A method for preparing a diamond sheet based on a magnetic sacrificial layer and in-line monitoring of exfoliation

Abstract

The application discloses a method for preparing a diamond sheet based on a magnetic sacrificial layer and online monitoring peeling, and steps are as follows: S1: a porous nickel sacrificial layer with ferromagnetism is prepared on a substrate, and the porous nickel sacrificial layer has a thickness gradient distribution with gradually increasing thickness from the center to the edge; S2: a two-step microwave plasma chemical vapor deposition process is performed on the porous nickel sacrificial layer to prepare a dense diamond layer; S3: the sample piece is placed in a nickel etching solution for transverse penetration etching; S4: a monitoring assembly is arranged outside the sample piece, and the transverse peeling progress of the porous nickel sacrificial layer is represented according to the time sequence characteristics of the magnetic response electrical signals of each monitoring area; when the magnetic response electrical signals of each monitoring area all reach preset values, etching is terminated, so that the diamond layer is separated from the substrate and a diamond sheet is obtained. The application realizes online monitoring of the etching progress of the sacrificial layer, improves the consistency and reliability of the separation of the thick diamond sheet, and improves the etching rate and shortens the process time.

Description

Technical Field

[0001] This invention relates to the field of semiconductor materials and thin film epitaxy technology, specifically to a method for preparing diamond wafers based on a magnetic sacrificial layer and online monitoring during peeling, and to online monitoring and etching endpoint detection technology in the wet etching process, which can be applied to the fields of semiconductor process control and related device fabrication. Background Technology

[0002] Diamond possesses excellent properties such as high thermal conductivity, wide bandgap, and high breakdown field strength, making it valuable for applications in power electronics, radio frequency devices, and quantum devices. To obtain large-size single-crystal diamond substrates, current technologies often employ heteroepitaxial growth to grow diamond layers on non-diamond substrates, followed by separation of the grown diamond layer from the substrate through sacrificial layer etching or laser lift-off.

[0003] In existing technologies, methods (such as patent application CN111051257A) involve forming metal sacrificial layers such as Ir and Ti on substrates like MgO and Si, and then heteroepitaxially growing a diamond layer on top of these layers. The sacrificial metal layers are then wet-etched to obtain a diamond sheet. However, materials like Ir and Ti typically exhibit high chemical stability, resulting in relatively low etching rates under wet etching conditions. Especially when used for separating large-area, thick diamond layers, the sacrificial layer between the diamond layer and the substrate usually only forms submicron-sized liquid penetration channels. For sacrificial layers on the order of 1 inch with gaps of hundreds of nanometers, these channels simultaneously possess millimeter-scale lateral mass transfer paths and nanometer-scale vertical gaps, constituting high aspect ratio confined liquid channels (the ratio of lateral mass transfer paths to vertical gaps can reach the order of 10^4). This makes it extremely difficult for the etchant to penetrate and renew into the central region, hindering the removal of reaction products. Consequently, the overall etching process is significantly limited in mass transfer, leading to a substantial increase in the etching cycle.

[0004] Furthermore, existing large-size diamond wet stripping processes generally suffer from insufficient online monitoring methods. Current wet etching endpoint detection technologies mostly employ optical reflection, resistance, and capacitance methods. However, in highly corrosive, non-transparent liquid etching environments, these methods are easily affected by factors such as liquid turbidity, structural obstruction, and conductive bubble disturbances, making it difficult to achieve stable, real-time monitoring of the lateral stripping progress and endpoint of the diamond sacrificial layer. Compared to the aforementioned optical or conventional electrical detection methods, magnetic detection does not rely on transparent optical paths and has penetrating sensing capabilities for the state of ferromagnetic materials and changes in their magnetic response. Although magnetic sensing technology has been used for macroscopic material state assessment in open environments such as steel structure corrosion monitoring, no publicly available literature has been found applying it to the endpoint detection of semiconductor wet etching. Attempting to directly transplant conventional magnetic sensing schemes to the diamond sacrificial layer stripping process will face three major engineering challenges:

[0005] (1) Liquid phase eddy current shielding: The high-concentration etching solution generates significant eddy currents under the excitation of an alternating magnetic field, which shields and interferes with the weak response signal of the nanoscale magnetic sacrificial layer;

[0006] (2) Array electromagnetic crosstalk: When multiple probes work in parallel in a conductive medium environment, they are prone to spatial electromagnetic coupling and magnetic field distortion.

[0007] (3) Lack of dynamic timing tracking: Traditional magnetic sensing systems lack multi-region timing difference analysis logic for radial chemical front propulsion processes.

[0008] There is currently no technical solution that can overcome the unique interference of the liquid phase environment and achieve accurate online monitoring of the transverse peeling process of the diamond sacrificial layer.

[0009] In the search for more suitable sacrificial layer materials, nickel and nickel-based alloys have attracted industry attention due to their low lattice mismatch with diamond, low cost, and natural ferromagnetic properties. However, there are still process limitations when directly applying conventional nickel materials to diamond heteroepitaxial sacrificial layers: on the one hand, Ni has a tendency to catalyze graphitization under high temperature conditions, which easily promotes the formation of non-diamond carbon phases at the interface, thereby reducing the crystal quality of the epitaxial diamond layer; on the other hand, the dense continuous nickel metal films commonly found in existing technologies often agglomerate, crack, or degrade in continuity after CVD high-temperature heat treatment due to thermal stress and expansion mismatch, affecting the subsequent liquid lateral penetration efficiency and the consistency and stability of magnetic response.

[0010] Therefore, existing technologies still lack a solution that can simultaneously address multi-dimensional engineering needs: suppressing graphitization and thermal instability of the nickel-based sacrificial layer during high-temperature epitaxy, substantially improving the liquid-phase lateral mass transfer efficiency during the peeling of large-size diamond wafers, and further utilizing the magnetic characteristics of the sacrificial layer to achieve precise online monitoring of etching progress and endpoint in complex liquid-phase environments. Overcoming the mass transfer bottleneck in the peeling process of large-size diamond wafers and achieving non-destructive, real-time, and accurate monitoring of the wet etching process remains a key technical problem urgently needing to be solved in this field. Summary of the Invention

[0011] The purpose of this invention is to address the limitations of existing large-size diamond heteroepitaxial and wet lift-off processes, such as the low etching efficiency caused by the limited lateral mass transfer of conventional sacrificial layers like Ir / Ti, and the structural degradation and magnetic monitoring reference failure caused by thermal mismatch of conventional dense nickel-based sacrificial layers during high-temperature thermal processes. The purpose of this invention is to provide a method for preparing diamond wafers based on magnetic sacrificial layers and online monitoring lift-off.

