JP6720043B2 - Processing method - Google Patents

Description

The present invention relates to a processing method for dividing a work piece into individual chips and then reducing the thickness of the chips.

In the semiconductor device manufacturing process, devices are formed on the surface of a silicon wafer thinned to a desired thickness by a wafer maker. Further, in a wafer maker, a silicon wafer on which a device is formed is cut by a cutting blade of a cutting device, and divided into individual chips to be individualized. Here, for example, in the development stage and the like, there is a demand to further reduce the thickness of the chip after singulation. In order to meet such a demand, as disclosed in Patent Document 1, a method is conceivable in which a tape is attached to the tip and the ring frame, and then the tip is thinned by a grinding device.

JP 2001-351890 A

In general, a wafer maker obtains a thinned silicon wafer by a processing maker, which is another company, and performs a step of forming a device. Therefore, when the method of Patent Document 1 is adopted in order to meet the demand for grinding chips after being divided into individual pieces, a grinding process is outsourced to a processing maker or a grinding device is purchased only for grinding such chips. There is a problem that it is not economical in any case.

The present invention has been made in view of the above points, and an object of the present invention is to provide a processing method capable of performing both cutting and chip grinding of a workpiece with a single cutting device.

A machining method according to one aspect of the present invention includes a chuck table that holds a workpiece, a cutting unit that includes a spindle that mounts a cutting blade at a tip thereof and a spindle housing that rotatably holds the spindle, a chuck table, and a cutting unit. A cutting device provided with a machining feed means for relatively moving the means in the machining feed direction, and an indexing feed means for relatively moving the chuck table and the cutting means in an indexing feed direction orthogonal to the machining feed direction. This is a processing method for processing a workpiece held by a chuck table with a cutting blade, in which a workpiece with a protective tape attached to the back side is placed on the chuck table, and the workpiece is cut with the cutting blade. A dividing step of dividing each chip along the streets formed on the surface, and at least one of the divided chips is attached to the protective tape on the surface side, and the chip is attached via the protective tape. The chip mounting step of mounting on the chuck table, and cutting cutting feed is performed from the back side of the chip with the cutting blade so that the desired thickness remains so that a cutting groove is formed and it overlaps with the cutting groove in the indexing feed direction. A chip thinning step of thinning the chip to a desired thickness by repeating the cutting by moving the cutting blade.

According to this method, the work piece can be cut into individual pieces on the chuck table of the same cutting device, and the back surface of the individualized chips can be thinned by the cutting blade. As a result, there is no need to outsource the processing for grinding the chips after singulation, or to prepare a grinding device only for thinning processing, which suppresses manufacturing costs and equipment costs and is economically advantageous. Can be something.

Further, in the above-described processing method, a flat dressing step is performed on the cutting blade used in the chip thinning step to make the tip shape of the cutting blade flat, and the flat dressing step performs the chip thinning step. You should do it before.

According to the present invention, since the chip is thinned to a desired thickness by the cutting blade, it is possible to perform both cutting of the workpiece and chip grinding with a single cutting device.

It is a perspective view showing an example of a cutting device used for a processing method concerning an embodiment. It is explanatory drawing of a division step. It is explanatory drawing of a chip mounting step. It is explanatory drawing of a chip thinning step. It is explanatory drawing of a chip thinning step. It is explanatory drawing of a flat dress step.

The processing method according to the present embodiment will be described below with reference to the accompanying drawings. FIG. 1 is a perspective view showing an example of a cutting device used in the processing method according to the embodiment. The cutting device used in the processing method according to the present embodiment is not limited to the configuration shown in FIG. 1, and any type of cutting device can be used as long as the workpiece can be processed as in the present embodiment. It may be a processing device.

As shown in FIG. 1, the cutting device 1 is a chuck that holds a workpiece W and a first cutting means 5a and a second cutting means 5b having cutting blades 52a and 52b (see FIG. 4 for the cutting blade 52b). The table W is moved relative to the table 3 to cut the workpiece W. The workpiece W is carried into the cutting device 1 while being supported by the ring frame 98 via the dicing tape (protective tape) 97. As the workpiece W, a semiconductor wafer in which devices such as IC and LSI are formed on a semiconductor substrate made of silicon, gallium arsenide, or an optical device such as LEDs is formed on a ceramic, glass, or sapphire-based inorganic material substrate. The illustrated optical device wafer can be illustrated. The surface of the workpiece W is partitioned into a plurality of grid-like streets (planned dividing lines) W1, and devices are formed in the partitioned regions.

