JPWO2011034020A1 - electronic microscope - Google Patents

Abstract

The electron microscope of the present invention uses a piezoelectric actuator (51, 61) controlled by a pulse signal to adjust the position of a drive object (43) in a housing that maintains an internal vacuum and shields a stray magnetic field. It is characterized by. As a result, even if the piezoelectric actuator is arranged in the housing, it is possible to suppress the occurrence of image obstruction, and it is possible to avoid a complicated structure such as when a metal rod is used for driving. Became.

Description

  The present invention relates to an electron microscope.

  As a conventional electron microscope, a scanning electron microscope (SEM: Scanning Electron Microscope) and a transmission electron microscope (TEM: Transmission Electron Microscope) are known (for example, refer to Patent Documents 1 and 2). In these electron microscopes, an electron lens or the like is arranged in a housing that maintains the internal vacuum and shields stray magnetic fields.

JP 2006-54094 A JP 2006-127805 A

  By the way, in the conventional electron microscope, position adjustments, such as a sample and a diaphragm, are performed from the outside of the casing through a metal rod. The reason why the metal rod is used in this way is that if a magnet motor is used as an actuator for adjusting the position of the sample, the diaphragm, etc., the magnetic field in the casing is changed, which leads to serious image failure. As a reference, the allowable stray magnetic field of the electron microscope may be limited to 100 to 200 nT (nano tesla). In such a case, even if the magnet motor is arranged outside the case, the magnetic field inside the case varies. May cause it.

  However, in order to perform a remote operation such as a sample or a diaphragm from the outside of the housing via the metal rod, a complicated airtight structure is required to maintain the degree of vacuum in the housing. In addition, it is difficult to adjust the position of the sample, the diaphragm, etc. with high accuracy due to a mechanical error due to a long operation distance, thermal expansion of the metal rod due to a temperature change, or the like.

  Therefore, the present invention has been made in view of such circumstances, and can suppress the occurrence of an image failure, and can adjust the position of a driving object disposed in a housing with a simple structure. And it aims at providing the electron microscope which can be performed with the speed and precision according to the objective.

  In order to achieve the above object, an electron microscope according to the present invention is an electron microscope that converges an electron beam using an electron lens and irradiates the sample with an electron beam in order to acquire an image of the sample. And a housing that houses the electron lens and maintains the degree of vacuum inside and shields the stray magnetic field, and a piezoelectric actuator that drives the driving object disposed in the housing, the piezoelectric actuator comprising: And is controlled by a pulse signal.

  The present inventor uses an actuator controlled by an electric signal to adjust the position of a driven object from the viewpoint of suppressing the occurrence of image obstruction (and, moreover, arranging such an actuator in a housing). Under the technical common sense in the field of electron microscope, which was not assumed, it was devised to use a piezoelectric actuator as a drive source for position adjustment of a drive object. At the same time, if the present inventor uses a pulse signal as the control signal of the piezoelectric actuator, the occurrence of image failure can be suppressed even when the piezoelectric actuator is arranged in the housing, and an image having no practical problem can be obtained. It has been found that a complicated airtight structure as in the case of using a metal rod is not required, and the position of the driven object can be adjusted with high accuracy. Therefore, according to the electron microscope according to the present invention, it is possible to suppress the occurrence of image obstruction, and to adjust the position of the driving object arranged in the housing with a simple structure and a speed according to the purpose. Can be done with precision.

  In the electron microscope according to the present invention, the driven object is preferably a diaphragm member that narrows the electron beam or a support member that supports the sample. In order to drive the aperture member and the support member, coarse motion is required for switching apertures of different sizes and samples of different types, and fine motion for highly accurate position adjustment is required. In addition, a control signal of the piezoelectric actuator for realizing such coarse / fine movement requires a signal that does not generate a magnetic field or that takes a very short time even if a magnetic field is generated. It is extremely effective to use a piezoelectric actuator controlled by a pulse signal as a drive source for a diaphragm member and a support member that satisfy such conditions.

  In the electron microscope according to the present invention, the pulse signal is preferably transmitted from the outside of the housing to the piezoelectric actuator via the wiring. According to this configuration, the piezoelectric actuator can be controlled easily and reliably from outside the housing while maintaining the degree of vacuum in the housing.

  In the electron microscope according to the present invention, the driving object is at least one of a diaphragm member that narrows the electron beam and a support member that supports the sample, and when the diaphragm member or the support member is driven at the first image magnification. The piezoelectric actuator is controlled by a pulse signal that is the first pulse signal. When the diaphragm member or the support member is driven at a second image magnification higher than the first image magnification, the piezoelectric actuator It is preferable to control by a pulse signal which is a second pulse signal having at least one of frequency and amplitude smaller than that of the first pulse signal. According to this, as the image magnification increases, at least one of the frequency and amplitude of the pulse signal decreases, so that the position adjustment can be performed with high accuracy by moving the diaphragm member or the support member at a low speed, The degree of image obstruction can be reduced.

  In the electron microscope according to the present invention, the driving object is at least one of a diaphragm member that narrows the electron beam and a support member that supports the sample, and when the diaphragm member or the support member is driven at the first image magnification. The piezoelectric actuator moves the diaphragm member or the support member at the first moving speed, and drives the diaphragm member or the support member at the second image magnification higher than the first image magnification. It is preferable to move the diaphragm member or the support member at a second movement speed lower than the first movement speed. According to this, as the image magnification is increased, the diaphragm member or the support member is moved at a low speed, so that the position adjustment of the diaphragm member or the support member can be performed with high accuracy and the degree of image obstruction can be reduced. Can do.

  In the electron microscope according to the present invention, the object to be driven is a diaphragm member that squeezes the electron beam. When the diaphragm member is driven at an image magnification of 40 to 60 times, the piezoelectric actuator is 1 to 2 m / s. When the diaphragm member is moved at a moving speed and the diaphragm member is driven at an image magnification of 100 to 200 times, the piezoelectric actuator moves the diaphragm member at a moving speed of 100 to 200 μm / s and is 3000 to 5000 times larger. When the diaphragm member is driven at an image magnification, the piezoelectric actuator preferably moves the diaphragm member at a moving speed of 5 to 10 μm / s. According to this, in the range of each image magnification, the position adjustment of the diaphragm member and the acquisition of the image can be realized at a level with no practical problem.

