JP2014003197A - Processing method of wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a processing method of a wafer which forms a groove bottom of an annular cutting groove into a flat shape thereby making the damage of the wafer less likely to be caused.SOLUTION: In a processing method of a wafer, a chamfered part of the wafer, which has the chamfered part at an outer periphery, is removed by a cutting blade. The processing method of the wafer includes: a holding step where the wafer is held by a chuck table; a cutting blade cutting step where the cutting blade cuts into an outer peripheral portion of the wafer so as to reach a predetermined depth after the holding step is conducted; a first processing step where the chuck table holding the wafer is rotated 360 degrees and thereby causes the cutting blade to cut the outer peripheral part of the wafer to form an annular cutting groove and partially remove the chamfered part after the cutting blade cutting step is conducted; and a second processing step where the chuck table is rotated 360 degrees and thereby flattens at least a bottom part of the annular cutting groove after the first processing step is conducted.

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 arc surface and the ground surface remains in the chamfered part, which is dangerous and the outer periphery is chipped, resulting in a deterioration in 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.

  Japanese Patent Application Laid-Open No. 11-54461 discloses that a wafer having a large diameter such as 8 inches or 12 inches is reduced to a wafer having a small diameter such as 4 inches or 6 inches by circle cutting (circular cutting) using a cutting blade. A method for circularly sizing a wafer is disclosed.

JP 2000-173961 A Japanese Patent Laid-Open No. 11-54461 JP-A-8-107092

  Concavities and convexities due to the protrusion of the abrasive grains of the cutting blade are formed on the bottom of the annular cutting groove formed when edge trimming that removes the chamfered part by the cutting blade or when the wafer is sir cut and the wafer is downsized. Is done. If the unevenness is large, cracks may occur in the wafer starting from the unevenness, and the wafer may be damaged by the generated cracks.

  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 capable of reducing the risk of wafer breakage by flatly forming the groove bottom of an annular cutting groove. It is to be.

  According to the present invention, there is provided a wafer processing method for removing a chamfered portion of a wafer having a chamfered portion on an outer periphery with a cutting blade, a holding step for holding the wafer with a chuck table, and a cutting step after performing the holding step. A cutting blade cutting step for cutting the blade into the outer peripheral portion of the wafer to a predetermined depth, and after performing the cutting blade cutting step, the chuck table holding the wafer is rotated once to rotate the outer periphery of the wafer with the cutting blade. To form an annular cutting groove and partially remove the chamfered portion, and after performing the first processing step, at least the annular cutting groove by rotating the chuck table once. And a second processing step for flattening the bottom of the wafer It is provided.

  Preferably, the wafer processing method includes a cutting step of further cutting the cutting blade into the wafer after performing the first processing step and before performing the second processing step. Preferably, in the first machining step, the angular velocity of the chuck table is 2 to 5 degrees / second, and in the second machining step, the angular velocity of the chuck table is 5 to 25 degrees / second.

  According to the wafer processing method of the present invention, the outer peripheral portion of the wafer is cut with a cutting blade by rotating the chuck table holding the wafer once to form an annular cutting groove, and the chamfered portion is partially removed. Since the cutting blade can be passed again through the annular cutting groove formed by rotating the chuck table one more time and the groove bottom of the annular cutting groove can be flattened, the possibility of damage to the wafer can be reduced.

  Before the second machining step is performed, the cutting blade is slightly cut into the wafer, so that the amount of cut removal is significantly reduced in the second machining step compared to the first machining step. Compared to the case where the first and second processing steps are continuously performed, the groove bottom of the annular cutting groove can be finished more flat.

  By setting the angular velocity of the chuck table in the first machining step to 2 to 5 degrees / second, the bottom of the annular cutting groove formed can be formed relatively flat. Furthermore, the machining time can be shortened by setting the angular velocity of the chuck table in the second machining step to be larger than that in the first machining step.

It is a surface side perspective view of a semiconductor wafer. It is a partial cross section side view which shows a holding | maintenance step. It is a partial cross section side view showing a cutting blade cutting step. It is a top view which shows a 1st process step. It is a partial cross section side view which shows a 1st process step. It is a top view which shows a 2nd process step. It is a partial cross section side view which shows a 2nd process step. It is a partial cross section side view which shows the 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.

  In the processing method of the present invention, as shown in FIG. 2, first, 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 FIG. 3, a cutting blade cutting step for cutting the cutting blade 16 into the outer peripheral portion (outer peripheral edge) of the wafer 11 by a predetermined depth t1 is performed.

