Electronic probe and electronic probe system

Abstract

The application provides an electronic detector and an electronic detection system. The electronic detector comprises: a Faraday cage for collecting secondary electrons; an electron multiplier fixed to a shielding outer cylinder, for performing primary amplification of the secondary electrons based on a first voltage at an input end of the electron multiplier and a second voltage at an output end of the electron multiplier; a power supply ring connected to the input end of the electron multiplier and the output end of the electron multiplier respectively, for providing the first voltage to the input end of the electron multiplier and the second voltage to the output end of the electron multiplier; a semiconductor detector fixed to the shielding outer cylinder, for applying a third voltage and a bias voltage to the secondary electrons to convert the secondary electrons into a current signal after performing secondary amplification; an amplifier circuit connected to the semiconductor detector, for converting the current signal into a voltage signal; and a signal amplification processing circuit, for converting an image signal from the voltage signal after amplification, so that the electronic detection efficiency can be improved and the image signal-to-noise ratio can be enhanced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electron detection, in particular, to an electron detector and an electron detection system. BACKGROUND

[0002] The scanning electron microscope device can obtain information such as the morphology, composition, energy spectrum and spectrum of the sample by using the interaction process of the charged particle beam and the substance. Among them, the secondary electrons, backscattered electrons, Auger electrons and X-rays generated by the interaction of the incident electron beam and the sample can achieve the purpose of characterizing the micro morphology and composition of the substance.

[0003] The secondary electron refers to the extranuclear electron of the sample bombarded by the high-energy incident electron beam, mainly from the depth of 1-10nm of the sample surface, and the energy range is usually between 0-50eV. The secondary electron can well display the micro morphology of the sample surface.

[0004] The mainstream secondary electron detector of the scanning electron microscope is usually an E-T (Everhart-Thornley) secondary electron detector, mainly used for out-of-lens detection. The working principle of the E-T secondary electron detector is to collect secondary electrons of a certain angle by using a Faraday cage. The collected secondary electrons are accelerated to impact a scintillator (usually +10Kv high voltage) to convert into a certain number of photons. The generated photons are transmitted to a photomultiplier tube (PMT) through a light guide medium for photoelectron conversion and electron multiplication. Then, the current formed after the electron multiplication is processed by an amplification circuit. The main processes of the E-T secondary electron detector from electron collection to input to the signal amplification circuit are: electron-photon conversion, photon transmission, photon-electron conversion, electron multiplication, current-voltage conversion and the like. Therefore, there are problems such as low quantum efficiency and mismatched spectral response peak. The light guide medium needs to be bonded by optical cement, and there is reflection loss in the light transmission process, which causes low electron detection efficiency, poor image signal-to-noise ratio and affects the final imaging quality. The PMT needs to increase the multiplication voltage when the signal is weak, which causes the noise to be amplified at the same time, and also limits the signal acquisition speed to some extent. The use of 10kV high voltage increases the difficulty of vacuum sealing and insulation; the special-shaped light-emitting material and the light guide medium increase the processing difficulty and cost. SUMMARY

[0005] The main purpose of the embodiment of the present application is to provide an electron detector and an electron detection system to reduce electron loss, enhance image signal-to-noise ratio, improve acquisition speed and optimize the structure of the detector.

[0006] In order to achieve the above purpose, the embodiment of the present application provides an electron detector, comprising:

[0007] a Faraday cage for collecting secondary electrons;

[0008] An electron multiplier fixed to the shielding outer cylinder, configured to perform primary amplification on the secondary electrons based on a first voltage at an input end of the electron multiplier and a second voltage at an output end of the electron multiplier;

[0009] A power supply ring connected to the input end of the electron multiplier and the output end of the electron multiplier respectively, configured to provide the first voltage to the input end of the electron multiplier and the second voltage to the output end of the electron multiplier;

[0010] A semiconductor detector fixed to the shielding outer cylinder, configured to apply a third voltage and a bias voltage to the secondary electrons after the primary amplification to perform secondary amplification on the secondary electrons and convert the secondary electrons into a current signal;

[0011] An amplifier circuit connected to the semiconductor detector, configured to convert the current signal into a voltage signal;

[0012] A signal amplification processing circuit, configured to amplify the voltage signal and convert the voltage signal into an image signal.

[0013] In one embodiment, the apparatus further comprises:

[0014] A first focusing lens fixed to the Faraday cage, configured to focus the secondary electrons.

[0015] In one embodiment, the apparatus further comprises:

[0016] An insulating ring, through which the first focusing lens is fixed to the shielding outer cylinder.

