Ultrasonic separation method and device for laser split crystal ingots in high-pressure liquid environment

Abstract

The invention belongs to the technical field of wafer processing, and particularly relates to a high-pressure liquid environment laser splinter crystal ingot separation method and device. And placing the crystal ingot in high-pressure liquid for ultrasonic treatment. And placing the crystal ingot subjected to laser splintering treatment in high-pressure liquid, and promoting microcracks generated by splintering of the crystal ingot to expand under the action of ultrasonic waves so as to complete wafer separation. The high-pressure liquid environment provides higher energy transfer efficiency, the cavitation effect of ultrasonic waves is enhanced, and the wafer separation efficiency is improved. Besides, in a high-pressure liquid environment, after liquid permeates into the crack, energy can be uniformly applied to the starting point and the end part of the crack in combination with the action of ultrasonic waves, so that the crack is more uniformly expanded; the uniform expansion not only improves the splitting effect, but also improves the overall separation quality of the wafer. By integrating the effects, the method has a good application prospect in the technical field of wafer processing.

Description

Technical Field

[0001] The present invention belongs to the technical field of wafer processing, and in particular relates to a method and device for separating a laser-splitting crystal ingot in a high-pressure liquid environment. Background Art

[0002] With the rapid development of the semiconductor industry, the requirements for cutting accuracy and separation efficiency of materials such as wafers are getting higher and higher. As an advanced processing technology, laser splitting technology uses laser to act on the ingot material to produce local cracks, thereby achieving the initial splitting of the ingot. Although laser splitting can produce precise splitting paths, these cracks will not directly separate the material. The cracks formed by the splitting still need to be further expanded and processed to achieve complete separation of the ingot. Subsequent physical methods are usually required to assist in the separation, among which ultrasonic processing technology is a common and effective means.

[0003] Ultrasonic separation technology uses high-frequency ultrasonic waves to act on liquid media, and utilizes the cavitation effect and micro-flow effect generated during ultrasonic propagation to promote the stratification of the ingot material after cleavage. In the liquid medium, the cavitation effect of ultrasonic waves produces a large number of micro-bubbles, which release local high-energy shock waves during the growth and collapse process, acting on the micro-cracks of the cleavage and accelerating the expansion of the cracks. In addition, the propagation of ultrasonic waves in the liquid can also cause local flow and vibration, thereby further weakening the bonding force between the layers of the ingot and promoting stratification or separation.

[0004] In practical applications, although the cracks produced by laser splitting are fine, they do not completely penetrate the ingot, and the depth and path of the cracks are only preliminary divisions. During separation, the split cracks may exist in local areas of the material, and the propagation of ultrasonic energy in liquid has scattering and attenuation characteristics, which cannot ensure that the ultrasonic energy is completely concentrated at the cracks, resulting in unsatisfactory crack expansion and reduced separation efficiency. Summary of the invention

[0005] To solve the above problems, the present invention provides a method for ultrasonic separation of laser-splitting crystal ingots in a high-pressure liquid environment, in which the crystal ingot is placed in a high-pressure liquid for ultrasonic separation. The crystal ingot that has been processed by laser splitting is placed in a high-pressure liquid, and the microcracks generated by the crystal ingot splitting are promoted to expand through the action of ultrasound to complete the wafer separation.

[0006] Under high pressure conditions, the acoustic impedance of the liquid increases, and ultrasonic energy can more effectively penetrate the liquid and act on the solid surface, reducing energy attenuation and scattering. Ultrasonic waves concentrate on the cracks and promote the expansion of the cracks. In other words, under high pressure, the opening of the cracks can be effectively enhanced, making the separation process smoother. In addition, in a high-pressure liquid environment, the cavitation effect of ultrasound is significantly enhanced. Cavitation refers to the generation and bursting of tiny bubbles caused by the propagation of ultrasound in a liquid. This process releases local high-energy shock waves. When a high-pressure environment is combined with the action of ultrasound, the cavitation effect becomes more intense, and the shock wave energy generated when the bubbles collapse is greater, directly acting on the crack area on the surface of the ingot. In other words, compared with ultrasonic separation under conventional pressure, the cavitation effect under high pressure conditions provides more energy support for crack expansion and improves the overall separation efficiency.

[0007] Furthermore, the liquid is water. As a medium, water has good acoustic conductivity and low viscosity, and can effectively transmit ultrasonic energy. At the same time, water has low cost and good environmental protection. The physical properties of water enable it to maintain good fluidity and stability under high pressure conditions, which helps to uniformly affect the cracks with ultrasonic waves. In addition, water also has a good cooling effect, which helps to prevent the ingot from being damaged due to local heating during ultrasonic treatment.

