JP6896346B2 - Processing method of work piece - Google Patents

Description

The present invention relates to a processing method for processing the back surface of a work piece on which a device is formed on the front surface.

In the manufacturing process of device chips used in electronic devices such as mobile phones and personal computers, first, a plurality of intersecting scheduled division lines are set on the surface of a wafer made of a material such as a semiconductor. Then, devices such as ICs (Integrated Circuits) and LSIs (Large Scale Integration) are formed in each area partitioned by the planned division line. Further, the device chip can be formed by thinning the wafer to a predetermined thickness and then dividing the wafer along the planned division line.

In recent years, a mounting technique called flip-chip bonding has been put into practical use in order to save space in a region required for mounting a device chip on a predetermined mounting target. In flip-chip bonding, metal protrusions called a plurality of bumps having a height of about 10 μm to 100 μm are formed on the surface side of the device via a wiring board, and these bumps are made to face the electrodes formed on the mounting target. It is a mounting technology that directly joins. The bump functions as a terminal of the device chip and is connected to the device via a wiring board and a thin metal wire.

Further, as a semiconductor packaging technology, bumps are formed directly on the device surface without internal wiring by thin metal wires, the wafer surface and the bumps are covered with a sealing material and sealed, and the wafers are individually sealed. The technology of dividing into device chips has been put into practical use. The packaging technique is called WL-CSP (Wafer-level Chip Size Package) (see Patent Document 1).

Since the heights of the plurality of bumps formed on the surface of the wafer are not always uniform, even if the plurality of bumps are directly bonded to the electrodes formed on the mounting target of the device chip, they are uniformly bonded. Is not easy. Therefore, the upper part of the sealing material and the upper part of the bump are cut with a tool using a tool cutting device equipped with a cutting tool having a cutting edge made of diamond to thin the sealing material and reduce the height of the bump. A processing method for making the uniform uniform has been developed (see Patent Document 2).

Japanese Unexamined Patent Publication No. 2001-7135 Japanese Unexamined Patent Publication No. 2000-173954

The cutting tool for cutting the surface side of the wafer on which the sealing material and the bump are formed cuts the sealing material having high processing resistance at the time of cutting the cutting material and the bump made of metal at the same time. To cut. Therefore, the machining load and machining heat generated by the cutting of the tool strongly act on the tool, and the cutting edge of the tool is severely worn.

Since further tool cutting cannot be performed with a severely worn tool, the tool must be replaced frequently. The tool cutting device cannot be used while the tool is being replaced, and the replacement tool is very expensive. Therefore, the machining efficiency of the tool cutting device becomes low, which causes a problem.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for machining a workpiece that can suppress wear of a cutting edge of a tool tool and improve the machining efficiency of a tool cutting device. It is to be.

According to one aspect of the present invention, a wafer in which a plurality of planned division lines are set in a grid pattern on the surface and a device is formed in each region partitioned by the plurality of planned division lines, and a wafer formed above the device. A method for processing a workpiece including a bump and a sealing material for embedding the bump and covering the surface of the wafer. In a cutting device provided with a cutting tool, the lower end of the cutting tool is the bump. The cutting tool is lowered so as to be higher than the height position of the upper end, and a plurality of concentric circles having a depth that does not reach the height position of the upper end of the bump on the sealing material of the workpiece whose surface side is exposed. In a cutting tool having a cutting groove forming step of forming shaped cutting grooves at predetermined intervals from each other and a cutting tool having a cutting tool made of diamond after the cutting groove forming step, the lower end of the cutting edge is The cutting tool is lowered so as to be lower than the height position of the upper end of the bump, and the upper part of the sealing material of the workpiece whose surface side is exposed while supplying cutting water to the cutting tool of the tool. Provided is a method for processing a workpiece, which comprises a tool cutting step for exposing the bump from the sealing material by cutting the upper part of the bump with a tool.

In one aspect of the present invention, a cutting groove forming step of forming a plurality of cutting grooves in the sealing material is performed before performing a tool cutting step of cutting the surface side of the workpiece. When a cutting groove is formed in the sealing material in the cutting groove forming step, the sealing material that occupies the area where the cutting groove is formed is removed. Can be reduced. By that amount, the machining load applied to the tool by cutting the tool is reduced.

Further, in the tool cutting step, cutting water is supplied to the tool in order to remove the machining chips generated by the tool cutting and to remove the machining heat generated by the machining. When a cutting groove is formed in the sealing material, the cutting water is accumulated in the cutting groove, and the cutting water is more efficiently supplied to the tool tool to efficiently remove the processing heat. .. In particular, since the concentric cutting grooves are formed at predetermined intervals from each other, the cutting water can be easily held uniformly over the entire work piece.

