JP2012040653A - Method of grinding workpiece - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of grinding a workpiece capable of more reducing the thickness of the workpiece which is formed by gathering electronic component elements easy to be broken in a certain direction by in-feed grinding, and capable of preventing the electronic component elements from being broken and chipped.SOLUTION: In the method of grinding the workpiece, the workpiece 6 is disposed on a chuck table 12 so that the rotation center O of the chuck table 12 to be driven for rotation is positioned outside a lower surface of the workpiece 6. A grinding wheel 13 which is driven to rotate in the same direction as the chuck table 12 is made to abut on the top surface of the workpiece 6 while rotating the chuck table 12 to grind the workpiece 6 from the top surface thereof.

Description

  The present invention relates to a workpiece grinding method for grinding a workpiece that is scheduled to be divided into a plurality of electronic component elements. More specifically, the present invention relates to a workpiece grinding method that reduces the thickness of a workpiece by grinding the workpiece by in-feed grinding. The present invention relates to a grinding method.

  Along with the thinning of semiconductor elements, various grinding methods are used to reduce the thickness of a semiconductor wafer made of silicon or the like.

  For example, Patent Document 1 below discloses a workpiece grinding apparatus shown in FIG. In the workpiece grinding apparatus 101, a workpiece 103 is placed on a chuck table 104 that is rotationally driven.

  A grinding wheel 105 is disposed above the workpiece 103. The grinding wheel 105 is driven to rotate in the same direction as the chuck table 104 but at a higher speed than the chuck table 104. The grinding wheel 105 is rotationally driven around the rotation shaft 106, but can be moved in the vertical direction by the vertical movement device 107. When grinding, the workpiece 103 is placed so that the center of the lower surface of the workpiece 103 is positioned on the center of rotation on the upper surface of the chuck table 104. Then, the grinding wheel 105 is brought into contact with the upper surface of the rotating work 103 to grind the work 103. In this case, in order to uniformly grind the entire upper surface of the workpiece 103, the grinding wheel 105 is placed on the upper surface of the workpiece 103 so that the trajectory due to the rotation of the lower surface of the grinding wheel 105 passes through the rotation center of the upper surface of the workpiece 103. Abutted. Thus, the method of polishing while rotating both the workpiece and the grinding wheel in the same direction is called in-feed grinding.

  On the other hand, the following Patent Document 2 discloses a wafer grinding method in which in-feed grinding and creep feed grinding are combined. In Patent Document 2, first, a semiconductor wafer is ground in the same manner as the in-feed grinding method described in Patent Document 1. As shown in FIG. 10, in the grinding method described in Patent Document 2, a wafer 112 is placed on a chuck table 111 that is rotationally driven. In FIG. 10, the wafer 112 has already been ground by in-feed grinding. In in-feed grinding, the wafer 112 is placed on the chuck table 111 so that the center of rotation of the chuck table 111 is positioned at the center of the disk-shaped wafer 112. Next, while rotating the chuck table 111, the upper surface of the wafer 112 is ground by a grinding wheel.

  According to the infeed grinding, as shown in FIG. 10, a large number of grinding marks 113 extending radially outward from the rotation center 112 a of the wafer 112 are generated. In order to eliminate such grinding marks 113, in the grinding method described in Patent Document 2, the infeed-ground wafer 112 is rotated in the direction indicated by the arrow B while the chuck table 111 is moved in the direction indicated by the arrow A. Further polishing is performed by the grinding wheel 114. That is, the wafer 112 is further ground by creep feed grinding. Therefore, the grinding marks 113 can be eliminated, and a wafer having a smooth upper surface can be obtained.

JP-A-7-32252 JP 2010-16181 A

  In the in-feed grinding as described in Patent Document 1, many grinding marks 113 as shown in FIG. 10 are generated. By the way, a workpiece made of silicon or the like has a direction that is easy to cleave, that is, a direction that is easily cracked, depending on the crystal orientation. Accordingly, there is a region in the workpiece where the grinding trace extends in the same direction as the fragile direction or near the fragile direction. In such a region, there has been a problem that the chip that has been separated into pieces is likely to be broken or chipped in the process of dividing the workpiece.

  In the grinding method described in Patent Document 2, it is said that such grinding marks can be eliminated by creep feed grinding. However, since in-feed grinding and creep feed grinding are combined, there is a problem that the grinding apparatus becomes complicated and the cost of the apparatus is high. In addition, when creep feed grinding is further performed on a wafer whose thickness has been reduced by in-feed grinding, there has been a problem that the wafer is cracked or chipped during operations such as wafer transfer.

