JP2010186971A - Wafer processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wafer processing method capable of reliably dividing a wafer into individual devices without impairing a handling property of the thinly ground wafer. <P>SOLUTION: The wafer processing method divides a wafer having a plurality of device regions 17 partitioned by predetermined division lines and an outer peripheral surplus region 19 encircling the device regions into individual devices. The wafer processing method includes the processes of: grinding the back of the device regions to have a given thickness and forming a ring-shaped reinforced portion on the back corresponding to the outer peripheral surplus region; adhering the wafer to a dicing frame 36 via a dicing tape 34 to support the wafer; cutting the predetermined division lines with a cutting blade to divide the wafer into individual devices while holding the wafer on a chuck table having a device region holding portion and a ring-shaped reinforced portion supporting portion; separating the boundary between the device regions 17 and the outer peripheral surplus region with the cutting blade for removal; and picking up the individual devices from the dicing tape. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a wafer processing method capable of dividing a thinly ground wafer into individual devices without impairing handleability.

  In the semiconductor device manufacturing process, a plurality of regions are partitioned by dividing lines called streets arranged in a lattice pattern on the surface of a semiconductor wafer having a substantially disk shape, and devices such as IC and LSI are divided into these partitioned regions. Form. Then, the semiconductor wafer is cut into individual semiconductor chips (devices) by cutting the semiconductor wafer along a street with a cutting device.

  The divided wafer is formed to have a predetermined thickness by grinding the back surface before cutting along the street. In recent years, in order to achieve a reduction in weight and size of electrical equipment, it has been required to make the wafer thinner, for example, about 50 μm.

  Such thinly formed wafers are not as elastic as paper and are difficult to handle, and may be damaged during transportation. Therefore, a grinding method in which only the back surface corresponding to the device region of the wafer is ground and a ring-shaped reinforcing portion is formed on the back surface of the wafer corresponding to the outer peripheral surplus region surrounding the device region is disclosed in, for example, Japanese Patent Application Laid-Open No. 2007-173487. Proposed in

  As a method of dividing the wafer having the ring-shaped reinforcing portion formed on the outer periphery of the back surface along the street (division planned line), after removing the ring-shaped reinforcing portion, a cutting blade is used from the front side of the wafer. A cutting method has been proposed (see JP 2007-19379 A).

JP 2007-173487 A JP 2007-19379 A

  However, the wafer from which the ring-shaped reinforcing portion is removed has a problem that it is easily damaged by handling during cutting. Therefore, when a wafer having a ring-shaped reinforcing portion formed on the outer periphery of the back surface is divided into individual devices, the timing at which the ring-shaped reinforcing portion should be removed becomes a problem.

  The present invention has been made in view of the above points, and the object of the present invention is to impair handling at the time of cutting a wafer whose central portion is thinly ground leaving a ring-shaped reinforcing portion on the outer periphery. It is to provide a wafer processing method that can be divided into individual devices without any problem.

  According to the present invention, there is provided a wafer dividing method for dividing a wafer having a device area in which a plurality of devices are partitioned by division lines and an outer peripheral surplus area surrounding the device area into individual devices. Grinding the back surface corresponding to the device area of the wafer and grinding it to a predetermined thickness and forming a ring-shaped reinforcing portion on the back surface corresponding to the outer peripheral surplus area, and affixing a dicing tape on the back surface of the wafer In addition, a wafer supporting step for supporting the wafer by the dicing frame by sticking the outer peripheral portion of the dicing tape to a dicing frame having an opening surrounding the wafer, and a device area holding section for sucking and holding an area corresponding to the device area of the wafer And a ring-shaped reinforcing portion supporting portion that supports the ring-shaped reinforcing portion. Hold the wafer supported by the dicing frame on the table, position the cutting blade on the planned dividing line, cut the planned dividing line and divide the wafer into individual devices, and the cutting blade on the device area and the outer circumference A step of removing the ring-shaped reinforcing portion by removing the ring-shaped reinforcing portion from the wafer by rotating the chuck table in a state where the chuck table is positioned at the boundary with the surplus region; and a pickup step of picking up individual devices from the dicing tape; A method for processing a wafer is provided.

