JP2010272586A - Charged particle beam device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charged particle beam device capable of accurately determining a state of conductivity of a sample with an insulating film to a ground even when a single contact pin is used. <P>SOLUTION: A surface electrometer 40 is arranged several millimeters above the sample 20 to measure a surface potential of the sample 20. The sample 20 is moved with respect to the surface electrometer 40 in a horizontal direction to measure a surface potential distribution of the sample 20. When the sample 20 and a contact pin 3 are not conductive to each other, the potential observed on a surface of the sample 20 has an uneven potential distribution. When the sample 20 and the contact pin 3 are conductive to each other, on the other hand, a potential shift value greatly decreases. A surface potential shift of the sample 20 is determined to determine whether the sample 20 and the contact pin 3 are conductive to each other. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a charged particle beam apparatus that performs defect observation, analysis, and the like, which cause defective electrical characteristics, in addition to shape defects and foreign matters such as semiconductor devices.

  Along with the high integration and high performance of semiconductor devices, the miniaturization of electronic circuit pattern processing technology has progressed, and the introduction of new manufacturing processes and new materials has been accelerated. Also, in order to improve device yield with short TAT (Turn Around Time), in addition to shape defects and foreign materials that occur during the manufacturing process of semiconductor devices, electrical characteristics such as poor contact holes and plug conduction and short wiring Technology that detects defects that become defects early and provides quick feedback to optimization of process conditions has become important.

  In order to meet this requirement, there are charged particle beam devices such as an SEM type inspection device (defect detection) using an electron beam and a review SEM device (defect observation, classification).

  In the semiconductor manufacturing process, the surface of a sample such as a wafer is often covered with an insulator such as a silicon oxide film or a silicon nitride film in order to prevent cross contamination. When the sample is irradiated with an electron beam using the above-mentioned device, the surface potential of the wafer rises as the electrons accumulate because the surface is covered with an insulating film if conduction with the earth is insufficient. Cause focus shift and image drift. The above charging phenomenon occurs in the same way also in the polarization of resist molecules due to friction during resist coating, and in an etching apparatus using plasma.

  As a solution to these problems, when using a mechanical holding method, two reference pins are provided on the outer periphery of the sample, the sample is held by the pressing force of the movable pin from the opposite direction, and the contact force between the sample and the movable pin Thus, there is a method in which the insulating film on the surface of the sample is destroyed and the sample is brought into contact with the reference pin which is electrically connected to the ground to release the accumulated charge on the insulating film.

  Further, a contact pin having one protrusion is inserted into the sample from the front or back surface of the sample, the insulating film is broken, the contact pin and the sample are brought into direct electrical contact, and the sample is connected to the ground. At this time, as for the contact condition between the contact pin and the sample, a voltage is applied to the contact pin, and the resistance value of the contact pin is monitored. Such an apparatus is disclosed in Patent Document 1.

  An example in which two or more contact pins are inserted into a sample, a voltage is applied between the two or more pins, a current value flowing between them is measured, and it is determined that the contact pin and the sample are conductive at a certain threshold value or more. There is.

  Using an electrostatic chuck as the sample stage, applying a voltage to the bipolar electrode in the initial stage of adsorption, and applying a voltage between the contact pin and one of the electrodes after adsorption eliminates the bias of charge during adsorption. An apparatus for performing accurate machining is disclosed in Patent Document 2.

  Furthermore, Patent Document 3 discloses an apparatus that is composed of a bipolar electrostatic chuck and a contact pin from the back of the sample, applies a potential between the bipolar electrode and the contact pin, and flows residual charges on the insulating film on the sample surface to ground. It is disclosed.

JP 2004-71786 A JP-A-5-177479 JP 2004-31840 A

  However, the techniques described in Patent Documents 1 to 3 have the following problems.

  When two contact pins are used, there is a problem that the possibility of contamination is increased and the yield reduction rate of semiconductor manufacturing is increased compared to the case where one contact pin is used due to the breakdown of the insulating film on the sample. . This becomes a more significant problem when three or more contact pins are used.

  Even if the two contact pins break the insulating film and are in contact with the sample, the contact resistance value changes depending on the contact condition between the contact pin and the sample.

  For this reason, the current I represented by the following formula (1) changes.

I = V / (Ra + Rb + Rc) (1)
In the above formula (1), V is an applied voltage between two contact pins, Ra is a contact resistance value between one contact pin and a sample, and Rb is an in-sample resistance value (insulating film resistance value >> sample) Rc is the contact resistance value between the other contact pin and the sample.

  The energization current value also changes depending on the material (electric resistance value, etc.) and shape of the sample and the insulating film. Therefore, when it is determined that conduction has occurred from a comparison with a certain threshold value, the determination accuracy may be reduced for various samples.

  When the electron beam is irradiated in a state where the contact is insufficient and not conductive, defects such as focus shift and beam drift may occur due to charging on the surface of the insulating film as described above.