[0012] This invention aims to significantly improve the fluid mass transfer conditions for large-area lateral deep trench etching by constructing a porous nickel-based sacrificial layer with an "outer thicker, inner thinner" gradient. This effectively absorbs and releases high-temperature thermal stress, maintains a macroscopic continuous magnetic detection benchmark, and simultaneously improves the etching process. Furthermore, by combining an alternating magnetic field with array dynamic monitoring logic, it enables spatially distributed and precise determination of the etching progress and endpoint of the sacrificial layer in a highly corrosive, opaque liquid environment. This invention not only effectively shortens the overall stripping cycle of large-size wafers but also fundamentally overcomes the risks of over-etching or wafer breakage caused by blind etching, significantly improving the consistency, reliability, and mass production yield of non-destructive separation of large-size thick-film diamond wafers.

[0013] A method for preparing diamond sheets based on a magnetic sacrificial layer and online monitoring of exfoliation, the method comprising the following steps:

[0014] S1: A porous nickel sacrificial layer with ferromagnetism is prepared on a substrate, and the porous nickel sacrificial layer has a thickness gradient distribution that gradually increases from the center to the outer edge. The material of the porous nickel sacrificial layer is pure nickel or a nickel-based alloy.

[0015] S2: A two-step microwave plasma chemical vapor deposition process is performed on the porous nickel sacrificial layer to sequentially perform closed nucleation of the diamond seed layer and epitaxial growth of the diamond body layer, thereby preparing a dense diamond layer to obtain a diamond heteroepitaxial structure.

[0016] S3: Place the sample with the above structure in a nickel etching solution and perform transverse penetration etching along the plane direction of the porous nickel sacrificial layer;

[0017] S4: A monitoring component including a multi-point distributed excitation unit and a magnetic sensor is arranged in the corresponding area outside the sample; an alternating detection magnetic field of a preset frequency is applied to the porous nickel sacrificial layer through the excitation unit, and the magnetic sensor is used to acquire the magnetic response electrical signals of multiple radially distributed monitoring areas in real time; according to the temporal characteristics of the magnetic response electrical signals of each monitoring area showing sequential decay along the etching front advancement direction, the magnetic response electrical signals of different areas are differentially compared to characterize the lateral peeling progress of the porous nickel sacrificial layer; when the magnetic response electrical signals of each monitoring area reach the preset etching completion judgment benchmark value related to the background magnetic response of the non-magnetic material etching solution, the etching is terminated, thereby realizing the separation of the diamond layer and the substrate to obtain a diamond sheet.

[0018] As a further improvement of the present invention, in step S1, the substrate is selected from any one of single crystal silicon (Si), silicon carbide (SiC), aluminum nitride (AlN) or sapphire.

[0019] As a further improvement of the present invention, in step S1, the thickness gradient distribution radially includes at least a central region, a middle ring region, and an outermost ring region; wherein, the thickness of the outermost ring region is greater than the thickness of the middle ring region, and the thickness of the middle ring region is greater than the thickness of the central region, so that the porous nickel sacrificial layer forms a fluid permeation channel that gradually expands from the inside to the outside in the cross-section; and from the central region to the outermost ring region, its initial magnetic response intensity is distributed in a sequentially increasing manner.

[0020] As a further improvement of the present invention, in step S1, the porous nickel sacrificial layer is grown in situ continuously by tilt angle deposition (GLAD) combined with mask step-by-step shielding technology, and the deposition process is carried out in a pure argon oxygen-free environment to avoid metal oxidation and ensure macroscopic strong ferromagnetism.

[0021] The porous nickel sacrificial layer is made of pure nickel or a nickel-based alloy; wherein, when the porous nickel sacrificial layer is made of a nickel-based alloy, the nickel-based alloy is a material that can maintain a detectable magnetic response after CVD high-temperature treatment;

[0022] Specifically, the nickel-based alloy is selected from any one of nickel-cobalt alloy (Ni-Co), nickel-chromium alloy (Ni-Cr), nickel-tungsten alloy (Ni-W), or nickel-molybdenum alloy (Ni-Mo), and the mass fraction of non-nickel elements therein is 5% to 25%.

[0023] As a further improvement of the present invention, before preparing the porous nickel sacrificial layer in step S1, a non-ferromagnetic metal buffer layer with a thickness of 10 to 50 nm is pre-deposited on the surface of the substrate; the non-ferromagnetic metal buffer layer is selected from any one or a combination of titanium (Ti), tantalum (Ta), tungsten (W) or chromium (Cr).

[0024] As a further improvement of the present invention, the diamond layer preparation in step S2 employs a two-step microwave plasma chemical vapor deposition (MPCVD) process, including:

[0025] In the first deposition stage, an oxygen-free gas system is used to nucleate and deposit a continuous and dense diamond seed layer with a thickness of 100-300 nm on the surface of the porous nickel sacrificial layer to physically isolate the porous nickel sacrificial layer.

[0026] In the second deposition stage, the epitaxial growth of the diamond body layer continues on the diamond seed layer to the target thickness; the second deposition stage uses an oxygen-free or oxygen-doped gas system.

[0027] As a further improvement of the present invention, in step S3, the conductivity of the nickel etching solution is configured such that the skin depth generated by the detection magnetic field in step S4 at the preset frequency is greater than the fluid gap thickness between the lower surface of the sample and the inner surface of the bottom plate of the etching tank, so as to reduce the shielding interference of the liquid phase eddy current on the magnetic response electrical signal; and the nickel etching solution has a selective dissolution effect on the porous nickel sacrificial layer, and the substrate maintains structural integrity in the nickel etching solution.

[0028] As a further improvement of the present invention, the nickel etching solution is a low-conductivity mixed aqueous solution containing an organic weak acid and an oxidant; the organic weak acid is selected from any one or a combination of citric acid, acetic acid, tartaric acid, or oxalic acid, with a concentration of 0.1–0.5 mol / L; the oxidant is selected from any one or a combination of hydrogen peroxide or nitric acid, wherein the hydrogen peroxide concentration is 0.05–0.1 mol / L, and the nitric acid mass fraction is 1%–3%. The nickel etching solution is configured with the above-mentioned component concentrations such that the ionic strength of the nickel etching solution meets the requirement that the skin depth is greater than the immersion depth.

