JP4790393B2 - Electron detector and beam device provided with the same - Google Patents

Description

  The present invention relates to an electron detector for detecting detected electrons generated from a sample irradiated with a primary beam such as an electron beam, and a beam apparatus including the electron detector.

  The specimen to be observed is irradiated with a primary beam such as an electron beam, thereby detecting detected electrons that are secondary information such as secondary electrons and reflected electrons generated from the specimen, and a detection signal at the time of detection is detected. A scanning electron microscope is known as a beam device that forms and displays a sample image based on the image.

  In this scanning electron microscope, an electron beam (primary beam) accelerated and emitted from an electron gun that is an electron beam source (primary beam source) is finely focused on a sample by a focusing lens and an objective lens and irradiated. At this time, the electron beam is deflected by the scanning coil, whereby the electron beam scans the sample.

  Electron beam scanning (irradiation) generates detected electrons such as secondary electrons and reflected electrons from the sample. The detected electrons are detected by an electron detector.

  The electron detector outputs a detection signal based on detection of detected electrons. The scanning electron microscope forms and displays a scanned image as a sample image based on the detection signal.

  In such a scanning electron microscope, detection of detected electrons generated from a sample and drawn into an objective lens has been studied, and it is important to efficiently detect the detected electrons without any trouble. Yes.

  Here, when detecting the detected electrons drawn into the objective lens by using an electron detector arranged outside the objective lens, an electric field or a magnetic field (hereinafter, “ It is necessary to induce the detected electrons to the electron detector side by acting a field).

  In this case, there is a problem that the trajectory of the electron beam, which is the primary beam, changes depending on the field. In order to avoid this, it is necessary to apply another field so that the trajectory of the electron beam does not change, and there is a problem that the configuration and control of the apparatus become complicated.

  Therefore, it has been studied to detect the detected electrons drawn into the objective lens with an electron detector arranged in the objective lens.

  In order to detect reflected electrons within the objective lens, an opening for passing an electron beam and secondary electrons is formed in a scintillator (detection element) provided in the light guide, and this opening is formed into an electron beam. Some are arranged coaxially with each other (see Patent Document 1).

JP 2000-299078 A

  When detecting the detected electrons drawn into the objective lens with an electron detector arranged in the objective lens, a flat detector with an opening for passing an electron beam as a primary beam is provided. It is conceivable to provide the inside of the objective lens so that the opening is positioned on the optical axis of the electron beam.

  However, in this case, the range through which the electron beam passes is limited by the size of the opening. As a result, when the observation field of view on the sample is enlarged, the electron beam deviates from the opening and is blocked by the electron detector itself, and there is a problem that the observation field is restricted.

  The present invention has been made in view of such a point, and an electron detector capable of efficiently and efficiently detecting detected electrons drawn into an objective lens, and a beam apparatus including the same The purpose is to provide.

An electron detector according to the present invention is an electron detector that is disposed in a beam passage hole of an objective lens and detects detected electrons generated from a sample irradiated with a primary beam that has passed through the beam passage hole. consists annulus integral with a through hole which the primary beam passes, on the inner surface of the annular body, is provided in multiple stages a plurality of detection elements for detecting the detected electrons along the optical axis of the primary beam, Thus, it is possible to detect the detected electrons depending on the emission angle from the sample .

  A beam apparatus according to the present invention is a beam apparatus that irradiates a sample with a primary beam that has passed through a beam passage hole of an objective lens, thereby detecting detected electrons generated from the sample. It is provided in the beam passage hole.

In the present invention, the electron detector disposed in the beam passage hole of the objective lens is an integral annular body having a through-hole through which the primary beam passes , and detects the detected electrons on the inner surface of the annular body. These detection elements are provided in multiple stages along the optical axis of the primary beam, thereby enabling detection of detected electrons depending on the emission angle from the sample .

In this case, in the beam passage hole of the objective lens, since the axis of the through hole of the annular body is along the beam optical axis, the observation field by the electron beam is not restricted by the annular body. Furthermore, since a detection signal is output individually for each detection element, the detection result of the detection electron for each detection element at each position on the inner surface of the annular body is known, and the detection target electrons depending on the emission angle from the sample Can be detected.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing a beam apparatus according to the present invention.

  In the figure, an accelerated electron beam (primary beam) 8 is emitted toward a sample 6 from an electron gun 1 which is a primary beam source. The emitted electron beam 8 is finely focused on the sample 6 by the focusing lens 2 and the objective lens 4 and irradiated. At this time, the electron beam 8 is deflected by the scanning coil 3. Thereby, the electron beam 8 scans on the sample 6.

