Diamond planarization methods and their applications

Abstract

This invention provides a diamond planarization method and its application. The diamond planarization method includes: ablating a diamond plane to be treated using a laser; grinding the ablated diamond plane in a polycrystalline diamond polishing slurry; performing chemical mechanical polishing (CMP) on the ground diamond plane, wherein CMP involves alternately injecting neutral polishing slurry and acidic polishing slurry into a polishing device; and cleaning the CMP-polished diamond plane with a cleaning solution to obtain a planarized diamond plane. This diamond planarization method is simple to operate and highly efficient, enabling rapid planarization of diamond planes, thereby meeting the planarization requirements for diamond substrates in semiconductor device fabrication processes.

Description

Technical Field

[0001] This invention relates to the fields of diamond planarization and semiconductor processing, and particularly to a diamond planarization method and its application. Background Technology

[0002] With the development of high-tech fields such as third-generation semiconductors, 5G communications, communication satellites, and radar, the demand for diamond-substrate components is increasing. These components need to meet the requirements of extreme operating conditions such as radiation resistance, high power, high frequency, and high temperature. Diamond has excellent thermal conductivity, an ultra-wide bandgap structure, and high carrier mobility, making it a promising material for high-power, high-frequency, and high-temperature electronic devices and considered an ideal material for improving the heat dissipation capabilities of power devices.

[0003] Diamond planarization technology is crucial for the fabrication of semiconductor devices with diamond substrates. It not only improves the performance of semiconductor devices but also helps solve application problems under extreme conditions. However, diamond planarization technology still faces many challenges. For example, diamond has a high hardness, and commonly used polishing slurries can only be made of materials with a hardness comparable to diamond. It is difficult to find materials with a higher hardness than diamond, making diamond removal extremely difficult.

[0004] Therefore, a more efficient and cost-effective diamond planarization method is needed. Summary of the Invention

[0005] In view of this, in order to at least partially solve at least one of the aforementioned technical problems, the present invention provides a diamond planarization method and its application.

[0006] According to one embodiment of the present invention, a diamond planarization method is provided, comprising:

[0007] The diamond surface to be treated is ablated using a laser.

[0008] The ablated diamond surface is then ground in a polycrystalline diamond polishing slurry.

[0009] The diamond surface after grinding is subjected to chemical mechanical polishing, which involves alternately injecting neutral polishing fluid and acidic polishing fluid into the polishing equipment.

[0010] The diamond surface after chemical mechanical polishing is cleaned with a cleaning solution to obtain a flattened diamond surface.

[0011] According to an embodiment of the present invention, the neutral polishing slurry includes polycrystalline diamond particles with a particle size of 20-30 nm and an alcohol solvent; the acidic polishing slurry includes a solution containing perchlorate, an acid and water; the volume ratio of the solution containing perchlorate, the acid and water in the acidic polishing slurry is (0.5-1.5):(4-6):(8-12).

[0012] According to an embodiment of the present invention, the volume ratio of the perchlorate-containing solution, the acid, and the water in the acid polishing solution is 1:(5~6):10; the perchlorate-containing solution includes at least one of KClO4, NaClO4, and HClO4; the acid includes at least one of H2SO4 and HCl.

[0013] According to embodiments of the present invention, the acidic polishing solution includes KClO4, H2SO4, and water. The volume ratio of KClO4:H2SO4:water in the acidic polishing solution includes (0.5~1.5):(4~6):(8~12), preferably 1:(5~6):10;

[0014] According to embodiments of the present invention, the alcohol solvent includes at least one of ethylene glycol, polyethylene glycol PEG-400, polyethylene glycol PEG-600, and polyethylene glycol PEG-6000.

[0015] According to an embodiment of the present invention, the polycrystalline diamond polishing slurry includes polycrystalline diamond particles with a particle size of 10 μm; the pH value of the polycrystalline diamond polishing slurry is 7~8.

