JPWO2020066467A1 - Method of dividing GaN substrate - Google Patents

Abstract

By scribing to the GaN substrate using a scribing wheel having a groove formed on the outer circumference, the scribing line required for division can be formed on the GaN substrate without generating unnecessary cracks in the horizontal direction. Provided is a method for dividing a GaN substrate capable of dividing the GaN substrate along the scribe line.
The method for dividing a GaN substrate of the present invention is a method for dividing a GaN substrate by using a scribing wheel (1) having a groove (5) formed on the outer periphery thereof, in which the cutting edge (2) of the scribing wheel (1) is GaNed. A scribing process in which the scribing wheel (1) is brought into vertical contact with the substrate and rolled by applying a load to form a scribing line (L), and a break that divides the GaN substrate on which the scribing line (L) is formed. It has a process.

Description

The present invention relates to a technique for dividing a GaN (gallium nitride) substrate used as a substrate for a light emitting device or an electronic device.

In recent years, even for a substrate made of a brittle material, particularly a crystalline material, a scribing wheel is used to transfer the cutting edge shape of the scribing wheel to the surface of the brittle material substrate (Fig. 1). (See) has been proposed to break the brittle material substrate with vertical cracks formed below the scribing line (see, for example, Patent Documents 1 to 3).

Patent Document 1 discloses a technique for scribing a sapphire substrate with high quality in a scribing wheel made of diamond.
Patent Documents 2 and 3 disclose a technique of applying pressure to a silicon carbide plate with a cutter wheel to roll the cutter wheel on the silicon carbide plate to carve and form a scribing line on the silicon carbide plate.

Japanese Unexamined Patent Publication No. 2018-086758 International Publication No. 2012/093422 Japanese Patent No. 5884852

As described above, there is a well-known technique for forming and dividing a scribe line on a brittle material substrate such as a sapphire substrate, a SiC substrate, and an alumina substrate.
By the way, there is a brittle material substrate called a GaN substrate. This GaN substrate can be used as a substrate for high-brightness LEDs, a substrate for light emitting devices such as a blue laser diode (LD) used for a projector light source or a Blu-ray disk drive, and a substrate for electronic devices such as power devices and high frequency devices. It is used in.

Of the brittle material substrates, the GaN substrate is generally divided by dicing or laser processing. Dicing is a commonly used dividing method, in which a wheel-shaped grindstone (blade) is rotated at high speed to cut a substrate. Further, the dicing process is a wet cutting method in which the cut portion is cooled with water because heat is generated during cutting.

For this reason, the dicing process has a slow processing speed, requires a large amount of cooling water, and cuts and divides the substrate, so that the substrate is lost by the width of the blade. That is, it is difficult to significantly improve the efficiency of dicing, and it is considered that dividing a GaN substrate by dicing is not the optimum dividing technique from the viewpoint of yield.
By the way, as shown in FIG. 5, for example, a glass substrate, a sapphire substrate, a SiC substrate, an alumina substrate, or the like is scribed on a general brittle material substrate using a disc-shaped scribing wheel having a cutting edge on the entire outer circumference. In this case, since a vertical crack C is generated below the scribe line L, it becomes easy to divide the substrate (wafer) along the scribe line L.

However, in a GaN substrate, even if scribe is performed using a disc-shaped scribing wheel whose entire outer circumference is a cutting edge, vertical cracks are less likely to occur directly under the scribing line as compared with a general brittle material substrate. It is not easy to divide the GaN substrate along the scribe line.
That is, even if an attempt is made to divide the GaN substrate along a scribing line formed by a disc-shaped scribing wheel whose entire outer circumference is a cutting edge, the GaN substrate is divided at another position without following the scribing line, or the divided cross section is rough. Or, the GaN substrate itself may be chipped.

Therefore, in view of the above problems, the present invention can form a scribe line required for division on the GaN substrate by scribing the GaN substrate using a scribing wheel having a groove formed on the outer periphery thereof. It is an object of the present invention to provide a method for dividing a GaN substrate, which can divide a GaN substrate along its scribe line without generating unnecessary cracks in the horizontal direction.

In order to achieve the above object, the following technical measures have been taken in the present invention.
The method for dividing a GaN substrate according to the present invention is a method for dividing a GaN substrate by using a scribing wheel having a groove formed on the outer periphery, in which the cutting edge of the scribing wheel is brought into vertical contact with the GaN substrate. It is characterized by having a scribing step of forming a scribing line by applying a load to the scribing wheel and rolling it, and a breaking step of dividing the GaN substrate on which the scribing line is formed.