  In the electron microscope according to the present invention, the driving object is a supporting member that supports the sample. When the supporting member is driven at an image magnification of 40 to 60 times, the piezoelectric actuator is 0.5 to When the support member is moved at a moving speed of 1 mm / s and the support member is driven at an image magnification of 100 to 200 times, the piezoelectric actuator moves the support member at a moving speed of 100 to 200 μm / s, and 3000 When the support member is driven at an image magnification of ˜5000 times, the piezoelectric actuator moves the support member at a moving speed of 5 to 10 μm / s and drives the support member at an image magnification of 30,000 to 50,000 times. The piezoelectric actuator moves the support member at a moving speed of 0.5 to 3 μm / s and drives the support member at an image magnification exceeding 50000 times. Actuator, it is preferable to move the support member at a movement speed of less than 0.5 [mu] m / s. According to this, in the range of each image magnification, the position adjustment of the support member and the image acquisition can be realized at a level with no practical problem.

  According to the present invention, it is possible to suppress the occurrence of image obstruction, and to adjust the position of a driving object disposed in a housing with a simple structure and at a speed and accuracy according to the purpose. .

It is a longitudinal cross-sectional view of the scanning electron microscope equipped with the thin film transmission image observation sample holder which is 1st Embodiment of the electron microscope which concerns on this invention. It is a disassembled perspective view of the thin film transmission image observation sample holder of the scanning electron microscope of FIG. It is sectional drawing along the YZ plane of the sample holder of FIG. It is sectional drawing along ZX plane of the sample holder of FIG. It is a bottom view of the assembly state of the top part, Y part, and X part of the sample holder of FIG. It is a bottom view of the top part of the sample holder of FIG. It is a bottom view of Y parts of the sample holder of FIG. It is a bottom view of X parts of the sample holder of FIG. It is sectional drawing along the YZ plane of the operation state of the sample holder of FIG. It is sectional drawing along ZX plane of the operation state of the sample holder of FIG. It is a bottom view of the operation state of the top part of the sample holder of FIG. 2, Y part, and X part. It is a perspective view of the piezoelectric actuator integrated in the sample holder of FIG. It is a figure which shows the principle of operation of the piezoelectric actuator of FIG. It is a disassembled perspective view of the aperture member drive mechanism of the scanning electron microscope of FIG. It is sectional drawing along the YZ plane of the aperture member drive mechanism of FIG. It is a longitudinal cross-sectional view of the transmission electron microscope which is 2nd Embodiment of the electron microscope which concerns on this invention. FIG. 17 is an exploded perspective view of a support member driving mechanism of the transmission electron microscope of FIG. 16. It is sectional drawing along the YZ plane of the drive mechanism of both the aperture_diaphragm | restriction for transmission electron microscopes, and a thin film sample. It is a figure of the visual field for demonstrating position adjustment with the sample and grid and observation position in the transmission electron microscope of FIG. It is a figure of the visual field for demonstrating position adjustment with the sample and grid and observation position in the transmission electron microscope of FIG. It is a figure of the visual field for demonstrating position adjustment with the sample and grid and observation position in the transmission electron microscope of FIG. It is a figure of the visual field for demonstrating position adjustment of the aperture member in the transmission electron microscope of FIG. It is a longitudinal cross-sectional view of the scanning electron microscope equipped with the bulk sample observation holder which is 3rd Embodiment of the electron microscope which concerns on this invention. FIG. 24 is a cross-sectional view along the YZ plane of the support member drive mechanism of FIG. 23.

DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the same or an equivalent part, and the overlapping description is abbreviate | omitted.
[First embodiment: Observation of transmission secondary electron image of thin film sample]

  As shown in FIG. 1, the scanning electron microscope 1 </ b> A includes a sample stage 4 to which a sample holder 20 is fixed by a bolt 3. The sample holder 20 holds a sample S to be observed. The scanning electron microscope 1A is an apparatus that converges an electron beam using an electron lens and irradiates the sample S with an electron beam in order to acquire an image of the sample S. Note that the position of the sample stage 4 can be manually adjusted.

  On the axis L, at a position facing the sample table 4, an electron gun 5 that emits an electron beam toward the sample table 4, and an anode 6 that accelerates the electron beam emitted from the electron gun 5 toward the sample table 4. Is installed. Between the anode 6 and the sample stage 4 on the axis L, an alignment coil 2 for aligning the center line of the electron beam with the axis L, a converging lens 7 as an electron lens for converging the electron beam, and an objective lens 8, In addition, a deflection coil 9 for deflecting the electron beam is provided.

  On the axis L, between the converging lens 7 and the deflection coil 9, a diaphragm member (driving object) 11 that restricts the electron beam converged by the converging lens 7 is installed. In addition, on the axis L, between the objective lens 8 and the sample stage 4, a diaphragm member (driving object) 12 that restricts the electron beam converged by the objective lens 8 is installed. Each diaphragm member 11, 12 is driven by a diaphragm member drive mechanism 30.

  Further, the scanning electron microscope 1A controls the secondary electron detector 13 that detects secondary electrons generated from the sample holder 20 by irradiation of the electron beam transmitted through the sample S, and the entire scanning electron microscope 1A. And a control device 14 for performing the operation. The control device 14 is, for example, a personal computer, and a transmission secondary electron image of the sample S is displayed on the display.

  Sample holder 20, sample stage 4, electron gun 5, anode 6, alignment coil 2, converging lens 7, objective lens 8, deflection coil 9, diaphragm member driving mechanism 30 for driving each diaphragm member 11, 12, and secondary The secondary electron detector of the electron detector 13 is accommodated in a housing 15 that is evacuated. An exhaust pipe 16 for evacuating the inside of the housing 15 is provided at the upper and lower portions of the housing 15, and the inside of the housing 15 is divided into an upper portion and a lower portion at an intermediate portion of the housing 15. A gate valve 17 for partitioning is provided. The housing 15 is made of, for example, iron or aluminum alloy, and maintains the internal vacuum and shields the stray magnetic field.

