TWI793331B - Chamfer processing method - Google Patents

Abstract

[Problem] To provide a chamfering method capable of efficiently chamfering the outer periphery of a wafer. [Solution] A chamfering processing method is at least composed of the following steps: a rough processing step, positioning the laser light focusing point on the outer periphery of the wafer to irradiate the laser light, and roughly roughing the surface by ablation performing chamfering processing; and a finishing step, using a grinding stone to grind the outer periphery of the ablated wafer to perform finishing processing.

Description

Chamfer processing method

field of invention The invention relates to a chamfering processing method for chamfering the outer periphery of a wafer.

Background of the Invention IC, LSI, LED and other components are formed by laminating functional layers on the front surface of a wafer made of Si (silicon) or Al ₂ O ₃ (sapphire) and dividing by predetermined lines. In addition, power devices, LEDs, etc. are formed by laminating functional layers on the front surface of a wafer made of SiC (silicon carbide) and dividing them by predetermined division lines. The wafer formed with components is divided into individual components by processing the dividing line with a dicing device and a laser processing device, and the divided components are used in electrical equipment such as mobile phones and personal computers.

A wafer on which devices are formed is generally produced by thinly cutting a cylindrical ingot with a wire saw. The front and back of the cut wafer are processed into mirror surfaces by grinding (see, for example, Patent Document 1). However, when cutting the crystal ingot with a wire saw and grinding the front and back sides of the cut wafer, it becomes necessary to discard most of the crystal ingot (70~80%), which is uneconomical. . In particular, in SiC ingots, there are problems in that productivity is poor because cutting with a wire saw is difficult due to its high hardness and takes considerable time, and the unit price of the ingot is high so that wafers must be produced efficiently.

Therefore, the applicant of the present case proposed the following technical scheme: the converging point of the laser light with a wavelength penetrating to SiC is positioned inside the SiC crystal ingot, and the SiC crystal ingot is irradiated with the laser light to cut the SiC crystal ingot. A separation layer is formed on the plane to be cut, and the wafer is separated from the SiC ingot along the plane to be cut on which the separation layer is formed (see, for example, Patent Document 2). prior art literature patent documents

Patent Document 1: Japanese Patent Laid-Open No. 2000-94221 Patent Document 2: Japanese Patent Laid-Open No. 2016-111143

Summary of the invention The problem to be solved by the invention However, when chamfering the wafer by pressing the grinding stone against the outer periphery of the wafer, it takes considerable time and has a problem of poor productivity.

The subject of this invention made|formed in view of the said fact is to provide the chamfering processing method which can perform chamfering processing to the outer periphery of a wafer efficiently. means to solve problems

In order to solve the above-mentioned problems, the present invention provides the following chamfering method. That is, a chamfering processing method for chamfering the outer periphery of a wafer, the aforementioned chamfering processing method is at least composed of the following steps: A rough processing step of irradiating the laser light by positioning the focal point of the laser light on the outer periphery of the wafer, and roughly performing chamfering by ablation; and In the finishing step, a grinding stone is used to grind the outer periphery of the ablated wafer to perform finishing.

Preferably, the roughing step comprises: In the first rough processing step, the laser light is irradiated from the first surface side of the wafer by irradiating the laser light by positioning the focus point of the laser light on the outer periphery of the wafer, and roughly performing chamfering processing by ablation; and In the second rough processing step, the laser light is irradiated from the second surface side of the wafer by positioning the laser light focusing point on the outer periphery of the wafer, and chamfering is roughly performed by ablation, This finishing step includes: The first finishing step is to perform finishing by grinding the outer periphery of the wafer from the first surface side of the wafer with a grinding stone; and The second finishing step is to perform finishing by grinding the outer periphery of the wafer from the second surface side of the wafer with a grinding stone. The wafer can also be a SiC wafer. Invention effect

The chamfering processing method provided by the present invention is composed of a rough processing step and a finishing step. The aforementioned rough processing step is to position the laser light focusing point on the outer periphery of the wafer to irradiate the laser light, and by Ablation roughly performs chamfering, and the above-mentioned finishing step uses a grinding stone to grind the outer periphery of the wafer that has been ablated to perform finishing, so chamfering can be efficiently performed on the outer periphery of the wafer. Corner processing.

form for carrying out the invention Hereinafter, suitable embodiments of the chamfering method of the present invention will be described with reference to the drawings.

Shown in FIG. 1 is a wafer 2 to be chamfered by the chamfering method of the present invention. The wafer 2 in the illustrated embodiment is a SiC wafer made of SiC (silicon carbide), and is formed in a disc shape with a thickness of about 200 μm. This wafer 2 has a first surface 4 and a second surface 6 opposite to the first surface 4 , and a first orientation flat 8 and a second orientation flat 10 representing crystal orientations are formed on the outer periphery of the wafer 2 . Furthermore, the length of the second orientation plane 10 is shorter than the length of the first orientation plane 8 .

