JP2009205891A - Secondary electron-reflected electron detecting device, and scanning electron microscope having secondary electron-reflected electron detecting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To selectively detect a secondary electron signal and a reflected electron signal regarding a secondary electron-reflected electron detecting device and a scanning electron microscope having the secondary electron-reflected electron detecting device. <P>SOLUTION: This is a secondary electron-reflected electron detecting device which detects secondary electrons or reflected electrons generated from a test piece of an electron microscope and includes a secondary electron detecting part 30 which is composed of a corona ring 31, a scintillator 32 to receive the secondary electrons, and a light pipe 33, a reflected electron detecting part 20 which is composed of a scintillator to receive the reflected electrons and a light guide 21 which guides generated light from the scintillator and has a prescribed length, a jointing part 34 to joint the light guide 21 and the light pipe 33, and a photomultiplier 35 which receives light from any of the scintillators that have received secondary electrons or reflected electrons. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a secondary electron / reflected electron detector and a scanning electron microscope having a secondary electron / reflected electron detector, and more specifically, a secondary electron / reflector capable of selectively detecting secondary electrons and reflected electrons. The present invention relates to improvement of an electronic detection device.

  FIG. 8 is a conceptual diagram of the configuration of a scanning electron microscope (SEM). The electron beam EB emitted from the electron gun 1 is focused by the condenser lens 2, and unnecessary components are removed by the diaphragm 3, and then passes through the deflector 4. At this time, the deflector 4 deflects the sample 6 so that the electron beam scans in a two-dimensional direction. The objective lens 5 arranged at the lower stage of the deflector 4 irradiates the sample 6 with a finely focused electron beam. The diaphragm 3 may be inside the objective lens 5.

  When the electron beam EB is irradiated (scanned) on the sample 6 in this way, various signals are generated from the surface of the sample 6. Reference numeral 7 denotes a secondary electron detector that detects secondary electrons e1 generated from the sample 6. The secondary electron detector 7 receives secondary electrons attracted by a corona ring to which a high voltage is applied and an electric field formed by the corona ring to which a high voltage is applied, and outputs the secondary electron signal. And a scintillator for converting into corresponding light (optical signal). Reference numeral 8 denotes a reflected electron detector that has a passage hole for the electron beam EB and detects reflected electrons e2 emitted from the surface of the sample 6. The backscattered electron detector 8 includes a scintillator that receives backscattered electrons and converts the backscattered electrons into corresponding light (optical signal).

  In the secondary electron detector 7, the optical signal is converted into an electric signal by a photomultiplier tube (PMT: not shown). On the other hand, in the backscattered electron detector 8, the optical signal is converted into an electrical signal by a photomultiplier tube (not shown). The secondary electron signal and the reflected electron signal converted into electric signals by both of these photomultiplier tubes are processed by a subsequent electric processing circuit, and then selectively selected as a secondary electron image or a reflected electron image by CRT or LCD. Are displayed by a display device. In this case, the secondary electron detector 7 is used in a high vacuum state, whereas the reflected electron detector 8 is used in a relatively low vacuum state.

  Here, when the secondary electrons and the reflected electrons are selectively detected, an electrode capable of applying a positive or negative voltage is provided at or near the tip of the secondary electron detector, and depending on the voltage applied to the electrodes. A technique is known in which a pure secondary electron signal generated from a sample is distinguished from a secondary secondary electron signal generated by reflected electrons (see, for example, Patent Document 1).

In addition, as a backscattered electron detector, an electron-to-light conversion film that emits light upon receiving electron irradiation is provided on one surface and a reflective foil that reflects light generated on the opposite back surface in a desired direction is provided. Reflection comprising a plate, a light propagating body that receives light reflected by the reflecting foil and propagates by total reflection on the surface, and a light detector at the end of the light propagating body that detects propagating light An electronic detector is known (see, for example, Patent Document 2).
JP-A-6-267484 (paragraphs 009 to 0012, FIGS. 1 and 2) Japanese Utility Model Publication No. 55-89256 (page 4, line 2, to page 5, line 2, FIG. 2)

  In the secondary electron detector and the backscattered electron detector provided in the conventional SEM, the secondary electron detector and the backscattered electron detector exist independently of each other, and amplifiers connected to the detection unit also exist independently. As described above, since the detection unit and the amplification unit are independent of each other, each control and user operation are complicated. Furthermore, there is a problem that the cost increases because two parts configuration and the number of parts are required.