  Here, the sample holder 20 described above will be described with reference to FIGS. As shown in each figure, the X axis, the Y axis, and the Z axis are set. Hereinafter, one side in the X-axis direction is the left side, and the opposite side is the right side. Further, in the Y-axis direction, the secondary electron detector 13 side is a front side, and the opposite side is a rear side. Furthermore, the electron gun 5 side in the Z-axis direction is the upper side, and the opposite side is the lower side.

  As shown in FIGS. 2 to 5, the sample holder 20 includes a rectangular parallelepiped base 21 made of, for example, an aluminum alloy. A cutout portion 22 having a V-shaped cross section is formed on the front surface of the base 21, and an electron beam passage hole 23 having a circular cross section is formed in a portion protruding from the cutout portion 22 in the base 21. Yes. Screw holes 24 are formed at the four corners of the upper surface of the base 21, and screw holes 25 into which the bolts 3 are screwed through the insertion holes of the sample table 4 are formed at the lower surface of the base 21. Yes.

  The inclined surface that defines the notch 22 in the base 21 and faces the electron beam passage hole 23 is a secondary electron generation surface that generates secondary electrons when irradiated with the electron beam that has passed through the electron beam passage hole 23. (Secondary electron generating section) 29. The secondary electron generating surface 29 is, for example, a polished surface of an aluminum alloy.

  As shown in FIGS. 2 to 6, a rectangular parallelepiped cap-shaped top part 26 made of, for example, an aluminum alloy is fixed to the upper surface of the base 21. The top part 26 is attached to the base 21 by screwing bolts into the screw holes 24 of the base 21 through the insertion holes 27 formed at the four corners. An electron beam passage hole 28 is formed in the top part 26 so as to face the electron beam passage hole 23 of the base 21 in the Z-axis direction, and the upper part of the electron beam passage hole 28 is widened in the radial direction. Yes. A grid 31 that supports the thin film sample S is disposed on the bottom surface of the widened portion 28a of the electron beam passage hole 28. The grid 31 is fixed by an annular pressing member 32 that fits into the widened portion 28a. ing.

  On the lower surface of the top part 26, an accommodating recess 33 having a rectangular cross section that is opened not only on the lower side but also on the front side is formed. The accommodating recess 33 is widened on the left side and the right side. A notch 34 is formed on the left side of the housing recess 33, and a notch 35 is formed on the rear side of the housing recess 33.

  As shown in FIGS. 2 to 5, a rectangular parallelepiped annular Y part 36 made of, for example, an aluminum alloy is disposed in the housing recess 33 of the top part 26. The Y part 36 is integrally provided with a protruding portion 36a protruding leftward and a protruding portion 36b protruding rightward. The protruding portion 36 a is disposed in the widened portion 33 a on the left side of the receiving recess 33 of the top part 26, while the protruding portion 36 b is disposed in the widened portion 33 b on the right side of the receiving recess 33 of the top part 26. Yes. Accordingly, the Y part 36 can reciprocate within a predetermined range in the Y-axis direction with respect to the base 21 and the top part 26.

  In a recess formed on the upper surface of the protrusion 36a of the Y part 36, a piezoelectric body 52 of a piezoelectric actuator 51 whose drive is controlled by a pulse signal is fixed by an elastic adhesive such as silicone. Both ends of the support shaft 53 of the piezoelectric actuator 51 protrude from the protrusion 36a toward the front side and the rear side, and are fixed in recesses 33c formed on the front side and the rear side of the widened portion 33a of the top part 26. The wiring 54 of the piezoelectric actuator 51 is, for example, a flexible printed circuit (FPC) or the like, and extends outside the sample holder 20 via the notch 34 of the top part 26.

  The Y part 36 has an opening 37 having a rectangular cross section so as to include the electron beam passage holes 23 and 28 when viewed from the Z-axis direction. The lower part of the opening 37 is widened to the front side and the rear side. A notch 38 is formed on the rear side of the opening 37.

  As shown in FIGS. 2 to 5, a rectangular parallelepiped plate-shaped X part 41 made of, for example, an aluminum alloy is disposed in the opening 37 of the Y part 36. The X part 41 is integrally provided with a protruding portion 41a protruding to the front side and a protruding portion 41b protruding to the rear side. The protruding portion 41 a is disposed in the widened portion 37 a on the front side of the opening 37 of the Y part 36, while the protruding portion 41 b is disposed in the widened portion 37 b on the rear side of the opening 37 of the Y part 36. ing. Thereby, the X part 41 can reciprocate within a predetermined range in the X-axis direction with respect to the base 21 and the top part 26.

  In a recess formed on the upper surface of the X part 41, a piezoelectric body 62 of a piezoelectric actuator 61 whose drive is controlled by a pulse signal is fixed by an elastic adhesive such as silicone. Both end portions of the support shaft 63 of the piezoelectric actuator 61 protrude from the X part 41 toward the left side and the right side, and are fixed in recesses 37 c formed on the left side and the right side of the opening 37 of the Y part 36. Note that the wiring 64 of the piezoelectric actuator 61 is, for example, a flexible printed circuit board or the like, and extends outside the sample holder 20 via the notch portion 38 of the Y part 36 and the notch portion 35 of the top part 26.

  The X part 41 faces the electron beam passage hole 23 of the base 21 and the electron beam passage hole 28 of the top part 26 in the Z-axis direction, and is included in the opening 37 of the Y part 36 when viewed from the Z-axis direction. As shown in the figure, an electron beam passage hole 42 having an oval cross section is formed, and the upper portion of the electron beam passage hole 42 is widened in the radial direction. On the bottom surface of the widened portion 42a of the electron beam passage hole 42, a throttle member 43 for narrowing the electron beam that has passed through the sample S is disposed. The throttle member 43 is an oval holding member that fits into the widened portion 42a. 44 is fixed. The diaphragm member 43 is a foil-like member made of, for example, molybdenum, and has two types of apertures 43a and 43b arranged in parallel along the X-axis direction.

