JP6016473B2 - Wafer processing method - Google Patents

Description

  The present invention relates to a wafer processing method in which a chamfered portion of a wafer having a chamfered portion on its outer periphery is removed with a cutting blade.

  In the manufacturing process of a semiconductor device, a grid-like division planned line called street is formed on the surface of a wafer made of silicon or a compound semiconductor. Then, a device such as an IC or LSI is formed in each area partitioned by the division lines.

  These wafers are ground and / or polished to a predetermined thickness and then thinned to a predetermined thickness, and then cut along the streets with a cutting device and divided into individual chips to manufacture semiconductor devices. . The semiconductor device manufactured in this way is widely used in various electric devices such as mobile phones and personal computers.

  A chamfered portion having an arc surface extending from the front surface to the back surface is formed on the outer periphery of the wafer. Therefore, if the wafer is thinned by grinding the backside of the wafer, the knife edge formed by the circular arc surface and the ground surface remains in the chamfered part, which is dangerous, and the outer periphery is chipped, resulting in deterioration of the device quality. I will let you.

  Japanese Patent Application Laid-Open No. 2000-173961 discloses a so-called edge trimming method, ie, a peripheral processing method in which a chamfered portion of a wafer is removed with a cutting blade before grinding the back surface of the wafer.

  The chamfered portion is removed, for example, by performing circular processing with a cutting blade having a thickness of 0.5 mm to 1 mm. The wafer from which the chamfered portion has been removed is ground along the back surface by a grinding apparatus, and then cut along the street with a cutting blade having a thickness of about 30 μm, for example, and divided into individual chips.

  When edge trimming is performed on a wafer with a cutting blade, a cutting blade having a higher cutting force is used because a larger processing load is applied to the cutting blade than with normal cutting. A cutting blade having a cutting force is a cutting blade having characteristics such as coarse grain size and / or high concentration.

JP 2000-173961 A JP-A-8-107092

  However, when the outer periphery of the wafer is cut with a cutting blade having a cutting force, large or many minute chips called chipping generated on the wafer are generated. If chipping is large or large, the wafer may be damaged starting from the chipping, and reduction of the chipping size and generation amount are desired.

  The present invention has been made in view of these points, and an object of the present invention is to provide a wafer processing method that can reduce chipping size and chipping generation amount.

According to the present invention, there is provided a wafer processing method in which a chamfered portion is removed by cutting an outer peripheral annular removal region having a predetermined radial direction from the outer periphery of a wafer having a chamfered portion on the outer periphery with a cutting blade attached to one spindle. The outer circumferential annular removal region having the predetermined width is at least twice as thick as the rough cutting blade on one surface side from the center in the thickness direction, and the other surface on the back surface of the one surface is the finishing cutting blade from the center in the thickness direction. The rough cutting blade and the finishing cutting blade are prepared with a laminated cutting blade having the same outer diameter, a laminated cutting blade preparation step, a holding step of holding a wafer with a chuck table, and the roughing blade of the laminated cutting blade. the outer peripheral ring of the cutting blade side held on the chuck table in a first direction with respect to the center of the chuck table wafer Coarse cutting in which the chamfered portion is partially removed by cutting the outer peripheral annular removal region with the stacked cutting blade by cutting the chuck table to at least the first depth by being positioned at the removal region and rotating the chuck table at least once. And after performing the rough cutting step, the finish cutting blade side of the laminated cutting blade is held on the chuck table opposite to the first direction with respect to the center of the chuck table . The chamfer is formed by cutting the outer peripheral annular removal region with the laminated cutting blade by positioning the outer peripheral annular removal region at a second depth deeper than the first depth and rotating the chuck table at least once. And a finishing cutting step of partially removing the portion.

  Preferably, the finishing cutting blade is composed of any one of or a combination of a fine abrasive grain, a soft bond agent, and a low concentration of abrasive grains compared to a coarse cutting blade.

  According to the wafer processing method of the present invention, after rough cutting is performed on the rough cutting blade side of the laminated cutting blade, the laminated cutting blade is further cut into the wafer and finish cutting is performed on the finish cutting blade side.

  In the finish cutting by the finish cutting blade side, since the rough cutting is performed on the rough cutting blade side in advance, the cutting removal volume is small compared to cutting to a predetermined depth at a time, so the generated chipping size can be reduced, The amount of chipping can be reduced.

