Diamond planarization method and application thereof

Abstract

The invention provides a diamond planarization method and application thereof. The diamond planarization method comprises the following steps: ablating a diamond plane to be treated through laser; placing the ablated diamond plane in a polycrystalline diamond grinding liquid for grinding; performing chemical mechanical polishing on the ground diamond plane, wherein the chemical mechanical polishing is as follows: alternately injecting neutral grinding liquid and acid polishing liquid into polishing equipment; and cleaning the diamond plane subjected to chemical mechanical polishing by adopting a cleaning solution to obtain the planarized diamond plane. The diamond planarization method is easy to operate and high in efficiency, planarization processing can be rapidly carried out on the diamond plane, and therefore the planarization requirement for the diamond substrate in the semiconductor device preparation technology is met.

Description

Technical Field

[0001] The present invention relates to the field of diamond planarization and semiconductor processing, and in particular to a diamond planarization method and application thereof. Background Art

[0002] With the development of high-tech fields such as third-generation semiconductors, 5G communications, communication satellites and radars, the demand for diamond substrate components is growing. These components need to meet the requirements of extreme working conditions such as radiation resistance, high power, high frequency, and high temperature. Diamond has excellent thermal conductivity, ultra-wide bandgap structure and high carrier mobility, which makes it show great application potential in electronic devices under high power, high frequency and high temperature environment, and is regarded as an ideal material for improving the heat dissipation capacity of power devices.

[0003] Diamond planarization technology is crucial for the processing of semiconductor devices with diamond as the substrate. It can not only improve the performance of semiconductor devices, but also help solve the application problems of semiconductor devices under extreme working conditions. However, there are still many problems in diamond planarization technology, such as the high hardness of diamond. Commonly used grinding fluids can only use high-hardness materials of the same level as diamond. It is difficult to find materials with higher hardness than diamond, so it is very difficult to remove diamond.

[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 above-mentioned technical problems, the present invention provides a diamond planarization method and application thereof.

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

[0007] A diamond plane to be processed is ablated by laser;

[0008] The ablated diamond plane is placed in a polycrystalline diamond grinding liquid for grinding;

[0009] The ground diamond surface is subjected to chemical mechanical polishing, and the chemical mechanical polishing is as follows: a neutral grinding liquid and an acid polishing liquid are alternately injected into a polishing device;

[0010] The diamond surface after chemical mechanical polishing is cleaned by using a cleaning liquid to obtain a diamond surface after flattening treatment.

[0011] According to an embodiment of the present invention, the neutral grinding liquid includes polycrystalline diamond particles with a particle size of 20-30 nm and an alcohol solvent; the acidic polishing liquid includes a solution containing perchlorate, an acid agent and water; the volume ratio of the solution containing perchlorate: the acid agent: the water in the acidic polishing liquid includes (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 in the acidic polishing liquid: the acid agent: the water is 1: (5-6): 10; the perchlorate-containing solution includes at least one of KClO4, NaClO4 and HClO4; the acid agent includes at least one of H2SO4 and HCL.

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

[0014] According to an embodiment 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 grinding liquid includes polycrystalline diamond particles with a particle size of 10 μm; the pH value of the polycrystalline diamond grinding liquid is 7-8.

[0016] According to an embodiment of the present invention, the laser used for laser ablation is a nanosecond ultraviolet laser, the laser power is 20-30w, and the laser ablation time is 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 processed to less than 10 μm;

[0018] Grinding is used to reduce the total thickness deviation of the diamond plane after ablation to less than 5μm;

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

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

[0021] The injection duration of the acid polishing liquid is 30 to 50 seconds, and the injection interval is 3 to 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 device includes a polishing disc and a fixture, wherein the polishing disc is used to drive the neutral polishing liquid and the acid polishing liquid to rotate, and the fixture is used to clamp the polished diamond surface;

[0024] The speed of the polishing disc is 50~70rpm and the speed of the fixture is 80~100rpm;

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

[0026] According to an embodiment of another aspect of the present invention, there is provided an application of a diamond planarization method in manufacturing a semiconductor device.