  Scanning (irradiation) of the electron beam 8 generates detected electrons 9 such as secondary electrons and reflected electrons from the sample 6. The detected electrons 9 generated from the sample 6 are detected by the electron detector 5. Here, the electron detector 5 has an annular shape and is disposed inside the objective lens 4 as will be described later.

  The electron detector 5 outputs a detection signal based on the detection of the detected electrons 9. The detection signal is amplified by the amplifier 5a, A / D converted, and sent to the image processing unit 5b.

  The image processing unit 5b creates image data (scanned image data) based on the detection signal after A / D conversion. The image data is sent to the display unit 12 via the bus line 10. The display unit 12 displays the image (scanned image) based on the image data.

  Here, a driving voltage is applied to the electron gun 1 by a high voltage power source 1a. The focusing lens 2 and the objective lens 4 are supplied with lens driving currents by lens power sources 2a and 4a, respectively. The scanning coil 3 is supplied with a coil driving current from a coil power supply 3a.

  Each of these power supplies 1a, 2a, 3a, 4a is connected to the bus line 10. A system control unit 11 is connected to the bus line 10. As a result, the electron gun 1, the focusing lens 2, the scanning coil 3, and the objective lens 4 are driven and controlled by the system control unit 11 via the corresponding power supplies 1a, 2a, 3a, and 4a.

  The sample 6 is placed on the stage mechanism 7. The stage mechanism 7 moves the sample 6 in the X direction, the Y direction, and the Z direction. Here, the XY plane is a horizontal plane, and the Z direction is a vertical direction. Further, the stage mechanism 7 tilts and rotates the sample 6 as necessary.

  A stage driving unit 7 a is connected to the stage mechanism 7. The stage driving unit 7 a supplies a driving signal to the stage mechanism 7. Thereby, the stage mechanism 7 is driven.

  The stage drive unit 7 a is connected to the system control unit 11 via the bus line 10. Accordingly, the system control unit 11 performs drive control of the stage mechanism 7 via the stage drive unit 7a.

  An input unit 13 is connected to the bus line 10. The input unit 13 includes a pointing device such as a mouse and a keyboard, and an operator of the beam apparatus manually inputs the input unit 13 to input instructions and the like necessary for the operation of the beam apparatus.

  Here, FIG. 2 shows an annular electron detector 5 arranged in the objective lens 4. As shown in the figure, the electron detector 5 is provided in a beam passage hole 24 in the objective lens 4.

  More specifically, the objective lens 4 includes a yoke portion 26, and a beam passage hole 24 through which the electron beam 8 passes is formed at the center of the yoke portion 26. The central axis of the beam passage hole 24 coincides with the optical axis of the electron beam 8.

  Then, the electron detector 5 is fixed to the inner side surface 24 a of the beam passage hole 24 via an insulating film (not shown), whereby the electron detector 5 is supported and provided in the beam passage hole 24.

  The electron detector 5 is made of a metal annular body 22 having a through-hole through which the electron beam 8 passes, and a detection element 21 is provided on the inside thereof. Thereby, the inner surface of the annular body 22 is a detection surface for detecting the detected electrons. The detection element 21 is composed of a PN junction (PN junction) element, and is arranged on the annular body 22 via an insulating layer (not shown). A detection signal based on the detected electrons 9 detected by the detection element 21 is sent from the detection element 21 to the amplifier 5a (see FIG. 1).

  A coil portion 25 is provided in the yoke portion 26 of the objective lens 4. The coil unit 25 is supplied with lens driving current from the lens power supply 4a (see FIG. 1). The tip 27 of the objective lens faces the sample 6, and the electron beam 8 that has entered the beam passage hole 24 of the objective lens 4 passes through the tip 27 and reaches the sample 6. Here, the objective lens 4 is at ground potential.

  Next, a first embodiment of the electron detector according to the present invention will be described with reference to FIG. In the electron detector 5, a continuously formed detection element 21 is provided on a metal annular body 22 through an insulating layer (not shown). As shown in the figure, a ground potential or a positive bias potential can be applied to the annular body 22 via the changeover switch S1. This bias potential is variable, and a desired potential can be set.