  Due to the above problems, creep feed grinding is not widely used in practice.

  In addition to semiconductor elements, various electronic component elements are required to be thinned at the assembly stage in order to reduce the thickness. Therefore, the grinding method as described above is used not only for wafers but also for grinding various electronic component element assemblies. However, in an assembly in which electronic component elements and the like having directions that are easily broken are gathered, there is a possibility that the ground electronic component elements may be cracked or chipped.

  The object of the present invention is to eliminate the above-mentioned disadvantages of the prior art, and to reduce the thickness of a work in which electronic component elements having a fragile direction are gathered by infeed grinding. An object of the present invention is to provide a method for grinding a workpiece, which is less likely to cause chipping.

  A workpiece grinding method according to the present invention is an assembly that is scheduled to be divided into a plurality of electronic component elements, and is a workpiece grinding method for grinding a workpiece having a fragile direction, and is rotationally driven. Placing the work on the table so that the center of rotation of the table is positioned outside the lower surface of the work and rotating the table; and on the upper surface of the work on the rotating table, A method of grinding a workpiece, comprising the step of abutting a grinding wheel that is rotationally driven in the same direction as the table and grinding the workpiece from the upper surface.

  In a specific aspect of the workpiece grinding method according to the present invention, a direction in which a grinding mark formed on the upper surface of the workpiece extends when the workpiece is ground by the grinding wheel intersects a direction in which the workpiece is easily cracked. It is. Therefore, it is possible to reliably suppress cracking and chipping.

  In another specific aspect of the workpiece grinding method according to the present invention, a plurality of the workpieces are arranged on the table so that the rotation center of the table is positioned outside the lower surface of each workpiece, and the grinding wheel The plurality of workpieces are ground. In this case, productivity can be improved.

  In still another specific aspect of the workpiece grinding method according to the present invention, the plurality of workpieces are uniformly distributed in a circumferential direction around the rotation center on the table. In this case, the processing efficiency can be further improved.

  In the workpiece grinding method according to the present invention, the workpiece is arranged such that the center of rotation of the chuck table is located outside the lower surface of the workpiece, and the grinding wheel is brought into contact with the upper surface of the workpiece while rotating the chuck table. Therefore, the grinding trace does not extend radially from the center of the workpiece, and the grinding trace extends in substantially the same direction on the upper surface of the workpiece. Therefore, by placing the work on the chuck table so that the direction in which the work is easily cracked and the grinding marks intersect, the work after grinding and the electronic component elements obtained by dividing the work can be reliably cracked or chipped. Can be suppressed.

  Therefore, it is possible to obtain an electronic component element that is less prone to cracking and chipping with high productivity by simple infeed grinding without using creep feed grinding with complicated equipment and processes.

It is a typical top view for demonstrating the positional relationship of a chuck table, a workpiece | work, and a grinding wheel in the grinding method of the workpiece | work of one Embodiment of this invention. It is a front view which shows schematic structure of the grinding device used for the grinding method of the workpiece | work which concerns on one Embodiment of this invention. (A)-(c) is each typical front sectional drawing for demonstrating the process in which a workpiece | work is ground by the workpiece | work grinding process in one Embodiment of this invention. It is a typical top view which shows the positional relationship of the chuck table in the grinding method of the workpiece | work of a comparative example, a workpiece | work, and a grinding wheel. It is a stereomicrograph for demonstrating the crack in each electronic component chip | tip in a workpiece | work in the grinding method of the workpiece | work of a comparative example. It is a schematic top view which shows the relationship between the rotation center position in the grinding method of the workpiece | work of a comparative example, and the part in which the crack and chipping have arisen in a workpiece | work. It is a typical top view showing the relation between the rotation center position in the grinding method of the work of an embodiment, and the part in which the crack and chipping in a work have arisen. It is a typical top view for demonstrating the positional relationship of the workpiece | work, the chuck table, and the grinding wheel in the grinding method of the workpiece | work which concerns on the modification of this invention. It is a typical front view for demonstrating the conventional workpiece grinding apparatus. It is a perspective view for demonstrating the other example of the grinding method of the conventional workpiece | work.

  Hereinafter, the present invention will be clarified by describing specific embodiments of the present invention with reference to the drawings.

  As a workpiece grinding method according to an embodiment of the present invention, a process of grinding a workpiece in which a plurality of surface acoustic wave element chips mounted on a substrate are integrated with a resin will be described.

