An automatic calibration device for electron beam deflection scanning accuracy

Abstract

This invention proposes an automatic calibration device for electron beam deflection scanning accuracy. By setting up a dedicated electron beam acquisition device, deflection scanning, and synchronous high-speed data acquisition circuit, and planning an automatic calibration scanning path, combined with specially designed deflection scanning accuracy calibration software, automatic calibration of large-angle electron beam deflection scanning accuracy is achieved, greatly improving the automation level and efficiency of calibration. By adopting a point-by-point scanning method, following an automatic calibration trajectory of clockwise square rotation and a path planning method for electron beam oscillation searching through the beam current maximum value, it can ensure that the current calibration point can be found and has a sufficiently high calibration accuracy, not less than 0.1d. The beam current through 81 calibration holes is collected by 81 independent Faraday tubes, which can ensure that the electron beam after passing through the upper electrode plate and the upper electrode plate insulation plate, as well as the secondary electrons generated by the electron beam bombarding the metal wall of the Faraday tube, are completely collected by the Faraday tube, thereby improving the calibration accuracy.

Description

Technical Field

[0001] This invention provides an automatic calibration device for electron beam deflection scanning accuracy, particularly a device for automatic calibration of high-frequency electron beam deflection scanning accuracy at large angles, belonging to the field of electron beam processing technology. Background Technology

[0002] High-frequency deflection scanning technology is one of the core technologies in electron beam additive manufacturing. Utilizing high-frequency deflection scanning not only enables substrate preheating and melting of powders or filaments, but also allows for control of the temperature field and temperature gradient on the surface of the formed part, thereby controlling the crystallization process and effectively improving the quality of rapidly manufactured parts. However, during the forming process, the electron beam deflection scanning relies on the magnetic field generated by the scanning coil to change the trajectory of the electron beam. The magnetic induction intensity of the magnetic field and its excitation current exhibit a non-linear relationship. As the deflection angle of the electron beam increases, its deflection scanning accuracy begins to decrease. This decrease in electron beam deflection scanning accuracy leads to a reduction in part forming accuracy, especially when forming large-sized parts, where the edges often fail to meet machining accuracy requirements. Therefore, improving the deflection scanning accuracy across the entire electron beam forming range is crucial for improving part forming accuracy. Thus, electron beam deflection scanning accuracy usually needs to be calibrated before electron beam processing.

[0003] Calibration, also known as calibration, involves deflecting and scanning the electron beam according to a preset state and position, and calibrating the deflection scanning accuracy of the electron beam using the position and dimensions of a small number of known points. Current calibration methods mainly include manual calibration and automated digital calibration. Manual calibration involves manually adjusting the electron beam deflection to a specified position. During the calibration process, the electron beam deflection current is adjusted primarily by visual observation until the electron beam spot coincides with the calibration point. Its disadvantages are reliance on human observation and experience, low accuracy, and low calibration efficiency. Automated digital calibration utilizes computers and imaging equipment to adjust the beam spot position to a predetermined state. As described in patent CN201610492848.X, the process generally involves using imaging equipment to capture electron beam scanning images, extracting the coordinates of the beam spot in actual space from the images, associating these coordinates with corresponding digital control quantities, and then using interpolation to calculate the digital control quantity corresponding to the coordinates of each point in actual space to achieve the correction effect. However, this calibration method suffers from difficulties in image distortion and graphic information extraction, affecting the accuracy of the beam spot position. Furthermore, it cannot achieve real-time monitoring of the beam spot position, hindering rapid and effective calibration. Patent CN201510415778.3 proposes a rapid and accurate calibration method. This method utilizes an opening in the upper electrode plate as a calibration point and collects the excitation current generated by the electron beam using the lower electrode plate, converting it into a voltage signal. Measuring this voltage signal allows for real-time monitoring of the electron beam spot position, enabling rapid and accurate calibration. In this scheme, all calibration points on the upper electrode plate are calibrated using the same upper and lower electrode plates to receive the electron beam. The calibration process requires manually adjusting the electron beam to the vicinity of each calibration point, and then manually fine-tuning the deflection and focusing currents to align the electron beam spot with the calibration opening. The entire process requires manual operation and has a low degree of automation. Secondly, during electron beam calibration, the secondary electrons generated by the upper plate are ignored when the lower plate receives the maximum through current. Since there is no insulation between the upper and lower plates, the secondary electrons generated by the upper plate after receiving the electron beam may be collected by the lower plate, leading to inaccurate measurement results. Furthermore, in this design, the micro-hole of the upper plate is a cylindrical through-hole, and the upper plate is relatively thick (approximately 10 mm). When the electron beam deflects at a large angle, it enters the calibration hole at a certain angle and may hit the sidewall of the through-hole, also causing inaccurate measurement results. This invention designs an automatic calibration device for electron beam deflection scanning accuracy, which can achieve automatic and high-precision calibration of electron beam deflection scanning accuracy. Summary of the Invention

[0004] 1. Purpose: The purpose of this invention is to provide an automatic calibration device for electron beam deflection scanning accuracy, thereby overcoming the shortcomings of existing electron beam deflection scanning accuracy calibration technology, and achieving automatic calibration by combining with specialized calibration software.

[0005] 2. Technical Solution: The objective of this invention is achieved through the following technical solution.

[0006] To achieve the above objectives, this invention provides an automatic calibration device for electron beam deflection scanning accuracy, comprising: an industrial control computer, deflection scanning accuracy calibration software, a PCI arbitrary waveform generator card, a PCI high-speed data acquisition card, an X-direction deflection coil drive circuit, a Y-direction deflection coil drive circuit, an electron gun, an electron beam, an X-direction deflection scanning coil, a Y-direction deflection scanning coil, an electron beam sampling device, an upper electrode beam signal amplification circuit, a Faraday cylinder beam signal amplification circuit, and a Faraday cylinder array sampling control circuit; wherein, the electron beam sampling device consists of an upper electrode plate, an upper electrode plate insulating plate, a ceramic insulating column, a Faraday cylinder array, a lower electrode plate insulating plate, a sampling device lower electrode plate, and an upper electrode plate beam sampling resistor R1.

[0007] The positional connection between them is as follows: the deflection scanning accuracy calibration software is installed in the industrial control computer to realize electron beam deflection current setting, automatic calibration path planning, synchronous acquisition of upper electrode beam current and Faraday tube array beam current signals, and determination of electron beam spot coincidence with calibration aperture, etc.; the industrial control computer transmits the electron beam deflection scanning current data to the PCI arbitrary waveform generator card to generate X-direction deflection coil drive waveform and Y-direction deflection coil drive waveform respectively, and connects them to the X-direction deflection coil drive circuit and Y-direction deflection coil drive circuit respectively through two independent channels for deflection. The scanning current is amplified and then connected to the X-direction deflection scanning coil and the Y-direction deflection scanning coil installed in the electron gun, respectively, generating X-direction and Y-direction deflection magnetic fields in the deflection scanning coils. After passing through the X-direction and Y-direction deflection scanning coils, the electron beam deflects to the vicinity of a calibration point of the electron beam sampling device. Then, the electron beam starts from the initial deflection position and performs calibration scanning according to the automatic calibration trajectory. The upper electrode plate of the electron beam sampling device is sequentially equipped with an upper electrode plate insulating plate, a Faraday cylinder array, a lower electrode plate insulating plate, and a lower electrode plate, wherein the upper electrode plate... The upper and lower electrode plates are metal plates. The upper electrode plate, upper electrode plate insulating plate, lower electrode plate insulating plate, and lower electrode plate are fixedly connected at the four corners of the sampling device by four ceramic insulating pillars. The Faraday cylinder array is fixed between the upper and lower electrode plate insulating plates and is insulated from the metal upper and lower electrode plates. The metal upper electrode plate is connected to ground through the sampling resistor R1, and the metal lower electrode plate is directly connected to ground to form an electron beam flow path. The centers of the upper electrode plate calibration hole, the upper electrode plate insulating plate beam-penetrating hole, and the Faraday cylinder beam-penetrating hole are aligned, especially to achieve large-angle electron beam deflection. Both the calibration aperture and the beam-penetrating aperture are tapered, with an inclination angle θ slightly greater than the incident angle α of the electron beam on the workpiece surface. This prevents the electron beam from being collected by the upper electrode plate and the insulating plate of the upper electrode plate when it passes through the calibration aperture and the beam-penetrating aperture at a certain angle after deflection, thus preventing measurement errors. At the same time, after passing through the calibration aperture and the beam-penetrating aperture, the electron beam hits the inner wall of the Faraday cylinder and then flows to the ground through the beam current acquisition resistor R2. Since the upper part of the Faraday cylinder is a tiny beam-penetrating aperture, most of the secondary electrons and backscattered electrons generated are captured by the Faraday cylinder, which helps to improve the accuracy of beam current acquisition.

[0008] When the electron beam starts from the initial deflection position and performs calibration scanning in a clockwise square rotation automatic calibration trajectory (the point spacing in both the X and Y directions is the diameter d of the beam calibration aperture), the electron beam current collected by the upper electrode of the electron beam sampling device is converted into a voltage signal through the sampling resistor R1, and then connected to the upper electrode beam signal amplification circuit for signal filtering and amplification, before being connected to an independent acquisition input channel of the PCI high-speed data acquisition card. The electron beam current passing through the calibration aperture of the upper electrode and the beam penetration aperture of the upper electrode insulating plate of the sampling device and entering the corresponding Faraday tube below is converted into a voltage signal through the sampling resistor R2, and then connected to the Faraday tube array sampling control circuit for signal filtering and amplification, before being connected to another independent acquisition input channel of the PCI high-speed data acquisition card. At the same time, the industrial control computer sends a beam synchronous acquisition control signal to the PCI high-speed data acquisition card to control the high-speed data acquisition card to synchronously acquire the upper electrode beam current signal and the Faraday tube beam current signal. At this point, if the electron beam passes through the calibration hole of the upper electrode plate, the electron beam current collected by the sampling resistor R2 of the Faraday cylinder below will reach its maximum value; if the electron beam only scans near the calibration hole of the upper electrode plate and does not pass through the calibration hole, the electron beam current collected by the sampling resistor R1 of the upper electrode plate will reach its maximum value. Therefore, the magnitude of the collected upper electrode plate beam current signal and the Faraday cylinder beam current signal can be used to determine whether the electron beam passes through the calibration hole of the current calibration point. Furthermore, when the ratio of the Faraday tube beam signal to the upper electrode beam signal is greater than 0.1, it indicates that part of the electron beam has passed through the calibration aperture. At this time, in order to improve the calibration accuracy, the calibration scanning strategy is changed: starting from the current position, the electron beam scans in the order of up→down→left→right at a spacing of 1 / 10 of the calibration aperture diameter. That is, the electron beam oscillates near the current position. The purpose is to find the maximum value of the beam signal collected by the Faraday tube. When this maximum value is found, it can be determined that the electron beam has passed through the current calibration aperture. The calibration software can then record the currently applied X-direction deflection scanning coil drive current value and Y-direction deflection scanning coil drive current value. This completes the calibration of the deflection scanning current at the current calibration point.