In the chamfering processing method of the present invention, firstly, the rough processing step is implemented. The aforementioned rough processing step is to position the laser light focusing point on the outer periphery of the wafer 2 to irradiate the laser light, and roughly Perform chamfering. The rough machining step can be carried out using, for example, a laser machining apparatus 12 shown partly in FIG. 1 . The laser processing apparatus 12 includes a chuck 14 for sucking and holding the wafer 2 , and a condenser 16 for irradiating the pulsed laser beam LB to the wafer 2 sucked and held on the chuck 14 .

As shown in Figure 1 (a), a porous circular suction chuck 18 that has been connected to a suction mechanism (not shown) is disposed on the upper end portion of the work clamp table 14. In the work clamp table 14, it is formed A suction mechanism is used to generate an attractive force on the upper surface of the suction chuck 18 to attract and hold the wafer 2 placed on the upper surface. In addition, the work chuck 14 is rotated with the vertical direction as the axis center by a rotation mechanism (not shown). Condenser 16 advances and retreats relative to work clamping table 14 in FIG. 1 toward the X-axis direction represented by arrow X by X-axis feed mechanism (not shown), and by Y-axis feed mechanism (FIG. not shown) advances and retreats in the Y-axis direction (the direction indicated by arrow Y in FIG. 1 ) which is perpendicular to the X-axis direction. Furthermore, the plane defined by the X-axis direction and the Y-axis direction is substantially horizontal.

In the rough processing steps in the illustrated embodiment, firstly, the first rough processing step is implemented. The aforementioned first rough processing step is to position the laser beam focusing point on the wafer 2 from the first surface 4 side of the wafer 2. The outer periphery of the circle 2 is irradiated with laser light, and chamfering is roughly performed by ablation.

In the first rough processing step, after the first surface 4 is turned upward and the upper surface of the work chuck 14 is used to attract and hold the wafer 2, the photographing mechanism (not shown) of the laser processing device 12 is used to photograph from above. Wafer 2. Then, according to the image of the wafer 2 captured by the camera mechanism, the light collector 16 is positioned above the outer circumference of the wafer 2, and the light-condensing point of the pulsed laser light LB is positioned on the first surface 4 side the periphery. Then, as shown in FIG. 1( b ), while rotating the chuck 14 at a predetermined rotational speed, the outer periphery on the first surface 4 side is irradiated with pulsed laser light LB from the condenser 16 . Thereby, chamfering processing (first rough processing) can be roughly performed by ablation on the outer periphery on the side of the first surface 4 . In FIG. 1( c ), the portion to which the first rough machining has been performed is indicated by reference numeral 20 .

Since the wafer 2 of the illustrated embodiment is formed with the first alignment plane 8 and the second alignment plane 10, when the pulsed laser light LB is irradiated along the first alignment plane 8 and the second alignment plane 10, except In addition to the rotation of the work clamp 14, the X-axis feed mechanism and the Y-axis feed mechanism are also used to move the light collector 16 appropriately, thereby moving the light focus point along the first orientation plane 8 and the second orientation plane 10 . This is done so that the entire outer periphery on the first surface 4 side is irradiated with the pulsed laser beam LB. Furthermore, the work clamping table 14 may be rotated and moved in the X-axis direction and the Y-axis direction without moving the light collector 16, or it may be set so that the work clamping table 14 is not actuated and only the light collector 16 is moved. .

In the rough processing step in the illustrated embodiment, the second rough processing step is implemented after the first rough processing step. The focus point of the wafer 2 is positioned on the outer periphery of the wafer 2 to irradiate laser light, and rough chamfering is performed by ablation.

Referring to FIG. 2 , in the second rough processing step, firstly, the second surface 6 is turned upward and the wafer 2 is sucked and held by the chuck 14 . Then, similar to the first rough processing step, the wafer 2 is photographed by the photographing mechanism, and the light collector 16 is positioned above the outer periphery of the wafer 2 according to the image of the wafer 2 photographed by the photographing mechanism, And the converging point of the pulsed laser beam LB is positioned on the outer periphery on the second surface 6 side. Then, as shown in FIG. 2( b ), while rotating the chuck 14 at a predetermined rotational speed, the outer periphery on the second surface 6 side is irradiated with pulsed laser light LB from the condenser 16 . Thereby, chamfering processing (second rough processing) can be roughly performed on the outer periphery on the second surface 6 side by ablation. In FIG. 2( c ), the portion to which the second rough machining has been performed is indicated by reference numeral 22 .

Even in the second rough processing step, the pulsed laser beam is irradiated along the first orientation plane 8 and the second orientation plane 10 by appropriately moving the converging point of the pulsed laser beam LB relative to the wafer 2. The laser beam LB is emitted, and the entire periphery of the second surface 6 side is irradiated with the pulsed laser beam LB.