  When the sample is held by an electrostatic chuck composed of an internal electrode, a dielectric layer, and a metal plate, when the insulating film is completely destroyed by the contact pin and is electrically connected to the internal electrode, the current I flowing through the contact pin is In a steady state, the internal resistance value of the power source that supplies current to the contact pins is ignored, and is roughly expressed by the following equation (2).

I = V / (Ra1 + Ra2 + Rb + Rc) (2)
In the above equation (2), V is a voltage applied between the contact pin and the electrostatic chuck internal electrode by the power source, Ra1 is a resistance value between the dielectric layers between the internal electrode and the electrostatic chuck surface, and Ra2 is an upper surface of the electrostatic chuck. The contact resistance value between the sample insulating films and the resistance value of the insulating film, Rb is the resistance value in the sample (in the case of the insulating film resistance value >> the sample resistance value), and Rc is the contact resistance value of the contact pin.

  As described above, the contact resistance value is the contact surface state and contact surface pressure, and the insulation film and sample resistance values are the insulation film, sample physical property values (electrical resistance value, etc.), shape (thickness, etc.), etc. It is greatly influenced by.

  Therefore, the energization current value varies greatly depending on the contact state of the contact pin, the sample film type, the film thickness, and the like, and it is not reliable to determine whether or not the conduction is made at the threshold value.

  An object of the present invention is to realize a charged particle beam apparatus that can accurately determine the state of conduction of a sample with an insulating film to the ground even when a single contact pin is used.

  In order to solve the above problems, the present invention is configured as follows.

  The charged particle beam apparatus according to the present invention includes a sample holder that holds a sample, a sample holder moving unit, a processing optical system that focuses and irradiates the sample with charged particles, and a sample that contacts the ground. A control terminal for controlling the operation of the sample holder moving means and the processing optical system, and a surface electrometer for measuring the potential of the surface of the sample with respect to the ground.

  The control unit moves the sample holder moving means, moves the sample with respect to the surface potential measuring instrument, measures the distribution of the surface potential of the sample, and based on the measured surface potential distribution of the sample Then, it is determined whether or not the contact terminal is in contact with the sample.

  According to the present invention, it is possible to realize a charged particle beam apparatus that can accurately determine the state of conduction between a sample with an insulating film and the ground even when a single contact pin is used.

1 is an overall configuration diagram of a charged particle beam apparatus to which Embodiment 1 of the present invention is applied. It is a figure which shows the structure which measures the sample surface potential in Example 1 of this invention. It is a figure which shows the moving mechanism for measuring the sample surface potential distribution in Example 1 of this invention. It is a figure which shows the measurement result of the sample surface potential in Example 1 of this invention. It is a modification of Example 1 of this invention, and is a figure which shows the example from which the structure of an internal electrode differs. It is a top view of the sample holder which hold | maintains a sample mechanically in Example 1 of this invention. It is a figure which shows schematic structure of the sample holding mechanism shown in FIG. It is a schematic sectional drawing of the sample holding mechanism shown in FIG. It is explanatory drawing of Example 2 of this invention, and is a figure which shows the relationship between the retarding voltage and the charging voltage of a sample. It is explanatory drawing of the sample electrification measurement of Example 3 of this invention. It is a figure which shows the measurement result for description of Example 3 of this invention. It is a figure which shows the contact pin raising / lowering mechanism of the mechanical chuck type | mold sample holder in the Example of this invention. It is a figure which shows the apparatus operation screen in the Example of this invention. It is an example different from the present invention and is a diagram showing a comparative example with the present invention. It is a different example from this invention, and is a figure which shows the other comparative example with this invention.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a schematic configuration diagram of a scanning electron microscope apparatus (SEM) to which an embodiment of the present invention is applied. In FIG. 1, there is a mount 12 composed of a spring and an attenuator on a gantry 11 installed on the floor. The mount 12 absorbs the vibration of the floor and supports the sample chamber 13.

  A load lock chamber 15 including a transfer robot 14 for transferring a sample is connected to the sample chamber 13. The sample is carried into a load lock chamber 15 in which the sample 20 such as a wafer is brought into an atmospheric pressure state from a FOUP (Front Opening Unified Pod) by a load port, a miniene, an atmospheric transfer robot or the like (not shown).

  Thereafter, evacuation of the load lock chamber 15 is performed by an exhaust system (not shown). When a predetermined pressure value is reached, a gate valve (not shown) is opened, and the sample 20 is removed from the sample holder by an elevating mechanism (not shown). 21.

  The sample holder 21 is fixed to the stage 22. A bar mirror 23 is mounted on the stage 22, and the position management of the sample 20 on the sample holder 21 is managed by measuring a relative distance change with the interferometer 24 attached to the sample chamber 13 with the laser beam 25. Do.