That is, if a cutting groove is formed in the sealing material in advance, the machining load applied to the tool by the tool can be reduced, and the machining heat generated by the tool can be efficiently removed. Then, the consumption of the cutting edge of the tool tool can be suppressed, the frequency of replacement of the tool tool can be reduced, and the machining efficiency of the tool cutting device can be improved.

Therefore, according to the present invention, there is provided a method for machining an workpiece that can suppress wear of the cutting edge of a tool tool and improve the machining efficiency of a tool cutting device.

FIG. 1 (A) is a perspective view schematically showing a work piece provided with bumps and a sealing material on the surface, and FIG. 1 (B) is a cover provided with bumps and a sealing material on the surface. It is sectional drawing which shows typically the workpiece. It is a perspective view which shows typically the cutting groove forming process. FIG. 3A is a side view schematically showing a tool cutting process, and FIG. 3B is a top view schematically showing a tool cutting process. FIG. 4A is a cross-sectional view schematically showing a state in which cutting water is supplied to a work piece in which a cutting groove is formed in a sealing material, and FIG. 4B is a schematic view of a cutting tool cutting process. It is sectional drawing which shows.

Embodiments of the present invention will be described with reference to the accompanying drawings. First, the workpiece of the processing method according to the present embodiment will be described with reference to FIGS. 1 (A) and 1 (B). FIG. 1A is a perspective view schematically showing a work piece. The workpiece 5 includes a wafer 1, bumps 7, and a sealing material 3.

The wafer 1 is, for example, a substantially disk-shaped substrate made of a material such as silicon, SiC (silicon carbide), or other semiconductor, or a material such as sapphire, glass, or quartz. A plurality of scheduled division lines (not shown) are set in a grid pattern on the surface 1a of the wafer 1, and ICs (Integrated Circuits), LSIs (Large Scale Integration), etc. are provided in each region partitioned by the scheduled division lines. Device 7a is formed. Finally, when the wafer 1 is divided along the planned division line, individual device chips are formed.

FIG. 1B is a cross-sectional view schematically showing the workpiece 5. The bump 7 is formed of a conductive material such as metal, and serves as a terminal for the device chip formed by dividing the wafer 1. Before the wafer 1 is divided, the workpiece 5 is tool-cut by a tool-cutting device equipped with a tool, and the upper part of the sealing material 3 covering the bump 7 and the upper part of the bump 7 are partially removed. Then, since the bump 7 is exposed from the sealing material 3, the bump 7 can be bonded to the electrode of the mounting target when the device chip is mounted on the predetermined mounting target.

Next, a processing method of the workpiece 5 according to one aspect of the present invention will be described. The processing method of the workpiece 5 includes a cutting groove forming step of forming a cutting groove in the sealing material 3 of the workpiece 5, and cutting the upper portion of the sealing material 3 and the upper portion of the bump 7 with a bite. This includes a cutting tool cutting step for exposing the bump 7 from the sealing material 3. Hereinafter, each step of the processing method of the workpiece 5 will be described.

First, the cutting groove forming process will be described with reference to FIG. FIG. 2 is a perspective view schematically showing a cutting groove forming process. The cutting groove forming step is carried out by the cutting device 2 shown in FIG. The cutting device 2 includes a cutting unit 4 having a spindle 6 along one direction in a plane parallel to the surface 1a of the wafer 1 and a cutting tool 8 mounted on the tip of the spindle 6. The cutting tool 8 can be rotated by rotating the spindle 6 around an axis along the direction.

The cutting tool 8 is, for example, an annular blade or a cemented carbide metal saw having a grindstone made of a binder and abrasive grains on the outer peripheral portion. When the cutting tool 8 is rotated and the rotating cutting tool 8 is brought into contact with the workpiece 5, the workpiece 5 is cut.

In the cutting groove forming step, first, the workpiece 5 is installed in the cutting device 2 with the sealing material 3 side facing upward. Next, the cutting unit 4 is positioned above the workpiece 5. Then, the spindle 6 of the cutting unit 4 is rotated, and the cutting tool 8 is lowered so that the lower end of the cutting tool 8 is higher than the height position of the upper end of the bump 7 of the workpiece 5. At this time, the workpiece 5 is rotated about an axis that penetrates the center of the surface 1a in a direction perpendicular to the surface 1a. Then, the cutting tool 8 is cut at a position away from the center by the diameter of the circular cutting groove 9 to be formed, and the sealing material 3 of the workpiece 5 is cut.

Then, a circular cutting groove 9 having a depth that does not reach the bump 7 is formed in the sealing material 3. In the cutting groove forming step, since the cutting tool 8 is positioned at a predetermined height position so that the cutting groove 9 is formed at such a depth, the cutting tool 8 is a bump 7 formed of a conductive material. Do not cut.