Preferably, in the scribe step, vertical cracks do not occur below the scribe line.
Preferably, in the scribe step, the load at the time of scribe is 1.2 N or more and 6.2 N or less.

According to the present invention, by scribing to a GaN substrate using a scribing wheel having a groove formed on the outer periphery, a scribe line required for division can be formed on the GaN substrate, and unnecessary cracks can be formed in the horizontal direction. The GaN substrate can be divided along the scribe line without generating the above.

It is an image which shows the example of the scribe line formed by a plurality of dents. It is an image which imaged the state of the scribe line formed in the direction parallel to the orientation flat (OF) on the Ga plane side of a GaN substrate. It is an image which imaged the state of the scribe line formed in the direction perpendicular to the orientation flat (OF) on the Ga plane side of a GaN substrate. It is the figure which examined the situation below the scribe line in the cross section of a GaN substrate. It is an image showing the situation of a normal scribe line formed on glass or the like. It is a front view of a scribing wheel. It is an enlarged view of the part surrounded by the alternate long and short dash line of FIG. 6, and is the enlarged view of the ridge line part of the cutting edge of a scribing wheel.

Hereinafter, embodiments of the method for dividing a GaN substrate according to the present invention will be described with reference to the drawings.
It should be noted that the embodiments described below are examples that embody the present invention, and the specific examples do not limit the configuration of the present invention.
The present invention is a technique for dividing a GaN (gallium nitride) substrate 10 by using a scribing wheel 1 having a groove 5 formed on the outer periphery thereof, and a scribing line L is formed on the GaN substrate by using the scribing wheel 1. It has a scribing step and a breaking step of dividing the GaN substrate on which the scribing line L is formed.

First, the scribe process will be described.
The scribe step is a step of forming a scribe line L, which serves as a guide for division, on a GaN substrate with a scribe device (not shown). First, a GaN substrate is installed in the scribe device. The scribe device is equipped with a scribing tool. A rotatable scribing wheel 1 is attached to the scribing tool. The outer circumference of the scribing wheel 1 is a cutting edge 2 forming a scribe line L.

Further, in the present embodiment, grooves (details will be described later) are formed at equal intervals on the outer periphery of the scribing wheel 1.
Therefore, when the cutting edge 2 of the scribing wheel 1 is brought into vertical contact with the GaN substrate and the scribing wheel is run while being pressed with a predetermined load, the scribing wheel 1 rolls on the GaN substrate and a plurality of hits are made. The scribe line L formed by the marks will be formed on the surface of the GaN substrate. As shown in FIG. 1, the scribe line L has recesses continuous in the traveling direction at regular intervals.

In the scribe step of the present embodiment, the scribe line L is formed from the Ga surface of the GaN substrate, but the scribe line L may be formed from the N surface.
Here, the configuration of the scribing wheel 1 will be described with reference to FIGS. 6 and 7.
As shown in FIG. 6, the scribing wheel 1 is a disk-shaped member when viewed from the front, and the scribing line L is formed by the cutting edge 2 on the outer circumference. The diameter of the scribing wheel 1 is 0.5 mm or more and 5 mm or less. Further, a through hole 3 (shaft hole) into which the rotating shaft is inserted is formed in the center of the scribing wheel 1. The scribing wheel 1 is rotatably supported around the axis of the rotating shaft inserted into the through hole 3. The outer circumference of the scribing wheel 1 is formed in a V shape including a ridge line 4 and inclined surfaces on both sides of the ridge line 4 in a side view.

As shown in FIG. 7, a plurality of minute groove portions 5 are formed at regular intervals on the outer periphery of the scribing wheel 1. Specifically, the groove portions 5 are formed at regular intervals over the entire circumference so as to divide the ridge line 4 that orbits the outer circumference of the scribing wheel 1. It can be said that the ridge line 4 on the outer circumference of the scribing wheel 1 is formed intermittently.
That is, the convex portion formed so as to connect between the groove portion 5 and the groove portion 5 adjacent to the groove portion 5 is the cutting edge 2 forming the scribe line L.