[0016] According to an embodiment of the present invention, the laser used for laser ablation is a nanosecond ultraviolet laser with a laser power of 20~30W and a laser ablation time of 2~10 hours.

[0017] According to an embodiment of the present invention, laser ablation is used to reduce the total thickness deviation of the diamond plane to be treated to below 10 μm;

[0018] Grinding is used to reduce the total thickness deviation of the ablated diamond surface to below 5 μm;

[0019] Chemical mechanical polishing is used to reduce the surface roughness Ra value of a polished diamond surface to below 2 nm.

[0020] According to an embodiment of the present invention, the duration of neutral abrasive injection is 3 to 5 seconds, and the injection interval is 30 to 50 seconds;

[0021] The duration of acid polishing slurry injection is 30–50 seconds, with an injection interval of 3–5 seconds.

[0022] According to an embodiment of the present invention, the cleaning solution includes NaClO; the pH value of the cleaning solution is 7.5~8.5.

[0023] According to an embodiment of the present invention, the polishing equipment includes a polishing disc and a clamp, wherein the polishing disc is used to drive the neutral polishing slurry and the acid polishing slurry to rotate, and the clamp is used to hold the polished diamond surface.

[0024] The polishing disc rotates at 50-70 rpm, and the clamp rotates at 80-100 rpm.

[0025] The chemical mechanical polishing time is 4 to 12 hours.

[0026] According to another aspect of the present invention, an application of a diamond planarization method in the fabrication of semiconductor devices is provided.

[0027] According to embodiments of the present invention, surface treatment by laser ablation can significantly reduce the total thickness deviation of the diamond plane, laying a good foundation for subsequent grinding and polishing processes. Grinding in a polycrystalline diamond polishing slurry with a hardness close to that of diamond effectively removes surface material while reducing scratches and damage, thus lowering surface roughness. Then, chemical mechanical polishing is used to planarize the diamond surface globally, reducing the total thickness deviation and improving surface smoothness. Alternating between neutral and acidic polishing slurries creates an acidic environment during polishing, optimizing the chemical reaction and improving polishing efficiency and quality. Finally, a cleaning solution is used to remove impurities and byproducts, resulting in a planarized diamond plane. This diamond planarization method prepares the diamond plane for subsequent heterogeneous material bonding processes, improving the performance of heterogeneous bonded circuit devices based on diamond substrates. The entire diamond planarization method is simple to operate, highly efficient, and low-cost, enabling rapid planarization of the diamond plane. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the diamond planarization method according to an embodiment of the present invention;

[0029] Figure 2 This is a schematic diagram of a laser ablation of diamond in an embodiment of the present invention;

[0030] Figure 3 This is a schematic diagram of diamond planar grinding according to an embodiment of the present invention;

[0031] Figure 4 This is a schematic diagram of a diamond planar chemical mechanical polishing process according to an embodiment of the present invention;

[0032] Figure 5 This is a schematic diagram of diamond plane cleaning according to an embodiment of the present invention;

[0033] Figure 6 This is a schematic diagram of the diamond crystal grains after planarization in Embodiment 1 of the present invention. Detailed Implementation

[0034] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the invention. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the invention for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0035] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "comprising" as used herein indicates the presence of features, steps, or operations, but does not exclude the presence or addition of one or more other features.

[0036] When using expressions such as "at least one of A, B, and C," the expression should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, and C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.). When using expressions such as "at least one of A, B, or C," the expression should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, or C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.).

[0037] In realizing the concept of this invention, it was discovered that diamond epitaxial materials, due to their superior physical properties, exhibit great application potential in the semiconductor field. Like carbon nanotubes and graphene, diamond materials are receiving increasing attention in the application of wide-bandgap semiconductor materials. Diamond's critical breakdown field strength, high-temperature resistance, and thermal conductivity are significantly superior to silicon (Si), which is crucial for improving the operating frequency and cutoff frequency of field-effect transistors (FETs).

