Method for processing tellurium-zinc-cadmium substrate through magnetic control polishing and magnetic control composite polishing solution

Abstract

The invention discloses a method for processing a tellurium-zinc-cadmium substrate through magnetic control polishing and a magnetic control composite polishing solution. The method comprises the steps of positioning ring and magnetic supporting ring installation, magnetic control reinforcement, substrate clamping and magnetic control composite polishing. The polishing solution comprises a SiO2atFe3O4 core-shell structure magnetic abrasive with specific core-shell size and concentration, an oxidizing agent, a dispersing agent, a pH regulator, a corrosion inhibitor and water. Through innovative edge magnetic control reinforcement and magnetic control composite polishing technologies and optimization of a polishing solution formula and the core-shell size of the magnetic abrasive in the polishing solution formula, the problems of edge collapse, deep damaged layer and the like easily occurring in the polishing process of the CZT soft and brittle substrate are effectively solved, and high-efficiency, ultra-smooth, low-damage and high-edge-integrity substrate processing is realized; and the yield and the substrate quality are remarkably improved, and the method is suitable for batch production of the CZT substrate for the high-performance detector.

Description

A method for magnetron polishing of cadmium zinc telluride substrates and a magnetron composite polishing slurry Technical Field

[0001] This invention belongs to the technical field of semiconductor material processing, specifically relating to a method for magnetron polishing of cadmium zinc telluride (CZT) substrates and a magnetron composite polishing slurry. Background Technology

[0002] CZT crystals, due to their tunable bandgap, high atomic number, and excellent lattice matching with mercury cadmium telluride, have become a key substrate material for fabricating high-performance radiation detectors and infrared focal plane detectors. However, CZT materials have low Mohs hardness and are typical soft and brittle crystals. In traditional processing, they are prone to microcracks, residual stress, surface / subsurface damage, and edge collapse, which seriously affect subsequent epitaxial growth, device performance, and yield.

[0003] Currently, the industry commonly employs a three-stage processing method: mechanical grinding, chemical mechanical polishing, and ultrasonic cleaning. This process has a long processing cycle and low yield in mass production, making it difficult to meet the stringent requirements of high-resolution, large-array detectors for ultra-smooth substrates, low damage, and high edge integrity. Therefore, there is an urgent need to develop a new CZT substrate processing method that can balance high efficiency, low damage, and high edge integrity. Summary of the Invention

[0004] After in-depth research, the inventors unexpectedly discovered that by using a magnetron polishing method for cadmium zinc telluride substrates, which includes the following steps, and combining a magnetron composite polishing slurry with a specific formula and magnetic abrasive parameters, they achieved efficient, ultra-precise, and low-damage polishing of CZT substrates.

[0005] Therefore, based on the above findings, in a first aspect, the present invention provides a method for magnetron polishing of a zinc cadmium telluride substrate, comprising:

[0006] 1) Install the positioning ring and magnetic support ring: Place the positioning ring in the center of the magnetic worktable, making the positioning ring coaxial with the magnetic worktable, and place the magnetic support ring in the inner ring of the positioning ring, so that it fits against the surface of the magnetic worktable.

[0007] 2) Magnetically controlled reinforcement: Turn on the vacuum to attract and pre-fix the positioning ring to the magnetic worktable, apply a magnetic field to fix the magnetic support ring to the magnetic worktable, turn off the vacuum, and remove the positioning ring;

[0008] 3) Substrate clamping: Place the zinc cadmium telluride substrate in the center of the inner ring of the magnetic support ring, and turn on the vacuum adsorption to fix the center of the zinc cadmium telluride substrate.

[0009] 4) Magnetron Polishing: Start the polishing equipment and use a polishing slurry containing magnetic abrasive to perform magnetron polishing on the cadmium zinc telluride substrate.

[0010] In one implementation, in step 2), the vacuum level is set to -60 to -80 kPa.

[0011] In one implementation, in step 2), applying the magnetic field includes: applying an initial magnetic field with a magnetic field strength of 50 mT for low magnetic field pre-fixation, and then gradually increasing the magnetic field strength to 120-180 mT for stable fixation.