[0029] In addition, during the etching process in step S3, the nickel etching solution is heated at a constant temperature of 50~70 ℃ or subjected to high-frequency megasonic waves with a frequency of 1~3 MHz to assist in penetration.

[0030] As a further improvement of the present invention, in step S4, before injecting the nickel etching solution, the initial magnetic response electrical signal of each monitoring area is obtained in advance as the initial reference value; the real-time magnetic response electrical signal in the subsequent etching process is normalized based on the initial reference value to eliminate the initial physical magnetic moment deviation; the magnetic response electrical signal is extracted using a lock-in amplifier.

[0031] As a further improvement of the present invention, in step S4, the monitoring component is arranged outside the etching tank, and the multi-point distributed excitation unit and the magnetic sensor contained therein are both arranged in the normal direction corresponding to the porous nickel sacrificial layer, and a magnetic field transmission path containing at least the nickel etching solution is formed between them.

[0032] The sample is horizontally suspended in the etching tank, and a fluid gap is maintained between the plane containing the lower surface of the sample and the inner surface of the bottom plate of the etching tank, and the fluid gap has a fluid gap thickness.

[0033] The monitoring components adopt a ring-shaped distribution architecture with the center of the sample as the center of symmetry. It includes a central monitoring unit group located at the center, and a middle ring monitoring unit group and an outermost ring monitoring unit group distributed at equal angles around the center along the circumference. Each monitoring unit group is equipped with an excitation unit and a magnetic sensor corresponding to the monitoring area.

[0034] When acquiring the magnetic response electrical signal, the multi-point distributed excitation unit adopts a time-division sequential gating excitation mode to independently apply alternating detection magnetic fields to different monitoring areas in sequence, so as to reduce electromagnetic crosstalk between adjacent monitoring areas; each magnetic sensor and the corresponding excitation unit perform independent addressing sampling to acquire the magnetic response electrical signal in sync with the excitation timing.

[0035] As a further improvement of the present invention, in step S4, the criterion for determining the completion of etching is determined by wet in-situ reference calibration. Specifically, the equivalent reference wafer without a magnetic sacrificial layer is placed in a working etching solution that matches the current process state. Under an alternating detection magnetic field of 50–300 kHz, the amplitude and phase parameters of the same-frequency response signal are extracted by a lock-in amplifier to obtain the steady-state background average value. For and allowable fluctuation range This is used as the criterion for determining the completion of the etching process. Since the porous nickel sacrificial layer has a thickness gradient, different annular regions have different initial magnetic response intensities. During the etching process, the magnetic response electrical signals of each annular region decay sequentially over time, and the lateral penetration etching progress is determined accordingly. When the magnetic response electrical signals corresponding to all monitored areas meet the criteria... At that time, it is determined that the porous nickel sacrificial layer has been completely etched away; wherein, The mean of the steady-state background is... The amplitude of the allowable fluctuation range, For the first in the same annular region A magnetic sensor in The real-time magnetic response electrical signal at any given moment.

[0036] As a further improvement of the present invention, the multi-point distributed magnetic sensor array includes a sensor array composed of any one of giant magnetoresistive (GMR) sensors, tunnel magnetoresistive (TMR) sensors, anisotropic magnetoresistive (AMR) sensors, fluxgate sensors or high-precision Hall sensors, or a hybrid sensor array composed of at least two different types of magnetic sensors.

[0037] Compared with the prior art, the present invention has the following significant technical effects:

[0038] 1. Overcoming the limitations of the liquid phase blind zone, achieving precise online control of the spatiotemporal progress of lateral stripping.

[0039] This invention overcomes the bottleneck of traditional Ir / Ti sacrificial layer systems being difficult to monitor in situ in non-transparent liquid phases. By extracting the magnetic response electrical signals of multiple monitoring regions under an alternating magnetic field, and utilizing the temporal characteristics and spatial differential logic of their sequential decay along the etching front direction, the microscopic chemical etching process is transformed into an intuitive and quantifiable dynamic evolution of macroscopic electrical signals. This enables the radial spatiotemporal evolution mapping and real-time tracking of the lateral peeling progress of large-size sacrificial layers.

[0040] 2. Construct a rigorous endpoint determination algorithm to eliminate the risk of fragment breakage during stripping and thus improve yield.

[0041] This invention does not rely on a single static threshold, but instead introduces a "steady-state background mean and allowable fluctuation range" based on wet in-situ reference calibration as the criterion for determining etching completion. This algorithm effectively identifies and accommodates localized progress differences caused by the fluid's "finding effect," ensuring that an etching termination command is only issued when all monitored areas meet the standards. This fundamentally avoids forced peeling and fragmentation due to over-etching damaging the crystal surface or under-etching, significantly improving the process yield of thick-film large-sheet diamond.

[0042] 3. Optimize mass transfer dynamics in confined spaces to significantly shorten the large-area etching cycle.

[0043] In terms of etching methods, this invention utilizes the thickness gradient characteristics of a porous nickel sacrificial layer to construct fluid penetration and product release channels that gradually expand from the inside out during the lateral penetration process in the liquid phase. This process design substantially reduces the deep trench penetration resistance from a hydrodynamic perspective, improves the mass transfer attenuation problem of reactant replenishment and bubble removal in the central region during the peeling of large-size wafers, and significantly increases the overall lateral etching rate without changing the highly corrosive liquid phase environment.

[0044] 4. Eliminating Eddy Currents and Spatial Crosstalk to Ensure High Signal-to-Noise Ratio In-situ Dynamic Detection. Addressing the electromagnetic interference challenges posed by the conductive liquid environment and multi-probe arrays, this invention employs a dual anti-interference mechanism combining physical and chemical methods and electromagnetic timing in process control: On one hand, by adjusting the complexation etching formula with low conductivity, the skin depth of the detection magnetic field is made much greater than the liquid immersion depth, reducing liquid-phase eddy current shielding; on the other hand, the "time-division sequential gating" excitation mode and synchronous independent addressing sampling are used in signal acquisition to completely eliminate spatial electromagnetic crosstalk between adjacent detection areas, ensuring the accuracy and purity of the endpoint monitoring signal.

[0045] 5. Possesses good process compatibility and technological scalability.

