A method of polishing a substrate

Abstract

The application discloses a polishing method of a substrate, comprising the following steps: mechanically polishing the edge of the substrate after chamfering the edge, so that the surface roughness of the edge of the substrate is less than 10nm; chemically mechanically polishing the edge of the substrate after mechanical polishing, and the chemical mechanical polishing comprises a rough polishing step and a fine polishing step in sequence; the rough polishing step comprises: using an acidic polishing liquid to rough polish the edge of the substrate, so that the surface roughness of the edge of the substrate is less than 0.2nm; the fine polishing step comprises: when the substrate is a silicon carbide substrate, using an alkaline polishing liquid to fine polish the edge of the substrate, so that the surface roughness of the edge of the substrate is less than 0.1nm; when the substrate is a gallium nitride substrate, using an acidic polishing liquid to fine polish the edge of the substrate, so that the surface roughness of the edge of the substrate is less than 0.1nm. The polishing method of the substrate is used for reducing the probability of surface defects generated by the substrate, and improving the yield and quality of the substrate.

Description

Technical Field

[0001] This invention relates to the field of polishing technology, and more particularly to a method for polishing a substrate. Background Technology

[0002] Substrates are the fundamental materials for semiconductor devices, and their quality directly affects the quality and cost of the devices. Silicon carbide (SiC) and gallium nitride (GaN) are typical materials for third-generation semiconductors, possessing wide bandgap, high thermal conductivity, high breakdown electric field, high electron saturation velocity, and high radiation resistance. They are suitable for fabricating high-temperature, high-frequency, high-power, radiation-resistant high-power devices, and have significant advantages in applications such as next-generation deep ultraviolet optoelectronic devices and high-voltage high-power power electronic devices. They are widely used in industries such as 5G communications, electric vehicles, charging piles, high-speed rail transportation, and high-voltage power transmission and transformation.

[0003] However, existing silicon carbide and gallium nitride substrates may have defects such as surface scratches and cracks during the manufacturing process, which will affect the yield and quality of the substrates. Summary of the Invention

[0004] Research and analysis of existing substrate fabrication processes revealed that, for example... Figure 1 and Figure 2 As shown, after the edges of the existing substrate are chamfered, micro-defects such as edge chipping and fragmentation, stress damage layers on the sides and ends, and impurities such as various metal ions will be formed at the chamfer. This may cause the chamfer of the substrate to peel off and chip in subsequent processes. The peeled material has high hardness and may scratch the surface of the substrate.

[0005] Further in-depth research and analysis of existing substrate manufacturing methods revealed that the above problems arise because existing technologies only chamfer the edges of substrate cut pieces. The edges have defects such as microcracks, micro-chipping, and low smoothness caused by the chamfering process. The substrate products do not undergo edge polishing processing.

[0006] Chamfering typically involves mechanically grinding the upper, end, and lower sides of the cutting disc using diamond grinding wheels with a grit size of 400#-1500#. This grinding process incurs high stress and easily disrupts crystal lattice integrity. Furthermore, the coarse diamond grit and poor particle uniformity result in several issues on the sides and ends of the cutting disc after chamfering: microscopic defects remaining from the chamfering process, such as chipping, breakage, stress damage layers, and impurities like various metal ions. The presence of these microscopic defects and damage layers can lead to the shedding and chipping of minute amounts of silicon carbide material during subsequent product processing. Silicon carbide has an extremely high Mohs hardness of 9.2, while gallium nitride has a Mohs hardness of 8.5. The detached material causes severe surface scratches during substrate processing, leading to a decrease in substrate product yield and quality.

[0007] If the edges of silicon carbide and gallium nitride substrates are not properly treated, harmful particles on the edges can easily be carried to the positive surface of the substrate. Lattice defects or damage on the edges can also easily cause the substrate to crack in subsequent processing or bring defects such as scratches to the positive surface.

[0008] To address the above problems, the present invention aims to provide a substrate polishing method to reduce the probability of surface defects on the substrate and improve the substrate yield and quality.

[0009] The objective of this invention is achieved through the following technical solution:

[0010] A method for polishing a substrate includes the following steps:

[0011] The edges of the substrate after chamfering are mechanically polished to make the surface roughness of the substrate edges less than 10 nm;

[0012] The edges of the substrate that have undergone mechanical polishing are subjected to chemical mechanical polishing, which includes a coarse polishing step and a fine polishing step in sequence.

[0013] The rough polishing step includes: using an acidic polishing solution to rough polish the edges of the substrate, so that the surface roughness of the substrate edges is less than 0.2 nm;

[0014] The fine polishing step includes: when the substrate is a silicon carbide substrate, using an alkaline polishing solution to finely polish the edges of the substrate so that the surface roughness of the substrate edges is less than 0.1 nm; when the substrate is a gallium nitride substrate, using an acidic polishing solution to finely polish the edges of the substrate so that the surface roughness of the substrate edges is less than 0.1 nm.

[0015] Preferably, mechanical polishing of the edges of the substrate includes:

[0016] The upper side, outer end face, and lower side of the substrate edge are mechanically polished using a diamond sintered grinding wheel with a particle size of 3000-30000#. The rotation speed of the diamond sintered grinding wheel is 45000-150000 rpm, and the rotation speed of the substrate is 1-20 rpm. The rotation direction of the diamond sintered grinding wheel is opposite to the rotation direction of the substrate.

[0017] Preferably, during the mechanical polishing process, deionized water or silica polishing slurry is sprayed onto the area to be polished.

[0018] Preferably, in the silica polishing slurry, the concentration of abrasive silica is 5-10 wt%, the particle size of the abrasive silica is 500-800 nm, the pH value of the silica polishing slurry is 9-11, the temperature of the silica polishing slurry is 40-45℃, and the polishing pressure of the silica polishing slurry is 200-250 g / cm. 2 Polishing time is 1-15 minutes;

[0019] When the substrate is a silicon carbide substrate, the dripping rate of the silicon dioxide polishing slurry is 0.5-1 L / min;

[0020] When the substrate is a gallium nitride substrate, the dripping rate of the silicon dioxide polishing slurry is 0.1-0.3 L / min.

[0021] Preferably, the substrate is a gallium nitride substrate, and mechanical polishing of the edges of the substrate includes:

[0022] The upper, end, and lower sides of the gallium nitride substrate edge are mechanically polished using a copper wheel with a purity of ≥99.5%. The copper wheel rotates at a speed of 45,000-150,000 rpm, and the substrate rotates at a speed of 1-20 rpm. The rotation direction of the copper wheel is opposite to that of the substrate.

[0023] Preferably, during the mechanical polishing process, liquid diamond is sprayed onto the area to be polished;

[0024] The diamond particles in the diamond solution have a diameter of 1-3 μm and a content of 5-10 wt%; the pH value of the diamond solution is 9-11; the temperature of the diamond solution is 30-40℃; and the polishing pressure of the diamond solution is 200-250 g / cm. 2 Polishing time is 1-15 minutes, and drip rate is 0.1-0.3 L / min.

[0025] Preferably, the polishing wheel for chemical mechanical polishing is provided with a polishing part for polishing, the polishing part is made of a flexible material, the polishing part is capable of storing and releasing polishing liquid, the rotation speed of the polishing wheel is 45,000-150,000 rpm, the rotation speed of the substrate is 1-20 rpm, and the rotation direction of the polishing wheel is opposite to the rotation direction of the substrate.

[0026] Preferably, the polishing section is used to simultaneously polish the upper side surface, outer end surface and lower side surface of the substrate edge, and the polishing section is retractably disposed on the polishing wheel.

[0027] Preferably, the acidic polishing solution in the coarse polishing step has a pH value of 5-6.5 and, by weight percentage, in addition to the remaining water and suspending agent, the acidic polishing solution further comprises:

[0028] Alumina, 2-15 wt%;

[0029] Potassium permanganate, 5-8 wt%.