[0017] In one embodiment, the apparatus further comprises:

[0018] An insulating cylinder, through which the electron multiplier, the semiconductor detector, and the insulating ring are fixed to the shielding outer cylinder.

[0019] In one embodiment, the apparatus further comprises:

[0020] A second focusing lens fixed to the insulating cylinder, configured to focus the secondary electrons after the primary amplification and send the focused secondary electrons into the semiconductor detector.

[0021] In one embodiment, the apparatus further comprises:

[0022] A vacuum connector configured to transmit the voltage signal to the signal amplification processing circuit, and the signal amplification processing circuit is connected to the amplifier circuit through the vacuum connector.

[0023] In one embodiment, the apparatus further comprises:

[0024] A vacuum sealing flange, through which the vacuum connector is fixed to the shielding outer cylinder.

[0025] In one embodiment, the electron multiplier is a non-continuous dynode electron multiplier, a channel-type electron multiplier, or a microchannel plate.

[0026] In one embodiment, the third voltage is greater than the second voltage, and the second voltage is greater than the first voltage.

[0027] The present application also provides an electron detection system, comprising:

[0028] An electron detector as described above; and

[0029] An objective lens for focusing an electron beam to a sample to generate secondary electrons.

[0030] The electron detector and the electron detection system of the present application can improve the electron detection efficiency, enhance the image signal-to-noise ratio, improve the acquisition speed, and optimize the structure of the detector. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort.

[0032] Figure 1 is a schematic diagram of an electron detector in the first embodiment of the present application;

[0033] Figure 2 is a schematic diagram of an electron detector in the second embodiment of the present application;

[0034] Figure 3 is a schematic diagram of an electron detector in the third embodiment of the present application;

[0035] Figure 4 is a schematic diagram of a non-continuous dynode electron multiplier in the embodiment of the present application;

[0036] Figure 5 is a schematic diagram of a channel-type electron multiplier in the embodiment of the present application;

[0037] Figure 6 is a schematic diagram of a microchannel plate without a center hole in the embodiment of the present application;

[0038] Figure 7 is a schematic diagram of a microchannel plate with a central hole in an embodiment of the present application;

[0039] Figure 8 is a schematic diagram of an electron detection system in an embodiment of the present application. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0041] Those skilled in the art will appreciate that the embodiments of the present application can be implemented as a system, device, apparatus, method or computer program product. Therefore, the present disclosure can be embodied in the form of entire hardware, entire software (including firmware, resident software, microcode, etc.), or hardware and software in combination.

[0042] In view of the low electron detection efficiency, poor image signal-to-noise ratio and influence on the final imaging quality of the existing E-T secondary electron detector, the embodiments of the present application provide an electron detector and an electron detection system, which can improve the electron detection efficiency, achieve the purposes and advantages of enhancing the image signal-to-noise ratio, improving the acquisition speed and optimizing the detector structure. The present application will be described in detail below with reference to the drawings.

[0043] Figure 1 is a schematic diagram of an electron detector in a first embodiment of the present application; Figure 2 is a schematic diagram of an electron detector in a second embodiment of the present application; Figure 3 is a schematic diagram of an electron detector in a third embodiment of the present application. As shown in Figures 1 to 3 The electron detector comprises:

[0044] a Faraday cage 5 for attracting and collecting secondary electrons;

[0045] a funnel-shaped first focusing lens 6 fixed to the Faraday cage 5 for focusing the secondary electrons. The first focusing lens 6 can be welded as a whole with the Faraday cage 5, can efficiently collect the secondary electrons, and make the secondary electrons directly accelerate and focus to the receiving surface of the electron multiplier device 7, thereby omitting the process of electron-photon-electron conversion of the photomultiplier, and also omitting the front-end glass and light pipe part in the device structure, which can reduce the loss of electrons, has a higher signal-to-noise ratio and detection efficiency.

[0046] The first focusing lens 6, which is welded with the Faraday cage 5 as a whole, is fixed to the front end of the shielding outer cylinder 17 through the insulating ring 13.

[0047] The electron multiplier 7 is fixed to the shielding outer cylinder 17, and is used for performing primary amplification of the secondary electrons based on a first positive voltage HV1 of the electron multiplier input end 14-1 and a second positive voltage HV2 of the electron multiplier output end 14-2, which belongs to direct amplification of electron-electron, and improves quantum conversion efficiency and response speed.

[0048] The power supply ring 14, which is connected with the electron multiplier input end 14-1 and the electron multiplier output end 14-2 respectively, is used for providing the first voltage to the electron multiplier input end 14-1 and providing the second voltage to the electron multiplier output end 14-2; wherein the power supply ring is welded in the inside of the electron multiplier 7 to facilitate voltage application.