[0009] The industrial control computer includes an industrial computer and an industrial display, etc.; the positional connection relationship between them is as follows: the industrial control computer is connected to the industrial display through a video cable; the industrial control computer is an Advantech IPC-610H industrial control computer; the industrial display is a QiCaiChuangJing embedded industrial LCD display QC-170IPE10T.

[0010] The deflection scanning accuracy calibration software is a self-developed calibration control software with functions such as setting electron beam deflection current, automatic calibration path planning, synchronous acquisition of upper electrode beam current and Faraday tube array beam current signals, and determination of electron beam spot coincidence with calibration aperture.

[0011] The PCI arbitrary waveform generator card can be a general-purpose PCI arbitrary waveform generator card with at least two independent and synchronously output channels for storing deflection scan drive current data in the X and Y directions. When the calibration program is started, the waveform generator card converts the above data into X-direction deflection scan waveforms and Y-direction deflection scan waveforms respectively, and controls the automatic calibration of each calibration point through synchronous output of the two independent channels.

[0012] The PCI high-speed data acquisition card can be a general-purpose PCI high-speed data acquisition card with at least two independent and synchronously input channels. It receives the beam synchronization acquisition control signal from the industrial control computer to realize the synchronous acquisition of the upper electrode beam signal and the Faraday tube beam signal.

[0013] The X-direction scanning coil drive circuit receives the X-direction deflection scanning waveform output by the PCI arbitrary waveform generator card, amplifies it, and then connects its output to the X-direction deflection scanning coil to generate a coil drive current, thereby generating an X-direction deflection scanning magnetic field, which causes the electron beam to deflect in the X direction.

[0014] The Y-direction scanning coil drive circuit receives the Y-direction deflection scanning waveform output by the PCI arbitrary waveform generator card, amplifies its power, and then connects its output to the Y-direction deflection scanning coil to generate a coil drive current, thereby generating a Y-direction deflection scanning magnetic field, causing the electron beam to deflect in the Y direction.

[0015] Both the X-direction deflection scanning coil and the Y-direction deflection scanning coil adopt a hollow Helmholtz coil structure with low inductive reactance and high uniform magnetic field.

[0016] The electron beam acquisition device includes an upper electrode plate, an upper electrode plate insulating plate, ceramic insulating pillars, a Faraday cylinder array, a lower electrode plate insulating plate, and a lower electrode plate. Their positional relationship is as follows: the upper electrode plate insulating plate, the Faraday cylinder array, the lower electrode plate insulating plate, and the lower electrode plate are sequentially installed below the upper electrode plate. The upper and lower electrode plates are metal plates. The upper electrode plate, the upper electrode plate insulating plate, the lower electrode plate insulating plate, and the lower electrode plate are fixedly connected at the four corners of the sampling device via four ceramic insulating pillars. The Faraday cylinder array is fixed between the upper and lower electrode plate insulating plates and is insulated from the metal upper and lower electrode plates. The metal upper electrode plate is connected to ground through a sampling resistor R1, and the metal lower electrode plate is directly connected to ground to form an electron beam flow path.

[0017] The upper electrode plate of the electron beam acquisition device is a 3mm thick metal plate with 81 calibration holes machined by machining. The diameter of the calibration holes is 1.5 times the diameter of the electron beam spot.

[0018] The upper and lower electrode insulating plates are made of 1mm thick insulating bakelite board.

[0019] The Faraday tube array consists of 81 Faraday tubes, each corresponding to one of the 81 calibration holes. At the bottom of each Faraday tube, an M3 bolt passes through the circular hole of the lower electrode plate and the circular hole of the lower electrode plate insulation plate to connect the Faraday tube beam sampling resistor R2 to the Faraday tube, converting the beam signal collected by the Faraday tube into a voltage signal. The beam signals collected by all 81 Faraday tubes are connected to the Faraday tube array sampling circuit.

[0020] The lower electrode plate is a 3mm thick metal plate.

[0021] The centers of the upper electrode calibration hole, the upper electrode insulating plate beam-penetrating hole, and the Faraday tube beam-penetrating hole are aligned. In particular, in order to achieve large-angle electron beam deflection, the calibration hole and the beam-penetrating hole are all tapered holes with an inclination angle θ slightly greater than the deflection angle of the electron beam. This can prevent the electron beam from passing through the beam-penetrating hole at a certain angle after deflection and hitting the hole wall, thus causing measurement errors.

[0022] The upper electrode beam signal amplification circuit and the Faraday tube beam signal amplification circuit are composed of an operational amplifier LM6172, a proportional amplifier resistor, an integrating capacitor, etc., and are used to filter and amplify the input beam signal.

[0023] The Faraday tube array sampling control circuit comprises a microcontroller control circuit, an RS485 communication circuit, six 16-to-1 channel selectors, and one 8-to-1 channel selector. Their positional relationship is as follows: the electron beam signals collected by the 81 Faraday tubes are connected to the six 16-to-1 channel selectors respectively. Specifically, Faraday tubes 1-16 are connected to 16-to-1 channel selector 1, Faraday tubes 17-32 are connected to 16-to-1 channel selector 2, Faraday tubes 33-48 are connected to 16-to-1 channel selector 3, Faraday tubes 49-64 are connected to 16-to-1 channel selector 4, Faraday tubes 65-80 are connected to 16-to-1 channel selector 5, and Faraday tube 81 is connected to 16-to-1 channel selector 6. The outputs of the six 16-to-1 channel selectors are then connected to the 8-to-1 channel selector. Ultimately, only the electron beam signal from the Faraday tube corresponding to the current calibration point is connected to the Faraday tube beam signal amplification circuit for signal filtering and amplification. The channel selection of the electron beam signals collected by the 81 Faraday lamps is achieved through a microcontroller control circuit. This circuit is connected to an industrial control computer via an RS485 communication circuit. After receiving channel control commands, it outputs 27 I / O signals, which are connected to six 16-to-1 channel selectors and one 8-to-1 channel selector to achieve channel selection control. Specifically, IO1-IO3 are connected to pins A, B, and C of the 8-to-1 channel selector for 8-to-1 channel selection; IO4-IO7 are connected to pins A, B, C, and D of 16-to-1 channel selector 1 for 16-to-1 channel selection; IO8-IO11 are connected to pins A, B, C, and D of 16-to-1 channel selector 2; IO12-IO15 are connected to 16-to-1 channel selector 3; IO16-IO19 are connected to pins A, B, C, and D of 16-to-1 channel selector 4; IO20-IO23 are connected to 16-to-1 channel selector 5; and IO24-IO27 are connected to pins A, B, C, and D of 16-to-1 channel selector 6.

[0024] The microcontroller control circuit mentioned above uses the PIC18F46K22 microcontroller from MicroChip.

[0025] The 16-to-1 channel selector mentioned is the CD4067 integrated 16-to-1 channel selector from TI.

[0026] The 8-to-1 channel selector mentioned is the CD4051 integrated 8-to-1 channel selector from TI.

[0027] The RS485 communication circuit shown is Maxim Integrated's Max485 conversion circuit.

[0028] 3. Advantages and effects:

[0029] 1) By setting up a dedicated electron beam acquisition device, deflection scanning and synchronous high-speed data acquisition circuit, planning an automatic calibration scanning path, and combining it with specially designed deflection scanning accuracy calibration software, the automatic calibration of large-angle electron beam deflection scanning accuracy is realized, which greatly improves the automation level and efficiency of calibration. The maximum calibration area of ​​the scanning area of ​​the automatic calibration device for electron beam deflection scanning accuracy can reach 360mm×3600mm.

[0030] 2) Employing a point-by-point scanning method, following an automatic calibration trajectory with clockwise square rotation and a path planning method that searches for the beam current maximum using electron beam oscillation, ensures that the current calibration point can be found with sufficiently high calibration accuracy, not less than 0.1. d ;

[0031] 3) Taking into full account the fact that the electron beam has a certain incident angle α on the workpiece surface during large-angle deflection scanning, the calibration hole of the upper electrode plate, the insulating plate of the upper electrode plate, and the beam-penetrating hole of the Faraday cylinder are all designed as conical holes. The inclination angle θ of the conical hole is slightly larger than the incident angle α of the electron beam. This can prevent the electron beam from hitting the hole wall and being collected by the upper electrode plate and the insulating plate of the upper electrode plate when passing through the beam-penetrating hole, thus preventing errors and improving the calibration accuracy.

[0032] 4) The beams passing through the 81 calibration holes are collected by 81 independent Faraday tubes, which ensures that the electron beam after passing through the upper electrode plate and the upper electrode plate insulation plate, as well as the secondary electrons generated by the electron beam bombarding the metal wall of the Faraday tube, are completely collected by the Faraday tube, thereby improving the calibration accuracy. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the system configuration of the automatic calibration device for electron beam deflection scanning accuracy of the present invention.

[0034] Figure 2 This is a schematic diagram of the upper electrode structure of the electron beam acquisition device in this invention.

[0035] Figure 3 This is a schematic cross-sectional view of a single Faraday cylinder in this invention.

[0036] Figure 4 This is a schematic diagram of the working principle of the beam signal amplification circuit in this invention.

[0037] Figure 5 This is a block diagram illustrating the working principle of the Faraday array sampling control circuit in this invention.

[0038] Figure 6 This is a schematic diagram of the automatic electron beam calibration scanning trajectory near a certain calibration point in this invention.

