CN116038923A

CN116038923A - Method for cutting diamond wire of 12 inch semiconductor crystal bar

Info

Publication number: CN116038923A
Application number: CN202310270168.3A
Authority: CN
Inventors: 张亮; 胡晓亮; 郭永伟; 张倩; 张昊; 刘元涛; 寇文杰
Original assignee: Mesk Electronic Materials Co ltd
Current assignee: Mesk Electronic Materials Co ltd
Priority date: 2023-03-20
Filing date: 2023-03-20
Publication date: 2023-05-02

Abstract

A method for cutting a 12 inch semiconductor crystal bar diamond wire, which relates to the field of 12 inch semiconductor crystal bar diamond wires, and the cutting process comprises the following three stages: s1, keeping a drainage channel of a splicing groove smooth from the start of cutting until the cutting depth reaches a first preset depth, and supplying water to a diamond wire by a water supply mechanism of a cutting machine in the cutting process; s2, in the process of cutting depth from the first preset depth to the second preset depth, plugging a drainage channel of the splicing groove, immersing the diamond wire in cooling water of the splicing groove to cut the semiconductor crystal bar, and bubbling the cooling water with the bubbling pressure which is reduced after rising in the cutting process; and S3, stopping bubbling cooling water from the second preset depth until the cutting is completed, and keeping the diamond wire immersed in the cooling water of the tab groove for cutting. The invention is used for solving the technical problems that the 12-inch semiconductor crystal bar is not easy to dissipate heat in the cutting process, and further the warping exceeds the standard.

Description

Method for cutting diamond wire of 12 inch semiconductor crystal bar

Technical Field

The invention relates to the field of 12-inch semiconductor crystal bar diamond wires, in particular to a method for cutting a 12-inch semiconductor crystal bar diamond wire.

Background

Semiconductor wafers are the substrate material for chip fabrication, and especially 12 inch semiconductor wafers are the main material for high-end chips, and the fabrication process is as follows: melting polycrystalline silicon and drawing the melted polycrystalline silicon into a high-quality monocrystalline silicon rod through a monocrystalline furnace; cutting off and barreling the monocrystalline silicon rod to obtain a crystal rod with the diameter of 12 inches; the crystal bar is divided into silicon wafers through linear cutting, and the silicon wafers are subjected to chamfering, grinding, polishing and other steps, so that the surface flatness of the silicon wafers is improved.

Currently, a 12-inch semiconductor crystal bar is usually cut by a mortar wire or a diamond wire, wherein the mortar wire is widely used for cutting the 12-inch crystal bar, and 6-inch and below 6-inch crystal bars are successfully developed, but the 12-inch crystal bar is in the initial stage of development. The diamond wire cutting mainly uses diamond powder on a diamond wire to strike a crystal bar at a high speed to cut the crystal bar into silicon wafers, and compared with the mortar wire cutting, the 12 inch semiconductor crystal bar diamond wire cutting has the following advantages: 1) Because the waste mortar generated by the mortar wire cutting is more and more difficult to treat and does not meet the environmental protection requirement, the cooling liquid used in the diamond wire cutting process is mixed with pure water and a small amount of diamond wire cutting liquid, and the large trend of environmental protection is complied with; 2) The cutting cost is reduced by more than 40%; 3) The cutting efficiency is high, and the cutting time is shortened by more than 30%; 4) The line loss is small, and the slicing yield is improved by more than 6%.

However, the wire saw of 12 inch semiconductor wafers has the following problems: unlike 8 inch and below 8 inch silicon wafers, the 12 inch semiconductor crystal bar is applied to a high-end chip, so that the surface morphology requirements of the cut silicon wafers are very high, such as parameters of crystal orientation, thickness uniformity, bending, warping and the like, and the stability of diamond wires in the cutting process is required to be good, and the heat dissipation is required to be sufficient; the water supply devices in the existing cutting equipment are generally positioned at two sides of the crystal bar, and cooling liquid is supplied towards the cutting wire mesh, as shown in fig. 1, the fluctuation range of the wire mesh is large in practice, so that the surface morphology of the cut silicon wafer is poor, when the water supply devices are used for cutting 8 inch silicon wafers and below, the use of the silicon wafer is not affected, but when the water supply devices are applied to 12 inch silicon wafers, the surface morphology of the cut silicon wafer is disqualified.