After the circular cutting groove 9 is formed, the cutting unit 4 is raised, and the workpiece 5 and the cutting unit 4 are relatively moved in the radial direction of the workpiece 5 by a predetermined distance. The cutting unit 4 is lowered again, and the sealing material 3 is cut one after another by the cutting tool 8. Then, a plurality of concentric cutting grooves 9 are formed in the sealing material 3 at predetermined intervals.

The concentric cutting grooves 9 may be formed by another method, and may be formed by using, for example, a cup wheel in which cutting grindstones are arranged on a circle having a predetermined radius. In this case, the cup wheel is positioned so that the center of the circle in which the cutting grindstones of the cup wheel are lined up is located above the center of the surface 1a, and the cup is placed around an axis penetrating the center of the circle in the vertical direction. Rotate the wheel.

Then, the cup wheel is lowered and brought into contact with the sealing material 3 of the workpiece 5, and the sealing material 3 is cut. After forming a circular cutting groove 9 by cutting with the cup wheel, cutting is performed one after another using a plurality of other cup wheels in which cutting grindstones are lined up on a circle having a diameter different from the diameter of the circle in which the cutting grindstones are lined up. When implemented, a plurality of cutting grooves 9 arranged concentrically can be formed.

In the method for processing a workpiece according to the present embodiment, a tool cutting step is performed after the cutting groove forming step. In the tool cutting step, in a tool cutting device provided with a tool having a cutting edge made of diamond, the upper portion of the sealing material 3 and the bump 7 of the workpiece 5 in which the cutting groove 9 is formed in the sealing material 3 The bump 7 is exposed from the sealing material 3 by cutting the upper part of the tool with a tool.

FIG. 3A is a side view schematically showing a tool cutting process. In the tool cutting step, for example, the tool cutting device 10 shown in FIG. 3A is used. The tool cutting device 10 includes a chuck table 12 and a tool cutting unit 14 arranged above the chuck table 12.

The chuck table 12 has a porous member (not shown) on the upper surface side. The upper surface of the porous member is a holding surface 12a for holding the workpiece 5. The chuck table 12 includes a suction path (not shown) having one end connected to a suction source (not shown). The other end of the suction path is connected to the porous member. When the workpiece 5 is placed on the holding surface 12a so as to expose the sealing material 3 side upward, the negative pressure generated by the suction source is applied to the workpiece 5 through the holes of the porous member. The workpiece 5 is suction-held on the chuck table 12.

The tool cutting unit 14 has a spindle 18, a tool wheel 16 held at one end of the spindle 18, and a tool tool 20 fixed to the tool wheel 16. A rotary drive source (not shown) such as a motor is connected to the other end of the spindle 18, and the rotary drive source rotates the spindle 18.

The tool cutting device 10 further includes an elevating means (not shown), and the elevating means can move the spindle 18 in the vertical direction. Further, a moving means (not shown) is further provided, and the chuck table 12 can be linearly moved in a plane parallel to the holding surface 12a by the moving means. The tool tool 20 is provided with a cutting edge 20a made of diamond at the lower end (see FIG. 4B), and when the cutting edge 20a comes into contact with the workpiece 5 held on the holding surface 12a, the workpiece 20 5 is cut with a tool.

A cutting water supply nozzle 22 (see FIG. 3B) for supplying cutting water to the tool tool 20 is arranged in the vicinity of the tool cutting unit 14 of the tool cutting device 10. When cutting the tool 5 with a tool, the cutting water supply nozzle 22 is supplied to the tool tool 20. The cutting water is, for example, pure water. The cutting water removes machining debris generated by cutting the cutting tool and cools the cutting tool 20 and the workpiece 5.

In the tool cutting step, first, the workpiece 5 is placed on the holding surface 12a of the chuck table 12 with the sealing material 3 side exposed on the upper surface, and the chuck table 12 sucks and holds the workpiece 5. .. Next, with the tool cutting wheel 16 rotated, the tool tool 20 is lowered so that the lower end of the cutting edge 20a is lower than the height position of the upper end of the bump 7.

FIG. 3B is a top view schematically showing a tool cutting process. After lowering the tool tool 20, as shown in FIG. 3B, the chuck table 12 is held in a direction parallel to the holding surface 12a while supplying cutting water from the cutting water supply nozzle 22 to the tool tool 20. Move it. When the tool tool 20 touches the workpiece 5 sucked and held by the chuck table 12, the workpiece 5 is cut with a tool.

Further, FIG. 4A schematically shows a cross section of the workpiece 5 immediately before the tool is cut. As shown in FIG. 4A, in the processing method of the workpiece according to the present embodiment, the cutting groove 9 is formed in the sealing material 3 by the cutting groove forming step before the tool cutting is performed. .. Then, in the tool cutting step, the cutting water is supplied to the tool tool 20 and the cutting water is scattered around. Then, the scattered cutting water enters the cutting groove 9.