[0012] In one embodiment, in step 3), the gap between the cadmium zinc telluride substrate and the inner wall of the magnetic support ring is adjusted to 20-30 μm.

[0013] In one embodiment, in step 4), the magnetic abrasive is a SiO2@Fe3O4 core-shell structured magnetic abrasive with a core particle size of 20-100 nm, a shell thickness of 5-20 nm, and a concentration of 3-12 wt% in the polishing slurry.

[0014] In a preferred embodiment, in step 4), the core particle size of the SiO2@Fe3O4 core-shell structured magnetic abrasive is 30-60 nm, the shell thickness is 8-12 nm, and the concentration in the polishing slurry is 6-10 wt%.

[0015] In one implementation, in step 4), the magnetron polishing process includes a pre-polishing stage and a fine polishing stage. In the pre-polishing stage, the magnetic field strength is set to 120-180 mT, the polishing pressure is set to 0.08-0.12 MPa, and the polishing head rotation speed is set to 60-80 rpm. In the fine polishing stage, the magnetic field strength is set to 80-120 mT, the polishing pressure is set to 0.03-0.05 MPa, and the polishing head rotation speed is set to 30-40 rpm.

[0016] In one implementation, during the magnetron polishing process in step 4), the edge warp height of the cadmium zinc telluride substrate is monitored by a displacement sensor, and the strength of the magnetic field is dynamically adjusted based on the monitoring results.

[0017] In another aspect of the present invention, a magnetron-controlled composite polishing slurry is provided, comprising SiO2@Fe3O4 core-shell structured magnetic abrasive, oxidant, dispersant, corrosion inhibitor, pH adjuster and deionized water, wherein the core particle size of the SiO2@Fe3O4 core-shell structured magnetic abrasive is 20-100 nm, the shell thickness is 5-20 nm, and the concentration in the polishing slurry is 3-12 wt%.

[0018] In a preferred embodiment, the core particle size of the SiO2@Fe3O4 core-shell structured magnetic abrasive is 30-60 nm, the shell thickness is 8-12 nm, and the concentration in the polishing slurry is 6-10 wt%.

[0019] In one embodiment, the oxidant is selected from H2O2 or peracetic acid, with H2O2 having a concentration of 1-3 wt% and peracetic acid having a concentration of 0.8-2 wt% in the polishing solution; the dispersant is selected from nonionic surfactant TX-100 or citric acid, with TX-100 having a concentration of 0.2-0.5 wt% and citric acid having a concentration of 0.3-0.8 wt% in the polishing solution; and the corrosion inhibitor is ethylene glycol, with a concentration of 2-5 wt% in the polishing solution.

[0020] In one embodiment, the pH adjuster is selected from acetate buffer, phosphate buffer or citrate buffer, preferably acetate-sodium acetate buffer, and the pH adjuster adjusts the polishing solution to pH 4.5-5.5.

[0021] Beneficial effects:

[0022] 1. Superior Polishing Quality: By combining optimized core-shell structured magnetic abrasives with magnetron polishing technology, ultra-smoothness (Ra as low as 0.28-0.35 nm), low damage (damage layer depth as low as 5-8 nm), and low defect (defect density as low as 2.2-3.0 × 10⁻⁶) of CZT substrates are achieved. 4 cm -2 Surface finishing.

[0023] 2. High processing efficiency: Under the premise of ensuring low damage, the material removal rate can reach 60-130 nm / min, which is significantly higher than the traditional CMP process.

[0024] 3. Excellent edge integrity: The innovative edge magnetron reinforcement technology fundamentally solves the edge collapse problem of soft and brittle CZT substrates, and significantly improves the edge quality and overall yield of CZT substrates.

[0025] 4. Strong process controllability: By utilizing the remote, non-contact, and real-time controllable characteristics of magnetic fields, precise control of the polishing process (especially the edge area) is achieved, resulting in good process consistency and suitability for mass production. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in this invention or related technologies, the accompanying drawings used in describing this invention or related technologies will be briefly introduced below. Obviously, the drawings in the following description only relate to some embodiments of the invention. For those skilled in the art, other drawings can be obtained based on these drawings without any inventive effort.

