JP6629086B2 - Division method of laminated wafer - Google Patents

Description

  The present invention relates to a method for dividing a laminated wafer in which a plurality of wafers are laminated.

  The surface of the wafer is divided into a plurality of sections by lattice-shaped streets, and devices such as ICs and LSIs are formed in the divided areas. In the device manufacturing process, individual device chips are formed by cutting a wafer along a street with a cutting blade. As a method for dividing a wafer, step cutting using a pair of cutting blades having different blade widths is known. In step cutting, the first step shallow groove is formed along the street with a wide cutting blade, and the second step deep groove is formed on the bottom surface of the shallow groove with a narrow cutting blade, whereby the wafer is completely cut ( For example, see Patent Document 1).

JP-A-2015-18965

  In recent years, a stacked device chip in which a plurality of device chips are stacked in the thickness direction has been put to practical use. The stacked device chip is manufactured, for example, by dividing a stacked wafer obtained by stacking wafers of a plurality of materials with a cutting blade. However, when the laminated wafer is divided by the cutting blade, there is a problem that the processing quality of the device chip after division is deteriorated. Even if such a laminated wafer is cut in two stages by two types of cutting blades having different widths in the above-described step cutting, the wafer cannot be appropriately divided depending on the material of the laminated wafer. .

  The present invention has been made in view of such a point, and an object of the present invention is to provide a method of dividing a laminated wafer that can appropriately divide the laminated wafer along a street.

The method for dividing a laminated wafer according to the present invention includes a first cutting unit including a chuck table for holding the laminated wafer, a first cutting blade for cutting the laminated wafer held on the chuck table, A second cutting means having a second cutting blade for further performing a cutting process on a region cut by the first cutting means, and a cutting device having an imaging means having a reference line for detecting a street, A method for dividing a laminated wafer in which a second wafer is laminated on a lower surface side of a first wafer along a street, wherein a street of the laminated wafer held on a chuck table is detected by the imaging means. Detecting step, along the street detected in the detecting step, a dividing step of dividing the laminated wafer for each street, The dividing step is to cut only the first wafer of the laminated wafer along the street by the first cutting means to expose the second wafer and form a first cut groove. After performing the first cutting step and the first cutting step, the second cutting blade, which is thinner than the width of the first cutting blade, is ultrasonically vibrated in the radial direction, and the second cutting means performs the ultrasonic vibration. A second cutting step of cutting the second wafer exposed along the first cutting groove to form a second cutting groove, and cutting a new street during the execution of the dividing step. A first cutting groove position measuring step of taking an image of the first cutting groove formed on the laminated wafer with the imaging means and measuring a positional relationship with a reference line at an arbitrary timing before performing the first cutting groove; The cutting groove is formed A measurement groove is formed on the surface of the first wafer by the second cutting means without applying ultrasonic waves, and the measurement groove is imaged by the imaging means to measure a positional relationship with a reference line. And a second cutting groove position measuring step .

  According to this configuration, the first and second wafers of the laminated wafer are cut in two stages by the first and second cutting blades having different blade widths. The first cutting blade forms a first dividing groove along the street in the first wafer, and the second wafer is partially exposed through the first dividing groove. A second cutting blade, which is thinner than the first cutting blade, is ultrasonically oscillated, and the ultrasonically oscillated cutting blade forms a second divisional groove along the first divisional groove on the exposed portion of the second wafer. Is formed. For this reason, even if the second wafer is formed of a material that is harder to cut than the first wafer, the stacked wafer can be appropriately divided by combining cutting with the first and second cutting blades.

  According to the present invention, the first wafer is cut by the first cutting blade, the second wafer is exposed along the street, and then the second wafer is ultrasonically vibrated by the second cutting blade. The exposed part of is cut. Therefore, even if the second wafer is a laminated wafer formed of a material that is harder to cut than the first wafer, the laminated wafer can be appropriately divided along the street.

It is the perspective view and sectional view of the lamination wafer of this embodiment. It is a schematic diagram of the cutting device of the present embodiment. It is explanatory drawing of the kerf check with respect to the laminated wafer of the comparative example. FIG. 4 is a diagram illustrating an example of a detection step according to the present embodiment. It is a figure showing an example of the division step of this embodiment. It is a figure which shows an example of the 1st, 2nd cutting groove position measurement step of this Embodiment.

