Wire with fixed abrasive grains and fixed abrasive grain wire saw

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to the structure of a wire with fixed abrasive grains and a fixed abrasive grain wire saw using the fixed abrasive grain wire, and particularly a fixed abrasive grain wire and a fixed abrasive grain wire saw for cutting brittle materials such as silicon, glass, and ceramics. Regarding.

【0002】

[Conventional technology]

A wire saw is one of the devices for cutting a rod-shaped material (ingot) to manufacture a thin plate (wafer). A wire saw is a device that simultaneously cuts a large number of wafers by running a wire row stretched at a predetermined pitch at high speed and pressing a work piece against the wire row.

【0003】

This wire saw includes a free abrasive grain wire saw based on a free abrasive grain method that has been mainly used conventionally and a fixed abrasive grain wire saw based on a fixed abrasive grain method that has been developed in recent years. In the fixed-abrasive wire saw, a wire row is formed by using a wire with fixed abrasive grains in which abrasive grains are fixed on the surface over the entire length of the wire, and the ingot is cut by running the wire row at high speed.

【0004】

The conventional method for manufacturing a wire with fixed abrasive grains is a method of electrodepositing abrasive grains on a wire of a metal wire. This wire manufacturing method is a slicing machine that cuts an ingot into a wafer-shaped thin plate by electrodepositing fixed abrasive grains on the inner or outer circumference of a conventional disk-shaped thin plate metal blade and rotating the metal blade at high speed. It was the same as the electrodeposition method of attaching fixed abrasive grains to a metal blade from the time of a dicing machine. However, in the case of this electrodeposition manufacturing method, the concentration ratio indicating the content of abrasive grains could only be 150 or more for manufacturing reasons.

【0005】

[Problems to be Solved by the Invention]

However, in a wire saw using the fixed abrasive grain method, when the silicon ingot is cut with a conventional wire with fixed abrasive grains having a concentration of 150 or more, the cutting powder of the ingot is likely to be clogged between the abrasive grains fixed to the wire. When the cutting powder is clogged between the abrasive grains in this way, the cutting performance deteriorates and the wafer on the cut surface is wavy.

【0006】

Further, in the wire saw by the fixed abrasive grain method, when the wire traveling speed is set to 600 to 800 (m / min) for processing, the processing alteration layer of the cut surface becomes deep, and the processing is performed in the post-processing process of the cut wafer. The wrapping process to remove the altered layer took a lot of time. The present invention has been made in view of such circumstances, and in the cutting process using a wire with fixed abrasive grains, fixing for maintaining the cutting surface accuracy of the workpiece in a good state and improving the production efficiency. It is an object of the present invention to provide a wire with abrasive grains and a fixed abrasive grain wire saw.

【0007】

[Means for solving problems]

In order to achieve the above object, the present invention is a wire with fixed abrasive grains for cutting a work piece by pressing a work piece while running a wire with fixed abrasive grains having abrasive grains fixed on the surface. It is characterized in that a wire with fixed abrasive grains having a concentration of 20 to 75 indicating the abrasive grain ratio of the wire with fixed abrasive grains is used.

【0008】

According to the present invention, by using the wire with fixed abrasive grains having a concentration ratio of 20 to 75 indicating the abrasive grain ratio of the wire with fixed abrasive grains, the dischargeability of cutting powder is improved and the cut surface of the wafer is improved. Since the amount of waviness is reduced, a good wafer can be obtained. Further, in order to achieve the above object, the invention according to claim 2 sets the wire traveling speed at the time of cutting to 1200 (m / min) or more in the fixed abrasive wire saw using the wire with fixed abrasive grains according to claim 1. , Or the average running speed is 850 (m / min) or more.

【0009】

According to the present invention, the wire traveling speed at the time of cutting is set to 1200 (m / min) or more, or the average traveling speed is set to 850 (m / min) or more. , High quality wafers can be cut efficiently.

