A method for cutting silicon rods and silicon wafers

Abstract

The present invention belongs to the technical fields of chips and silicon wafers for solar cells, and particularly relates to a method for cutting silicon rods and silicon wafers. The additional cutting includes a pre-recovery step and an additional cutting step carried out in sequence; in the pre-recovery step, the wire feeding amount from the wire take-up wheel to the wire supply wheel is 1600 m to 2000 m, the wire feeding amount from the wire supply wheel to the wire take-up wheel is 200 m to 400 m, the moving speed of the silicon rod is 40 μm / min to 60 μm / min, and the wire speed is 1100 m / min - 1200 m / min; in the additional cutting step, after keeping the parameter settings of the pre-recovery step and moving the silicon rod by 0.2 mm - 2 mm, the moving speed of the silicon rod is adjusted to 20 μm / min - 30 μm / min, the wire feeding amount from the wire take-up wheel to the wire supply wheel is adjusted to 2300 m to 2700 m, and the wire feeding amount from the wire supply wheel to the wire take-up wheel is adjusted to 1600 m to 2000 m, which can prevent the wire breakage of the diamond wire during the additional cutting process and improve the quality of the silicon wafers.

Description

Technical Field

[0001] The invention belongs to the technical field of chips and solar cell silicon wafers, and in particular relates to a silicon rod cutting method and a silicon wafer. Background Art

[0002] Single crystal silicon wafers are the basic materials for manufacturing chips and solar cells. Currently, single crystal silicon wafers are mainly obtained by growing single crystal silicon rods using the Czochralski method, and then cutting the single crystal silicon rods to obtain single crystal silicon wafers. The quality of single crystal silicon rod slices directly affects chip performance and solar cell efficiency.

[0003] Inner circle cutting technology and diamond wire cutting can be used to cut single crystal silicon rods. Inner circle cutting uses a ring-shaped inner circle blade with a diamond-coated edge, which is suitable for small batches of high-precision cutting, but has large material losses and is gradually being eliminated. Diamond wire cutting uses a high-speed moving diamond wire to cut silicon rods, with small cutting losses, high efficiency, and the ability to cut multiple pieces at the same time, making it suitable for large-size silicon rods.

[0004] When using diamond wire to cut silicon rods, it is easy to adjust the cutting program during the cutting process, adjust after the wire is disconnected during the cutting process, inaccurate cutting parameter settings, diamond wire abnormalities, insufficient diamond wire cutting force and other problems. These problems will lead to the silicon rod not being completely cut through after the cutting process is completed. At this time, additional cutting is required. The current additional cutting process that directly continues cutting is prone to cause the diamond wire to break, cracks and broken edges on the silicon rod edges, low surface quality of the silicon wafer, and increased silicon wafer losses.

[0005] It should be noted that this part of the present invention only provides background technology related to the present invention and does not necessarily constitute prior art or known technology. Summary of the invention

[0006] The purpose of the present invention is to overcome the defects of the prior art that the cutting process of diamond wire cutting silicon rods easily leads to diamond wire breakage, cracks and edge collapse at the edges of the silicon rods, low surface quality of silicon wafers, affecting the quality of silicon wafers and increasing silicon wafer losses. A silicon rod cutting method and silicon wafer are provided, which can prevent the diamond wire from breaking during the cutting process, inhibit the generation of cracks and edge collapse at the edges of the silicon rods, improve the quality of silicon wafers, and reduce silicon wafer losses.

[0007] In order to achieve the above-mentioned object, in a first aspect, the present invention provides a silicon rod cutting method, comprising:

[0008] Cutting is performed by cutting wire, the cutting wire is released by a wire supply wheel, the cutting wire passes around the cutting rollers in sequence and forms a cutting wire net between the cutting rollers arranged side by side, after the cutting wire net is formed, the wire is taken up by a wire take-up wheel, the silicon rod moves from one side of the cutting wire net to the cutting wire net, the cutting roller drives the cutting wire in the cutting wire net to reciprocate, and the silicon rod entering the cutting wire net is cut into multiple silicon wafers;

[0009] The cutting method includes additional cutting, and the additional cutting includes a pre-recovery step and an additional cutting step performed in sequence; the pre-recovery step includes: the wire feeding amount from the take-up reel to the wire supply reel is 1600 m to 2000 m, the wire feeding amount from the wire supply reel to the take-up reel is 200 m to 400 m, the moving speed of the silicon rod is 40 μm / min to 60 μm / min, and the wire speed is 1100 m / min - 1200 m / min; the additional cutting step includes: after maintaining the parameter settings of the pre-recovery step and moving the silicon rod by 0.2 mm - 2 mm, adjusting the moving speed of the silicon rod to 20 μm / min - 30 μm / min, adjusting the wire feeding amount from the take-up reel to the wire supply reel to 2300 m to 2700 m, and adjusting the wire feeding amount from the wire supply reel to the take-up reel to 1600 m to 2000 m.

[0010] In some preferred embodiments, the pre-recovery step includes: the cutting fluid flow rate is above 190 L / min; the additional cutting step includes: after maintaining the parameter settings of the pre-recovery step and moving the silicon rod by 0.2 mm - 2 mm, adjusting the cutting fluid flow rate to 170 L / min - 185 L / min.

[0011] In some preferred embodiments, the conditions of the cutting process before the pre-recovery step include: the moving speed of the silicon rod is above 100 μm / min, the wire speed is above 1200 m / min, and the cutting fluid flow rate is above 190 L / min.

[0012] In some preferred embodiments, the cutting method includes: after forming a continuous connection point after wire breakage, when the continuous connection point in the wire cutting network is in the middle or close to the take-up reel, the wire feeding amount from the wire supply reel to the take-up reel is greater than the wire feeding amount from the take-up reel to the wire supply reel, and the continuous connection point is sent towards the take-up reel; when the continuous connection point in the wire cutting network is close to the wire supply reel, the wire feeding amount from the take-up reel to the wire supply reel is greater than the wire feeding amount from the wire supply reel to the take-up reel, and the continuous connection point is sent towards the wire supply reel.

