An electrochemical mechanical polishing pad for semiconductor wafers

Abstract

The application provides a kind of electrochemical mechanical polishing disc / polishing pad for semiconductor wafer, and the conductive polishing disc / polishing pad is used as cathode in electrochemical mechanical polishing, and the semiconductor wafer is used as anode, and the exposed conductive particles on the surface of the polishing disc / polishing pad form a large number of and uniformly distributed "micro-electrode", and the "micro-electrode" contacts with electrolyte solution and semiconductor wafer in the process of polishing / polishing, and an anodic oxidation system for the semiconductor wafer is formed, so that the surface of the wafer is oxidized to form a softening layer with low hardness and small binding force, and through the control of electrochemical parameters, efficient, controllable, environmentally friendly and uniform polishing / polishing of the semiconductor wafer is realized.

Description

Technical Field

[0001] This invention relates to the field of precision grinding and ultra-precision polishing technology for semiconductor wafers, specifically to the application of an electrochemical mechanical grinding disc / polishing pad for semiconductor wafers. Background Technology

[0002] Third-generation semiconductor materials, represented by silicon carbide (SiC) and gallium nitride (GaN), possess significant advantages due to their wide bandgap characteristics, including high voltage resistance, high temperature resistance, and high frequency efficiency, far surpassing the performance of traditional silicon-based materials. Silicon carbide (SiC) is particularly suitable for high-voltage, high-power applications, such as main drive inverters for new energy vehicles, charging piles, and smart grids; gallium nitride (GaN) excels in high-frequency applications, serving as a core material for the radio frequency front-end of 5G communication base stations and is also widely used in fast chargers. However, the inherent high hardness (e.g., SiC's Mohs hardness is close to diamond) and brittleness of these materials pose significant challenges to wafer cutting, grinding, and polishing processes, as traditional purely mechanical processing easily causes surface damage. Therefore, there is an urgent need to develop advanced ultra-precision processing technologies such as efficient, low-damage chemical mechanical polishing (CMP) and chemical mechanical grinding (CMP) to achieve high-efficiency, low-damage wafer substrate manufacturing, supporting the industrialization of third-generation semiconductor devices.

[0003] In semiconductor manufacturing processes, chemical mechanical polishing (CMP) is a key technology for achieving global wafer planarization. Polishing pads and grinding discs, as the direct components executing the wafer material removal process, directly determine the wafer's surface quality, planarity, defect control, and overall process yield. Electrochemical mechanical polishing (EMP) combines anodizing with traditional grinding and polishing techniques. It uses an applied current to control the formation of an oxide layer on the wafer at the anode, which is then removed through mechanical action. The most significant characteristic of electrochemical mechanical grinding and electrochemical mechanical polishing is its high material removal rate. However, some challenges exist in its application: 1) In the grinding / polishing process, high efficiency requires efficient chemical oxidation, but a large current density can easily lead to excessively high local current, causing over-corrosion at the damaged areas of the wafer. The uneven corrosion increases the processing time for subsequent steps. 2) The current needs to be conducted from the electrolyte solution to the entire wafer surface, but the pores and grooves of the polishing pad affect the uniform distribution of the electrolyte solution during transmission. Furthermore, the potential difference between the edge and center of the wafer leads to uneven corrosion between the edge and center, directly affecting the wafer's uniformity and making it difficult to achieve global planarization. Currently, researchers commonly create holes in the polishing pad to allow the electrolyte to contact the wafer through the holes for anodic oxidation. However, the high pore density and small pore size result in poor fluidity of the electrolyte solution, making it difficult to achieve efficient and uniform oxidation of the workpiece surface. For example, patent CN202510600889.5 describes an elastic membrane containing more than 50% silver powder. Multiple interconnected annular grooves are provided on the back of the elastic membrane to place metal conductive sheets to ensure a stable electric field is formed between the elastic membrane and the polishing liquid. However, these silver powders are randomly distributed and do not form conductive chains. A larger mass fraction of silver powder material is required to increase the conductivity of the elastic membrane, which increases the cost of the elastic membrane.

[0004] Magnetorheological elastomers (MREs) are magnetically controlled smart materials composed of magnetic particles and a polymer matrix. Their properties (mechanical, electrical, optical, acoustic, and thermal properties) can be rapidly, continuously, and reversibly controlled by adjusting the strength of an applied magnetic field. In anisotropic MREs, by doping with conductive particles or introducing a conductive framework, the electron transport in the chain of MRE polishing pads can be directly modulated under the influence of an electric field.

