JP4537194B2 - Charged particle beam equipment - Google Patents

Description

  The present invention relates to a charged particle beam apparatus having a function of processing or observing a sample using a charged particle beam and a sample stage on which the sample is mounted.

  As the charged particle beam apparatus, there is an apparatus for processing a sample using a scanning electron microscope (SEM) or a focused ion beam (FIB) and observing the processed surface. The SEM focuses an electron beam emitted from an electron source at an acceleration voltage V0 (negative voltage) using an electromagnetic or electrostatic lens, scans the surface of the sample, detects secondary electrons generated from the sample, and detects the SEM. It is an apparatus that acquires images and observes the structure of the sample surface.

  In addition, the FIB apparatus focuses an ion beam emitted from a gallium (Ga) ion source at an acceleration voltage V0 (positive voltage) and scans and irradiates the sample surface, thereby causing the sample to be sputtered by ions. Is a device for processing. The FIB apparatus is used for the purpose of creating a thin film sample for a transmission electron microscope (TEM) or a scanning transmission electron microscope (STEM).

  By using the FIB, a thin film sample from a desired position of the device can be reliably produced in a short time. Regarding the TEM sample preparation method by FIB, it is described in Non-Patent Document 1 ["Transmission Electron Microscope Sample Preparation Using a Focused Ion Beam" (J. Electron Microsc. 43, 226-3 pp. 322-3 pp. 322-3). The FIB apparatus is also described in Patent Document 1 (Japanese Patent Laid-Open No. 6-168688).

“Transmission Electron Microscope Sample Preparation Using a Focused Ion Beam” (J. Electron Microsc. 43, pp.322-326, 1994). JP-A-6-168688

  In the FIB apparatus, the higher the acceleration voltage, the faster the processing speed and the narrower the beam diameter. However, the higher the acceleration voltage, the greater the depth and lateral extent of the portion where ions are implanted by FIB, thereby increasing the thickness of the damage layer formed in the vicinity of the FIB irradiated portion of the sample.

  As shown in FIG. 3A, when the processing with the focused ion beam is performed, ions are implanted into the surface of the sample 18 and a damaged layer 51 is formed. The width of the damaged layer 51 increases as the acceleration voltage V0 increases. For example, when a Ga ion beam is irradiated on a silicon substrate, the width of the damaged layer on the processed sidewall is about 15 nm when V0 = 30 kV. Become.

  For example, when the thin layer sample having a thickness of 60 nm is prepared as shown in FIG. 3B and the electron beam is irradiated from the direction shown in FIG. Half of this becomes a damaged layer, which hinders observation of the crystal structure inside the sample.

  Further, when the acceleration voltage is lowered, the thickness of the damaged layer is reduced. However, when the acceleration voltage is lowered, the beam focusing performance is deteriorated, the beam cannot be focused, the current is small, and processing takes time. For this reason, it can be considered that a deceleration voltage Vr is applied to the sample to reduce the irradiation energy (V0−Vr) to the sample.

  The technique of applying a voltage to a sample has been attempted with various charged particle beam apparatuses in order to obtain high beam focusing performance with low irradiation energy, as shown in Patent Document 1, for example.

  However, for example, in order to apply a voltage of several kV, in addition to the problem of the withstand voltage of the sample stage, the withstand voltage of the terminal for introducing the voltage from the atmosphere side to the sample chamber (in the vacuum) and the voltage power supply unit There are problems such as selection of wires from terminals to terminals and withstand voltage, and it was necessary to repeat withstand voltage tests to clear these problems. Further, the higher the applied voltage, the larger the voltage introduction terminal due to the problem of withstand voltage, and when miniaturizing the device, the size of the terminal is limited or the terminal becomes larger, so This vibration cannot be ignored when observing or processing the sample. In general, a thick high-voltage cable provided with a high-voltage insulation coating is hard, which is disadvantageous from the viewpoint of ensuring vibration resistance. As a result of these considerations, the sample stage has become large and expensive.

