JP2017112264A - Wafer processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a processing method which enables the production of a device chip of good quality from a WL-CSP wafer.SOLUTION: A wafer processing method comprises: a groove-forming step for forming a groove 19 along each scheduled division line in a wafer 11; a molding step for covering a surface of the wafer with a mold resin 21 to fill the groove; a protective member-providing step for providing a protective member on the mold resin; a backside-grinding step for holding, by suction, the wafer on a chuck table through the protective member and grinding a backside of the wafer to expose the mold resin from the backside of the wafer; a frame-supporting step for sticking the backside of the wafer to an adhesive tape T to support the wafer by an annular frame, and removing the protective member from the wafer surface; a division-start point-forming step for forming a division-start point by using a jig having a cutting blade 48 formed to adapt to the scheduled division line, in which the cutting blade is forced against the wafer in position; and a division step for dividing, by application of an external force, the wafer into a plurality of device chips each having a periphery surrounded by the mold resin.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a wafer processing method for dividing a wafer into individual device chips.

  In the manufacturing process of semiconductor device chips, grid-like division lines called streets are formed on the surface of a wafer made of silicon or a compound semiconductor, and devices such as ICs and LSIs are formed in each area partitioned by the division lines. Is done. After these wafers are ground and thinned to a predetermined thickness, the individual semiconductor device chips are manufactured by being divided by a cutting device along a predetermined division line.

  In recent years, a technology called WL-CSP (Wafer-Level Chip Size Package) has been actively used in the field of semiconductor devices. WL-CSP is a technology that forms a rewiring layer and electrodes (metal posts) in a wafer state, then seals the wafer surface with a resin, and divides the wafer into individual packages with a cutting blade or the like. Since the size of the package becomes the size of the semiconductor device chip, it is widely adopted from the viewpoint of miniaturization and weight reduction.

  The following processes are known as processes for manufacturing individual device chips with WL-CSP.

  (1) A cutting groove corresponding to the finished thickness of the device chip is formed on the division line of the wafer.

  (2) Cover the entire surface of the wafer with mold resin and embed the mold resin in the cutting groove.

  (3) After a protective member is attached to the front surface of the wafer, the back surface of the wafer is ground to expose the mold resin in the cutting groove to the back surface of the wafer.

  (4) The wafer back surface is attached to a dicing tape whose outer peripheral portion is attached to an annular frame, and the wafer is cut along a planned dividing line with a cutting blade having a thickness smaller than the thickness of the cutting blade used in the cutting groove forming process. Cut into individual device chips.

JP 2006-1000053 A

  However, when the back surface of the wafer whose surface is coated with the mold resin is ground to expose the cutting grooves on the back surface, the cutting grooves along the line to be divided are formed only by the mold resin, and the wafer is divided in the dividing process. When the line to be divided is cut, there is a problem that the cutting blade of the cutting blade is bent by the resistance of the mold resin, and the side surface of the device chip is damaged.

  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 generating a high-quality device chip from a WL-CSP wafer.

  According to the present invention, there is provided a wafer processing method for dividing a wafer in which a device is formed in each region of a surface partitioned by a plurality of division lines formed in a lattice shape into individual device chips, the device chip A groove forming step for forming a groove having a depth corresponding to the finished thickness along the line to be divided, and after performing the groove forming step, the surface of the wafer is coated with a mold resin and the groove is molded resin After performing the molding process, the protective member disposing process for disposing a protective member on the mold resin coated on the surface of the wafer, and the protective member disposing process The wafer is sucked and held by the chuck table through the protective member, the back surface of the wafer is ground, and the mold resin embedded in the groove is removed from the wafer. After performing the back surface grinding step to be exposed to the surface, and the back surface grinding step, the back surface of the wafer is adhered within the opening to an adhesive tape having an outer peripheral portion adhered to an annular frame having an opening that accommodates the wafer, The wafer is supported by the annular frame via an adhesive tape, and a frame support step for removing the protective member from the surface of the wafer, and after the frame support step, the cutting blades corresponding to the planned division lines are formed in a lattice shape. Using the formed jig, the cutting edge of the jig is positioned at the center of the line to be divided and pressed to form the division starting point, and after performing the division starting point forming step, external force is applied to the wafer. And a dividing step of dividing the wafer into a plurality of device chips, the outer periphery of which is surrounded by a mold resin, to provide a wafer processing method.