[0039] The symbols and codes in the diagram are explained as follows:

[0040] 101 is an industrial control computer;

[0041] 102 is a deflection scanning accuracy calibration software;

[0042] 103 is a PCI arbitrary waveform generator card;

[0043] 104 is a PCI high-speed data acquisition card;

[0044] 105 is the X-direction deflection coil drive circuit;

[0045] 106 is the Y-direction deflection coil drive circuit;

[0046] 107 is an electron gun;

[0047] 108 is the electron beam current;

[0048] 109 is the X-direction deflection scanning coil;

[0049] 110 is the Y-direction deflection scanning coil;

[0050] 111 is an electron beam sampling device;

[0051] 112 is the upper electrode plate;

[0052] 113 is the upper electrode plate insulation plate;

[0053] 114 is a ceramic insulating post;

[0054] 115 is a Faraday cylinder array;

[0055] 116 is the lower electrode plate insulation plate;

[0056] 117 is the lower electrode plate;

[0057] 118 is the upper electrode beam current sampling resistor R1;

[0058] 119 is the upper electrode beam signal amplification circuit;

[0059] 120 is a Faraday tube beam signal amplifier circuit;

[0060] 121 is the sampling control circuit for the Faraday cylinder array;

[0061] 301 is the sampling resistor R2 for collecting the beam current using the Faraday cage;

[0062] 401 is the proportional amplifier resistor R1;

[0063] 402 is the proportional amplifier resistor R3;

[0064] 403 is the proportional amplifier resistor R2;

[0065] 404 is the proportional amplifier resistor R4;

[0066] 405 is the op-amp filter capacitor C1;

[0067] 406 is the op-amp filter capacitor C2;

[0068] 407 is the op-amp filter capacitor C3;

[0069] 408 is an operational amplifier LM6172;

[0070] 501 is a microcontroller control circuit;

[0071] 502 is an RS485 communication circuit;

[0072] 503 is a 16-to-1 channel selector 1;

[0073] 504 is a 16-to-1 channel selector 2;

[0074] 505 is a 16-to-1 channel selector 3;

[0075] 506 is a 16-to-1 channel selector 4;

[0076] 507 is a 16-to-1 channel selector.

[0077] 508 is a 16-to-1 channel selector;

[0078] 509 is an 8-to-1 channel selector; Detailed Implementation

[0079] This invention provides an automatic calibration device for electron beam deflection scanning accuracy, the specific implementation of which is as follows:

[0080] The aforementioned automatic calibration device for electron beam deflection scanning accuracy includes:

[0081] See Figure 1 As shown, the components include: industrial control computer 101, deflection scanning accuracy calibration software 102, PCI arbitrary waveform generator card 103, PCI high-speed data acquisition card 104, X-direction deflection coil drive circuit 105, Y-direction deflection coil drive circuit 106, electron gun 107, electron beam 108, X-direction deflection scanning coil 109, Y-direction deflection scanning coil 110, electron beam sampling device 111, upper electrode plate 112, upper electrode plate insulating plate 113, ceramic insulating column 114, Faraday cylinder array 115, lower electrode plate insulating plate 116, sampling device lower electrode plate 117, upper electrode plate beam sampling resistor R1 118, upper electrode plate beam signal amplification circuit 119, Faraday cylinder beam signal amplification circuit 120, and Faraday cylinder array sampling control circuit 121.

[0082] The positional connection between them is as follows: the deflection scanning accuracy calibration software 102 is installed in the industrial control computer 101 to realize electron beam deflection current setting, automatic calibration path planning, synchronous acquisition of upper electrode beam current and Faraday tube array beam current signals, and determination of electron beam spot coincidence with calibration aperture, etc.; the industrial control computer 101 transmits the electron beam deflection scanning current data to the PCI arbitrary waveform generator card 103 to generate X-direction deflection coil drive waveform and Y-direction deflection coil drive waveform respectively, and connects them to the X-direction deflection coil drive circuit 105 and the Y-direction deflection coil drive circuit 106 through two independent channels to amplify the deflection scanning current, and then connects them to the X-direction deflection scanning coil 109 and the Y-direction deflection scanning coil 110 installed in the electron gun 107 respectively, generating X-direction and Y-direction deflection magnetic fields in the deflection scanning coils; the electron beam 108 passes through the X-direction deflection scanning coil 109 and the Y-direction deflection scanning coil 110 in the electron gun 107 to generate X-direction and Y-direction deflection magnetic fields in the deflection scanning coils; After the deflection scanning coil 109 and the Y-direction deflection scanning coil 110 are deflected to a certain calibration point near the electron beam sampling device 111, the electron beam then starts from the initial deflection position and performs calibration scanning according to the automatic calibration trajectory. Under the upper electrode plate 112 of the electron beam sampling device, an upper electrode plate insulating plate 113, a Faraday cylinder array 115, a lower electrode plate insulating plate 116, and a lower electrode plate 117 are sequentially installed. The upper electrode plate 112 and the lower electrode plate 117 are metal plates. The upper electrode plate 112, upper electrode plate insulating plate 113, lower electrode plate insulating plate 116, and lower electrode plate 117 are fixedly connected at the four corners of the sampling device 111 by four ceramic insulating pillars 114. The Faraday cylinder array 115 is fixed between the upper electrode plate insulating plate 113 and the lower electrode plate insulating plate 116 and is insulated from the metal upper electrode plate 112 and the lower electrode plate 117. The metal upper electrode plate 112 is connected to the sampling resistor R1. 118 is connected to the ground, and the lower metal plate 117 is directly connected to the ground to form an electron beam flow path. When the electron beam 108 starts from the initial deflection position and performs calibration scanning in a clockwise square rotation automatic calibration trajectory near the current calibration point, the electron beam current collected by the upper plate 112 of the electron beam sampling device 111 is converted into a voltage signal by the sampling resistor R1 118, and then connected to the upper plate beam current signal amplification circuit 119 for signal filtering and amplification, and then connected to an independent acquisition input channel of the PCI high-speed data acquisition card 104. The electron beam current passing through the calibration hole of the upper plate 112 of the sampling device, the beam penetration hole of the upper plate insulating plate 113, and entering the corresponding Faraday cylinder 115 below is sampled by the sampling resistor R2. 301 converts the signal into a voltage signal, which is then connected to the Faraday tube beam signal amplifier circuit 120 via the Faraday tube array sampling control circuit 121 for signal filtering and amplification. After that, it is connected to another independent acquisition input channel of the PCI high-speed data acquisition card 104. At the same time, the industrial control computer 101 sends a beam synchronization acquisition control signal to the PCI high-speed data acquisition card 104 to control the high-speed data acquisition card to synchronously acquire the upper electrode beam signal and the Faraday tube beam signal.

[0083] See Figure 2 As shown, in one embodiment of the upper electrode plate 112 of the electron beam acquisition device 111, the upper electrode plate 112 has an external dimension of 400mm×400mm and an effective calibration range of 360mm×360mm, divided into 9 rows and 9 columns. A total of 9×9=81 calibration points are set according to the intersection points of the rows and columns. The spacing in the X and Y directions is 45mm, and they are numbered from 1 to 81 from top to bottom and from left to right. Assuming that the diameter of the electron beam spot is 0.2mm, the diameter of the calibration hole is set to 0.3mm. Five key calibration points are selected on the upper electrode plate 112: center point O, left side point L0, right side point R0, upper point T0, and lower point B0.

[0084] In actual calibration, the following steps can be taken: (1) First, determine the origin O of the electron beam emitted by the current electron gun and the X and Y directions of the electron beam scan. The specific method is: set the deflection scanning current of the electron beam in the X and Y directions to 0 through calibration software, and then start the electron beam to make a point on the surface of the workpiece in the working plane. This point is the origin O of the electron beam; then set the deflection scanning current in the Y direction to 0 and the deflection scanning current in the X direction to change from -X0 to +X0 to obtain the X scanning direction of the electron beam. Similarly, set the deflection scanning current in the X direction to 0 and the deflection scanning current in the Y direction to change from -Y0 to +Y0 to obtain the Y scanning direction of the electron beam; (2) Place the electron beam acquisition device in the vacuum chamber so that the upper electrode plate is On the working plane of the electron beam, and the center point O of the upper electrode plate coincides with the origin O on the workpiece, and at the same time, the X direction of the calibration plate coincides with the X direction determined by the electron beam scanning on the workpiece, and the Y direction of the calibration plate coincides with the Y direction determined by the electron beam scanning on the workpiece. In this way, the position and direction of the upper electrode plate of the electron beam acquisition device are determined; (3) Calculate the deflection current of the key point L0 on the left side, and then start the calibration software. According to the calculated deflection current of L0, let the electron beam deflect to the vicinity of L0. Then, use the manual adjustment method to change the deflection current in the X direction and the deflection current in the Y direction so that the electron beam passes through the calibration hole of L0. Record the value of the deflection current in the X direction and the value of the deflection current in the Y direction at this time. The value of the deflection current in the X direction at this point is the value of the deflection current in the X direction when deflected to the leftmost side. I LM (4) Repeat step (3) to obtain the X-direction deflection current value and Y-direction deflection current value at point R0. The X-direction deflection current value at this point is the X-direction deflection current value when deflected to the rightmost position. I RM (5) Repeat step (3) to obtain the X-direction deflection current value and Y-direction deflection current value at point T0. The Y-direction deflection current value at this point is the Y-direction deflection current value when deflected to the top. I YM(6) Repeat step (3) to obtain the X-direction deflection current value and Y-direction deflection current value at point B0. The Y-direction deflection current value at this point is the Y-direction deflection current value when deflected to the bottom. I BM (7) Therefore, the maximum values ​​of the deflection current in the X and Y directions are obtained through the above steps (3) to (6). Next, the initial deflection current values ​​in the X and Y directions of calibration points 1 to 81 are calculated by linear interpolation. In this way, the initial deflection current values ​​of each calibration point are input into the deflection scanning coil drive circuit, and the electron beam can be deflected to the initial deflection position near each calibration point.

[0085] See Figure 3 The diagram shows a cross-sectional view near a calibration point of the electron beam acquisition device 111. It further reveals that the upper electrode plate 112 of the electron beam sampling device 111 is successively fitted with an upper electrode plate insulating plate 113, a Faraday cylinder 115, a lower electrode plate insulating plate 116, and a lower electrode plate 117. The upper electrode plate 112 and lower electrode plate 117 are metal plates, and the Faraday cylinder 115, also made of metal, is fixed between the upper electrode plate insulating plate 113 and the lower electrode plate insulating plate 116, and is insulated from the metal upper electrode plate 112 and lower electrode plate 117. The beam current acquisition resistor R2 301 is screwed onto the bottom of the Faraday cylinder via an M3 bolt through a through-hole in the lower electrode plate insulating plate 116 and the lower electrode plate 117 to acquire the beam current and convert it into a voltage signal. The 81 Faraday cylinders are connected to ground through 81 beam current acquisition resistors, forming their respective electron beam current paths and converting them into voltage signals.

