Wolfram filament scanning electron microscope filament mounting method, system and electron microscope

Abstract

The application discloses a tungsten filament scanning electron microscope filament mounting and saturation adjustment method, system and electron microscope. The method comprises the following steps: a filament centering step, the filament tip is aligned with the center of the grid cap by rotating the grid cap and adjusting the screw; a filament height preliminary adjustment step, the grid is placed at an angle of 45 degrees, and the filament height is adjusted until the tip is at a critical position of appearing and disappearing at the edge of the grid hole; a filament saturation adjustment step, the filament current is increased after installation until a saturated filament image is obtained; and a filament height fine adjustment step, the automatic bias value is read under high voltage and saturation conditions, and if the value is not in the range of 16%-40%, the lower part of the grid is rotated for adjustment. The experience-dependent adjustment process is converted into a standardized and quantitative operation process, the closed-loop fine adjustment is realized through the 45-degree angle critical method and combined with the quantitative feedback of the automatic bias, the operation difficulty is significantly reduced, and the adjustment accuracy and consistency are improved.

Description

Technical Field

[0001] This invention relates to the field of scanning electron microscopy, and in particular to a method for filament mounting, centering, height adjustment and saturation optimization of a tungsten filament scanning electron microscope, an adjustment system for implementing the method, and a scanning electron microscope including the system. Background Technology

[0002] A scanning electron microscope (SEM) is a precision instrument that uses a finely focused electron beam to scan and excite physical signals on the surface of a sample to create an image. Among these, the tungsten filament SEM is widely used due to its lower cost and wider applicability. In the operation and maintenance of a tungsten filament SEM, installing the filament in the appropriate position and adjusting it to saturation is a crucial step in achieving high-resolution imaging.

[0003] However, in existing technologies, the installation and adjustment of the filament heavily rely on the operator's personal experience. Specifically, steps such as filament alignment, distance control between the filament tip and the grid aperture, and filament saturation assessment lack quantifiable and visualized standard operating procedures. Operators often need to attempt repeatedly, which is not only inefficient but also prone to damaging the grid aperture edge due to improper operation (such as using excessively coarse polishing paste to clean the grid cap or applying excessive force), leading to a decrease in electron gun performance. Furthermore, the inconsistent filament settings achieved by different operators affect the stability of electron microscope imaging quality.

[0004] Therefore, it is necessary to provide a standardized, quantifiable, easy-to-operate method for tungsten filament scanning electron microscope filament installation and saturation adjustment with low risk of equipment damage. Summary of the Invention

[0005] This invention addresses the shortcomings of existing technologies by providing a filament mounting method, system, and microscope for a tungsten filament scanning electron microscope. By combining optical microscopy observation, 45° critical position determination, filament image saturation observation, and quantitative feedback of electron gun operating parameters (especially the automatic bias voltage value), this invention forms a complete, closed-loop adjustment process, significantly reducing operational difficulty and improving adjustment accuracy and consistency.

[0006] To achieve the above objectives, the present invention provides a filament mounting method for a tungsten filament scanning electron microscope, comprising the following steps: Filament alignment steps: Place the grid cap horizontally, rotate the grid cap and adjust the tightness of the three screws on the grid so that the tip of the filament is aligned with the center of the grid cap.

[0007] Initial adjustment steps for filament height: Place the assembled grid at a 45° angle with the tilt direction facing outwards, and adjust the filament height until, when viewed from directly above the grid hole, the tip of the filament is in a critical position where it is barely visible at the edge of the higher side of the grid hole.

[0008] Filament saturation adjustment steps: Mount the filament onto a scanning electron microscope, evacuate the vacuum, set the working distance and high voltage, and increase the filament current until a saturated filament image is obtained.

[0009] Fine-tuning steps for filament height: Under high voltage and filament saturation conditions, read the automatic bias voltage value of the electron gun. If the automatic bias voltage value is not within the range of 16%-40%, adjust the distance between the filament and the grid hole by rotating the lower part of the grid until the automatic bias voltage value falls within the range of 16%-40%.

