JP2015041628A - Division method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wafer division method which reduces a possibility for a wafer to be damaged by grinding.SOLUTION: The division method includes: a groove forming step of forming a groove (21) deeper than a thickness of a finished chip along a predetermined dividing line (17) of a wafer (11); an affixing step of affixing a protective tape (23) to a front face (11a) of the wafer; a wafer holding step of holding a front side of the wafer with a holding table (10); a grinding step of grinding a rear face (11b) of the wafer with grinding means (12) while supplying grinding water (Wc and Wh) to the wafer held by the holding table; and a detection step of detecting that the wafer is divided into individual chips suring implementation of the grinding step. Before detecting the division of the wafer in the detection step, grinding is implemented with the grinding water (Wc) at a first temperature. After the division of the wafer is detected in the detection step, the wafer is ground by the grinding water (Wh) at a second temperature that is higher than the first temperature.

Description

  The present invention relates to a dividing method for dividing a wafer on which a device such as an IC is formed into a plurality of chips.

  Wafers with ICs and other devices formed on the front surface are divided into multiple chips by, for example, forming grooves deeper than the finished thickness along the streets (division lines) and then grinding the back side. (For example, see Patent Document 1).

  In this dividing method called DBG (Dicing Before Grinding) process, grooves are formed before the wafer is thinly processed, so that chip breakage and the like can be suppressed as compared with the conventional dividing method in which the wafer is thinly processed and then cut. .

JP 11-40520 A

  By the way, in the DBG process described above, the wafer is ground and divided into a plurality of chips. Therefore, the divided chips may move under a grinding load and come into contact with adjacent chips. When the chips being ground come into contact with each other, the chips are damaged by the impact applied to the outer peripheral portion.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a wafer dividing method in which the possibility of breakage due to grinding is reduced.

  According to the present invention, there is provided a dividing method for dividing a wafer in which a device is formed in each region partitioned by a plurality of division planned lines intersecting the surface into individual chips along the planned division lines, A groove forming step for forming a groove deeper than the finished thickness of the chip along the division line, a bonding step for bonding a protective tape to the surface of the wafer after performing the groove forming step, and the bonding After performing the steps, the front surface side of the wafer is held by the holding table via the protective tape, the wafer holding step for exposing the back surface of the wafer, and grinding while supplying grinding water to the wafer held by the holding table A grinding step in which the back surface of the wafer is ground by a grinding means having a grindstone to reduce the thickness to the finished thickness, and the groove is formed on the back surface of the wafer during the grinding step. A detecting step for detecting that the wafer has been divided into individual chips, wherein the grinding step includes a first temperature grinding before the detection of the wafer division in the detecting step. After grinding with water and detecting the division of the wafer in the detecting step, the wafer is ground with a grinding water having a second temperature higher than the first temperature and thinned to the finished thickness. A division method characterized by this is provided.

  The dividing method of the present invention includes a grinding step for grinding a wafer to a finished thickness, and a detecting step for detecting that the wafer has been divided into chips during the grinding step, and before the division of the wafer is detected. After the wafer is ground with the first temperature grinding water and the wafer split is detected, the wafer is ground with the second temperature grinding water higher than the first temperature, so the wafer is split After that, the protective tape attached to the surface of the wafer with high-temperature grinding water is easily stretched, and the interval between adjacent chips can be sufficiently widened. That is, the possibility of breakage due to contact between the chips during grinding can be reduced.

It is a perspective view which shows a groove | channel formation step typically. It is a perspective view which shows a sticking step typically. It is a partial cross section side view which shows a wafer holding step typically. It is a partial cross section side view which shows typically the grinding step before the division | segmentation of a wafer is detected in a detection step. It is a partial cross section side view which shows typically the grinding step after the division | segmentation of a wafer was detected in the detection step.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. The dividing method according to the present embodiment includes a groove forming step (see FIG. 1), an attaching step (see FIG. 2), a wafer holding step (see FIG. 3), a grinding step (see FIGS. 4 and 5), and a detecting step. (See FIGS. 5 and 5).

