JP2019080025A - Processing method of workpiece - Google Patents

Abstract

To improve processing efficiency of a tool cutting device, by restraining abrasion of a cutting-edge of a byte tool.SOLUTION: A processing method of a workpiece including a wafer where a device is formed on a surface, a bump, and a sealant embedding the bump and covering the surface includes a cut groove formation step of descending a cutting tool toward the surface of the workpiece so that the lower end of the cutting tool is higher than a height position of the upper end of the bump in a cutting device including the cutting tool, and forming multiple linear cutting grooves in the sealant in a first direction or a second direction, and a byte cutting step of exposing the bump from the sealant, by byte cutting the upper part of the sealant of the workpiece, front side of which is exposed, while supplying cutting water to the cutting-edge of the byte tool, in the byte cutting device including the byte tool having a diamond cutting-edge, after the cutting groove formation step.SELECTED DRAWING: Figure 2

Description

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

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

  2. Description of the Related Art In recent years, mounting technology called flip chip bonding has been put to practical use in order to save a space required for mounting when mounting a device chip on a predetermined mounting target. In flip chip bonding, metal bumps called bumps of about 10 μm to 100 μm in height are formed on the surface side of the device through the wiring substrate, and these bumps are made to face the electrodes formed on the mounting object. Mounting technology for direct bonding. The bumps function as terminals of the device chip, and are connected to the device through the wiring substrate and the thin metal wires.

  Furthermore, as a semiconductor packaging technology, bumps are formed directly on the device surface without performing internal wiring with metal fine wires, and the wafer surface and the bumps are covered and sealed with a sealing material, and the wafers are individualized. The technology of dividing into device chips has been put to practical use. The packaging technology 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 necessarily uniform, even if the plurality of bumps are directly joined to the electrode formed on the mounting target of the device chip, they are uniformly joined. Is not easy. Therefore, the upper part of the sealing material and the upper part of the bump are cut by a cutting tool equipped with a cutting tool having a cutting edge made of diamond, thereby thinning the sealing material and setting the height of the bump A processing method to make it uniform has been developed (see Patent Document 2).

JP 2001-7135 A Japanese Patent Application Laid-Open No. 2000-173954

  A cutting tool for cutting a surface side of a wafer on which a sealing material and a bump are formed is a cutting tool that simultaneously has the sealing material having high machining resistance during cutting and a bump formed of metal. Cut. Therefore, the processing load and the processing heat generated by the cutting of the cutting tool strongly work on the cutting tool, and the cutting edge of the cutting tool is severely worn.

  Since it is not possible to carry out further cutting with a heavily worn tool, it is necessary to change the tool frequently. While changing the cutting tool, the cutting tool can not be used, and the replacement cutting tool is expensive. Therefore, the processing efficiency of the cutting tool becomes low, which causes a problem.

  The present invention has been made in view of such problems, and an object thereof is to provide a method of processing a workpiece capable of suppressing the wear of the cutting edge of the cutting tool and improving the processing efficiency of the cutting tool. It is to be.

  According to one aspect of the present invention, a plurality of division planned lines are set on the surface in the form of a grid, and a wafer is formed on each area divided by the plurality of division planned lines, and a device is formed above the device What is claimed is: 1. A method of processing a workpiece comprising: a bump; and a sealing material that embeds the bump and covers the surface of the wafer, wherein a cutting device provided with a cutting tool has a lower end of the cutting tool. The cutting tool is lowered so as to be higher than the height position of the upper end, and a plurality of straight lines of a depth not reaching the height position of the upper end of the bump on the sealing material of the workpiece whose surface side is exposed A cutting groove forming step of forming a cutting groove along a first direction or a second direction crossing the first direction, and a cutting edge made of diamond after the cutting groove forming step Equipped with a cutting tool with In the cutting device, the cutting tool is lowered so that the lower end of the cutting blade is lower than the height position of the upper end of the bump, and the surface side is exposed while supplying cutting water to the cutting blade of the cutting tool. And b) cutting the upper portion of the sealing material of the workpiece and the upper portion of the bump to expose the bump from the sealing material. Is provided.