[0030] Preferably, in the acidic polishing slurry, the particle size of the abrasive alumina is 100-300 nm, the temperature of the acidic polishing slurry is 40-45°C, the dripping rate of the acidic polishing slurry is 0.3-0.5 L / min, and the polishing pressure is 200-250 g / cm³. 2 Polishing time is 1-10 minutes; and / or,

[0031] The pH value of the acidic polishing solution is adjusted by adding 2-5% wt% KOH or Mg(OH)2 aqueous solution and 2-10 wt% dilute hydrochloric acid or nitric acid aqueous solution.

[0032] Preferably, the substrate is a silicon carbide substrate, and the alkaline polishing solution in the fine polishing step has a pH value of 9-11. In addition to the remaining water and suspending agent, the alkaline polishing solution, by weight percentage, further comprises:

[0033] Silica, 5-15 wt%;

[0034] Hydrogen peroxide, 0.5-3 wt%.

[0035] Preferably, in the alkaline polishing slurry, the particle size of the abrasive silica is 40-200 nm, the temperature of the polishing slurry is 40-45°C, the dripping rate of the alkaline polishing slurry is 0.3-0.5 L / min, and the polishing pressure is 200-250 g / cm³. 2 Polishing time is 1-15 minutes; and / or,

[0036] The pH value of the alkaline polishing solution is adjusted by adding one or more of the following: hydrochloric acid aqueous solution, acetic acid aqueous solution, citric acid aqueous solution, 5-20 wt% KOH aqueous solution, and 1-5 wt% HNO3 aqueous solution.

[0037] Preferably, the substrate is a gallium nitride substrate, and the fine polishing step includes: polishing the edge of the gallium nitride substrate with an acidic polishing solution to make the surface roughness of the edge of the gallium nitride substrate less than 0.1 nm;

[0038] The acidic polishing solution has a pH value of 6-7 and, by weight percentage, comprises, in addition to the balance of water and suspending agent:

[0039] Silicon dioxide, 3-10 wt%;

[0040] Hydrogen peroxide, 1-5 wt%.

[0041] Preferably, in the acidic polishing slurry, the particle size of the abrasive silica is 40-200 nm, the temperature of the polishing slurry is 30-45°C, the dripping rate of the acidic polishing slurry is 0.1-0.3 L / min, and the polishing pressure is 200-250 g / cm³. 2 Polishing time is 5-10 minutes; and / or,

[0042] The pH value of the acidic polishing solution is adjusted by adding one or more of the following: hydrochloric acid aqueous solution, acetic acid aqueous solution, citric acid aqueous solution, 1-3 wt% KOH aqueous solution, and 5-10 wt% HNO3 aqueous solution.

[0043] Compared with the prior art, the beneficial effects of the present invention include at least the following:

[0044] By performing mechanical polishing and chemical mechanical polishing on the chamfered substrate edges, a smooth frosted effect can be achieved, improving the substrate's smoothness and crystal integrity. At the same time, it can remove the damaged layer with defects such as scratches, pits, and microcracks from the substrate edges, thereby reducing the risk of particle shedding and substrate surface cracking caused by defects in the damaged layer in subsequent processes, and improving the substrate yield and quality. Attached Figure Description

[0045] Figure 1 These are atomic force microscope images of the upper and lower sides of the silicon carbide substrate after the edge beveling in an embodiment of the present invention;

[0046] Figure 2 These are atomic force microscope images of the outer end face of a silicon carbide substrate after edge beveling, according to an embodiment of the present invention.

[0047] Figure 3 These are atomic force microscope images of the upper and lower sides of the edge of a silicon carbide substrate after polishing, according to an embodiment of the present invention.

[0048] Figure 4 This is an atomic force microscope image of the outer end face of the edge of a silicon carbide substrate after polishing, according to an embodiment of the present invention.

[0049] Figure 5 This is a schematic diagram of the substrate edge polishing device and the substrate according to an embodiment of the present invention;

[0050] Figure 6 This is a schematic diagram of the substrate structure according to an embodiment of the present invention;

[0051] Figure 7This is a schematic diagram of the structure of a polishing wheel assembly according to an embodiment of the invention;

[0052] Figure 8 This is a schematic diagram of the substrate edge polishing device and substrate according to another embodiment of the invention;

[0053] Figure 9 This is a schematic diagram of the structure of a polishing wheel assembly according to another embodiment of the invention.

[0054] In the figure: 100, substrate; 101, upper side surface; 102, lower side surface; 103, outer end face; 1, mounting platform; 2, polishing wheel assembly; 21, substrate; 211, cavity; 212, adjustment component; 22, polishing part; 23, first contact part; 24, second contact part; 25, third contact part; 26, end face polishing wheel; 27, side polishing wheel; 3, liquid spraying component; 31, nozzle; 4, liquid baffle. Detailed Implementation

[0055] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, they are provided to make the invention more comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and therefore repeated descriptions of them will be omitted.

[0056] The terms used to express position and direction in this invention are illustrated with the accompanying drawings, but changes can be made as needed, and all such changes are included within the scope of protection of this invention.

[0057] This invention provides a method for polishing a substrate, which is a silicon carbide substrate or a gallium nitride substrate, and the polishing is performed after chamfering the substrate and before polishing the upper and lower surfaces of the substrate. The substrate polishing method includes steps S01 and S02.

[0058] Step S01: Mechanically polish the edges of the substrate after chamfering to make the surface roughness of the substrate edges less than 10nm.

[0059] Step S02: Perform chemical mechanical polishing on the edge of the substrate after mechanical polishing to make the surface roughness of the substrate edge less than 0.1 nm. Chemical mechanical polishing includes a rough polishing step and a fine polishing step.

[0060] In some specific embodiments, step S01, mechanical polishing of the substrate edge may include: using a sintered diamond wheel with a particle size of 3000-30000# to mechanically polish the upper side, outer end face, and lower side of the substrate edge. The rotational speed of the sintered diamond wheel is 45000-150000 rpm, the rotational speed of the substrate is 1-20 rpm, and the rotation direction of the sintered diamond wheel is opposite to the rotation direction of the substrate to enhance the polishing effect of the sintered diamond wheel on the substrate. The sintered diamond wheel may use a ceramic binder to fix the abrasive particles onto the wheel structure.

[0061] To improve the efficiency of mechanical polishing, deionized water or silica polishing slurry can be sprayed during the process. For substrates with high hardness, such as silicon carbide and gallium nitride substrates, spraying silica polishing slurry is preferred. In the silica polishing slurry, the concentration of abrasive silica can be 5-10 wt%, the particle size of the abrasive silica can be 500-800 nm, the pH value of the silica polishing slurry is 9-11, the temperature of the silica polishing slurry is 40-45℃, and the polishing pressure of the silica polishing slurry can be 200-250 g / cm³. 2 Polishing time can range from 1 to 15 minutes. The drip rate of the silica polishing slurry can vary depending on the substrate. For example, when mechanically polishing a silicon carbide substrate, the drip rate of the silica polishing slurry is 0.5-1 L / min; when mechanically polishing a gallium nitride substrate, the drip rate of the silica polishing slurry is 0.1-0.3 L / min.

[0062] During mechanical polishing, since silicon carbide crystals have a hardness of up to 9.2 on the Mohs scale, second only to diamond's 10, a high-hardness diamond grinding wheel is used to mechanically grind the silicon carbide crystals. A fine-grained sintered diamond grinding wheel is used to rotate and process the substrate. This allows the diamond particles on the sintered diamond grinding wheel to exert a strong physical crushing effect on the upper, outer, and lower edges of the substrate. Through mechanical friction between the diamond particles and the substrate, the damaged layer at the chamfered edges of the substrate is removed.

[0063] Furthermore, during mechanical polishing, silica polishing slurry can not only improve polishing efficiency and effect, but also remove the damaged layer that separates from the substrate during the polishing process. For example... Figure 3 and Figure 4 As shown, after mechanical polishing, the upper, outer, and lower sides of the substrate edge can form a smooth frosted effect. After removing the damaged layer, defects such as scratches, pits, and microcracks that were originally present on the upper, outer, and lower sides of the substrate edge can also be removed.

