Method for preparing detector supporting structure based on magnetron sputtering process

Abstract

The invention discloses a preparation method of a detector supporting structure based on a magnetron sputtering process, and relates to the technical field of microstructure gas detector preparation processes, the method comprises the following steps: S1, determining a detector supporting column target material, and calculating sputtering time required for setting a deposition thickness according to set power and parameters of a magnetron sputtering system; s2, a mask plate is attached to the upper surface of the substrate, and it is ensured that the collimation holes are aligned with the preset supporting columns in position; s3, sputtering a support column, vertically depositing a sputtering material on the surface of the substrate through the confinement effect of the collimation hole, and forming the support column with the diameter consistent with that of the collimation hole; s4, laying a metal wire mesh on the upper surface of the supporting column, and pressing the metal wire mesh through a mask plate; and S5, sputtering the covering columns, and depositing a sputtering material at the interface of the metal wire mesh and the supporting columns, so that the metal wire mesh is fixed at the tops of the supporting columns. The method provided by the invention can improve the dimensional precision and surface insulation performance of the support column, enhance the bonding strength of the metal wire mesh and the support column, and avoid mechanical looseness.

Description

Technical Field

[0001] This invention belongs to the field of microstructure gas detector fabrication technology, specifically relating to a method for fabricating a detector support structure based on magnetron sputtering technology. Background Technology

[0002] Micro-pattern Gas Detectors (MPGDs) are radiation detectors based on the principles of gas ionization and electron avalanche amplification. Their core feature is the use of micron-level precision structures (such as micropores, microstrips, and microgrids) to localize high-electric-field regions, thereby improving signal gain and spatial resolution. Their structure is shown in the attached figure. Figure 1 As shown. This detector is widely used in high-energy physics, medical imaging, deep space exploration, and other fields. Its core advantages lie in its low cost, low power consumption, and adaptability to extreme environments. Supporting the microgrid is a major challenge in the detector's fabrication process. Currently, there are three main methods for attaching the microgrid to microstructure detectors: fishing line technology, thermal adhesive film technology, and photolithography. These three methods will be briefly introduced below.

[0003] The technical principle and process of the fishing line process are as follows: Fine nylon thread (fishing line) is laid in a mesh on the PCB board to support the mesh and maintain a fixed distance between the mesh and the substrate to ensure a uniform electric field. The PCB board is cleaned, and grooves or anchor points for fixing the fishing line are etched. The fishing line is then stretched taut on the substrate at a fixed spacing (e.g., 400 micrometers) using a machine or manually, fixed at high temperature, and finally covered with a metal mesh. This process has the following drawbacks: In terms of precision, manual thread laying is prone to skewing, resulting in uneven spacing, requiring expensive equipment to improve accuracy; it is easily deformed, as nylon thread loosens with prolonged use and is prone to deformation at high temperatures, requiring frequent calibration; and it is susceptible to moisture, as water absorption and expansion can alter the spacing, affecting signal stability.

[0004] The hot-applied adhesive film process is one of the commonly used methods for supporting structures of microstructured gas detectors. Its technical principle and process flow are as follows: Laser engraving of support columns: A CO2 laser is used to engrave a micro-support column array with a diameter of 0.5-1mm and a height of 100-200μm on a polyimide or epoxy resin film; Manual / mechanical arrangement and fixing: The support columns are positioned one by one and bonded to the surface of the PCB readout electrode using manual or automated equipment. The positioning accuracy is usually ±50μm; Metal mesh laying: A metal mesh (such as 316L stainless steel, mesh density 400 mesh) is laid on top of the support column array. The film is softened and the mesh is bonded using a hot-pressing process (temperature 120-150℃, pressure 0.5-1MPa). The technology has the following technical defects: low precision, with the diameter deviation of the laser-engraved support column reaching ±20% (for example, nominally 0.5mm but actually 0.4-0.6mm), and manual arrangement leading to positional offset (error > ±50μm), affecting the uniformity of the detector's electric field; poor bonding strength, with the hot adhesive film having a bonding strength of only 10-15MPa, and it is prone to detachment under temperature cycling (-40℃ to 80℃) or mechanical vibration.