  Preferably, the dicing tape is composed of an adhesive tape whose adhesive strength is reduced by an external stimulus, and the ring-shaped reinforcing portion is adhered when the ring-shaped reinforcing portion is separated from the wafer in the ring-shaped reinforcing portion removing step. An external stimulus is applied to the dicing tape.

  According to the present invention, the wafer is divided into individual devices in a state where the wafer is reinforced by the ring-shaped reinforcing portion, and then the ring-shaped reinforcing portion is separated and removed from the wafer. The thinly formed wafer can be reliably divided into individual devices without causing any chipping in the device.

It is a surface side perspective view of a wafer. It is a back surface side perspective view of a wafer in the state where a protective tape was stuck on the surface. It is a perspective view which shows the principal part of a grinding device. It is explanatory drawing of the circular recessed part grinding process implemented by the grinding device. It is sectional drawing of the semiconductor wafer in which the circular recessed part grinding process was implemented. It is explanatory drawing of the wafer support process which supports a wafer with a dicing frame. It is sectional drawing of the wafer of the state with which the dicing frame was mounted | worn through the dicing tape. It is sectional drawing of the wafer of the state supported by the chuck table. It is explanatory drawing of a wafer division | segmentation process. It is explanatory drawing of a ring-shaped reinforcement part removal process. It is explanatory drawing of a pick-up process.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view of a semiconductor wafer before being processed to a predetermined thickness. The semiconductor wafer 11 shown in FIG. 1 is made of, for example, a silicon wafer having a thickness of 700 μm, and a plurality of streets 13 are formed in a lattice shape on the surface 11a, and a plurality of streets partitioned by the plurality of streets 13 are formed. A device 15 such as an IC or LSI is formed in the region.

  The semiconductor 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 that surrounds the device region 17. A notch 21 is formed on the outer periphery of the semiconductor wafer 11 as a mark indicating the crystal orientation of the silicon wafer.

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

  FIGS. 3 to 5 show a grinding method for forming a circular concave portion on the back surface corresponding to the device region 17 of the semiconductor wafer 11 and forming a ring-shaped reinforcing portion including an outer peripheral surplus region 19 on the outer peripheral side of the circular concave portion. The description will be given with reference. First, referring to FIG. 3, a perspective view of a main part of the grinding device 2 is shown.

  The grinding apparatus 2 includes a chuck table 4 that can rotate while holding a wafer, and a grinding unit 6 that performs grinding on the wafer. The grinding unit 6 includes a rotatable spindle 8 that can be raised and lowered, a grinding wheel 10 that is attached to the tip of the spindle 8, and a grinding wheel 12 that is fixed to the lower surface of the grinding wheel 10.

  The wafer 11 is sucked and held on the side of the protective tape 23 by the chuck table 4, and the back surface 11 b of the wafer 11 is set to face the grinding wheel 12. Here, the relationship between the wafer 11 held on the chuck table 4 and the grinding wheel 12 mounted on the grinding wheel 10 will be described with reference to FIG.

  The rotation center P1 of the chuck table 4 and the rotation center P2 of the grinding wheel 12 are eccentric, and the outer diameter of the grinding wheel 12 is smaller than the diameter of the boundary line 28 between the device region 17 and the outer peripheral surplus region 19 of the wafer 11. The size of the grinding wheel 12 is set so as to pass through the rotation center P 1 of the chuck table 4.

  While rotating the chuck table 4 in the direction indicated by an arrow 30 at, for example, 300 rpm, the grinding wheel 12 is rotated in the direction indicated by an arrow 32, for example, at 6000 rpm, and a grinding feed mechanism (not shown) is operated to operate the grinding wheel 12 of the grinding wheel 10. Is brought into contact with the back surface of the wafer 11. Then, the cutting wheel 10 is ground and fed downward by a predetermined amount at a predetermined grinding feed speed.