The center of the upper surface of the base 2 of the cutting device 1 is opened in a rectangular shape so as to extend in the X-axis direction, and a moving plate 31 and a waterproof cover 32 are provided so as to cover the opening. A chuck table 3 that is rotatable around the Z axis is provided on the moving plate 31. Below the waterproof cover 32 and the movable plate 31, processing feed means (not shown) for moving the chuck table 3 in the X-axis direction is provided. This machining feed means allows the chuck table 3 and the cutting means 5a, 5b to move relative to each other in the X-axis direction, which is the machining feed direction. A holding surface 33 for holding the workpiece W is formed on the upper surface of the chuck table 3. The central area of the holding surface 33 is a suction area by the porous material 34.

Around the chuck table 3, four clamp portions 36 for sandwiching and fixing the ring frame 98 around the workpiece W are provided. A sub-chuck table 40 is provided near the chuck table 3, and the sub-chuck table 40 sucks and holds a dresser board 41 used for a flat dress at the tip of the cutting blade 52b (see FIG. 4). There is.

On the upper surface of the base 2, a gate-shaped column portion 21 is provided upright so as to straddle an opening extending in the X-axis direction. The gate-shaped column portion 21 is provided with indexing feeding means 6 and cutting feeding means 7 for moving the cutting means 5a, 5b relative to the chuck table 3.

The indexing feed means 6 moves the first cutting means 5a and the second cutting means 5b in the indexing feed direction (Y-axis direction) orthogonal to the machining feed direction, whereby the chuck table 3 and the cutting means 5a, 5b are moved. And are relatively moved in the Y-axis direction. The cutting feed means 7 moves the first cutting means 5a and the second cutting means 5b in the cutting feed direction (Z-axis direction) perpendicular to the holding surface 33. The indexing feed means 6 includes a pair of guide rails 61 parallel to the front surface of the column portion 21 in the Y-axis direction, and a pair of motor-driven Y-axis tables 62 slidably installed on the pair of guide rails 61. Have Further, the cutting feed means 7 includes a pair of guide rails 71 arranged in front of each Y-axis table 62 and parallel to the Z-axis direction, and a motor-driven Z-axis table 72 slidably installed on the guide rails 71. And have.

Below each Z-axis table 72, cutting means 5a, 5b for cutting the workpiece W are provided. Further, a nut portion (not shown) is formed on the back side of each Y-axis table 62, and a ball screw 63 is screwed into these nut portions. Further, a nut portion (not shown) is formed on the back side of each Z-axis table 72, and a ball screw 73 is screwed into these nut portions. Drive motors 64 and 74 are connected to one ends of the ball screw 63 for the Y-axis table 62 and the ball screw 73 for the Z-axis table 72, respectively. By rotating the ball screws 63 and 73 by these drive motors 64 and 74, the cutting means 5a and 5b are moved in the Y-axis direction and the Z-axis direction along the guide rails 61 and 71.

The first cutting means 5a and the second cutting means 5b are composed of spindles 51a and 51b (see FIGS. 2 and 4) having cutting blades 52a and 52b mounted at their tips, and spindles 51a and 51b that are rotatably held. The housing 53a, 53b is provided. The spindle housings 53a and 53b are provided with image pickup means 55 for picking up an upper surface of the workpiece W, and the cutting blade 52 is aligned with the workpiece W based on the image picked up by the image pickup means 55. Further, each of the cutting means 5a and 5b is equipped with a jet nozzle (not shown) that jets cutting water to the processed portion of the cutting blades 52a and 52b.

The cutting blade 52a of the first cutting means 5a and the cutting blade 52b of the second cutting means 5b have different blade thicknesses, and are different from the cutting blade 52a of the first cutting means 5a in the second cutting means. The cutting blade 52b of 5b has a larger thickness. The cutting blade 52a of the first cutting means 5a cuts the workpiece W in the dividing step described later, and the cutting blade 52b of the second cutting means 5b grinds the back surface of the chip in the chip thinning step described later to reduce the thickness. Turn into. Each of the cutting blades 52a and 52b is formed into a disc shape, for example, by bonding (sintering) abrasive grains such as diamond with a bonding agent.

Next, a method of processing the workpiece will be described with reference to FIGS. 2 to 5. 2 is an explanatory diagram of the dividing step, FIG. 3 is an explanatory diagram of the chip mounting step, and FIGS. 4 and 5 are explanatory diagrams of the chip thinning step. It should be noted that the steps shown in the above figures are merely examples, and the present invention is not limited to this configuration. In the processing method by the cutting device of the present embodiment, the workpiece is divided into individual chips to be formed, and the chips are thinned to a desired thickness by a cutting blade.

