Magnetic deflection control system and scanning electron microscope

Abstract

The invention relates to the technical field of detection, in particular to a magnetic deflection control system and a scanning electron microscope. The magnetic deflection control system provided by the invention comprises a digital-to-analog conversion module, a control module, an amplification factor modulation module and an output module, the control module comprises a scanning deflection circuit and a scanning amplitude control circuit; the input end of the scanning deflection circuit and the input end of the scanning amplitude control circuit are electrically connected with the output end of the digital-to-analog conversion module. The output end of the scanning deflection circuit is electrically connected with the input end of the output module. The output end of the scanning amplitude control circuit is electrically connected with the input end of the amplification factor modulation module, and the output end of the amplification factor modulation module is electrically connected with the input end of the output module; the output end of the output module outputs a corresponding magnetic field to adjust the scanning path of the electron beam. According to the magnetic deflection control system, the problem that the imaging quality of a scanning image finally obtained by the scanning electron microscope is poor due to the fact that noise exists in a signal for controlling scanning deflection is solved.

Description

[Technical field]

[0001] The invention relates to the field of detection technology, in particular to a magnetic deflection control system and a scanning electron microscope. [Background technology]

[0002] As the process nodes of integrated circuits gradually shrink, optical inspection faces increasing challenges and it is difficult to detect fatal defects in the chip manufacturing process in a timely and effective manner. Electron beam inspection equipment with nanometer-level resolution has become the mainstream inspection equipment in semiconductor wafer fabs.

[0003] The scanning electron microscope is the core component of the electron beam detection equipment. The basic working principle of the scanning electron microscope is to accelerate the electrons emitted from the cathode through high voltage, and the electrons are reduced into a thin electron beam through a magnetic lens and focused on the pattern surface. The deflector (magnetic deflection coil) can control the path of the electron beam and scan the surface of the wafer to generate secondary electrons and backscattered electrons. Secondary electrons and backscattered electrons are used for imaging to analyze wafer defects.

[0004] The existing magnetic deflection scanning control circuit includes a scanning circuit, a deflection amplifier, a power amplifier and a magnetic deflection coil connected in sequence. The scanning circuit is used to send signals, and the signals mainly include a signal for controlling the scanning range and a signal for scanning deflection. The two signals are output to the magnetic deflection coil through the deflection amplifier and the power amplifier. However, when the signal for controlling the scanning deflection passes through the power amplifier, the signal will be affected by the power amplifier and generate noise. When scanning, the scanning electron microscope mainly controls the scanning path of the electron beam through the magnetic deflection coil. Therefore, when the signal for controlling the scanning deflection is transmitted to the magnetic deflection coil, due to the noise in the signal for controlling the scanning deflection, the magnetic deflection coil cannot stably control the electron beam for scanning, which leads to poor imaging quality of the scanning image finally obtained by the scanning electron microscope. [Summary of the invention]

[0005] In order to solve the problem that when the existing magnetic deflection scanning control circuit is used in a scanning electron microscope, due to the presence of noise in the signal controlling the scanning deflection, the magnetic deflection coil cannot stably control the electron beam to scan, thereby resulting in poor imaging quality of the scanned image finally obtained by the scanning electron microscope, the present invention provides a magnetic deflection control system and a scanning electron microscope.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions: a magnetic deflection control system, which is used to control the output magnetic field to adjust the scanning path of the electron beam in the scanning electron microscope, and the magnetic deflection control system includes a digital-to-analog conversion module, a control module, an amplification modulation module and an output module; the control module includes a scanning deflection circuit for generating a scanning deflection control signal and a scanning amplitude control circuit for generating a scanning range control signal.

[0007] The input end of the scanning deflection circuit and the input end of the scanning amplitude control circuit are electrically connected to the output end of the digital-to-analog conversion module respectively, and the output end of the scanning deflection circuit is electrically connected to the input end of the output module so as to directly transmit the scanning deflection control signal to the output module; the output end of the scanning amplitude control circuit is electrically connected to the input end of the amplification factor modulation module, and the output end of the amplification factor modulation module is electrically connected to the input end of the output module so that the scanning range control signal is amplified by the amplification factor modulation module and then transmitted to the output module; the input end of the output module receives the scanning deflection control signal and / or the scanning range control signal, and controls the output end of the output module to output a corresponding magnetic field to adjust the scanning path of the electron beam.

[0008] In this embodiment, the control circuit is respectively configured as a scanning deflection circuit 21 and a scanning amplitude control circuit 22, wherein the scanning deflection control signal generated by the scanning deflection circuit 21 is directly transmitted to the output module 4 for output, and there is no need to configure a power amplifier, and thus the scanning deflection control signal will not be affected by the power amplifier to generate noise. When the output module 4 receives the scanning deflection control signal, the output module 4 can stably control the magnetic field, and then control the electron beam to scan, so that the scanning image finally obtained by the scanning electron microscope is well imaged.

[0009] Preferably, the magnetic deflection control system also includes a scanning waveform generating module for generating a first digital signal, the output end of the scanning waveform generating module is connected to the input end of the digital-to-analog conversion module, and the digital-to-analog conversion module is used to convert the first digital signal generated by the scanning waveform generating module into an analog signal.