[0005] Photolithography constructs an integrated structure of support pillars and a mesh on the PCB surface through a photochemical reaction. A typical process flow is as follows: Coating photosensitive adhesive; rolling negative photoresist (such as the PC1025 series, approximately 100μm thick) onto the PCB electrode surface; pre-baking with a rolling mill to form a uniform adhesive layer; aligning the mesh with the photomask; covering the photoresist surface with a metal mesh; rolling the photosensitive film again to adhere the mesh to the photoresist; placing a thin-film photomask with a support pillar pattern (aperture 0.3-0.8mm, spacing 4-8mm); adjusting the deviation to ±10μm using an optical alignment system; exposure and development using ultraviolet light (wavelength 365nm, energy 200mJ / cm²). 2 The process involves exposing the photoresist through a photomask, dissolving the unexposed areas with a developer (such as PGMEA) to form a structure where the support pillars and the screen mesh are interlocked. This technology has the following drawbacks: high process complexity, requiring precise control of the photoresist thickness (error ±5μm); the tendency for side reactions such as oxidation or alkylation during exposure, leading to poor adhesion, low contrast, brittleness, and poor stability of the resulting optical film; poor material compatibility, weak adhesion between the photoresist and the PCB copper electrodes (peel strength <5N / cm), easy warping of the support pillar edges, and residual photoresist at the microstructure, resulting in an increased radius of curvature at the tip of the nickel microneedles after microelectroforming.

[0006] The table below compares the three process routes and their defects:

[0007]

[0008] The technical bottlenecks of the three processes can be summarized as follows:

[0009] Precision versus efficiency: hot adhesive film relies on manual operation, which is inefficient, while photolithography, although highly precise, is prohibitively expensive;

[0010] Insufficient interfacial adhesion: Neither the physical bonding of the hot adhesive film nor the chemical bonding of the photoresist can meet the mechanical requirement of >50MPa.

[0011] Environmental pollution: The hot adhesive film releases VOCs, and the photolithography developer contains strong solvents (such as PGMEA), neither of which meet green manufacturing standards.

[0012] In summary, current fishing line technology is rarely used due to precision limitations. While thermal adhesive film and photolithography can achieve preliminary integration of microstructure support pillars and metal mesh, their precision, strength, and stability cannot meet the requirements of future high-performance gas detectors. Therefore, traditional microstructure detector mesh attachment processes have significant bottlenecks, which restrict further improvements in detector performance. This invention aims to innovate the magnetron sputtering process, overcome existing technological limitations, and drive the field towards higher precision and reliability. Summary of the Invention

[0013] To address the shortcomings of existing technologies, the present invention aims to provide a method for fabricating a detector support structure based on magnetron sputtering technology. This method can improve the dimensional accuracy and surface insulation performance of the support column, enhance the bonding strength between the metal wire mesh and the support column, and prevent mechanical loosening.

[0014] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0015] A method for fabricating a detector support structure based on magnetron sputtering technology, the method being implemented on a magnetron sputtering system, the method comprising the following steps:

[0016] S1. Determine the target material for the detector support column, and calculate the sputtering time required to set the deposition thickness based on the set power and parameters of the magnetron sputtering system;

[0017] S2. Attach a mask to the upper surface of the substrate, ensuring that the alignment hole on the mask is aligned with the position of the preset support post.

[0018] S3. Sputtering of the support pillars: Sputtering material vertically onto the substrate surface through the confinement effect of the collimation hole to form a support pillar with a set height and diameter consistent with the collimation hole.

[0019] S4. A metal wire mesh is laid on the upper surface of the support column, and the metal wire mesh is pressed together by the mask plate;

[0020] S5. Perform cover column sputtering, and the sputtered material is deposited at the interface between the metal mesh and the support column, thereby fixing the metal mesh to the top of the support column and realizing the fabrication of the detector support structure.