[0049] The doped silicon-based semiconductor detector 16 is fixed to the shielding outer cylinder 17, and is spaced 1mm from the electron multiplier output end, and is used for performing secondary amplification of the secondary electrons after the secondary electrons are subjected to the third voltage HV3 and the bias voltage Vf, so as to convert the secondary electrons into current signals.

[0050] The third positive voltage HV3 is a working reference voltage, the third voltage HV3 is greater than the second voltage HV2, and the second voltage HV2 is greater than the first voltage HV1. For example, HV1 = 500V to 1000V, HV2 = HV1 + (500 to 1000V), and HV3 = HV2 + 1000V. HV1, HV2 and HV3 can be dynamically adjusted according to the signal intensity of the collected electrons (for example, the size of the primary amplification is adjusted by adjusting the voltage difference between HV2 and HV1, and the size of the secondary amplification is adjusted by adjusting the voltage difference between HV3 and HV2), which has an adjustable gain effect, and the voltage can also be optimized in real time according to the to-be-measured sample to obtain higher-quality image signals. As can be seen, the working voltage of the electron multiplier and the semiconductor detector in the application is generally lower than the 10kV power supply of the conventional E-T detector, which reduces the difficulty of insulation voltage resistance and vacuum sealing.

[0051] The amplifier circuit 9 is connected with the semiconductor detector 16 through a wire or a cable, and is installed on the shielding outer cylinder 17, and is used for converting the current signals into voltage signals.

[0052] The signal amplification processing circuit 12 is used for converting the voltage signals into image signals after amplification.

[0053] In an embodiment, the electron detector further comprises:

[0054] The insulating cylinder 8 is used for fixing the electron multiplier 7, the semiconductor detector 16 and the insulating ring 13 to the shielding outer cylinder 17.

[0055] The second focusing lens 15 fixed to the insulating cylinder 8 is used to focus the secondary electrons after the first amplification, and send the focused secondary electrons to the semiconductor detector 16. The second focusing lens 15 is a ring-shaped focusing lens, which can make the focused secondary electrons continue to accelerate and impact the receiving surface of the doped silicon-based semiconductor detector 16.

[0056] The vacuum connector 11 is used to transmit the voltage signal to the signal amplification processing circuit 12. The signal amplification processing circuit 12 is installed on the vacuum connector 11, and the amplifier circuit 9 is connected through the vacuum connector 11.

[0057] The vacuum sealing flange 10 is used to fix the vacuum connector 11 to the shielding outer cylinder 17. The electron detector of the present application can be used as a detector module, and is integrally installed on the corresponding interface of the scanning electron microscope device through the vacuum connector 11.

[0058] Figure 1 The electron multiplier in the present application is a non-continuous dynode electron multiplier, Figure 2 The electron multiplier in the present application is a channel-type electron multiplier, Figure 3 The electron multiplier in the present application is a micro-channel plate. As shown in Figures 1-3 , the electron multiplier can be a self-developed device with an electron emission coating, a non-continuous dynode electron multiplier, a channel-type electron multiplier (CEM, continuous dynode multiplier) or a micro-channel plate.

[0059] Figure 4 is a schematic diagram of the non-continuous dynode electron multiplier in the embodiment of the present application. As shown in Figure 1 and Figure 4 , the non-continuous dynode electron multiplier has a structure of multiple multiplication stages, and a positive voltage HV1 can be applied to the first electron multiplication electrode and a positive voltage HV2 can be applied to the last electron multiplication electrode through the power supply ring 14.

[0060] Figure 5 is a schematic diagram of the channel-type electron multiplier in the embodiment of the present application. As shown in Figure 2 and Figure 5 , the channel-type electron multiplier has a continuous multiplication stage structure, and a positive voltage HV1 can be applied to the input end of the electron multiplier and a positive voltage HV2 can be applied to the output end of the electron multiplier through the power supply ring 14.

[0061] Figure 6 is a schematic diagram of the micro-channel plate without a center hole in the embodiment of the present application. Figure 7 is a schematic diagram of the micro-channel plate with a center hole in the embodiment of the present application. As shown in Figure 3 , Figure 6 andFigure 7 As shown, the microchannel plate (MCP) is a continuous multiplication stage structure, and a positive voltage HV1 can be applied to the input end of the electron multiplier through the power supply ring 14, and a positive voltage HV2 can be applied to the output end of the electron multiplier.

[0062] Based on the same inventive concept, the embodiment of the present application also provides an electron detection system, since the principle of solving problems of the electron detection system is similar to that of the electron detector, the implementation of the system can be referred to the implementation of the electron detector, and the repeated parts will not be described herein.