[0010] Preferably, the analog signal includes a first analog signal and a second analog signal; the digital-to-analog conversion module includes a first digital-to-analog output terminal and a second digital-to-analog output terminal, the first digital-to-analog output terminal is connected to the input terminal of the scanning deflection circuit, so that the first analog signal is transmitted to the scanning deflection circuit and a scanning deflection control signal is generated; the scanning amplitude control circuit includes an analog-to-digital conversion module for converting the second analog signal into a second digital signal and a third digital signal, and also includes a horizontal axis scanning resolution offset circuit and a vertical axis scanning resolution offset circuit; the analog-to-digital conversion module includes an input terminal, a first analog-to-digital output terminal and a second analog-to-digital output terminal; the second digital-to-analog output terminal is connected to the input terminal of the analog-to-digital conversion module, so that the second analog signal is transmitted to the analog-to-digital conversion module and converted into a second digital signal and a third digital signal; the first analog-to-digital output terminal is connected to the input terminal of the horizontal axis scanning resolution offset circuit, so that the second digital signal is transmitted to the horizontal axis scanning resolution offset circuit and a first scanning range control signal is generated; the second analog-to-digital output terminal is connected to the input terminal of the vertical axis scanning resolution offset circuit, so that the third digital signal is transmitted to the horizontal axis scanning resolution offset circuit and a second scanning range control signal is generated.

[0011] Preferably, the scanning amplitude control circuit also includes a signal combination module, the input end of the signal combination module is respectively connected to the output end of the horizontal axis scanning resolution offset circuit and the output end of the vertical axis scanning resolution offset circuit, and the first scanning range control signal and the second scanning range control signal are generated into a scanning range control signal after passing through the signal combination module; the output end of the signal combination module is connected to the input end of the amplification factor modulation module to transmit the scanning range control signal to the amplification factor modulation module for amplification.

[0012] Preferably, the scanning amplitude control circuit also includes a power supply having a positive pole and a negative pole, the first digital-to-analog output terminal includes a first feedback pin and a first output pin, and the horizontal axis scanning resolution offset circuit includes a first op amp, a first coupling capacitor, a first positive filter capacitor and a first negative filter capacitor; the positive input terminal of the first op amp is grounded, the negative input terminal of the first op amp and the first output pin are connected to one end of the first coupling capacitor, and the output terminal of the first op amp and the first feedback pin are connected to the other end of the first coupling capacitor; the positive pole of the power supply and one end of the first positive filter capacitor are respectively connected to a power interface of the first op amp, and the other end of the first positive filter capacitor is grounded; the negative pole of the power supply and one end of the first negative filter capacitor are respectively connected to another power interface of the first op amp, and the other end of the first negative filter capacitor is grounded; the output terminal of the first op amp is connected to the input terminal of the signal combination module.

[0013] Preferably, the second digital-to-analog output terminal includes a second feedback pin and a second output pin, and the horizontal axis scanning resolution offset circuit includes a second op amp, a second coupling capacitor, a second positive filter capacitor and a second negative filter capacitor; the positive input terminal of the second op amp is grounded, the negative input terminal of the second op amp and the second output pin are connected to one end of the second coupling capacitor, and the output terminal of the second op amp and the second feedback pin are connected to the other end of the second coupling capacitor; the positive pole of the power supply and one end of the second positive filter capacitor are respectively connected to a power supply interface of the second op amp, and the other end of the second positive filter capacitor is grounded; the negative pole of the power supply and one end of the second negative filter capacitor are respectively connected to another power supply interface of the second op amp, and the other end of the second negative filter capacitor is grounded; the output terminal of the second op amp is connected to the input terminal of the signal combination module.

[0014] Preferably, the amplification modulation module includes a data selector and at least one amplification circuit electrically connected to the output end of the data selector; each of the amplification circuits includes a third op amp, a first resistor, a second resistor and a diode, the output end of the data selector is connected to the input end of the third op amp, the output end of the third op amp and the first resistor are respectively connected in series with the positive electrode of the diode and the second resistor, the second resistor is connected in parallel with the diode, and the cathode of the diode is connected to the input end of the output module. The data selector can realize the switching of different gain switches.

[0015] Preferably, the number of the amplifier circuits electrically connected to the output end of the data selector is at least two. The multiple amplifier circuits function as operational amplifiers with different gains, and can realize the switching of different magnifications of the scanning signal to control the size of the scanning field of view.

[0016] Preferably, a 16-bit digital-to-analog conversion chip is provided in the digital-to-analog conversion module.

[0017] To solve the above technical problems, the present invention provides another technical solution as follows: a scanning electron microscope, the scanning electron microscope comprises the above magnetic deflection control system. The present invention also provides a scanning electron microscope, which has the same beneficial effects as the above magnetic deflection control system, which will not be described in detail here.

Brief Description of the Drawings

[0018] Figure 1 It is a schematic diagram of the structure of a saddle-shaped magnetic deflector in the prior art.

[0019] Figure 2 It is a schematic diagram of the structure of a magnetic deflection control system provided by the first embodiment of the present invention.

[0020] Figure 3It is a schematic diagram of the control module structure of the magnetic deflection control system provided by the first embodiment of the present invention.