  Hereinafter, the present embodiment will be described with reference to the accompanying drawings. First, a laminated wafer to be cut will be described. FIG. 1 is a perspective view and a sectional view of a laminated wafer according to the present embodiment. FIG. 2 is a schematic diagram of the cutting device according to the present embodiment. FIG. 3 is an explanatory diagram of a kerf check on the laminated wafer of the comparative example.

  As shown in FIGS. 1A and 1B, the laminated wafer W is formed by laminating two types of substantially disk-shaped first and second wafers W1 and W2 having different materials. The first wafer W1 is a silicon wafer that is easy to cut with a normal hub blade, the second wafer W2 is a glass wafer that is difficult to cut with a normal hub blade, and the second wafer W2 is placed on the lower surface side of the first wafer W1. Are laminated. Streets are formed in a lattice shape on the surface of the first wafer W1, and devices D are formed in the respective regions divided into the streets. The laminated wafer W is supported on a ring frame F via a dicing tape T.

  Although the thicknesses of the first and second wafers W1 and W2 are not particularly limited, in the present embodiment, for example, the thickness of the first wafer W1 is 0.4 mm and the thickness of the second wafer W2 is 0.3 mm Is formed. The first wafer W1 may be a substrate formed of a material that can be easily cut by ordinary cutting, and may be, for example, a gallium arsenide wafer. The second wafer W2 may be a substrate formed of a hard-to-cut material that is difficult to cut by ordinary cutting, and may be, for example, a sapphire wafer. The hard-to-cut material is, for example, a material whose hardness and crystal hardness are higher than the first wafer W1 and whose processing quality is improved by ultrasonic cutting.

  Since the processing quality of such a laminated wafer W is deteriorated by single cutting in which the first and second wafers W1 and W2 are cut at a time, a method of cutting by step cutting using a pair of cutting blades having different blade widths. Is being considered. However, even if the first and second wafers W1 and W2 are individually cut by step cutting, the processing quality is degraded when cutting the second wafer W2 because the second wafer W2 is a difficult-to-cut material. Was. Therefore, in the present embodiment, the first and second cutting blades 22 (see FIG. 2) for normal cutting and the second cutting blades 27 for ultrasonic cutting (see FIG. 2) are used. Wafers W1 and W2 are step-cut.

  In this case, the first wafer W1 is normally cut by the first cutting blade 22 (see FIG. 2) along the street, and the second wafer W2 exposed from the first wafer W1 is cut by the second cutting blade. Ultrasonic cutting is performed at 27 (see FIG. 2). Since the first wafer W1 is relatively easy to cut with a silicon wafer, the processing quality does not deteriorate even in normal cutting, and the second wafer W2 is a glass wafer and is difficult to cut, but an ultrasonic wave is used. The machining quality is improved by being cut. As described above, the first and second cutting blades 22 and 27 are selectively used in accordance with the material of the first and second wafers W1 and W2 to perform step cutting, whereby the laminated wafer W is appropriately divided.

  As shown in FIG. 2, the cutting apparatus 1 is provided with a first cutting means 21 for a first wafer and a second cutting means 26 for a second wafer. A first cutting blade 22 for cutting the laminated wafer W held on the chuck table 11 is mounted on a spindle 23 of the first cutting means 21. On the spindle 28 of the second cutting means 26, a second cutting blade 27 for further cutting the area cut by the first cutting means 21 is mounted. The first and second cutting blades 22 and 27 have different blade widths, the first cutting blade 22 is formed wider, and the second cutting blade 27 is narrower and narrower than the first cutting blade 22. Is formed.

  The first cutting blade 22 is used for normal cutting of the first wafer W1, and the second cutting blade 27 is used for ultrasonic cutting of the second wafer W2. Ultrasonic vibration applying means 29 is attached to a spindle 28 of the second cutting blade 27. The blade of the second cutting blade 27 is instantaneously expanded and contracted in the radial direction by the ultrasonic vibration transmitted from the ultrasonic vibration applying means 29, and the second wafer W2 is cut while the abrasive grains of the blade repeatedly collide. . In this embodiment, for example, an electroformed hub blade having a grain size of # 2000 and a blade width of 0.1 mm is used as the first cutting blade 22, and a grain size of # 1000 as the second cutting blade 27 is used. A metal blade having a blade width of 0.08 mm is used.

