JP3403454B2 - Backscattered electron detector - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backscattered electron detector, and more particularly to a backscattered electron detector used for a surface analyzer such as a scanning electron microscope and an electron beam microanalyzer. . 2. Description of the Related Art In a surface analyzer such as a scanning electron microscope or an electron beam microanalyzer, a sample is irradiated with an electron beam and electrons called backscattered electrons or backscattered electrons scattered backward from the sample. The surface analysis of the sample is performed by detecting backscattered electrons by a backscattered electron detector. FIG. 5 is a schematic diagram for explaining the outline of a conventional backscattered electron detecting device. In FIG. 5, the incident electron beam 40 emitted from the electron gun 30 is applied to the sample S through the lens opening 34 of the final lens 33. Incident electron beam 40
Is reflected at the sample surface SS of the sample S, and the reflected electrons are detected by the detector 1 composed of a semiconductor type detector. This detector 1 has a sample chamber S in which a conventional sample S is installed.
Inside C, it is attached to the sample S side of the final lens 33. [0004] However, the above-mentioned conventional backscattered electron detection device has the following problems. (1) The angle of taking out the reflected electrons to be detected cannot be made too high. The inner diameter of the conventional detector is limited by the inner diameter of the lens opening 34 of the final lens 33. A detector smaller than the inner diameter cannot be used, and the take-out angle 44 of the detector 1 must be increased. Can not. In general, the reliability of the detection data decreases as the take-out angle of the backscattered electrons to be detected decreases due to the influence of the edge effect caused by the unevenness of the sample. Therefore, it is desirable to detect the backscattered electrons with a high takeout angle. In addition, the reliability of the detection data means
The purpose is to faithfully reflect the composition contrast of the sample on the image. (2) The S / N ratio decreases due to detection of low energy reflected electrons and secondary electrons generated by reflected electrons scattered in the sample chamber. [0008] Since the conventional detection device is arranged in the sample chamber SC, secondary electrons generated by low-energy reflected electrons and reflected electrons scattered in the sample chamber, as well as intended high-energy reflected electrons, are noise. As S
/ N ratio is reduced. (3) The sample may come into contact with the detector and damage the detector. [0010] Since the conventional detection device is installed in the sample chamber SC, there is a possibility that the detection device may come into contact with the sample S and be damaged in some cases. [0011] In order to achieve the above object, the present invention comprises a backscattered electron detector and an optical microscope,
In a backscattered electron detection device that irradiates the sample with an electron beam through a final lens and detects backscattered electrons scattered backward from the sample by the irradiation, the detector of the backscattered electron detection unit is disposed on the sample side of the last lens. On the side opposite to the sample with respect to the main surface, an optical cone for positioning the optical system device of the optical microscope inside is arranged at an end on the sample side of the optical cone. In order to achieve the above object, the present invention irradiates a sample with an electron beam through a final lens, and detects reflected electrons scattered backward from the sample by the irradiation. In the backscattered electron detection apparatus, a detector for detecting backscattered electrons is arranged at a position opposite to the sample with respect to the main surface of the final lens on the sample side. The backscattered electron detector can be applied to a surface analyzer such as a scanning electron microscope and an electron beam microanalyzer. According to the present invention, the sample is irradiated with an electron beam through the final lens, and reflected electrons scattered backward from the sample by the irradiation are detected by the reflected electron detector. This detector is located at the position opposite to the sample with respect to the main surface of the final lens on the sample side, and reflected electrons with a high take-out angle are incident on the detector. A low-energy reflected electron and a scattered electron in the sample chamber are cut by the action of an intervening lens, and only high-energy reflected electrons are detected from various electron beams reflected from the sample. Further, by providing a lens between the detector and the sample, contact between the detector and the sample is prevented. The configuration in which the detector is disposed at a position opposite to the sample with respect to the main surface of the final lens on the sample side allows the inner diameter of the detector to be reduced, and the smaller inner diameter of the detector allows the detector to have a smaller inner diameter. Increase the angle of taking back reflected electrons. Embodiments of the present invention will be described below in detail with reference to the drawings. However, the present invention is not limited to the embodiments. (Embodiment 1) (Configuration of Embodiment 1 of the Present Invention) FIGS. 1 and 2
FIG. 1 is a configuration diagram illustrating an outline of a backscattered electron detection device of the present invention. The backscattered electron detector of the present invention shown in FIG. 1 is schematically similar to the conventional backscattered electron detector shown in FIG.