  As a result, on the back surface of the semiconductor wafer 11, as shown in FIG. 5, a region corresponding to the device region 17 is ground and removed to form a recess 24 having a predetermined thickness (for example, 50 μm), and an outer peripheral surplus region 19. The region corresponding to is left and the ring-shaped reinforcing portion 26 including the outer peripheral surplus region 19 is formed.

  As shown in FIG. 6, the back surface 11 b of the semiconductor wafer 11 thus ground is pasted on the dicing tape 34, which is an adhesive tape stuck on the annular dicing frame 36.

  As shown in FIG. 7, the dicing tape 34 is attached so as to go around not only the ring-shaped reinforcing portion 26 but also the circular recess 24. Then, the protective tape 23 is peeled off from the surface of the wafer 11 as shown in FIG.

  Next, a wafer dividing step is performed in which the wafer 11 supported by the dicing frame 36 is held on a chuck table of a dicing apparatus (cutting apparatus), the dividing line 13 is cut by a cutting blade, and the wafer 11 is divided into individual devices 15. carry out.

  In this case, for example, it is preferable to use a chuck table 40 as shown exaggeratedly in FIG. The chuck table 40 includes a rotating shaft 42 on which a vacuum suction path 44 is formed, and a base 46 mounted and fixed on the rotating shaft 42.

  The base 46 is made of a metal such as SUS and has a mounting circular recess 48 and a vacuum suction path 50 communicated with the vacuum suction path 44 of the rotating shaft 42. The vacuum suction path 50 opens in the recess 48. The vacuum suction path 44 of the rotating shaft 42 is connected to a vacuum suction source (not shown).

  In the circular recess 48 of the base 46, a disc-shaped porous adsorbing portion 52 made of porous ceramic or the like is disposed. The suction surface of the porous suction portion 52 is formed to be higher than the upper surface of the base 46 by a predetermined height. The base 46 supports the ring-shaped reinforcing portion 26 of the wafer 11, and the porous suction portion 52 uses the dicing tape. The circular recess 24 can be sucked and held via 34.

  In the state where the wafer 11 is sucked and held by the chuck table 40 as described above, the wafer 11 is cut along the streets 13 using the cutting means 54 as shown in FIG. In FIG. 9, a spindle 56 that is rotationally driven by a servo motor (not shown) is rotatably accommodated in a spindle housing 62 of a spindle unit 60 of the cutting means 54, and a cutting blade 58 is attached to the tip of the spindle 56. ing.

  As shown in FIG. 9, when the wafer 11 held on the chuck table 40 is moved in the X-axis direction and the cutting blade 58 is rotated at a high speed to be positioned on the planned dividing line 13, the aligned street is obtained. 13 is cut.

  By performing cutting while indexing the cutting blade 58 in the Y-axis direction at every street pitch stored in the memory, all the streets 13 in the same direction are cut. Further, if the chuck table 40 is rotated 90 degrees and then the same cutting is performed, all the streets 13 in the other direction are also cut, and the wafer 11 is divided into individual devices (chips) 15.

  However, when this dividing step is completed, the ring-shaped reinforcing portion 26 formed on the outer peripheral portion of the wafer 11 has a thickness of 700 μm, so that it remains adhered to the dicing tape 34 without being completely cut. ing. Therefore, the ring-shaped reinforcing portion removing step is performed as the next step.

  In this ring-shaped reinforcing portion removing step, as shown in FIG. 10A, the cutting blade 58 is positioned at the boundary portion between the device region 17 and the outer peripheral surplus region 19, and the chuck table 40 is rotated at least once to obtain a curve 64. As shown, the boundary portion is cut, and the ring-shaped reinforcing portion 26 is separated from the wafer 11 and removed as shown in FIG.

  In the ring-shaped reinforcing portion removing step, as shown in FIG. 10B, when the ring-shaped reinforcing portion 26 is separated from the wafer 11, an external stimulus is applied to the dicing tape 34 to which the ring-shaped reinforcing portion 26 is attached. The ring-shaped reinforcing portion 26 is peeled off from the dicing tape 34 after the adhesive strength of the dicing tape 34 is reduced.