  Further, the cutting device 1 is provided with an imaging unit 15 having a reference line for detecting a street. Further, the cutting device 1 is provided with a control means 19 for controlling the respective parts of the device. The control unit 19 includes a processor for executing various processes, a memory, and the like. The memory includes one or a plurality of storage media such as a ROM (Read Only Memory) and a RAM (Random Access Memory) depending on the application. The memory stores, for example, a program for executing each step of the method of dividing the laminated wafer W, a program for image processing, and the like.

  By the way, in the cutting by the above-described cutting device 1, the cutting grooves formed by the first and second cutting blades 22 and 27 are used in order to correct the positional deviation of the processing position due to thermal expansion of the spindles 23 and 28 and the like. Is regularly checked. In the kerf check, in addition to observing the state of the cutting grooves, a positional deviation between each cutting groove and a reference line of the imaging unit 15 called a hairline is corrected. In the case of the step cut, since the cutting groove 50 (see FIG. 3) is formed in a stepped shape, the cut groove on the upper stage side (first wafer W1) formed by the first cutting blade 22 is kerf-checked. However, it is difficult to kerf-check the cutting groove on the lower side (second wafer W2) formed by the second cutting blade 27.

  For this reason, as shown in FIG. 3, it is necessary to cut the first wafer W1 with the second cutting blade 27 and kerf-check the cut grooves 41 formed in the first wafer W1. However, when the first wafer W1 such as a silicon wafer is ultrasonically cut by the second cutting blade 27, the processing quality of the cutting groove 41 deteriorates, and an appropriate kerf check cannot be performed. Therefore, in the present embodiment, when performing the kerf check on the second cutting blade 27, the first wafer W1 is cut by the second cutting blade 27 in a state where the ultrasonic wave is stopped, and the processing quality is reduced. A good cutting groove is formed (see FIG. 6A).

  Hereinafter, a method of dividing a laminated wafer according to the present embodiment will be described. FIG. 4 is a diagram illustrating an example of the detection step of the present embodiment, FIG. 5 is a diagram illustrating an example of the division step of the embodiment, and FIG. FIG. 5A shows a first cutting step, and FIG. 5B shows a second cutting step. 6A and 6B show a second cutting groove position measuring step, and FIGS. 6C and 6D show a first cutting groove position measuring step, respectively.

  As shown in FIG. 4, when the laminated wafer W is carried into the cutting device 1 (see FIG. 2), first, a detection step is performed. In the detection step, the street of the laminated wafer W held on the chuck table 11 is detected by the imaging unit 15. In this case, the upper surface of the laminated wafer W is imaged by the imager 15, image processing such as pattern matching is performed on the captured image, and the reference line of the imager 15 is positioned at the center of the street. The street of the first wafer W1 is detected by the imaging unit 15 by positioning the reference line of the imaging unit 15 on the street.

  As shown in FIG. 5A, after the detection step, a first cutting step of the division step is performed. In the first cutting step, only the first wafer W1 is cut along the streets by the first cutting means 21, so that the second wafer W2 is exposed and the first cutting groove 31 is formed. In this case, the first cutting blade 22 is aligned with the street of the laminated wafer W, and the chuck table 11 is cut and fed to the first cutting blade 22 that has been lowered to a height at which the first wafer W1 can be cut. You. As a result, the first wafer W1 on the chuck table 11 is cut along the street, and the second wafer W2 is partially exposed from the surface of the first wafer W1.

  As shown in FIG. 5B, after the first cutting step, a second cutting step of the dividing step is performed. In the second cutting step, the second wafer W2 exposed along the first cutting groove 31 is cut by the second cutting means 26 which ultrasonically vibrates the second cutting blade 27 in the radial direction. Thus, a second cutting groove 35 is formed. In this case, the second cutting blade 27 is aligned with the first cutting groove 31, and the chuck table 11 cuts and feeds the second cutting blade 27 that has been lowered to a height at which the second wafer W2 can be cut. Is done. Thereby, the second wafer W2 on the chuck table 11 is cut along the first cutting groove 31, and the laminated wafer 1W is completely cut.