【0010】

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the wire with fixed abrasive grains and the fixed abrasive grain wire saw according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing an exaggerated view of a wire 12 with fixed abrasive grains according to the present invention, in which a wire 12 with fixed abrasive grains cuts an ingot 30 which is a work piece.

【0011】

The structure of the wire 12 with fixed abrasive grains shown in FIG. 1 will be described below. As shown in FIG. 1, the wire 12 with fixed abrasive grains includes a wire wire 1 made of a material such as a high-strength wire, an abrasive grain 2 made of a material such as diamond, CBN, SiC, GC, and alumina, and a wire wire. It is composed of a fixing material 3 (binder) that fixes 1 and abrasive grains 2. As the method for fixing the abrasive grains, electrodeposition, fixing with an organic material or an inorganic material (thermosetting, etc.) with a resin, or the like is used, but the present invention is not limited thereto. However, according to the resin fixing method, it is possible to easily reduce the concentration ratio of the abrasive grains. Further, the material of the wire may be a piano wire or a high tensile strength non-metal fiber wire (including a fiber or the like). The object of the present invention can be achieved regardless of whether the cross-sectional shape of the wire is circular or square, and whether the structure is a single wire or a twisted wire. Further, the particle size of the abrasive grains 2 is not limited, and may be a single particle size or a mixed grain having a plurality of particle sizes. No. 4 is a cavity called a pore provided when the abrasive grains are fixed, and even if the abrasive grains 2 and the fixing material 3 fall off, the cutting powder 5 is clogged between the abrasive grains 2 and 2 and the cutting ability is reduced. It is a cavity that helps the cutting powder 5 to escape. In the example of FIG. 1, the ingot 30 which is the workpiece is fixed to the work feed table 28 as shown in FIG. 2, and the wire 12 with fixed abrasive grains traveling in one direction or both directions is shown in FIG. It shows a state in which the ingot 30 is cut while traveling in the direction. During the cutting process, the machining fluid 7 is sprayed from the pipe 6 with a nozzle, and the machining fluid 7 is applied to the cut portion of the ingot 30 and its vicinity. In addition, cutting powder 5 is generated during the cutting process of the ingot 30. The processing liquid 7 is used to reduce the cutting resistance between the wire with fixed abrasive grains and the ingot 30 generated during cutting, and to improve the discharge of cutting powder 5 accumulated between the abrasive grains 2 and 2 of the wire 12 with fixed abrasive grains. There are water-soluble and oil-based liquids to be used.

【0012】

In FIG. 2, the wire with fixed abrasive grains shown in FIG. 1 is wound around a plurality of groove rollers to form a wire row, and the ingot, which is a work piece, is pressed against the wire row while the wire is running. This is an example showing a wire path of a fixed-abrasive wire saw that cuts an ingot into a large number of wafers. As shown in FIG. 2, the wire 12 with fixed abrasive grains is wound around a pair of wire reels 14A and 14B, and the wire 12 with fixed abrasive grains guides a plurality of guides between the pair of wire reels 14A and 14B. It travels back and forth while being guided by rollers 16, 16 ... In the structural example shown in FIG. 2, traverse devices 22A and 22B and dancer rollers 24A and 24B are arranged on the wire path, respectively. The traverse devices 22A and 22B guide the fixed-abrasive wire 12 from the wire reels 14A and 14B according to a certain rule, and the dancer rollers 24A and 24B apply a constant tension to the traveling fixed-abrasive wire 12. Motors 26A and 26B are connected to the pair of wire reels 14A and 14B, respectively, and the motors 26A and 26B and motors for driving groove rollers 18, 18 ... Not shown are driven in synchronization with each other. As a result, the wire 12 with fixed abrasive grains travels between the pair of wire reels 14A and 14B. Then, the wires 12 with fixed abrasive grains are wound around the three groove rollers 18, 18, 18 to form a wire row 20 of the horizontal wires 12 with fixed abrasive grains. A work feed table 28 is installed below the wire row 20. The work feed table 28 moves up and down perpendicularly to the wire row 20, and an ingot 30 which is a work piece is held on the upper part of the work feed table 28.