  According to the wafer processing method of the present invention, a jig in which cutting edges corresponding to the division lines are formed in a lattice shape is used, and the cutting edge of the jig is positioned at the center of the division lines and is pressed to set the division starting point. After forming, the wafer is divided into individual device chips having outer peripheries surrounded by the mold resin by applying an external force, so that the cutting blade of the cutting blade bends and damages the side surface of the device chip. Thus, it is possible to reliably produce a device chip whose outer periphery is surrounded by a mold resin.

It is a surface side perspective view of a semiconductor wafer. It is a perspective view of the groove | channel formation process implemented with a cutting blade. 3A is a front perspective view of the semiconductor wafer after the groove forming step, and FIG. 3B is an enlarged sectional view taken along line 3B-3B of FIG. 3A. 4A is a front perspective view of the semiconductor wafer showing the molding process, and FIG. 4B is an enlarged sectional view taken along line 4B-4B of FIG. 4A. It is a perspective view which shows a back surface grinding process. It is a perspective view which shows a flame | frame support process. FIG. 7A is a cross-sectional view showing the division start point forming step, and FIG. 7B is a cross-sectional view of the wafer on which the division start point is formed. It is sectional drawing which shows a division | segmentation process. It is sectional drawing of the wafer after implementation of a division process. It is sectional drawing of CSP.

  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. The wafer 11 has a thickness of about 700 μm.

  The wafer 11 has a front surface 11a and a back surface 11b. A plurality of scheduled division lines 13 are formed on the front surface 11a so as to be orthogonal to each other. The device 15 is formed.

  As shown in the enlarged view of FIG. 1, each device 15 has a plurality of protruding electrodes (bumps) 17 protruding on the surface thereof. In this way, the wafer 11 having the bumps 17 on the surface is divided into flip chip bonding in which the wafer 11 is divided into individual device chips having the devices 15 and the bumps 17 are directly bonded to the electrodes formed on the wiring board. It is mounted on a wiring board by a so-called mounting technique.

  Referring to FIG. 2, a perspective view of an embodiment in which a groove forming process is performed by a cutting blade is shown. In FIG. 2, reference numeral 10 denotes a cutting unit of the cutting apparatus. The cutting unit 10 includes a cutting blade 14 attached to the tip of a spindle housed in a spindle housing 12 and a blade cover 16 that covers the upper half of the cutting blade 14. ing. The blade cover 16 is provided with a blade cooler nozzle 18 that ejects cutting water toward the wafer 11 and the cutting blade 14 that are being cut.

  In the groove forming process, the cutting blade 14 having a cutting blade having a predetermined width and rotating at high speed in the direction of arrow A is cut from the surface 11a of the wafer 11 to a depth corresponding to the finished thickness of the device chip, and the wafer 11 is held. By cutting and feeding a chuck table (not shown) in the direction of the arrow X1, a cutting groove 19 having a depth corresponding to the finished thickness of the device chip is formed along the planned dividing line 13.

  While indexing and feeding the wafer 11 in the Y-axis direction, similar cutting grooves 19 are formed one after another along the planned dividing line 13 extending in the first direction. Next, after the chuck table holding the wafer 11 is rotated by 90 °, similar cutting grooves 19 are formed one after another along the division line 13 extending in the second direction orthogonal to the first direction.

  FIG. 3A shows a front perspective view of the wafer 11 after completion of the groove forming step. As shown in FIG. 3B, which is an enlarged cross-sectional view taken along line 3B-3B in FIG. 3A, the cutting groove 19 formed in the groove forming step corresponds to a predetermined width W1 and a finished thickness of the device chip. Depth d1.

  Here, when the thickness of the wafer 11 is t1 = 700 μm, in this embodiment, the predetermined width W1 = 40 μm and the depth d1 = 300 μm corresponding to the finished thickness of the device chip. However, the predetermined width W1 and the depth d1 corresponding to the finished thickness of the device chip are not limited to these values.

  After performing the groove forming process, a molding process is performed in which the surface 11a of the wafer 11 is coated with a mold resin and the mold resin is embedded in the cutting groove 19 formed in the wafer 11.

  In this molding process, as shown in FIG. 4A, a liquid mold resin 21 containing a filler is dropped onto the surface 11a of the wafer 11, and a chuck table (not shown) for sucking and holding the wafer 11 is rotated to perform spin coating. Thus, the surface 11 a of the wafer 11 is covered with the mold resin 21 as shown in the enlarged sectional view of FIG. 4B, and the mold resin 21 is embedded in the cutting groove 19. The liquid mold resin 21 is cured when left at room temperature.