[0005] Currently, patent CN 113118967 B discloses a solid-state reactive grinding disc with abrasive orientation. It utilizes the directional arrangement of magnetic particles to force uniform abrasive distribution. Simultaneously, the magnetic particles can also act as a solid-state catalyst in the Fenton reaction to oxidize single-crystal SiC. However, this grinding disc uses hydrogen peroxide, which is corrosive and has limited grinding efficiency. Furthermore, in the polishing stage, patents CN202111058349.7 and CN202310946782.7 use magnetorheological elastomers as polishing pads in chemical mechanical polishing. The magnetic particles in the magnetorheological elastomer polishing pad act as a solid-state catalyst during polishing. Adding H2O2 during polishing triggers the Fenton reaction, generating highly oxidizing hydroxyl radicals (•OH), which can effectively increase the rate of the chemical reaction. However, Fenton reaction polishing is carried out by consuming H2O2, requiring continuous addition of H2O2 to enhance the oxidation effect. This results in high polishing costs and insufficient polishing stability. Moreover, the highly oxidizing hydrogen peroxide can accelerate the glazing of the polishing pad and corrode the polishing equipment.

[0006] Therefore, it is of great significance to develop a grinding / polishing technology that can achieve high efficiency, controllability, environmental protection and uniformity of semiconductor wafers. Summary of the Invention

[0007] In view of this, the present invention provides a novel application of electrochemical mechanical polishing pads / paddings for semiconductor wafers. The present invention utilizes the conductivity of magnetically linked polishing pads / paddings combined with electrochemical polishing to achieve efficient, controllable, environmentally friendly, and uniform polishing of semiconductor wafers.

[0008] Specifically, this invention provides an application of an electrochemical mechanical polishing (CMP) pad / disc for semiconductor wafers. The CMP pad / disc serves as a cathode in the electrochemical mechanical polishing / refining stage of the semiconductor wafer. The CMP pad / disc contains conductive magnetic particles. This application utilizes conductive and magnetically permeable particles to prepare CMP pads and CMP discs. The conductive magnetic particles form a chain of conductive channels within the CMP / disc, and the conductivity is controlled electrochemically to achieve electrochemical mechanical polishing and refining of the semiconductor wafer.

[0009] Furthermore, in the process of preparing the electrochemical mechanical polishing pad / padding for semiconductor wafers, conductive magnetic particles are poured into a mold from a mixture, and then a uniform magnetic field is applied to the mold. After being magnetized, the conductive magnetic particles are arranged along the direction of the magnetic field lines to form a chain structure.

[0010] In the application of the grinding disc / polishing pad of this application in the electrochemical mechanical grinding / polishing process of semiconductor wafers, the electric field is applied by an electrochemical workstation. The electrochemical workstation adopts a three-electrode system, which includes: a working electrode electrically connected to the semiconductor wafer; an auxiliary electrode connected to the grinding disc / polishing pad; and a reference electrode.

[0011] Furthermore, the specific application steps are as follows: Step S1: Connect the semiconductor wafer as the anode to the working electrode of the electrochemical workstation; Step S2: Connect the grinding disc / polishing pad as the cathode to the auxiliary electrode of the electrochemical workstation; Step S3: Supply a non-oxidizing electrolyte solution and abrasive between the grinding disc / polishing pad and the semiconductor wafer; Step S4: By applying a working potential, anodizing is performed on the surface of the semiconductor wafer to generate a softening layer, and the softening layer is removed by the mechanical action of the abrasive.

[0012] Furthermore, the electrochemical mechanical polishing pad / padding serves as the cathode, the semiconductor wafer as the anode, and the electrolyte polishing solution is placed between the polishing pad and the semiconductor wafer. During the polishing / grinding process, the polishing pad / padding, the electrolyte solution, and the semiconductor wafer come into contact with each other, forming an electrochemical oxidation system.

[0013] Furthermore, the magnetic chain structure formed by the conductive magnetic particles in the grinding disc / polishing pad becomes a conductive channel under applied voltage. The exposed conductive magnetic particles on the surface of the grinding disc / polishing pad can form a uniformly distributed microelectrode array when in contact with the semiconductor wafer surface. The microelectrode array, the electrolyte solution, and the semiconductor wafer surface are in contact simultaneously, and an electrochemical reaction occurs, generating hydroxyl radicals (•OH) with strong oxidizing properties. •OH oxidizes the semiconductor wafer, and then the oxide layer is mechanically removed by the abrasive.