  The position of the stage 22 is feedback position controlled by a control unit 70 and a stage moving mechanism 71 not shown in FIG. 1 so that there is no deviation between the current position and the target position.

  The sample chamber 13 is evacuated to a high vacuum by an evacuation system 30 constituted by a turbo molecular pump, a dry pump, or the like. In addition, an SEM column 32 that emits an electron beam 31 is mounted in the sample chamber 13. The electron beam 31 generated by the electron source 33 in the column 32 is focused by the primary focusing lens 34, and only the central electron beam of the beam 31 is taken out by the diaphragm 35. Further, the electron beam is focused by the secondary focusing lens 36 and is incident on the objective lens 19.

  The magnetic field generated by the objective lens coil 27 increases the magnetic field density by the magnetic path 26. The electron beam 31 is focused by this strong magnetic field and irradiated on the sample 20. In the first embodiment of the present invention, a Schottky emission electron source having excellent probe current stability is used as the electron source 33.

  The secondary electrons 42 emitted from the sample are bent by an E × B separator (orthogonal electromagnetic field deflector) 39, focused by the electric field of the electron detector 38, and incident on a scintillator (not shown). The secondary electrons are converted into photoelectrons by a scintillator, and the current value is increased by photoelectron multiplication not shown. This information is transmitted to the image control unit (not shown) together with the position control information of the deflector 37, and is displayed as an image on the monitor.

  The objective lens 19 includes an objective lens coil 27 and a booster electrode 29 connected to the magnetic path 26 through the magnetic path 26 and the insulator 28. By applying an arbitrary positive and negative potential to the booster electrode 29, the movement of the secondary electrons 42 can be controlled, and the surface potential of the sample 20 can be controlled.

  The sample chamber 13 has a Z sensor for measuring a sample height (not shown). The optical condition of the SEM is changed based on this information, and control is performed so as to always focus on the surface of the sample 20.

  A surface potential meter 40 is mounted in the sample chamber 13. The sample and the tip of the surface electrometer 40 are brought close to about several millimeters, and the electrode inside the surface electrometer 40 and the sample are capacitively coupled. The charged potential of the sample is obtained by taking out a displacement current signal due to capacitive coupling of the internal electrode of the surface potentiometer 40.

  The operation of each device is controlled by a control unit 70 described later. The control unit 70 includes a processing unit (microprocessor and the like) that performs various processing operations, a recording unit (HDD, ROM, RAM, and the like) that stores processing programs and processing results, and an input unit that inputs commands to the processing unit. (Keyboard etc.) and a display unit (monitor etc.) for displaying various processing results. And the said control part 70 is connected with various power supplies, and controls each of these power supplies etc. suitably using a process part.

  FIG. 2 is a schematic cross-sectional view of sample surface potential measurement according to an embodiment of the present invention. In FIG. 2, the contact pin (contact terminal) 3 is disposed in a hole formed in the internal electrode 7, the dielectric layer 8 and the metal plate 9. A potential V1 is applied between the contact pin 3 and the internal electrode 7 in the electrostatic chuck 10 by the power source 4a. The electric current 5 flows through the internal electrode 7, the dielectric layer 8, the insulating film 1, the sample 2, and the power source 4b to the ground by the potential V1.

  The electrostatic chuck 10 has a structure in which the internal electrode 7 is disposed in the dielectric layer 8. Since the surface of the electrostatic chuck 10 adsorbs an object to be adsorbed such as a silicon wafer, it has a smooth adsorbing surface. In order to reduce the number of foreign matters generated when the electrostatic chuck 10 and the sample 20 come into contact with each other, it is necessary to reduce the contact rate between the electrostatic chuck 10 and the sample 20. For this reason, dots are generally formed on the surface of the electrostatic chuck 10.

  The sample 20 is adsorbed by an electric force generated by positive and negative charges generated by polarization in the dielectric layer 8 and the insulating film 1. The internal electrode 7 in this case is composed of a single electrode and is called a monopolar electrode. The contact pin 3 is driven by a cylinder or the like (not shown) and is pressed in a direction that destroys the insulating film 1. When the contact pin 3 completely destroys the insulating film 1 and the contact pin 3 and the sample 2 are in contact, the surface potential is almost the same as the variable voltage V2 applied by the power source 4b. The variable voltage V <b> 2 is also applied to the metal plate 9 of the electrostatic chuck 10.

  The variable voltage V2 is called a retarding voltage. In the case of SEM, a negative voltage is generally applied.

  By applying a negative voltage to the sample 20, the energy of the electron beam 31 incident on the sample 20 can be reduced, damage to the sample 20 and charging can be reduced, and the objective lens 19 can be irradiated with the electron beam 31 with high energy. Can be incident. Therefore, it is possible to reduce chromatic aberration and the like and obtain a good image with high resolution.