[0064] In some other specific embodiments, when the substrate is a gallium nitride substrate, mechanical polishing of the substrate edge may include: using a copper wheel with a purity of ≥99.5% to mechanically polish the upper side, end face and lower side of the gallium nitride substrate edge, the copper wheel rotating at a speed of 45,000-150,000 rpm, the gallium nitride substrate rotating at a speed of 1-20 rpm, and the rotation direction of the copper wheel being opposite to the rotation direction of the gallium nitride substrate.

[0065] To improve the efficiency of mechanical polishing, molten diamond can be sprayed during the process. Molten diamond, combined with materials such as pure copper or resin-coated copper, is well-suited for precision machining of gallium nitride (GaN) materials, resulting in fewer scratches and a smoother surface. This is because copper is softer than other metals, preventing scratches during precision machining of GaN with molten diamond. Especially when large diamond particles are present in the molten diamond, the combined action of a copper wheel of appropriate hardness and the molten diamond can both grind away surface damage and achieve a smooth, polished surface.

[0066] The diamond particles in the diamond solution have a diameter of 1-3 μm and a content of 5-10 wt%; the pH value of the diamond solution is 9-11, the temperature is 30-40℃, and the polishing pressure is 200-250 g / cm. 2 The polishing time is 1-15 minutes, and the drip rate is 0.1-0.3 L / min. Using a diamond slurry with diamond particle diameters of 1-3 μm and a diamond particle content of 5-10 wt% avoids severe scratching of the substrate surface by large or high-content diamond particles; it also avoids low polishing efficiency due to small or low-content diamond particles, preventing completion of the polishing operation within the standard polishing time. For mechanical polishing, a polishing time of 1-15 minutes avoids damage to the surface quality of the substrate edges due to prolonged polishing time, and also avoids poor polishing results due to shorter polishing time. The polishing pressure of the diamond slurry is selected as 200-250 g / cm². 2 This approach avoids both low polishing pressure leading to low polishing efficiency and high polishing pressure causing "orange peel" defects at the substrate edges—a type of uneven, undulating, granular defect resembling orange peel texture. By selecting a diamond slurry temperature of 30-40℃, it avoids both low temperature leading to low polishing efficiency and high temperature causing "surface ablation" defects.

[0067] During mechanical polishing, a copper wheel is used to mechanically rub the upper, outer, and lower surfaces of the gallium nitride substrate edge to remove the damaged layer at the chamfered edge. After mechanical polishing, the upper, outer, and lower surfaces of the substrate edge will have a smooth frosted effect. Removing the damaged layer also removes existing defects such as scratches, pits, and microcracks from the upper, outer, and lower surfaces of the substrate edge.

[0068] The above-described mechanical polishing steps can be performed using existing polishing equipment. The chamfered substrate is placed on the stage of the existing polishing equipment and fixed by vacuum adsorption. A high-precision optical sensor is used to accurately measure and position the substrate, ensuring a measurement accuracy of + / -0.01 mm. During mechanical polishing, the polishing portion of the diamond sintered wheel or copper wheel is first positioned at the same height as the substrate, with the center of the diamond sintered wheel or copper wheel along the height direction deviating from the center of the substrate along the height direction by less than 0.01 mm. Then, the motor is started to perform the mechanical polishing steps.

[0069] In step S02, the polishing wheel for chemical mechanical polishing is provided with a polishing section for polishing. The polishing section can be made of a flexible material and can store and release polishing fluid. In some preferred embodiments, the polishing section can be used to simultaneously polish the upper side, outer end face, and lower side of the substrate edge to improve the efficiency of chemical mechanical polishing; and the polishing section is retractably mounted on the polishing wheel so that one polishing wheel can handle substrate edges of different shapes. During chemical mechanical polishing, the rotation speed of the polishing wheel is 45,000-150,000 rpm, the rotation speed of the substrate is 1-20 rpm, and the rotation direction of the polishing wheel is opposite to the rotation direction of the substrate.

[0070] In step S02, the rough polishing step includes: using an acidic polishing solution to rough polish the edge of the substrate so that the surface roughness of the substrate edge is less than 0.2 nm.

[0071] The pH value of the acidic polishing solution in the rough polishing step is 5-6.5. The acidic polishing solution can be an alumina polishing solution. Specifically, the pH value of the acidic polishing solution can be adjusted by adding 2-5% (w / w) of KOH or Mg(OH)₂ aqueous solution and 2-10% (w / w) of dilute hydrochloric acid or nitric acid aqueous solution. By weight percentage, the acidic polishing solution includes 2-15 wt% alumina, 5-8 wt% potassium permanganate, and the balance can be water and a suspending agent. The water content can be around 80 wt%, for example, 75-85 wt%. The suspending agent is one or more of polyurethane, polyvinyl alcohol, or sodium polyacrylate, etc. The particle size of the abrasive alumina is 100-300 nm. During rough polishing, the temperature of the acidic polishing solution is 40-45℃, the drip rate of the acidic polishing solution is 0.3-0.5 L / min, and the polishing pressure is 200-250 g / cm³. 2 The polishing time is 1-10 minutes. The silicon carbide substrate is chemically and mechanically polished by oxidizing and etching the upper, outer, and lower edges of the substrate with the strong oxidant potassium permanganate, followed by mechanical grinding with nano-sized alumina particles.

[0072] In step S02, the fine polishing step includes: when the substrate is a silicon carbide substrate, using an alkaline polishing solution to finely polish the edges of the substrate so that the surface roughness of the substrate edges is less than 0.1 nm; when the substrate is a gallium nitride substrate, using an acidic polishing solution to finely polish the edges of the substrate so that the surface roughness of the substrate edges is less than 0.1 nm.

[0073] When the substrate is silicon carbide, the pH value of the alkaline polishing solution in the fine polishing step is 9-11. The alkaline polishing solution can be a prepared silica polishing solution with good suspension, high dispersibility, high uniformity, and non-crystallization properties. Specifically, the pH value of the alkaline polishing solution can be adjusted by adding one or more of the following: hydrochloric acid aqueous solution, acetic acid aqueous solution, citric acid aqueous solution, 5-20 wt% KOH aqueous solution, and 1-5 wt% HNO3 aqueous solution. Using a mixture of KOH aqueous solution and HNO3 aqueous solution to form a buffer solution can improve the accuracy of pH adjustment. By weight percentage, the alkaline polishing solution includes 5-15 wt% silica, 0.5-3 wt% hydrogen peroxide, and the balance can be water and a suspending agent, with a water content of approximately 80 wt%, for example, 75-85 wt%. The suspending agent is one or more of the following: polyurethane, polyvinyl alcohol, or sodium polyacrylate. The abrasive silica particles have a size of 40-200 nm, the polishing slurry temperature is 40-45℃, the alkaline polishing slurry dripping rate is 0.3-0.5 L / min, and the polishing pressure is 200-250 g / cm³. 2The polishing time is 1-15 minutes. Using silica polishing slurry to finely polish the silicon carbide substrate can further improve the polishing effect, so that the roughness of the upper side, outer end face and lower side of the silicon carbide substrate edge can be less than 0.1nm, and there are no defects such as scratches, pits and microcracks on the upper side, outer end face and lower side of the silicon carbide substrate edge.

[0074] In fine polishing using an alkaline polishing slurry, silicon carbide reacts with the perhydroxyl groups in the slurry. Under the action of hydrogen peroxide as an oxidant and catalyst, a silicon oxide modified layer is formed on the surface of the silicon carbide edges, which is then removed by the polishing wheel. The reaction principle of silicon carbide with the alkaline polishing slurry is as follows:

[0075] H2O2→H + +HO2 - ;

[0076] H + +OH - →H2O;

[0077] H2O2+OH - →HO2 - +H2O;

[0078] 2SiC+4HO2 - +4H₂O₂→2SiO₃ 2- +2CO2+6H2O.