[0038] With the development of GaN microwave power devices and silicon carbide (SiC) high-temperature and high-voltage power electronic devices, heat dissipation has become a critical issue. Related technologies have developed heterogeneous material integration fabrication processes based on diamond substrates. By integrating different materials such as silicon (Si), silicon carbide (SiC), sapphire (Al2O3), and aluminum nitride (AlN) on diamond substrates, high-frequency, high-voltage, and high-power devices can be manufactured, effectively reducing the heat generated during operation and minimizing the impact of thermal defects on the performance of circuit devices.

[0039] Therefore, in order to achieve heterogeneous bonding technology between different substrates, there are strict requirements on the surface morphology of the substrate. This requires improving the flatness of the material through thinning and grinding processes, and reducing the roughness of the diamond substrate through grinding and polishing processes, in order to achieve a suitable surface state for bonding.

[0040] However, surface warping is a problem during the epitaxial growth of diamond materials, with the thickness difference of a 2-inch diamond typically exceeding 30 micrometers. Due to the extremely high hardness of diamond, commonly used polishing slurries, such as boron carbide (CBN) and other high-hardness materials, are ineffective at removing diamond materials. Furthermore, diamond planarization processes require acidic chemical reactions (pH < 7), while commonly used polishing slurries often employ alkaline dispersants (pH > 7), resulting in process incompatibility issues.

[0041] Furthermore, residues generated after diamond grinding tend to adhere to the wafer surface, and conventional cleaning processes struggle to completely remove these residues. This poses an additional challenge for achieving high-quality diamond substrate surfaces. Therefore, developing effective diamond planarization and cleaning technologies is crucial for enhancing the application of diamond in the semiconductor field.

[0042] Figure 1 This is a schematic diagram of the diamond planarization method according to an embodiment of the present invention; Figure 2 This is a schematic diagram of a laser ablation of diamond in an embodiment of the present invention; Figure 3 This is a schematic diagram of diamond planar grinding according to an embodiment of the present invention; Figure 4 This is a schematic diagram of a diamond planar chemical mechanical polishing process according to an embodiment of the present invention; Figure 5 This is a schematic diagram of diamond plane cleaning according to an embodiment of the present invention.

[0043] Based on this, according to one embodiment of the present invention, a diamond planarization method is provided, combined with Figures 1-5 The explanation includes the following steps S1 to S4.

[0044] Step S1: Ablate the diamond surface to be treated using a laser;

[0045] Step S2: Place the ablated diamond surface in a polycrystalline diamond polishing slurry for polishing;

[0046] Step S3: Perform chemical mechanical polishing on the ground diamond surface. Chemical mechanical polishing involves alternately injecting neutral polishing fluid and acidic polishing fluid into the polishing equipment.

[0047] Step S4: Clean the diamond surface after chemical mechanical polishing with a cleaning solution to obtain a flattened diamond surface.

[0048] According to embodiments of the present invention, surface treatment by laser ablation can significantly reduce the total thickness deviation of the diamond plane, laying a good foundation for subsequent grinding and polishing processes. Grinding in a polycrystalline diamond polishing slurry with a hardness close to that of diamond effectively removes surface material while reducing scratches and damage, thus lowering surface roughness. Then, chemical mechanical polishing is used to planarize the diamond surface globally, reducing the total thickness deviation and improving surface smoothness. Alternating between neutral and acidic polishing slurries creates an acidic environment during polishing, optimizing the chemical reaction and improving polishing efficiency and quality. Finally, a cleaning solution is used to remove impurities and byproducts, resulting in a planarized diamond plane. This diamond planarization method prepares the diamond plane for subsequent heterogeneous material bonding processes, improving the performance of heterogeneous bonded circuit devices based on diamond substrates. The entire diamond planarization method is simple to operate, highly efficient, and low-cost, enabling rapid planarization of the diamond plane.