Is irradiated on the sample S through the lens opening 34 of the final lens 33, and the reflected electrons reflected on the sample surface SS of the sample S are detected by the detector 10. Detector 1
Reference numeral 0 denotes a semiconductor type detector, which performs signal processing after amplifying the detected signal by the amplifier 35. In addition,
By utilizing the gain control in the amplifier 35, the detection sensitivity of the detector can be varied, so that a reflected electron image can be observed during WDX analysis. The difference between the configuration of the backscattered electron detector of the present invention and the conventional backscattered electron detector is the installation position and the diameter of the detector 10. In the backscattered electron detection device of the present invention, the detector 10 is installed at the electron gun 30 side opposite to the sample S with respect to the main surface 38 of the lens opening 34 of the final lens 33. In FIG. 1, for example, the detector 10 is installed near the sample S side end of the liner tube 32 which is the path of the incident electron beam 40. The attachment portion of the detector 10 is not limited to the vicinity of the end on the sample S side of the liner tube 32 in FIG.
If it is on the electron gun 30 side opposite to the sample S side with respect to the main surface 38 of the lens opening 34, it can be installed in other components. This arrangement of the detector 10 enables the diameter of the detector 10 to be smaller than the inner diameter of the lens opening 34 of the final lens 33 on the sample S side. Although the detector 10 is installed outside the magnetic field region of the final lens 33 in FIG.
The installation position of 0 is not limited to this, and can be installed in the magnetic field region of the final lens 33 as shown in FIG. The configuration of the backscattered electron detection device shown in FIG. 2 is the same as the configuration of FIG. Next, the configuration of the backscattered electron detector of the present invention will be described with reference to the schematic sectional view of the backscattered electron detector of the present invention shown in FIG. 3 and the schematic perspective view of the backscattered electron detector of the present invention shown in FIG. This will be described in more detail. FIG. 3 shows an example in which the backscattered electron detector of the present invention is used for a surface analyzer. FIG. 3 (a) shows a schematic cross section of the backscattered electron detector, and FIG. () Shows a schematic plan view of the backscattered electron detection device viewed from the sample S side. It should be noted that the dimensional ratios of the components shown in the drawings do not necessarily indicate actual dimensional ratios. In FIG. 1, the backscattered electron detector of the present invention comprises a backscattered electron detector 1, an optical system 2, and a component 3 of a surface analyzer. The components of the backscattered electron detector 1 are composed of a semiconductor type detector 10, a detector mounting bar 11 and a mounting screw 12, and the optical system device 2 includes a concave mirror 20.
, A convex mirror 21, a convex mirror support 22, and a 45-degree mirror 23. The component 3 of the surface analyzer includes an electron gun 30, an electron beam passage opening 31, a liner tube 32, and a final lens 3.
And 3. In the backscattered electron detecting section 1, a semiconductor type detector 10 is attached to a detector mounting bar 11 by mounting screws 12
Attached by. This detector mounting bar 11 is
For example, it is installed at an end of an optical cone 36 formed of heavy metal or the like. The mounting position of the detector 10 can be set at an arbitrary position closer to the electron gun 30 than the main surface 38 of the lens opening 34 of the final lens 33, and is set by the optical cone 36. With this set position, the diameter of the detector 10 can be reduced without being limited by the inner diameter of the lens opening 34. Therefore, the position of the detector 10 from the sample S and the angle at which the reflected electrons are taken out are set by the position of the detector mounting bar 11 in the optical cone 36 and the diameter of the detector 10. The inner diameter end of the detector mounting bar 11 is in contact with or fixed to the outer peripheral portion of the liner tube 32 so that the detector 10 with respect to the axis of the incident electron beam 40 can be detected.