[0021] Furthermore, in the detector support structure fabrication method based on magnetron sputtering technology described above, the target material of the support column in step S1 is a high-hardness ceramic target material, which is used to form a rigid support grid.

[0022] Furthermore, in the detector support structure fabrication method based on magnetron sputtering technology described above, the target material of the support column in step S1 is Al2O3.

[0023] Furthermore, in the detector support structure fabrication method based on magnetron sputtering process described above, the substrate in step S2 is gold-plated onto the PCB readout electrode to enhance adhesion.

[0024] Furthermore, in the detector support structure fabrication method based on magnetron sputtering technology described above, step S2 specifically includes:

[0025] S21. The substrate is pre-cleaned to remove surface organic matter;

[0026] S22. A mask plate is attached to the upper surface of the substrate. The mask plate has a collimation hole array evenly distributed to ensure that the collimation hole array is aligned with the position of the preset support column.

[0027] S23. Fix the substrate and the mask plate together on the sample stage of the magnetron sputtering system chamber, and evacuate the chamber to ensure that the mask plate and the substrate are tightly bonded without gaps.

[0028] Furthermore, in the detector support structure fabrication method based on magnetron sputtering technology described above, the mask plate in step S22 is made of metal, and the diameter of the collimation holes on it ranges from 0.3 to 0.8 mm, with a spacing of 4 to 8 mm.

[0029] Furthermore, in the detector support structure fabrication method based on magnetron sputtering technology described above, the process parameters for the first sputtering in step S3 are as follows:

[0030] The working gas pressure is 0.5 Pa; the sputtering power is RF 500 W; the target-substrate distance is 150 mm; and the height of the support column is 50 μm.

[0031] Furthermore, in the detector support structure fabrication method based on magnetron sputtering technology described above, step S4 specifically includes:

[0032] S41. Move the mask plate vertically upward to expose the top of the support column;

[0033] S42. Lay the pre-stretched wire mesh flat on the upper surface of the support column;

[0034] S43. Control the mask plate to slowly move down so that it is in close contact with the metal mesh, ensuring that the metal mesh fits the top of the support column without gaps.

[0035] Furthermore, in the detector support structure fabrication method based on magnetron sputtering technology described above, the metal mesh in step S42 is 400 mesh, made of stainless steel, with a wire diameter of 10-20 μm and a mesh size of 30-40 μm.

[0036] Furthermore, in the detector support structure fabrication method based on magnetron sputtering technology described above, the deposition thickness of the cover column in step S5 is 10 μm.

[0037] Compared with existing technologies, the detector support structure fabrication method based on magnetron sputtering provided by this invention significantly improves the performance and process reliability of the wire mesh support structure by combining magnetron sputtering with dynamic positioning of the mask. Specific advantages are reflected in the following aspects:

[0038] 1. Precise and controllable support column dimensions: Through the confined sputtering of the collimation hole of the mask plate, the height error is ≤±0.1% (the height error of 50μm is less than 1μm), which is far superior to the traditional screen printing (±20μm) or machining (±50μm) process.

[0039] 2. The volume resistivity of high-purity alumina reaches 10. 15 Ω·cm, which can increase the high voltage that the detector can withstand within a certain range;

[0040] 3. No interface contamination when fixing the wire mesh: The metal wire mesh formed by secondary sputtering is directly bonded to the support column, avoiding air gaps or chemical residues introduced by adhesives;

[0041] 4. Optimization of electric field uniformity and stability: The support column is made of high dielectric strength material (such as Al2O3) to ensure that the electric field distortion rate inside the detector is <1%, while the traditional process is 3-5%;

[0042] 5. High process efficiency: The integrated sputtering process reduces assembly steps. Support column forming, screen fixing, and conductive path integration are completed in one step, shortening the process by more than 30% compared with traditional processes (such as photolithography + electroplating + bonding). Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the structure of a microstructured gas detector;

[0044] Figure 2 This is a flowchart of a method for fabricating a detector support structure based on magnetron sputtering technology, provided in an embodiment of the present invention.

