阅读说明：本技术 SiC基板的切削方法 (Method for cutting SiC substrate ) 是由 大野胜利 平岩卓 于 2021-04-09 设计创作，主要内容包括：本发明提供SiC基板的切削方法,能够抑制切削刀具的破损和崩边,并且能够抑制对SiC基板进行切削时的切削刀具的消耗。SiC基板的切削方法是利用切削刀具(21)对SiC基板(200)进行切削的方法。在SiC基板的切削方法中,一边使切削刀具(21)的切削刃(212)在径向上进行超声波振动,一边对卡盘工作台(10)所保持的SiC基板(200)进行切削,该切削刀具(21)是利用对碳化钨和钴进行烧结而成的结合剂固定磨粒而得的。(The invention provides a method for cutting a SiC substrate, which can inhibit the damage and edge breakage of a cutting tool and can inhibit the consumption of the cutting tool when the SiC substrate is cut. A method for cutting a SiC substrate is a method for cutting a SiC substrate (200) with a cutting tool (21). In a method for cutting an SiC substrate, a SiC substrate (200) held by a chuck table (10) is cut while ultrasonic vibration is applied to a cutting edge (212) of a cutting tool (21) in the radial direction, the cutting tool (21) being obtained by fixing abrasive grains with a binder obtained by sintering tungsten carbide and cobalt.)

1. A method for cutting a SiC substrate by using a cutting tool, wherein,

the SiC substrate held by the chuck table is cut while the cutting tool, which is obtained by fixing abrasive grains with a binder obtained by sintering tungsten carbide and cobalt, is ultrasonically vibrated in the radial direction.

2. The method of cutting an SiC substrate according to claim 1,

the SiC substrate has a front surface and a back surface formed of a silicon surface on which silicon is exposed and a carbon surface on which carbon is exposed on a surface opposite to the silicon surface, and the SiC substrate is cut with the rotational direction of the cutting tool at the contact point between the cutting tool and the SiC substrate set to a direction from the carbon surface side toward the silicon surface side.

3. The method of cutting an SiC substrate according to claim 1 or 2,

the protrusion amount of the cutting edge of the cutting tool is set to be 20 times or more and 30 times or less of the blade thickness.

Technical Field

The present invention relates to a method for cutting a SiC substrate.

Background

SiC substrates are widely used as substrates for forming power semiconductors, and development is underway. When the SiC substrate is divided into chips, dicing by a cutting tool is used (for example, see patent document 1).

Patent document 1: japanese patent laid-open publication No. 2009-130315

However, since the SiC substrate is a difficult-to-cut material, it is necessary to cut with a cutting tool using a relatively easily consumable binder, and such a cutting tool is consumed drastically, increasing the amount of use. Therefore, it is desired to extend the amount of protrusion of the cutting edge of the cutting tool, and the cutting tool can be durable even when consumed, but meandering may occur during cutting. In addition, when cutting is performed using a strong binder (e.g., electroforming binder) that is difficult to consume, the cutting speed is difficult to increase, and further, the machining load during cutting becomes large due to dulling, resulting in breakage and large chipping of the cutting tool.

Disclosure of Invention

The present invention has been made in view of the above problems, and an object thereof is to provide a method for cutting an SiC substrate, which can suppress the breakage and chipping of a cutting tool and can suppress the consumption of the cutting tool when the SiC substrate is cut.

In order to solve the above problems and achieve the object, a method of cutting a SiC substrate according to the present invention is a method of cutting a SiC substrate by a cutting tool, wherein the cutting tool is made to ultrasonically vibrate in a radial direction while cutting the SiC substrate held by a chuck table, and the cutting tool is made by fixing abrasive grains with a binder obtained by sintering tungsten carbide and cobalt.

In the above method of cutting an SiC substrate, the SiC substrate may be cut with a front surface and a back surface formed of a silicon surface where silicon is exposed and a carbon surface where carbon is exposed on a surface opposite to the silicon surface, and a rotation direction of the cutting tool at a contact point between the cutting tool and the SiC substrate being set to a direction from the carbon surface side toward the silicon surface side.

In the method of cutting an SiC substrate, the protrusion amount of the cutting edge of the cutting tool may be set to be 20 times or more and 30 times or less of the blade thickness.