[0008] Furthermore, the high pressure range is 0.1MPa to 5.0MPa. High pressure conditions can enhance the acoustic impedance of the liquid, improve the propagation efficiency and energy concentration of ultrasonic waves in the liquid, and reduce energy attenuation. At the same time, the high pressure environment can promote water to penetrate deeper into the microcracks of the ingot split, thereby more effectively transmitting ultrasonic energy, promoting uniform crack expansion and accelerating separation. Selecting a high pressure range of 0.1MPa to 5.0MPa ensures that the promotion of high pressure to ultrasonic separation is maximized without damaging the ingot.

[0009] Furthermore, the direction of the ultrasonic wave is perpendicular to the surface of the ingot. When the ultrasonic wave acts perpendicularly on the surface of the ingot, the energy can be concentrated to the greatest extent on the microcracks generated by the split, promoting the crack to expand along the split path, reducing unnecessary lateral stress and energy waste. This directional ultrasonic wave can ensure the uniformity and reliability of crack expansion, improve separation accuracy, and avoid irregular separation and mechanical damage to the surface of the ingot.

[0010] On the other hand, the present invention provides a high-pressure liquid environment laser cracking crystal ingot ultrasonic separation device, including a high-pressure water tank, an ultrasonic transducer, a sample inlet, a top cover, a liquid inlet, a liquid outlet and a high-pressure liquid pump. The sample inlet is arranged on the top of the high-pressure water tank, and a top cover is provided on the sample inlet. The liquid inlet and the liquid outlet are arranged on the side of the high-pressure water tank. The liquid inlet is connected to the high-pressure liquid pump, and valves are provided at the liquid inlet and the liquid outlet. The ultrasonic transducer is attached to the high-pressure water tank.

[0011] Furthermore, the ultrasonic transducer is arranged at the bottom of the high-pressure water tank. The ultrasonic transducer is arranged at the bottom of the high-pressure water tank so that the ultrasonic wave acts vertically on the surface of the ingot, ensuring that the ultrasonic wave energy acts concentratedly on the micro-cracks generated by the split. The vertical ultrasonic wave transmission can more effectively promote the uniform expansion of the cracks, improve the separation effect, and reduce the damage to the surface and internal structure of the ingot.

[0012] Furthermore, it also includes a porous material, which is placed in the high-pressure water tank. The porous material is used to adsorb larger-sized powder particles in the water to reduce their obstruction to ultrasonic wave propagation, optimize the fluidity of the liquid and the energy transfer efficiency of the ultrasonic wave. By filtering larger particles, the porous material helps to enhance the cavitation effect of the ultrasonic wave, promote the expansion of the ingot cracks, thereby improving the separation efficiency and reducing the damage to the ingot surface. In addition, the liquid inlet and the liquid outlet are arranged on opposite sides of the high-pressure water tank. The liquid inlet and the liquid outlet are arranged on opposite sides to help form an effective liquid flow cycle and ensure that the liquid is evenly distributed in the water tank. Uniform liquid flow can not only ensure the stability of ultrasonic wave propagation, but also continuously update the pressure and temperature of the water through circulation, avoid local overheating, and improve the cooling efficiency during the separation process.

[0013] Furthermore, it also includes a clamping device, which is fixed to the bottom surface of the high-pressure water tank. The clamping device firmly fixes the ingot to prevent the sample from being displaced by ultrasonic waves or vibration or flow in a high-pressure liquid environment. Fixing the ingot helps ensure that the ultrasonic energy acts precisely on the split position, improves separation efficiency and accuracy, and avoids irregular separation and damage caused by ingot movement.

[0014] Furthermore, it also includes an inclined baffle plate, which is fixed on the top surface and the side surface of the high-pressure water tank. The inclined baffle plate improves the propagation effect of the ultrasonic wave and enhances the uniformity and efficiency of the split separation.

[0015] Furthermore, it also includes an exhaust port, which is arranged at the top of the high-pressure water tank and has a valve. The exhaust port can release excess gas in the high-pressure water tank to prevent the gas from affecting the ultrasonic propagation effect under high pressure. By exhausting the gas regularly, there are no bubbles in the liquid medium to interfere with the energy transfer of the ultrasonic wave, and an efficient separation process is maintained. The setting of the valve can control the exhaust time and pressure to ensure the stability of the internal environment of the high-pressure water tank.

[0016] Beneficial effects of the present invention: (1) The high-pressure liquid environment of the present invention provides higher energy transfer efficiency and enhances the cavitation effect of ultrasound, thereby improving the separation efficiency of wafers.