[0021] Figure 4 It is a partial structural diagram of the amplification modulation module of the magnetic deflection control system provided by the first embodiment of the present invention.

[0022] Figure 5a It is a schematic diagram of the scanning amplitude control circuit provided in the first embodiment of the present invention controlling the output module to adjust the electron beam scanning path.

[0023] Figure 5b It is a schematic diagram of the scanning amplitude control circuit provided in the first embodiment of the present invention controlling the output module to adjust the electron beam scanning path.

[0024] Figure 6a It is a scanned image taken by a scanning electron microscope using existing technology.

[0025] Figure 6b This is a scanned image taken by the magnetic deflection control system provided by the first embodiment of the present invention.

[0026] Figure 7 1 is a schematic diagram of the structure of a scanning electron microscope provided by the second embodiment of the present invention.

[0027] Description of the accompanying drawings:

[0028] 10. Magnetic deflection control system; 20. Scanning electron microscope;

[0029] 1. Digital-to-analog conversion module; 2. Control module; 3. Amplification modulation module; 4. Output module;

[0030] 11. first digital-analog output terminal; 12. second digital-analog output terminal; 21. scanning deflection circuit; 22. scanning amplitude control circuit; 31. data selector; 32. amplifier circuit;

[0031] 221, analog-to-digital conversion module; 222, horizontal axis scanning resolution offset circuit; 223, vertical axis scanning resolution offset circuit; 224, power supply; 321, third operational amplifier; 322, first resistor; 323, second resistor; 324, diode;

[0032] 2211, first analog-to-digital output terminal; 2212, second analog-to-digital output terminal; 221a, first feedback pin; 221b, first output pin; 221c, second feedback pin; 221d, second output pin; 2221, first operational amplifier; 2222, first coupling capacitor; 2223, first positive filter capacitor; 2224, first negative filter capacitor; 2231, second operational amplifier; 2232, second coupling capacitor; 2233, second positive filter capacitor; 2234, second negative filter capacitor. [Specific implementation method]

[0033] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and implementation examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0034] In the embodiments provided by the present invention, it should be understood that "B corresponding to A" means that B is associated with A, and B can be determined according to A. However, it should also be understood that determining B according to A does not mean determining B only according to A, and B can also be determined according to A and / or other information.

[0035] It should be understood that the "one embodiment" or "an embodiment" mentioned throughout the specification means that the specific features, structures or characteristics related to the embodiment are included in at least one embodiment of the present invention. Therefore, "in one embodiment" or "in an embodiment" appearing throughout the specification does not necessarily refer to the same embodiment. In addition, these specific features, structures or characteristics can be combined in one or more embodiments in any suitable manner. Those skilled in the art should also be aware that the embodiments described in the specification are all optional embodiments, and the actions and modules involved are not necessarily required for the present invention.

[0036] In various embodiments of the present invention, it should be understood that the size of the serial numbers of the above-mentioned processes does not mean the necessary order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0037] The flow chart and block diagram in the accompanying drawings of the present invention illustrate the possible architecture, function and operation of the system, method and computer program product according to various embodiments of the present application. In this regard, each box in the flow chart or block diagram can represent a module, a program segment or a part of a code, and the module, the program segment or a part of the code contains one or more executable instructions for realizing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in a sequence different from that marked in the accompanying drawings. For example, two boxes represented in succession can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, which is determined based on the functions involved. It should be particularly noted that each box in the block diagram and / or flow chart, and the combination of the boxes in the block diagram and / or flow chart can be implemented by a dedicated hardware-based system that performs a specified function or operation, or can be implemented by a combination of dedicated hardware and computer instructions.

[0038] As the process nodes of integrated circuits gradually shrink, optical inspection faces increasing challenges and it is difficult to detect fatal defects in the chip manufacturing process in a timely and effective manner. Electron beam inspection equipment with nanometer-level resolution has become the mainstream inspection equipment in semiconductor wafer fabs.

[0039] The scanning electron microscope is the core component of the electron beam detection equipment. The basic working principle of the scanning electron microscope is to accelerate the electrons emitted from the cathode through high voltage, and the electrons are reduced into a thin electron beam through a magnetic lens and focused on the surface of the pattern. The deflector (magnetic deflection coil) can control the path of the electron beam, scan the surface of the wafer to generate secondary electrons and backscattered electrons, and use secondary electrons and backscattered electrons for imaging to analyze the defects of the wafer, thereby generating a scanned image. When the electron beam needs to be deflected at a large angle, the deflection defocus of the magnetic deflection system is much smaller than that of the electrostatic deflector of the same size. Figure 1 It is a commonly used saddle-shaped magnetic deflector. The current waveform passing through the magnetic deflector is controlled by the scanning hardware circuit. After scanning resolution processing, magnification adjustment, image offset setting circuit and other operations, the scanning sawtooth wave generated acts on the magnetic deflector to generate a continuously changing magnetic field to control the electron beam to scan the sample.