  In view of the above problems, an object of the present invention is to provide a charged particle beam device that does not require a high voltage cable and is advantageous in terms of vibration resistance.

  The present invention relates to a charged particle beam generation source that generates a charged particle beam, a processing sample stage on which a sample irradiated with the charged particle beam is placed, and a charged particle beam that applies an acceleration voltage to the charged particle beam generation source. A high-voltage power source for the generation source, and a deceleration unit that applies a deceleration voltage to the sample stage for processing to decelerate the irradiation speed of the charged particle beam that irradiates the sample. And a step-up power supply unit provided on a processing sample stage.

  According to the present invention, since the high-voltage deceleration voltage is generated by the boosting power supply unit provided on the low-voltage sample stage supplied from the low-voltage supply external power supply unit, a thick high-voltage cable with a high withstand voltage insulation coating is used. It is possible to provide a charged particle beam device that does not require a voltage cable and is advantageous in terms of vibration resistance.

  Examples according to embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows a schematic configuration diagram of an ion beam apparatus (FIB apparatus) included in a charged particle beam apparatus.

  The Ga ion beam extracted by the extraction electrode 2 from the liquid metal ion source 1 that is a charged particle beam generation source is accelerated by the acceleration voltage Vo, and is supplied from the focusing lens 3, the beam limiting diaphragm 4, the deflection electrode 5, the objective lens 6, and the like. The sample 18 is focused and deflected by an ion optical system to scan the sample 18.

  At this time, the secondary signal, which is secondary charged particles generated from the sample surface by beam irradiation, is detected by the secondary signal detector 9, amplified by the amplifier 10, and synchronized with the deflection control, thereby causing the data processing unit 11. Are displayed as SIM images on the image display device 12. A sample table 29 on which a sample 18 such as a semiconductor wafer is mounted is mounted on a mounting base 24 installed on the moving stage 21.

  An arbitrary position on the sample 18 can be observed and processed by moving the movable stage 21 movable in at least the X, Y, and Z directions.

  Conditions such as the acceleration voltage Vo, each lens including the focusing lens 3 and the objective lens 6, the voltage applied to the secondary signal detector 9, the voltage of the deflection voltage generator, and the beam limiting aperture 4 are stored in the data processing unit 11. The Then, depending on the respective conditions, a high voltage power source 13 for the charged particle beam generation source that generates the acceleration voltage Vo, a high voltage power source 14 for the extraction voltage that generates the extraction voltage Vext, and a high voltage for the focusing lens that is applied to the focusing lens 3. The control unit 10 that controls the voltage power supply 15, the objective lens high voltage power supply 17 applied to the objective lens 6, the secondary signal detector high voltage power supply 19 applied to the secondary signal detector 9, etc. A series of beam conditions used for processing and observation are automatically set.

  The moving stage 21, the mounting base 24, the sample base 29, the sample 18 and the like are placed in the sample chamber 20. An ion optical system including the liquid metal ion source 1, the focusing lens 3, the beam limiting aperture 4, the deflection electrode 5, the objective lens 6 and the like is installed in the lens barrel portion 60. The interior of the lens barrel 60 and the sample chamber 20 is kept in a vacuum. Since the lens barrel 60 and the sample chamber 20 communicate with each other, they have the same degree of vacuum.

  The sample stage 29 is provided with a boost power source unit 7 serving as a deceleration means. The boost power supply unit 7 has a booster circuit. The low-voltage supply external power supply unit 8 is provided outside the sample chamber 20. The decelerating means includes a boosting power supply unit 7 and a low-voltage supply external power supply unit 8.

  The external power supply unit 8 for supply has a low voltage supply circuit. The step-up power supply unit 7 is supplied with DC low-voltage supply power from the low-voltage supply external power supply unit 8. The step-up power supply unit 7 controlled by the low voltage Vref generates a high DC voltage.

  The voltage Vref is DC24V or DC24V or less. The power of the supplied low voltage Vref is boosted to a DC high voltage of about 10 KV to 30 KV by the boost power supply unit 7.

