Method for controlling the shape of a silicon wafer by multi-wire sawing

Abstract

The application provides a method for controlling the shape of a cut silicon wafer by multi-wire cutting, and relates to the technical field of control methods for cutting silicon wafers. A second water cooling cavity is arranged in the axial direction of a main roller, a first water cooling cavity is opened on a rack, and the expansion amount of the main roller and the rack is monitored by a monitoring part. Cold water with a second predetermined temperature curve and a first temperature curve is introduced into the second water cooling cavity and the first water cooling cavity, and the temperature curve of the mortar liquid is matched, so that the position deviation and the displacement deviation of the main roller caused by the relative displacement of the position deviation and the displacement deviation of the main roller due to the thermal expansion of the crystal ingot are prevented, the large shape variable of the cut silicon wafer is prevented, and the expansion conditions of the crystal ingot in different cutting areas caused by the expansion of the rack are positively and negatively compensated. As a result, the shape of the whole cutting process is controllable, the flatness of the silicon wafer is improved, the NT 10*10 and NT 2*2 of the silicon wafer are reduced, and the nano is improved, so that the warp value of the silicon wafer is reduced as a whole, the area is flat, and the quality of the silicon wafer is better.

Description

Technical Field

[0001] This invention belongs to the technical field of control methods for cutting silicon wafers, and specifically relates to a method for controlling the morphology of silicon wafers through multi-wire cutting. Background Technology

[0002] In wafer fabrication, multi-wire dicing equipment is commonly used to process ingots into silicon wafers. During the dicing process, parameters such as wire tension, wire speed, wire feed / retreat ratio, slurry temperature, slurry flow rate, and main roller groove pitch are adjusted to control the thickness and total volumetric TV (TTV) of the silicon wafer. While these process parameter adjustments can improve some of the wafer morphology, the increasing demands for microdevice integration and yield have led to higher requirements for wafer flatness and warpage accuracy. Furthermore, the formation of multilayer integrated circuits is related to the production of uniform insulating films, ultimately stemming from issues with the precision of the wafer's nanoscale morphology. Therefore, improving the warpage that occurs during wafer dicing and the precision of the nanoscale morphology during wafer dicing are primary tasks.

[0003] In the prior art, such as Chinese invention application number 202010106029.3, a cutting process for improving the nano-morphology of large-diameter silicon wafers is disclosed. The specific steps include: cutting a silicon rod of a certain length in a low-viscosity slurry with a diamond wire of not less than 0.5 mm in diameter at a constant temperature. The viscosity of the slurry is not greater than 35 mPa·s. This invention reduces the surface flatness caused by wire cutting and improves the nano-morphology of silicon wafers for cutting large-size silicon wafers. Although it makes the average surface flatness of the silicon wafer <10 μm, and the average nano size in the obtained silicon wafer surface micro-nano morphology is <15 nm, it is not applicable to products with higher requirements for flatness and nano-size.

[0004] In the prior art, such as Chinese invention application number 201710068794.9, a method for manufacturing silicon wafers is disclosed, specifically including the following steps: providing a silicon wafer; simultaneously grinding the first and second surfaces of the silicon wafer, forming a gradually thickening morphology from the edge to the center on both surfaces; adsorbing the silicon wafer onto a suction cup device, with the second surface of the silicon wafer in contact with the suction cup device, and grinding the first surface of the silicon wafer; flipping the silicon wafer and adsorbing it onto the suction cup device, with the first surface of the silicon wafer in contact with the suction cup device, and grinding the second surface of the silicon wafer to form a bowl-shaped silicon wafer; simultaneously planarizing the first and second surfaces of the silicon wafer; and epitaxially growing an epitaxial layer on the first or second surface of the silicon wafer. Although this invention solves the problem of bulges or depressions in the middle of the silicon wafer obtained when growing an epitaxial layer on the silicon wafer in the traditional process through the grinding process, and also eliminates the wavy nanomorphic morphology generated during silicon wafer cutting, and has better local and overall flatness, it cannot change the influence of the silicon wafer morphology on the nanomorphic morphology.

