A method for diamond wire cutting of 12-inch semiconductor crystal rods

Abstract

A kind of 12 inch semiconductor crystal bar diamond wire cutting method relates to 12 inch semiconductor crystal bar diamond wire field, and cutting process includes following three stages: S1, from cutting start until cutting depth reaches first preset depth, keep the drainage passage of tab slot unobstructed, and water supply mechanism of cutting machine supplies water to diamond wire in the process of cutting;S2, in the process that cutting depth from first preset depth until second preset depth, the drainage passage of tab slot is blocked, so that diamond wire is immersed in the cooling water of tab slot to cut semiconductor crystal bar, and bubbling pressure is bubbled to cooling water in the process of cutting with first rise later drop;S3, when cutting depth from second preset depth until cutting is completed, stop bubbling to cooling water, keep diamond wire immersed in the cooling water of tab slot and cut.This application is used to solve the technical problem that 12 inch semiconductor crystal bar is not easy to dissipate heat in the process of cutting, and then causes the bending and warping of excessive standard.

Description

Technical Field

[0001] The present invention relates to the field of 12-inch semiconductor crystal rod diamond wire, and in particular to a method for cutting 12-inch semiconductor crystal rod diamond wire. Background Art

[0002] Semiconductor wafers are the substrate material for chip manufacturing, especially 12-inch semiconductor wafers are the main material for high-end chips. The manufacturing process is as follows: polycrystalline silicon is melted and then pulled into high-quality single crystal silicon rods through a single crystal furnace; the single crystal silicon rods are cut and rolled into 12-inch diameter crystal rods; the crystal rods are divided into silicon wafers through wire cutting, and the silicon wafers undergo chamfering, grinding, polishing and other steps to improve the surface flatness of the silicon wafers.

[0003] Currently, 12-inch semiconductor ingots are commonly cut using either mortar wire or diamond wire sawing. Mortar wire sawing of 12-inch ingots has been widely used, and diamond wire sawing of 6-inch and smaller ingots has also been successfully developed. However, diamond wire sawing of 12-inch ingots is still in the early stages of research and development. Diamond wire sawing primarily uses the diamond powder on a diamond wire to strike the ingot at high speed, thereby cutting it into silicon wafers. Compared to mortar wire sawing, diamond wire sawing of 12-inch semiconductor ingots has the following advantages: 1) Disposal of the waste mortar produced by mortar wire sawing is increasingly difficult and does not meet environmental protection requirements. The coolant used in diamond wire sawing is a mixture of pure water and a small amount of diamond wire cutting fluid, which conforms to the general trend of environmental protection; 2) Cutting costs are reduced by over 40%; 3) Cutting efficiency is high, with cutting time shortened by over 30%; and 4) Wire loss is low, increasing the slicing yield by over 6%.

[0004] However, there are the following problems when diamond wire cutting 12-inch semiconductor wafers: Unlike 8-inch and smaller silicon wafers, 12-inch semiconductor crystal rods are used in high-end chips. Therefore, the surface morphology of the silicon wafer after cutting is very demanding, such as crystal orientation, thickness uniformity, bending, warping and other parameters. This requires good stability of the diamond wire and sufficient heat dissipation during the cutting process. The water supply devices in existing cutting equipment are generally located on both sides of the crystal rod to provide cooling liquid towards the cutting wire mesh, such as Figure 1 As shown, in practice, it will cause large fluctuations in the wire mesh, resulting in poor surface morphology of the silicon wafer after cutting. When used for cutting 8-inch and below silicon wafers, it will not affect the use of the silicon wafers, but when applied to 12 inches, it will cause the surface morphology of the silicon wafer after cutting to be unqualified.

[0005] The biggest difficulty in cutting 12-inch semiconductor crystal rods is their large diameter, which makes heat dissipation difficult, leading to excessive bending and warping. To solve this problem, the applicant has previously applied for an invention patent entitled "A spray system and method for using diamond wire to cut 12-inch semiconductor silicon crystal rods", with application number CN202211262155.3. This patent can solve the heat dissipation problem during cutting while effectively reducing the fluctuation amplitude of the cutting wire mesh and improving the surface morphology parameters of the silicon wafer after cutting.