[0049] According to an embodiment of the present invention, in step S1, laser ablation is used to reduce the total thickness deviation of the diamond plane to be treated to below 10 μm;

[0050] In step S2, grinding is used to reduce the total thickness deviation of the ablated diamond plane to below 5 μm;

[0051] In step S3, chemical mechanical polishing is used to reduce the surface roughness Ra value of the polished diamond plane to below 2 nm and remove a thickness of 40~60 μm.

[0052] According to embodiments of the present invention, by using the diamond planarization method of the present invention, the roughness and warp of the diamond substrate can be effectively reduced, so that the warp reaches 5 μm and the roughness reaches the 0.1 nm level, thereby improving the device performance of heterobonded circuits based on diamond substrates.

[0053] According to an embodiment of the present invention, in step S1, as follows Figure 2 As shown, the laser used for laser ablation is a nanosecond ultraviolet laser with a power of 20~30W and an ablation time of 2~10 hours.

[0054] According to embodiments of the present invention, the laser power for laser ablation can be 20W, 22W, 25W, 28W, or 30W, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. The laser ablation time can be 2 hours, 4 hours, 6 hours, 8 hours, or 10 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0055] In some specific embodiments of the present invention, the heterogeneous material substrate is a supporting substrate for the diamond plane. The circuit can be fabricated on the diamond substrate after diamond planarization; alternatively, the diamond grown on the fabricated circuit can be planarized. In this case, before laser ablation, photoresist needs to be uniformly applied to the front side of the diamond wafer to be thinned and planarized to protect the circuit fabricated on the surface of the diamond wafer before laser ablation.

[0056] According to an embodiment of the present invention, diamond undergoes carbonization at 700-800°C. Excessive nanosecond ultraviolet laser power generates high temperatures, which can cause diamond carbonization and damage its crystal structure. Furthermore, high temperatures increase thermal stress, leading to diamond fragmentation. Excessive power also makes ablation products such as material debris difficult to remove. Therefore, by using low-power, high-frequency scanning, and long-duration laser ablation of the diamond plane, the impact of thermal stress is reduced.

[0057] According to an embodiment of the present invention, in step S2, as Figure 3 As shown, the polycrystalline diamond polishing slurry contains polycrystalline diamond particles with a diameter of 10 μm; the pH value of the polycrystalline diamond polishing slurry is 7~8.

[0058] According to embodiments of the present invention, the pH value of the polycrystalline diamond polishing slurry can be 7, 7.5, or 8, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0059] In some specific embodiments of the present invention, the grinding time includes 15 to 20 hours. The grinding time can be 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, or 20 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable. The grinding disc can be an iron grinding disc, a copper grinding disc, etc.

[0060] According to embodiments of the present invention, excessively large particle sizes of polycrystalline diamond particles in the polycrystalline diamond polishing slurry may lead to increased surface roughness, while excessively small particle sizes may reduce the removal rate and increase processing time. Therefore, using a 10 μm particle size can achieve a balance between removal rate and roughness. By using a slightly alkaline polycrystalline diamond polishing slurry, conflicts with the acidic environment in subsequent chemical mechanical polishing can be avoided, achieving process compatibility.

[0061] According to an embodiment of the present invention, in step S3, as Figure 4As shown, the neutral polishing slurry includes polycrystalline diamond particles with a particle size of 20-30 nm and an alcohol solvent. The particle size of the polycrystalline diamond particles can be 20 nm, 22 nm, 24 nm, 26 nm, 28 nm, or 30 nm, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. The alcohol solvent includes at least one of ethylene glycol, polyethylene glycol PEG-400, polyethylene glycol PEG-600, and polyethylene glycol PEG-6000, for example, it can be ethylene glycol and polyethylene glycol PEG-400, or a combination of ethylene glycol, polyethylene glycol PEG-400, polyethylene glycol PEG-600, and polyethylene glycol PEG-6000, etc.

[0062] According to an embodiment of the present invention, in step S3, the acidic polishing solution includes a solution containing perchlorate, an acid, and water.