The biggest difficulty of a 12 inch semiconductor crystal bar in the cutting process is that the diameter is large, heat dissipation is difficult, warping and exceeding standard are caused, in order to solve the problem, the applicant has previously applied for a patent with the name of a spraying system for diamond wire cutting 12 inch semiconductor silicon crystal bar and a using method, the application number is CN202211262155.3, the problem of heat dissipation in cutting can be solved, the fluctuation range of a cutting wire mesh is effectively reduced, and the surface morphology parameters of a cut silicon wafer are improved.

The prior art also discloses a Chinese patent invention of a splicing groove, a diamond wire slicing machine and a cutting method of a large-size silicon rod, and the application number of the Chinese patent invention is 202210307279.2. The utility model specifically discloses a diamond wire slicer includes controlling two cutting home rolls and splicing groove, and the splicing groove is including being used for splendid attire coolant liquid and setting up the groove body between two cutting home rolls, and the groove body is including controlling two groove lateral walls of arranging and connecting the tank bottom wall between two groove lateral walls, is fixed with the lateral wall ultrasonic vibration board respectively on two groove lateral walls in the groove body, is fixed with the diapire ultrasonic vibration board on the groove diapire in the groove body. However, the principle of the ultrasonic is high-frequency vibration, and in the implementation process, the ultrasonic is easy to instantly shake off the diamond wire with the diameter of only 0.08mm, and even if the diamond wire is not shaken off, the ultrasonic can cause high-frequency vibration, so that the cutting work cannot be smoothly carried out.

The invention provides an improvement scheme different from the prior art, so as to improve the heat dissipation efficiency of a 12-inch semiconductor crystal bar in the cutting process and improve the quality of a finished silicon wafer.

Disclosure of Invention

The invention aims to provide a method for cutting a diamond wire of a 12 inch semiconductor crystal bar, which aims to solve the technical problem that the 12 inch semiconductor crystal bar is not easy to dissipate heat in the cutting process, so as to cause warping exceeding standard.

In order to solve the technical problems, the invention adopts the following specific scheme: a method for cutting a 12 inch semiconductor crystal bar diamond wire includes that firstly, a semiconductor crystal bar is installed on a workpiece plate above a diamond wire net of a cutting machine; then the workpiece plate is pressed down, and meanwhile, a winding roller of the cutting machine drives the diamond wire to move, so that the semiconductor crystal bar is cut; the cutting process comprises the following three stages:

s1, keeping a drainage channel of a splicing groove smooth from the start of cutting until the cutting depth reaches a first preset depth, and supplying water to a diamond wire by a water supply mechanism of a cutting machine in the cutting process;

s2, in the process of cutting depth from the first preset depth to the second preset depth, plugging a drainage channel of the splicing groove, immersing the diamond wire in cooling water of the splicing groove to cut the semiconductor crystal bar, and bubbling the cooling water with the bubbling pressure which is reduced after rising in the cutting process;

and S3, stopping bubbling cooling water from the second preset depth until the cutting is completed, and keeping the diamond wire immersed in the cooling water of the tab groove for cutting.

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

As a further optimization of the technical scheme, when the cutting depth is 30-180mm, the bubbling pressure is 0.18-0.39 Mpa.

As a further optimization of the above-mentioned solution,

when the cutting depth is 30-50mm, the bubbling pressure is 0.18-0.22Mpa;

when the cutting depth is 50-80mm, the bubbling pressure is 0.27-0.33Mpa;

when the cutting depth is 80-120mm, the bubbling pressure is 0.33-0.39Mpa;

when the cutting depth is 120-150mm, the bubbling pressure is 0.27-0.33Mpa;

when the cutting depth is 150-180mm, the bubbling pressure is 0.18-0.22Mpa.