[0005] In conclusion, neither adjusting process parameters in the multi-wire cutting process nor grinding the silicon wafer in the grinding process can improve the warp and nanometer of the silicon wafer, resulting in poor wafer quality. Summary of the Invention

[0006] In view of this, the present invention provides a method for controlling the morphology of silicon wafers through multi-wire dicing to improve the quality of silicon wafers by improving the silicon wafer warp and nano.

[0007] The technical solution adopted by this invention to solve its technical problem is:

[0008] A method for controlling the morphology of silicon wafers through multi-wire cutting involves using a multi-wire cutter with balanced expansion and a temperature profile of slurry to cut ingots to obtain silicon wafers, thereby improving the quality of the silicon wafers.

[0009] The multi-wire cutting machine includes a deformation control component, steel wire, and ingot. The deformation control component includes a frame, main rollers, and monitoring units. There are two main rollers and two monitoring units. A first water-cooling chamber is formed in the frame, and a second water-cooling chamber is formed axially in the main rollers. The ingot is located above the main rollers and is perpendicular to the steel wire. The steel wire is wound around the two main rollers. The monitoring units are respectively installed on the frame and the main rollers. The ingot is connected to the frame, and the main rollers are connected to the frame. The first water-cooling chamber is circulated with cold water of a first predetermined temperature curve according to the expansion of the frame at different cutting positions monitored by the monitoring units to reduce the expansion of the frame. The second water-cooling chamber is circulated with cold water of a second predetermined temperature curve according to the temperature curve of the slurry and the expansion of the main rollers monitored by the monitoring units to reduce the expansion of the main rollers, resulting in a flatter wafer with reduced warp after cutting.

[0010] Preferably, the frame includes a horizontal section and a vertical section, which form an L-shape. The horizontal section is located on the upper part of the crystal ingot, and the vertical section is located on the side of the crystal ingot and the main roller. The crystal ingot is connected to the lower part of the horizontal section, one end of the horizontal section is connected to one end of the vertical section, the main roller is connected to the vertical section, and the water-cooling cavity is located on one side of the horizontal section and close to the vertical section.

[0011] Preferably, the monitoring unit includes a first monitoring element and a second monitoring element, wherein the first monitoring element is connected to the frame and the second monitoring element is connected to the main roller.

[0012] Preferably, the outer wall of the second water-cooling cavity is 5-15 cm away from the outer wall of the main roller.

[0013] Preferably, the frame further includes a coil section located inside the first water-cooling cavity. The coil section includes a first water-cooling coil, the inlet of which is close to the bottom of the first water-cooling cavity, and the outlet of which is close to the bottom of the first water-cooling cavity. The first water-cooling coil spirals upwards layer by layer parallel to the bottom of the first water-cooling cavity, and the first water-cooling coil of each layer is arranged in a serpentine pattern.

[0014] Preferably, the coil section further includes several delivery pipes, each of which is connected at both ends to the first water-cooling coil of each layer.

[0015] Preferably, the coil section further includes a support plate, on which connection holes are evenly distributed, and the support plate is connected to the first water-cooled coil located on the same vertical line through the connection holes.

[0016] Preferably, the range of the first predetermined temperature curve of the cold water flowing into the first water-cooled cavity is 14℃-17℃.

[0017] Preferably, the temperature curve of the mortar liquid varies from 18.5℃ to 22℃.

[0018] Preferably, the second temperature curve of the cold water in the second water-cooling chamber varies in the range of 15℃-25℃.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] The present invention provides a method for controlling the morphology of silicon wafers through multi-wire cutting. This method involves setting a second water-cooling cavity along the axial direction of the main roller and opening a first water-cooling cavity on the frame. A monitoring unit monitors the expansion of the main roller and frame, introducing cold water at predetermined temperatures (second and first) into the second and first water-cooling cavities, respectively. This is coordinated with the temperature curve of the slurry to prevent positional deviations caused by ingot thermal expansion and displacement deviations of the main roller from creating relative displacements that could lead to significant morphological variations in the cut silicon wafers. The method also provides positive and negative compensation for the expansion of the ingot in different cutting areas due to frame expansion. This makes the shape controllable throughout the cutting process, thereby improving the flatness of the silicon wafer, reducing NT values ​​(10*10 and 2*2), and increasing nanometer value. This results in a flatter overall area with reduced warp value, leading to better wafer quality. Attached Figure Description

[0021] Figure 1 This is a front view of a multi-wire cutting machine.