  For example, −3 kV is applied to the electron source 33 and −2.2 kV is applied to the sample 20. The electron beam 31 is incident on the objective lens 19 at 3 keV with respect to the ground, but can be incident on the sample 20 with a low energy of 0.8 keV which is the difference between 3 kV and 2.2 kV.

  A surface potential meter 40 is arranged on the upstream side of the electron beam 31 of the sample 20 at several millimeters, and the surface potential of the sample 20 is measured. The surface electrometer 40 has a lifting mechanism, and when the potential measurement is not performed, the surface electrometer 40 is raised and moved away from the sample 20 in order to prevent interference with the moving sample holder 21. Yes. In the figure, the surface electrometer 40 is arranged on the upper surface with respect to the sample 20, but it can also be arranged on the lower surface of the sample 20 if it can be made compact.

  FIG. 3 is a diagram showing a configuration for measuring the surface potential from the end (peripheral portion) to the end of the sample 20 through the central portion of the sample 20 with the surface potentiometer 40. In FIG. 3, the stage moving mechanism 71 moves the sample 20 in the horizontal direction with respect to the surface electrometer 40 by moving the stage 22 in the horizontal direction in accordance with a control command of the control unit 70. The surface potential of the sample 20 is measured by the surface potential meter 40 as the sample 20 moves in the horizontal direction. The surface potential measured by the surface potential meter 40 is transmitted to the control unit 70.

  FIG. 4 shows a measured voltage distribution obtained by measuring the surface potential at a plurality of points with the surface potentiometer 40 when the sample 20 and the contact pin 3 are conductive. FIG. 4 shows a characteristic example.

  When the sample 20 and the contact pin 3 are non-conductive, the potential observed on the surface of the sample 20 is not V2 due to the internal resistance value of the insulating film 1 between the contact pin 3 and the sample 20. Further, the sample surface has a non-uniform potential distribution.

  According to the experimental results, as shown in FIG. 4, when V2 = −1.2 kV and in the non-conductive state, the value varies depending on the film type and thickness of the insulating film 1, but from several tens of volts to several hundreds of volts. A potential shift was observed. In the case of non-conduction, non-uniformity of several tens to several hundreds V was observed in the wafer radial direction.

  On the other hand, when the sample 20 and the contact pin 3 are electrically connected, the potential shift value is remarkably reduced, and there is only a potential shift of about several volts to several tens of volts at the maximum. Was also significantly reduced compared to non-conduction.

  In this way, the potential from end to end passing through the surface of the sample is measured, and the control unit 70 determines the potential shift to correctly determine whether the sample 20 and the contact pin 3 are electrically connected or not. Is possible.

  In addition, a display can be provided and the surface potential of the sample 20 shown in FIG. 4 can be displayed on the display. Then, the control unit 70 determines whether or not the surface potential shift exceeds a certain value (for example, the shift potential is 40 V), and if it exceeds the certain value, an alarm display can be performed.

  FIG. 5 shows a case where a bipolar electrostatic chuck 10 having two internal electrodes 7a and 7b is used as the electrostatic chuck 10 instead of the unipolar internal electrode 7 shown in FIG. The two internal electrodes 7a and 7b may be two electrodes facing each other in the horizontal direction with the contact pin 3 interposed therebetween. The two internal electrodes 7a and 7b are formed in a comb shape on the sides facing each other, the comb teeth are alternately arranged, and the two electrodes facing each other in the horizontal direction with the contact pin 3 in between. It may be.

  Positive and negative voltages V1a and V1b are applied to the bipolar electrodes 7a and 7b by the power sources 4a and 4c with respect to the retarding voltage V2 by the power source 4b. A surface potential meter 40 is arranged above the sample 20 and the surface potential of the sample 20 from end to end is measured in the same manner as described above.

  FIG. 6 is a schematic view of the sample holder 21 mechanically holding and fixing the sample 20 as viewed from above. In FIG. 6, the sample holder 21 holds the sample 20. A hole 49 is formed in the sample holder 21 so that the movable pin 48 can move in the direction of the arrow 53.

  On the upper surface of the sample holder 21, there are three or more sample support bases 46 made of conductive resin. Further, the sample holder 21 has two or more fixed pins 47 and one or more movable pins 48. The fixed pin 47 is in contact with the outer peripheral surface of the sample 20 and positioning is performed. The outer periphery of the sample 20 is fixed at three points by the movement of the movable pin 48, and final positioning is performed.

  FIG. 7 is a diagram showing a schematic diagram of a moving structure of the movable pin 48. This moving structure is fixed to the back surface of the sample holder 21, that is, the surface opposite to the surface on which the sample is arranged. There is a bellows 51 in the moving structure. When the periphery of the bellows 51 is evacuated, the length of the bellows 51 extends in the major axis direction due to the pressure of the gas enclosed in the bellows 51, and the plate 49 to which the movable pin 48 is fixed is rotated around the shaft 52.