  The voltage Vref is controlled by selecting and using DC12, DC5V or the like as the voltage Vref.

  FIG. 2 shows a detailed view of the sample stage 29.

  A processing sample stage 29 on which the sample 18 to be processed by ion beam irradiation is placed includes a sample mounting part 34, a boosting power source mounting part 33, a sample base bottom plate part 31, a sample mounting part side insulating member 35, The boosting power source side insulating member 36, the boosting power source 7, a GND potential acquisition contact 38, a Vref voltage connection line 41, a deceleration voltage Vr connection line 42, and a GND potential connection line 43 are provided.

  The Vref voltage connection line 41 and the GND potential connection line 43 are on the input side of the booster circuit of the boost power supply unit 7. The deceleration voltage Vr connection line 42 is on the output side of the booster circuit. The input side is a low voltage of DC24V, and the output side is a DC high voltage of 10KV to 30KV.

  The sample base plate 31 and the boosting power source mounting portion 33 are separated by electrical insulation by the boost power source side insulating member 36 interposed between the sample base bottom plate portion 31 and the boosting power source mounting portion 33. The

  Further, the sample mounting portion 34 and the boosting power source mounting portion 33 are separated by insulation by the sample mounting portion side insulating member 35 interposed between the sample mounting portion 34 and the boosting power source mounting portion 33. For this reason, the step-up power supply unit mounting unit 33 is insulated from both the sample mounting unit 34 and the sample stage bottom plate unit 31.

  The sample base bottom plate portion 31, the boosting power source mounting portion 33, and the sample base bottom plate portion 31 are formed of a conductive metallic material. The GND potential connection line 43 is connected to the boosting power supply unit mounting unit 33, and the GND potential acquisition contact 38 contacts the boosting power supply unit mounting unit 33. Therefore, the GND side of the boosting power supply unit 7 is grounded. The The Vref voltage connection line 41 is connected to the sample stage bottom plate portion 31. That is, on the input side of the booster circuit, the Vref voltage connection line 41, which is one end on the plus side, is connected to the sample table bottom plate portion 31, and the GND potential connection line 43, which is the other end on the minus side, is mounted on the mounting portion for the boosting power supply unit. 33.

  On the output side of the booster circuit, a deceleration voltage Vr connection line 42 which is one end on the plus side is connected to the sample mounting portion 34, and the GND side which is the other end on the minus side is connected to the outer frame of the boost power supply unit 7. The boosting power source mounting unit 33 is connected via an outer frame.

  As shown in FIG. 5, the mounting base 24 on which the sample base bottom plate portion 31 of the sample base 29 is mounted is mounted on the moving stage 21 via the stage insulating material 25. The mounting base 24 is made of a metallic material having conductivity. The mounting base 24 is provided with a clamp 50, and this clamp 50 is also formed of a metallic material having conductivity.

  The clamp 50 holds a sample table 29 that is detachably mounted on the mounting base 24. The sample table bottom plate portion 31 of the sample table 29 has engaging portions 51 on both sides. The clamp 50 is hung on the engaging portion 51 to securely hold the sample table 29 on the mounting base 24.

  Since the clamp 50 is formed of a metallic material having conductivity, the mounting base 24 and the sample base bottom plate portion 31 are electrically connected via the clamp 50.

  The low pressure supply line 23 is wired to the sample chamber 20. One end of the low-pressure supply line 23 is connected to the mounting base 24, and the other end is connected to a connection terminal 22 that penetrates the sample chamber 20 and is provided outside the sample chamber 20. One end of the low-pressure supply circuit of the low-voltage supply external power supply unit 8 provided outside the sample chamber 20 is connected to the connection terminal 22 via another low-voltage supply line. The other end of the low voltage supply circuit is connected to ground.

  For this reason, the low-voltage supply circuit of the external power supply unit 8 for low-voltage supply is connected to the input side of the booster circuit of the boost power supply unit 7 through the low-voltage supply line 23, the clamp 50, the sample base bottom plate part 31, the Vref voltage connection line 41, and the like. Connected. As a result, DC 24V low-voltage power is supplied from the low-voltage supply external power supply unit 8 to the boost power supply unit 7.