[0086] The centers of the beam calibration hole of the upper electrode plate 112, the beam-penetrating hole of the upper electrode plate insulating plate 113, and the beam-penetrating hole of the Faraday cylinder 115 are aligned. In particular, in order to achieve large-angle electron beam deflection, the calibration hole and the beam-penetrating hole are both tapered holes, and their tilt angle θ is slightly larger than the incident angle α of the electron beam on the workpiece surface. This can prevent the electron beam from being collected by the hole walls of the upper electrode plate and the upper electrode plate insulating plate when it passes through the calibration hole and the beam-penetrating hole at a certain angle after deflection, thus preventing measurement errors. At the same time, after the electron beam passes through the calibration hole and the beam-penetrating hole, it hits the inner wall of the Faraday cylinder and then flows to the ground through the beam acquisition resistor R2 301. Since the top of the Faraday cylinder is a tiny beam-penetrating hole, most of the secondary electrons and backscattered electrons generated are captured by the Faraday cylinder, which is beneficial to improving the accuracy of beam acquisition.

[0087] See Figure 4As shown, both the upper plate beam signal amplification circuit 119 and the Faraday tube beam signal amplification circuit 120 use operational amplifiers such as LM6172 408, proportional amplifier resistors 401-404, and integrating capacitors 405-407 to form operational amplifier circuits, which filter and amplify the acquired upper plate beam signal and Faraday tube beam signal respectively, and their outputs are connected to the PCI high-speed data acquisition card 104.

[0088] See Figure 5 The diagram shows the working principle block diagram of the Faraday lamp array sampling control circuit 121, including a microcontroller control circuit 501, an RS485 communication circuit 502, six 16-to-1 channel selectors 503-508, and one 8-to-1 channel selector 509. Their positional relationship is as follows: the electron beam signals collected by the 81 Faraday lamps are connected to the six 16-to-1 channel selectors respectively. Specifically, Faraday lamps 1-16 are connected to 16-to-1 channel selector 1 503, Faraday lamps 17-32 are connected to 16-to-1 channel selector 2 504, Faraday lamps 33-48 are connected to 16-to-1 channel selector 3 505, Faraday lamps 49-64 are connected to 16-to-1 channel selector 4 506, Faraday lamps 65-80 are connected to 16-to-1 channel selector 5 507, and Faraday lamp 81 is connected to 16-to-1 channel selector 6 509. 508; then the outputs of the six 16-to-1 channel selectors are connected to the 8-to-1 channel selector 509. Ultimately, only the electron beam signal from the Faraday lamp corresponding to the current calibration point is connected to the Faraday lamp beam signal amplification circuit 120 for signal filtering and amplification. Channel selection of the electron beam signals collected by the 81 Faraday lamps is achieved through a microcontroller control circuit 501. The microcontroller control circuit 501 is connected to the industrial control computer 101 via an RS485 communication circuit 502. After receiving channel control commands, it outputs 27 I / O signals, which are respectively connected to the six 16-to-1 channel selectors 503-508 and the 8-to-1 channel selector 509 to achieve channel selection control. Specifically, IO1-IO3 are connected to pins A, B, and C of the 8-to-1 channel selector 509 to achieve 8-to-1 channel control; IO4-IO7 are connected to pins A, B, C, and D of the 16-to-1 channel selector 1 503 to achieve 16-to-1 channel control; IO8-IO11 are connected to pins A, B, C, and D of the 16-to-1 channel selector 2 504; IO12-IO15 are connected to the 16-to-1 channel selector 3 505; IO16-IO19 are connected to pins A, B, C, and D of the 16-to-1 channel selector 4 506; IO20-IO23 are connected to the 16-to-1 channel selector 5 507; and IO24-IO27 are connected to pins A, B, C, and D of the 16-to-1 channel selector 6 508.

[0089] See Figure 6The diagram shows the automatic calibration trajectory path planning for the deflection scanning electron beam at the calibration points. After the electron beam 108 deflects to its initial position, it uses a point-by-point scanning method to automatically calibrate along a clockwise square rotation trajectory (the point spacing in both the X and Y directions is the diameter of the beam calibration aperture). d The electron beam sampling device 111 performs point-by-point scanning near the current calibration point. The electron beam current collected by the upper plate 112 of the electron beam sampling device 111 is converted into a voltage signal by the sampling resistor R1 118, and then connected to the upper plate beam current signal amplification circuit 119 for signal filtering and amplification. After that, it is connected to an independent acquisition input channel of the PCI high-speed data acquisition card 104. The electron beam current passing through the calibration hole of the upper plate 112 and the beam penetration hole of the upper plate insulating plate 113 enters the corresponding Faraday tube 115 below. It is converted into a voltage signal by the sampling resistor R2 301, and then connected to the Faraday tube array sampling control circuit 121 for signal filtering and amplification. After that, it is connected to another independent acquisition input channel of the PCI high-speed data acquisition card 104. At the same time, the industrial control computer 101 sends a beam current synchronous acquisition control signal to the PCI high-speed data acquisition card 104 to control the high-speed data acquisition card 104 to synchronously acquire the upper plate beam current signal and the Faraday tube beam current signal. At this point, if the electron beam 108 passes exactly through the calibration aperture of the upper electrode 112, the electron beam current collected by the sampling resistor R2 301 of the corresponding Faraday cylinder 115 below will reach its maximum value; if the electron beam 108 only scans near the calibration aperture of the upper electrode 112 and does not pass through the calibration aperture, the electron beam current collected by the sampling resistor R1 118 of the upper electrode will reach its maximum value. Therefore, the magnitude of the collected upper electrode beam current signal and Faraday cylinder beam current signal can be used to determine whether the electron beam has passed through the calibration aperture of the current calibration point. Furthermore, when the ratio of the Faraday cylinder beam current signal to the upper electrode beam current signal is detected to be greater than 0.1, it indicates that part of the electron beam has passed through the calibration aperture. At this time, to improve calibration accuracy, the calibration scanning strategy is changed: starting from the current position, the electron beam scans at a speed of 1 / 10 of the calibration aperture diameter (0.1...). d The spacing of the electron beam is scanned in the order of top → bottom → left → right, meaning the electron beam oscillates near the current position. The purpose is to find the maximum value of the beam current signal collected by the Faraday tube. When the maximum value is found, it can be determined that the electron beam has entered the current calibration aperture. The calibration software can then record the currently applied X-direction deflection scanning coil drive current value and Y-direction deflection scanning coil drive current value, thus completing the calibration of the deflection scanning current at the current calibration point.

[0090] The aforementioned automatic calibration device for electron beam deflection scanning accuracy can automatically calibrate the accuracy of large-angle electron beam deflection scanning, greatly improving the automation level and efficiency of calibration.

[0091] The scanning area calibration domain of the aforementioned automatic calibration device for electron beam deflection scanning accuracy can reach up to 360mm × 3600mm;

[0092] The calibration accuracy of the aforementioned automatic electron beam deflection scanning accuracy calibration device is no less than 0.1. d ;

[0093] The aforementioned automatic calibration device for electron beam deflection scanning accuracy designs the calibration hole of the upper electrode plate, the insulating plate of the upper electrode plate, and the beam-penetrating hole of the Faraday tube as conical holes. The inclination angle θ of the conical hole is slightly larger than the incident angle α of the electron beam, which can prevent the electron beam from hitting the hole wall and being collected by the upper electrode plate and the insulating plate of the upper electrode plate when passing through the beam-penetrating hole, thus preventing errors.

[0094] The aforementioned automatic calibration device for electron beam deflection scanning accuracy uses a Faraday cylinder to collect the electron beam passing through the calibration aperture, which can ensure that secondary electrons and backscattered electrons are completely collected by the Faraday cylinder.

[0095] This invention addresses the need for high-precision, wide-range, and high-speed deflection scanning in electron beam rapid manufacturing technology by providing an automatic calibration device for electron beam deflection scanning accuracy. By setting up a dedicated electron beam acquisition device, deflection scanning, and synchronous high-speed data acquisition circuit, and planning an automatic calibration scanning path, combined with specially designed deflection scanning accuracy calibration software, automatic calibration of large-angle electron beam deflection scanning accuracy is achieved, significantly improving the automation level and efficiency of calibration. Employing a point-by-point scanning method based on an automatic calibration trajectory involving clockwise square rotation and a path planning method that searches for the path through the beam current maximum during electron beam oscillation, this ensures that the current calibration point can be found with sufficiently high calibration accuracy, not less than 0.1. d The design fully considers the certain incident angle α of the electron beam on the workpiece surface during large-angle deflection scanning. The calibration holes of the upper electrode plate, the insulating plate of the upper electrode plate, and the beam-penetrating holes of the Faraday cylinder are all designed as conical holes. The inclination angle θ of the conical holes is slightly larger than the incident angle α of the electron beam. This can prevent the electron beam from hitting the hole wall and being collected by the upper electrode plate and the insulating plate when passing through the beam-penetrating hole, thus preventing errors and improving calibration accuracy. The beam current passing through the 81 calibration holes is collected by 81 independent Faraday cylinders. This ensures that the electron beam after passing through the upper electrode plate and the insulating plate, as well as the secondary electrons and backscattered electrons generated by the electron beam bombarding the metal wall of the Faraday cylinder, are completely collected by the Faraday cylinder.

[0096] The present invention includes an industrial control computer 101, deflection scanning accuracy calibration software 102, a PCI arbitrary waveform generator card 103, a PCI high-speed data acquisition card 104, an X-direction deflection coil drive circuit 105, a Y-direction deflection coil drive circuit 106, an electron gun 107, an electron beam 108, an X-direction deflection scanning coil 109, a Y-direction deflection scanning coil 110, an electron beam sampling device 111, an upper electrode plate 112, an upper electrode plate insulating plate 113, a ceramic insulating column 114, a Faraday cylinder array 115, a lower electrode plate insulating plate 116, a sampling device lower electrode plate 117, an upper electrode plate beam sampling resistor R1 118, an upper electrode plate beam signal amplification circuit 119, a Faraday cylinder beam signal amplification circuit 120, and a Faraday cylinder array sampling control circuit 121.