The invention has the following effects: damage and chipping of the cutting tool can be suppressed, and consumption of the cutting tool when the SiC substrate is cut can be suppressed.

Drawings

Fig. 1 is a perspective view illustrating a method of cutting an SiC substrate according to embodiment 1.

Fig. 2 is a perspective view of a SiC substrate to be processed in the SiC substrate cutting method according to embodiment 1.

Fig. 3 is a cross-sectional view of a cutting unit of a cutting apparatus for implementing the method of cutting the SiC substrate shown in fig. 1.

Fig. 4 is a perspective view of a cutting tool of the cutting unit shown in fig. 3.

Fig. 5 is a side view illustrating a cutting method of the SiC substrate shown in fig. 1.

Description of the reference symbols

10: a chuck table; 21: a cutting tool; 200: a SiC substrate; 202: a silicon surface; 203: a carbon surface; 204: a front side; 205: a back side; 215: the extension amount of the tool nose; 216: the blade is thick; 218: the direction of rotation.

Detailed Description

A mode (embodiment) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited to the contents described in the following embodiments. The components described below include substantially the same components as can be easily conceived by those skilled in the art. The following structures can be combined as appropriate. Various omissions, substitutions, and changes in the structure can be made without departing from the spirit of the invention.

[ embodiment mode 1 ]

A method for cutting a SiC substrate according to embodiment 1 of the present invention will be described with reference to the drawings. Fig. 1 is a perspective view illustrating a method of cutting an SiC substrate according to embodiment 1. Fig. 2 is a perspective view of a SiC substrate to be processed in the SiC substrate cutting method according to embodiment 1. Fig. 3 is a cross-sectional view of a cutting unit of a cutting apparatus for implementing the method of cutting the SiC substrate shown in fig. 1. Fig. 4 is a perspective view of a cutting tool of the cutting unit shown in fig. 3. Fig. 5 is a side view illustrating a cutting method of the SiC substrate shown in fig. 1.

As shown in fig. 1, the method for cutting the SiC substrate according to embodiment 1 is a method in which the cutting apparatus 1 cuts the SiC substrate 200 with the cutting tool 21. The SiC substrate 200 to be processed by the SiC substrate cutting method of embodiment 1 is a disc-shaped semiconductor wafer having SiC (silicon carbide) as a substrate 201.

As shown in fig. 2, the SiC substrate 200 has a front surface 204 and a back surface 205 formed of a silicon surface 202 where Si (silicon) is exposed and a carbon surface 203 where C (carbon) is exposed on a surface opposite to the silicon surface 202. The SiC substrate 200 has devices 207 formed in regions defined by the grid-shaped lines to divide 206 of the silicon surface 202. In addition, the SiC substrate 200 has no device 207 formed on the carbon face 203.

In embodiment 1, the device 207 is a power device that performs power control and power supply, but the present invention is not limited to the power device.

In embodiment 1, the SiC substrate 200 is notched at its outer edge to form a long side portion 208 and a short side portion 209 perpendicular to each other. The long side 208 is longer than the short side 209. Further, if the long side 208 is positioned on the front side as a reference, as shown in fig. 2, the short side 209 is positioned on the left side of the long side 208 in a state where the silicon surface 202 is exposed upward, and the short side 209 is positioned on the right side of the long side 208 in a state where the carbon surface 203 is exposed upward.

In embodiment 1, the SiC substrate 200 is divided into the devices 207 along the lines 206 to be divided, and is singulated into so-called power semiconductors that perform power control and power supply.

In embodiment 1, as shown in fig. 2, the carbon surface 203 of the SiC substrate 200 is bonded to the center of the dicing tape 210 having a larger diameter than the SiC substrate 200, and an annular frame 221 having an inner diameter larger than the outer diameter of the SiC substrate 200 is bonded to the outer edge portion of the dicing tape 210, so that the SiC substrate 200 is supported in the opening 222 inside the annular frame 221.