  The secondary electron detection system includes a scintillator that emits light upon receiving secondary electrons, a corona ring to which a voltage of, for example, 10 kv is applied, a light guide, and a secondary electron detector that follows the PMT, It consists of an amplifier that amplifies the output.

The backscattered electron detection system is
1) A scintillator that emits light upon receiving reflected electrons, a PMT that follows the scintillator, and an amplifier that amplifies the output of the PMT,
2) A semiconductor detector (PN junction) for detecting reflected electrons and a high gain amplifier for amplifying the output of the semiconductor detector,
3) A multi-channel plate (MCP) that receives reflected electrons to generate an electrical signal and a dedicated high-gain amplifier,
There is. Currently, 2) is the mainstream.

The reason is that 1) the scintillator and the light guide are thick and thick due to the transmission of light, and high resolution short WD (work distance: distance from the objective lens to the sample) cannot be realized.
2) can be miniaturized, and can be highly sensitive and have a short WD. However, because of the small size, there is a problem that the sensitivity is lowered with a long WD. On the other hand, when the diameter is increased to improve the sensitivity, the response speed is lowered, and only a slow scan image can be obtained.
3) has a problem that the cost and the lifetime of the MCP receiving the reflected electron image are limited.

  The present invention has been made in view of such problems, and a secondary electron / reflected electron detector and a secondary electron / reflected electron detector capable of selectively obtaining a secondary electron image and a reflected electron image with a simple configuration. An object of the present invention is to provide a scanning electron microscope having a backscattered electron detector.

  (1) The invention described in claim 1 is a secondary electron / reflected electron detection device for detecting secondary electrons or reflected electrons generated from a sample, and corona ring for attracting the secondary electrons by applying a predetermined voltage. And a scintillator that receives the secondary electrons, a secondary electron detector comprising a light pipe that guides light generated from the scintillator based on the secondary electrons, a scintillator that receives reflected electrons, and generated from the scintillator based on the reflected electrons Photoelectron image receiving light from one of the scintillators that has received secondary electrons or reflected electrons, and a junction that joins the light guide and the light pipe; And a double tube.

  (2) The invention according to claim 2 is characterized in that the light guide is formed of an acrylic plate which is provided with a hole through which a primary electron beam passes and is bent to a critical angle or less, and the surface of the acrylic plate. The back surface is provided with an aluminum coating.

  (3) The invention according to claim 3 is characterized in that, in the joint portion, the connection end portion of the light guide and the light pipe are joined by a fixing ring and fixed by adhesion.

(4) The invention according to claim 4 is a scanning electron microscope provided with the secondary electron / reflected electron detection device according to any one of claims 1 to 3 in a sample chamber.
(5) The invention according to claim 5 comprises a vacuum detector for measuring the degree of vacuum inside the sample chamber, and when the value detected by the vacuum detector is lower than a predetermined threshold, When a predetermined voltage is not applied to the corona ring, the secondary electron / backscattered electron detector operates as a backscattered electron detector, and the detected value by the vacuum detector is higher than a predetermined threshold. Is characterized in that a predetermined voltage is applied to the corona ring, whereby the secondary electron / reflected electron detector operates as a secondary electron detector.

  (1) According to the first aspect of the invention, it is possible to selectively detect the outputs of the secondary electron detection unit and the backscattered electron detection unit with the PMT, and the secondary electron image and the backscattered electron image can be easily obtained. Can be obtained with a simple configuration.

(2) According to the invention described in claim 2, it is possible to guide the optical signal of the scintillator that has emitted light by entering reflected electrons to the PMT without being attenuated.
(3) According to the invention described in claim 3, the optical signal of the reflected electrons and the optical signal of the secondary electrons can be efficiently guided to the PMT.