The length of each groove 5 (the length in the outer peripheral direction of the scribing wheel 1), the depth of the groove 5 (the length in the inner diameter of the scribing wheel 1), the length of the ridge line 4, the length of the groove 5 and the ridge line. The ratio to the length of 4 (pitch of the cutting edge 2) and the like are set to be predetermined. That is, regarding the configuration of the scribing wheel 1, the outer diameter, the thickness, the inner diameter (through hole 3), the cutting edge angle, the number of groove portions 5 (the number of divisions of the ridge line 4), and the like are predetermined.

In the scribing wheel 1 used in the present embodiment, at least the outer periphery of the cutting edge 2 is formed of single crystal diamond. If the material of the scribing wheel 1 is, for example, sintered diamond, it will be damaged at an early stage. According to the findings, the formation of the scribe line L only once causes unusable damage.
On the other hand, when the material of the scribing wheel 1 is single crystal diamond, it is not damaged at an early stage. Therefore, the scribing wheel 1 may be formed of single crystal diamond. Similarly, the material of the cutting edge 2 of the scribing wheel 1 may be polycrystalline diamond that does not contain a sintering aid.

It was also found that the surface roughness Ra on the outer circumference (cutting edge 2) of the scribing wheel 1 should be 1 nm or more and 150 nm or less. At least, the surface roughness Ra of the ridge line 4 connecting the groove portion 5 formed in the scribing wheel 1 and the groove portion 5 adjacent to the groove portion 5 formed on the scribing wheel 1 and the inclined surfaces on both sides of the ridge line 4, which come into contact with the GaN substrate during scribe, is 1 nm. It is preferable that the thickness is 150 nm or less.
That is, it is preferable that the surface of the cutting edge 2 is smooth.

The scribe line L is a discontinuous recess formed at regular intervals. That is, the scribe line L is a broken line-shaped line in which a plurality of recesses are formed in the traveling direction as shown in FIG. In other words, the scribe line L is not a continuous line.
As described in detail above, by forming the groove 5 on the entire outer circumference of the scribing wheel 1, the ridge line 4 and the side portion 6 (hypotenuse) of the groove 5 become a convex cutting edge 2, and the cutting edge 2 is a GaN substrate. By biting into the surface layer on the Ga surface side, a plurality of recesses are transferred in the traveling direction by the cutting edge 2, and a scribe line L required for division is formed.

That is, when scribing from the Ga surface side of the GaN substrate using the scribing wheel 1 having a plurality of groove portions 5 (convex cutting edge 2) on the outer periphery, cracks do not occur below the scribing line in the thickness direction of the GaN substrate. Nevertheless, a scribe line L suitable for division is formed.
In the scribe process of the present embodiment, the load at the time of scribe is 1.2 N or more and 6.2 N or less. According to the knowledge, when the load at the time of scribe is out of the range, it is divided at another position without following the scribe line L, and it is not possible to break (divide) along the scribe line L. In addition, the cross section may be rough, the GaN substrate itself may be chipped, or the GaN substrate may not be able to be divided.

On the other hand, when the load at the time of scribe was within the range, it was possible to break along the scribe line L. In addition, the cross section was good, and the GaN substrate itself was not chipped. Therefore, the load at the time of scribe is within the above range.
Next, the break process will be described.
The break step is a step of cutting a GaN substrate along a scribe line L that serves as a guide for cutting with a break device (not shown) that employs, for example, a three-point bending method. First, a GaN substrate on which the scribe line L is formed is installed in the mounting portion of the break device. The placement portion includes a pair of left and right receiving portions that come into contact with both side portions along the scribe line L, and the scribe line L is directed downward so that the scribe line L is located at the center between these receiving portions. The GaN substrate is placed in this state. The break device is provided with a break member having a blade at the tip. Bring the break member closer to the position corresponding to the scribe line L on the surface on which the scribe line L is not formed. The cutting edge of the break member is pressed to press the position corresponding to the scribe line L. Then, the GaN substrate is divided along the scribe line L.
[Experimental example]
Here, based on this experimental example, the state of the scribe line L formed on the Ga surface side of the GaN substrate will be examined.

FIG. 2 shows an enlarged image of the scribe line L formed in the direction parallel to the orientation flat on the Ga surface side of the GaN substrate. Regarding FIG. 2, the scribe load = 2.6N.
FIG. 3 shows an enlarged image of the scribe line L formed in the direction perpendicular to the orientation flat on the Ga surface side of the GaN substrate. Regarding FIG. 3, the scribe load was set to 1.3 N.

