JP2014097551A - Grinding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grinding method allowing reduction of the grinding time, compared with conventional methods.SOLUTION: A grinding method is for grinding a wafer with grinding wheels having a grinding stone and comprises a holding step of holding a first surface side of a wafer with a chuck table in a rotatable way and making exposed a second surface opposite to the first surface, a grinding step of bringing a first grinding wheel having a diameter equal to or greater than the diameter of the wafer and a second grinding wheel having a diameter equal to or greater than the diameter of the wafer each into contact with the second surface of the wafer and rotating the first grinding wheel and the second grinding wheel, while rotating the wafer, to cause the first grinding wheel and the second grinding wheel to grind and feed the wafer in the approach direction in order to grind the wafer simultaneously by the first and second wheels. In the grinding step, the outer periphery of the first griding wheel and the outer periphery of the second wheel are each positioned near the center.

Description

  The present invention relates to a grinding method for grinding a wafer such as a semiconductor wafer.

  A semiconductor wafer in which a number of devices such as IC and LSI are formed on the surface, and each device is partitioned by a line to be divided (street), the back surface is ground by a grinding machine and processed to a predetermined thickness. A dividing line is cut by a cutting device (dicing device) to be divided into individual devices, and the divided devices are widely used in various electric devices such as mobile phones and personal computers.

  In order to reduce the size and weight of a semiconductor chip, the back surface of the wafer is usually ground to a predetermined thickness before the semiconductor wafer is cut along the planned dividing line and separated into individual device chips. Back grinding to be processed is performed.

  A grinding apparatus for grinding a wafer includes a chuck table having a holding surface for holding a wafer, and a grinding unit for rotatably supporting a grinding wheel in which a grinding wheel for grinding the wafer held on the chuck table is annularly arranged. And a grinding feed mechanism that moves the grinding unit toward or away from the chuck table to reduce the wafer to a desired thickness.

  In such a grinding apparatus, the position where the chuck table and the tip of the grinding wheel contact in the grinding feed direction (Z-axis direction) is set as the origin position, and the grinding amount (finish thickness) of a workpiece such as a wafer is controlled. Yes.

  When the chuck table is replaced with a new chuck table, or when the grinding wheel is replaced with a new grinding wheel, the workpiece cannot be accurately ground unless this origin positioning (setup) is performed.

  Conventionally, a manual setup method in which manual setup is performed has been the mainstream. However, since this has a problem that setup takes time, Japanese Patent Laid-Open No. 2012-135853 automatically performs origin position setting (setup). A grinding device capable of this is disclosed.

  Japanese Patent Laying-Open No. 2002-200545 discloses a grinding apparatus that can finish to a uniform thickness without causing a finished surface residue on a workpiece in a grinding apparatus having two grinding means. Yes.

JP 2012-135853 A JP 2002-200545 A

  By adopting the auto setup as disclosed in Patent Document 1 and the first and second grinding means as disclosed in Patent Document 2, the productivity of wafer grinding can be improved. In order to further improve productivity, there is a demand for further shortening of the grinding time.

  The present invention has been made in view of these points, and an object of the present invention is to provide a grinding method capable of shortening the grinding time as compared with the prior art.

  According to the present invention, there is provided a grinding method for grinding a wafer with a grinding wheel having a grinding wheel, wherein the first surface side of the wafer is rotatably held by a chuck table and a second surface opposite to the first surface is exposed. A holding step, a first grinding wheel having a diameter equal to or larger than the diameter of the wafer, and a second grinding wheel having a diameter equal to or larger than the diameter of the wafer are brought into contact with the second surface of the wafer, respectively. The first grinding wheel and the second grinding wheel are rotated while rotating the wafer, and the first grinding wheel and the second grinding wheel are ground and fed in the approaching direction with respect to the wafer. A grinding step in which the first grinding wheel and the second grinding wheel are ground simultaneously, wherein the grinding step includes an outer periphery of the first grinding wheel and the second grinding. Grinding method characterized by the outer periphery of the eel is positioned substantially at the center of each wafer is provided.

  In the grinding method of the present invention, since the wafer is ground at the same time by the first grinding wheel and the second grinding wheel, the grinding time can be shortened as compared with the prior art. Furthermore, since the wafer is ground simultaneously by the first grinding wheel and the second grinding wheel, it is possible to suppress the consumption of the grinding wheel as compared with the conventional case, and the replacement frequency of the grinding wheel can be reduced.

