

  When the sample 20 is positively charged and the charged potential is high, secondary electrons that reach the electron detection unit 35 among the secondary electrons emitted from the sample 20 due to a positive electric field on the surface of the sample 20. The electron detector 35 mainly detects secondary electrons having relatively high energy. Therefore, the SIM image becomes dark overall. In this case, an operation for increasing the contrast of the SIM image and brightening the entire SIM image is performed. Therefore, in this case as well, the negative probe voltage may be increased. As a result, when the probe 30 approaches the sample 20, secondary electrons are pulled back toward the sample 20, and the amount of change in luminance due to the probe approach increases.

  When the sample 20 is negatively charged, as described above, the secondary electrons emitted from the sample 20 obtain energy by the negative electric field generated by the sample 20, so that the amount of secondary electrons emitted is also large. To increase. However, when the charging potential is high, the amount of change in luminance due to the probe approach is small, so the negative voltage value applied to the probe 30 needs to be increased.

  The procedure for automatically bringing the probe 30 into contact with the microsample 40 will be described with reference to FIGS. FIG. 9 is a flowchart of a procedure for bringing the probe 30 into contact with the microsample 40.

  In step S1, the SIM image before the probe 30 contacts the sample, the SIM image after the contact, and the SIM image of the probe tip are registered in the central control unit 38. If these SIM images are imaged under the same conditions as when the microsampling operation is actually performed automatically, that is, with the same beam current and the same magnification, probe control becomes easy.

  FIG. 10A shows a SIM image 511 before the probe 30 contacts the sample. The SIM image 511 includes an image 540 of the micro sample 40, an image 543 of the surrounding groove 43, and an image 520 of the sample 20 outside the micro sample 40. FIG. 10B shows the SIM image 512 after the probe 30 contacts the sample. When the probe 30 comes into contact with the sample, the charged charge of the sample 20 flows to the probe 30, so that the luminance of the SIM image 512 is higher than the luminance of the SIM image 511.

  Instead of the SIM image 512 after the probe 30 contacts the sample, a SIM image immediately before the probe 30 contacts the sample may be registered. In this case, the brightness of the entire SIM image is low, but it is sufficient that there is sufficient contrast between the probe and the ground so that the position of the probe tip can be sufficiently recognized. In order to increase the contrast between the probe and the ground, the negative voltage value of the probe 30 may be increased.

  Since the probe 30 is initially in the retracted position, it does not appear in the SIM image. When the probe 30 is sufficiently close to the sample 20, an image of the probe 30 appears in the SIM image. FIG. 10C shows a SIM image 513 in which an image 530 of the tip of the probe 30 appears.

  In step S 2, the defective portion is moved to the irradiation region of the focused ion beam 9, that is, the intersection of the sample 20 and the focused ion beam 9. A coordinate value of a defective portion such as a foreign matter or a contact failure detected by an optical inspection device, an SEM type inspection device or the like is positioned on the order of several micrometers using a coordinate system linkage with the FIB device and the SEM device.

  In step S3, the irradiation conditions of the focused ion beam 9 are determined, and the focused ion beam 9 is irradiated. Irradiation conditions include beam current, irradiation area, scanning period, irradiation interval, beam stay time, and the like. The focused ion beam 9 is applied to the observation region including the microsample 40.

  In step S4, the charged potential in the measurement region 41 set on the micro sample 40 is measured.

  In step S5, it is determined whether or not the charging potential of the measurement region 41 is 0 V (earth potential). If the charging potential of the measurement region 41 is 0V, the probe voltage is set to 0V in step S6. If the charging potential of the measurement region 41 is not 0 V, that is, if it is positively or negatively charged, a predetermined negative potential v1 is applied to the probe in step S7.

  In step S8, it is determined whether the position of the tip of the probe can be recognized. If the image cannot be recognized, the negative voltage value of the probe is increased in step S9, and the process returns to step S8 again to determine whether or not the tip position of the probe can be recognized. Thus, the negative voltage value of the probe is increased until the position of the tip of the probe can be recognized.

  FIG. 11A shows a SIM image when the probe voltage is 0V, and FIG. 11B shows a SIM image when the probe voltage is −5V. When the probe is moved by automatic control, the position of the tip of the probe is detected by image recognition. As shown in FIG. 11A, when it is difficult to recognize the position of the tip of the probe when the probe voltage is 0 V, the probe voltage is set to −5 V as shown in FIG. The contrast with the sample 20 including the micro sample 40 is increased, and the position of the tip of the probe can be recognized.