It is a surface side perspective view of a semiconductor wafer. It is a top view which shows an outer periphery cyclic | annular removal area | region. It is sectional drawing which shows an outer periphery cyclic | annular removal area | region. It is a side view of the lamination cutting blade with which the spindle was equipped. It is a partial cross section side view which shows a holding | maintenance step. It is a top view which shows a rough cutting step. It is a partial cross section side view which shows a rough cutting step. It is a top view which shows a finish cutting step. It is a partial cross section side view which shows a finish cutting step.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1, there is shown a front side perspective view of a semiconductor wafer (hereinafter sometimes simply referred to as a wafer) 11 to be processed by the processing method of the present invention.

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

  The wafer 11 thus configured includes a device region 17 in which the device 15 is formed and an outer peripheral surplus region 19 surrounding the device region 17 at the flat end portion of the surface thereof. An arc-shaped chamfered portion 11 e is formed on the outer peripheral portion of the wafer 11. Reference numeral 21 denotes a notch as a mark indicating the crystal orientation of the silicon wafer.

  Referring to FIG. 2, there is shown a plan view for explaining an outer peripheral annular removal region 23 having a predetermined radial width W1 from the outer periphery of the wafer 11 to be cut and removed by the processing method of the present invention. FIG. 3 is a cross-sectional view showing the outer peripheral annular removal region 23. The outer peripheral annular removal region 23 has a predetermined width W1 in the radial direction from the outer periphery of the wafer 11 that can remove the chamfered portion 11e up to a depth t1 that reaches the grinding finish thickness.

  In the wafer processing method of the present invention, a layered cutting blade preparation step for preparing the layered cutting blade 16 as shown in FIG. 4 suitable for performing the processing method of the present invention is performed. In FIG. 4, the cutting unit 12 includes a spindle 14 that is rotationally driven by a motor, and a laminated cutting blade 16 that is attached to the tip of the spindle 14.

  The laminated cutting blade 16 has a thickness that is at least twice that of the outer peripheral annular removal region 23 having a predetermined width W1, one side from the center in the thickness direction is a rough cutting blade 16a, and the other side is finished from the center in the thickness direction. It consists of a cutting blade 16b.

  The finish cutting blade 16b is composed of any one or a combination of finer abrasive grains, softer bonding agent, and lower abrasive concentration compared to the coarse cutting blade 16a.

  Preferably, the rough cutting blade 16a is composed of an electroformed blade, a metal bond blade or the like, and the finish cutting blade 16b is composed of a metal resin blade, a resin blade or the like.

  After preparing the laminated cutting blade 16 in the laminated cutting blade preparation step, as shown in FIG. 5, the wafer 11 is sucked and held by the chuck table 10 of the cutting apparatus to expose the surface 11a.

  Next, as shown in FIGS. 6 and 7, the rough cutting blade 16 a side of the laminated cutting blade 16 is positioned in the outer peripheral annular removal region 23 of the wafer 11 held by the chuck table 10, and is cut to the first depth. The chamfered portion is cut by cutting the outer peripheral annular removal region 23 with the laminated cutting blade 16 by rotating the chuck table 10 at least once in the arrow R1 direction while rotating the laminated cutting blade 16 in the direction of arrow A at a high speed (for example, 30000 rpm). A rough cutting step is performed to partially remove 11e.

  In this rough cutting step, the chuck table 10 is rotated in a direction in which the rotation direction A of the laminated cutting blade 16 and the rotation direction R1 of the wafer 11 are in the same direction at a processing point where the laminated cutting blade 16 and the wafer 11 contact each other. preferable. This cutting method is called down cut.

  The first cutting depth in this rough grinding step is cut 1 to 20 μm shallower than the final target depth. At the time of this cutting, the laminated cutting blade 16 may be lowered from above the wafer 11 for cutting, or after the laminated cutting blade 16 is positioned at a predetermined height on the outer peripheral side of the wafer 11, the laminated cutting blade 16 is moved with respect to the wafer 11. Then, it may be cut into the first depth by relatively moving in the approaching direction.