Is set, and the detector mounting bar 11 is fixed.
The number of the mounting screws 12 and the detector mounting bar 1
The number of the screw holes for fixing one detector can be any number. FIG. 3B is a plan view of the backscattered electron detector 1 viewed from the sample S, and shows the backscattered electron beam 4 to the detector 10.
1 shows the state of the passage 1 and the passage of the image to the concave mirror 20. In the figure, the reflected electron beam 41 is incident on the detector 10 through the detection window 13, and the image of the sample S is
Through the optical system device 2. 3 and 4
, The reflected electron beam 41 is represented by a solid line.
Here, the detection window 13 is formed outside the liner tube 32, and the light passage 37 is further formed outside the detection window 13. The detection window 13 is formed in, for example, a fan shape. In the illustrated embodiment, two detection windows 13 can be provided with the radial portion of the detector mounting bar 11 as a boundary. The shape of the detector 10 can be formed in a fan shape corresponding to the detection window 13, and the diameter can be smaller than the inner diameter of the lens opening 34 of the final lens 33. Further, the detector 10 is installed outside the sample chamber SC. This is because the detector 10 is disposed closer to the electron gun 30 than the main surface 38 of the lens opening 34 of the final lens 33. The optical system apparatus 2 shown is an example of an optical microscope of a perforated objective type. An image of a sample S is formed by a concave mirror 20 and a convex mirror 21 like an optical path 42 indicated by a broken line in the figure. , Is guided to the outside of the apparatus through the 45-degree mirror 23 and observed. Here, the concave mirror 20 is installed on the electron gun 30 side with respect to the detector 10 with the reflection surface of the concave part facing the sample S side coaxially with the axis of the incident electron beam 40, and the convex mirror 21 is The detector 10 is installed on the electron gun 30 side of the detector 10 with the convex reflecting surface facing the concave mirror 20 coaxially with the axis. The 45-degree mirror 23 is a plane mirror that is installed at an angle of 45 degrees with respect to the axis of the incident electron beam 40 that is installed to face the convex mirror 21.
An electron beam passage opening 31 for passing the incident electron beam 40 is formed. Then, the image of the 45-degree mirror 23 is taken out of the apparatus. The convex mirror 21 can be attached to a convex mirror support 22 provided in a liner tube 32. In the component 3 of the surface analyzer,
Electron gun 30, electron beam passage opening 31, and liner tube 32
And the final lens 33 are installed on the same axis, and the incident electron beam 40 emitted from the electron gun 30 passes through the electron beam passage opening 31, the liner tube 32, the final lens 33, and the lens opening 3.
4 irradiates the sample S. (Operation of First Embodiment) Next, the operation of the first embodiment of the present invention will be described with reference to FIGS. First, detection of a reflected electron beam reflected from the sample S will be described. The incident electron beam 40 emitted from the electron gun 30 is guided to the final lens 33 via the electron beam passage opening 31 and the liner tube 32. The final lens 33 focuses the incident electron beam 40 on the sample surface SS of the sample S. Among the reflected electron beams reflected from the sample S, the reflected electron beam 41 having a high take-out angle and being substantially reflected toward the electron gun 30 is detected by the semiconductor-type detector 10 after passing through the detection window 13. This reflected electron beam 4
The take-out angle 45 of 1 makes the detector 10
And a configuration in which the diameter of the detector 10 is smaller than the main surface 38 of the lens opening 34, and the diameter of the detector 10 is small. The reflected electron beam detected by the detector 10 is subjected to signal processing by an amplifier and a processing circuit (not shown). Next, observation of an image of the sample S with an optical microscope will be described. The image of the sample S passes through the lens opening 34 of the final lens 33 and proceeds to the electron gun 30 side, and is reflected by the reflecting surface of the concave mirror 20. The image reflected by the concave mirror 20 is reflected toward the 45-degree mirror 23 by the convex mirror 21 fixed to the liner tube 32. The direction is changed by the 45-degree mirror 23 and observation is performed. Another operation of the surface analyzer will be described. In a surface analyzer such as EPMA, characteristic X-rays are also detected in addition to electron beams. Note that E