[0027] Figure 1 is a front view schematic diagram of the integrated device for edge magnetic reinforcement and magnetic composite polishing in an embodiment of the present invention;

[0028] Figure 2 is a front view schematic diagram of the positional relationship between the positioning ring, the magnetic support ring, and the substrate in the integrated device for edge magnetic reinforcement and magnetic composite polishing according to an embodiment of the present invention.

[0029] Explanation of reference numerals in the attached figures

[0030] 1. Magnetron polishing machine main unit (not shown), 2. Electromagnetic coil array, 3. Magnetic worktable, 4. Magnetic support ring, 5. Positioning ring, 6. CZT substrate, 7. Vacuum pipeline and pressure regulating valve (not shown), 8. Polishing pad, 9. Polishing fluid supply pipe (not shown), 10. Displacement sensor (not shown), 11. Magnetic field controller (not shown), 12. Polishing head, 13. Vacuum chamber, 14. Magnetron polishing machine (not shown) Detailed Implementation

[0031] To better illustrate the technical means and effects of the present invention, the present invention is further described below in conjunction with non-limiting embodiments. These embodiments (including descriptions mentioned in the embodiments) are intended to illustrate implementation methods of the present invention and are not intended to limit the scope of any claims. According to the present invention, those skilled in the art will understand that many changes can be made to the specific embodiments disclosed without departing from the spirit and scope of the present invention, and the same or similar results can still be obtained.

[0032] Unless otherwise stated, the terms used in this specification and claims have the following meanings.

[0033] In this paper, the term "edge collapse rate" refers to the phenomenon where, during processing, the material removal rate at the wafer edge is higher than that at the center due to insufficient material support or uneven stress at the edge, resulting in a sloped edge collapse. The calculation formula is: Edge collapse rate = [(Substrate center thickness - Edge specified point thickness) / Substrate center thickness] × 100%

[0034] In this paper, the term "magnetic-controlled composite polishing" refers to a polishing method that uses an external magnetic field to control the movement trajectory, distribution density, and force of magnetic abrasives in a polishing slurry to achieve material removal.

[0035] The main raw materials and instruments used in this invention are described in detail below:

[0036] SiO2@Fe3O4 core-shell structured magnetic abrasive: purchased from Nanjing Xianfeng Nanomaterials Technology Co., Ltd.;

[0037] Atomic force microscope (AFM): Model Dimension Icon, purchased from Bruker Instruments Ltd.;

[0038] Cross-sectional transmission electron microscope (TEM): Model JEM-2100, purchased from Nippon Electron Ltd.;

[0039] White light interferometer: Model VK-X200, purchased from Keyence (China) Co., Ltd.;

[0040] Magnetron polishing machine: Model MRF-1000, purchased from Shenyang Kejing Automation Equipment Co., Ltd.;

[0041] Magnetic worktable: Electromagnetic adsorption worktable, model MT-100, purchased from Shenyang Kejing Automation Equipment Co., Ltd.; (Magnetic poles: The surface of the magnetic worktable is S pole, magnetic field parameters: 0-200 mT continuously adjustable, uniformity ≤ ±5 mT, flatness: ≤0.005mm).

[0042] Magnetic support ring: neodymium iron boron + ceramic coating, inner diameter 100 mm (5 μm negative tolerance), width 2 mm, purchased from Ningbo Yunsheng Co., Ltd.

[0043] Positioning ring: made of polytetrafluoroethylene, with an inner diameter of 102 mm and an outer diameter of 105 mm (5 μm positive tolerance).

[0044] The edge magnetron hardening and magnetron composite polishing of the method for magnetron polishing of CZT substrates according to the present invention will now be described in detail with reference to Figures 1 and 2.

[0045] Calibrate the equipment: Start the magnetron polishing machine, set the initial magnetic field to 0 mT using the magnetic field strength controller, and calibrate the flatness of the magnetic worktable using an optical profilometer (ensure it is ≤0.005mm); adjust the height of the polishing head so that the distance between the polishing pad and the magnetic worktable is 5 mm (fine-tuning will be done after clamping).