[0046] The process described in this invention can be directly implemented on existing physical vapor deposition (PVD) and microwave plasma chemical vapor deposition (MPCVD) equipment without complex hardware modifications. Furthermore, the "magnetic sacrificial layer and dynamic magnetic monitoring" stripping scheme established in this invention, with its non-contact monitoring principle, can also be applied to manufacturing processes involving confined space wet stripping, such as the structural release of microelectromechanical systems (MEMS) or the thin film transfer of third-generation semiconductors (such as SiC and GaN), demonstrating substantial technological extension value. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of a diamond heteroepitaxial structure;

[0048] Figure 2 This is a schematic diagram of a diamond heteroepitaxial structure placed in a nickel etching solution within an etching tank for lateral penetration etching.

[0049] Figure 3 It is a top-plan view of the monitoring components, including multi-point distributed excitation units and magnetic sensors, arranged on a PCB board.

[0050] In the diagram: 100—Substrate; 110—Buffer layer; 120—Porous nickel sacrificial layer; 130—Diamond layer; 140—Etching tank; 150—Monitoring component; 160—PCB board; 170—Excitation coil; 180—Magnetic sensor; 190—Central monitoring unit group; 220—Middle ring monitoring unit group; 230—Outermost ring monitoring unit group. Detailed Implementation

[0051] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0052] A method for preparing diamond wafers based on a magnetic sacrificial layer and online monitoring is presented. This method features simple process, closed-loop error prevention, and no need for photolithography. It is particularly suitable for large-size (such as 1-2 inches or even larger diameter) porous nickel sacrificial layers and diamond epitaxial wafers. It can completely solve the problem of mass transfer deadlock under a large-area dense top layer and achieve simple, targeted, and internally visualized precise monitoring of the lateral etching process.

[0053] The method includes the following steps:

[0054] S1: Preparation of porous nickel sacrificial layer and buffer layer with thickness gradient

[0055] S1.1 Deposition of the metal buffer layer

[0056] A polished silicon substrate with a diameter of 2 inches and a thickness of approximately 500 μm is selected. After standard cleaning and drying, a non-ferromagnetic metal buffer layer with a thickness of 10–50 nm is pre-deposited on the substrate surface; the non-ferromagnetic metal buffer layer is selected from any one or a combination of titanium (Ti), tantalum (Ta), tungsten (W), or chromium (Cr). The buffer layer has extremely low magnetic susceptibility, resulting in minimal interference with subsequent alternating magnetic monitoring signals (i.e., maintaining electromagnetic silence). Simultaneously, this type of buffer layer exhibits excellent adhesion to both the substrate and the porous nickel sacrificial layer, and maintains thermal stability and chemical inertness under diamond CVD conditions. Preferably, a titanium (Ti) metal buffer layer with a thickness of approximately 20 nm is pre-deposited on the silicon substrate surface via magnetron sputtering.

[0057] S1.2 Gradient Construction of Porous Sacrificial Layers of Pure Nickel or Nickel-Based Alloys

[0058] S1.2 On the titanium buffer layer, a pure metallic porous nickel sacrificial layer with a thickness gradient of "thick outside and thin inside" is prepared by using high aspect ratio deposition (GLAD) combined with mechanical masking step-by-step shielding technology. To further improve the temperature stability of the magnetic monitoring signal or optimize the thermodynamic properties of the diamond nucleation interface, pure nickel can also be equivalently replaced by a nickel-based alloy that can maintain a detectable magnetic response after high-temperature CVD treatment. Specifically, the nickel-based alloy is selected from any one of nickel-cobalt alloy (Ni-Co), nickel-chromium alloy (Ni-Cr), nickel-tungsten alloy (Ni-W), or nickel-molybdenum alloy (Ni-Mo); and the mass fraction of non-nickel elements is 5% to 25%. Nickel-cobalt alloy (Ni-Co) is preferred, with a Co mass fraction of 5% to 25%. Through solid solution strengthening with appropriate amounts of non-nickel elements, the Curie temperature of some preferred alloys (such as Ni-Co with a specific proportion) is ≥400 ℃, and the saturation magnetization is ≥410 emu / cc. This helps ensure that the sacrificial layer maintains its macroscopic strong ferromagnetism and structural integrity after undergoing high-temperature diamond CVD treatment and cooling to the wet etching temperature, thus meeting the requirements for subsequent high signal-to-noise ratio online magnetic monitoring.

[0059] a) Pure Physical In-Situ Pore Formation: In a pure argon (Ar) oxygen-free environment, the working pressure of magnetron sputtering is increased to 2–5 Pa to reduce the mean free path of sputtered atoms, combined with a tilted substrate arrangement. Utilizing the self-shadowing effect during physical deposition, nickel atoms spontaneously form a tilted columnar porous network structure (porosity controlled at approximately 20–30%) upon reaching the substrate. Oxygen introduction is strictly prohibited throughout the deposition process to ensure that the deposited nickel layer retains its pure metallic phase and inherent strong ferromagnetism.

[0060] b) Continuous construction of thickness gradient:

[0061] During the deposition process, a stepwise masking technique is employed, gradually increasing the masking area from the center outwards to construct an in-situ interconnected three-dimensional pore network. This process includes the following stages:

[0062] Phase 1 (Global Base Thickness): Expose the entire 2-inch sample area (approximately 25.4 mm in radius) for deposition until the central area and overall deposition thickness reach approximately 80–100 nm (or a set value according to design requirements, such as 300 nm for the overall base thickness in this embodiment).

[0063] The second stage (thickening of the middle and outer rings): A first annular mask is placed to precisely block the central region of the sample (a circular area with a radius of 10–14 mm extending outward from the center of the sample), exposing only the middle and outer ring regions and continuing deposition for approximately 150 nm. At this point, the total thickness of the exposed middle and outer ring regions reaches approximately 450 nm.

[0064] The third stage (outermost ring formation): The second annular mask is replaced, expanding the shielding range to cover the central region and the middle ring region (i.e., the ring with a radial width of approximately 8–12 mm), leaving only the outermost ring region, approximately 2–3 mm from the outermost edge of the sample, for deposition of approximately 150 nm. At this point, the total thickness of the outermost ring region reaches approximately 600 nm.