  Conversely, when the surroundings of the bellows 51 become atmospheric pressure, the bellows 51 contracts in the axial direction, and the movable pin 48 rotates in a direction opposite to the direction in which the bellows 51 contracts. The plate 49 moves (rotates) in the direction of the arrow 53 when the surroundings change to vacuum and air.

  The above is not the case where the vacuum transfer robot 14 is mounted in the load lock chamber 15 as shown in FIG. 1, but instead of the vacuum transfer robot 14, the sample holder 21 is placed between the sample chamber 13 and the load lock chamber 15. It can be used when a transfer unit is used.

  That is, the sample holder 21 in the sample chamber 13 is moved to the load lock chamber 15 using the transfer unit. Thereafter, the load lock chamber 15 is opened to the atmosphere, and the wafer is mounted on the sample holder 21 by an atmospheric transfer robot, a lift pin or the like. Thereafter, the load lock chamber 15 is evacuated by an exhaust system. Thereby, the sample 20 is fixed by the fixed pin 47 and the movable pin 48 on the sample holder 21 as described above. In this state, the sample holder 21 is transferred to the sample chamber 13 and irradiated with an electron beam 31 to perform predetermined observation, analysis, and the like. When unloading the wafer, reverse the operation. When such a bellows is not used, it is necessary to drive the movable pin 48 by another means.

  FIG. 8 is a diagram showing a cross section of FIG. In FIG. 8, the contact pin 3 is accommodated in the sample holder 21, and the insulating film 1 is pierced and brought into contact with the sample 2 by the lifting and lowering operation of the contact pin 3. Whether or not the contact pin 3 and the sample 2 are in contact with each other is measured by a surface potential meter 40 disposed on the upper surface of the sample 20.

  As described above, according to Example 1 of the present invention, the surface potential of the sample 2 is measured from the end to the end on the diameter of the surface of the sample 2, and whether the measured potential distribution is within a certain range. It is determined whether or not the sample and the contact pin (terminal) are conducted.

  Therefore, it can be reliably determined whether or not the sample and the contact pin are electrically connected.

  That is, even when the surface potential of only a specific part of the sample is measured and within a certain potential range, the sample and the contact pin may not be electrically connected to each other as shown in FIG. If the surface potential distribution of the sample is measured and the conduction / non-conduction is determined as in Example 1, it can be reliably determined whether or not the sample and the contact pin are conductive.

  In addition, it is possible to reliably conduct the sample with the insulating film to the ground, and it is possible to prevent problems such as image drift and focus shift at the time of beam irradiation.

  Next, a second embodiment of the present invention will be described.

  As means for determining whether or not the electrical continuity between the contact pin 3 and the sample 20 is sufficient, there is a method other than directly measuring the surface potential of the sample as described above. This method is described below.

  Example 2 of the present invention is an example in which when the sample 20 is irradiated with the electron beam 31, the current value of the objective lens 19 to be focused, the applied voltage of the booster electrode 29, or the shift amount of the retarding voltage V2 is measured. It is.

  When the contact pin 3 and the sample 20 are non-conductive, residual charges are generated on the surface of the sample 20 due to the electron beam irradiation to the sample 20, and a charged potential is generated. For this reason, the energization current value of the objective lens 19 during focusing, the applied voltage of the booster electrode 29 during focusing, and the retarding voltage V2 are shifted.

  FIG. 9 is a graph showing a result obtained by experimentally obtaining the relationship between the charging voltage of the sample and the retarding voltage V2 at the time of focusing under a certain SEM optical condition. Since the relationship between the retarding voltage and the sample charging voltage is as shown in FIG. 9, the charging voltage of the sample can be calculated by measuring the shift amount of the retarding voltage. It can be determined whether or not the sample 20 is in contact. Although not shown, the second embodiment of the present invention includes a measuring means for the retarding voltage V2, and the control unit 70 calculates the shift amount of the retarding voltage measured by the retarding voltage measuring means. Is done.

  As described above, according to the second embodiment of the present invention, the energization current value of the objective lens 19 to be focused, the applied voltage of the booster electrode 29, or the shift amount of the retarding voltage due to the electron beam irradiation on the sample 2 is measured. Since the charging voltage of the sample is calculated and it is determined whether or not the contact pin 3 and the sample 2 are electrically connected, it is possible to reliably determine whether the contact pin 3 and the sample 2 are electrically connected or not. it can.

  Here, the focus operation of the SEM does not change the energization current value of the objective lens coil, but the focus operation can be performed at high speed by changing the retarding voltage applied to the sample. It is known that when an electromagnetic coil is used, it has a magnetic field hysteresis, but an operation for removing this hysteresis is necessary, and it is difficult to focus at a high speed due to the required time.

  When the retarding voltage to be focused is different from the retarding voltage when the sample is not charged, it is determined that the contact pin 3 and the sample 20 are not conducting, and the raising and lowering operation of the contact pin 3 is repeated to achieve conduction. Like that.