[0040] The existing magnetic deflection scanning control circuit includes a scanning circuit, a deflection amplifier, a power amplifier and a magnetic deflection coil connected in sequence. The scanning circuit is used to send signals, and the signals mainly include a signal for controlling the scanning range and a signal for scanning deflection. The two signals are output to the magnetic deflection coil through the deflection amplifier and the power amplifier. However, when the signal for controlling the scanning deflection passes through the power amplifier, the signal will be affected by the power amplifier and generate noise. When scanning, the scanning electron microscope mainly controls the scanning path of the electron beam through the magnetic deflection coil. Therefore, when the signal for controlling the scanning deflection is transmitted to the magnetic deflection coil, due to the noise in the signal for controlling the scanning deflection, the magnetic deflection coil cannot stably control the electron beam for scanning, which leads to poor imaging quality of the scanning image finally obtained by the scanning electron microscope.

[0041] To solve the above technical problems, please refer to Figure 2 The first embodiment of the present invention provides a magnetic deflection control system 10, which is used to control the output magnetic field to adjust the scanning path of the electron beam in the scanning electron microscope. The magnetic deflection control system 10 includes a digital-to-analog conversion module 1, a control module 2, an amplification factor modulation module 3 and an output module 4; the control module 2 includes a scanning deflection circuit 21 for generating a scanning deflection control signal and a scanning amplitude control circuit 22 for generating a scanning range control signal.

[0042] The input end of the scanning deflection circuit 21 and the input end of the scanning amplitude control circuit 22 are electrically connected to the output end of the digital-to-analog conversion module 1 respectively, and the output end of the scanning deflection circuit 21 is electrically connected to the input end of the output module 4 to directly transmit the scanning deflection control signal to the output module 4.

[0043] The output end of the scanning amplitude control circuit 22 is electrically connected to the input end of the amplification factor modulation module 3, and the output end of the amplification factor modulation module 3 is electrically connected to the input end of the output module 4, so that the scanning range control signal is amplified by the amplification factor modulation module 3 and then transmitted to the output module 4.

[0044] The input end of the output module 4 receives a scanning deflection control signal and / or a scanning range control signal, and controls the output end of the output module 4 to output a corresponding magnetic field to adjust the scanning path of the electron beam.

[0045] It can be understood that when the magnetic deflection control system 10 starts working, the digital-to-analog conversion module 1 can receive digital signals sent by other modules in the magnetic deflection control system 10, and the digital-to-analog conversion module 1 can be used to convert digital signals into analog signals. Further, the analog signal can be input into the control module 2. Specifically, the analog signal is input into the scanning deflection circuit 21 and the scanning amplitude control circuit 22 respectively. Among them, the scanning deflection circuit 21 can generate a scanning deflection control signal after receiving the analog signal, and the scanning amplitude control circuit 22 can generate a scanning range control signal after receiving the analog signal. The function of the scanning deflection control signal and the scanning range control signal is to control the output module 4, and then adjust the magnetic field output by the output module 4. Specifically, a scanning coil is provided in the output module 4. When the output module 4 receives the scanning deflection control signal and / or the scanning range control signal, the scanning coil can control the output to form a corresponding magnetic field. When the electron beam passes through the scanning coil, the magnetic field will affect the electron beam, and the change of the magnetic field can change the scanning path of the electron beam. Therefore, the stability of the magnetic field control of the output module 4 directly affects the quality of the scanning image obtained by the scanning electron microscope.

[0046] It should be understood that, unlike the magnetic deflection scanning control circuit of the prior art, in order to simplify the circuit structure, the scanning circuit used to send out the signal for controlling the scanning range and the signal for scanning deflection will pass through the power amplifier, and when the signal for controlling the scanning deflection passes through the power amplifier, the signal will be affected by the power amplifier to generate noise. In this embodiment, the control circuit is respectively set as a scanning deflection circuit 21 and a scanning amplitude control circuit 22, wherein the scanning deflection control signal generated by the scanning deflection circuit 21 is directly transmitted to the output module 4 for output, and there is no need to set a power amplifier, and then the scanning deflection control signal will not be affected by the power amplifier to generate noise. When the output module 4 receives the scanning deflection control signal, the output module 4 can stably control the magnetic field, and then control the electron beam to scan, so that the scanning image finally obtained by the scanning electron microscope is well imaged. Specifically, when the output module 4 receives the scanning range control signal, the magnetic field output by the scanning coil inside it is controlled, and then the scanning range of the electron beam in the scanning electron microscope is adjusted. Or, when the output module 4 receives the scanning deflection control signal, the magnetic field output by the scanning coil inside it is controlled, and then the scanning rotation angle of the electron beam in the scanning electron microscope is adjusted.

[0047] It should be noted that the digital-to-analog converter commonly used in the prior art is usually an 8-bit precision digital-to-analog conversion chip, which has low digital-to-analog conversion accuracy, poor scanning position control accuracy, and slow scanning speed. Specifically, the digital-to-analog conversion module 1 in this embodiment is internally provided with a 16-bit precision digital-to-analog conversion chip, which can achieve high-speed digital-to-analog conversion, faster data update rate, and higher bandwidth than the 8-bit precision digital-to-analog conversion chip in the prior art.