[0013] Preferably, after forming a continuous connection point after wire breakage, when the continuous connection point is in the middle or close to the take-up reel, reduce the moving speed of the silicon rod, increase the wire feeding amount from the wire supply reel to the take-up reel and / or reduce the wire feeding amount from the take-up reel to the wire supply reel.

[0014] Preferably, the reduction of the moving speed of the silicon rod includes: for every 2 mm movement of the silicon rod, the moving speed of the silicon rod is reduced by 200 μm / min - 300 μm / min.

[0015] Preferably, when the total wire amount change of increasing the wire feeding amount from the wire supply reel to the take-up reel and / or reducing the wire feeding amount from the take-up reel to the wire supply reel is L, when the wire bow is less than 10 mm, L is 15 m - 30 m, when the wire bow is 10 mm - 15 mm, L is 30 m - 50 m, and when the wire bow is greater than 15 mm, L is 50 m - 80 m.

[0016] Preferably, after the broken wire is subsequently connected to form a continuous connection point, when the continuous connection point is close to the wire supply wheel, the difference between the wire amount fed from the wire take-up wheel to the wire supply wheel and the wire amount fed from the wire supply wheel to the wire take-up wheel is kept unchanged, and the wire amount fed from the wire supply wheel to the wire take-up wheel is reduced.

[0017] Preferably, the wire amount fed from the wire supply wheel to the wire take-up wheel is reduced 2 to 4 times, and each time the wire amount is reduced by 50% to 75%.

[0018] Preferably, after the broken wire is continuously connected, when the proportion of the old wire on the cutting wire mesh is less than 50% and more than 50% respectively, when reducing the wire amount fed from the wire supply wheel to the wire take-up wheel, the moving distance of the silicon rod is within 4 mm and within 2 mm respectively.

[0019] In some preferred embodiments, the cutting method includes: when the wire bow is 10 mm or more, moving the silicon rod 30 mm - 60 mm, and the conditions for moving the silicon rod 30 mm - 60 mm include: reducing the moving speed of the silicon rod by 200 μm / min - 400 μm / min, and for every 2 mm of movement of the silicon rod, increasing the wire amount fed from the wire take-up wheel to the wire supply wheel by 15 m - 20 m;

[0020] After the silicon rod is moved 30 mm - 60 mm, when the wire bow is still 10 mm or more, the silicon rod is continuously moved 30 mm - 60 mm, and for every 2 mm of movement of the silicon rod, increasing the wire amount fed from the wire take-up wheel to the wire supply wheel by 40 m - 50 m.

[0021] In a second aspect, the present invention provides a silicon wafer obtained by cutting the silicon rod using the silicon rod cutting method described in the first aspect.

[0022] In the silicon rod cutting method of the present invention, in the pre-recovery step, the wire amount fed from the wire take-up wheel to the wire supply wheel is 1600 m to 2000 m, and the wire amount fed from the wire supply wheel to the wire take-up wheel is 200 m to 400 m. Gradually leaving enough old wire on the wire supply side can realize cutting with the cut wire, recycling the old wire, making full use of the old wire, and reducing the overuse of new wire; further, the moving speed of the silicon rod is 40 μm / min to 60 μm / min. Using a lower speed of the silicon rod pressing down on the cutting wire mesh can ensure accurate positioning before additional cutting and improve the additional cutting effect; further, the wire speed is 1100 m / min - 1200 m / min, which can reduce the tension of the cutting wire, prevent the cutting wire from breaking during additional cutting, inhibit the generation of microcracks and chipping on the edge of the silicon rod, improve the surface quality of the silicon wafer, and reduce the loss of the silicon wafer.

[0023] In the cutting process, the moving speed of the silicon rod is 20 um / min - 30 um / min, and the wire speed of 1100 m / min - 1200 m / min is continuously maintained, which can inhibit the generation of microcracks and chipping on the edge of the silicon rod; further, adjust the wire feeding amount from the take-up wheel to the wire supply wheel to 2300 m - 2700 m, and adjust the wire feeding amount from the wire supply wheel to the take-up wheel to 1600 m - 2000 m. Since during the cutting process, the cutting wire is already located at the edge of the silicon rod or the edge of the resin plate used to fix the silicon rod, etc., on the basis of making full use of the old wire cutting, the replacement speed of the new wire is accelerated, and the cutting process is carried out by gradually increasing the cutting force. By increasing the cutting force and accelerating the speed at which the cutting wire moves away from the ingot, the risk of chipping on the edge of the silicon rod can be further reduced, and the surface quality of the silicon wafer can be improved. Brief Description of the Drawings

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0025] Figure 1 is a schematic structural diagram of the silicon rod cutting device according to Embodiment 1 of the present invention.

[0026] Figure 2 is Figure 1 a top view of the structure in which the cutting wire and the cutting roller cooperate.

[0027] Figure 3 is a schematic diagram of the silicon rod cutting process according to Embodiment 1 of the present invention.

[0028] Figure 4 is a photo of the edge of the silicon rod in the silicon wafer cutting method according to Embodiment 1 of the present invention.

[0029] Figure 5 is a photo of the edge of the silicon rod in the silicon wafer cutting method according to Comparative Example 3 of the present invention.

[0030] Description of the Reference Numerals

[0031] 1. Wire supply wheel; 2. Take-up wheel; 3. Cutting roller; 4. Guide wheel; 5. Cutting wire. Detailed Embodiments

[0032] The endpoints and any values within the ranges disclosed herein are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed herein.

[0033] The inventors of the present invention have found through research that the existing cutting process of diamond wire cutting silicon rods easily leads to breakage of the diamond wire, cracks and chipping on the edges of the silicon rods, low surface quality of the silicon wafers, and increased loss of silicon wafers.