The method for cutting the SiC substrate according to embodiment 1 is implemented by a cutting apparatus 1 shown in fig. 1 as a main part. The cutting apparatus 1 is a machining apparatus as follows: the SiC substrate 200 is held by the chuck table 10, cut along the lines to divide 206 by the cutting tool 21, and the SiC substrate 200 is divided into the power semiconductors. As shown in fig. 1, the cutting apparatus 1 includes: a chuck table 10 that suctions and holds the SiC substrate 200 by a holding surface 11; a cutting unit 20 that cuts the SiC substrate 200 held by the chuck table 10 by a cutting tool 21; an imaging unit, not shown, that images the SiC substrate 200 held by the chuck table 10; and a control unit not shown.

As shown in fig. 1, the cutting apparatus 1 includes a moving unit 30 for relatively moving the chuck table 10 and the cutting unit 20. The mobile unit 30 includes: a processing feed unit 31 which moves the chuck table 10 in the X-axis direction which is a processing feed direction parallel to the horizontal direction; an index feeding unit 32 that moves the cutting unit 20 in the Y-axis direction, which is an index feeding direction parallel to the horizontal direction and perpendicular to the X-axis direction; a cutting feed unit 33 that moves the cutting unit 20 in a Z-axis direction that is a cutting feed direction parallel to a vertical direction perpendicular to both the X-axis direction and the Y-axis direction; and a rotation moving unit 34 that rotates the chuck table 10 about an axis parallel to the Z-axis direction.

The chuck table 10 has a disk shape, and the holding surface 11 for holding the SiC substrate 200 is formed of porous ceramic or the like. The chuck table 10 is provided to be movable in the X-axis direction by the machining feed unit 31, and is provided to be rotatable about an axis parallel to the Z-axis direction by the rotation movement unit 34. The chuck table 10 is connected to a vacuum suction source, not shown, and sucks and holds the SiC substrate 200 placed on the holding surface 11 by the vacuum suction source, as shown in fig. 1. In embodiment 1, the chuck table 10 sucks and holds the carbon surface 203 side of the SiC substrate 200 through the dicing tape 210. Further, a plurality of not-shown jig portions for clamping the annular frame 221 are provided around the chuck table 10.

The cutting unit 20 is a machining unit having a spindle 23, and the spindle 23 detachably mounts a cutting tool 21 for cutting the SiC substrate 200 held by the chuck table 10. The cutting unit 20 is provided to be movable in the Y-axis direction with respect to the SiC substrate 200 held by the chuck table 10 by the index feeding unit 32, and to be movable in the Z-axis direction with respect to the SiC substrate 200 held by the chuck table 10 by the cutting feeding unit 33. The cutting unit 20 can position the cutting tool 21 at an arbitrary position on the holding surface 11 of the chuck table 10 by the index feed unit 32 and the cutting feed unit 33.

As shown in fig. 3, the cutting unit 20 has: a cutting tool 21; a spindle housing 22 provided to be movable in the Y-axis direction and the Z-axis direction by an index feeding unit 32 and a cutting feeding unit 33; a spindle 23 provided in the spindle housing 22 to be rotatable about an axis, and having a cutting tool 21 attached to a tip thereof; a spindle motor 24 for rotating the spindle 23 around the axis; an ultrasonic vibration applying unit 25 for vibrating the cutting tool 21 attached to the tip of the spindle 23; and a nozzle 26 shown in fig. 1, which supplies cutting water to the cutting tool 21.

The cutting tool 21 is an extremely thin annular cutting grinding tool having a substantially annular shape. In embodiment 1, as shown in fig. 3 and 4, the cutting tool 21 is a so-called hub-shaped tool having a columnar base 211 and an annular cutting edge 212, and the cutting edge 212 is attached to the base 211 and cuts the SiC substrate 200.

In embodiment 1, the base 211 integrally includes: small diameter portions 213 provided at both ends in the axial direction and having the same outer diameter; and a large diameter portion 214 disposed between the small diameter portions 213 and having an outer diameter larger than the small diameter portion. The small diameter portion 213 and the large diameter portion 214 are coaxially arranged. In embodiment 1, the cutting edge 212 is fixed to one side surface of the large diameter portion 214.

The cutting edge 212 is formed to have a predetermined thickness by fixing abrasive grains such as diamond and CBN (Cubic Boron Nitride) with a metal bond obtained by sintering tungsten carbide and cobalt. In embodiment 1, the amount 215 of protrusion of the cutting edge of the cutting tool 21 from the large diameter portion 214 of the base 211 to the outer edge of the cutting edge 212 is set to be 20 times or more and 30 times or less of the thickness of the cutting edge 212, that is, the edge thickness 216.