The above-mentioned rough processing step can be implemented, for example, under the following processing conditions. Wavelength of pulsed laser light: 1064nm Average output: 5.0W Repetition frequency: 10kHz Pulse width: 100ns Focus distance: 100mm Rotation speed of work clamping table: 12 degrees/second Processing time: 30 seconds x 2 times (first and second rough processing steps) = 1 minute

In the chamfering processing method of the present invention, the finishing step is implemented after the rough processing step. The aforementioned finishing step is to perform finishing by grinding the outer periphery of the wafer 2 that has been ablated with a grinding stone. processing. The finishing step may be carried out using a grinding device 24 such as part of which is shown in FIG. 3 . The grinding device 24 includes a chuck 26 for sucking and holding the wafer 2 , and a grinding wheel 28 for grinding the outer periphery of the wafer 2 sucked and held by the chuck 26 .

The chuck table 26 is configured to attract and hold the wafer 2 from its upper surface, and is configured to rotate with the vertical direction as an axis. The grinding wheel 28 is configured to rotate around the X-axis direction, and is configured to relatively move in the X-axis direction and the vertical direction with respect to the chuck table 26 . Also, a ring-shaped grinding stone 30 is installed on the outer periphery of the disc-shaped grinding wheel 28. The aforementioned grinding stone 30 is formed by fixing diamond abrasive grains with a bonding material such as a metal bond, And the outer periphery is shaped at an angle corresponding to the angle of the chamfer.

In the finishing steps in the illustrated embodiment, at first the first finishing step is implemented. The aforementioned first finishing step is to grind the wafer 2 with the grinding stone 30 from the first surface 4 side of the wafer 2. Finishing is performed by grinding the outer periphery.

If the description continues with reference to FIG. 3 , in the first finishing step, after the first surface 4 is turned upward and the wafer 2 is sucked and held by the chuck table 26, the wafer 2 is photographed from above with a photographing mechanism (not shown). . Next, the grinding wheel 28 is positioned above the outer periphery of the wafer 2 according to the image of the wafer 2 captured by the camera mechanism. Then, while rotating the work chuck 26 at a predetermined rotational speed in the counterclockwise direction viewed from above, the grinding wheel 28 rotating in the direction indicated by the arrow A in FIG. The outer circumference is pushed against the outer circumference on the side of the first surface 4 (the portion 20 subjected to the first rough machining). Thereby, the outer periphery on the side of the first surface 4 that has been roughly chamfered by ablation can be ground and finished with the grinding stone 30 .

Since the wafer 2 of the illustrated embodiment is formed with the first orientation plane 8 and the second orientation plane 10, the grinding wheel 28 is directed toward the outer periphery of the wafer 2 by an appropriate potential energy member such as a spring. Potential energy or the like is applied to move the grinding wheel 28 along the first orientation plane 8 and the second orientation plane 10 . In this way, finishing is given to the entire outer periphery on the side of the first surface 4 .

In the finishing step in the illustrated embodiment, the second finishing step is implemented after the first finishing step. The aforementioned second finishing step is to grind the grinding stone 30 from the second surface of the wafer 2. On the 6 side, the outer periphery of the wafer 2 is ground and finished.

Referring to FIG. 4 , in the second finishing step, firstly, the second surface 6 is turned upward and the wafer 2 is sucked and held by the chuck 26 . Next, similarly to the first finishing step, the wafer 2 is photographed by the photographing mechanism, and the grinding wheel 28 is positioned above the outer periphery of the wafer 2 based on the image of the wafer 2 captured by the photographing mechanism. Then, while rotating the table 26 counterclockwise as viewed from above at a predetermined rotational speed, the grinding wheel 28 rotating in the direction A is lowered, and the outer periphery of the grinding stone 30 is pushed against the second surface. The outer periphery of side 6 (the portion 22 that has been subjected to the second rough machining). Thereby, the outer periphery on the side of the second surface 6 that has been roughly chamfered by ablation can be ground and finished with the grinding stone 30 .

Furthermore, even in the second finishing step, potential energy or the like is imparted by directing the grinding wheel 28 toward the outer periphery of the wafer 2 with an appropriate potential-imparting member such as a spring so that the grinding wheel 28 moves along the The first orienting plane 8 and the second orienting plane 10 are moved to perform finishing on the entire outer periphery on the second surface 6 side.

The finishing process as described above can be implemented, for example, under the following processing conditions. Diamond abrasive grains: 0.5~2.0μm (25% by weight) Binder: metal binder (75% by weight) Shape: diameter 60mm, thickness 10mm Front tilt angle: 45 degrees Rotation speed of grinding wheel: 20000rpm Rotation speed of work clamping table: 2 degrees/second Processing time: 3 minutes x 2 times (first and second finishing steps) = 6 minutes

As above, in the chamfering processing method of the illustrated embodiment, at least it is composed of a rough processing step and a finishing step. The outer periphery of the wafer 2 is irradiated with laser light LB, and chamfering is roughly performed by ablation. The aforementioned finishing step is to grind the outer periphery of the ablated wafer 2 with a grinding stone 30 Therefore, the amount of grinding and the grinding time of the grinding stone can be reduced, even if the wafer 2 is formed of a relatively hard material such as SiC, compared with the grinding only by the grinding stone In the case of chamfering after chipping, the outer periphery of the wafer 2 can be chamfered efficiently in a short time.

Furthermore, in the illustrated embodiment, although the example in which the second rough machining step is implemented after the first rough machining step is implemented, and then the second finishing step is implemented after the first finishing step is implemented, it may also be It is assumed that the first finishing step is carried out after the first rough processing step is carried out, and then the second finishing step is carried out after the second rough processing step is carried out.

2‧‧‧Wafer 4‧‧‧first side 6‧‧‧The second side 8‧‧‧First Orientation Plane 10‧‧‧Second Orientation Plane 12‧‧‧Laser processing device 14. 26‧‧‧Work clamping table 16‧‧‧Concentrator 18‧‧‧Absorptive Chuck 20‧‧‧The part that has been subjected to the first rough machining 22‧‧‧The part that has been subjected to the second rough machining 24‧‧‧Grinding device 28‧‧‧Grinding wheel 30‧‧‧grinding stone A‧‧‧arrow LB‧‧‧Laser light X, Y‧‧‧direction

(a) of Fig. 1 is a perspective view showing a state in which the first surface is placed upward and a wafer is placed on a work chuck of a laser processing device, (b) is a perspective view showing a state in which the first rough processing step is being implemented, (c) is a cross-sectional view of a wafer that has been subjected to the first rough processing step. (a) of FIG. 2 is a perspective view showing a state in which the second surface is placed upward and a wafer is placed on a work chuck of a laser processing device, and (b) is a perspective view showing a state in which a second rough processing step is being implemented. (c) is a cross-sectional view of a wafer that has undergone a second rough processing step. (a) of FIG. 3 is a perspective view showing the state in which the first finishing step is being carried out, and (b) is a cross-sectional view showing a state in which the first finishing step is being carried out. (a) of Fig. 4 is a perspective view showing a state in which the second finishing step is being implemented, (b) is a cross-sectional view showing a state in which the second finishing step is being implemented, and (c) is a view showing that the second finishing step has been implemented Cross-sectional view of the wafer.

2‧‧‧Wafer

4‧‧‧first side

6‧‧‧The second side

8‧‧‧First Orientation Plane

20‧‧‧The part that has been subjected to the first rough machining

22‧‧‧The part that has been subjected to the second rough machining

24‧‧‧Grinding device

26‧‧‧Work clamping table

28‧‧‧Grinding wheel

30‧‧‧grinding stone

A‧‧‧arrow

X‧‧‧direction

Claims (3)

A chamfering processing method is a method of chamfering the outer periphery of a wafer. The aforementioned chamfering processing method is at least composed of the following steps: a rough processing step, positioning the laser light focusing point on the outer periphery of the wafer. irradiating laser light to roughly perform chamfering by ablation; and a finishing step of grinding the outer periphery of the wafer that has been ablated with a grinding stone to perform finishing. Including: a first rough processing step, irradiating the laser light by positioning the focus point of the laser light on the outer periphery of the wafer from the first surface side of the wafer, and roughly performing chamfering processing by ablation; and the second The second rough processing step is to position the focal point of the laser light on the outer periphery of the wafer from the second surface side of the wafer to irradiate the laser light, and roughly perform chamfering processing by ablation. The finishing step includes : the first finishing step is to perform finishing by grinding the outer periphery of the wafer with the grinding stone from the first side of the wafer; and the second finishing step is to grind the grinding stone from the first surface side of the wafer Finishing is performed by grinding the outer periphery of the wafer on both sides. In this finishing step, a ring-shaped The outer periphery of the grinding stone is pressed against the outer periphery of the wafer on which the rough processing step has been performed to perform the finishing step. The aforementioned annular grinding stone is installed so as to be perpendicular to the axis of the work chuck. The outer circumference of a disc-shaped grinding wheel that rotates in the direction of the axis is shaped at an angle corresponding to the chamfering angle. The chamfering processing method according to claim 1, wherein in the rough processing step, a light collector for condensing and irradiating laser light is positioned on the wafer and irradiating laser light vertically to the first surface and the second surface. The chamfering processing method as claimed in item 1 or 2, wherein the wafer is a SiC wafer.

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