[0097] The deflection scanning accuracy calibration software 102 is installed in the industrial control computer 101 to realize electron beam deflection current setting, automatic calibration path planning, synchronous acquisition of upper electrode beam current and Faraday tube array beam current signals, and determination of electron beam spot coincidence with calibration aperture. The industrial control computer 101 transmits the electron beam deflection scanning current data to the PCI arbitrary waveform generator card 103 to generate X-direction deflection coil drive waveform and Y-direction deflection coil drive waveform respectively. These waveforms are then connected to the X-direction deflection coil drive circuit 105 and the Y-direction deflection coil drive circuit 106 through two independent channels for deflection scanning current amplification. These amplification currents are then connected to the X-direction deflection scanning coil 109 and the Y-direction deflection scanning coil 110 installed in the electron gun 107, respectively, to generate X-direction and Y-direction deflection magnetic fields in the deflection scanning coils. The electron beam 108 passes through the X-direction deflection scanning coil... After the Y-direction deflection scanning coil 110 deflects to a certain calibration point near the electron beam sampling device 111, the electron beam starts from the initial deflection position and performs calibration scanning according to the automatic calibration trajectory. The upper electrode plate 112 of the electron beam sampling device is sequentially equipped with an upper electrode plate insulating plate 113, a Faraday cylinder array 115, a lower electrode plate insulating plate 116, and a lower electrode plate 117. The upper electrode plate 112 and lower electrode plate 117 are metal plates. The upper electrode plate 112, upper electrode plate insulating plate 113, lower electrode plate insulating plate 116, and lower electrode plate 117 are fixedly connected at the four corners of the sampling device 111 by four ceramic insulating pillars 114. The Faraday cylinder array 115 is fixed between the upper electrode plate insulating plate 113 and the lower electrode plate insulating plate 116 and is insulated from the metal upper electrode plate 112 and lower electrode plate 117. The metal upper electrode plate 112 is connected to the sampling resistor R1. 118 is connected to ground, and the lower metal plate 117 is directly connected to ground to form an electron beam flow path. When the electron beam 108 starts from the initial deflection position and performs calibration scanning in a clockwise square rotation automatic calibration trajectory near the current calibration point, the electron beam current collected by the upper plate 112 of the electron beam sampling device 111 passes through the sampling resistor R1. 118 converts the signal into a voltage signal, which is then connected to the upper electrode beam signal amplification circuit 119 for signal filtering and amplification, and then connected to an independent acquisition input channel of the PCI high-speed data acquisition card 104; the electron beam passing through the calibration hole of the upper electrode plate 112 and the beam through hole of the upper electrode plate 113 enters the corresponding Faraday tube 115 below and is converted into a voltage signal by the sampling resistor R2301, and then connected to the Faraday tube beam signal amplification circuit 120 through the Faraday tube array sampling control circuit 121 for signal filtering and amplification, and then connected to another independent acquisition input channel of the PCI high-speed data acquisition card 104; at the same time, the industrial control computer 101 sends a beam synchronization acquisition control signal to the PCI high-speed data acquisition card 104 to control the high-speed data acquisition card to synchronously acquire the upper electrode beam signal and the Faraday tube beam signal.

[0098] After the electron beam 108 is deflected to its initial position, it is automatically calibrated using a point-by-point scanning method, rotating clockwise in a square pattern (the point spacing in both the X and Y directions is the diameter of the beam calibration aperture). d The electron beam sampling device 111 performs point-by-point scanning near the current calibration point. The electron beam current collected by the upper plate 112 of the electron beam sampling device 111 is converted into a voltage signal by the sampling resistor R1 118, and then connected to the upper plate beam current signal amplification circuit 119 for signal filtering and amplification. After that, it is connected to an independent acquisition input channel of the PCI high-speed data acquisition card 104. The electron beam current passing through the calibration hole of the upper plate 112 and the beam penetration hole of the upper plate insulating plate 113 enters the corresponding Faraday tube 115 below. It is converted into a voltage signal by the sampling resistor R2 301, and then connected to the Faraday tube array sampling control circuit 121 for signal filtering and amplification. After that, it is connected to another independent acquisition input channel of the PCI high-speed data acquisition card 104. At the same time, the industrial control computer 101 sends a beam current synchronous acquisition control signal to the PCI high-speed data acquisition card 104 to control the high-speed data acquisition card 104 to synchronously acquire the upper plate beam current signal and the Faraday tube beam current signal. At this point, if the electron beam 108 passes exactly through the calibration aperture of the upper electrode 112, the electron beam current collected by the sampling resistor R2 301 of the corresponding Faraday cylinder 115 below will reach its maximum value; if the electron beam 108 only scans near the calibration aperture of the upper electrode 112 and does not pass through the calibration aperture, the electron beam current collected by the sampling resistor R1 118 of the upper electrode will reach its maximum value. Therefore, the magnitude of the collected upper electrode beam current signal and Faraday cylinder beam current signal can be used to determine whether the electron beam has passed through the calibration aperture of the current calibration point. Furthermore, when the ratio of the Faraday cylinder beam current signal to the upper electrode beam current signal is detected to be greater than 0.1, it indicates that part of the electron beam has passed through the calibration aperture. At this time, to improve calibration accuracy, the calibration scanning strategy is changed: starting from the current position, the electron beam scans at a speed of 1 / 10 of the calibration aperture diameter (0.1...). d The spacing of the electron beam is scanned in the order of top → bottom → left → right, meaning the electron beam oscillates near the current position. The purpose is to find the maximum value of the beam current signal collected by the Faraday tube. When the maximum value is found, it can be determined that the electron beam has entered the current calibration aperture. The calibration software can then record the currently applied X-direction deflection scanning coil drive current value and Y-direction deflection scanning coil drive current value, thus completing the calibration of the deflection scanning current at the current calibration point.

[0099] The industrial control computer 101 includes an industrial computer and an industrial display, etc.; the positional connection relationship between them is as follows: the industrial control computer is connected to the industrial display through a video cable; the industrial control computer is an Advantech IPC-610H industrial control computer; the industrial display is a Qicai Chuangjing embedded industrial LCD display QC-170IPE10T.

[0100] The deflection scanning accuracy calibration software 02 is a self-developed calibration control software with functions such as setting electron beam deflection current, automatic calibration path planning, synchronous acquisition of upper electrode beam current and Faraday tube array beam current signals, and determination of electron beam spot coincidence with calibration aperture.

[0101] The PCI arbitrary waveform generator card 103 can be a general PCI arbitrary waveform generator card with at least two independent and synchronously output channels for storing deflection scan drive current data in the X and Y directions. When the calibration program is started, the waveform generator card converts the above data into X-direction deflection scan waveforms and Y-direction deflection scan waveforms respectively, and controls the automatic calibration of each calibration point through synchronous output of the two independent channels.

[0102] The PCI high-speed data acquisition card 104 can be a general-purpose PCI high-speed data acquisition card, with at least two independent and synchronously input channels, receiving the beam synchronization acquisition control signal from the industrial control computer to realize the synchronous acquisition of the upper electrode beam signal and the Faraday tube beam signal.

[0103] The X-direction scanning coil drive circuit 105 receives the X-direction deflection scanning waveform output by the PCI arbitrary waveform generator card 103, amplifies it, and then connects its output to the X-direction deflection scanning coil 109 to generate a coil drive current, thereby generating an X-direction deflection scanning magnetic field, which causes the electron beam to deflect in the X direction.

[0104] The Y-direction scanning coil drive circuit 106 receives the Y-direction deflection scanning waveform output by the PCI arbitrary waveform generator card 103, amplifies it, and then connects its output to the Y-direction deflection scanning coil to generate the driving current of the coil 110, thereby generating a Y-direction deflection scanning magnetic field, causing the electron beam to deflect in the Y direction.

[0105] The X-direction deflection scanning coil 109 and the Y-direction deflection scanning coil 110 both adopt a hollow Helmholtz coil structure with low inductive reactance and high uniform magnetic field.

[0106] The electron beam acquisition device 111 includes an upper electrode plate 112, an upper electrode plate insulating plate 113, a ceramic insulating column 114, a Faraday cylinder array 115, a lower electrode plate insulating plate 116, and a lower electrode plate 117. Their positional relationship is as follows: the upper electrode plate insulating plate 113, the Faraday cylinder array 115, the lower electrode plate insulating plate 116, and the lower electrode plate 117 are sequentially installed below the upper electrode plate 112. The upper electrode plate 112 and the lower electrode plate 117 are metal plates. The upper electrode insulating plate 113, the lower electrode insulating plate 116, and the lower electrode plate 117 are fixedly connected at the four corners of the sampling device by four ceramic insulating pillars 114. The Faraday cylinder array 115 is fixed between the upper electrode insulating plate 113 and the lower electrode insulating plate 116 and is insulated from the upper metal electrode plate 112 and the lower electrode plate 117. The upper metal electrode plate 112 is connected to the ground through the sampling resistor R1, and the lower metal electrode plate 117 is directly connected to the ground to form an electron beam flow path.

[0107] The upper electrode plate 112 of the electron beam acquisition device 111 is a 3mm thick metal plate with 81 calibration holes machined by machining. The diameter of the calibration holes is 1.5 times the diameter of the electron beam spot.

[0108] The upper electrode plate insulation plate 113 and the lower electrode plate insulation plate 116 are made of 1mm thick insulating bakelite board.

[0109] The Faraday tube array 115 consists of 81 Faraday tubes, each corresponding to one of the 81 calibration holes. At the bottom of each Faraday tube, an M3 bolt is used to pass through the circular hole of the lower electrode plate and the circular hole of the lower electrode plate insulation plate to connect the Faraday tube beam sampling resistor R2 301 to the Faraday tube, converting the beam signal collected by the Faraday tube into a voltage signal. The beam signals collected by all 81 Faraday tubes are connected to the Faraday tube array sampling circuit 121.

[0110] The lower electrode plate 117 is a metal plate with a thickness of 3mm.

[0111] The centers of the calibration hole 112 on the upper electrode plate, the beam-penetrating hole 113 on the upper electrode plate, and the beam-penetrating hole 115 on the Faraday cylinder are aligned. In particular, in order to achieve large-angle electron beam deflection, the calibration hole and the beam-penetrating hole are both tapered holes with an inclination angle θ slightly greater than the deflection angle of the electron beam. This can prevent the electron beam from passing through the beam-penetrating hole at a certain angle after deflection and hitting the hole wall, thus causing measurement errors.

[0112] The upper electrode beam signal amplification circuit 119 and the Faraday tube beam signal amplification circuit 120 are composed of an operational amplifier LM6172 408, proportional amplification resistors 401~404, and integrating capacitors 405~407. They are used to filter and amplify the input beam signal.