[0034] In view of this, on the one hand, the present invention provides a method for cutting a silicon rod, including: cutting with a cutting wire, the cutting wire is paid out by a wire supply wheel, the cutting wire sequentially bypasses cutting rollers and forms a cutting wire net between the juxtaposed cutting rollers, after forming the cutting wire net, it is taken up by a wire take-up wheel, the silicon rod moves from one side of the cutting wire net towards the cutting wire net, and the cutting rollers drive the cutting wire in the cutting wire net to reciprocate, cutting the silicon rod entering the cutting wire net into a plurality of silicon wafers;

[0035] The cutting method includes a pre-cutting step, and the pre-cutting step includes: the wire amount fed from the wire take-up wheel to the wire supply wheel is 1600m - 2000m, the wire amount fed from the wire supply wheel to the wire take-up wheel is 200m - 400m, the moving speed of the silicon rod is 40μm / min - 60μm / min, and the wire speed is 1100m / min - 1200m / min; the pre-cutting step includes: after maintaining the parameter settings of the pre-cutting step and making the silicon rod move 0.2mm - 2mm, adjusting the moving speed of the silicon rod to 20um / min - 30um / min, adjusting the wire amount fed from the wire take-up wheel to the wire supply wheel to 2300m - 2700m, and adjusting the wire amount fed from the wire supply wheel to the wire take-up wheel to 1600m - 2000m.

[0036] In the silicon rod cutting method of the present invention, in the pre-recovery step, the wire feeding amount from the take-up reel to the wire supply reel is 1600 m to 2000 m, and the wire feeding amount from the wire supply reel to the take-up reel is 200 m to 400 m. By gradually leaving enough old wires on the wire supply side, it is possible to use the cut wires for additional cutting, recycle the old wires, make full use of the old wires, and reduce the excessive use of new wires. Further, the moving speed of the silicon rod is 40 μm / min to 60 μm / min. By adopting a lower speed of the silicon rod pressing down on the cutting wire mesh, accurate positioning before additional cutting can be ensured, and the additional cutting effect can be improved. Since during additional cutting, the cutting wire is located inside the silicon rod and at a relatively deep depth, the probability of the cutting wire breaking increases. The additional cutting position is close to the edge of the silicon rod, and cracks and chipping are likely to occur at the edge. Further, the wire speed is 1100 m / min - 1200 m / min, which can reduce the tension of the cutting wire, prevent the cutting wire from breaking during additional cutting, inhibit the generation of microcracks and chipping at the edge of the silicon rod, improve the surface quality of the silicon wafer, and reduce the loss of silicon wafers.

[0037] In the additional cutting step, the moving speed of the silicon rod is 20 um / min - 30 um / min, and by continuing to maintain a wire speed of 1100 m / min - 1200 m / min, the generation of microcracks and chipping at the edge of the silicon rod can be inhibited. Adjust the wire feeding amount from the take-up reel to the wire supply reel to 2300 m to 2700 m, and adjust the wire feeding amount from the wire supply reel to the take-up reel to 1600 m to 2000 m. On the basis of making full use of the old wires for cutting, the replacement speed of the new wires is accelerated, and additional cutting is carried out by gradually increasing the cutting force. Since during the additional cutting process, the cutting wire is already located at the edge of the silicon rod or the edge of the resin plate used to fix the silicon rod, etc., by increasing the cutting force and accelerating the speed of the cutting wire away from the crystal rod, the risk of chipping at the edge of the silicon rod can be further reduced, and the surface quality of the silicon wafer can be improved.

[0038] The cutting depth standard for the cutting wire mesh of the present invention to cut the silicon rod is that the cutting wire mesh cuts through the crystal rod and cuts onto the resin plate. If the standard is not reached, additional cutting is required.

[0039] In the pre-recovery step of the present invention, the amount of wire sent from the take-up wheel to the supply wheel is, for example, 1600m, 1700m, 1800m, 1900m and 2000m, the amount of wire sent from the supply wheel to the take-up wheel is, for example, 200m, 250m, 300m, 350m and 400m, the silicon rod moving speed is, for example, 40μm / min, 45μm / min, 50μm / min, 55μm / min and 60μm / min, and the cutting step maintains the parameter settings of the pre-recovery step so that the silicon rod moves, for example, 0.2mm, 0.5mm, 0. 8mm, 1.2mm, 1.5mm, 1.8mm and 2mm, adjust the silicon rod moving speed to, for example, 20um / min, 22um / min, 24um / min, 26um / min, 28um / min and 30um / min, adjust the wire amount sent from the take-up wheel to the supply wheel to, for example, 2300m, 2400m, 2500m, 2600m and 2700m, adjust the wire amount sent from the supply wheel to the take-up wheel to, for example, 1600m, 1700m, 1800m, 1900m and 2000m.

[0040] The cutting wire of the present invention is preferably a diamond wire, a steel wire with diamond grit attached thereto.

[0041] In some preferred embodiments, the cutting device used in the silicon rod cutting method of the present invention may include, in addition to the cutting rollers arranged side by side, a roller for adjusting tension, etc., located on the side of the cutting rollers arranged side by side away from the silicon rod, and guide wheels may be included between the wire supply wheel and the cutting roller and between the wire take-up wheel and the cutting roller, for example, a wire arrangement guide wheel, a tension guide wheel and a wire feed guide wheel are arranged in sequence.

[0042] In some preferred embodiments, in the pre-recovery step of cutting, the silicon rod is moved by 0.2 mm to 2 mm.

[0043] In some preferred embodiments, the pre-recovery step includes: the cutting liquid flow rate is above 190 L / min; the additional cutting step includes: maintaining the parameter settings of the pre-recovery step so that the silicon rod moves 0.2 mm-2 mm, and then adjusting the cutting liquid flow rate to 170 L / min~185 L / min.