[0022] Figure 2 This is a schematic diagram of a multi-wire cutting machine.

[0023] Figure 3 This is a front view of the horizontal section.

[0024] Figure 4 for Figure 3 Cross-sectional view of the first water-cooled cavity in the AA direction.

[0025] Figure 5 This is a schematic diagram of the coil section.

[0026] Figure 6 for Figure 1 Sectional view along the BB direction.

[0027] Figure 7 This is a schematic diagram of the second and third water-cooling coils.

[0028] Figure 8 This is a graph showing the first predetermined temperature of the cold water in the first water-cooling coil in Example 1.

[0029] Figure 9 This is a graph showing the expansion of the frame in Example 1.

[0030] Figure 10 This is a graph showing the second predetermined temperature inside the second and third water-cooling coils in Example 1.

[0031] Figure 11 This is the temperature curve of the mortar liquid in Example 1.

[0032] Figure 12 This is a curve showing the expansion of the main roller in Example 1.

[0033] Figure 13 This is a comparison diagram of the warp lines of the ingot cutting in Example 1 and Comparative Example 3.

[0034] Figure 14 This is a warp distribution diagram for Example 1.

[0035] Figure 15 The image shows a comparison of the NT10*10 box line graphs of the silicon wafer nanostructure in Example 1 and Comparative Example 3.

[0036] Figure 16 The image shows a comparison of the NT2*2 box-shaped morphology of silicon wafers in Example 1 and Comparative Example 3.

[0037] Figure 17 This is a comparative example of a whole bar warp distribution.

[0038] Figure 18 This is a curve showing the expansion of the main roller in Comparative Example 2.

[0039] Figure 19 The image shows the warp distribution of the entire bar in the comparative example.

[0040] Figure 20 Comparison diagrams of the warp marks from the ingot cutting in Comparative Examples 1, 2, and 3.

[0041] Figure 21 Comparison diagram of the NT10*10 box line of the nanostructure of silicon wafers in Comparative Example 1, Comparative Example 2, and Comparative Example 3.

[0042] Figure 22 Comparison diagram of NT2*2 box lines of silicon wafer nanomorphology in Comparative Example 1, Comparative Example 2, and Comparative Example 3.

[0043] Figure 23 This is a schematic diagram of a silicon wafer warping.

[0044] Figure 24 This is a schematic diagram of a silicon wafer warping.

[0045] In the figure: the image before improvement is the test result of Comparative Example 3, the image after frame improvement is the test result of Comparative Example 1, the image after main roller temperature is the test result of Comparative Example 2, and the image after improvement is the test result of Example 1. The components are: multi-wire cutting machine 10, deformation control component 100, frame 110, first water cooling chamber 111, horizontal part 112, vertical part 113, coil part 114, first water cooling coil 1141, conveying pipe 1142, support plate 1143, connecting hole 11431, main roller 120, second water cooling chamber 121, second water cooling coil 122, first coil 1221, second coil 1222, third water cooling coil 123, monitoring part 130, first monitoring component 131, second monitoring component 132, steel wire 200, and ingot 300. Detailed Implementation

[0046] The technical solutions and effects of the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0047] Please refer to Figures 1 to 7 A method for controlling the morphology of silicon wafers through multi-wire cutting involves using a multi-wire cutter 10 with balanced expansion and a temperature profile of slurry to cut ingots 300 to obtain silicon wafers, thereby improving the quality of the silicon wafers.