[0113] The Faraday lamp array sampling control circuit 121 comprises a microcontroller control circuit 501, an RS485 communication circuit 502, six 16-to-1 channel selectors 503-508, and one 8-to-1 channel selector 509. Their positional relationship is as follows: the electron beam signals collected by the 81 Faraday lamps are respectively connected to the six 16-to-1 channel selectors. Specifically, Faraday lamps 1-16 are connected to 16-to-1 channel selector 1 503, Faraday lamps 17-32 are connected to 16-to-1 channel selector 2 504, Faraday lamps 33-48 are connected to 16-to-1 channel selector 3 505, Faraday lamps 49-64 are connected to 16-to-1 channel selector 4 506, Faraday lamps 65-80 are connected to 16-to-1 channel selector 5 507, and Faraday lamp 81 is connected to 16-to-1 channel selector 6 509. 508; then the outputs of the six 16-to-1 channel selectors are connected to the 8-to-1 channel selector 509. Ultimately, only the electron beam signal from the Faraday lamp corresponding to the current calibration point is connected to the Faraday lamp beam signal amplification circuit 120 for signal filtering and amplification. Channel selection of the electron beam signals collected by the 81 Faraday lamps is achieved through a microcontroller control circuit 501. The microcontroller control circuit 501 is connected to the industrial control computer 101 via an RS485 communication circuit 502. After receiving channel control commands, it outputs 27 I / O signals, which are respectively connected to the six 16-to-1 channel selectors 503-508 and the 8-to-1 channel selector 509 to achieve channel selection control. Specifically, IO1-IO3 are connected to pins A, B, and C of the 8-to-1 channel selector 509 to achieve 8-to-1 channel control; IO4-IO7 are connected to pins A, B, C, and D of the 16-to-1 channel selector 1 503 to achieve 16-to-1 channel control; IO8-IO11 are connected to pins A, B, C, and D of the 16-to-1 channel selector 2 504; IO12-IO15 are connected to the 16-to-1 channel selector 3 505; IO16-IO19 are connected to pins A, B, C, and D of the 16-to-1 channel selector 4 506; IO20-IO23 are connected to the 16-to-1 channel selector 5 507; and IO24-IO27 are connected to pins A, B, C, and D of the 16-to-1 channel selector 6 508.

[0114] The microcontroller control circuit 501 is a Microchip PIC18F46K22 microcontroller.

[0115] The RS485 communication circuit 502 shown is Maxim Integrated's Max485 conversion circuit.

[0116] The 16-to-1 channel selector 503-508 is the CD4067 integrated 16-to-1 channel selector from Ti Corporation.

[0117] The 8-to-1 channel selector 509 is the CD4051 integrated 8-to-1 channel selector from TI.

[0118] The invention will now be further described with reference to the accompanying drawings.

[0119] Figure 1 The system consists of an automatic calibration device for electron beam deflection scanning accuracy, including an industrial control computer 101, deflection scanning accuracy calibration software 102, a PCI arbitrary waveform generator card 103, a PCI high-speed data acquisition card 104, an X-direction deflection coil drive circuit 105, a Y-direction deflection coil drive circuit 106, an electron gun 107, an electron beam 108, an X-direction deflection scanning coil 109, a Y-direction deflection scanning coil 110, an electron beam sampling device 111, an upper electrode plate 112, an upper electrode plate insulating plate 113, a ceramic insulating column 114, a Faraday cylinder array 115, a lower electrode plate insulating plate 116, a sampling device lower electrode plate 117, an upper electrode plate beam current sampling resistor R1 118, an upper electrode plate beam current signal amplification circuit 119, a Faraday cylinder beam current signal amplification circuit 120, and a Faraday cylinder array sampling control circuit 121.

[0120] refer to Figure 1The deflection scanning accuracy calibration software 102 is installed in the industrial control computer 101 to realize electron beam deflection current setting, automatic calibration path planning, synchronous acquisition of upper electrode beam current and Faraday tube array beam current signals, and determination of electron beam spot coincidence with calibration aperture. The industrial control computer 101 transmits the electron beam deflection scanning current data to the PCI arbitrary waveform generator card 103 to generate X-direction deflection coil drive waveform and Y-direction deflection coil drive waveform respectively. These waveforms are then connected to the X-direction deflection coil drive circuit 105 and the Y-direction deflection coil drive circuit 106 through two independent channels for deflection scanning current amplification. These amplification currents are then connected to the X-direction deflection scanning coil 109 and the Y-direction deflection scanning coil 110 installed in the electron gun 107, respectively, to generate X-direction and Y-direction deflection magnetic fields in the deflection scanning coils. The electron beam 108 passes through the X-direction deflection scanning coil. After deflection of the Y-direction scanning coil 110 and coil 109, the electron beam deflects to a point near a calibration point of the electron beam sampling device 111. Then, the electron beam begins calibration scanning from its initial deflection position along an automatic calibration trajectory. Below the upper electrode plate 112 of the electron beam sampling device, an upper electrode plate insulating plate 113, a Faraday cylinder array 115, a lower electrode plate insulating plate 116, and a lower electrode plate 117 are sequentially installed. The upper electrode plate 112 and lower electrode plate 117 are metal plates. The upper electrode plate 112, upper electrode plate insulating plate 113, lower electrode plate insulating plate 116, and lower electrode plate 117 are fixedly connected at the four corners of the sampling device 111 by four ceramic insulating pillars 114. The Faraday cylinder array 115 is fixed between the upper electrode plate insulating plate 113 and the lower electrode plate insulating plate 116 and is insulated from the metal upper electrode plate 112 and lower electrode plate 117. The metal upper electrode plate 112 is connected to the sampling resistor R1. 118 is connected to the ground, and the lower metal plate 117 is directly connected to the ground to form an electron beam flow path. When the electron beam 108 starts from the initial deflection position and performs calibration scanning in a clockwise square rotation automatic calibration trajectory near the current calibration point, the electron beam current collected by the upper plate 112 of the electron beam sampling device 111 is converted into a voltage signal by the sampling resistor R1 118, and then connected to the upper plate beam current signal amplification circuit 119 for signal filtering and amplification, and then connected to an independent acquisition input channel of the PCI high-speed data acquisition card 104. The electron beam current passing through the calibration hole of the upper plate 112 of the sampling device, the beam penetration hole of the upper plate insulating plate 113, and entering the corresponding Faraday cylinder 115 below is sampled by the sampling resistor R2. 301 converts the signal into a voltage signal, which is then connected to the Faraday tube beam signal amplifier circuit 120 via the Faraday tube array sampling control circuit 121 for signal filtering and amplification. After that, it is connected to another independent acquisition input channel of the PCI high-speed data acquisition card 104. At the same time, the industrial control computer 101 sends a beam synchronization acquisition control signal to the PCI high-speed data acquisition card 104 to control the high-speed data acquisition card to synchronously acquire the upper electrode beam signal and the Faraday tube beam signal.

[0121] Figure 2 This is one embodiment of the upper electrode plate 112 of the electron beam acquisition device 111.

[0122] refer to Figure 2 The upper electrode plate 112 has external dimensions of 400mm×400mm and an effective calibration range of 360mm×360mm, divided into 9 rows and 9 columns. A total of 9×9=81 calibration points are set according to the intersection points of the rows and columns. The spacing in the X and Y directions is 45mm, and they are numbered from 1 to 81 from top to bottom and from left to right. Assuming that the electron beam spot diameter is 0.2mm, the diameter of the calibration hole is set to 0.3mm. Five key calibration points are selected on the upper electrode plate 112: center point O, left side point L0, right side point R0, upper point T0, and lower point B0.

[0123] In actual calibration, the following steps can be taken: (1) First, determine the origin O of the electron beam emitted by the current electron gun and the X and Y directions of the electron beam scan. The specific method is: set the deflection scanning current of the electron beam in the X and Y directions to 0 through calibration software, and then start the electron beam to make a point on the surface of the workpiece in the working plane. This point is the origin O of the electron beam; then set the deflection scanning current in the Y direction to 0 and the deflection scanning current in the X direction to change from -X0 to +X0 to obtain the X scanning direction of the electron beam. Similarly, set the deflection scanning current in the X direction to 0 and the deflection scanning current in the Y direction to change from -Y0 to +Y0 to obtain the Y scanning direction of the electron beam; (2) Place the electron beam acquisition device in the vacuum chamber so that the upper electrode plate is On the working plane of the electron beam, and the center point O of the upper electrode plate coincides with the origin O on the workpiece, and at the same time, the X direction of the calibration plate coincides with the X direction determined by the electron beam scanning on the workpiece, and the Y direction of the calibration plate coincides with the Y direction determined by the electron beam scanning on the workpiece. In this way, the position and direction of the upper electrode plate of the electron beam acquisition device are determined; (3) Calculate the deflection current of the key point L0 on the left side, and then start the calibration software. According to the calculated deflection current of L0, let the electron beam deflect to the vicinity of L0. Then, use the manual adjustment method to change the deflection current in the X direction and the deflection current in the Y direction so that the electron beam passes through the calibration hole of L0. Record the value of the deflection current in the X direction and the value of the deflection current in the Y direction at this time. The value of the deflection current in the X direction at this point is the value of the deflection current in the X direction when deflected to the leftmost side. I LM (4) Repeat step (3) to obtain the X-direction deflection current value and Y-direction deflection current value at point R0. The X-direction deflection current value at this point is the X-direction deflection current value when deflected to the rightmost position. I RM (5) Repeat step (3) to obtain the X-direction deflection current value and Y-direction deflection current value at point T0. The Y-direction deflection current value at this point is the Y-direction deflection current value when deflected to the top.I YM (6) Repeat step (3) to obtain the X-direction deflection current value and Y-direction deflection current value at point B0. The Y-direction deflection current value at this point is the Y-direction deflection current value when deflected to the bottom. I BM (7) Therefore, the maximum values ​​of the deflection current in the X and Y directions are obtained through the above steps (3) to (6). Next, the initial deflection current values ​​in the X and Y directions of calibration points 1 to 81 are calculated by linear interpolation. In this way, the initial deflection current values ​​of each calibration point are input into the deflection scanning coil drive circuit, and the electron beam can be deflected to the initial deflection position near each calibration point.

[0124] Figure 3 It is a cross-sectional view near a certain calibration point of the electron beam acquisition device 111.

[0125] refer to Figure 3 It can be further seen that the upper electrode plate 112 of the electron beam sampling device 111 is equipped with an upper electrode plate insulating plate 113, a Faraday cylinder 115, a lower electrode plate insulating plate 116, and a lower electrode plate 117 in sequence below it. The upper electrode plate 112 and the lower electrode plate 117 are metal plates, and the Faraday cylinder 115 is also made of metal and is fixed between the upper electrode plate insulating plate 113 and the lower electrode plate insulating plate 116. It is insulated from the metal upper electrode plate 112 and the lower electrode plate 117. The beam current acquisition resistor R2 301 is screwed to the bottom of the Faraday cylinder through the through holes on the lower electrode plate insulating plate 116 and the lower electrode plate 117 by M3 bolts to collect the beam current and convert it into a voltage signal. The 81 Faraday cylinders are connected to the ground through the 81 beam current acquisition resistors, forming their own electron beam current paths and converting them into voltage signals. The centers of the beam calibration hole of the upper electrode plate 112, the beam-penetrating hole of the upper electrode plate insulating plate 113, and the beam-penetrating hole of the Faraday cylinder 115 are aligned. In particular, in order to achieve large-angle electron beam deflection, the calibration hole and the beam-penetrating hole are both tapered holes, and their tilt angle θ is slightly larger than the incident angle α of the electron beam on the workpiece surface. This can prevent the electron beam from being collected by the hole walls of the upper electrode plate and the upper electrode plate insulating plate when it passes through the calibration hole and the beam-penetrating hole at a certain angle after deflection, thus preventing measurement errors. At the same time, after the electron beam passes through the calibration hole and the beam-penetrating hole, it hits the inner wall of the Faraday cylinder and then flows to the ground through the beam acquisition resistor R2 301. Since the top of the Faraday cylinder is a tiny beam-penetrating hole, most of the secondary electrons and backscattered electrons generated are captured by the Faraday cylinder, which is beneficial to improving the accuracy of beam acquisition.