  In order to determine whether or not the contact between the contact pin 3 and the sample 20 is sufficient, another method for measuring the sample charge is a method using an energy filter.

  Embodiment 3 of the present invention is an example using this energy filter.

  A mesh (energy filter) to which a predetermined potential is applied on the upstream side of the sample 20 is disposed. Secondary electrons having energy smaller than the potential applied to the mesh are pushed back by this electric field and cannot reach the electron detector 38. The amount of secondary electrons reaching the electron detector 38 can be controlled by changing the potential applied to the mesh.

  When the voltage applied to the mesh is taken on the horizontal axis and the signal amount detected by the electron detector 38 is taken on the vertical axis, when the voltage applied to the mesh is made smaller than a certain value, the amount of secondary electrons detected by the electron detector 38 is Decreases rapidly.

  FIG. 10 is a diagram showing an example in which an energy filter 55 is added and arranged on the upstream side of the sample 20 instead of the surface potentiometer 40 having the configuration of the example shown in FIG. In FIG. 10, the energy filter 55 is configured to be able to apply a positive / negative variable voltage V <b> 3 by a variable voltage power source 56. The secondary electrons 42 that have passed through the energy filter 55 are detected by the electron detector 38.

  FIG. 11 is a graph showing the relationship between the applied voltage V3 and the value of the current flowing through the electron detector 38 (proportional to the number of incident electrons) when the sample 20 is positively or negatively charged.

  In FIG. 11, when the sample (wafer) 20 is positively charged (broken line), the number of electrons incident on the detector 38 is decreased by charging the sample as compared to when the charge is 0 (solid line). As a result, the current value flowing through the detector 38 decreases.

  On the other hand, when the sample 20 is negatively charged (broken line), the number of electrons incident on the electron detector 38 is increased and the current value is increased as compared with the case where the charge is zero.

  When the sample 20 is positively charged, the voltage V3 applied to the energy filter 55 is increased by ΔV3 as shown in FIG. 11 in order to obtain the same current value as the potential = 0 (when not charged). This drift amount ΔV3 corresponds to the sample charging potential.

  Since the charging of the sample 20 can be known by the above method, if there is a drift amount ΔV3 that is equal to or greater than a certain determination value, the control unit 70 determines that the continuity is insufficient and makes contact with the contact pin 3 again.

  As described above, also in the third embodiment of the present invention, it can be reliably determined whether or not the sample and the contact pin are electrically connected.

  Next, the raising / lowering mechanism of the contact pin 3 is described. In addition, the raising / lowering mechanism of the contact pin 3 demonstrated below is common in Examples 1-3.

  FIG. 12 is a view showing an elevating mechanism of the contact pin 3. In FIG. 12, the contact pin 3 is moved up and down using a cylinder 56. The cylinder 56 shown in FIG. 12 is of a type that operates with compressed air 57. The pressure value of the compressed air 57 is adjusted by a regulator 58. The compressed air 57 is supplied from a suitable pump (not shown).

  If the sample 1 and the contact pin 3 are not in contact even if the contact pin 3 is moved up and down a specified number of times, the pressure value of the compressed air 57 is increased by the regulator 58. The command to the regulator 58 is performed by the control unit 70 of the scanning electron microscope apparatus. The cylinder 56 may be an electric drive type. In the example shown in FIG. 12, the sample holder 21 shows an example in which the sample 20 is held by a mechanical method, but the electrostatic chuck method described above can also be used.

  FIG. 13 is a diagram showing a display device (not shown) operation screen 60 provided in the scanning electron microscope apparatus according to the first to third embodiments of the present invention. In FIG. 13, a lower display portion of the operation screen 60 includes a control screen 61 such as a stage controller, an image controller, and a manual controller.

  In the example shown in FIG. 13, a stage controller screen 62 and an image control screen 63 are displayed. The image control screen 63 displays a setting unit 65 for displaying information such as the magnification and scan speed of the SEM image 64 and a selection screen 66 for selecting a beam acceleration voltage and mode.

  When the contact between the contact pin 3 and the sample 2 is insufficient (non-conduction), an alarm display screen 67 is displayed. The alarm display screen 67 displays "Contact is repeated because of insufficient contact. Please wait for a while." If the contact is insufficient, the alarm message “Contact failure. Replace the contact pin or contact a service person.” Is displayed.

  Next, a comparative example for comparison with the present invention, which is an example different from the present invention, will be described.

  FIG. 14 is a diagram illustrating a first comparative example. When two contact pins 3a and 3b are used as in the example of FIG. 14, the possibility of contamination is increased compared to the case where one contact pin is used due to the breakdown of the insulating film 1 on the sample 2. The yield reduction rate of semiconductor manufacturing increases. This becomes a more significant problem when three or more contact pins are used.

  Even if the two contact pins break the insulating film and are in contact with the sample, the contact resistance value changes depending on the contact condition between the contact pin and the sample.