  In the sample holder 20 configured as described above, as shown in FIGS. 9 to 11, a pulse signal is transmitted to the piezoelectric actuator 51 and the piezoelectric actuator 51 is operated, whereby the base 21 and the top part 26 are moved. The Y part 36 reciprocates within a predetermined range in the Y-axis direction. Further, when the pulse signal is transmitted to the piezoelectric actuator 61 and the piezoelectric actuator 61 operates, the X part 41 reciprocates in a predetermined range in the X axis direction with respect to the base 21 and the top part 26. Accordingly, it is possible to select the aperture 43a or the aperture 43b of the diaphragm member 43 as the field diaphragm for the sample S. In addition, the selected aperture 43a or aperture 43b can be matched to the entire region of the sample S.

  The piezoelectric actuators 51 and 61 are driven by pulse signals, and a SQUIGGLE (registered trademark) motor of New Scale Technologies, particularly a micro squiggle motor series is suitable. is there. As shown in FIG. 12, the squiggle motor 100 includes a square pillar nut (hereinafter referred to as “a screw”) 101 (hereinafter referred to as “screw”) 101 (corresponding to the support shafts 53 and 63). The piezoelectric element 103 (corresponding to the piezoelectric bodies 52 and 62) is attached to each of the four outer surfaces of the core 102).

  In the squiggle motor 100, when a pulse signal having a different phase is input to each piezo element 103, a rotation such as a hula hoop having two nodes J and rotating in one direction as shown in FIG. A movement (see the two-dot chain line in FIG. 13) occurs in the core 102. Thereby, the screw 101 with which the core 102 is screwed is rotated in one direction in a passive manner, and the screw 101 is controlled to move in one direction of the rotation axis. If the phase of the pulse signal input to each piezo element 103 is changed to reverse the rotational movement of the core 102, the rotational direction of the screw 101 is reversed, so that the screw 101 can be moved in the reverse direction. Refer to US Pat. No. 6,940,209, US Pat. No. 7,170,214, US Pat. No. 7,309,943, US Pat. No. 7,339,306 for more detailed operation principle. It is. You can also refer to http://www.newscaletech.com/.

  The external dimension of the squiggle motor 100 is, for example, SQL-1.8 and is a prismatic shape of 1.82 mm × 1.82 mm × 12 mm. Such a shape is a very convenient shape to be integrated into a driving object installed in the housing of the electron microscope. In addition, as described above, the squiggle motor 100 is assembled to the driving target because the core 102 needs to have a rotating motion like a hula hoop having two nodes J as described above. For example, the movement is allowed by an elastic adhesive without being firmly fixed.

  Next, the diaphragm member driving mechanism 30 described above will be described. As shown in FIGS. 14 and 15, the diaphragm member driving mechanism 30 is configured such that the base 21 has a rectangular plate shape, the top part 26 does not support the sample S, and the X part 41 includes the diaphragm member 11 (12 ) Is mainly different from the sample holder 20. Hereinafter, main differences from the sample holder 20 will be described.

  In the diaphragm member driving mechanism 30, the base 21 is a rectangular parallelepiped plate member made of, for example, an aluminum alloy. An electron beam passage hole 23 having a circular cross section is formed in the base 21, and screw holes 24 are formed at four corners thereof.

  An electron beam passage hole 28 having a circular cross section is formed in the top part 26 so as to face the electron beam passage hole 23 of the base 21 in the Z-axis direction. The top part 26 is attached to the base 21 by screwing bolts into the screw holes 24 of the base 21 through the insertion holes 27 formed at the four corners.

  The X part 41 faces the electron beam passage hole 23 of the base 21 and the electron beam passage hole 28 of the top part 26 in the Z-axis direction, and is included in the opening 37 of the Y part 36 when viewed from the Z-axis direction. As shown in the figure, an electron beam passage hole 42 having an oval cross section is formed, and the upper portion of the electron beam passage hole 42 is widened in the radial direction. An aperture member 11 (12) for narrowing the electron beam is disposed on the bottom surface of the widened portion 42a of the electron beam passage hole 42. The aperture member 11 (12) is an oval presser that fits into the widened portion 42a. It is fixed by the member 44. The diaphragm member 11 (12) is a foil-like member made of, for example, molybdenum, and has two types of apertures 11a and 11b (12a and 12b) arranged in parallel along the X-axis direction.

  In the diaphragm member drive mechanism 30 configured as described above, a pulse signal is transmitted to the piezoelectric actuator 51 and the piezoelectric actuator 51 operates, so that the Y part 36 moves in the Y-axis direction with respect to the base 21 and the top part 26. And reciprocating within a predetermined range. Further, when the pulse signal is transmitted to the piezoelectric actuator 61 and the piezoelectric actuator 61 operates, the X part 41 reciprocates in a predetermined range in the X axis direction with respect to the base 21 and the top part 26. As a result, the aperture 11a (12a) or the aperture 11b (12b) of the aperture member 11 (12) to be aligned with the axis L, or the axis 11 of the selected aperture 11a (12a) or aperture 11b (12b) is selected. Position adjustment is possible.

  As shown in FIG. 1, transmission of pulse signals to the piezoelectric actuators 51 and 61 is controlled outside the housing 15 via a wiring 19 such as a USB cable connected to the wirings 54 and 64 of the piezoelectric actuators 51 and 61. From the device 14. Thereby, the piezoelectric actuator can be controlled easily and reliably from the outside of the housing 15 while maintaining the degree of vacuum in the housing 15.

  In the scanning electron microscope 1A, when an electron beam is emitted from the electron gun 5, the electron beam that has passed through the sample S supported by the grid 31 and has passed through the selected aperture 43a or aperture 43b is secondary. The electron generation surface 29 is irradiated, whereby secondary electrons are generated from the secondary electron generation surface 29. The secondary electrons generated from the secondary electron generating surface 29 are detected by the secondary electron detector 13, whereby a transmission image of the sample S is displayed on the display of the control device 14. At this time, since scattered electrons from the sample S are blocked by the diaphragm member 43, the sample S can be observed with high resolution. Therefore, according to the scanning electron microscope 1 </ b> A and the sample holder 20, it is possible to acquire a transmission image of substantially the entire area of the sample S.

