JP7408232B2 - Manufacturing method of circular grindstone - Google Patents

Description

The present invention relates to an annular grindstone mounted on a cutting device.

A device chip mounted on an electronic device or the like is formed, for example, by cutting a disk-shaped wafer containing a semiconductor. A plurality of intersecting planned division lines are set on the surface of the wafer, and devices such as ICs (Integrated Circuits) containing the semiconductors are formed in each region partitioned by the planned division lines. Then, the wafer is divided along the planned dividing lines to form individual device chips.

A cutting device equipped with a cutting unit equipped with an annular grindstone (cutting blade) is used to divide the wafer. When cutting and dividing a workpiece such as a wafer using a cutting device, an annular grindstone is rotated in a plane perpendicular to the upper surface of the workpiece while cutting into the workpiece. The annular whetstone has a whetstone portion that includes abrasive grains and a binder in which the abrasive grains are dispersed and fixed, and the abrasive grains that are appropriately exposed from the binder come into contact with the workpiece, thereby reducing the workpiece. The workpiece is cut.

As the workpiece is cut, the abrasive grains are consumed, but the bonding material is also consumed and new abrasive grains are exposed from the bonding material one after another, so that the cutting ability of the annular grindstone is maintained. This type of action of the annular whetstone is called self-sharpening.

In recent years, power devices have been attracting attention as semiconductor devices that have a higher breakdown voltage than devices formed from silicon wafers and can control large current electrical signals. Power devices are used, for example, in electric vehicles, hybrid vehicles, power circuits for air conditioners, and the like. Silicon carbide (SiC) wafers, which have better electrical properties than silicon wafers, are used to manufacture power devices.

Since SiC wafers are hard materials, when cutting and dividing SiC wafers, for example, an annular grindstone made of nickel (Ni) as a bonding material has been used. However, since the bonding material made of nickel does not easily wear out, the self-sharpening effect may not be achieved at a sufficient level. Therefore, when a SiC wafer is cut with the annular grindstone, the cutting ability of the annular grindstone gradually decreases, and chips called chipping are likely to occur on the side surfaces of the formed device chips.

Therefore, as a method that can divide a SiC wafer with high processing quality, a method is known in which a laser beam is irradiated onto the SiC wafer along the dividing line to form a shield tunnel containing amorphous material in the SiC wafer (patented). (See Reference 1). Furthermore, a method is known in which a SiC wafer is cut while applying ultrasonic waves to an annular grindstone (see Patent Document 2).

JP2014-221483A Japanese Patent Application Publication No. 2014-13812

Laser processing devices and cutting devices that can apply ultrasonic waves to an annular grindstone are expensive, so processing using these devices is expensive. Therefore, there is a strong desire to develop an annular grindstone that can cut hard materials such as SiC wafers with high quality. If it is possible to cut hard materials with high quality by attaching the annular grindstone to an existing cutting device, there is no need to incorporate a special configuration into the cutting device, and processing costs can be reduced. Furthermore, the value of existing cutting equipment is increased because new uses are given to the existing cutting equipment.

The present invention has been made in view of this problem, and its purpose is to provide an annular grindstone that can cut hard materials such as SiC wafers with high quality.

According to one aspect of the present invention, the grindstone portion includes a bonding material made of a plating layer and abrasive grains dispersed and fixed in the bonding material, and the bonding material is a ring made of a tin-nickel alloy. A method for manufacturing a grindstone of the type, comprising: preparing a plating bath containing a plating solution mixed with the abrasive grains; immersing a base and a nickel electrode in the plating solution in the plating bath; The plating layer is deposited on the surface of the base by applying a direct current to the plating solution using the base as a cathode and the nickel electrode as an anode, and removing all or part of the base. An annular grinding wheel manufactured, characterized in that the plating solution is an electrolytic solution in which a salt containing nickel and a salt containing tin are dissolved, and the abrasive grains are mixed therein. A manufacturing method is provided. Preferably, the tin content in the tin-nickel alloy is 57 wt% or more and less than 75 wt%.

Preferably, the annular grindstone includes the above-mentioned grindstone portion. Alternatively, preferably , the annular grindstone further includes an annular base having a grip, and the grindstone is exposed at an outer peripheral edge of the annular base.