[0010] Furthermore, the setting of the working distance and high voltage is specifically as follows: the working distance is adjusted to 5-15mm according to the type of sample to be tested, and the high voltage is set to 15-30kV.

[0011] Furthermore, in the filament saturation adjustment step, the saturated filament image is elliptical and has uniform and full brightness, while the undersaturated filament image has a dark shadow in the center.

[0012] Furthermore, the filament alignment step specifically includes: placing the grid cap horizontally and observing the position of the filament in the grid hole under an eyepiece on one side; rotating the grid cap horizontally by 180°, if the filament is blocked by the grid hole or deviated to different sides before and after the rotation, adjusting the tightness of the three screws until the filament position remains unchanged after rotating 180°; rotating the grid cap by 90° and repeating the above position observation and screw adjustment steps.

[0013] Furthermore, in the filament alignment step, when selecting to output the image to the computer display using only one eyepiece, the adjustment is made in the following way: Using the fixed image from the monocular lens, the offset of the filament relative to the grid aperture is determined; Rotate the gate cap horizontally by 180° and compare the positions of the filament in the image before and after the rotation. If the positions are inconsistent, adjust the tightness of the three screws until the filament position remains unchanged after rotating 180°.

[0014] Furthermore, in the initial filament height adjustment step, the filament plane is placed parallel to the operator's chest when the grid is tilted.

[0015] Furthermore, in the initial filament height adjustment step, the assembled gate is placed at a 45° angle on the plastic ring, with the gate tilting direction facing away from the operator.

[0016] Furthermore, in the filament height fine-tuning step: if the automatic bias value is greater than 40%, it is determined that the filament is too far from the grid cap, and the filament is brought closer by rotating the lower part of the grid in the direction of decreasing the filament height by 1-2 scales; if the automatic bias value is less than 20%, it is determined that the filament is too close to the grid cap, and the filament is moved further away by rotating the lower part of the grid in the direction of increasing the filament height by 1-2 scales.

[0017] Furthermore, in the filament height fine-tuning step, the reference range of the automatic bias voltage value and the corresponding filament adjustment direction are pre-stored in the control system of the scanning electron microscope, and the current automatic bias voltage value and suggested adjustment direction are displayed in real time in the user interface.

[0018] Furthermore, in the filament height fine-tuning step, when the high voltage, filament saturation, and filament position are appropriate, the electron gun emission current is 95-110μA, the filament voltage is 1.98-2.18V, and the filament current is 2.58-2.82A.

[0019] Furthermore, when replacing the filament, before removing the old filament, lower its height by 0.1-0.15mm. After installing the new filament, raise its height by the same amount to return it to the working height of the old filament. Ideally, the distance between the filament tip and the grid hole should be 0.2mm. Furthermore, by holding the grid cap still with the left hand and rotating the lower part of the grid in the direction indicated by the arrow with the right hand, the filament height is reduced by 0.05mm for each rotation. Furthermore, it also includes pretreatment steps before filament replacement: Before removing the old filament, record the current filament height parameter or the scale position at the bottom of the grid; After inserting the new filament, restore the filament height to the recorded parameter or scale position; Furthermore, it also includes a filament state determination step based on the comprehensive operating parameters of the electron gun: Under conditions of 30kV high voltage and filament saturation, the automatic bias voltage, emission current, filament voltage and filament current are read simultaneously. If the four parameters fall within the ranges of 16-40, 95-110μA, 1.98-2.18V, and 2.58-2.82A respectively, then the filament height is determined to be in an ideal state.

[0020] Furthermore, by holding the grid cap still with the left hand and rotating the lower part of the grid in the direction indicated by the arrow with the right hand, the filament height is reduced by 0.05mm for each rotation.

[0021] Furthermore, under ideal operating conditions, the distance between the filament tip and the grid hole is 0.2 mm.

[0022] Furthermore, the following tools are used to assist in performing the filament alignment step and the initial filament height adjustment step: A 10-30x optical microscope or a binocular stereo microscope, wherein the distance between the two eyepieces of the binocular stereo microscope is adjusted so that the fields of view of both eyes coincide, and all operations are performed while wearing clean gloves.