[0048] Furthermore, the output end of the output module 4 provided in this embodiment is used to output a magnetic field to adjust the scanning path of the electron beam. In order to clearly understand how the scanning coil inside the output module 4 adjusts the scanning path of the electron beam. Figure 5a , wherein, when the electron beam passes through the scanning coil inside the output module 4, the scanning amplitude control circuit 22 transmits the scanning deflection control signal to the output module 4 after generating the scanning deflection control signal. Exemplarily, the scanning deflection control signal can be a small excitation current or a large excitation current. If the scanning amplitude control circuit 22 applies a small excitation current to the scanning coil of the output module 4, the electron beam scanning path is adjusted to scan the first area 5A. If the scanning amplitude control circuit 22 applies a large excitation current to the scanning coil of the output module 4, the electron beam scanning path is adjusted to scan the second area 5B. Furthermore, when the scanning deflection circuit 21 applies different current excitations to the output module 4, the control of different image angle rotations can be achieved. For example, please combine Figure 5bAfter the scanning path of the electron beam is adjusted, the first selected angle image 5P1 scanned by it can be deflected a° and turned into the second selected angle image 5P2.

[0049] Furthermore, the magnetic deflection control system 10 also includes a scanning waveform generating module for generating a first digital signal, the output end of the scanning waveform generating module is connected to the input end of the digital-to-analog conversion module 1, and the digital-to-analog conversion module 1 is used to convert the analog signal generated by the scanning waveform generating module into a digital signal.

[0050] It should be understood that the first digital signal generated by the waveform generating module is a starting digital signal, that is, the function of the first digital signal is to control the magnetic deflection control system 10 to start operating. When the digital-to-analog conversion module 1 receives the first digital signal, the digital-to-analog conversion module 1 can convert the first digital signal into an analog signal.

[0051] Further, please combine Figure 2 and Figure 3 The analog signal includes a first analog signal and a second analog signal; the digital-to-analog conversion module 1 includes a first digital-to-analog output terminal 11 and a second digital-to-analog output terminal 12, and the first digital-to-analog output terminal 11 is connected to the input terminal of the scanning deflection circuit 21, so that the first analog signal is transmitted to the scanning deflection circuit 21 and a scanning deflection control signal is generated through the scanning deflection circuit 21.

[0052] Furthermore, the scanning amplitude control circuit 22 includes an analog-to-digital conversion module 221 for converting the second analog signal into a second digital signal and a third digital signal, a horizontal axis scanning resolution offset circuit 222 and a vertical axis scanning resolution offset circuit 223; the analog-to-digital conversion module 221 includes an input end, a first analog-to-digital output end 2211 and a second analog-to-digital output end 2212.

[0053] The second analog-to-digital output terminal 12 is connected to the input terminal of the analog-to-digital conversion module 221, so that the second analog signal is transmitted to the analog-to-digital conversion module 221 and converted into a second digital signal and a third digital signal through the analog-to-digital conversion module 221; the first analog-to-digital output terminal 2211 is connected to the input terminal of the horizontal axis scanning resolution offset circuit 222, so that the second digital signal is transmitted to the horizontal axis scanning resolution offset circuit 222 and a first scanning range control signal is generated; the second analog-to-digital output terminal 2212 is connected to the input terminal of the vertical axis scanning resolution offset circuit 223, so that the third digital signal is transmitted to the horizontal axis scanning resolution offset circuit 222 and a second scanning range control signal is generated.

[0054] It should be understood that the digital-to-analog conversion module 1 can not only convert digital signals into analog signals, but also realize high-speed digital-to-analog conversion. The first analog signal converted and generated by the digital-to-analog conversion module 1 can be transmitted to the scanning deflection circuit 21 through the first digital-to-analog output terminal 11, and the second analog signal generated by the conversion can also be transmitted to the analog-to-digital conversion module 221 through the second digital-to-analog output terminal 12. The digital-to-analog conversion module 1 provided in this embodiment can realize high-speed digital-to-analog conversion, so that the data update rate is faster and the bandwidth is higher, thereby enabling the scanning electron microscope to achieve high-precision control of the scanning position, thereby improving the scanning speed of the scanning electron microscope. In addition, the user can change the size of the output current by changing the input value converted by the digital-to-analog conversion module 1, and the output current will eventually flow through the scanning coil. After the size of the current flowing through the scanning coil is changed, the scanning range can be enlarged.

[0055] Specifically, the scanning amplitude control circuit 22 also includes a signal combination module, the input end of the signal combination module is respectively connected to the output end of the horizontal axis scanning resolution offset circuit 222 and the output end of the vertical axis scanning resolution offset circuit 223, the first scanning range control signal and the second scanning range control signal are generated through the signal combination module to generate a scanning range control signal, and the output end of the signal combination module is connected to the input end of the amplification factor modulation module 3 to transmit the scanning range control signal to the amplification factor modulation module to amplify the scanning range control signal.