[0006] The prior art also discloses a Chinese invention patent for a splicing trough, a diamond wire slicer, and a method for cutting large-sized silicon rods, with application number 202210307279.2. Specifically, it is disclosed that the diamond wire slicer includes two left and right cutting main rollers and a splicing trough, and the splicing trough includes a trough body for containing coolant and arranged between the two cutting main rollers, the trough body includes two trough side walls arranged on the left and right, and a trough bottom wall connected between the two trough side walls, and the trough body is fixed with side wall ultrasonic vibration plates on the two trough side walls, and the trough body is fixed with a bottom wall ultrasonic vibration plate on the trough bottom wall. However, the principle of ultrasound is high-frequency vibration. During implementation, ultrasound can easily break the diamond wire with a diameter of only 0.08 mm instantly. Even if it is not broken, it will cause high-frequency vibration, which will prevent the cutting work from proceeding smoothly.

[0007] The present invention provides an improved solution that is different from the prior art, so as to improve the heat dissipation efficiency of 12-inch semiconductor crystal rods during the cutting process and improve the quality of finished silicon wafers. Summary of the Invention

[0008] The present invention aims to provide a method for diamond wire cutting of 12-inch semiconductor crystal rods to solve the technical problem that the 12-inch semiconductor crystal rods are difficult to dissipate heat during the cutting process, thereby causing excessive bending and warping.

[0009] To solve the above technical problems, the present invention adopts a specific solution: a method for diamond wire cutting of a 12-inch semiconductor crystal ingot. First, the semiconductor crystal ingot is mounted on a workpiece plate above the diamond wire mesh of a cutting machine. Then, the workpiece plate is pressed downward, and the winding roller of the cutting machine drives the diamond wire to move, thereby cutting the semiconductor crystal ingot. The cutting process includes the following three stages:

[0010] S1. From the start of cutting until the cutting depth reaches a first preset depth, the drainage channel of the splice slot is kept unobstructed, and water is supplied to the diamond wire by the water supply mechanism of the cutting machine during the cutting process;

[0011] S2. During the process of cutting from the first preset depth to the second preset depth, the drainage channel of the splice slot is blocked, the diamond wire is immersed in the cooling water of the splice slot to cut the semiconductor crystal ingot, and the cooling water is bubbled with bubbling pressure that first increases and then decreases during the cutting process;

[0012] S3. When the cutting depth increases from the second preset depth until the cutting is completed, stop bubbling the cooling water and keep the diamond wire immersed in the cooling water in the splicing groove while cutting.

[0013] As a further optimization of the above technical solution, the first preset depth is 30 mm and the second preset depth is 180 mm.

[0014] As a further optimization of the above technical solution, when the cutting depth is 30-180 mm, the bubbling air pressure is 0.18-0.39 MPa.

[0015] As a further optimization of the above technical solution,

[0016] When the cutting depth is 30-50mm, the bubbling air pressure is 0.18-0.22Mpa;

[0017] When the cutting depth is 50-80mm, the bubbling air pressure is 0.27-0.33Mpa;

[0018] When the cutting depth is 80-120mm, the bubble pressure is 0.33-0.39Mpa;

[0019] When the cutting depth is 120-150mm, the bubbling air pressure is 0.27-0.33Mpa;

[0020] When the cutting depth is 150-180mm, the bubbling air pressure is 0.18-0.22Mpa.

[0021] As a further optimization of the above technical solution, when the cutting depth is 30-50 mm, the bubbling air pressure is 0.2 MPa;

[0022] When the cutting depth is 50-80mm, the bubbling air pressure is 0.3Mpa;

[0023] When the cutting depth is 80-120mm, the bubbling air pressure is 0.35Mpa;

[0024] When the cutting depth is 120-150mm, the bubbling air pressure is 0.3Mpa;

[0025] When the cutting depth is 150-180mm, the bubbling air pressure is 0.2Mpa.