[0126] Figure 4This is a schematic diagram of the beam signal amplification circuit. It mainly consists of an operational amplifier LM6172 408, proportional amplifier resistors 401-404, and integrating capacitors 405-407. Both the upper plate beam signal amplification circuit 119 and the Faraday tube beam signal amplification circuit 120 use this circuit to amplify and filter the beam signal.

[0127] refer to Figure 4 The beam signal collected by the upper electrode plate 112 and the beam signal collected by the Faraday tube 115 are respectively transmitted to two beam signal amplification circuits, which filter and amplify the collected upper electrode plate beam signal and Faraday tube beam signal respectively, and their outputs are connected to the PCI high-speed data acquisition card 104.

[0128] Figure 5 This is a block diagram of the working principle of the Faraday cylinder array sampling control circuit 121, which consists of a microcontroller control circuit 501, an RS485 communication circuit 502, six 16-to-1 channel selectors 503-508, and one 8-to-1 channel selector 509.

[0129] refer to Figure 5The electron beam signals collected by the 81 Faraday tubes are connected to six 16-to-1 channel selectors. Faraday tubes 1-16 are connected to 16-to-1 channel selector 1503, Faraday tubes 17-32 are connected to 16-to-1 channel selector 2504, Faraday tubes 33-48 are connected to 16-to-1 channel selector 3505, Faraday tubes 49-64 are connected to 16-to-1 channel selector 4506, Faraday tubes 65-80 are connected to 16-to-1 channel selector 5507, and Faraday tube 81 is connected to 16-to-1 channel selector 6508. The outputs of the six 16-to-1 channel selectors are then connected to an 8-to-1 channel selector 509. Finally, only the electron beam signal of the Faraday tube corresponding to the current calibration point can be connected to the Faraday tube beam signal amplifier circuit 120 for signal filtering and amplification under the control of the microcontroller control circuit 501. The selection of channels for the electron beam signals collected by the 81 Faraday tubes is achieved by a microcontroller control circuit 501. The microcontroller control circuit 501 is connected to the industrial computer 101 via an RS485 communication circuit 502. After receiving the channel control command, it outputs 27 I / O signals, which are respectively connected to six 16-to-1 channel selectors 503-508 and one 8-to-1 channel selector 509 to achieve channel selection control. Specifically, IO1-IO3 are connected to pins A, B, and C of the 8-to-1 channel selector 509 to achieve 8-to-1 channel control; IO4-IO7 are connected to pins A, B, C, and D of the 16-to-1 channel selector 1 503 to achieve 16-to-1 channel control; IO8-IO11 are connected to pins A, B, C, and D of the 16-to-1 channel selector 2 504; IO12-IO15 are connected to the 16-to-1 channel selector 3 505; IO16-IO19 are connected to pins A, B, C, and D of the 16-to-1 channel selector 4 506; IO20-IO23 are connected to the 16-to-1 channel selector 5 507; and IO24-IO27 are connected to pins A, B, C, and D of the 16-to-1 channel selector 6 508.

[0130] Figure 6 This is a schematic diagram of the automatic calibration trajectory path planning for the deflection scanning electron beam at the calibration point.

[0131] See Figure 6 As shown, after the electron beam 108 is deflected to its initial position, it is automatically calibrated using a point-by-point scanning method, rotating clockwise in a square pattern (the point spacing in both the X and Y directions is the diameter of the beam calibration aperture). dThe electron beam sampling device 111 performs point-by-point scanning near the current calibration point. The electron beam current collected by the upper plate 112 of the electron beam sampling device 111 is converted into a voltage signal through the sampling resistor R1118, and then connected to the upper plate beam current signal amplification circuit 119 for signal filtering and amplification. After that, it is connected to an independent acquisition input channel of the PCI high-speed data acquisition card 104. The electron beam current passing through the calibration hole of the upper plate 112 and the beam penetration hole of the upper plate insulating plate 113 enters the corresponding Faraday tube 115 below. It is converted into a voltage signal through the sampling resistor R2301, and then connected to the Faraday tube array sampling control circuit 121 to the Faraday tube beam current signal amplification circuit 120 for signal filtering and amplification. After that, it is connected to another independent acquisition input channel of the PCI high-speed data acquisition card 104. At the same time, the industrial control computer 101 sends a beam current synchronous acquisition control signal to the PCI high-speed data acquisition card 104 to control the high-speed data acquisition card 104 to synchronously acquire the upper plate beam current signal and the Faraday tube beam current signal. At this point, if the electron beam 108 passes exactly through the calibration aperture of the upper electrode 112, the electron beam current collected by the sampling resistor R2 301 of the corresponding Faraday cylinder 115 below will reach its maximum value; if the electron beam 108 only scans near the calibration aperture of the upper electrode 112 and does not pass through the calibration aperture, the electron beam current collected by the sampling resistor R1118 of the upper electrode will reach its maximum value. Therefore, the magnitude of the collected upper electrode beam current signal and Faraday cylinder beam current signal can be used to determine whether the electron beam has passed through the calibration aperture of the current calibration point. Furthermore, when the ratio of the Faraday cylinder beam current signal to the upper electrode beam current signal is detected to be greater than 0.1, it indicates that part of the electron beam has passed through the calibration aperture. At this time, to improve calibration accuracy, the calibration scanning strategy is changed: starting from the current position, the electron beam scans at a speed of 1 / 10 of the calibration aperture diameter (0.1...). d The spacing of the electron beam is scanned in the order of top → bottom → left → right, meaning the electron beam oscillates near the current position. The purpose is to find the maximum value of the beam current signal collected by the Faraday tube. When the maximum value is found, it can be determined that the electron beam has entered the current calibration aperture. The calibration software can then record the currently applied X-direction deflection scanning coil drive current value and Y-direction deflection scanning coil drive current value, thus completing the calibration of the deflection scanning current at the current calibration point.

[0132] The high-precision, high-frequency deflection scanning device for electron beams described in this invention comprises an industrial control computer, deflection scanning accuracy calibration software, a PCI arbitrary waveform generator card, a PCI high-speed data acquisition card, an X-direction deflection coil drive circuit, a Y-direction deflection coil drive circuit, an electron gun, an electron beam, an X-direction deflection scanning coil, a Y-direction deflection scanning coil, an electron beam sampling device, an upper electrode beam signal amplification circuit, a Faraday tube beam signal amplification circuit, and a Faraday tube array sampling control circuit. By setting up a dedicated electron beam acquisition device, deflection scanning, and synchronous high-speed data acquisition circuit, and planning an automatic calibration scanning path, combined with specially designed deflection scanning accuracy calibration software, automatic calibration of large-angle electron beam deflection scanning accuracy is achieved, greatly improving the automation level and efficiency of calibration. The maximum calibration area of ​​the automatic electron beam deflection scanning accuracy calibration device can reach 360mm × 3600mm. Employing a point-by-point scanning method based on an automatic calibration trajectory that rotates clockwise in a square and a path planning method that searches for the path through the beam current maximum value using electron beam oscillation, it can ensure that the current calibration point can be found and has sufficiently high calibration accuracy, not less than 0.1. d The design fully considers the certain incident angle α of the electron beam on the workpiece surface during large-angle deflection scanning. The calibration holes of the upper electrode plate, the insulating plate of the upper electrode plate, and the beam-penetrating holes of the Faraday cylinder are all designed as conical holes. The inclination angle θ of the conical holes is slightly larger than the incident angle α of the electron beam. This can prevent the electron beam from hitting the hole wall and being collected by the upper electrode plate and the insulating plate when passing through the beam-penetrating hole, thus preventing errors and improving calibration accuracy. The beam current passing through the 81 calibration holes is collected by 81 independent Faraday cylinders. This ensures that the electron beam after passing through the upper electrode plate and the insulating plate, as well as the secondary electrons and backscattered electrons generated by the electron beam bombarding the metal wall of the Faraday cylinder, are completely collected by the Faraday cylinder.

[0133] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. An automatic calibration device for electron beam deflection scanning accuracy, characterized in that, include: The system includes an industrial control computer, deflection scanning accuracy calibration software, a PCI arbitrary waveform generator card, a PCI high-speed data acquisition card, an X-direction deflection coil drive circuit, a Y-direction deflection coil drive circuit, an electron gun, an electron beam, an X-direction deflection scanning coil, a Y-direction deflection scanning coil, an electron beam sampling device, an upper electrode beam signal amplification circuit, a Faraday cylinder beam signal amplification circuit, and a Faraday cylinder array sampling control circuit. The electron beam sampling device consists of an upper electrode, an upper electrode insulating plate, a ceramic insulating column, a Faraday cylinder array, a lower electrode insulating plate, a lower electrode of the sampling device, and an upper electrode beam sampling resistor R1. The positional connection between them is as follows: the deflection scanning accuracy calibration software is installed in the industrial control computer to realize the setting of electron beam deflection current, automatic calibration path planning, synchronous acquisition of upper electrode beam current and Faraday tube array beam current signals, and determination of electron beam spot coincidence with calibration aperture; the industrial control computer transmits electron beam deflection scanning current data to the PCI arbitrary waveform generator card to generate X-direction deflection coil drive waveform and Y-direction deflection coil drive waveform respectively, and connects them to the X-direction deflection coil drive circuit and Y-direction deflection coil drive circuit respectively through two independent channels for deflection scanning current amplification, and then connects them to the X-direction deflection scanning coil and Y-direction deflection scanning coil installed in the electron gun respectively, generating X-direction and Y-direction deflection magnetic fields in the deflection scanning coil; the electron beam passes through the X-direction deflection scanning coil and Y-direction deflection scanning coil. After the tracing coil deflects to a point near a calibration point of the electron beam sampling device, the electron beam begins calibration scanning from its initial deflection position along an automatic calibration trajectory. Below the upper electrode plate of the electron beam sampling device, an upper electrode plate insulating plate, a Faraday cylinder array, a lower electrode plate insulating plate, and a lower electrode plate are sequentially installed. The upper and lower electrode plates are metal plates. The upper electrode plate, upper electrode plate insulating plate, lower electrode plate insulating plate, and lower electrode plate are fixedly connected at the four corners of the sampling device via four ceramic insulating pillars. The Faraday cylinder array is fixed between the upper and lower electrode plate insulating plates and is insulated from the metal upper and lower electrode plates. The metal upper electrode plate is connected to ground through a sampling resistor R1, and the metal lower electrode plate is directly connected to ground to form an electron beam flow path. The centers of the upper electrode plate calibration hole, the upper electrode plate insulating plate beam-penetrating hole, and the Faraday cylinder beam-penetrating hole are aligned.