[0044] Under this preferred solution, in the pre-recovery step, when the moving speed of the silicon rod is 40 μm / min to 60 μm / min, the flow rate of the cutting fluid is made above 190 L / min. Flushing the cutting area with a relatively large flow rate of the cutting fluid above 190 L / min at a relatively low moving speed of the silicon rod is more conducive to fully removing the silicon chips and impurities generated during the cutting process, improving the cleanliness of the cutting area, reducing the accumulation of silicon chips at a wire speed of 1100 m / min - 1200 m / min, forming a clean protective film on the surface of the silicon wafer, reducing the surface damage and microcracks at the additional cutting position, reducing the influence of silicon chips and impurities on the subsequent additional cutting process, and improving the surface quality of the silicon wafer. In the additional cutting step, the flow rate of the cutting fluid is adjusted to 170 L / min to 185 L / min. Using a relatively low flow rate is more conducive to concentrating the landing points of the cutting fluid, enabling more landing points of the cutting fluid to hit the adhesive surfaces of the silicon rod and the resin plate, effectively cooling the adhesive surface area of the silicon rod, avoiding local overheating, reducing the microcracks or damage of the silicon wafer caused by thermal stress, effectively lubricating the contact area between the cutting wire and the silicon rod, reducing friction, reducing the cutting resistance, thereby reducing the surface damage of the silicon wafer, reducing the phenomenon of chipping at the edge of the silicon rod during the cutting process, improving the quality of the silicon wafer, effectively flushing the cutting area, removing silicon chips and impurities, avoiding the influence of silicon chip accumulation on the cutting quality, improving the cutting effect, and improving the surface quality of the silicon wafer. The flow rate of the cutting fluid in the additional cutting step is adjusted, for example, to 170 L / min, 173 L / min, 176 L / min, 179 L / min, 182 L / min, and 185 L / min.

[0045] In some preferred embodiments, the conditions of the cutting process before the pre-recovery step include: the moving speed of the silicon rod is above 100 μm / min, the wire speed is above 1200 m / min, and the flow rate of the cutting fluid is above 190 L / min. Under this preferred solution, it is more conducive to preventing the cutting wire from breaking, improving the surface quality of the silicon wafer, and reducing the loss of the silicon wafer.

[0046] In some preferred embodiments, the cutting method includes: after the broken wire is subsequently connected to form a connection point, when the connection point in the cutting wire mesh is located in the middle or near the take-up reel, the amount of wire fed from the wire supply reel to the take-up reel is greater than the amount of wire fed from the take-up reel to the wire supply reel, and the connection point is fed towards the take-up reel. When the connection point in the cutting wire mesh is close to the wire supply reel, the amount of wire fed from the take-up reel to the wire supply reel is greater than the amount of wire fed from the wire supply reel to the take-up reel, and the connection point is fed towards the wire supply reel. After the broken wire is connected and the cutting is restarted, the additional cutting process needs to be adopted. Under this preferred solution, it is more conducive to controlling the cutting process, reducing the cutting process deviation before the additional cutting, improving the additional cutting quality, suppressing the generation of microcracks and chipping at the edge of the silicon rod, improving the surface quality of the silicon wafer, reducing the loss of the silicon wafer. When the connection point is located in the middle, the amount of wire fed from the wire supply reel to the take-up reel is greater than the amount of wire fed from the take-up reel to the wire supply reel, and the connection point is fed towards the take-up reel, which is more conducive to having sufficient wire source supply for cutting.

[0047] Preferably, after the broken wire is subsequently connected to form a continuous contact point, when the continuous contact point is located in the middle or near the take-up reel, the moving speed of the silicon rod is reduced, the amount of wire fed from the wire supply reel to the take-up reel is increased and / or the amount of wire fed from the take-up reel to the wire supply reel is reduced. Under this preferred solution, reducing the moving speed of the silicon rod is more conducive to reducing the dynamic load during cutting, avoiding secondary wire breakage caused by excessive instantaneous stress. Especially after the broken wire is continuously cut, there may already be microcracks or stress concentration in the material at the cut. Reducing the moving speed of the silicon rod and feeding slowly can improve the cutting stability, prevent the cut from cracking, and provide a stable cutting environment for subsequent additional cutting; increasing the amount of wire fed from the wire supply reel to the take-up reel and / or reducing the amount of wire fed from the take-up reel to the wire supply reel. During the process of the cutting wire reciprocating to cut the silicon wafer, the wire supply reel sends out more wire in each step, sending out the old wire in time, and the alternating replacement speed of the new and old wires is faster, which is more conducive to improving the cutting force of the cutting wire, reducing the wire bow, reducing the pressure on the wire, reducing the wire tension, and avoiding the cutting wire from being too tight. Thus, on the one hand, it prevents secondary wire breakage, and on the other hand, by forming a stable wire bow, while reducing the cutting vibration, improving the flatness of the cutting surface, and enhancing the surface quality of the silicon wafer, the cutting wire is evenly stressed during subsequent additional cutting, ensuring that the cutting path is consistent, and reducing defects such as wafer warping and chipping. Under this preferred solution, reducing the moving speed of the silicon rod reduces the inducement of wire breakage, increases the amount of wire fed from the wire supply reel to the take-up reel and / or reduces the amount of wire fed from the take-up reel to the wire supply reel, buffers and balances the stress of the cutting wire network at low tension, reduces the wire bow, improves the dynamic stability, is more conducive to subsequent long-term continuous additional cutting, and can also improve the cutting efficiency of the single crystal silicon rod and the wafer output.

[0048] Preferably, the reduction of the moving speed of the silicon rod includes: for every 2 mm of movement of the silicon rod, the moving speed of the silicon rod is reduced by 200 μm / min - 300 μm / min. Under this preferred solution, it is more conducive to reducing the dynamic load during cutting, avoiding secondary wire breakage caused by excessive instantaneous stress, improving the cutting stability, preventing the cut from cracking, and providing a stable cutting environment for subsequent additional cutting. For every 2 mm of movement of the silicon rod, the reduction of the moving speed of the silicon rod is, for example, 200 μm / min, 220 μm / min, 240 μm / min, 260 μm / min, 280 μm / min, and 300 μm / min.