In PMA, this position is not only the focal point of the optical microscope, but also the position where the characteristic X-rays are extracted, and in the case of the present apparatus, it is also the position where high energy reflected electrons can be detected. 3 and 4, the X-ray 43 indicated by a dashed line and a diagonal line is detected by an X-ray detector (not shown). As shown, the X-rays 43 pass from the sample S through the gap between the final lens 33 and the optical cone 36 to reach an X-ray detector (not shown). Here, the optical cone 36 supports the backscattered electron detection unit 1 and cuts backscattered electrons reflected by a member or the like in the sample chamber SC to prevent the backscattered electrons from entering the detector 10. (Effect peculiar to the first embodiment of the present invention) With the above configuration, in the first embodiment, the installation position of the detector 10 can be set by the position of the detector mounting bar 11 installed on the optical cone 36. Further, the mounting and removing of the detector 10 to and from the detector mounting bar 11
2 facilitates adjustment and replacement of the detector 10. (Modification of Embodiment 1 of the Present Invention) As means for attaching the detector 10 to the detector attaching bar 11, instead of the attaching screws, fitting by deformation of an elastic member or other known detachable attaching means is used. be able to. (Embodiment 2) (Structure of Embodiment 2 of the Present Invention) FIG. 6 is a perspective view, partly in cross section, for explaining the outline of Embodiment 2 of the backscattered electron detector of the present invention. The second embodiment of the backscattered electron detector of the present invention shown in FIG. 6 is substantially the same as the backscattered electron detector of the first embodiment shown in FIGS. Are different from each other. Therefore, hereinafter, the configuration of the detector and the convex mirror which are different from the configuration of the first embodiment will be described, and the description of the same components as those of the first embodiment will be omitted. The detector 14 is removably mounted on the detector mounting bar 11 with the mounting screw 12 in the same manner as in the first embodiment. The diameter of the detection surface 15 for detecting reflected electrons is the same as that of the liner tube 32. It is formed close to the outer peripheral surface. The inner diameter of the detection surface of the detector 10 of the first embodiment is larger than the inner diameter of the convex mirror 21 because the convex mirror 21 is installed between the detector 10 and the liner tube 32. In Example 2, the inner diameter of the detection surface 15 is formed small by being formed close to the outer peripheral surface of the liner tube 32. On the other hand, the convex mirror 25 is the detection surface 1 of the detector 14.
5 is mounted on the back surface of the liner tube 32 at the back position facing the concave mirror (not shown) so as to face the outer peripheral surface of the liner tube 32. In this case, the curvature of the convex mirror 25 is selected so as to guide the image of the sample to the convex lens, and may be different from the curvature of the convex mirror 25 of the first embodiment. (Operation of the Second Embodiment of the Present Invention) The operation of the second embodiment will be described below. However, the operation of the second embodiment is almost the same as the operation of the first embodiment. Will be described only. First, detection of a reflected electron beam reflected from the sample S will be described. The incident electron beam 40 emitted from the electron gun 30 is guided to the final lens 33 via an electron beam passage opening and a liner tube 32 (not shown) in the same manner as in the first embodiment, and the final lens 33 causes the sample surface of the sample S to be exposed. Focusing on SS is performed. Among the reflected electron beams reflected from the sample S, a reflected electron beam 47 indicated by a solid line in the figure is incident on the detection surface 15 formed close to the outer peripheral surface of the liner tube 32, and the reflected electrons are detected. It is. The take-out angle 46 of this reflected electron beam 47
Since the diameter of the detector 14 is smaller than the diameter of the detector 10 of the first embodiment, the take-out angle becomes higher. The reflected electron beam detected by the detector 10 is subjected to signal processing by an amplifier and a processing circuit (not shown). Next, observation of an image of the sample S by an optical microscope will be described. As in the first embodiment, the image of the sample S passes through the lens opening of the final lens (not shown), advances to the electron gun 30 side, and is reflected by the reflecting surface of the concave mirror (not shown). The image reflected by the concave mirror is reflected by a convex mirror 25 fixed to a liner tube 32 toward a 45-degree mirror (not shown). The diameter of the convex mirror 25 is