First, as shown in FIG. 2, a dividing step is performed. In the dividing step, first, the dicing tape 97 is attached to the back surface side of the workpiece W and the ring frame 98, and the workpiece W is supported by the ring frame 98. Then, the work W with the dicing tape 97 attached is placed on the chuck table 3 and suction-held, and then the street W1 formed on the surface of the work W is detected. Based on the detection result, the cutting blade 52a of the first cutting means 5a is positioned along the street W1. Then, after positioning the lower end of the cutting blade 52a so as to reach the middle in the thickness direction of the dicing tape 97, the cutting blade 52a that rotates at a high speed and the workpiece W are relatively moved in the extending direction of the street W1. As a result, the workpiece W is cut by full cutting, and the workpiece W is divided into individual chips C along all the streets W1.

After carrying out the dividing step, as shown in FIG. 3, the chip placing step is carried out. In the chip mounting step, at least one chip C among the plurality of chips C divided and formed in the dividing step is adsorbed by a pickup collet (not shown) or the like and separated from the dicing tape 97. On the other hand, a protective tape T having a ring frame F different from the ring frame 98 attached to the outer peripheral side is prepared. Then, the front surface Ca side of the chip C separated from the dicing tape 97 is pressed and adhered to the protective tape T so that the back surface Cb of the chip C is exposed upward. The protective tape T to which the chip C is attached is placed on the chuck table 3 (see FIG. 4).

After carrying out the chip mounting step, as shown in FIG. 4, a chip thinning step for thinning the chip C to a desired thickness is carried out. In the chip thinning step, the cutting blade 52b of the second cutting means 5b is positioned outside the outer periphery of the chip C in the machining feed direction. Then, the lower end of the cutting blade 52b becomes lower than the back surface Cb of the chip C, and after being positioned at a height position corresponding to a desired thickness, the cutting blade 52b rotating at high speed and the chip C are relatively moved in the machining feed direction ( Processing feed). As a result, the chip C is cut from the back surface Cb side by the cutting blade 52b to form the cutting groove M, and the desired thickness remains from the back surface Cb side of the chip C. A plurality of cutting grooves M are formed for one chip C, and specifically, they are formed as described below.

5A to 5C are explanatory views showing the process of thinning the chip, and a plan view is shown in the upper stage of each figure and a sectional view is shown in the lower stage. First, as shown in FIG. 5A, when forming the first cutting groove M1 to be the first cutting groove, the cutting blade 52b in the indexing feed direction is protruded from the outer edge extending in the machining feed direction on the back surface Cb of the chip C. Position the position. After this positioning, the cutting blade 52b is processed and fed to cut the chip C and cut the first cutting groove M1.

As shown in FIG. 5B, in order to form the second cutting groove M2 which is the second cutting groove from the state where the first cutting groove M1 is formed, the cutting blade 52b is moved and positioned in the indexing feed direction. The index amount L, which is the amount of movement in the indexing feed direction, is set smaller than the thickness of the cutting blade 52b. Therefore, the cutting blade 52b comes to overlap the first cutting groove M1 in the indexing feed direction, and in this state, the cutting blade 52b is machine-fed to form the second cutting groove M2. In FIG. 5B, a region in which the first cutting groove M1 and the second cutting groove M2 overlap each other is shaded in the drawing. For example, when the thickness of the cutting blade 52b is 0.5 mm, the index amount in the indexing feed direction is 0. The width of the region where the first cutting groove M1 and the second cutting groove M2 overlap is 0.2 mm.

After forming the second cutting groove M2, as shown in FIG. 5C, when the third cutting groove M3 to be the third cutting groove is also formed, the cutting blade 52b is indexed and fed by the same index amount L and cut. .. When the formation of the cutting groove by the cutting blade 52b is repeated in this manner to form the cutting groove on the entire back surface Cb of the chip C, the back surface Cb of the chip C becomes flat and the chip C is thinned to a desired thickness. be able to.

Here, before carrying out the chip thinning step, a flat dressing step of carrying out a flat dressing on the cutting blade 52b of the second cutting means 5b may be carried out. FIG. 6 is an explanatory diagram of the flat dress step. As shown in FIG. 6, in the flat dress step, the dresser board 41 and the cutting blade 52b are relatively moved in the horizontal direction orthogonal to the cutting direction, whereby the tip shape of the cutting blade 52b is shaped flat.