[0048] The multi-wire cutting machine 10 includes a deformation control component 100, a steel wire 200, and an ingot 300. The deformation control component 100 includes a frame 110, main rollers 120, and monitoring units 130. There are two main rollers 120 and two monitoring units 130. The frame 110 has a first water-cooling cavity 111, and the main rollers 120 have a second water-cooling cavity 121 axially. The ingot 300 is located above the main rollers 120 and is perpendicular to the steel wire 200. The steel wire 200 is wound around the two main rollers 120. The monitoring units 130 are respectively installed on... On the frame 110 and the main roller 120, the ingot 300 is connected to the frame 110, and the main roller 120 is connected to the frame 110. The first water-cooling chamber 111 is supplied with cold water of a first predetermined temperature curve according to the expansion of the frame 110 at different cutting positions monitored by the monitoring unit 130, so as to reduce the expansion of the frame 110. The second water-cooling chamber 121 is supplied with cold water of a second predetermined temperature curve according to the temperature curve of the slurry and the expansion of the main roller 120 monitored by the monitoring unit 130, so as to reduce the expansion of the main roller 120, making the silicon wafer flatter and reducing warp after cutting.

[0049] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0050] The present invention provides a method for controlling the morphology of silicon wafers through multi-wire cutting. This method involves setting a second water-cooling cavity 121 along the axial direction of the main roller 120 and opening a first water-cooling cavity 111 on the frame 110. A monitoring unit 130 monitors the expansion of the main roller 120 and the frame 110. Cold water of a second predetermined temperature curve and a first temperature curve is introduced into the second water-cooling cavity 121 and the first water-cooling cavity 111, and coordinated with the temperature curve of the slurry. This prevents positional deviations caused by the thermal expansion of the ingot 300 and the displacement deviation of the main roller 120 from forming relative displacements that would result in significant morphological variations in the cut silicon wafers. The method also provides positive and negative compensation for the expansion of the ingot 300 in different cutting areas due to the expansion of the frame 110. This makes the shape controllable throughout the cutting process, thereby improving the flatness of the silicon wafer, reducing the NT 10*10 and NT 2*2 values, and increasing the nanometer value. This results in a flatter overall area of ​​reduced warp value in the silicon wafer, leading to better wafer quality.

[0051] Furthermore, the frame 110 includes a horizontal portion 112 and a vertical portion 113, which form an L-shape. The horizontal portion 112 is located on the upper part of the ingot 300, and the vertical portion 113 is located on the side of the ingot 300 and the main roller 120. The ingot 300 is connected to the lower part of the horizontal portion 112, one end of the horizontal portion 112 is connected to one end of the vertical portion 113, and the main roller 120 is connected to the vertical portion 113. The first water-cooling cavity 111 is located on one side of the horizontal portion 112 and close to the vertical portion 113. The horizontal portion 112 bears a heavy load and is unstable, and is prone to expansion when heated. Therefore, the first water-cooling cavity 111 is set on one side of the horizontal portion 112 and close to the vertical portion 113.

[0052] Furthermore, the monitoring unit 130 includes a first monitoring element 131 and a second monitoring element 132. The first monitoring element 131 is connected to the frame 110, and the second monitoring element 132 is connected to the main roller 120.

[0053] Furthermore, there are two first monitoring elements 131, which are located at one end of the vertical part 113 and one end of the horizontal part 112, respectively, and the two first monitoring elements 131 are located on the same side. The first monitoring element 131 is a light signal position sensor. There are two second monitoring elements 132, which are disposed at both ends of the main roller 120. The second monitoring element 132 is a pressure sensor.

[0054] Furthermore, the outer wall of the second water-cooling cavity 121 is 5-15cm away from the outer wall of the main roller 120 to ensure sufficient heat dissipation.

[0055] Furthermore, the frame 110 also includes a coil section 114, which is located inside the first water-cooling cavity 111. The coil section 114 includes a first water-cooling coil 1141, the inlet of which is close to the bottom of the first water-cooling cavity 111, and the outlet of which is close to the bottom of the first water-cooling cavity 111. The first water-cooling coil 1141 spirals upwards layer by layer parallel to the bottom of the first water-cooling cavity 111, and each layer of the first water-cooling coil 1141 is arranged in a serpentine pattern to increase the heat exchange path of each layer, increase the heat exchange area, and reduce the expansion of the frame 110.