the same as or larger than that of the first embodiment. Of diameter. When the detection area of the detector 15 is the same as that of the first embodiment, the diameter of the detector 15 is smaller than that of the first embodiment, and the light path through which the image of the sample S passes is obtained. Area becomes larger. (Effect peculiar to the second embodiment of the present invention) With the above configuration, in the second embodiment, the diameter of the detector can be reduced, so that the angle of taking out the reflected electrons can be increased. In addition, since the diameter of the detector can be reduced, the area of the light passage through which the image of the sample passes increases if the detection area of the detector is not changed, so that a bright observation image can be obtained. Can be. When the area of the light path through which the image of the sample passes is not changed, the detection area of the detector can be increased. (Modification of Second Embodiment of the Present Invention) Instead of mounting the convex mirror on the back surface of the detection surface of the detector, it is also possible to mount it on the liner tube itself. (Embodiment 3) (Structure of Embodiment 3 of the Present Invention) FIG. 7 is a perspective view, partly in cross section, for explaining an outline of Embodiment 3 of the backscattered electron detecting apparatus of the present invention. The outline of the backscattered electron detector of the present invention shown in FIG. 7 is substantially the same as that of the backscattered electron detector of the second embodiment shown in FIG. 6, and is different in the configuration for mounting the detector. . Therefore, in the following, the second embodiment
The installation configuration of the detector that is different from the configuration of
The description of the same components as those in the second embodiment is omitted. The detector 16 is formed coaxially with a liner tube (not shown) on the detector support 17, and the detector support 1 is provided on the inner peripheral portion of the end of the optical cone 36.
The installation is performed by attaching the outer peripheral portion of 7. The optical cone 36 of the detector support 17
Attachment can be performed by well-known detachable fixing means such as attachment screws. The reflected electron beam 47 from the sample S indicated by a solid line in the figure is detected by the detection surface of the detector 16. In addition, this detector 16
An opening is formed between an outer peripheral portion of the optical cone 36 and an inner peripheral portion of the end of the optical cone 36 except for a portion required for attachment, thereby forming a path for the light 18, and light 48 indicated by a broken line passes therethrough. The inner diameter of the detector 16 for detecting reflected electrons is formed close to the outer peripheral surface of a liner tube (not shown). The inner diameter of the detection surface of the detector 16 is the same as that of the second embodiment.
It is formed small similarly to. On the other hand, the convex mirror 26 is opposed to a concave mirror (not shown) at a back surface position that is back-to-back with the detection surface of the detector 16.
The inner diameter is attached close to the outer peripheral surface of a liner tube (not shown). The mounting position of the convex mirror 26 is
The position may be close to the back surface of the detection surface of the detector 16, or an arbitrary interval may be formed between the detector 16 and the detector 16. (Operation of the Third Embodiment of the Present Invention) The operation of the third embodiment will be described below. However, since the operation of the third embodiment is almost the same as the operation of the second embodiment, the operation different from that of the second embodiment will be described below. Will be described only. First, detection of a reflected electron beam reflected from the sample S will be described. The incident electron beam 40 emitted from an electron gun (not shown) is guided to the final lens via an electron beam passage opening and a liner tube (not shown) in the same manner as in the second embodiment, and is then applied to the sample surface of the sample S by the final lens. Focusing is performed. Among the reflected electron beams reflected from the sample S, a reflected electron beam 47 indicated by a solid line in the figure is incident on the detection surface of the detector 16 attached to the end of the optical cone 36, and the reflected electrons are detected. Done. The take-out angle 46 of the reflected electron beam 47 is determined by the distance between the detector 16 and the sample S and the diameter of the detector 16. Next, observation of an image of the sample S with an optical microscope will be described. The image of the sample S passes through the lens opening of the final lens (not shown), as in the second embodiment.