As described above, in the scanning electron microscope 1 </ b> A, the diaphragm members 11, 12, and 43 are driven by the piezoelectric actuators 51 and 61 through the Y part 36 and the X part 41 in the housing 15. In this way, if a piezoelectric actuator controlled by a pulse signal is used for position adjustment of an object to be driven, even if the piezoelectric actuator is arranged in the casing 15, the occurrence of an image failure is suppressed and there is no practical problem. An image can be obtained, and a complicated airtight structure as in the case where a metal rod is used is not required, so that the position of the driven object can be adjusted with high accuracy. That is, according to the scanning electron microscope 1 </ b> A, it is possible to suppress the occurrence of an image failure, and furthermore, the position adjustment of the driving object arranged in the housing 15 can be performed with a simple structure and high accuracy. It becomes possible.
[Second Embodiment: Movement of Sample and Aperture by Transmission Electron Microscope]

  As shown in FIG. 16, the transmission electron microscope 1B includes a support member drive mechanism 40 that supports a sample S to be observed. The transmission electron microscope 1B is a device that converges an electron beam using an electron lens and irradiates the sample S with an electron beam in order to acquire an image of the sample S.

  On the axis L, at a position facing the support member drive mechanism 40, the electron gun 5 that emits an electron beam toward the support member drive mechanism 40, and the electron beam emitted from the electron gun 5 to the support member drive mechanism 40 An anode 6 is installed for acceleration. On the axis L, between the anode 6 and the support member drive mechanism 40, a converging lens 7 is installed as an electron lens for converging the electron beam. On the other hand, on the axis L, a fluorescent plate 71 is installed on the side opposite to the electron gun 5 with respect to the support member drive mechanism 40. On the axis L, between the support member drive mechanism 40 and the fluorescent plate 71, the deflection coil 9 that deflects the electron beam, the intermediate lens 72 that enlarges the electron beam image, and the projection lens 73 that projects the electron beam image onto the fluorescent plate 71. Is installed. The fluorescent image generated on the fluorescent plate 71 is captured by a camera or the like and displayed on the display of the control device 14.

  On the axis L, between the converging lens 7 and the support member drive mechanism 40, a diaphragm member (drive object) 74 as a condenser diaphragm is installed. Further, on the axis L, between the support member drive mechanism 40 and the deflection coil 9, a diaphragm member (drive object) 75 as an objective diaphragm is installed. Further, on the axis L, between the deflection coil 9 and the intermediate lens 72, a diaphragm member (driving object) 76 as a field diaphragm is installed. The diaphragm members 74 to 76 are driven by the diaphragm member drive mechanism 30. The diaphragm member driving mechanism 30 that drives the diaphragm member 75 is configured integrally with the support member driving mechanism 40.

  Further, the transmission electron microscope 1B includes a control device 14 that controls the entire transmission electron microscope 1B. The control device 14 is, for example, a personal computer, and a transmission image of the sample S is displayed on the display.

  The support member drive mechanism 40, the electron gun 5, the anode 6, the converging lens 7, the deflection coil 9, the fluorescent plate 71, the intermediate lens 72, the projection lens 73, and the stop member drive mechanism 30 that drives the stop members 74 to 76 are vacuum. It is accommodated in the case 15 to be pulled. An exhaust pipe 16 for evacuating the inside of the housing 15 is provided at a predetermined portion of the housing 15. The housing 15 is made of, for example, iron or aluminum alloy, and maintains the internal vacuum and shields the stray magnetic field.

  Here, the above-described support member drive mechanism 40 will be described. As shown in FIGS. 17 and 18, the support member drive mechanism 40 is mainly different from the diaphragm member drive mechanism 30 of the first embodiment in that the X part 41 supports the sample S. Hereinafter, main differences from the diaphragm member driving mechanism 30 of the first embodiment will be described.

  The X part 41 faces the electron beam passage hole 23 of the base 21 and the electron beam passage hole 28 of the top part 26 in the Z-axis direction, and is included in the opening 37 of the Y part 36 when viewed from the Z-axis direction. As shown, an electron beam passage hole 77 having a circular cross section is formed, and the upper portion of the electron beam passage hole 77 is widened in the radial direction. A grid 31 that supports the thin film sample S is disposed on the bottom surface of the widened portion 77a of the electron beam passage hole 77, and the grid 31 is fixed by an annular pressing member 78 that fits into the widened portion 77a. ing.

  In the support member drive mechanism 40 configured as described above, a pulse signal is transmitted to the piezoelectric actuator 51 and the piezoelectric actuator 51 operates, so that the Y part 36 moves in the Y-axis direction with respect to the base 21 and the top part 26. And reciprocating within a predetermined range. Further, when the pulse signal is transmitted to the piezoelectric actuator 61 and the piezoelectric actuator 61 operates, the X part 41 reciprocates in a predetermined range in the X axis direction with respect to the base 21 and the top part 26. As a result, the position of the sample S with respect to the axis L can be adjusted. Similarly, the aperture member driving mechanism 30 can adjust the position of the apertures of the aperture members 74 to 76 with respect to the axis L.

And, by using a SQUIGGLE (registered trademark) motor of New Scale Technologies for the piezoelectric actuators 51 and 61, particularly a micro squiggle motor series, the diaphragm member drive mechanism 30 and the support member drive. The mechanism 40 can be reduced in size (particularly thinned), and even if the diaphragm member driving mechanism 30 and the support member driving mechanism 40 are integrally configured, a very narrow space between pole pieces in the electron lens is formed. It becomes possible to arrange in.
[Sample moving procedure in the second embodiment]

  Next, adjustment of the sample S and the grid 31 and the observation position in the transmission electron microscope 1B will be described. First, as shown in FIG. 19A, the entire grid 31 that is a sheet mesh having a diameter of 3 mm is observed at an image magnification of 40 to 60 times. A thin film sample S is stretched on the grid 31. Subsequently, as shown in FIG. 19B, while observing the sample S and the grid 31 and the observation position at an image magnification of 40 to 60 times, the observation desired site A is positioned at the center C of the visual field. The sample S and the grid 31 are driven by the support member driving mechanism 40.

  When the sample S and the grid 31 are driven at an image magnification of 40 to 60 times, the movement distance is 3 mm (corresponding to the diameter of the grid 31) at the maximum, so that the piezoelectric actuators 51 and 61 are 0.5 to 1 mm / It is preferable to move the sample S and the grid 31 at a moving speed of s. At this time, the piezoelectric actuators 51 and 61 are controlled by a pulse signal PS1 having a frequency F1.