As shown in FIG. 3A, a plurality of regions including a plurality of electrode lands 2a and 2b are formed on a substrate 1 made of alumina. In each region, a SAW element chip 3 using a piezoelectric substrate made of LiTaO ₃ is mounted by a flip chip bonding method. That is, the input / output and ground pads (not shown) of each SAW element chip 3 are electrically connected to the electrode lands 2a and 2b via the bumps 4a and 4b. Further, a resin layer 5 is formed on the substrate 1 so as to cover the plurality of SAW element chips 3. As described above, the workpiece 6 is an assembly of SAW elements in which a plurality of SAW element chips 3 mounted on the substrate 1 are integrated by the resin layer 5. Therefore, by dividing the work 6 later, a plurality of separated SAW elements can be obtained.

  In the workpiece grinding method of this embodiment, the workpiece 6 shown in FIG. 3A is polished from the upper surface, and the thickness thereof is reduced as shown in FIGS. 3B and 3C. In FIG. 3B, the resin layer 5 is ground from the upper surface of the work 6 and the upper surface of the piezoelectric substrate of the SAW element chip 3 is exposed. In this embodiment, the workpiece 6 is further polished, and the workpiece 6 is ground so as to reduce the thickness of the piezoelectric substrate of the SAW element chip 3 as shown in FIG. Thereby, a SAW element chip 3 having a piezoelectric substrate with a desired thickness is obtained.

  In grinding the workpiece 6, a workpiece grinding apparatus 11 shown in FIG. 2 is used. The workpiece grinding apparatus 11 is configured in substantially the same manner as the workpiece grinding apparatus 101 used for the conventional in-feed grinding shown in FIG. That is, the workpiece 6 is placed on the chuck table 12 that is rotationally driven and fixed by vacuum suction. The chuck table 12 is rotationally driven by a rotational drive source such as a motor built in the workpiece grinding apparatus 11.

  On the other hand, the grinding wheel 13 is connected to the vertical movement device 14. The grinding wheel 13 is moved in the vertical direction by the vertical movement device 14. Further, the grinding wheel 13 is connected to the rotary shaft 15, and the grinding wheel 13 is rotationally driven by rotationally driving the rotary shaft 15. The grinding wheel 13 has a shape in which an annular wheel portion 13b is connected to the lower surface of a substantially disc-shaped support portion 13a. A plurality of grindstones are fixed to the lower surface of the annular wheel portion 13b along the circumferential direction.

  FIG. 1 is a schematic plan view showing the positional relationship among the chuck table 12, the workpiece 6, and the wheel portion 13 b of the grinding wheel 13. Here, in order to illustrate a plurality of grindstones, the support portion 13a of the grinding wheel 13 is omitted, the wheel portion 13b is watermarked, and a plurality of grindstones 13c below are illustrated. The plurality of grindstones 13c are distributed and arranged at equal intervals in the circumferential direction of the wheel portion 13b.

  The workpiece grinding method of this embodiment is characterized in that the workpiece 6 is placed on the chuck table 12 so that the rotation center O of the chuck table 12 is located outside the lower surface of the workpiece 6 as shown in FIG. It is to perform polishing. In other words, the workpiece 6 is arranged at a position outside the rotation center O. In the workpiece grinding apparatus 11, the chuck table 12 is rotated counterclockwise around the rotation center O as indicated by the arrow in the figure.

  On the other hand, the grinding wheel 13 is also rotated counterclockwise, that is, in the same direction as the chuck table 12. That is, the wheel portion 13b is rotated counterclockwise around the center P of the annular wheel portion 13b as indicated by the arrow in the figure. The rotational speed of the grinding wheel 13 is higher than the rotational speed of the chuck table 12.

  When the grinding wheel 13 is rotated, the plurality of grindstones 13c fixed to the lower surface of the wheel portion 13b move counterclockwise. The locus by the movement of the grindstone 13c draws a circle.

  When grinding the workpiece 6, the vertical movement device 14 shown in FIG. 2 is driven to bring the rotating grinding wheel 13 into contact with the upper surface of the workpiece 6. Therefore, the upper surface of the workpiece 6 is ground by the grindstone 13c that describes the locus of the circle. In this case, the grinding wheel 13 is positioned with respect to the chuck table 12 so that the circle which is the locus by the movement of the grindstone 13c passes through the rotation center O.