An annular grindstone according to one aspect of the present invention includes a grindstone portion including a binding material and a grindstone dispersed and fixed in the binding material. The bonding material includes a tin-nickel alloy. When the annular grinding wheel cuts a hard material such as a SiC wafer, the bonding material is greatly consumed, so the self-sharpening action is appropriately developed and the cutting ability of the annular grinding wheel is maintained. Therefore, machining quality does not deteriorate while cutting hard materials. Moreover, since the annular grindstone can be attached to an existing cutting device, processing costs are suppressed.

Therefore, one aspect of the present invention provides an annular grindstone that can cut hard materials such as SiC wafers with high quality.

FIG. 1(A) is a perspective view schematically showing an annular grindstone including a grindstone portion, and FIG. 1(B) is a perspective view schematically showing an annular grindstone including an annular base and a grindstone portion. be. FIG. 2 is a cross-sectional view schematically showing the manufacturing process of an annular grindstone including a grindstone portion. FIG. 3(A) is a cross-sectional view schematically showing the formed plating layer, and FIG. 3(B) is a cross-sectional view schematically showing the removal of the base. FIG. 3 is a cross-sectional view schematically showing a manufacturing process of a ring-shaped grindstone including a grindstone portion and an annular base. FIG. 5(A) is a cross-sectional view schematically showing the formed plating layer, and FIG. 5(B) is a cross-sectional view schematically showing partial removal of the base. 2 is a graph showing the occurrence of chipping when a SiC wafer is cut using an annular grindstone whose binding material is made of nickel and an annular grindstone whose binding material is made of a tin-nickel alloy.

Embodiments according to the present invention will be described. FIG. 1A is a perspective view schematically showing an annular grindstone including a grindstone portion, as an example of an annular grindstone (cutting blade) according to the present embodiment. The annular grindstone 1a shown in FIG. 1(A) is an annular grindstone called a washer type.

The annular grindstone 1a includes an annular grindstone portion 3a having a through hole in the center. The annular grindstone 1a is attached to a cutting unit of a cutting device. At this time, a spindle included in the cutting unit is passed through the through hole. When cutting a workpiece, the rotation of the spindle causes the annular grindstone 1a to rotate in a plane perpendicular to the direction in which the through hole extends. When the grindstone portion 3a of the rotating annular grindstone 1a is brought into contact with the workpiece, the workpiece is cut.

Moreover, FIG. 1(B) is a perspective view schematically showing an annular grindstone including an annular base and a grindstone portion. The annular grindstone 1b shown in FIG. 1(B) is a so-called hub type grindstone in which a grindstone portion 3b is disposed on the outer peripheral edge of an annular base 5. The annular base 5 serves as a grip held by a user (operator) of the cutting device when mounting the annular grindstone 1b on the cutting unit of the cutting device. When the annular grindstone 1b is attached to a cutting unit of a cutting device, a spindle of the cutting unit is passed through a through hole formed in the annular base 5.

The grindstone parts 3a and 3b are manufactured by forming a bonding material containing abrasive grains such as diamond abrasive grains on a base made of metal such as aluminum using a method such as electrolytic plating, for example. Note that the annular grindstones 1a and 1b formed by a method such as electrolytic plating are also called electroplated grindstones or electroformed grindstones. The grindstone portions 3a and 3b of the annular grindstones 1a and 1b include a binding material and abrasive grains dispersed and fixed in the binding material. The workpiece is cut when the abrasive grains exposed from the binder come into contact with the workpiece.

As the cutting of the workpiece progresses, the abrasive grains fall off from the binder or are worn out and are consumed, so the cutting ability of the annular grindstones 1a and 1b gradually decreases. However, as the workpiece is cut, the bonding material is also consumed, and new abrasive grains are successively exposed from the bonding material. Therefore, the cutting ability of the annular grindstones 1a and 1b is maintained above a certain level. This effect is called spontaneous blade generation.

In recent years, power devices have been attracting attention as semiconductor devices that have a higher breakdown voltage than devices formed from silicon wafers and can control large current electrical signals. Power devices are used, for example, in electric vehicles, hybrid vehicles, power circuits for air conditioners, and the like. SiC (silicon carbide) wafers are used for manufacturing power devices.