[0065] Through the aforementioned three-stage regional selective deposition, the porous sacrificial layer forms a "trumpet-shaped" three-dimensional structure in cross-section, thickening in a stepped manner from the inside out. This gradient design with a specific radial proportion ensures the flatness of the central core production area (accounting for over 20%) while significantly widening the liquid inlet channels at the outer edges, thereby significantly reducing the capillary mass transfer resistance during subsequent wet stripping and deep trench penetration. Simultaneously, from the center to the outermost ring, the initial amount of ferromagnetic material and the corresponding initial magnetic response intensity naturally exhibit a stepped increasing distribution, laying the physical foundation for subsequent multi-region time-series differential monitoring.

[0066] S2: Two-step diamond deposition with magnetic protection

[0067] Current diamond heteroepitaxial technology mostly uses noble metal substrates such as Ir, while nickel and nickel-based materials have strong carbon dissolution and graphitization catalytic capabilities at high temperatures, and easily form a large number of sps at the interface under conventional deposition conditions. 2 Carbon phase, thereby suppressing sp 3 Due to the stable formation of diamond crystal nuclei, nickel-based materials are generally considered difficult to directly serve as stable diamond heteroepitaxial templates.

[0068] However, according to the general mechanism of bias-enhanced nucleation (BEN), a carbon-rich or amorphous carbon transition layer can be formed on the surface of a conductive substrate by applying a negative bias. Under high-energy ion bombardment, this layer undergoes local structural rearrangement, forming a stable spc structure. 3 This structure enables high-density diamond nucleation. Porous nickel possesses excellent electrical conductivity and can rapidly form the aforementioned carbon-rich or amorphous carbon transition layer under BEN conditions through its surface catalysis. More importantly, the inherent high curvature of the porous nickel structure's microsurface can induce significant local electric field distortion and tip field enhancement effects, further improving ion bombardment efficiency and thus significantly increasing nucleation density. This allows for the successful construction of the desired high-density, stable distribution of diamond nucleation sites, i.e., the diamond seed layer.

[0069] This diamond seed layer not only provides initial crystallization sites for the porous nickel framework surface, but its grain orientation also directly guides the crystallization direction of the primary grains. However, the final crystallization morphology of the diamond layer (polycrystalline, highly oriented, or locally monocrystalline) is not solely determined by the seed layer, but is the result of the coupling of the "seed layer orientation distribution" and the "subsequent CVD growth kinetics".

[0070] In the process of constructing porous nickel-diamond epitaxial structures, those skilled in the art can, based on this scheme, obtain a preferentially oriented seed layer and then effectively suppress secondary nucleation and promote the preferential growth of existing grains by precisely controlling subsequent cavity pressure, carbon source concentration, hydrogen ratio, bias parameters, and growth time. Under normal conditions, continuous polycrystalline diamond films can be obtained; under optimized parameters, highly oriented diamond (HOD) layers can be achieved, and even significant single-crystallization characteristics can be observed in local areas.

[0071] It should be noted that the scope of protection of this invention is not limited to specific diamond crystal morphologies. Whether it is polycrystalline diamond, highly oriented diamond (HOD), partially monocrystalline diamond, or monocrystalline diamond, as long as it is attached and grown on a porous nickel three-dimensional framework based on the mechanism described in this invention, it falls within the scope of protection of this invention. Furthermore, the successful implementation of this invention does not require the complete expansion of a single grain throughout the entire porous structure as a necessary prerequisite. This morphological tolerance precisely ensures the high controllability and process flexibility of this technical solution in actual industrial mass production.

[0072] The sample (i.e., the diamond heteroepitaxial structure) after completing step S1 is placed in a microwave plasma chemical vapor deposition (MPCVD) apparatus. This embodiment employs a two-step deposition strategy:

[0073] S2.1 First Deposition Stage (Anaerobic Seed Layer Closed Nucleation):

[0074] Strictly adhering to oxygen-free MPCVD (pure H2 / CH4 system). H2 concentration was 98.5-99.5 vol% (total flow rate 100-500 sccm); CH4 concentration was controlled at 0.5-1.5 vol% to suppress graphitization with extremely low carbon potential; substrate temperature was 600-850°C, preferably 650-800°C, with gradual temperature increase; cavity pressure was 80-150 Torr; bias voltage enhanced nucleation was -50 to ~150 V, preferably -100 V, with a bias voltage time of 5-30 min, and the overall growth time was 2-4 hours.

[0075] S2.2 Second Deposition Stage (Atmosphere-independent host extensional growth):

[0076] Since the underlying porous nickel sacrificial layer is perfectly isolated, either an oxygen-free or oxygen-doped system can be chosen to accelerate growth at this stage. For example: H2 is 87-97.8 vol% (total flow rate 200-800 sccm), CH4 is 2-10 vol%, and 0.2-2.0 vol% O2 is added; the substrate temperature is increased to 800-1050 ℃; the cavity pressure is 100-250 Torr; and growth takes 10-30 hours (or longer) until the diamond host layer reaches the target thickness.

[0077] Regardless of the chosen atmosphere, the porous nickel sacrificial layer retains its ferromagnetism after high-temperature CVD followed by cooling to room temperature. Depending on the requirements, the diamond layer can be polycrystalline diamond, highly oriented diamond (HOD), or single-crystal diamond. Because the micropores of the porous nickel sacrificial layer act like a sponge, effectively releasing biaxial thermal stress caused by differences in thermal expansion coefficients during cooling, the aforementioned extremely gentle 300 nm thickness gradient does not cause significant warping or crystal plane distortion in the diamond epitaxial layer.

[0078] S3: Lateral penetration etching process and formulation optimization

[0079] S3.1 Sample layout and gap control

[0080] Before placing the diamond heteroepitaxial sample after step S2 into the etching solution, the edge cladding layer is removed using conventional laser kerfing as needed to fully expose the sides of the porous nickel sacrificial layer (this step is omitted if the edges have already been exposed using a mask). Then, the sample is horizontally suspended in the etching tank (e.g., ...). Figure 2 As shown in the figure, a fluid gap thickness of 1-5 cm is maintained between the lower surface of the sample and the inner surface of the etching tank bottom plate. The etching solution penetrates from the exposed edge and, relying on the "thick outside and thin inside" funnel-shaped three-dimensional pore network of the porous sacrificial layer, performs transverse penetration etching from the outside to the inside.