[0063] According to embodiments of the present invention, the volume ratio of perchlorate solution, acid, and water in the acid polishing solution includes (0.5~1.5):(4~6):(8~12), and can be 0.5:4:8, 0.5:5:9, 1:5:10, 1:6:12, 1.5:5:10, 1.5:6:12, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0064] Preferably, the volume ratio of the perchlorate solution, acid, and water in the acid polishing solution can be 1:5:10 or 1:6:10.

[0065] According to an embodiment of the present invention, under the action of an acidic polishing slurry, H is provided by the acid agent. + Diamonds undergo relevant chemical reactions within a chemical mechanical polishing apparatus:

[0066] 4(ClO4) - +7C+4H + →2H2O+2Cl2+7CO2; Cl2+H2O→HCl+HClO→2HCl+O2.

[0067] In some specific embodiments of the present invention, the acid is at least one of H2SO4 and HCl. When the acid is H2SO4, the chemical mechanical polishing reaction is: H2SO4 + C = 2SO2 + CO2 + 2H2O.

[0068] In some specific embodiments of the present invention, the solution containing perchlorate ions includes at least one of KClO4, NaClO4, and HClO4. For example, it can be KClO4, or a mixed solution of KClO4 and NaClO4.

[0069] In some specific embodiments of the present invention, the water may be deionized water (DI).

[0070] According to embodiments of the present invention, polycrystalline diamond particles, due to their good toughness, can maintain high grinding force while being less prone to scratches during the grinding and polishing process. The alcohol solvent acts as a dispersant in the grinding fluid, which helps to uniformly disperse the abrasive and plays a role in dilution, lubrication and cooling. Moreover, due to the diversity of impurities in the grinding fluid, the use of various alcohol solvents can help improve the dispersibility and stability of the abrasive, reduce abrasive agglomeration, thereby improving grinding efficiency and workpiece surface quality.

[0071] Furthermore, by using an acidic polishing slurry containing perchlorate as an oxidant for chemical mechanical polishing, the oxidation reaction on the diamond surface can be promoted, thereby assisting in the removal of materials. Perchlorate ions promote the oxidation of the diamond surface, weakening the C-C bonds. The carbon atoms in the diamond substrate and the carbon atoms in the diamond abrasive grains form stronger C-C bonds. Under the combined mechanical and chemical action of the polycrystalline diamond particles in the polishing slurry, the carbon atoms in the substrate are carried away by the polycrystalline diamond particles, achieving the effect of surface polishing. The surface roughness of the diamond plane can be reduced to the nanometer level, and the roughness Ra of the diamond after polishing can be reduced by 2 nm. The grains can be seen under an atomic force microscope (AFM).

[0072] According to an embodiment of the present invention, in step S4, as Figure 5 As shown, the cleaning solution includes at least one of NaClO and KClO; the pH value of the cleaning solution is 7.5~8.5.

[0073] According to embodiments of the present invention, the pH value of the cleaning solution can be 7.5, 7.8, 8, 8.2, or 8.5, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0074] In some specific embodiments of the present invention, the cleaning time includes 10 to 20 minutes, followed by rinsing with deionized water and drying with N2.

[0075] In some specific embodiments of the present invention, the rotational speed of the clamp during the cleaning process includes 60-80 rpm, and the pressure of the cleaning brush includes 0.1-0.3 kg / inch. 2 .

[0076] According to embodiments of the present invention, a weakly alkaline NaClO or KClO is used as a weakly alkaline cleaning solution to remove acidic reaction byproducts. Using a strong alkaline cleaning solution may react with the cleaning brushes of the resin material, making it unsuitable for cleaning. By using a weakly alkaline cleaning solution corresponding to the acidic polishing solution used in chemical mechanical polishing, grinding residues such as byproducts and impurities can be removed simply, quickly, and efficiently, simplifying the cleaning process.