  In the state shown in FIG. 3, the movable contact T1 of the changeover switch S1 is in contact with the contact P1, and thereby the annular body 22 is set to the ground potential. In this state, the detected electrons 9 drawn into the beam passage hole 24 of the objective lens 4 are drawn to the annular body 22 having a ground potential. As a result, the detected electrons 9 are detected by the detection element 21.

  Here, when the detection efficiency of the detected electrons 9 by the detecting element 21 is further increased, the changeover switch S1 is switched to bring the movable contact T1 into contact with the contact Q1, thereby causing the annular body 22 to have a positive bias potential. Apply. As a result, the detected electrons 9 are further attracted to the annular body 22 having a positive potential, and the detection efficiency of the detection element 21 is improved.

  Next, a second embodiment of the electron detector according to the present invention will be described with reference to FIG. In the electron detector 5, a plurality of detection elements 31 are provided in multiple stages in the through-hole of the annular body 22, separately from each other along the optical axis of the electron beam 8. The plurality of detection elements 31 are fixed to the annular body 22 via an insulating layer (not shown).

  For each detection element 31, a detection signal is individually output to the amplifier 5a. Thereby, on the inner surface of the annular body 22, the detection result of the detected electrons 9 for each detection element 31 at each position is known. Therefore, a plurality of detection elements 31 in a specific position range on the inner surface of the annular body 22 can be designated, and the detection result of the detected electrons 9 in the position range can be acquired. Therefore, when the detection position ranges of the secondary electrons and the reflected electrons of the detected electrons 9 on the inner surface are different, it is possible to obtain a detection result for only one of the detected electrons.

  That is, secondary electrons generated from the sample 6 are mainly detected in the position range on the inner surface of the annular body 22 on the side close to the sample 6. Since surface information of the sample 6 can be obtained by detecting secondary electrons from the sample 6, in order to acquire surface information, a plurality of detection elements 31 in the position range are designated and secondary electrons are specified. Select to detect.

  In addition, in the position range far from the sample 6 on the inner surface of the annular body 22, reflected electrons generated from the sample 6 are mainly detected. Since the composition information of the sample 6 can be obtained by detecting the reflected electrons from the sample 6, in order to obtain the composition information, a plurality of detection elements 31 in the position range are designated and the reflected electrons are selected. To detect.

  Furthermore, also in the second embodiment, a ground potential or a positive bias potential can be applied to the annular body 22 via the changeover switch S2. The bias potential is variable, and a desired potential can be set.

In the state shown in FIG. 4, the movable contact T2 of the change-over switch S2 is in contact with the contact P 2, thereby the annular body 22 is the ground potential. In this state, the detected electrons 9 drawn into the beam passage hole 24 of the objective lens 4 are drawn to the annular body 22 having a ground potential. As a result, the detected electrons 9 are detected by the detection element 31 .

Here, in order to further increase the detection efficiency of the detected electrons 9 by the detection element 31 , the changeover switch S <b> 2 is switched to bring the movable contact T <b> 2 into contact with the contact Q <b> 2, thereby positively biasing the annular body 22. Apply potential. As a result, the detected electrons 9 are further attracted to the annular body 22 set to a positive potential, and the detection efficiency by the detection element 31 is improved.

  Further, a modification of the second embodiment will be described with reference to FIG. FIG. 5 is a view showing one side of a cross section of the electron detector in the modified example.

  As shown in the figure, a plurality of convex portions 32 a are formed on the inner surface of the annular body 32 constituting the electron detector 5. The detection elements 31 are individually provided on the surface 32b on the side on which the detected electrons 9 are incident in each convex portion 32a.

  Accordingly, each detection element 31 is arranged to be inclined so as to face the incident direction of the detected electrons 9. With this configuration, the detection efficiency of the detected electrons 9 by each detection element 31 can be further improved. In this modified example, as described above, a positive bias potential may be applied to the annular body 32 or the ground potential may be set.

  The beam apparatus according to the present invention irradiates the sample 6 with the electron beam 8 which is the primary beam through the objective lens 4 as shown in FIG. 1, thereby detecting the detected electrons 9 generated from the sample 6. As shown in FIG. 2, the objective lens 4 includes any one of the electron detectors 5 in a beam passage hole 24 through which the electron beam 8 passes. Thereby, the detected electrons 9 drawn into the beam passage hole 24 of the objective lens 4 can be efficiently detected by the electron detector 5.