Conventionally, for cutting SiC wafers, which are hard materials, for example, an annular grindstone in which the bonding material is made of nickel has been used. However, since the bonding material made of nickel is difficult to wear out, the annular grindstone sometimes does not exhibit a self-sharpening effect at a sufficient level. Therefore, when a SiC wafer is cut with the annular grinding wheel, the cutting ability of the annular grinding wheel gradually decreases, so that chips called chipping are likely to occur on the side surfaces of the device chips.

On the other hand, the annular grindstones 1a and 1b according to the present embodiment include grindstone portions 3a and 3b in which a tin-nickel (Sn--Ni) alloy is used as a bonding material. Preferably, the bonding material consists of a tin-nickel alloy. When a tin-nickel alloy is used as the bonding material, the bonding material is severely consumed when cutting a hard material with the annular grinding wheel, so that the self-sharpening action is appropriately developed. Therefore, the annular grindstone can cut hard materials without degrading processing quality.

In addition, in the annular grindstones 1a and 1b, the tin content (for example, the weight of tin in the total weight of tin and nickel) in the tin-nickel alloy used as the binding material is 57 wt% or more and less than 75 wt%. It is preferable that More preferably, the tin content in the tin-nickel alloy is 64 wt% or more and 70 wt% or less.

The tin-nickel alloy is particularly stable when the atomic ratio of tin to nickel is 1:1. The tin content in the tin-nickel alloy at this time is about 67 wt%. Therefore, if a binder whose main component is a tin-nickel alloy with a tin content of about 67 wt % is used for the grindstone portions 3a, 3b of the annular grindstones 1a, 1b, the performance of the annular grindstones 1a, 1b will be stabilized. In this case, the workpiece can be cut with extremely stable quality, and variations in machining quality are extremely small.

Generally, when determining cutting conditions for a workpiece, cutting conditions with some margin are selected in consideration of variations in cutting quality. That is, in order to obtain acceptable machining results even if some variation in cutting quality occurs, cutting conditions that are stricter than those considered to be sufficient to obtain a predetermined machining result must be selected. Therefore, if the expected variations in processing are large, the range of selectable processing conditions may be narrowed.

On the other hand, since the annular grindstone according to the present embodiment has a small variation in performance, when the annular grindstone is used to cut a workpiece, the variation in cutting quality is also small. Therefore, when determining cutting conditions for cutting a workpiece using the annular grindstone, there are relatively few restrictions on the cutting conditions, and the range of selection of cutting conditions is widened.

Furthermore, when a bonding material whose main component is a tin-nickel alloy is formed by electrolytic plating as described below, the atomic ratio of tin and nickel tends to be 1:1, so the bond has a tin content of approximately 67 wt%. The material is easy to manufacture stably and has good productivity. For example, when manufacturing the annular grindstone, even if the composition of the plating solution contained in the plating bath in which electrolytic plating is performed changes, the composition of the formed bonding material does not change significantly. Therefore, the manufacturing process of the annular grindstone according to this embodiment can be easily managed.

The annular grindstones 1a and 1b according to this embodiment are particularly suitable for cutting workpieces made of hard materials such as SiC (silicon carbide). However, the workpieces that can be cut with the annular grindstones 1a and 1b are not limited to this, and for example, workpieces made of materials such as semiconductors such as silicon, or materials such as sapphire, glass, and quartz can be cut. You may.

For example, the surface of a workpiece is divided by a plurality of dividing lines arranged in a grid, and devices such as ICs (Integrated Circuits) and LEDs (Light Emitting Diodes) are formed in each divided area. ing. Finally, the workpiece is divided along the planned division lines to form individual device chips.

Next, a method for manufacturing the washer-type annular grindstone 1a shown in FIG. 1(A) will be described. FIG. 2 is a cross-sectional view schematically showing the manufacturing process of an annular grindstone 1a consisting of a grindstone portion. The annular grindstone 1a is formed by a method such as electrolytic plating. In this manufacturing method, first, a plating bath 2 containing a plating solution 16 mixed with abrasive grains is prepared.