[0046] Installation of the positioning ring and the magnetic support ring: Place the polytetrafluoroethylene positioning ring 5 in the center of the magnetic worktable 3, and ensure that the coaxiality deviation between the positioning ring and the magnetic worktable is ≤0.1 mm by using the center of the positioning scale mark on the edge of the magnetic worktable; embed the magnetic support ring 4 into the inner ring of the positioning ring 5, and gently press the magnetic support ring 4 to make it fit against the surface of the magnetic worktable.

[0047] Magnetically controlled reinforcement: Activate the vacuum adsorption module of the magnetic worktable 3, adjust the vacuum level to -60 to -80 kPa, pre-adsorb and fix the positioning ring 5 to prevent displacement; activate the electromagnetic coil 2 through the magnetic field strength controller 11, set the initial magnetic field strength to 50 mT (low magnetic field pre-fixation), and observe whether the magnetic support ring is adsorbed stably; gradually increase the magnetic field strength to 120-180 mT, use a tension gauge to hook the edge of the magnetic support ring 4 and pull it horizontally, confirm that the adsorption force is ≥8 N / cm (to ensure no displacement during polishing). At this time, the magnetic support ring 4 (inner ring N pole) is firmly adsorbed by the magnetic worktable 3 (surface S pole); if the adsorption force is insufficient, continue to increase the magnetic field strength (maximum not exceeding 200 mT); turn off the vacuum adsorption module and remove the positioning ring 5.

[0048] Substrate clamping: Use a vacuum suction pen to place the CZT substrate 6 in the center of the inner ring of the magnetic support ring 4, ensuring that the center of the substrate coincides with the center of the magnetic stage; observe the gap between the edge of the substrate and the inner ring of the magnetic support ring 4 through an optical microscope, and adjust the position of the substrate to keep the gap at 20-30 μm. If the gap is too small, the edge will be easily scratched; if it is too large, the support will fail; start the pressure regulating valve of the vacuum pipeline and adjust the vacuum level to -70 to -90 kPa to adsorb and fix the central area of ​​the CZT substrate 6, and avoid overall displacement of the substrate.

[0049] Magnetron composite polishing:

[0050] Pre-polishing stage: magnetic field strength 120-180 mT, polishing pressure 0.08-0.12 MPa, polishing head speed 60-80 rpm, polishing fluid flow rate 30-50 mL / min, polishing time 10-15 min;

[0051] Fine polishing stage: magnetic field strength 80-120 mT, polishing pressure 0.03-0.05 MPa, polishing head speed 30-40 rpm, polishing fluid flow rate 20-30 mL / min, polishing time 10-15 min;

[0052] During the polishing process, the displacement sensor 10 monitors the substrate edge in real time. If the lifting height is greater than 2 μm, the system automatically increases the magnetic field strength by 10-20 mT to enhance the constraint on the edge.

[0053] During operation, the magnetic stage 3 adsorbs and fixes the central region of the CZT substrate 6; the electromagnetic coil 2 generates a magnetic field, forming a "controllable stiffness annular constraint band" between the magnetic support ring 4 and the edge of the substrate 6, providing an upward restoring force / lateral constraint on the substrate edge and suppressing edge collapse and warping. The magnetic support ring 4 forms a "barrier" above the substrate edge, preventing polishing fluid-carried particles from directly impacting the edge. The position of the CZT substrate 6 is observed and adjusted using an optical microscope to maintain a gap of 20-30 μm between the edge of the substrate 6 and the inner ring of the magnetic support ring 4. If the gap is too small (<20 μm), the substrate edge is easily scratched; if the gap is too large (>30 μm), the magnetic support ring cannot effectively constrain the substrate, resulting in edge collapse.

[0054] The magnetic field is provided by electromagnetic coil 2, which is continuously adjustable to avoid excessive edge stress caused by uncontrollable magnetic field of permanent magnet. Magnetic field strength: 0-200 mT (adjustable in the working area); magnetic field uniformity: ±5 mT; coil power supply: 0-5 A, 0-24 V (adjustable constant current source); response time: ≤200 ms (for closed-loop control).