[0079] The polishing method described above can be applied to conductive and semi-insulating silicon carbide substrates, or to silicon carbide substrates with different crystal forms such as 4H, 6H, and 3C. It can also be applied to silicon carbide substrates of various sizes, such as four-inch, six-inch, eight-inch, ten-inch, and twelve-inch substrates.

[0080] When the substrate is gallium nitride (GaN) substrate, the chemical mechanical polishing (CMP) step includes polishing the edges of the GaN substrate using an acidic polishing slurry to achieve a surface roughness of less than 0.1 nm. The acidic polishing slurry has a pH of 6-7, and its pH is adjusted by adding one or more of the following: 3-10 wt% hydrochloric acid aqueous solution, acetic acid aqueous solution, citric acid aqueous solution, 1-3 wt% KOH aqueous solution, and 5-10 wt% HNO3 aqueous solution. By weight percentage, the acidic polishing slurry comprises 3-10 wt% silica, 1-5 wt% hydrogen peroxide, and the balance may be water and a suspending agent. The water content may be approximately 80 wt%, for example, 75-85 wt%. The suspending agent is one or more of the following: polyurethane, polyvinyl alcohol, or sodium polyacrylate. The silica particles in the acidic polishing slurry have a particle size of 40-200 nm. During chemical mechanical polishing, the temperature of the acidic polishing solution is 30-45℃, the drip rate of the acidic polishing solution is 0.1-0.3 L / min, and the polishing pressure is 200-250 g / cm³. 2 Polishing time is 5-10 minutes.

[0081] Chemical mechanical polishing can be performed using a substrate edge polishing device, which includes a mounting stage 1, a polishing wheel assembly 2, and a liquid spraying component 3.

[0082] Further reference Figure 5 and Figure 6 Mounting stage 1 is used to mount substrate 100. The cross-sectional dimension of mounting stage 1 is smaller than that of substrate 100. For example, when substrate 100 is stacked on mounting stage 1 in its thickness direction, the cross-sectional dimension of mounting stage 1 in the horizontal direction is smaller than that of substrate 100 in the horizontal direction. Therefore, when substrate 100 is mounted on mounting stage 1, the outer end of substrate 100 can protrude outward from mounting stage 1. The outer end of substrate 100 can be the end of substrate 100 that is chamfered, i.e., the end of substrate 100 to be processed. Therefore, the end of substrate 100 to be processed can protrude outward from mounting stage 1, which facilitates polishing of the end of substrate 100 to be processed. The substrate 100 can be a silicon carbide substrate 100. The end of the substrate 100 to be processed is the outer end of the substrate 100 perpendicular to the thickness direction of the substrate 100. The end to be processed has an upper side surface 101 and a lower side surface 102 formed after polishing, and an outer end surface 103 connecting the upper side surface 101 and the lower side surface 102. The upper side surface 101 is a chamfered surface located above the substrate 100 after chamfering the substrate 100. The lower side surface 102 is another chamfered surface located below the substrate 100 after chamfering the substrate 100. The outer end surface 103 is the surface located between the upper side surface 101 and the lower side surface 102, and the outer end surface 103 is parallel or approximately parallel to the thickness direction of the silicon carbide substrate 100.

[0083] Mounting stage 1 can fix the substrate 100 by vacuum adsorption. For example, mounting stage 1 can be provided with multiple vacuum suction ports that can generate negative pressure suction. When the substrate 100 is mounted on mounting stage 1, the substrate 100 covers the multiple vacuum suction ports so that the suction generated by the vacuum suction ports can adsorb and fix the substrate 100. In addition, mounting stage 1 can also adopt other methods. For example, mounting stage 1 includes a table surface and a pressure plate disposed on the table surface, and the substrate 100 is pressed and fixed on the table surface by the pressure plate.

[0084] The mounting stage 1 can also rotate, allowing the substrate 100 mounted on it to rotate during polishing, thus eliminating the need for the polishing wheel assembly 2 to cover all areas of the substrate 100 requiring polishing. Structures enabling the rotation of the mounting stage 1 are widely used in the prior art and will not be described in detail here. Furthermore, the mounting stage 1 can be connected to a horizontal drive device, allowing it to move away from the polishing wheel assembly 2 when the substrate 100 needs to be mounted, and to move to the working position when polishing the substrate 100 is required. The horizontal drive device can be a hydraulic cylinder, pneumatic cylinder, motor, or similar structure.

[0085] The nozzle 31 of the spraying component 3 is positioned towards the polishing wheel assembly 2, so that the spraying component 3 can spray polishing liquid from the nozzle 31 towards the area to be polished at the edge of the substrate 100 and / or the polishing wheel assembly 2. By spraying polishing liquid onto the area to be polished and / or the polishing wheel assembly 2, the polishing wheel assembly 2 can cooperate with the polishing liquid to form chemical mechanical polishing, thereby effectively reducing or avoiding micro-defects such as edge chipping and breakage on the side and outer end face of the substrate chamfer, and improving the polishing effect.

[0086] In some specific embodiments, two spray nozzles 3 may be provided, located at opposite ends of the polishing wheel assembly 2, for example, at opposite ends of the polishing wheel assembly 2 along the thickness direction of the substrate 100. One spray nozzle 3 may be located diagonally above the polishing wheel assembly 2, and the other spray nozzle 3 may be located diagonally below the polishing wheel assembly 2. By providing two spray nozzles 3, polishing liquid can be sprayed onto opposite sides of the polishing wheel assembly 2, balancing the content of polishing liquid in different parts of the polishing wheel assembly 2, thereby balancing the polishing effect of the polishing wheel assembly 2 on different surfaces of the substrate 100.

[0087] Further reference Figure 7The polishing wheel assembly 2 includes a base 21 and at least a portion of a polishing part 22 disposed on the outer periphery of the base 21. The polishing part 22 is used to contact the substrate 100 to polish the substrate 100. The polishing part of the polishing part 22 is made of a flexible material. Using a flexible material can achieve both polishing and reduce or avoid microscopic defects such as edge chipping and breakage on the side and outer end face of the substrate chamfer. The polishing part 22 has multiple contact portions formed along the thickness direction of the substrate 100. Each contact portion can contact one surface of the substrate 100, thereby polishing one surface of the substrate 100. When the polishing part 22 contacts the substrate 100, multiple polishing parts 22 can contact the substrate 100 simultaneously to polish multiple surfaces of the substrate 100 at the same time.

[0088] The substrate 21 can be connected to a rotating device so that the rotating device can drive the substrate 21 to rotate, thereby allowing the polishing part 22 connected to the substrate 21 to rotate at a high speed during use, thereby performing a polishing operation on the substrate 100. The structure for driving the base to rotate is widely used in the prior art, so it will not be described in detail here.

[0089] The polishing section 22 may be provided with two contact portions to simultaneously polish two surfaces of the edge of the substrate 100. For example, the polishing section 22 may be provided with a first contact portion 23 and a second contact portion 24. The first contact portion 23 is used to contact the upper side surface 101 or the lower side surface 102 of the edge of the substrate 100 to polish the upper side surface 101 or the lower side surface 102 of the edge of the substrate 100. In this embodiment, the first contact portion 23 may be used to contact the upper side surface 101 of the edge of the substrate 100. The second contact portion 24 is used to contact the outer end surface 103 of the edge of the substrate 100 to polish the outer end surface 103 of the edge of the substrate 100.

[0090] In some specific embodiments, the polishing part 22 may be provided with a first contact part 23, a second contact part 24, and a third contact part 25; the first contact part 23, the second contact part 24, and the third contact part 25 are arranged sequentially along the thickness direction of the substrate 100. The first contact part 23 is used to contact the upper side surface 101 of the edge of the substrate 100, the second contact part 24 is used to contact the outer end surface 103 of the edge of the substrate 100, and the third contact part 25 is used to contact the lower side surface 102 of the edge of the substrate 100.