[0056] It can be understood that the digital-to-analog conversion module 1 can convert the first digital signal into a first analog signal and a second analog signal, and the scanning amplitude control circuit 22 can generate a scanning range control signal after receiving the second analog signal. Specifically, after the analog signal is output from the output end of the digital-to-analog conversion module 1, it is input into the analog-to-digital conversion module 221 through the input end of the analog-to-digital conversion module 221, and the analog-to-digital conversion module 221 is used to reconvert the second analog signal into a second digital signal and a third digital signal, and the second digital signal is transmitted to the horizontal axis scanning resolution offset circuit 222 through the first analog-to-digital output end 2211 to generate a first scanning range control signal, and the third digital signal is transmitted to the vertical axis scanning resolution offset circuit 223 through the second analog-to-digital output end 2212 to generate a second scanning range control signal. It should be understood that the functions of the horizontal axis scanning resolution offset circuit 222 and the vertical axis scanning resolution offset circuit 223 can both realize scanning offset when the scanning electron microscope normally scans the image, thereby eliminating the distortion of the edge of the scanned image. It should be noted that the horizontal axis scanning resolution offset circuit 222 and the vertical axis scanning resolution offset circuit 223 are only different in their control directions. For example, Figure 3As shown, the horizontal axis scanning resolution offset circuit 222 can generate a first scanning range control signal, and the vertical axis scanning resolution offset circuit 223 can generate a second scanning range control signal. After the first scanning range control signal and the second scanning range control signal are combined by the signal combination module, the scanning amplitude control circuit 22 finally outputs the scanning range control signal, and after the scanning range control signal is transmitted to the amplification modulation module 3, the amplification modulation module 3 can amplify the scanning range control signal.

[0057] Furthermore, the scanning amplitude control circuit 22 also includes a power supply 224 having a positive pole and a negative pole, the first digital-to-analog output terminal 11 includes a first feedback pin 221a and a first output pin 221b, and the horizontal axis scanning resolution offset circuit 222 includes a first op amp 2221, a first coupling capacitor 2222, a first positive filter capacitor 2223 and a first negative filter capacitor 2224.

[0058] The positive input terminal of the first operational amplifier 2221 is grounded (GND), the negative input terminal of the first operational amplifier 2221 and the first output pin 221b are connected to one end of the first coupling capacitor 2222, and the output terminal of the first operational amplifier 2221 and the first feedback pin 221a are connected to the other end of the first coupling capacitor 2222; the positive electrode of the power supply 224 and one end of the first positive filter capacitor 2223 are respectively connected to a power supply 224 interface of the first operational amplifier 2221, and the other end of the first positive filter capacitor 2223 is grounded; the negative electrode of the power supply 224 and one end of the first negative filter capacitor 2224 are respectively connected to another power supply 224 interface of the first operational amplifier 2221, and the other end of the first negative filter capacitor 2224 is grounded; the output terminal of the first operational amplifier 2221 is connected to the input terminal of the signal combination module.

[0059] Further, the second digital-analog output terminal 12 includes a second feedback pin 221c and a second output pin 221d, and the horizontal axis scanning resolution offset circuit 222 includes a second operational amplifier 2231, a second coupling capacitor 2232, a second positive filter capacitor 2233 and a second negative filter capacitor 2234;

[0060] The positive input terminal of the second operational amplifier 2231 is grounded, the negative input terminal of the second operational amplifier 2231 and the second output pin 221d are connected to one end of the second coupling capacitor 2232, and the output terminal of the second operational amplifier 2231 and the second feedback pin 221c are connected to the other end of the second coupling capacitor 2232; the positive electrode of the power supply 224 and one end of the second positive filter capacitor 2233 are respectively connected to a power supply 224 interface of the second operational amplifier 2231, and the other end of the second positive filter capacitor 2233 is grounded; the negative electrode of the power supply 224 and one end of the second negative filter capacitor 2234 are respectively connected to another power supply 224 interface of the second operational amplifier 2231, and the other end of the second negative filter capacitor 2234 is grounded; the output terminal of the second operational amplifier 2231 is connected to the input terminal of the signal combination module.

[0061] Understandably, Figure 3 X Feedback is the first feedback pin 221a, XOUT is the first output pin 221b, Y Feedback is the second feedback pin 221c, and Y OUT is the second output pin 221d. The horizontal axis scanning resolution shift circuit 222 and the vertical axis scanning resolution shift circuit 223 are used to perform scanning shift when the scanning electron microscope scans the image normally, thereby eliminating the distortion of the edge of the scanned image.

[0062] Specifically, the first feedback pin 221a and the second feedback pin 221c are used to stabilize the sampling value of the analog signal so that the analog-to-digital conversion module 221 can accurately convert the analog signal into a digital signal. The first output pin 221b and the second output pin 221d are the main output pins of the analog-to-digital conversion module 221, which output the converted digital signal. The accuracy and stability of the digital signal output by the output pin are crucial to the performance and accuracy of the entire system. The first operational amplifier 2221 and the second operational amplifier 2231 can amplify the input signal and output the amplified signal to the subsequent circuit. Specifically, the first operational amplifier 2221 and the second operational amplifier 2231 can select an ultra-low distortion, low-noise operational amplifier, which has a smaller equivalent input noise voltage, a higher conversion rate, a larger bandwidth gain and a larger common mode rejection ratio, and can effectively control image temperature drift and burrs.

[0063] Furthermore, the first coupling capacitor 2222 and the second coupling capacitor 2232 are used to couple signals, and their function is to transfer the digital signals output by the first output pin 221b and the second output pin 221d from the analog-to-digital conversion module 221 to the first op amp 2221 and the second op amp 2231, and isolate the DC component during the transmission of the digital signal to ensure that only the AC signal is amplified and processed.