  Note that in one aspect of the present invention, the first direction and the second direction may be orthogonal to each other.

  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 the cutting step of cutting the surface side of the workpiece is performed. 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, so the sealing material that the cutting tool removes by cutting the cutting tool is Can be reduced. The cutting load applied to the cutting tool is reduced by cutting the cutting tool.

  Furthermore, in the cutting process, cutting water is supplied to the cutting tool in order to remove machining chips generated by cutting the cutting tool and to remove processing heat generated by the processing. When a cutting groove is formed in the sealing material, the cutting water is collected in the cutting groove, and the cutting water is supplied to the cutting tool more efficiently, and the processing heat is efficiently removed. . In particular, since the cutting grooves are respectively formed along the first direction or the second direction intersecting the first direction, the cutting water is easily held uniformly throughout the workpiece.

  That is, when cutting grooves are formed in advance in the sealing material, the processing load on the cutting tool can be reduced by cutting the cutting tool, and the processing heat generated by cutting the cutting tool can be efficiently removed. As a result, wear of the cutting edge of the cutting tool can be suppressed, and the frequency of changing the cutting tool can be reduced to improve the processing efficiency of the cutting tool.

  Therefore, the present invention provides a method of processing a workpiece that can suppress the wear of the cutting edge of the cutting tool and improve the processing efficiency of the cutting tool.

FIG. 1A is a perspective view schematically showing a workpiece having bumps and a sealing material provided on the surface, and FIG. 1B shows a substrate having bumps and a sealing material provided on the surface. It is sectional drawing which shows a workpiece schematically. FIG. 2A is a perspective view schematically showing an example of the cutting groove forming step, and FIG. 2B is a perspective view schematically showing another example of the cutting groove forming step. FIG. 3 (A) is a side view schematically showing the cutting process of the cutting tool, and FIG. 3 (B) is a top view schematically showing the cutting process of the cutting tool. FIG. 4 (A) is a cross-sectional view schematically showing a state in which cutting water is supplied to a workpiece having a cutting groove formed in a sealing material, and FIG. 4 (B) schematically shows a cutting tool cutting process. 6 is a cross-sectional view schematically shown.

  Embodiments of the present invention will be described with reference to the accompanying drawings. First, the to-be-processed object of the processing method which concerns on this embodiment is demonstrated using FIG. 1 (A) and FIG. 1 (B). FIG. 1A is a perspective view schematically showing a workpiece. The workpiece 5 includes a wafer 1, bumps 7, and a sealing material 3.

  The wafer 1 is a substantially disc-like substrate made of, for example, a material such as silicon, SiC (silicon carbide) or other semiconductor, or a material such as sapphire, glass, quartz or the like. A plurality of planned dividing lines (not shown) are set in a lattice on the surface 1a of the wafer 1, and in each area partitioned by the planned dividing lines, IC (Integrated Circuit), LSI (Large Scale Integration), etc. Device 7a is formed. Finally, when the wafer 1 is divided along the dividing lines, individual device chips are formed.

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

  Next, a method of processing the workpiece 5 according to an aspect of the present invention will be described. In the method of processing the workpiece 5, 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 And b) a cutting process for exposing the bumps 7 from the sealing material 3. Hereinafter, each process of the processing method of the said to-be-processed object 5 is demonstrated.

  First, the cutting groove forming process will be described with reference to FIGS. 2 (A) and 2 (B). FIG. 2A is a perspective view schematically showing an example of the cutting groove forming step. The cutting groove forming process is performed by the cutting device 2 shown in FIG. 2 (A). The cutting apparatus 2 includes a cutting unit 4 having a spindle 6 along one direction in a plane parallel to the surface 1 a of the wafer 1 and a cutting tool 8 attached to the tip of the spindle 6. The cutting tool 8 can be rotated by rotating the spindle 6 about an axis along the direction.

  The cutting tool 8 is, for example, an annular blade or a cemented carbide metal saw provided with a grindstone composed of a bonding agent and abrasives 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 on the cutting device 2 with the sealing material 3 side facing upward. Next, the cutting unit 4 is positioned above the outer peripheral side of 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. Next, the cutting unit 4 and the work piece 5 are relatively linearly moved in the in-plane direction (first direction) parallel to the surface 1 a, and the cutting tool 8 The sealing material 3 of the workpiece 5 is cut.