[0027] According to an embodiment of the present invention, after surface treatment by laser ablation, the total thickness deviation of the diamond plane can be greatly reduced, laying a good foundation for subsequent grinding and polishing processes, and then grinding in a polycrystalline diamond grinding liquid with a hardness close to that of diamond can effectively remove surface materials, and at the same time can reduce scratches and damage while reducing surface roughness, and then chemical mechanical polishing is used to perform global flattening of the diamond surface, reduce the total thickness deviation of the diamond surface, and improve the flatness of the diamond surface. At the same time, alternating between neutral grinding liquid and acid polishing liquid can place the polishing process in an acidic environment, optimize chemical reactions, and improve polishing efficiency and quality. Finally, cleaning liquid is used to clean impurities and by-products to obtain a flattened diamond plane. The diamond flattening method of the present invention can prepare for flattening for subsequent heterogeneous material bonding processes, and improves the performance of heterogeneous bonding circuit devices based on diamond substrates. The entire diamond flattening method is simple to operate, highly efficient, and low cost, and can quickly flatten the diamond plane. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

[0031] Figure 4 This is a schematic diagram of chemical mechanical polishing of a diamond plane 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 Schematic diagram of diamond crystal grains after planarization in Example 1 of the present invention. DETAILED DESCRIPTION

[0034] Below, 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 present invention. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of embodiments of the present invention. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of concepts of the present invention.

[0035] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The term "comprising" used herein indicates the existence of features, steps, operations, but does not exclude the existence or addition of one or more other features.

[0036] In the case of using expressions such as "at least one of A, B, and C, etc.", it should generally be interpreted in accordance with the meaning of the expression generally understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.). In the case of using expressions such as "at least one of A, B, or C, etc.", it should generally be interpreted in accordance with the meaning of the expression generally understood by those skilled in the art (for example, "a system having at least one of A, B, or C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0037] In the process of realizing the concept of the present invention, it was found that diamond epitaxial materials have great application potential in the semiconductor field due to their excellent physical properties. Like carbon nanotubes and graphene, diamond materials are increasingly valued in the application of wide bandgap semiconductor materials. The critical breakdown field strength, high temperature resistance and thermal conductivity of diamond are significantly better than those of silicon (Si), which is crucial for improving the operating frequency of field effect transistors (FETs) and the cutoff frequency of devices.

[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 key issue. In related technologies, a heterogeneous material integration preparation process based on diamond substrates has been developed. 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 reducing the impact of thermal defects on circuit device performance.

[0039] Therefore, in order to realize 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 a thinning and grinding process, and using a grinding and polishing process to reduce the roughness of the diamond substrate to achieve a surface state suitable for bonding.

[0040] However, there is a surface warping problem during the epitaxial growth of diamond materials, and the thickness difference of 2-inch diamond is usually more than 30 microns. Due to the extremely high hardness of diamond, commonly used grinding fluids such as high-hardness materials such as boron carbide (CBN) are difficult to effectively remove diamond materials. In addition, the diamond flattening process requires an acidic chemical reaction (pH < 7), while commonly used polishing fluids mostly use alkaline dispersants (pH > 7), which makes the process incompatible.

[0041] Furthermore, the residues produced after diamond grinding are easily adsorbed on the wafer surface, and it is difficult to completely remove these residues by ordinary cleaning processes, which is an additional challenge for achieving high-quality diamond substrate surfaces. Therefore, the development of effective diamond planarization and cleaning technologies is crucial to improving the application of diamond in the semiconductor field.

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

[0043] Based on this, according to an embodiment of one aspect of the present invention, a diamond planarization method is provided, combining Figure 1~Figure 5 The description includes the following steps S1 to S4.

[0044] Step S1: ablating the diamond surface to be processed by laser;

[0045] Step S2: placing the ablated diamond plane in a polycrystalline diamond grinding liquid for grinding;

[0046] Step S3: chemical mechanical polishing is performed on the ground diamond surface. The chemical mechanical polishing is as follows: a neutral grinding liquid and an acidic polishing liquid are alternately injected into a polishing device;

[0047] Step S4: using a cleaning liquid to clean the diamond surface after chemical mechanical polishing to obtain a diamond surface after planarization.