[0014] In the above electrochemical oxidation system, the grinding disc / polishing pad is connected to the cathode, and electrons flow through the conductive channels formed by the chain of conductive magnetic particles. At the same time, a large number of evenly distributed "microelectrodes" are formed on the surface of the grinding disc / polishing pad as exposed conductive magnetic particles. Under the action of the electric field, the Fermi level of the conductive semiconductor wafer decreases, causing electrons to move from the wafer surface to the interior. A large number of holes (h+) are generated on the wafer surface, which react with the OH- adsorbed on the surface to generate hydroxyl radicals (•OH). •OH further reacts with the wafer surface to undergo an oxidation reaction.

[0015] The reaction that occurs at the cathode is as follows: (1); When the semiconductor wafer is single-crystal SiC, the following reaction occurs at the anode: (2); (3); (4); When the semiconductor wafer is GaN, the following reaction occurs at the anode: (5).

[0016] Furthermore, the grinding disc comprises: 30-60 wt% resin matrix material, 5-15 wt% abrasive, and 20-50 wt% conductive magnetic particles; the polishing pad comprises: 30-70 wt% polymer elastic matrix and 30-70 wt% conductive magnetic particles, and the polishing pad has a porosity of 10-30%.

[0017] Furthermore, the resin matrix material is composed of epoxy resin and a curing agent, wherein the epoxy resin is selected from bisphenol A type, bisphenol F type, alicyclic, and fluorinated epoxy resins. Further, the epoxy resin is selected from E-51, E-44, and TDE-85. This type of epoxy resin has the characteristics of strong adhesion, low shrinkage, and high mechanical strength, and can provide excellent mechanical removal during the grinding process.

[0018] Furthermore, the curing agent is selected from one of the following: amine-based, acid anhydride-based, and phenolic resin-based curing agents.

[0019] Furthermore, the curing agent is selected from one of DDS (4,4'-diaminodiphenyl sulfone), m-phenylenediamine (m-PDA), methyltetrahydrophthalic anhydride (MTHPA), and hexahydrophthalic anhydride (HHPA).

[0020] Furthermore, the abrasive is selected from one of diamond, alumina, silicon carbide, silicon dioxide, and cerium dioxide, and the abrasive is matched with a high electrochemical reaction rate during the grinding stage to quickly remove the oxide layer.

[0021] Furthermore, the abrasive of this application can remove the softened oxide layer (such as SiO2, GaO2, etc.) on the wafer without damaging the semiconductor wafer.

[0022] Furthermore, the elastic matrix material of the polishing pad is selected from one of the common polishing pad matrix materials such as polyurethane, silicone-modified polyurethane, silicone rubber, and natural rubber. The elastic matrix material is flexible and wear-resistant, resulting in a long service life during polishing. The micropores of the polishing pad are formed through nitrogen physical foaming, supercritical CO2 foaming, or by directly adding microsphere foaming agents. During polishing, the micropores allow for the uniform distribution and flow of the electrolyte solution, while simultaneously storing and transporting the polishing fluid and abrasive debris.

[0023] Furthermore, the conductive magnetic particles are selected from one or a combination of carbonyl iron powder (CIP) particles, silver-coated iron powder particles, graphene-coated carbonyl iron powder (CIP@GO) particles, and other particles with conductive and magnetic properties.

[0024] Furthermore, the conductive magnetic particles are oriented along the direction of the magnetic field by a uniform magnetic field, and after curing, an anisotropic chain structure is formed in the grinding disc / polishing pad.

[0025] Furthermore, the conductive magnetic particles have a particle size of 1-20 μm and a uniform magnetic field strength of 0.2T-1T, which allows the magnetic particles to form a regular and uniform chain structure.

[0026] Furthermore, the working potential during the grinding stage is 5-20V, and the working potential during the polishing stage is 1-15V. The applied voltage can be adjusted from high to low according to the polishing progress, thereby controlling the intensity of the electrochemical reaction. The higher the voltage, the greater the current density of the "microelectrode," the more •OH is generated, and the faster the oxidation rate of the semiconductor wafer surface. By controlling the electric field parameters, the intensity of the electrochemical oxidation system can be controlled, thereby controlling the anodic oxidation rate of the semiconductor wafer and controlling the polishing efficiency and quality.