[0056] Furthermore, the coil section 114 also includes several conveying pipes 1142, with each end of the conveying pipe 1142 connected to the first water-cooling coil 1141 of each layer. On the one hand, the conveying pipes 1142 enable the first water-cooling coils 1141 of each layer to support each other. On the other hand, the conveying pipes 1142 enable water to flow horizontally and vertically in each layer, accelerating water diffusion and extending heat exchange time.

[0057] Furthermore, the coil section 114 also includes a support plate 1143. The support plate 1143 has evenly spaced connection holes 11431. The support plate 1143 is connected to the first water-cooling coil 1141 located on the same vertical line through the connection holes 11431. On the one hand, this avoids the vibration of the first water-cooling coil 1141, thereby preventing the frame 110 from resonating and affecting the silicon wafer entry angle. On the other hand, the support plate 1143 increases the cold air propagation rate in the height direction.

[0058] Furthermore, the range of the first predetermined temperature curve of the cold water flowing into the first water-cooled cavity 111 is 14℃-17℃.

[0059] Furthermore, as the radial length of the ingot 300 is cut from the moment of entry to (2 / 3-5 / 6), the temperature of the cold water flowing into the first water-cooling chamber 111 changes from low to high. As the radial length of the ingot 300 is cut from (2 / 3-5 / 6) to the end of the cutting process, the temperature of the cold water flowing into the first water-cooling chamber 111 changes from high to low.

[0060] Furthermore, the temperature curve of the mortar liquid varies from 18.5℃ to 22℃.

[0061] Furthermore, the temperature of the mortar varies according to the radial length of the ingot 300 being cut. When the radial length of the ingot 300 being cut decreases from the initial cut to 2 / 10-3 / 10, the temperature of the mortar decreases. When the radial length of the ingot 300 being cut decreases from 2 / 10-3 / 10 to 7 / 10-9 / 10, the temperature of the mortar remains unchanged. When the radial length of the ingot 300 being cut decreases from 7 / 10-9 / 10 until the cutting is completed, the temperature of the mortar increases.

[0062] Furthermore, the second temperature curve of the cold water in the second water-cooling chamber 121 varies from 15℃ to 25℃.

[0063] Furthermore, when the radial length of the ingot 300 is cut from the entry point to 2 / 5-3 / 5, the cooling water temperature of the second water-cooling chamber 121 changes from high to low. When the radial length of the ingot 300 is cut from 2 / 5-3 / 5 to the end of the cutting process, the cooling water temperature of the second water-cooling chamber 121 changes from low to high.

[0064] Furthermore, the second water-cooling cavity 121 is rectangular or cylindrical. The main roller 120 also includes a second water-cooling coil 122 and a third water-cooling coil 123. The second water-cooling coil 122 and the third water-cooling coil 123 are perpendicular to each other and located within the second water-cooling cavity 121. The inlet and outlet of the second water-cooling coil 122 and the inlet and outlet of the third water-cooling coil 123 are located at the same end, and the ends of the second water-cooling coil 122 and the third water-cooling coil 123 are rotatably connected to the main roller 120. Cold water of a second predetermined temperature curve is introduced into 123. When the silicon wafer is cut, the main roller 120 rotates, while the second water-cooling coil 122 and the third water-cooling coil 123 do not rotate with the main roller 120. There is a gap between the second water-cooling cavity 121 and the second water-cooling coil 122 and the third water-cooling coil 123. The cold air emitted by the cold water in the second water-cooling coil 122 and the third water-cooling coil 123 is evenly distributed in the second water-cooling cavity 121 as the main roller 120 rotates, so that the main roller 120 will not overheat locally and affect the cooling effect.