[0048] According to an embodiment of the present invention, after surface treatment by laser ablation, the total thickness deviation of the diamond plane can be greatly reduced, laying a good foundation for subsequent grinding and polishing processes, and then grinding in a polycrystalline diamond grinding liquid with a hardness close to that of diamond can effectively remove surface materials, and at the same time can reduce scratches and damage while reducing surface roughness, and then chemical mechanical polishing is used to perform global flattening of the diamond surface, reduce the total thickness deviation of the diamond surface, and improve the flatness of the diamond surface. At the same time, alternating between neutral grinding liquid and acid polishing liquid can place the polishing process in an acidic environment, optimize chemical reactions, and improve polishing efficiency and quality. Finally, cleaning liquid is used to clean impurities and by-products to obtain a flattened diamond plane. The diamond flattening method of the present invention can prepare for flattening for subsequent heterogeneous material bonding processes, and improves the performance of heterogeneous bonding circuit devices based on diamond substrates. The entire diamond flattening method is simple to operate, highly efficient, and low cost, and can quickly flatten 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 processed to less than 10 μm;

[0050] In step S2, grinding is used to reduce the total thickness deviation of the diamond plane after ablation to less than 5 μm;

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

[0052] According to an embodiment of the present invention, by using the diamond planarization method of the present invention, the roughness and warping of the diamond substrate can be effectively reduced, so that the warping reaches 5μm and the roughness reaches 0.1nm level, thereby improving the device performance based on the diamond substrate heterogeneous bonding circuit.

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

[0054] According to an embodiment of the present invention, the laser power of laser ablation can be 20w, 22w, 25w, 28w, 30w, but is not limited to the listed values, and other values ​​not listed within the numerical range are equally applicable; the laser ablation can be 2 hours, 4 hours, 6 hours, 8 hours, 10 hours, but is not limited to the listed values, and other values ​​not listed within the numerical range are equally applicable.

[0055] In some specific implementations of the present invention, the foreign material substrate is a support substrate of a diamond plane. The circuit can be prepared on the diamond substrate after diamond planarization treatment. Alternatively, the diamond grown on the prepared circuit can be planarized. In this case, before laser ablation, photoresist needs to be uniformly applied on the front side of the diamond wafer to be thinned and planarized to protect the circuit prepared on the surface of the diamond wafer, and then laser ablation is performed.

[0056] According to the embodiments of the present invention, diamond will be carbonized at 700-800°C. If the power of nanosecond ultraviolet laser is too high, high temperature will be generated, thus carbonizing diamond and destroying the diamond lattice structure. High temperature will increase thermal stress and cause diamond to break. Excessive power will also make ablation products such as material debris difficult to remove. Then, by using low power, high frequency scanning and long-term laser to burn the diamond plane, the influence of thermal stress can be reduced.

[0057] According to an embodiment of the present invention, in step S2, as Figure 3 As shown, the polycrystalline diamond grinding liquid includes polycrystalline diamond particles with a particle size of 10 μm; the pH value of the polycrystalline diamond grinding liquid is 7-8.

[0058] According to an embodiment of the present invention, the pH value of the polycrystalline diamond polishing liquid may be 7, 7.5, or 8, but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

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

[0060] According to an embodiment of the present invention, a particle size of polycrystalline diamond particles in a polycrystalline diamond polishing liquid that is too large may increase the surface roughness, while a particle size that is too small may reduce the removal rate and increase the processing time, so using a particle size of 10 μm can balance the removal rate and roughness. By using a polycrystalline diamond polishing liquid that is alkaline, it is possible to avoid conflict with the acidic environment in subsequent chemical mechanical polishing and achieve compatibility of the process flow.

[0061] According to an embodiment of the present invention, in step S3, Figure 4As shown, the neutral grinding liquid includes polycrystalline diamond particles with a particle size of 20 to 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, 30 nm, but is not limited to the listed values, and other unlisted values ​​within the numerical 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, and it can also be a combination of ethylene glycol, polyethylene glycol PEG-400, polyethylene glycol PEG-600 and polyethylene glycol PEG-6000.