[0045] Figure 3 This is a schematic diagram of the overall process flow.

[0046] Figure 4 A schematic diagram of the process structure for sputtering a cover column;

[0047] Figure 5 This is a schematic diagram of the detector structure after sputtering is complete;

[0048] Figure 3 In the middle: 1. Target plate, 2. Mask plate, 3. Sliding support rod, 4. Readout electrode, 5. Support base, 6. Support column, 7. Wire mesh, 8. Cover column, 9. Collimation hole. Detailed Implementation

[0049] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0050] Figure 2 This diagram illustrates a flowchart of a method for fabricating a detector support structure based on magnetron sputtering technology, as provided in an embodiment of the present invention. Figure 3 This is a schematic diagram of the overall process flow, showing the electrode positions, mask positioning, two sputtering processes, and screen integration steps. The method includes the following steps:

[0051] S1. Determine the target material for the detector support column, and calculate the sputtering time required to set the deposition thickness based on the set power and parameters of the magnetron sputtering system.

[0052] The magnetron sputtering system used in this invention is a dual-pulse HiPIMS technology multi-target sputtering system (such as three-gun magnetron sputtering), equipped with a dual-mode power supply of radio frequency (RF) and direct current (DC), supporting co-sputtering of metals, ceramics and composite materials.

[0053] The support target used in this invention is a high-hardness ceramic target (such as Al2O3) to form a rigid support grid. The oxide is highly insulating and allows for fast sputtering. Gold plating is applied to the PCB readout electrodes on the substrate to enhance adhesion.

[0054] After determining the magnetron sputtering system and target, the sputtering time required to achieve the set deposition thickness is calculated based on the set power of the magnetron sputtering system and the magnetron system parameters.

[0055] S2. Attach a photomask to the upper surface of the substrate, ensuring that the alignment holes on the photomask are aligned with the positions of the preset support pillars. Specifically, this includes:

[0056] S11. Perform a pre-cleaning treatment on the PCB substrate with readout electrodes to remove surface organic matter and ensure that the surface cleanliness of the substrate meets the process requirements. Plasma cleaning can be used.

[0057] S12. A photomask is attached to the upper surface of the substrate. The photomask has a uniformly distributed array of collimating holes, ensuring alignment between the collimating hole array and the pre-set support pillars. The diameter of the collimating holes on the photomask ranges from 0.3 to 0.8 mm, and the spacing is 4 to 8 mm. The four corners of the photomask are fixed to sliding supports, allowing it to move up and down along the supports.

[0058] S13. Vacuum Fixing: Fix the substrate and mask as a whole on the sample stage of the magnetron sputtering system chamber, and evacuate to a background vacuum level ≤ 5 × 10⁻⁶. -4 Pa ensures that the mask plate and the substrate are tightly bonded without gaps.

[0059] S3. Perform support pillar sputtering, and use the confinement effect of the collimation hole to sputter material vertically deposited on the substrate surface to form a support pillar with a diameter consistent with the collimation hole and a set height.

[0060] The sputtering process parameters for the support pillars are set as follows:

[0061] Target material: High-hardness insulating material, such as Al2O3;

[0062] Working pressure: 0.5 Pa, Ar gas flow rate: 20 sccm;

[0063] Sputtering power: RF 500W, target-substrate distance 150mm;

[0064] Through the confinement effect of the collimation hole, sputtered material is vertically deposited on the substrate surface to form a cylindrical support pillar with a diameter consistent with the collimation hole and a height of 50 μm.

[0065] Thickness monitoring during sputtering: Calculated based on the parameters of the measurement and control instrument, and the deposition rate is monitored using a laser interferometer. The relationship between the height of the support column and time is calibrated, with an error ≤ ±2μm.