[0081] S3.2 Low Conductivity Etching Solution Formulation Mechanism

[0082] Traditional strong acid etching solutions have extremely high conductivity, which generates a strong eddy current shielding effect in low-frequency alternating detection magnetic fields, leading to a sharp reduction in skin depth and hindering the bottom sensor from acquiring the true magnetic response. Therefore, this embodiment strictly limits the conductivity of the etching solution, using a low-conductivity mixed aqueous solution containing a weak organic acid and an oxidant.

[0083] 1. Organic weak acids (0.1–0.5 mol / L): selected from any one or a combination of citric acid, acetic acid, tartaric acid, or oxalic acid. The incomplete ionization of weak acids significantly reduces the concentration of free ions. Furthermore, citric acid / tartaric acid, etc., possess excellent complexing properties and can react with the Ni produced in the reaction. 2+ It forms a stable soluble complex, preventing deposition and passivation on porous surfaces or within micropores.

[0084] 2. Oxidizing agent: Selected from hydrogen peroxide (0.05-0.1 mol / L) or nitric acid (1%-3% by mass). While efficiently oxidizing elemental nickel and accelerating its dissolution, the contribution of the reduction product of hydrogen peroxide (water) or the extremely low concentration of nitric acid to the conductivity of the system is limited to a very small range.

[0085] S3.3 Optimal Formula and Skin-Touching Depth Verification

[0086] The aforementioned mild formulation exhibits targeted high dissolution activity for porous nickel and provides chemical passivation protection for diamond and silicon substrates, enabling non-destructive reuse of the substrate. The specific optimized formulation and electromagnetic penetration performance calculations are as follows: Within the operating frequency band of 50 kHz to 300 kHz, even under the most unfavorable high conductivity conditions (σ≈20 S / m) and the highest detection frequency (300 kHz), the theoretical skin depth of the electromagnetic field in the etching solution is still approximately 20 cm or more, significantly greater than the liquid layer gap in the actual system (approximately 1–5 cm). Therefore, the electromagnetic field can penetrate the entire liquid layer without significant attenuation, achieving stable online detection of the magnetic response of the underlying porous nickel layer. This design effectively avoids the liquid-phase electromagnetic shielding effect caused by high conductivity liquids in traditional strong acid etching systems, ensuring a high signal-to-noise ratio and stability for magnetic signal detection.

[0087] S3.4 Reaction Kinetics and Megasound Assistance

[0088] Although the intrinsic reaction of low-concentration weak acid systems is slow, the extremely large specific surface area of ​​porous nickel allows etching to occur concurrently in three-dimensional space, significantly compensating for the stripping rate. To further overcome the mass transfer bottleneck within nanoscale aspect ratio channels, this embodiment simultaneously applies isothermal heating at 50–70 °C and high-frequency megasonic waves at 1–3 MHz to assist penetration during the etching process. The acoustic streaming effect generated by the megasonic waves effectively breaks up vapor locks within extremely narrow lateral channels, greatly reducing mass transfer resistance. At the same time, the mild formulation combined with megasonic waves completely avoids the mechanical impact and breakage risk caused by the violent gas generation of high-concentration strong acids on the suspended diamond film, achieving stable, stress-free, and uniform stripping.

[0089] S4: Online magnetic monitoring and stripping progress control

[0090] This embodiment deeply integrates the "thick outside and thin inside" funnel-shaped porous nickel morphology with bottom multi-point distributed magnetic sensing technology to achieve real-time, spatially distributed monitoring of the transverse capillary etching process in a closed space.

[0091] S4.1 Hardware Architecture

[0092] In actual etching operations, the sample is horizontally suspended in the etching tank, and a fluid gap is maintained between the plane containing the lower surface of the sample and the inner surface of the bottom plate of the etching tank, and the fluid gap has a fluid gap thickness.

[0093] To achieve online etching monitoring, the monitoring component PCB board, which includes a multi-point distributed excitation unit and a magnetic sensor, is arranged outside the etching tank (preferably close to the outside of the tank bottom plate) and corresponds to the porous nickel sacrificial layer in the normal direction. This arrangement creates a magnetic field transmission path between them that at least contains the nickel etching solution.

[0094] Specifically, the monitoring component adopts a ring-shaped distribution architecture with the sample center as the center of symmetry. It includes a central monitoring unit group located at the center, and middle ring monitoring unit groups and outermost ring monitoring unit groups distributed at equal angles around the central position along the circumference. Each monitoring unit group contains an excitation unit and a magnetic sensor corresponding to the monitoring area. In this embodiment, the multi-point distributed monitoring component preferably includes nine independent monitoring units, distributed radially symmetrically: including one central monitoring unit group, four middle ring monitoring unit groups, and four outermost ring monitoring unit groups, thereby comprehensively covering different spatial regions beneath the wafer on a two-dimensional plane. Figure 3 As shown.

[0095] In terms of sensor selection, to capture weak magnetic flux disturbances, the multi-point distributed magnetic sensor includes a sensor array composed of any one of giant magnetoresistive (GMR) sensors, tunnel magnetoresistive (TMR) sensors, anisotropic magnetoresistive (AMR) sensors, fluxgate sensors, or high-precision Hall sensors, or a hybrid sensor array composed of at least two different types of magnetic sensors, in order to adapt to the different needs of different regions for sensitivity and range.

[0096] S4.2 Signal Extraction and Time-Division Anti-Crosstalk Mechanism

[0097] In this invention, the operating frequency of the alternating detection magnetic field is configured in the range of 50 kHz to 300 kHz (preferably 100 kHz) to achieve an optimal balance between detection penetration depth and detection sensitivity. This frequency band ensures that the detection magnetic field can effectively penetrate the gaps in low-conductivity fluids without being severely shielded by liquid-phase eddy currents, while also exciting a sufficiently strong magnetic response signal in a thin (nano to micron-scale) porous nickel sacrificial layer. In actual operation, the detection magnetic field can be configured as a single fixed frequency within this frequency band, or as a time-division / frequency-division multi-frequency detection magnetic field composed of at least two discrete frequencies.

[0098] To eliminate spatial electromagnetic coupling caused by simultaneous excitation at multiple points when acquiring magnetic response electrical signals, the multi-point distributed excitation unit adopts a time-division sequential gating excitation mode. The system independently applies alternating magnetic fields to different monitoring areas in a predetermined sequence to isolate electromagnetic crosstalk between adjacent areas; simultaneously, each magnetic sensor and its corresponding excitation unit maintain excitation timing synchronization and perform independent addressing sampling.