  The chuck table 12 is rotated, and the workpiece 6 is rotated counterclockwise around the rotation center O on the chuck table 12. Then, the wheel portion 13b of the grinding wheel is rotated at a relatively high rotational speed in the counterclockwise direction as described above. Accordingly, the entire upper surface of the workpiece 6 is polished by the grinding wheel 13. Therefore, the workpiece 6 can be ground so that the upper surface of the workpiece 6 is thinned from the state shown in FIG. 3A to the state shown in FIG. 3C, that is, the thickness of the workpiece 6 is reduced.

  As described above, the workpiece grinding method of this embodiment is an infeed grinding method in which the apparatus and the process are relatively simple. In the infeed grinding method, grinding marks are generated on the upper surface of the workpiece 6. However, since the workpiece 6 is placed on the chuck table 12 at a position deviating from the rotation center O, the plurality of grinding marks S formed on the upper surface of the workpiece 6 extend in substantially the same direction. Here, “substantially the same direction” does not necessarily mean that the plurality of grinding traces S are parallel, but means that the curved grinding traces S extend in substantially the same direction at a predetermined interval. .

  Accordingly, when there is a direction in which the workpiece 6 is likely to be cracked or chipped, if the workpiece 6 is arranged so that the direction in which the crack or chip is likely to occur and the grinding mark S intersect, Cracking and chipping can be suppressed. Further, it is possible to suppress cracks and chippings in individual SAW elements obtained by dividing the workpiece 6 into regions where the SAW element chips 3 are mounted.

  Such an effect of the present embodiment will be specifically described by comparing with the grinding method of the comparative example shown in FIG.

  FIG. 4 is a schematic plan view for explaining a conventional method of grinding a workpiece by in-feed grinding as described in Patent Document 1. Here, in order to facilitate comparison, the reference numbers of the chuck table and the grinding wheel are the same as those in the above embodiment. In the conventional in-feed grinding method, the workpiece W is placed on the chuck table 12 so that the center of the lower surface of the workpiece W is positioned at the rotation center O of the chuck table 12. Then, the grinding wheel 13 is positioned and rotated so that the locus drawn by the grinding wheel 13c of the grinding wheel 13 passes through the rotation center O. In this case, the workpiece W is rotated around the rotation center O. Accordingly, the entire upper surface of the workpiece W can be ground, but the grinding trace 121 extends radially from the rotation center O on the upper surface of the workpiece 6. Therefore, the directions of the plurality of grinding marks 121 are various. Therefore, when the direction in which the workpiece W is easily cracked is, for example, a direction parallel to the diagonal direction of the upper surface of the rectangular workpiece W, the workpiece W is cracked or chipped in the portion where the grinding mark 121 is generated. Is likely to occur.

  On the other hand, in the workpiece 6 shown in FIG. 1, the plurality of grinding marks S have substantially the same direction so as to extend from one long side to the other long side of the workpiece 6 having a rectangular planar shape. ing. Therefore, for example, when the direction in which the workpiece is easily broken is a diagonal direction or a direction connecting a pair of short sides, the direction in which the workpiece is easily broken and the direction of the grinding mark S intersect with each other. .

In the present embodiment, as described above, as shown in FIGS. 3A to 3C, the thickness of the resin layer 5 is ground, and further, the SAW element chip 3 is ground until the thickness of the piezoelectric substrate is reduced. When the piezoelectric substrate is made of LiTaO _3, there is a direction that is easy to cleave due to the crystal orientation of LiTaO ₃ .

FIG. 5 is a stereomicrograph showing a state where cracks are generated in the piezoelectric substrate portion of each SAW element chip when the workpiece 6 is ground by the method of the comparative example shown in FIG. Here, the planar shape shows a structure in which the upper surfaces of a plurality of rectangular piezoelectric substrates are arranged in a matrix. In the plurality of piezoelectric substrates, cracks extending in a substantially diagonal direction are generated as indicated by arrows. A piezoelectric single crystal such as LiTaO ₃ or LiNbO ₃ has a cleavage direction depending on the crystal orientation. In the present embodiment, the crack direction indicated by an arrow in FIG. 5 corresponds to the cleavage direction of LiTaO ₃ used in the present embodiment. Therefore, when the cleavage direction coincides with or is close to the grinding mark, it is considered that a crack as shown in the figure has occurred.