As a further optimization of the technical scheme, when the cutting depth is 30-50mm, the bubbling pressure is 0.2Mpa;

when the cutting depth is 50-80mm, the bubbling pressure is 0.3Mpa;

when the cutting depth is 80-120mm, the bubbling pressure is 0.35Mpa;

when the cutting depth is 120-150mm, the bubbling pressure is 0.3Mpa;

when the cutting depth is 150-180mm, the bubbling pressure is 0.2Mpa.

As a further optimization of the technical scheme, the splicing groove comprises a groove body and a bubbling air pipe arranged in the groove body, wherein a drainage channel is formed in the groove wall of the groove body, and a baffle capable of blocking the drainage channel is movably arranged.

As a further optimization of the above technical solution, the drainage channels are provided at one end or at opposite ends of the tank body.

As a further optimization of the technical scheme, the bubbling air pipes are arranged at the bottom of the tank body and on the tank walls at two opposite sides, and bubbling openings are arranged on the bubbling air pipes at intervals.

As a further optimization of the technical scheme, the diameter of the bubbling air pipe is 8mm, the distance between the adjacent bubbling openings is 30-50mm, and the aperture of the bubbling opening is 0.5-1mm.

As a further optimization of the technical scheme, the distance between the bubbling air pipe and the upper edge of the lug groove is 50-230mm.

Compared with the prior art, the invention has the following beneficial effects: according to the invention, compressed air is introduced into the cooling water in the tab slot to bubble, and the bubbling operation drives the cooling liquid to flow, so that the heat dissipation efficiency of the semiconductor crystal bar in the cutting process is improved.

In the process of preparing the silicon wafer by cutting the semiconductor crystal bar by the diamond wire, silicon powder can be generated and accumulated between the diamond wire and the silicon wafer, the diamond wire sand on the surface of the diamond wire is wrapped, the cutting force is reduced, and the accumulation of the silicon powder can be effectively eliminated in the bubbling process, so that the cutting force is enhanced.

If the flow is too large, the liquid level fluctuation is larger, the fluctuation of the wire net is larger, the TTV of the silicon wafer is affected, and the thick sheet is formed.

Drawings

FIG. 1 is a schematic view of a cutter according to the present invention;

FIG. 2 is a schematic view of the external configuration of the tab slot;

FIG. 3 is a top view of a bubbler tube;

FIG. 4 is an enlarged view of FIG. 3 at A;

FIG. 5 is a process capability report for the BOW of comparative example 1;

FIG. 6 is a process capability report of the BOW of example 2;

FIG. 7 is a process capability report for WARP in comparative example 1;

FIG. 8 is a process capability report for WARP in example 2;

FIG. 9 is a graph of the interval of BOW (mean 95% confidence interval) for example 2, comparative example 1;

FIG. 10 is a graph of intervals (mean 95% confidence interval) for WARP in example 2, comparative example 1;

FIG. 11 is a top view of the surface topography of a silicon wafer cut according to example 2;

FIG. 12 is a side view of the surface topography of a silicon wafer cut according to example 2;

FIG. 13 is a top view of the topography of a silicon wafer cut according to comparative example 1;

FIG. 14 is a side view of the surface topography of a silicon wafer cut according to comparative example 1;

FIG. 15 is a tab slot without a baffle;

FIG. 16 is a tab slot after insertion of a baffle;

reference numerals: 1. the semiconductor crystal bar comprises a semiconductor crystal bar body, 2, a splicing groove, 3, a diamond wire net, 4, a water supply mechanism, 5, a winding roller, 6, a baffle plate, 7, a bubbling air pipe, 8, a bubbling port, 9 and a guide roller.