  Then, linear cutting grooves 9 having a depth not reaching the bumps 7 are formed in the sealing material 3. In the cutting groove forming step, in order to position the cutting tool 8 at a predetermined height position so that the cutting groove 9 is formed with such a depth, the cutting tool 8 is a bump 7 formed of a conductive material. Never cut.

  After the linear cutting groove 9 is formed, the workpiece 5 and the cutting unit 4 are relatively moved in a direction perpendicular to the extending direction of the cutting groove 9 by a predetermined distance, The cutting unit 4 is moved in the first direction and the sealing material 3 is cut by the cutting tool 8 one after another. Then, a plurality of linear cutting grooves 9 along the first direction are formed in the sealing material 3 along one direction with a predetermined interval.

  Next, the workpiece 5 is rotated about an axis perpendicular to the surface 1a. Then, similarly, the cutting unit 4 and the work piece 5 are relatively linearly moved in the direction parallel to the surface 1 a in the in-plane direction, and the cutting tool 8 makes the work piece 5 The sealing material 3 is cut. Then, in the sealing material 3, a plurality of linear cutting grooves 9 along a second direction intersecting the first direction are formed along one direction with a predetermined interval.

  When a plurality of cutting grooves 9 are formed along the first direction or a second direction crossing the first direction, the cutting groove forming process is completed. In the cutting groove forming step, as shown in FIG. 2A, the cutting groove 9 formed along the first direction is orthogonal to the cutting groove 9 formed along the second direction. May be Moreover, FIG. 2 (B) is a perspective view which shows another example of the cutting groove 9 formed at a cutting groove formation process. As shown in FIG. 2 (B), the first direction and the second direction may not be orthogonal to each other.

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

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

  The chuck table 12 has a porous member (not shown) on the top side. The upper surface of the porous member serves as a holding surface 12 a for holding the workpiece 5. The chuck table 12 internally includes a suction path (not shown) whose one end is connected to a suction source (not shown). The other end of the suction path is connected to the porous member. The workpiece 5 is placed on the holding surface 12 a so that the sealing material 3 side is exposed upward, and the negative pressure generated by the suction source is applied to the workpiece 5 through the hole of the porous member. The workpiece 5 is held by suction on the chuck table 12.

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

  The cutting tool 10 further includes elevating means (not shown), and the elevating means can move the spindle 18 in the vertical direction. In addition, moving means (not shown) is further provided, and the moving means can linearly move the chuck table 12 in a direction parallel to the holding surface 12a. The cutting tool 20 has a cutting blade 20a (see FIG. 4B) made of diamond at its lower end, and when the cutting blade 20a comes into contact with the workpiece 5 held by the holding surface 12a, the workpiece 5 is a cutting tool.

  In the vicinity of the cutting tool cutting unit 14 of the cutting tool 10, a cutting water supply nozzle 22 (see FIG. 3B) for supplying cutting water to the cutting tool 20 is disposed. The cutting water supply nozzle 22 is supplied to the cutting tool 20 when the cutting tool 5 cuts the workpiece 5. The cutting water is, for example, pure water. The cutting water removes cutting chips generated by cutting the tool and also cools the cutting tool 20 and the workpiece 5.

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

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

  Moreover, the cross section of the to-be-processed object 5 in front of cutting with a cutting tool is typically shown in FIG. 4 (A). As shown in FIG. 4A, in the method for processing a workpiece according to this embodiment, the cutting groove 9 is formed in the sealing material 3 in the cutting groove forming step before the cutting of the cutting tool. . Then, in the cutting process, cutting water is supplied to the cutting tool 20, and the cutting water is scattered around. Then, the scattered cutting water enters the cutting groove 9.

  When cutting water 24 enters the cutting groove 9, as shown in FIG. 4B, the cutting tool 20 cuts the sealing material 3 and the bumps 7 together with the cutting water 24 that has entered the cutting groove 9. 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 processing location, and the processing heat generated by the cutting of the cutting tool is more efficiently removed.