  When the tip position of the probe can be detected by image recognition, the tip of the probe 30 is brought close to the microsample 40 in step S10. The tip of the probe 30 of the SIM image 515 shown in FIG. 11B is compared with the image 531 of the tip of the probe 30 in the registered SIM image 512 shown in FIG. 10B. By comparison, a deviation between the positions of the tips of the probes 30 in both images is detected, and based on this deviation, the position of the probe 30 is corrected, and the probe 30 is brought closer to the micro sample 40.

  In step S11, the probe negative potential is returned to the original value v1. In step S12, the luminance of the measurement area is measured. In step S13, it is determined whether or not the luminance of the measurement region is smaller than the threshold value 1. When the luminance of the measurement area is not smaller than the threshold value 1, the process returns to step S8. When the luminance of the measurement area becomes smaller than the threshold value 1, the process proceeds to step S14, and the probe driving speed is decelerated.

  In step S15, it is determined whether an image of the position of the tip of the probe can be recognized while the probe is moving. The position of the tip of the probe is detected by image recognition while the probe is moving. However, when the base has a complicated shape, it is difficult to distinguish the contour of the tip of the probe from the pattern of the base shape. If the image cannot be recognized, the negative voltage value of the probe is increased in step S16, and the process returns to step S15 again to determine whether the tip position of the probe can be recognized. Thus, the negative voltage value of the probe is increased until the position of the tip of the probe can be recognized.

  When the tip position of the probe can be detected by image recognition, the tip of the probe 30 is brought close to the microsample 40 in step S17. Step S17 is the same as step S10.

  In step S18, the probe negative potential is returned to the original value v1. In step S19, the luminance of the measurement area is measured. In step S20, it is determined whether or not the brightness of the measurement region has suddenly increased. Step S20 is repeated until the brightness of the measurement area increases rapidly. When the brightness of the measurement region suddenly increases, the process proceeds to step S21, and the probe driving speed is set to zero. Thereby, the tip of the probe comes into contact with the microsample 40 in step S22.

  In this example, the probe drive speed was 300 micrometers / second until step S13, but was 20 micrometers / second in step S14. That is, the probe driving speed was reduced to 1/15. Accordingly, when the probe driving speed is set to zero in step S21, the probe is prevented from biting into the surface of the microsample 40 due to inertia. Therefore, the tip of the probe and the surface of the micro sample 40 can be prevented from being damaged.

  With reference to FIG. 12, a method of mounting the microsample 40 on a high-resolution STEM or TEM sample stage 48 will be described. The sample stage 48 is formed of a molybdenum mesh, and has a width of 500 micrometers, a diameter of 4 mm, and a semicircular shape.

  The micro sample 40 is connected to the probe 30. That is, the micro sample 40 is connected to the probe 30 by a tungsten deposition film 44 having a 1 μm square and a thickness of 0.5 μm. By placing the micro sample 40 on the sample stage 48 and cutting the tungsten deposition film 44, the micro sample 40 is separated from the probe 30 and mounted on the sample stage 48.

  Although not shown, the sample stage 48 has a protrusion for mounting the sample stage 48 on the cartridge. Therefore, the sample stage 48 can be arranged and fixed to the cartridge with tweezers. The cartridge has a cylindrical shape with a diameter of about 8 mm and a length of about 40 mm. The cartridge has a rotation mechanism and can move the microsample 40 mounted on the sample stage 48 at right angles to the focused ion beam 9 and the electron beam 22. In addition, it is possible to perform elemental analysis in a minute region from X-rays emitted by accelerating an electron beam 22 of several hundred picoamperes at a high voltage and irradiating the microsample 40. The cartridge is mounted on the sample holder. When the wafer is taken out, the cartridge is detached from the wafer holder by a cartridge carrying system different from the wafer carrying system and taken out of the apparatus. The cartridge is mounted on a common cartridge holder, and the micro sample 40 is made thin by the FIB apparatus, and high resolution analysis and analysis are performed by STEM and TEM.