【0013】

In the fixed abrasive grain wire saw 10 configured as described above, the ingot 30 is cut as follows. First, the ingot 30 is attached to the work feed table 28. Next, the motors 26A and 26B connected to the wire reels 14A and 14B and the motors for driving the groove rollers 18, 18 ... Not shown are synchronously driven to run the wire 12 with fixed abrasive grains. Then, when the running of the wire 12 with fixed abrasive grains is stable, the work feed table 28 is raised toward the wire row 20 and pressed against the wire row 20 running on the ingot 30. The contact portion of the ingot 30 pressed against the wire row 20 is ground by the wire 12 with fixed abrasive grains constituting the wire row 20, whereby the ingot 30 is cut into a wafer.

【0014】

The accuracy of the cut surface and the cutting conditions of the workpiece in the fixed-abrasive wire saw using the fixed-abrasive wire will be described below. When cutting with a fixed-abrasive wire saw, in order to improve the accuracy of the cut surface of the workpiece, the deflection of the fixed-abrasive wire 12 during cutting shown in FIG. 3 is reduced and the amount of deflection is kept constant. Is effective. The reason is that if the amount of bending of the wire 12 with fixed abrasive grains during cutting is large, the wire 12 with fixed abrasive grains tends to meander according to the amount of bending, and the wire spacing of the wire row 20 fluctuates, one wafer at a time. This is because the waviness of the cut surface of the sheet increases. To keep the amount of bending of the wire 12 small and constant is to keep the value of the cutting resistance FZ (g / cm) in the direction perpendicular to the traveling direction of the wire 12 with fixed abrasive grains shown in FIG. 3 small and constant. be equivalent to. The reason why the cutting resistance FZ, which is the cause of the deterioration of the wafer cut surface accuracy, increases is that the cutting powder 5 is poorly discharged between the abrasive grains 2, 2 ... of the wire 12 with fixed abrasive grains for cutting. This is because the powder discharge capacity cannot keep up.

【0015】

Therefore, in FIGS. 4 and 5, the swell amount FN of the wafer cut surface when only the concentration C is changed on the horizontal axis while the cutting conditions other than the concentration C, which is the abrasive grain ratio of the wire with fixed abrasive grains, are kept constant. The result of investigating the relationship between (μm) and the cutting resistance FZ (g / cm) is shown. Here, the workpiece used for cutting is a cylindrical ingot 30 as shown in FIGS. 2 and 3 for the purpose of keeping the contact length between the wire 12 with fixed abrasive grains and the workpiece constant. A prismatic Si single crystal wire (200 mm on a side) is used. When cutting the cylindrical ingot 30, it is preferable to control the wire traveling speed or the cutting feed speed so that the cutting work amount per unit time is constant. The measurement conditions in Fig. 4 and Fig. 5 are that the cutting feed rate is constant at 1 (mm / min), wire tension: 35 (N), maximum linear velocity: 1800 (m / min), and bidirectional cycle time: 30 (sec). ), Acceleration / deceleration time: 5 (sec), Processing liquid: Water + water-soluble coolant 3%, Abrasive grain size: # 600 single grain, Wire wire diameter: 0.18 (mm) The surface swell amount FN and the cutting resistance FZ are shown.

【0016】

As shown in FIG. 4, it can be seen that the concentration C of the wire with fixed abrasive grains should be set to 75 or less in order to suppress the wafer cut surface swell amount FN to the allowable value of the wafer cut surface swell amount or less. Further, as described above, since the cutting resistance FZ also sharply increases when the concentration ratio C is 75 or more, it can be said that the wafer cutting surface swell amount FN deteriorates as the cutting resistance FZ increases. The degree of concentration indicates the ratio of abrasive grains such as diamond and CBN contained in the abrasive grain layer containing the binder, that is, the abrasive grain ratio. A concentration ratio of 25% or 4.4 (ct / cm3) in percentage of volume is defined as a concentration ratio of 100 (1ct = 200mg).