(4) According to the invention described in claim 4, it is possible to realize a scanning electron microscope having the characteristics as described above, and to selectively observe a secondary electron image and a reflected electron image. .
(5) According to the invention described in claim 5, it is possible to decide whether to observe the secondary electron image or the reflected electron image in accordance with the output of the vacuum detector. In that case, it is possible to display on the display whether the secondary electron image is being observed or whether the reflected electron image is being observed.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[Embodiment 1]
FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, the same components as those in FIG. 8 are denoted by the same reference numerals. In the figure, 6 is a sample and EB is an electron beam. When the sample 6 is irradiated with an electron beam EB as a primary electron beam, secondary electrons e1 and reflected electrons e2 are emitted from the sample 6. The secondary electrons e1 and the reflected electrons e2 are emitted in the direction opposite to the direction in which the primary electron beam EB enters. The secondary electron e1 has an energy of 0 to 50 eV, and the reflected electron e2 has an energy of an electron beam of a substantially primary electron beam.

  Reference numeral 20 denotes a reflected electron detector that includes a passage hole 45 for an electron beam of a primary electron beam and detects reflected electrons e2 from the sample 6. In the reflected electron detector 20, reference numeral 21 denotes a light guide that guides light generated by a scintillator (not shown) that emits light when the reflected electrons e2 collide to a predetermined location.

  Reference numeral 30 denotes a secondary electron detection unit that detects secondary electrons e1 from the sample 6. In the secondary electron detector 30, 31 is a corona ring to which a voltage of, for example, 10 kV is applied in order to attract and accelerate the secondary electrons e 1, and 32 is disposed in contact with the corona ring 31 and is incident on the incident secondary A scintillator that emits light when the electron e1 collides, 33 is a light pipe that guides light (optical signal) generated from the scintillator 32, 34 is a joint that joins the light guide 21 and the light pipe 33, and 35 receives an optical signal. The photomultiplier tube (PMT) converts the optical signal into an electrical signal. On the surface of the scintillator 32, an aluminum vapor deposition film is attached so that light generated by the scintillator 32 can reach the light pipe 33 sufficiently so that the voltage applied to the corona ring 31 becomes uniform.

  The light guide 21 for guiding the light emitted by the reflected electrons e2 (optical signal) is joined to the light pipe 33 at one end thereof. As a material for the light guide 21, for example, an acrylic plate is used. As another material, YAG (yttrium, aluminum, garnet), YAP (yttrium, aluminum, phosphorus), plastic, or the like can be used. Here, a configuration in which the scintillator 32 and the light guide 21 are integrated can be used.

  Reference numeral 34 denotes the joint. A preamplifier 40 amplifies the output of the PMT 35 and a main amplifier 41 receives the output of the preamplifier 40. The preamplifier 40 includes a current / voltage conversion resistor R1 that converts a current signal from the PMT 35 into a voltage signal, an amplifier U1, a feedback resistor R2 connected between the input and output of the amplifier U1, and voltage dividing resistors R3 and R4. Composed.

  If this identification symbol is used as it is as the value of the voltage dividing resistors R3 and R4, the gain of the preamplifier 40 is given by 1+ (R3 / R4). A main amplifier 41 receives the output of the preamplifier 40 and supplies power. The main amplifier 41 is composed of an amplifier U2, and functions as a buffer amplifier here.

  FIG. 2 is a diagram illustrating a configuration example of the light guide 21. The same components as those in FIG. 1 are denoted by the same reference numerals. In the figure, 21 is a light guide. As the light guide 21, for example, an acrylic plate is used. A scintillator 21 a is formed in the light guide 21. The scintillator 21a is formed in a donut shape with respect to the hole 45 for passing the electron beam EB. The light guide 21 is configured, for example, by bending an acrylic plate at 39 ° and 35 ° within a critical angle (for example, the critical angle of visible light is 42 ° in the case of sodium D-line).