[0064] The four capacitors, namely the first positive filter capacitor 2223, the first negative filter capacitor 2224, the second positive filter capacitor 2233 and the second negative filter capacitor 2234, play a filtering role on the power supply 224 line, and are used to reduce high-frequency noise and fluctuations on the power supply 224 line, and ensure that the first op amp 2221 and the second op amp 2231 obtain a stable and low-noise power supply 224. The positive filter capacitor and the negative filter capacitor are usually connected to the positive and negative electrodes of the power supply 224, and filter the noise on the power supply 224 line respectively, so that the circuit can stably provide a clean power supply 224 when working.

[0065] Furthermore, please combine Figure 2 , Figure 3 and Figure 4 The gain modulation module 3 includes a data selector 31 and at least one amplifying circuit 32 electrically connected to an output end of the data selector 31 .

[0066] Each amplifier circuit 32 includes a third operational amplifier 321, a first resistor 322, a second resistor 323 and a diode 324. The output end of the data selector 31 is connected to the input end of the third operational amplifier. The output end of the third operational amplifier and the first resistor 322 are respectively connected in series with the positive electrode of the diode 324 and in series with the second resistor 323. The second resistor 323 and the diode 324 are connected in parallel. The cathode of the diode 324 is connected to the input end of the output module 4.

[0067] Preferably, the number of the amplifier circuits electrically connected to the output end of the data selector is at least two. It can be understood that after the digital signal is initially amplified by the scanning amplitude control circuit 22, the digital signal is further transmitted to the data selector 31 of the amplification factor modulation module 3. Further, the data selector 31 can realize the switching of different gain switches. Exemplarily, there are four amplifier circuits 32, and the four amplifier circuits 32 are respectively connected to the pins X1, X2, X3 and X4 of the data selector 31. The switching of different gain switches is realized by controlling the data selector 31, wherein the four amplifier circuits 32 are operational amplifiers with different gains, which can realize the switching of different magnifications of the scanning signal to control the size of the scanning field of view.

[0068] In addition, the deflection amplifier is removed in this embodiment, and the magnification modulation module 3 is selected to replace the power amplifier of the prior art. It should be noted that the signal of the control scanning range of the prior art passes through the deflection amplifier and the power amplifier to the magnetic deflection coil, and the magnetic deflection coil receives the signal of the control scanning range to mainly adjust the scanning range of the electron beam in the scanning electron microscope. Adjusting the scanning range of the electron beam in the scanning electron microscope is also called scanning magnification control. The prior art completely depends on the deflection amplifier and the power amplifier for scanning magnification control, and its defect is that the scanning magnification control is relatively simple and cannot achieve large-scale deflection. The magnification modulation module 3 in this embodiment includes these multiple amplifier circuits inside, and its control method is diverse, so that large-scale deflection can be achieved.

[0069] The magnetic deflection control system 10 provided in the embodiment of the present invention has the characteristics of low noise, low ripple, and low thermal drift. At the same time, the scanning amplitude control circuit 22 is added to adjust the magnification to achieve wide-range scanning.

[0070] Specifically, please combine Figure 6a and Figure 6b ,contrast Figure 6a and Figure 6b The scanning images taken by the scanning electron microscope using the prior art and the magnetic deflection control system 10 provided by this embodiment under the same environmental conditions can be clearly compared. It can be clearly seen that the technical solution of the present invention can well eliminate the image distortion caused by the scanning control circuit, and the obtained image can eliminate distortion and noise.

[0071] See also Figure 7 The second embodiment of the present invention further provides a scanning electron microscope 20, which includes the above-mentioned magnetic deflection control system 10. For example, the scanning range of the scanning electron microscope in the prior art is about less than 200um, while in this embodiment, the scanning field of view of the scanning electron microscope under the influence of the magnetic deflection control system 10 is between 1mm and 5mm.

[0072] The embodiment of the present invention further provides a scanning electron microscope, which has the same beneficial effects as the above-mentioned magnetic deflection control system 10, and will not be described in detail here.

[0073] A magnetic deflection control system and a scanning electron microscope disclosed in an embodiment of the present invention are introduced in detail above. Specific examples are used in this article to illustrate the principle and implementation mode of the present invention. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation mode and application scope. In summary, the content of this specification should not be understood as limiting the present invention. Any modifications, equivalent substitutions and improvements made within the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A magnetic deflection control system for controlling an output magnetic field to adjust the scanning path of an electron beam in a scanning electron microscope, characterized in that: The magnetic deflection control system includes a digital-to-analog conversion module, a control module, an amplification modulation module and an output module; the control module includes a scanning deflection circuit for generating a scanning deflection control signal and a scanning amplitude control circuit for generating a scanning range control signal; The input end of the scanning deflection circuit and the input end of the scanning amplitude control circuit are electrically connected to the output end of the digital-to-analog conversion module respectively, and the output end of the scanning deflection circuit is electrically connected to the input end of the output module to directly transmit the scanning deflection control signal to the output module; The output end of the scanning amplitude control circuit is electrically connected to the input end of the amplification modulation module, and the output end of the amplification modulation module is electrically connected to the input end of the output module, so that the scanning range control signal is amplified by the amplification modulation module and then transmitted to the output module; The input end of the output module receives the scanning deflection control signal and / or the scanning range control signal, and controls the output end of the output module to output a corresponding magnetic field to adjust the scanning path of the electron beam.