  As described above, in the dividing step, the laminated wafer W is divided for each street by being cut along the street detected in the detecting step by the first and second cutting steps. At this time, the first wafer W1 of a material which is easy to cut is usually cut by the first cutting blade 22 and the second wafer W2 of the hard-to-cut material is ultrasonically cut by the second cutting blade 27. Be cut. Since step cutting is performed by switching between normal cutting and ultrasonic cutting for each material of the first and second wafers W1 and W2, the laminated wafer W composed of the first and second wafers W1 and W2 can be appropriately removed. It is possible to split.

  In the dividing step, the first and second cutting steps are repeated along all the streets, but the positional deviation of the first and second cutting blades 22 and 27 due to thermal expansion of the spindles 23 and 28 is corrected. A regular calf check is needed to do this. Therefore, the first and second cut groove position measurement steps are periodically performed at an arbitrary timing before cutting a new street during the execution of the division step. In the following description, the first cutting groove position measurement step is performed after the second cutting groove position measurement step is performed. However, the second cutting groove position measurement is performed after the first cutting groove position measurement step. A groove position measurement step may be performed.

  As shown in FIG. 6A, in the second cutting groove position measuring step, the second cutting means 26 is applied to the surface of the first wafer W1 on which the first cutting groove 31 is not formed without applying ultrasonic waves. Thereby, a cutting groove 39 (measurement groove) for measurement is formed. In this case, the application of the AC voltage to the ultrasonic vibration applying means 29 of the second cutting means 26 is interrupted, and the ultrasonic vibration of the second cutting blade 27 in the radial direction is stopped. Further, the second cutting blade 27 is aligned with the street of the laminated wafer W, and the chuck table 11 is cut and fed to the second cutting blade 27 lowered to a height at which the first wafer W1 can be cut. . As a result, a shallow cut groove 39 for measurement is formed on the surface of the first wafer W1 on the chuck table 11.

  As shown in FIG. 6B, the measurement cutting groove 39 formed on the first wafer W1 is imaged by the imaging unit 15, and the measurement cutting groove 39 and the reference line of the imaging unit 15 are determined based on the captured image. The positional relationship is measured. At this time, since the cutting groove 39 for measurement is formed without ultrasonic vibration by the second cutting blade 27 (see FIG. 6A), the processing quality of the cutting groove 39 for measurement is not deteriorated, and The positional relationship between the cutting groove 39 and the reference line of the imaging means 15 can be measured with high accuracy. Then, the positional relationship between the imaging unit 15 and the second cutting blade 27 is corrected so that the reference line of the imaging unit 15 is positioned at an intermediate position of the width of the cutting groove 39 for measurement (hairline alignment).

  As shown in FIG. 6C, in the first cutting groove position measurement step, the first wafer W1 is cut by the first cutting means 21 into the measurement cutting groove 39 (FIG. 6B), similarly to the above-described first cutting step. 1) to form a first cut groove 31. In this case, the first cutting blade 31 wider than the second cutting blade 27 forms the first cutting groove 31 deeper than the cutting groove 39 for measurement. For this reason, even if the cutting groove 39 for measurement is formed along the street of the first wafer W1, the cutting groove 31 for measurement is formed on the first wafer W1 by forming the first cutting groove 31. 39 does not remain.

  As shown in FIG. 6D, the first cutting groove 31 formed on the first wafer W1 is imaged by the imaging unit 15, and the first cutting groove 31 and the reference line of the imaging unit 15 are determined based on the captured image. The positional relationship is measured. Then, the positional relationship between the imaging unit 15 and the first cutting blade 22 (see FIG. 6C) is corrected so that the reference line of the imaging unit 15 is positioned at an intermediate position of the groove width of the first cutting groove 31. (Hairline alignment). In this manner, by correcting the positional deviation of the first and second cutting blades 22 and 27 due to thermal expansion and the like by the periodic kerf check, the laminated wafer W can be accurately divided along the street. It has become.