Detailed Description

The technical solutions of the present invention will be further described in detail with reference to specific embodiments, and the parts of the following embodiments of the present invention that are not described and disclosed in detail should be understood as the prior art known or should be known to those skilled in the art, such as the structure of the cutting device, the assembly of the wire winding roller and the wire mesh, the control of the lifting of the ingot by the feeding mechanism, and the supply of cooling water in the water supply mechanism.

Example 1

As shown in fig. 1, the present invention discloses a cutting machine, which is the same as the prior art: the cutting machine comprises two winding rollers 5, wherein the winding rollers 5 are generally symmetrical, a guide roller 9 is arranged below the two winding rollers 5 to form triangular distribution, and finally a triangular roller group is formed. A diamond wire is wound on the roller set for a plurality of times to form a triangular diamond wire net 3; the triangular diamond wire mesh 3 has an uppermost horizontal plane formed by a plurality of diamond wire cutting wires parallel to each other to form a cutting area; the feeding mechanism of the cutting equipment is fixedly connected with a workpiece plate, and the workpiece plate is fixed with a resin plate bonded to the top of the semiconductor crystal bar 1, so that the semiconductor crystal bar 1 is fixed at the bottom of the feeding mechanism, and is lifted along with the feeding mechanism, gradually contacts with a cutting area of the diamond wire network 3 in the descending process, and is further gradually cut to form a plurality of silicon chips;

water supply mechanisms 4 are symmetrically arranged on two axial sides of the semiconductor crystal bar 1, cooling water is supplied to the surface of the diamond wire cutting net by the two groups of water supply mechanisms 4, and the water supply mechanisms 4 are water supply mechanisms 4 of the existing cutting equipment. The water supply mechanism 4 comprises a sealing box body with a liquid injection pipe, the liquid injection pipe is used for injecting cooling water into the sealing box body, the bottom of the sealing box body is communicated with an overflow area arranged on one side of the sealing box body through a plurality of communication holes, the overflow area is actually a horizontal plate, two ends of the horizontal plate are flush with two ends of the width direction of the diamond wire net 3, a slit is formed at the joint of the horizontal plate and the bottom of the sealing box body, the cooling water is uniformly distributed on the horizontal plate through the slit, the edge of the overflow area guides the cooling liquid onto the diamond wire net through a guide plate inclined downwards, and two ends of the guide plate are flush with the horizontal plate.

Unlike the prior art, a lug groove 2 is provided in the triangular region enclosed by the two winding rollers 5 and one guide roller 9, the upper end face of the lug groove 2 being close to the diamond wire mesh 3. The overall contour of the tab slot 2 is elongated with its length direction parallel to the axial direction of the winding roller 5 and the guide roller 9.

As shown in fig. 2, the tab slot 2 includes a slot body and a bubbling air pipe 7 disposed in the slot body, a drain channel is provided on the slot wall of the slot body, the drain channel is located at one or both ends of the tab slot 2 in the length direction, and a baffle 6 capable of blocking the drain channel is further disposed on the slot body.

Specifically, in this embodiment, two drainage channels are provided, and are respectively located at two ends of the drainage channel in the length direction, and each drainage channel is provided with a baffle 6. The inner wall of the tank body is provided with two mounting grooves (not shown in the figure) for mounting the baffle plate 6, the two mounting grooves are formed along the radial direction of the tank body, and the two mounting grooves are distributed at the two ends of the tank body. When the baffle plate 6 is used, the baffle plate 6 is inserted into the mounting groove to realize the blocking of the drainage channel, and the baffle plate 6 is removed from the mounting groove to realize the unblocking of the drainage channel. Fig. 2 is a schematic view of the baffle 6 inserted into the mounting groove, and at this time, the drainage channel is blocked, and the tab groove 2 can be filled with cooling water.