[0026] As a further optimization of the above technical solution, the connecting plate groove includes a groove body and a bubbling air tube arranged in the groove body. A drainage channel is opened on the groove wall of the groove body, and a baffle that can block the drainage channel is movably provided.

[0027] As a further optimization of the above technical solution, the drainage channel is provided at one end or two opposite ends of the trough body.

[0028] As a further optimization of the above technical solution, the bubbling air pipe is arranged at the bottom of the tank body and on the two opposite sides of the tank wall, and the bubbling air pipe is provided with bubbling ports at intervals.

[0029] As a further optimization of the above technical solution, the diameter of the bubbling air tube is 8 mm, the spacing between adjacent bubbling ports is 30-50 mm, and the aperture of the bubbling port is 0.5-1 mm.

[0030] As a further optimization of the above technical solution, the distance between the bubbling air tube and the upper edge of the connecting groove is 50-230 mm.

[0031] Compared with the prior art, the present invention has the following beneficial effects: the present invention controls the introduction of compressed air into the cooling water in the splice slot for bubbling, drives the flow of the coolant through the bubbling operation, and improves the heat dissipation efficiency of the semiconductor crystal rod during the cutting process.

[0032] During the process of diamond wire cutting of semiconductor crystal rods to prepare silicon wafers, silicon powder is generated and accumulated between the diamond wire and the silicon wafer, wrapping the diamond wire sand on the surface of the diamond wire and reducing the cutting force. The bubbling process can effectively eliminate the accumulation of silicon powder and enhance the cutting force.

[0033] If the bubbling flow rate is too large, it will cause greater fluctuations in the liquid level, resulting in greater fluctuations in the wire mesh, which will affect the TTV of the silicon wafer and cause thick and thin slices. By adopting the cutting method of the present invention, the bubbling air pressure is reasonably adjusted and the bubbling amount is controlled to achieve heat dissipation and increase cutting force while ensuring that TTV is not affected. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a structural schematic diagram of the cutting machine of the present invention;

[0035] Figure 2 Schematic diagram of the external structure of the splice slot;

[0036] Figure 3 It is a top view of the bubbler trachea;

[0037] Figure 4 for Figure 3 Enlarged view of point A in the middle;

[0038] Figure 5 This is the process capability report of BOW in comparative example 1;

[0039] Figure 6 The process capability report of BOW in Example 2;

[0040] Figure 7This is the process capability report of WARP in comparative example 1;

[0041] Figure 8 The process capability report of WARP in Example 2;

[0042] Figure 9 The interval diagram of BOW in Example 2 and Comparative Example 1 (95% confidence interval of the mean);

[0043] Figure 10 The interval diagram of WARP in Example 2 and Comparative Example 1 (95% confidence interval of the mean);

[0044] Figure 11 A top view of the surface morphology of the silicon wafer cut in Example 2;

[0045] Figure 12 This is a side view of the surface morphology of the silicon wafer cut in Example 2;

[0046] Figure 13 A top view of the surface morphology of a silicon wafer cut in Comparative Example 1;

[0047] Figure 14 This is a side view of the surface morphology of the silicon wafer cut in Comparative Example 1;

[0048] Figure 15 A splice slot without a baffle;

[0049] Figure 16 For inserting the tab slot behind the baffle;

[0050] Figure numerals: 1. semiconductor crystal rod, 2. splice slot, 3. diamond wire mesh, 4. water supply mechanism, 5. winding roller, 6. baffle, 7. bubbling air pipe, 8. bubbling port, 9. guide roller. DETAILED DESCRIPTION

[0051] The technical solution of the present invention is further elaborated in detail below with reference to specific embodiments. The parts not described and disclosed in detail in the following embodiments of the present invention should be understood as existing technologies known or should be known to those skilled in the art, such as the structure of the cutting equipment, the assembly of the winding roller and the diamond wire mesh, the feeding mechanism for controlling the lifting and lowering of the crystal rod, and the supply of cooling water in the water supply mechanism.