[0055] In the pre-polishing stage, strong adsorption of 120-180 mT is applied, the magnetic support ring 4 remains stationary, the polishing pressure is 0.08-0.12 MPa, and the polishing head speed is 60-80 rpm. This counteracts the edge shearing force under high pressure and prevents edge collapse. In the fine polishing stage, weak adsorption of 80-120 mT is applied, while maintaining flexible support. The polishing pressure is 0.03-0.05 MPa, and the speed is 30-40 rpm. This avoids stress on the substrate surface caused by the high magnetic field and ensures the quality of fine polishing.

[0056] The key process control logic is: when the polishing pressure increases, the magnetic field strength is increased simultaneously; when the polishing pressure decreases, the magnetic field strength is decreased simultaneously, so as to always maintain the balance between the constraint force of the magnetic support ring on the substrate edge and the polishing stress.

[0057] The magnetron sputtering composite polishing slurry provided by this invention comprises SiO2@Fe3O4 core-shell magnetic abrasive, an oxidant, a dispersant, a pH adjuster, a corrosion inhibitor, and deionized water. The SiO2@Fe3O4 core-shell magnetic abrasive has a core particle size of 20-100 nm, a SiO2 shell thickness of 5-20 nm, and a mass concentration of 3-12 wt% in the polishing slurry. Preferably, the SiO2@Fe3O4 core-shell magnetic abrasive has a core particle size of 30-60 nm, a shell thickness of 8-12 nm, and a concentration of 6-10 wt%. Within this preferred range, the polishing effect is optimal, achieving a surface roughness Ra ≤ 0.35 nm, a damage layer depth ≤ 8 nm, and a defect density ≤ 3.0 × 10⁻⁶ nm after polishing the CZT substrate. 4 cm -2 Meanwhile, the removal rate is ≥85 nm / min.

[0058] In this example, the SiO2@Fe3O4 core-shell magnetic abrasive achieves remote and precise control of the abrasive by utilizing the magnetism of the Fe3O4 core, while the outer shell of SiO2 provides the hardness, chemical stability, and low contamination required for grinding. Fe3O4 acts as the "brain and muscles" of the abrasive, responding promptly to an externally applied magnetic field to generate magnetic force. This force can be attractive, repulsive, or torque, thereby enabling precise control over the trajectory, density, and pressure of the abrasive particles. During magnetron sputtering, the abrasive particle trajectory is controlled by a magnetic field; under an alternating magnetic field, the abrasive can generate specific movements (such as rolling and vibration), achieving atomic-level material removal.

[0059] In some embodiments, the oxidant in the magnetron polishing slurry can be H2O2 or peracetic acid. When H2O2 is used as the oxidant, its concentration is preferably 1-3 wt%, more preferably 2 wt%; when peracetic acid is used as the oxidant, its concentration is preferably 0.8-2 wt%. The function of this oxidant is to oxidize the CZT surface to form an easily removable oxide layer.

[0060] In some implementations, the pH adjuster in the magnetron-controlled composite polishing slurry can be acetate buffer, phosphate buffer, or citrate buffer, preferably acetate-sodium acetate buffer, to adjust the polishing slurry system to pH 4-6, preferably pH 5.0, in order to optimize the oxidation-grinding synergy efficiency and avoid excessive corrosion.

[0061] To further understand the present invention, the method for magnetron polishing of CZT substrates and the magnetron composite polishing slurry are described in detail below with reference to embodiments. The scope of protection of the present invention is not limited by the following embodiments.

[0062] Example

[0063] Example 1: Method for magnetron polishing of CZT substrates

[0064] Calibration equipment: Start the main unit of the magnetic polishing machine, set the initial magnetic field to 0 mT through the magnetic field strength controller, calibrate the flatness of the magnetic worktable with an optical profilometer to ensure that the flatness is ≤0.005 mm; adjust the height of the polishing head so that the distance between the polishing pad and the magnetic worktable is 5 mm.

[0065] Install the positioning ring and magnetic support ring: Place the PTFE positioning ring in the center of the magnetic worktable, ensuring that the coaxiality deviation between the positioning ring and the magnetic worktable is ≤0.1 mm, using the center of the positioning scale mark on the edge of the worktable. Hold the magnetic support ring and place it inside the positioning ring, gently pressing the magnetic support ring to make it fit against the surface of the magnetic worktable.