  Next, with reference to FIG. 6, the 1st modification of the beam apparatus in this invention is demonstrated. As shown in the figure, an electron detector 5 is disposed in the beam passage hole 24 of the objective lens 4, and the electron detector (primary beam) 8 is irradiated in the irradiation direction with the electron detector 5 interposed therebetween. A first electrode 41 is provided on the downstream side, and a third electrode 43 is provided on the upstream side in the irradiation direction. These first and third electrodes 41 and 43 are also arranged in the beam passage hole 24 of the objective lens 4.

  The first electrode 41 has an annular shape in which a through hole through which the electron beam 8 passes is formed. Similarly, the third electrode 43 has an annular shape in which a through hole through which the electron beam 8 passes is formed.

  A first negative bias voltage is applied to the first electrode 41, and a third negative bias voltage is applied to the third electrode 43. In the example shown in FIG. 6, the electron detector 5 is set to the ground potential. Each bias voltage is variable and can be set as appropriate. However, the magnitude (absolute value) of the third negative bias voltage is set larger than the magnitude of the first negative bias voltage. .

Distribution map of potential at this case is shown in the right side of FIG. In this distribution diagram, the −Z direction corresponds to the irradiation direction (vertically downward direction) of the electron beam 8, and the potential direction corresponds to the magnitude of the negative potential.

  In the example of FIG. 6, the secondary electrons 9 a included in the detected electrons 9 cannot pass through the potential barrier due to the first electrode 41 to which the first negative bias voltage is applied. On the other hand, the reflected electrons 9b having higher energy than the secondary electrons 9a can pass through the potential barrier, and are detected by the electron detector 5 after the passage. Note that a third electrode 43 is disposed on the opposite side of the first electrode 41 with the electron detector 5 in between, and due to the potential due to the third negative bias voltage applied to the electrode 43, Further upward movement of the reflected electrons 9b is prevented. Thereby, the detection of the reflected electrons 9b by the electron detector 5 can be performed efficiently.

  According to such a configuration, it is possible to reliably and efficiently detect only the reflected electrons 9b in a state where the secondary electrons 9a are excluded.

  Furthermore, with reference to FIG. 7, the 2nd modification of the beam apparatus in this invention is demonstrated. Also in the example shown in the figure, the electron detector 5 is disposed in the beam passage hole 24 of the objective lens 4 and the irradiation direction of the electron beam (primary beam) 8 with the electron detector 5 interposed therebetween. A first electrode 41 is provided on the downstream side in FIG. 3, and a third electrode 43 is provided on the upstream side in the irradiation direction.

  The first electrode 41 and the third electrode 43 have an annular shape in which a through hole through which the electron beam 8 passes is formed.

  Further, in this example, a second electrode 42 is provided on the downstream side of the first electrode 41. Similarly, the second electrode 42 has an annular shape in which a through hole through which the electron beam 8 passes is formed. These first, second and third electrodes 41, 42 and 43 are also arranged in the beam passage hole 24 of the objective lens 4.

  A positive bias voltage is applied to the first electrode 41, and a second negative bias voltage is applied to the second electrode 42. In the example shown in FIG. 7, the electron detector 5 is set to the ground potential. Each bias voltage is variable and can be set as appropriate. However, the magnitude of the third negative bias voltage is set larger than the magnitude of the second negative bias voltage.

Distribution map of potential at this case is shown in the right side of FIG. Also in this distribution diagram, the −Z direction corresponds to the irradiation direction (vertically downward direction) of the electron beam 8, and the potential direction corresponds to the magnitude of the negative potential.

  In the example of FIG. 7, the secondary electrons 9a included in the detected electrons 9 cannot pass through the potential barrier caused by the second electrode 42 to which the second negative bias voltage is applied. On the other hand, the reflected electrons 9b having higher energy than the secondary electrons 9a can pass through the potential barrier. At this time, the reflected electrons 9b are accelerated by the positive bias voltage applied to the first electrode, and can pass through the potential barrier more reliably.

  Further, the reflected electrons 9b that have passed through the potential barrier are accelerated by the positive bias voltage, and as a result, the kinetic energy becomes high and are collided with the detection element of the electron detector 5 to be detected. Will improve. Note that a third electrode 43 is disposed on the opposite side of the first electrode 41 with the electron detector 5 in between, and due to the potential due to the third negative bias voltage applied to the electrode 43, Further movement of the reflected electrons 9b is prevented. Thereby, the detection of the reflected electrons 9b by the electron detector 5 can be performed more efficiently.