[0065] Furthermore, the second water-cooled coil 122 includes a first coil 1221 and a second coil 1222. The first coil 1221 and the second coil 1222 have the same structure. The first coil 1221 and the second coil 1222 are located on the same axis. The first coil 1221 and the second coil 1222 are axially symmetrical. One end of the first coil 1221 and the second coil 1222 are connected.

[0066] Furthermore, the third water-cooling coil 123 has the same structure as the second water-cooling coil 122, and the third water-cooling coil 123 is located between the first coil 1221 of the second water-cooling coil 122 and the second coil 1222 of the second water-cooling coil 122.

[0067] Furthermore, the density of the slurry is 1.4 g / cm³ to 1.58 g / cm³, the pH of the slurry is acidic, the water content is 8%-12%, the viscosity is 56 cpa / s-62 cpa / s, and the electrical conductivity is 200 μs / cm to 300 μs / cm. Using an aqueous cutting fluid ensures sufficient dispersion and reduces the density of the slurry, thereby reducing vibration during the slicing process. The slightly acidic pH of the slurry enhances its polarity and prevents the formation of silicates. Furthermore, the use of low-viscosity and high-specific-heat-capacity slurry promptly removes heat during the cutting process, preventing significant morphological variations in the cut silicon wafers caused by relative displacement due to positional deviations caused by the thermal expansion of the ingot 300 and the displacement deviations of the main roller 120.

[0068] Furthermore, the pH is 6.5±0.5. The acidity or alkalinity of the cutting fluid will affect the fatigue of the steel wire 200 and the durability of the equipment structure, preventing the formation of silicates and the decrease in conductivity during the mortar process.

[0069] Furthermore, the mortar is prepared in a ratio of cutting fluid to silicon carbide of 1:0.85-0.92. The silicon carbide has a particle size distribution of 5.5-11.3 μm, a particle size of 1200-1600 mesh, a D50 of 8.0±0.5, and a standard deviation of 1 μm. By controlling the particle size distribution of silicon carbide, the vibration of the silicon wafer, the depth of the damaged layer in local areas, and the heat generation during the constant cutting process are controlled, thereby controlling the wave problem caused by the elastic distortion layer in local areas.

[0070] Furthermore, the cutting fluid comprises: 1,2-propylene glycol, dispersant, wetting agent, pure water, and sodium citrate, with 80% 1,2-propylene glycol, 15% pure water, and a total of 5% dispersant, wetting agent, and sodium citrate, to ensure the dispersion and wetting properties of the cutting fluid, and to ensure that the cutting fluid has a constant specific heat and pH.

[0071] For ease of understanding, the present invention is further illustrated by the following embodiments: Example 1:

[0072] Cutting 12-inch ingots 300, each ingot 300mm long, the outer wall of the first water-cooling chamber 111 is 5cm from the outer wall of the main roller 120. The first predetermined temperature curve of the cooling water in the first water-cooling coil 1141 is as follows. Figure 8 As shown, the optical signal position sensor monitors the expansion of the frame 110 as follows: Figure 9 As shown; the second temperature curves of the cooling water in the second water-cooling coil 122 and the third water-cooling coil 123 are as follows. Figure 10 As shown, the temperature curve of the mortar liquid is as follows: Figure 11 As shown; the pressure sensor monitors the expansion of the main roller 120 as follows: Figure 12 As shown;

[0073] The steel wire 200 has a diameter of 0.16 mm, the silicon carbide particle size is 1500 mesh, D50 is 8 μm, and standard deviation is 1 μm. The mortar preparation ratio is cutting fluid: silicon carbide = 1.25:1. The cutting fluid is PG. The mortar density is 1.55 g / cm³, the mortar pH is 6.3, the mortar moisture content is 10.32%, the mortar viscosity is 62 MPa / s, the mortar conductivity is 200-300 μs / cm, and the mortar temperature is 20℃-24℃. Then, the ingot 300 is cut into silicon wafers using a multi-wire dicing machine 10. The silicon wafers are warped and their nano-morphology (NT2*2, NT10*10) is tested. The test results are as follows: Figures 13-16 As shown.