  Since the other end of the low-pressure supply circuit is grounded, the low-voltage supply line 23 and the low-pressure supply line wired outside the sample chamber 20 can supply low-voltage power with a single line. When wiring without ground connection, two low-voltage supply lines are used.

  Since the low-voltage supply line 23 has a low voltage of 24 V or less, the insulation coating is thinner than the high voltage of 30 KV, and the thickness of the line is much thinner than that of 30 KV. For this reason, the low-voltage supply line 23 is rich in flexibility unlike a thick, hard high-voltage cable with a high withstand voltage insulation coating, causing vibration during the moving operation of the moving stage 21 or obstructing the moving operation. There is no trouble to become. In addition, the thin low-voltage supply line is less expensive than a thick, hard high-voltage cable provided with a high breakdown voltage insulation coating. Furthermore, the terminals at the connection portion can be made smaller and less expensive than those for high voltage. Further, the through hole of the sample chamber 20 through which the low-pressure supply line is drawn out only needs to be sealed against vacuum. Since it is not necessary to provide high voltage insulation, the cost is reduced.

  The step-up power supply unit 7 generates a deceleration voltage Vr based on the low-voltage power supplied via the low-voltage supply line 23, the clamp 50, the sample base plate 31, the Vref voltage connection line 41, and the like. To be applied to the sample mounting portion 34.

  Since the sample 18 is mounted in a state of being electrically connected to the sample mounting portion 34, the deceleration voltage Vr is applied to the sample 18. By applying the deceleration voltage Vr, the acceleration voltage Vo is lowered, so that the irradiation speed of the beam irradiating the sample 18 is reduced, and damage caused to the sample 18 is alleviated.

  FIG. 6 is a diagram showing the potential of each part in an easy-to-understand manner.

  The sample mounting portion 34 and the Vref voltage connection line 41 become the Vref potential, and the GND potential acquisition contact 38, the sample mounting portion 34, and the GND potential connection line 43 become the GND potential. The Vr connection line 42, the sample mounting portion 34, and the sample 18 become the deceleration voltage Vr potential formed by the boost power source unit 7.

  FIG. 4 shows a schematic diagram of ion beam current measurement.

  The processing sample stage 29 (shown in FIG. 5) is removed from the mounting base 24, and instead, the measurement sample stage 70 is taken out from the spare chamber 26 and replaced with the mounting base 24. The removed sample stage 29 is placed in the spare chamber 26 as shown in FIG.

  The measurement sample stage 70 has a sample mounting part 71 for mounting the sample 18 and a sample stage bottom plate part 72 for mounting on the mounting base 24. The sample stage bottom plate portion 72 has an engaging portion on which the clamp 50 is hung.

  An ion beam current measuring machine (not shown) is connected to the connection terminal 22 in place of the low-voltage supply external power supply unit 8. The low-pressure supply line 23 serves as a measurement signal extraction line.

  As described above, this ion beam apparatus can be easily replaced by changing the processing sample stage and the measurement sample stage, and changing the connection between the low voltage supply external power supply unit and the ion beam current measuring machine. .

  In this embodiment, three axes of X, Y, and Z are mounted. However, a configuration in which a rotation (R) axis and a tilt (T) axis of the sample are mounted is also possible.

  The moving stage 21 is in contact with the sample chamber (GND potential) through the base portion 30, and the potential is the GND potential. A mounting base 24 is installed on the moving stage 21, and the moving stage 21 and the mounting base 24 are electrically insulated using a stage insulating material 25.

  Here, it aims at measuring the ion beam current irradiated on the sample, and is connected to the connection terminal 22 via the low voltage supply line 23 (signal line). This is not intended to apply a potential to the sample 18, so that the withstand voltage of the connection terminal 22, the low-voltage supply line 23, and the stage insulating material 25 may be about several hundred volts, and an inexpensive commercially available terminal or A signal line can be used.