As shown in fig. 2 and 3, a bubbling air pipe 7 is provided in the tab groove 2, and after cooling water is contained in the tab groove 2, the cooling water can be bubbled by introducing compressed air into the bubbling air pipe 7. The bubbling air pipes 7 are paved at the bottom of the tank body and at the inner sides of the tank walls at the two sides, and the bubbling air pipes 7 are distributed in an S shape along the bottom of the tank body and the tank walls.

The bubbling air pipe 7 is provided with bubbling openings 8 at intervals, and the bubbling openings 8 are air outlet holes arranged on the bubbling air pipe 7. The diameter of the bubbling pipe 7 is 8mm, the aperture of the bubbling port 8 is 0.5-1mm, and the interval between adjacent bubbling ports 8 is 30-50mm in the area where the bubbling pipe 7 is laid.

The number of the bubbling air pipes 7 arranged in the splicing groove 2 is 120-150, and each bubbling air pipe 7 is provided with an air inlet, compressed air for bubbling enters the bubbling air pipe 7 from the air inlet, and the number of bubbling ports 8 arranged on each bubbling air pipe 7 is 120-150.

The bubbling air pipe 7 is paved from the middle of the groove wall, the distance between the uppermost bubbling air pipe 7 on the groove wall 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 splicing groove 2 is 50-230mm.

Example 2

The invention also discloses a method for cutting the diamond wire of the 12 inch semiconductor crystal bar, which is implemented by using the cutting machine in the embodiment 1:

firstly, mounting a semiconductor crystal bar 1 on a workpiece plate above a diamond wire net 3 of a cutting machine; then the workpiece plate is pressed down by a feeding mechanism, and meanwhile, a wire winding roller 5 of the cutting machine drives the diamond wire to move so as to cut the semiconductor crystal bar 1; the cutting process comprises the following three stages:

s1, keeping a drainage channel of a splicing groove 2 smooth from the start of cutting to the time when the cutting depth reaches a first preset depth, and supplying water to a diamond wire by a water supply mechanism 4 of a cutting machine in the cutting process;

the first preset depth is 30mm, namely when the cutting depth is 0-30mm, the baffle plate 6 is taken out, the drain channels of the splicing groove 2 are kept smooth, water is supplied to the diamond wire by the water supply mechanism 4 of the cutting machine according to the prior art in the cutting process, and cooling water supplied to the diamond wire flows out from the drain channels at the two ends of the splicing groove 2;

s2, in the process of cutting depth from the first preset depth to the second preset depth, plugging a drainage channel of the splicing groove 2, immersing the diamond wire in cooling water in the splicing groove 2 to cut the semiconductor crystal bar 1, and bubbling the cooling water with the bubbling pressure which is reduced after rising in the cutting process; the bubbling pressure is the pressure at which compressed air is introduced into the bubbling air pipe to bubble in the cooling water.

The drainage channel for plugging the splicing groove 2 adopts a mode of inserting the baffle plate 6 into the installation groove, after the baffle plate 6 is inserted into the installation groove, the splicing groove 2 is fully filled with cooling water within ten seconds, the upper edge of the baffle plate 6 is flush with the upper edge of the splicing groove 2, then the water supply mechanisms 4 on two sides continuously supply water, and the splicing groove 2 is kept in an overflow state.

After the cutting depth reaches 30mm, the diamond wire net 3 forms a certain wire bow, the contact position of the diamond wire net 3 and the semiconductor crystal bar 1 contacts the water surface, the diamond wire net 3 is subjected to downward pressure, and the influence of silicon wafer fluctuation is small. And along with the continuous water injection of the water supply mechanisms 4 on two sides, the inside of the splicing groove 2 is overflowed continuously, as shown in fig. 15, which is a splicing groove picture when no baffle is arranged, and fig. 16, which is a splicing groove picture after the baffle is inserted, most of the water supplied by the water supply mechanisms on two sides falls into the splicing groove after the baffle is inserted, and most of the water falls into the splicing groove after the water falls onto the diamond wire net, because the diameter of the diamond wire is 0.08-0.1mm, and the gap between the gold steel wires is 0.8-1mm, and the splicing groove can be filled with water rapidly after the baffle is inserted. And bubbling is added, so that the liquid level only has certain fluctuation, and the cutting effect under the liquid level is achieved.