[0091] In some specific embodiments, the polishing section 22 may include multiple polishing cloths. The polishing section is capable of storing and releasing polishing fluid. The multiple polishing cloths may be distributed sequentially along the thickness direction of the substrate 100, and each polishing cloth is disposed around the outer periphery of the base 21. One end of the polishing cloth protrudes outward from the base 21 for contact with the substrate 100, and the other end of the polishing section 22 may be fixed to the outer wall of the base 21 or extend into the interior of the base 21. The polishing cloth may be a damping cloth or a non-woven fabric. The damping cloth or non-woven fabric can absorb and store the polishing fluid and slowly release the polishing fluid during the polishing process, thereby improving the utilization rate of the polishing fluid and ensuring that the area to be polished at the edge of the substrate 100 is fully wetted. Furthermore, using polishing cloth can further reduce or avoid microscopic defects such as edge chipping and breakage at the side and outer end faces of the substrate chamfer, thereby improving the polishing effect.

[0092] The ends of a plurality of polishing cloths that are used to contact the upper side surface 101 of the edge of the substrate 100 together form a first contact portion 23. The ends of a plurality of polishing cloths that are used to contact the outer end surface 103 of the edge of the substrate 100 together form a second contact portion 24. The ends of a plurality of polishing cloths that are used to contact the lower side surface 102 of the edge of the substrate 100 together form a third contact portion 25.

[0093] In one specific embodiment, since the upper side 101, lower side 102, and outer end face 103 of the edge of the substrate 100 are located on different planes, in order to facilitate the contact between the polishing part 22 and the substrate 100, at least part of the polishing cloth extends from the substrate 21 to different lengths in the direction toward the outer end face 103 of the edge of the substrate 100. For example, when the upper side 101 and lower side 102 are inclined surfaces, the outer end face 103 is a vertical surface, and the polishing cloth protrudes outward from the substrate 21 in the horizontal direction, the lengths of the multiple polishing cloths for contacting the upper side 101 of the edge of the substrate 100 and the multiple polishing cloths for contacting the lower side 102 of the edge of the substrate 100 extending from the substrate 21 toward the outer end face 103 of the edge of the substrate 100 are different, so that the first contact end forms an inclined surface adapted to the upper side 101 of the edge of the substrate 100, and the third contact end forms an inclined surface adapted to the lower side 102 of the edge of the substrate 100; the polishing cloths for contacting the outer end face 103 of the edge of the substrate 100 extend from the substrate 21 toward the outer end face 103 of the substrate 100 for the same length, so that one end of the second contact end forms a vertical contact surface adapted to the outer end face 103 of the edge of the substrate 100.

[0094] The distance between the first contact portion 23 and the third contact portion 25 and the substrate 21 can be greater than the distance between the second contact portion 24 and the substrate 21, so that when the polishing portion 22 polishes, the first contact portion 23, the second contact portion 24 and the third contact portion 25 form a concave shape. The upper side surface 101, the outer end surface 103 and the lower side surface 102 of the edge of the substrate 100 will also form a convex shape, and the concave shape formed by the first contact portion 23, the second contact portion 24 and the third contact portion 25 is adapted to the convex shape formed by the substrate 100.

[0095] Preferably, a cavity 211 extending along the thickness direction of the substrate 100 is formed within the substrate 21. The cavity 211 may house a plurality of adjusting members 212. One end of at least one polishing cloth penetrates the substrate 21 and is connected to at least one adjusting member 212. The adjusting member 212 is used to adjust the length of the polishing cloth protruding from the substrate 21, so that the shape or position of the first contact portion 23, the second contact portion 24, or the third contact portion 25 formed by the plurality of polishing cloths relative to the substrate 21 can be changed to achieve polishing operations on substrates 100 of different sizes.

[0096] The adjusting member 212 includes at least three members: at least one adjusting member 212 is connected to at least one polishing cloth forming the first contact portion 23, at least another adjusting member 212 is connected to at least one polishing cloth forming the second contact portion 24, and at least another adjusting member 212 is connected to at least one polishing cloth forming the third contact portion 25, so that the first contact portion 23, the second contact portion 24, and the third contact portion 25 can be adjusted independently.

[0097] In yet another specific embodiment, such as Figure 8 and Figure 9 As shown, the polishing wheel assembly 2 includes an end face polishing wheel 26 and at least one side polishing wheel 27.

[0098] The outer periphery of the end-face polishing wheel 26 forms a second contact portion 24, which is used to contact the outer end face 103 of the substrate 100 edge to polish the outer end face 103 of the substrate 100 edge. The end-face polishing wheel 26 may include a base 21 and a plurality of polishing cloths disposed around the outer periphery of the base 21, the plurality of polishing cloths being distributed sequentially along the circumference of the base 21. One end of each polishing cloth is fixedly connected to the base 21, and the other end of the polishing cloth is used to contact the outer end face 103 of the substrate 100 edge. The ends of the plurality of polishing cloths used to contact the outer end face 103 of the substrate 100 edge together form the second contact portion 24, and the length of the plurality of polishing cloths protruding from the substrate 100 may be the same.

[0099] At least one side polishing wheel 27 has a first contact portion 23 formed on its outer periphery, which is used to contact the upper side surface 101 or the lower side surface 102 of the edge of the substrate 100 to polish the upper side surface 101 or the lower side surface 102 of the edge of the substrate 100. In this embodiment, two side polishing wheels 27 are provided. The outer periphery of one side polishing wheel 27 forms the first contact portion 23, and the first contact portion 23 is specifically used to contact the upper side surface 101 of the edge of the substrate 100. The outer periphery of the other side polishing wheel 27 forms a third contact portion 25, which is used to contact the lower side surface 102 of the edge of the substrate 100. The two side polishing wheels 27 can be arranged on both sides of the end face polishing wheel 26 along the thickness direction of the substrate 100, and the end face polishing wheel 26 and the side polishing wheel 27 are staggered along the thickness direction of the substrate 100, so that the first contact portion 23 or the third contact portion 25 and the second contact portion 24 are staggered along the thickness direction of the substrate 100. Specifically, the distance between the two side polishing wheels 27 and the axis of the substrate 100 is smaller than the distance between the end face polishing wheel 26 and the axis of the substrate 100, so that the first contact portion 23 and the third contact portion 25 formed by the two side polishing wheels 27 and the second contact portion 24 formed by the end face polishing wheel 26 form a concave shape, which in turn matches the convex shape formed by the upper side surface 101, the outer end surface 103 and the lower side surface 102 of the edge of the substrate 100.

[0100] The side polishing wheel 27 can adopt a similar structure to the end face polishing wheel 26. That is, the side polishing wheel 27 can include a base 21 and a plurality of polishing cloths arranged around the base 21. The plurality of polishing cloths are distributed sequentially along the circumference of the base 21. One end of each polishing cloth is fixedly connected to the base 21, and the other end of the polishing cloth is used to contact the upper side 101 or the lower side 102 of the edge of the substrate 100. The ends of the plurality of polishing cloths that contact the upper side 101 of the edge of the substrate 100 together form a first contact portion 23, and the ends of the plurality of polishing cloths that contact the lower side 102 of the edge of the substrate 100 together form a third contact portion 25. The length of the plurality of polishing cloths protruding from the substrate 100 can be the same.

[0101] Both the end face polishing wheel 26 and the side polishing wheel 27 can be connected to a rotating device so that the rotating device can drive the base 21 to rotate. The way the base 21 is connected to the rotating device is the same as in Embodiment 1, so it will not be described again here.

[0102] The polishing wheel assembly 2 also includes a drive member, which can be connected to the end face polishing wheel 26 or the side polishing wheel 27 to drive the end face polishing wheel 26 or the side polishing wheel 27 to approach or move away from the edge of the substrate 100; thereby, the concave shape formed by the second contact portion 24 formed by the end face polishing wheel 26 and the first contact portion 23 or the third contact portion 25 formed by the side polishing wheel 27 can be adjusted so that one polishing wheel assembly 2 can be used to polish substrates 100 of different shapes.