[0099] To address the issue of weak probe echoes that are easily drowned out by broadband noise, the magnetic response signal is extracted using a lock-in amplifier. The lock-in amplifier uses the driving frequency of the excitation unit as a reference signal for narrowband demodulation at the same frequency, significantly improving the system's detection signal-to-noise ratio and thus enabling high-fidelity extraction of the magnetic response characteristics (including amplitude and phase) reflecting the localized porous nickel residue.

[0100] S4.3 Reference Calibration and Etching Progress Determination

[0101] 1. Initial state calibration and normalization:

[0102] Considering that the high-temperature CVD process can lead to differences in the initial equivalent magnetic permeability of different batches of samples, the initial magnetic response electrical signal of each monitoring area was pre-acquired as an initial reference value (i.e., 100% state) before the nickel etching solution was injected. The real-time magnetic response electrical signals during subsequent etching processes were all normalized based on this initial reference value to eliminate initial physical magnetic moment deviations.

[0103] 2. Extraction of the criteria for determining the completion of etching (wet in-situ reference calibration):

[0104] The criterion for determining the completion of etching is established through wet in-situ reference calibration. Specifically, the equivalent reference wafer without a magnetic sacrificial layer is placed in a working etching solution matching the current process state. Under an alternating detection magnetic field of 50–300 kHz, the amplitude and phase parameters of the same-frequency response signal are extracted using a lock-in amplifier to obtain the steady-state background average value S. ref The amplitude δ of the allowable fluctuation range is used as the criterion for determining the completion of the etching process. This calibration step completely eliminates common-mode interference from the intrinsic eddy currents of the substrate and the background of the liquid phase environment.

[0105] 3. Determination of lateral penetration progress and final erosion:

[0106] After the etching solution is injected, due to the thickness gradient ("thicker on the outside, thinner on the inside") of the porous nickel sacrificial layer, different annular regions have different initial magnetic response intensities. As the etching solution penetrates from the edge to the center, the magnetic response electrical signals of each annular region decay sequentially over time (i.e., from the outermost annular region, the middle annular region, to the central region) during the etching process, thereby determining the progress of lateral penetration etching in real time. The etching process continues until the magnetic response electrical signals of all monitored areas meet the determination criteria. At that time, it was finally determined that the porous nickel sacrificial layer had been completely etched away; wherein, S ref The mean steady-state background value is given by δ, where δ is the set allowable fluctuation range, and S is the mean value. i (t) represents the real-time magnetic response signal of the i-th magnetic sensor within the same annular region at time t. This synchronous determination logic overcomes the "fingering effect" or asymmetric etching caused by uneven liquid flow field in actual physical etching, fundamentally eliminating the risk of "false positive" fragmentation caused by local blind zone residue.

[0107] After the above conditions for complete etching are met, the etching endpoint is reached. At this point, a safe over-etching period (e.g., 10-30 minutes) can be set. Then, the etching solution is drained and the sample is removed, thus achieving high-yield, non-destructive separation of the diamond layer from the substrate.

[0108] In summary, this invention integrates physical morphology control (thickness gradient porous network) with electromagnetic non-destructive testing technology, fundamentally solving the industrial-level pain points of "slow etching" and "blind etching and peeling" in traditional diamond large-area heteroepitaxial peeling processes. This solution successfully achieves real-time magnetic monitoring and digital feedback of the lateral etching process in nanoscale confined spaces, greatly improving the consistency, reliability, and mass production yield of large-size diamond separation, and opening up a technological path with great application potential.

[0109] Finally, it should be noted that 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 preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing diamond sheets based on a magnetic sacrificial layer and online monitoring of exfoliation, characterized in that: The method includes the following steps: S1: A porous nickel sacrificial layer with ferromagnetism is prepared on a substrate, and the porous nickel sacrificial layer has a thickness gradient distribution that gradually increases from the center to the outer edge. The material of the porous nickel sacrificial layer is pure nickel or a nickel-based alloy. S2: A two-step microwave plasma chemical vapor deposition process is performed on the porous nickel sacrificial layer to sequentially perform closed nucleation of the diamond seed layer and epitaxial growth of the diamond body layer, thereby preparing a dense diamond layer to obtain a diamond heteroepitaxial structure. S3: Place the sample with the above structure in a nickel etching solution and perform transverse penetration etching along the plane direction of the porous nickel sacrificial layer; S4: A monitoring component including a multi-point distributed excitation unit and a magnetic sensor is arranged in the corresponding area outside the sample; an alternating detection magnetic field of a preset frequency is applied to the porous nickel sacrificial layer through the excitation unit, and the magnetic sensor is used to acquire the magnetic response electrical signals of multiple radially distributed monitoring areas in real time; according to the temporal characteristics of the magnetic response electrical signals of each monitoring area showing sequential decay along the etching front advancement direction, the magnetic response electrical signals of different areas are differentially compared to characterize the lateral peeling progress of the porous nickel sacrificial layer; when the magnetic response electrical signals of each monitoring area reach the preset etching completion judgment benchmark value related to the background magnetic response of the non-magnetic material etching solution, the etching is terminated, thereby realizing the separation of the diamond layer and the substrate to obtain a diamond sheet.

2. The method for preparing diamond sheets based on a magnetic sacrificial layer and online monitoring of exfoliation according to claim 1, characterized in that, In step S1, the thickness gradient distribution radially includes at least a central region, a middle ring region, and an outermost ring region; wherein the thickness of the outermost ring region is greater than the thickness of the middle ring region, and the thickness of the middle ring region is greater than the thickness of the central region, so that the porous nickel sacrificial layer forms a fluid permeation channel that gradually expands from the inside to the outside in the cross-section; and from the central region to the outermost ring region, its initial magnetic response intensity increases sequentially.

3. The method for preparing diamond sheets based on a magnetic sacrificial layer and online monitoring of exfoliation according to claim 1, characterized in that, In step S1, the porous nickel sacrificial layer is continuously grown in situ by tilt angle deposition (GLAD) combined with mask step-by-step shielding technology, and the entire deposition process is carried out in a pure argon oxygen-free environment to avoid metal oxidation and ensure macroscopic strong ferromagnetism. The porous nickel sacrificial layer is made of pure nickel or a nickel-based alloy; wherein, when the porous nickel sacrificial layer is made of a nickel-based alloy, the nickel-based alloy is a material that can maintain a detectable magnetic response after CVD high-temperature treatment; Specifically, the nickel-based alloy is selected from any one of nickel-cobalt alloy (Ni-Co), nickel-chromium alloy (Ni-Cr), nickel-tungsten alloy (Ni-W), or nickel-molybdenum alloy (Ni-Mo), and the mass fraction of non-nickel elements therein is 5% to 25%.