  In the groove forming step, grooves deeper than the finished thickness are formed along the streets (division planned lines) arranged on the front surface side of the wafer. In the attaching step, a protective tape is attached to the surface of the wafer. In the wafer holding step, the wafer is held by a holding table via a protective tape attached to the surface.

  In the grinding step, the back surface of the wafer is ground and divided into a plurality of chips, and the divided chips are processed to a finished thickness. In the detection step, the division of the wafer is detected during the grinding step. Hereinafter, the dividing method according to the present embodiment will be described in detail.

  In the dividing method of the present embodiment, first, a groove forming step is performed in which the surface side of the wafer is cut to form a groove. FIG. 1 is a perspective view schematically showing a groove forming step according to the present embodiment.

  As shown in FIG. 1, the wafer 11 is, for example, a semiconductor wafer having a disk-like outer shape, and the surface 11 a is divided into a central device region 13 and an outer peripheral surplus region 15 surrounding the device region 13. Yes.

  The device area 13 is further divided into a plurality of areas by streets (division planned lines) 17 arranged in a lattice pattern, and a device 19 such as an IC is formed in each area. The outer peripheral surface 11c of the wafer 11 is chamfered, and the cross-sectional shape thereof is an arc shape.

  In the groove forming step, first, the back surface 11b side of the wafer 11 described above is sucked by a chuck table (not shown) of the cutting apparatus 2, and then the cutting blade 4 is aligned with the street 17 on the front surface 11a side.

  As shown in FIG. 1, the cutting blade 4 is mounted on one end side of a spindle 6 that can rotate around a rotation axis extending in the horizontal direction. A motor (not shown) is connected to the other end side of the spindle 6, and the cutting blade 4 mounted on the spindle 6 is rotated by the rotational force of this motor.

  After the alignment, the cutting blade 4 is rotated and cut into the wafer 11, and the chuck table and the cutting blade 4 are relatively moved (processed) along the street 17 to be processed. As a result, a groove 21 is formed on the surface 11a side of the wafer 11 along the street 17 to be processed.

  Here, the cutting depth of the cutting blade 4 is set deeper than the finished thickness of the chip formed by division. That is, in this groove forming step, the groove 21 deeper than the finished thickness of the chip is formed. If the finished thickness of the chip with respect to the surface 11a is 80 μm, for example, the cutting depth of the cutting blade 4 may be set to about 110 μm from the surface 11a.

  Thereafter, the cutting blade 4 is raised, and the chuck table and the cutting blade 4 are moved relative to each other in a direction orthogonal to the machining target street 17 (index feed) to align the cutting blade 4 with the adjacent street 17. To do. After alignment, a similar groove 21 is formed along the adjacent street 17.

  After repeating this operation and forming the grooves 21 along all the streets 17 extending in the first direction, the chuck table is rotated by 90 ° along the streets 17 extending in the second direction orthogonal to the first direction. A similar groove 21 is formed. When the grooves 21 are formed along all the streets 17, the groove forming step ends.

  After the groove forming step, an attaching step of attaching a protective tape for protecting the device 19 to the surface 11a of the wafer 11 is performed. FIG. 2 is a perspective view schematically showing the attaching step according to the present embodiment.

  In the attaching step, first, the protective tape 23 is positioned above the wafer 11 so that the surface 11a side of the wafer 11 and the surface 23a side of the protective tape 23 face each other. Then, the protective tape 23 is lowered to bring the surface 23 a of the protective tape 23 into close contact with the surface 11 a of the wafer 11.

  The protective tape 23 is a resin film made of polyolefin, polyvinyl chloride, or the like, and an adhesive layer made of a rubber or acrylic adhesive is formed on the surface 23a side. Therefore, when the surface 23 a of the protective tape 23 is brought into close contact with the surface 11 a of the wafer 11, the protective tape 23 is attached to the wafer 11. The protective tape 23 is softened and easily stretched as the temperature rises.

  After the attaching step, a wafer holding step is performed in which the wafer 11 is sucked and held on the holding table of the grinding apparatus. FIG. 3 is a partial cross-sectional side view schematically showing the wafer holding step according to the present embodiment.