[0103] In some specific embodiments, the substrate edge polishing device may further include a baffle plate 4, which is disposed on one side and below the polishing wheel assembly 2, the mounting platform 1, and the nozzle 31. When the polishing liquid falls from the nozzle 31, the mounting platform 1, or the polishing wheel assembly 2 due to its own weight, the baffle plate 4 can collect the polishing liquid and guide and recycle the collected polishing liquid. The baffle plate 4 may be equipped with a collection tank for collecting the polishing liquid, or it may guide the polishing liquid to an external collection bucket or other collection device for collection. The collected polishing liquid can be filtered and recycled within a certain period of time to save the cost of production materials and consumables.

[0104] Example 1: Polishing of silicon carbide substrate.

[0105] The upper, outer, and lower sides of a 0.480 mm thick silicon carbide substrate with a size of 150 mm were mechanically polished using a 3000# diamond sintered grinding wheel. The diamond sintered grinding wheel rotated at 45,000 rpm, the silicon carbide substrate rotated at 2 rpm, and the rotation direction of the diamond sintered grinding wheel was opposite to that of the substrate.

[0106] During mechanical polishing, a silica polishing slurry is sprayed. The concentration of abrasive silica in the slurry is 5 wt%, the particle size of the abrasive silica is 600 nm, the pH value of the silica polishing slurry is 9, the temperature of the silica polishing slurry is 40℃, and the polishing pressure of the silica polishing slurry is 200 g / cm. 2 The polishing time was 1 minute, and the drop rate was 0.8 L / min. After mechanical polishing, the roughness of the upper, outer, and lower surfaces of the silicon carbide substrate was 9.2 nm.

[0107] Use such as Figure 5 The apparatus shown employs a polishing wheel to perform chemical mechanical polishing (CMP) on a silicon carbide substrate. The polishing wheel rotates at 50,000 rpm, while the substrate rotates at 10 rpm. The rotation direction of the polishing wheel is opposite to that of the substrate. In the CMP process, an acidic polishing slurry is first used to coarsely polish the edges of the silicon carbide substrate. The acidic polishing slurry comprises 5 wt% alumina, 5 wt% potassium permanganate, approximately 82 wt% water, and the remainder is a polyurethane suspending agent. The pH value of the acidic polishing slurry is 6. The alumina particles in the acidic polishing slurry have a particle size of 100 nm. During coarse polishing, the temperature of the acidic polishing slurry is 43°C, the drip rate of the acidic polishing slurry is 0.35 L / min, and the polishing pressure is 220 g / cm³. 2 The polishing time was 6 minutes. After rough polishing, the roughness of the upper, outer, and lower edges of the silicon carbide substrate was 0.17 nm.

[0108] After rough polishing, the edges of the silicon carbide substrate were finely polished using an alkaline polishing slurry. The alkaline polishing slurry consisted of 5 wt% silica, 1 wt% hydrogen peroxide, approximately 85 wt% water, and the remainder being a polyurethane suspending agent. The pH value of the alkaline polishing slurry was 9. The silica particles in the alkaline polishing slurry had a particle size of 80 nm. During fine polishing, the temperature of the alkaline polishing slurry was 45℃, the drip rate was 0.35 L / min, and the polishing pressure was 220 g / cm³. 2 The polishing time was 6 minutes. After fine polishing, the roughness of the upper side, outer end face, and lower side of the silicon carbide substrate edge was 0.0312 nm.

[0109] Example 2: Polishing of silicon carbide substrate.

[0110] The upper, outer, and lower sides of a 0.480 mm thick silicon carbide substrate with a size of 150 mm were mechanically polished using a diamond sintered grinding wheel with a particle size of 8000#. The diamond sintered grinding wheel rotated at a speed of 100,000 rpm, while the silicon carbide substrate rotated at a speed of 10 rpm. The rotation direction of the diamond sintered grinding wheel was opposite to that of the substrate.

[0111] During mechanical polishing, a silica polishing slurry is sprayed. The concentration of abrasive silica in the slurry is 10%, the particle size of the abrasive silica is 800 nm, the pH value of the silica polishing slurry is 11, the temperature of the silica polishing slurry is 45℃, and the polishing pressure of the silica polishing slurry is 250 g / cm. 2 The polishing time was 15 minutes, and the drop rate was 0.5 L / min. After mechanical polishing, the roughness of the upper, outer, and lower edges of the silicon carbide substrate was 9.7 nm.

[0112] Use such as Figure 5 The apparatus shown employs a polishing wheel to perform chemical mechanical polishing (CMP) on a silicon carbide substrate. The polishing wheel rotates at 150,000 rpm, while the substrate rotates at 20 rpm. The rotation direction of the polishing wheel is opposite to that of the substrate. In the CMP process, an acidic polishing slurry is first used to coarsely polish the edges of the silicon carbide substrate. The acidic polishing slurry comprises 15 wt% alumina, 5 wt% potassium permanganate, approximately 78 wt% water, and the remainder is a polyurethane suspending agent. The pH value of the acidic polishing slurry is 6. The alumina particles in the acidic polishing slurry have a particle size of 250 nm. During coarse polishing, the temperature of the acidic polishing slurry is 40°C, the drip rate of the acidic polishing slurry is 0.5 L / min, and the polishing pressure is 250 g / cm³. 2 The polishing time was 10 minutes. After rough polishing, the roughness of the upper side, outer end face, and lower side of the silicon carbide substrate edge was 0.16 nm.

[0113] After rough polishing, the edges of the silicon carbide substrate were finely polished using an alkaline polishing slurry. The slurry consisted of 15 wt% silica, 2 wt% hydrogen peroxide, approximately 80 wt% water, and the remainder being a polyurethane suspending agent. The pH of the slurry was 11. The silica particles in the slurry had a particle size of 100 nm. During fine polishing, the slurry temperature was 45°C, the drip rate was 0.5 L / min, and the polishing pressure was 200 g / cm³. 2 The polishing time was 15 minutes. After fine polishing, the roughness of the upper side, outer end face, and lower side of the silicon carbide substrate edge was 0.0335 nm.

[0114] Example 3: Polishing of silicon carbide substrate.

[0115] The upper, outer, and lower sides of a 0.475 mm thick silicon carbide substrate with a size of 150 mm were mechanically polished using a 30,000# diamond sintered grinding wheel. The rotation speed of the diamond sintered grinding wheel was 150,000 rpm, and the rotation speed of the silicon carbide substrate was 20 rpm. The rotation direction of the diamond sintered grinding wheel was opposite to that of the substrate.

[0116] During mechanical polishing, a silica polishing slurry is sprayed. The concentration of abrasive silica in the slurry is 10%, the particle size of the abrasive silica is 800 nm, the pH value of the silica polishing slurry is 9, the temperature of the silica polishing slurry is 45℃, and the polishing pressure of the silica polishing slurry is 250 g / cm. 2 The polishing time was 10 minutes, and the drop rate was 1 L / min. After mechanical polishing, the roughness of the upper, outer, and lower surfaces of the silicon carbide substrate was 9.3 nm.

[0117] Use such as Figure 5 The apparatus shown employs a polishing wheel to perform chemical mechanical polishing (CMP) on a silicon carbide substrate. The polishing wheel rotates at 150,000 rpm, while the substrate rotates at 20 rpm. The rotation direction of the polishing wheel is opposite to that of the substrate. In the CMP process, an acidic polishing slurry is first used to coarsely polish the edges of the silicon carbide substrate. The acidic polishing slurry comprises 15 wt% alumina, 8 wt% potassium permanganate, approximately 75 wt% water, and the remainder is a polyurethane suspending agent. The pH value of the acidic polishing slurry is 5. The alumina particles in the acidic polishing slurry have a particle size of 300 nm. During coarse polishing, the temperature of the acidic polishing slurry is 40°C, the drip rate of the acidic polishing slurry is 0.3 L / min, and the polishing pressure is 250 g / cm³. 2 The polishing time was 10 minutes. After rough polishing, the roughness of the upper side, outer end face, and lower side of the silicon carbide substrate edge was 0.16 nm.