2. The magnetic deflection control system according to claim 1, characterized in that: The magnetic deflection control system also includes a scanning waveform generating module for generating a first digital signal. The output end of the scanning waveform generating module is connected to the input end of the digital-to-analog conversion module. The digital-to-analog conversion module is used to convert the first digital signal generated by the scanning waveform generating module into an analog signal.

3. The magnetic deflection control system according to claim 2, characterized in that: The analog signal includes a first analog signal and a second analog signal; the digital-to-analog conversion module includes a first digital-to-analog output terminal and a second digital-to-analog output terminal, and the first digital-to-analog output terminal is connected to the input terminal of the scanning deflection circuit, so that the first analog signal is transmitted to the scanning deflection circuit and generates a scanning deflection control signal; The scanning amplitude control circuit includes an analog-to-digital conversion module for converting a second analog signal into a second digital signal and a third digital signal, and also includes a horizontal axis scanning resolution offset circuit and a vertical axis scanning resolution offset circuit; the analog-to-digital conversion module includes an input end, a first analog-to-digital output end and a second analog-to-digital output end; the second digital-to-analog output end is connected to the input end of the analog-to-digital conversion module so that the second analog signal is transmitted to the analog-to-digital conversion module and converted into the second digital signal and the third digital signal; the first analog-to-digital output end is connected to the input end of the horizontal axis scanning resolution offset circuit so that the second digital signal is transmitted to the horizontal axis scanning resolution offset circuit and a first scanning range control signal is generated; the second analog-to-digital output end is connected to the input end of the vertical axis scanning resolution offset circuit so that the third digital signal is transmitted to the horizontal axis scanning resolution offset circuit and a second scanning range control signal is generated.

4. The magnetic deflection control system according to claim 3, characterized in that: The scanning amplitude control circuit also includes a signal combination module, the input end of the signal combination module is respectively connected to the output end of the horizontal axis scanning resolution offset circuit and the output end of the vertical axis scanning resolution offset circuit, and the first scanning range control signal and the second scanning range control signal are generated into a scanning range control signal after passing through the signal combination module; the output end of the signal combination module is connected to the input end of the amplification factor modulation module to transmit the scanning range control signal to the amplification factor modulation module for amplification.

5. The magnetic deflection control system according to claim 4, characterized in that: The scanning amplitude control circuit also includes a power supply having a positive electrode and a negative electrode, the first digital-analog output terminal includes a first feedback pin and a first output pin, and the horizontal axis scanning resolution offset circuit includes a first operational amplifier, a first coupling capacitor, a first positive filter capacitor and a first negative filter capacitor; The positive input terminal of the first op amp is grounded, the negative input terminal of the first op amp and the first output pin are connected to one end of a first coupling capacitor, and the output terminal of the first op amp and the first feedback pin are connected to the other end of the first coupling capacitor; the positive electrode of the power supply and one end of the first positive filter capacitor are respectively connected to a power interface of the first op amp, and the other end of the first positive filter capacitor is grounded; the negative electrode of the power supply and one end of the first negative filter capacitor are respectively connected to another power interface of the first op amp, and the other end of the first negative filter capacitor is grounded; the output terminal of the first op amp is connected to the input terminal of the signal combination module.

6. The magnetic deflection control system according to claim 5, characterized in that: The second digital-to-analog output terminal includes a second feedback pin and a second output pin, and the horizontal axis scanning resolution offset circuit includes a second operational amplifier, a second coupling capacitor, a second positive filter capacitor and a second negative filter capacitor; The positive input terminal of the second op amp is grounded, the negative input terminal of the second op amp and the second output pin are connected to one end of the second coupling capacitor, and the output terminal of the second op amp and the second feedback pin are connected to the other end of the second coupling capacitor; the positive pole of the power supply and one end of the second positive filter capacitor are respectively connected to a power interface of the second op amp, and the other end of the second positive filter capacitor is grounded; the negative pole of the power supply and one end of the second negative filter capacitor are respectively connected to another power interface of the second op amp, and the other end of the second negative filter capacitor is grounded; the output terminal of the second op amp is connected to the input terminal of the signal combination module.

7. The magnetic deflection control system according to claim 1, characterized in that: The amplification factor modulation module includes a data selector and at least one amplification circuit electrically connected to an output end of the data selector; Each of the amplification circuits includes a third op amp, a first resistor, a second resistor and a diode. The output end of the data selector is connected to the input end of the third op amp. The output end of the third op amp, the first resistor and the positive electrode of the diode are connected in series, and the output end of the third op amp, the first resistor and the positive electrode of the diode are connected in series, and the second resistor is connected in series. The second resistor and the diode are connected in parallel, and the cathode of the diode is connected to the input end of the output module.

8. The magnetic deflection control system according to claim 7, characterized in that: The number of the amplifying circuits is at least two.

9. The magnetic deflection control system according to claim 1, characterized in that: The digital-to-analog conversion module is provided with a 16-bit digital-to-analog conversion chip.

10. A scanning electron microscope, characterized in that: The scanning electron microscope comprises a magnetic deflection control system as claimed in any one of claims 1 to 9.

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