  Since the bending angle is kept within a critical angle, light does not leak outside the light guide. The surface of the acrylic plate, etc. is coated with aluminum (AL) on the front, back, and side surfaces, for example, up to 15 mm from the connection end to remove the backscattered / secondary electron charges (including prevention of leakage of scintillator light emission). ing. For this reason, when the work distance (WD) of the sample is 5 mm to 50 mm or more, charging by reflected electrons and secondary electrons can be prevented. According to this embodiment, an acrylic plate can be used as the light guide. Here, as another material, a scintillator made of YAG, YAP, or plastic in which the scintillator and the light guide are integrated may be formed and used.

  Further, by arranging the joint between the light guide 21 and the light pipe 33 on the PMT 35 side from the position of the corona ring 31, it is possible to prevent a minute discharge due to charging. By keeping the current diameter of the corona ring 31 of the secondary electron detector 30, it is possible to secure a space distance of 8 mm from the light guide aluminum deposition surface to the 10 kV surface of the corona ring 31. Furthermore, a creepage distance of 20 mm can be ensured. Thereby, the micro discharge from the corona ring 31 to the light guide 21 can be avoided.

  The light guide connecting end and the light pipe 33 are bonded and fixed after the fixing ring is attached. FIG. 3 is a diagram showing a configuration example of the joint portion 34 of the present invention. The same components as those in FIG. 1 are denoted by the same reference numerals. In the figure, 21 is a light guide that transmits an optical signal of reflected electrons, and 33 is a light pipe that transmits an optical signal of secondary electrons. Reference numeral 37 denotes a fixing ring provided at the joint 34. After the light guide 21 and the light pipe 33 are joined by the fixing ring 37, they are bonded and fixed. The fixing ring 37 is used for adhesion reinforcement. Reference numeral 38 denotes a cut for inserting the light guide 21 into the light pipe 33. According to this embodiment, it is possible to securely fix the light guide connecting end and the light pipe. The operation of the apparatus configured as described above will be described as follows.

  When observing a conductive sample with an SEM, secondary electron detection is frequently used because of its good resolution. The non-conductive sample is usually observed by observing a secondary electron image after coating the surface with a conductive vapor deposition film. This will be referred to as HIVC (High Vacuum) for convenience. On the other hand, a non-conductive sample can be observed with a low vacuum of several Pa to 300 Pa or the like, using a reflected electron instead of a secondary electron, and image observation without sample charging. This is called LOVC (Low Vacuum) for convenience.

  The secondary electron / backscattered electron detection device according to the present invention is used in a sample chamber of an SEM having an HIVC and LOVC function, and a secondary electron detector section 30 (scintillator 32 and corona ring 31 and light applied to 10 kV). And a backscattered electron detector 20 (consisting of a light guide 21 and a scintillator 21a provided in the light guide 21) are joined together at a joint 34, followed by a PMT 35 and an amplifier section following the PMT 35. 40 and 41 are shared by each image observation. The output of the main amplifier 41 is sent to a signal processing unit (not shown) and processed so that it can be displayed on a display (not shown).

  In the secondary electron / backscattered electron detector according to the present invention, 10 kV (predetermined voltage) is applied to the corona ring 31 of the secondary electron detector 30 at the time of HIVC. The optical signal from the scintillator 32 is input to the PMT 35 via the light pipe 33, converted into an electrical signal by the PMT 35, and sent to the preamplifier 40 as a secondary electron signal.

  On the other hand, during LOVC, the voltage applied to the corona ring 31 of the secondary electron detector 30 is turned off. Then, an optical signal from the scintillator 21a of the reflected electron detector 20 is sent to the PMT 35 through the integrated light guide 21, converted into an electric signal as a reflected electron signal, and sent to the preamplifier 40 as a reflected electron signal.

  According to this embodiment, it becomes possible to selectively detect the outputs of the secondary electron detector 30 and the backscattered electron detector 20 by the PMT 35 by applying / not applying a predetermined voltage to the corona ring 31. A secondary electron image and a reflected electron image can be selectively obtained with a simple configuration.