[0017] (2) In a high-pressure liquid environment, after the liquid penetrates the crack, combined with the effect of ultrasound, energy can be evenly applied to the starting point and end of the crack to ensure that the crack expands more evenly; such uniform expansion not only improves the cracking effect, but also improves the overall separation quality of the wafer.

[0018] (3) Traditional ultrasonic separation is prone to uneven crack expansion or wafer surface damage under normal pressure. In a high-pressure liquid environment, the liquid can evenly coat the surface of the ingot, reducing the mechanical stress concentration generated during the ultrasonic action, thereby reducing the risk of wafer damage. In other words, high-pressure liquid provides a natural buffer for the wafer, making crack expansion more stable and controllable, and less prone to excessive splitting or local damage. This gentle separation process not only improves efficiency, but also enhances the integrity and quality of the wafer.

[0019] In summary of the above beneficial effects, the present invention has good application prospects not only in the field of wafer processing technology, but also in the fields of precision material cutting and brittle material separation. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of a high-pressure liquid environment laser splitting crystal ingot ultrasonic separation device.

[0021] In the figure: 1. high-pressure water tank; 2. sample inlet; 3. top cover; 4. liquid inlet; 5. liquid outlet; 6. ultrasonic transducer; 7. clamping device; 8. ingot. DETAILED DESCRIPTION

[0022] In order to make the objectives, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below with reference to the accompanying drawings and examples.

[0023] The present invention provides a high-pressure liquid environment laser splitting crystal ingot ultrasonic separation device, such as Figure 1As shown. The present invention includes a high-pressure water tank 1, an ultrasonic transducer 6, a sample inlet 2, a top cover 3, a liquid inlet 4, a liquid outlet 5 and a high-pressure liquid pump. The material of the high-pressure water tank 1 is stainless steel, which can withstand relatively high pressure. The shape of the high-pressure water tank 1 is designed according to the size of the ingot 8. When the ingot 8 is a plurality of wafers separated by ultrasonic separation at the same time, the high-pressure water tank 1 is square or rectangular. The sample inlet 2 is arranged at the top of the high-pressure water tank 1, and is dedicated to the loading and unloading of the ingot 8. A top cover 3 is provided on the sample inlet 2, and the top cover 3 can be opened. The top cover 3 of the high-pressure water tank 1 is sealed with a high-strength sealing ring to prevent leakage of high-pressure liquid and ensure the stability of the pressure in the high-pressure water tank 1 during operation. Preferably, a high-strength transparent observation window is provided on the side or top cover 3 of the high-pressure water tank 1, allowing the operator to monitor the operation conditions in the high-pressure water tank 1 in real time to ensure the controllability of the wafer separation process. The liquid inlet 4 and the liquid outlet 5 are arranged on opposite sides of the high-pressure water tank 1. Figure 1 In the embodiment, the liquid inlet 4 is arranged on the left side of the high-pressure water tank 1, and the liquid outlet 5 is arranged on the right side of the high-pressure water tank 1; the liquid inlet 4 is connected to the high-pressure liquid pump, which can continuously inject water into the high-pressure water tank 1. The high-pressure liquid pump injects and maintains the liquid pressure into the high-pressure water tank 1. The high-pressure liquid pump is equipped with a pressure sensor, which can adjust the pressure in real time according to the system requirements, so that the liquid is always in the set high-pressure range, thereby improving the efficiency of ultrasonic separation. The high-pressure liquid pump can also realize liquid circulation, ensuring that the liquid in the high-pressure water tank 1 always maintains the appropriate temperature and pressure, and avoids local heating or pressure fluctuations affecting the ingot separation effect. After the liquid passes through the high-pressure water tank, it flows out from the liquid outlet 5 and adjusts the pressure and temperature, and then circulates into the high-pressure water tank 1 again, so that the water is always in the appropriate pressure and temperature range. The liquid inlet 4 and the liquid outlet 5 are provided with valves, and the operator adjusts the water flow, pressure and flow direction in the high-pressure water tank 1 by controlling the valves, so that a uniform and stable high-pressure liquid environment can be continuously provided during the wafer separation process. The ultrasonic transducer 6 is arranged at the bottom of the high-pressure water tank 1, and the ultrasonic transducer 6 is attached to the high-pressure water tank 1. The ultrasonic transducer 6 generates ultrasonic waves of a specific frequency or a specific frequency range, and the power of the ultrasonic waves is adjustable, and the ultrasonic waves are transmitted to the ingot through the high-pressure liquid. The frequency range of the ultrasonic waves is 20kHz to 1MHz, and the power is adjusted according to the characteristics and size of the ingot. A clamping device 7 is also provided on the bottom surface of the high-pressure water tank 1 to stabilize the ingot 8. The clamping device 7 is designed according to the size and shape of the ingot, so that the ingot 8 remains stable under the action of high-pressure liquid and ultrasonic waves, and will not be displaced due to vibration or liquid flow. Preferably, the clamping device 7 can be adjusted according to ingots 8 of different sizes and shapes, so that the clamping device 7 can adapt to ingots 8 of various specifications. The inner side of the clamping device 7 is coated with a flexible material (such as rubber or polyurethane) to avoid mechanical damage to the surface of the ingot 8.