[0066] S4. Lay a wire mesh on the upper surface of the support column and press the wire mesh together using a mask. Specifically, this includes:

[0067] S41, Mask Lifting: The mask is vertically moved upward by 20mm using a precision robotic arm inside the chamber, exposing the top of the support column;

[0068] S42. Wire Mesh Installation: Lay the pre-stretched wire mesh flat on the upper surface of the support column. The wire mesh is 400 mesh, made of stainless steel, with a wire diameter of 10-20μm and a mesh size of 30-40μm.

[0069] S43. Mask Plate Pressing Down: Control the mask plate to slowly move down, so that it is in close contact with the wire mesh. Use the mask plate's own weight or external pressure (≤10N) to press the wire mesh together, ensuring that the wire mesh fits tightly with the top of the support column without gaps.

[0070] S5. Perform capping column sputtering. The sputtered material is deposited at the interface between the metal mesh and the support column, thereby fixing the metal mesh to the top of the support column and realizing the fabrication of the detector support structure. The capping column sputtering process structure is as follows: Figure 4 As shown.

[0071] The sputtering parameters for the cover column are the same as those for the support column sputtering in step S3.

[0072] Capping column deposition: A 10 μm thick capping column is sputtered at the interface between the wire mesh and the support column to form a conductive layer, thus fixing the wire mesh to the top of the support column. The detector structure after sputtering is as follows... Figure 5 As shown.

[0073] Example: Fabrication of a rigid PCB substrate support structure (MICROMEGAS detector application)

[0074] 1. Equipment and Material Configuration

[0075] Magnetron sputtering system: Employs a three-target DC / RF hybrid sputtering system, equipped with a plasma cleaning module and a vacuum pumping system (molecular pump + mechanical pump, background vacuum ≤ 5 × 10⁻⁶). -4 Pa);

[0076] Target material: Al2O3 ceramic target (purity ≥99.9%, diameter 100mm, thickness 6mm);

[0077] Conductive layer: Cu target (purity ≥ 99.99%, diameter 100 mm);

[0078] Substrate: FR-4 type PCB board (size 100mm×100mm, surface pre-plated with Au readout electrodes);

[0079] Mask plate: 304 alloy, 0.3mm thick, collimation hole diameter 0.5mm, spacing 6mm, distributed in a diamond array.

[0080] 2. Process Flow

[0081] Step 1: Substrate Pretreatment

[0082] Cleaning: Immerse the PCB substrate in pure water and ultrasonically clean for 3 minutes to remove surface organic matter.

[0083] Step 2: Mask installation

[0084] Mask bonding: Fix the mask onto the PCB surface using a vacuum suction clamp, ensuring that the collimation hole is aligned with the preset support post position, with an error ≤5μm.

[0085] Step 3: Sputtering of support columns

[0086] Vacuumed to a background vacuum of 5×10 -4Pa, introduce Ar gas (flow rate 20 sccm, working pressure 0.5 Pa).

[0087] The Al2O3 target was sputtered using an RF power supply (500W). The estimated deposition rate was approximately 0.4 μm / min, with a total deposition time of 125 min, resulting in an Al2O3 support column with a height of 50 μm. The sputtering thickness was monitored in real time using a laser interferometer, with an error of ±2 μm.

[0088] Step 4: Wire Mesh Installation

[0089] Mask plate lifting and wire mesh fixing: The mask plate is vertically moved up 20mm using a robotic arm to expose the top of the support column; then a stainless steel wire mesh (400 mesh, wire diameter 20μm, mesh size about 40μm, pre-tension 10N / m) is laid flat on the support column.

[0090] Step 5: Mask pressing down and cover column sputtering

[0091] Press the mask down until it contacts the wire mesh (pressure ≤ 5N, or press down by gravity);

[0092] Continue sputtering to deposit a 10 μm thick Al2O3 layer to bond the mesh to the support pillar interface, thus completing the fabrication of the detector mesh support structure.

[0093] After sputtering is complete, allow it to cool down before removing it and storing the detector in a clean, dry cabinet.