[0118] After rough polishing, the edges of the silicon carbide substrate were finely polished using an alkaline polishing slurry. The alkaline polishing slurry consisted of 15 wt% silica, 3 wt% hydrogen peroxide, approximately 80 wt% water, and the remainder being a polyurethane suspending agent. The pH of the alkaline polishing slurry was 11. The silica particles in the alkaline polishing slurry had a particle size of 40 nm. During fine polishing, the temperature of the alkaline polishing slurry was 45℃, the drip rate was 0.3 L / min, and the polishing pressure was 200 g / cm³. 2 The polishing time was 1 minute. After fine polishing, the roughness of the upper side, outer end face, and lower side of the silicon carbide substrate edge was 0.0323 nm.

[0119] Example 4: Polishing of gallium nitride substrate.

[0120] The upper, outer, and lower sides of a 0.470 mm thick gallium nitride substrate with a size of 50 mm were mechanically polished using a 30000# diamond sintered grinding wheel. The rotation speed of the diamond sintered grinding wheel was 45000 rpm, the rotation speed of the gallium nitride substrate was 20 rpm, and the rotation direction of the diamond sintered grinding wheel was opposite to the rotation direction of the substrate.

[0121] During mechanical polishing, a silica polishing slurry is sprayed. The concentration of abrasive silica in the slurry is 10%, the particle size of the abrasive silica is 500 nm, the pH value of the silica polishing slurry is 11, the temperature of the silica polishing slurry is 45℃, and the polishing pressure of the silica polishing slurry is 200 g / cm. 2 The silica polishing slurry was dripped at a rate of 0.1 L / min, and the polishing time was 1 minute. After mechanical polishing, the roughness of the upper, outer, and lower edges of the gallium nitride substrate was 9.1 nm.

[0122] Use such as Figure 5 The apparatus shown uses a polishing wheel to perform chemical mechanical polishing on a silicon carbide substrate. The polishing wheel rotates at 45,000 rpm, the substrate rotates at 1 rpm, and the rotation direction of the polishing wheel is opposite to that of the substrate.

[0123] In chemical mechanical polishing, the rough polishing process is the same as in Example 3. After rough polishing, the roughness of the upper side, outer end face and lower side of the gallium nitride substrate edge is 0.17 nm.

[0124] In chemical mechanical polishing (CMP), the fine polishing process involves polishing the edges of a gallium nitride substrate using an acidic polishing slurry. The slurry comprises 3 wt% silica, 1 wt% hydrogen peroxide, approximately 85 wt% water, and the remainder is a polyurethane suspending agent. The pH of the acidic polishing slurry is 6.5. The silica particles in the slurry have a particle size of 40 nm. During polishing, the temperature of the acidic polishing slurry is 45°C, the drip rate is 0.1 L / min, and the polishing pressure is 250 g / cm³. 2 The polishing time was 5 minutes. After chemical mechanical polishing, the roughness of the upper, outer, and lower edges of the silicon carbide substrate was 0.0314 nm.

[0125] Example 5: Polishing of gallium nitride substrate.

[0126] A copper wheel with a purity greater than 99.5% was used to mechanically polish the upper, end, and lower sides of a 0.48 mm thick, 50 mm diameter gallium nitride substrate. The copper wheel rotated at 150,000 rpm, the gallium nitride substrate rotated at 10 rpm, and the rotation direction of the copper wheel was opposite to that of the gallium nitride substrate.

[0127] Diamond molten metal is sprayed during mechanical polishing. The diamond particles in the molten metal have an average diameter of approximately 3 μm and a content of 10%. The pH value of the molten metal is 11, the temperature is 40℃, and the polishing pressure is 250 g / cm². 2 The diamond slurry was poured at a rate of 0.3 L / min, and the polishing time was 15 minutes. After mechanical polishing, the roughness of the upper, outer, and lower edges of the gallium nitride substrate was 9.2 nm.

[0128] Use such as Figure 5 The apparatus shown uses a polishing wheel to perform chemical mechanical polishing on a silicon carbide substrate. The polishing wheel rotates at 150,000 rpm, the substrate rotates at 20 rpm, and the rotation direction of the polishing wheel is opposite to that of the substrate.

[0129] In chemical mechanical polishing, the rough polishing process is the same as in Example 4. After rough polishing, the roughness of the upper side, outer end face and lower side of the gallium nitride substrate edge is 0.17 nm.

[0130] In chemical mechanical polishing (CMP), the fine polishing process includes polishing the edges of the silicon carbide substrate using an acidic polishing slurry. The acidic polishing slurry comprises 10 wt% silica, 5 wt% hydrogen peroxide, approximately 82 wt% water, and the remainder is a polyurethane suspending agent. The pH of the acidic polishing slurry is 6. The silica particles in the acidic polishing slurry have a particle size of 200 nm. During polishing, the temperature of the acidic polishing slurry is 30°C, the drip rate of the acidic polishing slurry is 0.3 L / min, and the polishing pressure is 200 g / cm³. 2 The polishing time was 10 minutes. After chemical mechanical polishing, the roughness of the upper, outer, and lower edges of the silicon carbide substrate was 0.0332 nm.

[0131] Comparative Example 1: Mechanical polishing in step 1 is omitted.

[0132] The polishing process of this comparative example is basically the same as that of Example 1. The difference is that the silicon carbide substrate in this comparative example is not mechanically polished, but the edge of the substrate after the chamfering is completed is directly chemically mechanically polished.

[0133] Comparative Example 2: The coarse polishing step in step 2 is omitted.

[0134] The polishing process of this comparative example is basically the same as that of Example 1. The difference is that the silicon carbide substrate in this comparative example does not undergo the rough polishing step in chemical mechanical polishing. After mechanical polishing is completed, the edge of the substrate is directly subjected to a fine polishing step.

[0135] Comparative Example 3: The fine polishing step in step 2 is omitted.

[0136] The polishing process of this comparative example is basically the same as that of Example 1. The difference is that the silicon carbide substrate in this comparative example did not undergo the fine polishing step in chemical mechanical polishing. Polishing was completed after the mechanical polishing and rough polishing steps.

[0137] Comparative Example 4: Changing the parameters in mechanical polishing.

[0138] The polishing process of this comparative example is basically the same as that of Example 1. The difference is that when mechanically polishing the silicon carbide substrate in this comparative example, a diamond sintered grinding wheel with a particle size of 40000# is used to mechanically polish the upper side, outer end face and lower side of the substrate edge.

[0139] Comparative Example 5: The application of silica polishing slurry during mechanical polishing was omitted.

[0140] The polishing process of this comparative example is basically the same as that of Example 1. The difference is that when the silicon carbide substrate in this comparative example is mechanically polished, silicon dioxide polishing liquid is not sprayed onto the area to be polished.

[0141] Comparative Example 6: The parameters in the coarse polishing step of Example 1 were changed.

[0142] The polishing process of this comparative example is basically the same as that of Example 1. The difference is that the pH value of the polishing solution used in the coarse polishing step of chemical mechanical polishing of the silicon carbide substrate in this comparative example is adjusted to neutral, about 7.5.

[0143] Comparative Example 7: Replace the parameters in the fine polishing step of Example 1.

[0144] The polishing process of this comparative example is basically the same as that of Example 1. The difference is that the pH value of the polishing solution used in the fine polishing step of chemical mechanical polishing of the silicon carbide substrate in this comparative example is adjusted to acidic, about 6.5.

[0145] Comparative Example 8: Mechanical polishing in step 1 is omitted.

[0146] The polishing process of this comparative example is basically the same as that of Example 4. The difference is that the gallium nitride substrate in this comparative example is not mechanically polished, but the edge of the substrate after the chamfering is completed is directly chemically mechanically polished.

[0147] Comparative Example 9: The parameters in the chemical mechanical polishing step of Example 4 were changed.

[0148] The polishing process in this comparative example is basically the same as that in Example 4. The difference is that the pH value of the polishing solution used in the fine polishing step of chemical mechanical polishing of the gallium nitride substrate in this comparative example is adjusted to neutral, about 7.5.