  According to such a configuration, it is possible to more reliably and efficiently detect only the reflected electrons 9b without the secondary electrons 9a.

  In each of the above modifications, a positive bias voltage may be applied to the electron detector 5 if necessary.

  As described above, in the present invention, the electron detector disposed in the beam passage hole of the objective lens is formed of an annular body having a through hole through which the primary beam passes, and the inner surface of the annular body detects the detected electrons. It is a detection surface for doing this.

In this case, the beam through holes of the pair objective lens, the axis of the through-holes of the annular body so and thus along the beam axis, will not be constrained in the observation field of view is caused by the electron beam by the annular body. Here, since the electron detector made of an annular body is arranged at a position that is axially symmetric with respect to the beam optical axis, the axial correction of the electron beam can be reduced.

  Since the annular electron detector is arranged in the beam passage hole of the objective lens, the space occupied by the electron detector can be reduced, and the detection area of the detected electrons can be increased. Since the electron detector approaches the sample surface serving as a signal source and surrounds the signal (electrons to be detected) itself, the detection efficiency is improved.

  In addition, the energy band of the secondary electrons and reflected electrons to be mixed can be continuously adjusted by the combination of voltage application to the detection elements and electrodes in a plurality of stages, and the optimum contrast of the image according to the observation purpose is obtained. It becomes possible.

  Furthermore, it becomes possible to increase the detection efficiency of low-energy reflected electrons of about 0.5 to 2.0 kV.

  Then, by arranging a plurality of detection elements in multiple stages, it becomes possible to detect reflected electrons depending on the emission angle.

  In the above example, the annular body is an integral body. However, the annular body is not limited to this, and the annular body is composed of a plurality of components divided by a plurality of boundary lines parallel to the axial direction of the through hole. They may be assembled so that the detected electrons can be detected individually for each component.

It is a schematic block diagram which shows the beam apparatus based on this invention. It is a figure which shows the electron detector arrange | positioned in an objective lens. It is a figure which shows 1st Example of the electron detector based on this invention. It is a figure which shows 2nd Example of the electron detector based on this invention. It is a figure which shows the principal part of 2nd Example of the electron detector based on this invention. It is a figure which shows the 1st modification of the beam apparatus based on this invention. It is a figure which shows the 2nd modification of the beam apparatus based on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electron gun, 2 ... Focusing lens, 3 ... Scanning coil, 4 ... Objective lens, 5 ... Electron detector, 6 ... Sample, 7 ... Stage mechanism, 8 ... Electron beam (primary beam), 9 ... Electron to be detected, 21 ... detection element, 22 ... annular body, 24 ... beam passage hole

Claims (10)

An electron detector that is disposed in a beam passage hole of an objective lens and detects detected electrons generated from a sample irradiated with a primary beam that has passed through the beam passage hole, and has a through-hole through which the primary beam passes. Consisting of an annular body, multiple detection elements for detecting the detected electrons are provided in multiple stages along the optical axis of the primary beam on the inner surface of the annular body , thereby depending on the emission angle from the sample. An electron detector capable of detecting detected electrons . 2. The electron detector according to claim 1 , wherein each detection element is fixed to an inner surface of the annular body through an insulating layer . Each detector element, an electron detector according to claim 1 or 2, characterized in that is provided obliquely so as to face the incident direction of the detected electrons.   4. A beam apparatus for irradiating a sample with a primary beam that has passed through a beam passage hole of an objective lens and thereby detecting detected electrons generated from the sample, wherein the electron detector according to claim 1 is passed through the beam passage. A beam device provided in a hole.   5. The beam according to claim 4, wherein in the beam passage hole of the objective lens, an annular first electrode having a through-hole through which the primary beam passes is disposed downstream of the electron detector. apparatus.   6. The beam apparatus according to claim 5, wherein a negative bias voltage is applied to the first electrode.   6. An annular second electrode having a through-hole through which a primary beam passes is disposed downstream of the first electrode in the beam passage hole of the objective lens. Beam device.   8. The beam apparatus according to claim 7, wherein a positive bias voltage is applied to the first electrode, and a negative bias voltage is applied to the second electrode.   9. The beam apparatus according to claim 4, wherein a positive bias voltage is applied to the electron detector.   In the beam passage hole of the objective lens, an annular third electrode having a through-hole through which the primary beam passes is arranged upstream of the electron detector, and a negative bias voltage is applied to the third electrode. The beam device according to claim 5, wherein the beam device is applied.

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