[0052] Example 1

[0053] like Figure 1As shown, the present invention discloses a cutting machine, which is the same as the prior art in that: the cutting machine includes a winding roller 5, which is generally two symmetrical winding rollers 5, and a guide roller 9 is provided below the two winding rollers 5, forming a triangular distribution, and finally forming a triangular roller group. A diamond wire is wound around the roller group multiple times to form a triangular diamond wire net 3; the triangular diamond wire net 3 has a horizontal surface at the top, which is composed of multiple parallel diamond wire cutting wires to form a cutting area; the feeding mechanism of the cutting equipment is fixedly connected to the workpiece plate, and the workpiece plate is fixed to the resin plate bonded to the top of the semiconductor crystal rod 1, so that the semiconductor crystal rod 1 is fixed to the bottom of the feeding mechanism, and rises and falls with the feeding mechanism, and gradually contacts the cutting area of ​​the diamond wire net 3 during the descent, and is then gradually cut into multiple silicon wafers;

[0054] Water supply mechanisms 4 are symmetrically arranged on both sides of the semiconductor crystal rod 1 in the axial direction. These two sets of water supply mechanisms 4 provide cooling water to the surface of the diamond wire cutting mesh. The water supply mechanisms 4 are the water supply mechanisms 4 that come with existing cutting equipment. The water supply mechanism 4 includes a sealed box with an injection pipe, which is used to inject cooling water into the sealed box. The bottom of the sealed box is connected to an overflow area on one side of the sealed box through a number of connecting holes. The overflow area is actually a horizontal plate, the ends of which are flush with the width ends of the diamond wire mesh 3. A slit is formed at the connection between the horizontal plate and the bottom of the sealed box. The cooling water is evenly distributed onto the horizontal plate through the slit. The edge of the overflow area guides the coolant onto the diamond wire mesh through a downward-sloping guide plate, and the ends of the guide plate are flush with the horizontal plate.

[0055] Unlike the prior art, a splice slot 2 is provided within the triangular region enclosed by the two winding rollers 5 and the guide roller 9, with the upper end surface of the splice slot 2 close to the diamond wire mesh 3. The overall profile of the splice slot 2 is an elongated strip, with its length parallel to the axial direction of the winding rollers 5 and the guide rollers 9.

[0056] like Figure 2 As shown, the splice slot 2 includes a slot body and a bubbling air pipe 7 arranged in the slot body. A drainage channel is opened on the slot wall of the slot body. The drainage channel is located at one end or both ends in the length direction of the splice slot 2. A baffle 6 that can block the drainage channel is also provided on the slot body.

[0057] Specifically, in this embodiment, two drainage channels are provided, one at each end along its length. Each channel is equipped with a baffle 6. Mounting slots (not shown) for mounting the baffles 6 are provided on the inner wall of the trough body. The two mounting slots are radially extending along the trough body, one at each end. During use, inserting the baffle 6 into the mounting slot blocks the drainage channel, and removing it from the mounting slot clears the drainage channel. Figure 2The diagram shown is a schematic diagram after the baffle 6 is inserted into the installation groove. At this time, the drainage channel is blocked and the connecting plate groove 2 can contain cooling water.

[0058] like Figure 2 、 Figure 3 As shown, a bubbling air pipe 7 is provided in the splice slot 2. After cooling water is filled in the splice slot 2, the cooling water can be bubbled by passing compressed air into the bubbling air pipe 7. The bubbling air pipe 7 is laid on the bottom of the slot body and the inner side of the slot walls on both sides. The bubbling air pipe 7 is distributed in an S shape along the bottom and slot walls of the slot body.

[0059] Bubble ports 8 are provided at intervals on the bubbling air tube 7, which are air outlet holes provided on the bubbling air tube 7. The diameter of the bubbling air tube 7 is 8 mm, the aperture of the bubbling ports 8 is 0.5-1 mm, and the spacing between adjacent bubbling ports 8 in the area where the bubbling air tube 7 is laid is 30-50 mm.