  In this embodiment, the thickness t2 of the mold resin 21 coated on the surface 11a of the wafer 11 is about 100 μm, and the heads of the bumps 17 are slightly exposed from the surface of the mold resin 21. When the heads of the bumps 17 are completely covered with the mold resin 21, the heads of the bumps 17 are exposed from the surface of the mold resin 21 by grinding or polishing.

  Here, when the width of the division line 13 of the wafer 11 in this embodiment is 50 μm, the width W1 of the cutting groove 19 is preferably about 40 μm, and the mold resin 21 is a mixture of silica as a filler in an epoxy resin. Is preferred.

Further, a mold resin containing silica (SiO ₂ ) 9 as a filler in a volume ratio with respect to the epoxy resin 1 is preferable, and an average particle diameter of silica is preferably 30 μm or less, more preferably 20 μm or less.

  After the molding process is performed, a protective member disposing process for disposing a protective member on the surface 11a of the wafer 11 is performed. Actually, since the surface 11 a of the wafer 11 is covered with the mold resin 21, a protective member such as a protective tape is stuck on the mold resin 21.

  After performing the protective member disposing step, a back surface grinding step is performed in which the back surface 11b of the wafer 11 is ground to expose the mold resin 21 embedded in the cutting groove 19 to the back surface 11b of the wafer 11.

  This back grinding process will be described with reference to FIG. In the back surface grinding process, the front surface 11a side of the wafer 11 is sucked and held via the protective tape 23 by the chuck table 20 of the grinding device, and the back surface 11b side of the wafer 11 is exposed.

  The grinding unit 22 of the grinding apparatus includes a spindle 24 that is rotationally driven by a motor, a wheel mount 26 that is fixed to the tip of the spindle 24, and a grinding wheel 30 that is detachably fixed to the wheel mount 26 with a plurality of screws 28. Is included. The grinding wheel 30 includes an annular wheel base 32 and a plurality of grinding wheels 34 that are annularly fixed to the outer periphery of the lower end of the wheel base 32.

  In the back grinding process, the grinding wheel 30 is rotated in the same direction as the chuck table 20, that is, in the arrow b direction, for example, at 6000 rpm while rotating the chuck table 20 in the direction indicated by the arrow a, for example, and a grinding unit (not shown). The feed mechanism is operated to bring the grinding wheel 34 into contact with the back surface 11 b of the wafer 11.

  Then, the grinding wheel 30 is ground and fed downward by a predetermined amount at a predetermined grinding feed speed (for example, 1 μm / s), and the back surface grinding of the wafer 11 is performed. When the grinding is continued and the wafer 11 is thinned to the finished thickness of the device chip, the mold resin 21 embedded in the cutting groove 19 is exposed on the back surface 11b of the wafer 11 as shown in FIG.

  After performing the back surface grinding step, as shown in FIG. 6, the wafer 11 is placed in the dicing tape T, which is an adhesive tape having an outer peripheral portion attached to an annular frame F having an opening F1 for accommodating the wafer. A back surface 11b is attached, the wafer 11 is supported by the annular frame F via the dicing tape T, and a frame support process is performed to remove the protective tape 23 from the front surface 11a of the wafer 11.

  In this frame support process, since the protective tape 23 is peeled off from the surface 11a of the wafer 11, the mold resin 21 coated on the surface 11a of the wafer 11 is exposed on the surface. After carrying out the frame supporting step, as shown in FIG. 7A, a split starting point forming jig 44 is used, using a split starting point forming jig 44 in which cutting edges 48 corresponding to the planned split lines 13 are formed in a lattice shape. A dividing starting point forming step of forming the dividing starting point 25 is performed by positioning and pressing the cutting blade 48 at the center of the scheduled dividing line 13.

  The split starting point forming jig 44 shown in FIG. 7A is configured by forming a plurality of cutting blades 48 corresponding to the planned split lines 13 of the wafer 11 below the plate 46 in a lattice shape. Each cutting edge 48 is formed to have a sharp tip, and after each cutting edge 48 of the division start point forming jig 44 is positioned at the center of each division planned line 13, the division start point forming jig 44 is moved in the direction of arrow A. When the wafer 11 is pressed against the wafer 11, as shown in FIG. 7B, a dividing starting point 25 is formed along the planned dividing line 13 in the center of the mold resin 21 corresponding to the planned dividing line 13.