[0077] According to embodiments of the present invention, such as Figure 4 As shown, the polishing equipment includes a polishing disc and a clamp. The polishing disc is used to drive the neutral polishing slurry and the acid polishing slurry to rotate, and the clamp is used to hold the polished diamond surface.

[0078] The polishing disc rotates at 50-70 rpm, and the clamp rotates at 80-100 rpm.

[0079] The chemical mechanical polishing time is 4 to 12 hours.

[0080] According to embodiments of the present invention, the rotational speed of the polishing disc can be 55 rpm, 60 rpm, 65 rpm, or 70 rpm, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. The clamping speed can be 80 rpm, 85 rpm, 90 rpm, 95 rpm, or 100 rpm, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. The chemical mechanical polishing time can be 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, or 12 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0081] Furthermore, the polishing disc and the fixture rotate in the same direction. The additional pressure of the fixture ranges from 0.5 to 1 kg / inch. 2 .

[0082] In some specific embodiments of the present invention, the polishing disc may be a nickel-tin-antimony alloy polishing disc, a polyurethane polishing disc, a polyester polishing disc, etc.

[0083] According to an embodiment of the present invention, the jig rotation speed depends on the stability of the equipment itself. While high-speed rotation results in faster polishing, it also generates significant vibration and heat, increasing thermal stress and potentially causing diamond breakage. Therefore, a moderate rotation speed must be selected. Furthermore, because diamonds are highly stressed and brittle, the additional pressure applied to the jig should not be excessive, exceeding 2 kg / inch. 2 The polishing rate does not increase significantly after applying pressure, therefore a range of 0.5–1 kg / inch is selected. 2 Pressure can achieve chemical mechanical polishing.

[0084] According to an embodiment of the present invention, the duration of neutral polishing slurry injection is 3-5 seconds, and the injection interval is 30-50 seconds; the duration of acidic polishing slurry injection is 30-50 seconds, and the injection interval is 3-5 seconds.

[0085] According to embodiments of the present invention, the injection duration of neutral polishing slurry can be 3 seconds, 4 seconds, or 5 seconds, and the injection interval can be 30 seconds, 35 seconds, 40 seconds, 45 seconds, or 50 seconds, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. The injection duration of acidic polishing slurry is 3 seconds, 4 seconds, or 5 seconds, and the injection interval can be 30 seconds, 35 seconds, 40 seconds, 45 seconds, or 50 seconds, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0086] According to embodiments of the present invention, an injection interval of 3-5 seconds for the neutral polishing slurry allows for uniform coating of the polishing disc with the neutral polishing slurry. Excessive time can lead to too many particles in the polishing slurry, resulting in poor flowability and waste. Too much neutral polishing slurry can also disrupt the pH environment required for polishing. An injection time of 30-50 seconds for the acidic polishing slurry ensures sufficient time for chemical reaction between the acidic polishing slurry and the diamond surface. Too short a time results in insufficient reaction, while too long a time leads to waste. An injection interval of 3-5 seconds allows for thorough and uniform mixing of the alternately injected neutral and acidic polishing slurries, enabling chemical mechanical polishing through reaction with the diamond surface.

[0087] According to another aspect of the present invention, an application of a diamond planarization method in the fabrication of semiconductor devices is provided.

[0088] According to embodiments of the present invention, the requirements for diamond substrates in semiconductor devices are generally a warpage of less than 30 μm and a roughness of less than 2 nm. The diamond plane treated by the diamond planarization method of the present invention can meet or even exceed the flatness requirements of the diamond plane for semiconductor devices, thereby improving the performance and reliability of semiconductor devices and optimizing the semiconductor device manufacturing process.

[0089] The diamond planarization method of the present invention will be further explained below with reference to specific embodiments. Unless otherwise specified, the reagents used in the following embodiments are all common commercially available reagents.

[0090] Example 1: Fine thinning and planarization of a plane on which a diamond crystal substrate is grown on a circuit.