The plating solution 16 is an electrolytic solution in which a salt containing nickel and a salt containing tin are dissolved. The respective salt is, for example, a sulfate, sulfamate, chloride, bromide, acetate, citrate, or pyrophosphate. Each salt is added to the plating solution 16 so that the atomic ratio of nickel to tin is approximately 1:1. However, even if the atomic ratio of the respective ions contained in the plating solution 16 is not 1:1, the composition of the formed plating layer is not easily affected. That is, management of the plating solution 16 is easy.

Further, a fluoride such as ammonium bifluoride or sodium fluoride may be added to the plating solution 16. Alternatively, alpha amino acids such as glycine may be added to the plating solution 16. When such an additive is introduced into the plating solution 16, the deposition potentials of Sn ²⁺ or Ni ²⁺ are brought closer to each other. Further, the plating solution 16 further contains abrasive grains such as diamond abrasive grains.

After the preparation of the plating bath 2 is completed, the base 20a on which the grindstone portion 3a is formed by electrodeposition and the nickel electrode 6 are immersed in the plating solution 16 in the plating bath 2. The base 20a is formed into a disk shape from a metal material such as stainless steel or aluminum, and a mask 22a having an opening in a shape corresponding to the desired shape of the grinding wheel 3a is formed on the surface of the base 20a. . In addition, in this embodiment, the mask 22a that can form the annular grindstone 1a is formed.

The base 20a is connected to a negative terminal (negative electrode) of a DC power supply 10 via a switch 8. On the other hand, the nickel electrode 6 is connected to a positive terminal (positive electrode) of a DC power supply 10. However, the switch 8 may be placed between the nickel electrode 6 and the DC power supply 10.

Thereafter, a direct current is applied to the plating solution 16 using the base 20a as a cathode and the nickel electrode 6 as an anode to deposit a plating layer on the surface of the base 20a not covered with the mask 22a. As shown in FIG. 2, a switch 8 disposed between a base 20a and a DC power source 10 is short-circuited while a fan 14 is rotated by a rotary drive source 12 such as a motor to agitate the plating solution 16.

FIG. 3(A) is a cross-sectional view schematically showing the formed plating layer 24a. When the plating layer 24a reaches a desired thickness, the switch 8 is turned off to stop the deposition of the plating layer 24a. The plating layer 24a is a tin-nickel alloy in which diamond abrasive grains are evenly dispersed.

Thereafter, the entire base 20a is removed and the plating layer 24a is peeled off. FIG. 3(B) is a cross-sectional view schematically showing the removal of the base 20a. As a result, a grindstone portion 3a including a binder containing a tin-nickel alloy and abrasive grains dispersed and fixed in the binder can be formed, and a washer-type annular grindstone 1a is completed.

Next, a method for manufacturing the hub-type annular grindstone 1b shown in FIG. 1(B) will be described. FIG. 4 is a cross-sectional view schematically showing the manufacturing process of an annular grindstone 1b including a grindstone portion and an annular base. The annular grindstone 1b is formed, for example, by a method such as electrolytic plating in the plating bath 2, similarly to the annular grindstone 1a. In this manufacturing method, a plating bath similar to the method for manufacturing the annular grindstone 1a is prepared.

The configurations of the plating bath 2 and the plating solution 16 are the same as those of the method for manufacturing the annular grindstone 1a described above, and therefore the description thereof will be omitted. However, since a part of the base 20b connected to the negative electrode of the DC power supply 10 becomes the annular base 5 that supports the grinding wheel portion 3b of the annular grindstone 1b, the shape of the base 20b is different from that of the annular base 5. Make it a corresponding shape. Further, a mask 22b having an opening corresponding to the shape of the grindstone portion 3b is formed on the surface of the base 20b. Then, similarly to the method for manufacturing the annular grindstone 1a described above, a plating layer is deposited on the exposed portion of the base 20b.

FIG. 5(A) is a cross-sectional view schematically showing the plating layer 24b formed on the surface of the base 20b. After forming the plating layer 24 to a predetermined thickness, as shown in FIG. 5(A), a part of the base 20b is removed to remove a part of the area of the plating layer 24b that was covered by the base 20b. expose. Furthermore, before performing the base removal step, the mask 22b is removed from the base 20b in advance.