[0023] The present invention also provides a filament adjustment device for a tungsten filament scanning electron microscope for implementing the above method, comprising: a grid cap having a scale and arrow on its grid base; a grid having three screws on its upper part for adjusting the alignment of the filament; and a filament fixing ring for fixing the filament; wherein, coarse and fine adjustment of the filament height are achieved by rotating the lower part of the grid relative to the grid cap.

[0024] This invention also provides a filament adjustment auxiliary system for a tungsten filament scanning electron microscope, comprising: a parameter acquisition module for acquiring the automatic bias voltage, emission current, filament voltage, and filament current of the electron gun when the filament is saturated and the high voltage is 30kV; a comparison and judgment module for comparing the acquired automatic bias voltage with a reference range of 16%-40% and determining the distance of the filament height relative to the grid cap; and a prompt output module for outputting adjustment suggestions on the user interface: if the automatic bias voltage is >40%, prompt "adjust closer to the filament"; if it is <20%, prompt "adjust further away from the filament".

[0025] Furthermore, the prompt output module is also used to output adjustment scale suggestions: each adjustment is 1-2 scale increments, corresponding to a filament height change of 0.05-0.10mm.

[0026] The present invention also provides a tungsten filament scanning electron microscope, including an electron gun, a grid cap, a filament, and the above-mentioned filament adjustment auxiliary system.

[0027] Compared with the prior art, the present invention has the following beneficial effects: 1. The traditional experience-based filament adjustment process is broken down into four standardized steps: centering, initial adjustment, saturation adjustment, and fine adjustment, making it easy to learn and operate.

[0028] 2. The 45° critical position observation method is introduced as an initial adjustment method, which can quickly determine whether the filament height is roughly appropriate without installing the equipment, reducing the number of times the vacuum is repeatedly pumped.

[0029] 3. Using the quantitative range (16%-40%) of the automatic bias value of the electron gun as the basis for fine adjustment, and providing clear adjustment directions (>40% to adjust closer, <20% to adjust further) and scale suggestions (1-2 divisions), a closed-loop, quantitative high-precision adjustment is achieved.

[0030] 4. Provides an ideal operating range for multi-parameter joint judgment (emission current, filament voltage, filament current), further ensuring that the electron gun is in optimal condition.

[0031] 5. It is proposed to use cork toothpick fibers instead of coarse abrasive paste to clean the gate holes, so as to avoid scratching or deforming the edges of the gate holes and protect the core components.

[0032] 6. Through the filament adjustment auxiliary system and user interface prompts, experience parameters are transformed into real-time guidance, reducing the skill requirements for operators and improving adjustment consistency and success rate. Attached Figure Description

[0033] Figure 1 : Schematic diagram of the mounting of the gate and gate base; Figure 2 Schematic diagram of the gate cap structure; Figure 3 Schematic diagram of the filament base structure; Figure 4 Schematic diagram of the filament retaining ring structure; Figure 5 : A schematic diagram of a structure in which the gate cap is placed at a 45° angle on a plastic ring.

[0034] Figure 6 : Schematic diagram of the observation angle when the gate cap is tilted at 45°; Figure 7 : A filament image with undersaturation and a dark shadow in the middle; Figure 8 : A filament image with undersaturation and a dark shadow in the middle; Figure 9 : A filament image with undersaturation and a dark shadow in the middle; Figure 10 : A saturated, oval shape resembling a full filament.

[0035] In the diagram: 1a-gate cap, 1b-gate hole, 2a-top of gate, 2b-screw, 3a-middle of gate, 4a-filament base, 5a-gate base, 5b-scale, 5c-arrow, 7a-filament retaining ring, 9-plastic ring. Detailed Implementation

[0036] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0037] Example 1: Complete Filament Installation and Saturation Adjustment Process This embodiment provides a filament mounting method for a tungsten filament scanning electron microscope. All operations are performed while wearing clean gloves and using a 10-30x optical microscope or a binocular stereo microscope. When using a binocular stereo microscope, the distance between the two eyepieces must be adjusted so that the fields of view of both eyes overlap.