  Subsequently, as shown in FIG. 20A, the field of view is enlarged so that the image magnification is 100 to 200 times. Thereby, the image is enlarged around the center C of the visual field. When it is confirmed that the desired observation site A is deviated from the center C of the field of view by enlarging the image, as shown in FIG. 20B, the sample S and the grid 31 are arranged at an image magnification of 100 to 200 times. While observing the center of the visual field, the sample S and the grid 31 are precisely driven by the support member driving mechanism 40 such that the desired observation site A is positioned at the center C of the visual field.

  When the sample S and the grid 31 are driven at an image magnification of 100 to 200 times, it is preferable that the piezoelectric actuators 51 and 61 move the sample S and the grid 31 at a moving speed of 100 to 200 μm / s. At this time, the piezoelectric actuators 51 and 61 are controlled by a pulse signal PS2 having a frequency F2 lower (smaller) than the frequency F1.

  Subsequently, as shown in FIG. 21A, the field of view is enlarged so that the image magnification is 3000 to 5000 times. Thereby, the image is enlarged around the center C of the visual field. When it is confirmed that the observation desired part A is shifted from the center C of the visual field by enlarging the image, the observation desired part is observed while observing the sample S and the grid 31 and the observation position at an image magnification of 3000 to 5000 times. The sample S and the grid 31 are driven more precisely by the support member driving mechanism 40 so that A is positioned at the center C of the visual field.

  When the sample S and the grid 31 are driven at an image magnification of 3000 to 5000 times, the piezoelectric actuators 51 and 61 preferably move the sample S and the grid 31 at a moving speed of 5 to 10 μm / s. At this time, the piezoelectric actuators 51 and 61 are controlled by a pulse signal PS3 having a frequency F3 lower (smaller) than the frequency F2. Note that, depending on the observation purpose, there is a case where it moves to the next window beyond the bar constituting the mesh of the grid 31. In such a case, a moving speed of about 50 μm / s may be required.

  Subsequently, as required, as shown in FIG. 21 (b), the field of view is enlarged so that the image magnification is 30000 to 50000 times. Thereby, the image is enlarged around the center C of the visual field. When it is confirmed that the desired observation site A is deviated from the center C of the visual field by enlarging this image, the desired observation site A is in the visual field while observing the sample S and the grid 31 at an image magnification of 30000 to 50000 times. The sample S and the grid 31 are driven by the support member drive mechanism 40 so as to be positioned at the center C.

  When the sample S and the grid 31 are driven at an image magnification of 30000 to 50000 times, the piezoelectric actuators 51 and 61 preferably move the sample S and the grid 31 at a moving speed of 0.5 to 3 μm / s. At this time, the piezoelectric actuators 51 and 61 are controlled by a pulse signal PS4 having a frequency F4 lower (smaller) than the frequency F3.

If the desired observation site A can be captured in the field of view with the desired image magnification, the desired site of observation A is observed and photographed, and thereafter, the expansion of the visual field and the movement of the sample S and the grid 31 are repeated. When the sample S and the grid 31 are driven at an image magnification exceeding 50000 times, the piezoelectric actuators 51 and 61 preferably move the sample S and the grid 31 at a moving speed of less than 0.5 μm / s. At this time, the piezoelectric actuators 51 and 61 are controlled by a pulse signal PS5 having a frequency F5 lower (smaller) than the frequency F4.
[Aperture Position Adjustment Procedure in Second Embodiment]

  Next, position adjustment of the diaphragm member 75 in the transmission electron microscope 1B will be described. As shown in FIG. 22A, the diaphragm member 75 as the objective diaphragm has an aperture 75a having a diameter of 300 μm and an aperture 75b having a diameter of 60 μm arranged in parallel along the X-axis direction. The aperture 75a is for a wide field of view, and the aperture 75b is for a high resolution. These are switched as necessary and further centered for use.

  First, as shown in FIG. 22A, the diaphragm member 75, the sample S, and the entire grid 31 are observed at an image magnification of 40 to 60 times. At this time, the diaphragm member 75 and the grid 31 are hardly overlapped. Subsequently, the desired observation site A is positioned at the center C of the visual field as described above. Thereafter, as shown in FIG. 22B, the aperture member drive mechanism is arranged so that the center of the aperture 75a is positioned at the center C of the visual field while observing the sample S and the grid 31 at an image magnification of 40 to 60 times. The diaphragm member 75 is driven by 30.

  When the diaphragm member 75 is driven at an image magnification of 40 to 60 times, the moving distance in the X-axis direction is about 5 mm at the maximum, so that the piezoelectric actuator 61 for driving in the X-axis direction is 1 to 2 mm. It is preferable to move the diaphragm member 75 at a moving speed of / s. On the other hand, the driving is only centering in the Y-axis direction, and the moving distance is 1 mm or less at the maximum. Therefore, the piezoelectric actuator 51 for driving in the Y-axis direction has a diaphragm member 75 at a moving speed of about 100 μm / s. Is preferably moved. At this time, the piezoelectric actuators 51 and 61 are controlled by a pulse signal PS1 having a frequency F1.

  Subsequently, the field of view is enlarged so that the image magnification is 100 to 200 times. Thereby, the image is enlarged around the center C of the visual field. When it is confirmed that the center of the aperture 75a is deviated from the center C of the field of view by enlarging the image, the center of the aperture 75a is the center C of the field of view while observing the diaphragm member 75 at an image magnification of 100 to 200 times. The diaphragm member 75 is driven by the diaphragm member driving mechanism 30 so as to be positioned at the position.

  When the diaphragm member 75 is driven at an image magnification of 100 to 200 times, the piezoelectric actuators 51 and 61 preferably move the diaphragm member 75 at a movement speed of about 100 to 200 μm / s. At this time, the piezoelectric actuators 51 and 61 are controlled by a pulse signal PS2 having a frequency F2 lower (smaller) than the frequency F1. When the diaphragm member 75 is driven at an image magnification of 3000 to 5000 times, it is preferable that the piezoelectric actuators 51 and 61 move the diaphragm member 75 at a moving speed of about 5 to 10 μm / s. At this time, the piezoelectric actuators 51 and 61 are controlled by a pulse signal PS3 having a frequency F3 lower (smaller) than the frequency F2.