  The output from the connection terminal 22 is connected to the sample chamber 20 (GND potential) to prevent the sample 18 from being charged up by ion beam irradiation.

  The measurement sample stage 70 has a sample mounting part 71 for mounting the sample 18 and a sample stage bottom plate part 72 for mounting on the mounting base 24.

  The sample stage 70 that is normally used includes a sample mounting part 71 and a sample stage bottom plate part 72. In order to adjust the height from the bottom surface of the sample stage bottom plate portion 72 to the surface of the sample 18, the sample mounting portion 71 can be adjusted in the vertical direction. The sample base plate 72 to the sample 18 are in a state when they are electrically connected. The sample stage 70 is moved from the preliminary exhaust chamber 26 into the sample chamber 20. Except when the sample stage 70 is moved, the sample chamber 20 and the preliminary exhaust chamber 26 are shut off in vacuum by the gate valve 27.

  For example, in order to be able to apply Vr of the order of several kV to the mounting base 24 described here, the connection terminal 22 is replaced with a connector capable of applying a high voltage, and the low-voltage supply line 23 is also high in the order of several kV. In place of the cable corresponding to the voltage, it is necessary to modify the stage insulating material 25 and the like so as to cope with the application of the high voltage. In addition, cables for applying high voltage are generally hard and heavy, so there is a possibility that the movement of the moving stage will be affected by the tension and weight of the cable, and external vibrations may be transmitted to the sample on the moving stage. Problem arises.

  However, as described above, in the embodiment of the present invention, the boosting power supply unit 7 is provided on the mounting unit 33 for the boosting power supply unit of the sample stage 29 and low voltage power is supplied to the sample mounting unit 34 by the boosting power supply unit 7. Since the high-speed deceleration voltage Vr to be applied is generated, the above problem is eliminated.

  That is, since the method is controlled by the voltage Vref (DC 24 V or less) of the low-voltage supply external power supply unit 8 provided in the sample chamber 20, the signal low-voltage supply line 23 for energizing the measurement signal can be used, so that it is inexpensive.

  When the voltage Vref is applied to the connection terminal 22, the mounting base 24 is also at the Vref potential via the low-voltage supply line 23, and the sample base bottom plate portion 31 that is in contact with the mounting base 24 is also at the Vref potential. That is, since the range extending from the connection terminal 22 to the sample table bottom plate portion 31 is the Vref potential (DC 24 V or less), accidents such as electric shock can be prevented.

  At the same time, the GND potential acquisition contact 38 is brought into contact with the moving stage 21 in order to obtain the ground potential. A deceleration voltage Vr boosted by the boost power supply unit 7 based on Vref is applied to the sample 18 via the deceleration voltage Vr connection line 42 and the sample mounting unit 34. The sample mounting portion 34 is insulated from the boosting power source mounting portion 33 by the sample mounting portion side insulating member 35. The sample mounting portion side insulating member 35 has a withstand voltage performance that does not cause discharge or dielectric breakdown even when Vr is applied to the sample mounting portion 34.

  If the sample table bottom plate portion 31 of the sample table 29 is not in the state of being mounted on the mounting base 24, the voltage Vref is applied to the step-up power supply unit 7, so that the high voltage deceleration voltage Vr is applied when the sample table 29 is not mounted. Does not occur. For this reason, troubles such as discharge cannot occur until the sample stage is attached, and safety is improved.