When the cutting water 24 has entered the cutting groove 9, as shown in FIG. 4 (B), the cutting tool 20 cuts the sealing material 3 and the bump 7 together with the cutting water 24 entering the cutting groove 9. To do. Therefore, as compared with the case where the cutting groove 9 is not formed in the sealing material 3, the cutting water is efficiently supplied to the machining portion, and the machining heat generated by the cutting tool is removed more efficiently.

Further, when the cutting groove 9 is formed in the sealing material 3, the volume of the sealing material 3 removed by the tool tool 20 is reduced. Then, the machining load applied to the tool tool 20 is reduced, and the amount of machining heat generated is also reduced. Therefore, the consumption of the cutting edge 20a of the tool tool 20 is suppressed, and the frequency of replacement of the tool tool 20 can be reduced. Since the stop time of the tool cutting device 10 is shortened and the number of times that one tool can cut a tool is increased, the machining efficiency of the tool cutting is increased.

As the volume of the sealing material 3 removed in the cutting groove forming step becomes larger, the volume of the sealing material 3 removed by the cutting tool 20 in the cutting tool 20 becomes smaller, and the machining load can be reduced. Since the width of the cutting groove 9 is determined by the thickness of the cutting tool 8 of the cutting device 2, the cutting groove 9 is formed with a width that allows the cutting water 24 to easily enter the formed cutting groove 9. It is desirable that the cutting tool 8 has a predetermined thickness. The thickness of the cutting tool 8 is preferably 0.4 mm to 2.0 mm.

Further, in order to uniformly exhibit the effect of removing the processing heat by the cutting water that has entered the cutting groove 9 over the entire area of the sealing material 3, each of the plurality of cutting grooves 9 formed in the sealing material 3 is formed. , It is desirable that the distance between the adjacent cutting grooves 9 is constant.

Further, as the amount of the sealing material 3 removed in the cutting groove forming step increases, the machining load applied to the tool tool 20 is reduced, so that the number of the cutting grooves 9 is preferably larger. Further, for example, the total area of the plurality of cutting grooves 9 formed in the sealing material 3 when viewed from above is preferably about 5% to 50% of the upper surface of the sealing material 3.

When the tool cutting step is performed, the bump 7 is exposed from the sealing material 3. Since the bump 7 is cut by the tool tool 20, the height position of the upper end of the bump 7 becomes uniform. Then, when the workpiece 5 is finally divided to form a device chip and the device chip is mounted on a predetermined mounting substrate, the bump 7 can be uniformly bonded to the electrode included in the mounting substrate.

The present invention is not limited to the description of the above embodiment, and can be implemented with various modifications. For example, in the above embodiment, the case where a plurality of concentric cutting grooves are formed at predetermined intervals in the cutting groove forming step has been described, but one aspect of the present invention is not limited to this. The plurality of cutting grooves of various shapes may be formed in the sealing material.

The structure, method, etc. according to the above-described embodiment can be appropriately modified and carried out as long as the scope of the object of the present invention is not deviated.

1 Wafer 1a Front surface 1b Back surface 3 Encapsulant 5 Work piece 7 Bump 7a Device 9 Cutting groove 2 Cutting device 4 Cutting unit 6 Spindle 8 Cutting tool 10-bit cutting device 12 Chuck table 12a Holding surface 14-bit cutting unit 16-bit cutting wheel 18 Spindle 20 Tool Tool 20a Cutting Blade 22 Cutting Water Supply Nozzle 24 Cutting Water

Claims (1)

A wafer in which a plurality of scheduled division lines are set on the surface in a grid pattern and a device is formed in each region partitioned by the plurality of scheduled division lines, a bump formed above the device, and the bump are embedded. A method for processing a workpiece including a sealing material that covers the surface of the wafer.
In a cutting device including a cutting tool, the cutting tool is lowered toward the surface of the workpiece so that the lower end of the cutting tool is higher than the height position of the upper end of the bump, and the encapsulant is subjected to the cutting tool. A cutting groove forming step of forming a plurality of concentric cutting grooves having a depth not reaching the height position of the upper end of the bump at predetermined intervals from each other.
After the cutting groove forming step, in a tool cutting device including a tool having a cutting edge made of diamond, the cutting tool is lowered so that the lower end of the cutting edge is lower than the height position of the upper end of the bump. By cutting the upper part of the sealing material and the upper part of the bump of the workpiece whose surface side is exposed while supplying cutting water to the cutting edge of the cutting tool, the bump is cut from the sealing material. A method for processing a workpiece, which comprises a tool cutting process for exposing.

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