That is, when the value obtained by dividing the edge extension 215 by the blade thickness 216 is defined as the aspect ratio, the aspect ratio of the cutting tool 21 used in the method for cutting an SiC substrate according to embodiment 1 is 20 or more and 30 or less.

In embodiment 1, the cutting tool 21 is attached to the distal end of the spindle 23 by screwing the bolt 27 inserted into the through hole 217 penetrating the center of the base 211 in the axial direction into the screw hole 231 of the distal end surface of the spindle 23.

In the present invention, the cutting insert 21 may be a so-called washer insert constituted only by the cutting edge 212. In this case, the amount 215 of protrusion of the edge from the mounting seat for fixing the cutting tool 21 to the tip of the spindle 23 to the outer edge of the cutting edge 212 is set to 20 times or more and 30 times or less the edge thickness 216 of the cutting edge 212.

The spindle motor 24 includes: a rotor 241 provided on the main shaft 23 and rotating integrally with the main shaft 23; and a stator 242 disposed on an outer peripheral side of the rotor 241, disposed in the spindle housing 22, and configured to rotate the rotor 241. The stator 242 of the spindle motor 24 rotates the rotor 241, thereby rotating the spindle 23 about the axis.

The ultrasonic vibration applying unit 25 ultrasonically vibrates the cutting tool 21 in a radial direction perpendicular to the Y-axis direction. The ultrasonic vibration according to the present invention is a vibration having an amplitude of several μm to several tens μm at a frequency of 20kHz to several GHz. The ultrasonic vibration applying unit 25 includes: an ultrasonic transducer 251 provided on the main shaft 23; and a resolver 252 provided at the rear end of the main shaft 23. The resolver 252 includes: a power receiving member 253 disposed at a rear end portion of the main shaft 23; and a power supply member 254 disposed at a rear end portion of the spindle housing 22. The power feeding member 254 is connected to the ultrasonic power supply unit 28.

The ultrasonic vibration applying unit 25 supplies power from the ultrasonic power supply unit 28 to the ultrasonic transducer 251 via the power feeding member 254 and the power receiving member 253, and ultrasonically vibrates the ultrasonic transducer 251 to ultrasonically vibrate the cutting tool 21 attached to the distal end of the spindle 23 in the radial direction.

The ultrasonic power supply unit 28 is connected to a power supply 29, and power is supplied from the power supply 29. Further, power supply 29 is also connected to stator 242 and supplies electric power to stator 242.

The axes of the cutting tool 21 and the spindle 23 of the cutting unit 20 are parallel to the Y-axis direction.

The imaging unit is fixed to the cutting unit 20 so as to move integrally with the cutting unit 20. The imaging unit includes an imaging element that images a region to be divided of the SiC substrate 200 before cutting held by the chuck table 10. The imaging element is, for example, a CCD (Charge-coupled Device) imaging element or a CMOS (Complementary MOS) imaging element. The imaging unit images the SiC substrate 200 held by the chuck table 10, obtains an image for performing alignment or the like of the SiC substrate 200 and the cutting tool 21, and outputs the obtained image to the control unit.

The control means controls each of the above-described means of the cutting apparatus 1, and causes the cutting apparatus 1 to perform a machining operation on the SiC substrate 200. In addition, the control unit is a computer having: an arithmetic processing unit having a microprocessor such as a CPU (Central processing unit); a storage device having a memory such as a ROM (read only memory) or a RAM (random access memory); and an input/output interface device. The arithmetic processing device of the control unit performs arithmetic processing in accordance with a computer program stored in the storage device, and outputs a control signal for controlling the cutting apparatus 1 to the above-described components of the cutting apparatus 1 via the input/output interface device.

The control means is connected to display means including a liquid crystal display device or the like for displaying a state of a machining operation, an image, and the like, and input means used when an operator registers machining content information or the like. The input unit is configured by at least one of an external input device such as a touch panel and a keyboard provided in the display unit.

When the control means receives the processing content information registered by the operator and receives a processing operation start instruction from the operator, the cutting apparatus 1 having the above-described configuration starts the processing operation, that is, the SiC substrate cutting method according to embodiment 1. In the method of cutting the SiC substrate, the cutting apparatus 1 suctions and holds the SiC substrate 200 on the holding surface 11 of the chuck table 10 via the dicing tape 210, and sandwiches the annular frame 221 with the jig portion.