  As described above, in the method for dividing the laminated wafer W of the present embodiment, the first and second wafers W1 and W2 of the laminated wafer W are divided into two by the first and second cutting blades 22 and 27 having different blade widths. It is cut in stages. A first cutting groove 31 is formed along the street on the first wafer W1 by the first cutting blade 22, and the second wafer W2 is partially exposed through the first cutting groove 31. Further, the second cutting blade 27, which is thinner than the first cutting blade 22, is ultrasonically oscillated, and the second oscillating blade 27 oscillates the first cutting groove 31 in the exposed portion of the second wafer W2. Is formed along the second cutting groove 35. Therefore, even if the second wafer W2 is formed of a material that is harder to cut than the first wafer W1, the stacked wafer W can be appropriately formed by combining the cutting with the first and second cutting blades 22 and 27. Can be split.

  Note that the present invention is not limited to the above embodiment, and can be implemented with various modifications. In the above embodiment, the size, shape, and the like illustrated in the accompanying drawings are not limited thereto, and can be appropriately changed within a range in which the effects of the present invention are exhibited. In addition, the present invention can be appropriately modified and implemented without departing from the scope of the object of the present invention.

  For example, in the above-described embodiment, in the second cutting groove position measuring step, the cutting groove 39 for measurement is formed by the second cutting blade 27 along the street between the devices of the first wafer W1. However, the present invention is not limited to this configuration. In the second cutting groove position measuring step, the measuring cutting groove 39 may be formed on the surface of the first wafer W1 where the first cutting groove 31 is not formed. For example, the first wafer W1 The cut groove 39 for measurement may be formed short in the outer peripheral region where the device is not formed. Even with such a short calf check, the positional relationship between the imaging means 15 and the second cutting blade 27 can be corrected.

  Further, in the above-described embodiment, the first and second cutting groove position measuring steps are configured to be performed at the same timing, but the present invention is not limited to this configuration. The first and second cutting groove position measurement steps may be performed at different timings.

  As described above, the present invention has an effect that a laminated wafer can be appropriately divided along a street, and is particularly useful for a method of dividing a laminated wafer in which a silicon wafer and a glass wafer are laminated.

DESCRIPTION OF SYMBOLS 1 Cutting device 11 Chuck table 15 Imaging means 19 Control part 21 First cutting means 22 First cutting blade 26 Second cutting means 27 Second cutting blade 31 First cutting groove 35 Second cutting groove 39 Measurement Grooves (measurement grooves)
W laminated wafer W1 first wafer W2 second wafer

Claims (1)

A chuck table for holding the laminated wafer, a first cutting unit having a first cutting blade for performing a cutting process on the laminated wafer held on the chuck table, and a region cut by the first cutting unit. Further, using a cutting device including a second cutting means having a second cutting blade for performing a cutting process, and an imaging means having a reference line for detecting a street,
A method of dividing a laminated wafer in which a laminated wafer in which a second wafer is laminated on a lower surface side of a first wafer is divided along a street,
A detection step of detecting a street of the laminated wafer held on the chuck table by the imaging unit;
A dividing step of dividing the laminated wafer for each street along the streets detected in the detecting step.
The dividing step includes:
A first cutting step of cutting only the first wafer of the laminated wafer along the street by the first cutting means to expose the second wafer and forming a first cut groove;
After performing the first cutting step, the second cutting blade, which is thinner than the width of the first cutting blade, is ultrasonically oscillated in the radial direction, and the second cutting means cuts the first cutting groove into the first cutting groove. A second cutting step of cutting the second wafer exposed along the second cutting groove to form a second cutting groove;
Consisting of
At any time before cutting a new street during the division step,
A first cutting groove position measuring step of taking an image of the first cutting groove formed on the laminated wafer by the imaging means and measuring a positional relationship with a reference line;
On the surface of the first wafer where the first cutting groove is not formed, a measuring groove is formed by the second cutting means without applying ultrasonic waves, and the measuring groove is imaged by the imaging means. A second cutting groove position measuring step of measuring a positional relationship with a reference line by using the method.

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