  A voltage of 10 kV is applied to the secondary signal detector 9 to collect secondary electrons. In this example, V0 = 15 kV and Vr = 8 kV were applied. Since the secondary electrons generated from the sample to which a voltage of Vr = 8 kV is applied has an energy of about 8 keV, it is attracted to the electric field formed by the voltage of 10 kV applied to the secondary signal detector 9 and is applied to the detector 9. It is captured. In the case of this example, the irradiation energy (V0−Vr) = 8 kV, and the thickness of the damaged layer when this beam was used could be reduced to about 3 nm.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic which concerns on the Example of this invention and shows the outline of an ion beam apparatus (FIB apparatus). The schematic diagram which concerns on the Example of this invention and shows the outline of a sample stand. The figure which showed the damage to the sample by FIB irradiation. The schematic diagram which concerns on the Example of this invention and shows the state which mounted the sample stand for a measurement which measures an ion beam current on the mounting base of a movement stage. The schematic diagram which concerns on the Example of this invention and shows the state which mounted the sample stand for ion beam processing on the mounting base of a movement stage. The schematic diagram of the electric potential distribution of a sample stand in connection with the Example of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Charged particle beam generation source, 29 ... Sample stage for processing, 13 ... High voltage power supply for charged particle beam generation source, 7 ... Boosting power supply part, 8 ... External power supply part for low voltage supply.

Claims (3)

A charged particle beam generation source for generating a charged particle beam, a sample stage on which a sample irradiated with the charged particle beam is mounted, and a high voltage for a charged particle beam generation source for applying an acceleration voltage to the charged particle beam generation source A power source, and a decelerating unit that applies a decelerating voltage to decelerate the irradiation speed of the charged particle beam that irradiates the sample to the sample stage,
The deceleration means has a boost power supply unit and a low-voltage supply external power supply unit,
The boost power supply unit is provided on the sample stage,
Between the sample mounting part for placing the sample and the mounting part for the boosting power supply part, the boosting power supply part side insulating member is interposed,
A step-up power supply side insulating member is interposed between the step-up power supply portion mounting portion on which the step-up power supply portion is placed and the sample table bottom plate portion,
Connect the step-up power supply unit and the sample mounting unit with the deceleration voltage Vr connection line,
Connect the step-up power supply unit and the sample base plate with the Vref voltage connection line,
The boosting power supply unit and the mounting unit for the boosting power supply unit are connected by a GND potential connection line,
The step-up power supply unit is connected to the GND potential acquisition contact and kept at GND,
A charged particle beam apparatus characterized in that low-voltage power is input from a low-voltage supply external power supply unit to a boosting power supply unit via a low-voltage supply line and a sample stage bottom plate . A charged particle beam generation source for generating a charged particle beam, a lens barrel portion in which the charged particle beam generation source is placed and the interior of which is kept in a vacuum, and a sample on which a sample irradiated with the charged particle beam is placed A sample chamber in which the sample table is placed and the interior is kept in a vacuum; a high-voltage power supply for a charged particle beam generation source that applies an acceleration voltage to the charged particle beam generation source; and the sample is irradiated Decelerating means for applying a decelerating voltage for decelerating the irradiation speed of the charged particle beam to the sample stage;
The deceleration means has a boost power supply unit and a low-voltage supply external power supply unit,
The boost power supply unit is provided on the sample stage,
The low-voltage supply external power supply unit is provided outside the sample chamber,
Between the sample mounting part for placing the sample and the mounting part for the boosting power supply part, the boosting power supply part side insulating member is interposed,
A step-up power supply side insulating member is interposed between the step-up power supply portion mounting portion on which the step-up power supply portion is placed and the sample table bottom plate portion,
Connect the step-up power supply unit and the sample mounting unit with the deceleration voltage Vr connection line,
Connect the step-up power supply unit and the sample base plate with the Vref voltage connection line,
The boosting power supply unit and the mounting unit for the boosting power supply unit are connected by a GND potential connection line,
The step-up power supply unit is connected to the GND potential acquisition contact and kept at GND,
A charged particle beam apparatus, wherein the step-up power supply unit and a low-voltage supply external power supply unit are connected via a low-voltage supply line and a sample stage bottom plate . In the charged particle beam device according to claim 1 or 2,
A secondary charged particle detecting means for detecting secondary charged particles generated from the sample by irradiation of the charged particle beam;
A charged particle beam apparatus, wherein a detection application voltage applied to the secondary charged particle detection means is higher than the deceleration voltage.

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