A method and system for polishing optoelectronic assisted wide bandgap semiconductor wafers

Abstract

The application discloses a kind of photoelectricity auxiliary wide band gap semiconductor wafer polishing method and system, belong to wafer polishing technical field, including the following steps: after cleaning processing, aluminum nitride or gallium nitride wafer is fixed on the vacuum adsorption fixture of polishing device, nitrogen is introduced into sealed cabin and maintains set pressure;Ultraviolet light is applied to polishing area, while being irradiated to polishing liquid and wide band gap semiconductor wafer, and specific current density and working electrode bias are applied to wide band gap semiconductor wafer using electrochemical workstation, according to the size of current and polishing rate, change polishing machine carrier piece pressure;Drive polishing machine carrier disc and clamp rotation, polish with polishing liquid containing photocatalyst and oxidizing agent;After polishing, wafer is cleaned and dried.The method will construct "light field-electric field-force field" multi-physical field coupling synergistic environment, realize the high efficiency, low damage, high stability planarization processing of gallium nitride, aluminum nitride and other wide band gap semiconductor wafers.

Description

Technical Field

[0001] This invention belongs to the field of wafer polishing technology, specifically relating to a photoelectric-assisted wide bandgap semiconductor wafer polishing method and system. Background Technology

[0002] Third-generation wide-bandgap semiconductor materials, including gallium nitride (GaN) and aluminum nitride (AlN), have become the core foundation for high-power power electronic devices, high-frequency radio frequency communication modules, and deep-ultraviolet optoelectronic devices due to their excellent electron mobility, ultra-wide bandgap characteristics, extremely high breakdown field strength, and excellent thermal conductivity. However, these materials generally possess high Vickers hardness (typically above 2000 HV), significant intrinsic brittleness, and extremely strong chemical inertness, resulting in severe technical bottlenecks in the fabrication of atomically flat and damage-free surfaces.

[0003] Traditional chemical mechanical polishing (CMP) processes are often limited by extremely low material removal rates (typically below 0.1 μm / h) when processing the aforementioned wide bandgap materials, and are highly susceptible to inducing surface microcracks, lattice distortion, and subsurface damage, making it difficult to balance efficiency and quality. Although ultraviolet photocatalytic assisted polishing technology, which has emerged in recent years, promotes surface oxidation reactions and improves removal efficiency to some extent by generating highly reactive hydroxyl radicals (·OH) through photocatalyst reactions, this technology still suffers from inherent drawbacks such as sluggish oxidation reaction kinetics, poor surface morphology consistency, and high operating costs, and cannot yet fully meet the stringent standards for surface integrity and batch stability required in high-end semiconductor manufacturing.

[0004] Existing photoelectric co-polishing technologies have limited applications, resulting in low material removal rates, insufficient surface roughness (Ra ≥ 0.5 nm), and a tendency to cause subsurface damage. Polishing large wafers (2-6 inches) presents even more stringent technical requirements. Balancing high conductivity with high UV transmittance and stable abrasive particle dispersion in the polishing slurry is technically extremely challenging. Furthermore, due to the involvement of multi-physics coupling and a narrow process window, these technologies are highly sensitive to minute fluctuations in illumination uniformity, electrolyte concentration (e.g., the choice between monovalent and divalent cations), and voltage and current. Improper control can easily lead to pitting, micro-scratches, and uneven material removal rates, thus limiting their stability and yield in large-scale industrial production. Summary of the Invention

[0005] In view of the above, the purpose of this invention is to provide a photoelectric-assisted wide bandgap semiconductor wafer polishing method and system, which introduces electrochemical and force field control mechanisms into the wide bandgap semiconductor polishing system, and constructs a synergistic environment of multi-physics field coupling of "optical field-electric field-force field": photogenerated electron-hole pairs are generated by optical field excitation, the carriers are driven to migrate in a directional manner and the interface reaction kinetics are controlled by an external electric field, and the material removal behavior is optimized by pressure field, thereby achieving high-efficiency, low-damage, and high-stability planarization processing of wide bandgap semiconductor wafers such as gallium nitride and aluminum nitride.

[0006] To achieve the above-mentioned objectives, an embodiment provides a photoelectric-assisted wide-bandgap semiconductor wafer polishing method, comprising the following steps: The wide bandgap semiconductor wafer, after cleaning, is fixed on the vacuum adsorption fixture of the polishing device, wherein the wide bandgap semiconductor wafer includes aluminum nitride wafer or gallium nitride wafer; Ultraviolet light is applied to the polishing area, simultaneously irradiating the polishing slurry and the wide bandgap semiconductor wafer. A specific current density and working electrode bias voltage are applied to the wide bandgap semiconductor wafer using an electrochemical workstation. The wafer pressure of the polishing machine is changed according to the magnitude of the current and the polishing rate. The polishing machine's carrier disk and fixture are rotated, and polishing is carried out in synergistic polishing using a polishing slurry containing photocatalysts and oxidants. After polishing, the wafer is cleaned and dried to obtain the final product.

[0007] In this invention, when a wide-bandgap semiconductor wafer is irradiated with ultraviolet light, photons with energy greater than the bandgap excite valence band electrons to transition to the conduction band, generating photogenerated electron-hole pairs. Under the influence of an electric field, these photogenerated electron-hole pairs are efficiently separated, promoting the generation of active free radicals on the wafer surface. Simultaneously, in the polishing slurry under ultraviolet light irradiation, the photocatalyst is excited to generate photogenerated electron-hole pairs, which are also efficiently separated under the influence of an electric field, further increasing the yield of active free radicals. The oxidant decomposes under ultraviolet light excitation to generate reactive oxygen species, including hydroxyl radicals. The active free radicals generated by the photoelectric synergy and the reactive oxygen species generated by the photo-excited oxidant jointly oxidize the wafer surface, forming reaction layers such as gallium oxide, gallium hydroxide, aluminum oxide, or aluminum hydroxide. These reaction layers are removed under the action of acidic polishing slurry and abrasive particles. Based on this, the synergistic effect of light, electricity, and force is achieved by controlling the wafer pressure, resulting in a polishing effect with high removal rate and low surface roughness.

[0008] Preferably, the inert gas is nitrogen, and the pressure inside the sealed chamber is 0.08–0.12 MPa. Nitrogen is blown into the optical path between the ultraviolet light source and the polishing area through the ultraviolet light path purging module to reduce the absorption of ultraviolet light by oxygen and water vapor.

[0009] Preferably, for GaN wafers, the wavelength range of the ultraviolet light is 280-340 nm, and for AlN wafers, the wavelength range of the ultraviolet light is 180-210 nm; the irradiance is 200-300 mW / cm². 2 More preferably, the light intensity is 200-250 mW / cm². 2 The polishing slurry temperature is maintained at 30-60°C during the polishing process. o C. More preferably, the temperature of the polishing slurry during the polishing process is maintained at 40-50°C. o C. Appropriately increasing the temperature of the polishing slurry can improve the polishing rate while keeping it within a controllable range, thus avoiding localized over-polishing.

[0010] Preferably, the wide-bandgap semiconductor wafer serves as the working electrode, the bottom polishing disk as the counter electrode, and Ag / AgCl (saturated KCl solution) as the reference electrode, constructing a three-electrode working system. The current density output by the electrochemical workstation is between 0.1 and 10.0 mA / cm². 2 The working electrode bias voltage is set between 0.5 and 1.5 V. vs Ag / AgCl (saturated KCl solution).

[0011] More preferably, the current density output by the electrochemical workstation is between 1.0 and 3.0 mA / cm². 2 The working electrode bias voltage is set between 1.2 and 1.4 V. vs Ag / AgCl (saturated KCl solution) promotes the photoelectrochemical reaction of wide-bandgap semiconductor wafers at this potential, thereby in-situ oxidizing the shallow surface of hard gallium nitride and aluminum nitride wafers to generate softer materials such as gallium oxide, aluminum oxide, and aluminum hydroxide, thus achieving material removal.

[0012] The contact pressure between the wafer itself and the polishing pad is called the wafer pressure. Adjusting the wafer pressure can also affect the polishing rate. The wafer pressure is 3-10 psi, and more preferably, the wafer pressure is 3-5 psi.

[0013] When the current density, light intensity and substrate pressure increase synergistically, the polishing rate increases accordingly, reaching approximately 500-1000 nm / h, while the surface roughness Ra is controlled within the range of 0.1-0.5 nm.

[0014] The polishing solution contains a photocatalyst, an oxidant, an abrasive, a dispersant, a corrosion inhibitor, and an electrolyte, and the pH value of the polishing solution is in the range of 2.0-3.0.

[0015] Preferably, the photocatalyst is one or more selected from 0.5-1.0 wt% TiO2, 0.2-0.6 wt% SnO2, 0.1-0.5 wt% ZnO, and 0.1-0.5 wt% ZrO2; the oxidant is one or more selected from 2.0-8.0 wt% H2O2, 2.0-5.4 wt% K2S2O8, and 2.0-5.0 wt% KBrO3.

[0016] Preferably, the abrasive is 15-25 wt% silica, the dispersant is 0.8-1.2 wt% graphene oxide, the corrosion inhibitor is 8-12 mmol / L PTA, and the electrolyte is 0.1-0.2 mol / L lithium sulfate.

[0017] Preferably, the polishing pad is made of polyurethane, the speed of the polishing machine's carrier disk is controlled at 50-60 rpm, the speed of the clamp is set at 45-55 rpm, and it can polish wafers compatible with 2-6 inches.

[0018] Preferably, the cleaning steps include heating to remove wax, ultrasonic cleaning with SPM solution, immersion in HF acid to remove impurities, and final drying. Specifically, the wafer is adhered to a quartz glass plate with paraffin wax for bonding, the surface is thinned and polished using a grinding device, and alcohol is used to clean and remove residues from the surface of the bond.

[0019] To achieve the above-mentioned objectives, an embodiment also provides a photoelectric-assisted wide-bandgap semiconductor wafer polishing system, the system being used to implement the above-mentioned method, the system comprising: A sealed chamber designed to contain the polishing environment; Vacuum adsorption fixtures and carriers are used to hold wafers and drive their rotation, and can polish wafers compatible with 2-6 inches; Ultraviolet light source is used to provide excitation energy; An electrochemical workstation is used to control the working electrode potential or current density. The closed-loop feedback control module is used to dynamically adjust the current output based on the real-time photocurrent density. Polishing slurry recycling system is used to reduce polishing slurry consumption.

[0020] The closed-loop feedback control module dynamically adjusts the current output and pressure based on the real-time photocurrent density. Within the closed-loop feedback control module, an incremental PID control algorithm is used to calculate the control increment at the current moment. After parameter tuning, the proportional, integral, and derivative coefficients are added to the control quantity at the previous moment to obtain the current output. This achieves rapid response to the controlled object, elimination of steady-state errors, and suppression of overshoot. The polishing fluid recycling system is used to reduce consumption.

[0021] Compared with the prior art, the beneficial effects of the present invention include at least the following: Regarding material removal efficiency, this invention utilizes an electric field driven by an optical field to drive hole migration, effectively suppressing photogenerated electron-hole recombination and enhancing the surface oxidation reaction rate. Simultaneously, by controlling the substrate pressure, a synergistic effect of light, electricity, and force is achieved, resulting in high removal efficiency and low surface roughness polishing for wide-bandgap semiconductor materials. Experimental data show that the material removal efficiency is increased from 50-100 nm / h in traditional processes to a maximum of 1 μm / h, an increase of approximately 20 times.

[0022] Regarding surface roughness, by utilizing the electric field to homogenize the spatial distribution of free radicals, local over-oxidation and thermal stress concentration are reduced. After polishing, the surface roughness (Ra) of GaN wafers is reduced from 0.30 nm to below 0.16 nm, with a surface quality improvement of more than 20%.

[0023] In terms of subsurface damage control, electrochemical selective dissolution was used instead of traditional mechanical friction removal to avoid stress accumulation during processing. C-AFM testing showed that there was no subsurface damage on the wafer surface after treatment, effectively suppressing the formation of microcracks.

[0024] Regarding process stability, a multi-parameter feedback mechanism was introduced to monitor and adjust current density and light intensity in real time. During a 3-hour continuous test, current density fluctuations were controlled within ±5%, and light intensity fluctuations were controlled within ±3%.

[0025] In terms of production costs, a polishing slurry recovery system was built and combined with formula optimization to reduce material consumption. Polishing slurry usage was reduced by more than 30%, resulting in a corresponding decrease in unit production costs.

[0026] In terms of product qualification rate, the comprehensive process window has been widened and the defect density has been reduced, increasing the product yield from 75% to over 98%, meeting the consistency and yield requirements of high-end semiconductor manufacturing. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the structure of the optoelectronic-assisted wide bandgap semiconductor wafer polishing system provided in the embodiment; Figure 2 This is a schematic flowchart of the optoelectronic-assisted wide bandgap semiconductor wafer polishing method provided in the embodiment. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the scope of protection of this invention.

[0030] The technical concept of this invention is as follows: to overcome the limitations of a single photocatalytic mode, an innovative electrochemical and force field modulation mechanism is introduced into a wide bandgap semiconductor polishing system. By constructing a synergistic environment of multi-physics field coupling of "light field-electric field-force field", the light field promotes the generation of photogenerated electron-hole pairs, the applied current precisely controls the interface reaction kinetics, and the applied pressure controls the polishing effect. This aims to provide a new path for wafer planarization of materials such as gallium nitride and aluminum nitride that combines high efficiency, ultra-low damage, and high stability. Based on the above inventive concept, the following embodiments and comparative examples are provided.

[0031] The embodiment employs a photoelectric-assisted wide-bandgap semiconductor wafer polishing system, such as... Figure 1 As shown, a sealed chamber is used to contain the polishing environment, and it also includes: a polishing slurry circulation and recovery system 1 to reduce polishing slurry consumption; an ultraviolet light source 2 to provide excitation energy; an electrochemical workstation 3 to control the working electrode potential or current density; an unlabeled three-electrode working system for precise control of the working voltage; a vacuum adsorption fixture 4 and a carrier disk 5 to fix the wafer and drive its rotation, capable of polishing wafers compatible with 2-6 inches; and an unlabeled closed-loop feedback control module to dynamically adjust the current output based on the real-time photocurrent density. The optoelectronic-assisted wide-bandgap semiconductor wafer polishing method implemented based on this semiconductor wafer polishing system, such as... Figure 2 As shown, it includes the following steps: S1, the wide bandgap semiconductor wafer after cleaning is fixed on the vacuum adsorption fixture of the polishing device, wherein the wide bandgap semiconductor wafer includes aluminum nitride wafer or gallium nitride wafer; S2, introduce nitrogen into the sealed chamber and maintain the set pressure; S3, apply ultraviolet light to the polishing area, simultaneously irradiating the polishing slurry and the wide bandgap semiconductor wafer, and use an electrochemical workstation to apply a specific current density and working electrode bias voltage to the wide bandgap semiconductor wafer, and change the wafer pressure of the polishing machine according to the magnitude of the current and the polishing rate. S4, drive the polishing machine carrier disk and fixture to rotate, and perform synergistic polishing using a polishing slurry containing photocatalyst and oxidant. After polishing, the wafer is cleaned and dried. Specific embodiments are given below.

[0032] Example 1: A 4-inch GaN wafer was polished using a polishing slurry containing a photocatalyst of 0.6 wt% TiO2, 0.3 wt% SnO2, 0.1 wt% ZnO, and 0.1 wt% ZrO2, and an oxidant of 4.0 wt% H2O2 and 2.5 wt% K2S2O8. In addition, the polishing slurry also included 20 wt% silica, 1.0 wt% graphene oxide dispersant, 10 mmol / L PTA corrosion inhibitor, and 0.15 mol / L lithium sulfate as an electrolyte; the pH of the polishing slurry was adjusted to approximately 2.4.

[0033] Before polishing, the sealed chamber was evacuated and purged with nitrogen to maintain the internal pressure at 0.10 MPa. Simultaneously, the optical path between the ultraviolet light source and the polishing area was purged with nitrogen using an ultraviolet light purging module. The nitrogen flow rate was 0.5–5 L / min. The ultraviolet light wavelength was set to 300 nm, and the polishing solution temperature was maintained at 45°C during the polishing process. o C. The bias voltage of the working electrode is stabilized at 1.2 V based on the actual polishing conditions. vs Ag / AgCl (saturated KCl solution), maintaining a slide pressure of 5 psi and an illumination intensity of 200 mW / cm² during polishing. 2 By controlling the pressure, light intensity, and polishing fluid composition, the current density was controlled at 2.0 mA / cm². 2 The polishing rate is approximately 600 nm / h, and the roughness Ra is approximately 0.16 nm.

[0034] Example 2: A 2-inch AlN wafer was polished using a polishing slurry containing a photocatalyst of 1.0 wt% TiO2, 0.6 wt% SnO2, 0.2 wt% ZnO, and 0.2 wt% ZrO2, and an oxidant of 8.0 wt% H2O2, 3.0 wt% K2S2O8, and 5.0 wt% KBrO3. In addition, the polishing slurry also included 20 wt% silica, 1.0 wt% graphene oxide dispersant, 10 mmol / L PTA corrosion inhibitor, and 0.15 mol / L lithium sulfate as an electrolyte; the pH of the polishing slurry was adjusted to approximately 2.3.

[0035] Before polishing, the sealed chamber was evacuated and purged with nitrogen to maintain the internal pressure at 0.10 MPa. Simultaneously, the UV light path between the UV light source and the polishing area was purged with nitrogen using a UV light path purging module. The nitrogen flow rate was 0.5–5 L / min. The UV wavelength was set to 206 nm, and the polishing solution temperature was maintained at 45°C during the polishing process. o C. Based on the sample reaction, set the bias voltage of the working electrode of the electrochemical workstation to 1.3 V. vs Ag / AgCl (saturated KCl solution), maintaining a slide pressure of 5 psi and an illumination intensity of 200 mW / cm² during polishing. 2 By controlling the pressure, light intensity, and polishing fluid composition, the current density was controlled at 1.0 mA / cm². 2 The polishing rate is approximately 500 nm / h, and the roughness Ra is 0.21 nm.

[0036] Comparative Example 1: A 4-inch GaN wafer was polished using a polishing slurry containing a photocatalyst of 0.6 wt% TiO2, 0.3 wt% SnO2, 0.1 wt% ZnO, and 0.1 wt% ZrO2, and an oxidant of 4.0 wt% H2O2 and 2.5 wt% K2S2O8. In addition, the polishing slurry also included 20 wt% silica, 1.0 wt% graphene oxide dispersant, 10 mmol / L PTA corrosion inhibitor, and 0.15 mol / L lithium sulfate as an electrolyte; the pH of the polishing slurry was adjusted to approximately 2.4.

[0037] Ultraviolet light irradiation was canceled and the polishing solution temperature was maintained at 45°C during the polishing process. o C. The bias voltage of the working electrode is stabilized at 1.2 V based on the actual polishing conditions. vs Ag / AgCl (saturated KCl solution), maintaining a substrate pressure of 5 psi and a current density of approximately 0.1 mA / cm² during polishing. 2 The polishing rate was approximately 100 nm / h, and the roughness Ra was around 0.31 nm. This was mainly due to the lack of light, which prevented the excitation of charge carrier reactions, resulting in a slow polishing rate and poor polishing quality.

[0038] Comparative Example 2: A 4-inch GaN wafer was polished using a polishing slurry containing a photocatalyst of 0.6 wt% TiO2, 0.3 wt% SnO2, 0.1 wt% ZnO, and 0.1 wt% ZrO2, and an oxidant of 4.0 wt% H2O2 and 2.5 wt% K2S2O8. In addition, the polishing slurry also included 20 wt% silica, 1.0 wt% graphene oxide dispersant, 10 mmol / L PTA corrosion inhibitor, and 0.15 mol / L lithium sulfate as an electrolyte; the pH of the polishing slurry was adjusted to approximately 2.4.

[0039] Before polishing, the sealed chamber was evacuated and purged with nitrogen to maintain the internal pressure at 0.10 MPa. Simultaneously, the optical path between the ultraviolet light source and the polishing area was purged with nitrogen using an ultraviolet light purging module. The nitrogen flow rate was 0.5–5 L / min. The ultraviolet light wavelength was set to 300 nm, and the polishing solution temperature was maintained at 45°C during the polishing process. o C. Without applying an electrical bias voltage, the substrate pressure was maintained at 5 psi during polishing, the polishing rate was approximately 80 nm / h, and the roughness Ra was around 0.42 nm. This was mainly due to the lack of an external electric field, resulting in low separation efficiency of photogenerated electron-hole pairs and insufficient interfacial oxidation reaction, leading to a low polishing rate and poor surface quality.

[0040] Comparative Example 3: A 2-inch AlN wafer was polished using a polishing slurry containing a photocatalyst of 1.0 wt% TiO2, 0.6 wt% SnO2, 0.2 wt% ZnO, and 0.2 wt% ZrO2, and an oxidant of 8.0 wt% H2O2, 3.0 wt% K2S2O8, and 5.0 wt% KBrO3. In addition, the polishing slurry also included 20 wt% silica, 1.0 wt% graphene oxide dispersant, 10 mmol / L PTA corrosion inhibitor, and 0.15 mol / L lithium sulfate as an electrolyte; the pH of the polishing slurry was adjusted to approximately 2.3.

[0041] The ultraviolet light wavelength was set to 360 nm and the polishing solution temperature was maintained at 45°C during the polishing process. o C. The bias voltage of the working electrode of the electrochemical workstation is set to 1.3 V. vs Ag / AgCl (saturated KCl solution), maintaining a slide pressure of 5 psi and an illumination intensity of 200 mW / cm² during polishing. 2 By controlling the pressure and light intensity, the current density could not be reached to 1.0 mA / cm². 2The polishing rate was approximately 50 nm / h, resulting in a sample roughness Ra of around 1 nm. This low polishing efficiency was mainly due to the mismatch between the polishing wavelength and the AlN wafer polishing process.

[0042] Comparative Example 4: A 4-inch GaN wafer is polished using a polishing slurry comprising a photocatalyst of 2.0 wt% TiO2, 0.6 wt% SnO2, 0.6 wt% ZnO, and 0.6 wt% ZrO2, and an oxidant of 10.0 wt% H2O2, 3.0 wt% K2S2O8, and 6.0 wt% KBrO3. Further preferably, the polishing slurry also includes: 20 wt% silica, 1.0 wt% graphene oxide dispersant, 10 mmol / L PTA corrosion inhibitor, and 0.10 mol / L lithium sulfate as an electrolyte; and the pH of the polishing slurry is adjusted to approximately 2.3.

[0043] The ultraviolet light wavelength was set to 300 nm and the polishing solution temperature was maintained at 45°C during the polishing process. o C. The bias voltage of the working electrode of the electrochemical workstation is set to 1.2 V. vs Ag / AgCl (saturated KCl solution), maintaining a slide pressure of 5 psi and an illumination intensity of 200 mW / cm² during polishing. 2 By controlling the pressure and light intensity, the current density was adjusted to approximately 3.0 mA / cm². 2 The polishing rate was approximately 1300 nm / h, resulting in a sample roughness Ra of around 2 nm. Due to the excessively high concentrations of photocatalyst and oxidant, the interfacial oxidation reaction was too rapid and unevenly distributed, leading to localized over-corrosion or over-removal, thus increasing the surface roughness.

[0044] Comparative Example 5: A 4-inch GaN wafer was polished using a polishing slurry containing a photocatalyst of 0.6 wt% TiO2, 0.3 wt% SnO2, 0.1 wt% ZnO, and 0.1 wt% ZrO2, and an oxidant of 4.0 wt% H2O2 and 2.5 wt% K2S2O8. In addition, the polishing slurry also included 20 wt% silica, 1.0 wt% graphene oxide dispersant, 10 mmol / L PTA corrosion inhibitor, and 0.15 mol / L lithium sulfate as an electrolyte; the pH of the polishing slurry was adjusted to approximately 2.4.

[0045] The ultraviolet light wavelength was set to 300 nm and the polishing solution temperature was maintained at 45°C during the polishing process. oC. The bias voltage of the working electrode of the electrochemical workstation is set to 2.1 V. vs Ag / AgCl (saturated KCl solution), maintaining a slide pressure of approximately 15 psi and an illumination intensity of 200 mW / cm² during polishing. 2 The current density is 25 mA / cm². 2 The polishing rate was approximately 600 nm / h, and the wafer cracked during the polishing process. The main reason was that the working electrode potential and the carrier pressure were too high, resulting in an excessively fast local reaction rate, which in turn caused cracks and led to wafer breakage.

[0046] The specific embodiments described above illustrate the technical solution and beneficial effects of the present invention in detail. It should be understood that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, additions, and equivalent substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for photoelectric-assisted polishing of wide-bandgap semiconductor wafers, characterized in that, Includes the following steps: The wide bandgap semiconductor wafer, after cleaning, is fixed on the vacuum adsorption fixture of the polishing device, wherein the wide bandgap semiconductor wafer includes aluminum nitride wafer or gallium nitride wafer; The sealed chamber was evacuated and replaced with inert gas to create a low-oxygen, low-moisture environment along the path of ultraviolet light propagation. Ultraviolet light was applied to the polishing area, simultaneously irradiating the polishing slurry and the wide-bandgap semiconductor wafer. A specific current density and working electrode bias voltage were applied to the wide-bandgap semiconductor wafer using an electrochemical workstation. The wafer carrier pressure of the polishing machine was adjusted according to the current magnitude and polishing rate. A three-electrode working system was constructed, with the wide-bandgap semiconductor wafer as the working electrode, the bottom polishing disk as the counter electrode, and Ag / AgCl as the reference electrode. The working electrode bias voltage was 0.5–1.5 V vs. Ag / AgCl, and the current density was maintained at 0.1–10.0 mA / cm². 2 Within the range; With a substrate pressure of 3-10 psi, the polishing rate increases accordingly when the current density, light intensity and substrate pressure are increased together. The polishing rate is 500-1500 nm / h, and the surface roughness Ra is controlled within the range of 0.1-0.3 nm. The polishing machine's carrier disk and fixture rotate, and the polishing is carried out in a synergistic process using a polishing slurry containing photocatalysts and oxidants. After polishing, the wafer is cleaned and dried.

2. The photoelectric-assisted wide bandgap semiconductor wafer polishing method according to claim 1, characterized in that, The inert gas is nitrogen, the pressure inside the sealed chamber is 0.08-0.12 MPa, and nitrogen is blown into the optical path between the ultraviolet light source and the polishing area to reduce the absorption of ultraviolet light by oxygen and water vapor.

3. The photoelectric-assisted wide bandgap semiconductor wafer polishing method according to claim 1, characterized in that, For GaN wafers, the wavelength range of the ultraviolet light is 280-340 nm; for AlN wafers, the wavelength range of the ultraviolet light is 180-210 nm; the irradiance is 100-300 mW / cm². 2 The polishing slurry temperature is maintained at 30-60°C during the polishing process. o C.

4. The photoelectric-assisted wide bandgap semiconductor wafer polishing method according to claim 1, characterized in that, The polishing solution contains a photocatalyst, an oxidant, an abrasive, a dispersant, a corrosion inhibitor, and an electrolyte, and the pH value of the polishing solution is in the range of 2.0-3.

0.

5. The photoelectric-assisted wide bandgap semiconductor wafer polishing method according to claim 4, characterized in that, The photocatalyst is one or more of the following: 0.5-1.0 wt% TiO2, 0.2-0.6 wt% SnO2, 0.1-0.5 wt% ZnO, and 0.1-0.5 wt% ZrO2; The oxidant is one or more selected from 2.0-8.0 wt% H2O2, 2.0-5.4 wt% K2S2O8, and 2.0-5.0 wt% KBrO3; The abrasive is 15-25 wt% silicon dioxide; The dispersant is 0.8-1.2 wt% graphene oxide; The corrosion inhibitor is 8-12 mmol / L PTA; The electrolyte is lithium sulfate at a concentration of 0.1-0.2 mol / L.

6. The photoelectric-assisted wide bandgap semiconductor wafer polishing method according to claim 1, characterized in that, The rotational speed of the polishing machine carrier is controlled at 50-60 rpm, and the rotational speed of the clamp is set at 45-55 rpm.

7. A photoelectric-assisted wide-bandgap semiconductor wafer polishing system, characterized in that, The system is used to implement the method according to any one of claims 1-6, the system comprising: A sealed chamber designed to contain the polishing environment; Vacuum adsorption fixtures and carriers are used to hold wafers and drive their rotation, and can polish wafers compatible with 2-6 inches; The ultraviolet light path purging module is used to introduce nitrogen or inert gas into the light path between the ultraviolet light source and the polishing area; Ultraviolet light source is used to provide excitation energy; An electrochemical workstation is used to control the working electrode potential or current density. A three-electrode working system is used for precise control of the working voltage; The closed-loop feedback control module is used to dynamically adjust the current output based on the real-time photocurrent density. Polishing slurry recycling system is used to reduce polishing slurry consumption.

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