The orientation flat (OF) is a notch in which a part of the outer circumference of the disk-shaped GaN substrate is cut in a straight line, and the notch indicates the direction of the crystal axis.
Regarding the scribing wheel 1 of this experimental example, the outer diameter: 2 mm, the thickness: 0.65 mm, the inner diameter (through hole 3): 0.8 mm, the cutting edge angle: 120 °, the number of grooves 5 (the number of divisions of the ridge line 4): The one having 370 pieces and the depth of the groove 5: 3.0 μm was used. The configuration of the scribing wheel 1 is an example.

As shown in FIG. 2, when the scribe line L is formed on the Ga surface side of the GaN substrate in the direction parallel to the orientation flat (OF), it can be confirmed that the recess is formed.
As shown in FIG. 3, when the scribe line L is formed on the Ga surface side of the GaN substrate in the direction perpendicular to the orientation flat (OF), it can be confirmed that the recess is formed.
In FIGS. 2 and 3, the line generated from the recess in the longitudinal direction along the direction of the scribe line L is a fine and shallow crack formed only on the surface layer of the GaN substrate, which is formed during scribe. It is considered that this crack occurs at the time of scribe, and in the present embodiment, it is considered that not the vertical crack but the fine crack on the surface layer is the starting point of the division.

FIG. 4 shows an examination of the situation below the recess of the scribe line L in the cross section of the GaN substrate.
As shown in FIG. 4, when the scribing wheel 1 described above is used, the vertical crack C (crack in the thickness direction toward the inner layer of the substrate) as shown in FIG. 5 does not occur below the scribe line L. , The scribe line L required as a starting point of division could be generated.

As described above, according to the method for dividing a GaN substrate of the present invention, a scribe line L having a plurality of recesses in the traveling direction is scribed from the Ga surface side of the GaN substrate using the scribing wheel 1 having a groove 5 formed on the outer periphery. Can be formed on the Ga surface side of the GaN substrate. On the other hand, in the scribe line L, cracks C in the vertical direction (cracks in the thickness direction toward the inner layer of the substrate) as shown in FIG. 4 are not generated immediately below the scribe line. However, since the break step can be divided along the fine cracks on the surface layer, the GaN substrate can be divided along the scribe line L without generating unnecessary cracks in the horizontal direction.

Further, according to the present invention, regardless of whether the scribing line L is formed in the direction perpendicular to or parallel to the orientation flat on the Ga surface side of the GaN substrate, the GaN substrate is formed along the scribing line L. Can be divided.

Summarizing the above, the method of dividing the GaN substrate according to the present invention includes a scribing process in which the cutting edge of the scribing wheel is brought into vertical contact with the GaN substrate, and a load is applied to the scribing wheel to roll the scribing wheel to form a scribing line. It is characterized by having a break step of dividing a GaN substrate on which a scribe line is formed.

Further, in the scribing process described above, vertical cracks are prevented from occurring below the scribing line. In addition, in the scribe process, the load at the time of scribe is 1.2 N or more and 6.2 N or less.
It should be noted that the embodiments disclosed this time are exemplary in all respects and are not considered to be restrictive.

In particular, in the embodiments disclosed this time, matters not specified, such as operating conditions, operating conditions, dimensions and weights of components, do not deviate from the range normally practiced by those skilled in the art, and are normal. If you are a person skilled in the art, you are adopting items that can be easily assumed.

1 Scrivener wheel 2 Cutting edge 3 Through hole 4 Ridge line 5 Groove 6 Side L Scrivener C Vertical crack

Claims (3)

In a method of dividing a GaN substrate by using a scribing wheel having a groove formed on the outer periphery,
A scribing process in which the cutting edge of the scribing wheel is brought into vertical contact with the GaN substrate and a load is applied to the scribing wheel to roll the scribing wheel to form a scribing line.
A method for dividing a GaN substrate, which comprises a break step for dividing the GaN substrate on which the scribe line is formed. The method for dividing a GaN substrate according to claim 1, wherein in the scribe step, vertical cracks do not occur below the scribe line. The method for dividing a GaN substrate according to claim 1 or 2, wherein in the scribe step, the load at the time of scribe is 1.2 N or more and 6.2 N or less.

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