  In order to observe the sample S at a higher image magnification, the aperture member driving mechanism 30 switches the aperture 75a for wide field of view to the aperture 75b for high resolution, and the center of the aperture 75b is positioned at the center C of the field of view. Thus, the diaphragm member 75 is driven by the diaphragm member driving mechanism 30.

  As described above, in the transmission electron microscope 1B, the piezoelectric actuators 51 and 61 increase as the image magnification increases when the diaphragm member 75 and the like (including the sample S and the grid 31, the diaphragm members 74 and 76, and the like) are driven. The frequency of the pulse signal for controlling the frequency becomes low (small). That is, as the image magnification increases, the diaphragm member 75 and the like are moved at a lower speed. Therefore, the position of the diaphragm member 75 and the like can be adjusted with high accuracy under a high image magnification. Furthermore, for pulse signals, the higher the image magnification, the lower the ratio of voltage application time per unit time, so the degree of image disturbance (for example, the ratio of noise in the entire image) is reduced under high image magnification. Can do.

  The preferred value of the moving speed with respect to the image magnification is as follows. That is, when the diaphragm member 75 is driven at an image magnification of 40 to 60 times, the piezoelectric actuators 51 and 61 move the diaphragm member 75 at a moving speed of 1 to 2 m / s, and an image magnification of 100 to 200 times. When the diaphragm member 75 is driven, the piezoelectric actuators 51 and 61 move the diaphragm member 75 at a moving speed of 100 to 200 μm / s and drive the diaphragm member 75 at an image magnification of 3000 to 5000 times. The piezoelectric actuators 51 and 61 preferably move the diaphragm member 75 at a moving speed of 5 to 10 μm / s. According to this, in the range of each image magnification, the position adjustment of the diaphragm member 71 and the acquisition of the image can be realized at a level with no practical problem.

  When the sample S and the grid 31 are driven at an image magnification of 40 to 60 times, the piezoelectric actuators 51 and 61 move the sample S and the grid 31 at a moving speed of 0.5 to 1 mm / s, and 100 When the sample S and the grid 31 are driven at an image magnification of ˜200 times, the piezoelectric actuators 51 and 61 move the sample S and the grid 31 at a moving speed of 100 to 200 μm / s to obtain an image of 3000 to 5000 times. When the sample S and the grid 31 are driven at a magnification, the piezoelectric actuators 51 and 61 preferably move the sample S and the grid 31 at a moving speed of 5 to 10 μm / s, and further, an image of 30000 to 50000 times. When the sample S and the grid 31 are driven at a magnification, the piezoelectric actuators 51 and 61 move at a moving speed of 0.5 to 3 μm / s. When the sample S and the grid 31 are moved and the sample S and the grid 31 are driven at an image magnification exceeding 50,000 times, the piezoelectric actuators 51 and 61 are moved at a moving speed of less than 0.5 μm / s. Is preferably moved. According to this, in the range of each image magnification, the position adjustment of the sample S and the grid 31 and the image acquisition can be realized at a level with no practical problem.

In addition, the piezoelectric actuators 51 and 61 are required to have a moving distance of 3 mm or more at the maximum, a moving speed that can be controlled according to the image magnification in the range of 0.5 μm / s to 2 mm / s, and a position hold function. Is done. Further, the piezoelectric actuators 51 and 61 are required to have a size that can be inserted into the gap of the objective lens pole piece having a height of about 10 mm and a depth and width of about 20 mm. As an actuator that satisfies such a requirement, for example, there is a SQUIGGLE (registered trademark) motor, SQL-RV-1.8 manufactured by New Scale Technologies.
[Third Embodiment: Observation of Secondary Electron and Reflected Electron Image of Bulk Sample by Scanning Electron Microscope]

  As shown in FIG. 23, the scanning electron microscope 1C is different from the scanning electron microscope 1A of the first embodiment in that a support member driving mechanism 50 is attached to the sample stage 4 instead of the sample holder 20. Mainly different. As shown in FIG. 24, the support member drive mechanism 50 is a diaphragm shown in FIGS. 14 and 15 in that the X part 41 supports the sample mounting table 50a instead of the diaphragm member 11 (12). Mainly different from the member driving mechanism 30. Hereinafter, main differences from the diaphragm member driving mechanism 30 will be described.

  The top part 26 has an opening 26a through which a leg 50b extending in the Z-axis direction passes from the sample mounting table 50a. The leg portion 50 b is formed integrally with the sample mounting table 50 a and is fitted and fixed in the widened portion 42 a of the X part 41.

  In the support member drive mechanism 50 configured as described above, a pulse signal is transmitted to the piezoelectric actuator 51 and the piezoelectric actuator 51 operates, whereby the Y part 36 is moved in the Y-axis direction with respect to the base 21 and the top part 26. Reciprocates within a predetermined range. Further, when the pulse signal is transmitted to the piezoelectric actuator 61 and the piezoelectric actuator 61 operates, the X part 41 reciprocates in a predetermined range in the X axis direction with respect to the base 21 and the top part 26. Thereby, the position adjustment with respect to the axis L of the sample S mounted on the sample mounting table 50a becomes possible. The opening 26 a is formed so that the leg portion 50 b does not contact the top part 26 in the operation range of the Y part 36 and the X part 41.

  In the scanning electron microscope 1C configured as described above, the electron beam is scanned with respect to the sample S, and morphological information of secondary electrons and reflected electrons excited thereby is drawn on the monitor. Also in the scanning electron microscope 1C, similarly to the transmission electron microscope 1B of the second embodiment, the image magnification is increased stepwise while the sample S, the grid 31 and the like (the diaphragm member 11, (Including 12 etc.) is adjusted. The frequency of the pulse signal for controlling the piezoelectric actuators 51 and 61 becomes lower (smaller) as the image magnification when driving the sample S, the grid 31, and the like becomes higher. That is, as the image magnification increases, the sample S, the grid 31, and the like are moved at a lower speed. Therefore, the position adjustment of the sample S, the grid 31 and the like can be performed with high accuracy under a high image magnification. Furthermore, for pulse signals, the higher the image magnification, the lower the ratio of voltage application time per unit time, so the degree of image disturbance (for example, the ratio of noise in the entire image) is reduced under high image magnification. Can do.