[0027] Furthermore, the electrolyte solution is a neutral electrolyte solution, selected from one or a combination of several of sodium nitrate, sodium chlorate, sodium chloride, sodium sulfate, and potassium sulfate. Its characteristics include low corrosivity, high safety, and equipment friendliness.

[0028] Furthermore, a semiconductor wafer is a material that is conductive or capable of electrochemical reactions. The semiconductor wafer is selected from one of silicon carbide (SiC), gallium nitride (GaN), ultra-wide bandgap semiconductor gallium arsenide (GaAs), indium phosphide (InP), and single crystal Si.

[0029] Compared with the prior art, the beneficial effects of the present invention are: (1) The present invention innovatively provides an application of an electrochemical mechanical grinding disc / polishing pad for semiconductor wafers. The grinding disc / polishing pad is connected to the auxiliary electrode of electrochemical operation as a cathode, so as to realize efficient, controllable, environmentally friendly and uniform grinding / polishing of semiconductor wafers.

[0030] (2) The grinding disc / polishing pad of the present invention has a regular conductive chain structure. During the electrochemical mechanical grinding / polishing process, this chain structure can form a conductive channel. At the same time, the conductive magnetic particles exposed on the surface of the grinding disc / polishing pad form a large number of evenly distributed "microelectrodes". The grinding disc / polishing pad, electrolyte solution and semiconductor wafer can come into contact with each other during grinding / polishing to form an electrochemical oxidation system. The grinding disc / polishing pad provided by the present invention has the performance of a general grinding disc / polishing pad, and also has conductivity. The "microelectrodes" formed by a large number of evenly distributed conductive magnetic particles on the surface of the grinding disc / polishing pad can realize the planarization process of semiconductor wafers.

[0031] (3) The application of the electrochemical mechanical polishing / refining pad provided by this invention in semiconductor wafers uses a conductive polishing pad / refining disk as the cathode and the semiconductor wafer as the anode in electrochemical mechanical polishing. Numerous and evenly distributed "microelectrodes" are formed on the exposed conductive particles on the surface of the polishing pad / refining disk. During the polishing / refining process, these "microelectrodes" come into contact with the electrolyte solution and the semiconductor wafer, forming an anodic oxidation system for the semiconductor wafer. This oxidizes the wafer surface to form a softening layer with lower hardness and weaker adhesion. Furthermore, the chemical reaction during the polishing / refining process is effectively controlled by adjusting the electrochemical parameters. This invention eliminates the need for traditional corrosive solutions through electrochemical reactions, making it both environmentally friendly and economical. Attached Figure Description

[0032] Figure 1 This is a schematic diagram illustrating the application of the electrochemical mechanical polishing disk / painting pad for semiconductor wafers according to the present invention; Figure 2 This is a schematic diagram of the particle chain distribution under a magnetic field during the preparation of the grinding disc / polishing pad; In the diagram: 1. Electrochemical workstation; 2. Workpiece tray; 3. Semiconductor wafer; 4. Worktable; 5. Wire; 6. Cathode; 7. Grinding disc / polishing pad; 8. Electrolyte solution; 9. Reference electrode; 10. Anode; 11. Magnet N pole; 12. Upper mold; 13. Middle mold; 14. Conductive magnetic particles; 15. Abrasive; 16. Resin / elastic matrix; 17. Lower mold; 18. Magnet S pole. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The technical solutions of the present invention will be further described below with reference to implementation examples.

[0034] like Figure 1 As shown, this invention provides an application of an electrochemical mechanical polishing pad / padding 7 for semiconductor wafers, with the specific steps as follows: Step S1: Connect the semiconductor wafer 3 to the anode 10, and connect it to the working electrode of the electrochemical workstation 1 through the wire 5. The workpiece disk 2 is used to fix the wafer and conduct current. Step S2: Connect the grinding disc / polishing pad 7 to the cathode 6, and connect it to the auxiliary electrode of the electrochemical workstation 1 through the wire 5. The worktable 4 supports the polishing pad and ensures electrical contact. Step S3: Supply a non-oxidizing electrolyte solution 8 and abrasive 15 between the grinding disc / polishing pad 7 and the semiconductor wafer 3; Step S4: An anodic oxidation is performed on the surface of the semiconductor wafer 3 by applying a working potential through the electrochemical workstation 1 to generate a softening layer. At the same time, the softening layer is removed by the mechanical action of the abrasive 15. The reference electrode 9 is used to monitor the potential stability.