A vacuum degree detector using a Pirani tube or the like is provided in the sample chamber of the SEM (see FIG. 8) having the functions of HIVC and LOVC, and the degree of vacuum in the sample chamber is detected. This vacuum degree detector can detect a vacuum (low pressure) higher than 10 ⁻² Pa at the time of HIVC, and can detect several Pa to 300 Pa at a higher pressure at LOVC.

When the degree of vacuum detected by the vacuum detector is higher than 10 ⁻² Pa, the control unit of the SEM (see FIG. 8 for example) applies a voltage of 10 kV to the corona ring 31 of the secondary electron detector 30. Apply. As a result, the apparatus shown in FIG. 1 functions as a secondary electron detector, and the output of the secondary electron detector 30 is input to the PMT 35, converted into an electrical signal by the PMT 35, and input to the subsequent amplifier section. The outputs of the amplifier sections 40 and 41 are input to the signal processing system of the SEM and displayed as a secondary electron image on the attached display.

  When the degree of vacuum detected by the vacuum detector is several Pa to 300 Pa, the controller of the SEM (see, for example, FIG. 8) applies an applied voltage of 10 kV applied to the corona ring 31 of the secondary electron detector 30. Turn off. When the sample chamber is set to a vacuum degree of several Pa to 300 Pa, for example, a needle valve provided in the sample chamber is opened. As a result, the pressure in the sample chamber increases and the degree of vacuum decreases, and the apparatus shown in FIG. 1 functions as a backscattered electron detector, and the output of the backscattered electron detector 20 is input to the PMT 35 and converted into an electrical signal by the PMT 35. Is input to the subsequent amplifier section. The outputs of the amplifiers 40 and 41 are input to the signal processing system of the SEM and displayed as a reflected electron image on the attached display.

  Thus, according to this embodiment, a secondary electron image or a reflected electron image can be automatically selected and displayed according to the output of the vacuum detector. In that case, it is possible to display on the display whether the secondary electron image is being observed or the reflected electron image is being observed.

In the above-described embodiment, the case where it is automatically operated as a backscattered electron detection device or a secondary electron detection device according to the output of the vacuum detector has been described as an example. However, the present invention is not limited to this, and it is possible to manually switch between the secondary electron image observation mode and the reflected electron image observation mode by switching a button attached to the SEM. In that case, the degree of vacuum in the sample chamber needs to be known in advance. That is, when the degree of vacuum is higher than 10 ⁻² Pa, the operator presses the secondary electron image observation mode button attached to the SEM, and when the degree of vacuum is several Pa to 300 Pa, the reflected electron observation mode is selected. Press the button. As a result, the control unit of the SEM can detect the secondary electron image or the reflected electron image depending on the type of the pressed button and display the image on the display.

  Conversion from HIVC to LOVC, or conversion from LOVC to HIVC switches between adjusting the vacuum degree of the sample chamber and applying 10 kV to the corona ring 31 of the secondary electron detector 20 on or off. This can be done easily.

  Optimal by adjusting the voltage applied to the PMT according to the intensity of the secondary electron signal and the reflected electron signal detected by the secondary electron / backscattered electron detector according to the present invention attached to the sample chamber. The digitized image can be observed.

As an optimization method, control link data may be provided. For example,
1) The irradiation current of the sample can be varied by controlling the excitation current of the focusing lens of the SEM.
2) Since the secondary electron and reflected electron signal intensity changes by varying the distance between the sample and the objective lens, that is, WD, the voltage applied to the PMT can be optimized.
3) By changing the acceleration voltage of the electron beam, the secondary electron and reflected electron signal intensity changes, so that the voltage applied to the PMT can be optimized.

Further, since the resolution (electron beam diameter) of the SEM changes due to variable acceleration voltage and variable WD, an upper limit value may be set for each of the secondary electron image and the reflected electron image for the observable magnification.
[Embodiment 2]
The scintillator 32 of the secondary electron detector 30 is applied with a corona ring 31 (10 kV) attached to the outer periphery where secondary electrons (energy: 0.2 to 50 eV) generated from the sample 6 are in contact with the scintillator 32 (φ25 mm). And is focused to a diameter of about 5 mm at the center of the scintillator (φ25 mm). Therefore, there is almost no light transmission leakage in the subsequent light pipe 33 and PMT 35.