【0017】

As described above, in the fixed abrasive wire saw, when the concentration of the fixed abrasive grains of the wire is 75 or less, the amount of undulation of the wafer cut surface, which is the work piece, falls within the permissible value, but the conventional cutting conditions remain unchanged. In this case, the processing alteration layer of the wafer is deep, and the fixed abrasive grains 2, 2 ... of the wire with fixed abrasive grains are easily dropped due to the resistance at the time of cutting, so that the life of the wire with fixed abrasive grains is short. appear. Since the wire with fixed abrasive grains is generally expensive, extending the life of the wire with fixed abrasive grains is an indispensable task for reducing the manufacturing cost of the wafer. A work-altered layer is a wafer in which a large number of brittle modes are contained in the shavings, and when shavings in this brittle mode occur, many microcracks are present on the cut surface, so that the wafer is suitable for semiconductor generation. It is a layer that cannot be used. On the contrary, on a good cut surface, the microcracks are shallow and the shaving marks are in ductile mode. If the processing alteration layer of the wafer is deep, a large amount of processing time is required in the lapping process in the subsequent process for finishing the surface of the wafer, so that the processing time and processing cost of the wafer increase.

【0018】

In order to make the work-altered layer shallow, the amount of cut of each abrasive grain into the wafer may be reduced. For that purpose, it is necessary to reduce the cutting feed amount or increase the traveling speed of the wire. In the present invention, when the cutting feed rate is slowed down, the cutting processing efficiency decreases, but since the improvement of the wire traveling speed is advantageous in terms of cutting efficiency, it cannot be set in terms of the processing liquid supply surface with the conventional free abrasive grain wire saw. The wire speed was increased.

【0019】

FIG. 6 shows an SEM (scanning electron microscope) photograph of the cut surface of the ingot 30 in which the brittle mode, the brittle mode and the ductile mode are mixed. Figure 6 shows the SEM observation results of the cut surface of the ingot 30 under the cutting conditions of wire traveling speed V = 900,1200,1800 (m / min) at shooting magnifications of 200x, 500x, and 1500x. It is shown. According to FIG. 6, it is shown that the faster the wire traveling speed V is as 1800 (m / min), the wider the cut surface in the ductile mode is, and the better the cut surface is.

【0020】

Figure 7 shows the results of measuring the relationship between the wire traveling speed V (m / min) and the work alteration layer depth D (μm). As shown in Fig. 7, the depth of the work-altered layer decreases sharply at a wire traveling speed of 1200 (m / min) or higher, and becomes about 5 (μm), which is about half of that at 900 (m / min). .. In the conventional free abrasive wire saw, the abrasive grains are contained in the machining fluid, and the ingot, which is the work piece, is cut by the abrasive grains in the machining fluid, so that the abrasive grains in the machining fluid do not get on the wire. If it was not sufficiently drawn into the cut part and spread, the saw marks on the cut surface would be excessive, and the ingot 30 could not be cut cleanly. Therefore, the maximum set value of the wire traveling speed in the free abrasive grain method was limited to about 600 to 800 (m / min). However, in the fixed abrasive grain wire saw, it has been found that the upper limit of the wire traveling speed can be raised because the processing liquid needs to be present to the extent that it lubricates the cut portion. When the wire is reciprocated, the deceleration stop of the wire is included, so the average speed is 850 (m / min).

【0021】

Figure 8 shows the relationship between the wire traveling speed V (m / min) and the cutting resistance FZ (gf / cm) on the horizontal axis. As shown in FIG. 8, the cutting resistance FZ tends to decrease as the wire traveling speed V increases. When the cutting resistance FZ is reduced, the amount of waviness on the cut surface of the wafer is reduced and a good wafer can be obtained. Due to these effects, the efficiency of cutting can be improved, and the work-altered layer on the cut surface can be made thinner, which makes it possible to manufacture high-quality wafers at low cost. Since the depth of cut in each of the above is reduced, the fixed abrasive grains 2, 2 ... are less likely to fall off, and the life of the wire with fixed abrasive grains can be extended.