[0038] Step 1: Prepare and remove the old filament Reference Figure 1-4 Confirm the status and condition of the following tools: grid cap 1a, grid hole 1b, three screws 2b on the upper end 2a of the grid, grid middle 3a, filament base 4a, scale 5b and arrow 5c on grid base 5a, and filament retaining ring 7a. Before removing the old filament, hold the grid cap still with your left hand and hold the lower part of the grid with your right hand. Twist the grid 2-3 turns in the direction indicated by arrow 5c to lower the height of the old filament by 0.1-0.15mm (0.05mm per turn), and then remove the old filament. Record the position of the lower part of the grid relative to the scale at this time.

[0039] Step 2: Install the new filament, align the filament, and assemble the grid. Will Figure 3 The filament shown is placed in Figure 1 After setting the grid as shown, position the filament base 4a at the center of the grid 3a. First, restore the filament height to the position recorded in step one, i.e., rotate it backward by the same number of divisions. Then, perform filament alignment: Figure 2 The gate cap shown is installed to Figure 1 The upper end 2a of the gate is shown, aligning the filament tip with the gate hole 1b in the center of the gate cap 1a. Place the entire gate under the objective lens of a binocular lens. With the binocular fields of view overlapping, observe the relative position of the filament and the gate hole. If a monocular lens is selected and the image is output to a computer screen, fix the image using the monocular lens and determine if the filament is misaligned. Rotate the gate cap horizontally 180°. If the filament position is inconsistent before and after rotation, adjust the tightness of the three screws 2b at the upper end of the gate until the filament position remains unchanged after 180° rotation. Then rotate the gate cap 90° and repeat the above operation to ensure good alignment in all directions, thus assembling the gate.

[0040] Step 3: Initial adjustment of filament height using the 45° angle method like Figure 5 As shown, the assembled gate is placed at a 45° angle on the plastic ring 9, with the gate tilted outwards and upwards. Specifically, a right-angled piece of paper can be folded diagonally to obtain a 45° reference angle to verify whether the gate's tilt angle is 45°. When tilting the gate, the axis of the gate aperture 1b should form a 45° angle with the operator's observation direction to reduce binocular parallax. The principle is as follows when viewed directly above the gate aperture 1b. Figure 6 As shown, when the filament height is appropriate, the tip of the filament is at a critical position, barely visible, at the edge of the higher side of the grid hole 1b, neither fully exposed nor completely obscured. If too much is exposed, the filament height should be appropriately reduced; if it is completely invisible, the filament height should be appropriately increased.

[0041] Step 4: Installation, Vacuuming, and Filament Saturation Adjustment The adjusted filament grid was installed into the electron microscope, and a vacuum was applied. The sample working distance was set to 10 mm, and the high voltage to 30 kV. The filament current was gradually increased on the control interface, and the changes in the filament image were observed. Figure 7-9 It is an undersaturated process, in which Figure 9 A shadow still looms in the center; continue increasing the current to... Figure 10 The state is characterized by an elliptical filament shape, uniform and full overall brightness, and no dark shadow in the center; this indicates saturation. Stop increasing the current.

[0042] Step 5: Fine-tuning based on electron gun operating parameters Under 30kV and filament saturation conditions, read the automatic bias value of the electron gun. Use either a 1-SourceControl or a 9-Filament Exchange; the preferred range for the automatic bias is 16%-40%.

[0043] If the automatic bias voltage is >40%, it indicates that the filament tip is too far from the grid hole. Rotate the lower part of the grid 1-2 increments (0.05mm per increment) in the direction of arrow 5c with your right hand to bring it closer to the filament.

[0044] If the automatic bias voltage is less than 20%, it indicates that the filament tip is too close to the grid hole. Rotate the lower part of the grid 1-2 scales in the opposite direction of arrow 5c with your right hand to move the filament further away.

[0045] Repeat the reading and fine-tuning until the automatic bias voltage stabilizes between 16% and 40%. At this point, the following parameters can be considered for a relatively ideal state: Emission Current 95-110μA, Filament Voltage 1.98-2.18V, and Filament Current 2.58-2.82A. If these parameters are also within the corresponding ranges, then the filament height is relatively ideal.