  In addition, when replacing the grinding wheel, it is necessary to perform various operations such as dressing of the new grinding wheel, setup work to find the origin of the height position, etc. Since the frequency of these various operations is also reduced by reducing the replacement frequency of the wafer, the productivity of wafer grinding is improved.

It is a surface side perspective view of a semiconductor wafer. It is a back surface side perspective view of the semiconductor wafer by which surface protection tape was stuck on the surface. It is a front view which shows a holding | maintenance step. It is a principal part front view of the grinding device which shows the grinding method of a 1st embodiment. It is a plane schematic diagram which shows the arrangement | positioning relationship of the grinding method of 1st Embodiment. It is a principal part side view of the grinding device which shows the grinding method of 2nd Embodiment. It is a plane schematic diagram which shows the arrangement | positioning relationship of the grinding method of 2nd Embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1, a perspective view of a semiconductor wafer 11 (hereinafter simply referred to as a wafer) 11 before being processed to a predetermined thickness is shown.

  A wafer 11 shown in FIG. 1 is made of, for example, a silicon wafer having a thickness of 700 μm. A plurality of division lines (streets) 13 are formed in a lattice shape on the surface 11a. A device 15 such as an IC or LSI is formed in each partitioned area.

  The wafer 11 configured as described above includes a device region 17 in which the device 15 is formed and an outer peripheral surplus region 19 surrounding the device region 17 on the surface 11a. A notch 21 is formed on the outer periphery of the wafer 11 as a mark indicating the crystal orientation of the silicon wafer.

  Before grinding the back surface 11b of the wafer 11, the surface protective tape 23 is attached to the front surface 11a of the wafer 11 by a protective tape attaching process. Therefore, the front surface 11a of the wafer 11 is protected by the surface protection tape 23, and the back surface 11b is exposed as shown in FIG.

  In the grinding method of the present invention, as shown in FIG. 3, the front surface (first surface) 11a side of the wafer 11 is rotatably held by the chuck table 10 of the grinding device, and the rear surface (second surface) 11b of the wafer 11 is held. Let it be in an exposed state (holding step).

  A grinding method according to the first embodiment of the present invention for grinding the back surface 11b of the wafer 11 after holding the wafer 11 by the chuck table 10 will be described with reference to FIGS. In FIG. 4, the chuck table 10 is moved in the X-axis direction by the chuck table feed mechanism. The first grinding unit 10 and the second grinding unit 12A are arranged in alignment in the X-axis direction parallel to the moving direction of the chuck table 10. As another embodiment, the first and second grinding units 12 and 12A may move instead of the chuck table 10.

  The first grinding unit 12 includes a spindle 14 that is rotationally driven by a motor, a wheel mount 16 that is fixed to the tip of the spindle 14, and a first grinding wheel 18 that is detachably attached to the wheel mount 16 with screws (not shown). Contains. The first grinding wheel 18 includes an annular base 20 and a plurality of grinding wheels 22 fixed to the outer periphery of the lower end of the annular base 20.

  Similarly, the second grinding unit 12A includes a spindle 14 that is rotationally driven by a motor, a wheel mount 16 that is fixed to the tip of the spindle 14, and a grinding wheel 18A that is detachably attached to the wheel mount 16 by screws (not shown). Is included. The grinding wheel 18 </ b> A includes an annular base 20 and a plurality of grinding wheels 22 fixed to the outer periphery of the lower end of the annular base 20.

  In the grinding method of the present embodiment, the outer periphery of the first grinding wheel 12 and the outer periphery of the second grinding wheel 12A are spaced apart by about 1 to 2 mm, and the outer periphery of the first grinding wheel 18 and the second grinding wheel 18A are further separated. The outer periphery is positioned at the approximate center of the wafer 11, but the grinding wheel 22 of the first grinding wheel 18 is disposed so as to pass through the center 11 c of the wafer 11. The wafer 11 is sucked and held on the chuck table 10 so that the center 10a of the chuck table 10 and the center 11c of the wafer 11 coincide.

  In the grinding method of the present embodiment, the first grinding unit 10 is rotated while rotating the chuck table 10 in the direction of arrow a at about 300 rpm and rotating the first grinding wheel 18 and the second grinding wheel 18A in the direction of arrow b at about 6000 rpm. 12 and the grinding unit feeding mechanism of the second grinding unit 12A is driven, and the grinding wheel is fed while grinding the first grinding wheel 18 and the second grinding wheel 18A downward at a predetermined grinding feed speed (for example, 6 μm / s). At 22, the back surface 11 b of the wafer 11 is ground.