4. The method for preparing diamond sheets based on a magnetic sacrificial layer and online monitoring of exfoliation according to claim 1, characterized in that, Before preparing the porous nickel sacrificial layer in step S1, a non-ferromagnetic metal buffer layer with a thickness of 10-50 nm is pre-deposited on the substrate surface; the non-ferromagnetic metal buffer layer is selected from any one or a combination of titanium (Ti), tantalum (Ta), tungsten (W) or chromium (Cr).

5. The method for preparing diamond sheets based on a magnetic sacrificial layer and online monitoring of exfoliation according to claim 1, characterized in that, The diamond layer preparation described in step S2 employs a two-step microwave plasma chemical vapor deposition (MPCVD) process, including: In the first deposition stage, an oxygen-free gas system is used to nucleate and deposit a continuous and dense diamond seed layer with a thickness of 100-300 nm on the surface of the porous nickel sacrificial layer to physically isolate the porous nickel sacrificial layer. In the second deposition stage, the epitaxial growth of the diamond body layer continues on the diamond seed layer to the target thickness; the second deposition stage uses an oxygen-free or oxygen-doped gas system.

6. The method for preparing diamond sheets based on a magnetic sacrificial layer and online monitoring of exfoliation according to claim 1, characterized in that, In step S3, the conductivity of the nickel etching solution is configured such that the skin depth generated by the detection magnetic field in step S4 at the preset frequency is greater than the fluid gap thickness between the lower surface of the sample and the inner surface of the etching tank bottom plate, so as to reduce the shielding interference of the liquid phase electric eddy current on the magnetic response electrical signal; and the nickel etching solution has a selective dissolution effect on the porous nickel sacrificial layer, and the substrate maintains structural integrity in the nickel etching solution.

7. The method for preparing diamond sheets based on a magnetic sacrificial layer and online monitoring of exfoliation according to claim 6, characterized in that, The nickel etching solution is a low-conductivity mixed aqueous solution containing an organic weak acid and an oxidant; the organic weak acid is selected from any one or a combination of citric acid, acetic acid, tartaric acid, or oxalic acid, with a concentration of 0.1–0.5 mol / L; the oxidant is selected from any one or a combination of hydrogen peroxide or nitric acid, wherein the hydrogen peroxide concentration is 0.05–0.1 mol / L, and the nitric acid mass fraction is 1%–3%; the nickel etching solution is configured with the above component concentrations so that the ionic strength of the nickel etching solution meets the requirement that the skin depth is greater than the fluid gap thickness. In addition, during the etching process in step S3, the nickel etching solution is heated at a constant temperature of 50~70 ℃ or subjected to high-frequency megasonic waves with a frequency of 1~3 MHz to assist in penetration.

8. The method for preparing diamond sheets based on a magnetic sacrificial layer and online monitoring of exfoliation according to claim 1, characterized in that, In step S4, before injecting the nickel etching solution, the initial magnetic response electrical signal of each monitoring area is obtained in advance as the initial reference value; the real-time magnetic response electrical signal in the subsequent etching process is normalized based on the initial reference value to eliminate the initial physical magnetic moment deviation; the magnetic response electrical signal is extracted using a lock-in amplifier.

9. The method for preparing diamond sheets based on a magnetic sacrificial layer and online monitoring of exfoliation according to claim 1, characterized in that: In step S4, the monitoring component is arranged outside the etching tank, and the multi-point distributed excitation unit and magnetic sensor included therein are both arranged in the normal direction corresponding to the porous nickel sacrificial layer, forming a magnetic field transmission path between them that includes at least the nickel etching solution. The sample is horizontally suspended in the etching tank, and a fluid gap is maintained between the plane containing the lower surface of the sample and the inner surface of the bottom plate of the etching tank, and the fluid gap has a fluid gap thickness. The monitoring components adopt a ring-shaped distribution architecture with the center of the sample as the center of symmetry. It includes a central monitoring unit group located at the center, and a middle ring monitoring unit group and an outermost ring monitoring unit group distributed at equal angles around the center along the circumference. Each monitoring unit group is equipped with an excitation unit and a magnetic sensor corresponding to the monitoring area. When acquiring the magnetic response electrical signal, the multi-point distributed excitation unit adopts a time-division sequential gating excitation mode to independently apply alternating detection magnetic fields to different monitoring areas in sequence, so as to reduce electromagnetic crosstalk between adjacent monitoring areas; each magnetic sensor and the corresponding excitation unit perform independent addressing sampling to acquire the magnetic response electrical signal in sync with the excitation timing.

10. The method for preparing diamond wafers based on a magnetic sacrificial layer and online monitoring of peeling according to claim 1, wherein in step S4, the criterion for determining the completion of etching is determined by wet in-situ reference calibration, specifically: an equivalent reference wafer without a magnetic sacrificial layer is placed in a working etching solution matching the current process state, and under an alternating detection magnetic field of 50–300 kHz, the amplitude and phase parameters of the same-frequency response signal are extracted by a lock-in amplifier to obtain the steady-state background average value. For and allowable fluctuation range And use it as the criterion for determining the completion of the etching; wherein, Because the porous nickel sacrificial layer has a thickness gradient, different annular regions have different initial magnetic response intensities. During the etching process, the magnetic response electrical signals of each annular region decay sequentially over time, and the lateral penetration etching progress is determined accordingly. When the magnetic response electrical signals corresponding to all monitored regions meet the requirements... At that time, it is determined that the porous nickel sacrificial layer has been completely etched away; wherein, The mean of the steady-state background is... The amplitude of the allowable fluctuation range, For the first in the same annular region A magnetic sensor in The real-time magnetic response electrical signal at any given moment.

11. A method for preparing diamond sheets based on a magnetic sacrificial layer and online monitoring of exfoliation according to any one of claims 1 to 10, characterized in that, The multi-point distributed magnetic sensor array includes a sensor array composed of any one of giant magnetoresistive (GMR) sensors, tunnel magnetoresistive (TMR) sensors, anisotropic magnetoresistive (AMR) sensors, fluxgate sensors, or high-precision Hall sensors, or a hybrid sensor array composed of at least two different types of magnetic sensors.

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