[0060] There are multiple bubbling air pipes 7 arranged in the connecting groove 2, and each bubbling air pipe 7 is provided with an air inlet. The compressed air used for bubbling enters the bubbling air pipe 7 from the air inlet. The number of bubbling ports 8 opened on each bubbling air pipe 7 is 120 to 150.

[0061] The bubbling air pipe 7 is laid from the middle of the groove wall. The distance between the top bubbling air pipe 7 and the upper edge of the groove wall is 50-60 mm, and the distance between the bubbling air pipe 7 and the upper edge of the connecting groove 2 is 50-230 mm.

[0062] Example 2

[0063] The present invention also discloses a method for diamond wire cutting of a 12-inch semiconductor crystal ingot, which is implemented using the cutting machine of the above-mentioned embodiment 1:

[0064] First, the semiconductor crystal ingot 1 is mounted on the workpiece plate above the diamond wire mesh 3 of the cutting machine. Then, the workpiece plate is pressed down by the feed mechanism, while the winding roller 5 of the cutting machine drives the diamond wire to move and cut the semiconductor crystal ingot 1. The cutting process includes the following three stages:

[0065] S1, from the start of cutting until the cutting depth reaches a first preset depth, the drainage channel of the splice slot 2 is kept unobstructed, and the water supply mechanism 4 of the cutting machine supplies water to the diamond wire during the cutting process;

[0066] The first preset depth is 30 mm, that is, when the cutting depth is between 0 and 30 mm, the baffle 6 is removed to keep the drainage channel of the splice slot 2 unobstructed. During the cutting process, the water supply mechanism 4 of the cutting machine supplies water to the diamond wire in accordance with the existing technology, and the cooling water provided to the diamond wire flows out from the drainage channels at both ends of the splice slot 2.

[0067] S2. During the process of cutting from the first preset depth to the second preset depth, the drainage channel of the splice slot 2 is blocked, so that the diamond wire is immersed in the cooling water in the splice slot 2 to cut the semiconductor crystal rod 1, and the cooling water is bubbled with a bubbling pressure that first increases and then decreases during the cutting process; the bubbling pressure refers to the pressure of compressed air introduced into the bubbling air pipe to cause it to bubble in the cooling water.

[0068] The drainage channel of the splice groove 2 is blocked by inserting the baffle 6 into the installation groove. After the baffle 6 is inserted into the installation groove, the cooling water is controlled to fill the splice groove 2 within ten seconds. The upper edge of the baffle 6 and the upper edge of the splice groove 2 are flush, and then the water supply mechanisms 4 on both sides continuously supply water to keep the splice groove 2 in an overflow state.

[0069] After the cutting depth reaches 30mm, the diamond wire mesh 3 forms a certain wire bow, and the position where the diamond wire mesh 3 contacts the semiconductor crystal rod 1 touches the water surface. At this time, the diamond wire mesh 3 is under downward pressure, and the impact of silicon wafer fluctuation is small. And as the water supply mechanisms 4 on both sides continue to inject water, the splicing groove 2 continues to overflow, as shown in the figure. Figure 15 The picture shows the splice slot when the baffle is not set. Figure 16 The image shows the splice slot after the baffle is inserted. After the baffle is inserted, water from the water supply mechanisms on both sides falls onto the diamond wire mesh, with the vast majority passing through the mesh and into the splice slot. Because the diamond wire diameter is 0.08-0.1mm, and the gaps between the diamond wires are 0.8-1mm, the splice slot quickly fills with water after the baffle is inserted. This, combined with bubbling, creates a certain level of fluctuation in the liquid surface, creating the effect of subsurface cutting.

[0070] It should be noted that the splice groove 2 can also be directly connected to a water pipe for inputting cooling water therein. When the water supply mechanism 4 on both sides is insufficient in water supply, water can be directly supplied to the splice groove 2 through the water pipe to ensure that the splice groove 2 is always in an overflow state during step S2.