  As shown in FIG. 3, the grinding apparatus 8 includes a holding table 10 that holds the wafer 11 by suction. The holding table 10 is connected to a rotation mechanism (not shown) such as a motor, and rotates around a rotation axis C1 (see FIGS. 4 and 5) extending in the vertical direction. A moving mechanism (not shown) is provided below the holding table 10, and the holding table 10 moves in the horizontal direction by this moving mechanism.

  The surface of the holding table 10 is a holding surface 10 a that holds the wafer 11 by suction. A negative pressure of a suction source (not shown) acts on the holding surface 10a through a flow path (not shown) formed inside the holding table 10, and a suction force for sucking the wafer 11 is generated.

  When the back surface 23 b of the protective tape 23 is brought into contact with the holding surface 10 a and the negative pressure of the suction source is applied, the wafer 11 is sucked and held by the holding table 10 via the protective tape 23. Thus, the wafer 11 is sucked and held by the holding table 10 so that the back surface 11b is exposed upward.

  After the wafer holding step, a grinding step is performed in which the back surface 11b of the wafer 11 is ground and divided into a plurality of chips, and the divided chips are processed to a finished thickness. FIG. 4 is a partial cross-sectional side view schematically showing a grinding step according to the present embodiment.

  In this grinding step, first, the holding table 10 is moved to position the wafer 11 below the grinding mechanism (grinding means) 12. As shown in FIG. 4, the grinding mechanism 12 includes a spindle 14 that rotates around a rotation axis C2 that extends in the vertical direction. The spindle 14 is lifted and lowered by a lifting mechanism (not shown).

  A disc-shaped wheel mount 16 is fixed to the lower end side of the spindle 14, and a grinding wheel 18 is attached to the wheel mount 16. The grinding wheel 18 includes a wheel base 18a formed of a metal material such as aluminum or stainless steel. A plurality of grinding wheels 18b are fixed to the annular lower surface of the wheel base 18a over the entire circumference.

  At a position adjacent to the grinding mechanism 12, a grinding water supply nozzle 20 that supplies grinding water to the back surface 11 b side of the wafer 11 that is a surface to be ground and a thickness measurement sensor 22 that measures the thickness of the wafer 11 are arranged. Yes.

  The thickness measurement sensor 22 is in contact with the holding surface 10a of the chuck table 10 and measures the height position, and the second probe is in contact with the back surface 11b side of the wafer 11 and measures the height position. 22b. Based on the difference between the height position of the holding surface 10a of the chuck table 10 measured by the first probe 22a and the height position of the back surface 11b side of the wafer 11 measured by the second probe 22a. Is calculated.

  In this grinding step, the spindle 14 is lowered while the chuck table 10 and the spindle 14 are rotated in predetermined rotation directions, and the grinding wheel 18 b is brought into contact with the back surface 11 b side of the wafer 11. By lowering the spindle 14 at a predetermined feed rate, the back surface 11b side of the wafer 11 is ground. Here, the grinding water Wc at a predetermined temperature (first temperature) is supplied from the grinding water supply nozzle 20 to the back surface 11 b side of the wafer 11.

  For example, the temperature of the grinding water Wc is set to 20 ° C. Further, the rotation speed of the chuck table 10 is set to 300 rpm, and the rotation speed of the spindle 14 is set to 6000 rpm. However, the temperature of the grinding water Wc and the rotation speeds of the chuck table 10 and the spindle 14 are not limited to these.

  Simultaneously with this grinding step, a detection step for detecting the division of the wafer 11 is performed. In the detection step, the thickness measurement sensor 22 is used to measure the thickness of the wafer 11, and the presence or absence of the division of the wafer 11 is detected by comparing with the cutting depth of the cutting blade 4 in the groove forming step. Processing such as comparison and determination related to the detection step is performed by, for example, a control device (not shown) connected to the thickness measurement sensor 22.

  Specifically, when the thickness of the wafer 11 detected by the thickness measurement sensor 22 is less than the cutting depth (for example, 110 μm) of the cutting blade 4 and the groove 21 is exposed to the back surface 11b side of the wafer 11, the control device It is determined that the wafer 11 is divided into chips.