In the SiC substrate cutting method, the cutting apparatus 1 rotates the spindle 23 around the axis, moves the chuck table 10 to a position below the imaging unit by the moving unit 30, and images the SiC substrate 200 sucked and held by the chuck table 10 by the imaging unit, thereby performing alignment.

In the method of cutting the SiC substrate, the cutting apparatus 1 moves the cutting tool 21 and the SiC substrate 200 relatively along the line to divide 206 by the moving means 30 according to the processing content information while supplying the cutting water from the nozzle 26 and ultrasonically vibrating the cutting tool 21 in the radial direction, and cuts the SiC substrate 200 by cutting the cutting tool 21 into the line to divide 206 of the SiC substrate 200 held by the chuck table 10 until the cutting tool reaches the dicing tape 210, as shown in fig. 1.

In the method of cutting an SiC substrate according to embodiment 1, as shown in fig. 5, the SiC substrate 200 is cut with the direction 218 of rotation of the cutting tool 21 at the contact point between the cutting edge 212 of the cutting tool 21 and the SiC substrate 200 set to a direction from the carbon surface 203 side toward the silicon surface 202 side. As shown in fig. 5, when the carbon surface 203 side is held on the chuck table 10 via the dicing tape 210, the rotation direction 218 of the cutting tool 21 at the contact point between the cutting edge 212 of the cutting tool 21 and the SiC substrate 200 is opposite to the movement direction of the chuck table 10 of the processing and feeding unit 31, that is, the processing and feeding direction 311.

In the case where the silicon surface 202 side is held on the chuck table 10 via the dicing tape 210, the rotation direction of the cutting tool 21 at the contact point between the cutting tool 21 and the SiC substrate 200 is the same direction as the machining feed direction 311. After all the lines to divide 206 of the SiC substrate 200 are cut, the cutting apparatus 1 ends the machining operation, that is, the SiC substrate cutting method.

In the method for cutting an SiC substrate according to embodiment 1 described above, the cutting edge 212 of the strong cutting tool 21, in which the abrasive grains are fixed by the binder obtained by sintering tungsten carbide and cobalt and are not easily consumed, is caused to ultrasonically vibrate in the radial direction and cut into the SiC substrate 200, and therefore the following effects are obtained: the SiC substrate 200 can be stably cut while suppressing breakage and chipping of the cutting tool 21, and consumption of the cutting edge 212 of the cutting tool 21 when the SiC substrate 200 is cut can be suppressed.

Next, the inventors of the present invention confirmed the effect of the method for cutting an SiC substrate according to embodiment 1. The results are shown in tables 1, 2, 3 and 4 below.

[ TABLE 1 ]

[ TABLE 2 ]

[ TABLE 3 ]

[ TABLE 4 ]

Tables 1, 2, 3, and 4 show the measurement results of the average size of edge chipping, the consumption amount (μm/m) of the cutting edge 212, and the spindle load current value when the SiC substrate 200 having a thickness of 100 μm was cut at the speed of the chuck table 10 in the machining feed direction 311, i.e., the machining feed speed of 20mm/sec, using the cutting tool 21 having the cutting edge 212 including the 1700 grit number abrasive particles having the outer diameter of 76.2mm and the edge thickness 216 of 0.05mm in examples 1, 2, 3, 5, 6, 7, and 8. The spindle load current value is a current value flowing through the stator 242 of the spindle motor 24, and when the cutting resistance increases due to an increase in the machining load caused by meandering or dulling of the cutting edge 212 during cutting, the spindle load current value tends to increase with time.

In examples 1, 2, comparative examples 1, 2, 3, 6, 7, and 8 in tables 1, 2, and 4, the cutting edge 212 of the cutting tool 21 was ultrasonically vibrated at a frequency of 50kHz and an amplitude of 5 μm in the radial direction. In comparative examples 4 and 5 of table 2, the cutting edge 212 of the cutting insert 21 was not ultrasonically vibrated in the radial direction.