  FIG. 15 is a diagram illustrating a second comparative example. In the example shown in FIG. 15, when the sample 2 is held by the electrostatic chuck 10 composed of the internal electrode 7, the dielectric layer 8, and the metal plate 9, the insulating film 1 is broken by one contact pin 3, and the internal electrode FIG.

  However, as described above, the contact resistance value is the contact surface state and the contact surface pressure, and the insulation film and sample resistance values are the insulation film, physical property values (electrical resistance value, etc.) and shape (thickness, etc.) of the sample. ) And so on.

  Therefore, the energization current value varies greatly depending on the contact state of the contact pin 3, the sample film type, the film thickness, etc., and it is not reliable to determine whether or not it is conducting at the threshold value.

  In contrast, according to the present invention, since the potential distribution of the sample is measured by the surface potentiometer to determine whether the contact pin and the sample are conductive or nonconductive, it is possible to accurately determine whether or not they are conductive. . In addition, whether or not the contact pin and the sample are electrically connected or not determined by the secondary electron detected by the secondary electron detector 38 using the amount of shift of the retarding voltage or the energy filter is accurately determined as to whether or not it is conductive. Can be judged.

  In addition, although the example mentioned above is an example at the time of applying this invention to a scanning electron microscope apparatus, this invention is not only a scanning electron microscope apparatus but the example using a surface electrometer is a charged particle beam apparatus. It is also established as a sample residual charge discharge device.

  DESCRIPTION OF SYMBOLS 1 ... Insulating film, 2 ... Sample, 3a, 3b ... Contact pin, 4a, 4b ... Power supply, 7, 7a, 7b ... Internal electrode, 8 ... Dielectric, 9. ··· Metal plate, 10 ... Electrostatic chuck, 11 ... Mount, 12 ... Mount, 13 ... Sample chamber, 14 ... Vacuum transfer robot, 15 ... Load lock chamber, 19 ..Objective lens 20 ... Sample 21 ... Sample holder 22 ... Stage 23 ... Bar mirror 24 ... Interferometer 25 ... Laser beam 26 ... Magnetic path 27 ... Objective lens coil, 28 ... Insulator, 29 ... Booster electrode, 30 ... Exhaust system, 31 ... Electron beam, 32 ... Column, 33 ... Electron source, 34 ... primary focusing lens, 35 ... aperture, 3 ... Secondary focusing lens, 37 ... Polarizing coil, 38 ... Electron detector, 39 ... ExB separator, 40 ... Surface electrometer, 46 ... Sample support, 47・ ・ ・ Fixed pin, 48 ・ ・ ・ movable pin, 49 ・ ・ ・ hole, 51 ・ ・ ・ bellows, 52 ・ ・ ・ rotation shaft, 55 ・ ・ ・ energy filter, 56 ・ ・ ・ variable voltage power source, 57 ・..Compressed air, 58 ... Regulator, 60 ... Operation screen, 61 ... Control screen, 62 ... Stage control screen, 63 ... Image control screen, 64 ... SEM image, 65. ..Setting unit 66 ... Selection screen 67 ... Alarm screen 70 ... Control unit 71 ... Stage moving mechanism

Claims (24)