2. The automatic calibration device for electron beam deflection scanning accuracy according to claim 1, characterized in that: To achieve large-angle electron beam deflection, both the calibration aperture and the beam-penetrating aperture are tapered, with an inclination angle θ greater than the incident angle α of the electron beam on the workpiece surface. Simultaneously, the electron beam, after passing through the calibration aperture and the beam-penetrating aperture, strikes the inner wall of the Faraday cylinder and then flows to the ground through the beam current acquisition resistor R2. When the electron beam starts from the initial deflection position and performs calibration scanning near the current calibration point using a point-by-point scanning method along a clockwise square rotation automatic calibration trajectory, the electron beam current collected by the upper plate of the electron beam sampling device is converted into a voltage signal through the sampling resistor R1. This signal is then connected to the upper plate beam current signal amplification circuit for signal filtering and amplification, and finally connected to an independent acquisition input channel of the PCI high-speed data acquisition card.

3. An automatic calibration device for electron beam deflection scanning accuracy according to claim 1 or 2, characterized in that: The electron beam, passing through the calibration hole of the upper electrode plate and the beam-passing hole of the upper electrode plate insulation plate, enters the corresponding Faraday cylinder below. This beam is converted into a voltage signal by the sampling resistor R2, and then connected to the Faraday cylinder beam signal amplification circuit via the Faraday cylinder array sampling control circuit for signal filtering and amplification. Finally, it is connected to another independent acquisition input channel of the PCI high-speed data acquisition card. The industrial control computer sends a beam synchronization acquisition control signal to the PCI high-speed data acquisition card, controlling the card to synchronously acquire the upper electrode plate beam signal and the Faraday cylinder beam signal. If the electron beam passes through the upper electrode plate calibration hole, the electron beam current collected by the corresponding Faraday cylinder sampling resistor R2 will reach its maximum value. If the electron beam only scans near the upper electrode plate calibration hole and does not pass through it, the electron beam current collected by the upper electrode plate sampling resistor R1 will reach its maximum value. The magnitude of the acquired upper electrode plate beam signal and Faraday cylinder beam signal determines whether the electron beam has passed through the calibration hole at the current calibration point.

4. The automatic calibration device for electron beam deflection scanning accuracy according to claim 3, characterized in that: When the ratio of the Faraday tube beam signal to the upper electrode beam signal is greater than 0.1, it indicates that part of the electron beam has passed through the calibration aperture. At this time, in order to improve the calibration accuracy, the calibration scanning strategy is changed: starting from the current position, the electron beam scans in the order of up→down→left→right at a spacing of 1 / 10 of the calibration aperture diameter. That is, the electron beam oscillates near the current position to find the maximum value of the beam signal collected by the Faraday tube. When this maximum value is found, it is determined that the electron beam has passed through the current calibration aperture. The calibration software records the currently applied X-direction deflection scanning coil drive current value and Y-direction deflection scanning coil drive current value. The calibration of the deflection scanning current at the current calibration point is thus completed.

5. The automatic calibration device for electron beam deflection scanning accuracy according to claim 1, characterized in that: The aforementioned PCI arbitrary waveform generator card uses a general-purpose PCI arbitrary waveform generator card and has at least two independent channels that can be output synchronously. These channels are used to store deflection scan drive current data in the X and Y directions. When the calibration program is started, the waveform generator card converts the above data into X-direction deflection scan waveforms and Y-direction deflection scan waveforms, respectively, and controls the automatic calibration of each calibration point through synchronous output via two independent channels. The aforementioned PCI high-speed data acquisition card uses a general-purpose PCI high-speed data acquisition card and has at least two independent channels that can be input synchronously. It receives the beam synchronization acquisition control signal from the industrial control computer to realize the synchronous acquisition of the upper electrode beam signal and the Faraday tube beam signal.

6. The automatic calibration device for electron beam deflection scanning accuracy according to claim 1, characterized in that: The X-direction deflection coil drive circuit receives the X-direction deflection scanning waveform output from the PCI arbitrary waveform generator card, amplifies its power, and then connects its output to the X-direction deflection scanning coil to generate a coil drive current, thereby generating an X-direction deflection scanning magnetic field, causing the electron beam to deflect in the X direction. The Y-direction deflection coil drive circuit receives the Y-direction deflection scanning waveform output from the PCI arbitrary waveform generator card, amplifies its power, and then connects its output to the Y-direction deflection scanning coil to generate a coil drive current, thereby generating a Y-direction deflection scanning magnetic field, causing the electron beam to deflect in the Y direction.

7. An automatic calibration device for electron beam deflection scanning accuracy according to claim 1 or 2, characterized in that: In the electron beam sampling device, an upper electrode insulating plate, a Faraday cylinder array, a lower electrode insulating plate, and a lower electrode plate are sequentially installed below the upper electrode plate. The upper and lower electrode plates are metal plates. The upper electrode plate, upper electrode insulating plate, lower electrode insulating plate, and lower electrode plate are fixedly connected at the four corners of the sampling device by four ceramic insulating pillars. The Faraday cylinder array is fixed between the upper and lower electrode insulating plates and is insulated from the metal upper and lower electrode plates. The metal upper electrode plate is connected to ground through a sampling resistor R1, and the metal lower electrode plate is directly connected to ground to form an electron beam flow path.

8. The automatic calibration device for electron beam deflection scanning accuracy according to claim 1, characterized in that: The Faraday tube array consists of 81 Faraday tubes, each corresponding to one of the 81 calibration holes. At the bottom of each Faraday tube, an M3 bolt passes through the circular hole of the lower electrode plate and the circular hole of the lower electrode plate insulation plate to connect the Faraday tube beam sampling resistor R2 to the Faraday tube, converting the beam signal collected by the Faraday tube into a voltage signal. The beam signals collected by all 81 Faraday tubes are connected to the Faraday tube array sampling circuit.

9. The automatic calibration device for electron beam deflection scanning accuracy according to claim 8, characterized in that: The Faraday tube array sampling control circuit comprises a microcontroller control circuit, an RS485 communication circuit, six 16-to-1 channel selectors, and one 8-to-1 channel selector. Their positional relationship is as follows: the electron beam signals collected by the 81 Faraday tubes are connected to the six 16-to-1 channel selectors respectively. Specifically, Faraday tubes 1-16 are connected to 16-to-1 channel selector 1, Faraday tubes 17-32 are connected to 16-to-1 channel selector 2, Faraday tubes 33-48 are connected to 16-to-1 channel selector 3, Faraday tubes 49-64 are connected to 16-to-1 channel selector 4, Faraday tubes 65-80 are connected to 16-to-1 channel selector 5, and Faraday tube 81 is connected to 16-to-1 channel selector 6. The outputs of the six 16-to-1 channel selectors are then connected to the 8-to-1 channel selector. Ultimately, only the electron beam signal from the Faraday tube corresponding to the current calibration point is connected to the Faraday tube beam signal amplification circuit for signal filtering and amplification. The channel selection of the electron beam signals collected by the 81 Faraday tubes is achieved through a microcontroller control circuit. The microcontroller control circuit is connected to the industrial control computer through an RS485 communication circuit. After receiving the channel control command, it outputs 27 I / O signals, which are respectively connected to six 16-to-1 channel selectors and one 8-to-1 channel selector to achieve channel selection control.

10. A calibration method for an automatic calibration device for electron beam deflection scanning accuracy, characterized in that: The steps include: (1) First, determine the origin O of the electron beam emitted by the current electron gun and the X and Y directions of the electron beam scan. The specific method is: set the deflection scanning current of the electron beam in the X and Y directions to 0 through calibration software, and then start the electron beam to make a point on the surface of the workpiece in the working plane. This point is the origin O of the electron beam. Then set the deflection scanning current in the Y direction to 0 and the deflection scanning current in the X direction to change from -X0 to +X0 to obtain the X scanning direction of the electron beam. Similarly, set the deflection scanning current in the X direction to 0 and the deflection scanning current in the Y direction to change from -Y0 to +Y0 to obtain the Y scanning direction of the electron beam. (2) Place the electron beam sampling device in the vacuum chamber, so that the upper electrode plate is on the working plane of the electron beam, and the center point O of the upper electrode plate coincides with the origin O on the workpiece. At the same time, the X direction of the calibration plate coincides with the X direction determined by the electron beam scanning on the workpiece, and the Y direction of the calibration plate coincides with the Y direction determined by the electron beam scanning on the workpiece. In this way, the position and direction of the upper electrode plate of the electron beam sampling device are determined. (3) Calculate the deflection current at the key point L0 on the left side. Then, start the calibration software and deflect the electron beam to the vicinity of L0 based on the calculated deflection current. Then, manually adjust the X-direction deflection current and Y-direction deflection current to make the electron beam pass through the calibration hole at L0. Record the X-direction deflection current value and Y-direction deflection current value at this time. The X-direction deflection current value at this point is the X-direction deflection current value when deflected to the leftmost position. I LM ; (4) Repeat step (3) to obtain the X-direction deflection current value and Y-direction deflection current value at point R0. The X-direction deflection current value at this point is the X-direction deflection current value when deflected to the rightmost position. I RM ; (5) Repeat step (3) to obtain the X-direction deflection current value and Y-direction deflection current value at point T0. The Y-direction deflection current value at this point is the Y-direction deflection current value when deflected to the top. I YM ; (6) Repeat step (3) to obtain the X-direction deflection current value and Y-direction deflection current value at point B0. The Y-direction deflection current value at this point is the Y-direction deflection current value when deflected to the bottom. I BM ; (7) The maximum values ​​of the deflection current in the X and Y directions were obtained through the above steps (3) to (6). The initial deflection current values ​​in the X and Y directions of calibration points 1 to 81 were calculated by linear interpolation. The initial deflection current values ​​of each calibration point were input into the deflection scanning coil drive circuit, that is, the electron beam was deflected to the initial deflection position near each calibration point.

Images