[0035] like Figure 2 As shown, the present invention provides a method for preparing a grinding disk / polishing pad for semiconductor wafers, and the specific steps are as follows: Step S1: Material Preparation and Weighing. Accurately weigh each component according to its mass fraction, based on the type of grinding disc / polishing pad 7. For the grinding disc, take 30-60 wt% of the resin matrix material 16, 5-15 wt% of the abrasive 15, and 20-50 wt% of the conductive magnetic particles 14; for the polishing pad, take 30-70 wt% of the elastic matrix material 16 and 30-70 wt% of the conductive magnetic particles 14, and add a microsphere foaming agent to form a porosity of 10-30%. All materials must be pre-dried to avoid moisture affecting the curing effect.

[0036] Step S2: Mixing and Dispersion. Place the weighed resin / elastic matrix 16, abrasive 15, conductive magnetic particles 14, and additives into a mixing tank. Mechanically stir at 800-1000 rpm at room temperature, while simultaneously ultrasonically vibrating for 10-15 minutes to ensure uniform particle dispersion without agglomeration. For grinding discs, add a curing agent and stir rapidly; for polishing pads, preheat the mixture and add a chain extender and catalyst.

[0037] Step S3: Casting and Magnetic Field Application. The mixture is cast into a precast mold, which includes an upper mold 12, a middle mold 13, and a lower mold 17, to form the geometry of the grinding disc / polishing pad. Then, magnets with N poles 11 and S poles 18 are placed above and below the mold, respectively, to apply a uniform magnetic field perpendicular to the mold surface. The conductive magnetic particles 14 are magnetized under the magnetic field and oriented along the magnetic field lines to form a chain structure, while the abrasive particles 15 are uniformly held in the gaps between the chains. The magnetic field is maintained until the mixture initially solidifies, ensuring stable particle arrangement.

[0038] Step S4: Curing and Post-treatment. After casting, the mold is moved to the curing equipment. Curing conditions are selected according to the substrate material: the grinding disc is cured at 80-100°C for 48 hours, and the polishing pad is cured at the vulcanization temperature for 16 hours. After demolding, the surface of the grinding disc / polishing pad is mechanically trimmed to remove burrs and ensure surface smoothness, ultimately obtaining a finished product with an anisotropic conductive chain structure.

[0039] Example 1 This embodiment provides an application of an electrochemical mechanical grinding disc.

[0040] Step 1: Prepare the grinding disc. The specific preparation steps are as follows: S1: By mass fraction, take 40 wt% of E-51 epoxy resin matrix, 10 wt% of diamond abrasive with a particle size of 5 μm, and 50 wt% of CIP conductive magnetic particles with a particle size of 5 μm; S2: Mechanically stir the three components in a mixing tank at 800 rpm and ultrasonically disperse them for 10 minutes, then add 70g of DDS curing agent and stir rapidly. S3: Pour the mixture into the mold. For example... Figure 2 As shown, the N pole and S pole of a magnet are placed above and below the mold, respectively, and a uniform magnetic field of 350 mT is applied, perpendicular to the mold surface. The abrasive is uniformly clamped in the gaps between the chains, and the magnetic field is maintained for 1 hour until initial solidification. S4: Demold and continue curing for 48 hours. Then, use a lathe tool to trim the disc to obtain the grinding disc.

[0041] like Figure 2 As shown, under the action of the solidification magnetic field, the CIP magnetic conductive particles are oriented along the direction of the magnetic field lines, while the diamond abrasive is uniformly clamped in the middle of the chain.

[0042] The second step involves electrochemical mechanical polishing of the single-crystal SiC using the prepared polishing disc. The specific steps are as follows: SS1: The grinding experiment was conducted using this grinding disc on a KD15BX single-sided grinding machine. The workpiece was the Si surface of 4H-SiC with an original surface roughness of Ra 120 nm.