[0049] Preferably, the total wire amount change for increasing the wire amount sent from the wire supply wheel to the wire take-up wheel and / or decreasing the wire amount sent from the wire take-up wheel to the wire supply wheel is L. When the wire bow is less than 10 mm, L is 15 m to 30 m; when the wire bow is 10 mm - 15 mm, L is 30 m - 50 m; when the wire bow is greater than 15 mm, L is 50 m - 80 m. Under this preferred solution, it is more conducive to improving the cutting force of the cutting wire, reducing the wire bow, reducing the pressure on the wire, reducing the wire tension, avoiding the cutting wire from being too tight, preventing secondary wire breakage, forming a stable wire bow, reducing cutting vibration, improving the flatness of the cutting surface, enhancing the surface quality of the silicon wafer, enabling the cutting wire to be evenly stressed during subsequent additional cutting, ensuring the consistency of the cutting path, and reducing defects such as wafer warping and chipping. When the wire bow is 10 mm - 15 mm and L is 30 m - 50 m, reducing the wire bow is more conducive to avoiding uneven cutting or side scratching of the silicon wafer caused by an excessive wire bow. When the wire bow is greater than 15 mm, an excessive wire bow may cause cutting vibration or even wire breakage again. When L is 50 m - 80 m, it provides a greater cutting force and is more conducive to avoiding cutting vibration or even wire breakage again. The total wire amount change L of the present invention refers to the sum of the increase in the wire amount sent from the wire supply wheel to the wire take-up wheel and the decrease in the wire amount sent from the wire take-up wheel to the wire supply wheel. When the wire bow is less than 10 mm, L is, for example, 15 m, 20 m, 25 m, and 30 m; when the wire bow is 10 mm - 15 mm, L is, for example, 30 m, 35 m, 40 m, 45 m, and 50 m; when the wire bow is greater than 15 mm, L is, for example, 50 m, 60 m, 70 m, and 80 m.

[0050] When the cutting force of the cutting wire is insufficient, the cutting wire mesh will be pressed down by the silicon rod. The wire bow of the present invention refers to the distance between the side line of the cutting wire mesh and the lowest point where the cutting wire mesh is pressed down by the crystal rod during cutting.

[0051] Preferably, after the wire break is subsequently connected to form a connection point, when the connection point is close to the wire supply wheel, the difference between the wire amount sent from the wire take-up wheel to the wire supply wheel and the wire amount sent from the wire supply wheel to the wire take-up wheel is kept unchanged, and the wire amount sent from the wire supply wheel to the wire take-up wheel is reduced. Before the wire break, the cutting wire is the used wire that has been cut. After the wire break and when cutting again, it is a new wire for cutting. The wear degree of the cutting wire before the wire break and the wear degree of the cutting wire after the wire break cannot be connected continuously, and color difference is likely to occur at the wire break position. Under this preferred solution, keeping the difference between the wire amount sent from the wire take-up wheel to the wire supply wheel and the wire amount sent from the wire supply wheel to the wire take-up wheel unchanged and reducing the wire amount sent from the wire supply wheel to the wire take-up wheel allows the new wire to come in slower during the process of the cutting wire reciprocating to cut the silicon wafer, which is more conducive to alleviating the color difference at the wire break position and reducing the color difference.

[0052] Preferably, the wire feeding amount from the wire supply wheel to the wire take-up wheel is reduced 2 to 4 times, and each time the wire feeding amount is reduced by 50% to 75%. Under this preferred scheme, each time the wire feeding amount is reduced by 50% to 75% and this is done 2 to 4 times, it is more conducive to alleviating the color difference at the wire break position and reducing the color difference. Each time the wire feeding amount is reduced, for example, by 50%, 55%, 60%, 65%, 70% and 75%.

[0053] Preferably, after the wire break is spliced, when the proportion of the old wire on the cutting wire mesh is below 50% and above 50% respectively, when reducing the wire feeding amount from the wire supply wheel to the wire take-up wheel, the moving distance of the silicon rod is within 4 mm and within 2 mm respectively. Under this preferred scheme, it is more conducive to alleviating the color difference at the wire break position, reducing the color difference, improving the cutting quality, suppressing the generation of microcracks and chipping on the edge of the silicon rod, improving the surface quality of the silicon wafer, and reducing the loss of the silicon wafer.

[0054] In some preferred embodiments, the cutting method includes: when the wire bow is 10 mm or more, moving the silicon rod 30 mm - 60 mm, and the conditions for moving the silicon rod 30 mm - 60 mm include: reducing the moving speed of the silicon rod by 200 um / min - 400 um / min, and for every 2 mm the silicon rod moves, increasing the wire feeding amount from the wire take-up wheel to the wire supply wheel by 15 m - 20 m;

[0055] After moving the silicon rod 30 mm - 60 mm, when the wire bow is still 10 mm or more, continue to move the silicon rod 30 mm - 60 mm, and for every 2 mm the silicon rod moves, increase the wire feeding amount from the wire take-up wheel to the wire supply wheel by 40 m - 50 m.

[0056] Under this preferred scheme, when the wire bow is 10 mm or more, reducing the moving speed of the silicon rod by 200 um / min - 400 um / min can reduce the downward pressure on the silicon rod, allowing the cutting wire mesh to have enough buffer time to pull the wire bow upward. For every 2 mm the silicon rod moves, increasing the wire feeding amount from the wire take-up wheel to the wire supply wheel by 15 m - 20 m. After moving the silicon rod 30 mm - 60 mm and when the wire bow is still 10 mm or more, continue to move the silicon rod 30 mm - 60 mm, and for every 2 mm the silicon rod moves, increase the wire feeding amount from the wire take-up wheel to the wire supply wheel by 40 m - 50 m. During the process of the cutting wire reciprocating to cut the silicon wafer, increasing the new wire replacement speed can increase the cutting ability of the cutting wire mesh, which is more conducive to reasonably controlling the wire bow before cutting, reducing the influence of the wire bow on the silicon wafer quality, and controlling the cutting process deviation, reducing the cutting deviation degree before cutting, and reducing the risks such as chipping caused by easy penetration of resin plates.

[0057] The wire running speed, acceleration / deceleration and wire tension of the cutting wire of the present invention can be controlled, for example, by the motors of the wire take-up wheel and the wire supply wheel.

[0058] Second aspect, the present invention provides a silicon wafer obtained by cutting a silicon rod using the silicon rod cutting method described in the first aspect. The silicon wafer obtained by the silicon wafer cutting method of the present invention has few edge cracks and chippings on the silicon rod, high silicon wafer quality, and small silicon wafer loss.