[0066] Magnetic reinforcement: Activate the vacuum adsorption module of the magnetic worktable and adjust the vacuum level to -60 kPa to temporarily fix the positioning ring. Activate the electromagnetic coil via the magnetic field strength controller, setting the initial magnetic field strength to 50 mT. Observe that the magnetic support ring does not slip. Gradually increase the magnetic field strength to 150 mT. At this point, the magnetic support ring is firmly adsorbed by the magnetic worktable. Use a force gauge to hook the magnetic support ring, ensuring there is no displacement. Turn off the vacuum adsorption module and remove the positioning ring.

[0067] Substrate clamping: Using a vacuum suction pen, place the CZT substrate in the center of the inner ring of the magnetic support ring. Observe the gap between the substrate edge and the inner ring of the magnetic support ring through an optical microscope, and adjust the substrate position to maintain this gap at 25 μm. Activate the pressure regulating valve of the vacuum line to adjust the vacuum level to -80 kPa, thus adsorbing and fixing the central area of ​​the CZT substrate.

[0068] Magnetron composite polishing

[0069] - Set polishing parameters:

[0070] Pre-polishing stage: magnetic field strength is 150 mT, polishing pressure is 0.10 MPa, polishing head speed is 70 rpm, polishing fluid flow rate is 40 mL / min, and polishing time is 12 min;

[0071] Fine polishing stage: magnetic field strength is 100 mT, polishing pressure is 0.04 MPa, polishing head rotation speed is 35 rpm, polishing fluid flow rate is 25 mL / min, and time is 13 min.

[0072] -Magnetic-controlled composite polishing:

[0073] The polishing program is initiated by first circulating the polishing slurry through the supply tube for 30 seconds to pre-wet the polishing pad. Then, the polishing head descends to contact the substrate surface and begins rotating for polishing. A displacement sensor monitors the substrate edge lift height in real time; if the lift exceeds 2 μm, the magnetic field strength automatically increases by 15 mT. During polishing, the polishing slurry distribution is observed every 5 minutes to ensure the substrate surface is evenly covered with the slurry, with no dry polishing areas.

[0074] Uninstallation and Post-processing

[0075] After polishing, first turn off the polishing head and the liquid supply tube, then gradually reduce the magnetic field strength to below 20 mT using the controller, and then turn off the vacuum adsorption module. Carefully remove the CZT substrate with a vacuum suction pen, place it in a cleaning basket, sonicate it with anhydrous ethanol for 3 minutes, then sonicate it with deionized water for 3 minutes, and finally dry it with nitrogen.

[0076] Comparative Example 1: CZT substrates processed using conventional methods

[0077] The same CZT substrate is processed using a chemical mechanical polishing process combining traditional mechanical grinding (SiC and diamond abrasives) with ordinary silica polishing slurry, including the following steps:

[0078] (1) Crystal rod slicing: The (110) crystal orientation was determined by X-ray orientation instrument, 4-inch crystal rods were fixed with epoxy resin, and sliced ​​by multi-wire cutting machine (cutting wire diameter 0.14 mm) at a linear speed of 300 m / min and a workpiece feed speed of 0.06 mm / min. The slice thickness was 500 μm, with a thickness deviation of ±3 μm.

[0079] (2) Mechanical grinding: coarse grinding uses 8 μm SiC abrasive, grinding disc speed is 70 rpm, pressure is 0.2 MPa, and removal amount is 15 μm; fine grinding uses 3 μm diamond abrasive, grinding disc speed is 50 rpm, pressure is 0.1 MPa, and removal amount is 8 μm.

[0080] (3) Conventional chemical mechanical polishing: a silica polishing slurry with a particle size of 60 nm was used, the polyurethane polishing pad was rotated at 80 rpm, the polishing pressure was 0.12 MPa, the slurry supply rate was 70 ml / min, and the polishing time was 60 min.

[0081] (4) Post-treatment: Ultrasonic cleaning with deionized water for 5 min, drying at 80℃ and then testing.