[0071] The second preset depth is 180 mm, and the cutting process from the first preset depth to the second preset depth is divided into five bubbling stages: the first bubbling stage is when the cutting depth is 30-50 mm, the second bubbling stage is when the cutting depth is 50-80 mm, the third bubbling stage is when the cutting depth is 80-120 mm, the fourth bubbling stage is when the cutting depth is 120-150 mm, and the fifth bubbling stage is when the cutting depth is 150-180 mm. During the entire process from the first bubbling stage to the fifth bubbling stage, the bubbling pressure in the bubbling air pipe 7 is provided in a manner that first increases and then decreases. From the first bubbling stage to the third bubbling stage, the bubbling pressure gradually increases, reaches a maximum in the third bubbling stage, and then gradually decreases. This is because if the bubbling flow rate is too large, it will cause greater fluctuations in the liquid level, resulting in greater fluctuations in the wire network, which will affect the TTV of the silicon wafer and cause thick or thin wafers. By adopting the cutting method of the present invention, the bubbling air pressure is adjusted in time with the change of the contact area between the diamond wire and the crystal rod, and the bubbling amount is controlled to achieve heat dissipation and increase the cutting force while ensuring that the TTV is not affected.

[0072] The bubbling air pressure ranges from 0.18 to 0.39 MPa. Specifically:

[0073] When the cutting depth is 30-50mm, the bubbling air pressure is 0.18-0.22Mpa;

[0074] When the cutting depth is 50-80mm, the bubbling air pressure is 0.27-0.33Mpa;

[0075] When the cutting depth is 80-120mm, the bubble pressure is 0.33-0.39Mpa;

[0076] When the cutting depth is 120-150mm, the bubbling air pressure is 0.27-0.33Mpa;

[0077] When the cutting depth is 150-180mm, the bubbling air pressure is 0.18-0.22Mpa.

[0078] The bubbling pressure values ​​used in this embodiment are as follows:

[0079] When the cutting depth is 30-50mm, the bubbling air pressure is 0.2Mpa;

[0080] When the cutting depth is 50-80mm, the bubbling air pressure is 0.3Mpa;

[0081] When the cutting depth is 80-120mm, the bubbling air pressure is 0.35Mpa;

[0082] When the cutting depth is 120-150mm, the bubbling air pressure is 0.3Mpa;

[0083] When the cutting depth is 150-180mm, the bubbling air pressure is 0.2Mpa.

[0084] S3, when the cutting depth increases from the second preset depth until the cutting is completed, stop bubbling the cooling water and keep the diamond wire immersed in the cooling water in the splice slot 2 while cutting.

[0085] The semiconductor diamond wire cutting in the industry generally adopts the method of pure water + cutting fluid. In order to save costs, this solution uses pure water to assist cutting. There is no need to add cutting fluid. Instead, the cooling effect of the cutting fluid is replaced by bubbling inside the splice slot 2.

[0086] The present invention controls the flow of compressed air into the cooling water within the splice slot 2 to cause bubbling. This bubbling operation drives the flow of the coolant, thereby improving the heat dissipation efficiency of the semiconductor crystal ingot 1 during the cutting process. By controlling the amount of bubbling, the purpose of increasing heat dissipation is achieved. The greater the amount of bubbling, the more bubbles there are, the greater the fluidity of the liquid, and the better the heat dissipation effect.

[0087] During the normal cutting process, when diamond wire is used to cut semiconductor ingots 1 into silicon wafers, silicon powder generated during the cutting process accumulates between the diamond wire and the silicon wafer, enveloping the diamond grit on the wire surface and reducing the cutting force. However, the bubbling process effectively eliminates this accumulation of silicon powder. The bursting of bubbles effectively removes the silicon powder trapped in the gaps between the silicon wafer and on the surface of the diamond wire. The higher the bubbling pressure, the greater the bubbling volume, the better the effect of eliminating silicon powder accumulation, and the more conducive it is to increasing cutting force.