[0059] The present invention will be further elaborated in detail below in conjunction with specific embodiments.

[0060] Example 1

[0061] A silicon rod cutting device, refer to Figure 1 and Figure 2 , including cutting rollers 3 arranged side by side. Wire grooves are formed on the cutting rollers 3 for wiring the wire mesh. The cutting wire 5 bypasses the wire supply wheel 1 of the wire inlet bin, passes through the guide wheel 4, then bypasses the cutting rollers 3 in sequence and forms a cutting wire mesh between the cutting rollers 3 arranged side by side. After the cutting wire 5 forms the cutting wire mesh, it passes through the guide wheel 4 and passes through the wire outlet hole and winds around the wire take-up wheel 2 of the wire take-up bin.

[0062] A silicon rod cutting method, the schematic diagram of the silicon rod cutting process refers to Figure 3 , including: cutting with a cutting wire. The cutting wire is paid off by the wire supply wheel, the cutting wire bypasses the cutting rollers 3 in sequence and forms a cutting wire mesh between the cutting rollers 3 arranged side by side. After the cutting wire mesh is formed, it is taken up by the wire take-up wheel. The silicon rod moves from one side of the cutting wire mesh towards the cutting wire mesh. The cutting rollers drive the cutting wire in the cutting wire mesh to reciprocate, and the silicon rod entering the cutting wire mesh is cut into multiple silicon wafers;

[0063] During the cutting process, it is found through the observation window of the silicon wafer cutting device that the wire bow is more than 10 mm. Under the condition of reducing the moving speed of the silicon rod by 300 μm / min and increasing the wire amount sent from the wire take-up wheel to the wire supply wheel by 15 m for every 2 mm movement of the silicon rod, the silicon rod is moved 40 mm. It is found through the observation window of the silicon wafer cutting device that the wire bow is less than 10 mm;

[0064] During the cutting process, a wire break occurs. The wire break position is close to the wire take-up wheel. A continuous connection point is formed after the wire break. The continuous connection point is close to the wire take-up wheel. The wire amount sent from the wire supply wheel to the wire take-up wheel is greater than the wire amount sent from the wire take-up wheel to the wire supply wheel. The continuous connection point is sent towards the wire take-up wheel. For every 2 mm movement of the silicon rod, the moving speed of the silicon rod is reduced by 240 μm / min. It is found through the observation window of the silicon wafer cutting device that the wire bow is less than 10 mm, and the wire amount sent from the wire supply wheel to the wire take-up wheel is increased by 20 m;

[0065] After the aforementioned wire break adjustment, the moving speed of the silicon rod is 100 μm / min, the wire speed is 1200 m / min, and the cutting fluid flow rate is 220 L / min. It is found that the silicon rod is not completely cut through, so additional cutting is carried out. The pre-recovery step and the additional cutting step are carried out in sequence. During the pre-recovery step, the wire amount sent from the take-up reel to the wire supply reel is 1800 m, the wire amount sent from the wire supply reel to the take-up reel is 300 m, the moving speed of the silicon rod is 50 μm / min, the wire speed is 1200 m / min, and the cutting fluid flow rate is 220 L / min. During the additional cutting step, after maintaining the parameter settings of the pre-recovery step and moving the silicon rod 2 mm, the moving speed of the silicon rod is adjusted to 20 μm / min, the wire amount sent from the take-up reel to the wire supply reel is adjusted to 2500 m, the wire amount sent from the wire supply reel to the take-up reel is adjusted to 1800 m, and the cutting fluid flow rate is adjusted to 180 L / min.

[0066] For the silicon rod cutting method of this embodiment, there are no obvious damages and microcracks at the additional cutting position, there is no obvious damage on the surface of the silicon wafer after additional cutting, and there are no obvious chipping phenomena and cracks at the edge of the silicon rod. For the silicon wafer cutting method of this embodiment, refer to the photo of the silicon rod edge Figure 4 。

[0067] Example 2

[0068] It is carried out with reference to the silicon rod cutting method of Example 1. The difference is that during the pre-recovery step, the cutting fluid flow rate is 180 L / min. For the silicon rod cutting method of this embodiment, there are very few microcracks at the additional cutting position, and there is very little damage on the surface of the silicon wafer after additional cutting.

[0069] Example 3

[0070] It is carried out with reference to the silicon rod cutting method of Example 1. The difference is that during the additional cutting step, the cutting fluid flow rate is maintained at 220 L / min. For the silicon rod cutting method of this embodiment, there is very little damage on the surface of the silicon wafer after additional cutting, and there is very little chipping phenomenon at the edge of the silicon rod.

[0071] Example 4

[0072] It is carried out with reference to the silicon rod cutting method of Example 1. The difference is that during the cutting process, a wire break occurs. The wire break position is close to the take-up reel. After the wire break, a splicing point is formed. The splicing point is close to the take-up reel. The splicing point is sent towards the take-up reel. Every time the silicon rod moves 2 mm, the moving speed of the silicon rod is reduced by 400 μm / min. For the silicon rod cutting method of this embodiment, there are very few microcracks at the additional cutting position, and there is very little damage on the surface of the silicon wafer after additional cutting.

[0073] Example 5

[0074] It is carried out according to the silicon rod cutting method of Embodiment 1. The difference is that during the cutting process, a wire break occurs. The position of the wire break is close to the take-up reel. After the wire break, a splicing point is formed. The splicing point is close to the take-up reel. The splicing point is sent towards the take-up reel. Through the observation window of the silicon wafer cutting device, it is found that the wire bow is less than 10 mm. The wire feeding amount from the wire supply reel to the take-up reel is increased by 10 m. For the silicon rod cutting method of this embodiment, there is very little damage on the surface of the silicon wafer after additional cutting, and there is very little chipping on the edge of the silicon rod.

[0075] Example 6

[0076] It is carried out according to the silicon rod cutting method of Embodiment 1. The difference is that during the cutting process, a wire break occurs. The position of the wire break is close to the take-up reel. After the wire break, a splicing point is formed. The splicing point is close to the take-up reel. The splicing point is sent towards the take-up reel, and the moving speed of the silicon rod is kept unchanged. For the silicon rod cutting method of this embodiment, there are fewer microcracks at the additional cutting position, and there is less damage on the surface of the silicon wafer after additional cutting.