Further, the light passes through the light passage 18 of the detector support portion 17 and is reflected by a reflecting surface of a concave mirror (not shown). The image reflected by the concave mirror is reflected by a convex mirror 26 fixed to a liner tube (not shown) toward a 45-degree mirror (not shown). The diameter of the convex mirror 26 is the same as that of the first embodiment or the same. The diameter can be larger than the above. When the detection area of the detector 16 is the same as that of the first embodiment, the outer diameter of the detector 16 is smaller than that of the first embodiment, and the light passing through the image of the sample S is smaller than that of the first embodiment. The area of the passage increases. (Effect peculiar to the third embodiment of the present invention) The detector support portion can be directly mounted on the optical cone without using the detector mounting bar. In the case where the convex mirror and the detector are attached at an interval from the liner tube, the diameter of the convex mirror can be determined without being limited by the diameter of the detector. It should be noted that the present invention is not limited to the above embodiment, and various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention. As described above, according to the present invention,
The backscattered electron detector detects backscattered electrons with a high take-off angle, cuts backscattered electrons with low energy and backscattered electrons in the sample chamber, improves the S / N ratio, and prevents damage to the detector due to the sample. can do. By detecting only the high-energy backscattered electrons scattered in the direction immediately behind the incident electron beam, the backscattered electron contrast caused by the average atomic number difference in the sample can be reduced without being affected by the unevenness of the sample. It can be detected with a high S / N ratio.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram schematically illustrating a backscattered electron detection device of the present invention. FIG. 2 is a configuration diagram illustrating an outline of a backscattered electron detection device of the present invention. FIG. 3 is a schematic sectional view of Embodiment 1 of the backscattered electron detection device of the present invention. FIG. 4 is a perspective view, partially in cross section, for explaining an outline of Embodiment 1 of the backscattered electron detection device of the present invention. FIG. 5 is a configuration diagram schematically illustrating a conventional backscattered electron detection device. FIG. 6 is a perspective view, partially in cross section, for explaining an outline of Embodiment 2 of the backscattered electron detection device of the present invention. FIG. 7 is a perspective view of a partial cross section for explaining an outline of Embodiment 3 of the backscattered electron detection device of the present invention. [Description of Signs] 1 ... backscattered electron detector, 2 ... optical system device, 3 ... component of surface analyzer, 10, 14, 16 ... detector, 11 ... detector mounting bar, 12 ... mounting screw, 13 ... Detection window, 15: detection surface, 17: detector support, 18: light path, 20: concave mirror, 21, 25, 26: convex mirror, 22: convex mirror support, 23: 45 degree mirror, 30: electron gun, 31: electron beam passage opening, 32: liner tube, 33: final lens,
34 lens opening, 35 amplifier, 36 optical cone, 37 light path, 40 incident electron beam, 4
1, 47: reflected electron beam, 42: optical path, 43, 49 ... X
Line, 45, 46 ... take-out angle, 48 ... ray, S ... sample, SS ... sample surface, SC ... sample chamber

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hideto Komi 380-1 Matsuba, Horiyamashita, Hadano-shi, Kanagawa Inside the Hadano Plant, Shimadzu Corporation (56) References JP-A-1-298633 (JP, A) 1984-587069 (JP, U) JP-A 61-167362 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01J 37/244 H01J 37/252 H01J 37/28 H01J 37/22

Claims (1)

(57) [Claims] 1. A backscattered electron detecting unit and an optical microscope are provided, and a sample is irradiated with an electron beam through a final lens, and reflected electrons scattered backward from the sample by the irradiation are detected. In the backscattered electron detecting device, the detector of the backscattered electron detecting unit is provided with an optical cone in which the optical system device of the optical microscope is positioned inside on the side opposite to the sample with respect to the main surface of the final lens on the sample side. A backscattered electron detection device, which is arranged at an end of the sample on the sample side.