However, the scintillator 21a of the backscattered electron detector 20 has a scintillator light guide 21 (thickness of 2 mm, mirror-finished front and back surfaces with aluminum vapor deposition) as shown in FIG. ) It is guided to the light pipe 33 while being scattered between the mirror surfaces of the front surface and the back surface. Then, the light is transmitted to the subsequent PMT 35. The items for which light transmission leakage during this period is predicted are as follows.
1) As a countermeasure against leakage in the thickness direction, light leakage occurs in the scintillator light guide 21 (thickness 2 mm, mirror-finished with aluminum deposition on the front and back surfaces). As a countermeasure against the leakage in the thickness direction, the scintillator light guide 21 is subjected to surface polishing and the front and back surfaces are mirror-finished by aluminum vapor deposition. The bending of the light guide 21 is suppressed to a critical angle of less than 42 ° of the acrylic material.

  There is also a method of tilting the secondary electron detector 30 without bending the light guide 21. FIG. 4 is a block diagram showing another embodiment of the present invention. The same components as those in FIG. 1 are denoted by the same reference numerals. In the figure, 21 is a light guide for transmitting an optical signal of reflected electrons, 31 is a corona ring for detecting secondary electrons, 33 is a light pipe for transmitting an optical signal of secondary electrons, and 36 is 2 The secondary electron detector cover 35 is a PMT that receives an optical signal and converts it into an electrical signal.

  In this embodiment, the light guide 21 that transmits the optical signal of the reflected electrons is linear. When the light guide 21 is linear, light leakage is reduced, and the reflected electron signal can be efficiently guided to the PMT 35. It is necessary to incline the secondary electron detector 30 by making the light guide 21 linear. In the figure, it can be seen that the light guide 21 is inserted linearly into the inclined light pipe 33 to form a joint 34.

  As countermeasures against leakage in the side direction of the light guide 21, the end surface (outer periphery) is mirror-finished and the surface is mirror-finished by aluminum vapor deposition. Further, as a countermeasure against light leakage, the configuration of the scintillator for detecting backscattered electrons is made circular, elliptical, and scooped so that the critical angle of the acrylic material is less than 42 ° as shown in FIG. FIG. 5 is a diagram showing a configuration example of the scintillator of the backscattered electron detector. Reference numeral 50 denotes a scintillator application surface, and in this example, a circular application surface is shown. 51 is a hole through which the electron beam passes.

  Next, the configuration of the joint 34 of the light guide 21 of the reflected electron detector and the light pipe 33 of the secondary electron detector will be described. FIG. 6 is a diagram showing another configuration example of the joint portion of the present invention. Reference numeral 34 denotes a joint. A in the figure shows the cross-sectional shape of the joint 34. Reference numeral 51 denotes an incident area for the reflected electron optical signal, and reference numeral 52 denotes an incident area for the secondary electron optical signal. From this, it can be seen that the light guide 21 is a quadrangular prism. A circular shape is preferable, but a quadrangular prism is used to reduce costs. The backscattered electron detector light guide 21 and the secondary electron detector light pipe 33 are joined at a right angle to eliminate light transmission leakage.

  The front and back surfaces of the backscattered electron detector light guide 21 are mirror-finished and then mirror-finished with an aluminum coating. The secondary electron detector 30 and the light guide 21 are manufactured integrally, and the portion of the light pipe 33 located on the opposite side of the corona ring 31 has a truncated cone shape. The inclination of the cone is made smaller than 42 ° which is the critical angle of acrylic. As shown in the figure, the truncated cone portion 39 is mirror-finished with an aluminum coating after mirroring the line portion including the conical surface.

  FIG. 7 is a structural conceptual diagram of a scanning electron microscope according to the present invention. The same components as those in FIG. 8 are denoted by the same reference numerals. 1 is an electron gun, EB is an electron beam, 2 is a condenser lens, 3 is a diaphragm, 4 is a deflector, 5 is an objective lens, and 6 is a sample. Reference numeral 10 denotes a secondary electron / backscattered electron detector according to the present invention provided on the top of the sample 6. The internal configuration of the secondary electron / reflected electron detection device 10 is as shown in FIG. 1 or FIG.