Then, as shown in FIG. 5(B), the outer peripheral area of the base 20b on the side where the plating layer 24b is not formed is partially etched to remove the area of the plating layer 24b that was covered by the base 20b. expose a part. As a result, a hub-type annular grindstone 1b in which the grindstone portion 3b is fixed to the outer peripheral area of the annular base 5 is completed.

In this example, an annular grindstone 1a was manufactured which includes a grindstone portion 3a containing a binder containing a tin-nickel alloy and abrasive grains dispersed and fixed in the binder. The produced annular grindstone will be referred to as an example blade. Then, a SiC single crystal substrate was cut as a workpiece using the example blade, and the workpiece after cutting was observed to measure the magnitude of damage such as chipping that occurred on the workpiece. Further, the diameter of the example blade after cutting was measured and compared with the diameter of the example blade before cutting to calculate the amount of wear.

In addition, in this example, for comparison, an annular grindstone was manufactured that includes a grindstone portion including a binder made of nickel and abrasive grains dispersed and fixed in the binder. The annular grindstone produced will be referred to as a comparative example blade. Then, a SiC single crystal substrate was similarly cut using the comparative example blade, and the magnitude of damage such as chipping that occurred on the workpiece was measured, and the amount of wear was calculated.

First, each of the produced annular grindstones 1a will be explained. The thickness of the example blade was such that when cutting the workpiece, the width of the cutting groove formed in the workpiece was 25 μm to 30 μm. In the grinding wheel part, a tin-nickel alloy was used as the binder and diamond abrasive grains were used as the abrasive grains. Here, the tin content in the tin-nickel alloy was 67 wt%.

Further, as the diamond abrasive grains, abrasive grains having a particle size of #2000 were used. Regarding particle size, please refer to JIS R6001-2:2017 (Particle size of abrasive material for grinding wheels - Part 2: Fine powder) established by the Japanese Industrial Standards Committee (JISC). Further, the degree of concentration of abrasive grains was set to 50.

The comparative example blade was produced in the same manner as the example blade, except that nickel (100 wt %) was used as the binder instead of the tin-nickel alloy.

A disk-shaped SiC single crystal substrate with a thickness of 130 μm and a diameter of 4 inches was prepared as a workpiece to be cut with the example blade and the comparative example blade. In this example, an adhesive tape is attached to the back side of the SiC single crystal substrate, the SiC single crystal substrate is placed on the holding table of a cutting device via the adhesive tape, and the SiC single crystal substrate is placed on the holding table. was held. Further, the example blade or the comparative example blade was attached to the cutting unit of the cutting device.

The example blade or the comparative example blade attached to the cutting unit was rotated at a speed of 50,000 revolutions per minute, the cutting unit was positioned at a predetermined height position, and the holding table and cutting unit were placed on the holding surface of the holding table. Move relative in parallel direction. Then, the rotating example blade or comparative example blade cuts the SiC single crystal substrate, and the SiC single crystal substrate is divided.

At this time, the height of the cutting unit was such that the lower end of the example blade or the comparative example blade was positioned at a height position approximately 30 μm below the upper surface of the adhesive tape attached to the back surface of the SiC single crystal substrate. That is, the SiC single crystal substrate was cut along with a portion of the adhesive tape using a cutting unit, thereby dividing the SiC single crystal substrate. Further, the relative speed between the holding table and the cutting unit was set to 5 mm/sec.

After cutting the SiC single crystal substrate, the back side of the SiC single crystal substrate was observed with an optical microscope to detect damage such as chipping. Specifically, 15 lines were cut from one end of the SiC single crystal substrate to the other end, and the SiC single crystal substrate was observed along each line. Then, the size of the largest chipping among the chippings that occurred on each line was measured.

Table 1 below shows the size of the largest chipping observed in each line of the cut SiC single crystal substrate when the example blade was used and when the comparative example blade was used. . Further, FIG. 6 shows the distribution of the maximum chipping size observed on each line.

Note that the maximum size of the chippings observed on the SiC single crystal substrate when the example blade was used was 13.3 μm, and the average value of the maximum chipping size for each line was 8.4 μm. Ta. Furthermore, regarding the distribution of the maximum chipping size of 15 lines, the value obtained by adding 3σ to the average value was 15.4 μm. That is, it is understood that when the SiC single crystal substrate is cut using the example blade, chipping exceeding 15.4 μm is extremely unlikely to occur.