[0046] Example 2: Quick recovery method during filament replacement Based on Example 1, to reduce the adjustment time each time the filament is replaced, the following steps are adopted: Before removing the old filament, follow the method in step one of Example 1 to lower the filament height by 0.1-0.15mm (screw it in 2-3 turns). Remove the old filament and install the new filament. Then, reverse the rotation of the lower part of the grid by the same number of turns to roughly restore the height of the new filament to the original working height of the old filament. Afterwards, only minor adjustments are needed to quickly achieve the desired state.

[0047] Example 3: Filament Adjustment Auxiliary System and User Interface This embodiment provides a filament adjustment auxiliary system integrated into the control software of a scanning electron microscope. The system includes: Parameter acquisition module: When the electron microscope is operating at 30kV and the filament is saturated, it automatically acquires the automatic bias voltage, emission current, filament voltage, and filament current.

[0048] Comparison and judgment module: compares the automatic bias voltage with the preset 16%-40% threshold.

[0049] The prompt output module displays the current parameters in real time on the user interface and outputs text prompts such as "Current automatic bias voltage XX, too high (>40%), it is recommended to adjust the filament closer by 1-2 scales" or "Too low (<20%), it is recommended to adjust the filament further away by 1-2 scales". It can also display parameters such as emission current as auxiliary references.

[0050] The system's control logic can be stored in a computer-readable storage medium and executed by the electron microscope's processor.

[0051] Example 4: Tungsten filament scanning electron microscope with auxiliary system A tungsten filament scanning electron microscope includes an electron gun, a grid cap, a tungsten filament, and the filament adjustment auxiliary system described in Example 3. When performing filament maintenance, the operator can follow the steps in Example 1 and refer in real time to the parameter feedback and adjustment suggestions provided by the auxiliary system on the display screen to complete filament installation and saturation adjustment.

[0052] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to the above embodiments without departing from the principles and spirit of the present invention, and all such changes fall within the protection scope of the present invention.

Claims

1. A method for mounting the filament of a tungsten filament scanning electron microscope, characterized in that, Includes the following steps: Filament alignment steps: Place the grid cap horizontally, rotate the grid cap and adjust the tightness of the three screws (2b) on the grid so that the tip of the filament is aligned with the center of the grid cap; Initial adjustment steps for filament height: Place the assembled grid at a 45° angle with the tilt direction of the grid facing outwards, and adjust the filament height until, when viewed from directly above the grid hole, the tip of the filament is in a critical position where it is barely visible at the edge of the higher side of the grid hole. Filament saturation adjustment steps: Mount the filament onto the scanning electron microscope, evacuate the vacuum, set the working distance and high voltage, and increase the filament current until a saturated filament image is obtained; Fine-tuning steps for filament height: Under high voltage and filament saturation conditions, read the automatic bias voltage value of the electron gun. If the automatic bias voltage value is not within the range of 16%-40%, adjust the distance between the filament and the grid hole by rotating the lower part of the grid until the automatic bias voltage value falls within the range of 16%-40%. and / or The specific settings for the working distance and high voltage are as follows: adjust the working distance to 5-10mm and set the high voltage to 15-30kV; and / or In the filament saturation adjustment step, the saturated filament image is elliptical and has uniform and full brightness, while the undersaturated filament image has a dark shadow in the center.

2. The method according to claim 1, characterized in that, The filament alignment step specifically includes: Place the grid cap horizontally and observe the position of the filament in the grid hole under one eyepiece; Rotate the grid cap horizontally by 180°. If the filament is blocked by the grid hole or biased to different sides before and after rotation, adjust the tightness of the three screws (2b) until the filament position remains unchanged after rotating 180°. Rotate the gate cap 90° and repeat the above steps of position observation and screw adjustment. and / or In the filament alignment step, when selecting to output the image from only one eyepiece to the computer screen, the following adjustments are made: Using the fixed image from the monocular lens, the offset of the filament relative to the grid aperture is determined; Rotate the gate cap horizontally by 180° and compare the positions of the filament in the image before and after the rotation. If the positions are inconsistent, adjust the tightness of the three screws (2b) until the filament position remains unchanged after rotating 180°.