[0043] SS2: SiC was attached to a copper workpiece disk with conductive adhesive. The copper workpiece disk was connected to the working electrode of the electrochemical workstation via wires, and a counterweight on the workpiece disk applied pressure to the wafer. The prepared polishing disk was attached to a copper sheet worktable with conductive adhesive, and the copper sheet was connected to the auxiliary electrode of the electrochemical workstation. The polishing parameters used were: polishing pressure 100 kPa, rotation speed 60 r / min, a peristaltic pump to deliver 0.1 M sodium sulfate electrolyte solution to the surface of the polishing disk at a flow rate of 800 ml / h, and a polishing time of 10 min. The reference electrode was directly inserted into the center of the polishing disk surface.

[0044] SS3: Using an electrochemical workstation, the grinding voltage was adjusted to 0V, 5V, 10V, 15V, and 20V to conduct a comparison of grinding under five different voltage conditions, and then the material removal rate and surface roughness were tested.

[0045] Material removal rate test: Before polishing, artificial scratches were created on the SiC surface with a depth of h1. After polishing, the artificial scratches became shallower, with a depth of h2. A white light interferometer (Contour GT-X3) was used to measure the scratch morphology before and after polishing, and the material removal rate was calculated using the difference in scratch contour depth h between the two processes. (6); Surface roughness test: The surface roughness Sa of single crystal SiC after polishing was detected using a white light interferometer (Contour GT-X3). For each test, four symmetrical points on a circle with a radius of 5 mm were selected, and the average value was taken as the surface roughness of single crystal SiC.

[0046] The test results are shown in Table 1: ; As can be seen from the grinding results in Table 1, without applying electrochemical grinding (grinding voltage of 0V), the material removal rate is significantly lower, and the surface roughness after grinding is still relatively large. After electrochemical mechanical grinding with different voltages, it can be seen that the material removal rate increases with increasing voltage, while the surface roughness first decreases and then increases. At a voltage of 15V, a relatively low surface roughness Sa of 1.873 nm is achieved.

[0047] As can be seen from Example 1, the electrochemical mechanical polishing disc of the present invention has a significant effect on polishing single-crystal SiC. Furthermore, with the increase of voltage, the electrochemical anodization of single-crystal SiC increases, which significantly reduces the difficulty of material removal, improves the material removal rate, and reduces surface roughness.

[0048] Example 2 This embodiment provides an application of an electrochemical mechanical polishing pad.

[0049] Step 1: Prepare the polishing pad. The specific preparation steps are as follows: S1: Calculated by mass fraction, take 50 wt% of polyurethane prepolymer composed of polytetrahydrofuran polyol (PTMG) / diphenylmethane diisocyanate (MDI), 1 wt% of UM115 microsphere foaming agent, and 49 wt% of CIP magnetic conductive particles (commercial, self-purchased) in a polytetrafluoroethylene container, and perform oil bath heating and mechanical stirring at 800 rpm, followed by ultrasonic vibration for 10 min to uniformly disperse the conductive magnetic particles and microsphere foaming agent in the prepolymer material. Preheat the mixture, and after 10 min, add 2.6 wt% of chain extender crosslinking agent MOCA and 1 / 1000 of catalyst stannous octoate in the polyurethane prepolymer and stir rapidly for 30 s. S2: After vacuum degassing in a vacuum drying oven, the mixture is poured into the mold of the polishing pad, as follows: Figure 2 As shown, the mold structure includes an upper mold, a middle mold, and a lower mold. The N pole and S pole of a magnet are placed above and below the mold, respectively. A curing magnetic field of 300 mT is applied to the upper and lower surfaces of the mold, with the direction perpendicular to the mold surface. The mold is then placed in a vacuum drying oven for vulcanization and curing for 16 hours. S3: After the vulcanization and curing are completed, and the mixture is left at room temperature for 48 hours, it is demolded and then dressed using a 400-mesh silicon carbide grinding wheel to obtain a polishing pad with a polyurethane matrix.

[0050] The second step involves electrochemical mechanical polishing of the single-crystal SiC using the prepared polyurethane-based polishing pad. The specific steps are as follows: SS1: Polishing experiments were conducted using this polishing pad on a KD15BX single-sided grinding machine. The workpiece was a Si surface of 4H-SiC with an original surface roughness of Ra 2.5 nm.