  When the sample 6 is irradiated with the electron beam EB, reflected electrons e2 and secondary electrons e1 are emitted from the sample 6. The reflected electrons e2 and the secondary electrons e1 are input to the secondary electron / reflected electron detector 10 according to the present invention, converted into an optical signal by the scintillator, and the optical signal is converted into an electrical signal by the PMT. This electrical signal is subjected to signal processing by a signal processing unit inside the SEM, and a reflected electron image or a secondary electron image is selectively displayed on a display (not shown) attached to the SEM.

  When a secondary electron image is observed, there is a possibility that a reflected electron signal is included in the detected signal although it is minute. However, the ratio is sufficiently low, and the secondary electron image can be accurately displayed.

  That is, in each embodiment, for example, when a sample is irradiated with an electron beam having an acceleration voltage of 2 kV or higher and a secondary electron image is observed based on the detected secondary electrons, reflected electrons are reflected in the secondary electron signal. The ratio of signal mixing is about 1/30. As described above, since the detected amount of secondary electron signals is about 30 times as large as the amount of reflected electron signals mixed, there is substantially no problem as a secondary electron image.

  As described above, according to the present invention, it is possible to selectively detect the outputs from the secondary electron detection unit and the backscattered electron detection unit, and the secondary electron image and the backscattered electron image can be easily configured. Can be obtained selectively.

It is a block diagram which shows one embodiment of this invention. It is a figure which shows the structural example of a light guide. It is a figure which shows the structural example of the junction part of this invention. It is a block diagram which shows other embodiment of this invention. It is a figure which shows the structural example of a backscattered electron detector. It is a figure which shows the other structural example of the junction part of this invention. 1 is a conceptual diagram of a configuration of a scanning electron microscope according to the present invention. It is a composition conceptual diagram of a scanning electron microscope.

Explanation of symbols

20 backscattered electron detector 21 light guide 30 secondary electron detector 31 corona ring 32 scintillator 33 light pipe 34 joint 35 PMT
40 Preamplifier 41 Main amplifier 45 EB passage hole e1 Secondary electron e2 Reflected electron U1 amplifier U2 amplifier R1 resistance R2 resistance R3 resistance R4 resistance

Claims (5)

A secondary electron / reflected electron detector for detecting secondary electrons or backscattered electrons generated from a sample,
A corona ring that attracts secondary electrons by applying a predetermined voltage; a scintillator that receives the secondary electrons; and a secondary electron detector that includes a light pipe that guides light generated from the scintillator based on the secondary electrons;
A reflected electron detector comprising a scintillator that receives reflected electrons and a light guide that guides light generated from the scintillator based on the reflected electrons;
A joint for joining the light guide and the light pipe;
A photoelectron image multiplier that receives light from any of the scintillators that has received secondary or reflected electrons;
Secondary electron / backscattered electron detection device.   The light guide is formed of an acrylic plate that is provided with a hole for the passage of a primary electron beam and is bent to a critical angle or less, and the front and back surfaces of the acrylic plate are coated with aluminum. The secondary electron / reflected electron detection device according to claim 1.   3. The secondary electron / reflected electron detection device according to claim 1, wherein the connection end of the light guide and the light pipe are joined to each other at the joint by a fixing ring and fixed by adhesion. 4. .   A scanning electron microscope comprising the secondary electron / reflected electron detection device according to claim 1 in a sample chamber. A vacuum detector for measuring the vacuum inside the sample chamber;
When the value detected by the vacuum detector is a vacuum lower than a predetermined threshold value, a predetermined voltage is not applied to the corona ring, whereby the secondary electron / backscattered electron detector is used as a backscattered electron detector. Work,
When the value detected by the vacuum detector is higher than a predetermined threshold, a predetermined voltage is applied to the corona ring, whereby the secondary electron / reflected electron detection device operates as a secondary electron detection device. The scanning electron microscope according to claim 4, wherein:

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