[0094] The key technological advantages of the detector support structure fabrication method based on magnetron sputtering technology provided by this invention are as follows:

[0095] Integrated molding: Mechanical fixation and electrical connection between the support column and the wire mesh are achieved through two sputtering processes, avoiding interface contamination caused by traditional adhesives or welding; High-precision alignment: The positioning accuracy of the mask lifting-pressing process is ≤5μm, ensuring precise adhesion between the wire mesh and the support column; Controllable electric field distribution: The combination of the insulating properties (Al2O3) of the support column and the wire mesh optimizes the uniformity of the electric field inside the detector.

[0096] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention is also intended to include these modifications and variations.

Claims

1. A method for fabricating a detector support structure based on magnetron sputtering technology, the method being implemented on a magnetron sputtering system, the method comprising the following steps: S1. Determine the target material for the detector support column, and calculate the sputtering time required to set the deposition thickness based on the set power and parameters of the magnetron sputtering system; S2. Attach a mask to the upper surface of the substrate, ensuring that the alignment hole on the mask is aligned with the position of the preset support post. S3. Sputtering of the support pillars: Sputtering material vertically onto the substrate surface through the confinement effect of the collimation hole to form a support pillar with a set height and diameter consistent with the collimation hole. S4. A metal wire mesh is laid on the upper surface of the support column, and the metal wire mesh is pressed together by the mask plate; S5. Perform cover column sputtering, and the sputtered material is deposited at the interface between the metal mesh and the support column, thereby fixing the metal mesh to the top of the support column and realizing the fabrication of the detector support structure.

2. The method for fabricating a detector support structure based on magnetron sputtering technology according to claim 1, characterized in that, The target material for the support column in step S1 is a high-hardness ceramic target material, which is used to form a rigid support grid.

3. The method for fabricating a detector support structure based on magnetron sputtering technology according to claim 2, characterized in that, The target material for the support column in step S1 is Al2O3.

4. The method for fabricating a detector support structure based on magnetron sputtering technology according to claim 2 or 3, characterized in that, In step S2, the substrate is plated with gold on the PCB readout electrode to enhance adhesion.

5. The method for fabricating a detector support structure based on magnetron sputtering technology according to claim 4, characterized in that, Step S2 specifically includes: S21. The substrate is pre-cleaned to remove surface organic matter; S22. A mask plate is attached to the upper surface of the substrate. The mask plate has a collimation hole array evenly distributed to ensure that the collimation hole array is aligned with the position of the preset support column. S23. Fix the substrate and the mask plate together on the sample stage of the magnetron sputtering system chamber, and evacuate the chamber to ensure that the mask plate and the substrate are tightly bonded without gaps.

6. The method for fabricating a detector support structure based on magnetron sputtering technology according to claim 5, characterized in that, The mask plate mentioned in step S22 is made of metal, and the diameter of the collimation holes on it ranges from 0.3 to 0.8 mm, with a spacing of 4 to 8 mm.

7. The method for fabricating a detector support structure based on magnetron sputtering technology according to claim 6, characterized in that, The process parameters for sputtering the support column in step S3 are as follows: The working gas pressure is 0.5 Pa; the sputtering power is RF 500 W; the target-substrate distance is 150 mm; and the height of the support column is 50 μm.

8. The method for fabricating a detector support structure based on magnetron sputtering technology according to claim 7, characterized in that, Step S4 specifically includes: S41. Move the mask plate vertically upward to expose the top of the support column; S42. Lay the pre-stretched wire mesh flat on the upper surface of the support column; S43. Control the mask plate to slowly move down so that it is in close contact with the metal mesh, ensuring that the metal mesh fits the top of the support column without gaps.

9. The method for fabricating a detector support structure based on magnetron sputtering technology according to claim 8, characterized in that, The metal wire mesh mentioned in step S42 is 400 mesh, made of stainless steel, with a wire diameter of 10-20μm and a mesh size of 30-40μm.

10. The method for fabricating a detector support structure based on magnetron sputtering technology according to any one of claims 5-9, characterized in that, The deposition thickness of the cover column in step 5 is 10 μm.

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