  After carrying out the division start point forming step, an external force is applied to the wafer 11 to carry out a division step of dividing the wafer 11 into a plurality of device chips having outer peripheries surrounded by the mold resin 21.

  In the dividing step, for example, the protective tape 23 is attached again to the mold resin 21 of the wafer 11 on which the dividing starting point 25 shown in FIG. As shown, the wafer 11 is mounted on the pair of support bases 42 of the splitting device 40 so that the split starting point 25 is positioned between the pair of support bases 42 spaced apart by a predetermined distance.

  Then, the wedge-shaped dividing bar 44 having the acute tip 44a is moved in the direction of arrow A, and the dividing bar 44 is pressed against the back surface 11b of the wafer 11 via the dicing tape T, so that the cutting groove starts from the dividing starting point 25. The mold resin 21 embedded in 19 is divided along the division line 13. Referring to FIG. 9, an enlarged cross-sectional view of the wafer 11 after being cut in the dividing step is shown. The thickness t4 is 20 μm in this embodiment.

  The division bar 44 is driven by, for example, an air cylinder. Since the division starting point 25 is formed in the mold resin 21 embedded in the cutting groove 19, two mold resins 21 embedded in the cutting groove 19 are relatively smoothly pressed by the wedge-shaped division bar 44. Cleaved.

  When the cutting along one split starting point 25 is completed, the wafer 11 is moved by one pitch in the horizontal direction, the next split starting point 25 is positioned at the middle part of the pair of support bases 42, and the split bar 44 is driven. Then, the wafer 11 is cleaved from the next division starting point 25.

  When division along all the planned division lines 13 extending in the first direction is completed, the wafer 11 is rotated by 90 ° in the second direction orthogonal to the division planned lines 13 extending in the first direction. The wafer 11 is divided from the division starting point 25 along the planned division line 13 that extends.

  Thus, the wafer 11 is divided into individual device chips 27 as shown in FIG. The device chip 27 is divided into chip size packages (CSP) 31 because the surface side and both side surfaces thereof are covered with the mold resin 21.

  In the embodiment described above, since the heads of the bumps 17 are exposed from the mold resin 21 after the division start point forming step is performed, the protective tape 23 is attached to the mold resin 21 again. The reattachment of the tape 23 is not necessarily essential, and the dividing step may be performed by directly mounting the mold resin 21 on the pair of support bases 42 without reattaching the protective tape 23.

DESCRIPTION OF SYMBOLS 10 Cutting unit 11 Semiconductor wafer 13 Scheduled division lines 14 and 14a Cutting blade 15 Device 17 Bump 19 Cutting groove 21 Mold resin 22 Grinding unit 23 Protection tape 25 Division start point 27 Device chip 30 Grinding wheel 31 CSP
40 Dividing device 42 Support base 44 Dividing bar 46 Dividing start point forming jig 48 Cutting blade

Claims (1)

A wafer processing method for dividing a wafer in which a device is formed in each region of a surface defined by a plurality of division lines formed in a lattice shape into individual device chips,
A groove forming step of forming a groove having a depth corresponding to the finished thickness of the device chip along the planned dividing line;
After performing the groove forming step, a molding step of covering the surface of the wafer with a mold resin and embedding the mold resin in the groove;
A protective member disposing step of disposing a protective member on the mold resin coated on the surface of the wafer after performing the molding step;
After performing the protective member disposing step, the wafer is sucked and held by the chuck table through the protective member, and the back surface of the wafer is ground to expose the mold resin embedded in the groove to the back surface of the wafer. Grinding process;
After carrying out the back surface grinding process, the back surface of the wafer is adhered within the opening to an adhesive tape having an outer peripheral portion attached to an annular frame having an opening for accommodating the wafer, and the wafer is annularly attached via the adhesive tape. A frame supporting process for supporting the frame and removing the protective member from the surface of the wafer;
After performing the frame support step, use a jig in which cutting edges corresponding to the planned division lines are formed in a lattice shape, and position the cutting blade of the jig at the center of the planned division lines and press to form the division starting point A split starting point forming step,
After performing the division starting point forming step, a division step of applying an external force to the wafer and dividing the wafer into a plurality of device chips surrounded by a mold resin;
A wafer processing method characterized by comprising: