Processing method of large-size lithium niobate wafer
By optimizing the cutting and grinding processes, and combining chemical mechanical polishing and stress relief treatment, the problems of cutting defects, precision and warping deformation in the processing of large-size lithium niobate wafers have been solved, achieving efficient and low-cost processing results.
Patent Information
- Application Number
- CN202510898644.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-01
- Publication Date
- 2025-11-18
AI Technical Summary
Existing technologies for processing large-size lithium niobate wafers suffer from numerous cutting defects, low grinding and polishing precision, easy wafer warping and deformation, high processing costs, and low efficiency.
High-precision multi-wire cutting equipment is used in conjunction with optimized diamond wire parameters and cutting fluid formulation, combined with step-by-step grinding and chemical mechanical polishing processes. A specific ratio of grinding fluid and polishing fluid is used, along with stress relief treatment. Internal stress is released through HF:HNO3 solution, and impurities are removed by ultrasonic cleaning.
Significantly reduces cutting defects, improves wafer dimensional accuracy and surface quality, lowers costs, increases yield and processing efficiency, and meets the requirements of high-end optoelectronic devices.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of lithium niobate wafer, and particularly relates to a processing method of large-size lithium niobate wafer. BACKGROUND
[0002] Lithium niobate crystal plays a key role in many fields such as optical communication, optical signal processing and microwave devices due to its excellent piezoelectric, electro-optic, acousto-optic and nonlinear optical properties. With the rapid development of related technologies, the demand for large-size lithium niobate wafers is increasing, but the processing process faces many challenges.
[0003] In the cutting link, due to the high hardness and brittleness of lithium niobate crystal, the cutting line is prone to wear when using traditional cutting methods, and defects such as edge collapse and cracks are easily generated on the wafer surface, which seriously affects the size accuracy and surface quality of the wafer, greatly increasing the difficulty of subsequent processing. In the grinding and polishing stage, the flatness and roughness of large-size lithium niobate wafers are difficult to control. In the traditional grinding process, the contact between the grinding disc and the wafer is uneven, resulting in inconsistent removal of different parts of the wafer, making it difficult to achieve high-precision flatness requirements; and in the polishing process, due to the dispersion of the polishing liquid and the uniformity of the chemical reaction, the surface roughness of the wafer is difficult to reduce to the level required by high-end applications. In addition, due to the action of mechanical stress and thermal stress during the processing of large-size wafers, the internal stress distribution is uneven, and warping deformation is easily generated, reducing the yield.
[0004] At present, the existing technology has limitations in solving the above problems. Although some improved cutting processes can reduce some defects, they cannot fundamentally solve the problems caused by cutting line wear and crystal brittleness. Some grinding and polishing processes have certain effect improvement, but there are still deficiencies in cost, efficiency and quality stability. Therefore, it is urgent to develop a large-size lithium niobate wafer processing method that can effectively overcome the above problems. SUMMARY
[0005] In view of the defects of the prior art, the purpose of the present application is to provide a processing method of large-size lithium niobate wafer, which aims to solve the problems of many cutting defects, low grinding and polishing precision, wafer warping deformation, high processing cost and low efficiency in the existing processing method.
[0006] The technical problem solved by the present application adopts the following technical scheme: The present application provides a processing method of large-size lithium niobate wafer, which comprises the following weight parts of raw materials: Step one, crystal cutting: fixing the large-size lithium niobate single crystal on a high-precision multi-line cutting equipment for cutting treatment; Step two, coarse grinding: the cut wafer is placed on a double-sided grinding machine, and a silicon carbide grinding disc with a particle size of 1000-1500 is used for coarse grinding treatment; Step three, fine grinding; Step four, stress relief: the ground wafer is placed in a basket in a solution of HF:HNO3=1:1 for 12-15 hours, so that the internal stress of the wafer is fully released, and then the wafer is placed in deionized water for immersion cleaning; Step five, chemical mechanical polishing, the fine ground wafer is placed in a CMP device for mechanical polishing treatment; Step six, ultrasonic cleaning: the polished wafer is placed in an ultrasonic cleaning tank containing a mixture of ethanol and deionized water, the ultrasonic frequency is set to 45-55 kHz, and the cleaning time is 12-18 min. The cavitation effect of ultrasonic waves is used to completely remove the polishing liquid and impurities on the wafer surface, ensuring the cleanliness of the wafer surface.
[0007] Preferably, a high-strength diamond wire with a diameter of 0.1-0.2 mm is selected for crystal cutting, and the diamond grit size on the surface of the diamond wire is controlled to be 5-8 μm; During cutting, the wire speed of the diamond wire is set to 1800-2200 m / min, and the tension of the diamond wire is stably maintained at 18-22 N through a precisely controlled tension adjustment system, ensuring the stability of the diamond wire during cutting, and a cutting liquid is used for cutting treatment.
[0008] Preferably, the cutting liquid cutting treatment uses a cutting liquid mixed by polyethylene glycol, triethanolamine and deionized water in a volume ratio of 3:1:10, which is uniformly sprayed in the cutting area by a high-pressure spraying system at a flow rate of 12-18 L / min, and a lithium niobate wafer with a thickness of 0.3-0.6 mm is cut out.
[0009] Preferably, the grinding pressure in the coarse grinding is controlled at 0.08-0.12 MPa, and the intelligent pressure control system is used to ensure that the pressure is uniformly distributed on the wafer surface, the grinding disc speed is set to 25-35 r / min, and the water-based grinding fluid containing 12-15 wt% silicon carbide abrasive, 3-5 wt% dispersant and 2-4 wt% lubricant is continuously supplied at a flow rate of 6-9 L / min. The wafer is ground to a thickness of 0.25-0.35 mm, and the damage layer on the cutting surface is effectively removed; the water-based lubricant for the grinding fluid is prepared by mixing nanometer tungsten disulfide and water in a weight ratio of 2:7, and the dispersant is sodium tripolyphosphate.
[0010] Preferably, the fine grinding is carried out by replacing the silicon carbide grinding disc with a granularity of 2500-3500 mesh, adjusting the grinding pressure to 0.03-0.06 MPa, setting the grinding disc rotation speed to 18-25 r / min, using the newly prepared water-based grinding fluid containing 10-13 wt% silicon carbide abrasive, 4-6 wt% lubricant and 1-3 wt% surfactant, and performing fine grinding at a flow rate of 4-7 L / min, so that the wafer thickness reaches 0.18-0.5 mm, the wafer surface flatness is significantly improved, and the surface roughness is reduced; the lubricant is molybdenum selenide; and the water-based grinding fluid of the surfactant is prepared by mixing sodium dodecyl benzene sulfonate and water at a weight ratio of 2:5.
[0011] Preferably, in step five, the polishing liquid is prepared by using silica sol, wherein the particle size of the silica particles is 60-90 nm, the concentration is 6-9 wt%, and 0.8-1.2 wt% of sodium hydroxide is added as a catalyst to promote the chemical corrosion reaction; the polishing pressure is 0.02-0.04 MPa, which is monitored and adjusted in real time by a high-precision pressure sensor; and the polishing pad rotation speed is 35-50 r / min, and the polishing time is 40-50 min.
[0012] Preferably, the volume ratio of the ethanol and deionized water mixed solution is 1:5.
[0013] Compared with the prior art, the present application has the following advantages: The present application is a processing method for large-size lithium niobate wafers, which aims to solve the problems of the existing processing methods, such as many cutting defects, low grinding and polishing precision, wafer warping and deformation, high processing cost, and low efficiency, etc., and to improve the size precision, surface quality and yield of large-size lithium niobate wafers by optimizing the processing technology and parameters, thereby meeting the strict requirements of optoelectronic devices for large-size lithium niobate wafers; High-precision cutting: by optimizing the parameters of the diamond wire, the cutting fluid formula and the cutting process parameters, the edge collapse and cracks during the cutting process of lithium niobate crystals are significantly reduced, the service life of the cutting wire is improved, and the size precision and surface quality of the wafers are ensured, providing a good foundation for subsequent processing, and compared with the traditional cutting method, the cutting defect rate is reduced by more than 50%; High-efficiency grinding and polishing: by adopting a process combining step-by-step grinding and chemical mechanical polishing, and using specially treated grinding discs and carefully prepared grinding fluid and polishing fluid, the damaged layer on the wafer surface can be quickly and accurately removed, and the surface flatness and roughness can be effectively improved; through detection, the surface roughness Ra of the wafer processed by the present application can reach below 0.2 nm, and the flatness error can be controlled within 1 µm, meeting the strict requirements of high-end optoelectronic devices for wafer surface quality, and the processing efficiency is improved by more than 30%; Stress relief: soaking in a mixture of hydrofluoric acid and nitric acid in a certain proportion can effectively eliminate the stress inside the wafer, make the stress distribution inside the wafer uniform, reduce the wafer warping deformation, improve the yield of the wafer, and the yield is increased by more than 10% compared with the traditional process, reaching more than 95%; Cost reduction: by reasonably selecting the processing materials and optimizing the process parameters, the material loss and equipment wear are reduced, the processing efficiency is improved, thereby the processing cost of the large-size lithium niobate wafer is reduced, and the comprehensive cost is reduced by more than 30%. DETAILED DESCRIPTION
[0014] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.
[0015] The large-size lithium niobate wafer processing method in the embodiment comprises the following raw materials by weight: Step one, crystal cutting: fixing the large-size lithium niobate single crystal on a high-precision multi-wire cutting device for cutting treatment; Step two, rough grinding: placing the cut wafer on a double-sided grinding machine and using a silicon carbide grinding disc with a particle size of 1000-1500 for rough grinding treatment; Step three, fine grinding; Step four, stress relief: placing the ground wafer in a flower basket in a solution of HF:HNO3=1:1 for 12-15 hours to fully release the stress inside the wafer, and then placing the wafer in deionized water for immersion cleaning; Step five, chemical mechanical polishing: placing the fine-ground wafer in a CMP device for mechanical polishing treatment; Step six, ultrasonic cleaning: placing the polished wafer in an ultrasonic cleaning tank containing a mixed solution of ethanol and deionized water, setting the ultrasonic frequency to 45-55 kHz, and cleaning for 12-18 min, so as to completely remove the polishing liquid and impurities remaining on the wafer surface by the cavitation effect of ultrasonic waves, and ensure the cleanliness of the wafer surface.
[0016] In the crystal cutting of the embodiment, high-strength diamond wire with a diameter of 0.1-0.2 mm is selected, and the particle size of the diamond grit on the surface of the diamond wire is controlled to be 5-8 μm; During cutting, the linear speed of the diamond wire is set to 1800-2200 m / min, the tension of the diamond wire is stably maintained at 18-22 N through a precisely controlled tension adjustment system, the stability of the diamond wire during cutting is ensured, and cutting liquid is used for cutting treatment.
[0017] The cutting liquid cutting treatment of the embodiment adopts a cutting liquid mixed by polyethylene glycol, triethanolamine and deionized water in a volume ratio of 3:1:10, and uniformly sprayed in the cutting area by a high-pressure spraying system at a flow rate of 12-18 L / min to cut lithium niobate wafers with a thickness of 0.3-0.6 mm.
[0018] In the rough grinding of the embodiment, the grinding pressure is controlled at 0.08-0.12 MPa, the pressure is uniformly distributed on the wafer surface through an intelligent pressure control system, the grinding disc rotation speed is set at 25-35 r / min, a water-based grinding liquid containing 12-15 wt% silicon carbide abrasive, 3-5 wt% dispersant and 2-4 wt% lubricant is continuously supplied at a flow rate of 6-9 L / min to grind the wafer to a thickness of 0.25-0.35 mm, and effectively remove the damage layer on the cutting surface; the water-based grinding liquid of the lubricant is prepared by mixing nano tungsten disulfide and water in a weight ratio of 2:7, and the dispersant is sodium tripolyphosphate.
[0019] In the fine grinding of the embodiment, the silicon carbide grinding disc with a granularity of 2500-3500 is replaced, the grinding pressure is adjusted to 0.03-0.06 MPa, the grinding disc rotation speed is set at 18-25 r / min, and a newly prepared water-based grinding liquid containing 10-13 wt% silicon carbide abrasive, 4-6 wt% lubricant and 1-3 wt% surfactant is used for fine grinding at a flow rate of 4-7 L / min to make the wafer thickness reach 0.18-0.5 mm, significantly improve the wafer surface flatness and reduce the surface roughness; the lubricant is molybdenum selenide; the water-based grinding liquid of the surfactant is prepared by mixing sodium dodecyl benzene sulfonate and water in a weight ratio of 2:5.
[0020] In step five of the embodiment, silica sol is used as the polishing liquid, the silica particle size is 60-90 nm, the concentration is 6-9 wt%, and 0.8-1.2 wt% of sodium hydroxide is added as a catalyst to promote the chemical corrosion reaction, the polishing pressure is 0.02-0.04 MPa, the pressure is monitored and adjusted in real time by a high-precision pressure sensor, the polishing pad rotation speed is 35-50 r / min, and the polishing time is 40-50 min.
[0021] The volume ratio of the ethanol and deionized water mixed solution in the embodiment is 1:5.
[0022] Example 1 1. Crystal cutting: select a lithium niobate wafer with a size of 2 inches x 2 inches x 0.5 mm. 100mm x 80mm lithium niobate single crystal is fixed on a high-precision multi-wire cutting device. A diameter of 0.15mm diamond wire is selected, the diamond grit size is 6μm, the wire speed is 2000m / min, the diamond wire tension is 20N, the cutting fluid is a mixed solution of polyethylene glycol, triethanolamine and deionized water with a volume ratio of 3:1:10, the cutting fluid is sprayed at a flow rate of 15L / min, and a lithium niobate wafer with a thickness of 0.35mm is cut.
[0023] 2. Rough grinding: the wafer blank is placed on a double-sided grinding machine, a 1200 mesh silicon carbide grinding disc is used, the grinding pressure is 0.1MPa, the grinding disc speed is 30r / min, a water-based grinding fluid containing 13wt% silicon carbide abrasive, 4wt% dispersant and 3wt% lubricant is used, the grinding fluid is supplied at a flow rate of 7L / min, and the wafer thickness is ground to 0.28mm.
[0024] 3. Fine grinding: replace the 3000 mesh silicon carbide grinding disc, the grinding pressure is 0.05MPa, the grinding disc speed is 20r / min, a water-based grinding fluid containing 12wt% silicon carbide abrasive, 5wt% lubricant and 2wt% surfactant is used, fine grinding is carried out at a flow rate of 5L / min, and the wafer thickness reaches 0.22mm.
[0025] 4. Stress relief: the ground wafer is placed in a flower basket in a solution of HF:HNO3=1:1 for 12 hours, so that the internal stress of the wafer is fully released, and then the wafer is placed in deionized water for 10 minutes of immersion cleaning.
[0026] 5. Chemical mechanical polishing (CMP): the fine ground wafer is placed in a CMP device, a silica sol polishing fluid is used, the silica particle size is 70nm, the concentration is 8wt%, 1wt% sodium hydroxide is added, the polishing pressure is 0.03MPa, the polishing pad speed is 40r / min, and the polishing time is 45min.
[0027] 6. Ultrasonic cleaning: the polished wafer is placed in an ultrasonic cleaning tank with a volume ratio of ethanol to deionized water of 1:5, the ultrasonic frequency is 50kHz, and the cleaning time is 15min.
[0028] Example 2 1. Crystal cutting: a lithium niobate single crystal with a size of 150mm x 60mm is selected, a diameter of 0.18mm diamond wire is used, the diamond grit size is 7μm, the wire speed is 2100m / min, the diamond wire tension is 21N, the cutting fluid is a mixed solution of polyethylene glycol, triethanolamine and deionized water with a volume ratio of 3:1:10, the cutting fluid flow rate is 16L / min, and a wafer with a thickness of 0.45mm is obtained.
[0029] 2. Coarse grinding: on double-sided grinder, 1300 mesh silicon carbide grinding disc, grinding pressure 0.11 MPa, rotation speed 32 r / min, water-based grinding fluid containing 14 wt% silicon carbide abrasive, 4.5 wt% dispersant and 3.5 wt% lubricant, flow rate 8 L / min, grinding to a thickness of 0.4 mm.
[0030] 3. Fine grinding: replace 3200 mesh silicon carbide grinding disc, grinding pressure 0.04 MPa, rotation speed 22 r / min, water-based grinding fluid containing 11 wt% silicon carbide abrasive, 5.5 wt% lubricant and 2.5 wt% surfactant, flow rate 6 L / min, wafer thickness after fine grinding is 0.36 mm.
[0031] 4. Stress relief: place the ground wafer in a flower basket in a solution of HF:HNO3=1:1 for 15 hours to fully release the internal stress of the wafer, then place the wafer in deionized water for 15 minutes of immersion cleaning.
[0032] 5. Chemical mechanical polishing (CMP): in the CMP equipment, the particle size of the silica sol polishing liquid is 80 nm, the concentration is 7 wt%, 1.1 wt% sodium hydroxide is added, the polishing pressure is 0.035 MPa, the polishing pad rotation speed is 45 r / min, and the polishing time is 50 min.
[0033] Ultrasonic cleaning: put into an ultrasonic cleaning tank with a volume ratio of ethanol to deionized water of 1:5, ultrasonic frequency 52 kHz, cleaning time 20 min.
[0034] Comparative Example 1. The difference from Example 1 is that no coarse grinding treatment is used.
[0035] Comparative Example 2. The difference from Example 3 is that no fine grinding treatment is used.
[0036] Comparative Example 3. The difference from Example 3 is that no stress relief treatment is used.
[0037] Comparative Example 4. The difference from Example 3 is that no chemical mechanical polishing treatment is used.
[0038] The product performance tests of Examples 1-2 and Comparative Examples 1-4 are as follows:
[0039] From the examples 1-2, comparative examples 1-4, it can be seen that the surface roughness and yield of the product of the example 1 of the present application and the effect of total thickness variation are excellent, while in the comparative examples 1-4, no coarse grinding treatment, no fine grinding treatment, no stress relief treatment, no chemical mechanical polishing treatment are adopted, and the performance of the product has a significant deterioration trend. Only by adopting the combined process of the present application, the effect of the product is the most significant, and the process of the product is indispensable. Only by adopting the specific process of the present application, the performance of the product is the most significant.
[0040] It is apparent to those skilled in the art that the present application is not limited to the details of the foregoing exemplary embodiments, and that the present application can be carried out in other specific forms without departing from the spirit or essential characteristics of the present application. Therefore, it is to be understood that the embodiments are to be considered in all respects as illustrative and not restrictive, and the scope of the present application is to be determined not by the foregoing description but by the appended claims, and all changes which come within the meaning and range of equivalents of the claims are to be embraced therein.
[0041] Furthermore, it should be understood that although the present specification is described in terms of embodiments, not every embodiment according to the present specification need necessarily include every independent technical feature mentioned in the specification, and that reference to a particular feature of the specification does not mean that every embodiment according to the present specification necessarily includes that particular feature. The description of the embodiments is merely exemplary in nature and is in no way intended to limit the present application, its application, or uses.
Claims
1. A method for processing large-size lithium niobate wafers, characterized in that, Including the following parts by weight of raw materials: Step 1, Crystal Cutting: The large-size lithium niobate single crystal is fixed on a high-precision multi-wire cutting device for cutting. Step 2, coarse grinding: Place the cut wafer on a double-sided grinding machine and coarsely grind it using a silicon carbide grinding disc with a grit size of 1000-1500 mesh. Step 3, fine grinding; Step 4, stress relief: Place the polished wafer in a HF:HNO3 = 1:1 solution for 12-15 hours using a basket to fully release the internal stress of the wafer, and then soak and clean the wafer in deionized water. Step 5, Chemical Mechanical Polishing (CMP): The finely ground wafer is placed in a CMP device for mechanical polishing. Step 6, Ultrasonic Cleaning: Place the polished wafer into an ultrasonic cleaning tank containing a mixed solution of ethanol and deionized water. Set the ultrasonic frequency to 45-55kHz and the cleaning time to 12-18 minutes. Utilize the cavitation effect of ultrasound to thoroughly remove residual polishing liquid and impurities from the wafer surface, ensuring the cleanliness of the wafer surface.
2. The method for processing large-size lithium niobate wafers according to claim 1, characterized in that, High-strength diamond wire with a diameter of 0.1-0.2 mm is selected for crystal cutting, and the diamond abrasive particle size on the surface of the diamond wire is controlled at 5-8 μm. During cutting, the linear speed of the diamond wire is set to 1800-2200 m / min. The tension of the diamond wire is kept stable at 18-22 N through a precisely controlled tension adjustment system to ensure the stability of the diamond wire during the cutting process. At the same time, cutting fluid is used for cutting treatment.
3. The method for processing large-size lithium niobate wafers according to claim 2, characterized in that, The cutting fluid is a mixture of polyethylene glycol, triethanolamine and deionized water in a volume ratio of 3:1:
10. It is uniformly sprayed onto the cutting area at a flow rate of 12-18 L / min using a high-pressure jet system to cut lithium niobate wafers with a thickness of 0.3-0.6 mm.
4. The method for processing large-size lithium niobate wafers according to claim 1, characterized in that, During rough grinding, the grinding pressure is controlled at 0.08-0.12MPa. Through an intelligent pressure control system, the pressure is ensured to be evenly distributed on the wafer surface. The grinding disc speed is set to 25-35r / min. A water-based grinding slurry containing 12-15wt% silicon carbide abrasive, 3-5wt% dispersant, and 2-4wt% lubricant is continuously supplied at a flow rate of 6-9L / min. Grinding is carried out until the wafer thickness is 0.25-0.35mm, effectively removing the damaged layer on the cutting surface. The water-based grinding slurry with lubricant is prepared by mixing nano-tungsten disulfide and water in a weight ratio of 2:7, and the dispersant is sodium tripolyphosphate.
5. The method for processing large-size lithium niobate wafers according to claim 1, characterized in that, In the fine grinding process, a silicon carbide grinding disc with a particle size of 2500-3500 mesh is replaced. The grinding pressure is adjusted to 0.03-0.06 MPa, and the grinding disc rotation speed is set to 18-25 r / min. A newly prepared water-based grinding slurry containing 10-13 wt% silicon carbide abrasive, 4-6 wt% lubricant, and 1-3 wt% surfactant is used for fine grinding at a flow rate of 4-7 L / min to achieve a wafer thickness of 0.18-0.5 mm, significantly improving the wafer surface flatness and reducing surface roughness. The lubricant is molybdenum selenide. The water-based grinding slurry containing surfactant is prepared by mixing sodium dodecylbenzenesulfonate and water in a weight ratio of 2:
5.
6. The method for processing large-size lithium niobate wafers according to claim 1, characterized in that, In step five, silica sol is used as the polishing slurry, wherein the silica particles have a particle size of 60-90nm and a concentration of 6-9wt%, and 0.8-1.2wt% sodium hydroxide is added as a catalyst to promote the chemical corrosion reaction. The polishing pressure is 0.02-0.04MPa, and the pressure is monitored and adjusted in real time by a high-precision pressure sensor. The polishing pad rotation speed is 35-50r / min, and the polishing time is 40-50min.
7. The method for processing large-size lithium niobate wafers according to claim 1, characterized in that, The volume ratio of the mixed solution of ethanol and deionized water is 1:5.