[0149] The substrates in the above embodiments and comparative examples were inspected using an atomic force microscope to obtain the roughness and smoothness of the substrate edges. Roughness is the average value of the substrate edge roughness; smoothness is expressed using the US military standard S / D, where S refers to the maximum length limit of surface scratches in μm, and D refers to the maximum diameter limit of surface pits or protrusions in μm. Furthermore, small-batch tests were conducted according to the above embodiments and comparative examples to measure the yield of the prepared substrates. The number of substrates tested in each batch could be 200-600. The test results are shown in Table 1.

[0150] Table 1

[0151]

[0152]

[0153] As can be seen from Table 1, the substrate polishing method of the present invention can significantly reduce the roughness of the substrate edge and achieve a high surface finish. This effectively reduces the microscopic defects and damage layers present at the substrate edge, and lowers the risk of particle shedding and substrate surface cracking in subsequent processes. The substrate polished by the substrate polishing method of the present invention can maintain a yield of over 94.2% after being prepared into a finished product, which is an improvement in both yield and quality compared to existing substrates.

[0154] By employing a method of first mechanical polishing and then chemical mechanical polishing (CMP), the substrate edge roughness can be rapidly reduced to less than 10 nm during mechanical polishing. This avoids the situation where CMP, due to its low contact force, fails to achieve the specified roughness standard when performed directly without mechanical polishing. During CMP, a highly efficient acidic polishing solution is used for rough polishing to further reduce the substrate edge roughness in a shorter time. Furthermore, the acidic polishing solution used for rough polishing is generally insufficient to achieve a substrate edge roughness of 0.1 nm. A fine polishing step further refines the substrate, reducing the edge roughness to less than 0.1 nm and improving the polishing effect, resulting in a substrate edge surface free of microcracks and chipping defects.

[0155] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the invention without departing from the principles and spirit of the invention, and all such changes should fall within the protection scope of the claims of the present invention.

Claims

1. A method for polishing a substrate, characterized in that, Includes the following steps: The edges of the substrate, after beveling, are mechanically polished to achieve a surface roughness of less than 10 nm. During the mechanical polishing process, deionized water or a silica polishing slurry is sprayed onto the area to be polished. The silica polishing slurry contains 5-10 wt% abrasive silica with a particle size of 500-800 nm, a pH of 9-11, a temperature of 40-45°C, and a polishing pressure of 200-250 g / cm². 2 The polishing time is 1-15 minutes; when the substrate is a silicon carbide substrate, the dripping rate of the silicon dioxide polishing slurry is 0.5-1 L / min; when the substrate is a gallium nitride substrate, the dripping rate of the silicon dioxide polishing slurry is 0.1-0.3 L / min. The edges of the substrate that have undergone mechanical polishing are subjected to chemical mechanical polishing, which includes a coarse polishing step and a fine polishing step in sequence. The rough polishing step includes: using an acidic polishing slurry to rough polish the edges of the substrate, making the surface roughness of the substrate edges less than 0.2 nm; wherein, the acidic polishing slurry has a pH value of 5-6.5, and by weight, excluding the balance of water and suspending agent, the acidic polishing slurry also includes: 2-15 wt% alumina and 5-8 wt% potassium permanganate; the particle size of the abrasive alumina is 100-300 nm, the temperature of the acidic polishing slurry is 40-45℃, the dripping rate of the acidic polishing slurry is 0.3-0.5 L / min, and the polishing pressure is 200-250 g / cm³. 2 The polishing time is 1-10 minutes; and / or, the pH value of the acidic polishing solution is adjusted by adding 2-5% wt% KOH or Mg(OH)2 aqueous solution and 2-10 wt% dilute hydrochloric acid or nitric acid aqueous solution. The fine polishing step includes: when the substrate is a silicon carbide substrate, using an alkaline polishing solution to finely polish the edges of the substrate so that the surface roughness of the substrate edges is less than 0.1 nm; when the substrate is a gallium nitride substrate, using an acidic polishing solution to finely polish the edges of the substrate so that the surface roughness of the substrate edges is less than 0.1 nm.

2. The substrate polishing method according to claim 1, characterized in that, Mechanical polishing of the edges of the substrate includes: The upper side, outer end face, and lower side of the substrate edge are mechanically polished using a diamond sintered grinding wheel with a particle size of 3000-30000#. The rotation speed of the diamond sintered grinding wheel is 45000-150000 rpm, and the rotation speed of the substrate is 1-20 rpm. The rotation direction of the diamond sintered grinding wheel is opposite to the rotation direction of the substrate.

3. The substrate polishing method according to claim 1, characterized in that, The substrate is a gallium nitride substrate, and the mechanical polishing of the edges of the substrate includes: The upper, end, and lower sides of the gallium nitride substrate edge are mechanically polished using a copper wheel with a purity of ≥99.5%. The copper wheel rotates at a speed of 45,000-150,000 rpm, and the substrate rotates at a speed of 1-20 rpm. The rotation direction of the copper wheel is opposite to that of the substrate.

4. The substrate polishing method according to claim 3, characterized in that, During mechanical polishing, liquid diamond is sprayed onto the area to be polished; The diamond particles in the diamond solution have a diameter of 1-3 μm and a content of 5-10 wt%; the pH value of the diamond solution is 9-11; the temperature of the diamond solution is 30-40℃; and the polishing pressure of the diamond solution is 200-250 g / cm. 2 Polishing time is 1-15 minutes, and drip rate is 0.1-0.3 L / min.

5. The substrate polishing method according to claim 1, characterized in that, The polishing wheel for chemical mechanical polishing is provided with a polishing part for polishing. The polishing part is made of a flexible material and can store and release polishing liquid. The rotation speed of the polishing wheel is 45,000-150,000 rpm, the rotation speed of the substrate is 1-20 rpm, and the rotation direction of the polishing wheel is opposite to the rotation direction of the substrate.

6. The substrate polishing method according to claim 5, characterized in that, The polishing section is used to simultaneously polish the upper side, outer end face and lower side of the substrate edge, and the polishing section is retractably mounted on the polishing wheel.

7. The substrate polishing method according to claim 1, characterized in that, The substrate is a silicon carbide substrate, and the alkaline polishing solution in the fine polishing step has a pH value of 9-11. By weight percentage, besides the remaining water and suspending agent, the alkaline polishing solution also includes: Silicon dioxide, 5-15 wt% Hydrogen peroxide, 0.5-3 wt%.

8. The substrate polishing method according to claim 7, characterized in that, In the alkaline polishing slurry, the particle size of the abrasive silica is 40-200 nm, the temperature of the polishing slurry is 40-45℃, the dripping rate of the alkaline polishing slurry is 0.3-0.5 L / min, and the polishing pressure is 200-250 g / cm³. 2 Polishing time is 1-15 minutes; and / or, The pH value of the alkaline polishing solution is adjusted by adding one or more of the following: hydrochloric acid aqueous solution, acetic acid aqueous solution, citric acid aqueous solution, 5-20 wt% KOH aqueous solution, and 1-5 wt% HNO3 aqueous solution.

9. The substrate polishing method according to claim 1, characterized in that, The substrate is a gallium nitride substrate, and the fine polishing step includes: polishing the edge of the gallium nitride substrate with an acidic polishing solution to make the surface roughness of the edge of the gallium nitride substrate less than 0.1 nm; The acidic polishing solution has a pH value of 6-7 and, by weight percentage, comprises, in addition to the balance of water and suspending agent: Silicon dioxide, 3-10 wt% Hydrogen peroxide, 1-5 wt%.

10. The substrate polishing method according to claim 9, characterized in that, In the acidic polishing slurry, the particle size of the abrasive silica is 40-200 nm, the temperature of the polishing slurry is 30-45℃, the dripping rate of the acidic polishing slurry is 0.1-0.3 L / min, and the polishing pressure is 200-250 g / cm³. 2 Polishing time is 5-10 minutes; and / or, The pH value of the acidic polishing solution is adjusted by adding one or more of the following: hydrochloric acid aqueous solution, acetic acid aqueous solution, citric acid aqueous solution, 1-3 wt% KOH aqueous solution, and 5-10 wt% HNO3 aqueous solution.

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