[0091] First, photoresist is uniformly applied to the front side of the diamond wafer to be thinned and planarized to protect the circuit fabricated on the front side. Then, the diamond plane to be processed is ablated by laser.

[0092] The ablated diamond surface is placed on an iron mill and polished with polycrystalline diamond polishing fluid.

[0093] The back side of the wafer is attached to a fixture, and neutral polishing slurry and acid polishing slurry are alternately injected into a chemical mechanical polishing (CMP) device to perform CMP on the polished diamond surface.

[0094] The diamond surface after chemical mechanical polishing is cleaned with a cleaning solution. The cleaning brush is swung left and right to obtain a flattened diamond surface, as shown below. Figure 6 As shown.

[0095] Figure 6 This is a schematic diagram of the diamond crystal grains after planarization in Embodiment 1 of the present invention.

[0096] according to Figure 6 It can be seen that the grain roughness Ra of the diamond crystal plane after planarization reaches the level of 0.1nm and the warpage reaches 5μm, which can meet the requirements of the diamond substrate planarization process in semiconductor device manufacturing.

[0097] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A diamond planarization method, comprising: The diamond surface to be treated is ablated using a laser. The ablated diamond surface is then ground in a polycrystalline diamond polishing slurry. The ground diamond surface is subjected to chemical mechanical polishing, wherein the chemical mechanical polishing involves alternately injecting neutral polishing slurry and acidic polishing slurry into the polishing equipment; the duration of the neutral polishing slurry injection is 3-5 seconds, and the injection interval is 30-50 seconds; the duration of the acidic polishing slurry injection is 30-50 seconds, and the injection interval is 3-5 seconds. The diamond surface after chemical mechanical polishing is cleaned with a cleaning solution to obtain a flattened diamond surface; the acidic polishing solution includes a solution containing perchlorate, an acid, and water; the acid includes at least one of H2SO4 and HCl.

2. The method according to claim 1, wherein, The neutral polishing slurry includes polycrystalline diamond particles with a particle size of 20-30 nm and an alcohol solvent; The volume ratio of the perchlorate-containing solution, the acid, and the water in the acidic polishing solution is (0.5~1.5):(4~6):(8~12).

3. The method according to claim 2, wherein, The volume ratio of the perchlorate-containing solution, the acid, and the water in the acidic polishing solution is 1:(5~6):10; The perchlorate-containing solution includes at least one of KClO4, NaClO4, and HClO4; The alcohol solvent includes at least one of ethylene glycol, polyethylene glycol PEG-400, polyethylene glycol PEG-600, and polyethylene glycol PEG-6000.

4. The method according to claim 1, wherein, The polycrystalline diamond polishing slurry contains polycrystalline diamond particles with a particle size of 10 μm. The pH value of the polycrystalline diamond polishing slurry is 7-8.

5. The method according to claim 1, wherein, The laser used for laser ablation is a nanosecond ultraviolet laser with a power of 20-30W and an ablation time of 2-10 hours.

6. The method according to claim 1, wherein, The laser ablation is used to reduce the total thickness deviation of the diamond plane to be treated to below 10 μm; The grinding is used to reduce the total thickness deviation of the ablated diamond plane to below 5 μm; The chemical mechanical polishing is used to reduce the surface roughness Ra value of the polished diamond plane to below 2 nm.

7. The method according to claim 1, wherein, The cleaning solution includes at least one of NaClO and KClO; The pH value of the cleaning solution is 7.5~8.

5.

8. The method according to claim 1, wherein, The polishing equipment includes a polishing disc and a clamp, wherein the polishing disc is used to drive the neutral polishing slurry and the acidic polishing slurry to rotate, and the clamp is used to hold the polished diamond surface; The polishing disc rotates at a speed of 50-70 rpm, and the fixture rotates at a speed of 80-100 rpm. The chemical mechanical polishing time is 4 to 12 hours.

9. The application of the diamond planarization method as described in any one of claims 1 to 8 in the fabrication of semiconductor devices.

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