On the other hand, when the comparative example blade was used, the maximum chipping size observed on the SiC single crystal substrate was 37.7 μm, and the average value of the maximum chipping size for each line was 26.6 μm. Met. Furthermore, regarding the distribution of the maximum chipping size for 15 lines, the value obtained by adding 3σ to the average value was 53.8 μm. That is, it is understood that chipping of 53.8 μm or less may occur when a SiC single crystal substrate is cut using the comparative example blade.

Therefore, it was confirmed from this example that the annular grindstone having the bonding material containing the tin-nickel alloy in the grindstone portion can perform extremely high-quality cutting even when the workpiece is a hard material.

Further, using the Example blade or the Comparative Example blade, the change in each diameter was measured as the amount of wear when cutting a SiC single crystal substrate until the cutting length was 5 m. As a result, the amount of wear in the example blade was 14.7 μm, while the amount of wear in the comparative example blade was 2.5 μm.

From this result, it is understood that the example blade is more easily worn out by cutting the workpiece than the comparative example blade, and the self-sharpening action occurs more actively. That is, an annular grindstone whose grindstone portion includes a binder containing a tin-nickel alloy maintains its cutting ability even when cutting a workpiece due to the action of self-generating blades. Therefore, it was suggested that the reason why the workpiece can be cut with high quality using the annular grindstone is that the self-sharpening action occurs sufficiently.

As described above, according to the present embodiment, an annular grindstone capable of cutting hard materials such as SiC wafers with high quality is provided. Since the annular grindstone according to this embodiment has the same shape as an existing annular grindstone, it can be easily attached to an existing cutting device. It enables high-quality cutting of hard materials using existing cutting equipment, reducing processing costs for workpieces. Furthermore, the value of existing cutting equipment is increased because new uses are given to the existing cutting equipment.

Note that, in the above embodiment, a case has been described in which a workpiece is cut and divided using an annular grindstone, but the annular grindstone according to one embodiment of the present invention may be used for other purposes. For example, an annular grindstone may be cut into the workpiece to a depth that does not reach the back surface side, and a cutting groove whose bottom surface does not reach the back surface may be formed in the workpiece. Even in this case, the annular grindstone according to one aspect of the present invention can cut the workpiece with high quality.

In addition, the structure, method, etc. according to the above embodiments can be modified and implemented as appropriate without departing from the scope of the objective of the present invention.

1a, 1b Annular grinding wheel 3a, 3b Grinding wheel part 5 Annular base 2 Plating bath 6 Nickel electrode 8 Switch 10 DC power supply 12 Rotation drive source 14 Fan 16 Plating solution 20a, 20b Base 22a, 22b Mask 24a, 24b Plating layer

Claims (4)

A method for manufacturing an annular grindstone comprising a bonding material made of a plating layer and abrasive grains dispersed and fixed in the bonding material , the bonding material being a tin-nickel alloy. ,
preparing a plating bath containing a plating solution mixed with the abrasive grains;
immersing a base and a nickel electrode in the plating solution in the plating bath;
Applying a direct current to the plating solution using the base as a cathode and the nickel electrode as an anode to deposit the plating layer on the surface of the base,
manufacturing the annular grindstone by removing all or part of the base;
A method for manufacturing an annular grindstone, characterized in that the plating solution is an electrolytic solution in which a salt containing nickel and a salt containing tin are dissolved, and the abrasive grains are mixed therein. 2. The method for manufacturing an annular grindstone according to claim 1, wherein the tin content in the tin-nickel alloy is 57 wt% or more and less than 75 wt%. A method for manufacturing an annular grindstone according to claim 1 or 2, comprising:
A method for manufacturing an annular grindstone, characterized in that the annular grindstone includes the above-mentioned grindstone portion. A method for manufacturing an annular grindstone according to claim 1 or 2, comprising:
The annular grindstone further includes an annular base having a grip,
A method for manufacturing an annular grindstone, wherein the grindstone portion is exposed at an outer peripheral edge of the annular base.