[0077] Example 7

[0078] It is carried out according to the silicon rod cutting method of Embodiment 1. The difference is that during the cutting process, a wire break occurs. The position of the wire break is close to the take-up reel. After the wire break, a splicing point is formed. The splicing point is close to the take-up reel. The splicing point is sent towards the take-up reel, and the wire feeding amount from the wire supply reel to the take-up reel is kept unchanged. For the silicon rod cutting method of this embodiment, there is less damage on the surface of the silicon wafer after additional cutting, and there is less chipping on the edge of the silicon rod.

[0079] Example 8

[0080] It is carried out according to the silicon rod cutting method of Embodiment 1. The difference is that during the cutting process, through the observation window of the silicon wafer cutting device, it is found that the wire bow is more than 10 mm. Under the condition that for every 2 mm of movement of the silicon rod, the wire feeding amount from the take-up reel to the wire supply reel is increased by 10 m, the silicon rod is moved 40 mm. For the silicon rod cutting method of this embodiment, there is very little damage on the surface of the silicon wafer after additional cutting, and there is very little chipping on the edge of the silicon rod.

[0081] Comparative Example 1

[0082] It is carried out according to the silicon rod cutting method of Embodiment 1. The difference is that in the pre-recovery step of the additional cutting process, the moving speed of the silicon rod is 70 μm / min. For the silicon rod cutting method of this comparative example, there is more damage on the surface of the silicon wafer after additional cutting, and there are more cracks on the edge of the silicon rod.

[0083] Comparative Example 2

[0084] It is carried out according to the silicon rod cutting method of Embodiment 1. The difference is that in the pre-recovery step of the additional cutting process, the wire speed is 1300 m / min. For the silicon rod cutting method of this comparative example, there is more damage on the surface of the silicon wafer after additional cutting, and there are more cracks and chipping on the edge of the silicon rod.

[0085] Comparative Example 3

[0086] The silicon rod cutting method of Example 1 is referred to, except that the additional cutting step of the additional cutting process maintains the wire feeding amount from the wire take-up wheel to the wire supply wheel and the wire feeding amount from the wire supply wheel to the wire take-up wheel in the pre-recovery step. In the silicon rod cutting method of this comparative example, the surface of the silicon wafer after additional cutting has more damage, and the edge of the silicon rod has more edge collapse. The silicon rod cutting method of this comparative example, the edge of the silicon rod refers to Figure 5 .

[0087] Comparative Example 1 and Comparative Example 1, in the pre-recovery step of the cutting process, the silicon rod moving speed is 40μm / min~60μm / min, which can reduce the surface damage of the silicon wafer after cutting, improve the surface quality of the silicon wafer, and reduce the edge cracks of the silicon rod; Comparative Example 2, in the pre-recovery step of the cutting process, the line speed is 1100m / min-1200m / min, which can reduce the surface damage of the silicon wafer after cutting, improve the surface quality of the silicon wafer, and reduce the edge cracks and edge collapse of the silicon rod; Comparative Example 3, in the cutting process, the parameter setting of the pre-recovery step is maintained so that the silicon rod moves 0.2mm-2mm, and then the amount of wire sent from the take-up wheel to the supply wheel is adjusted to 2300m~2700m, and the amount of wire sent from the supply wheel to the take-up wheel is adjusted to 1600m~2000m, which can reduce the surface damage of the silicon wafer after cutting, improve the surface quality of the silicon wafer, and reduce the edge collapse of the silicon rod.

[0088] Comparing Comparative Example 1 and Example 2, in the pre-recovery step, when the flow rate of the cutting fluid is above 190 L / min, it is more conducive to reducing the surface damage and microcracks at the cutting position, reducing the surface damage of the silicon wafer after cutting, and improving the surface quality of the silicon wafer. Comparing Comparative Example 1 and Example 3, in the cutting step, after keeping the parameter settings of the pre-recovery step and moving the silicon rod by 0.2 mm - 2 mm, adjusting the cutting fluid flow rate to 170 L / min - 185 L / min is more conducive to reducing the surface damage of the silicon wafer after cutting, improving the surface quality of the silicon wafer, and reducing the edge chipping phenomenon of the silicon rod. Comparing Comparative Example 1, 4, and 6, when wire breakage occurs during the cutting process, the wire breakage position is close to the take-up reel. After the wire breakage is spliced to form a splice point, the splice point is close to the take-up reel. Sending the splice point towards the take-up reel and reducing the moving speed of the silicon rod is more conducive to reducing the surface damage and microcracks at the cutting position, reducing the surface damage of the silicon wafer after cutting, and improving the surface quality of the silicon wafer. For every 2 mm movement of the silicon rod, reducing the moving speed of the silicon rod by 200 μm / min - 300 μm / min is further more conducive to reducing the surface damage and microcracks at the cutting position, reducing the surface damage of the silicon wafer after cutting, and improving the surface quality of the silicon wafer. Comparing Comparative Example 1, 5, and 7, when wire breakage occurs during the cutting process, the wire breakage position is close to the take-up reel. After the wire breakage is spliced to form a splice point, the splice point is close to the take-up reel. Sending the splice point towards the take-up reel and increasing the wire amount sent from the wire supply reel to the take-up reel and / or reducing the wire amount sent from the take-up reel to the wire supply reel is more conducive to reducing the surface damage of the silicon wafer after cutting, improving the surface quality of the silicon wafer, and reducing the edge chipping phenomenon of the silicon rod. When the wire bow is less than 10 mm as observed through the observation window of the silicon wafer cutting device, the total wire amount change L of increasing the wire amount sent from the wire supply reel to the take-up reel and / or reducing the wire amount sent from the take-up reel to the wire supply reel is 15 m - 30 m, which is further more conducive to reducing the surface damage of the silicon wafer after cutting, improving the surface quality of the silicon wafer, and reducing the edge chipping phenomenon of the silicon rod. Comparing Comparative Example 1 and Example 8, when the wire bow is above 10 mm, under the condition of increasing the wire amount sent from the take-up reel to the wire supply reel by 15 m - 20 m for every 2 mm movement of the silicon rod, moving the silicon rod by 30 mm - 60 mm is more conducive to reducing the surface damage of the silicon wafer after cutting, improving the surface quality of the silicon wafer, and reducing the edge chipping phenomenon of the silicon rod.