In example 1, the SiC substrate 200 was cut by the cutting edge 212 of the cutting tool 21 in which abrasive grains were fixed by a binder obtained by sintering tungsten carbide and cobalt and the nose of the cutting edge was 1.0 μm (that is, the aspect ratio was 20). In example 2, the SiC substrate 200 was cut by the cutting edge 212 of the cutting tool 21 in which the abrasive grains were fixed by bonding of tungsten carbide and cobalt and the nose extension of the cutting edge was 1.5 μm (that is, the aspect ratio was 30).

In comparative example 1, the SiC substrate 200 was cut by the cutting edge 212 of the cutting tool 21 in which abrasive grains were fixed by an electrocasting bond containing nickel and the nose extension amount was 1.0 μm (that is, the aspect ratio was 20). In comparative example 2, the SiC substrate 200 was cut by the cutting edge 212 of the cutting tool 21 in which abrasive grains were fixed by an electrocasting bond containing nickel and the nose extension was 1.2 μm (i.e., the aspect ratio was 24). In comparative example 3, the SiC substrate 200 was cut by the cutting edge 212 of the cutting tool 21 in which abrasive grains were fixed by an electrocasting bond containing nickel and the nose extension was 1.5 μm (i.e., the aspect ratio was 30).

In comparative example 4, the SiC substrate 200 was cut by the cutting edge 212 of the cutting tool 21 in which abrasive grains were fixed by a binder obtained by sintering tungsten carbide and cobalt and the nose of the cutting edge was 1.0 μm (that is, the aspect ratio was 20). In comparative example 5, the SiC substrate 200 was cut by the cutting edge 212 of the cutting tool 21 in which abrasive grains were fixed by an electrocasting bond containing nickel and the nose extension amount was 1.0 μm (that is, the aspect ratio was 20).

In comparative example 6, the SiC substrate 200 was cut by the cutting edge 212 of the cutting tool 21 in which abrasive grains were fixed by a metal bond containing copper or tin and the nose overhang was 1.0 μm (i.e., the aspect ratio was 20). In comparative example 7, the SiC substrate 200 was cut by the cutting edge 212 of the cutting tool 21 in which abrasive grains were fixed by a resin binder and the protrusion of the cutting edge was 1.0 μm (that is, the aspect ratio was 20). In comparative example 8, the SiC substrate 200 was cut by the cutting edge 212 of the cutting tool 21 in which abrasive grains were fixed by a ceramic bond and the protrusion of the cutting edge was 1.0 μm (that is, the aspect ratio was 20).

From table 2, the spindle load current value of comparative example 1 was stable, the average size of chipping was 16 μm, and chipping could be suppressed, but the consumption amount of the cutting edge 212 was as high as 4.3 μm. Further, according to tables 2, 3, and 4, the spindle load current values of comparative examples 2, 3, 4, 5, 6, 7, and 8 have a tendency to increase, the cutting tool 21 is damaged, and the average size of chipping and the consumption amount of the cutting edge 212 cannot be measured.

As compared with comparative examples 1, 2, 3, 4, 5, 6, 7 and 8, table 1 shows that the spindle load current values of examples 1 and 2 are stable, the average size of chipping is 17 μm, chipping can be suppressed, and the consumption amount of the cutting edge 212 can be suppressed to 0.5 μm. Therefore, as is apparent from tables 1, 2, 3, and 4, by cutting the SiC substrate 200 held by the chuck table 10 while ultrasonically vibrating the cutting edge 212 of the cutting tool 21, to which abrasive grains are fixed by a binder made of sintered tungsten carbide and cobalt, in the radial direction, it is possible to suppress breakage and chipping of the cutting tool 21 and to suppress consumption of the cutting tool 21 when cutting the SiC substrate 200.

As is clear from table 1, in examples 1 and 2, the spindle load current value is stable, the average size of chipping is 17 μm, chipping can be suppressed, and the consumption amount of the cutting edge 212 can be suppressed to 0.5 μm, so that by setting the edge protrusion 215 of the cutting edge 212 of the cutting tool 21 to 20 times or more and 30 times or less of the blade thickness 216, breakage and chipping of the cutting tool 21 can be suppressed, and consumption of the cutting tool 21 when cutting the SiC substrate 200 can be suppressed.

The present invention is not limited to the above embodiments. That is, various modifications can be made without departing from the scope of the present invention.