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

[0063] According to an embodiment of the present invention, the volume ratio of the perchlorate solution: the acid agent: water in the acidic polishing liquid includes (0.5~1.5):(4~6):(8~12), which 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, and other unlisted values ​​within the numerical range are also applicable.

[0064] Preferably, the volume ratio of the perchlorate-containing solution: the acid agent: the water in the acidic polishing liquid may be 1:5:10 or 1:6:10.

[0065] According to an embodiment of the present invention, under the action of the acidic polishing liquid, the acid agent provides H + , diamond undergoes relevant chemical reactions in the chemical mechanical polishing device:

[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 agent is at least one of H2SO4 and HCL. When the acid agent is H2SO4, the reaction of chemical mechanical polishing is: H2SO4+C=2SO2+CO2+2H2O.

[0068] In some specific embodiments of the present invention, the perchlorate-containing solution is 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 the embodiments of the present invention, polycrystalline diamond particles can maintain high grinding forces and are not prone to scratches during the grinding and polishing process due to their good toughness. The alcohol solvent acts as a dispersant in the grinding liquid, which helps to evenly disperse the abrasive and plays the role of dilution, lubrication and cooling. Moreover, due to the diversity of impurities in the grinding liquid, the use of multiple alcohol solvents can help improve the dispersion and stability of the abrasive and reduce abrasive agglomeration, thereby improving the grinding efficiency and the surface quality of the workpiece.

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

[0072] According to an embodiment of the present invention, in step S4, 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 an embodiment of the present invention, the pH value of the cleaning solution may be 7.5, 7.8, 8, 8.2, or 8.5, but is not limited to the listed values, and other values ​​not listed within the 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 speed of the fixture 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 an embodiment of the present invention, weakly alkaline NaClO or KClO is used as a weakly alkaline cleaning liquid to remove acidic reaction byproducts. If a strong alkaline cleaning liquid is used, it may react with the cleaning brush of the resin material and is not suitable for cleaning. By using a weakly alkaline cleaning liquid corresponding to the chemical mechanical polishing acidic polishing liquid, the post-grinding residues such as byproducts, impurities, etc. can be simply, quickly and efficiently removed, simplifying the cleaning process.

[0077] According to an embodiment of the present invention, Figure 4 As shown, the polishing equipment includes a polishing disc and a fixture, the polishing disc is used to drive the neutral grinding liquid and the acid polishing liquid to rotate, and the fixture is used to clamp the ground diamond surface;

[0078] The speed of the polishing disc is 50~70rpm and the speed of the fixture is 80~100rpm;

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

[0080] According to an embodiment of the present invention, the rotation speed of the polishing disc can be 55rpm, 60rpm, 65rpm, 70rpm, but is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable. The clamp rotation speed can be 80rpm, 85rpm, 90rpm, 95rpm, 100rpm, but is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable. The time of chemical mechanical polishing can be 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, but is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable.

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

[0082] In some specific implementations of the present invention, the polishing disk may be a nickel-tin-antimony alloy polishing disk, a polyurethane polishing disk, a polyester polishing disk, or the like.

[0083] According to the embodiment of the present invention, the speed of the fixture depends on the stability of the equipment itself. Although high-speed rotation can speed up the polishing speed, it also generates large vibrations, large heat, and increased thermal stress, which can easily lead to diamond breakage. Therefore, a moderate speed should be selected. At the same time, since diamonds are easily broken due to high stress, the additional pressure of the fixture should not be too large. If it exceeds 2kg / inch 2 After the pressure is increased, the polishing rate will not increase significantly, so 0.5-1kg / inch is selected 2 Pressure enables chemical mechanical polishing.

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

[0085] According to an embodiment of the present invention, the duration of neutral polishing liquid injection can be 3 sec, 4 sec, 5 sec, and the injection interval can be 30 sec, 35 sec, 40 sec, 45 sec, 50 sec, but it is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable. The duration of acid polishing liquid injection is 3 sec, 4 sec, 5 sec, and the injection interval can be 30 sec, 35 sec, 40 sec, 45 sec, 50 sec, but it is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable.