[0088] However, if the bubbling flow rate is too large, it will cause greater fluctuations in the liquid level, resulting in greater fluctuations in the diamond wire mesh 3, which will affect the TTV of the silicon wafer and cause thick and thin wafers.

[0089] By adopting the cutting method of the present invention, at the beginning of cutting, that is, when the diameter is 0-30 mm, the conventional water supply method is used to provide cooling water. At this time, the heat accumulation at the cutting point of the diamond wire is relatively low, and the conventional water supply method can achieve heat dissipation of the semiconductor crystal ingot 1. At the same time, since the contact surface between the diamond wire and the semiconductor crystal ingot 1 is relatively small, bubbling at this time will cause the diamond wire to shake, thereby affecting the cutting effect.

[0090] After the cutting depth reaches 30mm, as the contact area between the diamond wire and the semiconductor crystal rod 1 increases, the diamond wire mesh 3 forms a certain wire bow. The middle part of the diamond wire mesh 3 in contact with the semiconductor crystal rod 1 will touch the water surface. The diamond wire mesh 3 is subjected to downward pressure, and the impact of silicon wafer fluctuations is small. At this time, bubbling operation is applied, and the bubbling pressure is reasonably adjusted to control the bubbling amount, so as to achieve heat dissipation and increase cutting force while ensuring that TTV is not affected.

[0091] The cutting method of the present invention can not only achieve a better cooling effect, thereby improving the level of bending and warping, but also achieve a better lubrication effect, reducing the accumulation of silicon powder in the seams.

[0092] Comparative Example 1

[0093] This comparative example adopts the existing cutting method to cut the 12-inch semiconductor crystal rod 1 with diamond wire. The water supply mechanism 4 of the cutting machine supplies water to the diamond wire in the existing method during the entire cutting process.

[0094] Comparative Example 2

[0095] This comparative example uses the cutting machine of Example 1, and applies a bubbling air pressure of 0.4 MPa throughout the entire process from the beginning of cutting to the completion of cutting.

[0096] Comparative Example 3

[0097] This comparative example uses the cutting machine of Example 1, and applies a bubbling air pressure of 0.2 MPa throughout the entire process from the beginning of cutting to the completion of cutting.

[0098] Regarding Comparative Examples 2 and 3, when a constant bubbling pressure is applied throughout the entire process, the bubbling pressure does not change with the heat generated by the silicon wafer. In this case, if the constant pressure is too small, the cutting will reach the middle of the silicon wafer where the heat generated is the largest, and effective heat dissipation effect cannot be achieved. On the contrary, if the constant pressure is too large, the heat dissipation effect is too strong in the non-middle part, causing the cooling water and silicon wafer temperatures to be lower than the target values, thereby causing the cooling water fluidity to deteriorate, which is not conducive to the dispersion of silicon powder.

[0099] The quality of the silicon wafers cut in Example 2 (i.e., using the method of the present invention) and Comparative Example 1 (i.e., using the conventional method) were analyzed and tested, and the test data are shown in Table 1 below:

[0100] Table 1

[0101]

[0102]

[0103] Result analysis: From Figure 5 、 Figure 6 and Figure 9It can be seen from the BOW process capability analysis comparison chart that after using the method of the present invention, the CPK capability of BOW is improved from 2.020 to 3.197, the process capability of the data is improved by more than 50%, the data is more concentrated, and the absolute value of BOW is smaller and better; Figure 7 、 Figure 8 and Figure 10 It can be seen from the WARP process capability analysis comparison chart that after using the method of the present invention, the CPK capability of WARP is improved from 2.162 to 7.396, the process capability of the data is improved by more than 340%, the data is more concentrated, the WARP value is smaller and better, and the WARP mean value is reduced from 14.2μm to about 8.8μm.