[0051] SS2: SiC was attached to a copper workpiece disk with conductive adhesive. The copper workpiece disk was connected to the working electrode of the electrochemical workstation via wires, and a counterweight on the workpiece disk applied pressure to the wafer. The prepared polishing pad was attached to a copper sheet worktable with conductive adhesive, and the copper sheet was connected to the auxiliary electrode of the electrochemical workstation. The polishing parameters used were: polishing pressure 60 kPa, rotation speed 60 r / min, a peristaltic pump was used to deliver a 0.1 M sodium sulfate electrolyte solution to the surface of the polishing pad at a flow rate of 800 ml / h, and a diamond abrasive solution with a mass fraction of 0.5 wt% and a particle size of 0.2 μm was also delivered. The polishing time was 10 min, and the reference electrode was directly inserted into the center of the polishing disk surface.

[0052] SS3: Using an electrochemical workstation, the polishing voltage was adjusted to 0V, 3V, 6V, 9V, and 12V to conduct a comparison of five groups of polishing under different voltage conditions. Then, the material removal rate and surface roughness of the polished material were tested.

[0053] The material removal rate and surface roughness tested after polishing were consistent with the tests conducted during grinding in Example 1, and the results are shown in Table 2: ; As can be seen from the polishing results in Table 2, without electrochemical polishing (i.e., when the polishing voltage is 0V), the material removal rate is significantly low, resulting in incomplete removal of the original damage, and the surface roughness is Sa 0.653 nm. With increasing polishing voltage, the material removal rate increases, and the surface roughness initially decreases and then stabilizes. The polishing results in Example 2 demonstrate that the prepared polyurethane polishing pad significantly improves material removal and rapidly reduces surface roughness under electrochemical action.

[0054] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. An application of an electrochemical mechanical polishing pad / paste for semiconductor wafers, characterized in that, The grinding disc / polishing pad is used as a cathode in the electrochemical mechanical grinding / polishing stage of semiconductor wafers, and the grinding disc / polishing pad contains conductive magnetic particles.

2. The application according to claim 1, characterized in that, The specific application steps are as follows: Step S1: Connect the semiconductor wafer as the anode to the working electrode of the electrochemical workstation; Step S2: Connect the grinding disc / polishing pad as the cathode to the auxiliary electrode of the electrochemical workstation; Step S3: Supply a non-oxidizing electrolyte solution and abrasive between the grinding disc / polishing pad and the semiconductor wafer; Step S4: By applying a working potential, anodizing is performed on the surface of the semiconductor wafer to generate a softening layer, and the softening layer is removed by the mechanical action of the abrasive.

3. The application according to claim 2, characterized in that, The magnetic flux chain structure formed by the conductive magnetic particles in the grinding disc / polishing pad becomes a conductive channel under applied voltage. The exposed conductive magnetic particles on the surface of the grinding disc / polishing pad can form a uniformly distributed microelectrode array when in contact with the semiconductor wafer surface. The microelectrode array, electrolyte solution and semiconductor wafer surface are in contact at the same time, and an electrochemical reaction occurs, generating hydroxyl radicals (•OH) with strong oxidizing properties. •OH oxidizes the semiconductor wafer, and then the oxide layer is mechanically removed by the abrasive.

4. The application according to claim 3, characterized in that, The grinding disc comprises: 30-60 wt% resin matrix material, 5-15 wt% abrasive, and 20-50 wt% conductive magnetic particles; the polishing pad comprises: 30-70 wt% polymer elastic matrix and 30-70 wt% conductive magnetic particles, and the polishing pad has a porosity of 10-30%.

5. The application according to claim 4, characterized in that, The conductive magnetic particles are selected from one or more of the following particles that have conductivity and magnetism: carbonyl iron powder particles, silver-coated iron powder particles, and graphene-coated carbonyl iron powder particles.

6. The application according to claim 4, characterized in that, The conductive magnetic particles are oriented along the direction of the magnetic field by a uniform magnetic field, and after solidification, they form an anisotropic chain structure in the grinding disc / polishing pad.

7. The application according to claim 6, characterized in that, The conductive magnetic particles have a particle size of 1-20 μm, and the uniform magnetic field strength is 0.2T-1T.

8. The application according to claim 2, characterized in that, The working potential during the grinding stage is 5-20V, and the working potential during the polishing stage is 1-15V.

9. The application according to claim 2, characterized in that, The electrolyte solution is a neutral electrolyte solution, selected from one or a combination of several of sodium nitrate, sodium chlorate, sodium chloride, sodium sulfate, and potassium sulfate.

10. The application according to claim 2, characterized in that, The semiconductor wafer is selected from one of silicon carbide, gallium nitride, ultra-wide bandgap semiconductor gallium arsenide, indium phosphide, and single crystal Si.

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