[0024] Preferably, the high-pressure liquid environment laser splitting crystal ingot ultrasonic separation device of the present invention also includes an inclined baffle, which is fixed on the top and side surfaces in the high-pressure water tank 1. The inclined baffle is annular and is arranged around the side of the crystal ingot. The material of the inclined baffle is stainless steel, which can effectively reflect ultrasonic waves. The inclined angle of the inclined baffle is 45 degrees, which reflects ultrasonic waves from the bottom of the high-pressure water tank 1 to the cracks of the crystal ingot 8. The inclined baffle guides the ultrasonic wave in a direction, so that it enters the microcracks generated by the laser splitting more effectively, improves the utilization efficiency of the ultrasonic wave, and enhances the expansion effect in the crack.

[0025] Preferably, the high-pressure liquid environment laser splitting crystal ingot ultrasonic separation device of the present invention further includes an exhaust port, which is arranged at the top of the high-pressure water tank 1 and has a valve. Since the propagation efficiency of ultrasonic waves in liquid is significantly higher than that in gas, removing the air in the high-pressure water tank 1 can improve the energy transfer efficiency of ultrasonic waves and ensure the high efficiency of the separation process.

[0026] When ultrasonically separating wafers, powder is generated in the water. Powder with larger particles interferes with the ultrasonic propagation path, so that the energy cannot be effectively transferred to the crack area of ​​the split, thereby reducing the separation efficiency. In addition, larger-sized powder particles are easy to collide and rub the wafer surface, leaving scratches and affecting the quality of the wafer. Smaller-sized powder particles can act as "nucleation points" in the ultrasonic field, promoting the occurrence of cavitation effect. When small-sized powder particles are excited by ultrasonic waves, the powder particles move at high speed in the liquid and contact with the cracks. The powder particles produce a tiny grinding effect, further weakening the bonding force of the split and helping the crack to expand. Therefore, porous materials are used to adsorb larger-sized powder particles in the powder, reduce the harmful effects of large-sized powder particles, and retain the beneficial effects of small-sized powder particles. Specifically, foam ceramics are arranged in the high-pressure water tank 1. Foam ceramics are an inorganic material with a uniform porous structure, and the pore size range can be customized according to process requirements, which is convenient for application in the present invention. Further, the foam ceramics are installed near the liquid inlet 4 to effectively block large-particle powders entering the high-pressure water tank 1 from the outside and prevent them from entering the ultrasonic action area. A bracket is made of stainless steel to fix the foam ceramic at the liquid inlet 4 .

[0027] The angles of the liquid inlet 4 and the liquid outlet 5 will change the flow state of the liquid in the high-pressure water tank 1. The liquid inlet 4 is set relatively close to the bottom of the high-pressure water tank 1, and the angle of the liquid inlet 4 is set to be 30 to 45 degrees with the inner wall of the high-pressure water tank 1, so that the liquid flows along the side wall of the high-pressure water tank 1, forming a clockwise or counterclockwise rotating water flow. Furthermore, the liquid inlet is designed in the form of a nozzle to enhance the flow rate of the liquid and promote the liquid to rotate faster at a higher speed along the inner wall of the high-pressure water tank 1. The liquid outlet 5 is set relatively close to the top of the high-pressure water tank 1, which helps to guide the liquid to form a rotating flow in the high-pressure water tank 1. These rotating water flows are used to help expel bubbles in the cracks and enhance the efficiency of ultrasonic separation.