As described above, according to the processing method of the above-described embodiment, the workpiece W can be divided into individual chips C by the cutting blade 52a of the first cutting means 5a in the single cutting device 1, and The cutting blade 52b of the second cutting means 5b can be thinned so as to grind the chip C. That is, both the cutting of the workpiece W and the thinning of the chip C can be performed by the same cutting device 1 without adding another device, and compared with the case where a grinding device is used in addition to the cutting device. The economic burden on the equipment can be reduced. Further, compared with the case where the thinning of the chip C is outsourced, the processing cost including labor such as transportation and packing of the chip C can be reduced, and the thinning can be performed immediately after the chip C is divided, so that the processing time can be shortened. Can be planned.

Further, when the flat dressing step is carried out, the tip shape of the cutting blade 52b of the second cutting means 5b can be corrected to be flat at any time for processing, so that it is possible to maintain good processing accuracy for thinning processing. it can. Here, as the thinning process, it is conceivable to use a disk-shaped flat grinding wheel in which abrasive grains are electrodeposited on the outer periphery of the wheel base, but in this case, 1 to 2 abrasive grains are added to the wheel base. Since the number of layers is about the number of layers, dressing cannot be performed, or when dressing is performed, the frequency of replacement of the flat grinding wheel increases extremely. On the other hand, in the above-described embodiment, since the cutting blade 52b is used for thinning, it is possible to secure a large number of times that flat dressing can be performed, and it is possible to reduce the cost and work load of consumables required for replacement and the like.

Note that the embodiments of the present invention are not limited to the above-described embodiments, and may be variously changed, replaced, or modified without departing from the spirit of the technical idea of the present invention. Furthermore, if the technical idea of the present invention can be realized in another way by the advancement of the technology or another derivative technology, the method may be implemented. Therefore, the claims cover all embodiments that may be included in the scope of the technical idea of the present invention.

Although the cutting means 5a and 5b are two in the above-mentioned embodiment, they may be further added or one. In the case of one unit, the work W is divided by a single cutting blade and the back surface Cb of the chip C is thinned, the width of the cutting groove in the division and the cutting groove in the chip thinning step. The width of M is formed to be the same.

Further, in the above-described embodiment, a plurality of cutting grooves are formed in one chip to be thinned. However, when the size of the chip is small, the cutting may be repeated by one cutting groove without repeating the cutting.

As described above, the present invention has an effect that both cutting and chip grinding of a work piece can be performed by a single cutting device, and chips obtained by dividing the work piece into individual pieces can be manufactured at low cost. This is useful when performing thinning with.

1 Cutting Device 3 Chuck Table 5a First Cutting Means 51a Spindle 52a Cutting Blade 53a Spindle Housing 5b Second Cutting Means 51b Spindle 52b Cutting Blade 53b Spindle Housing 6 Indexing Feeding Means 97 Dicing Tape (Protective Tape)
C chip Ca front surface Cb back surface M cutting groove M1 first cutting groove (cutting groove)
M2 2nd cutting groove (cutting groove)
M3 3rd cutting groove (cutting groove)
T Protective tape W Workpiece W1 Street

Claims (2)

A chuck table for holding a workpiece, a cutting means equipped with a spindle for mounting a cutting blade at its tip and a spindle housing for rotatably holding the spindle, and a chuck table and the cutting means in the machining feed direction. A cutting blade is provided on the spindle housing by using a cutting device provided with a machining feed means for moving the chuck table and the cutting means relative to each other in an indexing feed direction orthogonal to the machining feed direction. A processing method for processing a workpiece mounted and held on the chuck table, comprising:
A work piece having a protective tape attached to the back surface is placed on the chuck table, and a dividing step of dividing the work piece into individual chips along the streets formed on the front surface of the work piece with a cutting blade,
A chip mounting step in which the front surface side of at least one of the plurality of divided chips is attached to a protective tape, and the chip is mounted on the chuck table via the protective tape;
The cutting blade is fed from the back side of the chip so as to leave a desired thickness to form a cutting groove, and the cutting blade is moved so as to overlap the cutting groove in the indexing feed direction to perform cutting. Repeating the above, a chip thinning step of thinning the chip to a desired thickness,
Processing method consisting of. Performing a flat dress to the cutting blade used in the chip thinning step, including a flat dress step to flatten the tip shape of the cutting blade,
The processing method according to claim 1, wherein the flat dressing step is performed before the chip thinning step.

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