  After performing the rough cutting step, as shown in FIGS. 8 and 9, the cutting unit 12 is moved in the Y-axis direction so that the finish cutting blade 16 b side of the laminated cutting blade 16 is on the wafer 11 on the opposite side to that during rough cutting. It is positioned in the annular cutting groove 18 formed by rough cutting of the first and second depths deeper than the first depth, and the chuck table 10 is rotated at least once in the direction of the arrow R2 while rotating the laminated cutting blade 16 at a high speed. Thus, the finishing cutting step of cutting the annular cutting groove 18 with the finishing cutting blade 16b and partially removing the chamfered portion 11e is performed. When this finishing cutting step is performed, the annular cutting groove 18 is cut to the final target depth.

  In the above-described finishing cutting step, the chuck table 10 is rotated so that the rotation direction A of the finishing cutting blade 16b and the rotation direction R2 of the wafer 11 are in the same direction at the processing point where the finishing cutting blade 16b and the wafer 11 contact each other. Although the down cut is performed, the finish cutting step may be performed by the upper cut with the rotation direction of the chuck table 10 being the opposite direction.

  When the finish cutting step is completed, the chamfered portion 11e of the wafer 11 is partially removed, and the bottom of the annular cutting groove 18 formed by the rough cutting step is again cut by the finishing cutting blade 16b. The bottom of is flattened.

  After the finish cutting step, the surface 11a of the wafer 11 is affixed to the surface 11a, and the surface 11a side of the wafer 11 is sucked and held by the chuck table of the grinding device to grind the back surface 11b of the wafer 11. The chamfered portion 11e remaining on the back surface side of the wafer 11 is removed by grinding, and the outer periphery of the wafer 11 becomes an end surface substantially perpendicular to the front surface 11a and the back surface 11b.

  In the machining step of the present embodiment, the cutting step for partially removing the chamfered part is divided into two steps of a rough cutting step and a finishing cutting step, so that chipping generated in each cutting step can be suppressed.

  Cutting blade (soft bond, fine abrasive, low abrasive) that cannot be used in a single cut in the final cutting step (there is no cutting force but the work is finished finely) by performing the rough cutting step first Can be used as a finishing cutting blade. As a result, it is possible to suppress chipping and chipping that occur in the part to be cut of the final wafer.

  In the above-described embodiment, the example in which the processing method of the present invention is applied to the semiconductor wafer 11 has been described. However, the processing method of the present invention can be similarly applied to other wafers such as an optical device wafer.

DESCRIPTION OF SYMBOLS 10 Chuck table 11 Semiconductor wafer 11a Surface 11e Chamfer 15 Device 16 Laminated cutting blade 16a Rough cutting blade 16b Finish cutting blade 18 Annular cutting groove

Claims (2)

A wafer processing method of removing a chamfered portion by cutting a peripheral annular removal region having a predetermined radial width from a wafer having a chamfered portion on the outer periphery with a cutting blade attached to one spindle ,
The outer circumferential annular removal region having the predetermined width is at least twice the thickness, and one surface side from the center in the thickness direction is a rough cutting blade, and the other surface side of the back surface from the center in the thickness direction is a finishing cutting blade. And a laminating cutting blade preparation step of preparing a laminating cutting blade in which the rough cutting blade and the finishing cutting blade have the same outer diameter ;
A holding step for holding the wafer on the chuck table;
The rough cutting blade side of the laminated cutting blade is positioned on the outer peripheral annular removal region of the wafer held by the chuck table on the first direction side with respect to the center of the chuck table , and cut to a first depth. A rough cutting step in which the chamfered portion is partially removed by cutting the peripheral annular removal region with the laminated cutting blade by rotating the chuck table at least once;
After performing the rough cutting step, the outer peripheral annular removal of the wafer held on the chuck table on the side of the finish cutting blade of the laminated cutting blade opposite to the first direction with respect to the center of the chuck table The chamfered portion is partially cut by cutting the outer peripheral annular removal region with the laminated cutting blade by cutting the chuck table at least once by positioning it in a region and cutting it to a second depth deeper than the first depth. A finishing cutting step to remove automatically,
A wafer processing method characterized by comprising:   2. The finish cutting blade is composed of any one of or a combination of fine grain size of abrasive grains, soft bond agent, and low concentration of abrasive grains compared to the coarse cutting blade. Wafer processing method.

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