  The application of the external stimulus is performed by, for example, ultraviolet irradiation or heating according to the type of the dicing tape 34. In the case where the dicing tape 34 is an ultraviolet curable tape such as a product name “UC series” manufactured by Furukawa Electric Co., Ltd., the adhesive strength is reduced by ultraviolet irradiation, and a product name “Riva Alpha” manufactured by Nitto Denko Corporation is used. In the case of a tape whose adhesive strength is reduced by heating such as "", the adhesive strength is reduced by heating.

  The wafer 11 from which the ring-shaped reinforcing portion 26 has been removed is then subjected to a device pickup process, and individual devices 15 are picked up from the dicing tape 34. In the device pick-up process, the dicing tape 34 is expanded in the radial direction by a tape expansion device 70 as shown in FIG. 11, and the device 15 is picked up after widening the gap between the devices to be picked up.

  The tape expansion device 70 includes a fixed cylinder 72 and a moving cylinder 74 that is moved in the vertical direction by driving means disposed outside the fixed cylinder 72. As shown in FIG. 11A, the dicing frame 36 that supports the wafer 11 from which the ring-shaped reinforcing portion 26 has been removed is mounted on a moving cylinder 74 and fixed by a clamp 76.

  At this time, the upper surface of the fixed cylinder 72 and the upper surface of the moving cylinder 74 are held substantially on the same plane. When the moving cylinder 74 moves in the direction of arrow A in FIG. 11A, the moving cylinder 74 descends with respect to the fixed cylinder 72 as shown in FIG. 11B, and accordingly the dicing tape 34 is expanded in the radial direction. , The gap between the devices is expanded.

  When the individual devices 15 are picked up by the pickup device 80 in a state where the gap between the devices is expanded in this way, the pickup operation can be performed easily and smoothly.

  According to the embodiment described above, since the wafer 11 is divided into the individual devices 15 and then the ring-shaped reinforcing portion 26 is removed, the handling ability at the time of wafer cutting is not hindered and the device 15 The wafer 11 can be surely divided into the individual devices 15 without causing chipping.

2 Grinding device 4 Chuck table 11 Semiconductor wafer 12 Grinding wheel 15 Device 17 Device area 19 Peripheral surplus area 23 Protective tape 24 Circular recess 26 Ring-shaped reinforcing part 34 Dicing tape 36 Dicing frame 40 Chuck table 52 Porous adsorption part 58 Cutting blade 70 Tape Expansion device 80 Pickup device

Claims (2)

A wafer processing method that divides a wafer having a device area in which a plurality of devices are partitioned by dividing lines and an outer peripheral surplus area surrounding the device area into individual devices,
Grinding the back surface corresponding to the device region of the wafer to grind to a predetermined thickness and forming a ring-shaped reinforcing portion on the back surface corresponding to the outer peripheral surplus region;
A wafer support step of attaching a dicing tape to the back surface of the wafer and attaching the outer periphery of the dicing tape to a dicing frame having an opening surrounding the wafer, and supporting the wafer with the dicing frame;
A wafer supported by a dicing frame is held on a chuck table having a device area holding section for sucking and holding an area corresponding to the device area of the wafer and a ring-shaped reinforcing section supporting section for supporting a ring-shaped reinforcing section. A wafer splitting process in which the blade is positioned on the planned split line and the split split line is cut to divide the wafer into individual devices;
A ring-shaped reinforcing part removing step of rotating and removing the ring-shaped reinforcing part from the wafer by rotating the chuck table in a state where the cutting blade is positioned at the boundary between the device area and the outer peripheral surplus area,
Pickup process for picking up individual devices from dicing tape,
A wafer processing method characterized by comprising: The dicing tape is composed of an adhesive tape whose adhesive strength is reduced by an external stimulus,
The wafer processing method according to claim 1, wherein, in the ring-shaped reinforcing portion removing step, when the ring-shaped reinforcing portion is separated from the wafer, an external stimulus is applied to the dicing tape to which the ring-shaped reinforcing portion is attached.

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