[0074] Comparative Example 1 (Rack Modification)

[0075] The mortar temperature is 20℃-24℃, and the main roller 120 is a solid structure. It does not have a second water-cooling chamber 121, a second water-cooling coil 122, or a third water-cooling coil 123. Otherwise, it is the same as in Embodiment 1. The first predetermined temperature curve of the cooling water in the first water-cooling coil 1141 is as follows: Figure 8 As shown, the optical signal position sensor monitors the expansion of the frame 110 as follows: Figure 9 As shown; then, the ingot 300 is cut into silicon wafers using a multi-wire dicing machine 10. The silicon wafers are then inspected for warping and nano-morphology (NT2*2, NT10*10). The inspection results are as follows. Figure 17 , 20 As shown in -22.

[0076] Comparative Example 2 (Main Roller Modification)

[0077] The frame 110 is a solid structure, without the first water-cooling cavity 111 and the first water-cooling coil 1141. Otherwise, it is the same as in Embodiment 1. The temperature profiles of the cooling water in the second water-cooling coil 122 and the third water-cooling coil 123 are as follows: Figure 10 As shown, the temperature curve of the mortar liquid is as follows: Figure 11 As shown; the pressure sensor monitors the expansion of the main roller 120 as follows: Figure 18 As shown, the ingot 300 is then diced into silicon wafers using a multi-wire dicing machine 10. The silicon wafers are then warped and tested for nanostructures (NT2*2, NT10*10). The test results are as follows. Figures 19-22 As shown.

[0078] Comparative Example 3 (without modification to the multi-wire cutting machine 10):

[0079] The mortar temperature is 20℃-24℃. The frame 110 and main roller 120 are solid. The first water-cooling chamber 111, second water-cooling chamber 121, first water-cooling coil 1141, second water-cooling coil 122, and third water-cooling coil 123 are not provided. Other conditions are the same as in Example 1. The cut silicon wafers are tested and compared. The test results are as follows: Figures 13-16 As shown in Figures 20-22.

[0080] As can be seen from Example 1, the frame 110 is made of steel. Silicon has a small coefficient of thermal expansion, while steel has a large coefficient of thermal expansion. When exposed to external temperature and heat radiation from various components, the frame 110 will expand due to heat first, causing the inlet and outlet of the blade to warp during slicing. Figure 23As shown, by opening a first water-cooling cavity 111 on the frame 110 and setting a first water-cooling coil 1141, cold water of a first predetermined temperature curve is introduced into the first water-cooling coil 1141 at different cutting positions of the silicon wafer according to the expansion of the frame 110 monitored by the first monitoring device 131. This positively and negatively compensates for the expansion of the ingot 300 in different cutting areas, thereby improving the entry and exit shape of the silicon wafer, controlling and improving the flatness of the silicon wafer, and making the silicon wafer morphology consistent with the MC side morphology, improving the silicon wafer warp, and avoiding the nano problem caused by rapid deformation of the ingot 300 in local areas of the silicon wafer, thus improving the quality of the silicon wafer. Moreover, during the cutting process: the heat generated by the high-speed rotation of the main roller 120, the heat carried out by the slurry, and the heat generated by the slurry and the ingot 300 being cut by the steel wire 200 will cause the main roller 120 to expand, such as Figure 24 As shown, the expansion steel wire 200 of the main roller 120 may cut along the movement direction of the main roller 120, resulting in a large displacement deviation between the actual processed shape and the theoretical processed shape. By controlling the expansion of the main roller 120 and the temperature of the slurry, the displacement of the silicon wafer cutting process caused by the expansion of the main roller 120 and the ingot 300 during the cutting process is reduced, making the entire silicon wafer flatter, and reducing the silicon wafer NT10*10 and NT 2*2, thereby increasing nanometer size.

[0081] As can be seen from the comparison between Example 1 and Comparative Examples 1 and 2, simply changing the frame 110 or the main roller 120 can only partially improve the nano-morphology of the silicon wafer, and the influence of the main roller 120 on the nano-morphology of the silicon wafer is greater than that of the frame.