It should be noted that, the water pipe for inputting cooling water into the tab slot 2 may be directly connected to the tab slot 2, and when the water supply of the water supply mechanisms 4 on both sides is insufficient, water may be directly supplied into the tab slot 2 through the water pipe, so as to ensure that the tab slot 2 is always in an overflow state in the process of step S2.

The second preset depth is 180mm, and the cutting process from the first preset depth to the second preset depth is divided into five bubbling stages; the cutting depth is the first bubbling stage when 30-50mm, the cutting depth is the second bubbling stage when 50-80mm, the cutting depth is the third bubbling stage when 80-120mm, the cutting depth is the fourth bubbling stage when 120-150mm, and the cutting depth is the fifth bubbling stage when 150-180 mm. The bubbling pressure in the bubbling air pipe 7 is provided in a manner of ascending and descending throughout the course from the first bubbling stage to the fifth bubbling stage, and gradually increases from the first bubbling stage to the third bubbling stage, reaches the maximum in the third bubbling stage, and then gradually decreases again. The cutting method of the invention is adopted to timely adjust the bubbling pressure along with the change of the contact area of the diamond wire and the crystal bar, control the bubbling quantity, achieve the purposes of heat dissipation and cutting force increase, and ensure that the TTV is not influenced.

The bubbling pressure ranges from 0.18 Mpa to 0.39Mpa, and is specifically:

when the cutting depth is 30-50mm, the bubbling pressure is 0.18-0.22Mpa;

when the cutting depth is 50-80mm, the bubbling pressure is 0.27-0.33Mpa;

when the cutting depth is 80-120mm, the bubbling pressure is 0.33-0.39Mpa;

when the cutting depth is 120-150mm, the bubbling pressure is 0.27-0.33Mpa;

when the cutting depth is 150-180mm, the bubbling pressure is 0.18-0.22Mpa.

The bubbling pressure values employed in this example are as follows:

when the cutting depth is 30-50mm, the bubbling pressure is 0.2Mpa;

when the cutting depth is 50-80mm, the bubbling pressure is 0.3Mpa;

when the cutting depth is 80-120mm, the bubbling pressure is 0.35Mpa;

when the cutting depth is 120-150mm, the bubbling pressure is 0.3Mpa;

when the cutting depth is 150-180mm, the bubbling pressure is 0.2Mpa.

And S3, stopping bubbling cooling water from the second preset depth until the cutting is completed, and keeping the diamond wire immersed in the cooling water of the splicing groove 2 for cutting.

In the industry, the semiconductor diamond wire cutting generally adopts the mode of pure water and cutting fluid, and in order to save cost, the scheme uses pure water to assist cutting, does not need to add cutting fluid any more, and replaces the cooling effect of the cutting fluid by the mode of pressure air bubbling in the splicing groove 2.

According to the invention, compressed air is introduced into the cooling water in the joint plate groove 2 to bubble, and the bubbling operation drives the cooling liquid to flow, so that the heat dissipation efficiency of the semiconductor crystal bar 1 in the cutting process is improved. The purpose of increasing heat dissipation is achieved by controlling the bubbling amount, and the larger the bubbling amount is, the more bubbles are, the stronger the fluidity of the liquid is, and the better the heat dissipation effect is.

In the normal cutting process, the diamond wire is used for cutting the semiconductor crystal bar 1 to prepare a silicon wafer, silicon powder generated in the cutting process is accumulated between the diamond wire and the silicon wafer, diamond wire sand on the surface of the diamond wire is wrapped, the cutting force is reduced, the accumulation of the silicon powder can be effectively eliminated in the bubbling process, and the silicon powder in gaps of the silicon wafer and on the surface of the diamond wire can be effectively taken away by utilizing bubble burst. The greater the pressure of the bubbling air, the greater the bubbling amount, the better the effect of eliminating the silicon powder accumulation, and the more favorable the cutting force increase.