  FIG. 6 is a plan view schematically showing the distribution of the cracked and chipped portions in the plurality of piezoelectric substrates in the workpiece W in the comparative example. FIG. 6 schematically shows the positions of the SAW element chips arranged in a matrix located in the workpiece W, and the hatched portion B indicates the above-described portion of the SAW element chip piezoelectric substrate. Indicates a portion where cracking or chipping has occurred. That is, a hatched portion B in FIG. 6 indicates a portion where the crack is generated. Further, in the SAW element chip portion C to which the diagonal hatching in the reverse direction is given, it indicates that chipping has occurred. Note that the chipping means that the piezoelectric substrate is chipped.

  As is apparent from FIG. 6, it can be seen that many chippings and cracks occur along the diagonal direction of the workpiece with respect to the rotation center O.

  FIG. 7 is a schematic plan view showing the distribution of portions where chipping and cracks occur when the workpiece 6 is similarly ground in the embodiment. As is apparent from FIG. 7, it can be seen that in the above embodiment, cracks and chipping hardly occur.

As described above, the workpiece 6 is shifted from the rotation center O of the chuck table 12, and the plurality of grinding marks S extend in a direction connecting a pair of long sides of the rectangular workpiece. This is because it intersects the cleavage direction of LiTaO ₃ .

  Therefore, if the workpiece is arranged in such a way that the grinding mark intersects the direction in which the workpiece being used is easily cracked, for example, the cleavage direction of the single crystal as described above, cracks and chips in the workpiece can be obtained as in the above embodiment. It turns out that it can suppress effectively.

  In placing the workpiece 6 on the chuck table, the workpiece 6 may be shifted from the rotation center so that the rotation center O is not located on the lower surface of the workpiece as described above. What is necessary is just to consider so that the direction in which the workpiece | work 6 is easy to crack and the direction where a grinding trace extends cross | intersect. The direction in which the workpiece is easily broken is known in advance depending on the material of the workpiece 6 to be used. Further, the direction of the grinding mark can be easily estimated from the mounting position of the workpiece 6 and the trajectory drawn by the plurality of grindstones 13 c provided on the grinding wheel 13. Therefore, it is possible to easily place the workpiece 6 on the chuck table 12 so that the cracking direction and the grinding mark intersect.

In the above embodiment, cracks and chipping due to grinding of LiTaO ₃ were suppressed, but the present invention is not limited to piezoelectric single crystals such as LiTaO ₃ and LiNbO _3, and various materials other than semiconductor wafers such as silicon wafers or semiconductors. However, it can be widely used for grinding electronic component materials having a direction that is easily broken in a specific direction.

  In the above embodiment, as shown in FIG. 1, one workpiece 6 is arranged on the chuck table 12. However, as shown in FIG. 8, a plurality of workpieces 6 </ b> A to 6 </ b> D are rotated on the chuck table 12. Dispersion may be uniformly distributed in the circumferential direction around the center O and ground. Even in this case, the plurality of workpieces 6A to 6C are arranged so that the rotation center O is positioned outside the lower surfaces of the workpieces 6A to 6D, in other words, the workpieces 6A to 6D are displaced from the rotation center O of the chuck table 12. What is necessary is just to arrange. Thereby, the plurality of workpieces 6A to 6D can be polished at the same time, and the productivity can be improved as compared with the above embodiment.

DESCRIPTION OF SYMBOLS 1 ... Board | substrate 2a, 2b ... Electrode land 3 ... SAW element chip 4a, 4b ... Bump 5 ... Resin layer 6, 6A-6D ... Workpiece | work 11 ... Work grinding apparatus 12 ... Chuck table 13 ... Grinding wheel 13a ... Support part 13b ... Wheel Part 14 ... Vertical movement device 15 ... Rotating shaft

Claims (4)

It is an assembly that is scheduled to be divided into a plurality of electronic component elements, a workpiece grinding method for grinding a workpiece having a fragile direction,
Placing the work on the table and rotating the table so that the rotation center of the table to be rotated is positioned outside the lower surface of the work;
A method for grinding a workpiece, comprising: bringing a grinding wheel that is rotationally driven in the same direction as the table into contact with an upper surface of the workpiece on the rotating table, and grinding the workpiece from the upper surface.   The workpiece grinding method according to claim 1, wherein a direction in which a grinding mark formed on the upper surface of the workpiece extends when the workpiece is ground by the grinding wheel is a direction intersecting with a direction in which the workpiece is easily cracked.   The plurality of workpieces are arranged on the table so that the rotation center of the table is positioned outside the lower surface of each workpiece, and the plurality of workpieces are ground by the grinding wheel. Workpiece grinding method.   The workpiece grinding method according to claim 3, wherein the plurality of workpieces are uniformly distributed in a circumferential direction around the rotation center on the table.

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