[0104] Figure 13 、 14 The top and side views of the surface morphology of a silicon wafer cut using a common method are shown. This figure is a contour map, with red representing high and blue representing low. The order from high to low is red → yellow → green → blue. The larger the height difference of a silicon wafer, the higher the degree of warping of the silicon wafer. Figure 11 、 12 The top view and side view of the surface morphology of the silicon wafer cut by the method of the present invention indicate that the higher the degree of warping of the silicon wafer, the greater the drop of the silicon wafer cut by the conventional method is, indicating that the degree of warping is significantly higher than that of the silicon wafer cut by the method of the present invention.

[0105] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for diamond wire cutting of a 12-inch semiconductor crystal ingot, comprising: firstly mounting the semiconductor crystal ingot (1) on a workpiece plate above a diamond wire mesh (3) of a cutting machine; then pressing down the workpiece plate, while a winding roller (5) of the cutting machine drives the diamond wire to move, thereby cutting the semiconductor crystal ingot (1); characterized in that: The cutting process consists of the following three stages: S1. From the start of cutting until the cutting depth reaches a first preset depth, the drainage channel of the splicing slot (2) is kept unobstructed, and water is supplied to the diamond wire by a water supply mechanism (4) of the cutting machine during the cutting process; wherein the splicing slot (2) comprises a slot body and a bubbling air pipe (7) disposed in the slot body, a drainage channel is provided on the slot wall of the slot body, and a baffle (6) capable of blocking the drainage channel is movably provided; S2, during the process of cutting from a first preset depth to a second preset depth, the drainage channel of the splice slot (2) is blocked, the diamond wire is immersed in the cooling water of the splice slot (2) to cut the semiconductor crystal rod (1), and during the cutting process, the cooling water is bubbled with a bubbling pressure that first increases and then decreases; S3, when the cutting depth increases from the second preset depth until the cutting is completed, stop bubbling the cooling water and keep the diamond wire immersed in the cooling water of the splicing groove (2) while cutting; The first preset depth is 30mm, and the second preset depth is 180mm; When the cutting depth is 30-50mm, the bubbling air pressure is 0.18-0.22Mpa; When the cutting depth is 50-80mm, the bubbling air pressure is 0.27-0.33Mpa; When the cutting depth is 80-120mm, the bubbling air pressure is 0.33-0.39Mpa; When the cutting depth is 120-150mm, the bubbling air pressure is 0.27-0.33Mpa; When the cutting depth is 150-180mm, the bubbling air pressure is 0.18-0.22Mpa.

2. The method for diamond wire sawing of a 12-inch semiconductor crystal ingot according to claim 1, characterized in that: When the cutting depth is 30-50mm, the bubbling air pressure is 0.2Mpa; When the cutting depth is 50-80mm, the bubbling air pressure is 0.3Mpa; When the cutting depth is 80-120mm, the bubbling air pressure is 0.35Mpa; When the cutting depth is 120-150mm, the bubbling air pressure is 0.3Mpa; When the cutting depth is 150-180mm, the bubbling air pressure is 0.2Mpa.

3. The method for diamond wire sawing of a 12-inch semiconductor crystal ingot according to claim 1, characterized in that: The drainage channel is provided at one end or at two opposite ends of the trough body.

4. The method for diamond wire sawing of a 12-inch semiconductor crystal ingot according to claim 1, characterized in that: The bubbling air pipe (7) is arranged on the bottom of the tank body and on the two opposite tank walls, and bubbling ports (8) are arranged at intervals on the bubbling air pipe (7).

5. The method for diamond wire sawing of a 12-inch semiconductor crystal ingot according to claim 4, characterized in that: The diameter of the bubbling air tube (7) is 8 mm, the spacing between adjacent bubbling ports (8) is 30-50 mm, and the aperture of the bubbling ports (8) is 0.5-1 mm.

6. The method for diamond wire sawing of a 12-inch semiconductor crystal ingot according to claim 4, characterized in that: The distance between the bubbling air pipe (7) and the upper edge of the connecting plate groove (2) is 50-230 mm.

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