  When the cutting groove 9 is formed in the sealing material 3, the volume of the sealing material 3 removed by the cutting tool 20 is reduced. Then, the processing load applied to the cutting tool 20 is reduced, and the amount of processing heat generated is also reduced. Therefore, wear of the cutting blade 20 a of the cutting tool 20 can be suppressed, and the frequency of replacement of the cutting tool 20 can be reduced. Since the stopping time of the cutting tool 10 is shortened and the number of times the cutting can be performed by one cutting tool is increased, the processing efficiency of cutting the cutting tool is increased.

  As the volume of the sealing material 3 removed in the cutting groove forming process increases, the volume of the sealing material 3 removed by the cutting tool 20 in the cutting process decreases, and the processing 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 in such a width that the cutting water 24 can easily enter the cutting groove 9 formed. It is desirable that the cutting tool 8 have a predetermined thickness. The thickness of the cutting tool 8 is preferably 0.4 mm to 2.0 mm.

  Further, in order to exert the effect of removal of the processing heat by the cutting water in the cutting groove 9 uniformly in the entire region of the sealing material 3, each of the plurality of cutting grooves 9 formed in the sealing material 3 is Preferably, the spacing between adjacent cutting grooves 9 formed along the same direction is constant.

  Furthermore, since the processing load on the cutting tool 20 is reduced as the removal amount of the sealing material 3 in the cutting groove forming step increases, the number of the cutting grooves 9 is preferably larger. In addition, for example, the total area of the plurality of cutting grooves 9 formed in the sealing material 3 in plan view from above is preferably about 5% to 50% of the upper surface of the sealing material 3.

  Further, in the cutting process, it is preferable to move the cutting tool 20 so as to intersect the plurality of linear cutting grooves 9 and cut the cutting tool. Then, since the cutting tool 20 always cuts the sealing material 3 and the like while traversing the cutting groove 9, cutting of the cutting tool is efficiently performed.

  When the cutting process is performed, the bumps 7 are exposed from the sealing material 3. Since the bumps 7 are cut by the cutting tool 20, the height positions of the upper ends of the bumps 7 become 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 bumps 7 can be uniformly bonded to the electrodes of the mounting substrate.

  In addition, this invention is not limited to the description of the said embodiment, It can change variously and can be implemented. For example, in the above embodiment, the case where the plurality of linear cutting grooves are formed in the cutting groove forming step along the first direction or the second direction intersecting the first direction is described. However, one embodiment of the present invention is not limited thereto. The plurality of cutting grooves of various shapes may be formed in the sealing material.

  The structures, methods, and the like according to the above embodiments can be appropriately modified and implemented without departing from the scope of the object of the present invention.

Reference Signs List 1 wafer 1a front surface 1b back surface 3 sealing material 5 workpiece 7 bump 7a device 9 cutting groove 2 cutting device 4 cutting unit 6 spindle 8 cutting tool 10 bite cutting device 12 chuck table 12a holding surface 14 bite cutting unit 16 bite cutting wheel 18 spindle 20 bit tool 20a cutting blade 22 cutting water supply nozzle 24 cutting water

Claims (2)

A plurality of planned dividing lines are set on the surface in a grid, and a wafer is formed with a device in each area divided by the dividing planned lines, a bump formed above the device, and the bumps are embedded. And a sealing material covering the surface of the wafer.
In a cutting device provided with a cutting tool, the cutting tool is lowered toward the surface of the workpiece such that the lower end of the cutting tool is higher than the height position of the upper end of the bump, and the sealing material A plurality of linear cutting grooves having a depth not reaching the height position of the upper end of the bump are respectively formed along one of the first direction and a second direction intersecting the first direction. Cutting groove forming process,
After the cutting groove forming step, in a cutting tool provided with a cutting 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. And by supplying cutting water to the cutting edge of the cutting tool and cutting the upper part of the sealing material and the upper part of the bump whose exposed surface side is exposed, the bump from the sealing material And B. a cutting process for exposing a workpiece.   The method according to claim 1, wherein the first direction and the second direction are orthogonal to each other.