In the scanning electron microscope 1C, when the sample S and the grid 31 are moved while observing the sample S and the grid 31 at a relatively low image magnification, a relatively fast scanning mode (for example, TV mode: 30 frames / second). Scanning at s) is performed. When observation or photography is performed, scanning in the high-definition scanning mode is performed. Thereby, an image having a good S / N can be obtained at the time of observation or photography.
[Sample moving procedure in the third embodiment]

  Next, observation position adjustment of the sample S in the scanning electron microscope 1C will be described. First, as shown in FIG. 23, the sample S is observed while gradually increasing the observation position from a low magnification to a necessary magnification. First, with the image magnification of 40 to 60 times, the observation position is determined from the entire sample S of several millimeters at the maximum, and the visual field is also moved to the center. The sample moving distance at this time is several mm, and the moving speed is 0.5-1 mm / s. Next, the image magnification is increased, and the image is gradually enlarged to the target image magnification. When the image magnification is 100 to 200 times, the moving speed is 100 to 200 μm / s. When the image magnification is 3000 to 5000 times, the moving speed is 5 to 10 μm / s. The image is moved at a moving speed of 0.5 to 3 μm / s at an image magnification of 30000 to 50000 times, and at a moving speed of less than 0.5 μm / s at an image magnification of more than 50000 times.

Finally, suitable values of the moving speed with respect to the image magnification are summarized in Table 1 below.

  The present invention is not limited to the embodiment described above. For example, the driving object driven by the piezoelectric actuator includes a probe for dissecting the sample in the housing, in addition to the support member for supporting the sample and the diaphragm member for narrowing the electron beam. In particular, when the object to be driven is a support member or a diaphragm member, high-accuracy position adjustment is required. Therefore, it is extremely difficult to use a piezoelectric actuator controlled by a pulse signal to drive it. It is valid.

  Further, the higher the image magnification when driving the object to be driven, the lower the frequency of the pulse signal for controlling the piezoelectric actuators 51 and 61 is not limited, and the higher the image magnification is, the higher the image magnification. The amplitude may be reduced, or both the frequency and amplitude of the pulse signal may be reduced. That is, as the image magnification increases, at least one of the frequency and amplitude of the pulse signal may be reduced so that the ratio of the voltage application time per unit time in the pulse signal decreases.

  According to the present invention, it is possible to suppress the occurrence of image obstruction, and to adjust the position of a driving object disposed in a housing with a simple structure and at a speed and accuracy according to the purpose. .

  DESCRIPTION OF SYMBOLS 1A, 1C ... Scanning electron microscope, 1B ... Transmission electron microscope, 7 ... Converging lens (electronic lens), 8 ... Objective lens (electronic lens), 11, 12, 43, 74-76 ... Diaphragm member (drive object) ), 15, housing, 19, wiring, 31, grid (driving object), 51, 61, piezoelectric actuator, 54, 64, wiring, S, sample.

Claims (8)

An electron microscope that converges an electron beam using an electron lens to irradiate the sample with the electron beam in order to obtain an image of the sample,
A housing for accommodating the sample and the electron lens, maintaining an internal vacuum and shielding a stray magnetic field;
A piezoelectric actuator that drives a driving object disposed in the housing, and
2. The electron microscope according to claim 1, wherein the piezoelectric actuator is integrated into the driving object and controlled by a pulse signal.   The electron microscope according to claim 1, wherein the driving object is a diaphragm member that squeezes the electron beam.   The electron microscope according to claim 1, wherein the driven object is a support member that supports the sample.   The electron microscope according to claim 1, wherein the pulse signal is transmitted from outside the housing to the piezoelectric actuator via a wiring. The drive object is at least one of a diaphragm member for narrowing the electron beam and a support member for supporting the sample,
When driving the diaphragm member or the support member at a first image magnification, the piezoelectric actuator is controlled by the pulse signal which is a first pulse signal,
When the diaphragm member or the support member is driven at a second image magnification higher than the first image magnification, the piezoelectric actuator has at least one of frequency and amplitude smaller than the first pulse signal. The electron microscope according to claim 1, wherein the electron microscope is controlled by the pulse signal which is a second pulse signal. The drive object is at least one of a diaphragm member for narrowing the electron beam and a support member for supporting the sample,
When driving the diaphragm member or the support member at a first image magnification, the piezoelectric actuator moves the diaphragm member or the support member at a first movement speed,
When the diaphragm member or the support member is driven at a second image magnification higher than the first image magnification, the piezoelectric actuator moves at a second movement speed lower than the first movement speed. The electron microscope according to claim 1, wherein the diaphragm member or the support member is moved. The driving object is a diaphragm member that squeezes the electron beam,
When driving the diaphragm member at an image magnification of 40 to 60 times, the piezoelectric actuator moves the diaphragm member at a moving speed of 1 to 2 m / s,
When driving the diaphragm member at an image magnification of 100 to 200 times, the piezoelectric actuator moves the diaphragm member at a movement speed of 100 to 200 μm / s,
2. The electron microscope according to claim 1, wherein when the diaphragm member is driven at an image magnification of 3000 to 5000 times, the piezoelectric actuator moves the diaphragm member at a moving speed of 5 to 10 [mu] m / s. . The drive object is a support member that supports the sample,
When driving the support member at an image magnification of 40 to 60 times, the piezoelectric actuator moves the support member at a moving speed of 0.5 to 1 mm / s,
When driving the support member at an image magnification of 100 to 200 times, the piezoelectric actuator moves the support member at a moving speed of 100 to 200 μm / s,
When driving the support member at an image magnification of 3000 to 5000 times, the piezoelectric actuator moves the support member at a moving speed of 5 to 10 μm / s,
When driving the support member at an image magnification of 30000 to 50000 times, the piezoelectric actuator moves the support member at a moving speed of 0.5 to 3 μm / s,
2. The electron microscope according to claim 1, wherein when the support member is driven at an image magnification exceeding 50,000 times, the piezoelectric actuator moves the support member at a moving speed of less than 0.5 μm / s. .