However, if the flow rate is too large, the fluctuation of the liquid level is large, and the fluctuation of the diamond wire network 3 is also large, so that the TTV of the silicon wafer is affected, and a thick sheet is formed.

By adopting the cutting method, at the beginning of cutting, namely 0-30mm, cooling water is provided by adopting the original common water supply mode, at the moment, the heat accumulation at the cutting position of the diamond wire is lower, the heat dissipation of the semiconductor crystal bar 1 can be realized by adopting the original water supply mode, and meanwhile, as the contact surface between the diamond wire and the semiconductor crystal bar 1 is smaller, the bubbling can generate the shaking of the diamond wire at the moment to influence the cutting effect;

after the cutting depth reaches 30mm, as the contact area of the diamond wire and the semiconductor crystal bar 1 increases, a certain wire bow is formed on the diamond wire net 3, the middle part of the diamond wire net 3 contacted with the semiconductor crystal bar 1 can contact the water surface, the diamond wire net 3 is subjected to downward pressure, and the influence of silicon wafer fluctuation is small; at the moment, bubbling operation is applied, the bubbling pressure is reasonably regulated, the bubbling quantity is controlled, and the TTV is not influenced while heat dissipation and cutting force increase are achieved.

By adopting the cutting method, not only can a better cooling effect be obtained, but also the warping level can be improved; better lubricating effect can be obtained, and accumulation of silicon powder in the seam is reduced.

Comparative example 1

The comparative example adopts the prior art cutting mode to cut the diamond wire of the 12 inch semiconductor crystal bar 1, and the whole cutting process is to supply water to the diamond wire by the water supply mechanism 4 of the cutting machine according to the prior art mode.

Comparative example 2

This comparative example uses the cutter of example 1, and a bubbling pressure of 0.4Mpa is applied throughout the process from the beginning of the cutting to the completion of the cutting.

Comparative example 3

This comparative example uses the cutter of example 1, and a bubbling pressure of 0.2Mpa is applied throughout the entire process from the beginning of the cutting to the completion of the cutting.

Regarding comparative examples 2 and 3, when a constant bubbling pressure is applied throughout the process, the bubbling pressure does not vary with the heat generation amount of the silicon wafer, in which case if the constant pressure is too small, cutting is performed to a place where the heat generation amount of the intermediate silicon wafer is maximum, and an effective heat dissipation effect cannot be achieved; if the constant pressure is too large, the heat dissipation effect is too strong at the non-middle part, so that the temperature of the cooling water and the silicon wafer is lower than the target value, the fluidity of the cooling water is poor, and the dispersion of the silicon powder is not facilitated.

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., conventional method) were analyzed and examined, respectively, and the examination data are shown in Table 1 below:

TABLE 1

Analysis of results: as can be seen from the analysis and comparison of the BOW process capability of the FIGS. 5, 6 and 9, after the method of the invention is used, the CPK capability of the BOW is improved from 2.020 to 3.197, the process capability of data is improved by more than 50%, the data is more concentrated, and the absolute value of the BOW is smaller and better; as can be seen from the analysis and comparison of WARP process capability in FIGS. 7, 8 and 10, the CPK capability of WARP is improved from 2.162 to 7.396, the process capability of data is improved by more than 340%, the data is more concentrated, the WARP value is smaller and better, and the WARP average value is reduced from 14.2 mu m to about 8.8 mu m.

FIGS. 13 and 14 are top views and side views of the surface morphology of a silicon wafer cut by a common method, wherein the top views are contour diagrams, red represents high, blue represents low, and the steps from high to low are red, yellow, green and blue in sequence, and the larger the drop of one silicon wafer is, the higher the bending and warping degree of the silicon wafer is; fig. 11 and 12 are top views and side views of the surface topography of a silicon wafer cut by the method of the invention, which show that the higher the bending and warping degree of the silicon wafer, the more the drop of the silicon wafer cut by the common method is than that of the silicon wafer cut by the invention, and the higher the bending and warping degree is obviously than that of the silicon wafer cut by the method of the invention.