3. The method according to claim 1, characterized in that, In the initial filament height adjustment step, when tilting the grid, the filament plane is placed parallel to the operator's chest. and / or In the initial filament height adjustment step, the assembled grid is placed at a 45° angle on the plastic ring, with the grid tilted away from the operator.

4. The method according to claim 1, characterized in that, In the filament height fine-tuning step: If the automatic bias value is greater than 40%, it is determined that the filament is too far from the grid cap. The filament can be brought closer by rotating the lower part of the grid in the direction of reducing the filament height by 1-2 scales. If the automatic bias value is less than 20%, it is determined that the filament is too close to the grid cap. The filament can be moved further away by rotating the lower part of the grid back 1-2 scales in the direction of increasing the filament height. and / or In the filament height fine-tuning step, the reference range of the automatic bias voltage value and the corresponding filament adjustment direction are pre-stored in the control system of the scanning electron microscope, and the current automatic bias voltage value and suggested adjustment direction are displayed in real time in the user interface.

5. The method according to claim 1 or 4, characterized in that, In the filament height fine-tuning step, when the high voltage, filament saturation, and filament position are appropriate, the electron gun emission current is 95-110μA, the filament voltage is 1.98-2.18V, and the filament current is 2.58-2.82A.

6. The method according to claim 1, characterized in that, When replacing the filament, before removing the old filament, lower its height by 0.1-0.15mm. After installing the new filament, raise its height by the same amount to return it to the working height of the old filament. Ideally, the distance between the filament tip and the grid hole should be 0.2mm. and / or By holding the grid cap still with your left hand and rotating the lower part of the grid in the direction indicated by the arrow with your right hand, the filament height is reduced by 0.05mm for each rotation. and / or It also includes pretreatment steps before filament replacement: Before removing the old filament, record the current filament height parameter or the scale position at the bottom of the grid; After inserting the new filament, restore the filament height to the recorded parameter or scale position; and / or It also includes a filament state determination step based on the overall operating parameters of the electron gun: Under conditions of 30kV high voltage and filament saturation, the automatic bias voltage, emission current, filament voltage and filament current are read simultaneously. If the four parameters fall within the ranges of 16-40, 95-110μA, 1.98-2.18V, and 2.58-2.82A respectively, then the filament height is determined to be in an ideal state.

7. The method according to claim 1, characterized in that, The following tools are used to assist in performing the filament alignment and initial filament height adjustment steps: A 10-30x optical microscope or a binocular stereo microscope, wherein the distance between the two eyepieces of the binocular stereo microscope is adjusted so that the fields of view of both eyes coincide, and all operations are performed while wearing clean gloves.

8. A tungsten filament scanning electron microscope filament adjustment device for implementing the method of claim 1, characterized in that, include: A gate cap with a scale (5b) and an arrow (5c) on its gate base; The grid has three screws (2b) on its upper part for adjusting the filament pair. Filament retaining ring (7a) is used to fix the filament; The coarse and fine adjustments of the filament height are achieved by rotating the lower part of the gate relative to the gate cap.

9. A filament adjustment auxiliary system for a tungsten filament scanning electron microscope, characterized in that, include: The parameter acquisition module is used to acquire the automatic bias voltage, emission current, filament voltage and filament current of the electron gun when the filament is saturated and the high voltage is 30kV. The comparison and judgment module is used to compare the collected automatic bias voltage value with a reference range of 16%-40% and to determine the distance of the filament height relative to the grid cap. The prompt output module is used to output adjustment suggestions on the user interface: if the automatic bias value is >40%, it prompts "Adjust closer to the filament"; if it is <20%, it prompts "Adjust further away from the filament". and / or The prompt output module is also used to output adjustment scale suggestions: each adjustment is 1-2 scale increments, corresponding to a filament height change of 0.05-0.10mm.

10. A tungsten filament scanning electron microscope, characterized in that, It includes an electron gun, a grid cap, a filament, and the filament adjustment auxiliary system as described in claim 9.

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