[0082] As can be seen from the comparison between Example 1 and Comparative Example 3, the present invention greatly improves the nano-morphology of silicon wafers by controlling the expansion of the main roller 120 and the frame 110, thereby reducing the warp of the silicon wafer to 4.86047, NT 10*10 to 9.2085, and NT2*2 to 4.03118.

[0083] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the invention. Those skilled in the art will understand that implementing all or part of the above-described embodiments and making equivalent changes in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A method for controlling the morphology of silicon wafers through multi-wire cutting, characterized in that, Silicon wafers are obtained by cutting ingots using a multi-wire cutting machine with balanced expansion and in conjunction with the temperature profile of the slurry, in order to improve the quality of silicon wafers. The multi-wire cutting machine includes a deformation control component, steel wire, and ingot. The deformation control component includes a frame, main rollers, and monitoring units. There are two main rollers and two monitoring units. A first water-cooling chamber is formed in the frame, and a second water-cooling chamber is formed axially in the main rollers. The ingot is located above the main rollers and is perpendicular to the steel wire. The steel wire is wound around the two main rollers. The monitoring units are respectively installed on the frame and the main rollers. The ingot is connected to the frame, and the main rollers are connected to the frame. The first water-cooling chamber is supplied with cold water of a first predetermined temperature curve based on the expansion of the frame at different cutting positions monitored by the monitoring units to reduce the expansion of the frame. The second water-cooling chamber is supplied with cold water of a second predetermined temperature curve based on the temperature curve of the slurry and the expansion of the main rollers monitored by the monitoring units to reduce the expansion of the main rollers, resulting in a flatter wafer with reduced warp after cutting. The first predetermined temperature curve of the cold water flowing into the first water-cooling chamber varies from 14℃ to 17℃; the temperature curve of the slurry liquid varies from 18.5℃ to 22℃; the second temperature curve of the cold water in the second water-cooling chamber varies from 15℃ to 25℃, so as to prevent the relative displacement caused by the position deviation of the crystal ingot due to thermal expansion and the displacement deviation of the main roller, which would result in a large morphological variable in the cut silicon wafer.

2. The method for controlling the morphology of silicon wafers through multi-wire cutting as described in claim 1, characterized in that: The frame includes a horizontal section and a vertical section, which form an L-shape. The horizontal section is located on the upper part of the crystal ingot, and the vertical section is located on the side of the crystal ingot and the main roller. The crystal ingot is connected to the lower part of the horizontal section, one end of the horizontal section is connected to one end of the vertical section, the main roller is connected to the vertical section, and the first water-cooling cavity is located on one side of the horizontal section and close to the vertical section.

3. The method for controlling the morphology of silicon wafers through multi-wire cutting as described in claim 1, characterized in that: The monitoring unit includes a first monitoring element and a second monitoring element. The first monitoring element is connected to the frame, and the second monitoring element is connected to the main roller.

4. The method for controlling the morphology of silicon wafers through multi-wire cutting as described in claim 1, characterized in that: The outer wall of the second water-cooling chamber is 5-15 cm away from the outer wall of the main roller.

5. The method for controlling the morphology of silicon wafers through multi-wire cutting as described in claim 1, characterized in that: The frame also includes a coil section located inside the first water-cooling cavity. The coil section includes a first water-cooling coil. The inlet of the first water-cooling coil is close to the bottom of the first water-cooling cavity, and the outlet of the first water-cooling coil is close to the bottom of the first water-cooling cavity. The first water-cooling coil spirals upward layer by layer parallel to the bottom of the first water-cooling cavity, and the first water-cooling coil of each layer is arranged in a serpentine pattern.

6. The method for controlling the morphology of silicon wafers through multi-wire cutting as described in claim 5, characterized in that: The coil section also includes several delivery pipes, each of which is connected at both ends to the first water-cooling coil of each layer.

7. The method for controlling the morphology of silicon wafers through multi-wire cutting as described in claim 6, characterized in that: The coil section also includes a support plate with evenly spaced connection holes. The support plate is connected to the first water-cooled coil located on the same vertical line through the connection holes.

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