The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the invention.

Claims

1. A method for cutting a 12 inch semiconductor crystal bar diamond wire comprises the steps of firstly, mounting a semiconductor crystal bar (1) on a workpiece plate above a cutting machine diamond wire net (3); then the workpiece plate is pressed down, and meanwhile, a winding roller (5) of the cutting machine drives the diamond wire to move, so that the semiconductor crystal bar (1) is cut; the cutting process is characterized by comprising the following three stages:

s1, keeping a drainage channel of a splicing groove (2) unblocked from the start of cutting until the cutting depth reaches a first preset depth, and supplying water to a diamond wire by a water supply mechanism (4) of a cutting machine in the cutting process;

s2, in the process of cutting depth from the first preset depth to the second preset depth, plugging a drainage channel of the splicing groove (2), immersing the diamond wire in cooling water of the splicing groove (2) to cut the semiconductor crystal bar (1), and bubbling the cooling water with rising and falling bubbling pressure in the cutting process;

and S3, stopping bubbling cooling water until the cutting depth reaches the second preset depth, and keeping the diamond wire immersed in the cooling water of the splicing groove (2) for cutting.

2. The method of claim 1, wherein the first predetermined depth is 30mm and the second predetermined depth is 180mm.

3. The method for diamond wire cutting of a 12 inch semiconductor ingot according to claim 2, wherein the bubbling pressure is 0.18 to 0.39Mpa when the cutting depth is 30 to 180mm.

4. A method of diamond wire cutting a 12 inch semiconductor ingot according to claim 3 wherein the bubbling pressure is 0.18 to 0.22Mpa when the depth of cut is 30 to 50 mm;

when the cutting depth is 50-80mm, the bubbling pressure is 0.27-0.33Mpa;

when the cutting depth is 80-120mm, the bubbling pressure is 0.33-0.39Mpa;

when the cutting depth is 120-150mm, the bubbling pressure is 0.27-0.33Mpa;

when the cutting depth is 150-180mm, the bubbling pressure is 0.18-0.22Mpa.

5. The method of claim 4, wherein the bubbling pressure is 0.2Mpa when the depth of cut is between 30 and 50 mm;

when the cutting depth is 50-80mm, the bubbling pressure is 0.3Mpa;

when the cutting depth is 80-120mm, the bubbling pressure is 0.35Mpa;

when the cutting depth is 120-150mm, the bubbling pressure is 0.3Mpa;

when the cutting depth is 150-180mm, the bubbling pressure is 0.2Mpa.

6. The method for cutting the diamond wire of the 12-inch semiconductor crystal bar according to claim 1, wherein the joint plate groove (2) comprises a groove body and a bubbling air pipe (7) arranged in the groove body, a drain channel is formed on the groove wall of the groove body, and a baffle plate (6) capable of blocking the drain channel is movably arranged on the groove wall of the groove body.

7. The method of claim 6, wherein the drainage channels are provided at one or both opposite ends of the tank body.

8. The method for cutting the diamond wire of the 12-inch semiconductor crystal bar according to claim 6, wherein the bubbling air pipes (7) are arranged at the bottom of the tank body and on two opposite tank walls, and bubbling openings (8) are arranged on the bubbling air pipes (7) at intervals.

9. A method of diamond wire cutting of a 12 inch semiconductor ingot according to claim 6 wherein the diameter of the bubbler tube (7) is 8mm, the spacing between adjacent bubbler openings (8) is 30-50mm and the pore size of the bubbler openings (8) is 0.5-1mm.

10. A method of diamond wire cutting of a 12 inch semiconductor ingot according to claim 6 wherein the distance between the bubbler tube (7) and the upper edge of the tab groove (2) is 50-230mm.