A sample holder for holding the sample; a sample holder moving means; a processing optical system for focusing and irradiating the sample with charged particles; a contact terminal for contacting the sample and conducting the sample and ground; and the sample holder In a charged particle beam apparatus having a moving unit and a control unit that controls the operation of the processing optical system,
A surface potentiometer that measures the potential of the surface of the sample with respect to the ground is provided.
The control unit moves the sample holder moving means, moves the sample with respect to the surface potential measuring instrument, measures the distribution of the surface potential of the sample, and determines the surface potential distribution of the measured sample. A charged particle beam device characterized by determining whether or not the contact terminal is in contact with the sample.   The charged particle beam apparatus according to claim 1, further comprising moving means for moving the contact terminal toward the sample in order to bring the contact terminal into contact with the sample, and the control unit includes the contact terminal on the sample. If it is determined that the contact terminal is not in contact, the moving means moves the contact terminal toward the sample, and moves toward the contact terminal sample until it is determined that the contact terminal has contacted the sample. A charged particle beam device characterized by repeatedly moving all of them.   2. The charged particle beam apparatus according to claim 1, further comprising contact force increasing means for increasing a contact force between the contact terminal and the sample, wherein the control unit determines that the contact terminal is not in contact with the sample. In this case, the charged particle beam device is characterized in that the contact force increasing means increases the contact force of the contact terminal to the sample.   3. The charged particle beam apparatus according to claim 2, further comprising an alarm output unit, wherein the control unit causes the alarm output unit to detect when the contact terminal has repeatedly moved toward the sample a predetermined number of times. A charged particle beam device characterized by outputting a warning.   5. The charged particle beam apparatus according to claim 4, wherein the alarm output means is a screen display means.   The charged particle beam apparatus according to claim 1, wherein the sample holder has a plurality of pins that mechanically support the sample.   The charged particle beam apparatus according to claim 1, wherein the sample holder is an electrostatic chuck that holds the sample by an electric attraction force.   8. The charged particle beam apparatus according to claim 7, wherein the electrostatic chuck includes a dielectric layer and a monopolar or bipolar electrode disposed in the dielectric layer. A sample holder for holding the sample, an objective lens for focusing and irradiating the sample with charged particles, a contact terminal for contacting the sample and conducting the sample and the ground, and a control unit for controlling the operation of the objective lens In a charged particle beam device having
The objective lens includes an objective lens coil and a booster electrode, and the control unit includes a shift amount of a current value of the objective lens coil, a shift amount of a voltage applied to the booster electrode, or the contact terminal and ground. The amount of retarding voltage applied during the calculation is calculated, the surface potential of the sample is calculated based on any of the calculated shift amounts, and the contact terminal is calculated based on the calculated surface potential of the sample. It is judged whether it contacted the said sample, The charged particle beam apparatus characterized by the above-mentioned.   10. The charged particle beam apparatus according to claim 9, further comprising moving means for moving the contact terminal toward the sample in order to bring the contact terminal into contact with the sample, and the control unit includes the contact terminal on the sample. If it is determined that the contact terminal is not in contact, the moving means moves the contact terminal toward the sample, and moves toward the contact terminal sample until it is determined that the contact terminal has contacted the sample. A charged particle beam device characterized by repeatedly moving all of them.   The charged particle beam device according to claim 9, further comprising contact force increasing means for increasing a contact force between the contact terminal and the sample, wherein the control unit determines that the contact terminal is not in contact with the sample. In this case, the charged particle beam device is characterized in that the contact force increasing means increases the contact force of the contact terminal to the sample.   11. The charged particle beam apparatus according to claim 10, further comprising an alarm output unit, wherein the control unit causes the alarm output unit to detect when the contact terminal has repeatedly moved toward the sample a predetermined number of times. A charged particle beam device characterized by outputting a warning.   13. The charged particle beam apparatus according to claim 12, wherein the alarm output means is a screen display means.   The charged particle beam apparatus according to claim 9, wherein the sample holder includes a plurality of pins that mechanically support the sample.   10. The charged particle beam apparatus according to claim 9, wherein the sample holder is an electrostatic chuck that holds the sample by an electrical attraction force.   16. The charged particle beam apparatus according to claim 15, wherein the electrostatic chuck includes a dielectric layer and a monopolar or bipolar electrode disposed in the dielectric layer. A sample holder for holding the sample, a processing optical system for focusing and irradiating the sample with charged particles, an electron detector for detecting secondary electrons emitted from the sample, and contacting the sample and conducting the sample and ground In a charged particle beam apparatus having a contact terminal for controlling and a control unit for controlling the operation of the processing optical system,
An energy filter that is disposed between the sample and the electron detector and is applied with a voltage is provided, and the control unit includes a voltage applied to the energy filter and a number of secondary electrons detected by the electron detector. The surface voltage of the sample is calculated from the shift amount of the relationship, the surface potential of the sample is calculated based on the calculated shift amount, and whether the contact terminal contacts the sample based on the calculated surface potential of the sample A charged particle beam device characterized by determining whether or not.   18. The charged particle beam apparatus according to claim 17, further comprising moving means for moving the contact terminal toward the sample in order to bring the contact terminal into contact with the sample, and the control unit includes the contact terminal on the sample. If it is determined that the contact terminal is not in contact, the moving means moves the contact terminal toward the sample, and moves toward the contact terminal sample until it is determined that the contact terminal has contacted the sample. A charged particle beam device characterized by repeatedly moving all of them.   The charged particle beam apparatus according to claim 17, further comprising contact force increasing means for increasing a contact force between the contact terminal and the sample, wherein the control unit determines that the contact terminal is not in contact with the sample. In this case, the charged particle beam device is characterized in that the contact force increasing means increases the contact force of the contact terminal to the sample.   19. The charged particle beam apparatus according to claim 18, further comprising an alarm output unit, wherein the control unit causes the alarm output unit to detect when the contact terminal has repeatedly moved toward the sample a predetermined number of times. A charged particle beam device characterized by outputting a warning.   21. The charged particle beam apparatus according to claim 20, wherein the alarm output means is a screen display means.   The charged particle beam apparatus according to claim 17, wherein the sample holder has a plurality of pins that mechanically support the sample.   The charged particle beam apparatus according to claim 17, wherein the sample holder is an electrostatic chuck that holds the sample by an electric attraction force.   24. The charged particle beam apparatus according to claim 23, wherein the electrostatic chuck includes a dielectric layer and a monopolar or bipolar electrode disposed in the dielectric layer.

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