[0082] Comparative Example 2: Fabrication method of edge-free magnetron-hardened CZT substrate

[0083] The same magnetron polishing process as in Example 1 was used to polish CZT substrates of the same specifications. The only difference was that the edge magnetron reinforcement was omitted, and the center of the CZT substrate was fixed by vacuum and polished.

[0084] Test case

[0085] The surface roughness, damaged layer depth, edge collapse rate, single-wafer processing cycle, and defect density of the CZT substrates obtained by the processing methods of Example 1, Comparative Examples 1 and 2 were measured. Surface roughness (Ra) was measured within a 10 μm × 10 μm range using atomic force microscopy (AFM); damaged layer depth was observed using cross-sectional transmission electron microscopy (TEM); edge collapse rate was calculated by measuring the thickness difference between the substrate center and a point 1 mm from the edge using white light interferometer; the total processing time per substrate from slicing to drying was statistically analyzed in the examples and comparative examples; and the batch yield was calculated based on a small-batch (10 wafers) trial production, simultaneously meeting the requirements of Ra < 0.4 nm, damaged layer < 8 nm, and edge collapse rate < 5%. The test results are shown in Table 1 below.

[0086] Table 1. Performance test results of CZT substrates obtained by the processing methods of Example 1 and Comparative Examples 1-2.

[0087]

[0088] Example 2 Preparation of Magnetron-Controlled Composite Polishing Fluid

[0089] This embodiment prepares a magnetic composite polishing slurry A containing SiO2@Fe3O4 core-shell structured magnetic abrasive with a core particle size of 30 nm, a shell thickness of 8 nm, and a concentration of 6 wt%.

[0090] Take an appropriate amount of deionized water, add 3 wt% ethylene glycol as a corrosion inhibitor, and stir at 500 r / min for 10 min at room temperature. Add acetate-sodium acetate buffer to adjust the pH of the system to 5.0, and continue stirring for 5 min. Slowly add 6 wt% SiO2@Fe3O4 core-shell magnetic abrasive (core diameter 30 nm, shell thickness 8 nm), and disperse at 100 W ultrasonic power for 20 min to ensure no agglomeration. Then add 2 wt% H2O2 (oxidant) and 0.3 wt% TX-100 (dispersant) sequentially, increase the stirring speed to 800 r / min, and mix at room temperature for 15 min. Finally, filter the obtained liquid through a 0.2 μm filter membrane to remove possible large particulate impurities, obtaining the polishing solution.

[0091] Magnetron-controlled composite polishing slurry BE was prepared using the same steps as magnetic composite polishing slurry A, except for the core particle size, shell thickness, and concentration of the SiO2@Fe3O4 core-shell structured magnetic abrasive. The specific parameters are shown in Table 2 below.

[0092] Table 2. Relevant parameters of magnetron-controlled composite polishing slurry AE

[0093]

[0094] Verification of the effect of magnetron-controlled composite polishing fluid AE

[0095] The CZT substrate was polished using the magnetron-controlled composite polishing slurry AE prepared in Example 2, as described in Example 1. The performance data obtained are summarized in Table 3 below.

[0096] Table 3: Processing effect of magnetron polishing slurry AE on CZT substrates

[0097]

[0098] As can be seen from the test results in Table 1, the method of Embodiment 1 of the present invention is significantly superior to the traditional process (Comparative Example 1) in all key indicators. Furthermore, a comparison with Comparative Example 2 leads to the conclusion that edge magnetic reinforcement technology is crucial for reducing edge collapse rate.

[0099] As can be seen from Tables 2 and 3, in the magnetron-controlled composite polishing slurry AE, when the core particle size of the SiO2@Fe3O4 core-shell structure magnetic abrasive is 30-60 nm, the shell thickness is 8-12 nm, and the concentration is 6-10 wt% (such as polishing slurries A, B, and E), it is possible to obtain an ultra-smooth surface (Ra≤0.35 nm) and a shallow damage layer (depth≤8 nm) while maintaining a high material removal rate (≥85 nm / min), thus achieving the best balance between high efficiency and low damage.