【0022】

Figure 9 shows the measurement results with the wire traveling speed V (m / min) on the horizontal axis and the wire life WL (mm2 / m) on the vertical axis. Here, the wire life WL indicates the cutting area (mm2) of the ingot that could be cut without the abrasive grains 2 falling off per unit wire length (m). Therefore, the larger the value of the wire life WL, the longer the wire life and the more economical it is. According to FIG. 9, when the wire traveling speed V = 1200 (m / min) or more, the wire life suddenly increases more than twice as much as the wire life in the state of V = 900 (m / min), and the wire traveling speed V further increases. As a result, the value of wire life WL increases.

【0023】

As means for improving the wire traveling speed, the drive motors of the groove rollers 18 and 18 ... Not shown, the wire reel motors 26A and 26B are increased in output (torque and rotation speed are improved), and the groove rollers 18 are used. , Change the drive reduction ratio of 18 ..., increase the diameter of groove rollers 18, 18 ..., reduce the weight of wire reels 14A and 14B, reduce the amount of wire with fixed abrasive grains used for cutting, and wire reel. Measures such as reducing the load on the motors 26A and 26B will be combined.

【0024】

[Effect of the invention]

As described above, according to the fixed-abrasive wire and the fixed-abrasive wire saw according to the present invention, a fixed-abrasive wire having a concentration of 20 to 75 indicating the abrasive grain ratio of the fixed-abrasive wire is used. As a result, the dischargeability of the cut powder is improved and the amount of waviness on the cut surface of the wafer is reduced, so that a good wafer can be obtained.

【0025】

Further, according to another aspect of the invention, the wire traveling speed at the time of cutting is set to 1200 (m / min) or more, or the average traveling speed is set to 850 (m / min) or more. The layers become thinner, and high-quality wafers can be cut efficiently.

[Simple explanation of drawings]

[Figure 1]

FIG. 5 is an exaggerated cross-sectional view showing a wire 12 with fixed abrasive grains according to the present invention cutting an ingot 30.

[Figure 2]

The wire path block diagram of the fixed abrasive grain wire saw which concerns on this invention.

[Fig. 3]

The figure which shows the value of the cutting resistance FZ (g / cm) in the direction perpendicular to the traveling direction of the wire 12 with fixed abrasive grains.

[Fig. 4]

The figure which shows the relationship with the swell amount FN (μm) of the wafer cut surface when the degree of concentration C is changed on the horizontal axis.

[Fig. 5]

The figure which shows the relationship with the cutting resistance FZ (g / cm) when the degree of concentration C is changed on the horizontal axis.

[Fig. 6]

The figure which shows the result (photograph) which recorded the SEM observation result of the ingot cut surface under the cutting condition of a wire running speed V = 900,1200,1800 (m / min) at a shooting magnification of 200 times, 500 times, 1500 times.

[Fig. 7]

The figure which shows the relationship with the processing alteration layer depth D (μm) when the wire traveling speed V (m / min) is changed on the horizontal axis.

[Fig. 8]

The figure which shows the relationship with the cutting resistance FZ (g / cm) when the wire running speed V (m / min) is changed on the horizontal axis.

[Fig. 9]

The figure which shows the relationship with the wire life WL (mm2 / m) when the wire traveling speed V (m / min) is changed on the horizontal axis.

[Explanation of symbols]

1 ... wire wire, 2 ... abrasive grains, 3 ... fixing material, 4 ... pores, 5 ... cutting powder, 10 ... fixed abrasive grain wire saw, 12 ... fixed abrasive Wire with grain, 30 ... ingot