[0086] According to an embodiment of the present invention, the neutral grinding liquid injection interval of 3 to 5 seconds can make the grinding disc evenly coated with neutral grinding liquid. If the time is too long, it is easy to cause too many grinding liquid particles and poor fluidity and cause waste. Too much neutral grinding liquid will also destroy the pH environment required for polishing. The acid polishing liquid injection time is 30 to 50 seconds to ensure the time for the acid polishing liquid to chemically react with the diamond plane. If the time is too short, the reaction is insufficient, and if the time is too long, it will cause waste. The injection interval of 3 to 5 seconds can make the alternately injected neutral grinding liquid and acid polishing liquid fully and evenly mixed, and react with the diamond plane to achieve chemical mechanical polishing.

[0087] According to an embodiment of another aspect of the present invention, there is provided an application of a diamond planarization method in manufacturing a semiconductor device.

[0088] According to the 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 processed by the diamond flattening method of the present invention can meet or even exceed the flatness requirements of the semiconductor device for the diamond plane, thereby improving the performance and reliability of the semiconductor device and optimizing the semiconductor device manufacturing process.

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

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

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

[0092] The ablated diamond plane is placed on an iron grinder and is ground with polycrystalline diamond grinding fluid;

[0093] The back of the wafer is adhered to a fixture, and neutral grinding liquid and acid polishing liquid are alternately injected into the chemical mechanical polishing equipment to perform chemical mechanical polishing on the ground diamond plane.

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

[0095] Figure 6 Schematic diagram of diamond crystal grains after planarization in Example 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 flattening reaches the 0.1nm level, and the warpage reaches 5μm, which can meet the requirements of the semiconductor device manufacturing process for the diamond substrate flattening process.

[0097] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is 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 in the scope of protection of the present invention.

Claims

1. A diamond planarization method, comprising: A diamond plane to be processed is ablated by laser; The ablated diamond plane is placed in a polycrystalline diamond grinding liquid for grinding; Performing chemical mechanical polishing on the ground diamond surface, wherein the chemical mechanical polishing is to alternately inject a neutral grinding liquid and an acidic polishing liquid into a polishing device; The diamond surface after chemical mechanical polishing is cleaned by using a cleaning liquid to obtain a diamond surface after flattening treatment.

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

3. The method according to claim 2, wherein: The volume ratio of the perchlorate-containing solution in the acidic polishing liquid: the acid agent: the water is 1: (5-6): 10; The perchlorate-containing solution includes at least one of KClO4, NaClO4 and HClO4; The acid agent includes at least one of H2SO4 and HCL; 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 grinding liquid includes polycrystalline diamond particles with a particle size of 10 μm; The pH value of the polycrystalline diamond grinding liquid is 7-8.

5. The method according to claim 1, wherein: The laser used for laser ablation is a nanosecond ultraviolet laser, the laser power is 20-30w, and the laser ablation time is 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 processed to less than 10 μm; The grinding is used to reduce the total thickness deviation of the diamond plane after the ablation to less than 5 μm; The chemical mechanical polishing is used to reduce the surface roughness Ra value of the ground diamond plane to below 2 nm.

7. The method according to claim 1, wherein: The neutral grinding liquid injection duration is 3 to 5 seconds, and the injection interval is 30 to 50 seconds; The injection duration of the acid polishing liquid is 30 to 50 seconds, and the injection interval is 3 to 5 seconds.

8. 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.

9. The method according to claim 1, wherein: The polishing device comprises a polishing disc and a fixture, wherein the polishing disc is used to drive the neutral grinding liquid and the acidic polishing liquid to rotate, and the fixture is used to clamp the ground diamond surface; The rotation speed of the polishing disc is 50-70 rpm and the rotation speed of the fixture is 80-100 rpm; The chemical mechanical polishing time is 4 to 12 hours.

10. Use of the diamond planarization method according to any one of claims 1 to 9 in the preparation of semiconductor devices.

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