[0028] When in use, loosen the fastening bolts of the top cover 3, open the top cover 3, and expose the inside of the high-pressure water tank 1. Put the ingot 8 that has been laser split into the inside of the high-pressure water tank 1 through the sample inlet 2 at the top of the high-pressure water tank 1. According to the size and shape of the ingot 8, adjust the size and fixing angle of the clamping device 7. The clamping device 7 is fixed to the bottom of the high-pressure water tank 1. Fix the ingot 8 with the clamping device 7, specifically, the clamping device 7 is locked by bolts or buckles. Then, close the top cover 3, tighten the top cover 3 with bolts to ensure a good seal. Then, slowly open the valve of the liquid inlet 4, start the high-pressure liquid pump, and inject water into the high-pressure water tank 1. During the filling process, pay attention to monitoring the water level and pressure changes in the high-pressure water tank 1. When the liquid completely fills the high-pressure water tank 1 and covers the ingot 8, close the valve of the liquid inlet 4. In the meantime, the air in the high-pressure water tank 1 is discharged by opening the exhaust port valve, so that there are no bubbles in the water tank. After starting the high-pressure liquid pump, set the liquid pressure to the required range, usually 0.1MPa to 5.0MPa, through the pressure regulating system of the high-pressure liquid pump. Set the operating frequency and power of the ultrasonic transducer 6, and then start the ultrasonic transducer 6, which generates ultrasonic waves. The ultrasonic wave is transmitted through the high-pressure liquid, acts on the crack area of ​​the ingot 8, and enhances the crack expansion process. During this process, the separation progress of the ingot 8 is monitored through the observation window. When the ingot 8 is separated, stop the operation of the ultrasonic transducer 6, turn off the liquid circulation system, and turn off the high-pressure liquid pump. Gradually reduce the liquid pressure in the high-pressure water tank, drain the water in the high-pressure water tank 1, loosen the top cover 3, and take out the separated wafers and the remaining ingot 8.

[0029] In summary, the present invention provides a method and device for separating a crystal ingot by laser cracking in a high-pressure liquid environment. The crystal ingot is placed in a high-pressure liquid for ultrasonic treatment. The crystal ingot that has been processed by laser cracking is placed in a high-pressure liquid, and the expansion of microcracks generated by the cracking of the crystal ingot is promoted by the action of ultrasonic waves to complete the wafer separation. The high-pressure liquid environment of the present invention provides higher energy transfer efficiency, enhances the cavitation effect of ultrasonic waves, and improves the separation efficiency of wafers. In addition, in a high-pressure liquid environment, after the liquid penetrates the crack, combined with the action of ultrasonic waves, energy can be evenly applied to the starting point and end of the crack to ensure that the crack expands more evenly; such uniform expansion not only improves the cracking effect, but also improves the overall separation quality of the wafer. Combining the above effects, the present invention has good application prospects in the field of wafer processing technology.

[0030] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A method for ultrasonic separation of laser-splitting crystal ingots in a high-pressure liquid environment, characterized in that: The ingot is placed in a high pressure liquid and ultrasonicated.

2. The high pressure liquid environment laser splitting crystal ingot ultrasonic separation method according to claim 1, characterized in that: The liquid is water.

3. The high pressure liquid environment laser splitting crystal ingot ultrasonic separation method according to claim 2, characterized in that: The high pressure ranges from 0.1 MPa to 5.0 MPa.

4. The high pressure liquid environment laser splitting crystal ingot ultrasonic separation method according to claim 3, characterized in that: The direction of the ultrasonic wave is perpendicular to the surface of the ingot.

5. A high-pressure liquid environment laser splitting crystal ingot ultrasonic separation device, characterized in that: The invention comprises a high-pressure water tank, an ultrasonic transducer, a sample inlet, a top cover, a liquid inlet, a liquid outlet and a high-pressure liquid pump. The sample inlet is arranged at the top of the high-pressure water tank, the sample inlet is provided with the top cover, the liquid inlet and the liquid outlet are arranged on the side of the high-pressure water tank, the liquid inlet is connected to the high-pressure liquid pump, the liquid inlet and the liquid outlet are provided with valves, and the ultrasonic transducer is attached to the high-pressure water tank.

6. The high pressure liquid environment laser splitting crystal ingot ultrasonic separation device as claimed in claim 5, characterized in that: The ultrasonic transducer is arranged at the bottom of the high-pressure water tank.

7. The high pressure liquid environment laser splitting crystal ingot ultrasonic separation device according to claim 6, characterized in that: It also includes a porous material, which is placed in the high-pressure water tank.

8. The high pressure liquid environment laser splitting crystal ingot ultrasonic separation device according to claim 6, characterized in that: It also includes a clamping device, which is fixed on the bottom surface of the high-pressure water tank.

9. The high pressure liquid environment laser splitting crystal ingot ultrasonic separation device according to claim 6, characterized in that: It also includes an inclined baffle, which is fixed on the top surface and the side surface in the high-pressure water tank.

10. The high pressure liquid environment laser splitting crystal ingot ultrasonic separation device according to claim 6, characterized in that: It also includes an exhaust port, which is arranged on the top of the high-pressure water tank and has a valve.

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