  In order to bring the micro sample 40 close to the sample stage 48 and arrange it on the sample stage 48, the same method as the operation of bringing the tip of the probe 30 close to the surface of the sample 40 and bringing it into contact with the sample 40 is used. it can. A measurement area 49 is set on the sample stage 48, and the luminance in the measurement area 49 is measured. When the sample stage 48 is positively or negatively charged, even if the microsample 40 is brought close to the sample stage 48, the luminance change in the measurement region 49 is small, and it is difficult to detect the approach. Therefore, the charged state of the measurement region 49 is monitored, and the negative potential applied to the probe 30 is changed according to the potential. Thereby, the change in luminance due to the approach of the microsample is increased, and it is possible to detect that the microsample 40 has approached the sample stage 48 and has made contact therewith. Therefore, even if the micro sample 40 is brought close to the high speed, the micro sample 40 can be arranged on the sample stage 48 without colliding with the sample stage 48.

  Since the microsample 40 is connected to the probe 30 via the tungsten deposition film 44, the same potential can be applied to the microsample 40 and the probe 30.

  FIG. 13 shows an example of a screen displayed on the monitor 39. On the screen, a charging potential monitor value 60, a probe voltage value monitor value 62, a luminance monitor value 62, a luminance change graph 63, a display mode 64 indicating a beam mode, a beam current value, etc., probe coordinates, sample table coordinates in the measurement area A display unit 65 such as a screen contrast, a brightness monitor value, an adjustment bar, a display unit 66 indicating navigation of a graphics user interface, and a screen 500 displaying a SIM image are displayed. In the image 500, as shown in FIG. 10, a probe image 530, a microsample image 540, a groove image 543, and a measurement region image 541 are displayed.

  The example of the present invention has been described above, but the present invention is not limited to the above-described example, and various modifications can be made by those skilled in the art within the scope of the invention described in the claims. It will be understood.

It is a figure which shows one example of the analyzer by this invention. It is a figure for demonstrating the moving method of a probe. It is a figure which shows the relationship between the charging potential in the measurement area | region of the surface of a micro sample, and a probe voltage. It is a figure which shows a SIM image when a sample is positively charged. It is a figure which shows the luminance change when the sample is positively charged. It is a figure which shows the SEM image in case a sample is negatively charged. It is a figure which shows the luminance change when the sample is negatively charged. It is a figure for demonstrating the reason for applying a negative voltage to a probe, when the sample is electrically charged. It is a figure explaining the procedure which makes a probe approach and contact a sample by automatic control. When a probe is brought into contact with a sample by automatic control, SIMs registered in advance are diagrams for explaining examples of images. It is a figure explaining the contrast of a SIM image changing with the applied voltage of a probe. It is a figure for demonstrating the method to arrange the cut-out micro sample on a sample stand It is a figure explaining the example of the screen of a monitor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Ion source, 2 ... Extraction electrode, 3 ... Condenser lens, 4 ... Diaphragm, 5 ... Deflection coil, 6 ... Objective lens, 7 ... Focused ion beam apparatus (FIB apparatus), 8 ... Focused ion beam control part, 9 ... Focused ion beam, 10 ... electronic chip, 11 ... anode, 12 ... focusing lens, 13 ... stop, 14 ... deflection coil, 15 ... ExB, 16 ... secondary electron detector, 17 ... objective lens, 18 ... scanning type Electron microscope device (SEM device), 19 ... Electron beam control unit, 20 ... Sample, 21 ... Sample stage, 22 ... Electron beam, 23 ... Vacuum chamber, 25 ... Charge detector, 26 ... Charge measurement unit, 27 ... Probe voltage Arithmetic unit, 28 ... probe voltage control unit, 30 ... probe, 31 ... probe drive unit, 32 ... probe control unit, 35 ... electron detection unit, 36 ... detection electron analysis unit, 37 ... sample stage control unit, 38 ... center 39: monitor, 40 ... micro sample, 41 ... measurement area, 42 ... lower end, 43 ... groove, 44 ... tungsten deposit film, 48 ... sample stage, 49 ... measurement area, 60 ... charged potential monitor value, 61 ... probe voltage monitor value, 62 ... luminance monitor value, 63 ... luminance change monitor diagram, 64, 65, 66 ... parameter display units, 81 ... resistance, 82 ... variable power supply, 83 ... equipotential surface

Claims (11)