[0063] Figure 8 Fig. 1 is a schematic diagram of an electron detection system in an embodiment of the present application. Figure 8 As shown, the electron detection system comprises:

[0064] an electron detector as described above; and

[0065] an objective lens 1 for focusing an electron beam 2 to a sample 3 to generate secondary electrons 4.

[0066] In the implementation, the objective lens 1 focuses the electron beam 2 to the sample 3, and the electron beam 2 sputters in the sample 3 to generate the secondary electrons 4. The Faraday cage 5 attracts and collects the secondary electrons, and then the electrons are effectively focused and directly accelerated to hit the receiving surface of the electron multiplier 7 through the funnel-shaped first focusing lens 6. The electron multiplier 7 performs primary amplification on the secondary electrons based on the first positive voltage HV1 of the electron multiplier input end 14-1 and the second positive voltage HV2 of the electron multiplier output end 14-2, and the amplified secondary electrons are focused and continue to accelerate to hit the receiving surface of the doped silicon-based semiconductor detector 16 through the annular second focusing lens 15. The semiconductor detector 16 converts the electrons into current signals after the second amplification, and the current signals are transmitted to the amplifier circuit 9 for current-voltage conversion. The voltage signals obtained by the conversion are transmitted to the signal amplification processing circuit 12 through the vacuum connector 11, and the signal amplification processing circuit 12 converts the voltage signals into high-quality image signals after amplification.

[0067] In summary, the electron detector and the electron detection system of the embodiment of the present application make the electron multiplier and the doped silicon-based semiconductor detector work in combination, the first-stage amplification is used to make enough incident beam current enter the semiconductor detector to realize the two-stage gain adjustable amplification of the low-voltage signal, the low-junction capacitance of the semiconductor detector can improve the bandwidth of the detector, and the combination of the two effectively realizes the detection of low noise, high bandwidth and wide beam current range, more effectively amplifies the signal electrons, and thus improves the scanning speed, information acquisition flux and image signal-to-noise ratio of the electron microscope instrument.

[0068] The above-described specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above-described specific embodiments are merely examples of the present application and are not intended to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An electronic detector, characterized in that, include: A Faraday cage is used to collect secondary electrons; An electron multiplier fixed to the shielding outer cylinder is used to amplify the secondary electrons by a first-order multiplication based on a first voltage at the input terminal of the electron multiplier and a second voltage at the output terminal of the electron multiplier. A power supply ring connected to the input terminal and the output terminal of the electron multiplier respectively is used to provide a first voltage to the input terminal of the electron multiplier and a second voltage to the output terminal of the electron multiplier. A semiconductor detector fixed to the shielded outer cylinder is used to apply a third voltage and a bias voltage to the secondary electrons after first-stage multiplication amplification to convert the secondary electrons into a current signal after second-stage multiplication amplification; the third positive voltage HV3 is the working reference voltage, the third voltage HV3 is greater than the second voltage HV2, and the second voltage HV2 is greater than the first voltage HV1; the magnitude of the first-stage multiplication is adjusted by adjusting the voltage difference between HV2 and HV1, and the magnitude of the second-stage multiplication is adjusted by adjusting the voltage difference between HV3 and HV2; An amplifier circuit connected to the semiconductor detector is used to convert the current signal into a voltage signal; A signal amplification and processing circuit is used to amplify the voltage signal and convert it into an image signal; A first focusing lens fixed to the Faraday cage is used to focus the secondary electrons; An insulating ring is provided, through which the first focusing lens is fixed to the shielding outer cylinder; An insulating cylinder is used to fix the electron multiplier, the semiconductor detector, and the insulating ring to the shielding outer cylinder. The second focusing lens, fixed to the insulating cylinder, is used to focus the secondary electrons that have been amplified by a first-stage multiplication, and then send the focused secondary electrons into the semiconductor detector.

2. The electronic detector according to claim 1, characterized in that, Also includes: A vacuum connector for transmitting the voltage signal to the signal amplification and processing circuit, which is connected to the amplifier circuit via the vacuum connector.

3. The electronic detector according to claim 2, characterized in that, Also includes: A vacuum sealing flange is used to fix the vacuum connector to the shielding outer cylinder.

4. The electronic detector according to claim 1, characterized in that, The electron multiplier is a discontinuous multiplier, a channel-type electron multiplier, or a microchannel plate.

5. The electronic detector according to claim 1, characterized in that, The third voltage is greater than the second voltage, and the second voltage is greater than the first voltage.

6. An electronic detection system, characterized in that, include: The electronic detector according to any one of claims 1-5; as well as Objective lens, used to focus an electron beam onto a sample to generate secondary electrons.

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