  In FIG. 3, reference numeral 12 denotes a cutting unit, which includes a spindle 14 that is rotationally driven by a motor (not shown), and a cutting blade 16 that is attached to the tip of the spindle 14. Here, the predetermined depth t1 is a depth corresponding to a grinding finish thickness to be performed in a later step.

  In the cutting blade cutting step, the cutting blade 16 positioned above the wafer 11 is lowered to cut the cutting blade 16 into the wafer 11 by a predetermined depth t1, and in addition to a predetermined height on the outer peripheral side of the wafer 11. The cutting blade 16 may be cut into the wafer 11 by a predetermined depth t <b> 1 by moving the cutting blade 16 positioned at the position relative to the wafer 11 in the approaching direction.

  After performing the cutting blade cutting step, as shown in FIGS. 4 and 5, the chuck table 16 holding the wafer 11 is rotated at a high speed in the direction of arrow A by rotating it once in the first direction which is the direction of arrow R1 ( A first machining step is performed in which the outer peripheral portion of the wafer 11 is cut with the cutting blade 16 (for example, 30000 rpm), the annular cutting groove 18 is formed, and the chamfered portion 11e of the wafer 11 is partially removed.

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

  Further, by setting the rotation speed (angular speed) of the chuck table 10 to 2 to 5 degrees / second, for example, the unevenness of the groove bottom 18a and the groove side surface 18b of the annular cutting groove 18 can be reduced.

  After performing the first machining step, the second machining step for flattening at least the bottom 18a of the annular cutting groove 18 is performed by further rotating the chuck table 10 once. In this second machining step, as shown in FIGS. 6 and 7, for example, the chuck table 10 is rotated while being rotated in a second direction indicated by an arrow R2 opposite to the first direction. The second machining step may be performed while rotating the chuck table 10 in the same direction as the first direction R1.

  Although the rotation speed of the chuck table 10 may be substantially the same as that of the first processing step, it is preferable to rotate the chuck table 10 at a higher speed than the first processing step in order to shorten the processing time.

  For example, in the second processing step, the rotation speed (angular speed) of the chuck table 10 is set to 5 to 25 degrees / second. If this 2nd processing step is implemented, the bottom part 18a of the annular cutting groove 18 can be finished flat.

  Preferably, after performing the first machining step and before performing the second machining step, as shown in FIG. 8, the cutting blade 16 is lowered by 1 to 5 μm in the direction of the arrow Z <b> 1 so as to slightly cut the wafer 11. Perform the steps. After the cutting step, the second processing step described with reference to FIGS. 6 and 7 is performed.

  As described above, if the cutting step is performed before the second machining step is performed, the cutting removal amount is significantly reduced in the second machining step as compared with the first machining step. As compared with the case where the first and second processing steps are continuously performed, the bottom portion 18a of the annular cutting groove 18 can be finished more flat.

  The annular cutting groove 18 formed in the above-described embodiment is an L-shaped cutting groove opened on the upper surface and the outer peripheral side, but the annular cutting groove naturally includes a cutting groove opened only on the upper surface.

  When the second machining step is completed, the chamfered portion 11e of the wafer 11 is partially removed, and the unevenness of the bottom portion 18a of the annular cutting groove 18 is removed to flatten the bottom portion 18a. After the second processing step is performed, a surface protection tape is attached to the front surface 11a of the wafer 11, and the front 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 11 e remaining on the back surface side of the steel 11 is removed by grinding, and the side surface 18 b of the annular cutting groove 18 remains on the outer periphery of the wafer 11.

  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.

10 chuck table 11 semiconductor wafer 11a surface 11e chamfer 15 device 16 cutting blade 18 annular cutting groove 18a bottom 18b groove side surface

Claims (3)

A wafer processing method for removing a chamfered portion of a wafer having a chamfered portion on the outer periphery with a cutting blade,
A holding step for holding the wafer on the chuck table;
After performing the holding step, a cutting blade cutting step for cutting the cutting blade into the outer peripheral portion of the wafer to a predetermined depth;
After performing the cutting blade cutting step, the outer periphery of the wafer is cut with the cutting blade by rotating the chuck table holding the wafer once, thereby forming an annular cutting groove and partially removing the chamfered portion. A first machining step,
A second machining step of flattening at least the bottom of the annular cutting groove by rotating the chuck table once after the first machining step;
A wafer processing method characterized by comprising:   The wafer processing method according to claim 1, further comprising a cutting step of further cutting the cutting blade into the wafer after performing the first processing step and before performing the second processing step. In the first processing step, the angular velocity of the chuck table is 2 to 5 degrees / second,
3. The wafer processing method according to claim 1, wherein an angular velocity of the chuck table is 5 to 25 degrees / second in the second processing step. 4.

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