A charged particle beam unit for irradiating the sample with a charged particle beam;
An electron detector for detecting electrons emitted from the irradiation region of the charged particle beam;
An image processing unit for obtaining an image of a sample based on a detection signal from the electron detection unit;
A probe capable of moving relative to the sample and applying a negative voltage;
A charge measuring unit for detecting the charged state of the sample;
Based on the charging state detected by the charging measurement unit, it has a control unit for setting a negative voltage value to the probe,
The control unit increases the negative voltage value applied to the probe when the absolute value of the charged potential of the sample is large, and the negative voltage value applied to the probe when the absolute value of the charged potential is small. Reduce the
The analysis device characterized in that the control unit sets a negative voltage value to be applied to the probe based on a table indicating a relationship between the charged potential of the sample and a negative voltage value to be applied to the probe. . The analysis device according to claim 1,
An absolute value of a negative voltage value applied to the probe is 5 V or less. The analysis device according to claim 1,
The image processing unit is configured to detect the position of the tip of the probe by performing image processing on the image of the sample, and when the position of the tip of the probe cannot be detected by the image processing, An analysis apparatus, wherein the control unit increases a negative voltage value applied to a probe. The analysis device according to claim 1,
An analysis apparatus, comprising: a control mechanism for automatically bringing a microsample connected to the probe into contact with a sample stage when the microsample is physically connected to the probe. The analysis device according to claim 1,
A monitor for displaying the image of the sample is provided, and the control unit displays on the display screen of the monitor the image of the sample, the charged state of the sample, the negative voltage value applied to the probe, and the luminance of the sample. An analysis apparatus for displaying at least one of a value and a graph showing a change in luminance of the sample when the probe is approaching the sample. A charged particle beam unit for irradiating the sample with a charged particle beam;
An electron detector for detecting electrons emitted from the irradiation region of the charged particle beam;
An image processing unit for obtaining an image of a sample based on a detection signal from the electron detection unit;
A probe capable of moving relative to the sample and applying a negative voltage;
A charge measuring unit for detecting the charged state of the sample;
A control unit that sets a negative voltage value to the probe based on the charged state detected by the charge measuring unit;
The image processing unit includes an image of a sample before the probe contacts the sample and an image of the sample after the probe contacts the sample, and an image of the sample while the probe is moving , by comparing the image of the sample stored in the image processing unit detects the position of the tip of the probe,
The control unit increases the negative voltage value applied to the probe when the absolute value of the charged potential of the sample is large, and the negative voltage value applied to the probe when the absolute value of the charged potential is small. Reduce the
The analysis system characterized in that the control unit sets a negative voltage value to be applied to the probe based on a table indicating a relationship between the charged potential of the sample and a negative voltage value to be applied to the probe. . A charged particle beam unit that irradiates a sample with a charged particle beam, an electron detection unit that detects electrons emitted from an irradiation region of the charged particle beam, and an image that obtains an image of the sample based on a detection signal from the electron detection unit Based on the processing unit, a probe that can move relative to the sample and can apply a negative voltage, a charge measuring unit that detects a charged state in the sample, and a charged state detected by the charged measuring unit In the control method of the probe in the analyzer having a control unit for setting a negative voltage value to the probe,
The control unit applies a negative initial voltage to the probe when it is determined that the sample is positively or negatively charged based on the charged state;
Measuring the brightness of the sample;
Reducing the relative movement speed of the probe with respect to the observation target when the luminance of the sample becomes smaller than a predetermined value;
Stopping the relative movement of the probe when the brightness of the sample further decreases and then increases abruptly;
The control unit increases the negative voltage value applied to the probe when the absolute value of the charged potential of the sample is large, and the negative voltage value applied to the probe when the absolute value of the charged potential is small. Reducing the
The control unit sets a negative voltage value to be applied to the probe based on a table indicating a relationship between the charged potential of the sample and a negative voltage value to be applied to the probe;
A method for controlling a probe including: The probe control method according to claim 7 ,
The control unit increases a negative initial voltage value applied to the probe when the absolute value of the charging voltage of the sample is large, and negative initial voltage applied to the probe when the absolute value of the charging voltage of the sample is small. A method for controlling a probe, wherein the value is reduced. The probe control method according to claim 7 ,
The control unit sets the probe voltage to a ground voltage when the sample is not charged. The probe control method according to claim 7 ,
The controller detects a negative voltage value to be applied to the probe when it is difficult to detect the position of the probe tip by image recognition during movement of the probe and to detect the position of the probe tip. And a method for controlling the probe, the method including increasing from an initial voltage. The control method of claim 10, wherein the probe,
The control unit returns the negative voltage value applied to the probe to the initial voltage when the position of the tip of the probe can be detected by increasing the negative voltage value applied to the probe. A probe control method characterized by the above.

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