[0089] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the technical concept scope of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A method for cutting silicon rods, characterized in that, Including: Cutting is performed using a cutting wire. The cutting wire is payed out by a wire supply wheel, and the cutting wire sequentially bypasses cutting rollers and forms a cutting wire net between the juxtaposed cutting rollers. After the cutting wire net is formed, the wire is taken up by a wire take-up wheel. The silicon rod moves from one side of the cutting wire net towards the cutting wire net, and the cutting rollers drive the cutting wire in the cutting wire net to reciprocate, cutting the silicon rod entering the cutting wire net into multiple silicon wafers. The cutting method includes additional cutting, and the additional cutting includes a pre-recovery step and an additional cutting step performed in sequence. The pre-recovery step includes: the wire amount fed from the wire take-up wheel to the wire supply wheel is 1600 m to 2000 m, the wire amount fed from the wire supply wheel to the wire take-up wheel is 200 m to 400 m, the moving speed of the silicon rod is 40 μm / min to 60 μm / min, and the wire speed is 1100 m / min - 1200 m / min. The additional cutting step includes: after maintaining the parameter settings of the pre-recovery step and making the silicon rod move 0.2 mm - 2 mm, adjusting the moving speed of the silicon rod to 20 μm / min - 30 μm / min, adjusting the wire amount fed from the wire take-up wheel to the wire supply wheel to 2300 m to 2700 m, and adjusting the wire amount fed from the wire supply wheel to the wire take-up wheel to 1600 m to 2000 m.

2. The silicon rod cutting method according to claim 1, characterized in that The pre-recovery step includes: the cutting fluid flow rate is above 190 L / min. The additional cutting step includes: after maintaining the parameter settings of the pre-recovery step and making the silicon rod move 0.2 mm - 2 mm, adjusting the cutting fluid flow rate to 170 L / min - 185 L / min.

3. The silicon rod cutting method according to claim 1, characterized in that, The conditions of the cutting process before the pre-recovery step include: the moving speed of the silicon rod is above 100 μm / min, the wire speed is above 1200 m / min, and the cutting fluid flow rate is above 190 L / min.

4. The silicon rod cutting method according to claim 1, characterized in that The cutting method includes: after a wire break is subsequently connected to form a connection point, when the connection point in the cutting wire net is in the middle or close to the wire take-up wheel, the wire amount fed from the wire supply wheel to the wire take-up wheel is greater than the wire amount fed from the wire take-up wheel to the wire supply wheel, and the connection point is sent towards the wire take-up wheel. When the connection point in the cutting wire net is close to the wire supply wheel, the wire amount fed from the wire take-up wheel to the wire supply wheel is greater than the wire amount fed from the wire supply wheel to the wire take-up wheel, and the connection point is sent towards the wire supply wheel.

5. The silicon rod cutting method according to claim 4, characterized in that, After a wire break is subsequently connected to form a connection point, when the connection point is in the middle or close to the wire take-up wheel, reduce the moving speed of the silicon rod, increase the wire amount fed from the wire supply wheel to the wire take-up wheel and / or reduce the wire amount fed from the wire take-up wheel to the wire supply wheel.

6. The silicon rod cutting method according to claim 5, wherein The reduction of the moving speed of the silicon rod includes: for every 2 mm of movement of the silicon rod, the moving speed of the silicon rod is reduced by 200 μm / min - 300 μm / min.

7. The silicon rod cutting method according to claim 5, characterized in that, The total change in the wire amount of increasing the wire amount fed from the wire supply wheel to the wire take-up wheel and / or reducing the wire amount fed from the wire take-up wheel to the wire supply wheel is L. When the wire bow is less than 10 mm, L is 15 m to 30 m. When the wire bow is 10 mm - 15 mm, L is 30 m - 50 m. When the wire bow is greater than 15 mm, L is 50 m - 80 m.

8. The silicon rod cutting method according to claim 4, wherein After a wire break is subsequently connected to form a connection point, when the connection point is close to the wire supply wheel, keep the difference between the wire amount fed from the wire take-up wheel to the wire supply wheel and the wire amount fed from the wire supply wheel to the wire take-up wheel unchanged, and reduce the wire amount fed from the wire supply wheel to the wire take-up wheel.

9. The silicon rod cutting method according to claim 8, wherein Perform the operation of reducing the wire feeding amount from the wire supply wheel to the wire take-up wheel 2 to 4 times, with each reduction being 50% to 75% of the wire amount.

10. The method for cutting a silicon rod according to claim 8, characterized in that, After the wire break is rejoined, when the proportion of the old wire on the cutting wire mesh is less than 50% and more than 50% respectively, when reducing the wire feeding amount from the wire supply wheel to the wire take-up wheel, the moving distance of the silicon rod is within 4 mm and within 2 mm respectively.

11. The silicon rod cutting method according to claim 1, wherein The cutting method includes: when the wire bow is 10 mm or more, moving the silicon rod 30 mm - 60 mm. The conditions for moving the silicon rod 30 mm - 60 mm include: reducing the moving speed of the silicon rod by 200 um / min - 400 um / min, and for every 2 mm movement of the silicon rod, increasing the wire feeding amount from the wire take-up wheel to the wire supply wheel by 15 m - 20 m; After moving the silicon rod 30 mm - 60 mm, when the wire bow is still 10 mm or more, continue to move the silicon rod 30 mm - 60 mm, and for every 2 mm movement of the silicon rod, increase the wire feeding amount from the wire take-up wheel to the wire supply wheel by 40 m - 50 m.

12. A silicon wafer, characterized in that, The silicon wafer is obtained by cutting using the silicon rod cutting method according to any one of claims 1 to 11.

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