  Thus, since the back surface 11b of the wafer 11 is ground simultaneously by the first grinding wheel 18 and the second grinding wheel 18A, the grinding time can be shortened as compared with the prior art. Further, since the grinding wheel 22 of the first grinding wheel 18 is disposed so as to pass through the center 11 c of the wafer 11, there is no possibility of causing a grinding residue on the wafer 11.

  Furthermore, since the wafer 11 is ground simultaneously by the first grinding wheel 18 and the second grinding wheel 18A, it is possible to suppress wear of the grinding wheel 22 as compared with the conventional case, and the first grinding wheel 18 and the second grinding wheel 18A. Replacement frequency can be reduced.

  When processing a plurality of wafers 11 continuously, the chuck table 10 is moved relative to the first and second grinding units 18 and 18A every time a predetermined number of wafers 11 are processed, and the center 11c of the wafer 11 is moved. Are alternately positioned on the grinding wheel 22 of the first grinding wheel 18 and the grinding wheel 22 of the second grinding wheel 18A, respectively, so that the wear amount of the grinding wheel 22 of the first and second grinding wheels 18 and 18A is reduced. Can be made equivalent.

  Next, with reference to FIG.6 and FIG.7, the grinding method of 2nd Embodiment of this invention is demonstrated. In the grinding apparatus employed in the present embodiment, the first grinding unit 12 and the second grinding unit 12A are aligned in the Y axis direction, which is the moving direction of the chuck table 10, with respect to the chuck table 10 moving in the Y axis direction. Has been placed.

  The first grinding wheel 18 of the first grinding unit 12 and the second grinding wheel 18A of the second grinding unit 12A are arranged 1 to 2 mm apart. Further, when the grinding of the wafer 11 is started, the outer periphery of the first grinding wheel 18 and the outer periphery of the second grinding wheel 18A are positioned at the approximate center 11c of the wafer 11 sucked and held by the chuck table 10, respectively, and grinding is started. .

  In the grinding method of the present embodiment, the first grinding wheel 18 and the second grinding wheel 18A are rotated at about 6000 rpm in the direction indicated by the arrow b while the chuck table 10 is rotated at about 300 rpm in the direction of the arrow a. 22 is pressed against the back surface 11b of the wafer 11, and the first grinding wheel 18 and the second grinding wheel 18A are ground and fed downward at a predetermined grinding feed speed (for example, 6 μm / s), thereby grinding the back surface 11b of the wafer 11. To implement.

  If the chuck table 10 is rotated and ground without moving, grinding remains on the back surface 11b of the wafer 11. Therefore, the back surface 11b of the wafer 11 is ground while moving the chuck table 10 back and forth in the Y-axis direction at a predetermined timing. To implement.

  Also in the grinding method of the present embodiment, since the wafer 11 is ground at the same time by the first grinding wheel 18 and the second grinding wheel 18A, the grinding time can be shortened as compared with the prior art. Moreover, it becomes possible to suppress wear of the grinding wheel 22 as compared with the conventional case, and the replacement frequency of the first grinding wheel 18 and the second grinding wheel 18A can be reduced.

  In the first and second embodiments described above, the holding surface of the chuck table 10 may not be flat but may be formed in a conical shape having a slight inclined surface.

  In the embodiment described above, an example in which the semiconductor wafer 11 is ground as a workpiece has been described. However, the workpiece is not limited to the semiconductor wafer 11, and the present invention is also applicable to grinding of other wafers such as an optical device wafer. The grinding method can be applied.

DESCRIPTION OF SYMBOLS 10 Chuck table 11 Semiconductor wafer 12 1st grinding unit 12A 2nd grinding unit 18 1st grinding wheel 18A 2nd grinding wheel 22 Grinding wheel 26, 26A Rotation locus of grinding wheel

Claims (1)

A grinding method for grinding a wafer with a grinding wheel having a grinding wheel,
A holding step in which the first surface side of the wafer is rotatably held by the chuck table and the second surface opposite to the first surface is exposed;
A first grinding wheel having a diameter equal to or larger than the diameter of the wafer and a second grinding wheel having a diameter equal to or larger than the diameter of the wafer are brought into contact with the second surface of the wafer, and the wafer is rotated while rotating the wafer. The first grinding wheel and the second grinding wheel are rotated, and the first grinding wheel and the second grinding wheel are ground and fed in the approaching direction with respect to the wafer, whereby the wafer is fed to the first grinding wheel and the first grinding wheel. A grinding step for grinding simultaneously with two grinding wheels,
In the grinding step, the outer periphery of the first grinding wheel and the outer periphery of the second grinding wheel are positioned at substantially the center of the wafer, respectively.

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