  When the wafer 11 is divided into chips, the chips divided by the grinding load may move and come into contact with adjacent chips. When the chips being ground come into contact with each other, the chips are damaged by an impact applied to the outer peripheral portion. Therefore, after the division of the wafer 11 is detected in the detection step, the grinding step is performed under conditions different from those before the division of the wafer 11 is detected.

  Specifically, after the division of the wafer 11 is detected, grinding is performed while supplying the grinding water Wh having a temperature higher than the grinding water Wc (second temperature) to the back surface 11b side of the wafer 11. The temperature of the grinding water Wh is set to 80 ° C. to 90 ° C., for example. The rotation speeds of the chuck table 10 and the spindle 14 do not need to be changed.

  Thereby, the protective tape 23 adhered to the surface 11a of the wafer 11 is easily stretched by the high-temperature grinding water Wh, so that the distance between the chips can be sufficiently widened by the processing load during grinding. As a result, it is possible to prevent the chips from being damaged by preventing the chips from contacting each other during grinding. When the wafer 11 is ground to a finished thickness (for example, 80 μm), the grinding step ends.

  As described above, the division method according to the present embodiment includes a grinding step for grinding the wafer 11 to a finished thickness, and a detection step for detecting that the wafer 11 is divided into chips during the grinding step. Before the division of the wafer 11 is detected, the wafer 11 is ground with the grinding water Wc having a predetermined temperature (first temperature). After the division of the wafer 11 is detected, the temperature is higher than that of the grinding water Wc (the first temperature). The wafer 11 is ground with a grinding water Wh having a second temperature higher than the first temperature.

  Thereby, after the wafer 11 is divided, the protective tape 23 attached to the surface 11a of the wafer 11 is easily stretched by the high temperature grinding water Wh, so that the interval between adjacent chips can be sufficiently widened. That is, the possibility of breakage due to contact during grinding can be reduced.

  In addition, this invention is not limited to description of the said embodiment, A various change can be implemented. For example, in the above embodiment, the division of the wafer 11 is detected using the contact-type thickness measurement sensor 22, but the division of the wafer 11 is detected using a non-contact-type thickness measurement sensor using a laser beam or the like. You may do it.

  Further, in the above embodiment, the division of the wafer 11 is detected using the thickness measurement sensor. However, the change of the load current value that varies according to the load of the spindle 14, the grinding time, etc., is used as a reference. Splits can also be detected.

  In addition, the configurations, methods, and the like according to the above-described embodiments can be changed as appropriate without departing from the scope of the object of the present invention.

2 Cutting device 4 Cutting blade 6 Spindle 8 Grinding device 10 Holding table 10a Holding surface 12 Grinding mechanism (grinding means)
14 Spindle 16 Wheel mount 18 Grinding wheel 18a Wheel base 18b Grinding wheel 20 Grinding water supply nozzle 22 Thickness measurement sensor 22a First probe 22b Second probe 11 Wafer 11a Surface 11b Back surface 11c Outer surface 13 Device region 15 Outer region 17 Street (division planned line)
19 device 21 groove 23 protective tape 23a surface 23b back surface Wc, Wh grinding water

Claims (1)

A division method for dividing a wafer in which a device is formed in each region partitioned by a plurality of division lines that intersect the surface into individual chips along the division lines,
A groove forming step for forming a groove deeper than the finished thickness of the chip along the division line;
After performing the groove forming step, an attaching step of attaching a protective tape to the surface of the wafer;
After performing the adhering step, the wafer holding step of holding the front side of the wafer with the holding table via the protective tape and exposing the back side of the wafer;
A grinding step of grinding the back surface of the wafer with a grinding means having a grinding wheel while supplying grinding water to the wafer held by the holding table and thinning it to the finished thickness;
Detecting during the execution of the grinding step that the groove is exposed on the back surface of the wafer and the wafer is divided into individual chips, and
In the grinding step, grinding is performed with the grinding water at the first temperature before the detection of the division of the wafer in the detection step. After the division of the wafer is detected in the detection step, the first division is performed. A dividing method, wherein the wafer is ground with a grinding water having a second temperature higher than the first temperature to reduce the thickness to the finished thickness.

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