[0100] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for magnetron polishing of a zinc-cadmium telluride substrate, comprising: 1) Install the positioning ring and magnetic support ring: Place the positioning ring in the center of the magnetic worktable, making the positioning ring coaxial with the magnetic worktable. Place the magnetic support ring in the inner ring of the positioning ring and make it fit against the surface of the magnetic worktable; 2) Magnetically controlled reinforcement: Turn on the vacuum to adsorb and pre-fix the positioning ring on the magnetic worktable. Apply a magnetic field to fix the magnetic support ring on the magnetic worktable. Turn off the vacuum and remove the positioning ring; 3) Substrate clamping: Place the zinc telluride (ZT) substrate in the center of the inner ring of the magnetic support ring and turn on the vacuum to adsorb and fix the center of the ZT substrate; 4) Magnetically controlled composite polishing: Start the polishing equipment and use a polishing slurry containing magnetic abrasive to perform magnetocontrolled polishing on the ZT substrate.

2. The method according to claim 1, wherein in step 2), the vacuum degree is set to -60 to -80 kPa.

3. The method according to claim 1 or 2, wherein in step 2), applying the magnetic field comprises: An initial magnetic field of 50 mT was applied for low magnetic field pre-fixation, and then the magnetic field strength was gradually increased to 120-180 mT for stable fixation.

4. The method according to any one of claims 1 to 3, wherein in step 3), the gap between the zinc cadmium telluride substrate and the inner wall of the magnetic support ring is adjusted to 20-30 μm.

5. The method according to any one of claims 1 to 4, wherein in step 4), the magnetic abrasive is a SiO2@Fe3O4 core-shell structure magnetic abrasive with a core particle size of 20-100 nm, a shell thickness of 5-20 nm, and a concentration of 3-12 wt% in the polishing solution; preferably, the SiO2@Fe3O4 core-shell structure magnetic abrasive has a core particle size of 30-60 nm, a shell thickness of 8-12 nm, and a concentration of 6-10 wt% in the polishing solution.

6. The method according to any one of claims 1 to 5, wherein in step 4), the magnetron composite polishing includes a pre-polishing stage and a fine polishing stage; in the pre-polishing stage, the magnetic field strength is set to 120-180 mT, the polishing pressure is set to 0.08-0.12 MPa, and the polishing head rotation speed is set to 60-80 rpm; in the fine polishing stage, the magnetic field strength is set to 80-120 mT, the polishing pressure is set to 0.03-0.05 MPa, and the polishing head rotation speed is set to 30-40 rpm.

7. The method according to any one of claims 1 to 6, wherein during the magnetron composite polishing process in step 4), the edge warping height of the zinc telluride substrate is monitored by a displacement sensor, and the strength of the magnetic field is dynamically adjusted according to the monitoring results.

8. A magnetron-controlled composite polishing slurry, comprising: SiO2@Fe3O4 core-shell structured magnetic abrasive, oxidant, dispersant, corrosion inhibitor, pH adjuster, and deionized water, wherein the core particle size of the SiO2@Fe3O4 core-shell structured magnetic abrasive is 20-100 nm, the shell thickness is 5-20 nm, and the concentration in the polishing slurry is 3-12 wt%. Preferably, the core particle size of the SiO2@Fe3O4 core-shell structured magnetic abrasive is 30-60 nm, the shell thickness is 8-12 nm, and the concentration in the polishing slurry is 6-10 wt%.

9. The magnetron-controlled composite polishing slurry according to claim 8, wherein the oxidant is selected from H2O2 and peracetic acid, wherein the concentration of H2O2 in the polishing slurry is 1-3 wt%, and the concentration of peracetic acid in the polishing slurry is 0.8-2 wt%; the dispersant is selected from nonionic surfactant TX-100 and citric acid, wherein the concentration of TX-100 in the polishing slurry is 0.2-0.5 wt%, and the concentration of citric acid in the polishing slurry is 0.3-0.8 wt%; and the corrosion inhibitor is ethylene glycol, with a concentration of 2-5 wt% in the polishing slurry.

10. The magnetron sputtering composite polishing fluid according to claim 8, wherein the pH adjuster is selected from acetate buffer, phosphate buffer and citrate buffer, preferably acetate-sodium acetate buffer, and the pH adjuster is used to adjust the polishing fluid to pH 4.5-5.5.

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